Reduced growth factor requirements and accelerated cell-cycle kinetics in adult human melanocytes transformed with SV40 large T antigen

Melanomas develop with high frequency in transgenic mice in which oncogenic sequences of the SV40 DNA tumor virus have been specifically targeted to melanocytes. To investigate the role of SV40 in melanomagenesis, cultured human melanocytes were transformed with a retroviral shuttle vector encoding the SV40 large T antigen and examined for changes in cell-cycle kinetics and growth-factor dependence. Colonies expressing the viral oncogene were morphologically indistinguishable from their non-T-antigen-transformed counterparts. Also like normal melanocytes, the infected cells remained anchorage dependent and non-tumorigenic in nude mice. However, T-antigen-positive cultures exhibited significantly accelerated population doubling times, increased saturation densities with highly confluent monolayers and a three- to fourfold extended life span. Most interestingly, cell-cycle analysis revealed a measurable shift from quiescent to cycling cells in T-antigen-expressing cultures and an acquired ability to progress more rapidly through G1. Moreover, T-antigen-positive melanocytes proliferated in the absence of PMA and required markedly reduced levels of exogenous bFGF. These studies indicate that the viral oncogen of simian virus 40 provides melanocytes with distinct growth advantages that may render these cells unusually susceptible to additional environmental challenges necessary for full expression of the malignant phenotype.     

Effects of age, breast density, ethnicity, and estrogen replacement therapy on screening mammographic sensitivity and cancer stage at diagnosis: review of 183,134 screening mammograms in Albuquerque, New Mexico

PURPOSE: To examine how common patient factors affect screening mammographic sensitivity and cancer stage at diagnosis. MATERIALS AND METHODS: The authors used a population-based database of 183,134 screening mammograms and a statewide tumor registry to identify 807 breast cancers detected at screening mammography. RESULTS: Sensitivity varied significantly with ethnicity, use of estrogen replacement therapy, mammographic breast density, and age. Sensitivity was 54% (13 of 24) in women younger than 40 years, 77% (121 of 157) in women aged 40-49 years, 78% (224 of 286) in women aged 50-64 years, and 81% (277 of 340) in women older than 64 years. Sensitivity was 68% (162 of 237) for dense breasts and 85% (302 of 356) for nondense breasts and 74% (180 of 244) in estrogen replacement therapy users and 81% (417 of 513) in nonusers. Sensitivity was most markedly reduced with the combination of dense breasts and estrogen replacement therapy use; there was little difference when only one factor was present. Median cancer size and the percentage of early cancers showed little change with any factors. CONCLUSION: Age is a minor determinant of mammographic sensitivity in women aged 40 years or older. Sensitivity is substantially decreased with the combination of higher breast density and estrogen replacement therapy use. There was not a notable shift in cancer outcomes in the groups with lower mammographic sensitivity. These data do not support different screening recommendations in women aged 40-49 years or in estrogen replacement therapy users.     

基于TCP／IP协议的网络教学系统设计

通过对高校网络教学现状的调查与分析，提出了总体的设计目标以及设计方案，包括系统运行环境以及系统展现内容．系统采用C／S模式，通过主机与客户机发送数据包，利用网络包截获的相应技术以及包过滤等策略，对特定的数据包进行分析，将各类协议首部用的二进制代码展现，可更直观的看到网络传输的具体方式，同时可将二进制代码转换为十进制，使系统具有更强的可视性．     

论邓小平发展科学技术的创新思想

全面地阐述了邓小平关于发展科学技术的思想.从发展科学技术的重要性与发展科学技术的方法、目标、前提、核心等方面,将邓小平关于我国发展科学技术的论述,概括为科的论述,概括为科技关键论、引进吸收创新论、科技前沿论、教育基础论和人才为本论.     

于锁集合算法的增强型数据竞争检测方法

针对锁集合算法误报率高的缺点,采用增强型数据竞争检测方法对锁集合算法及算法实现两方面进行改进.增强型锁集合算法提出了更强必要条件的检测算法.该算法通过分析线程结束情况和理解变量的线程信息,精化数据竞争检测条件.算法实现采用系统体系结构扩展的方法,通过扩展锁表部件,将集合操作精确映射到位图操作,进一步提高检测精度和减少误报.实现了无干扰免插桩检测技术,避免了二进制代码插桩带来的干扰性和不确定性问题.与同类系统的对比实验结果表明,该方法能够有效地将误报率减小到0.67,并且具有很高的检测效率.     

人体压力分布测量及其传感技术

体压分布测量系统是测试病人坐卧时,人体与接触面之间压力的可视化工具.介绍了人体压力分布测量系统的一般结构,对其关键点--传感器技术作了较为详细的叙述.它们分别是电容式压力传感器;用电阻油墨制成的电阻式压力传感器阵列;压电电阻传感器等.有针对的介绍了国外三种典型的人体压力测试产品,Xsensor、Tekscan和FSA;论述了它们的主要特点及优缺点,并对其主要性能作了对比.最后介绍了自行设计的体压分布测量系统,并给出了实测结果.     

基于Cross-EKF定位的多机器人协作围捕策略研究

针对目前多机器人协作围捕过程中收敛速度慢、稳定性差、定位精度低的问题,提出一种新的围捕策略.设计出Cross-EKF定位算法,对目标位置的后验估计协方差进行交叉计算,以取得最小协方差区域.以区域边缘点到均值中心最大距离为半径,构建收敛圆,将对动态点的收敛扩展为对动态面的收敛.实验结果表明,系统能快速平稳地收敛该圆,从而实现对目标的精确围捕,该方法具有较高的实用价值.