This experiment was carried out to study a simple and efficient method for in vitro production of rabbit embryos. Newly ejaculated rabbit spermatozoa were used to fertilize superovulated oocytes after capacitation in vitro with four different media: (A) isotonic defined medium (DM)+heparin, (B) DM only,(C) DM+ high ionic strength defined medium (HIS), and (D) DM supplemented with 10mM NaHCO3 (mDM) +HIS supplemented with 10mM NaHCO3 (mHIS). The presumptive zygotes were cultured in M199 supplemented with 10% FCS, 1.25mM Na Pyruvate and 0.1mM EDTA (mM199). The cleavage rates after 24h of incubation were 29.3%, 32.1%, 64.9%, and 91.6% respectively, and the rates of blastocyst formation after 72h were 0, 27.3%, 58.4% and 85.2%, respectively. The results in the (D) treatment were significantly better than the other three treatments (p<0.01). Developmental potential of in vivo and in vitro derived zygotes was also compared using the mM199. The percentages of blastocyst and hatching blastocyst in the two groups were 92.5% and 87.2% after 84h, and 84.9% and 83.7% after 108h, respectively, and the two groups were not significantly different (p>0.05). The developmental progress of the two groups was nearly synchronous towards the end of culture. When IVF embryos from 2- to 4-cell stage were transferred into recipients, the pregnancy rate did not differ from in vivo fertilization, but the rate of live young from IVF was significantly lower than from in vivo. The results of this experiment showed that ejaculated rabbit sperm could be capacitated efficiently after treatment of mDM and mHIS, and rabbit IVF embryos achieved great development in mM199 in vitro.

Abstract. Secondary flow is one of the main reasons for low efficiency in double suction centrifugal pump. In a 3-D inverse design method, the pump blade could be designed by a specified loading distribution to control the flow field in pump. In order to study the influence of loading distribution on secondary flow of a double suction centrifugal pump, the external characteristics and the internal flow field of the pump with three kinds of loading distributions are analysed by using CFD approach. According to the simulation results, it is found that the form of fore-loading distribution at shroud and aft-loading distribution at hub could improve the optimal efficiency and broaden the high efficiency area of the pump. Furthermore, the secondary flow in impeller exit region and volute could be significantly suppressed if the slope of loading distribution curve of shroud is set to be -0.7. 1.IntroductionDouble suction centrifugal pumps are widely used in water diversion, irrigation, drainage and water supply engineering. However, pump sometimes operates at partial design conditions and results in low efficiency. At this condition, the secondary flows including the backflow and vortex present in the pump chamber [1]. Therefore, it is a challenging issue to control the secondary flows inside a double suction centrifugal pump.The 3-D inverse design method is a new design tool in which the blade loading distribution has to be specified [2]. The flow field in a pump could be controlled by specifying a suitable blade loading distribution, so it is necessary to study the influence of the blade loading distribution on suppression of secondary flows in a double suction centrifugal pump.The blade loading distribution curve is a three-segment curve [3][4] consisting of a parabolic curve and a straight line section followed by another parabolic curve in the 3-D inverse design method. Zangeneh [5] designed a mixed-flow pump impeller by using the inverse design method with a small slope of the straight line, this kind of loading distribution improved the backflow and wake-jet of impeller exit. Ashihara [6] improved a centrifugal impeller by using aft-loading distribution at shroud and hub, the results showed that pump inlet suction performance was improved, but the backflow of impeller exit was obvious. Zangeneh [7] designed a centrifugal impeller by using two kinds of loading distribution, the first is fore-loading distribution at shroud and hub, and the second is fore-loading distribution at shroud + aft-loading distribution at hub. The results showed that the second loading distribution is better than former for both the backflow of impeller inlet and exit. To sum up, the form of aft-loading distribution at hub could helps to improve the suppression of secondary flows in pump,