TY - JOUR TI - Energy Production from Coal Syngas Containing H2S via Solid Oxide Fuel Cells AU - Cooper, Matthew E. AU - DeSilva, Channa AU - Bayless, David T2 - ECS Meeting Abstracts AB - Abstract not Available. DA - 2008/5/5/ PY - 2008/5/5/ DO - 10.1149/ma2008-01/10/386 VL - MA2008-01 IS - 10 SP - 386-386 J2 - Meet. Abstr. OP - SN - 2151-2043 UR - http://dx.doi.org/10.1149/ma2008-01/10/386 DB - Crossref ER - TY - CONF TI - Coal direct chemical looping process for hydrogen production - Experimental studies AU - Kim, H. AU - Li, F. AU - Sridhar, D. AU - Zeng, L. AU - Wang, F. AU - Fan, L.-S. C2 - 2008/// C3 - 25th Annual International Pittsburgh Coal Conference, PCC - Proceedings DA - 2008/// UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-70349597170&partnerID=MN8TOARS ER - TY - CONF TI - Chemical looping gasification AU - Fan, L.-S. AU - Li, F. AU - Velazquez-Vargas, L.G. AU - Ramkumar, S. C2 - 2008/// C3 - CFB 2008 - Proceedings of the 9th Int. Conference on Circulating Fluidized Beds, in Conjunction with the 4th International VGB Workshop "Operating Experience with Fluidized Bed Firing Systems" DA - 2008/// UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84904821279&partnerID=MN8TOARS ER - TY - CONF TI - Syngas chemical looping process for hydrogen production: Bench scale demonstration and process simulation AU - Li, F. AU - Sridhar, D. AU - Kim, H. AU - Zeng, L. AU - Wang, F. AU - Fan, L.-S. C2 - 2008/// C3 - AIChE Annual Meeting, Conference Proceedings DA - 2008/// UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-79952286256&partnerID=MN8TOARS ER - TY - CONF TI - Studies on the reduction mechanism of the iron oxide based composite particle in the ingas chemical looping process AU - Sridhar, D. AU - Fan, L.-S. AU - Li, F. AU - Kim, H. AU - Zeng, L. AU - Yeh, T. C2 - 2008/// C3 - 25th Annual International Pittsburgh Coal Conference, PCC - Proceedings DA - 2008/// UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-70349585239&partnerID=MN8TOARS ER - TY - CONF TI - Hydrogen production from coal direct chemical looping process-process simulation AU - Zeng, L. AU - Wang, F. AU - Li, F. AU - Yu, F.C. AU - Tong, A. AU - Fan, L.S. C2 - 2008/// C3 - 25th Annual International Pittsburgh Coal Conference, PCC - Proceedings DA - 2008/// UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-70349599344&partnerID=MN8TOARS ER - TY - CONF TI - Comparison of coal based hydrogen and electricity co-generation processes under a carbon constrained scenario AU - Zeng, L. AU - Li, F. AU - Sridhar, D. AU - Wang, F. AU - Kim, H.R. AU - Fan, L.-S. C2 - 2008/// C3 - AIChE Annual Meeting, Conference Proceedings DA - 2008/// UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-79952301368&partnerID=MN8TOARS ER - TY - CONF TI - Coal Direct Chemical Looping (CDCL) process AU - Li, F. AU - Kim, H. AU - Sridhar, D. AU - Zeng, L. AU - Wang, F. AU - Fan, L.-S. C2 - 2008/// C3 - AIChE Annual Meeting, Conference Proceedings DA - 2008/// UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-79952309196&partnerID=MN8TOARS ER - TY - CONF TI - Syngas chemical looping process for hydrogen production AU - Li, F. AU - Sridhar, D. AU - Kim, H. AU - Zeng, L. AU - Wang, F. AU - Fan, L.-S. C2 - 2008/// C3 - 25th Annual International Pittsburgh Coal Conference, PCC - Proceedings DA - 2008/// UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-70349590098&partnerID=MN8TOARS ER - TY - CONF TI - Particle size optimization for syngas chemical looping process AU - Wang, F. AU - Li, F. AU - Tong, A. AU - Sridhar, D. AU - Fan, L.-S. C2 - 2008/// C3 - AIChE Annual Meeting, Conference Proceedings DA - 2008/// UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-79952285828&partnerID=MN8TOARS ER - TY - JOUR TI - Utilization of chemical looping strategy in coal gasification processes AU - Fan, Liangshih AU - Li, Fanxing AU - Ramkumar, Shwetha T2 - Particuology AB - Abstract Three chemical looping gasification processes, i.e. Syngas Chemical Looping (SCL) process, Coal Direct Chemical Looping (CDCL) process, and Calcium Looping process (CLP), are being developed at the Ohio State University (OSU). These processes utilize simple reaction schemes to convert carbonaceous fuels into products such as hydrogen, electricity, and synthetic fuels through the transformation of a highly reactive, highly recyclable chemical intermediate. In this paper, these novel chemical looping gasification processes are described and their advantages and potential challenges for commercialization are discussed. DA - 2008/6// PY - 2008/6// DO - 10.1016/j.partic.2008.03.005 VL - 6 IS - 3 SP - 131-142 J2 - Particuology LA - en OP - SN - 1674-2001 UR - http://dx.doi.org/10.1016/j.partic.2008.03.005 DB - Crossref KW - chemical looping KW - gasification process KW - combustion KW - hydrogen ER - TY - JOUR TI - Clean coal conversion processes – progress and challenges AU - Li, Fanxing AU - Fan, Liang-Shih T2 - Energy & Environmental Science AB - Although the processing of coal is an ancient problem and has been practiced for centuries, the constraints posed on today's coal conversion processes are unprecedented, and utmost innovations are required for finding the solution to the problem. DA - 2008/// PY - 2008/// DO - 10.1039/b809218b VL - 1 IS - 2 SP - 248-267 SN - 1754-5692 1754-5706 UR - http://dx.doi.org/10.1039/b809218b ER - TY - CHAP TI - Functional Genomics of Stress Response in Extremophilic Archaea AU - Tachdjian, S. AU - Shockley, K.R. AU - Conners, S.B. AU - Kelly, R.M. T2 - Archaea: New Models for Prokaryotic Biology A2 - Blum, P. PY - 2008/// PB - Caister Academic Press SN - 9781904455271 9781910190982 ER - TY - BOOK TI - Science and Technology of Polymer Nanofibers. AU - Andrady, Anthony L. AB - Preface. Acknowledgments. 1 Introduction. 1.1 Historical Background. 1.2 Basic Experimental Approach. 1.3 Description of Electrostatic Spinning. 1.4 Nanofiber Applications Areas. 2 Introduction to Polymer Solutions. 2.1 Average Molecular Weight. 2.2 Selecting Solvents: Solubility Parameter. 2.3 Thermodynamic Criterion for Solubility. 2.4 Macromolecular Models. 2.5 Viscosity of Dilute Polymer Solutions. 2.6 Concentrated Polymer Solutions. 3 Electrospinning Basics. 3.1 Molecular Weight Effects 56 3.2 Electrical Charge. 3.3 Bead Formation in Electrospinning. 3.4 Introduction to Electrospinning Practice. 4 Factors Affecting Nanofiber Quality. 4.1 The Polymer Solution. 4.2 Environment. 4.3 Collector. 4.4 Applied Potential. 4.5 Feed Rate. 4.6 Capillary Tip. 4.7 Gap Distance. 4.8 Relative Importance of Variables. 4.9 Examples of Reported Data. 5 Characterization of Nanofibers and Mats. 5.1 Mat Porosity and Pore Size Distribution. 5.2 Nanofiber Diameters and Pore Sizes by Microscopy. 5.3 Mechanical Properties of Mats. 5.4 Single-Fiber Characterization. 5.5 Nanofiber Crystallinity. 6 Composite Nanofibers. 6.1 Carbon Nanotubes in Nanofibers. 6.2 Metal-Nanofiber Composites. 6.3 Polymer-Clay Composites. 6.4 Decorated or Exocomposite Nanofibers. 7 Biomedical Applications of Nanofibers. 7.1 Drug Delivery Applications. 7.2 Scaffolding Applications of Nanofibers. 7.2.1 Natural Biopolymers. 7.3 Other Applications. 7.4 Future Directions. 8 Applications of Nanofiber Mats. 8.1 Introduction to Air Filtration. 8.2 Nanofiber Sensors. 8.3 Inorganic Nanofibers. 9 Recent Developments in Electrospinning. 9.1 Nanofibers with Surface Porosity. 9.2 Core-Shell Nanofibers. 9.3 Highly Aligned Nanofiber Mats. 9.4 Mixed Polymer Nanofibers and Nanofiber Mats. 9.5 Crosslinked Nanofibers. Appendix I. Electrospun Polymers Used in Tissues Engineering and biomedical Applications. Appendix II: Summary Table of Electrospun Polymer Nanofibers. References. Index. DA - 2008/// PY - 2008/// DO - 10.1002/9780470229842 PB - John Wiley and Sons SN - 9780470229835, 0470229837 ER - TY - JOUR TI - Cellular Incorporation Into Electrospun Nanofibers AU - van Aalst, John A. AU - Reed, Courtney R. AU - Han, Li AU - Andrady, Tony AU - Hromadka, Michael AU - Bernacki, Susan AU - Kolappa, Kamalkumar AU - Collins, James B. AU - Loboa, Elizabeth G. T2 - Annals of Plastic Surgery AB - Nanofibers are an emerging scaffold for tissue engineering. To date no one has reported cell incorporation into nanofibers. Human foreskin fibroblasts and human adipose-derived adult stem cells (hADAS) were grown to confluence, resuspended in phosphate-buffered saline, and then solubilized in polyvinyl alcohol (PVA). Nanofibers were created using an electrospinning technique across an electric potential of 20 kV. Cell interaction with nanofibers was assessed with optical microscopic imaging and scanning electron microscopy. PVA nanofibers with incorporated cells were then solubilized in phosphate-buffered saline; cell viability was assessed by trypan blue exclusion. Viable cells were allowed to proliferate. Chondrogenesis in fibroblasts was induced with TGF-β1. Both fibroblasts and hADAS survived the electrospinning process and were incorporated into PVA nanofibers. hADAS cell proliferation was negligible; however, fibroblasts proliferated and showed retained ability to undergo chondrogenesis. Cells can be incorporated into nanofibers, with maintained viability, proliferation, and function. DA - 2008/5// PY - 2008/5// DO - 10.1097/sap.0b013e318168db3e VL - 60 IS - 5 SP - 577-583 LA - en OP - SN - 0148-7043 UR - http://dx.doi.org/10.1097/sap.0b013e318168db3e DB - Crossref KW - nanofibers KW - fibroblasts KW - adipose-derived adult stem cells KW - electrospinning KW - nanotechnology ER - TY - JOUR TI - Nanofiber Applications for Burn Care AU - Hromadka, Michael AU - Collins, James B. AU - Reed, Courtney AU - Han, Li AU - Kolappa, Kamal K. AU - Cairns, Bruce A. AU - Andrady, Tony AU - van Aalst, John A. T2 - Journal of Burn Care & Research AB - Nanotechnology is a growing field of manufactured materials with sizes less than 1 mum, and it is particularly useful in the field of medicine because these applications replicate components of a cell's in vivo environment. Nanofibers, which mimic collagen fibrils in the extracellular matrix (ECM), can be created from a host of natural and synthetic compounds and have multiple properties that may be beneficial to burn wound care. These properties include a large surface-area-to-volume ratio, high porosity, improved cell adherence, proliferation and migration, and controlled in vivo degradation rates. The large surface area of nanofiber mats allows for increased interaction with compounds and provides a mechanism for sustained release of antibiotics, analgesics, or growth factors into burn wounds; high porosity allows diffusion of nutrients and waste. Improved cell function on these scaffolds will promote healing. Controlled degradation rates of these scaffolds will promote scaffold absorption after its function is no longer required. The objective of this article is to review the current literature describing nanofibers and their potential application to burn care. DA - 2008/9// PY - 2008/9// DO - 10.1097/bcr.0b013e31818480c9 VL - 29 IS - 5 SP - 695-703 J2 - Journal of Burn Care & Research LA - en OP - SN - 1559-047X UR - http://dx.doi.org/10.1097/bcr.0b013e31818480c9 DB - Crossref ER - TY - JOUR TI - Cell population-based model of dermal wound invasion with heterogeneous intracellular signaling properties AU - Monine, Michael I. AU - Haugh, Jason M. T2 - Cell Adhesion & Migration AB - A deterministic model of dermal wound invasion, which accounts for the platelet-derived growth factor (PDGF) gradient sensing mechanism in fibroblasts mediated by cell surface receptors and the phosphoinositide 3-kinase (PI3K) signal transduction pathway, was previously described (Biophys J 2006; 90:2297-2308). Here, we extend that work and implement a hybrid modeling strategy that treats fibroblasts as discrete entities endowed with heterogeneous properties, namely receptor, PI3K and 3’ phosphoinositide phosphatase expression levels. Analysis of the model suggests that the wound environment fosters the advancement of cells within the population that are better fit to migrate and/or proliferate in response to PDGF stimulation. Thus, cell-to-cell variability results in a significantly higher rate of wound invasion as compared with the deterministic model, in a manner that depends on the way in which individual cell properties are sampled or inherited upon cell division. DA - 2008/4// PY - 2008/4// DO - 10.4161/cam.2.2.6511 VL - 2 IS - 2 SP - 137-145 KW - wound healing KW - chemotaxis KW - gradient sensing KW - mathematical model KW - stochastic KW - signal transduction KW - phosphoinositide 3-kinase KW - PDGF ER - TY - JOUR TI - Mathematical Modelling of Biological Signaling Networks AU - Haugh, Jason M. T2 - Wiley Encyclopedia of Chemical Biology AB - Abstract Intracellular signaling networks, which are composed of interconnected biochemical pathways, regulate and actuate responses such as cell‐cycle progression and cell migration, survival, and differentiation. Although our knowledge of the intricate biochemical mechanisms at the level of individual proteins and molecular interactions is ever expanding, those details leave us with an even murkier view of how the complex network operates as a whole. True understanding requires knowing not only what happens at the molecular level but also how these mechanisms influence the precise magnitude, timing, and spatial localization of signal transduction processes. Hence, mathematical modeling and analysis has emerged in recent years as a legitimate approach for interpreting experimental results and generating novel hypotheses for additional study and model refinement. Once conducted in isolation and scorned by most biologists, quantitative modeling has moved into the mainstream as a powerful tool for the analysis of cell signaling. In this article, the biological, chemical, and physical underpinnings of this approach are presented, as are its current applications and future challenges. DA - 2008/5// PY - 2008/5// DO - 10.1002/9780470048672.wecb646 ER - TY - JOUR TI - Inside Cover: Light-Powered Electrical Switch Based on Cargo-Lifting Azobenzene Monolayers (Angew. Chem. Int. Ed. 18/2008) AU - Ferri, Violetta AU - Elbing, Mark AU - Pace, Giuseppina AU - Dickey, Michael D. AU - Zharnikov, Michael AU - Samorì, Paolo AU - Mayor, Marcel AU - Rampi, Maria Anita T2 - Angewandte Chemie International Edition AB - A molecular cargo lifter based on tightly packed monolayers (SAMs) of rigid azobenzene rods is described by M. A. Rampi et al. in their Communication on page 3407 ff. The monolayer, sandwiched between Hg and Au electrodes, is irradiated in situ through a transparent gold surface. The current flowing through the electrodes increases and decreases reversibly under alternating irradiation at 370 and 450 nm. The azobenzene SAM exerts a mechanical force and lifts the Hg drop electrode, and thus the system operates as a photoswitch. DA - 2008/4/21/ PY - 2008/4/21/ DO - 10.1002/anie.200890080 VL - 47 IS - 18 SP - 3290-3290 J2 - Angew. Chem. Int. Ed. LA - en OP - SN - 1433-7851 1521-3773 UR - http://dx.doi.org/10.1002/anie.200890080 DB - Crossref ER - TY - JOUR TI - Cover Picture: Synthesis of Light-Diffracting Assemblies from Microspheres and Nanoparticles in Droplets on a Superhydrophobic Surface (Adv. Mater. 22/2008) AU - Rastogi, Vinayak AU - Melle, Sonia AU - Calderón, Oscar G. AU - García, Antonio A. AU - Marquez, Manuel AU - Velev, Orlin D. T2 - Advanced Materials AB - Orlin Velev and co-workers report on page 4263 on the synthesis of light-diffracting assemblies obtained from microspheres and nanoparticles in droplets on a superhydrophobic surface. The cover shows optical microscopy images of drying droplets from aqueous suspensions of monodisperse latex or latex/gold nanoparticle mixtures dispensed on superhydrophobic substrates. Colloidal crystals are formed in the surface layer of the droplets due to the flux of evaporating water. The colloidal crystals give rise to multicolored diffraction patterns upon illumination with collimated white light. Once completely dried, these templates yield structured “nanojewel” supraparticles. DA - 2008/11/18/ PY - 2008/11/18/ DO - 10.1002/adma.200890089 VL - 20 IS - 22 SP - NA-NA J2 - Adv. Mater. LA - en OP - SN - 0935-9648 1521-4095 UR - http://dx.doi.org/10.1002/adma.200890089 DB - Crossref ER - TY - JOUR TI - Nonplanar Surface Organization of Monodendrons in Side-Chain Modified Liquid Crystalline Block Copolymers. AU - Sivaniah, E. AU - Genzer, J. AU - Hexemer, A. AU - Kramer, E. J. AU - Xiang, M. L. AU - Li, X. F. AU - Ober, C. K. AU - Magonov, S. T2 - Macromolecules AB - Scanning force microscopy (SFM) is used to investigate the surface structures of diblock copolymers of poly(styrene)-block-poly(isoprene) where a portion of the isoprene segments were modified to contain a semifluorinated alkane monodendron side group. The monodendrons consisted of either a single, double or triple attachment of the liquid crystalline mesogen group, [-(CH2)p-(CF2)qF]. Previously we reported that the surfaces of thin films of these materials contained small (∼20−30 nm) dome-like structures that were independent of the coincident block copolymer microphase architecture. We show here that these surface features can also assume a worm-like structure depending on the composition of the monodendron. Furthermore thermal studies of the block copolymer and the isolated monodendron molecule using in situ SFM studies confirm the liquid crystalline origin of the surface structures. DA - 2008/12/23/ PY - 2008/12/23/ DO - 10.1021/ma8015097 VL - 41 IS - 24 SP - 9940-9945 J2 - Macromolecules LA - en OP - SN - 0024-9297 1520-5835 UR - http://dx.doi.org/10.1021/ma8015097 DB - Crossref ER - TY - JOUR TI - Statistical copolymers of 2-(trimethylsilyloxy)ethyl methacrylate and methyl methacrylate synthesized by ATRP AU - Ritz, Pavel AU - Látalová, Petra AU - Kříž, Jaroslav AU - Genzer, Jan AU - Vlček, Petr T2 - Journal of Polymer Science Part A: Polymer Chemistry AB - Abstract No Abtract. DA - 2008/// PY - 2008/// DO - 10.1002/pola.22436 VL - 46 IS - 5 SP - 1919-1923 J2 - J. Polym. Sci. A Polym. Chem. LA - en OP - SN - 0887-624X 1099-0518 UR - http://dx.doi.org/10.1002/pola.22436 DB - Crossref KW - atom transfer radical polymerization (ATRP) KW - copolymerization KW - functionalization of polymers KW - gradient copolymers KW - monomer KW - reactivity ratios ER - TY - JOUR TI - C–H activation and C–C coupling of 4-methylpyridine using palladium supported on nanoparticle alumina AU - Neal, Luke M. AU - Hagelin-Weaver, Helena E. T2 - Journal of Molecular Catalysis A: Chemical AB - The C–H activation and C–C coupling of 4-methyl pyridine to 4,4′-dimethyl-2,2′-bipyridine was studied over palladium catalysts supported on nanoparticle alumina [nano-Al2O3(+)]. Even though Pd/Al2O3 catalysts are traditionally poor catalysts in this reaction, the Pd/nano-Al2O3(+) catalysts prepared via the precipitation method give the highest yield observed to date for this reaction system. The catalytic activity is very dependent on the catalyst preparation as Pd/nano-Al2O3(+) catalysts prepared via the wet impregnation method exhibit poor activities in the reaction. Additionally, a catalyst prepared using another nanoparticle alumina with larger particle sizes [nano-Al2O3(−)] does not have a significant activity. It was shown that using a commercial bimodal γ-Al2O3 support can result in an active catalyst if prepared via the precipitation method, but compared to the best performing catalyst, Pd/nano-Al2O3(+), the yields obtained from Pd/bimodal-γ-Al2O3 are lower and less reproducible. Pd surface area measurements indicate that the reaction is structure sensitive as there is no correlation between the Pd surface area and the catalytic activity. The reaction is also very sensitive to reactant quality and the 4-methyl pyridine must be distilled over KOH to ensure reproducible yields. Additional experiments indicate that this reaction requires a solid phase for catalysis. DA - 2008/4// PY - 2008/4// DO - 10.1016/j.molcata.2008.01.008 VL - 284 IS - 1-2 SP - 141-148 J2 - Journal of Molecular Catalysis A: Chemical LA - en OP - SN - 1381-1169 UR - http://dx.doi.org/10.1016/j.molcata.2008.01.008 DB - Crossref KW - Pd/Al2O3 KW - nanoparticle oxide KW - pyridine KW - C-H activation KW - aromatic coupling ER - TY - JOUR TI - Steam reforming of methanol using Cu-ZnO catalysts supported on nanoparticle alumina AU - Jones, Samuel D. AU - Neal, Luke M. AU - Hagelin-Weaver, Helena E. T2 - Applied Catalysis B: Environmental AB - Methanol steam reforming was studied over several catalysts made by deposition of copper and zinc precursors onto nanoparticle alumina. The results were compared to those of a commercially available copper, zinc oxide and alumina catalyst. Temperature programmed reduction, BET surface area measurements, and N2O decomposition were used to characterize the catalyst surfaces. XRD was used to study the bulk structure of the catalysts, and XPS was used to determine the chemical states of the surface species. The nanoparticle-supported catalysts achieved similar conversions as the commercial reference catalyst but at slightly higher temperatures. However, the nanoparticle-supported catalysts also exhibited a significantly lower CO selectivity at a given temperature and space time than the reference catalyst. Furthermore, the turnover frequencies of the nanoparticle-supported catalysts were higher than that of the commercial catalyst, which means that the activity of the surface copper is higher. It was determined that high alumina concentrations ultimately decrease catalytic activity as well as promote undesirable CH2O formation. The lower catalytic activity may be due to strong Cu-Al2O3 interactions, which result in Cu species which are not easily reduced. Furthermore, the acidity of the alumina support appears to promote CH2O formation, which at low Cu concentrations is not reformed to CO2 and H2. The CO levels present in this study are above what can be explained by the reverse water-gas-shift (WGS) reaction. While coking is not a significant deactivation pathway, migration of ZnO to the surface of the catalyst (or of Cu to the bulk of the catalyst) does explain the permanent loss of catalytic activity. Cu2O is present on the spent nanoparticle catalysts and it is likely that the Cu+/Cu0 ratio is of importance both for the catalytic activity and the CO selectivity. DA - 2008/12// PY - 2008/12// DO - 10.1016/j.apcatb.2008.05.023 VL - 84 IS - 3-4 SP - 631-642 J2 - Applied Catalysis B: Environmental LA - en OP - SN - 0926-3373 UR - http://dx.doi.org/10.1016/j.apcatb.2008.05.023 DB - Crossref KW - Methanol steam reforming KW - Cu/ZnO/Al2O3 catalysts KW - Hydrogen production KW - Nanoparticle alumina KW - CO selectivity ER - TY - JOUR TI - Model‐guided design of ligand‐regulated RNAi for programmable control of gene expression AU - Beisel, Chase L AU - Bayer, Travis S AU - Hoff, Kevin G AU - Smolke, Christina D T2 - Molecular Systems Biology AB - Progress in constructing biological networks will rely on the development of more advanced components that can be predictably modified to yield optimal system performance. We have engineered an RNA-based platform, which we call an shRNA switch, that provides for integrated ligand control of RNA interference (RNAi) by modular coupling of an aptamer, competing strand, and small hairpin (sh)RNA stem into a single component that links ligand concentration and target gene expression levels. A combined experimental and mathematical modelling approach identified multiple tuning strategies and moves towards a predictable framework for the forward design of shRNA switches. The utility of our platform is highlighted by the demonstration of fine-tuning, multi-input control, and model-guided design of shRNA switches with an optimized dynamic range. Thus, shRNA switches can serve as an advanced component for the construction of complex biological systems and offer a controlled means of activating RNAi in disease therapeutics. DA - 2008/1// PY - 2008/1// DO - 10.1038/msb.2008.62 VL - 4 IS - 1 SP - 224 J2 - Mol Syst Biol LA - en OP - SN - 1744-4292 1744-4292 UR - http://dx.doi.org/10.1038/msb.2008.62 DB - Crossref KW - aptamer KW - mathematical modelling KW - RNA KW - shRNA KW - synthetic biology ER - TY - CONF TI - NIR responsive core/shell nanohybrids for smart drug delivery AU - Wei, Q. AU - Ji, J. AU - Shen, J. C2 - 2008/// C3 - 8th World Biomaterials Congress 2008 DA - 2008/// VL - 1 SP - 297 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84869034553&partnerID=MN8TOARS ER - TY - JOUR TI - Spatial expression of a mercury-inducible green fluorescent protein within a nanoporous latex-based biosensor coating AU - Schottel, Janet L. AU - Orwin, Paul M. AU - Anderson, C. Ron AU - Flickinger, Michael C. T2 - Journal of Industrial Microbiology & Biotechnology AB - Optimizing the reactivity of cell coatings developed as biosensors or biocatalysts requires measurements of gene expression in the immobilized cells. To quantify and localize gene expression within a latex-based mercury biosensor, a plasmid, pmerGFP, was constructed, which contains the green fluorescent protein (GFP) gene under transcriptional control of the mercury resistance operon regulatory sequences. When cells containing this plasmid were exposed to mercuric chloride, GFP synthesis was induced and could be quantified by fluorescence. E. coli strain JM109 (pmerGFP) was mixed with SF091 latex (Rohm & Haas), Tween 20, and glycerol, and coated as an approximate 20-microm thick nanoporous adhesive coating on a polyester substrate. The cell coat was overlaid with a nanoporous topcoat of latex, Tween 20, and glycerol. Different fluorescent microspheres were used to mark the topcoat and cell coat layers of the coating. Upon exposure to mercury(II), cells within the coating were induced to synthesize GFP, and laser scanning confocal microscopy was used to quantify expression spatially within the cell coat. GFP expression in the coatings increased with increasing mercury concentration (2-20 microM), temperature (21-37 degrees C), and time of incubation (0-39 h). There was a gradient of GFP expression through the cell coat with expression higher near the topcoat-cell coat interface relative to the bottom of the cell coat. The topcoat thickness did not significantly affect GFP expression indicating that diffusion of mercury(II) and oxygen through the topcoat was not limiting. DA - 2008/1/8/ PY - 2008/1/8/ DO - 10.1007/S10295-007-0288-3 VL - 35 IS - 4 SP - 283-290 J2 - J Ind Microbiol Biotechnol LA - en OP - SN - 1367-5435 1476-5535 UR - http://dx.doi.org/10.1007/S10295-007-0288-3 DB - Crossref KW - mercury KW - biosensor KW - nanoporous latex KW - laser scanning confocal microscopy KW - GFP ER - TY - JOUR TI - Electrochemical characterization ofGeobacter sulfurreducens cells immobilized on graphite paper electrodes AU - Srikanth, Shweta AU - Marsili, Enrico AU - Flickinger, Michael C. AU - Bond, Daniel R. T2 - Biotechnology and Bioengineering AB - Bacteria able to transfer electrons to conductive surfaces are of interest as catalysts in microbial fuel cells, as well as in bioprocessing, bioremediation, and corrosion. New procedures for immobilization of Geobacter sulfurreducens on graphite electrodes are described that allow routine, repeatable electrochemical analysis of cell-electrode interactions. Immediately after immobilizing G. sulfurreducens on electrodes, electrical current was obtained without addition of exogenous electron shuttles or electroactive polymers. Voltammetry and impedance analysis of pectin-immobilized bacteria transferring electrons to electrode surfaces could also be performed. Cyclic voltammetry of immobilized cells revealed voltage-dependent catalytic current similar to what is commonly observed with adsorbed enzymes, with catalytic waves centered at -0.15 V (vs. SHE). Electrodes maintained at +0.25 V (vs. SHE) initially produced 0.52 A/m(2) in the presence of acetate as the electron donor. Electrical Impedance Spectroscopy of coatings was also consistent with a catalytic mechanism, controlled by charge transfer rate. When electrodes were maintained at an oxidizing potential for 24 h, electron transfer to electrodes increased to 1.75 A/m(2). These observations of electron transfer by pectin-entrapped G. sulfurreducens appear to reflect native mechanisms used for respiration. The ability of washed G. sulfurreducens cells to immediately produce electrical current was consistent with the external surface of this bacterium possessing a pathway linking oxidative metabolism to extracellular electron transfer. This electrochemical activity of pectin-immobilized bacteria illustrates a strategy for preparation of catalytic electrodes and study of Geobacter under defined conditions. DA - 2008/// PY - 2008/// DO - 10.1002/bit.21671 VL - 99 IS - 5 SP - 1065-1073 J2 - Biotechnol. Bioeng. LA - en OP - SN - 0006-3592 1097-0290 UR - http://dx.doi.org/10.1002/bit.21671 DB - Crossref KW - Geobacter KW - microbial fuel cell KW - electrochemistry ER - TY - JOUR TI - novel polymer composite with double positive-temperature-coefficient transitions: effect of filler-matrix interface on the resistivity-temperature behavior AU - Zhang, X. W. AU - Pan, Y. T2 - Polymer International DA - 2008/// PY - 2008/// VL - 57 ER - TY - JOUR TI - Nanostructured Titania−Polymer Photovoltaic Devices Made Using PFPE-Based Nanomolding Techniques AU - Williams, Stuart S. AU - Hampton, Meredith J. AU - Gowrishankar, Vignesh AU - Ding, I-Kang AU - Templeton, Joseph L. AU - Samulski, Edward T. AU - DeSimone, Joseph M. AU - McGehee, Michael D. T2 - Chemistry of Materials AB - We fabricated ordered bulk heterojunction photovoltaic (PV) cells using a perfluoropolyether (PFPE) elastomeric mold to control the donor−acceptor interfacial morphology within devices. Anatase titania nanostructures with postlike features ranging from 30 to 100 nm in height and 30 to 65 nm in spacing were fabricated using the Pattern Replication In Nonwetting Templates (PRINT) process. The nanostructured devices showed a 2-fold improvement in both short-circuit current (Jsc) and power conversion efficiency (PCE) relative to reference bilayer cells. Additionally, the titania was functionalized with Z907 dye to increase both the short-circuit current (Jsc) and open-circuit voltage (Voc). As a result we observed a device efficiency (ηeff) of 0.6%, the highest recorded efficiency value so far for an imprinted titania−P3HT device. DA - 2008/8// PY - 2008/8// DO - 10.1021/cm800729q VL - 20 IS - 16 SP - 5229-5234 J2 - Chem. Mater. LA - en OP - SN - 0897-4756 1520-5002 UR - http://dx.doi.org/10.1021/cm800729q DB - Crossref ER - TY - JOUR TI - Reductively Labile PRINT Particles for the Delivery of Doxorubicin to HeLa Cells AU - Petros, Robby A. AU - Ropp, Patricia A. AU - DeSimone, Joseph M. T2 - Journal of the American Chemical Society AB - A Trojan horse PRINT particle composition was developed that incorporates a reductively labile cross-linker to achieve activated release of doxorubicin in vitro. Particles of discrete size and shape (cube side length = 2 µm) containing 30 wt % of a disulfide-based cross-linker and 2 wt % doxorubicin were synthesized. This PRINT composition was shown to release doxorubicin in response to a reducing environment as measured by flow cytometry and was found to be highly proficient at killing HeLa cells in vitro. DA - 2008/4// PY - 2008/4// DO - 10.1021/ja801436j VL - 130 IS - 15 SP - 5008-5009 J2 - J. Am. Chem. Soc. LA - en OP - SN - 0002-7863 1520-5126 UR - http://dx.doi.org/10.1021/ja801436j DB - Crossref ER - TY - JOUR TI - Molding Block Copolymer Micelles: A Framework for Molding of Discrete Objects on Surfaces AU - Yu-Su, Sherryl Y. AU - Thomas, David R. AU - Alford, Jonathan E. AU - LaRue, Isaac AU - Pitsikalis, Marinos AU - Hadjichristidis, Nikos AU - DeSimone, Joseph M. AU - Dobrynin, Andrey V. AU - Sheiko, Sergei S. T2 - Langmuir AB - Soft lithography based on photocurable perfluoropolyether (PFPE) was used to mold and replicate poly(styrene-b-isoprene) block-copolymer micelles within a broad range of shapes and sizes including spheres, cylinders, and torroids. These physically assembled nanoparticles were first formed in a selective solvent for one block then deposited onto substrates having various surface energies in an effort to minimize the deformation of the micelles due to attractive surface forces. The successful molding of these delicate nanoparticles underscores two advantages of PFPE as a molding material. First, it allows one to minimize particle deformation due to adsorption by using low energy substrates. Second, PFPE is not miscible with the organic micelles and thus prevents their dissociation. For spherical PS-b-PI micelles, a threshold value of the substrate surface energy for the mold to lift-off cleanly, that is, the particles remain adhered to the substrate after mold removal was determined to be around γ ≅ 54 mJ/m2. For substrates with higher surface energies (>54 mJ/m2), the micelles undergo flattening which increase the contact area and thus facilitate molding, although at the expense of particle deformation. The results are consistent with theoretical predictions of a molding range for substrate surface energies, which depends on the size, shape, and mechanical properties of the particles. In a similar fashion, cylindrical PS-b-PI micelles remain on the substrate at surface energies γ ≥ 54 mJ/m2 after a mold removal. However, cylindrical micelles behaved differently at lower surface energies. These micelles ruptured due to their inability to slide on the surfaces during mold lift-off. Thus, the successful molding of extended objects is attainable only when the particle is adsorbed on higher energy substrates where deformation can still be kept at a minimum by using stronger materials such as carbon nanotubes for the master. DA - 2008/11/4/ PY - 2008/11/4/ DO - 10.1021/la802549s VL - 24 IS - 21 SP - 12671-12679 J2 - Langmuir LA - en OP - SN - 0743-7463 1520-5827 UR - http://dx.doi.org/10.1021/la802549s DB - Crossref ER - TY - CHAP TI - Models of Porous Carbons AU - Bock, Henry AU - Gubbins, Keith E. AU - Pikunic, Jorge T2 - Adsorption by Carbons AB - Except for the fullerenes, carbon nanotubes, nanohorns, and schwarzites, porous carbons are usually disordered materials, and cannot at present be completely characterized experimentally. Methods such as X-ray and neutron scatter ing and high-resolution transmission electron microscopy (HRTEM) give partial structural information, but are not yet able to provide a complete description of the atomic structure. Nevertheless, atomistic models of carbons are needed in order to interpret experimental characterization data (adsorption isotherms, heats of adsorption, etc.). They are also a necessary ingredient of any theory or molecular simulation for the prediction of the behavior of adsorbed phases within carbons — including diffusion, adsorption, heat effects, phase transitions, and chemical reactivity. PY - 2008/// DO - 10.1016/b978-008044464-2.50009-2 SP - 103-132 OP - PB - Elsevier SN - 9780080444642 UR - http://dx.doi.org/10.1016/b978-008044464-2.50009-2 DB - Crossref ER - TY - CHAP TI - Molecular Modeling of Adsorption from the Gas Phase AU - Pikunic, Jorge AU - Lastoskie, Christian M. AU - Gubbins, Keith E. T2 - Handbook of Porous Solids AB - The prelims comprise: Introduction Methods Simple Geometric Models More Realistic Models Condusions Symbols and Abbreviations PY - 2008/4/25/ DO - 10.1002/9783527618286.ch7 SP - 182-236 OP - PB - Wiley-VCH Verlag GmbH SN - 9783527618286 9783527302468 UR - http://dx.doi.org/10.1002/9783527618286.ch7 DB - Crossref ER - TY - JOUR TI - Nanocomposites of TiO2and Siloxane Copolymers as Environmentally Safe Flame-Retardant Materials† AU - Mosurkal, Ravi AU - Samuelson, Lynne A. AU - Smith, Kenneth D. AU - Westmoreland, Phillip R. AU - Parmar, Virinder S. AU - Yan, Fadong AU - Kumar, Jayant AU - Watterson, Arthur C. T2 - Journal of Macromolecular Science, Part A AB - Composites of titanium dioxide (TiO2) nanoparticles and biocatalytically synthesized dimethylsiloxane copolyamides were prepared, and their thermal and flame-retardant properties were investigated. The flammability properties such as heat release capacity and total heat release were measured from microscale cumbustion calorimetry (MCC). The thermal degradation temperatures, char yields, and the heat-release capacities of these nanocomposites were significantly improved over the pure polymers. The heat-release capacities of the siloxane copolymer nanocomposites with 20wt% of TiO2 were found to be 167 and 129 J/g K, which is a 35% less than the pure polymers (260 and 194 J/g K, respectively). The SEM/EDAX surface-analysis studies on nanocomposite films and their char revealed that nanocrystalline-TiO2 plays an important role in forming carbonaceous silicate char on the surface as a protective layer. DA - 2008/9/26/ PY - 2008/9/26/ DO - 10.1080/10601320802380208 VL - 45 IS - 11 SP - 942-946 J2 - Journal of Macromolecular Science, Part A LA - en OP - SN - 1060-1325 1520-5738 UR - http://dx.doi.org/10.1080/10601320802380208 DB - Crossref KW - flame retardant KW - polysiloxanes KW - PCFC KW - microcalorimetry KW - TiO2 nanocomposites KW - environmentally-safe KW - heat release capacity ER - TY - CONF TI - Electric field-assisted convective assembly of large-domain colloidal crystals AU - Kleinert, J. AU - Kim, S. AU - Velev, O.D. C2 - 2008/// C3 - AIChE Annual Meeting, Conference Proceedings DA - 2008/// UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-79952294231&partnerID=MN8TOARS ER - TY - CONF TI - Dielectrophoretic assembly of new colloidal structures from janus and patchy metallodielectric particles AU - Velev, O.D. AU - Gangwal, S. AU - Pawar, A.B. AU - Kretzschmar, I. C2 - 2008/// C3 - AIChE Annual Meeting, Conference Proceedings DA - 2008/// UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-79952303416&partnerID=MN8TOARS ER - TY - CONF TI - Control of nanoscale flow in thin wetting films by electric field AU - Kleinert, J. AU - Kim, S. AU - Velev, O.D. C2 - 2008/// C3 - AIChE Annual Meeting, Conference Proceedings DA - 2008/// UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-79952301934&partnerID=MN8TOARS ER - TY - CONF TI - Computer simulation of self-assembly of dipolar colloid particles for the design of stimuli-responsive materials AU - Goyal, A. AU - Hall, C.K. AU - Velev, O.D. C2 - 2008/// C3 - AIChE Annual Meeting, Conference Proceedings DA - 2008/// UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-79952308978&partnerID=MN8TOARS ER - TY - JOUR TI - pH Controlled Synthesis of High Aspect-Ratio Gold Nanorods AU - Wei, Q. S. AU - Ji, J. AU - Shen, J. C. T2 - Journal of Nanoscience and Nanotechnology AB - Here we report the two-step synthesis of high aspect-ratio gold nanorods via combining low pH growth and higher cetyltrimethylammonium bromide concentration. The approach is motivated by the "slow growth principle", which has been demonstrated recently as a effective protocol to prepare high aspect-ratio one-dimensional nanostructures. When the pH value of the growth solution gradually decreased, the growth rate of nanorods was significantly decreased and a continuous morphological changing from uniform monodisperse gold nanospheres to extraordinary long gold nanorods occured. By simultaneously decreasing the growth pH and increasing the concentration of cetyltrimethylammonium bromide, the length of gold nanorods could be further elongated to above 2 microm with large aspect-ratio of above 80. This kind of high aspect-ratio gold nanorods could be excellent building blocks for optical or electrical nanodevices in future. DA - 2008/// PY - 2008/// DO - 10.1166/jnn.2008.302 VL - 8 IS - 11 SP - 5708-5714 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000261390800015&KeyUID=WOS:000261390800015 KW - Gold Nanorods KW - High Aspect-Ratio KW - pH Control Synthesis KW - Seed Mediated KW - Slow Growth ER - TY - JOUR TI - Two-Photon Luminescence Imaging of Bacillus Spores Using Peptide-Functionalized Gold Nanorods AU - He, W. AU - Henne, W. A. AU - Wei, Q. S. AU - Zhao, Y. AU - Doorneweerd, D. D. AU - Cheng, J. X. AU - Low, P. S. AU - Wei, A. T2 - Nano Research AB - Bacillus subtilis spores (a simulant of Bacillus anthracis) have been imaged by two-photon luminescence (TPL) microscopy, using gold nanorods (GNRs) functionalized with a cysteine-terminated homing peptide. Control experiments using a peptide with a scrambled amino acid sequence confirmed that the GNR targeting was highly selective for the spore surfaces. The high sensitivity of TPL combined with the high affinity of the peptide labels enables spores to be detected with high fidelity using GNRs at femtomolar concentrations. It was also determined that GNRs are capable of significant TPL output even when irradiated at near infrared (NIR) wavelengths far from their longitudinal plasmon resonance (LPR), permitting considerable flexibility in the choice of GNR aspect ratio or excitation wavelength for TPL imaging. DA - 2008/// PY - 2008/// DO - 10.1007/s12274-008-8047-y VL - 1 IS - 6 SP - 450-456 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000207467500002&KeyUID=WOS:000207467500002 KW - Bionanotechnology KW - nanorods KW - nonlinear optics KW - pathogen detection KW - peptides ER - TY - JOUR TI - The Escherichia coli O157 : H7 DNA detection on a gold nanoparticle-enhanced piezoelectric biosensor AU - Wang, L. J. AU - Wei, Q. S. AU - Wu, C. S. AU - Hu, Z. Y. AU - Ji, J. AU - Wang, P. T2 - Chinese Science Bulletin AB - This paper presents development of a quartz crystal microbalance (QCM) biosensor for real-time detection of E. coli O157:H7 DNA based on nanogold particles amplification. Many inner Au nanoparticles were immobilized onto the thioled surface of the Au electrode, then more specific thiolated single-stranded DNA (ssDNA) probes could be fixed through Au-SH bonding. The hybridization was induced by exposing the ssDNA probe to the complementary target DNA of E. coli O157:H7 gene eaeA, then resulted in a mass change and corresponding frequency shifts (Δf) of the QCM. The outer avidin-coated Au nanoparticles could combine with the target DNA to increase the mass. The electrochemical techniques, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were adopted to manifest and character each step. The target DNA corresponding to 2.0×103 colony forming unit (CFU)/mL E. coli O157:H7 cells can be detected by this biosensor, so it is practical to develop a sensitive and effective QCM biosensor for pathogenic bacteria detection based on specific DNA analysis. The piezoelectric biosensing system has potential for further applications, such as food safety and environment monitoring, and this approach lays the groundwork for incorporating the method into an integrated system for in-field bacteria detection. DA - 2008/// PY - 2008/// DO - 10.1007/s11434-007-0529-x VL - 53 IS - 8 SP - 1175-1184 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000254999100010&KeyUID=WOS:000254999100010 KW - piezoelectric biosensor KW - gold nanoparticle KW - E. coli O157 : H7 ER - TY - JOUR TI - Synthesis of near-infrared responsive gold nanorod/PNIPAAm core/shell nanohybrids via surface initiated ATRP for smart drug delivery AU - Wei, Q. S. AU - Ji, J. AU - Shen, J. C. T2 - Macromolecular Rapid Communications AB - Abstract Nanosized near infrared (NIR) responsive nanohybrids are synthesized by surface‐initiated atom transfer radical polymerization (SI‐ATRP) of N ‐isopropylacrylamide (NIPAAm) on gold nanorods (Au NRs). Transmission electron microscopy images demonstrate that the nanohybrids have a clear core/shell structure. Temperature‐variable 1 H NMR spectroscopy, quasi‐elastic light scattering (QELS), UV‐vis spectroscopy, and laser irradiation prove that the nanohybrids are both temperature and NIR responsive. Norvancomycin (NVan) loading and release experiments show that the drug release rate can be modulated by NIR irradiation. Such an intelligent drug‐delivery system might find applications in non‐invasive controlled drug release in future. magnified image DA - 2008/// PY - 2008/// DO - 10.1002/marc.200800009 VL - 29 IS - 8 SP - 645-650 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000255716800004&KeyUID=WOS:000255716800004 KW - drug delivery systems KW - gold nanorods KW - nanocomposites KW - near infrared responsive KW - stimuli-sensitive polymers ER - TY - JOUR TI - COLL 66-Gold nanostars with magnetic cores as dynamic optical imaging agents AU - Wei, Q. S. AU - Song, H. M. AU - Ong, Q. K. AU - Ritchie, K. AU - Wei, A. T2 - Abstracts of Papers of the American Chemical Society DA - 2008/// PY - 2008/// VL - 236 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000270256303742&KeyUID=WOS:000270256303742 ER - TY - JOUR TI - A Technique to Transfer Metallic Nanoscale Patterns to Small and Non-Planar Surfaces AU - Smythe, Elizabeth J. AU - Dickey, Michael D. AU - Whitesides, George M. AU - Capasso, Federico T2 - ACS Nano AB - Conventional lithographic methods (e.g., electron-beam lithography, photolithography) are capable of producing high-resolution structures over large areas but are generally limited to large (>1 cm(2)) planar substrates. Incorporation of these features on unconventional substrates (i.e., small (<1 mm(2)) and/or non-planar substrates) would open possibilities for many applications, including remote fiber-based sensing, nanoscale optical lithography, three-dimensional fabrication, and integration of compact optical elements on fiber and semiconductor lasers. Here we introduce a simple method in which a thin thiol-ene film strips arbitrary nanoscale metallic features from one substrate and is then transferred, along with the attached features, to a substrate that would be difficult or impossible to pattern with conventional lithographic techniques. An oxygen plasma removes the sacrificial film, leaving behind the metallic features. The transfer of dense and sparse patterns of isolated and connected gold features ranging from 30 nm to 1 mum, to both an optical fiber facet and a silica microsphere, demonstrates the versatility of the method. A distinguishing feature of this technique is the use of a thin, sacrificial film to strip and transfer metallic nanopatterns and its ability to directly transfer metallic structures produced by conventional lithography. DA - 2008/// PY - 2008/// DO - 10.1021/nn800720r VL - 3 IS - 1 SP - 59-65 KW - pattern transfer KW - soft lithography KW - metal nanoparticles KW - nanofabrication KW - nanopatterning ER - TY - JOUR TI - Light-Powered Electrical Switch Based on Cargo-Lifting Azobenzene Monolayers AU - Ferri, Violetta AU - Elbing, Mark AU - Pace, Giuseppina AU - Dickey, Michael D. AU - Zharnikov, Michael AU - Samorì, Paolo AU - Mayor, Marcel AU - Rampi, Maria Anita T2 - Angewandte Chemie AB - Hebebühne: Dicht gepackte selbstorganisierte Monoschichten (SAMs) aus starren konjugierten Azobenzolderivaten zwischen zwei Elektroden gehen eine reversible Photoisomerisierung ein (siehe Bild). Die Strom-Spannungs-Kurven identifizieren die Anordnung als Stromphotoschalter, in dem die SAM wie eine lichtgetriebene Hebebühne wirkt. DA - 2008/4// PY - 2008/4// DO - 10.1002/ange.200705339 VL - 120 IS - 18 SP - 3455-3457 ER - TY - JOUR TI - Unconventional Nanofabrication AU - Dickey, M.D. AU - Whitesides, G.M. T2 - Pharma Focus Asia DA - 2008/5// PY - 2008/5// VL - 5 N1 - Invited RN - Invited ER - TY - JOUR TI - Review: Structure Control of Electrospun Nanofibers and Their Assemblies AU - Zhang, Xiangwu T2 - International Journal of Electrospun Nanofibers and Applications DA - 2008/// PY - 2008/// VL - 2 SP - 75-102 ER - TY - JOUR TI - Preparation and characterization of silica nanoparticulate-polyacrylonitrile composite and porous nanofibers AU - Ji, Liwen AU - Saquing, Carl AU - Khan, Saad A. AU - Zhang, Xiangwu T2 - Nanotechnology DA - 2008/// PY - 2008/// DO - 085605 10.1088/0957-4484/19/8/085605 VL - 19 IS - 8 ER - TY - CONF TI - Preparation of Porous Carbon Nanofibers and Their Application in Lithium-Ion Batteries C2 - 2008/3// C3 - Third Annual NC State University Graduate Student Research Symposium DA - 2008/3// ER - TY - CONF TI - Porous Carbon Nanofibers: Preparation and Application as Anode Materials in Rechargeable Lithium-ion Batteries C2 - 2008/3// C3 - ACS Polymer Discussion Group Richard D. Gilbert Award Student Symposium DA - 2008/3// ER - TY - CONF TI - Nonwovens Containing Novel Polymer Fillers C2 - 2008/3// C3 - NSF Site Visit Meeting DA - 2008/3// ER - TY - CONF TI - Fabrication of Porous Carbon Nanofibers through Electrospinning C2 - 2008/2// C3 - Emerging Issues Forum DA - 2008/2// ER - TY - CONF TI - Fabrication of Porous Carbon Nano-Fibers from Electrospun PAN/PLA Blends C2 - 2008/4// C3 - 17th Annual Undergraduate Research Symposium DA - 2008/4// ER - TY - CONF TI - Electrospun Composite Nanofibers for Lithium Ion Battery Applications C2 - 2008/3// C3 - NSF Site Visit Meeting DA - 2008/3// ER - TY - JOUR TI - Solvents in organic synthesis: Replacement and multi-step reaction systems AU - Gani, Rafiqul AU - Gomez, Paola Arenas AU - Folic, Milica AU - Jimenez-Gonzalez, Concepcion AU - Constable, David J. C. T2 - COMPUTERS & CHEMICAL ENGINEERING AB - The solvent selection methodology developed earlier by Gani et al. [Gani, R., Jiménez-González, C., & Constable, D. J. C. (2005). Method for selection of solvents for promotion of organic reactions. Computers and Chemical Engineering, 29, 1661–1676] has been extended to handle multi-step reaction systems as well as solvent substitution for specific reaction steps for existing processing systems. The problems were formulated based on the methodology guidelines, and solved using ICAS software tool [ICAS Documentation. (2003). Internal report. CAPEC, Department of Chemical Engineering, Technical University of Denmark]. Highly promising results were obtained, either in accordance with results previously published in the literature, or with industrial process data. This shows that the methodology has potential for application to complex reaction schemes as well as on the problems of solvent replacement. DA - 2008/10/17/ PY - 2008/10/17/ DO - 10.1016/j.compchemeng.2008.01.006 VL - 32 IS - 10 SP - 2420-2444 SN - 1873-4375 KW - pharmaceutical synthesis KW - green chemistry KW - green engineering KW - solvent selection ER - TY - JOUR TI - Fabrication of conjugated polymer nanowires by edge lithography AU - Lipomi, Darren J. AU - Chiechi, Ryan C. AU - Dickey, Michael D. AU - Whitesides, George M. T2 - NANO LETTERS AB - This paper describes the fabrication of conjugated polymer nanowires by a three stage process: (i) spin-coating a composite film comprising alternating layers of a conjugated polymer and a sacrificial material, (ii) embedding the film in an epoxy matrix and sectioning it with an ultramicrotome (nanoskiving), and (iii) etching the sacrificial material to reveal nanowires of the conjugated polymer. A free-standing, 100-layer film of two conjugated polymers was spin-coated from orthogonal solvents: poly(2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylenevinylene) (MEH-PPV) from chloroform and poly(benzimidazobenzophenanthroline ladder) (BBL) from methanesulfonic acid. After sectioning the multilayer film, dissolution of the BBL with methanesulfonic acid yielded uniaxially aligned MEH-PPV nanowires with rectangular cross sections, and etching MEH-PPV with an oxygen plasma yielded BBL nanowires. The conductivity of MEH-PPV nanowires changed rapidly and reversibly by >103 upon exposure to I2 vapor. The result suggests that this technique could be used to fabricate high-surface-area structures of conducting organic nanowires for possible applications in sensing and in other fields where a high surface area in a small volume is desirable. DA - 2008/7// PY - 2008/7// DO - 10.1021/nl8009318 VL - 8 IS - 7 SP - 2100-2105 SN - 1530-6984 ER - TY - JOUR TI - Eutectic gallium-indium (EGaIn): A liquid metal alloy for the formation of stable structures in microchannels at room temperature AU - Dickey, Michael D. AU - Chiechi, Ryan C. AU - Larsen, Ryan J. AU - Weiss, Emily A. AU - Weitz, David A. AU - Whitesides, George M. T2 - ADVANCED FUNCTIONAL MATERIALS AB - Abstract This paper describes the rheological behavior of the liquid metal eutectic gallium‐indium (EGaIn) as it is injected into microfluidic channels to form stable microstructures of liquid metal. EGaIn is well‐ ;suited for this application because of its rheological properties at room temperature: it behaves like an elastic material until it experiences a critical surface stress, at which point it yields and flows readily. These properties allow EGaIn to fill microchannels rapidly when sufficient pressure is applied to the inlet of the channels, yet maintain structural stability within the channels once ambient pressure is restored. Experiments conducted in microfluidic channels, and in a parallel‐plate rheometer, suggest that EGaIn's behavior is dictated by the properties of its surface (predominantly gallium oxide, as determined by Auger measurement s); these two experiments both yield approximately the same number for the critical surface stress required to induce EGaIn to flow (∼0 .5 N/m). This analysis–which shows that the pressure that must be exceeded for EGaIn to flow through a microchannel is inversely proportional to the critical (i.e., smallest) dimension of the channel–is useful to guide future fabrication of microfluidic channels to mold EGaIn into functional microstructures. DA - 2008/4/11/ PY - 2008/4/11/ DO - 10.1002/adfm.200701216 VL - 18 IS - 7 SP - 1097-1104 SN - 1616-301X ER - TY - JOUR TI - Electrically Addressable Parallel Nanowires with 30 nm Spacing from Micromolding and Nanoskiving AU - Dickey, Michael D. AU - Lipomi, Darren J. AU - Bracher, Paul J. AU - Whitesides, George M. T2 - NANO LETTERS AB - This paper describes the fabrication of arrays of parallel, electrically addressable metallic nanowires by depositing alternating layers of thin films of metal and polymer—both planar and topographically patterned—and sectioning the laminated structures with an ultramicrotome (nanoskiving). The structures that resulted from this process had two distinct regions: one in which parallel Au nanowires were separated by a minimum distance of 30 nm, and one in which the nanowires diverged such that the distal ends were individually addressable by low-resolution (≥10 μm) photolithography. Conductive polyaniline (PANI) was electrochemically deposited across the nanowire electrodes to demonstrate their electrical addressability, continuity, and physical separation. Before deposition, the wires were electrically isolated; with the PANI, they were electrically connected. After dry etching to remove the polymer, the gap between the nanowire electrodes returned to an insulating state. This procedure provides a method for making wires with dimensions and separations of <50 nm without the use of e-beam or focused-ion-beam “writing” and opens applications in organic and molecular electronics, chemical and biological sensing, and other fields where nanoscale distances between parallel conductive electrodes are desirable. DA - 2008/12// PY - 2008/12// DO - 10.1021/nl8028174 VL - 8 IS - 12 SP - 4568-4573 SN - 1530-6992 ER - TY - JOUR TI - Thermal degradation of deoxybenzoin polymers studied by pyrolysis-gas chromatography/mass spectrometry AU - Ranganathan, T. AU - Beaulieu, Michael AU - Zilberman, Joseph AU - Smith, Kenneth D. AU - Westmoreland, Phillip R. AU - Farris, Richard J. AU - Coughlin, E. Bryan AU - Emrick, Todd T2 - POLYMER DEGRADATION AND STABILITY AB - The thermal degradation behavior of novel ultra-fire-resistant polymers and copolymers containing deoxybenzoin units in the backbone was studied by pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). The polymers were synthesized by the polycondensation of 4,4′-bishydroxydeoxybenzoin (BHDB) with isophthaloyl chloride (to give polyarylates), phenylphosphonic dichloride (to give polyphosphonates), and their mixtures (to give poly(arylate-co-phosphonate) copolymers). The thermal decomposition, under nitrogen conditions, of BHDB-polyarylate was characterized by a simultaneous degradation of both the bisphenolic (deoxybenzoin) and isophthalate sub-units, whereas a three-step decomposition phenomenon was observed for the BHDB-polyphosphonate. BHDB-polymers containing phosphonate groups in the backbone did not show any phosphorus-based volatile decomposition products, whereas the corresponding bisphenol A-based polyphosphonates released volatile decomposition products comprised mainly of phosphorus-containing compounds. DA - 2008/6// PY - 2008/6// DO - 10.1016/j.polymdegradstab.2008.03.021 VL - 93 IS - 6 SP - 1059-1066 SN - 1873-2321 KW - flame-retardant polymers KW - thermal degradation KW - pyrolysis-gas chromatography/mass KW - spectrometry studies KW - deoxybenzoin ER - TY - JOUR TI - Nanoskiving: A New Method To Produce Arrays of Nanostructures AU - Xu, Qiaobing AU - Rioux, Robert M. AU - Dickey, Michael D. AU - Whitesides, George M. T2 - ACCOUNTS OF CHEMICAL RESEARCH AB - This Account reviews nanoskiving−a new technique that combines thin-film deposition of metal on a topographically contoured substrate with sectioning using an ultramicrotome−as a method of fabricating nanostructures that could replace conventional top-down techniques in selected applications. Photolithography and scanning beam lithography, conventional top-down techniques to generate nanoscale structures and nanostructured materials, are useful, versatile, and highly developed, but they also have limitations: high capital and operating costs, limited availability of the facilities required to use them, an inability to fabricate structures on nonplanar surfaces, and restrictions on certain classes of materials. Nanoscience and nanotechnology would benefit from new, low-cost techniques to fabricate electrically and optically functional structures with dimensions of tens of nanometers, even if (or perhaps especially if) these techniques have a different range of application than does photolithography or scanning beam lithography. Nanoskiving provides a simple and convenient procedure to produce arrays of structures with cross-sectional dimensions in the 30-nm regime. The dimensions of the structures are determined by (i) the thickness of the deposited thin film (tens of nanometers), (ii) the topography (submicrometer, using soft lithography) of the surface onto which the thin film is deposited, and (iii) the thickness of the section cut by the microtome (≥30 nm by ultramicrotomy). The ability to control the dimensions of nanostructures, combined with the ability to manipulate and position them, enables the fabrication of nanostructures with geometries that are difficult to prepare by other methods. The nanostructures produced by nanoskiving are embedded in a thin epoxy matrix. These epoxy slabs, although fragile, have sufficient mechanical strength to be manipulated and positioned; this mechanical integrity allows the nanostructures to be stacked in layers, draped over curved surfaces, and suspended across gaps, while retaining the in-plane geometry of the nanostructures embedded in the epoxy. After removal of the polymer matrix by plasma oxidation, these structures generate suspended and draped nanostructures and nanostructures on curved surfaces. Two classes of applications, in optics and in electronics, demonstrate the utility of nanostructures fabricated by nanoskiving. This technique will be of primary interest to researchers who wish to generate simple nanostructures, singly or in arrays, more simply and quickly than can be accomplished in the clean-room. It is easily accessible to those not trained in top-down procedures for fabrication and those with limited or no access to the equipment and facilities needed for photolithography or scanning-beam fabrication. This Account discusses a new fabrication method (nanoskiving) that produces arrays of metal nanostructures. The defining process in nanoskiving is cutting slabs from a polymeric matrix containing embedded, more extended metal structures. DA - 2008/12// PY - 2008/12// DO - 10.1021/ar700194y VL - 41 IS - 12 SP - 1566-1577 SN - 1520-4898 ER - TY - JOUR TI - Nanocomposites of TiO2 and siloxane copolymers as environmentally safe flame-retardant materials AU - Mosurkal, R. AU - Samuelson, L. A. AU - Smith, K. D. AU - Westmoreland, P. R. AU - Parmar, V. S. AU - Yan, F. AU - Kumar, J. AU - Watterson, A. C. T2 - Journal of Macromolecular Science, Part A: Pure and Applied Chemistry DA - 2008/// PY - 2008/// VL - 45 IS - 11 SP - 943-947 ER - TY - JOUR TI - Light-powered electrical switch based on cargo-lifting azobenzene monolayers AU - Ferri, Violetta AU - Elbing, Mark AU - Pace, Giuseppina AU - Dickey, Michael D. AU - Zharnikov, Michael AU - Samori, Paolo AU - Mayor, Marcel AU - Rampi, Maria Anita T2 - ANGEWANDTE CHEMIE-INTERNATIONAL EDITION AB - We have liftoff! Tightly packed self-assembled monolayers (SAMs) of ultrarigid conjugated azobenzenes incorporated into a Hg-based junction undergo reversible photoisomerization (see picture). The current–voltage curves indicate that the junction operates as a current photoswitch as result of the forces expressed by the SAMs, which act as a light-powered cargo lifter. Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2002/2008/z705339_s.pdf or from the author. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article. DA - 2008/// PY - 2008/// DO - 10.1002/anie.200705339 VL - 47 IS - 18 SP - 3407-3409 SN - 1521-3773 KW - azo compounds KW - isomerization KW - molecular devices KW - molecular electronics KW - monolayers ER - TY - JOUR TI - Isomer-Specific Influences on the Composition of Reaction Intermediates in Dimethyl Ether/Propene and Ethanol/Propene Flame† AU - Wang, Juan AU - Struckmeier, Ulf AU - Yang, Bin AU - Cool, Terrill A. AU - Osswald, Patrick AU - Kohse-Höinghaus, Katharina AU - Kasper, Tina AU - Hansen, Nils AU - Westmoreland, Phillip R. T2 - The Journal of Physical Chemistry A AB - This work provides experimental evidence on how the molecular compositions of fuel-rich low-pressure premixed flames are influenced as the oxygenates dimethyl ether (DME) or ethanol are incrementally blended into the propene fuel. Ten different flames with a carbon-to-oxygen ratio of 0.5, ranging from 100% propene (ϕ = 1.5) to 100% oxygenated fuel (ϕ = 2.0), are analyzed with flame-sampling molecular-beam mass spectrometry employing electron- or photoionization. Absolute mole fraction profiles for flame species with masses ranging from m/z = 2 (H2) to m/z = 80 (C6H8) are analyzed with particular emphasis on the formation of harmful emissions. Fuel-specific destruction pathways, likely to be initiated by hydrogen abstraction, appear to lead to benzene from propene combustion and to formaldehyde and acetaldehyde through DME and ethanol combustion, respectively. While the concentration of acetaldehyde increases 10-fold as propene is substituted by ethanol, it decreases as propene is replaced with DME. In contrast, the formaldehyde concentration rises only slightly with ethanol replacement but increases markedly with addition of DME. Allyl and propargyl radicals, the dominant precursors for benzene formation, are likely to be produced directly from propene decomposition or via allene and propyne. Benzene formation through propargyl radicals formed via unsaturated C2 intermediates in the decomposition of DME and ethanol is negligibly small. As a consequence, DME and ethanol addition lead to similar reductions of the benzene concentration. DA - 2008/10/2/ PY - 2008/10/2/ DO - 10.1021/jp8011188 VL - 112 IS - 39 SP - 9255-9265 J2 - J. Phys. Chem. A LA - en OP - SN - 1089-5639 1520-5215 UR - http://dx.doi.org/10.1021/jp8011188 DB - Crossref ER - TY - JOUR TI - High-aspect ratio polymeric pillar arrays formed via electrohydrodynamic patterning AU - Dickey, Michael D. AU - Raines, Allen AU - Collister, Elizabeth AU - Bonnecaze, Roger T. AU - Sreenivasan, S. V. AU - Willson, C. Grant T2 - JOURNAL OF MATERIALS SCIENCE DA - 2008/1// PY - 2008/1// DO - 10.1007/s10853-007-2086-8 VL - 43 IS - 1 SP - 117-122 SN - 0022-2461 ER - TY - JOUR TI - Fabrication of arrays of metal and metal oxide nanotubes by shadow evaporation AU - Dickey, Michael D. AU - Weiss, Emily A. AU - Smythe, Elizabeth J. AU - Chiechi, Ryan C. AU - Capasso, Federico AU - Whitesides, George M. T2 - ACS NANO AB - This paper describes a simple technique for fabricating uniform arrays of metal and metal oxide nanotubes with controlled heights and diameters. The technique involves depositing material onto an anodized aluminum oxide (AAO) membrane template using a collimated electron beam evaporation source. The evaporating material enters the porous openings of the AAO membrane and deposits onto the walls of the pores. The membrane is tilted with respect to the column of evaporating material, so the shadows cast by the openings of the pores onto the inside walls of the pores define the geometry of the tubes. Rotation of the membrane during evaporation ensures uniform deposition inside the pores. After evaporation, dissolution of the AAO in base easily removes the template to yield an array of nanotubes connected by a thin backing of the same metal or metal oxide. The diameter of the pores dictates the diameter of the tubes, and the incident angle of evaporation determines the height of the tubes. Tubes up to approximately 1.5 mum in height and 20-200 nm in diameter were fabricated. This method is adaptable to any material that can be vapor-deposited, including indium-tin oxide (ITO), a conductive, transparent material that is useful for many opto-electronic applications. An array of gold nanotubes produced by this technique served as a substrate for surface-enhanced Raman spectroscopy: the Raman signal (per molecule) from a monolayer of benzenethiolate was a factor of approximately 5 x 10(5) greater than that obtained using bulk liquid benzenethiol. DA - 2008/4// PY - 2008/4// DO - 10.1021/nn800036r VL - 2 IS - 4 SP - 800-808 SN - 1936-086X KW - shadow evaporation KW - nanotube arrays KW - SERS (surface-enhanced Raman spectroscopy) KW - templated fabrication KW - ITO (indium-tin oxide) KW - AAO (anodized aluminum oxide) KW - nanofabrication KW - line-of-sight deposition ER - TY - JOUR TI - Eutectic gallium-indium (EGaIn): A moldable liquid metal for electrical characterization of self-assembled monolayers AU - Chiechi, Ryan C. AU - Weiss, Emily A. AU - Dickey, Michael D. AU - Whitesides, George M. T2 - ANGEWANDTE CHEMIE-INTERNATIONAL EDITION AB - A great GaIn: Micrometer-sized conformal electrodes formed from the title compound are shown to be ideal for measuring the electrical properties of self-assembled monolayers. The image shows the bifurcation of the EGaIn between a metal needle and an Ag surface (not shown) at the point indicated by the two white arrows. The portion above the arrows will form the EGaIn electrode. Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2002/2008/z703642_s.pdf or from the author. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article. DA - 2008/// PY - 2008/// DO - 10.1002/anie.200703642 VL - 47 IS - 1 SP - 142-144 SN - 1521-3773 KW - electrodes KW - gallium KW - indium KW - monolayers KW - tunnel junctions ER - TY - JOUR TI - Design and lipase catalyzed synthesis of 4-methylcoumarin-siloxane hybrid copolymers AU - Pandey, M. K. AU - Chandekar, A. AU - Tyagi, R. AU - Parmar, V. S. AU - Tucci, V. B. AU - Smith, K. D. AU - Westmoreland, P. R. AU - Mosurkal, R. AU - Kumar, J. AU - Watterson, A. C. T2 - Journal of Macromolecular Science, Part A: Pure and Applied Chemistry DA - 2008/// PY - 2008/// VL - 45 IS - 11 SP - 926-931 ER - TY - JOUR TI - Chemical engineering in the next 25 years AU - Westmoreland, P. R. T2 - Chemical Engineering Progress DA - 2008/// PY - 2008/// VL - 104 IS - 11 SP - 30-41 ER - TY - JOUR TI - A combined ab initio and photoionization mass spectrometric study of polyynes in fuel-rich flames AU - Hansen, N. AU - Klippenstein, S. J. AU - Westmoreland, P. R. AU - Kasper, T. AU - Kohse-Höinghaus, K. AU - Wang, J. AU - Cool, T. A. T2 - Phys. Chem. Chem. Phys. AB - Polyynic structures in fuel-rich low-pressure flames are observed using VUV photoionization molecular-beam mass spectrometry. High-level ab initio calculations of ionization energies for C2nH2 (n = 1–5) and partially hydrogenated CnH4 (n = 7–8) polyynes are compared with photoionization efficiency measurements in flames fuelled by allene, propyne, and cyclopentene. C2nH2 (n = 1–5) intermediates are unambiguously identified, while HCC–CC–CHCCH2, HCC–CC–CC–CHCH2 (vinyltriacetylene) and HCC–CC–CHCH–CCH are likely to contribute to the C7H4 and C8H4 signals. Mole fraction profiles as a function of distance from the burner are presented. C7H4 and C8H4 isomers are likely to be formed by reactions of C2H and C4H radicals but other plausible formation pathways are also discussed. Heats of formation and ionization energies of several combustion intermediates have been determined for the first time. DA - 2008/// PY - 2008/// DO - 10.1039/b711578d VL - 10 IS - 3 SP - 366-374 J2 - Phys. Chem. Chem. Phys. LA - en OP - SN - 1463-9076 1463-9084 UR - http://dx.doi.org/10.1039/b711578d DB - Crossref ER - TY - JOUR TI - "Imaging" combustion chemistry via multiplexed synchrotron-photoionization mass spectrometry AU - Taatjes, Craig A. AU - Hansen, Nils AU - Osborn, David L. AU - Kohse-Hoeinghaus, Katharina AU - Cool, Terrill A. AU - Westmoreland, Phillip R. T2 - PHYSICAL CHEMISTRY CHEMICAL PHYSICS AB - The combination of multiplexed mass spectrometry with photoionization by tunable-synchrotron radiation has proved to be a powerful tool to investigate elementary reaction kinetics and the chemistry of low-pressure flames. In both of these applications, multiple-mass detection and the ease of tunability of synchrotron radiation make it possible to acquire full sets of data as a function of mass, photon energy, and of the physical dimension of the system, e.g. distance from the burner or time after reaction initiation. The data are in essence an indirect image of the chemistry. The data can be quantitatively correlated and integrated along any of several dimensions to compare to traditional measurements such as time or distance profiles of individual chemical species, but it can also be directly interpreted in image form. This perspective offers an overview of flame chemistry and chemical kinetics measurements that combine tunable photoionization with multiple-mass detection, emphasizing the overall insight that can be gained from multidimensional data on these systems. The low-pressure flame apparatus is capable of providing isomer-resolved mass spectra of stable and radical species as a function of position in the flame. The overall chemical structure of the flames can be readily seen from images of the evolving mass spectrum as distance from the burner increases, with isomer-specific information given in images of the photoionization efficiency. Several flames are compared in this manner, with a focus on identification of global differences in fuel-decomposition and soot-formation pathways. Differences in the chemistry of flames of isomeric fuels can be discerned. The application of multiplexed synchrotron photoionization to elementary reaction kinetics permits identification of time-resolved isomeric composition in reacting systems. The power of this technique is illustrated by the separation of direct and dissociative ionization signals in the reaction of C2H5 with O2; by the resolution of isomeric products in reactions of the ethynyl (C2H) radical; and by preliminary observation of branching to methyl + propargyl products in the self-reaction of vinyl radicals. Finally, prospects for future research using multiplexed photoionization mass spectrometry are explored. DA - 2008/// PY - 2008/// DO - 10.1039/b713460f VL - 10 IS - 1 SP - 20-34 SN - 1463-9084 ER - TY - JOUR TI - TAZ controls Smad nucleocytoplasmic shuttling and regulates human embryonic stem-cell self-renewal AU - Varelas, Xaralabos AU - Sakuma, Rui AU - Samavarchi-Tehrani, Payman AU - Peerani, Raheem AU - Rao, Balaji M. AU - Dembowy, Joanna AU - Yaffe, Michael B. AU - Zandstra, Peter W. AU - Wrana, Jeffrey L. T2 - NATURE CELL BIOLOGY DA - 2008/7// PY - 2008/7// DO - 10.1038/ncb1748 VL - 10 IS - 7 SP - 837-848 SN - 1476-4679 ER - TY - JOUR TI - Phase behavior and conductivity of Et4NTFSI-LiTFSI mixtures - a model system for ionic liquid lithium battery electrolytes AU - Henderson, W. A. AU - Passerini, S. AU - De Long, H. C. AU - Trulove, P. C. T2 - ECS Transactions DA - 2008/// PY - 2008/// VL - 11 IS - 29 SP - 115-118 ER - TY - JOUR TI - Model-guided design of ligand-regulated RNAi for programmable control of gene expression AU - Beisel CL, Bayer TS AU - Hoff KG, AU - CD, Smolke T2 - Molecular Systems Biology DA - 2008/// PY - 2008/// VL - 4 SP - 224 ER - TY - JOUR TI - Advisers who rock: An approach to academic counseling AU - Bullard, L. G. T2 - Chemical Engineering Education DA - 2008/// PY - 2008/// VL - 42 IS - 4 SP - 218-220 ER - TY - JOUR TI - Colloidal stability and aggregation of lignocellulosic materials in aqueous suspension: A review AU - Hubbe, M. A. AU - Rojas, O. J. T2 - BioResources DA - 2008/// PY - 2008/// VL - 3 IS - 4 SP - 1419-1491 ER - TY - JOUR TI - Combinatorial Signal Transduction Responses Mediated by Interleukin-2 and-4 Receptors in a Helper T-H2 Cell Line AU - Comfort, Kristen K. AU - Haugh, Jason M. T2 - CELLULAR AND MOLECULAR BIOENGINEERING AB - The cytokines interleukin (IL)-2 and IL-4 are important regulators of the adaptive immune response, due in part to their effects on clonal expansion and differentiation of T cells. When IL-2 and IL-4 are administered together, both antagonistic and synergistic effects have been reported, but little is known in general concerning the mechanisms underlying such combinatorial effects. We found evidence for both effects in the proliferation responses of the IL-2 and IL-4 responsive T cell line, HT-2; IL-4 delays the onset of cell growth yet ultimately allows a higher cell density to be achieved in static culture. At the level of signal transduction pathways, we found that IL-4 partially inhibits IL-2 receptor-mediated pathways (PI3K/Akt, Ras/Erk, and STAT5a/b) and does not prolong their transient kinetics. This mode of antagonism, but not the effects on cell proliferation, is overcome at higher concentrations of IL-2 that are sufficient to saturate the signaling responses. By comparison, IL-4-stimulated activation of STAT6 is unaffected by IL-2 and shows sustained kinetics, and we speculate that this or another IL-4 receptor-specific pathway is responsible for the effects of IL-4 on IL-2-stimulated proliferation. A possibly related observation is that IL-4 induces a dramatic cell adhesion phenotype. DA - 2008/9// PY - 2008/9// DO - 10.1007/s12195-008-0015-9 VL - 1 IS - 2-3 SP - 163-172 SN - 1865-5033 KW - Cytokine receptor KW - Lymphocyte KW - Clonal expansion KW - Kinetic analysis KW - STAT KW - Phosphatidylinositol 3-kinase ER - TY - JOUR TI - Analysis of cellulose microfibril angle using a linear mixed model in Pinus taeda clones AU - Isik, Fikret AU - Gumpertz, Marcia AU - Li, Bailian AU - Goldfarb, Barry AU - Sun, Xuan T2 - CANADIAN JOURNAL OF FOREST RESEARCH AB - Variation in microfibril angle (MFA) (degrees) among loblolly pine ( Pinus taeda L.) full-sib families and clones was investigated using 43 clones from nine full-sib crosses tested at two locations. When the experiments were 12 years old, a total of 316 trees were drilled and 12 mm thick wood increment cores were collected. MFA for each growth ring in the wood core was measured using the SilviScan-2 tool. A quadratic mixed model was fitted to evaluate the MFA variation over different rings. Among the error covariance structures tested in the model, autoregressive order 1 was the best model for producing MFA estimates with the smallest errors. Estimated MFA was about 33° in the pith (ring 1) of the trees and decreased to 18° in the outer wood (ring 11). Full-sib crosses and clones within crosses explained about 12.5% of the total phenotypic variation. Repeatability of full-sib family means (H 2 f = 0.46) was moderate but repeatability of clone means was high (H 2 c = 0.79). Although it is possible to improve (decrease) MFA with recurrent selection in tree improvement programs to improve lumber quality, cost efficient and rapid methods for measuring MFA are needed. DA - 2008/6// PY - 2008/6// DO - 10.1139/X08-010 VL - 38 IS - 6 SP - 1676-1689 SN - 1208-6037 ER - TY - JOUR TI - Reframing Professional Development: A Systems Approach to Preparing Engineering Educators to Educate Tomorrow's Engineers AU - Adams, Robin S. AU - Felder, Richard M. T2 - JOURNAL OF ENGINEERING EDUCATION AB - Journal of Engineering EducationVolume 97, Issue 3 p. 239-240 Reframing Professional Development: A Systems Approach to Preparing Engineering Educators to Educate Tomorrow's Engineers Robin S. Adams, Robin S. Adams Assistant Professor School of Engineering Education Purdue UniversitySearch for more papers by this authorRichard M. Felder, Richard M. Felder Hoechst Celanese Professor Emeritus Department of Chemical and Biomolecular Engineering North Carolina State UniversitySearch for more papers by this author Robin S. Adams, Robin S. Adams Assistant Professor School of Engineering Education Purdue UniversitySearch for more papers by this authorRichard M. Felder, Richard M. Felder Hoechst Celanese Professor Emeritus Department of Chemical and Biomolecular Engineering North Carolina State UniversitySearch for more papers by this author First published: 02 January 2013 https://doi.org/10.1002/j.2168-9830.2008.tb00975.xCitations: 22AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article.Citing Literature Volume97, Issue3July 2008Pages 239-240 RelatedInformation DA - 2008/7// PY - 2008/7// DO - 10.1002/j.2168-9830.2008.tb00975.x VL - 97 IS - 3 SP - 239-240 SN - 1069-4730 ER - TY - JOUR TI - Feedstock pretreatment strategies for producing ethanol from wood, bark, and forest residues AU - Hu, G. AU - Heitmann, J. A. AU - Rojas, O. J. T2 - BioResources DA - 2008/// PY - 2008/// VL - 3 IS - 1 SP - 270-294 ER - TY - JOUR TI - Influence of pulse plating parameters on the synthesis and preferred orientation of nanocrystalline zinc from zinc sulfate electrolytes AU - Youssef, K. M. AU - Koch, C. C. AU - Fedkiw, P. S. T2 - ELECTROCHIMICA ACTA AB - The influence of pulse electrodeposition parameters (current on-time Ton, current off-time Toff, and pulse current density Jp) was investigated on the surface morphology and grain size of zinc electrodeposited from a sulfate bath containing polyacrylamide and thiourea additives. The grain size and surface morphology of zinc deposits were studied by field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM), and the preferred orientation of the deposits was studied by X-ray diffraction. At constant current off-time and pulse current density, the grain size decreased asymptotically with increasing current on-time. In contrast, increase in the current off-time at constant current on-time and pulse current density resulted in grain growth. A progressive decrease of the grain size was observed with increasing pulse current density at constant current on-time and off-time. Nanocrystalline zinc with an average grain size of 38 nm was obtained at a pulse current density of 1200 mA/cm2. The crystallographic orientations developed were correlated with the change in the cathodic overpotential, the angle between the preferred oriented plane and the lowest energy of formation plane (0 0 0 2), and the pulse electrodeposition parameters. DA - 2008/12/30/ PY - 2008/12/30/ DO - 10.1016/j.electacta.2008.07.048 VL - 54 IS - 2 SP - 677-683 SN - 1873-3859 KW - Pulse electrodeposition KW - Nanocrystalline KW - zinc KW - Preferred orientation ER - TY - JOUR TI - The Pursuit of a Scalable Nanofabrication Platform for Use in Material and Life Science Applications AU - Gratton, Stephanie E. A. AU - Williams, Stuart S. AU - Napier, Mary E. AU - Pohlhaus, Patrick D. AU - Zhou, Zhilian AU - Wiles, Kenton B. AU - Maynor, Benjamin W. AU - Shen, Clifton AU - Olafsen, Tove AU - Samulski, Edward T. AU - Desimone, Joseph M. T2 - ACCOUNTS OF CHEMICAL RESEARCH AB - In this Account, we describe the use of perfluoropolyether (PFPE)-based materials that are able to accurately mold and replicate micro- and nanosized features using traditional techniques such as embossing as well as new techniques that we developed to exploit the exceptional surface characteristics of fluorinated substrates. Because of the unique partial wetting and nonwetting characteristics of PFPEs, we were able to go beyond the usual molding and imprint lithography approaches and have created a technique called PRINT (Particle [or Pattern] Replication In Nonwetting Templates). PRINT is a distinctive "top-down" fabrication technique capable of generating isolated particles, arrays of particles, and arrays of patterned features for a plethora of applications in both nanomedicine and materials science. A particular strength of the PRINT technology is the high-resolution molding of well-defined particles with precise control over size, shape, deformability, and surface chemistry. The level of replication obtained showcases some of the unique characteristics of PFPE molding materials. In particular, these materials arise from very low surface energy precursors with positive spreading coefficients, can be photocured at ambient temperature, and are minimally adhesive, nonswelling, and conformable. These distinctive features enable the molding of materials with unique attributes and nanometer resolution that have unprecedented scientific and technological value. For example, in nanomedicine, the use of PFPE materials with the PRINT technique allows us to design particles in which we can tailor key therapeutic parameters such as bioavailability, biodistribution, target-specific cell penetration, and controlled cargo release. Similarly, in materials science, we can fabricate optical films and lens arrays, replicate complex, naturally occurring objects such as adenovirus particles, and create 2D patterned arrays of inorganic oxides. DA - 2008/12// PY - 2008/12// DO - 10.1021/ar8000348 VL - 41 IS - 12 SP - 1685-1695 SN - 1520-4898 ER - TY - JOUR TI - Synthesis of Light-Diffracting Assemblies from Microspheres and Nanoparticles in Droplets on a Superhydrophobic Surface AU - Rastogi, Vinayak AU - Melle, Sonia AU - Calderon, Oscar G. AU - Garcia, Antonio A. AU - Marquez, Manuel AU - Velev, Orlin D. T2 - ADVANCED MATERIALS AB - Aqueous suspension droplets of monodisperse latex or latex and gold nanoparticles mixtures assume spherical shape on superhydrophobic substrates. The drying sessile droplets serve as macroscopic templates for assembling microspheres into closed-packed structures. Upon illumination, the supraparticles display discrete colored rings because of the periodic arrangement of latex particles in the surface layer. The physical origin of the colored patterns is explained in detail. DA - 2008/11/18/ PY - 2008/11/18/ DO - 10.1002/adma.200703008 VL - 20 IS - 22 SP - 4263-4268 SN - 1521-4095 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-56349142461&partnerID=MN8TOARS ER - TY - JOUR TI - Nanoencapsulation and Stabilization of Single-Molecule/Particle Electronic Nanoassemblies Using Low-Temperature Atomic Layer Deposition AU - Na, Jeong-Seok AU - Ayres, Jennifer A. AU - Chandra, Kusum L. AU - Gorman, Christopher B. AU - Parsons, Gregory N. T2 - JOURNAL OF PHYSICAL CHEMISTRY C AB - This work addresses a significant challenge in engineered molecular systems regarding both understanding and controlling the stability of molecule/nanoparticle nanostructures under ambient exposure. Results deal specifically with molecular electronic junctions, where electronic contacts and transport are known to be sensitive to sample history and ambient exposure. We demonstrate that low-temperature atomic layer deposition can gently encapsulate and stabilize molecular electronic junctions, making it feasible to handle and transport junctions in air for many days with minimal change in electronic conduction. These findings indicate the potential for long-term stability of advanced synthetic nanoparticle/molecule nanoconstructs. For this study, conductivity through nanoparticle/molecule/nanoparticle junctions is analyzed and found to be consistent with nonresonant charge tunneling through a single or a small number of oligomeric phenylene ethynylene molecules in the electrical junction. The conductivity was stable in vacuum and inert gas, but under ambient exposure, the current initially decreased, then increased rapidly, followed by a slower rise, reaching a value exceeding 10 times larger than initially measured. After encapsulating functional devices using atomic layer deposition of aluminum oxide thin films at 30−50 °C, the junction showed conductance similar to the precoated values, and the current remained unchanged after more than 15 days under ambient exposure. The presence of the molecule junction after encapsulation was confirmed by the observed transition to Fowler−Nordheim tunneling and analysis of junction breakdown at high fields. The high conformality, precise thickness control, and low-temperature compatibility of the atomic layer deposition method make it uniquely qualified to stabilize and protect molecular junctions and systems. DA - 2008/12/25/ PY - 2008/12/25/ DO - 10.1021/jp8066298 VL - 112 IS - 51 SP - 20510-20517 SN - 1932-7447 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000261835000061&KeyUID=WOS:000261835000061 ER - TY - JOUR TI - Hydrogenesis in hyperthermophilic microorganisms: Implications for biofuels AU - Chou, Chung-Jung AU - Jenney, Francis E., Jr. AU - Adams, Michael W. W. AU - Kelly, Robert M. T2 - METABOLIC ENGINEERING AB - Hydrothermal microbiotopes are characterized by the consumption and production of molecular hydrogen. Heterotrophic hyperthermophilic microorganisms (growth T(opt)> or =80 degrees C) actively participate in the production of H(2) in these environments through the fermentation of peptides and carbohydrates. Hyperthermophiles have been shown to approach the theoretical (Thauer) limit of 4 mol of H(2) produced per mole of glucose equivalent consumed, albeit at lower volumetric productivities than observed for mesophilic bacteria, especially enterics and clostridia. Potential advantages for biohydrogen production at elevated temperatures include fewer metabolic byproducts formed, absence of catabolic repression for growth on heterogeneous biomass substrates, and reduced loss of H(2) through conversion to H(2)S and CH(4) by mesophilic consortia containing sulfate reducers and methanogens. To fully exploit the use of these novel microorganisms and their constituent hydrogenases for biohydrogen production, development of versatile genetic systems and improvements in current understanding of electron flux from fermentable substrates to H(2) in hyperthermophiles are needed. DA - 2008/11// PY - 2008/11// DO - 10.1016/j.ymben.2008.06.007 VL - 10 IS - 6 SP - 394-404 SN - 1096-7184 KW - Biohydrogen KW - Pyrococcus furiosus KW - Thermotoga maritima KW - Caldicellulosiruptor saccharolyticus KW - Hyperthermophiles KW - Hydrogenases ER - TY - JOUR TI - In situ Growth of Pd Nanoparticles in Crosslinked Polymer Matrices AU - Aberg, Christopher M. AU - Seyam, Mohamed A. AU - Lassell, Scott A. AU - Bronstein, Lyudmila M. AU - Spontak, Richard J. T2 - MACROMOLECULAR RAPID COMMUNICATIONS AB - Abstract Polymer nanocomposites continue to receive considerable attention as multifunctional hybrid materials, with most nanocomposites fabricated by physical dispersion of surface‐functionalized nanoscale objects. In this study, we explore the viability of growing Pd‐containing nanoparticles from Na 2 PdCl 4 in two different polymers: hypercrosslinked polystyrene (HPS) and an aromatic polyimide (PIm). In HPS, single Pd‐containing nanoparticles possessing a relatively narrow size distribution (ca. 1–4 nm) form upon reduction of the divalent PdCl ions. Single nanoparticles with a broad size distribution ranging from ≈2 to 16 nm develop in PIm, which simultaneously undergoes chemical crosslinking during ion reduction. Such hybrid materials hold promise in molecular catalysis and gas separation. magnified image DA - 2008/12/16/ PY - 2008/12/16/ DO - 10.1002/marc.200800505 VL - 29 IS - 24 SP - 1926-1931 SN - 1521-3927 KW - crosslinking KW - electron microscopy KW - membranes KW - nanoparticles KW - networks ER - TY - JOUR TI - Barrier layer mechanism engineering in calcium copper titanate thin film capacitors through microstructure control AU - Paisley, E. A. AU - Losego, M. D. AU - Aygun, S. M. AU - Craft, H. S. AU - Maria, J. -P. T2 - JOURNAL OF APPLIED PHYSICS AB - A peak permittivity greater than 10 000 has been achieved for calcium copper titanate (CCT) thin films by engineering a thin film microstructure that maximizes space charge contributions to polarizability. This permittivity is an order of magnitude greater than previous polycrystalline thin film efforts. This unique microstructure control is accomplished using a chemical solution deposition process flow that produces highly dense parallel layers ∼100 nm in thickness. We observe a thickness dependent permittivity where the entire film thickness constitutes the conducting region of a barrier layer capacitor despite the presence of multiple grain boundaries within that thickness. The model predictions are in good agreement with experimental data and are consistent with existing literature reports. These trends in permittivity with dielectric thickness raise new questions regarding the nature of barrier layers in CCT—and specifically, these results suggest that grain boundaries may not always participate as high resistance interlayers. DA - 2008/12/1/ PY - 2008/12/1/ DO - 10.1063/1.3033166 VL - 104 IS - 11 SP - SN - 1089-7550 ER - TY - JOUR TI - Surface water reactivity of polycrystalline MgO and CaO films investigated using x-ray photoelectron spectroscopy AU - Craft, H. S. AU - Collazo, R. AU - Losego, M. D. AU - Sitar, Z. AU - Maria, J. -P. T2 - JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A AB - The authors report a study comparing the surface reactivities of the alkaline earth oxides MgO and CaO with respect to water vapor under ultrahigh and high vacuum conditions. Using x-ray photoelectron spectroscopy and a series of in vacuo exposures spanning ∼10−10Torr vacuum, to 10−6Torr flowing oxygen, the extent of surface hydroxylation was investigated by monitoring the O 1s photoelectron line. After the most aggressive exposures, the MgO surface reacted to form a maximum hydroxyl coverage of ∼1.3 ML (monolayer), while the CaO surface reached a maximum coverage of ∼3.0 ML. Both surface hydroxides could be removed by in vacuo thermal anneals; exposure to 250 and 500°C were required for MgO and CaO, respectively. These results are framed in terms of the suitability of these oxides in complex oxide-compound semiconductor heteroepitaxial multifunctional devices and with respect to understanding the development of surface morphology in epitaxial 111-oriented CaO and MgO thin films. DA - 2008/11// PY - 2008/11// DO - 10.1116/1.3000058 VL - 26 IS - 6 SP - 1507-1510 SN - 0734-2101 KW - annealing KW - calcium compounds KW - epitaxial layers KW - magnesium compounds KW - monolayers KW - surface chemistry KW - surface morphology KW - X-ray photoelectron spectra ER - TY - JOUR TI - Microfabricated Particles for Engineered Drug Therapies: Elucidation into the Mechanisms of Cellular Internalization of PRINT Particles AU - Gratton, Stephanie E. A. AU - Napier, Mary E. AU - Ropp, Patricia A. AU - Tian, Shaomin AU - DeSimone, Joseph M. T2 - PHARMACEUTICAL RESEARCH AB - To investigate the cellular internalization pathways of shape- and size-specific particles as a function of zeta potential in different cell types. A top-down particle fabrication technique called PRINT was utilized to fabricate monodisperse 1 μm cylindrical particles. Cellular internalization of these PRINT particles was monitored using confocal microscopy, flow cytometry, and transmission electron microscopy. The endocytic pathway used by 1 μm cationic PRINT particles was evaluated using different inhibitory strategies. Cytotoxicity assays were used to determine the toxicity of both cationic and anionic PRINT particles in multiple cell types. Particle internalization was confirmed using confocal microscopy, flow cytometry and transmission electron microscopy. The mechanism of internalization of positively charged PRINT particles was found to be predominantly clathrin-mediated endocytosis and macropinocytosis with very few particles utilizing a caveolae-mediated endocytic pathway. The exposed charge on the surface of the particles had a significant effect on the rate of endocytosis in all cell types tested, except for the macrophage cells. No significant cytotoxicity was observed for all PRINT particles used in the present study. Cylindrical 1 μm PRINT particles were readily internalized into HeLa, NIH 3T3, OVCAR-3, MCF-7, and RAW 264.7 cells. Particles with a positive zeta potential exhibited an enhanced rate of endocytosis compared to negatively charged particles with identical sizes and shapes. It was found that PRINT particles with a positive zeta potential were endocytosed into HeLa cells using predominantely clathrin-mediated and macropinocytotic pathways. DA - 2008/12// PY - 2008/12// DO - 10.1007/s11095-008-9654-8 VL - 25 IS - 12 SP - 2845-2852 SN - 1573-904X KW - cellular uptake KW - endocytosis KW - particles KW - PRINT KW - surface charge ER - TY - JOUR TI - Characterization of Pd/gamma-Al2O3 Catalysts Prepared Using [Pd(hfac)(2)] in Liquid CO2 AU - Kelly, M. Jason AU - Kim, Jaehoon AU - Roberts, George W. AU - Lamb, H. Henry T2 - TOPICS IN CATALYSIS DA - 2008/8// PY - 2008/8// DO - 10.1007/s11244-008-9075-2 VL - 49 IS - 3-4 SP - 178-186 SN - 1572-9028 KW - Palladium-alumina catalysts KW - Palladium hexafluoroacetylacetonate KW - Catalyst preparation KW - CO pulse chemisorption KW - Diffuse-reflectance infrared spectroscopy KW - X-ray absorption fine structure spectroscopy ER - TY - JOUR TI - Identification of Components of Electron Transport Chains in the Extremely Thermoacidophilic Crenarchaeon Metallosphaera sedula through Iron and Sulfur Compound Oxidation Transcriptomes AU - Auernik, Kathryne S. AU - Kelly, Robert M. T2 - APPLIED AND ENVIRONMENTAL MICROBIOLOGY AB - ABSTRACT The crenarchaeal order Sulfolobales collectively contain at least five major terminal oxidase complexes. Based on genome sequence information, all five complexes are found only in Metallosphaera sedula and Sulfolobus tokodaii , the two sequenced Sulfolobales capable of iron oxidization. While specific respiratory complexes in certain Sulfolobales have been characterized previously as proton pumps for maintaining intracellular pH and generating proton motive force, their contribution to sulfur and iron biooxidation has not been considered. For M. sedula growing in the presence of ferrous iron and reduced inorganic sulfur compounds (RISCs), global transcriptional analysis was used to track the response of specific genes associated with these complexes, as well as other known and putative respiratory electron transport chain elements. Open reading frames from all five terminal oxidase or bc 1 -like complexes were stimulated on one or more conditions tested. Components of the fox (Msed0467 to Msed0489) and soxNL - cbsABA (Msed0500 to Msed0505) terminal/quinol oxidase clusters were triggered by ferrous iron, while the soxABCDD ′ terminal oxidase cluster (Msed0285 to Msed0291) were induced by tetrathionate and S 0 . Chemolithotrophic electron transport elements, including a putative tetrathionate hydrolase (Msed0804), a novel polysulfide/sulfur/dimethyl sulfoxide reductase-like complex (Msed0812 to Msed0818), and a novel heterodisulfide reductase-like complex (Msed1542 to Msed1550), were also stimulated by RISCs. Furthermore, several hypothetical proteins were found to have strong responses to ferrous iron or RISCs, suggesting additional candidates in iron or sulfur oxidation-related pathways. From this analysis, a comprehensive model for electron transport in M. sedula could be proposed as the basis for examining specific details of iron and sulfur oxidation in this bioleaching archaeon. DA - 2008/12// PY - 2008/12// DO - 10.1128/AEM.01545-08 VL - 74 IS - 24 SP - 7723-7732 SN - 1098-5336 ER - TY - JOUR TI - Water-in-Model Oil Emulsions Studied by Small-Angle Neutron Scattering: Interfacial Film Thickness and Composition AU - Verruto, Vincent J. AU - Kilpatrick, Peter K. T2 - LANGMUIR AB - The ever-increasing worldwide demand for energy has led to the upgrading of heavy crude oil and asphaltene-rich feedstocks becoming viable refining options for the petroleum industry. Traditional problems associated with these feedstocks, particularly stable water-in-petroleum emulsions, are drawing increasing attention. Despite considerable research on the interfacial assembly of asphaltenes, resins, and naphthenic acids, much about the resulting interfacial films is not well understood. Here, we describe the use of small-angle neutron scattering (SANS) to elucidate interfacial film properties from model emulsion systems. Modeling the SANS data with both a polydisperse core/shell form factor as well as a thin sheet approximation, we have deduced the film thickness and the asphaltenic composition within the stabilizing interfacial films of water-in-model oil emulsions prepared in toluene, decalin, and 1-methylnaphthalene. Film thicknesses were found to be 100-110 A with little deviation among the three solvents. By contrast, asphaltene composition in the film varied significantly, with decalin leading to the most asphaltene-rich films (30% by volume of the film), while emulsions made in toluene and methylnaphthalene resulted in lower asphaltenic contents (12-15%). Through centrifugation and dilatational rheology, we found that trends of decreasing water resolution (i.e., increasing emulsion stability) and increasing long-time dilatational elasticity corresponded with increasing asphaltene composition in the film. In addition to the asphaltenic composition of the films, here we also deduce the film solvent and water content. Our analyses indicate that 1:1 (O/W) emulsions prepared with 3% (w/w) asphaltenes in toluene and 1 wt % NaCl aqueous solutions at pH 7 and pH 10 resulted in 80-90 A thick films, interfacial areas around 2600-3100 cm (2)/mL, and films that were roughly 25% (v/v) asphaltenic, 60-70% toluene, and 8-12% water. The increased asphaltene and water film composition at pH 10 versus pH 7, along with unique dynamic interfacial tension profiles, suggested that the protonation state of carboxylic moieties within asphaltenes impacts the final film properties. This was further supported when we characterized similar asphaltenic emulsions that also contained 9-anthracence carboxylic acid (ACA). Addition of this aromatic acid led to slightly thinner films (70-80 A) that were characteristically more aqueous (up to 20% by volume) and 5-6% (v/v) ACA. This unique in situ characterization (deduced entirely from SANS data from emulsion samples) of the entire film composition calls for further investigation regarding the role this film-based water plays in emulsion stability. DA - 2008/11/18/ PY - 2008/11/18/ DO - 10.1021/la802095m VL - 24 IS - 22 SP - 12807-12822 SN - 0743-7463 ER - TY - JOUR TI - Nanoparticle-regulated phase behavior of ordered block copolymers AU - Gaines, Michelle K. AU - Smith, Steven D. AU - Samseth, Jon AU - Bockstaller, Michael R. AU - Thompson, Russell B. AU - Rasmussen, Kim O. AU - Spontak, Richard J. T2 - SOFT MATTER AB - Although block copolymer motifs have received considerable attention as supramolecular templates for inorganic nanoparticles, experimental observations of a nanostructured diblock copolymer containing inorganic nanoparticles—supported by theoretical trends predicted from a hybrid self-consistent field/density functional theory—confirm that nanoparticle size and selectivity can likewise stabilize the copolymer nanostructure by increasing its order–disorder transition temperature. DA - 2008/// PY - 2008/// DO - 10.1039/b805540h VL - 4 IS - 8 SP - 1609-1612 SN - 1744-6848 ER - TY - JOUR TI - Molecular-level simulations of chemical reaction equilibrium for nitric oxide dimerization reaction in disordered nanoporous carbons AU - Lisal, Martin AU - Cosoli, Paolo AU - Smith, William R. AU - Jain, Surendra K. AU - Gubbins, Keith E. T2 - FLUID PHASE EQUILIBRIA AB - We report a molecular-level simulation study of the effects of confinement on chemical reaction equilibrium for the NO dimerization reaction, 2NO ⇌ (NO)2, in disordered nanoporous carbons. We use the Reaction Ensemble Monte Carlo (RxMC) method [W.R. Smith, B. Tříska, J. Chem. Phys. 100 (1994) 3019–3027; J.K. Johnson, A.Z. Panagiotopoulos, K.E. Gubbins, Mol. Phys. 81 (1994) 717–733] to investigate the effects of temperature and bulk pressure on the reaction conversion in three models of disordered nanoporous carbons obtained from sucrose in equilibrium with a vapor reservoir. Atomistic models of the carbons used [S.K. Jain, R.J.-M. Pellenq, J.P. Pikunic, K.E. Gubbins, Langmuir 22 (2006) 9942–9948] were constructed using the Hybrid Reverse Monte Carlo method, differing by the processing conditions used in the preparation of the corresponding real material. In addition to the RxMC simulations, we test conventional macroscopic adsorption models, such as the Langmuir–Freundlich, multisite Langmuir, vacancy solution and ideal adsorption solution models, in connection with the ideal-gas model for the vapor reservoir to model the reaction equilibrium. Pure fluid adsorption isotherms needed as input to the macroscopic models for mixture adsorption are generated using the Gibbs Ensemble Monte Carlo or Grand Canonical Monte Carlo simulations. We analyze the effects of the confinement, temperature and bulk pressure on the NO dimerization reaction equilibrium in terms of the reactive adsorption isotherms. The RxMC simulations and thermodynamic modeling show that the sucrose-based carbons substantially increase the conversion of NO to (NO)2 with respect to the vapor reservoir, where the conversion is less than a few percent. DA - 2008/10/25/ PY - 2008/10/25/ DO - 10.1016/j.fluid.2008.07.015 VL - 272 IS - 1-2 SP - 18-31 SN - 0378-3812 KW - Disordered nanoporous carbon KW - Macroscopic adsorption model KW - Reaction Ensemble Monte Carlo KW - Reaction equilibrium KW - Reactive adsorption isotherm ER - TY - JOUR TI - Hydroentangling: A Novel Approach to High-Speed Fabrication of Carbon Nanotube Membranes AU - Zhang, Xiangwu T2 - ADVANCED MATERIALS AB - A tangled web: Hydroentangling, a simple, high-speed, low-cost, environmentally benign textile technology, is used to assemble individual carbon nanotubes (CNTs) into strong, electrical-conducting, multifunctional CNT nonwoven membranes. Hydroentangled CNT membranes with thicknesses ranging from 80 nm to 1.5 mm can be fabricated in as quick as 5 s per batch or up to 400 m min−1. DA - 2008/11/3/ PY - 2008/11/3/ DO - 10.1002/adma.200801919 VL - 20 IS - 21 SP - 4140-+ SN - 0935-9648 UR - https://publons.com/publon/7178335/ ER - TY - JOUR TI - Dielectrophoretic Assembly of Metallodielectric Janus Particles in AC Electric Fields AU - Gangwal, Sumit AU - Cayre, Olivier J. AU - Velev, Orlin D. T2 - LANGMUIR AB - "Janus" particles with two hemispheres of different polarizability or charge demonstrate a multitude of interesting effects in external electric fields. We reported earlier how particles with one metallic hemisphere and one dielectric hemisphere self-propel in low-frequency alternating current (AC) electric fields. Here, we demonstrate the assembly of such Janus particles driven by AC electric fields at frequencies above 10 kHz. We investigated the relation between field-induced dielectrophoretic force, field distribution, and structure of the assemblies. The phase space for electric field intensity and frequency was explored for particle concentrations large enough to form a monolayer on a glass surface between two gold electrodes. A rich variety of metallodielectric particle structures and dynamics were uncovered, which are very different from those obtained from directed assembly of plain dielectric or plain conductive particles under the action of fields of similar frequency and intensity. The metallodielectric particles assemble into new types of chain structures, where the metallized halves of neighboring particles align into lanes along the direction of the electric field, while the dielectric halves face in alternating direction. The staggered chains may assemble in various orientations to form different types of two-dimensional metallodielectric crystals. The experimental results on the formation of staggered chains are interpreted by means of numerical simulations of the electric energy of the system. The assembly of Janus metallodielectric particles may find applications in liquid-borne microcircuits and materials with directional electric and heat transfer. DA - 2008/12/2/ PY - 2008/12/2/ DO - 10.1021/la8015222 VL - 24 IS - 23 SP - 13312-13320 SN - 0743-7463 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-62249218852&partnerID=MN8TOARS ER - TY - JOUR TI - Berreman effect in infrared absorption spectroscopy of ionic oxide coatings formed by atomic layer deposition on three-dimensional structures AU - Scarel, Giovanna AU - Hyde, G. Kevin AU - Hojo, Daisuke AU - Parsons, Gregory N. T2 - JOURNAL OF APPLIED PHYSICS AB - We show through modeling and experimentation that the Berreman effect, physically manifested and investigated on planar surfaces for more than four decades, can be readily realized and studied in three-dimensional nonplanar structures. The Berreman effect is also used as a nonlocal probe to evaluate topography and homogeneity of insulating ionic oxide layers in nonplanar geometries. During infrared transmission studies the macroscopic angular dependence of the longitudinal optical mode absorbance deviates from that observed in the planar case, and the angular dependence is shown to be physically linked to geometry and homogeneity of the ionic oxide layer. Spectroscopic modeling confirms the observations on the angular dependence of longitudinal optical mode absorbance on various nonplanar systems. A linear combination of [sin(θ)]4 with appropriate coefficients is found to describe the trend of longitudinal optical mode absorbance in nonplanar structures. DA - 2008/11/1/ PY - 2008/11/1/ DO - 10.1063/1.3013439 VL - 104 IS - 9 SP - SN - 1089-7550 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000260941700110&KeyUID=WOS:000260941700110 ER - TY - CONF TI - Penetration of high-charge cationic polymers into silica gel particles and cellulosic fibers AU - Wu, N. AU - Hubbe, M. A. AU - Rojas, O. J. AU - Yamaguchi, T. C2 - 2008/// C3 - Proceedings of the 2nd IPEC Conference DA - 2008/// VL - Book B SP - 626-649 PB - Tianjin, China: Tianjin University of Science & Technology ER - TY - JOUR TI - Life in hot acid: Pathway analyses in extremely thermoacidophilic archaea AU - Auernik, Kathryne S. AU - Cooper, Charlotte R. AU - Kelly, Robert M. T2 - CURRENT OPINION IN BIOTECHNOLOGY AB - The extremely thermoacidophilic archaea are a particularly intriguing group of microorganisms that must simultaneously cope with biologically extreme pHs (≤4) and temperatures (Topt ≥ 60 °C) in their natural environments. Their expanding biotechnological significance relates to their role in biomining of base and precious metals and their unique mechanisms of survival in hot acid, at both the cellular and biomolecular levels. Recent developments, such as advances in understanding of heavy metal tolerance mechanisms, implementation of a genetic system, and discovery of a new carbon fixation pathway, have been facilitated by the availability of genome sequence data and molecular genetic systems. As a result, new insights into the metabolic pathways and physiological features that define extreme thermoacidophily have been obtained, in some cases suggesting prospects for biotechnological opportunities. DA - 2008/10// PY - 2008/10// DO - 10.1016/j.copbio.2008.08.001 VL - 19 IS - 5 SP - 445-453 SN - 1879-0429 ER - TY - JOUR TI - Field-driven surface segregation of biofunctional species on electrospun PMMA/PEO microfibers AU - Sun, Xiao-Yu AU - Nobles, Larrisha R. AU - Boerner, Hans G. AU - Spontak, Richard J. T2 - MACROMOLECULAR RAPID COMMUNICATIONS AB - Abstract The need to biofunctionalize polymer surfaces for targeted bio‐related applications continues to grow, and efforts designed to meet this need rely heavily on surface grafting or polymerization. In this study, we provide a viable alternative by demonstrating that the peptide segment of a polymer‐peptide conjugate can be selectively driven to the surface of polymer nano/microfibers during electrospinning due to contrast in polarizability. Judicious choice of the polymer sequence in the conjugate permits use of the conjugate with compatible fiber‐forming polymers. Here, we use a water soluble poly(ethylene oxide)‐containing conjugate in combination with a hydrophobic thermoplastic, poly(methyl methacrylate). Surface enrichment is measured by X‐ray photoelectron spectroscopy, and fiber morphology is investigated by electron microscopy. Microfibers generated from the blends examined here are largely resistant to long term water immersion and are thus suited as support scaffolds or filtration membranes. magnified image DA - 2008/9/1/ PY - 2008/9/1/ DO - 10.1002/marc.200800163 VL - 29 IS - 17 SP - 1455-1460 SN - 1521-3927 KW - fibers KW - functionalization of polymers KW - peptides KW - surfaces KW - toughness ER - TY - JOUR TI - Extended chemical crosslinking of a thermoplastic polyimide: Macroscopic and microscopic property development AU - Aberg, Christopher M. AU - Ozcam, Ali E. AU - Majikes, Jacob M. AU - Seyam, Mohamed A. AU - Spontak, Richard J. T2 - MACROMOLECULAR RAPID COMMUNICATIONS AB - Abstract Polyimides are well established as gas separation membranes due to their intrinsically low free volume and correspondingly high H 2 selectivity relative to other gases such as CO 2 . Prior studies have established that H 2 /CO 2 selectivity can be improved by crosslinking polyimides with diamines differing in spacer length. In this work, we follow the evolution of macroscopic and microscopic properties of a commercial polyimide over long crosslinking times ( t x ) with 1,3‐diaminopropane. According to spectroscopic analysis, the crosslinking reaction saturates after ≈24 h, whereas tensile, nanoindentation and stress relaxation tests reveal that the material stiffens, and possesses a long relaxation time that increases with increasing t x . Although differential scanning calorimetry shows that the glass transition temperature decreases systematically with increasing t x , permeation studies indicate that the permeabilities of H 2 and CO 2 decrease, while the H 2 /CO 2 selectivity increases markedly, with increasing t x . At long t x , the polyimide becomes impermeable to CO 2 , suggesting that it could be used as a barrier material. magnified image DA - 2008/9/1/ PY - 2008/9/1/ DO - 10.1002/marc.200800230 VL - 29 IS - 17 SP - 1461-1466 SN - 1022-1336 KW - barrier KW - calorimetry KW - crosslinking KW - networks KW - polyimides ER - TY - JOUR TI - Effect of solvent quality and chain confinement on the kinetics of polystyrene bromination AU - Jhon, Y. K. AU - Semler, J. J. AU - Genzer, Jan T2 - Macromolecules AB - We report on the kinetics of the bromination of free polystyrene (PS) chains in bulk solution and those anchored on flat solid substrates by performing the bromination reaction in different solvents, including nitrobenzene (NB), 1-chlorodecane (CD), 1-chloroundecane (CUD), and 1-chlorododecane (CDD), at various temperatures. We find that bulk bromination of PS follows the second-order kinetic in bromine and the reaction rate increases with increasing dielectric constant of the solvent (ε). In spite of εCDD > εCD, the bulk bromination kinetics of PS in CDD is slower than that in CD because of lower solubility of PS in CDD than in CD. In addition, we demonstrate that the reaction rates for brominating PS brushes anchored to flat solid substrates are much slower than those for brominating free PS chains in bulk solution. We attribute this behavior to steric hindrance due to PS confinement on the substrate. DA - 2008/// PY - 2008/// DO - 10.1021/ma8011653 VL - 41 IS - 18 SP - 6719–6727 ER - TY - JOUR TI - Cellulosic nanocomposites: A review AU - Hubbe, M. A. AU - Rojas, O. J. AU - Lucia, L. A. AU - Sain, M. T2 - BioResources DA - 2008/// PY - 2008/// VL - 3 IS - 3 SP - 929-980 ER - TY - JOUR TI - Autophobicity-driven surface segregation and patterning of core-shell microgel nanoparticles AU - Wei, Bin AU - Gurr, Paul A. AU - Gozen, Arif O. AU - Blencowe, Anton AU - Solomon, David H. AU - Qiao, Greg G. AU - Spontak, Richard J. AU - Genzer, Jan T2 - NANO LETTERS AB - Core−shell microgel (CSMG) nanoparticles, also referred to as core-cross-linked star (CCS) polymers, can be envisaged as permanently cross-linked block copolymer micelles and, as such, afford novel opportunities for chemical functionalization, templating, and encapsulation. In this study, we explore the behavior of CSMG nanoparticles comprising a poly(methyl methacrylate) (PMMA) shell in molten PMMA thin films. Because of the autophobicity between the densely packed, short PMMA arms of the CSMG shell and the long PMMA chains in the matrix, the nanoparticles migrate to the film surface. They cannot, however, break through the surface because of the inherently high surface energy of PMMA. Similar thermal treatment of CSMG-containing PMMA thin films with a polystyrene (PS) capping layer replaces surface energy at the PMMA/air interface by interfacial energy at the PMMA/PS interface, which reduces the energy barrier by an order of magnitude, thereby permitting the nanoparticles to emerge out of the PMMA bulk. This nanoscale process is reversible and can be captured at intermediate degrees of completion. Moreover, it is fundamentally general and can be exploited as an alternative means by which to reversibly pattern or functionalize polymer surfaces for applications requiring responsive nanolithography. DA - 2008/9// PY - 2008/9// DO - 10.1021/nl802109x VL - 8 IS - 9 SP - 3010-3016 SN - 1530-6992 ER - TY - JOUR TI - Physical and electrochemical properties of N-Alkyl-N-methylpyrrolidinium Bis(fluorosulfonyl)imide ionic liquids: PY13FSI and PY14FSI AU - Zhou, Q. AU - Henderson, W. A. AU - Appetecchi, G. B. AU - Montanino, M. AU - Passerini, S. T2 - Journal of Physical Chemistry. B, Condensed Matter, Materials, Surfaces, Interfaces & Biophysical DA - 2008/// PY - 2008/// VL - 112 IS - 43 SP - 13577-13580 ER - TY - JOUR TI - Optically Transparent, Amphiphilic Networks Based on Blends of Perfluoropolyethers and Poly(ethylene glycol) AU - Hu, Zhaokang AU - Chen, Liang AU - Betts, Douglas E. AU - Pandya, Ashish AU - Hillmyer, Marc A. AU - DeSimone, Joseph M. T2 - JOURNAL OF THE AMERICAN CHEMICAL SOCIETY AB - Amphiphilic networks of perfluoropolyethers (PFPE) and poly(ethylene glycol) (PEG) have been achieved to yield optically transparent, mechanically robust films over a wide range of compositions. Telechelic diols of these oligomers were transformed to a photocurable dimethacryloxy form (DMA) and free radically cured at various composition weight ratios to yield free-standing films. Clear and colorless amphiphilic networks could be achieved when low molar mass versions of both the PFPE-DMA (1 kg/mol) and the PEG-DMA (550 g/mol) were used. The bulk morphologies of the samples were extensively characterized by a variety of techniques including ultraviolet-visible spectroscopy, differential scanning calorimetry, dynamic mechanic thermal analysis, small-angle X-ray scattering, atomic force microscopy, X-ray photoelectron spectroscopy, and optical microscopy, which strongly suggest that nanoscopic to macroscopic phase-separated materials could be achieved. By incorporating a threshold amount of PFPEs into PEG-based hydrogel networks, water swelling could be significantly reduced, which may offer a new strategy for a number of medical device applications. Along these lines, strong inhibition of nonspecific protein adsorption could be achieved with these amphiphilic network materials compared with an oligo(ethylene glycol)-based self-assembled monolayer coated surface. DA - 2008/10/29/ PY - 2008/10/29/ DO - 10.1021/ja803991n VL - 130 IS - 43 SP - 14244-14252 SN - 0002-7863 ER - TY - JOUR TI - Microwave, Photo- and Thermally Responsive PNIPAm-Gold Nanoparticle Microgels AU - Budhlall, Bridgette M. AU - Marquez, Manuel AU - Velev, Orlin D. T2 - LANGMUIR AB - Microwave-, photo- and thermo-responsive polymer microgels that range in size from 500 to 800 μm and are swollen with water were prepared by a novel microarray technique. We used a liquid−liquid dispersion technique in a system of three immiscible liquids to prepare hybrid PNIPAm-co-AM core−shell capsules loaded with AuNPs. The spontaneous encapsulation is a result of the formation of double oil-in-water-in-oil (o/w/o) emulsion. It is facilitated by adjusting the balance of the interfacial tensions between the aqueous phase (in which a water-soluble drug may be dissolved), the monomer phase and the continuous phase. The water-in-oil (w/o) droplets containing 26 wt% NIPAm and Am monomers, 0.1 wt% Tween-80 surfactant, FITC fluorescent dye and colloidal gold nanoparticles spontaneously developed a core−shell morphology that was fixed by in situ photopolymerization. The results demonstrate new reversibly swelling and deswelling AuNP/PNIPAm hybrid core−shell microcapsules and microgels that can be actuated by visible light and/or microwave radiation (≤1250 nm) and/or temperature. This is the first study to demonstrate that incorporating AuNPs speeds up the response kinetics of PNIPAm, and hence enhances the sensitivity to external stimuli of PNIPAm. These microgels can have potential applications for microfluidic switches or microactuators, photosensors, and various nanomedicine applications in controlled delivery and release. DA - 2008/10/21/ PY - 2008/10/21/ DO - 10.1021/la8019556 VL - 24 IS - 20 SP - 11959-11966 SN - 0743-7463 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-55549140819&partnerID=MN8TOARS ER - TY - JOUR TI - Hydrogenomics of the Extremely Thermophilic Bacterium Caldicellulosiruptor saccharolyticus AU - Werken, Harmen J. G. AU - Verhaart, Marcel R. A. AU - VanFossen, Amy L. AU - Willquist, Karin AU - Lewis, Derrick L. AU - Nichols, Jason D. AU - Goorissen, Heleen P. AU - Mongodin, Emmanuel F. AU - Nelson, Karen E. AU - Niel, Ed W. J. AU - Stams, Alfons J. M. AU - Ward, Donald E. AU - Vos, Willem M. AU - Oost, John AU - Kelly, Robert M. AU - Kengen, Serve W. M. T2 - APPLIED AND ENVIRONMENTAL MICROBIOLOGY AB - ABSTRACT Caldicellulosiruptor saccharolyticus is an extremely thermophilic, gram-positive anaerobe which ferments cellulose-, hemicellulose- and pectin-containing biomass to acetate, CO 2 , and hydrogen. Its broad substrate range, high hydrogen-producing capacity, and ability to coutilize glucose and xylose make this bacterium an attractive candidate for microbial bioenergy production. Here, the complete genome sequence of C. saccharolyticus , consisting of a 2,970,275-bp circular chromosome encoding 2,679 predicted proteins, is described. Analysis of the genome revealed that C. saccharolyticus has an extensive polysaccharide-hydrolyzing capacity for cellulose, hemicellulose, pectin, and starch, coupled to a large number of ABC transporters for monomeric and oligomeric sugar uptake. The components of the Embden-Meyerhof and nonoxidative pentose phosphate pathways are all present; however, there is no evidence that an Entner-Doudoroff pathway is present. Catabolic pathways for a range of sugars, including rhamnose, fucose, arabinose, glucuronate, fructose, and galactose, were identified. These pathways lead to the production of NADH and reduced ferredoxin. NADH and reduced ferredoxin are subsequently used by two distinct hydrogenases to generate hydrogen. Whole-genome transcriptome analysis revealed that there is significant upregulation of the glycolytic pathway and an ABC-type sugar transporter during growth on glucose and xylose, indicating that C. saccharolyticus coferments these sugars unimpeded by glucose-based catabolite repression. The capacity to simultaneously process and utilize a range of carbohydrates associated with biomass feedstocks is a highly desirable feature of this lignocellulose-utilizing, biofuel-producing bacterium. DA - 2008/11// PY - 2008/11// DO - 10.1128/AEM.00968-08 VL - 74 IS - 21 SP - 6720-6729 SN - 0099-2240 ER - TY - JOUR TI - Enzymatic Hydrolysis of Native Cellulose Nanofibrils and Other Cellulose Model Films: Effect of Surface Structure AU - Ahola, S. AU - Turon, X. AU - Osterberg, M. AU - Laine, J. AU - Rojas, O. J. T2 - LANGMUIR AB - Model films of native cellulose nanofibrils, which contain both crystalline cellulose I and amorphous domains, were used to investigate the dynamics and activities of cellulase enzymes. The enzyme binding and degradation of nanofibril films were compared with those for other films of cellulose, namely, Langmuir−Schaefer and spin-coated regenerated cellulose, as well as cellulose nanocrystal cast films. Quartz crystal microbalance with dissipation (QCM-D) was used to monitor the changes in frequency and energy dissipation during incubation at varying enzyme concentrations and experimental temperatures. Structural and morphological changes of the cellulose films upon incubation with enzymes were evaluated by using atomic force microscopy. The QCM-D results revealed that the rate of enzymatic degradation of the nanofibril films was much faster compared to the other types of cellulosic films. Higher enzyme loads did not dramatically increase the already fast degradation rate. Real-time measurements of the coupled contributions of enzyme binding and hydrolytic reactions were fitted to an empirical model that closely described the cellulase activities. The hydrolytic potential of the cellulase mixture was found to be considerably affected by the nature of the substrates, especially their crystallinity and morphology. The implications of these observations are discussed in this report. DA - 2008/10/21/ PY - 2008/10/21/ DO - 10.1021/la801550j VL - 24 IS - 20 SP - 11592-11599 SN - 0743-7463 ER - TY - JOUR TI - Formation and properties of multivariant assemblies of surface-tethered diblock and triblock copolymers AU - Tomlinson, Michael R. AU - Genzer, Jan T2 - POLYMER AB - We present methodologies for fabricating block copolymer assemblies grafted onto flat solid substrates, where each block of the copolymer possesses a systematic and gradual variation of molecular weight as a function of the position on the substrate. We demonstrate the utility of this technique on two case studies. In the first project, we generate surface-tethered poly[(2-hydroxyethyl methacrylate)-b-(methyl methacrylate)] (PHEMA-b-PMMA) diblock copolymer brushes and study systematically morphological transitions associated with collapsing either the top PMMA or the bottom PHEMA block while keeping the other block solvated. Scanning force microscopy studies of systems having the top block collapsed reveal the presence of either flat (F), or micellar (M) or bicontinuous (BC) morphologies, whose locus in the phase diagram agrees with theoretical predictions and results of computer simulations. The second case study demonstrates the extension of the deposition method to the case of surface-anchored triblock copolymer brushes. Specifically, we present results pertaining to the formation of poly[(2-hydroxyethyl methacrylate)-b-(methyl methacrylate)-b-(dimethylaminoethyl methacrylate)] brushes with independent variation of all three block lengths. DA - 2008/10/17/ PY - 2008/10/17/ DO - 10.1016/j.polymer.2008.08.048 VL - 49 IS - 22 SP - 4837-4845 SN - 0032-3861 KW - Polymer brush KW - ATRP KW - Grafting from ER - TY - JOUR TI - Thermodynamic and kinetic origins of Alzheimer's and related diseases: a chemical engineer's perspective AU - Hall, Carol K. T2 - AICHE JOURNAL AB - Alzheimer's disease (AD) is an irreversible late-onset neurodegenerative disease characterized by a slow decline in thinking ability and memory, usually over a period of 5–10 years, culminating in severe dementia and death. There is no known cure. Although the exact causes of Alzheimer's disease are unknown, autopsies on the brains of its victims invariably find extracellular plaques composed of ordered aggregates, called fibrils or “amyloid”, of the A-beta protein.1 The disease was identified 100 years ago by Dr. Alois Alzheimer, who reported the appearance of abnormal clumps in the postmortem brain of his patient, Frau August D., a 55-year old woman with severe dementia.2 Five million Americans (approximately 5–10% of 65–74 year olds, and 50% of 85+ year olds) have Alzheimer's, at a cost to society of $148 billion/year. Despite the staggering projected costs of AD as the huge baby boomer generation hits their 60s, the U.S. research budget into Alzheimer's is a paltry $650 million (cf. 5.5 billion for cancer research).3, 4 Research into Alzheimer's disease is personal for me. It started with my father, Harris J. Klein (1906–1987), a dynamic Damon Runyon type figure who served as New York City Transit Commissioner in the 1950s, and chaired the now-famous JFK birthday party at Madison Square Garden. Our family's world fell apart in 1973, when he began to exhibit bizarre behavior, bewildering himself, his family and his “public”, at a time when Alzheimer's was not yet a household word. An autopsy performed after his death resulted in a posthumous diagnosis of Pick's disease, a rare amyloid disease (supposedly not hereditary) closely related to AD. My mother, Celia R. Klein (1918–2007), began showing symptoms of Alzheimer's disease when she entered her 80s. A woman before her time, she encouraged me to become a physicist (of all things) at a time when young women were discouraged from having careers, graduated with honors from college at age 63, and cared heroically for my father during the long course of his illness. She died last year at the age of 89, a shell of her former self, except for occasional flashes of humor and warmth, and impromptu sing-a-longs. Alzheimer's is only one of the many “amyloidoses”, which are also called “protein deposition diseases” or “protein conformational diseases.”5, 6 Thus far, 40 different proteins have been found in amyloid deposits in various human organs. The deposits can be extracellular or intracellular, neurodegenerative (when the aggregates occur in the brain), localized (for example in the liver or kidney) or systemic. The amyloidoses are usually associated with serious clinical manifestations; most are fatal. Examples of amyloidogenic proteins (and their associated diseases) are: beta amyloid (Alzheimer's), α-synuclein (Parkinson's), prion protein (transmissible spongiform encephalopathies, including Creutzfeldt-Jakob disease and Kuru), excessive glutamine repeats in the protein huntingtin (Huntington's), tau (Alzheimer's, Pick's), IAPP or amylin (Type II diabetes), and excessive alanine repeats in the protein PABP2 (oculopharyngeal muscular dystrophy). Interestingly, a large fraction of these proteins are natively unfolded, which means that they do not fold to a native state below a certain temperature, as most proteins do. Although some of the amyloidoses (∼10%) such as Huntington's are hereditary, most (∼85%) including Alzheimer's and Parkinson's are sporadic, although hereditary forms do exist. A small fraction (∼5%) of the diseases, particularly the spongiform encephalopathies, can be transmitted from human to human or mammal to human.6 The causes of amyloid formation are unknown. Particularly perplexing is the observation that many of these proteins are present in normal, as well as diseased individuals. Consider for example, Alzheimer's disease. The transmembrane protein APP (amyloid precursor protein) is present in healthy as well as diseased individuals; it is cleaved by secretases to form the 40- and 42-residue long Alzheimer's proteins, Aβ (1-40), and Aβ (1-42). In Alzheimer's these proteins aggregate to form fibrils; in healthy individuals they do not—we don't know why. Generally speaking, Aβ(1-42) is more likely to be associated with early-onset (hereditary) forms of Alzheimer's, with increased risk of getting Alzheimer's disease, with enhanced neurotoxicity, and with faster formation of fibrils in vitro.7-9 Alzheimer's disease is also characterized by the presence within neurons of fibrillary tangles, meshes of the microtubule-associated protein, tau. For the past twenty years a controversy has swirled over the question of which of the two proteins, beta amyloid or tau, is the cause of Alzheimer's disease. Current thinking favors the Aβ link, because amyloid plaques appear earlier in the disease process than tau tangles, and because mutations in the amyloid precursor protein APP are linked to hereditary forms of Alzheimer's disease.10 In this article, we focus primarily on amyloid. Despite a lack of similarity in the sequence, structure and function of the 40 different proteins associated with the 40 different amyloidoses, the fibrils share many basic structural features in common.6, 11, 12 All amyloid fibrils are ordered, insoluble structures 70–120 Å in dia., and can be as long as 1 μm. Most are made of up two or more smaller fibrillar structures, called protofilaments, which are themselves long ribbons containing two to four layers of “crossed” beta-sheets propagating along the fibril axis. A beta sheet is a planar array of beta-strands (peptides in elongated conformations) held together by hydrogen bonds between the backbone NH and CO group, with intrastrand distances of 4.7 to 4.8 Å. In a cross-beta structure, the beta sheets stack approximately 10 Å apart (to shield their hydrophobic side chains from contact with solvent), and extend in the direction of the fibril axis as shown in Figure 1a. There is an axial twist as shown in Figure 1b. Fibril structure can be measured using transmission electron microscopy (TEM), atomic force microscopy (AFM), X-ray diffraction, and solid-state NMR (ssNMR). (a) Generic protofilament containing three β-sheets (red, blue and green), with eight peptides per sheet. Hydrogen bonds between the backbone atoms (shown in gray) hold the peptides together in the sheet; hydrophobic interactions between the side chains (red, green and blue spheres) cause the sheets to stack on top of one another, and (b) another view of a protofilament showing the axial twist,11 the latter is reproduced with permission. Recent advances in solid-state NMR have led to exciting advances in our understanding of the structure of the fibrils formed by the Alzheimer's peptide β-amyloid.13-15 By combining ssNMR results with computational energy minimization, the Tycko group has proposed the structure shown in Figure 2 for the Aβ(1-40) protofilament.16, 17 Each A-β monomer loops back on itself due to a salt-bridge between Asp23 and Lys28, forming a U-shaped “β-strand (red)-loop (green)-β-strand (blue)” structure. The C-terminal of this structure (blue), then interacts with exposed hydrophobic residues on the C-terminal (blue) of a second U-shaped structure to form a protofilament. Residues 1–9 (green) appear to flop around off to the side. Cartoon taken from the Tycko group's research website (http://spin.niddk.nih.gov/tycko/rob_cv_2004_files/image004.jpg.) showing a cross-sectionof their proposed quaternary structure for the Aβ fibril.16 Each peptide has an unstructured N terminus (green), and two beta strands (red and blue) separated by a loop (green). The residues along the strands hydrogen bond to their neighboring peptides (red to red and blue to blue), creating a beta sheet folded back on itself. The two folded sheets are stacked together at their C terminus to form the fibril. Reproduced with permission. The cross-beta protofilament structure is also found in proteins other than those associated with amyloid diseases, which suggests that the forces that stabilize protofilaments are common to all proteins—hydrophobic interactions and backbone hydrogen bonding—and not associated with specific interactions between side chains.18, 19 The side chain interactions, and, hence, the specific sequence along the peptide chain do, however, influence the way that the sheets are arranged within the protofilaments (as described earlier for the Aβ protein), and the way that the protofilaments stack to form fibrils.6 The regularity of amyloid structures is being explored by numerous groups seeking to use peptides as the building blocks in supramolecular functional self-assembling nanostructures, with potential applications in nanoelectronics, templating, cell culture, biofiltration, biosensing, etc.20 The study of fibril structure is important for diagnostic as well as treatment purposes. Currently, absolute diagnosis of Alzheimer's is only possible post mortem. However, knowledge of the structure of Aβ fibrils could lead to new techniques that can detect and image these structures in the brain of living patients. A major breakthrough occurred in 2004 when Klunk et al. successfully imaged amyloid deposits in the brains of Alzheimer's patients by applying positron emission tomography (PET) using a new tracer, Pittsburgh compound B.21 Computer simulations offer an additional avenue for gaining a better understanding of the molecular-level events associated with amyloid formation.22 Atomistic simulations based on force-fields such as CHARMM and Amber are being used to assess the stability of different types of fibril structure.23 The idea here is to start with the structure of interest as an initial conformation, and then simulate for many nanoseconds to see if the structure changes or melts. For example, Zheng et al.24 recently applied all-atom molecular dynamics simulation to Aβ (17–42) in an attempt to learn which of the two possible sheet-sheet interfaces (C-terminal- C-terminal or N-terminal-N-terminal) in the β-strand-turn-β-strand U-shaped motif is more stable, and how Alzheimer's mutations influence the stability of the protofilament structures. They concluded that the C-terminal-C-terminal interface is more stable due to shape complementarity and strong hydrophobic contacts, in agreement with the Tycko group's proposed structure.16, 17 While atomistic simulations offer insights on the stability of postulated amyloid fibril structures, they do not tell us much about the assembly process due to their inability to access time scales greater than tens of nanoseconds. An alternative approach for the study of aggregate assembly is the class of models known as low-resolution models. Low-resolution or minimalist models rely on a coarse-grained representation of protein geometry and energetics.22 Typically, they account for the motion of groups of atoms along the protein and ignore the motion of the solvent atoms in order to enhance computational efficiency. The absence of solvent atoms in low-resolution models means that effective potentials, or potentials of mean force, must be used to describe the interactions between residues. The most common type of low-resolution model is the lattice model, which represents a protein as a linear chain of beads (residues) confined to a lattice. The group of Blanch/Prausnitz has employed lattice protein models to examine the competition between protein folding and aggregation on a fundamental level.25 By comparing the folding of proteins in isolation with folding in the presence of additional proteins, they were able to show that the free energy landscape of a protein loses its normal funnel-shape (with the native state at the bottom) as the environment becomes more crowded, portending the tendency for the protein to misfold to non-native states.26 Such misfolded proteins in turn expose their normally-buried hydrophobic residues to similarly-exposed hydrophobic residues on other misfolded proteins, leading to aggregation. In related work, the Blanch/Prausnitz group showed that mutations that have little effect on the folding of a protein in isolation can significantly alter the tendency of a protein to aggregate under crowded conditions.27 Intermediate-resolution protein models represent protein energetics and geometry at a resolution between those adopted in atomistic and low-resolution protein models.22 Our group has developed an implicit-solvent intermediate-resolution protein model, called PRIME, and applied it to a relatively simple protein, polyalanine, which forms fibrils in test tubes.28 In PRIME the level of molecular detail in the protein representation and interaction potential is reduced just to the point at which the key physical features governing protein folding and aggregation remain and the other features are neglected. Each amino acid residue is composed of four spheres: a 3-sphere backbone comprised of united atom NH, CαH, and CO, and a single-sphere side chain (CH3- for alanine). Ideal backbone bond angles, Cα-Cα distances and residue L-isomerization are maintained. The force field includes: steric interactions, hydrogen bonding between the backbone NH and CO, and hydrophobic interactions between the alanine side chains. By combining this model with the very-fast discontinuous molecular dynamics technique, we were able to simulate the spontaneous formation of a protofilament in a system of ninety-six 16-residue polyalanine peptides, KA14K—the first time that anyone had been able to simulate spontaneous formation of fibrils.29 Figure 3 contains a series of snapshots taken from a simulation of the formation of a protofilament. The thermodynamics, kinetics, and structure of the formed fibrils were in very good agreement with experimental observations. Discontinuous molecular dynamics simulation29 of a system of 48 polyalanine peptides at various reduced times t*. Hydrophobic side chains are red; the backbone atoms on each beta sheet have a unique color to make it easier to distinguish the various sheets in the resulting fibril. United atoms are not shown full size for ease of viewing. Reproduced with permission. A snapshot from a simulation of a 96-peptide protofilament is presented in Figure 4. Five to six sheets are stacked on top of each other; the fibril axis is into the page. The peptides are more or less in register, which means that there is little staggering of the peptides within a sheet. The figure on the cover shows a detail of this protofilament viewed from the side. Four beta sheets are depicted—colored pink, blue, green and purple. The alanine side chains (shown in red) oscillate from one side of the zig-zag sheet to the other, occupying the pockets created on the adjacent sheets. This structure is consistent with X-ray diffraction measurements.29 The structure of the protofilament formed spontaneously in our simulations is the same as the basic protofilament structure shown in Figure 1. The take home message here is that hydrogen bonding between backbone NH and CO, and hydrophobic interactions between side chains are the key driving forces for fibril formation. Final structure of protofilament formed in a discontinuous molecular dynamics simulation of a system of 96 polyalanine peptides.29 Five to six sheets are stacked on top of each other; the fibril axis is into the page. The color scheme is as indicated in Figure 3. Reproduced with permission. Fibril formation is believed to follow a nucleation and growth mechanism,6, 30, 31 which means that there is a time lag before fibrils first appear. During this time, the peptides associate one by one or in groups in a series of energetically unfavorable steps. Once a critical size and shape is reached, the so-called “nucleus”, the process rapidly proceeds downhill in free energy. Protofilaments form as the nucleus associates with monomers (single proteins) or oligomers (small groups of proteins), and elongate either through monomer addition at the tip or end-to-end association of short protofilaments. There is some debate as to how the protofilaments join together to from fibrils. As is the case in other nucleated phenomenon, e.g., crystallization, the addition of a preformed fibrillar seed to a system of proteins eliminates the lag time, presumably because it provides a ready-made nucleus. The events preceding the formation of a protofilament have received considerable attention lately, because they are thought to be likely candidates for intervention in the fibril formation process. In vitro studies have shown that before forming protofilaments, the Alzheimer's peptide Aβ forms “protofibrils”, metastable nonfibrillar structures 2–5 nm in dia. containing ∼ 20 molecules that are rich in beta sheet structure.19, 32, 33 These can be spherical beads, linear or curly chains of beads or annular structures formed from circular chains of beads. Recent studies of even earlier events in the fibril formation process have shown that unstructured oligomers containing 2–6 peptides form even before protofibrils; such oligomers have been observed in the brains of AD victims. As will be discussed later, both protofibrils and early oligomers are being investigated as the potential toxic species in AD. Murphy is one of the pioneers of the application of mathematical modeling to the kinetics of protein aggregation. She and Pallitto postulated a multistep pathway for Aβ fibril formation and growth, derived the appropriate differential and algebraic equations, and fit the model parameters to their own experimental data on aggregate mass and size as a function of time and concentration.31 Roberts and coworkers have developed an irreversible model of non-native protein aggregation kinetics that combines the classic Lumry-Eyring model with nucleation/polymerization ideas.34 A number of possible aggregation pathways were considered; the model was solved for several limiting cases. The “amyloid cascade hypothesis”, the idea that protein aggregation triggers the disease process, has evolved over the years particular as applied to Alzheimer's disease.7, 8, 35 Originally, the beta amyloid plaques (the mature fibrils) were thought to be at the root of the dementia and memory loss that characterize Alzheimer's disease. However, the lack of correlation between the extent of plaque formation in postmortem brains and the severity of Alzheimer's symptoms, the presence of multiple Aβ species (ranging in size from monomers to mature fibrils) in the brains of AD victims, and the appearance of plaques in the brains of symptom-free 70-year olds has caused the paradigm to shift in recent years. In the last five years there has been mounting evidence that the precursors to fibril formation—intermediates such as early oligomers or protofibrils that appear along the fibril formation pathway—are most toxic to cells. This is supported by observations that preparations enriched in protofibrils are toxic to cultured neurons, interfere with long-term potentiation in the hippocampus (a cellular mechanism for learning and memory), and adversely impact cognition and synaptic plasticity. In fact, it has been suggested that fibril formation might be nature's way of sequestering bad actors, preventing them from damaging cells. If this were indeed the case, then blocking the growth of mature fibrils or dissociating them could accelerate the disease process by allowing the toxic species to buildup. Despite the controversy over the nature of the toxic species, several drugs are in the pipeline aimed at disrupting the formation of fibrils. We don't yet know how Aβ protofibrils and/or early oligomers damage cells. Most likely it is a combination of effects.6 Since Aβ protofibrils and/or early oligomers are “misfolded”, they have significant numbers of exposed hydrophobic residues on their surfaces. This makes them susceptible to inappropriate interactions with cell membranes, proteins, and other parts of cell machinery, disrupting cell functioning including regulator mechanisms and clearance. The aforementioned reasoning is consistent with the fact that AD and the other amyloid diseases are late onset; the cell's ability to function in the face of disruption diminishes with age as its clearance mechanisms degrade, leading to an imbalance between Aβ production and clearance. Another possibility is that annular protofibrils insert themselves or assemble within cell membranes, forming channels that disrupt membrane permeability to calcium.36 Even though there is an ongoing debate on the identity of the toxic species, significant work toward developing therapeutic agents that either address the major symptoms of Alzheimer's disease (severe dementia and diminished cognitive function) or target the plaques (amyloid fibrils) is underway. Four drugs designed to reduce the symptoms of Alzheimer's disease are currently in use today. Three of these, donepezil (Aricept), rivastigmine (Exelon) and galantamine (Razadyne) are cholinesterase inhibitors, which means that they slow the action of an enzyme that degrades acetylcholine, a neurotransmitter vital to transmission of nerve signals across synapses. These are prescribed for mild to moderate AD. The fourth, memantine(Namenda), lowers levels of another neurotransmitter, glutamate, in the brain, and is prescribed for mild to severe AD. These four drugs produce marginal improvement of cognitive function in AD victims but do not slow the progression of the disease.37 Many potential strategies and drugs for treatment and prevention of AD are now being investigated. Examination of the NIH website, ClinicalTrials.gov, shows that they include familiar drugs: anti-inflammatory agents like celebrex and ibuprofen; cholesterol lowering statin drugs like Lipitor and Zocor; nutritional supplements like DHA (an omega 3 fatty acid); Avandia (a diabetes drug); vitamin E; resveratrol (a component of red wine); hormones like estrogen; ginkgo biloba, and the steroid prednisone. There are a number of AD drugs in clinical trials (see ClinicalTrials.gov) designed to reduce Aβ amyloid.8, 9, 35 These are based on two broad strategies: (1) partially inhibiting action of the secretases that cleave APP to form Aβ, or (2) preventing formation or enhancing clearance of Aβ protofibrils or early oligomers through passive or active vaccination against Aβ.7, 35 Passive vaccination is based on the principle that subjects exposed to an active agent, like Aβ42 will develop their own immune response to that agent by producing antibodies. In active vaccination the subjects are injected directly with laboratory- generated antibodies. Based on very promising results of antiamyloid immunotherapy in animal models, the Elan company conducted a Phase II trial in 2001 of the safety and efficacy of AN-1792, a drug based on active vaccination with Aβ 42 and a T- cell helper adjuvant. This study was halted after the second injection in January 2002 because 6% of the participants developed meningoencephalitis. Follow-on evaluation of the participants, however, has lent support to the immunological approach by showing that participants with the highest antibody levels experienced the least cognitive decline. Based on lessons learned from AN-1793, Elan and Wyeth have teamed up to test passive vaccination (a presumably safer approach). Their new drug is Bapineuzumad, a humanized monoclonal antibody, now in phase III trials. Another antiamyloid drug in Phase III clinical trials is Flurizan, a small molecule drug developed by Myriad Genetics that shifts the site of the APP cleavage by γ-secretase from Aβ 42 to shorter peptides. Alzhemed, a once considered promising small molecule drug that inhibits all Aβ aggregation by binding Aβ monomers, failed in recent Phase II trials to demonstrate efficacy (Ref. 37, ClinicalTrials.gov,www.alzforum.org). Further development of inhibitors to prevent Aβ aggregation in Alzheimer's disease is also being explored. The Good group has found that a novel small heat shock protein, HSP20, inhibits Aβ aggregation and toxicity.38 The Murphy group has developed inhibitors that are hybrid Aβ peptides. These combine a recognition element, a short sequence of hydrophobic residues from the Aβ peptide that binds to other Aβ peptides, with a disrupting sequence, for example, a sequence of charged or branched amino acids, that get in the way of Aβ aggregation.39 Interestingly, the most effective hybrids were found to be those that increased solvent surface tension. Necula et al. have examined 29 small-molecule inhibitors of Aβ aggregation, and divided them into three classes according to whether they: (1) inhibit oligomerization, but not fibrillization, (2) inhibit both oligomerization and fibrillization, or (3) inhibit fibrillization, but not oligomerization.40 An altogether different tack is being taken by Bodner et al. in investigations of therapeutic approaches for Huntington's and Parkinson's diseases. Based on the suggestion that fibrillization is nature's way of sequestering the more harmful early oligomers early oligomers, they have developed a drug that promotes the formation of “inclusions”, (large intracellular protein aggregates), and have found that it lessens cellular pathology.41 There are still many questions to be answered in the pursuit of treatments or cures for amyloid diseases. What is the structure of amyloid fibrils? What reaction pathways do proteins follow during aggregation? Why do the proteins aggregate more quickly in some people than in others? Do the pathways depend on protein sequence or change with environmental conditions? Which species or steps in the aggregation process are toxic, what are the toxicity mechanisms, and how can we get around these mechanisms? It seems obvious to me that chemical engineers, with their grounding in thermodynamics and chemical reaction kinetics, can play a unique role in the search for a cure for Alzheimer's and other amyloid diseases. In the meantime what should each of us do to protect ourselves against AD and related diseases? I wish I knew. I do know that hasty efforts to jump on any specific treatment bandwagon are not a good idea. In my efforts to avoid the fate of my father and mother, I threw out my aluminum pots and pans years ago, based on a now-disproved connection between aluminum and AD. Later I took estrogen hormones because epidemiological studies showed that postmenopausal women on estrogen replacement therapy (ERT) got AD later than average. What we didn't know then but know now is that ERT is associated with increased risk for breast cancer! So—be cautious. I am heartened these days by the great progress being made in our understanding of how to treat and/or prevent AD. It may be the optimist in me, but I believe that viable treatments will be available within this decade. The author gratefully acknowledges the assistance of Ms. Erin Phelps and Ms. Victoria Wagoner in preparing this manuscript. DA - 2008/8// PY - 2008/8// DO - 10.1002/aic.11589 VL - 54 IS - 8 SP - 1956-1962 SN - 1547-5905 KW - Alzheimer's disease KW - amyloid ER - TY - JOUR TI - Electrically driven alignment and crystallization of unique anisotropic polymer particles AU - Herlihy, Kevin P. AU - Nunes, Janine AU - DeSimone, Joseph M. T2 - LANGMUIR AB - Micrometer-sized monodisperse anisotropic polymer particles, with disk, rod, fenestrated hexagon (hexnut), and boomerang shapes, were synthesized using the particle replication in nonwetting templates (PRINT) process, and investigations were conducted on aqueous suspensions of these particles when subjected to alternating electric fields. A coplanar electrode configuration, with 1 to 2 mm electrode gaps (20−50 V ac, 0.5−5.0 kHz) was used, and the experiments were monitored with fluorescence microscopy. For all particle suspensions, the field brought about significant changes in the packing and orientation. Extensive particle chaining and packing were observed for the disk, rod, and hexnut suspensions. Because of the size and geometry of the boomerang particles, limited chaining was observed; however, the field triggered a change from random to a more ordered packing arrangement. DA - 2008/8/19/ PY - 2008/8/19/ DO - 10.1021/la801250g VL - 24 IS - 16 SP - 8421-8426 SN - 0743-7463 ER - TY - JOUR TI - Biological and synthetic self-cleaning surfaces AU - Genzer, Jan AU - Marmur, Abraham T2 - MRS BULLETIN DA - 2008/8// PY - 2008/8// DO - 10.1557/mrs2008.159 VL - 33 IS - 8 SP - 742-746 SN - 1938-1425 ER - TY - JOUR TI - Triblock copolymer organogels as high-performance dielectric elastomers AU - Shankar, Ravi AU - Krishnan, Arjun K. AU - Ghosh, Tushar K. AU - Spontak, Richard J. T2 - MACROMOLECULES AB - Block copolymers and nanostructured materials derived therefrom are becoming increasingly ubiquitous in a wide variety of (nano)technologies. Recently, we have demonstrated that triblock copolymer organogels composed of physically cross-linked copolymer networks swollen with a midblock-selective solvent exhibit excellent electromechanical behavior as dielectric elastomers. In-plane actuation of such organogels, collectively referred to as electroactive nanostructured polymers (ENPs) to reflect the existence of a self-organized copolymer morphology, is attributed to the development of an electric-field-induced surface-normal Maxwell stress. In this study, we examine the composition and molecular weight dependence of the electromechanical properties afforded by organogels prepared from poly[styrene-b-(ethylene-co-butylene)-b-styrene] (SEBS) triblock copolymers selectively swollen with EB-compatible aliphatic oligomers. These materials undergo ultrahigh actuation displacement at significantly reduced electric fields relative to previously reported dielectric elastomers and possess electromechanical coupling efficiencies, which relate the conversion from electrical input to mechanical output, greater than 90%. The design of ENPs with broadly tunable electromechanical properties represents an attractive route to responsive materials for advanced engineering, biomimetic and biomedical applications. DA - 2008/8/26/ PY - 2008/8/26/ DO - 10.1021/ma071903g VL - 41 IS - 16 SP - 6100-6109 SN - 1520-5835 ER - TY - JOUR TI - The effect of particle design on cellular internalization pathways AU - Gratton, Stephanie E. A. AU - Ropp, Patricia A. AU - Pohlhaus, Patrick D. AU - Luft, J. Christopher AU - Madden, Victoria J. AU - Napier, Mary E. AU - DeSimone, Joseph M. T2 - PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA AB - The interaction of particles with cells is known to be strongly influenced by particle size, but little is known about the interdependent role that size, shape, and surface chemistry have on cellular internalization and intracellular trafficking. We report on the internalization of specially designed, monodisperse hydrogel particles into HeLa cells as a function of size, shape, and surface charge. We employ a top-down particle fabrication technique called PRINT that is able to generate uniform populations of organic micro- and nanoparticles with complete control of size, shape, and surface chemistry. Evidence of particle internalization was obtained by using conventional biological techniques and transmission electron microscopy. These findings suggest that HeLa cells readily internalize nonspherical particles with dimensions as large as 3 mum by using several different mechanisms of endocytosis. Moreover, it was found that rod-like particles enjoy an appreciable advantage when it comes to internalization rates, reminiscent of the advantage that many rod-like bacteria have for internalization in nonphagocytic cells. DA - 2008/8/19/ PY - 2008/8/19/ DO - 10.1073/pnas.0801763105 VL - 105 IS - 33 SP - 11613-11618 SN - 0027-8424 KW - PRINT KW - shape KW - size KW - surface charge ER - TY - JOUR TI - Reactive patterning via post-functionalization of polymer brushes utilizing disuccinimidyl carbonate activation to couple primary amines AU - Diamanti, Steve AU - Arifuzzaman, Shafi AU - Elsen, Andrea AU - Genzer, Jan AU - Vaia, Richard A. T2 - POLYMER AB - Polymer brushes provide an exceptional route to surface functionalization due to their chemical and mechanical robustness, lack of large-area defects, and high density of functional groups. In spite of these benefits, the synthetic difficulty and complex surface structure associated with polymer brushes have hindered their utilization for constructing multifunctional, patterned surfaces. In this contribution we describe the use of a rapid and highly efficient polymer brush post-functionalization technique as a facile method for controlling surface functionality of polymer brushes. Poly(2-hydroxyethyl methacrylate) (PHEMA) brushes are post-functionalized via activation with N,N′-disuccinimidyl carbonate (DSC) and subsequent coupling to molecules containing α-amine moieties. This post-functionalization effectively tailors surface energy resulting in water contact angles ranging from 40° to 100° using different conjugate molecules. Furthermore, the solvent tolerance, insensitivity to reactant concentration, and rapid reaction time of the aminolysis reaction enable surface energy patterning of the polymer brushes through the use of “reactive” soft lithography. Finally, these surface energy patterns could be “developed” by exposure to gold nanoparticle solutions to yield surfaces with patterned nanoparticle density. DA - 2008/8/11/ PY - 2008/8/11/ DO - 10.1016/j.polymer.2008.06.020 VL - 49 IS - 17 SP - 3770-3779 SN - 1873-2291 KW - post-functionalization KW - polymer brush KW - patterning ER - TY - JOUR TI - Long-term stabilization of foams and emulsions with in-situ formed microparticles from hydrophobic cellulose AU - Wege, Hartmut A. AU - Kim, Sejong AU - Paunov, Vesselin N. AU - Zhong, Qixin AU - Velev, Orlin D. T2 - LANGMUIR AB - We report a simple method to produce foams and emulsions of extraordinary stability by using hydrophobic cellulose microparticles, which are formed in situ by a liquid-liquid dispersion technique. The hydrophobic cellulose derivative, hypromellose phthalate (HP), was initially dissolved in water-miscible solvents such as acetone and ethanol/water mixtures. As these HP stock solutions were sheared in aqueous media, micron sized cellulose particles formed by the solvent attrition. We also designed and investigated an effective and simple process for making HP particles without any organic solvents, where both the solvent and antisolvent were aqueous buffer solutions at different pH. Consequently, the HP particles adsorbed onto the water/air or water/oil interfaces created during shear blending, resulting in highly stable foams or foam/emulsions. The formation of HP particles and their ability for short-term and long-term stabilization of interfaces strongly depended on the HP concentration in stock solutions, as well as the solvent chemistry of both stock solutions and continuous phase media. Some foams and emulsion samples formed in the presence of ca. 1 wt% HP were stable for months. This new class of nontoxic inexpensive cellulose-based particle stabilizers has the potential to substitute conventional synthetic surfactants, especially in edible, pharmaceutical and biodegradable products. DA - 2008/9/2/ PY - 2008/9/2/ DO - 10.1021/la801634j VL - 24 IS - 17 SP - 9245-9253 SN - 0743-7463 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-51449120260&partnerID=MN8TOARS ER - TY - JOUR TI - Simulation of mechanically assembled monolayers and polymers in good solvent using discontinuous molecular dynamics AU - Strickland, L. Anderson AU - Hall, Carol K. AU - Genzer, Jan T2 - MACROMOLECULES AB - We present the results of discontinuous molecular dynamics simulations of mechanically assembled monolayers in good solvent. Polymers of chain lengths 5−100 were end-grafted to surfaces at low density and then compressed laterally at varying rates. Data for brush thickness and end-monomer density were collected as a function of surface density; they were shown to correspond well with theoretical predictions and simulation results performed at constant surface density. Brush thickness for all chain lengths could be controlled by judicious choice of the compression rate. Defects in the brush layer were dependent on chain length; it was shown that quick compression for relatively short chains allowed the layer no time to relax into coil form. Quick compression on long chain systems led to entanglement in the brush layer since the longer-chained system was not being afforded the long relaxation time required to form a fully relaxed brush. Hysteresis effects were examined by allowing the brush to relax to a lower surface density, and it was shown that higher surface compression/relaxation rates led to an increase in disparity between brush thickness found during the compression and relaxation stages; in large part, this disparity was due to inadequate equilibration time. Last, results from nonuniform compression in good solvent show negligible effects on monolayer height and structure. DA - 2008/9/9/ PY - 2008/9/9/ DO - 10.1021/ma8003218 VL - 41 IS - 17 SP - 6573-6581 SN - 0024-9297 ER - TY - JOUR TI - Signal transduction at point-blank range: Analysis of a spatial coupling mechanism for pathway crosstalk AU - Monine, Michael I. AU - Haugh, Jason M. T2 - BIOPHYSICAL JOURNAL AB - The plasma membrane provides a physical platform for the orchestration of molecular interactions and biochemical conversions involved in the early stages of receptor-mediated signal transduction in living cells. In that context, we introduce here the concept of spatial coupling, wherein simultaneous recruitment of different enzymes to the same receptor scaffold facilitates crosstalk between different signaling pathways through the local release and capture of activated signaling molecules. To study the spatiotemporal dynamics of this mechanism, we have developed a Brownian dynamics modeling approach and applied it to the receptor-mediated activation of Ras and the cooperative recruitment of phosphoinositide 3-kinase (PI3K) by activated receptors and Ras. Various analyses of the model simulations show that cooperative assembly of multimolecular complexes nucleated by activated receptors is facilitated by the local release and capture of membrane-anchored signaling molecules (such as active Ras) from/by receptor-bound signaling proteins. In the case of Ras/PI3K crosstalk, the model predicts that PI3K is more likely to be recruited by activated receptors bound or recently visited by the enzyme that activates Ras. By this mechanism, receptor-bound PI3K is stabilized through short-range, diffusion-controlled capture of active Ras and Ras/PI3K complexes released from the receptor complex. We contend that this mechanism is a means by which signaling pathways are propagated and spatially coordinated for efficient crosstalk between them. DA - 2008/9/1/ PY - 2008/9/1/ DO - 10.1529/biophysj.108.128892 VL - 95 IS - 5 SP - 2172-2182 SN - 0006-3495 ER - TY - JOUR TI - Selective endothelial cell attachment to peptide-modified terpolymers AU - Veleva, Anka N. AU - Heath, Daniel E. AU - Cooper, Stuart L. AU - Patterson, Cam T2 - BIOMATERIALS AB - In a previous report we screened a combinatorial peptide library to identify novel ligands that bind with high affinity and specificity to human blood outgrowth endothelial cells (HBOEC). In this study we demonstrate the use of the phage display-selected-HBOEC-specific peptides as a tool to direct and modulate endothelial cell (EC) behavior with a focus on designing functional biomaterials intended for use in cardiovascular applications. First, we ensured that our peptide ligands did not interfere with EC function as tested by proliferation, migration, tube formation, and response to vascular endothelial growth factor. Second, peptides that supported EC function were incorporated into methacrylic terpolymers via chain transfer free radical polymerization. The HBOEC-specific peptide, TPSLEQRTVYAK, when covalently coupled to a terpolymer matrix, retained binding affinity towards HBOEC in a serum-free medium. Under the same binding conditions, the attachment of human umbilical vein endothelial cells (HUVEC) was limited, thus establishing HBOEC specificity. To our knowledge, this is the first report demonstrating specificity in binding to peptide-modified biomaterials of mature EC, i.e., HUVEC, and EC of progenitor origin such as HBOEC. The findings from this work could facilitate the development of autologous cell therapies with which to treat cardiovascular disease. DA - 2008/9// PY - 2008/9// DO - 10.1016/j.biomaterials.2008.05.022 VL - 29 IS - 27 SP - 3656-3661 SN - 1878-5905 KW - phage display-selected-peptide ligands KW - cell-specific adhesion KW - HBOEC KW - bioactive terpolymers KW - autologous cell therapies ER - TY - JOUR TI - Three-component phase behavior of the sclareol-ethyl lactate-carbon dioxide system for GAS applications AU - Tombokan, Xenia C. AU - Aguda, Remil M. AU - Danehower, David A. AU - Kilpatrick, Peter K. AU - Carbonell, Ruben G. T2 - JOURNAL OF SUPERCRITICAL FLUIDS AB - This paper focuses on the extraction of sclareol from the leaves of Salvia sclarea Lamiaceae, more commonly known as Clary sage. The process involves the extraction of sclareol using a CO2-soluble GRAS solvent such as ethyl lactate, followed by GAS anti-solvent precipitation from ethyl lactate solution with carbon dioxide. The three-component phase behavior of the sclareol–ethyl lactate–CO2 system at various pressures has been determined and indicates a slight cybotactic effect. The ability of thermodynamic models to predict the complex three-component phase behavior of this system is discussed, together with the implications of the thermodynamic behavior of the system on process design. DA - 2008/6// PY - 2008/6// DO - 10.1016/j.supflu.2007.12.007 VL - 45 IS - 2 SP - 146-155 SN - 0896-8446 KW - GAS KW - GRAS solvents KW - nutraceuticals KW - sclareol KW - extraction KW - precipitation ER - TY - JOUR TI - Solubility and diffusivity of gases in mixed matrix membranes containing hydrophobic fumed silica: Correlations and predictions based on the NELF model AU - De Angelis, Maria Grazia AU - Sarti, Giulio C. T2 - INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH AB - The addition of fumed silica particles to glassy polymers such as PTMSP and Teflon AF 2400 results in an enhancement of gas diffusivity and permeability that is not captured by traditional models for composites because both volume and gas solubility of the composite material are underestimated by the additive rule based on pure component properties. Such effects have been attributed to the creation of additional free volume due to the insertion of filler in the polymeric matrix. In this work, we use the NELF model to relate gas solubility in the composite material to the variations induced by the addition of filler on polymer density and swellability. From these values, the fractional free volume (FFV) increase produced in the polymeric phase by filler incorporation may be evaluated and, in turn, also the diffusivity in the composite material can be calculated as a function of filler content on the basis of its relation to FFV. The gas diffusivity data for n-C4H10 in AF 2400 and AF 2400-based mixed matrices, as well as those relative to N2, CH4, C2H6, C3H8, and n-C4H10 in PTMSP, follow closely the correlation found, which contains only one adjustable parameter for each penetrant-polymer couple. DA - 2008/8/6/ PY - 2008/8/6/ DO - 10.1021/ie0714910 VL - 47 IS - 15 SP - 5214-5226 SN - 0888-5885 ER - TY - JOUR TI - Solid-liquid phase behavior of ternary mixtures AU - Attwood, Brian C. AU - Hall, Carol K. T2 - AICHE JOURNAL AB - Abstract The Gibbs Duhem integration technique is extended to calculate ternary phase diagrams at constant temperature and pressure. The technique is used to calculate solid–liquid–vapor phase equilibria for a system selected to roughly model a mixture of two diastereomeric molecules of similar melting point and diameter immersed in a solvent with a lower melting point and a slightly smaller diameter. The cross‐species well‐depth and diameter between the two diastereomers are varied to determine their impact on the phase equilibria. We find that when the interspecies well‐depth is lowered to less than that of either of the diastereomers, the solid phase separates into two solid solutions and consequently there is a region of three‐phase coexistence in the ternary phase diagram. We then calculate ternary phase diagrams at a series of temperatures for one set of molecular parameters. For an equimolar mixture of diastereomers, there is a range of temperature and solvent concentration at which only one of the diastereomers will precipitate, thus effecting a separation of the diastereomers. As the temperature is decreased the purity of the precipitate increases. © 2008 American Institute of Chemical Engineers AIChE J, 2008 DA - 2008/7// PY - 2008/7// DO - 10.1002/aic.11513 VL - 54 IS - 7 SP - 1886-1894 SN - 0001-1541 KW - solid-liquid equilibria KW - ternary phase diagrams classical resolution ER - TY - PAT TI - Process for preparing microrods using liquid-liquid dispersion AU - Velev, O. D. AU - Alargova, R. G. C2 - 2008/// DA - 2008/// PY - 2008/// ER - TY - JOUR TI - Low temperature metal oxide film deposition and reaction kinetics in supercritical carbon dioxide AU - Peng, Qing AU - Hojo, Daisuke AU - Park, Kie Jin AU - Parsons, Gregory N. T2 - THIN SOLID FILMS AB - An effective method is developed for low temperature metal oxide deposition through thermal decomposition of metal diketonates in supercritical carbon dioxide (scCO2) solvent. The rates of Al(acac)3 (Aluminum acetyl acetonate) and Ga(acac)3 (Gallium acetyl acetonate) thermal decomposition in scCO2 to form conformal Al2O3 and Ga2O3 thin films on planar surfaces were investigated. The thermal decomposition reaction of Al(acac)3 and Ga(acac)3 was found to be initialized at ∼ 150 °C and 160 °C respectively in scCO2 solvent, compared to ∼ 250 °C and 360 °C in analogous vacuum-based processes. By measuring the temperature dependence of the growth rates of metal oxide thin films, the apparent activation energy for the thermal decomposition of Al(acac)3 in scCO2 is found to be 68 ± 6 kJ/mol, in comparison with 80–100 kJ/mol observed for the corresponding vacuum-based thermal decomposition reaction. The enhanced thermal decomposition rate in scCO2 is ascribed to the high density solvent which effectively reduces the energy of the polar transition states in the reaction pathway. Preliminary results of thin film deposition of other metal oxides including ZrOx, FeOx, Co2O3, Cr2O3, HfOx from thermal decomposition of metal diketonates or fluorinated diketonates in scCO2 are also presented. DA - 2008/6/2/ PY - 2008/6/2/ DO - 10.1016/j.tsf.2007.10.057 VL - 516 IS - 15 SP - 4997-5003 SN - 0040-6090 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000256509100054&KeyUID=WOS:000256509100054 KW - supercritical carbon dioxide (scCO(2)) KW - metal oxides KW - solvation energy KW - thermal decomposition KW - metal diketonates ER - TY - JOUR TI - Improved epitaxy of barium titanate by molecular beam epitaxy through a single crystalline magnesium oxide template for integration on hexagonal silicon carbide AU - Goodrich, T. L. AU - Cai, Z. AU - Losego, M. D. AU - Maria, J. -P. AU - Kourkoutis, L. Fitting AU - Muller, D. A. AU - Ziemer, K. S. T2 - JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B AB - Crystalline MgO(111) has the potential to be an effective template for the heteroepitaxial integration of BTO(111) and other functional oxides on 6H-SiC(0001). Deposition of MgO on 6H-SiC(0001) at 140°C resulted in a twinned structure with only (111) orientation. By heating the MgO(111) after deposition to 650°C at a background pressure of 1.0×10−9Torr or depositing the MgO at 650°C, the twinned structure can be minimized, resulting in a reflection high energy electron diffraction (RHEED) pattern characteristic of random epitaxial islands. The use of a 2nm MgO(111) template layer proved optimal for deposition of crystalline BTO(111) by molecular beam epitaxy on 6H-SiC(0001). The BTO was found to be twinned with a 60° in-plane rotation. The grain formation of the BTO resulted in a transmission dominated RHEED pattern. Deposition of BTO at a higher substrate temperature resulted in large grain formation, 50nm in size, but an increased surface roughness of 1.4±0.1nm over a 1μm2 area. In order to integrate BTO in a multiferroic device with multilayers of BTO(111) and hexagonal ferrites, it will be necessary to optimize the processing conditions to establish a smoother BTO surface for the subsequent heteroepitaxy of the magnetic film. DA - 2008/5// PY - 2008/5// DO - 10.1116/1.2889389 VL - 26 IS - 3 SP - 1110-1114 SN - 2166-2746 ER - TY - JOUR TI - Diameter control of electrospun polyacrylonitrile/iron acetylacetonate ultrafine nanofibers AU - Du, Jinmei AU - Shintay, Samantha AU - Zhang, Xiangwu T2 - JOURNAL OF POLYMER SCIENCE PART B-POLYMER PHYSICS AB - Abstract Electrospinning is the process of producing ultrafine fibers by overcoming the surface tension of a polymer solution using high voltage. In this work, the effects of both solution properties (viscosity, conductivity, and surface tension) and operational conditions (voltage, feed rate, and spinneret‐collector distance), on the structure of electrospun polyacrylonitrile nanofibers, were systematically investigated. Iron acetylacetonate was added to the electrospinning solution to control fiber diameter by selectively adjusting solution properties. It was found that, with increased salt concentration, the fiber diameter increases and then passes through a maximum due to changes in solution viscosity, conductivity, and surface tension. In addition, the fiber diameter increases with increase in voltage, feed rate, and spinneret‐collector distance. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1611–1618, 2008 DA - 2008/8/1/ PY - 2008/8/1/ DO - 10.1002/polb.21500 VL - 46 IS - 15 SP - 1611-1618 SN - 0887-6266 UR - https://publons.com/publon/7178321/ KW - electrospinning KW - fibers KW - iron acetylacetonate KW - nanofibers KW - nanotechnology KW - polyacrylonitrile KW - structure ER - TY - JOUR TI - Effect of substrate geometry on polymer molecular weight and polydispersity during surface-initiated polymerization AU - Gorman, Christopher B. AU - Petrie, Randall J. AU - Genzer, Jan T2 - MACROMOLECULES AB - Poly(methyl methacrylate) (PMMA) anchored chains were grown on porous silicon (p-Si) and anodically etched aluminum oxide (AAO) substrates via surface-initiated atom transfer radical polymerization (ATRP). Using hydrogen fluoride, the chains could be cleaved from the substrates, as evidenced by infrared spectroscopy. The molecular weights and molecular weight distributions of PMMA could be analyzed directly on these substrates (after cleaving the chains from the support) using direct ionization mass spectrometry (DIOS-MS) and matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS). Two principal conclusions were drawn from the study. First, matrix-free DIOS-MS was effective at direct analysis of the polymers up to a molecular weight of ≈6 kDa; the signal-to-noise ratio for heavier polymer chains diminished rapidly. Second, under the same polymerization conditions, PMMA grown on both p-Si and AAO substrates had a much lower molecular weight and a broader molecular weight distribution than that grown in solution. Confinement effects imposed by the pores during the polymerization are proposed as the likely mechanism for the reduced growth rates and more polydisperse chains. DA - 2008/7/8/ PY - 2008/7/8/ DO - 10.1021/ma8004857 VL - 41 IS - 13 SP - 4856-4865 SN - 1520-5835 ER - TY - JOUR TI - Dependence of plasmon polaritons on the thickness of indium tin oxide thin films AU - Rhodes, C. AU - Cerruti, M. AU - Efremenko, A. AU - Losego, M. AU - Aspnes, D. E. AU - Maria, J. P. AU - Franzen, S. T2 - Journal of Applied Physics DA - 2008/// PY - 2008/// VL - 103 IS - 9 ER - TY - JOUR TI - Conformal metal oxide coatings on nanotubes by direct low temperature metal-organic pyrolysis in supercritical carbon dioxide AU - Peng, Qing AU - Spagnola, Joseph C. AU - Daisuke, Hojo AU - Park, Kie Jin AU - Parsons, Gregory N. T2 - JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B AB - The authors demonstrate that low temperature (&lt;200 °C) thermal decomposition of metal-organic precursors dissolved in supercritical carbon dioxide (scCO2) is an effective method to penetrate into dense three-dimensional networks and deposit conformal metal oxide films with tunable thickness. The results specifically show that thermal decomposition of gallium acetylacetonate in scCO2, leads to conformal coatings of gallium oxide on multiwalled carbon nanotube forests with a fast deposition rate (∼3–4 nm/min), without the need for any cosolvent. Moreover, as-formed metal oxide/nanotube structures can be further conformally coated by metal atomic layer deposition to produce nanotube/oxide/metal nanocomposites. DA - 2008/5// PY - 2008/5// DO - 10.1116/1.2917072 VL - 26 IS - 3 SP - 978-982 SN - 2166-2746 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000256304600016&KeyUID=WOS:000256304600016 ER - TY - JOUR TI - Catalytic role of carbons in methane decomposition for CO- and CO(2)-free hydrogen generation AU - Huang, Liping AU - Santiso, Erik E. AU - Nardelli, Marco Buongiorno AU - Gubbins, Keith E. T2 - JOURNAL OF CHEMICAL PHYSICS AB - Decomposition of methane is an environmentally attractive approach to CO- and CO(2)-free hydrogen production. Using first principles calculations at the density functional theory level, our studies demonstrate that the defective carbons can be used as catalysts for methane decomposition, without the need for other catalysts, such as transition metals or oxides, and the catalytic sites can be regenerated by the deposition of carbon decomposed from methane, to make the hydrogen production a continuous process. Additionally, since no other gases are produced in the process, the cost of CO(2) sequestration and hydrogen purification from CO contamination will be dramatically reduced. DA - 2008/6/7/ PY - 2008/6/7/ DO - 10.1063/1.2931456 VL - 128 IS - 21 SP - SN - 0021-9606 ER - TY - JOUR TI - Simulation of chemical reaction equilibria by the reaction ensemble Monte Carlo method: a review AU - Turner, C. Heath AU - Brennan, John K. AU - Lisal, Martin AU - Smith, William R. AU - Johnson, J. Karl AU - Gubbins, Keith E. T2 - MOLECULAR SIMULATION AB - Understanding and predicting the equilibrium behaviour of chemically reacting systems in highly non-ideal environments is critical to many fields of science and technology, including solvation, nanoporous materials, catalyst design, combustion and propulsion science, shock physics and many more. A method with recent success in predicting the equilibrium behaviour of reactions under non-ideal conditions is the reaction ensemble Monte Carlo method (RxMC). RxMC has been applied to reactions confined in porous solids or near solid surfaces, reactions at high temperature and/or high pressure, reactions in solution and at phase interfaces. The only required information is a description of the intermolecular forces among the system molecules and standard free-energy data for the reacting components. Extensions of the original method include its combination with algorithms for systems involving phase equilibria, constant-enthalpy and constant-internal energy adiabatic conditions, a method to include reaction kinetics, a method to study the dynamics of reacting systems, and a mesoscale method to simulate long-chain molecule phase separation. This manuscript surveys the various applications and adaptations of the RxMC method to date. Additionally, the relationship between the RxMC method and other techniques that simulate chemical reaction behaviour is given, along with insight into some technical nuances not found in the pioneering papers. DA - 2008/// PY - 2008/// DO - 10.1080/08927020801986564 VL - 34 IS - 2 SP - 119-146 SN - 1029-0435 KW - Monte Carlo KW - reaction KW - equilibria KW - simulation ER - TY - JOUR TI - Polysaccharide Degradation and Synthesis by Extremely Thermophilic Anaerobes AU - VanFossen, A.L. AU - Lewis, D.L. AU - Nichols, J.D. AU - Kelly, R.M. T2 - Annals of the New York Academy of Sciences AB - Extremely thermophilic fermentative anaerobes (growth T opt ≥ 70°C) have the capacity to use a variety of carbohydrates as carbon and energy sources. As such, a wide variety of glycoside hydrolases and transferases have been identified in these microorganisms. The genomes of three model extreme thermophiles—an archaeon Pyrococcus furiosus ( T opt = 98°C), and two bacteria, Thermotoga maritima ( T opt = 80°C) and Caldicellulosiruptor saccharolyticus (T opt = 70°C)—encode numerous carbohydrate‐active enzymes, many of which have been characterized biochemically in their native or recombinant forms. In addition to their voracious appetite for polysaccharide degradation, polysaccharide production has also been noted for extremely thermophilic fermentative anaerobes; T. maritima generates exopolysaccharides that aid in biofilm formation, a process that appears to be driven by intraspecies and interspecies interactions. DA - 2008/3// PY - 2008/3// DO - 10.1196/annals.1419.017 VL - 1125 IS - 1 SP - 322–337 SN - 0077-8923 KW - Pyrococcus furiosus KW - Thermotoga maritima KW - Caldicellulosiruptor saccharolyticus KW - extremely thermophilic organism KW - thermophile KW - glycoside hydrolases KW - exopolysaccharides ER - TY - JOUR TI - Identification of trimeric peptides that bind porcine parvovirus from mixtures containing human blood plasma AU - Heldt, Caryn L. AU - Gurgel, Patrick V. AU - Jaykus, Lee-Ann AU - Carbonell, Ruben G. T2 - BIOTECHNOLOGY PROGRESS AB - Virus contamination in human therapeutics is of growing concern as more therapeutic products from animal or human sources come into the market. All biopharmaceutical processes are required to have at least two distinct viral clearance steps to remove viruses. Most of these steps work well for enveloped viruses and large viruses, whether enveloped or not. That leaves a class of small non-enveloped viruses, like parvoviruses and hepatitis A, which are not easily removed by these typical steps. In this study, we report the identification of trimeric peptides that bind specifically to porcine parvovirus (PPV) and their potential use to remove this virus from process solutions. All of the trimeric peptides isolated completely removed all detectable PPV from buffer in the first nine column volumes, corresponding to a clearance of 4.5-5.5 log of infectious virus. When the virus was spiked into a more complex matrix consisting of 7.5% human blood plasma, one of the trimers, WRW, was able to remove all detectable PPV in the first three column volumes, after which human blood plasma began to interfere with the binding of the virus to the peptide resin. These trimer resins removed considerably more virus than weak ion exchange resins. The results of this work indicate that small peptide ligand resins have the potential to be used in virus removal processes where removal of contaminating virus is necessary to ensure product safety. DA - 2008/// PY - 2008/// DO - 10.1021/bp070412c VL - 24 IS - 3 SP - 554-560 SN - 1520-6033 ER - TY - JOUR TI - Extremely thermophilic microorganisms for biomass conversion: status and prospects AU - Blumer-Schuette, Sara E. AU - Kataeva, Irina AU - Westpheling, Janet AU - Adams, Michael W. W. AU - Kelly, Robert M. T2 - CURRENT OPINION IN BIOTECHNOLOGY AB - Many microorganisms that grow at elevated temperatures are able to utilize a variety of carbohydrates pertinent to the conversion of lignocellulosic biomass to bioenergy. The range of substrates utilized depends on growth temperature optimum and biotope. Hyperthermophilic marine archaea (T(opt)>or=80 degrees C) utilize alpha- and beta-linked glucans, such as starch, barley glucan, laminarin, and chitin, while hyperthermophilic marine bacteria (T(opt)>or=80 degrees C) utilize the same glucans as well as hemicellulose, such as xylans and mannans. However, none of these organisms are able to efficiently utilize crystalline cellulose. Among the thermophiles, this ability is limited to a few terrestrial bacteria with upper temperature limits for growth near 75 degrees C. Deconstruction of crystalline cellulose by these extreme thermophiles is achieved by 'free' primary cellulases, which are distinct from those typically associated with large multi-enzyme complexes known as cellulosomes. These primary cellulases also differ from the endoglucanases (referred to here as 'secondary cellulases') reported from marine hyperthermophiles that show only weak activity toward cellulose. Many extremely thermophilic enzymes implicated in the deconstruction of lignocellulose can be identified in genome sequences, and many more promising biocatalysts probably remain annotated as 'hypothetical proteins'. Characterization of these enzymes will require intensive effort but is likely to generate new opportunities for the use of renewable resources as biofuels. DA - 2008/6// PY - 2008/6// DO - 10.1016/j.copbio.2008.04.007 VL - 19 IS - 3 SP - 210-217 SN - 0958-1669 ER - TY - JOUR TI - Characterization of palladium (Pd) on alumina catalysts prepared using liquid carbon dioxide AU - Kim, Jaehoon AU - Kelly, M. Jason AU - Lamb, H. Henry AU - Roberts, George W. AU - Kiserow, Douglas J. T2 - JOURNAL OF PHYSICAL CHEMISTRY C AB - Palladium (II) hexafluoroacetylacetonate (Pd(hfac)2) dissolved in liquid carbon dioxide (L-CO2) was used to deposit Pd nanoparticles onto low-surface-area α-alumina (13 m2/g) and high-surface-area γ-alumina (207 m2/g). These nanoparticles were prepared by contacting Pd(hfac)2 dissolved in L-CO2 with the alumina at 6.9 MPa and 28.5 °C and then slowly venting gaseous CO2 until L-CO2 was completely evaporated. After depressurization to remove the CO2 and unabsorbed Pd(hfac)2, the impregnated Pd(hfac)2 was reduced in hydrogen at a relatively low temperature of 75 °C. The adsorption isotherm of Pd(hfac)2 on γ-alumina suggests a weak interaction between the organometallic compound and the support. The average Pd particle size on the low-surface-area α-alumina, measured by scanning electron microscopy, increased from 13.1 ± 3.5 to 59.9 ± 11.3 nm, and the metal dispersion, measured by pulsed CO chemisorption, decreased from 11 to 3%, as the Pd loading on the alumina was increased from 0.15 to 1.54 wt %. With the high-surface-area γ-alumina, Pd particle size, measured by scanning transmission electron microscopy, increased from 3.1 ± 1.9 to 7.0 ± 5.9 nm, and the metal dispersion decreased from 56 to 5%, as Pd loading was increased from 0.58 to 3.94 wt %. DA - 2008/7/17/ PY - 2008/7/17/ DO - 10.1021/jp711495n VL - 112 IS - 28 SP - 10446-10452 SN - 1932-7447 ER - TY - JOUR TI - Biophysics - Cells get in shape for a crawl AU - Haugh, Jason M. T2 - NATURE AB - A cell's shape changes as it moves along a surface. The forward-thinking cytoskeletal elements are all for progress, but the conservative cell membrane keeps them under control by physically opposing their movement. Cell shape is determined by the interaction of many elements such as the cytoskeleton, cell membrane and interaction of cells with their substrate. Keren et al. have analysed the natural cell-to-cell variability in a large population of motile cells (keratocytes) from fish skin to reveal mechanisms of shape determination. They develop a model that accurately predicts both cell shape and speed based on a physically realistic, molecularly detailed model of an actin network treadmilling in an inextensible membrane bag. DA - 2008/5/22/ PY - 2008/5/22/ DO - 10.1038/453461a VL - 453 IS - 7194 SP - 461-462 SN - 0028-0836 ER - TY - JOUR TI - Associative polymer facilitated electrospinning of nanofibers AU - Talwar, Sachin AU - Hinestroza, Juan AU - Pourdeyhimi, Benham AU - Khan, Saad A. T2 - MACROMOLECULES AB - Electrospun nanofibers present an exciting avenue for development of novel materials with well-defined functionalities; however, broadening the scope of electrospinning to a diverse range of polymers remains a major challenge. In particular, a recurring issue in this field is the inability to spin polymers at lower concentrations in order to achieve smaller fiber diameters. This work explores the use of associative polymers as a means to overcome this limiting factor that prevents the electrospinnning of nanofibers from low-concentration polymer solutions. Hydrophobically modified alkali-soluble emulsion (HASE) polymers are comblike associative polymers with pendant hydrophobes that form a network in aqueous media consisting of both intra- and intermolecular hydrophobic junctions. Rheological measurements reveal that addition of HASE polymers in small amounts to poly(ethylene oxide) solutions leads to considerable increase in viscosity as well as dynamic moduli of the system. More importantly, these rheological changes are translated into significant changes in fiber morphology, from beaded to uniform nanofibers, as well as reduction in fiber diameter. The concept of using rheology modifiers is further extended to another associative polymer, guar galactomannan, which associates through a different mechanism. Similar improvements in fiber formation are observed, thereby lending credence to the universality of this approach. DA - 2008/6/24/ PY - 2008/6/24/ DO - 10.1021/ma8004795 VL - 41 IS - 12 SP - 4275-4283 SN - 1520-5835 ER - TY - JOUR TI - The patterning of sub-500 nm inorganic oxide structures AU - Hampton, M. J. AU - Williams, S. S. AU - Zhou, Z. AU - Nunes, J. AU - Ko, D. H. AU - Templeton, J. L. AU - Samulski, E. T. AU - DeSimone, J. M. T2 - Advanced Materials AB - Elastomeric perfluoropolyether molds are applied to pattern arrays of sub-500 nm inorganic oxide features. This versatile soft-lithography technique can be used to pattern a wide range of materials; in this work inorganic oxides including TiO2, SnO2, ZnO, ITO, and BaTiO3 are patterned on a variety of substrates with different aspect ratios. An example of TiO2 posts is shown in the figure. DA - 2008/// PY - 2008/// DO - 10.1002/adma.200702495 VL - 20 IS - 14 SP - 2667- ER - TY - JOUR TI - Self-catalyzed hydrogenolysis of nickelocene: Functional metal coating of three-dimensional nanosystems at low temperature AU - Peng, Qing AU - Spagnola, Joseph C. AU - Parsons, Gregory N. T2 - JOURNAL OF THE ELECTROCHEMICAL SOCIETY AB - In this paper we demonstrate the hydrogenolysis of nickelocene can take place through a self-catalyzed process at low temperature in supercritical carbon dioxide to generate relatively uniform dispersed Ni (nickel) metal particles onto carbon nanotubes forests and Ni films on flat surfaces. The ability to form metal particles or films without a local catalyst at this low temperature is significant because it provides further insight into mechanisms for Ni deposition reactions, and it enables a new route for low-temperature metal coating on a range of nonmetal substrate materials with complex topographies and nanostructures, for example, to form Ni/polymer magnetic nanocomposites. DA - 2008/// PY - 2008/// DO - 10.1149/1.2946723 VL - 155 IS - 9 SP - D580-D582 SN - 0013-4651 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000258038800037&KeyUID=WOS:000258038800037 ER - TY - JOUR TI - Role of polymer-salt-solvent interactions in the electrospinning of polyacrylonitrile/iron acetylacetonate AU - Du, Jinmei AU - Zhang, Xiangwu T2 - JOURNAL OF APPLIED POLYMER SCIENCE AB - Abstract Electrospinning is a process of producing ultrafine fibers by overcoming the surface tension of a polymer solution with electrostatic force. In this study, iron acetylacetonate was added to a polyacrylonitrile solution, and the role of polymer–salt–solvent interactions in the electrospinning of the ultrafine fibers was investigated. The polymer–salt–solvent interactions were characterized by Fourier transform infrared spectroscopy; and the solution viscosity, conductivity and surface tension were measured in solutions with different salt concentrations. The formation of polymer–salt–solvent interactions increased the solution viscosity, conductivity, and surface tension values at low salt concentrations. At high concentrations, the solution viscosity and surface tension decreased, but the conductivity remained relatively constant. The polymer–salt–solvent interactions influenced the structures of the electrospun fibers by changing the balance among the solution viscosity, conductivity, and surface tension. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 DA - 2008/9/5/ PY - 2008/9/5/ DO - 10.1002/app.28396 VL - 109 IS - 5 SP - 2935-2941 SN - 1097-4628 UR - https://publons.com/publon/7178336/ KW - association KW - composites KW - fibers KW - nanocomposites KW - nanotechnology ER - TY - JOUR TI - Microwave activation of enzymatic catalysis AU - Young, Douglas D. AU - Nichols, Jason AU - Kelly, Robert M. AU - Deiters, Alexander T2 - JOURNAL OF THE AMERICAN CHEMICAL SOCIETY AB - Microwave irradiation can be used to regulate biocatalysis. Herein, the utilization of hyperthermophilic enzymes in a microwave reactor is reported. While these enzymes are inactive at low temperatures, they can be activated with microwave irradiation. To the best of our knowledge, this is the first illustration of a specific microwave effect in enzymatic catalysis. DA - 2008/8/6/ PY - 2008/8/6/ DO - 10.1021/ja802404g VL - 130 IS - 31 SP - 10048-+ SN - 0002-7863 ER - TY - JOUR TI - Melting behavior of water in cylindrical pores: carbon nanotubes and silica glasses AU - Sliwinska-Bartkowiak, M. AU - Jazdzewska, M. AU - Huang, L. L. AU - Gubbins, K. E. T2 - PHYSICAL CHEMISTRY CHEMICAL PHYSICS AB - We report a study of the effects of confinement in multi-walled carbon nanotubes and mesoporous silica glasses (SBA-15) on the solid structure and melting of both H2O and D2O ice, using differential scanning calorimetry, dielectric relaxation spectroscopy, and neutron diffraction. Multi-walled nanotubes of 2.4, 3.9 and 10 nm are studied, and the SBA-15 studied has pores of mean diameter 3.9 nm; temperatures ranging from approximately 110 to 290 K were studied. We find that the melting point is depressed relative to the bulk water for all systems studied, with the depression being greater in the case of the silica mesopores. These results are shown to be consistent with molecular simulation studies of freezing in silica and carbon materials. The neutron diffraction data show that the cubic phase of ice is stabilized by the confinement in carbon nanotubes, as well as in silica mesopores, and persists up to temperatures of about 240 K, above which there is a transition to the hexagonal ice structure. DA - 2008/// PY - 2008/// DO - 10.1039/b808246d VL - 10 IS - 32 SP - 4909-4919 SN - 1463-9084 ER - TY - JOUR TI - Influence of binary surfactant mixtures on the rheology of associative polymer solutions AU - Talwar, Sachin AU - Scanu, Lauriane AU - Raghavan, Srinivasa R. AU - Khan, Saad A. T2 - LANGMUIR AB - Hydrophobically modified alkali-soluble emulsion polymers (HASE) are a class of comblike associative polymers that can impart high viscosities to aqueous solutions. The rheology of HASE solutions can be tuned by the addition of surfactants, such as nonylphenol ethoxylates (NP e), where e is the length of the hydrophilic (ethoxylate) chain. While previous studies have considered individual surfactants, our focus here is on binary surfactant mixtures. We find that equimolar NP4-NP12 mixtures significantly enhance the zero-shear viscosities of HASE solutions as compared to equivalent amounts of NP8, especially at high overall surfactant concentrations. Dynamic rheological measurements suggest that the higher viscosities are due to increases in the lifetime of hydrophobic junctions in the polymer-surfactant network. In contrast to the above results, equimolar NP4-NP8 mixtures are rheologically identical to equivalent solutions of NP6. The differences between the two sets of mixtures are further correlated with cloud point measurements and thereby with the overall hydrophilic-lipophilic balance (HLB) of the surfactant system. DA - 2008/8/5/ PY - 2008/8/5/ DO - 10.1021/la801030n VL - 24 IS - 15 SP - 7797-7802 SN - 0743-7463 ER - TY - JOUR TI - Effect of prepolymer molecular weight on solid state polymerization of poly(bisphenol a carbonate) with nitrogen as a sweep fluid AU - Kim, Jaehoon AU - Roberts, George W. AU - Kiserow, Douglas J. T2 - JOURNAL OF POLYMER SCIENCE PART A-POLYMER CHEMISTRY AB - Abstract The effect of prepolymer molecular weight on the solid‐state polymerization (SSP) of poly(bisphenol A carbonate) was investigated using nitrogen (N 2 ) as a sweep fluid. Prepolymers with different number–average molecular weights, 3800 and 2400 g/mol, were synthesized using melt transesterification. SSP of the two prepolymers then was carried out at reaction temperatures in the range 120–190 °C, with a prepolymer particle size in the range 20–45 μm and a N 2 flow rate of 1600 mL/min. The glass transition temperature ( T g ), number–average molecular weight ( M n ), and percent crystallinity were measured at various times during each SSP. The phenyl‐to‐phenolic end‐group ratio of the prepolymers and the solid‐state synthesized polymers was determined using 125.76 MHz 13 C and 500.13 MHz 1 H nuclear magnetic resonance (NMR) spectroscopy. At each reaction temperature, SSP of the higher‐molecular‐weight prepolymer ( M n = 3800 g/mol) always resulted in higher‐molecular‐weight polymers, compared with the polymers synthesized using the lower molecular weight prepolymer ( M n = 2400 g/mol). Both the crystallinity and the lamellar thickness of the polymers synthesized from the lower‐molecular‐weight prepolymer were significantly higher than for those synthesized from the higher‐molecular‐weight prepolymer. Higher crystallinity and lamellar thickness may lower the reaction rate by reducing chain‐end mobility, effectively reducing the rate constant for the reaction of end groups. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4959–4969, 2008 DA - 2008/8/1/ PY - 2008/8/1/ DO - 10.1002/pola.22819 VL - 46 IS - 15 SP - 4959-4969 SN - 0887-624X KW - crystallization KW - poly(bisphenol A carbonate) KW - polycarbonates KW - prepolymer molecular weight KW - solid-state polymerization ER - TY - JOUR TI - Thermodynamics and kinetic processes of polymer blends and block copolymers in the presence of pressurized carbon dioxide AU - Walker, Teri A. AU - Frankowski, David J. AU - Spontak, Richard J. T2 - ADVANCED MATERIALS AB - Abstract Environmentally‐responsible materials processing is becoming an important global consideration in a wide variety of technologies, especially those wherein volatile and/or residual organic solvents cannot be tolerated. In this context, polymer processing has benefited tremendously from advances achieved using high‐pressure CO 2 as a viscosity modifier, plasticizing agent, foaming agent, and reaction medium. Pressurized CO 2 is environmentally benign, inexpensive, sustainable, and versatile owing to its gas‐like viscosity and liquid‐like solubility, which can be tuned through judicious choice of temperature and pressure. The addition of high‐pressure CO 2 to homopolymer blends and block copolymers can have a profound impact on polymer thermodynamics and kinetic processes since the number of interacting species increases. As a result, the compressibility as well as plasticization and intermolecular screening effects become non‐negligible. In this work, we review how these factors influence such polymeric systems, and discuss commercial polymer processes and applications that benefit from the use of high‐pressure CO 2 . DA - 2008/3/5/ PY - 2008/3/5/ DO - 10.1002/adma.200700076 VL - 20 IS - 5 SP - 879-898 SN - 1521-4095 ER - TY - JOUR TI - Surface-bound soft matter gradients AU - Genzer, Jan AU - Bhat, Rajendra R. T2 - LANGMUIR AB - This feature article describes the progress realized over the past half century in the field of surface-bound gradient structures created on or from soft materials (oligomers and/or polymers), or those enabling the study of the behavior of soft materials. By highlighting our work in the field and accounting for the contribution of other groups, we emphasize the exceptional versatility of gradient assemblies in facilitating fast screening of physicochemical phenomena, acting as "recording media" for monitoring a process, and playing a key role in the design and fabrication of surface-bound molecular and macromolecular motors capable of directing a transport phenomenon. DA - 2008/3/18/ PY - 2008/3/18/ DO - 10.1021/la7033164 VL - 24 IS - 6 SP - 2294-2317 SN - 0743-7463 ER - TY - JOUR TI - Spectroscopic analysis of the epitaxial CaO (111)-GaN (0002) interface AU - Craft, H. S. AU - Collazo, R. AU - Losego, M. D. AU - Mita, S. AU - Sitar, Z. AU - Maria, J. -P. T2 - APPLIED PHYSICS LETTERS AB - We report an x-ray photoelectron spectroscopy (XPS) study of the CaO∕GaN interface. Epitaxial films of CaO (111) were grown on GaN (0002) and analyzed in situ using XPS. We observe Stranski–Krastanov growth, in which CaO coalesces rapidly, then converts to a three-dimensional mode. Data suggest coalescence within the first nanometer of film growth, indicating growth behavior different from published reports of the analogous MgO–GaN system. We find 1.0±0.2eV for the valence band offset and a 2.5±0.2eV conduction band offset. The results are discussed in terms of their utility in oxide-nitride electronic devices. DA - 2008/2/25/ PY - 2008/2/25/ DO - 10.1063/1.2887878 VL - 92 IS - 8 SP - SN - 0003-6951 ER - TY - JOUR TI - Single-ion conductors for lithium batteries via silica surface modification AU - Zhang, Hanjun AU - Zhang, Xiangwu AU - Shiue, Eric AU - Fedkiw, Peter S. T2 - JOURNAL OF POWER SOURCES AB - Single-ion conductors (SICs) have been prepared by free-radical polymerization of sulfonic acid-containing monomer on high-purity silica surface that was first tailored with unsaturated functionality using a silanation reaction. It was found that steric effects limited polyelectrolyte surface loading even when large amount of silane molecules were grafted by forming a cross-linked structure. The results indicate that large surface area is an important factor to achieve high-surface loading of ionic moieties. Composite electrolytes were prepared by dispersing these SICs in aprotic solvents. The effects of filler content and solvent on ionic conductivity were investigated. DA - 2008/3/1/ PY - 2008/3/1/ DO - 10.1016/j.jpowsour.2007.11.064 VL - 177 IS - 2 SP - 561-565 SN - 0378-7753 UR - https://publons.com/publon/7178337/ KW - single-ion conductors KW - silanation KW - free-radical polymerization KW - electrolytes KW - conductivity KW - lithium batteries ER - TY - JOUR TI - Potential vorticity (PV) thinking in operations: The utility of nonconservation AU - Brennan, Michael J. AU - Lackmann, Gary M. AU - Mahoney, Kelly M. T2 - WEATHER AND FORECASTING AB - Abstract The use of the potential vorticity (PV) framework by operational forecasters is advocated through case examples that demonstrate its utility for interpreting and evaluating numerical weather prediction (NWP) model output for weather systems characterized by strong latent heat release (LHR). The interpretation of the dynamical influence of LHR is straightforward in the PV framework; LHR can lead to the generation of lower-tropospheric cyclonic PV anomalies. These anomalies can be related to meteorological phenomena including extratropical cyclones and low-level jets (LLJs), which can impact lower-tropospheric moisture transport. The nonconservation of PV in the presence of LHR results in a modification of the PV distribution that can be identified in NWP model output and evaluated through a comparison with observations and high-frequency gridded analyses. This methodology, along with the application of PV-based interpretation, can help forecasters identify aspects of NWP model solutions that are driven by LHR; such features are often characterized by increased uncertainty due to difficulties in model representation of precipitation amount and latent heating distributions, particularly for convective systems. Misrepresentation of the intensity and/or distribution of LHR in NWP model forecasts can generate errors that propagate through the model solution with time, potentially degrading the representation of cyclones and LLJs in the model forecast. The PV framework provides human forecasters with a means to evaluate NWP model forecasts in a way that facilitates recognition of when and how value may be added by modifying NWP guidance. This utility is demonstrated in case examples of coastal extratropical cyclogenesis and LLJ enhancement. Information is provided regarding tools developed for applying PV-based techniques in an operational setting. DA - 2008/2// PY - 2008/2// DO - 10.1175/2007WAF2006044.1 VL - 23 IS - 1 SP - 168-182 SN - 0882-8156 ER - TY - JOUR TI - Isomerization kinetics of small hydrocarbons in confinement AU - Santiso, Erik E. AU - Nardelli, Marco Buongiorno AU - Gubbins, Keith E. T2 - ADSORPTION-JOURNAL OF THE INTERNATIONAL ADSORPTION SOCIETY DA - 2008/6// PY - 2008/6// DO - 10.1007/s10450-007-9075-8 VL - 14 IS - 2-3 SP - 181-188 SN - 1572-8757 KW - chemical reactions KW - confinement KW - carbon KW - density functional theory KW - variational transition state theory ER - TY - JOUR TI - Enzymatic kinetics of cellulose hydrolysis: A QCM-D study AU - Turon, Xavier AU - Rojas, Orlando J. AU - Deinhammer, Randall S. T2 - LANGMUIR AB - The interactions between films of cellulose and cellulase enzymes were monitored using a quartz crystal microbalance (QCM). Real-time measurements of the coupled contributions of enzyme binding and hydrolytic reactions were fitted to a kinetic model that described closely significant cellulase activities. The proposed model combines simple Boltzmann sigmoidal and 1 - exp expressions. The obtained kinetics parameters were proven to be useful to discriminate the effects of incubation variables and also to perform enzyme screening. Furthermore, it is proposed that the energy dissipation of a film subject to enzymatic hydrolysis brings to light its structural changes. Overall, it is demonstrated that the variations registered in QCM frequency and dissipation of the film are indicative of mass and morphological transformations due to enzyme activities; these include binding phenomena, progressive degradation of the cellulose film, existence of residual, recalcitrant cellulose fragments, and the occurrence of other less apparent changes throughout the course of incubation. DA - 2008/4/15/ PY - 2008/4/15/ DO - 10.1021/la7032753 VL - 24 IS - 8 SP - 3880-3887 SN - 0743-7463 ER - TY - JOUR TI - Computational models of tandem Src homology 2 domain interactions and application to phosphoinositide 3-kinase AU - Barua, Dipak AU - Faeder, James R. AU - Haugh, Jason M. T2 - JOURNAL OF BIOLOGICAL CHEMISTRY AB - Intracellular signal transduction proteins typically utilize multiple interaction domains for proper targeting, and thus a broad diversity of distinct signaling complexes may be assembled. Considering the coordination of only two such domains, as in tandem Src homology 2 (SH2) domain constructs, gives rise to a kinetic scheme that is not adequately described by simple models used routinely to interpret in vitro binding measurements. To analyze the interactions between tandem SH2 domains and bisphosphorylated peptides, we formulated detailed kinetic models and applied them to the phosphoinositide 3-kinase p85 regulatory subunit/platelet-derived growth factor beta-receptor system. Data for this system from different in vitro assay platforms, including surface plasmon resonance, competition binding, and isothermal titration calorimetry, were reconciled to estimate the magnitude of the cooperativity characterizing the sequential binding of the high and low affinity SH2 domains (C-SH2 and N-SH2, respectively). Compared with values based on an effective volume approximation, the estimated cooperativity is 3 orders of magnitude lower, indicative of significant structural constraints. Homodimerization of full-length p85 was found to be an alternative mechanism for high avidity binding to phosphorylated platelet-derived growth factor receptors, which would render the N-SH2 domain dispensable for receptor binding. DA - 2008/3/21/ PY - 2008/3/21/ DO - 10.1074/jbc.M708359200 VL - 283 IS - 12 SP - 7338-7345 SN - 1083-351X ER - TY - JOUR TI - Addressing 'engineering solutions in global and societal context' through an integrated foreign language immersion experience AU - Ollis, D. F. AU - Kennedy, A. AU - Granger, M. AU - Brent, R. T2 - International Journal of Engineering Education DA - 2008/// PY - 2008/// VL - 24 IS - 2 SP - 304-313 ER - TY - JOUR TI - Ultrafine polyacrylonitrile/silica composite fibers via electrospinning AU - Ji, Liwen AU - Zhang, Xiangwu T2 - MATERIALS LETTERS AB - Polyacrylonitrile (PAN)/silica composite nanofibers, in the diameter of 200–300 nm, were prepared by a one-step electrospinning method. The PAN/silica nanofibers were characterized by SEM, TEM, ATR–FTIR and DSC. SEM and TEM images show that beads are formed and silica nanoparticles start to aggregate when the silica content is higher than 2 wt.% in nanofibers. ATR–FTIR spectra and DSC results indicate that there may exist interactions between silica nanoparticles and PAN. The addition of silica nanoparticles also changes the thermal properties of PAN/silica nanofibers. DA - 2008/5/15/ PY - 2008/5/15/ DO - 10.1016/j.matlet.2007.11.051 VL - 62 IS - 14 SP - 2161-2164 SN - 0167-577X UR - https://publons.com/publon/7178340/ KW - electrospinning KW - nanoparticles KW - PAN/silica composite nanofibers KW - DMF ER - TY - JOUR TI - Quantitative genetic analysis of sleep in Drosophila melanogaster AU - Harbison, Susan T. AU - Sehgal, Amita T2 - GENETICS AB - Although intensively studied, the biological purpose of sleep is not known. To identify candidate genes affecting sleep, we assayed 136 isogenic P-element insertion lines of Drosophila melanogaster. Since sleep has been negatively correlated with energy reserves across taxa, we measured energy stores (whole-body protein, glycogen, and triglycerides) in these lines as well. Twenty-one insertions with known effects on physiology, development, and behavior affect 24-hr sleep time. Thirty-two candidate insertions significantly impact energy stores. Mutational genetic correlations among sleep parameters revealed that the genetic basis of the transition between sleep and waking states in males and females may be different. Furthermore, sleep bout number can be decoupled from waking activity in males, but not in females. Significant genetic correlations are present between sleep phenotypes and glycogen stores in males, while sleep phenotypes are correlated with triglycerides in females. Differences observed in male and female sleep behavior in flies may therefore be related to sex-specific differences in metabolic needs. Sleep thus emerges as a complex trait that exhibits extensive pleiotropy and sex specificity. The large mutational target that we observed implicates genes functioning in a variety of biological processes, suggesting that sleep may serve a number of different functions rather than a single purpose. DA - 2008/4// PY - 2008/4// DO - 10.1534/genetics.107.081232 VL - 178 IS - 4 SP - 2341-2360 SN - 1943-2631 ER - TY - JOUR TI - Continuous copolymerization of vinylidene fluoride with hexafluoropropylene in Supercritical carbon dioxide: High-hexafluoropropylene-content amorphous copolymers AU - Ahmed, Tamer S. AU - DeSimone, Joseph M. AU - Roberts, George W. T2 - MACROMOLECULES AB - Copolymerization of vinylidene fluoride (VF2) and hexafluoropropylene (HFP) was carried out in supercritical carbon dioxide using a continuous stirred tank reactor. Three different HFP/VF2 molar feed ratios were studied, 59:41, 66:34, and 73:27, giving rise to amorphous copolymers containing about 23, 26, and 30 mol % HFP, respectively. The experiments were carried out at 40 °C with pressures in the range of 207–400 bar using perfluorobutyryl peroxide as the free radical initiator. Depending on the copolymer composition, the molecular weight, and the reaction pressure, either a homogeneous (solution) or a heterogeneous (precipitation) polymerization was observed. The effects of feed monomer concentration and reaction pressure were explored at otherwise constant conditions. The rate of polymerization (Rp) and the number-average molecular weight (Mn) increased linearly with the total monomer concentration, independent of the mode of polymerization, i.e., homogeneous or heterogeneous. Both Rp and Mn increased by about 20–30% when the reaction pressure was increased from 207 to 400 bar. This increase could be accounted for by the effect of pressure on the reaction rate constants. The molecular weight distributions were perfectly unimodal except for the lowest HFP-content copolymers at the highest monomer concentrations. The data suggest that the carbon-dioxide-rich fluid phase is the main locus of polymerization, even when the polymer precipitates during the reaction. DA - 2008/5/13/ PY - 2008/5/13/ DO - 10.1021/ma702526u VL - 41 IS - 9 SP - 3086-3097 SN - 0024-9297 ER - TY - JOUR TI - A novel polymer composite with double positive-temperature-coefficient transitions: effect of filler-matrix interface on the resistivity-temperature behavior AU - Zhang, Xiangwu AU - Pan, Yi T2 - POLYMER INTERNATIONAL AB - Abstract BACKGROUND: Sn–Pb alloy‐filled high‐density polyethylene (HDPE) composites exhibit double positive‐temperature‐coefficient (PTC) behavior, with the first transition at the melting point of HDPE and the second at that of Sn–Pb alloy. The objective of this study is to improve the reversibility and reproducibility of double‐PTC transitions of these composite materials by enhancing the filler–matrix interface. RESULTS: Fourier transform infrared spectroscopy, surface wettability and dynamic mechanical and rheological measurements confirm that surface‐treating Sn–Pb with titanate concentration ≤1 wt% enhances the interface adhesion between Sn–Pb alloy and HDPE matrix. Surface‐treating Sn–Pb with titanate concentration ≤1 wt% increases the PTC transition temperature, reduces the PTC intensity and improves the reversibility and reproducibility of the double‐PTC behavior of Sn–Pb/HDPE composites. CONCLUSION: It is demonstrated that adjusting the filler–matrix interface is an effective means to modify the double‐PTC behavior of Sn–Pb alloy‐filled HDPE composites. Copyright © 2007 Society of Chemical Industry DA - 2008/5// PY - 2008/5// DO - 10.1002/pi.2408 VL - 57 IS - 5 SP - 770-777 SN - 0959-8103 UR - https://publons.com/publon/7178348/ KW - positive temperature coefficient KW - alloy KW - polyethylene KW - composite KW - surface treatment KW - interface ER - TY - JOUR TI - Shape-specific, monodisperse nano-molding of protein particles AU - Kelly, Jennifer Y. AU - DeSimone, Joseph M. T2 - JOURNAL OF THE AMERICAN CHEMICAL SOCIETY AB - Herein we report nano-molding proteins for the fabrication of protein PRINT particles of monodisperse size and shape. Lyophilized protein particles are generally highly dispersed in particle size, aggregated, and often made through costly and complicated processes. Attempts to engineer monodisperse, discrete protein particles using wet-milling, spray−freeze−drying, microemulsion, or super critical fluid methods have realized little success. The PRINT technology enables a gentle, facile route to monodisperse particles of 100% protein as small as 200 nm cylinders. Protein PRINT particles of any shape and size are effortlessly achievable. Our research efforts include making PRINT particles composed of albumin and albumin 0.5 wt % siRNA, and Abraxane, the gold standard therapeutic used in metastatic breast cancer. DA - 2008/4/23/ PY - 2008/4/23/ DO - 10.1021/ja8014428 VL - 130 IS - 16 SP - 5438-+ SN - 0002-7863 ER - TY - PAT TI - Refractory metal-based electrodes for work function setting in semiconductor devices AU - Colombo, L. AU - Chambers, J. J. AU - Visokay, M. R. C2 - 2008/// DA - 2008/// PY - 2008/// ER - TY - JOUR TI - Preparation and characterization of composite electrolytes based on PEO(375)-grafted fumed silica AU - Zhang, Hanjun AU - Maitra, Prithwiraj AU - Wunder, Stephanie L. T2 - SOLID STATE IONICS AB - Recent developments in polymer electrolytes have focused on preparation of composites using nano/micron size ceramic particles such as SiO2, TiO2, Al2O3, BaTiO3, and MgO. We report here the preparation and characterization of an all-solid state polyethylene oxide (PEO) composite electrolyte from PEO(375)–SiO2, high molecular weight PEO (MW = 600 K) and LiClO4 (O/Li = 16/1). Oligomeric PEOs, with ethylene oxide (EO) repeat units 6–9 ( = 375 g/mol), were chemically grafted (~ 30 wt.%) to fumed silica (A380) using a trimethoxy PEO(375)-silane. The surface grafted PEO chains were disordered (no crystallization) and less mobile than the free chains, with the glass transition temperature (Tg) increasing from − 90 °C [PEO(375)-silane] to − 54 °C [PEO(375)–SiO2]; addition of LiClO4 (O/Li = 8/1) further raised Tg to − 34 °C. Nanocomposite electrolytes with good dimensional stability were obtained by blending 14-wt.% PEO(375)–SiO2 with semicrystalline PEO(600 K)/LiClO4 (O/Li = 16/1). Conductivities (σ) were 10 to 4 times greater [between 10 °C (σ = 2.1 × 10− 8 S/cm) and 40 °C (σ = 1.1 × 10− 5 S/cm), respectively] than for neat PEO(600 K) or for composite electrolytes having the same amount of native fumed silica, SiO2. No conductivity improvements were observed above Tm or for amorphous PEO(600 K)/LiClO4 (O/Li = 8/1) with addition of SiO2 or PEO(375)–SiO2. DA - 2008/3/15/ PY - 2008/3/15/ DO - 10.1016/j.ssi.2007.11.021 VL - 178 IS - 39-40 SP - 1975-1983 SN - 1872-7689 KW - solid polymer electrolyte KW - PEO-based solid polymer electrolyte KW - inorganic oxide/PEO-based polymer electrolyte ER - TY - JOUR TI - Phase diagram for stimulus-responsive materials containing dipolar colloidal particles AU - Goyal, Amit AU - Hall, Carol K. AU - Velev, Orlin D. T2 - PHYSICAL REVIEW E AB - Dipolar colloidal particles self-assemble into a rich variety of microstructures ranging from co-crystals of unusual symmetry, to open networks (gels) of cross-linked chains of particles. We use molecular dynamics computer simulation to explore the self-assembly, structure, crystallization and/or gelation of systems of colloid particles with permanent dipole moments immersed in a high-dielectric solvent. Particle-particle interactions are modeled with a discontinuous potential. The phase diagram in the temperature-packing fraction plane is calculated. Several types of phases are found in our simulations: ordered phases including face-centered-cubic, hexagonal-close-packed, and body-centered-tetragonal at high packing fractions, and fluid, string-fluid, and gel phases at low packing fractions. The very low volume fraction gel phases and the well-ordered crystal phases are promising for advanced materials applications. DA - 2008/3// PY - 2008/3// DO - 10.1103/physreve.77.031401 VL - 77 IS - 3 SP - SN - 1550-2376 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-40949099020&partnerID=MN8TOARS ER - TY - JOUR TI - On-chip electric field driven assembly of biocomposites from live cells and functionalized particles AU - Gupta, S. AU - Alargova, R.G. AU - Kilpatrick, P.K. AU - Velev, Orlin T2 - Soft Matter AB - Live cells and surface-functionalized synthetic microparticles are co-assembled on electrically controlled chips to yield permanent chains and one cell layer thick membranes that can be freely manipulated in external magnetic fields. DA - 2008/// PY - 2008/// DO - 10.1039/b717850f VL - 4 IS - 4 SP - 726-730 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-41149160380&partnerID=MN8TOARS ER - TY - JOUR TI - Molecular simulation study of temperature effect on ionic hydration in carbon nanotubes AU - Shao, Qing AU - Huang, Liangliang AU - Zhou, Jian AU - Lu, Linghong AU - Zhang, Luzheng AU - Lu, Xiaohua AU - Jiang, Shaoyi AU - Gubbins, Keith E. AU - Shen, Wenfeng T2 - PHYSICAL CHEMISTRY CHEMICAL PHYSICS AB - Molecular dynamics simulations have been performed to investigate the hydration of Li+, Na+, K+, F−, and Cl− inside the carbon nanotubes at temperatures ranging from 298 to 683 K. The structural characteristics of the coordination shells of ions are studied, including the ion-oxygen radial distribution functions, the coordination numbers, and the orientation distributions of the water molecules. Simulation results show that the first coordination shells of the five ions still exist in the nanoscale confinement. Nevertheless, the first coordination shell structures of cations change more significantly than those of anions because of the preferential orientation of the water molecules induced by the carbon nanotube. The first coordination shells of cations are considerably less ordered in the nanotube than in the bulk solution, whereas the change of the first coordination shell structures of the anions is minor. Furthermore, the confinement induces the anomalous behavior of the coordination shells of the ions with temperature. The first coordination shell of K+ are found to be more ordered as the temperature increases only in the carbon nanotube with the effective diameter of 1.0 nm, implying the enhancement of the ionic hydration with temperature. This is contrary to that in the bulk solution. The coordination shells of the other four ions do not have such behavior in the carbon nanotube with the effective diameter ranging from 0.73 to 1.00 nm. The easier distortion of the coordination shell of K+ and the match of the shell size and the nanotube size may play roles in this phenomenon. The exchange of water molecules in the first coordination shells of the ions with the solution and the ion diffusion along the axial direction of the nanotube are also investigated. The mobility of the ions and the stability of the coordination shells are greatly affected by the temperature in the nanotube as in the bulk solutions. These results help to understand the biological and chemical processes at the high temperature. DA - 2008/// PY - 2008/// DO - 10.1039/b719033f VL - 10 IS - 14 SP - 1896-1906 SN - 1463-9076 ER - TY - PAT TI - Method for controlling defects in gate dielectrics AU - Colombo, L. AU - Chambers, J. J. AU - Visokay, M. R. AU - Rotondo, A. L. C2 - 2008/// DA - 2008/// PY - 2008/// ER - TY - JOUR TI - Design approaches for a cycling adsorbent/photocatalyst system for moor air purification: Formaldehyde example AU - Chin, Paul AU - Ollis, David F. T2 - JOURNAL OF THE AIR & WASTE MANAGEMENT ASSOCIATION AB - A kinetic model for a cycling adsorbent/photocatalyst combination for formaldehyde removal in indoor air (Chin et al. J. Catalysis 2006, 237, 29-37) was previously developed in our lab, demonstrating agreement with lab-scale batch operation data of other researchers (Shiraishi et al. Chem. Engineer. Sci. 2003, 58, 929-934). Model parameters evaluated included adsorption equilibrium and rate constants for the adsorbent (activated carbon) honeycomb rotor, and catalytic rate constant for pseudo-first-order formaldehyde destruction in the titanium dioxide photoreactor. This paper explores design consequences for this novel system. In particular, the batch parameter values are used to model both adsorbent and photocatalyst behavior for continuous operation in typical residential home challenges. Design variables, including realistic make-up air fraction, adsorbent honeycomb rotation speed, and formaldehyde source emission rate, are considered to evaluate the ability of the system to achieve World Health Organization pollutant guidelines. In all circumstances, the size of the required rotating adsorbent bed and photoreactor for single-stage operation and the resultant formaldehyde concentration in the home are calculated. The ability of how well such a system might be accommodated within the typical dimensions of commercial ventilation ducts is also considered. DA - 2008/4// PY - 2008/4// DO - 10.3155/1047-3289.58.4.494 VL - 58 IS - 4 SP - 494-501 SN - 1047-3289 ER - TY - JOUR TI - p-aminophenol synthesis in an organic/aqueous system using Pt supported on mesoporous carbons AU - Min, Kyung-Il AU - Choi, Jung-Sik AU - Chung, Young-Min AU - Ahn, Wha-Seung AU - Ryoo, Ryong AU - Lim, P. K. T2 - APPLIED CATALYSIS A-GENERAL AB - The biphasic conversion of nitrobenzene to p-aminophenol (PAP) via Pt/C-catalyzed hydrogenation of nitrobenzene and an acid-catalyzed rearrangement of the N-phenylhydroxylamine intermediate was studied. The effects of Pt/C catalyst loading, type of carbon support, reaction temperature, acid catalyst concentration, and additives on the reaction rate and PAP selectivity were investigated. At a given catalyst loading, nitrobenzene conversion and PAP selectivity were favored under a high reaction temperature and a high aqueous acid concentration. An increase in Pt/C catalyst loading leads to an increased hydrogenation rate but a lower PAP selectivity. Nitrobenzene conversion and PAP selectivity are both promoted by a small addition of N,N-dimethyl-n-dodecylamine, which may act as a phase transfer agent or emulsifier. Pt catalysts supported on novel mesoporous carbons – CMK-1 and CMK-3, which have uniform pore diameters of 3 and 4.5 nm – significantly outperform their counterpart supported on activated carbon with micropores. Two percent Pt/CMK-1 shows a catalytic activity equivalent to that of 5% Pt/C, but with significantly better PAP selectivity, i.e., 84% compared to 72%. DA - 2008/3/15/ PY - 2008/3/15/ DO - 10.1016/j.apcata.2007.12.004 VL - 337 IS - 1 SP - 97-104 SN - 0926-860X KW - nitrobenzene hydrogenation KW - p-aminophenol KW - biphasic KW - mesoporous carbon KW - acid-catalyzed rearrangement ER - TY - JOUR TI - Solvent-induced stresses during sorption in glassy polycarbonate: Experimental analysis and model simulation for a novel bending cantilever apparatus AU - Ferrari, Maria-Chiara AU - Piccinini, Enrico AU - Baschetti, Marco Giacinti AU - Doghieri, Ferruccio AU - Sarti, Giulio C. T2 - INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH AB - A new experimental apparatus has been set up to analyze the polymer dilation as well as the stress profile induced by vapor sorption in constrained films. The device couples the bending cantilever technique with a new digital micrometer, which allows one to measure both deflection and polymer swelling at the same time. The apparatus has been applied to study the effects of acetonitrile mass uptake in polycarbonate at 40 °C, obtaining the time evolution of swelling and of cantilever deflection during integral sorption tests, in the activity range from 0 up to 0.35. A simulation model is also proposed, which couples Fick's law for diffusion to the study of strain and stress distributions in the cantilever; the mechanical problem has been formulated following the classical laminate theory. The relevant values of the material properties entering the model, such as solubility, diffusivity, and penetrant induced dilation, have all been determined through separate independent measurements, and the results obtained are in good agreement with the corresponding values reported in the literature. The simulation model is able to predict with good precision both the kinetics of deflection during sorption and its final equilibrium value, as well as the overall swelling kinetics, with no need of any adjustable parameters. The model also allows one to calculate the time evolution of the stress profile in the polymer film during sorption/desorption steps. DA - 2008/2/20/ PY - 2008/2/20/ DO - 10.1021/ie071084o VL - 47 IS - 4 SP - 1071-1080 SN - 0888-5885 ER - TY - PAT TI - Optimized ultraviolet reflecting multi-layer coating for energy efficient lamps AU - Chowdhury, A. I. AU - Israel, R. AU - Allen, G. R. C2 - 2008/// DA - 2008/// PY - 2008/// ER - TY - JOUR TI - Functional-genomics-based identification and characterization of open reading frames encoding alpha-glucoside-processing enzymes in the hyperthermophilic archaeon Pyrococcus furiosus AU - Comfort, Donald A. AU - Chou, Chung-Jung AU - Conners, Shannon B. AU - VanFossen, Amy L. AU - Kelly, Robert M. T2 - APPLIED AND ENVIRONMENTAL MICROBIOLOGY AB - ABSTRACT Bioinformatics analysis and transcriptional response information for Pyrococcus furiosus grown on α-glucans led to the identification of a novel isomaltase (PF0132) representing a new glycoside hydrolase (GH) family, a novel GH57 β-amylase (PF0870), and an extracellular starch-binding protein (1,141 amino acids; PF1109-PF1110), in addition to several other putative α-glucan-processing enzymes. DA - 2008/2// PY - 2008/2// DO - 10.1128/AEM.01920-07 VL - 74 IS - 4 SP - 1281-1283 SN - 1098-5336 ER - TY - JOUR TI - Diffusion dynamics of water controlled by topology of potential energy surface inside carbon nanotubes AU - Liu, Ying-Chun AU - Shen, Jia-Wei AU - Gubbins, Keith E. AU - Moore, Joshua D. AU - Wu, Tao AU - Wang, Qi T2 - PHYSICAL REVIEW B AB - The effect of topology of single-walled carbon nanotubes (CNTs) on the diffusion dynamics of water confined in the armchair and zigzag CNTs was investigated. It was found that the activation energy of molecular diffusion in zigzag CNTs is greater than that in armchair ones at similar diameters, which leads to water molecules in zigzag CNT diffusing much slower than in armchair CNT. Further calculations of potential energy surfaces (PESs) of water in these two types of CNTs explain the mechanism of diffusion dynamics of confined water. This research shows that the topology of PESs inside CNT could control the diffusion behaviors of water inside it. Since topology of PESs inside CNT could be modified by various chemical and/or physical methods, this work indicates the possibility of controlling the diffusion behaviors inside the CNTs by molecular engineering approach, without changing its pore size. DA - 2008/3// PY - 2008/3// DO - 10.1103/physrevb.77.125438 VL - 77 IS - 12 SP - SN - 2469-9969 ER - TY - JOUR TI - The genome sequence of the metal-mobilizing, extremely thermoacidophilic archaeon Metallosphaera sedula provides insights into bioleaching-associated metabolism AU - Auernik, Kathryne S. AU - Maezato, Yukari AU - Blum, Paul H. AU - Kelly, Robert M. T2 - APPLIED AND ENVIRONMENTAL MICROBIOLOGY AB - ABSTRACT Despite their taxonomic description, not all members of the order Sulfolobales are capable of oxidizing reduced sulfur species, which, in addition to iron oxidation, is a desirable trait of biomining microorganisms. However, the complete genome sequence of the extremely thermoacidophilic archaeon Metallosphaera sedula DSM 5348 (2.2 Mb, ∼2,300 open reading frames [ORFs]) provides insights into biologically catalyzed metal sulfide oxidation. Comparative genomics was used to identify pathways and proteins involved (directly or indirectly) with bioleaching. As expected, the M. sedula genome contains genes related to autotrophic carbon fixation, metal tolerance, and adhesion. Also, terminal oxidase cluster organization indicates the presence of hybrid quinol-cytochrome oxidase complexes. Comparisons with the mesophilic biomining bacterium Acidithiobacillus ferrooxidans ATCC 23270 indicate that the M. sedula genome encodes at least one putative rusticyanin, involved in iron oxidation, and a putative tetrathionate hydrolase, implicated in sulfur oxidation. The fox gene cluster, involved in iron oxidation in the thermoacidophilic archaeon Sulfolobus metallicus , was also identified. These iron- and sulfur-oxidizing components are missing from genomes of nonleaching members of the Sulfolobales , such as Sulfolobus solfataricus P2 and Sulfolobus acidocaldarius DSM 639. Whole-genome transcriptional response analysis showed that 88 ORFs were up-regulated twofold or more in M. sedula upon addition of ferrous sulfate to yeast extract-based medium; these included genes for components of terminal oxidase clusters predicted to be involved with iron oxidation, as well as genes predicted to be involved with sulfur metabolism. Many hypothetical proteins were also differentially transcribed, indicating that aspects of the iron and sulfur metabolism of M. sedula remain to be identified and characterized. DA - 2008/2// PY - 2008/2// DO - 10.1128/AEM.02019-07 VL - 74 IS - 3 SP - 682-692 SN - 1098-5336 ER - TY - JOUR TI - Surface-guided templating of particle assemblies inside drying sessile droplets AU - Kuncicky, Daniel M. AU - Velev, Orlin D. T2 - LANGMUIR AB - The particles suspended inside evaporating sessile droplets can be assembled into microscopic objects with long-ranged ordered structure. The air−water droplet interface guides the assembly and determines the shape of the resulting micropatches. We report the results of a systematic study of the mechanism of interface-templated assembly on substrates of controlled contact angle. The kinetics of drying were examined by measurements of droplet profiles, and it was found that the rate matched diffusion-limited evaporation well. The shape of the droplets and of the resulting assemblies was correlated to the dynamics of the receding contact line. The effects of major parameters controlling the process, including contact angle, particle concentration, and electrolyte, were investigated in detail. A variety of micropatch shapes were observed and categorized within the parameter space. The in-depth characterization of the process allowed the optimization of the assembly and the formulation of protocols for the deposition of nanostructured patches of different diameter, thickness, and shape. DA - 2008/2/19/ PY - 2008/2/19/ DO - 10.1021/la702129b VL - 24 IS - 4 SP - 1371-1380 SN - 0743-7463 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-40449101377&partnerID=MN8TOARS ER - TY - JOUR TI - Preparation and characterization of silica nanoparticulate-polyacrylonitrile composite and porous nanofibers AU - Ji, Liwen AU - Saquing, Carl AU - Khan, Saad A. AU - Zhang, Xiangwu T2 - NANOTECHNOLOGY AB - In this study, polyacrylonitrile (PAN) composite nanofibers containing different amounts of silica nanoparticulates have been obtained via electrospinning. The surface morphology, thermal properties and crystal structure of PAN/silica nanofibers are characterized using attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy, wide-angle x-ray diffraction (WAXD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and differential scanning calorimetry (DSC). The results indicate that the addition of silica nanoparticulates affects the structure and properties of the nanofibers. In addition to PAN/silica composite nanofibers, porous PAN nanofibers have been prepared by selective removal of the silica component from PAN/silica composite nanofibers using hydrofluoric (HF) acid. ATR-FTIR and thermal gravimetric analysis (TGA) experiments validate the removal of silica nanoparticulates by HF acid, whereas SEM and TEM results reveal that the porous nanofibers obtained from composite fibers with higher silica contents exhibited more nonuniform surface morphology. The Brunauer–Emmett–Teller (BET) surface area of porous PAN nanofibers made from PAN/silica (5 wt%) composite precursors is higher than that of pure nonporous PAN nanofibers. DA - 2008/2/27/ PY - 2008/2/27/ DO - 10.1088/0957-4484/19/8/085605 VL - 19 IS - 8 SP - SN - 1361-6528 UR - https://publons.com/publon/7178323/ ER - TY - JOUR TI - Importance of solution chemistry in preparing sol-gel PZT thin films directly on copper surfaces AU - Losego, Mark D. AU - Ihlefeld, Jon F. AU - Maria, Jon-Paul T2 - CHEMISTRY OF MATERIALS AB - The ferroelectric material lead zirconate titanate (PZT) has traditionally been considered incompatible with base metal technology because PbO volatility makes conventional thermodynamic equilibrium processing impractical. However, by strategically designing solution chemistry and processing conditions to avoid interfacial reaction, chemical-solution-deposited PZT films can be prepared on copper surfaces without oxidizing the base metal or cracking the oxide film. A limited set of thermal and atmospheric processing conditions to kinetically maintain an unoxidized copper substrate are available and not necessarily optimal for processing sol–gel films. Solutions processed within these confined conditions must form gels with sufficiently reduced organic content and properly consolidated gel networks such that phase-pure and crack-free ceramic films can be crystallized. The current work explores three solution chemistries that use different chelating ligands: alkanolamines, acetylactone, and acetic acid. It is found that the alkanolamine solution frustrates perovskite formation and is prone to cracking under processing conditions compatible with the copper substrate. The introduction of water vapor into the processing atmosphere is moderately successful in resolving these issues. Using a more volatile chelating ligand (acetylacetone or acetic acid) shifts the thermal process window nearer a copper-compatible regime. Because of its weaker chelation strength, acetic acid solutions are most compatible with the processing constraints required for copper substrate compatibility. DA - 2008/1/8/ PY - 2008/1/8/ DO - 10.1021/cm070999q VL - 20 IS - 1 SP - 303-307 SN - 0897-4756 ER - TY - JOUR TI - First International Conference on Biomolecular Engineering (ICBE) AU - DeLisa, M. AU - Haugh, J. T2 - Biotechnology Progress DA - 2008/// PY - 2008/// VL - 24 IS - 1 SP - 1-1 ER - TY - JOUR TI - Alternative fluoropolymers to avoid the challenges associated with perfluorooctanoic acid AU - Guo, Ji AU - Resnick, Paul AU - Efimenko, Kirill AU - Genzer, Jan AU - DeSimone, Joseph M. T2 - INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH AB - The degradation of stain-resistant coating materials leads to the release of biopersistent perfluorooctanoic acid (PFOA) to the environment. In order to find the environmentally friendly substitutes, we have designed and synthesized a series of nonbiopersistant fluorinated polymers containing perfluorobutyl groups in the side chains. The surface properties of the new coating materials were characterized by static and dynamic contact angle measurements. The new coating materials demonstrate promising hydrophobic and oleophobic properties with low surfaces tensions. The wetting properties and surface structure of the polymers were tuned by varying the “spacer” structures between the polymer backbones and the perfluorinated groups of the side chains. The relationship between orientations of the fluorinated side chains and performances of polymer surfaces were further investigated by near-edge X-ray fine absorption structure (NEXAFS) experiments and differential scanning calorimetry (DSC). DA - 2008/2/6/ PY - 2008/2/6/ DO - 10.1021/ie0703179 VL - 47 IS - 3 SP - 502-508 SN - 0888-5885 ER - TY - JOUR TI - Probing the stability of native and activated forms of alpha(2)-macroglobulin AU - Kaczowka, Steven J. AU - Madding, Lara S. AU - Epting, Kevin L. AU - Kelly, Robert M. AU - Cianciolo, George J. AU - Pizzo, Salvatore V. T2 - INTERNATIONAL JOURNAL OF BIOLOGICAL MACROMOLECULES AB - α2-Macroglobulin (α2M) is a 718 kDa homotetrameric proteinase inhibitor which undergoes a large conformational change upon activation. This conformational change can occur either by proteolytic attack on an ∼40 amino acid stretch, the bait region, which results in the rupture of the four thioester bonds in α2M, or by direct nucleophilic attack on these thioesters by primary amines. Amine activation circumvents both bait region cleavage and protein incorporation, which occurs by proteolytic activation. These different activation methods allow for examination of the roles bait region cleavage and thioester rupture play in α2M stability. Differential scanning calorimetry and urea gel electrophoresis demonstrate that both bait region cleavage and covalent incorporation of protein ligands in the thioester pocket play critical roles in the stability of α2M complexes. DA - 2008/1/1/ PY - 2008/1/1/ DO - 10.1016/j.ijbiomac.2007.09.019 VL - 42 IS - 1 SP - 62-67 SN - 0141-8130 KW - alpha M-2 KW - alpha(2)-macroglobulin KW - alpha(2)-macroglobulin and proteinase incorporation KW - alpha(2)-macroglobulin and norproteolytic incorporation of lysozyme KW - alpha(2)-macroglobulin stabilization ER - TY - JOUR TI - Epitaxial growth of the metastable phase ytterbium monoxide on gallium nitride surfaces AU - Losego, Mark D. AU - Mita, Seiji AU - Collazo, Ramon AU - Sitar, Zlatko AU - Maria, Jon-Paul T2 - JOURNAL OF CRYSTAL GROWTH AB - Molecular beam deposition systems allow for unparalleled control of film composition and structure. This article addresses the capacity for controlling metal and oxidant fluxes in the Yb/O2 system to access the metastable phase ytterbium monoxide (YbO). Experiments exploring the growth of polycrystalline YbOx films by molecular beam deposition demonstrate that a 2:1 molar ratio of Yb:O2 fluxes is necessary to achieve preferential growth of the divalent oxide. Applying similar deposition conditions to a (0 0 1) GaN surface leads to the growth of epitaxial (1 1 1) YbO films. Similar to other rocksalt oxides grown on GaN surfaces, YbO films display a 3D growth mechanism that leads to a grainy morphology with crystallites of 50 nm lateral dimensions. Rocking curves in ω and φ have full-width half-maximum values of 1.77° and 4.1°, respectively; further improvements in crystal quality appear to be limited by the thermal stability of the YbO phase. DA - 2008/1/4/ PY - 2008/1/4/ DO - 10.1016/j.jcrysgro.2007.10.002 VL - 310 IS - 1 SP - 51-56 SN - 0022-0248 KW - phase equilibria KW - molecular beam epitaxy KW - metastable compounds KW - oxides KW - rare earth compounds KW - ytterbium monoxide ER - TY - JOUR TI - A remarkable shape-catalytic effect of confinement on the rotational isomerization of small hydrocarbons AU - Santiso, Erik E. AU - Nardelli, Marco Buongiorno AU - Gubbins, Keith E. T2 - JOURNAL OF CHEMICAL PHYSICS AB - As part of an effort to understand the effect of confinement by porous carbons on chemical reactions, we have carried out density functional theory calculations on the rotational isomerization of three four-membered hydrocarbons: n-butane, 1-butene, and 1,3-butadiene. Our results show that the interactions with the carbon walls cause a dramatic change on the potential energy surface for pore sizes comparable to the molecular dimensions. The porous material enhances or hinders reactions depending on how similar is the shape of the transition state to the shape of the confining material. The structure of the stable states and their equilibrium distributions are also drastically modified by confinement. Our results are consistent with a doubly exponential behavior of the reaction rates as a function of pore size, illustrating how the shape of a catalytic support can dramatically change the efficiency of a catalyst. DA - 2008/1/21/ PY - 2008/1/21/ DO - 10.1063/1.2819238 VL - 128 IS - 3 SP - SN - 1089-7690 ER - TY - JOUR TI - Sensory irritation response in rats: Modeling, analysis and validation AU - Yokley, Karen A. AU - Tran, Hien AU - Schlosser, Paul M. T2 - BULLETIN OF MATHEMATICAL BIOLOGY DA - 2008/2// PY - 2008/2// DO - 10.1007/s11538-007-9268-z VL - 70 IS - 2 SP - 555-588 SN - 0092-8240 KW - sensory response KW - PBPK KW - formaldehyde ER - TY - JOUR TI - Direct utilization of carbon dioxide in chemical synthesis: Vinyl acetate via methane carboxylation AU - Spivey, James J. AU - Wilcox, Esther M. AU - Roberts, George W. T2 - CATALYSIS COMMUNICATIONS AB - The use of CO2 as a reactant for chemical synthesis generally is limited by the unfavorable equilibrium that results from the large, negative free energy of formation of CO2. Here, we report the direct catalytic synthesis of vinyl acetate from an equimolar gaseous mixture of CO2 + CH4 + C2H2 at 1 atm and temperatures between 200 and 400 °C. We are not aware of any previous reports of this reaction, which appears to proceed in two steps: (1) acetic acid is formed by the reaction of CO2 and CH4; (2) acetic acid then reacts with acetylene to form vinyl acetate. The formation of acetic acid from CO2 and CH4 is very unfavorable thermodynamically. However, the reaction of acetic acid with acetylene shifts the overall equilibrium to the right. Although 5% Pt/Al2O3 catalyzes the formation of vinyl acetate from the mixture of CO2 + CH4 + C2H2, the most effective catalyst system is an admixture of 5% Pt/Al2O3, which has been shown to catalyze the direct formation of acetic acid from CH4 + CO2, and Zn acetate/carbon, which is known to catalyze the formation of vinyl acetate from acetic acid and acetylene. DA - 2008/3/20/ PY - 2008/3/20/ DO - 10.1016/j.catcom.2007.08.023 VL - 9 IS - 5 SP - 685-689 SN - 1566-7367 ER - TY - JOUR TI - Defect chemistry of nano-grained barium titanate films AU - Ihlefeld, Jon F. AU - Losego, Mark D. AU - Collazo, Ramon AU - Borland, William J. AU - Maria, Jon-Paul T2 - JOURNAL OF MATERIALS SCIENCE DA - 2008/1// PY - 2008/1// DO - 10.1007/s10853-007-2135-3 VL - 43 IS - 1 SP - 38-42 SN - 1573-4803 ER - TY - JOUR TI - Spectroscopic analysis of poly(bisphenol A carbonate) using high resolution C-13 and H-1 NMR AU - Kim, Jaehoon AU - Gracz, Hanna S. AU - Roberts, George W. AU - Kiserow, Douglas J. T2 - POLYMER AB - Quantitative structural and end-group analysis of poly(bisphenol A carbonate) (BPA-PC) was carried out and number average molecular weights (Mn) were determined using 125.76 MHz 13C and 500.13 MHz 1H nuclear magnetic resonance (NMR) spectroscopy. BPA-PC with a wide range of end-group ratios (0.26–2.83) and number average molecular weights (1500–9000 g/mol) was synthesized using melt transesterification by changing the initial monomer (bisphenol A and diphenyl carbonate) ratios and reaction conditions. Results of the NMR analysis for the melt-polymerized samples were compared with those of a commercial BPA-PC with a Mn of 16,000 g/mol. It was demonstrated that NMR spectroscopy is a very selective and accurate method not only for quantification of both phenolic and phenyl chain end-groups but also in the structural analysis of main chain groups. Extremely small concentrations of end-groups (∼0.02 per repeating unit) were analyzed. In addition, NMR spectroscopy was found to be an excellent tool for detecting residual monomer and the presence of the reaction byproduct (phenol). The molecular weights that were determined using NMR end-group quantification agreed well with the molecular weights measured by gel-permeation chromatography (GPC). DA - 2008/1/21/ PY - 2008/1/21/ DO - 10.1016/j.polymer.2007.11.046 VL - 49 IS - 2 SP - 394-404 SN - 0032-3861 KW - poly(bisphenol A carbonate) KW - end-group analysis KW - NMR spectroscopy ER - TY - JOUR TI - Solubilizing amino acids and polypeptides in supercritical CO2 via reverse micelle formation AU - Soriano, Nestor U., Jr. AU - Venditti, Richard AU - Saquing, Carl D. AU - Bushey, Dean AU - Argyropoulos, Dirnitris S. T2 - COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS AB - Water-in-CO2 reverse micelles stabilized by ionic perfluoroalkyl and non-ionic perfluoropolyether surfactants were used to host amino acids and polypeptides in supercritical (SC) CO2. The minimum pressure at which micellization occurs (Ptrans) was found to be affected by the surfactant concentration and H2O/CO2 ratio. Due to the differences in hydrophilic/CO2 balance, the two surfactants exhibited different phase behaviors at 19.3 MPa and 40 °C. At certain H2O/CO2/surfactant compositions, while coagulation was more evident when using perfluoroalkyl surfactant, flocculation was found to dominate the system containing perfluoropolyether surfactant. The presence of amino acid and polypeptide in reverse micelles was found to increase the Ptrans of the system due to enthalpic and entropic changes. In perfluoroalkyl reverse micelles, the Ptrans was found to increase with increasing hydrophilicity of the amino acid added. The presence of hydrophobic moieties in amino acids promotes interfacial solubilization that eventually resulted in lower Ptrans. On the other hand, the nature of the amino acid was not found to affect Ptrans in perfluoropolyether reverse micelle. Overall, this work demonstrates that polypeptides with varying molecular weight could be solubilized in water-in-CO2 reverse micelles using perfluoropolyether while perfluoroakyl surfactants were ineffective. DA - 2008/2/15/ PY - 2008/2/15/ DO - 10.1016/j.colsurfa.2007.07.019 VL - 315 IS - 1-3 SP - 110-116 SN - 1873-4359 KW - amino acid KW - fluorinated surfactant KW - polypeptide KW - reverse micelle KW - supercritical carbon dioxide ER - TY - JOUR TI - Remotely powered distributed microfluidic pumps and mixers based on miniature diodes AU - Chang, Suk Tai AU - Beaumont, Erin AU - Petsev, Dimiter N. AU - Velev, Orlin D. T2 - LAB ON A CHIP AB - We demonstrate new principles of microfluidic pumping and mixing by electronic components integrated into a microfluidic chip. The miniature diodes embedded into the microchannel walls rectify the voltage induced between their electrodes from an external alternating electric field. The resulting electroosmotic flows, developed in the vicinity of the diode surfaces, were utilized for pumping or mixing of the fluid in the microfluidic channel. The flow velocity of liquid pumped by the diodes facing in the same direction linearly increased with the magnitude of the applied voltage and the pumping direction could be controlled by the pH of the solutions. The transverse flow driven by the localized electroosmotic flux between diodes oriented oppositely on the microchannel was used in microfluidic mixers. The experimental results were interpreted by numerical simulations of the electrohydrodynamic flows. The techniques may be used in novel actively controlled microfluidic–electronic chips. DA - 2008/// PY - 2008/// DO - 10.1039/b712108c VL - 8 IS - 1 SP - 117-124 SN - 1473-0189 ER - TY - JOUR TI - Induced-charge electrophoresis of metallodielectric particles AU - Gangwal, S. AU - Cayre, O.J. AU - Bazant, M.Z. AU - Velev, Orlin T2 - Physical Review Letters AB - The application of ac electric fields in aqueous suspensions of anisotropic particles leads to unbalanced liquid flows and nonlinear, induced-charge electrophoretic motion. We report experimental observations of the motion of Janus microparticles with one dielectric and one metal-coated hemisphere induced by uniform fields of frequency 100 Hz-10 kHz in NaCl solutions. The motion is perpendicular to the field axis and persists after particles are attracted to a glass wall. This phenomenon may find applications in microactuators, microsensors, and microfluidic devices. DA - 2008/// PY - 2008/// DO - 10.1103/PhysRevLett.100.058302 VL - 100 IS - 5 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-40049088118&partnerID=MN8TOARS ER - TY - JOUR TI - Characterization of monolayer formation on aluminum-doped zinc oxide thin films AU - Rhodes, Crissy L. AU - Lappi, Simon AU - Fischer, Daniel AU - Sambasivan, Sharadha AU - Genzer, Jan AU - Franzen, Stefan T2 - LANGMUIR AB - The optical and electronic properties of aluminum-doped zinc oxide (AZO) thin films on a glass substrate are investigated experimentally and theoretically. Optical studies with coupling in the Kretschmann configuration reveal an angle-dependent plasma frequency in the mid-IR for p-polarized radiation, suggestive of the detection of a Drude plasma frequency. These studies are complemented by oxygen depletion density functional theory studies for the calculation of the charge carrier concentration and plasma frequency for bulk AZO. In addition, we report on the optical and physical properties of thin film adlayers of n-hexadecanethiol (HDT) and n-octadecanethiol (ODT) self-assembled monolayers (SAMs) on AZO surfaces using reflectance FTIR spectroscopy, X-ray photoelectron spectroscopy (XPS), contact angle, and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. Our characterization of the SAM deposition onto the AZO thin film reveals a range of possible applications for this conducting metal oxide. DA - 2008/1/15/ PY - 2008/1/15/ DO - 10.1021/la701741m VL - 24 IS - 2 SP - 433-440 SN - 0743-7463 ER - TY - JOUR TI - Compressible lattice model for phase equilibria in CO2+polymer systems AU - Kasturirangan, Anupama AU - Grant, Christine AU - Teja, Amyn S. T2 - INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH AB - We present a compressible lattice model for representation of both low-pressure and high-pressure phase equilibria in CO2 + polymer systems. The model explicitly accounts for weak complex formation in these systems, using two parameters that are obtained by fitting experimental cloud point pressures or sorption equilibria. In addition, one of these parameters may be obtained from Fourier transform infrared (FTIR) spectroscopy measurements. We demonstrate the application of this model to the prediction of low-pressure sorption behavior in the CO2 + poly(vinyl acetate) (PVAc) system, using parameters obtained from high-pressure cloud point data. In addition, we show that we are able to predict the sorption behavior of CO2 + PLGA copolymer systems using a single parameter obtained from CO2 + poly(lactic acid) (PLA) cloud point data, together with enthalpies of association obtained from FTIR measurements. DA - 2008/2/6/ PY - 2008/2/6/ DO - 10.1021/ie071061+ VL - 47 IS - 3 SP - 645-649 SN - 0888-5885 ER -