Efecto de la presión sobre las fugas de agua en un sistema de tubería simple

Este artículo es un resultado del proyecto de investigación “Estudio del efecto de la presión en una red de distribución sobre las fugas de agua, utilizando una red de experimentación en laboratorio” y en él se analizan las relaciones entre la sobrepresión generada por el transiente hidráulico originado por el cierre rápido de una válvula y las fugas inducidas mediante orificios en un sistema experimental de tuberías. El presente artículo se concentra en describir las alteraciones en la onda depresión cuando se presentan fugas de agua en un sistema de tuberías simple. Para ello, se analizan los resultados obtenidos en un montaje experimental y se comparan las ondas obtenidas con y sin fuga, en condiciones similares de caudal. Se observó que existe un decaimiento en las presiones máximas en el sistema al comparar las presiones en los sistemas con fuga y sin fuga. Comparando los resultados obtenidos para el ensayo con fugas y sin fugas se observa una mayor atenuación de la onda ante la presencia de fugas

Ab-initio study on synthesis of new materials at high pressure : transition-metal nitrides and non-molecular CO2 phases

Now, I will proceed with a very brief description of the two main parts that form this thesis work, which are inspired by some new possibilities that high pressure has opened for the synthesis of new phases and compounds. The relevance of these new materials from a practical point of view, lies in the possibility of having them recovered to ambient conditions and then used in a wide variety of technical applications. The two examples covered here, include a new class of transition-metal nitrides, and the synthesis of extended forms of CO2. In Chapter 3, it is shown that the new family of late transition-metal nitrides: PtN2, OsN2 and IrN2, all synthesized at similar conditions ( 3c 50 GigaPascal and 2000 K) [10, 11], shares common structural properties among its members and opens the door to the synthesis of novel materials of this kind; with possible technological applications since they can be recovered to ambient conditions. The synthesis of these new nitrides is a clear example of how pressure can be used to form compounds between species that do not mix at ambient conditions. Chapter 4 reports our studies on a different class of high pressure synthesis, namely the chemical transformation of a molecular species (CO2) into an extended compound with entirely different mechanical and electronic properties. In particular it reports on the transition that molecular CO2 undergoes at pressures above 40GPa and mild temperatures, into an extended glassy phase. CO2\u2019s pressure-induced phase-transition from a molecular to an extended phase was first observed in 1999 when V. Iota and collaborators at Livermore, obtained a fully tetrahedral silica-like phase of CO2 whose precise structure remains unresolved up to these days [12]. Recently, two new extended phases that show strong similarities among themselves in many aspects, have been reported [13, 14]. The first [13], is a non-molecular amorphous phase named \u201ca-CO2\u201d or \u201ccarbonia\u201d, while the second [14], is a crystalline phase indexed by its discoverers as stishovite-like, i.e. with six-fold coordinated carbon atoms, that instead we believe is the crystalline counterpart of carbonia. However, in contrast with what is observed in the case of the transition-metal nitrides, for CO2 no recovery of any of the new extended phases to ambient conditions has yet been possible. In fact, it is observed that a-CO2 and phase VI go back to molecular phases at pressures around 20 GPa which coincides with the pressure at which the crossing between the enthalpies corresponding to the molecular and tetrahedral phases takes place. Finally, also in Chapter 4, I consider some first-principles high-pressure chemistry applied to the problem of the catalysis and recovery of new CO2 extended phases. Here, I will show that by means of introducing a transition metal (TM) as an impurity (Ti in our case) in a CO2 molecular sample (2% concentration) an activation of the amorphization reaction is observed and this leads to a transition that occurs much faster than in the case in which no TM is used. It is also expected that attempts succeeding to lower the transition pressure, will also lead to a lowering of the pressures at which the CO2\u2019s non-molecular phases can be recovered, with the final goal of bringing them to ambient conditions. In summary, in this thesis it is shown how first-principles calculation techniques can be effectively used in high-pressure physics and chemistry research for clarifying very important issues regarding structural and electronic properties that wouldn\u2019t be easily accessible by other means

Detection of Communities within the Multibody System Dynamics Network and Analysis of Their Relations

Multibody system dynamics is already a well developed branch of theoretical, computational and applied mechanics. Thousands of documents can be found in any of the well-known scientific databases. In this work it is demonstrated that multibody system dynamics is built of many thematic communities. Using the Elsevier’s abstract and citation database SCOPUS, a massive amount of data is collected and analyzed with the use of the open source visualization tool Gephi. The information is represented as a large set of nodes with connections to study their graphical distribution and explore geometry and symmetries. A randomized radial symmetry is found in the graphical representation of the collected information. Furthermore, the concept of modularity is used to demonstrate that community structures are present in the field of multibody system dynamics. In particular, twenty-four different thematic communities have been identified. The scientific production of each community is analyzed, which allows to predict its growing rate in the next years. The journals and conference proceedings mainly used by the authors belonging to the community as well as the cooperation between them by country are also analyzed

El fenómeno de la reproducibilidad en los procesos de formación de profesores en servicio. Un caso de la geometría escolar

El siguiente escrito presenta la descripción de un proyecto de investigación que está en curso. Este pretende hacer un estudio con profesores en formación continua, en particular con aquellos que han realizado un curso de perfeccionamiento y que hacen clases de matemáticas a estudiantes de 12 a 14 años. Estos docentes, actualizan saberes: matemáticos, didácticos y pedagógicos, diseñan situaciones de aprendizaje fundamentadas en marcos teóricos de la didáctica de la matemática o matemática educativa. Además, desarrollan la metodología de Estudio de Clases para reflexionar sobre su propia práctica entre pares. En este contexto, se pretende investigar sobre el “fenómeno de reproducibilidad”. Para ello se proyecta provocar una reflexión de tipo didáctica con elementos teóricos que emergen en la didáctica de la matemática como es el caso de la reproducibilidad. Nos proponemos observar qué elementos aportan al quehacer del profesor dicha reflexión para que los diseños didácticos sean aplicados en diferentes escenarios

Propuesta metodológica para el análisis morfo-sedimentológico en cuencas altamente urbanizadas. Caso de estudio quebrada Doña María (Colombia)

En este artículo se presenta una propuesta metodológica para hacer el análisis de morfología fluvial y transporte de sedimentos para cuencas altamente intervenidas por la acción humana. En dicha metodología se proponen diferentes actividades las cuales permitirán hacer un análisis detallado de la morfología fluvial y los sedimentos en una cuenca. Entre las etapas que se proponen para implementar esta metodología se tienen: análisis en planta de la cuenca, análisis de los perfiles altimétricos de las principales corrientes, levantamiento de información en campo (aforos líquidos, sólidos y observaciones generales de la morfología de la cuenca) y estimación de la carga y capacidad de carga de sedimentos en la quebrada principal. Una aplicación a la cuenca de la quebrada Doña María (en el Área Metropolitana del Valle de Aburrá, Colombia) es presentada

Treatment of xerostomia and hyposalivation in the elderly: a systematic review

Background: Therapeutic strategies for xerostomia, regardless of etiology, have so far not had definitive or clearly effective results. Objectives. To systematically revise the latest scientific evidence available regarding the treatment of dry mouth, regardless of the cause of the problem. Material and Methods: The literature search was conducted in March 2015, using the Medline and Embase databases. The “Clinical Trial”, from 2006 to March 2015, was carried out in English and only on human cases. The draft of the systematic review and assessment of the methodological quality of the trials was carried out following the criteria of PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) and the “Oxford Quality Scale”. Results: Finally, a total of 26 trials were identified that met the previously defined selection and quality criteria; 14 related to drug treatments for dry mouth, 10 with non-pharmacological treatment and 2 with alternative treatments. Conclusions: Pilocarpine continues to be the best performing sialogogue drug for subjects with xerostomia due to radiation on head and neck cancer or diseases such as Sjogren’s Syndrome. For patients with dry mouth caused solely by medication, there are some positive indications from the use of malic acid, along with other elements that counteract the harmful effect on dental enamel. In general, lubrication of oral mucous membrane reduces the symptoms, although the effects are short-live

Efecto de la presión sobre las fugas de agua en un sistema de tubería simple

Este artículo es un resultado del proyecto de investigación “Estudio del efecto de la presión en una red de distribución sobre las fugas de agua, utilizando una red de experimentación en laboratorio” y en él se analizan las relaciones entre la sobrepresión generada por el transiente hidráulico originado por el cierre rápido de una válvula y las fugas inducidas mediante orificios en un sistema experimental de tuberías. El presente artículo se concentra en describir las alteraciones en la onda depresión cuando se presentan fugas de agua en un sistema de tuberías simple. Para ello, se analizan los resultados obtenidos en un montaje experimental y se comparan las ondas obtenidas con y sin fuga, en condiciones similares de caudal. Se observó que existe un decaimiento en las presiones máximas en el sistema al comparar las presiones en los sistemas con fuga y sin fuga. Comparando los resultados obtenidos para el ensayo con fugas y sin fugas se observa una mayor atenuación de la onda ante la presencia de fugas