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101.
The small yellow croaker (Larimichthys polyactis) belongs to the family Sciaenidae, which is an offshore warm fish species and widely distributed in the western Pacific. In this study, the variation of genetic diversity and genetic differentiation among L. polyactis populations was analyzed by mitochondrial DNA control region. A total of 110 polymorphic sites were checked, which defined 134 haplotypes. High level of haplotype diversity (h=0.993±0.002) was detected in the examined range. Population genetic structure analyse (analysis of molecular variance, Fst) showed there were high gene flow among L. polyactis populations. The result showed that there were relatively high genetic diversity and low genetic differentiation among the Yellow Sea and the East China Sea populations, which can be attributed to diverse habitats, wide distribution range and high mutation rate of control region. Using phylogenetic methods, coalescent analyses (neutrality tests, mismatch distribution analysis, Bayesian skyline analyses) and molecular dating interpreted in conjunction with paleoclimatic and physiographic evidence, we inferred that the genetic make-up of extant populations of L. polyactis was shaped by Pleistocene environmental impacts on the historical demography of this species. Besides, relatively constant genetic diversity and larger effective population size were detected in recent L. polyactis population. The result showed that the fishing policy certainly, such as the summer closed fishing, played a role in protecting resources of L. polyactis. This study can offer a wealth of biological novelties which indicates genetic structure of L. polyactis population and provides the foundation for resources protection and policy setting. 相似文献
102.
基于微观视角的农村居民点发展评价与布局优化——以陕西省重点示范镇沙河子镇为例 总被引:1,自引:0,他引:1
将生态位态势理论应用于农村居民点布局研究,从发展水平和发展潜力两方面选取指标分别作为发展"态"和发展"势"的评价因素,构建农村居民点发展评价模型,对居民点的发展实力划分等级。然后结合加权Voronoi图,明确各发展等级居民点的搬迁去向,从而实现全镇整治分区规划。沙河子镇农村居民点的发展实力可划分为高、中、低和不适宜发展4个等级;农村居民点整体发展较好,高、中发展实力级的居民点用地面积为304.07hm2,占全区的84.23%;具有明显的地形分异特征,其发展等级呈现由中部向南北两侧递减的趋势;全镇以农村居民点城镇化为整理重点,划分为城镇化区、优先发展区、改造发展区和控制发展区4种整治分区。结合生态位态势理论和加权Voronoi图的农村居民点合理布局研究具有较强的现实指导意义。 相似文献
103.
赣北芙蓉―周溪断面下蜀黄土粒度特征及其指示意义 总被引:1,自引:0,他引:1
赣北鄱阳湖地区沙山南部近南北向的芙蓉―周溪断面上,分布由FZ-01、FZ-02~FZ-05和FZ-06~FZ-12三部分组成的下蜀土剖面,粒度分析结果表明:1)下蜀黄土砂粒组分自北往南变化为27.29%、1.94%~7.23%和0.45%~7.27%;粉砂组分质量分数大,且存在差异变化,分别为68.23%、81.71%~87.20%和66.9%~79.39%;黏土组分自北向南质量分数增加,变化为4.48%、8.46%~16.35%和18.13%~32.07%,总体表现为砂黄土―黄土―黏黄土等相态的逐渐过渡;2)粒度三组分、粒度参数散点图等均表现为从北而南的阶段性系统渐变特征;3)各种粒度参数与距长江的远近,均服从对数函数变化关系。这些特征初步揭示研究区的下蜀黄土是风成的,并可能与同样是风成堆积的沙山的形成存在某种联系,属于区域性风沙-风尘堆积体系。 相似文献
104.
Present studies on the coupling relationship and hydrology mechanism between basin ecosystem and hydrological process has become an international research frontier in hydrology. This paper investigates this coupling relationship, and also summarizes research and presents a method of combining isotopic technology with hydro-chemical methods, for the study of eco-hydrological process and function in different landscape zones. We then examine research trends for future direction and development of this field. 相似文献
105.
106.
动物型溶菌酶研究新进展 总被引:3,自引:0,他引:3
溶菌酶可以分解连接N-乙酰胞壁酸(NAM)和N-乙酰氨基葡萄糖(NAG)残基之间的β-1,4糖苷键。g型、c型和i型溶菌酶是3种动物型溶菌酶。近年来,越来越多的报道表明这3种类型的溶菌酶在动物界广泛存在,g型和c型溶菌酶主要存在于脊椎动物中,i型溶菌酶仅存在于无脊椎动物中,部分物种中同时存在2种动物型溶菌酶。本文简要概述了溶菌酶在动物各物种中的存在情况和组织分布情况、基因组结构与系统进化以及溶菌酶抑制剂的研究新进展。 相似文献
107.
Remote sensing data from passive microwave and satellite-based altimeters, associated with the data measured underway, were used to characterize seasonal and spatial changes in sea ice conditions along... 相似文献
108.
Real-Time Observation on Water-Soluble Ions of PM2.5in Beijing under the Influences of Different Air Masses in Summer简 下载免费PDF全文
To further understand the variations of water-soluble ions in PM2.5 in Beijing,the authors observed their concentrations continuously and in high temporal resolution by the system for rapid collection of fine particles and ion chromatography(RCFP-IC) during 12–18 July 2010.These results combined with those of earlier backward trajectory research are used analyzed to determine the causes of concentration changes in water-soluble ions under the influences of two kinds of air masses in summer.The results indicate that concentrations of NO3^-,SO4^2-,and NH4+ were influenced strongly by the continental air mass than by the marine air mass.Cl^- and Na^+ were not changed significantly.Because the sources of K^+,Mg^2+,and Ca^2+ are mainly concentrated on land,their concentration levels were slightly higher under the control of continental air mass than that of the marine air mass.Variations of NO2^- during the observation differed from those of other ions;its concentration was significantly higher under the influence of marine air mass.Moreover,the authors obtain the diurnal variations of eight water-soluble inorganic ions including NH4^+,K^+,Mg^2+,Ca^2+,Cl^-,NO2^-,NO3^-,and SO4^2-.Diurnal variations of NH4^+,NO3^-,and Cl^- showed single peak,which appeared before noon,while SO4^2- showed two peaks that appeared during rush hours.Those of Mg^2+,Ca^2+,and K+ showed single peak that appeared in the afternoon.That of NO2^- showed with a peak appearing at sunrise and a valley appearing at sunset. 相似文献
109.
Influence of Mass and Radius of Ice Crystals on Hydrometeors,Internal Energy,and Kinetic Energy: A Numeric Model Study简 下载免费PDF全文
Two cloud-scale experiments with two different ice-phase schemes were carried out for a precipitation event that occurred in eastern China in 2005.The results were analyzed to examine the influences of the change of ice-particle mass and radius on hydrometeors,internal energy,and kinetic energy,as well as the primary factors responsible.It was found that the ice content increases notably and the snow content decreases due to the change.This is the consequence of the modulation of cloud microphysical processes.In particular,the Bergeron process and the accretion of snow and cloud ice are markedly influenced.The differences of internal energy and kinetic energy between the two experiments are caused by adjustments to pressure-flux divergence,the coupling of temperature and divergence,and gravitational work,and the reason is that these three factors result in differences of local changes of internal and kinetic energy. 相似文献
110.
本文研究了水环境急性低氧胁迫对卵形鲳鲹Trachinotus ovatus选育群体血液生化指标的影响。实验设计了急性低氧试验组和对照组,每组3个平行。结果显示,急性低氧胁迫后选育群体的血清离子含量与对照组相比都有不同程度的升高,其中钠、氯、钙浓度与对照组相比差异显著(p0.05),铁浓度极显著高于对照组(p0.01);血清蛋白、尿酸、肌酐、血脂、血糖等指标的差异较大,其中尿酸、肌酐极显著高于对照组(p0.01),总蛋白、总胆固醇显著低于对照组(p0.05);血清中肌酸激酶含量极显著高于对照组(p0.01),肌酸激酶同工酶显著高于对照组(p0.05),γ-谷氨酰转肽酶含量显著低于对照组(p0.05);其他指标均有不同程度的升高或降低,但差异不显著。研究表明,急性低氧胁迫造成卵形鲳鲹鳃、肾、心脏和肝脏损伤,免疫力下降。 相似文献