Climate changes and trends over India

Based on the instrumental observations of over a century available in India, attempt is made to study if there is a clear-cut evidence of any climate change or trend over .India with particular reference to rainfall, surface temperature, atmospheric pressure and total ozone. The study concludes that while there are year to year random. fluctuations in these atmospheric variables and there are certain epochal increases and decreases in respect of rainfall and .surface temperature, .there appears to be no systematic climate charge or trend over India. There IS also no evidence of ozone depletion over India.

Ensuring power balance in a hybrid power system with a standby generator

The combination of several non-guaranteed random energy sources (RES), conventional sources, and nonconstant consumer loads in a local system leads to stochastic power imbalances. This study objective consists in determining the possibilities of ensuring the power balance in a hybrid power generation system with a standby generator and a search for the methods of calculating the optimal parameters to achieve energy balance. This objective is achieved by simulating the processes inherent in wind and solar power engineering and the regimes of energy consumption through a combination of random functions with a standard probability distribution. Aggregated data on weather factors for several years in a region with a high renewable energy potential which can be used to describe the behavior of wind and solar energy over time were used as experimental data. The use of multiple simulations of random processes with calculated parameters has made it possible to draw conclusions about the presence of certain ratios of power and the generator control modes. These ratios can determine minimum energy and consumption losses, reduce the likelihood of energy imbalance, more efficiently use the reserved power. Specific features of the stochastic nature of RES related to the presence of trends and random fluctuations at short hourly intervals were additionally taken into account. Possibilities of varying the conditions of and switching on and off of the standby generator were provided. The existence of some ranges was established for the installed power of the generator outside which its use becomes inefficient. The proposed approach makes it possible to find the probability of various system states, assess the reliability of energy supply, and minimize unproductive losses.

Effect of the FDA Black Box Suicidality Warnings for Antidepressants on Suicide Rates in the USA

Background: Some authors claimed that the US Food and Drug Administration (FDA) black box warning on treatment-emergent suicidality with antidepressants in adolescents (issued 2004) and young adults (issued 2006) led to an increase of suicides, based on the analyses of ecological data with debatable assumptions about putative changes in suicide rates. Aims: To explore if putative changes in suicide rates in adolescents and young adults at the time of the FDA warnings is a detectable signal in the data or compatible with random fluctuations. Method: We applied different changepoint analyses for adolescent and young adult suicide rates from 1981 to 2019 in the USA. Results: Changepoint analysis did not support a detrimental effect of the FDA black box warnings. The downward trend of suicides reversed several years after the warning in adolescents (2007–2009) and many years before in young adults (1999–2001). Limitations: Our analyses cannot rule out detrimental effects of the FDA warnings. However, even if there was such an effect, it was likely small and indistinguishable from random fluctuations in the available suicide data. Conclusion: There is no detectable change of trend in adolescent or young adult suicide rates in line with a detrimental effect of the FDA black box warnings on treatment-emergent suicidality.

Hypothesis of rational expectations in the international economy: developments in different countries

The article reveals the development of the hypothesis of rational expectations according to the theory of rational expectations (TRO), where economic entities in their forecasts make optimal use of all available information, including the assessment of government policy, to form an opinion on future developments. It turns out that expectations in the economy are very important. Rational expectations are those that can be systematically erroneous. They do not necessarily have to be performed exactly, but this is only because economic processes are subject to random fluctuations that do not depend on the actions of the state, or because the actions of the state in economic policy are unpredictable for economic agents.

Computational fluid dynamics modeling of cough transport in an aircraft cabin

To characterize the transport of respiratory pathogens during commercial air travel, Computational Fluid Dynamics simulations were performed to track particles expelled by coughing by a passenger assigned to different seats on a Boeing 737 aircraft. Simulation data were post-processed to calculate the amounts of particles inhaled by nearby passengers. Different airflow rates were used, as well as different initial conditions to account for random fluctuations of the flow field. Overall, 80% of the particles were removed from the cabin in 1.3–2.6 min, depending on conditions, and 95% of the particles were removed in 2.4–4.6 min. Reducing airflow increased particle dispersion throughout the cabin but did not increase the highest exposure of nearby passengers. The highest exposure was 0.3% of the nonvolatile mass expelled by the cough, and the median exposure for seats within 3 feet of the cough discharge was 0.1%, which was in line with recent experimental testing.

Deep Gene Networks and Response to Stress

We consider systems of differential equations with polynomial and rational nonlinearities and with a dependence on a discrete parameter. Such systems arise in biological and ecological applications, where the discrete parameter can be interpreted as a genetic code. The genetic code defines system responses to external perturbations. We suppose that these responses are defined by deep networks. We investigate the stability of attractors of our systems under sequences of perturbations (for example, stresses induced by environmental changes), and we introduce a new concept of biosystem stability via gene regulation. We show that if the gene regulation is absent, then biosystems sooner or later collapse under fluctuations. By a genetic regulation, one can provide attractor stability for large times. Therefore, in the framework of our model, we prove the Gromov–Carbone hypothesis that evolution by replication makes biosystems robust against random fluctuations. We apply these results to a model of cancer immune therapy.

Engineering transient dynamics of artificial cells by stochastic distribution of enzymes

Random fluctuations are inherent to all complex molecular systems. Although nature has evolved mechanisms to control stochastic events to achieve the desired biological output, reproducing this in synthetic systems represents a significant challenge. Here we present an artificial platform that enables us to exploit stochasticity to direct motile behavior. We found that enzymes, when confined to the fluidic polymer membrane of a core-shell coacervate, were distributed stochastically in time and space. This resulted in a transient, asymmetric configuration of propulsive units, which imparted motility to such coacervates in presence of substrate. This mechanism was confirmed by stochastic modelling and simulations in silico. Furthermore, we showed that a deeper understanding of the mechanism of stochasticity could be utilized to modulate the motion output. Conceptually, this work represents a leap in design philosophy in the construction of synthetic systems with life-like behaviors.

Study of the dynamics of two chemostats connected by Fickian diffusion with bounded random fluctuations

This paper investigates the dynamics of a model of two chemostats connected by Fickian diffusion with bounded random fluctuations. We prove the existence and uniqueness of non-negative global solution as well as the existence of compact absorbing and attracting sets for the solutions of the corresponding random system. After that, we study the internal structure of the attracting set to obtain more detailed information about the long-time behavior of the state variables. In such a way, we provide conditions under which the extinction of the species cannot be avoided and conditions to ensure the persistence of the species, which is often the main goal pursued by practitioners. In addition, we illustrate the theoretical results with several numerical simulations.

The role of noise in the tumor dynamics under chemotherapy treatment

Dynamical systems modeling tumor growth have been investigated to analyze the dynamics between tumor and healthy cells. Recent theoretical studies indicate that these interactions may lead to different dynamical outcomes under the effect of particular cancer therapies. In the present paper, we derive a system of nonlinear differential equations, in order to investigate solid tumors in vivo, taking into account the impact of chemotherapy on both tumor and healthy cells. We start by studying our model only in terms of deterministic dynamics under the variation of a drug concentration parameter. Later, with the introduction of noise, a stochastic model is used to analyze the impact of the unavoidable random fluctuations. As a result, new insights into noise-induced transitions are provided and illustrated in detail using techniques from dynamical systems and from the theory of stochastic processes.

A Stochastic Hierarchical Population System: Excitement, Extinction and Transition to Chaos

A problem of the mathematical modeling and analysis of noise-induced transformations of complex oscillatory regimes in hierarchical population systems is considered. As a key example, we use a three-dimensional food chain dynamical model of the interacting prey, predator, and top predator. We perform a comparative study of the impacts of random fluctuations on three key biological parameters of prey growth, predator mortality, and the top predator growth. A detailed investigation of the stochastic excitement, noise-induced transition from order to chaos, and various scenarios of extinction is carried out. Constructive abilities of the semi-analytical method of confidence domains in the analysis of the noise-induced extinction are demonstrated.