Our researchers

Sergio Ardanza-Trevijano Moras

Física y Matemática Aplicada
Facultad de Ciencias. Universidad de Navarra
Research lines
Topology, Topological Data Analysis, Applied Algebraic Topology, Topological Groups
6, (WoS, 30/08/2017)
7, (Scopus, 30/08/2017)

Most recent scientific publications (since 2010)

Authors: Ardanza-Trevijano Moras, Sergio; Chasco Ugarte, María Jesús; Elorza Barbajero, Jorge (Autor de correspondencia)
ISSN 0165-0114  Vol. 369  2019  pp. 122 - 131
We implement the notion of annihilator into fuzzy subgroups of an abelian group. There are different uses for the term annihilator in algebraic contexts that have been used fuzzy systems. In this paper we refer to another type of annihilator which is essential in classical duality theory and extends the widely applied notion of orthogonal complement in Euclidean spaces. We find that in the natural algebraic duality of a group, a fuzzy subgroup can be recovered after taking the inverse annihilator of its annihilator. We also study the behavior of annihilators with respect to unions and intersections. Some illustrative examples of annihilators of fuzzy subgroups are shown, both with finite and infinite rank.
Authors: Irurzun Arana, Itziar; Janda Galán, Álvaro; Ardanza-Trevijano Moras, Sergio; et al.
ISSN 1553-7358  Vol. 14  Nº 4  2018  pp. e1006087
Numerous problems encountered in computational biology can be formulated as optimization problems. In this context, optimization of drug release characteristics or dosing schedules for anticancer agents has become a prominent area not only for the development of new drugs, but also for established drugs. However, in complex systems, optimization of drug exposure is not a trivial task and cannot be efficiently addressed through trial-error simulation exercises. Finding a solution to those problems is a challenging task which requires more advanced strategies like optimal control theory. In this work, we perform an optimal control analysis on a previously developed computational model for the testosterone effects of triptorelin in prostate cancer patients with the goal of finding optimal drug-release characteristics. We demonstrate how numerical control optimization of non-linear models can be used to find better therapeutic approaches in order to improve the final outcome of the patients.
Authors: Irurzun Arana, Itziar; Janda Galán, Álvaro; Ardanza-Trevijano Moras, Sergio; et al.
ISSN 1567-567X  Vol. 45  2018  pp. S47 - S48
Authors: Muhammad Aslam, Raheema; Ardanza-Trevijano Moras, Sergio; Poduska, K. M.; et al.
ISSN 2470-0045  Vol. 95  Nº 3  2017  pp. 032607
Polycrystals of thin colloidal deposits, with thickness controlled by spin-coating speed, exhibit axial symmetry with local 4-fold and 6-fold symmetric structures, termed orientationally correlated polycrystals (OCPs). While spin-coating is a very facile technique for producing large-area colloidal deposits, the axial symmetry prevents us from achieving true long-range order. To obtain true long-range order, we break this axial symmetry by introducing a patterned surface topography and thus eliminate the OCP character. We then examine symmetryindependent methods to quantify order in these disordered colloidal deposits. We find that all the information in the bond-orientational order parameters is well captured by persistent homology analysis methods that only use the centers of the particles as input data. It is expected that these methods will prove useful in characterizing other disordered structures.
Authors: Ardanza-Trevijano Moras, Sergio; Zuriguel Ballaz, Iker; Arévalo, R.; et al.
ISSN 1539-3755  Vol. 89  2014  pp. 052212
We use the first Betti number of a complex to analyze the morphological structure of granular samples in mechanical equilibrium. We investigate two-dimensional granular packings after a tapping process by means of both simulations and experiments. States with equal packing fraction obtained with different tapping intensities are distinguished after the introduction of a filtration parameter which determines the particles (nodes in the network) that are joined by an edge. This is accomplished by just using the position of the particles obtained experimentally and no other information about the possible contacts, or magnitude of forces.
Authors: Ardanza-Trevijano Moras, Sergio; Chasco Ugarte, María Jesús; Domínguez, X.; et al.
Journal: Forum Mathematicum
ISSN 0933-7741  Vol. 24  Nº 2  2012  pp. 289 - 302
Authors: Goñi Cortes, Joaquín; Arrondo Ostíz, Gonzalo; Sepulcre Bernad, Jorge; et al.
Journal: Cognitive Processing - Heidelberg
ISSN 1612-4782  Vol. 12  Nº 2  2011  pp. 183 - 186
Semantic memory is the subsystem of human memory that stores knowledge of concepts or meanings, as opposed to life-specific experiences. How humans organize semantic information remains poorly understood. In an effort to better understand this issue, we conducted a verbal fluency experiment on 200 participants with the aim of inferring and representing the conceptual storage structure of the natural category of animals as a network. This was done by formulating a statistical framework for co-occurring concepts that aims to infer significant concept-concept associations and represent them as a graph. The resulting network was analyzed and enriched by means of a missing links recovery criterion based on modularity. Both network models were compared to a thresholded co-occurrence approach. They were evaluated using a random subset of verbal fluency tests and comparing the network outcomes (linked pairs are clustering transitions and disconnected pairs are switching transitions) to the outcomes of two expert human raters. Results show that the network models proposed in this study overcome a thresholded co-occurrence approach, and their outcomes are in high agreement with human evaluations. Finally, the interplay between conceptual structure and retrieval mechanisms is discussed.
Authors: Goñi Cortes, Joaquín; Martincorena, I.; Corominas-Murtra, B.; et al.
Journal: International Journal of Bifurcation and Chaos
ISSN 0218-1274  Vol. 20  Nº 3  2010  pp. 913 - 922
Semantic memory is the subsystem of human memory that stores knowledge of concepts or meanings, as opposed to life specific experiences. The organization of concepts within semantic memory can be understood as a semantic network, where the concepts (nodes) are associated (linked) to others depending on perceptions, similarities, etc. Lexical access is the complementary part of this system and allows the retrieval of such organized knowledge. While conceptual information is stored under certain underlying organization (and thus gives rise to a specific topology), it is crucial to have an accurate access to any of the information units, e. g. the concepts, for efficiently retrieving semantic information for real-time need. An example of an information retrieval process occurs in verbal fluency tasks, and it is known to involve two different mechanisms: "clustering", or generating words within a subcategory, and, when a subcategory is exhausted, "switching" to a new subcategory. We extended this approach to random-walking on a network (clustering) in combination to jumping (switching) to any node with certain probability and derived its analytical expression based on Markov chains. Results show that this dual mechanism contributes to optimize the exploration of different network models in terms of the mean first passage time. Additionally, this cognitive inspired dual mechanism opens a new framework to better understand and evaluate exploration, propagation and transport phenomena in other complex systems where switching-like phenomena are feasible.
Authors: Arévalo Turnes, Roberto; Zuriguel Ballaz, Iker; Ardanza-Trevijano Moras, Sergio; et al.
Journal: International Journal of Bifurcation and Chaos
ISSN 0218-1274  Vol. 20  Nº 3  2010  pp. 897 - 903
The existence of small order loops of contacts is presented as an intrinsic characteristic of force granular networks. Based on molecular dynamics simulations, it is proposed that the presence of these small order loops - and in particular third order loops of contacts - is important to understand the transition from fluid-like to solid-like behavior of granular packings. In addition, we show a close relationship between the development of third order loops and the small forces of the granular packing in the sense that almost all third order loops allocate a force component smaller than the average.

Teaching experience