Inertial waves in rapidly rotating flows: a dynamical systems perspective

An overview of recent developments in a wide variety of enclosed rapidly rotating flows is presented. Highlighted is the interplay between inertial waves, which have been predicted from linear inviscid considerations, and the viscous boundary layer dynamics which result from instabilities as the nonlinearities in the systems are increased. Further, even in the absence of boundary layer instabilities, nonlinearity in the system often leads to complicated interior flows due to subcritical instabilities, Eckhaus bands and heteroclinic dynamics. The ensuing spatio-temporally complex dynamics is analysed in terms of equivariant dynamical systems, providing a general perspective for the wide range of dynamics involved.Postprint (author's final draft

Small aspect ratio Taylor-Couette flow: onset of a very-low-frequency three-torus state

The nonlinear dynamics of Taylor-Couette flow in a small aspect ratio annulus (where the length of the cylinders is half of the annular gap between them) is investigated by numerically solving the full three-dimensional Navier-Stokes equations. The system is invariant to arbitrary rotations about the annulus axis and to a reflection about the annulus half-height, so that the symmetry group is SO(2)×Z2. In this paper, we systematically investigate primary and subsequent bifurcations of the basic state, concentrating on a parameter regime where the basic state becomes unstable via Hopf bifurcations. We derive the four distinct cases for the symmetries of the bifurcated orbit, and numerically find two of these. In the parameter regime considered, we also locate the codimension-two double Hopf bifurcation where these two Hopf bifurcations coincide. Secondary Hopf bifurcations (Neimark-Sacker bifurcations), leading to modulated rotating waves, are subsequently found and a saddle-node-infinite-period bifurcation between a stable (node) and an unstable (saddle) modulated rotating wave is located, which gives rise to a very-low-frequency three-torus. This paper provides the computed example of such a state, along with a comprehensive bifurcation sequence leading to its onset.Postprint (published version

The influence of gender and social roles on academic achievement

The analysis of the influence of certain social aspects across countries on gender differences in educational achievement has gained a great relevance. In this research the main objective is to deepen into the knowledge of these cultural factors. In order to accomplish this aim, international data from many countries has been used, grouped into education system characteristics, child qualities supported socially, views and opinions on gender roles, and risk-aversion attitudes. The empirical analysis carried out has shown that it is necessary to foster entrepreneurship attitudes during students’ tertiary education, with special emphasis on girls, as they are more affected by gender stereotypes and risk-aversion in comparison to boys. In spite of the existence of unexplained gender differences, individual and country-level factors may have a different effect on the academic achievement of boys and girls.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Organocatalysis in total synthesis

Peer Reviewe

Unbridled Imaginations: The Ethical Power of Creativity in Michael Chabon's The Amazing Adventures of Kavalier and Clay

Este trabajo de fin de grado se propone examinar la novela de Michael Chabon Las Asombrosas Aventuras de Kavalier y Clay en su relación con la tendencia, dentro de la narrativa estadounidense judía, a replantearse las ideas de tradición e identidad como respuesta al trágico período histórico que alcanzó su punto de inflexión tras el Holocausto. En este contexto, el autor contempla una intersección entre la reflexión sobre la propia escritura, propia del postmodernismo, y las posibilidades éticas de la narrativa. Teniendo en cuenta todas estas cuestiones, el objetivo de esta disertación es argumentar la posición de la novela con respecto al papel que juega la narrativa en la articulación del discurso de la alteridad. Con este fin, el trabajo se centra en analizar el uso de estrategias metaficcionales, así como el efecto que ejerce la lectura y la escritura sobre el plano ontológico de los protagonistas

Rapidly rotating cylinder flow with an oscillating sidewall

We present numerical simulations of a flow in a rapidly rotating cylinder subjected to a time-periodic forcing via axial oscillations of the sidewall. When the axial oscillation frequency is less than twice the rotation frequency, inertial waves in the form of shear layers are present. For very fast rotations, these waves approach the form of the characteristics predicted from the linearized inviscid problem first studied by Lord Kelvin. The driving mechanism for the inertial waves is the oscillating Stokes layer on the sidewall and the corner discontinuities where the sidewall meets the top and bottom end walls. A detailed numerical and theoretical analysis of the internal shear layers is presented. The system is physically realizable, and attractive because of the robustness of the Stokes layer that drives the inertial waves but beyond that does not interfere with them. We show that the system loses stability to complicated three-dimensional flow when the sidewall oscillation displacement amplitude is very large (of the order of the cylinder radius), but this is far removed from the displacement amplitudes of interest, and there is a large range of governing parameters which are physically realizable in experiments in which the inertial waves are robust. This is in contrast to many other physical realizations of inertial waves where the driving mechanisms tend to lead to instabilities and complicate the study of the waves. We have computed the response diagram of the system for a large range of forcing frequencies and compared the results with inviscid eigenmodes and ray tracing techniques.Postprint (published version

Stratified Taylor-Couette flow: nonlinear dynamics

A series of experiments on stratified Taylor–Couette flow in short aspect ratio wide-gap annuli found an intriguing and not-well-understood dynamics: nonlinear coherent structures appearing and disappearing periodically, along with density layering reminiscent of staircase profiles. A detailed numerical study is presented of the nonlinear dynamics near onset of instability in this setting, which explains most of the characteristics found in the experiments. The simulations show that centrifugal instability of the boundary layer on the inner rotating cylinder produces jets of angular momentum forming Taylor cells that are compressed axially due to the strong stratification. These cells are not axisymmetric from the onset, but are in fact two sets of Taylor cells displaced axially that meet in localized azimuthal defect regions where the cells are patched together; the whole structure is a rotating wave with azimuthal wavenumber m=1. The presence of endwalls in this short aspect ratio annulus is critical for the understanding of the dynamics. Their impact cannot be accounted for in idealized axially periodic models. Another key ingredient is the role played by the symmetries of the system. Although the axial reflection symmetry is weakly broken by centrifugal buoyancy effects, following instability there are various branches of solutions corresponding to the different ways the system's symmetries may be broken.Postprint (published version

"Notes from the Cracks: Histories, Trauma and the Ethics of Fiction in Michael Chabon’s Moonglow"

Este trabajo de fin de máster se propone analizar novela Moonglow, de Michael Chabon, como representativa del paso de la actitud escéptica tan poco constructiva de la cultura postmodernista a una motivación ética por la figura del Otro. Dicha transición tuvo lugar en las últimas décadas del siglo XX en el campo de la filosofía y la cultura. El énfasis que hace postmodernismo en la imposibilidad de separar la realidad de sus representaciones trajo consigo el cuestionamiento de las narrativas dominantes que gobiernan la sociedad y la identidad, de este modo favoreciendo las historias de aquellos individuos marginados por la Historia. Sin embargo, esta práctica culminó en un punto de no retorno, sin poder ofrecer una solución ética para el conflicto global por el poder de representarse a uno mismo y al otro. Aunque consciente de la dificultad de erradicar por completo las jerarquías impuestas por las grandes narrativas, la novela de Chabon expresa una esperanza en el carácter reconciliador de la narrativa y de la imaginación, en la manera en que transmite emociones comunes a la experiencia humana. El uso frecuente de juegos metaficcionales, así como formas y motivos propios de la ficción de género, por parte de Chabon, sirve a su narrador homodiegético, llamado igual que el autor, en la reconstrucción de la vida de su abuelo a partir de las historias que este último le contó antes de morir. El narrador transforma dicha colección de recuerdos en una historia en la que la verdad emerge desde múltiples voces, en respuesta al marco dominante de la Historia. La primera parte de mi disertación se centra en los mecanismos metaficcionales empleados en la novela y en el estilo fabulístico de la narración a fin de sentar las bases de la siguiente argumentación en la presencia del elemento ficcional en la manera en la que los seres humanos recuerdan, interpretan y representan el pasado. No obstante, esta percepción posestructuralista se pone en duda a la hora de abordar hechos trágicos. Es en estos casos donde la transparencia, la coherencia y la verosimilitud se imponen como las reglas básicas para una narración ética. En la segunda sección, hago una introducción a la dimensión socio-cultural de los estudios de trauma para examinar las diferentes formas en las que los personajes se aproximan al pasado, o bien al de sus antepasados. Argumento que algunas respuestas al trauma, alternativas a la forma testimonial que se impone como norma, pueden desafiar las estructuras sociales dentro de las que el trauma se transmite, de esta forma revelando casos de desigualdad que privilegian una perspectiva sobre otra. De acuerdo con ese planteamiento, en la última sección exploro las zonas de conflicto entre las narrativas hegemónicas y contra-hegemónicas. La novela interroga el mito nacionalista de la Frontera americana en el contexto de la “carrera espacial”, motivada por la búsqueda de la hegemonía mundial durante la guerra fría. Chabon critica esta narrativa mediante la caracterización del protagonista como una parodia del nuevo héroe de la Frontera y su revelación sobre el papel del científico nazi Wernher von Braun en la misión espacial. Desde esta perspectiva, la figura de la luna se presenta como una Frontera que divide. Sin embargo, la novela finalmente propone una visión del la luna como un borde simbólico que separa, y finalmente reúne a las personas más allá de diferencias nacionales, culturales y sexuales

Synthesis of interesting β-nitrohydrazides through a thiourea organocatalysed aza-Michael addition

The synthesis of antimicrobial β-nitrohydrazides, as the target product of our reaction, is reached for the first time under organocatalytic enantioselective conditions. We accomplish this goal by using a thiourea organocatalysed aza-Michael addition reaction of hydrazide to nitroalkenes, furnishing final products with good yields and good enantiomeric ratios. The developed methodology is one of the rare examples of catalytic reactivity using hydrazide where the reaction proceeds through its N2 atom. Our developed strategy extends the generality of this area of research due to the difficulties of designing new nitrogen nucleophiles with high activity, and in addition, this is one of the scarce examples where nitroalkenes and chiral thioureas have been used in asymmetric organocatalytic aza-Michael addition reactions. © 2014 The Royal Society of Chemistry.We thank the Spanish Ministry of Economía y Competitividad (MICINN. Madrid. Spain. Project CTQ2010-19606) and the Government of Aragón (Zaragoza. Spain. Research Group E-10) for financial support of our research.Peer Reviewe

Horizons in Asymmetric Organocatalysis: En Route to the Sustainability and New Applications

Nowadays, the development of new enantioselective processes is highly relevant in chemistry due to the relevance of chiral compounds in biomedicine (mainly drugs) and in other fields, such as agrochemistry, animal feed, and flavorings. Among them, organocatalytic methods have become an efficient and sustainable alternative since List and MacMillan pioneering contributions were published in 2000. These works established the term asymmetric organocatalysis to label this area of research, which has grown exponentially over the last two decades. Since then, the scientific community has attended to the discovery of a plethora of organic reactions and transformations carried out with excellent results in terms of both reactivity and enantioselectivity. Looking back to earlier times, we can find in the literature a few examples where small organic molecules and some natural products could act as effective catalysts. However, with the birth of this type of catalysis, new chemical architectures based on amines, thioureas, squaramides, cinchona alkaloids, quaternary ammonium salts, carbenes, guanidines and phosphoric acids, among many others, have been devel-oped. These organocatalysts have provided a broad range of activation modes that allow privileged interactions between catalysts and substrates for the preparation of compounds with high added value in an enantioselective way. Here, we briefly cover the history of this chemistry, from our point of view, including our beginnings, how the field has evolved during these years of research, and the road ahead. © 2022 by the authors. Licensee MDPI, Basel, Switzerland