3,803 research outputs found
High-velocity runaway stars from three-body encounters
We performed numerical simulations of dynamical encounters between hard
massive binaries and a very massive star (VMS; formed through runaway mergers
of ordinary stars in the dense core of a young massive star cluster), in order
to explore the hypothesis that this dynamical process could be responsible for
the origin of high-velocity (\geq 200-400 km/s) early or late B-type stars. We
estimated the typical velocities produced in encounters between very tight
massive binaries and VMSs (of mass of \geq 200 Msun) and found that about 3-4
per cent of all encounters produce velocities of \geq 400 km/s, while in about
2 per cent of encounters the escapers attain velocities exceeding the Milky
Ways's escape velocity. We therefore argue that the origin of high-velocity
(\geq 200-400 km/s) runaway stars and at least some so-called hypervelocity
stars could be associated with dynamical encounters between the tightest
massive binaries and VMSs formed in the cores of star clusters. We also
simulated dynamical encounters between tight massive binaries and single
ordinary 50-100 Msun stars. We found that from 1 to \simeq 4 per cent of these
encounters can produce runaway stars with velocities of \geq 300-400 km/s
(typical of the bound population of high-velocity halo B-type stars) and
occasionally (in less than 1 per cent of encounters) produce hypervelocity
(\geq 700 km/s) late B-type escapers.Comment: 4 pages, 2 figure, to appear in Star Clusters -- Basic Galactic
Building Blocks throughout Time and Space, Proceed. of the IAU Symp. 266,
eds. R. de Grijs and J. Lepin
Exact solutions for the spatial de Vaucouleurs and Sersic laws and related quantities
Using the Mathematica package, we find exact analytical expressions for the
so-called de-projected De Vaucouleurs and Sersic laws as well as for related
spatial (3D) quantities, such the mass, gravitational potential, the total
energy and the central velocity dispersion, generally involved in astronomical
calculations expressed in terms of the Meijer G functions.Comment: 11 pages, accepted in A
Route to turbulence in a trapped Bose-Einstein condensate
We have studied a Bose-Einstein condensate of atoms under an
oscillatory excitation. For a fixed frequency of excitation, we have explored
how the values of amplitude and time of excitation must be combined in order to
produce quantum turbulence in the condensate. Depending on the combination of
these parameters different behaviors are observed in the sample. For the lowest
values of time and amplitude of excitation, we observe a bending of the main
axis of the cloud. Increasing the amplitude of excitation we observe an
increasing number of vortices. The vortex state can evolve into the turbulent
regime if the parameters of excitation are driven up to a certain set of
combinations. If the value of the parameters of these combinations is exceeded,
all vorticity disappears and the condensate enters into a different regime
which we have identified as the granular phase. Our results are summarized in a
diagram of amplitude versus time of excitation in which the different
structures can be identified. We also present numerical simulations of the
Gross-Pitaevskii equation which support our observations.Comment: 6 pages, 3 figure
Molecular Mechanism and Potential Targets for Blocking HPV-Induced Lesion Development
Persistent infection with high-risk HPV is the etiologic agent associated with the development of cervical cancer (CC) development. However, environmental, social, epidemiological, genetic, and host factors may have a joint influence on the risk of disease progression. Cervical lesions caused by HPV infection can be removed naturally by the host immune response and only a small percentage may progress to cancer; thus, the immune response is essential for the control of precursor lesions and CC. We present a review of recent research on the molecular mechanisms that allow HPV-infected cells to evade immune surveillance and potential targets of molecular therapy to inhibit tumor immune escape
Uniportal fully robotic-assisted bronchovascular sleeve bilobectomy
info:eu-repo/semantics/publishedVersio
Uniportal robotic-assisted thoracic surgery for mediastinal tumors
info:eu-repo/semantics/publishedVersio
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