2,038 research outputs found

    Constraining Exoplanet Mass from Transmission Spectroscopy

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    Determination of an exoplanet's mass is a key to understanding its basic properties, including its potential for supporting life. To date, mass constraints for exoplanets are predominantly based on radial velocity (RV) measurements, which are not suited for planets with low masses, large semi-major axes, or those orbiting faint or active stars. Here, we present a method to extract an exoplanet's mass solely from its transmission spectrum. We find good agreement between the mass retrieved for the hot Jupiter HD189733b from transmission spectroscopy with that from RV measurements. Our method will be able to retrieve the masses of Earth-sized and super-Earth planets using data from future space telescopes that were initially designed for atmospheric characterization.Comment: 66 pages, 25 figures, published in the December 20, 2013 edition of Science Magazine. Includes supplementary material

    Changing Patterns of Rain or Power?: How an Idea of Adaptation to Climate Change Travels Up and Down to a Village in Simanjiro, Maasailand Northern Tanzania

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    Moving beyond objectivist stances that are largely dominating the climate change research agenda and international policy making, this paper explores an alternative ontology of the Adaptation to Climate Change discourse. By tracing a travelling idea about ‘Adaptation to Climate Change’ (ACC) along a variety of places and multiple encounters the epistemological and political challenges that are entailed by this narrative in the making are laid bare. It focuses on the power dynamics that are revealed by and fostered through the discursive practices that characterize the emergence of this nascent discourse in Tanzania. It is argued that this travelling idea – which is continuously coproduced and reshaped by varying actors in its journey to the ‘local’ level – brings longstanding tensions to the fore that exist between Maasai agropastoralists and the Tanzanian government. Whereas the government portrays the pastoralists in the debate both as victims as well as perpetrators of a changing climate, the grassroots organizations representing the pastoral communities view the Maasai rather as masters of adaptation. It will be shown how the ACC paradigm is wholeheartedly embraced by several actors along its journey until it reaches the rural village of Terrat, where it is by and large rejected. By shining light on these translation practices it is argued that in face of this emerging discourse, adaptation should not solely be seen as a collective human response to (external) changing bio-physical stimuli, but rather as an integrated process that cannot be detached from adaptations to its discursive formations

    Love in times of climate change: how an idea of adaptation to climate change travels to northern Tanzania

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    There is one remarkable feature of the way in which the story of global warming is advancing, at least as far as sub-Saharan Africa is concerned: we cease to treat it as a story. This thesis addresses this blind spot and follows a travelling story of adaptation to climate change from international platforms all the way to northern Tanzania where the Maasai pastoralists dwell. As such, it is demonstrated how this global discourse travels through systems of power, brings old frictions among different stakeholders to the fore and explores the varying lifeworlds that it entangles and brings to life along its way. Following this trajectory provides insight into how climate change, as a statistical description, becomes an agentive force and imaginative resource that is inexhaustible in meaning; a power that operates well beyond its atmospheric properties

    Towards consistent mapping of distant worlds: secondary-eclipse scanning of the exoplanet HD189733b

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    Mapping distant worlds is the next frontier for exoplanet infrared photometry studies. Ultimately, constraining spatial and temporal properties of an exoplanet atmosphere will provide further insight into its physics. For tidally-locked hot Jupiters that transit and are eclipsed by their host star, the first steps are now possible. Our aim is to constrain an exoplanet's shape, brightness distribution (BD) and system parameters from its light curve. Notably, we rely on the eclipse scanning. We use archived Spitzer 8-{\mu}m data of HD189733 (6 transits, 8 secondary eclipses, and a phase curve) in a global MCMC procedure for mitigating systematics. We also include HD189733's out-of-transit radial velocity measurements. We find a 6-{\sigma} deviation from the expected occultation of a uniformly-bright disk. This deviation emerges mainly from HD189733b's thermal pattern, not from its shape. We indicate that the correlation of the orbital eccentricity, e, and BD (uniform time offset) does also depend on the stellar density, \rho*, and the impact parameter, b (e-b-\rho*-BD correlation). For HD189733b, we find that relaxing the e-constraint and using more complex BDs lead to lower stellar/planetary densities and a more localized and latitudinally-shifted hot spot. We obtain an improved constraint on the upper limit of HD189733b's orbital eccentricity, e<0.011 (95%), when including the RV measurements. Our study provides new insights into the analysis of exoplanet light curves and a proper framework for future eclipse-scanning observations. Observations of the same exoplanet at different wavelengths will improve the constraints on its system parameters while ultimately yielding a large-scale time-dependent 3D map of its atmosphere. Finally, we discuss the perspective of extending our method to observations in the visible, in particular to better understand exoplanet albedos.Comment: Accepted for publication in A&A. Final version will be available soon at http://www.aanda.org by Free Open Acces

    Do presenting symptoms, use of pre-diagnostic endoscopy and risk of emergency cancer diagnosis vary by comorbidity burden and type in patients with colorectal cancer?

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    BACKGROUND: Cancer patients often have pre-existing comorbidities, which can influence timeliness of cancer diagnosis. We examined symptoms, investigations and emergency presentation (EP) risk among colorectal cancer (CRC) patients by comorbidity status. METHODS: Using linked cancer registration, primary care and hospital records of 4836 CRC patients (2011-2015), and multivariate quantile and logistic regression, we examined variations in specialist investigations, diagnostic intervals and EP risk. RESULTS: Among colon cancer patients, 46% had at least one pre-existing hospital-recorded comorbidity, most frequently cardiovascular disease (CVD, 18%). Comorbid versus non-comorbid cancer patients more frequently had records of anaemia (43% vs 38%), less frequently rectal bleeding/change in bowel habit (20% vs 27%), and longer intervals from symptom-to-first relevant test (median 136 vs 74 days). Comorbid patients were less likely investigated with colonoscopy/sigmoidoscopy, independently of symptoms (adjusted OR = 0.7[0.6, 0.9] for Charlson comorbidity score 1-2 and OR = 0.5 [0.4-0.7] for score 3+ versus 0. EP risk increased with comorbidity score 0, 1, 2, 3+: 23%, 35%, 33%, 47%; adjusted OR = 1.8 [1.4, 2.2]; 1.7 [1.3, 2.3]; 3.0 [2.3, 4.0]) and for patients with CVD (adjusted OR = 2.0 [1.5, 2.5]). CONCLUSIONS: Comorbid individuals with as-yet-undiagnosed CRC often present with general rather than localising symptoms and are less likely promptly investigated with colonoscopy/sigmoidoscopy. Comorbidity is a risk factor for diagnostic delay and has potential, additionally to symptoms, as risk-stratifier for prioritising patients needing prompt assessment to reduce EP

    Two-Dimensional CdSe-PbSe Heterostructures and PbSe Nanoplatelets: Formation, Atomic Structure, and Optical Properties

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    Cation exchange enables the preparation of nanocrystals (NCs), which are not reachable by direct synthesis methods. In this work, we applied Pb2+-for-Cd2+ cation exchange on CdSe nanoplatelets (NPLs) to prepare two-dimensional CdSe-PbSe heterostructures and PbSe NPLs. Lowering the reaction temperature slowed down the rate of cation exchange, making it possible to characterize the intermediary NCs ex situ with atomically resolved high-angle annular dark-field scanning transmission electron microscopy and optical spectroscopy. We observe that the Pb2+-for-Cd2+ cation exchange starts from the vertices of the NPLs and grows into the zinc blende CdSe (zb-CdSe) lattice as a rock salt PbSe phase (rs-PbSe), while the anion (selenium) sublattice is being preserved. In agreement with previous works on CdTe-PbTe films, the interfaces between zb-CdSe and rs-PbSe consist of shared {001} and {011} planes. The final PbSe NPLs are highly crystalline and contain protrusions at the edges, which are slightly rotated, indicating an atomic reconfiguration of material. The growth of PbSe domains into CdSe NPLs could also be monitored by the emission peak shift as a function of the exchange time. Temperature-dependent emission measurements confirm a size-dependent change of the band gap energy with temperature and reveal a strong influence of the anisotropic shape. Time-resolved photoluminescence measurements between 4 and 30 K show a dark-bright exciton-state splitting different from PbSe QDs with three-dimensional quantum confinement

    Evaluating Climate Variability of the Canonical Hot-Jupiters HD 189733b and HD 209458b through Multi-epoch Eclipse Observations

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    Here we present the analysis of multi-epoch secondary eclipse observations of HD 189733b and HD 209458b as a probe of temporal variability in the planetary climate using both Spitzer channels 1 and 2 (3.6 and 4.5 μm). We expect hot-Jupiter atmospheres to be dynamic environments exhibiting time varying weather. However, it is uncertain to what extent temporal variability will be observable when considering disk integrated observations. We do not detect statistically significant variability and are able to place useful upper limits on the infrared variability amplitudes in these atmospheres. There are very few planets with multi-epoch observations at the required precision to probe variability in dayside emission. The observations considered in this study span several years, providing insight into temporal variability at multiple timescales. In the case of HD 189733b, the best-fit eclipse depths for the channel 2 observations exhibit a scatter of 102 ppm about a median depth of 1827 ppm and in channel 1 exhibit a scatter of 88 ppm about a median depth of 1481 ppm. For HD 209458b, the best-fit eclipse depths for the channel 2 observations exhibit a scatter of 22 ppm about a median depth of 1406 ppm, and in channel 1 exhibit a scatter of 131 ppm about a median depth of 1092 ppm. The precision and scatter in these observations allow us to constrain variability to less than (5.6% and 6.0%) and (12% and 1.6%) for channels (1, 2) of HD 189733b and HD 209458b, respectively

    The mutation of Transportin 3 gene that causes limb girdle muscular dystrophy 1F induces protection against HIV-1 infection

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    The causative mutation responsible for limb girdle muscular dystrophy 1F (LGMD1F) is one heterozygous single nucleotide deletion in the stop codon of the nuclear import factor Transportin 3 gene (TNPO3). This mutation causes a carboxy-terminal extension of 15 amino acids, producing a protein of unknown function (TNPO3_mut) that is co-expressed with wild-type TNPO3 (TNPO3_wt). TNPO3 has been involved in the nuclear transport of serine/arginine-rich proteins such as splicing factors and also in HIV-1 infection through interaction with the viral integrase and capsid. We analyzed the effect of TNPO3_mut on HIV-1 infection using PBMCs from patients with LGMD1F infected ex vivo. HIV-1 infection was drastically impaired in these cells and viral integration was reduced 16-fold. No significant effects on viral reverse transcription and episomal 2-LTR circles were observed suggesting that the integration of HIV-1 genome was restricted. This is the second genetic defect described after CCR5Δ32 that shows strong resistance against HIV-1 infection.This work was supported by crowfunding site PRECIPITA from FECYT, the MERCKSALUD Foundation, the Spanish Ministry of Science (FIS PI12/00969; PI16CIII/00034; SAF2016-78480-R); the Spanish AIDS Research Network RD16CIII/0002/0001 that is included in Acción Estratégica en Salud, Plan Nacional de Investigación Científica, Desarrollo e Innovación Tecnológica 2016-2020, Instituto de Salud Carlos III, European Region Development Fund (FEDER); CIBERer-ISCIII (FIS PI16/00316) co-financed by the European Regional Development Founds (FEDER), IIS La Fe (2016-0388; 2018-0200), and Fundación Isabel Gemio (http://www.fundacionisabelgemio.com). The work of Dra. Sara Rodríguez-Mora is supported by the Asociación Conquistando Escalones, funded by Spanish LGMD1F patients and Sara Borrell grant from Instituto de Salud Carlos III. The work of Dra. María Rosa López-Huertas is financed by ISCIII-Subdirección General de Evaluación and European Funding for Regional Development (FEDER) and by Spanish Ministry of Economy and Competitiveness (PIE13/00040). The work of Elena Mateos is supported by the Spanish Ministry of Economy and Competitiveness SAF2016-78480-R. The work of Lorena Vigón is supported by a pre-doctoral grant from Instituto de Salud Carlos III. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.S
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