The optimal path cover problem is to find a minimum number of vertex disjoint paths which together cover all the vertices of the graph. Finding an optimal path cover for an arbitrary graph is known to be NP-complete [3]. However, polynornial-time algorithms exist for trees [4], cacti [4] and for interval graphs [9]. The solution presented in [2] For circular-arc graphs is known to be wrong. In ...

STUDY DESIGN This is a retrospective study comparing polyethylene wear between ceramic ball heads and metal ball heads in total hip arthroplasty. BACKGROUND The ceramic-on-polyethylene bearing option has been introduced as an alternative to metal-on-polyethylene to minimize polyethylene wear debris and reduce subsequent osteolysis and aseptic loosening. However, the reported data were debatab...

Polyethylene is widely used as a packing material for different purposes of human life. Accumulation of polyethylene in the environment may cause ecological threat. To prevent the accumulation of polyethylene in the environment, a total of seven actinomycetes were isolated from Koringa Mangrove sediments, near Kakinada, Andhra Pradesh. These isolates were able to grow on mineral salts medium co...

Apple growers face new challenges to produce organic apples and now many cover orchards with high-density polyethylene (HDPE) nets to exclude insects, rather than spraying insecticides. However, rainwater- associated wetness favours the development of apple scabs, Venturia inaequalis, whose lesions accumulate on the leaves and fruit causing unsightly spots. Treating the nets with a superhydroph...

Polyethylene/nanoclay specimens containing from 0 to 5% nanoclays were prepared from a commercially available premixed PE/nanoclay masterbatch containing 50%wt of nanoclay. The masterbatch was diluted to the desired concentration by adding PE along with various amounts of compatibilizer in order to achieve the best possible dispersion of the nanoclay platelets. The dielectric response of the co...

Chloropicrin (CP) is highly volatile and may pose strong exposure risks for humans and the environment. A gelatin capsule formulation was developed to reduce atmospheric CP emissions and to improve application safety. The objective of this study was to determine the distribution, atmospheric emissions, and soil residual of CP after application in gelatin capsules to soil columns. Two treatments...

The long-term durability of polyethylene lining total hip arthroplasty (THA) mainly depends on periprosthetic osteolysis due to wear particles, especially in young active patients. In hip simulator study, reports revealed significant wear reduction of the alumina ceramic-on-polyethylene articulation of THA compared with metal-on-polyethylene bearing surfaces. However, medium to long-term clinic...

Geopersia is published biannually by the College of Science, University of Tehran, Iran. The College of Science published Journal of Science, which covered all fields of basic science, from 1968 to 2010. It was then decided that the College’s journals should be more specialized, and hence publication of Geopersia was launched. Articles printed in Geopersia will be available online too. Aims an...

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