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34 result(s) for "Delabre, B"
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CUBES: cassegrain U-band Brazil-ESO spectrograph
CUBES is a high-efficiency, medium-resolution ( R ∼20,000) ground based UV (300–400 nm) spectrograph, to be installed in the cassegrain focus of one of ESO’s VLT unit telescopes in 2017/18. The CUBES project is a joint venture between ESO and IAG/USP, and LNA/MCTI. CUBES will provide access to a wealth of new and relevant information for stellar as well as extragalactic sources. Main science cases include the study of beryllium and heavy elements in metal-poor stars, the direct determination of carbon, nitrogen and oxygen abundances by study of molecular bands in the UV range, as well as the study of active galactic nuclei and the quasar absorption lines. With a streamlined modern instrument design, high efficiency dispersing elements and UV-sensitive detectors, it will give a significant gain in sensitivity over existing ground based medium-high resolution spectrographs, enabling vastly increased sample sizes accessible to the astronomical community. We present here a brief overview of the project including the status, science cases and a discussion of the design options.
Role of fibrates and HMG-CoA reductase inhibitors in gallstone formation: Epidemiological study in an unselected population
Fibrate derivatives and HMG-CoA reductase inhibitors modify homeostasis of cholesterol. The aim of this study was to assess in an unselected population whether these hypolipidemic drugs are risk factors for cholelithiasis or, conversely, are protective agents. Both sexes, all socioeconomic categories, pregnant women, and cholecystectomized subjects were included. Clinical data collection and gallbladder ultrasonography were both carried out in a double-blind fashion. Fibrate derivatives were predominantly fenofibrate, HMG-CoA reductase inhibitors were simvastatin and pravastatin. On univariate analysis, age (>50 years), sex, and use of fibrates were found to be significantly related to the presence of cholelithiasis. Age, sex, and fibrate treatment remained independently correlated with the presence of gallstones on multivariate analysis. With fibrates, the relative risk for lithiasis was 1.7 (P = 0.04). The HMG-CoA reductase inhibitors were not associated with a protective effect on univariate analysis. Of the lipid-lowering drugs, only fibrate derivatives were found to increase the risk of gallstone formation.
ESO Spectroscopic Facility
We present the concept of a novel facility dedicated to massively-multiplexed spectroscopy. The telescope has a very wide field Cassegrain focus optimised for fibre feeding. With a Field of View (FoV) of 2.5 degrees diameter and a 11.4m pupil, it will be the largest etendue telescope. The large focal plane can easily host up to 16.000 fibres. In addition, a gravity invariant focus for the central 10 arc-minutes is available to host a giant integral field unit (IFU). The 3 lenses corrector includes an ADC, and has good performance in the 360-1300 nm wavelength range. The top level science requirements were developed by a dedicated ESO working group, and one of the primary cases is high resolution spectroscopy of GAIA stars and, in general, how our Galaxy formed and evolves. The facility will therefore be equipped with both, high and low resolution spectrographs. We stress the importance of developing the telescope and instrument designs simultaneously. The most relevant R&D aspect is also briefly discussed.
CODEX: measuring the acceleration of the universe and beyond
The combination of the collecting power of an ELT with an ultra-stable high resolution spectrograph opens up the possibility to measure for the first time directly the dynamical effect of the acceleration of the Universe. CODEX will also provide unique opportunities for advance in many other branches of astrophysics. The CODEX design is based on an array of several identical spectrographs. It is highly modular and can be easily adapted to a large range of sky apertures and telescope diameters. CODEX is designed to work as a seeing limited instrument. The requirements for the telescope are moderate and clearly identified.
Prevalence of cholelithiasis: results of an epidemiologic investigation in Vidauban, southeast France. General Practitioner's Group of Vidauban
Cholelithiasis leads to 80,000 cholecystectomies being performed every year in France, but its prevalence is still unknown. The aim of this study was to assess the prevalence and risk factors of cholelithiasis in a random population of 1027 women and 727 men over the age of 30 in a small town in the southeast of France. Detailed clinical history, dietary investigation, and gallbladder ultrasound were collected for each subject and assessed by univariate analysis. A regression model was used in the multivariate analysis to detect the relative risk of cholelithiasis. Cholelithiasis was found in 130 individuals (global prevalence 13.9%). The relative risk for lithiasis was higher in women compared to men (1.89). Age (P<0.0001) and body mass index (BMI) >25 (P = 0.013) were also significant risk factors. Neither pregnancy nor oral contraceptive use proved to be risk factors. Typical biliary colic pain was the only symptom significantly associated with cholelithiasis (P<0.0001). These results show that the prevalence of gallstones in France is similar to that in Denmark and Italy.
New telescope designs suitable for massively-multiplexed spectroscopy
We present two novel designs for a telescope suitable for massively-multiplexed spectroscopy. The first is a very wide field Cassegrain telescope optimised for fibre feeding. It provides a Field Of View (FOV) of 2.5 degrees diameter with a 10m primary mirror. It is telecentric and works at F/3, optimal for fibre injection. As an option, a gravity invariant focus for the central 10 arc-minutes can be added, to host, for instance, a giant integral field unit (IFU). It has acceptable performance in the 360-1300 nm wavelength range. The second concept is an innovative five mirror telescope design based on a Three Mirror Anastigmatic (TMA) concept. The design provides a large FOV in a convenient, gravity- invariant focal plane, and is scalable to a range of telescope diameters. As specific example, we present a 10m telescope with a 1.5 degree diameter FOV and a relay system that allows simultaneous spectroscopy with 10,000 mini-IFUs over a square degree, or, alternatively a 17.5 square arcminutes giant IFU, by using 240 MUSE-type spectrographs. We stress the importance of developing the telescope and instrument designs for both cases.
Concerning the Alignment of Modern Telescopes: Theory, Practice, and Tolerances Illustrated by the ESO NTT
A recent paper by Bhatia (1995, TNG Tech. Rep. No. 43) suggests from calculations based on the optical geometry of the NTT that the zero-coma condition is a necessary but insufficient condition for the alignment of modern telescopes and that analysis of separate decenter effects is necessary to cope with decentering astigmatism aberrations near the field center. Here we show that, while Bhatia's calculations are quite correct, their basis shows a misunderstanding of how the NTT was actually aligned and that this \"passive\" alignment was sufficiently good that the decentering astigmatism effects he indicates are negligible. More dangerous are the wide-field effects of decentering astigmatism discussed by McLeod (1996, PASP, 108, 217). However, we show that these effects, linear with field, are also negligible with the NTT alignment quality achieved, provided the correct effective shift of the astigmatic field center is allowed for in the active correction software. This is of great importance in the NTT because the image analyzer operates at the edge of the field and the correct field astigmatism must be subtracted to give the necessary active correction at the mechanical field center. This approach is valid for the technical use of the edge field of an aplanatic (RC) telescope limited by field astigmatism. Decentering astigmatism will be much more critical at the field edge for anastigmatic telescopes if a wide field is also used for astronomical observations.
Prevalence of cholelithiasis : Results of an epidemiologic investigation in Vidauban, Southeast France
Cholelithiasis leads to 80,000 cholecystectomies being performed every year in France, but its prevalence is still unknown. The aim of this study was to assess the prevalence and risk factors of cholelithiasis in a random population of 1027 women and 727 men over the age of 30 in a small town in the southeast of France. Detailed clinical history, dietary investigation, and gallbladder ultrasound were collected for each subject and assessed by univariate analysis. A regression model was used in the multivariate analysis to detect the relative risk of cholelithiasis. Cholelithiasis was found in 130 individuals (global prevalence 13.9%). The relative risk for lithiasis was higher in women compared to men (1.89). Age (P<0.0001) and body mass index (BMI) >25 (P = 0.013) were also significant risk factors. Neither pregnancy nor oral contraceptive use proved to be risk factors. Typical biliary colic pain was the only symptom significantly associated with cholelithiasis (P<0.0001). These results show that the prevalence of gallstones in France is similar to that in Denmark and Italy.
The MUSE second-generation VLT instrument
The Multi Unit Spectroscopic Explorer (MUSE) is a second-generation VLT panoramic integral-field spectrograph currently in manufacturing, assembly and integration phase. MUSE has a field of 1x1 arcmin2 sampled at 0.2x0.2 arcsec2 and is assisted by the VLT ground layer adaptive optics ESO facility using four laser guide stars. The instrument is a large assembly of 24 identical high performance integral field units, each one composed of an advanced image slicer, a spectrograph and a 4kx4k detector. In this paper we review the progress of the manufacturing and report the performance achieved with the first integral field unit.