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Segment diffusion and nuclear magnetic resonance spin-lattice relaxation of polymer chains confined in tubes: Analytical treatment and Monte Carlo simulation of the crossover from Rouse to reptation dynamics

Alexei Denissov、Margarita Kroutieva、Nail Fatkullin 等 4 位作者2002-03-22The Journal of Chemical Physics

The frequency and molecular mass dependences of nuclear magnetic resonance spin-lattice relaxation and the time dependence of the mean-squared segment displacement of Kuhn segment chains confined in static straight and randomly coiled tubes with “soft” and “hard” walls were studied. “Soft” walls were modeled in the fo…

Polymer crystallization and propertiesMaterial Dynamics and PropertiesRheology and Fluid Dynamics Studies

Comparative analysis of space-grown and earth-grown crystals of an aminoacyl-tRNA synthetase: space-grown crystals are more useful for structural determination

Joseph D. Ng、C. Sauter、Bernard Lorber 等 6 位作者2002-03-22Acta Crystallographica Section D Biological Crystallography

Protein crystallization under microgravity aims at benefiting from the quasi-absence of convection and sedimentation to favor well ordered crystal nucleation and growth. The dimeric multidomain enzyme aspartyl-tRNA synthetase from Thermus thermophilus has been crystallized within dialysis reactors of the Advanced Prot…

Protein Structure and DynamicsRNA and protein synthesis mechanismsEnzyme Structure and Function

The application of structure envelopes in structure determination from powder diffraction data

S.E. Brenner、Lynne B. McCusker、Christian Baerlocher2002-03-22Journal of Applied Crystallography

A structure envelope is a special type of periodic nodal surface that separates regions of high electron density from those of low electron density. Once such a surface has been generated, it can be used in combination with direct-space methods to facilitate structure solution from powder data. To generate an informat…

Crystallography and molecular interactionsMachine Learning in Materials ScienceX-ray Diffraction in Crystallography

A structural double-mutant cycle: estimating the strength of a buried salt bridge in barnase

Cara K. Vaughan、Pia Harryson、Ashley M. Buckle 等 4 位作者2002-03-22Acta Crystallographica Section D Biological Crystallography

Double-mutant cycles are widely used in the field of protein engineering to measure intermolecular and intramolecular interactions. Ideally, there should be no structural rearrangement of the protein on making the two single mutations and the double mutation within the cycle. However, structural pertubation on mutatio…

Protein Structure and DynamicsProtein purification and stabilityEnzyme Structure and Function

Adsorption Characterization of Oligo(dimethylsiloxane)-Modified Silicas: An Example of Highly Hydrophobic Surfaces with Non-Aliphatic Architecture

Yuri Kazakevich、Alexander Y. Fadeev2002-03-22Langmuir

This paper describes adsorption characterization of oligo(dimethylsiloxane)-modified silicas, nonpolar, lyophobic adsorbents with non-aliphatic architecture of the surfaces. Synthesis and spectral and thermal characterization of these surfaces have been recently reported in: Fadeev, A. Y.; Kazakevich, Y. V. Langmuir 2…

Gas Sensing Nanomaterials and SensorsMesoporous Materials and CatalysisAnalytical Chemistry and Sensors

Upconversion luminescence in Yb3+ doped CsMnCl3: Spectroscopy, dynamics, and mechanisms

Rafael Valiente、Oliver S. Wenger、Hans U. Güdel2002-03-22The Journal of Chemical Physics

Single crystals of CsMnCl3 doped with 0.9% Yb3+ were grown from the melt by the Bridgman technique and studied by means of variable temperature optical spectroscopy. At cryogenic temperatures, near-infrared Yb3+-excitation around 1 μm leads to intense Mn2+ upconversion luminescence in the red spectral region. This ver…

Luminescence Properties of Advanced MaterialsSolid State Laser TechnologiesOptical properties and cooling technologies in crystalline materials

Organoborane-Modified Silica Supports for Olefin Polymerization: Soluble Models for Metallocene Catalyst Deactivation

Robert A. Metcalfe、David I. Kreller、Jun Tian 等 7 位作者2002-03-22Organometallics

Treatment of silsesquioxane 1 with 3.3 equiv of the reactive organoboranes 2 [(C 6 F 5 ) 2 BX; X = H or Cl] provides the novel, trifunctional organoborane 3, which was characterized by spectroscopic means and single-crystal X-ray crystallography. Compound 3 is an effective cocatalyst for ethylene polymerization in com…

Synthesis and characterization of novel inorganic/organometallic compoundsOrganoboron and organosilicon chemistrySilicone and Siloxane Chemistry

A Soluble Equivalent of the Supramolecular, Quasi-One-Dimensional, Semiconducting Magnus' Green Salt

Margherita Fontana、Henry Chanzy、Walter Caseri 等 7 位作者2002-03-22Chemistry of Materials

A soluble supramolecular, quasi-one-dimensional semiconducting complex comprising alternately stacked [Pt(NH 2 dmoc) 4 ] 2+ and [PtCl 4 ] 2 - units, where dmoc denotes ( S )-3,7-dimethyloctyl, has been synthesized and characterized with various methods. In contrast to earlier enunciated expectations and unlike nearly…

Magnetism in coordination complexesMolecular Junctions and NanostructuresOrganic and Molecular Conductors Research

CdS Nanoparticles Modified to Chalcogen Sites: New Supramolecular Complexes, Butterfly Bridging, and Related Optical Effects

Tong Ni、Dattatri Nagesha、Juvencio Robles 等 6 位作者2002-03-22Journal of the American Chemical Society

All present approaches to surface modification of nanoparticles (NPs) with organic ligands exploit metal (cadmium) sites as anchor points. To obtain efficient interaction of NP surface with p-orbitals of organic chromophores, we utilize the chalcogen (sulfur) sites on the NP surface. These sites present several advant…

Quantum Dots Synthesis And PropertiesChalcogenide Semiconductor Thin FilmsCopper-based nanomaterials and applications

Organically-modified mesoporous silica spheres with MCM-41 architecture

Mathieu Etienne、Bénédicte Lebeau、Alain Walcarius2002-03-22New Journal of Chemistry

New hybrid inorganic–organic materials displaying both an ordered mesoporous structure and spherical morphology have been synthesised by co-condensation of tetraethoxysilane and organoalkoxysilanes in water–ethanol solution containing ammonia in the presence of surfactant as templating agent.

Zeolite Catalysis and SynthesisMesoporous Materials and CatalysisPolyoxometalates: Synthesis and Applications

Cryophotolysis of caged compounds: a technique for trapping intermediate states in protein crystals

Thomas Ursby、Martin H. Weik、E. Fioravanti 等 6 位作者2002-03-22Acta Crystallographica Section D Biological Crystallography

Caged compounds in combination with protein crystallography represent a valuable tool in studies of enzyme reaction intermediates. To date, photochemical triggering of reactions has been performed close to room temperature. Synchronous reaction initiation has only been achieved with enzymes of relatively slow turnover…

Protein Structure and DynamicsEnzyme Structure and FunctionBiochemical and Molecular Research

Crystal structures of the relaxor oxide Pb2(ScTa)O6in the paraelectric and ferroelectric states

Patrick M. Woodward、K. Z. Baba‐Kishi2002-03-22Journal of Applied Crystallography

The crystal structure of the relaxor ferroelectric Pb 2 ScTaO 6 has been refined from high-resolution neutron time-of-flight powder diffraction data recorded at various temperatures from 4 to 400 K. Upon warming, Pb 2 ScTaO 6 undergoes a first-order transition at 295 K from the rhombohedral ferroelectric state into th…

Ferroelectric and Piezoelectric MaterialsAcoustic Wave Resonator TechnologiesSolid-state spectroscopy and crystallography

Ab initioinvestigation of phonon modes in the MgAl2O4spinel

Pascal Thibaudeau、François Gervais2002-03-22Journal of Physics Condensed Matter

Ab initio infrared and Raman phonon modes in the normal cubic MgAl 2 O 4 spinel are calculated at the first Brillouin zone centre using density functional theory with plane-wave basis and norm-conserving pseudopotentials. Good agreement with available experimental infrared and Raman spectra is found for both natural a…

Ferroelectric and Piezoelectric MaterialsGlass properties and applicationsNuclear materials and radiation effects

Temperature, density, and pressure dependence of relaxation times in supercooled liquids

Christiane Alba–Simionesco、Daniel Kivelson、Gilles Tarjus2002-03-22The Journal of Chemical Physics

We have examined experimental and simulation data on the relaxation times (τα) and the viscosities in liquids and supercooled liquids as functions of temperature (T), density (ρ), and pressure (p). We achieve a data collapse by placing the data on master curves that depend only on a single density- and species-depende…

Phase Equilibria and ThermodynamicsMaterial Dynamics and PropertiesTheoretical and Computational Physics

An AC Impedance Spectroscopic Study of LixCoO2 at Different Temperatures

Francesco Nobili、R. Tossici、R. Marassi 等 5 位作者2002-03-22The Journal of Physical Chemistry B

An AC impedance spectroscopic study of the Li x CoO 2 electrode in the temperature range of 0−30 °C is presented. The results are interpreted on the basis of an equivalent circuit that includes elements related to the electronic and ionic transport in addition to the charge transfer process. The evolution of the imped…

Gas Sensing Nanomaterials and SensorsConducting polymers and applicationsTransition Metal Oxide Nanomaterials

Spectroscopic Properties of Lu2O3/Eu3+ Nanocrystalline Powders and Sintered Ceramics

Eugeniusz Zych、D. Hreniak、W. Stręk2002-03-22The Journal of Physical Chemistry B

Europium-doped Lu 2 O 3 nanocrystalline powders with Eu concentrations of 1−13 m / 0 were prepared via a combustion route. Their morphology was determined with TEM measurements. It was found that the sizes of nanocrystallites were around 10−13 nm. These powders were sintered at 1700 °C into tablets whose grains were a…

Luminescence Properties of Advanced MaterialsRadioactive element chemistry and processingNuclear materials and radiation effects

Dynamical heterogeneities below the glass transition

Katharina Vollmayr-Lee、Walter Kob、Kurt Binder 等 4 位作者2002-03-22The Journal of Chemical Physics

We present molecular dynamics simulations of a binary Lennard-Jones mixture at temperatures below the kinetic glass transition. The “mobility” of a particle is characterized by the amplitude of its fluctuation around its average position. The 5% particles with the largest/smallest mean amplitude are then defined as th…

Liquid Crystal Research AdvancementsMaterial Dynamics and PropertiesGlass properties and applications

ENIGMA: maximum-entropy method program package for huge systems

Hiroshi Tanaka、Masaki Takata、Eiji Nishibori 等 6 位作者2002-03-22Journal of Applied Crystallography

ENIGMA ( Electron and Nuclear Image Generator by Max-ent Analysis ) is a program package to evaluate three-dimensional electron and nuclear density from X-ray and neutron diffraction data by using the maximum-entropy method (MEM). Compared with the previous program package MEED , ENIGMA saves computing time and frees…

High-pressure geophysics and materialsMachine Learning in Materials ScienceNuclear Physics and Applications

Neutron total scattering method: simultaneous determination of long-range and short-range order in disordered materials

Martin T Dove、Matthew G. Tucker、David A. Keen2002-03-22European Journal of Mineralogy

Neutron total scattering provides simultaneous information about long-range order through the Bragg peaks and short- range order through the diffuse scattering. We review recent progress in applying total scattering methods for the study of short- range structural order in silicates and other materials, focussing on c…

High-pressure geophysics and materialsGlass properties and applicationsX-ray Diffraction in Crystallography

Density-functional study ofFe3Al:LSDA versus GGA

Frank Lechermann、F. Welsch、Christian Elsässer 等 7 位作者2002-03-22Physical review. B, Condensed matter

The local-spin-density approximation and the generalized-gradient approximation (GGA) are used to perform density-functional total-energy calculations at zero temperature for ${\mathrm{Fe}}_{3}\mathrm{Al}$ in the ordered ${D0}_{3}$ and ${L1}_{2}$ structures. Our calculations show that commonly used GGA functionals fai…

Rare-earth and actinide compoundsIron-based superconductors researchInorganic Chemistry and Materials