A note on the phase transition in a topologically massive Ginzburg-Landau theory

We consider the phase transition in a model which consists of a Ginzburg-Landau free energy for superconductors including a Chern-Simons term. The mean field theory of Halperin, Lubensky and Ma [Phys. Rev. Lett. 32, 292 (1974)] is applied for this model. It is found that the topological mass, $\theta$, drives the system into different regimes of phase transition. For instance, there is a $\theta_{c}$ such that for $\theta<\theta_{c}$ a fluctuation induced first order phase transition occurs. On the other hand, for $\theta>\theta_{c}$ only the second order phase transition exists. The 1-loop renormalization group analysis gives further insight to this picture. The fixed point structure exhibits tricritical and second order fixed points.Comment: Revised version; uses a more physical parametrization of the renormalization group equations; new references added; one figure added; EuroLatex, 6 page

A non-perturbative approach to the Coleman- Weinberg mechanism in massless scalar QED

We rederive non-perturbatively the Coleman-Weinberg expression for the effective potential for massless scalar QED. Our result is not restricted to small values of the coupling constants. This shows that the Coleman- Weinberg result can be established beyond the range of validity of perturbation theory. Also, we derive it in a manifestly renormalization group invariant way. It is shown that with the derivation given no Landau ghost singularity arises. The finite temperature case is discussed. Pacs number: 11.10.Ef,11.10.Gh

Influência do solo de monocultura florestal e de área aberta no desenvolvimento de espécies arbóreas nativas.

Avaliou-se o desenvolvimento de Tapirira guianensis Aubl. (Anacardiaceae) em área de cerrado degradada e em sub-bosque de uma monocultura florestal de Pinus. As melhores condições do solo do sub-bosque de Pinus, principalmente maior acúmulo de matéria orgânica, possibilitaram um ambiente mais propício para o desenvolvimento inicial e sobrevivência da espécie. Este estudo contribui para investigar a possibilidade de usarem-se monoculturas florestais exóticas juntamente com espécies florestais nativas para a recomposição da Reserva Legal Florestal seguindo as recomendações para o Estado de São Paulo pelo Decreto nº 53.939, sancionado no ano de 2009

The superconducting phase transition and gauge dependence

The gauge dependence of the renormalization group functions of the Ginzburg-Landau model is investigated. The analysis is done by means of the Ward-Takahashi identities. After defining the local superconducting order parameter, it is shown that its exponent $\beta$ is in fact gauge independent. This happens because in $d=3$ the Landau gauge is the only gauge having a physical meaning, a property not shared by the four-dimensional model where any gauge choice is possible. The analysis is done in both the context of the $\epsilon$-expansion and in the fixed dimension approach. It is pointed out the differences that arise in both of these approaches concerning the gauge dependence.Comment: RevTex, 3 pages, no figures; accepted for publication in PRB; this paper is a short version of cond-mat/990527

Stability of casein micelles cross-linked with genipin: a physicochemical study as a function of pH

Chemical or enzymatic cross-linking of casein micelles (CMs) increases their stability against dissociating agents. In this paper, a comparative study of stability between native CMs and CMs cross-linked with genipin (CMs-GP) as a function of pH is described. Stability to temperature and ethanol were investigated in the pH range 2.0-7.0. The size and the charge ($\zeta$-potential) of the particles were determined by dynamic light scattering. Native CMs precipitated below pH 5.5, CMs-GP precipitated from pH 3.5 to 4.5, whereas no precipitation was observed at pH 2.0-3.0 or pH 4.5-7.0. The isoelectric point of CMs-GP was determined to be pH 3.7. Highest stability against heat and ethanol was observed for CMs-GP at pH 2, where visible coagulation was determined only after 800 s at 140 $^\circ$C or 87.5% (v/v) of ethanol. These results confirmed the hypothesis that cross-linking by GP increased the stability of CMs.Comment: 5 pages, 2 figures, International Dairy Journal, 201

Gauge dependenceof the order parameter anomalous dimension in the Ginzburg-Landau model and the critical fluctuations in superconductors

The critical fluctuations of superconductors are discussed in a fixed dimension scaling suited to describe the type II regime. The gauge dependence of the anomalous dimension of the scalar field is stablished exactly from the Ward-Takahashi identities. Its fixed point value gives the $\eta$ critical exponent and it is shown that $\eta$ is gauge independent, as expected on physical grounds. In the scaling considered, $\eta$ is found to be zero at 1-loop order, while $\nu\approx 0.63$. This result is just the 1-loop values for the XY model obtained in the fixed dimension renormalization group approach. It is shown that this XY behavior holds at all orders. The result $\eta=\eta_{XY}$ should be contrasted with the negative values frequently reported in the literature.Comment: EuroLaTex, 7 pages, 2 figures, reference updated; version to be published in Europhysics Letter

A importância da Comissão de Proteção contra Radiações no contexto da qualidade do Centro Hospitalar do Porto

Os meios complementares de diagnóstico e terapêutica transformaram-se em ferramentas essenciais para todos os ramos e especialidades da Medicina. Devido às suas propriedades únicas, a radiação ionizante apresenta múltiplas aplicações terapêuticas. Contudo, pode também originar potenciais danos para os utilizadores e para os pacientes. A quantificação da dose de radiação nos pacientes e o tempo de exposição dos procedimentos são uma preocupação crescente dos utilizadores. Este trabalho tem como objetivo apresentar a importância da Comissão de Proteção contra Radiações (CPCR) no contexto da qualidade do Centro Hospitalar do Porto (CHP). A CPCR detém múltiplas atividades, estando, atualmente, as suas sinergias direcionadas para a normalização do registo de dose no processo clínico dos pacientes e para a notificação, pelos Técnicos de Radiologia, dos eventos radiológicos contemplados nas normas pré--estabelecidas pela Comissão. A atribuição à CPCR da competência de identificação, acompanhamento e avaliação das exposições dos doentes a procedimentos específicos com radiação tem contribuído para reforçar a sensibilização dos profissionais para os valores de dose e os seus efeitos. A implementação dos procedimentos da Comissão permite assegurar um melhor acompanhamento dos doentes em risco, uma maior acuidade na monitorização das doses e uma otimização de protocolos.info:eu-repo/semantics/publishedVersio