1,764 research outputs found
Brane matter, hidden or mirror matter, their various avatars and mixings: many faces of the same physics
Numerous papers deal with the phenomenology related to photon-hidden photon
kinetic mixing and with the effects of a mass mixing on particle-hidden
particle oscillations. In addition, recent papers underline the existence of a
geometrical mixing between branes which would allow a matter swapping between
branes. These approaches and their phenomenologies are reminiscent of each
other but rely on different physical concepts. In the present paper, we suggest
there is no rivalry between these models, which are probably many faces of the
same physics. We discuss some phenomenological consequences of a global
framework.Comment: 9 pages. Typo corrected. Published in European Physical Journal
Circuits et modélisation
Les deux modèles présentés ci-dessous diffèrent non seulement par leur nature, mais aussi par leur champ de validité : ils n'ont pas été construits pour résoudre le même problème. Ils montrent bien la diversité des modèles qu'on peut construire et utiliser dans un domaine donné. Ils remplissent cependant les mêmes fonctions : interpréter des faits expérimentaux et si possible en prévoir d'autres. Ils illustrent la même méthode et c'est cette méthode (la modélisation) que devront peu à peu maîtriser nos élève
Sub-percent accuracy for the intensity of a near-infrared water line at 10,670 cm^{-1}: experiment and analysis
Laser measurements of the intensity of (201) 3_{22} - (000) 2_{21} near-infrared water absorption line at 10,670.1 cm^{-1} are made using three different Herriott cells. These measurements determine the line intensity with an standard deviation below of 0.3% by consideration of the new geometrically derived formula for the optical path length without approximations. This determination together with the current accepted value lead to an overall uncertainty of 0.7% of the experimentally assessed line intensity which is compared with previous ab initio predictions. It is found that steady improvements in both the dipole moment surface (DMS) and the potential energy surface (PES) used in the theoretical studies lead to a systematically better agreement with the observation, with the most recent prediction agreeing closely with the experiment
Exciton swapping in a twisted graphene bilayer as a solid-state realization of a two-brane model
It is shown that exciton swapping between two graphene sheets may occur under
specific conditions. A magnetically tunable optical filter is described to
demonstrate this new effect. Mathematically, it is shown that two turbostratic
graphene layers can be described as a "noncommutative" two-sheeted
(2+1)-spacetime thanks to a formalism previously introduced for the study of
braneworlds in high energy physics. The Hamiltonian of the model contains a
coupling term connecting the two layers which is similar to the coupling
existing between two braneworlds at a quantum level. In the present case, this
term is related to a K-K' intervalley coupling. In addition, the experimental
observation of this effect could be a way to assess the relevance of some
theoretical concepts of the braneworld hypothesis.Comment: 15 pages, 3 figures, final version published in European Physical
Journal
CaracterĂsticas quĂmicas de um gleissolo sob diferentes sistemas de uso, nas margens do rio Guamá, BelĂ©m, Pará.
Foram estudados os efeitos do uso do solo sobre a fertilidade, em Gleissolo sob trĂŞs diferentes sistemas de manejo. As coletas foram feitas antes do perĂodo chuvoso nos seguintes sistemas de manejo: área cultivada com arroz (Oriza sativa L.) há aproximadamente 40 anos, com algumas interrupções ao longo deste perĂodo, com o cultivo algumas vezes mecanizado e uso de aração e gradagem; área sob pastagem de canarana erecta lisa (Echinochloa pyramidalis Hitch.), formada há cerca de 20 anos sem uso de adubações ou calagens; e área sob vegetação natural de floresta tĂpica das áreas de várzea alta. As amostras de solo foram coletadas em dez pontos a partir de um transecto nas áreas, em quatro profundidades 0-10, 10-20, 20-30 e 30-40 cm. Os resultados demonstraram que o solo em condições naturais, de modo geral, apresentou atributos quĂmicos que variaram de bons a muito bons, o que demonstra um grande potencial para o uso agrĂcola. O cultivo agrĂcola dos solos das várzeas do rio Guamá provocou uma redução da concentração de P e de K. O sistema de uso com pastagem apresentou maior sustentabilidade da fertilidade do que o sistema sob cultivo com arroz, visto que, alĂ©m da melhoria das caracterĂsticas quĂmicas, a matĂ©ria orgânica elevou-se, tambĂ©m, em relação ao sistema natural
The effects of an experimental programme to support students’ autonomy on the overt behaviours of physical education teachers
Although the benefits of autonomy supportive behaviours are now well established in the literature, very few studies have attempted to train teachers to offer a greater autonomy support to their students. In fact, none of these studies has been carried out in physical education (PE). The purpose of this study is to test the effects of an autonomy-supportive training on overt behaviours of teaching among PE teachers. The experimental group included two PE teachers who were first educated on the benefits of an autonomy supportive style and then followed an individualised guidance programme during the 8 lessons of a teaching cycle. Their behaviours were observed and rated along 3 categories (i.e., autonomy supportive, neutral and controlling) and were subsequently compared to those of three teachers who formed the control condition. The results showed that teachers in the experimental group used more autonomy supportive and neutral behaviours than those in the control group, but no difference emerged in relation to controlling behaviours. We discuss the implications for schools of our findings
Setting the stage: social-environmental and motivational predictors of optimal training engagement
In this paper, we will firstly explore the central tenets of SDT. Research that has examined the social-environmental and motivation-related correlates of optimal training, performance and health-related engagement through the theoretical lens of SDT will be reviewed. Drawing from SDT-driven work undertaken in educational, sport and dance settings, we will draw conclusions and suggest future directions from a research and applied perspective
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