12 research outputs found
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 BiSrCaCuO single crystals
We have investigated the pressure dependence of the superconducting
transition temperature up to 18 GPa of
BiSrCaCuO single crystals ranging from the
highly underdoped through the nearly optimally doped to the highly overdoped
level. For all three samples studied, is found to increase initially
and then saturate at a critical pressure but decrease modestly with
further compression. Oxygen doping tends to reduce the increase in and
. A new high-pressure phase diagram between the saturated and
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 () with
an activation energy . 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 psicanalÃtico The supervision in the training of psychoanalytical psychotherapist
Este artigo consiste na revisão sistemática da literatura brasileira sobre supervisão em psicanálise e psicoterapia psicanalÃtica, em periódicos cientÃficos referenciados entre 2001 e 2006 nas bases de dados eletrônicas Lilacs, Scielo, Pepsic e Indexpsi, e localizada a partir do descritor 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