New class of turbulence in active fluids.

Turbulence is a fundamental and ubiquitous phenomenon in nature, occurring from astrophysical to biophysical scales. At the same time, it is widely recognized as one of the key unsolved problems in modern physics, representing a paradigmatic example of nonlinear dynamics far from thermodynamic equilibrium. Whereas in the past, most theoretical work in this area has been devoted to Navier-Stokes flows, there is now a growing awareness of the need to extend the research focus to systems with more general patterns of energy injection and dissipation.

Transition between saturation regimes of gyrokinetic turbulence.

A gyrokinetic model of ion temperature gradient driven turbulence in magnetized plasmas is used to study the injection, nonlinear redistribution, and collisional dissipation of free energy in the saturated turbulent state over a broad range of driving gradients and collision frequencies. The dimensionless parameter L(T)/L(C), where L(T) is the ion temperature gradient scale length and L(C) is the collisional mean free path, is shown to parametrize a transition between a saturation regime dominated by nonlinear transfer of free energy to small perpendicular (to the magnetic field) scales and a regime dominated by dissipation at large scales in all phase space dimensions.

Nonuniversal power-law spectra in turbulent systems.

Turbulence is generally associated with universal power-law spectra in scale ranges without significant drive or damping. Although many examples of turbulent systems do not exhibit such an inertial range, power-law spectra may still be observed. As a simple model for such situations, a modified version of the Kuramoto-Sivashinsky equation is studied.

[Helminthic cenosis of does in regions of Bulgaria].

Studies were carried out on the species composition of helminths as found in does in individual region of the Rhodope and Balkan Mountains and in the northeast part of this country. A total of 28 helminth species were found, belonging to 8 families as follows: class Trematoda--one family with one species; class Cestoda--one family with one species; and class Nematoda--6 families with 26 species. Most widespread were the species Chabertia ovina, with 82 per cent of infected animals; Spiculopteragia spiculoptera, with 74.