Implicações da Diversidade Genética na Taxonomia de Myotis Nigricans (chiroptera: Vespertilionidae)

Estudos de complexos de espécies crípticas tem grande importância para a biologia evolutiva, pois permitem uma estimativa mais precisa da diversidade biológica assim como auxiliam que os dados biológicos, como ecologia e comportamento, sejam atribuídos à entidade biológica correta. A identificação de espécies crípticas também permite estudos sobre partição e compartilhamento de nichos nestes grupos. Historicamente, dentre as espécies de morcegos, Myotis nigricans (Schinz, 1821) apresenta várias incertezas taxonômicas devido a muitos exemplares sul-americanos do gênero Myotis terem sido por muito tempo mal identificados, usualmente como M. nigricans, devido a problemas por chaves de identificação pouco precisas. Este problema na identificação dos indivíduos dificultou a determinação da distribuição geográfica dessa espécie, além da determinação dos limites entre as espécies do gênero. Pesquisas recentes têm mostrado que a abordagem molecular pode ser uma ferramenta poderosa na identificação de linhagens não reconhecidas pela taxonomia tradicional. Diante do cenário descrito, este estudo tem o intuito de determinar a diversidade genética de exemplares de morcegos identificados como M. nigricans e inferir as relações filogenéticas intraespecíficas de modo a auxiliar na resolução da identidade taxonômica dessa espécie. Para tal, foram obtidas e utilizadas sequências do marcador molecular mitocondrial Cytochrome c oxidase 1 (COI). Este estudo irá auxiliar na estimativa da diversidade genética, na compreensão da estrutura genética do grupo na América do Sul, assim como na classificação taxonômica da espécie em estudo. Palavras chave: Filogeografia, Taxonomia, Myotis, Vespertilionidae, Diversidade genétic

Localization properties of a tight-binding electronic model on the Apollonian network

An investigation on the properties of electronic states of a tight-binding Hamiltonian on the Apollonian network is presented. This structure, which is defined based on the Apollonian packing problem, has been explored both as a complex network, and as a substrate, on the top of which physical models can defined. The Schrodinger equation of the model, which includes only nearest neighbor interactions, is written in a matrix formulation. In the uniform case, the resulting Hamiltonian is proportional to the adjacency matrix of the Apollonian network. The characterization of the electronic eigenstates is based on the properties of the spectrum, which is characterized by a very large degeneracy. The $2\pi /3$ rotation symmetry of the network and large number of equivalent sites are reflected in all eigenstates, which are classified according to their parity. Extended and localized states are identified by evaluating the participation rate. Results for other two non-uniform models on the Apollonian network are also presented. In one case, interaction is considered to be dependent of the node degree, while in the other one, random on-site energies are considered.Comment: 7pages, 7 figure

Thermal Effects on Photon-Induced Quantum Transport

We theoretically investigate laser induced quantum transport in a two-level quantum dot attached to electric contacts. Our approach, based on nonequilibrium Green function technique, allows to include thermal effects on the photon-induced quantum transport and excitonic coherent dynamics. By solving a set of coupled integrodifferential equations, involving correlation and propagator functions, we obtain the photocurrent and the dot occupations as a function of time. The characteristic coherent Rabi oscillations are found in both occupations and photocurrent, with two distinct sources of decoherence: incoherent tunneling and thermal fluctuations. In particular, for increasing temperature the dot becomes more thermally occupied which shrinks the amplitude of the Rabi oscillations, due to Pauli blockade. Finally, due to the interplay between photon and thermal induced electron populations, the photocurrent can switch sign as time evolves and its stationary value can be maximized by tunning the laser intensity.Comment: 5 pages, 4 figure

Generalized entropy arising from a distribution of q-indices

It is by now well known that the Boltzmann-Gibbs (BG) entropy $S_{BG}=-k\sum_{i=1}^W p_i \ln p_i$ can be usefully generalized into the entropy $S_q=k (1-\sum_{i=1}^Wp_i^{q}) / (q-1)$ ($q\in \mathcal{R}; S_1=S_{BG}$). Microscopic dynamics determines, given classes of initial conditions, the occupation of the accessible phase space (or of a symmetry-determined nonzero-measure part of it), which in turn appears to determine the entropic form to be used. This occupation might be a uniform one (the usual {\it equal probability hypothesis} of BG statistical mechanics), which corresponds to $q=1$; it might be a free-scale occupancy, which appears to correspond to $q \ne 1$. Since occupancies of phase space more complex than these are surely possible in both natural and artificial systems, the task of further generalizing the entropy appears as a desirable one, and has in fact been already undertaken in the literature. To illustrate the approach, we introduce here a quite general entropy based on a distribution of $q$-indices thus generalizing $S_q$. We establish some general mathematical properties for the new entropic functional and explore some examples. We also exhibit a procedure for finding, given any entropic functional, the $q$-indices distribution that produces it. Finally, on the road to establishing a quite general statistical mechanics, we briefly address possible generalized constraints under which the present entropy could be extremized, in order to produce canonical-ensemble-like stationary-state distributions for Hamiltonian systems.Comment: 14 pages including 3 figure