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Shanghai as Female Space
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Tacrolimus and cyclosporine have differnetial effects on the risk of development of bronchiolitis obliterans syndrome: Results of a prospective^ randomized international trial in lung transplantation
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Synechococcus PCC7002의 세포 및 틸라코이드 막의 Polyvinylalcohol 고정화에 의한 광합성 특성
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Nature of Late Mesoproterozoic to Early Neoproterozoic magmatism in the western Gyeonggi massif^ Korean Peninsula and its tectonic significance
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Standard Setting in Medical Education
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A general formula for the horizon function of a convex composite function
- 검색키워드
- 저자 : Weichang Xu (검색결과 2 건)
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Modular synthesis of heparanase substrates
Peng Xu,Weichang Xu,Yuanwei Dai,Biao Yu 한국당과학회 2012 한국당과학회 학술대회 Vol.2012 No.1
Heparanase, preferentially expressed in many tumor cells, is an endoβDglucuronidase that cleaves specific sites of heparan sulfate. Elevated levels of heparanase expression correlate with tumor vasculatrity, metastatic potiential, and reduced postoperative survival of cancer patients. Consequencely, heparanase detection is considered a tool for cancer discovery. A library of 20 welldefined Tetra1 analogs were prepared in a convergent “2+2” glycosidation manner utilizing a relatively small number of protected disaccharide donors and acceptors. Among three different donors prepared for the fullprotected tetrasaccharide, trifluoroacetimidate donor was most suitable for the preservation and glycosidation reaction, and in each glycosylation, the yield was good and the major anomer was obtained. After coupling these 12 glycosydic reactions, the observation indicate that the coupling ratio is not only relating to the structure and exact nature of acceptors, but also correlated to the structure and size of donors. Key features of the approach include the use of Bz esters or PMB ethers for those hydroxyls that need sulfation, regioselective opening of the 4,6-O-benzylidene acetal for 4OBn that don’t need sulfation and 6OH that need oxidation, an anomeric TBS group for glycosyl donor synthesis, and benzyl ethers just as permanent protecting groups. The HS oligosaccharides will be employed to probe structural features of HS for cleavage of heparanase.
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Analysis and Accurate Modeling of a Flyback Converter on Conducted EMI
Weichang Cheng,Xiaoying He,Shen Xu,Weifeng Sun 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6
In this paper an accurate EMI model of a 5W flyback converter based on discrete devices modeling is presented. To improve the accuracy of EMI model, passive devices, active devices, power IC and the parameters of PCB are all taken into consideration. The simulation results show that, errors of main system-level parameters can be controlled in 5% and errors at the EMI peak values can be controlled in ± 5dB. Based on the proposed model, the existence of NIDM noise is verified and the impacts of parasitic parameters on PCB in this flyback converter are analyzed. The model-based analysis of EMI agrees well with the theory and measurement.
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