28,145 research outputs found
Finite size effects and equilibration in Bose-Hubbard chains with central well dephasing
We investigate Bose-Hubbard chains in a central depleted well configuration,
with dephasing in the middle well. We look at equilibration of populations,
pseudo-entropy, and entanglement measures. Using stochastic integration in the
truncated Wigner representation, we find that the initial quantum states of the
occupied wells has an influence on the subsequent dynamics, and that with more
than three wells, the chains do not reach a full equilibrium, with edge effects
becoming important, and the time to reach the steady state becoming longer. The
evolutions with and without phase diffusion are qualitatively different. We
find no convincing evidence of entanglement in the final states with phase
diffusion. Although at least one accepted measure indicates the presence of
mode entanglement, we are easily able to show that it can give ambiguous
predictions.Comment: 20 pages, 12 figures, theor
Tripartite and bipartite entanglement in continuous-variable tripartite systems
We examine one asymmetric adnd two fully symmetric Gaussian
continuous-variable systems in terms of their tripartite and bipartite
entanglement properties. We treat pure states and are able to find analytic
solutions using the undepleted pump approximation for the Hamiltonian models,
and standard beamsplitter relations for a model that mixes the outputs of
optical parametric oscillators. Our two symmetric systems exhibit perfect
tripartite correlations, but only in the unphysical limit of infinite
squeezing. For more realistic squeezing parameters, all three systems exhibit
both tripartite and bipartite entanglement. We conclude that none of the
outputs are completely analogous to either GHZ or W states, but there are
parameter regions where they produce T states introduced by Adesso \etal The
qualitative differences in the output states for different interaction
parameters indicate that continuous-variable tripartite quantum information
systems offer a versatility not found in bipartite systems.Comment: 18 pages, 6 figures. arXiv admin note: text overlap with
arXiv:1510.0182
Multi-object spectroscopy of low redshift EIS clusters. I
We report the results of the first multi-object spectroscopic observations at
the Danish 1.54m telescope at La Silla, Chile. Observations of five cluster
candidates from the ESO Imaging Survey Cluster Candidate Catalog are described.
From these observations we confirm the reality of the five clusters with
measured redshifts of 0.11<=z<=0.35. We estimate velocity dispersions in the
range 294-621km/s indicating rather poor clusters. This, and the measured
cluster redshifts are consistent with the results of the matched filter
procedure applied to produce the Cluster Candidate Catalog.Comment: 7pages, accepted by Astronomy and Astrophysic
Direct indication of particle size in fluidized beds
Differential pressure measurements indicate particle size and particle size distribution in fluidized beds. The technique is based on the relationship between bed particle size and the intensity and frequency of fluctuations. By measuring the fluctuations, an estimate of average particle size of the fluid-bed material can be made
Improved quantum correlations in second harmonic generation with a squeezed pump
We investigate the effects of a squeezed pump on the quantum properties and
conversion efficiency of the light produced in single-pass second harmonic
generation. Using stochastic integration of the two-mode equations of motion in
the positive-P representation, we find that larger violations of
continuous-variable harmonic entanglement criteria are available for lesser
effective interaction strengths than with a coherent pump. This enhancement of
the quantum properties also applies to violations of the Reid-Drummond
inequalities used to demonstrate a harmonic version of the
Einstein-Podolsky-Rosen paradox. We find that the conversion efficiency is
largely unchanged except for very low pump intensities and high levels of
squeezing.Comment: 19 pages, 7 figure
The lost sunspot cycle: New support from Be10 measurements
It has been suggested that the deficit in the number of spots on the surface
of the Sun between 1790 and 1830, known as the Dalton minimum, contained an
extra cycle that was not identified in the original sunspot record by Wolf.
Though this cycle would be shorter and weaker than the average solar cycle, it
would shift the magnetic parity of the solar magnetic field of the earlier
cycles. This extra cycle is sometimes referred to as the 'lost solar cycle' or
'cycle 4b'. Here we reanalyse Be10 measurements with annual resolution from the
NGRIP ice core in Greenland in order to investigate if the hypothesis regarding
a lost sunspot cycle is supported by these measurements. Specifically, we make
use of the fact that the Galactic cosmic rays, responsible for forming Be10 in
the Earth's atmosphere, are affected differently by the open solar magnetic
field during even and odd solar cycles. This fact enables us to evaluate if the
numbering of cycles earlier than cycle 5 is correct. For the evaluation, we use
Bayesian analysis, which reveals that the lost sunspot cycle hypothesis is
likely to be correct. We also discuss if this cycle 4b is a real cycle, or a
phase catastrophe, and what implications this has for our understanding of
stellar activity cycles in general.Comment: accepted for publication in A&
Effect of macromolecular crowding on the kinetics of glycolytic enzymes and the behaviour of glycolysis in yeast
Water is involved in all aspects of biological activity, both as a solvent and as a reactant. It is hypothesized that intracellular water is in a highly structured state due to the high concentrations of macromolecules in the cell and that this may change the activity of intracellular enzymes due to altered binding affinities and allosteric regulations. Here we first investigate the kinetics of two glycolytic enzymes in artificially crowded aqueous solutions and show that crowding does indeed change their kinetics. Based on our kinetic measurements we propose a new model of oscillating glycolysis that instead of Michaelis-Menten or Monod-Wyman-Changeux kinetics uses the Yang-Ling adsorption isotherm introduced by G. Ling in the frame of the Association-Induction (AI) hypothesis. Using this model, we can reproduce previous experimental observations of the coupling of glycolytic oscillations and intracellular water dynamics, e.g., (i) during the metabolic oscillations, the latter variable oscillates in phase with ATP activity, and (ii) the emergence of glycolytic oscillations largely depends on the extent of intracellular water dipolar relaxation in cells in the resting state. Our results support the view that the extent of intracellular water dipolar relaxation is regulated by the ability of cytoplasmic proteins to polarize intracellular water with the assistance of ATP, as suggested in the AI hypothesis. This hypothesis may be relevant to the interpretation of many other biological oscillators, including cell signalling processes.Fil: Thoke, Henrik S.. University Of Southern Denmark; DinamarcaFil: Bagatolli, Luis Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigación Médica Mercedes y Martín Ferreyra. Universidad Nacional de Córdoba. Instituto de Investigación Médica Mercedes y Martín Ferreyra; ArgentinaFil: Olsen, Lars F.. University Of Southern Denmark; Dinamarc
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