Interaction and coalescence of large bubbles rising in a thin gap

We present accurate measurements of the relative motion and deformation of two large bubbles released consecutively in a quiescent liquid confined in a thin-gap cell. Although the second injected bubble was smaller, we observed that, in all cases, it accelerated and caught up with the leading bubble. This acceleration is related to the wake of the leading bubble, which also induces significant changes in the width and curvature of the trailing bubble. On the contrary, the velocity of the leading bubble is unaltered during the whole interaction and coalescence process. Shape adaptation of the two bubbles is observed just prior to coalescence. After pinch-off, the liquid film is drained at a constant velocity

Motion of a single bubble rising in a countercurrent flow in a Hele-Shaw cell

We investigate experimentally the motion of isolated bubbles rising in a vertical Hele-Shaw cell in the presence of a downward flow. The bubbles are strongly flattened in the plane of the cell, their equivalent diameter d being large compared to the gap of the cell e . Furthermore, their dynamics is strongly influenced by the confinement which imposes thin liquid films between the bubble and the walls and strongly attenuates the flow perturbation in the liquid due to wall friction

UNQ: CAMBIOS , REFORMAS Y AUTOEVAOUACIÓN EN UNA UNIVERSIDAD EMPRENDEDORA

La Universidad Nacional de Quilmes fue creada por Ley del Congreso Nacional en setiembre de 1989 ; abrió sus puertas en el ciclo lectivo 1991, y en Diciembre de 1992 fue Normalizada constituyéndose su primer gobierno autonómo. La Universidad forma parte de un grupo de Nuevas Universidaddes creadas a entre fines de la decada del 80 y mediados del noventa en el Conurbano Bonaerense. La Universidad es una institución concebida como un conjunto interdisciplinario para el fomento y el ejercicio del conocimiento, de la investigación y la búsqueda artística, para la formación del ejercicio profesional y para dar respuestas a la demandas sociales promoviendo el desarrollo de los diferentes actores sociales . La UNQ fue concebida como una universidad flexible , emprendedora no solo por la oferta académica, sino porque gestiona de una forma innovadora, promoviendo logros que hablan del proyecto de una institución de excelencia. A contnuación analizaremos los cambios y las reformas que dan cuenta del crecimiento de nuestra universidad en donde el modelo de gestión estratégica promueve la capacidad de adaptación al entorno rápidamente cambiante y competitivo: 1992 Normalización de la Universidad Nacional de Quilmes 1996 Reforma Salarial Docente 1997 Reforma Académica 1998 Reforma de Gobierno 1999 Creación de la Universidad Virtual 1999 Reforma Administrativa 2001. Inicio del Proceso de Autoevaluación. Todos estos cambios forman parte de un continum en donde la planificación , el diagnóstico y la evaluacion garantizan un nivel satisfactorio de calidad en los procesos docentes, de investigación y de gestión. El proceso de autoevaluación institucional nos permitirá acreditar nuestra institución en un escenario de competitividad interinstitucional y de recursos que trasciende los limites de lo regional

Candida albicans UBI3 and UBI4 promoter regions confer differential regulation of invertase production to Saccharomyces cerevisiae cells in response to stress

Candida albicans ubiquitin genes UBI3 and UBI4 encode a ubiquitin-hybrid protein involved in ribosome biogenesis and polyubiquitin, respectively. In this work we show that UBI3 and UBI4 promoter regions confer differentialexpr ession consistent with the function of their encoded gene products. Hybrid genes were constructed containing the SUC2 coding region under the controlof UBI3 or UBI4 promoters in the yeast vector pLC7. Invertase production in Saccharomyces cerevisiae transformants was differentially regulated: the UBI4 promoter was induced by stress conditions (thermalupshift and/or starvation) whereas the UBI3 promoter conferred constitutive invertase production in growing yeast cells. These results indicate that the UBI4 promoter is regulated by stress-response signaling pathways, whereas the UBI3 promoter is controlled according to the requirement for protein synthesis to support cell growth.Gozalbo Flor, Daniel, [email protected]

Estudio de la inteligencia emocional en alumnos de enseñanza secundaria: influencia del sexo y del nivel educativo de los estudiantes y su relación con el rendimiento académico

Los objetivos de este estudio fueron analizar la inteligencia emocional entre alumnos de secundaria y la influencia del sexo, nivel educativo y rendimiento académico. La muestra fue de 151 alumnos. Se utilizó el EQ-i: YV y el promedio de calificaciones. Los resultados indicaron una fuerte relación entre inteligencia emocional y rendimiento académico, y diferencias significativas en función del sexo y nivel educativo.The main purposes of this study were to analyze the emotional intelligence among students of secondary school, and the influence of gender, academic level and academic performance. 151 students were involved in the sample. We used the EQ-i YV and their average grades. Results indicate a strong relationship between emotional intelligence and academic achievement, and significant differences concerning gender and academic level

Oscillatory motion and wake of a bubble rising in a thin-gap cell

We investigate the characteristics of the oscillatory motion and wake of confined bubbles freely rising in a thin-gap cell (h=3.1 mm width). Once the diameter d of the bubble in the plane of the cell is known, the mean vertical velocity of the bubble Vb is proportional to the gravitational velocity [...], where g is the gravitational acceleration. This velocity is used to build the Reynolds number [...] that characterizes the flow induced by the bubble in the surrounding liquid (of kinematic viscosity ν), and which determines at leading order the mean deformation of the bubble given by the aspect ratio χ of the ellipse equivalent to the bubble contour. We then show that in the reference frame associated with the bubble (having a fixed origin and axes corresponding to the minor and major axes of the equivalent ellipse) the characteristics of its oscillatory motion in the plane of the cell display remarkable properties in the range 1200<Re<3000 and h/d<0.4. In particular, the velocity of the bubble presents along its path an almost constant component along its minor axis (fluctuations in time of approximately 5 %), given by Va/Vb≃0.92 for all Re. The dimensionless amplitude of oscillation of the angular velocity is also constant for all Re, rd/Vb≃0.75, while that of the transverse velocity of the bubble (along its major axis) is given by Vt/Vb≃0.32χ, reaching values comparable to those of the axial velocity Va for the most deformed bubbles (χ≈3). Furthermore, the frequency f of oscillation scales with the inertial time scale based on the transverse velocity of the bubble Vt, corresponding to a constant Strouhal number St=[...]. Using high-frequency particle image velocimetry, we investigate in detail the properties of the wake associated with the oscillatory motion of sufficiently confined bubbles. We observe that vortex shedding occurs for a maximal transverse velocity Vt of the bubble, corresponding to a maximal drift angle of the bubble. Furthermore, the measured vorticity of the vortex at detachment corresponds to the estimation [...] of the vorticity produced at the bubble surface. Three stages then emerge concerning the evolution in time of the wake generated by the bubble. For one to two periods of oscillation Tx following the release of a vortex, a rapid decay of the vorticity of the released vortex is observed. Meanwhile, the released vortex located initially at a distance of approximately one diameter from the bubble centre moves outwards from the bubble path and expands. At intermediate times, the vortex street undergoes vortex pairing. When viscous effects become predominant at a time of the order of the viscous time scale τν=[...], the vortex street becomes frozen and decays exponentially in place

Trust-Based Community Assessment

In this paper we present Community Assessment (COMAS), a trust-based assessment service that helps compute group opinion from the perspective of a specific community member. We apply COMAS in the context of communities of learners, and we compute the group opinion from the perspective of the teacher. Specifically, our model relies on \emph{teacher assessments}, aggregations of \emph{student assessments} and \emph{trust measures} derived from student assessments to suggest marks to assignments that have not been assessed by the teacher. The proposed model intends to support intelligent online learning applications by 1) encouraging students to assess one another, and 2) benefiting from students' assessments. We believe the task of assessing massive numbers of students is of special interest to online learning communities, such as Massive Open Online Courses (MOOCs). Experimental results were conducted on a real classroom datasets as well as simulated data that considers different social network topologies (where we say students assess some assignments of socially connected students). Results show that our method 1) is sound, i.e. the error of the suggested assessments decreases for increasing numbers of teacher assessments; and 2) scales for large numbers of students. 2015 Elsevier Ltd. All rights reservedThis work is supported by the CollectiveMind project (Spanish Ministry of Economy and Competitiveness, under grant number TEC2013-49430-EXP), the MILESS project (Spanish Ministry of Economy and Competitiveness, under grant num- ber TIN2013-45039-P) and the PRAISE project (funded by the European Commission, under grant number 388770)Peer reviewe

Interaction of two oscillating bubbles rising in a thin gap

We investigate experimentally different mechanisms of hydrodynamic interaction between two oscillating bubbles rising in a liquid at rest confined in a thin gap cell. In order to understand the relation between the motion of a single bubble and its wake as well as the hydrodynamic interaction between two oscillating bubbles, we characterize the kinematics of the bubbles interaction using high speed cameras and we measure the associated liquid velocity by High-Frequency PIV. The motion of the trailing bubble is modified while passing through the unstable wake of the leading bubble: depending on the relative size of the bubbles and their relative position, we can observe horizontal attraction to the center of the leading bubble's wake, vertical entrainment, ejection of the second bubble by a vortex of the wake or a sequential combination of the three mechanisms

Identification of the best-performing novel microbial strains from naturally-aged graffiti for biocleaning research

Microorganisms that can act as biocleaning agents can potentially be isolated from existing graffiti. In this study, a total of 30 different isolates of bacteria, fungi and yeasts were obtained from black, blue, red and silver graffiti coatings exposed outdoors conditions for 10 years. An additional strain was obtained from samples of black powdered graffiti exposed under laboratory conditions for 5 years. Each of the isolates from the most prolific sources (i.e. red and silver graffiti coatings and black powdered graffiti) was evaluated alone and in combination with Tween® 20, to determine their potential as biocleaning agents, in test tube assays. Two strains isolated from the red graffiti coating (identified as "Candida parapsilosis") and one strain isolated from the black powered graffiti (identified as "Rhodococcus erythropolis") performed best alone. The quantity of live cells throughout the trials and biofilm formation indicated that both strains were able to utilize the paint as a substrate. When the microorganisms isolated were combined with Tween® 20, the quantity of live cells increased notably throughout the incubation time, and turbidity and graffiti discoloration were observed. Infrared spectroscopic examination revealed that "R. erythropolis" performed the best alone, while the addition of Tween® 20 to "C. parapsilosis" enhanced the oxidative degradation of the graffiti.Financiado para publicación en acceso aberto: Universidade de Vigo/CISUGMinisterio de Economía, Industria y Competitividad | Ref. IJCI-2017-3277Xunta de Galicia | Ref. ED431C 2018/3