Convergence and Cointegration

This paper provides a new, uni¯ed, and °exible framework to measure and characterize convergence in prices. We formally de¯ne this notion and propose a model to represent a wide range of transition paths that converge to a common steady-state. Our framework enables the econometric measurement of such transi- tional behaviors and the development of testing procedures. Speci¯cally, we derive a statistical test to determine whether convergence exists and, if so, which type: as catching-up or steady-state. The application of this methodology to historic wheat prices results in a novel explanation of the convergence processes experienced during the 19th century.Price convergence, cointegration, law of one price.

Development of Head Space Sorptive Extraction Method for the Determination of Volatile Compounds in Beer and Comparison with Stir Bar Sorptive Extraction

A headspace sorptive extraction method coupled with gas chromatography-mass spectrometry (HSSE-GC-MS) was developed for the determination of 37 volatile compounds in beer. After optimization of the extraction conditions, the best conditions for the analysis were stirring at 1000 rpm for 180 min, using an 8-mL sample with 25% NaCl. The analytical method provided excellent linearity values (R-2 > 0.99) for the calibration of all the compounds studied, with the detection and quantification limits obtained being low enough for the determination of the compounds in the beers studied. When studying the repeatability of the method, it proved to be quite accurate, since RSD% values lower than 20% were obtained for all the compounds. On the other hand, the recovery study was successfully concluded, resulting in acceptable values for most of the compounds (80-120%). The optimised method was successfully applied to real beer samples of different types (ale, lager, stout and wheat). Finally, an analytical comparison of the optimised HSSE method, with a previously developed and validated stir bar sorptive extraction (SBSE) method was performed, obtaining similar concentration values by both methods for most compounds

Creative and collective writing in the context of the new cultural practices

Se plantea en este artículo el cambio profundo que, en la nueva cultura del siglo XXI, ha sufrido el concepto de creación colectiva, por influencia de Internet. Las redes sociales, la cultura participativa, la convergencia de los medios y otros factores han favorecido nuevos modos de expresión, al margen de la escritura académica o profesional, como ha sido el caso de la ficción-manía. Sobre el concepto de creación colectiva se está escribiendo mucho, a propósito de la épica y de otros temas literarios y debe ser “iluminado” a la luz de lo que Internet o los nuevos fenómenos, como el auge de las sagas fantásticas o la ficción-manía, están suponiendo. Así, lo que actualmente se denomina escritura colaborativa es en realidad un concepto que ha ido evolucionando de forma acompasada con las poéticas y las prácticas sociales de la lectura en los últimos tiempos. Revisamos los rasgos de estas nuevas prácticas y se analizan las implicaciones para la educación del siglo XXI.The deep change that, in the new culture of the 21st century, has suffered the concept of collective creation, under the influence of the Internet is proposed in this article. Social networking, participatory culture, the convergence of media and other factors have favored new ways of expression, apart from academic or professional writing, as it has been the case of the fan fiction. There is a lot of studies nowadays on the concept of collective creation, with regard to epic and other literary topics and should be “enlightened” in the light of what Internet or new phenomena, such as the rise of fantasy sagas or the fan fiction, are involving. So, what is currently referred to as collaborative writing is actually a concept that has evolved in a measured way with the poetic and social practices of reading in last times. We review the features of these new practices and examine the implications for the education of the 21st century.peerReviewe

Cadmium removal by Anabaena sp. ATCC 33047 immobilized in polyurethane foam

The nitrogen-fixing cyanobacterium Anabaena sp. ATCC 33047, which generates substantial amounts of exopolysaccharide, was immobilized by entrapment within the reticulate network of polyurethane foam discs. The immobilized Anabaena sp. system has been investigated as a potential biosorbent for the removal of cadmium from aqueous solutions. The results showed that it was a highly fast process, with 80 % of the adsorption taking place in the first 10 min, reaching full equilibrium in about 50 min. Data analysis indicated that the behaviour of the system accurately fits to a monolayer adsorption model (Langmuir isotherm). The maximal biosorption capacity determined for the immobilized Anabaena sp. system was as high as 162 mg Cd (II) per gram dry biomass. The outstanding properties established for immobilized Anabaena sp. in polyurethane foam underline the relevance of such a system as an alternative to current treatments of variety effluents or wastewater contaminated with cadmium.Peer reviewe

Influence of the type of rare-earth cation on electrical properties of Ba(Zr,Ti)O3 ceramics

En este artículo es investigado el efecto del radio iónico de diferentes cationes de tierras raras sobre las propiedades eléctricas del compuesto Ba(Zr,Ti)O3. La cerámica BaZr0.09Ti0.9O3 fue dopada con iones de Gd3+, Pr3+ y La3+, sustituyendo un 5 % de contenido de cationes Ba2+. Los resultados muestran que el coeficiente de difusividad se incrementa con el aumento del radio iónico, mientras el carácter de la transición de fase permanece casi constante, de acuerdo con el modelo fenomenológico de Santos-Eiras. En todas las muestras se reporta un comportamiento no relajador. El proceso de conductividad iónica en el BaZr0.09Ti0.9O3 aparece a 200 ºC, valor inferior al observado en el material cerámico BaTiO3. El valor de energía de activación en el proceso de conductividad del BaZr0.09Ti0.9O3 (Ea= 0.81 eV) indica un mecanismo de compensación de carga en la estructura cristalina similar al BaTiO3, es decir vacancias de oxígeno simplemente ionizadas. Para el compuesto BaZr0.09Ti0.9O3 dopado con iones Gd3+, Pr3+ y La3+ aparece además un mecanismo de conducción de electrones, debido a la sustitución del Ba2+.Postprint (published version

Prospective towards implementation of electric vehicles in Colombia

The effects of climate change have led to reduces fossil fuel in vehicle, developing new technologies such as the electric vehicles. The research presents an identification of barriers and inhibitors according to international experiences, an evaluation with the MICMAC method and the identification of key factors to achieve development of electric vehicles in Colombia. The results allow to identify the elements of high influence, which may guide intervention strategies and be the basis for the formulation of guidelines and policies. The results conclude that the business models for the purchase and sale of energy are the catalyst for the encouraging of the stakeholders, the improvement of the distribution network and the management of the electricity market

How to measure inflation volatility: a note

Este documento propone un modelo estadístico y un marco conceptual para estimar la volatilidad de la inflación suponiendo rational inattention, donde la caída del nivel de atención responde a la llegada de noticias al mercado. Estimamos la tendencia y la volatilidad condicional de la inflación en Alemania, España, la Unión Económica y Monetaria y Estados Unidos empleando datos mensuales desde enero de 2002 hasta marzo de 2022, y contrastamos si la inflación fue igual o inferior al 2 % en ese período y esas regiones. Descomponemos la volatilidad de la inflación en sus componentes de sorpresas «negativas» y «positivas», y caracterizamos los diferentes escenarios de volatilidad de inflación durante la gran crisis financiera de 2008, la crisis de deuda soberana y el período pos-COVID. Nuestra medida de volatilidad supera a una modelización GARCH(1,1) y a la desviación típica móvil de la inflación en ejercicios de previsión un período hacia delante, tanto dentro como fuera de la muestra. La metodología propuesta en este artículo es apropiada para estimar la volatilidad condicional de variables macrofinancieras. Recomendamos incluir esta medida en tareas de seguimiento y previsión de la dinámica de la inflación.This paper proposes a statistical model and a conceptual framework to estimate inflation volatility assuming rational inattention, where the decay in the level of attention reflects the arrival of news in the market. We estimate trend inflation and the conditional inflation volatility for Germany, Spain, the euro area and the United States using monthly data from January 2002 to March 2022 and test whether inflation was equal to or below 2% in this period in these regions. We decompose inflation volatility into positive and negative surprise components and characterise different inflation volatility scenarios during the Great Financial Crisis, the Sovereign Debt Crisis, and the post-COVID period. Our volatility measure outperforms the GARCH(1,1) model and the rolling standard deviation in one-step ahead volatility forecasts both in-sample and out-of-sample. The methodology proposed in this article is appropriate for estimating the conditional volatility of macro-financial variables. We recommend the inclusion of this measure in inflation dynamics monitoring and forecasting exercises

Bioinspired algorithms for optimizing the harmonics contents of a PWM power inverter

Este trabajo se centra en la evaluación de diferentes técnicas de algoritmos bio-inspirados, que permitan reducir la distorsión armónica (THD) de la modulación de ancho de pulso (PWM) en inversores de potencia. Se realizó un amplio estudio que identifica y desarrolla algoritmos de optimización de inspiración biológica basados principalmente en la búsqueda tabú, algoritmos genéticos, optimización por enjambre de partículas y colonia de hormigas. Los métodos de optimización bio-inspirados son usados principalmente para encontrar los mejores parámetros operacionales de un PWM aplicado a inversores de potencia. Los mejores resultados fueron obtenidos cuando la posición de pulso (Pp) se localiza cerca a la posición central (Pp=0.5) o a la simetría del pulso. Dentro de los cuatro métodos estudiados el mejor resultado se encontró usando la técnica de optimización por colonia de hormigas, debido al valor de THD más bajo encontrado e igualmente con el 5 y 7 armónico con menos impulsos (Np= 38), casi 5 veces menor que el resultado usando la técnica optimización por enjambre de partículas, logrando reducir considerablemente las pérdidas bajando la frecuencia de conmutación (4560 Hz) de los dispositivos de potencia. Los algoritmos desarrollados pueden fácilmente adaptarse a cualquier problema de optimización, solo haciendo cambios en el número de variables y en la selección (o eliminación) de los criterios y así de esta manera obtener mejores resultados en problemas complejos.This paper deals with the evaluation of different bio-inspired algorithms techniques for reduction of harmonic distortion (THD) in pulse width modulation (PWM) of power inverters. A comprehensive study is performed, that identifies and develops biologically inspired optimization algorithms based mainly on tabu search, genetic algorithms (GA), particle swarm optimization (PSO), and ant colony optimization (ACO). These bio-inspired optimization methods were used to find the best operational parameters of a PWM applied to a power inverter. The best results were achieved when the pulse position is near to the middle position (Pp=0.5) or symmetry of the pulse. For the four methods analyzed he best result was obtained using ACO method based on the lowest THD content and less 5th and 7th harmonics magnitude with fewer pulses (Np=38), almost 5 times lower than the result of PSO (Np=179). It was achieved to reduce losses considerably with a reduction in the switching frequency of the power devices (4560 Hz). The algorithms developed can be easily adapted to any minimization problem, only making changes in the number of variables and selection (or elimination) criteria to obtain better results in complex problems

Feature Selection: A perspective on inter-attribute cooperation

High-dimensional datasets depict a challenge for learning tasks in data mining and machine learning. Feature selection is an effective technique in dealing with dimensionality reduction. It is often an essential data processing step prior to applying a learning algorithm. Over the decades, filter feature selection methods have evolved from simple univariate relevance ranking algorithms to more sophisticated relevance-redundancy trade-offs and to multivariate dependencies-based approaches in recent years. This tendency to capture multivariate dependence aims at obtaining unique information about the class from the intercooperation among features. This paper presents a comprehensive survey of the state-of-the-art work on filter feature selection methods assisted by feature intercooperation, and summarizes the contributions of different approaches found in the literature. Furthermore, current issues and challenges are introduced to identify promising future research and development.Comment: 17 pages, 2 figure