HST Observations of the Central-Cusp Globular Cluster NGC 6752. The Effect of Binary Stars on the Luminosity Function in the Core

We consider the effect of binary stars on the main-sequence luminosity functions observed in the core of globular clusters, with specific reference to NGC 6752. We find that mass segregation results in an increased binary fraction at fainter magnitudes along the main-sequence. If this effect is not taken into account when analyzing luminosity functions, erroneous conclusions can be drawn regarding the distribution of single stars, and the dynamical state of the cluster. In the core of NGC 6752, our HST data reveal a flat luminosity function, in agreement with previous results. However, when we correct for the increasing binary fraction at faint magnitudes, the LF begins to fall immediately below the turn-off. This effect appears to be confined to the inner core radius of the cluster.Comment: 10 pages, 3 figures Accepted to ApJ Lett Vol 513 Number

Efeitos da arborização na cobertura do solo em agrossistemas com café (Coffea Canephora) no Estado de Rondônia.

O objetivo deste trabalho, durante quatro anos foi de implantar e reduzir a presença de plantas invasoras no solo de aumentar a biomassa de liteira; Enquanto que o sistema café em pleno sol teve 60% da parcela coberta por plantas invasoras, principalmente por gramíneas, os consorciados com bandarra e teca tiveram 15% e 5%; Em contra partida, a biomassa de liteira das arvores sobre o solo e as coberturas das mesmas aumentaram por efeito da queda de material (folhas, galhos, frutos) e da sombra; A presença das espécies florestais reduziu o crescimento das plantas invasoras e aliteira formou uma barreira física acima do solo que dificulta a germinação de sementes de invasoras

What are the Best Hierarchical Descriptors for Complex Networks?

This work reviews several hierarchical measurements of the topology of complex networks and then applies feature selection concepts and methods in order to quantify the relative importance of each measurement with respect to the discrimination between four representative theoretical network models, namely Erd\"{o}s-R\'enyi, Barab\'asi-Albert, Watts-Strogatz as well as a geographical type of network. The obtained results confirmed that the four models can be well-separated by using a combination of measurements. In addition, the relative contribution of each considered feature for the overall discrimination of the models was quantified in terms of the respective weights in the canonical projection into two dimensions, with the traditional clustering coefficient, hierarchical clustering coefficient and neighborhood clustering coefficient resulting particularly effective. Interestingly, the average shortest path length and hierarchical node degrees contributed little for the separation of the four network models.Comment: 9 pages, 4 figure

Otimização de procedimentos de coleta de N2O e CH4 do solo na Amazônia Oriental para validação de metódo para medição por cromatografia gasosa (GC).

Objetivou-se otimizar o método de armazenamento e transporte de coleta dos gases - N2O; CH4 - para melhor integridade das amostras visando dados analíticos de medições químicas por cromatografia gasosa de melhor qualidade. Os frascos foram pesados e o vácuo extremamente controlado para estabilização do peso dois tipos de septos para selagem dos frascos de borossilicato, septos de borracha siliconizada cinza de tubos vacutainer® e septos de borracha siliconizada convencional vermelha de tubos vacutainer®. O septo de borracha siliconizada cinza apresentou melhores resultados na retenção de vácuo nos frascos. E indica-se a sua reutilização em no máximo duas coletas para coleta de N2O e CH4 do solo coletados sob o método da câmara estática

A systematic comparison of supervised classifiers

Pattern recognition techniques have been employed in a myriad of industrial, medical, commercial and academic applications. To tackle such a diversity of data, many techniques have been devised. However, despite the long tradition of pattern recognition research, there is no technique that yields the best classification in all scenarios. Therefore, the consideration of as many as possible techniques presents itself as an fundamental practice in applications aiming at high accuracy. Typical works comparing methods either emphasize the performance of a given algorithm in validation tests or systematically compare various algorithms, assuming that the practical use of these methods is done by experts. In many occasions, however, researchers have to deal with their practical classification tasks without an in-depth knowledge about the underlying mechanisms behind parameters. Actually, the adequate choice of classifiers and parameters alike in such practical circumstances constitutes a long-standing problem and is the subject of the current paper. We carried out a study on the performance of nine well-known classifiers implemented by the Weka framework and compared the dependence of the accuracy with their configuration parameter configurations. The analysis of performance with default parameters revealed that the k-nearest neighbors method exceeds by a large margin the other methods when high dimensional datasets are considered. When other configuration of parameters were allowed, we found that it is possible to improve the quality of SVM in more than 20% even if parameters are set randomly. Taken together, the investigation conducted in this paper suggests that, apart from the SVM implementation, Weka's default configuration of parameters provides an performance close the one achieved with the optimal configuration

Indicadores de sustentabilidade em lavouras de café arborizadas em Rondônia.

O trabalho teve como objetivo de acumular ao longo do tempo, a recuperação de qualidade perdidas durante a derruba e queima de sistemas de florestas primárias