Lagrangian acceleration statistics in a turbulent channel flow

Lagrangian acceleration statistics in a fully developed turbulent channel flow at $Re_\tau = 1440$ are investigated, based on tracer particle tracking in experiments and direct numerical simulations. The evolution with wall distance of the Lagrangian velocity and acceleration time scales is analyzed. Dependency between acceleration components in the near-wall region is described using cross-correlations and joint probability density functions. The strong streamwise coherent vortices typical of wall-bounded turbulent flows are shown to have a significant impact on the dynamics. This results in a strong anisotropy at small scales in the near-wall region that remains present in most of the channel. Such statistical properties may be used as constraints in building advanced Lagrangian stochastic models to predict the dispersion and mixing of chemical components for combustion or environmental studies.Comment: accepted for publication in Physical Review Fluid

Propuesta para el fortalecimiento de la cadena de valor del sector apicula de la zona de Chalatenango y Metapan.

Planteamiento del Problema -- Justificación de la propuesta -- Metodología de la investigación -- Generalidades de la Apicultura -- Las Abejas

Zeit für sich selbst : Muße, Langeweile und die Nutzung digitaler Medien im Alltag ; Zwei Forschungsberichte

Die erste Studie ("Langweilen wir uns noch? Nutzung von digitalen Medien zur unbewussten Prävention von Langeweile") beschäftigt sich mit der Nutzung digitaler Medien als Prävention von Langeweile. Dabei wird hinterfragt, ob die Mediennutzung die Langeweile tatsächlich verhindern kann oder ob dieser Erfolg ausbleibt. Zunächst wird ermittelt, auf welche Weise mit Langeweile umgegangen wird. Darauf aufbauend werden Motive herausgearbeitet, die hinter der digitalen Mediennutzung stehen. Aus dieser Kombination von Mediennutzung und Langeweile leitet sich die Frage nach der bewussten oder unbewussten präemptiven Nutzung von Medien zur Vermeidung von Langweile ab. Zur Beantwortung der Forschungsfragen dient eine qualitativ durchgeführte Gruppendiskussion. - Die zweite Studie ("Langeweile oder Muße: Gründe der Selbstdarstellung in den sozialen Medien") thematisiert potentielle Gründe der Selbstdarstellung in den sozialen Medien vor dem Hintergrund der modernen digitalen Gesellschaft. Dabei werden vorranging die Konstrukte der Muße und der Langeweile sowie deren Zusammenhänge als Gründe für das Posting selbstdarstellerischer Inhalte in Social Media theoretisch betrachtet und methodisch analysiert. Im Rahmen der Forschungsarbeit wird dabei Instagram als beispielhaftes Medium zum Gegenstandsbereich der Untersuchung gewählt. Zur Beantwortung der Forschungsfrage wird die Methode der narrativen Medienforschung angewandt. Basierend auf den Erkenntnissen von fünf qualitativ und narrativ durchgeführten Tiefeninterviews erfolgt mittels einer Inhaltsanalyse eine deduktive sowie induktive Kategorienbildung, die potentielle Gründe der Selbstdarstellung aufzeigt

Global overview of the management of acute cholecystitis during the COVID-19 pandemic (CHOLECOVID study)

Background: This study provides a global overview of the management of patients with acute cholecystitis during the initial phase of the COVID-19 pandemic. Methods: CHOLECOVID is an international, multicentre, observational comparative study of patients admitted to hospital with acute cholecystitis during the COVID-19 pandemic. Data on management were collected for a 2-month study interval coincident with the WHO declaration of the SARS-CoV-2 pandemic and compared with an equivalent pre-pandemic time interval. Mediation analysis examined the influence of SARS-COV-2 infection on 30-day mortality. Results: This study collected data on 9783 patients with acute cholecystitis admitted to 247 hospitals across the world. The pandemic was associated with reduced availability of surgical workforce and operating facilities globally, a significant shift to worse severity of disease, and increased use of conservative management. There was a reduction (both absolute and proportionate) in the number of patients undergoing cholecystectomy from 3095 patients (56.2 per cent) pre-pandemic to 1998 patients (46.2 per cent) during the pandemic but there was no difference in 30-day all-cause mortality after cholecystectomy comparing the pre-pandemic interval with the pandemic (13 patients (0.4 per cent) pre-pandemic to 13 patients (0.6 per cent) pandemic; P = 0.355). In mediation analysis, an admission with acute cholecystitis during the pandemic was associated with a non-significant increased risk of death (OR 1.29, 95 per cent c.i. 0.93 to 1.79, P = 0.121). Conclusion: CHOLECOVID provides a unique overview of the treatment of patients with cholecystitis across the globe during the first months of the SARS-CoV-2 pandemic. The study highlights the need for system resilience in retention of elective surgical activity. Cholecystectomy was associated with a low risk of mortality and deferral of treatment results in an increase in avoidable morbidity that represents the non-COVID cost of this pandemic

Relative dispersion of particle pairs in turbulent channel flow

International audienceLagrangian tracking of particle pairs is of fundamental interest in a large number of environmental applications dealing with contaminant dispersion and passive scalar mixing. The aim of the present study is to extend the observations available in the literature on relative dispersion of fluid particle pairs to wall-bounded turbulent flows, by means of particle pair tracking in direct numerical simulations (DNS) of a turbulent channel flow. The mean-square change of separation between particle pairs follows a clear ballistic regime at short times for all wall distances. The Eulerian structure functions governing this short-time separation are characterised in the channel, and allow to define a characteristic time scale for the ballistic regime, as well as a suitable normalisation of the mean-square separation leading to an overall collapse for different wall distances. Through fluid particle pair tracking backwards and forwards in time, the temporal asymmetry of relative dispersion is illustrated. At short times, this asymmetry is linked to the irreversibility of turbulence, as in previous studies on homogeneous isotropic flows. The influence of the initial separation (distance and orientation) as well as the influence of mean shear are addressed. By decomposing the mean-square separation into the dispersion by the fluctuating velocity field and by the average velocity, it is shown that the influence of mean shear becomes important at early stages of dispersion close to the wall but also near the channel centre. The relative dispersion tensor ∆ i j is also presented and particularly the sign and time evolution of the cross-term ∆ xy are discussed. Finally, a ballistic cascade model previously proposed for homogeneous isotropic turbulence is adapted here to turbulent channel flows. Preliminary results are given and compared to the DNS. Future developments and assumptions in two particle stochastic models can be gauged against the issues and results discussed in the present study

Measurement of mass exchange processes and coefficients in a simplified open-channel lateral cavity connected to a main stream

International audienceLateral cavities are major storage zones in riverine environments for which the mass exchanges with the main stream strongly impact The characteristics of the habitat in these dead zones. An experimental work is presented here with a controlled main stream and aconnected open-channel lateral cavity to assess the processe s responsible for these exchanges and to quantify the exchange capacities. In a first step, the measurements of passive scalar transport allow us to identify the physical processes involved in the exchange of mass from the main stream and its spreading within the cavity. In a second step, the quantitative mass exchange coefficient, representative of the exchange capacity, is measured for 28 flow and cavity configurations. The sensibility analysis to the governing parameters proposed by the dimensional analysis then reveals that changing the geometric aspect ratio of the cavity does not affect the exchange coefficient while increasing the normalized water depth or decreasing the Reynolds number of the main stream tend to increase this coefficient. Indeed, The se parameters modify both the growth rate of the mixing layer width at the interface and the amplitude of the alternating transverse Velocity across the interface, thus affect ing the exchange capacities from the main stream to the cavit

Model stochastyczny kwalifikacji i optymalizacji wplywu ryzka operacyjnego na zrownowazony rozwoj korporacyjny z wykorzystaniem symulacji Monte Carlo

Operational risk has been widely studied, and international guidelines provide procedures for the correct management of operational risk; however, this has not been studied from a corporate sustainability point of view. Therefore, this work seeks to find a way to model and optimize the impact of operational risks on corporate sustainability. The methodology used is based on the assignment of two distribution functions for the creation of a probabilistic model that allows quantifying the probability of occurrence (frequency) and the expected monetary impact (severity) on the sustainability variables (environmental, social, and economic). The result is a statistical convolution through Monte Carlo simulation, which makes it possible to quantify aggregate losses to finally make an optimization process of the variables and estimate the financial impact. Therefore, this study extends the literature on risk quantification, proposing a stochastic model that quantifies and optimizes the operational risks that are related to corporate sustainability. The proposed model offers a practical way to quantify operational risks related to corporate sustainability while also being flexible, as it does not require historical information and can be used with data collected from the company based on the proposed probability distributions. Finally, the proposed model has three limitations: the distribution functions, use of Solver (Excel), and exclusion of some risk management strategies, which future research can consider.Ryzyko operacyjne zostało szeroko zbadane, a międzynarodowe wytyczne dostarczają procedur do prawidłowego zarządzania ryzykiem operacyjnym; jednakże nie badano tego z punktu widzenia zrównoważonego rozwoju przedsiębiorstwa. Dlatego też niniejsza praca ma na celu znalezienie sposobu modelowania i optymalizacji wpływu ryzyka operacyjnego na zrównoważony rozwój przedsiębiorstwa. Zastosowana metodologia opiera się na przypisaniu dwóch funkcji rozkładu w celu stworzenia modelu probabilistycznego, który pozwala kwantyfikować prawdopodobieństwo wystąpienia (częstotliwość) i oczekiwany monetarny wpływ (ciężkość) na zmienne zrównoważone (środowiskowe, społeczne i ekonomiczne). Rezultatem jest statystyczna konwolucja poprzez symulację Monte Carlo, który umożliwia ilościowe określenie zagregowanych strat, aby ostatecznie przeprowadzić proces optymalizacji zmiennych i oszacować wpływ finansowy. Dlatego też niniejsze badanie poszerza literaturę w obszarze kwantyfikacji ryzyka, proponując model stochastyczny, który kwantyfikuje i optymalizuje ryzyko operacyjne związane ze zrównoważonym rozwojem przedsiębiorstwa. Proponowany model oferuje praktyczny sposób ilościowego określenia ryzyk operacyjnych związanych ze zrównoważonym rozwojem przedsiębiorstwa, a jednocześnie jest elastyczny, ponieważ nie wymaga informacji historycznych i może być stosowany w połączeniu z danymi zebranymi z przedsiębiorstwa w oparciu o proponowane rozkłady prawdopodobieństwa. Wreszcie proponowany model ma trzy ograniczenia: funkcje rozkładu, użycie Solvera (Excel) i wykluczenie niektórych strategii zarządzania ryzykiem, które mogą zostać uwzględnione w przyszłych badaniach.https://pjms.zim.pcz.pl/am2024Mechanical and Aeronautical EngineeringSDG-09: Industry, innovation and infrastructur

Una mezcla de bacteriófagos reduce los recuentos de Salmonella enterica serovar Enteritidis en tejidos de salmón fresco y ahumado

The use of bacteriophages for the biocontrol of food-borne pathogens is increasingly gaining acceptance. In this study, the effectiveness of bacteriophages to reduce Salmonella Enteritidis counts was evaluated in raw and smoked salmon tissues. Groups of 25 samples each were contaminated with S. Enteritidis, treated with a phage mix and then incubated for ten days at 18 °C and 4 °C. A signifi cant bacterial reduction was obtained on days 3, 6 and 10 in raw salmon samples incubated at 18 °C (from 0.75 to 3.19 log10 CFU/g) and at 4 °C (from 2.82 to 3.12 log10 CFU/g), whereas in smoked salmon lower reductions were achieved (from 1.02 to 1.96 log10 CFU/g at 18°C and from 0.50 to 1.16 log10 CFU/g at 4 °C). These results show the potential effectiveness of this bacteriophage cocktail as a biocontrol agent against S. Enteritidis in raw and smoked salmon tissues.El uso de bacteriófagos en el biocontrol de patógenos está adquiriendo cada vez más aceptación. En este estudio se evaluó la efectividad de bacteriófagos en la reducción de los recuentos de Salmonella Enteritidis en salmón fresco y ahumado. Para ello, 25 muestras por grupo fueron contaminadas con S. Enteritidis, tratadas con una mezcla de bacteriófagos e incubadas durante 10 días a 18 °C o a 4 °C. A los días 3, 6 y 10 se obtuvo una reducción signifi cativa de los recuentos de S. Enteritidis en las muestras de salmón fresco incubadas a ambas temperaturas: la reducción fue de entre 0,75 y 3,19 log10 UFC/g a 18 °C y de entre 2,82 y 3,12 log10 UFC/g a 4 °C. En salmón ahumado las reducciones fueron menores (entre 1,02 y 1,96 log10 UFC/g a 18 °C y entre 0,50 y 1,16 log10 UFC/g a 4 °C). Los resultados indican que estos bacteriófagos constituyen una potencial herramienta de biocontrol de S. Enteritidis en tejidos de salmón fresco y ahumado

Prueba adaptativa para medir el progreso de los estudiantes: colegios en Bogotá, Colombia

In the school environment, the loss of reliability of the evaluation has become an increasingly evident problem. In this sense, this research aimed to analyze the results of the application of an adaptive test, in students of cycle III of some schools in Bogotá, Colombia. For which, a quantitative-transectional methodological design with correlational scope was used, and an intentional non-probabilistic sample was selected. The test instrument corresponded to that of a Rasch technique, with a logistic model of a parameter associated with the item response theory, from which the performance data of 544 students were obtained, which were interpreted based on the statistical analysis. The results showed that: The designed test could identify and adapt to the characteristics of the students considering the curricular evaluation criteria; There are no significant differences among the students’ findings that indicate some factor of instability in the applied test. It is concluded that the application of this test in Educational Institutions of Colombia can help to strengthen components of the school evaluation and student progress, compared to the expected learning for the process, if they focus on competency performances.En el ámbito escolar la pérdida de fiabilidad de la evaluación ha venido constituyéndose en una problemática cada vez más evidente. En ese sentido, esta investigación tuvo como objetivo analizar los resultados de aplicación de una prueba adaptativa, en estudiantes de ciclo III de algunos colegios de Bogotá, Colombia. Para lo cual, se utilizó un diseño metodológico cuantitativo-transeccional con alcance correlacional, y se seleccionó una muestra intencionada no-probabilística. El instrumento de prueba correspondió al de una técnica Rasch, con modelo logístico de un parámetro asociado a la teoría de respuesta al ítem, desde el cual se obtuvieron los datos de desempeño de 544 estudiantes, los cuales fueron interpretados con base en el análisis estadístico. Los resultados evidenciaron que: El test diseñado pudo identificar y adaptarse a las características de los estudiantes considerando los criterios curriculares de evaluación; entre los hallazgos de los estudiantes no se muestran diferencias significativas que indiquen algún factor de inestabilidad en la prueba aplicada. Se concluye, que la aplicación de esta prueba en Instituciones Educativas de Colombia, puede ayudar a fortalecer componentes de la evaluación escolar y progreso de los alumnos, frente a los aprendizajes esperados para el proceso, si se enfocan en desempeños de competenci

Transcriptome profiling of lentil in response to Ascochyta lentis infection

Aim of study: The purpose was to identify some general and genotypic-specific defense responses, in order to obtain a set of candidate genes presumably involved in the resistance.Area of study: The experiment was carried out in León, Spain.Material and methods: We have analyzed the response of three lentil genotypes to Ascochyta lentis (isolate AL 84) at transcriptomic level using the Massive Analysis of cDNA Ends (MACE) technique: the susceptible cultivar 'Lupa', the moderately resistant 'ILL5588' and the resistant wild accession 'BG 16880' (L. culinaris subsp. orientalis).Main results: MACE results yielded a total of 50,935 contigs. The average number of detected contigs in each of the six samples was approximately of 40,000. In response to Ascochyta infection, the jasmonic acid pathway and the lignin biosynthesis were up-regulated in resistant genotypes, while they were down-regulated in the susceptible one. The response to chitin, the salicylic pathway and the auxin response were activated only in the resistant L. c. culinaris genotype, while the giberellin synthesis was only induced in the susceptible L. c. culinaris cv. 'Lupa'. A set of 18 lentil gene sequences putatively involved in the response to the pathogen were validated by RT-qPCR.Research highlights: It can be concluded that in response to the infection by Ascochyta, the lignin biosynthesis and the JA pathway were critical for the resistance, while the giberellin synthesis seems to be related with susceptibility to the pathogen