Biomedical subjects

Alexander B Medvinsky

Publications and source records attributed to Alexander B Medvinsky.

5 recordsLinked to original sources

PubMed2006

Invasion of pests resistant to Bt toxins can lead to inherent non-uniqueness in genetically modified Bt-plant dynamics: mathematical modeling.

Genetically modified crops are effective pest management tools for worldwide growers. However, there is a concern that pests may develop resistance to Bt-toxins produced by genetically modified Bt-plants. We study the impact of the Bt-resistant pests on Bt-crops. Furthermore, the dynamics of the Bt-plant-Bt-susceptible insects-Bt-resistant insects system is analysed and it is shown that throughout the insect reproduction period the plant biomass dynamics resulting from invasion of Bt-resistant insects is non-unique. Namely, the chaotic attractor and the limit cycle, which are responsible for the plant and insect biomass dynamics, are shown to coexist. As a result, the Bt-plant-Bt-resistant insect system can manifest either chaotic or regular oscillations of plant and insect biomass depending on spatial patterns resulting from invasion of Bt resistant insects into the Bt plant-Bt susceptible insect system. We show that the non-uniqueness of the system dynamics under unfavorable environmental conditions, such as in the so-called zones of risky agriculture in many developing countries and industrialized countries, can lead to essential decrease in the plant biomass.

Animals↗

PubMed2005

Will transgenic plants adversely affect the environment?

Transgenic insecticidal plants based on Bacillus thuringiensis (Bt) endotoxins, on proteinase inhibitors and on lectins, and transgenic herbicide tolerant plants are widely used in modern agriculture. The results of the studies on likelihood and non-likelihood of adverse effects of transgenic plants on the environment including: (i) effects on nontarget species; (ii) invasiveness; (iii) potential for transgenes to 'escape' into the environment by horizontal gene transfer; and (iv) adverse effects on soil biota are reviewed. In general, it seems that large-scale implementation of transgenic insecticidal and herbicide tolerant plants do not display considerable negative effects on the environments and, moreover, at least some transgenic plants can improve the corresponding environments and human health because their production considerably reduces the load of chemical insecticides and herbicides.

Animals↗

PubMed2004

Modeling the invasion of recessive Bt-resistant insects: an impact on transgenic plants.

There is a growing public concern on ecological and evolutionary consequence of the use of genetically modified organisms. We study the impact of Bt-resistant pests on genetically modified Bt crops. We develop and analyse a conceptual reaction-diffusion model of the Bt crop-Bt-susceptible insects-Bt-resistant insects to simulate the invasion of Bt-resistant insects. We show by means of computer simulations that there is a key parameter, which we define as the growth number that characterizes the insects' fitness. We also show that the Bt-resistant insect invasion can lead to inhomogeneity in plant and insect spatial distributions. The plant biomass is found to be essentially dependent on the duration of the Bt-resistant insect reproduction period. There are two types of this dependence. One of them exhibits, respectively, higher plant biomass in comparison with another. The ambiguity in the response of the Bt crop-Bt-susceptible insects system to the invasion of Bt-resistant insects can lead to serious complications in attempts to regulate the dynamics of the system.

Animals↗

PubMed2004

Time delay as a key factor of model plankton dynamics.

Studies of the mechanisms underlying complex dynamics of ecological systems at various spatial and time scales bring increasing awareness that complexity is an intrinsic feature of ecological functioning. This paper is to investigate the role of such an ecologically significant parameter as the time delay due to maturation processes in the complex plankton dynamics. We show that the time lag T1, associated with the zooplankton maturation period can lead to essential changes in the plankton dynamics. Particularly, we show that the coexistence of limit cycle and chaotic attractor we have recently found to be typical of the system at T1 = 0 [A.B. Medvinsky, I.A. Tikhonova, R.R. Aliev, B.-L. Li, Z.-S. Lin, H. Malchow, Patchy environment as a factor of complex plankton dynamics, Phys. Rev. E 64 (2001) 021915] is replaced by pure chaotic plankton dynamics as T1 becomes more than a critical value. The results obtained imply that chaos is a rather common phenomenon in the plankton functioning.

Animals↗

PubMedDate not supplied

Chaos and order in plankton dynamics. Complex behavior of a simple model.

The role of the diffusive interaction between fish-populated and fish-free habitats in a patchy environment in plankton pattern formation is studied by means of a minimal reaction-diffusion model of the nutrient-plankton-fish food chain. It is shown that such interaction can give rise to spatio-temporal plankton patterns. The fractal dimension of the patterns is shown dependent on the fish predation rate. The spatially averaged plankton dynamics depending on both fish predation rate and distance between fish-populated habitats can exhibit chaotic and regular behavior. The chaotic plankton dynamics is characteristic of a wide parameter range.

Animals↗