Propagation of Bankruptcy Risk over Scale-Free Economic Networks.

The propagation of bankruptcy-induced shocks across domestic and global economies is sometimes very dramatic; this phenomenon can be modelled as a dynamical process in economic networks. Economic networks are usually scale-free, and scale-free networks are known to be vulnerable with respect to targeted attacks, i.e.

Generation of large pollution patches via collisions of sticky floating parcels driven by wind and surface currents.

We study the evolution of large systems of sticky patches of pollution that float on the sea surface and are moved around by realistic wind and simulated surface currents. The study area is the Gulf of Finland in the eastern Baltic Sea that hosts extremely heavy cargo and tanker traffic. It is assumed that patches merge at collision.

Integration of differences in EEG analysis reveals changes in human EEG caused by microwave.

Three different methods in combination with integration of differences in signals were applied for EEG analysis to distinguish changes in EEG caused by microwave: S-parameter, power spectral density and length distribution of low variability periods. The experiments on the effect of modulated low-level microwaves on human EEG were carried out on four different groups of healthy volunteers exposed to 450 MHz microwave radiation modulated with 7 Hz, 14 Hz, 21 Hz, 40 Hz, 70 Hz, 217 or 1000 Hz frequencies. The field power density at the scalp was 0.

Methods of electroencephalographic signal analysis for detection of small hidden changes.

The aim of this study was to select and evaluate methods sensitive to reveal small hidden changes in the electroencephalographic (EEG) signal. Two original methods were considered.Multifractal method of scaling analysis of the EEG signal based on the length distribution of low variability periods (LDLVP) was developed and adopted for EEG analysis.

Sticky particles in compressible flows: aggregation and Richardson's law.

The evolution of the distance r(t) between a pair of passive tracer particles in rough compressible velocity fields is studied. The scaling behavior depends on the stickiness of the particles. Sticky particles start aggregating in moderately compressible flows, which can be realized on the free-slip surface of a turbulent fluid; nonsticky particles can aggregate only in less common strongly compressible flows (even then, the aggregation rate remains lower).

Non-linear analysis of the electroencephalogram for detecting effects of low-level electromagnetic fields.

The study compared traditional spectral analysis and a new scale-invariant method, the analysis of the length distribution of low-variability periods (LDLVPs), to distinguish between electro-encephalogram (EEG) signals with and without a weak stressor, a low-level modulated microwave field. During the experiment, 23 healthy volunteers were exposed to a microwave (450 MHz) of 7 Hz frequency on-off modulation. The field power density at the scalp was 0.

Relationships between recovery-stress state and performance in sprinters and jumpers.

This study investigated the possible relationship between recovery-stress state and competition results in sprinters and jumpers. The Recovery-Stress Questionnaire for Athletes of Kellmann and Kallus was used. The subjects were tested one day before the Estonian Indoor Championships (n = 10; 4 men and 6 women) and Outdoor Championships (n= 11; 4 men and 7 women).

What does measure the scaling exponent of the correlation sum in the case of human heart rate?

It is shown that in the case of human heart rate, the scaling behavior of the correlation sum (calculated by the Grassberger-Procaccia algorithm) is a result of the interplay of various factors: finite resolution of the apparatus (finite-size effects), a wide dynamic range of mean heart rate, the amplitude of short-time variability being a decreasing function of the mean heart rate. This is done via constructing a simple model of heart rhythm: a signal with functionally modulated Gaussian noise. This model reproduces the scaling behavior of the correlation sum of real medical data.

Gradient-limited surfaces: formation of geological landscapes.

A simple scenario of the formation of geological landscapes is suggested, and the respective lattice model is derived. Numerical analysis shows that the arising non-Gaussian surfaces are characterized by the scale-dependent Hurst exponent varying from 0.7 to 1, in agreement with experimental data.

Description of random Gaussian surfaces by a four-vertex model.

A lattice model of random self-affine surfaces is derived using the inverse order of applying the six-vertex model. The well-argued simplification of such an approach results in the four-vertex model. The high numerical efficiency of the four-vertex model is demonstrated by calculating the fractal dimension of contour loops (isolines) of fractional Brownian surfaces as the function of the roughness exponent.

Simple model of intermittent passive scalar turbulence.

The passive scalar convection by chaotic two-dimensional incompressible flow is studied. Analytically solvable equations are suggested to describe the evolution of the probability density functions of tracer gradients and power spectra. The parameters of the model are expressed explicitly via the correlation functions of the velocity field.