Atividade óptica de um meio dielétrico diluído: Pasteur e as simetrias moleculares

Em 1848 Pasteur conjeturou que a rotação do plano de polarização da luz em um meio diluído é gerada pelas propriedades de simetria das moléculas do meio no qual a luz se propaga. O objetivo do nosso artigo é de mostrar que Pasteur estava correto usando conhecimentos de eletromagnetismo e mecânica quântica de um curso de graduação em física. Faremos um breve retrospecto das ideias básicas da teoria eletromagnética necessárias para o estudo da atividade óptica. A seguir, usando a teoria de perturbações em mecânica quântica e levando em conta as simetrias das moléculas calcularemos a atividade óptica do meio. Mostraremos que as previsões teóricas, que estão plenamente de acordo com os resultados experimentais, comprovam a hipótese de Pasteur.

Avaliação sensorial de cachaça

The hedonic level of commercial cachaças, was evaluated by consumers and by a tasters. The results of sensorial methods analyzed trough Principal Components Analysis, Hierarchical Cluster Analysis and the Pearson linear correlation indicated that the best classified cachaças were produced in copper stills and aged in oak casks. By contrast the worst classified exhibited as the main features be not aged and high alcohol percentage. The index of preference is positively correlated with the intensity of yellow color, wood flavor, sweetness and fruit aroma. There is a negative preference correlation with the acidity, the taste of alcohol and bitterness.

Stability of fruit bases and chocolate fillings

Syrups with high sugar content and dehydrated fruits in its composition can be added to chocolate fillings to reduce the need of artificial flavor and dyes attributing a natural appeal to the product. Fruit bases were produced with lyophilized strawberry, passion fruit, and sliced orange peel. Rheological dynamic oscillatory tests were applied to determine the products stability and tendency of shelf life. Values of G´< G´´ were observed for strawberry and passion fruit flavor, whereas values of G´ > G´´ were found for orange flavor during the 90 days of storage. It was observed that shear stress values did not vary significantly suggesting product stability during the studied period. For all fillings, it was found a behavior similar to the fruit base indicating that it has great influence on the filling behavior and its stability. The use of a sugar matrix in fillings provided good shelf life for the fruit base, which could be kept under room temperature conditions for a period as long as one year. The good stability and storage conditions allow the use of fruit base for handmade products as well as for industrialized products.

Consumo de bebidas e refrigerantes por adolescentes de uma escola pública

OBJETIVO: Avaliar o consumo de bebidas e refrigerantes por adolescentes de uma escola pública de São Paulo (SP). MÉTODOS: Participaram do estudo 71 adolescentes com idade entre 14 e 17 anos, de ambos os gêneros, matriculados no ensino médio em uma escola técnica da região metropolitana de São Paulo. Avaliaram se o tipo de bebida consumida durante as refeições, os locais onde se consome refrigerante e o motivo que leva ao consumo. RESULTADOS: A bebida mais consumida durante as refeições foi o suco de frutas industrializado (38,1%), seguido do refrigerante do tipo comum (28,6%) e do suco de frutas natural (22,2%). Os locais do consumo de refrigerantes foram a casa (38,2%), seguida da escola (22,1%). O principal fator apontado para o consumo de refrigerantes foi o sabor (75,4%). CONCLUSÕES: O consumo de bebidas açucaradas foi frequente entre adolescentes, especialmente o refrigerante. Essas bebidas são disponíveis e consumidas tanto em casa como na escola e consideradas saborosas. Os programas de educação nutricional devem pensar em como priorizar o consumo de outras bebidas, além de controlar a comercialização de refrigerantes nas escolas, com o objetivo de estimular o consumo de bebidas mais saudáveis para essa faixa etária.

Propriedades físico-químicas e sensoriais de embutidos fermentados formulados com diferentes proporções de carne suína e de ovelhas de descarte

Avaliou-se a inclusão de diferentes níveis de carne de ovelhas de descarte (animais Texel × Ile de France com idade superior a seis anos) em relação à carne suína sobre a qualidade de embutidos fermentados do tipo salame. Os embutidos foram elaborados com 0, 15, 35, 55 ou 75% de carne da perna, paleta e pescoço das ovelhas, acrescidos de pernil suíno e 10% de toucinho suíno. A evolução do pH e da atividade de água (a w) foi avaliada nos dias zero, três, sete e 14 após o embutimento. Após a maturação dos salames, foram determinadas, ainda, a perda de peso, a qualidade microbiológica e as características sensoriais dos embutidos prontos. A inclusão de carne ovina na formulação não alterou a evolução do pH e a w. Entretanto, influenciou (P<0,05) os valores finais de pH, a w e a perda de peso. Os embutidos com carne ovina na formulação apresentaram valores de pH final inferiores àquele observado para o embutido elaborado somente com carne suína. Este último apresentou a w inferior e maior perda de peso, em comparação ao produto contendo 15% de carne ovina na formulação. Todas as formulações atenderam a legislação quanto à qualidade microbiológica. Na análise sensorial, o embutido elaborado com 15% de carne ovina foi considerado superior ao embutido elaborado somente com carne suína para os aspectos cor, sabor e textura; contudo, não diferiu dos demais embutidos elaborados com carne ovina. Assim, é possível elaborar embutido fermentado com até 75% de carne de ovelhas de descarte na formulação.

Fatores determinantes de consumo alimentar: por que os indivíduos comem o que comem?

Objetivo: O presente trabalho teve como objetivo realizar uma revisão de literatura sobre os fatores determinantes do consumo alimentar. Método: Foi realizada uma revisão de literatura em bases de dados, como Medline e na biblioteca da Faculdade de Saúde Pública daUniversidade de São Paulo (FSP-USP). Resultados: Foram criadas quatro categorias de fatores determinantes do consumo alimentar: biológica, econômica, oferta/disponibilidade dos alimentos e social. Entre os fatores biológicos, podem-se destacar as características sensoriais dos alimentos, principalmente o sabor, apontado como um dos principais determinantes. Na categoria econômica são incluídos a renda familiar, o preço dos alimentos e a escolaridade. A oferta e a disponibilidade dos alimentos abrangem as influências do meio ambiente na aquisição dos alimentos e quanto aos determinantes sociais estão relacionados à estrutura, dinâmica e influência da família. Pouco se conhece sobre os fatores que determinam as escolhas e o consumo alimentar dos brasileiros. É necessária a realização de mais estudos para conhecê-los

Effect of glutamate and inosinate on sensory and instrumental texture of extruded products

Expanded products have been developed by extrusion of non-conventional highly nutritious raw materials such as amaranth and chickpea blended with bovine lung. As sensory acceptance of these snacks is restricted, this study aimed at improving their texture, through the addition of monosodium glutamate (MSG) and disodium inosinate (IMP) flavor enhancers to the feeding material, or to the flavor added after the extrusion. Sensory and mechanical analyses showed that both enhancers affected texture, assessed by sensory and instrumental methods. Addition of IMP together with MSG to the chickpea-based snacks presented the best results. This beneficial effect was not observed in the amaranth-based snack, suggesting that IMP and MSG can favorably impact texture of extruded products depending on the amount and type of protein present

Measurement of neutrino oscillations with the MINOS detectors in the NuMI beam

This Letter reports new results from the MINOS experiment based on a two-year exposure to muon neutrinos from the Fermilab NuMI beam. Our data are consistent with quantum-mechanical oscillations of neutrino flavor with mass splitting vertical bar Delta m(2)vertical bar = (2.43 +/- 0.13) x 10(-3) eV(2) (68% C.L.) and mixing angle sin(2)(2 theta) > 0.90 (90% C.L.). Our data disfavor two alternative explanations for the disappearance of neutrinos in flight: namely, neutrino decays into lighter particles and quantum decoherence of neutrinos, at the 3.7 and 5.7 standard-deviation levels, respectively.

Probability currents and entropy production in nonequilibrium lattice systems

The structure of probability currents is studied for the dynamical network after consecutive contraction on two-state, nonequilibrium lattice systems. This procedure allows us to investigate the transition rates between configurations on small clusters and highlights some relevant effects of lattice symmetries on the elementary transitions that are responsible for entropy production. A method is suggested to estimate the entropy production for different levels of approximations (cluster sizes) as demonstrated in the two-dimensional contact process with mutation.

Lepton sector of a fourth generation

In extensions of the standard model with a heavy fourth generation, one important question is what makes the fourth-generation lepton sector, particularly the neutrinos, so different from the lighter three generations. We study this question in the context of models of electroweak symmetry breaking in warped extra dimensions, where the flavor hierarchy is generated by choosing the localization of the zero-mode fermions in the extra dimension. In this setup the Higgs sector is localized near the infrared brane, whereas the Majorana mass term is localized at the ultraviolet brane. As a result, light neutrinos are almost entirely Majorana particles, whereas the fourth-generation neutrino is mostly a Dirac fermion. We show that it is possible to obtain heavy fourth-generation leptons in regions of parameter space where the light neutrino masses and mixings are compatible with observation. We study the impact of these bounds, as well as the ones from lepton flavor violation, on the phenomenology of these models.

Aetherlike Lorentz-breaking actions

We show that CPT-even aetherlike Lorentz-breaking actions, for the scalar and electromagnetic fields, are generated via their appropriate Lorentz-breaking coupling to spinor fields, in three, four, and five space-time dimensions. Besides, we also show that aetherlike terms for the spinor field can be generated as a consequence of the same couplings. We discuss the dispersion relations in the theories with aetherlike Lorentz-breaking terms and find the tree-level effective (Breit) potential for fermion scattering and the one-loop effective potential corresponding to the action of the scalar field.

New strongly coupled sector at the Tevatron and the LHC

We examine the possibility that a new strong interaction is accessible to the Tevatron and the LHC. In an effective theory approach, we consider a scenario with a new color-octet interaction with strong couplings to the top quark, as well as the presence of a strongly coupled fourth generation which could be responsible for electroweak symmetry breaking. We apply several constraints, including the ones from flavor physics. We study the phenomenology of the resulting parameter space at the Tevatron, focusing on the forward-backward asymmetry in top pair production, as well as in the production of the fourth-generation quarks. We show that if the excess in the top production asymmetry is indeed the result of this new interaction, the Tevatron could see the first hints of the strongly coupled fourth-generation quarks. Finally, we show that the LHC with root s = 7 TeV and 1 fb(-1) integrated luminosity should observe the production of fourth-generation quarks at a level at least 1 order of magnitude above the QCD prediction for the production of these states.

Measurement of the Bottom Quark Contribution to Nonphotonic Electron Production in p plus p Collisions at root s=200 GeV

The contribution of B meson decays to nonphotonic electrons, which are mainly produced by the semileptonic decays of heavy-flavor mesons, in p + p collisions at root s = 200 GeV has been measured using azimuthal correlations between nonphotonic electrons and hadrons. The extracted B decay contribution is approximately 50% at a transverse momentum of p(T) >= 5 GeV/c. These measurements constrain the nuclear modification factor for electrons from B and D meson decays. The result indicates that B meson production in heavy ion collisions is also suppressed at high p(T).

Interpretation of MINOS data in terms of nonstandard neutrino interactions

The MINOS experiment at Fermilab has recently reported a tension between the oscillation results for neutrinos and antineutrinos. We show that this tension, if it persists, can be understood in the framework of nonstandard neutrino interactions (NSI). While neutral current NSI (nonstandard matter effects) are disfavored by atmospheric neutrinos, a new charged current coupling between tau neutrinos and nucleons can fit the MINOS data without violating other constraints. In particular, we show that loop-level contributions to flavor-violating tau decays are sufficiently suppressed. However, conflicts with existing bounds could arise once the effective theory considered here is embedded into a complete renormalizable model. We predict the future sensitivity of the T2K and NOvA experiments to the NSI parameter region favored by the MINOS fit, and show that both experiments are excellent tools to test the NSI interpretation of the MINOS data.

Spontaneous long and short-range ferroelectric ordering in Pb(0.55)La(0.30)TiO(3) ceramics

In this work, we investigated the temperature dependence of short and long-range ferroelectric ordering in Pb(0.55)La(0.30)TiO(3) relaxor composition. High-resolution x-ray powder diffraction measurements revealed a clear spontaneous macroscopic cubic-to-tetragonal phase transition in the PLT relaxor sample at similar to 60 K below the maximum of the dielectric constant peak (T(m)). Indeed, the x-ray diffraction (XRD) data showed that at 300 K (above T(m) but below the Burns temperature, T(B)) the long-range order structure corresponds to a macroscopic cubic symmetry, space group number 221 (Pm-3m), whereas the data collected at 20 K revealed a macroscopic tetragonal symmetry, space group number 99 (P4mm) with c/a=1.0078, that is comparable to that of a normal ferroelectric. These results show that for samples with tetragonal composition, the long-range ferroelectric order may be recovered spontaneously at cryogenics temperatures, in contrast to ferroelectric samples with rhombohedral symmetry. On the other hand, x-ray absorption spectroscopy investigations intriguingly revealed the existence of local tetragonal disorder around Ti atoms for temperatures far below T(m) and above T(B), for which the sample presents macroscopic tetragonal and cubic symmetries, respectively. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3431024]