类星体Lyα吸收线密度与其发射线红移的关系     

陆建隆  黄克谅 《天文学报》1995,36(4):367-378

本文利用７２个具有中等分辨率的类星体Ｌｙα线资料，研究了Ｌｙα吸收线数密度Ｎ（Ｚａｂｓ）与类星体发射红移Ｚｅｍ的变化关系，结果表明：对于Ｚｅｍ越大的类星体其全部Ｌｙα吸收线的平均数密度Ｎ（Ｚａｂｓ）也越大，但对于相同的吸收红移值而言，Ｎ（Ｚａｂｓ）在统计意义上与Ｚｅｍ并无关系。本文还将所得结果与其他的有关工作作了比较及讨论。  相似文献   

尼罗罗非鱼(Oreochromis niloticus Linn)胃酸的PH值,周日变化及其在消化兰藻中的作用     

吉滨河  周路  曾纪财 《广东海洋大学学报》1989,(Z1)

通过测定喂食水华微囊藻的尼罗罗非鱼胃PH值、不同颜色粪便的叶綠素/脱镁叶綠素比例,发现尼罗罗非鱼具有一个与摄食相关的胃酸分泌周期。摄食旺期胃平均PH值为1.47,最低值为0.8。停食后PH值升高,最大值为6.0。用不同浓度的盐酸处理水华微囊藻和对不同颜色粪便的营养分析结果表明,高浓度的胃酸(PH<2)溶解了水华微囊藻细胞壁,为肠消化酶对细胞内含物进行消化创造了先决条件。  相似文献   

Early stage differentiation of thallus cells ofPorphyra haitanensis (Rhodophyta)   总被引：1，自引：0，他引：1  

Wang Sujuan  Sun Yunlong  Lu Anming  Wang Guangyuan 《中国海洋湖沼学报》1987,5(3):217-221

The early stage differentiation of thallus cells ofPorphyra haitanensis T. J. Chang et B. F. Zheng was studied. Protoplasts or single cells were isolated from the blades using enzyme mixture comprising 2% sea snail gut enzyme and 1% cellulase. The isolated protoplasts or single cells were incubated in the MES medium. The cell differentiations were examined under the microscope at intervals after incubation. Four types of cell differentiation, namely, normal, abnormal, carposporangial and spermatorangial, and rhizoidal types, were observed. Since normal cell differentiations occur mostly in small thalli 50 mm in length and middle portions of big thalli 200 mm in length, it is essential to select tissues from these two kinds of thalli essential for commercial production.  相似文献   

关于加快长江上游干,支流综合开发治理的建议     

林华  陆钦侃 《云南地理环境研究》1989,1(2):47-52

笔者通过考察认为,以水电建设为龙头,加快长江上游干、支流综合开发治理是长江流域开发的一个重要组成部分,对推动整个流域经济的持续稳定发展具有重大的意义。文中论述了:1、先期开发治理长江上游干、支流是合理利用长江水资源,防治长江洪水灾害的关键。2、综合开发治理长江上游干、支流将能获得的巨大社会、经济与环境效益。3、加快开发长江上游干、支流的政策与措施。  相似文献   

Thresholds of geographic environmental elements in sediment yield of drainage basins     

CHEN Hao  ZHOU Jinxing  CAI Qiangguo  LU Zhongchen & LI Zhongyan Institute of Geographic Sciences  Natural Resources Research  Chinese Academy of Sciences  Beijing  China  Institute of Forestry Science  Chinese Academy of Forestry Science  Beijing  China  Research Center for Eco-Environment Sciences  Chinese Academy of Sciences  Beijing  China  Computing Institute of Science  Engineering  North China Electric Power University  Beijing  China 《中国科学D辑(英文版)》2005,48(2):230-240

Threshold of environmental elements in drainage basin sediment yield refers to, under effect of climate, underlying surface and human activity, a turning point of abrupt changes in drainage sediment yield related to environmental element characteristics. Previous studies on threshold of sediment yield of relevant drainage basins were mainly concentrated on impact of natural zones with a few researches on impact of other environmental elements. Particularly studies on compound environmental element threshold in drainage basin sediment yield remain blank today. Studies indicate that sediment yield in drainage basins is affected by compound interactions and complex actions. Based on single element analysis, the present paper gives quantitatively compound threshold of environmental elements affecting sediment yield of the drainage basin between Hekouzhen and Tongguan in the middle Yellow River by the method of multi-variant, polynomial formula regression analysis.  相似文献   

Cataclastic rheology of carbonate rocks     

LU Xiancai  SUN Yan  SHU Liangshu  GU Lianxing  GUO Jichun & ZHU Wenbin State Key Laboratory of Mineral Deposits Research  Department of Earth Sciences  Nanjing University  Nanjing  China 《中国科学D辑(英文版)》2005,48(8):1227-1233

  相似文献   

用钢粒取心钻进钻穿孤石的方法     

吕尚顺  宋文廉 《福建地质》1996,15(2):107-110

本文通过在厦门地区大直径桩孔钻遇“孤石”的施工实践，总结了一套利用钢粒取心钻进“孤石”的技术方法，有效地解决了钻进“孤石”效率低，易偏斜，事故多的技术难题。  相似文献   

Recent glacial retreat in High Asia in China and its impact on water resource in Northwest China   总被引：48，自引：0，他引：48  

YAO Tandong    WANG Youqing  LIU Shiying    PU Jianchen    SHEN Yongping & LU Anxin  .Institute of Tibetan Plateau Research  Chinese Academy of Sciences  Beijing  China  .Cold  Arid Regions Environmental  Engineering Research Institute  Chinese Academy of Sciences  Lanzhou  China 《中国科学D辑(英文版)》2004,47(12):1065-1075

There are about 46298 glaciers in the High Asiain China, the total glacial area is about 59406 km , andtotal glacial volume about 5590 km3. These glaciersmainly concentrate around the Himalayas Mountains,Nyainqentanglha Mountains, Kunlun Mountains,Karakoram Mountains and Tianshan Mountains. Theglaciers in the Tibetan Plateau are the major compo-nent of the glaciers in the High Asia in China. Theseglaciers extend north to the arid and desert regions,and become the main water resource in …  相似文献   

U–Pb and Hf-isotope analysis of zircons in mafic xenoliths from Fuxian kimberlites: evolution of the lower crust beneath the North China craton     

Jianping?Zheng  W.?L.?GriffinEmail author  Suzanne?Y.?O’Reilly  Fengxiang?Lu  Chunmei?Yu  Ming?Zhang  Huimin?Li 《Contributions to Mineralogy and Petrology》2004,148(1):79-103

Mafic xenoliths from the Paleozoic Fuxian kimberlites in the North China craton include garnet granulite, and minor pyroxene amphibolite, metagabbro, anorthosite and pyroxenite. The formation conditions of the amphibolites are estimated at 745–820 °C and 7.6–8.8 Kb (25–30 km); the granulites probably are derived from greater depths in the lower crust. LAM-ICPMS U–Pb dating of zircons from four granulites reveals multiple age populations, recording episodes of magmatic intrusion and metamorphic recrystallisation. Concordant ages and upper intercept ages, interpreted as minimum estimates for the time of magmatic crystallisation, range from 2,620 to 2,430 Ma in three granulites, two amphibolites and two metagabbros. Lower intercept ages, represented by near-concordant zircons, are interpreted as reflecting metamorphic recrystallisation, and range from 1,927 to 1,852 Ma. One granulite contains two metamorphic zircon populations, dated at 1,927±55 Ma and 600–700 Ma. Separated minerals from one granulite and one amphibolite yield Sm–Nd isochron ages of 1,619±48 Ma (¹⁴³Nd/¹⁴⁴Nd)i=0.51078), and 1,716±120 Ma (¹⁴³Nd/¹⁴⁴Nd)i=0.51006), respectively. These ages are interpreted as recording cooling following metamorphic resetting; model ages for both samples are in the range 2.40–2.66 Ga. LAM-MC-ICPMS analyses of zircon show a range in ¹⁷⁶Hf/¹⁷⁷Hf from 0.28116 to 0.28214, corresponding to a range of _Hf from –34 to +12. The relationships between ²⁰⁷Pb/²⁰⁶Pb age and _Hf show that: (1) the granulites, amphibolites and metagabbro were derived from a depleted mantle source at 2.6–2.75 Ga; (2) zircons in most samples underwent recrystallisation and Pb loss for 100–200 Ma after magmatic crystallisation, consistent with a residence in the lower crust; (3) metamorphic zircons in several samples represent new zircon growth, incorporating Hf liberated from breakdown of silicates with high Lu/Hf; (4) in other samples metamorphic and magmatic zircons have identical ¹⁷⁶Hf/¹⁷⁷Hf, and the younger ages reflect complete resetting of U–Pb systems in older zircons. The Fuxian mafic xenoliths are interpreted as the products of basaltic underplating, derived from a depleted mantle source in Neoarchean time, an important period of continental growth in the North China craton. Paleoproterozoic metamorphic ages indicate an important tectonic thermal event in the lower crust at 1.8–1.9 Ga, corresponding to the timing of collision between the Eastern and Western Blocks that led to the final assembly of the North China craton. The growth of metamorphic zircon at 600–700 Ma may record an asthenospheric upwelling in Neoproterozoic time, related to uplift and a regional disconformity in the North China craton.  相似文献   

The use of the marine biotic index AMBI in the assessment of the ecological status of the Obidos lagoon (Portugal)     

Carvalho S  Gaspar MB  Moura A  Vale C  Antunes P  Gil O  da Fonseca LC  Falcão M 《Marine pollution bulletin》2006,52(11):1414-1424

This study reports the longitudinal distribution of sediment properties, including inorganic and organic contaminants, and the structure of the benthic community in Obidos lagoon, a coastal system permanently connected to the sea and with negligible freshwater sources. Sediments from the upper to central lagoon consist of fine particles (91%) and from the lower lagoon of sands (94%). Chemical composition is strongly correlated to the percentage of fine particles. Contamination is relatively low in those sediments suggesting the effect of diffuse sources. The increase in organic matter content from down- to upstream areas was associated with the dominance of opportunistic species, while sensitive and indifferent species to organic enrichment were mainly associated to the clean sandy downstream area. The marine biotic index (AMBI) was suitable for the discrimination of the biological and environmental gradients in the Obidos lagoon and was highly related with the gradient of organic matter content in this system.  相似文献