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191.
Graphitic carbon is a widespread precipitate in terrestrial and extraterrestrial samples. However it has a range of possible origins, which can be difficult to distinguish, including the in situ alteration of organic matter, thermal alteration of hydrocarbons, and precipitation from C–O–H fluids. Petrographic characteristics help to understand the origin of the graphite, including relationships with rock fabric, paragenetic sequences and evidence for fluid mobility. Characterization of a range of terrestrial samples will allow better interpretation of the petrography of carbon in extraterrestrial samples. In particular, improved petrographic data from carbonaceous chondrites and ureilite meteorites should help to distinguish the origin of carbon in their parent bodies. 相似文献
192.
Stephanie K. Kampf Scott W. Tyler Cristin A. Ortiz Jos F. Muoz Paula L. Adkins 《Journal of Hydrology》2005,310(1-4):236-252
Playa systems are driven by evaporation processes, yet the mechanisms by which evaporation occurs through playa salt crusts are still poorly understood. In this study we examine playa evaporation as it relates to land surface energy fluxes, salt crust characteristics, groundwater and climate at the Salar de Atacama, a 3000 km2 playa in northern Chile containing a uniquely broad range of salt crust types. Land surface energy budget measurements were taken at eight representative sites on this playa during winter (August 2001) and summer (January 2002) seasons. Measured values of net all-wave radiation were highest at vegetated and rough halite crust sites and lowest over smooth, highly reflective salt crusts. Over most of the Salar de Atacama, net radiation was dissipated by means of soil and sensible heat fluxes. Dry salt crusts tended to heat and cool very quickly, whereas soil heating and cooling occurred more gradually at wetter vegetated sites. Sensible heating was strongly linked to wind patterns, with highest sensible heat fluxes occurring on summer days with strong afternoon winds. Very little energy available at the land surface was used to evaporate water. Eddy covariance measurements could only constrain evaporation rates to within 0.1 mm d−1, and some measured evaporation rates were less than this margin of uncertainty. Evaporation rates ranged from 0.1 to 1.1 mm d−1 in smooth salt crusts around the margin of the salar and from 0.4 to 2.8 mm d−1 in vegetated areas. No evaporation was detected from the rugged halite salt crust that covers the interior of the salar, though the depth to groundwater is less than 1 m in this area. These crusts therefore represent a previously unrecorded end member condition in which the salt crusts form a practically impermeable barrier to evaporation. 相似文献
193.
The ratios of the carbon isotopes 13C and 12C of twenty-four graphite samples from Bogala Mine, Sri Lanka have been determined. The graphites are isotopically very similar (mean value ; range ). Three models for the biogenic or abiogenic origin of the graphite deposit are discussed. 相似文献
194.
The thermodynamics of quadrilateral pyroxene solutions have been analysed with the ternary non-convergent site-disorder model developed in Part I. Solution parameters have been refined for this model with a non-linear least squares technique to fit experimentally determined phase equilibria for the assemblages orthopyroxene-clinopyroxene (opx-cpx), pigeonite-augite (pig-aug), and opx-pig-aug. Calculated phase relations agree, within error, with experiments. Predicted cation distributions and enthalpies of solution for opx are also in agreement with measurements. Predicted cation distributions for cpx are more disordered than indicated by most available measurements. Two types of pyroxene thermometers are presented: (a) a single-pyroxene (aug) thermometer, and (b), a two-pyroxene thermometer which approximates the temperature of an observed pig-aug or cpx-opx assemblage as that of its nearest model tieline. Pyroxene pairs from two granulite suites, whose compositions were projected to the ternary system by the method of Lindsley and Andersen (1983), yield temperatures that are 25° C higher by thermometers (a) and (b) than determined from Lindsley's (1983) graphical thermometer. Temperatures calculated for projected compositions of coexisting pig-aug are within 20° C of run temperatures in experiments by Grove and Bryan (1983). 相似文献
195.
The purpose of this study is to analyze the development of the HIV epidemic in Finland in 1983–1994, and to predict the spatial distribution of new cases through 1997. The analysis is based on seroepidemiological data of all reported HIV carriers and a number of explaining variables based on individual level register data. Instead of focusing on populations of carriers and susceptibles, emphasis is placed on identifying the primary influences directing the epidemic as a spatial process. This is done by dividing Finland into 62 functional small area units and by assigning the risk of obtaining the virus to each unit based on behavioral, socioeconomic, interaction, and structural characteristics of the population. The approach is a multistep procedure including multivariate regression analysis, the potential model, and time series analysis. The model was used to produce a three-year forecast of the distribution of new HIV carriers in Finland. Compared with earlier studies of similar nature based on the use of administrative regional units, in this paper the forecast distribution of HIV cases is more closely related to the functional structure of the spatial system in Finland. Such an approach offers a method for producing more reliable short-term forecasts of the spatial distribution of new HIV cases. Three different spatial diffusion patterns were identified. 相似文献
196.
Although studies have demonstrated significant associations between ENSO events and dengue fever, few have explored regional impacts on dengue fever of separate events. This study explores the impacts of two ENSO events on regional patterns of dengue/ dengue haemorrhagic fever (DHF) incidence in Indonesia. Data consist of monthly cases of dengue/DHF from 1992 to 2001 for each of Indonesia's 27 provinces, and monthly figures for rainfall, rainfall anomalies, temperature, relative humidity and the Southern Oscillation Index (SOI). We conducted Pearson correlation analyses for each independent variable against dengue/DHF incidence, using a direct month‐by‐month correlation and applying a lag of between one and six months to each variable with respect to dengue/DHF incidence. Based on the SOI value, we identified two ENSO events between 1992 and 2001. To explore each event, we created two dummy variables and in regression analyses for eight provinces. The variance of between 12.9 per cent and 24.5 per cent in provincial dengue/DHF incidence is explained by two or three climate variables in each of the provinces (p < 0.01 to 0.1). During the 1997/98 event, the explained variance increased by between 7 per cent and 15 per cent in provinces whose climate regimes were most affected by this event. This study demonstrates that indicators of ENSO such as the SOI may assist in the forecast of potential dengue/DHF incidence and distribution in Indonesia. 相似文献
197.
Victor?Brunini?MoretoEmail author Glauco?de Souza?Rolim Bruno?Gustavo?Zacarin Ana?Paula?Vanin Leone?Maia?de?Souza Rodrigo?Rocha?Latado 《Theoretical and Applied Climatology》2017,130(3-4):847-864
Forecasting is the act of predicting unknown future events using available data. Estimating, in contrast, uses data to simulate an actual condition. Brazil is the world’s largest producer of oranges, and the state of São Paulo is the largest producer in Brazil. The “Valência” orange is among the most common cultivars in the state. We analyzed the influence of monthly meteorological variables during the growth cycle of Valência oranges grafted onto “Rangpur” lime rootstocks (VACR) for São Paulo, and developed monthly agrometeorological models for forecasting the qualitative attributes of VACR in mature orchard. For fruits per box for all months, the best accuracy was of 0.84 % and the minimum forecast range of 4 months. For the relation between °brix and juice acidity (RATIO) the best accuracy was of 0.69 % and the minimum forecast range of 5 months. Minimum, mean and maximum air temperatures, and relative evapotranspiration were the most important variables in the models. 相似文献
198.
Fatal landslides in Europe 总被引:4,自引:3,他引:1
Ubydul Haque Philipp Blum Paula F. da Silva Peter Andersen Jürgen Pilz Sergey R. Chalov Jean-Philippe Malet Mateja Jemec Auflič Norina Andres Eleftheria Poyiadji Pedro C. Lamas Wenyi Zhang Igor Peshevski Halldór G. Pétursson Tayfun Kurt Nikolai Dobrev Juan Carlos García-Davalillo Matina Halkia Stefano Ferri George Gaprindashvili Johanna Engström David Keellings 《Landslides》2016,13(6):1545-1554
Landslides are a major hazard causing human and large economic losses worldwide. However, the quantification of fatalities and casualties is highly underestimated and incomplete, thus, the estimation of landslide risk is rather ambitious. Hence, a spatio-temporal distribution of deadly landslides is presented for 27 European countries over the last 20 years (1995–2014). Catastrophic landslides are widely distributed throughout Europe, however, with a great concentration in mountainous areas. In the studied period, a total of 1370 deaths and 784 injuries were reported resulting from 476 landslides. Turkey showed the highest fatalities with 335. An increasing trend of fatal landslides is observed, with a pronounced number of fatalities in the latest period from 2008 to 2014. The latter are mostly triggered by natural extreme events such as storms (i.e., heavy rainfall), earthquakes, and floods and only minor by human activities, such as mining and excavation works. Average economic loss per year in Europe is approximately 4.7 billion Euros. This study serves as baseline information for further risk mapping by integrating deadly landslide locations, local land use data, and will therefore help countries to protect human lives and property. 相似文献
199.
200.
Paula Meth 《Area》2003,35(2):195-205
This paper explores the use of personal solicited diaries as a qualitative research tool within social geography. Diaries were used with women from South Africa who recorded their experiences of violence over a period of one month. The paper analyses diaries in terms of their longitudinal benefits, their socially constituted nature, their use in conjunction with interviews and finally their potential for empowerment. The paper concludes with a discussion of the limitations of the diary as a methodological tool. 相似文献