Velocidad terminal de una esfera descendente y la viscosidad de fluidos: diferencia entre fluidos newtonianos y no newtonianos

An alternative method to calculate the terminal velocity of a descending sphere on a viscous media is presented in this work. From a digital video filmed of the sphere's movement inside the fluid, which is processed with DivYX software for obtaining the position and time, it is possible to get the pathline of the sphere inside the media as well as the exact moment in which the terminal velocity is reached. Fluid's viscosity can be determined with the value of the terminal velocity and making a force balance on the sphere. A didactic alternative is presented with this method in order to help students understand the difference betwen Newtonian and Non-Newtonian fluids.En este trabajo se presenta un método alternativo para determinar la velocidad límite, o terminal, de una esfera que desciende dentro de un fluido. Este método consiste en capturar en video el movimiento de la esfera dentro del fluido. El video digital se procesa con el software DivYX que permite obtener el tiempo y posición de la esfera en el medio. A partir del análisis de estas cantidades, es posible determinar la trayectoria de la esfera en el medio y el momento en que ésta alcanza la velocidad límite. Conociendo el valor de la velocidad terminal y haciendo un balance de las fuerzas que actúan sobre la esfera, se puede determinar la viscosidad del fluido. Asimismo, con este método se presenta una alternativa didáctica que ayude a los estudiantes a diferenciar entre fluidos newtonianos y los no newtonianos

Determinación de la viscosidad de fluidos newtonianos y no newtonianos (una revisión del viscosímetro de Couette)

Newtonian viscosity is studied in the theoretical and laboratory courses of physics of fluids in natural sciences and engineering. Because of the increasing use of Non-Newtonian fluids is necessary to include them in these courses. To driving experiences that enable to the students to distinguish between Newtonian and non-Newtonian fluids will allow to improve their knowledge about fluids. The purpose of this work is to give a didactic tool to differentiate between Newtonian and Non-Newtonian fluids by using their flow curves. In addition, the details of a concentric cylinders viscometer (Couette Viscometer) construction of low cost are shown, the which one can be manufactured by the students. Finally, the characterization of two commercial fluids is included.En los cursos elementales de física de fluidos, teóricos y de laboratorio, a nivel licenciatura e ingeniería, se estudia el tema de viscosidad haciendo referencia únicamente a los fluidos newtonianos. Sin embargo, el creciente empleo de fluidos no newtonianos, obliga a incluir el estudio de este tipo de fluidos. Por lo que conducir experiencias que permitan al estudiante distinguir entre los fluidos newtonianos y no newtonianos ampliará su conocimiento general en este tema. El objetivo de este trabajo es dar una herramienta didáctica para diferenciar entre fluidos newtonianos y no newtonianos a partir de las curvas de flujo. Además, se presentan detalles para la construcción de un viscosímetro de cilindros concéntricos (de Couette) de bajo costo, el cual puede ser fabricado por los mismos estudiantes. Finalmente, se muestran los resultados de la caracterización viscosa de dos fluidos comerciales usando el viscosímetro construido

Diseño y construcción de una máquina de torsión de bajo costo para la determinación del módulo de corte

A subject that is theoretically studied in introductory Physics courses is one that analyzes the torsion of a metal bar, from which it is possible to understand the concept of the torsion or shear modulus. However, carrying out the experiment using commercial machinery is very expensive, since it can cost several thousand dollars. In this work, we present the design and construction of a static torsion machine where an angular measurement system was implemented using a signal conditioning mechanism for digital reading of the voltage and a multi-turn linear potentiometer, which allows increasing the resolution in the torsion angle measurement. The verification of the operation of the built design was carried out for a set of four bars of different metals, the results show a difference of less than 5% with respect to values reported in the literature. This static torsion prototype is proposed to be manufactured by students allowing the development of their experimental skills.Un tema que se estudia teóricamente en los cursos introductorios de Física es aquel que analiza la torsión de una barra metálica, a partir de la cual es posible entender el concepto del módulo de torsión o de corte. No obstante, realizar el experimento empleando maquinaria comercial resulta muy caro, ya que ésta puede alcanzar un costo de varios miles de dólares. En este trabajo, se presenta el diseño y construcción de una máquina de torsión estática en donde se implementó un sistema de medición angular usando un mecanismo acondicionador de señal para lectura digital del voltaje y un potenciómetro lineal multivueltas, lo que permite aumentar la resolución en la medición del ángulo de torsión. La verificación del funcionamiento del diseño construido se realizó para un conjunto de cuatro varillas de distintos metales, los resultados muestran una diferencia menor al 5% con respecto a valores reportados en la literatura. Este prototipo de torsión estática se propone para ser fabricado por estudiantes permitiendo el desarrollo de sus habilidades experimentales

Overview of recent TJ-II stellarator results

The main results obtained in the TJ-II stellarator in the last two years are reported. The most important topics investigated have been modelling and validation of impurity transport, validation of gyrokinetic simulations, turbulence characterisation, effect of magnetic configuration on transport, fuelling with pellet injection, fast particles and liquid metal plasma facing components. As regards impurity transport research, a number of working lines exploring several recently discovered effects have been developed: the effect of tangential drifts on stellarator neoclassical transport, the impurity flux driven by electric fields tangent to magnetic surfaces and attempts of experimental validation with Doppler reflectometry of the variation of the radial electric field on the flux surface. Concerning gyrokinetic simulations, two validation activities have been performed, the comparison with measurements of zonal flow relaxation in pellet-induced fast transients and the comparison with experimental poloidal variation of fluctuations amplitude. The impact of radial electric fields on turbulence spreading in the edge and scrape-off layer has been also experimentally characterized using a 2D Langmuir probe array. Another remarkable piece of work has been the investigation of the radial propagation of small temperature perturbations using transfer entropy. Research on the physics and modelling of plasma core fuelling with pellet and tracer-encapsulated solid-pellet injection has produced also relevant results. Neutral beam injection driven Alfvénic activity and its possible control by electron cyclotron current drive has been examined as well in TJ-II. Finally, recent results on alternative plasma facing components based on liquid metals are also presented.ISSN:0029-5515ISSN:1741-432

[Correspondencia de Camilo Díaz Baliño] , 1917-1936

Mss. (algúns en fotocopia) autógrafo e mecanografiadoResumen: Correspondencia recibida por Camilo Díaz Baliño entre os anos 1917-1936 relacionada con asuntos persoais e laboraisBiblioteca de GaliciaForma de ingreso: Depósito. Fuente de ingreso: Díaz Pardo, Isaac. Fecha de ingreso: 2011. Propietario: Herdeiros de Isaac Díaz PardoDixitalización Telefónica-IDP 2012Contén : Cartas de: Manuel Abelenda (1 páx.) -- Cesar Alvarez (1 páx.) -- Carlos Amigo Collía (2 páxs.) -- Banco Hispano-Americano (2 páxs.) -- Alfonso Barreiro (3 páxs.) -- Eliseo Barros Gamallo (1 páx.),(2 páxs.) -- Ramón Beade (2 páxs.) -- Benito(2 páxs.) -- Fernando Blanco(1 páx.) -- José Bouzas y Cardama (1 páx.) -- Albino Bouzó Fernández (1 páx.),(2 páxs) -- José Cabada Vázquez (4 páxs.),(1 páx.),(1 páx.) --Salvador Cabeza (1 páx.) -- Antonio Carballa (1 páx.) -- Leandro y Euxenio Carré (2 páxs.) -- V. Carro (1 páx.) -- Santiago Casares (1 páx.) -- Alvaro Cebreiro (2 páxs.) -- Centro Gallego de Buenos Aires (1 páx.),(1 páx.) -- Compostela (2 páxs.) -- Manolo: Continental (2 páxs.) -- Coral de Ruada (1 páx.),(2 páxs.) -- Amando Cotarelo(1 páx.),(1 páx.) -- Eduardo Dorado Xaneiro (8 páx.) -- Círculo Mercantil e Idustrial: Ramón Fernández (1 páx.) --Virgilio Fernández(3 páxs.) -- Ramón Fernández Mato (2 páxs.) -- B. Ferreiro(1 páx.) -- Jenaro de la Fuente (1 páx.) -- Isaac Fraga: Espéctaculos Empresa Fraga (1 páx.),(1 páx.) -- Antonio Folgar Lema(1 páx.)--Alicio Garcitoral (1 páx.) -- Cándido González Raño (1 páx.) -- Daniel González Rodriguez (2 páxs.),(2 páxs.) -- Edurardo G.del Río (1 páx.) -- Hermanos Hernández (2 páxs.),(1 páx.),(1 páx.),(1 páx.) -- José Iglesias Sánchez (2 páxs.) -- Irmandades da Fala (1 páx.) -- José Silva? (2 páxs.) -- Arturo Longa (1 páx.) -- Casimiro López (1 páx.) -- Edmundo López (1 páx.),(1 páx.) -- Eduardo R. Losada y Rebellón (2 páx.) -- Carlos Maside (1 páx.) -- Enrique Mayer (1 páx.) -- Antonio Méndez Laserna (1 páx.) -- Anselmo Padín (1 páx.) -- Xavier Pardo (1 páx.) -- Partido Republicano Radical Socialista (1 páx.) -- Pérez Bustamante (1 páx.) -- Modesto Piñeiro (2 páxs.) -- Salustiano Portela (2 páxs.) -- José Seijo Rubio (2 páxs.) -- Suarez Picallo (2 páxs.) -- Luis Losada (1 páx), (1 páx.) -- Ricardo Valdés (2 páxs.),(2 páxs.),(2 páxs.),(1 páx.) -- A.Nilo Varela (1 páx.),(2 páxs.),(2 páxs.) -- Juan Varela de Limia (1 páx.) -- Victorino? Varela (1 páx.) -- Jesús Varela (3 páxs.) -- F.Vázquez Suarez (1 páx.) -- Santiago Vidal Gimeno (1 páx.) -- Pedro Vieitez (1 páx.) -- M. Villar (2 páxs.) -- Anónima (1 páx.) -- Anónima (1 páx.

Memorias IX Congreso Geológico Venezolano (1)

Memorias del IX Congreso Geológico Venezolan

Switching TNF antagonists in patients with chronic arthritis: An observational study of 488 patients over a four-year period

The objective of this work is to analyze the survival of infliximab, etanercept and adalimumab in patients who have switched among tumor necrosis factor (TNF) antagonists for the treatment of chronic arthritis. BIOBADASER is a national registry of patients with different forms of chronic arthritis who are treated with biologics. Using this registry, we have analyzed patient switching of TNF antagonists. The cumulative discontinuation rate was calculated using the actuarial method. The log-rank test was used to compare survival curves, and Cox regression models were used to assess independent factors associated with discontinuing medication. Between February 2000 and September 2004, 4,706 patients were registered in BIOBADASER, of whom 68% had rheumatoid arthritis, 11% ankylosing spondylitis, 10% psoriatic arthritis, and 11% other forms of chronic arthritis. One- and two-year drug survival rates of the TNF antagonist were 0.83 and 0.75, respectively. There were 488 patients treated with more than one TNF antagonist. In this situation, survival of the second TNF antagonist decreased to 0.68 and 0.60 at 1 and 2 years, respectively. Survival was better in patients replacing the first TNF antagonist because of adverse events (hazard ratio (HR) for discontinuation 0.55 (95% confidence interval (CI), 0.34-0.84)), and worse in patients older than 60 years (HR 1.10 (95% CI 0.97-2.49)) or who were treated with infliximab (HR 3.22 (95% CI 2.13-4.87)). In summary, in patients who require continuous therapy and have failed to respond to a TNF antagonist, replacement with a different TNF antagonist may be of use under certain situations. This issue will deserve continuous reassessment with the arrival of new medications. © 2006 Gomez-Reino and Loreto Carmona; licensee BioMed Central Ltd