Counting Integer flows in Networks

This paper discusses new analytic algorithms and software for the enumeration of all integer flows inside a network. Concrete applications abound in graph theory \cite{Jaeger}, representation theory \cite{kirillov}, and statistics \cite{persi}. Our methods clearly surpass traditional exhaustive enumeration and other algorithms and can even yield formulas when the input data contains some parameters. These methods are based on the study of rational functions with poles on arrangements of hyperplanes

Computation of the highest coefficients of weighted Ehrhart quasi-polynomials of rational polyhedra

This article concerns the computational problem of counting the lattice points inside convex polytopes, when each point must be counted with a weight associated to it. We describe an efficient algorithm for computing the highest degree coefficients of the weighted Ehrhart quasi-polynomial for a rational simple polytope in varying dimension, when the weights of the lattice points are given by a polynomial function h. Our technique is based on a refinement of an algorithm of A. Barvinok [Computing the Ehrhart quasi-polynomial of a rational simplex, Math. Comp. 75 (2006), pp. 1449--1466] in the unweighted case (i.e., h = 1). In contrast to Barvinok's method, our method is local, obtains an approximation on the level of generating functions, handles the general weighted case, and provides the coefficients in closed form as step polynomials of the dilation. To demonstrate the practicality of our approach we report on computational experiments which show even our simple implementation can compete with state of the art software.Comment: 34 pages, 2 figure

implantologia post extraccion inmediata protocolo operativo y evaluaciones oclusales periodontales y esteticas

Objetivos: Evaluar la eficacia clinica del protocolo quirurgico relativo a la colocacion inmediata del tornillo en el alveolo post-extrativo. Material y metodos: Han sido evaluados, segun los criterios de Albrekston y Buser 45 implantes colocados con la tecnica post-extractiva, a los 6 meses y a los 3 anos tras la colocacion del implante. Resultados: El protocolo aplicado se ha demostrado valido, los porcentajes de exito han sido parecidos con aquellos de la tecnica tradicional, con la ventaja de disminuir notablemente el tiempo para la rehabilitacion oclusal y con importantes ventajas esteticas para el paciente. Conclusiones: Con este nuevo protocolo quirurgico implantologico se puede garantizar un elevado porcentaje de exito con una importante disminucion de los tiempos de intervencion con mayores ventajas esteticas, funcionales y oclusales. PALABRAS CLAVE Implante, alveolo, estetica

Allele frequency and selection efficiency in cross populations of Andean x Mesoamerican common beans (Phaseolus vulgaris L. Fabales, Fabaceae).

Strategies were investigated for improving efficiency in the use of segregating common bean (Phaseolus vulgaris) populations using crosses between the Andean cultivar BRS-Radiante and the Mesoamerican parent cultivar Carioca-MG by developing populations with 12.5%, 25%, 50%, 75% and 87.5% of the allele frequency of one of the parents. For each of the five populations we evaluated for two traits, the number of days to the beginning of flowering and grain yield (g plot -1), in the F2:3 (sown in February 2006) and F2:4 (sown in July 2006) generation progenies using 15 x 15 lattice design experiments, with 44 progenies (n = 220 plants) plus the two parents and three controls being evaluated for each generation. In terms of variability release, the populations with different parental allele frequencies presented no consistent tendency of alteration. In general, genetic variance was stated among progenies in all populations, indicating success with selection. For grain yield, the lowest mean was observed in the populations with 50% of the alleles of both parents. If, for instance, the objective is to develop earlier flowering lines, the best strategy is to perform two, or at least one, backcross with the earliest parent. The most suitable allele frequency is to be determined according to the desired grain type

Essential Dynamics on Different Biological Systems: Fis Protein, tvMyb1 Transcriptional Factor and BACE1 Enzyme

Proteins and enzymes poses a non-covalent 3D structure and therefore their intrinsic flexibility allows the existence of an ensemble of different conformers which are separated by a low-energy barrier. These ranges of available conformers for proteins in solution are due to the relative movements among the different domains. Domain motions are important for a variety of protein functions, including catalysis, regulation of activity, transport of metabolites, formation of protein assemblies, and cellular locomotion. Considering the importance of these conformational changes it is obvious that the different techniques to evaluate these behaviours are very important in order to understand the biological effects. In the present chapter we report molecular dynamics (MD) trajectories analyzed by essential dynamics method on three different molecular systems of biological interest: i) DNA-bending protein Fis (Factor for Inversion Stimulation), ii) DNA-tvMyb1 (Trichomonas vaginalis transcriptional factor) and iii) the BACE1 (beta site amyloid cleaving enzyme 1). Although the general structural characteristics for the above systems are well known, comparatively little information is available about their flexibility and dynamics. This is in part due to difficulties with obtaining such information experimentally. Thus, our primary interest was the comparison between the unligated and the complexed state, because the corresponding conclusions may reveal motions of functional relevance.Fil: Gutiérrez, Lucas J.. Universidad Nacional de San Luis. Facultad de Química, Bioquímica y Farmacia. Área Química General e Inorgánica; ArgentinaFil: Enriz, Ricardo Daniel. Universidad Nacional de San Luis. Facultad de Química, Bioquímica y Farmacia. Área Química General e Inorgánica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Baldoni, Hector Armando. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Matemática Aplicada de San Luis "Prof. Ezio Marchi". Universidad Nacional de San Luis. Facultad de Ciencias Físico, Matemáticas y Naturales. Instituto de Matemática Aplicada de San Luis "Prof. Ezio Marchi"; Argentin