Investigating the flyby scenario for the HD 141569 system

HD 141569, a triple star system, has been intensively observed and studied for its massive debris disk. It was rather regarded as a gravitationally bound triple system but recent measurements of the HD 141569A radial velocity seem to invalidate this hypothesis. The flyby scenario has therefore to be investigated to test its compatibility with the observations. We present a study of the flyby scenario for the HD141569 system, by considering 3 variants: a sole flyby, a flyby associated with one planet and a flyby with two planets. We use analytical calculations and perform N-body numerical simulations of the flyby encounter. The binary orbit is found to be almost fixed by the observational constraint on a edge-on plane with respect to the observers. If the binary has had an influence on the disk structure, it should have a passing time at the periapsis between 5000 and 8000 years ago and a distance at periapsis between 600 and 900 AU. The best scenario for reproducing the disk morphology is a flyby with only 1 planet. For a 2 Mj (resp. 8 Mj) planet, its eccentricity must be around 0.2 (resp. below 0.1). In the two cases, its apoapsis is about 130 AU. Although the global disk shape is reasonably well reproduced, some features cannot be explain by the present model and the likehood of the flyby event remains an issue. Dynamically speaking, HD 141569 is still a puzzling system

Thermochemistry of iron manganese oxide spinels

Oxide melt solution calorimetry has been performed on iron manganese oxide spinels prepared at high temperature. The enthalpy of formation of (MnxFe1−x)3O4 at 298 K from the oxides, tetragonal Mn3O4 (hausmannite) and cubic Fe3O4 (magnetite), is negative from x=0 to x=0.67 and becomes slightly positive for 0.670.6) spinels of intermediate compositions. The enthalpies of formation are discussed in terms of three factors: oxidation–reduction relative to the end-members, cation distribution, and tetragonality. A combination of measured enthalpies and Gibbs free energies of formation in the literature provides entropies of mixing. ΔSmix, consistent with a cation distribution in which all trivalent manganese is octahedral and all other ions are randomly distributed for x>0.5, but the entropy of mixing appears to be smaller than these predicted values for x<0.4

The environmental Kuznets curve for deforestation: a threatened theory? A meta-analysis

Although widely studied, deforestation remains a topical and typical issue. The relationship between economic development and deforestation is still at stake. This paper presents a meta-analysis of Environmental Kuznets Curve (EKC) studies for deforestation. Using 71 studies, offering 631 estimations, we shed light on why EKC results differ. We investigate the incidence of choices made by authors (econometric strategy, deforestation measure, temporal coverage, geographical area, measure of economic development...) on the probability of finding an EKC. After a phase of work corroborating the EKC, we find a turning point after the year 2001. Building on our results, we conclude that the EKC story will not fade until theoretical alternatives will be provided

Bivariate lifetime distributions

A thorough investigation of a bivariate Gompertz hazard function for failure time (x,y) and its joint survival distribution

Uniqueness results for an ODE related to a generalized Ginzburg-Landau model for liquid crystals

We study a singular nonlinear ordinary differential equation on intervals {[}0, R) with R <= +infinity, motivated by the Ginzburg-Landau models in superconductivity and Landau-de Gennes models in liquid crystals. We prove existence and uniqueness of positive solutions under general assumptions on the nonlinearity. Further uniqueness results for sign-changing solutions are obtained for a physically relevant class of nonlinearities. Moreover, we prove a number of fine qualitative properties of the solution that are important for the study of energetic stability

QUALITE PERÇUE ET SATISFACTION DES CLIENTS BUSINESS-TO-CONSUMER DE LA TELEPHONIE MOBILE EN CONTEXTE CAMEROUNAIS

Cet article s’inscrit dans le cadre de l’amélioration permanente de la satisfaction de la clientèle business-to-consumer, particulièrement dans le secteur de la téléphonie mobile. Son objet a été de mettre en exergue le rôle modérateur du traitement des réclamations dans la relation entre la qualité perçue et la satisfaction des clients business-to-consumer des services de téléphonie mobile en contexte camerounais. Une recherche documentaire nous a permis de cerner l’approche conceptuelle. Dans l’approche méthodologique, une enquête par sondage nous a permis de collecter les données à partir d’un questionnaire administré auprès d’un échantillon de convenance constitué de 399 personnes issues de l’ensemble des abonnés à la téléphonie mobile au Cameroun. Le traitement et l’analyse de ces données se sont effectués à l’aide du logiciel SPSS et AMOS. Nous avons utilisé le modèle d’équations structurelles pour le test des hypothèses. Les principaux résultats obtenus montrent que (i) les clients b- to-c de la téléphonie mobile ne sont satisfaits de la qualité de service offert par les opérateurs de téléphonie mobile et (ii) que le traitement des réclamations influence (modérateur) dans la relation entre la qualité perçue et la satisfaction globale des clients b-to-c de la téléphonie mobile en contexte camerounais

Condensed tannin changes along the digestive tract in lambs fed with sainfoin pellets or hazelnut skins

The variable anthelmintic efficacy of condensed tannins (CT) against gastrointestinal nematodes may depend on CT concentration, composition, or fate along the digestive tract. We analyzed CT concentration and composition by acetone−HCl−butanol and thiolysis coupled to HPLC-MS in digesta and feces of lambs. Lambs had been infected with Haemonchus contortus and Trichostrongylus colubriformis and received sainfoin pellets and hazelnut skins of contrasting prodelphinidin/procyanidin ratios. The digesta and feces had lower CT concentrations than the original feeds but similar concentration patterns across the digestive compartments. The changes in assayable CT concentrations between rumen, abomasum, and small intestine may be due to complex formation between CT and other dietary components. However, the large CT disappearance (61−85%) from feed to feces could also indicate that CT may have been structurally modified, degraded, or absorbed during digestion. Interestingly, there were no changes in the structural features of assayable CT in the digesta