Neutron scattering study of the effects of dopant disorder on the superconductivity and magnetic order in stage-4 La_2CuO_{4+y}

We report neutron scattering measurements of the structure and magnetism of stage-4 La_2CuO_{4+y} with T_c ~42 K. Our diffraction results on a single crystal sample demonstrate that the excess oxygen dopants form a three-dimensional ordered superlattice within the interstitial regions of the crystal. The oxygen superlattice becomes disordered above T ~ 330 K, and a fast rate of cooling can freeze-in the disordered-oxygen state. Hence, by controlling the cooling rate, the degree of dopant disorder in our La_2CuO_{4+y} crystal can be varied. We find that a higher degree of quenched disorder reduces T_c by ~ 5 K relative to the ordered-oxygen state. At the same time, the quenched disorder enhances the spin density wave order in a manner analogous to the effects of an applied magnetic field.Comment: 4 figures included in text; submitted to PR

High-pressure phase relations of Bi2_{2}Sr2_{2}CaCu2_{2}O8+δ_{8+\delta} single crystals

We have investigated the pressure dependence of the superconducting transition temperature $T_{c}$ up to 18 GPa of Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+\delta}$ single crystals ranging from the highly underdoped through the nearly optimally doped to the highly overdoped level. For all three samples studied, $T_{c}$ is found to increase initially and then saturate at a critical pressure $P_{c}$ but decrease modestly with further compression. Oxygen doping tends to reduce the increase in $T_{c}$ and $P_{c}$. A new high-pressure phase diagram between the saturated $T_{c}$ and $P_{c}$ is then obtained. Theoretical interpretation is given by using the competition between the hole carrier density and pairing interaction strength based on the high-pressure transport data of the resistivity and Hall coefficient in this system.Comment: 8 pages, 7 figures, to appear in Physical Review

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

High Pressure Effects on Superconductivity

The review is devoted to a discussion of the effects of high pressure imposed on superconducting materials. Low-temperature superconductors, high-temperature superconducting cuprates, and some unconventional superconducting compounds are investigated. Experimental as well as theoretical results regarding the pressure effects on Tc and other interesting properties are summarized.Comment: To be published in: "Frontiers in Superconducting Materials", Edt. A. Narlikar, Springer Verla

Der Einfluss von hohem hydrostatischen Druck auf die Uebergangstemperatur ausgewaehlter Hochtemperatursupraleiter

Available from TIB Hannover: DW 8801 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

A supervisão na formação do analista e do psicoterapeuta psicanalítico The supervision in the training of psychoanalytical psychotherapist

Este artigo consiste na revisão sistemática da literatura brasileira sobre supervisão em psicanálise e psicoterapia psicanalítica, em periódicos científicos referenciados entre 2001 e 2006 nas bases de dados eletrônicas Lilacs, Scielo, Pepsic e Indexpsi, e localizada a partir do descritor supervisão psic$. A busca resultou em 64 artigos, posteriormente reduzidos para 13, em função de criteriosa leitura e descarte daqueles que não abordavam diretamente o tema. Os treze artigos foram lidos novamente e submetidos à análise de conteúdo, configurando 11 categorias de discussão. Concluiu-se que: poucos estudos que tratam do tema da supervisão assumem o formato de pesquisas empíricas; artigos não discutem os passos que supervisor e supervisionando devem seguir para atingir os objetivos desejados; as patologias na atualidade são discutidas, mas não há sugestões de mudanças na técnica e na estratégia da supervisão; poucos artigos trazem como foco o aspecto controle da supervisão; artigos com exemplos de casos não mencionam consentimento informado do paciente.<br>The present paper is a systematic review of the Brazilian literature regarding supervision in psychoanalysis and psychoanalytical psychotherapy, in scientific journals indexed between 2001 and 2006 in the electronic databases Lilacs, Scielo, Pepsic, Indexpsi. The descriptor supervisão psic$ led to 64 articles which were reduced for 13, after a careful examination that disregarded those in which the theme was not approached directly. The articles were reread and categorized per content analysis method. Eleven categories of discussion emerged. Results show: few studies that focused supervision were empirical researches; articles do not mention the steps that supervisor and supervisee need to follow to reach the desirable objectives; new pathologies are mentioned but there are no suggestions about technical changes in supervision strategies to deal with them; few articles mention the controlling aspect of supervision; articles that use cases as examples do not mention informed consent by the patients