The use of O_2^{\begin{array}{*{20}c}--\\\cdot \\ \end{array} } radical anions as spin probes for testing nanostructured materials based on zirconium oxide

The conditions of formation of $O_2^{\begin{array}{*{20}c}--\\\cdot \\ \end{array} } $ radical anions on the surface of zirconium oxide systems including nanostructured pillared clays, in interaction with hydrogen peroxide and an NO + O₂ mixture of gases were studied by the EPR method. The special features of the formation of these radicals depending on the phase composition, structure, and degree of hydroxylation of the surface are discussed.     

Atomic and Electronic Structures of Metal-Rich Noncentrosymmetric ZrO<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>

The atomic and electronic structures of metal-rich noncentrosymmetric zirconium oxide synthesized by the ion beam sputtering of a metallic target in an oxygen atmosphere has been studied by X-ray photoelectron spectroscopy, Raman scattering, spectral ellipsometry, and quantum-chemical simulation. It has been established that ZrO_{x < 2} consists of ZrO₂, metallic Zr, and zirconium suboxides ZrO_y. The stoichiometry parameter of ZrO_y has been estimated. It has been shown that the optical properties of ZrO_{x < 2} are determined by metallic Zr. A model of fluctuation of the width of the band gap and a potential for electrons and holes in ZrO_{x < 2} based on spatial fluctuations of the chemical composition has been proposed.     

High-temperature carbonization of humic acids and a composite of humic acids with graphene oxide

Humic acids (HAs) isolated from high-moor peat have been studied by magic-angle spinning solid-state nuclear magnetic resonance (NMR) spectroscopy, differential scanning calorimetry (DSC), thermogravimetry (TG), and Raman spectroscopy. A composite of HAs with graphene oxide (GO) has been prepared for the first time, and the thermal carbonization (900°C) of both HAs and the HA–GO composite has been carried out. With the use of mass spectrometry, it has been found that CO₂ and H₂O molecules are mainly released from HAs into the gas phase at a low temperature (to 150°C). At higher temperatures, carbon monoxide and different low-molecular-weight hydrocarbons also begin to be released. From microscopic examinations, it follows that HA forms small agglomerates with sharply outlined edges as a result of carbonization, whereas the composite forms only large aggregates.     

The features of rewetting dynamics of the overheated surface by a falling film of cryogenic liquid

The dynamic process of rewetting of the overheated surface by gravitationally falling film of cryogenic liquid was firstly modeled numerically with consideration of local distribution of heat transfer coefficient in the wetting zone along the 2D front. The front shape corresponding to self-organizing regular structures observed in experiments was obtained in the numerical experiment. Evolution of the front shape was studied. It was shown that local motion velocities of different areas of the 2D wetting front differed significantly. Total time of transitional process was determined by the minimal velocity of evaporating liquid boundaries in the front zones between boiling jets. This model allows quantitative determination for the wetting front velocity, variable in time and space, and temperature fields in the heater. Reliability of calculation results was proved by direct comparison with experimental data.     

Magnetic Field Influence on the Gas Detonation Induced by Spark Discharge

The present paper describes the influence of magnetic field on the spark discharge utilized for initialization of detonation. The method of schlieren time-based scanning shows the increase of shock wave velocity in the case when magnetic field was applied to the area of electrical discharge in the air. The critical energy values are obtained for a direct initialization of detonation in hydrogen–air and hexane–air mixtures. Magnetic field has a significant influence on the deflagration–combustion transition in both mixtures at the critical energy values. Pressure and velocity of the shock front were measured by ICP pressure transducers, flame front was recorded by photo-diodes. Two cases were studied experimentally: external magnetic field is produced by inductance coils connected to capacitor; own magnetic field is induced directly by discharge current in the cables positioned in special way.     

AFM detection of the mechanical resonances of coiled carbon nanotubes

We introduce a method for atomic force microscopy (AFM)-based detection of mechanical resonances in helix-shaped multi-walled carbon nanotubes. After deposition on an oxidized silicon substrate, the three-dimensional structure of suspended nanotubes, which bridges an artificially created step on the surface, can be visualized using AFM operating in the non-contact mode. The suspended coiled nanotubes are resonantly excited, in situ, at the fundamental frequency by an ultrasonic transducer connected to the substrate. When the AFM tip is positioned above the coiled nanotube, the cantilever is unable to follow the fast nanotube oscillations. Nevertheless, an oscillation amplitude-dependent signal is generated due to the non-linear force-to-distance dependence. Measurement of the mechanical resonances of the helix-shaped carbon nanotubes can be used to quantitatively determine their elastic properties. Assuming that a coiled nanotube can be modeled as a suspended helix-shaped uniformly thin elastic beam, the obtained resonance frequency is consistent with a Young's modulus of 0.17ǂ.05 TPa.     

Influence of the Magnetic Moment of the Probe of a Magnetic Resonance Force Microscope on the Spin-Wave Resonance Spectra

Physics of the Solid State - Abstract—The ferromagnetic resonance in an array of permalloy microstrips 3000 × 500 × 30 nm3 in size, which are ordered on a rectangular 3.5 × 6...     

Guaranteed statistical inference procedures (determination of the optimal sample size)

Translated from Issledovaniya po Prikladnoi Matematike, No. 10, pp. 13–53, 1984.     

Rate of convergence of random sums of random vectors to Marshall-Olkin distribution

Translated from Problemy Ustoichivosti Stokhasticheskikh Modelei, Trudy Seminara, pp. 15–19, 1987.