897 research outputs found
Contribution of lymphatic drainage through stomata to albumin removal from pleural space
No full textThe contribution of lymphatic drainage through the stomata of parietal mesothelium to the overall removal of labeled albumin from the pleural space was found 89% in sheep with very large hydrothoraces (10 ml/kg), a condition involving a approximately 20 times increase in lymphatic drainage [Broaddus et al., J. Appl. Physiol. 64 (1988) 384]. We determined this contribution in anesthetized rabbits with small (0.12 ml/kg) and large (2.4 ml/kg) hydrothoraces of Ringer-albumin with labeled albumin and labeled dextran-2000 kDa. This dextran was used as marker of liquid removal through the stomata because it should essentially leave the pleural space through the stomata only, owing to its size. The removal of labeled albumin by lymphatic drainage through the stomata was 39% of the overall removal in the small hydrothoraces, and 64% in the large ones. Hence, lymphatic drainage through the stomata does not contribute most of protein and liquid removal from the pleural space under physiological conditions, as it has been maintained. It markedly increases with the increase in pleural liquid volume
A thermodynamic study of the hydrogenation of the pseudo-binary Mg6Pd0.5Ni0.5 intermetallic compound
No full textHydrogenation thermodynamic properties of a new pseudo-binary Mg6Pd0.5Ni0.5 intermetallic compound (IMC) are presented. This IMC disproportionates reversibly on hydrogenation into MgH2, Mg5Pd2 and Mg2NiH4 compounds. Pressure-Composition-Temperature measurements in the temperature range 590-650 K have been acquired. The enthalpy and entropy of the hydrogenation reaction are respectively, -63 +/- 3 kJ/molH(2) and -114 +/- 4 J/K molH(2). They agree well with those calculated from the enthalpy and entropy of formation of the several phases involved in the disproportionation reaction. In particular, the Miedema model has been used to calculate the standard enthalpy of formation of the several Mg-Pd IMC's, ranging from -21.8 to -61.5 kJ/mol atoms for Mg6Pd and MgPd, respectively. As for the standard entropy changes, an inverse relationship between entropy and density was used to calculate the formation entropy of the Mg-Pd IMC's
Isotope effects in the kinetics of simultaneous H and D thermal desorption from Pd
No full textThe kinetics of simultaneous hydrogen and deuterium thermal desorption from PdHxDy has been investigated. A novel experimental approach for the study of the transition state (TS) characteristics of the surface recombination reaction is proposed based on the analysis of the H and D partitioning into H-2, HD and D-2 molecules. It has been found that the hydrogen molecular isotopes distribution is determined by the energy differences of the corresponding TS of the atom-atom recombination reactions. On the other hand, the mechanisms and activation energies of the desorption process have been obtained. At 420 K, the desorption reaction changes from a surface recombination limiting mechanism during desorption from beta-PdHxDy to a reaction limited by the rate of beta to alpha phase transformation during the two phase coexistence. Surface recombination reaction becomes again rate limiting above 480 K, due to a change in the catalytic properties of the Pd surface. TS energies obtained from the kinetic analysis of the thermal desorption spectra are in good accordance with those obtained from the analysis of the H-2, HD and D-2 distributions. Anomalous TS energies have been observed for the H-D recombination reaction, which may be related to the heteronuclear character of this molecule. (C) 2007 Elsevier Ltd. All rights reserved
An experimental system to investigate kinetics and isotopic properties of the electrolytic metal hydride formation
No full textAn investigation on the thermodynamics and kinetics of magnesium hydride decomposition based on isotope effects
No full textThis work investigates the thermodynamics and kinetics of magnesium hydride decomposition by analyzing isotope effects in hydride and deuteride samples. Complete pressure composition desorption isotherm measurements of MgD(2) are reported for the first time. Deuterium desorption enthalpy and entropy obtained from the van't Hoff plot of the middle plateau fugacities are 73.8 +/- 0.4 kJ/mol and 135.5 +/- 0.6 J/mol K, respectively, which are in good accordance with the values obtained more than fifty years ago from plateau pressure measurements. This result reveals that the enthalpy of desorption of MgD2 is slightly lower than that of MgH(2), whereas the entropy change is higher for the deuteride than for the hydride. Although the differences in the enthalpy and entropy of both isotopes are weak, the synergy of both effects is capable of explaining the higher equilibrium pressures for the deuteride than for the hydride. On the other hand, kinetics of magnesium hydride decomposition has been investigated by simultaneous H and D desorption experiments from mixed hydride-deuteride samples. The obtained results reveal that that decomposition is controlled by the nucleation and growth of the Mg phase. Because this reaction step is not affected by the isotopic replacement of H for D no isotope effect is observed in the kinetics of magnesium hydride decomposition. On the contrary, a marked isotope effect is observed in the kinetics of H(2)(D(2)) absorption by magnesium. In this case, the lighter isotope shows faster kinetics than the heavier one, what has been related to the fact that absorption is rate limited by H(D) diffusion through the hydride(deuteride) phase
Diseño de un stand para una bodega de vinos
No full textCarbonell Juan, J. (2006). Diseño de un stand para una bodega de vinos. https://riunet.upv.es/handle/10251/30341.Archivo delegad
Reaction pathways for hydrogen desorption from magnesium hydride/hydroxide composites: bulk and interface effects
No full textThis manuscript investigates the thermal desorption behaviour of MgH(2)/Mg(OH)(2) composites by means of thermal desorption spectroscopy. Besides the H(2)O and H(2) desorption events due to Mg(OH)(2) dehydration and MgH(2) decomposition reactions, respectively, two additional H(2) desorption peaks arise at lower temperatures. These peaks are related to solid-state reactions between magnesium hydride and magnesium hydroxide through different channels. The low temperature H(2) peak (similar to 150 degrees C) is related to reaction between a H atom diffusing from MgH(2) and a surface OH group, whereas the intermediate temperature H(2) peak (similar to 350 degrees C) is due to an interface reaction between the hydride and the hydroxide. The present work supports the theory that the onset of the H(2) desorption coming from MgH(2) decomposition is controlled by an incubation process, consisting in the formation of catalytically active vacancies at the MgO/Mg(OH)(2) surface by dehydration. Possible ways to improve the H(2) desorption kinetics from MgH(2) are discussed in the light of the results obtained
Interaction of Hydrogen with the Beta-Al3Mg2 Complex Metallic Alloy: Experimental Reliability of Theroretical Preditictions
No full textIn this paper we report on some hydrogenation characteristics of beta-Al3Mg2. Pressure-composition-temperature (PCT) absorption curves were obtained in the temperature range 573-658 K up to 4 MPa of H-2-pressure. During the H-absorption process, (beta-Al3Mg2 disproportionates into MgH2 and the solid solution of Al(Mg). This reaction is reversible at the temperatures studied. The enthalpy and entropy of the reaction were determined from the Van't Hoff plot as -62(4) kJ/mol H-2 and -122(6)J/K mol H-2, respectively. A detailed analysis of the sample microstructure at several stages of the absorption and desorption processes has been carried out. The microstructure can be explained by hydrogen diffusion and the disproportionation/recombination reactions of the (3 phase. (C) 2008 Elsevier B.V. All rights reserved
Ejecución de una instalación eléctrica y neumática de una bodega de vino
No full text[ES] El objetivo principal del proyecto es el cálculo de la instalación eléctrica de una nave industrial destinada al uso de una bodega de vinos ubicada en Requena (Valencia) así como el cálculo de la parte neumática que podamos encontrar en una bodega.[EN] This project includes the calculation and design of the electrical and pneumatic installation of a wine cellar.Martínez Orero, J. (2017). Ejecución de una instalación eléctrica y neumática de una bodega de vino. https://riunet.upv.es/handle/10251/97827TFG
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