18,494 research outputs found
Shape-changing Collisions of Coupled Bright Solitons in Birefringent Optical Fibers
Wecritically review the recent progress in understanding soliton propagation
in birefringent optical fibers.By constructing the most general bright
two-soliton solution of the integrable coupled nonlinear Schroedinger equation
(Manakov model) we point out that solitons in birefringent fibers can in
general change their shape after interaction due to a change in the intensity
distribution among the modes even though the total energy is conserved.
However, the standard shape-preserving collision (elastic collision) property
of the (1+1)-dimensional solitons is recovered when restrictions are imposed on
some of the soliton parameters. As a consequence the following further
properties can be deduced using this shape-changing collision. (i) The exciting
possibility of switching of solitons between orthogonally polarized modes of
the birefringent fiber exists. (ii) When additional effects due to periodic
rotation of birefringence axes are considered, the shape changing collision can
be used as a switch to suppress or to enhance the periodic intensity exchange
between the orthogonally polarized modes. (iii) For ultra short optical soliton
pulse propagation in non-Kerr media, from the governing equation an integrable
system of coupled nonlinear Schroedinger equation with cubic-quintic terms is
identified. It admits a nonlocal Poisson bracket structure. (iv) If we take the
higher-order terms in the coupled nonlinear Schroedinger equation into account
then their effect on the shape-changing collision of solitons, during optical
pulse propagation, can be studied by using a direct perturbational approach.Comment: 14 pages, ROMP31, 4 EPS figure
Comment of Global dynamics of biological systems
In a recent study, (Grigorov, 2006) analyzed temporal gene expression
profiles (Arbeitman et al., 2002) generated in a Drosophila experiment using
SSA in conjunction with Monte-Carlo SSA. The author (Grigorov, 2006) makes
three important claims in his article, namely:
Claim1: A new method based on the theory of nonlinear time series analysis is
used to capture the global dynamics of the fruit-fly cycle temporal gene
expression profiles.
Claim 2: Flattening of a significant part of the eigen-spectrum confirms the
hypothesis about an underly-ing high-dimensional chaotic generating process.
Claim 3: Monte-Carlo SSA can be used to establish whether a given time series
is distinguishable from any well-defined process including deterministic chaos.
In this report we present fundamental concerns with respect to the above
claims (Grigorov, 2006) in a systematic manner with simple examples. The
discussion provided especially discourages the choice of SSA for inferring
nonlinear dynamical structure form time series obtained in any biological
paradigm.Comment: 6 pages, 2 figure
The eggs of marine crabs - an unexploited resource
Marine crabs belonging to the family Portunidae form bycatch of shrimp trawlers in India. They are sold at low prices and consumers discard eggs and consume the meat. The paper details the nutritional value of eggs of Portunus pelagicus
Fast algorithms for combustion kinetics calculations: A comparison
To identify the fastest algorithm currently available for the numerical integration of chemical kinetic rate equations, several algorithms were examined. Findings to date are summarized. The algorithms examined include two general-purpose codes EPISODE and LSODE and three special-purpose (for chemical kinetic calculations) codes CHEMEQ, CRK1D, and GCKP84. In addition, an explicit Runge-Kutta-Merson differential equation solver (IMSL Routine DASCRU) is used to illustrate the problems associated with integrating chemical kinetic rate equations by a classical method. Algorithms were applied to two test problems drawn from combustion kinetics. These problems included all three combustion regimes: induction, heat release and equilibration. Variations of the temperature and species mole fraction are given with time for test problems 1 and 2, respectively. Both test problems were integrated over a time interval of 1 ms in order to obtain near-equilibration of all species and temperature. Of the codes examined in this study, only CREK1D and GCDP84 were written explicitly for integrating exothermic, non-isothermal combustion rate equations. These therefore have built-in procedures for calculating the temperature
Measurement of two particle pseudorapidity correlations in Pb+Pb collisions at = 2.76 TeV with the ATLAS detector
Two-particle pseudorapidity correlations, measured using charged particles
with 0.5 GeV and 2.4, from = 2.76
TeV Pb+Pb collisions collected in 2010 by the ATLAS experiment at the LHC are
presented. The correlation function is measured for
different centrality intervals as a function of the pseudorapidity of the two
particles, and . The correlation function shows an enhancement
along 0 and a suppression at large
values. The correlation function also shows a quadratic dependence
along the + direction. These structures are
consistent with a strong forward-backward asymmetry of the particle
multiplicity that fluctuates event to event. The correlation function is
expanded in an orthonormal basis of Legendre polynomials,
, and corresponding coefficients are
measured. These coefficients are related to mean-square values of the Legendre
coefficients, , of the single particle longitudinal multiplicity
fluctuations: . Significant values are
observed for the diagonal terms and mixed terms
. Magnitude of is the largest and the higher order terms decrease quickly with
increase in . The centrality dependence of the leading coefficient is compared to that of the mean-square
value of the asymmetry of the number of participating nucleons between the two
colliding nuclei, and also to the
calculated from HIJING.Comment: 4 pages, 3 figures, proceedings of the 7th International Conference
on Hard and Electromagnetic Probes of High Energy Nuclear Collisions (Hard
Probes 2015), Montrea
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