7,047 research outputs found
Research on the Dynamic Change of the Retail TFP in China and its Macro Influence Factors
随着我国居民财富的积累,消费需求对我国经济发展的推动作用愈加明显,同时也对我国经济的消费服务水平提出了更高的要求,零售是实现消费过程中重要的环节。21世纪初,外资零售和网络零售的发展给我国零售业带来了变革,但由于我国经济发展区域不均衡,我国零售业的发展亦存在较大的区域差异,因此本文基于我国零售业发展区域不平衡的客观事实,深入研究我国东、中、西部地区零售业发展过程中零售业效率的动态变化,并研究各地区影响零售业效率变化的宏观环境因素,提出政策建议以促进我国零售业区域均衡发展,提高零售业的消费服务水平。 本文主要运用MalmquistDEA模型对我国东、中、西部地区零售业2008年至2014年的全...As Chinese residents become richer and richer, the role of promoting Chinese economy by consumption demand is becoming more and more important, also the capability of services for consumption has been put forward higher requirements. At the beginning of the 21st century, retail industry of our country has been promoted to revolution by foreign-invested retail and online retail, but because of the ...学位:经济学硕士院系专业:经济研究所_产业经济学学号:1602013115223
The role of appoptosin in regulating oxidative stress and mitochondrial morphology
氧化压力是指细胞或体内氧自由基的含量超出抗氧化物及抗氧化酶类清除能力时对细胞或机体造成的氧化胁迫。氧化压力参与了包括炎症、衰老、心血管疾病、癌症、糖尿病、艾滋病、神经退行性疾病等多种疾病的发病过程。氧化压力通过多个下游信号通路对细胞造成胁迫,如JNK、Foxo等,但其中的具体参与蛋白仍有待于深入阐明。Appoptosin也被称为SLC25A38,是一种定位于线粒体内膜的转运蛋白,负责转入甘氨酸并转出D-氨基乙酰丙酸,进而调节血红素(heme)的合成。我们实验室前期的研究结果表明appoptosin是一种促凋亡蛋白,但是目前对于appoptosin更为具体的功能研究仍然十分有限。 为了更好地理...Reactive oxygen species (ROS) can cause oxidative stress when not adequately counterbalanced by the defense system, which usually constitutes non-enzymatic molecules and enzymatic scavengers. ROS is involved in the pathogenesis of diseases such as inflammation, cardiovascular diseases, cancer, diabetes, AIDS and neurodegenerative diseases. Appoptosin/SLC25A38 is a nuclear encoded mitochondrial inn...学位:理学博士院系专业:药学院_化学生物学学号:3232011015412
洪泽湖大型底栖动物群落结构及其与环境因子的关系
洪泽湖是我国第四大淡水湖,然而关于洪泽湖大型底栖动物的报道较少。为了研究洪泽湖大型底栖动物群落结构特征及其影响因子,在洪泽湖设置20个采样点,进行了为期1周年的季度调查(2010年5月-2011年2月)。共采集到大型底栖动物14种,寡毛类、摇蚊科幼虫和软体动物分别有5种(占总物种数的35.7%)、3种(21.4%)和6种(42.9%)。河蚬为第一优势种(优势度Y=0.18),其次分别为苏氏尾鳃蚓(0.09)、羽摇蚊(0.07)、霍甫水丝蚓(0.06)和铜锈环棱螺(0.06)。群落的平均密度和平均生物量分别为(45.45±7.38)个/m2和(52.43±12.04)g/m2,其中软体动物平均密度和平均生物量最高[(24.80±6.20)个/m2和(49.55±11.94)g/m2],摇蚊类次之[(13.76±2.87)个/m2和(2.28±0.71)g/m2],寡毛类最低[(6.96±2.41)个/m2和(0.60±0.18)g/m2]。全湖Shannon-Wiener、Margalef和Pielou指数分别为2.69、1.10和0.71,各指数季节差异不明显。冗余分析(RDA)结果共解释物种数据累计方差的35.0%;MonteCarlo检验表明,洪泽湖水体中硝酸盐氮、总氮和化学耗氧量是影响底栖动物群落分布最关键的环境因子(F=2.181~3.277,P<0.05)
Spatial distribution and abundance of small fishes in Xiaosihai Lake,a shallow lake along the Changjiang (Yangtze) River, China
Spatial distribution and abundance of small fishes were studied in autumn 2007 in the Xiaosihai Lake, a shallow lake along the middle reach of the Changjiang (Yangtze) River. Based on the plant cover, the lake was divided into three major habitats: Myriophyllum spicatum habitat (MS habitat), Trapa bispinosa habitat (TB habitat), and non-vegetation habitat (NV habitat). A modified pop-net was used for quantitative sampling of small fishes in the three habitats, and the Zippin’s removal method was used for estimating densities of the small fishes. A total of 13 species belonging to 5 families were collected, with 11 species in MS habitat, 7 species in TB habitat, and 5 species in NV habitat. Habitat type had significant effect on the spatial distribution of small fishes. The Shannon-Wiener diversity index in the MS, TB and NV habitats were 1.28, 0.56 and 0.54, respectively. The total density and biomass of small fishes were significantly higher in the MS habitat (13.68 ind/m2 and 4.44 g/m2) than in the TB habitat (1.41 ind/m2 and 0.54 g/m2) and the NV habitat (1.08 ind/m2 and 0.40 g/m2), and were not significantly different between the TB habitat and the NV habitat. Water depth had no significant effect on spatial distribution of the small fishes. It was suggested that vegetation type played an important role in habitat selectivity of small fishes, and the presence of submersed vegetation should be of significance in the conservation of small fish diversity
七种捕食性鱼类对中华绒螯蟹幼蟹捕食风险的评估
分别以鲤、鳜、斑点叉尾、黄颡鱼、瓦氏黄颡鱼、大口鲇和乌鳢作为捕食者,以中华绒螯蟹幼蟹作为猎物,在室内水泥池(2.4 m3)进行捕食试验。以日捕获率和日摄食率为指标,评估这些鱼类对幼蟹的捕食作用和危害程度,为提高湖泊幼蟹放流效果、建立蟹—鱼复合的优质高效养殖模式提供科学依据。在幼蟹完全暴露的条件下,经过多次(至少9次)重复的试验(短期1d和长期7d),鳜对不同大小的硬壳和软壳(刚蜕壳的)幼蟹没有任何捕食作用;黄颡鱼对硬壳和软壳幼蟹也没有捕食作用,但还需做进一步观察;虽然鲤、瓦氏黄颡鱼对硬壳蟹的捕获率低,但对软壳的幼蟹有较大的危害性,对幼蟹的日摄食率分别为0.070%、0.012%;大口鲇、斑点叉尾、乌鳢对幼蟹具有较强的捕食能力,对幼蟹的日摄食率分别为0.122%、0.188%和0.284%。根据这些研究结果,可以建议:(1)在池塘和湖泊河蟹养殖中,完全可以将鳜作为套养或混养对象,以期提高养殖效益;(2)在河蟹放养的湖泊,需要抑制乌鳢和大口鲇种群,适当减少鲤和瓦氏黄颡鱼丰度,以期减少这些鱼类的捕食作用,提高幼蟹存活率;(3)在河蟹养殖池塘,不能放养乌鳢、大口鲇、斑点叉尾、瓦氏黄颡鱼和鲤
牛山湖两种优势小型鱼类空间分布与沉水植被的关系!
运用8种网目规格的成套浮性刺网作为鱼类采样工具,于2005年夏季在长江中游浅水草型湖泊牛山湖进行鱼类定量采样,通过比较不同茂密程度黄丝草生境中的小型鱼类组成、数量和大小结构,探讨此类湖泊小型鱼类的空间分布特征及其与沉水植被的关系.采样期间共捕获13种1124尾鱼,依据其等级丰度和出现频次,和红鳍原!为该湖优势上层小型鱼类.在调查的沉水植物生物量范围内,鱼类物种丰富度和Shannon多样性指数与沉水植物生物量之间呈现倒抛物线关系;两种优势小型鱼类的种群丰度均与沉水植物生物量有着显著的线性正相关关系,且其平均个体大小在裸地生境较高、沉水植被茂密区较低,幼鱼更倾向群聚于厚密的黄丝草生境中;其他生境因子(水深和离岸距离)对和红鳍原!空间分布的影响不显著.黄丝草植被生境是牛山湖两种优势小型鱼类的重要保护生境,应加强对黄丝草等沉水植被的保护及恢复
长江中游三个湖泊中华绒螯蟹生长变化研究
选择长江中游的牛山湖、武湖和东汤逊湖三个典型的河蟹养殖湖区作为研究地点,从2009年2月起逐月调查湖泊放流河蟹体重和壳宽的生长变化,并同时记录投喂管理情况和收集试验湖区的水化特征及底栖生物资源状况。调查发现,河蟹在4、5、6月特定生长率最大,此时为河蟹生长的高峰期。在三个湖区间,生长有显著性差异,在收获季节,武湖河蟹的平均壳宽和体重均显著性大于另外两个湖区(P0.05);这种情形可能主要与为湖泊的天然饵料资源的种类和丰度有关
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