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MICROCOSTATUSGEN. NOV., A NEW AEROPHILIC DIATOM GENUS BASED ONNAVICULA KRASSKEIHUSTEDT

Jeffrey R. Johansen、Julie C. Sray1998-05-01Diatom Research

Navicula krasskei Hustedt has been considered to belong to the group of diatoms including Fallacia festiva (Krasske) Mann & Stickle and F. monoculata (Hustedt) Mann & Stickle. Examination of N. krasskei in the SEM revealed that this taxon does not, in fact, share features with either Fallacia or Navicula sensu stricto…

Paleontology and Stratigraphy of FossilsAnalytical chemistry methods developmentDiatoms and Algae Research

Isothermal and Nonisothermal Melt Crystallization Kinetic Behavior of Poly(Aryl Ether Biphenyl Ether Ketone Ketone): PEDEKK

Tianxi Liu、Zhao Mo、Houcheng Zhang1998-05-01Journal of Polymer Engineering

Article Isothermal and Nonisothermal Melt Crystallization Kinetic Behavior of Poly(Aryl Ether Biphenyl Ether Ketone Ketone): PEDEKK was published on May 1, 1998 in the journal Journal of Polymer Engineering (volume 18, issue 4).

Polymer crystallization and propertiesbiodegradable polymer synthesis and propertiesPolymer Science and PVC

Mutation of an Active Site Residue of Tryptophan Synthase (β-Serine 377) Alters Cofactor Chemistry

Kwang-Hwan Jhee、Lihong Yang、Salman Ahmed 等 6 位作者1998-05-01Journal of Biological Chemistry

To better understand how an enzyme controls cofactor chemistry, we have changed a tryptophan synthase residue that interacts with the pyridine nitrogen of the pyridoxal phosphate cofactor from a neutral Ser (beta-Ser377) to a negatively charged Asp or Glu. The spectroscopic properties of the mutant enzymes are altered…

Enzyme Structure and FunctionAmino Acid Enzymes and MetabolismBiochemical and Molecular Research

Mixed-valence Hexanuclear Cobalt(II, III) Complex Made Up of Two Defective Cubane Cores

Masahiro Mikuriya、Mika Fukuya1998-05-01Chemistry Letters

Abstract A mixed-valence cobalt(II, III) complex, [Co6L2(CH3COO)2(CH3O)6L′]·2CH3OH(H3L=2,6-bis(saliclylideneaminomethyl)-4-methylphenol and H2L′=salicylazine), has been isolated and characterized by X-ray crystallography, which reveals a unique hexanuclear structure consisting of two defective cubane-cores.

Metal complexes synthesis and propertiesMagnetism in coordination complexesMetal-Catalyzed Oxygenation Mechanisms

Azimuth-angle-dependent reflectivity data from metallic gratings

Alastair P. Hibbins、J. R. Sambles、Christopher R. Lawrence1998-05-01Journal of Modern Optics

In this work, we have used a new technique to characterize optically a periodically modulated metal–dielectric interface involving the measurement of the azimuthal-angle-dependent specular reflectivity. This method presents advantages over the conventional polar angle scan experiment since it requires no moving signal…

Optical Coatings and GratingsNear-Field Optical MicroscopySurface Roughness and Optical Measurements

Elastic properties of amorphous and crystalline B1−C and boron at low temperatures

Paul A. Medwick、B. E. White、R. O. Pohl1998-05-01Journal of Alloys and Compounds

We present measurements of the internal friction (Q−1) and speed of sound variation (δv/v0) of amorphous boron (a-B) and amorphous B9C (a-B9C). The elastic properties of these materials, which can only be produced as thin films, are consistent with those of other amorphous solids measured to date and exhibit good agre…

Advanced ceramic materials synthesisDiamond and Carbon-based Materials ResearchThermal properties of materials

Carbon deposition leading to filament growth on metals

José L. Figueiredo1998-05-01Materials and Corrosion

The kinetics and mechanisms of metal catalysed filamentous carbon formation and gasification are reviewed. In the process of filament growth metal crystallites are removed from the surface, so that cycles of coking/decoking can severely damage reactor surfaces and supported metal catalysts. These effects are exemplifi…

Catalytic Processes in Materials ScienceElectron and X-Ray Spectroscopy Techniquesnanoparticles nucleation surface interactions

Lateral deformation of plastic bottles: experiments, simulations and prevention

R. van Dijk、J. C. Sterk、D. Sgorbani 等 4 位作者1998-05-01Packaging Technology and Science

Mass reduction of plastic bottles containing non-carbonated liquids calls for advanced design approaches. Weight reduction of bottles consequently influences the mechanical performance of the bottle. This performance involves top load, vacuum and impact resistance. The present paper studies the lateral deformation of…

Natural Fiber Reinforced CompositesMicroplastics and Plastic PollutionTextile materials and evaluations

Dynamics of the smectic layer reorientation of ferroelectric liquid crystals

Ingo Dierking、L. Komitov、S. T. Lagerwall1998-05-01Liquid Crystals

Detailed experimental results of a systematic investigation of the dynamics of the in-plane smectic layer reorientation in SmC* ferroelectric liquid crystals on application of different types of asymmetric electric fields are reported. The reversible reorientation of smectic layers is characterized as a function of fi…

Liquid Crystal Research AdvancementsNonlinear Dynamics and Pattern FormationPlant Reproductive Biology

Electron transport and emission properties of diamond

J. E. Yater、A. Shih、R.H. Abrams1998-05-01Journal of Vacuum Science & Technology A Vacuum Surfaces and Films

The electron transport and emission properties of hydrogenated and cesiated single-crystal and chemical-vapor-deposited (CVD) diamond are investigated using secondary electron emission spectroscopy. The kinetic energy of the electrons and the height of the surface energy barrier are measured relative to the conduction…

Semiconductor materials and devicesDiamond and Carbon-based Materials ResearchElectronic and Structural Properties of Oxides

Mutational analysis of the active site of indoleglycerol phosphate synthase fromEscherichia coli

Beatrice Darimont、Catherine Stehlin、Halina Szadkoski 等 4 位作者1998-05-01Protein Science

Indoleglycerol phosphate synthase catalyzes the ring closure of 1-(2-carboxyphenylamino)-1-deoxyribulose 5'-phosphate to indoleglycerol phosphate, the fifth step in the pathway of tryptophan biosynthesis from chorismate. Because chemical synthesis of indole derivatives from arylamino ketones requires drastic solvent c…

Protein Structure and DynamicsMicrobial Natural Products and BiosynthesisEnzyme Structure and Function

Comparative study of mechanical and electrical relaxations in poly(etherimide). Part 2

Ricardo Díaz Calleja、S. Friederichs、Catherine Jaime's 等 8 位作者1998-05-01Polymer International

The curves describing the relaxation behaviour of poly(etherimide) at several frequencies shows in the dielectric loss–temperature plot γ and β relaxations centred at -95°C and 100°C, respectively, at 10Hz. The glass–rubber relaxation or α process appears at 225°C at 10Hz; at this temperature free charge conductivity…

Polymer Nanocomposites and PropertiesConducting polymers and applicationsDielectric materials and actuators

Quantum tunneling and classical barrier reduction for a mesoscopic spin

Jonathan R. Friedman1998-05-01Physical review. B, Condensed matter

I show that for a large spin with uniaxial anisotropy it is, in principle, impossible to distinguish classical energy-barrier reduction due to a transverse magnetic field from an increase in the tunneling rate of excited levels. Given a suitable definition of the quantum energy barrier, I derive an expression for the…

Quantum and electron transport phenomenaMagnetism in coordination complexesElectron Spin Resonance Studies

Thermoluminescence of Strontium Tetraborate

M. Santiago、M. Santiago、Araceli E. Lavat 等 11 位作者1998-05-01physica status solidi (a)

The thermoluminescent properties of crystalline strontium tetraborate are reported. Without activators it has an efficiency comparable to that of TLD-700 powders. Its fading after 40 days amounts to less than 2%. The isometric plot shows that most of the emitted light is concentrated at wavelengths ranging from 350 to…

Luminescence Properties of Advanced MaterialsSilicon Nanostructures and PhotoluminescenceRadiation Detection and Scintillator Technologies

Molecular Modelling of the Mechanism of Action of Borate Retarders on Hydrating Cements at High Temperature

Iain S. Bell、Peter V. Coveney1998-05-01Molecular Simulation

We consider the class of borate additives in an attempt to understand, on the basis of molecular modelling techniques, why they are effective high temperature cement setting retarder aids. Borates are known to act as cement retarders under ambient conditions, for which the Billingham-Coveney clock reaction scheme [1]…

High-pressure geophysics and materialsBoron and Carbon Nanomaterials ResearchX-ray Diffraction in Crystallography

Novel one-pot syntheses of sulfur-containing polymers from a bifunctional five-membered cyclic dithiocarbonate

Wonmun Choi、Fumio Sanda、Takeshi Endo1998-05-01Journal of Polymer Science Part A Polymer Chemistry

Novel one-pot syntheses of sulfur-containing polymers from a bifunctional five-membered cyclic dithiocarbonate (1a) were carried out. Polythiourethanes were obtained by the polyaddition of 4,4′-methylenebis(phenyl isocyanate), tolylene 2,6-diisocyanate, and hexamethylene diisocyanate with a dithiol (2a) obtained by th…

Chemical Synthesis and ReactionsSynthesis and properties of polymersSulfur-Based Synthesis Techniques

Temperature Dependence of the High‐Frequency Viscoelastic Behavior of a Soda‐Lime‐Silica Glass

L. Duffrène、René Gy、J. E. Masnik 等 5 位作者1998-05-01Journal of the American Ceramic Society

The high‐frequency viscoelastic behavior of a soda‐lime‐silica glass has been investigated using the Brillouin scattering technique. The temperature dependence of instantaneous elastic constants and very short‐time relaxation mechanisms have been measured in a temperature range between 100° and 1000°C. Variations in t…

High-pressure geophysics and materialsMaterial Dynamics and PropertiesGlass properties and applications

P -type transparent conducting In2O3–Ag2O thin films prepared by rf magnetron sputtering

Tadatsugu Minami、Koya Shimokawa、Toshihiro Miyata1998-05-01Journal of Vacuum Science & Technology A Vacuum Surfaces and Films

P -type transparent conducting oxide films consisting of a new multicomponent oxide composed of In2O3 and Ag2O have been prepared by rf magnetron sputtering. After postannealing at a temperature of 500 °C in air, In2O3–Ag2O thin films prepared using In2O3–Ag2O targets with Ag2O contents of 40–60 wt % exhibited p-type…

ZnO doping and propertiesGas Sensing Nanomaterials and SensorsTransition Metal Oxide Nanomaterials

Growing length scale related to the solidlike behavior in a supercooled liquid

Rajeev Ahluwalia、Shankar P. Das1998-05-01Physical review. E, Statistical physics, plasmas, fluids, and related interdisciplinary topics

The behavior of propagating shear waves in a supercooled liquid is analyzed, taking into account the proper structural effects at high density. The longest wavelength for the propagating shear waves that the undercooled liquid can sustain grows with density. This length scale, which is linked to a characteristic solid…

Material Dynamics and PropertiesTheoretical and Computational PhysicsRheology and Fluid Dynamics Studies

Dynamical aspect of a generalized Cahn–Hilliard equation based on a microforce balance

Alain Miranville、Alain Piétrus、Jean‐Michel Rakotoson1998-05-01Asymptotic Analysis

Our aim in this article is to study the existence of finite dimensional attractors for a class of generalized Cahn–Hilliard equations based on a microforce balance introduced by M. Gurtin (Physica D 92 (1996), 178–192). We first consider some general results on the existence of finite dimensional attractors, and then…

Solidification and crystal growth phenomenaAdvanced Mathematical Modeling in EngineeringDifferential Equations and Numerical Methods