Structures and Stabilities of Doubly-charged (MgO)nMg2+ (n=1-29) Cluster Ions

Ab initio perturbed ion plus polarization calculations are reported for doubly-charged nonstoichiometric (MgO)nMg2+ (n=1-29) cluster ions. We consider a large number of isomers with full relaxations of the geometries, and add the correlation correction to the Hartree-Fock energies for all cluster sizes. The polarization contribution is included at a semiempirical level also for all cluster sizes. Comparison is made with theoretical results for neutral (MgO)n clusters and singly-charged alkali-halide cluster ions. Our method is also compared to phenomenological pair potential models in order to asses their reliability for calculations on small ionic systems. The large coordination-dependent polarizabilities of oxide anions favor the formation of surface sites, and thus bulklike structures begin to dominate only after n=24. The relative stabilities of the cluster ions against evaporation of a MgO molecule show variations that are in excellent agreement with the experimental abundance spectra.Comment: Final version accepted in Journal of Chemical Physics; 8 pages plus 8 figures (6 GIFs and 2 PSs). The main difference with respect to the original submission is the inclusion of coordination-dependent polarizabilities for oxide anions. That results in substantial changes in the result

Sparse Linear Models applied to Power Quality Disturbance Classification

Power quality (PQ) analysis describes the non-pure electric signals that are usually present in electric power systems. The automatic recognition of PQ disturbances can be seen as a pattern recognition problem, in which different types of waveform distortion are differentiated based on their features. Similar to other quasi-stationary signals, PQ disturbances can be decomposed into time-frequency dependent components by using time-frequency or time-scale transforms, also known as dictionaries. These dictionaries are used in the feature extraction step in pattern recognition systems. Short-time Fourier, Wavelets and Stockwell transforms are some of the most common dictionaries used in the PQ community, aiming to achieve a better signal representation. To the best of our knowledge, previous works about PQ disturbance classification have been restricted to the use of one among several available dictionaries. Taking advantage of the theory behind sparse linear models (SLM), we introduce a sparse method for PQ representation, starting from overcomplete dictionaries. In particular, we apply Group Lasso. We employ different types of time-frequency (or time-scale) dictionaries to characterize the PQ disturbances, and evaluate their performance under different pattern recognition algorithms. We show that the SLM reduce the PQ classification complexity promoting sparse basis selection, and improving the classification accuracy

Bayesian analysis of 210Pb dating

In many studies of environmental change of the past few centuries, 210Pb dating is used to obtain chronologies for sedimentary sequences. One of the most commonly used approaches to estimate the ages of depths in a sequence is to assume a constant rate of supply (CRS) or influx of `unsupported' 210Pb from the atmosphere, together with a constant or varying amount of `supported' 210Pb. Current 210Pb dating models do not use a proper statistical framework and thus provide poor estimates of errors. Here we develop a new model for 210Pb dating, where both ages and values of supported and unsupported 210Pb form part of the parameters. We apply our model to a case study from Canada as well as to some simulated examples. Our model can extend beyond the current CRS approach, deal with asymmetric errors and mix 210Pb with other types of dating, thus obtaining more robust, realistic and statistically better defined estimates.Comment: 22 Pages, 4 Figure

La calidad de vida oral en un grupo de adultos mayores de la ciudad de Medellín, Colombia

Antecedentes/Objetivos: La transición demográfica que se presenta en la última década implica un esfuerzo para los profesionales de la salud bucal en conocer como es el comportamiento de los pacientes mayores de 65 años y en especial la comprensión de los impactos que se generan a nivel de su Calidad de Vida Oral-CVO. Muchos estudios se plantean hoy para el análisis en estas dimensiones subjetivas que resumen el vínculo estrecho entre la salud oral y general del paciente mayor, sin embargo, nuestro objetivo es conocer el impacto de las condiciones bucales en la calidad de vida de un grupo de pacientes mayores que frecuentan la red pública hospitalaria en la ciudad de Medellín. Métodos: Estudio de corte trasversal con muestreo aleatorio de 2 etapas en unidades hospitalarias y centros de salud de la red de salud pública “METROSALUD”. La muestra incluyó 352 adultos ≥ 65 años quienes se sometieron a un examen bucal y una encuesta estructurada. Se analizaron las características socio-demográficas y se aplicó el Índice de Calidad de Vida Oral en Geriatría –GOHAI con análisis por separado para los hombres (H) y mujeres (M). Resultados: Siendo enfocada la atención pública de la red hospitalaria principalmente para usuarios de niveles socioeconómico medio-bajo, los hallazgos ratifican que el 84% de los mayores viven particularmente en este entorno. Los indicadores muestran un CAOD de 23,8; IC95%: 22,7-24,8 (H: 23,3; IC95% 21,8-24,8 y M: 24,3; IC95% 23,0-25,6) y una tendencia del GOHAI hacia niveles bajos en el 67,9% de los entrevistados (M: 68,9%, M: 67,3%) con diferencias estadísticamente significativas según el sexo. Un indicador GOHAI de 44,42 (IC95%) en CVO indica una interpretación negativa del índice, sin embargo, estudios realizados con una metodología similar en países como Brasil (GOHAI: 33,8-CAOD: 26,7) y Arabia Saudí (GOHAI: 32,1-CAOD: 20,7), reportan valores muy negativos respecto a los encontrados en nuestro estudio. La Calidad de Vida Oral de los pacientes mayores de la ciudad de Medellín, se aproxima a niveles de comunidades estudiadas en China (GOHAI: 48,9-CAOD: 18,8), Malasia (GOHAI: 46,2-CAOD: 20,2) e incluso Francia (GOHAI: 46). Conclusiones: La calidad de vida oral con niveles bajos en la población adulta mayor de la ESE Metrosalud de Medellín, se ve impactada negativamente según los resultados asociados al estado de la dentición. Se plantea el análisis de las dimensiones de malestar psicológico, dolor físico y limitación funcional y la oportunidad para priorizar con estrategias que fortalezcan la Atención Primaria

Structural and morphological evolution of powders nanostructured ceramics: transitional aluminas

This work aims with the study of the transformation of boehmite into transitional aluminas. Boehmite was obtained by a sol-gel method from an aluminium hazardous waste. The thermal behaviour of boehmite was followed by thermogravimetry and differential thermal analysis to determine the transformation temperatures.  By calcinations of boehmite at temperatures ranging between 250-1000ºC, transitional aluminas (?, ? , ?-Al2O3)  were synthesized and characterized by XRD, TEM and FTIR. All the transitional aluminas exhibit nanometric crystallite size, ranging from 2.5-15nm. ?-Al2O3 was obtained as a nanostructured material at 500ºC with a cell parameter a=7.923Å. ?-phase stars to appear at 850ºC with a crystallite size of 6nm and cell parameters a=5.672Å and c=24.600Å. For ?-Al2O3 the cell parameters, in Å, were a=11.817, b=2.912, c=5.621 and ?=103.8º. The progressive conversion of the transitional phase ?-Al2O3 into the stable polymorph ?-alumina, takes place gradually and a four-phases region is achieved at 1000ºC, where coexist with other transitional phase such as  ?- and ?-Al2O3