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311.
312.
There is little empirical evidence on the association between household experience with HIV/AIDS and shifts in the use of natural resources in developing countries, where residents of rural regions remain highly dependent on often-declining local supplies of natural resources. This study examines household strategies with regard to fuelwood and water among impoverished rural South African households having experienced a recent adult mortality and those without such mortality experience. Quantitative survey data reveal higher levels of natural resource dependence among mortality-affected households, as well as differences in collection strategies. Qualitative interview data provide insight into subtle and complex adjustments at the household level, revealing that impacts vary by the role of the deceased within the household economy. Resource management and public health implications are explored. 相似文献
313.
Li isotopes and trace elements as a petrogenetic tracer in zircon: insights from Archean TTGs and sanukitoids 总被引:1,自引:0,他引:1
Anne-Sophie Bouvier Takayuki Ushikubo Noriko T. Kita Aaron J. Cavosie Reinhard Kozdon John W. Valley 《Contributions to Mineralogy and Petrology》2012,163(5):745-768
We report δ7Li, Li abundance ([Li]), and other trace elements measured by ion probe in igneous zircons from TTG (tonalite, trondhjemite,
and granodiorite) and sanukitoid plutons from the Superior Province (Canada) in order to characterize Li in zircons from typical
Archean continental crust. These data are compared with detrital zircons from the Jack Hills (Western Australia) with U–Pb
ages greater than 3.9 Ga for which parent rock type is not known. Most of the TTG and sanukitoid zircon domains preserve typical
igneous REE patterns and CL zoning. [Li] ranges from 0.5 to 79 ppm, typical of [Li] in continental zircons. Atomic ratios
of (Y + REE)/(Li + P) average 1.0 ± 0.7 (2SD) for zircons with magmatic composition preserved, supporting the hypothesis that
Li is interstitial and charge compensates substitution of trivalent cations. This substitution results in a relatively slow
rate of Li diffusion. The δ7Li and trace element data constrain the genesis of TTGs and sanukitoids. [Li] in zircons from granitoids is significantly
higher than from zircons in primitive magmas in oceanic crust. TTG zircons have δ7Li (3 ± 8‰) and δ18O in the range of primitive mantle-derived magmas. Sanukitoid zircons have average δ7Li (7 ± 8‰) and δ18O higher than those of TTGs supporting genesis by melting of fluid-metasomatized mantle wedge. The Li systematics in sanukitoid
and TTG zircons indicate that high [Li] in pre-3.9-Ga Jack Hills detrital zircons is a primary igneous composition and suggests
the growth in proto-continental crust in magmas similar to Archean granitoids. 相似文献
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315.
Stephen Serjeant † Alberto Carramiñana † Eduardo Gonzáles-Solares Phillipe Héraudeau Raúl Mújica † Ismael Perez-Fournon Nicola Sedgwick † Michael Rowan-Robinson Alberto Franceschini Thomas Babbedge Carlos del Burgo Paolo Ciliegi reas Efstathiou Fabio La Franca Carlotta Gruppioni David Hughes Carlo Lari Seb Oliver Francesca Pozzi Manfred Stickel Mattia Vaccari 《Monthly notices of the Royal Astronomical Society》2004,355(3):813-818
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Lourdes De Juan Luis Colina Ismael Pérez-Fournon 《Astrophysics and Space Science》1993,205(1):209-216
We have used a numerical method based on elliptical fitting of isophotes to analyse the structural parameters of three pairs of elliptical galaxies containing radio jets. The relationship between tidal interactions and radio activity is also investigated. 相似文献
319.
Christina R. Pondell Aaron J. Beck Steven A. Kuehl Elizabeth A. Canuel 《Aquatic Geochemistry》2016,22(2):97-115
The determination of sediment accumulation rates in environments with temporal variations in texture is challenging using traditional radioisotope methods, largely due to low activities associated with coarse sediments. This study used Englebright Lake, an impoundment in northern California, as a model system to examine the application of plutonium isotopes in lacustrine environments where the interlayering of coarse and fine sediments complicates the geochronology. Inductively coupled plasma mass spectrometry was used to quantify plutonium isotopes and low limits of detection allowed for the measurement of plutonium in sand, clay, and silt fractions. Although measurable levels of plutonium were found in sand fractions, over 75 % of the total plutonium activity was found in fine-grain-size fractions (<63 μm). Correlations between cesium-137 and plutonium activities in fine-grained sediments (r = 0.81–0.98, p < 0.005) suggest that plutonium isotopes may be substituted for cesium isotopes in coarse-grained sediments where cesium is typically below detectable levels. Sediment accumulation rates calculated from grain-size normalized plutonium activity profiles ranged from 6 to 145 cm year?1 in Englebright Lake and identified a sediment depocenter at the delta front upstream of Englebright Dam. Progradation of the delta front reflected changes in sediment supply from the watershed in response to flood events, whereas average annual accumulation responded to human impacts. This study extends the application of plutonium isotopes for sediment geochronology to aquatic environments dominated by coarse sediments and provides new information that contributes to a better understanding of the processes influencing sediment deposition in Englebright Lake. 相似文献
320.
In this article we explore the spatial variation of support for former Soviet leader Joseph Stalin in his home country, Georgia. This research contributes to the literature on reputational politics by highlighting the role of spatial, rather than only social, factors in the construction of public opinion about Stalin. We illustrate how geographic factors impact Georgians' perceptions of the Soviet dictator by examining various aspects of place at various scales—including distance to Gori, Stalin's birthplace, the history of urbanization, and economic and political indices. To this end we map attitudes toward the Soviet dictator and use a multilevel spatial regression technique to explain variance in support for Stalin across forty-seven districts of Georgia. This enables us to explore the impact of place on people's attitudes by examining (1) whether there are local and regional hotspots of Stalin admiration and, if so, (2) what the contextual explanations of these attitudes are. 相似文献