Light curves and colours of the faint Uranian irregular satellites Sycorax, Prospero, Stephano, Setebos and Trinculo

After the work of Gladman et al. (1998), it is now assessed that many irregular satellites are orbiting around Uranus. Despite many studies have been performed in past years, very few is know for the light-curves of these objects and inconsistencies are present between colours derived by different authors. This situation motivated our effort to improve both the knowledge of colours and light curves. We present and discuss time series observations of Sycorax, Prospero, Stephano, Setebos and Trinculo, five faint irregular satellites of Uranus, carried out at VLT, ESO Paranal (Chile) in the nights between 29 and 30 July, 2005 and 25 and 30 November, 2005. We derive light curves for Sycorax and Prospero and colours for all of these these bodies. For Sycorax we obtain colours B-V =0.839 +/- 0.014, V-R = 0.531 +/- 0.005 and a light curve which is suggestive of a periodical variation with period about 3.6 hours and amplitude about 0.067 +/- 0.004 mag. The periods and colours we derive for Sycorax are in agreement with our previous determination in 1999 using NTT. We derive also a light-curve for Prospero which suggests an amplitude of about 0.2 mag and a periodicity of about 4 hours. However, the sparseness of our data, prevents a more precise characterization of the light-curves, and we can not determine wether they are one-peaked or two-peaked. Hence, these periods and amplitudes have to be considered preliminary estimates. As for Setebos, Stephano and Trinculo the present data do not allow to derive any unambiguous periodicity, despite Setebos displays a significant variability with amplitude about as large as that of Prospero. Colours for Prospero, Setebos, Stephano and Trinculo are in marginal agreement with the literature.Comment: Submitted to A&A 13 Dec 2006, Accepted 17 Apr 2007. 18 pages, 8 colours figures BW printable, 6 tables. LaTeX 2.09, with packages: natbib, graphicx, longtable, aa4babbage included in the submission file (tar gzipped of 349 KBytes

Physical Investigation of the Potentially Hazardous Asteroid (144898) 2004 VD17

In this paper we present the observational campaign carried out at ESO NTT and VLT in April and May 2006 to investigate the nature and the structure of the Near Earth Object (144898) 2004 VD17. In spite of a great quantity of dynamical information, according to which it will have a close approach with the Earth in the next century, the physical properties of this asteroid are largely unknown. We performed visible and near--infrared photometry and spectroscopy, as well as polarimetric observations. Polarimetric and spectroscopic data allowed us to classify 2004 VD17 as an E-type asteroid. A good agreement was also found with the spectrum of the aubrite meteorite Mayo Belwa. On the basis of the polarimetric albedo (p_v=0.45) and of photometric data, we estimated a diameter of about 320 m and a rotational period of about 2 hours. The analysis of the results obtained by our complete survey have shown that (144898) 2004 VD17 is a peculiar NEO, since it is close to the breakup limits for fast rotator asteroids, as defined by Pravec and Harris (2000). These results suggest that a more robust structure must be expected, as a fractured monolith or a rubble pile in a "strength regime" (Holsapple 2002).Comment: 32 pages, 7 figure, paper accepted for publication in Icaru

Exploring the surface properties of Transneptunian Objects and Centaurs with polarimetric FORS1/VLT observations

Polarization is a powerful remote-sensing method to investigate solar system bodies. It is an especially sensitive diagnostic tool to reveal physical properties of the bodies whose observational characteristics are governed by small scatterers (dust, regolith surfaces). For these objects, at small phase angles, a negative polarization is observed, i.e., the electric vector E oscillates predominantly in the scattering plane, contrary to what is typical for rather smooth homogeneous surfaces. The behavior of negative polarization with phase angle depends on the size, composition and packing of the scatterers. These characteristics can be unveiled by modelling the light scattering by the dust or regolith in terms of the coherent backscattering mechanism. We have investigated the surface properties of TNOs and Centaurs by means of polarimetric observations with FORS1 of the ESO VLT. TNOs Ixion and Quaoar, and Centaur Chiron show a negative polarization surge. The Centaur Chiron has the deepest polarization minimum (-1.5 - 1.4%). The two TNOs show differing polarization curves: for Ixion, the negative polarization increases rapidly with phase; for Quaoar, the polarization is relatively small (~ -0.6%), and nearly constant at the observed phase angles. For all three objects, modelling results suggest that the surface contains an areal mixture of at least two components with different single-scatterer albedos and photon mean-free paths.Comment: 11 pages, 7 postscript figures, accepted by A&A; astro-ph abstract has been replaced with a more complete on

Where to from here for preventing childhood obesity : an international perspective

Over a quarter of a century ago, the childhood obesity epidemic started its upswing in high-income countries (1) but it was not until the early 2000s that the issue hit the headlines and really forced the public and politicians to take note (2). That awareness has sparked a surge in research, policies, and programs, but what is the current state of action and, more importantly, where to from here for the prevention of childhood obesity?<br /

Desmatamento no bioma Pantanal até o ano 2002: relações com a fitofisionomia e limites municipais.

O objetivo deste trabalho é mapear e quantificar a área desmatada no Bioma Pantanal ocorrida até o ano de 2002, relacionando-a às principais classes fisionômicas de vegetação e aos municípios formadores do Pantanal

Análise do desmatamento no bioma Pantanal até o ano de 2002.

O objetivo deste trabalho é mapear e quantificar a área desmaiada no Bioma Pantanal ocorrida até o ano de 2002, relacionando-a às principais classes fisionómicas de vegetação e aos municípios formadores do Pantanal. O Bioma Pantanal situa-se na região Centro-Oeste, inserido na bacia hidrográfica do Alto rio Paraguai (BAP), que por sua vez está inserida na bacia do Prata. Para compor a área do Pantanal foram necessárias 16 imagens de satélite Landsat-ETM+ e 20 cartas topográficas na escala de 1:250.000. Inicialmente foi elaborado um mosaico do Pantanal composto pelas 16 imagens nas bandas 3, 4 e 5 utilizando o software Envi-4.0. Em seguida foi realizada uma segmentação utilizando-se o software SPRING. Após esse procedimento a área do Bioma Pantanal foi recortada para cada uma das 20 cartas topográficas na escala de 1:250000, dentro dos limites definidos pelo IBGE. O processo de interpretação do desmatamento foi realizado com ampliações da imagem na tela do computador, utilizando o SIG SPRING, o qual foi efetuado após os procedimentos de edição das cartas para a realização de limpeza e generalização dos polígonos de acordo com os temas a serem classificados. Adotou-se o Sistema Fisionômico-ecológico para classificação da vegetação, acrescido de novas informações, quando necessário. Na interpretação das imagens foram considerados os elementos textura, cor, padrão, forma e localização (distribuição geográfica) e os levantamentos efetuados durante os trabalhos de campo na região do Pantanal. Os mapas de desmatamento foram gerados no sistema de projeção cartográfica UTM (Universal Transversa de Mercator), com Datum SAD69 (South América Datum). O erro admitido para o georreferenciamento das imagens de satélite ficou dentro da precisão do erro cartográfico (PEC) admitido para cartas na escala de 1:250.000, que é de 125 metros. A menor área mapeada foi em tomo de 40 ha.Geopantanal 2006

Uso de um sistema de informações geográficas para a base de dados dos solos brasileiros.

O objetivo deste trabalho é estruturar a base de solos da Bacia do Alto Paraguai (BAP), na escala 1:1.000.000, utilizando o Sistema de Processamento de Informações Georreferenciadas - SPRING. Esta etapa faz parte de um projeto maior da Embrapa Informática Agropecuária que objetiva inserir a base de solo brasileira em um Sistema de Informações Geográficas. Atualmente a base de solos do Brasil nessa escala recobre um pouco mais de 91% do território, sendo publicados em 35 volumes pelo projeto Radam e IBGE, recobrindo 47 folhas ao milionésimo. As folhas ao milionésimo foram adquiridas do IBGE em meio digital e formato PDF. Esses mapas foram georreferenciados e digitalizados no SPRING via ampliações tela do computador. Como resultado obteve-se a base digital georreferenciada ao milionésimo dos solos brasileiro, cujo produto para a BAP é apresentado neste artigo. Esta base encontra-se atributada no sistema de classificação de solo original. Além disso, os textos estão devidamente ajustados a cada polígono mapeado. Para cada mapa digitalizado elaborou-se um relatório com a identificação das principais ocorrências de desconfomidades, saber: polígono sem classificação, polígono com duas classes, polígono sem fechamento e sobreposição de informação. No caso da BAP somente as desconformidades do tipo polígono sem classificação e polígono com duas classes foram observados.Geopantanal 2006

Heart failure and the risk of stroke: the Rotterdam Study

Patients with heart failure used to have an increased risk of stroke, but this may have changed with current treatment regimens. We assessed the association between heart failure and the risk of stroke in a population-based cohort that was followed since 1990. The study uses the cohort of the Rotterdam Study and is based on 7,546 participants who at baseline (1990–1993) were aged 55 years or over and free from stroke. The associations between heart failure and risk of stroke were assessed using time-dependent Cox proportional hazards models, adjusted for cardiovascular risk factors (smoking, diabetes mellitus, BMI, ankle brachial index, blood pressure, atrial fibrillation, myocardial infarction and relevant medication). At baseline, 233 participants had heart failure. During an average follow-up time of 9.7 years, 1,014 persons developed heart failure, and 827 strokes (470 ischemic, 75 hemorrhagic, 282 unclassified) occurred. The risk of ischemic stroke was more than five-fold increased in the first month after diagnosis of heart failure (age and sex adjusted HR 5.79, 95% CI 2.15–15.62), but attenuated over time (age and sex adjusted HR 3.50 [95% CI 1.96–6.25] after 1–6 months and 0.83 [95% CI 0.53–1.29] after 0.5–6 years). Additional adjustment for cardiovascular risk factors only marginally attenuated these risks. In conclusion, the risk of ischemic stroke is strongly increased shortly after the diagnosis of heart failure but returns to normal within 6 months after onset of heart failure