An experimental and field-based investigation into decimetre-scale bedforms formed by turbidity currents

Decimetre-scale cross-stratification is relatively rare in turbidites, yet it has been identified in both ancient and modern systems. However, the type of bedform associated with cross-stratification development and the processes involved in its formation remain poorly understood. Similarly, variations in the styles of decimetre-scale cross-stratification occurrence, the sedimentary character of individual turbidite beds and their evolution downstream remain poorly constrained. Consequently, the extent to which the occurrence of decimetre-scale cross stratification may be used as a diagnostic tool to interpret the likely downstream evolution of a system remains uncertain. Three work elements are presented within this thesis. The first describes a series of laboratory experiments that investigate the controls on bedform development under both steady and waning saline density currents. Decimetre-scale bedforms developed within and scaled with a lower denser layer of the current below the height of the velocity maximum, whose dynamics dictated the bedform type. Dunes were distinguished from ripples, downstream migrating antidunes and upstream migrating antidunes on the basis of their out-of-phase relationship with the upper surface of the lower layer of the current. The associated flow regimes were calculated using the bulk Froude number based on the less stratified lower layer of the flow. Using this approach, the new experimental data refine the subcritical bedform phase spaces and antidune phase-spaces of the bedform phase diagram for density currents. The second work element describes a series of experiments that test how beds of non-uniform, bimodally distributed sediment impact bedform development and kinematics, with application to both open channel flows and turbidity currents. Bedform phase diagrams that characterise sediment using the median grain-size, are found to inaccurately predict bedform development from non-uniform sediment beds made up of different grain-size distributions. The new data further refine bedform phase diagrams and improve understanding of the stabilising effect on the substrate of the fine grain-size fraction in sediment mixtures. The final work element characterizes the occurrence of decimeter-scale cross-stratification within the turbidites of the Peïra Cava outlier, of the Tertiary Foreland Basin of SE France. Within the Peïra Cava system a greater level of variability is observed in the cross-stratified bed types than has hitherto been recognised. This facies is interpreted as being formed by dunes, which are confined to the proximal regions. Bed correlations indicate that dunes are not associated with ‘significant bypass’ of sediment to distal locations, as predicted by some existing facies tract models

Relating the Flow Processes and Bedforms of Steady-State and Waning Density Currents

© Copyright© 2020 de Cala, Ohata, Dorrell, Naruse, Patacci, Amy, Simmons, McLelland and McCaffrey. The interaction between turbidity currents and mobile substrates can lead to the development of different types of bedforms. Although much research has been conducted on bedform development beneath open channel flows, research into bedform development beneath waning gravity currents is relatively rare. Analysis of density current-related bedform development has therefore relied upon open channel flow phase diagrams. We report on an experimental study designed to assess the development of bedforms under steady and waning saline density currents. The experimental density currents developed stepped density profiles in which a higher-density basal zone was separated from the ambient fluid by a zone of intermediate density; any bedforms that developed were contained within the bottom layer of the current. Under different conditions ripples, dunes, downstream migrating antidunes and long wavelength antidunes were observed to form and could be distinguished based on their interactions and phase relationships with the upper surface of the lower denser layer of the current. Due to limited mixing between the upper and lower layer of the current and maintenance of current momentum, currents set with slowing discharge flow rates maintained a steady flow velocity in the lower layer of the flow. As a result, sustained bedform formative conditions were achieved within this lower layer, while waning current conditions effected the rest of the flow. Under waning currents, it was seen how pre-existing bed states can determine the subsequent evolution of bedforms. This illustrates the limitations of existing phase diagrams as they do not account for trajectory or rate of passage of flows through different bedform phase spaces. In order to establish a reliable quantitative association between the flow regime and the type of bedform development, it is critical to adopt an appropriate Froude number calculation method for stratified flow. The updated density current phase diagram indicates supercritical flow can be achieved at lower flow velocities than for open channel flows due to the effects of reduced gravity. Bedform depositional structures found in outcrop and on the modern sea floor provide data that helps to interpret the hydrodynamic and sedimentological character of the current that formed them. Therefore, understanding the processes involved in bedform development beneath density currents will enable more accurate estimation of the properties of flows

Música y educación : revista internacional de pedagogía musical

Resumen tomado de la revista. Resumen en InglésEl buen uso de la voz es fundamental para los profesores de cualquier asignatura, pero en el caso de los profesores de música observamos un empleo extra de su voz, pues además de utilizar la voz hablada, necesitan conocer la técnica de la voz cantada, ya que recae en ellos la responsabilidad de cuidar la voz de sus alumnos para evitar que la fuercen, especialmente en una etapa tan comprometida como es la adolescencia.MadridBiblioteca de Educación del Ministerio de Educación, Cultura y Deporte; Calle San Agustín, 5 – 3 Planta; 28014 Madrid; Tel. +34917748000; [email protected]

Density stratification controls the bedform phase diagram of saline‐gravity currents versus open‐channel flows

Sedimentary bedforms such as ripples and dunes are generated both by river flows and sediment-laden gravity currents. Gravity current deposits are usually parameterized using existing bedform phase diagrams which are based on data from laboratory experiments and field observations of open-channel flows. Yet, it is not evident that open-channel flow bedform phase diagrams are applicable to gravity current deposits. Gravity current hydrodynamics are dependent on vertical density variation, i.e. density stratification, and therefore are fundamentally different from open-channel flows. New experiments to produce gravity current deposits are conducted and compared to existing open-channel flow data. It is shown that a parameter phase-space based on the lower layer of stratified gravity currents (i.e. that part below the velocity maximum) significantly improves the prediction of bedform type compared to bedform phase diagrams derived from layer-averaged parameters. These results confirm that bedforms produced by gravity currents can only be accurately predicted using the characteristics of the lower layer of stratified flow

Actividad física, barreras, estrés percibido y consumo de medicamentos de estudiantes de la Escuela Latinoamericana de Medicina

Objetivo: determinar el nivel de actividad física de los estudiantes de la Escuela Latinoamericana de Medicina y de factores a él asociados como barreras, estrés percibido y consumo de medicamentos Materiales y métodos: se empleó una muestra de 97 estudiantes de ambos años de la carrera: 32 (21%) de primero y 65 (42%) de segundo. Se aplicaron, para la revelación de los datos, los cuestionarios: Global de Actividad Física en la determinación del nivel de actividad física; Quiz de las barreras a la actividad física, para determinar las barreras y, la Escala de Estrés percibido en la determinación del estrés percibido por los participantes Resultados: expresan que 72,9 estudiantes de la muestra (75,2%) tienen un bajo nivel de actividad física. El 62,5% consumió medicamentos de manera continua y el 100% de manera discontinua en el último mes. Se percibieron como barreras para las prácticas: falta de tiempo (67%), de voluntad (54%) y de energía (53%). De acuerdo con la escala establecida, percibieron los niveles de estrés: bajo (43,3%), medio (32,9%) y alto, el 23,7% de los alumnos. Conclusiones: La investigación constituye un resultado parcial del proyecto “Andando” que se despliega en la institución para promover la actividad física. Los hallazgos obtenidos pueden contribuir al perfeccionamiento del sistema sanitario de la institución y justifican, en buena medida, los esfuerzos que emanan del proyecto investigativo en que se insertan, en aras de contribuir a perfeccionar el sistema de salud existente en la institució

Proceso de evaluación de pictogramas: Catálogo de señalización accesible andaluz

Everyone needs to rely on elements in their context to move around their own environment with independence. People with permanent or temporary comprehension difficulties need specific support to be able to do so. Pictograms are some of the supports that can render a context cognitively and universally accessible. They are signs which need to be validated using standardized norms such as ISO 9186. This study aimed to increase the number of pictograms available for signposting buildings, and to evaluate their accessibility. Data were collected both via online interviews and self-administered questionnaires, in two phases: assessment of comprehensibility and translucency, and perceptual quality. A total of 1462 participants assessed the pictograms' comprehension and 270 evaluated their perceptual quality. The sample included individuals of different groups and cognitive profiles. One hundred and fifty one pictograms were evaluated and 55 were selected after fulfilling comprehension, translucency, and perceptual quality criteria. The study is a relevant contribution to the database of pictograms available for use in private and public buildings and provides a group of validated signs that can benefit everyone by facilitating cognitive accessibility in spatial environments.Todas las personas necesitan apoyarse en elementos del contexto para desenvolverse por los entornos de manera autónoma. Esta necesidad se concreta en apoyos específicos cuando las personas tienen dificultades en comprensión permanentes o circunstanciales. Para que un contexto sea accesible universal y cognitivamente se emplean pictogramas para identificar los entornos. Estos pictogramas constituyen una señalética que debe ser validada por procesos estandarizados como describe la Normativa ISO-9186. El objetivo del estudio fue ampliar la base de pictogramas disponibles para la señalización de edificios y evaluar su diseño accesible. Los datos se recogieron por entrevista online y por formulario autocompletado online, en dos fases, la evaluación de la comprensibilidad y la translucidez, así como la calidad perceptual de los pictogramas. Un total de 1462 personas evaluaron la comprensión de los pictogramas y 270 su calidad perceptiva. Dicha muestra incluye participantes de diferentes colectivos y perfiles cognitivos. Se evaluaron 151 pictogramas y fueron 55 los seleccionados por cumplir criterios de comprensión, translucidez y calidad perceptiva. Este resultado supone una contribución relevante a las bases de pictogramas de uso público y privado existentes y aporta recursos señaléticos validados que pueden beneficiar a todas las personas facilitando la accesibilidad cognitiva en los espacios

La literatura popular impresa en España y en la América Colonial. Formas y temas, géneros, funciones, difusión, historia y teoría

El libro, publicado bajo la dirección del prof. Pedro M. Cátedra, contiene más de treinta monografías sobre la literatura popular impresa de los siglos XV al XVIII en España y América, con acercamientos muy variados y desde las perspectivas de la historia de la cultura popular, la historia de la imprenta, la aculturación tipográfica, los generos editoriales, etc., etc