• Nonparametric Methods
• Imaging of magnetic materials based on magnetic resonance
• Classification of sleep stages
• Mechanochemical syntheses of nanocrystalline oxides
• Study of the influence of individual patient torso geometry on the result of the inverse localization of ischemic lesions in the heart

Result 1: Nonparametric Methods

Projects: VEGA 1/0077/09 a APVV RPEU-0008-06 (Ústav merania SAV)

Author: F. Rublík

The monograph provides an ample, well-knit and well-structured exposition of the mathematical statistical theory of nonparametric methods with strong emphasis also on their practical use. The topic of the book are nonparametric statistical methods, mainly the ones based on ranks. The book is written in such a way that it can serve the readers interested in the mathematical theory of these methods, as well as the readers practically oriented. Along with a detailed presentation of theoretical results, a considerable space is devoted to examples illustrating the use of the studied methods. The first eight chapters deal with the analysis of nonparametric models and methods. Less complicated proofs are included in this part of the book, more complicated proofs are in the Appendix., which simplifies the reading of the monograph. In addition to classical procedures the book contains also many new results, including the results of the author (inference in location-scale models, random blocks and multiple comparisons, simultaneous confidence intervals for ratios of variances). The monograph contains also new detailed proofs of some fundamental assertions, e.g. of the assertions on statistical inference in the presence of ties. The Appendix contains also a chapter dealing with probability theory, containing many interesting assertions, mainly limiting theorems or theorems on conditional expectations. Since applications of statistical procedures often require the use of computer, also a chapter on the package MATLAB is included into the Appendix. The tables at the end of the monograph facilitate the practical use of the methods.

Publication:

1. FRANTIŠEK RUBLÍK: Nonparametric Methods. Veda, Publishing House of the Slovak Academy of Sciences, Bratislava 2011, 709 pages.

Result 2: Imaging of magnetic materials based on magnetic resonance

Projects: VEGA 2/0090/11 and ŠPVV 2003SP200280203 (Institute of Measurement Science, SAS)

Authors: P. Andris, I. Frollo, O. Štrbák, L.Valkovič, J. Přibil, D. Gogola, T. Dermek

Imaging of magnetic materials based on magnetic resonance comes under non-specific methods, that if using special sensors and homogeneous static magnetic field can image very small changes of magnetic field in human organism, or also in-vitro on small physical samples.
Series of new techniques of biogenic magnetite imaging based on tests of relaxation processes after excitation has been developed. New method of testing of weak magnetic materials has been designed using magnetic resonance techniques as well as CT imaging.
Unavoidable condition of applications of the proposed techniques is achieving the optimal homogeneity and stability of the static magnetic field. Suggested procedure of the optimization enables fast and accurate setting of the homogeneity of the magnetic field in the target volume. The method has been successfully tested by experiments using small samples. The procedure can be applied in the subsequent research for examination of interactions between the magnetic field and a living organism as well as for research of new magnetic materials.

Fig. 1. Left: Map of the static magnetic field in the centre of an NMR scanner after the optimization procedure. Right: MR image of the material sample - a cross, similar to the number sign, cut from weak-magnetic strips.

Publications:

• ANDRIS, Peter - FROLLO, Ivan. Optimized measurement of magnetic field maps using nuclear magnetic resonance (NMR). In Measurement Science and Technology, 2011, vol. 22, no. 4, art. no. 045501. ISSN 0957-0233. (1.350-IF2010)
• ŠTRBÁK, Oliver - KOPČANSKÝ, P. - FROLLO, Ivan. Biogenic magnetite in humans and new magnetic resonance hazard questions. In Measurement Science Review, 2011, vol. 11, no. 3, p. 85-91. ISSN 1335-8871. (0.400-IF2010)
• FROLLO, Ivan - HAIN, Miroslav - ŠEVČÍK, Robert. Mapping of weak magnetic materials using CT and NMR imaging methods - a comparison. In Použitie moderných nedeštruktívnych meracích metód vo výskume nových materiálov v rámci centra excelentnosti CEKOMAT. Editori M. Hain, K. Karovič, J. Jerz. - Bratislava : Ústav merania SAV, 2011. ISBN 978-80-969672-3-0, p. 18-21.
• ŠTRBÁK, Oliver - GOGOLA, Daniel - FROLLO, Ivan. Cube model approach in simulating of magnetite nanoparticles behaviour in external magnetic fields. In MEASUREMENT 2011 : Proceedings of the 8th International Conference on Measurement. Editori J. Maňka, V. Witkovský, M. Tyšler, I. Frollo. - Bratislava : Institute of Measurement Science SAS, 2011. ISBN 978-80-969-672-4-7, p. 115-118.
• FROLLO, Ivan - ANDRIS, Peter - PŘIBIL, Jiří - VOJTÍŠEK, Lubomír - DERMEK, Tomáš - VALKOVIČ, Ladislav - GOGOLA, Daniel - ŠTRBÁK, Oliver. Magnetic resonance imaging methods used for weak magnetic materials detection. In MEASUREMENT 2011 : Proceedings of the 8th International Conference on Measurement. Editori J. Maňka, V. Witkovský, M. Tyšler, I. Frollo. - Bratislava : Institute of Measurement Science SAS, 2011. ISBN 978-80-969-672-4-7, p. 319-322.
• ANDRIS, Peter - FROLLO, Ivan. Static magnetic field instability and its inhomogeneity distribution mapping in NMR. In MEASUREMENT 2011 : Proceedings of the 8th International Conference on Measurement. Editori J. Maňka, V. Witkovský, M. Tyšler, I. Frollo. - Bratislava : Institute of Measurement Science SAS, 2011. ISBN 978-80-969-672-4-7, p. 166-169.

Result 3: Classification of sleep stages

Projects: VEGA 2/0019/10

Authors: A. Krakovská, K. Mezeiová

The objective of the study was to analyze all-night polysomnographic signals (EEG, EMG, EOG, and ECG) of 20 subjects. A selection was made from 74 measures, including spectral measures and modern characteristics known from the theory of nonlinear dynamical system. Some untraditional measures (e.g.

fractal dimension, fractal exponent, or entropy) turned out to be markedly successful in decision-making between different sleep stages. It is an argument to support the results about important role of scale-invariant processes in brain dynamics. The most hardly distinguishable states are the lightest sleep stage S1 and the REM (paradoxical) sleep. In this case the fractal exponent of the EMG or other EMG characteristics are the most effective. More simple tasks enable use of ratio between the beta and delta frequency bands in the EEG. The successful measures are potentially useful also for more precise analysis of sleep evolution, or as a nonsubjective benchmark for sleep research. It is impossible to satisfactorily separate the five sleep stages by one single measure. However addition of four carefully selected characteristics lowers the classification error below 20 %. This result agrees with a level of experts of visual scoring of sleep stages.

The methodology and software implemented in MatLab can serve successfully as a base for designing an automatic classifier of sleep stages. The classifier can be applied in sleep laboratories, in neurological diagnostic or therapy, and in search for effective strategies of control of loss of vigilance.

Fig. (a): Hypnogram made by experts of visual sleep scoring. Fig. (b): The best classifier was based on set of 14 features. Fig. (c): Successful classifier based on 4 features only.

Publications:

• ŠUŠMÁKOVÁ, K. - KRAKOVSKÁ, A.: Discrimination ability of individual measures used in sleep stages classification. Artificial Intelligence in Medicine, 44, 2008, 261-277.
• KRAKOVSKÁ, Anna - MEZEIOVÁ, Kristína. Automatic sleep scoring: a search for an optimal combination of measures. Artificial Intelligence in Medicine, 2011, vol. 53, no. 1, p. 25-33. ISSN: 0933-3657.

Result 4: Mechanochemical syntheses of nanocrystalline oxides

Projects: ASFEU project 26240120019 (CENTE II) and VEGA 2/0020/11

Authors: P. Billik, A. Cigáň, J. Maňka, A. Dvurečenskij

Solvent-free chemical reactions are well achievable during high-energy milling process. This process changes the reactivity of chemical reactants substantially and leads to the formation of new materials and nanostructures, Fig. 1. Moreover, mechanochemical syntheses represent the low-cost strategy for large-scale productivity of such materials. Our recent results focused on the mechanochemical synthesis of oxides such as Al2O3 or VO2, and characterization of their electric and morphologic properties [1, 2]. These oxides represent important smart material in the new Li-ion cells as electrode materials, or acts as superfine milling abrasive in the surface finishing.

These results have been obtained in the collaboration with the following institutes: Department of Inorganic Chemistry and Department of Geology of Mineral Deposits, Faculty of Natural Sciences, Comenius University in Bratislava; Institute of Materials Science, Faculty of Materials Science and Technology in Trnava, Slovak University of Technology.

Fig. 1. TEM of α-Al2O3 nanocrystals prepared by new mechanochemical synthesis. (Foto: M. Čaplovičová [1]).

Publications:

• Billik, P., Čaplovičová, M., Turányi, T., Čaplovič, L. & Horváth, B. 2011, "Low-temperature mechanochemical-thermal synthesis of α-Al2O3 nanocrystals", Materials Research Bulletin, vol. 46, no. 11, pp. 2135-2140.
• Billik, P., Čaplovičová, M., Maňka, J., Čaplovič, L., Cigáň, A., Koňakovský, A., Bystrický, R. & Dvurečenskij, A. 2011, "Synthesis and transport properties of nanostructured VO2 by mechanochemical processing", Measurement Science Review, vol. 11, no. 1, pp. 29-33.

Result 5: Study of the influence of individual patient torso geometry on the result of the inverse localization of ischemic lesions in the heart.

Projects: VEGA 2/0210/10 a APVV-0513-10

Authors: J. Švehlíková, J. Lenková, M. Tyšler

The influence of the patient torso shape and internal organs on the inverse localization of ischemic lesions was investigated. First, real difference integral maps (DI_BSPMs) obtained from ecg measurements at rest and during the excercise test in 8 patients with diagnosed coronary artery disease were used. From the results it is implied, that the influence of the outer thorax shape and size is more important than the influence of internal organs, namely lungs although their presence in the model is unavoidable. Second, in simulation study small single lesions were localized in the left ventricle´s myocardium. The input data were DI_BSPMs simulated on various realistically shaped torso models obtained by MRI. The localization error of the inverse solution was 0,56cm when the originally shaped torso model was used and 1,77cm for the general standard model. When the standard model was adjusted to the corresponding original torso, the localization error dropped to 1,04cm. Therefore in practice, if the individual torso model obtained by imaging technique such as CT or MRI is not available, it is better to use individualized standard torso model adjusted to the real patient's measures than using the standard or averaged torso model.

Fig. 1. Torso models used in the study (from left to right): original patient torso model, standard torso model, standard torso model adjusted to patient torso model shape.

Publications:

• Svehlikova, J. - Lenkova, J - Turzova, M. - Tysler, M. et al.: Influence of individual torso geometry on inverse solution to 2 dipoles. J Electrocardiol, 2012, vol.45, No.1 ,7-12. ISSN 0022-0736. (1.109-IF2010).
• Lenkova, J. - Svehlikova, J. - Tysler, M.: Individual vs. Adjusted standard torso model in the solution of the inverse problem in electrocardiology. Measurement 2011 8th International Conference on Measurement Proceedings, 2011. ISBN 978-80-969-672-4-7.