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1.
云南地区处于印度板块与欧亚板块中国大陆碰撞带的东缘,地壳运动剧烈,活动块体特征明显,中强以上地震频发,是研究大震活动规律的理想场所。通过过去一个世纪的6.7级以上地震活动的时空分布以及地震动力分析认为,云南地区存在的4个具东西交替活动特征的地震活跃期,可能是东、西部各自地震活跃与平静过程叠加的结果,100a左右可能出现1次东、西部同时爆发大震的时段;云南地区地震活动与外围地区存在较好的呼应关系,安达曼-缅甸弧形带的巨震活动对云南地区地震活跃期的启动有一定的指示意义,而云南东部强震也与四川西部大震密切相关,四川大震活动往往滞后于云南地区;中强地震连发—平静—首发大震可能是云南以东部为活动主体的地震活跃期的启动模式。这些认识对云南地区大震预测、地震机理以及板缘动力学研究会有所帮助 相似文献
2.
Structure and Significance of S-wave Velocity and Poisson’s Ratio in the Crust beneath the Eastern Side of the Qinghai-Tibet Plateau 总被引：2，自引：0，他引：2
The receiver functions of body waves of distant earthquakes obtained for the regions beneath 41 digital stations (Lhasa and
GANZ in Tibet, Mandalay and Rangoon in Myanmar, SHIO in India, CHTO in Thailand, and station network in Sichuan and Yunnan)
were used to invert for S-wave structure in the crust and upper mantle in Sichuan, Yunnan, and their surrounding areas. Meanwhile
the distribution characteristics of the Poisson’s ration and the crustal thickness in Sichuan and Yunnan areas were also obtained.
Results indicate that the depth of Moho beneath the eastern side of Qinghai-Tibetan plateau varies strikingly. It is obvious
that the greatest changes in crustal thickness occur in a north-south direction. The crustal thickness decreases from north
to south, being as thick as 70 km in eastern Tibet, the northern portion of our area of interest, and less than 30 km in Chaing
Mai and Rangoon, the southern portion of our area. There are, however, exceptions regarding the trend. The thickness exhibits
an east-west variation trend in the area from Ma’erkong-Kongding in Sichuan to Lijiang in Yunnan. In general the Jinpingshan-Longmenshan
fault and Anninghe fault can be taken as the boundaries of this exception area. The thickness in Kongding in the west is 68 km,
while it is only 39 km in Yongchuan in the east. Moreover the Poisson’s ratio values in the blocks of central Sichuan and
Sichuan-Yunnan Diamond are high, and a low velocity layer in the crust of this area can be obviously detected. The distribution
characteristics of the high Poisson’s ratio and the low velocity of the crust in this block correspond to the tectonic structure,
being in contrast with the surrounding areas. Combining with the distribution features of the modern tectonic stress field,
it is deduced that the Sichuan-Yunnan area is probably the channel through which the materials of the lithosphere flow eastward. 相似文献
3.
Nineteen trace elements were determined in liver, muscle, kidney, gonads, and hair of 18 harp seals (Phoca groenlandica) from Pangnirtung in the Baffin Island, Canada. Concentrations of V, Mn, Fe, Cu, Mo, Ag, and Hg in the liver, Co, Cd, and Tl in the kidney, and Ba and Pb in the hair were significantly higher than those in other tissues. Significant positive correlations between Hg concentrations in the hair, and liver, kidney and testis imply usefulness of the hair sample for non-destructive monitoring of Hg in the harp seals. It is suggested that whereas Hg preferentially accumulates in the liver, the accumulation in other tissues is induced at higher hepatic Hg levels. In contrast, Se may not be accumulated in other tissues compared with the liver even at higher hepatic Hg levels because of the presence of excess Se for Hg detoxification in other tissues. 相似文献
4.
A history of British seismology 总被引：1，自引：1，他引：0
R. M. W. Musson 《Bulletin of Earthquake Engineering》2013,11(3):715-861
The work of John Milne, the centenary of whose death is marked in 2013, has had a large impact in the development in global seismology. On his return from Japan to England in 1895, he established for the first time a global earthquake recording network, centred on his observatory at Shide, Isle of Wight. His composite bulletins, the “Shide Circulars” developed, in the twentieth century, into the world earthquake bulletins of the International Seismological Summary and eventually the International Seismological Centre, which continues to publish the definitive earthquake parameters of world earthquakes on a monthly basis. In fact, seismology has a long tradition in Britain, stretching back to early investigations by members of the Royal Society after 1660. Investigations in Scotland in the early 1840s led to a number of firsts, including the first network of instruments, the first seismic bulletin, and indeed, the first use of the word “seismometer”, from which words like “seismology” are a back-formation. This paper will present a chronological survey of the development of seismology in the British Isles, from the first written observations of local earthquakes in the seventh century, and the first theoretical writing on earthquakes in the twelfth century, up to the monitoring of earthquakes in Britain in the present day. 相似文献
5.
包尚联 《CT理论与应用研究》1998,(3)
本文介绍了国际医用磁共振协会及其主办的国际会议情况,即ＩｎｔｅｒｎａｔｉｏｎａｌＳｏｃｉｅｔｙｆｏｒＲｅｓｏｎａｎｃｅｉｎＭｅｄｉｃｉｎｅ－ＩＳＭＲＭ。该协会代表了世界上医用磁共振成像方面的最高水平,从第４次年会开始,会议在每年的４月份进行。本文作者参加了１９９７年在加拿大温哥华召开和１９９８年在澳大利亚悉尼召开的年会。会议主要讨论的题目包括功能磁共成像（ｆＭＲＩ）,结构磁共振成像（ａＭＲＩ）波谱成像（ＭＲＩ／Ｓ）和血管造影等方面的内容,以及磁共振成像技术协会方面关于诊断方法,显像增强剂技术,磁共振成像设备及其部件技术,以及数据处理方面的技术进步等课题。推动该领域发展的主要动力显然是对人类自身的研究和对疾病诊疗的需要,尤其对脑功能研究、功能性疾病的诊断和治疗的需要。但是磁共振成像目前在心脏、肺脏以至软骨方面的诊断已经有很大进步,在设备技术和数据处理方法方面的进步同样也是很快的。 相似文献
6.
To investigate the stratification of hydrolytic enzyme activities and importance of subsurface layers in depolymerization of detritus biopolymers,nine hydrolytic enzyme activities involved in the cycling of carbon,phosphorus,nitrogen and sulphur were measured in various sediment layers and their extracts at Kylaniemi in Lake Saimaa in southern Finland and in Lake Ahvenjarvi in northern Finland. The results show that for each lake all nine hydrolytic enzyme activities were higher in all sediment layers than in comparable sediment extracts indicating that the major part of enzymes was bound to the sediment particles in all layers in both lakes.Carbohydratase,P-cellobiosidase,activities did not show any gradient with sediment depth at Kylaniemi in Lake Saimaa indicating that there was rapid turnover of carbohydrates in the entire sediment column.The activities of acetate esterase,butyrate esterase,phosphomonoesterase,aminopeptidase,N-acetyl glucosaminidase,sulphatase andβ-glucosidase in the deepest layers were 19-53%of those in the surface sediment indicating that depolymerization of biopolymers involved in the cycling of carbon,nitrogen,phosphorus and sulphur was substantial in subsurface sediment. 相似文献
7.
于2005年11月采集了大通湖及东洞庭湖区湖水和水生生物样品,并测定了水和水生生物样品中重金属(Cd、Pb、Hg、As)的含量,并对湖区生物体重金属进行了污染评价.研究结果表明,大通湖及东洞庭湖区湖水中重金属含量较小,绝大部分采样点水质都属于国家Ⅰ类水标准;水生生物体内CD、Pb含量为虾＞螺＞鱼,Hg的含量为鱼＞螺＞虾,As的含量为螺＞虾＞鱼;而鱼类重金属含量则为底栖鱼类＞中上层鱼类,肉食性鱼类＞植食性鱼类.大通湖及东洞庭湖区生物体中CD、Pb的污染指数为虾＞螺＞鱼,Hg的污染指数则为鱼＞螺＞虾,As的污染指数则为螺＞虾＞鱼. 相似文献
8.
Specific features of the water balance of river deltas located in different geographic zones are discussed. Variations in the mean long-term water runoff in river deltas are estimated. As revealed, the river water runoff increases in the deltas located in subarctic, subequatorial, and equatorial regions, where precipitation exceeds evaporation, while the river water runoff decreases in deltas located in the temperate zone, subtropics, and tropics, where evaporation exceeds precipitation. It is noted that increase in water runoff is typical of the river deltas of the world as a whole. 相似文献
9.
介绍了正在建设中的全球湖泊数据库的情况,以及该数据库的水位资料所反映的晚更新世末期以来全球湿润状况的变化。通过大尺度湖水位变化的时空分析,结果显示当今湖泊水位状态较历史时期而言,位于低纬干旱或半干旱地区的湖泊水位较低,而中纬及高纬湿润地区的湖泊水位较高。自末次冰盛期以来,北美大陆中南部地区湖泊水位自高至低,反映出该地区气候条件由湿变干,至早、中全新世达最干旱。而在非洲及南亚季风地区,冷期偏干,暖期偏湿。特别是在早、中全新世的温暖时期,为历史上最湿润时期。北半球中纬度地带的气候干湿变化与北半球冰盖的存在及其消融导致的西风带的南北摆动有关;而北半球季风区在早、中全新世出现的高潮面与北半球夏季辐射的增加有密切联系。 相似文献
10.
整理了近40年菲律宾MS≥7级地震公开的灾害数据,采用可公度计算、蝴蝶结构图、可公度结构系等方法分析判断未来地震的时间;利用相邻地震震源经、纬度差变化分析震中的空间迁移;并利用震中经向、纬向迁移进行佐证,实现对其时空结构的未来趋势判断。通过判断发现菲律宾MS≥7级地震在2014年、2015年发生的信号较强;未来地震震中可能会在2013年10月15日菲律宾地震震中的东北方向,空间位置大致在9.8°N以北,126.704°E以东。菲律宾MS≥7级地震与地球自转速度变化有一定的关系,减速期发生地震的可能性更大,且速率转换的时间越长越易发生地震;同时发现太阳活动处于活跃强烈期内时,太阳黑子峰值、次峰值前后发生地震的概率很大。目前地球自转正处于减速期、太阳活动处于太阳黑子第24周期极大年附近,所以2014—2015年菲律宾发生MS≥7级地震的可能性很大。 相似文献
11.
应用1949～2005年热带气旋（台风）年鉴资料，对西太平洋以及登陆我国东南沿海地区的热带气旋活动的特征进行了分析，发现西太平洋生成热带气旋个数和登陆我国热带气旋的个数有略为减少的趋势，而登陆我国热带气旋的强度有显著增强趋势.2005年西太平洋生成热带气旋数偏少，但其中登陆我国的强热带气旋比例却明显偏高.对导致这种异常现象的大尺度环流条件的分析表明，前期南亚高压和副热带高压势力偏强，台风期副高偏强、东亚夏季风偏弱、水平风垂直切变等因子不利于热带气旋生成；而西太平洋西部异常的水汽输送、弱风垂直切变、海表面温度异常以及中低纬系统之间相互作用等则可能是导致登陆我国热带气旋强度异常偏强的主要原因. 相似文献
12.
Spatial and temporal distributions of the trends of extreme precipitation indices were analysed between 1986 and 2005, over the Iberian Peninsula (IP). The knowledge of the patterns of extreme precipitation is important for impacts assessment, development of adaptation and mitigation strategies. As such, there is a growing need for a more detailed knowledge of precipitation climate change.This analysis was performed for Portuguese and Spanish observational datasets and results performed by the Weather Research and Forecast (WRF) model forced by the ERA-Interim reanalysis. Extreme precipitation indices recommended by the Expert Team for Climate Change Detection Monitoring and Indices were computed, by year and season. Then, annual and seasonal trends of the indices were estimated by Theil-Sen method and their significance was tested by the Mann-Kendal test. Additionally, a second simulation forced by the Max Planck Institute Earth System Model (MPI-ESM), was considered. This second modelling configuration was created in order to assess its performance when simulating extremes of precipitation.The annual trends estimated for the 1986–2005, from the observational datasets and from the ERA-driven simulation reveal: 1) negative statistically significant trends of the CWD index in the Galicia and in the centre of the IP; 2) positive statistically significant trends of the CDD index over the south of the IP and negative statistically significant trends in Galicia, north and centre of Portugal; 3) positive statistically significant trends of the R75p index in some regions of the north of the IP; 4) positive statistically significant trends in the R95pTOT index in the Central Mountains Chain, Leon Mountains and in the north of Portugal.Seasonally, negative statistically significant trends of the CWD index were found in Galicia, in winter and in the south of the IP, in summer. Positive statistically significant trends of the CWD index were identified in the Leon Mountains, in spring, and in Galicia, in autumn. For the CDD index, negative statistically significant trends were seen in Valencia, in the spring, and, in Galicia and Portugal (north and centre), in summer. Positive statistically significant trends of the CDD index were found: in the east of the IP, in the winter; in the Cantabrian Mountain, in the spring; and, in the south of the IP, in summer. Regarding to the R75p index, negative statistically significant trends were found in Galicia, in winter and positive statistically significant trends in the north of Portugal, in spring and in the Central Mountains Chain and north of Portugal, in autumn. For the R95pTOT index, negative statistically significant trends were found over the Sierra Cuenca and Sierra Cazorla, in winter and positive statistically significant trends were found over the Sierra Cebollera, in winter and in Castile-la Mancha region, in spring.The results of the annual and seasonal trends of the extreme precipitation indices performed for observational datasets and the simulation forced by ERA-Interim, are similar. The results obtained for the simulation forced by MPI-ESM are not satisfactory, and can be a source of criticism for the use of simulation forced by MPI-ESM in this type of climate change studies. Even for the relatively short period used, the WRF model, when properly forced is a useful tool due to the similar results of Portuguese and Spanish observational datasets and the simulation forced by ERA-Interim. 相似文献
13.
Drylands account for approximately 41% of the global total land area. Significant warming and rare precipitation in drylands result in a fragile ecology and deterioration of the living environment, making it more sensitive to global climate change. As an important regulator of the Earth's climate system, the oceans play a vital role in the process of climate change in drylands. In modern climate change in particular, the impact of marine activities on climate change in drylands cannot be neglected. This paper reviews the characteristics of climate change in drylands over the past 100 years, and summarizes the researches conducted on the impact of marine activities on these changes. The review focuses on the impact of the Pacific Decadal Oscillation(PDO), Atlantic Multidecadal Oscillation(AMO), El Ni?o and La Ni?a on climate change in drylands, and introduces the mechanisms by which different oceanic oscillation factors synergistically affect climate change in drylands.Studies have shown that global drylands have experienced a significant intensification in warming in the past 100 years, which shows obvious characteristics of interdecadal dry/wet variations. The characteristics of these changes are closely related to the oscillatory factors of the oceanic interdecadal scale. Different phase combinations of oceanic oscillation factors significantly change the land-sea thermal contrast, which in turn affects the westerly jet, planetary wave and blocking frequency, resulting in changes in the temperature and dry/wet characteristics of drylands. With the intensification of climate change in drylands, the impact of marine activities on these regions will reveal new characteristics in the future, which will increase the uncertainty of future climate change in drylands and intensify the impact of these drylands on global climate. 相似文献
14.
东南沿海地震区的现代构造应力场 总被引：11，自引：3，他引：11
根据断层面的最新错动方向，震源机制解和地壳形变等资料，研究了东南沿海地区的现代构造应力场，结果表明：本区构造应力场可大致划分为两个分区：长乐－诏安断裂带以东地区主压应力轴为近东西向；以西地区的主压应力轴近南北向。 相似文献
15.
Various types of endocrine disruptors or environmental hormones flow from their sources down into harbours through rivers and other watercourses, and are accumulated in sediment on the sea bottom. Tributyltin, which has been used as paint for ship bottoms, is considered one of the endocrine disruptors.In close cooperation with the other ministries and agencies, the Ports and Harbours Bureau of the Ministry of Land, Infrastructure and Transport carried out an investigation in 1999 to determine the actual condition of 12 endocrine disruptors in the sediment of 39 harbours, in order to gather fundamental data to be used in future examinations of policy. Furthermore, in 2000 the bureau chose seven harbours out of the above 39 harbours as subjects of an additional investigation regarding the surface distribution of endocrine disruptors in the harbour areas and the synchronistic change of accumulation of dioxin and other substances. As the result of the investigation regarding the surface distribution of endocrine disruptors accumulated in seven harbours, relatively high concentrations were measured in the innermost parts of harbours and the mouths of rivers. Synchronistic changes in the amount of dioxin and other substances accumulated in sediments of five harbours were determined. Small amounts of dioxin and other substances, including an especially small amount of coplanar-PCBs, were found in the layers formed before or around 1950. Relatively large amounts of these substances were measured in the upper layers formed during roughly 1960-1990, though no significant yearly differences in concentration could be identified. This result coincides with the facts that, during roughly 1960-1980, PCP and CNP were used as agricultural chemicals and full-scale production of PCBs started in 1960. 相似文献
16.
This study investigated the subcellular distribution of Cu, Zn, Cd and Ag in liver of mallard (Anas platyrhynchos), spot-billed duck (A. poecilorhyncha) and great cormorant (Phalacrocorax carbo) to better understand metal fractionation and dynamics in avian liver. Most of the total Cu, Zn, Cd and Ag were present in hepatocytosol, and their concentrations increased with total hepatic levels in all the three avian species. Copper, Zn and Cd in hepatocytosol were present mostly in metallothionein fractions (MTs), and Cu and Cd contents in this fraction were positively correlated with hepatocytosol levels in all the species. Silver was observed mostly in both high-molecular weight and MT fractions in hepatocytosol in mallard and great cormorant, whereas it was present in both low-molecular weight and MT fractions in spot-billed duck, suggesting that distribution of Ag in the hepatocytosol was species-specific. The elution profile of metals in MT fractions revealed six metallic peaks in mallard and spot-billed duck, and three peaks in great cormorant, implying the presence of multiple MT isoforms in the liver of these avian species. The present study demonstrated that MTs are closely associated with metal regulation, especially Cu and Cd, in these three aquatic birds. 相似文献
17.
The interrelation between sudden increases in the solar wind dynamic pressure, auroral proton flashes on the dayside equatorward
of the oval, and geomagnetic pulsations in the Pc1 range is considered on the basis of simultaneous observations of the solar
wind plasma parameters, proton auroras on the IMAGE satellite, and geomagnetic pulsations at the Lovozero Observatory. It
is indicated that proton luminosity flashes were observed in 70% of cases equatorward of the auroral oval during sudden changes
in the solar wind pressure. In this case, flashes of proton auroras were observed in 85% of cases during sudden changes in
the pressure, which were related to interplanetary shocks. Increases in pressure during tangential discontinuities were accompanied
by flashes of proton auroras only in 45% of cases. When the ground station was conjugate to the region occupied by a proton
aurora flash, the appearance or intensification of existent pulsations in the Pc1 range was observed in 96% of cases. When
the ground station was not conjugate to the region of a proton luminosity flash, the response in geomagnetic pulsations was
observed in 32% of events. When a sudden change in the solar wind pressure was not accompanied by a proton luminosity flash,
the response in pulsations in the Pc1 range was hardly observed. 相似文献
18.
A mathematical model based on average long-term data on water temperature, illumination, transparency, and nutrient content is used to calculate annual variations in the concentrations of organic and inorganic fractions of nutrients (C, N, Si, and P) in ten water areas in the Caspian Sea. The eutrophication of sea environment is examined with special emphasis on the increase in the biomass of aquatic animals (in particular, phyto- and zooplankton), the rate and duration of periods of plankton blooming, and changes in the conditions of nutrient limiting of primary production processes in different parts of the sea. Relationships between the inorganic components of N and P in river runoff and sea water areas are established. The obtained Nmin/DIP ratios show P primary production to be limited in the zone of influence of the Volga runoff, P and N primary production to be limited in other northern parts of the sea, and N primary production to be mainly limited in the middle and southern parts of the sea. 相似文献
19.
目的:探讨胸部CT及CT淋巴管成像（CTL）在原发性肺淋巴管扩张症（CPL）的诊断价值。材料及方法:回顾性分析2012年8月至2021年7月41例经临床及影像确诊为CPL患者的临床及影像学资料,所有患者均于直接淋巴管造影术（DLG）前行胸部CT检查,并于DLG后行CTL检查,分析胸部CT及CTL图像,所得结果采用分类变量资料中的构成比进行统计描述。结果:41例患者中胸部CT表现为支气管血管束增粗33例,小叶间隔增厚32例,小叶内间质增厚4例,磨玻璃密度影26例,肺实变5例,肺不张14例,胸腔积液24例。CTL碘油异常沉积于胸导管末端35例,支气管血管束31例,肺门32例,胸膜17例,纵膈36例,心包17例,横膈3例,腹腔内10例,腹膜后10例,盆腔及会阴20例。结论:CT和CTL可显示淋巴管异常的范围及分布,为CPL诊断和治疗提供影像学依据。 相似文献
20.
通过对广西及邻区(以下简称研究区)地震活动的背景,包括研究区地震活动特征、断裂带的分布、主压应力轴方向与强震发生的主体地区、地震活动时空扫描异常特点、强震发生的时间特点进行了分析,说明该地区存在发生中强震的可能。并对2004年广东阳江4.9级2、005年云南文山5.3级、2005年广西平果4.4级地震前的异常进行了分析,说明研究区地震活动特征显著。同时获得了区域中强以上地震前的主要异常指标,对今后地震预测有一定指导意义。 相似文献