Stability of Liquid Bridges between Unequal Disks under Zero-Gravity Conditions

The stability, of axisymmetric equilibrium shapes of a liquid bridge between two coaxial disks of different radii under zero-gravity conditions is investigated. The stability regions have been evaluated for different values of the ratio of the disk radii in terms of the dimensionless parameters which characterize the length and the volume of the bridge. It has been found that disk radii unequality radically changes the upper boundary of the stability region. The analysis of the shape of marginally stable equilibrium surfaces has been carried out. Relationships between the critical values of the parameters have been deduced for some particular cases, which are of special interest for the materials purification processes and growing of single crystals by the floating zone method: for typical values of the growing angle for semiconductor materials and for liquid volumes close to that of the cylinder having a radius equal to the mean radius of the disk

The CreC regulator of Escherichia coli, a new target for metabolic manipulations

The CreBC (carbon source-responsive) two-component regulation system of Escherichia coli affects a number of functions, including intermediary carbon catabolism. The impacts of different creC mutations (a ΔcreC mutant and a mutant carrying the constitutive creC510 allele) on bacterial physiology were analyzed in glucose cultures under three oxygen availability conditions. Differences in the amounts of extracellular metabolites produced were observed in the null mutant compared to the wild-type strain and the mutant carrying creC510 and shown to be affected by oxygen availability. The ΔcreC strain secreted more formate, succinate, and acetate but less lactate under low aeration. These metabolic changes were associated with differences in AckA and LdhA activities, both of which were affected by CreC. Measurement of the NAD(P)H/NAD(P)+ ratios showed that the creC510 strain had a more reduced intracellular redox state, while the opposite was observed for the ΔcreC mutant, particularly under intermediate oxygen availability conditions, indicating that CreC affects redox balance. The null mutant formed more succinate than the wild-type strain under both low aeration and no aeration. Overexpression of the genes encoding phosphoenolpyruvate carboxylase from E. coli and a NADH-forming formate dehydrogenase from Candida boidinii in the ΔcreC mutant further increased the yield of succinate on glucose. Interestingly, the elimination of ackA and adhE did not significantly improve the production of succinate. The diverse metabolic effects of this regulator on the central biochemical network of E. coli make it a good candidate for metabolic-engineering manipulations to enhance the formation of bioproducts, such as succinate.Fil: Godoy, Manuel Santiago. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales; ArgentinaFil: Nikel, Pablo Ivan. Consejo Superior de Investigaciones Científicas; EspañaFil: Cabrera Gomez, José Gregorio. Unviversidad de San Pablo; BrasilFil: Pettinari, María Julia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales; Argentin

La sensibilité interculturelle chez des étudiantes et étudiants universitaires de premier cycle en administration des affaires: description des facteurs liés à son développement

Les gestionnaires de l’environnement mondialisé d'aujourd'hui doivent travailler avec des pairs dont les valeurs, normes et perceptions sont diverses. De plus en plus de tâches sont exécutées en équipes qui rassemblent des participantes et participants de diverses origines ethnoculturelles, se situant, ou non, dans le même lieu physique. Cela signifie qu’il est primordial de recruter des individus possédant les compétences pour réussir dans cet environnement. En interrogeant des dirigeants de compagnies internationales de Fortune 500 et des gestionnaires nord-américains , il appert qu'en dehors des compétences de gestion traditionnellement exigées des femmes et des hommes d'affaires, comme la capacité de prendre des décisions, le travail d'équipe, la vision stratégique, la vision globale et la capacité de construire des réseaux de contacts, les entreprises devraient recruter des personnes qui possèdent des compétences essentielles. Ces habiletés, qui permettent aux hommes d’affaires de mieux comprendre les cultures d’ailleurs et d’interagir de manière effective avec leurs collègues à l’étranger (Jyoti et Kour, 2015), ont été désignées de manières diverses, mais pour le propos de cette thèse, elles seront définies comme la sensibilité interculturelle et la compétence interculturelle. Comme nous l’expliciterons plus avant, nous adopterons, pour la définition de ces construits, le paradigme développemental. En effet, le paradigme développemental considère la sensibilité interculturelle non pas comme un facteur faisant partie intégrante de la compétence interculturelle, mais comme un prédicteur de la compétence interculturelle. Les résultats obtenus suggèrent des relations significatives entre plusieurs des facteurs considérés et d’une part, le développement de la sensibilité interculturelle, et d’autre part, la perception des conditions de contact dans l’échantillon de recherche

Mechanical Imperfections Effect on the Minimum Stability Limit of Liquid Bridges

The bifurcation to unstable equilibrium shapes in the neighborhood of the minimum volume stability limit of liquid bridges has been described by using the Lyapunov–Schmidt technique. Prior to the bifurcation analysis, the stability limits of axisymmetric liquid bridges (both that of maximum and that of minimum volume) have been analytically calculated when the liquid bridge supports are two circular, coaxial disks. The interface shapes have been parametrically described and the parameters corresponding to the marginally stable shapes have been determined in terms of elliptic variables. Bifurcation equations have been obtained analytically describing the behavior near the critical points previously calculated and the effect of small axisymmetric imperfections has been considered. The considered imperfections are inequality in the diameter of the supporting disks, small body forces due to an axial gravity, and liquid bridge rotation as a solid bod

On the Stability Limit Change due to Imperfections

The minimum volume stability limit of axisymmetric liquid bridges has been obtained in the past for zero Bond number, no solid body rotation and equal disks. When gravity, rotation or different disk diameters are considered, only a few numerical results are available and the singular case of small values of these parameters have been only partly considered. An analytical study using the Lyapunov-Schmidt method considering small values of gravity, disk diameter ratio and rotation rate is presented and the variation of the stability limit determined

Effects of Axial and Centrifugal Forces on the Stability of Liquid Bridges

The equilibrium and stability equations for liquid bridges are well known, but they are nonlinear and it is difficult to guess real behavior, such as the sensitivity of the shape to axial and rotational forces (measured by Bond and Weber numbers, respectively) or to the geometry of the solid supports that support the bridge. A parametric study by numerical methods of the different effects and the analytical solutions at the bifurcation points in the stability diagrams is presented. The well known shooting method to numerically compute equilibrium shapes of liquid bridges, and their stability limits, is applied to a five parameter case, when different disc sizes (measured by H), bridge lengths (Lr), liquid volumes (Vr), residual axial acceleration (Bo), and solid body centrifugation (We) are contemplated. The bundle of diagrams presented give an idea of the complexities of such a multiparametric analysis and may help in further research to delimitate other forms of instability. The numerical results were used to check the validity of several analytical asymptotic expressions, with perfect agreement over the range of interest (long liquid bridges), but these models only take into consideration the subset (Lr, Vr = 1, H = 0, Bo, We) of the five parameter family. These results will be of great help to plan future space experiments on liquid columns and floating zones in space and in particular will show a method to easily measure very weak residual forces in microgravity platforms

Notícias da Actividade Cultural. III Seminário de Arqueologia do Noroeste Peninsular. Ante aspectos economicos del Noroeste hispanico el la protohistoria y antiguedade.

95 Jan.-Dez. 1985, p. 213-224

Los Verdaderos artífices del arte rupestre animalístico del Levante español.

80 (3-4) Jul.-Dez. 1970, p. 263-318

La Funcion ternaria en el sacrificio celtiberico. Concepciones místicas indo-europeas en la España prerromana.

76 (1-2) Jan.-Jun. 1966, p. 85-108

A Systematic Literature Review of Digital Game-based Assessment Empirical Studies: Current Trends and Open Challenges

Technology has become an essential part of our everyday life, and its use in educational environments keeps growing. In addition, games are one of the most popular activities across cultures and ages, and there is ample evidence that supports the benefits of using games for assessment. This field is commonly known as game-based assessment (GBA), which refers to the use of games to assess learners' competencies, skills, or knowledge. This paper analyzes the current status of the GBA field by performing the first systematic literature review on empirical GBA studies, based on 66 research papers that used digital GBAs to determine: (1) the context where the study has been applied, (2) the primary purpose, (3) the knowledge domain of the game used, (4) game/tool availability, (5) the size of the data sample, (6) the data science techniques and algorithms applied, (7) the targeted stakeholders of the study, and (8) what limitations and challenges are reported by authors. Based on the categories established and our analysis, the findings suggest that GBAs are mainly used in formal education and for assessment purposes, and most GBAs focus on assessing STEM content and cognitive skills. Furthermore, the current limitations indicate that future GBA research would benefit from the use of bigger data samples and more specialized algorithms. Based on our results, we discuss the status of the field with the current trends and the open challenges (including replication and validation problems) providing recommendations for the future research agenda of the GBA field.Comment: 23 pages, 12 figures, 1 tabl