Shiga Toxin Detection Methods : A Short Review

The Shiga toxins comprise a family of related protein toxins secreted by certain types of bacteria. Shigella dysenteriae, some strain of Escherichia coli and other bacterias can express toxins which caused serious complication during the infection. Shiga toxin and the closely related Shiga-like toxins represent a group of very similar cytotoxins that may play an important role in diarrheal disease and hemolytic-uremic syndrome. The outbreaks caused by this toxin raised serious public health crisis and caused economic losses. These toxins have the same biologic activities and according to recent studies also share the same binding receptor, globotriosyl ceramide (Gb3). Rapid detection of food contamination is therefore relevant for the containment of food-borne pathogens. The conventional methods to detect pathogens, such as microbiological and biochemical identification are time-consuming and laborious. The immunological or nucleic acid-based techniques require extensive sample preparation and are not amenable to miniaturization for on-site detection. In the present are necessary of techniques of rapid identification, simple and sensitive which can be employed in the countryside with minimally-sophisticated instrumentation. Biosensors have shown tremendous promise to overcome these limitations and are being aggressively studied to provide rapid, reliable and sensitive detection platforms for such applications.Comment: 16 pages, 2 figure

Investigation of Mountain Waves in the Mesosphere over the Andes Mountains

An image processing algorithm has been developed to analyze data from a NIR All-Sky Imager of OH airglow emission (from about 87 km altitude), located in the Andes, with the purpose of investigating the atmospheric gravity waves generated when low level wind blows over the high mountains (referred to as Mountain Waves). These types of waves are a special case of atmospheric gravity waves, which carry significant momentum and exert strong forcing to the background upper atmosphere. The imager is located at the Andes Lidar Observatory (ALO) at Cerro Pachón, Chile (30°S, 71°W), which also houses a Na Doppler Lidar and other passive optical instruments. This thesis work reports the successful identification of numerous strong mountain wave events during the austral winters (2010 - 2014) when low level horizontal winds are eastward and exceed 40 m/s. These events span hundreds of kilometers in the night sky with average wavelengths of 20 to 40 km. A database of high resolution videos and statistics on the wave parameters has been produced. Additionally, an airglow imager simulation model has been built for testing the image processing algorithm

Acoustic/Gravity Wave Phenomena in Wide-Field Imaging: From Data Analysis to a Modeling Framework for Observability in the Mlt Region and Beyond

Acoustic waves, gravity waves, and larger-scale tidal and planetary waves are significant drivers of the atmosphere’s dynamics and of the local and global circulation that have direct and indirect impacts on our weather and climate. Their measurements and characterization are fundamental challenges in Aeronomy that require a wide range of instrumentation with distinct operational principles. Most measurements share the common features of integrating optical emissions or effects on radio waves through deep layers of the atmosphere. The geometry of these integrations create line-of-sight effects that must be understood, described, and accounted for to properly present the measured data in traditional georeferenced frames or in thin-layer representations. These effects include intensity enhancements/cancellations, filtering of scales, and apparent phase shifts relative to the underlying wave dynamics. We have designed a simulation framework that uses 2D and 3D input model data to perform these line-of-sight integrations based on ray tracing and geodesic transformations. The primary objective is to characterize these effects, to define quantifiable impacts on measurable parameters, and to create a basis for synthetic data for processes to be revealed in current and future measurements

Machine learning techniques applied to multiband spectrum sensing in cognitive radios

This research received funding of the Mexican National Council of Science and Technology (CONACYT), Grant (no. 490180). Also, this work was supported by the Program for Professional Development Teacher (PRODEP).In this work, three specific machine learning techniques (neural networks, expectation maximization and k-means) are applied to a multiband spectrum sensing technique for cognitive radios. All of them have been used as a classifier using the approximation coefficients from a Multiresolution Analysis in order to detect presence of one or multiple primary users in a wideband spectrum. Methods were tested on simulated and real signals showing a good performance. The results presented of these three methods are effective options for detecting primary user transmission on the multiband spectrum. These methodologies work for 99% of cases under simulated signals of SNR higher than 0 dB and are feasible in the case of real signalsPeer ReviewedPostprint (published version

Auditoría de gestión a la Cooperativa de Ahorro y Crédito Chibuleo, ubicada en el cantón Ambato, provincia de Tungurahua, para el período comprendido del 1 de enero al 31 de diciembre del 2011

El presente estudio se enfocó en la Auditoria de Gestión a la Cooperativa de Ahorro y Crédito CHIBULEO, ubicada en el Cantón Ambato Provincia de Tungurahua durante el periodo del 1 de enero al 31 de diciembre del 2011, con el objetivo de evaluar el grado de cumplimiento de la misión, visión, objetivos, disposiciones legales, utilización de recursos y el sistema de control interno. Los instrumentos utilizados fueron las técnicas de Auditoria como entrevistas, encuestas, observación, cuestionario de Control interno. La metodología utilizada fue analítica, descriptiva, deductiva, bibliográfica y de campo. La Auditoria de Gestión examino los procedimientos necesarios para contar con evidencia suficiente y así tener una seguridad razonable para determinar las respectivas conclusiones del examen de Auditoría. Se realizó la visita Preliminar a la institución para tener un conocimiento global de la misma. También se aplicó entrevistas a los jefes departamentales con el propósito de dar a conocer el inicio del examen y cuestionarios de control interno por departamentos lo que nos ayudó a determinar deficiencias preliminares. Consecutivamente se planifico la Auditoria de Gestión realizando el análisis y evaluación de la información y documentación recabada en la fase preliminar, en esta etapa se aplicó las técnicas y pruebas de Auditoria las mismas que nos ayudó a sustentar las deficiencias encontradas. Luego se procedió al análisis de hallazgos significativos del examen con sus respectivos atributos. Por último se realizó la comunicación de resultados y el informe de Auditoría con las respectivas conclusiones y recomendaciones de cada hallazgo significativo arrojado luego del examen realizado, las mismas que ayudaran a corregir deficiencias y a mejorar la gestión de la Cooperativa de Ahorro y Crédito CHIBULEO

Influencia del procesado térmico sobre la reología de geles de albumen de huevo

El objetivo del trabajo ha consistido en la caracterización del proceso de gelificación térmica de dispersiones de albumen de huevo mediante ensayos viscoelásticos dinámicos. Las variables estudiadas han sido el tiempo de procesado térmico, manteniendo constante la velocidad de calentamiento y enfriamiento, la concentración de proteína y el pH del medio acuoso. Durante el procesado térmico se ha encontrado un aumento drástico de las propiedades viscoelásticas lineales durante el cual se produce una transición sol-gel. La contribución más importante para dicho incremento corresponde a la etapa de calentamiento y a la primera parte de la etapa isotérmica a 90°C, en las que se produce la formación de entre cruzamientos entre segmentos de proteínas, originando un entramado tridimensional. Tanto el tiempo de procesado como la concentración de albumen conllevan un aumento de propiedades viscoelásticas que reflejan un reforzamiento de la estructura de gel, pudiendo normalizarse los espectros mecánicos obtenidos en ambos casos. Los geles formados mediante procesado térmico presentan un mejor grado de estructuración en la proximidad del punto isoeléctrico del albumen de huevo. Cuando nos alejamos del punto isoeléctrico la presencia de interacciones electrostáticas dificulta la formación del entramado estructural, conduciendo a geles de menor consistencia

Un modelo del gasto con factores sociodemográficos y de hábitos de viaje en Pueblos Mágicos del Estado de Guanajuato, México

En este trabajo se presenta un panorama de la industria turística mexicana que incluye un análisis de las tendencias y la competitividad del sector en el contexto de la aplicación del Programa Nacional de Pueblos Mágicos. Se desarrolla un modelo econométrico con el fin de analizar el comportamiento del gasto de los visitantes a los Pueblos Mágicos del Estado de Guanajuato. Los coeficientes del modelo son estimados con una base de datos de la Secretaría de Turismo del Estado de Guanajuato. La información se generó a partir de una encuesta aplicada en los cinco Pueblos Mágicos de esa entidad en el año 2013. El modelo permite estimar elasticidades de los factores de impacto y generar niveles de referencia de gasto en diferentes escenarios. El modelo se plantea como una regresión log-lineal con variables explicativas que capturan características sociodemográficas y de hábitos de viaje. Tomando en cuenta los resultados del modelo, se discuten estrategias para estimular el crecimiento de la demanda turística en estos Pueblos Mágicos.This paper provides a general vision of the tourism industry in Mexico with an analysis of its overall trends and competitiveness with especial emphasis in the Pueblos Magicos National Programme. An econometric analysis has been carried out in order to analyze the expenditure patters of visitors to the Pueblos Magicos of Guanajuato State. The expenditure model coefficients are calculated using a data base of the Secretaria de Turismo de Guanajuato – SECTUR-GTO (Guanajuato Tourist Office). The data base was created from a survey questionnaire administered to the five Pueblos Magicos of the State in 2013. The model enables the computation of expenditure elasticities for the impact factors and the generation of reference expenditures under different scenarios. The model is a log-linear regression with explicative variables that capture socio demographic characteristics and travel habits. The results are used in order to discuss strategies for stimulating tourist demand growth in these Pueblos Magicos

Sequence variability of Rhizobiales orthologs and relationship with physico-chemical characteristics of proteins

<p>Abstract</p> <p>Background</p> <p>Chromosomal orthologs can reveal the shared ancestral gene set and their evolutionary trends. Additionally, physico-chemical properties of encoded proteins could provide information about functional adaptation and ecological niche requirements.</p> <p>Results</p> <p>We analyzed 7080 genes (five groups of 1416 orthologs each) from Rhizobiales species (<it>S. meliloti, R. etli</it>, and <it>M. loti</it>, plant symbionts; <it>A. tumefaciens</it>, a plant pathogen; and <it>B. melitensis</it>, an animal pathogen). We evaluated their phylogenetic relationships and observed three main topologies. The first, with closer association of <it>R. etli </it>to <it>A. tumefaciens</it>; the second with <it>R. etli </it>closer to <it>S. meliloti</it>; and the third with <it>A. tumefaciens </it>and <it>S. meliloti </it>as the closest pair. This was not unusual, given the close relatedness of these three species. We calculated the synonymous (dS) and nonsynonymous (dN) substitution rates of these orthologs, and found that informational and metabolic functions showed relatively low dN rates; in contrast, genes from hypothetical functions and cellular processes showed high dN rates. An alternative measure of sequence variability, percentage of changes by species, was used to evaluate the most specific proportion of amino acid residues from alignments. When dN was compared with that measure a high correlation was obtained, revealing that much of evolutive information was extracted with the percentage of changes by species at the amino acid level. By analyzing the sequence variability of orthologs with a set of five properties (polarity, electrostatic charge, formation of secondary structures, molecular volume, and amino acid composition), we found that physico-chemical characteristics of proteins correlated with specific functional roles, and association of species did not follow their typical phylogeny, probably reflecting more adaptation to their life styles and niche preferences. In addition, orthologs with low dN rates had residues with more positive values of polarity, volume and electrostatic charge.</p> <p>Conclusions</p> <p>These findings revealed that even when orthologs perform the same function in each genomic background, their sequences reveal important evolutionary tendencies and differences related to adaptation.</p> <p>This article was reviewed by: Dr. Purificación López-García, Prof. Jeffrey Townsend (nominated by Dr. J. Peter Gogarten), and Ms. Olga Kamneva.</p