10,205 research outputs found
Near threshold rotational excitation of molecular ions by electron-impact
New cross sections for the rotational excitation of H by electrons are
calculated {\it ab initio} at low impact energies. The validity of the
adiabatic-nuclei-rotation (ANR) approximation, combined with -matrix
wavefunctions, is assessed by comparison with rovibrational quantum defect
theory calculations based on the treatment of Kokoouline and Greene ({\it Phys.
Rev. A} {\bf 68} 012703 2003). Pure ANR excitation cross sections are shown to
be accurate down to threshold, except in the presence of large oscillating
Rydberg resonances. These resonances occur for transitions with
and are caused by closed channel effects. A simple analytic formula is derived
for averaging the rotational probabilities over such resonances in a 3-channel
problem. In accord with the Wigner law for an attractive Coulomb field,
rotational excitation cross sections are shown to be large and finite at
threshold, with a significant but moderate contribution from closed channels.Comment: 3 figures, a5 page
Electron-impact rotational and hyperfine excitation of HCN, HNC, DCN and DNC
Rotational excitation of isotopologues of HCN and HNC by thermal
electron-impact is studied using the molecular {\bf R}-matrix method combined
with the adiabatic-nuclei-rotation (ANR) approximation. Rate coefficients are
obtained for electron temperatures in the range 56000 K and for transitions
among all levels up to J=8. Hyperfine rates are also derived using the
infinite-order-sudden (IOS) scaling method. It is shown that the dominant
rotational transitions are dipole allowed, that is those for which . The hyperfine propensity rule is found to be stronger
than in the case of HeHCN collisions. For dipole allowed transitions,
electron-impact rates are shown to exceed those for excitation of HCN by He
atoms by 6 orders of magnitude. As a result, the present rates should be
included in any detailed population model of isotopologues of HCN and HNC in
sources where the electron fraction is larger than 10, for example in
interstellar shocks and comets.Comment: 12 pages, 4 figures, accepted in MNRAS (2007 september 3
Many parameter Hoelder perturbation of unbounded operators
If is a -mapping, for , having
as values unbounded self-adjoint operators with compact resolvents and common
domain of definition, parametrized by in an (even infinite dimensional)
space, then any continuous (in ) arrangement of the eigenvalues of is
indeed in .Comment: LaTeX, 4 pages; The result is generalized from Lipschitz to Hoelder.
Title change
Entropy of complex relevant components of Boolean networks
Boolean network models of strongly connected modules are capable of capturing
the high regulatory complexity of many biological gene regulatory circuits. We
study numerically the previously introduced basin entropy, a parameter for the
dynamical uncertainty or information storage capacity of a network as well as
the average transient time in random relevant components as a function of their
connectivity. We also demonstrate that basin entropy can be estimated from
time-series data and is therefore also applicable to non-deterministic networks
models.Comment: 8 pages, 6 figure
Discussion on a new model for the Hercynian Orogen of Gondwana France and Iberia by D. Shelley & G. Bossière.
In spite of numerous studies, the geodynamic evolution of the Hercynian Orogeny of Western Europe is still controversial. In a recent paper, Shelley and Bossière (2000) propose that the Hercynian Orogeny in Iberia and France was a ‘collage' of distinct fault-bounded ‘terranes' developed during a major dextral wrenching of more than 2000 km. This interpretation is in line with that already proposed by Badham (1982) but is at variance with most other published models that emphazise tangential tectonics, that is to say thrusting and collision tectonics driven by oceanic and continental subduction (e.g. Matte; Ledru; Dias and Faure and references therein). The Shelley and Bossière model has been criticized for parts dealing with the Iberian branch of the orogen by Pereira and Silva (2001). In the following, we shall comment on the strike-slip model for the S. Armorican branch of the belt, on the basis of first-hand geological data aquired from the SE part of the Armorican Massif ( Cartier and Cartier) and general considerations on the Hercynian Belt
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