Thermal analysis of LEDS for liquid crystal display's backlighting

This paper investigated the thermal design of the light emitting diode (LED)onto the board and its packaging. The LED was a 6-lead MultiLED with three chips designed for LCD backlighting and other lighting purposes. A 3D finite element model of this LED was built up and thermal analysis was carried out using the multi physics software package PHYSICA. The modeling results were presented as temperature distributions in each LED, and the predicted junction temperature was used for thermal resistance calculation. The results for the board structure indicated that (1) removing the foil attach decreased the thermal resistance, (2) Increasing the copper foil thickness reduced the thermal resistance. package design indicated that the SMT designed LED with integrated slug gave lower thermal resistance. Pb-free solder material gave lower thermal resistance and junction temperature when compared with conductive adhesive

Multiple-locus sequence typing analysis of Bacillus thuringiensis recovered from the phylloplane of clover (Trifolium hybridum) in vegetative form

The chromosomal genotype, as judged by multi locus sequence typing, and the episomal genotype, as judged by plasmid profile and cry gene content, were analyzed for a collection of strains of Bacillus thuringiensis. These had been recovered in vegetative form over a period of several months from the leaves of a small plot of clover (Trifolium hybridum). A clonal population structure was indicated, although greater variation in sequence types (STs) was discovered than in previous collections of B. cereus/B. thuringiensis. Isolates taken at the same time had quite different genotypes, whereas those of identical genotypes were recovered at different times. The profiles of plasmid content and cry genes generally bore no relation to each other nor to the STs. Evidently, although relatively little recombination was occurring in the seven chromosomal genes analyzed, a great deal of conjugal transfer, and perhaps recombination, was occurring involving plasmids. A clinical diarrheal isolate of B. cereus and the commercial biopesticide strain HD-1 of B. thuringiensis, both included as out-groups, were found to have very similar STs. This further emphasizes the role of episomal elements in the characteristics and differentiation of these two species.