A Link Between the Semi-Major Axis of Extrasolar Gas Giant Planets and Stellar Metallicity

The fact that most extrasolar planets found to date are orbiting metal-rich stars lends credence to the core accretion mechanism of gas giant planet formation over its competitor, the disc instability mechanism. However, the core accretion mechanism is not refined to the point of explaining orbital parameters such as their unexpected semi-major axes and eccentricities. We propose a model, which correlates the metallicity of the host star with the original semi-major axis of its most massive planet, prior to migration, considering that the core accretion scenario governs giant gas planet formation. The model predicts that the optimum regions for planetary formation shift inward as stellar metallicity decreases, providing an explanation for the observed absence of long period planets in metal-poor stars. We compare our predictions with the available data on extrasolar planets for stars with masses similar to the mass of the Sun. A fitting procedure produces an estimate of what we define as the Zero Age Planetary Orbit (ZAPO) curve as a function of the metallicity of the star. The model also hints that the lack of planets circling metal-poor stars may be partly caused by an enhanced destruction probability during the migration process, since the planets lie initially closer to the central stars.Comment: Nature of the replacement: According to recent simulations, the temperature profile, T, is more adequately reproduced by beta = 1 rather than beta = 2. We have introduced a distance scale factor that solves the very fast drop of T for low metallicity and introduces naturally the inferior distance limit of our ZAPO. Under this modification all the fitting process was altere

Boron Doses Applied To Soil During Coffee Development

The range between boron deficiency and toxicity in the coffee crop is narrow and the crop toxicity tolerance depends on the soil type, initial soil content and plant age. The objective of this study was to evaluate different levels of boron in the coffee crop during development and grown in a red clayey Oxisol. Treatments consisted of boron applications (zero; 2.48; 4.96; 9.92; 19.8 and 39.68 kg ha-1) in the boric acid form and applied to soil surface in the area of the tree crown projection. The six treatments were outlined in a randomized block design with four replications and ten plants per plot. The cultivar used was Catuaí IAC 144 with sixteen months old, grown in an Oxisol in Campinas, SP, Brazil. Foliar boron content was analyzed as a function of time by regression analysis. The levels in fruit and yield were analyzed by regression according to boron doses. It can be concluded that higher boron doses in the plant can be observed when fruits are at the first development stage. High doses can reduce yield productivity, being each kilogram of applied boron responsible for a reduction of 0.33 coffee bags. ha-1.71495

Quality of life in Brazilian obese adolescents: effects of a long-term multidisciplinary lifestyle therapy

© 2009 Lofrano-Prado et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution Licens

Comportamento espectral de fitofisionomias do Cerrado e desenvolvimento de índices utilizando bandas sintéticas derivadas de Modelos Lineares de Mistura Espectral aplicados na discriminação de fitofisionomias.

ABSTRACT - The Cerrado biome covers more than two million km² in the central region of Brazil. It is the second largest biome in this country, presenting rich biodiversity. Remote sensing is a useful tool for characterizing land covers. However, because of its particularities and vegetation diversity, Cerrado is not easily distinguishable in optical images. So the use of remote sensing for discriminating Cerrado vegetation requires an investigation of the behavior of their spectral characteristics. This paper analyzes the behavior of vegetation cover in the Cerrado biome through the Landsat5/TM spectral bands and the corresponding synthetic bands derived from mixing models. It also seeks the ways to facilitate the discrimination of the vegetation type classes by defining specific indices using remote sensing tools. The Brasília National Park was chosen as the study area for this research. The methodology used the Linear Spectral Mixture Model applied to two sets of endmembers (green vegetation, bare soil and shade; and green vegetation, dry vegetation and shade) to generate the corresponding fraction images (synthetic bands), which could discriminate the vegetation classes of interest. The use of dry vegetation as one of the endmembers showed more promising results than the use of bare soil for distinguishing Cerrado?s phytophysiognomies