Results 261 to 270 of about 34,135 (304)

Nitrogen and Oxygen Isotopic Studies of the Marine Nitrogen Cycle

Annual Review of Marine Science, 2016
The 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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Isotopic Labelling of Leaf Litter Nitrogen

2020
Plant material enriched in stable isotopes such as 13C and 15N can provide detailed insights into the fate of carbon and nitrogen during litter decomposition on land and in water. Large amounts (>1 kg) of labelled material are often needed for partitioning isotopic tracers in food webs and quantifying elemental fluxes at the ecosystem scale.
Bernd Zeller, Severine Bienaimé, Etienne Dambrine   +2 more
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Stable isotope studies of soil nitrogen

2020
Sound generalisations and predictions of soil processes are difficult to make with confidence because of the chemical, physical and biological variations that occur in soil at all scales in both space and time. Natural abundance studies have been used in a wide range of soil-nitrogen (N) investigations and have provided some insights to the complexity ...
D.W. Hopkins, R.E. Wheatley, D. Robinson
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Nitrogen Isotope Distribution as a Presumptive Indicator of Nitrogen Fixation

Botanical Gazette, 1979
The generally lower 15N/14N ratio of nitrogen-fixing organisms provides an opportunity to screen mixed populations for individuals fixing nitrogen. Samplings of associated California native species, along with the soil on which they were found, show differences in 15N/14N ratios suggesting a capability among some for the fixation of nitrogen.
C. C. Delwiche, P. J. Zinke, C. M. Johnson, R. A. Virginia   +3 more
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Isotopic evidence of nitrogen sources and nitrogen transformation in arsenic-contaminated groundwater

Science of The Total Environment, 2017
High concentrations of naturally occurring arsenic (As) are typically found in young alluvial and deltaic deposits, and high concentrations of ammonium (NH4+) and nitrate (NO3-) are often present in groundwater affected by anthropogenic activities. In this study, on the basis of physicochemical characteristics of groundwater and the nitrogen and oxygen
Tsung-Nan, Weng, Chen-Wuing, Liu, Yu-Hsuan, Kao, Silver Sung-Yun, Hsiao   +3 more
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Theoretical Analysis of Separating Nitrogen Isotopes by Ion-Exchange, (II).

Journal of Nuclear Science and Technology, 1997
To mathematically simulate the ion exchange isotope separation processes, a set of differential equations have been derived and numerically solved with the second order accurate explicit TVD scheme, using the system parameters for 15N isotope separation reported by Spedding et al.
Eiji AOKI, Tsunetoshi KAI, Yasuhiko FUJII   +2 more
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Assay of Isotopic Nitrogen by Mass-Spectrometer

Nature, 1958
IN a recent communication, Capindale and Tomlin1 have pointed out some of the difficulties in measuring accurately the abundance of isotopic nitrogen (nitrogen-15), a measurement which is generally required when this isotope is used as a tracer in biological experiments.
A. P. SIMS, E. C. COCKING
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Isotope Shifts of Nitrogen around 800 nm

Chinese Journal of Chemical Physics, 2016
The Doppler-limited absorption spectra of 14N and 15N atoms were measured around 800 nm using concentration modulation spectroscopy to study their isotope shifts. The nitrogen atoms were generated by discharging molecular nitrogen buffered with helium in a home-made discharge tube.
Jiao Bai, Hai-ling Wang, Xue Ni, Lun-hua Deng   +3 more
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Reporting of nitrogen-isotope abundances (Technical Report)

Pure and Applied Chemistry, 1992
Abstract
Tyler B. Coplen, H. R. Krouse, John Karl Böhlke   +2 more
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Isotopic composition of atmospheric oxygen and nitrogen

Geochimica et Cosmochimica Acta, 1954
High altitude air samples collected in glass bulbs during balloon flights up to heights of 87,000 ft were found to contain oxygen with a normal isotope ratio, deviations less than ±0·05%. Air samples collected in Aerobee rockets up to altitudes of 51·6 km contained nitrogen having a normal isotope ratio, deviations less than ±0·15%.
Malcolm Dole, G.A. Lane, D.P. Rudd, D.A. Zaukelies   +3 more
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