The effect of counterface roughness on the wear of conventional gamma-sterilized, and electron-beam-crosslinked ultrahigh molecular weight polyethylene was studied with a circularly translating pin-on-disk device. The counterfaces, CoCr disks, were either polished, or roughened so that they represented the type of roughening and the range of surface roughness values (R(a) = 0.014-0.24 microm) o...

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The smaller acetabular components used in total hip replacement may have a polyethylene liner that is too thin, resulting in higher polyethylene stress and an increased potential for wear. The authors present a case that highlights the problem of acute polyethylene fracture. To compensate for the thinness of the polyethylene, the authors recommend the use of a smaller head size to allow polyeth...

Cross-linked polyethylene has been explored as an alternative to conventional polyethylene in total joint replacement in order to reduce wear volume and decrease failure through polyethylene wear debris induced osteolysis [1]. Due to the demands of a total knee replacement, moderately cross-linked polyethylene is recommended to retain mechanical properties [2]. This study aims to investigate th...

polyethylene is a synthetic polymer which is used in our daily life for different purposes. increased use of polyethylene causes severe environmental problems. there are different methods to decrease problem caused by polyethylene for example source reduction, incineration and land filling and all of them have their own drawbacks. so, the best way to reduce the problem caused by polyethylene is...

In cooperative games, a key question is to find a division of payoffs to coalition members in a fair manner. Nucleolus is one of such solution concepts that provides a stable solution for the grand coalition. We study the computation of the nucleolus of a number of cooperative games, including fractional matching games and fractional edge cover games on general weighted graphs, as well as verte...

Inside Cover: Biaxial melt-drawing of blend films composed ultrahigh molecular weight polyethylene (UHMW-PE) and normal (NMW-PE) produce a unique network structure consisting 30 nm thick homogeneous folded chain crystals. Subsequent biaxial solid-drawing produces nanoporous covering large area the membrane surface (120 mm × 120 mm). Consistence porousness robustness is highly desirable for vari...

Motivated by the need for succinct representations of all “small” transversals (or hitting sets) of a hypergraph of fixed rank, we study the complexity of computing such a representation. Next, the existence of a minimal hitting set of at least a given size arises as a subproblem. We give one algorithm for hypergraphs of any fixed rank, and we largely improve an earlier algorithm (by H. Fernau,...

Article history: Received 21 October 2013 Received in revised form 30 September 2014 Accepted 21 October 2014 Available online 28 October 2014 Communicated by G. Ausiello

The main objective of this work was to analyze the microclimate generated inside a low tunnel (floating row cover) installed in an Almería-type greenhouse. Low tunnels are commonly used open field protect plants against insect attack and improve production muskmelon strawberry. Floating covers can also be greenhouses during first few weeks after transplantation watermelon crops spring-summer cy...