The Gaia satellite: a tool for Emission Line Stars and Hot Stars

The Gaia satellite will be launched at the end of 2011. It will observe at least 1 billion stars, and among them several million emission line stars and hot stars. Gaia will provide parallaxes for each star and spectra for stars till V magnitude equal to 17. After a general description of Gaia, we present the codes and methods, which are currently developed by our team. They will provide automatically the astrophysical parameters and spectral classification for the hot and emission line stars in the Milky Way and other close Local Group galaxies such as the Magellanic Clouds.Comment: SF2A2008, session GAIA, invited tal

La libéralisation des chemins de fer européens au regard de l’histoire

La table ronde « La libéralisation des chemins de fer européens au regard de l’histoire : avancée, risque ou régression ? » avait pour mission de mettre en perspective historique la libéralisation des chemins de fer européens : son évolution et sa place dans une histoire à long terme, ses résultats, les nouvelles relations que ces mesures ont instituées entre gestionnaires des réseaux et exploitants de transport, entre le secteur des transports et les pouvoirs nationaux, régionaux ou locaux. Après une introduction historique assurée par Michèle Merger, chargée de recherche au CNRS, qui rappelle la directive 91/440 et ses quatre recommandations – séparation juridique et comptable de l’infrastructure des réseaux et de leur exploitation, indépendance de gestion des entreprises ferroviaires, leur assainissement financier et le libre accès de nouvelles entreprises exploitantes à l’infrastructure –, qui ont conduit à une évolution très rapide du secteur en quinze ans, quatre questions sont posées aux participants : quels sont les pays et les acteurs européens les plus réfractaires et les plus favorables à cette évolution, et quels sont leurs arguments respectifs ? Existe-t-il une typologie des réformes entreprises, conduisant à des modèles plus u moins largement diffusés ? Quel type de service ferroviaire attendons-nous et pouvons-nous attendre de cette réforme, en d’autres termes, quel est le devenir du concept de service public ferroviaire ? Qu’en est-il de la revitalisation du fret ferroviaire au lendemain de l’ouverture des corridors de fret favorisés par ces directives, quelle est la nouvelle Europe du fret ferroviaire ? Patrice Leroy, directeur honoraire de la SNCF, ancien secrétaire général adjoint du CEEP, président délégué de l’AHICF anime ensuite le débat qui réunit Yves Crozet, professeur à l’université Lumière-Lyon 2, Michel Lebœuf, directeur Développement à Voyageurs France Europe, SNCF, Hubert du Mesnil, président de RFF et Émile Quinet, professeur émérite à l’École nationale des Ponts et Chaussées.ROUND TABLE with Yves CROZET, Michel LEBŒUF, Patrice LEROY, Michèle MERGER, Hubert du MESNIL and Emile QUINET The purpose of the round table discussion of “The liberalization of European railways from a historical perspective: progress, risk, or regression?” was to put the liberalization of European railways into a historical perspective: the discussants’ goal was to define the place and evolution of this trend in an open-ended history, its results, and the new relationships that such measures have brought about between network managers and transportation operators, as well as between the transportation sector and national, regional, and local authorities. After an historical introduction provided by Michèle Merger, a researcher at the CNRS, who reminded us of the 91/440 directive and its four recommendations—the legal and accounting separation of network infrastructures and their operations, the independent management of the railway companies and their financial streamlining, and open access to the infrastructure for new operating companies—led to a very rapid evolution of the sector in fifteen years, the participants were asked four questions: which European countries and players are the most opposed to and the most in favor of this evolution, and what are their respective arguments? Is there a typology of business reform that leads to more or less widespread models? What kind of railway service is in store for us and what should we expect from such reforms? In other words, what is the future of the concept of public railway service? What will be the impact of the revitalization of rail freight in the aftermath of the opening of freight corridors advantaged by these directives? What will the new Europe of rail freight look like? Patrice Leroy, honorary director of the SNCF, former adjunct secretary general of the CEEP, and Deputy Chairman of the AHICF, then moderated the debate that brought together Yves Crozet, professor at the university Lumière-Lyon 2, Michel Leboeuf, developmental director of Voyageurs France Europe, SNCF, Hubert du Mesnil, President of the RFF, and Emile Quinet, professor emeritus at the Ecole nationale des Ponts et Chaussées

The linear polarisation of southern bright stars measured at the parts-per-million level

We report observations of the linear polarisation of a sample of 50 nearby southern bright stars measured to a median sensitivity of ~4.4 x 10^{-6}. We find larger polarisations and more highly polarised stars than in the previous PlanetPol survey of northern bright stars. This is attributed to a dustier interstellar medium in the mid-plane of the Galaxy, together with a population containing more B-type stars leading to more intrinsically polarised stars, as well as using a wavelength more sensitive to intrinsic polarisation in late-type giants. Significant polarisation had been identified for only six stars in the survey group previously, whereas we are now able to deduce intrinsic polarigenic mechanisms for more than twenty. The four most highly polarised stars in the sample are the four classical Be stars (alpha Eri, alpha Col, eta Cen and alpha Ara). For the three of these objects resolved by interferometry, the position angles are consistent with the orientation of the circumstellar disc determined. We find significant intrinsic polarisation in most B stars in the sample; amongst these are a number of close binaries and an unusual binary debris disk system. However these circumstances do not account for the high polarisations of all the B stars in the sample and other polarigenic mechanisms are explored. Intrinsic polarisation is also apparent in several late type giants which can be attributed to either close, hot circumstellar dust or bright spots in the photosphere of these stars. Aside from a handful of notable debris disk systems, the majority of A to K type stars show polarisation levels consistent with interstellar polarisation.Peer reviewe

A mechanized semantics for C++ object construction and destruction, with applications to resource management

International audienceWe present a formal operational semantics and its Coq mechanization for the C++ object model, featuring object construction and destruction, shared and repeated multiple inheritance, and virtual function call dispatch. These are key C++ language features for high-level system programming, in particular for predictable and reliable resource management. This paper is the first to present a formal mechanized account of the metatheory of construction and destruction in C++, and applications to popular programming techniques such as "resource acquisition is initialization." We also report on irregularities and apparent contradictions in the ISO C++03 and C++11 standards

Circulating and Hepatic BDCA1+, BDCA2+, and BDCA3+ Dendritic Cells Are Differentially Subverted in Patients With Chronic HBV Infection

Background and aims: Chronic hepatitis B virus (HBV) infection is a major health burden potentially evolving toward cirrhosis and hepatocellular carcinoma. HBV physiopathology is strongly related to the host immunity, yet the mechanisms of viral evasion from immune-surveillance are still misunderstood. The immune response elicited at early stages of viral infection is believed to be important for subsequent disease outcome. Dendritic cells (DCs) are crucial immune sentinels which orchestrate antiviral immunity, which offer opportunity to pathogens to subvert them to escape immunity. Despite the pivotal role of DCs in orientating antiviral responses and determining the outcome of infection, their precise involvement in HBV pathogenesis is not fully explored.Methods: One hundred thirty chronically HBV infected patients and 85 healthy donors were enrolled in the study for blood collection, together with 29 chronically HBV infected patients and 33 non-viral infected patients that were included for liver biopsy collection. In a pioneer way, we investigated the phenotypic and functional features of both circulating and intrahepatic BDCA1+ cDC2, BDCA2+ pDCs, and BDCA3+ cDC1 simultaneously in patients with chronic HBV infection by designing a unique multi-parametric flow cytometry approach.Results: We showed modulations of the frequencies and basal activation status of blood and liver DCs associated with impaired expressions of specific immune checkpoints and TLR molecules on circulating DC subsets. Furthermore, we highlighted an impaired maturation of circulating and hepatic pDCs and cDCs following stimulation with specific TLR agonists in chronic HBV patients, associated with drastic dysfunctions in the capacity of circulating DC subsets to produce IL-12p70, TNFα, IFNα, IFNλ1, and IFNλ2 while intrahepatic DCs remained fully functional. Most of these modulations correlated with HBsAg and HBV DNA levels.Conclusion: We highlight potent alterations in the distribution, phenotype and function of all DC subsets in blood together with modulations of intrahepatic DCs, revealing that HBV may hijack the immune system by subverting DCs. Our findings provide innovative insights into the immuno-pathogenesis of HBV and the mechanisms of virus escape from immune control. Such understanding is promising for developing new therapeutic strategies restoring an efficient immune control of the virus

A stepwise algorithm using an at-a-glance first-line test for the non-invasive diagnosis of advanced liver fibrosis and cirrhosis

BACKGROUND & AIMS: Chronic liver diseases (CLD) are common, and are therefore mainly managed by non-hepatologists. These physicians lack access to the best non-invasive tests of liver fibrosis, and consequently cannot accurately determine the disease severity. Referral to a hepatologist is then needed. We aimed to implement an algorithm, comprising a new first-line test usable by all physicians, for the detection of advanced liver fibrosis in all CLD patients. METHODS: Diagnostic study: 3754 CLD patients with liver biopsy were 2:1 randomized into derivation and validation sets. Prognostic study: longitudinal follow-up of 1275 CLD patients with baseline fibrosis tests. RESULTS: Diagnostic study: the easy liver fibrosis test (eLIFT), an "at-a-glance" sum of points attributed to age, gender, gamma-glutamyl transferase, aspartate aminotransferase (AST), platelets and prothrombin time, was developed for the diagnosis of advanced fibrosis. In the validation set, eLIFT and fibrosis-4 (FIB4) had the same sensitivity (78.0% vs. 76.6%, p=0.470) but eLIFT gave fewer false positive results, especially in patients ≥60years old (53.8% vs. 82.0%, p<0.001), and was thus more suitable as screening test. FibroMeter with vibration controlled transient elastography (VCTE) was the most accurate among the eight fibrosis tests evaluated. The sensitivity of the eLIFT-FM algorithm (first-line eLIFT, second-line FibroMeter) was 76.1% for advanced fibrosis and 92.1% for cirrhosis. Prognostic study: patients diagnosed as having "no/mild fibrosis" by the algorithm had excellent liver-related prognosis with thus no need for referral to a hepatologist. CONCLUSION: The eLIFT-FM algorithm extends the detection of advanced liver fibrosis to all CLD patients and reduces unnecessary referrals of patients without significant CLD to hepatologists. LAY SUMMARY: Blood fibrosis tests and transient elastography accurately diagnose advanced liver fibrosis in the large population of patients having chronic liver disease, but these non-invasive tests are only currently available in specialized centers. We have developed an algorithm including the easy liver fibrosis test (eLIFT), a new simple and widely available blood test. It is used as a first-line procedure that selects at-risk patients who need further evaluation with the FibroMeter, an accurate fibrosis test combining blood markers and transient elastography result. This new algorithm, called the eLIFT-FM, accurately identifies the patients with advanced chronic liver disease who need referral to a specialist, and those with no or mild liver lesions who can remain under the care of their usual physician. CLINICAL TRIAL REGISTRATION: No registration (analysis of pooled data from previously published diagnostic studies)

Un diagnostic fiable de fibrose hépatique ou de cirrhose peut être fait avec un seul test sanguin et sans biopsie nécessaire

Date du colloque&nbsp;: 09/2008</p

A New Combination of Blood Test and Fibroscan for Accurate Non-Invasive Diagnosis of Liver Fibrosis Stages in Chronic Hepatitis C

OBJECTIVES: Precise evaluation of the level of liver fibrosis is recommended in patients with chronic hepatitis C (CHC). Blood fibrosis tests and Fibroscan are now widely used for the non-invasive diagnosis of liver fibrosis. Detailed fibrosis stage classifications have been developed to provide an estimation of the liver fibrosis stage from the results of these non-invasive tests. Our aim was to develop a new and more accurate fibrosis stage classification by using new scores combining non-invasive fibrosis tests.METHODS: In all, 729 patients with CHC (exploratory set: 349; validation set: 380) had liver biopsy for Metavir fibrosis (F) staging, and 6 fibrosis tests: Fibroscan, Fibrotest, FibroMeter, Hepascore, FIB-4, APRI. RESULTS: Exploratory set: Fibroscan and FibroMeter were the independent predictors of different diagnostic targets of liver fibrosis. New fibrosis indexes combining FibroMeter and Fibroscan were thus developed for the diagnosis of clinically significant fibrosis (CSF-index) or severe fibrosis (SF-index). The association of CSF- and SF-indexes provided a new fibrosis stage classification (CSF/SF classification): F0/1, F1/2, F2±1, F2/3, F3±1, F4. Validation set: CSF/SF classification had a high diagnostic accuracy (85.8% well-classified patients), significantly higher than the diagnostic accuracies of FibroMeter (69.7%, P&lt;0.001), Fibroscan (63.3%, P&lt;0.001), or Fibrotest (43.9%, P&lt;0.001) classifications. CONCLUSIONS: The association of new fibrosis indexes combining FibroMeter and Fibroscan provides a new fibrosis stage classification. This classification is significantly more accurate than Fibrotest, FibroMeter, or Fibroscan classifications, and improves the accuracy of the non-invasive diagnosis of liver fibrosis stages to 86% without any liver biopsy

Comparison of accuracy of fibrosis degree classifications by liver biopsy and non-invasive tests in chronic hepatitis C

<p>Abstract</p> <p>Background</p> <p>Non-invasive tests have been constructed and evaluated mainly for binary diagnoses such as significant fibrosis. Recently, detailed fibrosis classifications for several non-invasive tests have been developed, but their accuracy has not been thoroughly evaluated in comparison to liver biopsy, especially in clinical practice and for Fibroscan. Therefore, the main aim of the present study was to evaluate the accuracy of detailed fibrosis classifications available for non-invasive tests and liver biopsy. The secondary aim was to validate these accuracies in independent populations.</p> <p>Methods</p> <p>Four HCV populations provided 2,068 patients with liver biopsy, four different pathologist skill-levels and non-invasive tests. Results were expressed as percentages of correctly classified patients.</p> <p>Results</p> <p>In population #1 including 205 patients and comparing liver biopsy (reference: consensus reading by two experts) and blood tests, Metavir fibrosis (F_M) stage accuracy was 64.4% in local pathologists vs. 82.2% (p < 10^-3) in single expert pathologist. Significant discrepancy (≥ 2F_Mvs reference histological result) rates were: Fibrotest: 17.2%, FibroMeter^2G: 5.6%, local pathologists: 4.9%, FibroMeter^3G: 0.5%, expert pathologist: 0% (p < 10^-3). In population #2 including 1,056 patients and comparing blood tests, the discrepancy scores, taking into account the error magnitude, of detailed fibrosis classification were significantly different between FibroMeter^2G(0.30 ± 0.55) and FibroMeter^3G(0.14 ± 0.37, p < 10^-3) or Fibrotest (0.84 ± 0.80, p < 10^-3). In population #3 (and #4) including 458 (359) patients and comparing blood tests and Fibroscan, accuracies of detailed fibrosis classification were, respectively: Fibrotest: 42.5% (33.5%), Fibroscan: 64.9% (50.7%), FibroMeter^2G: 68.7% (68.2%), FibroMeter^3G: 77.1% (83.4%), p < 10^-3(p < 10^-3). Significant discrepancy (≥ 2 F_M) rates were, respectively: Fibrotest: 21.3% (22.2%), Fibroscan: 12.9% (12.3%), FibroMeter^2G: 5.7% (6.0%), FibroMeter^3G: 0.9% (0.9%), p < 10^-3(p < 10^-3).</p> <p>Conclusions</p> <p>The accuracy in detailed fibrosis classification of the best-performing blood test outperforms liver biopsy read by a local pathologist, i.e., in clinical practice; however, the classification precision is apparently lesser. This detailed classification accuracy is much lower than that of significant fibrosis with Fibroscan and even Fibrotest but higher with FibroMeter^3G. FibroMeter classification accuracy was significantly higher than those of other non-invasive tests. Finally, for hepatitis C evaluation in clinical practice, fibrosis degree can be evaluated using an accurate blood test.</p