1,187 research outputs found

    Simulation of iced wing aerodynamics

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    The sectional and total aerodynamic load characteristics of moderate aspect ratio wings with and without simulated glaze leading edge ice were studied both computationally, using a three dimensional, compressible Navier-Stokes solver, and experimentally. The wing has an untwisted, untapered planform shape with NACA 0012 airfoil section. The wing has an unswept and swept configuration with aspect ratios of 4.06 and 5.0. Comparisons of computed surface pressures and sectional loads with experimental data for identical configurations are given. The abrupt decrease in stall angle of attack for the wing, as a result of the leading edge ice formation, was demonstrated numerically and experimentally

    Physical Activity Interventions for Older Adults in the Age of COVID-19 and Beyond

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    Topics in Exercise Science and Kinesiology Volume 2: Issue 1, Article 6, 2021. As the coronavirus (COVID-19) pandemic continues, it is important to understand why older adults are at higher risk for more severe morbidity and higher mortality compared to younger age groups. At the same time, there is a growing body of evidence suggesting physical activity and exercise can have positive benefits for older adults’ health. Point of application #1: The first step in keeping older adults active is motivating them to adhere to a structured program either at home, in a community setting, or in a long-term care facility. Point of application #2: There are many exercise programs that can be utilized to encourage older adults to stay active in order to improve their immune function and overall fitness. Point of application #3: Bingocize® is an example of an evidence-based program that has been successful during the pandemic in keeping participants motivated by being enjoyable, encouraging intergenerational connections and being feasible for older adults with a wide range of abilities

    The Rise and Fall of Debris Disks: MIPS Observations of h and chi Persei and the Evolution of Mid-IR Emission from Planet Formation

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    We describe Spitzer/MIPS observations of the double cluster, h and χ\chi Persei, covering a \sim 0.6 square-degree area surrounding the cores of both clusters. The data are combined with IRAC and 2MASS data to investigate \sim 616 sources from 1.25-24 μm\mu m. We use the long-baseline KsK_{s}-[24] color to identify two populations with IR excess indicative of circumstellar material: Be stars with 24 μm\mu m excess from optically-thin free free emission and 17 fainter sources (J\sim 14-15) with [24] excess consistent with a circumstellar disk. The frequency of IR excess for the fainter sources increases from 4.5 μm\mu m through 24 μm\mu m. The IR excess is likely due to debris from the planet formation process. The wavelength-dependent behavior is consistent with an inside-out clearing of circumstellar disks. A comparison of the 24 μm\mu m excess population in h and χ\chi Per sources with results for other clusters shows that 24 μm\mu m emission from debris disks 'rises' from 5 to 10 Myr, peaks at \sim 10-15 Myr, and then 'falls' from \sim 15/20 Myr to 1 Gyr.Comment: 48 pages, 15 figures, accepted for publication in The Astrophysical Journa

    Stable Isotope and Modelling Evidence for CO2 as a Driver of Glacial-Interglacial Vegetation Shifts in Southern Africa

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    Atmospheric CO2 concentration is hypothesized to influence vegetation distribution via tree-grass competition, with higher CO2 concentrations favouring trees. The stable carbon isotope (delta C-13) signature of vegetation is influenced by the relative importance of C-4 plants (including most tropical grasses) and C-3 plants (including nearly all trees), and the degree of stomatal closure - a response to aridity in C-3 plants. Compound-specific delta C-13 analyses of leaf-wax biomarkers in sediment cores of an offshore South Atlantic transect are used here as a record of vegetation changes in subequatorial Africa. These data suggest a large increase in C3 relative to C4 plant dominance after the Last Glacial Maximum. Using a process-based biogeography model that explicitly 10 simulates 13 C discrimination, we show that climate change alone cannot explain the observed shift in δ13 C values. The physiological effect of increasing CO2 concentration is decisive, altering the C3/ C4 balance and bringing the simulated and observed δ 13C values into line. It is concluded that CO2 concentration itself was a key agent of tropical vegetation 15 change during the last glacial-interglacial transition. Two additional inferences follow. First, long-term variations in terrestrial δ13 C values are not simply a proxy for regional rainfall as has sometimes been assumed. Such interpretations need to be re-examined. Second, rising CO2 concentration today is likely to be influencing tree-grass competition in a similar way, and thus contributing to the “woody thickening” observed in savannas worldwide. This second inference points to the importance of experiments to determine how vegetation composition in savannas is likely to be influenced by the continuing rise in CO2 concentratio

    A 4% Geometric Distance to the Galaxy NGC4258 from Orbital Motions in a Nuclear Gas Disk

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    The water maser in the mildly active nucleus in the nearby galaxy NGC4258 traces a thin, nearly edge-on, subparsec-scale Keplerian disk. Using the technique of very long baseline interferometry, we have detected the proper motions of these masers as they sweep in front of the central black hole at an orbital velocity of about 1100 km/s. The average maser proper motion of 31.5 microarcseconds per year is used in conjunction with the observed acceleration of the masers to derive a purely geometric distance to the galaxy of 7.2 +- 0.3 Mpc. This is the most precise extragalactic distance measured to date, and, being independent of all other distance indicators, is likely to play an important role in calibrating the extragalactic distance scale.Comment: 11 pages, 3 figures. Accepted for publication in Natur

    Coulomb correlation effects in zinc monochalcogenides

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    Electronic structure and band characteristics for zinc monochalcogenides with zinc-blende- and wurtzite-type structures are studied by first-principles density-functional-theory calculations with different approximations. It is shown that the local-density approximation underestimates the band gap and energy splitting between the states at the top of the valence band, misplaces the energy levels of the Zn-3d states, and overestimates the crystal-field-splitting energy. Regardless of the structure type considered, the spin-orbit-coupling energy is found to be overestimated for ZnO and underestimated for ZnS with wurtzite-type structure, and more or less correct for ZnSe and ZnTe with zinc-blende-type structure. The order of the states at the top of the valence band is found to be anomalous for ZnO in both zinc-blende- and wurtzite-type structure, but is normal for the other zinc monochalcogenides considered. It is shown that the Zn-3d electrons and their interference with the O-2p electrons are responsible for the anomalous order. The typical errors in the calculated band gaps and related parameters for ZnO originate from strong Coulomb correlations, which are found to be highly significant for this compound. The LDA+U approach is by and large found to correct the strong correlation of the Zn-3d electrons, and thus to improve the agreement with the experimentally established location of the Zn-3d levels compared with that derived from pure LDA calculations

    Assessing the impact of care farms on quality of life and offending: a pilot study among probation service users in England

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    OBJECTIVES: To assess the feasibility of conducting a cost-effectiveness study of using care farms (CFs) to improve quality of life and reduce reoffending among offenders undertaking community orders (COs). To pilot questionnaires to assess quality of life, connection to nature, lifestyle behaviours, health and social-care use. To assess recruitment and retention at 6 months and feasibility of data linkage to Police National Computer (PNC) reconvictions data and data held by probation services. DESIGN: Pilot study using questionnaires to assess quality of life, individually linked to police and probation data. SETTING: The pilot study was conducted in three probation service regions in England. Each site included a CF and at least one comparator CO project. CFs are working farms used with a range of clients, including offenders, for therapeutic purposes. The three CFs included one aquaponics and horticulture social enterprise, a religious charity focusing on horticulture and a family-run cattle farm. Comparator projects included sorting secondhand clothes and activities to address alcohol misuse and anger management. PARTICIPANTS: We recruited 134 adults (over 18) serving COs in England, 29% female. RESULTS: 52% of participants completed follow-up questionnaires. Privatisation of UK probation trusts in 2014 negatively impacted on recruitment and retention. Linkage to PNC data was a more successful means of follow-up, with 90% consenting to access their probation and PNC data. Collection of health and social-care costs and quality-adjusted life year derivation were feasible. Propensity score adjustment provided a viable comparison method despite differences between comparators. We found worse health and higher reoffending risk among CF participants due to allocation of challenging offenders to CFs, making risk of reoffending a confounder. CONCLUSIONS: Recruitment would be feasible in a more stable probation environment. Follow-up was challenging; however, assessing reconvictions from PNC data is feasible and a potential primary outcome for future studies

    Quantum Nondemolition State Measurement via Atomic Scattering in Bragg Regime

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    We suggest a quantum nondemolition scheme to measure a quantized cavity field state using scattering of atoms in general Bragg regime. Our work extends the QND measurement of a cavity field from Fock state, based on first order Bragg deflection [9], to any quantum state based on Bragg deflection of arbitrary order. In addition a set of experimental parameters is provided to perform the experiment within the frame work of the presently available technology.Comment: 11 pages text, 4 eps figures, to appear in letter section of journal of physical society of Japa
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