An excess of damped Lyman α galaxies near quasi-stellar objects     

David M. Russell  Sara L. Ellison  Chris R. Benn 《Monthly notices of the Royal Astronomical Society》2006,367(1):412-422

We present a sample of 33 damped Lyman α systems (DLAs) discovered in the Sloan Digital Sky Survey (SDSS) whose absorption redshifts ( z _abs) are within 6000 km s⁻¹ of the quasi-stellar object's (QSO) systemic redshift ( z _sys). Our sample is based on  731 2.5 < z _sys < 4.5  non-broad absorption line (non-BAL) QSOs from Data Release 3 (DR3) of the SDSS. We estimate that our search is ≈100 per cent complete for absorbers with N (H  i )  ≥ 2 × 10²⁰ cm⁻²  . The derived number density of DLAs per unit redshift, n ( z ), within  Δ v < 6000 km s⁻¹  is higher (3.5σ significance) by almost a factor of 2 than that of intervening absorbers observed in the SDSS DR3, i.e. there is evidence for an overdensity of galaxies near the QSOs. This provides a physical motivation for excluding DLAs at small velocity separations in surveys of intervening 'field' DLAs. In addition, we find that the overdensity of proximate DLAs is independent of the radio-loudness of the QSO, consistent with the environments of radio-loud and radio-quiet QSOs being similar.  相似文献   

河南省早二叠世早期岩相古地理及聚煤作用研究     

盛吉虎  张恩惠  王家德  杜慧英  郭辉 《河南国土资源》1997,(3)

早二叠世早期，华北地台陆表海不断向南退缩，早期沉积了一套潮坪相泥岩，中、晚期沉积了一套以河流作用为主的三角洲体系。二１煤形成于潮坪上的泥炭沼泽环境，煤层厚度大，分布广，富煤带位于濮阳、长垣、太康以西和鹤壁、焦作、宜阳一线以东地区。二２煤发育在上、下三角洲平原过渡带上，富煤带分布于兰考、淮阳一带。山西组沉积时古构造对聚煤作用具有控制作用。坳陷区通常为富煤带分布区。  相似文献   

STUDY ON EMBRYONIC DEVELOPMENT AND EARLY GROWTH OF TRIPLOID AND GYNOGENETIC DIPLOID LEFI—EYED FLOUNDER, PARALICHTHYS OLIVACEUS （T. et S. ）   总被引：1，自引：0，他引：1  

尤锋 刘静王新成  徐永立黄瑞东 张培军 《中国海洋湖沼学报》2001,19(2):147-151

The early effects of chromosomal manipulation of eggs and sperm on the yields of trip-loid and gynogenefic diploid larvae of Paralichthys olivaceus were investigated. Triploidy was achieved by cold shocking fen.ilized eggs at 0 - 2℃ for 45 minutes duration 5 minutes after fen.ilization, and the in-duced triploidy rates were 31.2% - 50% and the relative hatching rates were 53.3% - 99%. Gynnge-aetic diploids were obtained when eggs were inseminated with irradiated sperm and cold shocked at 0 -2℃ for 45 minutes duration 5 minutes after fertihzation. The induced gynogenetic diploid rates and the relative hatching rates were 94 % - 96 % and 48.5 % - 68.5 % respectively. The embryonic development of the triploid experimental group and of the gynogenetic diploid experimental group was delayed at first compared with the control group. But from the gastrula stage, it was not delayed anymore. There were no significant differences in the growth of the triploid experimental group larvae and the control group larvae, and in the growth of the gynogenetic diploid experimental group larvae and the control group larvae ac-cording to Student‘s t-test (α = 0.05). The relationship between the early growth of the triploid experi-mental group larvae and that of gynogenetic diploid experimental group larvae was also studied.  相似文献   

The power spectrum of SUSY-CDM on subgalactic scales     

Anne M. Green  Stefan Hofmann  Dominik J. Schwarz 《Monthly notices of the Royal Astronomical Society》2004,353(3):L23-L27

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北天山巴音沟蛇绿岩形成时代的精确厘定及意义   总被引：15，自引：1，他引：14  

徐学义  马中平  夏林圻  李向民  夏祖春  王立社 《地球科学与环境学报》2005,27(2):17-20

应用SHRIMP方法对北天山巴音沟蛇绿岩中侵入辉长岩内的斜长花岗岩进行了锆石UPb年龄测定,表明斜长花岗岩形成于(324.8±7.1)Ma(2σ)。这一年龄精确反映了巴音沟蛇绿岩的形成时代于早石炭世晚期。巴音沟蛇绿岩形成于强烈大陆伸展作用导致的大陆裂谷向大洋裂谷转变的一种动力学环境,记录了由于裂谷作用强烈拉伸形成的初始洋壳,是晚古生代天山地区“红海型”洋盆的地质记录。  相似文献   

Early structure in ΛCDM     

L. Gao  S. D. M. White  A. Jenkins  C. S. Frenk  V. Springel 《Monthly notices of the Royal Astronomical Society》2005,363(2):379-392

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A new Eocene catostomid (Teleostei: Cypriniformes) from northeastern China and early divergence of Catostomidae     

CHANG Mee-mann 《中国科学D辑(英文版)》2009,52(2):189-202

A new Eocene catostomid genus and species, Plesiomyxocyprinus arratiae, is described from Huadian, Jilin Province, northeastern China. The materials include a nearly complete skeleton, dozens of pharyngeal bones with teeth, and a number of disarticulated bones. The new articulated specimen is large-sized and deep-bodied, with an estimated standard length of ca. 300 mm and body depth of 156 mm or about half of its standard length. The assignment of the fish to the Catostomidae is based on its falciform pharyngeal bone with one row of numerous (more than 50) compressed teeth, and the bone is much smaller than in cyprinids, especially given the size of the fish. The new fish distinguishes itself from all known catostomids (both extinct and extant) in its long anal fin with four unbranched and 17–18 branched rays, and its extremely short caudal peduncle that is only about one fourth of its depth. Plesiomyxocyprinus arratiae resembles the Eocene-Oligocene transpacific-distributed Amyzon in many general skeletal characters. However, it shows a few characters uniquely shared with the Recent catostomid Myxocyprinus asiaticus. Those include a very long dorsal fin with about 50 branched fin rays, the end of dorsal fin rays being close to the caudal fin base, and anal rays stretching posteriorly beyond the base of caudal fin. It is the first fossil catostomid that shows a close relationship to the endemic Myxocyprinus now living in the Yangtze River and Minjiang River, China. The discovery of Plesiomyxocyprinus arratiae, along with two previously described possible catostomid genera Jianghanichthys and Vasnetzovia, may indicate that the divergence of the Catostomidae started much earlier, in the middle Eocene or earlier, on the western side of the Pacific than on its eastern side. Supported by National Natural Science Foundation of China (Grant No. 40432003, J0630965), Cypriniformes Tree of Life under the U.S. National Science Foundation to R. Mayden (Grant No. EF0431326), and Ecocarp Project (European Commission, INCO-DEV Programme) (Grant No. ICA4-CT-2001- 10024)  相似文献   

准噶尔盆地深层相对优质储层发育机理——淋滤与溶蚀作用     

胡海燕  王国建 《中国岩溶》2009,28(1):35-41

准噶尔盆地腹部侏罗系砂岩埋藏深(>5800m),深部是否发育相对优质储层是制约深层勘探的科学问题.采用镜下观察、测井、试验测试等手段研究了准噶尔盆地深层砂岩的成岩机制和优质储层的发育机理.研究结果表明:(1)准噶尔盆地深层侏罗系砂岩为晚期超压,砂岩粒度细,以粉砂岩和细砂岩为主,岩屑含量高达69%,成分成熟度低,颗粒包壳对砂岩的孔隙度保存有利,但会堵塞喉道,降低渗透率,而且早期充注的油气中的有机酸会溶蚀砂岩地层中的长石和岩屑等矿物,造成高岭石和石英沉淀,对储层的发育与保存不大有利;(2)盆地腹部深层侏罗系西山窑组顶部砂岩中存在一个次生孔隙发育带,孔隙度和渗透率增大,孔隙度从7%增大至11%,渗透率从0.5md增加至2.5md.这个次生孔隙发育带位于侏罗系与白垩系之间的不整合面(埋深5 850m)之下的半风化砂岩中,主要是表生期大气淡水的淋滤作用和深埋后溶蚀作用形成.   相似文献   

基于ARCGIS的矿山开采沉陷灾害预警系统   总被引：4，自引：2，他引：2  

张春会  赵全胜 《岩土力学》2009,30(7):2197-2202

为了实现与环境协调的矿产资源开采,提出建立并开发了矿山开采沉陷灾害预警系统。以美国大型软件ARCGIS为开发平台,采用ARCMap Object开发方法开发了矿山开采沉陷灾害预警系统;建立了该系统计算参数的位移反分析模型,引入单纯形优化方法,编制了系统计算参数的位移反分析模块;进行了实例计算分析。第1个实例分析了某工作面开采引起的地表沉陷灾害,并与CXYJ2001的计算结果对比,验证了系统的计算可靠性,并展示了系统的功能。第2个实例是对江苏姚桥煤矿开采方案引起的地表沉陷灾害预警分析,优化了开采方案。研究表明,系统是实现与环境协调的矿产资源开采的重要辅助手段。最后,介绍了进一步工作的方向。  相似文献   

基于设计安全系数及破坏模式的边坡开挖过程动态变形监测预警方法研究   总被引：2，自引：1，他引：1  

张振华  冯夏庭  周辉  张传庆  崔强 《岩土力学》2009,30(3):603-612

由于地质和结构特征的不同造成的边坡变形破坏机制存在差异以及同一边坡在不同施工开挖阶段的变形规律和量值也存在差别,采用工程类比方法获得的单一的静态的边坡监测预警指标无法表达某一边坡在施工开挖过程中动态的变形规律和特征,针对该问题提出了基于设计安全系数和破坏模式的边坡开挖过程中动态变形监测预警指标的研究思路和方法,并将其应用于糯扎渡水电站溢洪道消力塘边坡755～740 m开挖过程变形监测预警指标的确定,通过与现场监测结果的对比分析表明,该边坡开挖过程中是稳定的,分析与工程实际是相符的。研究表明,基于设计安全系数和破坏模式的边坡开挖过程动态监测预警指标的研究思路和方法用于边坡在开挖过程中动态变形监测预警是可行和有效的。  相似文献