نتایج جستجو برای: environmental isotopes
تعداد نتایج: 393385 فیلتر نتایج به سال:
a total of 40 samples from carbonates and 8 samples from silicate rocks were analyzed from the sangan iron skarn deposit to examine behavior of the oxygen and carbon isotopes. the higher values of ?18o are from metamorphic calcite and dolomite and lower ones are from granitic rocks. although the ?18o and ?13c values of calcite and dolomite in marble yield the highest values in the sangan deposi...
a total of 40 samples from carbonates and 8 samples from silicate rocks were analyzed from the sangan iron skarn deposit to examine behavior of the oxygen and carbon isotopes. the higher values of ?18o are from metamorphic calcite and dolomite and lower ones are from granitic rocks. although the ?18o and ?13c values of calcite and dolomite in marble yield the highest values in the sangan deposi...
We demonstrate that nucleosynthesis in rapid, high-entropy expansions of proton-rich matter from high temperature and density can result in a wider variety of abundance patterns than heretofore appreciated. In particular, such expansions can produce iron-group nuclides, p-process nuclei, or even heavy, neutron-rich isotopes. Such diversity arises because the nucleosynthesis enters a little expl...
Study of nucleosynthesis in accretion disks around black holes was initiated by Chakrabarti et al. (1987). In the present work we do the similar analysis using the state-of-the-art disk model, namely, Advective Accretion Disks. During the infall, matter temperature and density are generally increased which are first computed. These quantities are used to obtain local changes in composition, amo...
Between 1950 and 1963 approximately 11 million kilograms of mercury (Hg) were used at the Oak Ridge Y-12 National Security Complex (Y-12 NSC) for lithium isotope separation processes. About 3% of the Hg was lost to the air, soil and rock under facilities, and East Fork Poplar Creek (EFPC) which originates in the plant site. Smaller amounts of Hg were used at other Oak Ridge facilities with simi...
OBJECTIVES The Rapa Nui "ecocide" narrative questions whether the prehistoric population caused an avoidable ecological disaster through rapid deforestation and over-exploitation of natural resources. The objective of this study was to characterize prehistoric human diets to shed light on human adaptability and land use in an island environment with limited resources. MATERIALS AND METHODS Ma...
Large numbers of the Globe Skimmer dragonfly (Pantala flavescens) appear in the Maldives every October-December. Since they cannot breed on these largely waterless islands, it has recently been suggested that they are "falling out" during a trans-oceanic flight from India to East Africa. In addition, it has been suggested that this trans-oceanic crossing is just one leg of a multi-generational ...
Trophic segregation has been proposed as a major mechanism explaining the coexistence of closely related animal taxa. However, how such segregation varies throughout the annual cycle is poorly understood. Here, we examined the feeding ecology of the two subspecies of Cory's shearwater, Calonectris diomedea diomedea and Calonectris diomedea borealis, breeding in sympatry in a Mediterranean colon...
This paper describes an ecological study investigating whether there is an excess incidence of acute leukaemia among children aged 0-14 years living in the vicinity of the nuclear sites in Belgium. Poisson regression modelling was carried out for proximity areas of varying sizes. In addition, the hypothesis of a gradient in leukaemia incidence with increasing levels of surrogate exposures was e...
Stable heavy isotopes co-exist with their lighter counterparts in all elements commonly found in biology. These heavy isotopes represent a low natural abundance in isotopic composition but impose great retardation effects in chemical reactions because of kinetic isotopic effects (KIEs). Previous isotope analyses have recorded pervasive enrichment or depletion of heavy isotopes in various organi...
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