一种酪氨酸酶基因在笠贝初生壳形成中的表达分析     

谭素建  郇聘  刘保忠 《海洋科学》2018,42(9):17-21

软体动物初生壳形成是贝壳早期发育研究的重要内容。目前,初生壳形成的机制尚不清晰。本文从笠贝(Lottia goshimai)中克隆了一个酪氨酸酶基因(lgo-tyr1),聚类分析表明其与长牡蛎基因cgi-tyr1是直系同源基因。Lgo-TYR1的序列分析显示它具有两个典型的铜离子结合结构域和一个信号肽。通过整装原位杂交和电子扫描显微镜观察,检测到lgo-tyr1在担轮幼虫的圆形贝壳区以及紧邻的环状细胞带中表达,表明lgo-tyr1可能参与了担轮幼虫初生贝壳的生物合成以及贝壳区边界的确立。  相似文献   

基于重力测点和段差变化的前郭5.8级震群研究与三维反演     

王同庆  张品  刘金钊  陈兆辉  张双喜  朱传东 《大地测量与地球动力学》2019,39(5):469-475

利用东北地区近几年流动重力观测数据，分析前郭5.8级震群周边重力点值的时序变化特征，并基于重力段差变化对东北地区整体和局部重力变化引入能够反映异常显著性程度的指标量G和C值，最后对前郭5.8级震群前的重力场动态变化作三维密度反演。结果表明：1）前郭5.8级震群发震构造两侧的局部重力变化具有较明显的差异性，其变化趋势可作为识别构造活化或解耦运动的标志；2）显著性指标量G和C值能够为地震重力前兆的定量描述提供新思路；3）震前重力变化的反演结果显示地震发生在质量运移的过渡区域，垂向反演结果对本次地震的震源深度有一定的揭示意义。  相似文献   

Relationship between footwall composition,crustal contamination,and fluid–rock interaction in the Platreef,Bushveld Complex,South Africa     

Julie Pronost  Chris Harris  Christian Pin 《Mineralium Deposita》2008,43(8):825-848

In the northern limb of the 2.06-Ga Bushveld Complex, the Platreef is a platinum group elements (PGE)-, Cu-, and Ni-mineralized zone of pyroxenite that developed at the intrusion margin. From north to south, the footwall rocks of the Platreef change from Archaean granite to dolomite, hornfels, and quartzite. Where the footwall is granite, the Sr-isotope system is more strongly perturbed than where the footwall is Sr-poor dolomite, in which samples show an approximate isochron relationship. The Nd-isotope system for samples of pyroxenite and hanging wall norite shows an approximate isochron relationship with an implied age of 2.17 ± 0.2 Ga and initial Nd-isotope ratio of 0.5095. Assuming an age of 2.06 Ga, the ɛNd values range from −6.2 to −9.6 (ave. −7.8, n = 17) and on average are slightly more negative than the Main Zone of the Bushveld. These data are consistent with local contamination of an already contaminated magma of Main Zone composition. The similarity in isotope composition between the Platreef pyroxenites and the hanging wall norites suggests a common origin. Where the country rock is dolomite, the Platreef has generally higher plagioclase and pyroxene δ ¹⁸O values, and this indicates assimilation of the immediate footwall. Throughout the Platreef, there is considerable petrographic evidence for sub-solidus interaction with fluids, and the Δ _{plagioclase–pyroxene} values range from −2 to +6, which indicates interaction at both high and low temperatures. Whole-rock and mineral δD values suggest that the Platreef interacted with both magmatic and meteoric water, and the lack of disturbance to the Sr-isotope system suggests that fluid–rock interaction took place soon after emplacement. Where the footwall is granite, less negative δD values suggest a greater involvement of meteoric water. Consistently higher values of Δ _{plagioclase–pyroxene} in the Platreef pyroxenites and hanging wall norites in contact with dolomite suggest prolonged interaction with CO₂-rich fluid derived from decarbonation of the footwall rocks. The overprint of post crystallization fluid–rock interaction is the probable cause of the previously documented lack of correlation between PGE and sulfide content on the small scale. The Platreef in contact with dolomite is the focus of the highest PGE grades, and this suggests that dolomite contamination played a role in PGE concentration and deposition, but the exact link remains obscure. It is a possibility that the CO₂ produced by decarbonation of assimilated dolomite enhanced the process of PGE scavenging by sulfide precipitation.  相似文献   

三峡工程对河口及邻近海域渔业影响的初步探讨     

罗秉征  薛频  卢继武  黄颂芳 《海洋科学集刊》1992,(33):341-352

河口只是河流与海洋之间的一小部分水域,但对人类社会的发展和生物的进化起着重要的作用。它不仅是生物种群繁殖、育幼和栖息的场所,而且是溯河和降海鱼类洄游的必经之路,因此,河口对生物种群的繁衍延续和资源补充,以及保持生态平衡具有十分重要的意义。 然而,河口又是生态环境十分脆弱和敏感的水域,同时也是受人类干扰最为严重的区域。因此,河口的生态环境问题愈来愈引起人们的关注,其中包括长江三峡水库的兴建对长江口及其附近海域生态、环境的影响,特别是对位于河口两侧的我国著名两大渔场——舟山渔场和吕四渔场的影响问题。影响渔业资源的因子是多方面而且错综复杂的。本文主要通过长江径流的变化与环境因子变量的相关分析,并根据三峡水库不同蓄水方案,对河口近海渔业的影响问题进行初步探讨。  相似文献   

南海北部陆缘地壳结构探测结果分析   总被引：29，自引：4，他引：29  

阎贫  刘海龄 《热带海洋学报》2002,21(2):1-12

深部地震和重力资料反演揭示了南海北部陆缘地壳结构在总体上由北部的华南沿海（厚约30km）向南部的洋盆（5──8km）逐渐减薄。南海的近SN向拉张不仅造成南北方向地壳结构的巨大变化，也造成东西向的明显变化。在南海北部陆缘的西部，局部拉张产生了一系列裂谷构造。西沙海槽作为一条狭窄的陆内裂谷向西延伸，海槽南北两侧地壳厚度超过25km，海槽中部地壳减薄至不足10km。西端的莺歌海盆地地壳厚仅5km，缺少明显的壳内反射－折射。在珠江口盆地中部，地壳厚度在下陆坡明显减薄，地壳下部存在较薄的（3──4km）高速层（地震波速7．2──7．5km·s－1）；在珠江口盆地东部，地壳底部存在约 10km厚、300km宽的高速层。在台湾地区，由于弧陆碰撞，曾经减薄的陆壳在碰撞带增厚，莫霍面深度超过30km。南海北部陆缘在裂谷拉张和海底扩张期间岩浆活动平静，表明南海北部陆缘为非火山型陆缘。  相似文献   

南沙海区中生界岩相分布及构造特征   总被引：3，自引：0，他引：3       下载免费PDF全文

刘海龄  谢国发  阎贫  刘迎春  郑红波 《海洋与湖沼》2007,38(3):272-278

为了了解南中国海南部南沙群岛陆架-陆坡区中生代地层发育情况,作者通过综合分析该海区钻井、拖网及1987年以来采集的20000多公里的多道反射地震勘探等资料,得到了对该区中生界基本特征的如下新认识:空间分布上,南沙的中生界具有从北部的郑和-礼乐隆起南缘向南增厚的趋势;沉积岩相方面,东部三叠纪时为深海相,侏罗纪为浅海与三角洲相,白垩纪为浅海-内浅海相,而往西南部中生代的海水深度有变深的趋势;中-新生代变形上,在南沙西部的曾母盆地,中生界褶皱为复式的、非协调性的,南沙中部多为舒缓褶皱,东部仅在近巴拉望海槽地带出现小幅度的褶皱。结合围区中生界及特提斯构造域的发育特征,作者提出南沙地块上的海相中生界在大地构造上归属于残留在中特提斯洋北部减薄陆缘地壳上的中特提斯期海相沉积地层,是该海域油气资源勘探不可忽视的对象。  相似文献   

滤食性贝类在对虾综合养殖生态系统中的作用   总被引：6，自引：0，他引：6  

吴桂汉  陈品健  江瑞胜 《台湾海峡》2001,20(4):447-452

就混养虾池中滤食性贝类如何影响虾池整个生态系统这个问题，综合了国内外这方面的文献，从滤食性贝类对混养虾池的水质、底质和其中的浮游植物、浮游动物的影响，以及混养对养殖效益的影响这几个方面作了探讨。  相似文献   

浅析省级基础测绘数据在城市建模中的应用     

刘秀娟  杨爱玲  王品 《测绘与空间地理信息》2008,31(4)

利用基础测绘数据中房屋数据获取和编辑的方法,探讨1:10 000基础测绘数据中的建筑物在城市地理信息服务和建模中的应用以及目前基础测绘数据与城市建模数据间的差距.  相似文献   

基于免疫多智能体的网络入侵主动防御模型   总被引：2，自引：0，他引：2  

刘孙俊  王电刚  杨频  张建华 《武汉大学学报(信息科学版)》2008,33(10):1055-1058

构建了一种基于免疫多智能体的网络入侵主动防御模型ADNIIMA(the active defense model for net-work intrusion based on immune multi-agent),提出免疫智能体概念,建立免疫智能体的逻辑结构及其运行机制,实现了对网络入侵的多层次、分布式主动防御机制,为网络安全保障提供一种新的思路.  相似文献   

Neoproterozoic alkaline magmatism at Sivamalai, southern India     

D. Upadhyay  S. Jahn-Awe  C. Pin  J.L. Paquette  I. Braun 《Gondwana Research》2006,10(1-2):156

The Sivamalai alkaline complex lies at the southern margin of the Cauvery Shear System that separates the Archaean and Proterozoic domains of the Southern Granulite Terrain in India. U–Pb TIMS dating of zircon from a pegmatitic syenite sample in the complex yields a concordant age of 590.2 ± 1.3 (2σ) Ma which is interpreted to date the intrusion of the alkaline rocks. A lower concordia intercept at 168 ± 210 Ma defined by two grains with high common lead may indicate post-magmatic disturbances due to recrystallisation which is also evident in the CL images of the zircons. EPMA dating of monazite from a post-kinematic pegmatite which intrudes the crystalline basement hosting the alkaline rocks yields an age of 478 ± 29 (2σ) Ma and provides a lower bracket for the main phase of tectonism in this part of the Southern Granulite Terrain. The Pan-African high-grade metamorphism and ductile deformation has thus most likely affected the alkaline rocks. This is supported by the presence of a metamorphic foliation and extensive recrystallisation textures seen in the rocks. The major and trace element concentrations measured on selected samples reveals the presence of both enriched and depleted rock types. The enriched group includes ferrosyenite and nepheline syenite while the depleted group has only nepheline syenites. The trace element depletion of some nepheline syenites is interpreted to be a result of fractional crystallization involving the removal of accessory phases like zircon, titanite, apatite and allanite.  相似文献