祁连山地区能量平衡特征的模拟分析研究

利用VIC大尺度分布式水文模型,对祁连山地区2007年1—12月的能量平衡特征进行模拟分析.结果表明:该地区的地表能量平衡中感热通量占有主导地位,而潜热较小.春季,日尺度上的冻融循环过程造成的土壤湿度的增加是潜热通量较大原因;秋季的潜热通量主要是夏季的降水引起的,祁连山地区土壤湿度对大气的反馈效应较干旱区所需的时间尺度长.     

Geographical pattern analysis of income migration in the United States

"How one conceptualises the impacts of migration depends on whether one takes the viewpoint of aggregate area-level income change, of per capita change, or of longer-term (future earnings) change. Several empirical analytical measures are proposed in order to conceptualise the various income impacts of migration.... [A] decomposition procedure is developed for examining how the changes in per capita income of states reflect three different income differentials: those between (a) in-migrants and 'stayers', (b) out-migrants and 'stayers', and (c) in-migrants and out-migrants. Examination of these measures, and of typologies based on them, highlights how income migration significantly and differentially impacts upon U.S. states. The methods are illustrated here in the context of an important new American data source: the 1993-94 migrant income data released by the U.S. Internal Revenue Service."     

Acquisition and processing of data for isotope-ratio-monitoring mass spectrometry

Methods are described for continuous monitoring of signals required for precise analyses of 13C, 18O, and 15N in gas streams containing varying quantities of CO2 and N2. The quantitative resolution (i.e. maximum performance in the absence of random errors) of these methods is adequate for determination of isotope ratios with an uncertainty of one part in 10(5); the precision actually obtained is often better than one part in 10(4). This report describes data-processing operations including definition of beginning and ending points of chromatographic peaks and quantitation of background levels, allowance for effects of chromatographic separation of isotopically substituted species, integration of signals related to specific masses, correction for effects of mass discrimination, recognition of drifts in mass spectrometer performance, and calculation of isotopic delta values. Characteristics of a system allowing off-line revision of parameters used in data reduction are described and an algorithm for identification of background levels in complex chromatograms is outlined. Effects of imperfect chromatographic resolution are demonstrated and discussed and an approach to deconvolution of signals from coeluting substances described.     

藏南冲木达铜矿地质特征

藏南冲木达铜矿床属矽卡岩型铜矿床。矿区出露地层为上侏罗统—下白垩统桑日群比马组,遭受不同程度的矽卡岩化蚀变或区域浅变质作用。矿区铜矿(化)体主要赋存于比马组3~4段透辉石榴矽卡岩、矽卡岩化大理岩中,并主要产出于断裂构造带及其断裂两侧附近。铜矿(化)的形成经历了矽卡岩化阶段和热液硫化物阶段。     

Spatial and temporal variation in seagrass coverage in Southwest Florida: assessing the relative effects of anthropogenic nutrient load reductions and rainfall in four contiguous estuaries

The estuaries of Tampa Bay, Sarasota Bay, Lemon Bay, and Upper Charlotte Harbor are contiguous waterbodies located within the subtropical environment of Southwest Florida. Based on an examination of rainfall data over the period of record (1916-2001) within the watersheds of these estuaries, there is no evidence for spatial differences (at the watershed level) or monotonic trends in annual rainfall. During the 1980s, nitrogen loads into Tampa Bay and Sarasota Bay (generated primarily by domestic wastewater treatment facilities) were reduced by 57% and 46%, respectively. In response, both Tampa Bay and Sarasota Bay have lower phytoplankton concentrations, greater water clarity and more extensive seagrass coverage in 2002 than in the early 1980s. As there is no evidence of a concurrent trend in rainfall during the period of 1982-2001, it is unlikely that variation in rainfall can account for the observed increase in seagrass coverage in these two bays. In contrast, seagrass coverage has remained relatively constant since the mid 1980s in Lemon Bay and Charlotte Harbor. Domestic wastewater treatment facilities are minor sources of nitrogen to Lemon Bay, and water clarity in Charlotte Harbor varies mostly as a function of dissolved organic matter and non-chlorophyll associated turbidity, not phytoplankton levels. Even in estuaries that share boundaries and are within 100 km of each other, varied responses to anthropogenic changes and natural phenomena were observed in water quality and associated seagrass extent. Resource management strategies must take into account system-specific factors-not all strategies will result in similar results in different systems.     

Oxygen Absorption in Cooling Flows

The inhomogeneous cooling flow scenario predicts the existence of large quantities of gas in massive elliptical galaxies, groups, and clusters that have cooled and dropped out of the flow. Using spatially resolved, deprojected X-ray spectra from the ROSAT PSPC, we have detected strong absorption over energies approximately 0.4-0.8 keV intrinsic to the central approximately 1&arcmin; of the galaxy NGC 1399, the group NGC 5044, and the cluster A1795. These systems have among the largest nearby cooling flows in their respective classes and low Galactic columns. Since no excess absorption is indicated for energies below approximately 0.4 keV, the most reasonable model for the absorber is warm, collisionally ionized gas with T=105-106 K in which ionized states of oxygen provide most of the absorption. Attributing the absorption only to ionized gas reconciles the large columns of cold H and He inferred from Einstein and ASCA with the lack of such columns inferred from ROSAT and also is consistent with the negligible atomic and molecular H inferred from H i and CO observations of cooling flows. The prediction of warm ionized gas as the product of mass dropout in these and other cooling flows can be verified by Chandra and X-Ray Multimirror Mission.