Hydrogen and carbon isotope ratios of cellulose nitrate and oxygen isotope ratios of cellulose from C(3), C(4), and Crassulacean acid metabolism (CAM) plants were determined for plants growing within a small area in Val Verde County, Texas. Plants having CAM had distinctly higher deuterium/hydrogen (D/H) ratios than plants having C(3) and C(4) metabolism. When hydrogen isotope ratios are plotte...

BACKGROUND & AIMS The reference method to study protein and arginine metabolism in critically ill children is measuring plasma amino acid appearances with stable isotopes during a short (4-8 h) time period and extrapolate results to 24-h. However, 24-h measurements may be variable due to critical illness related factors and a circadian rhythm could be present. Since only short duration stable i...

The kinetic mechanism of Pseudomonas cepacia salicylate hydroxylase has been examined by steady state initial rate measurements, and stopped flow and equilibrium studies. Results indicate that salicylate and NADH bind to the hydroxylase randomly. The enzyme is reduced and NAD+ is released. Oxygen subsequently binds to the reduced enzyme . substrate complex, leading to the production of hydroxyl...

Literature data on H /D isotope effects on polarizability are reviewed. An argument based on perturbation theory correlates the isotopic differences with electronic transition moments via vibra­ tional averaging. The contribution of the second moment isotope effect is especially important. The approach is first illustrated with a calculation on H 2/D 2 and then employed to correlate differentia...

We used results from the analysis of microsatellite DNA variation and hydrogen stable-isotope ratios to characterize the population structure of a neotropical migrant passerine, the Wilson's warbler (Wilsonia pusilla). The resulting information was then used to infer migration patterns and population connectivity between breeding grounds in North America and overwintering areas in Mexico and Ce...

Many bird species show spatial or habitat segregation of the sexes during the non-breeding season. One potential ecological explanation is that differences in bill morphology favour foraging niche specialisation and segregation. Western sandpipers Calidris mauri have pronounced bill size dimorphism, with female bills averaging 15% longer than those of males. The sexes differ in foraging behavio...