Coherent dissociation of relativistic 12N nuclei

The dissociation of relativistic ¹²N nuclei having a momentum of 2 GeV/c per nucleon and undergoing the most peripheral interactions in a track emulsion is studied. The picture of charged topology of product ensembles of relativistic fragments and special features of their angular distributions are presented.     

Bifurcation regimes of free convection in the presence of thermal radiation and cavity inclination

The bifurcation regimes of free convection in closed cavities with heating from below have been investigated numerically by many authors [1]. In the situations considered the equilibrium solution conditions were disturbed by only one factor, e.g. the inclination of the cavity to the vertical, the motion of one of the boundaries, a change in the equilibrium temperature distribution, etc. In this paper, the simultaneous influence of two factors that disturb the fluid equilibrium conditions, namely thermal radiation and a slight inclination of the cavity relative to the vertical, are investigated. It is shown that, for the simultaneous action of two destabilizing factors, a near-equilibrium solution is possible. Perm’. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 1, pp. 42–47, January–February, 2000. The work received financial support from the Russian Foundation for Basic Research (project No. 96-01-01737).     

Topology of “white stars” in the relativistic fragmentation of light nuclei

Experimental observations of the multifragmentation of relativistic light nuclei by means of emulsions are surveyed. Events that belong to the type of “white stars” and in which the dissociation of relativistic nuclei is not accompanied by the production of mesons and target-nucleus fragments are considered. An almost complete suppression of the binary splitting of nuclei to fragments of charge in excess of two, Z > 2, is a feature peculiar to charge topology in the dissociation of Ne, Mg, Si, and S nuclei. An increase in the degree of nuclear fragmentation manifests itself in the growth of the multiplicity of singly and doubly charged fragments (Z = 1, 2) as the charge of the unexcited fragmenting-nucleus part (which is the main part) decreases. Features of the production of systems formed by extremely light nuclei α, d, and t are studied in the dissociation of the stable isotopes of Li, Be, B, C, N, and O to charged fragments. Manifestations of ³He clustering can be observed in “white stars” in the dissociation of neutron-deficient isotopes of Be, B, C, and N.     

Dispersion equations for ion plasma with allowance for electron spin

Wave propagation in ionic magnetoactive plasma along an external magnetic field with allowance for electron spin is considered. It is shown that considering particle spin reveals the emergence of a new plasma mode in a band of frequencies close to the cyclotron frequency. A dispersion equation for wave propagation in a boundless plasma medium is obtained and special cases are considered.     

Solid Phase Luminescence and Thermal Transformations of Palladium(II) Complexes with 3-(2-Pyridyl)-1,2,4-Triazoles

Theoretical and Experimental Chemistry - The thermal behavior and luminescent properties of palladium(II) Pd(LR)2 complexes with 3-(2-pyridyl)-5-R-1,2,4-triazoles (LR , where R = H, Ph, Me) in...     

Study of the mechanism of the thermochemical reaction of polyimides with hydroxyl groups via vibrational-spectroscopy and quantum-chemistry methods

The thermochemical transformation of polyimides with one hydroxyl group in a diamine fragment that leads to changes in the polymer structure is studied. It is found that in an inert atmosphere in the temperature range 400–450°C, an intramolecular thermochemical reaction accompanied by evolution of carbon dioxide occurs. The FTIR spectra of all studied polyimide films prepared from different solvents and annealed in an inert atmosphere in the range 25–450°C show similar changes that do not agree with the structures of the reaction products (polybenzoxazole and polydehydrocyclobutabenzene) described in the literature. Possible reaction paths are calculated via quantum-chemistry methods. A mechanism of the intramolecular thermochemical transformation and the related structure of the formed polymer (aromatic lactam) are proposed.     

Luminescence of the free bases of chelate-substituted tetraphenylporphyrin derivatives and their complexes with lutetium

The absorption and luminescence spectra of the free-base forms of some new tetrarphenylporphyrin derivatives bearing a chelating group or lutetium chelate as a substituent on the phenyl ring were studied with reference to the properties of unsubstituted tetrarphenylporphyrin. The fluorescence and phosphorescence quantum yields were measured for solutions of these compounds at various temperatures. The nature of the absorption and luminescence spectral bands of the complexes and their relation to the structure are discussed.     

Entanglement for two-atom Tavis–Cummings model with degenerate two-photon transitions in the presence of the Stark shift

The dynamics of atom–field entanglement for two two-level atoms with degenerate two-photon transitions interacting with one-mode radiation field with taking into account the Stark shift is investigated. Asymptotic solutions for system state vectors are obtained in the approximation of large initial coherent fields. The atom–field entanglement is investigated also on the basis of the linear atomic entropy dynamics. The possibility of the system being initially in a pure disentangled state to revive into this state during the evolution process is shown. Conditions and times of disentanglement are derived.     

Spectrophotometric determination of mangiferin

A spectrophotometric method is proposed for determining mangiferin in a crystalline powder and in sweetvetch herbage. The relative accuracy of the method is ± 0.34% for the powder and ± 2.63% for the herbage.