Search results for "Graph theory"
showing 10 items of 784 documents
Pseudo-abelian integrals: Unfolding generic exponential case
2009
The search for bounds on the number of zeroes of Abelian integrals is motivated, for instance, by a weak version of Hilbert's 16th problem (second part). In that case one considers planar polynomial Hamiltonian perturbations of a suitable polynomial Hamiltonian system, having a closed separatrix bounding an area filled by closed orbits and an equilibrium. Abelian integrals arise as the first derivative of the displacement function with respect to the energy level. The existence of a bound on the number of zeroes of these integrals has been obtained by A. N. Varchenko [Funktsional. Anal. i Prilozhen. 18 (1984), no. 2, 14–25 ; and A. G. Khovanskii [Funktsional. Anal. i Prilozhen. 18 (1984), n…
A Characterization of Quintic Helices
2005
A polynomial curve of degree 5, @a, is a helix if and only if both @[email protected]^'@? and @[email protected]^'@[email protected]^''@? are polynomial functions.
Recent mathematical approaches to reconstruct phylogenies: A chemosystematist's and botanist's view
1989
Some basic problems of mathematical phylogenetics are discussed. While algorithms regularly depend on the principle of parsimony, some features of phylogenesis interfere with that principle. Nonrandomness of the distribution of mutations as well as the inconstancy of the molecular clock in time and within a given sequence can bias the calculated relationships of closely related taxa. True comparability of sequences is difficult to establish, since this requires defining of homology of positions and of functions of amino acids as well. Parallelism and convergence can give rise to errors in establishing homology. Furthermore, they are difficult to be integrated into a consistent mathematical …
Brief communication: Vehicle routing problem and UAV application in the post-earthquake scenario
2017
Abstract. In this paper we simulate a Unmanned Aerial Vehicle's (UAV) recognition after a possible case of diffuse damage after a seismic event in the town of Acireale (Sicily, Italy). Given a set of sites (84 relevant buildings) and the range of the UAV, we are able to find the number of vehicles to employ and the shortest survey path. The problem of finding the shortest survey path is an operational research problem called Vehicle Routing Problem (VRP) whose solution is known to be computationally time-consuming. We used the Simulated Annealing (SA) heuristic that is able to provide stable solutions in relatively short computing time. We also examined the distribution of the cost of the s…
Empirical and theoretical study of atelostomate (Echinoidea, Echinodermata) plate architecture: using graph analysis to reveal structural constraints.
2015
AbstractDescribing patterns of connectivity among organs is essential for identifying anatomical homologies among taxa. It is also critical for revealing morphogenetic processes and the associated constraints that control the morphological diversification of clades. This is particularly relevant for studies of organisms with skeletons made of discrete elements such as arthropods, vertebrates, and echinoderms. Nonetheless, relatively few studies devoted to morphological disparity have considered connectivity patterns as a level of morphological organization or developed comparative frameworks with proper tools. Here, we analyze connectivity patterns among apical plates in Atelostomata, the m…
From Requirements to Code in a Model Driven Way
2010
Though there is a lot of support for model driven development the support for complete model driven path from requirements to code is limited. The approach proposed in this paper offers such a path which is fully supported by model transformations. The starting point is semiformal requirements containing behaviour description in a controlled natural language. A chain of models is proposed including analysis, platform independent and platform specific models. A particular architecture style is chosen by means of selecting a set of appropriate design patterns for these models. It is shown how to define informally and then implement in model transformation language MOLA the required transforma…
Unirationality of Hurwitz spaces of coverings of degree <= 5
2011
Let $Y$ be a smooth, projective curve of genus $g\geq 1$ over the complex numbers. Let $H^0_{d,A}(Y)$ be the Hurwitz space which parametrizes coverings $p:X \to Y$ of degree $d$, simply branched in $n=2e$ points, with monodromy group equal to $S_d$, and $det(p_{*}O_X/O_Y)$ isomorphic to a fixed line bundle $A^{-1}$ of degree $-e$. We prove that, when $d=3, 4$ or $5$ and $n$ is sufficiently large (precise bounds are given), these Hurwitz spaces are unirational. If in addition $(e,2)=1$ (when $d=3$), $(e,6)=1$ (when $d=4$) and $(e,10)=1$ (when $d=5$), then these Hurwitz spaces are rational.
Literature, Simulation, and the Path Towards Deeper Learning
2019
This paper investigates the role of teaching literature for deeper learning. It draws on models of simulation, which have usually been more common in psychology, law, and political science. Teaching literature may be ideally suited for deeper learning since literary texts can be seen as experimental social action. Each text confronts its readers with ethical choices. This property of literature as a medium can in turn be transformed into new models for teaching literature. Ultimately, literary simulations can hence constitute a path towards civic education and social responsibility. Such approaches, in turn, may contribute not only to discussions of the “relevance” of the humanities as such…
Sequence Determines Degree of Knottedness in a Coarse-Grained Protein Model
2015
Knots are abundant in globular homopolymers but rare in globular proteins. To shed new light on this long-standing conundrum, we study the influence of sequence on the formation of knots in proteins under native conditions within the framework of the hydrophobic-polar (HP) lattice protein model. By employing large scale Wang-Landau simulations combined with suitable Monte Carlo trial moves we show that, even though knots are still abundant on average, sequence introduces large variability in the degree of self-entanglements. Moreover, we are able to design sequences which are either almost always or almost never knotted. Our findings serve as proof of concept that the introduction of just o…
Extracting similar sub-graphs across PPI Networks
2009
Singling out conserved modules (corresponding to connected sub-graphs) throughout protein-protein interaction networks of different organisms is a main issue in bioinformatics because of its potential applications in biology. This paper presents a method to discover highly matching sub-graphs in such networks. Sub-graph extraction is carried out by taking into account, on the one side, both protein sequence and network structure similarities and, on the other side, both quantitative and reliability information possibly available about interactions. The method is conceived as a generalization of a known technique, able to discover functional orthologs in interaction networks. Some preliminar…