Molecular design of heterocycles. 4. Utilization of computers in the chemistry of heterocycles (review)

Fundamental principals of the utilization of computers in the design of heterocyclic structures and reactions are examined and systematized in this review. The authors' original GREN program, which lists the recyclizations of heterocycles, and Heterocycland program, which is based on the previously proposed [2] structure-synthesis concept and is used for the retrosynthesis of six-membered heterocycles, are examined concisely.For Communication 3, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1299–1318, October, 1993.     

Study on the influence of isotope exchange of hydrogen with deuterium on the vibrational spectrum of lysozyme by inelastic neutron scattering

The influence of isotope exchange of hydrogen with deuterium on the lysozyme dynamics was studied by incoherent inelastic neutron scattering. The generalized vibrational densities of states G(ω) were constructed from experimental results for protonated and deuterated protein samples at 200, 280, and 311 K. The major isotope effect was observed in G(ω) in the frequency region higher than 100 cm^?1. At all temperatures, both the Debye mode and the region of G(ω), whose spectral dimension corresponds to the fracton mode, are observed in the low-frequency region of the densities of states of both protonated and deuterated lysozyme. The influence of the hydrogen isotope exchange on the low-frequency region of G(ω) is insignificant.     

Investigation of the flows in axisymmetric and plane divergent channels with preseparation boundary layers on their walls

The method of matched asymptotic expansions is used to develop a procedure for constructing separationless plane and axisymmetric diffusers for incompressible high-Reynolds-number flows with a given pressure distribution over the diffuser surface and minimum friction losses. The problem for the region of interaction between the boundary layer and the inviscid outer flow is numerically solved and the effect of variation of the on-design flow parameters in the entry section on the diffuser flow parameters is studied.     

Fully parallel algorithm for simulating dispersion-managed wavelength-division-multiplexed optical fiber systems

An efficient numerical algorithm is presented for massively parallel simulations of dispersion-managed wavelength-division-multiplexed optical fiber systems. The algorithm is based on a weak nonlinearity approximation and independent parallel calculations of fast Fourier transforms on multiple central processor units (CPUs). The algorithm allows one to implement numerical simulations M/2 times faster than a direct numerical simulation by a split-step method, where M is a number of CPUs in a parallel network.     

Cluster modeling of the electronic structure of ideal MgF2 crystals

Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 54, No. 6, pp. 986–990, June, 1991.     

Surface plasmons in small metal particles

The dielectric response of a small metal particle to a perturbing potentialv _L =r ^L Y _LM e ^iωt is considered within the random phase approximation (RPA). The static dielectric polarizability is found and the size dependence of the surface plasmon frequencies are then determined from sum rule calculations. When the particle radiusa is large compared to the Thomas-Fermi screening lengthr ₀ the RPA equation is transformed into a form appropriate for an analytical solution. The dynamic electric polarizability, the position and the width of the surface plasma resonance are found in the limita/r ₀?1.     

Dispersion-managed soliton in optical fibers with zero average dispersion

A dispersion-managed optical system with stepwise periodic variation of dispersion is studied in the framework of a path-averaged Gabitov-Turitsyn equation. The soliton solution is obtained by means of iterating the path-averaged equation. The dependence of soliton parameters on dispersion map strength is investigated, together with the oscillating tails of the soliton.