Radiation embryology

Summary Prenatal development, characterized by intensive cell proliferation, cell differentiation and cell migration, shows a high radiosensitivity. Therefore, radiation exposure of embryos and fetuses is of great concern for radiological protection and human health. Irradiation during gestation can cause death, growth disorders, malformations, functional impairment and malignant diseases in childhood. These effects are strongly dependent on the developmental stage at exposure and on the radiation dose. The first trimester of pregnancy is regarded as the period with the highest risk for malformation and cancer induction. The developing nervous system shows a special susceptibility to ionizing radiation over a long period and is therefore of great significance for risk estimation. Knowledge about radiation effects on prenatal development has been derived from animal experimentation and from the exposure of human embryos. There is evidence that doses between 1 and 10 cGy may lead to developmental anomalies and that the radiation response can be modified by additional factors.     

基于UGNX的电脑机箱跌落特性分析

为改变传统物理样机验证的高成本和低效率，针对电脑机箱的耐跌落特性分析，经过一系列的等效转换后，UGNX软件提供的CAE模块，可以分析出电脑机箱CAD模型上的缺陷和结构上的薄弱环节，为机箱的设计修改提供强有力依据，所述结果与实际情况比较吻合。不谨如此，UGNX软件主模型还能实现电脑机箱CAD／CAE设计和验证参数化。所述方法能适用于其它家电产品的设计和分析上。     

A novel theoretical model for mass transfer of hollow fiber hemodialyzers

Hemodialyzers have been applied to hemodialysiswidely. In order to get accurate mass transfer coefficient and clearance to determine treatment time, their masstransfer models have been studied deeply. The domesticstudy on hemodialyzers is later, focuses on experiment, and seldom refers to theoretical mechanism[1,2], but theoverseas research is more in-depth. Simple one-dimensional models have been used to simulate mass transfer in hemodialyzers by many re-searchers[3—7]. Their models assumed …     

空心桥墩封顶施工工艺

结合桥梁施工实例，介绍在施工薄壁空心桥墩墩顶实心部位时，采用在墩壁预留孔，孔内安装钢棒牛腿作为现浇实心墩顶的竖向支撑，进行空心墩顶部实心段施工的工艺。     

多用途薄壁杆最轻重量优化设计

本文在给定抗弯、抗扭刚度约束下,对具有定周长、等壁厚的多用途薄壁杆进行最轻重量优化设计。优化采用求总极值的统计试验法,求得了各刚度比所对应的优化截面中心线方程及最小厚度值。与常用的圆形截面薄壁杆相比,优化结果显示了较明显的减轻杆件自重的效果。     

柑桔果实微生长规律及其在温室节水灌溉控制中的应用

果实主要因水分含量变化而引起的体积微变化包括日收缩和日净增长两个过程,果实水分含量日变化过程受到诸多环境因子的综合影响,其中土壤水分起主导作用。树体缺水时果实净增长量主要因水分向其它器官转运过多而受到影响,相比较而言,依据果实微生长规律控制灌水,不仅能节水,同时可使柑桔生长速率明显提高。     

机械CAD的开发应用方法探讨

探讨了机械CAD应用开发的两个途径以及几个主要的开发内容,并以圆柱齿轮CAD为实例介绍机械CAD的一种开发方法。     

Accumulation of drastic mutants in selection lines for resistance to the insecticides dichlorvos and malathion inDrosophila melanogaster

Summary Viability tests were performed on second and third chromosomes from lines ofDrosophila melanogaster selected for increased resistance to the organophosphorus insecticides dichlorvos and malathion, in order to evaluate the accumulation of drastic alleles. Our results show that malathion reduces significantly the relative viability of chromosome 3 and also increases the frequency of drastic alleles in this chromosome, while dichlorvos increases significnatly the frequency of drastic alleles in chromosome 2.Work supported in part by the Spanish Ministry of Education and Science (Grant No. 0577/84 CAICYT).—We are grateful to Productos Cruz Verde S.A. and Agrocrós S.A. for generously supplying the insecticides dichlorvos and malathion, respectively.     

碳载型Pd—Pt—Ag空壳纳米催化剂用于甲酸高效电氧化

通过Ag纳米颗粒部分置换预先吸附在活性碳表面的PdCl4^2-及PtCl4^2离子,制备了碳载型Pd—Pt—Ag空壳纳米催化剂．催化剂中不同Pd和Pt比例可通过控制前驱体溶液中的金属浓度方便实现．将得到的二元及三元空壳纳米催化剂用于甲酸电氧化,发现pd2．6Pt0．4Ag／C表现出了最佳的电催化活性,初步归因于表面活性位的增加及合金协同效应．