Predizendo riqueza de espécies de plantas com imagens de satélite, no maior núcleo de florestas secas da América do Sul Areia 2016

The assessment of biodiversity has been recognized as an indicator of ecosystem health for several initiatives worldwide. Satellite remote sensing (SRS) have introduced tools that facilitate the search for information related to plant diversity. With this perspective, this study aimed to verify if spectral variables, from Landsat satellite, can be used as plant species diversity indicators in the Caatinga, the largest dry forests core of South America. To obtain the plant diversity data (richness and Shannon index), an exhaustive exploration of phytosociological researches was carried out in the study area. To evaluate the possible association between spectral variables and plant diversity, Pearson correlation analyzes were performed. Regressions were performed to verify the best predictive models for species richness. The results indicate that there is a high positive association between richness and the infrared band near (R = 0,744; P <0.001). This spectral variable can be used as an indicator of species richness using the potential and quadratic regression functions (R² = 0,61 and R ² = 0,56 p <0.001, respectively). Thus, it is concluded that Landsat satellite potential to estimate species richness in dry forest from South America, lies mainly in the near infrared band, allowing to assess biodiversity at multiple scales and providing a continuous source of information for monitoring purposes.A avaliação da biodiversidade tem sido reconhecida como indicadora da saúde dos ecossistemas por várias iniciativas em todo o mundo. Os dados de sensoriamento remoto por satélite (SRS) têm apresentado ferramentas capazes de auxiliar a busca prática de informações relativas à diversidade vegetal. Com essa perspectiva, esse trabalho teve por objetivo verificar se variáveis espectrais provenientes do satélite Landsat podem ser usadas como indicadores de diversidade de espécies de plantas na Caatinga, o maior núcleo de florestas secas da América do Sul. Para obtenção dos dados de diversidade vegetal (riqueza e índice de Shannon), foi realizada uma busca exaustiva de trabalhos fitossociológicos realizados na área de estudo. Para avaliar a existência de associação entre as variáveis espectrais e a diversidade vegetal, foram feitas análises de Correlação de Pearson. Regressões foram realizadas para verificar os melhores modelos de explicação da riqueza de espécies. Os resultados indicam que existe uma associação alta e positiva entre a riqueza e a banda do infravermelho próximo (R=0,744; P < 0,001). Essa variável espectral pode ser usada como indicadora da riqueza de espécies a partir das funções de regressão potencial e quadrática (R²=0,61 e R²=0,56 p <0,001, respectivamente). Assim, conclui-se que o potencial do uso do satélite Landsat para estimar riqueza de espécies em florestas secas da América do Sul reside principalmente na banda do infravermelho próximo, possibilitando avaliar a biodiversidade em múltiplas escalas e fornecendo uma fonte contínua de informações para seu monitoramento

Giant Electroresistance in Ferroelectric Tunnel Junctions

The interplay between the electron transport in metal/ferroelectric/metal junctions with ultrathin ferroelectric barriers and the polarization state of a barrier is investigated. Using a model which takes into account screening of polarization charges in metallic electrodes and direct quantum tunneling across a ferroelectric barrier we calculate the change in the tunneling conductance associated with the polarization switching. We find the conductance change of a few orders of magnitude for metallic electrodes with significantly different screening lengths. This giant electroresistance effect is the consequence of a different potential profile seen by transport electrons for the two opposite polarization orientations.Comment: 4 page

Comparative Molecular Transporter Efficiency of Cyclic Peptides Containing Tryptophan and Arginine Residues

Cyclic peptides containing tryptophan (W) and arginine (R) residues, [WR]5, [WR]6, [WR]7, [WR]8, and [WR]9, were synthesized through Fmoc solid-phase chemistry to compare their molecular transporter efficiency. The in vitro cytotoxicity of the peptides was evaluated using human leukemia carcinoma cell line (CCRF-CEM) and normal kidney cell line (LLC-PK1). [WR]6, [WR]7, [WR]8, and [WR]9 were not significantly cytotoxic to LLC-PK1cells at a concentration of 10 μM after 3 h incubation. Among all the peptides, [WR]9 was found to be a more efficient transporter than [WR]5, [WR]6, [WR]7, and [WR]8 in CCRF-CEM cells for delivery of a cell-impermeable fluorescence-labeled negatively charged phosphopeptide (F′-GpYEEI). [WR]9 (10 μM) improved the cellular uptake of F′-GpYEEI (2 μM) by 20-fold. The cellular uptake of a fluorescent conjugate of [WR]9, F′-[W9R8K], was increased in a concentration- and time-dependent pattern in CCRF-CEM cells. The uptake of F′-[W9R8K] was slightly reduced in CCRF-CEM cells in the presence of different endocytic inhibitors, such as nystatin, 5-(N-ethyl-N-isopropyl)amiloride, chlorpromazine, chloroquine, and methyl β-cyclodextrin. Furthermore, the uptake of F′-[W9R8K] was shown to be temperature-dependent and slightly adenosine 5′-triphosphate-dependent. The intracellular/cellular localization (in the nucleus and cytoplasm) of F′-[W9R8K] was confirmed by fluorescent microscopy in CCRF-CEM cells. These studies suggest that large cyclic peptides containing arginine and tryptophan can be used as a molecular transporter of specific compounds

Cohabitation in Brazil : historical legacy and recent evolution

The availability of the micro data in the IPUMS samples for several censuses spanning a period of 40 years permits a detailed study of differentials and trends in cohabitation in Brazil than has hitherto been the case. The gist of the story is that the historical race/class and religious differentials and the historical spatial contrasts have largely been maintained, but are now operating at much higher levels than in the 1970s. During the last 40 years cohabitation has dramatically increased in all strata of the Brazilian population, and it has spread geographically to all areas in tandem with further expansions in the regions that had historically higher levels to start with. Moreover, the probability of cohabiting depends not only on individual-level characteristics but also on additional contextual effects operating at the level of meso-regions. The rise of cohabitation in Brazil fits the model of the "Second demographic transition", but it is grafted onto a historical pattern which is still manifesting itself in a number of ways

Dynamics of relaxor ferroelectrics

We study a dynamic model of relaxor ferroelectrics based on the spherical random-bond---random-field model and the Langevin equations of motion. The solution to these equations is obtained in the long-time limit where the system reaches an equilibrium state in the presence of random local electric fields. The complex dynamic linear and third-order nonlinear susceptibilities $\chi_1(\omega)$ and $\chi_3(\omega)$, respectively, are calculated as functions of frequency and temperature. In analogy with the static case, the dynamic model predicts a narrow frequency dependent peak in $\chi_3(T,\omega)$, which mimics a transition into a glass-like state.Comment: 15 pages, Revtex plus 5 eps figure

First principles based atomistic modeling of phase stability in PMN-xPT

We have performed molecular dynamics simulations using a shell model potential developed by fitting first principles results to describe the behavior of the relaxor-ferroelectric (1-x)PbMg1/3Nb2/3O3-xPbTiO3 (PMN-xPT) as function of concentration and temperature, using site occupancies within the random site model. In our simulations, PMN is cubic at all temperatures and behaves as a polar glass. As a small amount of Ti is added, a weak polar state develops, but structural disorder dominates, and the symmetry is rhombohedral. As more Ti is added the ground state is clearly polar and the system is ferroelectric, but with easy rotation of the polarization direction. In the high Ti content region, the solid solution adopts ferroelectric behavior similar to PT, with tetragonal symmetry. The ground state sequence with increasing Ti content is R-MB-O-MC-T. The high temperature phase is cubic at all compositions. Our simulations give the slope of the morphotropic phase boundaries, crucial for high temperature applications. We find that the phase diagram PMN-xPT can be understood within the random site model.Comment: 27 pages, 9 figure