Programación del Fixture de la Segunda División del Fútbol de Chile mediante Investigación de Operaciones

Presentamos en este trabajo la aplicación de técnicas de Investigación de Operaciones a la programación del fixture de la Segunda División del fútbol de Chile. Este fixture debe cumplir una serie de condiciones solicitadas por la Asociación Nacional de Fútbol Profesional (ANFP), entidad que organiza el torneo. El criterio geográfico es particularmente importante, debido a que la disposición de algunos equipos en lugares extremos del país implica largos desplazamientos, a menudo realizados por vía terrestre. Abordamos el problema mediante un modelo de programación lineal entera que define cuándo y dónde se juega cada partido del torneo, sujeto a que todas las condiciones se cumplen. Para las instancias más difíciles, desarrollamos un modelo adicional también de programación lineal entera que genera patrones de localías y los asigna a los equipos, previo a la ejecución del modelo que define la programación de los partidos. Los fixtures así generados han sido exitosamente utilizados en los cinco torneos de Segunda División que se han disputado entre 2007 y 2010, reemplazando la metodología aleatoria que la ANFP utilizaba anteriormente. Durante este período, el tipo de torneo ha sufrido diversas modificaciones, incluyendo un cuádruple round-robin y un torneo en dos etapas que considera fases regionales y nacionales. Hemos debido entonces adaptar nuestros modelos temporada tras temporada, según el tipo de torneo. Esta aplicación marca un nuevo avance en el uso de Investigación de Operaciones para la gestión del fútbol chileno, que se suma a otros proyectos desarrollados en la misma línea en los últimos años.Fil: Duran, Guillermo Alfredo. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Matemática; Argentina. Universidad de Chile; Chile. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Guajardo, Mario. Norwegian School of Economics and Business Administration; NoruegaFil: Wolf Yadlin, Rodrigo. Universidad de Chile; Chil

Operations research techniques for scheduling chile's second division soccer league

In this paper, we use operations research (OR) techniques to schedule the Second Division of the Chilean professional soccer league. The solution must satisfy a series of conditions requested by league officials. Because the teams generally travel long distances by bus, geographical restrictions are particularly important. We specify the scheduling problem and solve it using an integer linear programming (ILP) model that defines when and where each match is played, subject to constraints. For the most difficult instances, we formulate a second ILP model that generates home-away patterns and assigns them to the teams; we then run the model, which determines the match schedule. Chilean league officials have successfully used the models to schedule all five Second Division tournaments between 2007 and 2010, replacing the random scheduling methodology that they used previously. Since 2007, the two formulations have been adapted to various formats with which the Second Division has experimented; these include a quadruple round robin and a two-phase tournament with zonal and national phases. The application we present is one of a number of such projects that the authors and their colleagues developed over the past few years, and it represents an expansion of the use of OR techniques for managing tasks in Chilean soccer.Fil: Duran, Guillermo Alfredo. Universidad de Chile; Chile. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Investigaciones Matemáticas "Luis A. Santaló". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Matemáticas "Luis A. Santaló"; ArgentinaFil: Guajardo, Mario. NHH Norwegian School of Economics; NoruegaFil: Wolf Yadlin, Rodrigo. Universidad de Chile; Chil

Evolution of the local superconducting density of states in ErRh4_4B4_{4} close to the ferromagnetic transition

We present local tunneling spectroscopy experiments in the superconducting and ferromagnetic phases of the reentrant superconductor ErRh$_4$B$_{4}$. The tunneling conductance curves jump from showing normal to superconducting features within a few mK close to the ferromagnetic transition temperature, with a clear hysteretic behavior. Within the ferromagnetic phase, we do not detect any superconducting correlations. Within the superconducting phase we find a peculiar V-shaped density of states at low energies, which is produced by the magnetically modulated phase that coexists with superconductivity just before ferromagnetism sets in.Comment: 5 pages, 4 figure

Failure of hydrogenation in protecting polycyclic aromatic hydrocarbons from fragmentation

A recent study of soft X-ray absorption in native and hydrogenated coronene cations, C$_{24}$H$_{12+m}^+$ $m=0-7$, led to the conclusion that additional hydrogen atoms protect (interstellar) Polycyclic Aromatic Hydrocarbon (PAH) molecules from fragmentation [Reitsma et al., Phys. Rev. Lett. 113, 053002 (2014)]. The present experiment with collisions between fast (30-200 eV) He atoms and pyrene (C$_{16}$H$_{10+m}^+$, $m=0$, 6, and 16) and simulations without reference to the excitation method suggests the opposite. We find that the absolute carbon-backbone fragmentation cross section does not decrease but increases with the degree of hydrogenation for pyrene molecules.Comment: 10 pages, 5 figure

Bases termodinámicas en metalurgia: Diagramas de fases de aleaciones

La formación en ciencias básicas en cualquier rama de la ingeniería es tarea fundamental para el desarrollo de competencias que requieren ambientes en que se requiere cada vez más supervisión de procesos automatizados. En el pasado la ausencia de programas y la capacidad de procesamiento de datos de la tecnología disponible hacía muy complejo el proceso de cálculo de equilibrio para sistemas a partir de bases de datos. Ya en la década de los sesentas se comenzaban a proponer metodologías para el cálculo de diagramas de equilibrio de fases, situación que en la actualidad ha motivado la disponibilidad de varios programas para cálculos de equilibrio a partir de bases de datos termodinámicos (teóricos y experimentales) en corto tiempo. Los resultados de estos cálculos que han de cumplir con las leyes de la termodinámica y la regla de las fases entre otros. En Metalurgia, el uso de diagramas de equilibrio de aleaciones permite a los ingenieros evaluar la pertinencia de un determinado tratamiento térmico para la formación de una microestructura que maximice el desempeño de una pieza de ingeniería o definir las condiciones mediantes las cuales podemos refinar metales. La evaluación de la validez de los datos obtenidos mediante el uso de programas computacionales para cálculo de diagramas de fase requiere de una fuerte comprensión de las bases termodinámicas que los rigen. Es por esta razón que el aprendizaje significativo en termodinámica es un proceso que de ser exitoso facilita el entendimiento de lo que ocurre en un sistema al modificar variables como presión o temperatura. Este trabajo, en lenguaje simple, ejemplifica cómo la comprensión de conceptos base de la termodinámica como la regla de las fases, permite una evaluación de la validez de los diagramas de fases Fe-C obtenidos mediante Thermo-Calc. Se pretende que los comentarios aquí pre- sentados puedan ser transferidos a otros sistemas por los lectores con mentes más inquietas

Supersymmetry of gravitational ground states

A class of black objects which are solutions of pure gravity with negative cosmological constant are classified through the mapping between the Killing spinors of the ground state and those of the transverse section. It is shown that these geometries must have transverse sections of constant curvature for spacetime dimensions d below seven. For d > 6, the transverse sections can also be Euclidean Einstein manifolds. In even dimensions, spacetimes with transverse section of nonconstant curvature exist only in d = 8 and 10. This classification goes beyond standard supergravity and the eleven dimensional case is analyzed. It is shown that if the transverse section has negative scalar curvature, only extended objects can have a supersymmetric ground state. In that case, some solutions are explicitly found whose ground state resembles a wormhole.Comment: 16 pages, CECS style, minor correction

Functional annotation and distribution overview of RNA families in 27 Streptococcus agalactiae genomes

Background: Streptococcus agalactiae, also known as Group B Streptococcus (GBS), is a Gram-positive bacterium that colonizes the gastrointestinal and genitourinary tract of humans. This bacterium has also been isolated from various animals, such as fish and cattle. Non-coding RNAs (ncRNAs) can act as regulators of gene expression in bacteria, such as Streptococcus pneumoniae and Streptococcus pyogenes. However, little is known about the genomic distribution of ncRNAs and RNA families in S. agalactiae. Results: Comparative genome analysis of 27 S. agalactiae strains showed more than 5 thousand genomic regions identified and classified as Core, Exclusive, and Shared genome sequences. We identified 27 to 89 RNA families per genome distributed over these regions, from these, 25 were in Core regions while Shared and Exclusive regions showed variations amongst strains. We propose that the amount and type of ncRNA present in each genome can provide a pattern to contribute in the identification of the clonal types. Conclusions: The identification of RNA families provides an insight over ncRNAs, sRNAs and ribozymes function, that can be further explored as targets for antibiotic development or studied in gene regulation of cellular processes. RNA families could be considered as markers to determine infection capabilities of different strains. Lastly, pan-genome analysis of GBS including the full range of functional transcripts provides a broader approach in the understanding of this pathogen.Fil: Wolf, Ivan Rodrigo. Universidade Estadual de Londrina; BrasilFil: Paschoal, Alexandre Rossi. Universidade Federal do Paraná; BrasilFil: Quiroga, Cecilia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Investigaciones en Microbiología y Parasitología Médica. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Investigaciones en Microbiología y Parasitología Médica; ArgentinaFil: Domingues, Douglas Silva. Universidade Estadual Paulista Julio de Mesquita Filho; BrasilFil: de Souza, Rogério Fernandes. Universidade Estadual de Londrina; BrasilFil: Pretto Giordano, Lucienne Garcia. Universidade Estadual de Londrina; BrasilFil: Vilas Boas, Laurival Antonio. Universidade Estadual de Londrina; Brasi

The application of a social cognition model in explaining fruit intake in Austrian, Norwegian and Spanish schoolchildren using structural equation modelling

<p>Abstract</p> <p>Background</p> <p>The aim of this paper was to test the goodness of fit of the Attitude – Social influence – self-Efficacy (ASE) model in explaining schoolchildren's intentions to eat fruit and their actual fruit intake in Austria, Norway and Spain; to assess how well the model could explain the observed variance in intention to eat fruit and in reported fruit intake and to investigate whether the same model would fit data from all three countries.</p> <p>Methods</p> <p>Samples consisted of schoolchildren from three of the countries participating in the cross-sectional part of the Pro Children project. Sample size varied from 991 in Austria to 1297 in Spain. Mean age ranged from 11.3 to 11.4 years. The initial model was designed using items and constructs from the Pro Children study. Factor analysis was conducted to test the structure of the measures in the model. The Norwegian sample was used to test the latent variable structure, to make a preliminary assessment of model fit, and to modify the model to increase goodness of fit with the data. The original and modified models were then applied to the Austrian and Spanish samples. All model analyses were carried out using structural equation modelling techniques.</p> <p>Results</p> <p>The ASE-model fitted the Norwegian and Spanish data well. For Austria, a slightly more complex model was needed. For this reason multi-sample analysis to test equality in factor structure and loadings across countries could not be used. The models explained between 51% and 69% of the variance in intention to eat fruit, and 27% to 38% of the variance in reported fruit intake.</p> <p>Conclusion</p> <p>Structural equation modelling showed that a rather parsimonious model was useful in explaining the variation in fruit intake of 11-year-old schoolchildren in Norway and Spain. For Austria, more modifications were needed to fit the data.</p

Scanning Tunneling Spectroscopy in MgB 2

We present extensive Scanning Tunneling Spectroscopy (STM/S) measurements at low temperatures in the multiband superconductor MgB$_2$. We find a similar behavior in single crystalline samples and in single grains, which clearly shows the partial superconducting density of states of both the $\pi$ and $\sigma$ bands of this material. The superconducting gaps corresponding to both bands are not single valued. Instead, we find a distribution of superconducting gaps centered around 1.9mV and 7.5mV, corresponding respectively to each set of bands. Interband scattering effects, leading to a single gap structure at 4mV and a smaller critical temperature can be observed in some locations on the surface. S-S junctions formed by pieces of MgB$_2$ attached to the tip clearly show the subharmonic gap structure associated with this type of junctions. We discuss future developments and possible new effects associated with the multiband nature of superconductivity in this compound.Comment: 11 pages, 6 figures, submitted to Physica

Predicting 30-Day Mortality in Hospitalized Patients with Community-Acquired Pneumonia Using Statistical and Machine Learning Approaches

Background: Predicting if a hospitalized patient with community-acquired pneumonia (CAP) will or will not survive after admission to the hospital is important for research purposes as well as for institution of early patient management interventions. Although population-level mortality prediction scores for these patients have been around for many years, novel patient-level algorithms are needed. The objective of this study was to assess several statistical and machine learning models for their ability to predict 30-day mortality in hospitalized patients with CAP. Methods: This was a secondary analysis of the University of Louisville (UofL) Pneumonia Study database. Six different statistical and/or machine learning methods were used to develop patientlevel prediction models for hospitalized patients with CAP. For each model, nine different statistics were calculated to provide measures of the overall performance of the models. Results: A total of 3249 unique hospitalized patients with CAP were enrolled in the study, 2743 were included in the model building (training) dataset, while the remaining 686 were included in the testing dataset. From the full population, death at 30-days post discharge was documented in 458 (13.4%) patients. All models resulted in high variation in the ability to predict survivors and non-survivors at 30 days. Conclusions: In conclusion, this study suggests that accurate patient-level prediction of 30-day mortality in hospitalized patients with CAP is difficult with statistical and machine learning approaches. It will be important to evaluate novel variables and other modeling approaches to better predict poor clinical outcomes in these patients to ensure early and appropriate interventions are instituted