نتایج جستجو برای: isotope
تعداد نتایج: 32576 فیلتر نتایج به سال:
Estimates of terrestrial carbon isotope discrimination are useful to quantify the terrestrial carbon sink. Carbon isotope discrimination by terrestrial ecosystems may vary on seasonal and interannual time frames, because it is affected by processes (e.g. photosynthesis, stomatal conductance, and respiration) that respond to variable environmental conditions (e.g. air humidity, temperature, ligh...
A one-dimensional chemistry model is applied to study the stable hydrogen (D) and stable oxygen isotope (17O, 18O) composition of water vapour in stratosphere and mesosphere. In the troposphere, this isotope composition is determined by “physical” fractionation effects, that are phase changes (e.g. during cloud formation), diffusion processes (e.g. during evaporation from the ocean), and mixing...
For over a century, a Neogene fossil mammal fauna has been known in the Irrawaddy Formation in central Myanmar. Unfortunately, the lack of accurately located fossiliferous sites and the absence of hominoid fossils have impeded paleontological studies. Here we describe the first hominoid found in Myanmar together with a Hipparion (s.l.) associated mammal fauna from Irrawaddy Formation deposits d...
To document the evolution of the early cryosphere, stable isotope analyses were conducted on the planktonic and benthic foraminifers from Ocean Drilling Program Site 1218. We generated two parallel 54m-long records at 10-cm resolution and thus produced a standard Pacific stable isotope reference curve for the 26.4to 30.0-Ma interval within the Oligocene. These data are necessary to document the...
The foundations of stable isotope geochemistry were laid in 1947 by Urey’s classic paper on the thermodynamic properties of isotopic substances and by Nier’s development of the ratio mass spectrometer. Before discussing details of the naturally occurring variations in stable isotope ratios, it is useful to describe some generalities that are pertinent to the field of non-radiogenic isotope geoc...
In this editorial, we provide a brief introduction and summarize the 10 research articles included in this Special Issue on Applications of stable isotope analysis in mammalian ecology. The first three articles report correction and discrimination factors that can be used to more accurately estimate the diets of extinct and extant mammals using stable isotope analysis. The remaining seven appli...
A great deal of current biological and clinical research is directed at the interpretation of the information contained in the human genome sequence in terms of the structure, function and control of biological systems and processes. Proteomics, the systematic analysis of proteins, is becoming a critical component in this endeavor because proteomic measurements are carried out directly on prote...
Picarro WS-CRDS-based analyzers are the first instruments to combine simple, turnkey operation with sensitivity and precision better than or equal to the IRMS (isotope ratio mass spectrometer) systems traditionally used in stable isotope labs. This opens the door for widespread exploitation of stable isotope studies in fields such as carbon/water cycle research, GHG (greenhouse gas) monitoring,...
An atomic spectral line is characteristic of the element producing the spectrum. The line also depends on the isotope. The program ris3 (Relativistic Isotope Shift) calculates the electron density at the origin and the normal and specific mass shift parameters. Combining these electronic quantities with available nuclear data, isotope-dependent energy level shifts are determined.
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