830 research outputs found
Effect of extreme data loss on long-range correlated and anti-correlated signals quantified by detrended fluctuation analysis
We investigate how extreme loss of data affects the scaling behavior of
long-range power-law correlated and anti-correlated signals applying the DFA
method. We introduce a segmentation approach to generate surrogate signals by
randomly removing data segments from stationary signals with different types of
correlations. These surrogate signals are characterized by: (i) the DFA scaling
exponent of the original correlated signal, (ii) the percentage of
the data removed, (iii) the average length of the removed (or remaining)
data segments, and (iv) the functional form of the distribution of the length
of the removed (or remaining) data segments. We find that the {\it global}
scaling exponent of positively correlated signals remains practically unchanged
even for extreme data loss of up to 90%. In contrast, the global scaling of
anti-correlated signals changes to uncorrelated behavior even when a very small
fraction of the data is lost. These observations are confirmed on the examples
of human gait and commodity price fluctuations. We systematically study the
{\it local} scaling behavior of signals with missing data to reveal deviations
across scales. We find that for anti-correlated signals even 10% of data loss
leads to deviations in the local scaling at large scales from the original
anti-correlated towards uncorrelated behavior. In contrast, positively
correlated signals show no observable changes in the local scaling for up to
65% of data loss, while for larger percentage, the local scaling shows
overestimated regions (with higher local exponent) at small scales, followed by
underestimated regions (with lower local exponent) at large scales. Finally, we
investigate how the scaling is affected by the statistics of the remaining data
segments in comparison to the removed segments
Size- and density-controlled deposition of Ag nanoparticle films by a novel low-temperature spray chemical vapour deposition method—research into mechanism, particle growth and optical simulation
Ag nanoparticles have attracted interest for plasmonic absorption enhancement of solar cells. For this purpose, well-defined particle sizes and densities as well as very low deposition temperatures are required. Thus, we report here a new spray chemical vapour deposition method for producing Ag NP films with independent size and density control at substrate temperatures even below 100 °C, which is much lower than for many other techniques. This method can be used on different substrates to deposit Ag NP films. It is a reproducible, low-cost process which uses trimethylphosphine (hexafluoroacetylacetonato) silver as a precursor in alcoholic solution. By systematic variation of deposition parameters and classic experiments, mechanisms of particle growth and of deposition processes as well as the low decomposition temperature of the precursor could be explained. Using the 3D finite element method, absorption spectra of selected samples were simulated, which fitted well with the measured results. Hence, further applications of such Ag NP films for generating plasmonic near field can be predicted by the simulation
Higher order glass-transition singularities in colloidal systems with attractive interactions
The transition from a liquid to a glass in colloidal suspensions of particles
interacting through a hard core plus an attractive square-well potential is
studied within the mode-coupling-theory framework. When the width of the
attractive potential is much shorter than the hard-core diameter, a reentrant
behavior of the liquid-glass line, and a glass-glass-transition line are found
in the temperature-density plane of the model. For small well-width values, the
glass-glass-transition line terminates in a third order bifurcation point, i.e.
in a A_3 (cusp) singularity. On increasing the square-well width, the
glass-glass line disappears, giving rise to a fourth order A_4 (swallow-tail)
singularity at a critical well width. Close to the A_3 and A_4 singularities
the decay of the density correlators shows stretching of huge dynamical
windows, in particular logarithmic time dependence.Comment: 19 pages, 12 figures, Phys. Rev. E, in prin
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Neuronal noise as an origin of sleep arousals and its role in sudden infant death syndrome
In addition to regular sleep/wake cycles, humans and animals exhibit brief arousals from sleep. Although much is known about consolidated sleep and wakefulness, the mechanism that triggers arousals remains enigmatic. Here, we argue that arousals are caused by the intrinsic neuronal noise of wake-promoting neurons. We propose a model that simulates the superposition of the noise from a group of neurons, and show that, occasionally, the superposed noise exceeds the excitability threshold and provokes an arousal. Because neuronal noise decreases with increasing temperature, our model predicts arousal frequency to decrease as well. To test this prediction, we perform experiments on the sleep/wake behavior of zebrafish larvae and find that increasing water temperatures lead to fewer and shorter arousals, as predicted by our analytic derivations and model simulations. Our findings indicate a previously unrecognized neurophysiological mechanism that links sleep arousals with temperature regulation, and may explain the origin of the clinically observed higher risk for sudden infant death syndrome with increased ambient temperature
Multipulse phases in k-mixtures of Bose-Einstein condensates
For a competitive system of k coupled nonlinear Schroedinger equations we
prove the existence, when the competition parameter is large, of positive
radial solutions on R^N. We show that, when the competition parameter goes to
infinity, the profile of each component separates, in many pulses, from the
others. Moreover, we can prescribe the location of such pulses in terms of the
oscillations of the changing-sign solutions of the scalar nonlinear
Schroedinger equation. Within an Hartree-Fock approximation, this provides a
theoretical indication of phase separation into many nodal domains for the
k-mixtures of Bose-Einstein condensates.Comment: 21 page
Final State Interaction Effects in pol 3He(pol e,e'p)
Asymmetries in quasi-elastic pol 3He(pol e,e'p) have been measured at a
momentum transfer of 0.67 (GeV/c)^2 and are compared to a calculation which
takes into account relativistic kinematics in the final state and a
relativistic one-body current operator. With an exact solution of the Faddeev
equation for the 3He-ground state and an approximate treatment of final state
interactions in the continuum good agreement is found with the experimental
data.Comment: 11 pages, 6 figures, submitted to Phys. Lett. B, revised version,
sensitivity study to relativity and NN-potential adde
Precise Neutron Magnetic Form Factors
Precise data on the neutron magnetic form factor G_{mn} have been obtained
with measurements of the ratio of cross sections of D(e,e'n) and D(e,e'p) up to
momentum transfers of Q^2 = 0.9 (GeV/c)^2. Data with typical uncertainties of
1.5% are presented. These data allow for the first time to extract a precise
value of the magnetic radius of the neutron.Comment: 10 pages, 2 figures, submitted to Physics Letters
Infrastructure for Detector Research and Development towards the International Linear Collider
The EUDET-project was launched to create an infrastructure for developing and
testing new and advanced detector technologies to be used at a future linear
collider. The aim was to make possible experimentation and analysis of data for
institutes, which otherwise could not be realized due to lack of resources. The
infrastructure comprised an analysis and software network, and instrumentation
infrastructures for tracking detectors as well as for calorimetry.Comment: 54 pages, 48 picture
Involvement of hippocampal AMPA glutamate receptor changes and the cAMP/protein kinase A/CREB-P signalling pathway in memory consolidation of an avoidance task in rats
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