Maximum Estrada Index of Bicyclic Graphs

Let $G$ be a simple graph of order $n$, let $\lambda_1(G),\lambda_2(G),...,\lambda_n(G)$ be the eigenvalues of the adjacency matrix of $G$. The Esrada index of $G$ is defined as $EE(G)=\sum_{i=1}^{n}e^{\lambda_i(G)}$. In this paper we determine the unique graph with maximum Estrada index among bicyclic graphs with fixed order

Walk entropies on graphs

Entropies based on walks on graphs and on their line-graphs are defined. They are based on the summation over diagonal and off-diagonal elements of the thermal Green’s function of a graph also known as the communicability. The walk entropies are strongly related to the walk regularity of graphs and line-graphs. They are not biased by the graph size and have significantly better correlation with the inverse participation ratio of the eigenmodes of the adjacency matrix than other graph entropies. The temperature dependence of the walk entropies is also discussed. In particular, the walk entropy of graphs is shown to be non-monotonic for regular but non-walk-regular graphs in contrast to non-regular graphs

La exégesis de Tomás de Aquino de la noción de pasión estoica

La autora se propone examinar la exégesis de Tomás de Aquino de la noción de pasión estoica reconstruyendo, por una parte, su recepción de tesis centrales de la ética de la escuela acerca del contenido del bien humano y, en ese contexto, de las que conciernen al papel de los movimientos de la pasión en relación con el acto virtuoso. El artículo examina más de cincuenta pasajes del “corpus” tomístico en relación con las temáticas mencionadas. Por otra parte, y con el objeto de atender en su contexto histórico-filosófico propio la lectura tomista de posturas estoicas, la autora se detiene en la consideración de la problemática de los siglos XII y XIII en torno a las afecciones sensibles tras los efectos del primer pecado, y en la gravitación que en dicha especulación tuvieron sobre Tomás de Aquino posturas antecedentes en relación con el papel de los movimientos de la afectividad sensible. En este contexto, el artículo subraya y examina las aportaciones de Guillermo de Auxerre y de Felipe Canciller.The author intends to examine Thomas Aquinas’ exegesis of the Stoic notion of passion reconstructing, on the one hand, his reception of some central thesis of the School’s ethics about the content of human good and, in that context, of those concerning the role of the movements of passion in relation to the virtuous act. The article examines over fifty passages of the Thomistic corpus in relation to the aforementioned topics. On the other hand, and in order to deal with the Thomistic reading of Stoic postures within its historical-philosophical context, the author dwells on the consideration of the problem of the XIIth and the XIIIth centuries around sensible affections after the effects of original sin, as well as on the influence that former postures relating to the role of the movementes of sensible affectivity have had over Thomas Aquinas on such speculation. In this context, the article stresses and examines William of Auxerre’s and Philip the Chancellor’s contributions

A statistical mechanics description of environmental variability in metabolic networks

Many of the chemical reactions that take place within a living cell are irreversible. Due to evolutionary pressures, the number of allowable reactions within these systems are highly constrained and thus the resulting metabolic networks display considerable asymmetry. In this paper, we explore possible evolutionary factors pertaining to the reduced symmetry observed in these networks, and demonstrate the important role environmental variability plays in shaping their structural organization. Interpreting the returnability index as an equilibrium constant for a reaction network in equilibrium with a hypothetical reference system, enables us to quantify the extent to which a metabolic network is in disequilibrium. Further, by introducing a new directed centrality measure via an extension of the subgraph centrality metric to directed networks, we are able to characterise individual metabolites by their participation within metabolic pathways. To demonstrate these ideas, we study 116 metabolic networks of bacteria. In particular, we find that the equilibrium constant for the metabolic networks decreases significantly in-line with variability in bacterial habitats, supporting the view that environmental variability promotes disequilibrium within these biochemical reaction system

A global set of Fourier-transformed remotely sensed covariates for the description of abiotic niche in epidemiological studies of tick vector species

[Background]: Correlative modelling combines observations of species occurrence with environmental variables to capture the niche of organisms. It has been argued for the use of predictors that are ecologically relevant to the target species, instead of the automatic selection of variables. Without such biological background, the forced inclusion of numerous variables can produce models that are highly inflated and biologically irrelevant. The tendency in correlative modelling is to use environmental variables that are interpolated from climate stations, or monthly estimates of remotely sensed features. [Methods]: We produced a global dataset of abiotic variables based on the transformation by harmonic regression (time series Fourier transform) of monthly data derived from the MODIS series of satellites at a nominal resolution of 0.1°. The dataset includes variables, such as day and night temperature or vegetation and water availability, which potentially could affect physiological processes and therefore are surrogates in tracking the abiotic niche. We tested the capacities of the dataset to describe the abiotic niche of parasitic organisms, applying it to discriminate five species of the globally distributed tick subgenus Boophilus and using more than 9,500 published records. [Results]: With an average reliability of 82%, the Fourier-transformed dataset outperformed the raw MODIS-derived monthly data for temperature and vegetation stress (62% of reliability) and other popular interpolated climate datasets, which had variable reliability (56%-65%). The transformed abiotic variables always had a collinearity of less than 3 (as measured by the variance inflation factor), in contrast with interpolated datasets, which had values as high as 300. [Conclusions]: The new dataset of transformed covariates could address the tracking of abiotic niches without inflation of the models arising from internal issues with the descriptive variables, which appear when variance inflation is higher than 10. The coefficients of the harmonic regressions can also be used to reconstruct the complete original time series, being an adequate complement for ecological, epidemiological, or phylogenetic studies. We provide the dataset as a free download under the GNU general public license as well as the scripts necessary to integrate other time series of data into the calculations of the harmonic coefficients.Parts of this work were supported by EU FP7 ANTIGONE project number 278976.Peer Reviewe

Rubén Peretó Rivas (ed), La antropología cisterciense del siglo XII. Guillermo de Saint-Thierry, De natura corporis et animae; Isaac de Stella, De anima, Ediciones Universidad de Navarra (EUNSA), Colección de pensamiento medieval y renacentista, Pamplona, 2008, ISBN 978-84-313-2595-4, 156 pp.

Fil: Corso de Estrada, Laura. Universidad Católica Argentina. Sede Buenos Aire