1,620 research outputs found

    A new approach to analysing HST spatial scans: the transmission spectrum of HD 209458 b

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    The Wide Field Camera 3 (WFC3) on Hubble Space Telescope (HST) is currently one of the most widely used instruments for observing exoplanetary atmospheres, especially with the use of the spatial scanning technique. An increasing number of exoplanets have been studied using this technique as it enables the observation of bright targets without saturating the sensitive detectors. In this work we present a new pipeline for analyzing the data obtained with the spatial scanning technique, starting from the raw data provided by the instrument. In addition to commonly used correction techniques, we take into account the geometric distortions of the instrument, whose impact may become important when combined to the scanning process. Our approach can improve the photometric precision for existing data and also push further the limits of the spatial scanning technique, as it allows the analysis of even longer spatial scans. As an application of our method and pipeline, we present the results from a reanalysis of the spatially scanned transit spectrum of HD 209458 b. We calculate the transit depth per wavelength channel with an average relative uncertainty of 40 ppm. We interpret the final spectrum with T-Rex, our fully Bayesian spectral retrieval code, which confirms the presence of water vapor and clouds in the atmosphere of HD 209458 b. The narrow wavelength range limits our ability to disentangle the degeneracies between the fitted atmospheric parameters. Additional data over a broader spectral range are needed to address this issue.Comment: 13 pages, 15 figures, 7 tables, Accepted for publication in Ap

    An evaluation of immunoreactivity for c-erbB-2 protein as a marker of poor short-term prognosis in breast cancer.

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    Eighty-five breast carcinomas from the same number of patients have been assessed immunohistochemically using the antiserum 21N for the presence of the c-erbB-2 protein. Twenty-two of the patients had evidence of advanced disease (tumour fixation or distant metastases) at presentation. Follow-up was for a median of 24 months. c-erbB-2 protein was detected in the majority of cells in 14 (16.5%) carcinomas, and to a lesser extent in a further six (7%) tumours. There was no relationship between staining and stage, node status or size but more poorly differentiated carcinomas had evidence of staining (36%) than well (17%) or moderately (14%) differentiated carcinomas (P = 0.02). There was a significant association between staining and mortality (P = 0.009) and recurrence (P = 0.0002). The relative risk of death for staining compared to no staining (after adjusting for node status, stage and grade) was 2.97 (95% confidence interval 1.29, 6.84) and the relative risk of recurrence for staining compared to no staining after similar adjustment was 3.85 (95% confidence interval 1.86-7.97). In this particular group of patients immunoreactivity for c-erbB-2 protein is an independent indicator of poor short-term prognosis

    Detection of an atmosphere around the super-Earth 55 Cancri e

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    We report the analysis of two new spectroscopic observations of the super-Earth 55 Cancri e, in the near infrared, obtained with the WFC3 camera onboard the HST. 55 Cancri e orbits so close to its parent star, that temperatures much higher than 2000 K are expected on its surface. Given the brightness of 55 Cancri, the observations were obtained in scanning mode, adopting a very long scanning length and a very high scanning speed. We use our specialized pipeline to take into account systematics introduced by these observational parameters when coupled with the geometrical distortions of the instrument. We measure the transit depth per wavelength channel with an average relative uncertainty of 22 ppm per visit and find modulations that depart from a straight line model with a 6σ\sigma confidence level. These results suggest that 55 Cancri e is surrounded by an atmosphere, which is probably hydrogen-rich. Our fully Bayesian spectral retrieval code, T-REx, has identified HCN to be the most likely molecular candidate able to explain the features at 1.42 and 1.54 μ\mum. While additional spectroscopic observations in a broader wavelength range in the infrared will be needed to confirm the HCN detection, we discuss here the implications of such result. Our chemical model, developed with combustion specialists, indicates that relatively high mixing ratios of HCN may be caused by a high C/O ratio. This result suggests this super-Earth is a carbon-rich environment even more exotic than previously thought.Comment: 10 pages, 10 figures, 4 tables, Accepted for publication in Ap

    Agrammatic but numerate

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    A central question in cognitive neuroscience concerns the extent to which language enables other higher cognitive functions. In the case of mathematics, the resources of the language faculty, both lexical and syntactic, have been claimed to be important for exact calculation, and some functional brain imaging studies have shown that calculation is associated with activation of a network of left-hemisphere language regions, such as the angular gyrus and the banks of the intraparietal sulcus. We investigate the integrity of mathematical calculations in three men with large left-hemisphere perisylvian lesions. Despite severe grammatical impairment and some difficulty in processing phonological and orthographic number words, all basic computational procedures were intact across patients. All three patients solved mathematical problems involving recursiveness and structure-dependent operations (for example, in generating solutions to bracket equations). To our knowledge, these results demonstrate for the first time the remarkable independence of mathematical calculations from language grammar in the mature cognitive system

    EChOSim: The Exoplanet Characterisation Observatory software simulator

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    EChOSim is the end-to-end time-domain simulator of the Exoplanet Characterisation Observatory (EChO) space mission. EChOSim has been developed to assess the capability EChO has to detect and characterize the atmospheres of transiting exoplanets, and through this revolutionize the knowledge we have of the Milky Way and of our place in the Galaxy. Here we discuss the details of the EChOSim implementation and describe the models used to represent the instrument and to simulate the detection. Software simulators have assumed a central role in the design of new instrumentation and in assessing the level of systematics affecting the measurements of existing experiments. Thanks to its high modularity, EChOSim can simulate basic aspects of several existing and proposed spectrometers for exoplanet transits, including instruments on the Hubble Space Telescope and Spitzer, or ground-based and balloon borne experiments. A discussion of different uses of EChOSim is given, including examples of simulations performed to assess the EChO mission

    The relationship between radiation-induced G1arrest and chromosome aberrations in Li-Fraumeni fibroblasts with or without germline TP53 mutations

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    We previously showed that cultured fibroblasts from patients with the cancer-prone Li-Fraumeni (LF) syndrome, having heterozygous germline TP53 mutations, sustain less ionizing radiation-induced permanent G1 arrest than normal fibroblasts. In contrast, fibroblast strains from LF patients without TP53 mutations showed normal G1 arrest. We have now investigated the relationship between the extent of G1 arrest and the level of structural chromosome damage (mainly dicentrics, rings and acentric fragments) in cells at their first mitosis after G1 irradiation, in 9 LF strains with TP53 mutations, 6 without TP53 mutations and 7 normal strains. Average levels of damage in the mutant strains were 50% higher than in normals, whereas in non-mutant LF strains they were 100% higher. DNA double strand breaks (dsb) are known to act as a signal for p53-dependent G1 arrest and to be the lesions from which chromosome aberrations arise. These results suggest that a minimal level of dsb is required before the signal for arrest is activated and that p53-defective cells have a higher signal threshold than p53-proficient cells. Dsb that do not cause G1 blockage can progress to mitosis and appear as simple deletions or interact to form exchange aberrations. The elevated levels in the non-mutant strains may arise from defects in the extent or accuracy of dsb repair. In LF cells with or without TP53 mutations, the reduced capacity to eliminate or repair chromosomal damage of the type induced by ionising radiation, may contribute to cancer predisposition in this syndrome. © 2001 Cancer Research Campaign http://www.bjcancer.co

    Highly consistent genetic alterations in childhood adrenocortical tumours detected by comparative genomic hybridization

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    We have examined 11 cases of childhood adrenocortical tumours for copy number changes using comparative genomic hybridization (CGH). The changes seen are highly consistent between cases, and are independent of tumour type (carcinoma versus adenoma) or the presence of a germline TP53 mutation. The regions of chromosomal gain and loss identified in this study indicate the location of genes that are potentially important in the development and progression of childhood adrenocortical tumours. Finally, the copy number changes identified in childhood tumours are distinctly different to those seen in adult cases (Kjellman et al (1996) Cancer Res56: 4219–4223), and we propose that this indicates that childhood tumours are of embryonal origin. © 1999 Cancer Research Campaig
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