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Statistical geometry of particle packings. I. Algorithm for exact determination of connectivity, volume, and surface areas of void space in monodisperse and polydisperse sphere packings

Srikanth Sastry、David S. Corti、Pablo G. Debenedetti 等 4 位作者1997-11-01Physical review. E, Statistical physics, plasmas, fluids, and related interdisciplinary topics

Packings of spheres serve as useful models of the geometry of many physical systems; in particular, the description of the void region in such packings (the region not occupied by the spheres) is crucial in many studies. The void region is, in general, composed of disconnected cavities. We present an algorithm for dec…

Material Dynamics and PropertiesPolysaccharides Composition and ApplicationsAdsorption, diffusion, and thermodynamic properties of materials

An Analysis of Porphyrin Molecular FlexibilityUse of Porphyrin Diacids

Beisong Cheng、Orde Q. Munro、Helder M. Marques 等 4 位作者1997-11-01Journal of the American Chemical Society

The crystal structures of three porphyrin diacid species, [H 4 OEP](ClO 4 ) 2, [H 4 TPP](ClO 4 ) 2, and [H 4 TMP](ClO 4 ) 2, have been determined from low-temperature X-ray diffraction data to delineate how the peripheral substituents of the porphyrin affect the overall molecular flexibility . [H 4 OEP](ClO 4 ) 2 (|C…

Porphyrin and Phthalocyanine ChemistryHemoglobin structure and functionPorphyrin Metabolism and Disorders

Ionic Effects of Sodium Chloride on the Templated Deposition of Polyelectrolytes Using Layer-by-Layer Ionic Assembly

Sarah L. Clark、Martha F. Montague、Paula T. Hammond1997-11-01Macromolecules

A new method for the patterning of ionic layer-by-layer assembled films with micron-sized features is presented. Self-assembled monolayers (SAMs) were used as templates to direct the deposition of sulfonated polystyrene (SPS) and poly(diallyldimethylammonium chloride) (PDAC) multilayers onto a surface. Both polyelectr…

Polymer Surface Interaction StudiesMolecular Junctions and NanostructuresDendrimers and Hyperbranched Polymers

Preparation of Hyperbranched Polyacrylates by Atom Transfer Radical Polymerization. 3. Effect of Reaction Conditions on the Self-Condensing Vinyl Polymerization of 2-((2-Bromopropionyl)oxy)ethyl Acrylate

Krzysztof Matyjaszewski、Scott G. Gaynor1997-11-01Macromolecules

The homopolymerization of 2-((2-bromopropionyl)oxy)ethyl acrylate (BPEA) by atom transfer radical polymerization (ATRP), a “living”/controlled radical polymerization system, has yielded a hyperbranched polymer. Variation of the reaction conditions and especially the concentration of copper(II) in the polymerization sy…

Advanced Polymer Synthesis and CharacterizationDendrimers and Hyperbranched PolymersSynthesis and properties of polymers

Monte Carlo simulation of topological defects in the nematic liquid crystal matrix around a spherical colloid particle

R. W. Ruhwandl、Eugene M. Terentjev1997-11-01Physical review. E, Statistical physics, plasmas, fluids, and related interdisciplinary topics

We use a Monte Carlo algorithm to simulate the director field around a spherical inclusion in a uniform nematic liquid crystal matrix. The resulting structure crucially depends on the relative strength of the nematic bulk elasticity and the director anchoring on the particle surface. When this anchoring is weak, the d…

Liquid Crystal Research AdvancementsPhotonic Crystals and ApplicationsAdvanced Materials and Mechanics

Domain Growth in Pb(Mg 1/3 Ta 2/3 )O 3 Perovskite Relaxor Ferroelectric Oxides

Mehmet A. Akbas、Peter K. Davies1997-11-01Journal of the American Ceramic Society

Extensive studies that have been conducted on the Pb(Mg 1/3 Nb 2/3 )O 3 (PMN) family of relaxor ferroelectrics have led to the establishment and acceptance of the“space‐charge” model as a basis for explaining their structures and dielectric properties. In this model, the arrangement of the metal cations on the octahed…

Ferroelectric and Piezoelectric MaterialsMultiferroics and related materialsMicrowave Dielectric Ceramics Synthesis

X-ray diffraction studies of freezing and melting of water confined in a mesoporous adsorbent (MCM-41)

Kunimitsu Morishige、Keiichi Nobuoka1997-11-01The Journal of Chemical Physics

In order to study the freezing/melting behavior of pore water, we performed x-ray diffraction measurements of water confined inside the cylindrical pores of two kinds of siliceous MCM-41 with different pore size and one kind of aluminosilicate MCM-41 as a function of temperature. The results show that its freezing/mel…

Zeolite Catalysis and SynthesisMesoporous Materials and CatalysisAerogels and thermal insulation

Size Effects in Barium Titanate Particles and Clusters

Xiaoping Li、Wei‐Heng Shih1997-11-01Journal of the American Ceramic Society

Clustering has an important effect on the tetragonal‐cubic transformation of barium titanate (BaTiO 3 ) particles. Small particles that would be cubic if they were by themselves can be tetragonal if they are in a cluster. The effects of clustering are shown in the behavior of the c/a ratio of the particles and the ent…

Ferroelectric and Piezoelectric MaterialsMicrowave Dielectric Ceramics SynthesisElectronic and Structural Properties of Oxides

Preparation of Hyperbranched Polyacrylates by Atom Transfer Radical Polymerization. 2. Kinetics and Mechanism of Chain Growth for the Self-Condensing Vinyl Polymerization of 2-((2-Bromopropionyl)oxy)ethyl Acrylate

Krzysztof Matyjaszewski、Scott G. Gaynor、Axel H. E. Müller1997-11-01Macromolecules

The self-condensing vinyl polymerization (SCVP) of 2-((2-bromopropionyl)oxy)ethyl acrylate (BPEA) has resulted in the formation of hyperbranched polyacrylates. The polymerization mechanism used to polymerize the BPEA was atom transfer radical polymerization (ATRP), a “living”/controlled radical polymerization. This pa…

Advanced Polymer Synthesis and CharacterizationDendrimers and Hyperbranched PolymersSynthesis and properties of polymers

Properties and Microstructure of Plasticized Zein Films

Huey‐Min Lai、Graciela W. Padua1997-11-01Cereal Chemistry

ABSTRACT A new method for preparation of zein films involving plasticization of zein with oleic acid to form an intermediate moldable resin was presented. The resin was stretched over rigid frames to form thin membranes that were set in flexible films. The objective of the study was to investigate the effect of film p…

Nanocomposite Films for Food PackagingPolymer Surface Interaction StudiesSilk-based biomaterials and applications

Hydrogen Oxidation at the Nickel and Platinum Electrodes on Yttria‐Tetragonal Zirconia Electrolyte

San Ping Jiang、S. P. S. Badwal1997-11-01Journal of The Electrochemical Society

H{sub 2} oxidation has been studied for Pt and Ni electrodes for different H{sub 2}/H{sub 2}O ratios at 1,000 C in solid oxide fuel cells using yttria-tetragonal zirconia electrolyte by galvanostatic current interruption and electrochemical impedance spectroscopy. The results clearly indicate that the mechanism and ki…

Electrocatalysts for Energy ConversionAdvancements in Solid Oxide Fuel CellsFuel Cells and Related Materials

Effects of Orbital Ordering on Electronic Communication in Multiporphyrin Arrays

Jon‐Paul Strachan、Steve Gentemann、Jyoti Seth 等 7 位作者1997-11-01Journal of the American Chemical Society

The rational design of molecular photonic devices requires a thorough understanding of all factors affecting electronic communication among the various constituents. To explore how electronic factors mediate both excited- and ground-state electronic communication in multiporphyrin arrays, we have conducted a detailed…

Porphyrin and Phthalocyanine ChemistryMolecular Junctions and NanostructuresPhotochemistry and Electron Transfer Studies

Probes of Pore Environment and Molecule−Matrix Interactions in Sol−Gel Materials

Bruce Dunn、Jeffrey I. Zink1997-11-01Chemistry of Materials

The use of molecular probes to study the nature of the local environment around dopants in silicate sol−gel materials is reviewed. The review selectively focuses on probes of pore solvent composition and molecule−matrix interactions using electronic spectroscopy. The sol−gel environment is complex; to systematize the…

Mesoporous Materials and CatalysisPhotochemistry and Electron Transfer StudiesAnalytical Chemistry and Sensors

Synthesis, Characterization, and Preliminary Host−Guest Binding Studies of Porphyrinic Molecular Squares Featuring fac-Tricarbonylrhenium(I) Chloro Corners

Robert V. Slone、Joseph T. Hupp1997-11-01Inorganic Chemistry

Luminescent multiporphyrin molecular square assemblies have been synthesized in high yield from Re(CO)5Cl and a highly soluble dipyridylporphyrin ligand. Both free-base and ZnII-metalated variants of squares have been synthesized. The ZnII-containing squares are capable of strongly binding selected polyimine ligands i…

Molecular Sensors and Ion DetectionSupramolecular Chemistry and ComplexesPorphyrin and Phthalocyanine Chemistry

Accumulation of natural organic matter on the surfaces of living cells: implications for the interaction of toxic solutes with aquatic biota

Peter G. C. Campbell、Michael R. Twiss、Kevin J. Wilkinson1997-11-01Canadian Journal of Fisheries and Aquatic Sciences

Reference humic substances (fulvic and humic acid) were used to demonstrate the adsorption of natural dissolved organic marter (DOM) onto the surfaces of phytoplankton (<i>Chlorella pyrenoidosa</i>, <i>Synechococcus leopoliensis</i>) and isolated fish gill cells (<i>Salmo salar</i>)…

Marine and coastal ecosystemsAlgal biology and biofuel productionDiatoms and Algae Research

Selective Deposition of Conducting Polymers on Hydroxyl-Terminated Surfaces with Printed Monolayers of Alkylsiloxanes as Templates

Zheyuan Huang、Pen‐Cheng Wang、Alan G. MacDiarmid 等 5 位作者1997-11-01Langmuir

This paper describes the use of patterned self-assembled monolayers (SAMs) in area-selective deposition of conducting polymers (polypyrrole and polyaniline) on insulating, hydroxyl-terminated surfaces such as Si/SiO 2 and glass. Patterned SAMs of octadecylsiloxane were generated on the hydroxyl-terminated surfaces usi…

Advanced Sensor and Energy Harvesting MaterialsConducting polymers and applicationsMolecular Junctions and Nanostructures

Micromachined reactors for catalytic partial oxidation reactions

Ravi Srinivasan、I‐Ming Hsing、Peter E. Berger 等 9 位作者1997-11-01AIChE Journal

Abstract Silicon‐based microfabrication of a novel chemical reactor (microreactor) having submillimeter flow channels with integrated heaters, and flow and temperature sensors is described. The potential application of this reactor to partial‐oxidation reactions is explored by using Pt‐catalyzed NH 3 oxidation as a mo…

Electrocatalysts for Energy ConversionCatalytic Processes in Materials ScienceSemiconductor materials and devices

Thiol-Derivatized Nanocrystalline Arrays of Gold, Silver, and Platinum

K. Vijaya Sarathy、Gargi Raina、Ramkuber T. Yadav 等 5 位作者1997-11-01The Journal of Physical Chemistry B

A simple procedure has been developed to prepare thiol-derivatized nanoparticles of metals. The procedure involves the transfer of well-characterized metal hydrosols to a hydrocarbon medium containing the thiol. Thiol-derivatized nanoparticles Au, Ag, and Pt of near spherical shape forming nanocrystalline arrays have…

Gold and Silver Nanoparticles Synthesis and ApplicationsQuantum Dots Synthesis And PropertiesNanocluster Synthesis and Applications

Stabilization of Mesoporous Molecular Sieves by Trimethylsilylation

Keiko A. Koyano、Takashi Tatsumi、Yoshinori Tanaka 等 4 位作者1997-11-01The Journal of Physical Chemistry B

The stability of Si-MCM-48 to moisture and compression can be improved by trimethylsilylation, as a result of the increase in hydrophobicity. Moreover, the stability is retained after calcination, although the calcined material is no longer hydrophobic. This stabilizing effect was also observed for Si-MCM-41 and Ti-MC…

Metal-Organic Frameworks: Synthesis and ApplicationsZeolite Catalysis and SynthesisMesoporous Materials and Catalysis

Thermally activated resonant magnetization tunneling in molecular magnets:Mn12Acand others

D. A. Garanin、Eugene M. Chudnovsky1997-11-01Physical review. B, Condensed matter

The dynamical theory of thermally activated resonant magnetization tunneling in uniaxially anisotropic magnetic molecules such as Mn${}_{12}\mathrm{Ac}$$(S=10)$ is developed. The observed slow dynamics of the system is described by master equations for the populations of spin levels. The latter are obtained by the adi…

Magnetism in coordination complexesLanthanide and Transition Metal ComplexesElectron Spin Resonance Studies