An algorithmic approach for simulating realistic irregular lattices.

There is a wide variety of computational experiments, or statistical simulations, in which regional scientists require regular and irregular lattices with a predefined number of polygons. While most commercial and free GIS software offer the possibility of generating regular lattices of any size, the generation of instances of irregular lattices is not a straightforward task. The most common strategy in this case is to find a real map that matches as closely as possible the required number of polygons. This practice is usually conducted without considering whether the topological characteristics of the selected map are close to those for an “average” map sampled in different parts of the world. In this paper, we propose an algorithm, RI-Maps, that combines fractal theory, stochastic calculus and computational geometry for simulating realistic irregular lattices with a predefined number of polygons. The irregular lattices generated with RI-Maps have guaranteed consistency in their topological characteristics, which reduces the potential distortions in the computational or statistical results due to an inappropriate selection of the lattices

Application of large area SiPMs for the readout of a plastic scintillator based timing detector

In this study an array of eight 6 mm x 6 mm area SiPMs was coupled to the end of a long plastic scintillator counter which was exposed to a 2.5 GeV/c muon beam at the CERN PS. Timing characteristics of bars with dimensions 150 cm x 6 cm x 1 cm and 120 cm x 11 cm x 2.5 cm have been studied. An 8-channel SiPM anode readout ASIC (MUSIC R1) based on a novel low input impedance current conveyor has been used to read out and amplify SiPMs independently and sum the signals at the end. Prospects for applications in large-scale particle physics detectors with timing resolution below 100 ps are provided in light of the results

Application of large area SiPMs for the readout of a plastic scintillator based timing detector

In this study an array of eight 6 mm x 6 mm area SiPMs was coupled to the end of a long plastic scintillator counter which was exposed to a 2.5 GeV/c muon beam at the CERN PS. Timing characteristics of bars with dimensions 150 cm x 6 cm x 1 cm and 120 cm x 11 cm x 2.5 cm have been studied. An 8-channel SiPM anode readout ASIC (MUSIC R1) based on a novel low input impedance current conveyor has been used to read out and amplify SiPMs independently and sum the signals at the end. Prospects for applications in large-scale particle physics detectors with timing resolution below 100 ps are provided in light of the results

Análisis de la distribución espacial de la reducción en la demanda de agua potable como efecto de políticas de ahorro en su consumo en el Área Metropolitana del Valle de Aburrá.

El presente estudio presenta un análisis, espacialmente desagregado, de la disminución en el consumo residencial de agua en el Área Metropolitana del Valle de Aburrá (AMVA) durante el periodo 2005 – 2010 e identificar las características socioeconómicas asociadas a estos patrones. Además, se analiza la forma cómo las políticas y campañas para incentivar la disminución del consumo de agua potable han sido acogidas en el AMVA. Los resultados obtenidos muestran claras diferencias espaciales (y por estrato) en los niveles de consumo de agua, así como en los niveles de reducción de dicho consumo en el período analizado. También, por medio de modelos de econometría espacial, se encuentra que las características socioeconómicas juegan un papel relevante a la hora de explicar los niveles de consumo de agua y que estos consumos presentan autocorrelación espacial sustantiva que indica que los niveles de consumo de agua potable en un área determinada no solo dependen de las características socioeconómicas del área, sino también de los niveles de consumo de las áreas vecinas. Por último, se encuentra que los impactos derivados del desincentivo económico al consumo excesivo, tiene un efecto inmediato que no perdura en el tiemp

CRANKITE: a fast polypeptide backbone conformation sampler

Background: CRANKITE is a suite of programs for simulating backbone conformations of polypeptides and proteins. The core of the suite is an efficient Metropolis Monte Carlo sampler of backbone conformations in continuous three-dimensional space in atomic details. Methods: In contrast to other programs relying on local Metropolis moves in the space of dihedral angles, our sampler utilizes local crankshaft rotations of rigid peptide bonds in Cartesian space. Results: The sampler allows fast simulation and analysis of secondary structure formation and conformational changes for proteins of average length

Factorial structure and reliability of the academic satisfaction questionnaire on Chilean medical students

Indexación: Web of Science; Scopus.El presente estudio analiza la estructura factorial y confiabilidad del cuestionario de satisfacción académica (CSA) en una muestra de 563 estudiantes de medicina, entre 19 y 29 años (media de 20,42); provenientes de cuatro universidades chilenas. Una vez finalizada la traducción al castellano se exploró la validez de contenido de los ítems mediante un juicio de expertos. La estructura factorial del cuestionario se analizó a través de un análisis factorial exploratorio empleando el método Análisis de Ejes Principales (AEP). Los resultados preliminares de la fiabilidad y validez del instrumento han mostrado que la estructura de un factor es viable y adecuada de acuerdo a los requisitos psicométricos establecidos, aunque se recomiendan futuros estudios que evalúen su validez y confiabilidad en otros programas de pregrado.The present study examines the factorial structure and reliability of the academic satisfaction questionnaire (CSA) in a sample of 563 medical students, between 19 and 29 years (average of 20.42); from four Chilean universities. Once translated into Spanish explored the validity of the items content was evaluated through experts opinions. The factorial structure of the scale was analyzed through an exploratory factor analysis using the Principal Axis Analysis method (AEP).The preliminary results of the reliability and validity of the instrument have shown that a factor structure is viable and appropriate according to the established psychometric requirements, although future studies to evaluate its validity and reliability in other undergraduate programs are recommended.http://www.redalyc.org/articulo.oa?id=45964543200

Deriving amino acid contact potentials from their frequencies of occurence in proteins: a lattice model study

The possibility of deriving the contact potentials between amino acids from their frequencies of occurence in proteins is discussed in evolutionary terms. This approach allows the use of traditional thermodynamics to describe such frequencies and, consequently, to develop a strategy to include in the calculations correlations due to the spatial proximity of the amino acids and to their overall tendency of being conserved in proteins. Making use of a lattice model to describe protein chains and defining a "true" potential, we test these strategies by selecting a database of folding model sequences, deriving the contact potentials from such sequences and comparing them with the "true" potential. Taking into account correlations allows for a markedly better prediction of the interaction potentials