Accretion of a satellite onto a spherical galaxy. II. Binary evolution and orbital decay

We study the dynamical evolution of a satellite orbiting outside of a companion spherical galaxy. The satellite is subject to a back-reaction force resulting from the density fluctuations excited in the primary stellar system. We evaluate this force using the linear response theory developed in Colpi and Pallavicini (1997). The force is computed in the reference frame comoving with the primary galaxy and is expanded in multipoles. To capture the relevant features of the physical process determining the evolution of the detached binary, we introduce in the Hamiltonian the harmonic potential as interaction potential among stars. The dynamics of the satellite is computed self-consistently. We determine the conditions for tidal capture of a satellite from an asymptotic free state. If the binary comes to existence as a bound pair, stability against orbital decay is lost near resonance. The time scale of binary coalescence is computed as a function of the eccentricity and mass ratio. In a comparison with Weinberg's perturbative technique we demonstrate that pinning the center of mass of the galaxy would induce a much larger torque on the satellite.Comment: 13 pages, Tex,+ 10 .ps figures Submitted to The Astrophysical Journa

Sondage archéologique sur l'oppidum du Camp de César à Laudun-l'Ardoise. Étude d'une structure du Haut-Empire réutilisée au cours de l'Antiquité tardive.

National audienceDans le cadre des recherches sur les dynamiques de peuplement dans la basse vallée de la Cèze, le sondage réalisé dans cette structure en bordure orientale de l'oppidum du Camp de César à Laudun-l'Ardoise (Gard), a permis d'établir sa construction au cours du Ier siècle de notre ère et de sa réfection au cours des Ve-VIe siècles. L'abondance de mobilier céramique tardo-républicain, et du Haut-Empire, au sein du bâti ou en stratigraphie, ne permettent pas de dater exclusivement cette structure de l'Antiquité tardive, bien que les couches tardo-antiques directement au contact de l'affleurement rocheux, sont un terminus post quem recevable pour la datation de la réfection du bâtiment. Il semble qu'au cours des Ve-VIe siècles de nouveaux constructeurs ont procédé à des terrassements mettant à jour les maçonneries préexistantes du Ier siècle, qui ont alors été réutilisées

Dynamical friction and the evolution of satellites in virialized halos: the theory of linear response

The evolution of a small satellite inside a more massive truncated isothermal spherical halo is studied using both the Theory of Linear Response for dynamical friction and N-Body simulations. The analytical approach includes the effects of the gravitational wake, of the tidal deformation and the shift of the barycenter of the primary, so unifying the local versus global interpretation of dynamical friction. Sizes, masses, orbital energies and eccentricities are chosen as expected in hierarchical clustering models. We find that in general the drag force in self-gravitating backgrounds is weaker than in uniform media and that the orbital decay is not accompanied by a significant circularization. We also show that the dynamical friction time scale is weakly dependent on the initial circularity. We provide a fitting formula for the decay time that includes the effect of mass and angular momentum loss. Live satellites with dense cores can survive disruption up to an Hubble time within the primary, notwithstanding the initial choice of orbital parameters. Dwarf spheroidal satellites of the Milky Way, like Sagittarius A and Fornax, have already suffered mass stripping and, with their present masses, the sinking times exceed 10 Gyr even if they are on very eccentric orbits.Comment: 27 pages including 9 figures. Accepted for publication in the Astrophysical Journal. Part 2, issue November 10 1999, Volume 52

Organic farming and climate change: major conclusions of the Clermont-Ferrand seminar (2008)

This seminar confirmed that less greenhouse gas (GHG) is emitted per unit area under organic agriculture than under conventional agriculture, and that our eating patterns have a strong impact on factors involved in climate change. Moreover, it shed new light on and contributed original information to a variety of fields. The two major advantages of organic farming in terms of the mitigation of GHG emissions are its ability to store carbon in the ground and the non-use of synthetic nitrogen fertilisers. Means for improving practices and research priorities were identified

Model Driven Engineering and Dependability Analyses: The Topcased Approach

International audienceModel Driven Engineering approaches are widely promoted to overcome difficulties to design, validate and maintain large complex systems. They present interesting dependability characteristics especially in terms of prevention of design faults and validation of design correctness. However industrial needs, practices and applicable standards impose constraints on the dependability activities to perform and justify. Therefore it is necessary to analyze how a complete dependability and safety process can be integrated with model-driven approaches within a seamless global process: which dependability activities are naturally covered or facilitated by model-driven approaches, and which additional activities are needed with which support. This paper presents the results of a study aiming at the establishment of requirements to model-driven engineering methods and tools, to support dependability analyses

Lead in the marine environment: concentrations and effects on invertebrates

Lead (Pb) is a non-essential metal naturally present in the environment and often complexed with other elements (e.g., copper, selenium, zinc). This metal has been used since ancient Egypt and its extraction has grown in the last centuries. It has been used until recently as a fuel additive and is currently used in the production of vehicle batteries, paint, and plumbing. Marine ecosystems are sinks of terrestrial contaminations; consequently, lead is detected in oceans and seas. Furthermore, lead is not biodegradable. It remains in soil, atmosphere, and water inducing multiple negative impacts on marine invertebrates (key species in trophic chain) disturbing ecological ecosystems. This review established our knowledge on lead accumulation and its effects on marine invertebrates (Annelida, Cnidaria, Crustacea, Echinodermata, and Mollusca). Lead may affect different stages of development from fertilization to larval development and can also lead to disturbance in reproduction and mortality. Furthermore, we discussed changes in the seawater chemistry due to Ocean Acidification, which can affect the solubility, speciation, and distribution of the lead, increasing potentially its toxicity to marine invertebrates

Heliophysics Event Knowledgebase for the Solar Dynamics Observatory and Beyond

The immense volume of data generated by the suite of instruments on SDO requires new tools for efficient identifying and accessing data that is most relevant to research investigations. We have developed the Heliophysics Events Knowledgebase (HEK) to fill this need. The HEK system combines automated data mining using feature-detection methods and high-performance visualization systems for data markup. In addition, web services and clients are provided for searching the resulting metadata, reviewing results, and efficiently accessing the data. We review these components and present examples of their use with SDO data.Comment: 17 pages, 4 figure

A Wellness Approach to Investigating Student Veterans’ Career Goals

A qualitative methodology was utilized to assess the wellness factors student Veterans (N = 10) perceived as influential to their decision to separate from the military and choice of intended career path. Participants included prior enlisted student Veterans pursuing undergraduate degrees at a mid-sized Midwestern university. Interview transcripts were coded according to the Indivisible Self Model of Wellness (IS-Wel; Myers & Sweeney, 2004) and analyzed phenomenologically. Participants referenced Control and Self-Worth as motivators for separation from military service; Work and Thinking were the main themes regarding choice of future profession. Additional themes emerged in reference to how Veterans’ priorities changed during their time in service. The IS-Wel serves as an innovative approach for facilitating student Veteran career development

A Defensin-Like Gene Expressed in the Black-Legged Tick, Ixodes scapularis (Acari: Ixodidae)

The black-legged tick Ixodes scapularis linnaeus (Acari: Ixodidae) is an important vector of microbial pathogens. Knowledge of the tick\u27s innate immune response, particularly defensin and other antimicrobial peptides, is important for understanding how microbes survive in this tick. A defensin gene (slnA) from I. scapularis was obtained by reverse transcription-polymerase chain reaction (RT-PCR) using mRNA extracted from tissues of female ticks. RT-PCR indicated the gene was expressed in the midgut, haemocytes, and fat-body, although no evidence of a peptide was found. Sequencing a cloned cDNA fragment revealed a 225 bp open reading frame encoding a 74 amino acid pre-prodefensin, including the putative 38 amino acid mature peptide. Similarity between the defensin amino acid sequences of I. scapularis and Dermacentor variabilis (Say) (Acari: Ixodidae) was 62.2% for the pre-prodefensin region; for the mature defensins from these two species the similarity was 78.9%, with the six cysteine residues being located in the same relative position. PCR amplification and sequencing of chromosomal DNA suggests that slnA, along with vsnA, the defensin gene from D. variabilis, does not contain any introns. This is in contrast to the defensins described for the soft tick, Ornithodoros moubata (sensu Walton) (Acari: Argasidae). The role of defensin in the innate immune response of I. scapularis following microbial invasions is discussed

Results from a European multi-cohort study

Publisher Copyright: © 2021 The Author(s) 2021. Published by Oxford University Press on behalf of the British Society for Antimicrobial Chemotherapy. All rights reserved.Background: INSTIs have become a pillar of first-line ART. Real-world data are needed to assess their effectiveness in routine care. Objectives: We analysed ART-naive patients who started INSTI-based regimens in 2012-19 whose data were collected by INTEGRATE, a European collaborative study including seven national cohorts. Methods: Kaplan-Meier analyses assessed time to virological failure (VF), defined as one viral load (VL) ≥1000 copies/mL, two consecutive VLs ≥50 copies/mL, or one VL ≥50 copies/mL followed by treatment change after ≥24 weeks of follow-up, and time to INSTIs discontinuation (INSTI-DC) for any reason. Factors associated with VF and INSTI-DC were explored by logistic regression analysis. Results: Of 2976 regimens started, 1901 (63.9%) contained dolutegravir, 631 (21.2%) elvitegravir and 444 (14.9%) raltegravir. The 1 year estimated probabilities of VF and INSTI-DC were 5.6% (95% CI 4.5-6.7) and 16.2% (95% CI 14.9-17.6), respectively, and were higher for raltegravir versus both elvitegravir and dolutegravir. A baseline VL ≥100 000 copies/mL [adjusted HR (aHR) 2.17, 95% CI 1.55-3.04, P 3 drugs versus 3 drugs (aHR 2.73, 95% CI 1.55-4.79, P < 0.001) and starting ART following availability of dolutegravir (aHR 0.64, 95% CI 0.48-0.83, P = 0.001). Major INSTI mutations indicative of transmitted drug resistance occurred in 2/1114 (0.2%) individuals. Conclusions: This large multi-cohort study indicates high effectiveness of elvitegravir- or dolutegravir-based first-line ART in routine practice across Europe.publishersversionpublishe