3,071 research outputs found

    Compton telescope with coded aperture mask: Imaging with the INTEGRAL/IBIS Compton mode

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    Compton telescopes provide a good sensitivity over a wide field of view in the difficult energy range running from a few hundred keV to several MeV. Their angular resolution is, however, poor and strongly energy dependent. We present a novel experimental design associating a coded mask and a Compton detection unit to overcome these pitfalls. It maintains the Compton performance while improving the angular resolution by at least an order of magnitude in the field of view subtended by the mask. This improvement is obtained only at the expense of the efficiency that is reduced by a factor of two. In addition, the background corrections benefit from the coded mask technique, i.e. a simultaneous measurement of the source and background. This design is implemented and tested using the IBIS telescope on board the INTEGRAL satellite to construct images with a 12' resolution over a 29 degrees x 29 degrees field of view in the energy range from 200 keV to a few MeV. The details of the analysis method and the resulting telescope performance, particularly in terms of sensitivity, are presented

    Affective iconic words benefit from additional sound–meaning integration in the left amygdala

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    Recent studies have shown that a similarity between sound and meaning of a word (i.e., iconicity) can help more readily access the meaning of that word, but the neural mechanisms underlying this beneficial role of iconicity in semantic processing remain largely unknown. In an fMRI study, we focused on the affective domain and examined whether affective iconic words (e.g., high arousal in both sound and meaning) activate additional brain regions that integrate emotional information from different domains (i.e., sound and meaning). In line with our hypothesis, affective iconic words, compared to their non‐iconic counterparts, elicited additional BOLD responses in the left amygdala known for its role in multimodal representation of emotions. Functional connectivity analyses revealed that the observed amygdalar activity was modulated by an interaction of iconic condition and activations in two hubs representative for processing sound (left superior temporal gyrus) and meaning (left inferior frontal gyrus) of words. These results provide a neural explanation for the facilitative role of iconicity in language processing and indicate that language users are sensitive to the interaction between sound and meaning aspect of words, suggesting the existence of iconicity as a general property of human language

    Enhanced Trabeculectomy: The Moorfields Safer Surgery System

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    Trabeculectomy with antifibrotic treatment is still the most popular incisional procedure for glaucoma filtration surgery (GFS) worldwide. The advent of antifibrotic agents reduced failure due to scarring but resulted in increased complications. Advances in trabeculectomy surgery have been driven by the need to minimise the risk of: (1) complications and (2) surgical failure. This chapter covers preoperative, intraoperative, and postoperative strategies, which improve the outcome of GFS. Strategies to reduce the risk of complications centre on the prevention of postoperative hypotony by minimising the risk of overdrainage, postoperative wound leaks, and poor bleb morphology. Surgical techniques to reduce the risk of postoperative fibrosis by the use of antifibrotic agents (including mitomycin C) are discussed in detail. These techniques are based on a combination of considerable clinical experience, observation, and laboratory research. The need to address pre-, intra-, and postoperative issues in each individual patient is emphasised. These changes are embodied in the system we call the "Moorfields Safer Surgery System." The use of these strategies has considerably reduced the incidence of major complications, including hypotony, cystic blebs, and endophthalmitis in practices around the world. Most of these techniques are simple, require minimal equipment, and can be easily mastered. They are associated with an improvement in overall outcome and it is hoped that this chapter will help the reader benefit from these advances

    Detection of Water Vapor in the Thermal Spectrum of the Non-Transiting Hot Jupiter upsilon Andromedae b

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    The upsilon Andromedae system was the first multi-planet system discovered orbiting a main sequence star. We describe the detection of water vapor in the atmosphere of the innermost non-transiting gas giant ups~And~b by treating the star-planet system as a spectroscopic binary with high-resolution, ground-based spectroscopy. We resolve the signal of the planet's motion and break the mass-inclination degeneracy for this non-transiting planet via deep combined flux observations of the star and the planet. In total, seven epochs of Keck NIRSPEC LL band observations, three epochs of Keck NIRSPEC short wavelength KK band observations, and three epochs of Keck NIRSPEC long wavelength KK band observations of the ups~And~system were obtained. We perform a multi-epoch cross correlation of the full data set with an atmospheric model. We measure the radial projection of the Keplerian velocity (KPK_P = 55 ±\pm 9 km/s), true mass (MbM_b = 1.7 0.24+0.33^{+0.33}_{-0.24} MJM_J), and orbital inclination \big(ibi_b = 24 ±\pm 4^{\circ}\big), and determine that the planet's opacity structure is dominated by water vapor at the probed wavelengths. Dynamical simulations of the planets in the ups~And~system with these orbital elements for ups~And~b show that stable, long-term (100 Myr) orbital configurations exist. These measurements will inform future studies of the stability and evolution of the ups~And~system, as well as the atmospheric structure and composition of the hot Jupiter.Comment: Accepted to A

    Simulating the Multi-Epoch Direct Detection Technique to Isolate the Thermal Emission of the Non-Transiting Hot Jupiter HD187123B

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    We report the 6.5σ\sigma detection of water from the hot Jupiter HD187123b with a Keplerian orbital velocity KpK_p of 53 ±\pm 13 km/s. This high confidence detection is made using a multi-epoch, high resolution, cross correlation technique, and corresponds to a planetary mass of 1.40.3+0.5^{+0.5}_{-0.3} MJM_J and an orbital inclination of 21 ±\pm 5^{\circ}. The technique works by treating the planet/star system as a spectroscopic binary and obtaining high signal-to-noise, high resolution observations at multiple points across the planet's orbit to constrain the system's binary dynamical motion. All together, seven epochs of Keck/NIRSPEC LL-band observations were obtained, with five before the instrument upgrade and two after. Using high resolution SCARLET planetary and PHOENIX stellar spectral models, along with a line-by-line telluric absorption model, we were able to drastically increase the confidence of the detection by running simulations that could reproduce, and thus remove, the non-random structured noise in the final likelihood space well. The ability to predict multi-epoch results will be extremely useful for furthering the technique. Here, we use these simulations to compare three different approaches to combining the cross correlations of high resolution spectra and find that the Zucker 2003 log(L) approach is least affected by unwanted planet/star correlation for our HD187123 data set. Furthermore, we find that the same total S/N spread across an orbit in many, lower S/N epochs rather than fewer, higher S/N epochs could provide a more efficient detection. This work provides a necessary validation of multi-epoch simulations which can be used to guide future observations and will be key to studying the atmospheres of further separated, non-transiting exoplanets.Comment: Accepted to AJ, 14 pages, 10 figure

    Ground- and Space-based Detection of the Thermal Emission Spectrum of the Transiting Hot Jupiter KELT-2Ab

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    We describe the detection of water vapor in the atmosphere of the transiting hot Jupiter KELT-2Ab by treating the star-planet system as a spectroscopic binary with high-resolution, ground-based spectroscopy. We resolve the signal of the planet's motion with deep combined flux observations of the star and the planet. In total, six epochs of Keck NIRSPEC LL-band observations were obtained, and the full data set was subjected to a cross correlation analysis with a grid of self-consistent atmospheric models. We measure a radial projection of the Keplerian velocity, KPK_P, of 148 ±\pm 7 km s1^{-1}, consistent with transit measurements, and detect water vapor at 3.8σ\sigma. We combine NIRSPEC LL-band data with SpitzerSpitzer IRAC secondary eclipse data to further probe the metallicity and carbon-to-oxygen ratio of KELT-2Ab's atmosphere. While the NIRSPEC analysis provides few extra constraints on the SpitzerSpitzer data, it does provide roughly the same constraints on metallicity and carbon-to-oxygen ratio. This bodes well for future investigations of the atmospheres of non-transiting hot Jupiters.Comment: accepted to A
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