Keynote – Nonlinear natural convection in porous media and the collapse of the wave function

A short review of the problem of nonlinear natural convection in a fluid saturated porous layer heated from below is presented. When the conditions for the onset of convection are met a wave function is obtained as the solution of the linearized equations expressed in terms of a Fourier expansion. Only one mode of this expansion survives at the onset of convection, a result that can be seen as the Collapse of the Wave function in a very similar fashion as in quantum mechanics, although the explanations of the latter are very distinct from the ones in quantum mechanics. The reasons behind the Collapse of the Wave function result in natural convection are discussed and the analysis is extended into the nonlinear domain of convection, by using a weak nonlinear analysis

Heat transfer augmentation in nanofluids via nanofins

Theoretical results derived in this article are combined with experimental data to conclude that, while there is no improvement in the effective thermal conductivity of nanofluids beyond the Maxwell's effective medium theory (J.C. Maxwell, Treatise on Electricity and Magnetism, 1891), there is substantial heat transfer augmentation via nanofins. The latter are formed as attachments on the hot wire surface by yet an unknown mechanism, which could be related to electrophoresis, but there is no conclusive evidence yet to prove this proposed mechanism

Rendering the transient hot wire experimental method to dual-phase applications

Paper presented at the 5th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, South Africa, 1-4 July, 2007.The Transient Hot Wire method is well established as the most accurate, reliable and robust technique for evaluating the thermal conductivity of fluids and solids. Unfortunately its direct application to dual-phase systems such as solid suspensions in fluids or porous media cannot be supported by the very principles and methodology underlying this method. The derivation of possible ways of rendering the transient hot wire method to dual-phase applications including the development of validity criteria for such applications is proposed and discussed.cs201

Autoimmunity and Novel Therapies in Immune-Mediated Thrombocytopenia

Immune-mediated thrombocytopenic purpura (ITP) is recognized as a cell-specific autoimmune disorder, yet, multifactorial in origin. The development of thrombocytopenia is well proven to be mediated by both humoral (anti-platelet antibodies) and cellular (T-cell) mediated mechanisms. In some cases other autoantibodies are also induced, eg, antinuclear antibody (ANA), anti-dsDNA, and anti-cardiolipin, in addition to anti-platelet antibodies. The persistance of these autoantibodies during the course of ITP could herald future development of another autoimmune disease, eg, systemic lupus erythematosus (SLE) or anti-phospholipid syndrome (APS). Due to the better understanding of the pathophysiology of ITP, new novel therapies were introduced aiming to achieve long-lasting remissions. In this review we will focus on the autoimmune nature of the disease and on some of the mechanisms of action of these new therapies

Mathematical modelling of the dynamical interactions between killer and sensitive wine yeast subjected to nutritional stress.

Thesis (M.Sc.Eng.)-University of Durban-Westville, 2000.No abstract available

Spatio-temporal dynamics of heterogeneously distributed populations.

Thesis (Ph.D)-University of Durban-Westville, 2003.No abstract available

Heat transfer enhancement in nano-fluids suspensions : thermal wave effects and hyperbolic heat conduction.

Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2005.The spectacular heat transfer enhancement revealed experimentally in nanofluids suspensions is being investigated theoretically at the macro-scale level aiming at explaining the possible mechanisms that lead to such impressive experimental results. In particular, the possibility that thermal wave effects via hyperbolic heat conduction could have been the source of the excessively improved effective thermal conductivity of the suspension is shown to provide a viable explanation although the investigation of alternative possibilities is needed prior to reaching an ultimate conclusion

Essays in banking theory

In the first essay (joint with Dr. Kebin Ma) we analyse a possible informational impact of banking regulations. Banks can take costly actions (such as higher capitalization, liquidity holding, and advanced risk management) to fend off runs. While such actions directly affect bank risks, they also carry informational content as signals of the banks' fundamentals. A separating equilibrium due to such signalling, however, involves two types of inefficiency: the high type chooses excessively costly signals, whereas the low type is vulnerable to runs. This provides a novel rationale for financial regulations: by restricting banks' actions, regulators can maintain a pooling equilibrium where the cross-subsidy among types promotes financial stability. We build a theoretical model to illustrate the point and also obtain supporting evidence from the US capital and liquidity regulations. The second essay (joint with Prof. John Thanassoulis) seeks to provide a theoretical explanation of the variety of pricing schemes and product bundling observed in personal current account (PCA) markets. The main motivating fact is the widespread proliferation of `free-if-in-credit' (FIIC) current accounts in certain countries (US, UK), in contrast to some other European countries (France, Italy, Hungary), where even basic current account services are subject to excessive monthly fees. Existing evidence is consistent with the possibility that FIIC current accounts are cross-subsidized by exploitative and complicated fee structures on connected products, in particular by the excessive usage of overdraft facilities. In this research we propose a novel approach to model competitive aftermarkets, and demonstrate how certain sources of market power, namely customer naiveté and adverse selection interact in equilibrium. This helps to better understand why some markets are more likely to develop FIIC pricing than others. In the last chapter I demonstrate how illiquidity is determined endogenously during crises as a result of equilibrium behaviour of financial institutions subject to leverage constraints. I show in a simple and intuitive framework that asset liquidation decisions exhibit similar characteristic to a Prisoners' dilemma: although financial institutions are given the possibility to dampen the cost of fire-sale spillovers, the only Nash-equilibrium is where banks 'defect', and end up coordinating on selling the more liquid common asset, which in turn becomes illiquid. This reduces welfare compared to the socially optimal de-leveraging rule

Limit and Dead Center Positions of a Geared Five-Link Mechanism

Mechanical Engineerin