Spin-polarized transport in ferromagnetic multilayered semiconductor nanostructures

The occurrence of inhomogeneous spin-density distribution in multilayered ferromagnetic diluted magnetic semiconductor nanostructures leads to strong dependence of the spin-polarized transport properties on these systems. The spin-dependent mobility, conductivity and resistivity in (Ga,Mn)As/GaAs,(Ga,Mn)N/GaN, and (Si,Mn)/Si multilayers are calculated as a function of temperature, scaled by the average magnetization of the diluted magnetic semiconductor layers. An increase of the resistivity near the transition temperature is obtained. We observed that the spin-polarized transport properties changes strongly among the three materials.Comment: 3 pages, 4 figure

Sistemas de criação de capivaras.

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Desempenho reprodutivo da capivara (Hydrochaeris hydrochaeris) em criação semi-intensiva na região Costeira Sul do Rio Grande do Sul.

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Efficiency of low versus high airline pressure in stunning cattle with a pneumatically powered penetrating captive bolt gun

The efficiency of stunning cattle was assessed in 443 animals (304 pure Zebu and 139 crossbred cattle), being mainly mature bulls and cows. Cattle were stunned using a Jarvis pneumatically powered penetrating captive bolt gun operating with low (160–175 psi, N = 82) and high (190 psi, N = 363) airline pressure, which was within the manufactures specifications. Signs of brain function and the position of the shots on the heads were recorded after stunning. Velocity of the captive bolt and its physical parameters were calculated. Cattle shot with low pressures showed more rhythmic respiration (27 vs. 8%, P < 0.001), less tongue protrusion (4 vs. 12%, P = 0.03) and less masseter relaxation (22 vs. 48%, P < 0.001). There was an increased frequency of shots in the ideal position when cattle were shot with the low compared to high airline pressures (15.3 vs. 3.1%). Bolt velocity and its physical parameters were significantly (P < 0.01) higher when using high pressure. Airline pressures below 190 psi are inappropriate when shooting adult Zebu beef cattle with pneumatically powered penetrating captive bolt guns

Origem do adensamento em solos do tabuleiro sertanejo do Estado de Pernambuco: caracterização morfológica e física.

Objetivando fornecer subsídios para propor práticas de manejo que minimizem suas restrições ao cultivo

Fixed points and vacuum energy of dynamically broken gauge theories

We show that if a gauge theory with dynamical symmetry breaking has non-trivial fixed points, they will correspond to extrema of the vacuum energy. This relationship provides a different method to determine fixed points.Comment: 17 pages, uuencoded latex file, 3 figures, uses epsf and epsfig. Submitted to Mod. Phys. Lett.

Caracterização agronômica de diferentes porta-enxertos cítricos enxertados sob laranja pêra.

As laranjeiras-doces compreendem o grupo mais importante de frutas cítricas cultivadas. O Brasil, atualmente, é o maior produtor mundial da fruta (18,06 milhões de toneladas), e também o maior exportador mundial de suco concentrado de laranja, respondendo sozinho por 81% do comercio mundial (AGRIANUAL, 2008). No Estado do Acre, a laranja representa a segunda frutífera de maior expressão, sendo superada somente pela cultura da banana (IBGE, 2008). O Estado apresenta boas características edafoclimáticas para exploração da citricultura, no entanto, a produção não atende à demanda do mercado local, dependendo da importação, em larga escala, de frutas de outros estados brasileiros (Gondim, et al., 2001). Os principais fatores limitantes à expansão do agronegócio citrícola no Acre (Ledo et al., 1999), seria a baixa qualidade das mudas e a inexistência de informações sobre o comportamento de cultivares nas condições do Estado, aliado ao manejo inadequado