Showing papers by "Mansour Youseffi published in 2009"

Corrosion of mild steel and 316L austenitic stainless steel with different surface roughness in sodium chloride saline solutions

Abstract: The corrosion behaviour of mild steel and 316L austenitic stainless steel was investigated in saline solution containing 1 and 3%NaCl. Specimens with surface roughness of 200, 600 grit emery paper and 1μm diamond paste were investigated. The anodic polarization measurement technique was performed at a scan rate of 1mV/s for a fixed period of 1 hour. The experimental results revealed that chloride ions have a significant effect on the corrosion behaviour of both steels as expected. As the surface roughness of 316L stainless steel increased, the breakdown potential (Ebreak), the free corrosion potential (Ecorr) and the width of passivity decreased, hence the corrosion rate increased. However, in the case of mild steel specimens, improving surface finish lead to shifts in the corrosion potential to more noble states and increased the corrosion rate. Metallographic examination of corroded specimens after electrochemical corrosion tests confirmed that the breakdown of the passive region was due to pitting corrosion.

Characterisation and biocompatibility study of nematic and cholesteric liquid crystals

Abstract:  Abstract— Intensive research in bio-engineering has been conducted in the search for flexible biomaterials that could support cell growth and cells attachment. Flexible synthetic materials that support cell growth without the aid of synthetic extracellular matrix proteins are still rare. Cholesteryl liquid crystal containing cholesteryl moieties may have suitable biological affinity. Human keratinocytes (HaCat) were cultured with a nematic liquid crystal and three cholesteryl liquid crystals of different formulation. Subsequently, the trypan blue dye exclusion assay was used to determine cell viability in the liquid crystals. The two classes of liquid crystal were characterized by Differential Scanning Calorimeter (DSC) and polarizing microscope (POM) to understand the nature of the interface material. The cell viability study in medium containing liquid crystals verified that liquid crystals had no effects on cell viability. However, only the surface of cholesteryl liquid crystal has shown affinity to HaCat cells. In addition, cells continued to proliferate in the presence of liquid crystals without a change of medium for eight days. No sign of exothermic and endothermic activities at 37 0 C were observed from the DSC test results for the three samples. Biological and mechanical test result of the cholesteryl liquid crystals has shown that cholesteryl liquid crystals are non toxic and support cell attachment without extracellular matrix protein at very low elasticity.

Interactions of cells with elastic cholesteryl liquid crystals

Abstract: Exploitation of elastic property of the liquid crystal to sense cells mechanics is a novel application. Both quantitative and qualitative analysis of cholesteryl liquid crystal has shown flexibility and elasticity of the material to sense cell contraction and relaxation over a period of time. Importantly, cells adhesion was precluded with the use of extracellular matrix proteins in this technique. The optimum operating range with linear elasticity of the cholesteryl liquid crystal is ≤ 0.1s− 1 which has a good correlation with the shear rate of the cells originated from the focal adhesions. Localized contraction was observed with a good resolution. In addition, clear definition of deformation lines between two cells has shown their interacting path through active mechano-sensing.

The effect of clearance upon friction of large diameter hip resurfacing prostheses using blood, clotted blood and bovine serum as lubricants

Abstract: Total hip joint implantation is an effective solution for reducing pain and ailing induced by arthritis or other diseases at the hip joint. Hence, a conventional metal on polyethylene (PE) bearing device has been introduced since late 1950’s for implantation. However, due to significant release of PE wear debris causing swelling at joints and osteolysis leading to implant loosening and failure in fixation, attempts are made to optimize implant design, manufacturing and surgical procedures for a relatively new metal on metal hip resurfacing prostheses of larger diameters to have lower friction and wear, better fixation and reduced risk of dislocation.

Transforming growth factor β 3 causes decreased HaCaT cell alignment to extracellular matrix proteins Fibronectin, Laminin and Collagen type I as a result of an enhanced migratory phenotype

Abstract: There has been much focus on the role of transforming growth factor β (TGFβ) and more spicifically TGFβ3 in wound healing, with a variety of cell types being studied. There is however, little understanding of the actions of TGFβ3 and how this particular isoforms mediates its scarless healing effects. Studying cellular responses to different extracellular matrix proteins enables the identification of candidate integrins that may be up/down regulated in response to such growth factors. In this study, microcontact printing was used to assess the responses of a human keratinocyte cell line (HaCaT cells) to fibronectin, laminin and collagen type I patterned on glass substrates via microcontact printing and how these responses were changed by treatment with TGFβ3. We demonstrate that HaCaT cell alignment to patterned ECM molecules is decreased by treatment with TGFβ3 and that this response is mediated by an increased keratinocyte migration associated with an enhanced deposition of laminin onto the culture substrate.