We fed broad-tailed hummingbirds (Selasphorus platycercus) diets of contrasting carbon isotope composition and measured changes in the delta(13)C of expired breath through time. By measuring the delta(13)C in the breath of fed and fasted birds we were able to quantify the fraction of metabolism fueled by assimilated sugars and endogenous energy reserves. These measurements also allowed us to es...

We examine the relationship between mesowear variables and carbon and nitrogen isotopes in 16 species of African antelope (Mammalia: Bovidae). We show significant differences in carbon and nitrogen isotope values between individuals exhibiting sharp versus round cusps, and high versus low occlusal relief. We show significant correlations between mesowear variables and both carbon and nitrogen i...

We report that the most abundant C1 units of terrestrial plants, the methoxyl groups of pectin and lignin, have a unique carbon isotope signature exceptionally depleted in 13C. Plant-derived C1 volatile organic compounds (VOCs) are also anomalously depleted in 13C compared with Cn+1 VOCs. The results confirm that the plant methoxyl pool is the predominant source of biospheric C1 compounds of pl...

(18)O-isotope labelled titania (anatase, rutile) was synthesized. The products were characterized by Raman spectra together with their quantum chemical modelling. The interaction with carbon dioxide was investigated using high-resolution FTIR spectroscopy, and the oxygen isotope exchange at the Ti(18)O(2)/C(16)O(2) interface was elucidated.

We measure the clumped isotopic signature of carbonatites to assess the integrity of the clumped isotope paleothermometer over long timescales (10–10 years) and the susceptibility of the proxy to closed system re-equilibration of isotopes during burial diagenesis. We find pristine carbonatites that have primary oxygen isotope signatures, along with a Carrara marble standard, do not record clump...

We analyzed the diversity of bacterial epibionts and trophic ecology of a new species of Kiwa yeti crab discovered at two hydrothermal vent fields (E2 and E9) on the East Scotia Ridge (ESR) in the Southern Ocean using a combination of 454 pyrosequencing, Sanger sequencing, and stable isotope analysis. The Kiwa epibiont communities were dominated by Epsilon- and Gammaproteobacteria. About 454 se...

[1] The kinetic isotope effects (KIEs) for several ozonealkene reactions in the gas phase were studied in a 30 L PTFE reaction chamber. The time dependence of the stable carbon isotope ratios and the concentrations were determined using a gas chromatography combustion isotope ratio mass spectrometry (GCC-IRMS) system. The following average KIE values were obtained: 18.9 ± 2.8 (ethene), 9.5 ± 2....

Rigorous mathematical modeling of carbon-labeling experiments allows estimation of fluxes through the pathways of central carbon metabolism, yielding powerful information for basic scientific studies as well as for a wide range of applications. However, the mathematical models that have been developed for flux determination from 13C labeling data have commonly neglected the influence of kinetic...

The most important demand in an efficient carbon isotope separation is to keep the cryogenic distillation column parameters at their required set points, despite disturbances or uncertainties. One of the key parameters is the column temperature that has a direct influence on the carbon separation coefficient. The nonlinear model of the separation process considers the top and bottom column temp...

Portulacaria afra L. is a dominant facultative CAM species growing in the Southeastern Cape of South Africa. P. afra is well adapted to regions of the Spekboom thicket in areas of limited and sporadic rainfall. P. afra populations occur in isolated drainages. We hypothesized the utilization of CAM would vary in the different populations in response to rainfall and temperature gradients. Carbon ...