320 research outputs found
Lattice renormalisation of O(a) improved heavy-light operators
The analytical expressions and the numerical values of the renormalisation
constants of improved static-light currents are given at one-loop
order of perturbation theory in the framework of Heavy Quark Effective Theory:
the static quark is described by the HYP action and the light quark is
described either with the Clover or the Neuberger action. These factors are
relevant to extract from a lattice computation the decay constants ,
and the set of bag parameters associated with
mixing phenomenology in the Standard Model and beyond.Comment: 16 pages, 2 figures, 4 tables; few comments and references added;
version to be published in Phys Rev
A strategy for implementing non-perturbative renormalisation of heavy-light four-quark operators in the static approximation
We discuss the renormalisation properties of the complete set of four-quark operators with the heavy quark treated in the static
approximation. We elucidate the role of heavy quark symmetry and other symmetry
transformations in constraining their mixing under renormalisation. By
employing the Schroedinger functional, a set of non-perturbative
renormalisation conditions can be defined in terms of suitable correlation
functions. As a first step in a fully non-perturbative determination of the
scale-dependent renormalisation factors, we evaluate these conditions in
lattice perturbation theory at one loop. Thereby we verify the expected mixing
patterns and determine the anomalous dimensions of the operators at NLO in the
Schroedinger functional scheme. Finally, by employing twisted-mass QCD it is
shown how finite subtractions arising from explicit chiral symmetry breaking
can be avoided completely.Comment: 41 pages, 6 figure
APENet: LQCD clusters a la APE
Developed by the APE group, APENet is a new high speed, low latency,
3-dimensional interconnect architecture optimized for PC clusters running
LQCD-like numerical applications. The hardware implementation is based on a
single PCI-X 133MHz network interface card hosting six indipendent
bi-directional channels with a peak bandwidth of 676 MB/s each direction. We
discuss preliminary benchmark results showing exciting performances similar or
better than those found in high-end commercial network systems.Comment: Lattice2004(machines), 3 pages, 4 figure
Improving Male Partner Involvement in HIV-Positive Women's Care Through Behavioral Change Interventions in Malawi (WeMen Study): A Prospective, Controlled Before-and-After Study
Several strategies and interventions have been implemented to improve male partner involvement (MI) in Sub-Saharan Africa, but evidence on successful interventions is scarce. This controlled before-and-after intervention study aims to evaluate the impact of three interventions on male partners' involvement in HIV+ women's care in Malawi. We piloted these three interventions: the organization of a special day for men, the deployment of male champions in communities to increase awareness on MI, and the delivery of an incentive (food package) for couples attending the facility. We observed a significant increase in the number of women accompanied by their partners (from 48.5 to 81.4%) and the number of women feeling safe at home (from 63.5 to 95.2%) after the special day intervention. This outcome increased after the deployment of male champions in communities (from 44.0 to 75.0%). No significant improvement was observed in the site where we delivered the incentive to couples. Our findings showed that the special day for men and the use of male champions might effectively increase the male involvement in the health of their female partners
Measurement of viral load by the automated Abbott real-time HIV-1 assay using dried blood spots collected and processed in Malawi and Mozambique
Background. The use of dried blood spots (DBS) for HIV-1 viral load quantification can greatly improve access to viral monitoring for HIV-infected patients receiving treatment in resource-limited settings.Objectives. To evaluate and validate HIV viral load measurement from DBS in sub-Saharan Africa, with a reliable, all-automated, standard commercial assay such as the Abbott m2000.Methods. A total of 277 DBS were collected in different health centres in Malawi and Mozambique and analysed for viral load determination using the Abbott m2000 assay with the corresponding plasma samples as gold standard. Samples were extracted using the m2000SP automatic extractor and then processed as the plasma samples using the specific 1.0 mL HIV-RNA DBS protocol.Results. Among samples with detectable HIV-RNA the correlation between viral load obtained from the paired 131 plasma and DBS samples was high (r=0.946). Overall, viral load values between DBS and plasma differed by less than 0.5 log unit in 90.1% of cases and by less than 1 log unit in 100% of cases. Using a threshold of 1 000 copies/mL (defining virological failure in resource-limited settings), sensitivity was 94.2% and specificity 98.6%, and both positive and negative predictive values were high (98.5% and 94.5%, respectively).Conclusion. DBS extracted and processed using the Abbott automated system can be reliably used in resource-limited setting to diagnose virological failure
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