1,025 research outputs found
Feedback-limited Accretion: Luminous Signatures from Growing Planets
Planets form in discs of gas and dust around stars, and keep growing by
accretion of disc material while available. Massive planets clear a gap in that
protoplanetary disc, but still accrete through spiral wakes. On its way to the
planet, the gas will settle on a \emph{circumplanetary} disc around the planet
and slowly accrete on to it. The energy of the accreted gas will be released,
heating the planet surroundings in a feedback process. For high enough
accretion rates the planet should be detectable at infrared wavelengths. We aim
to find whether detectable planet luminosities, , can occur when considering that the planet luminosity is
coupled to the accretion, and also to study which other effects has the
feedback on the dynamics of the circumplanetary and the gap regions. We model a
planet with mass ratio , orbiting at 10 AU from a solar mass star,
using a modified version of the 2D code FARGO-AD, which includes a prescription
for the accretion and feedback luminosity of the planet. We find that the
planetary feedback is able to partially deplete the circumplanetary disc, and
to reduce the accretion rate onto the planet. However, detectable luminosities
of are still produced. The
feedback also contributes to partially refilling the gap, to heat up the
coorbital region, and to perturb the orbital velocity of the gas.Comment: Submitted to MNRA
Marites Culture in the Philippines: An Emergent Online Gossip Phenomenon
This research article explores the emergence and characteristics of Marites culture in the Philippines, specifically focusing on its role in shaping social relations and communication during the pandemic and the present. Utilizing literature review approach and sociological perspectives, the study analyzes media reports and online sources to investigate the origins, features, and implications of Marites culture. The research emphasizes the significance of Marites culture as a reflection of broader social and cultural trends in the Philippines, including the increasing importance of online communication and the influence of traditional gossip practices. Moreover, the study examines the potential advantages and disadvantages of Marites culture, such as its ability to disseminate information and shape public opinion, as well as its potential to spread misinformation and trigger social tensions. The findings underscore the necessity for a critical and nuanced understanding of emerging cultural phenomena, considering their historical, social, and cultural contexts and implications
Dusty spirals triggered by shadows in transition discs
Context. Despite the recent discovery of spiral-shaped features in
protoplanetary discs in the near-infrared and millimetric wavelengths, there is
still an active discussion to understand how they formed. In fact, the spiral
waves observed in discs around young stars can be due to different physical
mechanisms: planet/companion torques, gravitational perturbations or
illumination effects. Aims. We study the spirals formed in the gaseous phase
due to two diametrically opposed shadows cast at fixed disc locations. The
shadows are created by an inclined non-precessing disc inside the cavity, which
is assumed to be optically thick. In particular, we analyse the effect of these
spirals on the dynamics of the dust particles and discuss their detectability
in transition discs. Methods. We perform gaseous hydrodynamical simulations
with shadows, then we compute the dust evolution on top of the gaseous
distribution, and finally we produce synthetic ALMA observations of the dust
emission based on radiative transfer calculations. Results. Our main finding is
that mm- to cm-sized dust particles are efficiently trapped inside the
shadow-triggered spirals. We also observe that particles of various sizes
starting at different stellocentric distances are well mixed inside these
pressure maxima. This dynamical effect would favour grain growth and affect the
resulting composition of planetesimals in the disc. In addition, our radiative
transfer calculations show spiral patterns in the disc at 1.6 {\mu}m and 1.3
mm. Due to their faint thermal emission (compared to the bright inner regions
of the disc) the spirals cannot be detected with ALMA. Our synthetic
observations prove however that shadows are observable as dips in the thermal
emission.Comment: 15 pages, 11 figures, accepted for publication in A&
Producción de Anabaena sp. ATCC 33047 y valorización de la fracción proteica de su biomasa.
La cianobacteria Anabaena sp. ATCC 33047, se ha cultivado en 3 medios de cultivo exentos de nitrógeno, que varÃan ligeramente en su composición, más otro medio con fuente de nitrógeno asimilable. Con ello se determinó que el uso de fertilizantes agrÃcolas exentos de nitrógeno en la formulación de éstos, es adecuado para la producción de esta cianobacteria en sistemas a gran escala. Por otro lado, la adición de una fuente de nitrógeno en el medio de cultivo, mejoró la viabilidad y velocidad de crecimiento de la cianobacteria. La biomasa obtenida de Anabaena, se ha utilizado para la obtención de un suplemento nutricional para plantas, mediante la hidrólisis enzimática de las proteÃnas contenidas en esta biomasa. Este producto, con una concentración en aminoácidos sobre 36 g/L, se obtiene de la separación de la masa sólida residual y de la fase acuosa, de la mezcla hidrolizada enzimáticamente
Estimation of <i>Vs</i> profile using its natural frequency and Rayleigh-wave dispersion characteristics
International audienceThe evaluation of the natural frequency of random Vs profiles before analyzing the fundamental Rayleigh-wave dispersion characteristics is proposed in this paper. The inclusion of this parameter optimizes the effectiveness of random inverse searching to estimate Vs profiles. To demonstrate this method, a numerical test was performed using the "experimental" Rayleigh-wave dispersion curve obtained for a fictitious TEST site
Limiting eccentricity of sub-parsec massive black hole binaries surrounded by self-gravitating gas discs
We study the dynamics of supermassive black hole binaries embedded in
circumbinary gaseous discs, with the SPH code Gadget-2. The sub-parsec binary
(of total mass M and mass ratio q=1/3) has excavated a gap and transfers its
angular momentum to the self--gravitating disc (M_disc=0.2 M). We explore the
changes of the binary eccentricity e, by simulating a sequence of binary models
that differ in the initial eccentricity e_0, only. In initially low-eccentric
binaries, the eccentricity increases with time, while in high-eccentric
binaries e declines, indicating the existence of a limiting eccentricity e_crit
that is found to fall in the interval [0.6,0.8]. We also present an analytical
interpretation for this saturation limit. An important consequence of the
existence of e_crit is the detectability of a significant residual eccentricity
e_LISA} by the proposed gravitational wave detector LISA. It is found that at
the moment of entering the LISA frequency domain e_LISA ~ 10^{-3}-10^{-2}; a
signature of its earlier coupling with the massive circumbinary disc. We also
observe large periodic inflows across the gap, occurring on the binary and disc
dynamical time scales rather than on the viscous time. These periodic changes
in the accretion rate (with amplitudes up to ~100%, depending on the binary
eccentricity) can be considered a fingerprint of eccentric sub-parsec binaries
migrating inside a circumbinary disc.Comment: 10 pages, 7 figures, accepted for publication in MNRA
Evaluation of RegCM4 over the CORDEX South America Domain: Sensitivity analysis to the Land Surface Scheme for the Amazon Basin.
Comparison of RegCM4 and gauges for temperature and precipitation characteristics in Sao Paulo on high frequency timescales.
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