10,006 research outputs found

    Reply to Comment on "Dynamical corrections to the DFT-LDA electron conductance in nanoscale systems"

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    We reply to the comment by Jung, Bokes, and Godby (arXiv:0706.0140) on our paper Phys. Rev. Lett. 94, 186810 (2005). We show that the results in their comment should not be taken as an indication that the viscosity corrections to the conductance of real nanoscale structures are small. A more accurate treatment of the density and current density distribution and of the electronic correlations may yield much larger corrections in realistic systems.Comment: Reply to the comment by Jung et al (arXiv:0706.0140). 1 page, no figures, to appear in PR

    Bacterial Source Tracking to Support the Development and Implementation of Watershed Protection Plans for the Lampasas and Leon Rivers: Lampasas River Watershed Final Report

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    The Bacterial Source Tracking to Support the Development and Implementation of Watershed Protection Plans for the Lampasas and Leon Rivers project was developed to provide supplemental information to stakeholders engaged in the development and implementation of watershed protection plans for each watershed. The Leon River is listed as an impaired water body for elevated levels of E. coli and does not support its designated contact recreation use. The Lampasas River was also considered impaired for elevated E. coli levels until 2010 when it was determined that the data listing the segment no longer met the state’s criteria for assessment. Through the watershed protection planning process, stakeholders in each watershed will use adaptive management to refine management strategies that will mitigate bacteria loading from potential sources of pollution within the watershed

    A quantum mechanical insight into SN2 reactions: Semiclassical initial value representation calculations of vibrational features of the Cl^---CH3_3Cl pre-reaction complex with the VENUS suite of codes

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    The role of vibrational excitation of reactants in driving reactions involving polyatomic species has been often studied by means of classical or quasi-classical trajectory simulations. We propose a different approach based on investigation of vibrational features of the Cl^---CH3_3Cl pre-reaction complex for the Cl^- + CH3_3Cl SN2_2 reaction. We present vibrational power spectra and frequency estimates for the title pre-reaction complex calculated at the level of classical, semiclassical, and second-order vibrational perturbation theory on a pre-existing analytical potential energy surface. The main goals of the paper are the study of anharmonic effects and understanding of vibrational couplings that permit energy transfer between the collisional kinetic energy and the internal vibrations of the reactants. We provide both classical and quantum pictures of intermode couplings and show that the SN2 mechanism is favored by the coupling of a C--Cl bend involving the Cl^- projectile with the CH3_3 rocking motion of the target molecule. We also illustrate how the routines needed for semiclassical vibrational spectroscopy simulations can be interfaced in a user-friendly way to pre-existing molecular dynamics software. In particular, we present an implementation of semiclassical spectroscopy into the VENUS suite of codes, thus providing a useful computational tool for users who are not experts of semiclassical dynamics

    Observation of bosonic coalescence of photon pairs

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    Quantum theory predicts that two indistinguishable photons incident on a beam-splitter interferometer stick together as they exit the device (the pair emerges randomly from one port or the other). We use a special photon-number-resolving energy detector for a direct loophole-free observation of this quantum-interference phenomenon. Simultaneous measurements from two such detectors, one at each beam-splitter output port, confirm the absence of cross-coincidences.Comment: 4 pages, 2 figures, submitted to Phys. Rev. Let

    Finding Your Literature Match -- A Recommender System

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    The universe of potentially interesting, searchable literature is expanding continuously. Besides the normal expansion, there is an additional influx of literature because of interdisciplinary boundaries becoming more and more diffuse. Hence, the need for accurate, efficient and intelligent search tools is bigger than ever. Even with a sophisticated search engine, looking for information can still result in overwhelming results. An overload of information has the intrinsic danger of scaring visitors away, and any organization, for-profit or not-for-profit, in the business of providing scholarly information wants to capture and keep the attention of its target audience. Publishers and search engine engineers alike will benefit from a service that is able to provide visitors with recommendations that closely meet their interests. Providing visitors with special deals, new options and highlights may be interesting to a certain degree, but what makes more sense (especially from a commercial point of view) than to let visitors do most of the work by the mere action of making choices? Hiring psychics is not an option, so a technological solution is needed to recommend items that a visitor is likely to be looking for. In this presentation we will introduce such a solution and argue that it is practically feasible to incorporate this approach into a useful addition to any information retrieval system with enough usage.Comment: Contribution to the proceedings of the colloquium Future Professional Communication in Astronomy II, 13-14 April 2010, Cambridge, Massachusetts. 11 pages, 4 figures

    On EPR paradox, Bell's inequalities and experiments which prove nothing

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    This article shows that the there is no paradox. Violation of Bell's inequalities should not be identified with a proof of non locality in quantum mechanics. A number of past experiments is reviewed, and it is concluded that the experimental results should be re-evaluated. The results of the experiments with atomic cascade are shown not to contradict the local realism. The article points out flaws in the experiments with down-converted photons. The experiments with neutron interferometer on measuring the "contextuality" and Bell-like inequalities are analyzed, and it is shown that the experimental results can be explained without such notions. Alternative experiment is proposed to prove the validity of local realism.Comment: 27 pages, 8 figures. I edited a little the text and abstract I corrected equations (49) and (50

    New 23-phosphodiester derivatives of Silibin and DHS: synthesis and preliminary evaluation of antioxidant properties

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    Silybin is the major flavonolignan of silymarin which is widely used as a natural remedy for the treatment of cirrhosis, chronic hepatitis, and liver diseases associated with alcohol consumption and exposure to environmental toxins. Different studies recently made on the antiradical activity of silybin and DHS have elucidated the functional groups responsible for this activity. The results suggest that the C-23 position could be a site for useful modifications aimed to improve the bioactivity of silybin and/or DHS analogues. Recently we describe an efficient synthetic strategy to obtain a variety of new silybin and 2,3-dehydrosilybin (DHS) derivatives in which the 23-hydroxyl group was converted to a sulfate, phosphodiester, or amine group, using a solution-phase approach. The antioxidant properties of the new compounds were evaluated in a cellular model in vivo and most of them displayed an antioxidant activity comparable or higher to silybin and DHS. These results confirmed the assumption that modifications in position C–23 do not affect the radical scavenging activity of these analogues. With the final goal to expand the repertoire of silybin and DHS C-23 modified, we describe here the synthesis and preliminary evaluation of antioxidant properties of a variety of new silybin and DHS conjugated with different labels through a phosphodiester bond The antioxidative properties of the above-synthesized compounds were determined by free radical scavenging (DPPH) assay

    Dynamic Critical Behavior of the Chayes-Machta Algorithm for the Random-Cluster Model. I. Two Dimensions

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    We study, via Monte Carlo simulation, the dynamic critical behavior of the Chayes-Machta dynamics for the Fortuin-Kasteleyn random-cluster model, which generalizes the Swendsen-Wang dynamics for the q-state Potts ferromagnet to non-integer q \ge 1. We consider spatial dimension d=2 and 1.25 \le q \le 4 in steps of 0.25, on lattices up to 1024^2, and obtain estimates for the dynamic critical exponent z_{CM}. We present evidence that when 1 \le q \lesssim 1.95 the Ossola-Sokal conjecture z_{CM} \ge \beta/\nu is violated, though we also present plausible fits compatible with this conjecture. We show that the Li-Sokal bound z_{CM} \ge \alpha/\nu is close to being sharp over the entire range 1 \le q \le 4, but is probably non-sharp by a power. As a byproduct of our work, we also obtain evidence concerning the corrections to scaling in static observables.Comment: LaTeX2e, 75 pages including 26 Postscript figure
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