Flicker-noise Spectroscopy Research Articles

Space weather monitoring with a system of ground-based cosmic ray detectors

For remote identification of the processes of powerful solar activity in the form of CME directed towards the Earth, a technique of flicker noise spectroscopy has been developed. The results of the analysis of geo-effective events ( G1) are presented according to the data of the international network of neutron monitors and the multidirectional muon hodoscope URAGAN, which indicate the appearance of predictors (with an outstrip of 1–2 days) of the CME approach to the Earthʼs orbit.

Recognition of motor imagery electroencephalogram based on flicker noise spectroscopy and weighted filter bank common spatial pattern

Due to the high complexity and subject variability of motor imagery electroencephalogram, its decoding is limited by the inadequate accuracy of traditional recognition models. To resolve this problem, a recognition model for motor imagery electroencephalogram based on flicker noise spectrum (FNS) and weighted filter bank common spatial pattern ( wFBCSP) was proposed. First, the FNS method was used to analyze the motor imagery electroencephalogram. Using the second derivative moment as structure function, the ensued precursor time series were generated by using a sliding window strategy, so that hidden dynamic information of transition phase could be captured. Then, based on the characteristic of signal frequency band, the feature of the transition phase precursor time series and reaction phase series were extracted by wFBCSP, generating features representing relevant transition and reaction phase. To make the selected features adapt to subject variability and realize better generalization, algorithm of minimum redundancy maximum relevance was further used to select features. Finally, support vector machine as the classifier was used for the classification. In the motor imagery electroencephalogram recognition, the method proposed in this study yielded an average accuracy of 86.34%, which is higher than the comparison methods. Thus, our proposed method provides a new idea for decoding motor imagery electroencephalogram.

Direct evidence for the electroconvective mechanism of neutral amino acid transport during electrodialysis

For the first time, direct evidence was obtained using laser interferometry and flicker-noise spectroscopy that the main cause of the increase in the transport of amino acids through a sulfonated cation-exchange membrane in intense current modes is electroconvection. The turbulent nature of electroconvective vortices at the solution/membrane interface, acidification of the solution in the demineralization compartment and a substantial intensification of amino acid fluxes under over-limiting current modes were revealed. This indicates the electroconvective destruction of the barrier effect of the solution layer with a high pH value near the cation-exchange membrane.

The development of statistical analysis methods for the study of correlations and statistical memory effects in the recorded data of physical experiments

In this paper, we discuss the prospects for the use of statistical analysis methods in the study of correlations and statistical memory effects in the experimental data of physical experiments. Developed methods under consideration: Memory Functions Formalism and Flicker-Noise Spectroscopy allow obtaining a large set of quantitative parameters and qualitative characteristics directly from temporal signals generated by complex physical systems. Additionally, for the study of collective phenomena and effects, one- and two-parameter cross-correlation functions are proposed, which allow studying cross-correlations between simultaneously recorded signals in spatially separated areas of the object under study. The introduced analytical relations and numerical algorithms can be applied to solve the problems of metrology of surface structures at the nano- and microlevels, to study collective phenomena in the plasma of astrophysical objects, the structure of molecules, and their complexes.

FNS-parameterization of human magnetoencephalograms for the diagnosis of photosensitive epilepsy

This work presents the results of parameterization of magnetoencephalogram signals from healthy subjects and a patient with photosensitive epilepsy. Diagnostic criteria were established during the extraction of resonant and high-frequency (chaotic) components of the initial time signals. It is shown that an increase in the intensity of the chaotic components of the studied signals in the high-frequency region leads to a violation of cross-correlation relationships and a decrease in the level of manifestation of frequency-phase synchronization. The discovered signs of photosensitive epilepsy will contribute to the development of new methods for the diagnosis and medical control of this disease based on Flicker-Noise Spectroscopy.

Simple Does Not Mean Trivial: Behavior of Phosphatidic Acid in Lipid Mono- and Bilayers.

Phosphatidic acid (PA) is one of the simplest membrane phospholipids, yet it plays a crucial role in various biologically relevant processes that take place in cells. Since PA generation may be triggered by a variety of factors, very often of antagonistic character, the specific nature of physiological responses driven by PA is not clear. In order to shed more light on these issues, we carried out a systematic characterization of membranes containing one of the three biologically significant PA molecular species. The effect of these molecules on the properties of membranes composed of phosphatidylcholine and/or cholesterol was assessed in a multidisciplinary approach, including molecular dynamic simulations, flicker noise spectroscopy, and Langmuir monolayer isotherms. The first enables the determination of various macroscopic and microscopic parameters such as lateral diffusion, membrane thickness, and defect analysis. The obtained data revealed a strong interaction between unsaturated PA species and phosphatidylcholine. On the other hand, the behavior of saturated PA was greatly influenced by cholesterol. Additionally, a strong effect on mechanical properties was observed in the case of three-component systems, which could not be explained by the simple extrapolation of parameters of the corresponding two-component systems. Our data show that various PA species are not equivalent in terms of their influence on lipid mono- and bilayers and that membrane composition/properties, particularly those related to the presence of cholesterol, may strongly modulate PA behavior.

The Elucidation of the Molecular Mechanism of the Extrusion Process.

Extrusion is a popular method for producing homogenous population of unilamellar liposomes. The technique relies on forcing a lipid suspension through cylindrical pores in a polycarbonate membrane. The quantification of the extrusion and/or recalibration processes make possible the acquisition of experimental data, which can be correlated with the mechanical properties of the lipid bilayer. In this work, the force needed for the extrusion process was correlated with the mechanical properties of a lipid bilayer derived from other experiments. Measurements were performed using a home-made dedicated device capable of maintaining a stable volumetric flux of a liposome suspension through well-defined pores and to continuously measure the extrusion force. Based on the obtained results, the correlation between the lipid bilayer bending rigidity and extrusion force was derived. Specifically, it was found that the bending rigidity of liposomes formed from well-defined lipid mixtures agrees with data obtained by others using flicker-noise spectroscopy or micromanipulation. The other issue addressed in the presented studies was the identification of molecular mechanisms leading to the formation of unilamellar vesicles in the extrusion process. Finally, it was demonstrated that during the extrusion, lipids are not exchanged between vesicles, i.e., vesicles can divide but no membrane fusion or lipid exchange between bilayers was detected.

COMPARATIVE EVALUATION OF RESISTANCE OF HEATING EXCHANGE APPARATUS FOR NEW CONSTRUCTIONS FOR GAS COMPRESSOR STATIONS

The main volume of gas produced in the Republic of Azerbaijan is formed in offshore fields. Some of this gas is transported to the shore, and the other part is used in gas-operated wells. In both cases, multi-stage compressors on SOCAR's balance sheet are used. In the process of compressing gas in compressor stations, its temperature rises (T = 115 ÷ 118 ℃) and it is important to cool it to T = 35 ÷ 38 ℃ before sending it to the outlet. The heat exchanger proposed by the authors differs in this respect by its simplicity and functional advantages. The article provides a comparative analysis of the durability of existing and newly constructed heat exchangers used in compressor stations. Keywords: heat exchanger, selection, flicker noise spectroscopy, multitaper spectral evaluation.

The FNS-based analysis of precursors and cross-correlations in EEG signal related to an imaginary motor task

Flicker noise spectroscopy (FNS) is a time series analysis method to extract information contained in complex nonlinear systems using parameters characterizing the chaotic component of signal in different frequency ranges. In the paper, FNS (precursor function and cross-correlations) is used to study electroencephalography (EEG) signal related to the hand movement imagination. Our analysis of the precursor function calculated for different electrodes reveals a distinct peak just before the imagination which allows for detection of the motor task and distinction of the hand being a subject of the imagination. The EEG rhythms in subsequent stages of the task are determined based on cross-correlation maps which are furthermore used to describe directions of flows between different parts of the sensorimotor cortex.

Mechanical Properties Determination of DMPC, DPPC, DSPC, and HSPC Solid-Ordered Bilayers

Lipid bilayers are active participants in many crucial biological processes. They can be observed in different phases, liquid and solid, respectively. The liquid phase is predominant in biological systems. The solid phase, both crystalline and gel phases, is under investigation due to its resilience to mechanical stress and tight packing of lipids. The mechanical properties of lipids affect their dynamics, therefore influencing the transformation of cell plasma and the endomembrane. Mechanical properties of lipid bilayers are also an important parameter in the design and production of supramolecular lipid-based drug delivery systems. To this end, in this work, we focused on investigating the effect of solid phases of lipid bilayers on their structural parameters and mechanical properties using theoretical molecular dynamics studies on atomistic models of whole vesicles. Those include area per lipid, membrane thickness, density vesicle profiles, bending rigidity coefficient, and area compressibility. Additionally, the bending rigidity coefficient was measured using the flicker noise spectroscopy. The two approaches produced very similar and consistent results. We showed that, contrary to our expectations, bending rigidity coefficients of solid-ordered bilayers for vesicles decreased with an increase in lipid transition temperature. This tendency was reverse in planar systems. Additionally, we have observed an increase of membrane thickness and area compressibility and a decrease of area per lipid. We hope these results will provide valuable mechanical insight for the behavior in solid phases and differences between spherical and planar confirmations.

Effect of the resin content in cation-exchange membranes on development of electroconvection

Comparative analysis of the effect of ion-exchanger content in heterogeneous sulfonated ion-exchange membranes Ralex CM Pes produced by MEGA a.s. (Czech Republic) on their microstructure, current-voltage characteristics and intensity of electroconvective instability was carried out. Using the SEM method, it has been found that with an increase in resin content from 45 to 70 wt%, fraction of the ion-exchanger on the surface of swollen membranes increases 1.8 times, and the distance between them is halved. At the cross-section of membranes, the growth of fraction of ion-exchange regions is 46%. An increase in the resin loading into the membrane causes a 1.7-fold and a twofold increase in the fraction of macropore on the surface and on the cross-section, respectively.With an increase in the ion-exchanger content in membranes, a decrease in the potential of the onset of the overlimiting state and a decrease in the plateau length of the limiting current on the current-voltage curve were revealed. It is shown that a change in resin/inert binder ratio determines the occurrence and development of heteroelectroconvection. Using laser interferometry and flicker noise spectroscopy, evidences of more intense electroconvective mixing of the solution at the boundary with the Ralex cation-exchange membrane with maximum resin loading were obtained.

FNS-parameterization of non-stationarity effects in the solar activity dynamics

In paper we present the findings of analyzing the non-stationary effects to a solar activity dynamics. Within the framework of Flicker-Noise Spectroscopy (FNS) we study the Zurich series of Wolf numbers from 1849 to 2009. According to the FNS methodology the properties of complex system evolution are manifested in the low frequency component (the “resonant” part of the signal) of time signal and contain in the specific sets of the frequencies. For another thing the signal also has the high frequency component (“chaotic” part) including the noise and the different types of short time irregularities. The FNS methodology allows to discover the intermittency phenomena in studied dynamics by analyzing the behavior of the nonstationarity factor. We will show that the maximum value of this parameter corresponds the maximum of Wolf number i.e. the solar activity.

Measurement of the activation energies of oxygen ion diffusion in yttria stabilized zirconia by flicker noise spectroscopy

The low-frequency noise in a nanometer-sized virtual memristor consisting of a contact of a conductive atomic force microscope (CAFM) probe to an yttria stabilized zirconia (YSZ) thin film deposited on a conductive substrate is investigated. YSZ is a promising material for the memristor application since it is featured by high oxygen ion mobility, and the oxygen vacancy concentration in YSZ can be controlled by varying the molar fraction of the stabilizing yttrium oxide. Due to the low diameter of the CAFM probe contact to the YSZ film (∼10 nm), we are able to measure the electric current flowing through an individual filament both in the low resistive state (LRS) and in the high resistive state (HRS) of the memristor. Probability density functions (Pdfs) and spectra of the CAFM probe current in both LRS and HRS are measured. The noise in the HRS is found to be featured by nearly the same Pdf and spectrum as the inner noise of the experimental setup. In the LRS, a flicker noise 1/fγ with γ ≈ 1.3 is observed in the low-frequency band (up to 8 kHz), which is attributed to the motion (drift/diffusion) of oxygen ions via oxygen vacancies in the filament. Activation energies of oxygen ion motion determined from the flicker noise spectra are distributed in the range of [0.52; 0.68] eV at 300 K. Knowing these values is of key importance for understanding the mechanisms of the resistive switching in YSZ based memristors as well as for the numerical simulations of memristor devices.

Studying Powerful Coronal Mass Ejections That Occurred in September 2017, According to Data from the URAGAN Muon Hodoscope

At the beginning of September 2017, the Sun was characterized by anomalously high solar activity (SA), which was unusual for the region of the minimum of the 11-year cycle. A great many powerful flares of the M- and X-classes were observed; these were accompanied by powerful coronal mass ejections (CMEs). These events caused strong magnetic storms on the Earth (the Kp index was as high as 8; the Dst index was <−140 nT). In this work, the effect these ejections had on the flux of cosmic rays (CRs) is considered using data from the URAGAN muon hodoscope at the Moscow Engineering Physics Institute. The study is based on an analysis of variations in the cosmic ray muon flux. Results are presented from processing flux intensity via flicker-noise spectroscopy in order to identify geoeffective disturbances of the Earth’s magnetosphere. A predictor that precedes by more than one day the emergence in near-Earth space of disturbances related to CME propagation is obtained.

Rapid confocal imaging of vesicle-to-sponge phase droplet transition in dilute dispersions of the C10E3 surfactant

The lamellar-to-sponge phase transition of fluorescently labelled large unilamellar vesicles (LUVs) of the non-ionic surfactant triethylene glycol mono n-decyl ether (C10E3) was investigated in situ by confocal laser scanning microscopy (CLSM). Stable dispersions of micrometer-sized C10E3 LUVs were prepared at 20 °C and quickly heated at different temperatures close to the lamellar-to-sponge phase transition temperature. Phase transition of the strongly fluctuating individual vesicles into micrometre-sized sponge phase droplets was observed to occur via manyfold multilamellar morphologies with increasing membrane confinement through inter- and intra- lamellar fusion. The very low bending rigidity and lateral tension of the C10E3 bilayer were supported by quantitative image analysis of a stable fluctuating membrane using both flicker noise spectroscopy and spatial autocorrelation function.

Identification of Geoeffective Disturbances of Solar Wind in the Flux of Cosmic-Ray Muons

The method of flicker-noise spectroscopy is used for remote identification of geoeffective disturbances of the solar wind. The method is based on the study of short-term variations in the cosmic-ray flux that arise when it crosses the perturbed regions in the inner heliosphere. The magnitude of the effect is usually small and it is hidden in statistical noise. The analysis uses data from a continuous flux of secondary atmospheric muons. Bumps of the “nonstationarity” parameter of time series of muons indicate the emergence of advanced signals (predictors) 1–3 days before the disturbances enter the Earth’s magnetosphere. Geoeffective events with a low threshold (Ap > 30 nT) for various types of solar wind are analyzed. The results are obtained using a ground-based muon hodoscope URAGAN (Moscow). The technique can be used for continuous monitoring of space weather.

Statistical Analysis of Bending Rigidity Coefficient Determined Using Fluorescence-Based Flicker-Noise Spectroscopy.

Bending rigidity coefficient describes propensity of a lipid bilayer to deform. In order to measure the parameter experimentally using flickering noise spectroscopy, the microscopic imaging is required, which necessitates the application of giant unilamellar vesicles (GUV) lipid bilayer model. The major difficulty associated with the application of the model is the statistical character of GUV population with respect to their size and the homogeneity of lipid bilayer composition, if a mixture of lipids is used. In the paper, the bending rigidity coefficient was measured using the fluorescence-enhanced flicker-noise spectroscopy. In the paper, the bending rigidity coefficient was determined for large populations of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine and 1,2-dioleoyl-sn-glycero-3-phosphocholine vesicles. The quantity of obtained experimental data allows to perform statistical analysis aiming at the identification of the distribution, which is the most appropriate for the calculation of the value of the membrane bending rigidity coefficient. It has been demonstrated that the bending rigidity coefficient is characterized by an asymmetrical distribution, which is well approximated with the gamma distribution. Since there are no biophysical reasons for that we propose to use the difference between normal and gamma fits as a measure of the homogeneity of vesicle population. In addition, the effect of a fluorescent label and types of instrumental setups on determined values has been tested. Obtained results show that the value of the bending rigidity coefficient does not depend on the type of a fluorescent label nor on the type of microscope used.

Nonlinear Dynamics of the Fluctuations of Extrinsic Photoconductivity in Cadmium Sulfoselenide Crystals Doped with Potassium

The results of a quantitative evaluation of the characteristics of the fluctuations of extrinsic photoconductivity in single crystals of cadmium sulfoselenide doped with potassium during their irradiation with extrinsic light are presented. The occurrence of deterministic chaos in the system under investigation is demonstrated based on the description of the dynamics of the occurring processes by the methods of a discrete Fourier transform, flicker-noise spectroscopy, the reconstruction of the dynamics by the time series, and the calculation of the Lyapunov characteristic exponents and the Kolmogorov–Sinai entropy.

Non-stationarity and cross-correlation effects in the MHD solar activity

The analysis of turbulent processes in sunspots and pores which are self-organizing long-lived magnetic structures is a complicated and not yet solved problem. The present work focuses on studying such magneto-hydrodynamic (MHD) formations on the basis of flicker-noise spectroscopy using a new method of multi-parametric analysis. The non-stationarity and cross-correlation effects taking place in solar activity dynamics are considered. The calculated maximum values of non-stationarity factor may become precursors of significant restructuring in solar magnetic activity. The introduced cross-correlation functions enable us to judge synchronization effects between the signals of various solar activity indicators registered simultaneously.

Flicker Noise Spectroscopy in the Analysis of Electrochemical Noise of Hydrogen-air PEM Fuel Cell During its Degradation

Flicker Noise Spectroscopy in the Analysis of Electrochemical Noise of Hydrogen-air PEM Fuel Cell During its Degradation