5,132 research outputs found
Separation of two bodies in space. A machine programmed analysis using the Lagrange equations and Eulerian angles
Fortran computer program and Lagrangian motion equations for separation analysis of two bodies in spac
Separation of two bodies in space
Computer program analyzes the motion of two rigid bodies in space, separating as a result of any one, or a combination of, the following mechanisms - springs with ball ends, springs with one end guided, pyrotechnics, rockets, cold-gas jets, air pistons, and Coulomb drag
In-Situ Particle Acceleration in Extragalactic Radio Hot Spots: Observations Meet Expectations
We discuss, in terms of particle acceleration, the results from optical VLT
observations of hot spots associated with radio galaxies. On the basis of
observational and theoretical grounds, it is shown that:
1. relatively low radio-radio power hot spots are the optimum candidates for
being detected at optical waves. This is supported by an unprecedented optical
detection rate of 70% out of a sample of low radio power hot spots.
2. the shape of the synchrotron spectrum of hot spots is mainly determined by
the strength of the magnetic field in the region. In particular, the break
frequency, related to the age of the oldest electrons in the hot spots, is
found to increase with decreasing synchrotron power and magnetic field
strength.
Both observational results are in agreement with an in-situ particle
acceleration scenario.Comment: 5 pages, TeX (or Latex, etc), 4 figures, to appear in MNRAS Letter,
Updated reference
ALMA polarization observations of the particle accelerators in the hot spot of the radio galaxy 3C 445
We present Atacama Large Millimeter Array (ALMA) polarization observations at
97.5 GHz of the southern hot spot of the radio galaxy 3C 445. The hot spot
structure is dominated by two bright components enshrouded by diffuse emission.
Both components show fractional polarization between 30 and 40 per cent,
suggesting the presence of shocks. The polarized emission of the western
component has a displacement of about 0.5 kpc outward with respect to the total
intensity emission, and may trace the surface of a front shock. Strong
polarization is observed in a thin strip marking the ridge of the hot spot
structure visible from radio to optical. No significant polarization is
detected in the diffuse emission between the main components, suggesting a
highly disordered magnetic field likely produced by turbulence and
instabilities in the downstream region that may be at the origin of the
extended optical emission observed in this hot spot. The polarization
properties support a scenario in which a combination of both multiple and
intermittent shock fronts due to jet dithering, and spatially distributed
stochastic second-order Fermi acceleration processes are present in the hot
spot complex.Comment: 5 pages, 3 figures; accepted for publication in MNRAS Lette
Theoretical Analysis of Acceptance Rates in Multigrid Monte Carlo
We analyze the kinematics of multigrid Monte Carlo algorithms by
investigating acceptance rates for nonlocal Metropolis updates. With the help
of a simple criterion we can decide whether or not a multigrid algorithm will
have a chance to overcome critial slowing down for a given model. Our method is
introduced in the context of spin models. A multigrid Monte Carlo procedure for
nonabelian lattice gauge theory is described, and its kinematics is analyzed in
detail.Comment: 7 pages, no figures, (talk at LATTICE 92 in Amsterdam
Signatures in a Giant Radio Galaxy of a Cosmological Shock Wave at Intersecting Filaments of Galaxies
Sensitive images of low-level, Mpc-sized radio cocoons offer new
opportunities to probe large scale intergalactic gas flows outside clusters of
galaxies. New radio images of high surface brightness sensitivity at
strategically chosen wavelengths of the giant radio galaxy NGC 315 (Mack et al.
1997,1998) reveal significant asymmetries and particularities in the
morphology, radio spectrum and polarization of the ejected radio plasma. We
argue that the combination of these signatures provides a sensitive probe of an
environmental shock wave. Analysis of optical redshifts in NGC 315 vicinity
confirms its location to be near, or at a site of large-scale flow collisions
in the 100 Mpc sized Pisces-Perseus Supercluster region. NGC 315 resides at the
intersection of several galaxy filaments, and its radio plasma serves there as
a `weather station' (Burns 1998) probing the flow of the elusive and previously
invisible IGM gas. If our interpretation is correct, this is the first
indication for a shock wave in flows caused by the cosmological large scale
structure formation, which is located in a filament of galaxies. The
possibility that the putative shock wave is a source of gamma-rays and ultra
high energy cosmic rays is briefly discussed.Comment: accepted by Astrophysical Journal Letters, 4 pages, 3 figures (incl.
2 color), uses emulateapj5.sty (included), aastex.sty (included) and
psfig.st
Quality assurance in stereotactic radiosurgery/radiotherapy according to DIN 6875-1
The new DIN (' Deutsche Industrie- Norm') 6875- 1, which is currently being finalised, deals with quality assurance ( QA) criteria and tests methods for linear accelerator and Gamma Knife stereotactic radiosurgery/ radiotherapy including treatment planning, stereotactic frame and stereotactic imaging and a system test to check the whole chain of uncertainties. Our existing QA program, based on dedicated phantoms and test procedures, has been refined to fulfill the demands of this new DIN. The radiological and mechanical isocentre corresponded within 0.2 mm and the measured 50% isodose lines were in agreement with the calculated ones within less than 0.5 mm. The measured absorbed dose was within 3%. The resultant output factors measured for the 14-, 8- and 4- mm collimator helmet were 0.9870 +/- 0.0086, 0.9578 +/- 0.0057 and 0.8741 +/- 0.0202, respectively. For 170 consecutive tests, the mean geometrical accuracy was 0.48 +/- 0.23 mm. Besides QA phantoms and analysis software developed in- house, the use of commercially available tools facilitated the QA according to the DIN 6875- 1 with which our results complied. Copyright (C) 2004 S. Karger AG, Basel
Variational solution of the Yang-Mills Schr\"odinger equation in Coulomb gauge
The Yang-Mills Schr\"odinger equation is solved in Coulomb gauge for the
vacuum by the variational principle using an ansatz for the wave functional,
which is strongly peaked at the Gribov horizon. A coupled set of
Schwinger-Dyson equations for the gluon and ghost propagators in the Yang-Mills
vacuum as well as for the curvature of gauge orbit space is derived and solved
in one-loop approximation. We find an infrared suppressed gluon propagator, an
infrared singular ghost propagator and a almost linearly rising confinement
potential.Comment: 24 pages, revtex, 13 figure
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