2,423 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

    A Novel Sequence-Based Antigenic Distance Measure for H1N1, with Application to Vaccine Effectiveness and the Selection of Vaccine Strains

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    H1N1 influenza causes substantial seasonal illness and was the subtype of the 2009 influenza pandemic. Precise measures of antigenic distance between the vaccine and circulating virus strains help researchers design influenza vaccines with high vaccine effectiveness. We here introduce a sequence-based method to predict vaccine effectiveness in humans. Historical epidemiological data show that this sequence-based method is as predictive of vaccine effectiveness as hemagglutination inhibition (HI) assay data from ferret animal model studies. Interestingly, the expected vaccine effectiveness is greater against H1N1 than H3N2, suggesting a stronger immune response against H1N1 than H3N2. The evolution rate of hemagglutinin in H1N1 is also shown to be greater than that in H3N2, presumably due to greater immune selection pressure.Comment: 26 pages, 7 figures, 2 tables, supplemen

    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

    New azasilatranes: sterically induced transannular bond weakening and cleavage

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    Silylation of azasilatrane I (R = R1 = R2 = H) with ClSiMe3/NEt3 gives disilylated I (R = R1 = Me3Si, R2 = H) (II), via the spectroscopically detected monosilylated intermediate. Treatment of II with BuLi gives the stable lithiated deriv. I (R = R1 = Me3Si, R2 = Li) which can be converted to I [R = R1 = Me3Si, R2 = Me, Me3Si (III)], via reaction with MeI or ClSiMe3, resp. The novel structure of III, inferred from NMR data and confirmed by x-ray means, features an Nax nitrogen in a nearly trigonal pyramidal stereochem. with an exceptionally long NaxSi bond [ 2.775(7)?]. Reaction of III with MeOSO2CF3 gives IV, the Nax methylated product

    New azasilatranes: bidentate and tridentate coordination modes of the novel ligand EtOSi(Ph2PNCH2CH2)2(HNCH2CH2)N

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    The synthesis and characterization of EtOSi(Ph2PNCH2CH)2(HNCH2CH2)N (ethoxy-N,N'·bis(di-phenylphosphino)azasilatrane, the title compound 3b) is reported. Its reactions with sulfur and MeI proceed easily via quaternization at the phosphorus sites to give the bis(phosphonium) salt and the bis(phosphine) sulfide, respectively. Synthesis and characterization of the coordination compounds (3b) Ni(CO)2, (3b) PtCl2, (3b) M(CO)4 (M = Mo, W), and (3b) M(CO)3 (M = Mo, W) give evidence for the existence of two possible coordination modes; one wherein 3b behaves as a bidentate (P,P') ligand and the other as a tridentate (P,P',O) ligand. The latter coordination mode provides a rare example of coordination of a silyl ether to a transition metal. NMR spectroscopic studies in solution and the solid state establish the presence of transannular Si-N bonding and hypercoordination at silicon. Solid-state 31P NMR spectra give direct evidence for the presence of a twisted, helically chiral conformation of the silatranyl cage, which in solution is lost as a consequence of rapid conformational mobility on the NMR time scale. These findings are further corroborated by the results of crystal structure determinations of the bis(phosphine) sulfide and (3b) PtCl2

    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
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