Structural characterization and mass spectrometry fragmentation signatures of macrocyclic alkanes isolated from a Sydney Basin torbanite,Australia

Individual hydrocarbons identified to be macrocyclic alkanes in a torbanite from the Sydney Basin(Australia)were successfully isolated from its extracts using preparative gas chromatography and analyzed by NMR.Saturated cyclic structures were confirmed by single peaks in the NMR~1H and~(13)C spectra indicating single forms of H and C atoms exist in these biomarker molecules.This is consistent with the methylene unit in a ring system assignment of the macrocyclic alkanes and accounts for a formula of(CH2)n.The unusual molecular structures of these compounds are consistent with those that were identified from previous GC retention index data and co-injection with a standard supports the previous research.The mass spectral fragmentation behaviors of representative cyclic alkanes were further investigated by comparing them with the mass spectra of isolated individual macrocyclic alkanes.The characteristic fragment ions in the macrocyclic alkanes of(M–28)+and base peaks of m/z 97,111,125,etc.,can be assigned as being generated by simple a-/i-cleavage and hydrogen rearrangement.These fragmentation pathways combined with retention indices should assist in differentiating these compounds from monounsaturated alkenes and alkylated monocyclics having similar mass spectral characteristics in other geological samples.

Intervention Effect of Repetitive TMS on Behavioral Adjustment After Error Commission in Long-Term Methamphetamine Addicts： Evidence From a Two-Choice Oddball Task

Behavioral adjustment plays an important role in the treatment and relapse of drug addiction. Nonetheless,few studies have examined behavioral adjustment and its plasticity following error commission in methamphetamine（METH） dependence, which is detrimental to human health. Thus, we investigated the behavioral adjustment performance following error commission in long-term METH addicts and how it varied with the application of repetitive transcranial magnetic stimulation（r TMS） of the left dorsolateral prefrontal cortex（DLPFC）. Twenty-nine male long-term METH addicts（for [ 3 years） were randomly assigned to high-frequency（10 Hz, n = 15） or sham（n = 14） r TMS of the left DLPFC during a two-choice oddball task. Twenty-six age-matched, healthy male adults participated in the two-choice oddball task pretest to establish normal performance for comparison. The results showed that 10 Hz r TMS over the left DLPFC significantly decreased the post-error slowing effect in response times of METH addicts. In addition, the 10 Hz r TMS intervention remarkably reduced the reaction times during post-error trials but not post-correct trials. While the 10 Hz r TMS group showed a more pronounced post-error slowing effect than the healthy participants during the pretest, the posterror slowing effect in the posttest of this sample was similar to that in the healthy participants. These results suggest that high-frequency r TMS over the left DLPFC is a useful protocol for the improvement of behavioral adjustment after error commission in long-term METH addicts.