In the present study, the prevalence of chromatin instability in the fertilizing-competent sperm population in the porcine oviduct in vivo was examined through qualitative analysis of the chromatin structure status of accessory boar sperm found in in vivo-derived embryos. The binding of chromatin-unstable sperm to oviductal epithelium in vitro was also studied. To examine the sperm chromatin state, a modified fluorescence microscopic sperm chromatin structure assay was used. Among a population of 173 fertile boars, individuals were selected for according to their chromatin status: 25 animals showed more than 5% of chromatin-unstable sperm in their ejaculates, and 7 showed consistently elevated percentages of chromatin-unstable sperm in three successively collected semen samples. A positive correlation was found between incidence of chromatin instability and attached cytoplasmic droplets (r=0.44, P<0.01). Analyses of accessory spermatozoa from in vivo-derived embryos demonstrated that the proportion of chromatin-unstable sperm was significantly (P<0.05) reduced in the population of fertilizing-competent sperm in the oviduct compared with the inseminated sperm. Populations of sperm bound to the oviduct in vitro had significantly (P<0.05) lower percentages of chromatin instability than in the original diluted semen sample. In conclusion, numbers of sperm with unstable chromatin are reduced in the oviductal sperm reservoir, possibly because of associated changes in the plasma membrane that prevent sperm from binding to the oviductal epithelium. We conclude that in vivo the likelihood that sperm with unstable chromatin will reach the egg and fertilize it is low. 相似文献
For the integration of smart antennas into third generation code division multiple access (CDMA) base stations, it still remains as a challenging task to implement smart antenna algorithms on programmable processors. In this paper, we study implementations of some CDMA compatible beamforming algorithms, namely least mean square (LMS), constant modulus (CM), and space code correlator (SCC) algorithms, using Xilinx??s Virtex family FPGAs. This study exhibits feasibility of implementing even simple, practical, and computationally small algorithms based on today??s most powerful FPGA technologies. 16 and 32 bits floating point implementations of the algorithms are investigated using both Virtex II and Virtex IV FPGAs. CDMA2000 reverse link baseband signal format is used in the signal modeling. Randomly changing fading and Direction-of-arrivals (DOAs) of multipaths are considered as a channel condition. The implementation results in terms of beamforming accuracy, FPGA resource utilization, weight vector computation time, and DOA estimation error are presented. Beamformer weight vectors using LMS and CM can be computed within less than 20 ??s on Virtex II FPGA and 10 ??s on Virtex IV FPGA, and using SCC it can be achieved within less than 22 ??s on Virtex IV FPGA. These results show that FPGAs provide approximately 500 times faster speed in implementations than our previous work with DSPs. 相似文献
Thermodynamic irreversibility in the flow system provides information on the energy and power losses in the system. Minimization
of entropy generation in the flow system enables for the parametric optimization of the system operation. In the present study,
parallel plates, in between, filled with the fluid are considered. The fluid motion resulted from the bi-vertical compression
of the top plate of the parallel plates is examined. The entropy generation rate in the flow system is formulated after considering
the constant movement of the top plate, constant applied load, and the combination of the constant velocity and applied load
to the top plate. The optimum operating conditions related to the fluid motion in between the parallel plates is determined
through the entropy analysis. It is found that the combination of the constant velocity and the constant applied load resulted
in the low entropy generation rate. 相似文献
The object of this work, a study of the junction recombination velocity limiting the short circuit (Sfsc) of a silicon solar cell under magnetic field in the dynamic frequency regime is presented. From the continuity equation, the density of minority Charge carrier’s in the base and the photocurrent are determined. The study of this photocurrent, according to the junction recombination velocity, allows us to determine the junction recombination velocity limiting the short circuit. The photocurrent density is studied as a function of the junction recombination velocity for different modulation frequencies. From the variation profile of the photocurrent density as a function of the junction recombination velocity, a technique for determining junction recombination velocity initiating the short-circuit situation is presented.
This study investigates pre-service teachers' perspectives of the diffusion of information and communication technologies (ICTs) in elementary education and the effect of case-based discussions (CBDs). The sample consisted of 170 first-year pre-service teachers from elementary teacher education programs of the largest teacher education college in Turkey. The cases used in the study were obtained from a case repository at http://ornekolay.org, indexing teaching cases from elementary classrooms of the capital city of Turkey. The cases were mainly text-based and presented stories of elementary teachers' in-class usage of ICTs. A quasi-experimental pretest-posttest design was executed to test the effect of pre-service teachers' perspectives on ICTs diffusion in elementary teaching. Three scales were developed based on Rogers' Diffusion of Innovation Theory (2003) to measure pre-service teachers' preferred innovativeness, innovation perceptions, and innovation decisions in the use of ICTs. The results showed that pre-service teachers had pre-established perspectives, mainly positive, about the diffusion of ICTs in elementary teaching; their perceptions about innovativeness and relative advantage were the main indicators of persuasion and decision; and CBDs positively affected their perceptions such that their computer-related persuasion and decisions positively increased. 相似文献
Thermodynamics and thermal stress analysis of thermo-electric power generator is carried out. The influence of device geometry on thermal stress, thermal efficiency and output power is examined. The finite element method is incorporated to predict temperature and stress fields in the thermo electric device. It is found that thermal efficiency improves for certain geometric configuration of the device. In this case; the maximum thermal stress developed in the pin reduces slightly indicating improved life expectation of the device. 相似文献