1,471 research outputs found

    Interference between resonant and Auger mechanisms for charge-exchange processes near surfaces

    Get PDF
    In this work we solve the dynamics of the Newns-Anderson Hamiltonian supplemented with Auger termsand analyze the case of He1 scattered off an Al ~100! surface. The dynamical solution is compared with resultsof calculations based on much simpler approximations. We prove that resonant and Auger processes can betreated separately and independently in this case and that charge exchange between He and Al proceeds viaresonant and Auger exchange of electrons between the promoted molecular orbital of He and the conductionband states of Al.Fil: García, Evelina Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Wang, N.P.. Universidad Autónoma de Madrid; EspañaFil: Monreal, R.C.. Universidad Autónoma de Madrid; EspañaFil: Goldberg, Edith Catalina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentin

    Vorticity, phase stiffness and the cuprate phase diagram

    Full text link
    We review results obtained from vortex-Nernst experiments in cuprates. Evidence for a loss of phase coherence at the Meissner transition Tc0T_{c0} is derived from vortex-like excitations that persist to high temperature. Below Tc0T_{c0}, the Nersnt signal provides a determination of the upper critical field Hc2H_{c2} vs. doping xx. Implications for the cuprate phase diagram are discussed.Comment: 6 pages, 8 figures, Plenary talk of the 7th International Conference on Materials and Mechanisms of Superconductivity and High Temperature Superconductors. To appear in Physica C, the proceeding of M2S-HTSC-VI

    Depairing field, onset temperature and the nature of the transition in cuprates

    Full text link
    The depairing (upper critical) field Hc2H_{c2} in hole-doped cuprates has been inferred from magnetization curves MM-HH measured by torque magnetometry in fields HH up to 45 T. We discuss the implications of the results for the pair binding energy, the Nernst onset temperature, fluctuations and the nature of the Meissner transition at TcT_c.Comment: 4 pages, 5 figs., proc. M2S-HTSC-VIII, Dresden 2006, Physica (in press

    Matrix Tensor Product Approach to the Equivalence of Multipartite States under Local Unitary Transformations

    Full text link
    The equivalence of multipartite quantum mixed states under local unitary transformations is studied. A criterion for the equivalence of non-degenerate mixed multipartite quantum states under local unitary transformations is presented.Comment: 7 page

    Cold Induction of EARLI1, a Putative Arabidopsis Lipid Transfer Protein, Is Light and Calcium Dependent

    Get PDF
    As sessile organisms, plants must adapt to their environment. One approach toward understanding this adaptation is to investigate environmental regulation of gene expression. Our focus is on the environmental regulation of EARLI1, which is activated by cold and long-day photoperiods. Cold activation of EARLI1 in short-day photoperiods is slow, requiring several hours at 4ºC to detect an increase in mRNA abundance. EARLI1 is not efficiently cold-activated in etiolated seedlings, suggesting that photomorphogenesis is necessary for its cold activation. Cold activation of EARLI1 is inhibited in the presence of the calcium channel blocker lanthanum chloride or the calcium chelator EGTA. Addition of the calcium ionophore Bay K8644 results in cold-independent activation of EARLI1. These data suggest that EARLI1 is not an immediate target of the cold response, and that calcium flux affects its expression. EARLI1 is a putative secreted protein and has motifs found in lipid transfer proteins. Over-expression of EARLI1 in transgenic plants results in reduced electrolyte leakage during freezing damage, suggesting that EARLI1 may affect membrane or cell wall stability in response to low temperature stress

    Chemical Instability of the Cobalt Oxyhydrate Superconductor under Ambient Conditions

    Full text link
    The layered sodium cobalt oxyhydrate superconductor Na0.3CoO2*1.4H2O is shown through X-ray diffraction and thermogravimetric studies to be one of a series of hydrated phases of Na0.3CoO2. Further, it is shown that the material is exceptionally sensitive to both temperature and humidity near ambient conditions, easily dehydrating to a non-superconducting lower hydrate. The observation of this stable lower hydrate with c=13.8 angstroms implies that the superconductivity turns on in this system between CoO2 layer spacings of 6.9 and 9.9 angstroms at nominally constant chemical doping.Comment: 10 pages and 4 figure

    Nernst Effect in Electron-Doped Pr2x_{2-x}Cex_{x}CuO4_4

    Full text link
    The Nernst effect of Pr2x_{2-x}Cex_{x}CuO4_4 (x=0.13, 0.15, and 0.17) has been measured on thin film samples between 5-120 K and 0-14 T. In comparison to recent measurements on hole-doped cuprates that showed an anomalously large Nernst effect above the resistive Tc_c and Hc2_{c2} \cite{xu,wang1,wang2,capan}, we find a normal Nernst effect above Tc_c and Hc2_{c2} for all dopings. The lack of an anomalous Nernst effect in the electron-doped compounds supports the models that explain this effect in terms of amplitude and phase fluctuations in the hole-doped cuprates. In addition, the Hc2_{c2}(T) determined from the Nernst effect shows a conventional behavior for all dopings. The energy gap determined from Hc2_{c2}(0) decreases as the system goes from under-doping to over-dopingin agreement with the recent tunnelling experiments

    Dirac Equation at Finite Temperature

    Full text link
    In this paper, we propose finite temperature Dirac equation, which can describe the quantum systems in an arbitrary temperature for a relativistic particle of spin-1/2. When the temperature T=0, it become Dirac equation. With the equation, we can study the relativistic quantum systems in an arbitrary temperature.Comment: arXiv admin note: text overlap with arXiv:1005.2751, arXiv:hep-ph/0004125, arXiv:hep-ph/0005272 by other author

    Quantitative transcription factor binding kinetics at the single-molecule level

    Full text link
    We have investigated the binding interaction between the bacteriophage lambda repressor CI and its target DNA using total internal reflection fluorescence microscopy. Large, step-wise changes in the intensity of the red fluorescent protein fused to CI were observed as it associated and dissociated from individually labeled single molecule DNA targets. The stochastic association and dissociation were characterized by Poisson statistics. Dark and bright intervals were measured for thousands of individual events. The exponential distribution of the intervals allowed direct determination of the association and dissociation rate constants, ka and kd respectively. We resolved in detail how ka and kd varied as a function of 3 control parameters, the DNA length L, the CI dimer concentration, and the binding affinity. Our results show that although interaction with non-operator DNA sequences are observable, CI binding to the operator site is not dependent on the length of flanking non-operator DNA.Comment: 34 pages, 10 figures, accepted by Biophysical Journa
    corecore