Evidence of spontaneous spin polarized transport in magnetic nanowires

The exploitation of the spin in charge-based systems is opening revolutionary opportunities for device architecture. Surprisingly, room temperature electrical transport through magnetic nanowires is still an unresolved issue. Here, we show that ferromagnetic (Co) suspended atom chains spontaneously display an electron transport of half a conductance quantum, as expected for a fully polarized conduction channel. Similar behavior has been observed for Pd (a quasi-magnetic 4d metal) and Pt (a non-magnetic 5d metal). These results suggest that the nanowire low dimensionality reinforces or induces magnetic behavior, lifting off spin degeneracy even at room temperature and zero external magnetic field.Comment: 4 pages, 3 eps fig

Mapping and analysis of geodiversity indices in the Xingu river basin, Amazonia, Brazil

First published online: 14 October 2014From the 1990s, geodiversity studies have been widely carried out in order to understand, describe and preserve the natural heritage of the abiotic environment. Geodiversity assessments have principally been conducted using geological (minerals, rocks and fossils), geomorphological (landforms and processes) and pedological variables. This concept has been widespread and consolidated in scientific circles, where early studies focused on methods that assessed the spatial variability of the geodiversity, with a particular focus on quantitative aspects. In this study, a geodiversity quantification methodology (Pereira et al. 2013) has been applied to the Xingu River basin (Amazônia, Brazil), which covers approximately 51 million hectares. This methodology is based on measuring and integrating abiotic elements, which are spatialised using thematic maps at scales varying between 1:250,000 and 1:1,000,000 and using a 1:25,000 systematic linkage grid. This methodology was adapted for the Amazonian environment by including parameters related to river channel patterns, as approximately 12.6 % of the area is a fluvial environment (channels and floodplains). After applying the methodology, geodiversity indices varying between 4 and 32 were obtained, and a geodiversity hot spot in the basin was identified in the region known as “Volta Grande do Xingu” (The Great Bend of the Xingu). The results of the study highlight the fragility of legal tools for environmental protection of the area, primarily those related to aspects of the physical environment. Although large portions of the basin are partially or fully protected (as indigenous lands and conservation units), the area with the greatest geodiversity is precisely the one which has fewer legal protection devices and is where the Belo Monte hydroelectric power plant is being built

On the connection of Gamma-rays, Dark Matter and Higgs searches at LHC

Motivated by the upcoming Higgs analyzes we investigate the importance of the complementarity of the Higgs boson chase on the low mass WIMP search in direct detection experiments and the gamma-ray emission from the Galactic Center measured by the Fermi-LAT telescope in the context of the $SU(3)_c\otimes SU(3)_L\otimes U(1)_N$. We obtain the relic abundance, thermal cross section, the WIMP-nucleon cross section in the low mass regime and network them with the branching ratios of the Higgs boson in the model. We conclude that the Higgs boson search has a profound connection to the dark matter problem in our model, in particular for the case that ($M_{WIMP} < 60$ GeV) the BR($H \rightarrow 2$ WIMPs) $\gtrsim 90$. This scenario could explain this plateau of any mild excess regarding the Higgs search as well as explain the gamma-ray emission from the galactic center through the $b\bar{b}$ channel with a WIMP in the mass range of 25-45 GeV, while still being consistent with the current limits from XENON100 and CDMSII. However, if the recent modest excesses measured at LHC and TEVATRON are confirmed and consistent with a standard model Higgs boson this would imply that $M_{WIMP} > 60$ GeV, consequently ruling out any attempt to explain the Fermi-LAT observations.Comment: 8 pages, 9 figure

Explaining ATLAS and CMS Results Within the Reduced Minimal 3-3-1 model

Recently the ATLAS and CMS collaborations announced the discovery of a higgs particle with a mass of $\sim 125$ GeV. The results are mildly consistent with the Standard Model Higgs boson. However, the combined data from these collaborations seem to point to an excess in the $h \rightarrow \gamma \gamma$ channel. In this work we analyze under which conditions this excess may be plausibly explained within the reduced minimal 3-3-1 model, while being consistent with bb, WW, ZZ and $\tau^+\tau^-$ channels. Moreover, we derive the properties of the heavy neutral and the doubly charged scalars predicted by the model. We then conclude that at a scale of a few TeV, this model provides a good fit to the ATLAS and CMS signal strength measurements, and therefore stands as an appealing alternative to the standard model.Comment: 23 pages, 9 figures. References adde

The minimal 3-3-1 model with only two Higgs triplets

The simplest non-abelian gauge extension of the electroweak standard model, the $SU(3)_c\otimes SU(3)_L\otimes U(1)_N$, known as 3-3-1 model, has a minimal version which demands the least possible fermionic content to account for the whole established phenomenology for the well known particles and interactions. Nevertheless, in its original form the minimal 3-3-1 model was proposed with a set of three scalar triplets and one sextet in order to yield the spontaneous breaking of the gauge symmetry and generate the observed fermion masses. Such a huge scalar sector turns the task of clearly identifying the physical scalar spectrum a clumsy labor. It not only adds an obstacle for the development of its phenomenology but implies a scalar potential plagued with new free coupling constants. In this work we show that the framework of the minimal 3-3-1 model can be built with only two scalar triplets, but still triggering the desired pattern of spontaneous symmetry breaking and generating the correct fermion masses. We present the exact physical spectrum and also show all the interactions involving the scalars, obtaining a neat minimal 3-3-1 model far more suited for phenomenological studies at the current Large Hadron Collider.Comment: about 20 pages, no figur

Combining type I and type II seesaw mechanisms in the minimal 3-3-1 model

The minimal 3-3-1 model is perturbative until energies around 4-5TeV, posing a challenge to generate neutrino masses at eV scale, mainly if one aims to take advantage of the seesaw mechanism. As a means to circumvent this problem we propose a modification of the model such that it accommodates the type I and type II seesaw mechanisms altogether. We show that the conjunction of both mechanisms yield a neutrino mass expression suppressed by a high power of the cutoff scale, $M^5$, in its denominator. With such a suppression term we naturally obtain neutrino masses at eV scale when $M$ is around few TeV. We also investigate the size of lepton flavor violation through the process $\mu \rightarrow e\gamma$.Comment: about 15 pages, no figure

Liquid mixtures involving fluorinated alcohols: The equation of state (p, r, T, x) of (Ethanol + Trifluoroethanol) Experimental and Simulation

Liquid mixtures involving fluorinated alcohols: The equation of state (p, r, T, x) of (Ethanol + Trifluoroethanol) Experimental and Simulation Pedro Duartea, Djêide Rodriguesa, Marcelo Silvaa, Pedro Morgadoa, Luís Martinsa,b and Eduardo J. M. Filipea* aCentro de Química Estrutural, Instituto Superior Técnico, 1049-001 Lisboa, Portugal bCentro de Química de Évora, Universidade de Évora, 7000-671 Évora, Portugal Fluorinated alcohols are substances with unique properties and high technological value in the pharmaceutical and chemical industries. Trifluoroethanol (TFE), in particular, displays a number of unusual properties as a solvent. For example, it dissolves nylon at room temperature and is effectively used as solvent in bioengineering. The presence of the three fluorines atoms gives the alcohol a high ionization constant, strong hydrogen bonding capability and stability at high temperatures. In the pharmaceutical industry, TFE finds use as the major raw material for the production of inhalation anesthetics. Mixtures of TFE and water (known as Fluorinols®) are used as working fluids for Rankine cycle heat engines for terrestrial and space applications, as a result of a unique combination of physical and thermodynamic properties such as high thermal efficiency and excellent turbine expansion characteristics. Environmentally, TFE is a CFC substitute with an acceptable short lifetime and with small ozone depletion potential. Additionally, TFE is known to induce conformational changes in proteins and it is used as a co-solvent to analyze structural features of partially folded states. The (ethanol + TFE) system displays an interesting and peculiar behaviour, combining a negative azeotrope with high positive excess volumes. In this work, liquid mixtures of (ethanol + TFE) were investigated. The densities of the mixtures were measured as a function of composition between 278K and 338K and at pressures up to 700 bar. The corresponding excess volumes as a function of temperature and pressure, the isothermal compressibilities and thermal expansivities were calculated from the experimental results. The mixtures are highly non-ideal with excess volumes ranging from 0.8 - 1.0 cm3mol-1. Finally, molecular dynamic simulations were performed to model and interpret the experimental results. The Trappe force field was used to simulate the (TFE + ethanol) mixtures and calculate the corresponding excess volumes. The simulation results are able to reproduce the correct sign and order of magnitude of the experimental VE without fitting to the experimental data. Furthermore, the simulations suggest the presence of a particular type of hydrogen bridge between ethanol and TFE, that can help to rationalize the experimental results

Escolas públicas no campo: retrospectiva e perspectivas em um contexto de projetos políticos em disputa. Public schools in the countryside: A retrospective and perspectives in a context of political projects in dispute

Neste artigo, são apresentadas reflexões acerca do processo de fechamento de escolas públicas no campo, no Brasil. Por meio de levantamento bibliográfico, assim como de pesquisa documental, procedeu-se a uma análise retrospectiva do momento histórico em que ocorre a implementação das políticas de educação em massa, voltadas aos povos do campo, bem como se buscou levantar aspectos sócio-político-econômicos do momento em que o processo de fechamento dessas escolas é intensificado. A partir dos resultados, é possível sugerir possíveis implicações dessa política de fechamento e, ademais, apontar alguns dos desafios postos para a política pública de educação do país. Pode ser citado, como exemplo desses desafios, o contexto federativo brasileiro e as limitações orçamentárias impostas aos governos subnacionais no tocante ao financiamento da educação escolar, em especial no que se refere aos municípios de pequeno porte e/ou àqueles municípios com baixo montante de arrecadação própria. Tal situação ocorre, Isso porque, não raramente, esses municípios dispõem de reduzido orçamento, dependendo, de maneira majoritária, dos repasses de recursos financeiros provenientes de outras esferas governamentais, sejam federal ou estadual, as denominadas transferências orçamentárias intergovernamentais, em especial do Fundo de Participação dos Municípios. Tais questões que demandam que sejam retomados ou (re)problematizados os debates acerca do pacto federativo, em especial no que se refere ao federalismo fiscal, haja vista que a capacidade financeira de cada governo subnacional é determinante para a execução das políticas educacionais. In present article, we present reflections on the process of closing public schools in the countryside in Brazil. Through bibliographical survey, as well as documental research, we carried out a retrospective analysis of the historical moment in which the implementation of policies of mass education directed to people living in rural areas occurs. We have also sought to raise socio-political-economic aspects of the moment in which the process of closing these schools is intensified. The results obtained suggest possible implications of this closure policy, in addition to indicating some of the challenges posed to the public policy of education in the country; for example, the Brazilian federal context and the budget limitations imposed to subnational governments with regard to the funding of school education, particularly in relation to small municipalities and/or municipalities with low tax revenues. This situation quite often occurs because these municipalities present reduced budgets, depending largely on transfers of financial resources from other spheres of the Government, either federal or state, the so-called intergovernmental budgetary transfers; namely, the Municipalities Participation Fund. Such issues demand the resumption of debates about the federative pact, in particular with regard to fiscal federalism, given that the financial capacity of each subnational government is crucial to the implementation of educational policies