Kinetics of MgWO4 Formation in the Solid State Reaction between MgO and WO3

The solid state reaction of MgWO4 formation from MgO (single crystals) and WO3 was investigated in the temperature range 800 - 985 °C under both air and argon atmosphere. The techniques employed for the kinetic study (contact and thermogravimetric methods) allowed to point out that the process follows the linear rate law in the early stages and the parabolic one in the subsequent stages. From inert marker experiments, kinetic determinations under the two different atmospheres and conductivity measurements, it was possible to state that the reaction is governed by a cation counterdiffusion mechanis

On the Mechanism of CaWO4 Formation in the Solid State from CaO and WO3

The formation in the solid state of CaWO4 from CaO (single crystal) or Ca3WO6 and WO3 was investigated by the contact method between 800 and 1000 °C in air and in argon. The results obtained indicate that these reactions are governed by the diffusion of the W6+ and O2- ions. From the CaWO4 structure, along with the lattice disorder predominant in this compound (0 vacancies and 0 interstitials) and the values of ionic mobilities, it was possible to state that the oxygen diffusion, via V0 2·, represents the rate - determining step in the considered reaction

Kinetics of Formation of SrWO4 in the Solid State Reaction Between WO3 and SrCO3

The solid state reaction WO3 + SrCO3 → SrWO4 + CO2 was studied with the reactants in form both of separate pellets and of powder mixtures. As for pellets, by an application of Wagner's method it was possible to state that the governing process is the cation counterdiffusion involving W6+ and Sr2+. Thermogravimetric measurements in the temperature range 663° - 755 °C on equimolar powder mixtures and with SrCO3 in a specially prepared spherulitic form were interpreted using Dünwald- Wagner's equatio

Kinetics and Mechanism of Solid State Reactions in the Agl-TlI System

The kinetics of the solid state reactions AgI + TiI → AgTlI2 (I) Agl + AgTl2I3 → 2 AgTlI2 (II) AgTlI2 + Til → AgTl2I3 (III) are investigated with reactant pellets by the contact method. With the aid of inert marker experiments and transport number determinations it was possible to state that the governing mechanism is the cation counter-diffusion in all cases and that the rate determining step is the diffusion of Tl+. The experimental reaction rate constants agree reasonably with those calculated on the basis of the Wagner's thermodynamic theory

Effect of Unsaturation, Cyclization and Isotopic Substitution on Critical Demixing Temperatures

The demixing curves in binary systems of nitromethane with 11 1-alkenes, 6 cycloalkanes and 2 cycloalkenes, and of CD8COCD3 with 5 n.alkanes were measured. Critical demixing temperatures: a) are additively affected by unsaturation and cyclization in the first group of systems; b) are increased by a constant amount in the second group, in comparison to the corresponding systems containing CH3COCH3

La responsabilidad social: del capitalismo salvaje al capitalismo benévolo

The world born of the globalization is marked by the emergence of social responsi­bility generalized and extended to all human activity fields as a consequence of the diversity and complexity that clearly define Third Milennium’s aspects. In this new context, the University’s social responsibility is fundamental to the actual passage from wild capitalism to benevolent capitalism, accompanied not only by new tech­nologies but also by solidarity and ethical principles as a distinguishable mark.El mundo generado por la globalización se caracteriza por la aparición de la respon­sabilidad social generalizada y extendida a todos los campos de la actividad humana como consecuencia de la diversidad y la complejidad que definen claramente las características del Tercer Milenio. En este nuevo contexto, la responsabilidad so­cial de la Universidad es fundamental para que el tránsito del capitalismo salvaje al capitalismo benévolo se realice, no solamente acompañando a las nuevas tecnolo­gías, sino que éstas tengan como marco la solidaridad y los principios éticos

La responsabilidad social: del capitalismo salvaje al capitalismo benévolo

The world born of the globalization is marked by the emergence of social responsi­bility generalized and extended to all human activity fields as a consequence of the diversity and complexity that clearly define Third Milennium’s aspects. In this new context, the University’s social responsibility is fundamental to the actual passage from wild capitalism to benevolent capitalism, accompanied not only by new tech­nologies but also by solidarity and ethical principles as a distinguishable mark.El mundo generado por la globalización se caracteriza por la aparición de la respon­sabilidad social generalizada y extendida a todos los campos de la actividad humana como consecuencia de la diversidad y la complejidad que definen claramente las características del Tercer Milenio. En este nuevo contexto, la responsabilidad so­cial de la Universidad es fundamental para que el tránsito del capitalismo salvaje al capitalismo benévolo se realice, no solamente acompañando a las nuevas tecnolo­gías, sino que éstas tengan como marco la solidaridad y los principios éticos

Shwachman Diamond Syndrome: an emergency challenge

Shwachman Diamond Syndrome is a rare congenital disorder characterized by pancreatic insufficiency, bone marrow dysfunction and skeletal abnormalities. No specific test is available for a definitive diagnosis for SDS. In the presence of clinical features of SDS, pancreatic insufficiency should be tested for or lipomatosis radiologically demonstrated. New directions might be found in genetic analysis. Sometimes, a life-threatening event may be the first clinical manifestation of the syndrome

Agronomic and environmental benefits of ‘re-using’ a biodegradable mulching film for two consecutive lettuce cycles

Biodegradable films are a valuable and sustainable alternative to plastic films for mulching soils since they avoid the environmental and economic problems related to plastic removal and dis posal. Nevertheless, the fast degradation of such materials could make them unsuitable for mid-to long-term use. In a field experiment, the agronomic performance of a biodegradable mulching film (MB) was compared to that of conventional low-density polyethylene (LDPE) film for two consecutive lettuce cycles (winter and spring). In the conditions of this trial, MB showed good resistance to atmospheric agents, with a reduction of its integrity and mechanical properties only after six months. The effects on soil temperature and lettuce yield did not differ from those obtained with LDPE films. The effect on harvest timing was the same as that with LDPE in the spring cycle, while in the winter cycle, the harvest was delayed by about five days compared to LDPE. Mulching films reduced nitrate accumulation in leaves mainly during the winter cycle. However, the effect needs to be further explored with experiments in different pedoclimatic conditions that consider the effects of mulching on nitrification and nitrate-reductase activity that could be affected by changes in soil temperature and moisture