Axiomatization and Models of Scientific Theories

In this paper we discuss two approaches to the axiomatization of scien- tific theories in the context of the so called semantic approach, according to which (roughly) a theory can be seen as a class of models. The two approaches are associated respectively to Suppes’ and to da Costa and Chuaqui’s works. We argue that theories can be developed both in a way more akin to the usual mathematical practice (Suppes), in an informal set theoretical environment, writing the set theoretical predicate in the language of set theory itself or, more rigorously (da Costa and Chuaqui), by employing formal languages that help us in writing the postulates to define a class of structures. Both approaches are called internal, for we work within a mathematical framework, here taken to be first-order ZFC. We contrast these approaches with an external one, here discussed briefly. We argue that each one has its strong and weak points, whose discussion is relevant for the philosophical foundations of science

An exact master equation for the system-reservoir dynamics under the strong coupling regime and non-Markovian dynamics

In this paper we present a method to derive an exact master equation for a bosonic system coupled to a set of other bosonic systems, which plays the role of the reservoir, under the strong coupling regime, i.e., without resorting to either the rotating-wave or secular approximations. Working with phase-space distribution functions, we verify that the dynamics are separated in the evolution of its center, which follows classical mechanics, and its shape, which becomes distorted. This is the generalization of a result by Glauber, who stated that coherent states remain coherent under certain circumstances, specifically when the rotating-wave approximation and a zero-temperature reservoir are used. We show that the counter-rotating terms generate fluctuations that distort the vacuum state, much the same as thermal fluctuations.Finally, we discuss conditions for non-Markovian dynamics

Biochemical parameters for Piaractus mesopotamicus, Colossoma macropomum (Characidae) and hybrid tambacu (P. mesopotamicus X C. macropomum).

Estudaram-se os valores de glicose plasmática, proteína total sérica e íons séricos (cálcio, potássio, magnésio, sódio e cloreto) em jovens de Colossomoma macropomum Cuvier 1818, Piaractus mesopotamicus Holmberg 1887 e híbrido tambacu (P. mesopotamicus x C. macropomum), mantidos em cultivo intensivo. As concentrações plasmáticas de glicose no híbrido tambacu foram maiores que em P. mesopotamicus e C. macropomum. Os níveis de proteínas totais em P. mesopotamicus foram maiores em C. macropomum e híbrido tambacu. O C. macropomum apresentou maior concentração de sódio e cloreto, ao passo que o P. mesopotamicus mostrou maior concentração de potássio e magnésio. Porém, os níveis de cálcio mostraram-se similares nas três espécies estudadas. O híbrido tambacu apresentou os menores níveis de proteínas totais e níveis intermediários de potássio, sódio, magnésio e cloreto quando comparado ao P. mesopotamicus e C. macropomum. Foram estabelecidos valores basais para peixes sadios criados em cativeiro, os quais poderão ser usados em estudos de comparação futura em populações selvagens de P. mesopotamicus e C. macropomum

Visibility graphs of critical and non-critical time series for absorbing state phase transitions

It is possible to describe many real systems using time-ordered data. However, classical time series analysis is usually conditioned by data accuracy and quantity. A modern method is to map time series onto graphs and study these structures using the toolbox available in complex network analysis. An important practical problem to investigate the criticality in experimental systems is to determine whether an observed time series is associated with a critical phenomenon or not. We contribute to this problem by investigating the mapping called visibility graph (VG) of time series generated in dynamical processes with absorbing-state phase transitions. Analyzing degree correlation patterns of the VGs, we were able to distinguish between critical and non-critical regimes. One central hallmark is an asymptotic disassortative correlation on the degree for series near the critical regime in contrast with a pure assortative correlation observed for non-critical dynamics. We were also able to distinguish between continuous and discontinuous absorbing state phase transitions, which are commonly involved in catastrophic phenomena. The determination of critical behavior converges very quickly in higher dimensions, where many complex system dynamics are relevant.Comment: 9 pages, 8 figure

Transcriptional co-expression and co-regulation of genes coding for components of the oxidative phosphorylation system

<p>Abstract</p> <p>Background</p> <p>The mitochondrial oxidative phosphorylation (OXPHOS) is critical for energy (ATP) production in eukaryotic cells. It was previously shown that genes coding for mitochondrial proteins involved in energy production co-express at the RNA level. Because the OXPHOS enzymes are multimeric complexes, we tested the hypothesis that genes coding for components of specific complexes are also co-regulated at the transcriptional level, and share common regulatory elements in their promoters.</p> <p>Results</p> <p>We observed for the first time that, not only OXPHOS genes as a group co-express, but there is a co-expression of genes within each of the five OXPHOS enzyme complexes, showing a higher degree of complexity in gene co-regulation. <it>In silico </it>analysis of homologous promoter sequences in mammals identified the likely core promoter elements for most genes encoding OXPHOS subunits/assembly factors. The results included a significant abundance of previously identified sites (e.g. NRF1, NRF2, ERRA and YY1), as well as several sites that had not been previously detected. Although we identified patterns that correlated to OXPHOS gene expression, we did not detect an OXPHOS complex-specific arrangement of transcription factor binding sites within the core promoter that could explain the tight co-expression of these functionally related genes.</p> <p>Conclusion</p> <p>This study mapped the core promoters of most OXPHOS related genes and provided an example of gene expression regulation based on the final protein arrangement within a linear metabolic pathway.</p

Enraizamento de estacas de mangostão com diferentes concentrações de auxinas.

Ensaio para verificar a possibilidade de obtencao de estacas enraizadas de mangostao sob nebulizacao intermitente de auxinas. Os resultados preliminares indicam a possibilidade de obtencao de mudas de estacas enraizadas de mangostao, embora haja necessidade de ensaios mais elaborados, onde serao estudados os tipos de estacas, epocas e dosagens de fitormonios. Mesmo obtendo-se taxas de enraizamento nao muito altas, o tamanho da muda obtida pelo tratamento com fitormonio equivale a uma muda de um ano proveniente de sementes apomiticas, o que valida os resultados obtidos e corrobora com a continuidade da pesquisa.bitstream/item/89231/1/PA-35.pd

Defects in the biosynthesis of mitochondrial heme c and heme a in yeast and mammals

AbstractDefects in heme biosynthesis have been associated with a large number of diseases, but mostly recognized in porphyrias, which are neurovisceral or cutaneous disorders caused by the accumulation of biosynthetic intermediates. However, defects in the maturation of heme groups that are part of the oxidative phosphorylation system are now also recognized as important causes of disease. The electron transport chain contains heme groups of the types a, b and c, all of which are directly involved in electron transfer reactions. In this article, we review the effect of mutations in enzymes involved in the maturation of heme a (the prosthetic group of cytochrome c oxidase) and heme c (the prosthetic group of cytochrome c) both in yeast and in humans. COX10 and COX15 are two genes, initially identified in Saccharomyces cerevisiae that have been found to cause infantile cytochrome c oxidase deficiency in humans. They participate in the farnesylation and hydroxylation of heme b, steps that are necessary for the formation of heme a, the prosthetic group required for cytochrome oxidase assembly and activity. Deletion of the cytochrome c heme lyase gene in a single allele has also been associated with a human disease, known as Microphthalmia with Linear Skin defects (MLS) syndrome. The cytochrome c heme lyase is necessary to covalently attach the heme group to the apocytochrome c polypeptide. The production of mouse models recapitulating these diseases is providing novel information on the pathogenesis of clinical syndromes