10,580 research outputs found
A Ternary Lattice Boltzmann Model for Amphiphilic Fluids
A lattice Boltzmann model for amphiphilic fluid dynamics is presented. It is
a ternary model, in that it conserves mass separately for each chemical species
present (water, oil, amphiphile), and it maintains an orientational degree of
freedom for the amphiphilic species. Moreover, it models fluid interactions at
the microscopic level by introducing self-consistent forces between the
particles, rather than by positing a Landau free energy functional. This
combination of characteristics fills an important need in the hierarchy of
models currently available for amphiphilic fluid dynamics, enabling efficient
computer simulation and furnishing new theoretical insight. Several
computational results obtained from this model are presented and compared to
existing lattice-gas model results. In particular, it is noted that lamellar
structures, which are precluded by the Peierls instability in two-dimensional
systems with kinetic fluctuations, are not observed in lattice-gas models, but
are easily found in the corresponding lattice Boltzmann models. This points out
a striking difference in the phenomenology accessible to each type of model.Comment: 12 pages, 6 figures included with graphic
Pillars of creation amongst destruction: Star formation in molecular clouds near R136 in 30 Doradus
New sensitive CO(2-1) observations of the 30 Doradus region in the Large
Magellanic Cloud are presented. We identify a chain of three newly discovered
molecular clouds we name KN1, KN2 and KN3 lying within 2--14 pc in projection
from the young massive cluster R136 in 30 Doradus. Excited H 2.12m
emission is spatially coincident with the molecular clouds, but ionized
Br emission is not. We interpret these observations as the tails of
pillar-like structures whose ionized heads are pointing towards R136. Based on
infrared photometry, we identify a new generation of stars forming within this
structure.Comment: Accepted for publication in ApJ (includes 13 pages, 8 figures). For
higher resolution figures please see
http://www.das.uchile.cl/~vkalari/staplervk.pd
Measurements of the effect of collisions on transverse beam halo diffusion in the Tevatron and in the LHC
Beam-beam forces and collision optics can strongly affect beam lifetime,
dynamic aperture, and halo formation in particle colliders. Extensive
analytical and numerical simulations are carried out in the design and
operational stage of a machine to quantify these effects, but experimental data
is scarce. The technique of small-step collimator scans was applied to the
Fermilab Tevatron collider and to the CERN Large Hadron Collider to study the
effect of collisions on transverse beam halo dynamics. We describe the
technique and present a summary of the first results on the dependence of the
halo diffusion coefficient on betatron amplitude in the Tevatron and in the
LHC.Comment: 4 pages, 2 figures. Submitted to the Proceedings of the ICFA
Mini-Workshop on Beam-beam Effects in Hadron Colliders (BB2013), Geneva,
Switzerland, 18-22 March 201
Comments on discrete time in quantum mechanics
The possibility that time can be regarded as a discrete parameter is
re-examined. We study the dynamics of the free particle and find in some cases
superluminal propagation
Beam halo dynamics and control with hollow electron beams
Experimental measurements of beam halo diffusion dynamics with collimator
scans are reviewed. The concept of halo control with a hollow electron beam
collimator, its demonstration at the Tevatron, and its possible applications at
the LHC are discussed.Comment: 5 pages, 4 figures, in Proceedings of the 52nd ICFA Advanced Beam
Dynamics Workshop on High-Intensity and High-Brightness Hadron Beams
(HB2012), Beijing, China, 17-21 September 201
Studies on Energy-Yielding Reactions in Thymus Nuclei. 2. Pathways of Aerobic Carbohydrate Catabolism.
Landau Model for Commensurate-Commensurate Phase Transitions in Uniaxial Improper Ferroelectric Crystals
We propose the Landau model for lock-in phase transitions in uniaxially
modulated improper ferroelectric incommensurate-commensurate systems of class
I. It includes Umklapp terms of third and fourth order and secondary order
parameter representing the local polarization. The corresponding phase diagram
has the structure of harmless staircase, with the allowed wave numbers obeying
the Farey tree algorithm. Among the stable commensurate phases only those with
periods equal to odd number of lattice constants have finite macroscopic
polarizations. These results are in excellent agreement with experimental
findings in some A2BX4 compounds.Comment: 9 pages, 5 figures, revtex, to be published in Journal of Physics:
Cond. Matter as a Letter to the Edito
Studies of Energy-Yielding Reactions in Thymus Nuclei. 1. Comparison of Nuclear and Mitochondrial Phosphorylation.
Studies on Energy-Yielding Reactions in Thymus Nuclei. 3. Participation of Glycolysis and the Citric Acid in Nuclear Adenosine Triphosphate Synthesis.
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