669 research outputs found

    An Analytical Expression for the Hubble diagram of supernovae and gamma-ray bursts

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    A recent paper by Harmut Traunm\"uller shows that the most adequate equation to interpret the observations on magnitude and redshift from 892 type 1a supernovae would be mu = 5 log[(1+z) ln(1+z)] + const. We discuss this result which is exacly the one we have obtained few years ago when postulating a relation between the speed of light and the expansion of the universe. We also compare our analytical result to the conclusion of Marosi who studied 280 supernovae and gamma-ray bursts in the range 0.1014 < z < 8.1. The difference between his results and ours is at worst of 0.3 %.Comment: 7 pages, 1 figur

    Feasibility and effect of in-home physical exercise training delivered via telehealth before bariatric surgery

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    Abstract : Optimal physical activity (PA) interventions are needed to increase PA in individuals with severe obesity, and optimize the results of bariatric surgery (BS). The aim of this study was to assess the feasibility and effect of in-home Pre-Surgical Exercise Training delivered via telehealth (TelePreSET) in subjects awaiting BS. Six women following the TelePreSET were compared to the women from a previous study (12 performing the PreSET in a gymnasium and 11 receiving usual care). In-home TelePreSET (12-weeks of endurance and strength training) was supervised twice weekly using videoconferencing. Physical fitness, quality of life, exercise beliefs, anthropometric measures, and telehealth perception were assessed before and after 12-weeks. Satisfaction was evaluated with questionnaires at the end of the intervention. The TelePreSET participants attended 96 % of the exercise sessions, and were very satisfied by the TelePreSET. The baseline telehealth perception score was high, and increased significantly after the intervention. The TelePreSET group significantly increased their physical fitness compared to the usual care group. No significant change was noted in other outcomes. The TelePreSET is feasible and seems effective to improve the physical fitness of women awaiting BS. Further studies will confirm beneficial effects of this innovative mode of delivery

    Development of an ELT XAO testbed using a self referenced Mach-Zehnder wavefront sensor

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    Extreme adaptive optics (XAO) has severe difficulties meeting the high speed (>1kHz), accuracy and photon efficiency requirements for future extremely large telescopes. An innovative high order adaptive optics system using a self-referenced Mach-Zehnder wavefront sensor (MZWFS) allows counteracting these limitations. In addition to its very high accuracy, this WFS is the most robust alternative to segments gaps and telescope spiders which can result in strong wavefront artifacts. In particular in XAO systems when the size of these gaps in the wavefront measurement is comparable to the sub aperture size, loss in performance can be very high. The MZWFS estimates the wavefront phase by measuring intensity differences between two outputs, with a λ/4 path length difference between its two legs, but is limited in dynamic range. During the past few years, such an XAO system has been studied by our team in the framework of 8-meter class telescopes. In this paper, we report on our latest results with the XAO testbed recently installed in CRAL laboratory, and dedicated to high contrast imaging with 30m-class telescopes (such as the E-ELT or the TMT). A woofer-tweeter architecture is used in order to deliver the required high Strehl ratio (>95%). It consists of a 12x12 deformable mirror (DM) and a 512x512 Spatial Light Modulator (SLM) characterized both using monochromatic and polychromatic light. We present our latest experimental results, including components characterization, close loop performances and sensitivity to calibration errors. This work is carried out in synergy with the validation of fast iterative wavefront reconstruction algorithms and the optimal treatment of phase ambiguities in order to mitigate the dynamical range limitation of such a wavefront sensor

    Simulation of Seasonal Snow Microwave TB Using Coupled Multi-Layered Snow Evolution and Microwave Emission Models

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    The accurate quantification of SWE has important societal benefits, including improving domestic and agricultural water planning, flood forecasting and electric power generation. However, passive-microwave SWE algorithms suffer from variations in TB due to snow metamorphism, difficult to distinguish from those due to SWE variations. Coupled snow evolution-emission models are able to predict snow metamorphism, allowing us to account for emissivity changes. They can also be used to identify weaknesses in the snow evolution model. Moreover, thoroughly evaluating coupled models is a contribution toward the assimilation of TB, which leads to a significant increase in the accuracy of SWE estimates

    Stringy invariants for horospherical varieties of complexity one

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    We determine the stringy motivic volume of log terminal horospherical varieties of complexity one and obtain a smoothness criterion using a comparison of stringy and usual Euler characteristics
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