Functional centrality in graphs

In this paper we introduce the functional centrality as a generalization of the subgraph centrality. We propose a general method for characterizing nodes in the graph according to the number of closed walks starting and ending at the node. Closed walks are appropriately weighted according to the topological features that we need to measure

Apendicitis aguda en gestante: Un Reporte de Caso: Acute appendicitis in pregnant women: A Case Report

Acute appendicitis is the most common pathology from acute abdomen during pregnancy, which hasa difficult diagnosis because of the physiological changes during pregnancy which results in confusingclinical presentations. We reported the case of a multiparous woman of 27 years with 22 3/7 weeksdiagnosed with acute appendicitis, undergoing surgery without complications and with a necrosedappendix that was evidenced through pathological examination. It is important to emphasis the roleof the anamnesis with the physical examination guided by the physiological pregnancy changesrelated to the appendix. A timely diagnosis and treatment with an interdisciplinary approach wouldsignificantly reduce the maternal-fetal risks related to this pathology, the appendix removal and thecontinuation of the pregnancy.La apendicitis aguda es una patología de Abdomen Agudo Quirúrgico (AAQ) frecuente en el embarazo, siendo de difícil diagnóstico debido a los cambios fisiológicos del embarazo que ocasionan cuadros clínicos confusos. Reportamos el caso de una gran multigesta de 27 años de 22 semanas 3/7 en el cual se diagnosticó clínicamente apendicitis aguda, siendo intervenida quirúrgicamente sin complicaciones, encontrándose un apéndice necrosado corroborado posteriormente con anatomía patológica. Es importante enfatizar el rol de la anamnesis dirigida aunado al examen clínico orientado por los cambios fisiológicos del embarazo. Un diagnóstico oportuno junto al manejo interdisciplinario permitirá reducir significativamente los riesgos materno-fetales relacionados a esta patología, y tanto la extirpación del apéndice como la continuación del embarazo

Enhancing the spectral gap of networks by node removal

Dynamics on networks are often characterized by the second smallest eigenvalue of the Laplacian matrix of the network, which is called the spectral gap. Examples include the threshold coupling strength for synchronization and the relaxation time of a random walk. A large spectral gap is usually associated with high network performance, such as facilitated synchronization and rapid convergence. In this study, we seek to enhance the spectral gap of undirected and unweighted networks by removing nodes because, practically, the removal of nodes often costs less than the addition of nodes, addition of links, and rewiring of links. In particular, we develop a perturbative method to achieve this goal. The proposed method realizes better performance than other heuristic methods on various model and real networks. The spectral gap increases as we remove up to half the nodes in most of these networks.Comment: 5 figure

Quantum transport on small-world networks: A continuous-time quantum walk approach

We consider the quantum mechanical transport of (coherent) excitons on small-world networks (SWN). The SWN are build from a one-dimensional ring of N nodes by randomly introducing B additional bonds between them. The exciton dynamics is modeled by continuous-time quantum walks and we evaluate numerically the ensemble averaged transition probability to reach any node of the network from the initially excited one. For sufficiently large B we find that the quantum mechanical transport through the SWN is, first, very fast, given that the limiting value of the transition probability is reached very quickly; second, that the transport does not lead to equipartition, given that on average the exciton is most likely to be found at the initial node.Comment: 8 pages, 8 figures (high quality figures available upon request

Spectral analysis of deformed random networks

We study spectral behavior of sparsely connected random networks under the random matrix framework. Sub-networks without any connection among them form a network having perfect community structure. As connections among the sub-networks are introduced, the spacing distribution shows a transition from the Poisson statistics to the Gaussian orthogonal ensemble statistics of random matrix theory. The eigenvalue density distribution shows a transition to the Wigner's semicircular behavior for a completely deformed network. The range for which spectral rigidity, measured by the Dyson-Mehta $\Delta_3$ statistics, follows the Gaussian orthogonal ensemble statistics depends upon the deformation of the network from the perfect community structure. The spacing distribution is particularly useful to track very slight deformations of the network from a perfect community structure, whereas the density distribution and the $\Delta_3$ statistics remain identical to the undeformed network. On the other hand the $\Delta_3$ statistics is useful for the larger deformation strengths. Finally, we analyze the spectrum of a protein-protein interaction network for Helicobacter, and compare the spectral behavior with those of the model networks.Comment: accepted for publication in Phys. Rev. E (replaced with the final version

Spectral Measures of Bipartivity in Complex Networks

We introduce a quantitative measure of network bipartivity as a proportion of even to total number of closed walks in the network. Spectral graph theory is used to quantify how close to bipartite a network is and the extent to which individual nodes and edges contribute to the global network bipartivity. It is shown that the bipartivity characterizes the network structure and can be related to the efficiency of semantic or communication networks, trophic interactions in food webs, construction principles in metabolic networks, or communities in social networks.Comment: 16 pages, 1 figure, 1 tabl

Asymptotic charges in 3d gravity with torsion

We discuss some new developments in three-dimensional gravity with torsion, based on Riemann-Cartan geometry. Using the canonical approach, we study the structure of asymptotic symmetry, clarify its fundamental role in defining the gravitational conserved charges, and explore the influence of the asymptotic structure on the black hole entropy.Comment: 6 pages, LATEX file (+jpconf.cls,jpconf11.clo), Talk presented at Constrained Dynamics and Quantum Gravity 05, Cala Gonone (Sardinia, Italy), September 12-16, 200

Testing the toughness of polypropylene filled with glass powder

Svrha rada je da se polimerni otpad prikaže kao sirovina ili na drugi način iskoristljiv materijal dobijen djelimičnim razdvajanjem komunalnog otpada. U radu je obrađena mogućnost ponovne upotrebe polipropilena recikliranjem uz dodatak staklenog praha, sa stanovišta žilavosti usljed udarnog opterećenja. Ispitivane su standardne epruvete, napravljene od osnovnog materijala - polipropilena i uz dodatak 0%, 5%, 10%, 15%, 20%, 25% i 30% staklenog praha granulacije manje od 0,5 mm, kroz šest ciklusa prerade. Izmjerene vrijednosti dale su mogućnost formiranja obrazaca promjene žilavosti posmatranog materijala sa različitim sadržajem stranog tijela, kroz cikluse prerade, što može pomoći u daljim istraživanjima i analizama.The purpose of this paper is to show polymer waste as a raw material or otherwise usable material derived from a partial separation of communal waste. This paper describes the possibilities of polypropylene re-use through recycling with addition of glass powder, from the point of view of toughness caused by impact load. Standard test specimens, made of basic material - polypropylene, with addition of 0%, 5%, 10%, 15%, 20%, 25% and 30% of glass powder with granulation less than 0,5 mm, have been tested through six processing cycles. The measured values gave a possibility of forming patterns for changes of the observed material with different content of additives, through processing cycles, which can be helpful in further research and analysis

On a new conformal functional for simplicial surfaces

We introduce a smooth quadratic conformal functional and its weighted version $$W_2=\sum_e \beta^2(e)\quad W_{2,w}=\sum_e (n_i+n_j)\beta^2(e),$$ where $\beta(e)$ is the extrinsic intersection angle of the circumcircles of the triangles of the mesh sharing the edge $e=(ij)$ and $n_i$ is the valence of vertex $i$. Besides minimizing the squared local conformal discrete Willmore energy $W$ this functional also minimizes local differences of the angles $\beta$. We investigate the minimizers of this functionals for simplicial spheres and simplicial surfaces of nontrivial topology. Several remarkable facts are observed. In particular for most of randomly generated simplicial polyhedra the minimizers of $W_2$ and $W_{2,w}$ are inscribed polyhedra. We demonstrate also some applications in geometry processing, for example, a conformal deformation of surfaces to the round sphere. A partial theoretical explanation through quadratic optimization theory of some observed phenomena is presented.Comment: 14 pages, 8 figures, to appear in the proceedings of "Curves and Surfaces, 8th International Conference", June 201

Adakite-like and Normal Arc Magmas: Distinct Fractionation Paths in the East Serbian Segment of the Balkan-Carpathian Arc

New age and whole-rock 87Sr/86Sr and 143Nd/144Nd isotopic data are used to assess petrogenetic and regional geodynamic processes associated with Late Cretaceous subvolcanic intrusions within the sparsely studied Timok Magmatic Complex (TMC) and Ridanj-Krepoljin Zone (RKZ) of eastern Serbia. The TMC and RKZ form part of the Apuseni-Banat-Timok-Srednogorie (ABTS) magmatic belt, a Cu-Au mineralized calc-alkaline magmatic arc related to closure of the Tethys Ocean that extends through Romania, Serbia, and Bulgaria in SE Europe. Zircon ages based on U-Pb laser ablation inductively coupled plasma mass spectrometry supplemented by existing isotope dilution thermal ionization mass spectrometry data respectively range from 89 to 79 Ma and from 76 to 71 Ma for the TMC and RKZ. This age pattern corresponds to cross-arc younging away from the European continent. Adakite-like trace element signatures (Y ≤18 ppm) are linked with samples that extend across the arc. These overlap in space and time with samples that conform to a normal arc differentiation trend. We performed energy-constrained assimilation-fractional crystallization (EC-AFC) modeling of Sr-La-Nd-Yb concentrations and Sr and Nd isotopic data. Results suggest that the two distinct fractionation trends may be explained in terms of a common mantle-derived parental magma but distinct fractionation and assimilation paths in the lower and upper crust. Petrogenesis of the adakite-like magmas is consistent with extensive high-pressure amphibole fractionation in the lower crust followed by ascent and plagioclase-dominant fractionation and assimilation in the upper crust. In contrast, normal arc signatures appear to have evolved exclusively via an upper-crustal differentiation process. Overall, our interpretation supports mantle wedge melting related to weak extension during progressive rollback of a subducting sla