Boufana B.,University of Salford |
Boufana B.,University of Benghazi |
Lett W.,University of Salford |
Lahmar S.,Parasitology Laboratory |
And 13 more authors.
Journal of Helminthology | Year: 2015
Canids, particularly dogs, constitute the major source of cystic echinococcosis (CE) infection to humans, with the majority of cases being caused by Echinococcus granulosus (G1 genotype). Canine echinococcosis is an asymptomatic disease caused by adult tapeworms of E. granulosus sensu lato (s.l.). Information on the population structure and genetic variation of adult E. granulosus is limited. Using sequenced data of the mitochondrial cytochrome c oxidase subunit 1 (cox1) we examined the genetic diversity and population structure of adult tapeworms of E. granulosus (G1 genotype) from canid definitive hosts originating from various geographical regions and compared it to that reported for the larval metacestode stage from sheep and human hosts. Echinococcus granulosus (s.s) was identified from adult tapeworm isolates from Kenya, Libya, Tunisia, Australia, China, Kazakhstan, United Kingdom and Peru, including the first known molecular confirmation from Gaza and the Falkland Islands. Haplotype analysis showed a star-shaped network with a centrally positioned common haplotype previously described for the metacestode stage from sheep and humans, and the neutrality indices indicated population expansion. Low Fst values suggested that populations of adult E. granulosus were not genetically differentiated. Haplotype and nucleotide diversities for E. granulosus isolates from sheep and human origin were twice as high as those reported from canid hosts. This may be related to self-fertilization of E. granulosus and/or to the longevity of the parasite in the respective intermediate and definitive hosts. Improved nuclear single loci are required to investigate the discrepancies in genetic variation seen in this study. © Cambridge University Press 2015.
Alwahdi F.A.M.,University of Omar Almukhtar |
Kapoor A.,Swinburne University of Technology |
Franklin F.J.,Northumbria University
Wear | Year: 2013
Ductile materials commonly exhibit plastic deformation at and near the contact surface and their flow behaviour at large strain has a clear effect on wear resistance. These materials almost always fail while under high levels of compression, but behaviour under these conditions cannot be investigated by standard materials tests at atmospheric pressure. In this work, the characteristics of the near-surface region of one new and four used rails are examined using samples from rails which have been in service in the UK. The results are presented as stress-strain response curves from the materials under high hydrostatic compression conditions, which are typical of rail-wheel contacts. In addition, shear strain and hardness variation with depth below the worn rail surface are presented, along with micrographs of the sites examined. A thin white surface layer, frequently called white etching layer (WEL), with high hardness (up to 1040HV) was observed on the surface of one of the used rails. These results have application in the modelling of rail failure by wear and in modelling rolling contact fatigue crack initiation, and can therefore be used to improve rail maintenance planning and risk assessments. © 2013 Elsevier B.V.