Experimental characterization of starting jet dynamics

The dynamics of a laminar starting jet are explored in a series of laboratory experiments and numerical simulations. We identify new, objective methods for characterizing the leading vortex ring, enabling robust comparisons with results from a numerical model. Observations of circulation in the initial vortex ring and for the total jet are reported along with strain rate at the leading stagnation point. Growth and pairing of shear instabilities trailing the leading vortex ring is observed. Development of these secondary vortices and their subsequent interactions with the leading vortex has significant effects on the characteristics of the primary vortex ring. Strong fluctuations in strain rate at the leading edge are associated with the pairing of the initial vortex ring with a trailing secondary ringSupport for this research was provided by the Spanish MEC and European Union under Projects # ENE2005-08580-C02-01 and DPI2005-08654-C04-01Publicad

Negatively buoyant starting jets

The initial development of negatively buoyant jets has been investigated experimentally and numerically, focusing on the role played by gravity in the evolution of the leading vortex ring. Under the experimental conditions considered in this work, the densimetric Froude number, Fr= ρjU²j/[(ρ₀ − ρj) gD] , which represents the ratio between the jet momentum and the buoyancy forces, emerges as the most relevant parameter characterizing the dynamics of the flow. Two different flow regimes have been observed depending on the Froude number: for sufficiently small Fr, the vortex ring generated initially is pushed radially away by gravity forces before it has time to detach from the shear layer originating at the orifice. On the other hand, when the Froude number is larger than a critical value, Fr> Frc∼ 1, the vortex ring detaches from the injection orifice and propagates downstream into the stagnant ambient followed by a trailing jet until it eventually reaches a maximum penetration depth. In order to clarify the mechanisms leading to the transition between the two regimes, and to gain physical understanding of the formation dynamics of negatively buoyant starting jets, the total and the vortex circulation, as well as the trajectory of the vortex center, have been measured and compared to the case of neutrally buoyant jets. Finally, based on the experimental measurements and on the results of the numerical computations, a kinematic model that successfully describes the evolution of both total circulation and vortex trajectory is proposed.This work was supported by the Spanish Ministry of Education under Project Nos. DPI2008-06624-C03-02 and ENE2008-0615-C04. This work has been extracted from the Ph.D. thesis of Marugán-CruzPublicad

Seroprevalencia de la toxoplasmosis humana en Córdoba

Se realiza un estudio sobre seroprevalencia de la toxoplasmosis humana en Córdoba, mediante inmunofluorescencia indirecta y hemaglutinación indirecta. La muestra encuestada se compone de 443 sueros, 356 personas supuestamente sanas (estudiantes fundamentalmente) y 87, consideradas de “alto riesgo” (enfermos del Hospital “Reina Sofía”). La positividad obtenida para el total de la muestra ha sido del 43,79 % con IFI y 53,50 % para HAI. Con respecto al sexo, la prevalencia es superior en mujeres con un 54,36 % y 70,47 % con IFI y HAI, respectivamente, en varones el 38,43 % y 44,90 % para las mismas pruebas. En relación con la procedencia de la muestra, 31,lB % con IFI y 43,25 % para HAI sobre la población normal, en la de “alto riesgo” para ambas pruebas el 95,40 %. Entre ambas pruebas hay diferencias significativas a títulos bajos, no así en diluciones altas, Concluimos que la toxoplasmosis humana está presente y difundida en las poblaciones estudiadasA seroprevalency study of human toxoplasmosis was carried out in Córdoba, using indirect immunofluorescence and indirect haemoglutination. The sample of people interviewed was made up of 443 serums, 356 supposedly healthy people (mainly students) and 87, considered “high risk” (pafients from the “Reina Sofia” Hospital). The positiveness obtained for the total of the sample was 43,79 % with IFI and 53,59 % for HAI. As regards sex of the person tested, prevalence is higher in women, with 54,36 % and 70,47 % with IFI and HAI respectively, in men the scores were 38,43 % and 44,90 % for the same tests. As far as the origin of the sample was concerned, there were 31,lB % with IFI and 43,25 % for HAI of the nornal population, in the “high risk” sample, for both tests it was 9540 %. With both tests there are significative differences in low amounts, but not in high dilutions. We conclude that human toxoplasmosis is present and widespread in the studied population

New Physics effects in the flavor-changing neutral couplings of the Top quark

We survey the flavor-changing neutral couplings (FCNC) of the top quark predicted by some extensions of the Standard Model: THDM, SUSY, L-R symmetric, TC2, 331, and models with extra quarks. Since the expected sensitivity of the LHC and ILC for the tcV (V=\gamma,g,Z) and tcH couplings is of order of a few percent, we emphasize the importance of any new physics effect that gives a prediction for these FCNC couplings within this limit. We also review the constraints imposed on these couplings from low-energy precision measurements.Comment: 19 pages, 7 figures. Accepted as a review paper in Int. J. of Mod. Phys.

Mineralogical analysis of the clays of Lower-Middle Miocene transition in Loma Negra section (Bardenas Reales de Navarra, Ebro Basin)

A continuous succession of Lower and Middle Miocene continental sediments, ranging from 20.5 to 15.5 Ma, crops out in the Natural Park of Bardenas Reales de Navarra. The good characteristics of the outcrops has favoured numerous studies in the area in order to reconstruct the palaeoenvironmental conditions between the Ramblian and Aragonian, where the beginning Miocene Climatic Optimum is included. This work presents the first results of mineralogical study in the Loma Negra section, which previously has been subject of palaeontological studies. Total rock analyses show that mineralogy reflects changes previously established from lithologic criteria, suggesting an evolution from a distal alluvial environment to the establishment of a shallow lacustrine environment. The clay mineralogy indicates constant environmental conditions in the series, except for the samples LN-64a and b, with a high value of smectite perhaps representing a semiarid environment characterized by short rainy season compared to dry environment represented by illite and chloriteEn el Parque Natural de Las Bardenas Reales de Navarra aflora una serie casi continua de los sedimentos continentales del Mioceno inferior y medio, abarcando desde 20,5 hasta 15,5 Ma. La buena calidad de los afloramientos ha propiciado que en la zona se hayan realizado numerosos estudios con el fin de reconstruir las condiciones paleoambientales entre el Rambliense y el Aragoniense, en el cual se incluye el comienzo del Óptimo Climático del Mioceno. En este trabajo se presentan los primeros resultados del estudio mineralógico de la sección de Loma Negra, que anteriormente ya ha sido objeto de estudios paleontológicos. Los análisis de roca total muestran que la mineralogía refleja los cambios previamente establecidos a partir de criterios litológicos, que marcan una evolución desde un medio aluvial distal hasta la instauración de un medio lacustre somero. La mineralogía de arcillas indica unas condiciones secas poco cambiantes representadas por la illita y la clorita, con excepción de las muestras LN-64a y b, en los que el alto valor de esmectita pudiera indicar un ambiente semiárido caracterizado por una corta estación de lluvia