Study of the thermal stages of the photoinitiated cyclization of diarylamines with polyhalogenated methanes

On the basis of a study of the kinetics of the dark stages of the photoinitiated formation of acridines from substituted diphenylamines and bromoform the ionic nature of these stages was confirmed. Quantum chemical calculations confirmed the assumption of the dependence of the efficiency of cyclization on the charge state of the reacting molecules.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 564–569, March, 1991.     

Comparative nonempirical study and isodesmic calculations of heats of formation of HNCO and HPCO isomers

The structural, electronic, and energetic characteristics of CHNO and CHOP isomers, and also of several related compounds, were calculated by a nonempirical method. Enthalpies of these isomers, obtained using the method of isodesmic reactions, are given.V. I. Lenin Moscow Pedagogical State University, 117913 Moscow. Institute of Physiologically Active Compounds, Russian Academy of Sciences, 142432 Chernogolovka. Institute of New Chemical Problems, Russian Academy of Sciences, 142432 Chernogolovka. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 7, pp. 1585–1590, July, 1992.     

The aromatic diboracyclopropenyl (diboriranyl) anion; CB2H3 −: An ab initio study

The most stable structure of CB₂H₃ ^–, as established computationally, is the aromatic diboracyclopropenyl (diboriranyl) anion (5), while open-chainC _2v, isomer H₂BCBH (7) is only 3 kcal/mol higher in energy at the QCISD(T)/6-311 +G^**//MP2/6-31+G^*+ZPE (HF/6-31 +G^*). The 47-kcal/mol barrier between cyclic,5, and open-chain,7, structures suggests that both of them may be observed. The aromatic stabilization energy of the diboriranyl anion (18 kcal/mol) is half the value in the isoelectronic cyclopropenium ion, C₃H₃ ⁺. The computed, by IGLO method (5a), and experimental (6a) chemical shifts,(¹³C) and(¹¹B), agree within 4 ppm range. The theoretical vibrational frequencies of the most stable isomers,5 and7, are presented for experimental verification of these species.     

Polysila analogs of aromatic hydrocarbon ions: Structures and energies of Si3H3+, Si4H,and Si5H5−

Silicon analogs of aromatic monocyclic ions, (SiH) ( 4 ), (SiH) ( 5 ), and (SiH) ( 6 ) have been studied ab initio at MP 2(full)/6-31G *. The D_3h structure of Si₃H₃⁺ is the global minimum, whereas other two ions are nonplanar. The D_2d structure of (SiH) is less folded than the carbon analog and possesses a higher stabilization energy. Stabilization energies for the monocharged ions are diminished with respect to the corresponding carbons © 1993 John Wiley & Sons, Inc.     

Analysis of the radiative transfer equation with highly assymetric phase function

This paper considers a scalar radiative transfer problem with high scattering anisotropy. Two computational methods are presented based on decomposition of the diffuse light field into a regular and anisotropic part. The first algorithm (DOMAS) singles out the anisotropic radiance in the forward scattering peak using the Small-Angle Modification of RTE. The second algorithm (DOM2+) separates the single scattering radiance as an anisotropic part, which largely defines the fine detail of the total radiance in the backscattering directions. In both cases, the anisotropic part is represented analytically. With anisotropy subtraction, the regular part of the signal, which requires a numerical solution, is essentially smoothed as a function of angles. Further, the transport equation is obtained for the regular part that contains an additional source function from the anisotropic part of the signal. This equation is solved with the discrete ordinates method. A conducted numerical analysis of this work showed that algorithm DOMAS has a strong advantage as compared to the standard discrete ordinates method for simulation of the radiance transmission, and DOM2+ is the best of the three for the reflection computations. Both algorithms offer at least a factor of three acceleration of convergence of the azimuthal series for highly anisotropic phase functions.     

The relation between the maximum entropy of a quantized surface and its area

It is shown that the maximum entropy of a quantized surface in the classical limit is proportional to its area. The result is valid for the loop quantum gravitation as well as for a more general class of approaches to surface quantization. For some special cases, the maximum entropy is calculated in explicit form.     

Nonthermal radiation of rotating black holes

The nonthermal radiation of a Kerr black hole is considered as the tunneling of particles being produced through an effective Dirac gap. In the leading semiclassical approximation, this approach is also applicable to bosons. Our semiclassical results for photons and gravitons are consistent with those obtained previously. For neutrinos, the result of our complete quantum-mechanical calculation is about twice as large as the previous one.     

Space-angle distribution of the reflected charged particles adjusted for spin calculations

The efficiency of the proposed method of solution for the spin-considered highly anisotropic multiple scattering problem is based, following optics, upon the admission that the complete solution of the vectorial transport equation boundary problem is the superposition of the anisotropic and smooth parts, calculated separately. We use a vectorial small angle modification of the spherical harmonics method to evaluate the anisotropic part and the vectorial discrete ordinates method to obtain a smooth one. Some calculation examples for reflected radiation are given.