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Simulated-annealing real-space refinement as a tool in model building

А.A. Коростелев、Richard Bertram、Michael S. Chapman2002-04-26Acta Crystallographica Section D Biological Crystallography

Methods have been developed that further automate the building of macromolecular structures into electron-density maps. The software supports molecular-dynamics real-space refinement of an atomic model to local regions of a map within the context of a popular molecular-modeling program, O [Jones et al. (1991), Acta Cr…

Advanced Chemical Physics StudiesProtein Structure and DynamicsEnzyme Structure and Function

Self-Assembly of a Lamellar ABC Triblock Copolymer Thin Film

Kenji Fukunaga、Takeji Hashimoto、Hubert Elbs 等 4 位作者2002-04-26Macromolecules

We study the self-assembly in thin films of a lamella-forming polystyrene- block -poly(2-vinylpyridine)- block -poly( tert -butyl methacrylate) triblock copolymer by means of scanning force microscopy (SFM) and cross-sectional transmission electron microscopy (TEM). We follow the time development of the microdomain st…

Polymer Surface Interaction StudiesBlock Copolymer Self-AssemblyFluid Dynamics and Thin Films

EPR studies of the effect ofZn2+ion impurities in phase transition ofCaCd(CH3COO)4⋅6H2Ocrystals

D. K. De2002-04-26Physical review. B, Condensed matter

The effect of ${\mathrm{Zn}}^{2+}$ ion impurities on the phase transition temperature of single crystals of calcium cadmium acetate hexahydrate (CCDAH) has been studied using the electron-paramagnetic-resonance technique. The lowering of the phase transition temperature as a function of increasing ${\mathrm{Zn}}^{2+}$…

Crystal structures of chemical compoundsSolid-state spectroscopy and crystallographyElectron Spin Resonance Studies

Engineering Reactions in Crystalline Solids: Predicting Photochemical Decarbonylation from Calculated Thermochemical Parameters

Luis M. Campos、Hung Dang、Danny Ng 等 6 位作者2002-04-26The Journal of Organic Chemistry

A detailed thermochemical analysis of the alpha-cleavage and decarbonylation reactions of acetone and several ketodiesters was carried out with the B3LYP/6-31G* density functional method. The heats of formation of several ground-state ketones and radicals were calculated at 298 K to determine bond dissociation energie…

Thermal and Kinetic AnalysisChemical Thermodynamics and Molecular StructureChemistry and Chemical Engineering

Preparation and characteristics of NR/EPDM rubber blends

S. H. Botros2002-04-26Polymer-Plastics Technology and Engineering

Ethylene propylene diene monomer rubber (EPDM) was modified with maleic anhydride (MA). Benzoyl peroxide was used as an initiator. Then the produced MA-EPDM was mixed with natural rubber (NR)/EPDM blends with various compositions. The scanning electron micrographs demonstrated that the addition of MA-EPDM (10 phr) imp…

Polymer crystallization and propertiesPolymer Nanocomposites and PropertiesTribology and Wear Analysis

FIP: a highly automated beamline for multiwavelength anomalous diffraction experiments

M. Roth、Philippe Carpentier、O. Kaı̈kati 等 13 位作者2002-04-26Acta Crystallographica Section D Biological Crystallography

FIP is a French Collaborating Research Group (CRG) beamline at the European Synchrotron Radiation Facility (ESRF) dedicated exclusively to crystallography of biological macromolecules, with a special emphasis on multiwavelength anomalous diffraction data collection in the 0.7-1.81 A wavelength range. The optics, consi…

Protein Structure and DynamicsEnzyme Structure and FunctionMolecular spectroscopy and chirality

Rearrangement of Cruickshank's formulae for the diffraction-component precision index

D. M. Blow2002-04-26Acta Crystallographica Section D Biological Crystallography

The formulae for the diffraction-component precision index introduced by Cruickshank [(1999), Acta Cryst. D55, 583-601] are simplified using two approximations. A rearranged formula for the precision index is presented which can readily be calculated from experimental data. It is shown that the precision varies as (re…

Enzyme Structure and FunctionCultural Heritage Materials AnalysisX-ray Diffraction in Crystallography

Control of Polymer Topology through Transition-Metal Catalysis: Synthesis of Hyperbranched Polymers by Cobalt-Mediated Free Radical Polymerization

Zhibin Guan2002-04-26Journal of the American Chemical Society

A novel approach was demonstrated for the synthesis of hyperbranched polymers by direct free radical polymerization of divinyl monomers controlled by a cobalt chain transfer catalyst (1). By controlling the competition between propagation and chain transfer with 1, the free radical polymerization of ethylene glycol di…

RNA Interference and Gene DeliverySynthetic Organic Chemistry MethodsDendrimers and Hyperbranched Polymers

Effect of modification by poly(ethylene oxide) on the reversibility of insertion/extraction of Li+ ion in V2O5 xerogel films

Wen Chen、Qing Xu、Yong Hu 等 5 位作者2002-04-26Journal of Materials Chemistry

V2O5 xerogel films modified by poly(ethylene oxide) (PEO) were obtained via the sol–gel method. Investigations were conducted by X-ray diffractometry (XRD), Fourier transformation infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS) and cyclic voltammetry. The results show that when the V2O5 xerogel i…

Gas Sensing Nanomaterials and SensorsConducting polymers and applicationsTransition Metal Oxide Nanomaterials

Deliberate Design of Ligand Architecture Yields Dramatic Enhancement of Metal Ion Affinity

Gregg J. Lumetta、Brian M. Rapko、Priscilla A. Garza 等 7 位作者2002-04-26Journal of the American Chemical Society

Evaluation of the malonamide substructure with respect to binding site preorganization and complementarity for lanthanide metal ions suggests a new ligand architecture specifically designed to enhance lanthanide ion affinity. Consideration of conformational reorganization, restricted bond rotation, and donor group ori…

Inorganic and Organometallic ChemistryMachine Learning in Materials ScienceNanomaterials for catalytic reactions

Highly Luminescent Eu3+and Tb3+Macrocyclic Complexes Bearing an Appended Phenanthroline Chromophore

Silvio Quici、Giovanni Marzanni、Marco Cavazzini 等 9 位作者2002-04-26Inorganic Chemistry

A two-component ligand system (1) containing 1,4,7,10-tetraazacyclododecane-1,4,7-triacetic acid (DO3A) as the hosting unit for the lanthanide cations and an appended asymmetrically functionalized 1,10-phenanthroline (phen) as the chromophore was synthesized. The 1:1 complexes with Eu(3+), Gd(3+), Tb(3+), and Yb(3+) h…

Magnetism in coordination complexesRadioactive element chemistry and processingLanthanide and Transition Metal Complexes

Thermochemistry and Aqueous Solubilities of Hydrotalcite-Like Solids

Rama Kumar Allada、Alexandra Navrotsky、Hillary Thompson Berbeco 等 4 位作者2002-04-26Science

Hydrotalcites are used in technology as catalysts and anion exchangers and are important sinks for environmental contaminants. Their compositional variability makes it important, but difficult, to estimate their aqueous solubility. We report calorimetric measurements of the heats of formation of cobalt-aluminum hydrot…

Clay minerals and soil interactionsLayered Double Hydroxides Synthesis and ApplicationsThermal Expansion and Ionic Conductivity

Characterization of Silica-Based Monoliths with Bimodal Pore Size Distribution

Felix C. Leinweber、Dieter Lubda、Karin Cabrera 等 4 位作者2002-04-26Analytical Chemistry

Band dispersion was studied and the retention thermodynamics addressed for insulin and angiotensin II on C18 silica monoliths with a bimodal pore size distribution, covering linear mobile-phase velocities up to 1 cm/s and different temperatures. These data suggest that the influence of average column pressure on reten…

Mesoporous Materials and CatalysisAnalytical Chemistry and ChromatographyHeat and Mass Transfer in Porous Media

Resonance Raman scattering in semiconductor quantum dots: Adiabatic vs. time-dependent perturbation theory

E. Menendez-Proupin、Nana Cabo-Bisset2002-04-26arXiv

The adiabatic theory of resonance one-phonon Raman scattering in semiconductor nanocrystals is revised and extended with perturbative non-adiabatic corrections, given by the Albrecht's B term. This theory is confronted with the time-dependent perturbation approach, pointing at their differences and similarities. It is…

Mesoscale and Nanoscale PhysicsMaterials Science

Absence of correlation between built-in electric dipole moment and quantum Stark effect in InAs/GaAs self-assembled quantum dots

Weidong Sheng、Jean-Pierre Leburton2002-04-26arXiv

We report significant deviations from the usual quadratic dependence of the ground state interband transition energy on applied electric fields in InAs/GaAs self-assembled quantum dots. In particular, we show that conventional second-order perturbation theory fails to correctly describe the Stark shift for electric fi…

Mesoscale and Nanoscale PhysicsMaterials Science

Barrier-controlled carrier transport in microcrystalline semiconducting materials: Description within a unified model

T. Weis、R. Lipperheide、U. Wille 等 4 位作者2002-04-26arXiv

A recently developed model that unifies the ballistic and diffusive transport mechanisms is applied in a theoretical study of carrier transport across potential barriers at grain boundaries in microcrystalline semiconducting materials. In the unified model, the conductance depends on the detailed structure of the band…

Materials Science

Signatures of collective local and nanoscale distortions in diffraction experiments

Angel J. Garcia-Adeva、Dylan R. Conradson、Phillip Villella 等 4 位作者2002-04-26arXiv

The effects of periodic and aperiodic distortions on the structure factor and radial distribution function of single-component lattices are investigated. To this end, different kinds of distortions are applied to the otherwise perfect square lattice and the corresponding radial distribution function and structure fact…

Materials Science

Selective spin-state switch and metal-insulator transition inGdBaCo2O5.5

Carlos Frontera、J. L. Garcı́a-Muñoz、A. Llobet 等 4 位作者2002-04-26Physical review. B, Condensed matter

Ultrahigh resolution synchrotron diffraction data for ${\mathrm{GdBaCo}}_{2}{\mathrm{O}}_{5.5}$ throw new light on the metal-insulator transition of ${\mathrm{Co}}^{3+}$ Ba-cobaltites. An anomalous expansion of ${\mathrm{CoO}}_{6}$ octahedra is observed at the phase transition on heating, while ${\mathrm{CoO}}_{5}$ py…

Physics of Superconductivity and MagnetismMagnetic and transport properties of perovskites and related materialsAdvanced Condensed Matter Physics

Interplay between Time-Temperature Transformation and the Liquid-Liquid Phase Transition in Water

Masako Yamada、Stefano Mossa、H. Eugene Stanley 等 4 位作者2002-04-26Physical Review Letters

We study the new water model proposed by Mahoney and Jorgensen [J. Chem. Phys. 112, 8910 (2000)], which is closer to real water than previously proposed classical pairwise additive potentials. We simulate the model in a wide range of deeply supercooled states and find (i) the existence of a nonmonotonic "nose-shaped"…

Material Dynamics and PropertiesTheoretical and Computational PhysicsAdvanced Thermodynamics and Statistical Mechanics

Nanotubes in a Flash--Ignition and Reconstruction

P. M. Ajayan、Mauricio Terrones、A. de la Guardia 等 9 位作者2002-04-26Science

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