2,751 research outputs found
Multiple resonance compensation for betatron coupling and its equivalence with matrix method
Analyses of betatron coupling can be broadly divided into two categories: the
matrix approach that decouples the single-turn matrix to reveal the normal
modes and the hamiltonian approach that evaluates the coupling in terms of the
action of resonances in perturbation theory. The latter is often regarded as
being less exact but good for physical insight. The common opinion is that the
correction of the two closest sum and difference resonances to the working
point is sufficient to reduce the off-axis terms in the 4X4 single-turn matrix,
but this is only partially true. The reason for this is explained, and a method
is developed that sums to infinity all coupling resonances and, in this way,
obtains results equivalent to the matrix approach. The two approaches is
discussed with reference to the dynamic aperture. Finally, the extension of the
summation method to resonances of all orders is outlined and the relative
importance of a single resonance compared to all resonances of a given order is
analytically described as a function of the working point.Comment: 22 pages, 10 figure
ICE encounter operations
The operations encompassing the International Cometary Explorer's (ICE) encounter with the Comet Giacobini-Zinner on September 11, 1985 are documented. The ICE mission presented new challenges for the Deep Space Network (DSN) 64 meter subnetwork. Because of poor telemetry link margin predicted for Giacobini-Zinner (GZ) encounter, supplemental support by the Japanese Institute for Space and Astronautical Sciences 64-meter antenna at Usuda, Japan and the 305-meter Arecibo Radio Observatory in Puerto Rico was required. To improve the 64 meter subnetwork telemetry performance the following were also implemented: (1) Real time antenna array of 64 meter and 34 meter at a single complex and the required performance testing; and (2) Nonreal time antenna array of two complexes was implemented as a backup in the event of ground or spacecraft failure
Chaotic dynamics in a storage-ring Free Electron Laser
The temporal dynamics of a storage-ring Free Electron Laser is here
investigated with particular attention to the case in which an external
modulation is applied to the laser-electron beam detuning. The system is shown
to produce bifurcations, multi-furcations as well as chaotic regimes. The
peculiarities of this phenomenon with respect to the analogous behavior
displayed by conventional laser sources are pointed out. Theoretical results,
obtained by means of a phenomenological model reproducing the evolution of the
main statistical parameters of the system, are shown to be in a good agreement
with experiments carried out on the Super-ACO Free Electron Laser.Comment: submitted to Europ Phys. Journ.
Intrinsic noise and two-dimensional maps: Quasicycles, quasiperiodicity, and chaos
We develop a formalism to describe the discrete-time dynamics of systems
containing an arbitrary number of interacting species. The individual-based
model, which forms our starting point, is described by a Markov chain, which in
the limit of large system sizes is shown to be very well-approximated by a
Fokker-Planck-like equation, or equivalently by a set of stochastic difference
equations. This formalism is applied to the specific case of two species: one
predator species and its prey species. Quasi-cycles --- stochastic cycles
sustained and amplified by the demographic noise --- previously found in
continuous-time predator-prey models are shown to exist, and their behavior
predicted from a linear noise analysis is shown to be in very good agreement
with simulations. The effects of the noise on other attractors in the
corresponding deterministic map, such as periodic cycles, quasiperiodicity and
chaos, are also investigated.Comment: 21 pages, 12 figure
Suppressing escape events in maps of the unit interval with demographic noise
We explore the properties of discrete-time stochastic processes with a
bounded state space, whose deterministic limit is given by a map of the unit
interval. We find that, in the mesoscopic description of the system, the large
jumps between successive iterates of the process can result in probability
leaking out of the unit interval, despite the fact that the noise is
multiplicative and vanishes at the boundaries. By including higher-order terms
in the mesoscopic expansion, we are able to capture the non-Gaussian nature of
the noise distribution near the boundaries, but this does not preclude the
possibility of a trajectory leaving the interval. We propose a number of
prescriptions for treating these escape events, and we compare the results with
those obtained for the metastable behavior of the microscopic model, where
escape events are not possible. We find that, rather than truncating the noise
distribution, censoring this distribution to prevent escape events leads to
results which are more consistent with the microscopic model. The addition of
higher moments to the noise distribution does not increase the accuracy of the
final results, and it can be replaced by the simpler Gaussian noise.Comment: 14 pages, 13 figure
Risk of Crimean Congo haemorrhagic fever virus (CCHFV) introduction and spread in CCHF-free countries in southern and Western Europe: A semi-quantitative risk assessment
Crimean-Congo hemorrhagic fever (CCHF) is a severe tick-borne viral zoonotic disease caused by Crimean-Congo hemorrhagic fever virus (CCHFV). The disease is usually asymptomatic in domestic and wild animals, both of which may act as reservoirs of the virus. CCHF is endemic in parts of Africa, Asia, the Middle East and Eastern Europe. During the last decade, the emergence or re-emergence of CCHF was described in several countries in the Eastern Mediterranean Region, with an increasing risk of extension into new areas. Given the public health importance, this study undertakes a semi-quantitative risk assessment to analyse the likelihood of entry and exposure of CCHFV into 9 CCHF-free countries in Southern and Western Europe. Based on a framework outlining the probability of the virus entry and exposure, the risk estimates were assessed for each individual country. The risk assessment was performed using information from public databases and the available scientific literature. The likelihood of entry was conducted considering 3 main pathways: infected tick vectors, wildlife and livestock. The likelihood of exposure was assessed considering the probability of survival of the infected ticks once introduced in CCHF-free countries (depending on abiotic and biotic factors), and the exposure of resident uninfected susceptible ticks to infected imported wildlife and livestock. The risk estimates (combined CCHFV introduction and exposure) were low for the majority of the countries (Austria, Belgium, Germany, Luxembourg, Netherlands, Slovenia and Switzerland) and medium for France and Italy, if accounting only for animal health consequences. Considering the public health consequences only, the risks were rated low for all the countries, except for Italy where it was assessed to be medium
Resonance families and their action on betatron motion
The present paper takes one step beyond the single-resonance theory for betatron motion by summing all the members of a given resonance family and expressing the joint influence in a single driving term. As a demonstration and confirmation of this work, the family driving terms are used to derive the classic closed-orbit and betatron-modulation equations of Courant and Snyder. A more serious demonstration is made by applying the family driving terms to the compensation of linear coupling and showing how numerical matrix-based and resonance compensation schemes are related. In a final phase, the HĂ©non map is used to compare the efficiency of different coupling compensation schemes with respect to dynamic aperture
Can a microscopic stochastic model explain the emergence of pain cycles in patients?
A stochastic model is here introduced to investigate the molecular mechanisms
which trigger the perception of pain. The action of analgesic drug compounds is
discussed in a dynamical context, where the competition with inactive species
is explicitly accounted for. Finite size effects inevitably perturb the
mean-field dynamics: Oscillations in the amount of bound receptors
spontaneously manifest, driven by the noise which is intrinsic to the system
under scrutiny. These effects are investigated both numerically, via stochastic
simulations and analytically, through a large-size expansion. The claim that
our findings could provide a consistent interpretative framework to explain the
emergence of cyclic behaviors in response to analgesic treatments, is
substantiated.Comment: J. Stat. Mech. (Proceedings UPON2008
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