Effective thermal conductivity of porous solder layers

Microscopic voids in the die attachment solder layers of power semiconductor devices degrade their overall thermal transfer performance. This paper presents analytical results of the effect of spherical and spheroidal void geometries on the thermal conductivity of bulk media. Analytical results are compared with axially symmetric and three-dimensional thermal simulations of single and multiple cavity defects in planar structures. The effective thermal conductivity of the die to the case attachment solder layer of two commercial metal oxide semiconductor field effect transistor (MOSFET) devices is estimated using these results, with cavity dimensions and distributions obtained by electron microscopy

Investigation and analysis of testing and modelling strategies for epoxy resin impregnated paper (ERIP) high voltage bushings

SIGLEAvailable from British Library Document Supply Centre-DSC:DXN032354 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Variation in limits to germination temperature and rates across the seed-seedling transition in the palm Oenocarpus bataua from the Brazilian Amazon

Germination efficiency can be quantified using the optimal temperature and the temperature limits for germinating seeds. Such estimates generally pertain to the earliest phase of germination, that of radicle emergence. Few comparisons have been made on the subsequent stages of growth, even though the seed-seedling transition is critical for establishment. We assessed the thermal parameters for development of four developmental stages over the seed-seedling transition (germination button, primary root, 1st cataphyll and 2nd cataphyll) in the Amazonian palm tree Oenocarpus bataua. Germination was observed under eight constant and two alternating temperatures with four replicates of 25 seeds for each condition. Constant temperatures of 25 and 30°C resulted in the highest final germination in the shortest time period for all four germination criteria. Alternating temperatures did not enhance germination and seedling development. The four germination stages differed in temperature tolerances. While the germination button formed over a large range of constant temperatures (10 to 40°C), development of the 2nd cataphyll (i.e., seedling development) over 60 days was limited to 25 to 30°C. These results indicate that the thermal responses for growth in this species vary with developmental stage and that early seedling growth, when seed reserves are being mobilised, occurs over the most restricted range of temperature across the four stages of development

Genetic diversity is retained in a bottlenecked Cinereous Vulture population in Turkey

Vulture populations worldwide have suffered precipitous declines in recent decades. The Cinereous Vulture Aegypius monachus, a highly philopatric scavenger distributed across southern Europe and the central Asian plateau, is threatened in many parts of its range. Turkey holds the second largest population of this species in the Western Palaearctic, but there has been no research on its genetic structure and the possible implications of this structure for the future of the species. Here we report nuclear diversity and relatedness determined by short tandem repeat genotyping of 81 individuals from the four largest colonies. Our results demonstrated no significant genetic structuring, suggesting a single panmictic metapopulation connected by frequent dispersal. Furthermore, we show that the study population has retained moderate levels of genetic diversity, despite passing through a recent demographic bottleneck. We estimated the effective population size to be 112 individuals (95% confidence interval 74–201). Our results imply that the observed lack of increase in population size since the 1990s has not been caused by lowered fitness due to genetic inbreeding but rather by increased mortality via demographic processes. In the short term, we suggest that conservation efforts should treat the Turkish subpopulations as a single management unit and aim to increase population size through effective protection, especially during the breeding season