Motivation: Nucleic acid sequences in public databases should not contain vector contamination, but many sequences in GenBank do (or did) contain vectors. The National Center for Biotechnology Information uses the program VecScreen to screen submitted sequences for contamination. Additional tools are needed to distinguish true-positive (contamination) from false-positive (not contamination) VecScreen matches. Results: A principal reason for false-positive VecScreen matches is that the sequence and the matching vector subsequence originate from closely related or identical organisms (for example, both originate in Escherichia coli). We collected information on the taxonomy of sources of vector segments in the UniVec database used by VecScreen. We used that information in two overlapping software pipelines for retrospective analysis of contamination in GenBank and for prospective analysis of contamination in new sequence submissions. Using the retrospective pipeline, we identified and corrected over 8000 contaminated sequences in the nonredundant nucleotide database. The prospective analysis pipeline has been in production use since April 2017 to evaluate some new GenBank submissions. Availability and implementation: Data on the sources of UniVec entries were included in release 10.0 (ftp://ftp.ncbi.nih.gov/pub/UniVec/). The main software is freely available at https://github.com/aaschaffer/vecscreen_plus_taxonomy. Contact: [email protected]. Supplementary information: Supplementary data are available at Bioinformatics online.

In this paper, a high efficiency and high power factor single-stage balanced forward-flyback converter merging a foward and flyback converter topologies is proposed. The conventional AC/DC flyback converter can achieve a good power factor but it has a high offset current through the transformer magnetizing inductor, which results in a large core loss and low power conversion efficiency. And, the conventional forward converter can achieve the good power conversion efficiency with the aid of the low core loss but the input current dead zone near zero cross AC input voltage deteriorates the power factor. On the other hand, since the proposed converter can operate as the forward and flyback converters during switch on and off periods, respectively, it cannot only perform the power transfer during an entire switching period but also achieve the high power factor due to the flyback operation. Moreover, since the current balanced capacitor can minimize the offset current through the transformer magnetizing inductor regardless of the AC input voltage, the core loss and volume of the transformer can be minimized. Therefore, the proposed converter features a high efficiency and high power factor. To confirm the validity of the proposed converter, theoretical analysis and experimental results from a prototype of 24W LED driver are presented.

In this paper, a low voltage stress and high efficiency voltage-clamped coupled-inductor boost converter is proposed. The conventional coupled-inductor boost converter has a serious drawback of high voltage stresses across all power semiconductors due to the high surge voltage caused by the resonance between leakage inductor of coupled-inductor and stray capacitors. Therefore, the conventional converter must be equipped with the dissipative snubber for absorbing this surge voltage, which will degrade the overall power conversion efficiency. To overcome these drawbacks, the proposed converter employs the diode-clamping circuit instead of the dissipative snubber. Proposed clamping circuit can clamp voltages across the power switch and output diode on the link capacitor voltage and output voltage, respectively. In addition, the leakage inductor energy is stored in the link capacitor, and then transferred to the output side together with the input energy. Therefore, the proposed converter can achieve the higher efficiency than the conventional coupled-inductor boost converter. The proposed converter is expected to be well suited to various applications demanding the high efficiency and high-voltage gain. To confirm the validity of the proposed circuit, the theoretical analysis and experimental results of the proposed converter are presented.