Yonsei University

About: Yonsei University is a education organization based out in Seoul, South Korea. It is known for research contribution in the topics: Population & Cancer. The organization has 50162 authors who have published 106172 publications receiving 2279044 citations. The organization is also known as: Yonsei.

Redox-transmetalation process as a generalized synthetic strategy for core-shell magnetic nanoparticles.

Abstract: Although multicomponent core-shell type nanomaterials are one of the highly desired structural motifs due to their simultaneous multifunctionalities, the fabrication strategy for such nanostructures is still in a primitive stage. Here, we present a redox-transmetalation process that is effective as a general protocol for the fabrication of high quality and well-defined core-shell type bimetallic nanoparticles on the sub-10 nm scale. Various core-shell type nanomaterials including Co@Au, Co@Pd, Co@Pt, and Co@Cu nanoparticles are fabricated via transmetalation reactions. Compared to conventional sequential reduction strategies, this transmetalation process has several advantages for the fabrication of core-shell type nanoparticles: (i) no additional reducing agent is needed and (ii) spontaneous shell layer deposition occurs on top of the core nanoparticle surface and thus prevents self-nucleation of secondarily added metals. We also demonstrate the versatility of these core-shell structures by transferring Co@Au nanoparticles from an organic phase to an aqueous phase via a surface modification process. The nanostructures, magnetic properties, and reaction byproducts of these core-shell nanoparticles are spectroscopically characterized and identified, in part, to confirm the chemical process that promotes the core-shell structure formation.

Ecological Patterns of nifH Genes in Four Terrestrial Climatic Zones Explored with Targeted Metagenomics Using FrameBot, a New Informatics Tool

Abstract: Biological nitrogen fixation is an important component of sustainable soil fertility and a key component of the nitrogen cycle. We used targeted metagenomics to study the nitrogen fixation-capable terrestrial bacterial community by targeting the gene for nitrogenase reductase ( nifH ). We obtained 1.1 million nifH 454 amplicon sequences from 222 soil samples collected from 4 National Ecological Observatory Network (NEON) sites in Alaska, Hawaii, Utah, and Florida. To accurately detect and correct frameshifts caused by indel sequencing errors, we developed FrameBot, a tool for frameshift correction and nearest-neighbor classification, and compared its accuracy to that of two other rapid frameshift correction tools. We found FrameBot was, in general, more accurate as long as a reference protein sequence with 80% or greater identity to a query was available, as was the case for virtually all nifH reads for the 4 NEON sites. Frameshifts were present in 12.7% of the reads. Those nifH sequences related to the Proteobacteria phylum were most abundant, followed by those for Cyanobacteria in the Alaska and Utah sites. Predominant genera with nifH sequences similar to reads included Azospirillum , Bradyrhizobium , and Rhizobium , the latter two without obvious plant hosts at the sites. Surprisingly, 80% of the sequences had greater than 95% amino acid identity to known nifH gene sequences. These samples were grouped by site and correlated with soil environmental factors, especially drainage, light intensity, mean annual temperature, and mean annual precipitation. FrameBot was tested successfully on three ecofunctional genes but should be applicable to any. IMPORTANCE High-throughput phylogenetic analysis of microbial communities using rRNA-targeted sequencing is now commonplace; however, such data often allow little inference with respect to either the presence or the diversity of genes involved in most important ecological processes. To study the gene pool for these processes, it is more straightforward to assess the genes directly responsible for the ecological function (ecofunctional genes). However, analyzing these genes involves technical challenges beyond those seen for rRNA. In particular, frameshift errors cause garbled downstream protein translations. Our FrameBot tool described here both corrects frameshift errors in query reads and determines their closest matching protein sequences in a set of reference sequences. We validated this new tool with sequences from defined communities and demonstrated the tool’s utility on nifH gene fragments sequenced from soils in well-characterized and major terrestrial ecosystem types.

Can vascularity at power Doppler US help predict thyroid malignancy

Abstract: Intranodular vascularity itself, as well as a combination of vascularity and suspicious gray-scale US features, performed less well for differentiating benign and malignant thyroid nodules than did the combination of four suspicious gray-scale US features.