101 research outputs found

    Earth-Science Data Co-Locating Tool

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    This software is used to locate Earth-science satellite data and climate-model analysis outputs in space and time. This enables the direct comparison of any set of data with different spatial and temporal resolutions. It is written in three separate modules that are clearly separated for their functionality and interface with other modules. This enables a fast development of supporting any new data set. In this updated version of the tool, several new front ends are developed for new products. This software finds co-locatable data pairs for given sets of data products and creates new data products that share the same spatial and temporal coordinates. This facilitates the direct comparison between the two heterogeneous datasets and the comprehensive and synergistic use of the datasets

    Effect of wetting layers on the strain and electronic structure of InAs self-assembled quantum dots

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    The effect of wetting layers on the strain and electronic structure of InAs self-assembled quantum dots grown on GaAs is investigated with an atomistic valence-force-field model and an empirical tight-binding model. By comparing a dot with and without a wetting layer, we find that the inclusion of the wetting layer weakens the strain inside the dot by only 1% relative change, while it reduces the energy gap between a confined electron and hole level by as much as 10%. The small change in the strain distribution indicates that strain relaxes only little through the thin wetting layer. The large reduction of the energy gap is attributed to the increase of the confining-potential width rather than the change of the potential height. First-order perturbation calculations or, alternatively, the addition of an InAs disk below the quantum dot confirm this conclusion. The effect of the wetting layer on the wave function is qualitatively different for the weakly confined electron state and the strongly confined hole state. The electron wave function shifts from the buffer to the wetting layer, while the hole shifts from the dot to the wetting layer.Comment: 14 pages, 3 figures, and 3 table

    Implications on SUSY breaking mediation mechanisms from observing Bsμ+μB_s \to \mu^+ \mu^- and the muon (g2)(g-2)

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    We consider Bsμ+μB_s \to \mu^+ \mu^- and the muon (g2)μ(g-2)_\mu in various SUSY breaking mediation mechanisms. If the decay Bsμ+μB_s \to \mu^+ \mu^- is observed at Tevatron Run II with a branching ratio larger than 2×108\sim 2 \times 10^{-8} , the noscale supergravity (including the gaugino mediation), the gauge mediation scenario with small number of messenger fields and low messenger scale, and a class of anomaly mediation scenarios will be excluded, even if they can accommodate a large muon (g2)μ(g-2)_\mu. On the other hand, the minimal supergravity scenario and similar mechanisms derived from string models can accommodate this observation.Comment: 4 pages, 3 figure

    Gene knockouts reveal separate functions for two cytoplasmic dyneins in Tetrahymena thermophila

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    In many organisms, there are multiple isoforms of cytoplasmic dynein heavy chains, and division of labor among the isoforms would provide a mechanism to regulate dynein function. The targeted disruption of somatic genes in Tetrahymena thermophila presents the opportunity to determine the contributions of individual dynein isoforms in a single cell that expresses multiple dynein heavy chain genes. Substantial portions of two Tetrahymena cytoplasmic dynein heavy chain genes were cloned, and their motor domains were sequenced. Tetrahymena DYH1 encodes the ubiquitous cytoplasmic dynein Dyh1, and DYH2 encodes a second cytoplasmic dynein isoform, Dyh2. The disruption of DYH1, but not DYH2, resulted in cells with two detectable defects: 1) phagocytic activity was inhibited, and 2) the cells failed to distribute their chromosomes correctly during micronuclear mitosis. In contrast, the disruption of DYH2 resulted in a loss of regulation of cell size and cell shape and in the apparent inability of the cells to repair their cortical cytoskeletons. We conclude that the two dyneins perform separate tasks in Tetrahymena

    Diagnostic for new physics in BπKB \to \pi K decays

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    A recent analysis of BπKB \to \pi K decays concludes that present data do not clearly indicate whether (i) the standard model (or ΔI=0\Delta I=0 new physics) is sufficient, or (ii) ΔI=1\Delta I=1 new physics is needed. We show that these two possibilities can be distinguished by whether a sum rule relating the CP asymmetries of the four BπKB \to \pi K decays is valid. If case (i) is favored, the sum rule holds, and one predicts ACP(π0K0)=0.15A_{CP}(\pi^0 K^0) = -0.15, while in case (ii) fits to new physics involving large values of a color-suppressed tree amplitude entail ACP(π0K0)=0.03A_{CP}(\pi^0 K^0) = -0.03. The current experimental average ACP(π0K0)=0.01±0.10A_{CP}(\pi^0 K^0) = -0.01 \pm 0.10 must be measured a factor of at least three times more precisely in order to distinguish between the two cases.Comment: 10 pages, no figures. Submitted to Physics Letters B. Slight clarification adde

    Direct detection of neutralino dark matter in supergravity

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    The direct detection of neutralino dark matter is analysed in general supergravity scenarios, where non-universal soft scalar and gaugino masses can be present. In particular, the theoretical predictions for the neutralino-nucleon cross section are studied and compared with the sensitivity of dark matter detectors. We take into account the most recent astrophysical and experimental constraints on the parameter space, including the current limit on B(Bs-> mu+ mu-). The latter puts severe limitations on the dark matter scattering cross section, ruling out most of the regions that would be within the reach of present experiments. We show how this constraint can be softened with the help of appropriate choices of non-universal parameters which increase the Higgsino composition of the lightest neutralino and minimise the chargino contribution to the b->s transition.Comment: 27 pages, 22 figure

    Probing SUSY-induced CP violations at B factories

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    In the minimal supersymmetric standard model (MSSM), the \mu-parameter and the trilinear coupling A_t may be generically complex and can affect various observables at B factories. Imposing the edm constraints, we find that there is no new large phase shift in the B^0 - \bar{B^0} mixing, CP violating dilepton asymmetry is smaller than 0.1 %, and the direct CP violation in B\to X_s \gamma can be as large as \sim \pm 16 %.Comment: 4 pages, 2 figures. Version to appear in Phys. Rev. Let

    Two-loop Barr-Zee type Contributions to (g2)μ(g-2)_\mu in the MSSM

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    We consider the contribution of a two-loop Barr-Zee type diagram to (g2)μ(g-2)_\mu in the minimal supersymmetric standard model (MSSM). At relatively large tanβ\tan\beta, we show that the contribution of light third generation scalar fermions and neutral CP-even Higgs, h0(H0)h^0(H^0), can easily explain the very recent BNL experimental data. In our analysis (g2)μ(g-2)_\mu prefers negative AfA_{f} and positive μ\mu. It is more sensitive to the chirality flipping h^0(H^0)\wt{f}_R^*\wt{f}_L rather than chirality conserving couplings.Comment: 10 pages, 5 figures, references adde
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