2,587 research outputs found
The B Meson Decay Constant from Unquenched Lattice QCD
We present determinations of the B meson decay constant f_B and of the ratio
f_{B_s}/f_B using the MILC collaboration unquenched gauge configurations which
include three flavors of light sea quarks. The mass of one of the sea quarks is
kept around the strange quark mass, and we explore a range in masses for the
two lighter sea quarks down to m_s/8.
The heavy b quark is simulated using Nonrelativistic QCD, and both the
valence and sea light quarks are represented by the highly improved (AsqTad)
staggered quark action.
The good chiral properties of the latter action allow for a much smoother
chiral extrapolation to physical up and down quarks than has been possible in
the past. We find f_B = 216(9)(19)(4) (6) MeV and f_{B_s} /f_B = 1.20(3)(1).Comment: 4 pages, 2 figure
The Upsilon spectrum and m_b from full lattice QCD
We show results for the Upsilon spectrum calculated in lattice QCD including
for the first time vacuum polarization effects for light u and d quarks as well
as s quarks. We use gluon field configurations generated by the MILC
collaboration. The calculations compare the results for a variety of u and d
quark masses, as well as making a comparison to quenched results (in which
quark vacuum polarisation is ignored) and results with only u and d quarks. The
b quarks in the Upsilon are treated in lattice Nonrelativistic QCD through NLO
in an expansion in the velocity of the b quark. We concentrate on accurate
results for orbital and radial splittings where we see clear agreement with
experiment once u, d and s quark vacuum polarisation effects are included. This
now allows a consistent determination of the parameters of QCD. We demonstrate
this consistency through the agreement of the Upsilon and B spectrum using the
same lattice bare b quark mass. A one-loop matching to continuum QCD gives a
value for the b quark mass in full lattice QCD for the first time. We obtain
m_b^{\bar{MS}}(m_b^{\bar{MS}}) = 4.4(3) GeV. We are able to give physical
results for the heavy quark potential parameters, r_0 = 0.469(7) fm and r_1 =
0.321(5) fm. Results for the fine structure in the spectrum and the Upsilon
leptonic width are also presented. We predict the Upsilon - eta_b splitting to
be 61(14) MeV, the Upsilon^{\prime} - eta_b^{\prime} splitting as 30(19) MeV
and the splitting between the h_b and the spin-average of the chi_b states to
be less than 6 MeV. Improvements to these calculations that will be made in the
near future are discussed.Comment: 24 pages, 19 figures. Version to be published. Minor changes made and
typographical errors corrected. Experimental leptonic widths updated in
section
Innovation sustainability in challenging health-care contexts : embedding clinically led change in routine practice
The need for organizational innovation as a means of improving health-care quality and containing costs is widely recognized, but while a growing body of research has improved knowledge of implementation, very little has considered the challenges involved in sustaining change – especially organizational change led ‘bottom-up’ by frontline clinicians. This study addresses this lacuna, taking a longitudinal, qualitative case-study approach to understanding the paths to sustainability of four organizational innovations. It highlights the importance of the interaction between organizational context, nature of the innovation and strategies deployed in achieving sustainability. It discusses how positional influence of service leads, complexity of innovation, networks of support, embedding in existing systems, and proactive responses to changing circumstances can interact to sustain change. In the absence of cast-iron evidence of effectiveness, wider notions of value may be successfully invoked to sustain innovation. Sustainability requires continuing effort through time, rather than representing a final state to be achieved. Our study offers new insights into the process of sustainability of organizational change, and elucidates the complement of strategies needed to make bottom-up change last in challenging contexts replete with competing priorities
Human T-cell lymphotropic virus (HTLV)-associated encephalopathy: an under-recognised cause of acute encephalitis? Case series and literature review
Human T-cell lymphotropic virus (HTLV)-1-associated myelopathy (HAM) is well described. Clinical features are predominantly consistent with cord pathology, though imaging and autopsy studies also demonstrate brain inflammation. In general, this is subclinical; however, six cases have previously been reported of encephalopathy in HTLV-1-infected patients, without alternative identified aetiology. We describe three further cases of encephalitis in the UK HAM cohort (n = 142), whereas the annual incidence of acute encephalitis in the general population is 0.07-12.6 per 100,000. Clinical features included reduced consciousness, fever/hypothermia, headaches, seizures, and focal neurology. Investigation showed: raised CSF protein; pleocytosis; raised CSF:peripheral blood mononuclear cell HTLV-1 proviral load ratio; and MRI either normal or showing white matter changes in brain and cord. Four of the six previous case reports of encephalopathy in HTLV-infected patients also had HAM. Histopathology, reported in three, showed perivascular predominantly CD8+ lymphocytic infiltrates in the brain. One had cerebral demyelination, and all had cord demyelination. We have reviewed the existing six cases in the literature, together with our three new cases. In all seven with HAM, the spastic paraparesis deteriorated sub-acutely preceding encephalitis. Eight of the nine were female, and four of the seven treated with steroids improved. We propose that HTLV-associated encephalopathy may be part of the spectrum of HTLV-1-induced central nervous system disease
B, Bs, K and pi weak matrix elements with physical light quarks
Calculations of pseudoscalar decay constants of B, Bs, K and pi mesons with
physical light quarks are presented. We use HISQ ensembles that include u,d,s
and c sea quarks at three lattice spacings. HISQ is used for the valence light
quarks and a radiatively improved NRQCD action for the heavy quarks. The key
results are f_{B^+}=0.184(4)$ GeV, f_{B_s}=0.224(4) GeV,
f_{B_s}/f_{B^+}=1.217(8), f_{K^+}/f_{pi^+}=1.1916(21), f_{K^+}=155.37(34) MeV,
giving a significant improvement over previous results that required chiral
extrapolation. We also calculate the Wilson flow scale w_0, finding
w_0=0.1715(9) fm
Neutral B-meson mixing from full lattice QCD at the physical point
We calculate the bag parameters for neutral -meson mixing in and beyond the Standard Model, in full four-flavour lattice QCD for the first time. We work on gluon field configurations that include the effect of , , and sea quarks with the Highly Improved Staggered Quark (HISQ) action at three values of the lattice spacing and with three quark masses going down to the physical value. The valence quarks use the improved NRQCD action and the valence light quarks, the HISQ action. Our analysis was blinded. Our results for the bag parameters for all five operators are the most accurate to
date. For the Standard Model operator between and mesons we find:
, . Combining our results with lattice QCD calculations of the decay constants using HISQ quarks from the Fermilab/MILC collaboration and with experimental values for and oscillation frequencies allows determination of the CKM elements and . We find , and . Our results agree well (within ) with values determined from CKM unitarity constraints based on tree-level processes (only). Using a ratio to in which CKM elements cancel in the Standard Model, we determine the branching fractions
and
. We also give results for matrix elements of the operators , and
that contribute to neutral -meson width differences.This work was funded by STFC, the Royal Society, the Wolfson Foundation and the US DOE and National Science Foundation
A systematic review of interventions to enhance access to best practice primary health care for chronic disease management, prevention and episodic care
Background: Although primary health care (PHC) is a key component of all health care systems, services are not always readily available, accessible or affordable. This systematic review examines effective strategies to enhance access to best practice processes of PHC in three domains: chronic disease management, prevention and episodic care. Methods. An extensive search of bibliographic data bases to identify peer and non-peer reviewed literature was undertaken. Identified papers were screened to identify and classify intervention studies that measured the impact of strategies (singly or in combination) on change in use or the reach of services in defined population groups (evaluated interventions). Results: The search identified 3,148 citations of which 121 were intervention studies and 75 were evaluated interventions. Evaluated interventions were found in all three domains: prevention (n=45), episodic care (n=19), and chronic disease management (n=11). They were undertaken in a number of countries including Australia (n=25), USA (n=25), and UK (n=15). Study quality was ranked as high (31% of studies), medium (61%) and low (8%). The 75 evaluated interventions tested a range of strategies either singly (n=46 studies) or as a combination of two (n=20) or more strategies (n=9). Strategies targeted both health providers and patients and were categorised to five groups: practice re-organisation (n=43 studies), patient support (n=29), provision of new services (n=19), workforce development (n=11), and financial incentives (n=9). Strategies varied by domain, reflecting the complexity of care needs and processes. Of the 75 evaluated interventions, 55 reported positive findings with interventions using a combination of strategies more likely to report positive results. Conclusions: This review suggests that multiple, linked strategies targeting different levels of the health care system are most likely to improve access to best practice PHC. The proposed changes in the structure of PHC in Australia may provide opportunities to investigate the factors that influence access to best practice PHC and to develop and implement effective, evidence based strategies to address these. © 2012 Comino et al.; licensee BioMed Central Ltd
Recommended from our members
Effects of copper and zinc on proteoglycan metabolism in articular cartilage.
Co-Cultures of porcine articular cartilage and synovium or synovial conditioned medium were used as an in vitro model to mimic inflammatory events at the cartilage/synovial junction in degenerative joint disease. This model provides a useful tool to assess the anti-inflammatory and antiarthritic properties of pharmacological agents. In this study the effects of copper and zinc on (i) PG synthesis by cartilage and (ii) synovial-induced PG depletion have been investigated. Copper sulphate at a concentration of 0.01 mM did not stimulate PG synthesis significantly in cultured cartilage explants but completely abrogated the inhibitory effects of synovial tissue in co-culture experiments. This finding was supported by the histological demonstration of copper-dependent reversal of the PG depletion in cartilage exposed to synovial conditioned medium. Zinc sulphate at 0.01 mM had no effect on PG synthesis and was unable to protect cartilage against synovialinduced PG depletion. These results reveal possible mechanisms by which copper exerts its anti-inflammatory and anti-arthritic actions.Peer Reviewe
- …