Solid Echo in Three-Spin Groups with Arbitrary Constants of Dipole–Dipole Interaction

Applied Magnetic Resonance - The suggested approach allowed us to derive analytical expressions for modeling the shape of solid-echo signal and its time evolution for a system of three-spin groups...     

Porphyrins 34. Mass spectrometric study of ethane- and ethylene-bis-porphyrins

The mass spectral behavior of 1, 2-di (mesoetioporphyr inyl-1)- and 1, 2-di (mesooctaethylporphyrlnyl) ethanes and ethylenes, their Cu and Ni complexes, as well as Ni Schiff bases of 1, 2-di (mesooctaethylporphyrinyl)ethane complexes, under ionization by electron impact and bombardment by accelerated atoms, was studied. Peaks of molecular ions, for which the basic decomposition pathways were established on the basis of an analysis of the parent and daughter ions, were observed in the electron impact mass spectra of all these compounds.For Communication 29, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 24–29, January, 1994.     

Two-limit problems for almost semicontinuous processes defined on a Markov chain

We consider almost upper-semicontinuous processes defined on a finite Markov chain. The distributions of functionals associated with the exit of these processes from a finite interval are studied. We also consider some modifications of these processes. __________ Translated from Ukrains’kyi Matematychnyi Zhurnal, Vol. 59, No. 4, pp. 555–565, April, 2007.     

Stimulated echo method for investigation of structural and dynamic characteristics of branched polymers

The theory of stimulated echo (SE) without magnetic field gradient is proposed. The theory made it possible for the first time to establish a relationship between the stimulated echo signal and correlation function of molecular mobility. Signals of free induction decay (FID) and SE in polymer networks and branched polymers were modeled. The type of the correlation function at different average chain lengths N ₀ between knots and different distribution functions of the knots was determined. A strong influence of the molecular weight distribution (MWD) on the type of the correlation function in polymer melts was shown. Two methods were proposed for the numerical determination of the correlation function from the observed FID and SE signals. These methods gave an information about the molecular mobility and topological structure in the samples of branched polymethyl methacrylates of different structures and various molecular weights.

     

Risk process with stochastic income and two-step premium rate

In this paper we deal with the risk reserve process with stochastic premium function. We assume that the premiums sizes have exponential distribution with the rate depending on some threshold level. The representation for the discounted defective joint density of surplus and deficit at ruin is obtained.     

Porphyrins. 29. Mass spectra of functionally substituted tetraarylporphyrin derivatives

The mass spectral behavior of functionally substituted meso(p-adamantylphenyl)triphenylporphyrins and their p-methoxy-substituted analogs was studied. Breakdown of the M⁺ ions of these compounds proceeds chiefly-with a loss of the functional substituent in the adamantane ring with the formation of ions, which make it possible to determine the nature of this substituent.For Communication 28, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1642–1644, December, 1993.     

A generalized solution in W2 1(0,1) of a problem concerning the deflection of a beam

A new method is proposed for formulating a boundary-value problem for a fourth-order ordinary differential equation with a solution in W₂ ¹(0, 1). This generalized formulation is based on a system of second-order equations with coefficients in W₂ ^–1 (0, 1). The existence and uniqueness of the indicated solution in this class is proven.Translated fromVychislitel'naya i Prikladnaya Matematika, No. 69, pp. 90–96, 1989.     

Relation of self-diffusion and the topological structure of flexible polymers as studied by NMR

A general approach to deriving formulas for calculating the diffusion attenuation of spin echo decay signal is developed and applied to obtaining data on random processes in linear and crosslinked polymers with different topological structures. The analysis explains the experimentally observed anomalous diffusion in polymer networks.     

Porphyrins

A mass spectrometric investigation has been carried out on chlorins, porphyrins, and their metal complexes containing -diketone residues in the meso and -pyrrole positions. Porphyrins containing acetyl or benzoylethyl groups in the meso position are characterized by the loss from the molecular ion M⁺ of a -diketone residue and then the alkyl substituents of the porphyrin nucleus. Diacetylcydopropylchlorins are characterized by the sequential loss from the molecular ion of an acetyl residue and a molecule of ketene.For Communication 27, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1478–1483, November, 1993.