Human Immunodeficiency Virus Type 1 exists in vivo as quasispecies, and one of the genome's characteristics is its diversity. During the antiretroviral therapy, drug resistance is the main obstacle to effective vi...Human Immunodeficiency Virus Type 1 exists in vivo as quasispecies, and one of the genome's characteristics is its diversity. During the antiretroviral therapy, drug resistance is the main obstacle to effective viral prevention. Understanding the molecular evolution process is fundamental to analyze the mechanism of drug resistance and develop a strategy to minimize resistance. Objective: The molecular evolution of drug resistance of one patient who had received reverse transcriptase inhibitors for a long time and had treatment which replaced Nevirapine with Indinavir was analyzed, with the aim of observing the drug resistance evolution pathway. Methods: The patient, XLF, was followed-up for six successive times. The viral populations were amplified and sequenced by single-genome amplification. All the sequences were submitted to the Stanford HIV Drug Resistance Database for the analysis of genotypic drug resistance. Results: 149 entire protease and 171 entire reverse transcriptase sequences were obtained from these samples, and all sequences were identified as subtype B. Before the patient received Indinavir, the viral population only had some polymorphisms in the protease sequences. After the patient began Indinavir treatment, the variants carrying polymorphisms declined while variants carrying the secondary mutation G73S gained the advantage. As therapy was prolonged, G73S was combined with M46I/L90M to form a resistance pattern M46I/G73S/L90M, which then became the dominant population. 97.9% of variants had the M46I/G73S/L90M pattern at XLF6. During the emergence of protease inhibitors resistance, reverse transcriptase inhibitors resistance maintained high levels. Conclusion: Indinavirresistance evolution was observed by single-genome amplification. During the course of changing the regimen to incorporate Indinavir, the G73S mutation occurred and was combined with M46I/L90M.展开更多
Due to the highly demand on the renewable energy sources as a free and a clean power resource, extracting energy from unsteady flow using marine and tidal current turbines has a distinct focusing nowadays. For their r...Due to the highly demand on the renewable energy sources as a free and a clean power resource, extracting energy from unsteady flow using marine and tidal current turbines has a distinct focusing nowadays. For their resource characteristic, extracting energy from marine/tidal current needs a simple and robust converter, which could overcome the drawbacks of the mechanical system such as gearbox and enhance conversion system stability. In this paper a new AC-DC-AC conversion system has been proposed. The new conversion system contains a middle stage DC-DC boost converter, which boost the generated rectified DC voltage higher enough that can enable the PWM inverter to generate the required voltage with the synchronized frequency. In order to investigate the efficient performance of the proposed conversion system especially at low current speed compared to the conventional one, different operating conditions have been studied. Moreover, the effect of including boost converter on the THD （total harmonic distortion） has also been checked. The new conversion system presents its capability to enhance and improve system performance not only with low current speed but also with high current speed.展开更多
基金National Natural Science Foundation of China (30830088 and 30800938)The National Key and Special Projects on Major Infectious Disease Grant (2008 ZX10001-004)
文摘Human Immunodeficiency Virus Type 1 exists in vivo as quasispecies, and one of the genome's characteristics is its diversity. During the antiretroviral therapy, drug resistance is the main obstacle to effective viral prevention. Understanding the molecular evolution process is fundamental to analyze the mechanism of drug resistance and develop a strategy to minimize resistance. Objective: The molecular evolution of drug resistance of one patient who had received reverse transcriptase inhibitors for a long time and had treatment which replaced Nevirapine with Indinavir was analyzed, with the aim of observing the drug resistance evolution pathway. Methods: The patient, XLF, was followed-up for six successive times. The viral populations were amplified and sequenced by single-genome amplification. All the sequences were submitted to the Stanford HIV Drug Resistance Database for the analysis of genotypic drug resistance. Results: 149 entire protease and 171 entire reverse transcriptase sequences were obtained from these samples, and all sequences were identified as subtype B. Before the patient received Indinavir, the viral population only had some polymorphisms in the protease sequences. After the patient began Indinavir treatment, the variants carrying polymorphisms declined while variants carrying the secondary mutation G73S gained the advantage. As therapy was prolonged, G73S was combined with M46I/L90M to form a resistance pattern M46I/G73S/L90M, which then became the dominant population. 97.9% of variants had the M46I/G73S/L90M pattern at XLF6. During the emergence of protease inhibitors resistance, reverse transcriptase inhibitors resistance maintained high levels. Conclusion: Indinavirresistance evolution was observed by single-genome amplification. During the course of changing the regimen to incorporate Indinavir, the G73S mutation occurred and was combined with M46I/L90M.
文摘Due to the highly demand on the renewable energy sources as a free and a clean power resource, extracting energy from unsteady flow using marine and tidal current turbines has a distinct focusing nowadays. For their resource characteristic, extracting energy from marine/tidal current needs a simple and robust converter, which could overcome the drawbacks of the mechanical system such as gearbox and enhance conversion system stability. In this paper a new AC-DC-AC conversion system has been proposed. The new conversion system contains a middle stage DC-DC boost converter, which boost the generated rectified DC voltage higher enough that can enable the PWM inverter to generate the required voltage with the synchronized frequency. In order to investigate the efficient performance of the proposed conversion system especially at low current speed compared to the conventional one, different operating conditions have been studied. Moreover, the effect of including boost converter on the THD （total harmonic distortion） has also been checked. The new conversion system presents its capability to enhance and improve system performance not only with low current speed but also with high current speed.
