Relation between the intensity of ir absorption bands of stretching vibrations of nitrogroups and their number in aromatic nitrocompounds

Yaroslavl' State University, 9 Matrosov Ave., Yaroslavl', 150023, Russia. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 62, No. 6, pp. 30–37, November–December, 1995.     

Studying hyperbolicity in chaotic systems

On the basis of method [1] proposed for diagnosing 2-dimensional chaotic saddles we present a numerical procedure to distinguish hyperbolic and nonhyperbolic chaotic attractors in three-dimensional flow systems. This technique is based on calculating the angles between stable and unstable manifolds along a chaotic trajectory in R³. We show for three-dimensional flow systems that this serves as an efficient characteristic for exploring chaotic differential systems. We also analyze the effect of noise on the structure of angle distribution for both 2-dimensional invertible maps and a 3-dimensional continuous system.     

Folding thermodynamics of pseudoknotted chain conformations

We develop a statistical mechanical framework for the folding thermodynamics of pseudoknotted structures. As applications of the theory, we investigate the folding stability and the free energy landscapes for both the thermal and the mechanical unfolding of pseudoknotted chains. For the mechanical unfolding process, we predict the force-extension curves, from which we can obtain the information about structural transitions in the unfolding process. In general, a pseudoknotted structure unfolds through multiple structural transitions. The interplay between the helix stems and the loops plays an important role in the folding stability of pseudoknots. For instance, variations in loop sizes can lead to the destabilization of some intermediate states and change the (equilibrium) folding pathways (e.g., two helix stems unfold either cooperatively or sequentially). In both thermal and mechanical unfolding, depending on the nucleotide sequence, misfolded intermediate states can emerge in the folding process. In addition, thermal and mechanical unfoldings often have different (equilibrium) pathways. For example, for certain sequences, the misfolded intermediates, which generally have longer tails, can fold, unfold, and refold again in the pulling process, which means that these intermediates can switch between two different average end-end extensions.     

Present and future experiments in nonequilibrium reactor antineutrino energy spectrum

Considerable efforts that have been undertaken in recent years in low-energy antineutrino experiments require further systematic investigations in line of reactor antineutrino spectroscopy as a metrological basis of these experiments. We consider some effects associated with the nonequilibrium of reactor radiation and residual emission from spent reactor fuel in contemporary experiments. The text was submitted by the authors in English.     

Description of the dispersive refraction effect by space-time ray method

A certain type of refraction, exhibited in time-dispersive linear media for special wave forms, is considered in this paper. This phenomenon, referred to as dispersive refraction, resembles nonlinear refraction. For example, both dispersive and nonlinear refraction can exist in a homogeneous medium, which is impossible in the case of ordinary linear refraction.     

Kinetics of the Reactions of 4-Nitrochlorobenzene with Substituted Phenolates in an Aprotic Polar Solvent

The kinetics of 4-nitrochlorobenzene reactions with substituted phenolates in the medium of N,N-dimethylacetamide was studied. The BrØnsted relation is fulfilled by substituted potassium phenolates: the nucleophilicity of phenolates increases with an increase in their basicity. The rate-limiting step in the reactions of 4-nitrochlorobenzene with substituted phenolates and potassium resorcinate is changed from the phenoxide anion to the phenoxide dianion. In the latter case, electron transfer from the resorcinate dianion with the generation of radical species can be responsible for the reaction rate.