Background: Vasectomy is one of the most effective tools of population control. Controversies are arisen with respect to the effects of vasectomy on testis and the process of spermatogenesis, thus the present study was carried out to determine the effects of closed-END and open-END vasectomies on rats testis in Kashan University in 2000. Materials and methods: For this experimental study, 20 Sprague Dawely rats were randomly selected. They were 8-12 weeks old and assigned in two groups of closed-END and open-END vasectomies. For the first group (closed-END) right vas deferens underwent closed-END operation and vas deferens of the left side underwent Sham operation, however for the other group (open-END) right and left vas deferens underwent open-END and Sham operations, respectively. 4 months later, their testes were removed and their weight, volume and macroscopic appearance were determined. Then, microscopic changes including histologic changes, seminoferous ducts, interstitial tissue, number of spermatogonia, number and type of spermatocytes, etc were all recorded. T-test was used for data analysis. Results: Histologic studies revealed that testicular tissue was normal in control group but have changes in the case group. In injured ducts detachment of immature cells from epithelium, epithelial vacuolization, thickening and folding of periductal membrane, and removal of germ cells were prominent changes. Quantitative evaluation of normal ducts revealed that there was significant differences between groups regarding: number of spermatogonia, spermatocyte, round spermatid, long spermatid, the proportion of long spermatid to sertoli, ductal diameter, and volume and weight of testis. Conclusion: There was no significant difference between the closed- and open-END vasectomies, however both affect the testicular tissue. Effects of increased hydrostatic pressure were less prominent in closed-END technique. Further studies with special attention on increased antisperm antibody , and seminoferous ductal structure wit0.h ultrastructure and immunochemistry are strongly suggested.

Routing methods for optimal distribution of traffic in data networks that can also provide quality of service (QoS) for users is one of the challenges in recent years' research on next generation networks. The major QoS requirement in most cases is an upper bound on END-to-END path delay. In multipath virtual circuit switched networks each session distributes its traffic among a set of available paths. If all possible paths are considered available, then the source's decision on its traffic distribution can be considered as routing. A model of the routing function as a mathematical problem which distributes the input traffic over possible paths for each session is proposed here. A distributed and iterative algorithm which will keep the average END-to-END delay for individual paths below a required bound is introduced. This algorithm minimizes the total average delay of all packets in the network. The convergence of the algorithm is illustrated.

Sensor networks are eligible candidates for military and scientific applications such as border security and environmental monitoring. They are usually deployed in unattENDed or hostile environments; therefore, security is a major concern with these networks. A fundamental requirement is the capability to establish pairwise keys between sensors. Many key establishment protocols have been proposed to address the security issues in wireless sensor networks. However, most of these protocols have security and/or performance restriction. In this article, we propose a new key establishment protocol based on symmetric polynomials and random key pre-distribution. In our protocol, contrary to others, we use several symmetric polynomials to generate polynomial shares for a group of sensors, and the distribution of polynomial shares to each sensor is done using a combinatorial design. Since a limited number of shares are generated from a symmetric polynomial, the polynomial degree is very low. As a result, the common key between sensors can be generated without imposing significant overhead to them. Further, in the proposed protocol, key establishment between near sensors is provided via symmetric polynomials, while key establishment between far sensors is accomplished via random key pre-distribution. Using these two techniques simultaneously allows END to END key establishment between every pair of sensors with reasonable overhead.

Background: Chronic renal failure (CRF) patients have integrally required an arteriovenous fistula (A VF) to establish a vascular access for hemodialysis. The present study was performed on CRF patients in Shohada Tajrish Hospital between 1999 and 2000 to compare the efficacy of different types of AVF. Materials and methods: It was a clinical trial. 60 patients have been randomly distributed in two equal groups, according to the time of referral. AVF in the snuff box region was constructed between the cephalic vein and a branch of the radial artery, either side to side (STS) or END to side (ETS). Patients were followed for at least 6 months and the efficacy rate, failure rate, and venous hypertension following AVF construction were compared and analyzed statistically. Results: AVF was failed in 6 patients (20%) of STS group, of which 4 were due to thrombosis of the fistula and 2 were due to venous hypertension, however, in ETS group 5 cases (16.6%) developed failure, all of which were due to thrombosis. Conclusion: There was no significant difference in AVF efficacy between the two groups after 6 months follow up. Further with greater sample size are highly recommENDed.