24,865 research outputs found

    Double minimum in the surface stabilized ferroelectric liquid crystal switching response

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    A double minimum has recently been observed in the time–voltage switching response for a smectic C* liquid crystal layer in the surface stabilized geometry (“Ferroelectric Liquid Crystal Device,” K. P. Lymer and J. C. Jones, U.K. Patent No. GB2338797, 17th June 1999). Liquid crystal continuum theory is used to demonstrate that this unusual switching behavior arises if the equilibrium orientation of the molecular director rotates around the smectic cone as a function of distance through one half of the layer only. The double minimum is shown to evolve for large differences between the ε2 and ε1 components of the smectic C biaxial permittivity tensor

    Molecular footprints of the Holocene retreat of dwarf birch in Britain

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    © 2014 The Authors. Molecular Ecology Published by John Wiley & Sons Ltd. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited

    Comparison of human uterine cervical electrical impedance measurements derived using two tetrapolar probes of different sizes

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    BACKGROUND We sought to compare uterine cervical electrical impedance spectroscopy measurements employing two probes of different sizes, and to employ a finite element model to predict and compare the fraction of electrical current derived from subepithelial stromal tissue. METHODS Cervical impedance was measured in 12 subjects during early pregnancy using 2 different sizes of the probes on each subject. RESULTS Mean cervical resistivity was significantly higher (5.4 vs. 2.8 Ωm; p < 0.001) with the smaller probe in the frequency rage of 4–819 kHz. There was no difference in the short-term intra-observer variability between the two probes. The cervical impedance measurements derived in vivo followed the pattern predicted by the finite element model. CONCLUSION Inter-electrode distance on the probes for measuring cervical impedance influences the tissue resistivity values obtained. Determining the appropriate probe size is necessary when conducting clinical studies of resistivity of the cervix and other human tissues

    The relationships between rugby players’ tackle training attitudes and behaviour and their match tackle attitudes and behaviour

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    Background The tackle event in rugby is a technical and physical contest between opposing players. A player's ability to tolerate and contest during a tackle is a prerequisite for safe participation and success in rugby. Little is known about the relationship between tackle training and tackling in matches in rugby union. Therefore, we investigated the relationships between players’ training attitudes and behaviour and their match attitudes and behaviour for tackling in rugby union. Method A questionnaire was designed to assess attitude (importance) and behaviours (frequency and quantity) among junior (under 19) players on a 5-point Likert Scale. Questionnaires were handed out to 220 players (10 schools) at a tournament and 75% (9 schools, n=164) were returned for analysis. Associations between training attitudes and behaviours were tested using the χ2 test, Cramer's V and τ-b. Results The more time spent on emphasising proper technique to prevent injuries in training, the more important players rated ‘own safety’ (τ-b=0.21, moderate, z=3.1, p<0.01), ‘going for the ball only’ (τ-b=0.27, moderate, z=4.6, p<0.001) and ‘staying on feet’ (τ-b=0.23, moderate, z=3.6, p<0.001) in match play. The more time spent on emphasising proper technique to improve performance in training, the more important players rated actions ‘going for ball only’ (τ-b=0.23, moderate, z=3.7, p<0.001) and ‘preventing the ball carrier from retaining position’ (τ-b=0.20, moderate, z=3.1, p<0.01) in match play. Conclusions This is the first study to report on the relationships between players’ training attitudes and behaviour and their match attitudes and behaviours for tackling in rugby union. The importance of tackle training to prevent injury, and the amount of time spent on technique to prevent injuries, was associated with behaviours that reduce the risk of injury in matches

    Introducing stable microgrooves in to fluid-leaving surface of plastic compressed collagen by embossing

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    Micropatterning of polymers is a technique used in tissue engineering to create additional features on the surface usually to manipulate cell behaviour. However, methods used for fabrication of such features on the surface of synthetic polymers are not always suitable for natural polymers. Here we describe a method of embossing developed for plastic compressed collagen constructs. Plastic compression (PC) of collagen is a technique that allows cell-independent fabrication of dense, tissue-like collagen constructs without compromising viability of resident cells (1). Method of PC creates potential anisotropy of the opposite surfaces – stiffer fluid leaving (closest to the blotting elements) and more elastic non-fluid leaving surface. We hypothesized that embossing into these surfaces will give more stable features on the fluid-leaving surface (FLS) as opposed to non fluid-leaving surface (NFLS). Objectives were to develop methods of embossing onto both surfaces, assess these features and to determine stability of the embossed pattern over time with and without cells. Slow-dissolving phosphate-based glass fibers were used as the embossing template in this study as fiber diameter and spacing is easily controlled
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