709 research outputs found
Attendance of MSM at Genitourinary Medicine services in England: implications for selective HPV vaccination programme (a short communication)
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
New Analysis of the Delta I = 1/2 Rule in Kaon Decays and the B_K Parameter
We present a new analysis of the Delta I = 1/2 rule in K --> pi pi decays and
the B_K parameter. We use the 1/N_c expansion within the effective chiral
lagrangian for pseudoscalar mesons and compute the hadronic matrix elements at
leading and next-to-leading order in the chiral and the 1/N_c expansions.
Numerically, our calculation reproduces the dominant Delta I = 1/2 K --> pi pi
amplitude. Our result depends only moderately on the choice of the cutoff scale
in the chiral loops. The Delta I = 3/2 amplitude emerges sufficiently
suppressed but shows a significant dependence on the cutoff. The B_K parameter
turns out to be smaller than the value previously obtained in the 1/N_c
approach. It also shows a significant dependence on the choice of the cutoff
scale. Our results indicate that corrections from higher order terms and/or
higher resonances are large for the Delta I = 3/2 K --> pi pi amplitude and the
(|Delta S| = 2) K^0 -- anti K^0 transition amplitude.Comment: 50 pages, LaTeX, 13 eps figure
Analyzing epsilon'/epsilon in the 1/N_c Expansion
We present a recent analysis of epsilon'/epsilon in the 1/N_c expansion. We
show that the 1/N_c corrections to the matrix element of Q_6 are large and
positive, indicating a Delta I=1/2 enhancement similar to the one of Q_1 and
Q_2 which dominate the CP conserving amplitude. This enhances the CP ratio and
can bring the standard model prediction close to the measured value for central
values of the parameters.Comment: One reference corrected. 5 pages, talk presented by P.H. Soldan at
the 3. International Conference on B Physics and CP Violation, Taipei,
Taiwan, December 3 - 7, 1999. Slightly expanded version of the article
submitted to the proceeding
Interpretation of runaway electron synchrotron and bremsstrahlung images
The crescent spot shape observed in DIII-D runaway electron synchrotron
radiation images is shown to result from the high degree of anisotropy in the
emitted radiation, the finite spectral range of the camera and the distribution
of runaways. The finite spectral camera range is found to be particularly
important, as the radiation from the high-field side can be stronger by a
factor than the radiation from the low-field side in DIII-D. By
combining a kinetic model of the runaway dynamics with a synthetic synchrotron
diagnostic we see that physical processes not described by the kinetic model
(such as radial transport) are likely to be limiting the energy of the
runaways. We show that a population of runaways with lower dominant energies
and larger pitch-angles than those predicted by the kinetic model provide a
better match to the synchrotron measurements. Using a new synthetic
bremsstrahlung diagnostic we also simulate the view of the Gamma Ray Imager
(GRI) diagnostic used at DIII-D to resolve the spatial distribution of
runaway-generated bremsstrahlung.Comment: 21 pages, 11 figure
Ultracold collisions involving heteronuclear alkali metal dimers
We have carried out the first quantum dynamics calculations on ultracold
atom-diatom collisions in isotopic mixtures. The systems studied are
spin-polarized 7Li + 6Li7Li, 7Li + 6Li2, 6Li + 6Li7Li and 6Li + 7Li2. Reactive
scattering can occur for the first two systems even when the molecules are in
their ground rovibrational states, but is slower than vibrational relaxation in
homonuclear systems. Implications for sympathetic cooling of heteronuclear
molecules are discussed.Comment: 4 pages, 3 figure
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