Correlations, Risk and Crisis: From Physiology to Finance

We study the dynamics of correlation and variance in systems under the load of environmental factors. A universal effect in ensembles of similar systems under the load of similar factors is described: in crisis, typically, even before obvious symptoms of crisis appear, correlation increases, and, at the same time, variance (and volatility) increases too. This effect is supported by many experiments and observations of groups of humans, mice, trees, grassy plants, and on financial time series. A general approach to the explanation of the effect through dynamics of individual adaptation of similar non-interactive individuals to a similar system of external factors is developed. Qualitatively, this approach follows Selye's idea about adaptation energy.Comment: 42 pages, 15 figures, misprints corrections, a proof is added, improved journal versio

Evolution of adaptation mechanisms: adaptation energy, stress, and oscillating death

In 1938, H. Selye proposed the notion of adaptation energy and published "Experimental evidence supporting the conception of adaptation energy". Adaptation of an animal to different factors appears as the spending of one resource. Adaptation energy is a hypothetical extensive quantity spent for adaptation. This term causes much debate when one takes it literally, as a physical quantity, i.e. a sort of energy. The controversial points of view impede the systematic use of the notion of adaptation energy despite experimental evidence. Nevertheless, the response to many harmful factors often has general non-specific form and we suggest that the mechanisms of physiological adaptation admit a very general and nonspecific description. We aim to demonstrate that Selye's adaptation energy is the cornerstone of the top-down approach to modelling of non-specific adaptation processes. We analyse Selye's axioms of adaptation energy together with Goldstone's modifications and propose a series of models for interpretation of these axioms. {\em Adaptation energy is considered as an internal coordinate on the `dominant path' in the model of adaptation}. The phenomena of `oscillating death' and `oscillating remission' are predicted on the base of the dynamical models of adaptation. Natural selection plays a key role in the evolution of mechanisms of physiological adaptation. We use the fitness optimization approach to study of the distribution of resources for neutralization of harmful factors, during adaptation to a multifactor environment, and analyse the optimal strategies for different systems of factors

Body composition data from the rat subjects of Cosmos 1129 experiment K-316

The effects of 18.5 days of weightlessness on the body composition of young, growing, male laboratory rats were examined. Three groups of 5 rats each were examined. It is indicated that exposure of young, growing, male rats to 18.5 days of weightlessness produces: (1) no effect on the quantity of fat stored by the body; (2) a slight reduction in the quantity of fat free tissue laid down by the body; (3) a small reduction in the fraction of water contained by the fat free body mass; (4) a similar reduction in the fraction of water contained by the fat free skin and fat free carcass; (5) a shift in relative distribution of the total body water from skin to viscera; (6) a diminution in the fraction of extracellular water contained by the fat free body; (7) no effect on the fraction of total skeletal musculature contained by the fat free body, as indicated by body creatine content; (8) a sizeable reduction in the fraction of bone mineral contained by the fat free body, as calculated from body calcium content. The nature of the physiological changes induced by unloading from Earth gravity in the mammalian organism are illustrated

Dynamic and Thermodynamic Models of Adaptation

The concept of biological adaptation was closely connected to some mathematical, engineering and physical ideas from the very beginning. Cannon in his "The wisdom of the body" (1932) used the engineering vision of regulation. In 1938, Selye enriched this approach by the notion of adaptation energy. This term causes much debate when one takes it literally, i.e. as a sort of energy. Selye did not use the language of mathematics, but the formalization of his phenomenological theory in the spirit of thermodynamics was simple and led to verifiable predictions. In 1980s, the dynamics of correlation and variance in systems under adaptation to a load of environmental factors were studied and the universal effect in ensembles of systems under a load of similar factors was discovered: in a crisis, as a rule, even before the onset of obvious symptoms of stress, the correlation increases together with variance (and volatility). During 30 years, this effect has been supported by many observations of groups of humans, mice, trees, grassy plants, and on financial time series. In the last ten years, these results were supplemented by many new experiments, from gene networks in cardiology and oncology to dynamics of depression and clinical psychotherapy. Several systems of models were developed: the thermodynamic-like theory of adaptation of ensembles and several families of models of individual adaptation. Historically, the first group of models was based on Selye's concept of adaptation energy and used fitness estimates. Two other groups of models are based on the idea of hidden attractor bifurcation and on the advection--diffusion model for distribution of population in the space of physiological attributes. We explore this world of models and experiments, starting with classic works, with particular attention to the results of the last ten years and open questions.Comment: Review paper, 48 pages, 29 figures, 183 bibliography, the final version accepted in Phys Life Re

Agrogeosystems of Krasnoyarsk krai: natural resource potential, environmental stability, optimization of functioning

The article presents the estimation of natural resource potential (NRP) of agrogeosystems of taiga-forest and forest-steppe zones, environmental stability and anthropogenic transformation to further optimization of their functionin

New Lower Kazanian (Upper Permian) terebratulids (Brachiopoda) from the Northeastern Russian Platform: Family Dielasmatidae Schuchert, 1913

The study of Lower Kazanian terebratulids from the eastern Russian Platform displayed a well-pronounced homeomorphy. The examination of the inner shell morphology revealed a wide diversity of brachiopod species and genera. The new genera Gruntelasma, with the type species G. bajtuganensis sp. nov., and Grigorjevaelasma, with the type species G. rossica sp. nov., are described and assigned to the family Dielasmatidae. © 2004 by MAIKA "Nauka/Interperiodica" (Russia)