Magnetic Properties of a Pressure-induced Superconductor UGe2_2

We performed the DC-magnetization and neutron scattering experiments under pressure {\it P} for a pressure-induced superconductor UGe$_2$. We found that the magnetic moment is enhanced at a characteristic temperature {\it T}$^{*}$ in the ferromagnetic state, where {\it T}$^{*}$ is smaller than a Curie temperature {\it T}$_{\rm C}$. This enhancement becomes remarkable in the vicinity of {\it P}$_{\rm C}^{*}$ = 1.20 GPa, where {\it T}$^{*}$ becomes 0 K and the superconducting transition temperature {\it T}$_{\rm SC}$ shows a maximum. The characteristic temperature {\it T}$^{*}$, which decreases with increasing pressure, also depends on the magnetic field.Comment: To be published in J.Phys.Soc.Jp

Critical properties and Bose Einstein Condensation in dimer spin systems

We analyze the spin relaxation time $1/T_1$ for a system made of weakly coupled one dimensional ladders.This system allows to probe the dimensional crossover between a Luttinger liquid and a Bose-Einstein condensateof magnons. We obtain the temperature dependence of $1/T_1$ in the various dimensional regimes, and discuss the experimental consequences.Comment: 4 pages, RevTeX 4, 3 EPS figure

Lesiones radiográficas y participación de factores individuales en la espondilosis deformante y la esclerosis vertebral en perros

Este estudio resalta la importancia de dos procesos degenerativos de la columna vertebral de la especie canina, espondilosis deformante y esclerosis laminar, abordando aspectos ligados a la descripción y gravedad de las lesiones radiográficas y la participación decisiva de las características del individuo en perros asintomáticos

Signatures of Planets in Spatially Unresolved Disks

Main sequence stars are commonly surrounded by debris disks, composed of cold dust continuously replenished by a reservoir of undetected dust-producing planetesimals. In a planetary system with a belt of planetesimals (like the Solar System's Kuiper Belt) and one or more interior giant planets, the trapping of dust particles in the mean motion resonances with the planets can create structure in the dust disk, as the particles accumulate at certain semimajor axes. Sufficiently massive planets may also scatter and eject dust particles out of a planetary system, creating a dust depleted region inside the orbit of the planet. In anticipation of future observations of spatially unresolved debris disks with the Spitzer Space Telescope, we are interested in studying how the structure carved by planets affects the shape of the disk's spectral energy distribution (SED), and consequently if the SED can be used to infer the presence of planets. We numerically calculate the equilibrium spatial density distributions and SEDs of dust disks originated by a belt of planetesimals in the presence of interior giant planets in different planetary configurations, and for a representative sample of chemical compositions. The dynamical models are necessary to estimate the enhancement of particles near the mean motion resonances with the planets, and to determine how many particles drift inside the planet's orbit. Based on the SEDs and predicted $\it{Spitzer}$ colors we discuss what types of planetary systems can be distinguishable from one another and the main parameter degeneracies in the model SEDs.Comment: 40 pages (pre-print form), including 16 figures. Published in ApJ 200

Pressure-induced Superconductivity in a Ferromagnet UGe2_2 -- Resistivity Measurements in Magnetic Field --

The electrical resistivity measurements in the magnetic field are carried out on the pressure-induced superconductor UGe$_2$. The superconductivity is observed from 1.06 to 1.44 GPa. The upper critical field of $H_{C2}$ is anisotropic where $H_{C2}(T)$ exhibits positive curvature for $H//b$ and $c$-axis. The characteristic enhancement of $H_{C2}$ is reconfirmed for $H//a$-axis. In the temperature and field dependence of resistivity at $P > P_{C}$ where the ferromagnetic ordering disappears, it is observed that the application of the external field along the {\it a}-axis increases the coefficient of Fermi liquid behavior $AT^{2}$ correspondingly to the metamagnetic transition.Comment: To be published in the proceeding of the International Conference on High Pressure Science and Technology(AIRAPT-18),Beijing,China,23-27 July 200

Multi-Triplet Magnons in SrCu2_2(BO3_3)2_2 Studied by Thermal Conductivity Measurements in Magnetic Fields

We have measured the thermal conductivity parallel to the a-axis of the Zn-free and 1% Zn-substituted SrCu$_{2-x}$Zn$_x$(BO$_3$)$_2$ in magnetic fields up to 14 T, in order to examine the thermal conductivity due to the multi-triplet magnons. It has been found that the thermal conductivity peak observed in the spin gap state is suppressed by the substitution of Zn for Cu in high magnetic fields above 6 T, while it is not changed in low magnetic fields below 6 T. The results suggest that the thermal conductivity peak in the spin-gap state of SrCu$_2$(BO$_3$)$_2$ is composed of not only thermal conductivity due to phonons but also that due to the multi-triplet magnons in high fields above 6 T.Comment: 7 pages, 2 figure

Produção de álcool etílico de colmos de sorgo sacarino em microdestilaria.

A producao de etanol a partir de acucares fermentesciveis de fontes renovaveis de energia, despontou como a mais viavel para substituir os combustiveis derivados de petroleo. As tecnologias para transformar carboidratos em etanol sao bem conhecidos desde longa data, sendo utilizadas como principais fontes de obtencao de acucares fermentesciveis a cana-de-acucar e a beterraba acucareira. Entretanto, nao ha nenhuma limitacao no uso do sorgo sacarino como materia-prima para producao de etanol. Com o aumento do interesse em um melhor uso desta nova fonte de biomassa energetica, informacoes adicionais devem ser obtidas para avaliar o real potencial dessa nova fonte renovavel de energia. Pelo fato de se adaptar as condicoes climaticas diversas, rapido crescimento, moderada exigencia de agua e elevado conteudo de carboidrato, o sorgo sacarino podera vir a se constituir em uma cultura de alto valor para as regioes tropicais e sub-tropicais. Nos experimentos a cultivar de sorgo sacarino BR-505, originaria da cultivar norte-americana Wray, foi plantada nos anos agricolas de 1984/85 e 1985/86, para avaliar o seu comportamento como materia-prima para producao de alcool etilico em microdestilaria. Amostras de colmos foram retiradas por algumas semanas, a partir do aparecimento das paniculas ate que os graos atingissem o estadio firme, que ocorreu 120 dias apos o plantio. Foram determinados nos colmos os teores de acucares redutores, acucares totais e sacarose. O teor em acucares redutores decresceu durante a maturacao do grao, provavelmente pelo fato de ser assimilado na forma de outros metabolicos. O teor em sacarose aumentou significativamente atingindo valores altos quando os graos estavam maduros, bem firmes. Deste modo, e possivel cultivar o sorgo sacarino com dupla finalidade: uso dos colmos para producao de etanol, e uso dos graos para racao animal e/ou consumo humano. Foram obtidos rendimentos de colmos e folhas de 40-50 t.ha no estadio de maturacao completa das paniculas, com uma producao adicional de graos de 2, 5-3, 5 t/ha. Os colmos e folhas foram processadas em uma microdestilaria com sistema de difusao, obtendo-se alta taxa de extracao de acucares fermentesciveis, que permitiu a obtencao de cerca de 50 litros de etanol por tonelada de materia-prima

Time-Dependent Density Functional Theory of Open Quantum Systems in the Linear-Response Regime

Time-Dependent Density Functional Theory (TDDFT) has recently been extended to describe many-body open quantum systems (OQS) evolving under non-unitary dynamics according to a quantum master equation. In the master equation approach, electronic excitation spectra are broadened and shifted due to relaxation and dephasing of the electronic degrees of freedom by the surrounding environment. In this paper, we develop a formulation of TDDFT linear-response theory (LR-TDDFT) for many-body electronic systems evolving under a master equation, yielding broadened excitation spectra. This is done by mapping an interacting open quantum system onto a non-interacting open Kohn-Sham system yielding the correct non-equilibrium density evolution. A pseudo-eigenvalue equation analogous to the Casida equations of usual LR-TDDFT is derived for the Redfield master equation, yielding complex energies and Lamb shifts. As a simple demonstration, we calculate the spectrum of a C$^{2+}$ atom in an optical resonator interacting with a bath of photons. The performance of an adiabatic exchange-correlation kernel is analyzed and a first-order frequency-dependent correction to the bare Kohn-Sham linewidth based on Gorling-Levy perturbation theory is calculated.Comment: 18 pages, 4 figure

Experiences in Interagency and International Interfaces for Mission Support

The Flight Dynamics Division (FDD) of the National Aeronautics and Space Administration (NASA) Goddard Space Flight Center (GFSC) provides extensive support and products for Space Shuttle missions, expendable launch vehicle launches, and routine on-orbit operations for a variety of spacecraft. A major challenge in providing support for these missions is defining and generating the products required for mission support and developing the method by which these products are exchanged between supporting agencies. As interagency and international cooperation has increased in the space community, the FDD customer base has grown and with it the number and variety of external interfaces and product definitions. Currently, the FDD has working interfaces with the NASA Space and Ground Networks, the Johnson Space Center, the White Sands Complex, the Jet propulsion Laboratory (including the Deep Space Network), the United States Air Force, the Centre National d'Etudes Spatiales, the German Spaceflight Operations Center, the European Space Agency, and the National Space Development Agency of Japan. With the increasing spectrum of possible data product definitions and delivery methods, the FDD is using its extensive interagency experience to improve its support of established customers and to provide leadership in adapting/developing new interfaces. This paper describes the evolution of the interfaces between the FDD and its customers, discusses many of the joint activities ith these customers, and summarizes key lessons learned that can be applied to current and future support