http://hdl.handle.net/2117/3228 2013-05-23T11:55:29Z http://hdl.handle.net/2117/18778 Title: Alternative tests for functional and pointwise output-controllability of linear time-invariant systems Authors: García Planas, María Isabel; Domínguez García, José Luis Abstract: This paper deals with the description of a new method for calculating the functional output-controllability. It is computed by means of the rank of a certain constant matrix which can be associated to the system. Moreover, a new method for the pointwise output-controllability determination by means of constructing the output-controllability matrix associated to the system using the residues of the given linear system is developed. Finally, a simple physical example is presented 2013-04-12T10:12:39Z http://hdl.handle.net/2117/18733 Title: Nonsingular models of universes in teleparallel theories Authors: Haro Cases, Jaume; Amorós Torrent, Jaume Abstract: Different models of universes are considered in the context of teleparallel theories. Assuming that the universe is filled by a fluid with an equation of state P ¼ f ð Þ , for different teleparallel theories and different equation of state we study its dynamics. Two particular cases are studied in detail: in the first one we consider a function f with two zeros (two de Sitter solutions) that mimics a huge cosmological constant at early times and a pressureless fluid at late times; in the second one, in the context of loop quantum cosmology with a small cosmological constant, we consider a pressureless fluid ( P ¼ 0 , f ð Þ¼ ) which means there are de Sitter and anti–de Sitter solutions. In both cases one obtains a nonsingular universe that at early times is in an inflationary phase; after leaving this phase, it passes trough a matter dominated phase and finally at late times it expands in an accelerated way Description: PACS Numbers: 04.50.Kd, 98.80.Jk 2013-04-09T11:50:58Z http://hdl.handle.net/2117/17957 Title: GenNon-h: Generating multiple sequence alignments on nonhomogeneous phylogenetic trees Authors: Kedzierska, A.M.; Casanellas Rius, Marta Abstract: Background: A number of software packages are available to generate DNA multiple sequence alignments (MSAs) evolved under continuous-time Markov processes on phylogenetic trees. On the other hand, methods of simulating the DNA MSA directly from the transition matrices do not exist. Moreover, existing software restricts to the time-reversible models and it is not optimized to generate nonhomogeneous data (i.e. placing distinct substitution rates at different lineages). Results: We present the first package designed to generate MSAs evolving under discrete-time Markov processes on phylogenetic trees, directly from probability substitution matrices. Based on the input model and a phylogenetic tree in the Newick format (with branch lengths measured as the expected number of substitutions per site), the algorithm produces DNA alignments of desired length. GenNon-h is publicly available for download. Conclusion: The software presented here is an efficient tool to generate DNA MSAs on a given phylogenetic tree. GenNon-h provides the user with the nonstationary or nonhomogeneous phylogenetic data that is well suited for testing complex biological hypotheses, exploring the limits of the reconstruction algorithms and their robustness to such models. 2013-02-25T12:43:58Z http://hdl.handle.net/2117/17905 Title: The equations of Rees algebras of equimultiple ideals of deviation one. Authors: Muiños, Ferran; Planas Vilanova, Francesc d'Assís Abstract: We describe the equations of the Rees algebra R(I) of an equimultiple ideal I of deviation one provided that I has a reduction generated by a regular sequence x1, . . . , xs such that the initial forms x∗ 1, . . . , x∗ s−1 are a regular sequence in the associated graded ring. In particular, we prove that there is a single equation of maximum degree in a minimal generating set of the equations of R(I), which recovers some previous known results. 2013-02-21T10:48:36Z http://hdl.handle.net/2117/17877 Title: On the ring of global sections of the blowing-up along a two-generated ideal. Authors: Giral, José M; Planas Vilanova, Francesc d'Assís Abstract: The effective relations and the relation type of an ideal generated by two regular elements can be expressed in terms of the ring of global sections of the blowing-up along the ideal. As a consequence, we find the minimal overring where the ideal is syzygetic or of linear type. 2013-02-19T12:19:04Z http://hdl.handle.net/2117/17875 Title: Special section on celestial mechanics and applications 3rd Conference on Nonlinear Science and Complexity 2010 – NSC10 Authors: Gidea, Marian; Masdemont Soler, Josep 2013-02-19T11:58:56Z http://hdl.handle.net/2117/17874 Title: The space of phylogenetic mixtures for equivariant models Authors: Casanellas Rius, Marta; Fernández Sánchez, Jesús; Kedzierska, A.M. Abstract: The selection of the most suitable evolutionary model to analyze the given molecular data is usually left to biologist's choice. In his famous book, J Felsenstein suggested that certain linear equations satisfied by the expected probabilities of patterns observed at the leaves of a phylogenetic tree could be used for model selection. It remained open the question regarding whether these equations were enough for characterizing the evolutionary model. Here we prove that, for equivariant models of evolution, the space of distributions satisfying these linear equations coincides with the space of distributions arising from mixtures of trees on a set of taxa. In other words, we prove that an alignment is produced from a mixture of phylogenetic trees under an equivariant evolutionary model if and only if its distribution of column patterns satisfies the linear equations mentioned above. Moreover, for each equivariant model and for any number of taxa, we provide a set of linearly independent equations defining this space of phylogenetic mixtures. This is a powerful tool that has already been successfully used in model selection. We also use the results obtained to study identifiability issues for phylogenetic mixtures. 2013-02-19T11:45:51Z http://hdl.handle.net/2117/17857 Title: Vaccination behaviour influences self-report of influenza vaccination status: A cross-sectional study among health care workers Authors: Llupià, Anna; García-Basteiro, Alberto L.; Mena, Guillermo; Puig Sadurní, Joaquim; Bayas, Jose M.; Trilla, Antoni Abstract: Published influenza vaccination coverage in health care workers (HCW) are calculated using two sources: self-report and vaccination records. The objective of this study was to determine whether self-report is a good proxy for recorded vaccination in HCW, as the degree of the relationship is not known, and whether vaccine behaviour influences self-reportin 2013-02-18T15:54:09Z http://hdl.handle.net/2117/17364 Title: On the existence of a common eigenvector for all matrices in the commutant of a single matrix Authors: Magret Planas, Maria dels Dolors; Montoro López, María Eulalia Abstract: The main purpose of this paper is to study common invariant subspaces of any matrix in the centralizer of a given matrix A∈Mn(F), where F denotes an algebraically closed field. In particular, we obtain a necessary and sufficient condition for the existence of a common eigenvector for all the matrices in this set. 2013-01-15T10:17:54Z http://hdl.handle.net/2117/17323 Title: Analysis of control properties of concatenated convolutional codes Authors: García Planas, María Isabel; Souidi, El Mamoun; Um, Laurence Abstract: In this paper we consider two models of concatenated convolutional codes from the perspective of linear systems theory. We present an input-state-output representation of these models and we study the conditions for control properties for concatenated convolutional codes. 2013-01-14T10:25:51Z http://hdl.handle.net/2117/17107 Title: Analysis of behavior of the eigenvalues and eigenvectors of singular linear systems Authors: García Planas, María Isabel; Tarragona Romero, Sonia Abstract: Let E(p)x˙ = A(p)x + B(p)u be a family of singular linear systems smoothly dependent on a vector of real parameters p = (p1, . . . , pn). In this work we construct versal deformations of the given differentiable family under an equivalence relation, providing a special parametrization of space of systems, which can be effectively applied to perturbation analysis. Furthermore in particular, we study the behavior of a simple eigenvalue of a singular linear system family E(p)x˙ = A(p)x + B(p)u. 2012-12-12T08:51:49Z http://hdl.handle.net/2117/17085 Title: The Hirsch conjecture has been disproved : an interview with Francisco Santos Authors: Miranda Galcerán, Eva Abstract: The famous Hirsch conjecture was formulated in 1957 in a conversation of Warren Hirsch with George Dantzig, the father of the simplex method. It asserts that given a polytope of dimension d and n facets, its combinatorial diameter is smaller than or equal to n–d, i.e. any two vertices of the polytope can be connected to each other by a path of at most n–d edges. The conjecture is related to the problem of complexity of the simplex method (it gives a lower bound). The conjecture has been open for 53 years and has attracted the interest of many mathematicians in discrete, combinatorial and computational geometry. The simplicity of its statement has also attracted mathematicians in other areas. On 10 May 2010, the entry about the Hirsch Conjecture in Wikipedia was updated, announcing that Francisco Santos had found a counterexample to the Hirsch conjecture. Later, on 14 June, Francisco Santos posted a preprint where the first counterexample was given. It was a polytope in dimension 43 and with 86 facets. The paper is now published in Annals of Mathematics [Sa4]. The HirschConjecture has been disproved. 2012-12-10T11:56:27Z http://hdl.handle.net/2117/17030 Title: Abundance of attracting, repelling and elliptic periodic orbits in two-dimensional reversible maps Authors: Delshams Valdés, Amadeu; Gonchenko, S.V.; Lázaro Ochoa, José Tomás; Stenkin, Oleg Abstract: We study dynamics and bifurcations of two-dimensional reversible maps having non-transversal heteroclinic cycles containing symmetric saddle fixed points. We consider one-parameter families of reversible maps unfolding the initial heteroclinic tangency and prove the existence of infinitely many sequences (cascades) of bifurcations and birth of asymptotically stable, unstable and elliptic periodic orbits 2012-11-27T10:17:32Z http://hdl.handle.net/2117/17025 Title: The hydrodynamic Chaplygin sleigh Authors: Fedorov, Yuri; García Naranjo Ortiz de la Huert, Luis Constantino Abstract: We consider the motion of rigid bodies in a potential fluid subject to certain nonholonomic constraints and show that it is described by Euler–Poincar´e– Suslov equations. In the two-dimensional case, when the constraint is realized by a blade attached to the body, the system provides a hydrodynamic generalization of the classical Chaplygin sleigh problem, one of the best known examples of nonholonomic systems. The dynamics of the generalized sleigh is studied in detail. Namely, the equations of motion are integrated explicitly, and the asymptotic behavior of the system is described analytically and from the qualitative point of view. It is shown that the presence of the fluid brings new features to such a behavior. 2012-11-27T08:31:49Z http://hdl.handle.net/2117/16852 Title: Reconstrucción filogenética usando Geometría Algebraica Authors: Casanellas Rius, Marta; Fernández Sánchez, Jesús Abstract: Una nueva aproximación a la reconstrucción filogenética basada en la geometría algebraica está ganando fuerza en los últimos años. Fijado un modelo evolutivo para un conjunto de especies, las distribuciones teóricas de los nucleótidos de estas especies satisfacen ciertas relaciones algebraicas que llamamos invariantes. Estos invariantes son de interés teórico y práctico dado que se pueden utilizar para inferir filogenias. En este artículo, explicamos cómo usar los invariantes para implementar algoritmos de reconstrucción filogenética y mostramos cómo el uso de técnicas y resultados teóricos procedentes del álgebra conmutativa y la geometría algebraica puede contribuir en la mejora en la eficacia y la eficiencia de estos algoritmos. 2012-11-07T10:38:00Z