NGC 2782: a merger remnant with young stars in its gaseous tidal tail

We have searched for young star-forming regions around the merger remnant NGC 2782. By using GALEX FUV and NUV imaging and HI data we found seven UV sources, located at distances greater than 26 kpc from the center of NGC 2782, and coinciding with its western HI tidal tail. These regions were resolved in several smaller systems when Gemini/GMOS r-band images were used. We compared the observed colors to stellar population synthesis models and we found that these objects have ages of ~1 to 11 Myr and masses ranging from 10^3.9 to 10^4.6 Msun. By using Gemini/GMOS spectroscopic data we confirm memberships and derive high metallicities for three of the young regions in the tail (12+log(O/H)=8.74\pm0.20, 8.81\pm0.20 and 8.78\pm0.20). These metallicities are similar to the value presented by the nuclear region of NGC 2782 and also similar to the value presented for an object located close to the main body of NGC 2782. The high metallicities measured for the star-forming regions in the gaseous tidal tail of NGC 2782 could be explained if they were formed out of highly enriched gas which was once expelled from the center of the merging galaxies when the system collided. An additional possibility is that the tail has been a nursery of a few generations of young stellar systems which ultimately polluted this medium with metals, further enriching the already pre-enriched gas ejected to the tail when the galaxies collided.Comment: 11 pages, 5 figures. Accepted for publication in MNRA

Task planning and control synthesis for robotic manipulation in space applications

Space-based robotic systems for diagnosis, repair and assembly of systems will require new techniques of planning and manipulation to accomplish these complex tasks. Results of work in assembly task representation, discrete task planning, and control synthesis which provide a design environment for flexible assembly systems in manufacturing applications, and which extend to planning of manipulatiuon operations in unstructured environments are summarized. Assembly planning is carried out using the AND/OR graph representation which encompasses all possible partial orders of operations and may be used to plan assembly sequences. Discrete task planning uses the configuration map which facilitates search over a space of discrete operations parameters in sequential operations in order to achieve required goals in the space of bounded configuration sets

Avaliação de diferentes métodos para estimativa de áreas marginais de cursos d'água na bacia do rio Ji-Paraná (RO).

Brazilian legislation considers river margins as environmental preservation areas that should not be used for agricultural production or other commercial activities. For small areas, were detailed cartographic data is available, the definition of these areas are simpler tasks however, Country wide estimates of protected area is still a mater of debate. For large area estimates, two mains uncertainties occur. The lack of detailed cartographic data at suitable scales under-represents the river channels and thus, makes it difficult to estimate total river length. Also, marginal preservation areas are a function of channel width, an information often lacking but crucial for the correct estimation of protected areas in large river basins. Here, three methods for estimating marginal preservation areas are applied to the Ji-Paraná river basin (RO, Brazil) in order to evaluate the importance of channel width. The first considers a constant width along the entire river network for estimating preserved area. The second divides the basin according to the location of fluviometric stations and prescribes different widths for each sub-basin while the third estimates channel width based on an area:width relationship. Total protected area for the three methods ranges from 2% to 21% of basin area, making it clear that channel width should be taken into account when estimating protected areas for large regions and that the methods and assumption used in defining such areas should be clearly stated in order to avoid precipitated conclusions

Métodos para estimativa de áreas de preservação permanente nas margens dos cursos d'água em grandes bacias: avaliação para a bacia do Rio Ji-Paraná, RO.

O Código Florestal brasileiro, juntamente com a resolução Conama no 303/2002, definiu áreas do território nacional classificadas como de preservação permanente (APP). Essas áreas englobam margens dos cursos e corpos d'água, terrenos com declividade acentuada, bordas de chapadas, topos de morro, entre outras feições. No entanto, a escassez de dados cartográficos em escala adequada e de abrangência nacional dificultam ou até impossibilitam as estimativas do alcance territorial da legislação ambiental brasileira. Um exemplo é a delimitação das APPs nas margens dos rios, que, para identificação correta, requer, além da localização, informações sobre a largura dos cursos d'água na época de cheias, dados raramente disponíveis. Este trabalho utilizou dados provenientes da Agência Nacional de Águas (ANA) para estimar as APPs das margens dos rios pertencentes à bacia do Rio Ji-Paraná, RO, identificados na escala 1:1.000.000, levando-se em consideração as larguras dos cursos d'água. Dados de todas as dez estações fluviométricas presentes na bacia com medidas de cota e perfil transversal da calha foram utilizados para estimar a largura máxima do canal de duas maneiras distintas. A primeira delimitou as sub-bacias definidas pelas estações fluviométricas e considerou que todos os cursos d'água pertencentes à sub-bacia apresentavam a mesma largura observada em seu ponto final. A segunda utilizou a relação empírica obtida entre a área de drenagem e a largura da calha nas nove estações para definir a largura de todos os trechos dos cursos d'água da bacia. Por fim, as APPs nas margens dos rios foram delimitadas seguindo os critérios estabelecidos na resolução Conama no 303/2002. A título de comparação, foram também delimitadas as APPs utilizando larguras constantes de 100 m, 200 m e 500 m de faixa marginal para toda a bacia. Entre os diferentes métodos utilizados, a APP nas margens dos rios variou de 1.541 km2 a 15.876 km2 (2,04% a 21,04% da área da bacia, respectivamente). A grande variação na delimitação das áreas marginais deixa claro que estimativas efetuadas para grandes regiões estarão sempre sujeitas a incertezas, de acordo com os métodos utilizados, e que, portanto, é imprescindível o detalhamento dos procedimentos efetuados para esclarecer as vantagens e limitações a que tais estimativas estão sujeitas.bitstream/item/31009/1/BPD-9.pd

Delimitação das áreas de proteção permanente da bacia hidrográfica do Ji-Paraná.

Sistemas de Informação Geográfica (SIG) são importantes ferramentas para o monitoramento de bacias hidrográficas, indispensáveis na tomada de decisões voltadas para práticas de manejo em conformidade com a legislação ambiental. O objetivo deste trabalho foi empregar a ferramenta de SIG na montagem do banco de dados de hidrografia, como largura e perfil da calha dos rios inseridos na bacia hidrográfica do rio Ji-Paraná, Estado de Rondônia, e, a partir dela, gerar um mapa com a delimitação das Áreas de Preservação Permanente (APPs) nas margens dos cursos d?água. Para tal, foi utilizada a rede hidrográfica da Agência Nacional de Águas (ANA) na escala 1:1.000.000, juntamente com informações de cota e largura de rios de diversas estações fluviométricas. A delimitação das sub-bacias foi realizada utilizando dados do sensor Shuttle Radar Topography Mission (SRTM) disponibilizados pela National Aeronautics and Space Administration (NASA). Como resultados, foram delimitadas as APPs nas margens dos cursos d?água, diferenciando a largura da faixa de proteção de acordo com a largura dos rios, conforme a Resolução Conama

Nonplanar integrability at two loops

In this article we compute the action of the two loop dilatation operator on restricted Schur polynomials that belong to the su(2) sector, in the displaced corners approximation. In this non-planar large N limit, operators that diagonalize the one loop dilatation operator are not corrected at two loops. The resulting spectrum of anomalous dimensions is related to a set of decoupled harmonic oscillators, indicating integrability in this sector of the theory at two loops. The anomalous dimensions are a non-trivial function of the 't Hooft coupling, with a spectrum that is continuous and starting at zero at large N, but discrete at finite N.Comment: version to appear in JHE

Vacuum Polarization for a Massless Spin-1/2 Field in the Global Monopole Spacetime at Nonzero Temperature

In this paper we present the effects produced by the temperature in the renormalized vacuum expectation value of the zero-zero component of the energy-momentum tensor associated with massless left-handed spinor field in the pointlike global monopole spacetime. In order to develop this calculation we had to obtain the Euclidean thermal Green function in this background. Because the expression obtained for the thermal energy density cannot be expressed in a closed form, its explicit dependence on the temperature is not completely evident. So, in order to obtain concrete information about its thermal behavior, we develop a numerical analysis of our result in the high-temperature limit for specific values of the parameter $\alpha$ which codify the presence of the monopole.Comment: 22 pages, LaTex format, 5 figure

Spin-1 Particles with Light-Front Approach

For the vector sector, i.e, mesons with spin-1, the electromagnetic form factors and anothers observables are calculated with the light-front approach. However, the light-front quantum field theory have some problems, for example, the rotational symmetry breaking. We solve that problem added the zero modes contribuition to the matrix elements of the electromagnetic current, besides the valence contribuition. We found that among the four independent matrix elements of the plus component in the light-front helicity basis only the $0\to 0$ one carries zero mode contributions.Comment: 5 pages. 3 Figures, use latex and EPJ styl