TY - BOOK TI - Hyperthermophilic Enzymes, Part C A3 - Adams, M.W.W. A3 - Kelly, R.M. DA - 2001/// PY - 2001/// VL - 334 PB - Academic Press SE - 3-526 ER - TY - BOOK TI - Hyperthermophilic Enzymes, Part B A3 - Adams, M.W.W. A3 - Kelly, R.M. DA - 2001/// PY - 2001/// VL - 331 PB - Academic Press SE - 3-494 ER - TY - BOOK TI - Hyperthermophilic Enzymes, Part A A3 - Adams, M.W.W. A3 - Kelly, R.M. DA - 2001/// PY - 2001/// VL - 330 PB - Academic Press SE - 3–513 ER - TY - JOUR TI - β-Mannanases from Thermotoga species AU - Chhabra, S.R. AU - Parker, K.N. AU - Lam, D. AU - Callen, W. AU - Snead, M.A. AU - Mathur, E.J. AU - Short, J.M. AU - Kelly, R.M. T2 - Methods in Enzymology AB - Thermostable mannanases have been identified from Thermotoga neapolitana, Rhodothermus marinus, Bacillus stearotherrnophilus, Thermo- anaerobacterium polysaccharolyticum, Caldocellosiruptor saccharolyticus," and Dictyoglomus thermophilum. The β-mannanases from T. Neapolitana (family 5) and R. marinus (family 26) are the most thermostable of these. The mannanase from T. neapolitana is less stable at 85°, but more stable at 90°, than the corresponding enzyme from R. marinus. The former has a half-life of 34 hr at 85° and 13 hr at 90°, whereas the latter has a half life of 45.3 and 4.5 hr at the respective temperatures. Hyperthermophilic mannanases are useful in several industrial applications where thermostability and thermoactivity are desirable. These include coffee extraction, oil/gas well stimulation, and wood pulp treatment. This chapter describes the purification and characterization of a β-mannanase from T. neapolitana, as well as cloning and sequencing of this enzyme from T. neapolitana and T. maritima. DA - 2001/// PY - 2001/// DO - 10.1016/S0076-6879(01)30378-6 VL - 330 SP - 224–238 ER - TY - RPRT TI - Methods and compositions for fracturing subterranean formations AU - Kelly, R.M. AU - Khan, S.A. AU - Leduc, P. AU - Tayal, A. AU - Prud'homme, R. DA - 2001/3// PY - 2001/3// M1 - 6,197,730 M3 - U.S. Patent SN - 6,197,730 ER - TY - CHAP TI - Homomultimeric protease and putative bacteriocin homolog from Thermotoga maritima AU - Hicks, Paula M AU - Chang, Lara S AU - Kelly, Robert M T2 - Methods in Enzymology AB - Publisher Summary Thermotoga maritima is an anaerobic heterotroph belonging to the bacterial order Thermotogales that grows optimally at 80° by fermentation of carbohydrates and proteins, including starch, glucose, galactose, glycogen, and yeast extract. The bacterium is also able to reduce thiosulfate to sulfide, with an improved growth rate. Although the microorganism is a facultative sulfur reducer, the reduction of sulfur does not provide an energetic boost as seen by the lack of effect on growth yields and fermentation balances. T. maritima appears to be motile, migrating at a speed proportional to the temperature. This chapter describes the purification protocols used to isolate maritimacin, as well as the biochemical assays used to measure its activity. PY - 2001/// DO - 10.1016/s0076-6879(01)30397-x SP - 455-460 OP - PB - Elsevier SN - 9780121822316 UR - http://dx.doi.org/10.1016/s0076-6879(01)30397-x DB - Crossref ER - TY - CHAP TI - Protease I from Pyrococcus furiosus AU - Chang, Lara S AU - Hicks, Paula M AU - Kelly, Robert M T2 - Methods in Enzymology AB - Pyrococcus furiosus is a hyperthermophilic archaeon from the order Thermococcales capable of growth on a variety of proteinaceous and carbohydrate-containing substrates. Analysis of gelatin-containing sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDSPAGE) gels indicates that at least 11 endoproteinases are active in the cell extracts of this organism 2'3 and the following proteases have been characterized: protease I (PfpI), pyrolysin, proteasome, prolyl oligopeptidase, and proline dipeptidase. The gene encoding the 19-kDa subunit of PfpI has homologs in nearly every organism and cell examined to date, ranging from Escherichia coli to Homo sapiens; this ubiquity and evolutionary conservation indicates that it may play a fundamental physiological role. Efforts to study this issue have been exacerbated by difficulties encountered in obtaining significant amounts of a particular assembly of PfpI in either a native or a recombinant form. Native PfpI undergoes autoproteolysis and/or disassembly during direct purification from P. furiosus biomass and exists in multiple (singleto multisubunit) forms in vitro. The production of a recombinant form of PfpI is also problematic due to its toxicity toward mesophilic hosts. This chapter describes several methods that have been used to purify PfpI directly from P. Furiosus cell extracts are described here, together with an assay to detect proteolytic activity, a procedure to determine its molecular mass, and approaches to minimize PfpI-catalyzed proteolysis of other P. furious proteins. PY - 2001/// DO - 10.1016/s0076-6879(01)30392-0 SP - 403-413 OP - PB - Elsevier SN - 9780121822316 UR - http://dx.doi.org/10.1016/s0076-6879(01)30392-0 DB - Crossref ER - TY - CHAP TI - β-Endoglucanase from Pyrococcus furiosus AU - Cady, Susan G AU - Bauer, Michael W AU - Callen, Walter AU - Snead, Marjory A AU - Mathur, Eric J AU - Short, J.M AU - Kelly, Robert M T2 - Methods in Enzymology AB - Glycosylhydrolases have been isolated from a variety of heterotrophic hyperthermophiles and include glucanases, hemicellulases, and cellulases. Pyrococcus furiosus, a hyperthermophilic heterotroph isolated by Fiala and Stetter from geothermal regions of Vulcano Island, Italy, grows on a wide range of α- and β-1inked carbohydrates, a property supported by the enzyme inventory revealed in its genome sequence. This chapter describes the approaches used for the cloning and expression in Escherichia coli of the eglA gene, which encodes the P. furiosus endoglucanase, and protocols used to study the biochemical properties of the recombinant enzyme. It is also interesting to know that P. furiosus and other heterotrophic hyperthermophilic archaea do not seem to produce enzymes for the hydrolysis of nonglucan polysaccharides, such as mannan or xylan, even though Thermotoga maritima, a hyperthermophilic bacterium, does. Whether this is a distinguishing feature of archaeal growth physiology remains to be seen. PY - 2001/// DO - 10.1016/s0076-6879(01)30387-7 SP - 346-354 OP - PB - Elsevier SN - 9780121822316 UR - http://dx.doi.org/10.1016/s0076-6879(01)30387-7 DB - Crossref ER - TY - CHAP TI - αa-D-Galactosidases from Thermotoga species AU - Miller, E.S, Jr. AU - Parker, Kimberley N AU - Liebl, Wolfgang AU - Lam, David AU - Callen, Walter AU - Snead, Mabjory A AU - Mathur, Eric J AU - Short, J.M AU - Kelly, Robert M T2 - Methods in Enzymology AB - Publisher Summary Based on similarities in primary structure and hydrophobic cluster analyses, αGals have been grouped into three well-conserved families in the general classification of glycosylhydrolases Those from bacteria have been grouped into families 4 and 36 and those of eukaryotic origin into family 27. To date, only α Gals of the hyperthermophilic bacteria Thermotoga maritima ( Tm GalA) and T. neapolitana ( Tn GalA) have demonstrated activity and prolonged stability above 75°. These two enzymes are therefore of considerable interest from a biotechnological standpoint. Potential applications include the high temperature hydrolysis of galactomannans used for well stimulation in the oil and gas industry and oligosaccharide synthesis via glycosyltransferase reactions. Genes encoding both Tm GalA and Tn GalA have been cloned and expressed in Escherichia coli . Although these enzymes are structurally related, they exhibit different biochemical properties in terms of pH optima, activity, and thermostability. This chapter discusses the purification, cloning, and expression of recombinant α Gal from T. neapolitana and T. maritima , in addition to some of their biochemical properties. PY - 2001/// DO - 10.1016/s0076-6879(01)30380-4 SP - 246-260 OP - PB - Elsevier SN - 9780121822316 UR - http://dx.doi.org/10.1016/s0076-6879(01)30380-4 DB - Crossref ER - TY - CHAP TI - Xylose isomerases from Thermotoga AU - Vieille, Claire AU - Sriprapundh, Dinlaka AU - Kelly, Robert M AU - Zeikus, J.Gregory T2 - Methods in Enzymology AB - Typically present in microorganisms that grow on xylose, xylose isomerise (XI) converts xylose to xylulose, which is then phosphorylated and enters the pentose-phosphate pathway. Because it also accepts glucose as substrate, XI is used extensively to isomerize glucose to fructose in the manufacture of high fructose corn syrup (HFCS). Performed at temperatures around 55-60°, this isomerization process requires thermostable enzymes. XIs have been characterized from a number of eubacterial sources and from rice and barley, but they have not been reported in fungi or archaea. XIs from the hyperthermophilic eubacteria Thermotoga maritima and Thermotoga neapolitana are the most thermostable yet characterized XIs. PY - 2001/// DO - 10.1016/s0076-6879(01)30377-4 SP - 215-224 OP - PB - Elsevier SN - 9780121822316 UR - http://dx.doi.org/10.1016/s0076-6879(01)30377-4 DB - Crossref ER - TY - CHAP TI - Carboxylesterase from Sulfolobus solfataricus P1 AU - Sehgal, A.C AU - Callen, Walter AU - Mathur, Eric J AU - Short, J.M AU - Kelly, Robert M T2 - Methods in Enzymology AB - To date, relatively few investigations regarding the purification and characterization of thermostable (Topt > 60 °) esterases have been conducted. Thus far, esterases from Bacillus acidocaldarius, Pyrococcus furiosus, Bacillus stearothermophilus, Sulfolobus shibatae, Thermoanaerobacterium sp, Pyrococcus abyssi, and Sulfolobus acidocaldarius have been studied to varying extents. Those thermostable esterases that have been evaluated vary significantly with respect to molecular mass, although their biochemical properties, such as pH optimum and substrate specificity, are quite similar. This chapter describes the cloning, expression, purification, and characterization of a recombinant carboxylesterase (Sso P1 carboxylesterase) from the extreme thermoacidophile Sulfolobus solfataricus P1. S. solfataricus, which is a member of the Crenarchaeota, can be found in sulfurous caldrons and volcanic muds. PY - 2001/// DO - 10.1016/s0076-6879(01)30398-1 SP - 461-471 OP - PB - Elsevier SN - 9780121822316 UR - http://dx.doi.org/10.1016/s0076-6879(01)30398-1 DB - Crossref ER - TY - CHAP TI - α-Glucosidase from Pyrococcus furiosus AU - Chang, Stephen T AU - Parker, Kimberley N AU - Bauer, Michael W AU - Kelly, Robert M T2 - Methods in Enzymology AB - Hyperthermophilic α-glucosidases could also provide valuable insights into protein function, structure, and stability at high temperatures. Indeed, it is the intrinsic high temperature activity and stability of these proteins that have fueled considerable effort into the development of these and other glycosylhydrolases for use in starch conversion technology. Currently employed mesophilic enzymes exhibit limited tolerance to the high temperatures and pH variations encountered during starch solubilization and degradation. These mesophilic enzymes often have metal ion requirements for activity, whereas their counterpart hyperthermophilic versions often do not. Although pullulanases and glucoamylases (also known as amyloglucosidases) are typically used for saccharification of intermediate starch degradation products to glucose, heat-stable α-glucosidases, together with pullulanases, could theoretically fill that role more efficiently. However, despite the potential impact of hyperthermophilic enzymes on industrial processes, including starch conversion, their application is still largely unrealized. One readily apparent obstacle is developing a costefficient method for producing sufficient quantities of enzyme either directly from the source organism or through recombinant means. PY - 2001/// DO - 10.1016/s0076-6879(01)30381-6 SP - 260-269 OP - PB - Elsevier SN - 9780121822316 UR - http://dx.doi.org/10.1016/s0076-6879(01)30381-6 DB - Crossref ER - TY - CHAP TI - β-Mannosidase from Thermotoga species AU - Parker, Kimberley N AU - Chhabra, Swapnil AU - Lam, David AU - Snead, Marjorie A AU - Mathur, Eric J AU - Kelly, Robert M T2 - Methods in Enzymology AB - Publisher Summary β -Mannosidase is an exo-acting glycosylhydrolase whose function is to cleave mannose residues from the nonreducing termini of mannan oligosaccharides. In microorganisms, β -mannosidases often act in concert with endo-acting β -mannanases to completely hydrolyze mannan-based carbohydrates to be subsequently used for nutritional purposes. In mammals, the deficiency of mannosidase can lead to β -mannosidosis, a genetic disorder resulting from the storage and excretion of undegraded substrates. Hyperthermophilic β -mannosidases have been identified in archaea such as Pyrococcus furiosus and in the bacteria Thermotoga maritima and T. neapolitana . This chapter presents the protocols used to purify the β -mannosidase from T. Neapolitana together with the results of cloning and expression of genes encoding the analogous enzyme of T. maritima in Escherichia coli. PY - 2001/// DO - 10.1016/s0076-6879(01)30379-8 SP - 238-246 OP - PB - Elsevier SN - 9780121822316 UR - http://dx.doi.org/10.1016/s0076-6879(01)30379-8 DB - Crossref ER - TY - BOOK TI - Molecular Simulation of Fluids AU - Gubbins, Keith AU - Sadus, R.J. DA - 2001/// PY - 2001/// PB - Elsevier ER - TY - CONF TI - Simulations of Capillary Condensation in Porous Glasses AU - Gelb, Lev D. AU - Gubbins, Keith E. T2 - Foundations of Molecular Modeling and Simulation (FOMMS) Conference A2 - Cummings, P.T. A2 - Westmorland, P.R. T3 - American Institute of Chemical Engineers Symposium Series C2 - 2001/// C3 - Foundations of molecular modeling and simulation : proceedings of the First International Conference on Molecular Modeling and Simulation, Keystone, Colorado, July 23-28, 2000 CY - Keystone, CO DA - 2001/// PY - 2001/7/23/ SP - 292–295 PB - American Institute of Chemical Engineers SN - 9780816908394 ER - TY - CONF TI - Molecular Simulation: Some Recent Applications to Phase and Chemical Equilibria AU - Gubbins, Keith E. T2 - Foundations of Molecular Modeling and Simulation (FOMMS) Conference A2 - Cummings, P.T. A2 - Westmorland, P.R. T3 - American Institute of Chemical Engineers Symposium Series C2 - 2001/// C3 - Foundations of molecular modeling and simulation : proceedings of the First International Conference on Molecular Modeling and Simulation, Keystone, Colorado, July 23-28, 2000 CY - Keystone, CO DA - 2001/// PY - 2001/7/23/ SP - 26–34 PB - American Institute of Chemical Engineers SN - 9780816908394 ER - TY - CONF TI - Molecular Model of Gamma-Alumina: Nitrogen Adsorption and Pore Size Distribution AU - Figueroa-Gerstenmaier, S. AU - Vega, L.F. AU - Blas, F.J. AU - Gubbins, K.E. T2 - Foundations of Molecular Modeling and Simulation (FOMMS) Conference A2 - Cummings, P.T. A2 - Westmorland, P.R. T3 - American Institute of Chemical Engineers Symposium Series C2 - 2001/// C3 - Foundations of molecular modeling and simulation : proceedings of the First International Conference on Molecular Modeling and Simulation, Keystone, Colorado, July 23-28, 2000 CY - Keystone, CO DA - 2001/// PY - 2000/7/23/ SP - 317–320 PB - American Institute of Chemical Engineers ER - TY - CONF TI - Water in Porous Carbons: A Simulation Study AU - Brennan, John K. AU - Thomson, Kendall T. AU - Gubbins, Keith E. T2 - Foundations of Molecular Modeling and Simulation (FOMMS) Conference A2 - Cummings, P.T. A2 - Westmoreland, P.R. T3 - American Institute of Chemical Engineers Symposium Series C2 - 2001/// C3 - Foundations of molecular modeling and simulation : proceedings of the First International Conference on Molecular Modeling and Simulation, Keystone, Colorado, July 23-28, 2000 CY - Keystone, CO DA - 2001/// PY - 2001/7/23/ SP - 264–268 PB - American Institute of Chemical Engineers SN - 9780816908394 ER - TY - BOOK TI - Foundations of molecular modeling and simulation : proceedings of the First International Conference on Molecular Modeling and Simulation, Keystone, Colorado, July 23-28, 2000 T2 - AIChE Symposium Series A3 - Cummings, P.T. A3 - Westmoreland, P.R. A3 - Carnahan, Brice DA - 2001/// PY - 2001/// VL - 97 SP - 328 M1 - 325 PB - American Institute of Chemical Engineers SN - 0816908397 9780816908394 ER - TY - BOOK TI - Applying Molecular Simulation and Computational Chemistry : an AIChE Topical Conference : Reno, Nevada, November 4-9, 2001 T2 - AIChE Pub. A3 - Westmoreland, P.R. A3 - Heffelfinger, G.S. DA - 2001/// PY - 2001/// M1 - 147 PB - American Institute of Chemical Engineers SN - 0816997594 9780816997596 ER - TY - CONF TI - Pericyclic chemistry in polymer thermal decomposition AU - Westmoreland, P.R. AU - Rotem, K. T2 - First International Conference on Molecular Modeling and Simulation A2 - Cummings, P.T. A2 - Westmoreland, P.R. A2 - Carnahan, B. T3 - AIChE Symposium Series C2 - 2001/// C3 - Foundations of molecular modeling and simulation : proceedings of the First International Conference on Molecular Modeling and Simulation, Keystone, Colorado, July 23-28, 2000 CY - Keystone, Colorado DA - 2001/// PY - 2000/7/23/ SP - 127–130 PB - American Institute of Chemical Engineers ER - TY - CONF TI - Complete Phase Diagrams for Binary Mixtures Via Gibbs Duhem Integration AU - Hitchcock, M.R. AU - Hall, C.K. T2 - First International Conference on Molecular Modeling and Simulation A2 - Cummings, P.T. A2 - Westmoreland, P.R. T3 - AlChE Symposium Series C2 - 2001/// C3 - Foundations of Molecular Modeling and Simulation: proceedings of the First International Conference on Molecular Modeling and Simulation, Keystone, Colorado, July 23-28, 2000 CY - Keystone, Colorado DA - 2001/// PY - 2000/7/23/ SP - 195 PB - American Institute of Chemical Engineers SN - 9780816908394 ER - TY - JOUR TI - Latest Applications of Compressed Carbon Dioxide AU - Crette, S.A. AU - DeSimone, J.M. T2 - Nachrichten Aus der Chemie AB - Abstract In der Nahrungsmittelindustrie seit einigen Jahrzehnten im Einsatz, rückt überkritisches oder fast überkritisches Kohlendioxid nun auch in der Polymersynthese, Textilreinigung, Oberflächenbeschichtung und Mikrolithographie in den Blickpunkt. Die Gründe für den Aufschwung neuer Kohlendioxidtechniken sind in Verfahrens‐ und ökologischen Vorteilen zu suchen. DA - 2001/// PY - 2001/// DO - 10.1002/nadc.20010490407 VL - 49 IS - 4 SP - 462–466 ER - TY - CHAP TI - Surfactants for Supercritical and Near-Critical Fluids AU - Carson, T. AU - Wells, S.L. AU - DeSimone, J.M. T2 - Reactions and Synthesis in Surfactant Systems A2 - Texter, John PY - 2001/// SP - 129–143 PB - Marcel Dekker, Inc. ER - TY - CHAP TI - Critical Phase Polymerizations AU - Jones, III, C.A. AU - DeSimone, J.M. T2 - Encyclopedia of Polymer Science and Engineering A2 - Mark, H. PY - 2001/// ET - 3rd SP - 111–127 PB - Wiley-Interscience ER - TY - JOUR TI - Four- and Five-Coordinate CO Insertion Mechanisms in d8-Nickel(II) Complexes AU - Shultz, C. Scott AU - DeSimone, Joseph M. AU - Brookhart, Maurice T2 - Journal of the American Chemical Society AB - ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTFour- and Five-Coordinate CO Insertion Mechanisms in d8-Nickel(II) ComplexesC. Scott Shultz, Joseph M. DeSimone, and Maurice BrookhartView Author Information Department of Chemistry University of North Carolina at Chapel Hill Chapel Hill, North Carolina 27599-3290 Cite this: J. Am. Chem. Soc. 2001, 123, 37, 9172–9173Publication Date (Web):August 24, 2001Publication History Received26 April 2001Published online24 August 2001Published inissue 1 September 2001https://doi.org/10.1021/ja0160896Copyright © 2001 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views1209Altmetric-Citations37LEARN 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. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit Read OnlinePDF (46 KB) Get e-AlertsSupporting Info (1)»Supporting Information Supporting Information SUBJECTS:Acyls,Alkyls,Carbonylation,Coordination compounds,Hydrocarbons Get e-Alerts DA - 2001/9// PY - 2001/9// DO - 10.1021/ja0160896 VL - 123 IS - 37 SP - 9172-9173 J2 - J. Am. Chem. Soc. LA - en OP - SN - 0002-7863 1520-5126 UR - http://dx.doi.org/10.1021/ja0160896 DB - Crossref ER - TY - JOUR TI - Separation of Positional Isomers of Oxidation Catalyst Precursors AU - Hartshorn, Chris M. AU - Maxwell, Kimberly A. AU - White, Peter S. AU - DeSimone, Joseph M. AU - Meyer, Thomas J. T2 - Inorganic Chemistry AB - A series of polypyridyl ruthenium complexes of the general formula [Ru(tpy)(bpy‘)Cl]+ where tpy is 2,2‘:6‘,2‘ ‘-terpyridine and bpy‘ is 4-carboxy-4‘-methyl-2,2‘-bipyridine (4-CO2H-4‘-Mebpy), a proline derivative (4-CO-Pra(Boc)(OMe)-4‘-Mebpy), or 4-((diethoxyphosphinyl)methyl)-4‘-methyl-2,2‘-bipyridine (4-CH2PO3Et2-4‘-Mebpy) are prepared. For each complex, two isomers exist, and these are separated chromatographically. The structure of the hexafluorophosphate salt of cis-[Ru(tpy)(4-CO2H-4‘-Mebpy)Cl]+, cis-1, is determined by X-ray crystallography. The salt crystallizes in the monoclinic space group Cc with a = 12.4778(6) Å, b = 12.6086(6) Å, c = 20.1215(9) Å, β = 107.08200(1)°, Z = 4, R = 0.058, and Rw = 0.072. The structures of the remaining complexes are assigned by 1H NMR comparisons with cis-1. The complexes are potentially important precursors for the incorporation of RuIVO2+ oxidants into polymers or peptides or for their adsorption onto oxide surfaces. Preliminary electrochemical results for the isomers of [Ru(tpy)(4-CH2PO3H2-4‘-Mebpy)(H2O)]2+, 4, adsorbed on ITO (In2O3:Sn) surfaces add support to a recently proposed electron-transfer mechanism involving cross-surface proton-coupled electron transfer. DA - 2001/2// PY - 2001/2// DO - 10.1021/ic9911724 VL - 40 IS - 4 SP - 601-606 J2 - Inorg. Chem. LA - en OP - SN - 0020-1669 1520-510X UR - http://dx.doi.org/10.1021/ic9911724 DB - Crossref ER - TY - JOUR TI - CO2 Technology Platform: An Important Tool for Environmental Problem Solving AU - Wells, Sharon L. AU - DeSimone, Joseph T2 - Angewandte Chemie International Edition AB - CO(2) is a good solvent for many substances when compressed into its liquid or supercritical fluid state. Above the critical temperature and critical pressure (T(c)=31 degrees C, P(c)=73.8 bar, see Figure 1 for the phase diagram for CO(2)), CO(2) has both gaslike viscosities and liquidlike densities. These moderate critical conditions allow CO(2) to be used within safe commercial and laboratory operating conditions. Small changes in temperature and pressure cause dramatic changes in the density, viscosity, and dielectric properties of CO(2), making it a tunable solvent that can be tailored for various applications. Combined, these unique properties make CO(2) a "solvent of choice" for the new millennium. DA - 2001/1/30/ PY - 2001/1/30/ DO - 10.1002/1521-3773(20010202)40:3<518::aid-anie518>3.0.co;2-4 VL - 40 IS - 3 SP - 518-527 J2 - Angew. Chem. Int. Ed. LA - en OP - SN - 1433-7851 UR - http://dx.doi.org/10.1002/1521-3773(20010202)40:3<518::aid-anie518>3.0.co;2-4 DB - Crossref ER - TY - JOUR TI - Nucleophilic Displacements in Supercritical Carbon Dioxide Using Silica-Supported Phase-Transfer Agents AU - DeSimone, Joseph AU - Selva, Maurizio AU - Tundo, Pietro T2 - The Journal of Organic Chemistry AB - ADVERTISEMENT RETURN TO ISSUEPREVNoteNEXTNucleophilic Displacements in Supercritical Carbon Dioxide Using Silica-Supported Phase-Transfer AgentsJoseph DeSimone, Maurizio Selva, and Pietro TundoView Author Information Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290, and Dipartimento di Scienze Ambientali dell'Universita' Ca' Foscari, Calle Larga S. Marta, 2137-30123 Venezia, Italy [email protected]Cite this: J. Org. Chem. 2001, 66, 11, 4047–4049Publication Date (Web):May 4, 2001Publication History Received8 September 2000Published online4 May 2001Published inissue 1 June 2001https://doi.org/10.1021/jo001337mCopyright © 2001 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views294Altmetric-Citations19LEARN 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. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit Read OnlinePDF (38 KB) Get e-AlertsSUBJECTS:Anions,Salts,Silica,Solvents,Substitution reactions Get e-Alerts DA - 2001/6// PY - 2001/6// DO - 10.1021/jo001337m VL - 66 IS - 11 SP - 4047-4049 J2 - J. Org. Chem. LA - en OP - SN - 0022-3263 1520-6904 UR - http://dx.doi.org/10.1021/jo001337m DB - Crossref ER - TY - JOUR TI - Developments in CO2 research AU - Behles, Jacqueline A. AU - DeSimone, Joseph M. T2 - Pure and Applied Chemistry AB - Abstract CO 2 can be a good solvent for many compounds when used in its compressed liquid or supercritical fluid state. Above its critical temperature and critical pressure (Tc = 31 C, Pc = 73.8 bar), CO 2 has liquid-like densities and gas-like viscosities, which allows for safe commercial and laboratory operating conditions. Many small molecules are readily soluble in CO 2 , whereas most macromolecules are not. This has prompted development of several classes of small molecule and polymeric surfactants that enable emulsion and dispersion polymerizations as well as other technological processes. DA - 2001/8/1/ PY - 2001/8/1/ DO - 10.1351/pac200173081281 VL - 73 IS - 8 SP - 1281-1285 OP - SN - 1365-3075 0033-4545 UR - http://dx.doi.org/10.1351/pac200173081281 DB - Crossref ER - TY - JOUR TI - Cationic Four- and Five-Coordinate Nickel(II) Complexes:  Insights into the Nickel(II)-Catalyzed Copolymerization of Ethylene and Carbon Monoxide AU - Shultz, C. Scott AU - DeSimone, Joseph M. AU - Brookhart, Maurice T2 - Organometallics AB - Using the dppp-derived Ni(II) catalyst system 2, several four- and five-coordinate intermediates relevant to the alternating copolymerization of ethylene and carbon monoxide have been characterized. In addition, the activation barriers for the migratory insertion steps corresponding to chain growth have been determined to be at or below ca. 10 kcal/mol, indicating that a strongly stabilized catalyst resting state is most likely responsible for the low activity of 2 for copolymerization. DA - 2001/1// PY - 2001/1// DO - 10.1021/om0008023 VL - 20 IS - 1 SP - 16-18 J2 - Organometallics LA - en OP - SN - 0276-7333 1520-6041 UR - http://dx.doi.org/10.1021/om0008023 DB - Crossref ER - TY - JOUR TI - Study of the Association of a Diblock Copolymer and Absorption of an Insoluble Homopolymer in CO2 AU - Wells, Sharon L. AU - Taylor, Darlene AU - Adam, Mireille AU - DeSimone, J. M. AU - Farago, Bela T2 - Macromolecules AB - ADVERTISEMENT RETURN TO ISSUEPREVCommunication to the...Communication to the EditorNEXTStudy of the Association of a Diblock Copolymer and Absorption of an Insoluble Homopolymer in CO2Sharon L. Wells, Darlene Taylor, Mireille Adam, J. M. DeSimone, and Bela FaragoView Author Information Department of Chemistry, University of North Carolina at Chapel Hill, Venable Hall CB#3290, Chapel Hill, North Carolina 27599, and Institute Laue Langevin, B.P. 156, F-38042, Grenoble, France Cite this: Macromolecules 2001, 34, 18, 6161–6163Publication Date (Web):July 24, 2001Publication History Received22 December 2000Revised23 May 2001Published online24 July 2001Published inissue 1 August 2001https://doi.org/10.1021/ma002187kCopyright © 2001 American Chemical SocietyRequest reuse permissionsArticle Views78Altmetric-Citations6LEARN 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. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit Read OnlinePDF (43 KB) Get e-AlertscloseSUBJECTS:Copolymers,Homopolymers,Micelles,Scattering,Solvents Get e-Alerts DA - 2001/8// PY - 2001/8// DO - 10.1021/ma002187k VL - 34 IS - 18 SP - 6161-6163 J2 - Macromolecules LA - en OP - SN - 0024-9297 1520-5835 UR - http://dx.doi.org/10.1021/ma002187k DB - Crossref ER - TY - JOUR TI - Diffusive Transport of Micelles and Monomeric Solutes in Supercritical CO2 AU - Lee, Dongil AU - Hutchison, John C. AU - DeSimone, Joseph M. AU - Murray, Royce W. T2 - Journal of the American Chemical Society AB - ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTDiffusive Transport of Micelles and Monomeric Solutes in Supercritical CO2Dongil Lee, John C. Hutchison, Joseph M. DeSimone, and Royce W. MurrayView Author Information Kenan Laboratories of Chemistry and NSF Center for Environmentally Responsible Solvents and Processes University of North Carolina Chapel Hill, North Carolina 27599 Cite this: J. Am. Chem. Soc. 2001, 123, 34, 8406–8407Publication Date (Web):August 2, 2001Publication History Received25 May 2001Revised9 July 2001Published online2 August 2001Published inissue 1 August 2001https://doi.org/10.1021/ja0162818Copyright © 2001 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views268Altmetric-Citations19LEARN 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. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit Read OnlinePDF (38 KB) Get e-AlertsSupporting Info (1)»Supporting Information Supporting Information SUBJECTS:Diffusion,Emulsions,Micelles,Probes,Surfactants Get e-Alerts DA - 2001/8// PY - 2001/8// DO - 10.1021/ja0162818 VL - 123 IS - 34 SP - 8406-8407 J2 - J. Am. Chem. Soc. LA - en OP - SN - 0002-7863 1520-5126 UR - http://dx.doi.org/10.1021/ja0162818 DB - Crossref ER - TY - JOUR TI - Ultrafast Excited-State Energy Migration Dynamics in an Efficient Light-Harvesting Antenna Polymer Based on Ru(II) and Os(II) Polypyridyl Complexes AU - Fleming, Cavan N. AU - Maxwell, Kimberly A. AU - DeSimone, Joseph M. AU - Meyer, Thomas J. AU - Papanikolas, John M. T2 - Journal of the American Chemical Society AB - A detailed study of the excited state energy migration dynamics that take place within an assembly of Ru(II) and Os(II) polypyridyl complexes linked together through a polymer backbone is presented. The energy migration process is initiated by the photoexcitation of the metal-to-ligand charge transfer (MLCT) transition in one of the Ru(II) complexes and terminated by energy transfer to a lower energy Os(II) trap. Energy transfer sensitization of Os(II) can occur in a single step if the excited state is formed adjacent to a trap, or after a series of hops between isoenergetic rutheniums prior to reaching a trap. The dynamics of the energy transfer process are followed by monitoring the growth of Os(II)* luminescence at 780 nm. The kinetics of the growth are complex and can be fit by a sum of two exponentials. This kinetic complexity arises both from the presence of a distribution of donor−acceptor distances and the variety of time scales by which Os(II)* can be formed. We have augmented the time-resolved experiments with Monte Carlo simulations, which provide insight into the polymer array's structure and at the same time form the basis of a molecular-level description of the energy migration dynamics. The simulations indicate that the most probable Ru*→Os energy transfer time is ∼400 ps while the time scale for Ru*→Ru hopping is approximately 1−4 ns. The time scale for Ru*→Ru hopping relative to its natural lifetime (1000 ns) suggests that this polymer system could be extended to considerably longer dimensions without an appreciable loss in its overall efficiency. DA - 2001/10// PY - 2001/10// DO - 10.1021/ja016304i VL - 123 IS - 42 SP - 10336-10347 J2 - J. Am. Chem. Soc. LA - en OP - SN - 0002-7863 1520-5126 UR - http://dx.doi.org/10.1021/ja016304i DB - Crossref ER - TY - JOUR TI - Bond Angle Effects on the Migratory Insertion of Ethylene and Carbon Monoxide into Palladium(II)−Methyl Bonds in Complexes Bearing Bidentate Phosphine Ligands AU - Ledford, John AU - Shultz, C. Scott AU - Gates, Derek P. AU - White, Peter S. AU - DeSimone, Joseph M. AU - Brookhart, Maurice T2 - Organometallics AB - Labile (P−P)Pd(CH3)(OEt2)+BAr‘4- complexes (2) have been prepared via protonation of (P−P)PdMe2 (1), where P−P = cis-1,2-bis(diphenylphosphino)ethylene (a, dppee), 1,2-bis(diphenylphosphino)benzene (b, dpbz), 1,2-bis(diphenylphosphino)ethane (c, dppe), 1,2-bis(dimethylphosphino)ethane (d, dmpe), 1,3-bis(diphenylphosphino)propane (e, dppp), 1,3-bis(diisopropylphosphino)propane (f, dippp), 1,4-bis(diphenylphosphino)butane (g, dppb) and Ar‘ = 3,5-(CF3)2C6H3. Unstable complex 2d (P−P = dmpe) was generated in situ. X-ray structures are reported for 1e and 2e−g. Treatment of 2a−g with CO in CH2Cl2 at −90 °C yields the (P−P)Pd(CH3)(CO)+ complexes 3a−g. Barriers to migratory insertion in 3a−g were determined with the ordering to be: 3f (dippp) ≈ 3g (dppb) < 3e (dppp) ≪ 3a (dppee) ≈ 3b (dpbz) ≈ 3c (dppe) < 3d (dmpe). Exposure of 2a−g to ethylene at −80 °C yields the ethylene complexes (P−P)Pd(CH3)(C2H4)+ (5a−g). Barriers to migratory insertion in these complexes were determined by NMR spectroscopy to be: 5b (dpbz) ≈ 5e (dppp) ≈ 5f (dippp) ≈ 5g (dppb) < 5a (dppee) ≈ 5c (dppe) < 5d (dmpe). Complexes (P−P)Pd(CH2CH3)(C2H4)+ (6a−e,g) produced from 5a−e,g under C2H4 are catalyst resting states for the dimerization of C2H4 to butenes. In the case of 5f (P−P = dippp), the catalyst resting state produced is the β-agostic ethyl complex (dippp)Pd(CH2CH2-μ-H)+ (8f), which has been isolated. This complex exhibits two dynamic processes studied by VT-NMR: interchange of Cα and Cβ (ΔG⧧ = 10.3(2) kcal/mol) and rotation of the agostic methyl group (ΔG⧧ ca. 6.4 kcal/mol). The β-agostic propyl complex 7f has been generated and identified as the n-propyl isomer (dippp)Pd(CH2CH2-μ-HCH3)+. DA - 2001/12// PY - 2001/12// DO - 10.1021/om010489k VL - 20 IS - 25 SP - 5266-5276 J2 - Organometallics LA - en OP - SN - 0276-7333 1520-6041 UR - http://dx.doi.org/10.1021/om010489k DB - Crossref ER - TY - JOUR TI - Polymers with Multiple Ligand Sites for Metal Extractions in Dense-Phase Carbon Dioxide† AU - Powell, Kimberly R. AU - McCleskey, T. Mark AU - Tumas, William AU - DeSimone, Joseph M. T2 - Industrial & Engineering Chemistry Research AB - We have synthesized a series of CO2-soluble polymeric extractants with multiple ligand sites for CO2-based metal extractions. The CO2-soluble polymers were prepared via free-radical copolymerization of a fluorinated acrylate with a series of acrylate- or styrene-based monomers functionalized with ligand sites or ligand precursors. These polymers have high solubility in CO2; up to 30 wt % of a polymer with 15 mol % of a ligand-based monomer can be solubilized in liquid CO2 at 25 °C at 140 bar. Copper and europium extractions have been performed with β-diketone- and phosphonate-functionalized polymers, respectively. Preliminary extractions with copper nitrate were carried out at ligand-to-metal ratios of 1:1 and 2.7:1, resulting in 25−37% and 59% efficiency, respectively, suggesting a ligand binding stoichiometry of 2 for efficient extraction. Europium luminescence studies demonstrate that europium is bound to the polymer along with four water molecules in the inner coordination sphere. DA - 2001/3// PY - 2001/3// DO - 10.1021/ie000811b VL - 40 IS - 5 SP - 1301-1305 J2 - Ind. Eng. Chem. Res. LA - en OP - SN - 0888-5885 1520-5045 UR - http://dx.doi.org/10.1021/ie000811b DB - Crossref ER - TY - CHAP TI - Characterization of porous materials using molecular theory and simulation AU - Lastoskie, Christian M AU - Gubbins, Keith E T2 - Advances in Chemical Engineering Volume 28 PY - 2001/// DO - 10.1016/s0065-2377(01)28007-7 SP - 203-250 OP - PB - Elsevier SN - 9780120085286 UR - http://dx.doi.org/10.1016/s0065-2377(01)28007-7 DB - Crossref ER - TY - CHAP TI - Improved Molecular Models for Porous Carbons AU - Pikunic, J. AU - Pellenq, R. J.-M. AU - Thomson, K.T. AU - Rouzaud, J.-N. AU - Levitz, P. AU - Gubbins, K.E. T2 - Studies in Surface Science and Catalysis PY - 2001/// DO - 10.1016/s0167-2991(01)82174-1 VL - 132 SP - 647-652 PB - Elsevier SN - 9780444506511 UR - http://dx.doi.org/10.1016/s0167-2991(01)82174-1 ER - TY - JOUR TI - Chemistry and life sciences in a new vision of chemical engineering AU - Westmoreland, P.R. T2 - Chemical Engineering Education DA - 2001/// PY - 2001/// VL - 35 IS - 4 SP - 248–255 ER - TY - JOUR TI - Student Use (and Non-Use) of Instructional Software AU - Roskowski, A.M. AU - Felder, R.M. AU - Bullard, L.G. T2 - Journal of Science, Math, Engineering, and Technology (SMET) Education DA - 2001/// PY - 2001/// VL - 2 SP - 41 – 45 ER - TY - JOUR TI - Study on interaction of lithium and dry Nafion membrane with ac impedance, SEM and EDAX AU - Zhang, Yali AU - Fedkiw, P.S. T2 - Qingdao Daxue Xuebao, Ziran Kexueban DA - 2001/// PY - 2001/// VL - 14 SP - 51–61 ER - TY - JOUR TI - Structured metallic films for optical and spectroscopic applications via colloidal crystal templating AU - Tessier, P.M. AU - Velev, O.D. AU - Kalambur, A.T. AU - Lenhoff, A.M. AU - Rabolt, J.F. AU - Kaler, E.W. T2 - Advanced Materials DA - 2001/// PY - 2001/// DO - 10.1002/1521-4095(200103)13:6<396::AID-ADMA396>3.0.CO;2-T VL - 13 IS - 6 SP - 396-400 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-0035896129&partnerID=MN8TOARS ER - TY - JOUR TI - Dielectrophoretic assembly of electrically functional microwires from nanoparticle suspensions AU - Hermanson, K.D. AU - Lumsdon, S.O. AU - Williams, J.P. AU - Kaler, E.W. AU - Velev, O.D. T2 - Science AB - A new class of microwires can be assembled by dielectrophoresis from suspensions of metallic nanoparticles. The wires are formed in the gaps between planar electrodes and can grow faster than 50 micrometers per second to lengths exceeding 5 millimeters. They have good ohmic conductance and automatically form electrical connections to conductive islands or particles. The thickness and the fractal dimension of the wires can be controlled, and composite wires with a metallic core surrounded by a latex shell can be assembled. The simple assembly process and their high surface-to-volume ratio make these structures promising for wet electronic and bioelectronic circuits. DA - 2001/// PY - 2001/// DO - 10.1126/science.1063821 VL - 294 IS - 5544 SP - 1082-1086 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-0035798184&partnerID=MN8TOARS ER - TY - JOUR TI - Assembly of gold nanostructured films templated by colloidal crystals and use in surface-enhanced Raman spectroscopy AU - Tessier, P.M. AU - Ong, K.K. AU - Christesen, S.D. AU - Lenhoff, A.M. AU - Kaler, E.W. AU - Velev, O.D. T2 - Proceedings of SPIE - The International Society for Optical Engineering AB - Surface-enhanced Raman spectroscopy (SERS) is a highly sensitive technique for quantifying trace amounts of analyte adsorbed at a roughened metal surface. Many techniques, including electrochemical etching and e-beam lithography, have been used previously to produce roughened metallic surfaces. In this work we demonstrate how novel gold nanostructured films, which are simply fabricated using gold nanoparticles and latex microspheres, can be used as highly sensitive SERS substrates. The gold films are templated by 3D colloidal crystals and display long ranged ordered regions. Since the films are porous on two length scales and, therefore, possess a high surface area, we have investigated their SERS activity using sodium cyanide as a model compound. We have integrated these substrates into a flow chamber and demonstrated the quantitative detection of sodium cyanide form 5 to 500 ppb. Our results also reveal that cyanide detection can be significantly enhanced by lowering the pH after cyanide adsorption, likely indicating a conformational change of the bound cyanide. This study illustrates how novel materials formed by simple wet chemistry techniques can be used in practical devices for the detection of chemical agents, and, more generally, illustrates how material design and spectroscopic evaluation can be rapidly integrated. DA - 2001/// PY - 2001/// DO - 10.1117/12.455751 VL - 4577 SP - 53-64 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-0035776524&partnerID=MN8TOARS ER - TY - PAT TI - Miniaturized immunosensor assembled from colloidal particles between micropatterned electrodes AU - Kaler, E.W. AU - Velev, O.D. C2 - 2001/// DA - 2001/// PY - 2001/// ER - TY - JOUR TI - New insights into fuel-lean ethylene flames AU - Law, M. E. AU - Carriere, T. AU - Westmoreland, P. R. T2 - Chemical and Physical Processes in Combustion DA - 2001/// PY - 2001/// SP - 194-197 ER - TY - JOUR TI - Flammability kinetics from TGA/DSC/GCMS, microcalorimetry and computational quantum chemistry AU - Westmoreland, Phillip R. AU - Inguilizian, Taline AU - Rotem, Karin T2 - Thermochimica Acta AB - Flammability hazards and mechanisms have been analyzed for mg-scale samples of polymers by integrating the use of a new TGA/DSC/GCMS technique, the PCFC microcalorimeter developed by Lyon, and computational quantum chemistry. The first apparatus is based on a Rheometrics STA 1500. Head space immediately above the polymer is sampled through a microprobe and heated transport line into a multiport valve of a Hewlett-Packard 5890 Series II GC with 5972 Mass Selective Detector. The PCFC microcalorimeter is based on continuous analysis of the oxygen required to consume pyrolysis gases. The two apparatus yield complementary data on the rate and composition of gases evolved in pyrolysis, and they are shown here to be in good agreement. Kinetics of decomposition are established from the data and from computed rate constants. DA - 2001/3// PY - 2001/3// DO - 10.1016/s0040-6031(00)00661-4 VL - 367-368 SP - 401-405 J2 - Thermochimica Acta LA - en OP - SN - 0040-6031 UR - http://dx.doi.org/10.1016/s0040-6031(00)00661-4 DB - Crossref KW - flammability hazards KW - pyrolysis gases KW - fire-safe polymers ER - TY - PAT TI - Production of Amino Acids using Auxotrophic Mutants of Methylotrophic Bacillus AU - Hanson, R.S. AU - Flickinger, M.C. AU - Schendel, F.J. AU - Guettler, M.V. C2 - 2001/// DA - 2001/// PY - 2001/// ER - TY - JOUR TI - PEO-LiN(SO2CF2CF3)2 polymer electrolytes I. XRD, DSC, and ionic conductivity characterization AU - Appetecchi, G. B. AU - Henderson, W. AU - Villano, P. AU - Berrettoni, M. AU - Passerini, S. T2 - Journal of the Electrochemical Society DA - 2001/// PY - 2001/// VL - 148 IS - 10 SP - A1171-A1178 ER - TY - JOUR TI - Piezoresistance of conductor filled insulator composites AU - Zhang, XW AU - Pan, Y AU - Zheng, Q AU - Yi, XS T2 - POLYMER INTERNATIONAL AB - Several series of electrically conducting composites composed of a conducting filler randomly dispersed into an insulating polymer matrix were prepared. The fillers were the tin–lead alloy powder, copper powder, aluminium powder and carbon black, and the matrices were polyethylene, polystyrene and epoxy resin. The piezoresistance effects of these composites have been investigated under uniaxial presses. It was observed that the piezoresistance depends on the applied stress, filler particle diameter, filler volume fraction, matrix compressive modulus and potential barrier height. Piezoresistance increases with increase of applied stress, filler particle diameter and potential barrier height, but decreases with increases of filler volume fraction and matrix compressive modulus. A model based on the change in interparticle separation under applied stress, is developed. By analysing this model, the piezoresistance of composites is studied and the effects of influencing factors are theoretically predicted quantitatively, showing good agreement with the experimental data. © 2001 Society of Chemical Industry DA - 2001/2// PY - 2001/2// DO - 10.1002/1097-0126(200102)50:2<229::AID-PI612>3.0.CO;2-U VL - 50 IS - 2 SP - 229-236 SN - 0959-8103 UR - https://publons.com/publon/7178387/ KW - conducting composite KW - piezoresistance KW - interparticle separation KW - tunneling current ER - TY - PAT TI - Method of forming a multi-layered dual-polysilicon structure AU - Chittipeddi, S. AU - Kelly, M. J. C2 - 2001/// DA - 2001/// PY - 2001/// ER - TY - PAT TI - Kolbe electrolysis in a polymer electrolyte membrane reactor AU - Law, C. G. AU - Fedkiw, P. S. AU - Hicks, M. T. C2 - 2001/// DA - 2001/// PY - 2001/// ER - TY - BOOK TI - Unit operations of chemical engineering (6th ed.) AU - McCabe, W. L. CN - TP155.7 .M3 2005 DA - 2001/// PY - 2001/// PB - Boston: McGraw Hill SN - 0070393664 ER - TY - JOUR TI - Studies of the binding of alpha-lactalbumin to immobilized peptide ligands AU - Gurgel, PV AU - Carbonell, RG AU - Swaisgood, HE T2 - JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY AB - The present work investigates the mechanism of binding of alpha-lactalbumin to the peptide ligand WHWRKR and its variants HWRKR and acetylated WHWRKR immobilized on a polymethacrylate chromatographic resin. The presence of two temperature-dependent binding mechanisms and one temperature-independent mechanism was demonstrated. Injections of different forms of alpha-lactalbumin (apo-alpha-lactalbumin, D87A mutant alpha-lactalbumin) displayed similar behaviors when compared to native alpha-lactalbumin, while lysozyme showed little or no binding to the WHWRKR and AcWHWRKR resins. An alternative process for isolation of alpha-lactalbumin from WPI was shown, using consecutive injections of WPI with limited elution. DA - 2001/12// PY - 2001/12// DO - 10.1021/jf010462b VL - 49 IS - 12 SP - 5765-5770 SN - 1520-5118 KW - alpha-lactalbumin KW - peptide ligands KW - bioselective adsorption KW - binding mechanism ER - TY - CONF TI - SUCCEED: a multiple university collaborative approach to systemic curriculum change AU - Anderson, T. AU - Hoit, M. AU - Felder, R. AU - Brent, R. AU - Zorowski, C. AU - Ollis, D. AU - Ohland, M. AU - Phillips, H. C2 - 2001/// C3 - 2001 International Conference on Engineering Education Proceedings, Oslo, Norway, August 2001 DA - 2001/// M1 - 2001 August ER - TY - CONF TI - New faculty 101: an orientation to the profession AU - Brent, R. AU - Felder, R. M. AU - Rajala, S. A. AU - Gilligan, J. G. AU - Lee, G. AB - In August 2000 the North Carolina State University College of Engineering (USA) with partial sponsorship from the SUCCEED Coalition organized and presented a one-week orientation workshop for new faculty members. The workshop goal was to equip new faculty members to become what Robert Boice calls "quick starters", who meet or exceed their institution's expectations for both research productivity and teaching effectiveness in their first one to two years. Two days were devoted to research program startup and management, two to effective teaching, and the final morning to managing time, integrating into campus culture, and earning tenure and promotion. The participants were unanimously and overwhelmingly positive in their responses following the workshop, and their enthusiasm has continued at gatherings and in surveys in the months that followed. This paper describes the workshop content and activities, summarizes follow-up support and assessment plans, and offers suggestions for planning and implementing similar programs. C2 - 2001/// C3 - 2001 Frontiers in Education Conference Proceedings, Reno, NV, October 2001 DA - 2001/// DO - 10.1109/fie.2001.964046 M1 - 2001 October ER - TY - JOUR TI - Ionic conductivity of alkali-metal salts in sub- and supercritical carbon dioxide plus methanol mixtures AU - Jun, J AU - Fedkiw, PS T2 - JOURNAL OF ELECTROANALYTICAL CHEMISTRY AB - Abstract Ionic conductivity of lithium, sodium, and potassium perfluoroacetate salts and lithium acetate in sub- and supercritical carbon dioxide+methanol mixtures is reported as a function of CO 2 pressure and temperature. Although the mole fraction of salts was low (10 −4 –10 −2 ), the ionic conductivity was large (∼10 −5 –10 −4 S cm −1 ) compared with pure CO 2 (below measurement capabilities) and CO 2 +methanol (∼10 −7 –10 −8 S cm −1 ). In the sub-critical two-phase region, the ionic conductivity in the CO 2 -rich phase increased with pressure, but the conductivity decreased in the supercritical region with CO 2 pressure. Solvent viscosity and ion diffusivity in the single-phase region predominantly influence conductivity, whereas it is affected by salt solubility in the two-phase region. DA - 2001/11/30/ PY - 2001/11/30/ DO - 10.1016/S0022-0728(01)00636-2 VL - 515 IS - 1-2 SP - 113-122 SN - 1873-2569 KW - supercritical CO2 KW - conductivity KW - alkali metal perfluoroacetate salts KW - solubility KW - diffusivity ER - TY - CONF TI - Instructional software: if you build It, they may or may not come AU - Roskowski, A. M. AU - Felder, R.M. AU - Bullard, L. G. C2 - 2001/// C3 - 2001 ASEE Annual Conference Proceedings, ASEE, June 2001 CN - T62. A47 2001 DA - 2001/// PB - Washington, D.C.: American Society for Engineering Education ER - TY - JOUR TI - FAQs-4. dealing with student background deficiencies and low student motivation AU - Felder, R. M. AU - Brent, R. T2 - CEE, Chemical Engineering Education DA - 2001/// PY - 2001/// VL - 35 IS - 4 SP - 266-267 ER - TY - JOUR TI - FAQs-3 AU - Felder, R. M. AU - Brent, R. T2 - CEE, Chemical Engineering Education DA - 2001/// PY - 2001/// VL - 35 IS - 2 SP - 102-103 ER - TY - JOUR TI - How to prepare tunable planar molecular chemical gradients AU - Efimenko, K AU - Genzer, J T2 - ADVANCED MATERIALS AB - Advanced MaterialsVolume 13, Issue 20 p. 1560-1563 Communication How to Prepare Tunable Planar Molecular Chemical Gradients K. Efimenko, K. Efimenko Department of Chemical Engineering, North Carolina State University, Raleigh, NC 27695-7905 (USA)Search for more papers by this authorJ. Genzer, J. Genzer jan_genzer@ncsu.edu Department of Chemical Engineering, North Carolina State University, Raleigh, NC 27695-7905 (USA)Search for more papers by this author K. Efimenko, K. Efimenko Department of Chemical Engineering, North Carolina State University, Raleigh, NC 27695-7905 (USA)Search for more papers by this authorJ. Genzer, J. Genzer jan_genzer@ncsu.edu Department of Chemical Engineering, North Carolina State University, Raleigh, NC 27695-7905 (USA)Search for more papers by this author First published: 04 October 2001 https://doi.org/10.1002/1521-4095(200110)13:20<1560::AID-ADMA1560>3.0.CO;2-ZCitations: 48AboutPDF 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 Mechanically assembled monolayers (MAMs) can be employed to adjust the surface density of the initiators and consequently that of molecular gradients prepared on flexible supports. The steepness and the position of the gradient of molecules on a substrate are fine-tuned by a combination of grafting and mechanical manipulation of the films. Planar molecular gradients ranging from several millimeters to several centimeters can thus be fabricated. In addition, the wetting properties of the hydrophobic part of the substrate can be adjusted by altering the chemical nature of the films. Citing Literature Volume13, Issue20October, 2001Pages 1560-1563 RelatedInformation DA - 2001/10/16/ PY - 2001/10/16/ DO - 10.1002/1521-4095(200110)13:20<1560::AID-ADMA1560>3.0.CO;2-Z VL - 13 IS - 20 SP - 1560-+ SN - 0935-9648 ER - TY - JOUR TI - How do you select the `greenest? technology? Development of guidance for the pharmaceutical industry AU - Jimenez-Gonzalez, C. AU - Curzons, A. AU - Constable, D. AU - Overcash, M. AU - Cunningham, V. T2 - Clean Products and Processes DA - 2001/// PY - 2001/// DO - 10.1007/pl00011310 VL - 3 IS - 2001 SP - 35-41 ER - TY - JOUR TI - High-pressure rheology and viscoelastic scaling predictions of polymer melts containing liquid and supercritical carbon dioxide AU - Royer, Joseph R. AU - DeSimone, Joseph M. AU - Khan, Saad A. T2 - Journal of Polymer Science Part B: Polymer Physics AB - Abstract High‐pressure rheological behavior of polymer melts containing dissolved carbon dioxide (CO 2 ) at concentrations up to 6 wt % were investigated using a high‐pressure extrusion slit die rheometer. In particular, the steady shear viscosity of poly(methyl methacrylate), polypropylene, low‐density polyethylene, and poly(vinylidene fluoride) with dissolved CO 2 were measured for shear rates ranging from 1 to 500 s −1 and under pressure conditions up to 30 MPa. The viscosity of all samples revealed a reduction in the presence of CO 2 with its extent dependent on CO 2 concentration, pressure, and the polymer used. Two types of viscoelastic scaling models were developed to predict the effects of both CO 2 concentration and pressure on the viscosity of the polymer melts. The first approach utilized a set of equations analogous to the Williams–Landel–Ferry equation for melts between the glass‐transition temperature ( T g ) and T g + 100 °C, whereas the second approach used equations of the Arrhenius form for melts more than 100 °C above T g . The combination of these traditional viscoelastic scaling models with predictions for T g depression by a diluent (Chow model) were used to estimate the observed effects of dissolved CO 2 on polymer melt rheology. In this approach, the only parameters involved are physical properties of the pure polymer melt that are either available in the existing literature or can be measured under atmospheric conditions in the absence of CO 2 . The ability of the proposed scaling models to accurately predict the viscosity of polymer melts with dissolved high‐pressure CO 2 were examined for each of the polymer systems. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 3055–3066, 2001 DA - 2001/// PY - 2001/// DO - 10.1002/polb.10057 VL - 39 IS - 23 SP - 3055-3066 J2 - J. Polym. Sci. B Polym. Phys. LA - en OP - SN - 0887-6266 1099-0488 UR - http://dx.doi.org/10.1002/polb.10057 DB - Crossref KW - rheology KW - high pressure KW - supercritical fluids KW - viscoelastic scaling ER - TY - JOUR TI - Concentration fluctuations in CTAB/NaSal solutions AU - Amin, S AU - Kermis, TW AU - Zanten, RM AU - Dees, SJ AU - Zanten, JH T2 - LANGMUIR AB - This report details a dynamic light scattering investigation of CTAB/NaSal solution concentration fluctuations over a wide range of CTAB concentration and NaSal:CTAB mole ratio. Two distinct relaxation times are observed for CTAB concentrations greater than or equal to 0.02 M. The hydrodynamic correlation length, ξH, associated with the fast relaxation mode is observed to depend on both the CTAB concentration and NaSal:CTAB mole ratio. In particular, the CTAB concentration scaling of ξH is shown to vary in a nonmonotonic manner with the NaSal:CTAB mole ratio. The scaling exponent is found to range from −0.25 to −0.67, where its minimum value is found for NaSal:CTAB mole ratios near 1.5−2.0. The amplitude of the slow relaxation mode is strongly correlated with the hydrodynamic correlation length for NaSal:CTAB mole ratios less than or equal to 2 thereby suggesting polymer/polyelectrolyte solution behavior at these conditions. The overall picture that emerges is that of a system where the competition among micellar charge, electrostatic screening, and micelle breaking controls the system dynamics. The behavior of the hydrodynamic correlation length and slow-mode amplitude can be understood quite well within a framework of micelle ionization and electrostatic screening effects. However, the NaSal:CTAB mole ratio and CTAB concentration dependence of the slow relaxation time cannot be entirely explained within the context of electrostatic interactions. To account for the observed behavior it is proposed that the micelle breaking time is influenced by bound salicylate ions whose degree of binding depends on both the NaSal:CTAB mole ratio and CTAB concentration. DA - 2001/12/25/ PY - 2001/12/25/ DO - 10.1021/la010844b VL - 17 IS - 26 SP - 8055-8061 SN - 0743-7463 ER - TY - JOUR TI - Processing of polyamide 11 with supercritical carbon dioxide AU - Martinache, JD AU - Royer, , JR AU - Siripurapu, S AU - Henon, FE AU - Genzer, J AU - Khan, SA AU - Carbonell, RG T2 - INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH AB - The supercritical carbon dioxide induced swelling and plasticization of polyamide 11 were investigated. The swelling kinetics exhibit an initial region of large swelling, in which the diffusion of CO2 into the polymer follows Fickian behavior, and a subsequent region of small volume increase that asymptotically approaches an equilibrium swelling value. The diffusion coefficient of CO2 in polyamide 11 was calculated from the initial slope of the swelling kinetics data. CO2, injected up to 3 wt % using an extrusion rheometer, is shown to be an effective plasticizer for polyamide 11, lowering the viscosity of the polymer melt by as much as 50%. The use of CO2 as a blowing agent was also investigated, and we report preliminary foaming attempts using a batch process. We obtained homogeneously distributed foams, featuring well-defined closed cells with an average diameter of 30 μm that had an unfoamed skin layer. DA - 2001/11/14/ PY - 2001/11/14/ DO - 10.1021/ie010410b VL - 40 IS - 23 SP - 5570-5577 SN - 0888-5885 ER - TY - JOUR TI - Light scattering study of poly(tert-butyl methacrylate) -block-poly(1,1-dihydroperfluorooctyl methacrylate) in liquid and supercritical carbon dioxide - Towards the reversible control of self-assembly AU - Yoshida, E AU - Wells, SL AU - DeSimone, JM T2 - KOBUNSHI RONBUNSHU AB - 二酸化炭素に両親媒性のブロック腫合体であるポリメタクリル酸tert-ブチル-block-ポリ (メタクリル酸1, 1-ジヒドロパーフルオロオクチル) ジブロック共重合体 (P' BMA-block-PFOMA) の, 液体および超臨界二酸化炭素中でのミセル形成について光散乱解析を用いて検討を行った. 動的光散乱解析の結果, P' BMAセグメントの分子量が4000以上のプロック共重合体は, 超臨界二酸化炭素中で分子量分布の狭いミセルを形成することがわかった. 特に, 半径が13~21nmの範囲にあるミセルを形成するP' BMA-block-PFOMAは, CO2密度0.87~1.04g/cm3にミセルから単量体への転移をもつことが見いだされた. その転移は温度およびジブロック共重合体備成する両方のポリマー鎖長に依存した. 本研究は, CO2中におけるブロック共重合体のミセルから単量体への転移が, ジブロック共重合体のセグメント鎖長によって制御されることを初めて実証したものである. このことは, CO2の溶媒特性だけでなくジブロック共重合体のセグメント鎖長の選択によっても, 共重合体の自己組織化の制御が可能であることを示している. DA - 2001/// PY - 2001/// DO - 10.1295/koron.58.507 VL - 58 IS - 10 SP - 507-513 SN - 0386-2186 KW - supercritical carbon dioxide KW - poly(tert-butyl methacrylate)-block-poly(1,1-dihydroperfluorooctyl methacrylate) diblock KW - copolymers KW - micelles-to-unimers transition KW - CO2 density KW - copolymer concentration KW - cloud points KW - aggregation number KW - hydrodynamic radius of micelles ER - TY - CONF TI - The impact of faculty development activities on engineering faculty teaching practices AU - Brawner, C. E. AU - Felder, R. M. AU - Allen, R. H. AU - Brent, R. C2 - 2001/// C3 - 2001 ASEE Annual Conference Proceedings, ASEE, June 2001 CN - T62. A47 2001 DA - 2001/// PB - Washington, D.C.: American Society for Engineering Education ER - TY - JOUR TI - Surfactants and self-assembly in carbon dioxide AU - DeSimone, JM AU - Keiper, JS T2 - CURRENT OPINION IN SOLID STATE & MATERIALS SCIENCE AB - Amphiphilic compounds have played a vital role in the emergence of carbon dioxide in both its liquid and supercritical states as a versatile, environmentally benign solvent. This review serves to describe recent efforts in three major areas of the field: (1) polymeric amphiphile self-assembly in carbon dioxide solutions, (2) use of surfactants as stabilizing agents for polymerizations, and (3) studies involving ‘small molecule’ surfactant assemblies in carbon dioxide. DA - 2001/8// PY - 2001/8// DO - 10.1016/s1359-0286(00)00041-3 VL - 5 IS - 4 SP - 333-341 SN - 1879-0348 ER - TY - JOUR TI - Strain and dislocation reduction in maskless pendeo-epitaxy GaN thin films AU - Roskowski, A. M. AU - Miraglia, P. Q. AU - Preble, E. A. AU - Einfeldt, S. AU - Stiles, T. AU - Davis, R. F. AU - Schuck, J. AU - Grober, R. AU - Schwarz, U. T2 - Physica Status Solidi. A, Applications and Materials Science AB - Measurement of strain in GaN films grown via pendeo-epitaxy (PE) indicates that the overgrowth, or wing, material is crystallographically relaxed. An increase of ≈0.02% in the c-axis lattice parameter of the wing material was measured via high-resolution X-ray diffraction (HRXRD); additional evidence for this increase was indicated by an upward shift of the E2 Raman line frequency. Atomic force microscopy studies revealed a reduction in the density of mixed-type dislocations in the wing. A reduction in screw-type dislocations in the wings with respect to the stripes is indicated by a reduction in HRXRD rocking curve FWHM of the (0002) reflections from 646 to 354 arcsec. The off-axis FWHM of the wing area was 126 arcsec compared to 296 arcsec for the stripe indicating a reduction in the edge-type dislocations as well. Pendeo-epitaxy growth of wings off the (110) surface of a GaN stripe produced a material that is crystallographically relaxed, contains fewer defects compared to the stripe and is atomically smooth on the (110) surface. DA - 2001/// PY - 2001/// DO - 10.1002/1521-396x(200112)188:2<729::aid-pssa729>3.0.co;2-w VL - 188 IS - 2 SP - 729-732 ER - TY - JOUR TI - Rheology, particle size distribution, and asphaltene deposition of viscous asphaltic crude oil-in-water emulsions for pipeline transportation AU - Zaki, N AU - Butz, T AU - Kessel, D T2 - PETROLEUM SCIENCE AND TECHNOLOGY AB - The rheology of an asphaltic heavy crude oil-in-water emulsions stabilized by an anionic (RN) and a nonionic (TEP) surfactants individually or in a mixture has been studied. The investigated crude oil has a non-Newtonian, time dependent, shear thickening, rheopectic behavior with a relatively high yield stress. The relatively high yield stress of this crude oil is attributed to the presence of a relatively high asphaltene and resins content. The viscosity ofhe crude oil decreases when it is emulsified with synthetic formation water in the form of an oil-in-water type of emulsion using a nonionic or an anionic surfactant. It has been found that, the maximum oil content required for forming an oil-in-water emulsion of acceptable viscosity is the 60% oil-containing emulsion. However, the 70% oil-containing emulsion is not an oil-in-water type of emulsion but it is rather a complicated mixture of oil-in-water-in-oil type of emulsion. The presence of the anionic and the nonionic surfactants together has a synergistic effect in decreasing the total surfactant concentration required to stabilize the emulsion and to form low viscosity emulsion. It has been emphasized that the nonionic surfactant has a positive contribution in forming emulsions with low viscosity. Meanwhile, the anionic surfactant contributes in stabilizing the emulsion at lower concentrations. Flocculation point measurements showed that the added surfactants caused no sign of asphaltene deposition. This implies that it is safe to use the investigated surfactants in forming oil-in-water emulsion for viscous asphaltic crude oils without any fear of asphaltene deposition. DA - 2001/// PY - 2001/// DO - 10.1081/LFT-100000774 VL - 19 IS - 3-4 SP - 425-435 SN - 1532-2459 KW - heavy crude oil-in-water emulsions KW - anionic-nonionic surfactants mixture KW - emulsion stability KW - salinity KW - viscosity reduction ER - TY - JOUR TI - Polymer chain relaxation: Surface outpaces bulk AU - Wallace, WE AU - Fischer, DA AU - Efimenko, K AU - Wu, WL AU - Genzer, J T2 - MACROMOLECULES AB - ADVERTISEMENT RETURN TO ISSUEPREVCommunication to the...Communication to the EditorNEXTPolymer Chain Relaxation: Surface Outpaces BulkWilliam E. Wallace, Daniel A. Fischer, Kirill Efimenko, Wen-Li Wu, and Jan GenzerView Author Information National Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, Maryland 20899-8541, and Department of Chemical Engineering, North Carolina State University, Raleigh, North Carolina 27695-7905 Cite this: Macromolecules 2001, 34, 15, 5081–5082Publication Date (Web):June 19, 2001Publication History Received6 December 2000Revised9 April 2001Published online19 June 2001Published inissue 1 July 2001https://doi.org/10.1021/ma002075tCopyright © 2001 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views894Altmetric-Citations87LEARN 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. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. 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Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit Read OnlinePDF (68 KB) Get e-AlertsSUBJECTS:Aromatic compounds,Hydrocarbons,Phenyls,Polymer chains,X-ray absorption near edge spectroscopy Get e-Alerts DA - 2001/7/17/ PY - 2001/7/17/ DO - 10.1021/ma002075t VL - 34 IS - 15 SP - 5081-5082 SN - 1520-5835 ER - TY - JOUR TI - Molecular simulation of complete phase diagrams for binary mixtures AU - Lamm, MH AU - Hall, CK T2 - AICHE JOURNAL AB - Abstract Vapor‐liquid, vapor‐solid and liquid‐solid coexistence lines are calculated for binary mixtures of Lennard‐Jones spheres using Monte Carlo simulation and the Gibbs‐Duhem integration technique. Complete phase diagrams showing equilibrium between vapor, liquid and solid phases are constructed for binary Lennard‐Jones mixtures with diameter ratios ranging from σ 11 /σ 22 = 0.85–1.0 and attractive well‐depth ratios ranging from ϵ 11 /ϵ 22 = 0.625−1.6, at a reduced pressure P*≡Pσ /ϵ 11 = 0.002. The Lorentz‐Berthelot combining rules are used to calculate the cross‐species interaction parameters σ 12 and ϵ 12 . The variation in the shape of the complete phase diagrams change as a function of the diameter ratio σ 11 /σ 22 and well‐depth ratio ϵ 11 /ϵ 22 is systematically explored. The phase diagrams found here resemble those found experimentally for argon‐methane, iodine‐sulfur, water‐sodium chloride, water‐silver nitrate, water‐potassium nitrate, and p‐dichlorobenzene‐p‐dibromobenzene. DA - 2001/7// PY - 2001/7// DO - 10.1002/aic.690470718 VL - 47 IS - 7 SP - 1664-1675 SN - 1547-5905 ER - TY - JOUR TI - Molecular modeling of carbon aerogels AU - Gavalda, S AU - Kaneko, K AU - Thomson, KT AU - Gubbins, KE T2 - COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS AB - Carbon aerogels are prepared via pyrolysis of resorcinol-formaldehyde gels. The structure consists of a highly porous three-dimensional network made up of interconnected, roughly spherical carbon particles. The aerogel studied in this work was mesoporous and had carbon particles having a diameter of ≈6 nm, connected in an open-cell structure with a porosity of ≈0.55. In addition to the mesopores between the carbon particles, the carbon particles themselves possess slit-shaped micropores with a width of ≈0.7 nm. We present a molecular model of this material, consisting of carbon spheres of diameter 6 nm in a connected network. This matrix is prepared by first generating a random close-packed structure of slightly overlapping spheres, followed by random removal of spheres to match the targeted porosity. Structural characteristics of the model have been studied using different MC techniques and compare well with those for the laboratory material. Nitrogen adsorption in this model aerogel was studied using a parallelized Grand Canonical Monte Carlo algorithm based on a domain-decomposition scheme. Large systems are needed for this simulation in order to represent the pore network in a realistic fashion. Adsorption occurs in the micropores at very low pressure, followed by adsorption in the mesopores, with capillary condensation occurring at the higher pressures. DA - 2001/8/31/ PY - 2001/8/31/ DO - 10.1016/S0927-7757(01)00641-0 VL - 187 IS - 2001 Aug. 31 SP - 531-538 SN - 0927-7757 KW - carbon aerogel KW - molecular simulation KW - adsorption ER - TY - JOUR TI - Mathematical model of the deactivation of Pt/alumina catalyst during the hydrodechlorination of 1,1,1-trichloroethane AU - Frankel, K. A. AU - Spivey, J. J. AU - Roberts, G. W. T2 - Catalyst deactivation 2001: Proceedings of the 9th international symposium, Lexington, KY, USA, 7-10 October 2001 (Studies in surface science and catalysis; 139) CN - TP156.C35 C3794 2001 DA - 2001/// PY - 2001/// VL - 139 SP - 439-446 ER - TY - JOUR TI - Issues relating to group composition AU - Felder, R. M. AU - Brent, R. T2 - Learning together: Peer tutoring in higher education CN - LB1031.5 .F35 2001 DA - 2001/// PY - 2001/// SP - 201-204 ER - TY - JOUR TI - Interfacial and topological measurements of bicontinuous polymer morphologies - art. no. 010803 AU - Jinnai, H. AU - Kajihara, T. AU - Watashiba, H. AU - Nishikawa, Y. AU - Spontak, R. J. T2 - Physica. E, Low-dimensional Systems & Nanostructures DA - 2001/// PY - 2001/// VL - 6401 IS - 1 SP - 0803- ER - TY - JOUR TI - Influence of chemical and physical surface heterogeneity on chemical reaction equilibria in carbon micropores AU - Turner, CH AU - Pikunic, J AU - Gubbins, KE T2 - MOLECULAR PHYSICS AB - Abstract Recent simulation results are presented for the equilibrium yield of the ammonia synthesis reaction in various model microporous carbons. It is found that the reaction equilibria within the micropores is affected by many factors, including pore size, pore shape, connectivity, surface roughness, and surface chemical activation. In order to probe these effects, reactive Monte Carlo simulations of the reaction were performed in several microporous carbon models: smooth slit-shaped carbon pores, a realistic carbon model generated from experimental diffraction data, single-walled carbon nanotubes, and smooth slit-shaped pores activated by carboxyl surface groups. The simulations show that the ammonia conversion is most sensitive to the carbon pore width and to the amount of surface chemical activation. Effects of surface corrugation and pore connectivity on the equilibrium reaction yield are minimal. DA - 2001/12// PY - 2001/12// DO - 10.1080/00268970110087254 VL - 99 IS - 24 SP - 1991-2001 SN - 1362-3028 ER - TY - CONF TI - A comparison of electronic surveying by e-mail and web AU - Brawner, C. E. AU - Felder, R. M. AU - Allen, R. H. AU - Brent, R. AU - Miller, T. K. C2 - 2001/// C3 - 2001 ASEE Annual Conference Proceedings, ASEE, June 2001 CN - T62. A47 2001 DA - 2001/// PB - Washington, D.C.: American Society for Engineering Education ER - TY - JOUR TI - Synthesis and characterization of templated mesoporous materials using molecular simulation AU - Siperstein, FR AU - Gubbins, KE T2 - MOLECULAR SIMULATION AB - Abstract Lattice Monte Carlo simulations are used to calculate equilibrium properties of surfactant-solvent-silica liquid-crystal systems under no-polymerization conditions. The formation of a high-surfactant high-silica concentration phase in equilibrium with a dilute phase is observed when the surfactant-silica interactions are stronger than the surfactant-solvent interactions. Different silica structures that are similar to the M41 family are observed, depending on the overall concentration of the system. The formation of a hexagonal phase is favored at a surfactant/silica ratio of 0.2, whereas a lamellar phase is observed a surfactant/silica ratio of 1. Argon adsorption properties on a model porous structure of the MCM-41 type prepared using this mimetic simulation protocol are calculated using grand canonical Monte Carlo simulation. Heats of adsorption are calculated from fluctuations in the energy and number of molecules [1] following the work of Nicholson and Parsonage [Computer Simulation and the Statistical Mechanics of Adsorption (Academic Press, London), 1982, p 97 8 pp]. A decrease in the heats of adsorption for coverage less than one statistical monolayer is evidence of surface heterogeneity. The results are in qualitative agreement with experimental measurements for argon on MCM-41. DA - 2001/// PY - 2001/// DO - 10.1080/08927020108031357 VL - 27 IS - 5-6 SP - 339-352 SN - 0892-7022 KW - templated materials KW - surfactant KW - silica KW - hexagonal phase ER - TY - JOUR TI - Protein refolding versus aggregation: Computer simulations on an intermediate-resolution protein model AU - Smith, AV AU - Hall, CK T2 - JOURNAL OF MOLECULAR BIOLOGY AB - Computer simulations are performed on a system of eight model peptide chains to study how the competition between protein refolding and aggregation affects the optimal conditions for refolding of four-helix bundles. The discontinuous molecular dynamics algorithm is utilized along with an intermediate-resolution protein model that we developed for this work. Physically, the model is much more detailed than any model used to date for simulations of protein aggregation. Each model residue consists of a detailed, three-bead backbone and a simplified, single-bead side-chain. Excluded volume, hydrogen bond, and hydrophobic interactions are modeled with discontinuous (i.e. hard-sphere and square-well) potentials. Simulations efficiently sample conformational space, and complete folding trajectories from random initial configurations to two four-helix bundles are possible within two days on a single processor workstation. Folding of the bundles follows two main pathways, one through a trimeric intermediate and the other through an intermediate with two dimers. The proportion of trajectories that follow each route is significantly different for the eight-peptide system in this work than in a previously studied four-peptide system, which yields one four-helix bundle, suggesting, as our previous simulations have, that protein folding properties are strongly influenced by the presence of other proteins. Folding of the bundles is optimal within a fixed temperature range, with the high-temperature boundary a function of the complexity of the protein (or oligomer) to be folded and the low-temperature boundary a function of the complexity of the protein's environment. Above the optimal temperature range for folding, the model chains tend to unfold; below the optimal range, the model chains tend to aggregate. As has been seen previously, aggregates have substantial levels of native secondary structure, suggesting that aggregates are composed largely of partially folded intermediates, not denatured chains. DA - 2001/9/7/ PY - 2001/9/7/ DO - 10.1006/jmbi.2001.4845 VL - 312 IS - 1 SP - 187-202 SN - 1089-8638 KW - discontinuous molecular dynamics KW - protein folding KW - protein misfolding KW - aggregation KW - four-helix bundle ER - TY - JOUR TI - Physical and electrical characterization of ultrathin yttrium silicate insulators on silicon AU - Chambers, JJ AU - Parsons, GN T2 - JOURNAL OF APPLIED PHYSICS AB - This article describes the oxidation of yttrium on silicon to form yttrium silicate films for application as high dielectric constant insulators. The high reactivity of yttrium metal with silicon and oxygen is utilized to form amorphous yttrium silicate films with a minimal interfacial silicon dioxide layer. Yttrium silicate films (∼40 Å) with an equivalent silicon dioxide thickness of ∼11 Å and k∼14 are formed by oxidizing yttrium on silicon. The physical properties of yttrium silicate films on silicon are investigated using x-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. The oxidation of yttrium silicide results in films nearly identical, although with a higher silicon fraction, to films formed by oxidation of yttrium on silicon. The oxidation of yttrium on silicon results in a competition for yttrium between silicide formation and oxidation. This competition yields yttrium silicate films for thin (&lt;40 Å) initial metal thickness and a Y2O3/silicate bilayer for thick (&gt;80 Å) initial metal thickness. Annealing yttrium films on silicon in vacuum to form yttrium silicide and then oxidizing the silicide is used to eliminate the competition and control the yttrium/silicon reaction. Analysis of the oxidation of yttrium on silicon reveals fast oxidation during silicate formation and a slow rate during oxidation of the silicon substrate to form SiO2. Oxidation of other metals, such as Hf, Zr, and La, on silicon is expected to result in metal silicate films through a similar simultaneous (or controlled sequential) silicide/oxidation reactions. DA - 2001/7/15/ PY - 2001/7/15/ DO - 10.1063/1.1375018 VL - 90 IS - 2 SP - 918-933 SN - 0021-8979 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000169660000057&KeyUID=WOS:000169660000057 ER - TY - JOUR TI - Monte Carlo simulations of complete phase diagrams for binary Lennard-Jones mixtures AU - Lamm, MH AU - Hall, CK T2 - FLUID PHASE EQUILIBRIA AB - Vapor–liquid, vapor–solid, liquid–liquid, and liquid–solid coexistence lines are calculated for binary mixtures of Lennard–Jones spheres with diameter ratio σ11/σ22=0.85, well-depth ratio ϵ11/ϵ22=0.45, and binary interaction parameters δ12=1.0, 0.9, and 0.75, using Monte Carlo simulation and the Gibbs–Duhem integration technique. These calculations allow us to construct complete phase diagrams, i.e. showing equilibrium between vapor, liquid, and solid phases. For the mixture with δ12=1, we find a completely miscible vapor–liquid coexistence region with a eutectic solid–liquid coexistence region. These two regions are separated by a completely miscible liquid phase. For the mixtures with δ12<1, we find that the vapor–liquid and solid–liquid coexistence regions interfere. This interference results in a vapor–solid coexistence region bounded above and below by solid–liquid–vapor coexistence lines. We also find that the mixtures with δ12<1 have a region of liquid–liquid immiscibility that is metastable with respect to the solid–fluid phase equilibria. DA - 2001/6/5/ PY - 2001/6/5/ DO - 10.1016/S0378-3812(01)00378-8 VL - 182 IS - 1-2 SP - 37-46 SN - 1879-0224 KW - molecular simulation KW - liquid-liquid equilibria KW - solid-fluid equilibria KW - Lennard-Jones ER - TY - JOUR TI - Effect of confinement on melting in slit-shaped pores: Experimental and simulation study of aniline in activated carbon fibers AU - Sliwinska-Bartkowiak, M AU - Radhakrishnan, R AU - Gubbins, KE T2 - MOLECULAR SIMULATION AB - Abstract We report both experimental and molecular simulation studies of the melting behavior of aniline confined within an activated carbon fiber having slit-shaped pores. Dielectric relaxation spectroscopy is used to determine the transition temperatures and also the dielectric relaxation times over the temperature range 240 to 340 K. For the confined system two transitions were observed, one at 298 K and a second transition at 324 K. The measured relaxation times indicate that the low temperature phase (below 298 K) is a crystalline or partially crystalline solid phase, while that above 324 K is a liquid-like phase; for the intermediate phase, in the range 298–324 K, the relaxation times are of the order 10−5s, which is typical of a hexatic phase. The melting temperature of the confined system is well above that of bulk aniline, which is 267 K. The simulations are carried out using the Grand Canonical Monte Carlo method together with Landau free energy calculations, and phase transitions are located as state points where the grand free energies of two confined phases are equal. The nature of these phases is determined by analysis of in-plane pair positional and orientational correlation functions. The simulations also show two transitions. The first is a transition from a two-dimensional hexagonal crystal phase to a hexatic phase at 296 K; the second transition is from the hexatic to a liquid-like phase at 336 K. Confinement within the slit-shaped pores appears to stabilize the hexatic phase, which is the stable phase over a wider temperature range than for quasi-two-dimensional thin films. DA - 2001/// PY - 2001/// DO - 10.1080/08927020108031356 VL - 27 IS - 5-6 SP - 323-337 SN - 1029-0435 KW - melting KW - aniline KW - carbon fibers KW - dielectric relaxation spectroscopy ER - TY - JOUR TI - Computer simulation of isothermal mass transport in graphite slit pores AU - Travis, KP AU - Gubbins, KE T2 - MOLECULAR SIMULATION AB - Abstract Results are presented from a simulation study of the mass transport of oxygen and nitrogen through graphite slit pores. The work is motivated by an attempt to understand the molecular origins of the kinetic selectivity displayed when air is separated into its major components using pressure swing adsorption. A combination of non-equilibrium molecular dynamics (NEMD), equilibrium molecular dynamics (EMD) and grand canonical Monte Carlo methods has been employed in our study to extract the maximum information. Transport diffusivities, self-diffusivities, permeabilities and Darken thermodynamic factors have been calculated as a function of pore width and temperature for pure component oxygen and nitrogen. In addition, new EMD simulation data for an 80:20 mixture of nitrogen and oxygen is reported, including a direct calculation of the Stefan-Maxwell coefficients. The results are discussed in terms of the oxygen selectivity and the possible mechanisms, which increase or decrease this quantity. We find that the pore width behaviour of the diffusion coefficients consists of three distinct regimes: a regime at larger pore widths in which single component diffusion coefficients are largely independent of pore width, an optimum pore width at which both diffusivities increase substantially but the slit pore is selective towards nitrogen, and a regime at very low pore widths at which the diffusivities decrease sharply, but the slits are selective towards oxygen. The mechanism behind each of these regimes is discussed in terms of “entropic” effects and potential barrier heights. We have also found that permeability selectivity is substantially reduced in a mixture of the two gases with a composition similar to that of air. Cross diffusion coefficients in the mixture have been calculated and shown to be non-negligible. DA - 2001/// PY - 2001/// DO - 10.1080/08927020108031361 VL - 27 IS - 5-6 SP - 405-439 SN - 1029-0435 KW - transport diffusion KW - non-equilibrium molecular dynamics KW - air separation KW - Stefan-Maxwell coefficients KW - micropores KW - adsorption ER - TY - JOUR TI - American College of Zoological Medicine recommendations on veterinary curricula AU - Stoskopf, MK AU - Paul-Murphy, J AU - Kennedy-Stoskopf, S AU - Kaufman, G T2 - JOURNAL OF THE AMERICAN VETERINARY MEDICAL ASSOCIATION DA - 2001/12/1/ PY - 2001/12/1/ DO - 10.2460/javma.2001.219.1532 VL - 219 IS - 11 SP - 1532-1535 SN - 0003-1488 ER - TY - JOUR TI - Viscosity effects on the thermal decomposition of bis(perfluoro-2-N-propoxypropionyl) peroxide in dense carbon dioxide and fluorinated solvents AU - Bunyard, WC AU - Kadla, JF AU - DeSimone, JM T2 - JOURNAL OF THE AMERICAN CHEMICAL SOCIETY AB - The thermal decomposition of the free-radical initiator bis(perfluoro-2-N-propoxyprionyl) peroxide (BPPP) was studied in dense carbon dioxide and a series of fluorinated solvents. For the fluorinated solvents, the observed first-order decomposition rate constants, kobs, increased with decreasing solvent viscosity, suggesting a single-bond decomposition mechanism. The kobs values are comparatively larger in dense carbon dioxide and similar to the “zero-viscosity” rate constants extrapolated from the decomposition kinetics in the fluorinated solvents. The decomposition activation parameters demonstrate a compensation behavior of the activation enthalpy with the activation entropy upon change in solvent viscosity. Comparison of the change in activation parameter values upon change in solvent viscosity for BPPP with two additional initiators, acetyl peroxide (AP) and trifluoroacetyl peroxide (TFAP), further suggests that carbon dioxide exerts a very minimal influence on the decomposition mechanism of these initiators through solvent-cage effects. DA - 2001/8/1/ PY - 2001/8/1/ DO - 10.1021/ja0103344 VL - 123 IS - 30 SP - 7199-7206 SN - 0002-7863 ER - TY - JOUR TI - Supercritical carbon dioxide dewaxing of old corrugated containers AU - Stauffer, TC AU - Venditti, RA AU - Gilbert, RD AU - Kadla, JF AU - Chernyak, Y AU - Montero, GA T2 - JOURNAL OF APPLIED POLYMER SCIENCE AB - Abstract Wax‐coated old corrugated containers (OCC) are not part of the paper recycling stream because a process to remove the wax coating is not presently available. Residual waxes influence fiber–fiber bonding, reducing the paper properties of recycled OCC as well as the paper machine operating efficiency. A procedure to dewax OCC is a major objective of the paper industry. Here we describe a novel process to quantitatively dewax OCC by using supercritical carbon dioxide to remove the wax. The results obtained for the extraction of both saturated and curtain‐coated waxed containers are reported and compared with Soxhlet extraction with hexane. Quantitative removal of the waxes was obtained under a variety of operating conditions. Gas chromatographic analysis of the extracted paraffin wax shows that supercritical fluid extraction does not chemically alter the paraffin wax, indicating the recovered wax may be recycled. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1107–1114, 2001 DA - 2001/8/1/ PY - 2001/8/1/ DO - 10.1002/app.1533 VL - 81 IS - 5 SP - 1107-1114 SN - 0021-8995 KW - supercritical fluid extraction KW - supercritical carbon dioxide KW - corrugated containers KW - wax removal KW - fiber recycling ER - TY - JOUR TI - Studying the buried interfacial region with an immobilized fluorescence probe AU - Lenhart, JL AU - Zanten, JH AU - Dunkers, JP AU - Parnas, RS T2 - MACROMOLECULES AB - The properties of a buried epoxy/glass interfacial region were studied by covalently grafting a fluorescent probe to the glass surface. A (dimethylamino)nitrostilbene (DMANS) fluorophore was tethered to a triethoxysilane coupling agent, generating a fluorescently labeled silane coupling agent (FLSCA). The glass surface was coated with a silane layer that was doped with small amounts of FLSCA. The emission maximum from grafted FLSCA was different than when the dye was dissolved in bulk resin, suggesting a different interfacial structure. When the dye was dissolved in bulk cured resin, a red shift in the emission maximum was detected as the resin temperature was increased. A distinct break in the fluorescence maximum vs temperature slope was detected at the glass transition of the bulk resin. The slope became larger at temperatures above Tg. A similar break was observed from grafted FLSCA, suggesting that the grafted dye was sensitive to an apparent glass transition in the buried interfacial region. The temperature of the apparent interfacial transition measured by grafted FLSCA could be lower or higher than the bulk polymer Tg, depending on the initial structure of the grafted silane layer. DA - 2001/3/27/ PY - 2001/3/27/ DO - 10.1021/ma0015572 VL - 34 IS - 7 SP - 2225-2231 SN - 0024-9297 ER - TY - JOUR TI - Spray-dried iron Fischer-Tropsch catalysts. 1. Effect of structure on the attrition resistance of the catalysts in the calcined state AU - Zhao, R AU - Goodwin, JG AU - Jothimurugesan, K AU - Gangwal, SK AU - Spivey, JJ T2 - INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH AB - The use of Fe Fischer−Tropsch (F−T) catalysts in slurry bubble column reactors (SBCRs) has been problematic in the past because of their poor attrition resistance. Recently, we have reported the preparation of spray-dried Fe F−T catalysts having attrition resistance suitable for SBCR use, but the reason for this improvement was not clear. This paper focuses on research done to better understand the reason for the high attrition resistance of some of the Fe catalysts prepared. Understanding the relationship between the catalyst attrition resistance and composition/structure is important for the preparation of attrition-resistant Fe catalysts. In the present study, two series of spray-dried Fe F−T catalysts having the composition Fe/Cu/K/SiO2 but with different amounts of precipitated and/or binder SiO2 were investigated. All of the catalysts studied were evaluated in their calcined form. This was done to minimize any possible attrition due to Fe phase change (such as can occur during activation and F−T synthesis) in order to address the effect of the other catalyst properties. A companion paper addresses attrition due to phase change after carburization. It was found that particle density, principally among other particle properties of the catalysts, correlated with the intrinsic catalyst attrition resistance. Changes in fluidization in the jet cup attrition test with changes in particle density only had minimal effects on the results. Particle density differences reflected differences in the catalyst inner structure. Differences in SiO2 type and concentration resulted in different structures for the SiO2 network and therefore affected the catalyst structure. DA - 2001/2/21/ PY - 2001/2/21/ DO - 10.1021/ie000644f VL - 40 IS - 4 SP - 1065-1075 SN - 0888-5885 ER - TY - JOUR TI - Molecular-based equations of state for associating fluids: A review of SAFT and related approaches AU - Muller, EA AU - Gubbins, KE T2 - INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH AB - We present a review of recent advances in the statistical associating fluid theory (SAFT). In contrast to the “chemical theory”, in which nonideality is explained in terms of chemical reactions between the species, SAFT and similar approaches relate nonideality to the intermolecular forces involved. Such physical theories can be tested against molecular simulations, and improvements to the theory can be made where needed. We describe the original SAFT approach and more recent modifications to it. Emphasis is placed on pointing out that SAFT is a general method and not a unique equation of state. Applications to a wide variety of fluids and mixtures are reviewed, including aqueous mixtures and electrolytes, liquid−liquid immiscible systems, amphiphilic systems, liquid crystals, polymers, petroleum fluids, and high-pressure phase equilibria. DA - 2001/5/16/ PY - 2001/5/16/ DO - 10.1021/ie000773w VL - 40 IS - 10 SP - 2193-2211 SN - 0888-5885 ER - TY - PAT TI - Methods and apparatus for separating Fischer-Tropsch catalysts from liquid hydrocarbon product AU - Roberts, G. W. AU - Kilpatrick, P. K. C2 - 2001/// DA - 2001/// PY - 2001/// ER - TY - JOUR TI - Kinetics and gas-surface dynamics of GaN homoepitaxial growth using NH3-seeded supersonic molecular beams AU - McGinnis, AJ AU - Thomson, D AU - Davis, RF AU - Chen, E AU - Michel, A AU - Lamb, HH T2 - SURFACE SCIENCE AB - The kinetics of homoepitaxial growth of GaN thin films on metal-organic chemical vapor deposition (MOCVD)-grown GaN(0 0 0 1)/AlN/6H-SiC substrates was probed using NH3-seeded supersonic molecular beams. NH3 was seeded in H2 and He and antiseeded in N2 and Ar in order to obtain incident kinetic energies of 0.08–1.8 eV. Nozzle temperatures of 35–600 °C were used to adjust the NH3 internal energy. Intense NH3 beams (fluxes >2×1015cm−2s−1 at the substrate) are produced for low seeding percentages (<5%) in the lighter carrier gases, because the heavier species (NH3) is focused along the centerline of the beam. The NH3 flux is proportional to the ratio of its molecular weight to the average molecular weight of the binary gas mixture. A steady-state Langmuir–Hinshelwood kinetics model was used to extract zero-coverage NH3 sticking coefficient (αNH30) values from GaN growth kinetics data. An αNH30 value of 0.14 at 750 °C was determined using seeded supersonic beams of NH3 in He with incident kinetic energies of 0.4–0.5 eV. In comparison, GaN growth rates using low-energy NH3 molecules (0.03 eV) from a leak valve indicate an αNH30 of 0.29. Growth rate measurements using NH3 beams with kinetic energies of 0.08–1.8 eV confirmed that αNH30 generally decreases with increasing incident kinetic energy, leading us to conclude that NH3 chemisorption on GaN(0 0 0 1) is unactivated and occurs via a precursor-mediated mechanism. Internal energy enhancement of NH3 chemisorption via a precursor-mediated channel is proposed to explain the effects of nozzle temperature on GaN growth kinetics. The effects of NH3 incident kinetic energy on film morphology are indirect. Rough, highly faceted films are observed under Ga-limited growth conditions. The surface morphology of films grown under NH3-limited conditions changes from rough to smooth as the effective V/III ratio is decreased. DA - 2001/11/10/ PY - 2001/11/10/ DO - 10.1016/S0039-6028(01)01466-2 VL - 494 IS - 1 SP - 28-42 SN - 1879-2758 KW - gallium nitride KW - epitaxy KW - ammonia KW - chemisorption KW - adsorption kinetics KW - growth KW - surface structure, morphology, roughness, and topography ER - TY - JOUR TI - Improved network development in bidisperse AB/ABA block copolymer gels AU - Spontak, RJ AU - Wilder, EA AU - Smith, SD T2 - LANGMUIR AB - Blending a B-selective solvent and an ordered ABA triblock copolymer can, at sufficiently high solvent concentrations, produce a physical gel composed of a network of B midblocks stabilized by A-rich micelles. We demonstrate here that addition of short AB diblock copolymer molecules to such a gel at constant copolymer composition can enhance the solid-like character of the gel, as indicated by an increase in the magnitude of the dynamic elastic modulus. Similarly, addition of AB molecules to a nongelled ABA/solvent system can induce gelation. In light of recent theoretical predictions and related experimental evidence, these results are consistent with a scenario in which tail-induced volume exclusion (due to the presence of AB molecules) within the micellar coronas improves network development through an increase in the population of bridged B midblocks. DA - 2001/4/17/ PY - 2001/4/17/ DO - 10.1021/la0015819 VL - 17 IS - 8 SP - 2294-2297 SN - 0743-7463 ER - TY - JOUR TI - beta-Mannosidase from Thermotoga species AU - Parker, K. N. AU - Chhabra, S. AU - Lam, D. AU - Snead, M. A. AU - Mathur, E. J. AU - Kelly, R. M. T2 - Hyperthermophilic enzymes. Part A CN - QP601 .M49 vol. 330 DA - 2001/// PY - 2001/// VL - 330 SP - 238-246 ER - TY - JOUR TI - beta-Mannanases from Thermotoga species AU - Chhabra, S. AU - Parker, K. N. AU - Lam, D. AU - Callen, W. AU - Snead, M. A. AU - Mathur, E. J. AU - Short, J. M. AU - Kelly, R. M. T2 - Hyperthermophilic enzymes. Part A CN - QP601 .M49 vol. 330 DA - 2001/// PY - 2001/// VL - 330 SP - 224-238 ER - TY - JOUR TI - beta-Endoglucanase from Pyrococcus furiosus AU - Cady, S. G. AU - Bauer, M. W. AU - Callen, W. AU - Snead, M. A. AU - Mathur, E. J. AU - Short, J. M. AU - Kelly, R. M. T2 - Hyperthermophilic enzymes. Part A CN - QP601 .M49 vol. 330 DA - 2001/// PY - 2001/// VL - 330 SP - 346-354 ER - TY - JOUR TI - alpha-Glucosidase from Pyrococcus furiosus AU - Chang, S. T. AU - Parker, K. N. AU - Bauer, M. W. AU - Kelly, R. M. T2 - Hyperthermophilic enzymes. Part A CN - QP601 .M49 vol. 330 DA - 2001/// PY - 2001/// VL - 330 SP - 260-269 ER - TY - JOUR TI - alpha-D-galactosidases from Thermotoga species AU - Miller, E. S. AU - Parker, K. N. AU - Liebl, W. AU - Lam, D. AU - Callen, W. AU - Snead, M. A. AU - Mathur, E. J. AU - Short, J. M. AU - Kelly, R. M. T2 - Hyperthermophilic enzymes. Part A CN - QP601 .M49 vol. 330 DA - 2001/// PY - 2001/// VL - 330 SP - 246-260 ER - TY - JOUR TI - Xylose isomerases from Thermotoga AU - Vieille, C. AU - Sriprapundh, D. AU - Kelly, R. M. AU - Zeikus, J. G. T2 - Hyperthermophilic enzymes. Part A CN - QP601 .M49 vol. 330 DA - 2001/// PY - 2001/// VL - 330 SP - 215-224 ER - TY - JOUR TI - Sorption and transport of linear alkane hydrocarbons in biaxially oriented polyethylene terephthalate AU - Dhoot, SN AU - Freeman, BD AU - Stewart, ME AU - Hill, AJ T2 - JOURNAL OF POLYMER SCIENCE PART B-POLYMER PHYSICS AB - Abstract Equilibrium sorption and uptake kinetics of n ‐butane and n ‐pentane in uniform, biaxially oriented, semicrystalline polyethylene terephthalate films were examined at 35 °C and for pressures ranging from 0 to approximately 76 cmHg. Sorption isotherms were well described by the dual‐mode sorption model. Sorption kinetics were described either by Fickian diffusion or a two‐stage model incorporating Fickian diffusion at short times and protracted polymer structural relaxation at long times. Diffusion coefficients increased with increasing penetrant concentration. n ‐Butane solubility was lower than that of n ‐pentane, consistent with the more condensable nature of n ‐pentane. However, n ‐butane diffusion coefficients were higher than those of n ‐pentane. Infinite‐dilution, estimated amorphous phase diffusion and solubility coefficients were well correlated with penetrant critical volume and critical temperature, respectively. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 1160–1172, 2001 DA - 2001/6/1/ PY - 2001/6/1/ DO - 10.1002/polb.1092 VL - 39 IS - 11 SP - 1160-1172 SN - 1099-0488 KW - sorption KW - diffusion KW - hydrocarbons KW - polyethylene terephthalate ER - TY - JOUR TI - Self-consistent field study of copolymer adsorption at planar chemically 'rough' surfaces: an interplay between the substrate chemical pattern and copolymer sequence distribution AU - Genzer, J T2 - ADVANCES IN COLLOID AND INTERFACE SCIENCE AB - We extend the one-dimensional self-consistent field (SCF) scheme of Scheutjens-Fleer to three dimensions (3D) and use this three-dimensional SCF model to investigate the adsorption of A–B copolymers from A homopolymer matrices onto planar substrates composed of two chemically distinct sites (C and D), one of which has a preferential affinity for the B segments of the copolymer. To address the role of the substrate chemical heterogeneity on copolymer adsorption, we keep the fraction of the C and D sites constant (50% of each site) and vary their spatial distribution on the substrate. The interplay between the surface chemical heterogeneity and the chain microstructure is examined for A–B diblock, A–B–A, B–A–B triblock, and A–alt–B alternating copolymers. Our results indicate that regardless of the type of the surface chemical heterogeneity, the A–B diblock and triblock copolymers adopt ‘brush’-like and ‘bridge’-like structures, respectively, with the B block being anchored to the substrate. In contrast, the A–alt–B macromolecule is found to be ‘zipped’ to the substrate. For a fixed chemical potential of the copolymer in the A–B/A mixture and the surface adsorption energy of B, the amount of the adsorbed copolymer depends on: (1) the number of the B segments; (2) the copolymer microstructure; and (3) the distribution of the C and D regions on the substrate. Three-dimensional maps of the spatial density of copolymer segments provide insight into copolymer conformation at the mixture/substrate interface and also the ability of the copolymer to recognize and mimic the substrate pattern. In addition, we discuss the circumstances under which the substrate pattern is transferred deep inside the A–B/A mixture and those, which lead to strong damping of the substrate motif as one moves away from the substrate/mixture interface. DA - 2001/11/15/ PY - 2001/11/15/ DO - 10.1016/S0001-8686(01)00057-4 VL - 94 IS - 1-3 SP - 105-134 SN - 0001-8686 KW - copolymer KW - adsorption KW - self-consistent field KW - modeling KW - heterogeneous substrate KW - sequence distribution ER - TY - JOUR TI - Reaction kinetics of the solid state polymerization of poly(bisphenol A carbonate) AU - Shi, CM AU - Gross, SM AU - DeSimone, JM AU - Kiserow, DJ AU - Roberts, GW T2 - MACROMOLECULES AB - The kinetics of solid-state polymerization (SSP) of poly(bisphenol A carbonate) was investigated with N2 as the sweep gas. The N2 flow rate and prepolymer particle size were chosen to eliminate the influence of both external and internal phenol diffusion, and to ensure that the kinetics was controlled by the rate of the forward transesterification reaction. The forward reaction rate constants were evaluated at different temperatures between 120 and 165 °C, and the activation energy for SSP of poly(bisphenol A carbonate) with N2 as the sweep gas was determined to be 99.6 kJ/mol. At each temperature, the polymer molecular weight increased with time, eventually reaching an asymptotic value. The asymptotic molecular weight increased with temperature. The glass transition temperature (Tg) of the polymer increased as the molecular weight increased. At lower reaction temperatures, Tg approaches the reaction temperature as the polymerization proceeds, and the achievable molecular weight appears to be limited by decreased end group mobility. At the highest reaction temperature, which was well above the final Tg of the polymer, the stoichiometric ratio of the two end groups appears to determine the achievable molecular weight. DA - 2001/3/27/ PY - 2001/3/27/ DO - 10.1021/ma001942r VL - 34 IS - 7 SP - 2060-2064 SN - 0024-9297 ER - TY - JOUR TI - Life cycle assessment study of color computer monitor AU - Kim, S AU - Hwang, T AU - Overcash, M T2 - INTERNATIONAL JOURNAL OF LIFE CYCLE ASSESSMENT DA - 2001/// PY - 2001/// DO - 10.1007/BF02977594 VL - 6 IS - 1 SP - 35-43 SN - 1614-7502 KW - cathode ray tube KW - color computer monitor KW - consumer electronic product KW - data collection KW - identification of hot spots KW - LCA KW - Life Cycle Assessment KW - sensitivity analysis ER - TY - JOUR TI - Homomultimeric protease and putative bacteriocin homolog from Thermotoga maritima AU - Hicks, P. M. AU - Chang, L. S. AU - Kelly, R. M. T2 - Hyperthermophilic enzymes. Part A CN - QP601 .M49 vol. 330 DA - 2001/// PY - 2001/// VL - 330 SP - 455-460 ER - TY - JOUR TI - Gas permeability and free volume of highly branched substituted acetylene polymers AU - Yampolskii, YP AU - Korikov, AP AU - Shantarovich, VP AU - Nagai, K AU - Freeman, BD AU - Masuda, T AU - Teraguchi, M AU - Kwak, G T2 - MACROMOLECULES AB - Gas permeation, sorption, and structural properties of two highly branched polyacetylenes, poly[1-phenyl-2-[p-(triphenylsilyl)phenyl]acetylene] (PPhSiDPA) and poly[1-phenyl-2-[p-(triisopropylsilyl)phenyl]acetylene] (PPrSiDPA), are reported. Structurally, both polymers have much in common; however, their transport properties are quite different. PPhSiDPA has dramatically lower permeability coefficients than PPrSiDPA. For example, the O2 permeability coefficients of PPhSiDPA and PPrSiDPA are 12 × 10-10 and 230 × 10-10 cm3 (STP) cm/(cm2 s cmHg), respectively, at 22 °C. Gas solubility is very high in PPrSiDPA, similar to that observed in poly(1-trimethysilyl-1-propyne) (PTMSP), the most permeable polymer known. Gas solubility coefficients of PPhSiDPA are 2−3 times lower than those of PPrSiDPA. Free volume size and size distribution were characterized using positron annihilation lifetime (PAL) spectroscopy. Results from these studies (i.e., a bimodal size distribution of free volume elements and large free volume element size) are consistent with the observed transport and sorption properties of PPrSiDPA. In contrast, the PAL spectrum of PPhSiDPA is similar to that of conventional low free volume glassy polymers. DA - 2001/3/13/ PY - 2001/3/13/ DO - 10.1021/ma000628u VL - 34 IS - 6 SP - 1788-1796 SN - 1520-5835 ER - TY - JOUR TI - Effects of surface pretreatments on interface structure during formation of ultra-thin yttrium silicate dielectric films on silicon AU - Chambers, JJ AU - Busch, BW AU - Schulte, WH AU - Gustafsson, T AU - Garfunkel, E AU - Wang, S AU - Maher, DM AU - Klein, TM AU - Parsons, GN T2 - APPLIED SURFACE SCIENCE AB - X-ray photoelectron spectroscopy (XPS) and medium energy ion scattering (MEIS) are used to determine chemical bonding and composition of ultra-thin films of mixed yttrium, silicon, and oxygen, formed by oxidation of metal on clean and pre-treated silicon. XPS and MEIS analyses indicate that oxidation of yttrium on bare silicon results in a fully oxidized film with a significant fraction of Y–O–Si bonding. The mixed Y–O–Si structure results from the relatively rapid reaction between Y and the Si substrate to form yttrium silicide, followed by oxidation. The effect of various silicon pretreatments, including in situ oxidation and nitridation, on bulk and interface film composition are also examined. Transmission electron microscopy (TEM) of 40 Å thick films indicates that the yttrium silicate films are amorphous with uniform contrast throughout the layer. MEIS shows evidence for a graded metal concentration in the dielectric near the silicon interface, with uniform oxygen concentration (consistent with full oxidation) throughout the film. Angle resolved XPS (ARXPS) shows no significant signal related to Si+4, as would be expected from a substantial SiO2 interface layer. Capacitance–voltage analysis demonstrates that a ∼10 Å equivalent oxide thickness can be achieved. The effects of ultra-thin silicon oxide, nitrided-oxide and nitrided silicon interfaces on silicon consumption during the oxidation of yttrium are investigated. When yttrium is deposited on a thin (∼10 Å) SiO2 film and oxidized, a yttrium silicate film is formed with bonding and composition similar to films formed on bare silicon. However, when the interface is a thin nitride, the silicon consumption rate is significantly reduced, and the resulting film composition is closer to Y2O3. The consumption of the silicon substrate by metal is shown to occur during oxidation and during vacuum annealing of yttrium on silicon. The relatively rapid formation of metal–silicon bonds suggests that metal–silicon structures may also be important reactive intermediates in silicon/dielectric interface formation reactions during chemical vapor deposition. In addition to thermodynamic stability, understanding the relative rates of elementary reaction steps in film formation is critical to control composition and structure at the dielectric/Si interface. DA - 2001/9/3/ PY - 2001/9/3/ DO - 10.1016/S0169-4332(01)00373-7 VL - 181 IS - 1-2 SP - 78-93 SN - 0169-4332 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000171063300009&KeyUID=WOS:000171063300009 KW - X-ray photoelectron spectroscopy KW - transmission electron microscopy KW - capacitance-voltage curve ER - TY - JOUR TI - Dispersion polymerization of glycidyl methacrylate in supercritical carbon dioxide AU - Shiho, H AU - DeSimone, JM T2 - MACROMOLECULES AB - Herein we report a successful dispersion polymerization of glycidyl methacrylate (GMA) in carbon dioxide using a block copolymer consisting of polystyrene and poly(1,1-dihydroperfluorooctyl acrylate) (PFOA) as a stabilizer. Poly(GMA) was effectively emulsified in carbon dioxide using the amphiphilic diblock copolymer surfactant. Spherical particles were produced, although PFOA homopolymer was not particularly effective as a stabilizer. The initial concentrations of the monomer and stabilizer and the reaction pressure had substantial effects on the resulting size of the colloidal particles. DA - 2001/2/27/ PY - 2001/2/27/ DO - 10.1021/ma0010074 VL - 34 IS - 5 SP - 1198-1203 SN - 0024-9297 ER - TY - JOUR TI - Deactivation of hydrodechlorination catalysts II - Experiments with 1,1-dichloroethylene and 1,1-dichloroethane AU - Frankel, KA AU - Jang, BWL AU - Roberts, GW AU - Spivey, JJ T2 - APPLIED CATALYSIS A-GENERAL AB - In an earlier paper [K.A. Frankel, B.W.-L. Jang, J.J. Spivey, G.W. Roberts, Appl. Catal. A, in press], it was shown that certain alumina and Pt/alumina catalysts deactivated rapidly during the hydrodechlorination (HDC) of 1,1,1-trichloroethane (111-TCA) at temperatures between 423 and 623 K. Large quantities of coke were formed on these catalysts at some conditions. In the present research, the deactivation associated with four intermediates in the HDC of 111-TCA; 1,1-dichloroethylene (11-DCE), 1,1-dichloroethane (11-DCA), chloroethane, and ethylene, was investigated. Experiments were carried out with ηδ-alumina and 3% Pt/η-alumina at 423 and 523 K, atmospheric pressure, and at a H2/chlorinated hydrocarbon/He ratio of 10/1/89. The ηδ-alumina, without Pt, catalyzed the removal of one molecule of HCl from each of the saturated chlorocarbons. Deactivation of the ηδ-alumina was rapid with 111-TCA and 11-DCA, and relatively slow with chloroethane. There was no reaction over ηδ-alumina when 11-DCE was fed. The fresh Pt/η-alumina catalyst was able to remove all of the Cl from the chlorocarbons. This catalyst deactivated with 111-TCA and 11-DCA, but no deactivation was observed with 11-DCE and chloroethane. At comparable conditions, much more coke was deposited on the Pt/η-alumina catalyst with 111-TCA than with any of the other compounds. Hydrochloric acid did not appear to cause deactivation. A reaction scheme is proposed to summarize the major reaction pathways and to identify potential causes of catalyst deactivation. DA - 2001/2/28/ PY - 2001/2/28/ DO - 10.1016/S0926-860X(00)00784-5 VL - 209 IS - 1-2 SP - 401-413 SN - 0926-860X KW - 1,1,1-trichloroethane KW - 1,1-dichloroethane KW - 1,1-dichloroethylene KW - hydrodechlorination KW - platinum KW - alumina KW - deactivation KW - coke ER - TY - JOUR TI - Cryogenic mechanical alloying as an alternative strategy for the recycling of tires AU - Smith, AP AU - Ade, H AU - Koch, CC AU - Spontak, RJ T2 - POLYMER AB - Cryogenic mechanical alloying (CMA) is investigated as a viable strategy by which to produce highly dispersed blends composed of thermoplastics and tire, thereby providing a potentially new route by which to recycle discarded tires. Morphological characterization of these blends by near-edge X-ray absorption fine structure (NEXAFS) microscopy demonstrates that, upon CMA, ground tire is highly dispersed within poly(methyl methacrylate) (PMMA) and poly(ethylene terephthalate) (PET) matrices at sub-micron size scales. Incorpo-ration of polyisoprene (PI) homopolymer into the blends to improve dispersion efficacy is also examined. Neither PI nor the tire is found to interact chemically with PMMA or PET under the milling conditions employed here. DA - 2001/4// PY - 2001/4// DO - 10.1016/S0032-3861(00)00804-1 VL - 42 IS - 9 SP - 4453-4457 SN - 0032-3861 KW - polymer recycling KW - cryogenic mechanical alloying KW - polymer blends ER - TY - JOUR TI - Copolymer-assisted generation of three-dimensional patterns by replicating two-dimensional substrate motifs - art. no. 022601 AU - Genzer, J. T2 - Physical Review. E, Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics DA - 2001/// PY - 2001/// VL - 6302 IS - 2 SP - 2601 ER - TY - JOUR TI - Continuous cultivation of hyperthermophiles AU - Pysz, M.A. AU - Rinker, K.D. AU - Shockley, K.R. AU - Kelly, R.M. T2 - Methods in Enzymology AB - This chapter describes a continuous culture system that can generate biomass from hyperthermophiles on a scale suitable for enzyme purification. Hightemperature chemostats have several advantages over large-scale batch systems. Long-term, stable, steady-state operation (arising from minimal problems with contamination) can provide biomass generated from exponential growth phase—that is, balanced growth. Because of the smaller operating volumes, continuous systems are inexpensive to construct and minimize problems with handling toxic and explosive gas substrates and products—for example, H2S, He, CH4. Small operating volumes also minimize problems associated with the growth of sulfide-producing anaerobes and thermoacidophiles in terms of choosing a proper material for reactor construction—for example, glass and gold. Continuous cultivation has also been useful for studying the bioenergetics and physiology of hyperthermophiles and for developing media formulations that induce enzyme expression. CN - QP601 .M49 vol. 330 DA - 2001/// PY - 2001/// DO - 10.1016/S0076-6879(01)30369-5 VL - 330 SP - 31–40 ER - TY - PAT TI - Compositions for fracturing subterranean formations AU - Kelly, R. M. AU - Khan, S. A. AU - Leduc, P. AU - Tayal, A. AU - Prud'homme, R. K. C2 - 2001/// DA - 2001/// PY - 2001/// ER - TY - JOUR TI - Carboxylesterase from Sulfolobus solfataricus P1 AU - Sehgal, A. C. AU - Callen, W. AU - Mathur, E. J. AU - Short, J. M. AU - Kelly, R. M. T2 - Hyperthermophilic enzymes. Part A CN - QP601 .M49 vol. 330 DA - 2001/// PY - 2001/// VL - 330 SP - 461-471 ER - TY - JOUR TI - Anomalous phase inversion in polymer blends prepared by cryogenic mechanical alloying AU - Smith, AP AU - Ade, H AU - Smith, SD AU - Koch, CC AU - Spontak, RJ T2 - MACROMOLECULES AB - ADVERTISEMENT RETURN TO ISSUEPREVCommunication to the...Communication to the EditorNEXTAnomalous Phase Inversion in Polymer Blends Prepared by Cryogenic Mechanical AlloyingArchie P. Smith, Harald Ade, Steven D. Smith, Carl C. Koch, and Richard J. SpontakView Author Information Departments of Materials Science and Engineering, Physics, and Chemical Engineering, North Carolina State University, Raleigh, North Carolina 27695; and Corporate Research Division, The Procter and Gamble Company, Cincinnati, Ohio 45239 Cite this: Macromolecules 2001, 34, 6, 1536–1538Publication Date (Web):February 16, 2001Publication History Received5 July 2000Published online16 February 2001Published inissue 1 March 2001https://doi.org/10.1021/ma001151pCopyright © 2001 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views242Altmetric-Citations27LEARN 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. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit Read OnlinePDF (288 KB) Get e-AlertsSUBJECTS:Organic compounds,Polymer morphology,Polymers,Viscosity,X-ray absorption near edge spectroscopy Get e-Alerts DA - 2001/3/13/ PY - 2001/3/13/ DO - 10.1021/ma001151p VL - 34 IS - 6 SP - 1536-1538 SN - 1520-5835 ER - TY - JOUR TI - Surface prechlorination of anatase TiO(2) for enhanced photocatalytic oxidation of toluene and hexane AU - d'Hennezel, O AU - Ollis, DF T2 - HELVETICA CHIMICA ACTA AB - We report the influence of prechlorination of TiO2 powder on the activity for the photocatalyzed oxidation of hydrocarbons (toluene, hexane) and oxygenates (acetone, butan-1-ol). Water- and HCl-pretreated catalyst are prepared by impregnation of TiO2 powder in H2O and in HCl solutions, respectively, followed by drying at room temperature. X-Ray photoelectron spectroscopy (XPS) analysis demonstrates the surface prechlorination efficiency: 1 g of TiO2 impregnated with 3 ml of 3n HCl solution results in a chlorine surface concentration of 1.6%. Prechlorination results in a photo-oxidation-rate enhancement for toluene and hexane, no change for butan-1-ol, and inhibition for acetone. This pattern is the same as that demonstrated earlier by us when these reactants are co-fed with the chlorine source trichloroethylene (TCE). DA - 2001/// PY - 2001/// DO - 10.1002/1522-2675(20011114)84:11<3511::AID-HLCA3511>3.0.CO;2-K VL - 84 IS - 11 SP - 3511-3518 SN - 0018-019X ER - TY - JOUR TI - Spray-dried iron Fischer-Tropsch catalysts. 2. Effect of carburization on catalyst attrition resistance AU - Zhao, R AU - Goodwin, JG AU - Jothimurugesan, K AU - Gangwal, SK AU - Spivey, JJ T2 - INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH AB - Spray drying has been recently used by this research team in the preparation of Fe Fischer−Tropsch catalysts with higher attrition resistance for use in slurry bubble column reactors. In the first paper in this series, the effects of the type, concentration, and network structure of SiO2 on the attrition resistance of two series of spray-dried Fe catalysts in their calcined state were explored and the dependence of catalyst attrition resistance on catalyst particle density was discussed. As a continuation of our previous effort, the effect of carburization on catalyst attrition resistance was studied and is presented in this paper. After carburization, the majority component of the catalysts, hematite (Fe2O3), was converted to iron carbides, mostly χ-carbide (Fe2C5). Breakage of individual catalyst particles and fines formation, which can be considered as evidence of chemical attrition, was only observed during carburization of the catalyst with low SiO2 concentration <9 wt %. With an increase in the total concentration of SiO2, such chemical attrition during the Fe phase change appeared to be eliminated or negligible except for the breakup of large agglomerates during carburization. There were, generally, significant decreases in the Brunauer−Emmett−Teller surface areas and average particle sizes of the catalysts upon carburization. Surprisingly, carburization of these Fe catalysts did not weaken the particle structures with regards to physical attrition. In fact, depending on catalyst composition, the overall attrition resistances of the carburized catalysts measured using a jet cup system were similar to or better than those of the same catalysts in their calcined form. However, any seeming improvement in attrition resistance is suggested to be related mainly to the increase in catalyst particle density (related to catalyst inner structure) after carburization. DA - 2001/3/7/ PY - 2001/3/7/ DO - 10.1021/ie0006458 VL - 40 IS - 5 SP - 1320-1328 SN - 0888-5885 ER - TY - JOUR TI - Solubility and diffusivity of sodium chloride in phase-separated block copolymers of poly(2-dimethylaminoethyl methacrylate), poly (1,1'-dihydroperfluorooctyl methacrylate) and poly(1,1,2,2-tetrahydroperfluorooctyl acrylate) AU - Nagai, K AU - Tanaka, S AU - Hirata, Y AU - Nakagawa, T AU - Arnold, ME AU - Freeman, BD AU - Leroux, D AU - Betts, DE AU - DeSimone, JM AU - DiGiano, FA T2 - POLYMER AB - Solubility and diffusivity of sodium chloride were determined in a series of dense films of phase-separated diblock and triblock copolymers composed of poly(2-dimethylaminoethyl methacrylate) (PDMAEMA) and either poly(1,1′-dihydroperfluorooctyl methacrylate (PFOMA) or poly(1,1,2,2-tetrahydroperfluorooctyl acrylate) (PTAN). As the content of hydrophilic PDMAEMA increases in PDMAEMA-b-PFOMA films, total water uptake increases. The salt partition coefficient of these films increases with increasing PDMAEMA content and weight fraction of water in the PDMAEMA domains. In contrast, salt diffusivity is not monotonically correlated with PDMAEMA content and effective hydration. Triblock copolymers exhibit different values of total water uptake, total hydration, salt partition, and diffusion coefficients than those of diblock copolymers (PDMAEMA-b-PFOMA) at the same PDMAEMA concentration. The total water uptake of PFOMA-b-PDMAEMA-b-PFOMA copolymers is lower than that of PDMAEMA-b-PFOMA, while water uptake of PTAN-b-PDMAEMA-b-PTAN films is higher than that of PDMAEMA-b-PFOMA. Salt partition and diffusion coefficients increase monotonically with the amount of freezing water in the hydrophilic domains, suggesting that the state of water in the phase-separated block copolymers is an important factor influencing their salt uptake and transport properties. DA - 2001/12// PY - 2001/12// DO - 10.1016/S0032-3861(01)00549-3 VL - 42 IS - 25 SP - 9941-9948 SN - 0032-3861 KW - block copolymers KW - freezing water KW - salt transport ER - TY - JOUR TI - Reaction Kinetics of the Solid-State Polymerization of Poly(bisphenol A carbonate) Facilitated by Supercritical Carbon Dioxide AU - Shi, Chunmei AU - DeSimone, Joseph M. AU - Kiserow, Douglas J. AU - Roberts, George W. T2 - Macromolecules AB - The kinetics of solid-state polymerization (SSP) of poly(bisphenol A carbonate) was investigated with supercritical CO2 (scCO2) as the sweep fluid. The CO2 flow rate and polymer particle size were chosen to ensure that the kinetics was controlled by the rate of the forward transesterification reaction, i.e., so that both external and internal phenol diffusion limitations were negligible. The forward reaction rate constants were determined between 90 and 135 °C, at CO2 pressures of 138, 207, and 345 bar. At a given temperature, the reaction rate was higher with scCO2 as the sweep fluid than with N2, especially at lower temperatures. The rate constant for the forward transesterification reaction increased with increasing CO2 pressure up to about 207 bar, at which point the rate constant was no longer sensitive to CO2 pressure. The activation energy decreased from 23.9 kcal/mol in N2 to 15.5, 11.6, and 11.4 kcal/mol at CO2 pressures of 138, 207, and 345 bar, respectively. The effect of scCO2 on the rate of polymerization can be understood in terms of the solubility of CO2 in the polymer. DA - 2001/10// PY - 2001/10// DO - 10.1021/ma011068h VL - 34 IS - 22 SP - 7744-7750 J2 - Macromolecules LA - en OP - SN - 0024-9297 1520-5835 UR - http://dx.doi.org/10.1021/ma011068h DB - Crossref ER - TY - JOUR TI - Propane and propylene sorption in solid polymer electrolytes based on poly(ethylene oxide) and silver salts AU - Sunderrajan, S AU - Freeman, BD AU - Hall, CK AU - Pinnau, I T2 - JOURNAL OF MEMBRANE SCIENCE AB - The sorption of propylene and propane in solid polymer electrolytes based on blends of poly(ethylene oxide) (PEO) and silver nitrate, AgNO3, silver triflate, AgCF3SO3, silver trifluoroacetate, AgCF3CO2, or silver tetrafluoroborate, AgBF4, are reported. These solid polymer electrolytes exhibit preferential sorption for propylene over propane due to complexation of propylene with silver ions in the polymer matrix and reduced propane solubility in the solid polymer electrolyte films relative to that in PEO alone. The order of olefin solubility in blends containing 1 mol of silver ions per mole of ethylene oxide (EO) units is: AgBF4⪢AgCF3SO3>AgCF3CO2>AgNO3. At 35°C and 40 cmHg pressure, a PEO/AgBF4 film containing 1 mol of silver ions per mole of EO sorbed 5.3 g propylene but only 0.083 g propane per 100 g of solid polymer electrolyte. AgBF4 is highly soluble in PEO and completely disrupts polymer crystallinity even at low salt concentration (approximately 10 wt.%) without significantly altering the glass transition temperature. Other silver salts (e.g. AgNO3) do not dissolve completely in PEO and are much less effective at promoting enhanced olefin solubility. DA - 2001/2/15/ PY - 2001/2/15/ DO - 10.1016/S0376-7388(00)00569-X VL - 182 IS - 1-2 SP - 1-12 SN - 0376-7388 KW - olefin/paraffin separation KW - solid polymer electrolyte KW - poly(ethylene oxide) KW - facilitated transport ER - TY - JOUR TI - Preparing high-density polymer brushes by mechanically assisted polymer assembly AU - Wu, T AU - Efimenko, K AU - Genzer, J T2 - MACROMOLECULES AB - ADVERTISEMENT RETURN TO ISSUEPREVCommunication to the...Communication to the EditorNEXTPreparing High-Density Polymer Brushes by Mechanically Assisted Polymer AssemblyTao Wu, Kirill Efimenko, and Jan GenzerView Author Information Department of Chemical Engineering, North Carolina State University, Raleigh, North Carolina 27695-7905 Cite this: Macromolecules 2001, 34, 4, 684–686Publication Date (Web):January 12, 2001Publication History Received10 October 2000Revised4 December 2000Published online12 January 2001Published inissue 1 February 2001https://doi.org/10.1021/ma001750wCopyright © 2001 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views591Altmetric-Citations41LEARN 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. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit Read OnlinePDF (60 KB) Get e-AlertsSUBJECTS:Nitrogen,Polymer brushes,Polymers,Radical polymerization,X-ray absorption near edge spectroscopy Get e-Alerts DA - 2001/2/13/ PY - 2001/2/13/ DO - 10.1021/ma001750w VL - 34 IS - 4 SP - 684-686 SN - 1520-5835 ER - TY - JOUR TI - Platinum-containing hyper-cross-linked polystyrene as a modifier-free selective catalyst for L-sorbose oxidation AU - Sidorov, SN AU - Volkov, , IV AU - Davankov, VA AU - Tsyurupa, MP AU - Valetsky, PM AU - Bronstein, LM AU - Karlinsey, R AU - Zwanziger, JW AU - Matveeva, VG AU - Sulman, EM AU - Lakina, NV AU - Wilder, EA AU - Spontak, RJ T2 - JOURNAL OF THE AMERICAN CHEMICAL SOCIETY AB - Impregnation of hyper-cross-linked polystyrene (HPS) with tetrahydrofuran (THF) or methanol (ML) solutions containing platinic acid results in the formation of Pt(II) complexes within the nanocavities of HPS. Subsequent reduction of the complexes by H2 yields stable Pt nanoparticles with a mean diameter of 1.3 nm in THF and 1.4 nm in ML. The highest selectivity (98% at 100% conversion) measured during the catalytic oxidation of L-sorbose in water is obtained with the HPS-Pt-THF complex prior to H2 reduction. During an induction period of about 100 min, L-sorbose conversion is negligible while catalytic species develop in situ. The structure of the catalyst isolated after the induction period is analyzed by X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy. Electron micrographs reveal a broad distribution of Pt nanoparticles, 71% of which measure less than or equal to 2.0 nm in diameter. These nanoparticles are most likely responsible for the high catalytic activity and selectivity observed. The formation of nanoparticles measuring up to 5.9 nm in diameter is attributed to the facilitated intercavity transport and aggregation of smaller nanoparticles in swollen HPS. The catalytic properties of these novel Pt nanoparticles are highly robust, remaining stable even after 15 repeated uses. DA - 2001/10/31/ PY - 2001/10/31/ DO - 10.1021/ja0107834 VL - 123 IS - 43 SP - 10502-10510 SN - 0002-7863 ER - TY - JOUR TI - Physiologically based pharmacokinetic modeling of benzene metabolism in mice through extrapolation from in vitro to in vivo AU - Cole, CE AU - Tran, HT AU - Schlosser, PM T2 - JOURNAL OF TOXICOLOGY AND ENVIRONMENTAL HEALTH-PART A AB - Benzene (C6H6) is a highly flammable, colorless liquid. Ubiquitous exposures result from its presence in gasoline vapors, cigarette smoke, and industrial processes. Benzene increases the incidence of leukemia in humans when they are exposed to high doses for extended periods; however, leukemia risks in humans at low exposures are uncertain. The exposure-dose-response relationship of benzene in humans is expected to be nonlinear because benzene undergoes a series of metabolic transformations, detoxifying and activating, in the liver, resulting in multiple metabolites that exert toxic effects on the bone marrow. We developed a physiologically based pharmacokinetic model for the uptake and elimination of benzene in mice to relate the concentration of inhaled and orally administered benzene to the tissue doses of benzene and its key metabolites, benzene oxide, phe nol, and hydroquinone. As many parameter values as possible were taken from the literature; in particular, metabolic parameters obtained from in vitro studies with mouse liver were used since comparable parameters are also available for humans. Parameters estimated by fitting the model to published data were first-order rate constants for pathways lacking in vitro data and the concentrations of microsomal and cytosolic protein, which effectively alter overall enzyme activity. The model was constrained by using the in vitro metabolic parameters (maximum velocities, first-order rate constants, and saturation parameters), and data from multiple laboratories and experiments were used. Despite these constraints and sources of variability, the model simulations matched the data reasonably well in most cases, showing that in vitro metabolic constants can be successfully extrapolated to predict in vivo data for benzene metabolism and dosimetry. Therefore in vitro metabolic constants for humans can subsequently be extrapolated to predict the dosimetry of benzene and its metabolites in humans. This will allow us to better estimate the risks of adverse effects from low-level benzene exposures. DA - 2001/3// PY - 2001/3// DO - 10.1080/00984100150501178 VL - 62 IS - 6 SP - 439-465 SN - 1528-7394 ER - TY - JOUR TI - Nitrogen incorporation in ultrathin gate dielectrics: A comparison of He/N2O and He/N-2 remote plasma processes AU - Khandelwal, A AU - Smith, BC AU - Lamb, HH T2 - JOURNAL OF APPLIED PHYSICS AB - Ultrathin Si oxynitride films grown by low-temperature remote plasma processing were examined by on-line Auger electron spectroscopy and angle-resolved x-ray photoelectron spectroscopy to determine the concentration, spatial distribution, and chemical bonding of nitrogen. The films were grown at 300 °C on Si(100) substrates using two radio-frequency remote plasma processes: (i) He/N2O remote plasma-assisted oxidation (RPAO) and (ii) two-step remote plasma oxidation/nitridation. A 5 min He/N2O RPAO process produces a 2.5 nm oxynitride film incorporating approximately 1 monolayer of nitrogen at the Si–SiO2 interface. The interfacial nitrogen is bonded in a N–Si3 configuration, as in silicon nitride (Si3N4). By comparison, a 90 s He/N2 remote plasma exposure of a 1 nm oxide (grown by 10 s He/O2 RPAO) consumes substrate Si atoms creating a 1 nm subcutaneous Si3N4 layer. The nitrogen areal density obtained via the two-step process depends on the initial oxide thickness and the He/N2 remote plasma exposure time. Moreover, as the oxide thickness is increased (by increasing the He/O2 remote plasma exposure), the nitrogen distribution shifts away from the Si–SiO2 interface and into the oxide. More nitrogen with a tighter distribution is incorporated using He versus Ar dilution. Insight into the remote plasma chemistry was provided by optical emission spectroscopy. Strong N2 first positive and second positive emission bands were observed for He/N2O and He/N2 remote plasmas indicating the presence of N2 metastables and ground-state N atoms. DA - 2001/9/15/ PY - 2001/9/15/ DO - 10.1063/1.1397286 VL - 90 IS - 6 SP - 3100-3108 SN - 0021-8979 ER - TY - JOUR TI - Mixed-gas permeation of syngas components in poly(dimethylsiloxane) and poly(1-trimethylsilyl-1-propyne) at elevated temperatures AU - Merkel, TC AU - Gupta, RP AU - Turk, BS AU - Freeman, BD T2 - JOURNAL OF MEMBRANE SCIENCE AB - The permeability of poly(dimethylsiloxane) (PDMS) and poly(1-trimethylsilyl-1-propyne) (PTMSP) to a simulated syngas feed containing H2, CO, CO2, and H2S was determined as a function of temperature up to 240°C (464°F). The permeation properties of rarely studied CO and H2S were found to be consistent with their molecular properties (i.e. critical temperature) in both rubbery PDMS and high free volume, glassy PTMSP. At room temperature, PDMS and PTMSP are more permeable to the more condensable gases CO2 and H2S than to H2. However, both polymers become hydrogen selective at elevated temperatures. Activation energies of permeation are highest for H2 in both polymers and decrease regularly with increasing gas condensability. PTMSP exhibits evidence of accelerated physical aging at high temperature. DA - 2001/9/30/ PY - 2001/9/30/ DO - 10.1016/S0376-7388(01)00452-5 VL - 191 IS - 1-2 SP - 85-94 SN - 0376-7388 KW - poly(dimethylsiloxane) KW - poly(1-trimethylsilyl-1-propyne) KW - permeability KW - activation energy of permeation KW - syngas KW - hydrogen sulfide ER - TY - JOUR TI - Gas permeation properties of poly(1,1 '-dihydroperfluorooctyl acrylate), poly(1,1 '-dihydroperfluorooetyl methacrylate), and poly(styrene)-b-poly(1,1 '-dihydroperfluorooctyl acrylate) block copolymers AU - Arnold, ME AU - Nagai, K AU - Freeman, BD AU - Spontak, RJ AU - Betts, DE AU - DeSimone, JM AU - Pinnau, I T2 - MACROMOLECULES AB - The permeabilities of rubbery poly(1,1‘-dihydroperfluorooctyl acrylate) (PFOA), glassy poly(1,1‘-dihydroperfluorooctyl methacrylate) (PFOMA), and poly(styrene)-b-poly(1,1‘-dihydroperfluorooctyl acrylate) (PS-b-PFOA) diblock copolymers to N2, O2, H2, CH4, C2H6, and CO2 at 446 kPa and to C3H8 at 308 kPa are reported as a function of temperature. In general, PFOMA has lower fractional free volume, smaller gas permeability coefficients, and larger activation energies of permeation than PFOA, consistent with the more restricted long-range segmental mobility of PFOMA. The PS-b-PFOA copolymers exhibit complex microphase-separated morphologies, and their gas permeability coefficients are intermediate between those of glassy PS and rubbery PFOA, decreasing in magnitude with increasing PS content. DA - 2001/7/31/ PY - 2001/7/31/ DO - 10.1021/ma010355i VL - 34 IS - 16 SP - 5611-5619 SN - 0024-9297 ER - TY - JOUR TI - Broadening of molecular-weight distribution in solid-state polymerization resulting from condensate diffusion AU - Goodner, MD AU - Gross, SM AU - Desimone, JM AU - Roberts, GW AU - Kiserow, DJ T2 - JOURNAL OF APPLIED POLYMER SCIENCE AB - A kinetic model for the solid-state polymerization of poly(bisphenol A carbonate) in a single particle has been developed and used to investigate the broadening of molecular-weight distribution as a result of slow condensate diffusion. The model is based on melt-phase transesterification kinetics and Fickian diffusion of phenol, the condensate, in the amorphous regions of the semicrystalline particle. Model predictions compare favorably to experimental data. When diffusion is slow compared to reaction, a condensate concentration gradient is established. This gradient induces a molecular-weight gradient, which results in a broadened overall molecular-weight distribution with an overall polydispersity above the theoretical limit for homogenous step-growth polymerization. As the mass transfer resistance inside the particle is decreased, the average molecular weight increases faster with time, and the overall polydispersity decreases. A stoichiometric imbalance of end groups decreases the obtainable molecular weight but mitigates the deleterious effects of slow condensate diffusion. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 928–943, 2001 DA - 2001/1/31/ PY - 2001/1/31/ DO - 10.1002/1097-4628(20010131)79:5<928::AID-APP170>3.0.CO;2-X VL - 79 IS - 5 SP - 928-943 SN - 0021-8995 KW - diffusion KW - molecular-weight distribution KW - phenol KW - poly(bisphenol A carbonate) KW - solid-state polymerization KW - stoichiometry ER - TY - JOUR TI - Bivalent cations and amino-acid composition contribute to the thermostability of Bacillus licheniformis xylose isomerase AU - Vieille, C AU - Epting, KL AU - Kelly, RM AU - Zeikus, JG T2 - EUROPEAN JOURNAL OF BIOCHEMISTRY AB - Comparative analysis of genome sequence data from mesophilic and hyperthermophilic micro-organisms has revealed a strong bias against specific thermolabile amino-acid residues (i.e. N and Q) in hyperthermophilic proteins. The N + Q content of class II xylose isomerases (XIs) from mesophiles, moderate thermophiles, and hyperthermophiles was examined. It was found to correlate inversely with the growth temperature of the source organism in all cases examined, except for the previously uncharacterized XI from Bacillus licheniformis DSM13 (BLXI), which had an N + Q content comparable to that of homologs from much more thermophilic sources. To determine whether BLXI behaves as a thermostable enzyme, it was expressed in Escherichia coli, and the thermostability and activity properties of the recombinant enzyme were studied. Indeed, it was optimally active at 70-72 degrees C, which is significantly higher than the optimal growth temperature (37 degrees C) of B. licheniformis. The kinetic properties of BLXI, determined at 60 degrees C with glucose and xylose as substrates, were comparable to those of other class II XIs. The stability of BLXI was dependent on the metallic cation present in its two metal-binding sites. The enzyme thermostability increased in the order apoenzyme < Mg2+-enzyme < Co2+-enzyme approximately Mn2+-enzyme, with melting temperatures of 50.3 degrees C, 53.3 degrees C, 73.4 degrees C, and 73.6 degrees C. BLXI inactivation was first-order in all conditions examined. The energy of activation for irreversible inactivation was also strongly influenced by the metal present, ranging from 342 kJ x mol(-1) (apoenzyme) to 604 kJ x mol(-1) (Mg2+-enzyme) to 1166 kJ x mol(-1) (Co2+-enzyme). These results suggest that the first irreversible event in BLXI unfolding is the release of one or both of its metals from the active site. Although N + Q content was an indicator of thermostability for class II XIs, this pattern may not hold for other sets of homologous enzymes. In fact, the extremely thermostable alpha-amylase from B. licheniformis was found to have an average N + Q content compared with homologous enzymes from a variety of mesophilic and thermophilic sources. Thus, it would appear that protein thermostability is a function of more complex molecular determinants than amino-acid content alone. DA - 2001/12// PY - 2001/12// DO - 10.1046/j.0014-2956.2001.02587.x VL - 268 IS - 23 SP - 6291-6301 SN - 0014-2956 KW - Bacillus licheniformis KW - metal binding KW - thermostability KW - xylose isomerase ER - TY - JOUR TI - Synthesis of high molecular weight polycarbonate by solid-state polymerization AU - Gross, SM AU - Roberts, GW AU - Kiserov, DJ AU - DeSimone, JM T2 - MACROMOLECULES AB - The solid-state polymerization (SSP) of small particles (20 μm) of poly(bisphenol A carbonate) resulted in high molecular weight material (Mw of 36 000 g/mol). Molecular weight distribution broadening was not observed in polycarbonate in the form of small granulated powders but did occur in large polycarbonate beads (3.6 mm diameter). We hypothesize that this broadening is due to slow diffusion of phenol inside the larger polymer particles. A systematic investigation of the role of CO2 pressure and temperature was performed. It was found that the increase in molecular weight was a strong function of CO2 pressure and temperature. Additionally, the chain extension reactions occurred faster at higher supercritical CO2 flow rates. The SSP of polycarbonate in the presence of supercritical CO2 can be accomplished at temperatures as low as 90 °C, which is 60 °C lower than the Tg of polycarbonate at normal conditions. This should suppress the side reactions that lead to color body formation, thereby resulting in a product with good optical clarity and color. DA - 2001/6/5/ PY - 2001/6/5/ DO - 10.1021/ma001958h VL - 34 IS - 12 SP - 3916-3920 SN - 1520-5835 ER - TY - JOUR TI - On the similarity of macromolecular responses to high-energy processes: mechanical milling vs. irradiation AU - Smith, AP AU - Spontak, RJ AU - Ade, H T2 - POLYMER DEGRADATION AND STABILITY AB - Recent efforts to blend and compatibilize intrinsically immiscible polymers in the solid state by high-energy methods have shown that macromolecules may undergo scission, crosslinking or amorphization, depending on the chemical nature of the repeat unit, the processing temperature and the initial degree of polymer crystallinity. Identical process-induced molecular and structural modifications have been previously observed in polymers exposed to large doses of electron and γ radiation, suggesting that the responses of polymers to high-energy processes may be mechanistically similar. In this work, we explore a variety of similarities between mechanically-milled and irradiated polymers in terms of molecular characteristics, process temperature and polymer crystallinity, and we demonstrate that these similarities provide predictive guidance for the selection of polymers to be subjected to solid-state processing. DA - 2001/// PY - 2001/// DO - 10.1016/S0141-3910(01)00055-6 VL - 72 IS - 3 SP - 519-524 SN - 0141-3910 KW - mechanical milling KW - solid-state processing KW - chemical structure KW - radiation damage ER - TY - JOUR TI - Copolymer adsorption on planar substrates with a random distribution of chemical heterogeneities AU - Genzer, J T2 - JOURNAL OF CHEMICAL PHYSICS AB - We use a 3D SCF model of polymer adsorption to investigate the adsorption of A-B copolymers from A-B/homopolymer A mixtures onto planar substrates composed of two chemically distinct randomly distributed sites, one of which has a preferential affinity for the B segments of the copolymer. Our results show that when the chemically heterogeneous substrate motifs are recognized by the copolymer, the copolymers can transcript them with a relatively high fidelity into three dimensions. The way the surface motif is transferred is strongly dictated by the copolymer sequence. We show that block copolymers are capable of detecting small clusters of the substrate adsorption sites. The fidelity of the pattern shape and the distance from the substrate to which the pattern gets transferred increases with decreasing the length of the adsorbing block of the copolymer. Our results also indicate that increasing (i) the interactions between the copolymer adsorbing segments and the “sticky” points at the substrate, and/or (ii) the repulsion between the copolymer segments increases the total adsorbed amount of the copolymer at the mixture/substrate interface but it decreases the fidelity of the substrate chemical pattern transfer into the mixture. We show that, in contrast to the block copolymers, macromolecules with alternating sequence distributions adopt different conformations on random substrates in that they tend to localize at the boundaries between the C/D surface sites, where the substrate chemical pattern more closely matches the sequence distribution of the B stickers along the copolymer. We claim that this feature allows us to use alternating copolymers in situations where one needs to suppress the chemical pattern transfer on such random substrates. DA - 2001/9/8/ PY - 2001/9/8/ DO - 10.1063/1.1391254 VL - 115 IS - 10 SP - 4873-4882 SN - 1089-7690 ER - TY - JOUR TI - A review of quantitative studies of benzene metabolism AU - Lovern, MR AU - Cole, CE AU - Schlosser, PM T2 - CRITICAL REVIEWS IN TOXICOLOGY AB - Benzene is a ubiquitous, highly flammable, colorless liquid that is a known hematotoxin, myelotoxin, and human leukemogen. Benzene-induced toxicity in animals is clearly mediated by its metabolism. The mechanisms of acute hemato- and myelotoxicity in humans are almost certainly the same as in animals, and there is compelling evidence that metabolism is requisite for the induction of leukemia in humans. A very large number of experimental investigations of benzene metabolism have been conducted with animals, both in vivo and in vitro. There have also been many investigations of benzene metabolism in humans and with human tissues, Although the blood or tissue concentrations of benzene metabolites in humans resulting from benzene exposure have never been measured. Further, a number of mathematical models of benzene metabolism and dosimetry have been developed. In this article, we consider results from both experimental and mathematical modeling research, with particular emphasis on the last decade, and discuss the factors that are likely to be most influential in the metabolism of benzene. DA - 2001/// PY - 2001/// DO - 10.1080/20014091111703 VL - 31 IS - 3 SP - 285-311 SN - 1547-6898 ER - TY - JOUR TI - Freezing behavior in porous materials: Theory and experiments AU - Sliwinska-Bartkowiak, M. AU - Dudziak, G. AU - Sikorski, R. AU - Gras, R. AU - Gubbins, K. E. AU - Radhakrishnan, R. AU - Kaneko, K. T2 - Polish Journal of Chemistry DA - 2001/// PY - 2001/// VL - 75 IS - 4 SP - 547-555 ER - TY - JOUR TI - Dynamic rheological behavior of DBS-induced poly(propylene glycol) physical gels AU - Mercurio, DJ AU - Khan, SA AU - Spontak, RJ T2 - RHEOLOGICA ACTA DA - 2001/1// PY - 2001/1// DO - 10.1007/s003970000119 VL - 40 IS - 1 SP - 30-38 SN - 1435-1528 KW - physical gels KW - dibenzylidene sorbitol KW - network recovery KW - nanofibrils KW - organogels ER - TY - JOUR TI - Dielectric studies of freezing behavior in porous materials: Water and methanol in activated carbon fibres AU - Sliwinska-Bartkowiak, M AU - Dudziak, G AU - Sikorski, R AU - Gras, R AU - Gubbins, KE AU - Radhakrishnan, R T2 - PHYSICAL CHEMISTRY CHEMICAL PHYSICS AB - We report both experimental measurements and molecular simulations of the melting and freezing behavior of two dipolar fluids, water and methanol, in activated carbon fibres. Differential scanning calorimetry (DSC) and dielectric relaxation spectroscopy (DS) were used to determine the melting point in these porous materials. The melting point was found to be very sensitive to the relative strength of the fluid–wall interaction compared to the fluid–fluid interaction. Monte Carlo simulations and the Landau free energy formalism were used to determine the shift in the melting point, Tm, for simple fluids in pores having weakly attractive and strongly attractive walls. The strength of the interaction of the fluid with the pore wall is shown to have a large effect on the shift in Tm, with Tm being reduced for weakly attracting walls and elevated for strongly attracting walls. DA - 2001/// PY - 2001/// DO - 10.1039/b009792f VL - 3 IS - 7 SP - 1179-1184 SN - 1463-9076 ER - TY - JOUR TI - alpha-helix formation: Discontinuous molecular dynamics on an intermediate-resolution protein model AU - Smith, AV AU - Hall, CK T2 - PROTEINS-STRUCTURE FUNCTION AND BIOINFORMATICS AB - Abstract An intermediate‐resolution model of small, homogeneous peptides is introduced, and discontinuous molecular dynamics simulation is applied to study secondary structure formation. Physically, each model residue consists of a detailed three‐bead backbone and a simplified single‐bead side‐chain. Excluded volume and hydrogen bond interactions are constructed with discontinuous (i.e., hard‐sphere and square‐well) potentials. Simulation results show that the backbone motion of the model is limited to realistic regions of Φ–Ψ conformational space. Model polyalanine chains undergo a locally cooperative transition to form α‐helices that are stabilized by backbone hydrogen bonding, while model polyglycine chains tend to adopt nonhelical structures. When side‐chain size is increased beyond a critical diameter, steric interactions prevent formation of long α‐helices. These trends in helicity as a function of residue type have been well documented by experimental, theoretical, and simulation studies and demonstrate the ability of the intermediate‐resolution model developed in this work to accurately mimic realistic peptide behavior. The efficient algorithm used permits observation of the complete helix–coil transition within 15 min on a single‐processor workstation, suggesting that simulations of very long times are possible with this model. Proteins 2001;44:344–360. © 2001 Wiley‐Liss, Inc. DA - 2001/8/15/ PY - 2001/8/15/ DO - 10.1002/prot.1100 VL - 44 IS - 3 SP - 344-360 SN - 1097-0134 KW - helix-coil transition KW - computer simulation KW - four-bead protein model ER - TY - JOUR TI - Time-dependent Si etch behavior and its effect on oxide/Si selectivity in CF4+D-2 electron cyclotron resonance plasma etching AU - Min, K AU - Lamb, HH AU - Hauser, , JR T2 - JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B AB - Transient poly-Si etching behavior in CF4+D2 electron cyclotron resonance plasmas containing different D2 proportions was investigated. Higher D2 proportions resulted in lower atomic F and higher CF2 concentration in the plasma, as evidenced by optical emission spectroscopy (OES), and in greater oxide-to-Si etch selectivity. A high initial poly-Si etch rate that declined very rapidly to a finite-steady-state value was observed for plasma etching under conditions giving low (3:1) oxide-to-Si etch selectivity. In contrast, a lower initial etch rate that declined to approximately zero over a longer (∼45 s) period was observed for poly-Si etching under plasma conditions giving (∼15:1) selectivity. In the latter case, Si consumption during overetching would be significantly underestimated if calculated on the basis of the conventional 60 s selectivity ration. X-ray photoelectron spectroscopy analysis indicated that a thick, more F-deficient fluorocarbon film was deposited on Si under the high-selectivity etching conditions. Real-time SiF4 and atomic F signals, which were measured during SiO2 etching using OES and mass spectroscopy, respectively, evidenced significantly different end-point trends for the high- and low-selectivity etching conditions. These trends are interpreted in light of the transient etching behavior observed for poly-Si under equivalent plasma conditions. DA - 2001/// PY - 2001/// DO - 10.1116/1.1371318 VL - 19 IS - 3 SP - 695-700 SN - 1071-1023 ER - TY - JOUR TI - Identification of peptide ligands generated by combinatorial chemistry that bind alpha-lactalbumin AU - Gurgel, PV AU - Carbonell, RG AU - Swaisgood, HE T2 - SEPARATION SCIENCE AND TECHNOLOGY AB - α-Lactalbumin is a whey protein with high digestibility and low potential for causing allergic problems in infants, making it a strong candidate for use in infant formulas. The development of an efficient and scalable process for isolation of α-lactalbumin is necessary to allow its use on a large scale. Affinity chromatography using short peptides as ligands is a promising technique because it allows the recovery of specific proteins without the use of harsh chemicals or problems due to ligand release. In the present paper we describe the identification of the hexapeptide WHWRKR, obtained from a combinatorial library, that shows affinity for α-lactalbumin. DA - 2001/// PY - 2001/// DO - 10.1081/SS-100106100 VL - 36 IS - 11 SP - 2411-2431 SN - 0149-6395 ER - TY - JOUR TI - Hysteresis and the dynamic phase transition in thin ferromagnetic films - art. no. 066119 AU - Jang, H. B. AU - Grimson, M. J. T2 - Physical Review. E, Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics DA - 2001/// PY - 2001/// VL - 6306 IS - 6 SP - 6119 ER - TY - JOUR TI - Galactomannanases man2 and man5 from Thermotoga species: Growth physiology on galactomannans, gene sequence analysis, and biochemical properties of recombinant enzymes AU - Parker, KN AU - Chhabra, , SR AU - Lam, D AU - Callen, W AU - Duffaud, GD AU - Snead, MA AU - Short, JM AU - Mathur, EJ AU - Kelly, RM T2 - BIOTECHNOLOGY AND BIOENGINEERING AB - Abstract The enzymatic hydrolysis of mannan‐based hemicelluloses is technologically important for applications ranging from pulp and paper processing to food processing to gas and oil well stimulation. In many cases, thermostability and activity at elevated temperatures can be advantageous. To this end, the genes encoding β‐mannosidase ( man2 ) and β‐mannanase ( man5 ) from the hyperthermophilic bacteria Thermotoga neapolitana 5068 and Thermotoga maritima were isolated, cloned, and expressed in Escherichia coli. The amino acid sequences for the mannosidases from these organisms were 77% identical and corresponded to proteins with an M r of approximately 92 kDa. The translated nucleotide sequences for the β‐mannanase genes ( man5 ) encoded polypeptides with an M r of 76 kDa that exhibited 84% amino acid sequence identity. The recombinant versions of Man2 and Man5 had similar respective biochemical and biophysical properties, which were also comparable to those determined for the native versions of these enzymes in T. neapolitana. The optimal temperature and pH for the recombinant Man2 and Man5 from both organisms were approximately 90°C and 7.0, respectively. The presence of Man2 and Man5 in these two Thermotoga species indicates that galactomannan is a potential growth substrate. This was supported by the fact that β‐mannanase and β‐mannosidase activities were significantly stimulated when T. neapolitana was grown on guar or carob galactomannan. Maximum cell densities increased by at least tenfold when either guar or carob galactomannan was added to the growth medium. For T. neapolitana grown on guar at 83°C, Man5 was secreted into the culture media, whereas Man2 was intracellular. These localizations were consistent with the presence and lack of signal peptides for Man5 and Man2, respectively. The identification of the galactomannan‐degrading enzymes in these Thermotoga species adds to the list of biotechnologically important hemicellulases produced by members of this hyperthermophilic genera. © 2001 John Wiley & Sons, Inc. Biotechnol Bioeng 75: 322–333, 2001. DA - 2001/11/5/ PY - 2001/11/5/ DO - 10.1002/bit.10020 VL - 75 IS - 3 SP - 322-333 SN - 0006-3592 KW - Thermotoga KW - hyperthermophile KW - hemicellulase KW - glycosyl hydrolase KW - galactomannan KW - beta-mannanase KW - beta-mannosidase ER - TY - JOUR TI - Fiber optic flow and cure sensing for liquid composite molding AU - Dunkers, JP AU - Lenhart, JL AU - Kueh, , SR AU - Zanten, JH AU - Advani, SG AU - Parnas, RS T2 - OPTICS AND LASERS IN ENGINEERING AB - The Polymer Composites group at the National Institute of Standards and Technology has efforts in both on-line flow and cure sensing for liquid composite molding. For our flow program, a novel fiber optic real-time sensor system has been developed that can sense resin at various locations on a single fiber using long-period gratings and a polychromatic source. The sensor operation and characterization will be discussed along with sensor performance during mold filling with various types of reinforcement. The cure sensing program focuses on the interface-sensitive fluorescence response of a dye molecule grafted to a high-index glass fiber. The fluorescence emission of the fluorophore undergoes a blue shift as the resin cures. The fluorescence sensor is made by grafting a silane functional fluorophore onto the surface of the glass with close attention to layer thickness. Fluorescence emission of the grafted fluorophore film is shown to be sensitive to epoxy resin cure, co-silane, and layer thickness. The response of the grafted fluorophore to cure on a high-index fiber is demonstrated. DA - 2001/2// PY - 2001/2// DO - 10.1016/S0143-8166(00)00110-X VL - 35 IS - 2 SP - 91-104 SN - 0143-8166 KW - sensor KW - flow KW - long-period gratings KW - cure KW - fluorescence KW - fiber optic KW - liquid composite molding ER - TY - JOUR TI - Effect of colloidal fillers on the cross-linking of a UV-curable polymer: Gel point rheology and the Winter-Chambon criterion AU - Chiou, BS AU - Raghavan, , SR AU - Khan, SK T2 - MACROMOLECULES AB - The effect of colloidal silica fillers on the cross-linking behavior of a model UV-curable polymer system (thiol−ene) is studied using in situ rheology and real-time FTIR spectroscopy. The validity of the Winter−Chambon criterion (convergence of the loss tangents at the gel point) is examined for the cross-linking of these filled polymers, some of which are strongly flocculated dispersions (physical gels) prior to chemical cross-linking. Two different types of colloidal silica particles are studied: one with octyl chains tethered to the surface and the other with methyl surface groups. The Winter−Chambon criterion is satisfied for all samples containing the methyl-terminated silica. However, the criterion breaks down for samples containing the octyl-modified silica, with the loss tangents not converging at any single point. This suggests the absence of a self-similar critical gel at the gel point in the latter case. Neither type of silica particles alters the mechanism of the cross-linking reaction, as revealed by FTIR spectroscopy, but they do retard the cross-linking kinetics. An alternate method is suggested for determining the chemical gel point of filled systems that fail to obey the Winter−Chambon criterion. This method involves monitoring the critical strain (limit of the linear viscoelastic region) at various UV exposure times. A dramatic increase is observed in the critical strain at the gel point, indicating a transition from weak, physical bonds to strong, covalent cross-links. DA - 2001/6/19/ PY - 2001/6/19/ DO - 10.1021/ma010281a VL - 34 IS - 13 SP - 4526-4533 SN - 1520-5835 ER - TY - JOUR TI - Assembly of a tetrameric α-Helical bundle: Computer simulations on an intermediate-resolution protein model AU - Marchut, A.J. AU - Smith, A.V. AU - Hall, C.K. T2 - Proteins: Structure, Function, and Genetics AB - Abstract Discontinuous molecular dynamics (DMD) simulation on an intermediate‐resolution protein model is used to study the folding of an isolated, small model peptide to an amphipathic α‐helix and the assembly of four of these model peptides into a four‐helix bundle. A total of 129 simulations were performed on the isolated peptide, and 50 simulations were performed on the four‐peptide system. Simulations efficiently sample conformational space allowing complete folding trajectories from random initial configurations to be observed within 15 min for the one‐peptide system and within 15 h for the four‐peptide system on a 500‐MHz workstation. The native structures of both the α‐helix and the four‐helix bundle are consistent with experimental characterization studies and with results from previous simulations on these model peptides. In both the one‐ and four‐peptide systems, the native state is achieved during simulations within an optimal temperature range, a phenomenon also observed experimentally. The ease with which our simulations yield reasonable estimates of folded structures demonstrates the power of the intermediate‐resolution model developed for this work and the DMD algorithm and suggests that simulations of very long times and of multiprotein systems may be possible with this model. Proteins 2001;44:376–391. © 2001 Wiley‐Liss, Inc. DA - 2001/// PY - 2001/// DO - 10.1002/prot.1103 VL - 44 IS - 3 SP - 376-391 SN - 0887-3585 1097-0134 UR - http://dx.doi.org/10.1002/prot.1103 KW - discontinuous molecular dynamics KW - protein folding KW - protein misfolding ER - TY - JOUR TI - Well-defined glycopolyrner amphiphiles for liquid and supercritical carbon dioxide applications AU - Ye, WJ AU - Wells, S AU - DeSimone, JM T2 - JOURNAL OF POLYMER SCIENCE PART A-POLYMER CHEMISTRY AB - Abstract Well‐defined D ‐glucose‐containing glycopolymers, poly(3‐ O ‐methacryloyl‐1,2 : 5,6‐di‐ O ‐isopropylidene‐ D ‐glucofuranose) (PMAIpGlc), and diblock copolymers of PMAIpGlc with poly(1,1‐dihydroperfluorooctyl methacrylate) (PFOMA) were synthesized by living anionic polymerization in THF at −78 °C with 1,1‐diphenylhexyllithium in the presence of lithium chloride. The resulting polymers were found to possess predictable molecular weights and very narrow molecular weight distributions (MWD, M w / M n ≤ 1.16). Removal of the acetal protective groups from the protected glycopolymer block copolymer was carried out using 90% trifluoroacetic acid at room temperature, yielding a hydrophilic block copolymer with pendant glucose moieties. Both protected (lipophilic/CO 2 ‐philic) and deprotected (hydrophilic/CO 2 ‐philic) fluorocopolymers were proved to be CO 2 amphiphiles. Their solubility in CO 2 was heavily influenced by the amphiphilic structure, such as the copolymer compositions and the polarities of sugar block. Light‐scattering studies showed that, after removal of the protective groups, the deprotected block copolymer formed aggregate structures in liquid CO 2 with an average micellar size of 27 nm. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3841–3849, 2001 DA - 2001/11/1/ PY - 2001/11/1/ DO - 10.1002/pola.10018 VL - 39 IS - 21 SP - 3841-3849 SN - 0887-624X KW - anionic polymerization KW - glycopolymers KW - block copolymers KW - amphiphiles ER - TY - JOUR TI - Ordering of cylindrical microdomains in thin films of hybrid isotropic/liquid crystalline triblock copolymers AU - Figueiredo, P AU - Geppert, S AU - Brandsch, R AU - Bar, G AU - Thomann, R AU - Spontak, RJ AU - Gronski, W AU - Samlenski, R AU - Muller-Buschbaum, P T2 - MACROMOLECULES AB - We have investigated the roles of liquid crystallinity (LC) and substrate interactions on the ordering of isotropic cylindrical microdomains in thin films of two hybrid isotropic/LC triblock copolymers. Each copolymer consists of polystyrene (PS) end blocks and a side-chain LC midblock that exhibits either a nematic or smectic mesophase up to temperatures beyond the glass transition temperature (Tg) of PS. In thin films measuring on the same order as the lattice period, the orientation of the cylinders relative to the substrate is sensitive to the interactions of the mesogens at internal microdomain boundaries and external interfaces. Upon annealing such copolymer films at temperatures below the LC → isotropic transition but above the PS Tg on a neutral NaCl substrate, the PS cylinders within the nematic matrix adopt a long-range parallel orientation, whereas those within the smectic matrix lie perpendicular to the substrate and exhibit liquidlike order. After long annealing times, the cylinders residing near the film surface within the smectic matrix reorganize from perpendicular to parallel orientation due to surface tension at the film/air interface. On a polished Si substrate that promotes homeotropic mesogen anchoring, the perpendicular cylindrical orientation within the smectic mesophase remains stable. DA - 2001/1/16/ PY - 2001/1/16/ DO - 10.1021/ma0011441 VL - 34 IS - 2 SP - 171-180 SN - 0024-9297 ER - TY - JOUR TI - Melting/freezing behavior of a fluid confined in porous glasses and MCM-41: Dielectric spectroscopy and molecular simulation AU - Sliwinska-Bartkowiak, M AU - Dudziak, G AU - Sikorski, R AU - Gras, R AU - Radhakrishnan, R AU - Gubbins, KE T2 - JOURNAL OF CHEMICAL PHYSICS AB - We report both experimental measurements and molecular simulations of the melting and freezing behavior of fluids in nanoporous media. The experimental studies are for nitrobenzene in the silica-based pores of controlled pore glass, Vycor, and MCM-41. Dielectric relaxation spectroscopy is used to determine melting points and the orientational relaxation times of the nitrobenzene molecules in the bulk and the confined phase. Monte Carlo simulations, together with a bond orientational order parameter method, are used to determine the melting point and fluid structure inside cylindrical pores modeled on silica. Qualitative comparison between experiment and simulation are made for the shift in the freezing temperatures and the structure of confined phases. From both the experiments and the simulations, it is found that the confined fluid freezes into a single crystalline structure for average pore diameters greater than 20σ, where σ is the diameter of the fluid molecule. For average pore sizes between 20σ and 15σ, part of the confined fluid freezes into a frustrated crystal structure with the rest forming an amorphous region. For pore sizes smaller than 15σ, even the partial crystallization did not occur. Our measurements and calculations show clear evidence of a novel intermediate “contact layer” phase lying between liquid and crystal; the contact layer is the confined molecular layer adjacent to the pore wall and experiences a deeper fluid–wall potential energy compared to the inner layers. We also find evidence of a liquid to “hexatic” transition in the quasi-two-dimensional contact layer at high temperatures. DA - 2001/1/8/ PY - 2001/1/8/ DO - 10.1063/1.1329343 VL - 114 IS - 2 SP - 950-962 SN - 0021-9606 ER - TY - JOUR TI - Deactivation of hydrodechlorination catalysts I. Experiments with 1.1.1-trichloroethane AU - Frankel, KA AU - Jang, BWL AU - Spivey, JJ AU - Roberts, GW T2 - APPLIED CATALYSIS A-GENERAL AB - In order to understand the cause(s) of catalyst deactivation, microreactor studies were carried out on the catalytic hydrodechlorination (HDC) of 1,1,1-trichloroethane (111-TCA) using a fixed-bed reactor divided into three segments. The catalysts studied were: ηδ-alumina, α-alumina, Pt/α-alumina, Pt/η-alumina, and Pt/ηδ-alumina. Experiments were carried out at atmospheric pressure over a temperature range of 423–623 K and at H2/111-TCA molar ratios between 10 and 99. Only the Pt-containing catalysts were able to remove all three Cl atoms from 111-TCA. However, increasing amounts of partially-dechlorinated compounds were formed as the Pt/ηδ-alumina and the Pt/η-alumina catalysts deactivated. The only product with ηδ-alumina was 1,1-dichloroethylene (11-DCE). The conversion of 111-TCA decreased more rapidly with time for Pt/ηδ-alumina than for ηδ-alumina without Pt. Much larger quantities of coke were formed on the Pt/ηδ-alumina than on the ηδ-alumina, at similar conditions. The ηδ-alumina was essentially completely regenerated by heating in flowing He at 773 K. The Pt/η-alumina was only partially regenerated by this technique. The apparent stability of the Pt/ηδ-alumina catalysts increased with increasing Pt concentration. Poisoning by hydrochloric acid, a reaction product, did not cause significant deactivation of either the ηδ-alumina or the Pt/ηδ-alumina catalysts. DA - 2001/1/8/ PY - 2001/1/8/ DO - 10.1016/S0926-860X(00)00577-9 VL - 205 IS - 1-2 SP - 263-278 SN - 0926-860X KW - deactivation KW - alumina KW - 1,1,1-trichloroethane KW - hydrodechlorination KW - platinum KW - coke ER - TY - JOUR TI - In situ cleaning of GaN/6H-SiC substrates in NH3 AU - McGinnis, AJ AU - Thomson, D AU - Davis, RF AU - Chen, E AU - Michel, A AU - Lamb, HH T2 - JOURNAL OF CRYSTAL GROWTH AB - Metalorganic chemical vapor deposition-grown GaN on 6H-SiC substrates were cleaned by annealing in an NH3 flux. Oxygen contamination was removed by thermal desorption, and carbon removal was facilitated by reaction with NH3. The GaN(0 0 0 1) surface after NH3 beam cleaning at 730°C was smooth with distinct atomic steps. The roughness (0.20 nm RMS) was only slightly greater than that of the untreated substrate (0.17 nm RMS). Carbon and oxygen concentrations were reduced to background levels (∼1 at%) by annealing in an NH3 flux at 800°C. The surface step structure was destroyed by annealing in an NH3 flux of 4×1015 cm−2 s−1 from a seeded supersonic beam; however, annealing in an NH3 flux of 7×1015 cm−2 s−1 from a leak valve inhibited surface roughening and produced a relatively smooth surface (0.28 nm RMS) with a 3×3 R30° reconstruction. We infer from the effects of annealing temperature and NH3 flux that the observed surface roughening is due to GaN decomposition. DA - 2001/1// PY - 2001/1// DO - 10.1016/s0022-0248(00)00947-7 VL - 222 IS - 3 SP - 452-458 SN - 0022-0248 KW - gallium nitride KW - surface preparation KW - ammonia KW - homoepitaxy ER - TY - JOUR TI - Effect of confinement on chemical reaction equilibria: The reactions 2NO <->(NO)(2) and N-2+3H(2)<-> 2NH(3) in carbon micropores AU - Turner, CH AU - Johnson, JK AU - Gubbins, KE T2 - JOURNAL OF CHEMICAL PHYSICS AB - We report reactive Monte Carlo (RMC) simulations of reaction equilibria for both the nitric oxide dimerization and the ammonia synthesis reactions. We have applied the RMC technique to both a single bulk phase and also to a two-phase system, composed of the bulk gas and a slit-shaped pore, with pore parameters chosen to model activated carbon fibers. We achieve close agreement with the experimentally measured conversions of nitric oxide and ammonia in the bulk phase. Both reactions involve a stoichiometric decrease in mole number, which should cause the yield of each to be enhanced by the increased density within the pore phase. We show that the effect of confinement on the yield of both reactions is significant, and is particularly dramatic for the nitric oxide reaction; in addition, the ammonia synthesis reaction is affected by the selective adsorption of nitrogen over hydrogen in the pore under certain conditions. DA - 2001/1/22/ PY - 2001/1/22/ DO - 10.1063/1.1328756 VL - 114 IS - 4 SP - 1851-1859 SN - 1089-7690 ER - TY - JOUR TI - Truth in advertising AU - Felder, R. M. T2 - CEE, Chemical Engineering Education DA - 2001/// PY - 2001/// VL - 35 IS - 1 SP - 25 ER - TY - JOUR TI - Technology-based instruction and cooperative learning AU - Felder, R. M. T2 - Interface (IEEE Education Society) DA - 2001/// PY - 2001/// IS - 2001 August SP - 2-3 ER - TY - JOUR TI - Monitoring DNA/poly-L-lysine polyplex formation with time-resolved multiangle laser light scattering AU - Lai, E AU - Zanten, JH T2 - BIOPHYSICAL JOURNAL AB - Nonviral DNA complexes show promise as alternative and attractive gene delivery vectors for treating genetic diseases. Nonviral DNA complexes are typically formed by combining DNA with various condensing/complexing agents such as lipids, polyelectrolytes, polymers, polypeptides, and surfactants in solution. DNA/poly-L-lysine polyplex formation kinetics are probed by time-resolved multiangle laser light scattering (TR-MALLS), which yields the time evolution of the supramolecular complex mass and geometric size. Primary polyplexes whose geometric size is smaller than individual DNA molecules in solution are formed very rapidly upon mixing DNA and poly-L-lysine. Over time, these primary polyplexes aggregate into larger structures whose ultimate size is determined primarily by the relative concentrations of DNA and poly-L-lysine. This final polyplex size varies with the DNA/poly-L-lysine mass ratio in a non-monotonic fashion, with the maximum polyplex size occurring at a DNA/poly-L-lysine mass ratio of approximately two to three (charge ratio near unity). The utility of TR-MALLS for monitoring the temporal evolution of DNA loading and supramolecular complex size growth (mean square radius and molar mass) throughout the DNA/poly-L-lysine polyplex formation process is demonstrated. The polyplex DNA loading and size, both geometric and molar mass, are key to understanding the transfection process and for developing optimal gene therapy vectors. DA - 2001/2// PY - 2001/2// DO - 10.1016/s0006-3495(01)76065-1 VL - 80 IS - 2 SP - 864-873 SN - 0006-3495 ER - TY - JOUR TI - Formation of perfluoropolyether coatings by the rapid expansion of supercritical solutions (RESS) process. Part 2: Numerical modeling AU - Franklin, RK AU - Edwards, , JR AU - Chernyak, Y AU - Gould, RD AU - Henon, F AU - Carbonell, RG T2 - INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH AB - The rapid expansion of supercritical solutions (RESS) process is a promising method for the production of ultrafine powders and aerosols of narrow size distribution for coatings and other applications. In this article, part 2 of a two-part study, the nucleation and subsequent growth of 2500 Mw perfluoropolyether diamide (PFD) from supercritical carbon dioxide (CO2) by expansion through a small-diameter nozzle is modeled in a three-stage, multidimensional fashion. The stages include a hydrodynamic solution, solvent−solute phase equilibria analyses, and an aerosol transport model. The hydrodynamics model successfully captures the vapor−liquid transition that occurs as carbon dioxide is expanded to ambient conditions. Cloud-point pressures and equilibrium compositions of the separated solvent−solute system are determined and are used in a multidimensional aerosol transport model. This model incorporates various mechanisms influencing droplet growth. Parametric studies are conducted to investigate the influences of the interfacial tension, the equilibrium addition of carbon dioxide, and the diffusion coefficient on the predicted droplet diameter. Turbulent coagulation in the ambient region downstream of the expansion nozzle is found to be the dominant mechanism responsible for the production of micron-sized droplets observed in companion experiments. DA - 2001/12/26/ PY - 2001/12/26/ DO - 10.1021/ie010268e VL - 40 IS - 26 SP - 6127-6139 SN - 0888-5885 ER - TY - JOUR TI - Formation of perfluoropolyether coatings by the rapid expansion of supercritical solutions (RESS) process. Part 1: Experimental results AU - Chernyak, Y AU - Henon, F AU - Harris, RB AU - Gould, RD AU - Franklin, RK AU - Edwards, , JR AU - DeSimone, JM AU - Carbonell, RG T2 - INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH AB - The rapid expansion of supercritical solutions (RESS) process is a promising environmentally benign technology for fine droplet or particle formation. The absence of organic solvents and narrow size distribution of RESS precipitates make this process attractive for polymer coating applications. In our work, this technique has been used to produce droplets of perfluoropolyethers from CO2 solutions without the aid of cosolvents for the coating of porous materials applied in monumental and civil infrastructures. The present work is aimed at gaining an understanding of the relationship between droplet and spray characteristics and RESS process conditions. As such, a combined experimental/computational approach is applied to a representative binary system consisting of a low-molecular-weight perfluoropolyether diamide (PFD) dissolved in supercritical CO2. Part 1 of this work presents phase equilibria measurements and polymer droplet size characterizations under different operating conditions. The effects of temperature, solute concentration, and nozzle configuration on droplet and spray characterization and transfer efficiency are discussed. Part 2 of this work presents a multidimensional computational fluid dynamics model of the RESS expansion process and describes the use of the model in further analyzing and interpreting experimental data. DA - 2001/12/26/ PY - 2001/12/26/ DO - 10.1021/ie010267m VL - 40 IS - 26 SP - 6118-6126 SN - 0888-5885 ER - TY - JOUR TI - Effective strategies for cooperative learning AU - Felder, R. M. AU - Brent, R. T2 - Journal of Cooperation & Collaboration in College Teaching DA - 2001/// PY - 2001/// VL - 10 IS - 2 SP - 69-75 ER - TY - JOUR TI - A brief history of elementary principles of chemical processes AU - Felder, R. M. T2 - CEE, Chemical Engineering Education DA - 2001/// PY - 2001/// VL - 35 IS - 3 SP - 180-181 ER - TY - JOUR TI - Water in porous carbons AU - Brennan, JK AU - Bandosz, TJ AU - Thomson, KT AU - Gubbins, KE T2 - COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS AB - We present an overview of progress in understanding the behavior of water in porous carbons at the molecular level. We survey experimental investigations, semi-empirical approaches, and simulation studies. Experimental work faces a number of challenges: the determination of the distribution of carbon microcrystal sizes, the densities and species of surface groups, the topological nature of the connected pore structure, and pore size distributions. The lack of experimental characterization, together with the uncertainty in the intermolecular potentials involved, has thwarted molecular simulation efforts thus far. A concerted approach that links experimental and simulation efforts appears promising in gaining a better understanding of the behavior of water in porous carbons. Experimental results could aid in the development of realistic carbon models and improve the intermolecular potentials used in the simulation studies. In a complementary fashion, molecular simulation could help improve characterization methods of both the carbon structure and the surface chemistry. DA - 2001/8/31/ PY - 2001/8/31/ DO - 10.1016/S0927-7757(01)00644-6 VL - 187 IS - 2001 Aug. 31 SP - 539-568 SN - 1873-4359 KW - water KW - activated carbons KW - adsorption KW - molecular modeling KW - molecular simulation ER - TY - JOUR TI - Waste treatment modules - a partial life cycle inventory AU - Jimenez-Gonzalez, C AU - Overcash, MR AU - Curzons, A T2 - JOURNAL OF CHEMICAL TECHNOLOGY AND BIOTECHNOLOGY AB - Abstract In the cases in which the Life Cycle Inventory (LCI) data available in the literature only include pretreatment information, there is a need to use a model for waste treatment to estimate the post‐treatment data. In other cases, it is desirable to back calculate pretreatment information from final environmental emissions. This paper presents treatment modules for Wastewater Treatment Plant (WWTP), Solvent Incinerator, and Solvent Recovery. The modules were developed based on design equations and average literature data. The methodology and basis for the models are presented and results are shown for the three modules. The modules developed present an easy and scientifically‐based method to obtain post‐treatment LCI data. The modules are expected to be particularly useful in the instances when process design techniques are employed for the estimation of LCI data, especially in chemical, biochemical and pharmaceutical industries. © 2001 Society of Chemical Industry DA - 2001/7// PY - 2001/7// DO - 10.1002/jctb.426 VL - 76 IS - 7 SP - 707-716 SN - 0268-2575 KW - LCI waste treatment data KW - wastewater treatment KW - thermal oxidizer KW - solvent incinerator KW - gate-to-gate LCI KW - life cycle inventory KW - chemical oxygen demand KW - total organic carbon KW - biochemical oxygen demand KW - VOC emissions ER - TY - JOUR TI - Protease I from Pyrococcus furiosus AU - Chang, L. S. AU - Hicks, P. M. AU - Kelly, R. M. T2 - Hyperthermophilic enzymes. Part A CN - QP601 .M49 vol. 330 DA - 2001/// PY - 2001/// VL - 330 SP - 403-413 ER - TY - JOUR TI - Perfectly-alternating linear (AB)(n) multiblock copolymers: Effect of molecular design on morphology and properties AU - Spontak, RJ AU - Smith, SD T2 - JOURNAL OF POLYMER SCIENCE PART B-POLYMER PHYSICS AB - Abstract Perfectly‐alternating linear (AB) n multiblock copolymers consist of n AB block pairs covalently linked in an alternating sequence. Although these copolymers can microphase‐order in the same fashion as their lower‐order ( n = 1) diblock analogs, the 2( n − 1) biconformational midblocks comprising each copolymer molecule have a considerable impact on microstructural characteristics and bulk properties. We have applied transmission electron microscopy, differential scanning calorimetry (DSC), and extensional rheometry to examine and compare the morphologies and properties of two series of compositionally symmetric (lamellar) poly(styrene‐ b ‐isoprene) n (SI) n (1 ≤ n ≤ 4) multiblock copolymers. In one series, chain length was held constant allowing block mass ( M b ) to decrease with increasing n . In the second copolymer series, M b remained relatively invariant. Increasing n in these two series generally promoted reductions in both the lamellar period and upper (styrenic) glass‐transition temperature, but noticeable increases in tensile modulus and yield strength. These observed trends are more pronounced in the copolymer series with constant chain length due to the coupled relationship between n and M b . © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 947–955, 2001 DA - 2001/5/1/ PY - 2001/5/1/ DO - 10.1002/polb.1070 VL - 39 IS - 9 SP - 947-955 SN - 0887-6266 KW - block copolymer KW - polymer nanostructure KW - segmented copolymer KW - polymer network ER - TY - JOUR TI - On the need for engineering models of integrated chemical and biological oxidation of wastewaters AU - Ollis, DF T2 - WATER SCIENCE AND TECHNOLOGY AB - Experimental examples of sequential chemical and biological oxidation treatment have been previously reviewed by Scott and Ollis, and economic estimates proposed by Esplugas and Ollis. Despite the prevalence of examples evident in these reviews and in recent conferences, very little use of kinetic models to codify and rationalize results on complex or simulated wastewaters has appeared. In consequence, models are not widely available nor have they yet received widespread acceptance as a method of analysis and reporting. To ameliorate this situation we here report a summary of important kinetic behaviors characteristic of individual chemical and biological kinetics, and provide experimental examples from recent works which illustrate the utility of such simple kinetic forms to construct two step treatment engineering models for complex wastewater and waters. DA - 2001/// PY - 2001/// DO - 10.2166/wst.2001.0265 VL - 44 IS - 5 SP - 117-123 SN - 0273-1223 KW - chemical oxidation KW - biological oxidation KW - process integration ER - TY - JOUR TI - Numerical studies of nonuniform deformation, stress state evolution, and subgrain formation in bicrystals in (110) channel die compression AU - Yu, PG AU - Havner, KS T2 - JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS AB - Abstract An elastoplastic numerical model for f.c.c. bicrystals in (110) channel die compression is investigated to a logarithmic strain of 10% and compared with the analytical rigid-plastic solution at the yield point. Three lattice orientations of an aluminum bicrystal are calculated between constraint directions [00 1 ] and [1 1 2 ] . It is found that the elastoplastic results for each of stress state, velocity field and lattice-rotation rate (indicating subgrain formation) pass very close to the analytical solution at 0.2% strain for two of the orientations. This is in spite of small tangential velocity discontinuities along characteristic directions of that solution which are not permitted in the numerical (finite element) modeling. The results are never as close in the third orientation, for which there are much greater tangential velocity discontinuities in the rigid-plastic model. It is suggested that the elastoplastic comparisons with the rigid-plastic model may provide insight into realistic strain levels at the beginning of fully plastic response. However, it also is concluded that a deeper analytical representation of the tangential velocity discontinuities is needed. DA - 2001/1// PY - 2001/1// DO - 10.1016/s0022-5096(00)00021-1 VL - 49 IS - 1 SP - 173-208 SN - 1873-4782 KW - grain boundaries KW - crystal plasticity KW - finite strain KW - characteristics KW - finite elements ER - TY - JOUR TI - Morphological characteristics of 1,3 : 2,4-dibenzylidene sorbitol/poly(propylene glycol) organogels AU - Mercurio, DJ AU - Spontak, RJ T2 - JOURNAL OF PHYSICAL CHEMISTRY B AB - The organic gelator 1,3:2,4-dibenzylidene sorbitol (DBS) self-organizes to form a 3-D network stabilized by hydrogen bonds at relatively low concentrations in a variety of nonpolar organic solvents and polymers. The resultant network consists of nanofibrils and is responsible for the physical gelation of the matrix component. In this work, the morphological characteristics of organogels composed of DBS and poly(propylene glycol) (PPG) are investigated as functions of DBS concentration, PPG molecular weight, and temperature through the use of polarized light microscopy, transmission electron microscopy, X-ray diffractometry, and spectrophotometry. Polarized light microscopy reveals thermally reversible features that become increasingly more pronounced with increasing DBS concentration. Electron microscopy verifies that these features arise due to the presence of a DBS nanofibrillar network, with nanofibrils measuring ca. 10 nm in diameter. Comparison of X-ray diffraction patterns of pure DBS crystals and DBS networks from which PPG is removed by supercritical fluid extraction reveals that the DBS nanofibrils are crystalline, differing slightly from the structure of pure DBS. Spectrophotometry is used to probe the temperature-dependent development of the molecular network in DBS/PPG organogels. DA - 2001/3/22/ PY - 2001/3/22/ DO - 10.1021/jp002247o VL - 105 IS - 11 SP - 2091-2098 SN - 1520-5207 ER - TY - JOUR TI - Molecular, nanostructural and mechanical characteristics of lamellar triblock copolymer blends: Effects of molecular weight and constraint AU - Kane, L AU - Norman, DA AU - White, SA AU - Matsen, MW AU - Satkowski, MM AU - Smith, SD AU - Spontak, RJ T2 - MACROMOLECULAR RAPID COMMUNICATIONS AB - While theoretical and experimental efforts have thoroughly addressed microphase-ordered AB diblock copolymer blends with a parent homopolymer (hA or hB) or a second block copolymer, surprisingly few studies have considered comparable ABA triblock copolymers in the presence of hB or an AB diblock copolymer. In this study, we elucidate the roles of additive molecular weight and constraint by examining three matched series of miscible ABA/hB and ABA/AB blends. Self-consistent field theory is employed to analyze molecular characteristics, e. g., segmental distributions, microdomain periods and midblock bridging fractions, as functions of blend composition. Predictions are compared to morphological characteristics discerned by transmission electron microscopy and small-angle X-ray scattering. The corresponding mechanical properties of these blends are measured by dynamic mechanical analysis. The results of this comprehensive work reveal that addition of hB swells the B-lamellae of the ABA copolymer and has a generally deleterious effect on both the dynamic elastic modulus and midblock bridging fraction. In contrast, addition of a lamellar or cylindrical AB copolymer to the same ABA copolymer can promote an increase or decrease in lamellar period and bridging fraction, depending on relative block sizes. DA - 2001/3/26/ PY - 2001/3/26/ DO - 10.1002/1521-3927(20010301)22:5<281::AID-MARC281>3.0.CO;2-G VL - 22 IS - 5 SP - 281-296 SN - 1521-3927 ER - TY - JOUR TI - Gas and vapor sorption and diffusion in poly(ethylene terephthalate) AU - Serad, GE AU - Freeman, BD AU - Stewart, ME AU - Hill, AJ T2 - POLYMER AB - Equilibrium sorption of n-butane and acetaldehyde in melt-processed poly(ethylene terephthalate) (PET) microtomed flakes is reported. The n-butane sorption isotherm at 35°C is well described by the dual-mode model with the following parameters: kD=0.017cm3 (STP)/(cm3 amorphous polymer cmHg), C′H=1.3cm3 (STP) (cm3 amorphous polymer) and b=0.029cmHg−1. Acetaldehyde isotherms at 35 and 45°C may be described by the Flory–Huggins sorption model, suggesting that penetrant uptake in the non-equilibrium excess volume associated with the glassy polymer made a negligible contribution to the overall sorption level at the conditions of this study. The heat of sorption was essentially equal to the enthalpy of condensation of pure acetaldehyde. At 45°C and acetaldehyde pressures at or above 40.0 cmHg, acetaldehyde triggers significant crystallization of PET (up to 37 wt%) with increasing concentration. Subsequent sorption experiments at very low penetrant activity reveal solubility coefficients that are markedly higher in the penetrant-crystallized sample than in the initially highly amorphous sample. This result suggests the acetaldehyde-induced formation of microvoids (which act as highly efficient penetrant sorption sites) in the polymer sample. Based on these and literature data, the logarithm of infinite dilution penetrant solubility in amorphous regions of PET was well-correlated with penetrant condensability as characterized by Tc, penetrant critical temperature, or by (Tc/T)2, where T is the experiment temperature. Infinite dilution, amorphous phase penetrant diffusion coefficients in PET decreased according to a power law relation with increasing penetrant critical volume. DA - 2001/7// PY - 2001/7// DO - 10.1016/S0032-3861(01)00120-3 VL - 42 IS - 16 SP - 6929-6943 SN - 1873-2291 KW - sorption KW - diffusion KW - n-butane ER - TY - JOUR TI - Freezing behavior in porous glasses and MCM-41 AU - Sliwinska-Bartkowiak, M. AU - Dudziak, G. AU - Gras, R. AU - Sikorski, R. AU - Radhakrishnan, R. AU - Gubbins, Keith T2 - Colloids and Surfaces. A, Physicochemical and Engineering Aspects AB - We report experimental measurements of the melting and freezing behavior of fluids in nano-porous media. The experimental studies are for nitrobenzene in the silica based pores of controlled pore glass (CPG), Vycor and MCM-41. Dielectric relaxation spectroscopy was used to determine melting points and the orientational relaxation times of the nitrobenzene molecules in the bulk and the confined phase. It was found that the confined fluid freezes into a single crystalline structure for average pore diameters greater than 20 σ, where σ is the diameter of the fluid molecule. For average pore sizes between 20 and 15 σ, part of the confined fluid freezes into a frustrated crystal structure with the rest forming an amorphous region. For pore sizes smaller than 15 σ, even the partial crystallization did not occur. DA - 2001/// PY - 2001/// DO - 10.1016/S0927-7757(01)00637-9 VL - 187 IS - 2001 Aug. 31 SP - 523–529 ER - TY - JOUR TI - Cyclopropyl amino acids of Amanita AU - Chilton, W. S. AU - Drehmel, D. C. T2 - Biochemical Systematics and Ecology DA - 2001/// PY - 2001/// VL - 29 IS - 8 SP - 853-855 ER -