93,986 research outputs found

    London 2012 and the impact of the UK’s Olympic and Paralympic legislation: protecting commerce or preserving culture?

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    The general commercial rights associated with the Olympic Movement are protected in the UK by the Olympic Symbols etc (Protection) Act 1995. In addition, the UK Government, in response to a requirement of the Host City Contract with the International Olympic Committee, created the London Olympic Association Right under section 33 and Schedule 4 of the London Olympic and Paralympic Games Act 2006. These provisions enable the London Organising Committee of the Olympic Games to exploit, to the fullest extent, the commercial rights associated with the London Olympic Games. This article questions whether the IOC’s requirement for legislative protection and state enforcement of the commercial rights are compatible with the Fundamental Principles of Olympism as defined in the Olympic Charter, and its stated aim of being a celebration of sporting endeavour, culture and education

    Mechanical properties and thermomechanical behaviour of poly (ethylene-co-vinyl acetate) based shape memory polymer composites

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    Shape memory polymers (SMPs) are an emerging class of intelligent material that can program in to a temporary shape and recover to its original by exposing to a particular external stimulus. Poly (ethyleneco-vinyl acetate) (EVA) is one of the commercial polymers, which has been used to produce SMPs activated by heat. However, its low mechanical properties, low recovery stress and flexible behaviour restrict the potential applications under robust conditions. Herein, we developed a series of EVA based shape memory polymer composites (SMPCs) with glass fibre, carbon fibre and multi-walled carbon nanotube reinforcements. The effects of different reinforcements on tensile strength have been investigated. Moreover, the dynamic mechanical analysis has been carried out to characterize the glass transition temperature. The shape memory performance of the neat SMP and SMPCs were examined by measuring the angle recovery of 90° bended strips. Subsequently, the shape fixity and recovery ratios of the samples were calculated. This paper presents the manufacturing methods and performance of the fibre and particle reinforced EVA based SMPCs. The inclusion of reinforcements have enhanced the applicability of EVA based SMPCs in wider range of engineering application. In this paper the applicability of such SMPCs for machine elements are deliberated. Accordingly, a conceptual design of a SMPC made mechanical coupler is presented

    X-ray spectroscopy of the IP PQ Gem

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    Using RXTE and ASCA data, we investigate the roles played by occultation and absorption in the X-ray spin pulse profile of the intermediate polar PQ Gem. From the X-ray light curves and phase-resolved spectroscopy, we find that the intensity variations are the result of a combination of varying degrees of absorption and the accretion regions rotating behind the visible face of the white dwarf. These occultation and absorption effects are consistent with those expected from the accretion structures calculated from optical polarization data. We can reproduce the changes in absorber covering fraction either from geometrical effects, or by considering that the material in the leading edge of the accretion curtain is more finely fragmented than in other parts of the curtain. We determine a white dwarf mass of ∼ 1.2 using the RXTE data

    Defined mutations in the 5' nontranslated sequence of Sindbis virus RNA

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    We have constructed 24 deletion mutants which contain deletions of from 1 to 15 nucleotides in the 5' nontranslated region of Sindbis virus RNA and tested the effect of these mutations on virus replication. The results showed that the first 44 nucleotides, which are capable of forming a hairpin structure, are important for virus replication, as all deletions tested in this region were either lethal or resulted in virus that grew poorly in comparison to the parental virus. Many of these deletions had different effects in mosquito cells than in chicken cells, suggesting that cellular factors, presumably proteins, bind to this region. This domain may function in at least two processes in viral replication. It seems likely that in the minus strand, this sequence element is bound by the viral replicase and promotes RNA replication. In the plus strand, this element may modulate initiation of translation of the nonstructural proteins. The results suggest that the hairpin structure itself is important. All deletions within it had deleterious effects on virus replication, and in particular, deletion of one of the G residues at nucleotide 7 or 8 or of one of the C residues at nucleotide 36 or 37 which are theoretically base-paired with these G's resulted in temperature-sensitive viruses that behaved very similarly. In contrast, large deletions between the 44-nucleotide hairpin and the translation start site at nucleotides 60 to 62 resulted in virus that grew as well as or better than the parental virus in both chicken and mosquito cells. The A residue at position 5 of the HRSP strain used was examined in more detail. Deletion of this A was lethal, whereas substitution by G resulted in a virus that grew poorly, despite the fact that G is present at position 5 in the AR339 parent of HRSP. U at position 5 resulted in a virus that grew less well than the A5 strain but better than the G5 mutant

    Mutagenesis of the conserved 51-nucleotide region of Sindbis virus

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    We have constructed 25 site-specific mutations in a domain of 51 nucleotides in Sindbis virus that is highly conserved among all alphaviruses sequenced to date. These 51 nucleotides are capable of forming two hairpin structures and are found from nucleotides 155 to 205 in Sindbis virus within the region encoding nsP1. Of the mutations, 21 were silent and did not lead to a change in the amino acid sequence encoded. These silent mutations changed not only the linear sequence but also the stability of the hairpins in most cases. Two double mutants that were constructed led to the replacement of one base pair by another so that the linear sequence was altered but the nature of the hairpins was not. All of the mutants with silent mutations were viable, but 19 of the 21 mutants were severely impaired for growth in both chicken and mosquito cells. Compared with the parental virus, they grew slowly and produced virus at rates of 10(-1) to 10(-4) times the parental rate. Surprisingly, however, the plaques produced by these mutants were indistinguishable from those produced by the parental virus. Two of the silent mutations, found within the first hairpin structure, produced virus at a faster rate than the parental virus. It is clear that the exact sequence of this region is important for some aspect of virus replication. We suggest that one or more proteins, either virus encoded or cellular, bind to the hairpin structures in a sequence-specific fashion in a step that promotes replication of the viral RNA. Of the mutations that resulted in a change of coding, only one of four was viable, suggesting that the amino acid sequence encoded in this domain is essential for virus replication

    Spike frequency adaptation affects the synchronization properties of networks of cortical oscillators

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    Oscillations in many regions of the cortex have common temporal characteristics with dominant frequencies centered around the 40 Hz (gamma) frequency range and the 5–10 Hz (theta) frequency range. Experimental results also reveal spatially synchronous oscillations, which are stimulus dependent (Gray&Singer, 1987;Gray, König, Engel, & Singer, 1989; Engel, König, Kreiter, Schillen, & Singer, 1992). This rhythmic activity suggests that the coherence of neural populations is a crucial feature of cortical dynamics (Gray, 1994). Using both simulations and a theoretical coupled oscillator approach, we demonstrate that the spike frequency adaptation seen in many pyramidal cells plays a subtle but important role in the dynamics of cortical networks. Without adaptation, excitatory connections among model pyramidal cells are desynchronizing. However, the slow processes associated with adaptation encourage stable synchronous behavior
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