Vivre et penser le sida en Afrique = Experiencing and understanding AIDS in Africa

Dans un contraste de plus en plus accusé entre le Nord et le Sud, qui met en relief deux sortes de sida - l'un traitable et en voie de stabilisation, l'autre incurable et en voie d'expansion -, des chercheurs francophones et anglophones en sciences sociales tentent de répondre ici à une double exigence. Travaillant en Afrique subsaharienne sur une épidémie qui représente 70% des cas mondiaux, ils entendent contribuer à rendre intelligible les programmes d'information et de prévention. Se démarquant nettement des stéréotypes par trop répandus d'un continent où les cultures immémoriables et une certaine "promiscuité sexuelle" seraient le terreau de l'épidémie, leurs diverses approches mettent l'accent sur les contextes de vulnérabilité économique, sociale et politique des populations africaines et sur la façon dont celles-ci interprètent l'épidémie au regard de leurs conditions concrètes d'existence et des multiples difficultés et tensions auxquelles elles sont confrontées. Non réductible à un problème sanitaire, le "phénomène sida" appelle des politiques publiques qui ne se contentent pas de délivrer des messages de prévention sur le préservatif ou la fidélité, mais qui diversifient leurs interventions en fonction des situations sociales et des significations auxquelles le sida a déjà donné lieu. Mais cette démarche analytique des chercheurs en sciences sociales est prolongée d'un point de vue plus critique : parler de politiques publiques, c'est d'abord, pour eux, refuser que perdure en Afrique l'image d'un sida incurable et que ne soient pas transférés les progrès thérapeutiques qui ont considérablement modifié cette image au Nord. C'est par conséquent au prix d'une mobilisation de la communauté internationale que les Etats africains seront amenés eux-mêmes à manifester une plus grande volonté politique et à faire en sorte que le sida devienne un sujet central du débat public. (Résumé d'auteur

A radio-map of the colliding winds in the very massive binary system HD 93129A

Radio observations are an effective tool to discover particle acceleration regions in colliding-wind binaries, through detection of synchrotron radiation; these regions are natural laboratories for the study of relativistic particles. Wind-collision region (WCR) models can reproduce the radio continuum spectra of massive binaries that contain both thermal and non-thermal radio emission; however, key constraints for models come from high-resolution imaging. Only five WCRs have been resolved to date at radio frequencies at milliarcsec (mas) angular scales. The source HD 93129A, prototype of the very few known O2 I stars, is a promising target for study: recently, a second massive, early-type star about 50 mas away was discovered, and a non-thermal radio source detected in the region. Preliminary long-baseline array data suggest that a significant fraction of the radio emission from the system comes from a putative WCR. We sought evidence that HD 93129A is a massive binary system with colliding stellar winds that produce non-thermal radiation, through spatially resolved images of the radio emitting regions. We completed observations with the Australian Long Baseline Array (LBA) to resolve the system at mas angular resolutions and reduced archival Australia Telescope Compact Array (ATCA) data to derive the total radio emission. We also compiled optical astrometric data of the system in a homogeneous way. We reduced historical Hubble Space Telescope data and obtained absolute and relative astrometry with milliarcsec accuracy. The astrometric analysis leads us to conclude that the two stars in HD 93129A form a gravitationally bound system. The LBA data reveal an extended arc-shaped non-thermal source between the two stars, indicative of a WCR. The wind momentum-rate ratio of the two stellar winds is estimated. The ATCA data show a point source with a change in flux level ...Comment: Accepted in Astronomy and Astrophysic

Dominant particle-hole contributions to the phonon dynamics in the spinless one-dimensional Holstein model

In the spinless Holstein model at half-filling the coupling of electrons to phonons is responsible for a phase transition from a metallic state at small coupling to a Peierls distorted insulated state when the electron-phonon coupling exceeds a critical value. For the adiabatic case of small phonon frequencies, the transition is accompanied by a phonon softening at the Brillouin zone boundary whereas a hardening of the phonon mode occurs in the anti-adiabatic case. The phonon dynamics studied in this letter do not only reveal the expected renormalization of the phonon modes but also show remarkable additional contributions due to electronic particle-hole excitations.Comment: 7 pages, 4 figures and 1 table included; v2: discussion of Luttinger liquid parameters adde

3.3 ICP-PR Bee Brood Working Group – Variability of brood termination rates in reference to validity criteria and limited effectiveness of method improvement in honeybee semi-field studies (OECD GD 75)

OECD Guidance Document 75 (2007) outlines a test method to assess effects of plant protection products (PPPs) on honeybee brood under semi-field conditions. The assessment of bee brood development is conducted by mapping cells containing eggs and following their development until emergence. Evaluated parameters are: brood termination rate (BTR), brood compensation index (CI) and brood index (BI). Due to high variability of BTRs within treatments and high control mortality in a number of studies no definite conclusions regarding effects on brood were possible in the past and studies needed to be repeated (Pistorius et al. 2012). To address this variance, effort was taken by ICP-PR and AG Bienenschutz to improve the method by further analyzing current and historical data considering possible influencing factors (Pistorius et al. 2012, Becker et al. 2015) to give recommendations for future testing. The main findings were that reliability of the test method was questionable and that further method improvement and data evaluation was required. Therefore in this paper data evaluation of studies conducted between 2014 and 2017 is carried out and potential key parameters influencing outcome of studies are given.To evaluate the improvement of the OECD 75 test method following the recommendations from 2015, a data analysis of 86 studies conducted in Germany, France, Spain and US was performed. The mean BTR value in the control group was 30.2% for studies conducted in Germany (mean of 61 studies), 19.4% in France (mean of 3 studies), 41.8% in Spain (mean of 5 studies) and 50.6% in US (mean of 17 studies). Results from Spain and US displayed higher BTRs in control compared to data from Germany. Evaluation of BTRs for Germany displayed only a slight improvement (historical value of 32.9%). Analysis of data shows a limitation of options to improve the method as no main driver for high variability of BTRs in the control group was found. The cause for low precision may be multifactorial and driven by “caging effect”. There are alternative test methods available to observe bee brood development, without confinement in the tunnels, under field conditions (Oomen et al. (1992), OECD GD 75 field test design). Therefore it is necessary to investigate differences between these open field methods and semi-field testing with regard to routes of exposure, residues in brood and brood mortality, to choose the most reliable and adequate testing method assessing potential effects of PPP on honeybee brood development.OECD Guidance Document 75 (2007) outlines a test method to assess effects of plant protection products (PPPs) on honeybee brood under semi-field conditions. The assessment of bee brood development is conducted by mapping cells containing eggs and following their development until emergence. Evaluated parameters are: brood termination rate (BTR), brood compensation index (CI) and brood index (BI). Due to high variability of BTRs within treatments and high control mortality in a number of studies no definite conclusions regarding effects on brood were possible in the past and studies needed to be repeated (Pistorius et al. 2012). To address this variance, effort was taken by ICP-PR and AG Bienenschutz to improve the method by further analyzing current and historical data considering possible influencing factors (Pistorius et al. 2012, Becker et al. 2015) to give recommendations for future testing. The main findings were that reliability of the test method was questionable and that further method improvement and data evaluation was required. Therefore in this paper data evaluation of studies conducted between 2014 and 2017 is carried out and potential key parameters influencing outcome of studies are given.To evaluate the improvement of the OECD 75 test method following the recommendations from 2015, a data analysis of 86 studies conducted in Germany, France, Spain and US was performed. The mean BTR value in the control group was 30.2% for studies conducted in Germany (mean of 61 studies), 19.4% in France (mean of 3 studies), 41.8% in Spain (mean of 5 studies) and 50.6% in US (mean of 17 studies). Results from Spain and US displayed higher BTRs in control compared to data from Germany. Evaluation of BTRs for Germany displayed only a slight improvement (historical value of 32.9%). Analysis of data shows a limitation of options to improve the method as no main driver for high variability of BTRs in the control group was found. The cause for low precision may be multifactorial and driven by “caging effect”. There are alternative test methods available to observe bee brood development, without confinement in the tunnels, under field conditions (Oomen et al. (1992), OECD GD 75 field test design). Therefore it is necessary to investigate differences between these open field methods and semi-field testing with regard to routes of exposure, residues in brood and brood mortality, to choose the most reliable and adequate testing method assessing potential effects of PPP on honeybee brood development

On Feedback Vertex Set: New Measure and New Structures

We present a new parameterized algorithm for the {feedback vertex set} problem ({\sc fvs}) on undirected graphs. We approach the problem by considering a variation of it, the {disjoint feedback vertex set} problem ({\sc disjoint-fvs}), which finds a feedback vertex set of size $k$ that has no overlap with a given feedback vertex set $F$ of the graph $G$. We develop an improved kernelization algorithm for {\sc disjoint-fvs} and show that {\sc disjoint-fvs} can be solved in polynomial time when all vertices in $G \setminus F$ have degrees upper bounded by three. We then propose a new branch-and-search process on {\sc disjoint-fvs}, and introduce a new branch-and-search measure. The process effectively reduces a given graph to a graph on which {\sc disjoint-fvs} becomes polynomial-time solvable, and the new measure more accurately evaluates the efficiency of the process. These algorithmic and combinatorial studies enable us to develop an $O^*(3.83^k)$-time parameterized algorithm for the general {\sc fvs} problem, improving all previous algorithms for the problem.Comment: Final version, to appear in Algorithmic

D-SPACE4Cloud: A Design Tool for Big Data Applications

The last years have seen a steep rise in data generation worldwide, with the development and widespread adoption of several software projects targeting the Big Data paradigm. Many companies currently engage in Big Data analytics as part of their core business activities, nonetheless there are no tools and techniques to support the design of the underlying hardware configuration backing such systems. In particular, the focus in this report is set on Cloud deployed clusters, which represent a cost-effective alternative to on premises installations. We propose a novel tool implementing a battery of optimization and prediction techniques integrated so as to efficiently assess several alternative resource configurations, in order to determine the minimum cost cluster deployment satisfying QoS constraints. Further, the experimental campaign conducted on real systems shows the validity and relevance of the proposed method