Correlation between Mn oxidation state and magnetic behavior in Mn/ZnO multilayers prepared by sputtering

Compositional, microstructural, and magnetic characterization of ZnO 30 Å/Mn x n multilayers prepared by sputtering is presented to study the observed ferromagnetism in the Mn-ZnO system. The nominal Mn layer thickness, x, is varied from 3 to 60 Å, while the number of bilayers, n, is increased to maintain the total amount of Mn constant. Microstructure information was deduced from x-ray reflectivity, Mn oxidation state was determined by x-ray absorption spectroscopy, and magnetic properties were measured over a temperature range of 5–400 K. Magnetic behavior of these samples is found to be related to the Mn layer thickness x. Multilayers with x 30 Å exhibit ferromagnetism with a Curie temperature above 400 K, while mostly paramagnetic behavior is obtained for x15 Å. Magnetic behavior is discussed in terms of electronic and structural parameters of samples. Mn-ZnO interface effect is related to the ferromagnetic order of the samples, but it is not a sufficient condition. The essential role of the Mn oxidation state in the magnetic behavior of this system is pointed out. It is shown a correlation between the obtained ferromagnetism and a Mn oxidation state close to 2+.Ministerio de Educación y Ciencias de España-MAT2003-01880 y MAT2006-0100

Environmental management decision-making in certified hotels

This paper analyses environmental decision-making against two axes, motivations and decision-making processes, to understand the reasons for pro-environmental behaviour by the managements of Spanish Eco-management and Audit Scheme (EMAS)-certified hotels. Mixed methods were used to study perceptions of EMAS and reasons for being certified, with current and lapsed EMAS-certified firms triangulated against expert interviews and documentary evidence. Four groups of hotels were differentiated: Strategic hotels (22%) (with high levels of integrated environmental management), Followers (48%), Greenwashers (11%) and Laggers (19%) (with low levels of integrated environmental management). Most hotels were found to be internally driven in their purpose and ad hoc in their decision-making, with limited understanding of externally driven benefits and motivation for more systematic management systems. This questions the success of EMAS as both a continuous improvement management and as a market-based regulation tool for hotels. Few hotels overall related high environmental standards to the possibilities of gaining market advantage: most wished to avoid legal challenges. The paper also illustrates the ways in which hotels opportunistically switch certification systems to get what they see as a better deal. © 2011 Taylor & Francis

Effects of discontinued endurance methods on VO2max in judokas

Este estudio tuvo como objetivo investigar el efecto de dos diferentes planes de entrenamiento de resistencia basados en la metodología discontinua (intermitente e interválica), sobre el VO2Máx de atletas Antioqueños de Judo de rendimiento. Para ello, 21 Judokas de la Selección Antioqueña pertenecientes a la categoría Senior (20,43±4,18 años), fueron distribuidos aleatoriamente en tres grupos, dos grupos experimentales y un grupo control. Ambos grupos experimentales entrenaron la resistencia durante 4 semanas con 4 estímulos por semana, uno de los grupos experimentales basó su entrenamiento en el método interválico y el otro en el intermitente. Por su parte, el grupo control no realizó ningún tipo de entrenamiento de la resistencia. No se hallaron diferencias significativas entre pretest y postest de ninguno de los grupos ni experimentales ni el de grupo control (p>0,05). Se concluyó que el entrenamiento de la resistencia basado en métodos discontinuos no produjo diferencias significativas en el VO2Máx

Sorption and fractionation of dissolved organic matter and associated phosphorus in agricultural soil

Molibility of dissolved organic matter (DOM) strongly affects the export of nitrogen (N) and phosphorus (P) from oils to surface waters. To study the sorption an mobility of dissolved organic C and P (DOC, DOP) in soil, the pH-dependent sorption of DOM to samples from Ap, EB, and Bt horizons from a Danish agircultural Humic Hapludult was investigated and a kinetic model applicable in field-scale model tested. Sorption experiments of 1 to 72 h duration were conducted at two pH levels (pH 5.0 and 7.0) and six initial DOC concentrtions (0-4.7 mmol L-1). Most sorption/desorption occurred during the first few hours. Dissolved organic carbon and DOP sorption decreased strongly with increased pH and desorption dominated at pH 7, especially for DOC. Due to fractionation during DOM sorption/desorption at DOC concentrations up to 2 mmol L-1, the solution fraction of DOM was enriched in P indicating preferred leaching of DOP. The kinetics of sorption was expressed as a function of how far the solution DOC or DOP concentrations deviate from "equilibrium". The model was able to simulate the kinetics of DOC and DOP sorption/desorption at all concentrations investigated and at both pH levels making it useful for incorporation in field-scale models for quantifying DOC and DOP dynamics

Leishmania spp. epidemiology of canine leishmaniasis in the Yucatan Peninsula

Canine Leishmaniasis is widespread in various Mexican states, where different species of Leishmania have been isolated from dogs. In the present study, we describe the detection of L. braziliensis, L. infantum, and L. mexicana in serum of dogs from the states of Yucatan and Quintana Roo in the Yucatan Peninsula (Mexico). A total of 412 sera were analyzed by ELISA using the total extract of the parasite and the iron superoxide dismutase excreted by different trypanosomatids as antigens. We found the prevalence of L. braziliensis to be 7.52%, L. infantum to be 6.07%, and L. mexicana to be 20.63%, in the dog population studied. The results obtained with ELISA using iron superoxide dismutase as the antigen were confirmed by western blot analysis with its greater sensitivity, and the agreement between the two techniques was very high

Effect of Activated Carbon Made from Cocoa (Theobroma Cacao L.) Shells on the Adsorption of Iron in Aquifer Water

This research aims to determine the effect of activated carbon obtained from cocoa husks (Theobroma cacao L.) on the adsorption of iron (II) present in water of an aquifer for human consumption. Charcoal was prepared at different carbonization temperatures (500, 600 and 700 °C) for 30 minutes and activated with phosphoric acid in the proportions of 1:1. Iron (II) adsorption was determined as a function of variations in mixing speed, contact time, charcoal dosage and stirring speed. It was determined that, over the range considered, agitation speeds had no significant effect on the percentage of iron (II) removal, being the dose of activated carbon and temperature, the most influential variables. The water samples had an initial iron concentration of 3.15 mg/L and 4 mg/L. The best iron (II) adsorption result was obtained with activated carbon at the carbonization temperature of 700 °C, with a mass of 1.5 g of carbon, with efficiencies of 93 % and 98 % for both samples considered. Based on the results, it was concluded water for human consumption is treatable with activated carbon derived from Theobroma cacao L. for the adsorption of iron (II), considering that this parameter is below the maximum limit of 0.3 mg/L allowed by current regulations

Stochastic semiclassical gravity

In the first part of this paper, we show that the semiclassical Einstein-Langevin equation, introduced in the framework of a stochastic generalization of semiclassical gravity to describe the back reaction of matter stress-energy fluctuations, can be formally derived from a functional method based on the influence functional of Feynman and Vernon. In the second part, we derive a number of results for background solutions of semiclassical gravity consisting of stationary and conformally stationary spacetimes and scalar fields in thermal equilibrium states. For these cases, fluctuation-dissipation relations are derived. We also show that particle creation is related to the vacuum stress-energy fluctuations and that it is enhanced by the presence of stochastic metric fluctuations.Comment: 26 pages, RevTeX, no figure