X-ray study of microcrystalline Hg<Subscript>2</Subscript><Emphasis Type="Italic">Hal</Emphasis><Subscript>2</Subscript> ferroelastics

The rhombic splitting of basal plane reflections and the thermal behavior of fundamental and diffuse reflections from X-points of the Brillouin zone characterizing the behavior of an order parameter and its fluctuations, respectively, were studied in polycrystalline Hg₂Cl₂ and Hg₂Br₂ samples. In the case of polycrystalline samples, a strong broadening of phase transition effects was observed, due to damaged surface layers and elastic and plastic stress fields inducing order parameter fluctuations over a wide temperature range.     

Usage of polarization approximation for the estimation of scintillator intrinsic energy resolution

A set of recurrent equations for characteristic functions which describes the photon statistics of the scintillation event is presented. The solution of this set of equations provides non-Monte-Carlo approach for estimation of the yield and intrinsic energy resolution of a scintillator based on the electronic structure and corresponding dielectric functions of the substance. It is shown that the yield and energy resolution is connected not only with statistics of δ-electrons and Auger cascades, but also with peculiarities of luminescence excitation spectra for photons with energies below 100–200 eV.     

Iodine- and xenon-isotope yield ratio in photofission fragments of heavy nuclei

The ratios of cumulative yields of the ¹³⁵I isotope and the independent yield of ¹³⁵Xe at photofission of ²³²Th, ²³⁸U, ²³⁷Np, ²⁴³Am, and ²³⁸Cm by bremsstrahlung radiation with a boundary energy of 25 MeV are measured. The selective gas transportation of fission fragments and a measurement of the spectra of their γ radiation were used. A large difference in the ratios of the yields for these targets was discovered: from 34 for ²³⁸U to 1.3 for ²⁴³Am. This difference is discussed based on the known ideas of the formation mechanism of fission fragments.     

Hamiltonian description and 6D calculations on the ammonia vibrational levels

In this work, a Hamiltonian formalism and a 6D vibrational calculation procedure is described and implemented, designed for the exploration of vibrational motion in ammonia (and any XH₃ molecule). The 6D potential energy surface of ammonia was modelled in simple analytical form (including the inversion potential) at the planar, totally symmetric (D_3h) reference configuration. Using the described method (which is an adaptation of the formalism, previously developed and applied to benzene), 6D calculations were carried out on the vibrational level system of ammonia ¹⁴NH₃, at the lower levels of vibrational excitation. On the basis of the satisfactory agreement between the calculated and the experimentally measured vibrational frequencies, the values of some important harmonic and anharmonic force constants, characterizing the ammonia PES were determined.     

Some constructions of linearly optimal group codes

We continue here the research on (quasi)group codes over (quasi)group rings. We give some constructions of [n,n-3,3]_q-codes over F_q for n=2q and n=3q. These codes are linearly optimal, i.e. have maximal dimension among linear codes having a given length and distance. Although codes with such parameters are known, our main results state that we can construct such codes as (left) group codes. In the paper we use a construction of Reed-Solomon codes as ideals of the group ring F_qG where G is an elementary abelian group of order q.     

Estimates of the local convergence rate of spectral expansions for even-order differential operators

We study the convergence rate of biorthogonal series expansions of functions in systems of root functions of a wide class of even-order ordinary differential operators defined on a finite interval. These expansions are compared with the trigonometric Fourier series expansions of the same functions in the integral or uniform metric on an arbitrary interior compact set of the main interval as well as on the entire interval. We show the dependence of the equiconvergence rate of these expansions on the distance from the compact set to the boundary of the interval, on the coefficients of the differential operation, and on the existence of infinitely many associated functions in the system of root functions.     

Design of self-cleaning TiO2 coating on clay roofing tiles

The phenomenon of heterogeneous photocatalysis takes place in the degradation process of many organic contaminants on solid surfaces. Photocatalysis is based on the excitation of the semiconductor by irradiation with supraband gap photons and the migration of electron-hole pairs to the surface of the photocatalysts, leading to the reaction of the holes with adsorbed H₂O and OH^? to form hydroxyl radicals. Due to the stability and photosensitivity of TiO₂ semiconductors, this system is well studied and is of great interest from an ecological and industrial point of view for use in the field of building materials. Clay roofing tiles, due to their long-term exploitation, are subject to physical, chemical and biological degradation that leads to deterioration. Ceramic systems have a high percentage of total porosity and considering their non-tolerance of organic coating, the use of surface active materials (SAM) that induce porosity in TiO₂ coatings is of vital significance. Photocatalytic coatings applied on clay roofing tiles under industrial conditions were designed by varying the quantity of TiO₂ (mass/cm²) on the tile surface (thin and thick TiO₂ layer). The positive changes in specific surface area and mesopore structure of the designed coatings were made by the addition of PEG 600 as a surface active material. It was shown that a thin photocatalytic layer (0.399 mg suspension/cm² tile surface), applied onto ceramic tiles under industrial conditions, had better photocatalytic activity in methylene blue decomposition, hydrophilicity and antimicrobial activity than a thick photocatalytic coating (0.885 mg suspension/cm²).     

Density ducts formed by heating the Earth’s ionosphere with high-power HF radio waves

The parameters of plasma disturbances at altitudes 660 and 840 km, measured by the instruments onboard the French DEMETER satellite and the US DMSP satellites passing through the magnetic flux tube footed at the region of intense modification of the F ₂ ionospheric layer by the high-power HF radio waves of the Sura heating facility, are presented. The formation of artificial enhanced-density plasma ducts in the outer ionosphere is observed experimentally. Conditions facilitating the formation of such ducts are pointed out.     

Synthesis of Novel Polycyclic Carbamate Derivatives of 2-Hydroxy-2,2′-biindane-1,1′,3,3′-tetrone

Russian Journal of Organic Chemistry - Methyl 1,3,11′-trioxo-1,3,10a′,11′-tetrahydro-4β′H-spiro[inden-2,10′-indeno[1,2-b]chromene]-7′(8′)-ylcarbamates...     

Investigation into the significant effect of CuO additive on the synthesis of ZrSiO4: phase formation and crystallization at low temperature

Journal of Thermal Analysis and Calorimetry - The ZrSiO4 has been synthesized with CuO as mineralizer by sol–gel route at low temperature. The mineralization effect of the CuO on mechanism of...