2,484 research outputs found
Geostrophic adjustment in a shallow-water numerical model as it relates to thermospheric dynamics
The theory of geostrophic adjustment and its application to the dynamics of the high latitude thermosphere have been discussed in previous papers based on a linearized treatment of the fluid dynamical equations. However, a linearized treatment is only valid for small Rossby numbers given by Ro = V/fL, where V is the wind speed, f is the local value of the Coriolis parameter, and L is a characteristic horizontal scale for the flow. For typical values in the auroral zone, the approximation is not reasonable for wind speeds greater than 25 m/s or so. A shallow-water (one layer) model was developed that includes the spherical geometry and full nonlinear dynamics in the momentum equations in order to isolate the effects of the nonlinearities on the adjustment process. A belt of accelerated winds between 60 deg and 70 deg latitude was used as the initial condition. The adjustment process was found to proceed as expected from the linear formulation, but that an asymmetry between the response for an eastward and westward flow results from the nonlineawr curvature (centrifugal) terms. In general, the amplitude of an eastward flowing wind will be less after adjustment than a westward wind. For instance, if the initial wind velocity is 300 m/s, the linearized theory predicts a final wind speed of 240 m/s, regardless of the flow direction. However, the nonlinear curvature terms modify the response and produce a final wind speed of only 200 m/s for an initial eastward wind and a final wind speed of almost 300 m/s for an initial westward flow direction. Also, less gravity wave energy is produced by the adjustment of the westward flow than by the adjustment of the eastward flow. The implications are that the response of the thermosphere should be significantly different on the dawn and dusk sides of the auroral oval. Larger flow velocities would be expected on the dusk side since the plasma will accelerate the flow in a westward direction in that sector
Near-threshold production of , and at a fixed-target experiment at the future ultra-high-energy proton colliders
We outline the opportunities to study the production of the Standard Model
bosons, , and at "low" energies at fixed-target experiments
based at possible future ultra-high-energy proton colliders, \ie\ the
High-Energy LHC, the Super proton-proton Collider and the Future Circular
Collider -- hadron-hadron. These can be indeed made in conjunction with the
proposed future colliders designed to reach up to TeV by using
bent crystals to extract part of the halo of the beam which would then impinge
on a fixed target. Without disturbing the collider operation, this technique
allows for the extraction of a substantial amount of particles in addition to
serve for a beam-cleaning purpose. With this method, high-luminosity
fixed-target studies at centre-of-mass energies above the , and
masses, GeV, are possible. We also discuss the
possibility offered by an internal gas target, which can also be used as
luminosity monitor by studying the beam transverse shape
Bremsstrahlung from relativistic heavy ions in a fixed target experiment at the LHC
We calculate the emission of bremsstrahlung from lead and argon ions in A
Fixed Target ExpeRiment (AFTER) that uses the LHC beams. With nuclear charges
of equal and respectively, these ions are accelerated to
energies of TeV. The bremsstrahlung peaks around
GeV and the spectrum exposes the nuclear structure of the incoming ion. The
peak structure is significantly different from the flat power spectrum
pertaining to a point charge. Photons are predominantly emitted within an angle
of to the direction of ion propagation. Our calculations are based
on the Weizs\"{a}cker-Williams method of virtual quanta with application of
existing experimental data on photonuclear interactions.Comment: 9 pages, 3 figures. Submitted to Advances in High Energy Physic
Effect of early supervised progressive resistance training compared to unsupervised home-based exercise after fast-track total hip replacement applied to patients with preoperative functional limitations. A single-blinded randomised controlled trial
SummaryObjectiveTo examine if 2 weekly sessions of supervised progressive resistance training (PRT) in combination with 5 weekly sessions of unsupervised home-based exercise is more effective than 7 weekly sessions of unsupervised home-based exercise in improving leg-extension power of the operated leg 10 weeks after total hip replacement (THR) in patients with lower pre-operative function.MethodA total of 73 patients scheduled for THR were randomised (1:1) to intervention group (IG, home based exercise 5 days/week and PRT 2 days/week) or control group (CG, home based exercise 7 days/week). The primary endpoint was change in leg extension power at 10 week follow up. Secondary outcomes were isometric hip muscle strength, sit-to-stand test, stair climb test, 20Â m walking speed and patient-reported outcome (HOOS).ResultsSixty-two completed the trial (85%). Leg extension power increased from baseline to the 10 week follow up in both groups; mean [95% CI] IG: 0.29 [0.13; 0.45] and CG: 0.26 [0.10; 0.42] W/kg, with no between-group difference (primary outcome) (PÂ =Â 0.79). Maximal walking speed (PÂ =Â 0.008) and stair climb performance (PÂ =Â 0.04) improved more in the IG compared to CG, no other between-group differences existed.ConclusionsIn this trial, supervised PRT twice a week in addition to 5 weekly sessions of unsupervised exercise for 10 weeks was not superior to 7 weekly sessions of unsupervised home-based exercise for 10 weeks in improving the primary outcome, leg-extension power of the operated leg, at the primary endpoint 10 weeks after surgery in THR patients with lower pre-operative function.Trial registration: NCT01214954
Two-years-worth of turbulence data recorded by a sonic-anemometer-based data acquisition system
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