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Number of results: 5
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Abstract

Sperm-mediated gene transfer (SMGT) is based on the ability of spermatozoa to bind exoge- nous DNA and transfer it into oocytes by fertilization. However, SMGT is still undergoing opti- mization to improve its efficiency to produce transgenic animals. The acrosome reaction is neces- sary for spermatozoa to carry the exogenous DNA into oocytes. In this study, the effect of the acrosome reaction on the efficiency of spermatozoa carrying exogenous DNA was evalua- ted. The results showed that the efficiency of the acrosome reaction was significantly higher (p<0.05) after incubation with 50 μmol/L progesterone compared to incubation without proges- terone. It was significantly higher (p<0.05) in the 20, 40, and 60 min of progesterone treatment groups than in the 0 min treatment group. The spermatozoa were further incubated with cyanine dye Cy5 labeled DNA (Cy5-DNA) for 30 min at 37°C, and positive fluorescence signals were detected after the acrosome reaction was induced by progesterone at concentrations of 0 and 50 μmol/L for 40 min. The percentage of positive Cy5-DNA signals in spermatozoa was 96.61±2.06% and 97.51±2.03% following exposure to 0 and 50 μmol/L progesterone, respective- ly. The percentage of partial spermatozoa heads observed following combination with Cy5-DNA was 39.73±3.03% and 56.88±3.12% following exposure to 0 and 50 μmol/L progesterone, respec- tively. The ratio of positively stained spermatozoa combined with exogenous DNA showed no reduction after the acrosome reaction. These results suggest that the acrosome reaction might not be the key factor affecting the efficiency of SMGT.
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Abstract

A novel phase shift full bridge (PSFB) converter with voltage-doubler and decoupling integrated magnetics in photovoltaic (PV) systems is proposed. Considering the demand that the output voltage is higher than the input voltage in PV systems, the voltage-doubler is added to achieve higher voltage gain compared with the traditional PSFB. In order to avoid current oscillation caused by the voltage-doubler and obtain the wide zero voltage switching (ZVS) ranges, an external inductor is imposed on the circuit. Especially, to obtain much higher power density, the external inductor and transformer are integrated into one magnetic core. The operation and voltage gain of proposed converter are analyzed. Also, in order to reveal the effects the integrated magnetics gives to the converter, the decoupling condition and the expression of leakage inductor of integrated magnetics are obtained in detail. Finally a 100 W prototype converter is made and the experimental results are given to verify the analysis.
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Abstract

Based on the theory of heat transfer, the influence of expansion joints on the temperature and stress distribution of ladle lining is discussed. In view of the current expansion joint, the mathematical model of heat transfer and the three dimensional finite element model of ladle lining brick are established. By analyzing the temperature and stress distribution of ladle lining brick when the expansion joints are in different sizes, the thermal mechanical stress caused by the severe temperature difference can be reduced by the suitable expansion joint of the lining brick during the ladle baking and working process. The analysis results showed that the thermal mechanical stress which is caused by thermal expansion can be released through the 2 mm expansion joint, which is set in the building process. So we can effectively reduce the thermal mechanical stress of the ladle lining, and there is no risk of steel leakage, thus the service life of ladle can be effectively prolonged.
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