Numerical simulation of EHD flows using Discontinuous Galerkin Finite Element methods

The aim of this paper is to explore the capability of Discontinuous Galerkin Finite Element methods to solve numerically the charge transport equation in EHD convective flows, in both strong and weak injection regimes. These methods are especially suited to treat purely hyperbolic problems, as it is the charge transport equation in most EHD problems. We consider the 2D electroconvective flow between two parallel plates. We compare our com- putations with the analytical results in the hydrostatic regime, the linear and non-linear stability analysis, computing both the electric and velocity fields. The stability of the finite amplitude electroconvection is also anal- ysed. Comparisons are made with computations in the literature obtained with other numerical techniques. The results show that DG-FEM are a very good alternative to simulate numerically EHD convective flows

Influence of magnesium on salivary gland secretion: physiological and pathophysiological studies

The divalent abundant cation Magnesium (Mg2+) has been known to play an important regulatory role in the stimulus-secretion coupling events in a number of epithelial secretory cells including the exocrine pancreas, lachrymal and the parietal cells. Since the salivary glands acinar cells have a similar structure and function as the exocrine pancreas, the stomach and the lachrymal gland, it was decided to investigate specifically the effect of perturbation of extracellular magnesium ([Mg2+]0) on both basal and secretagogue-evoked amylase secretion and total protein output and intracellular free calcium concentrations ([Ca2+]i) in the rat submandibular and parotid glands using spectrofluorimetry and spectroscopic techniques. The results have shown that both zero and elevated (5 and 10 mM) [Mg2+]0 can significantly (P<0.01) inhibit basal amylase or protein output compared to normal (1.1 mM) [Mg2+]0 Either acetylcholine (ACh), noradrenaline (NA) or Phenylephrine (Phe) can elicit marked increases in amylase secretion and total protein output from the isolated parotid and submandibular gland segments respectively in normal [Mg2+]0. In contrast, in the presence of either zero or elevated (5 and 10 mM) [Mg2+]0 the ACh, NA and Phe-evoked amylase secretion and total protein output were markedly attenuated when compared to normal (1.1 mM) Mg2+]0. The inhibitory effect of zero [Mg2+]0 was much more pronounced when compared to 10 mM [Mg2+]0. A perturbation of [Mg2+]0 had little or no effect on the Electrical Field Stimulation (EFS) -evoked amylase responses in the parotid gland. Isoprenaline-evoked amylase secretion revealed a different pattern of secretion in the presence of [Mg2+]0 perturbation. In Fura-2 loaded salivary acinar cells a perturbation of [Mg2+]0 had no significant effect on basal [Ca2+]i in the parotid gland but elevated (5 and 10 mM) [Mg2+]0 attenuated [Ca2+]i in acinar cells taken from submandibular gland. In acinar cells from both glands ACh (105 M), evoked a marked increase in [Ca2+]i above basal level in [Mg2+]0. The response comprises of an initial rise (peak response) followed by a plateau phase (plateau response) before declining back and stabilising a little above control level. In the presence of either zero or elevated (5 and 10 mM) [Mg2+]0 the ACh evoked increases (both peak and plateau phases) in [Ca2+]i was significantly (P<0.05) attenuated compared to normal (1.1 mM) [Mg2+]0. In a nominally free Ca2+ medium containing 1mM Ethyl Glycol Tetracetic Acid (EGTA), ACh evoked only the initial Ca2+ peak, which was sensitive to Mg2+ perturbation. Reperfusion of acinar cells with normal Ca2+ medium resulted in marked increases in [Ca2+]i, which was also sensitive to perturbation of [Mg2+]0. These results indicate that Mg2+ is regulating cellular Ca2+ homeostasis. In Magfura 2-loaded parotid acinar cells an increasing perturbation of [Mg2+]0 resulted in a gradual increase in intracellular free Mg2+ concentrations ([Mg2+])i. Stimulation of the cells with ACh resulted in a significant (P<0.01) decrease in [Mg2+]i. Treatment of Magftira-2 loaded parotid acinar cells with either zero extracellular sodium ([Na+]0) (substituting it with N-Methyl-D-Glucamine (NMDG)), dinitrophenol (DNP) bumetanide, amiloride, quinidine or lidocaine resulted in significant (P<0.01) increases in [Mg2+]i. In the presence of these inhibitors ACh still stimulated a reduction in {Mg2+]i. Taken together, these studies on animal model have demonstrated marked interactions between Ca2+ and Mg2+ signalling during the stimulus-secretion coupling process in the salivary glands. The study also employs male and female human subjects to investigate the rate of salivary secretion and the quality of saliva during normal healthy and such pathophysiolgical conditions such as ageing, diabetes and surgical procedures. The results have demonstrated that either the ageing process or type I and type II diabetes are associated with significant (P<0.01) decreases in salivary secretion. However, both ageing and type I (but not type II diabetes) are associated with increased levels of protein in the saliva. Both ageing and diabetes are associated with significant (P<0.05) increases in Ca2+ levels and significant decreases in Mg2+ and Zn2+ levels in saliva compared to age-matched controls. Ageing and diabetes are also associated with reduced levels of K in the saliva. Although type II diabetic patients presented the same type of salivary changes these were less intense when compared to type I diabetic. Surgical procedures had little or no effect on the various salivary parameters measured except for small increase in resting salivary output and protein concentration. These results indicate that both ageing and diabetes can affect markedly the function of the salivary glands leading to decreased secretion in saliva and to a variation in its composition

Numerical analysis of the stability of the Electrohydrodynamic (EHD) electroconvection between two plates

The time evolution of the problem of Electrohydrodynamic (EHD) convection in a liquid between two plates is analysed numerically. The equations are nondimensionalized using the ion drift velocity and the viscous time scales. Following the non-dimensionalisation of the respective model, two different techniques have been used to describe the charge evolution, namely the Finite-Element Flux-Corrected Transport Method and the Particle-In-Cell technique. The results obtained with the two schemes, apart from showing good agreement, have revealed the appearance of a two-roll structure not described in previous works. This is investigated in detail for both strong and weak injection.Ministerio de ciencia y tecnología FQM-42

Verba volant, statuae (nonnumquam) manent. Aproximación a la problemática de las estatuas funerarias romanas de Corduba-Colonia Patricia

The study of the funerary statuary of Corduba-Colonia Patricia only could be undertaken until recently from a small number of sculptural and epigraphic testimonies, found isolated and without context. Nevertheless, this situation has begun to change after the discovery in 2004, during an archaeological excavation, of a female statue linked to her correspondent funerary monument. The analysis of this piece and of those other elements allows us to approach towards the phenomenon of the self-representation of the cordovans elites of Late Republic and Early Empire across their sepulchral statues.El estudio de la estatuaria funeraria de Corduba-Colonia Patricia sólo podía acometerse hasta fechas muy recientes a partir de un reducido número de testimonios escultóricos y epigráficos hallados de forma aislada y fuera de contexto. Sin embargo, esta situación ha comenzado cambiar tras el descubrimiento en 2004, en el transcurso de una excavación arqueológica, de una estatua femenina vinculada a su correspondiente monumento funerario. El examen de esta pieza y de aquellos otros elementos nos permite realizar aquí un primer acercamiento al fenómeno de la autorrepresentación de las elites cordubenses de época tardorrepublicana y altoimperial a través de sus estatuas sepulcrales

Los retratos imperiales romanos del cortijo de Alcurrucén (Pedro Abad, Córdoba): ¿Testimonios de un grupo estatuario julioclaudio?

Der vorliegende Artikel untersucht die Gruppe romischer Skulpturen, die vor einigen Jahrzehnten im cortijo de Alcurrucen (Pedro Abad, Cordoba) gefunden wurde. Zu diesen Skulpturen záhlen drei Kaiserportr ä ts, die aufgrund ihrer Herkunñ und vor allem wegen ihrer Zeitstellung (alie datieren in sp ä ttiberische-frühclaudische Zeit) m ö glicherweise eine iulisch-claudische Statuengruppe bildeten, die einst in der antiken Stadt Sacili aufgestellt war.Se estudian aquí, de manera conjunta, las esculturas romanas halladas hace varias décadas en el cortijo de Alcurrucén (Pedro Abad, Córdoba). Entre ellas se encuentran tres retratos imperiales que, por compartir procedencia y, sobre todo, por poseer una cronología semejante -entre tiberiana tardía y claudia temprana- tal vez hubiesen constituido un grupo estatuario julioclaudio erigido en la antigua Sacili

Reflexiones en torno al denominado "Foro de Altos de Santa Ana" y a los comienzos del culto dinástico en Colonia Patricia Corduba

In this paper, we analyze the diverse archeological information (specially the sculptures) of Augustan and Julio-Claudian ages found in the so-called «foro de Altos de Santa Ana », located in Ángel de Saavedra's street and its environs. This public area of the ancient Colonia Patricia was related with the imperial cult from the first time and was presided over a sacred place dedicated to Diana and, perhaps, to Apolo.En este artículo analizamos la diversa documentación arqueológica -especialmente la de carácter escultórico- de las épocas augustea y julioclaudia hallada en el denominado «foro de Altos de Santa Ana» de Córdoba, situado en la C / Ángel de Saavedra y su entorno. Dicho espacio público de la antigua Colonia Patricia estuvo relacionado desde un primer momento con el culto imperial y estuvo presidido por un recinto sagrado dedicado a Diana y, tal vez, a Apolo

Molecular dynamics simulations of homogeneous solids using multi-layered structures

The main goal of this work is to model a homogeneous computer material with well-defined mechanical properties. To carry out the model material, an internal structure arranged in layers with different atom sizes is implemented using a simple interatomic law of Lennard-Jones type (LJ). We show that imposing an appropriate scaling law between the interatomic potentials from different layers, we obtain the same mechanical properties as if the material was homogeneous. Employing this scheme, given a fixed space volume to be occupied by the solid, this structural arrangement allows to decrease drastically (∼30-80%) the required number of atoms as compared with the case of a homogeneous solid, decreasing the computational effort and speeding up calculations. In that respect, this procedure is an analogous to mesh refinements methodologies usually applied in the continuum approaches.Ministerio de Educación y Ciencia FIS2006-03645Junta de Andalucía FQM-42

Dynamics of EHD Laminar Plumes: scaling analysis and integral model

In this paper electrohydrodynamic (EHD) plumes are examined in the region far from the injecting electrode and the collector plate, for both two-dimensional and axisymmetric geometries. The relative importance of the conduction mechanisms (convection, drift and diffusion of electric charge) is analyzed. Diffusion turns out to be negligible compared to convection and drift for the experimental conditions. But the transverse drift (Coulomb repulsion) is of the same order of magnitude than convection. We find a set of three differential equations giving the evolution of the velocity at the center of the plume and the widths of the plume and the charged core inside.Ministerio de Ciencia y Tecnología PB96-137