نتایج جستجو برای: stable oxygen and carbon isotope
تعداد نتایج: 16944832 فیلتر نتایج به سال:
Abstract Stable hydrogen, carbon, nitrogen, oxygen and sulfur (HCNOS) isotope compositions expressed as isotope-delta values are typically reported relative to international standards such Vienna Standard Mean Ocean Water (VSMOW), Peedee belemnite (VPDB) or Cañon Diablo Troilite (VCDT). These chosen by convention the calibration methods used realise them in practice undergo occasional changes. ...
Rock powder of dolomite samples from the Renison mine area of Tasmania, Australia were analyzed by electron paramagnentic resonance spectroscopy (EPR), Atomic Absorption and Mass Spectrometer to identify alteration related to mineralisation. The least-altered dolomite samples, which are not effected by circulation of diagenetic and hydrothermal fluids are characterised by low Mn and Fe and ...
cosmic rays in the upper troposphere (9000 meters to 15000 meters) initiate the followingnuclear chemical reaction: 1n + 14n => 14c + 1h. previous research has shown a strong effect of latitude onthe abundance of neutrons from cosmic rays. however, to date, there has been little exploration of therelationship between the latitude effect for cosmic-ray neutrons and latitudinal variations of stab...
Stable isotopes (Deuterium and Oxygen-18) have a broad application in many of water related sciences. Precipitation is the most important input to the water cycle which shows considrable spatial and temporal variability in its isotope content. To study the precipitation isotope content, 51 samples from August 2015 to July 2016 have been collected mainly on a monthly basis with few events based ...
RATIONALE Isotope analysis of wood is an important tool in dendrochronology and ecophysiology. Prior to mass spectrometry analysis, wood must be homogenized, and a convenient method involves a ball mill capable of milling samples directly in sample tubes. However, sample-tube plastic can contaminate wood during milling, which could lead to biological misinterpretations. METHODS We tested poss...
Cellulose is usually isolated from the other components of plant material for analysis of carbon stable isotope ratios (dC). However, many studies have shown a strong correlation between whole-wood and cellulose dC values, prompting debate about the necessity of cellulose extraction for tree-ring studies. The dC values were measured in whole wood, extractive-free wood, purified cellulose, aceto...
The Toarcian oceanic anoxic event (T-OAE; ∼ 183 million y ago) is possibly the most extreme episode of widespread ocean oxygen deficiency in the Phanerozoic, coinciding with rapid atmospheric pCO2 increase and significant loss of biodiversity in marine faunas. The event is a unique past tipping point in the Earth system, where rapid and massive release of isotopically light carbon led to a majo...
Dietary adaptations of prehistoric hunter-gatherers from Neolithic and Early Bronze Age cemeteries in the Little Sea region of Cis-Baikal (the region to the west and north of Lake Baikal) are explored using stable isotopes of carbon and nitrogen. Stable isotope data, including stable carbon isotopes from bone carbonate, are presented for 22 individuals from the site of Kurma XI, dated to approx...
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