On the quantum and classical scattering times due to charged dislocations in an impure electron gas

We derive the ratio of transport and single particle relaxation times in three and two - dimensional electron gases due to scattering from charged dislocations in semiconductors. The results are compared to the respective relaxation times due to randomly placed charged impurities. We find that the ratio is larger than the case of ionized impurity scattering in both three and two-dimensional electron transport.Comment: 4 pages, 3 figure

Integration of molecular biology tools for identifying promoters and genes abundantly expressed in flowers of Oncidium Gower Ramsey

<p>Abstract</p> <p>Background</p> <p>Orchids comprise one of the largest families of flowering plants and generate commercially important flowers. However, model plants, such as <it>Arabidopsis thaliana </it>do not contain all plant genes, and agronomic and horticulturally important genera and species must be individually studied.</p> <p>Results</p> <p>Several molecular biology tools were used to isolate flower-specific gene promoters from <it>Oncidium </it>'Gower Ramsey' (<it>Onc</it>. GR). A cDNA library of reproductive tissues was used to construct a microarray in order to compare gene expression in flowers and leaves. Five genes were highly expressed in flower tissues, and the subcellular locations of the corresponding proteins were identified using lip transient transformation with fluorescent protein-fusion constructs. BAC clones of the 5 genes, together with 7 previously published flower- and reproductive growth-specific genes in <it>Onc</it>. GR, were identified for cloning of their promoter regions. Interestingly, 3 of the 5 novel flower-abundant genes were putative trypsin inhibitor (<it>TI</it>) genes (<it>OnTI1</it>, <it>OnTI2 </it>and <it>OnTI3</it>), which were tandemly duplicated in the same BAC clone. Their promoters were identified using transient GUS reporter gene transformation and stable <it>A. thaliana </it>transformation analyses.</p> <p>Conclusions</p> <p>By combining cDNA microarray, BAC library, and bombardment assay techniques, we successfully identified flower-directed orchid genes and promoters.</p

The Brown Dwarf Kinematics Project (BDKP): V. Radial and rotational velocities of T Dwarfs from Keck/NIRSPEC high-resolution spectroscopy

Stars and planetary system

Conductance behavior of tetraphenyl-Aza-Bodipys

We studied the electrical conductance of single-molecule junctions formed from molecular wires with four anchor groups. Three tetraphenyl-aza-BODIPYs with four or two thiomethyl anchor groups were synthesized, and their single-molecule conductance was measured using break-junction-STM. Using DFT based calculations these compounds were shown to display a combination of a high and low conductance, depending on the molecule's connectivity in the junction. A scissor correction is employed to obtain the corrected HOMO-LUMO gaps and a tight binding model (TBM) is used to highlight the role of transport through the pi system of the tetraphenyl-aza-BODIPY central unit. The three higher-conductance geometries follow the sequence 3 > 4 > 2, which demonstrates that their conductances are correlated with the number of anchors

Nanocrystal and surface alloy properties of bimetallic Gold-Platinum nanoparticles

We report on the correlation between the nanocrystal and surface alloy properties with the bimetallic composition of gold-platinum(AuPt) nanoparticles. The fundamental understanding of whether the AuPt nanocrystal core is alloyed or phase-segregated and how the surface binding properties are correlated with the nanoscale bimetallic properties is important not only for the exploitation of catalytic activity of the nanoscale bimetallic catalysts, but also to the general exploration of the surface or interfacial reactivities of bimetallic or multimetallic nanoparticles. The AuPt nanoparticles are shown to exhibit not only single-phase alloy character in the nanocrystal, but also bimetallic alloy property on the surface. The nanocrystal and surface alloy properties are directly correlated with the bimetallic composition. The FTIR probing of CO adsorption on the bimetallic nanoparticles supported on silica reveals that the surface binding sites are dependent on the bimetallic composition. The analysis of this dependence further led to the conclusion that the relative Au-atop and Pt-atop sites for the linear CO adsorption on the nanoparticle surface are not only correlated with the bimetallic composition, but also with the electronic effect as a result of the d-band shift of Pt in the bimetallic nanocrystals, which is the first demonstration of the nanoscale core-surface property correlation for the bimetallic nanoparticles over a wide range of bimetallic composition

Low-temperature co-sintering for fabrication of zirconia/ceria bi-layer electrolyte via tape casting using a Fe2O3 sintering aid

Bilayer electrolytes have potential in solid oxide cells to improve ionic conduction whilst blocking electronic conduction. GDC/YSZ bilayer electrolyte processinghas provenproblematic due to thermochemical instability at high sintering temperatures. We first match the shrinkage profile of the two bulk materials using a Fe2O3 sintering additive. Additions of 5 mol% of Fe2O3 in the GDC layer and 2 mol% of Fe2O3 in the YSZ layer prevents delamination during co-sintering. The addition of Fe2O3 promotes densification, enabling achievement of a dense bilayer at a reduced sintering temperature of 1300 ◦C; ∼150 ◦C below conventional sintering temperatures. Elemental analysis showed the compositional distribution curves across the bilayer interface to be asymmetric when Fe2O3 is employed. The Fe2O3 increases the total conductivity of the bilayer electrolyte by an order of magnitude; this is explained by the effect of Fe2O3 on reducing the resistive solid solution interlayer at YSZ/GDC interface from ∼15 to ∼5 m

Ion transport through homogeneous and heterogeneous ion-exchange membranes in single salt and multicomponent electrolyte solutions

The increasing demand for clean industrial processes has intensified the use of electrodialysis in the treatment of metal containing effluents and encourages the investigation of the different phenomena involved in the transport of metal ions through cation-exchange membranes. Ion sorption, chronopotentiometric and current–voltage characteristics have been obtained to characterize the transport of sodium and iron through homogeneous and heterogeneous cation-exchange membranes. The heterogeneous membranes having a broader pore size distribution showed increased electrical resistances with solutions of trivalent iron, which may be caused by the blockage of the smallest pores by multivalent ions. However, for both types of membranes an unexpected decrease of the electrical resistance with increasing current densities was verified with concentrated solutions of Fe2(SO4)3. This behavior was explained to be a consequence of the dissociation of FeSO4+ ions into more conductive Fe3+ and SO42− ions as the depleting solution layer becomes diluted. When tested with multicomponent mixtures, the homogeneous perfluorosulfonic membranes show an increased preference for Na+ ions at low current densities and, once Na+ ions are depleted from the membrane surface Fe3+ ions are transported preferentially at higher current densities. On the contrary, both Na+ ions and Fe(III) species are responsible for the ion transport through the heterogeneous membranes within the ohmic regime of currents.This work was supported by the Ministerio de Economia y Competitividad (Spain) with the Project number CTQ2012-37450-C02-01/PPQ. M.C. Marti-Calatayud is grateful to the Universitat Politecnica de Valencia for a postgraduate grant (Ref. 2010-12). D.C. Buzzi wants to express her gratitude to CAPES (Brazil) for a postgraduate grant (Proc. BEX 8747/11-3).Martí Calatayud, MC.; Buzzi, DC.; García Gabaldón, M.; Bernardes, AM.; Tenório, JAS.; Pérez Herranz, V. (2014). Ion transport through homogeneous and heterogeneous ion-exchange membranes in single salt and multicomponent electrolyte solutions. Journal of Membrane Science. 466:45-57. https://doi.org/10.1016/j.memsci.2014.04.033S455746

Search for direct production of charginos and neutralinos in events with three leptons and missing transverse momentum in √s = 7 TeV pp collisions with the ATLAS detector

A search for the direct production of charginos and neutralinos in final states with three electrons or muons and missing transverse momentum is presented. The analysis is based on 4.7 fb−1 of proton–proton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with Standard Model expectations in three signal regions that are either depleted or enriched in Z-boson decays. Upper limits at 95% confidence level are set in R-parity conserving phenomenological minimal supersymmetric models and in simplified models, significantly extending previous results

Jet size dependence of single jet suppression in lead-lead collisions at sqrt(s(NN)) = 2.76 TeV with the ATLAS detector at the LHC

Measurements of inclusive jet suppression in heavy ion collisions at the LHC provide direct sensitivity to the physics of jet quenching. In a sample of lead-lead collisions at sqrt(s) = 2.76 TeV corresponding to an integrated luminosity of approximately 7 inverse microbarns, ATLAS has measured jets with a calorimeter over the pseudorapidity interval |eta| < 2.1 and over the transverse momentum range 38 < pT < 210 GeV. Jets were reconstructed using the anti-kt algorithm with values for the distance parameter that determines the nominal jet radius of R = 0.2, 0.3, 0.4 and 0.5. The centrality dependence of the jet yield is characterized by the jet "central-to-peripheral ratio," Rcp. Jet production is found to be suppressed by approximately a factor of two in the 10% most central collisions relative to peripheral collisions. Rcp varies smoothly with centrality as characterized by the number of participating nucleons. The observed suppression is only weakly dependent on jet radius and transverse momentum. These results provide the first direct measurement of inclusive jet suppression in heavy ion collisions and complement previous measurements of dijet transverse energy imbalance at the LHC.Comment: 15 pages plus author list (30 pages total), 8 figures, 2 tables, submitted to Physics Letters B. All figures including auxiliary figures are available at http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/HION-2011-02