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Thiaw, Cheikh, Habiboula Lemrabott, Moustapha Thiame, Khady Loum, Sega Gueye, Issa Diagne e Gregoire Sissoko. "MAGNETO RESISTANCE SERIE DANS LA PHOTOPILE (N+/P/P+) AU SILICIUM SOUS ECLAIREMENT POLYCHROMATIQUE PAR LA FACE (N+)". International Journal of Advanced Research 12, n.º 03 (31 de março de 2024): 1025–39. http://dx.doi.org/10.21474/ijar01/18488.
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Dans ce travail, la photopile (n+/p/p+) au silicium cristallin est sous eclairement polychromatique par la face (n+) et placee dans un champ magnetique (B) constant. Letude de la caracteristique de la densite de courant en fonction de la tension, pour chaque valeur du coefficient de diffusion (D(B))des porteurs minoritaires de charge dans la base (p), depaisseur optimum (Hopt(B)) requise, permet detablir lexpression de la resistance serie (Rs(Hot(B)).De sa courbe de calibaration en fonction de la vitesse de recombinaison (Sf) des porteurs minoritaire de charge à la jonction, la resistance serie est extraite en fonction du champ magnetique applique et de lepaisseur optimum de la base.
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Taibi, M., J. Aride, E. Antic-Fidancev, M. Lemaitre-Blaise e P. Porcher. "Etude de la fluorescence de Eu3+ dans BaRE2O4 (RE = Gd, Y). Détermination des paramètres du champ cristallin". Physica Status Solidi (a) 144, n.º 2 (16 de agosto de 1994): 453–59. http://dx.doi.org/10.1002/pssa.2211440226.
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Guiselin, Benjamin, e Ludovic Berthier. "Le verre est-il une phase de la matière ?" Reflets de la physique, n.º 74 (dezembro de 2022): 28–33. http://dx.doi.org/10.1051/refdp/202274028.
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Quoi de plus usuel que le verre ? Nous portons des lunettes, nos conversations sont transmises par fibres optiques, nos villes sont peuplées d’immeubles aux façades de verre. L’existence du verre est tangible dans notre vie quotidienne. Et pourtant… Du point de vue microscopique, la structure du verre ressemble à celle du liquide à partir duquel il a été obtenu, mais le verre est indéniablement aussi rigide qu’un matériau cristallin sans en avoir la structure ordonnée. La définition du verre en tant que phase de la matière obtenue au travers d’une transition de phase s’accompagnant de la brisure de symétrie d’un paramètre d’ordre macroscopique reste un problème fondamental ouvert. Alors, existe-t-il une phase « verre » ?
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Rojas, Eveling Y., Leonardo Ordoñez, Victor Hernandez, Jose E. Guzman, Juan Izquierdo, Jose Gabriel Lora e Jose Prieto. "S235 – Diagnostic Test Validation: CHAMP in Endolymphatic Hydrops". Otolaryngology–Head and Neck Surgery 139, n.º 2_suppl (agosto de 2008): P154. http://dx.doi.org/10.1016/j.otohns.2008.05.410.
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Objectives The Cochlear Hydrops Analysis Masking Procedure (CHAMP) has been reported with a high sensibility and specificity for the diagnosis of endolymphatic hydrops (ELH). Nevertheless, a complete validation of CHAMP with precise methods has not been done. Our objectives: To determine whether CHAMP has a diagnostic value in patients with definite, probable/possible diagnosis of Meniere's disease or endolymphatic hydrops, based on the criteria of the AAO-HNS. Methods Prospective validation study for a diagnostic test: phase II. Latency of wave V was assessed using CHAMP. We classified subjects in 5 groups: 1-Definite ELH, 2-Probable ELH, 3-Possible ELH, 4-subjects with other otovestibular symptoms, 5-normal hearing subjects. We included cases (groups 1–4) with an episode of vertigo with duration equal or longer than 20 minutes, with or without other otovestibular symptoms. Results We included 67 cases (132 ears). 38 cases (76 ears) completed the follow up and their results are presented. In group 1, the sensibility of CHAMP was 43% and its specificity was 100%. In groups 2–3, the sensitivity was 20% and the specificity 100%, with 0% false positive and 80% false negative results. Other indicators of validity for this diagnostic test are presented. Conclusions CHAMP has a high specificity and low sensibility for the diagnosis of ELH when the delay in wave V latency is used. Future studies may assess the relationship between wave amplitudes to improve the clinical value of CHAMP.
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Michielsen-Effinger, Janine. "Étude, Par la Théorie du Champ Cristallin, de la Structure des Solutions Aqueuses des Éléments de Transition. I Scission des Termes dn Dans des Champs Faibles". Bulletin des Sociétés Chimiques Belges 71, n.º 5-6 (1 de setembro de 2010): 276–305. http://dx.doi.org/10.1002/bscb.19620710504.
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Logbi, Hanène. "Hybridite generique et posture chez Nora Sari dans Constantine, l´exil et la guerre". Káñina 47, n.º 3 (22 de novembro de 2023): 159–74. http://dx.doi.org/10.15517/rk.v47i3.57724.
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Dans cet article, nous avons voulu montrer que l’hybridité générique perçue et avérée dans le texte de Nora Sari était un effet des enjeux de diverses tendances du contexte de production dans le choix du sujet à traiter, d’une part la vie de la famille et le récit de soi du principal personnage du roman, d’autre part le contexte historique prévalant durant la période concernant cette tranche de vie. Cette hybridité révèle un souci de posture en phase avec les discours et orientations du champ social et littéraire au sein duquel la romancière cherche à inscrire sa place. Elle montre également une volonté de dépasser un clivage profond installé dans la problématique des langues dans ce même champ.
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Berlan, J., P. Giboreau, S. Lefeuvre e C. Marchand. "Synthese organique sous champ microondes : premier exemple d'activation specifique en phase homogene". Tetrahedron Letters 32, n.º 21 (maio de 1991): 2363–66. http://dx.doi.org/10.1016/s0040-4039(00)79924-2.
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Verbanac, G., M. Mandea, M. Bandić e S. Subašić. "Magnetic observatories: biases over CHAMP satellite mission". Solid Earth 6, n.º 2 (26 de junho de 2015): 775–81. http://dx.doi.org/10.5194/se-6-775-2015.
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Abstract. Taking advantage of 9 years of the CHAMP (CHAllenging Minisatellite Payload) satellite mission (June 2000–August 2009), we investigate the temporal evolution of the observatory monthly magnetic biases. To determine these biases we compute X (northward), Y (eastward) and Z (vertically downward) monthly means from 42 observatory 1 min values or hourly values, and compare them to synthetic monthly means obtained from a G field model (Lesur et al., 2015). Afterwards, the average of biases at all observatories over 9 years is calculated and analyzed. Both the long-term trends and short-period variations (hereafter ε variations) around these averages are then investigated. The simple oscillatory pattern of ε, found at all observatories and in each component over the entire considered period, indicates that the crustal field has not changed. A comparison with both MAGSAT and Ørsted biases given for epochs 1979.92 and 1999.92 which are based on 2 single months (November and December) of MAGSAT and Ørsted satellite data, respectively, further shows that the crustal field has probably remained constant over last 3 decades. The long-trend seen in ε reflects the changes within the solar cycle 23. The short period variations observed in the ε time series are related to the external field. The amplitudes of these variations are found to be in phase with solar cycle periods, being remarkably larger over 2000–2005 than 2006–2009. Furthermore, clear semi-annual variations are observed in ε, with larger extremes appearing mostly around October and November, and around May and June of each year in X, and vice versa in Y and Z. A common external field pattern is found for the European monthly biases. The dependence of the bias monthly variations on geomagnetic latitudes is not found for non-European observatories. The results from this study represent a base to further exploit the magnetic biases computed for observatories and repeat station locations together by using data from the new satellite mission Swarm.
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Verbanac, G., M. Mandea, M. Bandić e S. Subašić. "Observatory crustal magnetic biases during CHAMP satellite mission". Solid Earth Discussions 7, n.º 1 (30 de janeiro de 2015): 495–508. http://dx.doi.org/10.5194/sed-7-495-2015.
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Abstract. Taking advantage of nine years of CHAMP satellite mission (June 2000–August 2009), we investigate the temporal evolution of the observatory monthly crustal magnetic biases. To determine biases we compute X (northward), Y (eastward) and Z (vertically downward) monthly means from 42 observatory one-minute or hourly values, and compare them to synthetic monthly means obtained from a GRIMM3 core field model (V. Lesur, personal communication, 2014). Both short period variations and long term trends in the monthly bias time series are analyzed. A comparison with biases based on MAGSAT and Ørsted satellite data, related to the 1979.92 and 1992.92 epochs is performed. Generally, the larger biases averaged over nine years and the larger differences between biases based on different models are found in Z component. This can be the signature of the induced magnetic fields. Although annual trends in most bias series are observed, no clear evidence that the constant crustal field changed significantly over the studied period is found. Time series of monthly biases exhibit distinct oscillatory pattern in the whole time span, which we assign to the external field contributions. The amplitudes of these variations are linked with the phase of the solar cycle, being significantly larger in the period 2000–2005 than in the period 2006–2009. Clear semi-annual variations are evident in all components, with extremes in spring and fall months of each year. Common external field pattern is found for European monthly biases. A dependence of the bias monthly variations on geomagnetic latitudes is not found for the non-European observatories. The results from this study represent a base to further exploit the observatory and repeat stations magnetic biases together with the data from the new satellite mission SWARM.
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Wu, Dong L. "Small-scale fluctuations and scintillations in high-resolution GPS/CHAMP SNR and phase data". Journal of Atmospheric and Solar-Terrestrial Physics 68, n.º 9 (junho de 2006): 999–1017. http://dx.doi.org/10.1016/j.jastp.2006.01.006.
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Thuillier, Jean-Paul. "Circensia 3. Les supporters des factions du cirque romain". Revue des Études Anciennes 121, n.º 2 (2019): 455–61. http://dx.doi.org/10.3406/rea.2019.6924.
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On présente ici une nouvelle hypothèse – celle d’un diversium possible dès le Haut‑Empire – pour tenter d’expliquer une phase très énigmatique et souvent commentée dans la carrière du célèbre cocher des Rouges Dioclès. C’est l’occasion de revenir sur le comportement des groupes de supporters actuellement connus dans le monde du cirque romain, en particulier parce que les locaux de la faction rouge, avec la mention épigraphique des Russatiani, ont été identifiés récemment dans la zone méridionale du Champ de Mars.
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Thevenard-Puthod, Catherine, Christian Picard e Barthélemy Chollet. "Pertinence du tutorat comme dispositif d’accompagnement du repreneur individuel après la reprise. Une étude empirique à l’échelle européenne". Management international 18, n.º 4 (5 de agosto de 2014): 80–96. http://dx.doi.org/10.7202/1026030ar.
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Si l’accompagnement entrepreneurial est un champ de recherche en croissance, il existe encore peu de travaux sur l’accompagnement « repreneurial ». Cet article s’intéresse donc à la spécificité des besoins des repreneurs en matière d’accompagnement post-reprise et aux formes que cet accompagnement peut prendre. S’appuyant sur un projet test réalisé à l’échelle européenne sur un échantillon de 889 reprises, les auteurs confirment empiriquement la pertinence du tutorat comme forme particulière d’accompagnement dans cette phase délicate. Ils montrent ensuite dans quels types de situation et pour quels types de repreneur un tutorat s’avère le plus bénéfique.
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Švehla, D., e M. Rothacher. "Kinematic and reduced-dynamic precise orbit determination of low earth orbiters". Advances in Geosciences 1 (17 de junho de 2003): 47–56. http://dx.doi.org/10.5194/adgeo-1-47-2003.
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Abstract. Various methods for kinematic and reduced-dynamic precise orbit determination (POD) of Low Earth Orbiters (LEO) were developed based on zero- and double-differencing of GPS carrier-phase measurements with and without ambiguity resolution. In this paper we present the following approaches in LEO precise orbit determination: – zero-difference kinematic POD, – zero-difference dynamic POD, – double-difference kinematic POD with and without ambiguity resolution, – double-difference dynamic POD with and without ambiguity resolution, – combined GPS/SLR reduced-dynamic POD. All developed POD approaches except the combination of GPS/SLR were tested using real CHAMP data (May 20-30, 2001) and independently validated with Satellite Laser Ranging (SLR) data over the same 11 days. With SLR measurements, additional combinations are possible and in that case one can speak of combined kinematic or combined reduced-dynamic POD. First results of such a combined GPS/SLR POD will be presented, too. This paper shows what LEO orbit accuracy may be achieved with GPS using different strategies including zerodifference and double-difference approaches. Kinematic versus dynamic orbit determination is presently an interesting issue that will also be discussed in this article.Key words. POD, kinematic orbit, dynamic orbit, LEO, CHAMP, ambiguity resolution, GPS, SLR
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Sokolovskiy, S., Y.-H. Kuo e W. Wang. "Evaluation of a Linear Phase Observation Operator with CHAMP Radio Occultation Data and High-Resolution Regional Analysis". Monthly Weather Review 133, n.º 10 (1 de outubro de 2005): 3053–59. http://dx.doi.org/10.1175/mwr3006.1.
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Abstract In this study a nonlocal, linear observation operator for assimilating radio occultation data is evaluated. The operator consists of modeling the excess phase, that is, integrating the refractivity along straight lines tangent to rays, below a certain height. The corresponding observable is the excess phase integrated through the Abel-retrieved refractivity, along the same lines, below the same height. The operator allows very simple implementation (computationally efficient) while accurately accounting for the horizontal refractivity gradients. This is due to significant cancellation of the linearization and discretization errors when modeling the observable. Evaluation of the operator with Challenging Minisatellite Payload (CHAMP) radio occultation data and grid refractivity fields from high-resolution regional analysis over the continental United States showed reduction of the observation error in the troposphere (below 7 km) 1.5–2 times, compared to the error of local refractivity. The operator is useful for the assimilation of radio occultation data by high-resolution weather models in the troposphere.
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Vuattoux, Jean-Christophe, e Frédérique Dejean. "Caractériser un champ institutionnel en phase de structuration : monographie d’une approche de la prévention des risques psychosociaux". Management international 24, n.º 6 (2020): 78. http://dx.doi.org/10.7202/1077350ar.
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Liu, Hui, Jeffrey Anderson, Ying-Hwa Kuo, Chris Snyder e Alain Caya. "Evaluation of a Nonlocal Quasi-Phase Observation Operator in Assimilation of CHAMP Radio Occultation Refractivity with WRF". Monthly Weather Review 136, n.º 1 (1 de janeiro de 2008): 242–56. http://dx.doi.org/10.1175/2007mwr2042.1.
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Abstract A nonlocal quasi-phase radio occultation (RO) observation operator is evaluated in the assimilation of Challenging Minisatellite Payload (CHAMP) radio occultation refractivity using a Weather Research and Forecasting (WRF) ensemble data assimilation system at 50-km resolution. The nonlocal operator calculates the quasi phase through integration of the model refractivity along the observed ray paths. As a comparison, a local refractivity operator that calculates the model refractivity at the observed ray perigee points is also evaluated. The assimilation is done over North America during January 2003 in two different situations: in conjunction with dense, high-quality radiosonde observations and with only satellite cloud drift wind observations. Analyses of temperature and water vapor with the RO refractivity assimilated using the local and nonlocal operator are verified against nearby withheld radiosonde observations. The bias and RMS errors of the analyses of water vapor and temperature using the nonlocal operator are significantly reduced compared with those using the local operator in the troposphere when the only additional observations are satellite cloud drift winds. The reduction of the bias and RMS errors is reduced when radiosonde observations are assimilated.
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Kramer, Ueli. "Les méthodes d’études de cas en psychothérapie : perspectives actuelles". Santé mentale au Québec 36, n.º 1 (16 de setembro de 2011): 201–16. http://dx.doi.org/10.7202/1005821ar.
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Les études de cas en psychothérapie connaissent une phase de renouveau auprès des chercheurs en psychothérapie et des psychothérapeutes. L’auteur discute de deux paradigmes qui ont grandement influencé ce nouvel intérêt : le paradigme pragmatique et le paradigme qui vise la construction d’une théorie. L’article présente les origines, les développements et les concepts clés des deux paradigmes et leurs spécificités méthodologiques et éthiques. Des exemples d’études de cas ou de modèles au sein des paradigmes sont évoqués. L’influence différentielle des courants postmodernes sur les deux paradigmes, et leurs apports respectifs dans le champ des méthodes d’études de cas, sont discutés et évalués par rapport aux implications pour le chercheur et le psychothérapeute.
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Venkat Ratnam, M., T. Tsuda, T. Kozu e S. Mori. "Long-term behavior of the Kelvin waves revealed by CHAMP/GPS RO measurements and their effects on the tropopause structure". Annales Geophysicae 24, n.º 5 (3 de julho de 2006): 1355–66. http://dx.doi.org/10.5194/angeo-24-1355-2006.
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Abstract. The vertical and temporal variations of Kelvin waves and the associated effects on the tropical tropopause were studied using long-term (from May 2001 to October 2005) CHAMP/GPS (CHAllenging Mini satellite Payload/Global Positioning System) radio occultation (RO) measurements. The periods of these waves were found to be varying in between 10 and 15 days, with vertical wavelengths 5–8 km. These variations clearly show eastward phase propagation in the time-longitude section and eastward phase tilts with height in altitude-longitude, displaying the characteristics of Kelvin waves. The peak variance in the temperature is found over the Indian Ocean and into the western Pacific within the broad region of the equator. Kelvin wave amplitudes were found significantly enhanced in the eastward shear of the quasi-biennial oscillation (QBO) and are confined in and around the tropopause during westward phase of QBO, where it extends between 17 and 25 km during the eastward phase of QBO and is damped away above, consistent with earlier reported results. The amplitudes are increasing during the months of Northern Hemisphere winter and sometimes they are highly sporadic in nature. Seasonal and inter-annual variations in the Kelvin wave amplitudes near the tropical tropopause coincide exactly with the tropopause height and temperature, with a sharp tropopause during maximum Kelvin wave activity. A clear annual oscillation, along with a month-to-month coincidence is evident most of the time in both the tropopause height and Kelvin wave activity, with maximum and minimum Kelvin wave amplitudes during the Northern Hemisphere winter and summer, respectively. In addition, a signature of quasi-biennial oscillation (QBO) in the tropopause structure is also seen in long-term tropopause variations, although the amplitudes are less when compared to the annual oscillation. In the westward phase of QBO (during strong Kelvin wave activity) at 20km (in 2001–2002 winter and 2003–2004 winter), the tropopause height was slightly larger with a sharp tropopause and low temperature. The process behind these observed features has been discussed.
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Lenfant, Louis, e Morgan Rouprêt. "Immunothérapie et cancer de la vessie : état des connaissances actuelles et perspectives futures". Biologie Aujourd'hui 212, n.º 3-4 (2018): 81–84. http://dx.doi.org/10.1051/jbio/2018028.
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Le traitement des cancers par immunothérapie est basé sur l’activation du système immunitaire de l’hôte afin d’induire une activité antitumorale. Le traitement par le BCG en instillation endovésicale, décrit en 1976, fait partie de l’arsenal thérapeutique des tumeurs de vessie n’infiltrant pas le muscle (TVNIM) dans les recommandations des sociétés savantes. Les anticorps monoclonaux dirigés contre des inhibiteurs de checkpoint ont ouvert le champ des traitements possibles en oncologie et ont été largement étudiés depuis 2011, en urologie notamment. L’avènement des immunothérapies systémiques seules ou en combinaison avec le BCG intra-vésical est déjà en cours d’exploration dans des essais thérapeutiques de phase 2 et 3 dans le cancer localisé, infiltrant le muscle et métastatique.
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Colas, Caroline, Yves Naze, Corinne Thevenet e Frédéric Gransar. "Le site de Cuiry-lès-Chaudardes "Le Champ Tortu" (Aisne) un village Michelsberg d’un nouveau type ?" Revue archéologique de Picardie 3, n.º 1 (2015): 229–48. http://dx.doi.org/10.3406/pica.2015.3646.
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Bei der Ausgrabung einer neuen Fundstätte der Michelsberger Kultur in der Gemeinde Cuiry-lès-Chaudardes (Departement Aisne, Region Picardie) wurden vier bis sieben unterschiedliche Gebäudegrundrisse entdeckt. Deren Assoziation mit Gräbern und Siedlungsstrukturen erlauben eine Interpretation der Fundstätte als Dorf. Die Radiokarbondatierung dieser Grundrisse, die sich von allen bekannten Grundrissen unterscheiden, in eine späte Michelsberger Phase steht im Einklang mit der Entdeckung eines geschlossenen Keramikensembles in einem kleinen Silo des Dorfes. Die Grundrisse schließen die Lücke zwischen der Michelsberger Periode mit wenigen bekannten Gebäudegrundrisse, und dem Jung-und Endneolithikum, für das zahlreiche Grundrisse bekannt sind, die denen der Michelsberger Periode architektonisch sehr nahe stehen.
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Uhlrich, Gilles, e Serge Éloi. "Formation à l’observation de futurs intervenants éducatifs en rugby : quelles conséquences pour leur conception du jeu?" Revue des sciences de l’éducation 42, n.º 2 (21 de dezembro de 2016): 123–47. http://dx.doi.org/10.7202/1038464ar.
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Cet article théorique s’inscrit dans le champ de l’analyse de l’activité humaine. Nous nous intéressons au développement d’étudiants en formation initiale en Sciences et techniques des activités physiques et sportives, spécialistes de rugby. Nous repérons les moments d’un processus de genèse instrumentale (Rabardel, 1995) d’étudiants qui utilisent un artefact matériel, sous la forme d’un logiciel informatique dédié à la description du jeu de rugby à 7. En mobilisant la démarche technologique, nous identifions au fil du module de formation des comportements révélateurs d’une appropriation du logiciel. La controverse entre les étudiants à propos de la qualification des phases de jeu, que l’utilisation de l’outil informatique provoque, contribue à développer autant la phase d’instrumentation (prise en mainde l’outil) que la phase d’instrumentalisation (mise à leur mainde l’instrument). Ce double processus amène les étudiants à alimenter initialement le registre de technicité de lecture du rugby, développant ainsi leur compétence àlirele jeu qui se déroule sous leurs yeux.
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Maus, Stefan. "Mysterious misalignments between geomagnetic and stellar reference frames seen in CHAMP and Swarm satellite measurements". Geophysical Journal International 203, n.º 3 (28 de outubro de 2015): 1873–76. http://dx.doi.org/10.1093/gji/ggv409.
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AbstractThe orientation of a spacecraft in Low Earth Orbit can be determined accurately from either magnetic field measurements or star camera images. Ideally, the independently computed spacecraft attitudes should agree. However, we find that the German CHAMP and European Space Agency triple-satellite Swarm geomagnetic satellites exhibit consistent misalignments between the stellar and geomagnetic reference frames, which oscillate with the local time of the orbit. Having an amplitude of 20 arcsec, these oscillations are more than an order of magnitude larger than the stability of the optical bench, which cohosts the magnetometers and star cameras. The misalignments could originate either from the magnetometer or star camera measurements. On one hand, as-yet-unknown external magnetic field contributions could appear as a rotation of the geomagnetic reference frame. On the other hand, the observed misalignments agree in amplitude and phase with the effects of stellar aberration, caused by the movement of the star cameras relative to the light rays emitted by the stars. This is surprising because stellar aberration is allegedly already corrected for by the star image processing system. Resolving these mysterious misalignments is key to fulfilling the measurement accuracy requirements and science objectives of the ongoing Swarm mission. If caused by stellar aberration, fully correcting for this effect could significantly improve the attitude accuracy not only of CHAMP and Swarm, but also of several other past and ongoing scientific satellite missions.
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Park, J., H. Lühr e J. Rauberg. "Global characteristics of Pc1 magnetic pulsations during solar cycle 23 deduced from CHAMP data". Annales Geophysicae 31, n.º 9 (5 de setembro de 2013): 1507–20. http://dx.doi.org/10.5194/angeo-31-1507-2013.
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Abstract. We present a global climatology of Pc1 pulsations as observed by the CHAMP satellite from 2000 to 2010. The Pc1 center frequency and bandwidth are about 1 and 0.5 Hz, respectively. The ellipticity is mostly linear with the major axis almost aligned with the magnetic zonal direction. The diurnal variation of Pc1 occurrences shows a primary maximum early in the morning and a secondary maximum during pre-midnight hours. The annual variations of the occurrence rates exhibit a clear preference for local summer. The solar cycle dependence of the occurrence rate reveals a maximum at the declining phase (2004–2005). Neither magnetic activity nor solar wind velocity controls the Pc1 occurrence rate significantly. Pc1 occurrence rate peaks at subauroral latitudes, but the steep cutoff towards higher latitudes is due to auroral field-aligned currents masking the Pc1 pulsations. The center frequency of Pc1 pulsations does not show a clear dependence on latitude. The global distribution of Pc1 exhibits highest occurrence rates near the longitude sector of the South Atlantic Anomaly. Pc1 events at auroral latitudes, although they are rarely detected, show a clear occurrence peak around local noon. A majority of the auroral Pc1 events are observed during solar minimum years.
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Fong, Karen Pei Yi, Ismail A. Ahmed, Marco Mravic, Hyunil Jo, William F. DeGrado, Feng Gai e Joel S. Bennett. "Direct Visualization of Platelet Integrins Using ANTI-Transmembrane Domain Peptides Containing a BLUE Fluorescent Amino Acid". Blood 134, Supplement_1 (13 de novembro de 2019): 2344. http://dx.doi.org/10.1182/blood-2019-128363.
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Antibodies containing a fluorescent label or recombinant proteins containing a fluorescent reporter are commonly used to visualize proteins in situ. However, antibodies and bulky reporters can perturb protein structure and function. To overcome this problem, we have designed a minimally perturbing blue fluorescent unnatural amino acid that enables the direct imaging of intrinsically-fluorescent proteins with their interaction partners. Specifically, we used a nitrile-derivatized tryptophan, 4-cyanotryptophan (4CNTrp), which differs by only two atoms from native tryptophan. 4CNTrp has unique photophysical properties in the visible blue region: an absorption maximum at ~325 nm, an emission maximum at ~420 nm, a large fluorescence quantum yield (>0.8 in aqueous solution), a long fluorescence lifetime (ca. 13 ns), and good photostability (Hilaire et al. PNAS 2017; 114: 6005-09). Based on these properties, 4CNTrp-labeling was recently used to visualize the binding of a model peptide pHLIP (pH-(Low) Insertion Peptide) to cell membranes via wide-field fluorescence microscopy. 4CNTrp is also a viable FRET donor for acceptor pairs in the green visible region. 4CNTrp can be prepared by a simple, high-yielding cost-effective synthetic route and because it does not inhibit bacterial growth, it may be practical for cellular applications (Zhang et al. Chem. Comm. 2019; 55: 5095-98). Here, we used 4CNTrp-labeled peptides to directly image integrins on cell surfaces. Previously, we described the synthesis of peptides, called CHAMP peptides for Computed Helical Anti-Membrane Protein, that target the transmembrane (TM) domains of integrins in a sequence-specific manner (Yin et al. Science 2007; 315: 1817-22). Thus, the CHAMP peptides anti-αIIb and anti-αv specifically bind to the TM domains of αIIb and αv in platelet membranes, causing separation of the αIIbβ3 and αvβ3 TM domains and αIIbβ3 and αvβ3 activation. Anti-αIIb also caused αIIbβ3 clustering that was visualized using the β3-specific monoclonal antibody SSA6 labeled with Alexa Fluor 488 but only after the platelets were fixed with paraformaldehyde to prevent antibody-induced clustering. To enable the direct visualization of αIIβ3, αvβ3, and α2β1 on cell surfaces, we used solid-phase peptide synthesis to generate CHAMP peptides labeled with 4CNTrp at their N-termini (CN-αIIb, CN-αv, CN-β1). We found that 4CNTrp labeling did not perturb the ability of the CHAMP peptides to bind to integrins and to cause specific integrin activation. Thus, CN-αIIb caused αIIbβ3-dependent platelet aggregation, CN-αv caused the αvβ3-dependent platelet adhesion to osteopontin, and CN-α1 caused α2β1-mediated platelet adhesion to collagen. We then used high resolution wide-field deconvolution microscopy to image 4CNTrp-containing integrins on the surface of platelets, HEL cells, and transfected CHO cells. Compared to 4CNTrp-containing random peptides that uniformly decorate cell surfaces, the CN-labeled CHAMP peptides were present as a limited number of discrete foci on the cell surface. To confirm that these foci represented CN-peptide containing integrins, we co-stained the cells with Alexa Fluor 488-labeled integrin-specific monoclonal antibodies and found that CN-peptide and antibody fluorescence coincided. Thus, these studies demonstrate the specific and direct imaging of integrins embedded in cell membranes in their activated state using 4CNTrp-labeled anti-integrin TM peptides. Because 4CNTrp can readily be incorporated into proteins and peptides with little if any structural perturbation, 4CNTrp-labeling provides a facile way to directly monitor protein behavior and protein-protein interactions in cellular environments. Disclosures No relevant conflicts of interest to declare.
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Lühr, Hermann, e Yun-Liang Zhou. "Relation between the asymmetric ring current effect and the anti-sunward auroral currents, as deduced from CHAMP observations". Annales Geophysicae 38, n.º 3 (24 de junho de 2020): 749–64. http://dx.doi.org/10.5194/angeo-38-749-2020.
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Abstract. During magnetically active periods the storm-time disturbance signal on the ground commonly develops an azimuthal asymmetry. Negative deflections of the magnetic horizontal (H) component are enhanced in the 18:00 local time sector and smallest in the morning sector. This is commonly attributed to the asymmetric ring current effect. In this study we investigate the average characteristics of anti-sunward net currents that are not closing in the ionosphere. Their intensity is growing proportionally with the amount of solar wind input to the magnetosphere. There is almost twice as much current flowing across the polar region in the winter hemisphere as on the summer side. This seasonal dependence is more pronounced in the dusk sector than in the dawn sector. Event studies reveal that anti-sunward currents are closely related to the main phase of a magnetic storm. Since the asymmetry of storm-time disturbances also builds up during the main phase, we suggest a relation between these two phenomena. From a statistical study of ground-based disturbance levels during magnetically active periods, we obtain support for our suggestion. We propose a new 3D current system responsible for the zonally asymmetric storm-time disturbance signal that does not involve the ring current. The high-latitude anti-sunward currents are connected at their noon and midnight ends to field-aligned currents that lead the currents to the outer magnetosphere. The auroral net current branch on the morning side is closed along the dawn flank near the magnetopause, and the evening side currents flow along the dusk flank magnetosphere. Regardless through which loop the current is flowing, near-Earth storm-time disturbance levels will in both cases be reduced in the morning sector and enhanced in the evening.
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Weil-Halpern, Françoise. "Histoires de mort annoncées." Revue française de psychanalyse o 60, n.º 1 (1 de janeiro de 1996): 141–56. http://dx.doi.org/10.3917/rfp.g1996.60n1.0141.
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Résumé L'irruption du VIH dans le champ pédiatrique a bouleversé la vie et l'avenir d'une famille. La mère, un des enfants, parfois le père, livrent un combat sans merci, contre la maladie, la discrimination, l'isolement, le secret, la souffrance, la peur de la-mort. Face à ce séisme, l'auteur s'est demandé ce que ressentent, deviennent les enfants non infectés qui se retrouvent seuls survivants. A travers deux destins d'un frère indemne et d'une soeur en phase terminale du SIDA, l'auteur tente de montrer leur sort tragique. Comment survivent-ils à cette hécatombe ? Comment se fait ou non le travail de deuil ? Quel souvenir gardent-ils ou sont-ils autorisés à garder de leur mère, de leur père? Quelle histoire construiront-ils? Qu'en est-il de la culpabilité? Autant de questions pour lesquelles il n'y a pas toujours de réponse.
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Lego, Gaëlle. "Le « projet individualisé », ou l’histoire d’un quiproquo ?" VST - Vie sociale et traitements N° 162, n.º 2 (17 de maio de 2024): 66–72. http://dx.doi.org/10.3917/vst.162.0066.
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Le terme de « projet » institué par les derniers textes de re-modernisation sociale implique un changement de paradigme plus en phase avec le système néolibéral dans le champ social et médico-social. D’une clinique de l’écoute et de la relation, celui-ci se projette dans le « dispositif » de contrôle (cher à Foucault) dont la spécificité est de séparer l’être de son ontologie structurante. Le philosophe italien Giorgio Agamben précise que son aspect normatif soutenu par un appareillage de techno-surveillance reste un puissant mécanisme de désubjectivation. Comment peut-on sortir de ce quiproquo qui voudrait faire du « dispositif » le nouveau prisme par lequel appréhender nos pratiques ? Le parcours de Simon R., en esat , tente de repositionner la valeur d’un accompagnement de qualité axé sur la problématique du sujet, ici, psychotique. Celui-ci se fait, toujours, selon un cheminement singulier.
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Wang, H., H. Lühr, A. Ridley, P. Ritter e Y. Yu. "Storm time dynamics of auroral electrojets: CHAMP observation and the Space Weather Modeling Framework comparison". Annales Geophysicae 26, n.º 3 (26 de março de 2008): 555–70. http://dx.doi.org/10.5194/angeo-26-555-2008.
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Abstract. We investigate variations of the location and intensity of auroral currents during two magnetic storm periods based on magnetic field measurements from CHAMP separately for both hemispheres, as well as for the dayside and nightside. The corresponding auroral electrojet current densities are on average enhanced by about a factor of 7 compared to the quiet time current strengths. The nightside westward current densities are on average 1.8 (2.2) times larger than the dayside eastward current densities in the Northern (Southern) Hemisphere. Both eastward and westward currents are present during the storm periods with the most intense electrojets appearing during the main phase of the storm, before the ring current maximizes in strength. The eastward and westward electrojet centers can expand to 55° MLat during intense storms, as is observed on 31 March 2001 with Dst=−387 nT. The equatorward shift of auroral currents on the dayside is closely controlled by the southward IMF, while the latitudinal variations on the nightside are better described by the variations of the Dst index. However, the equatorward and poleward motion of the nightside auroral currents occur earlier than the Dst variations. The Space Weather Modeling Framework (SWMF) can capture the general dynamics of the storm time current variations. Both the model and the actual data show that the currents tend to saturate when the merging electric field is larger than 10 mV/m. However, the exact prediction of the temporal development of the currents is still not satisfactory.
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Xiong, C., Y. L. Zhou, H. Lühr e S. Y. Ma. "Tidal signatures of the thermospheric mass density and zonal wind at midlatitude: CHAMP and GRACE observations". Annales Geophysicae 33, n.º 2 (4 de fevereiro de 2015): 185–96. http://dx.doi.org/10.5194/angeo-33-185-2015.
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Abstract. By using the accelerometer measurements from CHAMP and GRACE satellites, the tidal signatures of the thermospheric mass density and zonal wind at midlatitudes have been analyzed in this study. The results show that the mass density and zonal wind at southern midlatitudes are dominated by a longitudinal wave-1 pattern. The most prominent tidal components in mass density and zonal wind are the diurnal tides D0 and DW2 and the semidiurnal tides SW1 and SW3. This is consistent with the tidal signatures in the F region electron density at midlatitudes as reported by Xiong and Lühr (2014). These same tidal components are observed both in the thermospheric and ionospheric quantities, supporting a mechanism that the non-migrating tides in the upper atmosphere are excited in situ by ion–neutral interactions at midlatitudes, consistent with the modeling results of Jones Jr. et al. (2013). We regard the thermospheric dynamics as the main driver for the electron density tidal structures. An example is the in-phase variation of D0 between electron density and mass density in both hemispheres. Further research including coupled atmospheric models is probably needed for explaining the similarities and differences between thermospheric and ionospheric tidal signals at midlatitudes.
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Couégnas, Nicolas, e Aurore Famy. "La part sémiotique de l’anthropologie des modernes". Semiotica 2017, n.º 219 (27 de novembro de 2017): 435–54. http://dx.doi.org/10.1515/sem-2017-0071.
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RésuméLes propositions de Bruno Latour, qui ont trouvé une forme d’achèvement dans l’Enquête sur les modes d’existence, offrent à la sémiotique greimassienne, et post-greimassienne, une voie de développement extrêmement fructueuse et novatrice, susceptible de fournir les fondements d’une « anthropo-sémiotique des modernes ». Il ne s’agit pas d’adopter sans discussion les propositions du sociologique, ni de les traduire dans l’appareil sémiotique de l’Ecole de Paris, mais d’exploiter la part foncièrement sémiotique de ces propositions. Une première phase de la recherche, montre que chacun des quinze modes d’existence décrits par Latour, qui structurent le champ social en domaines (la science, le droit, la fiction, la technique, la politique, etc.), mobilise une scène actantielle spécifique et repose sur une composante énonciative, de l’ordre de l’effectuation qui confère au mode d’existence son poids existentiel. Deuxième phase de la réflexion, la part sémiotique inhérente aux modes d’existence donne en quelque sorte les moyens de leur dépassement par la sémiotique elle-même. Il appert en effet que l’on peut identifier, derrière chacun des modes d’existence, une sémiose particulière. Ce dernier point, fondamental, conduit à ébaucher les traits d’une anthropo-sémiotique qui interroge l’économie générale de la théorie sémiotique post-greimassienne.
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Губенко, Владимир, Vladimir Gubenko, Иван Кириллович e Ivan Kirillovich. "Modulation of sporadic E layers by small-scale atmospheric waves in Earth’s high-latitude ionosphere". Solar-Terrestrial Physics 5, n.º 3 (30 de setembro de 2019): 98–108. http://dx.doi.org/10.12737/stp-53201912.
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We have used radio occultation measurements of the satellite CHAMP (Challenging Minisatellite Payload) to examine sporadic E layers (altitudes 90–130 km) in Earth’s high-latitude ionosphere. We have developed a new method for determining characteristics of internal atmospheric waves based on the use of inclined sporadic E layers of Earth’s ionosphere as a detector. The method relies on the fact that an internal wave propagating through the initially horizontal sporadic E layer causes the plasma density gradient to rotate in the direction of the wave vector, which leads to the fact that the layer ionization plane is set parallel to the phase wave front. The developed method enables us to study the interrelations between small-scale internal waves and sporadic E layers in Earth’s ionosphere and significantly expands the capabilities of traditional radio occultation monitoring of the atmosphere. We have found that the internal atmospheric waves under study have periods from 35 to 46 min and vertical phase speeds from 1.2 to 2.0 m/s, which are in good agreement with the results of independent experiments and simulation data on sporadic E layers at a height of ~100 km in Earth’s polar cap.
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Губенко, Владимир, Vladimir Gubenko, Иван Кириллович e Ivan Kirillovich. "Modulation of sporadic E layers by small-scale atmospheric waves in Earth’s high-latitude ionosphere". Solnechno-Zemnaya Fizika 5, n.º 3 (30 de setembro de 2019): 116–29. http://dx.doi.org/10.12737/szf-53201912.
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We have used radio occultation measurements of the satellite CHAMP (Challenging Minisatellite Payload) to examine sporadic E layers (altitudes 90–130 km) in Earth’s high-latitude ionosphere. We have developed a new method for determining characteristics of internal atmospheric waves based on the use of inclined sporadic E layers of Earth’s ionosphere as a detector. The method relies on the fact that an internal wave propagating through the initially horizontal sporadic E layer causes the plasma density gradient to rotate in the direction of the wave vector, which leads to the fact that the layer ionization plane is set parallel to the phase wave front. The developed method enables us to study the interrelations between small-scale internal waves and sporadic E layers in Earth’s ionosphere and significantly expands the capabilities of traditional radio occultation monitoring of the atmosphere. We have found that the internal atmospheric waves under study have periods from 35 to 46 min and vertical phase speeds from 1.2 to 2.0 m/s, which are in good agreement with the results of independent experiments and simulation data on sporadic E layers at a height of ~100 km in Earth’s polar cap.
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Kwantes, Gemma. "Essay Review: Contemporary Kabbalah: New Scholarship, New Insights, New Contexts and Issues". ARIES 13, n.º 2 (2013): 205–35. http://dx.doi.org/10.1163/15700593-13130203.
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Le présent article recense cinq publications traitant de la kabbale contemporaine ou y faisant référence, toutes apparues autour de 2011. Il entend à la fois rendre compte de chaque ouvrage pris individuellement, et de l’ensemble en tant que contribution collective à l’étude d’un nouveau domaine de recherches. Avant tout, on défend l’idée que ces ouvrages marquent l’émergence d’une nouvelle phase dans l’étude académique contemporaine de la kabbale—une phase qui ne se limite plus au simple constat d’existence de cette dernière mais aborde l’exploration de ses manifestations concrètes, au demeurant très diversifiées. A eux cinq, ces travaux posent en tant que tels la question des modalités du rapport à la kabbale contemporaine, en montrant les bénéfices que l’on retire en particulier d’une approche multidisciplinaire et non-orthonormée du phénomène. Ajoutés à des publications antérieures, et bien que représentant encore un état préliminaire des études dans ce domaine, ces cinq ouvrages permettent de surcroît d’ouvrir un panorama déjà assez vaste sur le champ de recherches en question. C’est une telle vue d’ensemble que l’auteur voudrait fournir dans la seconde moitié de cet article, en associant ses propres découvertes à celles de la recherche actuelle.
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McKinley, Maxime, Sandeep Bhagwati, Frans Ben Callado, Julie-Anne Derome, Wolf Edwards, André Hamel, Nicolas-Alexandre Marcotte e Rodney Sharman. "Musique de création et spiritualité : forum à sept voix". Circuit 21, n.º 1 (11 de março de 2011): 61–74. http://dx.doi.org/10.7202/1001163ar.
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Cette enquête sur les rapports entre musique de création et spiritualité, qui se veut avant tout un espace de réflexion, prend la forme d’un forum à sept voix, présenté et commenté par l’auteur. Sept musiciens de générations, pratiques et esthétiques variées ont accepté de répondre, par courriel, à l’automne 2010, aux questions mises au point par la rédaction de Circuit. Il s’agit de Sandeep Bhagwati, Frans Ben Callado, Julie-Anne Derome, Wolf Edwards, André Hamel, Nicolas-Alexandre Marcotte et Rodney Sharman. Le champ lexical du questionnaire, particulièrement polysémique (« spiritualité », « sacré », « transcendance », « absolu »), a stimulé des réponses d’une frappante variété de points de vue. Toutefois, des constantes se détachent, notamment l’absence presque complète de la foi dans les propos tenus. On peut ainsi penser que les acteurs de la musique de création, en phase avec leur époque, tendent vers une « spiritualité sans Dieu », telle que décrite par le philosophe André Comte-Sponville.
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Lühr, H., T. A. Siddiqui e S. Maus. "Global characteristics of the lunar tidal modulation of the equatorial electrojet derived from CHAMP observations". Annales Geophysicae 30, n.º 3 (8 de março de 2012): 527–36. http://dx.doi.org/10.5194/angeo-30-527-2012.
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Abstract. It has been known since many decades that lunar tide has an influence on the strength of the equatorial electrojet (EEJ). There has, however, never been a comprehensive study of the tidal effect on a global scale. Based on the continuous magnetic field measurements by the CHAMP satellite over 10 years it is possible to investigate the various aspects of lunar effects on the EEJ. The EEJ intensity is enhanced around times when the moon is overhead or at the antipode. This effect is particularly strong around noon, shortly after new and full moon. The lunar tide manifests itself as a semi-diurnal wave that precesses through all local times within one lunar month. The largest tidal amplitudes are observed around December solstice and smallest around June solstice. The tidal wave crest lags behind the moon phase. During December this amounts to about 4 days while it is around 2 days during other times of the year. We have not found significant longitudinal variations of the lunar influence on the EEJ. When comparing the average EEJ amplitude at high solar activity with that during periods of solar minimum conditions a solar cycle dependence can be found, but the ratio between tidal amplitude and EEJ intensity stays the same. Actually, tidal signatures standout clearer during times of low solar activity. We suggest that the tidal variations are caused by a current system added to the EEJ rather than by modulating the EEJ. Gravitational forcing of the lower atmosphere by the moon and the sun is assumed to be the driver of an upward propagating tidal wave. The larger tidal amplitudes around December solstice can be related to stratospheric warming events which seem to improve the conditions for upward propagation. The results described here have to large extent been presented as a Julius-Bartels Medal Lecture during the General Assembly 2011 of the European Geosciences Union.
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Adam, Matthieu, e Georges-Henry Laffont. "Une approche dialectique de la ville en train de se faire : confrontation des représentations des concepteurs et des habitants de l’écoquartier de Bottière-Chénaie". Nouvelles perspectives en sciences sociales 10, n.º 1 (4 de fevereiro de 2015): 193–235. http://dx.doi.org/10.7202/1028440ar.
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Cet article entend participer à une démarche de caractérisation de la production de la ville en ce début de XXIe siècle. Pour ce faire, il s’appuie sur une modélisation du projet urbain en phase de réalisation comme un dispositif de médiation entre ces les représentations de ses concepteurs et ses récepteurs (les habitants). Nous souhaitons comprendre comment elles se construisent et s’influencent mutuellement afin d’appréhender pourquoi elles ne se rejoignent pas.Cette approche dialectique met en exergue la pluralité de sens qui peuvent être accordés aux propriétés matérielles et symboliques d’un territoire. Par l’analyse des représentations des concepteurs et des habitants de l’écoquartier de Bottière-Chénaie à Nantes, nous montrerons les relations qui existent entre celles-ci et la nécessité de dépasser la vision simplificatrice d’un processus linéaire du projet – conception, réalisation, réception – et qu’il faut intégrer dans le champ de la recherche urbaine des modèles intégrant les influences des effets sur les causes.
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Kergosien, Eric, Marie-Noelle Bessagnet e Mauro Gaio. "Exploitation d’une cartographie sémantique à des fins de validation : application à l’indexation experte de corpus documentaires". Documentation et bibliothèques 57, n.º 1 (25 de fevereiro de 2015): 19–28. http://dx.doi.org/10.7202/1028961ar.
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Notre approche vise à aider le travail d’indexation des bibliothécaires via les concepts provenant d’un vocabulaire contrôlé par des relations de sens contenues dans les notices descriptives. Dans notre travail de recherche, nous définissons automatiquement le thésaurus TERRIDOC en exploitant les spécificités du corpus liées à des termes qui « ont fait sens » au bibliothécaire lors de la constitution de la notice descriptive. Une phase de conceptualisation a permis dans un premier temps de définir en détails les différents modules pour créer automatiquement la structure sémantique représentant le travail d’indexation des experts, puis dans un second temps de proposer des interfaces représentant visuellement ce travail à des fins de validation du travail d’indexation des bibliothécaires et de navigation dans le fonds documentaire. À la suite de l’analyse et de la création de ce premier outil, nous proposons des moyens de contrôler et de valider le travail d’indexation. Notre travail s’inscrit dans le champ de la classification documentaire et de ses usages en environnement « réseauté ».
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Glad, Vincent. "Des usages de Twitter en temps de pandémie : circulation des connaissances, agit-prop et controverses enflammées". Annales des Mines - Enjeux numériques N° 14, n.º 2 (24 de fevereiro de 2021): 78–81. http://dx.doi.org/10.3917/ennu.014.0078.
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Jamais sans doute la science n’a eu tant d’effet sur la vie de la cité. Dans un contexte de pandémie où chaque nouvelle découverte peut bouleverser le quotidien de millions de personnes, la circulation de l’information scientifique est un enjeu majeur. Tant pour partager leurs connaissances que pour effectuer une veille sur le Covid-19, de nombreux scientifiques se sont convertis au réseau social Twitter à l’occasion de cette pandémie. L’usage de cet outil a élargi le champ de l’expertise scientifique, et permis des avancées majeures sur certains sujets comme la transmission aérienne du virus, ainsi que la remise en cause d’études controversées. La place qu’a prise Twitter dans cette crise, concomitante de l’explosion des preprints (productions scientifiques mises en ligne avant la phase de relecture par les pairs), met en question le statut de ces écrits non évalués par les pairs : la production scientifique n’a jamais été aussi accessible, mais son contrôle qualité n’a jamais été aussi faible.
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Karpachev, Alexander. "Sub-Auroral, Mid-Latitude, and Low-Latitude Troughs during Severe Geomagnetic Storms". Remote Sensing 13, n.º 3 (2 de fevereiro de 2021): 534. http://dx.doi.org/10.3390/rs13030534.
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The dynamics of ionospheric troughs during intense geomagnetic storms is considered in this paper. The study is based on electron density measurements at CHAMP satellite altitudes of 405–465 km in the period from 2000 to 2002. A detailed analysis of four storms with Kp from 5+ to 9− is presented. Three troughs were identified: sub-auroral, mid-latitude, and low-latitude. The sub-auroral trough is usually defined as the main ionospheric trough (MIT). The mid-latitude trough is observed equatorward of the MIT and is associated with the magnetospheric ring current; therefore, it is named the ring ionospheric trough (RIT). The RIT appears at the beginning of the storm recovery phase at geomagnetic latitudes of 40–45° GMLat (L = 1.75–2.0) and exists, for a long time, at the late stage of the recovery phase at latitudes of the residual ring current 50–55° GMLat (L ~ 2.5–3.0). The low-latitude trough (LLT) is discovered for the first time. It forms only during great storms at the latitudes of the internal radiation belt (IRB), 34–45° GMLat (L = 1.45–2.0). The LLT’s lowest latitude of 34° GMLat was recorded in the night sector (2–3 LT). The occurrence probability and position of the RIT and LLT depend on the hemisphere and longitude.
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Pavelyev, A. G., K. Zhang, J. Wickert, T. Schmidt, Y. A. Liou, V. N. Gubenko, A. A. Pavelyev, R. R. Salimzjanov e Y. Kuleshov. "Identification and localization of layers in the ionosphere using the eikonal and amplitude of radio occultation signals". Atmospheric Measurement Techniques Discussions 4, n.º 2 (1 de março de 2011): 1465–92. http://dx.doi.org/10.5194/amtd-4-1465-2011.
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Abstract. Conditions for communication, navigation, and remote sensing in the ionosphere and atmosphere depend strongly on the ionospheric impact on the radio waves propagation. By use of the CHAllenge Minisatellite Payload (CHAMP) radio occultation (RO) data a description of different types of the ionospheric contributions to the RO signals at the altitudes 30–90 km of the RO ray perigee is introduced and compared with results of measurements obtained earlier in the communication link satellite-to-Earth at frequency 1.5415 GHz. An analytical model is introduced for description of the radio waves propagation in a stratified medium consisting of sectors having the spherically symmetric distributions of refractivity. Model presents analytical expressions for the phase path and refractive attenuation of radio waves. Model is applied for analysis of the radio waves propagation effects along a prolonged path including the atmosphere and two parts of the ionosphere. Model explains significant amplitude and phase variations at the altitudes 30–90 km of the RO ray perigee as connected with influence of the inclined ionospheric layers. An innovative eikonal acceleration technique is described and applied for the identification of the inclined ionospheric layers contributions and their location. Possibility to separate the influence of layered structures from contributions of irregularities and turbulence is analyzed.
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Awuor, Adero Ochieng, Paul Baki, Joseph Olwendo e Pieter Kotze. "Storm-Time Behaviour of Meso-Scale Field-Aligned Currents: Case Study with Three Geomagnetic Storm Events". Journal of Astronomy and Space Sciences 36, n.º 3 (setembro de 2019): 133–47. http://dx.doi.org/10.5140/jass.2019.36.3.133.
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Challenging Minisatellite Payload (CHAMP) satellite magnetic data are used to investigate the latitudinal variation of the storm-time meso-scale field-aligned currents by defining a new metric called the FAC range. Three major geomagnetic storm events are considered. Alongside SymH, the possible contributions from solar wind dynamic pressure and interplanetary magnetic field (IMF) BZ are also investigated. The results show that the new metric predicts the latitudinal variation of FACs better than previous studies. As expected, the equatorward expansion and poleward retreat are observed during the storm main phase and recovery phase respectively. The equatorward shift is prominent on the northern duskside, at ~58° coinciding with the minimum SymH and dayside at ~59° compared to dawnside and nightside respectively. The latitudinal shift of FAC range is better correlated to IMF BZ in northern hemisphere dusk-dawn magnetic local time (MLT) sectors than in southern hemisphere. The FAC range latitudinal shifts responds better to dynamic pressure in the duskside northern hemisphere and dawnside southern hemisphere than in southern hemisphere dusk sector and northern hemisphere dawn sector respectively. FAC range exhibits a good correlation with dynamic pressure in the dayside (nightside) southern (northern) hemispheres depicting possible electrodynamic similarity at day-night MLT sectors in the opposite hemispheres.
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Luo, Weihua, Chao Xiong, Jisheng Xu, Zhengping Zhu e Shanshan Chang. "The Low-Latitude Plasma Irregularities after Sunrise from Multiple Observations in Both Hemispheres during the Recovery Phase of a Storm". Remote Sensing 12, n.º 18 (7 de setembro de 2020): 2897. http://dx.doi.org/10.3390/rs12182897.
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The daytime plasma density disturbances in the low-latitude ionosphere, referred to as plasma irregularities, mainly occur during the nighttime and are an unusual phenomenon. Based on the observations from multiple low Earth orbiting (LEO) satellites, e.g., the Defense Meteorological Satellite Program (DMSP) F13 and F15, the first Satellite of the Republic of China (ROCSAT-1), the Gravity Recovery and the Climate Experiment (GRACE), and Challenging Mini-satellite Payload (CHAMP) satellites, as well as the ground-based Global Positioning System (GPS) receivers, we report a special event of low-latitude plasma irregularities that were observed after sunrise in the Pacific longitudes on 18 August, 2003, following a moderate geomagnetic storm. Observations from three ground-based GPS stations in both hemispheres showed remarkable total electron content (TEC) disturbances during 20:00 to 21:00 UT (around local sunrise), agreeing well with the in situ plasma density irregularities recorded by the nearby flying LEO satellites. The plasma irregularities observed by these LEO satellites showed quite different depletion intensities at different altitudes. We suggest that the plasma irregularities were freshly generated near sunrise hours due to the disturbance of the dynamo electric field (DDEF), evolving into the post-sunrise and morning sector, but were not the remnant of the plasma irregularities generated during the previous nighttime.
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Franchon, Claudine Marie Jeanne. "L'intercompréhension (IC) : Des fondements d'une didactique de langues en contact aux interactions plurilingues sur la plateforme Miriadi". Revista Letras Raras 10 (29 de novembro de 2021): 148. http://dx.doi.org/10.35572/rlr.v10i0.2307.
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Au début des années 1990 naissait un nouveau champ didactique résolument plurilingue et européen, celui de l'intercompréhension. Depuis, lieux et produits de formation et de recherche se sont multipliés (Galatea, Galanet, Galapro, Eurocomcenter, Redinter, Miriadi...). Si dans la première phase de son développement, toute une série de définitions ont surgi sans que l’on parvienne à s’accorder sur une formule optimale permettant d’en saisir les éléments essentiels, la plupart des spécialistes de l’intercompréhension s’accordent aujourd’hui sur une définition du concept dont le dénominateur commun est que l’intercompréhension est une forme de communication dans laquelle chaque personne s’exprime dans sa propre langue et comprend celle de l’autre. Cette définition permet de clarifier deux points : l’intercompréhension inclut la communication tant orale qu’écrite et exclut l’utilisation active de la langue étrangère. Cet article aura pour objectif de montrer à travers l'analyse qualitative de corpus extraits de la plateforme Miriadi, qui permet de générer un espace de formation adapté à son public, comment les principes fondateurs et la méthodologie de cette nouvelle approche à l'éducation plurilingue sont mis en pratique dans les échanges en ligne.
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Meilliez, Francis. "Industrial and scientific heritages from the Nord – Pas-de-Calais coal basin (Upper Carboniferous), a long history (XVIth – XXIVth centuries)". Annales de la Société géologique du Nord - (2e Série), Tome 24, n.º 24 (1 de dezembro de 2017): 17–31. http://dx.doi.org/10.54563/asgn.1548.
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La phase d'extraction du charbon dans le bassin houiller du Nord et du Pas-de-Calais s'est étendue de la fin du XVIIe siècle à la fin du XXe siècle. Elle a contribué à l'émergence d'un scientisme triomphant qui a marqué notre culture occidentale. Elle a aussi bénéficié de ses effets en termes de développement économique, jusqu'à l'étouffement, puisque l'arrêt de l'extraction sur ce bassin est un résultat inévitable du jeu économique mondial. Mais elle a aussi contribué au développement de la connaissance (géologie, chimie, sociologie pour l'essentiel) et, par voie de conséquence, d'une société très dépendante de l'industrie. Au cours des vingt dernières années d'exploitation la prise de conscience progressive et mondiale des effets environnementaux de toutes ces activités ouvrait un nouveau champ d'investigation scientifique, pluridisciplinaire : celui du développement durable. L'UNESCO a labellisé en 2012 un important héritage mobilier, immobilier et culturel. Une façon de le valoriser est de poursuivre l'étude scientifique dont une part participe à cet héritage (archives). Les scientifiques de la région peuvent encore s'en faire une spécialité, déjà nécessaire ailleurs dans le monde.
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Brot, Claude. "Liquides de toupies symétriques: leur tenseur de polarisabilité optique intrinsèque via deux expériences sous champ statique: CH3CN". Canadian Journal of Chemistry 68, n.º 9 (1 de setembro de 1990): 1490–93. http://dx.doi.org/10.1139/v90-228.
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NMR line splitting under a strong static electric field (EF-NMR) allows one to measure the average alignment (second spherical harmonic) of the molecule studied under the influence of the field. This average alignment (per unit squared field) can be formulated theoretically by an expression involving the permanent dipole moment, the anisotropy of the static polarizability, etc. and possibly orientational intercorrelations within the liquid. On the other hand the Kerr constant per molecule can be represented by the same expression, multiplified by a factor that is independent of any static electrical property of the molecule (for a gas this factor would be simply proportional to the anisotropy of the optical polarizability). Consequently the ratio of the above experimental results contains information bearing only on the optical properties. The formalism of the "tensor of polarizability increment" developed by the author for liquids made up of ellipsoidal molecules is employed. It is shown that by combining the above ratio with the constitutive equation for the refractivity of the liquid, the two distinct principal elements of the tensor of polarizability increment of the symmetric top molecules constituting the liquid are immediately obtained. Using then the molecular volume, a van der Waals estimate for the elongation of the molecule, and the index of refraction of the liquid, one can calculate the elements of the optical polarizability tensor invacuo. The method is illustrated by neat acetonitrile for which the necessary experimental data exist in the literature. One finds, in units 1040 C2 m2 J−1 5.06 for the mean polarizability and 2.52 for its anisotropy. A published experimental study using depolarized light scattering in the gas phase indicates that the corresponding figures are 4.96 and 2.49 respectively at λ = 633 nm. Finally and accessorily, it is suggested that dipolar intercorrelations are weak in acetonitrile. Indeed, using an analogous formalism for the static permittivity of the liquid, a value for the permanent moment of the molecule is deduced. This value is within 1% of the experimental gas value. Keywords: polarizability tensors, liquids, Kerr constant, NMR.
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Pavelyev, A. G., Y. A. Liou, K. Zhang, C. S. Wang, J. Wickert, T. Schmidt, V. N. Gubenko, A. A. Pavelyev e Y. Kuleshov. "Identification and localization of layers in the ionosphere using the eikonal and amplitude of radio occultation signals". Atmospheric Measurement Techniques 5, n.º 1 (4 de janeiro de 2012): 1–16. http://dx.doi.org/10.5194/amt-5-1-2012.
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Abstract. By using the CHAllenge Minisatellite Payload (CHAMP) radio occultation (RO) data, a description of different types of the ionospheric impacts on the RO signals at the altitudes 30–90 km of the RO ray perigee is given and compared with the results of measurements obtained earlier in the satellite-to-Earth communication link at frequency 1.5415 GHz. An analytical model is introduced for describing propagation of radio waves in a stratified medium consisting of sectors with spherically symmetric refractivity distribution. This model gives analytical expressions for the phase, bending angle, and refractive attenuation of radio waves and is applied to the analysis of radio wave propagation phenomena along an extended path including the atmosphere and two parts of the ionosphere. The model explains significant amplitude and phase variations at altitudes 30–90 km of the RO ray perigee and attributes them to inclined ionospheric layers. Based on this analytical model, an innovative technique is introduced to locate layers in the atmosphere and ionosphere. A necessary and sufficient criterion is obtained for a layer to be located at the RO ray perigee. This criterion gives both qualitative and quantitative estimation of the displacement of an ionospheric and/or atmospheric layer from the RO ray perigee. This is important, in particular, for determining the location of wind shears and directions of the internal wave propagation in the lower ionosphere, and, possibly, in the atmosphere.
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Schwarz, Jakob, Gottfried Kirchengast e Marc Schwaerz. "Integrating uncertainty propagation in GNSS radio occultation retrieval: from excess phase to atmospheric bending angle profiles". Atmospheric Measurement Techniques 11, n.º 5 (4 de maio de 2018): 2601–31. http://dx.doi.org/10.5194/amt-11-2601-2018.
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Abstract. Global Navigation Satellite System (GNSS) radio occultation (RO) observations are highly accurate, long-term stable data sets and are globally available as a continuous record from 2001. Essential climate variables for the thermodynamic state of the free atmosphere – such as pressure, temperature, and tropospheric water vapor profiles (involving background information) – can be derived from these records, which therefore have the potential to serve as climate benchmark data. However, to exploit this potential, atmospheric profile retrievals need to be very accurate and the remaining uncertainties quantified and traced throughout the retrieval chain from raw observations to essential climate variables. The new Reference Occultation Processing System (rOPS) at the Wegener Center aims to deliver such an accurate RO retrieval chain with integrated uncertainty propagation. Here we introduce and demonstrate the algorithms implemented in the rOPS for uncertainty propagation from excess phase to atmospheric bending angle profiles, for estimated systematic and random uncertainties, including vertical error correlations and resolution estimates. We estimated systematic uncertainty profiles with the same operators as used for the basic state profiles retrieval. The random uncertainty is traced through covariance propagation and validated using Monte Carlo ensemble methods. The algorithm performance is demonstrated using test day ensembles of simulated data as well as real RO event data from the satellite missions CHAllenging Minisatellite Payload (CHAMP); Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC); and Meteorological Operational Satellite A (MetOp). The results of the Monte Carlo validation show that our covariance propagation delivers correct uncertainty quantification from excess phase to bending angle profiles. The results from the real RO event ensembles demonstrate that the new uncertainty estimation chain performs robustly. Together with the other parts of the rOPS processing chain this part is thus ready to provide integrated uncertainty propagation through the whole RO retrieval chain for the benefit of climate monitoring and other applications.
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Prigent, Michel, e Juan Obregon. "Outil de CAO pour la simulation non linéaire des spectres de bruit de phase et d’amplitude des oscillateurs à transistor à effet de champ". Annales Des Télécommunications 44, n.º 11-12 (novembro de 1989): 656–71. http://dx.doi.org/10.1007/bf02999679.
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Thomasset, Muriel. "Métrologie à SOLEIL. Des outils de mesure de la forme des miroirs synchrotron : un microscope interférométrique à balayage de phase et raccordement de champ". Photoniques, n.º 72 (julho de 2014): 36–38. http://dx.doi.org/10.1051/photon/20147236.
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Kwon, Jay Hyoun, Dorota Grejner-Brzezinska, Tae-Suk Bae e Chang-Ki Hong. "A Triple Difference Approach to Low Earth Orbiter Precision Orbit Determination". Journal of Navigation 56, n.º 3 (26 de agosto de 2003): 457–73. http://dx.doi.org/10.1017/s0373463303002376.
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A geometric approach to Low Earth Orbiter (LEO) precision orbit determination (POD) based exclusively on triple-differenced GPS carrier phase observables is presented. The algorithm is fast and efficient because there is no ambiguity-resolution requirement, which is a complicated and time-consuming task for long-range kinematic GPS. However, the triple-difference kinematic LEO POD requires careful screening for cycle slips, as the orbit quality depends on the accuracy and the geometry of the observations. It is shown that the signal-to-noise-ratio (SNR) combined with residual screening offers a good approach to data cleaning. Data from a CHAMP (Challenging Minisatellite Payload, altitude ~450 km) mission are used to present the accuracy, speed and efficiency of the processing algorithms. The methods of data screening and the effects of geometry on the orbit quality are discussed and the final achievable accuracy including the limitations and benefits of this method are quantified. It is demonstrated that the triple-difference method offers short processing times and is currently capable of achieving a 3D RMS fit to the dynamic orbit of 15–30 cm and 1 mm/s to the velocity.