13,843 research outputs found

    Review of literature relating to the modeling of soil temperatures based on meteorological factors

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    Abstracts of 72 papers, journal articles, and other publications are presented. The applicabilities of each is assessed for use in improving winterkill parameters for a winter wheat model

    Next generation solid boosters

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    Space transportation solid rocket motor systems; Shuttle derived heavy lift launch vehicles; advanced launch system (ALS) derived heavy lift launch vehicles; large launch solid booster vehicles are outlined. Performance capabilities and concept objectives are presented. Small launch vehicle concepts; enabling technologies; reusable flyback booster system; and high-performance solid motors for space are briefly described. This presentation is represented by viewgraphs

    Impact of Rubin Observatory LSST Template Acquisition Strategies on Early Science from the Transients and Variable Stars Science Collaboration: Non-time-critical Science Cases

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    Vera C. Rubin Observatory Legacy Survey of Space and Time, LSST, will revolutionize modern astronomy by producing an extremely deep (coadded depth ~27 mag) depth-limited survey of the entire southern sky (LSST Science Collaboration et al. 2009). The 8.4 m large-aperture, wide-field telescope, which is based in Cerro Pachón, will image the entire Southern sky every three nights in multiple bands (SDSS-u, g, r, i, z, y) and produce a fire-hose of data, 20 Tb each night, concluding in a 60 petabyte data set as the legacy of the 10 yr survey. Extracting meaningful light curves from variable objects requires difference imaging to both identify variability and calibrate light curve data products. Templates, co-added groups of visits that act as an image of the "static" sky, are a key component of Difference Imaging Analysis (DIA) and as such are of paramount importance for all science that involves variable objects. As the "non-time-critical" science cases discussed here are mostly periodic, they generally do not depend upon the survey alert stream; however, templates are still crucial for performing science and calibrations during the first year. We provide recommendations for observing strategies for template acquisition starting from commissioning and through Year 1 of the survey

    Effectiveness of a minimal resource fracture liaison service

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    Purpose The purpose of this study was to investigate if a 2-year intervention with a minimal resource fracture liaison service (FLS) was associated with increased investigation and medical treatment and if treatment was related to reduced re-fracture risk. Methods The FLS started in 2013 using existing secretaries (without an FLS coordinator) at the emergency department and orthopaedic wards to identify risk patients. All patients older than 50 years of age with a fractured hip, vertebra, shoulder, wrist or pelvis were followed during 2013–2014 (n = 2713) and compared with their historic counterparts in 2011–2012 (n = 2616) at the same hospital. Re-fractures were X-ray verified. A time-dependent adjusted (for age, sex, previous fracture, index fracture type, prevalent treatment, comorbidity and secondary osteoporosis) Cox model was used. Results The minimal resource FLS increased the proportion of DXA-investigated patients after fracture from 7.6 to 39.6 % (p < 0.001) and the treatment rate after fracture from 12.6 to 31.8 %, which is well in line with FLS types using the conventional coordinator model. Treated patients had a 51 % lower risk of any re-fracture than untreated patients (HR 0.49, 95 % CI 0.37–0.65 p < 0.001). Conclusions We found that our minimal resource FLS was effective in increasing investigation and treatment, in line with conventional coordinator-based services, and that treated patients had a 51 % reduced risk of new fractures, indicating that also non-coordinator based fracture liaison services can improve secondary prevention of fractures

    Rapid Grain Boundary Mobility at Ambient Temperatures

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    Understanding and measuring the influence of grain boundaries (planar defects in the crystalline structure of materials) and their motion has become a dominant aspect in materials research, with applications in additive manufacturing, fatigue prevention, and material modeling. However, modeling grain boundaries and grain boundary mobility (GBM) is difficult due to the high temperatures or external stresses, imaging solutions compatible with the material system, and long time-scales required to create measurable experimental results. In this paper, we introduce a novel material system that allows for easy and fast visualization of GBM. A drop of liquid metal eutectic gallium indium (eGaIn) placed on indium foil will penetrate along grain boundaries, decreasing the internal stresses at grain boundary interfaces and enabling rapid GBM on the order of minutes. Due to the low melting temperature of indium, the entire process is observable without requiring special temperature-control equipment. Using a scanning electron microscope, the GBM of several grains of indium can be observed at a high resolution simultaneously. The value of the material choice and visualization process is shown by measuring the motion as a function of curvature for several grain boundaries

    Stellar granulation as seen in disk-integrated intensity. II. Theoretical scaling relations compared with observations

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    A large set of stars observed by CoRoT and Kepler shows clear evidence for the presence of a stellar background, which is interpreted to arise from surface convection, i.e., granulation. These observations show that the characteristic time-scale (tau_eff) and the root-mean-square (rms) brightness fluctuations (sigma) associated with the granulation scale as a function of the peak frequency (nu_max) of the solar-like oscillations. We aim at providing a theoretical background to the observed scaling relations based on a model developed in the companion paper. We computed for each 3D model the theoretical power density spectrum (PDS) associated with the granulation as seen in disk-integrated intensity on the basis of the theoretical model. For each PDS we derived tau_eff and sigma and compared these theoretical values with the theoretical scaling relations derived from the theoretical model and the Kepler measurements. We derive theoretical scaling relations for tau_eff and sigma, which show the same dependence on nu_max as the observed scaling relations. In addition, we show that these quantities also scale as a function of the turbulent Mach number (Ma) estimated at the photosphere. The theoretical scaling relations for tau_eff and sigma match the observations well on a global scale. Our modelling provides additional theoretical support for the observed variations of sigma and tau_eff with nu_m max. It also highlights the important role of Ma in controlling the properties of the stellar granulation. However, the observations made with Kepler on a wide variety of stars cannot confirm the dependence of our scaling relations on Ma. Measurements of the granulation background and detections of solar-like oscillations in a statistically sufficient number of cool dwarf stars will be required for confirming the dependence of the theoretical scaling relations with Ma.Comment: 12 pages, 6 figures,accepted for publication in A&

    Multivortex Solutions of the Weierstrass Representation

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    The connection between the complex Sine and Sinh-Gordon equations on the complex plane associated with a Weierstrass type system and the possibility of construction of several classes of multivortex solutions is discussed in detail. We perform the Painlev\'e test and analyse the possibility of deriving the B\"acklund transformation from the singularity analysis of the complex Sine-Gordon equation. We make use of the analysis using the known relations for the Painlev\'{e} equations to construct explicit formulae in terms of the Umemura polynomials which are Ď„\tau-functions for rational solutions of the third Painlev\'{e} equation. New classes of multivortex solutions of a Weierstrass system are obtained through the use of this proposed procedure. Some physical applications are mentioned in the area of the vortex Higgs model when the complex Sine-Gordon equation is reduced to coupled Riccati equations.Comment: 27 pages LaTeX2e, 1 encapsulated Postscript figur

    Universal aspects of string propagation on curved backgrounds

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    String propagation on D-dimensional curved backgrounds with Lorentzian signature is formulated as a geometrical problem of embedding surfaces. When the spatial part of the background corresponds to a general WZW model for a compact group, the classical dynamics of the physical degrees of freedom is governed by the coset conformal field theory SO(D-1)/SO(D-2), which is universal irrespective of the particular WZW model. The same holds for string propagation on D-dimensional flat space. The integration of the corresponding Gauss-Codazzi equations requires the introduction of (non-Abelian) parafermions in differential geometry.Comment: 15 pages, latex. Typo in Eq. (2.12) is corrected. Version to be published in Phys. Rev.
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