In an earlier publication [1] it has been claimed that oxidative coupling of methane to higher hydrocarbons had been obtained with close to 100% selectivity at 600~ and atmospheric pressure in the presence of steam over a CaNiK oxide catalyst. These results have been confirmed in longer runs. Artifacts, such as carbonate formation on the catalyst, have been excluded. The reaction is slightly ex...

Many 4øAr/39Ar age spectra for alkali feldspars are significantly different from the model age spectra calculated for slowly cooled samples composed of diffusion domains of a single size, and the Arrhenius plots for these samples show departures from linearity that are inconsistent with diffusion from domains of equal size. The most plausible explanation for these discrepancies is the existence...

The stability of andrographolide, the major active diterpene lactone from Andrographis paniculata (BURM. f.) WALL. ex NEES., was determined to show that, while crystalline andrographolide was highly stable even at 70 degrees C (75% relative humidity) over a period of 3 months, its amorphous phase degraded promptly. Heat-accelerated conditions revealed second-order kinetics of the decomposition ...

The temperature variations of the 6 3 Cu, 6 5 Cu and 5 V N M R spectra and 5 V spin-lattice relaxation rate 1 / T have been measured in a thiospinel CuV 2 S 4 . Drastic changes in the spectra and relaxation rates were observed at the charge density wave (CDW) transition temperature. With decreasing temperature T, 1 /Ti decreases exponentially due to the C D W transition (75 K < T< 90 K). The en...

The degradation behavior of cefquinome sulphate in alkaline medium at different temperatures was investigated using both first derivative spectrophotometric and HPLC methods. The drug degradation was found to be pH and temperature dependant. The pH-rate profile indicated a first order dependence of Kobs on [OH(-)] at pHs ranging between 9 and 11. Arrhenius plot obtained at pH 10 was linear betw...

Kinetic parameters for the thermal inactivation of several enzymes in carrot and potato homogenates have been determined. In carrots the most heat-resistant activity was polygalacturonase, followed by peroxidase and pectinmethylesterase. In potatoes peroxidase was the most resistant, followed by pectin methylesterase, polyphenol oxidase, and lipoxygenase. There were several notable similarities...

When saturated with ATP, sea cucumber myosin hydrolyzes ATP about 15 times more slowly than rabbit myosin, as expected from the slower contraction time of the muscle. The Arrhenius plots coincide at low temperatures, but only the rabbit plot changes slope at higher temperatures. This unexpected change in slope apparently results from the use of Verona1 buffer. At high substrate concentrations i...

We study the dynamic susceptibility chi_{T}(Q,t) of deeply supercooled water by means of quasielastic neutron scattering and molecular dynamics simulations. Both techniques show an increase in the peak height of chi_{T}(Q,t) as the temperature is lowered toward the dynamic crossover temperature T_{L} . Below T_{L} , the peak height decreases steadily. We attribute this phenomenon to the change ...

The transport of ion-implanted F in amorphous Si is studied using secondary ion mass spectroscopy and transmission electron microscopy. Significant redistribution of F is observed at temperatures in the range 600–700 °C. The measured F depth profiles are modeled using a simple Gaussian solution to the diffusion equation, and the diffusion coefficient is deduced at each temperature. An activatio...

Chemolithoautotrophic bacteria were enriched from mine water at incubation temperatures ranging from 4 to 46 degrees C, using elemental sulfur as a substrate in acid mineral salts media. Thiobacillus-type bacteria were successfully enriched for at all test temperatures except 46 degrees C. Changes in pH (-dpH/dt) were used to estimate the rate constants for the enrichment cultures. The rate con...