Reflectance of Polytetrafluoroethylene (PTFE) for Xenon Scintillation Light

Gaseous and liquid xenon particle detectors are being used in a number of applications including dark matter search and neutrino-less double beta decay experiments. Polytetrafluoroethylene (PTFE) is often used in these detectors both as electrical insulator and as a light reflector to improve the efficiency of detection of scintillation photons. However, xenon emits in the vacuum ultraviolet wavelength region (175 nm) where the reflecting properties of PTFE are not sufficiently known. In this work we report on measurements of PTFE reflectance, including its angular distribution, for the xenon scintillation light. Various samples of PTFE, manufactured by different processes (extruded, expanded, skived and pressed) have been studied. The data were interpreted with a physical model comprising both specular and diffuse reflections. The reflectance obtained for these samples ranges from about 47% to 66% for VUV light. Fluoropolymers, namely ETFE, FEP and PFA were also measured

Identificação de geoambientes e solos de duas barragens subterrâneas em municípios do estado da Paraíba.

O presente trabalho tem como objetivo identificar de forma expedita os domínios geológicos e as principais classes de solos das áreas de duas Barragens Subterrâneas nos municípios de Puxinanã e Queimadas no Estado da Paraíba

Teor de nutrientes, crescimento e produção de rizomas de açafrão em resposta a adubação nitrogenada.

Este trabalho teve por objetivo avaliar o efeito de doses de nitrogênio (N) sobre acessos de açafrão

Magnetic behavior of the NixFe1-xNb2O6 quasi-one-dimensional system: Isolation of Ising chains by frustration

International audiencePhysical properties of the NixFe1-xNb2O6 compounds are investigated combining x-ray and neutron powder diffraction with magnetic and calorimetry measurements as well as 57Fe Mössbauer spectroscopy. This system is known to present quasi-one-dimensional magnetism with the magnetic moments arranged along weakly interacting Ising chains. Partial substitution of the magnetic ion tends to suppress the magnetic ordering observed in the end members of the series. When this happens, the low-temperature magnetic specific heat agrees well with what is expected for isolated Ising chains. The lowest temperature powder neutron-diffraction patterns exhibit evidence for the occurrence of short-range order, and analysis of these diffuse neutron-scattering patterns allow us to obtain information on the magnetic correlations. The suppression of magnetism is consistently interpreted as resulting from the magnetic-cation disorder induced by substitution, which enhances the system's tendency for frustration of geometrical origin

Caracterização de atributos do solo em áreas de barragem subterrânea no semi-árido brasileiro.

bitstream/CNPS-2009-09/13994/1/bpd128_2008barragem_semi_arido.pd