Beyond the virtual intracranial stenting challenge 2007: non-Newtonian and flow pulsatility effects

The attached article is a post print version of the final published version which may be accessed at the link below. Crown Copyright (c) 2010 Published by Elsevier Ltd. All rights reserved.The Virtual Intracranial Stenting Challenge 2007 (VISC’07) is becoming a standard test case in computational minimally invasive cerebrovascular intervention. Following views expressed in the literature and consistent with the recommendations of a report, the effects of non-Newtonian viscosity and pulsatile flow are reported. Three models of stented cerebral aneurysms, originating from VISC’07 are meshed and the flow characteristics simulated using commercial computational fluid dynamics (CFD) software. We conclude that non-Newtonian and pulsatile effects are important to include in order to discriminate more effectively between stent designs

Enhanced visualisation of complex thermofluid data: Vertical and horizontal combined convection and microscale heat transfer cases

Copyright @ 2000 UITIn general, convective heat transfer is an 'n-dimensional' problem where n is well in excess of 3 for steady flows. Traditionally, the method of dimensional analysis results in a small number of dimensionless groups. In the case of steady forced convection these can reduce to three, namely the Nusselt (Nu), Reynolds (Re) and Prandtl (Pr) numbers, for heat transfer, fluid flow regime and fluid properties respectively. Again, traditionally, data are presented on log-log graphs, say of Nu versus Re, with Pr being a possible third parameter. For natural convection, the Grashof number (Gr) expresses buoyancy effects in place of Re, while for combined (natural and forced) convection Gr becomes additional to, rather than replacing, Re. Using sets of data for: (a) vertical combined convection in nuclear safety, (b) horizontal combined convection review material, and (c) microchannel heat transfer, in the first part of this paper we survey this problem. We reach the following conclusions: that heat transfer data are presented in either 'holistic' or 'reductive' modes, and that other thermodynamic performance data are related to the generic scientific cases of (a) 3-dimensional space and (b) multi-dimensional space. In the second part of the paper we present a first attempt at applying design-type procedures to specifying this problem. Visualisation priorities are suggested from which particular solutions will be developed in future

University, gender and sexual identities: Training course for students of the University of Granada

Existen datos fehacientes que resaltan la necesidad de acciones formativas en relación con el acoso lgbtiq+fóbico y la inequidad hacia las personas de género no normativo (lgbtiq+: lesbianas, gays, bisexuales, trans, intersex, queer, etc.)8 en los entornos escolares españoles9. En el presente texto, se expone la experiencia de un curso de formación de treinta horas lectivas que se ofreció gratuitamente al estudiantado universitario a través de la Unidad de Igualdad y Conciliación de la Universidad de Granada. Fue impartido por ocho docentes/facilitadores y fue eminentemente práctico donde se presentaron fundamentos teóricos basados en la teoría queer y en la pedagogía trans*formadora (Bedford, 2009) y, sobre todo, cómo tratar situaciones de acoso lgbtiq+fóbico en la universidad y en la vida cotidiana. En este trabajo se analizan los contenidos y los resultados principales del curso, así como la evaluación del estudiantado participanteThere are studies undertaken in Spain that demonstrate a latent lgbtiq+phobia and inequity towards gender non-conforming people (lgbtiq+) in the Spanish education system, which underline the necessity to offer professional training. In this text, I will analyse the experience of a thirty-hour training course offered to university students through the Unidad de Igualdad y Conciliación of the University of Granada, in Spain. The course was facilitated by eight teachers and was predominantly practical. The participants learnt theoretical aspects related to queer theory and trans*formative pedagogy (Bedford, 2009) and especially how to deal with lgbtiq+phobic situations at university and in their everyday life. In this work, I will present the contents and main results of the course, as well as the participants’ course evaluatio

Application of method of lines in chemical engineering problems

In this work, two problems in chemical engineering are studied and solved. Estimation of an important parameter of dust explosions, the deflagration index kST , and a study of unsteady state with axial diffusion Plug Flow Reactors are presented. Both problems are approached by characterizing the physical phenomena involved with suitable transport equations. Such equations have been developed with the synergy of both consolidated theoretical models and ad hoc assumptions and semi-empiric approaches, according to the specific problem analyzed. The final equation systems result in a system of non-linear Partial Differential Equations. The numerical solution of such equations has been performed by implementing the Method of Lines, a numerical method based on the discretization of spatial derivative operators, transforming a system of PDEs into a system of ODEs or DAEs. The resulting ODEs/DAEs systems have been implemented and solved inside MAT LABTMenvironment. The Method of Lines is presented for uniform and non-uniform grids, generalized with the use of spatial derivatives discretization stencils of several orders of accuracy. For the estimation of kST , we validated the model with 8 organic dust: Aspirin, Cork, Corn starch, Niacin, Polyethylene, Polystyrene, Sugar and Wheat flour. Results showed an interesting match between experimental and simulated data: predictions for the deflagration index were good, while the evolution of process variables (such as the temperature of the gas phase), still leaves room for improvements. For the PFR study, we propose 1-D models, taking in account the reactor start-up, thermal and material axial diffusion, and the presence of a heating/cooling system. In order to judge the quality of the results, we took as case study a reaction well studied in the literature over the years: the oxidation of Naphthalene. We developed the so-called Runaway Boundaries for the reaction considered. Our results found good matches with the available literature data and analysis. We also noticed a shifting of the Runaway Boundaries when considering a more realistic heating/cooling system

"Language is my second language": Dangerous writing and hiv-affected communities in Tom Spanbauer's In the City of Shy Hunters

This paper aims to analyse the U.S. writer and teacher Tom Spanbauer’s novel In the City of Shy Hunters (2001) by means of theoretical perspectives that embrace both queer and communitarian epistemologies. The novel, set mainly in New York City in the mid1980s, is narrated in first person by the protagonist and shows how HIV/AIDS, and the elevated social stigma surrounding it, affects different classes and ethnicities, as well as gender, sexual and corporal diversities. It experiments with a particular writing style and teaching method that Spanbauer calls dangerous writing; that is, how to expose our inner life and secrets, which are often related to social taboos. The main objective of this paper, which underlines its originality, is to demonstrate the connection between dangerous writing, queer studies and community theory by adopting a multidisciplinary approach to literary critical analysis. The novel is about an inwards as well as outwards journey taken by a young protagonist, who is both a queer singularity and a shy hunter, looking for the sore truth that lies within his own and other human hearts. Firstly, I will explore Spanbauer’s dangerous writing style, then I will investigate the HIV/AIDS crisis through a queer perspective (Judith Butler, Teresa de Lauretis, Michel Foucault and Annamarie Jagose). Furthermore, different community configurations (Jean-Luc Nancy’s in/operative community, Maurice Blanchot’s community of lovers and Roberto Esposito’s concept of immunitas) will be discussed. The main result demonstrates that the singularities represented in the novel, who are mostly queer and affected by HIV/AIDS, can create inoperative communities and communities of lovers, open to otherness and secret sharing, as well as being spontaneous, antisocial and momentary, with a recognition and acceptance of mortality

Vascular device interaction with the endothelium

Copyright @ 2008 Elsevier. This is the post-print version of the article.Cerebral stents and Intra Aortic Balloon Pumps (IABP) are examples of mechanical devices that are inserted into arteries to restore flows to clinically healthy states. The stent and the IABP ‘correct’ the arterial flow by static dilation and by cyclical occlusion respectively. As this presentation shows, these functions are effectively modelled by current engineering practice. As interventions however, by their very nature they involve physical contact between a non-biological structure and the sensitive endothelial surface. The possible damage to the endothelium is not currently well addressed and we also consider this issue. Cerebral stents generally have two primary clinical objectives: to mechanically dilate a stenosed artery and to have minimal detrimental impact upon local blood flow characteristics. These objectives are well served at the arterial scale as these devices are evidently effective in opening up diseased arteries and restoring vital flows. However, at the near-wall micro-scale the picture is less satisfactory, as thin stent wires apply stresses to the endothelium and glycocalyx and the local flow is disturbed rather than being ideally streamlined. This causes further interaction with this endothelium topography. Wall Shear Stress (WSS) is the measure commonly used to indicate the interaction between fluid and wall but it is a broad brush approach that loses fidelity close to the wall. We will present simulation results of blood flow through a stented cerebral saccular aneurysm under these limitations of WSS. The Intra Aortic Balloon Pump (IABP) is a widely used temporary cardiac assist device. The balloon is usually inserted from the iliac artery, advanced in the aorta until it reaches the desired position; with its base just above the renal bifurcation and the tip approximately 10cm away from the aortic valve. The balloon is inflated and deflated every- (1:1), every other- (1:2) or every second (1:3) cardiac cycle. Balloon inflation, which takes place during early diastole, causes an increase in the pressure of the aortic root which leads to an increase in coronary flow. Balloon deflation which takes place during late diastole achieves one of the main IABP therapeutic effects by reducing left ventricular afterload. Unavoidably, the balloon contacts the inner wall of the aorta with every inflation/deflation cycle. This repeated event and possible contact with atherosclerotic plaque have been reported to be responsible for balloon rupture. However, there has not been a methodical study to investigate the mechanical effects of balloon-wall interaction. For example, during inflation the balloon approaches the endothelium as it displaces a volume of blood proximally and distally. This squeezing process generates shear stresses, which hasn't yet been quantified. Similarly, when the balloon moves away from the endothelium during deflation, it generates micro pressure differences that may impose stretching (pulling) stresses on the endothelium cells. Both of the above cases indicate that a very high spatial resolution is required in order to fully understand the process of interaction between device and endothelium, and to interpret the effects at the cellular level

Application of method of lines in chemical engineering problems

In this work, two problems in chemical engineering are studied and solved. Estimation of an important parameter of dust explosions, the deflagration index kST , and a study of unsteady state with axial diffusion Plug Flow Reactors are presented. Both problems are approached by characterizing the physical phenomena involved with suitable transport equations. Such equations have been developed with the synergy of both consolidated theoretical models and ad hoc assumptions and semi-empiric approaches, according to the specific problem analyzed. The final equation systems result in a system of non-linear Partial Differential Equations. The numerical solution of such equations has been performed by implementing the Method of Lines, a numerical method based on the discretization of spatial derivative operators, transforming a system of PDEs into a system of ODEs or DAEs. The resulting ODEs/DAEs systems have been implemented and solved inside MAT LABTMenvironment. The Method of Lines is presented for uniform and non-uniform grids, generalized with the use of spatial derivatives discretization stencils of several orders of accuracy. For the estimation of kST , we validated the model with 8 organic dust: Aspirin, Cork, Corn starch, Niacin, Polyethylene, Polystyrene, Sugar and Wheat flour. Results showed an interesting match between experimental and simulated data: predictions for the deflagration index were good, while the evolution of process variables (such as the temperature of the gas phase), still leaves room for improvements. For the PFR study, we propose 1-D models, taking in account the reactor start-up, thermal and material axial diffusion, and the presence of a heating/cooling system. In order to judge the quality of the results, we took as case study a reaction well studied in the literature over the years: the oxidation of Naphthalene. We developed the so-called Runaway Boundaries for the reaction considered. Our results found good matches with the available literature data and analysis. We also noticed a shifting of the Runaway Boundaries when considering a more realistic heating/cooling system