Nuclear tracks created by 90 MeV carbon ions in ZnO crystal

The distribution of the lengths of the tracks, created by 90 Mev Carbon ions in Zno crystal consists of three groups with an average value about 52, 67 and 102 micrometers. The first group of the tracks may be treated as unchannelling particles. The second group corresponds to channeling particles and the third one represents superchannelling particles.     

Calculation of the stress-strain state of bent annular plates taking account of material damage during creep

Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, No. 3, pp. 142–146, May–June, 1993.     

Kinetics of nitrous acid formation in nitric acid solutions under the effect of power ultrasound

Sonochemical nitrous acid formation was investigated in 0.1-4.0 mol dm(-3) aqueous nitric acid solutions under the effect of power ultrasound with 20 kHz frequency. HNO2 steady-state concentration was obtained under long-time sonication; the excess HNO2 formed is decomposed and evoluted from the solution as NO and NO2 gases. The HNO2 steady-state concentration and the HNO2 initial formation rate depend linearly on the HNO3 concentration and acoustic intensity (1.8-3.5 W cm(-2)) and decrease with rising temperature in the range 21-50 degrees C. The HNO2 formation rate depends on the type of saturating gas as follows: Ar > N2 > He > air. NO and O2 are the major gaseous products of HNO3 sonication. The NO2 accumulation of in the gas phase is observed only when the decomposition of HNO2 formed becomes noticeable. The gaseous products formation rates depend on the HNO3 concentration, acoustic intensity and the type of saturating gas. The mechanism of HNO2 sonochemical formation is assumed to be the thermal decomposition of HNO3 in the gaseous vicinity of collapsing bubbles or in the overheated liquid reaction zone surrounding the cavitational bubbles.     

Magnetic and Superconducting Properties of the Heterogeneous Layered Structures V/Fe0.7V0.3/V/Fe0.7V0.3/Nb and Nb/Ni0.65(0.81)Cu0.35(0.19)

Journal of Experimental and Theoretical Physics - The heterogeneous ferromagnetic–superconducting layered heterostructures V/Fe0.7V0.3/V/Fe0.7V0.3/Nb and Nb/Ni0.65(0.81)Cu0.35(0.19), which...     

Direct experimental study of the effect of dislocations on the magnetization reversal in a quasi-two-dimensional ferromagnet with unidirectional anisotropy

The effect of dislocations on the elementary acts of the magnetization reversal in the epitaxial heterostructure NiFe/NiO/MgO(001) has been studied using the magneto-optical indicator film technique. It has been found that the edge dislocations grouped along the 〈110〉 slip planes lead to the formation of quasi-one-dimensional domains in the permalloy film with the induced uniaxial anisotropy oriented along these planes the direction of which differs by 90° from that of the uniaxial anisotropy in the dislocation-free part of the heterostructure. The micromechanism of the observed effect has been discussed taking into account the effect of dislocations on the orientation of spins in the antiferromagnet and their exchange interaction with the spins of the ferromagnet on the interphase plane.     

Study of the isotope effect in the isotope exchange reaction between PuIV and PuIII by extraction redox-chromatography

The equilibrium isotope effect in the isotope exchange reaction between Pu^IV extracted with tributyl phosphate and Pu^III in an aqueous nitric acid solution has been studied by extraction chromatography. For the 238/242Pu isotope pair the isotope separation coefficient () at 25 °C has been found to be 1.0022±0.0005.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1557–1558, September, 1994.The authors are grateful to Prof. N. N. Krot for discussion of the results and valuable remarks and to V. P. Perminov for help in designing the computer programs.This work was financially supported by the International Science Foundation (Grant MDB 000).     

Promotion effects in the oxidation of CO over zeolite-supported Pt nanoparticles

Well-defined Pt-nanoparticles with an average diameter of 1 nm supported on a series of zeolite Y samples containing different monovalent (H+, Na+, K+, Rb+, and Cs+) and divalent (Mg2+, Ca2+, Sr2+, and Ba2+) cations have been used as model systems to investigate the effect of promotor elements in the oxidation of CO in excess oxygen. Time-resolved infrared spectroscopy measurements allowed us to study the temperature-programmed desorption of CO from supported Pt nanoparticles to monitor the electronic changes in the local environment of adsorbed CO. It was found that the red shift of the linear Pt-coordinated CO vibration compared to that of gas-phase CO increases with an increasing cation radius-to-charge ratio. In addition, a systematic shift from linear (L) to bridge (B) bonded CO was observed for decreasing Lewis acidity, as expressed by the Kamlet-Taft parameter alpha. A decreasing alpha results in an increasing electron charge on the framework oxygen atoms and therefore an increasing electron charge on the supported Pt nanoparticles. This observation was confirmed with X-ray absorption spectroscopy, and the intensity of the experimental Pt atomic XAFS correlates with the Lewis acidity of the cation introduced. Furthermore, it was found that the CO coverage increases with increasing electron density on the Pt nanoparticles. This increasing electron density was found to result in an increased CO oxidation activity; i.e., the T(50%) for CO oxidation decreases with decreasing alpha. In other words, basic promotors facilitate the chemisorption of CO on the Pt particles. The most promoted CO oxidation catalyst is a Pt/K-Y sample, which has a T(50%) of 390 K and a L:B intensity ratio of 2.7. The obtained results provide guidelines to design improved CO oxidation catalysts.     

Search for heavy neutral MSSM Higgs bosons with CMS: reach and Higgs mass precision

The search for MSSM Higgs bosons will be an important goal at the LHC. We analyze the search reach of the CMS experiment for the heavy neutral MSSM Higgs bosons with an integrated luminosity of 30 or 60 fb^-1. This is done by combining the latest results for the CMS experimental sensitivities based on full simulation studies with state-of-the-art theoretical predictions of the MSSM Higgs-boson properties. The results are interpreted in MSSM benchmark scenarios in terms of the parameters tan β and the Higgs-boson mass scale, M_A. We study the dependence of the 5σ discovery contours in the M_A–tan β plane on variations of the other supersymmetric parameters. The largest effects arise from a change in the higgsino mass parameter μ, which enters both via higher-order radiative corrections and via the kinematics of Higgs decays into supersymmetric particles. While the variation of μ can shift the prospective discovery reach (and correspondingly the ”LHC wedge” region) by about Δtan β=10, we find that the discovery reach is rather stable with respect to the impact of other supersymmetric parameters. Within the discovery region we analyze the accuracy with which the masses of the heavy neutral Higgs bosons can be determined. We find that an accuracy of 1–4% should be achievable, which could make it possible in favorable regions of the MSSM parameter space to experimentally resolve the signals of the two heavy MSSM Higgs bosons at the LHC.     

Creation of a diagnostic complex for the characterization of cryogenic laser-fusion targets using the tomography method with probing irradiation in the visible spectrum

We present our results on developing a diagnostic complex for high-precision characterization of the parameters of laser-fusion microobjects, such as microspheres and cryogenic targets (the microobject size is 1–2 mm). The complex operates based on the principle of tomography. The complex consists of (a) the scanning system providing a set of shadow projections of a microobject in the visible range of radiation and (b) specially developed software for 3D reconstruction of the microobject from the set of projections. The spatial resolution of the optical system is 1 μm for a probing-radiation wavelength of 490 nm. The distinctive features of the diagnostic complex are (1) operation with both free-standing and mounted targets and (2) the possibility of scanning the targets from room to cryogenic temperatures. The operation of the complex was demonstrated in the reconstruction of polystyrene microspheres by a large set (80–90) of shadow projections at room and cryogenic temperatures.     

Kinetics of nitrous acid formation in a two-phase tri-n-butylphosphate-diluent/aqueous nitric acid extraction system under the effect of power ultrasound

The kinetics of nitrous acid formation were investigated in two-phase tri-n-butylphosphate (TBP)-diluent/HNO3 (1.5-6.0 mol l-1) systems, where diluent is n-C16H34, n-C12H26, n-C9H20 and i-C8H18, under the effect of power ultrasound at 20 kHz frequency under Ar atmosphere. The rate of HNO2 sonochemical formation decreases with the rise in diluent vapor pressure. The HNO2 formed is distributed between the aqueous and organic phases due to its extraction with TBP. The kinetics of HNO2 sonochemical formation in the two-phase system exhibits induction periods due to NOx (NO + NO2) gas reactions in the HNO3 medium. This induction period decreases with increasing HNO3 concentration and ultrasound intensity. The HNO2 steady-state concentration was obtained under long-time sonication as the result of HNO2 sonochemical decomposition. HNO2 decomposes faster under sonication in the aqueous phase than in the organic phase.