Results 301 to 310 of about 1,418,943 (330)
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Deuterium abundance of natural waters
Geochimica et Cosmochimica Acta, 1960Abstract The deuterium abundance of natural water of various sources has been determined by the use of a deuterium mass spectrometer. The absolute deuterium contents of the reference sample nos. 1 and 1a of the U.S. National Bureau of Standards were found to be 0·0149 and 0·0128 mole % D2O, respectively, by the comparison of the samples with the ...
Yoshio Horibe, Mituko Kobayakawa
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Natural 15N abundance in soils
1997According to the classical definition, the isotopic composition or relative abundance of an element is a fixed value, and the behaviour of the light and heavy isotopes in chemical reactions is strictly identical. These are two basic assumptions for conducting tracer experiments with stable isotopes.
Guangxi Xing, Guo-Qing Sun, Ya-Cheng Cao
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Geochimica et Cosmochimica Acta, 1962
Abstract Upper limits of less than one part per billion have been established by mass spectrometry for U-233, U-236, and U-237 isotopes in uranium from samples of Belgian Congo pitchblende and Colorado Carnotite. The new upper limit of one-half part per billion U-236 in the pitchblende is smaller than would be expected from the measured Pu-239:U-238 ...
W.D Davis, J.L Mewherter
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Abstract Upper limits of less than one part per billion have been established by mass spectrometry for U-233, U-236, and U-237 isotopes in uranium from samples of Belgian Congo pitchblende and Colorado Carnotite. The new upper limit of one-half part per billion U-236 in the pitchblende is smaller than would be expected from the measured Pu-239:U-238 ...
W.D Davis, J.L Mewherter
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NMR imaging of 15N at natural abundance
Journal of Magnetic Resonance (1969), 1992*‘N observation at natural abundance (0.37% of total nitrogen) has become conventional in NMR spectroscopic studies on liquids since the first report in 197 1 ( 1) . This technique has also been useful for solving problems in solids (2). Experiments involving enriched material have proved to be important in labeling studies in chemical applications (3))
Edward W. Randall +2 more
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THE NATURAL ABUNDANCES OF THE URANIUM ISOTOPES
Canadian Journal of Chemistry, 1956Using a surface-ionization mass spectrometer, the natural U238/U235 abundance ratio in uranium obtained from Great Bear Lake Pitchblende has been measured to be 137.80 ± 0.14. From a survey of results reported in the literature on U234 a best value of 17,325 ± 550 was estimated for the natural U238/U234 abundance ratio.
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Specialization dynamics and natural resources abundance
Review of World Economics, 2012This paper uses a large sample of countries for the last four decades to document how specialization dynamics differ depending on the abundance of natural resources. We show interesting stylized facts on two main issues. First, we do not find evidence that comparative advantage in resource-intensive products is necessarily more persistent than ...
Alvarez, Roberto, Rodrigo Fuentes, J.
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Abundances and Nature of the Absorbers
1995Observations of low redshift (z < 0.5) Lymanα lines by HST and detection of galaxies in the neighbourhood of the corresponding clouds have cast a new light and a shadow on the question of what is the nature of the Lymanα forest and in particular what is the connection between the absorbing gas and galaxies.
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Tritium Abundance in Belgrade Natural Waters
Isotopenpraxis Isotopes in Environmental and Health Studies, 1990Data on the tritium abundance in precipitation, the Sava, the Danube and water bearing layers at the Sava alluvium in Belgrade region during 1976–88 are presented. Tritium content in precipitation mostly fluctuates from 1.1 to 18.3 Bq/l. Similar values between 0.4 and 16.8 Bq/l were obtained in the Sava and in the lower layer (17–30m), while in the ...
Nada Miljević +5 more
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Species Abundance: Natural Regulation of Insular Variation [PDF]
Science, 1963 Variation in numbers of land plant species on islands in the Galapagos Archipelago can be predicted on the basis of elevation, area of the adjacent island, distance from the nearest island, and distance from the center of the archipelago, but not on the basis of the area of the host island. Multiple linear regression (y = bx 1
Terrell H. Hamilton +3 more
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Natural Abundance of the Lithium Isotopes
Physical Review, 1954The natural abundance ratio of the lithium isotope of mass 7 to the isotope of mass 6 has been determined from the density and x-ray data for certain crystals. Consideration of the maximum limits of variation of this ratio in nature and the error assignments of the data used in this calculation have resulted in the value 11.53\ifmmode\pm\else\textpm\fi{
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