Ab initio study of the effect of water adsorption on the carbon nanotube field-effect transistor

We perform density-functional calculations to investigate the effect of adsorbed water molecules on carbon nanotubes (CNTs). Noting that the H2 O molecule has much wider energy gap than the CNT, we find that the charge transfer between them is negligible. We discuss that several recent publications, which claimed a substantial electron transfer from the water molecule to the CNT, have been based on incautious interpretations of the Mulliken population analysis. We suggest that the effect of humidity on nanotube devices may be attributed to various indirect effects enhanced by water vapors, rather than the carrier generations by the physisorbed H2 O molecules.open292

Evolution of ribosomal DNA-derived satellite repeat in tomato genome

<p>Abstract</p> <p>Background</p> <p>Tandemly repeated DNA, also called as satellite DNA, is a common feature of eukaryotic genomes. Satellite repeats can expand and contract dramatically, which may cause genome size variation among genetically-related species. However, the origin and expansion mechanism are not clear yet and needed to be elucidated.</p> <p>Results</p> <p>FISH analysis revealed that the satellite repeat showing homology with intergenic spacer (IGS) of rDNA present in the tomato genome. By comparing the sequences representing distinct stages in the divergence of rDNA repeat with those of canonical rDNA arrays, the molecular mechanism of the evolution of satellite repeat is described. Comprehensive sequence analysis and phylogenetic analysis demonstrated that a long terminal repeat retrotransposon was interrupted into each copy of the 18S rDNA and polymerized by recombination rather than transposition via an RNA intermediate. The repeat was expanded through doubling the number of IGS into the 25S rRNA gene, and also greatly increasing the copy number of type I subrepeat in the IGS of 25-18S rDNA by segmental duplication. Homogenization to a single type of subrepeat in the satellite repeat was achieved as the result of amplifying copy number of the type I subrepeat but eliminating neighboring sequences including the type II subrepeat and rRNA coding sequence from the array. FISH analysis revealed that the satellite repeats are commonly present in closely-related <it>Solanum </it>species, but vary in their distribution and abundance among species.</p> <p>Conclusion</p> <p>These results represent that the dynamic satellite repeats were originated from intergenic spacer of rDNA unit in the tomato genome. This result could serve as an example towards understanding the initiation and the expansion of the satellite repeats in complex eukaryotic genome.</p

Taxonomic notes on Phyllocnistis citrella (Lepidoptera: Gracillariidae) with genital structures and DNA barcode from Korea

Until now, only one species, Phyllocnistis citrella Stainton, of the genus Phyllocnistis belonging to the family Gracillariidae is listed in Korea, without available information on its identification and morphology, which is now a very serious and important insect pest species in southern area. This study was carried out to provide the illustration with genital structure and DNA barcode data for rapid monitoring, which has not been presented in this country to date

Preliminary survey of indigenous parasites associated with Phyllocnistis citrella Stainton (Lepidoptera, Gracillariidae) in Jeju, Korea

In order to identify the parasitoids of Phyllocnistis citrella Stainton [commonly known as the citrus leafminer (CLM)], we collected CLM larvae and pupae in the Seogwipo area of Jeju-do, identified parasitoid species, and determined parasitism rates. In May 2014, nine parasitoids were identified from the CLM larvae and pupae that infested 300 fresh citrus leaves, yielding a parasitism rate of 3.03%. In August 2014, 53 parasitoid wasps emerged from 203 collected CLM larvae and pupae, indicating that the parasitism rate rose to 25.84%. The parasitoid wasps observed in May 2014 consisted of five individuals of Sympiesis sp. 1 (Eulophidae), one Pnigalio sp. 1 (Eulophidae), and three Aphelinus sp. 1 (Aphelinidae). The highest proportion of the parasitic wasps that emerged in August 2014 were Sympiesis sp. 1 (n = 49), followed by Quadrastichus sp. 1 (Eulophidae; n = 4). This study documents the seasonal parasitism rate of parasitic wasps and basic characteristics of each parasitoid in Korea

The tomato genome sequence provides insights into fleshy fruit evolution

Tomato (Solanum lycopersicum) is a major crop plant and a model system for fruit development. Solanum is one of the largest angiosperm genera1 and includes annual and perennial plants from diverse habitats. Here we present a high-quality genome sequence of domesticated tomato, a draft sequence of its closest wild relative, Solanum pimpinellifolium2, and compare them to each other and to the potato genome (Solanum tuberosum). The two tomato genomes show only 0.6% nucleotide divergence and signs of recent admixture, but show more than 8% divergence from potato, with nine large and several smaller inversions. In contrast to Arabidopsis, but similar to soybean, tomato and potato small RNAs map predominantly to gene-rich chromosomal regions, including gene promoters. The Solanum lineage has experienced two consecutive genome triplications: one that is ancient and shared with rosids, and a more recent one. These triplications set the stage for the neofunctionalization of genes controlling fruit characteristics, such as colour and fleshiness