The complex channel networks of bone structure

Bone structure in mammals involves a complex network of channels (Havers and Volkmann channels) required to nourish the bone marrow cells. This work describes how three-dimensional reconstructions of such systems can be obtained and represented in terms of complex networks. Three important findings are reported: (i) the fact that the channel branching density resembles a power law implies the existence of distribution hubs; (ii) the conditional node degree density indicates a clear tendency of connection between nodes with degrees 2 and 4; and (iii) the application of the recently introduced concept of hierarchical clustering coefficient allows the identification of typical scales of channel redistribution. A series of important biological insights is drawn and discussedComment: 3 pages, 1 figure, The following article has been submitted to Applied Physics Letters. If it is published, it will be found online at http://apl.aip.org

Gauge fields in a string-cigar braneworld

In this work we investigate the properties of an Abelian gauge vector field in a thin and in a smoothed string-like braneworld, the so-called string-cigar model. This thick brane scenario satisfies the regularity conditions and it can be regarded as an interior and exterior string-like solution. The source undergoes a geometric Ricci flow which is connected to a variation of the bulk cosmological constant. The Ricci flow changes the width and amplitude of the massless mode at the brane core and recover the usual thin string-like behavior at large distances. By numerical means we obtain the Kaluza-Klein (KK) spectrum for both the thin brane and the string-cigar. It turns out that both models exhibit a mass gap between the massless and the massive modes and between the high and the low mass regimes. The KK modes are smooth near the brane and their amplitude are enhanced by the string-cigar core. The analogue Schr\"odinger potential is also tuned by the geometric flow.Comment: The discussion about the Kaluza-Klein spectrum of the gauge field was improved. Numerical analysis was adapted to the conventional notation on Kaluza-Klein number. Some graphics were modified for considering other notation. Results unchanged. References added. Corrected typos. 17 pages. 6 figures. To match version to appears in Physics Letters

Critical Behavior of a Three-State Potts Model on a Voronoi Lattice

We use the single-histogram technique to study the critical behavior of the three-state Potts model on a (random) Voronoi-Delaunay lattice with size ranging from 250 to 8000 sites. We consider the effect of an exponential decay of the interactions with the distance,$J(r)=J_0\exp(-ar)$, with $a>0$, and observe that this system seems to have critical exponents $\gamma$ and $\nu$ which are different from the respective exponents of the three-state Potts model on a regular square lattice. However, the ratio $\gamma/\nu$ remains essentially the same. We find numerical evidences (although not conclusive, due to the small range of system size) that the specific heat on this random system behaves as a power-law for $a=0$ and as a logarithmic divergence for $a=0.5$ and $a=1.0$Comment: 3 pages, 5 figure

Majority-Vote Model on a Random Lattice

The stationary critical properties of the isotropic majority vote model on random lattices with quenched connectivity disorder are calculated by using Monte Carlo simulations and finite size analysis. The critical exponents $\gamma$ and $\beta$ are found to be different from those of the Ising and majority vote on the square lattice model and the critical noise parameter is found to be $q_{c}=0.117\pm0.005$.Comment: 4 pages, 6 figure

Análise de um projeto político pedagógico implementado em Belém do Pará

O presente estudo aborda o tema Projeto Político Pedagógico e tem como meta compreender a estrutura teórica de um projeto, fazendo um paralelo com o que de fato acontece na prática dentro de uma escola privada que já possui o seu PPP estruturado. Procuramos conhecer e analisar como ocorreu a elaboração do Projeto Político Pedagógico, assim como identificar as percepções dos educadores, as implicações e eventuais contradições entre o que é exigido por lei e o real das escolas e confrontar o PPP como instrumento norteador do fazer pedagógico e analisar se os objetivos postos são alcançados. Visamos a análise de um exemplo do que acontece nas instituições de ensino, servindo como guia para uma melhor prática educacional. A vertente empírica do estudo, para além da análise bibliográfica, contou com um importante corpus de dados qualitativos, recolhidos por meio de entrevistas individuais semiestruturadas, baseadas em um guião devidamente validado. A análise feita dos depoimentos das participantes do estudo sugere que o Projeto Político Pedagógico constitui para elas um núcleo de desenvolvimento das ações, assim como referência para eventuais dúvidas, para uma escola. Porém, demonstraram insatisfação de não terem mais detalhamento sobre o projeto por parte da gestão, mas acreditam que apesar de não se ter feito uma divulgação maior, conseguem manter os objetivos comuns. Contudo, consideram necessário reavaliar, assim como ouvir cada setor antes de reestruturar um novo documento; ABSTRACT: This research approaches the topic Political-Pedagogic Project (PPP) and it aims to comprehend the theoretical framework of a project, drawing a parallel with what actually happens in a private school which already has its own structured PPP. With this work, we seek to know and examine how the elaboration of the Political-Pedagogic Project occurred, as well as to identify the perceptions of educators, its implications and possible contradictions between what is required by law and the school reality and also view the PPP as a guiding tool for the school guidelines and examine whether the goals proposed are achieved. We aim mainly to explore an example of what happens in educational institutions and a guide to a better educational practice. The empirical aspects of the study, in addition to the bibliographic analysis, had an important corpus of qualitative data collected through semi-structured individual interviews, based on a script properly validated. The analysis of the testimonies of the study participants suggests that the Political-Pedagogic Project constituted for them the center of development actions, as well as a reference for possible doubts for a school. They demonstrated, however, disappointment since they have no access to the details of the project, but they believe that although there is no greater disclosure, they have managed to maintain the common goals. However, they need to review, as well as listen to each school sector before they restructure a new document