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It is shown that the potassium polytitanate powder (PPT) synthesized at 500 °C via the treatment of powdered TiO2 (rutile) in molten mixtures of KOH and KNO3 is a cheap and effective catalyst of H2O2 chemical decomposition in aqueous solutions. At the same time, the PPT catalytic activity strongly depends on the [TiO2]:[KOH]:[KNO3] weight ratio in the mixture used for the synthesis, increasing with [KNO3] in the order of PPT (30:30:40) < PPT (30:50:20) < PPT (30:70:0). The obtained results are explained by increased [Ti3+] in the PPT structure (XPS data), which is grown in this order from 0 to 4.0 and 21.9 at.%, respectively, due to the reduced oxidation activity of the melt used for PPT synthesis. The mechanism of the autocatalytic process taking place in the PPT-H2O2-H2O system is analyzed. Taking into account the data of FT-IR spectroscopy, it is assumed that the increased catalytic activity of the investigated materials is related to the increased surface concentration of the Ti4+-O(H)-Ti4+ groups, formed from the Ti3+-O(H3O+)-Ti4+ clusters and further transformed into Ti-O-O-H catalytic centers. Some possible applications of the PPT-H2O2-H2O catalytic system, including the oxidation processes of green chemistry and photo-catalysis, are discussed.

The composition and the electronic and atomic structure of palladium nanoparticles stabilized in high-pressure polyethylene (with 10 and 20 wt % palladium) have been studied using transmission electron microscopy, X-ray diffraction, and X-ray absorption spectroscopy. It has been found that these nanoparticles have metallic (Pd) and oxide (Pd2O3) components, and their mean size and coordination numbers in the Pd sphere decrease from 7 to 6 nm and from 7 to 5.7, respectively, together with the metal concentration.

Pt–Fe nanoparticles with a core–shell structure stabilized in polyethylene are studied via X-ray absorption spectroscopy. The temperature-dependent PtLIII-edge EXAFS (extended X-ray absorption fine structure) spectra of nanoparticle nuclei, consisting of platinum atoms, provide information on the interatomic-potential anharmonicity parameters along with the melting point Tmelt and the Debye temperature, which are found to be 1630 and 208 K, respectively. This is much lower than for bulk platinum, where the values are 2041.4 and 233 K, respectively.

The wavelet transform modulus maxima method was applied to study pairwise synchrony of irregular fluctuations in insect population size in several localities throughout the United Kingdom. The North Atlantic Oscillation index was shown to affect the population dynamics and spatial pairwise synchrony in the green spruce aphid Elatobium abietinum across the United Kingdom. Synchrony between localities was associated with the relative positions of the localities and climatic effects.

The electronic structure of the polynuclear iron carbonyl complexes [Et2N][Fe4N(CO)12], [Et4N]2[Fe5C(CO)14], and [Et4N]2[Fe6C(CO)16] has been studied by X-ray emission spectroscopy and quantum-chemical calculations. The fine structure of the FeKβ5 X-ray emission spectra characterizes the distribution of iron valence p electrons over the molecular orbitals of the compounds. Comparison of the fine structure of the FeKβ5 X-ray emission spectra with the densities of states of all atoms in the molecules has made it possible to determine in detail the character and specific features of chemical bonding in the complexes.

Transmission electron microscopy, X-ray powder diffraction, and X-ray absorption spectroscopy techniques were used to study the atomic structure of gold nanoparticles involving 1, 5, 10, and 20 wt % of Au which were stabilized in a high-pressure polyethylene matrix. The average sizes of the Au-containing nanoparticles amounted to 7 and 50 nm. The atomic structure of the Au-containing nanoparticles was similar to that of metallic gold in the bulk state. When the Au concentration in polyethylene was equal to 1 wt %, gold atoms were found on the surface of nanoparticles, which interacted with light atoms C/O.

The work studies the flow characteristics in a channel with periodic hills on the basis of three algorithms for calculating the flow velocity fields through the images: Particle Image Velocimetry, Particle Tracking Velocimetry, and Pyramid Correlation. Descriptions of algorithms, detailed information about the experiment and parameters of the received data processing, as well as the results of calculations of instantaneous velocity fields at selected time points obtained by corresponding methods are provided. In addition, the presented techniques are compared on the basis of experimental data.

We report on a parallel study on properties of large-scale vortical structures in low- and high-swirl turbulent jets by means of the time-resolved tomographic particle image velocimetry technique. The high-swirl jet flow is featured by a well-established bubble-type vortex breakdown with a central recirculation zone. In the low-swirl flow, the mean axial velocity, while intermittently acquiring negative values, remains positive in the mean but with a local velocity defect immediately downstream from the nozzle exit, followed by a spiralling vortex core system and its eventual breakdown. Measurements of the 3D velocity fields allowed direct analysis of the azimuthal/helical modes via Fourier transform over the azimuthal angle and proper orthogonal decomposition (POD) analysis in the Fourier space. A precessing vortex core is detected for both swirl cases, whereas the POD analysis showed that the one originating in the bubble-type vortex breakdown is much more energetic and easier to detect.

A numerical method is proposed for solving the Thomson problem – finding stable positions for a system of N point charges distributed on a sphere that minimize the potential energy of the system. The behavior of this system is essentially nonlinear, and the number of metastable structures grows exponentially with N. This makes the problem of finding all stable configurations extremely difficult. The results of testing of the developed algorithm and of numerical study of the properties of the local potential energy minima for a system of point charges are presented.

The anharmonicity parameters of the interatomic potential in ~4-nm palladium nanoparticles deposited on poly(tetra)fluoroethylene microgranules 0.2–0.5 μm in average size were studied by X-ray absorption spectroscopy from an analysis of temperature-dependent EXAFS Pd K edges. The parameters of the interatomic potential obtained were used to calculate melting temperature Tmelt = 1591 K and Debye temperature ΘD = 257 K of palladium nanoparticles; these temperatures are significantly lower than those in metallic palladium: 277 K and 1825 K, respectively.

A cross-correlation algorithm, which enables the obtaining of the velocity field in the flow with a spatial resolution up to a single pixel per vector, has been realized in the work. It gives new information about the structure of microflows as well as increases considerably the accuracy of the measurement of the flow velocity field. In addition, the realized algorithm renders information about the velocity fluctuations in the flow structure. The algorithm was tested on synthetic data at a different number of test images the velocity distribution on which was specified by the Siemens star. The experimental validation was done on the data provided within the international project “4th International PIV Challenge”. Besides, a detailed comparison with the Particle Image Velocimetry algorithm, which was realized previously, was carried out.

Cobalt-containing particles are synthesized on the surface of silicon dioxide micrograins prepared by the Stober-Fink method. The composition and structure of nanoparticles are determined by transmission electron microscopy, X-ray diffraction analysis, and EXAFS. The average size of cobalt nanoparticles in the samples is found to be 14 ± 5 nm. The resulting composites are shown to be ferromagnetics with low specific magnetization values.

X-ray diffraction in combination with X-ray emission and EXAFS spectroscopy were used to study the electronic and atomic structure of metal nanoparticles stabilized on a carbon support in novel PtxCo/C catalysts of different composition with the molar ratio Pt:Co (x) of 1 to 3. Cobalt atoms in nanoparticles, which average size was 2–4 nm, were shown to form chemical bonds both with platinum atoms and carbon atoms of the support material.

The K X-ray absorption near-edge fine structure spectra of metallic Cu, Ni, Co (hexagonal close-packed and face-centered cubic phases), and Cr have been studied. The experimental spectrum of cobalt has been measured in the high-temperature face-centered cubic phase. The calculations have been performed by the full multiple scattering method in the cluster approximation using the semiempirical muffin-tin potential. The spectra have been calculated for clusters containing from 13 to 935 atoms. It has been demonstrated that the spectra cease to depend on the cluster size for clusters containing about 400 atoms. It has been established that the intensity ratio of two peaks located at the fundamental edge of all the spectra under investigation sharply changes with a variation in the atomic potential strength. The mechanisms responsible for the formation of the near-edge structure of the spectra have been revealed using the results of the model calculations. The studies resulted in good agreement of the calculated spectra with the experiment.