Relaxation Effects in the Transition Temperature of Superconducting HgBa2CuO4+delta

In previous studies on a number of under- and overdoped high temperature superconductors, including YBa_{2}Cu_{3}O_{7-y} and Tl_{2}Ba_{2}CuO_{6+\delta}, the transition temperature T_c has been found to change with time in a manner which depends on the sample's detailed temperature and pressure history. This relaxation behavior in T_c is believed to originate from rearrangements within the oxygen sublattice. In the present high-pressure studies on HgBa_{2}CuO_{4+\delta} to 0.8 GPa we find clear evidence for weak relaxation effects in strongly under- and overdoped samples ($T_c\simeq 40 - 50 K$) with an activation energy $E_{A}(1 bar) \simeq 0.8 - 0.9 eV$. For overdoped HgBa_{2}CuO_{4+\delta} E_{A} increases under pressure more rapidly than previously observed for YBa_{2}Cu_{3}O_{6.41}, yielding an activation volume of +11 \pm 5 cm^{3}; the dependence of T_c on pressure is markedly nonlinear, an anomalous result for high-T_c superconductors in the present pressure range, giving evidence for a change in the electronic and/or structural properties near 0.4 GPa

Migration and risk an empirical application to the coca economy in Peru

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La coordinacion de politicas fiscales en el marco de una union economica y monetaria

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Fixed agenda social choice correspondences

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Condorcet choice correspondences for weak tournaments

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Informe preliminar del sistema SAMAR: sistema automatico de medidas absolutas de radionucleidos

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Nota sobre la produccion de rotiferos Brachionus plicatilis Muller en grandes volumenes de cultivo

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Numerical representation of choice functions

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