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951.
广西百朗地下河水和沉积物中有机氯农药的分布特征 总被引:4,自引:2,他引:2
为了解典型岩溶地区广西乐业百朗地下河表层水和沉积物中有机氯农药的分布特征,采集地下河不同断面的水和沉积物样品,利用气相色谱仪测定了19种有机氯农药。结果表明:(1)百朗地下河表层水中19种有机氯农药总量(∑OCPs)浓度为1.95~71.45ng/L,HCHs和DDTs浓度分别为未检出至58.40ng/L和未检出至0.44ng/L;(2)沉积物中∑OCPs浓度为0.75~14.85ng/g,HCHs和DDTs浓度分别为0.11~3.52ng/g和0.03~2.90ng/g;(3)地下河表层水和沉积物中有机氯农药的分布与吸附作用、环境温度以及和地下河连通的天坑的底部的土壤侵蚀有关,即因温差作用,大气沉降的有机氯农药易富集在天坑底部(“冷陷阱效应”),并在土壤侵蚀作用下向水体移动,使地下河沉积物中有机氯农药浓度升高;(4)百朗地下河出口沉积物吸附系数最低,但水中有机氯农药浓度较高且种类最多,推测可能是地下河沉积物中因有机氯农药被释放而引起二次污染;(5)表层沉积物中大多数断面的异狄氏剂浓度及乐业县城附近断面的DDTs和DDD浓度在风险评估低值与风险评估中值之间,表明百朗地下河处于较低的生态风险水平;(6)目前,流域部分断面尚有新的γ-HCH(林丹)和DDTs农药输入。由于有机氯农药长期累积,可能对地下河生态系统造成危害,应采取防治措施。 相似文献
952.
Perciformes, the largest order of vertebrates with 20 suborders, is the most diverse fish order that dominates vertebrate
ocean life. The complete mitochondrial control region (CR) of Trichiurus japonicus (Trichiuridae, Scombroidei) and Pampus sp. (Stromateidae, Stromateoidei) were amplified and sequenced. Together with data from GenBank, the tandem repeats in the
mitochondrial CR from 48 species, which covered nine suborders of Perciformes, are reported in this study. The tandem repeats
tend to be long in the suborder Percoidei and Stromateoidei. The identical repeats in 21 species of Cichlidae suggest a common
origin and have existed before species divergence. Larimichthys crocea shows tandem repeats instead of the typical structure of the central conserved sequence blocks, which was first reported
in Perciformes and vertebrates. This might have resulted from interruption of the polymerase activity during the H-strand
synthesis. The four broader patterns presented here for the tandem repeats, including those in both the 5′ and 3′ ends, only
in the either 5′ or 3′ end, and in the central conserved domain of the control region, will be useful for understanding the
evolution of species. 相似文献
953.
The Gram-negative Vibrio parahaemolyticus is a common pathogen in humans and marine animals. Bacteria flagellins play an important role during infection and induction
of the host immune response. Thus, flagellin proteins are an ideal target for vaccines. We amplified the complete flagellin
subunit gene (flaA) from V. parahaemolyticus ATCC 17802. We then cloned and expressed the gene into Escherichia coli BL21 (DE3) cells. The gene coded for a protein that was 62.78 kDa. We purified and characterized the protein using Ni-NTA
affinity chromatography and Anti-His antibody Western blotting, respectively. Our results provide a basis for further studies
into the utility of the FlaA protein as a vaccine candidate against infection by Vibrio parahaemolyticus. In addition, the purified FlaA protein can be used for further functional and structural studies. 相似文献
954.
Sediment cores (∼40–100 cm) were collected at 12 locations in the western Bohai Bay, the Haihe River estuary, the Yongding
River estuary and the Tianjin Harbor, China, during 24–26 July 2007, and analyzed for 7Be and 210Pb activities. Due to localized hydrodynamic patterns and frequent disturbance from dredging activities, steady-state sedimentation
features were not observed in this study. As demonstrated in the 7Be and 210Pb profiles, the temporal and spatial variations of these radionuclides support a non-steady state depositional environment
in the study area. By comparing 7Be and 210Pb inventories in the sediments with those of the atmospheric source, we found that: 1) sediments dredged from the Tianjin
Harbor or eroded from nearby estuarine and coastal areas are retained in the western Bohai Bay for relatively short intervals
(several months), as reflected in the relatively high 7Be inventories in the western Bohai Bay; 2) over the long-term (years to decades), 210Pb inventories in the sediments imply that there is a net on-shore transport of sediments, and the sediments are mass-balanced
in the entire study area. Overall, our results suggest that the sediments are retained in the estuaries and the western Bohai
Bay despite local variability in sediment dynamics and disturbance due to human activities. 相似文献
955.
Fish assemblage structure in the hypoxic zone in the Changjiang (Yangtze River) estuary and its adjacent waters were analyzed
based on data from bottom trawl surveys conducted on the R/V Beidou in June, August and October 2006. Four fish assemblages were identified in each survey using two-way indicator species analysis
(TWIA). High fish biomass was found in the northern part, central part and coastal waters of the survey area; in contrast,
high fish diversity was found in the southern part of the survey area and the Changjiang estuary outer waters. Therefore,
it is difficult to maintain high fishery production when high fish diversity is evenly distributed in the fish community.
Fish became smaller and fish size spectra tended to be narrower because of fish species variations and differences in growth
characteristics. Fish diversity increased, the age to maturity was reduced and some migrant species were not collected in
the surveys. Fish with low economic value, small size, simple age structure and low tropic level were predominant in fish
assemblages in the Changjiang estuary and its adjacent waters. The lowest hypoxic value decreased in the Changjiang estuary
and its adjacent waters. 相似文献
956.
三维可视化已成GIS发展的潮流,这必然会导致空间数据量的激增,通过集群系统和并行数据库系统可以很方便地解决海量数据的存储管理问题。但是,在海量环境下,一般数据库管理系统提供的查询接口,仍然难以满足实时三维场景可视化的速度需求。因此研究C/S模式下海量三维空间数据的高效调度成为三维GIS发展亟须突破的难点。在数据库服务器端和客户端之间加上应用服务器端,提供数据缓存、预调度等功能,减少服务器端磁盘I/O所带来的时间消耗,可以明显加速数据调度。本文系统分析了这种客户端/应用服务器端/数据服务器端模式下三维空间数据通信的难点和主要设计挑战,并针对三维GIS的数据访问特征,设计了一套能满足三维GIS实时调度的通信应用层协议。以ACE中前摄器框架为基础,结合线程池技术提出分层策略,搭建了海量三维空间数据的通信架构,它是一种面向对象的构架,可以方便地进行功能的定制和扩展。 相似文献
957.
目的:探讨黄精复方治疗气阴两虚型2型糖尿病的临床疗效。方法:将气阴两虚型2型糖尿病患者64 例随机分为治疗组和对照组,每组各32 例。所有患者均采取饮食、运动等生活方式干预,对照组口服二甲双胍片治疗,治疗组在对照组基础上加用黄精复方治疗,疗程均为12周。观察2组综合疗效及治疗前后中医证候积分、体质量指数(BMI)、空腹血糖(FBG)、餐后2 h血糖(2hPG)、糖化血红蛋白(HbA1c)、空腹胰岛素(FINS)、胰岛素抵抗指数(HOMA-IR)、总胆固醇(TC)、三酰甘油(TG)、高密度脂蛋白胆固醇(HDL-C)、低密度脂蛋白胆固醇(LDL-C)的变化,记录2组不良反应。结果:总有效率治疗组为87.50%(28/32),高于对照组的59.37%(19/32),差异有统计学意义(P<0.05)。2组中医证候积分、BMI、FBG、2hPG、HbA1c、FINS、HOMA-IR、TC、TG、LDL-C、HDL-C治疗前后组内比较及治疗后组间比较,差异均有统计学意义(均P<0.05)。结论:黄精复方治疗气阴两虚型2型糖尿病可以缓解患者的中医证候,降低血糖、血脂,改善胰岛功能,从而提高临床疗效。 相似文献
958.
959.
Fangli Qiao Yeli Yuan Tal Ezer Changshui Xia Yongzeng Yang Xingang Lü Zhenya Song 《Ocean Dynamics》2010,60(5):1339-1355
A theoretical framework to include the influences of nonbreaking surface waves in ocean general circulation models is established
based on Reynolds stresses and fluxes terms derived from surface wave-induced fluctuation. An expression for the wave-induced
viscosity and diffusivity as a function of the wave number spectrum is derived for infinite and finite water depths; this
derivation allows the coupling of ocean circulation models with a wave number spectrum numerical model. In the case of monochromatic
surface wave, the wave-induced viscosity and diffusivity are functions of the Stokes drift. The influence of the wave-induced
mixing scheme on global ocean circulation models was tested with the Princeton Ocean Model, indicating significant improvement
in upper ocean thermal structure and mixed layer depth compared with mixing obtained by the Mellor–Yamada scheme without the
wave influence. For example, the model–observation correlation coefficient of the upper 100-m temperature along 35° N increases
from 0.68 without wave influence to 0.93 with wave influence. The wave-induced Reynolds stress can reach up to about 5% of
the wind stress in high latitudes, and drive 2–3 Sv transport in the global ocean in the form of mesoscale eddies with diameter
of 500–1,000 km. The surface wave-induced mixing is more pronounced in middle and high latitudes during the summer in the
Northern Hemisphere and in middle latitudes in the Southern Hemisphere. 相似文献
960.
松辽盆地三肇凹陷扶余油层(下白垩统泉 4段)储集层的渗透率平均值为1.53 × 10-3 μ m2,属于典
型的低渗透储集层。文中通过岩石铸体薄片、扫描电镜及 X衍射等技术,对三肇凹陷扶余油层储集层的岩石组
分、孔隙类型、成岩作用特征进行了识别鉴定。分析认为:储集层主要岩石类型为长石岩屑细砂岩和岩屑细砂
岩,成熟度较低;次生溶蚀孔隙提供了大量有效储集空间,所占比例甚至可达25%;储集层经历了压实、胶结、
交代、溶解、破裂等成岩作用,主要处于晚成岩阶段 A1期和A2期。压实、胶结作用等破坏性成岩作用使原生
孔隙遭到破坏,形成致密储集层;交代作用对储集层物性影响不大;溶解、破裂作用等建设性成岩作用使储集
层物性得到改善,形成次生孔隙发育带。孔隙度随深度增加呈逐渐增大趋势,与由有机质分解形成的酸性流体
使储集层中不稳定矿物发生溶蚀密切相关。这一研究对三肇凹陷低渗透储集层的开发具有指导作用。 相似文献