Iron oxidation state in the Fe‐rich layer and silica matrix of Libyan Desert Glass: A high‐resolution XANES study     

Gabriele Giuli  Eleonora Paris  Giovanni Pratesi  Christian Koeberl  Curzio Cipriani 《Meteoritics & planetary science》2003,38(8):1181-1186

Abstract— Libyan Desert Glass (LDG) is an enigmatic type of glass that occurs in western Egypt in the Libyan Desert. Fairly convincing evidence exists to show that it formed by impact, although the source crater is currently unknown. Some rare samples present dark‐colored streaks with variable amounts of Fe, and they are supposed to contain a meteoritic component. We have studied the iron local environment in an LDG sample by means of Fe K‐edge highresolution X‐ray absorption near edge structure (XANES) spectroscopy to obtain quantitative data on the Fe oxidation state and coordination number in both the Fe‐poor matrix and Fe‐rich layers. The pre‐edge peak of the high‐resolution XANES spectra of the sample studied displays small but reproducible variations between Fe‐poor matrix and Fe‐rich layers, which is indicative of significant changes in the Fe oxidation state and coordination number. Comparison with previously obtained data for a very low‐Fe sample shows that, while iron is virtually all trivalent and in tetrahedral coordination (^[4]Fe³⁺) in the low‐Fe sample, the sample containing the Fe‐rich layers display a mixture of tetra‐coordinated trivalent iron (^[4]Fe³⁺) and penta‐coordinated divalent iron (^[5]Fe²⁺), with the Fe in the Fe‐rich layer being more reduced than the matrix. From these data, we conclude the following: a) the significant differences in the Fe oxidation state between LDG and tektites, together with the wide intra‐sample variations in the Fe‐oxidation state, confirm that LDG is an impact glass and not a tektite‐like glass; b) the higher Fe content, coupled with the more reduced state of the Fe, in the Fe‐rich layers suggests that some or most of the Fe in these layers may be directly derived from the meteoritic projectile and that it is not of terrestrial origin.  相似文献   

Technique for Controlling Spread of Limnotic Oncomelania   总被引：1，自引：0，他引：1  

李大美  王祥三  LAI Yonggen 《中国海洋湖沼学报》2003,21(3):251-260

Schistosomiasis is a parasitic disease mostly found in areas along the Changjiang River of China. The disease is spread solely through an intermediary named oncomelania, so its spread of schistosomiasis can be controlled by properly designing water intakes which prevent oncomelania from entering farming land or residential areas. This paper reports a successful design process and a new oncomelania-free intake device. The design of the new intake is based on a sound research program in which extensive experimental studies were carried out to gain knowledge of oncomelania eco-hydraulic behavior and detailed flow field information through CFD simulation.  相似文献   

MHD simulations of the long-term evolution of a dipolar magnetosphere surrounded by an accretion disk     

Christian Fendt 《Astrophysics and Space Science》2003,287(1-4):59-64

The evolution of a stellar, initially dipole type magnetosphere interacting with an accretion disk is investigated using numerical ideal MHD simulations. The simulations follow several 1000 Keplerian periods of the inner disk (for animated movies see http://www.aip.de～cfendt).Our model prescribes a Keplerian disk around a rotating star as a fixed boundary condition. The initial magnetic field distribution remains frozen into the star and the disk. The mass flow rate into the corona is fixed for both components. The initial dipole type magnetic field develops into a spherically radial outflow pattern with two main components – a disk wind and a stellar wind – both evolving into a quasi-stationary final state. A neutral field line divides both components, along which small plasmoids are ejected in irregular time intervals. The half opening angle of the stellar wind cone varies from 30° to55° depending on the ratio of the mass flow rates of disk wind and stellar wind. The maximum speed of the outflow is about the Keplerian speed at the inner disk radius. An axial jet forms during the first decades of rotations. However, this feature does not survive on the very long time scale and a pressure driven low velocity flow along the axis evolves. Within a cone of 15° along the axis the formation of knots may be observed if the stellar wind is weak. With the chosen mass flow rates and field strength we see almost no indication for a flow self-collimation. This is due to the weak net poloidal electric current in the magnetosphere which is in difference to typical jet models.  相似文献   

Report on Pontoniinae shrimps （Crustacea：Decapoda）collected by Joint Chinese—German Marine Biology Expeditions to Hainan lsland ,South China Sea：Ⅱ.Harpiliopsis,Ischnopontonia,Jocaste,Palae—mone     

李新正  刘瑞玉 《中国海洋湖沼学报》2003,21(2):154-165

The present paper reports 9 species of pontoniine shrimps collected from Hainan IS-land ,South China Sea ,by the Joint Chinese-German Marine Biology Expeditions,in which Peri-climenaeus arabicus (Calman,1939) and Periclimenaeus hecate (Nobili,1904) are recorded for the first time from Hainan Island.  相似文献   

Carbon isotope fractionation between graphite and diamond during shock experiments     

Teruyuki Maruoka  Christian Koeberl  Jun‐ichi Matsuda  Yasuhiko Syono 《Meteoritics & planetary science》2003,38(8):1255-1262

Abstract— Carbon isotopic compositions were measured for shock‐produced diamond and shocked graphite formed at peak pressures ranging from 37 to 52 GPa. The δ¹³C values of diamonds produced in a sealed container were generally lower than that of the initial graphite. The differences in the carbon isotopic composition between initial graphite and shocked graphite/diamond may reflect kinetic isotopic fractionation during the oxidation of the graphite/diamond and/or analytical artifacts possibly induced by impurities in the samples. The pressure effect on the isotopic fractionations between graphite and diamond can be estimated from the δ¹³C values of impurity‐free diamonds produced using a vented container from which gases, including oxygen, in pore spaces escaped during or after the diamond formation (e.g., 0.039 ± 0.085‰ at a peak pressure of 52 GPa). Any isotopic fractionation induced by shock conversion of graphite to diamond is too small to be detected in natural shock‐induced diamond‐graphite systems related to terrestrial impact cratering processes.  相似文献   

APPLICATION OF GEOGRAPHICAL PARAMETER DATABASE TO ESTABLISHMENT OF UNIT POPULATION DATABASE   总被引：1，自引：1，他引：0  

DONG Chun  ZHAO Rong  LIU Ji-ping  WANG Gui-xin  WU Xi-zhi 《中国地理科学(英文版)》2003,13(1):34-38

Now GIS is turning into a good tool in handling geographical, economical, and population data, so we can obtain more and more information from these data. On the other hand, in some cases, for a calamity, such as hurricane, earthquake, flood, drought etc., or a decision-making, such as setting up a broadcasting transmitter, building a chemical plant etc., we have to evaluate the total population in the region influenced by a calamity or a project. In this paper, a method is put forward to evaluate the population in such special region. Through exploring the correlation of geographical parameters and the distribution of people in the same region by means of quantitative analysis and qualitative analysis, unit population database (1km× 1km) is established. In this way, estimating the number of people in a special region is capable by adding up the population in every grid involved in this region boundary. The geographical parameters are obtained from topographic database and DEM database on the scale of  相似文献   

EMERGY ANALYSIS OF GRAIN PRODUCTION SYSTEM IN JIANGSU AND SHAANXI PROVINCES     

LIUXin-wei CHENBai-ming ZHANGDing-xiang 《中国地理科学(英文版)》2004,14(3):209-214

Efficiency and sustainability of grain production are now important in China. In this study, the grain production systems of Jiangsu and Shaanxi Provinces were compared, to analyze their efficiency and sustainability in terms of utilization of natural resources, inputs of purchased energy and materials, and outputs. Flows of energy and materials between environment and human society were identified, and the natural and human work involved in generating inputs as materials or energy were valued in terms of equivalent amount of solar energy required for their production using emergy method. The results showed environmental resources were continually playing a less important role in the systems, when inorganic subsidiary emergy inputs increased drastically while organic ones decreased or increased little. Deterioration of input emergy structure affected the systems‘ efficiency and sustainability, resulting in emergy investment ratios and environmental loading ratios increasing while yield ratios and sustainability indices decreasing. In general, efficiency and sustainability of grain production in Jiangsu are worse than those in Shaanxi. This analysis also suggested that inorganic subsidiary emergy should be introduced properly, and peasants in Jiangsu should utilize natural conditions wisely while those in Shaanxi pay enough attention to soil and surface water conservation.  相似文献   

CORRESPONDENCE ANALYSIS ON IMAGES OF JIANGXI PROVINCE AS A TOURIST DESTINATION   总被引：4，自引：0，他引：4  

MAO Duan-qian ZHANG Jie BAO Hao-sheng 《中国地理科学(英文版)》2005,15(3):275-280

1IN T R O D U C T IO NAn image isa setofbelief,s ideasand impressionsthatapersonholdsaboutan object(KOTLER,1991).Similar-lydefinitionistheimage of a destinationas thesum ofbelief,sideasand impressionsthatpeoplehave ofa placeor destination(CROMPTON,1979;KO…  相似文献   

Petroleum Hydrocarbon Distribution Features in Water and Sediment off Fujian Shore   总被引：1，自引：0，他引：1  

王宪  徐鲁荣  李文权  李凌云  钱爱红 《中国海洋湖沼学报》2003,21(2):187-192

This study on the distribution features of petroleum hydrocarbon in water and sedi-ment off the Fujian shore using data obtained from the baseline research on oceanic contamination in Fujian showed that:during the research preiod,petroleum hydrocarbon concentrations in water varied from 5.77μg/L to 37.28μg/L,averaged 14.48 μg/L;was lower in the wet seasson than in the dry season;and was highest in the Minjiang Estuary and Jiulong Estuary in both seasons ,The petorleum hydrocarbon concentrations in shore sediment varied from 14.48 mg/kg to 784.36 mg/kg,averaged 133.3 mg/kg ,and was closely related to sediment types (granularity).  相似文献   

Is Precipitation the Dominant Controlling Factor of High Inorganic Nitrogen Content in the Changjiang River and Its Mouth？   总被引：1，自引：1，他引：0  

沈志良 《中国海洋湖沼学报》2003,21(4):368-376

The main reasons for the high content of inorganic N and its increase by several times in the Changjiang River and its mouth during the last 40 years were analysed in this work. The inorganic N in precipitation in the Changjiang River catchment mainly comes from gaseous loss of fertilizer N, N resulting from the increases of population and livestock, and from high temperature combustions of fossil fuels. N from precipitation is the first N source in the Changjiang River water and the only direct cause of high content of inorganic N in the Changjiang River and its mouth. The lost N in gaseous form and from agriculture non-point sources fertilizer comprised about 60% of annual consumption of fertilizer N in the Changjiang River catchment and were key factors controlling the high content of inorganic N in the Changjiang River mouth. The fate of the N in precipitation and other N sources in the Changjiang River catchment are also discussed in this paper.  相似文献