45 research outputs found
A ground-based transmission spectrum of the super-Earth exoplanet GJ 1214b
No full textIn contrast to planets with masses similar to that of Jupiter and higher, the bulk compositions of planets in the so-called super-Earth regime (masses 2-10 times that of the Earth) cannot be uniquely determined from a measurement of mass and radius alone. For these planets, there is a degeneracy between the mass and composition of both the interior and a possible atmosphere in theoretical models(1,2). The recently discovered transiting super-Earth exoplanet GJ 1214b is one example of this problem(3). Three distinct models for the planet that are consistent with its mass and radius have been suggested(4). Breaking the degeneracy between these models requires obtaining constraints on the planet's atmospheric composition(5,6). Here we report a ground-based measurement of the transmission spectrum of GJ 1214b between wavelengths of 780 and 1,000 nm. The lack of features in this spectrum rules out (at 4.9 sigma confidence) cloud-free atmospheres composed primarily of hydrogen. If the planet's atmosphere is hydrogen-dominated, then it must contain clouds or hazes that are optically thick at the observed wavelengths at pressures less than 200 mbar. Alternatively, the featureless transmission spectrum is also consistent with the presence of a dense, water vapour atmosphere.European Commissions; NAS
THE FLAT TRANSMISSION SPECTRUM OF THE SUPER-EARTH GJ1214b FROM WIDE FIELD CAMERA 3 ON THE HUBBLE SPACE TELESCOPE
No full textCapitalizing on the observational advantage offered by its tiny M dwarf host, we present Hubble Space Telescope/Wide Field Camera 3 (WFC3) grism measurements of the transmission spectrum of the super-Earth exoplanet GJ1214b. These are the first published WFC3 observations of a transiting exoplanet atmosphere. After correcting for a ramp-like instrumental systematic, we achieve nearly photon-limited precision in these observations, finding the transmission spectrum of GJ1214b to be flat between 1.1 and 1.7 mu m. Inconsistent with a cloud-free solar composition atmosphere at 8.2 sigma, the measured achromatic transit depth most likely implies a large mean molecular weight for GJ1214b's outer envelope. A dense atmosphere rules out bulk compositions for GJ1214b that explain its large radius by the presence of a very low density gas layer surrounding the planet. High-altitude clouds can alternatively explain the flat transmission spectrum, but they would need to be optically thick up to 10 mbar or consist of particles with a range of sizes approaching 1 mu m in diameter
The proverb in three works of Laurence Sterne A sentimental journey, a journal to Eliza, and a political romance: a compilation and commentary
No full textThe present thesis deals with proverbial usage in A Sentimental Journey, A Journal to Eliza, and A Political Romance. It consists of three compilations of proverbs, three commentaries, and a listing of the proverbial expressions cited in each work. In the 'Compilations', those parts of the text in which proverbs occur are quoted followed by the proverbs as they are cited in both modem and contemporary dictionaries. The 'Commentary' deals with the significance of the proverb in each work. In chapter 1, the different devices employed by Sterne when manipulating proverb lore are categorised and examined. In chapters 2, 3 and 4 the different ways in which proverb lore reflects upon the principal themes and ideas, in the three works, are analysed. In the 'Lists of Proverbs' following the commentary, all the proverbs, and the repeated proverbs, cited in Sterne's three works are listed in the order in which they occur in the different texts. The 'Compilations', the 'Commentary' and the 'Lists of Proverbs' complement one another: while the first part of the thesis testifies to Sterne's familiarity with his tradition and the degree of his reliance upon it, the third comprises a synopsis of Part I, and the second deals with the significance of proverb lore in each work. The present endeavour highlights an important aspect of Sterne's writings and makes a contribution to the corpus of literary criticism about the author
A qualitative process evaluation of electronic session-by-session outcome measurement in child and adolescent mental health services
No full textBackground: Regular monitoring of patient progress is important to assess the clinical effectiveness of an intervention. Recently, initiatives within UK child and adolescent mental health services (CAMHS) have advocated the use of session-by-session monitoring to continually evaluate the patient’s outcome throughout the course of the intervention. However, the feasibility and acceptability of such regular monitoring is unknown. Method: Semi-structured qualitative interviews were conducted with clinicians (n= 10), administrative staff (n=8) and families (n= 15) who participated in a feasibility study of an electronic session-by-session outcome monitoring tool, (SxS), which is based on the Strengths and Difficulties Questionnaire (SDQ). This study took place in three CAMHS clinics in Nottinghamshire. The interview transcripts were thematically analysed. Results: We found clinicians accepted the need to complete outcome measures, particularly valuing those completed by the patient. However, there were some difficulties with engaging clinicians in this practice and in the training offered. Generally, patients were supportive of completing SxS in the waiting room prior to the clinic session and assistance with the process from administrative staff was seen to be a key factor
BROADBAND TRANSMISSION SPECTROSCOPY OF THE SUPER-EARTH GJ 1214b SUGGESTS A LOW MEAN MOLECULAR WEIGHT ATMOSPHERE
No full textIn the shadow of the Australian legend: Re-reading Australian literature
No full textThe Australian legend worked as a romantic myth of survival, a foundational grand narrative that legitimised white Australian belonging to the land. The construction of an identity based on the bush ethos and on those values and characteristics recognised as quintessentially Australian helped in the creation of an imagined community. This myth carried a racist underpinning which limited the typical Australian to the category 'white'. Drawing on Foucault 18s discourse analysis I argue that the legend is a discourse, grounded in an untheorised whiteness which defines Australianness. The national identity was modelled on the exclusion of the 'other' from any sense of belonging because Australianness was simply a substitute for whiteness. This exclusion worked on two levels; while it ensured cohesion among whites against a common enemy, it also provided a sense of belonging that could not be questioned because the 'real' Australians, the indigenous people as the common enemy, were left out of a definition of Australianness. Over time this discourse evolved slightly, altering its characteristics, but maintaining its power position and ensuring that its core whiteness remained unaltered. Despite the current claim of a multicultural nation, in fact, the legend is still central to Australian identity and still constitutes the defining characteristic of Australianness. Thus even in a multicultural context where 'white' Australians claim to be just one category among others, they are the ones who define the 'rules' that govern who belongs and who may be granted recognition. In this thesis the evolution of the Australian legend is analysed through readings of key literary texts. While before Federation literature was the major instrument for the construction of the legend and a sense of national identity through an uncritical celebration of the foundational myth, later writing engaged in a critique of the legend and the discourses constructed around it. Contemporary white authors have exposed the discourses of terra nullius and the violence at the foundation of the nation, thus deconstructing the legend. However, their critique is still influenced by their privileged white perspective so that even in their dismantling of the legend there is an implicit celebration of it. It is only when indigenous authors challenge the legend that we find a more radical challenge to the legend and the discourse of whiteness which underpin it. Even then, as argued in this thesis, the legend permeates Australian life and continues to play a role in one 18s understanding of 'Australianness'
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The Flat Transmission Spectrum of the Super-earth Gj1214b From Wide Field Camera 3 on the Hubble Space Telescope
No full textCapitalizing on the observational advantage offered by its tiny M dwarf host, we present Hubble Space Telescope/Wide Field Camera 3 (WFC3) grism measurements of the transmission spectrum of the super-Earth exoplanet GJ1214b. These are the first published WFC3 observations of a transiting exoplanet atmosphere. After correcting for a ramp-like instrumental systematic, we achieve nearly photon-limited precision in these observations, finding the transmission spectrum of GJ1214b to be flat between 1.1 and 1.7 mu m. Inconsistent with a cloud-free solar composition atmosphere at 8.2 sigma, the measured achromatic transit depth most likely implies a large mean molecular weight for GJ1214b's outer envelope. A dense atmosphere rules out bulk compositions for GJ1214b that explain its large radius by the presence of a very low density gas layer surrounding the planet. High-altitude clouds can alternatively explain the flat transmission spectrum, but they would need to be optically thick up to 10 mbar or consist of particles with a range of sizes approaching 1 mu m in diameter.Version of Recor
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Observational Evidence for a Metal-rich Atmosphere on the Super-earth Gj1214b
No full textWe report observations of two consecutive transits of the warm super-Earth exoplanet GJ 1214b at 3.6 and 4.5 mu m with the Infrared Array Camera instrument on board the Spitzer Space Telescope. The two transit light curves allow for the determination of the transit parameters for this system. We find these parameters to be consistent with the previously determined values and no evidence for transit timing variations. The main investigation consists of measuring the transit depths in each bandpass to constrain the planet's transmission spectrum. Fixing the system scale and impact parameters, we measure R-p/R-star = 0.1176(-0.0009)(+0.0008) and 0.1163(-0.0008)(+0.0010) at 3.6 and 4.5 mu m, respectively. Combining these data with the previously reported MEarth Observatory measurements in the red optical allows us to rule out a cloud-free, solar composition (i.e., hydrogen-dominated) atmosphere at 4.5 sigma confidence. This independently confirms a recent finding that was based on a measurement of the planet's transmission spectrum using the Very Large Telescope (VLT). The Spitzer, MEarth, and VLT observations together yield a remarkably flat transmission spectrum over the large wavelength domain spanned by the data. Consequently, cloud-free atmospheric models require more than 30% metals (assumed to be in the form of H2O) by volume to be consistent with all the observations.Version of Recor
