1,090 research outputs found
La convección y su tratamiento en los modelos de predicción numérica del tiempo
Los modelos de predicción numérica del tiempo han constituido uno de los avances más importantes de la meteorología, tanto de la investigación meteorológica como de la llamada meteorología operativa. Las predicciones del tiempo han mejorado como resultado de la constante mejora de los modelos numéricos. Como no es posible simular en laboratorio los procesos atmosféricos cualquier estudio sobre alguno de estos procesos debe hacerse en el marco de un modelo numérico que aporte el comportamiento general de la atmósfera. La convección atmosférica es uno de los procesos más importantes de los que regulan la redistribución energética en la atmósfera y uno de los temas más importantes en la investigación meteorológica. Este artículo realiza una revisión general y simplificada de los distintos esquemas que parametrizan los procesos convectivos dentro de los modelos numéricos. Tras una breve descripción de diferentes esquemas mostraremos los resultados de aplicar algunos de ellos a una situación de lluvias fuertes convectivas en España
Network perspective of histamine related diseases
Histamine is the most pleiotropic biogenic amine. Produced and stored by a limited set of cells—histaminergic neurons, enterochromaffin-like cells, and mast cells—it broadcasts intercellular communication signals to a wide variety of cell types through its tissue-specific receptors.
The many molecular interactions of these receptors and other mediators result in complex cellular networks whose alteration result in disease. Therefore, complex diseases map to modules of these cellular networks in the diseasomes.
In this communication, we survey the histamine cellular networks to map the histamine diseasome, presenting a network view of the pleiotropy of histamine and its role in several complex diseases.A.A. Moya is a CIBERER fellow. The "CIBER de Enfermedades Raras" is an initiative from the ISCIII (Spain)]. This communication has the support of a travel grant "Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech"
Age determination of the HR8799 planetary system using asteroseismology
Discovery of the first planetary system by direct imaging around HR8799 has
made the age determination of the host star a very important task. This
determination is the key to derive accurate masses of the planets and to study
the dynamical stability of the system. The age of this star has been estimated
using different procedures. In this work we show that some of these procedures
have problems and large uncertainties, and the real age of this star is still
unknown, needing more observational constraints. Therefore, we have developed a
comprehensive modeling of HR8799, and taking advantage of its gamma
Doradus-type pulsations, we have estimated the age of the star using
asteroseismology. The accuracy in the age determination depends on the rotation
velocity of the star, and therefore an accurate value of the inclination angle
is required to solve the problem. Nevertheless, we find that the age estimate
for this star previously published in the literature ([30,160] Myr) is
unlikely, and a more accurate value might be closer to the Gyr. This
determination has deep implications on the value of the mass of the objects
orbiting HR8799. An age around 1 Gyr implies that these objects are
brown dwarfs.Comment: 5 pages, 3 figures, accepted in MNRAS Letter
Measuring mean densities of delta Scuti stars with asteroseismology. Theoretical properties of large separations using TOUCAN
We aim at studying the theoretical properties of the regular spacings found
in the oscillation spectra of delta Scuti stars. We performed a multi-variable
analysis covering a wide range of stellar structure and seismic properties and
model parameters representative of intermediate-mass, main sequence stars. The
work-flow is entirely done using a new Virtual Observatory tool: TOUCAN (the VO
gateway for asteroseismic models), which is presented in this paper. A linear
relation between the large separation and the mean density is predicted to be
found in the low frequency frequency domain (i.e. radial orders spanning from 1
to 8, approximately) of the main-sequence, delta Scuti stars' oscillation
spectrum. We found that such a linear behavior stands whatever the mass,
metallicity, mixing length, and overshooting parameters considered in this
work. The intrinsic error of the method is discussed. This includes the
uncertainty in the large separation determination and the role of rotation. The
validity of the relation found is only guaranteed for stars rotating up to 40
percent of their break-up velocity. Finally, we applied the diagnostic method
presented in this work to five stars for which regular patterns have been
found. Our estimates for the mean density and the frequency of the fundamental
radial mode match with those given in the literature within a 20 percent of
deviation. Asteroseismology has thus revealed an independent direct measure of
the average density of delta Scuti stars, analogous to that of the Sun. This
places tight constraints on the mode identification and hence on the stellar
internal structure and dynamics, and allows a determination the radius of
planets orbiting around delta Scuti stars with unprecedented precision. This
opens the way for studying the evolution of regular patterns in pulsating
stars, and its relation with stellar structure and evolution.Comment: 11 pages, 6 figures, A&A in pres
Sensitivity of the g-mode frequencies to pulsation codes and their parameters
From the recent work of the Evolution and Seismic Tools Activity (ESTA,
Lebreton et al. 2006; Monteiro et al. 2008), whose Task 2 is devoted to compare
pulsational frequencies computed using most of the pulsational codes available
in the asteroseismic community, the dependence of the theoretical frequencies
with non-physical choices is now quite well fixed. To ensure that the accuracy
of the computed frequencies is of the same order of magnitude or better than
the observational errors, some requirements in the equilibrium models and the
numerical resolutions of the pulsational equations must be followed. In
particular, we have verified the numerical accuracy obtained with the Saclay
seismic model, which is used to study the solar g-mode region (60 to
140Hz). We have compared the results coming from the Aarhus adiabatic
pulsation code (ADIPLS), with the frequencies computed with the Granada Code
(GraCo) taking into account several possible choices. We have concluded that
the present equilibrium models and the use of the Richardson extrapolation
ensure an accuracy of the order of in the determination of the
frequencies, which is quite enough for our purposes.Comment: 10 pages, 5 figures, accepted in Solar Physic
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