Results 211 to 220 of about 128,824 (253)
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Nitrogen Isotopes in Palaeolimnology
2002Nitrogen is a small but essential constituent of all organisms and as such can be regarded as a key nutrient. Together with phosphorous and silicon, it is commonly viewed as one of the nutrients that ultimately limit organic productivity. Indeed, in many lakes, N is probably the limiting nutrient.
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Nitrogen isotope equilibration on molybdenum
Transactions of the Faraday Society, 1967The efficiency of a molybdenum wire as a catalyst for the nitrogen isotope equilibration reaction, 28N2+30N2= 229N2, has been studied for filament temperatures between 800 and 1900°K and nitrogen pressures between 1.8 × 10–7 and 1.8 × 10–6 torr. The efficiency was essentially independent of pressure and passed through a maximum of about 1.4 % at 1300°K.
R. P. H. Gasser, A. Hale, C. J. Marsay
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Nitrogen and Oxygen Isotopic Studies of the Marine Nitrogen Cycle
Annual Review of Marine Science, 2016The marine nitrogen cycle is a complex web of microbially mediated reactions that control the inventory, distribution, and speciation of nitrogen in the marine environment. Because nitrogen is a major nutrient that is required by all life, its availability can control biological productivity and ecosystem structure in both surface and deep-ocean ...
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Nitrogen Isotopes in the Ocean
2019This article outlines the isotope systematics of processes in the ocean nitrogen (N) cycle and their impact on the isotopic compositions of the major N forms, with an eye toward how the N isotopes may record current N fluxes and past changes.
Sigman, Daniel M, Fripiat, François
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Nitrogen Isotope Ratios in Comets
2008We used high S/N, high spectral resolution observations to determine the isotope ratios 12C/13C and 14N/15N in comets. Observations were obtained with resolving powers R=λ/δλ ≫ 60,000 with telescopes at McDonald Observatory, VLT, NOT and Keck. We have now observed 13 comets on 20 different dates with heliocentric distances ranging from 0.6 au to 3.7 au.
Anita L. Cochran +6 more
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Physiological mechanisms influencing plant nitrogen isotope composition
Trends in Plant Science, 2001Whole-plant and leaf nitrogen isotope composition are determined by the isotope ratio of the external nitrogen source and physiological mechanisms within the plant. Whole-plant isotope composition can reflect that of the nitrogen source when plant demand exceeds nitrogen supply.
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The marine nitrogen cycle: new developments and global change
Nature Reviews Microbiology, 2022David A Hutchins, Douglas G Capone
exaly