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Hyperbranched polymers as scaffolds for multifunctional reversible addition–fragmentation chain‐transfer agents: A route to polystyrene‐core‐polyesters and polystyrene‐block‐poly(butyl acrylate)‐core‐polyesters

Martin Jesberger、Leonie Barner、Martina H. Stenzel 等 6 位作者2003-10-23Journal of Polymer Science Part A Polymer Chemistry

Abstract Polydisperse hyperbranched polyesters were modified for use as novel multifunctional reversible addition–fragmentation chain‐transfer (RAFT) agents. The polyester‐core‐based RAFT agents were subsequently employed to synthesize star polymers of n ‐butyl acrylate and styrene with low polydispersity (polydispers…

Advanced Polymer Synthesis and CharacterizationFuel Cells and Related MaterialsDendrimers and Hyperbranched Polymers

3D Composition of Epitaxial Nanocrystals by Anomalous X-Ray Diffraction: Observation of a Si-Rich Core in Ge Domes on Si(100)

Ângelo Malachias、S. Kycia、G. Medeiros‐Ribeiro 等 6 位作者2003-10-23Physical Review Letters

Three-dimensional composition maps of nominally pure Ge domes grown on Si(001) at 600 degrees C were obtained from grazing incidence anomalous x-ray scattering data at the Ge K edge. The data were analyzed in terms of a stack of layers with laterally varying concentration. The results demonstrated that the domes conta…

Silicon Nanostructures and PhotoluminescenceSemiconductor materials and interfacesSemiconductor Quantum Structures and Devices

Quasiparticle band structure of carbon nanotubes

Takashi Miyake、Susumu Saito2003-10-23Physical review. B, Condensed matter

We study the electronic structure of carbon nanotubes theoretically by first-principles techniques. Geometry is optimized with the local-density approximation (LDA) in density functional theory, and many-body effects between electrons are taken into account within the $\mathrm{GW}$ approximation. We find that the (5,0…

Carbon Nanotubes in CompositesGraphene research and applicationsBoron and Carbon Nanomaterials Research

Correlation between the Extraordinary Hall Effect and Resistivity

A. Gerber、A. Milner、A. Finkler 等 9 位作者2003-10-23arXiv

We study the contribution of different types of scattering sources to the extraordinary Hall effect. Scattering by magnetic nano-particles embedded in normal-metal matrix, insulating impurities in magnetic matrix, surface scattering and temperature dependent scattering are experimentally tested. Our new data, as well…

Materials Science

Low-temperature dynamics of weakly localized Frenkel excitons in disordered linar chains

M. Bednarz、J. Knoester、V. A. Malyshev2003-10-23arXiv

We calculate the temperature dependence of the fluorescence Stokes shift and the fluorescence decay time in linear Frenkel exciton systems resulting from the thermal redistribution of exciton population over the band states. The following factors, relevant to common experimental conditions, are accounted for in our ki…

cond-mat.dis-nnMaterials Science

Inhomogeneous magnetism in La-dopedCaMnO3.I. Mesoscopic phase separation due to lattice-coupled ferromagnetic interactions

Chris D. Ling、E. Granado、J. J. Neumeier 等 5 位作者2003-10-23Physical review. B, Condensed matter

A detailed investigation of mesoscopic magnetic and crystallographic phase separation in ${\mathrm{Ca}}_{1\ensuremath{-}x}{\mathrm{La}}_{x}{\mathrm{MnO}}_{3},$ $0.00<~x<~0.20,$ is reported. Neutron powder diffraction and dc-magnetization techniques have been used to isolate the different roles played by electron…

Rare-earth and actinide compoundsMagnetic and transport properties of perovskites and related materialsAdvanced Condensed Matter Physics

Inhomogeneous magnetism in La-dopedCaMnO3. II. Nanometric-scale spin clusters and long-range spin canting

E. Granado、Chris D. Ling、J. J. Neumeier 等 5 位作者2003-10-23Physical review. B, Condensed matter

Neutron measurements on ${\mathrm{Ca}}_{1\ensuremath{-}x}{\mathrm{La}}_{x}{\mathrm{MnO}}_{3}$ $(0.00<~x<~0.20)$ reveal the development of magnetic droplets showing a liquidlike intercluster spatial distribution. The average size of the droplets is $\ensuremath{\sim}10\mathrm{\AA{}},$ the concentration of which i…

Magnetic and transport properties of perovskites and related materialsAdvanced Condensed Matter PhysicsRare-earth and actinide compounds

Charge Ordering due to Magnetic Symmetry Breaking

I. V. Solovyev2003-10-23Physical Review Letters

It is argued that both transitions observed in 50% doped manganites, at the Néel temperature (T(N)) and the so-called charge ordering temperature (T(CO)), are magnetic. T(N) corresponds to the order-disorder transition, which takes place between ferromagnetic zigzag chains, while the coherent motion of spins within th…

Magnetic and transport properties of perovskites and related materialsAdvanced Condensed Matter PhysicsElectronic and Structural Properties of Oxides

Resonant photoluminescence and excitation spectroscopy of CdSe/ZnSe and CdTe/ZnTe self-assembled quantum dots

T. A. Nguyen、S. Mackowski、H. Rho 等 11 位作者2003-10-23arXiv

We show that two major carrier excitation mechanisms are present in II-VI self-assembled quantum dots. The first one is related to direct excited state - ground state transition. It manifests itself by the presence of sharp and intense lines in the excitation spectrum measured from single quantum dots. Apart from thes…

Materials Science

Temperature dependent fluorescence in disordered Frenkel chains: interplay of equilibration and local band-edge level structure

M. Bednarz、V. A. Malyshev、J. Knoester2003-10-23arXiv

We model the optical dynamics in linear Frenkel exciton systems governed by scattering on static disorder and lattice vibrations, and calculate the temperature dependent fluorescence spectrum and lifetime. The fluorescence Stokes shift shows a nonmonotonic behavior with temperature, which derives from the interplay of…

cond-mat.dis-nnMaterials Science

Energy Dissipation Mechanisms in Carbon Nanotube Oscillators

Yang Zhao、Chi-Chiu Ma、GuanHua Chen 等 4 位作者2003-10-23Physical Review Letters

Energy transfer from the translational degrees of freedom to phonon modes is studied for isolated systems of two coaxial carbon nanotubes, which may serve as a nearly frictionless nano-oscillator. It is found that for oscillators with short nanotubes (less than 30 A) a rocking motion, occurring when the inner tube is…

Force Microscopy Techniques and ApplicationsCarbon Nanotubes in CompositesMechanical and Optical Resonators

Substructure search procedures for macromolecular structures

Ralf W. Grosse‐Kunstleve、Paul D. Adams2003-10-23Acta Crystallographica Section D Biological Crystallography

This paper accompanies a lecture given at the 2003 CCP4 Study Weekend on experimental phasing. The first part is an overview of the fundamentals of Patterson methods and direct methods with the audience of the CCP4 Study Weekend in mind. In the second part, a new hybrid substructure search is outlined.

Electron and X-Ray Spectroscopy TechniquesEnzyme Structure and FunctionProtein Structure and Dynamics

Quantum-dot optical temperature probes

Glen W. Walker、Vikram Sundar、Christina M. Rudzinski 等 6 位作者2003-10-23OpenAlex

The steady-state photoluminescence (PL) properties of cadmium selenide quantum dots (QDs) with a zinc sulfide overlayer [(CdSe)ZnS] can be strongly dependent on temperature in the range from 100 to 315 K. The PL intensity from 50 to 55 Å (CdSe)ZnS QDs in poly(lauryl methacrylate) matrices increases by a factor of ∼5 w…

Luminescence Properties of Advanced MaterialsQuantum Dots Synthesis And PropertiesChalcogenide Semiconductor Thin Films

Preferential End-to-End Assembly of Gold Nanorods by Biotin−Streptavidin Connectors

K. K. Caswell、James N. Wilson、Uwe H. F. Bunz 等 4 位作者2003-10-23OpenAlex

A major challenge in nanoscience and nanotechnology is the rational assembly of nanoscale objects. Here we report that gold nanorods, aspect ratio 18, can be functionalized with a biotin disulfide, and subsequent addition of streptavidin links the rods together in an end-to-end manner much more often than expected.

Advanced biosensing and bioanalysis techniquesMolecular Junctions and NanostructuresQuantum Dots Synthesis And Properties

Recent Developments in Ring Opening Polymerization of Lactones for Biomedical Applications

Ann‐Christine Albertsson、I. K. Varma2003-10-23OpenAlex

Aliphatic polyesters prepared by ring-opening polymerization of lactones are now used worldwide as bioresorbable devices in surgery (orthopaedic devices, sutures, stents, tissue engineering, and adhesion barriers) and in pharmacology (control drug delivery). This review presents the various methods of the synthesis of…

biodegradable polymer synthesis and propertiesAdvanced Polymer Synthesis and CharacterizationBone Tissue Engineering Materials

Site Titration with Organic Bases During Catalysis: Selectivity Modifier and Structural Probe in Methanol Oxidation on Keggin Clusters

Haichao Liu、Nader Bayat、Enrique Iglesia2003-10-22Angewandte Chemie

Die selektive und permanente Titration von Protonen mit organischen Basen (2,6‐Di‐ tert ‐butylpyridin oder Pyridin) liefert ein genaues Maß für die Dispersion von Keggin‐Strukturen während der katalytischen Oxidation von Methanol. Die Titration ermöglicht die systematische Steuerung der Redox‐ und Säureeigenschaften v…

Metal-Organic Frameworks: Synthesis and ApplicationsPolyoxometalates: Synthesis and ApplicationsCatalysis and Oxidation Reactions

Polymeric dihydroxydiphthalatotricobalt(II)

Shi-Yao Yang、La‐Sheng Long、Rong-Bin Huang 等 5 位作者2003-10-22Acta Crystallographica Section C Crystal Structure Communications

In the crystal structure of dihydroxydiphthalatotricobalt(II), [Co(3)(C(8)H(4)O(4))(2)(OH)(2)](n), two of the four independent Co atoms lie at special positions of site symmetry 2. The hydroxy groups link three Co atoms to form a pyramidal Co(3)O unit, and adjacent Co(3)O units are linked through the Co base atoms int…

Layered Double Hydroxides Synthesis and ApplicationsChemical Synthesis and CharacterizationCrystal Structures and Properties

Lead and Zinc Partition Coefficients of Selected Soils Evaluated by Langmuir, Freundlich, and Linear Isotherms

Jean Diatta、W. Z. Kociałkowski、W. Grzebisz2003-10-22Communications in Soil Science and Plant Analysis

The paper outlines some approaches that should be considered in the calculation of partition coefficients based on Langmuir, Freundlich and Linear isotherms. It was found that the Langmuir partition coefficient (K Lg ), whose calculation involved the maximal amount of lead (Pb) and zinc (Zn) adsorbed and their appropr…

Heavy metals in environmentClay minerals and soil interactionsSoil and Unsaturated Flow

Microkinetic Videomicroscopic Analysis of Olefin Polymerization with a Supported Metallocene Catalyst

Stefan Knoke、Daniela Ferrari、B. Tesche 等 4 位作者2003-10-22Angewandte Chemie International Edition

Picture this: The simultaneous growth of many single grains of catalyst culminating in polymer particles can be observed by videomicroscopy, and single-grain kinetics can be studied. The gas-phase polymerization of ethylene on 40 particles was examined in an autoclave equipped with a glass window by automatic image pr…

Advanced Polymer Synthesis and CharacterizationMachine Learning in Materials ScienceCatalysis and Oxidation Reactions

A new hydrated ammonium hydroxyborate, (NH4)2[B10O14(OH)4]·H2O

Lin-Yan Li、Guo-Bao Li、Ming Xiong 等 5 位作者2003-10-22Acta Crystallographica Section C Crystal Structure Communications

The structure of a new synthetic compound, diammonium tetrahydroxydecaborate monohydrate, has been determined by single-crystal X-ray diffraction. It crystallizes in triclinic space group P-1 and all atoms occupy general sites. The title compound is composed of [B(10)O(15)(OH)(4)](4-) ions as the fundamental building…

Crystal structures of chemical compoundsCrystal Structures and PropertiesX-ray Diffraction in Crystallography