Special features of magnetic susceptibility dispersion in nanocrystalline magnets

It is demonstrated theoretically that the initial (both elastic and viscous) magnetic susceptibility components for nanocrystalline magnets caused by the processes of rotations (in the region of linear response) have resonant rather than relaxation character typical already for the susceptibility component caused by displacements of domain boundaries. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 88–92, June, 2007.     

Spectrum and polarization of electrons in neutron beta-decay in an electromagnetic wave field

A study is made on a polarized neutron undergoing -decay induced by an intense electromagnetic wave. The angular distribution of electrons in the decay is obtained and their polarization is studied. A comparison is made with the decay of a moving neutron.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 33–37, March, 1987.The authors are grateful to L. I. Lapidus, B. K. Kerimov, and G. A. Chizhov for their interest in this work and for their constructive criticism.     

Quantum-chemical investigation of the influence of the vacant orbitals of the heteroatom on the shaping of the electronically excited states and luminescence-spectroscopic properties of triphenylgallium

The electronic structure of the triphenylgallium molecule in the ground and electronically excited states has been calculated in the framework of the CNDO/S-CI method in sp and spd bases. The electron density in the AO's and atoms, the first ionization potential the energies and matrices of the changes in the electron density of the S_n and T_n states, the matrix elements of the spin-orbit coupling operator $$ " align="middle" border="0"> and $$ " align="middle" border="0"> , the intensities and directions of polarization of the S_n S_o and T₂ T_n transitions, and the phosphorescence lifetimes have been calculated. The following spectroscopic parametrization has been proposed for the Ga atom in the sp and spd bases: 1/2(I_s + a_s) = 10.075 eV, 1/2(I_p + A_p) = 4.265 eV, 1/2(I_d + A_d)=0, _Ga ^p =5 eV, _Ga ^d =O, _Ga ^sp =–7 eV, _Ga ^spd =–10 eV, and _s,p,d=1.433. The influence of the d AO's on the shaping of the orbital nature of the S₁ and T₂ states has been analyzed.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 21, No. 5, pp. 584–590, September–October, 1985.     

Selective mono-and diamination of polyfluorinated benzenes and pyridines with liquid ammonia

Amination of pentafluoropyridine, 2,3,5,6-tetrafluoropyridine, 4-chlorotetrafluoropyridine, 3,5-dichlorotrifluoropyridine, octafluorotoluene, α,α,α,2,3,5,6-heptafluorotoluene, decafluoro-m-xylene, decafluorobiphenyl, hexafluorobenzene, and pentafluorobenzene with liquid ammonia was investigated. Bis-aminodefluorination temperatures for the majority of substrates were shown to exceed significantly the corresponding temperatures of monoaminodefluorination. The optimal conditions for selective preparation of mono-and diaminopolyfluoro(het)arenes were elucidated. An efficient method for isolation of particular polyfluorophenylenediamines from product mixtures formed in nonselective reactions of pentafluorobenzene and hexafluorobenzene with aqueous ammonia based on complexation with a crown ether is proposed. Dedicated to the memory of Academician N. N. Vorozhtsov on the occasion of his 100th anniversary. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2163–2170, November, 2007.     

The number of propagating species and some rate constants of elementary acts for the polymerization of ethylene and α-olefins using supported Ziegler catalysts

Concentrations of propagating species (PS) and chain propagation constants (k_p) were determined for the polymerizations of ethylene, propylene, butene-1 and hexene-1 using TiCl₄/MgO-Al(C₂H₅)₃ (i) and TiCl₄/Al₂O₃. SiO₂-Al(C₂H₅)₃ (II) catalytic systems. The concentrations of propagating species for all monomers and a particular catalytic system are close. They give an idea of high degree of application of transition metal ($\text{? 35–39\%}$ of total Ti for system I and $\text{? 20–23\%}$ for system II). Values of k_p for ethylene, propylene, butene-1, hexene-1 at 70° for system I are 2440 ± 240, 4.8 ± 0.5, 4.6 ± 0.5 and 2.5 ± 0.3 l/mol·sec respectively. For system II, k_p values for the first three monomers are 110 ± 11, 1.0 ± 0.1 and 0.13 ± 0.01 l/mol·sec. These results indicate the relation of reactivity of propagating species and chemical nature of the support to the surface of which they are fixed. Rate constants for chain transfer to monomer or triethyl aluminium and spontaneous disproportionation (at 70°) were compard for the polymerizations of ethylene and propylene using catalytic system I.     

Properties of Hill’s estimator of extreme value index for impure samples

The consistency and asymptotic normality of the Hill estimator of the extreme value index is considered for a sample from a sequence of independent and identically distributed random variables with asymptotically increasing additive impurity. In addition, the cases when the statistical construction of the estimator is possible are analyzed.