On planetary mass determination in the case of super-Earths orbiting active stars. The case of the CoRoT-7 system

This investigation uses the excellent HARPS radial velocity measurements of CoRoT-7 to re-determine the planet masses and to explore techniques able to determine mass and elements of planets discovered around active stars when the relative variation of the radial velocity due to the star activity cannot be considered as just noise and can exceed the variation due to the planets. The main technique used here is a self-consistent version of the high-pass filter used by Queloz et al. (2009) in the first mass determination of CoRoT-7b and CoRoT-7c. The results are compared to those given by two alternative techniques: (1) The approach proposed by Hatzes et al. (2010) using only those nights in which 2 or 3 observations were done; (2) A pure Fourier analysis. In all cases, the eccentricities are taken equal to zero as indicated by the study of the tidal evolution of the system; the periods are also kept fixed at the values given by Queloz et al. Only the observations done in the time interval BJD 2,454,847 - 873 are used because they include many nights with multiple observations; otherwise it is not possible to separate the effects of the rotation fourth harmonic (5.91d = Prot/4) from the alias of the orbital period of CoRoT-7b (0.853585 d). The results of the various approaches are combined to give for the planet masses the values 8.0 \pm 1.2 MEarth for CoRoT-7b and 13.6 \pm 1.4 MEarth for CoRoT 7c. An estimation of the variation of the radial velocity of the star due to its activity is also given.The results obtained with 3 different approaches agree to give masses larger than those in previous determinations. From the existing internal structure models they indicate that CoRoT-7b is a much denser super-Earth. The bulk density is 11 \pm 3.5 g.cm-3 . CoRoT-7b may be rocky with a large iron core.Comment: 12 pages, 11 figure

Sorption of Cr(III) from aqueous solutions by spent brewery grain

Two types of spent brewery grains were tested for Cr(III) uptake from aqueous solutions: not treated spent grains (NTSG), obtained by abundant washing of spent grain obtained from a Portuguese brewing industry with distilled water, and treated spent grain (TSG), prepared by treating NTSG with NaOH 0.5 M for four hours followed by washing with distilled water. Both materials were mixed with chromium solutions (50 and 100 mg Cr(III)/L), varying medium pH from 3 to 5. Maximum metal uptake occurred at pH 5. Langmuir isotherm model well describes Cr(III) biosorption by NTSG and TSG. The maximum uptake capacity obtained was 17.84 mg Cr(III)/g NTSG and 13.87 mg Cr(III)/g TSG. Considering that Langmuir constant, b, reflecting the affinity between the sorbent and the sorbate is lower for NTSG (0.0749 L/mg) it is possible to conclude that the alkalis treatment does not improve spent grain uptake capacity for Cr(III).Fundação para a Ciência e a Tecnologia (FCT) - PRAXIS XXI/BD/15945/98

Cr(III) removal and recovery from Saccharomyces cerevisiae

Heavy metal recovery from biosorbents is of major importance in the assessment of competitiveness of biosorption processes. Several desorption agents (H2SO4, HNO3, HCl, CH3COOH and EDTA) were tested for the selection of the optimal elution conditions for Cr(III) recovery from Saccharomyces cerevisiae cells. Sorption time was optimised as it plays an important role in the sorption–desorption process, being shown that a 30 min sorption period is the best option to ensure metal removal from solution and good recovery from biosorbent. The optimal contact time with desorption agents was also studied, as long exposures to these ones may cause cell damage, affecting biosorbent metal uptake capacity in subsequent sorption cycles. Each eluant was analysed in terms of its desorption capacity and its effect on the biomass metal uptake capacity in multiple sorption–desorption cycles. Considering the effectiveness of chromium desorption from loaded biomass, it was possible to conclude that H2SO4 (pH≈1) was the most effective eluant tested, accomplishing the highest Cr(III) recovery from S. cerevisiae in three consecutive sorption/desorption cycles. Regarding the damage caused by acid treatment on S. cerevisiae cells, assessed by the reduction on metal uptake capacity after elution, it was possible to observe that sulphuric acid was the most harmful eluant causing long term negative effects in metal uptake. By the time the experiments were interrupted (nearly 26 h of continuous cycles) biomass uptake capacity was reduced to about 77% of the value reached before acid treatment.Fundação para a Ciência e a Tecnologia (FCT) – PRAXIS XXI/BD/15945/98

A new analysis of the GJ581 extrasolar planetary system

We have done a new analysis of the available observations for the GJ581 exoplanetary system. Today this system is controversial due to choices that can be done in the orbital determination. The main ones are the ocurrence of aliases and the additional bodies - the planets f and g - announced in Vogt et al. 2010. Any dynamical study of exoplanets requires the good knowledge of the orbital elements and the investigations involving the planet g are particularly interesting, since this body would lie in the Habitable Zone (HZ) of the star GJ581. This region,for this system, is very attractive of the dynamical point of view due to several resonances of two and three bodies present there. In this work, we investigate the conditions under which the planet g may exist. We stress the fact that the planet g is intimately related with the orbital elements of the planet d; more precisely, we conclude that it is not possible to disconnect its existence from the determination of the eccentricity of the planet d. Concerning the planet f, we have found one solution with period $\approx 450$ days, but we are judicious about any affirmation concernig this body because its signal is in the threshold of detection and the high period is in a spectral region where the ocorruence of aliases is very common. Besides, we outline some dynamical features of the habitable zone with the dynamical map and point out the role played by some resonances laying there.Comment: 12 pages, 9 figure

Cr (III) recovery from Saccharomyces cerevisiae by elution : a preliminary study

To recover adsorbed metals from biosorbents, in order to recycle metal and reuse biomass in several adsorption/desorption cycles, elution conditions need to be optimized. The present work aimed to study the following elution parameters: eluant type and concentration (H2SO4, HNO3, HCl, CH3COOH and Na2CO3 0.1, 0.5 and 1.0 M, and EDTA 0.01, 0.05 and 0.1 M); biosorbent contact time with Cr (III) solution (15 min, 2 and 24 h), and S/L ratio (4 and 8 g/L). Experimental data show a decrease in Cr recovery efficiency with increasing sorption time, probably due to metal bioaccumulation. Concerning the S/L ratio, it was possible to observe, in most essays, that best recoveries were achieved using biosorbent concentration of 8 g/L. Comparing the eluants tested according to their metal recovery efficiencies, it can be concluded that Na2CO3 is not a good eluant (maximum recovery of 21 %). All the others showed equivalent behaviours, being necessary more assays to determine eluant treatment effect in Cr uptake capacity in subsequent sorption cycles.Fundação para a Ciência e a Tecnologia (FCT

Mechanisms of Cr(III) biosorption onto residual brewer's yeast

The knowledge and understanding of metal-biomass interactions is crucial to develop and maximize biosorption processes potential to the concentration, removal and recovery of heavy metals from dilute solutions, as well as to define strategies to regenerate and reuse biosorbent in multiple cycles (Ahluwalia and Goyal, 2007; Volesky, 2001). It also turns possible biosorption optimization at a molecular level, including biomass genetic modification to induce changes in morphologic and physiologic characteristics in order to increase metal uptake (Srinath et al., 2002; Volesky, 2001). To reach that purpose, and considering that several mechanisms may contribute to the overall metal uptake depending on the metal and the biosorbent used, environmental factors, and the cell metabolic activity (Dhankhar and Hooda, 2011), it is necessary to study in detail the interactions established in each biosorption system. Heavy metal biosorption involves a combination of several passive accumulation processes, that may include: i) physical adsorption; ii) chemisorption, including ion exchange, coordination, complexation and chelation; iii) and inorganic precipitation (Ahluwalia and Goyal, 2007; Wang and Chen, 2006). According to Gadd (2004), metal-microorganism interactions may be seen as natural strategies to remove, recover or diminish metal toxicity in organic or inorganic forms. Different organisms exhibit different responses to the exposure to toxic ions, varying from transport through cellular membrane, biosorption onto cell walls, entrapment in extracellular structures, precipitation, complexation and redox reactions

Coffee crop coefficient prediction as a function of biophysical variables identified from RGB UAS images

Because of different Brazilian climatic conditions and the different plant conditions, such as the stage of development and even the variety, wide variation may exist in the crop coefficients () values, both spatially and temporally. Thus, the objective of this study was to develop a methodology to determine the short-term using biophysical parameters of coffee plants detected images obtained by an Unmanned Aircraft System (UAS). The study was conducted in Travessia variety coffee plantation. A UAS equipped with a digital camera was used. The images were collected in the field and were processed in Agisoft PhotoScan software. The data extracted from the images were used to calculate the biophysical parameters: leaf area index (LAI), leaf area (LA) and . GeoDA software was used for mapping and spatial analysis. The pseudo-significance test was applied with p < 0.05 to validate the statistic. Moran's index (I) for June was 0.228 and for May was 0.286. Estimates of values in June varied between 0.963 and 1.005. In May, the values were 1.05 for 32 blocks. With this study, a methodology was developed that enables the estimation of using remotely generated biophysical crop data

Avaliação de agroecossistemas em propriedades de produção orgânica no município de Jaguariúna, SP, através de indicadores de sustentabilidade.

A extensão universitária pode dar grande contribuição ao processo de transição da agricultura convencional para modelos de agricultura de base ecológica, que buscam o desenvolvimento sustentável e incorporam princípios e técnicas da Agroecologia. Neste contexto, duas ferramentas vêm sendo associadas com grande eficiência: as metodologias participativas e o uso de indicadores de sustentabilidade. Este trabalho avaliou a sustentabilidade de duas propriedades orgânicas no município de Jaguariúna, através de indicadores construídos e avaliados participativamente. A metodologia empregada permitiu avaliar o estado de cada unidade produtiva, além de classificar a fase de transição agroecológica destas, estabelecendo os gargalos para a sustentabilidade e gerando discussões sobre alternativas que podem embasar seu gerenciamento