48,997 research outputs found

    Process for synthesizing and formulating condensed ring polymers

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    Chemical process for forming low molecular weight, fully cyclized heteroaromatic prepolymers under conditions which limit chain extension or branching is described. Exact procedures used in conducting chemical reaction are defined. Advantages of process over conventional methods are presented

    Method for forming pyrrone molding powders and products of said method

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    The formation of pyrrone resins of the ladder or semiladder structure is described. The technique involves initial formation of fully cyclized prepolymers having an average degree of polymerization of about 1.5, one with acidic terminal groups, another with amine terminal groups. Thereafter the prepolymers are intimately admixed on a 1:1 stoichiometric basis. The resulting powder mixture is molded at elevated pressures and temperatures to form a fully cyclized resin

    Attendance of MSM at Genitourinary Medicine services in England: implications for selective HPV vaccination programme (a short communication)

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    Background Human papillomaviruses (HPV) immunisation programmes for female adolescents in the UK offer relatively little benefit to men who have sex with men (MSM). Targeted HPV vaccination for MSM may reduce the high incidence of HPV-related disease among MSM. We used national data from sexual health clinics to calculate the number of MSM attending these clinics throughout England from 2009 to 2014 and to identify their characteristics, to inform the implementation of a targeted HPV vaccination programme in MSM. Methods We used the Genitourinary Medicine Clinic Activity Dataset (GUMCADv2) to obtain data for men aged 15–70 years who had attended a GUM clinic in England from 2009 to 2014. We analysed both numbers of MSM attending and number of GUM attendances, age at first attendance, ethnicity and geographical area of the clinic in England. Results A total of 374 983 MSM attended sexual health services in England between 2009 and 2014. Median age of presentation was 32 years (IQR 25–41) and showed regional geographical variation. Of all men attending sexual health clinics in England, the highest proportion of those identifying as MSM was in London (21%). Excluding visits within 1 month of an initial attendance, 49% of all MSM re-attended within 12 months and 58% within 24 months. MSM aged ≥36 years reattended more frequently than younger MSM. 51% reattended at least twice within 24 months of initial visit. Conclusions The majority of MSM reattend clinic at least once within a 24-month period, potentially facilitating the delivery of a three-dose HPV vaccination programme. This would reduce the burden on sexual health clinics and cost to local authorities due to extra visits if HPV vaccination were to be delivered through these services

    Variational approximation of flux in conforming finite element methods for elliptic partial differential equations: a model problem

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    We consider the approximation of elliptic boundary value problems by conforming finite element methods. A model problem, the Poisson equation with Dirichlet boundary conditions, is used to examine the convergence behavior of flux defined on an internal boundary which splits the domain in two. A variational definition of flux, designed to satisfy local conservation laws, is shown to lead to improved rates of convergence

    New methods for B meson decay constants and form factors from lattice NRQCD

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    We determine the normalisation of scalar and pseudoscalar current operators made from non-relativistic bb quarks and Highly Improved Staggered light quarks in lattice Quantum Chromodynamics (QCD) through O(αs)\mathcal{O}(\alpha_s) and ΛQCD/mb\Lambda_{\text{QCD}}/m_b. We use matrix elements of these operators to extract BB meson decay constants and form factors, then compare to those obtained using the standard vector and axial-vector operators. This provides a test of systematic errors in the lattice QCD determination of the BB meson decay constants and form factors. We provide a new value for the BB and BsB_s meson decay constants from lattice QCD calculations on ensembles that include uu, dd, ss and cc quarks in the sea and those which have the u/du/d quark mass going down to its physical value. Our results are fB=0.196(6)f_B=0.196(6) GeV, fBs=0.236(7)f_{B_s}=0.236(7) GeV and fBs/fB=1.207(7)f_{B_s}/f_B =1.207(7), agreeing well with earlier results using the temporal axial current. By combining with these previous results, we provide updated values of fB=0.190(4)f_B=0.190(4) GeV, fBs=0.229(5)f_{B_s}=0.229(5) GeV and fBs/fB=1.206(5)f_{B_s}/f_B = 1.206(5).Comment: 14 pages, 10 figure

    The inverse-square law and quantum gravity

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    A program is described which measures the gravitational acceleration of antiprotons. This idea was approached from a particle physics point of view. That point of view is examined starting with some history of physics over the last 200 years

    Element-by-element factorization algorithms for heat conduction

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    Element-by-element solution strategies are developed for transient heat conduction problems. Results of numerical tests indicate the effectiveness of the procedures proposed. The small database requirements and attractive architectural features of the algorithms suggest considerable potential for solving large scale problems
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