173581 research outputs found
Sort by
Observational study of tidal mixing asymmetry and eddy viscosity-shear covariance – induced residual flow in the Jiulong River estuary
Get PDFAbstract(#br)An observation study was conducted at three stations in the inner regime of the Jiulong River estuary to examine the tidal mixing asymmetry and its associated residual flow induced by eddy viscosity-shear covariance (ESCO). The water columns at the observation stations were approximately well-mixed during the later flood and were stratified during the early ebb, a typical tidal mixing asymmetry. Corresponding to the tidal variation of stratification, the Reynolds stress and vertical eddy viscosity, which were obtained using the ADCP variance method, exhibited distinct differences in the magnitude and vertical structure between flood and ebb tides. The ESCO flow was calculated using the decomposition method for estuarine circulation, revealing a two-layer vertical structure similar to density-driven flow but with a much greater magnitude, confirming the findings of previous generic model studies that the ESCO flow dominates the density-driven flow in periodically stratified estuaries. The drivers of tidal mixing asymmetry were explored using the potential energy anomaly method. Longitudinal straining reduced stratification during flood tides and reinforced stratification during ebb tides, whereas longitudinal advection acted in the opposite manner. Although the contribution of lateral circulation to stratification was neglected due to the lack of lateral observation data, scaling analysis revealed that lateral advection was important in the longitudinal dynamics and tidal evolution of stratification and warrants further study
Evaluation of the Structure and Biological Activities of Condensed Tannins from Acanthus ilicifolius Linn and Their Effect on Fresh-Cut Fuji Apples
Get PDFAbstract(#br)Condensed tannins (CT S ) have been isolated and purified from leaves of Acanthus ilicifolius Linn. And their structures were investigated by three methods: 13 C nuclear magnetic resonance ( 13 C NMR), reversed-phase high-performance liquid chromatography (RP-HPLC), and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). The results showed that the CT S were a mixture of catechin/epicatechin, galatechin/epicatechin, and amphicin/epigalin, and that the polymer chain lengths were 3-mers to 14-mers. Antityrosinase activities and antioxidant activities of the CT S from A . ilicifolius leaves were further studied. The IC 50 of the CT S on mushroom tyrosinase activity was determined to be 19.7 ± 0.13 μg/mL, and inhibition type analyses..
Metal/metalloid and phosphorus characteristics in porewater associated with manganese geochemistry: A case study in the Jiulong River Estuary, China
Get PDFAbstract(#br)Sediment porewater can be an important source of contaminants in the overlying water, but the mechanisms of metal(loid) and phosphorus (P) remobilization remain to be investigated. In this study, high-resolution dialysis (HR-Peeper) and diffusive gradients in thin films (DGT) samplers were used to determine the porewater dissolved iron (Fe), manganese (Mn), cobalt (Co), chromium (Cr), vanadium (V), selenium (Se), arsenic (As), P and DGT-Labile S in coastal sediments in the Jiulong River Estuary (JRE), China. The results showed that high concentrations of dissolved Mn, Se and P were present in the overlying water, indicating potential water pollution with excessive amounts of Mn, Se and P. The dissolved Mn concentrations in the porewater were higher than the dissolved Fe concentrations, especially at submerged sites, demonstrating that Mn(III/IV) reduction is the dominant diagenetic pathway for organic carbon (OC) degradation, which directly affects Fe cycling by the competitive inhibition of Fe(III) reduction and Fe(II) reoxidation. Dissolved Co, Cr, V, Se, As and P show significant positive correlations with Mn but nearly no correlations with Fe, suggesting that the mobility of these metal(loid)s and P is associated with Mn but not Fe cycling in this region. In addition, the coelevated concentrations of the metal(loid)s, P and Mn at the submerged sites are attributed to the strengthened Mn reduction coupled with OC degradation fueled by hypoxia. The higher positive diffusion fluxes of Mn, Se and P were consistent with the excess Mn, Se and P concentrations in the overlying water, together with the approximately positive fluxes of the other metal(loid)s, indicating that sediment Mn(III/IV) reduction and concomitant metal(loid) and P remobilization might be vital pathways for metal(loid) and P migration to the overlying water
大洋溶解铁的物质来源及其同位素示踪
Get PDF铁(Fe)作为海洋初级生产所必需的微量和限制性营养元素影响着海洋生物群落结构、生态功能以及碳循环,理解溶解Fe的物质来源及其对气候变化的响应具有重要的科学意义。早期研究多强调风尘输入是维持大洋Fe循环的主要机制。近年来,随着海水Fe分析数据的积累,尤其是痕量元素及其同位素海洋生物地球化学循环研究计划(GEOTRACES)的开展,陆架沉积物和热液活动所释放Fe的贡献开始越来越受到重视。尽管如此,不同物源对开阔大洋溶解Fe的影响依然存在相当的不确定性。以海水溶解Fe的化学组分为出发点,强调有机配体对大洋Fe循环的决定性作用,综述了不同来源Fe的通量估计和第四纪大洋Fe来源的研究争议。铁同位素为理解大洋Fe的物源演变提供了新的工具。讨论了不同物源的Fe同位素特征,并提出结合沉积物的活动性Fe同位素和组分研究可能为理解过去陆架-热液活动-风尘输出与输运Fe的机制提供全新视角。西太平洋地球系统多圈层相互作用重大计划培育项目“上新世以来西太平洋沉积铁同位素演化研究”(91858105)国家海洋局海洋沉积与环境地质重点实验室开放基金资助项目“晚第四纪北太平洋深水铁同位素演化重建:对大洋铁循环的新约束”(MASEG201711)青岛海洋科学与技术试点国家实验室海洋地质过程与环境功能实验室创新团队资助项目“利用西太平洋铁锰结壳微量金属重建新生代火山喷气历史”(MGQNLM-TD201701
An Alternative Hot Start PCR Method Using a Nuclease-Deficient ExoIII from Escherichia coli.
Get PDFThe Hot Start polymerase chain reaction (Hot Start PCR) is designed to reduce off-target amplification by blocking DNA polymerase extension at room temperature until the desired temperature is reached. In this study, we investigated a new method of Hot Start PCR that uses a modified Escherichia coli Exonuclease III (EcoExoIIIM) by substituting residues in the DNA-binding pocket and catalytic center. The results showed that PCR amplification yield and specificity were significantly promoted by the addition of EcoExoIIIM. We hypothesize that non-specific binding of primers at room temperature is prevented by binding of the primed template by EcoExoIIIM, which is then released from the DNA by heat denaturation before the first PCR cycle. Through this mechanism, PCR would be enhanced by reducing off-target extension at room temperature
中国海洋生物研究70年
Get PDF随着中国"海洋强国"战略的提出,加快建设海洋类学科的发展成为历史必然,海洋生物是海洋不可分割的一部分,海洋环境和生物相互依存,相互作用,海洋生物研究重要性日益凸显。为纪念中国科学家在海洋生物领域的突出贡献,本文回顾了建国以来中国海洋生物相关的重要研究进展,梳理了中国科学家在海洋生物领域的突出贡献,系统总结并讨论了未来研究方向,抛砖引玉,希望籍此助推中国海洋生物研究的新高潮。国家自然科学基金项目(41876134,41876171)中国大洋矿产资源研究开发协会专项项目(DY135-E2-5-03)教育部长江学者特聘教授项目(T2014253
Characteristics and Evolutionary Analysis of Photosynthetic Gene Clusters on Extrachromosomal Replicons: from Streamlined Plasmids to Chromids.
Get PDFAerobic anoxygenic photoheterotrophic bacteria (AAPB) represent a bacteriochlorophyll a -containing functional group. Substantial evidence indicates that highly conserved photosynthetic gene clusters (PGCs) of AAPB can be transferred between species, genera, and even phyla. Furthermore, analysis of recently discovered PGCs carried by extrachromosomal replicons (exPGCs) suggests that extrachromosomal replicons (ECRs) play an important role in the transfer of PGCs. In this study, 13 Roseobacter clade genomes from seven genera that harbored exPGCs were used to analyze the characteristics and evolution of PGCs. The identification of plasmid-like and chromid-like ECRs among PGC-containing ECRs revealed two different functions: the spread of PGCs among strains and the maintenance of PGCs within genomes. Phylogenetic analyses indicated two independent origins of exPGCs, corresponding to PufC-containing and PufX-containing puf operons. Furthermore, the two different types of operons were observed within different strains of the same Tateyamaria and Jannaschia genera. The PufC-containing and PufX-containing operons were also differentially carried by chromosomes and ECRs in the strains, respectively, which provided clear evidence for ECR-mediated PGC transfer. Multiple recombination events of exPGCs were also observed, wherein the majority of exPGCs were inserted by replication modules at the same genomic positions. However, the exPGCs of the Jannaschia strains comprised superoperons without evidence of insertion and therefore likely represent an initial evolutionary stage where the PGC was translocated from chromosomes to ECRs without further combinations. Finally, a scenario of PGC gain and loss is proposed that specifically focuses on ECR-mediated exPGC transfer to explain the evolution and patchy distribution of AAPB within the Roseobacter clade. IMPORTANCE The evolution of photosynthesis was a significant event during the diversification of biological life. Aerobic anoxygenic photoheterotrophic bacteria (AAPB) share physiological characteristics with chemoheterotrophs and represent an important group associated with bacteriochlorophyll-dependent phototrophy in the environment. Here, characterization and evolutionary analyses were conducted for 13 bacterial strains that contained photosynthetic gene clusters (PGCs) carried by extrachromosomal replicons (ECRs) to shed light on the evolution of chlorophototrophy in bacteria. This report advances our understanding of the importance of ECRs in the transfer of PGCs within marine photoheterotrophic bacteria
底拖网作业对珠江口香港海域底层鱼类的影响
Get PDF【目的】研究底拖网作业对珠江口香港海域底层鱼类的影响。【方法】根据2007-2009年及2014-2016年在珠江口香港海域进行的定点底拖网调查数据,分析该海域在禁止底拖网捕捞实施前后鱼类种类组成及生物量和生态多样性指数,评估5种典型底层鱼类资源的变化。【结果与结论】该海域捕获鱼类种类数在禁止底拖网作业后明显增加,鱼类种类数量从44种升至73种。种类丰富度指数D变化范围为:2007至2009年,4.937～5.711,2014至2016年,6.559～7.074;多样性指数H’变化范围为:2007至2009年,1.945～2.841,2014至2016年,2.220～2.381;均匀度指数J变化范围为:2007至2009年,0.539～0.776,2014至2016年,0.557～0.600。卵鳎Solea ovata、韦式羊舌鮃Arnoglossus waitei、尖嘴魟Dasyatis zugei这3种底层鱼类禁止底拖网实施后在数量(number)和生物量(biomass)上都增幅明显。不同站位数量和生物量的数值在"禁拖令"实施后也都有所增加,其中以站位2(大屿山以北,较靠近香港国际机场海域)增加最为显著
复方中草药及其与抗生素联用对斜带石斑鱼溶藻弧菌病的治疗效果
Get PDF通过药物体外抑菌效果及对斜带石斑鱼抗病力影响的研究,筛选有效治疗斜带石斑鱼溶藻弧菌病复方中草药与中西药联用配方。用诃子、白芍、甘草比例分别为0.9∶1.3∶0.9、1.2∶0.9∶1.0和1∶1∶1...福建省自然科学基金(2016NZ0001-3,2018J01455);; 国家自然科学基金(31702384);; 省高校产学合作项目(2016N5009);; 鳗鲡现代产业技术教育部工程研究中心开放基金(16PZY002SF18)~
基于UNO-2178A的远程自动化水质监测系统
Get PDF文中基于嵌入式工业控制机UNO-2178A设计了一款远程自动化水质监测系统。该系统布放于待监测海域,在信息管理平台的指令控制下,可以自动完成海水样品采集、水质参数分析与处理等。同时,系统将监测结果反馈回信息管理平台,可以在线监测温度、盐度、溶解氧、电导率、有色可溶性有机物(CDOM)、叶绿素等多种环境参数。系统基于高效、紧凑的嵌入式平台设计而成,有利于在待研究海域大面积多点布放,保证对海域水质监测的可靠性、准确性和便捷性