A Study of the Density Variations of Mesospheric Ozone in the Case of Ionospheric Perturbation by The “Sura” Facility Radiation with Simultaneous Diagnostics of Ionospheric Plasma

Radiophysics and Quantum Electronics - We present the results of microwave observations of atmospheric radiation in the ozone line in the case of ionospheric perturbation by powerful high-frequency...     

Effect of D2O and cryosolvents on the redox properties of bacteriochlorophyll dimer and electron transfer processes in Rhodobacter sphaeroides reaction centers

Effects of environmental changes on the reaction pattern of excitation energy trapping and transformation into the "stable" radical pair P+Q(A)-, have been analyzed in isolated reaction centers of the anoxygenic purple bacterium Rhodobacter sphaeroides. The following results were obtained: (a) replacement of exchangeable protons by deuterons significantly retarded the electron transfer steps of primary charge separation, leading to the radical pair P+I- and of the subsequent reoxidation of I- by the quinone acceptor Q(A) but has virtually no effect on the midpoint potential of P/P+ that was found to be 430+/-20 mV; (b) addition of 70% (v/v) glycerol causes a shift of Em by about 30 mV towards higher values whereas the kinetics of the electron transfer reactions remain almost unaffected; (c) in the presence of the cryoprotectant DMSO, a combined effect arises, i.e. a retardation of the electron transfer kinetics comparable to that induced by H/D exchange and simultaneously an upshift of the Em value to 475+/-20 mV, resembling the action of glycerol. These results are discussed within the framework of effects on the midpoint potential due to the dielectric constant of the medium and changes of the charge distribution in the vicinity of the redox groups and the influence of relaxation processes on electron transfer reactions.     

Application of Empirical Orthogonal Functions Parameterization in the Problem of Retrieval of the Tropospheric Thermal Structure by Radiometric Data

Radiophysics and Quantum Electronics - We describe the mathematical tools of the optimal estimation method for retrieval of tropospheric temperature profiles (0–10 km) from radiometric data...     

Single polymer molecules in a protein nanopore in the limit of a strong polymer-pore attraction

The capture and release of single poly(ethylene glycol) molecules by the alpha-Hemolysin pore are observed as time-resolved reversible steps in ion conductance. The capture on rate, inferred from the step frequency, decreases monotonically with polymer size. However, the polymer residence time shows a crossover behavior, first increasing and then decreasing with molecular weight. Our interpretation is that, in the case of polymers which are too large to be accommodated within the pore, the out-of-the-pore part of the molecule pulls on the trapped part, thus acting as an entropic spring.     

A search for extragalactic sources of cosmic rays in the ultra-high energy domain

The arrival directions of ultra-high energy cosmic rays detected with the Yakutsk extensive air shower array are analyzed in comparison with the available data from other giant arrays. A correlation with the coordinates of active galaxy nuclei as hypothesized sources of ultra-high energy cosmic rays is sought for.     

A Non-Finitely Based Variety of Centre-by-Abelian-by-Nilpotent Groups of Exponent 8

The first example of a non-finitely based variety of centre-by-abelian-by-nilpotentgroups was found in 1995. This example has an infinite exponentbut it can be seen that the method used to construct it alsogives a variety that has an exponent of 128. Later it was provedthat there exists a variety with similar properties but withan exponent of 32. The paper constructs a non-finitely basedvariety of centre-by-abelian-by-nilpotent groups which has anexponent of 8.     

Elastic phase transitions in plutonium

The rich phase diagram of plutonium with a large number of different transitions in a narrow temperature interval has been puzzling scientists for decades. We offer a theoretical proof that most of the structural transformations in plutonium at temperatures exceeding the Debye temperature are the elastic phase transitions. The proof is given in the framework of the Landau theory of phase transitions and space group theory taking into account the anomalously small value of the elastic shear constants related to tetragonal and orthorhombic lattice deformations.     

Cooperative grain boundary sliding in nanocrystalline materials

Superplastic behaviour of microcrystalline materials is now believed to be controlled by cooperative grain boundary sliding (CGBS). An increasing role of grain boundary mediated plasticity with decreasing grain size down to the nanoscale was predicted leading to the prospect of enhanced superplasticity in nanocrystalline materials. Nevertheless, materials with nanosized grains have revealed a significant decrease in plasticity contrary to theoretical prediction. Direct evidence of CGBS in nanocrystalline Ni₃Al alloy from SEM surface analysis and in-situ TEM tensile testing was detected, confirming one similarity in the rheology of deformation processes between micro- and nanomaterials. Thus, differences in deformation behaviour of materials at these two length scales are related to the probability of sliding surface formation, sliding distance and related accommodation mechanisms.     

Transformation of a Si(111) stepped surface during the formation of a Si(3 × 1)Ca superstructure

The morphological changes of a Si(111) stepped surface during the formation of a Si(3 × 1)Ca surface structure have been studied using ultra high vacuum reflection electron microscopy (UHV REM). Monoatomic step clustering during surface reconstruction and an influence of adatom electromigration on step clustering have been found. The mechanism and conditions of step cluster formation during superstructural transitions are discussed.