Local climate and environment broadly affect the deuterium/hydrogen (D/H) ratios of plant materials, however the degree to which an individual plant’s leaf waxes D/H ratios are affected by these parameters remains in question. Understanding these issues is particularly important in order to reconstruct past floral transitions and changes in the paleohydrologic cycle. For this study, we sampled ...

We have explored mechanically embedded three-layer QM/QM/MM ONIOM models for computational studies of binding in Al-substituted zeolites. In all the models considered, the high-level-theory layer consists of the adsorbate molecule and of the framework atoms within the first two coordination spheres of the Al atom and is treated at the M06-2X/6-311G(2df,p) level. For simplicity, flexibility and ...

Microcosm experiments were conducted to quantify carbon isotope fractionation during aerobic biodegradation of n-alkanes (from C3 to C10) and monoaromatic hydrocarbons in unsaturated alluvial sand. In single compound experiments with n-alkanes, the largest enrichment factor was obtained for propane ( 10.8 ± 0.7‰). The magnitude of the enrichment factor decreased with increasing number of carbon...

The anisotropic united atoms (AUA4) model has been used for linear and branched alkanes to predict the surface tension as a function of temperature by Monte Carlo simulations. Simulations are carried out for n-alkanes ( n-C5, n-C6, n-C7, and n-C10) and for two branched C7 isomers (2,3-dimethylpentane and 2,4-dimethylpentane). Different operational expressions of the surface tension using both t...

An equilibrated mixture of pentene isomers was produced by dehydroisomerization of n-pentane on catalysts consisting of Pt clusters within [Fe]ZSM-5 channels. These catalysts showed high isomerization rates, excellent stability even without added H2, and isopentene selectivities above 60%. Metal sites on Pt clusters dehydrogenate n-alkanes and n-alkenes formed undergo skeletal rearrangements wi...

Leaf-wax n-alkanes (2)H/(1)H ratios are widely used as a proxy in climate reconstruction. Although the broad nature of the relationship between n-alkanes δ(2)H values and climate is appreciated, the quantitative details of the proxy remain elusive. To examine these details under natural environmental conditions, we studied a riparian broadleaf angiosperm species, Populus angustifolia, growing o...

Pathways of initial oxidation of n-alkanes were examined in two strains of Cladosporium resinae. Cells grow on dodecane and hexadecane and their primary alcohol and monoic acid derivatives. The homologous aldehydes do not support growth but are oxidized by intact cells and by cell-free preparations. Hexane and its derivatives support little or no growth, but cell extracts oxidize hexane, hexano...

Organogel is a viscoelastic carrier system, can be regarded as a semi-solid preparation which has an immobilized external organic (apolar) phase. Organogels have evolved as one of the potential carrier system for topical delivery. When compared to other lipid based carrier systems, these prove to be better in terms of efficacy, feasibility and shelf life. Organogelator such as n-alkanes, fatty ...