Reversible ferromagnetic switching in ZnO:(Co,Mn) powders

We report here on the magnetic properties of ZnO:Mn- and ZnO:Co-doped nanoparticles. We have found that the ferromagnetism of ZnO:Mn can be switched on and off by consecutive low-temperature annealings in O2 and N2, respectively, while the opposite phenomenology was observed for ZnO:Co. These results suggest that different defects (presumably n-type for ZnO:Co and p-type for ZnO:Mn) are required to induce a ferromagnetic coupling in each case. We will argue that ferromagnetism is likely to be restricted to a very thin, nanometric layer at the grain surface. These findings reveal and give insight into the dramatic relevance of surface effects to the occurrence of ferromagnetism in ZnO-doped oxides

Difusão do gadolínio no combustível nuclear UO2 Diffusion of gadolinium in the UO2 nuclear fuel

Coeficientes de difusão do gadolínio foram medidos em volume e em contornos de grão de pastilhas do combustível nuclear UO2. Entre 1505 e 1703 ºC, em atmosfera de hidrogênio, o coeficiente de difusão em volume pode ser descrito pela seguinte equação de Arrhenius: D (cm²/s) = 5,3x10-3 exp (-5,1(eV)/kT). Na mesma faixa de temperaturas e na mesma atmosfera, o coeficiente de difusão do gadolínio em contornos de grão do UO2 pode ser descrito pela expressão: D' delta (cm³ / s) = 1,1x1,0-2 exp (-6,3 (eV) / kT), onde D&acute; é o coeficiente de difusão em contornos de grão e delta é a largura do contorno de grão. Nossos resultados mostram que a difusão em contornos de grão é cerca de quatro ordens de grandeza maior do que a difusão em volume nas mesmas condições experimentais. Para os diferentes isótopos do gadolínio utilizados nas experiências não foi observado efeito isotópico para a difusão do gadolínio no UO2. Não há na literatura dados sobre a difusão do gadolínio no UO2 para comparação com os resultados obtidos neste trabalho.<br>Bulk and grain-boundary diffusion coefficients were measured for gadolinium diffusion in UO2 nuclear fuel pellets. Between 1500 and 1703 ºC, in hydrogen atmosphere, the bulk diffusion coefficient can be described by the following Arrhenius equation: D (cm²/s) = 5,3x10-3 exp (-5,1(eV)/kT) . In the same temperature range and in the same atmosphere, the Gd grain-boundary coefficient in UO2 can be described as follows: D' delta (cm³ / s) = 1,1x1,0-2 exp (-6,3 (eV) / kT), where D&acute; is the grain-boundary diffusion coefficient and delta is the grain-boundary width. Our results show that the grain-boundary diffusion is ca. 4 orders of magnitude greater than the bulk diffusion in the same experimental conditions. Isotopic effect was not observed for the diffusion of the different gadolinium isotopes used in this work. There is no data in the literature about gadolinium diffusion in UO2 to compare to the present results

Natural Horse Boarding Vs Traditional Stable: A Comparison of Hormonal, Hematological and Immunological Parameters, Journal of Applied Animal Welfare Science,

In the equestrian world, two different types of management can be distin-guished: traditional management and natural boarding. The aim of this researchwas to compare hormonal, hematological and immunological parameters of 47horses kept in these two different managements. Blood and horsehair of thehorses were sampled to determine DHEA (dehydroepiandrosterone) and cortisolconcentration through RIA. Moreover, blood count was conducted, and flowcytometry was employed to phenotype lymphocyte subpopulations. Resultsshowed that, in horsehair, DHEA concentration was significantly higher innatural horses, whereas cortisol concentration and cortisol/DEHA ratio signifi-cantly lower. These hormonal parameters are used to assess the stress conditionand the welfare of animals. The most favorable endocrine framework found inhorses kept in natural boarding suggests that this management conveys mostwith ethological and physiological needsof the species. The research underlinesthe need of a modification of horses\u2019husbandry systems. For the first time, thisstudy validates the assay of DHEA in horsehair

Natural Horse Boarding Vs Traditional Stable: A Comparison of Hormonal, Hematological and Immunological Parameters

In the equestrian world, two different types of management can be distinguished: traditional management and natural boarding. The aim of this research was to compare hormonal, hematological and immunological parameters of 47 horses kept in these two different managements. Blood and horsehair of the horses were sampled to determine DHEA (dehydroepiandrosterone) and cortisol concentration through RIA. Moreover, blood count was conducted, and flow cytometry was employed to phenotype lymphocyte subpopulations. Results showed that, in horsehair, DHEA concentration was significantly higher in natural horses, whereas cortisol concentration and cortisol/DEHA ratio significantly lower. These hormonal parameters are used to assess the stress condition and the welfare of animals. The most favorable endocrine framework found in horses kept in natural boarding suggests that this management conveys most with ethological and physiological needs of the species. The research underlines the need of a modification of horses\u2019 husbandry systems. For the first time, this study validates the assay of DHEA in horsehair