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Nucleation and Growth of Lead Sulfide Nano- and Microcrystallites in Supramolecular Polymer Assemblies

Ashim Kumar Dutta、Thaotrang Ho、Liqin Zhang 等 4 位作者2000-03-14Chemistry of Materials

Multilayer thin film assemblies fabricated by the sequential adsorption of polyelectrolytes on a quartz substrate were used as a supramolecular reaction template to study the in situ nucleation and growth of PbS nano- and microparticles. Chemical reaction within the polymer film was initiated by absorbing Pb 2+ from a…

Quantum Dots Synthesis And PropertiesChalcogenide Semiconductor Thin FilmsPolymer Surface Interaction Studies

Lipases Provide a New Mechanistic Model for Polyhydroxybutyrate (PHB) Synthases: Characterization of the Functional Residues in Chromatium vinosum PHB Synthase

Yong Jia、T. Joseph Kappock、T D Frick 等 5 位作者2000-03-14Biochemistry

Polyhydroxybutyrate (PHB) synthases catalyze the conversion of beta-hydroxybutyryl coenzyme A (HBCoA) to PHB. These enzymes require an active site cysteine nucleophile for covalent catalysis. A protein BLASTp search using the Class III Chromatium vinosum synthase sequence reveals high homology to prokaryotic lipases w…

Biofuel production and bioconversionbiodegradable polymer synthesis and propertiesMicrobial Metabolic Engineering and Bioproduction

The retro -GCN4 leucine zipper sequence forms a stable three-dimensional structure

Peer R. E. Mittl、Christine Deillon、David F. Sargent 等 8 位作者2000-03-14Proceedings of the National Academy of Sciences

The question of whether a protein whose natural sequence is inverted adopts a stable fold is still under debate. We have determined the 2. 1-A crystal structure of the retro-GCN4 leucine zipper. In contrast to the two-stranded helical coiled-coil GCN4 leucine zipper, the retro-leucine zipper formed a very stable, para…

Protein Structure and DynamicsGlycosylation and Glycoproteins ResearchEnzyme Structure and Function

Magnetic and electrical resistance behaviour of the oxides, Ca$_{3-x}$Y$_x$LiRuO$_6$ (x= 0.0, 0.5 and 1.0)

M. Mahesh Kumar、E. V. Sampathkumaran2000-03-14arXiv

We have investigated the magnetic and electrical resistance behaviour of Ca$_{3-x}$Y$_x$LiRuO$_6$. The parent compound exhibits magnetic ordering from Ru sublattice at a rather high temperature, 113 K. Though the paramagnetic Curie temperature ($θ$$_p$) is negative indicative of antiferromagnetic ordering, the large m…

Materials ScienceStrongly Correlated Electrons

Reconstructions of diamond (100) and (111) surfaces: Accuracy of the Brenner potential

A. V. Petukhov、A. Fasolino2000-03-14arXiv

We present a detailed comparison of the structural predictions of the effective many-body Brenner potential with those of ab-initio studies for known reconstructions of diamond (100) and (111) surfaces. These results suggest high reliability of the Brenner potential for dealing with carbon-based structures where diffe…

Materials Science

Optical transitions in broken gap heterostructures

E. Halvorsen、Y. Galperin、K. A. Chao2000-03-14arXiv

We have used an eight band model to investigate the electronic structures and to calculate the optical matrix elements of InAs-GaSb broken gap semiconductor heterostructures. The unusual hybridization of the conduction band states in InAs layers with the valence band states in GaSb layers has been analyzed in details.…

Materials Science

Giant AC magnetoresistance and anisotropic AC magnetoresistance in granular magnetic alloys

A. B. Pakhomov、J. C. Denardin、M. Knobel 等 4 位作者2000-03-14arXiv

(withdrawn)AC resistance of melt-spun granular magnetic Cu85Co15 ribbons was measured as a function of temperature in the range 5-300 K, magnetic field Hdc in the range -60 kOe to 60 kOe, and frequency in the range 1-1000 Hz. A sharp peak of zero-field resistance, which scales with frequency, and an associated isotrop…

Materials Science

Atomic Quadrupolar Photoemission Asymmetry Parameters from a Solid State Measurement

GDF Jackson、Bruce C. C. Cowie、D.P. Woodruff 等 8 位作者2000-03-13Physical Review Letters

A method for measuring the asymmetry parameter gamma arising from dipole-quadrupole interference in core-level photoemission is proposed which is based on condensed thin films and exploits the influence of this asymmetry in photoemission monitoring of x-ray standing wave field absorption. The high density of material…

X-ray Spectroscopy and Fluorescence AnalysisElectron and X-Ray Spectroscopy TechniquesIon-surface interactions and analysis

Squeezing Alcohols into Sonoluminescing Bubbles: The Universal Role of Surfactants

Rüdiger Tögel、Sascha Hilgenfeldt、Detlef Lohse2000-03-13Physical Review Letters

We conduct an experimental study of the dependence of single bubble sonoluminescence intensity on the concentration of various alcohols. The light intensity is reduced by one-half at a molar fraction of ethanol of approximately 2.5x10(-5); butanol achieves the same reduction at a concentration 10 times smaller. We acc…

Ultrasound and Hyperthermia ApplicationsUltrasound and Cavitation PhenomenaPhotoacoustic and Ultrasonic Imaging

Thermal amplification of photoinduced optical anisotropy of p-cyanoazobenzene polymer films monitored by temperature scanning ellipsometry

Masatoshi Kidowaki、Takenori Fujiwara、Shin’ya Morino 等 5 位作者2000-03-13Applied Physics Letters

The in situ observation of thermal alteration of photoinduced optical anisotropy of ultrathin films of polymethacrylates having p-cyanoazobenzene side chains exhibiting amorphous, crystalline, and liquid-crystalline phases was performed by means of temperature scanning ellipsometry. Whereas photogenerated optical anis…

Liquid Crystal Research AdvancementsPhotochemistry and Electron Transfer StudiesOptical Polarization and Ellipsometry

Anisotropic magnetic susceptibility of multiwalled carbon nanotubes

F. Tsui、L. Jin、Otto Zhou2000-03-13Applied Physics Letters

Magnetic susceptibility of partially aligned multiwalled carbon nanotubes has been studied using superconducting quantum interference device magnetometry. Partial alignment of multiwalled nanotubes was produced by uniaxially straining composites of carbon nanotubes embedded in polymer matrices. The degree of alignment…

Carbon Nanotubes in CompositesGraphene research and applicationsMechanical and Optical Resonators

Formation dynamics of silicon nanoparticles after laser ablation studied using plasma emission caused by second-laser decomposition

Tetsuya Makimura、Taiji Mizuta、Kouichi Murakami2000-03-13Applied Physics Letters

We have investigated the dynamic formation of silicon nanoparticles after pulsed-laser ablation of a silicon target into argon gas, in order to fabricate the nanoparticles that exhibit visible photoluminescence with higher efficiency. The nanoparticles growing in argon gas were detected by measuring plasma emission re…

Silicon Nanostructures and PhotoluminescenceNanowire Synthesis and ApplicationsLaser-Ablation Synthesis of Nanoparticles

Importance of intermolecular interactions in the nonlinear optical properties of poled polymers

Ilias Liakatas、Chengzhi Cai、M. Bösch 等 8 位作者2000-03-13Applied Physics Letters

A series of phenylbithiophene stilbenes and phenyltetraenes were synthesized and their first-order molecular hyperpolarizabilities determined. Optical nonlinearities up to μβo=9300×10−69 C m5/V were measured at 1907 nm. We show that intermolecular interactions have a large influence on the optical nonlinearity of the…

Liquid Crystal Research AdvancementsNonlinear Optical Materials ResearchNonlinear Optical Materials Studies

Quantum dots in photonic dots

Mikhail Artemyev、U. Woggon2000-03-13Applied Physics Letters

A micrometer-sized spherical microcavity, the photonic dot, is made from semiconductor nanocrystals, the quantum dots. The coupling of electronic and photonic states is demonstrated for a single photonic dot by the observation of whispering gallery modes in the spectrum of spontaneous emission of the embedded CdSe qua…

Semiconductor Quantum Structures and DevicesQuantum Dots Synthesis And PropertiesPhotonic Crystals and Applications

Integration of Pb(Zr0.52Ti0.48)O3 epilayers with Si by domain epitaxy

Anand Sharma、J. Narayan、Chendong Jin 等 6 位作者2000-03-13Applied Physics Letters

High-quality lead zirconate titanate films (PZT) have been grown on yttrium barium copper oxide (YBCO) bottom electrode by domain epitaxy where integral multiples of lattice constants match across the interface. The YBCO films were epitaxially fabricated on Si (100) by introducing epilayer geometry of strontium titana…

Ferroelectric and Piezoelectric MaterialsSemiconductor materials and devicesElectronic and Structural Properties of Oxides

Magnetoresistance of Ferromagnetic Tunnel Junctions in the Double-Exchange Model

H. Itoh、Tomokatsu Ohsawa、Jun-ichiro Inoue2000-03-13Physical Review Letters

We conduct a theoretical study of the temperature dependence of the spin polarization ( P) and the magnetoresistance (MR) ratio using the double exchange (DE) model for ferromagnetic tunnel junctions with half-metallic systems. It is shown that the strong exchange coupling in the DE model plays an important role in th…

Physics of Superconductivity and MagnetismMagnetic properties of thin filmsMagnetic and transport properties of perovskites and related materials

Structures and optical properties of silicon nanocrystallites prepared by pulsed-laser ablation in inert background gas

Nobuyasu Suzuki、Toshiharu Makino、Yuka Yamada 等 5 位作者2000-03-13Applied Physics Letters

Silicon (Si) nanocrystallites have been synthesized using pulsed-laser ablation in inert background gases, for studying the structures and optical properties as one of the quantum confinement effects. We extracted a process condition where well-dispersed Si nanocrystallites devoid of droplets and debris are prepared,…

Thin-Film Transistor TechnologiesSilicon Nanostructures and PhotoluminescenceNanowire Synthesis and Applications

Gapping by Squashing: Metal-Insulator and Insulator-Metal Transitions in Collapsed Carbon Nanotubes

Paul E. Lammert、Peihong Zhang、Vincent H. Crespi2000-03-13Physical Review Letters

Squashing brings circumferentially separated areas of a carbon nanotube into close proximity, drastically altering the low-energy electronic properties and (in some cases) reversing standard rules for metallic versus semiconducting behavior. Such a deformation mode, not requiring motion of tube ends, may be useful for…

Carbon Nanotubes in CompositesGraphene research and applicationsBoron and Carbon Nanomaterials Research

Effect of short range order on electronic and magnetic properties of disordered Co based alloys

Subhradip Ghosh、Chhanda Basu Chaudhuri、Biplab Sanyal 等 4 位作者2000-03-13arXiv

We here study electronic structure and magnetic properties of disordered CoPd and CoPt alloys using Augmented Space Recursion technique coupled with the tight-binding linearized muffin tin orbital (TB-LMTO) method. Effect of short range ordering present in disordered phase of alloys on electronic and magnetic properti…

Materials Science