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Chemical localization

V. F. Gantmakher2002-11-30Physics-Uspekhi

The current status of research and development in the realm of physics and technology of collective ion acceleration in systems with a virtual cathode (VC) is reviewed. Three major acceleration methods and devices developed on their basis are considered: reflex triodes and their modifications, gas-filled vircators, an…

Quasicrystal Structures and Properties

Spiral symmetry and general Bloch's theorem

Z. C. Tu2002-11-30arXiv

In this paper, spiral symmetry in cylindrical coordinate and general Bloch's theorem induced from it are discussed. This general Bloch's theorem is useful for considering the properties related to single-walled carbon nanotubes.

Materials ScienceMesoscale and Nanoscale Physics

Quantum tunneling of two coupled single-molecular magnets

J. M. Hu、Z. D. Chen、S. Q. Shen2002-11-30arXiv

Two single-molecule magnets are coupled antiferromagnetically to form a supramolecule dimer. We study the coupling effect and tunneling process by means of the numerical exact diagonalization method, and apply them to the recently synthesized supramoleculer dimer [Mn4]2 The model parameters are calculated for the dime…

Mesoscale and Nanoscale PhysicsMaterials Science

Singlet-energy transfer in quadruple hydrogen-bonded oligo(p-phenylenevinylene)perylene-diimide dyads

Edda E. Neuteboom、Edwin H. A. Beckers、Stefan C. J. Meskers 等 5 位作者2002-11-29Organic & Biomolecular Chemistry

The photophysical properties of a supramolecular donor-acceptor dyad consisting of an oligo(p-phenylenevinylene) unit and a perylene-diimide unit are described. The dyad is created by functionalising the two chromophores with quadruple hydrogen bonding 2-ureido-4[1H]-pyrimidinone units, which provide a high associatio…

Luminescence and Fluorescent MaterialsPorphyrin and Phthalocyanine ChemistryPhotochemistry and Electron Transfer Studies

Determining the structure of active sites, transition states and intermediates in heterogeneously catalysed reactions

John Meurig Thomas、C. Richard A. Catlow、Gopinathan Sankar2002-11-29Chemical Communications

With open-structure (nanoporous) oxidic solids, numerous distinct kinds of single-site catalysts may be precisely designed. Apart from serving as a means of generating a range of powerful new catalysts (especially for selective oxidations), in which well-defined active sites are carefully engineered, the detailed loca…

Catalysis and Oxidation ReactionsMesoporous Materials and CatalysisCatalytic Processes in Materials Science

Granular systems in the Coulomb blockade regime

D. P. Arovas、F. Guinea、C. Herrero 等 4 位作者2002-11-29arXiv

Disordered granular systems, at temperatures where charging effects are important, are studied, by means of an effective medium approximation. The intragrain charging energy leads to insulating behavior at low temperatures, with a well defined Coulomb gap. Non equilibrium effects can give rise to a zero temperature tr…

Materials ScienceStrongly Correlated ElectronsMesoscale and Nanoscale Physics

High quality GaMnAs films grown with As dimers

RP Campion、KW Edmonds、LX Zhao 等 7 位作者2002-11-29arXiv

We demonstrate that GaMnAs films grown with As2 have excellent structural, electrical and magnetic properties, comparable or better than similar films grown with As4. Using As2, a Curie temperature of 112K has been achieved, which is slightly higher than the best reported to date. More significantly, films showing met…

Materials Science

Phasons and the Plastic Deformation of Quasicrystals

Maurice Kleman2002-11-29arXiv

The plastic deformation of a quasicrystal (QC) is ruled by singularities of its 'phonon' strain field and of its 'phason' strain field. In the framework of the topological theory of defects, and the QC being defined as an irrational subset of a high dimensional crystal, both types of defects appear as distinct compone…

Materials Science

Ferroelectricity, SSFLC, bistability and all that

Ingolf Dahl2002-11-29arXiv

In the book "Ferroelectric and Antiferroelectric Liquid Crystals" by S. T. Lagerwall, the concept "polar liquid crystals" is proposed for the concept earlier known as "ferroelectric liquid crystals", reserving the word "ferroelectric liquid crystals" for the case of "surface stabilization". Thus Lagerwall in this way,…

Materials ScienceSoft Condensed Matter

Adsorbate-induced Surface Stiffening: Surface Lattice Dynamics of Ru(001)-(1x1)-O

T. Moritz、W. Widdra、D. Menzel 等 5 位作者2002-11-29arXiv

The dynamical properties of the high-density Ru(001)-(1$\times$1)-O phase has been investigated by a combined high-resolution electron energy loss spectroscopy and density functional theory study. Due to a strong static outward relaxation of the first Ru layer a soft Rayleigh phonon mode is expected. However, a Raylei…

Materials Science

Anisotropic Magnetoresistance in GaMnAs films

K. Y. Wang、K. W. Edmonds、R. P. Campion 等 8 位作者2002-11-29arXiv

The magnetoresistance in a series of Ga1-xMnxAs samples with 0.2 =< x =< 0.8 have been measured for three mutually orthogonal orientations of the external magnetic field. The anisotropy magnetoresistance decreases with increasing of the Mn content, which means that the magnetic disorder or defects scattering increases…

Materials ScienceMesoscale and Nanoscale Physics

In Vivo Imaging of Quantum Dots Encapsulated in Phospholipid Micelles

Benoît Dubertret、Paris A. Skourides、David J. Norris 等 6 位作者2002-11-29OpenAlex

Fluorescent semiconductor nanocrystals (quantum dots) have the potential to revolutionize biological imaging, but their use has been limited by difficulties in obtaining nanocrystals that are biocompatible. To address this problem, we encapsulated individual nanocrystals in phospholipid block-copolymer micelles and de…

Quantum Dots Synthesis And PropertiesRNA Interference and Gene DeliveryAdvanced biosensing and bioanalysis techniques

Inner-Sphere Complexation of Cobalt(II) 2,9-Dimethyl-1,10-phenanthroline ([Co(neo)]2+) with Commercial and Sol−Gel Derived Silica Gel Surfaces

Colleen M. Taylor、Stephen P. Watton、Peter A. Bryngelson 等 4 位作者2002-11-28Inorganic Chemistry

[Co(2,9-dimethyl-1,10-phenanthroline)(solvent)4]2+ ([Co(neo)]2+) undergoes a significant decrease in symmetry to form an inner-sphere surface complex when grafted directly on performed silica or introduced during the sol-gel process. The visible and X-ray absorption spectra of the surface adducts are interpreted in te…

Mesoporous Materials and CatalysisSurface Chemistry and CatalysisPorphyrin and Phthalocyanine Chemistry

Design and analysis of modified Rotman type multiple beam forming lens

P. K. Singhal、Rakesh Gupta、Priyanka Sharma2002-11-28OpenAlex

A modified approach to design Rotman (1963) type multiple beam forming lens has been proposed. The path length error at the wavefront has been calculated. The error obtained by the proposed approach and by the conventional approach has been compared. Two-dimensional electromagnetic field analysis of the lens obtained…

Laser and Thermal Forming TechniquesOptical Coatings and GratingsEngineering Applied Research

Effects of oxygen annealing on the physical properties and surface microstructures of La0.8Ba0.2MnO3films

P. Murugavel、J H Lee、K-B Lee 等 7 位作者2002-11-28Journal of Physics D Applied Physics

We have investigated the effects of oxygen annealing on the transport properties and surface microstructures of epitaxial La 0.8 Ba 0.2 MnO 3 (LBMO) films deposited on SrTiO 3 substrate at different oxygen pressures using the pulsed laser deposition technique. The thickness dependence of the transport properties was s…

Electronic and Structural Properties of OxidesAdvanced Condensed Matter PhysicsMagnetic and transport properties of perovskites and related materials

Qualitative analysis of a bulk ferromagnetic hysteresis model

R. Venkataraman、P. S. Krishnaprasad2002-11-28OpenAlex

We present a set of equations for a bulk ferromagnetic hysteresis model. We establish the connection between this set of equations and classical energy loss expressions for ferromagnetic hysteresis. We show analytically that for periodic inputs the system of equations has a limit set that is a periodic orbit in the H-…

Magnetic Properties and ApplicationsMetallurgy and Material FormingMicrostructure and Mechanical Properties of Steels

Atomic thermal motions studied by variable-temperature X-ray diffraction and related to non-linear optical properties of crystalline meta-di-nitrobenzene

G. Wójcik、Izabela Mossakowska、J. Holband 等 4 位作者2002-11-28Acta Crystallographica Section B Structural Science

The meta-dinitrobenzene crystal structure has been determined at five temperatures in the 100-300 K temperature range. The thermal expansion coefficients have been calculated from the temperature variation of the lattice parameters. Rigid-body motion analysis with allowance for large-amplitude internal motions provide…

Structural and Chemical Analysis of Organic and Inorganic CompoundsNonlinear Optical Materials ResearchChemical Thermodynamics and Molecular Structure

The structure of orange HgI2. I. Polytypic layer structure

M. Hostettler、Henrik Birkedal、D. Schwarzenbach2002-11-28Acta Crystallographica Section B Structural Science

The metastable orange crystals of HgI(2) comprise three different crystal structures, all of which are built from corner-linked Hg(4)I(10) supertetrahedra. Two of them are end members with the maximum degree of order (MDO) of a polytypic layer structure; the third shows a three-dimensional linkage. This paper presents…

Optical and Acousto-Optic TechnologiesCrystal Structures and PropertiesSolid-state spectroscopy and crystallography

Synthesis of a nonionic water soluble semiconductive polymer

Kenichi Kuroda、Timothy M. Swager2002-11-28Chemical Communications

A new nonionic water-soluble fluorescent conjugated polymer is reported with hydroxyl and amide side chains surrounding an aromatic polymer backbone.

Conducting polymers and applicationsLuminescence and Fluorescent MaterialsOrganic Electronics and Photovoltaics