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ABSTRACTSubtype-dependent selection of HIV-1 reverse transcriptase resistance mutation K65R was previously observed in cell culture and small clinical investigations. We compared K65R prevalence across subtypes A, B, C, F, G, and CRF02_AG separately in a cohort of 3,076 patients on combination therapy including tenofovir. K65R selection was significantly higher in HIV-1 subtype C. This could not be explained by clinical and demographic factors in multivariate analysis, suggesting subtype sequence-specific K65R pathways.

A rigorous kinetic model was derived for the formation on a nickel catalyst of filamentous carbon by the Boudouard reaction and for the gasification of filamentous carbon by carbon dioxide, by hydrogen, and by steam. The experimental study was performed in an electrobalance unit. Carbon formation and gasification experiments were performed at temperatures ranging from 773 to 848 K. The partial pressures of the various components were chosen in the ranges encountered in industrial steam reformers. The influence of the carbon formation reaction on the subsequent gasification process was also investigated. The mode of experimentation ensured that the rates of growth or gasification of the carbon filaments were always based on the same number of carbon filaments. The same reaction mechanism was derived from the study both of methane cracking and the Boudouard reaction and of the reverse reactions, gasification by hydrogen and carbon dioxide. Using the results of the parameter estimation, energy diagrams were constructed for the Boudouard reaction and for gasification by carbon dioxide and by hydrogen.

A rigorous kinetic model for the formation and gasification of filamentous carbon on a nickel steam-reforming catalyst is derived. Carbon formation and gasification experiments were performed in an electrobalance unit at temperatures ranging from 773 to 823 K and partial pressures of the various components in the range encountered in industrial steam reformers. The rates of growth or gasification of the carbon filaments were always based on the same number of carbon filaments. The gasification by carbon dioxide and by steam proceed through adsorbed oxygen, generated by the dissociation of steam and carbon dioxide. Relationships between the various carbon formation and gasification reactions are accounted for, to ensure that the kinetic model is thermodynamically sound. The lower net rate of carbon formation on an alkalized catalyst can be explained by a lower lumped forward rate coefficient for the methane cracking and an increased surface concentration of oxygen.

A detailed description is given of the formation and the gasification of filamentous carbon. The diffusion of carbon through nickel originates from a concentration gradient, which implies a different solubility at the nickel–gas and the nickel–carbon interface. A thermodynamic basis for the different solubilities is provided. The segregation of carbon, taking place at the gas side of the nickel particle, is added as one of the steps in the global mechanism of carbon filament formation and gasification. The segregation process may be described in a way similar to that of gas adsorption. The coupling of the surface reactions, the segregation process, and the diffusion of carbon through the nickel particle leads to a detailed model of the process of carbon filament formation, which forms the basis for the kinetic modeling of carbon formation and gasification reactions. Experimental results for the methane cracking revealed that the number of carbon filaments that is able to nucleate strongly depends upon the affinity for carbon formation.

SummaryThe antihypertensive and clinical effects of two centrally acting drugs, guanabenz and clonidine, were compared in a double-blind trial in 29 patients with established hypertension. After a 1-week baseline period and 2 weeks on placebo, patients received treatment with either guanabenz (mean dose 24 mg daily) or clonidine (mean dose 0.45 mg daily) alone for 8 weeks. Both drugs produced equivalent and highly significant (p < 0.001) reductions in systolic and diastolic blood pressures in the standing and supine positions. They also reduced significantly the standing and supine pulse rates. Normal orthostatic responses were maintained with both regimens. AN but 1 patient in each group reported side-effects during active treatment, the most frequent being dry mouth and sedation with each drug. No laboratory or ECG abnormalities related to treatment were observed.

The nature of the species adsorbed on a Cu/ZnO/Al2O3 catalyst while it was producing methanol has been elucidated in this study using DRIFTS. The species are carbonates, formate, CO, oxygen atoms (~ 2% of a monolayer) and methoxy on the Cu and methoxy on the ZnO. The frequencies observed for the C-O stretch on Cu, 2076, 2092, 2105 and 2132 cm-1, have revealed the morphology of the copper component of the operating catalyst. The surface of the copper is predominantly the (111) face (~ 65%) (the 2076 cm-1 peak) with the (755) (the 2092 cm-1 peak) and the (311) (the 2105 cm-1 peak) faces occupying roughly 20% and 15%, respectively, of the copper area. The 2132 cm-1 peak derives from CO adsorbed on Cu+ site on the copper which is ~ 2% of a monolayer.

A rigorous kinetic model for the formation of filamentous carbon on a nickel catalyst by methane cracking is derived. The experimental study was performed in an electrobalance unit. The temperature ranged from 773 to 823 K and the partial pressure of methane ranged from 1.5 to 10 bar. The mode of experimentation ensured that the rate of growth of the carbon filaments was always based upon the same number of filaments. A kinetic model is selected in which the abstraction of the first hydrogen atom from molecularly adsorbed methane is the rate-determining step. Based on the results of the parameter estimation, an energy diagram for the methane cracking is constructed.