2,259 research outputs found
Chaos control in random Boolean networks by reducing mean damage percolation rate
Chaos control in Random Boolean networks is implemented by freezing part of
the network to drive it from chaotic to ordered phase. However, controlled
nodes are only viewed as passive blocks to prevent perturbation spread. This
paper proposes a new control method in which controlled nodes can exert an
active impact on the network. Controlled nodes and frozen values are
deliberately selected according to the information of connection and Boolean
functions. Simulation results show that the number of nodes needed to achieve
control is largely reduced compared to previous method. Theoretical analysis is
also given to estimate the least fraction of nodes needed to achieve control.Comment: 10 pages, 2 figure
SLOCC determinant invariants of order 2^{n/2} for even n qubits
In this paper, we study SLOCC determinant invariants of order 2^{n/2} for any
even n qubits which satisfy the SLOCC determinant equations. The determinant
invariants can be constructed by a simple method and the set of all these
determinant invariants is complete with respect to permutations of qubits.
SLOCC entanglement classification can be achieved via the vanishing or not of
the determinant invariants. We exemplify the method for several even number of
qubits, with an emphasis on six qubits.Comment: J. Phys. A: Math. Theor. 45 (2012) 07530
Prolactin responses to stress induced by a competitive swimming effort
Purpose:The aim of the present study was to investigate the changes in prolactin (PRL) plasma concentrations induced by competitive swimming practice. Methods:Twenty-three males, 13 trained swimmers (experimental group) and 10 sedentary and healthy students (age-matched control group) took part in this investigation. The swimmers were assessed at three points: basal conditions, pre-and post-swimming competition (100 m freestyle), whereas subjects from the control group only undertook the basal trial. The variables analysed were: several body composition measures, anxiety level (STAI questionnaire), PRL and lactic acid concentrations. Results:No statistical differences were observed in PRL basal levels between groups. An evident PRL response to pre-competition psychological stress was observed in the experimental group, since the PRL plasma concentration rosefrom 4.02Ā±0.53 ng/ml (basal conditions) to 5.52Ā±0.53 ng/ml (pā¤0.05). The PRL response to the competitive effort produced an important increase in its plasma concentration (10.07Ā±1.59 ng/ml), showed statistical differences from pre-competition (pā¤0.01) and from basal conditions (pā¤0.001). A significant rise in plasma lactate levels just at the end of the effort was found, although it did not correlate with PRL levels in the same situation. Conclusion:While we observed a remarkable response of PRL to psychological and physiological stress induced by a short term competitive effort in swimming, no changes in PRL basal levels were exhibitedwith swim training. More research is needed to clarify these findings
Powers of the Vandermonde determinant, Schur Functions, and recursive formulas
Since every even power of the Vandermonde determinant is a symmetric
polynomial, we want to understand its decomposition in terms of the basis of
Schur functions. We investigate several combinatorial properties of the
coefficients in the decomposition. In particular, we give recursive formulas
for the coefficient of the Schur function s_{\m} in the decomposition of an
even power of the Vandermonde determinant in variables in terms of the
coefficient of the Schur function s_{\l} in the decomposition of the same
even power of the Vandermonde determinant in variables if the Young diagram
of \m is obtained from the Young diagram of \l by adding a tetris type
shape to the top or to the left. An extended abstract containing the statement
of the results presented here appeared in the Proceedings of FPSAC11Comment: 23 pages; extended abstract appeared in the Proceedings of FPSAC1
Prolactin responses to stress induced by a competitive swimming effort
Purpose: The aim of the present study was to investigate the changes in prolactin (PRL) plasma concentrations induced by competitive swimming practice. Methods: Twenty-three males, 13 trained swimmers (experimental group) and 10 sedentary and healthy students (age-matched control group) took part in this investigation. The swimmers were assessed at three points: basal conditions, pre- and post-swimming competition (100 m freestyle), whereas subjects from the control group only undertook the basal trial. The variables analysed were: several body composition measures, anxiety level (STAI questionnaire), PRL and lactic acid concentrations. Results: No statistical differences were observed in PRL basal levels between groups. An evident PRL response to pre-competition psychological stress was observed in the experimental group, since the PRL plasma concentration rose from 4.02Ā±0.53 ng/ml (basal conditions) to 5.52Ā±0.53 ng/ml (pā¤0.05). The PRL response to the competitive effort produced an important increase in its plasma concentration (10.07Ā±1.59 ng/ml), showed statistical differences from pre-competition (pā¤0.01) and from basal conditions (pā¤0.001). A significant rise in plasma lactate levels just at the end of the effort was found, although it did not correlate with PRL levels in the same situation. Conclusion: While we observed a remarkable response of PRL to psychological and physiological stress induced by a short term competitive effort in swimming, no changes in PRL basal levels were exhibited with swim training. More research is needed to clarify these findings
Probing background ionization: Positive streamers with varying pulse repetition rate and with a radioactive admixture
Positive streamers need a source of free electrons ahead of them to
propagate. A streamer can supply these electrons by itself through
photo-ionization, or the electrons can be present due to external background
ionization. Here we investigate the effects of background ionization on
streamer propagation and morphology by changing the gas composition and the
repetition rate of the voltage pulses, and by adding a small amount of
radioactive Krypton 85.
We find that the general morphology of a positive streamer discharge in high
purity nitrogen depends on background ionization: at lower background
ionization levels the streamers branch more and have a more feather-like
appearance. This is observed both when varying the repetition rate and when
adding Krypton 85, though side branches are longer with the radioactive
admixture. But velocities and minimal diameters of streamers are virtually
independent of the background ionization level. In air, the inception cloud
breaks up into streamers at a smaller radius when the repetition rate and
therefore the background ionization level is higher. When measuring the effects
of the pulse repetition rate and of the radioactive admixture on the discharge
morphology, we found that our estimates of background ionization levels are
consistent with these observations; this gives confidence in the estimates.
Streamer channels generally do not follow the paths of previous discharge
channels for repetition rates of up to 10 Hz. We estimate the effect of
recombination and diffusion of ions and free electrons from the previous
discharge and conclude that the old trail has largely disappeared at the moment
of the next voltage pulse; therefore the next streamers indeed cannot follow
the old trail.Comment: 30 pages, 13 figure
Extending the scope of microscopic solvability: Combination of the Kruskal-Segur method with Zauderer decomposition
Successful applications of the Kruskal-Segur approach to interfacial pattern
formation have remained limited due to the necessity of an integral formulation
of the problem. This excludes nonlinear bulk equations, rendering convection
intractable. Combining the method with Zauderer's asymptotic decomposition
scheme, we are able to strongly extend its scope of applicability and solve
selection problems based on free boundary formulations in terms of partial
differential equations alone. To demonstrate the technique, we give the first
analytic solution of the problem of velocity selection for dendritic growth in
a forced potential flow.Comment: Submitted to Europhys. Letters, No figures, 5 page
Probing photo-ionization: simulations of positive streamers in varying N2:O2 mixtures
Photo-ionization is the accepted mechanism for the propagation of positive
streamers in air though the parameters are not very well known; the efficiency
of this mechanism largely depends on the presence of both nitrogen and oxygen.
But experiments show that streamer propagation is amazingly robust against
changes of the gas composition; even for pure nitrogen with impurity levels
below 1 ppm streamers propagate essentially with the same velocity as in air,
but their minimal diameter is smaller, and they branch more frequently.
Additionally, they move more in a zigzag fashion and sometimes exhibit a
feathery structure. In our simulations, we test the relative importance of
photo-ionization and of the background ionization from pulsed repetitive
discharges, in air as well as in nitrogen with 1 ppm O2 . We also test
reasonable parameter changes of the photo-ionization model. We find that photo-
ionization dominates streamer propagation in air for repetition frequencies of
at least 1 kHz, while in nitrogen with 1 ppm O2 the effect of the repetition
frequency has to be included above 1 Hz. Finally, we explain the feather-like
structures around streamer channels that are observed in experiments in
nitrogen with high purity, but not in air.Comment: 12 figure
A comparison of 3D particle, fluid and hybrid simulations for negative streamers
In the high field region at the head of a discharge streamer, the electron
energy distribution develops a long tail. In negative streamers, these
electrons can run away and contribute to energetic processes such as
terrestrial gamma-ray and electron flashes. Moreover, electron density
fluctuations can accelerate streamer branching. To track energies and locations
of single electrons in relevant regions, we have developed a 3D hybrid model
that couples a particle model in the region of high fields and low electron
densities with a fluid model in the rest of the domain. Here we validate our 3D
hybrid model on a 3D (super-)particle model for negative streamers in
overvolted gaps, and we show that it almost reaches the computational
efficiency of a 3D fluid model. We also show that the extended fluid model
approximates the particle and the hybrid model well until stochastic
fluctuations become important, while the classical fluid model underestimates
velocities and ionization densities. We compare density fluctuations and the
onset of branching between the models, and we compare the front velocities with
an analytical approximation
Screening of suitable cationic dopants for solar absorber material CZTS/Se: A first principles study
The earth abundant and non-toxic solar absorber material kesterite Cu2ZnSn(S/Se)(4) has been studied to achieve high power conversion efficiency beyond various limitations, such as secondary phases, antisite defects, band gap adjustment and microstructure. To alleviate these hurdles, we employed screening based approach to find suitable cationic dopant that can promote the current density and the theoretical maximum upper limit of the energy conversion efficiency (P(%)) of CZTS/Se solar devices. For this task, the hybrid functional (Heyd, Scuseria and Ernzerhof, HSE06) were used to study the electronic and optical properties of cation (Al, Sb, Ga, Ba) doped CZTS/Se. Our in-depth investigation reveals that the Sb atom is suitable dopant of CZTS/CZTSe and also it has comparable bulk modulus as of pure material. The optical absorption coefficient of Sb doped CZTS/Se is considerably larger than the pure materials because of easy formation of visible range exciton due to the presence of defect state below the Fermi level, which leads to an increase in the current density and P(%). Our results demonstrate that the lower formation energy, preferable energy gap and excellent optical absorption of the Sb doped CZTS/Se make it potential component for relatively high efficient solar cells
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