2-Aryl-4H-3,1-benzoxazin-4-ones alcoholysis

The reaction of 2-(2-tosylaminophenyl)-4H-3,1-benzoxazine-4-one with alcohols in pyridine gives tosylanthraniloylanthranilic acid esters. The synthesized compounds luminesce in the crystalline state and in solutions at room temperature. The anomalously high Stokesian shift characteristic for this series of compounds is due to intramolecular hydrogen bonding with the participation of the tosylamino group. Interaction of polar solvents and irradiation with UV light lead to cleavage of the hydrogen bond, and as a consequence, to a decrease in the Stokesian shift.     

Quasi-energy statistics for regular and chaotic regimes in quantum systems with Hamiltonians periodic in time

Quantum mechanical systems with Hamiltonians varying periodically in time are considered. It is assumed that the spectrum of the Floquet operator has no absolutely continuous part and spacings between quasi-energies may be statistically described by means of a continuous density. It is shown that the induced statistical density of spacings between fractional parts of the quasi-energies defined with respect tomod (w), suitably normalized, approaches arbitrarily close to an exponential distribution when the number of levels is infinitely increased. This result does not depend on the original distribution. An alternate method of statistically describing fractional parts is proposed which makes it possible to distinguish between the original quasi-energy distribution laws for regular and chaotic regimes.Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 108, No. 3, pp. 431–447, September, 1996.     

Structural characteristics of different types of nanoparticles synthesised in mesomorphic metal alkanoates

The class of thermotropic ionic liquid crystals (LCs) of the metal alkanoates possesses a number of unique properties, such as intrinsic ionic conductivity, high dissolving ability and ability to form time-stable mesomorphic glasses. These ionic LCs can be used as nanoreactors for the synthesis and stabilisation of different types of nanoparticles (NPs). Thus, some semiconductors, metals and core/shell NPs were chemically synthesised in the thermotropic ionic liquid crystalline phase (smectic A) of the cadmium octanoate (CdC₈) and of the cobalt octanoate (CoC₈). By applying the scanning electron microscopy, the cadmium and cobalt octanoate composites containing CdS, Au, Ag and core/shell Au/CdS NPs have been studied. NPs’ sizes and dispersion distribution of the NPs’ size in the nanocomposites have been obtained.     

Effect of damping on the postcritical behaviour of autonomous non-conservative systems

Postcritical behavior of non-linear autonomous non-conservative systems is studied with special attention to the effects produced by the damping forces non-uniformly distributed among the natural modes (or the degrees of freedom). The objective is to find out, to what degree the well-known destabilization effect of damping primarily observed in linear systems affects the postcritical behaviour of a system if non-linearities are taken into account. As a bench model, an initially planar elastic panel is considered subjected to the supersonic gas flow. However, the qualitative conclusions may be extrapolated upon a wide class of phenomena in non-linear autonomous non-conservative systems such as airfoils and panel flutter, instabilities induced by the jet thrust or jet pressure, etc. The main conclusion confirms the already formulated statement that, from the rigorous viewpoint, all these phenomena are to be treated taking into account the initial complete positive damping, however small. There are no “paradoxes” neither in the linear nor the non-linear statement of a problem under the condition that the concept of stability is used in the proper sense. On the other hand, a strong effect is demonstrated by the ratio of partial damping factors on the postcritical behaviour. In general, the ratio of these factors influences the postcritical behaviour to a higher degree that their absolute magnitudes, at least if the latter are small or moderate.     

Influence of Initial Conditions on the Postcritical Behavior of a Nonlinear Aeroelastic System

The behavior of a nonlinear, non-Hamiltonian system in the postcritical (flutter) domain is studied with special attention to the influence of initial conditions on the properties of attractors situated at a certain point of the control parameter space. As a prototype system, an elastic panel is considered that is subjected to a combination of supersonic gas flow and quasistatic loading in the middle surface. A two natural modes approximation, resulting in a four-dimensional phase space and several control parameters is considered in detail. For two fixed points in the control parameter space, several plane sections of the four-dimensional space of initial conditions are presented and the asymptotic behavior of the final stationary responses are identified. Amongst the latter there are stable periodic orbits, both symmetric and asymmetric with respect to the origin, as well as chaotic attractors. The mosaic structure of the attraction basins is observed. In particular, it is shown that even for neighboring initial conditions can result in distinctly different nonstationary responses asymptotically approach quite different types of attractors. A number of closely neighboring periodic attractors are observed, separated by Hopf bifurcations. Periodic attractors also are observed under special initial conditions in the domains where chaotic behavior is usually expected.     

Complexation of the antibiotic daunomycin with desoxytetraribonucleoside triphosphate 5’-d(CpGpCpG) in aqueous solution

This paper presents the results of our study of the complexation of the antibiotic daunomycin with desoxytetranucleotide 5’-d(CpGpCpG) in aqueous salt solution by one- and two-dimensional (2D-TOCSY and 2D-NOESY)¹H NMR spectroscopy (500 MHz). The concentration and temperature dependences of the proton chemical shifts of molecules were measured and used to calculate the equilibrium reaction constants, the relative contents of different types of complex as functions of concentration and temperature, the limiting values of the proton chemical shifts of daunomycin in various complexes, and the thermodynamic parameters of complexation δH and δS. It is concluded that the triplet nucleotide sequences are the preferable sites at which daunomycin is attached. The binding of the second daunomycin molecule to both single-stranded and duplex forms of tetramer is markedly anticooperative. This is explained by the presence in the antibiotic of a positively charged amino sugar residue creating steric hindrances for the attachment of the second antibiotic molecule to the short tetranucleotide sequence. The most plausible spatial structure of the 1:2 complex of antibiotic with desoxytetranucleotide is constructed using the calculated values of the induced proton chemical shifts of daunomycin and 2D-NOE data. Translated fromZhurnal Strukturnoi Khimii, Vol.40, No. 2, pp. 276–286, March–April, 1999.     

Lead Sulfide Nanocrystal-Polymer Composites for Optoelectronic Applications

Summary: Nanocomposite films were prepared by two methods in which lead sulfide (PbS) nanocrystals were contained in an organic matrix. One method used a wet chemical synthesis of the nanocrystals in the direct presence of a polymer, where the polymer controlled nanocrystal growth. The second method was gaseous deposition of nanocrystals into the organic phase. The two methods were similar in that the nanocrystals in the composites were free from surfactant capping layers that otherwise would add an interfacial region between the nanocrystal and the organic matrix. The gaseous deposition technique had several advantages over the wet chemical synthesis in that it allowed direct control over nanocrystal size and density, improved flexibility in the choice of organic phase, and was compatible with lithographic methods.     

Complex Formation by Galacturonic Acid with Copper(II) and Neodymium(III) Ions in Water Solution

Complex formation by galacturonic acid with copper(II) ion in water solution is studied by themethods of EPR spectroscopy. At the pH > 3 the EPR signal (g 2.174) confirms the complex formation at theligand carboxylic group. The following complex formation parameters are measured: equilibrium constant'g factor, hyperfine coupling constant, average complex lifetime. From the data of electron spectra invisible region the complex composition and stability constant is defined for copper(II) and neodymium(III).     

Crossing of the Critical Energy Level in Hamiltonian Systems with Slow Dependence on Time

Mathematical Notes -