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1.
In order to understand the relationship between the community structure of bacteria in ice core and the past climate and environment, we initiated the study on the microorganisms in the three selected ice samples from the Malan ice core drilled from the Tibetan Plateau. The 16S ribosomal DNA (rDNA) molecules were directly amplified from the melt water samples, and three 16S rDNA clone libraries were established. Among 94 positive clones, eleven clones with unique restriction pattern were used for partial sequence and compared with eight reported sequences from the same ice core. The phylotypes were divided into 5 groups: alpha, beta, gamma proteobacteria; CFB, and other eubacteria group. Among them, there were many “typical Malan glacial bacteria“ pertaining to psychrophilies and new bacteria found in the ice core. At a longer time scale, the concentration distribution of “typical Malan glacial bacteria“ with depth showed negative correlation with temperature variations and was coincident with dirty layer. It implied the influence of temperature on the microbial record through impact on the concentrations of the “typical Malan glacial bacteria“. In addition, the nutrition contained in ice was another important factor controlling the distribution of microbial population in ice core section. Moreover, the result displayed an apparent layer distribution of bacterial community in the ice core section, which reflected the microbial response to the past climatic and environmental conditions at the time of deposition.  相似文献   

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近年来,研究发现中子星的转动惯量I和四极矩Q存在着一个关系式,即I-Q关系.而且,该关系式不依赖于中子星内部的物态方程,与引力理论相关.因此,对该关系式的研究可用来检验引力理论.de Rham-GabadadzeTolley(dRGT)massive gravity是一种自洽的引力子静止质量不为零的修正引力理论,是目前国际引力理论研究的热点.本论文主要基于该修正引力理论,在慢速旋转近似下,利用多方指数n=0的物态方程,计算了dRGT massive gravity中牛顿极限下的I-Q关系.我们将dRGT massive gravity与爱因斯坦引力中的I-Q关系进行比较,发现引力子质量不会影响I与Q的平方之间无量纲化后的正比关系,但会改变其比例系数.  相似文献   

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乳酸乳球菌电转化条件的研究   总被引:10,自引:0,他引:10  
以质粒pTRKH2为材料,对乳酸乳球菌MG1614进行电转化条件的研究.实验结果表明,在电转化过程中,电场强度、电阻大小、细胞生长状态和电击后菌株复苏时间均对转化效率有明显影响,得到了乳酸乳球菌的最适电转化条件为:对数生长中期的细胞,经1%甘氨酸处理,在10kVcm电场强度、400Ω电阻下电转化,转化后细胞在SGM17培养液中培养2h后涂布选择性培养基,转化率(转化子个数与DNA质量之比)可达1.2×103个μg,比优化前的转化效率提高近100倍.  相似文献   

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气候资源是农业生产的基本要素之一,当前全球气候变暖对农业造成一定的影响。本文对1990-2016年期间新疆生产建设兵团(以下简称兵团)农业气候资源,农业生产要素、农业生产效率以及气候对农业生产效率的影响进行了研究。首先梳理了兵团气温、降水和日照的变化特征和趋势;然后利用主成分分析兵团农业生产的影响因素,基于投入产出理论利用数据包络模型分析兵团农业生产效率,进一步构建农业生产效率和气象因素的多元线性回归模型。研究结果表明:多年来兵团气温升高,降水增加,日照时长减少,南疆气温升高趋势比北疆明显,降水增量低于北疆;年平均气温变化以中长周期为主,降水从频繁的短周期转变为中长周期,波动幅度加剧;研究期内,气温和降水变化没有明显的突变点;自然资源、科技、现代农业生产条件和资金投入对兵团农业生产影响较大;兵团农业生产效率稳步提高,在当前气象变化条件下,气温和降水都对农业生产效率产生正效应,气温对农业生产效率的促进作用远高于降水。保障兵团农业生产的长期稳定,要积极应对气候变化,充分利用气象资源变化带来的有利方面,预防极端天气带来的危害,提高农业生产的适应性和自我缓解能力。  相似文献   

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追求社会发展是每个国家和民族的共同愿望,而如何看待社会发展和经济发展的关系。树立什么样的“发展观”,则是至关重要的问题。要实现真正的发展——可持续的全面的社会发展,就要为其寻找真实的动力和坚实的基础,这真实的动力和坚实的基础就是提高劳动生产率、提高科技贡献率、提高管理效益、优化产业结构、提高国家经济质量,而这一切只能依靠科技、文化、教育、卫生等社会事业的发展和社会整体素质的提高。  相似文献   

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Using the definition of vulnerability provided by the Intergovernmental Panel on Climate Change,this paper assesses the vulnerability of areas affected by Chinese cryospheric changes from 2001 to 2020 and from 2001 to 2050 in A1 and B1scenarios.Seven indices are used in the vulnerability assessment:glacial area fraction,interannual variability of permafrost depth,interannual variability of surface snow area fraction,interannual variability of surface runoff,interannual variability of surface temperature,interannual variability of vegetation growth,and interannual variability of the human development index.Assessment results show that the overall vulnerability of the studied areas in China increases from east to west.The areas in the middle and eastern parts of China are less vulnerable compared with western parts and parts of the Tibetan Plateau.The highest vulnerability values are found from 1981 to 2000,and the least ones are found from 2001 to 2050.The vulnerable areas increase from the period of 1981 to 2000 to the period of 2001 to 2050,and the less vulnerable areas decrease.The highly vulnerable areas increase from the period of 1981 to 2000 to the period of 2001 to 2020 and then decrease from the period of 2001 to 2020 to the period of 2001 to 2050.This decrease in vulnerability is attributed to the decrease in exposure and sensitivity to Chinese cryospheric changes along with a concomitant increase in adaptation.  相似文献   

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Raising crop water use efficiency (WUE) is the physiological basis to implement crop high efficiently using water. The present soil column and field experiments are designed to investigate the change of wheat WUE (Triticum aestivum L.) at whole plant level and root system growth in evolution and the relationship between WUE and its root system growth using 10 wheat evolution genotypes with different ploidy chromosomes sets. Results show that in wheat evolution from 2n→6n, WUE at whole plant level increases with the increase of ploidy chromosomes, and root system growth (root weight, root length) and root/shoot ratio of wheat decrease with the increase of ploidy chromosomes under dry and irrigated conditions. WUE is negatively correlated with root weight and root/shoot ratio of wheat in evolution, significantly. Root system growth has an adverse redundancy for WUE in wheat evolution, and the root redundancy reduces with the increase of ploidy chromosomes, which result in the increase of wheat WUE at whole plant level.  相似文献   

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借助荧光猝灭可以观测和研究导电高聚物与富勒烯之间的电子转移效率及机理.但对链长较短的低聚噻吩(2T~7T)来说,由于不能避开富勒烯的吸收范围而仅对低聚噻吩进行选择性激发,从而导致获取的猝灭率失实.给出了富勒烯吸收作用对荧光猝灭效率影响的校正方法、物理模型和数学推导过程.校正后,在低聚噻吩/富勒烯混合液中荧光光谱波形轮廓与低聚噻吩溶液中荧光光谱波形轮廓的一致性,证实了该校正方法的可行性.  相似文献   

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汪云  陈安 《科技促进发展》2014,10(1):97-102
为落实《纲要》中"食品安全与出入境检验检疫"优先主题的规划部署,国务院办公厅、科技部、卫生部八部门联合以及各省市相关部门都发布了一系列食品安全监管文件及科技发展规划,实施了众多相关科研及专项课题项目,在食品安全检测与危害识别、风险评估、出入境检验检疫风险评估和监测监管等方面均取得了一定成绩。本文综合报道了该优先主题的实施情况和研究进展,以及许多领域专家指出的我国食品安全科技创新的发展方向。  相似文献   

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山东省济宁市社会经济发展与土地利用关系研究   总被引:1,自引:0,他引:1  
在阐述研究社会经济发展与土地利用关系的重要意义和辩证关系的基础上,运用定量分析和定性分析的方法手段揭示了山东省济宁市社会经济发展与土地利用的相互关系,从社会经济发展的角度对土地利用主要指标进行了预测.文章指出凝聚在社会经济发展与土地利用二者内部的关联属性是区域社会经济持续发展必须把握的基本规律.从社会经济发展的角度,山东省济宁市2020年农用地总量(Y1)、耕地面积(Y2)、园地面积(Y3)、林地面积(Y4)、建设用地面积(Y5)、居民点及工矿用地面积(Y6)、交通用地面积(Y7)分别是872 151.98 hm2、602 594.2 hm2、27 619.92 hm2、31 456.79 hm2、186 335.24 hm2、139 410.5 hm2、47 232.56 hm2.  相似文献   

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We characterized yield-relevant characters and their variations over genotypes and environments (locations and years) by examining two rice varieties (9746 and Jinfeng) with high yield potential. 9746 and Jinfeng were planted in two locations of Shanghai, China, during 2005 and 2006. The results show that there was a large variation in grain yield between locations and years. The realization of high yield potential for the two types of rice was closely related to the improved sink size, such as more panicles per square meter or grains per panicle. Stem and leaf biomasses were mainly accumulated from tillering stage to heading stage, and showed slow decline during grain filling. Meanwhile, some photosynthetic characters including net photosynthesis rate (Pn), leaf area index (LAI), specific leaf area (SLA), fluorescence parameter (maximum quantum yield ofPSll, Fv/Fm), chlorophyll content (expressed as SPAD value), as well as nutrient (N, P, K) uptake were also measured to determine their variations over genotypes and environments and their relationships with grain yield. Although there were significant differences between years or locations for most measurements, SLA at tillering and heading stages, Fv/Fm and LAI at heading stage, stem biomass at heading and maturity stages, and leaf nitrogen concentration at tillering and heading stages remained little changed, indicating their pos- sible applications as selectable characters in breeding programs. It was also found that stem nitrogen accumulation at tillering stage is one of the most important and stable traits for high yield formation.  相似文献   

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河南省人口流动特点及对社会经济发展影响   总被引:1,自引:0,他引:1  
陈仁禹  闫国平 《河南科学》2003,21(1):122-126
河南省是全国人口最多的省份,也是人口流动最多的省份。本文从综合特点,全面分析了河南省人口流动的特点及对社会经济发展影响的正负效应,同时,通过调查分析,提出了几点启示。  相似文献   

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Human intolerance to bacteria as food   总被引:4,自引:0,他引:4  
C I Waslien  D H Calloway  S Margen 《Nature》1969,221(5175):84-85
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随着中国对外开放的深化以及经济的快速发展,社会对复合型外语人才的需求不断增长,在此背景下商务英语专业得到了快速发展,然而随着市场的需求发生变化以及专业建设多方面条件的限制,目前商务英语专业发展遭遇到了瓶颈期。本文首先概括了商务英语专业发展存在的主要问题,然后分析了问题存在的主要原因,最后有针对性地提出了解决问题的思路。  相似文献   

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