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

Tunable nonlinear graphene metasurfaces

We introduce the concept of nonlinear graphene metasurfaces employing the controllable interaction between a graphene layer and a planar metamaterial. Such hybrid metasurfaces support two types of subradiant resonant modes, asymmetric modes of structured metamaterial elements ("metamolecules") and graphene plasmons exhibiting strong mutual coupling and avoided dispersion crossing. High tunability of graphene plasmons facilitates strong interaction between the subradiant modes, modifying the spectral position and lifetime of the associated Fano resonances. We demonstrate that strong resonant interaction, combined with the subwavelength localization of plasmons, leads to the enhanced nonlinear response and high efficiency of the second-harmonic generation.Comment: 6 pages, 5 figure

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

Even harmonic generation in isotropic media of dissociating homonuclear molecules

Isotropic gases irradiated by long pulses of intense IR light can generate very high harmonics of the incident field. It is generally accepted that, due to the symmetry of the generating medium, be it an atomic or an isotropic molecular gas, only odd harmonics of the driving field can be produced. Here we show how the interplay of electronic and nuclear dynamics can lead to a marked breakdown of this standard picture: a substantial part of the harmonic spectrum can consist of even rather than odd harmonics. We demonstrate the effect using ab-initio solutions of the time-dependent Schr\"odinger equation for $H$$_2$$^+$ and its isotopes in full dimensionality. By means of a simple analytical model, we identify its physical origin, which is the appearance of a permanent dipole moment in dissociating homonuclear molecules, caused by light-induced localization of the electric charge during dissociation. The effect arises for sufficiently long laser pulses and the region of the spectrum where even harmonics are produced is controlled by pulse duration. Our results (i) show how the interplay of femtosecond nuclear and attosecond electronic dynamics, which affects the charge flow inside the dissociating molecule, is reflected in the nonlinear response, and (ii) force one to augment standard selection rules found in nonlinear optics textbooks by considering light-induced modifications of the medium during the generation process.Comment: 7 pages, 6 figure

Structure of coenopopulations and phytocoenotic confinement of Paeonia tenuifolia L. in floristic complexes of Oka-Don lowland

Paeonia tenuifolia L. is a rare and protected plant of Saratov region classified as 2 (V) vulnerable species. It has been established that in Kalininsky district, Saratov region, this plant is characterized by narrow environmental amplitude and is exerted to anthropogenic impacts, the coenopopulations are isolated from each other. Existence of the species in communities of the meadow–steppe floristic complexes of Kalininsky district has confirmed that peony is heliophyte, xeromesophyte, eutrophic plant and calcicole. Photophily of P. tenuifoliais confirmed first of all by its high abundance and occurrence in open steppe communities. In both coenopopulations of P.tenuifolia, the indices of recovery have been higher than 1 (CP 1 Irec = 3.38, CP 2 Irec = 1.67), that is, the coenopopulations are relatively steady, numerous seeds are generated giving birth to viable individuals. The index of replacement showing the ratio of the density of regrowth to total mature fraction of the population has been higher in CP 1 (Irepl = 0.80) and lower in CP 2 (Irepl = 0.67). Moderate index of maturing evidence long-term existence of the species in the generative state

Systemacity and categorization in functioning of verbs

The article focuses on the issues of systemacity in language, the category of causation, functioning of causatives of the informative-modificative class. In this article, the causation is examined from the perspective of functional approach, suggested by A. Bondarko. A verb of causative semantics is related to a more general class on the basis of its essential properties. In the centre of our attention is a lexical causative of interpersonal semantics which is the core of the functional-semantic field of causationyesBelgorod State National Research Universit