588 research outputs found

    Analytic models of plausible gravitational lens potentials

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    Gravitational lenses on galaxy scales are plausibly modelled as having ellipsoidal symmetry and a universal dark matter density profile, with a Sersic profile to describe the distribution of baryonic matter. Predicting all lensing effects requires knowledge of the total lens potential: in this work we give analytic forms for that of the above hybrid model. Emphasising that complex lens potentials can be constructed from simpler components in linear combination, we provide a recipe for attaining elliptical symmetry in either projected mass or lens potential. We also provide analytic formulae for the lens potentials of Sersic profiles for integer and half-integer index. We then present formulae describing the gravitational lensing effects due to smoothly-truncated universal density profiles in cold dark matter model. For our isolated haloes the density profile falls off as radius to the minus fifth or seventh power beyond the tidal radius, functional forms that allow all orders of lens potential derivatives to be calculated analytically, while ensuring a non-divergent total mass. We show how the observables predicted by this profile differ from that of the original infinite-mass NFW profile. Expressions for the gravitational flexion are highlighted. We show how decreasing the tidal radius allows stripped haloes to be modelled, providing a framework for a fuller investigation of dark matter substructure in galaxies and clusters. Finally we remark on the need for finite mass halo profiles when doing cosmological ray-tracing simulations, and the need for readily-calculable higher order derivatives of the lens potential when studying catastrophes in strong lenses.Comment: 24 pages, 10 figures, matches published versio

    A systematic review of techniques and effects of self-help interventions for tinnitus: application of taxonomies from health psychology

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    Objective: Self-help interventions are followed by people independently with minimal or no therapist contact. This review aims to assess the effectiveness of self-help interventions for adults with chronic tinnitus and systematically identify the self-help techniques used. Design: Systematic review and application of health psychology taxonomies. Electronic database searches were conducted, supplemented by citation searching and hand-searching of key journals. Prospective controlled trials, which used measures of tinnitus distress, functional management, anxiety, depression, and quality of life, were included. Michie et al’s behaviour change techniques (BCTs) taxonomy and Taylor et al’s PRISMS taxonomy of self-management components were applied to describe interventions. Study sample: Five studies were included, providing low-to-moderate levels of evidence. Results: Randomized controlled trial studies were too few and heterogeneous for meta-analysis to be performed. Studies comparing self-help interventions to therapist-guided interventions and assessing non tinnitus-specific psychosocial outcomes and functional management were lacking. Fifteen BCTs and eight self-management components were identified across interventions. Conclusions: A lack of high-quality and homogeneous studies meant that confident conclusions could not be drawn regarding the efficacy of self-help interventions for tinnitus. Better reporting and categorization of intervention techniques is needed for replication in research and practice and to facilitate understanding of intervention mechanisms

    Mid‐Holocene site formation, diagenesis and human activity at the foothills of Serra da Estrela (Portugal)

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    UIDB/00749/2020 UIDP/00749/2020The Neolithic occupation of Penedo dos Mouros in the foothills of Serra da Estrela, Portugalʼs highest mountain, dates to the 5th to 4th millennia cal B.C. The siteʼs faunal assemblage is extremely rare in the regional prehistoric archaeological record, due to the acidity of the granitic geology. This underlines Penedo dos Mouros importance as a reference site for understanding early pastoralism in the region. Due to the insufficient survival of bone collagen for radiocarbon dating and the homogeneity of the stratigraphy, where most visible contacts are due to postdepositional processes, we chose micromorphology to address the reasons behind the bone preservation and to assess the stratigraphic integrity of the prehistoric deposit. Reworking of eroding saprolitic soils was a major factor in the sediment accumulation, with remains of short human occupation events. Possible evidence for clearance fires linked to the first occurrences of pastoralism practised in the region, creating open spaces for grazing, was identified. Post‐depositional carbonate cementation derived from ashes, identifiable at the microscopic scale, enabled bone preservation. Carbonate and spodic‐like features document water saturation once the sedimentation ceased. This sedimentary dynamic has broader geomorphological implications, such as an inferred post‐Neolithic incision of the stream valley adjacent to the site.publishersversionpublishe

    Measurement of the partial widths of the Z into up- and down-type quarks

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    Using the entire OPAL LEP1 on-peak Z hadronic decay sample, Z -> qbarq gamma decays were selected by tagging hadronic final states with isolated photon candidates in the electromagnetic calorimeter. Combining the measured rates of Z -> qbarq gamma decays with the total rate of hadronic Z decays permits the simultaneous determination of the widths of the Z into up- and down-type quarks. The values obtained, with total errors, were Gamma u = 300 ^{+19}_{-18} MeV and Gamma d = 381 ^{+12}_{-12} MeV. The results are in good agreement with the Standard Model expectation.Comment: 22 pages, 5 figures, Submitted to Phys. Letts.

    Search for R-Parity Violating Decays of Scalar Fermions at LEP

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    A search for pair-produced scalar fermions under the assumption that R-parity is not conserved has been performed using data collected with the OPAL detector at LEP. The data samples analysed correspond to an integrated luminosity of about 610 pb-1 collected at centre-of-mass energies of sqrt(s) 189-209 GeV. An important consequence of R-parity violation is that the lightest supersymmetric particle is expected to be unstable. Searches of R-parity violating decays of charged sleptons, sneutrinos and squarks have been performed under the assumptions that the lightest supersymmetric particle decays promptly and that only one of the R-parity violating couplings is dominant for each of the decay modes considered. Such processes would yield final states consisting of leptons, jets, or both with or without missing energy. No significant single-like excess of events has been observed with respect to the Standard Model expectations. Limits on the production cross- section of scalar fermions in R-parity violating scenarios are obtained. Constraints on the supersymmetric particle masses are also presented in an R-parity violating framework analogous to the Constrained Minimal Supersymmetric Standard Model.Comment: 51 pages, 24 figures, Submitted to Eur. Phys. J.

    Measurement of the Strong Coupling alpha s from Four-Jet Observables in e+e- Annihilation

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    Data from e+e- annihilation into hadrons at centre-of-mass energies between 91 GeV and 209 GeV collected with the OPAL detector at LEP, are used to study the four-jet rate as a function of the Durham algorithm resolution parameter ycut. The four-jet rate is compared to next-to-leading order calculations that include the resummation of large logarithms. The strong coupling measured from the four-jet rate is alphas(Mz0)= 0.1182+-0.0003(stat.)+-0.0015(exp.)+-0.0011(had.)+-0.0012(scale)+-0.0013(mass) in agreement with the world average. Next-to-leading order fits to the D-parameter and thrust minor event-shape observables are also performed for the first time. We find consistent results, but with significantly larger theoretical uncertainties.Comment: 25 pages, 15 figures, Submitted to Euro. Phys. J.
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