3,226 research outputs found

    Stochastic energy-cascade model for 1+1 dimensional fully developed turbulence

    Full text link
    Geometrical random multiplicative cascade processes are often used to model positive-valued multifractal fields such as the energy dissipation in fully developed turbulence. We propose a dynamical generalization describing the energy dissipation in terms of a continuous and homogeneous stochastic field in one space and one time dimension. In the model, correlations originate in the overlap of the respective spacetime histories of field amplitudes. The theoretical two- and three-point correlation functions are found to be in good agreement with their equal-time counterparts extracted from wind tunnel turbulent shear flow data

    Experimental measurement of stress at a four-domain junction in lead zirconate titanate

    Get PDF
    A junction between two lamellar bands of ferroelectric domains in a lead zirconate titanate (PZT) ceramic is analysed using Kikuchi diffraction patterns in the transmission electron microscope. Indexing of the diffraction patterns allowed the determination of the 3D relative orientation of the 4 different domains at the junction and thus the characterisation of the domain boundaries. The local c/a ratio could also be determined from the misorientations at the domain boundaries. Analysis of the data showed that large stresses were concentrated at the junction, and that this is inevitable at such band junctions. Such stress concentrations could act as nuclei for cracking of the ceramic under additional loading in service, perhaps particularly as a consequence of extended electromechanical cycling. Moreover, the stresses would increase with increasing c/a making the issues all the more serious for Ti-rich compositions having larger c/a ratios

    Molecular Simulation Study on the Influence of the Scratching Velocity on Nanoscopic Contact Processes

    Get PDF
    The influence of the scratching velocity on mechanical and thermal properties of a nanoscopic contact process was studied by molecular dynamics simulations. Simulations with different scratching velocities were conducted in dry and lubricated systems. The contact process consisted of a lateral scratching of a spherical indenter on a planar substrate. All molecular interactions were described by the Lennard-Jones truncated and shifted potential. The forces on the indenter, the coefficient of friction and the work done by the indenter as well as the power applied on the indenter were sampled. Furthermore, an analysis of thermal properties was conducted: The change of the energy of the substrate, the indenter and the fluid was evaluated and the local temperature field was determined. The forces, the coefficient of friction and the work done by the indenter show practically no influence of the scratching velocity. The work done by the indenter was found to be the same for all velocities. As a consequence, the power supplied to the system depends linearly on the scratching velocity, which affects the temperature of the contact zone. As expected, the presence of a lubricant reduces the temperature of the substrate in the vicinity of the contact

    Biobanking from the patient perspective

    Get PDF
    Biobanks and biobanking research plays an increasingly important role in healthcare research and delivery as health systems become more patient-centred and medicine becomes more personalised. There is also growing acceptance and appreciation of the value that patients, patient advocacy organisations and the public can bring as stakeholders in biobanking and more generally in research. Therefore, the importance of active, early and sustained engagement and involvement of patient and public representatives in biobanks will become increasingly relevant. Organising and facilitating patient and public involvement in biobanking takes considerable time and effort for all stakeholders involved. Therefore, for any biobank operator considering involving patients and the public in their biobanking activities, consideration of best practices, current guidance, ethical issues and evaluation of involvement will be important. In this article, we demonstrate that patients are much more than donors to biobanks—they are collaborators at the heart of biobanking with an important voice to identify perspective, which can be an extremely valuable resource for all biobanks to utilise. The case studies herein provide examples of good practice of patient involvement in biobanking as well as outcomes from these practices, and lessons learned. Our aim is to provide useful insights from these efforts and potential future strategies for the multiple stakeholders that work with patients and the public involved in biobank-based research

    Planet Hunters. VI: An Independent Characterization of KOI-351 and Several Long Period Planet Candidates from the Kepler Archival Data

    Get PDF
    We report the discovery of 14 new transiting planet candidates in the Kepler field from the Planet Hunters citizen science program. None of these candidates overlapped with Kepler Objects of Interest (KOIs) at the time of submission. We report the discovery of one more addition to the six planet candidate system around KOI-351, making it the only seven planet candidate system from Kepler. Additionally, KOI-351 bears some resemblance to our own solar system, with the inner five planets ranging from Earth to mini-Neptune radii and the outer planets being gas giants; however, this system is very compact, with all seven planet candidates orbiting 1\lesssim 1 AU from their host star. A Hill stability test and an orbital integration of the system shows that the system is stable. Furthermore, we significantly add to the population of long period transiting planets; periods range from 124-904 days, eight of them more than one Earth year long. Seven of these 14 candidates reside in their host star's habitable zone.Comment: 27 pages, 6 figures, 5 tables, Accepted to AJ (in press) (updated title from original astro-ph submission

    Further Experimental Studies of Two-Body Radiative \Upsilon Decays

    Full text link
    Continuing our studies of radiative Upsilon(1S) decays, we report on a search for Upsilon to gamma eta and Upsilon to gamma f_{J}(2220) in 61.3 pb^{-1} of e^{+}e^{-} data taken with the CLEO II detector at the Cornell Electron Storage Ring. For the gamma eta search the three decays of the eta meson to pi^{+}pi^{-}pi^{0}, pi^{0}pi^{0}pi^{0}, and gamma gamma were investigated. We found no candidate events in the two (3\pi)^{0} modes and no significant excess over expected backgrounds in the gamma gamma mode to set a limit on the branching fraction of B(Upsilon to gamma eta) < 2.1 x 10^{-5} at 90% C.L. The three charged two-body final states h h-bar (h = pi^{+}, K^{+}, p) were investigated for f_{J}(2220) production, with one, one, and two events found, respectively. Limits at 90% C.L. of B(\Upsilon to gamma f_{J}) x B(f_{J} to h h-bar) ~ 1.5 x 10^{-5} have been set for each of these modes. We compare our results to measurements of other radiative Upsilon decays, to measurements of radiative J/psi decays, and to theoretical predictions.Comment: 19 pages postscript, also available through http://w4.lns.cornell.edu/public/CLNS, submitted to Physical Review

    Searches at HERA for Squarks in R-Parity Violating Supersymmetry

    Get PDF
    A search for squarks in R-parity violating supersymmetry is performed in e^+p collisions at HERA at a centre of mass energy of 300 GeV, using H1 data corresponding to an integrated luminosity of 37 pb^(-1). The direct production of single squarks of any generation in positron-quark fusion via a Yukawa coupling lambda' is considered, taking into account R-parity violating and conserving decays of the squarks. No significant deviation from the Standard Model expectation is found. The results are interpreted in terms of constraints within the Minimal Supersymmetric Standard Model (MSSM), the constrained MSSM and the minimal Supergravity model, and their sensitivity to the model parameters is studied in detail. For a Yukawa coupling of electromagnetic strength, squark masses below 260 GeV are excluded at 95% confidence level in a large part of the parameter space. For a 100 times smaller coupling strength masses up to 182 GeV are excluded.Comment: 32 pages, 14 figures, 3 table

    Long-Baseline Neutrino Facility (LBNF) and Deep Underground Neutrino Experiment (DUNE) Conceptual Design Report Volume 2: The Physics Program for DUNE at LBNF

    Full text link
    The Physics Program for the Deep Underground Neutrino Experiment (DUNE) at the Fermilab Long-Baseline Neutrino Facility (LBNF) is described
    corecore