327 research outputs found
Theory for planetary exospheres: III. Radiation pressure effect on the Circular Restricted Three Body Problem and its implication on planetary atmospheres
The planetary exospheres are poorly known in their outer parts, since the
neutral densities are low compared with the instruments detection capabilities.
The exospheric models are thus often the main source of information at such
high altitudes. We present a new way to take into account analytically the
additional effect of the stellar radiation pressure on planetary exospheres. In
a series of papers, we present with an Hamiltonian approach the effect of the
radiation pressure on dynamical trajectories, density profiles and escaping
thermal flux. Our work is a generalization of the study by Bishop and
Chamberlain (1989). In this third paper, we investigate the effect of the
stellar radiation pressure on the Circular Restricted Three Body Problem
(CR3BP), called also the photogravitational CR3BP, and its implication on the
escape and the stability of planetary exospheres, especially for Hot Jupiters.
In particular, we describe the transformation of the equipotentials and the
location of the Lagrange points, and we provide a modified equation for the
Hill sphere radius that includes the influence of the radiation pressure.
Finally, an application to the hot Jupiter HD 209458b reveals the existence of
a blow-off escape regime induced by the stellar radiation pressure
Theory for planetary exospheres: I. Radiation pressure effect on dynamical trajectories
The planetary exospheres are poorly known in their outer parts, since the
neutral densities are low compared with the instruments detection capabilities.
The exospheric models are thus often the main source of information at such
high altitudes. We present a new way to take into account analytically the
additional effect of the radiation pressure on planetary exospheres. In a
series of papers, we present with an Hamiltonian approach the effect of the
radiation pressure on dynamical trajectories, density profiles and escaping
thermal flux. Our work is a generalization of the study by Bishop and
Chamberlain (1989). In this first paper, we present the complete exact
solutions of particles trajectories, which are not conics, under the influence
of the solar radiation pressure. This problem was recently partly solved by
Lantoine and Russell (2011) and completely by Biscani and Izzo (2014). We give
here the full set of solutions, including solutions not previously derived, as
well as simpler formulations for previously known cases and comparisons with
recent works. The solutions given may also be applied to the classical Stark
problem (Stark,1914): we thus provide here for the first time the complete set
of solutions for this well-known effect in term of Jacobi elliptic functions
Correcting Errors Using the Framework of Argumentation: Towards Generating Argumentative Correction Propositions from Error Annotation Schemas
PACLIC 23 / City University of Hong Kong / 3-5 December 200
Nonlinear dynamics of waves and modulated waves in 1D thermocapillary flows. I: General presentation and periodic solutions
We present experimental results on hydrothermal traveling-waves dynamics in
long and narrow 1D channels. The onset of primary traveling-wave patterns is
briefly presented for different fluid heights and for annular or bounded
channels, i.e., within periodic or non-periodic boundary conditions. For
periodic boundary conditions, by increasing the control parameter or changing
the discrete mean-wavenumber of the waves, we produce modulated waves patterns.
These patterns range from stable periodic phase-solutions, due to supercritical
Eckhaus instability, to spatio-temporal defect-chaos involving traveling holes
and/or counter-propagating-waves competition, i.e., traveling sources and
sinks. The transition from non-linearly saturated Eckhaus modulations to
transient pattern-breaks by traveling holes and spatio-temporal defects is
documented. Our observations are presented in the framework of coupled complex
Ginzburg-Landau equations with additional fourth and fifth order terms which
account for the reflection symmetry breaking at high wave-amplitude far from
onset. The second part of this paper (nlin.PS/0208030) extends this study to
spatially non-periodic patterns observed in both annular and bounded channel.Comment: 45 pages, 21 figures (elsart.cls + AMS extensions). Accepted in
Physica D. See also companion paper "Nonlinear dynamics of waves and
modulated waves in 1D thermocapillary flows. II: Convective/absolute
transitions" (nlin.PS/0208030). A version with high resolution figures is
available on N.G. web pag
Nonlinear dynamics of waves and modulated waves in 1D thermocapillary flows. II: Convective/absolute transitions
We present experimental results on hydrothermal waves in long and narrow 1D
channels. In a bounded channel, we describe the primary and secondary
instabilities leading to waves and modulated waves in terms of
convective/absolute transitions. Because of on the combined effect of finite
group velocity and of the presence of boundaries, the wave-patterns are
non-uniform in space. We also investigate non-uniform wave-patterns observed in
an annular channel in the presence of sources and sinks of hydrothermal waves.
We connect our observations with the complex Ginzburg-Landau model equation in
the very same way as in the first part of the paper (nlin.PS/0208029).Comment: 37 pages, 23 figures (elsart.cls + AMS extensions). Accepted in
Physica D. See also companion paper "Nonlinear dynamics of waves and
modulated waves in 1D thermocapillary flows. I: General presentation and
periodic solutions" (nlin.PS/0208029). A version with high resolution figures
is available on N.G. webpag
Mental maps of students - Volume 5
This eurobroadmap working paper, split in 5 different volumes, presents the synthesis of a large survey launched in 2009 on 9000 undergraduate students from 18 different countries. The volume 1 includes the executive summary, plus elements regarding the five different volumes (references, list of figures, etc). The second one presents the aims and the organisation of the survey. The third one deals with the scale of the feeling of belonging. The fourth one presents explanatory models about countries and cities attractiveness. The final volume presents Europe representations in both cartographic and lexical ways
Convective and absolute Eckhaus instability leading to modulated waves in a finite box
We report experimental study of the secondary modulational instability of a
one-dimensional non-linear traveling wave in a long bounded channel. Two
qualitatively different instability regimes involving fronts of spatio-temporal
defects are linked to the convective and absolute nature of the instability.
Both transitions appear to be subcritical. The spatio-temporal defects control
the global mode structure.Comment: 5 pages, 7 figures (ReVTeX 4 and amsmath.sty), final versio
Females tend to prefer genetically similar mates in an island population of house sparrows
BACKGROUND: It is often proposed that females should select genetically dissimilar mates to maximize offspring genetic diversity and avoid inbreeding. Several recent studies have provided mixed evidence, however, and in some instances females seem to prefer genetically similar males. A preference for genetically similar mates can be adaptive if outbreeding depression is more harmful than inbreeding depression or if females gain inclusive fitness benefits by mating with close kin. Here, we investigated genetic compatibility and mating patterns in an insular population of house sparrow (Passer domesticus), over a three-year period, using 12 microsatellite markers and one major histocompability complex (MHC) class I gene. Given the small population size and the distance from the mainland, we expected a reduced gene flow in this insular population and we predicted that females would show mating preferences for genetically dissimilar mates. RESULTS: Contrary to our expectation, we found that offspring were less genetically diverse (multi-locus heterozygosity) than expected under a random mating, suggesting that females tended to mate with genetically similar males. We found high levels of extra-pair paternity, and offspring sired by extra-pair males had a better fledging success than those sired by the social male. Again, unexpectedly, females tended to be more closely related to extra-pair mates than to their social mates. Our results did not depend on the type of genetic marker used, since microsatellites and MHC genes provided similar results, and we found only little evidence for MHC-dependent mating patterns. CONCLUSIONS: These results are in agreement with the idea that mating with genetically similar mates can either avoid the disruption of co-adapted genes or confer a benefit in terms of kin selection
Filière « Histoire sociale et démographie »
Stéphane Baciocchi, Pascal Cristofoli, Jean-Daniel Gronoff, ingénieurs d’études et Matthieu Loitron, doctorant avec Arnaud Bringé et Bénédicte Garnier, ingénieurs à l’INED Atelier informatique. Analyse des données relationnelles Initié par des ingénieurs en sciences sociales soucieux de partager leur savoir-faire et leurs différentes expériences de recherche à l’EHESS et à l’INED, l’atelier a pris cette année un tour plus pédagogique que proprement technique. Face au nombre croissant des util..
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