4,309 research outputs found
On a study and applications of the Concentration-compactness type principle for Systems with critical terms in
In this paper, we obtain some important variants of the Lions and Chabrowski
Concentration-compactness principle, in the context of fractional Sobolev
spaces with variable exponents, especially for nonlinear systems. As an
application of the results, we show the existence and assymptotic behaviour of
nontrivial solutions for elliptic systems involving a new class of general
nonlocal integrodifferential operators with exponent variables and critical
growth conditions in
Interference and complementarity for two-photon hybrid entangled states
In this work we generate two-photon hybrid entangled states (HES), where the
polarization of one photon is entangled with the transverse spatial degree of
freedom of the second photon. The photon pair is created by parametric
down-conversion in a polarization-entangled state. A birefringent double-slit
couples the polarization and spatial degrees of freedom of these photons and
finally, suitable spatial and polarization projections generate the HES. We
investigate some interesting aspects of the two-photon hybrid interference, and
present this study in the context of the complementarity relation that exists
between the visibilities of the one- and two-photon interference patterns.Comment: 10 pages, 4 figures. Accepted in Physical Review
Ribosomal DNA heterochromatin in plants
The aim of this review is to integrate earlier
results and recent findings to present the current state-of-the art
vision concerning the dynamic behavior of the ribosomal
DNA (rDNA) fraction in plants. The global organization and
behavioral features of rDNA make it a most useful system to
analyse the relationship between chromatin topology and gene expression patterns. Correlations between several heterochromatin
fractions and rDNA arrays demonstrate the heterochromatic
nature of the rDNA and reveal the importance of the
genomic environment and of developmental controls in modulating
its dynamicsFCT - Fundação para a Ciência e Tecnologi
Maximum-confidence discrimination among symmetric qudit states
We study the maximum-confidence (MC) measurement strategy for discriminating
among nonorthogonal symmetric qudit states. Restricting to linearly dependent
and equally likely pure states, we find the optimal positive operator valued
measure (POVM) that maximizes our confidence in identifying each state in the
set and minimizes the probability of obtaining inconclusive results. The
physical realization of this POVM is completely determined and it is shown that
after an inconclusive outcome, the input states may be mapped into a new set of
equiprobable symmetric states, restricted, however, to a subspace of the
original qudit Hilbert space. By applying the MC measurement again onto this
new set, we can still gain some information about the input states, although
with less confidence than before. This leads us to introduce the concept of
"sequential maximum-confidence" (SMC) measurements, where the optimized MC
strategy is iterated in as many stages as allowed by the input set, until no
further information can be extracted from an inconclusive result. Within each
stage of this measurement our confidence in identifying the input states is the
highest possible, although it decreases from one stage to the next. In
addition, the more stages we accomplish within the maximum allowed, the higher
will be the probability of correct identification. We will discuss an explicit
example of the optimal SMC measurement applied in the discrimination among four
symmetric qutrit states and propose an optical network to implement it.Comment: 14 pages, 4 figures. Published versio
Avaliação econômica da implantação e manutenção de um sistema agroflorestal com cultivo diversificado.
Resumo: Este trabalho apresenta a análise dos custos de implantação e manutenção de um sistema agroflorestal com cultivos diversificados. Esta avaliação é uma etapa preliminar de uma análise integrada que considerará, além dos fatores socioeconômicos, a recuperação ambiental da área. São apresentados o modelo empregado no sistema, alguns resultados iniciais e os custos de implantação e manutenção. A análise dos dados mostra que houve uma concentração dos gastos na implantação e no primeiro ano deste sistema. Na implantação, o custo principal foi com a aquisição de mudas, enquanto na manutenção os custos se concentraram na mão de obra. Abstract: This paper presents an analysis of the costs of implementation and maintenance of a agroforestry system with diversified crops. This evaluation is a preliminary step in an integrated analysis that will consider also the environmental restoration of the area. The model used in the system, some initial results and the costs of implementation and maintenance are presented. The data analysis indicated that there was a concentration of spending in the implementation and first year of this system. The seedlings was the main cost in the deployment of the system, differently the costs are concentrated in manpower in themaintenance stage
Infecções parasitárias de híbridos tambatinga (Colossoma macropomum x Piaractus brachypomus) cultivados em pisciculturas de Macapá, Estado do Amapá.
Resumo simples
Balanço de energia em uma cultura de feijão caupi (Vigna unguiculata L.) no estado do Pará.
Este trabalho teve como objetivo estudar a variação do balanço de energia e analisar a partição do saldo de radiação em termos dos fluxos de calor latente e calor sensível, para a cultura de feijão caupi (Vigna unguiculata L.) Foram feitas medições contínuas dos fluxos de calor sensível, calor latente e saldo de radiação, no feijão caupi, cultivado na cidade de Tracuateua-PA, no período de agosto a setembro de 2002, usando-se a covariância dos vórtices turbulentos. O saldo de radiação representou, em média, 62% da radiação solar global. A maior porção do saldo de radiação foi usada como fluxo de calor sensível (61 %), enquanto o fluxo de calor latente respondeu apenas por 21 % do saldo de radiação. Esse baixo percentual do saldo de radiação usado como fluxo de calor latente ocorreu devido a restrições hídricas impostas pela falta de chuvas durante o período experimental
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