Oxydation menagee du chromite de fer stoechiometrique a basse température,réduction du composé obtenu

The influence of oxygen on stoichiometric, finely crystallized iron chromite gives a compound with formula FeCr₂O_4,5. The overall rate of the transformation is controlled by the diffusion of iron cations in the spinel lattice and the simultaneous formation of iron vacancies. Oxidation is followed by means of thermogravimetric, radiocrystallographic, E.P.R. and electrical conductivity analysis. The system can be brought back to the initial state by reduction of the oxidized product with hydrogen. This reverse reaction occurs with the same experimental energy of activation and the same rate pressure law. The data obtained are explained by a vacancy Fe³⁺ ion association mechanism.     

Creosote Bush (Larrea tridentata) Resin Increases Water Demands and Reduces Energy Availability in Desert Woodrats (Neotoma lepida)

Although many plant secondary compounds are known to have serious consequences for herbivores, the costs of processing them are generally unknown. Two potential costs of ingestion and detoxification of secondary compounds are elevation of the minimum drinking water requirement and excretion of energetically expensive metabolites (i.e., glucuronides) in the urine. To address these impacts, we studied the costs of ingestion of resin from creosote bush (Larrea tridentata) on desert woodrats (Neotoma lepida). The following hypotheses were tested: ingestion of creosote resin by woodrats (1) increases minimum water requirement and (2) reduces energy available by increasing fecal and urinary energy losses. We tested the first hypothesis, by measuring the minimum water requirement of woodrats fed a control diet with and without creosote resin. Drinking water was given in decreasing amounts until woodrats could no longer maintain constant body mass. In two separate experiments, the minimum drinking water requirement of woodrats fed resin was higher than that of controls by 18-30% (about 1-1.7 ml/d). We tested several potential mechanisms of increased water loss associated with the increase in water requirement. The rate of fecal water loss was higher in woodrats consuming resin. Neither urinary water nor evaporative water loss was affected by ingestion of resin. Hypothesis 2 was tested by measuring energy fluxes of woodrats consuming control vs. resin-treated diets. Woodrats on a resin diet had higher urinary energy losses and, thus, metabolized a lower proportion of the dietary energy than did woodrats on control diet. Fecal energy excretion was not affected by resin. The excretion of glucuronic acid represented almost half of the energy lost as a consequence of resin ingestion. The increased water requirement and energy losses of woodrats consuming a diet with resin could have notable ecological consequences.     

Comportement electrochimique de la galene (PbS) dans les conditions de pH proches de celles de la flottation

The electrochemical behaviour of lead sulphide mineral (galena) has been investigated by cyclic voltammetry and controlled potential electrolyses. In the pH range 5–9, the oxidation leads—at + 0.5 V vs sce—to the formation of elemental sulphur and lead species: Pb²⁺, Pb(OH)₂ or Pb(OH)Cl depending on the pH, and on the nature of the electrolyte.

The reactions involved in the overall anodic/cathodic cycle have been interpreted; at pH 9, galena is reduced at − 1.3 V, to lead metal and HS⁻ ions.     

Effect of time of application of fertiliser nitrogen on the distribution and identity of the nitrogenous constituents of young apple trees

The initial response to an application of fertiliser N appeared always as a rise in the level of asparagine. Following spring and summer N applications this high level of asparagine later decreased as those of arginine and the insoluble N increased, but after autumn N application both asparagine and arginine accumulated, especially in the roots. Leaves were exceptional both in containing a high proportion of insoluble N at all times and in containing a large amount of soluble glutamine soon after spring N application, in addition to the arginine and asparagine. Direct analyses have been transformed on to a weight basis and the results are given diagrammatically as the total weight of N present in each tissue of the tree as each of the four components: insoluble N, soluble arginine, soluble asparagine, or the total of all other soluble compounds. This has enabled the movement of N within the whole tree and the interchange between compounds in response to season and to fertiliser application to be recognised more readily. The possible significance of the relative mobilities of arginine and asparagine is also discussed, together with the possible merits of sampling leaves or other tissues, for example the roots, for predicting the future crop potential of apple trees.     

Group cognitive-behavioral treatment for the nonpurging bulimic: An initial evaluation.

This study tested the initial effects of cognitive-behavioral therapy for binge eating in Ss who do not purge. Forty-four female binge eaters were randomized to either cognitive-behavioral treatment (CB) or a waiting-list (WL) control. Treatment was administered in small groups that met for 10 weekly sessions. At posttreatment a significant difference was found, with 79% of CB Ss reporting abstinence from binge eating and a 94% decrease in binge eating compared with a nonsignificant reduction (9%) in binge eating and zero abstinence rate in WL Ss. Following the posttest assessment, WL Ss were treated and evidenced an 85% reduction in binge episodes and a 73% abstinence rate. Binge eating significantly increased at 10-week follow-up for initially treated Ss; however, the frequency remained significantly improved compared with baseline levels. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Basic Zeolites: Characterization and Uses in Adsorption and Catalysis

The presence of basic centers in some oxides has been recognized for a long time as being important in catalysis [1-4]. Usually both basic and acid sites exist simultaneously. The two centers may work independently or in a concerted way. For instance, in alcohol transformation, dehydration is favored on acidic sites and dehydrogenation on basic centers [3,5]. A large variety of materials are cited as having basic character. They include single-metal oxides (MgO, CaO, ZnO), supported alkali metals (Na/MgO, K/K₂CO₃), mixed-metal oxides (MgO-A1₂O₃, ZnO-SiO₂, MgO-TiO₂), zeolites (X and Y saturated with alkaline cations of low electronegativity), hydrotalcite-type anionic clays, asbestoslike materials, carbon-supported basic catalysts, and basic organic resins.     

Correlation of the wetting behaviour of sodium on nimonic PE16 with the surface O/Cr ratio determined by Auger spectroscopy

The contact angle of liquid sodium on Nimonic PE16 was measured by the sessile drop technique, as a function of temperature of the substrate. Prior surface treatments given to the PE16 included mechanical polishing, chemical polishing, and oxidation at 700°C; the effect of subsequent argon-ion bombardment was also studied. Surface analyses by Auger spectroscopy were performed on duplicate specimens after each of the above treatments, and again after ion bombardment. Although on any of the surfaces at any stage there were between six and nine elements present, the only obvious correlation was that between the low-temperature (160°C) contact angle and the oxygen/chromium atomic ratio at the surface. Up to about 260°C the sodium was apparently inert and non-wetting but beyond that temperature the contact angle dropped rapidly until at about 500°C irreversible wetting occurred. At the same time the correlation with the oxygen/chromium surface atomic ratio disappeared.     

Differential experience of siblings in the same family.

The Sibling Inventory of Differential Experience (SIDE), developed by the authors, was completed by 396 12–28 yr old White siblings from both adoptive and nonadoptive homes. The SIDE asks each individual to compare his/her experiences to those of one of his/her siblings in the domains of sibling interaction, parental treatment, peer characteristics, and events specific to the individual. Results indicate that, on the average, siblings experienced quite different environments, especially in the areas of differential sibling interaction and differential peer characteristics. Differential sibling experience as assessed by the SIDE showed little genetic influence, which implies that its origin is primarily environmental. (23 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)