Processamento digital da imagem WorldView-2 para mapeamento do uso e cobertura da terra no Noroeste do Estado do RJ.

A necessidade de compreender as mudanças nos tipos de uso e cobertura da terra tornou indispensável à realização do mapeamento de detalhe - na escala 1:10.000 - do uso e cobertura da terra para a Bacia do Córrego Barro Branco, no Noroeste do Rio de Janeiro. Está região do Estado do Rio de Janeiro ainda apresenta fragmentos de Mata Atlântica que totalizam apenas 9,64% da área do Norte-Noroeste Fluminense. Sendo assim, o uso de imagem de alta resolução neste trabalho, tem como objetivo final a obtenção de um mapa de uso e cobertura da terra que atenda a escala cartográfica de detalhe, e que seja capaz de auxiliar na formulação de planejamentos conservacionistas. Para alcançar tal objetivo, seguiu-se a metodologia de Cruz et al.(2007), e iniciou-se o trabalho através do Processamento Digital de Imagens (PDI) das bandas espectrais azul (450-510 nm), verde (510-580 nm), vermelho (630-690 nm) e infravermelho próximo (770-895) - fusionadas com a pancromática de 0,5 m - do sensor BGRN1, à bordo do satélite Worldview-2, aquisitadas em janeiro de 2010, com a resolução espacial de 2 metros. Optou-se por segmentar a área baseando-se apenas nas bandas espectrais do vermelho e do infravermelho próximo, às quais foi atribuído o mesmo peso; tal escolha baseou-se em testes de inserção/exclusão das demais bandas e verificação do isolamento dos objetos pretendidos. Na obtenção dos objetos de análise, foi empregada na imagem Worldview-2 a segmentação multirresolução por algoritmo desenvolvido para extrair segmentos espectralmente homogêneos com base tanto no valor do pixel quanto na forma do objeto e que são definidos pelos Planos de Informação inseridos. Realizou-se a inserção de cada uma das classes e a modelagem fuzzy de seus descritores. Estes foram selecionados de acordo com a maior separabilidade em relação às demais classes; também foram testadas combinações diversas e as respostas das bandas do vermelho e infravermelho próximo novamente mostraram-se eficientes para aplicação na legenda proposta. As classes foram escolhidas com base nos objetivos propostos neste trabalho, assim como da adequação às resoluções da imagem, amparados pelo Manual Técnico de Uso da Terra (IBGE, 2006). Desta forma, os resultados evidenciaram a matriz de vegetação herbácea predominante na área, com cerca de 80% que majoritariamente apresenta o uso de pastagem extensiva, e os isolados remanescentes florestais com alto índice de fragmentação que somam pouco mais de 10% da cobertura da bacia. Pontualmente, destacam-se a vegetação em regeneração (arbustivo, 1,35%), as culturas temporárias de tomate e milho (3,41%) predominantes nas encostas e os afloramentos rochosos no alto curso (0,82%)

Spin - Phonon Coupling in Nickel Oxide Determined from Ultraviolet Raman Spectroscopy

Nickel oxide (NiO) has been studied extensively for various applications ranging from electrochemistry to solar cells [1,2]. In recent years, NiO attracted much attention as an antiferromagnetic (AF) insulator material for spintronic devices [3-10]. Understanding the spin - phonon coupling in NiO is a key to its functionalization, and enabling AF spintronics' promise of ultra-high-speed and low-power dissipation [11,12]. However, despite its status as an exemplary AF insulator and a benchmark material for the study of correlated electron systems, little is known about the spin - phonon interaction, and the associated energy dissipation channel, in NiO. In addition, there is a long-standing controversy over the large discrepancies between the experimental and theoretical values for the electron, phonon, and magnon energies in NiO [13-23]. This gap in knowledge is explained by NiO optical selection rules, high Neel temperature and dominance of the magnon band in the visible Raman spectrum, which precludes a conventional approach for investigating such interaction. Here we show that by using ultraviolet (UV) Raman spectroscopy one can extract the spin - phonon coupling coefficients in NiO. We established that unlike in other materials, the spins of Ni atoms interact more strongly with the longitudinal optical (LO) phonons than with the transverse optical (TO) phonons, and produce opposite effects on the phonon energies. The peculiarities of the spin - phonon coupling are consistent with the trends given by density functional theory calculations. The obtained results shed light on the nature of the spin - phonon coupling in AF insulators and may help in developing innovative spintronic devices.Comment: 16 pages; 2 figure

Identificação de polimorfimos de base única (SNPs) em genes relacionados à taxa de ovulação em ovinos.

Resumo 708

Bose-Einstein Condensation of S = 1 Ni spin degrees of freedom in NiCl2-4SC(NH2)2

It has recently been suggested that the organic compound NiCl$_2$-4SC(NH$_2$)$_2$ (DTN) exhibits Bose-Einstein Condensation (BEC) of the Ni spin degrees of freedom for fields applied along the tetragonal c-axis. The Ni spins exhibit 3D XY-type antiferromagnetic order above a field-induced quantum critical point at $H_{c1} \sim 2$ T. The Ni spin fluid can be characterized as a system of effective bosons with a hard-core repulsive interaction in which the antiferromagnetic state corresponds to a Bose-Einstein condensate (BEC) of the phase coherent $S = 1$ Ni spin system. We have investigated the the high-field phase diagram and the occurrence of BEC in DTN by means of specific heat and magnetocaloric effect measurements to dilution refrigerator temperatures. Our results indicate that a key prediction of BEC is satisfied; the magnetic field-temperature quantum phase transition line $H_c(T)-H_{c1} \propto T^\alpha$ approaches a power-law at low temperatures, with an exponent $\alpha = 1.47 \pm 0.06$ at the quantum critical point, consistent with the BEC theory prediction of $\alpha = 1.5$.Comment: 4 pages, 4 figure

Estimativa da energia cultural na cotonicultura arbórea no Nordeste brasileiro, comparando-se o Mocó tradicional com o precoce.

bitstream/item/33352/1/ESTIMA-DA-ENERGIA-CULTURAL.pd

Modeling of polar clusters in disordered perovskites: The S-K model with tunneling

The polar clusters generated by random non-central impurities in quantum paraelectrics determine to a great extent the complex dielectric behaviour observed in systems like SCT, KTN or KTL. The competition between a quantum paraelectric phase and an impurity-driven ferroelectric or glass phase depends on the concentration and on the nature of the interaction between clusters. This work presents a simple model in which each cluster is represented by a quantum two level system involving an effective Ising dipolar moment and a tunneling energy A. The interactions between clusters are taken into account by following the guide-lines of the Sherrington-Kirkpatrick model for spin glasses. General expressions for the polarization (P) and the Edwards-Anderson order parameter (q) are given and the phase diagram involving temperature, the normalized mean interaction energy J0/J and tunneling energy A/J0 is built.This work was partially supported by Projecto Praxis XXI/2/2.1/FIS/26/9

Ergodicity breaking in stronium calcium titanate

This work reports experimental results obtained from series of measurements of pyroelectric currents in samples of strontium calcium titanate (SCT) corresponding to contents of Ca of x = 0.002, x = 0.005 and x = 0.011. Sequences of zero field cooling (zfc), field heating (fh), field cooling (fc) and zero field heating (zfh) runs, under different applied electric fields, allowed the observation of the temperature and field dependence of the electric polarization under different initial conditions. The results show the existence of a weak non-ergodic regime in the compositions x = 0.005 and x = 0.011 and allow the tracing of the corresponding Almeida–Thouless line in the T –E diagram. For the three compositions investigated, a small zero field polarization is detected and interpreted as due to defect induced internal fields.We thank gratefully Professor J G Bednorz for providing excellent single crystals. We are very much indebted to A Costa for his technical assistance in the dielectric and pyroelectric measurements. This work was partially supported by Projecto Praxis XXI/P/FIS/14287/9