Emergence of Complex Dynamics in a Simple Model of Signaling Networks

A variety of physical, social and biological systems generate complex fluctuations with correlations across multiple time scales. In physiologic systems, these long-range correlations are altered with disease and aging. Such correlated fluctuations in living systems have been attributed to the interaction of multiple control systems; however, the mechanisms underlying this behavior remain unknown. Here, we show that a number of distinct classes of dynamical behaviors, including correlated fluctuations characterized by $1/f$-scaling of their power spectra, can emerge in networks of simple signaling units. We find that under general conditions, complex dynamics can be generated by systems fulfilling two requirements: i) a ``small-world'' topology and ii) the presence of noise. Our findings support two notable conclusions: first, complex physiologic-like signals can be modeled with a minimal set of components; and second, systems fulfilling conditions (i) and (ii) are robust to some degree of degradation, i.e., they will still be able to generate $1/f$-dynamics

The stability of metal complexes with 8-mercaptoquinoline and alkyl-substituted 8-mercaptoquinolines in dimethylformamide

The stoichiometry and stability constants of 8-mercaptoquinoline and alkyl-8-mercaptoquinoline complexes of Zn(II), Cd(II), Pb(II), Ni(II), Bi(III) and Ag(I) were determined potentiometrically in dimethylformamide. The stability of the 8-mercaptoquinolinates decreases in the order Ag(I) ≫ Bi(III) ≫ Ni(II) ≫ Pb(II) ≫ Cd(II) ≫ Zn(II). Metal 7-methyl-8-mercaptoquinolinates are the most stable. The presence of the alkyl group in the 2-position (which has a steric effect) lowers the strength of metal-ligand bonding. © 1984

Electron beam energy continuous measuring device

Developing the device for controlling electron energy in sterilization process. As the electron beam goes through the set of aluminum plates, electric charges are formed in them. Charge distribution in the depth of the absorber allows one to determine primary beam’s electron energy

Glucose metabolism and oscillatory behavior of pancreatic islets

A variety of oscillations are observed in pancreatic islets.We establish a model, incorporating two oscillatory systems of different time scales: One is the well-known bursting model in pancreatic beta-cells and the other is the glucose-insulin feedback model which considers direct and indirect feedback of secreted insulin. These two are coupled to interact with each other in the combined model, and two basic assumptions are made on the basis of biological observations: The conductance g_{K(ATP)} for the ATP-dependent potassium current is a decreasing function of the glucose concentration whereas the insulin secretion rate is given by a function of the intracellular calcium concentration. Obtained via extensive numerical simulations are complex oscillations including clusters of bursts, slow and fast calcium oscillations, and so on. We also consider how the intracellular glucose concentration depends upon the extracellular glucose concentration, and examine the inhibitory effects of insulin.Comment: 11 pages, 16 figure

The regulatory system for diabetes mellitus: Modeling rates of glucose infusions and insulin injections

Novel mathematical models with open and closed-loop control for type 1 or type 2 diabetes mellitus were developed to improve understanding of the glucose-insulin regulatory system. A hybrid impulsive glucose-insulin model with different frequencies of glucose infusions and insulin injections was analysed, and the existence and uniqueness of the positive periodic solution for type 1 diabetes, which is globally asymptotically stable, was studied analytically. Moreover, permanence of the system for type 2 diabetes was demonstrated which showed that the glucose concentration level is uniformly bounded above and below. To investigate how to prevent hyperinsulinemia and hyperglycaemia being caused by this system, we developed a model involving periodic intakes of glucose with insulin injections applied only when the blood glucose level reached a given critical glucose threshold. In addition, our numerical analysis revealed that the period, the frequency and the dose of glucose infusions and insulin injections are crucial for insulin therapies, and the results provide clinical strategies for insulin-administration practices

DEVELOPMENT OF DEVICE FOR CONTINUOUS MEASUREMENT OF ELECTRON ENERGY OF ACCELERATOR УЭЛР-10-10C FOR RADIATION STERILIZATION PROCESS CONTROL

The goal of the work is to develop a device for control process of sterilization. The appliance allows to judge primary energy of electron beam by electric current, given from aluminum plates

Complex Dynamics and Multistability in a Damped Harmonic Oscillator with Delayed Negative Feedback

A center manifold reduction and numerical calculations are used to demonstrate the presence of limit cycles, two-tori, and multistability in the damped harmonic oscillator with delayed negative feedback. This model is the prototype of a mechanical system operating with delayed feedback. Complex dynamics are thus seen to arise in very plausible and commonly occurring mechanical and neuromechanical feedback systems