3,551 research outputs found

    C5AC_5^A axial form factor from bubble chamber experiments

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    A careful reanalysis of both Argonne National Laboratory and Brookhaven National Laboratory data for weak single pion production is done. We consider deuteron nuclear effects and normalization (flux) uncertainties in both experiments. We demonstrate that these two sets of data are in good agreement. For the dipole parametrization of C5A(Q2)C_5^A(Q^2), we obtain C5A(0)=1.19±0.08C_5^A(0)=1.19\pm 0.08, MA=0.94±0.03M_A=0.94\pm 0.03 GeV. As an application we present the discussion of the uncertainty of the neutral current 1π0\pi^0 production cross section, important for the T2K neutrino oscillation experiment.Comment: 16 pages, 8 figures, 2 table

    Comparative analysis of hepatitis C virus phylogenies from coding and non-coding regions: the 5' untranslated region (UTR) fails to classify subtypes

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    BACKGROUND: The duration of treatment for HCV infection is partly indicated by the genotype of the virus. For studies of disease transmission, vaccine design, and surveillance for novel variants, subtype-level classification is also needed. This study used the Shimodaira-Hasegawa test and related statistical techniques to compare phylogenetic trees obtained from coding and non-coding regions of a whole-genome alignment for the reliability of subtyping in different regions. RESULTS: Different regions of the HCV genome yield inconsistent phylogenies, which can lead to erroneous conclusions about classification of a given infection. In particular, the highly conserved 5' untranslated region (UTR) yields phylogenetic trees with topologies that differ from the HCV polyprotein and complete genome phylogenies. Phylogenetic trees from the NS5B gene reliably cluster related subtypes, and yield topologies consistent with those of the whole genome and polyprotein. CONCLUSION: These results extend those from previous studies and indicate that, unlike the NS5B gene, the 5' UTR contains insufficient variation to resolve HCV classifications to the level of viral subtype, and fails to distinguish genotypes reliably. Use of the 5' UTR for clinical tests to characterize HCV infection should be replaced by a subtype-informative test

    Einstein metrics in projective geometry

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    It is well known that pseudo-Riemannian metrics in the projective class of a given torsion free affine connection can be obtained from (and are equivalent to) the solutions of a certain overdetermined projectively invariant differential equation. This equation is a special case of a so-called first BGG equation. The general theory of such equations singles out a subclass of so-called normal solutions. We prove that non-degerate normal solutions are equivalent to pseudo-Riemannian Einstein metrics in the projective class and observe that this connects to natural projective extensions of the Einstein condition.Comment: 10 pages. Adapted to published version. In addition corrected a minor sign erro

    Getting more from heterogeneous HIV-1 surveillance data in a high immigration country: estimation of incidence and undiagnosed population size using multiple biomarkers

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    BACKGROUND: Most HIV infections originate from individuals who are undiagnosed and unaware of their infection. Estimation of this quantity from surveillance data is hard because there is incomplete knowledge about (i) the time between infection and diagnosis (TI) for the general population, and (ii) the time between immigration and diagnosis for foreign-born persons. METHODS: We developed a new statistical method for estimating the incidence of HIV-1 and the number of undiagnosed people living with HIV (PLHIV), based on dynamic modelling of heterogeneous HIV-1 surveillance data. The methods consist of a Bayesian non-linear mixed effects model using multiple biomarkers to estimate TI of HIV-1-positive individuals, and a novel incidence estimator which distinguishes between endogenous and exogenous infections by modelling explicitly the probability that a foreign-born person was infected either before or after immigration. The incidence estimator allows for direct calculation of the number of undiagnosed persons. The new methodology is illustrated combining heterogeneous surveillance data from Sweden between 2003 and 2015. RESULTS: A leave-one-out cross-validation study showed that the multiple-biomarker model was more accurate than single biomarkers (mean absolute error 1.01 vs ≥1.95). We estimate that 816 [95% credible interval (CI) 775-865] PLHIV were undiagnosed in 2015, representing a proportion of 10.8% (95% CI 10.3-11.4%) of all PLHIV. CONCLUSIONS: The proposed methodology will enhance the utility of standard surveillance data streams and will be useful to monitor progress towards and compliance with the 90-90-90 UNAIDS target

    Yrast line for weakly interacting trapped bosons

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    We compute numerically the yrast line for harmonically trapped boson systems with a weak repulsive contact interaction, studying the transition to a vortex state as the angular momentum L increases and approaches N, the number of bosons. The L=N eigenstate is indeed dominated by particles with unit angular momentum, but the state has other significant components beyond the pure vortex configuration. There is a smooth crossover between low and high L with no indication of a quantum phase transition. Most strikingly, the energy and wave function appear to be analytical functions of L over the entire range 2 < L < N. We confirm the structure of low-L states proposed by Mottelson, as mainly single-particle excitations with two or three units of angular momentum.Comment: 9 pages, 3 EPS-figures, uses psfig.st

    Financial flow diagrams to promote policy-making, based on 20 community management case studies from India

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    This paper reports the development of ‘Financial Flow Diagrams’ as a means of better communicating complex financial information, directly inspired by the development of ‘Shit Flow Diagrams’, in this case highlighting, for policy-makers, donors and service providers financial challenges. We describe the design considerations investigated during the preparation of visual oriented financial communications. This includes arguments about the merits and limitations of visuals and associated tools/software that best display flows of resources (in our case financial). We then present visuals that were submitted for testing across a panel of informants, some closely related to the Community Water Plus project, a 20 case study, 17 States research project of ‘successful’ community managed water schemes in India, which provided the source financial information. Finally, we provide a critical analysis and feedback on the limitations of using Financial Flow Diagrams as a mean to convey messages on funding distribution in the context rural water supply

    Nonergodic Behavior of Interacting Bosons in Harmonic Traps

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    We study the time evolution of a system of interacting bosons in a harmonic trap. In the low-energy regime, the quantum system is not ergodic and displays rather large fluctuations of the ground state occupation number. In the high energy regime of classical physics we find nonergodic behavior for modest numbers of trapped particles. We give two conditions that assure the ergodic behavior of the quantum system even below the condensation temperature.Comment: 11 pages, 3 PS-figures, uses psfig.st

    Recombination rate and selection strength in HIV intra-patient evolution

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    The evolutionary dynamics of HIV during the chronic phase of infection is driven by the host immune response and by selective pressures exerted through drug treatment. To understand and model the evolution of HIV quantitatively, the parameters governing genetic diversification and the strength of selection need to be known. While mutation rates can be measured in single replication cycles, the relevant effective recombination rate depends on the probability of coinfection of a cell with more than one virus and can only be inferred from population data. However, most population genetic estimators for recombination rates assume absence of selection and are hence of limited applicability to HIV, since positive and purifying selection are important in HIV evolution. Here, we estimate the rate of recombination and the distribution of selection coefficients from time-resolved sequence data tracking the evolution of HIV within single patients. By examining temporal changes in the genetic composition of the population, we estimate the effective recombination to be r=1.4e-5 recombinations per site and generation. Furthermore, we provide evidence that selection coefficients of at least 15% of the observed non-synonymous polymorphisms exceed 0.8% per generation. These results provide a basis for a more detailed understanding of the evolution of HIV. A particularly interesting case is evolution in response to drug treatment, where recombination can facilitate the rapid acquisition of multiple resistance mutations. With the methods developed here, more precise and more detailed studies will be possible, as soon as data with higher time resolution and greater sample sizes is available.Comment: to appear in PLoS Computational Biolog

    Direct CP Violation, Branching Ratios and Form Factors BπB \to \pi, BKB \to K in BB Decays

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    The BπB \to \pi and BKB \to K transitions involved in hadronic B decays are investigated in a phenomenological way through the framework of QCD factorization. By comparing our results with experimental branching ratios from the BELLE, BABAR and CLEO Collaborations for all the B decays including either a pion or a kaon, we propose boundaries for the transition form factors BπB \to \pi and BKB \to K depending on the CKM matrix element parameters ρ\rho and η\eta. From this analysis, the form factors required to reproduce the experimental data for branching ratios are FBπ=0.31±0.12F^{B \to \pi}= 0.31 \pm 0.12 and FBK=0.37±0.13F^{B \to K}= 0.37\pm 0.13. We calculate the direct CP violating asymmetry parameter, aCPa_{CP}, for Bπ+ππB \to \pi^{+} \pi^{-} \pi and Bπ+πKB \to \pi^{+} \pi^{-} K decays, in the case where ρω\rho-\omega mixing effects are taken into account. Based on these results, we find that the direct CP asymmetry for Bπ+ππB^{-} \to \pi^{+} \pi^{-} \pi^{-}, Bˉ0π+ππ0\bar{B}^{0} \to \pi^{+} \pi^{-} \pi^{0}, Bπ+πKB^{-} \to \pi^{+} \pi^{-} K^{-}, and Bˉ0π+πKˉ0\bar{B}^{0} \to \pi^{+} \pi^{-} \bar{K}^{0}, reaches its maximum when the invariant mass π+π\pi^{+} \pi^{-} is in the vicinity of the ω\omega meson mass. The inclusion of ρω\rho-\omega mixing provides an opportunity to erase, without ambiguity, the phase uncertainty mod(π)(\pi) in the determination of the CKM angles α\alpha in case of bub\to u and γ\gamma in case of bsb \to s.Comment: 74 pages, 15 figures, 8 tables. A few misprints corrected, two references adde

    Stardust in STARDUST - the C, N, and O Isotopic Compositions of Wild 2 Cometary Matter in Al foil Impacts

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    In January 2006, the STARDUST mission successfully returned dust samples from the tail of comet 81P/Wild 2 in two principal collection media, low density silica aerogel and Al foil. While hypervelocity impacts at 6.1 km/s, the encounter velocity of STARDUST, into Al foils are generally highly disruptive for natural, silicate-dominated impactors, previous studies have shown that many craters retain sufficient residue to allow a determination of the elemental and isotopic compositions of the original projectile. We have used the NanoSIMS to perform C, N, and O isotope imaging measurements on four large (59-370 microns diameter) and on 47 small (0.32-1.9 microns diameter) Al foil impact craters as part of the STARDUST Preliminary Examination. Most analyzed residues in and around these craters are isotopically normal (solar) in their C, N, and O isotopic compositions. However, the debris in one large crater shows an average 15N enrichment of approx. 450 %, which is similar to the bulk composition of some isotopically primitive interplanetary dust particles. A 250 nm grain in another large crater has an O-17 enrichment with approx. 2.65 times the solar O-17/O-16 ratio. Such an O isotopic composition is typical for circumstellar oxide or silicate grains from red giant or asymptotic giant branch stars. The discovery of this circumstellar grain clearly establishes that there is authentic stardust in the cometary samples returned by the STARDUST mission. However, the low apparent abundance of circumstellar grains in Wild 2 samples and the preponderance of isotopically normal material indicates that the cometary matter is a diverse assemblage of presolar and solar system materials
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