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Geringer J.,Center for Biomedical and Healthcare Engineering | Geringer J.,University of California at Berkeley | Macdonald D.D.,University of California at Berkeley | Macdonald D.D.,King Fahd University of Petroleum and Minerals
Materials Letters | Year: 2014

Lifetime of orthopedic implants is a key issue for patient life and health issues all over the world. Metals used for implants were specifically submitted to friction/fretting corrosion processes; with a specific attention on the main differences between these two types of degradations. This study allows highlighting the best mechanical parameters in both cases of degradations. Free corrosion potential, or Open circuit potential, follows the trend of the chlorides content in the studied solution. Describing behaviors in terms of wear and morphologies of wear track area is the interesting point. Moreover the synergistic approach, contribution of wear on corrosion and vice versa is relevant for understanding the role of each mode of degradations. Theoretical and practical issues are related to understanding these phenomena and revealing insights for the future opportunities and challenges. © 2014 Elsevier B.V. Source

Ali Q.,University of Western Ontario | Ali Q.,Center for Biomedical and Healthcare Engineering | Elkamel A.,University of Waterloo | Gruy F.,Center for Biomedical and Healthcare Engineering | And 2 more authors.
Canadian Journal of Chemical Engineering | Year: 2016

The progression of a cell population where each individual is characterized by the value of an internal variable varying with time (e.g. size, mass, and protein concentration) is typically modelled by a population balance equation, a first-order linear hyperbolic partial differential equation. The characteristics described by internal variables usually vary monotonically with the passage of time. A particular difficulty appears when the characteristic curves exhibit different slopes from each other and therefore cross each other at certain times. In particular, such a crossing phenomenon occurs during T-cell immune response when the concentrations of protein expressions depend upon each other and also when some global protein (e.g. Interleukin signals) that is shared by all T-cells is involved. At these crossing points, the linear advection equation is not possible by using the hyperbolic conservation laws in a classical way. Therefore, a new transport method is introduced in this article that is able to find the population density function for such processes. A multi-scale mathematical modelling framework is employed. At the first scale, two processes, the activation and reaction terms (assimilated as nucleation and growth in particulate processes), are studied as independent processes. At the second scale, the dynamic variation in the population density of activated T-cells is investigated in the presence of activation and reaction terms. The newly-developed transport method is shown to work in the case of crossing characteristics and to provide a smooth solution at the crossing points in contrast to the classical numerical techniques. © 2016 Canadian Society for Chemical Engineering. Source

Geringer J.,Center for Biomedical and Healthcare Engineering | Demanget N.,Center for Biomedical and Healthcare Engineering | Pellier J.,Center for Biomedical and Healthcare Engineering
Journal of Physics D: Applied Physics | Year: 2013

Surface treatments of dental implants aim at promoting osseointegration, i.e. the anchorage of the metallic part. Titanium-, grade II-V, based material is used as a bulk material for dental implants. For promoting the anchorage of this metallic biomaterial in human jaw, some strategies have been applied for improving the surface state, i.e. roughness, topography and coatings. A case study, experimental study, is described with the method of acid etching on titanium grade 4, CpTi. The main goal is to find the right proportion in a mixture of two acids in order to obtain the best surface state. Finally, a pure theoretical prediction is quite impossible and some experimental investigations are necessary to improve the surface state. The described acid etching is compared with some other acid etching treatments and some coatings available on dental implants. Thus, the discussion is focused on the tribocorrosion behaviour of titanium-based materials. The purpose of the coating is that the lifetime under tribocorrosion is limited. Moreover, the surgery related to the implantation has a huge impact on the stability of dental implants. Thus, the performance of dental implants depends on factors related to surgery (implantation) that are difficult to predict from the biomaterial characteristics. From the tribocorrosion point of view, i.e. during the mastication step, the titanium material is submitted to some deleterious factors that cause the performance of dental implants to decrease. © 2013 IOP Publishing Ltd. Source

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