TY - CONF TI - Electrochemical H2S Scrubbing of a Coal Syngas Fuel Stream via SOFCs AU - Cooper, M. AU - Silva, C.De AU - Bayless, D. T2 - ASME 5th International Fuel Cell Science, Engineering & Technology Conference C2 - 2007/// C3 - ASME 5th International Fuel Cell Science, Engineering & Technology Conference CY - New York, NY DA - 2007/// PY - 2007/// ER - TY - CONF TI - Enhanced hydrogen production with integrated carbon capture and sequestration AU - Kim, H.R. AU - Park, A.-H.A. AU - Velazquez-Vargas, L.G. AU - Li, F. AU - Fan, L.-S. C2 - 2007/// C3 - 2007 AIChE Annual Meeting DA - 2007/// UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-58049103718&partnerID=MN8TOARS ER - TY - CONF TI - Chemical looping reforming Ppocess for the production of hydrogen from coal AU - Fan, L.S. AU - Velazquez-Vargas, L.G. AU - Li, F. C2 - 2007/// C3 - ACS National Meeting Book of Abstracts DA - 2007/// UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-37349080664&partnerID=MN8TOARS ER - TY - CONF TI - Exergy analysis on chemical looping reforming process AU - Li, F. AU - Velazquez-Vergas, L.G. AU - Zeng, L. AU - Chen, J. AU - Fan, L.-S. C2 - 2007/// C3 - AIChE Annual Meeting, Conference Proceedings DA - 2007/// UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-80053655723&partnerID=MN8TOARS ER - TY - CONF TI - Enhanced production of liquid fuels by using a syngas chemical looping process AU - Velazquez-Vargas, L.G. AU - Li, F. AU - Sirdar, D. AU - Kim, R. AU - Fan, L.-S. C2 - 2007/// C3 - AIChE Annual Meeting, Conference Proceedings DA - 2007/// UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-80053656406&partnerID=MN8TOARS ER - TY - JOUR TI - Clean coal AU - Fan, L.-S. AU - Li, F. T2 - Physics World DA - 2007/// PY - 2007/// VL - 20 IS - 7 SP - 37-41 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-34547305472&partnerID=MN8TOARS ER - TY - CONF TI - Exergy analysis on chemical looping reforming process AU - Li, F. AU - Velazquez-Vargas, L.G. AU - Zeng, L. AU - Chen, J. AU - Fan, L.-S. C2 - 2007/// C3 - 2007 AIChE Annual Meeting DA - 2007/// UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-58049127071&partnerID=MN8TOARS ER - TY - CHAP TI - Biochemical/Biomolecular engineering AU - Haugh, J.M. AU - Kelly, R.M. T2 - McGraw-Hill encyclopedia of science & technology PY - 2007/// ET - 10th PB - McGraw-Hill SN - 9780071441438 ER - TY - CONF TI - Solar U.V.-Induced Damage Common Polymers. AU - Andrady, Anthony L. T2 - Chemtech 2007 Convention C2 - 2007/7/22/ CY - BMICH Convention Center, Colombo, Sri Lanka DA - 2007/7/22/ PY - 2007/7/22/ ER - TY - CHAP TI - Archaeal 20S Proteasome: A Simple and Thermostable Model System for the Core Particle AU - Michel, Joshua K. AU - Kelly, Robert M. T2 - Thermophiles A2 - Robb, Frank A2 - Antranikian, Garabed A2 - Grogan, Dennis A2 - Driessen, Arnold PY - 2007/12/13/ DO - 10.1201/9781420008852-29 SP - 347–360 PB - CRC Press SN - 9780429118418 UR - http://dx.doi.org/10.1201/9781420008852-29 ER - TY - JOUR TI - Effects of stratospheric ozone depletion and climate change on materials damage AU - Andrady, A. L. AU - Hamid, H. S. AU - Torikai, A. T2 - Photochemical & Photobiological Sciences AB - Nanoscale inorganic fillers with average particle sizes smaller by an order of magnitude or more compared to those of conventional fillers are becoming commercially available. The efficacy of these fillers used in polymer formulations and particularly their effect as photostabilizers are beginning to be investigated. These may enhance or retard photodegradation depending on the surface coating of the particles or their chemical nature. Some recent data indicate their use as effective photostabilizers in some common polymers. However, the potential deleterious interaction of the nanoscale fillers with other additives in the formulation has also been pointed out. Depending on the efficiency of stabilization and the economics of their use nanofillers may provide a useful route to UV-stabilization of plastics and rubber used outdoors. Insufficient data are available at this time to assess their potential impact on material and coatings stabilization. Organic fillers such as lignocellulose continue to be investigated for outdoor applications. Their cost advantage makes them attractive despite the somewhat reduced engineering properties of their composites. Recent reports, however, suggest the photostability of these composites to depend on the source of fiber as well as the processing techniques employed in fabricating products from them. Identification of the key determinants in terms of species, isolation and processing of polymer-wood composites is critical to developing them for long-term outdoor use. Efforts are continuing on the synthesis of new light stabilizers, particularly those based on a hindered amine light stabilizers (HALS), and on identifying synergistic combinations of known stabilizers for common thermoplastics. Variants of HALS-type stabilizers that reduce the loss of stabilizer via leaching or migration were recently reported. Studies on the permanence of the stabilizers themselves when exposed to solar UV wavelengths have also been reported in recent work. Identification of relevant mechanisms is important not only to understand the interactions of climate changes and higher UV solar environments with materials damage, but also to guide future design of light-stabilizers. DA - 2007/// PY - 2007/// DO - 10.1039/b700023e VL - 6 IS - 3 SP - 311 J2 - Photochem. Photobiol. Sci. LA - en OP - SN - 1474-905X 1474-9092 UR - http://dx.doi.org/10.1039/b700023e DB - Crossref ER - TY - CHAP TI - Biodegradability of Polymers AU - Andrady, Anthony L. T2 - Physical Properties of Polymers Handbook PY - 2007/// DO - 10.1007/978-0-387-69002-5_56 SP - 951-964 OP - PB - Springer New York SN - 9780387312354 9780387690025 UR - http://dx.doi.org/10.1007/978-0-387-69002-5_56 DB - Crossref ER - TY - CHAP TI - Ultraviolet Radiation and Polymers AU - Andrady, Anthony L. T2 - Physical Properties of Polymers Handbook PY - 2007/// DO - 10.1007/978-0-387-69002-5_51 SP - 857-866 OP - PB - Springer New York SN - 9780387312354 9780387690025 UR - http://dx.doi.org/10.1007/978-0-387-69002-5_51 DB - Crossref ER - TY - CHAP TI - Functional Genomics AU - Jenney, F.E., Jr AU - Tachdijan, Sabrina AU - Chou, Chung-Jung AU - Kelly, Robert M. AU - Adams, M.W.W. T2 - Archaea: Molecular and Cellular Biology A2 - Cavicchioli, Rick AB - As genetic systems for archaea become further developed and implemented, functional genomics tools can be expanded to enable a full systems biology approach to studying archaea. This chapter provides a review of the current status of functional genomics efforts to investigate archaea. In this discussion, functional genomics refers to transcriptional response (transcriptomics), protein inventory and differential abundance (proteomics), and protein structural attributes (structural genomics) examined in the context of entire genomes. Currently, certain archaea are emerging as model systems for functional genomics studies. This realization was sobering given the need for highly sophisticated, analytical, and statistical skills, as well as the significant expense, that are typically part and parcel of functional genomics approaches. As is the case with many facets of archaeal biology, the field of proteomics can be divided into accomplishments achieved with three different groups of archaea: methanogens, halophiles, and organisms that fit into neither category. A proteomics approach to investigate protein levels in cells grown at low (4°C) and optimal temperatures was recently reported. This study represented the first global analysis of proteins involved in cold adaptation. Coupled with useful genetic systems, strategic use of functional genomics approaches will form the basis for complete and accurate genome annotation. Information gained from ongoing and emerging functional genomics efforts focusing on archaea will provide clues and insights that will accelerate the genetic system's development. PY - 2007/// DO - 10.1128/9781555815516.ch20 SP - 434–462 PB - ASM Press SN - 9781119738312 9781683671688 ER - TY - CHAP TI - Transcriptomics, Proteomics, and Structural Genomics ofPyrococcus Furiosus AU - Adams, Michael W. W. AU - Jenney, Francis E., Jr AU - Chou, Chung-Jung AU - Hamilton-Brehm, Scott AU - Poole, Farris L., II AU - Shockley, Keith R. AU - Tachdjian, Sabrina AU - Kelly, Robert M. T2 - Archaea AB - This chapter contains sections titled: Introduction The P. furiosus genome and problems with genome annotation The number of genes in the P. furiosus genome The response of P. furiosus to growth phase and growth rate The response of P. furiosus to the presence of elemental sulfur The response of P. furiosus to changes in the primary carbon source The response of P. furiosus to cold shock and cold adaptation The response of P. furiosus to heat shock Use of a P. furiosus DNA microarray to assess species relationships The P. furiosus proteome Structural genomics of P. furiosus Conclusions PY - 2007/11/30/ DO - 10.1002/9780470750865.ch21 SP - 239-246 OP - PB - Blackwell Publishing Ltd SN - 9780470750865 9781405144049 UR - http://dx.doi.org/10.1002/9780470750865.ch21 DB - Crossref ER - TY - JOUR TI - Engineered Alkane-Hydroxylating Cytochrome P450BM3 Exhibiting Nativelike Catalytic Properties AU - Fasan, Rudi AU - Chen, Mike M. AU - Crook, Nathan C. AU - Arnold, Frances H. T2 - Angew. Chem. Int. Ed. AB - Divide, evolve, and conquer: A domain-based strategy (see scheme) was used to engineer high catalytic and coupling efficiency for propane hydroxylation in a multidomain cytochrome P450 enzyme. The engineered enzymes exhibit high total activities in whole-cell bioconversions of propane to propanol under mild conditions, using air as oxidant. Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2002/2007/z702616_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 - 2007/11// PY - 2007/11// DO - 10.1002/anie.200702616 VL - 46 IS - 44 SP - 8414-8418 KW - alkane oxidation KW - biotransformations KW - cytochrome P450 KW - directed evolution KW - protein engineering ER - TY - JOUR TI - Engineered Alkane-Hydroxylating Cytochrome P450BM3 Exhibiting Nativelike Catalytic Properties AU - Fasan, Rudi AU - Chen, Mike M. AU - Crook, Nathan C. AU - Arnold, Frances H. T2 - Angew. Chem. AB - Eine Domänenstrategie (siehe Schema) führte zu einer hoch effizienten Katalyse der Propanhydroxylierung in einem Mehrdomänen-Cytochrom-P450-Enzym. Die entwickelten Enzyme zeichnen sich durch hohe Gesamtaktivitäten bei der Biotransformation von Propan zu Propanol in ganzen Zellen unter milden Bedingungen aus, wobei Luft als Oxidans wirkt. DA - 2007/11// PY - 2007/11// DO - 10.1002/ange.200702616 VL - 119 IS - 44 SP - 8566-8570 ER - TY - JOUR TI - Inside Front Cover: Field-Driven Biofunctionalization of Polymer Fiber Surfaces during Electrospinning (Adv. Mater. 1/2007) AU - Sun, X.-Y. AU - Shankar, R. AU - Börner, H. G. AU - Ghosh, T. K. AU - Spontak, R. J. T2 - Advanced Materials AB - Abstract Surface‐biofunctionalized synthetic polymer fibers composed of a fiber‐forming host polymer and an oligopeptide conjugate can be prepared from electrospinning, report Spontak and co‐workers on p. 87. The conjugate consists of a polypeptide segment and a polymer block that is compatible with the host polymer. Because the more polarizable peptide segment migrates to the surface during electrospinning, peptide surface‐enrichment is achieved in a single step without further treatment. DA - 2007/1/8/ PY - 2007/1/8/ DO - 10.1002/adma.200790004 VL - 19 IS - 1 SP - NA-NA J2 - Adv. Mater. LA - en OP - SN - 0935-9648 1521-4095 UR - http://dx.doi.org/10.1002/adma.200790004 DB - Crossref ER - TY - JOUR TI - Thermal Control of Amide Product Distributions at the Ge(100)-2×1 Surface AU - Keung, Albert J. AU - Filler, Michael A. AU - Bent, Stacey F. T2 - The Journal of Physical Chemistry C AB - We have investigated the adsorption of a series of primary, secondary, and tertiary amides including formamide, N-methylformamide, N-methylacetamide, and N,N-dimethylacetamide on the Ge(100)-2×1 surface using multiple internal reflection Fourier transform infrared spectroscopy and density functional theory. At 310 K, primary and secondary amides were observed to form thermodynamically favored N−H dissociation structures with interdimer interactions as well as kinetically favored oxygen dative-bonded structures. The relative surface product distributions could be controlled thermally. Dative-bonded adducts were isolated by exposing the amides to the surface at 240 K, whereas N−H dissociation products were formed by annealing to 450 K. While the acetamides could potentially form “-ene” type products, such products were not observed and instead the acetamides exhibited the same reactivity pattern as the formamides in this study. DA - 2007/1// PY - 2007/1// DO - 10.1021/jp065278d VL - 111 IS - 1 SP - 411-419 J2 - J. Phys. Chem. C LA - en OP - SN - 1932-7447 1932-7455 UR - http://dx.doi.org/10.1021/jp065278d DB - Crossref ER - TY - JOUR TI - Bacillus methanolicus: a candidate for industrial production of amino acids from methanol at 50°C AU - Brautaset, Trygve AU - Jakobsen, Øyvind M. AU - Josefsen, Kjell D. AU - Flickinger, Michael C. AU - Ellingsen, Trond E. T2 - Applied Microbiology and Biotechnology DA - 2007/1/11/ PY - 2007/1/11/ DO - 10.1007/S00253-006-0757-Z VL - 74 IS - 1 SP - 22-34 J2 - Appl Microbiol Biotechnol LA - en OP - SN - 0175-7598 1432-0614 UR - http://dx.doi.org/10.1007/S00253-006-0757-Z DB - Crossref ER - TY - JOUR TI - Characterization of Mo additions in iron-based Fischer–Tropsch catalysts using X-ray absorption spectroscopy and X-ray diffraction AU - Campos, A. AU - Spivey, J.J. AU - Roy, A. AU - Lohitharn, N. AU - Goodwin, J. AU - Lotero, E. AU - Lamb, H. T2 - Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment AB - An iron-based Fischer–Tropsch catalyst with a low concentration of molybdenum (90Fe/10Mo/5Cu/17Si) used as a promoter was characterized by X-ray absorption spectroscopy (XAS) and X-ray diffractometry (XRD). The catalyst was prepared using coprecipitation, pretreated in CO, then one sample passivated and one calcined. The XRD data show that after CO pretreatment the calcined and passivated catalysts are almost amorphous with respect to Fe2O3 with nanoparticle size of 10 and 100 Å for Fe3C (only present in the passivated sample). Least squares fitting of the XANES region show that the calcined and passivated samples were similar in the bulk and surface structures, with the calcined samples completely oxidized. As expected, K and LIII edges Mo-XANES shows only small molybdenum carbide formation compared to iron carbide. DA - 2007/11// PY - 2007/11// DO - 10.1016/j.nima.2007.08.135 VL - 582 IS - 1 SP - 236-238 J2 - Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment LA - en OP - SN - 0168-9002 UR - http://dx.doi.org/10.1016/j.nima.2007.08.135 DB - Crossref KW - molybdenum KW - iron KW - XANES KW - Fischer-Tropsch ER - TY - JOUR TI - Deposition of poly[2-(perfluorooctyl)ethyl acrylate] from liquid CO2 high-pressure free meniscus coating—Uniformity and morphology AU - Kim, Jaehoon AU - Carbonell, Ruben G. T2 - The Journal of Supercritical Fluids AB - Abstract Ultrathin fluoropolymer films were prepared by depositing poly[2-(perfluorooctyl)ethyl acrylate] (PFOEA) on 12.5 cm diameter silicon wafer substrates using high-pressure free meniscus coating (hFMC) with liquid CO2 (l-CO2) as a coating solvent. Dry film thickness across the wafer substrate and the morphology of deposited films were characterized as a function of coating conditions—withdrawal velocities, solution concentrations and evaporation driving forces (ΔP). Thickness measurements by ellipsometry revealed that at zero or low evaporation driving forces (ΔP = 0–0.0138 MPa), highly uniform films with thicknesses in the range of 7–30 nm were deposited over the entire concentration range (1–7 wt.%). However, films deposited at high evaporation driving forces (ΔP = 0.0414–0.0552 MPa) or larger concentrations (5–7 wt.%) with a ΔP of 0.0276 MPa were thicker (35–70 nm) and less uniform. Optical microscopy and atomic force microscopy (AFM) were used to characterize film morphology including drying defects and film roughness. Films deposited at zero or low ΔP of 0.0138 MPa and low concentrations of 1–3 wt.% exhibited few drying defects and a low root mean square (RMS) roughness (∼2 nm). At higher evaporation driving forces and higher concentrations, ring-like drying defects were observed with diameters ranging 5–30 μm. The film thickness and morphology of PFOEA films deposited from l-CO2 hFMC were compared to those deposited from 1,1,2-trichlorotrifluoroethane (Freon113) by normal atmospheric dip coating. Films deposited from l-CO2 hFMC were much thinner and more uniform, and exhibit much fewer drying defects and lower RMS roughness. DA - 2007/8// PY - 2007/8// DO - 10.1016/j.supflu.2007.01.012 VL - 42 IS - 1 SP - 129-141 J2 - The Journal of Supercritical Fluids LA - en OP - SN - 0896-8446 UR - http://dx.doi.org/10.1016/j.supflu.2007.01.012 DB - Crossref KW - liquid carbon dioxide KW - free meniscus coating KW - poly [2-(perfluorooctyl)ethyl acrylate] KW - thin fluorinated film ER - TY - JOUR TI - Painting and Printing Living Bacteria: Engineering Nanoporous Biocatalytic Coatings to Preserve Microbial Viability and Intensify Reactivity AU - Flickinger, M.C. AU - Schottel, J.L. AU - Bond, D.R. AU - Aksan, A. AU - Scriven, L.E. T2 - Biotechnology Progress AB - Latex biocatalytic coatings containing approximately 50% by volume of microorganisms stabilize, concentrate and preserve cell viability on surfaces at ambient temperature. Coatings can be formed on a variety of surfaces, delaminated to generate stand-alone membranes or formulated as reactive inks for piezoelectric deposition of viable microbes. As the latex emulsion dries, cell preservation by partial desiccation occurs simultaneously with the formation of pores and adhesion to the substrate. The result is living cells permanently entrapped, surrounded by nanopores generated by partially coalesced polymer particles. Nanoporosity is essential for preserving microbial viability and coating reactivity. Cryo-SEM methods have been developed to visualize hydrated coating microstructure, confocal microscopy and dispersible coating methods have been developed to quantify the activity of the entrapped cells, and FTIR methods are being developed to determine the structure of vitrified biomolecules within and surrounding the cells in dry coatings. Coating microstructure, stability and reactivity are investigated using small patch or strip coatings where bacteria are concentrated 102- to 103-fold in 5-75 microm thick layers with pores formed by carbohydrate porogens. The carbohydrate porogens also function as osmoprotectants and are postulated to preserve microbial viability by formation of glasses inside the microbes during coat drying; however, the molecular mechanism of cell preservation by latex coatings is not known. Emerging applications include coatings for multistep oxidations, photoreactive coatings, stabilization of hyperthermophiles, environmental biosensors, microbial fuel cells, as reaction zones in microfluidic devices, or as very high intensity (>100 g.L-1 coating volume.h-1) industrial or environmental biocatalysts. We anticipate expanded use of nanoporous adhesive coatings for prokaryotic and eukaryotic cell preservation at ambient temperature and the design of highly reactive "living" paints and inks. DA - 2007/2/2/ PY - 2007/2/2/ DO - 10.1021/bp060347r VL - 23 IS - 1 SP - 2-17 J2 - Biotechnol. Prog. LA - en OP - SN - 8756-7938 UR - http://dx.doi.org/10.1021/bp060347r DB - Crossref ER - TY - JOUR TI - Modelling diffusivity in porous polymeric membranes with an intermediate layer containing microbial cells AU - Mota, Manuel AU - Yelshin, Alexander AU - Fidaleo, Marcello AU - Flickinger, Michael C. T2 - Biochemical Engineering Journal AB - Three-layer systems (membrane – composite layer (cells + polymer) – membrane) are important in different biochemical applications. Models of latex layered-membranes were evaluated and compared with experimental data in order to predict the diffusivity of substrates in the composite layer containing living E.coli microbial cells. Diffusivity predictions are dependent on the presence or the absence of a ‘skin’ layer, on the degree of polymer particle coalescence and on the thickness of each layer. Simulations with layered models were made to identify the dominant mechanisms in the three-layer system. It was found that the layered system is sensitive to the latex coatings porosity when the composite layer occupies less than 50% of the total membrane system thickness. Whenever the control of polymer particle coalescence and of the layers (coating/composite layer) thickness may be achieved, multi-layer systems presenting a wide range of relative diffusion conductivities may be built for different types of living cells and for a wide variety of practical applications. The diffusivity of the latex layer is proportional to the square of latex porosity. © 2007 Elsevier B.V. All rights reserved. DA - 2007/12// PY - 2007/12// DO - 10.1016/j.bej.2007.05.008 VL - 37 IS - 3 SP - 285-293 J2 - Biochemical Engineering Journal LA - en OP - SN - 1369-703X UR - http://dx.doi.org/10.1016/j.bej.2007.05.008 DB - Crossref KW - diffusion KW - microporous membrane KW - immobilised cells KW - modelling KW - packing KW - mass transfer 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. AU - Pan, Y. T2 - Polymer International DA - 2007/// PY - 2007/// VL - 57 ER - TY - JOUR TI - Weak surface anchoring energy of 4-cyano-4′-pentyl-1,1′-biphenyl on perfluoropolyether Langmuir-Blodgett films AU - Russell-Tanner, Joette M. AU - Takayama, Sadao AU - Sugimura, Akihiko AU - DeSimone, Joseph M. AU - Samulski, Edward T. T2 - The Journal of Chemical Physics AB - Functional director alignment layers are needed for high performance liquid crystal displays (LCDs). Reported herein is a novel polymer material for LC alignment, namely, perfluoropolyether (PFPE), which exhibits a weak surface anchoring energy for bend deformation and is amenable to simple fabrication of grooved surfaces by soft lithography, a surface topography desired for multistable LCDs. Liquid crystal optical cells fabricated using Langmuir-Blodgett films of PFPE (of variable thickness) exhibited weak surface anchoring energies on the order of 10−5J∕m2 for the nematic liquid crystal 4-cyano-4′-pentyl-1,1′-biphenyl with no dependence on film thickness. DA - 2007/6/28/ PY - 2007/6/28/ DO - 10.1063/1.2743404 VL - 126 IS - 24 SP - 244706 J2 - The Journal of Chemical Physics LA - en OP - SN - 0021-9606 1089-7690 UR - http://dx.doi.org/10.1063/1.2743404 DB - Crossref ER - TY - JOUR TI - Dynamics of CO2-Plasticized Electron Transport in Au Nanoparticle Films:  Opposing Effects of Tunneling Distance and Local Site Mobility AU - Choi, Jai-Pil AU - Coble, Melissa M. AU - Branham, Matthew R. AU - DeSimone, Joseph M. AU - Murray, Royce W. T2 - The Journal of Physical Chemistry C AB - The electron-transport properties of unlinked and linked solid-state films of very small “Au38” nanoparticles (monolayer protected clusters, or MPCs) remarkably change in opposing directions upon contact with increasing pressures of CO2 gas (0∼6.6 MPa). Electronic conductivities (σEL) of dropcast, unlinked Au MPC films increase up to 31-fold with increasing CO2 pressure, while σEL of dithiol-linked Au MPC films decreases with increasing CO2 pressure. In conductivity by electron hopping between electron donor and acceptor Au MPC cores, the organic protecting ligands serve as a solvent shell whose properties influence the dynamics of electron transport. Exposure of Au MPC films to CO2 and consequent swelling by CO2 (or organic vapor) sorption into the monolayers changes two key factors: core edge-to-edge electron tunneling distances (dHOP) and a previously underappreciated effect of dimension and/or frequency of local core thermal motions. Swelling induces increases in both, but depending on which factor is dominant, the net σEL can increase or decrease. In unlinked films under increasing CO2 pressure, increased thermal motions of Au MPC cores and their monolayers enhance electron-hopping rates more than swelling-induced increases in dHOP decrease them. The net effect is increasing σEL (i.e., increased local mobility negates increased average tunneling distances). In contrast, in dithiol-linked films local thermal motions are constrained by the dithiol linker between Au MPC cores, leaving CO2 sorption-induced swelling and increase in dHOP as the more dominant factor; σEL now decreases with increasing CO2 pressure. DA - 2007/2/14/ PY - 2007/2/14/ DO - 10.1021/jp068349h VL - 111 IS - 9 SP - 3778-3785 J2 - J. Phys. Chem. C LA - en OP - SN - 1932-7447 1932-7455 UR - http://dx.doi.org/10.1021/jp068349h DB - Crossref ER - TY - JOUR TI - Etching SiO[sub 2] with HF/pyridine-supercritical carbon dioxide solutions and resultant interfacial electronic properties AU - Li, Y. X. AU - Yang, D. AU - Jones, C. A. AU - DeSimone, J. M. AU - Irene, E. A. T2 - Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures AB - Silicon dioxide (SiO2) films grown on single crystal Si in high temperature O2 were etched using nonaqueous HF/pyridine solutions in supercritical CO2. The etch rate of SiO2 films were studied in the solutions with HF concentration up to 1000μM at 1.38×107Pa and at 35, 45, and 55°C. Capacitance versus voltage, conductance versus voltage, and leakage current measurements were performed on capacitor structures fabricated after SiO2 regrowth on completely etched Si surfaces. The electronic results revealed no systematic differences of etched and unetched samples with various etch times concentrations and that the Si–SiO2 interface of completely etched samples was comparable to the unetched control sample in terms of interface electronic charge and states and leakage current. DA - 2007/// PY - 2007/// DO - 10.1116/1.2743651 VL - 25 IS - 4 SP - 1139 J2 - J. Vac. Sci. Technol. B LA - en OP - SN - 1071-1023 UR - http://dx.doi.org/10.1116/1.2743651 DB - Crossref ER - TY - JOUR TI - Nanoparticle Drug Delivery Platform AU - Napier, Mary E. AU - DeSimone, Joseph M. T2 - Polymer Reviews AB - The use of polymers and polymeric structures in the treatment, diagnosis, and monitoring of biological systems is continuing to increase in sophistication. Research exploring the use of nanoparticles for drug delivery applications has included the exploration and development of nanocolloids, liposomes, micelles, nanogels, polymer‐drug conjugates, and a variety of other polymeric nanoparticles that are composed of organic polymers with specific physical or chemical properties that make them relevant delivery vehicles. One of the current trends is the fabrication of tunable, mono‐dispersed, polymeric nanostructures to be used as nanoparticle drug delivery platforms. The PRINT technology used to fabricate monodisperse particles from a wide range of particle matrix materials including biocompatible poly(ethylene glycol) and bioabsorbable poly(d‐lactic acid) is described along with an abbreviated overview of other polymeric drug delivery platforms. Keywords: drug deliverynanoparticlesnanotechnologypolymeric nanoparticlespolymers DA - 2007/7// PY - 2007/7// DO - 10.1080/15583720701454999 VL - 47 IS - 3 SP - 321-327 J2 - Polymer Revs. LA - en OP - SN - 1558-3724 UR - http://dx.doi.org/10.1080/15583720701454999 DB - Crossref KW - drug delivery KW - nanoparticles KW - nanotechnology KW - polymeric nanoparticles KW - polymers ER - TY - CHAP TI - Modeling Protein Aggregate Assembly and Structure AU - Guo, Jun-tao AU - Hall, Carol K. AU - Xu, Ying AU - Wetzel, Ronald T2 - Computational Methods for Protein Structure Prediction and Modeling A2 - Xu, Y. A2 - Xu, D. A2 - Liang, J. T3 - Biological and Medical Physics Biomedical Engineering PY - 2007/8/24/ DO - 10.1007/978-0-387-68372-0_9 ET - Basic Characterization VL - 1 SP - 279-317 PB - Springer Verlag SN - 9780387333199 UR - http://dx.doi.org/10.1007/978-0-387-68372-0_9 ER - TY - JOUR TI - Theoretical Study of Kinetics of Hybridization in DNA Microarrays AU - Jayaraman, A. AU - Santiso, E.E. AU - Hall, C.K. AU - Genzer, J. T2 - Physical Review E DA - 2007/// PY - 2007/// VL - 76 SP - 011915 ER - TY - JOUR TI - Sorption of acid violet 17 and direct red 80 dyes on cotton fiber from aqueous solutions AU - Saleem, M. AU - Pirzada, T. AU - Qadeer, R. T2 - Colloids and Surfaces A: Physicochemical and Engineering Aspects AB - Sorption of acid violet 17 and direct red 80 azo dyes on locally available cotton fiber from aqueous solution has been investigated as a function of shaking time, pH, dyes concentration and temperature. Maximum sorption of acid violet 17 and direct red 80 on cotton fiber was achieved within 30 and 60 min of shaking time and at pH 8 and 8.5, respectively. Sorption isotherms for acid violet 17 and direct red 80 dyes were obtained at pH 8 and 8.5, respectively, at constant temperature. These isotherms are L-3 types having small plateaus, and the upward trends in sorption capacity after the plateaus points towards the possibility of multilayer formation. The increasing temperature induces a negative effect on the sorption of acid violet 17 (exothermic) and positive effect on the sorption of directs red 80 (endothermic). Isosteric heat of adsorption (qst) have also been calculated at different surface coverage indicating that cotton fiber possessed heterogeneous surface with site of different activity. The results also indicate that initial sorption, whether chemical or physical means, occurs first on the most active sites and then on the sites of lesser activity. DA - 2007/// PY - 2007/// DO - 10.1016/j.colsurfa.2006.06.035 VL - 292 IS - 2-3 SP - 246-250 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-33845483355&partnerID=MN8TOARS KW - cotton fiber KW - acid violet 17 KW - direct red 80 KW - sorption KW - aqueous solutions ER - TY - CONF TI - STRUCTURAL MODELING OF POROUS CARBONS USING A HYBRID REVERSE MONTE CARLO METHOD AU - Jain, S. K. AU - Pellenq, R. J. M. AU - Gubbins, K. E. T2 - Selected Reports at the 4th Pacific Basin Conference on Adsorption Science and Technology AB - We present molecular models for 3 saccharose based carbons of different densities obtained using a Reverse Monte Carlo (RMC) protocol which incorporates an energy constraint. The radial distribution functions of the simulated models are in good agreement with experiment. Moreover, 3 and 4 member carbon rings, reported in the literature for many modeling studies of carbon, are absent or extremely rare in our final structural models. These small member rings are high energy structures and are believed to be an artifact of the usual RMC method. The presence of the energy penalty term in our simulation protocol penalizes the formation of these structures. Using a ring connectivity analysis method that we developed, we find that these atomistic models of carbons are made up of defective graphene segments twisted in a complex way. These graphene segments are largely made up of 6 carbon member rings, but also contain some 5 and 7 carbon member rings. We also found that in addition to the graphene segments there are some carbon chains which do not belong to any graphene segments. To characterize our models, we calculated the geometric pore size distribution and also simulated the adsorption of argon at 77.4 K in the models using GCMC simulations. The adsorption isotherm obtained for all three models are representative of microporous carbons. C2 - 2007/9// C3 - Adsorption DA - 2007/9// DO - 10.1142/9789812770264_0007 PB - WORLD SCIENTIFIC SN - 9789812770257 9789812770264 UR - http://dx.doi.org/10.1142/9789812770264_0007 DB - Crossref ER - TY - CHAP TI - Simulations of Protein Aggregation AU - Hall, Carol K. AU - Nguyen, Hung D. AU - Marchut, Alexander J. AU - Wagoner, Victoria T2 - Misbehaving Proteins PY - 2007/10/11/ DO - 10.1007/978-0-387-36063-8_3 SP - 47-77 OP - PB - Springer New York SN - 9780387305080 UR - http://dx.doi.org/10.1007/978-0-387-36063-8_3 DB - Crossref ER - TY - CHAP TI - Ab Initio Simulations of Chemical Reactions in Nanostructured Carbon Materials AU - Santiso, Erik E. AU - Huang, Liping AU - Kostov, Milen K. AU - George, Aaron M. AU - Gubbins, Keith E. AU - Nardelli, Marco Buongiorno T2 - Quantum Chemical Calculations of Surfaces and Interfaces of Materials A2 - Basiuk, V.A. A2 - Ugliengo, P. PY - 2007/// PB - American Scientific Publishers ER - TY - JOUR TI - Confinement Effects on Chemical Reactions — Toward an Integrated Rational Catalyst Design AU - Santiso, Erik E. AU - Kostov, Milen K. AU - George, Aaron M. AU - Nardelli, Marco Buongiorno AU - Gubbins, Keith E. T2 - ChemInform AB - Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. DA - 2007/8/21/ PY - 2007/8/21/ DO - 10.1002/chin.200734275 VL - 38 IS - 34 J2 - ChemInform LA - en OP - SN - 0931-7597 1522-2667 UR - http://dx.doi.org/10.1002/chin.200734275 DB - Crossref ER - TY - CHAP TI - Confinement effects on freezing of binary mixtures AU - Coasne, Benoit AU - Czwartos, Joanna AU - Gubbins, Keith E. AU - Hung, Francisco R. AU - Sliwinska-Bartkowiak, Malgorzata T2 - Studies in Surface Science and Catalysis AB - We report molecular simulations and experimental measurements of the freezing and melting of mixtures confined in nanopores. Dielectric relaxation spectroscopy was used to determine the experimental phase diagram of mixtures confined in activated carbon fibers. Grand Canonical Monte Carlo simulations combined with the parallel tempering technique were used to model the freezing of several Lennard - Jones mixtures in graphite slit pores. The effect of confinement is discussed for mixtures having a simple solid solution or an azeotropic solid - liquid phase diagram. We also investigate how the competition between the wall -fluid and fluid - fluid interactions affects the freezing temperature of the confined system. The structure of the crystal phase in the simulations is also investigated by means of positional and bond-orientational pair correlation functions and bond-order parameters. PY - 2007/// DO - 10.1016/s0167-2991(07)80086-3 VL - 160 SP - 667-674 OP - PB - Elsevier SN - 9780444520227 UR - http://dx.doi.org/10.1016/s0167-2991(07)80086-3 DB - Crossref ER - TY - JOUR TI - Remotely powered distributed microfluidic pumps and mixers based on miniature diodes AU - Chang, S.T. AU - Beaumont, E. AU - Petsev, D.N. AU - Velev, Orlin T2 - Lab on a Chip - Miniaturisation for Chemistry and Biology 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 - 2007/// PY - 2007/// DO - 10.1039/b712108c VL - 8 IS - 1 SP - 117-124 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-37349032809&partnerID=MN8TOARS ER - TY - JOUR TI - Norvancomycin-capped silver nanoparticles: Synthesis and antibacterial activities against E-coli AU - Wei, Q. S. AU - Ji, J. AU - Fu, J. H. AU - Shen, J. C. T2 - Science in China Series B-Chemistry DA - 2007/// PY - 2007/// DO - 10.1007/s11426-007-0028-6 VL - 50 IS - 3 SP - 418-424 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000247829200017&KeyUID=WOS:000247829200017 KW - silver nanoparticle KW - norvancomycin KW - Gram-negative bacterial strain KW - bioconjugate ER - TY - CONF TI - Detection of E. coli O157:H7 DNA by a novel QCM biosensor coupled with gold nanoparticles amplification AU - Wang, L. AU - Wei, Q. AU - Wu, C. AU - Ji, A. AU - Liu, Q. AU - Yang, M. AU - Wang, P. AB - In recent years, quartz crystal microbalance (QCM) plays an important role in many biological detections, and the enhancement of a single strain DNA probe linked to the sensor surface is of crucial importance in DNA molecule recognition. By means of nanogold modification and mass amplification, a QCM biosensor for Escherichia coli O157:H7 DNA detection was explored and developed in this work. As a suitable surfactant, 1,6-Hexanedithiol was introduced onto the Au surface of QCM, then self-assembled to provide a thioled interface for the inner goldnano immobilization. Based on the Au-SH binding mechanism, thiolated single-stranded DNA (ssDNA) probes which was specific to E. coli O157:H7 eaeA gene would link to the nanoparticle-modified electrode surface. The hybridization was induced by exposing the ssDNA probe to the complementary target DNA, but the frequency change caused by the captured target DNA was negligible. In order to amplify the signal, outer nanogold as the mass enhancer were applied to combine with the target DNA by the biotin-avidin system. The electrochemical techniques, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), are adopted to manifest and character each step, which supplied some reasonable and powerful supports for the frication and detection of this QCM biosensor. The target DNA corresponding to 2.0 times 10 3 colony forming unit (CFU)/ml E. coli O157:H7 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. In order to attract more attention, this DNA biosensor should be combined with some micro- and nano-fabrication techniques to realize more promising and pratical applications, and more attention should be focused on the further improvement of the sensitivity and the shorten of analysis time. C2 - 2007/// C3 - 2007 7th IEEE International Conference on Nanotechnology - IEEE-NANO 2007, Proceedings DA - 2007/// DO - 10.1109/NANO.2007.4601201 SP - 330-333 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-52949115337&partnerID=MN8TOARS ER - TY - CONF TI - A QCM biosensor based on gold nanoparticles amplification for real-time bacteria DNA detection AU - Wang, L. AU - Wei, Q. AU - Wu, C. AU - Ji, J. AU - Wang, P. AB - A DNA piezoelectric biosensing method for real-time detection of E.coli O157:H7 in a circulating-flow system was developed in this study. The thioled surface of the Au electrode could be immobilized by many inner Au nanoparticles, then more thiolated single-stranded DNA (ssDNA) probes which was specific to E.coli O157:H7 eaeA gene could be fixed through Au-SH bonding. The hybridization was induced by exposing the ssDNA probe to the complementary target DNA, then resulted in the 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 inner and outer Au nanoparticles with different diameters would play the "signal amplifier" role at different layer for improving the detection limit and sensitivity. The electrochemical techniques, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), are adopted to demonstrate and character each treatment. The target DNA corresponding to 2.0X10 3 colony forming unit (CFU)/ml E.coli 0157: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. C2 - 2007/// C3 - Proceedings of the 2007 International Conference on Information Acquisition, ICIA DA - 2007/// DO - 10.1109/ICIA.2007.4295695 SP - 46-51 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-47349090524&partnerID=MN8TOARS 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 - 2007/9// PY - 2007/9// DO - 10.1007/s10853-007-2086-8 VL - 43 IS - 1 SP - 117-122 ER - TY - CONF TI - Unique Nanofiber Structures for Filtration Applications C2 - 2007/11// C3 - MemFAST Meeting DA - 2007/11// ER - TY - CONF TI - Polyacrylonitrile-Based Composite and Carbon Nanofibers for Lithium-Ion Battery Applications C2 - 2007/10// C3 - 212th Electrochemical Society Meeting DA - 2007/10// ER - TY - CONF TI - Nonwovens Containing Polymer Fillers C2 - 2007/11// C3 - TE/ECE Symposium DA - 2007/11// ER - TY - CONF TI - Nonwovens Containing Polymer Fillers C2 - 2007/11// C3 - MemFAST Meeting DA - 2007/11// ER - TY - CONF TI - Electrospinning Parameters and Their Effect on the Fabrication of Catalyst-Loaded Nanofibers for Fuel Cells C2 - 2007/11// C3 - 3rd Annual State of North Carolina Undergraduate Research Symposium, DA - 2007/11// ER - TY - JOUR TI - Study on thermal behaviors of Li/H atom in the bulk graphite by molecular dynamics method AU - Deng, B. AU - Ding, K. AU - Wu, Z.-W. AU - Shan, L.-Y. AU - Lim, P. K. AU - Gu, C.-X. T2 - Journal of Materials Science DA - 2007/// PY - 2007/// DO - 10.1007/s10853-006-1124-2 VL - 42 IS - 18 SP - 7972-7976 ER - TY - JOUR TI - Effect of hydrogen on dangling bond in a-Si thin film AU - Lim, P. K. AU - Tam, W. K. AU - Yeung, L. F. AU - Lam, F. M. T2 - PROCEEDINGS OF THE INTERNATIONAL CONFERENCE ON NANOSCIENCE AND TECHNOLOGY AB - Concentrations of the Si-H vibration bond and the dangling bond in amorphous silicon films were studied using FTIR and ESR techniques respectively as a function of annealing temperature in the range from 20°C to 950°C. It was found that the concentration of Si-H did not change much for temperatures up to 350°C and then dropped monotonically and became negligible at temperatures above 850°C, while the concentration of SiH2 increased with temperature and attained a maximum at 450°C and then decreased with temperature there after. The ESR signal dropped with temperature, up to 200°C, and fell below the detection limit of our spectrometer in the range 200°C-500°C. The ESR signal recovered when annealing temperature was higher than 550°C. The Si-H, SiH2, ESR and optical absorption signals were found to be highly correlated to each other and could be interpreted in a consistent manner. DA - 2007/// PY - 2007/// DO - 10.1088/1742-6596/61/1/142 VL - 61 SP - 708-712 SN - 1742-6588 ER - TY - CONF TI - Modeling of self-assembly dynamics of photolithographically patterned MUFFINS biosensor arrays AU - Lee, S. AU - Carmichael, P. AU - Meiring, J. AU - Dickey, Michael AU - Grayson, S. AU - Bonnecaze, R. T. AU - Wilson, C. G. C2 - 2007/// C3 - Materials Research Society Symposium Proceedings DA - 2007/// DO - 10.1557/proc-1002-n07-08 VL - 102 ER - TY - JOUR TI - The influence of ethanol addition on premixed fuel-rich propene–oxygen–argon flames AU - Kohse-Höinghaus, Katharina AU - Oßwald, Patrick AU - Struckmeier, Ulf AU - Kasper, Tina AU - Hansen, Nils AU - Taatjes, Craig A. AU - Wang, Juan AU - Cool, Terrill A. AU - Gon, Saugata AU - Westmoreland, Phillip AU - al. T2 - Proceedings of the Combustion Institute AB - The role of ethanol as a fuel additive was investigated in a fuel-rich, non-sooting (C/O = 0.77) flat premixed propene–oxygen–argon flame at 50 mbar (5 kPa). Mole fractions of stable and radical species were derived using two different in situ molecular beam mass spectrometry (MBMS) set-ups, one located in Bielefeld using electron impact ionization (EI), and the other at the Advanced Light Source (ALS) at Berkeley using vacuum UV photoionization (VUV-PI) with synchrotron radiation. A rich propene flame, previously studied in detail experimentally and with flame model calculations, was chosen as the base flame. Addition of ethanol is believed to reduce the concentrations of benzene and small aromatic compounds, while augmenting the formation of other regulated air toxics such as aldehydes. To study the chemical pathways responsible for these effects, quantitative concentrations of about 35 species were determined from both experiments. This is also the first time that a detailed comparison of quantitative species concentrations from these independent MBMS set-ups is available. Effects of ethanol addition on the species pool are discussed with special attention on benzene precursor chemistry and aldehyde formation. DA - 2007/1// PY - 2007/1// DO - 10.1016/j.proci.2006.07.007 VL - 31 IS - 1 SP - 1119-1127 J2 - Proceedings of the Combustion Institute LA - en OP - SN - 1540-7489 UR - http://dx.doi.org/10.1016/j.proci.2006.07.007 DB - Crossref KW - ethanol-blended flame KW - propene KW - molecular beam mass spectrometry KW - benzene formation KW - aldehyde formation ER - TY - JOUR TI - RMDff: A smoothly transitioning, forcefield-based representation of kinetics for reactive molecular dynamics simulations AU - Smith, K. D. AU - Stoliarov, S. I. AU - Nyden, M. R. AU - Westmoreland, P. R. T2 - MOLECULAR SIMULATION AB - RMDff is a new forcefield that smoothly couples the reactive intersections of potential energy surfaces to model chemical reactions. The method uses switching functions to accomplish a smooth transition from reactant to product atom types. This paper demonstrates and tests RMDff for homolytic scissions. The reaction networks are described by localized events involving only a few atoms, so that the complex mechanisms employed in conventional kinetics modeling are not needed. Unlike quantum chemical calculations, which are feasible only for small molecules, this new valence-bond forcefield can be coupled with Reactive Molecular Dynamics to describe chemical reactions in large domains. DA - 2007/4/15/ PY - 2007/4/15/ DO - 10.1080/08927020601156392 VL - 33 IS - 4-5 SP - 361-368 SN - 1029-0435 KW - molecular dynamics KW - forcefields KW - reactive forcefield KW - finetics KW - homolysis ER - TY - JOUR TI - Photoionization mass spectrometry and modeling studies of the chemistry of fuel-rich dimethyl ether flames AU - Cool, Terrill A. AU - Wang, Juan AU - Hansen, Nils AU - Westmoreland, Phillip R. AU - Dryer, Fredrick L. AU - Zhao, Zhenwei AU - Kazakov, Andrei AU - Kasper, Tina AU - Kohse-Höinghaus, Katharina T2 - Proceedings of the Combustion Institute AB - Reaction paths are identified for dimethyl ether (DME) combustion using modeling of new data from fuel-rich DME flat flames. A molecular-beam flame-sampling photoionization mass spectrometer, employing VUV synchrotron radiation, is applied to the measurement of mole fractions for 21 flame species in low-pressure premixed fuel-rich (Φ = 1.2, 1.68) DME/oxygen/argon flat flames. This approach is capable of resolving and identifying isomers and other flame species of near equal masses with ionization thresholds that differ by as little as 0.1 eV. The measurements agree well with flame modeling predictions, using a recently revised high-temperature DME kinetic mechanism, which identify reaction paths quite analogous to alkane combustion. They further reveal the presence of ethyl methyl ether, a molecule previously unobserved in flames and not included in present flame models. DA - 2007/1// PY - 2007/1// DO - 10.1016/j.proci.2006.08.044 VL - 31 IS - 1 SP - 285-293 J2 - Proceedings of the Combustion Institute LA - en OP - SN - 1540-7489 UR - http://dx.doi.org/10.1016/j.proci.2006.08.044 DB - Crossref KW - dimethyl ether KW - kinetics KW - molecular-beam mass spectrometry KW - flames KW - photoionization ER - TY - JOUR TI - Photoionization mass spectrometric studies and modeling of fuel-rich allene and propyne flames AU - Hansen, Nils AU - Miller, James A. AU - Taatjes, Craig A. AU - Wang, Juan AU - Cool, Terrill A. AU - Law, Matthew E. AU - Westmoreland, Phillip R. T2 - Proceedings of the Combustion Institute AB - Flame-sampling photoionization mass spectrometry is used for measurements of the absolute molar composition of fuel-rich (ϕ = 1.8) low-pressure laminar flames of allene and propyne. The experiment combines molecular-beam mass spectrometry with photoionization by tunable vacuum–ultraviolet synchrotron radiation. This approach provides selective detection of individual isomers and unambiguous identifications of other flame species of near-equal mass by near threshold photoionization efficiency measurements. Mole fraction profiles for more than 30 flame species with ion masses ranging from 2 to 78 are presented. The isomeric composition is resolved for most intermediates, for example, mole fraction profiles are presented for both benzene and the fulvene isomer. The results are compared with predictions based on current kinetic models. The mole fractions of the major species are predicted quite accurately, however, some discrepancies are observed for minor species. DA - 2007/1// PY - 2007/1// DO - 10.1016/j.proci.2006.07.045 VL - 31 IS - 1 SP - 1157-1164 J2 - Proceedings of the Combustion Institute LA - en OP - SN - 1540-7489 UR - http://dx.doi.org/10.1016/j.proci.2006.07.045 DB - Crossref KW - mass spectrometry KW - photoionization KW - premixed laminar flames ER - TY - JOUR TI - Isomer-Specific Fuel Destruction Pathways in Rich Flames of Methyl Acetate and Ethyl Formate and Consequences for the Combustion Chemistry of Esters† AU - Osswald, Patrick AU - Struckmeier, Ulf AU - Kasper, Tina AU - Kohse-Höinghaus, Katharina AU - Wang, Juan AU - Cool, Terrill A. AU - Hansen, Nils AU - Westmoreland, Phillip R. T2 - The Journal of Physical Chemistry A AB - The influences of fuel-specific destruction pathways on flame chemistry are determined for two isomeric ester fuels, methyl acetate, CH3(CO)OCH3, and ethyl formate, H(CO)OC2H5, used as model representatives for biodiesel compounds, and their potential for forming air pollutants is addressed. Measurements are presented of major and intermediate species mole fractions in premixed, laminar flat flames using molecular-beam sampling and isomer-selective VUV-photoionization mass spectrometry. The observed intermediate species concentrations depend crucially on decomposition of the different radicals formed initially from the fuels. The methyl acetate structure leads to preferential formation of formaldehyde, while the ethyl formate isomer favors the production of acetaldehyde. Ethyl formate also yields higher concentrations of the C2 species (C2H2 and C2H4) and C4 species (C4H2 and C4H4). Benzene concentrations, while larger for ethyl formate, are at least an order of magnitude smaller for both flames than seen for simple hydrocarbon fuels (ethylene, ethane, propene, and propane). DA - 2007/5// PY - 2007/5// DO - 10.1021/jp068337w VL - 111 IS - 19 SP - 4093-4101 J2 - J. Phys. Chem. A LA - en OP - SN - 1089-5639 1520-5215 UR - http://dx.doi.org/10.1021/jp068337w DB - Crossref ER - TY - JOUR TI - Initial Steps of Aromatic Ring Formation in a Laminar Premixed Fuel-Rich Cyclopentene Flame† AU - Hansen, N. AU - Kasper, T. AU - Klippenstein, S. J. AU - Westmoreland, P. R. AU - Law, M. E. AU - Taatjes, C. A. AU - Kohse-Höinghaus, K. AU - Wang, J. AU - Cool, T. A. T2 - The Journal of Physical Chemistry A AB - A fuel-rich, nonsooting, premixed laminar cyclopentene flame (φ = 2.0) at 37.6 Torr (50 mbar) is investigated by flame-sampling photoionization molecular-beam mass spectrometry utilizing vacuum-ultraviolet synchrotron radiation. Mole fractions as a function of distance from the burner are measured for 49 intermediates with ion masses ranging from 2 (H2) to 106 (C8H10), providing a broad database for flame modeling studies. The isomeric composition is resolved for most species, and the identification of several C4Hx, C7H6, and C7H8 isomers is discussed in detail. The presence of C5H5CCH/C5H4CCH2 and cycloheptatriene is revealed by comparisons between flame-sampled photoionization efficiency data and theoretical simulations, based on calculated ionization energies and Franck−Condon factors. This insight suggests a new potential molecular- weight growth mechanism that is characterized by C5−C7 ring enlargement reactions. DA - 2007/5// PY - 2007/5// DO - 10.1021/jp0683317 VL - 111 IS - 19 SP - 4081-4092 J2 - J. Phys. Chem. A LA - en OP - SN - 1089-5639 1520-5215 UR - http://dx.doi.org/10.1021/jp0683317 DB - Crossref ER - TY - JOUR TI - Benzene precursors and formation routes in a stoichiometric cyclohexane flame AU - Law, Matthew E. AU - Westmoreland, Phillip R. AU - Cool, Terrill A. AU - Wang, Juan AU - Hansen, Nils AU - Taatjes, Craig A. AU - Kasper, Tina T2 - Proceedings of the Combustion Institute AB - Benzene formation was found to be dominated by stepwise radical dehydrogenation of cyclohexane in a stoichiometric flat flame of cyclohexane/O2/32.5% Ar, 30.00 Torr pressure, and 35.0 cm s−1 feed velocity. This route, involving H-abstractions and β-scissions, is in contrast to conventional propargyl routes. Three types of analyses lead to this conclusion: identification of key flame species by mass and ionization energy; measurement and use of mole-fraction profiles in the flat flame; and mechanistic reactive-flow modeling of the flame, interpreted by analyzing the dominant reaction steps giving rise to the prediction. For relevant species, profiles of mole fraction were mapped by molecular-beam mass spectrometry in separate apparatuses with identical burners using electron ionization (UMass Amherst) and synchrotron VUV photoionization (LBNL ALS), respectively. In the latter, recently developed apparatus, ionization energies can be measured with greatly enhanced resolution, yielding improvements in species identification that include precise resolution of hydrocarbon isomers, crucial to the findings of this study. DA - 2007/1// PY - 2007/1// DO - 10.1016/j.proci.2006.07.259 VL - 31 IS - 1 SP - 565-573 J2 - Proceedings of the Combustion Institute LA - en OP - SN - 1540-7489 UR - http://dx.doi.org/10.1016/j.proci.2006.07.259 DB - Crossref KW - cyclohexane KW - molecular-beam mass spectrometry KW - flames KW - benzene KW - dehydrogenation ER - TY - JOUR TI - What makes an ionic liquid a liquid? The impact of structure on ionic liquid properties AU - Henderson, W. A. AU - Trulove, P. C. AU - DeLong, H. C. AU - Young, V. G., Jr. T2 - ECS Transactions DA - 2007/// PY - 2007/// VL - 3 IS - 35 SP - 83-88 ER - TY - JOUR TI - The preparation and characterization of bombyx mori silk nanocomposites using ionic liquids AU - Fox, D. M. AU - Fylstra, P. AU - Hanley, M. AU - Henderson, W. AU - Trulove, P. C. AU - Bellayer, S. AU - Gilman, J. W. AU - De Long, H. C. T2 - ECS Transactions DA - 2007/// PY - 2007/// VL - 3 IS - 35 SP - 11-20 ER - TY - JOUR TI - Amino acid based ionic liquids: Solvents for improved biopolymer dissolution AU - Hanley, M. G. AU - Green, J. M. AU - Henderson, W. A. AU - Fox, D. M. AU - De Long, H. C. AU - Trulove, P. C. T2 - ECS Transactions DA - 2007/// PY - 2007/// VL - 3 IS - 35 SP - 41-48 ER - TY - JOUR TI - Spectroscopic and ab initio characterization of the conformational states of the bis(perfluoroethane-sulfonyl)imide anion (BETI-) AU - Grondin, J. AU - Talaga, D. AU - Lassegues, J. C. AU - Johansson, P. AU - Henderson, W. A. T2 - Journal of Raman Spectroscopy: JRS DA - 2007/// PY - 2007/// VL - 38 IS - 1 SP - 53-60 ER - TY - JOUR TI - Relative volatilities of ionic liquids by vacuum distillation of mixtures AU - Widegren, J. A. AU - Wang, Y.-M. AU - Henderson, W. A. AU - Magee, J. W. T2 - Journal of Physical Chemistry. B, Condensed Matter, Materials, Surfaces, Interfaces & Biophysical DA - 2007/// PY - 2007/// VL - 111 IS - 30 SP - 8959-8964 ER - TY - JOUR TI - Niche-mediated control of human embryonic stem cell self-renewal and differentiation AU - Peerani, Raheem AU - Rao, Balaji M. AU - Bauwens, Celine AU - Yin, Ting AU - Wood, Geoffrey A. AU - Nagy, Andras AU - Kumacheva, Eugenia AU - Zandstra, Peter W. T2 - EMBO JOURNAL AB - Complexity in the spatial organization of human embryonic stem cell (hESC) cultures creates heterogeneous microenvironments (niches) that influence hESC fate. This study demonstrates that the rate and trajectory of hESC differentiation can be controlled by engineering hESC niche properties. Niche size and composition regulate the balance between differentiation-inducing and -inhibiting factors. Mechanistically, a niche size-dependent spatial gradient of Smad1 signaling is generated as a result of antagonistic interactions between hESCs and hESC-derived extra-embryonic endoderm (ExE). These interactions are mediated by the localized secretion of bone morphogenetic protein-2 (BMP2) by ExE and its antagonist, growth differentiation factor-3 (GDF3) by hESCs. Micropatterning of hESCs treated with small interfering (si) RNA against GDF3, BMP2 and Smad1, as well treatments with a Rho-associated kinase (ROCK) inhibitor demonstrate that independent control of Smad1 activation can rescue the colony size-dependent differentiation of hESCs. Our results illustrate, for the first time, a role for Smad1 in the integration of spatial information and in the niche-size-dependent control of hESC self-renewal and differentiation. DA - 2007/11/14/ PY - 2007/11/14/ DO - 10.1038/sj.emboj.7601896 VL - 26 IS - 22 SP - 4744-4755 SN - 1460-2075 KW - embryonic stem cell KW - micropatterning KW - niche KW - self-renewal KW - Smad signaling ER - TY - JOUR TI - A student-centered approach to teaching material and energy balances: 1. Course design AU - Bullard, L. G. AU - Felder, R. M T2 - Chemical Engineering Education DA - 2007/// PY - 2007/// VL - 41 IS - 2 SP - 93-100 ER - TY - JOUR TI - A student-centered approach to teaching material and energy balances 2. Course delivery and assessment AU - Bullard, L. G. AU - Felder, R. M T2 - Chemical Engineering Education DA - 2007/// PY - 2007/// VL - 41 IS - 3 SP - 167-176 ER - TY - CONF TI - Manipulating siloxane surfaces: Obtaining the desired surface function via engineering design AU - Crowe, J. A. AU - Efimenko, Kirill AU - Genzer, Jan AB - We present a synopsis of recent accomplishment in our group in the area of surface-functionalized silicone elastomer networks. Specifically, we show that by combining mechanical manipulation of poly(dimethylsiloxane) (PDMS) networks with activation via ultraviolet/ozone (UVO) treatment and subsequent chemical modification of the pre-activated surfaces, one can generate so-called mechanically assembled monolayers (MAMs). This technology can be successfully applied to create a variety of surfaces, including dense polymer brushes, long-lived superhydrophobic surfaces, molecular gradients comprising tunable length scales and two-dimensional chemical gradients. In addition, the UVO modification of mechanically strained PDMS sheets provides a convenient route for creating "buckled" elastomeric sheets. These surfaces have a multitude of applications; ranging from anti-fouling surfaces to directed particle assembly. Finally we demonstrate control of surface wettability and responsiveness using poly(vinylmethylsiloxane) (PVMS) networks. We have shown that PVMS surfaces can be chemically tailored by reacting with thiols. The degree of response (including response rate) of such surfaces to hydrophobic-hydrophilic interactions can be adjusted by varying the chemical and structural properties of the side-group modifiers. C2 - 2007/// C3 - Science and technology of silicones and silicone-modified materials DA - 2007/// DO - 10.1021/bk-2007-0964.ch015 VL - 964 SP - 222–255 ER - TY - JOUR TI - Skin pressure profiles and variations with body postural changes beneath medical elastic compression stockings AU - Liu, Rong AU - Kwok, Yi Lin AU - Li, Yi AU - Lao, Terence T. AU - Zhang, Xin T2 - INTERNATIONAL JOURNAL OF DERMATOLOGY AB - Medical elastic compression stockings (GCSs) are one of the most widely used mechanical compression approaches to relieve venous disorders of the lower limb. The skin pressure profiles applied by compression stockings may be altered with body postural changes, thus exerting influences on their therapeutic efficiency.To examine and quantify objectively the skin pressure distribution and magnitude beneath GCSs with body postural changes, and to analyze the possible reasons for skin pressure variations.The pressure levels of four different kinds of commonly used GCS were measured using piezoelectric sensors and a multichannel measuring system in six female healthy volunteers in 10 different body positions.Body postural changes significantly influenced the skin pressure profiles (P < 0.001). Skin pressures at the ankle and on the anterior side of the leg were always highest when tested in all positions. Extension and flexion of the knee joint significantly influenced the skin pressure at the anterior and posterior aspects of the leg, especially when tested in the sitting position with the knee flexed at 90 degrees and in the supine position with the knee flexed at more than 90 degrees (P < 0.001). Plantar flexion of the ankle joint, such as up-heel standing and heel-off walking, significantly increased the skin pressure in the ankle region. Contraction, extension, and relaxation of the calf muscle did not produce large fluctuations in skin pressure when tested in positions with full knee extension.Body postures may be one of the most important factors influencing the skin pressure profiles applied by compression stockings. The anatomic structure of individual legs, the special design of compression stockings, and the physical properties of stocking materials also influence skin pressure variations at different tested locations in different body positions. Appropriate leg postural changes and exercise may improve the therapeutic effectiveness of GCSs. DA - 2007/5// PY - 2007/5// DO - 10.1111/j.1365-4632.2007.03175.x VL - 46 IS - 5 SP - 514-523 SN - 0011-9059 UR - https://publons.com/publon/8072788/ ER - TY - JOUR TI - Nanotechnology: a fiber perspective AU - Lucia, L. AU - Rojas, O. J. AU - eds. T2 - Cellulose DA - 2007/// PY - 2007/// VL - 14 IS - 6 ER - TY - JOUR TI - Research ethics education: beyond RCR training AU - Comstock, G. L. AU - Alston-Mills, B. AU - Grant, C. T2 - FCTL Newsletter DA - 2007/// PY - 2007/// VL - 2 SP - 1-4 ER - TY - CHAP TI - Oxidative chemistry of lignin In supercritical carbon dioxide & expanded liquids AU - Argyropoulos, D. S. AU - Saquing, C. D. AU - Gaspar, A. R. AU - Soriano, N. U. AU - Lucia, L. A. AU - Rojas, O. J. T2 - Materials, chemicals and energy from forest biomass AB - This chapter describes the use of supercritical carbon dioxide (scCO2) and scCO2-expanded liquids, as reaction media for the oxidative fragmentation of lignin using hydrogen peroxide as the oxidant. Kraft Indulin Lignin (KIL) is oxidized with peroxide in neat scCO2 but more extensive oxidation occurs in scCO2-expanded liquids, selectively inducing the formation of large amounts of carboxylic acids via the elimination of phenolic moieties. Interestingly, the weight average molecular weight of the lignin oxidized in neat scCO2 decreased while it increased in scCO2-expanded liquid, most likely via the preferential elimination of the lower molecular weight fragments. Notably, all these significant oxidative transformations occur in total absence of alkali, which is essential when such reactions occur in aqueous media. PY - 2007/// DO - 10.1021/bk-2007-0954.ch020 VL - 954 SP - 311-331 PB - Washington, DC: ACS Books SN - 9780841239814 ER - TY - CHAP TI - Measurement of cellulase activity with piezoelectric resonators AU - Rojas, O. J. AU - Jheong, C. AU - Turon, X. AU - Argyropoulos, D. S. T2 - Materials, chemicals and energy from forest biomass PY - 2007/// VL - 954 SP - 478-494 PB - Washington, DC: ACS Books SN - 9780841239814 ER - TY - CHAP TI - Lignin as emulsion stabilizers: Materials, chemicals and energy from forest biomass AU - Rojas, O. J. AU - Bullon, J. AU - Ysambertt, F. Forgiarini AU - A., Argyropoulos AU - D. S., AU - Salager, J.-L. T2 - Materials, chemicals and energy from forest biomass PY - 2007/// VL - 954 SP - 182-199 PB - Washington, DC: ACS Books SN - 9780841239814 ER - TY - JOUR TI - What happens to cellulosic fibers during papermaking and recycling? A review AU - Hubbe, M. A. AU - Venditti, R. A. AU - Rojas, O. J. T2 - BioResources DA - 2007/// PY - 2007/// VL - 2 IS - 4 SP - 739-788 ER - TY - JOUR TI - Water treatment in papermaking white water loops using membrane separation techniques AU - Bullon, J. AU - Rennola, L. AU - Salazar, F. AU - Hoeger, M. AU - Cardenas, A. AU - Rojas, O. J. T2 - Revista Tecnica de la Facultad de Ingenieria Universidad Del Zulia DA - 2007/// PY - 2007/// VL - 30 SP - 90-97 ER - TY - PAT TI - Reliable high voltage gate dielectric layers using a dual nitridation process AU - Khamankar, R. AU - Grider, D. T. AU - Niimi, H. AU - Gurba, A. AU - Tran, T. AU - Chambers, J. J. C2 - 2007/// DA - 2007/// PY - 2007/// ER - TY - PAT TI - Process for manufacturing dual work function metal gates in a microelectronics device AU - Colombo, L. AU - Chambers, J. J. AU - Visokay, M. R. C2 - 2007/// DA - 2007/// PY - 2007/// ER - TY - PAT TI - Methods and systems to mitigate etch stop clipping for shallow trench isolation fabrication AU - Quevedo-Lopez, M. AU - Chambers, J. J. AU - Olsen, L. C. C2 - 2007/// DA - 2007/// PY - 2007/// ER - TY - JOUR TI - Solid-liquid phase equilibria for mixtures containing diatomic Lennard-Jones molecules AU - Galbraith, A. L. AU - Hall, Carol T2 - Fluid Phase Equilibria AB - Solid—liquid phase diagrams are calculated for systems containing pure Lennard–Jones dumbbell molecules and their mixtures. We begin by calculating the equations of state for systems containing C2H6, CO2 and F2, all of which are modeled by a two-center Lennard–Jones potential for linear diatomic molecules. We then use the Frenkel–Ladd thermodynamic integration method to calculate the free energies. The equations of state and the free energies are used to obtain solid–liquid coexistence points which are needed to start the Gibbs–Duhem integration. The solid–liquid phase equilibria for pure C2H6, CO2 and F2 and binary mixtures of Lennard–Jones dumbbells are predicted using the Gibbs–Duhem integration method. We investigate the effects of molecular size and intermolecular attractions on the solid–liquid phase diagrams of binary Lennard–Jones mixtures. DA - 2007/// PY - 2007/// DO - 10.1016/j.fluid.2007.07.064 VL - 262 IS - 1-2 SP - 1–13 ER - TY - JOUR TI - Morphological development and rheological changes of phenoxy/SAN blends during in-situ polymerization AU - Guo, Qipeng AU - Arends, Peter AU - Thomann, Ralf AU - Spontak, Richard J. AU - Gronski, Wolfram T2 - JOURNAL OF POLYMER SCIENCE PART B-POLYMER PHYSICS AB - Abstract This article reports the results of an investigation into the time‐dependent morphological and rheological changes that accompany the in‐situ polymerization of blends composed of poly(hydroxyether of bisphenol A) (phenoxy) and poly(styrene‐ co ‐acrylonitrile) (SAN). The rheological behavior was monitored continuously during the in‐situ polymerization, whereas the miscibility and phase structure of blends formed in situ were examined at discrete stages of polymerization by differential scanning calorimetry and transmission electron microscopy. In the blend with 30 wt % SAN, a co‐continuous blend morphology was associated with gradual changes in the dynamic moduli, suggesting that phase separation proceeded by spinodal decomposition (SD). In contrast, phenoxy‐rich dispersions were uniformly dispersed in a continuous SAN‐rich matrix in the blend with 50 wt % SAN, and the corresponding rheological signature revealed a sharp initial increase in the dynamic moduli, followed by slower growth after long times, indicative of phase separation via nucleation and growth (NG). The rheological property changes are closely related to morphology development and mechanisms of phase separation induced during in‐situ polymerization. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2614–2619, 2007 DA - 2007/9/15/ PY - 2007/9/15/ DO - 10.1002/polb.21267 VL - 45 IS - 18 SP - 2614-2619 SN - 1099-0488 KW - blends KW - in-situ polymerization KW - morphology KW - polymer blends KW - rheology ER - TY - JOUR TI - Impact of substrate glycoside linkage. and elemental sulfur on bioenergetics, of and hydrogen production by the hyperthermophilic Archaeon Pyrococcus furiosus AU - Chou, Chung-Jung AU - Shockley, Keith R. AU - Conners, Shannon B. AU - Lewis, Derrick L. AU - Comfort, Donald A. AU - Adams, Michael W. W. AU - Kelly, Robert M. T2 - APPLIED AND ENVIRONMENTAL MICROBIOLOGY AB - ABSTRACT Glycoside linkage (cellobiose versus maltose) dramatically influenced bioenergetics to different extents and by different mechanisms in the hyperthermophilic archaeon Pyrococcus furiosus when it was grown in continuous culture at a dilution rate of 0.45 h −1 at 90°C. In the absence of S 0 , cellobiose-grown cells generated twice as much protein and had 50%-higher specific H 2 generation rates than maltose-grown cultures. Addition of S 0 to maltose-grown cultures boosted cell protein production fourfold and shifted gas production completely from H 2 to H 2 S. In contrast, the presence of S 0 in cellobiose-grown cells caused only a 1.3-fold increase in protein production and an incomplete shift from H 2 to H 2 S production, with 2.5 times more H 2 than H 2 S formed. Transcriptional response analysis revealed that many genes and operons known to be involved in α- or β-glucan uptake and processing were up-regulated in an S 0 -independent manner. Most differentially transcribed open reading frames (ORFs) responding to S 0 in cellobiose-grown cells also responded to S 0 in maltose-grown cells; these ORFs included ORFs encoding a membrane-bound oxidoreductase complex (MBX) and two hypothetical proteins (PF2025 and PF2026). However, additional genes (242 genes; 108 genes were up-regulated and 134 genes were down-regulated) were differentially transcribed when S 0 was present in the medium of maltose-grown cells, indicating that there were different cellular responses to the two sugars. These results indicate that carbohydrate characteristics (e.g., glycoside linkage) have a major impact on S 0 metabolism and hydrogen production in P. furiosus . Furthermore, such issues need to be considered in designing and implementing metabolic strategies for production of biofuel by fermentative anaerobes. DA - 2007/11// PY - 2007/11// DO - 10.1128/AEM.00597-07 VL - 73 IS - 21 SP - 6842-6853 SN - 1098-5336 ER - TY - JOUR TI - Continuous copolymerization of vinylidene fluoride with hexafluoropropylene in Supercritical carbon dioxide: Low hexafluoropropylene content semicrystalline copolymers AU - Ahmed, Tamer S. AU - DeSimone, Joseph M. AU - Roberts, George W. T2 - MACROMOLECULES AB - The copolymerization of vinylidene fluoride with hexafluoropropylene (HFP) was carried out in supercritical carbon dioxide by precipitation polymerization using a continuous stirred tank reactor. Copolymers with ca. 10 mol % HFP were synthesized at 40 °C and pressures in the range of 207−400 bar using perfluorobutyryl peroxide as the free radical initiator. The effects of feed monomer concentration and reaction pressure were both explored at otherwise constant conditions. The rate of polymerization (Rp) and the number-average molecular weight (Mn) increased linearly with the total monomer concentration up to about 6 M, the highest concentration investigated. The Rp and the Mn were strongly influenced by the reaction pressure. An 80% increase in both Rp and Mn was observed when the reaction pressure rose from 207 to 400 bar. The molecular weight distributions of the synthesized copolymer showed a long tail that increased to become a broad shoulder with increasing total monomer concentration. This tail increased with increasing reaction pressure. The data suggest that the carbon dioxide-rich fluid phase is the primary locus of polymerization. DA - 2007/12/25/ PY - 2007/12/25/ DO - 10.1021/ma0713613 VL - 40 IS - 26 SP - 9322-9331 SN - 0024-9297 ER - TY - JOUR TI - The stability of water-in-crude and model oil emulsions AU - Sullivan, A. P. AU - Zaki, N. N. AU - Sjoblom, J. AU - Kilpatrick, P. K. T2 - Canadian Journal of Chemical Engineering DA - 2007/// PY - 2007/// VL - 85 IS - 6 SP - 793-807 ER - TY - JOUR TI - Synthesis and structural properties of porphyrin analogues of bacteriochlorophyll c AU - Ptaszek, Marcin AU - Yao, Zhen AU - Savithri, Dhanalekshmi AU - Boyle, Paul D. AU - Lindsey, Jonathan S. T2 - TETRAHEDRON AB - The self-assembling photosynthetic pigment bacteriochlorophyll c contains α-hydroxyethyl and keto groups on opposite sides of the macrocycle. A porphyrin has been synthesized that contains a 3-hydroxymethyl group and a 15-ethoxycarbonyl group (ZnP2-OH). X-ray analysis of ZnP2-OH and the related porphyrin containing 5-hydroxymethyl and 15-ethoxycarbonyl groups (ZnP1-OH) in each case revealed infinite coordination polymers wherein the zinc porphyrins are bound by Zn–O coordination and are cofacially offset in a staircase architecture. DA - 2007/12/17/ PY - 2007/12/17/ DO - 10.1016/j.tet.2007.10.023 VL - 63 IS - 51 SP - 12629-12638 SN - 0040-4020 ER - TY - JOUR TI - Real-time conductivity analysis through single-molecule electrical junctions AU - Na, Jeong-Seok AU - Ayres, Jennifer AU - Chandra, Kusum L AU - Gorman, Christopher B AU - Parsons, Gregory N T2 - Nanotechnology AB - Conductance through single-molecule junctions, consisting of nanoparticle/molecule/nanoparticle units between nanoscale planar electrodes, was monitored in real time during several process sequences, including dielectrophoretic directed self-assembly and post-assembly modification. Assembly faults are directly detected in real time when non-ideal assembly conditions result in molecular junction failure and nanoparticle fusion in the junction. The real-time conductivity measured through the junction was sensitive to ambient conditions, and changes persisted over several days of exposure. Atomic layer deposition of Al(2)O(3) was used to encapsulate and isolate the molecular junctions, and the effect of the deposition process sequence on current through the junction was evaluated in real time. Results indicate that the current measured during atomic layer deposition is sensitive to the chemical oxidation and reduction reactions proceeding in the 1-2 nm confined region between assembled nanoparticles. DA - 2007/9/13/ PY - 2007/9/13/ DO - 10.1088/0957-4484/18/42/424001 VL - 18 IS - 42 SP - 424001 J2 - Nanotechnology OP - SN - 0957-4484 1361-6528 UR - http://dx.doi.org/10.1088/0957-4484/18/42/424001 DB - Crossref ER - TY - JOUR TI - Kinetic Modeling of photocatalyzed soot oxidation on titanium dioxide thin films AU - Chin, Paul AU - Roberts, George W. AU - Ollis, David F. T2 - INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH AB - Recent research [Mills et al. Chemosphere 2006, 64, 1032−1035; Lee and Choi J. Phys. Chem. B 2002, 106, 11818−11822] has demonstrated photocatalytic oxidation of “soot” by titanium dioxide thin films. However, little attention has been paid to developing kinetic models of photocatalyzed soot destruction. We develop here a series/parallel kinetic model for soot oxidation and use it to analyze the CO2 data of Mills et al. and the mass loss data of Lee and Choi. The model assumes two oxidation pathways: a single step yielding CO2 directly and a serial sequence through a solid intermediate species, which is subsequently oxidized to CO2. We extend this simple model to include variable O2 partial pressure, which is used to evaluate the initial CO2 data of Lee and Choi. These models fit the experimental CO2 data of Mills et al. and Lee and Choi well. The simple kinetic model also describes the mass loss data of Lee and Choi for the front mode of sample irradiation. DA - 2007/11/7/ PY - 2007/11/7/ DO - 10.1021/ie070083t VL - 46 IS - 23 SP - 7598-7604 SN - 0888-5885 ER - TY - JOUR TI - Fiber nanotechnology: a new platform for "green" research and technological innovations AU - Lucia, Lucian A. AU - Rojas, Orlando J. T2 - CELLULOSE DA - 2007/12// PY - 2007/12// DO - 10.1007/s10570-007-9177-1 VL - 14 IS - 6 SP - 539-542 SN - 0969-0239 ER - TY - JOUR TI - Facile method of controlling monomer sequence distributions in random copolymers AU - Semler, J. J. AU - Jhon, Y. K. AU - Tonelli, A. AU - Beevers, M. AU - Krishnamoorti, R. AU - Genzer, Jan T2 - Advanced Materials AB - Advanced MaterialsVolume 19, Issue 19 p. 2877-2883 Communication Facile Method of Controlling Monomer Sequence Distributions in Random Copolymers† J. J. Semler, J. J. Semler Department of Chemical & Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina 27 695-7905 (USA) Present address: Lexmark International Inc., Lexington, KY 40511, USASearch for more papers by this authorY. K. Jhon, Y. K. Jhon Department of Chemical & Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina 27 695-7905 (USA)Search for more papers by this authorA. Tonelli, A. Tonelli College of Textiles, North Carolina State University, Raleigh, North Carolina 27695-8301 (USA)Search for more papers by this authorM. Beevers, M. Beevers Department of Chemical & Biomolecular Engineering & Applied Chemistry, Aston University, Birmingham B4 7ET (UK)Search for more papers by this authorR. Krishnamoorti, R. Krishnamoorti Department of Chemical Engineering, University of Houston, Houston, Texas 77204-4004 (USA)Search for more papers by this authorJ. Genzer, J. Genzer Jan_Genzer@ncsu.edu Department of Chemical & Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina 27 695-7905 (USA)Search for more papers by this author J. J. Semler, J. J. Semler Department of Chemical & Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina 27 695-7905 (USA) Present address: Lexmark International Inc., Lexington, KY 40511, USASearch for more papers by this authorY. K. Jhon, Y. K. Jhon Department of Chemical & Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina 27 695-7905 (USA)Search for more papers by this authorA. Tonelli, A. Tonelli College of Textiles, North Carolina State University, Raleigh, North Carolina 27695-8301 (USA)Search for more papers by this authorM. Beevers, M. Beevers Department of Chemical & Biomolecular Engineering & Applied Chemistry, Aston University, Birmingham B4 7ET (UK)Search for more papers by this authorR. Krishnamoorti, R. Krishnamoorti Department of Chemical Engineering, University of Houston, Houston, Texas 77204-4004 (USA)Search for more papers by this authorJ. Genzer, J. Genzer Jan_Genzer@ncsu.edu Department of Chemical & Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina 27 695-7905 (USA)Search for more papers by this author First published: 11 September 2007 https://doi.org/10.1002/adma.200602359Citations: 43 † This work was supported by the National Science Foundation (Grant No. DMR-0353102). We acknowledge the support of the National Institute of Standards and Technology, U.S. Department of Commerce, in providing the neutron facilities used in this work. This work utilized facilities supported in part by the National Science Foundation under Agreement No. DMR-0454672. The authors gratefully acknowledge Angelica Sanchez for carrying out the DSC measurements and Hanna Gracz for performing the NMR experiments. We also thank Jack Douglas and Rajendra R. Bhat for useful discussions and comments. AboutPDF 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 Abstract Copolymers of poly(styrene-co-4-bromostyrene) (PBrxS) with adjustable monomer sequence distribution of styrene (S) and 4-bromostyrene (4-BrS) and composition (x = content of 4-BrS) are prepared by brominating parent polystyrene (PS). While bromination reaction carried out above the theta temperature (Θ) leads to PBrxS with random monomer distribution, bromination of PS performed at temperatures below Θ produces PBrxS having a random-blocky character. Citing Literature Volume19, Issue19October, 2007Pages 2877-2883 RelatedInformation DA - 2007/// PY - 2007/// DO - 10.1002/adma.200602359 VL - 19 IS - 19 SP - 2877- ER - TY - JOUR TI - Development and evaluation of realistic microbioassays in freely suspended droplets on a chip AU - Rastogi, V. AU - Velev, Orlin T2 - Biomicrofluidics AB - A novel technique for biomolecular detection in microliter droplets floating on the surface of high density oil is presented. Each droplet was captured and manipulated dielectrophoretically and was used as a site for a microscopic bioassay based on agglutination of antibody-conjugated particles. The results were read out by the pattern of unagglomerated gold nanoparticles collected on the droplet surface. Two formats of bioassays, namely gold only agglutination and gold and latex agglutination, were investigated experimentally by varying analyte concentration, particle size and concentration, number of antigen binding sites per particle, time for incubation, and rate of particle collection on the droplet surface. The microbioassays performance was also evaluated with ricin antibodies and compared to the ricin assays in field use. It is estimated that the droplet based assays require 100x smaller sample volume and are ten times more sensitive, though they require longer times to complete. The experiments were interpreted by modeling the kinetics of particle agglutination and mass transfer processes inside the droplets. The incubation time and antigen concentration values calculated by the model correlate well with the experimental results. The results could allow for development of efficient immunoassays on a chip requiring even smaller sample volumes. DA - 2007/// PY - 2007/// DO - 10.1063/1.2714185 VL - 1 IS - 1 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-57349200274&partnerID=MN8TOARS ER - TY - JOUR TI - Consequences of the nanoporosity of cellulosic fibers on their streaming potential and their interactions with cationic polyelectrolytes AU - Hubbe, Martin A. AU - Rojas, Orlando J. AU - Lucia, Lucian A. AU - Jung, Tae Min T2 - CELLULOSE AB - Electrokinetic tests, based on the streaming potential method, were used to elucidate interactions between cationic polyelectrolytes and cellulosic fibers and to reveal aspects of fibers’ nanoporosity. The fibrillated and nanoporous nature of bleached kraft fibers gave rise to time-dependent changes in streaming potential, following treatment of the wetted fibers with poly-diallyldimethylammonium chloride. Electrokinetic test results were consistent with an expected longer time required for higher-mass polyelectrolytes to diffuse into pore spaces, compared to lower-mass polyelectrolytes. Further evidence of the relative inability of polyelectrolyte molecules to diffuse into the pores of cellulose was obtained by switching back and forth between high and low ionic strength conditions during repeated measurement of streaming potential, after the fibers had been treated with a moderate amount of cationic polymer. By changing the concentration of sodium sulfate it was possible to switch the sign of streaming potential repeatedly from positive to negative and back again. Such results imply that a continuous path for liquid flow exists either in a fibrillar layer or within the cell walls. The same concepts also helped to explain the dosages of high-charge cationic polymer needed to achieve maximum dewatering rates, as well as the results of retention experiments using positively and negatively charged microcrystalline cellulose particles. DA - 2007/12// PY - 2007/12// DO - 10.1007/s10570-006-9098-4 VL - 14 IS - 6 SP - 655-671 SN - 1572-882X KW - adsorption KW - cellulose KW - polyelectrolytes KW - porosity KW - streaming potential ER - TY - JOUR TI - Theoretical study of kinetics of zipping phenomena in biomimetic polymers AU - Jayaraman, Arthi AU - Santiso, Erik E. AU - Hall, Carol K. AU - Genzer, Jan T2 - PHYSICAL REVIEW E AB - In this work we use theory to obtain a mathematical expression for a time correlation function c(l,t) that provides insight into the zipping phenomena along a polymer going through a conformational transition. The polymer is modeled as an Ising-like chain with each segment being in one of two states: bound (+1) or unbound (-1). The time correlation function c(l,t) predicts the correlation between the state of the jth polymer segment at time 0 and the state of the (j+/-l)th polymer segment at time t . The expressions for c(0,t) , c(1,t), and c(2,t) obtained from our theory are dependent on the values of k0 and k1, where 2k0 is the rate coefficient for one segment changing from an unbound state to a bound state when both the neighboring segments are in an unbound state, and 2k1 is the rate coefficient for one segment changing from an unbound state to a bound state when both the neighboring segments are in a bound state. The ratio k1/k0 is an indication of the extent of cooperativity of binding adjacent segments on the polymer. We observe that c(0,t), c(1,t), and c(2,t) decay to 0 (no correlation) more slowly and the maximum values of c(1,t) and c(2,t) are lower for low values of k1/k0 as compared to high values of k1/k0. This is because at low values of k1/k0 the consecutive binding of adjacent segments along the polymer occurs slowly, while at high values of k1/k0 the cooperativity of binding adjacent segments is high and the segments along the polymer bind in a fast zipping mechanism. DA - 2007/7// PY - 2007/7// DO - 10.1103/physreve.76.011915 VL - 76 IS - 1 SP - SN - 1550-2376 ER - TY - JOUR TI - New B2O3 crystals predicted from concurrent molecular dynamics simulations and first-principles calculations AU - Huang, Liping AU - Durandurdu, Murat AU - Kieffer, John T2 - JOURNAL OF PHYSICAL CHEMISTRY C AB - Molecular dynamics (MD) simulations, based on a new coordination-dependent charge-transfer potential, were used to study the behavior of crystalline B2O3 in response to various thermal and mechanical constraints. This interaction potential allows for the charges on atoms to redistribute upon the formation and rupture of chemical bonds and dynamically adjusts to multiple coordination states for a given species. Our MD simulations predict that upon isotropic expansion and compression, the B2O3-I crystal transforms into new low- and high-density B2O3 crystals, the stability of which we have further verified using first-principles calculations. The low-density B2O3 crystals (B2O3-0) provide a key to understanding the anomalous thermomechanical behaviors of vitreous B2O3 and the crystallization anomaly of this compound. The high-density B2O3 crystal (B2O3-III), predicted from concurrent MD simulations and first-principles calculations, is different from the known high-pressure phase of B2O3-II crystal, even though the bonding is the same in these two phases. B2O3-III is characterized by a higher energy than B2O3-II at low pressures, but upon further compression the energies of these two phases become indistinguishable. The transformation from B2O3-I to B2O3-III appears to be kinetically favored, especially at low temperatures. Our studies indicate that the phase diagram of B2O3 is much richer than previously known. DA - 2007/9/20/ PY - 2007/9/20/ DO - 10.1021/jp0735583 VL - 111 IS - 37 SP - 13712-13720 SN - 1932-7447 ER - TY - JOUR TI - Fabrication of magnetically-functionalized lens- and donut-shaped microparticles by a surface-formation technique AU - Wege, H.A. AU - Dyab, A.K.F. AU - Velev, Orlin AU - Paunov, V.N. T2 - Physical Chemistry Chemical Physics AB - We report a simple method for the preparation of magnetically-functionalized lens-like and donut-shaped polymeric microparticles, based on spreading a magnetite-doped paraffin–polymer solution at the air/water interface in the presence of an external magnetic field. We examine the parameters that affect the particle morphology and interfacial aggregation behaviour. DA - 2007/// PY - 2007/// DO - 10.1039/b705046a VL - 9 IS - 48 SP - 6300-6303 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-36949005258&partnerID=MN8TOARS ER - TY - JOUR TI - Engineered deposition of coatings from nano- and micro-particles: A brief review of convective assembly at high volume fraction AU - Prevo, Brian G. AU - Kuncicky, Daniel M. AU - Velev, Orlin D. T2 - COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS AB - In this paper, we review the state of the art of a simple, easily controlled convective assembly technique for rapid deposition of structured micro- and nano-particle coatings. The advantages afforded by this method are improved process efficiency and reduced material consumption relative to standard dipcoating techniques. Structured coatings larger than a few square centimeters are deposited in minutes from aqueous suspension volumes of approximately 10–20 μl. The governing mechanism of particle deposition is convective assembly at high volume fractions. Our research with monodisperse polystyrene latex showed that a volumetric flux balance incorporating the evaporating solvent and assembling particle fluxes can accurately relate the deposition process parameters to the coating structure and properties. Operational ’phase’ diagrams were constructed that demonstrate good correspondence between coating thickness and structure to the operational parameters of the coatings process predicted on the basis of the material balance model. These ’phase’ diagrams may be instrumental in turning the colloidal deposition into a usable and scaleable technology. This deposition technique can be applied to a variety of colloidal systems, including the fabrication of conductive and antireflective coatings, surface-enhancing Raman scattering (SERS) substrates, and lithographic masks. DA - 2007/12/1/ PY - 2007/12/1/ DO - 10.1016/j.colsurfa.2007.08.030 VL - 311 IS - 1-3 SP - 2-10 SN - 1873-4359 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-35648966536&partnerID=MN8TOARS KW - colloidal crystals KW - convective assembly KW - nanoparticle coatings KW - antireflective coatings KW - SERS ER - TY - JOUR TI - Decolorization of organic dyes on Pilkington Activ (TM) photocatalytic glass AU - Chin, Paul AU - Ollis, David F. T2 - CATALYSIS TODAY AB - The air–solid photocatalytic degradation of organic dye films Acid Blue 9 (AB9) and Reactive Black 5 (RBk5) is studied on Pilkington Activ™ glass. The Activ™ glass comprises of a colorless TiO2 layer deposited on clear glass. The Activ™ glass is characterized using atomic force microscopy (AFM) and X-ray diffraction (XRD). Using AFM, the TiO2 average agglomerate particle size is 95 nm, with an apparent TiO2 thickness of 12 nm. The XRD results indicate the anatase phase of TiO2, with a calculated crystallite size of 18 nm. Dyes AB9 and RBk5 are deposited in a liquid film and dried on the Activ™ glass to test for photodecolorization in air, using eight UVA blacklight-blue fluorescent lamps with an average UVA irradiance of 1.4 mW/cm2. A novel horizontal coat method is used for dye deposition, minimizing the amount of solution used while forming a fairly uniform dye layer. About 35–75 monolayers of dye are placed on the Activ™ glass, with a covered area of 7–10 cm2. Dye degradation is observed visually and via UV–vis spectroscopy. The kinetics of photodecolorization satisfactorily fit a two-step series reaction model, indicating that the dye degrades to a single colored intermediate compound before reaching its final colorless product(s). Each reaction step follows a simple irreversible first-order reaction rate form. The average k1 is 0.017 and 0.021 min−1 for AB9 and RBk5, respectively, and the corresponding average k2 is 2.0 × 10−3 and 1.5 × 10−3 min−1. Variable light intensity experiments reveal a p = 0.44 ± 0.02 exponent dependency of initial decolorization rate on the UV irradiance. Solar experiments are conducted outdoors with an average temperature, water vapor density, and UVA irradiance of 30.8 °C, 6.4 g water/m3 dry air, and 1.5 mW/cm2, respectively. For AB9, the average solar k1 is 0.041 min−1 and k2 is 5.7 × 10−3 min−1. DA - 2007/5/30/ PY - 2007/5/30/ DO - 10.1016/j.cattod.2007.01.069 VL - 123 IS - 1-4 SP - 177-188 SN - 0920-5861 KW - photocatalysis KW - dyes KW - acid blue 9 KW - reactive black 5 KW - titanium dioxide KW - TiO2 KW - decolorization KW - Activ (TM) ER - TY - JOUR TI - Computer simulation study of probe-target hybridization in model DNA microarrays: Effect of probe surface density and target concentration AU - Jayaraman, Arthi AU - Hall, Carol K. AU - Genzer, Jan T2 - JOURNAL OF CHEMICAL PHYSICS AB - We use lattice Monte Carlo simulations to study the thermodynamics of hybridization of single-stranded "target" genes in solution with complementary "probe" DNA molecules immobilized on a microarray surface. The target molecules in our system contain 48 segments and the probes tethered on a hard surface contain 8-24 segments. The segments on the probe and target are distinct, with each segment representing a sequence of nucleotides that interacts exclusively with its unique complementary target segment with a single hybridization energy; all other interactions are zero. We examine how surface density (number of probes per unit surface area) and concentration of target molecules affect the extent of hybridization. For short probe lengths, as the surface density increases, the probability of binding long stretches of target segments increases at low surface density, reaches a maximum at an intermediate surface density, and then decreases at high surface density. Furthermore, as the surface density increases, the target is less likely to bind completely to one probe; instead, it binds simultaneously to multiple probes. At short probe lengths, as the target concentration increases, the fraction of targets binding completely to the probes (specificity) decreases. At long probe lengths, varying the target concentration does not affect the specificity. At all target concentrations as the probe length increases, the fraction of target molecules bound to the probes by at least one segment (sensitivity) increases while the fraction of target molecules completely bound to the probes (specificity) decreases. This work provides general guidelines to maximizing microarray sensitivity and specificity. Our results suggest that the sensitivity and specificity can be maximized by using probes 130-180 nucleotides long at a surface density in the range of 7 x 10(-5)- 3 x 10(-4) probe molecules per nm(2). DA - 2007/10/14/ PY - 2007/10/14/ DO - 10.1063/1.2787618 VL - 127 IS - 14 SP - SN - 1089-7690 ER - TY - JOUR TI - Behavior of surface-anchored poly(acrylic acid) brushes with grafting density gradients on solid substrates: 2. Theory AU - Gong, Peng AU - Wu, Tao AU - Genzer, Jan AU - Szleifer, Igal T2 - MACROMOLECULES AB - We apply a molecular theory to predict the structural properties of poly(acrylic acid) macromolecules grafted via one of their ends to solid surfaces. The theory explicitly incorporates the acid−base equilibrium responsible for the charge regulation of the acrylic groups, as well as the conformations, size, shape, and charge distributions of all the molecular species present. We compare the predictions of the theory with experimental observations presented in the preceding article for the height of the layer as a function of ionic strength for different polymer molecular weight and polymer surface coverage. The calculated heights are found to be in good agreement with the experimental observations. The theory predicts the distribution of charges within the layer. We find that the counterions adsorb to the grafting surface, overcompensating the charge of the polymer. The charge regulation within the polymer layer is determined by the interplay between the bulk pH, the ionic strength, and the density of polymer. The system tends to become uncharged with decreasing ionic strength of the solution and increasing polymer density. In all cases the charge regulation acts in order to minimize the electrostatic repulsions in the system. The local distribution of protons within the polymer layer is predicted to be very different from that of the bulk solution. The local pH within the polymer layer can be tuned by varying the solution ionic strength and the polymer surface coverage; the variation can be large as two pH units, relative to the bulk pH. This large variation of the local pH within a couple of nanometers within the brush can be used in the design of biosensors. DA - 2007/11/27/ PY - 2007/11/27/ DO - 10.1021/ma071018y VL - 40 IS - 24 SP - 8765-8773 SN - 0024-9297 ER - TY - JOUR TI - Behavior of surface-anchored poly(acrylic acid) brushes with grafting density gradients on solid substrates: 1. Experiment AU - Wu, Tao AU - Gong, Peng AU - Szleifer, Igal AU - Vlcek, Petr AU - Subr, Vladimir AU - Genzer, Jan T2 - MACROMOLECULES AB - We describe experiments pertaining to the formation of surface-anchored poly(acrylic acid) (PAA) brushes with a gradual variation of the PAA grafting densities on flat surfaces and provide detailed analysis of their properties. The PAA brush gradients are generated by first covering the substrate with a molecular gradient of the polymerization initiator, followed by the “grafting from” polymerization of tert-butyl acrylate (tBA) from these substrate-bound initiator centers, and finally converting the PtBA into PAA. We use spectroscopic ellipsometry to measure the wet thickness of the grafted PAA chains in aqueous solutions at three different pH values (4, 5.8, and 10) and a series of ionic strengths (IS). Our measurements reveal that at low grafting densities, σ, the wet thickness of the PAA brush (H) remains relatively constant, the polymers are in the mushroom regime. Beyond a certain value of σ, the macromolecules enter the brush regime, where H increases with increasing σ. For a given σ, H exhibits a nonmonotonic behavior as a function of the IS. At large IS, the H is small because the charges along PAA are completely screened by the excess of the external salt. As IS decreases, the PAA enters the so-called salt brush (SB) regime, where H increases. At a certain value of IS, H reaches a maximum and then decreases again. The latter is a typical brush behavior in so-called osmotic brush (OB) regime. We provide detailed discussion of the behavior of the grafted PAA chains in the SB and OB regimes. DA - 2007/11/27/ PY - 2007/11/27/ DO - 10.1021/ma0710176 VL - 40 IS - 24 SP - 8756-8764 SN - 1520-5835 ER - TY - JOUR TI - Band offsets and growth mode of molecular beam epitaxy grown MgO (111) on GaN (0002) by x-ray photoelectron spectroscopy AU - Craft, H. S. AU - Collazo, R. AU - Losego, M. D. AU - Mita, S. AU - Sitar, Z. AU - Maria, J.-P. T2 - JOURNAL OF APPLIED PHYSICS AB - MgO is a proposed dielectric for use as a tunneling barrier in devices integrating GaN and ferroelectric oxides. In this study, we present data regarding the growth mode and band offsets of MgO grown epitaxially on GaN (0002) surfaces using molecular beam epitaxy. Using in situ x-ray photoelectron spectroscopy (XPS) and molecular beam epitaxy, we determine, from sequential growth experiments, that the growth of MgO proceeds via the Volmer-Weber (three-dimensional) mode, and full coalescence of the film does not occur until approximately 12nm of MgO has been deposited. The observation of a three-dimensional growth mode is in agreement with previously published data. For the valence band offset, we find a value of 1.2±0.2eV, which corresponds to a 3.2eV conduction band offset. XPS measurements suggest a chemically abrupt interface and no effect on band lineup due to the slow coalescence behavior. DA - 2007/10/1/ PY - 2007/10/1/ DO - 10.1063/1.2785022 VL - 102 IS - 7 SP - SN - 1089-7550 ER - TY - JOUR TI - Synthesis of amphiphilic copolymers by ATRP initiated with a bifunctional initiator containing trichloromethyl groups AU - Ritz, P. AU - Latalova, P. AU - Janata, M. AU - Toman, L. AU - Kriz, J. AU - Genzer, J. AU - Vlcek, P. T2 - REACTIVE & FUNCTIONAL POLYMERS AB - Bifunctional polystyrene macroinitiators, having various molecular weights, were prepared by atom transfer radical polymerization (ATRP), initiated with bifunctional initiator 1,3-bis{1-methyl-1[(2,2,2-trichloroethoxy) carbonylamino]ethyl}benzene in conjunction with CuCl catalyst and polyamine ligands. These macroinitiators were subsequently used for ATRP of tert-butyl acrylate (t-BuA), giving BAB triblocks poly[(t-BuA)-b-(Sty)-b-(t-BuA)] as precursors of amphiphilic copolymers. Both the polymerization steps proceeded as controlled processes with linear semi-logarithmic conversion plots and lengths of the blocks following theoretical predictions. Hydrolysis of outer poly(t-BuA) blocks led to triblock copolymers with the central polystyrene block and outer blocks of poly(acrylic acid), the molecular weights of which ranged from ca. 5 × 103 to almost 1 × 105 Da. DA - 2007/10// PY - 2007/10// DO - 10.1016/j.reactfunctpolym.2007.06.007 VL - 67 IS - 10 SP - 1027-1039 SN - 1873-166X KW - ATRP KW - block copolymer KW - polyhalogenated initiator KW - amphiphilic copolymer KW - surfmer ER - TY - JOUR TI - Solubility and aggregation of commercial alpha-lactalbumin at neutral pH AU - McGuffey, Matthew K. AU - Otter, Donald E. AU - Zanten, John H. AU - Foegeding, E. Allen T2 - INTERNATIONAL DAIRY JOURNAL AB - The aggregation behavior of two commercial samples of α-lactalbumin (α-La) heated at 95 °C at neutral pH in a complex mineral salt environment was investigated. The objective was to understand the effects of variability between α-La samples and relative concentration of β-lactoglobulin (β-Lg) on aggregate size development, as measured by light scattering and turbidity development. The effect of protein net charge was evaluated with a solubility method and the role of thiol groups was evaluated by reaction with DTNB. The sample with the highest level of β-Lg had higher solubility at pH 6.75 and 6.8, yielded more reactive thiol groups, had a 25% faster first-order rate constant, and formed spherical aggregates with a much higher molecular weight than those produced in the sample containing less β-Lg. Adding increasing quantities of β-Lg to the samples generally decreased reversibility and altered the aggregation process; however, other factors appear to be involved in determining aggregate properties. DA - 2007/10// PY - 2007/10// DO - 10.1016/j.idairyj.2007.04.003 VL - 17 IS - 10 SP - 1168-1178 SN - 1879-0143 KW - beta-lactoglobulin KW - thiol KW - hydrophobic KW - solubility KW - light scattering KW - turbidity ER - TY - JOUR TI - Molecular simulation of the adsorption and structure of benzene confined in mesoporous silicas AU - Coasne, Benoit AU - Alba-Simionesco, Christiane AU - Audonnet, Fabrice AU - Dosseh, Gilberte AU - Gubbins, Keith E. T2 - ADSORPTION-JOURNAL OF THE INTERNATIONAL ADSORPTION SOCIETY DA - 2007/12// PY - 2007/12// DO - 10.1007/s10450-007-9051-3 VL - 13 IS - 5-6 SP - 485-490 SN - 0929-5607 KW - benzene KW - capillary condensation KW - Monte Carlo simulation KW - nanoporous material ER - TY - JOUR TI - Molecular dynamics study on diameter effect in structure of ethanol molecules confined in single-walled carbon nanotubes AU - Shao, Q. AU - Huang, L. L. AU - Zhou, J. AU - Lu, L. H. AU - Zhang, L. Z. AU - Lu, X. H. AU - Jiang, S. Y. AU - Gubbins, Keith AU - Zhu, Y. D. AU - Shen, W. F. AU - al. T2 - JOURNAL OF PHYSICAL CHEMISTRY C AB - Equilibrium molecular dynamics simulations have been performed to investigate the structural characteristics of ethanol molecules confined in single-walled, pristine armchair carbon nanotubes with a length of 2.5 nm and diameters ranging from 0.68 to 1.35 nm in an open ethanol reservoir at 298.0 K and 100.0 kPa by all-atom and united-atom models. Both models present similar results. Structural properties of confined ethanol molecules are analyzed in terms of the average number of hydrogen bonds, radial density distributions of methyl and hydroxyl groups, orientation distributions of the methyl−methylene bond, oxygen−hydrogen bond and dipole moment, and molecular conformations as a function of the diameter of carbon nanotubes. The results indicate that the behavior of the nonpolar part of confined ethanol molecules changes monotonically with the diameter, whereas that of the polar part changes non-monotonically. The different dependence on diameter indicates that the wall−fluid interactions determine the behavior of nonpolar groups, whereas that of polar groups is determined by the fluid−fluid interactions. Only in the nanotube with a diameter of 1.081 nm did the confined ethanol molecules have a highly preferred dipole orientation. The conformational equilibrium also varies considerably with the diameter non-monotonically. The largest proportion of gauche ethanol corresponds to the most preferred dipole orientation. DA - 2007/11/1/ PY - 2007/11/1/ DO - 10.1021/jp0736140 VL - 111 IS - 43 SP - 15677-15685 SN - 1932-7455 ER - TY - JOUR TI - Growth and crystallization of metal-containing block copolymer nanotubes in a selective solvent AU - Wang, Xiaosong AU - Wang, Hai AU - Frankowski, David J. AU - Lam, Peter G. AU - Welch, Paul M. AU - Winnik, Mitchell A. AU - Hartmann, Juergen AU - Manners, Ian AU - Spontak, Richard J. T2 - ADVANCED MATERIALS AB - Highly asymmetric metal-containing block copolymers are capable of forming nanotubes in solutions containing a nonpolar solvent. In this study, the time-dependent formation of these nanotubes is investigated and reveals how the aggregate nanostructures develop (see figure for an example at an early stage). These nanotubes are semicrystalline (see the diffraction pattern in the inset), suggesting that crystallization is at least partially responsible for the unique morphology formed by these block copolymers. DA - 2007/9/3/ PY - 2007/9/3/ DO - 10.1002/adma.200602230 VL - 19 IS - 17 SP - 2279-+ SN - 1521-4095 ER - TY - JOUR TI - Electroactive nanostructured polymers as tunable actuators AU - Shankar, Ravi AU - Ghosh, Tushar K. AU - Spontak, Richard J. T2 - ADVANCED MATERIALS AB - Lightweight and conformable electroactive actuators stimulated by low electric fields are required for emerging responsive technologies. In this work, we demonstrate that selectively swollen triblock copolymers yield electroactive nanostructured polymers (ENPs) that exhibit excellent displacement (>200% areal strain) under an applied electric field (see figure). Such ENPs possess properties that can be broadly tailored and represent a viable avenue to designer organic actuators for advanced engineering, biomimetic, and biomedical applications. DA - 2007/9/3/ PY - 2007/9/3/ DO - 10.1002/adma.200602644 VL - 19 IS - 17 SP - 2218-+ SN - 1521-4095 ER - TY - JOUR TI - Does faculty research improve undergraduate teaching? An analysis of existing and potential synergies AU - Prince, Michael J. AU - Felder, Richard M. AU - Brent, Rebecca T2 - JOURNAL OF ENGINEERING EDUCATION AB - Abstract Academicians have been arguing for decades about whether or not faculty research supports undergraduate instruction. Those who say it does—a group that includes most administrators and faculty members—cite many ways in which research can enrich teaching, while those on the other side cite numerous studies that have consistently failed to show a measurable linkage between the two activities. This article proposes that the two sides are debating different propositions: whether research can support teaching in principle and whether it has been shown to do so in practice. The article reviews the literature on the current state of the research‐teaching nexus and then examines three specific strategies for integrating teaching and scholarship: bringing research into the classroom, involving undergraduates in research projects, and broadening the definition of scholarship beyond frontier disciplinary research. Finally, ways are suggested to better realize the potential synergies between faculty research and undergraduate education. DA - 2007/10// PY - 2007/10// DO - 10.1002/j.2168-9830.2007.tb00939.x VL - 96 IS - 4 SP - 283-294 SN - 2168-9830 KW - research-teaching nexus KW - research KW - teaching ER - TY - JOUR TI - Deposition of poly[2-(perfluorooctyl)ethyl acrylate] on silicon wafers by the displacement of two immiscible supercritical phases (DISP) AU - Kim, Jaehoon AU - McClain, James B. AU - Carbonell, Ruben G. T2 - JOURNAL OF SUPERCRITICAL FLUIDS AB - Abstract Deposition from two immiscible supercritical phases (DISP), in which a solution of supercritical carbon dioxide (scCO2) with a desired solute is displaced by supercritical helium (scHe), has been applied to deposit poly[2-(perfluorooctyl)ethyl acrylate] (PFOEA) on silicon wafer substrate coupons. The polymer was precipitated at the interfacial boundary between the supercritical He phase and the supercritical CO2/PFOEA solution phase and deposited on the substrates. Depending on the deposition conditions, two different deposition regimes – a particle formation regime and a film formation regime – were found. At low solution concentration or high displacement velocity, particles in the range of 1–3 μm in diameter formed while at high solution concentration or low displacement velocity, films in the range of 30–500 nm in thickness formed. The solute concentration, displacement velocity, and pressure all had a strong effect on the particle size and film thickness. Optical microscopy and atomic force microscopy (AFM) were used to characterize film morphology including drying defects and film roughness. Highly uniform films with no drying defects and low root-mean-square (RMS) roughness (∼2–3 nm) were obtained at high solution concentration. Films formed at low-to-moderate solution concentration displayed ring-like drying defects. The thickness and morphology of films deposited from DISP were compared with films prepared from high-pressure free meniscus coating (hFMC) with liquid CO2 (l-CO2) as a solvent and from normal dip coating with an organic solvent (1,1,2-trifluorotrichloroethane, Freon113). The film deposited from DISP was much thicker and more uniform than the film formed using Freon113. DA - 2007/11// PY - 2007/11// DO - 10.1016/j.supflu.2007.05.003 VL - 43 IS - 1 SP - 139-149 SN - 1872-8162 KW - supercritical carbon dioxide KW - supercritical helium KW - immiscibility KW - coating KW - poly[2-(perfluorooctyl)ethyl acrylate] KW - thin fluorinated film ER - TY - JOUR TI - Crossover from normal to inverse temperature dependence in the adsorption of nonionic surfactants at hydrophilic surfaces and pore walls AU - Dietsch, Oliver AU - Eltekov, Anton AU - Bock, Henry AU - Gubbins, Keith E. AU - Findenegg, Gerhard H. T2 - JOURNAL OF PHYSICAL CHEMISTRY C AB - The adsorption of the nonionic surfactant C8E4 from its aqueous solutions to the pore walls of four controlled-pore silica glass (CPG) materials of different mean pore widths (10−50 nm) has been studied in a temperature range from 5 to 45 °C, that is, close to the lower critical temperature of liquid−liquid phase separation of the bulk system (Tc ≈ 40 °C). Pronounced S-shaped isotherms, with a normal temperature dependence of the adsorption in the initial low-affinity region but an inverse temperature dependence in the plateau region, are found with all CPG materials. The experimental adsorption isotherms are compared with predictions of a theoretical model (Phys. Rev. Lett. 2004, 92, 135701), which takes into account H-bonding and micelle formation in the bulk and at the surface. It is found that this model reproduces all peculiarities of the adsorption in the present systems. The following conclusions emerge from this analysis: (1) At low bulk concentrations, the surfactant is adsorbed only in monomeric form (Henry's law behavior). In this regime, there is an energetic driving force for surfactant adsorption (in spite of the fact that nonselective pore walls are assumed), in agreement with the observed normal temperature dependence of the adsorption in this regime. (2) Surface aggregation observed at higher concentrations involves an energy penalty due to the loss of H bonds, which is overcompensated by the gain of (rotational) entropy of the H-bonding sites of the surfactant heads. Accordingly, surface aggregation is entropy-driven and endothermic and thus shows inverse temperature dependence. Hence, the model accounts for the observed crossover in the temperature dependence of the adsorption at the critical surface aggregation concentration. DA - 2007/11/1/ PY - 2007/11/1/ DO - 10.1021/jp0747656 VL - 111 IS - 43 SP - 16045-16054 SN - 1932-7455 ER - TY - JOUR TI - Cellular uptake of gold nanoparticles passivated with BSA-SV40 large T antigen conjugates AU - Ryan, Joseph A. AU - Overton, K. Wesley AU - Speight, Molly E. AU - Oldenburg, Christine M. AU - Loo, Lina AU - Robarge, Wayne AU - Franzen, Stefan AU - Feldheim, Daniel L. T2 - ANALYTICAL CHEMISTRY AB - Internalization and subcellular localization in HeLa cells of gold nanoparticles modified with the SV40 large T antigen were quantified using inductively coupled plasma optical emission spectroscopy (ICP-OES). Internalization was monitored as a function of incubation time, temperature, nanoparticle diameter, and large T surface coverage. Increasing the amount of large T peptides per gold nanoparticle complex, by either increasing the coverage at constant nanoparticle diameter or by increasing the nanoparticle diameter at constant large T coverage, resulted in more cellular internalization. In addition, nuclear fractionation was performed to quantify nuclear localization of these complexes as a function of large T coverage. In contrast to our prior qualitative investigations of nuclear localization by video-enhanced color differential interference contrast microscopy (VEC-DIC), ICP-OES was able to detect nanoparticles inside fractionated cell nuclei. Although increasing the large T coverage was found to afford higher cell internalization and nuclear targeting, quantitative evaluation of cytotoxicity revealed that higher large T coverages also resulted in greater cytotoxicity. The ICP-OES and nuclear fractionation techniques reported here are valuable tools that can add important quantitative information to optical and electron imaging methods such as VEC-DIC and transmission electron microscopy regarding the fate of nanoparticles in cells. DA - 2007/12/1/ PY - 2007/12/1/ DO - 10.1021/ac0715524 VL - 79 IS - 23 SP - 9150-9159 SN - 1520-6882 ER - TY - JOUR TI - Argon and krypton adsorption on templated mesoporous silicas: molecular simulation and experiment AU - Hung, Francisco R. AU - Bhattacharya, Supriyo AU - Coasne, Benoit AU - Thommes, Matthias AU - Gubbins, Keith E. T2 - ADSORPTION-JOURNAL OF THE INTERNATIONAL ADSORPTION SOCIETY DA - 2007/12// PY - 2007/12// DO - 10.1007/s10450-007-9034-4 VL - 13 IS - 5-6 SP - 425-437 SN - 1572-8757 KW - templated mesoporous silica materials KW - MCM-41 KW - SBA-15 KW - gas adsorption KW - molecular simulation KW - Monte Carlo ER - TY - JOUR TI - Anisotropic self-diffusion in nanofluidic structures AU - Bock, Henry AU - Gubbins, Keith E. AU - Schoen, Martin T2 - JOURNAL OF PHYSICAL CHEMISTRY C AB - By means of equilibrium molecular dynamics simulations, we investigate self-diffusion in a “simple” fluid confined to nanoscopic slit-pores. The pore walls are decorated with wettable and nonwettable chemical “stripes” that alternate in the x direction and are assumed infinitely long in the y direction. We consider the impact of pore width as well as variations of the width of the wettable stripes dwet. Depending on these model parameters and the thermodynamic conditions, the confined fluid may exist as one of three morphologically distinct phases: a thin fluid film adsorbed by the wettable stripes, a fluid bridge spanning the gap between the (aligned) stripes on the two opposite substrates, or a nanostructured liquid where molecules occupy the entire space between the substrate surfaces. By analyzing mean square displacements, velocity autocorrelation functions, and their power spectra, a detailed picture of mass transport and its relation to substrate decoration emerges. In particular, we find that the axial symmetry of the self-diffusion tensor D with respect to the z axis is approximately preserved in liquidlike phases, whereas no such symmetry exists as far as both film and bridge phases are concerned. DA - 2007/11/1/ PY - 2007/11/1/ DO - 10.1021/jp071861y VL - 111 IS - 43 SP - 15493-15504 SN - 1932-7455 ER - TY - JOUR TI - A psychometric study of the Index of Learning Styles (c) AU - Litzinger, Thomas A. AU - Lee, Sang Ha AU - Wise, John C. AU - Felder, Richard M. T2 - JOURNAL OF ENGINEERING EDUCATION AB - Abstract A study was conducted on the Felder‐Soloman Index of Learning Styles© (ILS) to assess reliability, factor structure, and construct validity as well to determine whether changing its dichotomous response scale to a five‐option response scale would improve reliability and validity. Data collected in this study had internal consistency reliability ranging from 0.55 to 0.77 across the four learning style scales of the ILS. Factor analysis revealed that multiple factors were present within three of the learning style scales, which correspond to known aspects of the scale definitions. The factor analysis and direct feedback from students on whether they felt their scores accurately represented their learning preferences provide evidence of construct validity for the ILS. Changing the response scale improved reliability, but it did not change the factor structure substantially nor did it affect the strength of the evidence for construct validity based on student feedback. DA - 2007/10// PY - 2007/10// DO - 10.1002/j.2168-9830.2007.tb00941.x VL - 96 IS - 4 SP - 309-319 SN - 2168-9830 KW - learning styles KW - reliability KW - validity ER - TY - JOUR TI - A life cycle inventory of carbon dioxide as a solvent and additive for industry and in products AU - Overcash, Michael AU - Li, Yong AU - Griffing, Evan AU - Rice, Gareth T2 - JOURNAL OF CHEMICAL TECHNOLOGY AND BIOTECHNOLOGY AB - Abstract Life cycle inventories of four industrial carbon dioxide production processes are reported. The inventory data were calculated using design‐based methodology. Energy consumptions and critical emissions of the four processes are compared. Quasi‐microscopic allocation was applied to processes with multiple products. The inventory data of this study are transparent and can be used in other life cycle studies. Copyright © 2007 Society of Chemical Industry DA - 2007/11// PY - 2007/11// DO - 10.1002/jctb.1747 VL - 82 IS - 11 SP - 1023-1038 SN - 0268-2575 KW - carbon dioxide KW - life cycle analysis KW - quasi-microscopic allocation KW - life cycle inventory ER - TY - JOUR TI - Preparation of zwitterionic cotton fabrics and their wrinkle-resistant performance AU - Vargantwar, P. H. AU - Smith, B. AU - Hauser, P. T2 - AATCC Review DA - 2007/// PY - 2007/// VL - 7 IS - 12 SP - 42-46 ER - TY - JOUR TI - Nanocomposite gel electrolytes based on fumed silica for lithium-ion batteries AU - Li, Yangxing AU - Fedkiw, Peter S. T2 - JOURNAL OF THE ELECTROCHEMICAL SOCIETY AB - Nanocomposite gel electrolytes based on silica particles dispersed in lithium bis(perfluoroethylsulfonyl)imide (LiBETI) -carbonate solvent are examined as an electrolyte system for a lithium-ion battery. Gel behavior is observed with both hydrophilic (A200) and hydrophobic (R805) fumed silicas. The silica nanoparticles affect a small decrease in conductivity but increase mechanical strength significantly (elastic modulus ). Chronoamperometry and linear sweep voltammetry results show that an Al current collector is stable in LiBETI carbonates up to . Cycling Li(Ni)/electrolyte/Li cells shows that silica nanoparticles improve the coulombic efficiency and interfacial stability in the order: 10% R805 LiBETI liquid. Cycling cells shows that both liquid and 10% R805 gel electrolytes provide good capacity and cycle performance, but the average charge/discharge voltages for the latter are more stable. Both and Li/graphite cells have less capacity fade using LiBETI than electrolyte. The gel electrolyte provides better cycle performance than its liquid counterpart because of its increased interfacial stability due to improved rheology and ability to scavenge residual moisture. Silica-based LiBETI carbonate nanocomposite gel electrolytes appear to be a promising candidate for lithium-ion batteries. DA - 2007/// PY - 2007/// DO - 10.1149/1.2794292 VL - 154 IS - 12 SP - A1140-A1145 SN - 1945-7111 ER - TY - PAT TI - Methods of surface modification of a flexible substrate to enhance cell adhesion AU - Liebmann-Vinson, A. AU - Chaney, B. AU - Efimenko, K. AU - Genzer, J. C2 - 2007/// DA - 2007/// PY - 2007/// ER - TY - JOUR TI - Introduction AU - Loo, Yueh-Lin AU - Genzer, Jan T2 - JOURNAL OF POLYMER SCIENCE PART B-POLYMER PHYSICS AB - Fifteen years in its tradition, the December issue of the Journal of Polymer Science, Polymer Physics features a series of papers by members of the Division of Polymers (DPOLY) who presented their work at the annual meeting of the American Physical Society (APS). Two years ago, this special APS DPOLY issue received a significant “face-lift.” Kari Dalnoki-Veress (recipient of the 2008 Dillon Medal) from McMaster University in Canada, who served as the Editor of the special issue, introduced a new and exciting layout which incorporated a series of feature articles by invited authors1 in addition to regular contributed papers. In these feature articles, experts in their respective fields shared their points-of-views on current and future developments in polymer physic related topics; these articles were meant to provide perspective to non-experts in the field. Additionally, the winners of the Polymer Physics Prize and the Dillon Medal wrote review articles pertaining to their research. This fresh blueprint introduced by Kari made a very favorable impression on the readers of the journal and a similar format was chosen by the co-editors of the special issue last year, Chang Y. Ryu and Rahmi Ozisik from the Rensselaer Polytechnic Institute, the following year.2 Inspired by our predecessors and by the success of the new format of the special APS issue, the decision for us to replicate the existing layout was thus very easy. The 2007 DPOLY special issue of Journal of Polymer Science, Polymer Physics highlights a paper co-authored by Glenn Fredrickson, the winner of the 2007 DPOLY Polymer Physics Prize. Concentrating on recent advances in the simulation of charged polymeric systems, Glenn's review article provides an excellent overview of the field, which we hope will inspire theorists and experimentalists alike. The subsequent 6 articles represent viewpoints/opinions by experts in the diverse fields of polymer physics. The section commences with a paper authored by Buck Christ, who commemorates the 50th anniversary of chain folding. Steve Granick and Janet Wong share their perspectives on friction in polymer systems. Ron Larson's article examines entanglements in polymer dynamics by computer simulations. Marc Hillmyer highlights the influence of molecular weight distribution on microstructure development in block copolymers. New insights into polymer nanocomposites are presented by Ramanan Krishnamoorti and Rich Vaia. And if you ever wondered how polymer physics is related to foodstuffs, you should not miss Athene Donald's article. The second part of the journal features 13 contributed papers, including several from finalists of the Frank J. Padden, Jr. Award, highlighting selected works presented during the March 2007 APS meeting. It has been our pleasure to co-edit the 2007 special issue of Journal of Polymer Science, Polymer Physics. We would like to take this opportunity to thank the authors for their contributions and the reviewers for their assistance in assessing these manuscripts. And last but not least, we would like to express our sincere gratitude to Ms. Hope Inman, the journal's managing editor, for her help and superb organization and managing skills. Enjoy! YUEH-LIN (LYNN) LOO Professor Loo recently joined Princeton University as an associate professor in the Chemical Engineering Department. She received bachelor degrees in Chemical Engineering as well as Materials Science and Engineering from the University of Pennsylvania in 1996 and a doctoral degree in Chemical Engineering from Princeton University in 2001. In 2002, Lynn joined the University of Texas at Austin as Assistant Professor in Chemical Engineering and General Dynamics Endowed Faculty Fellow in Engineering. Lynn's research focuses on developing patterning and processing tools for making organic electronic devices and understanding the structure-property relationships in organic electrically-active materials, especially solution-processable organic molecular semiconductors and polymer conductors. Her honors include a Camille and Henry Dreyfus New Faculty Award (2002), a DuPont Young Professor Grant (2003), an NSF-CAREER Award (2004), and an Arnold and Mabel Beckman Young Investigator Award (2005). In 2004, Lynn was also selected as one of Top 100 Young Innovators under 35 by MIT's Technology Review. More recently, Lynn was the inaugural recipient of the Peter and Edith O'Donnell Award in Engineering awarded by the Academy of Medicine, Science, and Engineering of Texas and the 2006 recipient of the Alan P. Colburn Award of the AIChE. Lynn will be presenting the 2007 Thiele Lecture in the Chemical Engineering Department at the University of Notre Dame this fall. JAN GENZER Professor Genzer is a professor of Chemical & Biomolecular Engineering at North Carolina State University. He received the "Diploma-engineer" degree (Dipl.-Ing.) in Chemical & Materials Engineering from the Institute of Chemical Technology in Prague, Czech Republic in 1989 and Ph.D. in Materials Science & Engineering from the University of Pennsylvania in 1996. Between 1996 and 1998 he was a post-doctoral fellow at Cornell University and the University of California at Santa Barbara, working with Professor Ed Kramer. In the fall 1998 he joined the faculty of chemical engineering at the North Carolina State University as an assistant professor and was promoted to the associate and full professor in 2004 and 2006, respectively. He also holds a position of an adjunct professor at the Norwegian University of Science & Technology (NTNU) in Trondheim, Norway. His honors include: Camille Dreyfus Teacher-Scholar Award, Sigma Xi research award, NSF CAREER award, John H. Dillon Award of the American Physical Society, NSF Award for Special Creativity, and NCSU's Outstanding Teacher award. He has published over 100 peer-reviewed journal articles and delivered more than 100 invited lectures. His group at North Carolina State University is actively involved in research related to the behavior of polymers at interfaces and in confined geometries, with particular emphasis on self-assembly and forced assembly and combinatorial methods. DA - 2007/12/15/ PY - 2007/12/15/ DO - 10.1002/polb.21356 VL - 45 IS - 24 SP - 3221-3222 SN - 0887-6266 ER - TY - JOUR TI - Composite solid polymer electrolytes based on pluronics: Does ordering matter? AU - Bronstein, Lyudmila M. AU - Karlinsey, Robert L. AU - Yi, Zheng AU - Carini, John AU - Werner-Zwanziger, Ulli AU - Konarev, Peter V. AU - Svergun, Dmitri I. AU - Sanchez, Angelica AU - Khan, Saad T2 - CHEMISTRY OF MATERIALS AB - Composite solids polymer electrolytes (SPEs) based on Pluronic block copolymers, PEOx-b-PPOy-b-PEOx, and silicate organic–inorganic component (OIC) formed in situ have been synthesized and characterized using solid-state NMR, Raman spectroscopy, differential scanning calorimetry (DSC), small-angle X-ray scattering (SAXS), rheology, and electrochemical measurements. Raman spectroscopy, DSC, and rheological data reveal that the block copolymer and OIC are intermixed in the composite SPEs, and the degree of intermixing determines the SPE properties. Comparison of the SAXS and electrochemical results leads us to conclude that ordering in block copolymer-based composite SPEs is not a crucial parameter for the improved conductivity, while the combination of the ratios of the SPE components and their intermixing gives rise to extended interfaces that control the electrochemical performance. DA - 2007/12/11/ PY - 2007/12/11/ DO - 10.1021/cm7022218 VL - 19 IS - 25 SP - 6258-6265 SN - 1520-5002 ER - TY - JOUR TI - Charge and the dry-strength performance of polyampholytes. Part 3: Streaming potential analysis AU - Wang, Yun AU - Hubbe, Martin A. AU - Rojas, Orlando J. AU - Argyropoulos, Dimitris S. AU - Wang, Xingwu AU - Sezaki, Takao T2 - COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS AB - Results reported in Part 1 of this series showed that paper strength improvements could be optimized by varying pH and the overall content of ionic groups in random terpolymers containing a fixed molar ratio of acidic and basic monomeric groups. Further treatment of kraft fiber slurries with polyaluminum chloride (PAC), after polyampholyte addition, yielded significant strength benefits. The present paper shows how these results can be explained in terms of the streaming potential (SP) of glass fibers, which were used as a model substrate. The data suggest that aluminum ions interact both with the anionic carboxyl groups of the polyampholytes and with anionic silanol groups at fiber surfaces. The streaming potential of the treated surfaces could be changed by varying the pH, the overall density of charged groups of the polyampholytes, the ratio of cationic to anionic groups on the polymer and by post-treatment with polyaluminum chloride. DA - 2007/7/5/ PY - 2007/7/5/ DO - 10.1016/j.colsurfa.2006.11.052 VL - 301 IS - 1-3 SP - 33-40 SN - 1873-4359 KW - polyampholytes KW - dry strength KW - paper strength KW - streaming potential KW - electrokinetics KW - polyaluminum chloride ER - TY - JOUR TI - Charge and the dry-strength performance of polyampholytes. Part 2. Colloidal effects AU - Hubbe, M. A. AU - Rojas, O. J. AU - Argyropoulos, D. S. AU - Wang, Y. AU - Song, J. AU - Sulic, N. AU - Sezaki, T. T2 - Colloids and Surfaces. A, Physicochemical and Engineering Aspects AB - Polyampholytes, which are macromolecules that contain both positive and negative ionizable groups, can provide superior strength improvements for paper manufacture, compared to the addition of simple polyelectrolytes. Colloidal effects, which were measured in solution and in fiber suspensions, were consistent with observed bonding effects. The same colloidal effects were found to correlate with the effects of pH and of the density of the ionizable groups on the polyampholytes. Tests were carried out with a series of polyampholytes having a constant ratio of cationic to anionic monomeric groups and molecular mass. Their charge density varied in the ratio 1:2:4:8. The greatest strength gains were obtained at intermediate charge density and under conditions of pH favoring instability of the aqueous polymer mixtures. Colloidal phenomena were elucidated by turbidimetric tests, sediment volumes of treated fiber suspensions, flocculation tendencies of treated fiber suspensions, and zeta potentials of probe particles. DA - 2007/// PY - 2007/// DO - 10.1016/j.colsurfa.2006.11.053 VL - 301 SP - 23-32 ER - TY - JOUR TI - An apparent critical point in binary mixtures of m-nitrotoluene with n-alkanes; experimental and simulation study AU - Ratajczak, B. AU - Sliwinska-Bartkowiak, M. AU - Coasne, B. AU - Gubbins, K. E. T2 - JOURNAL OF NON-CRYSTALLINE SOLIDS AB - We report a simulation study of the system m-nitrotoluene–n-decane, showing an apparent critical point, which lies in their metastable, experimentally inaccessible state, below their melting point, affecting physical and chemical properties of this systems in the stable liquid phase. The presence of the apparent critical point in this mixture has been experimentally observed by the non-linear dielectric effect (NDE) as an anomalous increase in the NDE values typical of critical concentrations. The phase diagrams of this mixture have evidenced that the system freezes in the homogenous phase and its melting point is higher than its critical temperature [M. Śliwińska-Bartkowiak, B. Szurkowski, T. Hilczer, Chem. Phys. Lett. 94 (1983) 609, M. Śliwińska-Bartkowiak, Ber. Bunsengess. Phys. Chem. 94 (1990) 64, M. Śliwińska-Bartkowiak, Phys. Lett. A 128 (1988) 84]. For such a system, we performed Monte Carlo simulations aimed at analyzing the kind of phase transition observed, and their conditions of their occurrence in a Lennard-Jones mixture. The enthalpy, configurational energy and radial distribution function have been estimated by the MC simulation method in the NPT system. Immiscibility conditions according to Hoheisel [M. Schoen, C. Hoheisel, Mol. Phys. 57 (1986) 65] approach have also been discussed. DA - 2007/12/1/ PY - 2007/12/1/ DO - 10.1016/j.jnoncrysol.2007.01.090 VL - 353 IS - 47-51 SP - 4565-4569 SN - 1873-4812 KW - dielectric properties KW - relaxation KW - electric modulus KW - Monte Carlo simulations KW - phases and equilibria ER - TY - JOUR TI - Two-dimensional nanoparticle arrays derived from ferritin monolayers AU - Yuan, Zhen AU - Petsev, Dimiter N. AU - Prevo, Brian G. AU - Velev, Orlin D. AU - Atanassov, Plamen T2 - LANGMUIR AB - A scalable technique for making silica coatings with embedded two-dimensional arrays of iron oxide nanoparticles is presented. The iron oxide nanoparticle arrays were formed by depositing quasi-crystalline ferritin layers, an iron storage protein with an iron oxide mineral core, on solid substrates by a spread-coating technique based on evaporation-induced convective assembly. The layer of protein molecular arrays was then encapsulated in a silica matrix film deposited from a sol precursor. The organic protein shell of the ferritin molecules was then removed by controlled pyrolysis, leaving ordered iron oxide cores bound in the silica matrix. This article is the first report on combining convective self-assembly of proteins with sol−gel techniques of oxide film formation. The technique is technologically feasible and scalable to make coatings of encapsulated ordered magnetic clusters tens of cm2 or larger in size. DA - 2007/5/8/ PY - 2007/5/8/ DO - 10.1021/la062891f VL - 23 IS - 10 SP - 5498-5504 SN - 0743-7463 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-34249704060&partnerID=MN8TOARS ER - TY - JOUR TI - Thin, crystalline MgO on hexagonal 6H-SIC(0001) by molecular beam epitaxy for functional oxide integration AU - Goodrich, T. L. AU - Cai, Z. AU - Losego, M. D. AU - Maria, J.-P. AU - Ziemer, K. S. T2 - JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B AB - MgO thin films are proposed as a template for the effective integration of three and four element oxides on wide band gap SiC for next generation multifunctional devices. Oriented, crystalline MgO(111) of 20–380Å is grown on 6H-SiC(0001) by molecular beam epitaxy at a substrate temperature of 140°C using a magnesium effusion cell and a remote oxygen plasma source with ion deflection plates located at the end of the plasma discharge tube and approximately 7in. from the sample surface. Films are conformal to the steps of the cleaned SiC surface with a rms roughness of 0.45±0.05nm. Magnesium adsorption controls the growth rate in an excess oxygen environment with Mg:O flux ratios of 1:99–1:20, where the oxygen flux is the equivalent molecular oxygen. The oxygen plasma, which was determined to be free of ions when the ion deflection plates are energized, does impact nucleation and initial stages of the MgO film formation, and there may be evidence of etching mechanisms involved in the thicker film growth. Chemical and structural thermal stability of 20Å MgO(111)‖6H-SiC(0001) was demonstrated up to 740°C in vacuum for 90min through reflection high-energy electron diffraction and x-ray photoelectron spectroscopy analyses. X-ray diffraction was used to further test the thermal stability of 380Å films in vacuum and in an oxygen environment up to 790°C. As a proof of concept for MgO(111) as an interface for aligned functional oxide growth, barium titanate (111) was deposited on 100Å MgO(111)‖6H-SiC(0001) by rf magnetron sputtering. DA - 2007/// PY - 2007/// DO - 10.1116/1.2734979 VL - 25 IS - 3 SP - 1033-1038 SN - 2166-2746 ER - TY - JOUR TI - Influence of indium-tin oxide surface structure on the ordering and coverage of carboxylic acid and thiol monolayers AU - Cerruti, Marta AU - Rhodes, Crissy AU - Losego, Mark AU - Efremenko, Alina AU - Maria, Jon-Paul AU - Fischer, Daniel AU - Franzen, Stefan AU - Genzer, Jan T2 - JOURNAL OF PHYSICS D-APPLIED PHYSICS AB - This paper analyses the variability of self-assembled monolayers (SAMs) formation on ITO depending on the substrate surface features. In particular, we report on the formation of carboxylic acid- and thiol-based SAMs on two lots of commercially prepared indium–tin oxide (ITO) thin films. Contact angle measurements, electrochemical experiments, and near-edge x-ray absorption fine structure (NEXAFS) spectroscopy showed that the quality of monolayers formed differed substantially between the two ITO batches. Only one of the two ITO substrates was capable of forming well-organized thiol- and carboxylic acid-based SAMs. In order to rationalize these observations, atomic force microscopy and x-ray diffraction analyses were carried out, and SAMs were prepared on ITO substrates fabricated by sputtering in our laboratories. An attempt was made to influence the film microstructure and surface morphology by varying substrate temperatures during ITO deposition. Good-quality thiol and carboxylic acid SAMs were obtained on one of the ITO substrates prepared in-house. While our characterization could not single out conclusively one specific parameter in ITO surface structure that could be responsible for good SAMs formation, we could point out homogeneous surface morphology as a relevant factor for the quality of the SAMs. Evidence was also found for ITO crystallographic orientation to be a parameter influencing SAMs organization. DA - 2007/7/21/ PY - 2007/7/21/ DO - 10.1088/0022-3727/40/14/016 VL - 40 IS - 14 SP - 4212-4221 SN - 1361-6463 ER - TY - JOUR TI - Epitaxial calcium oxide films deposited on gallium nitride surfaces AU - Losego, Mark D. AU - Mita, Seiji AU - Collazo, Ramon AU - Sitar, Zlatko AU - Maria, Jon-Paul T2 - JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B AB - Solid solutions of rocksalt oxides are proposed for lattice-matched dielectrics in gallium nitride (GaN) electronics. This article explores the epitaxial growth of the rocksalt oxide calcium oxide (CaO) by molecular beam epitaxy on gallium nitride surfaces. As a possible end member to a rocksalt oxide solid solution, it is important to understand the processing space that allows for epitaxial CaO growth. Exposing the GaN surface to the oxidant flux prior to the metal flux is shown to be critical in eliminating polycrystalline growth. The effect of deposition temperature, metal flux, and oxidant flux on the film’s epitaxial crystalline quality is also examined. Optimal epitaxial quality is found for growth temperatures of ⩾600°C and near oxygen pressures of 10−6Torr. Thermal stability of the CaO∕GaN interface is experimentally evaluated. No reaction phases are observed by x-ray diffraction up to 850°C in air and &gt;1100°C in a reducing atmosphere. However, CaO films are found to be extremely reactive with H2O, forming Ca(OH)2 within a few hours when exposed to ambient atmosphere at room temperature. DA - 2007/// PY - 2007/// DO - 10.1116/1.2710243 VL - 25 IS - 3 SP - 1029-1032 SN - 1071-1023 ER - TY - JOUR TI - Emulsions stabilised by food colloid particles: Role of particle adsorption and wettability at the liquid interface AU - Paunov, Vesselin N. AU - Cayre, Olivier J. AU - Noble, Paul F. AU - Stoyanov, Simeon D. AU - Velikov, Krassimir P. AU - Golding, Matt T2 - JOURNAL OF COLLOID AND INTERFACE SCIENCE AB - We study the effect of the particle wettability on the preferred type of emulsion stabilised solely by food colloid particles. We present results obtained with the recently developed gel trapping technique (GTT) for characterisation of wettability and surface structuring of individual food colloid particles adsorbed at air–water and oil–water interfaces. This method allows us to replicate a particle monolayer onto the surface of polydimethylsiloxane (PDMS) without altering the position of the particles. By observing the polymer surface with scanning electron microscopy (SEM), we are able to determine the contact angle of the individual particles at the initial liquid interface. We demonstrate that the GTT can be applied to fat crystal particles, calcium carbonate particles coated with stearic acid and spray-dried soy protein/calcium phosphate particles at air–water and oil–water interfaces. Subsequently, we prepare emulsions of decane and water stabilised by the same food colloid particles and correlate the wettability data obtained for these particles to the preferred type of emulsions they stabilise. DA - 2007/8/15/ PY - 2007/8/15/ DO - 10.1016/j.jcis.2007.03.031 VL - 312 IS - 2 SP - 381-389 SN - 0021-9797 KW - food particles KW - solid-stabilised emulsions KW - fat crystals KW - wettability KW - contact angle ER - TY - JOUR TI - Dynamics of vapor-phase organophosphates on silicon and OTS AU - Neeyakorn, Worakarn AU - Varma, Manju AU - Jaye, Cherno AU - Burnette, James E. AU - Lee, Sang M. AU - Nemanich, Robert J. AU - Grant, Christine S. AU - Krim, Jacqueline T2 - TRIBOLOGY LETTERS DA - 2007/9// PY - 2007/9// DO - 10.1007/s11249-007-9224-y VL - 27 IS - 3 SP - 269-276 SN - 1573-2711 KW - vapor phase lubricants KW - friction KW - QCM KW - nanotribology KW - SAMS KW - silicon ER - TY - JOUR TI - Dissolution of polymer films in supercritical carbon dioxide using a quartz crystal microbalance AU - Hussain, Yazan AU - Wu, You-Ting AU - Ampaw, Paa-Joe AU - Grant, Christine S. T2 - JOURNAL OF SUPERCRITICAL FLUIDS AB - Abstract The dissolution kinetics of polymeric materials in CO 2 is crucial to the understanding, design and control of CO 2 -based environmentally benign lithography processes. This study utilizes the quartz crystal microbalance (QCM) to monitor and evaluate the dissolution of poly(1,1-dihydroperfluorooctyl methacrylate- r -2-tetrahydropyranyl methacrylate), poly(FOMA- r -THPMA), polymer films in supercritical CO 2 over a range of temperatures and pressures. Polymer dissolution rates at the range of pressures studied were evaluated to quantify the dissolution kinetics for the polymer. The experiments revealed that the polymer dissolution in supercritical CO 2 undergoes two apparent processes: a rapid absorption of CO 2 into the polymer film followed by a gradual dissolution of polymer film into the CO 2 at the polymer–CO 2 interface. The nature of these interfacial phenomena and their associated effect on the rate are discussed. DA - 2007/9// PY - 2007/9// DO - 10.1016/j.supflu.2007.03.011 VL - 42 IS - 2 SP - 255-264 SN - 1872-8162 KW - quartz crystal microbalance KW - polymer dissolution KW - carbon dioxide KW - sorption KW - fluoropolymer ER - TY - JOUR TI - Determination of the liquid pool surfactant and protein concentration for semi-batch foam fractionation columns AU - Rosa, P. T. V. AU - Santana, C. C. AU - Carbonell, R. G. T2 - BRAZILIAN JOURNAL OF CHEMICAL ENGINEERING AB - A model is derived for the change with time of the concentration of a surface-active component in the liquid pool of a semi-batch foam fractionation process. The transport of surface-active material to the gas-liquid interface was assumed to be limited by the mass transfer rates, and the concentration of the adsorbed material at the interface was assumed to be in equilibrium with the concentration of liquid adjacent to the bubble gas surface. This model was compared to experimental data obtained for semi-batch foam fractionation of aqueous solutions of bovine serum albumin and cetyltrimetylammonium bromide. DA - 2007/// PY - 2007/// DO - 10.1590/S0104-66322007000100001 VL - 24 IS - 1 SP - 1-14 SN - 0104-6632 KW - foam fractionation KW - proteins KW - surfactant KW - bubble column ER - TY - JOUR TI - Coarse graining of nonbonded degrees of freedom AU - Bock, H. AU - Gubbins, K. E. AU - Klapp, S. H. L. T2 - PHYSICAL REVIEW LETTERS AB - We investigate the physical meaning of coarse-grained beads generated by coarse graining of nonbonded particles such as solvent molecules in a solution. Starting from the partition function, we analytically coarse grain an N-particle fluid to a system containing N-2 of the original particles plus a bead representing the two remaining particles. As a direct consequence of the lack of bonding interactions, the resulting effective potential becomes independent of the bead coordinates, i.e., ideal-gas-like, in the thermodynamic limit. Thus, there are no conservative forces between coarse-grained beads representing assemblies of nonbonded molecules nor between these beads and any other species in the system. DA - 2007/6/29/ PY - 2007/6/29/ DO - 10.1103/physrevlett.98.267801 VL - 98 IS - 26 SP - SN - 1079-7114 ER - TY - JOUR TI - Chain-scission-induced intercalation as a facile route to polymer nanocomposites AU - Frankowski, David J. AU - Khan, Saad A. AU - Spontak, Richard J. T2 - ADVANCED MATERIALS AB - Immiscible polystyrene (PS)/clay nanocomposites undergo intercalation upon spatially tuned and atmosphere-regulated thermal-oxidative chain scission (see figure), with resultant increases in moduli and thermal stability. Shortened PS chains generated by scission predominantly locate in the clay galleries and not in the bulk where they would detrimentally affect mechanical properties. DA - 2007/5/7/ PY - 2007/5/7/ DO - 10.1002/adma.200600793 VL - 19 IS - 9 SP - 1286-+ SN - 1521-4095 ER - TY - JOUR TI - Best practices involving teamwork in the classroom: Results from a survey of 6435 engineering, student respondents AU - Oakley, Barbara A. AU - Hanna, Darrin M. AU - Kuzmyn, Zenon AU - Felder, Richard M. T2 - IEEE TRANSACTIONS ON EDUCATION AB - A teamwork survey was conducted at Oakland University, Rochester, MI, in 533 engineering and computer science courses over a two-year period. Of the 6435 student respondents, 4349 (68%) reported working in teams. Relative to the students who only worked individually, the students who worked in teams were significantly more likely to agree that the course had achieved its stated learning objectives (p < 0.001). Regression analysis showed that roughly one-quarter of the variance in belief about whether the objectives were met could be explained by four factors: 1) student satisfaction with the team experience; 2) the presence of instructor guidance related to teamwork; 3) the presence of slackers on teams; and 4) team size. Pearson product-moment correlations revealed statistically significant associations between agreement that the course objectives had been fulfilled and the use of student teams and between satisfaction with teams and the occurrences of instructor guidance on teamwork skills. These and other results suggest that assigning work to student teams can lead to learning benefits and student satisfaction, provided that the instructor pays attention to how the teams and the assignments are set up. DA - 2007/8// PY - 2007/8// DO - 10.1109/TE.2007.901982 VL - 50 IS - 3 SP - 266-272 SN - 0018-9359 KW - correlation KW - evaluation KW - instructor KW - satisfaction KW - student KW - team KW - teamwork ER - TY - JOUR TI - Atomic layer deposition of Conformal inorganic nanoscale coatings on three-dimensional natural fiber systems: Effect of surface topology on film growth characteristics AU - Hyde, G. Kevin AU - Park, Kie Jin AU - Stewart, S. Michael AU - Hinestroza, Juan P. AU - Parsons, Gregory N. T2 - LANGMUIR AB - Atomic-scale material deposition is utilized to achieve uniform coverage and modification of the surface properties of natural fiber and woven fabric materials, where irregular nanoscale features are embedded in a macroscale interpenetrating fiber network. The complex surface topology of the woven fabric results in significantly different film-growth thickness per ALD cycle as compared to planar surfaces coated using the same process conditions, likely due to reactant adsorption within the fiber starting material, as well as impeded reactant transport out of the fabric system during the purge cycle. Cotton textiles modified with conformal nanoscale Al2O3 are found to show extreme hydrophobic effects, distinctly different from planar surfaces that receive the same coatings. The results highlight key concerns for achieving controlled conformal coatings on complex surfaces and open the possibility for new textile finishing approaches to create novel fabric-based materials with specialized function and performance. DA - 2007/9/11/ PY - 2007/9/11/ DO - 10.1021/la701449t VL - 23 IS - 19 SP - 9844-9849 SN - 0743-7463 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000249241300048&KeyUID=WOS:000249241300048 ER - TY - JOUR TI - Viscoelastic behavior of cellulose acetate in a mixed solvent system AU - Appaw, Collins AU - Gilbert, Richard D. AU - Khan, Saad A. T2 - BIOMACROMOLECULES AB - The effect of increasing water composition on the rheological and microstructural behavior of a ternary cellulose acetate (CA)/N,N-dimethylacetamide (DMA)/water system is examined. Addition of water to the CA/DMA system results in enhanced steady shear viscosity and dynamic viscoelastic properties and ultimately to phase-separated gel formation. The changes in dynamic rheological behavior of the system during gelation correlate well with the combined solubility parameter (delta) and, in particular, the Hansen hydrogen-bonding solubility parameter index (delta(h)) of the solvent system, suggesting hydrogen-bonding interactions may be the major route initiating the sol-gel process. For all gels studied, the elastic modulus and the critical stress to yield shifts to higher values with increasing CA concentration and/or water content. In addition, the elastic modulus exhibits a power-law behavior with water content, with the same power-law exponent observed for gels containing different CA concentrations. Addition of water leads to formation of a denser gel network, as evidenced from direct visualization of the gel microstructure through confocal microscopy. DA - 2007/5// PY - 2007/5// DO - 10.1021/bm0611681 VL - 8 IS - 5 SP - 1541-1547 SN - 1526-4602 ER - TY - JOUR TI - Structure-based kinetic models of modular signaling protein function: Focus on Shp2 AU - Barua, Dipak AU - Faeder, James R. AU - Haugh, Jason M. T2 - BIOPHYSICAL JOURNAL AB - We present here a computational, rule-based model to study the function of the SH2 domain-containing protein tyrosine phosphatase, Shp2, in intracellular signal transduction. The two SH2 domains of Shp2 differentially regulate the enzymatic activity by a well-characterized mechanism, but they also affect the targeting of Shp2 to signaling receptors in cells. Our kinetic model integrates these potentially competing effects by considering the intra- and intermolecular interactions of the Shp2 SH2 domains and catalytic site as well as the effect of Shp2 phosphorylation. Even for the isolated Shp2/receptor system, which may seem simple by certain standards, we find that the network of possible binding and phosphorylation states is composed of over 1000 members. To our knowledge, this is the first kinetic model to fully consider the modular, multifunctional structure of a signaling protein, and the computational approach should be generally applicable to other complex intermolecular interactions. DA - 2007/4/1/ PY - 2007/4/1/ DO - 10.1529/biophysj.106.093484 VL - 92 IS - 7 SP - 2290-2300 SN - 0006-3495 ER - TY - JOUR TI - Stability of organically modified montmorillonites and their polystyrene nanocomposites after prolonged thermal treatment AU - Frankowski, David J. AU - Capracotta, Michael D. AU - Martin, James D. AU - Khan, Saad A. AU - Spontak, Richard J. T2 - CHEMISTRY OF MATERIALS AB - Melt intercalation of montmorillonite (MMT) into polymeric matrices to improve the mechanical properties of polymers has evolved into a subject of tremendous fundamental and technological interest. The thermal treatment experienced during processing or end use can substantially affect the clay and diminish the target properties of polymer/clay nanocomposites (NCs) because of deintercalation or degradation of surface modifiers. In this work, changes in morphology, chemistry, and thermal stability of organically modified (OM) MMT after annealing in O2-rich and N2 environments are investigated. Degradation of the alkyl ammonium cation occurs at temperatures as low as 105 °C upon prolonged exposure in an O2-rich environment. X-ray diffractometry (XRD) performed in situ establishes the response of two OM-MMTs to elevated temperatures at short times, whereas ex situ XRD provides insight into high-temperature exposure at long times. Active sites on the silicate surfaces are found to induce scission of, as well as chemical interaction with, the chains comprising a polystyrene (PS) matrix. Size-exclusion chromatography indicates that PS chain scission occurs primarily after relatively short annealing times, whereas branching and cross-linking are more prevalent after long exposure times in an O2-rich environment. DA - 2007/5/29/ PY - 2007/5/29/ DO - 10.1021/cm061953k VL - 19 IS - 11 SP - 2757-2767 SN - 0897-4756 ER - TY - JOUR TI - Rheological properties of guar galactomannan solutions during hydrolysis with galactomannanase and alpha-galactosidase enzyme mixtures AU - Mahammad, Shamsheer AU - Comfort, Donald A. AU - Kelly, Robert M. AU - Khan, Saad A. T2 - BIOMACROMOLECULES AB - Guar galactomannan, a naturally occurring polysaccharide, is susceptible to hydrolysis by three enzymes: β-mannosidase, β-mannanase, and α-galactosidase. The β-mannosidase cleaves a single mannose unit from the nonreducing end of the guar molecule, the β-mannanase cleaves interior glycosidic bonds between adjacent mannose units, and the α-galactosidase cleaves the galactose side branches off the guar. In this study, hydrolysis of guar solutions using hyperthermopilic versions of these enzymes together in different proportions and combinations are examined. The enzymatic reactions are carried out in situ in a rheometer, and the progress of the reaction is monitored through measuring the variation in zero shear viscosity. We find the presence of α-galactosidase to affect the action of both β-mannanase and β-mannosidase with respect to solution rheology. However, this effect is more pronounced when the α-galactosidase and β-mannanase or β-mannosidase enzymes were added sequentially rather than simultaneously. This likely is the result of debranching of the guar, which facilitates attack on β-1,4-linkages by both the β-mannanase and the β-mannosidase enzymes and increases hydrolytic rates by the individual enzymes. A rheology-based kinetic model is developed to estimate the reaction rate constants and interpret synergistic effects of multiple enzyme contributions. The model fits the experimental data well and reveals that both the native and the debranched guar have the same activation energy for β-mannanase action, although debranching considerably increases the frequency of enzyme−guar interactions. DA - 2007/3// PY - 2007/3// DO - 10.1021/bm0608232 VL - 8 IS - 3 SP - 949-956 SN - 1526-4602 ER - TY - JOUR TI - Preferential solvent partitioning within asphaltenic aggregates dissolved in binary solvent mixtures AU - Verruto, Vincent J. AU - Kilpatrick, Peter K. T2 - ENERGY & FUELS AB - The heaviest fraction of crude oils, asphaltenes, has been shown to play a central role in the stabilization of troublesome water-in-crude oil emulsions. In previous model oil systems, emulsion stability was observed to depend notably on the properties of self-assembled interfacially active asphaltenic aggregates. Thus, careful characterization of these aggregates is of great importance for better understanding of asphaltene-stabilized emulsions. Small-angle neutron scattering (SANS) has proven to be a powerful tool for such characterization. Described here is the application of SANS on asphaltenes from Hondo crude oil dissolved in binary solvent mixtures of toluene with n-heptane, decalin, or 1-methylnaphthalene. A polydisperse oblate cylinder (POC) form factor model was used to fit the aggregate scattering data, and subsequent calculations of minimum error were performed to ascertain the entrained solvent composition within the aggregates. When toluene was paired with either a weak solvent (decalin) or a precipitant (n-heptane), the entrained solvent composition was nearly pure toluene (>90%). Conversely, for the toluene/1-methlnaphthalene pairing, methylnaphthalene demonstrated slight preferential entrainment (∼60%) compared with the bulk composition (∼57%). This is the first such in situ experimental determination of the aggregate composition for asphaltenes dissolved in binary solvents, reinforcing the important role of asphaltene−solvent interactions in asphaltene self-assembly. DA - 2007/// PY - 2007/// DO - 10.1021/ef060456n VL - 21 IS - 3 SP - 1217-1225 SN - 0887-0624 ER - TY - JOUR TI - Dynamic asphaltene-resin exchange at the oil/water interface: Time-dependent W/O emulsion stability for asphaltene/resin model oils AU - Yang, Xiaoli AU - Verruto, Vincent J. AU - Kilpatrick, Peter K. T2 - ENERGY & FUELS AB - The critical electric field (CEF) technique was used to determine the time-dependent stability of water-in-oil emulsions in which asphaltenes stabilize the film. Stabilizing films comprising purely asphaltenes were observed to increase monotonically in stability with time. However, in the presence of resins, particularly in mass ratios of resins to asphaltenes of 0.5−1.0, the stability of the emulsions as probed by CEF were observed to exhibit a very sharp local maximum. Similar behavior was observed in dilatational interfacial rheology experiments using an oscillating drop tensiometer. The dilatational modulus (ε) for the stabilizing film, as obtained from the variation of interfacial tension with interfacial area, of an aging asphaltene/resin model oil droplet in water exhibited a time-dependent local maximum. Values of ε were nominally lower for asphaltene/resin model oil systems than asphaltene model oil systems, qualitatively similar to CEF trends. These observed phenomena are similar to the “Vroman effect”, observed in competitive protein adsorption. One plausible explanation is that resin-solvated asphaltenic aggregates are able to diffuse and adsorb to the interface more quickly than larger pure asphaltenic aggregates, but then a molecular rearrangement occurs in which resins become the primary adsorbent in the monolayer by reptation through the consolidated asphaltene network, displacing the asphaltenes and reducing the stability and the dilatational elasticity. DA - 2007/// PY - 2007/// DO - 10.1021/ef060465w VL - 21 IS - 3 SP - 1343-1349 SN - 1520-5029 ER - TY - JOUR TI - Dielectric elastomers as next-generation polymeric actuators AU - Shankar, Ravi AU - Ghosh, Tushar K. AU - Spontak, Richard J. T2 - SOFT MATTER AB - Due to their versatile properties, robust behavior, facile processability and low cost, organic polymers have become the material of choice for an increasing number of mature and cutting-edge technologies. In the last decade or so, a new class of polymers capable of responding to external electrical stimulation by displaying significant size or shape change has emerged. These responsive materials, collectively referred to as electroactive polymers (EAPs), are broadly classified as electronic or ionic according to their operational mechanism. Electronic EAPs generally exhibit superior performance relative to ionic EAPs in terms of actuation strain, reliability, durability and response time. Among electronic EAPs, dielectric elastomers exhibit the most promising properties that mimic natural muscle for use in advanced robotics and smart prosthetics, as well as in haptic and microfluidic devices. Elastomers derived from homopolymers such as acrylics and silicones have received considerable attention as dielectric EAPs, whereas novel dielectric EAPs based on selectively swollen nanostructured block copolymers with composition-tailorable properties have only recently been reported. Here, we provide an overview of various EAPs in terms of their operational mechanisms, uses and shortcomings, as well as a detailed account of dielectric elastomers as next-generation actuators. DA - 2007/// PY - 2007/// DO - 10.1039/b705737g VL - 3 IS - 9 SP - 1116-1129 SN - 1744-6848 ER - TY - JOUR TI - Cyclodextrin - hydrophobe complexation in associative polymers AU - Mahammad, Shamsheer AU - Roberts, George W. AU - Khan, Saad A. T2 - SOFT MATTER AB - We develop a new rheology-based method to study the complexation of cyclodextrins with hydrophobes in hydrophobically modified associative polymer solutions. The associative polymers have comb-like structure with hydrophobic groups randomly attached to the polymer backbone. Intermolecular interactions between the hydrophobic groups form a transient network resulting in thickening of the polymer solutions. On addition of cyclodextrins (CD) to the solution, the hydrophobes are encapsulated within the hydrophobic cavity of the cyclodextrins. This reduces viscoelastic properties of the polymer solution by several orders of magnitude. We exploit the existence of a dynamic equilibrium between CD adsorbed to the hydrophobes and free CD in the solution, to develop a rheology-based Langmuir-type adsorption isotherm for estimating the binding constant for molecular complexation. The model is based on the assumption that the amount of CD adsorbed is proportional to the reduction in elastic modulus of the polymer solution due to the encapsulation of the network junctions by CD. The effects of temperature on binding constant are studied to estimate the enthalpy and entropy of complexation. Experiments are conducted with both α-and β-CD at different polymer concentrations and temperatures to estimate the relative strength of binding of the CDs. At a given temperature and a polymer concentration, α-CD has a lower binding constant compared to that of β-CD, indicating higher affinity of α-CD to adsorb onto the hydrophobes. Since α-CDs have a smaller ring size, they can snugly fit to the hydrophobes and the association leads to higher enthalpy and entropy change. DA - 2007/// PY - 2007/// DO - 10.1039/b700167c VL - 3 IS - 9 SP - 1185-1193 SN - 1744-683X ER - TY - JOUR TI - Crystallization kinetics of glyme-LiX and PEO-LiX polymer electrolytes AU - Henderson, Wesley A. T2 - MACROMOLECULES AB - The crystallization kinetics of oligomeric polyethers (glymes) and poly(ethylene oxide) (PEO) with a wide range of lithium salts including LiBETI, LiTFSI, LiAsF6, LiPF6, LiClO4, LiI, LiBF4, LiCF3SO3, LiNO3, and LiCF3CO2 have been examined in detail. Wide variations exist between the rates of crystallization of the phases. These variations are strongly dependent upon the lithium salt present and are well correlated with the ionic association behavior of the different lithium salts in aprotic solvents. DA - 2007/7/10/ PY - 2007/7/10/ DO - 10.1021/ma061866d VL - 40 IS - 14 SP - 4963-4971 SN - 1520-5835 ER - TY - JOUR TI - Atomic layer deposition on electrospun polymer fibers as a direct route to Al2O3 microtubes with precise wall thickness control AU - Peng, Qing AU - Sun, Xiao-Yu AU - Spagnola, Joseph C. AU - Hyde, G. Kevin AU - Spontak, Richard J. AU - Parsons, Gregory N. T2 - NANO LETTERS AB - Atomic layer deposition (ALD) of Al2O3 on electrospun poly(vinyl alcohol) microfiber templates is demonstrated as an effective and robust strategy by which to fabricate long and uniform metal-oxide microtubes. The wall thickness is shown to be precisely controlled within a molecular layer or so by adjusting the number of ALD cycles utilized. By judicious selection of the electrospinning and ALD parameters, designer tubes of various sizes and inorganic materials can be synthesized. DA - 2007/3// PY - 2007/3// DO - 10.1021/nl062948i VL - 7 IS - 3 SP - 719-722 SN - 1530-6984 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000244867400032&KeyUID=WOS:000244867400032 ER - TY - JOUR TI - A review of gaseous ammonia emissions from slurry pits in pig production systems AU - Griffing, E. M. AU - Overcash, M. AU - Westerman, P. T2 - BIOSYSTEMS ENGINEERING AB - Twenty-six experimental studies of ammonia emissions from pig buildings that utilise some form of pit/slurry system have been analysed and compared. Using standard values for pig weight and total Kjeldahl nitrogen (TKN) content in the waste when these quantities were unspecified, experimental ammonia emissions were compared on a per cent loss (of excreted TKN) basis. Correction factors were determined for measurements made during specific parts of the year, with corresponding differences in temperature, or time of day, and adjustments were made to put emission data on an annual average basis, when applicable. When corrected in this way, measurements made in the United States and in Europe were 22% and 21%, respectively. The standard deviation and standard error of the mean were 9% and 1.8%, respectively. The 95% confidence interval of the mean was 17.6–24.9%. The proposed emission factor data are reasonably consistent and emission factors higher or lower must be critically compared to the existing experimental base. DA - 2007/7// PY - 2007/7// DO - 10.1016/j.biosystemseng.2007.02.012 VL - 97 IS - 3 SP - 295-312 SN - 1537-5110 ER - TY - JOUR TI - Selection and initial characterization of novel peptide ligands that bind specifically to human blood outgrowth endothelial cells AU - Veleva, Anka N. AU - Cooper, Stuart L. AU - Patterson, Cam T2 - BIOTECHNOLOGY AND BIOENGINEERING AB - Abstract Using phage display technology, we have isolated 12‐mer peptide ligands that bind to human blood outgrowth endothelial cells (HBOEC). To avoid non‐specific binding we apply negative–positive selection approach by pre‐incubating the library with non‐HBOEC. The selected phage clones bind to their target cell population with high recovery. Moreover, the isolated clones display outstanding cell specificity as no significant binding is observed on a panel of other cell types. We anticipate the findings from this work to be exploited in the development of future cell‐based therapeutic revascularization approaches to ischemic disease and endothelial injury or in combination with biomedical devices. Biotechnol. Bioeng. 2007; 98: 306–312. © 2007 Wiley Periodicals, Inc. DA - 2007/9/1/ PY - 2007/9/1/ DO - 10.1002/bit.21420 VL - 98 IS - 1 SP - 306-312 SN - 1097-0290 KW - human blood outgrowth endothelial cells (HBOEC) KW - phage displayed peptide library screening KW - cell-specific KW - peptides KW - progenitor cell-based therapies ER - TY - JOUR TI - Polyelectrolyte diode: Nonlinear current response of a junction between aqueous ionic gels AU - Cayre, Olivier J. AU - Chang, Suk Tai AU - Velev, Orlin D. T2 - JOURNAL OF THE AMERICAN CHEMICAL SOCIETY AB - We demonstrate that a fixed junction between two aqueous gels containing oppositely charged polyelectrolytes could rectify electric current. The agarose-based gels were "doped" with sodium poly(styrene sulfonic acid) and poly(diallyl dimethylammonium chloride). The unidirectional current response of the interface between the cationic and anionic gels originates directly from anisotropy in the mobile ionic charges in the gels. The current depends on the concentration of polyelectrolyte, the background ionic concentration, and the distance traveled by the ions. The I-V curves from the devices demonstrated a combination of transient and stationary rectification effects. The current densities achieved were comparable to or higher than those obtained with previously reported organic semiconductor diodes. The diodes had good long-term stability in both DC and AC conduction modes. The materials and the process of preparation of these devices are simple, inexpensive, and scalable. They could be used in flexible and biocompatible electronic circuits. DA - 2007/9/5/ PY - 2007/9/5/ DO - 10.1021/ja072449z VL - 129 IS - 35 SP - 10801-10806 SN - 1520-5126 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-35948967966&partnerID=MN8TOARS ER - TY - JOUR TI - Nanofabricated particles for engineered drug therapies: A preliminary Biodistribution study of PRINT (TM) nanoparticles AU - Gratton, Stephanie E. A. AU - PohhauS, Patrick D. AU - Lee, Jin AU - Guo, , Ii AU - Cho, Moo J. AU - DeSimone, Joseph M. T2 - JOURNAL OF CONTROLLED RELEASE AB - A novel method for the fabrication of polymeric particles on the order of tens of nanometers to several microns is described. This imprint lithographic technique called PRINT™ (Particle Replication In Non-wetting Templates), takes advantage of the unique properties of elastomeric molds comprised of a low surface energy perfluoropolyether network, allowing the production of monodisperse, shape-specific nanoparticles from an extensive array of organic precursors. This engineered nature of particle production has a number of advantages over the construction of traditional nanoparticles such as liposomes, dendrimers, and colloidal precipitates. The gentle “top down” approach of PRINT enables the simultaneous and independent control over particle size and shape, composition, and surface functionality, and permits the loading of delicate cargos such as small organic therapeutics and biological macromolecules. Thus, this single tool serves as a comprehensive platform for the rational design and investigation of new nanocarriers in medicine, having applications ranging from therapeutics to advanced diagnostics. Preliminary in vitro and in vivo studies were conducted, demonstrating the future utility of PRINT particles as delivery vectors in nanomedicine. Monodisperse 200 nm poly(ethylene glycol)-based (PEG) particles were fabricated using PRINT methodology and characterized via scanning electron microscopy and dynamic light scattering. Incubation with HeLa cells showed very little cytotoxicity, even at high concentrations. The biodistribution and pharmacokinetics of [125I]-labeled particles were studied in healthy mice following bolus tail vein administration. The particles were distributed mainly to the liver and the spleen with an apparent distribution t1/2 of approximately 17 min followed by slow redistribution with a t1/2 of 3.3 h. The volume of distribution for the central and peripheral compartments was found to be approximately 3 mL and 5 mL, respectively. DA - 2007/8/16/ PY - 2007/8/16/ DO - 10.1016/j.jconrel.2007.05.027 VL - 121 IS - 1-2 SP - 10-18 SN - 0168-3659 KW - PRINT KW - biodistribution KW - nanoparticles KW - pharmacokinetics KW - nanomedicine ER - TY - JOUR TI - In situ Auger electron spectroscopy study of atomic layer deposition: Growth initiation and interface formation reactions during ruthenium ALD on Si-H, SiO2, and HfO2 surfaces AU - Park, Kie Jin AU - Terry, David B. AU - Stewart, S. Michael AU - Parsons, Gregory N. T2 - LANGMUIR AB - Growth initiation and film nucleation in atomic layer deposition (ALD) is important for controlling interface composition and achieving atomic-scale films with well-defined composition. Ruthenium ALD is studied here using ruthenocene and oxygen as reactants, and growth initiation and nucleation are characterized on several different growth surfaces, including SiO2, HfO2, and hydrogen terminated silicon, using on-line Auger electron spectroscopy and ex-situ X-ray photoelectron spectroscopy. The time needed to reach the full growth rate (typically approximately 1 A per deposition cycle) is found to increase as the surface energy of the starting surface (determined from contact angle measurements) decreased. Growth starts more readily on HfO2 than on SiO2 or Si-H surfaces, and Auger analysis indicates distinct differences in surface reactions on the various surfaces during film nucleation. Specifically, surface oxygen is consumed during ruthenocene exposure, so the nucleation rate will depend on the availability of oxygen and the energetics of surface oxygen bonding on the starting substrate surface. DA - 2007/5/22/ PY - 2007/5/22/ DO - 10.1021/la061898u VL - 23 IS - 11 SP - 6106-6112 SN - 0743-7463 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000246456700038&KeyUID=WOS:000246456700038 ER - TY - JOUR TI - Biochemical analysis of Thermotoga maritima GH36 alpha-galactosidase (TmGalA) confirms the mechanistic commonality of clan GH-D glycoside hydrolases AU - Comfort, Donald A. AU - Bobrov, Kirill S. AU - Ivanen, Dina R. AU - Shabalin, Konstantin A. AU - Harris, James M. AU - Kulminskaya, Anna A. AU - Brumer, Harry AU - Kelly, Robert M. T2 - BIOCHEMISTRY AB - Organization of glycoside hydrolase (GH) families into clans expands the utility of information on catalytic mechanisms of member enzymes. This issue was examined for GH27 and GH36 through biochemical analysis of GH36 alpha-galactosidase from Thermotoga maritima (TmGalA). Catalytic residues in TmGalA were inferred through structural homology with GH27 members to facilitate design of site-directed mutants. Product analysis confirmed that the wild type (WT) acted with retention of anomeric stereochemistry, analogous to GH27 enzymes. Conserved acidic residues were confirmed through kinetic analysis of D327G and D387G mutant enzymes, azide rescue, and determination of azide rescue products. Mutation of Asp327 to Gly resulted in a mutant that had a 200-800-fold lower catalytic rate on aryl galactosides relative to the WT enzyme. Azide rescue experiments using the D327G enzyme showed a 30-fold higher catalytic rate compared to without azide. Addition of azide to the reaction resulted in formation of azide beta-d-galactopyranoside, confirming Asp327 as the nucleophilic residue. The Asp387Gly mutation was 1500-fold catalytically slower than the WT enzyme on p-nitrophenyl alpha-d-galactopyranoside. Analysis at different pH values produced a bell-shaped curve of the WT enzyme, but D387G exhibited higher activity with increasing pH. Catalyzed reactions with the D387G mutant in the presence of azide resulted in formation of azide alpha-d-galactopryanoside as the product of a retaining mechanism. These results confirm that Asp387 is the acid/base residue of TmGalA. Furthermore, they show that the biochemical characteristics of GH36 TmGalA are closely related to GH27 enzymes, confirming the mechanistic commonality of clan GH-D members. DA - 2007/3/20/ PY - 2007/3/20/ DO - 10.1021/bi061521n VL - 46 IS - 11 SP - 3319-3330 SN - 0006-2960 ER - TY - JOUR TI - Swine waste characterization: A review AU - Barker, J. C. AU - Overcash, M. R. T2 - Transactions of the ASABE DA - 2007/// PY - 2007/// VL - 50 IS - 2 SP - 651-657 ER - TY - JOUR TI - Supramolecular nanomimetics: Replication of micelles, viruses, and other naturally occurring nanoscale objects AU - Maynor, Benjamin W. AU - LaRue, Isaac AU - Hu, Zhaokang AU - Rolland, Jason P. AU - Pandya, Ashish AU - Fu, Qiang AU - Liu, Jie AU - Spontak, Richard J. AU - Sheiko, Sergei S. AU - Samulski, Richard J. AU - Samulski, Edward T. AU - DeSimone, Joseph M. T2 - SMALL AB - Replicas of naturally occurring structures, including viruses (see image, left), micelles (center), and carbon nanotubes (right) are made from fluoropolymer molds templated from naturally occurring objects. The successful integration of imprint fabrication with bottom-up self-assembly is demonstrated for integrated nanopatterning, which may have applications in many diverse areas such as sensors, implantable biomaterials, and medical therapies. Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2296/2007/z600507_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 - 2007/5// PY - 2007/5// DO - 10.1002/smll.200600507 VL - 3 IS - 5 SP - 845-849 SN - 1613-6810 KW - carbon nanotubes KW - molding KW - replication KW - supramolecular chemistry ER - TY - JOUR TI - Responses of wild-type and resistant strains of the hyperthermophilic bacterium Thermotoga maritima to chloramphenicol challenge AU - Montero, Clemente I. AU - Johnson, Matthew R. AU - Chou, Chung-Jung AU - Conners, Shannon B. AU - Geouge, Sarah G. AU - Tachdjian, Sabrina AU - Nichols, Jason D. AU - Kelly, Robert M. T2 - APPLIED AND ENVIRONMENTAL MICROBIOLOGY AB - Transcriptomes and growth physiologies of the hyperthermophile Thermotoga maritima and an antibiotic-resistant spontaneous mutant were compared prior to and following exposure to chloramphenicol. While the wild-type response was similar to that of mesophilic bacteria, reduced susceptibility of the mutant was attributed to five mutations in 23S rRNA and phenotypic preconditioning to chloramphenicol. DA - 2007/8// PY - 2007/8// DO - 10.1128/AEM.00453-07 VL - 73 IS - 15 SP - 5058-5065 SN - 0099-2240 ER - TY - JOUR TI - Propagating waves of self-assembly in organosilane monolayers AU - Douglas, Jack F. AU - Efimenko, Kirill AU - Fischer, Daniel A. AU - Phelan, Fredrick R. AU - Genzer, Jan T2 - PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA AB - Wavefronts associated with reaction–diffusion and self-assembly processes are ubiquitous in the natural world. For example, propagating fronts arise in crystallization and diverse other thermodynamic ordering processes, in polymerization fronts involved in cell movement and division, as well as in the competitive social interactions and population dynamics of animals at much larger scales. Although it is often claimed that self-sustaining or autocatalytic front propagation is well described by mean-field “reaction–diffusion” or “phase field” ordering models, it has recently become appreciated from simulations and theoretical arguments that fluctuation effects in lower spatial dimensions can lead to appreciable deviations from the classical mean-field theory (MFT) of this type of front propagation. The present work explores these fluctuation effects in a real physical system. In particular, we consider a high-resolution near-edge x-ray absorption fine structure spectroscopy (NEXAFS) study of the spontaneous frontal self-assembly of organosilane (OS) molecules into self-assembled monolayer (SAM) surface-energy gradients on oxidized silicon wafers. We find that these layers organize from the wafer edge as propagating wavefronts having well defined velocities. In accordance with two-dimensional simulations of this type of front propagation that take fluctuation effects into account, we find that the interfacial widths w ( t ) of these SAM self-assembly fronts exhibit a power-law broadening in time, w ( t ) ≈ t β , rather than the constant width predicted by MFT. Moreover, the observed exponent values accord rather well with previous simulation and theoretical estimates. These observations have significant implications for diverse types of ordering fronts that occur under confinement conditions in biological or materials-processing contexts. DA - 2007/6/19/ PY - 2007/6/19/ DO - 10.1073/pnas.0703620104 VL - 104 IS - 25 SP - 10324-10329 SN - 0027-8424 KW - fluctuation-induced interfacial broadening KW - frontal self-assembly KW - mean-field Fisher-Kolmogorov equation KW - reaction-diffusion fronts KW - self-assembled monolayers ER - TY - JOUR TI - Obtaining concentration profiles from computer simulation structure factors AU - Schultz, Andrew J. AU - Hall, Carol K. AU - Genzer, Jan T2 - MACROMOLECULES AB - ADVERTISEMENT RETURN TO ISSUEPREVCommunication to the...Communication to the EditorNEXTObtaining Concentration Profiles from Computer Simulation Structure FactorsAndrew J. Schultz, Carol K. Hall, and Jan GenzerView Author Information Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina 27695, and Department of Chemical and Biological Engineering, University at Buffalo, The State University of New York, Buffalo, New York 14260 Cite this: Macromolecules 2007, 40, 8, 2629–2632Publication Date (Web):March 15, 2007Publication History Received11 December 2006Revised7 February 2007Published online15 March 2007Published inissue 17 April 2007https://doi.org/10.1021/ma062836dCopyright © 2007 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views392Altmetric-Citations11LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. 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Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit Read OnlinePDF (176 KB) Get e-AlertsSUBJECTS:Chemical structure,Copolymers,Crystal structure,Interfaces,Quantum mechanics Get e-Alerts DA - 2007/4/17/ PY - 2007/4/17/ DO - 10.1021/ma062836d VL - 40 IS - 8 SP - 2629-2632 SN - 1520-5835 ER - TY - PCOMM TI - Membrane-binding/modification model of signaling protein activation and analysis of its control by cell morphology AU - Haugh, Jason M. AB - A mechanism for cell shape control of intracellular signal transduction, whereby the average concentration of activated proteins in the cytosol increases as the height of the cell decreases, has been described recently. An important modification of this analysis is offered, recognizing that signaling proteins are not only activated at the plasma membrane but must first form complexes with signaling molecules that reside there, such as receptors and lipids. With these more realistic boundary conditions, it is shown that the region of parameter space where cell shape amplifies the average cytosolic activity is greatly expanded. Moreover, this model allows for amplification of the activated protein bound at the membrane, which is considered more relevant for certain, spatially driven signaling processes in cell migration. DA - 2007/6/1/ PY - 2007/6/1/ DO - 10.1529/biophysj.107.105213 SP - L93-L95 PB - Elsevier BV ER - TY - JOUR TI - Freezing of argon in ordered and disordered porous carbon AU - Coasne, Benoit AU - Jain, Surendra K. AU - Naamar, Linda AU - Gubbins, Keith E. T2 - PHYSICAL REVIEW B AB - We report a molecular simulation study on the freezing of argon within two models of activated porous carbons. Model A is a regular slit-shaped nanopore, which represents an ordered graphitic porous carbon with a single pore width. Model B is a realistic sample of a disordered porous carbon obtained from reverse Monte Carlo. The morphological (pore shape) and topological (pore connectivity) disorders of model B represent in a realistic way the complex porous structure of materials obtained after carbonization and activation of pure saccharose. This study is aimed at estimating how the effect of disorder of the porous material affects freezing and melting of simple adsorbates. Freezing of argon in the slit pore model conforms to the classical behavior for an adsorbate confined in a strongly attractive pore; the in-pore freezing temperature is higher than that of the bulk fluid, and the shift in freezing temperature increases with decreasing pore size. It is found that the two-dimensional crystal layers of argon within the slit pores have a hexagonal structure (i.e., triangular symmetry). Freezing of argon within model B strongly departs from that observed for model A. No crystallization is observed for argon in the complex porosity of model B. Nevertheless the confined phase undergoes structural changes at a temperature $T=115\phantom{\rule{0.3em}{0ex}}\mathrm{K}$; this temperature is close to the freezing temperature found for the slit pore with width $H=1.1\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$, which corresponds to the mean pore size in model B. For temperatures larger than $T=115\phantom{\rule{0.3em}{0ex}}\mathrm{K}$, the confined phase in model B exhibits a liquid-like behavior as revealed from pair correlation functions and bond-order parameters. On the other hand, the confined phase for $T<115\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ has more short-range order than the liquid phase but its overall behavior remains liquid-like. Our results indicate that the changes observed at $T\ensuremath{\sim}115\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ are due (1) to the appearance in the confined phase of a small amount of crystal atoms and (2) to the fact that the fraction of liquid-like atoms having at least seven nearest neighbors reaches a plateau value of 80%. The results provide a basis for the interpretation of experiments such as NMR and scattering experiments on freezing in disordered porous materials. DA - 2007/8// PY - 2007/8// DO - 10.1103/physrevb.76.085416 VL - 76 IS - 8 SP - SN - 1098-0121 ER - TY - JOUR TI - Direct observation of two-dimensional growth at SiO2/Si(111) interface AU - Hojo, Daisuke AU - Tokuda, Norio AU - Yamabe, Kikuo T2 - THIN SOLID FILMS AB - Abstract The residue of the two-dimensional (2D) oxide-island growth was directly investigated by observing the morphology change of the SiO2/Si(111) interface with atomic force microscopy, after removing SiO2. It was found that oxidation progressed by the bilayers in the (111) orientation instead of by the monolayers. Oxidation created the oxide-islands in an atomic layer, while the Si-islands were found to exist in the previous atomic layer. This result indicates that thermal oxidation progresses not by a strict layer-by-layer process. Furthermore, the deviation from the layer-by-layer process was increased as the oxidation temperature was decreased. This morphology degradation at low-oxidation temperatures ( DA - 2007/7/31/ PY - 2007/7/31/ DO - 10.1016/j.tsf.2007.05.011 VL - 515 IS - 20-21 SP - 7892-7898 SN - 0040-6090 KW - oxidation KW - silicon KW - interface KW - atomic force microscopy KW - Step/Terrace KW - surface roughness ER - TY - JOUR TI - Confinement effects on chemical reactions - Toward an integrated rational catalyst design AU - Santiso, Erik E. AU - Kostov, Milen K. AU - George, Aaron M. AU - Nardelli, Marco Buongiorno AU - Gubbins, Keith E. T2 - APPLIED SURFACE SCIENCE AB - Most chemical reactions of practical interest are carried out in nano-structured materials, which can enhance reactions due to their large specific surface area, their interactions with the reacting mixture and confinement effects. An experimental investigation of the role of each possible catalytic effect is challenging, since experimental measurements reflect an integration over multiple effects. In this work, we present a review of our most recent research on some of the factors that can influence a chemical reaction in confinement through the study of several model systems. We first consider the influence of steric hindrance on the equilibrium and kinetics for the rotational isomerizations of several small hydrocarbons [E.E. Santiso, M. Buongiorno Nardelli, K.E. Gubbins, Proc. Natl. Acad. Sci. U.S.A., (2007), in press]. These examples illustrate how reaction rates can vary doubly exponentially with the dimensions of the confining material (the ‘shape-catalytic’ effect). As a second example, we consider the unimolecular decomposition of formaldehyde on graphitic carbon pores of various sizes [E.E. Santiso, A.M. George, K.E. Gubbins, M. Buongiorno Nardelli, J. Chem. Phys. 125 (2006) 084711]. These results illustrate the influence of electrostatic interactions with the supporting material on the reaction mechanism and equilibrium yield for reactions involving a charge transfer. As a final example, we consider the interaction of a water molecule with a defective carbon substrate as an example of a chemical interaction that can be enhanced through a shape-catalytic effect. We first show using ab initio calculations how a vacancy site on a graphene surface can induce the thermal splitting of water at relatively low temperatures [M.K. Kostov, E.E. Santiso, A.M. George, K.E. Gubbins, M. Buongiorno Nardelli, Phys. Rev. Lett. 95 (2005) 136105]. We then examine the dissociation on a vacancy site on a nanotube surface, which shows the shape-catalytic effect of the surface curvature. These results are a first step toward the design of catalytic materials that take advantage of different enhancing effects simultaneously. DA - 2007/4/30/ PY - 2007/4/30/ DO - 10.1016/j.apsusc.2006.12.121 VL - 253 IS - 13 SP - 5570-5579 SN - 1873-5584 KW - confinement effects KW - catalyst design KW - chemical reactions KW - graphitic carbons ER - TY - JOUR TI - Surface properties of poly[2-(perfluorooctyl)ethyl acrylate] deposited from liquid CO2 high-pressure free meniscus coating AU - Kim, Jaehoon AU - Efimenko, Kirill AU - Genzer, Jan AU - Carbonell, Ruben G. T2 - MACROMOLECULES AB - The surface characteristics of poly[2-(perfluorooctyl)ethyl acrylate] (PFOEA) films deposited using a high-pressure free meniscus coating (hFMC) process with liquid CO2 (l-CO2) as the coating solvent on 12.5 cm diameter silicon wafer substrates were investigated using contact angle measurements, atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and near-edge X-ray adsorption fine structure (NEXAFS) spectroscopy. The results were compared with surface property measurements of PFOEA films deposited from 1,1,2-trichlorotrifluoroethane (Freon 113) under normal dip coating conditions at atmospheric pressure. NEXAFS measurements showed that perfluoroalkyl groups in the films from l-CO2 and Freon 113 were well-organized and oriented normal to the substrate at the air/polymer interface. AFM images and XPS measurements revealed that a terrace-like structure of the PFOEA film from l-CO2 resulted in carbonyl group exposure at the air/polymer interface. This leads to smaller contact angles on the films cast from l-CO2 relative to the specimens deposited from Freon 113. Annealing the films deposited from the solvents resulted in droplet formation on the surface due to dewetting. The critical surface tension (γc) after annealing the film prepared from Freon 113 increased from 6.5 to 8.5 mJ/m2, whereas γc of the film deposited from l-CO2 decreased slightly from 9.7 to 8.9 mJ/m2. We discuss how surface morphology changes before and after annealing play a role in the variation of γc. DA - 2007/2/6/ PY - 2007/2/6/ DO - 10.1021/ma0623791 VL - 40 IS - 3 SP - 588-597 SN - 1520-5835 ER - TY - JOUR TI - Study of the packing density and molecular orientation of bimolecular self-assembled monolayers of aromatic and aliphatic organosilanes on silica AU - Smith, Matthew B. AU - Efimenko, Kirill AU - Fischer, Daniel A. AU - Lappi, Simon E. AU - Kilpatrick, Peter K. AU - Genzer, Jan T2 - LANGMUIR AB - Bimolecular self-assembled monolayers (SAMs) of aromatic and aliphatic chlorosilanes were self-assembled onto silica, and their characteristics were established by contact angle measurement, near-edge X-ray absorption fine structure spectroscopy, and Fourier transform infrared spectroscopy. Three aromatic constituents (phenyltrichlorosilane, benzyltrichlorosilane, and phenethyltrichlorosilane) were studied in combination with four aliphatic coadsorbates (butyltrichlorosilane, butyldimethylchlorosilane, octadecyltrichlorosilane, and octadecyldimethylchlorosilane). Our results demonstrate that whereas SAMs made of trichlorinated organosilanes are densely packed, SAMs prepared from monochlorinated species are less dense and poorly ordered. In mixed systems, trichlorinated aromatics and trichlorinated aliphatics formed SAMs with highly tunable compositions; their surfaces were compositionally homogeneous with no large-scale domain separation. The homogeneous nature of the resulting SAM was a consequence of the formation of in-plane siloxane linkages among neighboring molecules. In contrast, when mixing monochlorinated aliphatics with trichlorinated aromatics, molecular segregation occurred. Although the two shortest aromatic species did not display significant changes in orientation upon mixing with aliphatics, the aromatic species with the longest polymethylene spacer, phenethyltrichlorosilane, displayed markedly different orientation behavior in mixtures of short- and long-chain aliphatics. DA - 2007/1/16/ PY - 2007/1/16/ DO - 10.1021/la062475v VL - 23 IS - 2 SP - 673-683 SN - 0743-7463 ER - TY - JOUR TI - Silk fibroin membranes from solvent-crystallized silk fibroin/gelatin blends: Effects of blend and solvent composition AU - Gil, Eun S. AU - Frankowski, David J. AU - Hudson, Samuel M. AU - Spontak, Richard J. T2 - MATERIALS SCIENCE & ENGINEERING C-BIOMIMETIC AND SUPRAMOLECULAR SYSTEMS AB - Protein membranes have been prepared by mixing gelatin (G) with Bombyx mori silk fibroin (SF) and using aqueous methanol (MeOH) to induce SF crystallization. Amorphous blends of these polymers appear quasi-homogeneous, as discerned from visual observation, electron microscopy and Fourier-transform infrared (FTIR) spectroscopy. Upon subsequent exposure to aqueous MeOH, SF undergoes a conformational change from random-coil to β-sheet. This transformation occurs in pure SF, as well as in each of the G/SF blends, as discerned from FTIR spectroscopy and thermal calorimetry. The influence of MeOH-induced SF crystallization on structure and property development has been measured as functions of blend and solvent composition. By preserving a support scaffold above the G helix-to-coil transition temperature, the formation of crystalline SF networks in G/SF blends can be used to stabilize G-based hydrogels or generate SF membranes for biomaterial, pharmaceutical and gas-separation purposes. The present study not only examines the properties of G/SF blends before and after SF crystallization, but also establishes the foundation for future research into thermally-responsive G/SF bioconjugates. DA - 2007/4// PY - 2007/4// DO - 10.1016/j.msec.2006.05.017 VL - 27 IS - 3 SP - 426-431 SN - 0928-4931 KW - silk fibroin KW - gelatin KW - biomacromolecules KW - membranes KW - protein blends KW - bioconjugates ER - TY - JOUR TI - Role of the beta 1 subunit in the function and stability of the 20S proteasome in the hyperthermophilic archaeon Pyrococcus furiosus AU - Madding, Lara S. AU - Michel, Joshua K. AU - Shockley, Keith R. AU - Conners, Shannon B. AU - Epting, Kevin L. AU - Johnson, Matthew R. AU - Kelly, Robert M. T2 - JOURNAL OF BACTERIOLOGY AB - The hyperthermophilic archaeon Pyrococcus furiosus genome encodes three proteasome component proteins: one alpha protein (PF1571) and two beta proteins (beta1-PF1404 and beta2-PF0159), as well as an ATPase (PF0115), referred to as proteasome-activating nucleotidase. Transcriptional analysis of the P. furiosus dynamic heat shock response (shift from 90 to 105 degrees C) showed that the beta1 gene was up-regulated over twofold within 5 minutes, suggesting a specific role during thermal stress. Consistent with transcriptional data, two-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed that incorporation of the beta1 protein relative to beta2 into the 20S proteasome (core particle [CP]) increased with increasing temperature for both native and recombinant versions. For the recombinant enzyme, the beta2/beta1 ratio varied linearly with temperature from 3.8, when assembled at 80 degrees C, to 0.9 at 105 degrees C. The recombinant alpha+beta1+beta2 CP assembled at 105 degrees C was more thermostable than either the alpha+beta1+beta2 version assembled at 90 degrees C or the alpha+beta2 version assembled at either 90 degrees C or 105 degrees C, based on melting temperature and the biocatalytic inactivation rate at 115 degrees C. The recombinant CP assembled at 105 degrees C was also found to have different catalytic rates and specificity for peptide hydrolysis, compared to the 90 degrees C assembly (measured at 95 degrees C). Combination of the alpha and beta1 proteins neither yielded a large proteasome complex nor demonstrated any significant activity. These results indicate that the beta1 subunit in the P. furiosus 20S proteasome plays a thermostabilizing role and influences biocatalytic properties, suggesting that beta subunit composition is a factor in archaeal proteasome function during thermal stress, when polypeptide turnover is essential to cell survival. DA - 2007/1// PY - 2007/1// DO - 10.1128/JB.01382-06 VL - 189 IS - 2 SP - 583-590 SN - 0021-9193 ER - TY - JOUR TI - Ring connectivity: Measuring network connectivity in network covalent solids AU - Jain, Surendra K. AU - Gubbins, Keith E. T2 - LANGMUIR AB - In atomistic models of amorphous materials, ring statistics provide a measure of medium-range order. However, while ring statistics tell us the number of rings present in the model, they do not give us any information about the arrangement of rings, e.g., whether the rings are clustered and how big the cluster is. In this work we present a method to calculate the ring connectivity, or clustering, of rings. We first calculate the rings present in the model using the shortest path criteria of Franzblau and then find the rings that are connected together and group them into clusters. We apply our method to a set of models of disordered carbons, obtained using a reverse Monte Carlo procedure developed in a recent work. We found that in these carbon models the five-, six-, and seven-membered rings are connected together, forming clusters. After isolating the clusters, we found that they resemble defective graphene segments twisted in a complex way. The clusters give further insight about the arrangement of carbon atoms in microporous carbons at a larger length scale. Moreover, the method can be applied to any network covalent solid that contains rings and thus gives information about the ring connectivity present in such materials. DA - 2007/1/30/ PY - 2007/1/30/ DO - 10.1021/la0534017 VL - 23 IS - 3 SP - 1123-1130 SN - 0743-7463 ER - TY - JOUR TI - Physicochemical variables affecting the rheology and microstructure of rennet casein gels AU - Zhong, Qixin AU - Daubert, Christopher R. AU - Velev, Orlin D. T2 - JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY AB - The rheology and microstructure of a rennet casein system were studied in the pH range from 5.8 to 12.0 during cooling from 80 to 5 °C at four cooling rates: 0.5, 0.1, 0.05, and 0.025 °C/min. A dramatic increase in storage modulus with pH was observed during cooling at a fixed cooling rate. Continuous networks were formed for gels at pH 7.2 and above, while a discontinuous network was observed for gels below pH 6.5. The monotonic increase in storage modulus with pH could be correlated to the number of net (negative) charges and the strength of the hydrophobic interactions. At a higher pH, the protein micelles were larger due to weaker hydrophobic interactions and stronger repulsive electrostatic interactions resulting from more charges. When these protein micelles aggregated into flocs during cooling, the flocs had similar sizes at different pH values but a smaller fractal dimension at a higher pH. Consequently, for systems of the same protein and salt concentrations, more flocs were present in the gels at a higher pH, which subsequently generated more cross-links and a higher storage modulus. The pH also determined how the cooling rate affected the gel properties. At pH 5.8 and 6.5, the gels were firmest at the fastest cooling schedule, and the cooling rate did not show a trend in affecting the gel strength at the other three rates. On the other hand, a slower cooling rate generated a firmer gel at pH 7.2 and 12.0. The analysis of casein interactions suggests that the cooling rate affected the casein floc size only when repulsive interactions enabled a slow flocculation (at higher pH values) comparable with temperature change rates during cooling. For rennet casein gels of pH within the range of processed cheese products (pH 5.8 and 6.5), particle or cluster rearrangements created more uniform networks for gels cooled at slower schedules and weakened the structure. Keywords: Processed cheese; rennet casein; gelation; pH; cooling rate DA - 2007/4/4/ PY - 2007/4/4/ DO - 10.1021/jf0625914 VL - 55 IS - 7 SP - 2688-2697 SN - 1520-5118 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-34247203562&partnerID=MN8TOARS KW - processed cheese KW - rennet casein KW - gelation KW - pH KW - cooling rate ER - TY - JOUR TI - Phase behavior and charge regulation of weak polyelectrolyte grafted layers AU - Gong, Peng AU - Genzer, Jan AU - Szleifer, I. T2 - PHYSICAL REVIEW LETTERS AB - The stability of weak polyelectrolytes end grafted to a planar surface has been studied with a molecular theory. The effective quality of the solvent is found to depend on the interplay between polymer grafting density, acid-base equilibrium, and salt concentration. Our results reveal that increasing salt concentration results in a thermodynamically more stable layer. This reverse salt effect is due to the competition between the solvent quality and the dual role of the ionic strength in screening the electrostatic interactions (reducing stability with increasing salt concentration), and regulating the charge on the polymer (increasing charge with increasing salt concentration). Grafted weak polyelectrolyte layers are found to be thermodynamically unstable at intermediate surface coverages. Additionally, it is established that the increased solubility of the layer at low surface coverage is due to the relatively large charge of the grafted polymers. The range of stability of the film with regard to polymer surface coverage, temperature, bulk $p\mathrm{H}$ and salt concentration is demonstrated. DA - 2007/1/5/ PY - 2007/1/5/ DO - 10.1103/physrevlett.98.018302 VL - 98 IS - 1 SP - SN - 1079-7114 ER - TY - JOUR TI - Hydrothermal oxidation treatment of solid particles between 250 and 350 degrees C: Modelling and experiments AU - Marias, F. AU - Mancini, F. AU - Cansell, F. AU - Mercadier, J. T2 - JOURNAL OF SUPERCRITICAL FLUIDS AB - Abstract Hydrothermal oxidation is an efficient and clean way for the treatment of wastewater containing organic matter. The purpose of this work is to develop a mathematical model of a reactor for hydrothermal oxidation. This reactor is of the tank type and it is designed for the oxidation of solid particles of waste or biomass. According to some previous work, the experimental device developed by the Institut de Chimie et de la Matiere condensee de Bordeaux is known to behave as a battery of three completely stirred tank reactors (CSTR). To reach our goal, governing equations are written within each of the three CSTR. This set of equations is composed of the mass, species and energy balances for the fluid phase as well as equations allowing for the evaluation of the rate of shrinkage of a particle (shrinking core model) and a population balance. Thanks to this model, the particle size distribution (PSD) of the output of the reactor is computed as a function of the incoming one and of the operating parameters (temperature, residence time, pressure, …). The numerical predictions of the model are compared to experimental profiles obtained in the case of hydrothermal oxidation treatment of black carbon. These comparisons show very good agreement. DA - 2007/7// PY - 2007/7// DO - 10.1016/j.supflu.2007.01.002 VL - 41 IS - 3 SP - 352-360 SN - 1872-8162 KW - hydrothermal oxidation KW - modelling KW - reactor KW - experimental device KW - solid particles KW - particle size distribution ER - TY - JOUR TI - Enhanced conduction through isocyanide terminal groups in alkane and biphenylene molecules measured in molecule/nanoparticle/molecule junctions AU - Chu, Changwoong AU - Ayres, J. A. AU - Stefanescu, D. M. AU - Walker, B. R. AU - Gorman, Christopher B. AU - Parsons, Gregory N. T2 - JOURNAL OF PHYSICAL CHEMISTRY C AB - Electrical conductance through conjugated biphenyl and saturated alkane molecules on gold electrodes is characterized using a molecule/nanoparticle/molecule electrical test-bed assembly, and comparisons are made between molecules containing isocyanide (−NC) and thiol (−S) terminal groups bound to the gold. Current versus voltage analysis is consistent with charge tunneling through all systems studied. For molecules containing biphenyl, diphenyl acetylene, and alkane bridges, those containing an isocyanide terminal group show an order of magnitude increase in conductance as compared to those containing a thiol terminal group. Various theoretical predictions of the effect of isocyanide terminal groups on charge transfer through conjugated molecular systems are discussed and related to the results observed for charge transfer through conjugated and saturated molecules. The similar trends in charge transport observed for the different metal/linker interfaces suggest that the metal/linker contact plays an important role in interface electronic structure, even when the molecules are expected to have very different electron delocalization across the backbone. DA - 2007/6/7/ PY - 2007/6/7/ DO - 10.1021/jp065377r VL - 111 IS - 22 SP - 8080-8085 SN - 1932-7447 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000246842400037&KeyUID=WOS:000246842400037 ER - TY - JOUR TI - Electromechanical response of nanostructured polymer systems with no mechanical pre-strain AU - Shankar, Ravi AU - Ghosh, Tushar K. AU - Spontak, Richard J. T2 - MACROMOLECULAR RAPID COMMUNICATIONS AB - Abstract A dielectric elastomer derived from a polystyrene‐ block ‐poly(ethylene‐ co ‐butylene)‐ block ‐polystyrene triblock copolymer swollen with a midblock‐selective solvent is reported to show promise as a nanostructured organic actuator requiring no pre‐strain. This might provide an attractive alternative to conventional acrylic, siloxane, and polyurethane elastomers since the electromechanical properties are composition‐tunable. magnified image DA - 2007/5/16/ PY - 2007/5/16/ DO - 10.1002/marc.200700033 VL - 28 IS - 10 SP - 1142-1147 SN - 1521-3927 KW - actuator KW - block copolymers KW - EAP KW - electroactive KW - electroelastomer KW - micelles ER - TY - JOUR TI - Characterization and optimization of gold nanoparticle-based silver-enhanced immunoassays AU - Gupta, Shalini AU - Huda, Sabil AU - Kilpatrick, Peter K. AU - Velev, Orlin D. T2 - ANALYTICAL CHEMISTRY AB - Silver-enhanced nanoparticle-labeled immunoassays provide a simple, low-cost, and effective way of detecting antigens in dilute solutions. The physical mechanisms behind their operation, however, have not been fully investigated. We present a semiquantitative approach for optimizing sandwich nanoparticle immunoassays using an adsorption-controlled kinetic model. Primary antibodies were immobilized on a solid substrate to bind the target antigens in solution. An optical signal was measured by secondary labeling of antigens with gold nanoparticles and their enhancement by silver nucleation. The opacity of the silver-enhanced spots was quantified by densitometry. The selectivity of the sandwich immunoassays was adequately high, and antigen concentrations as low as 0.1 microg cm(-3) (4 ng total) were detected reproducibly. The role of mass transfer was investigated, and a model was developed to optimize the performance of immunoassays by correlating the opacities of silver spots to the concentration and incubation times of antigens and gold nanoparticles. The results could allow the development of more rapid and reliable nanoparticle immunoassays. DA - 2007/5/15/ PY - 2007/5/15/ DO - 10.1021/ac062341m VL - 79 IS - 10 SP - 3810-3820 SN - 1520-6882 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-34249093580&partnerID=MN8TOARS ER - TY - JOUR TI - Adsorption and dynamics of argon in porous carbons AU - Coasne, B. AU - Jain, S. K. AU - Gubbins, Keith T2 - European Physical Journal. Special Topics DA - 2007/// PY - 2007/// DO - 10.1141/epjst/e2007-00022-2 VL - 141 SP - 121–125 ER - TY - JOUR TI - Unique behavior of polyampholytes as dry-strength agents AU - Hubbe, M. A. AU - Rojas, O. J. AU - Sulic, N. AU - Sezaki, T. T2 - Appita Journal DA - 2007/// PY - 2007/// VL - 60 IS - 2 SP - 106-111 ER - TY - JOUR TI - Titanium complexes: A possible catalyst for controlled radical polymerization AU - Kwark, Y. J. AU - Kim, J. AU - Novak, B. M. T2 - Macromolecular Research DA - 2007/// PY - 2007/// DO - 10.1007/BF03218749 VL - 15 IS - 1 SP - 31-38 ER - TY - JOUR TI - Porous organic-inorganic hybrid electrolytes for high-temperature proton exchange membrane fuel cells AU - Zhang, Xiangwu T2 - JOURNAL OF THE ELECTROCHEMICAL SOCIETY AB - A family of porous silica-based organic-inorganic hybrid electrolytes containing surface propanesulfonic acid groups or polystyrenesulfonic acid (PSS) chains for high-temperature proton exchange membrane fuel cells (PEMFCs) is described. Porous silica-propanesulfonic acid (porous silica-PS) has higher proton conductivity than the primary porous silica, but still has limited operating temperature and low water uptake at . Porous silica-polystyrenesulfonic acid (porous silica-PSS) has high proton conductivity, large water uptake, and improved operating temperature, which are influenced by the proton density on the inner surface of nanopores. A maximum conductivity of is achieved at a relative humidity of 40% and a temperature of for porous silica-PSS with a surface proton density of . The porous silica-PSS-based fuel cell has good cell performance at . DA - 2007/// PY - 2007/// DO - 10.1149/1.2429045 VL - 154 IS - 3 SP - B322-B326 SN - 1945-7111 UR - https://publons.com/publon/7178315/ ER - TY - JOUR TI - Effects of chain length on the aggregation of model polyglutamine peptides: Molecular dynamics simulations AU - Marchut, Alexander J. AU - Hall, Carol K. T2 - PROTEINS-STRUCTURE FUNCTION AND BIOINFORMATICS AB - Abstract Aggregation in the brain of polyglutamine‐containing proteins is either a cause or an associated symptom of nine hereditary neurodegenerative disorders including Huntington's disease. The molecular level mechanisms by which these proteins aggregate are still unclear. In an effort to shed light on this important phenomenon, we are investigating the aggregation of model polyglutamine peptides using molecular‐level computer simulation with a simplified model of polyglutamine that we have developed. This model accounts for the most important types of intra‐ and inter‐molecular interactions—hydrogen bonding and hydrophobic interactions—while allowing the folding process to be simulated in a reasonable time frame. The model is used to examine the folding of isolated polyglutamine peptides 16, 32, and 48 residues long and the folding and aggregation of systems of 24 model polyglutamine peptides 16, 24, 32, 36, 40, and 48 residues long. Although the isolated polyglutamine peptides did form some α and β backbone–backbone hydrogen bonds they did not have as many of these bonds as they would have if they had folded into a complete α helix or β sheet. In one of the simulations on the isolated polyglutamine peptide 48 residues long, we observed a structure that resembles a β helix. In the multi‐chain simulations we observed amorphous aggregates at low temperatures, ordered aggregates with significant β sheet character at intermediate temperatures, and random coils at high temperatures. We have found that the temperature at which the model peptides undergo the transition from amorphous aggregates to ordered aggregates and the temperature at which the model peptides undergo the transition from ordered aggregates to random coils increase with increasing chain length. Our finding that the stability of the ordered aggregates increases as the peptide chain length increases may help to explain the experimentally observed relation between polyglutamine tract length and aggregation in vitro and disease progression in vivo. We have also observed in our simulations that the optimal temperature for the formation of β sheets increases with chain length up to 36 glutamine residues but not beyond. Equivalently, at fixed temperature we find a transition from a region dominated by random coils at chain lengths less than 36 to a region dominated by relatively ordered β sheet structures at chain lengths greater than 36. Our finding of this critical chain length of 36 glutamine residues is interesting because a critical chain length of 37 glutamine residues has been observed experimentally. Proteins 2007. © 2006 Wiley‐Liss, Inc. DA - 2007/1// PY - 2007/1// DO - 10.1002/prot.21132 VL - 66 IS - 1 SP - 96-109 SN - 0887-3585 KW - protein aggregation KW - polyglutamine KW - amyloid KW - molecular dynamics KW - intermediate resolution model ER - TY - JOUR TI - Conductivity in alkylamine/gold and alkanethiol/gold molecular junctions measured in molecule/nanoparticle/molecule bridges and conducting probe structures AU - Chu, Changwoong AU - Na, Jeong-Seok AU - Parsons, Gregory N. T2 - JOURNAL OF THE AMERICAN CHEMICAL SOCIETY AB - Charge transport through alkane monolayers on gold is measured as a function of molecule length in a controlled ambient using a metal/molecule/nanoparticle bridge structure and compared for both thiol and amine molecular end groups. The current through molecules with an amine/gold junction is observed to be more than a factor of 10 larger than that measured in similar molecules with thiol/gold linkages. Conducting probe atomic force microscopy is also used to characterize the same monolayer systems, and the results are quantitatively consistent with those found in the nanoparticle bridge geometry. Scaling of the current with contact area is used to estimate that ∼100 molecules are probed in the nanoparticle bridge geometry. For both molecular end groups, the room-temperature conductivity at low bias as a function of molecule length shows a reasonable fit to models of coherent nonresonant charge tunneling. The different conductivity is ascribed to differences in charge transfer and wave function mixing at the metal/molecule contact, including possible effects of amine group oxidation and molecular conformation. For the amine/Au contact, the nitrogen lone pair interaction with the gold results in a hybrid wave function directed along the molecule bond axis, whereas the thiol/Au contact leads to a more localized wave function. DA - 2007/2/28/ PY - 2007/2/28/ DO - 10.1021/ja064968s VL - 129 IS - 8 SP - 2287-2296 SN - 1520-5126 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000244330800030&KeyUID=WOS:000244330800030 ER - TY - JOUR TI - Sessile droplet templating of miniature porous hemispheres from colloid crystals AU - Kuncicky, Daniel M. AU - Bose, Kunal AU - Costa, Kevin D. AU - Velev, Orlin D. T2 - CHEMISTRY OF MATERIALS AB - A technique for fabrication of porous hemispherical particle assemblies by drying small droplets on silanized surfaces is presented. The resulting uniform, flat-end porous microidenters are being used in biological research. DA - 2007/1/23/ PY - 2007/1/23/ DO - 10.1021/cm062217j VL - 19 IS - 2 SP - 141-143 SN - 1520-5002 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-33846892531&partnerID=MN8TOARS ER - TY - JOUR TI - Remotely powered self-propelling particles and micropumps based on miniature diodes AU - Chang, Suk Tai AU - Paunov, Vesselin N. AU - Petsev, Dimiter N. AU - Velev, Orlin D. T2 - NATURE MATERIALS DA - 2007/3// PY - 2007/3// DO - 10.1038/nmat1843 VL - 6 IS - 3 SP - 235-240 SN - 1476-4660 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-33847678889&partnerID=MN8TOARS ER - TY - JOUR TI - Effect of gel electrolytes containing silica nanoparticles on aluminum corrosion AU - Li, Yangxing AU - Fedkiw, Peter S. T2 - ELECTROCHIMICA ACTA AB - We have investigated corrosion of aluminum current collectors in electrolytes containing LiTFSI salt by chronopotentiometry, cyclic voltammetery, chronoamperometry, electrochemical impedance spectroscopy, and optical microscopy. Open-circuit potentials for cells with gel electrolytes containing silica nanoparticles are relatively stable in comparison to the corresponding baseline liquid, which suggests that the Al/electrolyte interface is more stable in presence of silica nanoparticles. Cyclic voltammetery and chronoamperometry data show that the current density for Li/electrolyte/Al cells with gel electrolytes containing fumed silica was less than that for baseline liquid electrolyte. The Nyquist plot for liquid electrolyte after chronoamperometry is semicircular-like, that is a corrosion reaction occurred. After cell disassembly, black particulates are evident and pits are observed on the aluminum foil. In comparison, no corrosion products are observed for cells containing gel electrolytes, and the Nyquist plots indicate that corrosion does not occur appreciably. Gel electrolytes produce impedance spectra with a large phase lag over a wide frequency range, which is not observed for the baseline liquid electrolyte. These phenomena may be interpreted as a good film-coating behavior associated with gel electrolytes, which results in a lower aluminum corrosion rate. DA - 2007/2/1/ PY - 2007/2/1/ DO - 10.1016/j.electacta.2006.08.066 VL - 52 IS - 7 SP - 2471-2477 SN - 1873-3859 KW - aluminum corrosion KW - gel electrolytes KW - silica nanoparticle KW - composites KW - lithium-ion battery ER - TY - JOUR TI - Assembly and characterization of colloid-based antireflective coatings on multicrystalline silicon solar cells AU - Prevo, Brian G. AU - Hon, Emily W. AU - Velev, Orlin D. T2 - JOURNAL OF MATERIALS CHEMISTRY AB - Evaporation from a moving meniscus was used for controlled convective assembly of colloidal silica nanoparticles into antireflective coatings (ARCs) onto the rough uneven surfaces of polycrystalline silicon solar cells. The nanocoatings reduced the reflectance of the solar cells by approximately 10% across the near UV to near IR spectral range, which provided a 17% increase in the output power of the devices (which translated to a 10% relative increase in the efficiency). Microstructural analysis via SEM showed that while the surface coverage was uniform over long ranges, the thickness of the particle coatings varied locally due to the rough, undulating substrate surface. The UV/vis reflectance data of the silica coated solar cells could be modelled with the Fresnel reflectance relation by assuming a distributed range of thicknesses for the coatings, in good agreement with the microstructural data. We show that particulate films deposited on rough surfaces can function as ARCs even though they do not attain 0% reflectance. These silica particle-based coatings can be further modified by attachment of monolayers of fluorosilanes, which may make them superhydrophobic and/or self-cleaning. DA - 2007/// PY - 2007/// DO - 10.1039/b612734g VL - 17 IS - 8 SP - 791-799 SN - 0959-9428 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-33847048603&partnerID=MN8TOARS ER - TY - JOUR TI - Tuning the number density of nanoparticles by multivariant tailoring of attachment points on flat substrates AU - Bhat, Rajendra R. AU - Genzer, Jan T2 - NANOTECHNOLOGY AB - We report on the organization of nanoparticles on a flat surface when there is strong yet tunable interaction between the particles and the surface. Specifically, we tailor the number density of citrate-stabilized gold nanoparticles on flat substrates by varying the concentration of the grafted amino groups on the surfaces and their degree of ionization. While the former effect is accomplished by decorating silica-based substrates with a molecular gradient of (3-aminopropyl)triethoxysilane (APTES), the latter effect is achieved by varying the degree of ionization of the −NH2 groups in APTES by varying the pH of the gold sol. We show that the measurement of particle number density on an APTES concentration gradient substrate at different pH values provides a simple, non-spectroscopic means to deduce the relative molecular concentration profile of APTES on the substrate. DA - 2007/1/17/ PY - 2007/1/17/ DO - 10.1088/0957-4484/18/2/025301 VL - 18 IS - 2 SP - SN - 0957-4484 ER - TY - JOUR TI - Conduction mechanisms and stability of single molecule nanoparticle/molecule/nanoparticle junctions AU - Na, Jeong-Seok AU - Ayres, Jennifer AU - Chandra, Kusum L AU - Chu, Changwoong AU - Gorman, Christopher B AU - Parsons, Gregory N T2 - Nanotechnology AB - Nanoparticle/molecule/nanoparticle dimer assemblies have been successfully trapped by dielectrophoresis across nanogap electrodes, enabling temperature dependent charge transport measurements through an oligomeric phenylene ethynylene molecule, and transition from direct tunnelling to Fowler-Nordheim tunnelling is observed at approximately 1.5 V. Samples formed by dielectrophoresis show better contact stability than those formed by receding meniscus. The junction shows stable operation over several weeks in a vacuum, but current increases with time upon exposure to air, possibly due to the adsorbed water molecules near the molecule/gold nanoparticle contacts. DA - 2007/1/3/ PY - 2007/1/3/ DO - 10.1088/0957-4484/18/3/035203 VL - 18 IS - 3 SP - 035203 J2 - Nanotechnology OP - SN - 0957-4484 1361-6528 UR - http://dx.doi.org/10.1088/0957-4484/18/3/035203 DB - Crossref ER - TY - JOUR TI - A novel gel deformation technique for fabrication of ellipsoidal and discoidal polymeric microparticles AU - Courbaron, A. C. AU - Cayre, O. J. AU - Paunov, V. N. T2 - Chemical Communications (Cambridge, England) DA - 2007/// PY - 2007/// IS - 6 SP - 628-630 ER - TY - JOUR TI - Field-driven biofunctionalization of polymer fiber surfaces during electrospinning AU - Sun, Xiao-Yu AU - Shankar, Ravi AU - Boerner, Hans G. AU - Ghosh, Tushar K. AU - Spontak, Richard J. T2 - ADVANCED MATERIALS AB - Surface-biofunctionalized synthetic polymer fibers composed of a fiber-forming host polymer and an oligopeptide conjugate are prepared by electrospinning. The conjugate consists of a polypeptide segment and a polymer block that is compatible with the host polymer. Because the more polarizable peptide segment migrates to the surface during electrospinning, peptide surface enrichment (see figure and inside cover) is achieved in a single step without further treatment. DA - 2007/1/8/ PY - 2007/1/8/ DO - 10.1002/adma.200601345 VL - 19 IS - 1 SP - 87-+ SN - 1521-4095 ER - TY - JOUR TI - Distinctive electrokinetic behavior of nanoporous silica particles treated with cationic polyelectrolyte AU - Hubbe, Martin A. AU - Rojas, Orlando J. AU - Lee, Sa Yong AU - Park, Sunkyu AU - Wang, Yun T2 - COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS AB - In this study we show, for the first time, that the streaming potential of aqueous suspensions of nanoporous silica gel, after treatment with the cationic polyelectrolyte poly-diallyldimethylammonium chloride (poly-DADMAC), can depend very strongly on the concentration of background electrolyte. An increase in the electrical conductivity from 60 to 1000 μS/cm resulted in an approximately 1000-fold increase in the amount of poly-DADMAC that was required to reach an endpoint of zero streaming potential. Results were explained by two contributions to the overall electrokinetic behavior—one due to the outer surfaces and another due to the interior surfaces of nanopore spaces that were inaccessible to the polyelectrolytes. Experiments with cyclical changes in salt content revealed a high degree of reversibility; such observations help to rule out explanations based on salt-induced desorption or enhancement of pore penetration. Supplementary tests with non-porous glass fibers showed no evidence of the distinctive electrokinetic behavior observed in the case of nanoporous particles. Effects of polymer molecular mass and pH, evaluated under similar experimental conditions, agreed with well-established trends. DA - 2007/1/15/ PY - 2007/1/15/ DO - 10.1016/j.colsurfa.2006.06.034 VL - 292 IS - 2-3 SP - 271-278 SN - 0927-7757 KW - streaming potential KW - pores KW - nanopores KW - polyelectrolytes ER - TY - JOUR TI - A delayed nonlinear PBPK model for genistein dosimetry in rats AU - Zagera, Michael G. AU - Schlosser, Paul M. AU - Tran, Hien T. T2 - BULLETIN OF MATHEMATICAL BIOLOGY AB - Genistein is an endocrine-active compound (EAC) found in soy products. It has been linked to beneficial effects such as mammary tumor growth suppression and adverse endocrine-related effects such as reduced birth weight in rats and humans. In its conjugated form, genistein is excreted in the bile, which is a significant factor in its pharmacokinetics. Experimental data suggest that genistein induces a concentration-dependent suppression of biliary excretion. In this article, we describe a physiologically based pharmacokinetic (PBPK) model that focuses on biliary excretion with the goal of accurately simulating the observed suppression. The mathematical model is a system of nonlinear differential equations with state-dependent delay to describe biliary excretion. The model was analyzed to examine local existence and uniqueness of a solution to the equations. Furthermore, unknown parameters were estimated, and the mathematical model was compared against published experimental data. DA - 2007/1// PY - 2007/1// DO - 10.1007/s11538-006-9068-x VL - 69 IS - 1 SP - 93-117 SN - 1522-9602 KW - genistein KW - biliary excretion KW - pharmacokinetics KW - delay-differential equations ER -