17β-Estradiol-sensitivity of cultured myometrial cells

Summary The estrogen sensitivity of cells cultured from the rat myometrium was studied by growing the cells in the absence or presence of 1 nM 17-estradiol. Following a time lag of 10 days, exposure to estrogen resulted in increased incorporation of radiothymidine by the cells. Estrogen treatment also decreased isoproterenol-dependent and GTP-dependent adenylate cyclase activity, but had no effect on basal activity. These cultured cells have been shown previously to have some properties of uterine smooth muscle. The effects estrogen has in viyro, therefore, may reflect important properties in vivo that account for the mechanism by which the sex steroid decreases the sensitivity of the myometrium to isoproterenol.     

Prothoracic gland synthesis of 3-dehydroecdysone and its hemolymph 3β-reductase mediated conversion to ecdysone in representative insects

Summary The prothoracic glands of a variety of insects were tested for their ability to synthesize ecdysteroids in vitro. More specifically, they were evaluated for their ability to produce 3-dehydroecdysone and ecdysone using both radioimmunoassay and reverse phase high performance liquid chromatography. Three categories of insect prothoracic glands were noted: a) those producing much more 3-dehydroecdysone than ecdysone; b) glands synthesizing almost equivalent amounts of each of these two ecdysteroids; c) prothoracic glands that yielded more ecdysone than 3-dehydroecdysone. In addition, the 3-oxoecdysteroid 3-reductase activity of the hemolymph of these insects was evaluated for its ability to convert 3-dehydroecdysone to ecdysone. The lepidopteran species tested yielded the most potent enzyme activity, although activity was demonstrated in members of other orders. These data indicate that the dehydroecdysone-ecdysone axis is not restricted to moths and butterflies.     

Genetic and molecular approaches to synthesis and action of the yeast killer toxin

Summary The K1 killer toxin ofSaccharomyces cerevisiae is a secreted, virally-coded protein lethal to sensitive yeasts. Killer yeasts are immune to the toxin they produce. This killer system has been extensively examined from genetic and molecular perspectives. Here we review the biology of killer yeasts, and examine the synthesis and action of the protein toxin and the immunity component. We summarise the structure of the toxin precursor gene and its protein products, outline the proteolytic processing of the toxin subunits from the precursor, and their passage through the yeast secretory pathway. We then discuss the mode of action of the toxin, its lectin-like interaction with a cell wall glucan, and its probable role in forming channels in the yeast plasma membrane. In addition we describe models of how a toxin precursor species functions as the immunity component, probably by interfering with channel formation. We conclude with a review of the functional domains of the toxin structural gene as determined by site-directed mutagenesis. This work has identified regions associated with glucan binding, toxin activity, and immunity.     

黄土夹砂层的持水机制

为研究黄土高原西北干旱区农业采用的"压砂"保墒方法机理,进行3种室内土柱(均质土柱、夹3 cm厚砂层的土柱、夹5 cm厚砂层的土柱)的降雨入渗试验,并建立微观模型对夹砂层阻水现象进行分析。通过烘干法和MAT253稳定气体同位素质谱仪测定土柱不同深度2个时间点(13 d、197 d)的含水率和土壤水的δD、δ18O,得到不同时间含水率随深度变化规律和土壤水δD~δ18O关系。结果表明:(a)黄土中夹砂层的存在起到了减缓水流下渗的作用,而不是阻止水分下渗。(b)夹砂层的这种阻水效果一方面是由于砂层薄膜水的持水量远小于黄土,从而阻滞了水流的下渗;另一方面是由于在介质突变界面处过水断面面积突然减小,以致降低了水流的下渗速度。     

CaF2--SiO2型硅传感器辅助电极的制备及其定硅性能

以CaF2+SiO2作为硅传感器辅助电极材料,将其均匀涂覆于ZrO2( MgO)固体电解质表面,在高纯Ar气保护下,1400℃焙烧30 min制备得到定硅传感器.利用X射线衍射仪、扫描电子显微镜以及能量色散谱仪系统研究了制备条件对于焙烧后形成的辅助电极膜层组成、物相和微观形貌的影响.膜层中不存在CaF2,而是以SiO2固体颗粒、CaO·MgO·2SiO2固溶体及ZrSiO4为主.另外,探讨了辅助电极膜层中物相的变化对于膜层黏结性以及定硅性能的影响.在1450℃下对铁液中硅含量进行测试,传感器响应时间在10 s左右,稳定时间在20 s以上,而且传感器的重复性也很理想.当铁液中硅质量分数在0.5%~1.5%时,硅传感器测量值与化学分析法分析值相吻合.     

湿度影响下的重载交通沥青路面动力响应

考虑地下水和雨水入渗的影响,运用ABAQUS软件建立重载交通沥青路面动力分析模型,分析地下水上升和降雨入渗引发路基湿度变化后的路基动态回弹模量分布规律,以及三轴双轮移动重载作用下沥青路面的动力响应.分析结果表明,地下水距路基顶面越近,对路基模量的分布影响也越显著,降雨入渗与动载共同作用处的路基模量折减更明显;地下水位距路基顶面高度从6 m减至2 m时,面层层底拉应变由70×10~(-6)增至173×10~(-6);降雨强度增大对外侧车道处的面层层底拉应变影响巨大,对中间车道的影响较小;降雨天数增加,两侧车道的面层层底拉应变反而减小,而中间车道的趋势相反,拉应变随着降雨天数增加而增大.     

某矿区瓦斯地质与瓦斯防治方案探析

通过井田瓦斯地质资料,分析了构造演化、地质构造、煤系地层岩性、煤层埋深与煤层厚度对瓦斯赋存产生的作用。研究表明,构造演化是影响区域瓦斯赋存的首要因素,在井田内,随着煤层埋藏深度的增加,煤层瓦斯含量逐渐升高,并且是影响瓦斯赋存的主控因素,地质构造、煤系地层岩性同样发挥着重要作用。在某矿的瓦斯地质基础上根据《防治煤与瓦斯突出规定》探析了某矿的瓦斯地质问题,并探讨了安全生产中应注意的问题。     

对外汉语个别实习中的语法教学

实习是＂对外汉语＂专业实践能力培养的一种重要方式。杨晓黎等提出了＂个别实习＂这种新的实习形式。讨论了个别实习中进行语法教学需要特别注意的性质、地位、内容、原则和方法等问题。提出实习中一方面要以教材、大纲为基础,另一方面要根据留学生习得顺序,调整语法点的选择和编排;实习中要注意以培养留学生汉语交际能力为目标;正确处理个别实习语法教学与留学生其他学习活动的关系;正确处理语法教学中汉语和其他语言的关系;处理好语法讲解和留学生操练的关系。     

《线性代数》教学之我见

《线性代数》是工科各专业学生的一门重要基础课，同时，它也是一门不可缺少的工具课；如何使学生较好地掌握课程的主要内容，培养学生熟练的运算能力及严密的逻辑思维能力，是我们教学工作者日常教学活动中所面临的主要问题。本文针对《线性代数》的特点，并结合教学中的问题，浅谈对《线性代数》教学的几点看法。     

论越南汉文小说《圣宗遗草》的真伪与思想内容

越南汉文小说《圣宗遗草》是一部优秀的传奇小说集。其中《鼠精传》模仿了中国小说《包龙图判百家公案》中的《决戮五鼠闹东京》，《百家公案》最早刊于明万历二十二年（1594），而黎圣宗则卒于公元1497年，可知《圣宗遗草》乃伪作，非黎圣宗所作。《圣宗遗草》或以寓言游戏笔墨，或藉鬼神影射人间，具有深厚的思想内容，表达了作者对社会现实的激愤。