Browsing by Author "Akbulut, H"

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    Elastic-plastic stress analysis and plastic zone propagation in fibre-reinforced thermoplastic laminates using finite element method
    Aykul, H; Atas, C; Akbulut, H
    The results of a study of elastic-plastic stress analysis and plastic zone propagation in a low density polyethylene thermoplastic composite plate subjected to uniform transverse load are presented. Thermoplastic matrix, polyethylene (LDPE), and steel fibres were used to fabricate the composite plates. Yield points and elastic, elastic-plastic and residual stresses are calculated numerically for both symmetric and antisymmetric laminated plates with different ply orientations by using Finite Element Method. First order shear deformation theory was used as an equivalent single-layer laminate theory for small deformations. Contour plots corresponding to 100, 150 and 200 load steps display the expansion of the plastic zone. Mechanical properties of a layer were obtained experimentally.
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    Elasto-plastic stress analysis of aluminum metal-matrix composite laminated plates under in-plane loading
    Sayman, O; Akbulut, H; Meriç, C
    The study presents an elasto-plastic stress analysis of symmetric and antisymmetric cross-ply, angle-ply laminated metal-matrix composite plates. Long stainless steel fiber reinforced aluminum metal-matrix composite layer is manufactured by using moulds under the action of 30 MPa pressure and heating up to 600 degrees C. A laminated plate consists of four metal-matrix layers bonded symmetrically or antisymmetrically. The first-order shear deformation theory and nine-node Lagrangian finite element is used. The in-plane load is increased gradually. (C) 2000 Elsevier Science Ltd. All rights reserved.
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    WNT1 gene expression alters in heterogeneous population of prostate cancer cells; decreased expression pattern observed in CD133+/CD44+ prostate cancer stem cell spheroids
    Goksel, G; Bilir, A; Uslu, R; Akbulut, H; Guven, U; Oktem, G
    Purpose: Established cancer cell lines contain cancer stem cells (CSCs) which can propagate to form three dimensional (3D) tumor spheroids in vitro. Aberrant activation of WNT signaling is strongly implicated in the progression of cancer and controls CSCs properties. In this study we hypothesized that when cells were maintained as spheroids, the structure of CSCs could show differentiation between CSCs and non-CSCs. Methods: CD133(+)/CD44(+) cancer-initiating cells were isolated from DU-145 human prostate cancer cell line monolayer cultures, propagated as tumor spheroids and compared with the remaining heterogeneous cancer cells bulk population. The expression levels of WNT1, FZD1, ADAR, APC, AXIN, BTRC, FRAT1 and PPARD genes were measured by polymerase chain reaction (PCR) array assay and the protein expression levels of WNT1, FZD and AXIN by immunohistochemistry. Results: The expression levels of WNT pathway-related molecules were found to increase in both CSCs and non-CSCs when CSCs were maintained as spheroids. However, different expression profiles were observed when CSCs and non-CSCs were compared. In spheroids, the expression levels of FZD1, APC, ADAR, WNT1, PPARD genes in CSCs decreased when compared to non-CSCs. Interestingly, when CSCs from spheroids were compared with CSCs from monolayers the most significant decrease was observed in FZD1 and increase in APC genes. Conclusion: It is possible to assume that intracellular signaling of WNT-related molecules in the nucleus and/or cytoplasm might play an important role but it is independent from increased ligand expression and this expression strongly differentiate CSCs and non-CSCs population. This unexpected expression could be important for CSCs behavior and targeting this pathway could have therapeutic implications in cancer.