The Identity and Chemistry of CH Radicals Observed during Soot Formation.

We used aerosol mass spectrometry coupled with tunable synchrotron photoionization to measure radical and closed-shell species associated with particle formation in premixed flames and during pyrolysis of butane, ethylene, and methane. We analyzed photoionization (PI) spectra for the CH radical to identify the isomers present during particle formation. For the combustion and pyrolysis of all three fuels, the PI spectra can be fit reasonably well with contributions from four radical isomers: benzyl, tropyl, vinylcyclopentadienyl, and -tolyl.

Carbon isotope ratios of central Mexican Crassulaceae in natural and greenhouse environments.

Measurements of carbon isotope ratios of central Mexican Crassulaceae collected over a broad habitat range show consistent patterns of CAM activity with no indications of substantial flexible photosynthetic pathways between C and CAM. The three genera studied - Echeveria, Pachyphytum, and Graptopetalum - are all closely related to Dudleya in which considerable flexible metabolic response has been demonstrated. Comparative measurements of carbon isotope ratios for field collected and greenhouse reared samples of the same taxa showed a uniform occurrence of slightly more negative δ C values, but no indication of substantial flexible metabolic response.