The uranium isotope effect in the exchange system uranyl(VI)-malate ligand at 288–343 K has been studied by ion exchange displacement chromatography. At all temperatures 235U is enriched at the front of the uranium band. The single stage separation coefficient, (e =a – 1), increased from (0.9 ± 0.1)× 10 at 288 K to (2.9 ± 0.3)× 10–4 at 343 K. The equilibrium constant of the isotope exchange rea...

The rapid, degenerate 1,2-hydride shift in 2,3-dimethyl-2-butyl cation in stable solution in SbF5/ S02C1F was perturbed by deuterium and 13C leading to splittings observed by 13C NMR spectros­ copy over a range of temperatures. Accurate values for equilibrium isotope effects were obtained from these data. Theoretical calculations of the equilibrium isotope effects were performed using the Gauss...

Cytochrome P-450 (P-450)-catalyzed oxidation of 2,6-dimethyl-4-phenyl-3,5-pyridinedicarboxylic acid diethyl ester gives rise to 2,6-dimethyl-4-phenyl-3,5-pyridinedicarboxylic acid monoethyl ester and to 2-hydroxymethyl-6-methyl-4-phenyl-3,5-pyridinedicarboxylic acid diethyl ester, identified in this work. A pyridine hydroxymethyl diester of the sort of the latter compound is novel; under acidic...

The key processes responsible for the rise in groundwater salinization Mio–Pliocene aquifer system of Sousse (Tunisia, eastern coastline) were identified through a multidisciplinary approach based on use geochemical, stable (2H, 13C, 18O and 37Cl) radioactive (3H 14C) isotope methods. In study region, mineralization groundwaters is related to water–rock interaction ascribed dissolution minerals...

We examine groundwater recharge processes and their relationship to rainfall intensity in the semi-arid, southwestern Lake Chad Basin of Nigeria using a newly compiled database stable isotope data (?2H, ?18O) from rainfall. ?18O signatures proximate surface waters are enriched 18O relative regional trace focused evaporated via ephemeral river discharge Chad; remote channels is comparatively dep...

Zinc oxide (ZnO) thin films were grown by atomic layer deposition using diethylzinc (DEZ) and water. In addition to depositions with normal water, heavy water (2H2O) was used in order study the reaction mechanisms hydrogen incorporation at different temperatures from 30 200 ?C. The total concentration found increase as temperature decreased. When decreased close room temperature, main source of...

Incubation of the pyrimidine [3'-3H]UDP with ribonucleotide reductase resulted in an isotope effect on the conversion to dUDP which varied as a function of pH and allosteric effectors (pH, kH/kT, effector): 6.6, 4.7, ATP; 7.6, 3.3, ATP; 7.6, 2.6, dATP; 7.6, 2.0, TTP; 8.4, 2.8, ATP. During this reaction 3H2O was also released. The lower the pH of the reaction, the larger the isotope effect, and ...