3,570 research outputs found
Sub-Poissonian statistics of Rydberg-interacting dark-state polaritons
Interfacing light and matter at the quantum level is at the heart of modern
atomic and optical physics and enables new quantum technologies involving the
manipulation of single photons and atoms. A prototypical atom-light interface
is electromagnetically induced transparency, in which quantum interference
gives rise to hybrid states of photons and atoms called dark-state polaritons.
We have observed individual dark-state polaritons as they propagate through an
ultracold atomic gas involving Rydberg states. Strong long-range interactions
between Rydberg atoms give rise to an effective interaction blockade for
dark-state polaritons, which results in large optical nonlinearities and
modified polariton number statistics. The observed statistical fluctuations
drop well below the quantum noise limit indicating that photon correlations
modified by the strong interactions have a significant back-action on the
Rydberg atom statistics.Comment: 7 pages, 4 figure
A quantum trampoline for ultra-cold atoms
We have observed the interferometric suspension of a free-falling
Bose-Einstein condensate periodically submitted to multiple-order diffraction
by a vertical 1D standing wave. The various diffracted matter waves recombine
coherently, resulting in high contrast interference in the number of atoms
detected at constant height. For long suspension times, multiple-wave
interference is revealed through a sharpening of the fringes. We use this
scheme to measure the acceleration of gravity
CMOS detectors for space applications: from R&D to operational program with large volume foundry
Nowadays, CMOS image sensors are widely considered for space applications. The use of CIS (CMOS Image sensor)
processes has significantly enhanced their performances such as dark current, quantum efficiency and conversion gain. However, in order to fulfil specific space mission requirements, dedicated research and development work has to be performed to address specific detector performance issues. This is especially the case for dynamic range improvement through output voltage swing optimisation, control of conversion gain and noise reduction. These issues have been addressed in a 0.35ÎŒm CIS process, based on a large volume CMOS foundry, by several joint ISAE- EADS Astrium R&D programs. These results have been applied to the development of the visible and near-infrared multi-linear imager for the SENTINEL 2 mission (LEO Earth observation mission for the Global Measurement Environment and Security program). For this high performance multi-linear device, output voltage swing improvement is achieved by process optimisation done in collaboration with foundry. Conversion gain control is also achieved for each spectral band by managing photodiode capacitance. A low noise level at sensor output is reached by the use of an architecture allowing Correlated Double Sampling readout in order to eliminate reset noise (KTC noise). KTC noise elimination reveals noisy pixels due to RTS noise. Optimisation of transistorsâs dimensions, taking into account conversion gain constraints, is done to minimise these noisy pixels. Additional features have been also designed: 1) Due to different integration times between spectral bands required by mission, a specific readout mode was developed in order to avoid electrical perturbations during the integration time and readout. This readout mode leads to specific power supply architecture. 2)Post processing steps can be achieved by alignment marks design allowing a very good accuracy. These alignment marks can be used for a black coating deposition between spectral bands (pixel line) in order to minimise straight lighteffects. In conclusion a review of design improvements and performances of the final component is performed
Méritocratie ou cooptation ?
La France se caractĂ©rise par une stabilitĂ© du modĂšle de formation des Ă©lites et par une logique de reproduction particuliĂšrement fortes au regard dâautres pays. Cela tient pour une part au fait que le mode de formation des Ă©lites, dans les classes prĂ©paratoires puis dans les grandes Ă©coles, y prĂ©sente une stabilitĂ© relativement grande dans le temps. Cependant, le systĂšme des grandes Ă©coles nâest pas complĂštement Ă lâĂ©cart des transformations parmi lesquelles lâentrĂ©e des filles depuis quelques annĂ©es, le dĂ©veloppement des formations Ă la gestion et surtout lâinternationalisation croissante (mise en rĂ©seau, accords, frĂ©quentation dâinstitutions Ă©trangĂšres, doubles diplĂŽmes, etc.). Ces processus peuvent ĂȘtre Ă lâorigine de recompositions et de nouveaux principes de hiĂ©rarchisation sociale. Rien nâautorise en effet Ă penser pour le moment que ces transformations favorisent un Ă©largissement du recrutement ou une formation plus indĂ©pendante des modes de cooptation, qui caractĂ©risent si fortement les processus de sĂ©lection et de formation des Ă©lites en France.France stands out for the stability of its elite training model and a particularly strong desire for consistency, when compared to other countries. This is due partly to the fact that the elite training programmes, from the preparatory courses to the elite institutions offer relatively high stability over time. However, the elite institution system is not completely exempt from keeping up with the times, for instance when it opened its doors to females a few years ago, began developing instruction in management and, above all, became increasingly international (networking, agreements, attendance at foreign establishments, double-degrees, etc.). Such processes could give rise to various forms of regrouping and new principles for establishing social hierarchies. For the time being, there is no evidence that the aforementioned changes have fostered broader enrolment or training programmes free from co-opting, a tendency that so strongly colours elite selection and training processes in France.Francia se caracteriza por una estabilidad del modelo de formaciĂłn de las Ă©lites y por una lĂłgica de reproducciĂłn particularmente fuertes respecto a otros paĂses. Esto se debe, por un lado, al hecho de que el modo de formaciĂłn de las Ă©lites, en las clases preparatorias y despuĂ©s en las âgrandes Ă©colesâ, presenta una estabilidad relativamente grande en el tiempo. No obstante, el sistema de las âgrandes Ă©colesâ no estĂĄ completamente fuera de las transformaciones, entre ellas la entrada de las niñas desde hace algunos años, el desarrollo de las formaciones en la gestiĂłn y sobre todo la creciente internacionalizaciĂłn (puesta en red, acuerdos, frecuentaciĂłn de instituciones extranjeras, dobles diplomas, etc.). Estos procesos pueden estar en el origen de recomposiciones y nuevos principios de jerarquizaciĂłn social. En realidad nada permite pensar por el momento que estas transformaciones favorezcan una ampliaciĂłn del reclutamiento o una formaciĂłn mĂĄs independiente de los modos de cooptaciĂłn, que caracterizan tan marcadamente los procesos de selecciĂłn y formaciĂłn de las Ă©lites en Francia
Sociologie du pouvoir et des Ă©lites
Monique de Saint Martin, directrice dâĂ©tudes Reconversions et dĂ©conversions Ayant fait lâhypothĂšse dâune spĂ©cificitĂ© des reconversions, qui se distinguent dâune forme de reproduction, celles-ci ne pouvaient ĂȘtre analysĂ©es seulement Ă partir des caractĂ©ristiques le plus souvent prises en compte : transmutation de ressources Ă©conomiques, culturelles, sociales ou symboliques, en ressources dâun autre type, mobilisation des ressources, changement dâactivitĂ©s et dĂ©placement dans lâespace social. A..
Sociologie du pouvoir et des Ă©lites
Monique de Saint Martin, directrice dâĂ©tudes Transformations et restructurations des Ă©lites et des pouvoirs Le sĂ©minaire sâest attachĂ© Ă lâĂ©tude des processus dâinternationalisation croissante des Ă©lites et des institutions dâenseignement supĂ©rieur et de formation, ainsi quâĂ lâĂ©tude des transformations et des recompositions des Ă©lites, anciennes et nouvelles, face Ă cette internationalisation dans un contexte dâĂ©changes Ă©conomiques gĂ©nĂ©ralisĂ©s, et de dĂ©veloppement de processus dâintĂ©gration ..
Sociologie du pouvoir et des Ă©lites
Monique de Saint Martin, directrice dâĂ©tudes Transformations et restructurations des Ă©lites et des pouvoirs Dans un contexte dâĂ©changes Ă©conomiques gĂ©nĂ©ralisĂ©s, de dĂ©veloppement de processus dâintĂ©gration rĂ©gionale (Union europĂ©enne, Mercosud), de multiplication des instances dâĂ©valuation et dâexpertise, les processus dâinternationalisation des Ă©lites, et des institutions dâenseignement supĂ©rieur, qui ne sont certes pas rĂ©cents, se dĂ©veloppent de façon croissante et intensive. On a poursuivi ..
Sociologie du pouvoir et des Ă©lites
Monique de Saint Martin, directrice dâĂ©tudes Reconversions et dĂ©conversions Ayant fait lâhypothĂšse dâune spĂ©cificitĂ© des reconversions, qui se distinguent dâune forme de reproduction, celles-ci ne pouvaient ĂȘtre analysĂ©es seulement Ă partir des caractĂ©ristiques le plus souvent prises en compte : transmutation de ressources Ă©conomiques, culturelles, sociales ou symboliques, en ressources dâun autre type, mobilisation des ressources, changement dâactivitĂ©s et dĂ©placement dans lâespace social. A..
Que disent les Ă©lĂšves de CLIS 1 de leur(s) places(s) dans l'Ă©cole ? Un empan liminal
Within the French primary school, CLIS 1 are specialised classes which accept children with cognitive disabilities. These children should partake in inclusion times in regular classes, called "inclusion classes". My thesis focuses on what CLIS 1 students say about their place(s) in the school, from the perspective of liminality, as defined by Murphy. I suggest that the CLIS is a place of liminality, allowing children to stay at school without their total inclusion.I question the liminal status of students in CLIS 1, by discussing the situation and place of disabled children, from both socio-historical and socio-clinical perspectives. The CLIS 1 can be thought of as a liminal space, regarding the definition of mental disability and its various denominations, from the historical perspective of the education of disabled children and from the current policy which claims inclusive desire. In support of the methodological frameworks of institutional analysis and the sociology of childhood, I developed a socio-clinical institutional device to guide a collective reflection with the children of three CLIS 1. It did not seek to match children's reflections to observable reality, The aim was not to compare exactly what the children said to observable reality, but to express to the children the contradictions between what they say and my observations, to analyse their place in the school.My data lead me to enrich the initial theoretical framework. The liminality of the children in CLIS 1 is a plural liminality, which depends on social, cultural, environmental, institutional, as well as individual factors. The research has updated the concept of liminal span, which is a dynamic process that weakens different liminal situations according to the inclusion time in regular classes of each child. My empirical work as well as my theoretical work, has led me to question the methods of the implementation of the inclusion policy in primary school.Au sein de l'Ă©cole Ă©lĂ©mentaire, les CLIS 1 sont des classes spĂ©cialisĂ©es qui accueillent des Ă©lĂšves porteurs de troubles des fonctions cognitives. Ces Ă©lĂšves doivent connaĂźtre des temps d'inclusion en classe ordinaire, alors nommĂ©e « classe d'inclusion ». Ma thĂšse s'intĂ©resse Ă ce que disent les Ă©lĂšves de CLIS 1 de leur(s) place(s) dans l'Ă©cole, Ă partir du concept de liminalitĂ©, tel qu'il a Ă©tĂ© dĂ©fini par Murphy. Il Je postule que la CLIS est un lieu de la liminalitĂ©, permettant aux Ă©lĂšves de rester dans l'Ă©cole sans les y inclure totalement.Je questionne la situation liminale des Ă©lĂšves de CLIS 1 par la dialectisation du statut, de la situation et de la place de la personne handicapĂ©e, dans une double perspective socio-historique et socio-clinique. La CLIS 1 peut ĂȘtre pensĂ©e comme un espace liminal, au regard de la dĂ©finition du handicap mental et de ses diffĂ©rentes dĂ©nominations, de la perspective historique de la scolarisation des enfants en situation de handicap et de la politique actuelle qui revendique une volontĂ© inclusive. A l'appui des cadres mĂ©thodologiques de l'analyse institutionnelle et de la sociologie de l'enfance, j'ai Ă©laborĂ© un dispositif de socio-clinique institutionnelle pour mener une rĂ©flexion collective avec les Ă©lĂšves de trois CLIS 1. Il ne s'agissait pas rechercher une adĂ©quation des discours des Ă©lĂšves Ă la rĂ©alitĂ© observable, mais de confronter leurs reprĂ©sentations aux observations faites, de façon Ă analyser leur(s) place(s) au sein de l'institution scolaire.Mes donnĂ©es me conduisent Ă enrichir le cadre thĂ©orique initial. La liminalitĂ© des Ă©lĂšves de CLIS1 est une liminalitĂ© plurielle, qui dĂ©pend de facteurs sociaux, culturels, environnementaux, institutionnels, mais aussi individuels. La recherche a mis Ă jour le concept d'empan liminal, Ă savoir un processus dynamique qui se dĂ©cline diffĂ©rentes situations liminales selon les temps d'inclusion en classe ordinaire de chaque Ă©lĂšve. Mon travail empirique d'une part et thĂ©orique d'autre part me conduit Ă interroger les modalitĂ©s de la mise en Ćuvre de la politique d'inclusion au sein de l'Ă©cole Ă©lĂ©mentaire
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