871 resultados para Right-handed neutrinos


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Studies of the band gap properties of one-dimensional superlattices with alternate layers of air and left-handed materials are carried out within the framework of Maxwell's equations. By left-handed material, we mean a material with dispersive negative electric and magnetic responses. Modeling them by Drude-type responses or by fabricated ones, we characterize the n(ω) = 0 gap, i.e., the zeroth order gap, which has been predicted and detected. The band structure and analytic equations for the band edges have been obtained in the long wavelength limit in case of periodic, Fibonacci, and Thue-Morse superlattices. Our studies reveal the nature of the width of the zeroth order band gap, whose edge equations are defined by null averages of the response functions. Oblique incidence is also investigated, yielding remarkable results. © 2010 Springer Science+Business Media B.V.

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Presently it is well known that neutrino oscillation data are well described by massive neutrinos and their mixing. This suggests changes in the standard model (SM) and makes the flavor physics even more interesting. Recently, it has been proposed a multi-Higgs extension of the SM with Abelian and non-Abelian discrete symmetries which seeks to explain the origin of the masses and mixing matrices in all charge sectors. © 2012 Elsevier B.V.

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We show the results and discussions of the study of a possible suppression of the extragalactic neutrino flux during its propagation due to a nonstandard interaction with a candidate field to dark matter. In particular, we show the study of neutrino interaction with an ultra-light scalar field. It is shown that the extragalactic neutrino flux may be suppressed by such an interaction, leading to a mechanism to reduce the ultra-high energy neutrino flux. We calculate both the cases of non-self-conjugate as well as self-conjugate ultra-light dark matter. In the first case, the suppression is independent of the neutrino and dark matter masses. We conclude that care must be taken when explaining limits on the neutrino flux through source acceleration mechanisms only, since there could be other mechanisms, as absorption during propagation, for the reduction of the neutrino flux [1], © Published under licence by IOP Publishing Ltd.

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The morphologically undivided ventricle of the heart in non-crocodilian reptiles permits the mixing of oxygen-rich blood returning from the lungs and oxygen-poor blood from the systemic circulation. A possible functional significance for this intra-cardiac shunt has been debated for almost a century. Unilateral left vagotomy rendered the single effective pulmonary artery of the South American rattlesnake, Crotalus durissus, unable to adjust the magnitude of blood flow to the lung. The higher constant perfusion of the lung circulation and the incapability of adjusting the right-left shunt in left-denervated snakes persisted over time, providing a unique model for investigation of the long-term consequences of cardiac shunting in a squamate. Oxygen uptake recorded at rest and during spontaneous and forced activity was not affected by removing control of the cardiac shunt. Furthermore, metabolic rate and energetic balance during the post-prandial metabolic increment, plus the food conversion efficiency and growth rate, were all similarly unaffected. These results show that control of cardiac shunting is not associated with a clear functional advantage in adjusting metabolic rate, effectiveness of digestion or growth rates. © 2013. Published by The Company of Biologists Ltd.

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The knowledge of the mechanisms underlying circulating volume control may be achieved by stretching a balloon placed at the junction of the superior vena cava-right atrial junction (SVC-RAJ). We investigated whether the inflation of a balloon at the SVC-RAJ inhibits the intake of 0.3M NaCl induced by GABAA receptor activation in the lateral parabrachial nucleus (LPBN) in euhydrated and satiated rats. Male Wistar rats (280-300g) with bilateral stainless steel LPBN cannulae and balloons implanted at the SVC-RAJ were used. Bilateral injections of the GABAA receptor agonist muscimol (0.5ηmol/0.2l) in the LPBN with deflated balloons increased intake of 0.3M NaCl (30.1±3.9 vs. saline: 2.2±0.7)ml/210min, n=8) and water (17.7±1.9 vs. saline: 2.9±0.5ml/210min). Conversely, 0.3M NaCl (27.8±2.1ml/210min) and water (22.8±2.3ml/210min) intake were not affected in rats with inflated balloons at the SVC-RAJ. The results show that sodium and water intake induced by muscimol injected into the LPBN was not affected by balloon inflation at the SVC-RAJ. We suggest that the blockade of LPBN neuronal activity with muscimol injections impairs inhibitory mechanisms activated by signals from cardiopulmonary volume receptors determined by balloon inflation. © 2013 The Authors.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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Pós-graduação em Física - IFT

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Incluye bibliografía.

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A disturbing token of child and adolescent vulnerability in Latin America and the Caribbean is that so many are deprived of any legal identity by failure to report their birth. This bars them from exercising basic citizen rights and can hinder their access to productive employment, social benefits and the justice system and deny them recognition as full citizens and the right to well-being, capacity development and political participation.

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Healthy environment: unresolved debts that affect childhood and adolescenceIn this new edition, we point out the right of children and adolescents to live in a healthy environment with emphasis on adequate access to drinking water and sanitation, including diagnosis as well as policy perspective. It is our contribution to the challenges set out by the Millennium Development Goals and the Convention on the Rights of the Child.

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The right to education.Our newsletter once again takes on the challenges set forth by the Millennium Declaration and the human rights approach embedded in the Convention on the Rights of the Child. In this issue, we will examine the right of children and adolescents to education.

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The inalienable right of all people to education is enshrined in various international covenants, conventions and agreements, yet the actual fulfilment of this right varies in quantity and quality from one country to the other. On average, the compulsory length of schooling in the countries of the region is 10 years. Half of these countries have already made all secondary education mandatory, which is eminently reasonable since it is commonly accepted as a minimum threshold for lifelong well-being and skills-building. The main article in this edition of Challenges discusses this subject in depth, and shows how far behind we are in ensuring that all adolescents have access to the education to which they are entitled. It focuses on the low secondary school-completion rate and low level of learning acquisition, the strong socioeconomic and sociocultural stratification, the lack of citizenship skills, and the persistence of a relatively high dropout rate at all levels of secondary education. The main challenge in guaranteeing the right to education lies in reducing learning and attainment gaps by helping the groups that are presently lagging behind the most. As is customary, there are also reports on relevant meetings and conferences held in the region over the past half-year, together with the opinions of experts and adolescents and success stories in promoting school attendance in Uruguay and the Dominican Republic.

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Words can make a difference sometimes.Brazil is – together with the other ´BRIC´- a large economy, with an increasingly high profile in the international scenario. Large domestic market makes it more likely to obtain ‘growth-led exports’ rather than ‘export-led growth’, which implies a pro-active role in international relations. The option for intensifying regional trade links is a reasonable one and perhaps even inevitable, taking into account the experience elsewhere, but the actual regional conditions raise a number of questions that have to do both with further empirical assessment and to more specific identification of expectations with regard to probable achievements. This article has shown that the road to reach significant progress in this direction is not flat and requires more clear signalling to economic agents, strong political will and a good deal of specific measures. But it has also suggested that it might provide positive results.