28,751 research outputs found
Polydispersity Effects in the Dynamics and Stability of Bubbling Flows
The occurrence of swarms of small bubbles in a variety of industrial systems
enhances their performance. However, the effects that size polydispersity may
produce on the stability of kinematic waves, the gain factor, mean bubble
velocity, kinematic and dynamic wave velocities is, to our knowledge, not yet
well established. We found that size polydispersity enhances the stability of a
bubble column by a factor of about 23% as a function of frequency and for a
particular type of bubble column. In this way our model predicts effects that
might be verified experimentally but this, however, remain to be assessed. Our
results reinforce the point of view advocated in this work in the sense that a
description of a bubble column based on the concept of randomness of a bubble
cloud and average properties of the fluid motion, may be a useful approach that
has not been exploited in engineering systems.Comment: 11 pages, 2 figures, presented at the 3rd NEXT-SigmaPhi International
Conference, 13-18 August, 2005, Kolymbari, Cret
Mercury and selenium binding biomolecules in terrestrial mammals (Cervus elaphus and Sus scrofa) from a mercury exposed area
Acknowledgements The authors are grateful to Junta de Comunidades de Castilla-La Mancha (PCC-05-004-2, PAI06-0094, PCI-08-0096, PEII09-0032-5329) and the Ministerio de Economía y Competitividad (CTQ2013-48411-P) for financial support. M.J. Patiño Ropero acknowledges the Junta de Comunidades de Castilla-La Mancha for her PhD. fellowship.Peer reviewedPostprin
Interplay between Zeeman interaction and spin-orbit coupling in a two-dimensional semiconductor system
We analyse the interplay between Dresselhaus, Bychkov-Rashba, and Zeeman
interactions in a two-dimensional semiconductor quantum system under the action
of a magnetic field. When a vertical magnetic field is considered, we predict
that the interplay results in an effective cyclotron frequency that depends on
a spin-dependent contribution. For in-plane magnetic fields, we found that the
interplay induces an anisotropic effective gyromagnetic factor that depends on
the orientation of the applied field as well as on the orientation of the
electron momentum.Comment: 5 page
Probing equilibrium glass flow up to exapoise viscosities
Glasses are out-of-equilibrium systems aging under the crystallization
threat. During ordinary glass formation, the atomic diffusion slows down
rendering its experimental investigation impractically long, to the extent that
a timescale divergence is taken for granted by many. We circumvent here these
limitations, taking advantage of a wide family of glasses rapidly obtained by
physical vapor deposition directly into the solid state, endowed with different
"ages" rivaling those reached by standard cooling and waiting for millennia.
Isothermally probing the mechanical response of each of these glasses, we infer
a correspondence with viscosity along the equilibrium line, up to exapoise
values. We find a dependence of the elastic modulus on the glass age, which,
traced back to temperature steepness index of the viscosity, tears down one of
the cornerstones of several glass transition theories: the dynamical
divergence. Critically, our results suggest that the conventional wisdom
picture of a glass ceasing to flow at finite temperature could be wrong.Comment: 4 figures and 1 supplementary figur
Radiative capture reaction for Ne formation within a full three-body model
Background: The breakout from the hot Carbon-Nitrogen-Oxigen (CNO) cycles can
trigger the rp-process in type I x-ray bursts. In this environment, a
competition between and the
two-proton capture reaction is
expected.
Purpose: Determine the three-body radiative capture reaction rate for
formation including sequential and direct, resonant and
non-resonant contributions on an equal footing.
Method: Two different discretization methods have been applied to generate
Ne states in a full three-body model: the analytical transformed
harmonic oscillator method and the hyperspherical adiabatic expansion method.
The binary --O interaction has been adjusted to reproduce the known
spectrum of the unbound F nucleus. The dominant contributions to
the reaction rate have been
calculated from the inverse photodissociation process.
Results: Three-body calculations provide a reliable description of Ne
states. The agreement with the available experimental data on Ne is
discussed. It is shown that the
reaction rates computed within the two methods agree in a broad range of
temperatures. The present calculations are compared with a previous theoretical
estimation of the reaction rate.
Conclusions: It is found that the full three-body model provides a reaction
rate several orders of magnitude larger than the only previous estimation. The
implications for the rp-process in type I x-ray bursts should be investigated.Comment: 10 pages, 10 figures. Corrected versio
On the stability of Hamiltonian relative equilibria with non-trivial isotropy
We consider Hamiltonian systems with symmetry, and relative equilibria with
isotropy subgroup of positive dimension. The stability of such relative
equilibria has been studied by Ortega and Ratiu and by Lerman and Singer. In
both papers the authors give sufficient conditions for stability which require
first determining a splitting of a subspace of the Lie algebra of the symmetry
group, with different splittings giving different criteria. In this note we
remove this splitting construction and so provide a more general and more
easily computed criterion for stability. The result is also extended to apply
to systems whose momentum map is not coadjoint equivariant
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