RESUMO
Electrical and optical characteristics of InGaN-based green micro-light-emitting diodes (µLEDs) with different active areas are investigated; results are as follows. Reverse and forward leakage currents of µLED increase as emission area is reduced owing to the non-radiative recombination process at the sidewall defects; this is more prominent in smaller µLED because of larger surface-to-volume ratio. Leakage currents of µLEDs deteriorate the carrier injection to light-emitting quantum wells, thereby degrading their external quantum efficiency. Reverse leakage current originate primarily from sidewall edges of the smallest device. Therefore, aggressive suppression of sidewall defects of µLEDs is essential for low-power and downscaled µLEDs.
RESUMO
Identification of plant species is important for standardizing herbal medicine. Cynanchum wilfordii (Baekshuoh in Korean) and Polygonum multiflorum (Hashuoh in Korean) are important oriental medicinal herbs in Korea, Japan, and China. Cynanchum auriculatum is a faster growing and more productive plant than C. wilfordii; and, it is not recognized as a medicinal plant in the Korean Pharmacopoeia. C. wilfordii, P. multiflorum, and C. auriculatum are often misidentified in the Korean herbal medicine marketplace due to their morphological similarities and similar names. In this study, we investigated molecular authentication of these three medicinal plants using DNA sequences in the TrnL-F chloroplast intergenic region. Specific species identification was achieved by detecting allelic variations of single nucleotide polymorphisms (SNPs) using amplification refractory mutation system-polymerase chain reaction (ARMS-PCR) and high resolution melting curve analysis. Our results demonstrate that the intraspecific genetic distance between C. wilfordii and C. auriculatum is relatively low. We also developed a quantitative PCR assay using species-specific TrnL-F primers, which allowed us to estimate the ratio of C. wilfordii and C. auriculatum using varying ratios of mixed genomic DNA template from the two species. Additionally, to identify species in hybrid plants produced by cross-fertilization, we analyzed nuclear ribosomal DNA internal transcribed spacer regions in C. wilfordii and C. auriculatum by ARMS-PCR. Our results indicate that SNP-based molecular markers, usable to barcode tools could provide efficient and rapid authentication of these closely related medicinal plant species, and will be useful for preventing the distribution of products contaminated with adulterants.
