منابع مشابه
Laser Spectroscopy of Unstable Isotopes
High-resolution methods of o p t i c a l spectroscopy i n unstable isotopes a r e discussed, with emphasis on fast-beam l a s e r spectroscopy. The chief goal i s t o ob ta in information about nuclear ground-state p roper t i es from hyperfine s t r u c t u r e and isotope s h i f t s . The methods have t o be s u i t a b l e f o r use with minute samples, due t o t h e small amount of rad ioa...
متن کاملUsing Stable Isotopes
Introduction Direct measurement of de novo lipogenesis has not previously been possible in humans. We measured de novo hepatic lipogenesis in normal men by means of stable isotopes and by combining the acetylated-xenobiotic probe technique with mass isotopomer analysis of secreted very low density lipoproteinfatty acids (VLDL-FA). Sulfamethoxazole (SMX) was administered with ['3Clacetate during...
متن کاملStable Isotopes Issue
We tested the competing hypotheses that (1) nitrogen discrimination in mammals and birds increases with dietary nitrogen concentration or decreasing C:N ratios and, therefore, discrimination will increase with trophic level as carnivores ingest more protein than herbivores and omnivores or (2) nitrogen discrimination increases as dietary protein quality decreases and, therefore, discrimination ...
متن کاملforaminifera and stable isotopes
Foraminiferal stable isotopes and assemblages from Franz Victoria and St. Anna troughs provide a valuable record of freshwater and Atlantic Water flows to the northern Barents and Kara seas from deglaciation to present. The dO and dC of planktonic Neogloboquadrina pachyderma (s) and benthic Elphidium excavatum were up to 1.4% lower than present at ca 13, 11.5, and 10 Cka (global sea-level corre...
متن کاملStable Isotopes Issue
Plant metabolic activity in arid and semi-arid environments is largely tied to episodic precipitation events or ‘‘pulses’’. The ability of plants to take up and utilize rain pulses during the growing season in these water-limited ecosystems is determined in part by pulse timing, intensity and amount, and by hydrological properties of the soil that translate precipitation into plant-available so...
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ژورنال
عنوان ژورنال: Nature
سال: 1994
ISSN: 0028-0836,1476-4687
DOI: 10.1038/372725a0