Mixed-state microwave response in superconducting cuprates

We report measurements of the magnetic-field induced microwave complex resistivity in REBa$_{2}$Cu$_{3}$O$_{7-\delta}$ thin films, with RE = Y, Sm. Measurements are performed at 48 GHz by means of a resonant cavity in the end-wall-replacement configuration. The magnetic field dependence is investigated by applying a moderate (0.8 T) magnetic field along the c-axis. The measured vortex state complex resistivity in YBa$_{2}$Cu$_{3}$O$_{7-\delta}$ and SmBa$_{2}$Cu$_{3}$O$_{7-\delta}$ is analyzed within the well-known models for vortex dynamics. It is shown that attributing the observed response to vortex motion alone leads to inconsistencies in the as-determined vortex parameters (such as the vortex viscosity and the pinning constant). By contrast, attributing the entire response to field-induced pair breaking leads to a nearly quantitative description of the data.Comment: 6 pages, 4 figures, to be published in J. Supercond. as proceedings of 8th HTSHFF (May 26th-29th, 2004, Begur, Spain

Prey selection by an apex predator : the importance of sampling uncertainty.

The impact of predation on prey populations has long been a focus of ecologists, but a firm understanding of the factors influencing prey selection, a key predictor of that impact, remains elusive. High levels of variability observed in prey selection may reflect true differences in the ecology of different communities but might also reflect a failure to deal adequately with uncertainties in the underlying data. Indeed, our review showed that less than 10% of studies of European wolf predation accounted for sampling uncertainty. Here, we relate annual variability in wolf diet to prey availability and examine temporal patterns in prey selection; in particular, we identify how considering uncertainty alters conclusions regarding prey selection. Over nine years, we collected 1,974 wolf scats and conducted drive censuses of ungulates in Alpe di Catenaia, Italy. We bootstrapped scat and census data within years to construct confidence intervals around estimates of prey use, availability and selection. Wolf diet was dominated by boar (61.5±3.90 [SE] % of biomass eaten) and roe deer (33.7±3.61%). Temporal patterns of prey densities revealed that the proportion of roe deer in wolf diet peaked when boar densities were low, not when roe deer densities were highest. Considering only the two dominant prey types, Manly's standardized selection index using all data across years indicated selection for boar (mean = 0.73±0.023). However, sampling error resulted in wide confidence intervals around estimates of prey selection. Thus, despite considerable variation in yearly estimates, confidence intervals for all years overlapped. Failing to consider such uncertainty could lead erroneously to the assumption of differences in prey selection among years. This study highlights the importance of considering temporal variation in relative prey availability and accounting for sampling uncertainty when interpreting the results of dietary studies

A bright impulsive solar burst detected at 30 THz

Ground- and space-based observations of solar flares from radio wavelengths to gamma-rays have produced considerable insights but raised several unsolved controversies. The last unexplored wavelength frontier for solar flares is in the range of submillimeter and infrared wavelengths. Here we report the detection of an intense impulsive burst at 30 THz using a new imaging system. The 30 THz emission exhibited remarkable time coincidence with peaks observed at microwave, mm/submm, visible, EUV and hard X-ray wavelengths. The emission location coincides with a very weak white-light feature, and is consistent with heating below the temperature minimum in the atmosphere. However, there are problems in attributing the heating to accelerated electrons. The peak 30 THz flux is several times larger than the usual microwave peak near 9 GHz, attributed to non-thermal electrons in the corona. The 30 THz emission could be consistent with an optically thick spectrum increasing from low to high frequencies. It might be part of the same spectral component found at sub-THz frequencies whose nature remains mysterious. Further observations at these wavelengths will provide a new window for flare studies.Comment: 9 pages, 11 figures, accepted by Astrophysical Journal, March 23, 201

Nível de energia metabolizável aparente sobre o desempenho zootécnico de frangos de corte.

O milho é o principal ingrediente energético utilizado nas rações brasileiras para frango de corte. O frango de corte macho de desempenho superior necessita segundo Rostagno (1) cerca de 3.150 e 3.200 kcal/kg no período de 22 à 33 e 34 à 42 dias de idade, respectivamente. Para atender essa demanda energética óleos e gordura são incluídos nas formulações. O objetivo do trabalho foi avaliar o requerimento energia metabolizável aparente (EMA) de frangos de corte machos consumindo dieta peletizada/triturada de 21 a 42 dias com base nas variáveis de desempenho zootécnico

Parâmetros sanguíneos da arraia de água doce Potamotrygon orbignyi Castelnau, 1855 (Potamotrygonidae) da Bacia do Rio Negro, Amazonas, Brasil.

A região Amazônica apresenta a maior diversidade de espécies de potamotrigonídeos, algumas com distribuição ampla como as arraias Paratrygon aiereba, Potamotrygon motoro e Potamotrygon orbignyi, sendo essa última encontrada nas bacias dos rios Amazonas, Orinoco e nos rios das Guianas e do Suriname. No Amazonas, as arraias de água doce são exploradas há mais de duas décadas pela pesca ornamental e, atualmente, cerca de 10.000 espécimes/ano são exportados. Deste total, 10% pertencem à espécie P. orbignyi, mesmo com participação aparentemente baixa, esta espécie é a mais valorizada entre todos os peixes ornamentais comercializados junto ao mercado internacional. A grande valorização de P. orbignyi se deve ao alto policromatismo, além da dificuldade de captura, uma vez que essa arraia vive associada às praias, margens de ilhas e igarapés de fundo arenoso e sem folhas. Embora a hematologia de peixes seja uma ferramenta biológica valiosa, o progresso no estabelecimento de parâmetros hematológicos das diversas espécies de peixes é lento e na literatura os dados são isolados e frequentemente incompletos, principalmente, no que se refere às arraias de água doce. Desta forma, este trabalho teve por objetivo descrever os parâmetros bioquímicos e hematológicos da arraia P. orbignyi

Parâmetros hematológicos e bioquímicos de Podocnemis erythrocephala (Reptilia: Podocnemididae) do Arquipélago de Mariuá, médio Rio Negro, Amazonas.

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