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SourceAvailable from: Emilia Kaivosoja[Show abstract] [Hide abstract]
ABSTRACT: The hypothesis of this work was that human bone marrow-derived mesenchymal stem cells (MSCs) are regulated by pulsed electromagnetic fields (PEMFs) and by intracrine conversion of an adrenal prohormone to dihydrotestosterone. The effect of PEMF and dehydroepiandrosterone (DHEA) on viability and osteogenic differentiation of human MSCs and on the viability of osteoblastic SaOS-2 cells was evaluated. It was found that PEMF promoted the viability rate of both cell types, whereas DHEA decreased the viability rate in a concentration-dependent manner. PEMF did not have major effects on osteo-induction at this low seeding density level (3000 cells/cm(2) ). Instead, DHEA, after MSC-mediated and 5α-reductase-dependent conversion to dihydrotestosterone, clearly promoted the osteo-induction of MSCs induced with β-glyserophosphate, ascorbate and dexamethasone. Alkaline phosphatase (ALP), SMAD1, RUNX2, osteopontin (OP) and osteocalcin (OC) RNA levels were increased and alizarin red S- and hydroxyapatite-specific OsteoImage(TM) stainings disclosed a promoted mineralization process. In addition, DHEA increased OP and OC mRNA levels of non-induced MSCs. A sequential use of mitogenic PEMF early during the fracture healing, followed by later administration of DHEA with osteogenic differentiating effect, might be worth subjecting to a randomized clinical trial. Copyright © 2012 John Wiley & Sons, Ltd.Journal of Tissue Engineering and Regenerative Medicine 01/2015; 9(1). DOI:10.1002/term.1612
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ABSTRACT: A numerical approach to modelling contact problems with a unified friction and cohesion interface is formulated. A new nonlinear friction law is suggested for modelling micro-slip of metallic junctions due to contact asperities, and an associated cohesive zone due to adhesion describes the linear portion of the unified total interfacial hysteresis. A variational equality including both the regularized friction and cohesion terms is formulated for the numerical solution of the derived boundary value problem. The suggested modelling technique is readily implementable in the finite element method. There is an application on the representative problem involving the adhesively bonded and significantly normal-stressed contact surface. Macroscopic constitutive relationships between the cyclic tangential load and micro-displacements are established for the set of constant compressive normal loads. The related micromechanical arguments and experimental observations supporting the modelling theory are addressed.European Journal of Mechanics - A/Solids 01/2015; 49:205–213. DOI:10.1016/j.euromechsol.2014.08.002
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ABSTRACT: A power outage brings in economic losses for both the customers and the utilities. Studying these unwanted events and making solid predictions about the outcomes of the interruptions has been an attractive area of interest for the researchers for the last couple of decades. By making use of a customer survey study conducted in Finland, this paper benefits from both the reported cost data collected from customers and from the analytical data that are available and then presents a new hybrid approach to estimate the customer interruption costs of service sector customer segment. Making use of Value Added information of the customers is a common practice for the cost normalization purposes. This paper verifies the approach by comparing the findings of the customer survey and the econometric model suggested here. This study is a unique source in terms of providing a reliable, easy to apply, and a straightforward model for calculating the economic impacts of power outages.International Journal of Electrical Power & Energy Systems 01/2015; 64:588–595. DOI:10.1016/j.ijepes.2014.07.046
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