10,723 research outputs found
Cross border Classical Swine Fever control: Improving Dutch and German crisis management systems by an integrated public-private approach
The objective of this research approach is to analyse in which ways crisis management measures against Classical Swine Fever (CSF) can be improved by a public private cross border model. A core activity contains the analysis of information and communication systems: In a case study it has been empirically analysed if a sufficient supply of public and private information enables crisis managers at both sides of the Dutch-German border area to take decisions about CSF control more efficient. At the end of this approach a new crisis management model had been developed. One of the most important aspects thereby is the assessment of data: (1) within private quality management systems in normal times according to the benefit for public management tasks in times of crisis and (2) within public crisis management systems according to the benefit for cross-border CSF-control activities. To this effect two different methodological approaches have been combined within the model: (1) a method to identify and illustrate public actors and their options in crisis management decision making and (2) a system of communication and information exchange between public and private as well as Dutch and German actors (engage& exchange model) which permit to collect and to evaluate data in addition for a predefined time period are activated
Anti-de Sitter boundary in Poincare coordinates
We study the space-time boundary of a Poincare patch of Anti-de Sitter (AdS)
space. We map the Poincare AdS boundary to the global coordinate chart and show
why this boundary is not equivalent to the global AdS boundary. The Poincare
AdS boundary is shown to contain points of the bulk of the entire AdS space.
The Euclidean AdS space is also discussed. In this case one can define a
semi-global chart that divides the AdS space in the same way as the
corresponding Euclidean Poincare chart.Comment: In this revised version we add a discussion of the physical
consequences of the choice of a coordinate system for AdS space. We changed
figure 1 and added more references. Version to be published in Gen. Relat.
Grav
Variable Stars in the Unusual, Metal-Rich Globular Cluster NGC 6388
We have undertaken a search for variable stars in the metal-rich globular
cluster NGC 6388 using time-series BV photometry. Twenty-eight new variables
were found in this survey, increasing the total number of variables found near
NGC 6388 to ~57. A significant number of the variables are RR Lyrae (~14), most
of which are probable cluster members. The periods of the fundamental mode RR
Lyrae are shown to be unusually long compared to metal-rich field stars. The
existence of these long period RRab stars suggests that the horizontal branch
of NGC 6388 is unusually bright. This implies that the metallicity-luminosity
relationship for RR Lyrae stars is not universal if the RR Lyrae in NGC 6388
are indeed metal-rich. We consider the alternative possibility that the stars
in NGC 6388 may span a range in [Fe/H]. Four candidate Population II Cepheids
were also found. If they are members of the cluster, NGC 6388 would be the most
metal-rich globular cluster to contain Population II Cepheids. The mean V
magnitude of the RR Lyrae is found to be 16.85+/-0.05 resulting in a distance
of 9.0 to 10.3 kpc, for a range of assumed values of for RR Lyrae. We
determine the reddening of the cluster to be E(B-V)=0.40+/-0.03 mag, with
differential reddening across the face of the cluster. We discuss the
difficulty in determining the Oosterhoff classification of NGC 6388 and NGC
6441 due to the unusual nature of their RR Lyrae, and address evolutionary
constraints on a recent suggestion that they are of Oosterhoff type II.Comment: 35 pages, 16 figures, emulateapj5/apjfonts style. Astronomical
Journal, in press. We recommend the interested reader to download instead the
preprint with full-resolution figures, which can be found at
http://www.noao.edu/noao/staff/pritzl/clusters.htm
Trapping in the random conductance model
We consider random walks on among nearest-neighbor random conductances
which are i.i.d., positive, bounded uniformly from above but whose support
extends all the way to zero. Our focus is on the detailed properties of the
paths of the random walk conditioned to return back to the starting point at
time . We show that in the situations when the heat kernel exhibits
subdiffusive decay --- which is known to occur in dimensions --- the
walk gets trapped for a time of order in a small spatial region. This shows
that the strategy used earlier to infer subdiffusive lower bounds on the heat
kernel in specific examples is in fact dominant. In addition, we settle a
conjecture concerning the worst possible subdiffusive decay in four dimensions.Comment: 21 pages, version to appear in J. Statist. Phy
Variable stars in the Fornax dSph Galaxy. II. Pulsating stars below the horizontal branch
We have carried out an intensive survey of the northern region of the Fornax
dwarf spheroidal galaxy with the aim of detecting the galaxy's short--period
pulsating stars (P<0.25 days). Observations collected over three consecutive
nights with the Wide Field Imager of the 2.2m MPI telescope at ESO allowed us
to detect 85 high-amplitude (0.20-1.00 mag in B-light) variable stars with
periods in the range from 0.046 to 0.126 days, similar to SX Phoenicis stars in
Galactic metal-poor stellar populations. The plots of the observed periods vs.
the B and V magnitudes show a dispersion largely exceeding the observational
errors. To disentangle the matter, we separated the first-overtone from the
fundamental-mode pulsators and tentatively identified a group of subluminous
variables, about 0.35 mag fainter than the others. Their nature as either
metal-poor intermediate-age stars or stars formed by the merging of close
binary systems is discussed. The rich sample of the Fornax variables also led
us to reconstruct the Period-Luminosity relation for short-period pulsating
stars. An excellent linear fit, M(V)=-1.83(+/-0.08)-3.65(+/-0.07) log P(fund),
was obtained using 153 Delta Scuti and SX Phoenicis stars in a number of
different stellar systems.Comment: 11 pages plus 1 on-line figure and 1 on-line table; accepted for
publication in ApJ. Part of this work has been the subject of the Laurea
thesis of LDA. His supervisor and our colleague, Prof. Laura E. Pasinetti,
suddendly passed away on September 13, 2006. Several astronomers have been
trained under her tutelage and we gratefully honor her memor
Four New Delta Scuti Pulsators from a Variability Survey of 131 Stars
In a photometric variability survey of 131 stars with B < 14 mag, we have
found four new Delta Scuti stars. We were sensitive to oscillation amplitudes
as low as a few mmag. The detection rate of short-period (P < 0.1 d) pulsating
variable stars, which may be relevant for planned large variability surveys
such as GAIA, POI, and even the LSST, was therefore 3%. All four new variable
stars have low pulsation amplitude (tens of mmag), and one has a very short
period (0.0198 d). This star is one of the fastest known Delta Scuti pulsators.
The short period of this variable star makes it observationally tractable, and
it may therefore be a particularly good candidate for asteroseismological
studies. All four new variable stars will add to the cadre of low-amplitude and
relatively short-period Delta Scuti stars that are potentially useful for
learning about the structure of stars on or near the main sequence, slightly
more massive than the Sun.Comment: To appear in the June 2002 issue of PASP, 9 pages, 6 figure
Hierarchical model for the scale-dependent velocity of seismic waves
Elastic waves of short wavelength propagating through the upper layer of the
Earth appear to move faster at large separations of source and receiver than at
short separations. This scale dependent velocity is a manifestation of Fermat's
principle of least time in a medium with random velocity fluctuations. Existing
perturbation theories predict a linear increase of the velocity shift with
increasing separation, and cannot describe the saturation of the velocity shift
at large separations that is seen in computer simulations. Here we show that
this long-standing problem in seismology can be solved using a model developed
originally in the context of polymer physics. We find that the saturation
velocity scales with the four-third power of the root-mean-square amplitude of
the velocity fluctuations, in good agreement with the computer simulations.Comment: 7 pages including 3 figure
Heat conduction in 1D lattices with on-site potential
The process of heat conduction in one-dimensional lattice with on-site
potential is studied by means of numerical simulation. Using discrete
Frenkel-Kontorova, --4 and sinh-Gordon we demonstrate that contrary to
previously expressed opinions the sole anharmonicity of the on-site potential
is insufficient to ensure the normal heat conductivity in these systems. The
character of the heat conduction is determined by the spectrum of nonlinear
excitations peculiar for every given model and therefore depends on the
concrete potential shape and temperature of the lattice. The reason is that the
peculiarities of the nonlinear excitations and their interactions prescribe the
energy scattering mechanism in each model. For models sin-Gordon and --4
phonons are scattered at thermalized lattice of topological solitons; for
sinh-Gordon and --4 - models the phonons are scattered at localized
high-frequency breathers (in the case of --4 the scattering mechanism
switches with the growth of the temperature).Comment: 26 pages, 18 figure
Monte-Carlo Simulations of Radiation-Induced Activation in a Fast-Neutron and Gamma- Based Cargo Inspection System
An air cargo inspection system combining two nuclear reaction based
techniques, namely Fast-Neutron Resonance Radiography and Dual-Discrete-Energy
Gamma Radiography is currently being developed. This system is expected to
allow detection of standard and improvised explosives as well as special
nuclear materials. An important aspect for the applicability of nuclear
techniques in an airport inspection facility is the inventory and lifetimes of
radioactive isotopes produced by the neutron and gamma radiation inside the
cargo, as well as the dose delivered by these isotopes to people in contact
with the cargo during and following the interrogation procedure. Using MCNPX
and CINDER90 we have calculated the activation levels for several typical
inspection scenarios. One example is the activation of various metal samples
embedded in a cotton-filled container. To validate the simulation results, a
benchmark experiment was performed, in which metal samples were activated by
fast-neutrons in a water-filled glass jar. The induced activity was determined
by analyzing the gamma spectra. Based on the calculated radioactive inventory
in the container, the dose levels due to the induced gamma radiation were
calculated at several distances from the container and in relevant time windows
after the irradiation, in order to evaluate the radiation exposure of the cargo
handling staff, air crew and passengers during flight. The possibility of
remanent long-lived radioactive inventory after cargo is delivered to the
client is also of concern and was evaluated.Comment: Proceedings of FNDA 201
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