Did the Sun’s Prairie Ever Stop Burning?     

P. Foukal  J. Eddy 《Solar physics》2007,245(2):247-249

The presence of the red flash at total solar eclipses requires the existence of an extended chromosphere and therefore of a photospheric magnetic network that gives rise to spicules. We draw attention to the earliest historical reports of a red flash at the 1706 and 1715 eclipses, which therefore imply a substantial, widespread photospheric field during at least the last decade of the Maunder Minimum. Our finding is consistent with reports of a persistent photospheric field throughout the Maunder Minimum from analyses of ¹⁰Be radioisotope evidence. We note, however, that the last decade may not be representative of conditions throughout the roughly 1645 – 1715 extent of that prolonged activity minimum.  相似文献   

Distribution of clay minerals in marine sediments off Chennai,Bay of Bengal,India： Indicators of sediment sources and transport processes     

Subramanian VEERASINGAM  tamdoss VENKATACHALAPATHY  Thirunavukkarasu RAMKUMAR 《国际泥沙研究》2014,29(1):11-23

Clay mineralogy, texture size and statistical analyses were carried out on surface sediments from the continental shelf of Chennai, Bay of Bengal, India. The purpose of this study is to characterize the clay mineral distribution and its relation to the hydrodynamics off Chennai to identify the sources and transport pathways of the marine sediments. Characterization of clay minerals in coastal sediments by Fourier Transform Infrared （FTIR） spectroscopy has provided the association of quartz, feldspar, kaolinite, chlorite, illite and iron oxides （magnetite and hematite） derived from river catchments and coastal erosion. Kaolinite, chlorite, illite, iron oxides, and organic matter are the dominant minerals in Cooum, and Adayar region. High quartz and feldspar zones were identified in Marina, which are being confined the sand zone and paralleling the coast. The strong relationships among the wave energy density, sand, quartz and carbonate revealed that wave induced littoral drift system play a dominant role in transportation and deposition of sediments in the Chennai coast. The sediment texture and minerals data are in agreement well with the previous results of hydrodynamics and littoral drift models in this region. Multivariate statistical analyses （correlation, cluster and factor analyses） were carried out and obtained results suggested that clay minerals and organic matter are trapped in silt and clay particles, whereas quartz, feldspar and carbonate are associated with sand particles. Results of sediment sources and transport processes from this study will be useful to predict the fate of the pollutants released from land or the potential change in sediment delivery to coastal areas.  相似文献   

Study of moisture migration in clay soils considering rate of freezing     

Kudryavtsev S A  Kazharskii A V  Goncharova E D  Berestianyi I B 《地下水科学与工程》2014,2(4):35-40

The paper presents some methods of numerical modelling and a study of moisture changing in frozen clay soils considering rates of freezing in the foundation. An impact assessment of moisture changes in clay soils affecting strength characteristics during thawing was carried out in stability tests.  相似文献   

Mass-induced sea level variations in the Red Sea from GRACE,steric-corrected altimetry,in situ bottom pressure records,and hydrographic observations     

《Journal of Geodynamics》2014

An annual amplitude of ∼18 cm mass-induced sea level variations (SLV) in the Red Sea is detected from the Gravity Recovery and Climate Experiment (GRACE) satellites and steric-corrected altimetry from 2003 to 2011. The annual mass variations in the region dominate the mean SLV, and generally reach maximum in late January/early February. The annual steric component of the mean SLV is relatively small (<3 cm) and out of phase of the mass-induced SLV. In situ bottom pressure records at the eastern coast of the Red Sea validate the high mass variability observed by steric-corrected altimetry and GRACE. In addition, the horizontal water mass flux of the Red Sea estimated from GRACE and steric-corrected altimetry is validated by hydrographic observations.  相似文献   

西藏吉隆-沃马盆地龙骨沟剖面古地磁年代学及喜马拉雅山抬升记录   总被引：12，自引：0，他引：12       下载免费PDF全文

岳乐平  邓涛  张睿  张兆群  F.Heller  王建其  杨利荣 《地球物理学报》2004,47(6):1009-1016

研究了西藏吉隆—沃马盆地龙骨沟剖面新近纪沉积环境,作了古地磁年代学研究,认为喜马拉雅山北坡新生代断陷盆地发育始于7.2MaB.P., 3.2MaB.P.湖盆萎缩消亡,标志着喜马拉雅山地区在7.2MaB.P.和3.2MaB.P.发生过强烈的隆升事件.沃马盆地龙骨沟剖面所含三趾马动物群化石层年龄大约为7.0～6.7MaB.P.,隐示着此时青藏地区三趾马生活区与当时的华北平原三趾马生活区有着大体相当的地理、气候环境.之后由于喜马拉雅山持续抬升,断陷盆地下沉,并在5.9～3.6MaB.P.期间湖盆面积最为广阔.青藏高原抬升而华北平原沉降, 中国西部地区地形高于东部,东西部气候环境发生重大差异.3.6MaB.P.由于青藏地区持续强烈隆升,西部地区河流切穿古老湖盆,3.20MaB.P.吉隆—沃马湖盆萎缩,于1.7MaB.P.逐渐消失,进入侵蚀切割阶段.  相似文献   

红河断裂带大型右旋走滑运动与伴生构造地貌变形   总被引：19，自引：2，他引：17       下载免费PDF全文

向宏发  韩竹军  虢顺民  张晚霞  陈立春 《地震地质》2004,26(4):597-610

调查研究表明,自中新世以来,红河断裂大规模右旋走滑运动及其伴生构造变形有如下一些主要特征在几何结构上,可将整个红河断裂系分为北、中、南3个变形区。北区东侧为滇西北伸展裂陷区,以轴向NNW,NNE和近SN向3组上新世以来的裂陷型断盆为特征,北段西侧为兰坪—云龙古近纪、新近纪压缩变形区;中段变形以右旋剪切走滑运动为特征,南部断裂东侧有滇东中新世以来的压缩变形,西侧为藤条河中新世拉伸断陷区。上述变形特征反映在构造地貌上为北部盆岭构造、中段线性断谷断盆构造及南部压(张)性盆地变形,其中苍山—洱海一带断裂两侧主夷平面的巨大落差是红河断裂上新世以来断陷正断作用的显著代表。在时空演化上,从古近纪经中新世至上新世,断裂主体活动部位在南段,并呈由南向北的“撕裂”格局,上新世以后至第四纪,尤其是晚第四纪以来,主体活动部位已转移至北段,表现为由N向SE的滑移伸展变形;变形区的范围大小和变形幅度表明红河断裂的东盘地块始终是作为地块相对运动的主动盘  相似文献   

CRUSTAL STRUCTURE FROM YUNXIAN-NINGLANG WIDE-ANGLE SEISMIC REFLECTION AND REFRACTION PROFILE IN NORTHWESTERN YUNNAN,CHINA          下载免费PDF全文

CHEN Si-wen  WANG Bao-shan  TIAN Xiao-feng  WANG Fu-yun  LIU Bao-feng  LI Lu 《地震地质》2016,38(1):91-106

The Red River Fault in western Yunnan is one of the longest strike-slip faults in China and has a high seismic potential. To investigate its complicated structure, a near-NS directed 300km long wide-angle reflection/refraction seismic profile was laid out from Yunxian to Ninglang, across the Red River Fault. The 2-D velocity structure model along the profile was obtained through 1-D and 2-D analysis and fitting the observed data with combination of first-arrival traveltime tomography and forward modeling. The results indicate:In the crust, the average P-wave velocity is 6.2~6.3km/s and basically shows a positive gradient structure, but there are some low velocity anomalies at different area in upper and lower crust. Regarding the crust boundary, a relative large lateral variation exists in the depth of Moho, which goes deeper from south to north, ranging from 45km to as deep as 54km; compared to other typical continental crust, the study area demonstrates a striking thickening. It should be mentioned that the crustal thickening is mainly observed in the lower crust, while the upper and middle crust possess nearly constant thickness. We observed strong seismic velocity contrast across the Red River Fault, which emphasizes the role of the fault as an important tectonic boundary between Yangtze paraplatform and Sanjiang geosynclinal system. Along the profile, the Moho depth has no remarkable variation when crossing the Red River Fault. Combining with other study results on nearby area, it proves that there is notable heterogeneity between different parts of the Red River Fault.  相似文献   

Quantitative characterization and comprehensive evaluation of regional water resources using the Three Red Lines method   总被引：1，自引：1，他引：0  

Zheng Zang  Xinqing Zou  Xu Xi  Yu Zhang  Defeng Zheng  Caizhi Sun 《地理学报(英文版)》2016,26(4):397-414

Based on the synergetic development of new industrialization, rapid urbanization and agricultural modernization (IUAM), and from the viewpoint of interactive relationships between water resources and regional population, eco-environment, economy and society, the concepts of water resources intensity (WRI), water environment intensity (WEI), water resources relative efficiency (WRRE) and water environment relative efficiency (WERE) are defined with reference to energy intensity, resources efficiency and environment efficiency theory. On the basis of benchmarking theory, the quantitative characterization and evaluation method of “Three Red Lines” (the upper limit of water resources allocation, the baseline of utilization efficiency of water resources and the upper limit of sewage discharge) is proposed. According to these concepts and models, an empirical analysis of the Three Red Lines of water resources on the Chinese mainland between 2003 and 2012 was carried out. The results showed that total water consumption in eastern, central and western parts of China possesses “club convergence” characteristics, which means these areas have similar internal conditions appeared convergence in the development. Inter-provincial differences in water consumption continue to decrease, but the north–south differentiation characteristics in the eastern and central regions were still relatively obvious, while provincial differences in the eastern part were at a minimum and the central region had the largest. Water Resources Efficiency (WRE) of all four sectors in the Southwest rivers and Huaihe River basins were generally high. Industrial WRRE in the Songhua River, Yangtze River and Pearl River basins, agricultural WRRE in the Songhua River, Yellow River and northwestern river basins and domestic WRRE in the Liaohe River, Yangtze River and Pearl River basins were all low. Eco-environmental WRRE in the southeastern rivers and Yangtze River basins were low but showed an upward trend. Other river basins, except for the Northwestern rivers basin, had high eco-environmental WRRE with a downward trend. Western China, especially the northwestern part, had a low relative intensity of the water environment (WERI) and high integrated water environment management (IWEM) performance, but the relative intensities of the water resources (WRRI) were fairly high, and the comprehensive performance of integrated water resources management (IWRM) in these regions was low. In southern China, especially the southeastern part, the IWEM was fairly high, but the overall IWRM was lower.  相似文献   

A Multi‐Element Mineral Conditioner: A Supplement of Essential Cations for Red Soil and Crops Growth          下载免费PDF全文

Gongning Chen  Lin Shi 《洁净——土壤、空气、水》2016,44(12):1690-1699

  相似文献   

The red swamp crayfish Procambarus clarkii in Europe: Impacts on aquatic ecosystems and human well-being     

《Limnologica》2016

Procambarus clarkii is currently recorded from 16 European territories. On top of being a vector of crayfish plague, which is responsible for large-scale disappearance of native crayfish species, it causes severe impacts on diverse aquatic ecosystems, due to its rapid life cycle, dispersal capacities, burrowing activities and high population densities. The species has even been recently discovered in caves. This invasive crayfish is a polytrophic keystone species that can exert multiple pressures on ecosystems. Most studies deal with the decline of macrophytes and predation on several species (amphibians, molluscs, and macroinvertebrates), highlighting how this biodiversity loss leads to unbalanced food chains. At a management level, the species is considered as (a) a devastating digger of the water drainage systems in southern and central Europe, (b) an agricultural pest in Mediterranean territories, consuming, for example, young rice plants, and (c) a threat to the restoration of water bodies in north-western Europe. Indeed, among the high-risk species, P. clarkii consistently attained the highest risk rating. Its negative impacts on ecosystem services were evaluated. These may include the loss of provisioning services such as reductions in valued edible native species of regulatory and supporting services, inducing wide changes in ecological communities and increased costs to agriculture and water management. Finally, cultural services may be lost. The species fulfils the criteria of the Article 4(3) of Regulation (EU) No 1143/2014 of the European Parliament (species widely spread in Europe and impossible to eradicate in a cost-effective manner) and has been included in the “Union List”. Particularly, awareness of the ornamental trade through the internet must be reinforced within the European Community and import and trade regulations should be imposed to reduce the availability of this high-risk species.  相似文献