6,242 research outputs found

    Water facilities in retrospect and prospect: An illuminating tool for vehicle design

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    Water facilities play a fundamental role in the design of air, ground, and marine vehicles by providing a qualitative, and sometimes quantitative, description of complex flow phenomena. Water tunnels, channels, and tow tanks used as flow-diagnostic tools have experienced a renaissance in recent years in response to the increased complexity of designs suitable for advanced technology vehicles. These vehicles are frequently characterized by large regions of steady and unsteady three-dimensional flow separation and ensuing vortical flows. The visualization and interpretation of the complicated fluid motions about isolated vehicle components and complete configurations in a time and cost effective manner in hydrodynamic test facilities is a key element in the development of flow control concepts, and, hence, improved vehicle designs. A historical perspective of the role of water facilities in the vehicle design process is presented. The application of water facilities to specific aerodynamic and hydrodynamic flow problems is discussed, and the strengths and limitations of these important experimental tools are emphasized

    Ladders for Wilson Loops Beyond Leading Order

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    We set up a general scheme to resum ladder diagrams for the quark-anti-quark potential in N=4 super-Yang-Mills theory, and do explicit calculations at the next-to-leading order. The results perfectly agree with string theory in AdS(5)xS(5) when continued to strong coupling, in spite of a potential order-of-limits problem.Comment: 18 pages, 5 figure

    Holography of Wilson-Loop Expectation Values with Local Operator Insertions

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    We study the expectation values of Wilson-loop operators with the insertionsof local operators Z^J and Zbar^J with large R-charge J from the bulk viewpoint of AdS/CFT correspondence. Classical solutions of strings attached to such deformed Wilson loops at the conformal boundary are constructed and are applied to the computation of Wilson-loop expectation values. We argue that in order to have such solutions for general insertions at finite positions in the base spacetime of the gauge theory, it is crucial to interpret the holographic correspondence in the semi-classical picture as a tunneling phenomenon, as has been previously established for holographic computations of correlators of BMN operators. This also requires to use the Euclideanized AdS background and Euclidean super Yang-Mills theory.Comment: 16 pages, 5 figures, version to be published in JHEP, no change from the previous version, only extraneous figure file is remove

    Evaluation of Revalor-XH for beef heifers fed different days on feed

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    Heifers were treated with either no implant, an initial implant of Revalor-200 and re-implanted with Revalor-200, or Revalor-XH and assigned to one of four serial slaughter harvests at 151, 165, 179, and 193 days on feed to determine the effects on feedlot performance and carcass characteristics. Implanting heifers increased final BW, ADG and HCW while decreasing marbling score and improving feed efficiency compared to non-implanted heifers. Increasing days on feed decreased ADG while increasing feed efficiency, HCW, fat thickness, marbling score, and calculated yield grade. By increasing HCW sold, implanting revenue can be maximized, assuming added risk for YG discounts

    Radio Recombination Lines at Decametre Wavelengths: Prospects for the Future

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    This paper considers the suitability of a number of emerging and future instruments for the study of radio recombination lines (RRLs) at frequencies below 200 MHz. These lines arise only in low-density regions of the ionized interstellar medium, and they may represent a frequency-dependent foreground for next-generation experiments trying to detect H I signals from the Epoch of Reionization and Dark Ages ("21-cm cosmology"). We summarize existing decametre-wavelength observations of RRLs, which have detected only carbon RRLs. We then show that, for an interferometric array, the primary instrumental factor limiting detection and study of the RRLs is the areal filling factor of the array. We consider the Long Wavelength Array (LWA-1), the LOw Frequency ARray (LOFAR), the low-frequency component of the Square Kilometre Array (SKA-lo), and a future Lunar Radio Array (LRA), all of which will operate at decametre wavelengths. These arrays offer digital signal processing, which should produce more stable and better defined spectral bandpasses; larger frequency tuning ranges; and better angular resolution than that of the previous generation of instruments that have been used in the past for RRL observations. Detecting Galactic carbon RRLs, with optical depths at the level of 10^-3, appears feasible for all of these arrays, with integration times of no more than 100 hr. The SKA-lo and LRA, and the LWA-1 and LOFAR at the lowest frequencies, should have a high enough filling factor to detect lines with much lower optical depths, of order 10^-4 in a few hundred hours. The amount of RRL-hosting gas present in the Galaxy at the high Galactic latitudes likely to be targeted in 21-cm cosmology studies is currently unknown. If present, however, the spectral fluctuations from RRLs could be comparable to or exceed the anticipated H I signals.Comment: 9 pages; Astron. & Astrophys., in pres

    Identifying depressed fathers during a home visit: why and how.

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    The knowledge and expertise required for child and family health nursing practice has continued to evolve as a consequence of research-based interventions and policy changes affecting families. The benefits of sustained home visiting on family health and wellbeing are now accepted and Australian trials have demonstrated improvements in maternal–infant attachment and mothers’ relationship with their child. At the level of clinical practice, best practice approaches for nurses visiting new mothers have moved away from delivering specific clinical procedures to focusing on the particular needs and circumstances of the parent and family, emphasising psychological support and health promotion in partnership and collaboration with parents. A particular focus on detecting postnatal maternal depression has arisen due to the development of the National Perinatal Depression Initiative. Child and family health nurses now regularly screen mothers using the Edinburgh Postnatal Depression Scale (EPDS). Recent evidence of the impact of fathers’ depression on children and mothers has drawn attention to fathers’ mental health in the perinatal period. Fathers’ postnatal depression has been shown to impact on children’s development at similar levels to mothers’ and while children are most affected by two depressed parents, the effect of fathers’ depression is independent of mood disorder in the mother. Nurses making home visits have an opportunity to engage with fathers and many do so when the father is available. In this paper we present the evidence and rationale for assessing fathers’ depression or anxiety at the postnatal home visit

    Evaluation of Two Implant Strategies, Revalor- XH or a Combination Revalor- IH/Revalor- 200 on Heifer Growth Performance and Carcass Characteristics

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    A commercial feedlot trial examined effects of two implant strategies (Revalor- IH on d 1 and re- implanted with Revalor- 200 on d 101 or Revalor- XH on d 1) on growth performance and carcass characteristics of heifers fed 183 days. Th ere were no differences between implant strategies for final body weight, dry matter intake, and average daily gain. Heifers implanted with the combination IH/200 treatment had improved carcassadjusted feed conversion, greater LM area, and lower calculated yield grade compared to heifers implanted with XH. Th e response in growth performance between the two implant strategies suggests that the partiallycoated Revalor- XH implant can be used in place of a more aggressive implant strategy when heifers are fed to similar days

    Upper Limits on the Continuum Emission from Geminga at 74 and 326 MHz

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    We report a search for radio continuum emission from the gamma-ray pulsar Geminga. We have used the VLA to image the location of the optical counterpart of Geminga at 74 and 326 MHz. We detect no radio counterpart. We derive upper limits to the pulse-averaged flux density of Geminga, taking diffractive scintillation into account. We find that diffractive scintillation is probably quenched at 74 MHz and does not influence our upper limit, S < 56 mJy (2\sigma), but that a 95% confidence level at 326 MHz is S < 5 mJy. Owing to uncertainties on the other low-frequency detections and the possibility of intrinsic variability or extrinsic variability (refractive interstellar scintillation) or both, our non-detections are nominally consistent with these previous detections.Comment: 8 pages, LaTeX2e with AASTeX 4.0, 3 figures; to be published in Ap

    Shock-induced prompt relativistic electron acceleration in the inner magnetosphere

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    Abstract We present twin Van Allen Probes spacecraft observations of the effects of a solar wind shock impacting the magnetosphere on 8 October 2013. The event provides details both of the accelerating electric fields associated with the shock and the response of inner magnetosphere electron populations across a broad range of energies. During this period, the two Van Allen Probes observed shock effects from the vantage point of the dayside magnetosphere at radial positions of L = 3 and L = 5, at the location where shock-induced acceleration of relativistic electrons occurs. The extended (~1 min) duration of the accelerating electric field across a broad extent of the dayside magnetosphere, coupled with energy-dependent relativistic electron gradient drift velocities, selects a preferred range of energies (3–4 MeV) for the initial enhancement. Those electrons—whose drift velocity closely matches the azimuthal phase velocity of the shock-induced pulse—stayed in the accelerating wave as it propagated tailward and received the largest increase in energy. Drift resonance with subsequent strong ULF waves further accentuated this range of electron energies. Phase space density and positional considerations permit the identification of the source population of the energized electrons. Observations detail the promptness (\u3c20 min), energy range (1.5–4.5 MeV), energy increase (~500 keV), and spatial extent (L* ~3.5–4.0) of the enhancement of the relativistic electrons. Prompt acceleration by impulsive shock-induced electric fields and subsequent ULF wave processes therefore comprises a significant mechanism for the acceleration of highly relativistic electrons deep inside the outer radiation belt as shown clearly by this event

    Carcass Gain, Efficiency, and Profitability of Steers at Extended Days on Feed

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    Steers were individually fed for 22 and 44 days longer than the industry average marketing point of 0.5” backfat to determine carcass- based gain, efficiency, and deposition changes throughout the feeding period (142, 163, and 184 days on feed). Premiums and discounts for yield grade, quality grade, and overweight carcasses were applied to determine profitability. Feeding steers for 22 and 44 days longer increased carcass weight, quality grade, and yield grade 4 and 5s. Steers fed 44 days longer had increased total revenue and profit per head despite a decrease in live gain and efficiency
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