A comparison of robust Kalman filtering methods for artifact correction in heart rate variability analysis

La variabilidad de la frecuencia cardiaca (HRV) ha recibido una atención considerable por mucho años, ya que esta proporciona un valor cuantitativo para examinar el ritmo sinusal modulado para el sistema nervioso autónomo (SNA). El SNA juega un papel importante en campos clínicos y fisiológicos. El análisis de la HRV se puede realizar calculando varias medidas tanto en el domino del tiempo como en la frecuencia. Sin embargo, el cálculo de estas medidas se puede ver afectado por la presencia de artefactos o latidos ectópicos en registros de electrocardiogramas (ECG). Esto es particularmente cierto para registros ECG desde un monitor Holter. El objetivo de este trabajo fue estudiar el rendimiento de varios filtros de Kalman robustos para la corrección de artefactos. Para nuestros experimentos, se usaron dos bases de datos reales: el primer conjunto de datos incluye 10 series de tiempo de intervalos RR a partir de un generador de series de tiempo de intervalos RR realista. La segunda base de datos contiene 10 conjuntos de series de intervalos RR de cinco pacientes sanos y cinco pacientes que sufren una insuficiencia cardiaca congestiva. Se calculó la desviación estándar de los intervalos RR a partir de las señales filtradas. Los resultados se compararon con un reconocido software de procesamiento, mostrando comportamientos y valores similares. Adicionalmente, los métodos propuestos ofrecen resultados satisfactorios en comparación con el filtro de Kalman estándar.Heart rate variability (HRV) has received considerable attention for many years, since it provides a quantitative marker for examining the sinus rhythm modulated by the autonomic nervous system (ANS). The ANS plays an important role in clinical and physiological fields. HRV analysis can be performed by computing several time and frequency domain measurements. However, the computation of such measurements can be affected by the presence of artifacts or ectopic beats in the electrocardiogram (ECG) recording. This is particularly true for ECG recordings from Holter monitors. The aim of this work was to study the performance of several robust Kalman filters for artifact correction in Inter-beat (RR) interval time series. For our experiments, two data sets were used: the first data set included 10 RR interval time series from a realistic RR interval time series generator. The second database contains 10 sets of RR interval series from five healthy patients and five patients suffering from congestive heart failure. The standard deviation of the RR interval was computed over the filtered signals. Results were compared with a state of the art processing software, showing similar values and behavior. In addition, the proposed methods offer satisfactory results in contrast to standard Kalman filtering

Structural properties of various sodium thiogermanate glasses through DFT-based molecular dynamics simulations

We present a study of the structural properties of (x)Na$_2$S-(1-x)GeS$_2$ glasses through DFT-based molecular dynamics simulations, at different sodium concentrations ($0<x<0.5$). We computed the radial pair correlation functions as well as the total and partial structure factors. We also analyzed the evolution of the corner- and edge-sharing intertetrahedral links with the sodium concentration and show that the sodium ions exclusively destroy the former. With the increase of the sodium concentration the ``standard'' FSDP disappears and a new pre-peak appears in the structure factor which can be traced back in the Na-Na partial structure factor. This self organization of the sodium ions is coherent with Na-rich zones that we find at high modifier concentration.Comment: 9 pages, 7 figures; to be published in Phys. Rev.

Operational realization of quantum vacuum ambiguities

We provide a reinterpretation of the quantum vacuum ambiguities that one encounters when studying particle creation phenomena due to an external and time-dependent agent. We propose a measurement-motivated understanding: Each way of measuring the number of created particles selects a particular vacuum. This point of view gives a clear and physical meaning to the time evolution of the number of particles produced by the agent as the counts in a specific detector and, at the same time relates commonly used quantization prescriptions to particular measurement setups.Comment: 6 pages, 3 figure

El arte del retrato en los textos periodísticos de Manuel Chaves Nogales

Este artículo estudia el arte de la caracterización del periodista Manuel Chaves Nogales (Sevilla, 1897 (Madrid, 1944) en una selección de sus textos periodísticos publicados en Espa- ña. Se trata de 18 piezas de diferentes géneros (crónicas, semblanzas, reportajes, entrevistas) en los que la caracterización es elemento central. A través de ellos se puede observar la evolución en la caracterización de Chaves y su afán por desvelar el carácter de personajes de actualidad a través de escenas signifcativas, mediante unas pocas pinceladas que, indirectamente, muestran sus preocupaciones políticas, sociales y periodísticas

El periodismo en la biografía literaria en la España de los años 20: Pla, González-Ruano y Gómez de la Serna

Este artículo estudia la escritura biográfica de tres escritores y periodistas españoles desde finales de los años 20 y hasta el comienzo de la Guerra Civil (1936), una época de cambios políticos en la que las biografías reflejaron la búsqueda de seres humanos ejemplares para afrontar el presente. La nueva biografía, un tipo de biografía literaria o novelada popularizada en Europa por Lytton Strachey, Virginia Woolf, André Maurois o Stefan Zweig llegó también a España. Se dio en ese momento un giro en la forma de relatar la historia de la vida de una persona que conectaba con el periodismo: el biógrafo seleccionaba solo escenas importantes en la vida del biografiado, se ahondaba en la psicología en detrimento del relato de hechos y se caracterizaba a los personajes utilizando técnicas novelescas. Las biografías de Josep Pla, César González-Ruano y Gómez de la Serna son buen ejemplo de esa tendencia.This article studies the writing of the biography of three writers and journalists in Spain in the years prior to the Second Spanish Republic and until the beginning of the Spanish Civil War in 1936. The new biography, a type of literary biography or novella following the European model of Lytton Strachey, Virginia Woolf, André Maurois or Stefan Zweig also arrived in Spain. At that moment, there was a turning in the way of telling the story of a person’s life: the biographer selected only important scenes in the life of the biography, delving into psychology to the detriment of the story of events and characterizing the characters using techniques from the novel. The biographies of Josep Pla, César González-Ruano and Gómez de la Serna are good examples of this.Este artigo estuda a escrita biográfica de três escritores e jornalistas espanhóis desde o final da década de 1920 até ao início da Guerra Civil (1936), uma época de mudanças políticas em que as biografias reflectiam a procura de seres humanos exemplares para enfrentar o presente. A nova biografia, um tipo de biografia literária ou romance tornado popular na Europa por Lytton Strachey, Virginia Woolf, André Maurois ou Stefan Zweig também chegou a Espanha. Nessa altura, houve uma mudança na forma de contar a história da vida de uma pessoa que se relacionava com o jornalismo: o biógrafo seleccionou apenas cenas importantes na vida do biógrafo, mergulhou na psicologia em detrimento da narração de factos e caracterizou as personagens através de técnicas inovadoras. As biografias de Josep Pla, César González-Ruano e Gómez de la Serna são bons exemplos desta tendência

El periodismo y la historia: Chaves Nogales y la Revolución rusa

El objetivo de este artículo es mostrar cómo la imagen que dio Manuel Chaves Nogales de la revolución rusa a través de sus artículos en los años treinta, siendo vanguardia del periodismo de entonces, tuvo un sentido histórico. La hipótesis es que el periodismo, informando sobre el presente, puede aportar a los historiadores alguna lección. Para mostrar la conciencia histórica del periodismo de Chaves Nogales se contextualiza al autor entre otros viajeros de la época a la Unión Soviética, se analiza la manera en la que Chaves interpreta las huellas de la revolución en las personas y en su entorno y se relaciona con la microhistoria.The objective of this article is to show how the picture Manuel Chaves Nogales presented of the Russian Revolution through his articles in the 30’s, the vanguard of journalism of that time, had a historical meaning. The hypothesis proposed is that journalism reporting on the present can also provide historians with some lessons. To show the historical awareness of Chaves Nogales’ journalism, the author is contextualized among other travelers to the Soviet Union of that time. The way in which Chaves interprets the traces of the Revolution in people and their environment and how these relate to microhistory are studied

Sound event detection for music signals using gaussian processes

En este artículo se propone una metodología para detectar eventos sonoros en señales de música usando procesos Gaussianos. En el algoritmo presentado, las señales de audio de entrada son transformadas a un espacio tiempo-frecuencia utilizando la Transformada de Tiempo Corto de Fourier para obtener el espectrograma, cuya dimensión es posteriormente reducida pasando de la frecuencia en escala lineal en Hertz a la escala logarítmica en Mel por medio de un banco de filtros triangulares. Finalmente, se clasifica entre “evento” y “no evento” cada uno de los espectros de tiempo corto contenidos en el espectrograma en escala Mel por medio de un clasificador binario basado en procesos Gaussianos. Como parte del proceso de evaluación, se compara el desempeño de la metodología propuesta con el desempeño de algunas técnicas ampliamente utilizadas para detectar eventos en este tipo de señales. Para tal fin, se implementa en MATLAB® cada una de estas técnicas y se ponen a prueba utilizando dos bases de datos compuestas por segmentos de audio de diferente complejidad; definida por el tipo y cantidad de instrumentos tocados al mismo tiempo. Los resultados indican que la metodología propuesta supera el desempeño de las técnicas hasta ahora planteadas, presentando un mejoramiento en la medida F de 1,66 % para la base de datos uno y de 0,45 % para la base de datos dos. In this paper we present a new methodology for detecting sound events in music signals using Gaussian Processes. Our method firstly takes a time-frequency representation, i.e. the spectrogram, of the input audio signal. Secondly the spectrogram dimension is reduced translating the linear Hertz frequency scale into the logarithmic Mel frequency scale using a triangular filter bank. Finally every short-time spectrum, i.e. every Mel spectrogram column, is classified as “Event” or “Not Event” by a Gaussian Processes Classifier. We compare our method with other event detection techniques widely used. To do so, we use MATLAB® to program each technique and test them using two datasets of music with different levels of complexity. Results show that the new methodology outperforms the standard approaches, getting an improvement by about 1.66 % on the dataset one and 0.45 % on the dataset two in terms of F-measure

Failure under stress of grapevine wood: The effects of the cerambycid xylotrechus arvicola on the biomechanics properties of vitis vinifera

Xylotrechus arvicola is an insect pest on Vitis vinifera in the main wine-producing regions of Spain. X. arvicola larvae bore inside grapevine wood, which cause structural damages in the plants´ biomechanical properties. Grapevine wood affected and unaffected by larvae, were collected from vineyards. Compression and flexural tests were used to quantify biomechanical wood properties. Affected wood broke more quickly and endured a lower supported force than unaffected wood in both varieties and moisture states. Tempranillo was the most resistant variety on trunks, while Cabernet-Sauvignon was the most resistant variety on branches, where all infested varieties showed a lower rate of bending. Grapevine wood affected by X. arvicola larvae shows an important decrease in its resistance in both moisture states - dry and wet wood - and it is observed due to the faster break in time and a lower supported force. These damages give the affected wood greater sensitivity to external mechanical factors in the vineyards, such as strong winds, harvest weight and the vibration exerted by harvesting machines. The aspect of stress-time curves in all cases follow similar patterns, so in future studies might be possible to stablish relationships between both wet and dry samples and different infestation levels

A reliable turning process by the early use of a deep simulation model at several manufacturing stages

The future of machine tools will be dominated by highly flexible and interconnected systems, in order to achieve the required productivity, accuracy, and reliability. Nowadays, distortion and vibration problems are easily solved in labs for the most common machining operations by using models based on the equations describing the physical laws of the machining processes; however, additional efforts are needed to overcome the gap between scientific research and real manufacturing problems. In fact, there is an increasing interest in developing simulation packages based on "deep-knowledge and models" that aid machine designers, production engineers, or machinists to get the most out of the machine-tools. This article proposes a methodology to reduce problems in machining by means of a simulation utility, which uses the main variables of the system and process as input data, and generates results that help in the proper decision-making and machining plan. Direct benefits can be found in (a) the fixture/ clamping optimal design; (b) the machine tool configuration; (c) the definition of chatter-free optimum cutting conditions and (d) the right programming of cutting toolpaths at the Computer Aided Manufacturing (CAM) stage. The information and knowledge-based approach showed successful results in several local manufacturing companies and are explained in the paper.The work presented in this paper was supported in some sections within the project entitled MuProD-Innovative Proactive Quality Control System for In-Process Multi-Stage Defect Reduction- of the Seventh Framework Program of the European Union [FoF.NMP.2011-5] and UPV/EHU under program UFI 11/29. Thanks are given to Tecnalia, for collaboration in testing, and especially to Ainhoa Gorrotxategi and Ander Jimenez for the sound work in the project. Thanks to Gamesa Eolica and Guruzpe, for the time, technical advices, and efforts during the analysis in examples