[Effect of the rate of phytoplankton growth on the spaced-time dynamics of plankton communities in an homogeneous environment]. / Vliianie skorosti rosta fitoplanktona na prostranstvenno-vremennuiu dinamiku planktonnykh soobshchestv v neodnorodnoi srede obitaniia.

We use a conceptual mathematical reaction-diffusion model to investigate the mechanisms of spatial structure formation and complex temporal dynamics of plankton in a heterogeneous environment. We take into account basic trophic interactions, namely, "prey-predator" interactions between phytoplankton, zooplankton, and fish in upper layers of natural waters. We consider plankton as a passive contaminant in turbulent waters. We show that plankton structure formation can result from the difference in phytoplankton growth rate in neighboring habitats. Phytoplankton and zooplankton biomass is shown to undergo both regular and chaotic oscillations. The fish predation rate substantially affects the spatial and temporal dynamics of plankton in a heterogeneous environment.

[Interdependence of plankton spatial distribution and plancton biomass temporal oscillations: mathematical simulation]. / Vzaimozavisimost' raspredeleniia planktona v prostranstve i izmenenii biomassy planktona vo vremeni: matematicheskoe modelirovanie.

The dynamics of aquatic biological communities in a patchy environment is of great interest in respect to interrelations between phenomena at various spatial and time scales. To study the complex plankton dynamics in relation to variations of such a biologically essential parameter as the fish predation rate, we use a simple reaction-diffusion model of trophic interactions between phytoplankton, zooplankton, and fish. We suggest that plankton is distributed between two habitats one of which is fish-free due to hydrological inhomogeneity, while the other is fish-populated. We show that temporal variations in the fish predation rate do not violate the strong correspondence between the character of spatial distribution of plankton and changes of plankton biomass in time: regular temporal oscillations of plankton biomass correspond to large-scale plankton patches, while chaotic oscillations correspond to small-scale plankton patterns. As in the case of the constant fish predation rate, the chaotic plankton dynamics is characterized by coexistence of the chaotic attractor and limit cycle.

Crown compounds for anions: sandwich and half-sandwich complexes of cyclic trimetric perfluoro-o-phenylenemercury with polyhedral closo-[B10H10]2- and closo-[B12H12]2- anions.

It has been shown by IR and NMR spectroscopy that cyclic trimeric perfluoro-o-phenylenemercury (o-C6F4-Hg)3 (1) is capable of binding closo-[B10H10]2- and closo-[B12H12]2- anions to form complexes [[(o-C6F4Hg)3](B10-H10)]2- (2), [[(o-C6F4Hg)3]2(B10H10)]2-(3), [[(o-C6F4Hg)3](B12H12)]2- (4), and [[(o-C6F4Hg)3]2(B12H12)]2- (5). According to IR data, the bonding of the [B10H10]2- and [B12H12]2- ions to the macrocycle in these complexes is accomplished through the formation of B-H-Hg bridges. Complexes 2, 3, and 5 have been isolated in analytically pure form and have been characterized by spectroscopic means. X-ray diffraction studies of 3 and 5 have revealed that these compounds have unusual sandwich structures, in which the polyhedral di-anion is located between the planes of two molecules of 1 and is bonded to each of them through two types of B-H-Hg bridges. One type is the simultaneous coordination of a B-H group to all three Hg atoms of the macrocycle. The other type is the coordination of a B-H group to a single Hg atom of the cycle. According to X-ray diffraction data, complex 2 has an analogous but half-sandwich structure. The obtained complexes 2-5 are quite stable; their stability constants in THF/acetone (1:1) at 20 degrees C have been determined as 1.0 x 10(2)Lmol(-1), 2.6 x 10(3)L(2)mol(2), 0.7 x 10(2)Lmol(-1), and 0.98 x 10(3)L(2)mol(-2), respectively.

Patchy environment as a factor of complex plankton dynamics.

We study the role of the diffusive interaction in plankton dynamics in a patchy environment. We use a minimal reaction-diffusion model of the nutrient-plankton-fish food chain to simulate the diffusive interaction between fish-populated and fish-free habitats. We show that such interaction can give rise to spatiotemporal plankton patterns. The plankton dynamics depend on the fish predation rate and can exhibit both regular and chaotic behavior. We show that limit cycle and chaotic attractor coexist in the system. The entire basin of attraction of the limit cycles is found to be riddled with "holes" leading to the competitive chaotic attractors. The chaotic dynamics is typical of a wide range of the fish predation rates.

Biological factors underlying regularity and chaos in aquatic ecosystems: simple models of complex dynamics.

This work is focused on the processes underlying the dynamics of spatially inhomogeneous plankton communities. We demonstrate that reaction-diffusion mathematical models are an appropriate tool for searching and understanding basic mechanisms of complex spatio-temporal plankton dynamics and fractal properties ofplanktivorous fish school walks

Chaos and regular dynamics in model multi-habitat plankton-fish communities.

This work is focused on the role of diffusive interaction between separate habitats in a patchy environment in plankton pattern formation. We demonstrate that conceptual reaction-diffusion mathematical models constitute an appropriate tool for searching and understanding basic mechanisms of plankton pattern formation and complex spatio-temporal plankton dynamics

[The role of carnivorous zooplankton in dynamics of trophic interaction of fish and plankton]. / Rol' plotoiadnogo zooplanktona v dinamike troficheskikh vzaimodeistvii ryby i planktona.

A conceptual (minimal) model of the aquatic community is proposed, which includes phytoplankton, zooplankton, fish and fish larvae. It is shown that carnivorous zooplankton increases the system stability when the fish predation changes. As a result, the system collapse followed by algal bloom becomes less probable.

[Dependence of the fish school movement and plankton special distribution on the phytoplankton growth rate]. / Zavisimost' dvizheniia rybnykh kosiakov i prostranstvennogo raspredeleniia planktona ot skorosti rosta fitoplanktona.

In this paper we investigate the spontaneous emergence and the dynamics of patchiness in spatially distributed communities of plankton, which plays a key role in the matter rotation on earth. Patchiness is often supposed to be due to hydrodynamical factors (diffusion and advection). In contrast to this approach, we consider the formation of plankton patches as a result of interactions in the trophic chain nutrient--phytoplankton--zooplankton-fish. We present a mathematical model of such interactions, which combines a continuous description of the plankton spatio-temporal dynamics and a discrete description of the fish school movement. We show that the fish school can give rise to plankton patches. In turn, fish school walks are shown to depend on phytoplankton growth rate. We show also that the Hurst exponent characterizing the fish school movement in the diffusion approximation depends on phytoplankton growth rate.

[Transforming activity of Escherichia coli DNA fragments obtained following endonucleolytic splitting by EcoRI restrictase]. / Transformiruiushchaia aktivnost' fragmentov DNK Escherichia coli, poluchennykh posle éndonukleoliticheskogo rasshchepleniia restriktazoi EcoRI

Escherichia coli DNA with molecular weight of 20 - 10(6) daltons was digested by restriction endonuclease EcoR1, and the transforming activity of resctricts was studied. The transforming activity of restricts for two markers (Leu and Arg) was 2-5 fold increased, for two other markers (Thr and His) was not changed, and for one marker (Pro) was completely absent. The molecular weight of E. coli DNA restricts was 7,5-10(6) daltons. An increase and a decrease of the transforming activity for different markers appeared to be the result of two effects: 1) more efficient uptake of low molecular weight DNA into the cell and 2) the inactivation of markers as a result of location close to EcoR1 induced break.