573 research outputs found
Irradiated disks and planet population synthesis
No full textRecent planet population synthesis models (Alibert et al. 2010, submitted) have emphasized the key role played by the proto-planetary disk properties in determining the overall planet population characteristics. We present a disk model that takes into account viscous heating and irradiation by a central star. We consider the case of an equilibrium flaring angle. We illustrate the consequences of the resulting changes in the disk structure on the planet population by the synthetic populations corresponding to each of the different structures
Testing planet formation models against observations
No full textIn this paper we present a short review of statistical properties
of extrasolar planets, and of the core-accretion model and some of its
extensions. We also present results of population synthesis models
based on extended core-accretion planet formation models
(taking into account disk structure and evolution and migration
of the protoplanet, see Alibert et al. 2005a).
The population synthesis is carried out by calculating
the evolution of many disk-protoplanet
systems, assuming initial conditions (in particular
disk mass, disk lifetime and metallicity of the system)
taken from observations. Taking into account the
observational bias introduced by radial velocity surveys,
we statistically compare the results of our
models and the population of known extrasolar
planets. We show that our models are able to quantitatively reproduce the
mass and semimajor axes
of extrasolar planets around solar type
stars. Finally, we discuss the effect of the mass of the central star on the planet
formation process and on the final planetary population
Volatiles enrichments and composition of Jupiter
No full textWe use the giant planets extended core-accretion model of Alibert et al. (2004, 2005) and the clathrate hydrate trapping theory to calculate the enrichments in O, C, N, S, Xe, Ar and Kr with respect to their solar abundances in Jupiter's atmosphere
Volatiles enrichments in Saturn - Predictions for Cassini
No full textWe use the giant planets extended core-accretion model of Alibert et al. (2004, 2005) and the clathrate hydrate trapping theory to calculate the enrichments in O, C, N, S, Xe, Ar and Kr with respect to their solar abundances in Saturn's atmosphere
Nosologie naturelle; ou les maladies du corps humain distribuées par familles. Tome premier
No full textAlibert, reconocido médico francés, conocido por su trabajo en dermatología y su clasificación de enfermedades propone una clasificación de las enfermedades del cuerpo humano basándose en un enfoque "natural", es decir agrupándolas por "familias" que presentan similitudes. es una obra trascendental en la historia de la medicina, que marcó un paso importante en la clasificación y el estudio de las enfermedades, particularmente en dermatología. Contiene unos grabados en color muy bonitos.[6], LXXXVIII, 616 p., : 31 hojas de láminas de grabados en color ; 35 c
Serie de casos diagnosticados con el síndrome de Alibert-Bazines en fase tumoral / A case series diagnosed with Alibert-Bazin syndrome in the tumor phase
No full textIntroducción: La micosis fungoide o síndrome de Alibert-Bazines es el linfoma primario cutáneo de células T más frecuente. La enfermedad progresa desde la aparición de máculas eritematosas hasta la formación de tumores, los que resulta poco común.Objetivo: Describir las particularidades de una serie de casos diagnosticados con el síndrome de Alibert-Bazines en fase tumoral.Casos clínicos: Se presentaron cuatro pacientes con lesiones tumorales y adenopatías causadas por micosis fungoide, que fueron atendidos en el Hospital Universitario "Manuel Ascunce Domenech" de Camagüey, en los últimos 10 años. En relación con al género, tres correspondieron al masculino y uno al femenino. Las edades oscilaron entre los 52 y 78 años, mientras la totalidad de los casos eran de tez blanca. El 75 % recibieron el esquema de tratamiento de quimioterapia, conformado por ciclofosfamida, doxorrubicina, vincristina y prednisona, más radioterapia adyuvante, mientras en los restantes casos se aplicó terapia con radiaciones. El paciente de mayor edad falleció por sepsis generalizada y los demás se mantuvieron asintomáticos.Conclusiones: La micosis fungoide es una enfermedad que, aunque afecta la piel debe ser conocida por otras especialidades médicas, pues el diagnóstico precoz y el tratamiento oportuno resultan elementos a tener en cuenta en el pronóstico. Aunque aún se desconoce la etiología, queda claro que el estudio histopatológico es fundamental para el dictamen médico, una vez instaurada la enfermedad
En Italie avec André Gide
No full text« Lundi, 19 mai. Retour d’Italie depuis mercredi dernier » : cette note du Journal d’André Gide contient tout ce que nous savions jusqu’ici de ce voyage du printemps 1913, fait en compagnie de ses amis Henri Ghéon, Eugène Rouart et François-Paul Alibert... Mais celui-ci avait conservé un journal de ces quinze jours où il était allé de découvertes émerveillées en émotions sans cesse renouvelées. Et ce texte inédit nous restitue les enchantements du poète dont, l’an dernier, les PUL révélaient les quarante années de sa belle correspondance avec Gide ; on y vit quelques jours dans la familiarité de celui-ci, alors déjà vieil amoureux de l’Italie... Ces pages se lisent comme on relit Stendhal, pour s’enchanter d’un rêve. Sa tendresse, son humour, son goût pour les êtres, sa passion pour l’amour qui passe, une certaine malédiction, tout cela qui constitue le vrai Alibert ne peut se dire simplement. Il faut le lire dans la confidence de ce récit. C’est la part d’infini dont il était secrètement en peine..
Planetesimal formation at the gas pressure bump following a migrating planet
No full textContext. Many scenarios have been proposed to avoid known difficulties in planetesimal formation such as drift or fragmentation barriers. However, in these scenarios planetesimals in general only form at some specific locations in protoplanetary discs. On the other hand, it is generally assumed in planet formation models and population synthesis models that planetesimals are broadly distributed in the protoplanetary disc.
Aims. We propose a new scenario in which planetesimals can form in broad areas of these discs. Planetesimals form at the gas pressure bump formed by a first-generation planet (e.g. formed by pebble accretion) and the formation region spreads inward in the disc as the planet migrates.
Methods. We used a simple 1D Lagrangian particle model to calculate the radial distribution of pebbles in the gas disc perturbed by a migrating embedded planet. We consider that planetesimals form by streaming instability at the points where the pebble-to-gas density ratio on the mid-plane becomes larger than unity. In this work, we fixed the Stokes number of pebbles and the mass of the planet to study the basic characteristics of this new scenario. We also studied the effect of some key parameters, such as the gas disc model, the pebble mass flux, the migration speed of the planet, and the strength of turbulence.
Results. We find that planetesimals form in wide areas of protoplanetary discs provided the flux of pebbles is typical and the turbulence is not too strong. The planetesimal surface density depends on the pebble mass flux and the migration speed of the planet. The total mass of the planetesimals and the orbital position of the formation area strongly depend on the pebble mass flux. We also find that the profile of the planetesimal surface density and its slope can be estimated by very simple equations.
Conclusions. We show that our new scenario can explain the formation of planetesimals in broad areas. The simple estimates we provide for the planetesimal surface density profile can be used as initial conditions for population synthesis models
Maximum mass of planetary embryos that formed in core-accretion models
No full textContext. In the core-accretion model, the typical size of solids that are accreted to form planetary embryos and planetary cores is debated. First, models assumed that the main part of planetary cores came from large-sized planetesimals, but other more recent models
are based on the accretion of small-sized pebbles.
Aims. The goal of this paper is to compute the maximum mass a growing planetary embryo can reach depending on the size of accreted planetesimals or pebbles, and to infer the possibility of growing the cores of giant planets and giant planets themselves.
Methods. We computed the internal structure of the gas envelope of planetary embryos to determine the core mass that is necessary to bind an envelope large enough to destroy planetesimals or pebbles while they are gravitationally captured. We also considered the
effect of the advection wind originating from the protoplanetary disk, following the results of Ormel et al. (2015).
Results.We show that for low-mass pebbles the envelope is large enough to destroy and vaporize pebbles completely before they can reach the core once the planetary embryo is larger than a fraction of the Earth mass. The material constituting pebbles is therefore
released in the planetary envelope and is later on dispersed in the protoplanetary disk if the advection wind is strong enough. As a consequence, the growth of the planetary embryo is stopped at a mass that is so low that Kelvin-Helmholtz accretion cannot lead to
the accretion of significant amounts of gas. For larger planetesimals, a similar process occurs but at much higher mass, on the order of ten Earth masses, and it is followed by rapid accretion of gas.
Conclusions. If the effect of the advection wind is as effcient as described in Ormel et al. (2015), the combined effect of the vaporization of accreted solids in the envelope of forming planetary embryos and of this advection wind prevents the growth of the planets
at masses lower than or similar to the Earth mass in the case of formation by pebble accretion, up to a distance on the order of 10 AU. In the case of formation by accretion of high-mass planetesimals, the growth of the planetary core is limited at masses on the order of ten Earth masses. However, in contrast to the case of pebble accretion, further growth is still possible and proceeds either through the accretion of gas or through the accretion of solids that are destroyed in the planetary envelope when the effect of the advection wind has ceased and the planetary Hill radius becomes comparable to the disk scale height
- …
