Wyniki wyszukiwania - Biblioteka Nauki

1

A new simple fractal method for nanomaterials science and nanosensors

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Klonowski W. , Olejarczyk E. , Stępień R.

Materials Science Poland

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2005

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tom Vol. 23, No. 3

607--612

EN

We proposed a very simple new method of quantitative assessment of surface roughness and texture. We have combined methods that have been used in medicine (histopathology) with methods used in nonlinear time series analysis. A greyscale 2-D image of a 3-D surface is used for calculations of the surface fractal dimension which is a good measure of surface roughness. In the pre-processing step, the image is transformed into 1-D signals ("landscapes") that are subsequently analyzed. The method draws from multiple disciplines and has multidisciplinary applications. One of the possible applications is quality assessment of nanosensors. The same methods of analysis may be used for processing of (bio)signals generated by these nanosensors.

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Comparison of different SPECT images analysis methods for inter-hemispheric asymmetry detection in patients with epileptic symptoms

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Olejarczyk E. , Przytulska M. , Bajera A. , Królicki L.

Biocybernetics and Biomedical Engineering

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2008

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tom Vol. 28, no. 4

33-41

EN

The aim of this work was examination of asymmetries in activity of the left and right cerebral hemispheres as well as localization and contouring of the regions of reduced or increased activity on the basis of single photon emission computed tomography (SPECT) images. The mean and standard deviation of normalized intensities inside the contoured areas of images, entropy based on intensity histograms and Chen's fractal dimension were calculated.

3

Susceptibility of switching between in-phase and anti-phase patterns in the network of relaxation oscillators

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Olejarczyk E. , Ostaszewski H. , Meyrand P. , Bem T.

Biocybernetics and Biomedical Engineering

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2014

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tom Vol. 34, no. 4

250--257

EN

Neural networks composed of two or four cells with combined, electrical and inhibitory, synapses and realized for various network topologies were examined. The aim of this study was to determine a set of phases of oscillatory cycle in which different patterns of activity, characteristic for such networks, can be switched under an external stimulus. In particular, we studied susceptibility of switching between in-phase (IP) and anti-phase (AP) patterns (and vice versa). Our results demonstrate that windows of switching between patterns are similar for networks with electrical and mixed synapses and, in general, relatively independent of the network topology. The only effect of the network topology is an increase of the robustness of the AP pattern in networks of ring-like connectivity. The switching window width and thereby the robustness of the transitions between patterns decreases with the increase of the electrical coupling strength.

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Spectral analysis of the EEG-signal registered during anaesthesia induced by propofol and maintained by fluorinated inhalation anaesthetics

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Olejarczyk E. , Sobieszek A. , Rudner R. , Marciniak R. , Wartak M. , Stasiowski M. , Jałowiecki P.

Biocybernetics and Biomedical Engineering

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2010

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tom Vol. 30, no. 1

55-70

EN

The aim of this study was to identify the effects of different volatile anaesthetics (isoflurane, desflurane or sevoflurane) on the spectro-temporal pattern of EEG during all of the stages of anaesthesia recorded at the frontal derivations in 64 adult patients. The relative powers of EEG for delta, theta, alpha and beta frequency bands as well as the characteristics of their time evolution and their relationships with the concentrations of anaesthetics were used as the EEG spectra indices. The time evolutions of the individual wave powers in 75% of patients were similar for all the anaesthetics used in this study at the same method of administration. Well correlated biphasic changes in the slow and fast wave powers emerged after propofol induction as well as in association with the volatile anaesthetics action. Wave powers as well as their relationships with the anaesthetic concentrations were not hampered by the variability across the patients and anaesthetics used in this study. Comparing the branches of increasing and decreasing concentration, the hysteresis phenomenon, i.e. systematic decrease or increase of each wave power, was observed at the end of anaesthesia for each of the volatile anaesthetics. A rapid increase of sevoflurane concentration at the initial phase of anaesthesia caused more effective attenuation of beta waves than in the case of gradual anaesthetic administration but it happened at the cost of the intensification of delta waves.

5

Evaluation of the EEG-signal during Volatile Anaesthesia: Methodological Approach

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Olejarczyk E. , Sobieszek A. , Rudner R. , Marciniak R. , Wartak M. , Stasiowski M. , Jałowiecki P.

Biocybernetics and Biomedical Engineering

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2009

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tom Vol. 29, no. 1

3-28

EN

The presence of the EEG patterns showing some similarities with epileptiform activity as well as epileptic EEG discharges and motor seizures observed in some people during anaesthesia conducted with volatile anaesthetics is now well-recognized. Nevertheless the practical as well as theoretical implications indicate for the necessity of better understanding of the nature and mechanism of these patterns. The aim of this study was to verify the usefulness of some methods of the EEG analyses to characterize the atypical forms of EEG. It was shown that the estimation of Higuchi's fractal dimension and mean phase coherence as well as the analysis of time-frequency distributions (spectrograms and scalograms) revealed the quantitative features of atypical patterns and their relationships with the depth of anaesthesia.