6,404 research outputs found

    Representations of the Necklace Braid Group: Topological and Combinatorial Approaches

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    The necklace braid group NBn is the motion group of the n+1 component necklace link Ln in Euclidean R3. Here Ln consists of n pairwise unlinked Euclidean circles each linked to an auxiliary circle. Partially motivated by physical considerations, we study representations of the necklace braid group NBn, especially those obtained as extensions of representations of the braid group Bn and the loop braid group LBn. We show that any irreducible Bn representation extends to NBn in a standard way. We also find some non-standard extensions of several well-known Bn-representations such as the Burau and LKB representations. Moreover, we prove that any local representation of Bn (i.e., coming from a braided vector space) can be extended to NBn, in contrast to the situation with LBn. We also discuss some directions for future study from categorical and physical perspectives

    The significance of hazardous chemicals in wastewater treatment works effluents

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    This is the post-print version of the final paper published in Science of The Total Environment. The published article is available from the link below. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. Copyright @ 2012 Elsevier B.V.The advent of increasingly stringent and wider ranging European Union legislation relating to water and the environment has required regulators to assess compliance risk and to respond by formulating appropriate pollution control measures. To support this process the UK Water Industry has completed a national Chemicals Investigation Programme (CIP), to monitor over 160 wastewater treatment works (WwTWs) for 70 determinands. Final effluent concentrations of zinc, polynuclear aromatic hydrocarbons (fluoranthene, benzo(a)pyrene, benzo(b)fluoranthene, benzo(k)fluoranthene, benzo(g,h,i)perylene and indeno(1,2,3-cd)pyrene), “penta” congeners (BDEs) 47 and 99, tributyltin, triclosan, erythromycin, oxytetracycline, ibuprofen, propranolol, fluoxetine, diclofenac, 17β-estradiol and 17α-ethinyl estradiol exceeded existing or proposed Environmental Quality Standards (EQSs) in over 50% of WwTWs. Dilution by receiving water might ensure compliance with EQSs for these chemicals, apart from the BDEs. However, in some cases there will be insufficient dilution to ensure compliance and additional management options may be required

    Adaptability among science teachers in schools: A multi-nation examination of its role in school outcomes

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    Adaptability helps teachers to navigate change, novelty, and uncertainty at work. We sought to extend understanding of adaptability by considering it at the school-level in 2189 high schools across eight nations. We investigated whether two job demands (disruptive student behavior, student diversity) and a job resource (teacher collaboration) are associated with school-average teacher adaptability. We also examined the association that school-average teacher adaptability has with teacher self-efficacy and, in turn, student self-efficacy. Findings showed, for example, that greater school-average teacher adaptability was positively associated with teacher self-efficacy and, in turn, student self-efficacy. Findings were similar across the eight nations

    Stellar Disk Truncations: Where do we stand ?

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    In the light of several recent developments we revisit the phenomenon of galactic stellar disk truncations. Even 25 years since the first paper on outer breaks in the radial light profiles of spiral galaxies, their origin is still unclear. The two most promising explanations are that these 'outer edges' either trace the maximum angular momentum during the galaxy formation epoch, or are associated with global star formation thresholds. Depending on their true physical nature, these outer edges may represent an improved size characteristic (e.g., as compared to D_25) and might contain fossil evidence imprinted by the galaxy formation and evolutionary history. We will address several observational aspects of disk truncations: their existence, not only in normal HSB galaxies, but also in LSB and even dwarf galaxies; their detailed shape, not sharp cut-offs as thought before, but in fact demarcating the start of a region with a steeper exponential distribution of starlight; their possible association with bars; as well as problems related to the line-of-sight integration for edge-on galaxies (the main targets for truncation searches so far). Taken together, these observations currently favour the star-formation threshold model, but more work is necessary to implement the truncations as adequate parameters characterising galactic disks.Comment: LaTeX, 10 pages, 6 figures, presented at the "Penetrating Bars through Masks of Cosmic Dust" conference in South Africa, proceedings published by Kluwer, and edited by Block, D.L., Freeman, K.C., Puerari, I., & Groess, R; v3 to match published versio

    Posterior Bearing Overhang Following Medial and Lateral Mobile Bearing Unicompartmental Knee Replacements

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    This study explores the extent of bearing overhang following mobile bearing Oxford unicompartmental knee replacement (OUKR) (Oxford Phase 3, Zimmer Biomet). The Oxford components are designed to be fully congruent, however knee movements involve femoral rollback, which may result in bearing overhang at the posterior margin of the tibial implant, with potential implications for; pain, wear, and dislocation. Movement is known to be greater, and therefore posterior overhang more likely to occur, with; lateral compared to medial implants, anterior cruciate ligament deficiency, and at extremes of movement. 24 medial, and 20 domed lateral, OUKRs underwent sagittal plane knee fluoroscopy during step‐up and forward lunge exercises. The bearing position was inferred from the relative position of the femoral and tibial components. Based on the individual component sizes and geometry the extent the posterior part of the bearing which overhung the posterior part of the tibial component was calculated. There was no significant posterior overhang in knees with medial implants. Knees with lateral domed implants exhibited overhang at flexion angles beyond 60°, the magnitude of which increased with increasing flexion angle, reaching a maximum of 50% of the bearing length at 140° (range 0‐140°). This demonstrates a clear difference between the kinematics, and prevalence and extent of posterior bearing overhang between medial and lateral OUKRs

    Characterising hyperinsulinaemia induced insulin resistance in human skeletal muscle cells

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    Hyperinsulinaemia potentially contributes to insulin resistance in metabolic tissues, such as skeletal muscle. The purpose of these experiments was to characterise glucose uptake, insulin signalling and relevant gene expression in primary human skeletal muscle-derived cells (HMDCs), in response to prolonged insulin exposure (PIE) as a model of hyperinsulinaemia-induced insulin resistance. Differentiated HMDCs from healthy human donors were cultured with or without insulin (100 nM) for 3 days followed by an acute insulin stimulation. HMDCs exposed to PIE were characterised by impaired insulin-stimulated glucose uptake, blunted IRS-1 phosphorylation (Tyr612) and Akt (Ser473) phosphorylation in response to an acute insulin stimulation. Glucose transporter 1 (GLUT1), but not GLUT4, mRNA and protein increased following PIE. The mRNA expression of metabolic (PDK4) and inflammatory markers (TNF-α) was reduced by PIE but did not change lipid (SREBP1 and CD36) or mitochondrial (UCP3) markers. These experiments provide further characterisation of the effects of PIE as a model of hyperinsulinaemia-induced insulin resistance in HMDCs
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