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1.
对黄土高原的灵台和泾川黄土 -红粘土序列进行了磁性地层学和沉积学研究.古地磁研究表明,泾川剖面的底界年龄为 8.0Ma,这比灵台剖面的底界年龄老 1.0Ma.通过空间上红粘土剖面的地层对比,发现灵台红粘土序列相对较为完整和连续.该剖面可以作为中国北方晚第三纪红粘土的标准剖面.野外观察和粒度分析均表明灵台和泾川红粘土沉积为风成沉积.通过对南北向黄土大断面粒度参数的系统分析,初步建立了 粉尘沉积的粒度参数———沉积区距源区最小距离"的半定量模型.根据这些模型推测,红粘土的主要源区可能在现代的巴丹吉林沙漠及其以西地区.灵台剖面的游离铁/全铁值变化表明,晚中新世以来东亚夏季风经历了非线性的演化历史.约 4.1～ 4.8Ma间为黄土高原地区 7.0Ma以来东亚夏季风最为强盛的时期.该气候事件的出现可能同全球温度背景较高及全球冰量较小有着动力学上的联系. 相似文献
2.
对黄土高原的灵台和泾川黄土-红粘土序列进行了磁性地层学和沉积学研究.古地磁研究表明,泾川剖面的底界年龄为8.0
Ma,这比灵台剖面的底界年龄老1.0 Ma.通过空间上红粘土剖面的地层对比,发现灵台红粘土序列相对较为完整和连续.该剖面可以作为中国北方晚第三纪红粘土的标准剖面.野外观察和粒度分析均表明灵台和泾川红粘土沉积为风成沉积.通过对南北向黄土大断面粒度参数的系统分析,初步建立了"粉尘沉积的粒度参数一沉积区距源区最小距离"的半定量模型.根据这些模型推测,红粘土的主要源区可能在现代的巴丹吉林沙漠及其以西地区.灵台剖面的游离铁/全铁值变化表明,晚中新世以来东亚夏季风经历了非线性的演化历史.约4.1～4.8
Ma间为黄土高原地区7.0 Ma以来东亚夏季风最为强盛的时期.该气候事件的出现可能同全球温度背景较高及全球冰量较小有着动力学上的联系. 相似文献
3.
以塔克拉玛干沙漠风积砂为例,利用多尺度微观结构测试技术,重点测定了风积砂中石英、硅酸盐矿物和碳酸盐矿物的形态与粒度分布特征。结果表明:①塔克拉玛干沙漠风积砂颗粒形态多样,粒脊磨圆程度以次棱为主,碳酸盐矿物颗粒磨圆度较好,硅酸盐次之,石英颗粒磨圆度较差。②样品中石英(20.72%)、硅酸盐矿物(28.28%)和碳酸盐矿物(42.24%)之间存在着镶嵌、包裹、咬合现象;经发现部分硅酸盐矿物以针片状形式存在。③3种矿物的粒度分布曲线都存在明显的峰值。初步认为矿物粒度分布曲线不同的峰值数目及峰值区间大小对矿物的风化程度、源区的气候特征等具有一定指示意义;多尺度微观结构分析技术可以有效地表征风积砂中矿物形态与粒度分布特征。 相似文献
4.
本文以北京东部新近沉积细粒土为对象,结合扫描电镜和高压压汞实验对黏土组分微观结构展开研究,观察黏土微观形貌并对其结构进行分类,分析不同黏土含量的细粒土的孔隙分布特征,明确不同类型黏土结构对细粒土孔隙结构的贡献。结果表明,细粒土内黏土成分存在形式包括基质和集合体,其中集合体可根据微观形貌分为黏土团粒、黏土碎屑、絮状黏土集合体3类;压汞实验中细粒土在高压区的进汞特征受黏土组分控制,孔径分布曲线说明黏土的结构与含量共同控制细粒土的孔隙结构特征,各类黏土结构分别贡献了细粒土内不同尺度范围的孔隙;黏土基质与3类集合体的结构特征来源于不同的形成过程,结构内部矿物连接方式导致不同黏土结构在受力作用下和流体介质中的变形响应差异巨大,从而引起土体宏观性质具有较强的空间变异性。 相似文献
5.
按照花粉外壁表面纹饰的不同，可将春黄菊族中下列各属分为两大类群：(1)明显具刺：亚菊
属Ajania Poljak., 女蒿属Hippolytia Poljak., 百花蒿属Stilpnolepis Krasch.。 (2)具退化状小刺：紊蒿属
Elachanthemum Ling et Y.R.Ling，线叶菊属Filifolium Kitam., 画笔菊属Ajaniopsis Shih，喀什菊属
Kaschgaria Poljak．)，栉叶蒿属Neopallasia Poljak．，绢蒿属Seriphidium Poljak．。根据花粉形态特征，我们认为将紊蒿属和百花蒿属仍分为两个相互独立的属较为适宜。 相似文献
6.
《科技通报》2018,(11)
针对冲积扇自旋回储层沉积相模拟实验进行观察,研究将冲积扇分为两类,分别为干旱扇与湿润扇,在冲积扇储层形成沉积相特征中,砾石颗粒对冲积扇沉积相特征产生的影响。研究的结果表明,在冲积扇的扇根中,冲积扇沉积沟流的优势方向和砾石颗粒的分布具有相关性,砾石颗粒分布对沉积相特征沟流的改道进行有效控制,在冲积扇沉积特征形成的过程中,在牵引流作用下砾石颗粒产生移动,对冲积扇沉积沟道存在控制作用,主要体现在沉积沟道的形成和沉积砂坝的形成。通过对冲积扇剖面产生的辫流水道的叠置以及沉积相特征的分布,能验证冲积扇表面产生的现象,由此,砾石颗粒对冲积扇根砂坝以及沟流等沉积相特征存在影响作用。 相似文献
7.
河南西部是我国湿陷性黄土分布的主要地区之一,黄土总厚度约0～94m,湿陷性黄土厚度约0～10m,豫西黄土堆积从第四纪中更新世开始,直到全新世都有堆积（。1）全新世黄土（Q4eol）：褐灰色亚砂土,土壤结构清晰的现代耕作层和全新世古土壤（S0）,厚度小于1.0m（。2）晚更新世马兰组黄土（Q3eol）：包括1层黄土（L1）和1层红褐色古土壤（S1）,黄土厚度小于10m,土质疏松多孑L,古土壤厚度0.4～1.0m（。3）中更新世离石组黄土（Q2eol）：平行整合于马兰黄土之下,厚度34.91～70.0m,其中含7层红褐色古土壤（s2～S8）,层序清晰完整,第五层古土壤（S）由密集的三个单层合成（红三条）,土壤结构清晰,各土层下均有含钙结核（层）。 相似文献
8.
准噶尔盆地基底的属性和时代，长期以来一直是地质界激烈争论的问题。根据区域地质背景分析，准噶尔盆地东北缘卡拉麦里蛇绿岩带南侧出露的一套基本连续的、被置于中志留统．下石炭统的浅海相陆源碎屑沉积岩系的物源区，位于准噶尔盆地东部盆地堆积物之下。为此选择其中被1：20万区调置于中泥盆世卡拉麦里组上部层位的砂岩进行碎屑锆石SHRIMPU．Pb定年研究，以期获得准噶尔盆地东部基底时代和属性的信息。测定的86颗碎屑锆石、89个点的年龄分布范围AL（327±8）Ma至（3073±10）Ma；其中碎屑锆石的表面年龄主要集中分布在320Ma～540Ma，显示出多峰的特征，其主峰为365Ma，次要的峰分别为460～480Ma、510～520Ma和530—540Ma。该样品中还含有至少22粒表面年龄大于550Ma的碎屑锆石，其中550～690Ma的碎屑锆石有4粒，827Ma～1083Ma的碎屑锆石有8粒，1513Ma和1700Ma锆石各1粒，1942Ma～2051Ma的锆石有2粒，2464～2490Ma和2876Ma-3073Ma的碎屑锆石各3粒。根据样品的岩石学特征和碎屑锆石的矿物学特征及表面年龄，结合区域岩浆活动的分析，我们获得如下初步结论：（1）所研究砂岩的沉积时代不是泥盆纪的，可能是早石炭世晚期，其源区位于准噶尔盆地东部；（2）源区地质体组成主体是奥陶纪至石炭纪活动陆缘岩浆岩，寒武纪至新元古代中期和新元古代早期至中元古代等时期的岩浆杂岩等组成，以及推测的少量早前寒武纪杂岩；表明准噶尔盆地东部的基底为奠基在前奥陶纪陆壳基底之上的古生代岛弧。 相似文献
9.
10.
本文应用扫描电镜对国产茨藻科植物的外种皮和内种皮微形态特征进行了研究，结果表明茨藻科植物在种子表面细胞形态、表面纹饰和内种皮内层细胞形态及小瘤状突起的大小和密度等方面存在差异，可作为种级水平分类的依据，并首次发现外种皮微形态特征也与内种皮内层小瘤状突起一样具有重要的系统学意义。根据种皮微形态特征的研究结果，我们支持Miki(1937)和Shaffer-Fehre(1991b)等关于茨藻科与水鳖科近缘，而不应放在眼子菜目的观点。对弯果茨藻Najas ancistrocarpa A．Br．ex Magnus和草茨藻N.graminea Del.外种皮的研究结果表明其外种皮细胞表面具瘤状颗粒而非网状加厚。 相似文献
11.
A research group led by Prof. ZHAI Qiwei from the Institute for Nutritional Sciences under the CAS Shanghai Institutes for Biological Sciences has discovered that even relatively low doses of resveratrol-a chemical found in the skins of red grapes in red wine-can improve the sensitivity of mice to the hormone insulin according to a report in the October issue of Cell Metabolism.…… 《中国科学院院刊(英文版)》2008,22(1):14-15
Aresearch group led by Prof. ZHAI Qiwei from the Institute for Nutritional Sciences under the CAS Shanghai Institutes for Biological Sciences has discovered that even relatively low doses of resveratrol--a chemical found in the skins of red grapes and in red wine--can improve the sensitivity of mice to the hormone insulin, according to a report in the October,2007 issue of Cell Metabolism. As insulin resistance is often characterized as the most critical factor contributing to the development of Type 2 diabetes, the findings“provide a potential new therapeutic approach for preventing or treating” both conditions, the researchers said. 相似文献
12.
《中国科学院院刊(英文版)》2008,22(1):2-3
CAS should stick to the principle of rendering service to, and giving impetus for, the development of China＇s science enterprise by making S＆T innovations, said CAS President LU Yongxiang. The CAS president made the remarks in a recent talk to communicate the gist of the winter session of the Party＇s Leading-member Group at CAS, which was held from 7 to 11 January in Beijing. 相似文献
13.
Marjorie Armstrong-Stassen Margaret Landstrom Ramona Lumpkin 《The Information Society》1998,14(2):153-164
This study examined how students who had no prior experience with videoconferencing would react to the use of videoconferencing as an instructional medium. Students enrolled in seven different courses completed a questionnaire at the beginning of the semester and again at the end of the semester. Students at the origination and remote sites did not differ in their reactions toward videoconferencing but there was a significant difference for gender. Women reacted less favorably to videoconferencing. Compared to the beginning of the semester, students reported significantly less positive attitudes toward taking a course through videoconferencing at the end of the semester. There were no significant differences in students' attitudes toward videoconferencing across courses at the beginning of the semester but there were significant differences across the courses at the end of the semester. The results suggest the need for better preparation for both students and instructors. 相似文献
14.
《中国科学院院刊(英文版)》2008,22(1)
With great care, Dr. ZHOU Zhonghe takes out a package wrapped by cotton tissue from a drawer and says: "This is the gem of our collections: the fossil of a bird that lived 125 million years ago!" Then, pointing at a tiny mound, he explains: "Look, this is the claw and that is the head. It was in the egg shell and ready to hatch ... The species fell into a family of waterside inhabitants." 相似文献
15.
A joint study by Prof. ZHANG Zhibin from the CAS Institute of Zoology his co-workers from Norway US Swiss have indicated that historical outbreaks of migratory locusts in China were associated with cold spells suggesting that China's projected climate warming could decrease the pest's numbers. The study was published in Proceedings of the National Academy of Sciences on September .…… 《中国科学院院刊(英文版)》2008,22(1):6-7
Ajoint study by Prof. ZHANG Zhibin from the CAS Institute of Zoology and his co-workers from Norway, US and Swiss have indicated that historical outbreaks of migratory locusts in China were associated with cold spells, suggesting that China＇s projected climate warming could decrease the pest＇s numbers. The study was published in Proceedings of theNational Academy of Sciences on 17 September, 2007. 相似文献
16.
Active biological molecules functional structures can be fabricated into a bio-mimetic system by using molecular assembly method. Such materials can be used for the drug delivery disease diagnosis therapy new nanodevice construction.…… 《中国科学院院刊(英文版)》2008,22(1):22-22
Active biological molecules and functional structures can be fabricated into a bio-mimetic system by using molecular assembly method. Such materials can be used for the drug delivery, disease diagnosis and therapy, and new nanodevice construction. 相似文献
17.
Caroline Haythornthwaite 《The Information Society》2001,17(3):211-226
A computer-mediated group is a complex entity whose members exchange many types of information via multiple means of communication in pursuit of goals specific to their environment. Over time, they coordinate technical features of media with locally enacted use to achieve a viable working arrangement. To explore this complex interaction, a case study is presented of the social networks of interactions and media use among members of a class of computer-supported distance learners. Results show how group structures associated with project teams dominated who communicated with whom, about what, and via which media over the term, and how media came to occupy their own communication niches: Webboard for diffuse class-wide communication; Internet Relay Chat more to named others but still for general communication across the class; and e-mail primarily for intrateam communication. Face-to-face interaction, occurring only during a short on-campus session, appears to have had a catalytic effect on social and emotional exchanges. Results suggest the need to structure exchanges to balance class-wide sharing of ideas with subgroup interactions that facilitate project completion, and to provide media that support these two modes of interaction. 相似文献
18.
Electronic data interchange (EDI) provides means for interorganizational communication, creates network externalities, requires an advanced information technology (IT) infrastructure, and relies on standards. In the diffusion of such innovations, institutional involvement is imperative. Such institutions contain governmental agencies, national and global standardization organizations, local government, and nonprofit private organizations like industry associations. The last type of organizations we call intermediating institutions. They intermediate or coordinate ("inscribe") the activities of a group of would-be adopters. Unfortunately, little is known of how these organizations shape the EDI diffusion trajectory. In this article we examine one specific type of intermediating organizations?industry associations?and how they advanced the EDI diffusion process in the grocery sectors of Hong Kong, Denmark and Finland. We identify six institutional measures, placed into a matrix formed by the mode of involvement (influence vs. regulation) and the type of diffusion force (supply push vs. demand pull), that can be mobilized to further the EDI diffusion. Industry associations were found to be active users of all these measures to varying degrees. Their role was critical especially in knowledge building, knowledge deployment, and standard setting. Furthermore, institutional involvement varied due to policy and cultural contingencies and power dependencies. 相似文献
19.
Leah A. Lievrouw 《The Information Society》2000,16(2):155-159
This essay focuses on universal service and the Internet as means to support social and political participation. The emphasis on access to telecommunications systems in conventional approaches to universal service is contrasted with access to content. A model of the information environment is described that accounts for the roles of content and conduit, both of which are necessary conditions to achieve true access. A method is outlined for employing information indicators to observe or measure the information environment. 相似文献
20.
Puay Tang 《The Information Society》1998,14(1):19-31
The increasing prospects of digital piracy has prompted the perceived need by electronic publishers to adopt technical systems of protection, and governments to reform their copyright laws. This article is a preliminary study of the management of intellectual property by electronic publishers, defined as those involved in the production of online databases, and CD-ROMs. It focuses on three main issues: (1) how electronic publishers view the increasing threat of piracy; (2) the methods of protection employed to protect intellectual property in digital format; and (3) the importance of technological protection of intellectual property in electronic publications. The analysis is based on a sample of 23 UK electronic publishers. The interviews revealed an interesting assortment of protection methods and did not show that technological protection was a preferred way. Instead, the means of protection, in addition to copyright law, comprised niche markets, pricing, trust, bad publicity, and nontechnical and technical means. 相似文献