24 research outputs found
A large topographic feature on the surface of the trans-Neptunian object (307261) 2002 MS measured from stellar occultations
This work aims at constraining the size, shape, and geometric albedo of the
dwarf planet candidate 2002 MS4 through the analysis of nine stellar
occultation events. Using multichord detection, we also studied the object's
topography by analyzing the obtained limb and the residuals between observed
chords and the best-fitted ellipse. We predicted and organized the
observational campaigns of nine stellar occultations by 2002 MS4 between 2019
and 2022, resulting in two single-chord events, four double-chord detections,
and three events with three to up to sixty-one positive chords. Using 13
selected chords from the 8 August 2020 event, we determined the global
elliptical limb of 2002 MS4. The best-fitted ellipse, combined with the
object's rotational information from the literature, constrains the object's
size, shape, and albedo. Additionally, we developed a new method to
characterize topography features on the object's limb. The global limb has a
semi-major axis of 412 10 km, a semi-minor axis of 385 17 km, and
the position angle of the minor axis is 121 16. From
this instantaneous limb, we obtained 2002 MS4's geometric albedo and the
projected area-equivalent diameter. Significant deviations from the fitted
ellipse in the northernmost limb are detected from multiple sites highlighting
three distinct topographic features: one 11 km depth depression followed by a
25 km height elevation next to a crater-like depression with an
extension of 322 39 km and 45.1 1.5 km deep. Our results present an
object that is 138 km smaller in diameter than derived from thermal
data, possibly indicating the presence of a so-far unknown satellite. However,
within the error bars, the geometric albedo in the V-band agrees with the
results published in the literature, even with the radiometric-derived albedo
Prediction and estimation of effective population size
Effective population size (Ne) is a key parameter in population genetics. It has important applications in evolutionary biology, conservation genetics, and plant and animal breeding, because it measures the rates of genetic drift and inbreeding and affects the efficacy of systematic evolutionary forces such as mutation, selection and migration. We review the developments in predictive equations and estimation methodologies of effective size. In the prediction part, we focus on the equations for populations with different modes of reproduction, for populations under selection for unlinked or linked loci, and for the specific applications to conservation genetics. In the estimation part, we focus on methods developed for estimating the current or recent effective size from molecular marker or sequence data. We discuss some underdeveloped areas in predicting and estimating Ne for future research
Results on stellar occultations by (307261) 2002 MS4
Transneptunian Objects (TNOs) are the remnants of our planetary system and can retain information about the early stages of the Solar System formation. Stellar occultation is a groundbased method used to study these distant bodies which have been presenting exciting results mainly about their physical properties. The big TNO called 2002 MS4 was discovered by Trujillo, C. A., & Brown, M. E., in 2002 using observations made at the Palomar Observatory (EUA). It is classified as a hot classical TNO, with orbital parameters a = 42 AU, e = 0.139, and i = 17.7º. Using thermal measurements with PACS (Herschel) and MIPS (Spitzer Space Telescope) instruments, Vilenius et al. 2012 obtained a radius of 467 +/- 23.5 km and an albedo of 0.051.Predictions of stellar occultations by this body in 2019 were obtained using the Gaia DR2 catalogue and NIMA ephemeris (Desmars et al. 2015) and made available in the Lucky Star web page (https://lesia.obspm.fr/lucky-star/). Four events were observed in South America and Canada. The first stellar occultation was detected on 09 July 2019, resulting in two positives and four negatives chords, including a close one which proven to be helpful to constrain the body’s size. This detection also allowed us to obtain a precise astrometric position that was used to update its ephemeris and improve the predictions of the following events. Two of them were detected on 26 July 2019, separated by eight hours. The first event was observed from South America and resulted in three positive detections, while the second, observed from Canada, resulted in a single chord. Another double chord event was observed on 19 August 2019 also from Canada.Facultad de Ciencias Astronómicas y Geofísica
A comparison of the interaction, with two types of environment, of pure strains or strain crosses of poultry
Microwave loss and intermodulation in Tl(2)Ba(2)CaCu(2)O(y) thin films
Willemsen BA, Kihlstrom KE, Dahm T, et al. Microwave loss and intermodulation in Tl(2)Ba(2)CaCu(2)O(y) thin films. Physical Review B. 1998;58(10):6650-6654.A superconducting microstrip hairpin resonator is used as a tool to study the linear and nonlinear microwave response of TBCCO thin films. We extract the surface resistance R(S)(T), penetration depth lambda(T), and intermodulation critical current J(IMD)(T) for such a resonator at 4.2 GHz. The surface impedance results compare well with cavity perturbation measurements on portions of the same wafer. J(IMD)(T) is compared against theoretical models for the intrinsic nonlinear response of s- and d-wave superconductors. We demonstrate that the de critical current J(c) and J(IMD) are distinct material parameters, describing different physical regimes
Cancer metastase de la prostate: Aspects socio-économiques, radiologiques et évolutifs en cote d’ivoire
Objectifs: Présenter les aspects épidémiologiques, diagnostiques et évolutifs du cancer métastasé de la prostate.
Sujets et méthodes: Il s’agissait d’une étude rétrospective portant sur 146 patients hospitalisés pour cancer métastasé de la prostate, de mars 2001 à février 2011.
Resultats: l’âge moyen des malades était de 68 ans [46-90 ans]. 57% des patients n’étaient pas salariés et aucun ne disposait d’une assurance maladie. La majorité (85%) consultait tardivement entre 2 et 3 ans. le type histologique était exclusivement l’adénocarcinome de la prostate. Il s’agissait très souvent de cancer indifférencié (80%). Les lésions osseuses radiologiques étaient mixtes et ostéo-condensantes en majorité, atteignant plus le rachis lombaire et le bassin (60%). Le traitement était palliatif dominé par l’orchidectomie (82%), avec une survie moyenne de 18 mois.
Conclusion: le cancer de la prostate en Côte d’Ivoire est un cancer de découverte métastatique. C’est un cancer fréquent, agressif. Son traitement repose essentiellement sur l’orchidectomie compte tenu de la pauvreté des patients. La survie moyenne des malades était de 18 mois