Comparative Planetary Atmospheres: Models of TrES-1 and HD209458b

We present new self-consistent atmosphere models for transiting planets TrES-1 and HD209458b. The planets were recently observed with the Spitzer Space Telescope in bands centered on 4.5 and 8.0 $\mu$m, for TrES-1, and 24 $\mu$m, for HD209458b. We find that standard solar metallicity models fit the observations for HD209458b. For TrES-1, which has an T_eff ~300 K cooler, we find that models with a metallicity 3-5 times enhanced over solar abundances can match the 1$\sigma$ error bar at 4.5 $\mu$m and 2$\sigma$ at 8.0$\mu$m. Models with solar abundances that included energy deposition into the stratosphere give fluxes that fall within the 2$\sigma$ error bars in both bands. The best-fit models for both planets assume that reradiation of absorbed stellar flux occurs over the entire planet. For all models of both planets we predict planet/star flux ratios in other Spitzer bandpasses.Comment: Accepted to the Astrophysical Journal Letters, May 17, 200

First Space-Based Microlens Parallax Measurement: Spitzer Observations of OGLE-2005-SMC-001

We combine Spitzer and ground-based observations to measure the microlens parallax of OGLE-2005-SMC-001, the first such space-based determination since S. Refsdal proposed the idea in 1966. The parallax measurement yields a projected velocity \tilde v ~ 230 km/s, the typical value expected for halo lenses, but an order of magnitude smaller than would be expected for lenses lying in the Small Magellanic Cloud (SMC) itself. The lens is a weak (i.e., non-caustic-crossing) binary, which complicates the analysis considerably but ultimately contributes additional constraints. Using a test proposed by Assef et al. (2006), which makes use only of kinematic information about different populations but does not make any assumptions about their respective mass functions, we find that the likelihood ratio is L_halo/L_SMC = 20. Hence, halo lenses are strongly favored but SMC lenses are not definitively ruled out. Similar Spitzer observations of additional lenses toward the Magellanic Clouds would clarify the nature of the lens population. The Space Interferometry Mission could make even more constraining measurements.Comment: ApJ, in press. Text and figures are updated to match the journal versio

Sustainability disclosure and reputation: a comparative study

“This is a post-peer-review, pre-copyedit version of an article published in Corporate Reputation Review. The definitive publisher-authenticated version Corporate Reputation Review 14(2), pp.79-96 is available online at: http://www.palgrave-journals.com/crr/index.html”Drawing on legitimacy theory, we discuss that a company’s reputation is a determinant of sustainability disclosure. Specifically, we consider the concept of reputation into three dimensions for analysis: stakeholders’ commitment, financial performance and media exposure. This paper differs from previous social and environmental reporting studies in that it investigates both internal and external contextual factors that influence disclosure practice. We claim that companies with a good financial performance, that are adopting an active strategic position towards stakeholders and that are exposed to significant public pressure are more likely to use sustainability disclosure in order to communicate their legitimacy to operate to stakeholders. Moreover the paper analyses a wide range of corporate reports for their social and environmental content using an international sample that allows for a comparison of disclosure practices among Continental European, UK and USA companies. Our results show that stakeholder commitment and media exposure are positively associated with sustainability disclosure. Moreover, we find evidence that the drivers of disclosure vary by information type

The Spitzer Survey of Interstellar Clouds in the Gould Belt. III. A Multi-Wavelength View of Corona Australis

We present Spitzer Space Telescope IRAC and MIPS observations of a 0.85 deg^2 field including the Corona Australis (CrA) star-forming region. At a distance of 130 pc, CrA is one of the closest regions known to be actively forming stars, particularly within its embedded association, the Coronet. Using the Spitzer data, we identify 51 young stellar objects (YSOs) in CrA which include sources in the well-studied Coronet cluster as well as distributed throughout the molecular cloud. Twelve of the YSOs discussed are new candidates, one of which is located in the Coronet. Known YSOs retrieved from the literature are also added to the list, and a total of 116 candidate YSOs in CrA are compiled. Based on these YSO candidates, the star formation rate is computed to be 12 M_o Myr^-1, similar to that of the Lupus clouds. A clustering analysis was also performed, finding that the main cluster core, consisting of 68 members, is elongated (having an aspect ratio of 2.36), with a circular radius of 0.59 pc and mean surface density of 150 pc^-2. In addition, we analyze outflows and jets in CrA by means of new CO and H_2 data. We present 1.3 mm interferometric continuum observations made with the Submillimeter Array (SMA) covering R CrA, IRS 5, IRS 7, and IRAS 18595-3712 (IRAS 32). We also present multi-epoch H_2 maps and detect jets and outflows, study their proper motions, and identify exciting sources. The Spitzer and ISAAC/VLT observations of IRAS 32 show a bipolar precessing jet, which drives a CO (2-1) outflow detected in the SMA observations. There is also clear evidence for a parsec-scale precessing outflow, E-W oriented, and originating in the SMA 2 region, likely driven by SMA 2 or IRS 7A.Comment: Accepted for publication in ApJS. 112 pages, 42 figures (quality reduced), 13 tables. Full resolution version can be found at http://www.cfa.harvard.edu/~dpeterson/CrA/CrA_highres.pd

The dermal skeleton of the jawless vertebrate Tremataspis mammilata (Osteostraci, stem-Gnathostomata)

Osteostracans are the closest jawless relatives of jawed vertebrates, informing the gradual assembly of the vertebrate mineralised skeleton. Conflicting interpretations of their dermal skeletal histology arise from failure to account for topological variation, obscuring their significance in elucidating vertebrate skeletal evolution. To resolve this, we characterize the cranial and trunk dermal skeleton of a single individual of Tremataspis mammilata (Osteostraci, Thyestiida) at submicron resolution using synchrotron tomography. Our results show that the architecture of the Tremataspis dermal skeleton is, for the most part, conserved over the skeleton and is broadly consistent with previous histological hypotheses based on 2-dimensional thin section study. We resolve debate over the homology of the basal layer, identifying it as osteogenic acellular isopedin rather than odontogenic elasmodine or metaplastic ossification of the stratum compactum of the dermis. We find topological variation between all dermal skeletal elements studied, and particularly between the cranial and postcranial dermal skeleton. This variation can be largely explained by reduction in differentiation due to geometric constraints imposed within smaller skeletal elements, such as scales. Our description of the dermal skeleton of Tremataspis mammilata provides a foundation for interpreting data from cursory topological samples of dermal skeletal diversity obtained in other osteostracans. This reveals general aspects of histological structure that must be primitive for osteostracans and, likely, ancestral jawed vertebrates. Finally, we draw the distinction between hypotheses and descriptions in palaeohistology

Pseudo-single crystal electrochemistry on polycrystalline electrodes : visualizing activity at grains and grain boundaries on platinum for the Fe2+/Fe3+ redox reaction

The influence of electrode surface structure on electrochemical reaction rates and mechanisms is a major theme in electrochemical research, especially as electrodes with inherent structural heterogeneities are used ubiquitously. Yet, probing local electrochemistry and surface structure at complex surfaces is challenging. In this paper, high spatial resolution scanning electrochemical cell microscopy (SECCM) complemented with electron backscatter diffraction (EBSD) is demonstrated as a means of performing ‘pseudo-single-crystal’ electrochemical measurements at individual grains of a polycrystalline platinum electrode, while also allowing grain boundaries to be probed. Using the Fe2+/3+ couple as an illustrative case, a strong correlation is found between local surface structure and electrochemical activity. Variations in electrochemical activity for individual high index grains, visualized in a weakly adsorbing perchlorate medium, show that there is higher activity on grains with a significant (101) orientation contribution, compared to those with (001) and (111) contribution, consistent with findings on single-crystal electrodes. Interestingly, for Fe2+ oxidation in a sulfate medium a different pattern of activity emerges. Here, SECCM reveals only minor variations in activity between individual grains, again consistent with single-crystal studies, with a greatly enhanced activity at grain boundaries. This suggests that these sites may contribute significantly to the overall electrochemical behavior measured on the macroscale

A new view of electrochemistry at highly oriented pyrolytic graphite

Major new insights on electrochemical processes at graphite electrodes are reported, following extensive investigations of two of the most studied redox couples, Fe(CN)64–/3– and Ru(NH3)63+/2+. Experiments have been carried out on five different grades of highly oriented pyrolytic graphite (HOPG) that vary in step-edge height and surface coverage. Significantly, the same electrochemical characteristic is observed on all surfaces, independent of surface quality: initial cyclic voltammetry (CV) is close to reversible on freshly cleaved surfaces (>400 measurements for Fe(CN)64–/3– and >100 for Ru(NH3)63+/2+), in marked contrast to previous studies that have found very slow electron transfer (ET) kinetics, with an interpretation that ET only occurs at step edges. Significantly, high spatial resolution electrochemical imaging with scanning electrochemical cell microscopy, on the highest quality mechanically cleaved HOPG, demonstrates definitively that the pristine basal surface supports fast ET, and that ET is not confined to step edges. However, the history of the HOPG surface strongly influences the electrochemical behavior. Thus, Fe(CN)64–/3– shows markedly diminished ET kinetics with either extended exposure of the HOPG surface to the ambient environment or repeated CV measurements. In situ atomic force microscopy (AFM) reveals that the deterioration in apparent ET kinetics is coupled with the deposition of material on the HOPG electrode, while conducting-AFM highlights that, after cleaving, the local surface conductivity of HOPG deteriorates significantly with time. These observations and new insights are not only important for graphite, but have significant implications for electrochemistry at related carbon materials such as graphene and carbon nanotubes

The Infrared Array Camera (IRAC) for the Spitzer Space Telescope

The Infrared Array Camera (IRAC) is one of three focal plane instruments in the Spitzer Space Telescope. IRAC is a four-channel camera that obtains simultaneous broad-band images at 3.6, 4.5, 5.8, and 8.0 microns. Two nearly adjacent 5.2x5.2 arcmin fields of view in the focal plane are viewed by the four channels in pairs (3.6 and 5.8 microns; 4.5 and 8 microns). All four detector arrays in the camera are 256x256 pixels in size, with the two shorter wavelength channels using InSb and the two longer wavelength channels using Si:As IBC detectors. IRAC is a powerful survey instrument because of its high sensitivity, large field of view, and four-color imaging. This paper summarizes the in-flight scientific, technical, and operational performance of IRAC.Comment: 7 pages, 3 figures. Accepted for publication in the ApJS. A higher resolution version is at http://cfa-www.harvard.edu/irac/publication

Dual task interference during gait in patients with unilateral vestibular disorders

<p>Abstract</p> <p>Background</p> <p>Vestibular patients show slower and unsteady gait; they have also been shown to need greater cognitive resources when carrying out balance and cognitive dual tasks (DT). This study investigated DT interference during gait in a middle-aged group of subjects with dizziness and unsteadiness after unilateral vestibular neuronitis and in a healthy control group.</p> <p>Methods</p> <p>Fourteen individuals with subacute unilateral vestibular impairment after neuronitis and seventeen healthy subjects performed gait and cognitive tasks in single and DT conditions. A statistical gait analysis system was used and spatio-temporal parameters were considered. The cognitive task, consisting of backward counting by three, was tape recorded and the number of right figures was then calculated.</p> <p>Results</p> <p>Both patients and controls showed a more conservative gait during DT and between groups significant differences were not found. A significant decrease in cognitive performance during DT was found only in the vestibular group.</p> <p>Conclusions</p> <p>Results suggest that less attentional resources are available during gait in vestibular patients compared to controls, and that a priority is given in keeping up the motor task to the detriment of a decrease of the cognitive performance during DT.</p