Weinberg power counting and the quark determinant at small chemical potential

We construct an effective action for QCD by expanding the quark determinant in powers of the chemical potential at finite temperature in the case of massless quarks. To cut the infinite series we adopt the Weinberg power counting criteria. We compute the minimal effective action (~p^4), expanding in the external momentum, which implies the use of the hard thermal loop approximation. Our main result is a gauge invariant expression for the phase theta of the functional determinant in QCD, and recovers dimensional reduction in the high-temperature limit. We compute, analytically, in the range of p << 2 pi T, including perturbative and nonperturbative contributions, the latter treated within the mean field approximation. Implications for lattice simulations are briefly discussed.Comment: 5 pages, 2 figures. v2: title changed, expanded discussion and added example (calculation of at high temperature). Published in PR

Mass and chemical asymmetry in QCD matter

We consider two-flavor asymmetric QCD combined with a low-energy effective model inspired by chiral perturbation theory and lattice data to investigate the effects of masses, isospin and baryon number on the pressure and the deconfinement phase transition. Remarkable agreement with lattice results is found for the critical temperature behavior. Further analyses of the cold, dense case and the influence of quark mass asymmetry are also presented.Comment: 4 pages, 4 figures; to appear in the Proceedings of Strong and Electroweak Matter 2008 (SEWM08), August 26-29, Amsterdam, The Netherland

Treatment of bimodality in proficiency test of pH in bioethanol matrix

The pH value in bioethanol is a quality control parameter related to its acidity and to the corrosiveness of vehicle engines when it is used as fuel. In order to verify the comparability and reliability of the measurement of pH in bioethanol matrix among some experienced chemical laboratories, reference material (RM) of bioethanol developed by Inmetro - the Brazilian National Metrology Institute - was used in a proficiency testing (PT) scheme. There was a difference of more than one unit in the value of the pH measured due to the type of internal filling electrolytic solutions (potassium chloride, KCl or lithium chloride, LiCl) from the commercial pH combination electrodes used by the participant laboratories. Therefore, bimodal distribution has occurred from the data of this PT scheme. This work aims to present the possibilities that a PT scheme provider can use to overcome the bimodality problem. Data from the PT of pH in bioethanol were treated by two different statistical approaches: kernel density model and the mixture of distributions. Application of these statistical treatments improved the initial diagnoses of PT provider, by solving bimodality problem and contributing for a better performance evaluation in measuring pH of bioethanol.Comment: 20 pages, 6 figures, Accepted for publication in Accreditation and Quality Assurance (ACQUAL

Role of “mate tea” extracts modulating DNA methylation: in vitro studies for future significances for human health

It is known that a healthy and balanced diet is essential for maintaining a state of good health of the individual, and that the onset of many diseases is related to inadequate nutrition. Many small molecules contained in foods (Food Small Molecules, SFMs) have the ability to influence the functioning of many cellular metabolic pathways. The term nutrigenomics, in fact, refers to an emerging branch of genetics and biochemistry which has the aim of identifying how the nutrients can determine the innate risk of developing diseases (diabetes, obesity, cardiovascular disease and some cancers). In addition, with the help of epigenetics, it is possible to further understand how the SFMs act on DNA, influencing gene expression and, perhaps its transmission to the future generations. Today it is known, in fact, that the gene expression depends not only from the primary sequence of its promoter, but also from the local chromatin status: the methylation of cytosine in a DNA is one among the most studied mechanisms of chromatin remodeling and, thus, of regulation of gene expression. Recently was reported that plant derived SFMs, can act as epigenetic modulators. For example, epigallocatechin gallate and indicaxanthin, flavonoids present in green tea and Opuntia Ficus Indica, respectively, are, for these reasons, in process to be labelled as anticancer agents. It is known that drinks made from "Mate tea", highly consumed in Argentina, as well as in other South American countries, may provide important health effects. This project is aimed to investigate whether "Mate tea" extracts and components, given to cultured cell lines may act as a modulator of DNA methylation. If this epigenetic action can be proved, it could promote the consumption of Mate tea – based beverages as precise nutritional strategy to prevent disease, as well as identify the component(s) that could have pharmacological property

Quantum statistical correlations in thermal field theories: boundary effective theory

We show that the one-loop effective action at finite temperature for a scalar field with quartic interaction has the same renormalized expression as at zero temperature if written in terms of a certain classical field $\phi_c$, and if we trade free propagators at zero temperature for their finite-temperature counterparts. The result follows if we write the partition function as an integral over field eigenstates (boundary fields) of the density matrix element in the functional Schr\"{o}dinger field-representation, and perform a semiclassical expansion in two steps: first, we integrate around the saddle-point for fixed boundary fields, which is the classical field $\phi_c$, a functional of the boundary fields; then, we perform a saddle-point integration over the boundary fields, whose correlations characterize the thermal properties of the system. This procedure provides a dimensionally-reduced effective theory for the thermal system. We calculate the two-point correlation as an example.Comment: 13 pages, 1 figur

Uniform semiclassical approximation in quantum statistical mechanics

We present a simple method to deal with caustics in the semiclassical approximation to the partition function of a one-dimensional quantum system. The procedure, which makes use of complex trajectories, is applied to the quartic double-well potential.Comment: 5 pages, 1 figure, Latex. Contribution to the Proceedings of the XXI Brazilian National Meeting on Particles and Fields (Sao Lourenco, October 23-27, 2000