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Theory of dynamic crack branching in brittle materials

E. Katzav、M. Adda-Bedia、R. Arias2007-02-21arXiv

The problem of dynamic symmetric branching of an initial single brittle crack propagating at a given speed under plane loading conditions is studied within a continuum mechanics approach. Griffith's energy criterion and the principle of local symmetry are used to determine the cracks paths. The bifurcation is predicte…

Materials Science

Surface Reconstruction with a Fractional Hole:(5×5)R26.6°LaAlO3(001)

Courtney H. Lanier、James M. Rondinelli、Bin Deng 等 6 位作者2007-02-21Physical Review Letters

The structure of the (sqrt[5] x sqrt[5])R26.6 degrees reconstruction of LaAlO3 (001) has been determined using transmission electron diffraction combined with direct methods. It has a lanthanum oxide termination with one lanthanum vacancy per surface unit cell. Density functional calculations indicate that charge comp…

Electronic and Structural Properties of OxidesZnO doping and propertiesSemiconductor materials and devices

Effect of lattice-mismatch-induced strains on coupled diffusive and displacive phase transformations

Mathieu Bouville、Rajeev Ahluwalia2007-02-21Physical Review B

Materials which can undergo slow diffusive transformations as well as fast displacive transformations are studied using the phase-field method. The model captures the essential features of the time-temperature-transformation (TTT) diagrams, continuous cooling transformation (CCT) diagrams, and microstructure formation…

Shape Memory Alloy TransformationsSolidification and crystal growth phenomenaMicrostructure and Mechanical Properties of Steels

Strain relaxation in GaN grown on vicinal 4H-SiC(0001) substrates

Julien Pernot、Etienne Bustarret、Mariusz Rudzinski 等 5 位作者2007-02-21arXiv

The strain of GaN layers grown by Metal Organic Chemical Vapor Deposition (MOCVD) on three vicinal 4H-SiC substrates (0, 3.4 and 8 offcut from [0001] towards [11-20] axis) is investigated by X-ray Diffraction (XRD), Raman Scattering and Cathodoluminescence (CL). The strain relaxation mechanisms are analyzed for each m…

Materials Science

Nernst effect in semi-metals: the meritorious heaviness of electrons

Kamran Behnia、Marie-Aude Measson、Yakov Kopelevich2007-02-21arXiv

We present a study of electric, thermal and thermoelectric transport in elemental Bismuth, which presents a Nernst coefficient much larger than what was found in correlated metals. We argue that this is due to the combination of an exceptionally low carrier density with a very long electronic mean-free-path. The low t…

Strongly Correlated ElectronsMaterials Science

Kohn anomalies and non-adiabaticity in doped carbon nanotubes

Nicolas Caudal、A. Marco Saitta、Michele Lazzeri 等 4 位作者2007-02-21arXiv

The high-frequency Raman-active phonon modes of metallic single-walled carbon nanotubes (SWNTs) are thought to be characterized by Kohn anomalies (KAs), which are expected to be modified by the doping-induced tuning of the Fermi energy level $ε_F$, obtained through the intercalation of SWNTs with alkali atoms or by th…

Soft Condensed MatterMaterials Science

Orbital Interaction Mechanisms of Conductance Enhancement and Rectification by Dithiocarboxylate Anchoring Group

Zhenyu Li、D. S. Kosov2007-02-21arXiv

We study computationally the electron transport properties of dithiocarboxylate terminated molecular junctions. Transport properties are computed self-consistently within density functional theory and nonequilibrium Green's functions formalism. A microscopic origin of the experimentally observed current amplification…

cond-mat.stat-mechMaterials Science

Lanthanide-Doped NaYF4 Nanocrystals in Aqueous Solution Displaying Strong Up-Conversion Emission

Helmut Schäfer、Pavel Ptáček、Karsten Kömpe 等 4 位作者2007-02-21Chemistry of Materials

NaYF 4:Yb 3+,Er 3+ nanocrystals showing high colloidal solubility in water have been obtained by treating the nanocrystals with 1-hydroxyethane-1,1-diphosphonic acid (HEDP). HEDP attaches to the surface of the nanoparticles and leads to well-separated particles in aqueous solution as verified by IR spectroscopy and dy…

Inorganic Fluorides and Related CompoundsQuantum Dots Synthesis And PropertiesLuminescence Properties of Advanced Materials

Highly Reducible CeO2 Nanotubes

Kebin Zhou、Zhiqiang Yang、Sen Yang2007-02-21Chemistry of Materials

Ceria nanotubes with extended cavities can be obtained by a facile oxidation−coordination-assisted dissolution process of the partially oxidized one-dimensional Ce(OH)3. Moreover, the ceria nanotubes with large cavities and thin walls exhibit excellent reducibility and high oxygen storage capacity, indicating they are…

Catalytic Processes in Materials ScienceAdvanced Photocatalysis TechniquesElectrocatalysts for Energy Conversion

His-tag impact on structure

Mike Carson、David H. Johnson、Heather M. McDonald 等 5 位作者2007-02-21Acta Crystallographica Section D Biological Crystallography

Crystallographers are increasingly determining structures of protein constructs that include His tags. Many have taken for granted that these tags have little effect on the native structure. This paper surveys and compares crystal structures with and without His tags. It is observed that actual refined tag residues fi…

Enzyme Structure and FunctionRNA and protein synthesis mechanismsProtein Structure and Dynamics

Attributing Effects of Aqueous C60 Nano-Aggregates to Tetrahydrofuran Decomposition Products in Larval Zebrafish by Assessment of Gene Expression

Theodore B. Henry、Fu‐Min Menn、James T. Fleming 等 6 位作者2007-02-21Environmental Health Perspectives

BACKGROUND: C(60) is a highly insoluble nanoparticle that can form colloidal suspended aggregates in water, which may lead to environmental exposure in aquatic organisms. Previous research has indicated toxicity from C(60) aggregate; however, effects could be because of tetrahydrofuran (THF) vehicle used to prepare ag…

Advanced oxidation water treatmentEnvironmental Toxicology and EcotoxicologyNanoparticles: synthesis and applications

Condensation and Wetting Transitions on Microstructured Ultrahydrophobic Surfaces

Christian Dorrer、Jürgen Rühe2007-02-21Langmuir

On rough surfaces, two distinct wetting modes can appear. These two states are usually described by the theories of Cassie (drops suspended on top of roughness features) and Wenzel (drops impaled on roughness features). Whereas the wetting transition from the Cassie to the Wenzel state has been relatively well studied…

Surface Modification and SuperhydrophobicityAdhesion, Friction, and Surface InteractionsFluid Dynamics and Heat Transfer

Efficient and Color-Tunable Mn-Doped ZnSe Nanocrystal Emitters: Control of Optical Performance via Greener Synthetic Chemistry

Narayan Pradhan、Xiaogang Peng2007-02-21OpenAlex

Formation of Mn-doped ZnSe quantum dots (Mn:ZnSe d-dots) using nucleation-doping strategy was studied systematically and optimized through greener approaches. The resulting d-dots were with high ( approximately 50%) photoluminescence (PL) quantum yield (QY), which was achieved by the controlled formation of small-size…

Quantum Dots Synthesis And PropertiesNanocluster Synthesis and ApplicationsChalcogenide Semiconductor Thin Films

Interfacial plasticity governs strain rate sensitivity and ductility in nanostructured metals

Ting Zhu、Ju Li、Amit Samanta 等 5 位作者2007-02-21OpenAlex

Nano-twinned copper exhibits an unusual combination of ultrahigh strength and high ductility, along with increased strain-rate sensitivity. We develop a mechanistic framework for predicting the rate sensitivity and elucidating the origin of ductility in terms of the interactions of dislocations with interfaces. Using…

Metal and Thin Film MechanicsHigh-Velocity Impact and Material BehaviorMicrostructure and mechanical properties

Ab initio simulation of the vibrationally resolved photoelectron spectrum of Si3−

Pablo García‐Fernández、James E. Boggs、John F. Stanton2007-02-20The Journal of Chemical Physics

Electron photodetachment spectra provide a wealth of information about the electronic and vibrational level structures of neutral molecules that form stable anions. Experiments carried out for the smallest polyatomic silicon cluster anion (Si3-+hupsilon-->Si3*+e-) show vibrational progressions in six observed electron…

Electron and X-Ray Spectroscopy TechniquesAdvanced Chemical Physics StudiesX-ray Spectroscopy and Fluorescence Analysis

ORBITAL INSULATORS AND ORBITAL ORDER–DISORDER INDUCED METAL–INSULATOR TRANSITION IN TRANSITION-METAL OXIDES

Dongmeng Chen、Liang‐Jian Zou2007-02-20International Journal of Modern Physics B

The role of orbital ordering on metal–insulator transition in transition-metal oxides is investigated by the cluster self-consistent field approach in the strong correlation regime. A clear dependence of the insulating gap of single-particle excitation spectra on the orbital order parameter is found. The thermal fluct…

Advanced Condensed Matter PhysicsMagnetic and transport properties of perovskites and related materialsHigh-pressure geophysics and materials

An Anomalous Spin-Polarization Mechanism in High-Spin Manganese(III) Porphyrin Complexes

Ru-Jen Cheng、Shu-Hao Chang、Kuo-Cheng Hung2007-02-20Inorganic Chemistry

Confluence of NMR for paramagnetic molecules and the complementary density functional theory calculations reveals an anomalous spin-polarization mechanism that is maximized in high-spin d(4) complexes. It is critical to realize this mechanism to correctly rationalize the spin-density distribution around the porphyrin…

Porphyrin and Phthalocyanine ChemistryMagnetism in coordination complexesMetal-Catalyzed Oxygenation Mechanisms

CATION DISTRIBUTION OF MnFe2O4 NANOPARTICLES SYNTHESIZED UNDER AN INDUCED MAGNETIC FIELD

Jun Wang、Yejun Wu、Yuejin Zhu2007-02-20International Journal of Modern Physics B

Nanoparticles of MnFe 2 O 4 have been synthesized under an induced magnetic field by a hydrothermal process. A strong correlation between the cation distribution and the magnetic properties of MnFe 2 O 4 nanoparticles has been identified. From the results of Mössbauer spectroscopy it has been found that the nanopartic…

Magnetic Properties and Synthesis of FerritesIron oxide chemistry and applicationsMultiferroics and related materials

The Effect of Halide Salts on the Production of Gymnoascus reessii Polyenylpyrroles

Benjamin R. Clark、Ernest Lacey、Jennifer H. Gill 等 4 位作者2007-02-20Journal of Natural Products

Addition of NaCl to the solid-phase fermentation of an Australian isolate of Gymnoascus reessii resulted in enhanced production of chloropolyenylpyrroles, while the addition of NaBr suppressed chloropolyenylpyrrole production in favor of bromo and dechloro analogues. Access to a wider selection of polyenylpyrroles pro…

Phytochemistry and Bioactive Compounds