Estrutura genética e demográfica do caranguejo-uçá (Ucides cordatus) na costa do Brasil

O caranguejo Ucides cordatus, popularmente conhecido no Brasil como caranguejo-uçá, é encontrado em manguezais desde o estado de Santa Catarina até a Flórida, nos Estados Unidos. No Brasil, a grande demanda por esta espécie na indústria alimentícia é a causa da cata de várias toneladas de indivíduos todos os anos. Somados a este fator, a destruição dos manguezais e o surgimento de uma doença letal vêm sendo apontados como agentes causadores de severas reduções nos estoques naturais de U. cordatus. Uma vez que reduções populacionais severas tendem a provocar eventos de efeito gargalo e, consequentemente, redução da aptidão dos indivíduos ao longo do tempo, estudos de genética de populações que se dediquem a entender o padrão da distribuição genética, quantificar o fluxo gênico e avaliar as tendências demográficas das populações, são essenciais na elaboração de estratégias de manejo e de conservação. Portanto, neste trabalho, utilizamos sequências de 568 pb da subunidade 1 do gene mitocondrial citocromo c oxidase de 181 espécimes de U. cordatus coletados em 15 localidades ao longo da costa brasileira, entre os estados de Santa Catarina e Maranhão, que compreendem praticamente toda a região de ocorrência da espécie no Brasil. Do total de sequências, 80 haplótipos foram revelados, caracterizando uma elevada diversidade haplotípica (h=0,925). Por outro lado, a diversidade nucleotídica foi baixa (π =0,00462), dada a diferença de poucos pares de bases entre os haplótipos. A relação hierárquica entre os haplótipos não demonstrou nenhuma estruturação geográfica da diversidade genética. Além disso, a análise de variância molecular e os valores da estatística-Φ (Φst=0,00231) revelaram que a maior parte da variação genética em U. cordatus está contida no nível intrapopulacional (98,8%), e apenas uma fração sutil entre os grupos de populações (2,5%). Os valores de Fs de Fu e D de Tajima revelaram-se negativos, indicando que as populações de U. cordatus sofreram eventos de expansão populacional recente. Este cenário também foi confirmado através da análise de mismatch distribution, na qual distribuições unimodais foram encontradas para todas as populações. Nossos dados são concordantes com trabalhos prévios que indicam que o fluxo gênico em U. cordatus é suficientemente amplo a fim de produzir homogeneidade genética entre as populações. Este perfil é condizente com a estratégia de exportação das larvas desta espécie para alto mar, no qual fatores oceanográficos, como correntes marinhas, podem agir de forma a ampliar a dispersão destas formas imaturas

Witnessed Entanglement

We present a new measure of entanglement for mixed states. It can be approximately computable for every state and can be used to quantify all different types of multipartite entanglement. We show that it satisfies the usual properties of a good entanglement quantifier and derive relations between it and other entanglement measures.Comment: Revised version. 7 pages and one figur

Quantum Correlations and Coherence in Spin-1 Heisenberg Chains

We explore quantum and classical correlations along with coherence in the ground states of spin-1 Heisenberg chains, namely the one-dimensional XXZ model and the one-dimensional bilinear biquadratic model, with the techniques of density matrix renormalization group theory. Exploiting the tools of quantum information theory, that is, by studying quantum discord, quantum mutual information and three recently introduced coherence measures in the reduced density matrix of two nearest neighbor spins in the bulk, we investigate the quantum phase transitions and special symmetry points in these models. We point out the relative strengths and weaknesses of correlation and coherence measures as figures of merit to witness the quantum phase transitions and symmetry points in the considered spin-1 Heisenberg chains. In particular, we demonstrate that as none of the studied measures can detect the infinite order Kosterlitz-Thouless transition in the XXZ model, they appear to be able to signal the existence of the same type of transition in the biliear biquadratic model. However, we argue that what is actually detected by the measures here is the SU(3) symmetry point of the model rather than the infinite order quantum phase transition. Moreover, we show in the XXZ model that examining even single site coherence can be sufficient to spotlight the second-order phase transition and the SU(2) symmetry point.Comment: 8 pages. 5 figure

Integral equation approach to tropical ocean dynamics: Part I-Theory and computational methods

In linear, three-dimensional, continuously stratified equatorial β-plane ocean models with arbitrary eastern and western boundaries the shallow water equations for each vertical mode must be solved numerically in the horizontal variables. This paper introduces a new numerical method of solution for the time-Fourier transformed shallow water equations with slip boundary conditions at boundaries of arbitrary geometry. The method is based on a boundary integral equation (BIE) for the pressure perturbation response to the specified wind-stress forcing field. All other dependent variables are expressed as boundary functionals of the pressure perturbation. The kernels of all functionals are constructed from the Green\u27s function for the Laplace Tidal Equation on the β-plane and its derivatives. The efficient computation of these kernels from their exact meridional mode representations may be performed by use of asymptotic methods especially developed for the numerical evaluation of functions expressed as slowly converging series of Hermite functions. The solution of the basic BIE and the computation of the boundary functionals involve the discretization of the ocean boundaries into a number of boundary segments (boundary elements). It is shown that the terms of the BIE involving the wind-stress field over the ocean may be reduced to a boundary integral, which effectively reduces the simulation problem to the solution of a one-dimensional BIE. The method incorporates the ocean physics through the relationship between the coastal pressure field and the basin-wide variables, pointing out to the possibility that the dynamic topography of the ocean may be estimated directly from the wind-stress field and coastal sea-level data

Integral equation approach to tropical ocean dynamics: Part II-Rossby wave scattering from the equatorial Atlantic western boundary

We develop a linear theory for the scattering of equatorial waves of a fixed frequency ω by islands and continental margins of arbitrary geometry by use of the boundary integral equation (BIE) method of Vianna and Holvorcem (Part I of this work). All the solutions of the equatorial β-plane dispersion relations at frequency ω are treated explicitly through the extensive use of exact Green\u27s functions, so that the approach is more general and more rigorous than previous attempts to solve equatorial scattering problems, many of which employ the low-frequency and long-wave approximations. The numerical solution of the HIE is obtained through application of the boundary element method. A numerical study of the scattering of Rossby waves with periods between 50 and 90 days from the equatorial Atlantic western boundary is presented. Some of the resulting interference patterns exhibit a sharp amplitude maximum, whose center lies between 3-9N, 35-47W. The position, width and intensity of this maximum all depend on wave period. We find evidences that this maximum arises from the superposition of zonally damped equatorial modes (evanescent waves) excited at the western boundary. The largest pressure amplitudes along the boundary are found in the southern hemisphere between the Equator and 5S. The phase propagation along the boundary is generally northwestward, except at a few positions where the phase is stationary. We discuss similarities and differences between the calculated responses and observations of intraseasonal oscillations in the tropical Atlantic Ocean

Separable Multipartite Mixed States - Operational Asymptotically Necessary and Sufficient Conditions

We introduce an operational procedure to determine, with arbitrary probability and accuracy, optimal entanglement witness for every multipartite entangled state. This method provides an operational criterion for separability which is asymptotically necessary and sufficient. Our results are also generalized to detect all different types of multipartite entanglement.Comment: 4 pages, 2 figures, submitted to Physical Review Letters. Revised version with new calculation

A Robust Semidefinite Programming Approach to the Separability Problem

We express the optimization of entanglement witnesses for arbitrary bipartite states in terms of a class of convex optimization problems known as Robust Semidefinite Programs (RSDP). We propose, using well known properties of RSDP, several new sufficient tests for the separability of mixed states. Our results are then generalized to multipartite density operators.Comment: Revised version (minor spell corrections) . 6 pages; submitted to Physical Review