2,801 research outputs found
Probing models of information spreading in social networks
We apply signal processing analysis to the information spreading in
scale-free network. To reproduce typical behaviors obtained from the analysis
of information spreading in the world wide web we use a modified SIS model
where synergy effects and influential nodes are taken into account. This model
depends on a single free parameter that characterize the memory-time of the
spreading process. We show that by means of fractal analysis it is possible
-from aggregated easily accessible data- to gain information on the memory time
of the underlying mechanism driving the information spreading process.Comment: 6 pages, 6 figure
Intrazeolite assembly and pyrolysis of polyacrylonitrile
Radical polymerization of acrylonitrile within the pores of zeolites Y and mordenite produces intrazeolite polyacrylonitrile that can be pyrolysed to form conducting carbon filaments
Non-equilibrium dynamics of bosonic atoms in optical lattices: Decoherence of many-body states due to spontaneous emission
We analyze in detail the heating of bosonic atoms in an optical lattice due
to incoherent scattering of light from the lasers forming the lattice. Because
atoms scattered into higher bands do not thermalize on the timescale of typical
experiments, this process cannot be described by the total energy increase in
the system alone (which is determined by single-particle effects). The heating
instead involves an important interplay between the atomic physics of the
heating process and the many-body physics of the state. We characterize the
effects on many-body states for various system parameters, where we observe
important differences in the heating for strongly and weakly interacting
regimes, as well as a strong dependence on the sign of the laser detuning from
the excited atomic state. We compute heating rates and changes to
characteristic correlation functions based both on perturbation theory
calculations, and a time-dependent calculation of the dissipative many-body
dynamics. The latter is made possible for 1D systems by combining
time-dependent density matrix renormalization group (t-DMRG) methods with
quantum trajectory techniques.Comment: 17 pages, 14 figure
Measuring entanglement growth in quench dynamics of bosons in an optical lattice
We discuss a scheme to measure the many-body entanglement growth during
quench dynamics with bosonic atoms in optical lattices. By making use of a 1D
or 2D setup in which two copies of the same state are prepared, we show how
arbitrary order Renyi entropies can be extracted using tunnel-coupling between
the copies and measurement of the parity of on-site occupation numbers, as has
been performed in recent experiments. We illustrate these ideas for a
Superfluid-Mott insulator quench in the Bose-Hubbard model, and also for
hard-core bosons, and show that the scheme is robust against imperfections in
the measurements.Comment: 4+ pages plus supplementary materia
Predicitions for high-energy real and virtual photon-photon scattering from color dipole BFKL-Regge factorization
High-energy virtual photon-virtual photon scattering can be viewed as
interaction of small size color dipoles from the beam and target photons, which
makes scattering at high energies
(LEP, LEP200 & NLC) an indispensable probe of short distance properties of the
QCD pomeron exchange. Based on the color dipole representation, we investigate
consequences for the scattering of the
incorporation of asymptotic freedom into the BFKL equation which makes the QCD
pomeron a series of isolated poles in the angular momentum plane. The emerging
color dipole BFKL-Regge factorization allows us to relate in a
model-independent way the contributions of each BFKL pole to
scattering and DIS off protons.
Numerical predictions based on our early works on color dipole BFKL
phenomenology of DIS on protons are in a good agreement with the experimental
data on the photon structure function and most recent data on the
cross section from OPAL and
L3 experiments at LEP200.
We discuss the role of non-perturbative dynamics and predict pronounced
effect of the Regge-factorization breaking due to large unfactorizable
non-perturbative corrections to the perturbative vacuum exchange. We comment on
the salient features of the BFKL-Regge expansion for
scattering including the issue of
decoupling of subleading BFKL poles and the soft plus rightmost hard BFKL pole
dominance .Comment: 16 pages, 10 figures; treatment of the soft component is modified,
one more figure with the description of the recent data from OPAL is added.
The version to appear in Eur. Phys. J.
Chromosome condensation in mitosis and meiosis of rye (Secale cereale L.)
Structural investigation and morphometry of meiotic chromosomes by scanning electron microscopy (in comparison to light microscopy) of all stages of condensation of meiosis I + II show remarkable differences during chromosome condensation in mitosis and meiosis I of rye (Secale cereale) with respect to initiation, mode and degree of condensation. Mitotic chromosomes condense in a linear fashion, shorten in length and increase moderately in diameter. In contrast, in meiosis I, condensation of chromosomes in length and diameter is a sigmoidal process with a retardation in zygotene and pachytene and an acceleration from diplotene to diakinesis. The basic structural components of mitotic chromosomes of rye are ``parallel fibers{''} and ``chromomeres{''} which become highly compacted in metaphase. Although chromosome architecture in early prophase of meiosis seems similar to mitosis in principle, there is no equivalent stage during transition to metaphase I when chromosomes condense to a much higher degree and show a characteristic ``smooth{''} surface. No indication was found for helical winding of chromosomes either in mitosis or in meiosis. Based on measurements, we propose a mechanism for chromosome dynamics in mitosis and meiosis, which involves three individual processes: (i) aggregation of chromatin subdomains into a chromosome filament, (ii) condensation in length, which involves a progressive increase in diameter and (iii) separation of chromatids. Copyright (C) 2003 S. Karger AG, Basel
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