Search results for "Statistical"
showing 10 items of 4960 documents
Suppression of the speckle noise in solid polymer samples: a light scattering study
1994
The speckle effect disturbs the measurement of spatial correlation functions in solid polymer samples by light scattering. To be able to extract the desired correlations from the measurements, the speckle noise must be suppressed. This is possible by moving the sample during the measurement. In this paper we demonstrate that a sufficient reduction of speckle contrast can be achieved even in samples of restricted dimensions or with a preferential direction.
Multi-speckle autocorrelation spectroscopy — a new strategy to monitor ultraslow dynamics in dense and nonergodic media
2007
We present a modification of the conventional dynamic light scattering set-up which allows to monitor the intensity fluctuations of many independent spatial Fourier components of the density fluctuations, i.e. “speckles”, simultaneously by using a charge-coupled device (CCD) camera as area detector. By averaging over the intensity autocorrelation function the final 10–20% decay of the intermediate scattering function in very dense colloidal dispersions is obtained with much higher accuracy. At the same time this multi-speckle autocorrelation spectroscopy provides an alternative route for constructing ensemble-averaged intermediate scattering functions in nonergodic media by replacing the av…
The Tan 2Θ Theorem in fluid dynamics
2017
We show that the generalized Reynolds number (in fluid dynamics) introduced by Ladyzhenskaya is closely related to the rotation of the positive spectral subspace of the Stokes block-operator in the underlying Hilbert space. We also explicitly evaluate the bottom of the negative spectrum of the Stokes operator and prove a sharp inequality relating the distance from the bottom of its spectrum to the origin and the length of the first positive gap.
Multispectral colour analysis for quantitative evaluation of pseudoisochromatic color deficiency tests
2010
Multispectral color analysis was used for spectral scanning of Ishihara and Rabkin color deficiency test book images. It was done using tunable liquid-crystal LC filters built in the Nuance II analyzer. Multispectral analysis keeps both, information on spatial content of tests and on spectral content. Images were taken in the range of 420-720nm with a 10nm step. We calculated retina neural activity charts taking into account cone sensitivity functions, and processed charts in order to find the visibility of latent symbols in color deficiency plates using cross-correlation technique. In such way the quantitative measure is found for each of diagnostics plate for three different color deficie…
Dynamic aphasia and the generation of language
2004
Severely reduced propositional speech in the context of intact nominal language skills (i.e., repetition, naming, comprehension, and reading) is the hallmark of dynamic aphasia (Luria, 1970). Recent evidence suggests there may be different types of dynamic aphasia as some patients do not produce any response on verbal generation tasks, whilst others are able to perform normally on verbal genera- tion tasks. For example, Robinson and colleagues (Robinson, Blair, & Cipolotti, 1998; Robinson, Shallice, & Cipolotti, 2004) reported two dynamic aphasics who failed to produce a verbal response when many verbal response options were activated by a stimulus, but not when a dominant response was avai…
Noise-assisted persistence and recovery of memory state in a memristive spiking neuromorphic network
2021
Abstract We investigate the constructive role of an external noise signal, in the form of a low-rate Poisson sequence of pulses supplied to all inputs of a spiking neural network, consisting in maintaining for a long time or even recovering a memory trace (engram) of the image without its direct renewal (or rewriting). In particular, this unique dynamic property is demonstrated in a single-layer spiking neural network consisting of simple integrate-and-fire neurons and memristive synaptic weights. This is carried out by preserving and even fine-tuning the conductance values of memristors in terms of dynamic plasticity, specifically spike-timing-dependent plasticity-type, driven by overlappi…
Static and dynamic glass transitions in the 10-state Potts glass: What can Monte Carlo simulations contribute?
2002
The p-state Potts glass with infinite range Gaussian interactions can be solved exactly in the thermodynamic limit and exhibits an unconventional phase behavior if p >4: A dynamical transition from ergodic to non-ergodic behavior at a temperature T D is followed by a first order transition at T 0 < T D, where a glass order parameter appears discontinuously, although the latent heat is zero. If one assumes that a similar scenario occurs for the structural glass transition as well (though with the singular behavior at T D rounded off), the p-state Potts glass should be a good test case to develop methods to deal with finite size effects for the static as well as the dynamic transition, and to…
Performance potential for simulating spin models on GPU
2012
Graphics processing units (GPUs) are recently being used to an increasing degree for general computational purposes. This development is motivated by their theoretical peak performance, which significantly exceeds that of broadly available CPUs. For practical purposes, however, it is far from clear how much of this theoretical performance can be realized in actual scientific applications. As is discussed here for the case of studying classical spin models of statistical mechanics by Monte Carlo simulations, only an explicit tailoring of the involved algorithms to the specific architecture under consideration allows to harvest the computational power of GPU systems. A number of examples, ran…
The stochastic limit in the analysis of the open BCS model
2004
In this paper we show how the perturbative procedure known as {\em stochastic limit} may be useful in the analysis of the Open BCS model discussed by Buffet and Martin as a spin system interacting with a fermionic reservoir. In particular we show how the same values of the critical temperature and of the order parameters can be found with a significantly simpler approach.
Lysozyme crystallization rates controlled by anomalous fluctuations
2005
Abstract Nucleation of protein aggregates and crystals is a process activated by statistical fluctuations of concentration. Nucleation rates may change by several orders of magnitude upon apparently minor changes in the multidimensional space of parameters (temperature, pH, protein concentration, salt type and concentrations, additives). We use available data on hen egg lysozyme crystal induction times in different solution conditions. We measure by static and dynamic light scattering the amplitudes and lifetimes of anomalously ample and long-lived fluctuations occurring in proximity of the liquid–liquid demixing region of the given lysozyme solutions. This allows determining the related sp…