Transition amplitude, partition function and the role of physical degrees of freedom in gauge theories

This work explores the quantum dynamics of the interaction between scalar (matter) and vectorial (intermediate) particles and studies their thermodynamic equilibrium in the grand-canonical ensemble. The aim of the article is to clarify the connection between the physical degrees of freedom of a theory in both the quantization process and the description of the thermodynamic equilibrium, in which we see an intimate connection between physical degrees of freedom, Gibbs free energy and the equipartition theorem. We have split the work into two sections. First, we analyze the quantum interaction in the context of the generalized scalar Duffin-Kemmer-Petiau quantum electrodynamics (GSDKP) by using the functional formalism. We build the Hamiltonian structure following the Dirac methodology, apply the Faddeev-Senjanovic procedure to obtain the transition amplitude in the generalized Coulomb gauge and, finally, use the Faddeev-Popov-DeWitt method to write the amplitude in covariant form in the no-mixing gauge. Subsequently, we exclusively use the Matsubara-Fradkin (MF) formalism in order to describe fields in thermodynamical equilibrium. The corresponding equations in thermodynamic equilibrium for the scalar, vectorial and ghost sectors are explicitly constructed from which the extraction of the partition function is straightforward. It is in the construction of the vectorial sector that the emergence and importance of the ghost fields are revealed: they eliminate the extra non-physical degrees of freedom of the vectorial sector thus maintaining the physical degrees of freedom

The "glass transition'' as a topological defect driven transition in a distribution of crystals and a prediction of a universal viscosity collapse

Topological defects are typically quantified relative to ordered backgrounds. The importance of these defects to the understanding of physical phenomena including diverse equilibrium melting transitions from low temperature ordered to higher temperatures disordered systems (and vice versa) can hardly be overstated. Amorphous materials such as glasses seem to constitute a fundamental challenge to this paradigm. A long held dogma is that transitions into and out of an amorphous glassy state are distinctly different from typical equilibrium phase transitions and must call for radically different concepts. In this work, we critique this belief. We examine systems that may be viewed as simultaneous distribution of different ordinary equilibrium structures. In particular, we focus on the analogs of melting (or freezing) transitions in such distributed systems. The theory that we arrive at yields dynamical, structural, and thermodynamic behaviors of glasses and supercooled fluids that, for the properties tested thus far, are in qualitative and quantitative agreement with experiment. We arrive at a prediction for the viscosity and dielectric relaxations that is universally satisfied for all experimentally measured supercooled liquids and glasses over 15 decades.Comment: 21 pages, 2 figure

Prevalence of Pre-Obesity/Obesity in Pre and Basic School Children at Vila Nova de Gaia, Portugal

Introduction: Over 30% of Portuguese children present overweight. Being a serious public health problem with multiple causes, only a cross-sectorial and concerted action could contribute to their resolution. Municipalities have a set of skills that make them ideal for effective intervention in the fight against this problem. For this action to be effective there must be a local assessment of the extent of the problem and their spatial distribution. The aim of this study was to characterize, from the point of view of the prevalence of overweight, the population of pre-school and first cycle basic education under the responsibility of the municipality of Vila Nova de Gaia, the third most populous municipality in the country. Material and Methods: Were evaluated 8 974 pre and basic-school children, in school year 2013/14. The assessment of the nutritional status of the sample was made using anthropometric measures height and weight. In the classification of nutritional status was considered z-scores or percentiles of body mass index for age according to the World Health Organization, Centers for Disease Control and Prevention and International Obesity Task Force. Results: The prevalence of overweight by the World Health Organization requirements was 37.4%. There were some disparities in the distribution of overweight in schools of the municipality. Discussion: The results were slightly higher than those of other national and international studies, being the sampling size the possible justification for the differences founded. Conclusion: The prevalence found is high and with irregular geographical distribution, which could help identifying the main causes of the problem at the local level

Co-limitation of phytoplankton by N and P in a shallow coastal lagoon (Ria Formosa): implications for eutrophication evaluation

The Ria Formosa coastal lagoon is a highly productive shallow ecosystem in southern Portugal, subjected to nutrient inputs from anthropogenic and natural sources. Nutrients are major abiotic drivers of phytoplankton in this system, but their effects on phytoplankton assemblages and the occurrence of nutrient limitation are still poorly understood. The main goal of this study was, thus, to evaluate the occurrence, type, and effects of nutrient limitation on phytoplankton community and specific functional groups in the Ria Formosa coastal lagoon. We conducted nutrient enrichment experiments with factorial additions of nitrogen (N) and phosphorus (P) using natural phytoplankton assemblages from distinct locations in the Ria Formosa, throughout a yearly cycle. Phytoplankton composition and abundance were evaluated using inverted and epifluorescence microscopies, and spectrophotometric methods were used for biomass. Limitation was defined as higher phytoplankton growth following enrichment with a particular nutrient in relation to the non-enriched control. The most common type of phytoplankton limitation was simultaneous co-limitation by N and P; diatoms, as r-strategists, were the most frequently limited group. Single N and P limitation, and serial P limitation were also observed, as well as negative responses to nutrient enrichment. Group-specific responses to nutrient enrichment were not reflected in the relative abundance of phytoplankton groups within the whole assemblage, due to the numerical dominance of pico-sized groups (cyanobacteria and eukaryotic picophytoplankton). Ambient nutrient ratios and concentrations did not predict phytoplankton nutrient limitation, given the different nutrient utilisation traits among phytoplankton functional groups. Therefore, nutrient ratios should not be used as indicators of nutrient limitation in eutrophication assessment.LA/P/0069/2020info:eu-repo/semantics/publishedVersio

Mechanical characterization of the Amazonian Pomacea dolioides (Reeve, 1856) shell

We investigated the mechanical behavior of freshwater mollusk shells, Pomacea dolioides, collected from a floodplain area located in Amazonas, Brazil. With the purpose of characterizing the mechanical properties of the shells, bending, hardness and roughness tests were carried out. To determine the shell flexural strength, a new methodology was proposed for the calculation of it, considering the curved geometry of the specimens taken from the shells. It was also described the mechanical properties as a function of shell position and thickness, variation of the surface hardness along the shell and the low level of superficial irregularity in the inner layer of the shells. Shell presented a mean flexural rupture modulus (MOR) of 128.0 MPa, Rockwell HR15N hardness = 50 ± 8.3 and a low level of irregularities in the inner layer, roughness Ra = 0.160 μm.Investigamos el comportamiento mecánico de las conchas de moluscos de agua dulce, Pomacea dolioides, recolectados en un área de llanuras aluviales en Amazonas, Brasil. Con el fin de caracterizar las propiedades mecánicas de éstas, se utilizaron ensayos de flexión, dureza y rugosidad. Para determinar la resistencia a la flexión del material, se propuso una nueva metodología para el cálculo de la resistencia a la flexión, considerando la geometría curva de los cuerpos de prueba retirados de las conchas. También se describieron las propiedades mecánicas analizados en función de la posición y de la espesura de la concha, la variación de la superficie de la rigidez con el concha y el nivel bajo de irregularidad superficial en la superficie interna de las conchas. La concha presentó el Módulo de Ruptura a la Flexión (MOR) medio de 128.0 MPa, dureza superficial Rockwell HR15N = 50 ± 8.3 y un bajo nivel de irregularidades en la capa interna, con rugosidad Ra = 0.160 μm