Time delays in gravitationally lensed quasars

Doctoral thesis (2012)

Starting with a concise introduction on gravitational lensing, time delays between lensed quasars and its importance as a cosmological probe to estimate the Hubble constant, we present our contribution to ... [more ▼]

Starting with a concise introduction on gravitational lensing, time delays between lensed quasars and its importance as a cosmological probe to estimate the Hubble constant, we present our contribution to this domain. In a first part, we explain the details of the Numerical Model Fit, a method to estimate time delays between two or more lensed quasar images. We apply this technique to the light curves of 11 lensed quasars with known time delays in order to analyse these published delays in a more homogeneous way. Some results can be confirmed, but others prove to be unreliable. The second part is devoted to the most recent results of our contribution to the COSMOGRAIL collaboration. We briefly summarize the data reduction and analysis tools before the presentation of the photometry and time delay analysis of 6 lensed quasars. On top of the confirmation of time delays in two objects, SDSS J1206+4332 and SDSS J1650+4251, we are the first to measure the time delay in three doubly lensed quasar systems: HS 2209+1914, SDSS J0903+5028, and SDSS J1155+6346. The time delay analysis of the well-known quadruply lensed quasar PG 1115+080 reveals interesting elements, and asks for further investigation of longer light curves. [less ▲]

La voix juste: la science au service du chant

Scientific conference (2012, December 12)

Le chant est une activité largement répandue et partagée. Afin de déterminer si une performance vocale est « juste » ou « fausse », de mieux comprendre les causes d’un trouble de justesse ou encore de ... [more ▼]

Le chant est une activité largement répandue et partagée. Afin de déterminer si une performance vocale est « juste » ou « fausse », de mieux comprendre les causes d’un trouble de justesse ou encore de porter un jugement sur la qualité d’un chanteur, des outils d’évaluation sont nécessaires. Quatre études réalisées dans le cadre d’une thèse de Doctorat permettent de valider une méthode objective d’analyse de la justesse mais aussi d’observer les effets à prendre en compte pour une évaluation pertinente de la justesse vocale. Dans un premier temps, l’analyse de mélodies chantées par des chanteurs entraînés et non entraînés nous a permis de mettre au point une méthode d’évaluation objective de la justesse vocale sur base d’analyses acoustiques. La confrontation de cette méthode objective avec le jugement d’experts en voix ou en musique nous a permis d’affiner les critères à prendre en compte dans l’évaluation objective de la justesse. Dans un second temps, nous avons observé les effets du contexte d’évaluation et de la technique vocale sur l’évaluation de la justesse vocale. Les différents résultats mettent en évidence la possibilité d’analyser objectivement une performance vocale chantée mais également la complexité du processus de jugement. Les perspectives expérimentales, artistiques et pédagogiques seront discutées à la lumière des conclusions de ces études. [less ▲]

Empathy for pain and Alexithymia : a rTMS study

Poster (2012, December 12)

Empathy is a multi-facet function regulating social life. In this study, we investigated empathy in relation to alexithymia. Alexithymia is considered as a state showing difficulties in identification and ... [more ▼]

Empathy is a multi-facet function regulating social life. In this study, we investigated empathy in relation to alexithymia. Alexithymia is considered as a state showing difficulties in identification and distinction of one’s own emotional life, as well as difficulties in identification/distinction of others emotions. Thus, alexithymia is considered as an empathy trouble. Previous studies demonstrated that alexithymia is characterized by a particular pattern of cerebral activation comprising some important zones of emotional control (i.e., left DLPFC hyperactivation, left ACC hypoactivation). In the present study, we investigated the electrodermal response of participants during an empathy for pain task before and after an inhibiting rTMS on the right DLPFC to facilitate the ACC activation, with the aim to enhance the emotional expression for alexithymic population. Results showed that rTMS on the right DLPFC increase the relaxation of the alexithymic participants facing the stimuli. This can match our assumptions but further research is needed to clarify this situation. [less ▲]

IMPACT DE LA STEAM EXPLOSION ET DE L’HOMOGENEISATION SUR LES PROPRIETES PHYSICOCHIMIQUES ET L’HYDROLYSE ENZYMATIQUE DE LA CELLULOSE

Doctoral thesis (2012)

In the economic and energetic context of our society, it is universally recognized that an alternative to fossil fuels and oil based product will be needed in the nearest future. A potential solution is ... [more ▼]

In the economic and energetic context of our society, it is universally recognized that an alternative to fossil fuels and oil based product will be needed in the nearest future. A potential solution is to develop second generation biofuel and biobased product that utilizes non-food plant materials. The major component of these materials is lignocellulose, which is a complex composed by widely available biological polymers such as cellulose, hemicelluloses and lignin. This thesis is a part of this approach and is focused on a well-define part of these materials: the cellulose. The first part of this work was focused on the impact of two pretraitements (steam explosion and homogenization) on physico-chemical properties and hydrolysis yield of pure cellulose fiber. In contrast with literature, results obtained showed that moderate steam explosion treatments did not appear to improve the enzymatic hydrolysis yield of the cellulose fibers. In Parralel, a model that predicts the effect of the intensity of the steam explosion treatment in correlation with temperature and time was assessed. Links between this model and the evolution physico-chemical properties of the cellulose during pretreatment and cellulose hydrolysis yield were established In a second way, a theoretical diagram predicting the degradation of the cellulose during the steam explosion treatment was established. Regarding the homogenization, it was shown that homogenization increase significatively the cellulose hydrolysis (from 25 to 100%). Results highlights potential of this technology to be used as a pretreatment Finally, enzymatic hydrolysis step has been studied in order to improve cellulose hydrolysis and to obtain high concentrated hydrolysate. In this way, two methods based on successive addition of enzyme and substrate were assessed [less ▲]

Serial population extinctions in a small mammal indicate Late Pleistocene ecosystem instability

in Proceedings of the National Academy of Sciences of the United States of America (2012), 109(50), 20532-20536

The Late Pleistocene global extinction of many terrestrial mammal species has been a subject of intensive scientific study for over a century, yet the relative contributions of environmental changes and ... [more ▼]

The Late Pleistocene global extinction of many terrestrial mammal species has been a subject of intensive scientific study for over a century, yet the relative contributions of environmental changes and the global expansion of humans remain unresolved. A defining component of these extinctions is a bias toward large species, with the majority of small-mammal taxa apparently surviving into the present. Here, we investigate the population-level history of a key tundra-specialist small mammal, the collared lemming (Dicrostonyx torquatus), to explore whether events during the Late Pleistocene had a discernible effect beyond the large mammal fauna. Using ancient DNA techniques to sample across three sites in North-West Europe, we observe a dramatic reduction in genetic diversity in this species over the last 50,000 y. We further identify a series of extinction-recolonization events, indicating a previously unrecognized instability in Late Pleistocene small-mammal populations, which we link with climatic fluctuations. Our results reveal climate-associated, repeated regional extinctions in a keystone prey species across the Late Pleistocene, a pattern likely to have had an impact on the wider steppe-tundra community, and one that is concordant with environmental change as a major force in structuring Late Pleistocene biodiversity. [less ▲]

Interdépendances et classes sociales dans la sociologie de l’éducation de Bernard Lahire

Conference (2012, December 11)

Comparaison de l’analyse de carottes sédimentaires par fluorescence X mobile et par PIXE

Poster (2012, December 11)

Questions à Dominique Pradelle ("Par-delà la révolution copernicienne")

Speech (2012)

Discussion of D. Pradelle, "Par-delà la révolution copernicienne. Sujet transcendantal et facultés chez Kant et Husserl" (Paris, PUF, 2012).

Ateliers "L'activité un prisme multifacettes": L'institution, fin de la vie active ?

Conference (2012, December 11)

En attendant la fin des temps: deux espèces d'apocalypticiens

Article for general public (2012)

A l'approche de la date fatidique du 21 décembre 2012, l'article revient sur la posture "catastrophiste" en insistant sur le rôle de la fiction et de l'imagination dans nos stratégies collectives d ... [more ▼]

A l'approche de la date fatidique du 21 décembre 2012, l'article revient sur la posture "catastrophiste" en insistant sur le rôle de la fiction et de l'imagination dans nos stratégies collectives d'évitement du pire. Assimilés à tort aux prophètes de malheur, les auteurs de dystopie comme Orwell ou Huxley ne nous décrivent l'avènement d'une menace que pour mieux la conjurer. Sans cette espèce d' "apocalypticiens prophylactiques", comme se décrivait Günther Anders, il est probable que notre capacité à penser la catastrophe serait sérieusement atrophiée. [less ▲]