93 research outputs found
Properties of low variability periods in financial time series
Properties of low-variability periods in the time series are analysed. The
theoretical approach is used to show the relationship between the multi-scaling
of low-variability periods and multi-affinity of the time series. It is shown
that this technically simple method is capable of reveling more details about
time-series than the traditional multi-affine analysis. We have applied this
scaling analysis to financial time series: a number of daily currency and stock
index time series. The results show a good scaling behaviour for different
model parameters. The analysis of high-frequency USD-EUR exchange rate data
confirmed the theoretical expectations.Comment: 14 pages, 5 figures, 3 tables, Submitted to Physica
Econophysics studies in Estonia
A short review of the econophysics research done in Estonia, devoted to the
15th anniversary of the term "econophysics".Comment: Submitted to the special issue on "Econophysics" of the journal
Science & Culture (http://www.scienceandculture-isna.org/journal.htm), a
publication of the Indian Science News Association, established in 193
Gradient-limited surfaces
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, which varies from 0.7 to 1, in agreement with experimental data.Comment: 4 pages, 5 figure
Current-sheet formation in incompressible electron magnetohydrodynamics
The nonlinear dynamics of axisymmetric, as well as helical, frozen-in vortex
structures is investigated by the Hamiltonian method in the framework of ideal
incompressible electron magnetohydrodynamics. For description of current-sheet
formation from a smooth initial magnetic field, local and nonlocal nonlinear
approximations are introduced and partially analyzed that are generalizations
of the previously known exactly solvable local model neglecting electron
inertia. Finally, estimations are made that predict finite-time singularity
formation for a class of hydrodynamic models intermediate between that local
model and the Eulerian hydrodynamics.Comment: REVTEX4, 5 pages, no figures. Introduction rewritten, new material
and references adde
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
Family medicine in the Baltic countries
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Family doctors' involvement with families in Estonia
BACKGROUND: Family doctors should care for individuals in the context of their family. Family has a powerful influence on health and illness and family interventions have been shown to improve health outcomes for a variety of health problems. The aim of the study was to investigate the Estonian family doctors' (FD) attitudes to the patients' family-related issues in their work: to explore the degree of FDs involvement in family matters, their preparedness for management of family-related issues and their self-assessment of the ability to manage different family-related problems. METHODS: A random sample (n = 236) of all FDs in Estonia was investigated using a postal questionnaire. Altogether 151 FDs responded to the questionnaire (response rate 64%), while five of them were excluded as they did not actually work as FDs. RESULTS: Of the respondents, 90% thought that in managing the health problems of patients FDs should communicate and cooperate with family members. Although most of the family doctors agreed that modifying of the health damaging risk factors (smoking, alcohol and drug abuse) of their patients and families is their task, one third of them felt that dealing with these problems is ineffective, or perceived themselves as poorly prepared or having too little time for such activities. Of the respondents, 58% (n = 83) were of the opinion that they could modify also relationship problems. CONCLUSIONS: Estonian family doctors are favourably disposed to involvement in family-related problems, however, they need some additional training, especially in the field of relationship management
Community composition and activity of insectivorous bats in Mediterranean olive farms
Olive (Olea europaea L.) farming is one of the most widespread agricultural practice throughout the Mediterranean basin. Current trends even predict an increase in land area devoted to olive farms as well as the intensification of farming practices. However, knowledge of the effects of olive farming on animal species still remains elusive and conservation and management guidelines for the relevant stakeholders are therefore urgently needed. Here, we investigate community composition
and activity patterns of insectivorous bats in Mediterranean olive monocultures in Southern Portugal. Bats surveys were carried out in three types of olive farms representing increasing levels of management intensity: (1) traditional olive farms, managed with few or no chemical inputs or manual labor; (2) semi-intensive olive farms, which share certain characteristics with traditional plantations, but are more intensively managed; (3) intensive olive farms, which are managed with high and frequent chemical inputs, and highly mechanized systems.
We found differences in species richness and activity levels between farming practices. Both the number of species and foraging activity declined with increasing management intensity. However, olive groves as a whole showed a lower number of species compared with the regional species pool and extremely low activity levels, suggesting that large and homogeneous olive monocultures may serve more as commuting areas than true foraging habitats for bats. To our knowledge, this is the first study explicitly demonstrating the pervasive impact of olive farming on the community composition and activity levels of insectivorous bats. In the face of an even-increasing proportion of land surface devoted to olive farming in Mediterranean landscapes, our findings are therefore of great concern.
We suggest that increasing habitat heterogeneity would contribute to preserve the community composition and ecological functionality of insectivorous bats in
extensive olive monocultures
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