Effect of sulphur poisoning on perovskite catalysts prepared by flame-pyrolysis

ABO(3) perovskite-like catalysts are known to be sensitive to sulphur-containing compounds. Possible solutions to increase resistance to sulphur are represented by either catalyst bed protection with basic guards or catalyst doping with different transition or noble metals. In the present work La((1-x))A(x)'CoO(3), La((1-x))A(x)'MnO(3) and La((1-x))A(x)'FeO(3), with A' = Ce, Sr and x = 0, 0.1, 0.2, either pure or doped with noble metals (0.5 wt% Pt or Pd), were prepared in nano-powder form by flame-pyrolysis. All the catalysts were tested for the catalytic flameless combustion of methane, monitoring the activity by on-line mass spectrometry. The catalysts were then progressively deactivated in operando with a new procedure, consisting of repeated injection of some doses of tetrahydrothiophene (THT), usually employed as odorant in the natural gas grid, with continuous analysis of the transient response of the catalyst. The activity tests were then repeated on the poisoned catalyst. Different regenerative treatments were also tried, either in oxidising or reducing atmosphere. Among the unsubstituted samples, higher activity and better resistance to poisoning have been observed in general with manganites with respect to the corresponding formulations containing Co or Fe at the B-site. The worst catalyst showed LaFeO(3), from both the points of view of activity and of resistance to sulphur poisoning. La(0.9)Sr(0.1)MnO(3) showed, the best results, exhibiting very high activity and good resistance even after the addition of up to 8.4 mg of THT/g of catalyst. Interesting results were attained also by adding Sr to Co-based perovskites. Sr showed a first action by forcing Mn or Co in their highest oxidation state, but, in addition, it could also act as a sulphur guard, likely forming stable sulphates due to its basicity. Among noble metals, Pt doping proved beneficial in improving the activity of both the fresh and the poisoned catalyst

X-ray and Radio Interactions in the Cores of Cooling Flow Clusters

We present high resolution ROSAT x-ray and radio observations of three cooling flow clusters containing steep spectrum radio sources at their cores. All three systems exhibit strong signs of interaction between the radio plasma and the hot intracluster medium. Two clusters, A133 and A2626, show enhanced x-ray emission spatially coincident with the radio source whereas the third cluster, A2052, exhibits a large region of x-ray excess surrounding much of the radio source. Using 3-D numerical simulations, we show that a perturbed jet propagating through a cooling flow atmosphere can give rise to amorphous radio morphologies, particularly in the case where the jet was ``turned off'' and allowed to age passively. In addition, the simulated x-ray surface brightness produced both excesses and deficits as seen observationally.Comment: 25 pages, 10 figures, accepted for publication in A

A Derivation of a Variable Vertical Mesh Spacing for Les Models: Application To a CBL

A derivation of a variable vertical mesh spacing for LESmodels: application to a CB

Prediction of Postprandial Glycemic Exposure Utility of fasting and 2-h glucose measurements alone and in combination with assessment of body composition, fitness, and strength

OBJECTIVE —To determine the best predictors of total postprandial glycemic exposure and peak glucose concentrations in nondiabetic humans. RESEARCH DESIGN AND METHODS —Data from 203 nondiabetic volunteers who ingested a carbohydrate-containing mixed meal were analyzed. RESULTS —Fasting glucose and insulin concentrations were poor predictors of postprandial glucose area above basal ( R 2 = ∼0.07, P < 0.001). The correlation was stronger for 2-h glucose concentration ( R 2 = 0.55, P < 0.001) and improved slightly but significantly ( P < 0.001) with the addition of fasting glucose, insulin, age, sex, and body weight to the model ( r 2 = 0.58). The 2-h glucose concentration also predicted the peak glucose concentration ( R 2 = 0.37, P < 0.001) with strength of the prediction increasing ( P < 0.001) modestly with the addition of fasting glucose, insulin, age, sex, and body weight to the model ( R 2 = 0.48, P < 0.001). On the other hand, addition of measures of body function and composition did not improve prediction of total glycemic exposure or peak glucose concentration. CONCLUSIONS —Isolated measures of fasting or 2-h glucose concentrations alone or in combination with more complex measures of body composition and function are poor predictors of postprandial glycemic exposure or peak glucose concentration. This may explain, at least in part, the weak and at times inconsistent relationship between these parameters and cardiovascular risk

A score including ADAM17 substrates correlates to recurring cardiovascular event in subjects with atherosclerosis

Atherosclerosis disease is a leading cause for mortality and morbidity. The narrowing/rupture of a vulnerable atherosclerotic plaque is accountable for acute cardiovascular events. However, despite of an intensive research, a reliable clinical method which may disclose a vulnerable patient is still unavailable

Simulações Les de uma Camada Limite Convectiva Empregando um Espaçamento de Grade Vertical Variável

Simulações LES de uma camada limite convectivaempregando um espaçamento de grade vertical variáv