نتایج جستجو برای: isotope composition

تعداد نتایج: 288405  

Journal: :Plant physiology 1979
A Shomer-Ilan A Nissenbaum M Galun Y Waisel

delta(13)C values of the lichens Ramalina duriaei and Teloschistes villosus collected in their natural habitat were repeatedly measured during 2 years. Results show variations in the stable carbon isotope ratios ((13)C/(12)C). Such variations are correlated to the seasonal rainfall, i.e. low values of delta(13)C of the lichens during the winter and high values of delta(13)C during the dry summe...

Journal: :Proceedings of the National Academy of Sciences of the United States of America 2012
Emily C Pope Dennis K Bird Minik T Rosing

Oxygen and hydrogen isotope compositions of Earth's seawater are controlled by volatile fluxes among mantle, lithospheric (oceanic and continental crust), and atmospheric reservoirs. Throughout geologic time the oxygen mass budget was likely conserved within these Earth system reservoirs, but hydrogen's was not, as it can escape to space. Isotopic properties of serpentine from the approximately...

2013
Jamie Wallis Nori Miyake Richard B. Hoover Andrew Oldroyd Daryl H. Wallis Anil Samaranayake K. Wickramarathne M. K. Wallis Carl H. Gibson N. C. Wickramasinghe

Results of X-Ray Diffraction (XRD) analysis, Triple Oxygen Isotope analysis and Scanning Electron Microscopic (SEM) studies are presented for stone fragments recovered from the North Central Province of Sri Lanka following a witnessed fireball event on 29 December 2012. The existence of numerous nitrogen depleted highly carbonaceous fossilized biological structures fused into the rock matrix is...

2003
D. E. Pataki D. R. Bowling J. R. Ehleringer

[1] Atmospheric CO2 mixing ratios and carbon and oxygen isotope composition were measured at 18 m above the ground in Salt Lake City, Utah, United States, for a one-year period. Mixing ratios were highest in the wintertime with maximum values approaching 600 mmolmol 1 during atmospheric inversions. Nighttime carbon and oxygen isotope ratios of source CO2 showed a seasonal pattern with isotopica...

2016
Jamileh Javidpour Ashlie N. Cipriano-Maack Agnes Mittermayr Jan Dierking

A temporal change in the stable isotope (SI) composition of jellyfish in the Kiel Fjord, Western Baltic Sea, was documented by analyzing δ13C, δ15N and δ34S of bell tissue of Aurelia aurita and Cyanea capillata in the period between June and October 2011. A strong and significant temporal change in all SI values of A. aurita was found, including an increase of ~3 ‰ in δ13C, a decrease of ~4 ‰ i...

2013
Arthur Gessler Elke Brandes Claudia Keitel Sonja Boda Zachary E Kayler André Granier Margaret Barbour Graham D Farquhar Kerstin Treydte

The oxygen stable isotope composition of plant organic matter (OM) (particularly of wood and cellulose in the tree ring archive) is valuable in studies of plant-climate interaction, but there is a lack of information on the transfer of the isotope signal from the leaf to heterotrophic tissues. We studied the oxygen isotopic composition and its enrichment above source water of leaf water over di...

2003
Takuya Tamura Atsunori Kamegawa Hitoshi Takamura Masuo Okada

Ti–Cr–V alloys are known to absorb protium (hydrogen atom) up to H/M = 2, while Cr-rich alloys absorb up to H/M = 1 because of the formation of mono-protides (mono-hydrides). However, few hydrogen isotope effects of the Ti–Cr–V alloys have been reported. This paper aims to clarify the hydrogen isotope effects on the absorption properties of the Ti–Cr–V alloys in a composition range near the bou...

Journal: :Tree physiology 2007
Adam M Taylor J Renée Brooks Barbara Lachenbruch Jeffrey J Morrell

Heartwood extractives (nonstructural wood components) are believed to be formed from a combination of compounds present in the adjacent sapwood and materials imported from the phloem. The roles of local compounds and imported material in heartwood formation could have important implications for the wood quality of species having naturally durable wood. Stable isotope composition (delta(13)C) wa...

2002
A. M. Brenninkmeijer

Measurements of the complete isotopic composition of atmospheric CO (13CO, 14CO, C17O, C18O) have been carried out at the high northern latitude stations Spitsbergen, Norway, and Alert, Canada. The annual changes of the isotope signatures reflect the seasonally varying contributions from the individual CO sources and the OH sink. Short-term variability is small at the remote sampling locations....

2013
B. H. Lomax C. A. Knight

[1] Previous work suggests that the relationship between the carbon isotope composition of air (dCa) and plant leaf tissue (dCp) can be used to track changes in the carbon isotope composition of paleo-atmospheric CO2. Here we test this assertion in a series of experiments using the model plant Arabidopsis thaliana grown under a range of atmospheric CO2 concentrations relevant to geologic time (...

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