Air–water properties in rectangular free-falling jets

This study analyzes the air–water flow properties in overflow nappe jets. Data were measured in several cross-sections of rectangular free-falling jets downstream of a sharp-crested weir, with a maximum fall distance of 2.0 m. The flow properties were obtained using a conductivity phase-detection probe. Furthermore, a back-flushing Pitot-Prandtl probe was used in order to obtain the velocity profiles. Five specific flows rates were analyzed, from 0.024 to 0.096 m3/s/m. The measurements of the air–water flow allowed us to characterize the increment of the air entrainment during the fall, affecting the flow characteristic distributions, reducing the non-aerated water inner core, and increasing the lateral spread, thereby leading to changes in the jet thickness. The results showed slight differences between the upper and lower nappe trajectories. The experimental data of the jet thickness related to a local void fraction of 50% seemed to be similar to the jet thickness due only to gravitational effects until the break-up length was reached. The amount of energy tended to remain constant until the falling distance was over 15 times greater than the total energy head over the weir crest, a distance at which the entrained air affected the entire cross-section, and the non-aerated core tended to disappear. The new experiments related with air–water properties in free-falling jets allow us to improve the current knowledge of turbulent rectangular jets

Experimental characterization of air entrainment in rectangular free falling jets

This experimental study presents an analysis of the air–water flow in rectangular free-falling jets. The measurements were obtained downstream of a 1.05mwide sharp-crested weir. The properties of the air–water flow were registered in several cross-sections of the nappe. A conductivity phase detection probe was employed, sampling at 20 kHz. Three different specific flows were considered, with energy head over the crest of 0.080, 0.109 and 0.131 m to avoid scale effects. To analyze the flow properties, air–water parameters during the fall, such as the phase change spatial distribution, air–water phase change of frequency, Sauter mean diameter, bubble chord length, turbulent intensities and spectral analyses, were studied. The jet thickness behaviors (inner jet core and free surface) were also analyzed in the falling jet. The jet thickness related to a void fraction of 90% seems to be similar to the theoretical proposal obtained by Castillo et al. (2015), while the jet thickness related to a void fraction of 10% seems to be similar to the jet thickness due to gravitational effects. The results show relative differences in the behavior of the upper and lower sides of the nappe. The experimental data allow us to improve on and complement previous research.This research was funded by the “Ministerio de Ciencia, Innovación y Universidades” (MCIU), the “Agencia Estatal de Investigación” (AEI) and the “Fondo Europeo de Desarrollo Regional” (FEDER), through the Project “La aireación del flujo en el vertido en lámina libre por coronación de presas a nivel de prototipo y su efecto en cuencos de disipación de energía”, grant number RTI2018-095199-B-I00, and by the “Comunidad Autónoma de la Región de Murcia” through the “Programa Regional de Fomento de la Investigación Científica y Técnica (Plan de Actuación 2018) de la Fundación Séneca-Agencia de Ciencia y Tecnología de la Región de Murcia”, Project “Análisis de la capacidad de descarga de vertederos tipo laberinto y de la disipación de energía aguas abajo de los mismos”, grant number 20879/PI/18

Effect of viral storm in patients admitted to intensive care units with severe COVID-19 in Spain: a multicentre, prospective, cohort study

Background: The contribution of the virus to the pathogenesis of severe COVID-19 is still unclear. We aimed to evaluate associations between viral RNA load in plasma and host response, complications, and deaths in critically ill patients with COVID-19. Methods: We did a prospective cohort study across 23 hospitals in Spain. We included patients aged 18 years or older with laboratory-confirmed SARS-CoV-2 infection who were admitted to an intensive care unit between March 16, 2020, and Feb 27, 2021. RNA of the SARS-CoV-2 nucleocapsid region 1 (N1) was quantified in plasma samples collected from patients in the first 48 h following admission, using digital PCR. Patients were grouped on the basis of N1 quantity: VIR-N1-Zero ([removed]2747 N1 copies per mL). The primary outcome was all-cause death within 90 days after admission. We evaluated odds ratios (ORs) for the primary outcome between groups using a logistic regression analysis. Findings: 1068 patients met the inclusion criteria, of whom 117 had insufficient plasma samples and 115 had key information missing. 836 patients were included in the analysis, of whom 403 (48%) were in the VIR-N1-Low group, 283 (34%) were in the VIR-N1-Storm group, and 150 (18%) were in the VIR-N1-Zero group. Overall, patients in the VIR-N1-Storm group had the most severe disease: 266 (94%) of 283 patients received invasive mechanical ventilation (IMV), 116 (41%) developed acute kidney injury, 180 (65%) had secondary infections, and 148 (52%) died within 90 days. Patients in the VIR-N1-Zero group had the least severe disease: 81 (54%) of 150 received IMV, 34 (23%) developed acute kidney injury, 47 (32%) had secondary infections, and 26 (17%) died within 90 days (OR for death 0·30, 95% CI 0·16–0·55; p<0·0001, compared with the VIR-N1-Storm group). 106 (26%) of 403 patients in the VIR-N1-Low group died within 90 days (OR for death 0·39, 95% CI 0·26–0·57; p[removed]11 página

Clonal chromosomal mosaicism and loss of chromosome Y in elderly men increase vulnerability for SARS-CoV-2

The pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2, COVID-19) had an estimated overall case fatality ratio of 1.38% (pre-vaccination), being 53% higher in males and increasing exponentially with age. Among 9578 individuals diagnosed with COVID-19 in the SCOURGE study, we found 133 cases (1.42%) with detectable clonal mosaicism for chromosome alterations (mCA) and 226 males (5.08%) with acquired loss of chromosome Y (LOY). Individuals with clonal mosaic events (mCA and/or LOY) showed a 54% increase in the risk of COVID-19 lethality. LOY is associated with transcriptomic biomarkers of immune dysfunction, pro-coagulation activity and cardiovascular risk. Interferon-induced genes involved in the initial immune response to SARS-CoV-2 are also down-regulated in LOY. Thus, mCA and LOY underlie at least part of the sex-biased severity and mortality of COVID-19 in aging patients. Given its potential therapeutic and prognostic relevance, evaluation of clonal mosaicism should be implemented as biomarker of COVID-19 severity in elderly people. Among 9578 individuals diagnosed with COVID-19 in the SCOURGE study, individuals with clonal mosaic events (clonal mosaicism for chromosome alterations and/or loss of chromosome Y) showed an increased risk of COVID-19 lethality

Ciencia Odontológica 2.0

Libro que muestra avances de la Investigación Odontológica en MéxicoEs para los integrantes de la Red de Investigación en Estomatología (RIE) una enorme alegría presentar el segundo de una serie de 6 libros sobre casos clínicos, revisiones de la literatura e investigaciones. La RIE está integrada por cuerpos académicos de la UAEH, UAEM, UAC y UdeG

Retos, avances y reflexiones transdisciplinares desde contextos educativos diversos

La publicación de las ponencias que conformaron el V Congreso Internacional de Educación de la Universidad Nacional de Educación, titulado Retos, avances y reflexiones transdisciplinares desde contextos educativos diversos, ofrece una visión comprensiva y multifacética de la educación contemporánea. A través de ocho ejes temáticos, entre los que se incluye la formación integral y el desarrollo profesional, la teoría y la práctica en la formación profesional docente, la relación entre sociedad y escuela, la gestión educativa y las tecnologías para la educación, esta recopilación busca contribuir al conocimiento académico sobre la educación y, al mismo tiempo, ser fuente de información e inspiración para educadores, investigadores y todas aquellas personas interesadas en el desarrollo educativo

3MT UPCT2020: Aireación y disipación de energía en laminas vertientes en presas

Los nuevos requerimientos de diseño en seguridad de presas frente a inundaciones y eventos extremos conducen a escenarios más exigentes en el diseño hidráulico de una presa. Uno de los mecanismos aceptados ante un eventual tránsito extraordinario de una crecida en una presa es el sobrevertido por coronación. Este fenómeno es complejo debido a la auto-aireación de la lámina libre y el frenado de la velocidad durante la caída; acompañado de un proceso de desintegración del núcleo interno y de disipación de energía. Este fenómeno tendrá un efecto significativo en el cuenco de disipación, la estabilidad de la presa y los márgenes del río aguas abajo de la estructura hidráulica. El objetivo del presente trabajo es avanzar en la comprensión de este fenómeno. Para la campaña experimental se utiliza una sonda de conductividad que permite medir distintas propiedades en flujos agua-aire (fracción de vacío, frecuencia de cambio de fase, tamaño de burbuja). Adicionalmente se utiliza un tubo Pitot-Prandtl con un sistema de back-flushing para la medición de la velocidad. De esta forma se avanzará en la comprensión de este fenómeno complejo y así mejorar los criterios de diseño hidráulico de pequeñas y grandes presas, ahorro significativo en la construcción y mantenimiento de los cuencos de disipación de energía, así como en la evaluación de las acciones hidrodinámicas en presas existente

Analysis of rectangular free-falling jets in overtopping of concrete dams

[SPA] Las nuevas normativas en el diseño y funcionamiento de grandes presas y embalses han planteado la necesidad de una reevaluación de las presas existentes y de sus órganos de desagüe, incluyendo el análisis de nuevas acciones hidrodinámicas durante todas las fases de su vida útil. Diferentes estudios previos han demostrado que la capacidad de descarga de diversas presas existentes puede ser insuficiente frente a los escenarios de avenidas extraordinarias. Estas nuevas solicitaciones plantean posibles escenarios a corto plazo donde las presas deban evacuar caudales mayores a los previstos de forma segura y controlada. Frente a estas nuevas exigencias, diferentes organismos referentes en el diseño, construcción y operación de presas (Federal Emergencia Management Agency, FEMA; United States Army Corp of Engineers, USBR; International Commission on Large Dams, ICOLD) han planteado la posibilidad de un desbordamiento por la coronación de la presa (overtopping) como una solución de emergencia y puntual frente a avenidas hidrológicas extraordinarias. Detectar esta problemática es prioritario para realizar la caracterización hidrodinámica de los chorros de sobrevertido de la presa y su efecto incidente en el pie de esta. La interacción del chorro con la atmósfera requiere un estudio profundo del mecanismo de introducción de aire en el chorro, su influencia en la desintegración del chorro, en el campo de velocidades, así como en la disipación de energía que se produce durante la caída. Hasta la presente fecha existen pocos estudios sobre la auto-aireación de la lámina vertiente en chorros rectangulares y su efecto en las presiones del cuenco situado a pie de presa (por ejemplo: Castillo 2006 y Castillo et al. 2015). En la presente Tesis Doctoral se ha realizado un análisis experimental de la lámina vertiente en chorros rectangulares. Esta caracterización implica el análisis de diferentes variables hidrodinámicas de flujos bifásicos agua-aire en chorros rectangulares tales como: fracción de vacío, frecuencia de cambio de fase, campo de velocidades, disipación de energía, expansión lateral del chorro, diámetro medio de burbuja, longitud de cuerda de burbujas de aire, y análisis espectral de las señales, entre otros. Para medir los flujos agua-aire se han utilizado una sonda de conductividad diseñada y construida en el marco de esta Tesis y un tubo Pitot-Prandtl con sistema back-flushing. El estudio busca avanzar en el conocimiento y comprensión del fenómeno de autoaireación en chorros rectangulares de vertido libre de presas. El análisis de distintas variables hidrodinámicas permite entender con mayor profundidad los mecanismos de disipación e interacción con la atmósfera durante la caída del chorro. [ENG] New regulations in design and operation of large dams and reservoirs have raised the need for a re-evaluation of existing dams and their spillways, including the analysis of new hydrodynamic actions during all their phases. Previous studies have shown that the discharge capacity of some existing dams may be insufficient in extraordinary flood scenarios. These new demands rise possible short-term scenarios in which the dams must evacuate flows greater than those expected in safely conditions and in a controlled way. In front of these new requirements, several organizations involved in the design, construction and operation of dams (Federal Emergency Management Agency, FEMA; United States Army Corp of Engineers, USBR; International Commission on Large Dams, ICOLD) have raised the possibility of overtopping of the dam as an emergency and timely solution to extraordinary hydrological floods. Detecting this problem is a priority in order to carry out the hydrodynamic characterization of the overtopping jets of the dam and their effect on its toe. The interaction of the jet with the atmosphere requires an in-depth study of the mechanism of air introduction into the jet and its influence on the disintegration of the jet, on the velocity field, as well as on the energy dissipation that occurs during the fall. To date, there are few studies analyzing self-aeration of rectangular free-falling jets and their effect on the pressures in the plunge pool located at the toe of the dam (for example, Castillo 2006 and Castillo et al. 2015). In this Doctoral Thesis an experimental analysis of the rectangular free-falling jets has been carried out. This characterization involves the analysis of different hydrodynamic variables of two-phase water-air flows in rectangular jets such as: void fraction, airwater phase count rate, velocity field, energy dissipation, jet lateral spread, mean bubble diameter, air bubble chord length, and spectral analysis of the signals, among others. To measure the air-water flows, a conductivity probe designed and built within the framework of this Thesis and a Pitot-Prandtl tube with a back-flushing system have been used. The study seeks to advance in the knowledge and understanding of the phenomenon of self-aeration in rectangular free-falling jets of dams. The analysis of different hydrodynamic variables allows a deeper understanding of the mechanisms of dissipation and interaction with the atmosphere during the fall.Escuela Internacional de Doctorado de la Universidad Politécnica de CartagenaUniversidad Politécnica de CartagenaPrograma de Doctorado en Tecnología y Modelización en Ingeniería Civil, Minería y Ambienta