11,114 research outputs found
Irreversibility line and low-field grain-boundary pinning in electron-doped superconducting thin films
AC magnetic susceptibilities of electron-doped Pr_{1.85}Ce_{0.15}CuO_4 (PCCO)
and Sm_{1.85}Ce_{0.15}CuO_4 (SCCO) granular thin films have been measured as a
function of temperature and magnetic-field strength. Depending on the level of
homogeneity of our films, two different types of the irreversibility line (IL)
defined as the intergrain-loss peak temperature in the imaginary part of
susceptibility have been found. The obtained results are described via the
critical-state model taking into account the low-field grain-boundary pinning.
The extracted pinning-force densities in more granular SCCO films turn out to
be four times larger than their counterparts in less granular PCCO films
Analysis of the velocity field of granular hopper flow
We report the analysis of radial characteristics of the flow of granular
material through a conical hopper. The discharge is simulated for various
orifice sizes and hopper opening angles. Velocity profiles are measured along
two radial lines from the hopper cone vertex: along the main axis of the cone
and along its wall. An approximate power law dependence on the distance from
the orifice is observed for both profiles, although differences between them
can be noted. In order to quantify these differences, we propose a Local Mass
Flow index that is a promising tool in the direction of a more reliable
classification of the flow regimes in hoppers
Fungos associados a podridão penduncular em mangueira irrigada no submedio São Francisco e eficiencia de fungicidas in vitro e in vivo.
Fungos associados à podridão peduncular foram identificados e a eficiência de fungicidas foi avaliada
Avaliação do controle quÃmico na malformação da mangueira irrigada, no Submédio do Vale do rio São Francisco, Brasil.
O cultivo de espécies frutÃferas na região semi-árida do Nordeste brasileiro vem crescendo continuamente, destacando-se a mangueira pelo valor comercial de seus frutos nos mercados nacional e internacional. As caracterÃsticas edafoclimáticas da região e o manejo fitotécnico empregado nesta cultura têm possibilitado a obtenção de produtividades elevadas. No entanto, com a intensificação do cultivo o potencial de inóculo de patógenos tem aumentado, tornando as doenças uma ameaça constante. Dentre eles, merece especial atenção, a malformação floral e/ou vegetativa, dada a sua rápida disseminação e elevada redução da produtividade. Esses fatores motivaram a realização do presente trabalho visando avaliar o efeito de produtos quÃmicos sobre a doença, em mangueiras irrigadas na região do Submédio do Vale do rio São Francisco. O experimento foi instalado em 01/06/1999, em pomar comercial, cultivar Tommy Atkins, de 4,5 anos de idade, em estádio inicial de florescimento. O Ãndice de infestação inicial da doença foi determinado em 5,21%. O delineamento experimental composta de três plantas. Os produtos com suas respectivas dosagens, em p. c. por 100 litros de água, foram: thiabendazole 600 PM (75g), tebuconazole 200 CE + benomyl 500 PM (100 ml + 60g), tolylfluanid PM + tebuconazole 200 CE (150g + 100 ml), benomyl 500 PM (60 g), carboxin + thiram 200 SC (100 ml, kresoxim-methyl SC (20 ml), Azoxystrobin WG (20 g), epoxiconnazole 125 SC (150 ml). A testemunha foi representada por um tratamento sem produto. Utilizaram-se como parâmetros, o número de panÃculas malformadas e Ãndice de infestação da doença. Os resultados obtidos aos 60 dias após a aplicação dos produtos, não evidenciaram diferenças estatÃsticas entre os tratamentos em relação aos parâmetros avaliados.Coordenado por Abel Rebouças São José, Tiyoko Nair Hojo Rebouça~s, Daniel Nieto Angel, Ivan Vilas Bôas Souza, Nilma Oliveira Dias, Marinês Pereira Bomfim. Trabalhos apresentados no I Simpósio Latino Americano sobre Produção de Manga, 1999, Vitória da Conquista, BA
Physical properties of single-crystalline fibers of the colossal-magnetoresistance manganite La0.7Ca0.3MnO3
We have grown high-quality single crystals of the colossal-magnetoresistance
(CMR) material La0.7Ca0.3MnO3 by using the laser heated pedestal growth (LHPG)
method. Samples were grown as fibers of different diameters, and with lengths
of the order of centimeters. Their composition and structure were verified
through X-ray diffraction, scanning electron microcopy with EDX (Energy
Dispersive X-ray Analysis) and by Rietveld analysis. The quality of the
crystalline fibers was confirmed by Laue and EBSD (Electron Backscatter
Diffraction) patterns. Rocking curves performed along the fiber axis revealed a
half-height width of 0.073 degrees. The CMR behavior was confirmed by
electrical resistivity and magnetization measurements as a function of
temperature.Comment: 11 pages (including 3 figures); to appear in Appl. Phys. Let
Dynamical reentrance and geometry imposed quantization effects in Nb-AlOx-Nb Josephson junction arrays
In this paper, we report on different phenomena related to the magnetic
properties of artificially prepared highly ordered (periodic) two-dimensional
Josephson junction arrays (2D-JJA) of both shunted and unshunted Nb-AlOx-Nb
tunnel junctions. By employing mutual-inductance measurements and using a
high-sensitive bridge, we have thoroughly investigated (both experimentally and
theoretically) the temperature and magnetic field dependence of complex AC
susceptibility of 2D-JJA. We also demonstrate the use of the scanning SQUID
microscope for imaging the local flux distribution within our unshunted arrays
Genesis and evolution of voçorocas on Botucatu formation rocks (Uper Araguaia river, Goiás and Mato Grosso states, Brazil).
Editors: Francisco Gutiérrez, Mateo Gutiérrez, Gloria Desir, Jesús Guerrero, Pedro Lucha, Cinta MarÃn, José MarÃa GarcÃa-Ruiz
Integrated pests management on mangoes at the São Francisco river Valley, Brazil.
Aiming at a rational pest control for this crop, sampling strategies for monitoring and action threshold for the main mango pests were determined based on field and laboratory observations, national and international literature reviews, and tests/adaptations of IPM strategies already in use in other countries
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