El mercado mas especulatico del mundo sigue creciendo mucho

Postprint (published version)

Nuevos elementos paradigmáticos para salir realmente de la crisis

Postprint (published version)

Informe tècnic d'aerodinàmica

Determinació del coeficient aerodinàmic de resistencia a l'avanç de la luminària ELEDGANT

Measurement of a Structured Backflow in an Open Small Channel Induced by Surface-Tension Gradients

We present experiments in which the laterally confined flow of a surfactant film driven by controlled surface tension gradients causes the subtended liquid layer to self-organize into an inner upstream microduct surrounded by the downstream flow. The anomalous interfacial flow profiles and the concomitant backflow are a result of the feedback between two-dimensional and three-dimensional microfluidics realized during flow in open microchannels. Bulk and surface particle image velocimetry data combined with an interfacial hydrodynamics model explain the dependence of the observed phenomena on channel geometry.

Cooperative motion of intrinsic and actuated semiflexible swimmers

We examine the phenomenon of hydrodynamic-induced cooperativity for pairs of flagellated micro-organism swimmers, of which spermatozoa cells are an example. We consider semiflexible swimmers, where inextensible filaments are driven by an internal intrinsic force and torque-free mechanism (intrinsic swimmers). The velocity gain for swimming cooperatively, which depends on both the geometry and the driving, develops as a result of the near-field coupling of bending and hydrodynamic stresses. We identify the regimes where hydrodynamic cooperativity is advantageous and quantify the change in efficiency. When the filaments' axes are parallel, hydrodynamic interaction induces a directional instability that causes semiflexible swimmers that profit from swimming together to move apart from each other. Biologically, this implies that flagella need to select different synchronized collective states and to compensate for directional instabilities (e.g., by binding) in order to profit from swimming together. By analyzing the cooperative motion of pairs of externally actuated filaments, we assess the impact that stress distribution along the filaments has on their collective displacements.

Accounting for adsorption and desorption in Lattice Boltzmann simulations

We report a Lattice-Boltzmann scheme that accounts for adsorption and desorption in the calculation of mesoscale dynamical properties of tracers in media of arbitrary complexity. Lattice Boltzmann simulations made it possible to solve numerically the coupled Navier-Stokes equations of fluid dynamics and Nernst-Planck equations of electrokinetics in complex, heterogeneous media. With the moment propagation scheme, it became possible to extract the effective diffusion and dispersion coefficients of tracers, or solutes, of any charge, e.g., in porous media. Nevertheless, the dynamical properties of tracers depend on the tracer-surface affinity, which is not purely electrostatic and also includes a species-specific contribution. In order to capture this important feature, we introduce specific adsorption and desorption processes in a lattice Boltzmann scheme through a modified moment propagation algorithm, in which tracers may adsorb and desorb from surfaces through kinetic reaction rates. The method is validated on exact results for pure diffusion and diffusion-advection in Poiseuille flows in a simple geometry. We finally illustrate the importance of taking such processes into account in the time-dependent diffusion coefficient in a more complex porous medium.

De Bonn, el juny del 2014, a la COP 20 de Lima a finals de l'any

Postprint (published version)

Cavitation in 3He-4He liquid mixtures at low temperatures

Bubble formation in solutions of 3He and 4He is studied within a density-functional approach. In particular, the temperature dependence of the cavitation pressure for different 3He concentrations is calculated at low temperatures and compared to that of pure 4He. The presence of Andreev states lowers the surface tension and, consequently, nucleation barriers are drastically reduced. This fact means that even at low 3He concentrations the cavitation process takes place at higher pressures than the spinodal pressure, which is not the case for pure 4He.

La Phoronomia (1716) de Jacob Hermann (1678 -1733): entre la filosofía natural y la mecánica analítica

La "Phoronomia", primer libro de mecánica escrito tras los "Principia", es representativo del proceso de transición que transformó la dinámica a principios del XVIII y que concluye con la "Mecánica" de Euler (1736). Está escrita en estilo geométrico y algebraico, y mezcla los conceptos y métodos de Leibniz y Newton de forma idiosincrásica. En esta obra se encuentra por primera vez la segunda ley de Newton escrita en la forma en que hoy la conocemos, así como un intento de construcción de la estática y la dinámica de sólidos y fluidos basado en reglas generales diferenciales.

Simulació numèrica de fenòmens de transferència de calor i dinàmics de fluids transitoris

The work carried out during the 4 year research activity can be barely classified in two main lines. On the one hand, a considerable effort is taken to address issues related with the verification of multi-dimensional and transient solutions that are obtained by numerical simulations. Within the studied cases, we can consider cases of piston-cylinder ows within geometries similar to those of hermetic reciprocating compressors.This issue is mentioned in Part I. On the other hand, numerical simulations of different phenomena have been performed. More emphasis has been given to the natural convection ow within enclosures. This is explained in Part II. The case extensively studied has been the natural convection ow. The natural convection ow within enclosures has attracted the attention of many researchers due to its potential to model numerous applications of engineering interest, such as cooling of electronic devices, air ow in buildings, heat transfer in solar collectors, among others. The natural convection studies corresponding to the parallelepipedic enclosures can be classified into two elementary classes: i) heating from a horizontal wall (heating from below); ii) heating from a vertical wall. The characteristic example of the former case is the Rayleigh-B_enard ow, however this research is on the cavities heated from the side. This configuration is referred commonly as the differentially heated cavity.

Estudi i simulació aerodinàmica amb programari de dinàmica de fluids computacional (CFD) en un model bàsic de vehicle de competició de la categoria CM (curses de muntanya)

Aquest projecte té com a objectiu la simulació numérica de la carrosseria d’ un vehicle de curses de muntanya de categoria CM

Uma intervenção educativa para profissionais de saúde na prevenção de pneumonia associada à ventilação mecânica

Quasi-experimental study, prospective with quantitative approach, performed at the Hospital do Coração in Natal, aimed at verified the existence of difference between the care given by health professionals to the patients under mechanical ventilation (MV) in the Intensive Care Unit, before and after an educative intervention. The population was of 31 professionals, with data collected between november 05 of 2007 to march 27 of 2008. The results show a yong population, female gender, middle level of education, nursing technique, working between 05 and 09 years on nursing profession, and 01 to 04 years on Intensive Care Unit; almost all, never had an kind of training over prevent pneumonia associated to mechanical ventilation; from those that had training, occur on the work place with duration from 12 to 24 hours. About endotracheal intubation, the cuff was tested with a sterilized syringe had a positive change after a educative intervention, increased from 75,0% to 100,0%; the sterile guide was used on 75,0% before and 100,0% after an educative intervention. Regarding endotracheal suction procedure, was not informed to the patient on 72,7% before, however was informed on 56,7% after; the hands was not previously washed 68,5% before, however was 63,3% after the procedure; mask was used on 74,2 % opportunities before and 76,7% after; the aspiration catheter had adequated size on 98,9% observation before and 100,0% after; the gaze was sterilized on 95,7% before and 100,0% after; the ventilator was connected to the patient during the aspiration intervals on 94,4% observation before and 100,0% after; the ambu bag was clean and protected on 76,1% before and 85,7% after; the aspiration catheter was discarded after be used on 98,9% before and 100,0% after; FIO2 was turned to the begging value on 32,9% observation before and 12,0% after; before the procedure 71,9% professions washed their hands and 73,3% after; before, notes of aspiration results were performed on 70,8% observation and 86,7% after. Regarding devices used on respiratory tract, aspirator flasks were not swapped on 84,6% observations before and 71,0% after; daily látex extention change was not performed on 93,6% observation before and 87,1% after; the ambu bag change was not performed on 50,0% observation before even if was duty or unprotected and on 75,8% opportunities was changed, after; nebulization was not prepared with sterile fluids or manipulated aseptically on 65,2% observation before, perhaps was on 71,7% after; before nebulizers were not changed on 65,2% observations, perhaps were on 60,9% after. Concerning ventilator breathing circuits, condense fluids cumulated on circuits were removed on 55,0% opportunities before, and 64,0% after; moisturizer was not filled with sterile water when already had small amount of liquid inside on 78,4% observations before, and 90,2% after; MV circuits were changed on 97,0% observations on presence of visible duty or when presents some kind of failure, before and 98,4% after. About body position, on 51,3% observations the decubitus position change were done before and 78,2% after; fowler position was maitened on 95,5% observations before and 98,2% after; Regarding respiratory physiotherapy, enteral diet was not interrupted before respiratory physiotherapy on 94,9% before and 90,0% after; respiratory physiotherapy devices were not disinfected or sterile on 69,6% observations before but they re on 60,0% after; before the cateter was not tested before introduction enteral diet or medications on 100,0% but after was done on 15,2%. About enteral feeding, intestine motility and measure of stomach contents were not done on 100,0% observations before, but was 15,2% after. We conclude that 05 of 07 valuated procedures in relation to MV, had a significant improvement on quality of care given after educative intervention, when compared before intervention

Investigação reológica e análise mecânica de compósitos não-newtonianos

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

The carreau-yasuda fluids: a skin friction equation for turbulent flow in pipes and kolmogorov dissipative scales

In this work the turbulent flow of the Non-Newtonian Carreau-Yasuda fluid will be studied. A skin friction equation for the turbulent flow of Carreau-Yasuda fluids will be derived assuming a logarithmic behavior of the turbulent mean velocity for the near wall flow out of the viscous sub layer. An alternative near wall characteristic length scale which takes into account the effects of the relaxation time will be introduced. The characteristic length will be obtained through the analysis of viscous region near the wall. The results compared with experimental data obtained with Tylose (methyl hydroxil cellulose) solutions showing good agreement. The relations between scales integral and dissipative obtained for length, time, velocity, kinetic energy, and vorticity will be derived for this type of fluid. When the power law index approach to unity the relations reduces to Newtonian case.