2,042 research outputs found

    Host–Guest Complex of β-Cyclodextrin and Disulfide Form of 4-Aminothiophenol

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    An inclusion complex of β-cyclodextrin and 4-aminothiophenol was assembled by hydrophobic interaction of the host (β-cyclodextrin) and guest (4-aminothiophenol). The complex was isolated as crystalline solid and studied by single crystal X-ray diffraction method along with NMR and IR spectroscopy. Two cyclodextrin rings each containing one disulfide form of 4-aminothiophenol were found to pair up by hydrogen bonding of the outer rim -OH groups. The phenyl disulfide moiety of 4-aminophenyl disulfide molecule was found in the core of β-cyclodextrin, while the amino functional groups were positioned to the exterior of the cyclodextrin ring. Phenyl rings of the guest molecule from each partner of the paired cyclodextrin complex were found parallel to each other, indicating possible π-π stacking interaction between them

    Levonorgestrel-releasing intrauterine system vs. usual medical treatment for menorrhagia: An economic evaluation alongside a randomised controlled trial

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    Objective: To undertake an economic evaluation alongside the largest randomised controlled trial comparing Levonorgestrel-releasing intrauterine device ('LNG-IUS') and usual medical treatment for women with menorrhagia in primary care; and compare the cost-effectiveness findings using two alternative measures of quality of life. Methods: 571 women with menorrhagia from 63 UK centres were randomised between February 2005 and July 2009. Women were randomised to having a LNG-IUS fitted, or usual medical treatment, after discussing with their general practitioner their contraceptive needs or desire to avoid hormonal treatment. The treatment was specified prior to randomisation. For the economic evaluation we developed a state transition (Markov) model with a 24 month follow-up. The model structure was informed by the trial women's pathway and clinical experts. The economic evaluation adopted a UK National Health Service perspective and was based on an outcome of incremental cost per Quality Adjusted Life Year (QALY) estimated using both EQ-5D and SF-6D. Results: Using EQ-5D, LNG-IUS was the most cost-effective treatment for menorrhagia. LNG-IUS costs £100 more than usual medical treatment but generated 0.07 more QALYs. The incremental cost-effectiveness ratio for LNG-IUS compared to usual medical treatment was £1600 per additional QALY. Using SF-6D, usual medical treatment was the most cost-effective treatment. Usual medical treatment was both less costly (£100) and generated 0.002 more QALYs. Conclusion: Impact on quality of life is the primary indicator of treatment success in menorrhagia. However, the most costeffective treatment differs depending on the quality of life measure used to estimate the QALY. Under UK guidelines LNG-IUS would be the recommended treatment for menorrhagia. This study demonstrates that the appropriate valuation of outcomes in menorrhagia is crucial. Copyright: © 2014 Sanghera et al

    Burst avalanches in solvable models of fibrous materials

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    We review limiting models for fracture in bundles of fibers, with statistically distributed thresholds for breakdown of individual fibers. During the breakdown process, avalanches consisting of simultaneous rupture of several fibers occur, and the distribution D(Δ)D(\Delta) of the magnitude Δ\Delta of such avalanches is the central characteristics in our analysis. For a bundle of parallel fibers two limiting models of load sharing are studied and contrasted: the global model in which the load carried by a bursting fiber is equally distributed among the surviving members, and the local model in which the nearest surviving neighbors take up the load. For the global model we investigate in particular the conditions on the threshold distribution which would lead to anomalous behavior, i.e. deviations from the asymptotics D(Δ)∼Δ−5/2D(\Delta) \sim \Delta^{-5/2}, known to be the generic behavior. For the local model no universal power-law asymptotics exists, but we show for a particular threshold distribution how the avalanche distribution can nevertheless be explicitly calculated in the large-bundle limit.Comment: 28 pages, RevTeX, 3 Postscript figure

    Gradient Clogging in Depth Filtration

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    We investigate clogging in depth filtration, in which a dirty fluid is ``cleaned'' by the trapping of dirt particles within the pore space during flow through a porous medium. This leads to a gradient percolation process which exhibits a power law distribution for the density of trapped particles at downstream distance x from the input. To achieve a non-pathological clogging (percolation) threshold, the system length L should scale no faster than a power of ln w, where w is the width. Non-trivial behavior for the permeability arises only in this extreme anisotropic geometry.Comment: 4 pages, 3 figures, RevTe

    Signatures of exciton coupling in paired nanoemitters

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    An exciton formed by the delocalized electronic excitation of paired nanoemitters is interpreted in terms of the electromagnetic emission of the pair and their mutual coupling with a photodetector. A formulation directly tailored for fluorescence detection is identified, giving results which are strongly dependent on geometry and selection rules. Signature symmetric and antisymmetric combinations are analyzed and their distinctive features identified

    Historical geography II: traces remain

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    The second report in this series turns to focus on the trace in relation to life-writing and biography in historical geography and beyond. Through attention to tracing journeys, located moments and listening to the presence of ghosts (Ogborn, 2005), this report seeks to highlight the range of different ways in which historical geographers have explored lives, deaths, and their transient traces through varied biographical terrains. Continuing to draw attention in historical geography to the darkest of histories, this piece will pivot on moments of discovering the dead to showcase the nuanced ways in which historical geography is opening doors into uncharted lives and unspoken histories

    Failure due to fatigue in fiber bundles and solids

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    We consider first a homogeneous fiber bundle model where all the fibers have got the same stress threshold beyond which all fail simultaneously in absence of noise. At finite noise, the bundle acquires a fatigue behavior due to the noise-induced failure probability at any stress. We solve this dynamics of failure analytically and show that the average failure time of the bundle decreases exponentially as the stress increases. We also determine the avalanche size distribution during such failure and find a power law decay. We compare this fatigue behavior with that obtained phenomenologically for the nucleation of Griffith cracks. Next we study numerically the fatigue behavior of random fiber bundles having simple distributions of individual fiber strengths, at stress less than the bundle's strength (beyond which it fails instantly). The average failure time is again seen to decrease exponentially as the stress increases and the avalanche size distribution shows similar power law decay. These results are also in broad agreement with experimental observations on fatigue in solids. We believe, these observations regarding the failure time are useful for quantum breakdown phenomena in disordered systems.Comment: 13 pages, 4 figures, figures added and the text is revise
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