武汉地区24个豆科品种种子萌发期耐盐性评价

选取了武汉地区常见的24个豆类品种进行实验,比较其在不同浓度Na Cl溶液下发芽率、发芽指数、胚根胚芽比的生理指标差异。结果显示,在相同Na Cl浓度下,不同品种的发芽率、发芽指数、胚根胚芽比差异极显著(P0.01),品种间发芽率的变异系数随着Na Cl浓度的增加而加大,在150 mol/L时达到最大,且各品种间的发芽率、发芽指数、胚根胚芽比差异均极显著,品种间各指标差异最大。聚类分析表明,Na Cl浓度150 mol/L可作为豆科种子萌发期耐盐性鉴定的最佳浓度。     

种植模式对稻田土壤微生物数量及活度的影响

为了明确种植模式对稻田土壤微生物的影响情况，进行了少耕和翻耕时不同种植模式对稻田土壤微生物数量及活度的影响研究，结果表明：种植马铃薯、紫云英、黑麦草、油菜、小黑麦等冬季作物能够不同程度的影响土壤中微生物的数量与活度，影响程度可以表示为马铃薯〉黑麦草〉小黑麦〉紫云英〉油菜〉冬闲。在晚稻收割期，少耕土壤中的好气性细菌、厌气性细菌、真菌、放线菌数量都多于翻耕土壤。早稻收割期翻耕比少耕的微生物活度略高，而晚稻收割期翻耕比少耕的微生物略低，这与所测的几类微生物数量的基本变化规律是一致的。少耕能激活土壤中的微生物，改良土壤。     

烟草连作对旱地土壤微生物及酶活性的影响

测定了烟草不同连作年限的旱地土壤中微生物数量、活度及酶活性.结果 表明,连作8年以下的旱地土壤中的好气性细菌、厌气性细菌、放线菌及真菌的数量随连作年限增加而有上升趋势,连作8年以上的微生物数量却有下降趋势.烟草连作对旱地土壤的细菌数量影响最大,对真菌数量的影响次之,对放线菌数量的影响最小.烟草连作对旱地土壤微生物活度及土壤酶活性的影响不大.烟草长期连作将改变土壤微生物的数量及多样性,会影响连作病害的发生,不利于土壤生态系统的健康发展.     

移植器官可能携带癌症"种子"

一个国际科学家小组的最新研究显示 ,移植器官带有引发癌症的“种子” ,导致接受器官移植的病人卡波西氏肉瘤的发病率特别高。卡波西氏肉瘤是一种发作于皮肤的恶性癌症 ,也是器官移植手术最常见的“后遗症”之一。据统计 ,美国接受器官移植的病人 ,平均每 2 0 0人中就有一人会患上这种疾病 ,发病率比普通人高 4 0 0到 5 0 0倍。专家对造成这种现象的原因看法不一。有研究指出 ,导致卡波西氏肉瘤的疱疹病毒会由器官捐献者传染给器官的接受者 ,但也有研究人员认为 ,接受者体内本来就存在病毒 ,器官移植过程中使用的免疫系统抑制药物 ,也许为病…     

半埋式超长地下混凝土结构的温度应力分析

以株洲市某住宅小区为例,研究半埋式超长地下混凝土结构的温度场边界条件,运用有限元软件ABAQUS模拟其在使用期间降温和升温两种不利工况下的结构温度场和温度应力,并与全埋式地下结构温度应力进行比较。结果表明,两种结构的墙角、板墙连接处等均存在温度应力集中现象;对半埋式超长地下混凝土结构,应力变化最大的是完全暴露在空气中的剪力墙,其最大拉应力比覆土条件下大13.4%;处于半埋条件下剪力墙中部的极大应力差出现在墙体的顶、底部两端,在覆土与裸露交界处发生正负转折,均呈直线分布且变化值相同。此外,结构拐角角度对温度应力分布规律也有很大影响。     

变截面纳米线声子输运蒙特卡洛模拟

采用蒙特卡洛(MC)方法建立了声子在变截面硅纳米线内的输运模型, 以渐扩几何体与渐缩几何体为物理模型, 分别研究了在等热量与非等热量输入条件下2种模型的热整流效应和声子的输运特性. 模拟结果表明在2种条件下, 渐缩模型的热传导性能均高于渐扩模型. 在非等热量输入的条件下, 渐缩模型的热整流效应要大于等热量输入条件下的热整流效应.2种物理模型的主要区别在于体积的分布不同, 虽然在纳米尺度下边界散射作用明显, 但模拟结果表明边界散射对热传导的影响小于质量分布不同对声子输运的影响.     

白菜病害生防原生质体融合菌株的筛选

为了获得同时具有白菜软腐病和黑斑病生防功能的原生质体融合菌株,对白菜软腐病生防菌株芽孢杆菌KR和白菜黑斑病生防菌株假单胞菌B13的融合子进行了筛选.结果表明:2.0单位/mL的硫酸妥布霉素和5×10-3 g/mL的氯霉素可分别抑制假单胞茵B13和芽孢杆菌KR,培养基中添加这两种抗生素可选出融合子.对得到的182个融合子进行传代,连续传10代后,得到一株能稳定遗传的融合子KB1.     

正反弹道Taylor撞击变形等效性研究

反弹道撞击试验在材料与结构的动力学响应研究领域已有广泛应用,相比正向Taylor试验,反弹道条件下Taylor撞击试验可获得更全面的弹/杆结构响应数据及量化测试结果.为研究正反弹道结构响应的等效性条件,开展不同长径比Taylor杆的正反撞击试验,获得了试件微秒量级的实时动态响应数据.利用数值模拟方法研究了不同撞击速度下结构变形、能量变化与塑性波的传播规律,从能量角度建立了两种撞击条件下结构变形的等效关系,在靶弹质量比大于20的条件下,正反撞击塑性功偏差小于5%.     

多环芳烃的毒理学特征与生物标记物研究

多环芳烃主要来自于碳氢化合物不充分燃烧,在大气、水体和土壤中广泛地存在,由于多环芳烃具有疏水性、致癌性、致畸性、致突变性和生物难降解性,因此多环芳烃被看作是持久性有机污染物的主要代表。目前,多环芳烃的毒理学研究是环境科学领域的热点问题之一,研究主要集中在多环芳烃及其在环境中的降解和转化产物在体内的吸收、分布、排泄和代谢转化,以及阐明多环芳烃对人体毒作用的发生、发展和消除的各种条件和机理。生物标记物是有机污染物风险评价的核心内容,可以探索多环芳烃对人体健康损害的早期观察指标,即用最灵敏的探测手段,找出环境污染物作用于机体后最初出现的生物学变化,以便及早发现并设法排除。本文阐述了环境中多环芳烃的来源、性质和分布,评述了多环芳烃的毒理学研究进展,并对今后多环芳烃的毒理学的发展方向进行了论述。     

重庆四面山根系及土壤特性对优先路径分布的影响

通过分析不同土地利用状况(林地,灌草地和农地)下优先路径分布特征、土壤特性、及根系状况,探讨根系和土壤特性时优先路径的影响.采用染色法分析了三种不同土地利用状况下6块样地的优先路径分布,并分析了优先路径与根长密度、根孔和根面积之间的关系.结果表明,所有土地利用状况下0～10 cm土壤染色面积超过50％,在20 cm以下...     

烟草内生活性放线菌的筛选

为了发掘抗菌菌株,以分离的烟草内生放线菌为研究对象,用其活体和发酵液分别进行了抑制金黄色葡萄球菌、大肠杆菌以及对根结线虫2龄幼虫的押杀实验,结果表明：烟草内生放线菌及其发酵液对供试菌株的抑制效果均较明显,菌株Y12、菌株A7只能分别对金黄色葡萄球菌和大肠杆菌有抑制作用,发酵液抑菌圈直径分别为15mm和21mm,而Y7菌株则对金黄色葡萄球菌和大肠杆菌都有一定的抑制作用。内生菌及其发酵液抑杀根结线虫的效果并不明显,说明这些菌株的杀根结线虫活性与抑制病原菌活性之间没有相关性。     

Sur l'action de l'acide 2,4-dichlorophénoxyacétique sur la croissance des racines deZea mays et dePisum cultivéesin vitro

Summary (1) A response ofZea mays andPisum roots cultured aseptically to 2,4-dichlorophenoxyacetic acid has been observed.Depending on the concentrationZea mays shows an increase of the growth rate (optimal concentration 10^–11 mol) which turns over to an inhibition (above 10^–7 mol). The curve is similar to that obtained by 3-indoleacetic acid, which proves the phytohormonal character of 2,4-D.(2) ThePisum root is more sensitive than theZea mays root. A concentration of 10^–7 molinhibitsPisum in a high degree, whileZea mays is no more inhibited, thus demonstrating the selective herbicidal action of 2,4-D against isolated roots of Dicotyledons culturedin vitro.     

Opsonic activity against zymosan of normal human serum of different blood types

Summary Serum opsonic activity against zymosan was found to be decreased more markedly in highly diluted O type serum than in the other 3 types, among which no difference was noted. Heat-killed bacteria were equally well opsonized with any type of serum. This peculiar activity of O type serum against zymosan was not affected by the removal of isohemagglutinins. No inhibitory activity was demonstrable in O type serum.This work was supported in part by a Grant-in-Aid from the Japan Medical Research Foundation and Grants-in-Aid (Project Nos. 157253 and 544050) from the Ministry of Education, Science and Culture of Japan.     

Low pressure storage of seeds

Summary Storage of celery, cabbage and onion seed for 14 weeks under conditions of reduced atmospheric pressure decreased the deleterious effects of high temperature and high relative humidity upon the germination of these short-lived seeds.Acknowledgments. The authors gratefully acknowledge the financial support of the National Research Council of Canada.     

Über Substitutionsgene und Transfer der Genfunktion

Summary In some favorable cases it can be shown that in a given genotype there are more genes present than necessary to produce a certain character. By the aid of such substitute-genes evolved under the protection of present genes of analogous action the phylogenetic stability of a character can be assured with more certainty. On the other hand, in the case of loss of the older ancestral gene the identity of the phenotype is safeguarded now by the substitute-gene formerly present merely in a latent condition. The substitute-gene takes over the function of the gene lost. In the course of phylogenetic divergence of two forms those of their characters being of the same phenotypical manifestation can be produced by different systems of substitute-genes, added to the genotypes under divergent evolution.     

Estimation and forecasting in first‐order vector autoregressions with near to unit roots and conditional heteroscedasticity

This paper investigates the effects of imposing invalid cointegration restrictions or ignoring valid ones on the estimation, testing and forecasting properties of the bivariate, first‐order, vector autoregressive (VAR(1)) model. We first consider nearly cointegrated VARs, that is, stable systems whose largest root, l_max, lies in the neighborhood of unity, while the other root, l_min, is safely smaller than unity. In this context, we define the ‘forecast cost of type I’ to be the deterioration in the forecasting accuracy of the VAR model due to the imposition of invalid cointegration restrictions. However, there are cases where misspecification arises for the opposite reasons, namely from ignoring cointegration when the true process is, in fact, cointegrated. Such cases can arise when l_max equals unity and l_min is less than but near to unity. The effects of this type of misspecification on forecasting will be referred to as ‘forecast cost of type II’. By means of Monte Carlo simulations, we measure both types of forecast cost in actual situations, where the researcher is led (or misled) by the usual unit root tests in choosing the unit root structure of the system. We consider VAR(1) processes driven by i.i.d. Gaussian or GARCH innovations. To distinguish between the effects of nonlinear dependence and those of leptokurtosis, we also consider processes driven by i.i.d. t(2) innovations. The simulation results reveal that the forecast cost of imposing invalid cointegration restrictions is substantial, especially for small samples. On the other hand, the forecast cost of ignoring valid cointegration restrictions is small but not negligible. In all the cases considered, both types of forecast cost increase with the intensity of GARCH effects. Copyright © 2009 John Wiley & Sons, Ltd.     

(S)-(+)-4,4,4-Trifluoro-3-(indole-3-)butyric acid,a novel fluorinated plant growth regulator

Racemic 4,4,4-trifluoro-3-(indole-3-)butyric acid (TFIBA) has been synthesized and shown to inhibitAvena coleoptile elongation. (S)-(+)-TFIBA (fig. 1), which was prepared by an enzymatic method and markedly promotes root growth of Chinese cabbage, lettuce and rice plants, is a novel fluorinated plant growth regulator. Activity of the (S)-(+)-enantiomer of TFIBA was 10-fold greater than that of the (R)-(–)-enantiomer in the first two plant species and 5-fold greater in rice.     

Qualitative vs quantitative conceptions of homogeneity in nineteenth century dimensional analysis

The emergence of dimensional analysis in the early nineteenth century involved a redefinition of the pre-existing concepts of homogeneity and dimensions, which entailed a shift from a qualitative to a quantitative conception of these notions. Prior to the nineteenth century, these concepts had been used as criteria to assess the soundness of operations and relations between geometrical quantities. Notably, the terms in such relations were required to be homogeneous, which meant that they needed to have the same geometrical dimensions. The latter reflected the nature of the quantities in question, such as volume vs area. As natural philosophy came to encompass non-geometrical quantities, the need arose to generalize the concept of homogeneity. In 1822, Jean Baptiste Fourier consequently redefined it to be the condition an equation must satisfy in order to remain valid under a change of units, and the ‘dimension' correspondingly became the power of a conversion factor. When these innovations eventually found an echo in France and Great Britain, in the second half of the century, tensions arose between the former, qualitative understanding of dimensions as reflecting the nature of physical quantities, and the new, quantitative conception based on unit conversion and measurement. The emergence of dimensional analysis thus provides a case study of how existing rules and concepts can find themselves redefined in the context of wider conceptual changes; in the present case this redefinition involved a generalization, but also a shift in meaning which led to conceptual tensions.