缓冲区结构效率分析

I/O设备与CPU的速度不匹配,制约了计算机系统性能的进一步提高。为此,根据计算机体系结构,对缓冲区结构的效率进行分析,使用EDA计算机辅助设计软件QuartusII设计异步双时钟FIFO缓冲区,并对其进行仿真验证及数据记录,通过对数据的分析,证明系统整体效率与FIFO效率密切相关,只有实现FIFO效率的最大化,才能使系统整体效率最大化,同时FIFO效率最大化也只能在完成系统效率最大化的过程中得以实现。     

构皮滩水电站观景供水系统大型长轴深井泵站设计

乌江构皮滩水电站大坝上游的观景供水系统，为满足上游水位变化的需要，设计成分阶段分级竖井供水的方式。供水设备选用高工效、低能耗的RJC型大型长轴深井泵，运行方式为开敞式串联运行，单机单台生产能力为1010m3／h，最大扬程96．51m，最大井下安装深度89．475m，经安装调试运行效果良好。大型长轴深井泵在乌江构皮滩水电站供水系统中的成功应用为中国类似工程泵站设计提供了很好的借鉴，也将促进中国大型长轴深井泵的进一步发展。     

Assessment of genomic damage in colorectal cancer by DNA fingerprinting: prognostic applications

PURPOSE: Here we evaluate the prognostic significance of the relative value of genomic damage assessed by DNA fingerprinting in colorectal cancer. MATERIALS AND METHODS: Sixty-three tumor and paired normal mucosa samples were included in the study. Genomic damage was assessed by comparative analysis of paired normal and tumor tissue DNA fingerprints by the arbitrarily primed polymerase chain reaction (AP-PCR). Decreases and increases of intensity in bands were computed and referred to the total number of visualized bands per case. An index reflecting the genomic damage fraction (GDF), with separated values for losses and gains, was obtained for each tumor. This index was used to determine molecular and clinicopathologic correlates after exclusion of eight cases displaying microsatellite instability. RESULTS: Fifty-five cases were considered for the statistical analysis. The average fraction of altered bands per tumor was 0.287+/-0.121. When losses and gains were computed separately, the average fraction of changes was 0.126+/-0.113 and 0.161+/-0.120, respectively. Tumors lacking a ras mutation showed an increased GDF, primarily because of a higher fraction of gains. Tumors that were at advanced Dukes' stages and that were poorly differentiated also displayed a higher GDF. Finally, disease-free survival was significantly diminished in tumors with a GDF greater than 0.314 (P < .001). The prognostic significance of the GDF was independent of Dukes' stage (Cox multivariate analysis, P = .005). CONCLUSION: The degree of genomic damage assessed by unbiased DNA fingerprinting correlates with genotypic, phenotypic, and clinical variables in colorectal carcinoma and may be useful in assessing prognosis in colorectal cancer.     

Management considerations for treating vesicoureteral reflux in children with solitary kidneys

OBJECTIVES: To evaluate the management approach for vesicoureteral reflux (reflux) into a solitary kidney. METHODS: Outcomes of all children with solitary kidneys and reflux managed between 1981 and 1996 were reviewed. Solitary kidneys were documented by nuclear renography and ultrasonography; reflux was graded after cystography. Management consisted of observation and antimicrobial prophylaxis or surgery by ureteroneocystostomy or subureteric injection of polytetrafluoroethylene (STING). Follow-up ranged from 3 months to 14 years and included serial cystography, sonography, and serum creatinine measurement. RESULTS: Twenty-one patients with a median follow-up of 26 months were identified. Etiologies included contralateral renal agenesis (14 children), multicystic dysplastic kidney (5 children), or nonfunctioning ureteropelvic junction obstruction (2 children). Low-grade (I to II) reflux was identified in 6 children, and high grade (III to V) was identified in 15. Reflux resolved in 20 patients. Five children with low-grade reflux were managed without surgery and demonstrated reflux resolution after a mean of 20.5 months. Renal function deteriorated in only 1 child. Ureteroneocystostomy was performed in 13 children with grades III to V reflux, and STING was performed in 1 child with grade II reflux. Every surgical patient maintained stable renal function and was infection-free during a mean follow-up of 56 months. Management by observation in 2 children with grades IV to V reflux resulted in spontaneous resolution in one and stable grade IV in the other. CONCLUSIONS: Reflux into the solitary functioning kidney may be managed by the same strategies used to manage unilateral reflux in children with two normally functioning kidneys: low-grade reflux by observation/ chemoprophylaxis until spontaneous resolution occurs, and higher grades by surgery to protect renal function; however, chemoprophylaxis and serial imaging may be used until well-defined indications for surgery are satisfied. Renal function should be monitored diligently.