1,964 research outputs found
Current-mediated synchronization of a pair of beating non-identical flagella
The basic phenomenology of experimentally observed synchronization (i.e., a
stochastic phase locking) of identical, beating flagella of a biflagellate alga
is known to be captured well by a minimal model describing the dynamics of
coupled, limit-cycle, noisy oscillators (known as the noisy Kuramoto model). As
demonstrated experimentally, the amplitudes of the noise terms therein, which
stem from fluctuations of the rotary motors, depend on the flagella length.
Here we address the conceptually important question which kind of synchrony
occurs if the two flagella have different lengths such that the noises acting
on each of them have different amplitudes. On the basis of a minimal model,
too, we show that a different kind of synchrony emerges, and here it is
mediated by a current carrying, steady-state; it manifests itself via
correlated "drifts" of phases. We quantify such a synchronization mechanism in
terms of appropriate order parameters and - for an ensemble of
trajectories and for a single realization of noises of duration ,
respectively. Via numerical simulations we show that both approaches become
identical for long observation times . This reveals an ergodic
behavior and implies that a single-realization order parameter is
suitable for experimental analysis for which ensemble averaging is not always
possible.Comment: 10 pages, 2 figure
Group Theoretical Quantum Tomography
The paper is devoted to the mathematical foundation of the quantum tomography
using the theory of square-integrable representations of unimodular Lie groups.Comment: 13 pages, no figure, Latex2e. Submitted to J.Math.Phy
Suppression of stimulated Brillouin scattering in optical fibers using a linearly chirped diode laser
The output of high power fiber amplifiers is typically limited by stimulated Brillouin scattering (SBS). An analysis of SBS with a chirped pump laser indicates that a chirp of 2.5 × 10^(15) Hz/s could raise, by an order
of magnitude, the SBS threshold of a 20-m fiber. A diode laser with a constant output power and a linear chirp of 5 × 10^(15) Hz/s has been previously demonstrated. In a low-power proof-of-concept experiment, the threshold for SBS in a 6-km fiber is increased by a factor of 100 with a
chirp of 5 × 10^(14) Hz/s. A linear chirp will enable straightforward coherent combination of multiple fiber amplifiers, with electronic compensation of path length differences on the order of 0.2 m
How long does it take to pull an ideal polymer into a small hole?
We present scaling estimates for characteristic times and
of pulling ideal linear and randomly branched polymers of
monomers into a small hole by a force . We show that the absorbtion process
develops as sequential straightening of folds of the initial polymer
configuration. By estimating the typical size of the fold involved into the
motion, we arrive at the following predictions: and , and we also confirm them by
the molecular dynamics experiment.Comment: 4 pages, 3 figure
Longest increasing subsequence as expectation of a simple nonlinear stochastic PDE with a low noise intensity
We report some new observation concerning the statistics of Longest
Increasing Subsequences (LIS). We show that the expectation of LIS, its
variance, and apparently the full distribution function appears in statistical
analysis of some simple nonlinear stochastic partial differential equation
(SPDE) in the limit of very low noise intensity.Comment: 6 pages, 4 figures, reference adde
Two-dimensional non-LTE \ion{O}{I} 777\,nm line formation in radiation hydrodynamics simulations of Cepheid atmospheres
Oxygen abundance measurements are important for understanding stellar
structure and evolution. Measured in Cepheids, they further provide clues on
the metallicity gradient and chemo-dynamical evolution in the Galaxy. However,
most of the abundance analyses of Cepheids to date have been based on
one-dimensional (1D) hydrostatic model atmospheres. Here, we test the validity
of this approach for the key oxygen abundance diagnostic, the \ion{O}{I}
~triplet lines. We carry out 2D non-LTE radiative transfer
clculations across two different 2D radiation hydrodynamics simulations of
Cepheid atmospheres, having stellar parameters of K,
solar chemical compositions, and and , corresponding to
pulsation periods of 9 and 3 days, respectively. We find that the 2D non-LTE
versus 1D LTE abundance differences range from ~dex to ~dex
depending on pulsational phase. The 2D non-LTE versus 1D non-LTE abundance
differences range from ~dex to ~dex. The abundance differences are
smallest when the Cepheid atmospheres are closest to hydrostatic equilibrium,
corresponding to phases of around to , and we recommend these phases
for observers deriving the oxygen abundance from \ion{O}{I}
triplet with 1D hydrostatic models.Comment: 9 pages, 10 figures; Published in Astronomy and Astrophysic
Hydrogen Spectroscopy with a Lamb-shift Polarimeter - An Alternative Approach Towards Anti-Hydrogen Spectroscopy Experiments
A Lamb-shift polarimeter, which has been built for a fast determination of
the polarization of protons and deuterons of an atomic-beam source and which is
frequently used in the ANKE experiment at COSY-J\"ulich, is shown to be an
excellent device for atomic-spectroscopy measurements of metastable hydrogen
isotopes. It is demonstrated that magnetic and electric dipole transitions in
hydrogen can be measured as a function of the external magnetic field, giving
access to the full Breit-Rabi diagram for the and the
states. This will allow the study of hyperfine structure, factors and the
classical Lamb shift. Although the data are not yet competitive with
state-of-the-art measurements, the potential of the method is enormous,
including a possible application to anti-hydrogen spectroscopy.Comment: 6 pages, 7 figures, accepted by European Physical Journal
Application of Fuzzy Algorithms for Controlling the Modes of Solar Panels in Technological Monitoring at Peak Load
The functional structure of geoecological and technological monitoring systems is analyzed. It is shown that the complication of the multifunctional automated system of geoecological and technological monitoring (MF AS) and the increase in its dynamics aggravates uncertainty of its condition estimation. An uncertainty model of the state of a multifunctional automated system of geoecological and technological monitoring has been developed. To implement the model, fuzzy sets of linguistic estimates fluctuating in time are obtained. The application of fuzzy algorithms to control the modes of solar panels and the detection of failures in thermoelectric systems has been carried out. As a result of the simulation, an increase in the efficiency of the thermoelectric system was revealed by reducing peak loads by 28% and, accordingly, reducing the probability of failures by almost 2 times
Compensation method of geodynamic trend in the systems of geoelectric control
Compensation method of geodynamic trend in the systems of geoelectric control To ensure the safety of important national economic objects in the conditions of technogenic, biogenic and anthropogenic interference, it is advisable to carry out automated electromagnetic control of geodynamic processes on the basis of multipolar sensing system
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