30 research outputs found
Quantum Disordered Regime and Spin Gap in the Cuprate Superconductors
We discuss the crossover from the quantum critical, , to the quantum
disordered regime in high-T materials in relation to the experimental data
on the nuclear relaxation, bulk susceptibility, and inelastic neutron
scattering. In our scenario, the spin excitations develop a gap
well above T, which is supplemented by the
quasiparticle gap below T. The above experiments yield consistent estimates
for the value of the spin gap, which increases as the correlation length
decreases.Comment: 14 pages, REVTeX v3.0, PostScript file for 3 figures is attached,
UIUC-P-93-07-06
Hidden Order in the Cuprates
We propose that the enigmatic pseudogap phase of cuprate superconductors is
characterized by a hidden broken symmetry of d(x^2-y^2)-type. The transition to
this state is rounded by disorder, but in the limit that the disorder is made
sufficiently small, the pseudogap crossover should reveal itself to be such a
transition. The ordered state breaks time-reversal, translational, and
rotational symmetries, but it is invariant under the combination of any two. We
discuss these ideas in the context of ten specific experimental properties of
the cuprates, and make several predictions, including the existence of an
as-yet undetected metal-metal transition under the superconducting dome.Comment: 12 pages of RevTeX, 9 eps figure
Scientific rationale for Uranus and Neptune <i>in situ</i> explorations
The ice giants Uranus and Neptune are the least understood class of planets in our solar system but the most frequently observed type of exoplanets. Presumed to have a small rocky core, a deep interior comprising âŒ70% heavy elements surrounded by a more dilute outer envelope of H2 and He, Uranus and Neptune are fundamentally different from the better-explored gas giants Jupiter and Saturn. Because of the lack of dedicated exploration missions, our knowledge of the composition and atmospheric processes of these distant worlds is primarily derived from remote sensing from Earth-based observatories and space telescopes. As a result, Uranus's and Neptune's physical and atmospheric properties remain poorly constrained and their roles in the evolution of the Solar System not well understood. Exploration of an ice giant system is therefore a high-priority science objective as these systems (including the magnetosphere, satellites, rings, atmosphere, and interior) challenge our understanding of planetary formation and evolution. Here we describe the main scientific goals to be addressed by a future in situ exploration of an ice giant. An atmospheric entry probe targeting the 10-bar level, about 5 scale heights beneath the tropopause, would yield insight into two broad themes: i) the formation history of the ice giants and, in a broader extent, that of the Solar System, and ii) the processes at play in planetary atmospheres. The probe would descend under parachute to measure composition, structure, and dynamics, with data returned to Earth using a Carrier Relay Spacecraft as a relay station. In addition, possible mission concepts and partnerships are presented, and a strawman ice-giant probe payload is described. An ice-giant atmospheric probe could represent a significant ESA contribution to a future NASA ice-giant flagship mission
Hydraulic conductivity and porosity under conventional and no-tillage and the effect of three species of cover crop in northern France
Emprego experimental da placa de compósito poli-hidroxibutirado/hidroxiapatita na fixação femoral em gatos
Avaliou-se o compĂłsito de poli-hidroxibutirado (PHB) 70% e hidroxiapatita (HA) 30% na forma de placas para fixação Ăłssea em gatos. Foram usadas placas do compĂłsito com 60mm de comprimento por 10mm de largura e espessura variando de 3mm no centro a 5mm nas extremidades, com seis orifĂcios. A placa do compĂłsito foi empregada na fixação de osteotomia de fĂȘmur em quatro gatos, totalizando seis intervençÔes. Verificou-se a ruptura de cinco placas (83,3%) atĂ© o quarto dia e de uma placa (16,7%) aos 21 dias, quando se observou um calo Ăłsseo exuberante. O resultado da implantação da placa no gato mostrou que o compĂłsito nĂŁo possui resistĂȘncia suficiente para ser empregado como placas de fixação de fĂȘmur em gatos