In this article we describe the setup of a mechanical system that simulate the stochastic propagation process of a brownian particle inside a fluid. Our system consist of a mechanical oscillator coupled to a recipient which is shacked constantly. Inside the recipient we deposit small “fluid particles” that remain in constant agitation. Inside this “fluid” we insert one bigger test Brownian particle (bigger than the fluid particles) over which the small fluid particles exert random stochastic forces. We analyze the zigzag movement of the Brownian particles by filming the motion and using the free software Tracker in order to realize the image analysis. Our results show an excellent qualitative agreement between the predictions of the brownian motion theory and our experimental results. The advantage of introducing in this way the concepts of brownian motion and molecular diffusion is that we can observe by the naked eye this phenomenon happening.

Neste artigo é descrita a montagem de um sistema mecânico que simula o processo de propagação estocástica de uma partícula browniana em um fluido. O sistema consta de um oscilador mecânico que agita constantemente um recipiente onde pequenas partículas de um “fluido” são depositadas e se mantém em movimento. Dentro deste “fluido”, uma outra partícula browniana (maior) é inserida sobre a qual as pequenas partículas do fluido exercem forças estocásticas. O movimento em zigue-zague das partículas brownianas é analisado mediante a filmagem do movimento e pela utilização do software Tracker para o estudo das imagens. Os resultados denotam um excelente acordo entre as previsões da teoria do movimento browniano e o experimento proposto. A vantagem de induzir desta forma os conceitos do movimento browniano e da difusão molecular é que se pode observar ao olho nu este fenômeno acontecendo e sua visualização pode ajudar na melhor compreensão desses conceitos.

Neste artigo realizamos uma breve discussão das leis de conservação do momento linear e da energia em colisões mecânicas. Apresentamos alguns roteiros experimentais para constatar estas leis de conservação em diversas situações onde existem colisões. A lei de conservação do momento será verificada diretamente, medindo as velocidades dos objetos, enquanto que para a lei de conservação da energia exploramos a noção de Coeficiente de Restituição Elástica. Obtivemos os valores experimentais das variáveis do movimento utilizando vídeo-análise e o software livre Tracker. Analisamos colisões binárias entre dois corpos idênticos, colisões rígidas oblíquas de um corpo com uma superfície imóvel e colisões rígidas frontais de um corpo em queda livre com uma superfície horizontal. Para estes casos, analisamos a dependência do coeficiente de restituição com o ângulo de colisão ou com a energia do choque. Verificamos que o coeficiente de restituição depende da energia, sendo menor para altas energia, implicando que nos afastamos do regime linear elástico ao aumentar a energia das colisões. mecânicas diretamente objetos Elástica vídeoanálise vídeo análise Tracker idênticos horizontal casos choque

In this article, we conducted a brief discussion of the laws of conservation of linear momentum and energy in mechanical collisions. We presented some experimental procedures to confirm these conservation laws in various situations involving collisions. The law of conservation of momentum will be directly verified by measuring the objects’ velocities, while for the law of conservation of energy, we explored the concept of the Coefficient of Restitution. We will obtain the experimental values of the motion variables using video analysis and the free software Tracker. We analyzed binary collisions between two identical bodies, oblique rigid collisions of a body with an immovable surface, and frontal rigid collisions of a freely falling body with a horizontal surface. For these cases, we examined the dependence of the coefficient of restitution on the collision angle or the impact energy. We found that the coefficient of restitution varies with energy, being lower for higher energies, implying that we move away from the regime of linear elasticity as the collision energy increases. article objects velocities Restitution Tracker bodies surface cases energies increases

ABSTRACT During the last decade, in several localities of the Cuban provinces of Matanzas, Villa Clara, Cienfuegos and Sancti Spíritus, seismic movements have been perceived, causing great concern on their population and institutional managers. The purpose of this research was to evaluate the possible causes of the seismicity originating in the aforementioned provinces based on the analysis of the Cuban seismic catalogues and the available geological and geophysical articles and reports. It was possible to reveal that release of seismic energy accumulated in the rocks is the cause of reactivating regional and minor order faults, what justifies the seismicity in this zone. The different performance of seismic activity recorded in these territories is due to the unequal response to tensions accumulated mainly by the geological-tectonic complexity and its relationship or not with gravitational and isostatic blocks.

RESUMEN Durante el último decenio, en varias localidades de las provincias cubanas de Matanzas, Villa Clara, Cienfuegos y Sancti Spíritus han sido percibidos movimientos sísmicos causantes de gran preocupación por parte de su población y de los directivos institucionales. El propósito de esta investigación fue realizar una valoración de las posibles causas de la sismicidad originada en las provincias mencionadas con base en el análisis de los catálogos sísmicos cubanos y los artículos e informes geológicos y geofísicos realizados en estas provincias. Se pudo revelar que la reactivación de las fallas regionales y de órdenes menores debido a la liberación de la energía sísmica acumulada en las rocas justifica la sismicidad del territorio investigado, así como que el diferente comportamiento de la actividad sísmica registrada en estos territorios se debe a la respuesta desigual a las tensiones acumuladas, principalmente por la complejidad geológico-tectónica y su relación o no con bloques gravitacionales e isostáticos.

ABSTRACT Performance and possible causes of seismic activity in the southern of Santiago de Cuba province were evaluated, based on the geological and tectonic information available and records of the earthquakes occurred in this region in January 17, 2016 at 08:17 UTC. The analysis of the space-time-energy parameters of the earthquakes showed the coherence between the results of three of the networks monitoring the region, namely, the Cuban National Seismological Service (SSNC), the United States Geological Service (USGS) and the German Center for Geo-scientific Research (GEOFON)). For three of the earthquakes, the seismic moment tensors were calculated by reversing the corresponding waveforms. Comparing the results of two of them with those obtained by other agencies that monitor the area was totally consistent with fault planes oriented N-S with compressive focal mechanisms. The third earthquake, which occurred a week later in the east of the province, also had a compressive mechanism, although with a NW-SE orientation on the fault plane. The seismic activity that initially performed like a swarm of earthquakes, performed differently later; similar to aftershocks registered after a higher-energy earthquake, following Omori's Law, that is, the type of premonitory-main earthquake event -aftershocks.

Resumen Se evaluó comportamiento y las posibles causas de la actividad sísmica al sur de la provincia de Santiago de Cuba, a partir de la información geológica y tectónica disponible y de los registros de los sismos ocurridos en esta región desde el 17 de enero del 2016 a las 08:17 UTC. El análisis de los parámetros espacio-temporal-energéticos de los terremotos evidenció la coherencia entre los resultados de tres de las redes que monitorean la región, a saber, Servicio Sismológico Nacional Cubano (SSNC), Servicio Geológico de los Estados Unidos (USGS) y el Centro Alemán de Investigaciones Geocientíficas (GEOFON)). Para tres de los terremotos se calcularon los tensores del momento sísmico mediante el proceso de inversión de las correspondientes formas de ondas. La comparación de los resultados de dos de ellos con los obtenidos por otras agencias que monitorean el área fue totalmente coherente con planos de fallas de orientación N-S con mecanismos focales compresivos. El tercer sismo, ocurrido una semana más tarde al este de la provincia, también tuvo un mecanismo compresivo, aunque con orientación NW-SE en el plano de falla. La actividad sísmica que en sus inicios se comportó como un enjambre de terremotos, manifestó posteriormente un comportamiento distinto, similar al de réplicas registradas tras un sismo de mayor energía, siguiendo la Ley de Omori, es decir, del tipo de evento premonitores-sismo principal-replicas.

ABSTRACT Earthquakes of 1 to 3 magnitudes eventually reaching up to 8, take place in Cuba and adjacent areas. Although those with a magnitude greater than 3 are generally perceptible, the ones usually causing damage are those with a magnitude greater than 5; however, its negative impact largely depends on the state of the built infrastructure and the hypocenter. This essay is a contribution to risk perception in Cuban population and it introduces the concept of cities in seismic alert, which is based on the principle that where destructive seismic events occurred in the past it is very likely they will be repeated in the future, unless the infrastructure be substantially improved. A set of recommendations is also proposed for Cuban cities defined in seismic alert.

RESUMEN En el territorio de la República de Cuba y áreas adyacentes ocurren sismos con magnitudes de 1 a 3, que eventualmente han alcanzado hasta 8. Aunque los de magnitud mayor de 3 generalmente son perceptibles, los que suelen ocasionar daños son los de magnitud mayor de 5; no obstante, su impacto negativo depende en gran medida del estado de la infraestructura construida y de la cercanía del foco. El presente ensayo constituye una contribución a la percepción del riesgo en la población cubana e introduce el concepto ciudades en alerta sísmica, que se fundamenta en el principio de que donde ocurrieron eventos sísmicos destructivos en el pasado, es muy probable que se repitan en el futuro, a menos que la infraestructura construida se hubiese mejorado sustancialmente. Se propone, además, un conjunto de recomendaciones para las ciudades cubanas definidas en alerta sísmica.

Resumen Los entornos virtuales han ganado su espacio en la educación contemporánea. Se trata de nuevos escenarios de aprendizaje que pretenden dinamizar los contenidos académicos. Las plataformas online constituyen un impulso para la práctica pedagógica, pues utilizan recursos innovadores al emplear, entre otras herramientas, las tecnologías de la información y la comunicación. En este sentido, el propósito de esta investigación es analizar las tecnologías aplicadas a la educación y la innovación educativa, específicamente a los nuevos entornos de aprendizaje que se han desarrollado en la Facultad de Filosofía, Letras y Ciencias de la Educación de la Universidad Técnica de Manabí, con sede en Portoviejo, Ecuador. Circunstancias como la vivencia de la pandemia producida por la Covid-19 evidencian que deben optimizarse y potenciarse nuevos escenarios de enseñanza, porque se ha demostrado que en la actualidad el aprendizaje no sólo ocurre dentro del aula, sino también fuera de esta, gracias al fuerte desarrollo de diversas herramientas tecnológicas incorporadas al proceso académico. En este sentido, hay recursos como plataformas Zoom, Moodle, redes sociales, el uso de Whatsaap y el correo electrónico que se han empleado con óptimos resultados. Por ello, tanto los docentes y estudiantes incorporan herramientas tecnológicas y procesos a su contexto educativo para fomentar un cambio en su práctica y sobre todo en su pensamiento. Sin embargo, su uso debe ser responsable y reflexivo para ayudar tanto al quehacer docente como a las actividades que deben realizar los alumnos.

Abstract Virtual environments have gained their space in contemporary education. These are new learning scenarios that aim to energize academic content. Online platforms are a driving force for pedagogical practice, using innovative resources when using, among other tools, information and communication technologies. In this sense, the purpose of this research is to analyze the technologies applied to education and educational innovation, specifically to the new learning environments that have been developed in the Faculty of Philosophy, Letras y Ciencias de la Educación de la Universidad Técnica de Manabí, based in Portoviejo, Ecuador. Circumstances such as the experience of the pandemic produced by the Covid-19 show that new teaching scenarios should be optimized and enhanced, because it has been shown that today learning occurs not only within the classroom, but also outside the classroom, thanks to the strong development of various technological tools incorporated into the academic process. In this sense, there are resources such as Zoom platforms, Moodle, social networks, the use of Whatsaap and email that have been used with optimal results. Therefore, both teachers and students incorporate technological tools and processes into their educational context to encourage a change in their practice and especially in their thinking. However, its use must be responsible and thoughtful to help both the teaching and the activities that students must perform.

Resumen La importancia del liderazgo de los directivos como uno de los elementos que contribuyen a la calidad de la educación hace que su valoración resulte un asunto de enorme interés. En este estudio de tipo descriptivo, con empleo del método análisis documental, nos planteamos como objetivo caracterizar el liderazgo en instituciones de educación superior, porque es un reto que las instituciones de educación tienen como premisa fundamental en nuestra sociedad contemporánea; este incluye el guiar, inspirar e impulsar a los seguidores a realizar acciones éticas con valores y responsabilidad social, por ello el liderazgo en el ámbito de la educación superior deberá tener estas características mencionadas con el fin de mejorar la sociedad. A la hora de plantear la eficacia de las instituciones de educación superior y la calidad de este ámbito se suele considerar al liderazgo como uno de los factores clave. En términos generales podemos concluir que el liderazgo sigue siendo uno de los temas más controvertidos en el campo de la elaboración teórica, en el de las políticas educativas y prácticas concernientes a la organización de las instituciones educativas en el ámbito superior.

Abstract The importance of the leadership of the directors as one of the elements that contribute to the quality of education makes their assessment an issue of enormous interest. Leadership in higher education institutions is undoubtedly a challenge that educational institutions have as a fundamental premise in our contemporary society, this includes guiding, inspiring and encouraging followers to perform ethical actions with values and social responsibility, therefore the Leadership in the field of higher education should have these characteristics mentioned in order to improve society. When considering the effectiveness of higher education institutions and the quality of this area, leadership is usually considered one of the key factors. However, leadership remains one of the most controversial issues in the field of theoretical elaboration, in educational policies and practices concerning the organization of educational institutions in the higher field.

Nowadays, similarity search on metric spaces is becoming a research field of interest due to the fact of its application to different scientific areas. However, when these applications produce a huge amount of data, it is necessary to accelerate the searching process by means of parallel architectures such as clusters, multiprocessors (multicores) or clusters of multiprocessors (multicores). Currently, graphic accelerators have emerged as a technology that allows for good performance at a low cost. In order to exploit the underlined architecture formed by multicores and a graphic accelerator it is nedeed to carry out heterogeneous programming, where CPUs and GPU are working at the same time taking benefits of the complete architecture. In this paper, a suitable generic structure adapted to the multicore/GPU system is presented and the experimental results, obtained in terms of execution time and speed-up, show the advantages of using this heterogeneous system, as well as a study of power consumption.

En la actualidad, la búsqueda por similitud en espacios métricos representa una línea de investigación de interés debido a sus múltiples campos de aplicación. Sin embargo, cuando en dichas aplicaciones aparecen grandes volúmenes de datos, se hace más que necesario el poder acelerar la búsqueda de las diferentes consultas en tales cantidades de datos. Una manera de llevar a cabo dicha aceleración pasa por el uso de clusters, multiprocesadores o clusters de multiprocesadores. En la actualidad, ha surgido con fuerza la posibilidad de utilizar aceleradores gráficos (GPU) como vehículo para acelerar aplicaciones a un muy bajo coste. En estos casos, la relación CPU/GPU no es de par a par y por tanto se denominan sistemas heterogéneos. Para explotar dichos sistemas heterogéneos se requiere una programación también heterogénea que emplee a la vez la CPU y la GPU. En este trabajo se realiza una verdadera programación heterogénea en el que tanto CPU como GPU están trabajando en forma simultánea y por tanto se aprovecha al máximo la arquitectura subyacente. Se presenta la implementación de una estructura genérica adaptada para un sistema multiprocesador con una GPU, mostrando los resultados experimentales en términos de tiempo y speed-up. Se muestra experimentalmente las ventajas comparativas al insertar GPU a una plataforma multicore, así como el análisis del consumo energético.

Este trabalho comparou os tempos de soroconversão negativos obtidos pela sorologia convencional (CS) e teste ELISA-F29 em uma coorte de pacientes chagásicos crônicos tratados com nifurtimox ou benznidazol. Um estudo retrospectivo foi realizado com soro preservado de 66 adultos chagásicos assintomáticos com acompanhamento clínico e sorológico semestral ao longo de um seguimento médio de 23 anos. 29 pacientes receberam tratamento tripanossomicida e 37 outras permaneceram sem tratamento. O teste ELISA-F29 usou um antígeno recombinante obtido por expressão do gene de uma proteína flagelar de Trypanosoma cruzi de ligação de cálcio em Escherichia coli. Entre os pacientes não tratados, 36 mantiveram os títulos da CS. Um paciente apresentou sorologia duvidosa em alguns controles. ELISA-F29 apresentou reatividade constante em 35/37 e foi negativo no paciente com CS flutuante. Os pacientes tratados foram agrupados de acordo com os títulos da CS, em três grupos: 13 tornaram-se negativos, 12 diminuíram e quatro permaneceram inalterados. ELISA-F29 foi negativo nos dois primeiros grupos. O tempo de negativização foi significativamente menor para o teste ELISA-F29 do que para CS (14,5 ± 5,7 e 22 ± 4,9 anos, respectivamente). A soroconversão negativa foi observada somente nos pacientes tratados. Os resultados obtidos confirmam que o teste ELISA-F29 é útil como um indicador precoce de soronegativação em pacientes crônicos tratados.

This work compared the time at which negative seroconversion was detected by conventional serology (CS) and by the ELISA-F29 test on a cohort of chronic chagasic patients treated with nifurtimox or benznidazole. A retrospective study was performed using preserved serum from 66 asymptomatic chagasic adults under clinical supervision, and bi-annual serological examinations over a mean follow-up of 23 years. Twenty nine patients received trypanocide treatment and 37 remained untreated. The ELISA-F29 test used a recombinant antigen which was obtained by expressing the Trypanosoma cruzi flagellar calcium-binding protein gene in Escherichia coli. Among the untreated patients, 36 maintained CS titers. One patient showed a doubtful serology in some check-ups. ELISA-F29 showed constant reactivity in 35 out of 37 patients and was negative for the patient with fluctuating CS. The treated patients were divided into three groups according to the CS titers: in 13 they became negative; in 12 they decreased and in four they remained unchanged. ELISA-F29 was negative for the first two groups. The time at which negativization was detected was significantly lower for the ELISA-F29 test than for CS, 14.5 ± 5.7 and 22 ± 4.9 years respectively. Negative seroconversion was observed in treated patients only. The results obtained confirm that the ELISA-F29 test is useful as an early indicator of negative seroconversion in treated chronic patients.

ABSTRACT 'San Antonio 05' was developed at the Bajio Experimental Station of INIFAP, Mexico and evaluated during four years during the fall-winter cycle in six environments of three counties in the region Cienega de Chapala, Jalisco (La Barca, Atotonilco El Alto and Jamay), where it was grown under residual moisture and irrigated production systems. Tests for root-rot resistance were conducted at Valle de Culiacan Experimental Station in Sinaloa and at Atotonilco El Alto, Jalisco. Results indicated that San Antonio 05 is resistant to root-rots and its yield average in all conducted trials was 2.04 t ha-1 for grain and 2.31 for straw, being superior to the commercial check 'Lerma' by 490 kg (31.6%)

A transversal study was performed on sera from chronic chagas ic patients treated with nifurtimox (Nx) or benznidazole (Bz), in order to evaluate the Trypanosoma cruzi flagellar calcium-binding protein (F29) as a marker for therapeutic effectiveness. An ELISA was used with these F29 recombinant antigen, and its relation to conventional serology (CS) and parasitological and clinical evolution was analysed. Sera from 118 patients with retrospective, serological, parasitological and clinical information was available, were analyzed. Patients were grouped into: A) 30 treated patients whose CS became negative after treatment; B) 34 treated patients whose CS remained positive; C) 54 untreated patients. A double-blind trial was conducted simultaneously in all serum samples, by means ofCS (indirect hemagglutination, direct agglutination and indirect immunofluorescence) and ELISA F29. The ELISA F29 test was non reactive in: 100% of group A, 82.4% of group B and 13%> of group C. The infected patients who presented electrocardiographic alterations compatible with chronic chagasic myocardiopathy (n = 11) were reactive for ELISA F29. All patients whose parasitological studies (xenodiagnosis and/or strout method) were positive presented a high reactivity to the ELISA F29 test. The correlation between ELISA F29 and CS was statistically significant (p < 005) in the treated group whose CS was non reactive (group A) and the untreated group (group C). As opposed to this, in the group of treated patients whose CS remained positive (group B), the ELISA F29 test was reactive only in a 17.6%>. These results suggest that the fast and user-friendly ELISA F29 test could be useful to monitor changes after trypanocidal treatment.

La proteína flagelar F29 es una proteína ligadora de calcio del Trypanosoma cruzi. En el presente trabajo se realizó un estudio transversal en sueros de pacientes con infección crónica por T. cruzi tratados con nifurtimox (Nx) o benznidazol (Bz) y no tratados, para evaluar el antígeno F29 como marcador de eficacia terapéutica. Se utilizó un ensayo inmuno-enzimático con la proteína recombinante F29 (ELISA F29) y se analizó su relación con la serología convencional (SC) y la evolución parasitológica y clínica en esos pacientes. Se estudiaron 118 sueros de pacientes que formaban parte de una cohorte, de los cuales se disponía de información retrospectiva, serológica, parasitológica y clínica.Los pacientes se dividieron en 3 grupos: A) 30 tratados negativizaron SC post-tratamiento; B) 34 tratados permanecieron con SC reactiva; C) 54 no tratados. Las muestras de suero se procesaron a doble ciego en forma simultánea mediante serología convencional (hemoaglutinación indirecta, aglutinación directa e inmunofluorescencia indirecta) y ELISA F29. El test ELISA F29 resultó no reactivo en: 100% del grupo A, 82,4% del grupo B y 13% del grupo C. Los infectados con alteraciones electrocar-diográficas compatibles con miocardiopatía chagásica crónica (n = 11) fueron reactivos al ELISA F29. Los pacientes en quienes los estudios parasitológicos (xenodiagnóstico y/o strout) fueron (+) presentaron elevada reactividad al ELISA F29. La correlación entre ELISA F29 y SC en los pacientes tratados con SC no reactiva (grupo A) y no tratados (grupo C), fue significativa (p < 0,05). En cambio, en pacientes tratados que mantuvieron la SC reactiva (grupo B) el test de ELISA F29 fue reactivo sólo en 17,6%. Estos resultados sugieren que el test ELISA F29, rápido y sencillo, podría ser útil para monitorear cambios post-tratamiento tripanocida.

Avaliamos a eficácia do nifurtimox e/ou benznidazol, durante 21 anos em média, em adultos chagásicos crônicos sem alterações eletrocardiográficas iniciais, mediante sorologia convencional, xenodiagnóstico, exames clínicos, eletrocardiográficos e radiografia do tórax. Estudamos 111 pacientes (17 a 46 anos): 54 foram tratados (27 com nifurtimox e 27 com benznidazol) e 57 formaram o grupo controle. Foram submetidos ao xenodiagnóstico 65% dos pacientes estudados: 36/38 tratados e 9/34 do grupo controle com xenodiagnóstico positivo prévio. Após tratamento, foram realizados 133 xenodiagnósticos em 41 pacientes, sendo todos negativos. Foram realizados 29 xenodiagnósticos em 14 pacientes do grupo controle, 2 foram positivos. A sorologia convencional foi realizada em soros estocados durante o seguimento. Evolução sorológica. Grupo tratado: a) 37% negativaram (nifurtimox 11, benznidazol 9); b) 27,8% diminuíram a titulação (nifurtimox 9, benznidazol 6), 9 deles apresentaram sorologia final discordante (nifurtimox 7, benznidazol 2; c) 35,2% permaneceram positivos com titulação constante (nifurtimox 7, benznidazol 12). Grupo controle: conservou os níveis iniciais de anticorpos durante o seguimento. Evolução clínica: 2/54 (3,7%) pacientes tratados e 9/57 não tratados apresentaram alterações eletrocardiográficas atribuíveis a miocardiopatia chagásica. Diferenças estatisticamente significantes (p<0,05). O tratamento produziu efeito de combate ao parasita em pelo menos 37% dos infetados crônicos adultos e efeito protetor na evolução clínica.

The efficacy of treatment with nifurtimox and/or benznidazole among adults with chronic Chagas disease with no previous electrocardiographic disturbances was evaluated over a mean follow-up of 21 years, by means of conventional serology, xenodiagnosis, clinical examination, electrocardiograms and chest X-ray. One hundred and eleven patients, between 17 and 46 years old, were studied: 54 underwent treatment (nifurtimox 27, benznidazole 27) and 57 remained untreated (control group). Xenodiagnosis was performed on 65% of them: 36/38 of the treated and 9/34 of the untreated patients had previous positive xenodiagnosis. Post-treatment, 133 xenodiagnoses were performed on 41 patients, all resulting negative. In the control group, 29 xenodiagnoses were performed on 14 patients; 2 resulted positive. Sera stored during the follow-up were simultaneously analyzed through conventional serology tests (IHA; DA-2ME; IIF). The serological evolution in the treated group was: a) 37% underwent negative seroconversion (nifurtimox 11, benznidazole 9); b) 27.8% decreased titers (nifurtimox 9, benznidazole 6), 9 showed inconclusive final serology (nifurtimox 7, benznidazole 2); c) 35.2% remained positive with constant titers (nifurtimox 7; benznidazole 12). The control group conserved the initial antibody levels during the follow-up. In the clinical evolution, 2/54 (3.7%) of the treated and 9/57 (15.8%) of the untreated patients showed electrocardiographic disturbances attributable to Chagas myocardiopathy, with a statistically relevant difference (p<0.05). Treatment caused deparasitation in at least 37% of the chronically infected adults and a protective effect on their clinical evolution.

A method for the study of the pantograph-catenary dynamic interaction in railways is presented. A non linear system of differential equations with constraints has been obtained, and the models for pantograph, catenary and constraints, are discussed. The equations have been solved as ordinary differential equations using the central differences method. This procedure has been used to develop high performance software in Visual C, to simulate the mechanical behavior of several pantographs interacting with the contact aerial line (catenary), in order to obtain optimal installation values both in conventional and high-speed lines.

Se desarrolla un procedimiento para el estudio de la interacción dinámica pantógrafo-catenaria en líneas ferroviarias. Se ha obtenido un sistema de ecuaciones diferenciales no lineales con restricciones, comentándose las modelizaciones de los sistemas pantógrafo, catenaria, así como de las condiciones de restricción. Las ecuaciones se han integrado numéricamente como ecuaciones diferenciales ordinarias mediante el método de las diferencias centrales. El procedimiento expuesto ha servido de base para el desarrollo de un software de altas prestaciones en Visual C, que permite simular el comportamiento mecánico de varios pantógrafos interactuando con la línea aérea de contacto (catenaria), con objeto de obtener unos valores óptimos de montaje, tanto en líneas convencionales como de alta velocidad

Apresenta-se a avaliação clinicoepidemiológica de 95 crianças chagásicas crônicas em idades entre 1 e 14 anos moradoras de Santa Fé, Argentina, não tratadas e tratadas com nifurtimox ou benznidazol, com acompanhamento de até 24 anos. Todas tinham vários antecedentes de risco para transmissão do Trypanosoma cruzi: vetorial, congênito e/ou transfusão sangüínea. O diagnóstico da infecção foi feito através de sorologia convencional. O exame clínico foi complementado por eletrocardiograma, radiografias de tórax e, análise de sangue e urina para avaliação das funções hepáticas. No pós-tratamento, utilizaram-se técnicas idênticas às do diagnóstico, sendo que 33 crianças tiveram, também, avaliação parasitológica. Dentre 24 crianças não tratadas, 14 foram controlados por 8 a 24 anos e mantiveram sorologia positiva e o estado clínico inicial. Das 71 crianças tratadas, 49 tiveram acompanhamento de 4 a 24 anos: 14 mantiveram anticorpos anti-Trypanosoma cruzi; 6 resultados discordantes e 29 negativaram a sorologia. Destas, 9 apresentaram oscilações sorológicas, antes da negativação definitiva. A mediana do tempo de negativação pós-tratamento foi, respectivamente, de 3,5 e 8 anos para crianças de 1 a 6 e 7 a 14 anos. A percentagem de soronegativos diminuiu com a idade em que se medicou, desde 75% em <4 anos até 43% em > 9 anos. A intolerância ao tratamento foi de 3,8%. Nenhuma criança modificou seu estado clínico nesta observação.

Clinical and epidemiological results of 95 treated and untreated chronic chagasic children, with an up to 24 years follow-up period are presented. This population studied in the 1/14 age bracket, residing in Santa Fe city, Argentina, was diagnosed through Chagas-specific conventional serologic reactions. Clinical examination was supplemented with electrocardiogram, chest X-rays, and blood and urine tests for evaluating hepatic function. The drugs employed were nifurtimox or benznidazole. In post treatment period xenodiagnosis was made in 33 patients. Regarding Trypanosoma cruzi transmission, the studied individuals presented multi-risk antecedents: vectorial, congenital and/or blood transfusion. Among 24 untreated children 14 were controlled during 8/24 years: all this patients maintained the initial antibody concentration and clinical status. From 71 treated patients 49 were followed-up 4/24 years: 14 remained positive, 6 presented dubious results, and 29 showed final non-reactive results. 9 of this presented sometimes oscilating results. In 1/6 age bracket children, the serology turned negative after 3.5 years (median) once the treatment was finished, while patients treated in the 7/14 age bracket, the median of negativization was 8 years. 3.8% did not tolerate the drug. None of the groups changed their clinical condition. The untreated children did not change the serology. The percentage of treated children presenting negative serological results decrease according to the age when treatment was given: 75% became negative when treated at <4 years old and 43% when treated at >9 years old.