RESUMO
The light extraction efficiency of light-emitting diodes (LEDs) patterned with photonic crystals is investigated based on an incoherent multi-reflection-transmission model. The formulas of the extraction efficiency are obtained in an analytic form similar to the unpatterned case. Besides, we generalize the Rouard formulas commonly used in thin-film optics to the case of multilayered photonic crystal slabs. The influence of various types of backside reflectors and the absorption of the semiconductor on the efficiency are demonstrated for GaN-based LEDs. The optimization of the photonic crystal slab based on the LED model is also presented and briefly discussed.
RESUMO
Rice sheath blight, caused by Rhizoctonia solani is one of the major diseases of rice. The pathogen infects rice plants directly through stomata or using lobate appressoria and hyphal masses called infection cushions. The infection structures were normally found at 36 h post-inoculation. During infection, the pathogenesis-related genes, PR1b and PBZ1 were induced in rice plants. To identify rice genes induced early in the defense response, suppression subtractive hybridization (SSH) was used to generate a cDNA library enriched for transcripts differentially expressed during infection by R. solani. After differential screening by membrane-based hybridization and subsequent confirmation by reverse Northern blot analysis, selected clones were sequenced. Fifty unique cDNA clones were found and assigned to five different functional categories. Most of the genes were not previously identified as being induced in response to pathogens. We examined expression of 100 rice genes induced by infection with Magnaporthe grisea, Xanthomonas oryzae pv. oryze (Xoo) and X. oryzae pv. oryzicola (Xooc). Twenty-five of them were found to be differentially expressed after the sheath blight infection, suggesting overlap of defense responses to different fungal and bacterial pathogens infection.
