992 resultados para Surfaces in the 3-dimensional Sphere


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We implement the mechanism of spontaneous CP violation in the 3-3-1 model with right-handed neutrinos and recognize their sources of CP violation. Our main result is that the mechanism works already in the minimal version of the model and new sources of CP violation emerges as an effect of new physics at energies higher than the electroweak scale.

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The goal of this article is to derive the Feynman rules involving single charginos, neutralinos, double charged gauge bosons, and sleptons in a 3-3-1 supersymmetric model. Using these Feynman rules we calculate the production of double charged charginos with neutralinos and also the production of a pair of single charged charginos, both in an electron-electron linear collider.

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The negative-dimensional integration method is a technique which can be applied, with success, in usual covariant gauge calculations. We consider three two-loop diagrams: the scalar massless non-planar double-box with six propagators and the scalar pentabox in two cases, where six virtual particles have the same mass, and in the case all of them are massless. Our results are given in terms of hypergeometric functions of Mandelstam variables and also for arbitrary exponents of propagators and dimension D.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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The negative-dimensional integration method (NDIM) is revealing itself as a very useful technique for computing massless and/or massive Feynman integrals, covariant and noncovanant alike. Up until now however, the illustrative calculations done using such method have been mostly covariant scalar integrals/without numerator factors. We show here how those integrals with tensorial structures also can be handled straightforwardly and easily. However, contrary to the absence of significant features in the usual approach, here the NDIM also allows us to come across surprising unsuspected bonuses. Toward this end, we present two alternative ways of working out the integrals and illustrate them by taking the easiest Feynman integrals in this category that emerge in the computation of a standard one-loop self-energy diagram. One of the novel and heretofore unsuspected bonuses is that there are degeneracies in the way one can express the final result for the referred Feynman integral.

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The Archean (3.45-2.70Ga) rocks of the São José do Campestre Massif (SJCM) in the Borborema Province (NE Brazil) make up a small area (~6000km2) and are composed of granitoids and metasupracrustal rocks that define a complex magmatic and deformational history. The massif provides the opportunity to study mantle- and crustal-derived magmas generated since the Palaeoarchean. The orthogneisses of the SJCM are composed of: (1) tonalite to granodiorite with diorite enclaves (Bom Jesus gneiss, 3412±8Ma; TDM Nd model ages from 4.1 to 3.5Ga and negative epsilon Nd values); (2) biotite and ferroan-diopside monzogranite (Presidente Juscelino complex, 3356±21Ma and 3251±44Ma; TDM model ages range from 4.1 to 3.4Ga and epsilon Nd values that are slightly positive to negative); (3) hornblende tonalite to granodiorite (Brejinho complex, 3333±77Ma and 3187±8Ma; dominantly positive epsilon Nd values and TDM ages from 3.6 to 3.2Ga); (4) biotite monzogranite (São Pedro do Potengi gneiss, 3120±22Ma; TDM =3.5Ga; negative epsilon Nd value); (5) ferroan-diopside-grossular anorthosite and metagabbro (Senador Elói de Souza complex, 3033±3Ma); and (6) quartz diorite to syenogranite (São José do Campestre complex; 2685±9Ma and 2655±4Ma; negative epsilon Nd values and TDM ages from 3.9 to 3.3Ga). The orthogneisses are subalkaline to faintly alkaline, magnesian to ferroan, M- and I-type granitoids that follow either the K-enrichment or the trondhjemite trends. Each group has a subset with REE characteristics similar to Archean TTG and another that is analogous to Phanerozoic granitoids. They have negative Ta-Nb and Ti anomalies and have trace element contents of granitoids from subduction zones. Geochemical and Nd isotope data suggest that subducted oceanic crust and a depleted and metasomatised mantle wedge both acted as the magma sources. We propose a convergent tectonic model in which hybridisation of the upper mantle occurs through interactions with adakitic or trondhjemitic melts and recycling of earlier crust. The results imply that both the subducted oceanic crust and the mantle wedge played major roles in continent formation throughout successive episodes of arc accretion in Palaeo- and Mesoarchean times. The Archean rocks of the SJCM shares some similarities with the Pilbara, Kaapvaal, West African, and São Francisco cratons. However, the most reliable comparisons with the SJCM are with the neighbouring basement of the Nigeria and Cameroon shields. © 2012 Elsevier B.V.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Coding region alterations of ZIC2 are the second most common type of mutation in holoprosencephaly (HPE). Here we use several complementary bioinformatic approaches to identify ultraconserved cis-regulatory sequences potentially driving the expression of human ZIC2. We demonstrate that an 804 bp element in the 3' untranslated region (3'UTR) is highly conserved across the evolutionary history of vertebrates from fish to humans. Furthermore, we show that while genetic variation of this element is unexpectedly common among holoprosencephaly subjects (6/528 or >1%), it is not present in control individuals. Two of six proband-unique variants are de novo, supporting their pathogenic involvement in HPE outcomes. These findings support a general recommendation that the identification and analysis of key ultraconserved elements should be incorporated into the genetic risk assessment of holoprosencephaly cases.

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We have performed multicanonical simulations to study the critical behavior of the two-dimensional Ising model with dipole interactions. This study concerns the thermodynamic phase transitions in the range of the interaction delta where the phase characterized by striped configurations of width h = 1 is observed. Controversial results obtained from local update algorithms have been reported for this region, including the claimed existence of a second-order phase transition line that becomes first order above a tricritical point located somewhere between delta = 0.85 and 1. Our analysis relies on the complex partition function zeros obtained with high statistics from multicanonical simulations. Finite size scaling relations for the leading partition function zeros yield critical exponents. that are clearly consistent with a single second-order phase transition line, thus excluding such a tricritical point in that region of the phase diagram. This conclusion is further supported by analysis of the specific heat and susceptibility of the orientational order parameter.

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Reaching and grasping an object is an action that can be performed in light, under visual guidance, as well as in darkness, under proprioceptive control only. Area V6A is a visuomotor area involved in the control of reaching movements. V6A, besides neurons activated by the execution of reaching movements, shows passive somatosensory and visual responses. This suggests fro V6A a multimodal capability of integrating sensory and motor-related information, We wanted to know whether this integration occurrs in reaching movements and in the present study we tested whether the visual feedback influenced the reaching activity of V6A neurons. In order to better address this question, we wanted to interpret the neural data in the light of the kinematic of reaching performance. We used an experimental paradigm that could examine V6A responses in two different visual backgrounds, light and dark. In these conditions, the monkey performed an istructed-delay reaching task moving the hand towards different target positions located in the peripersonal space. During the execution of reaching task, the visual feedback is processed in a variety of patterns of modulation, sometimes not expected. In fact, having already demonstrated in V6A reach-related discharges in absence of visual feedback, we expected two types of neural modulation: 1) the addition of light in the environment enhanced reach-related discharges recorded in the dark; 2) the light left the neural response unmodified. Unexpectedly, the results show a complex pattern of modulation that argues against a simple additive interaction between visual and motor-related signals.

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Nowadays the environmental issues and the climatic change play fundamental roles in the design of urban spaces. Our cities are growing in size, many times only following immediate needs without a long-term vision. Consequently, the sustainable development has become not only an ethical but also a strategic need: we can no longer afford an uncontrolled urban expansion. One serious effect of the territory industrialisation process is the increase of urban air and surfaces temperatures compared to the outlying rural surroundings. This difference in temperature is what constitutes an urban heat island (UHI). The purpose of this study is to provide a clarification on the role of urban surfacing materials in the thermal dynamics of an urban space, resulting in useful indications and advices in mitigating UHI. With this aim, 4 coloured concrete bricks were tested, measuring their emissivity and building up their heat release curves using infrared thermography. Two emissivity evaluation procedures were carried out and subsequently put in comparison. Samples performances were assessed, and the influence of the colour on the thermal behaviour was investigated. In addition, some external pavements were analysed. Albedo and emissivity parameters were evaluated in order to understand their thermal behaviour in different conditions. Surfaces temperatures were recorded in a one-day measurements campaign. ENVI-met software was used to simulate how the tested materials would behave in two typical urban scenarios: a urban canyon and a urban heat basin. Improvements they can carry to the urban microclimate were investigated. Emissivities obtained for the bricks ranged between 0.92 and 0.97, suggesting a limited influence of the colour on this parameter. Nonetheless, white concrete brick showed the best thermal performance, whilst the black one the worst; red and yellow ones performed pretty identical intermediate trends. De facto, colours affected the overall thermal behaviour. Emissivity parameter was measured in the outdoor work, getting (as expected) high values for the asphalts. Albedo measurements, conducted with a sunshine pyranometer, proved the improving effect given by the yellow paint in terms of solar reflection, and the bad influence of haze on the measurement accuracy. ENVI-met simulations gave a demonstration on the effectiveness in thermal improving of some tested materials. In particular, results showed good performances for white bricks and granite in the heat basin scenario, and painted concrete and macadam in the urban canyon scenario. These materials can be considered valuable solutions in UHI mitigation.