1,880 research outputs found

    Graffiti, greenery, and obesity in adults: secondary analysis of European cross sectional survey

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    Obesity levels are high and increasing worldwide. Being overweight is linked with increased death rates and contributes to a wide range of conditions, including ischaemic heart disease, hypertension, stroke, diabetes, certain cancers, and diseases of the gall bladder.1 The principal cause of obesity is an imbalance between energy intake and energy expenditure. And there is growing recognition that, independently of individual characteristics, place of residence may be associated with health outcomes, including body size2 and health related behaviours, such as level of physical exercise.3 Few studies have explored which features of the local neighbourhood might be related to these outcomes or behaviours, although perceived attractiveness has been found to be related to levels of physical activity.4 Levels of incivilities, such as litter and graffiti, are associated with poorer health outcomes such as general wellbeing but not, to our knowledge, with levels of physical activity. Few studies use objectively measured indicators of the residential environment or similar research instruments across different settings. Based on our previous work, we hypothesised that areas which are pleasant with lots of greenery and few incivilities might encourage people to take exercise and thereby influence levels of obesity

    Interpreting the photometry and spectroscopy of directly imaged planets: a new atmospheric model applied to beta Pictoris b and SPHERE observations

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    We aim to interpret future photometric and spectral measurements from these instruments, in terms of physical parameters of the planets, with an atmospheric model using a minimal number of assumptions and parameters. We developed Exoplanet Radiative-convective Equilibrium Model (Exo-REM) to analyze the photometric and spectro- scopic data of directly imaged planets. The input parameters are a planet's surface gravity (g), effective temperature (Teff ), and elemental composition. The model predicts the equilibrium temperature profile and mixing ratio profiles of the most important gases. Opacity sources include the H2-He collision-induced absorption and molecular lines from eight compounds (including CH4 updated with the Exomol line list). Absorption by iron and silicate cloud particles is added above the expected condensation levels with a fixed scale height and a given optical depth at some reference wavelength. Scattering was not included at this stage. We applied Exo-REM to photometric and spectral observations of the planet beta Pictoris b obtained in a series of near-IR filters. We derived Teff = 1550 +- 150 K, log(g) = 3.5 +- 1, and radius R = 1.76 +- 0.24 RJup (2-{\sigma} error bars from photometric measurements). These values are comparable to those found in the literature, although with more conservative error bars, consistent with the model accuracy. We were able to reproduce, within error bars, the J- and H-band spectra of beta Pictoris b. We finally investigated the precision to which the above parameterComment: 15 pages, 14 figures, accepted by A&

    Sparse aperture masking at the VLT II. Detection limits for the eight debris disks stars β\beta Pic, AU Mic, 49 Cet, η\eta Tel, Fomalhaut, g Lup, HD181327 and HR8799

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    Context. The formation of planetary systems is a common, yet complex mechanism. Numerous stars have been identified to possess a debris disk, a proto-planetary disk or a planetary system. The understanding of such formation process requires the study of debris disks. These targets are substantial and particularly suitable for optical and infrared observations. Sparse Aperture masking (SAM) is a high angular resolution technique strongly contributing to probe the region from 30 to 200 mas around the stars. This area is usually unreachable with classical imaging, and the technique also remains highly competitive compared to vortex coronagraphy. Aims. We aim to study debris disks with aperture masking to probe the close environment of the stars. Our goal is either to find low mass companions, or to set detection limits. Methods. We observed eight stars presenting debris disks ( β\beta Pictoris, AU Microscopii, 49 Ceti, η\eta Telescopii, Fomalhaut, g Lupi, HD181327 and HR8799) with SAM technique on the NaCo instrument at the VLT. Results. No close companions were detected using closure phase information under 0.5 of separation from the parent stars. We obtained magnitude detection limits that we converted to Jupiter masses detection limits using theoretical isochrones from evolutionary models. Conclusions. We derived upper mass limits on the presence of companions in the area of few times the diffraction limit of the telescope around each target star.Comment: 7 pages, All magnitude detection limits maps are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5

    Investigation of the Potential Impacts of the Entry of Very Light Jets in the National Airspace System

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    Very Light Jets (VLJs) constitute a class of three to eight passenger turbofan-powered aircraft that will enter service in 2006 and will need to be integrated into the National Airspace System. An aircraft performance analysis showed similarities between the predicted performance and capability of Very Light Jets and the performance of existing Light Jets. Based on this an analysis of operating patterns of existing Light Jets was used to predict how Very Light Jets will be operated. Using 396 days of traffic data from the FAA Enhanced Traffic Management System (ETMS), the operating patterns of existing Light Jets were analyzed. It was found that 64% of all the flights flown by Light Jets had their origin, destination or both within the top 23 regional airport systems in the continental United States. This concentration of LJ traffic was found in areas of the air transportation system that are currently exhibiting dense traffic and capacity constraints. The structure of the network of routes flown by existing Light Jets was also studied and a model of network growth was developed. It is anticipated that this concentration will persist with emerging Very Light Jet traffic. This concentration of traffic at key areas in the system will have implications for air traffic control management and airport activity. For regional airport systems, core airports are expected to saturate and, reliever airports will become critical for accommodating traffic demand. The entry of Very Light Jets will significantly increase the traffic load at the terminal airspace; Terminal Radar Approach Control (TRACON). These impacts need to be taken into account to allow a successful integration of these aircraft in the National Airspace System

    Emergence of Secondary Airports and Dynamics of Regional Airport Systems in the United States

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    With the growing demand for air transportation and limited capacity at major airports, there is a need to increase the capacity of airport systems at the metropolitan area level. The increased use of secondary airports has been and is expected to be one of the key mechanisms by which future demand is met in congested metropolitan areas. This thesis provides an analysis of the factors influencing the emergence of secondary airports and the dynamics of multi-airport systems. The congestion of the core airport, the distribution of population at the regional level, the existence and the proximity of a secondary basin of population close to secondary airports were identified as major factors. Ground access and airport infrastructure, the low level of connecting passengers at the core airport were also identified as a contributing factors. The entry of an air carrier –generally a low-cost carrier- was determined to be an essential stimulus in the emergence phenomenon impacting fares and airport competition levels resulting in market stimulation. But the emergence of secondary airports imposes new constraints that need to be taken into account in the national air transportation system improvements. By providing an identification of the factors that influence the emergence of secondary airports and an understanding of the dynamics of regional airport systems this research provides useful support for the planning and the future development of multi-airport systems.NASA Langley, NAG-1-203

    A library of near-infrared integral field spectra of young M-L dwarfs

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    We present a library of near-infrared (1.1-2.45 microns) medium-resolution (R~1500-2000) integral field spectra of 15 young M6-L0 dwarfs, composed of companions with known ages and of isolated objects. We use it to (re)derive the NIR spectral types, luminosities and physical parameters of the targets, and to test (BT-SETTL, DRIFT-PHOENIX) atmospheric models. We derive infrared spectral types L0+-1, L0+-1, M9.5+-0.5, M9.5+-0.5, M9.25+-0.25, M8+0.5-0.75, and M8.5+-0.5 for AB Pic b, Cha J110913-773444, USco CTIO 108B, GSC 08047-00232 B, DH Tau B, CT Cha b, and HR7329B, respectively. BT-SETTL and DRIFT-PHOENIX models yield close Teff and log g estimates for each sources. The models seem to evidence a 600-300+600 K drop of the effective temperature at the M-L transition. Assuming the former temperatures are correct, we derive new mass estimates which confirm that DH Tau B, USco CTIO 108B, AB Pic b, KPNO Tau 4, OTS 44, and Cha1109 lay inside or at the boundary of the planetary mass range. We combine the empirical luminosities of the M9.5-L0 sources to the Teff to derive semi-empirical radii estimates that do not match "hot-start" evolutionary models predictions at 1-3 Myr. We use complementary data to demonstrate that atmospheric models are able to reproduce the combined optical and infrared spectral energy distribution, together with the near-infrared spectra of these sources simultaneously. But the models still fail to represent the dominant features in the optical. This issue casts doubts on the ability of these models to predict correct effective temperatures from near-infrared spectra alone. We advocate the use of photometric and spectroscopic data covering a broad range of wavelengths to study the properties of very low mass young companions to be detected with the planet imagers (Subaru/SCExAO, LBT/LMIRCam, Gemini/GPI, VLT/SPHERE).Comment: 27 pages, 14 tables, 19 figures, accepted for publication in Astronomy & Astrophysic

    High resolution imaging of young M-type stars of the solar neighborhood: Probing the existence of companions down to the mass of Jupiter

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    Context. High contrast imaging is a powerful technique to search for gas giant planets and brown dwarfs orbiting at separation larger than several AU. Around solar-type stars, giant planets are expected to form by core accretion or by gravitational instability, but since core accretion is increasingly difficult as the primary star becomes lighter, gravitational instability would be the a probable formation scenario for yet-to-be-found distant giant planets around a low-mass star. A systematic survey for such planets around M dwarfs would therefore provide a direct test of the efficiency of gravitational instability. Aims. We search for gas giant planets orbiting around late-type stars and brown dwarfs of the solar neighborhood. Methods. We obtained deep high resolution images of 16 targets with the adaptive optic system of VLT-NACO in the Lp band, using direct imaging and angular differential imaging. This is currently the largest and deepest survey for Jupiter-mass planets around Mdwarfs. We developed and used an integrated reduction and analysis pipeline to reduce the images and derive our 2D detection limits for each target. The typical contrast achieved is about 9 magnitudes at 0.5" and 11 magnitudes beyond 1". For each target we also determine the probability of detecting a planet of a given mass at a given separation in our images. Results. We derived accurate detection probabilities for planetary companions, taking into account orbital projection effects, with in average more than 50% probability to detect a 3MJup companion at 10AU and a 1.5MJup companion at 20AU, bringing strong constraints on the existence of Jupiter-mass planets around this sample of young M-dwarfs.Comment: Accepted for publication in A&

    Search for cool giant exoplanets around young and nearby stars - VLT/NaCo near-infrared phase-coronagraphic and differential imaging

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    [Abridged] Context. Spectral differential imaging (SDI) is part of the observing strategy of current and future high-contrast imaging instruments. It aims to reduce the stellar speckles that prevent the detection of cool planets by using in/out methane-band images. It attenuates the signature of off-axis companions to the star, such as angular differential imaging (ADI). However, this attenuation depends on the spectral properties of the low-mass companions we are searching for. The implications of this particularity on estimating the detection limits have been poorly explored so far. Aims. We perform an imaging survey to search for cool (Teff<1000-1300 K) giant planets at separations as close as 5-10 AU. We also aim to assess the sensitivity limits in SDI data taking the photometric bias into account. This will lead to a better view of the SDI performance. Methods. We observed a selected sample of 16 stars (age < 200 Myr, d < 25 pc) with the phase-mask coronagraph, SDI, and ADI modes of VLT/NaCo. Results. We do not detect any companions. As for the sensitivity limits, we argue that the SDI residual noise cannot be converted into mass limits because it represents a differential flux, unlike the case of single-band images. This results in degeneracies for the mass limits, which may be removed with the use of single-band constraints. We instead employ a method of directly determining the mass limits. The survey is sensitive to cool giant planets beyond 10 AU for 65% and 30 AU for 100% of the sample. Conclusions. For close-in separations, the optimal regime for SDI corresponds to SDI flux ratios >2. According to the BT-Settl model, this translates into Teff<800 K. The methods described here can be applied to the data interpretation of SPHERE. We expect better performance with the dual-band imager IRDIS, thanks to more suitable filter characteristics and better image quality.Comment: 19 pages, 16 figures, accepted for publication in A&A, version including language editin
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