35,335 research outputs found
The formation of planetary disks and winds: an ultraviolet view
Planetary systems are angular momentum reservoirs generated during star
formation. This accretion process produces very powerful engines able to drive
the optical jets and the molecular outflows. A fraction of the engine energy is
released into heating thus the temperature of the engine ranges from the 3000K
of the inner disk material to the 10MK in the areas where magnetic reconnection
occurs. There are important unsolved problems concerning the nature of the
engine, its evolution and the impact of the engine in the chemical evolution of
the inner disk. Of special relevance is the understanding of the shear layer
between the stellar photosphere and the disk; this layer controls a significant
fraction of the magnetic field building up and the subsequent dissipative
processes ougth to be studied in the UV.
This contribution focus on describing the connections between 1 Myr old suns
and the Sun and the requirements for new UV instrumentation to address their
evolution during this period. Two types of observations are shown to be needed:
monitoring programmes and high resolution imaging down to, at least,
milliarsecond scales.Comment: Accepted for publication in Astrophysics and Space Science 9 figure
Resetting a functional G1 nucleus after mitosis
© The Author(s) 2015. The maintenance of the correct cellular information goes beyond the simple transmission of an intact genetic code from one generation to the next. Epigenetic changes, topological cues and correct protein-protein interactions need to be re-established after each cell division to allow the next cell cycle to resume in the correct regulated manner. This process begins with mitotic exit and re-sets all the changes that occurred
during mitosis thus restoring a functional G1 nucleus in preparation for the next cell cycle. Mitotic exit is triggered by inactivation of mitotic kinases and the reversal of their phosphorylation activities on many cellular components, from nuclear lamina to transcription factors and chromatin itself. To reverse all these phosphorylations, phosphatases act during mitotic exit in a timely and spatially controlled manner directing the events that lead to a functional G1 nucleus. In this review, we will summarise the recent developments on the
control of phosphatases and their known substrates during mitotic exit, and the key steps that control the restoration of chromatin status, nuclear envelope reassembly and nuclear body re-organisation. Although pivotal work has been conducted in this area in yeast, due to differences between the mitotic exit network between yeast and vertebrates, we will mainly concentrate on the vertebrate system.BBSRC grant (BB/K017632/1)
Super Five Brane Hamiltonian and the Chiral Degrees of Freedom
We construct the Hamiltonian of the super five brane in terms of its physical
degrees of freedom. It does not depend on the inverse of the induced metric.
Consequently, some singular configurations are physically admissible, implying
an interpretation of the theory as a multiparticle one. The symmetries of the
theory are analyzed from the canonical point of view in terms of the first and
second class constraints. In particular it is shown how the chiral sector may
be canonically reduced to its physical degrees of freedom.Comment: 16 pages, typos correcte
Recommended from our members
Catalina Quesada y Kristine Vanden Berghe, editores. El libro y la vida. Ensayos críticos sobre la obra de Héctor Abad Faciolince. Liège; Medellín: Presses Universitaires de Liège; Editorial Eafit, 2019. 204 pp.
Catalina Quesada y Kristine Vanden Berghe, editores. El libro y la vida. Ensayos críticos sobre la obra de Héctor Abad Faciolince. Liège; Medellín: Presses Universitaires de Liège; Editorial Eafit, 2019.
204 pp
Derivation of a multilayer approach to model suspended sediment transport: application to hyperpycnal and hypopycnal plumes
We propose a multi-layer approach to simulate hyperpycnal and hypopycnal
plumes in flows with free surface. The model allows to compute the vertical
profile of the horizontal and the vertical components of the velocity of the
fluid flow. The model can describe as well the vertical profile of the sediment
concentration and the velocity components of each one of the sediment species
that form the turbidity current. To do so, it takes into account the settling
velocity of the particles and their interaction with the fluid. This allows to
better describe the phenomena than a single layer approach. It is in better
agreement with the physics of the problem and gives promising results. The
numerical simulation is carried out by rewriting the multi-layer approach in a
compact formulation, which corresponds to a system with non-conservative
products, and using path-conservative numerical scheme. Numerical results are
presented in order to show the potential of the model
Modeling non-thermal emission from stellar bow shocks
Runaway O- and early B-type stars passing throughout the interstellar medium
at supersonic velocities and characterized by strong stellar winds may produce
bow shocks that can serve as particle acceleration sites. Previous theoretical
models predict the production of high energy photons by non-thermal radiative
processes, but their efficiency is still debated. We aim to test and explain
the possibility of emission from the bow shocks formed by runaway stars
traveling through the interstellar medium by using previous theoretical models.
We apply our model to AE Aurigae, the first reported star with an X-ray
detected bow shock, to BD+43 3654, in which the observations failed in
detecting high energy emission, and to the transition phase of a supergiant
star in the late stages of its life.From our analysis, we confirm that the
X-ray emission from the bow shock produced by AE Aurigae can be explained by
inverse Compton processes involving the infrared photons of the heated dust. We
also predict low high energy flux emission from the bow shock produced by BD+43
3654, and the possibility of high energy emission from the bow shock formed by
a supergiant star during the transition phase from blue to red supergiant.Bow
shock formed by different type of runaway stars are revealed as a new possible
source of high energy photons in our neighbourhood
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