515 research outputs found

    Some Remarks on IBNR Evaluation Techniques

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    In this short paper we discuss a new methodology for estimating reserves for IBNR (incurred but not reported) claims.

    Object identification and characterization with hyperspectral imagery to identify structure and function of Natura 2000 habitats

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    Habitat monitoring of designated areas under the EU Habitats Directive requires every 6 years information on area, range, structure and function for the protected (Annex I) habitat types. First results from studies on heathland areas in Belgium and the Netherlands show that hyperspectral imagery can be an important source of information to assist the evaluation of the habitat conservation status. Hyperspectral imagery can provide continuous maps of habitat quality indicators (e.g., life forms or structure types, management activities, grass, shrub and tree encroachment) at the pixel level. At the same time, terrain managers, nature conservation agencies and national authorities responsible for the reporting to the EU are not directly interested in pixels, but rather in information at the level of vegetation patches, groups of patches or the protected site as a whole. Such local level information is needed for management purposes, e.g., exact location of patches of habitat types and the sizes and quality of these patches within a protected site. Site complexity determines not only the classification success of remote sensing imagery, but influences also the results of aggregation of information from the pixel to the site level. For all these reasons, it is important to identify and characterize the vegetation patches. This paper focuses on the use of segmentation techniques to identify relevant vegetation patches in combination with spectral mixture analysis of hyperspectral imagery from the Airborne Hyperspectral Scanner (AHS). Comparison with traditional vegetation maps shows that the habitat or vegetation patches can be identified by segmentation of hyperspectral imagery. This paper shows that spectral mixture analysis in combination with segmentation techniques on hyperspectral imagery can provide useful information on processes such as grass encroachment that determine the conservation status of Natura 2000 heathland areas to a large extent. A limitation is that both advanced remote sensing approaches and traditional field based vegetation surveys seem to cause over and underestimations of grass encroachment for specific categories, but the first provides a better basis for monitoring if specific species are not directly considered

    TESS unveils the phase curve of WASP-33b. Characterization of the planetary atmosphere and the pulsations from the star

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    We present the detection and characterization of the full-orbit phase curve and secondary eclipse of the ultra-hot Jupiter WASP-33b at optical wavelengths, along with the pulsation spectrum of the host star. We analyzed data collected by the Transiting Exoplanet Survey Satellite (TESS) in sector 18. WASP-33b belongs to a very short list of highly irradiated exoplanets that were discovered from the ground and were later visited by TESS. The host star of WASP-33b is of delta Scuti-type and shows nonradial pulsations in the millimagnitude regime, with periods comparable to the period of the primary transit. These completely deform the photometric light curve, which hinders our interpretations. By carrying out a detailed determination of the pulsation spectrum of the host star, we find 29 pulsation frequencies with a signal-to-noise ratio higher than 4. After cleaning the light curve from the stellar pulsations, we confidently report a secondary eclipse depth of 305.8 +/- 35.5 parts-per-million (ppm), along with an amplitude of the phase curve of 100.4 +/- 13.1 ppm and a corresponding westward offset between the region of maximum brightness and the substellar point of 28.7 +/- 7.1 degrees, making WASP-33b one of the few planets with such an offset found so far. Our derived Bond albedo, A_B = 0.369 +/- 0.050, and heat recirculation efficiency, epsilon = 0.189 +/- 0.014, confirm again that he behavior of WASP-33b is similar to that of other hot Jupiters, despite the high irradiation received from its host star. By connecting the amplitude of the phase curve to the primary transit and depths of the secondary eclipse, we determine that the day- and nightside brightness temperatures of WASP-33b are 3014 +/- 60 K and 1605 +/- 45 K, respectively. From the detection of photometric variations due to gravitational interactions, we estimate a planet mass of M_P = 2.81 +/- 0.53 M$_J.Comment: 19 pages, 15 figure

    UN RIVOLUZIONARIO DURANTE L'ANTICO REGIME: JACQUES-VINCENT DELACROIX (1766-1789).

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    The research aims to provide a first introductory look to the life and thought of Jacques-Vincent Delacroix (1743-1831), Avocat au Parlement in Paris during the Ancien R\ue9gime, a well-known professor of Public law at the Lyc\ue9e from 1789 to 1793, Judge in Versailles since 1795 and author of a real bestsellers of the Revolutionary Era, the \u201cConstitutions des principaux \uc9tats de l\u2019Europe et des \uc9tats-Unis\u201d. Lawyer and man of letters who lived between the reign of Louis XV and the French Revolution of 1830, Delacroix has been both a prolific writer and an eye-witness of the political and cultural changes who finally lead to the creation of the Modern France. So, the life of Delacroix became a case of study due to the fact that it helps to understand better the many ups-and-downs and the late successes of an entire generation, who asserted itself only at the end of the Ancien R\ue9gime and slowly became the trait d\u2019union between the revolutionaries of 1789 and the men who arose again in defense of freedom in 1830. This study, who wants also be a first contribution to a future fulfillment of a more specific political biography of Delacroix, takes shape as an interdisciplinary approach to his life \u2013 where the first part is a description of the put on trial of Delacroix in front of the Revolutionary Tribunal in 1795 and a report of both the contemporary and the historical debate that surrounded the event, the second one is a complete and revisited biographic profile, and the third one is a reconstruction of his carrier during the Ancien R\ue9gime \u2013 that finally lead to explain how Delacroix came closer to the revolutionary line-up and what are the origins of his following faithful, but always critical, acceptation of the ideals of 1789

    Chiral Molecular Tweezers: Synthesis and Reactivity in Asymmetric Hydrogenation

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    We report the synthesis and reactivity of a chiral aminoborane displaying both rapid and reversible H-2 activation. The catalyst shows exceptional reactivity in asymmetric hydrogenation of enamines and unhindered imines with stereoselectivities of up to 99% ee. DFT analysis of the reaction mechanism pointed to the importance of both repulsive steric and stabilizing intermolecular non-covalent forces in the stereodetermining hydride transfer step of the catalytic cycle
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