西双版纳热带雨林树种斜叶榕F. tinctoria水分利用方式的季节变化

 以斜叶榕F.tinctoria为研究对象,通过测定其木质部与其各种潜在水源的氢氧同位素组成,揭示西双版纳地区斜叶榕在不同季节的水分利用变化.结果表明在干热季时的30cm土壤处水势达到最低值-30.5kPa,在雾凉季时此深度土壤处出现最大水势,为-14.5kPa,在各个季节70cm处的土壤水势几乎没有变化.雨季时的土壤含水量比雾凉季与干热季都高(P<0.001),而雾凉季与干热季的土壤含水量则没有显著差异(P=0.64).通过对雨水、雾水、浅层土壤水、深层土壤水、树干腐殖质水及植物木质部水的稳定同位素分析得出,在雨季,雨水与浅层土壤水是斜叶榕的最主要水源;雾凉季时,斜叶榕主要利用土壤水(包括浅层土壤水与深层土壤水).干热季时,浅层土壤水是斜叶榕的最主要水源.因此,斜叶榕的水分利用存在季节变化.     

浅谈身边既熟悉又陌生的电磁辐射

电磁辐射在当今社会已经是家喻户晓,但是对于大多数人来说,“电磁辐射”只是一个名词,并不知道身边到底有哪些电磁辐射,有多少,对人体有多大伤害。而另一些人又对“电磁辐射”谈虎色变。本论文将通过对“电磁辐射”的初浅介绍,对“电磁辐射”的来源进行分析,探讨“电磁辐射”对人体健康的危害和日常生活防护措施。     

SWCC测定时吸力计算公式与最佳离心时间的探讨

采用离心机法测定了南京市栖霞区东阳镇0～20cm,20～40cm,40～60cm 3层土壤的水分特征曲线(SWCC),分析了密度变化对吸力的影响、质量含水量与时间的关系、土壤吸力与质量含水量的关系;根据分析结果改进了传统的吸力求解公式,得出了离心机法测定粉砂壤土水分特征曲线时的最佳离心时间.改进公式克服了传统公式计算吸力时没有考虑土壤压缩的弊端,计算得到的土壤体积含水量可以随土壤干密度的变化而变化,土壤水分特征曲线更能合理地反映土壤水分的保持和运动规律.     

吨钢钢液面积对钢质量的影响

本文利用示踪法对高T[O]条件下钢中夹杂物的来源及特点进行研究.结果表明:正常浇注条件下,钢水一次脱氧不彻底,钢中T[O]高,造成钢中氧化物夹杂含量高,铸坯内大型非金属夹杂物主要来源于脱氧产物.吨钢钢液面积大对钢质量不利,宜减小吨钢的钢液面积.显微夹杂总体积率为0.15%,各类夹杂占显微夹杂总量的比例为:硅钙酸盐夹杂55.4%,硅铝酸盐夹杂34.4%,硫化物夹杂10.2%.     

A half century of radioisotope neutron sources in China

Near 50 years history of the development of radioisotope neutron sources in China is briefly reviewed. The structure design, preparing technology and production status of routine neutron sources including 210Po-Be sources, 210po mock fission sources, 241 Am-Be sources, 238pu-Be sources, 252Cf spontaneous fission sources and other special-shape neutron sources are summarized. In addition, the prospects of development on radioisotope neutron source in China are predicted from the needs of nuclear power construction, oil well-logging, neutron moisture gauge and neutron brachytherapy.     

Climate change impacts on crop yield,crop water productivity and food security-A review

This paper provides a comprehensive review of literature related to the assessment of climate change impacts on crop productivity using climate,water and crop yield models.The existing studies present that climate change models with higher spatial resolution can be a way forward for future climate projections.Meanwhile,stochastic projections of more than one climate model are necessary for providing insights into model uncertainties as well as to develop risk management strategies.It is projected that water availability will increase in some parts of the world,which will have its own effect on water use efficiency and water allocation.Crop production can increase if irrigated areas are expanded or irrigation is intensified,but these may increase the rate of environmental degradation.Since climate change impacts on soil water balance will lead to changes of soil evaporation and plant transpiration,consequently,the crop growth period may shorten in the future impacting on water productivity.Crop yields affected by climate change are projected to be different in various areas,in some areas crop yields will increase,and for other areas it will decrease depending on the latitude of the area and irrigation application.Existing modelling results show that an increase in precipitation will increase crop yield,and what is more,crop yield is more sensitive to the precipitation than temperature.If water availability is reduced in the future,soils of high water holding capacity will be better to reduce the impact of drought while maintaining crop yield.With the temperature increasing and precipitation fluctuations,water availability and crop production are likely to decrease in the future.If the irrigated areas are expanded,the total crop production will increase;however,food and environmental quality may degrade.     

丛枝菌根真菌对水分胁迫下红橘实生苗根系矿质营养元素的影响

在温室盆栽条件下研究丛枝菌根真菌Glomus versiforme(Karsten)Berch对正常水分和水分胁迫下的红橘(Citrus tangerine Holt.ex Tanaka)实生苗根系大量元素和微量元素含量的影响.结果表明,水分胁迫显著抑制丛枝菌根真菌对根系的侵染.无论在正常水分还是水分胁迫下,丛枝菌根真菌的感染对根系Fe没有显著影响,但显著增加根系P、Ca、Mg、Cu和Mn的含量.丛枝菌根真菌的接种仅显著增加水分胁迫下根系N含量和正常水分下根系K含量.丛枝菌根真菌处理对根系Zn的效果依土壤水分状况而异.     

广西喀斯特地区城镇用地扩张及来源预测——以河池市金城江区为例

以河池市金城江区1991,1999,2006年三期TM/ETM+遥感影像为数据源,分析了城镇用地的遥感信息机理,提取了研究区三期土地利用现状图,并采用GIS空间分析技术,对城镇用地扩张的时空过程进行了研究.分析表明:城镇用地规模不断扩大,增长速度不均匀,城镇用地变化区域差异较大,城镇用地在中心城镇高度集聚.旱地、荒草地、独立工矿用地和坑塘水面是城镇用地扩张的主要来源.     

水分胁迫下玉米幼苗光合变化和生理特性分析

对不同水分胁迫下玉米幼苗光合变化和生理特性的系统研究表明,在轻度干旱初期,玉米叶片光合速率(Pn)、蒸腾速率(Tr)有所下降,同正常供水(CK)条件相比差异不显著;在中度和重度干旱条件下,Pn,Tr开始就比CK明显降低并不断增大,其间气孔导度(Gs)则同光合速率、蒸腾速率几乎呈平行关系,同时幼苗生长也受到了明显抑制;3种胁迫下,叶片含水量也逐渐减少,丙二醛(MDA)含量、细胞膜透性和渗透调节物质含量随着胁迫程度加深和胁迫时间延长明显增加,保护酶系统(SOD,POD,CAT)活性随着胁迫时间的延长,总体呈现出先升高后降低的趋势.     

关于《实验动物科学与管理》更名为《实验动物科学》的启事

《实验动物科学与管理》迄今已出版、发行了20多年,承蒙广大读者、作者的支持和厚爱及各届编委的悉心呵护和辛勤耕耘,不仅相继被评为“中国科技核心期刊”、“中国科技论文统计源期刊”和《中国学术期刊综合评价数据库》来源期刊,而且所载全文或文献还被中国期刊全文数据库、万方数据一数字化期刊群、中国生物文献数据库、中文生物医学期刊文献数据库、中文科技资料目录一医药卫生光盘数据库、