Pure xenon hexafluoride prepared for thermal properties studies

Preparation of a xenon hexafluoride and sodium fluoride salt yields a sample of the highest possible purity for use in thermal measurements. The desired hexafluoride can easily be freed from the common contaminants, xenon tetra-fluoride, xenon difluoride, and xenon oxide tetrafluoride, because none of these compounds reacts with sodium fluoride

Área experimental silvipastoril no sul do Paraná.

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Relationship between resistivity and specific heat in a canonical non-magnetic heavy fermion alloy system: UPt_5-xAu_x

UPt_(5-x)Au_x alloys form in a single crystal structure, cubic AuBe_5-type, over a wide range of concentrations from x = 0 to at least x = 2.5. All investigated alloys, with an exception for x = 2.5, were non-magnetic. Their electronic specific heat coefficient $\gamma$ varies from about 60 (x = 2) to about 700 mJ/mol K^2 (x = 1). The electrical resistivity for all alloys has a Fermi-liquid-like temperature variation, \rho = \rho_o + AT^2, in the limit of T -> 0 K. The coefficient A is strongly enhanced in the heavy-fermion regime in comparison with normal and transition metals. It changes from about 0.01 (x = 0) to over 2 micro-ohm cm/K^2 (x = 1). A/\gamma^2, which has been postulated to have a universal value for heavy-fermions, varies from about 10^-6 (x = 0, 0.5) to 10^-5 micro-ohm cm (mol K/mJ)^2 (x > 1.1), thus from a value typical of transition metals to that found for some other heavy-fermion metals. This ratio is unaffected, or only weakly affected, by chemical or crystallographic disorder. It correlates with the paramagnetic Curie-Weiss temperature of the high temperature magnetic susceptibility.Comment: 5 pages, 5 eps figures, RevTe

Characterization Work and Comparative Testing of Expanded Glass Granulate as a Round Robin Material for Thermal Conductivity at Higher Temperatures

For laboratories within the scheme of the voluntary surveillance system for technical insulation materials in Europe (VDI/Keymark), a proficiency test is the basis for obtaining a “registered laboratory.” The VDI/Keymark is a cooperation between the VDI, The Association of German Engineers, and the Keymark Group dealing with European voluntary product certification systems, within the scope of thermal insulation materials. Registered laboratories are allowed to conduct measurements to verify the declared thermal conductivity curve of technical insulation materials under the umbrella of the quality mark “VDI/Keymark”. The initial characterization work on a round robin material for the determination of thermal conductivity at higher temperatures led to the selection of an expanded glass granulate. With all the results of the round robin tests produced by five European laboratories, the expanded glass granulate has become a very important material for establishing a reliable European level of thermal conductivity at higher temperatures with a moderate uncertainty. The German expert group “AKThermophysik” of the Association of Thermal Analysis (GEFTA, Gesellschaft für Thermische Analyse e.V.) further initiated a round robin test for thermal conductivity in 2012. With this additional use of the expanded glass granulate, more experience with transient methods and thermal conductivity values in the extended temperature range could be obtained. A comparison with the reference curve of the VDI/Keymark indicates very good compliance for most cases. Since August 2012, comparative tests with the expanded glass granulate as a round robin material are very important. Furthermore, the European CE marking became mandatory for industrial insulation products and temperature-dependent thermal conductivity, declared by the manufacturer, was introduced as a limit value. The challenge to determine the thermal conductivity at higher temperatures for a material using different methods and apparatuses was also an important step to evaluate the level of “True Thermal Conductivity.

Culturas intercalares de milho (Zea mays L.) em reflorestamentos de Pinus taeda L. no sul do Paraná.

Este trabalho foi planejado com o objetivo de se avaliar, na região dos Campos Gerais do Paraná, o rendimento de associações de Pinus taeda L. com milho (Zea mays L.), em função de três densidades populacionais desta cultura: 50 mil, 67 mil e 83 mil plantas/ha, dispostas, respectivamente, em duas, três e quatro linhas, entre as linhas do Pinus plantado no espaçamento de 3 x 2 m. O plantio do Pinus e o da primeira cultura de milho foram efetuados no ano agrícola 1981/82; duas novas culturas de milho foram plantadas em 1982 e em 1983. Até a terceira colheita do milho, não se registraram diferenças entre as sobrevivências do Pinus associado com duas, três e quatro linhas do cereal, nem entre estas e as da testemunha sem consórcio (média de 91,33%). Quanto à altura e ao diâmetro da espécie florestal, no entanto, os incrementos registrados no consórcio com quatro linhas de milho (3,65 m e 5,73 cm) foram menores que na testemunha sem consórcio (4,17 m e 6,92 cm), enquanto que nos consórcios com duas e três linhas, estes ficaram em posição intermediária. As produções de milho, no primeiro e no segundo ano, propiciaram, respectivamente, retornos sobre o capital investido nesta cultura, da ordem de 135 e 94%. Já no terceiro ano, quando o desenvolvimento do Pinus tornou-se suficiente para sombrear parcialmente a cultura agrícola, sua produção foi deficitária, embora em pequeno grau. A população de 50 mil plantas de milho por hectare, dispostas em duas linhas, entre as linhas do Pinus, mostrou-se a mais indicada para o sistema