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A Cautionary Tale: Dark Energy in Single-Field, Slow-Roll Inflationary Models
No full textInternational audienceThe current epoch of accelerated cosmic expansion is postulated to be driven by dark energy, which in the standard model takes the form of a cosmological constant with equation of state parameter . We propose an innovative perspective over the nature of dark energy by drawing a parallel with inflation, which we assume to be driven by a single scalar field, the inflaton. The inflaton was not a cosmological constant, as indicated by the fact that inflation ended and by the Planck satellite's constraint of at confidence. Therefore, it is interesting to verify whether its equation of state parameter was measurably different from . We analyze this question for a class of single-field slow-roll inflationary models, where the hierarchy of Hubble slow-roll parameters is truncated at different orders. Based on the latest Planck and BICEP2/Keck data, we obtain a upper bound of for the three-parameter model, which gives the best description to the data. This provides a cautionary tale for drawing conclusions about the nature of today's dark energy based upon the non-detection of a deviation from with current and upcoming cosmological surveys
A hybrid nodal-staggered pseudo-spectral electromagnetic particle-in-cell method with finite-order centering
No full textInternational audienceElectromagnetic particle-in-cell (PIC) codes are widely used to perform computer simulations of a variety of physical systems, including fusion plasmas, astrophysical plasmas, plasma wakefield particle accelerators, and secondary photon sources driven by ultra-intense lasers. In a PIC code, Maxwell's equations are solved on a grid with a numerical method of choice. This article focuses on pseudo-spectral analytical time-domain (PSATD) algorithms and presents a novel hybrid PSATD PIC scheme that combines the respective advantages of standard nodal and staggered methods. The novelty of the hybrid scheme consists in using finite-order centering of grid quantities between nodal and staggered grids, in order to combine the solution of Maxwell's equations on a staggered grid with the deposition of charges and currents and the gathering of electromagnetic forces on a nodal grid. The correctness and performance of the novel hybrid scheme are assessed by means of numerical tests that employ different classes of PSATD equations in a variety of physical scenarios, ranging from the modeling of electron-positron pair creation in vacuum to the simulation of laser-driven and particle beam-driven plasma wakefield acceleration. It is shown that the novel hybrid scheme offers significant numerical and computational advantages, compared to purely nodal or staggered methods, for all the test cases presented
" Vol de locuste et bond de salicoque : rencontre entre Ponge et Saint-John Perse dans les remous des bêtes"
No full textInternational audienc
From Kabul to Kyiv, Pakistan’s persistent diplomatic course
No full textOn February 23, Pakistan’s Prime Minister (PM) Imran Khan arrived in Moscow for a two-days visit. According to open sources, the PM’s Russia trip was for a ‘exchange of views on major regional and international issues’1, aiming at a reset of bilateral ties and ‘expanding cooperation in the energy sector’. When opening the discussions, Imran Khan chose a remarkably peculiar statement. Referring to the then current situation, he said: ‘What a time I have come, so much excitement’. Putin’s “bullying” of the Ukraine reached at that very moment and once again a dramatic peak (after the illegal annexation of Ukrainian Crimea in 2014). Even before Khan’s departure to Moscow it was well-known that Russia is again taking unprovoked, coercive measures against Ukraine. For example, the unacceptable threatening of the Ukrainian government and its people by a massive build-up of forces along the country’s borders, or pushing the level of violations to the Ukraine’s territorial integrity and sovereignty to new heights. Making the situation worse, just a few hours after Khan’s dubious remark, Russia conducted a full-scale invasion of its neighbor, an independent European country. As such, it does not come by surprise that Khan’s appearance in Moscow raised criticisms. […
The German Community in Siam between 1850 and 1917. A History of Transculturation and Integration
No full textThis research paper deals with the history of the German community in Bangkok from its emergence in the mid-19th century until 1917. It is divided into two parts: the first presents the development process of the German community; the second analyses the facts presented in the first part. The researcher draws on a variety of different sources, including Thai and German political files and documents, tombstones in the two cemeteries for Western foreigners in Bangkok, and interviews with descendants of the community living in Thailand. The first part of the paper (Chapters I-IV) shows how the German community in Siam formed and developed between 1850 and 1917 against the backdrop of global-local interplay of macro- and micro-historical factors. The German community developed in two phases. The first phase began with Siam's policy of opening up in 850 in response to the first wave of colonial expansion by European powers in continental Southeast Asia. The second phase of community development followed Siam’s modernisation on the Western model to counter the second colonial expansion from the 1880s onwards. The German-speaking cultural community in the first phase transformed into the national German community in the second phase. This research paper shows not only how the social structure of the community developed, but also how the process deepened in terms of occupation, and family circumstances in the residential society. The second part of the research paper (Chapter V) analyses the individual biographies of the German members of the community in the context of cultural transfer, transnational and transcultural developments. The research paper shows how members of European-German and Siamese communities interacted with each other, intermingled and finally formed new hybrid societies. The research paper points out that such a process of cultural transfer and transculturation took place beyond national borders, arguing that the history of the German community in Bangkok is also part of transnational history. Chapter VI provides a summary of the findings
Multimodal O/W emulsion structuration characterization using water and emulsion thickening ranges
No full textInternational audienceTo ensure the stability of emulsions, a thickening agent is often used to induce a higher viscosity of the continuous aqueous phase and reduce the possibility of gravitational separation(1). In some cases, these agents require a base to increase the thickening of emulsions and this process can be observed by following the viscosity as a function of the pH(2). Our work attempts to show the link between gelation process and emulsion stability investigated through the use of two innovative measurement techniques at the mesoscopic scale: micro-rheology by ultrasounds and electrical complex dielectric characterization by contactless radiofrequency spectroscopy. The first one allows to better understand the emulsion structuration through the measurement of the visco-elastic properties(3). The second one is used to get information about polarizability of the mixing and conductivity of the continuous phase(4). A comparison is done between the aqueous phase (water + Carbopol® CETD 2050: gel phase) and the equivalent emulsion (aqueous phase + oil: Isopropyl Palmitate + surfactants: Eumulgin® SMO 20/Cutina® GMS V), for different pH by changing the amount of base (Triethanolamine). Both are made on the same pH range (3.5 – 6) to emphasize steric behavior rather than the electrical one. The mesoscopic characterizations highlight the impact of oil on the gelation state. They also show the limits of pH adjustments on increasing viscosity and electronic repulsion between oil droplets, which are stability-promoting factors. The results are completed by complementary classical characterizations such as conductivity, rheological and optical microscopy measurements, to correlate them with documented macroscopic knowledge(5). (1) Piorkowski D.T., et al, 2014(2) Abdolmaleki K., et al, 2016(3) Gauthier V., et al, 2017(4) Dinh T.H.N., et al, 2016(5) Gutowski I., et al, 200
Inclusion scolaire
No full textde Saint Martin, Claire, Duval, Julie & Epstein, Muriel (2022). Inclusion scolaire, Dictionnaire des termes utilisés en formation, dir. Guilhem Labinal et Virginie Tellier, Laboratoire EMA, Hypotheses.orgInternational audienc
Usage de Facebook par les enseignants du Burkina Faso pour la construction de leur professionnalité : entre conflit interpersonnel et conflit sociocognitif
No full textOur research work focuses on the use of Facebook for the construction of teacher professionality in Burkina Faso : from interpersonal conflict to socio-cognitive conflict. It aims at understanding whether this digital social network could be a framework for the construction of teacher professionality, therefore, for informal learning. It also aims at establishing whether interpersonal conflicts (IPC), which are often part of this social network, have effects on socio-cognitive conflict (SCC), used to account for informal learning. To conduct this research, we assumed that Facebook contributes to the construction of teacher professionality and informal learning by means of dialectical collaboration/conflict.An exploratory survey allowed us to report the proportion of users and the frequency of Facebook use among teachers. The literature enables us to understand how teachers use Facebook for informal learning with their students, and how it is also used for the construction of their professionality. This literature also made it possible to understand concepts related to professionality, sociocognitive conflict, interpersonal conflict and to design grids which were used to encode our data.We have proposed a methodology for researching professional Facebook groups, and for choosing threads for the purpose of this study. We have proposed a methodology for encoding digital traces deriving from threads, and based on the use of meaningful clauses as an encoding unit. After the encoding of the categories of professionality, and elements of socio-cognitive and interpersonal conflicts, after the interview carried out with teachers, after processing the data, we reached the following results :Teachers effectively discuss issues on different categories of teaching professionality. These discussions based on confrontation of opposing points of view or otherwise socio-cognitive conflicts, lead to an awareness reflecting the learning achieved. The results also highlight the existence of interpersonal conflicts (IPC). The IPC occupies 28.28% of the exchanges from the threads. Questioning teacher skills, anger, reproaches and intentional provocations are the main causes of this IPC. There are situations where IPC has no effect on SCC and situations where it does affect SCC. The conditions under which IPC can have an effect on SCC have been identified.Keywords: Facebook, usage, professionality, socio-cognitive conflict, interpersonal conflictNotre travail de recherche porte sur l’usage de Facebook par les enseignants du Burkina Faso pour la construction de leur professionnalité : entre conflit interpersonnel (CIP) et conflit sociocognitif (CSC). L’objectif est de chercher à comprendre si ce réseau socio-numérique pourrait être un cadre de construction de la professionnalité, donc de l’apprentissage informel des enseignants. Ensuite, il s’agit de chercher à savoir si les conflits interpersonnels, qui pourraient exister sur ce réseau social, ont des effets sur le conflit sociocognitif pris comme élément pour rendre compte de l’apprentissage informel. Pour ce faire nous avons postulé que Facebook participe à la construction de la professionnalité des enseignants et à leur formation informelle par une dialectique collaboration/conflits.Une enquête exploratoire nous a permis de rendre compte de la proportion des usagers et des fréquences d’usages de Facebook parmi les enseignants. La littérature nous a permis de cerner non seulement l’utilisation de Facebook par les enseignants, dans leur rapport aux élèves pour des apprentissages informels, mais aussi les usages faits pour la construction de leur professionnalité. Cette littérature a également permis de cerner les concepts relatifs à la professionnalité, au conflit sociocognitif, au conflit interpersonnel et de parvenir à des grilles qui ont servi à l’encodage de nos données.Nous avons proposé une méthodologie de recherche des groupes professionnels Facebook, de choix de fils de discussion. Nous avons proposé une méthodologie d’encodage des traces numériques issues des fils de discussion Facebook en s’appuyant sur la proposition comme unité d’encodage. Après l’encodage des catégories de professionnalité, des éléments caractéristiques du confit sociocognitif et du conflit interpersonnel, après l’entretien réalisé avec des enseignants, après le traitement des données, nous sommes parvenu aux résultats suivants :Les enseignants échangent effectivement sur toutes les catégories de la professionnalité. Ces échanges se font dans une confrontation de points de vue opposés, de conflits sociocognitifs pour aboutir à une prise de conscience traduisant l’apprentissage réalisé. Les résultats font ressortir également l’existence de conflits interpersonnels (CIP). Le CIP est présent dans les fils de discussions et occupe 28,28% des échanges de l’ensemble des fils de discussion. La remise en cause des compétences, les colères exprimées, les reproches, les provocations expresses sont les principales causes de ce CIP. Il y a des situations où le CIP n’a pas d’effets sur le CSC et des situations où le CIP affecte effectivement le CSC. Les conditions dans lesquelles le CIP peut avoir un effet sur le CSC ont été identifiées.Mots clés : Facebook, usage, professionnalité, conflit sociocognitif, conflit interpersonne
