Search

Working on alternatives for harnessing and transforming different forms of energy in a clean and efficient way, like piezoelectric phenomena, allows considering collecting energy that is commonly wasted. For example, the piezoelectricity facilitates the harvesting of energy derived from the weight discharged by humans when walking on a surface conditioned with piezoelectric transducers. However, the technology in this field has always advanced in the opposite direction, i.e. the conversion of electric energy into vibrations for different applications. In this work, the design of the material structure for a piezoelectric device of low resonance frequency for the capture of electricity is considered. The purpose of this device is the efficient transformation of mechanical energy into electrical energy; for this reason, the design of its configuration counts with a resonance frequency of less than 100 kHz. For this, the characteristics of the area dimensions and their relationship to the thickness according to the deposited material and the performance according to the projected impact were established. Moreover, the selection of the substrate was established according to the fracture requirements, acknowledging the mechanical loading loads of the transducer. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Optometry is the property of Elsevier B.V. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Acta Medica Colombiana is the property of Acta Medica Colombiana and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Revista Mexicana de Biodiversidad is the property of Universidad Nacional Autonoma de Mexico, Instituto de Biologia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal de Ciencia e Ingeniería is the property of Corporacion Universitaria Autonoma del Cauca and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Revista Signos is the property of Pontificia Universidad Catolica de Valparaiso and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Background: Odontogenic cysts are asymptomatic. They are diagnosed radiographically (80%) or through sporadic symptomatology (20%). There is scarce epidemiological data regarding this pathology in Colombia. Purpose: To describe the frequency of odontogenic cysts, based on the 2017 WHO classification, among patients of the National University of Colombia dental school. Methods: A cross-sectional study was carried out using clinical records of patients with diagnosis of odontogenic cysts (confirmed through histopathological analysis), whose age, sex, and cyst location (affected area) data were correctly completed. Fisher's test was used to evaluate independence between variables (p=0.05). Results: The most frequent odontogenic cysts were: dentigerous cyst (66.6%), radicular cyst (22.2%), and odontogenic keratocyst (11.2%). 77.7% were observed in men. 38.9% were diagnosed between the first and second decades of life (p=0.041) and the posterior mandibular area was the most affected (44.4%) (p=0.017). Conclusions: Dentigerous cyst were found most frequently during the second decade of life, affecting men and the posterior mandibular area. Radicular cysts did not show preference for one gender, occurred during and after the fourth decade of life and affected the anterior maxilla. Odontogenic keratocyst showed no predilection for sex or affected area and was mainly present in two different decades of life. [ABSTRACT FROM AUTHOR]

The objective was to determine the frequency of Cryptosporidium spp., and to identify the species or genotype of the oocysts found, in suckling lambs kept grazing in the Huasteca Alta region, State of Veracruz, Mexico. Fecal samples were collected from 210 lambs Pelibuey, Black Belly, and Katahdin, 7 to 21 d old from 21 sheep farms. Samples were stained with Kinyoun, nested PCR was used to amplify the 18S rRNA gene region of the parasite (830 bp), and positive samples were sequenced. The frequency of animals positive to Cryptosporidium spp by microscopy was 19.5 % (41/210), with a 10 to 50 % range among herds; with molecular techniques, the frequency of positive lambs was 26.8 % (11/41) with a 14 to 50 % range; all other samples were negative to both tests. All 11 samples sequenced showed 100 % homology with the 18S rRNA region of C. parvum. Results confirm the relevance of C. parvum as a major etiology of cryptosporidiosis in lactating lambs and show its broad distribution in this region of Mexico. This identification highlights that sheep can be considered as a significant potential source of human cryptosporidiosis, since it is considered a zoonotic disease, mainly for the people handling the flocks. [ABSTRACT FROM AUTHOR]

Copyright of Colombia Forense is the property of Universidad Cooperativa de Colombia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Agro Productividad is the property of Colegio de Postgraduados and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Polylepis woodlands are vulnerable ecosystems that are under strong anthropogenic pressure. These woodlands are fragmented, forming patches on the slopes of high andean and rocky mountains, where we find Polylepis tomentella. They are distributed in the departments of Ayacucho, Apurimac and Arequipa. In 2010, we evaluated the community structure of the order Coleoptera in a representative patch of the Chaviña district. Two surveys (wet and dry season) were carried out. Ten sampling stations were established and pitfall traps, bait traps, chromotropic traps, active collection and Malaise traps were used. Forty-five species were identified and distributed in 18 families, being Curculionidae and Carabidae the most representative. Estimated richness was between 43 and 47 species. The best richness estimator was ACE. These data can be useful for subsequent diversity studies and also to estimate the degree of disturbance of these woodlands. [ABSTRACT FROM AUTHOR]

Este trabajo se propone examinar la validez de la frecuencia como criterio para ordenar las colocaciones que se deben tratar en los sucesivos niveles de aprendizaje del español. Para ello se han estudiado los siguientes aspectos: (i) la opinión de profesionales de la enseñanza de español como lengua extranjera/segunda con respecto a los criterios que ellos emplearían para nivelar vocabulario; (ii) las propuestas de dichos profesionales al respecto; (iii) su intuición sobre frecuencia colocacional; y (iv) el distinto grado de dificultad que presentan a los aprendices colocaciones clasificadas en distintos niveles según su frecuencia. Los datos para valorar estas cuatro dimensiones se han obtenido mediante cuestionarios presentados a profesores y aprendices de español. Los resultados sugieren que los profesionales de la enseñanza consideran la frecuencia un criterio importante para secuenciar el vocabulario y sus propuestas coinciden de forma notable con una nivelación basada en la frecuencia. Los resultados con respecto a la intuición de los profesores sobre frecuencia colocacional y a la correlación entre el nivel asignado a las colocaciones y la dificultad que presentan a los aprendices son menos concluyentes.

El control por pendiente garantiza la regulación de frecuencia y el reparto de potencia activa entre los inversores de una microrred aislada, sin embargo, introduce desviaciones respecto a la frecuencia de referencia. Cuando un generador adicional basado en inversores se conecta a la microrred se reduce la desviación en frecuencia y se aumenta la capacidad de potencia de todo el sistema; lo mismo ocurre cuando se interconectan microrredes en modo isla. El control por pendiente ha mostrado ser efectivo en microrredes basadas en inversores, sin embargo, cuando uno o más generadores sincrónicos se conectan directamente a la microrred, cambian las condiciones de dicho control. Para analizar que ocurre cuando se interconectan microrredes en modo isla se analizan los casos cuando ambas microrredes constan únicamente de inversores, y cuando una microrred o ambas tienen al menos un generador sincrónico. De esta manera, los resultados de simulación presentados demuestran las mejoras de la regulación de frecuencia utilizando el aumento de inercia de microrredes Interconectadas.

El presente estudio parte del interés por el comportamiento informacional de los jóvenes universitarios. En concreto, se centra en el análisis de la frecuencia de búsqueda y recuperación de noticias. Además de tener en cuenta los motivos que les incita al acceso a las noticias, también se abordan los medios y modos de comunicación utilizados por los jóvenes para informarse. También se pretende establecer una relación entre la frecuencia de consulta y su disposición a difundir las noticias y definir las fórmulas que se utilizan para este cometido. El estudio tiene como base una encuesta con muestreo no probabilístico realizada a jóvenes universitarios. Como resultados destacan el alto nivel de consulta y el uso combinado de medios convencionales y digitales, independientemente de la frecuencia de acceso a la información de actualidad. También se descarta la influencia directa de la frecuencia de acceso a la información de actualidad en lo relativo a la difusión de noticias por parte de los jóvenes.

Se presentan los resultados obtenidos tras evaluar las actitudes hacia la inclusión de alumnos con necesidades educativas especiales en aulas ordinarias. En este estudio preliminar la muestra está compuesta por 91 participantes, todos ellos estudiantes del grado de Maestro. , de los cuales un 22% son hombres y un 78% son mujeres, de edades comprendidas entre los 22 y los 45 años (M=28,13; Dt=6,4). Se aplicó el Cuestionario de Opiniones hacia la Integración, que está formado por 30 items con un formato de respuesta tipo Likert de 5 puntos y puntuaciones más altas denotan actitudes más favorables. Los resultados indicaron que las mujeres y quienes tienen contacto con el referente actitudinal consideran que el profesorado está mejor preparado para hacer frente a los retos de la inclusión. Sin embargo, no parece existir una relación lineal entre frecuencia de contacto y actitudes hacia la integración, por lo que es necesario profundizar en el tipo de contacto y en los tipos de necesidades educativas con los que se está familiarizado, para poder determinar el peso de estos factores en la conformación de unas actitudes más o menos favorables. Los presentes hallazgos así como la continuación del presente estudio nos permitirán establecer pautas para la intervención con maestros en formación, quienes serán elementos clave de la promoción de la inclusión en las aulas del futuro.

Introduction: Non-adherence to the prescribed dialysis sessions frequency ranges from 2% to 50% of patients. The objective of this study was to evaluate the impact of detecting and measuring the non-adherence to the prescribed dialysis frequency and to determine the importance of a multidisciplinary approach with the aim of improving adherence. Methods: longitudinal cohort study including 8,164 prevalent hemodialysis patients in April 2010, with more than 90 days of treatment, in Fresenius Medical Care Argentina units that were monitored for 3 years. The survey evaluated: interruption of at least one dialysis session in a month or reduction at least 10 minutes of a dialysis session in a month, during 6 months prior to the survey. Relative mortality risks were evaluated among groups. Results: 648 patients (7.9%) interrupted dialysis sessions: 320 (3.9%) interrupted one session per month and 328 (4.01%) interrupted more than one session per month. After 3 years monitoring, 349 patients (53.8 %) remained active in hemodialysis and 299 were inactive due to different reasons: 206 deceased (31.8 %), 47 transfers or monitoring losses (7.25 %), 36 transplanted (5.55 %), 8 changes to PD modality (1.2%) and 2 recovered their kidney function (0.3 %).Interrupting one session per month significantly increased the mortality risk comparing both groups (interrupters and non-interrupters): RR 2.65 (IC 95% 2.24 – 3.14). Interrupting more than one dialysis session also increased significantly mortality risk comparing to the non-interrupters: RR 2.8 (IC 95% 2.39 – 3.28). After 3 years monitoring, 41.6 % of interrupters at the beginning had improved their adherence through a multidisciplinary program of quality improvement. Conclusion: Global mortality was greater among patients who interrupted dialysis sessions. A considerable proportion of interrupter patients at the beginning modified their behavior through the implementation of a multidisciplinary program of quality improvement.

La difusión de servicios inalámbricos de comunicación (telefonía, internet, etc) es cada vez mayor en la actualidad. El costo de los equipamientos necesarios para brindar el servicio con calidad adecuada es elevado. La selección de un conjunto de puntos geográficos que permitan una cobertura óptima de una señal de radio frecuencia minimizando uso de recursos es fundamental. A esta tarea se la denomina diseño de la red de radio y es un problema NP – duro de optimización, por lo tanto, es factible de ser tratado con metaheurísiticas. Las metaheurísiticas son métodos que integran procedimientos de mejora local y estrategias de alto nivel para realizar una búsqueda robusta en el espacio del problema. El presente trabajo propone analizar y evaluar la capacidad de tres algoritmos genéticos canónicos de encontrar una solución aceptable mediante una función objetivo que combina el grado de cobertura del terreno y el uso eficiente de recursos en diferentes escenarios poblacionales. Los resultados obtenidos son promisorios.

This study aims to establish whether there is any relation between the correctness of collocations present in the writings of learners of Spanish and the association their members display in a representative corpus of this language. In order to do that, starting from a sample of collocations extracted from a learner corpus where they have previously been identified by means of phraseological criteria, I study their frequency in a representative corpus of Spanish. Based on these data, I try to establish if the association between the constituents of a collocation, as measured in terms of frequency of co-occurrence and mutual information, has any influence on the probability wherewith learners produce such collocation correctly. [ABSTRACT FROM AUTHOR]

The use of laminated composite materials has increased in modern engineering, mainly in those projects that require an assurance of good strength and durability. It has been found that some properties of the material that ensure proper performance can be affected by the occurrence of residual stresses caused by the manufacturing process. In this paper, the influence of thermal residual stresses on the free vibration of reinforced plates is analyzed. For the experimental study, a square, reinforced, prepreg laminate was used. The laminate was reinforced using two different types of reinforcement: lateral and perimetral. The plates were prepared using two different techniques. The first group of laminates was prepared by curing the reinforcement at 177 °C. The second group of laminates was prepared by secondary bonding of the reinforcement to the laminate at room temperature (22 °C). A numerical model was elaborated for comparison with the experimental results. Accuracy was observed when comparing experimental and numerical results, showing that the presence of residual thermal stress affects the value of the natural frequencies of free vibration and the characteristic modal form of reinforced plates. Regardless of the type of reinforcement used, a notable increase in these values was observed, even when the element was simply supported. [ABSTRACT FROM AUTHOR]

The aim of this study was to analyse the relationship among several social-cognitive predictors of sexual behaviour (beliefs, knowledge, attitudes and values), sexual behaviours, the frequency of sexual activities and several dimensions of sexual satisfaction (individual/with the partner and actual/desired sexual satisfaction). A mixed-method study was conducted. The data were collected using a semi-structured interview specially designed for this study, which was administered to 14- to 20-year-old women. Correlation analyses revealed that the expected direct associations between the explored social-cognitive predictors, sexual behaviour and sexual satisfaction were not established; consequently, possible indirect effects were explored. The results of the mediational model that better fit the data indicated that sexual behaviour is related to (actual) sexual satisfaction not only direcdy but also indirecdy through the frequency of sexual activities in a (probable) effect of partial mediation. These findings have interesting applications in terms of sexual education and sexual health promotion among young women. [ABSTRACT FROM AUTHOR]

Copyright of Ingeniería Solidaria is the property of Universidad Cooperativa de Colombia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Objective: This paper is intended to be a reflection on the trends in Human Papilloma Virus (VPH) research in Latin America, compared to high income countries. Materials and methods: Answers are provided regarding HPV in terms of frequency, research trends, education programmes for patients and healthcare staff, and preventive strategies. An extensive review was conducted of the published research and of the studies presented during the I South American Meeting on HPV. Results: Research work in HPV is focused on basic and applied studies on HVP and cervical cancer (CC). There are limitations to scientific development in our region compared to high income countries and this is reflected in disease prevalence and vaccination rates. Prevention programs at each level are undergoing slow transformations as the natural hurdles of the region are overcome. Conclusion: The impact of HPV infection and cervical cancer is huge in Latin America, requiring the development of public policy and organized preventive interventions. [ABSTRACT FROM AUTHOR]

Droop control guarantee frequency regulation and power sharing among the inverters in an islanded microgrid, however, frequency deviations are introduced respect to reference values. When an aditional distributed generator base on inverters is connected to the microgrid, such deviations are reduced and the power capacity of the system is improved; same way happens when islanded microgrids are interconnected. Droop control has shown to be effective in inverter based microgrids, however, when one or more synchronous generators are directly connected to the microgrid the conditions of the controller change. To analaize what happen when islanded microgrids are interconected different cases are considered: first when both microgrid are based only in inverters and other case in which one microgrid has at least one synchronous generator. In this way, the simulation results show the regulation frequency improvements using the inertia increase of networked microgrids. [ABSTRACT FROM AUTHOR]

Copyright of Etudes Romanes de Brno is the property of Masaryk University, Faculty of Arts and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This work treats about design and construction of a nuts sorting machine that basically separates them according to their sizes, using bent plates and applying mechanical vibration principles along with the gravity force. Some parameters like bend angle, plates separation and vibrations frequency are taken into account too. [ABSTRACT FROM AUTHOR]

The statistical structure of texts and textual corpora is a topic to which little attention has been paid in Hispanic linguistics. This paper tries to review some of their more relevant aspects in two different senses. On the one hand, through the application of the techniques previously applied to CREA on an intermediate version of CORPES. On the other hand, working on the morphosyntactically tagged version of CORPES, taking into consideration not only orthographic forms, but also lemmas. [ABSTRACT FROM AUTHOR]

Copyright of Arquivos de Ciências Veterinárias e Zoologia da Unipar is the property of Associacao Paranaense de Ensino e Cultura and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

For the design of the experimental prototype of the boost converter with adjustable PWM, this project was divided into 4 stages, the first stage of a study modules oriented teaching power converters in the second design of the converter is performed is performed in the third stage the experimental module (construction adjustable PWM is constructed, whose purpose is to make changes in real time on the circuit, frequency and variable duty cycle, construction of the power circuit with the specifications given finally designs converter housing) in the fourth stage the theoretical and practical module values are analyzed. [ABSTRACT FROM AUTHOR]

El objetivo principal del estudio fue definir las características del esfuerzo desde el punto de vista de la carga externa en jugadoras de baloncesto de alto nivel en dos competiciones: Euroliga femenina y Campeonato del Mundo. Para ello, se analizaron ocho partidos de las fases finales de ambas competiciones. Se llevó a cabo un análisis detallado de los patrones de movimiento de 96 jugadoras pertenecientes a ocho selecciones nacionales y a cinco equipos profesionales. Se utilizaron ocho categorías de actividad a la hora de clasificar las acciones y los desplazamientos en los partidos: parado/caminando, trote, carrera, sprint, salto y shuffle baja, media y alta intensidad. Se calculó el tiempo total en cancha, el tiempo real y el porcentaje de tiempo real respecto del tiempo total. Por otro lado se analizó la frecuencia y la duración media de cada actividad así como el porcentaje de tiempo real empleado en cada una de ellas. Los resultados obtenidos confirman la naturaleza híbrida del esfuerzo, en el que se alternan fases aeróbicas y anaeróbicas, predominando las primeras sobre las segundas. Se observa que los esfuerzos anaeróbicos son los que marcan la diferencia entre niveles competitivos y entre posiciones habituales de juego. Asimismo se observa que sólo las jugadoras en la posición de base presentan un perfil específico de esfuerzo que las diferencia de aleros y pívots.AbstractThe main aim of the current study was to establish the competitive demands, in terms of external load, of elite female basketball players during the final phase of Euroleague and World Championship. Eight matches corresponding to the play-offs of these competitions were analyzed. A detailed analysis of the movement patterns of 96 players was performed. Eight categories were employed to classify the movements: stand/walk, jog, run, stride/sprint, low shuffle, medium shuffle, high shuffle and jump. Total time in court, live time and percentage of live time over total time were calculated. On the other hand, the frequency and the mean duration of each movement category were also measured. Results illustrate the intermittent nature of female basketball. The majority of time appears to be devoted to activities more aerobic in nature, and only a small percentage of time is spent engaged in high-intensity activity. However, anaerobic capacity seems to be a better predictor of basketball performance. On the other hand, only guards seem to have a specific movement pattern different from that of centers or forwards.http://dx.doi.org/10.5232/ricyde2013.03405

Los azúcares son hidratos de carbono con sabor dulce que proveen energía al organismo. El cerebro adulto utiliza aproximadamente 140 g de glucosa al día, cantidad que puede representar hasta el 50% del total de hidratos de carbono que se consumen. En nuestro país el patrón de consumo de azúcar en alimentos permanece constante, mientras que el consumo de bebidas refrescantes presenta un aumento en los últimos cuatro años. La Encuesta Nacional de Ingesta Dietética de España (ENIDE, 2010-11) estimó que un 20% de la ingesta calórica de los españoles procede de los hidratos de carbono denominados azúcares. Se ha asociado el consumo de azúcar con diversas patologías (diabetes, obesidad, caries, cardiovasculares) si bien estas relaciones no presentan consistencia en las evidencias encontradas. La información alimentaria a través del etiquetado nutricional, incluida la relativa a los azúcares presentes en los alimentos, facilitada al consumidor persigue proteger la salud de los mismos y garantizar su derecho a la información para que puedan tomar decisiones con criterio. A la vista de las distintas valoraciones y estudios existentes y sobre todo, en ausencia de una evidencia científica sólida que arroje datos concretos sobre los que realizar recomendaciones, el mejor consejo nutricional para la población general podría ser llevar una dieta variada y equilibrada con alimentos y nutrientes procedentes de diversas fuentes, combinando dicha dieta con el ejercicio y la actividad física. De manera más concreta, un consumo moderado de azúcar (< 10% de la energía total) en el anterior contexto de dieta variada y equilibrada, es compatible.

Título en ingles: New alternative for micropropagation in temporary immersion system of plantain cultivar "INIVITPV-2011" (AAB). Resumen El trabajo fue desarrollado en el Laboratorio de Biotecnología Vegetal del Instituto de Investigaciones en Viandas Tropicales (INIVIT) con el objetivo de incrementar el coeficiente de multiplicación en el cultivar de plátano vianda "INIVITPV-2011" (AAB) en el Sistema de Inmersión Temporal (SIT). Se estudiaron diferentes tiempos de inmersión (10, 20 (control) y 30 minutos) y frecuencias de inmersión (3, 6 (control) y 8 horas) en frascos Nalgene de 10 L de capacidad, se estudió además el volumen de medio de cultivo por explante (20, 40 (control) y 60 ml de medio de cultivo/explante), así como el tiempo de subcultivo (15, 18, 21 (control) y 25 días) y la densidad de explantes por frasco (20, 40 (control), 60 y 80 explantes/frasco de cultivo). Se utilizó el medio de cultivo de multiplicación MS suplementado 2,0 mg.L-1 de 6-BAP; 3,5 mg.L-1de AIA; 30,0 g.L-1 de sacarosa; 10,0 mg.L-1 de ácido ascórbico. Los resultados obtenidos permitieron establecer una metodología para la micropropagación en el Sistema de Inmersión Temporal del cultivar de plátano vianda "INIVITPV-2011" (AAB) la cual consistió en utilizar un tiempo de inmersión de 10 minutos con una frecuencia cada 3 horas, es decir, 8 inmersiones al día, además para cada frasco de 10 L se inocularon 60 explantes y la renovación con 3600 ml de medio de cultivo y un tiempo de cultivo de 18 días permitió alcanzar la mayor productividad del material en fase de multiplicación. Estos resultados, utilizando el Sistema de Inmersión Temporal permitieron establecer una metodología eficiente para la micropropagación del cultivar de plátano vianda "INIVITPV-2011" (AAB). Palabras clave: propagación in vitro; tiempo; frecuencia; inmersión; multiplicación. Abstract This work was developed at the Plant Biotechnology Laboratory from the Research Institute of Tropical Root and Tuber Crops (INIVIT) in order to increase the multiplication coefficient in plantain cultivar "INIVITPV-2011" (AAB) in Temporary Immersion Systems (TIS). Different immersion times (10, 20 (control) and 30 minutes) and immersion frequencies (3, 6 (control) and 8 hours) in 10 L Nalgene flasks, and culture medium volume per explants (20, 40 (control) and 60 ml culture medium / explants) were studied, as well as, subculture time (15, 18, 21(control) and 25 days) and explants density per flask (20, 40 (control), 60 and 80 explants / culture flask). The multiplication culture medium MS supplemented with 2.0 mg.L-1 6-BAP, 3.5 mg.L-1 IAA, 30.0 gL-1 sucrose, 10.0 mg.L-1 ascorbic acid was used. Results obtained allowed to establish a methodology for micro-propagation of plantain cultivar "INIVITPV-2011" (AAB) in temporary immersion system, which consisted of using a 10 minute immersion time with 3 hour frequency (8 immersions per day). Besides, 60 explants were inoculated in each 10 L flask, and the renewal with 3600 ml culture medium and 18 day culture time allowed to obtain the highest productivity in the multiplication stage. These results, using the temporary immersion system allowed to establish a method for micro-propagation of plantain cultivar "INIVITPV-2011" (AAB). Key words: in vitro propagation; time; frequency; immersion; multiplication.

El presente articulo presenta la simulación e implementación de un controlador PID, mediante el uso del $software$ MATLAB y LabView. El proceso controlado es un sistema eléctrico de potencia a escala, el cual se encuentra operativo en los laboratorios de la Universidad Politécnica Salesiana de Cuenca. El controlador descrito tiene el objetivo de mantener fijos los valores de frecuencia y voltaje producido por un generador síncrono y un motor trifásico acoplado por sus ejes mediante una banda, ante los distintos agentes externos de perturbaciones como la variación de la carga en la red eléctrica.

g="justify">Este trabajo aborda la respuesta de líneas de potencia como canales de comunicación (PLC por su sigla en inglés).Para esto se modela, simula y analiza la respuesta en frecuencia de los parámetros resistencia, inductancia, capacitancia y conductancia de tres líneas de potencia: una de núcleo sólido y dos de núcleo entorchado. Posteriormente se simula y analiza la respuesta en frecuencia y longitud de las líneas como canales PLC para sistemas de banda angosta. Parte de un modelo de parámetros distribuidos R´, L´, C´, y G´ de una línea de potencia como línea de transmisión con teoría de dos puertos; se obtienen los parámetros en función de la frecuencia y las funciones de transferencia de las líneas dependientes de la frecuencia y longitud. Se observa en la respuesta en frecuencia de la línea de núcleo entorchado menor resistencia frente a la línea de núcleo sólido debido a su característica geométrica. En la respuesta en frecuencia y longitud, se muestra mayor atenuación de la señal en la línea de núcleo sólido que en núcleo entorchado. En la respuesta en frecuencia y longitud, se muestra mayor atenuación de la señal en la línea de núcleo sólido que en núcleo entorchado, siendo el tipo de línea de núcleo entorchado el más indicado para comunicar dispositivos PLC sin requerir esquemas de modulación y codificación robustos.