Vol 80, No 5 (2016)

Hexagonal holmium manganite is investigated by means of high-temperature X-ray radiography and thermal analysis. At 1200°C, the manganite transitions from the structural P6₃cm modification into the P6₃/mmc form. Mechanoactivation in a high-energy ball mill results in the emergence of the orthorhombic phase of HoMnO₃, which undergoes the Jahn–Teller transition in the temperature range of 1000–1160°C.

The size dependence of the heats of melting of transition metal nanoclusters (Ni, Au, Cu and Ag) is investigated using two alternative methods of computer simulation (isothermal molecular dynamics and Monte Carlo). Au and Cu nanoclusters are subjected to more detailed study over a wide range of their sizes. The heats of melting are shown to fall along with nanocluster size and to tend in some approximation to a linear dependence on inverse particle radii.

Experimental measurements of the effect high pressure and temperature have on the thermal conductivity of silicon carbide SiC–BeO ceramics are presented. The pressure is varied in an interval of up to 400MPa; temperature, in the range of 273–523 K. The results reveal there is a reversible second-order phase transition at pressures of 100–150 MPa.

The static method and thermal analysis are used to study the thermal stability of compound PrMnO₃. The equilibrium oxygen pressure of the dissociation reaction is measured and the thermodynamic characteristics of the reaction with the formation of PrMnO₃ from its elements are calculated.

Using tightly focused laser beams, features of space charge fields (∼107 V/m) are studied through the photoionization of doped Jahn–Teller Fe²⁺ ions in LiNbO₃ single crystals. These fields can be used for selective formation of the inverse domain state following the additional application of a field with a strength below the coercive field. The characteristics of laser-induced domains and periodic domain structures are studied by laser-acoustic means.

The behavior of wairakite CaAl₂Si₄O₁₂ · 2H₂O and dawsonite NaAlCO₃(OH)₂ in a water medium is studied by means of in situ Raman spectroscopy at the simultaneously high temperatures and pressures (up to T = 723 K and P = 1 GPa). After the initial minerals are partially dissolved, phillipsite forms in the wairakite–water system, and a glass-like phase is generated in the dawsonite–water system. These minerals show no signs of overhydration. The amorphization of the wairakite structure that occurs at high temperatures and pressures was reversible.

The effect a constant external magnetic field has on the magnitude and direction of an energy flux carried by evanescent TM or TE wave in a two-component one-dimensional magnetic photonic crystal of the centroantisymmetric antiferromagnetic type (a nonmagnetic insulator) is investigated.

The region of the electrolytic deposition of bialkaline sodium–cesium molybdenum-oxide bronzes is established. A correlation between the nonstoichiometry of bronzes and Mo_nO_3n–x oxides with respect to molybdenum charge density, crystal structure, and type of electrical conduction is found. The importance of the Mo_nO_3n–x homologous series in the formation of the nonstoichiometry of bronzes and their physical properties is shown. The electrophoretic deposition of coatings with binary bronzes for the anticorrosion protection of metals is investigated.

Certain properties of photons viewed as quanta (particles of an electromagnetic field) are discussed. Specifically, the nature of localization (size) of photons along and across the direction of wave propagation is examined.

Wave propagation in ionic magnetoactive plasma along an external magnetic field with allowance for electron spin is considered. It is shown that considering particle spin reveals the emergence of a new plasma mode in a band of frequencies close to the cyclotron frequency. A dispersion equation for wave propagation in a boundless plasma medium is obtained and special cases are considered.

The origin of an excess of hadrons observed in deep homogeneous lead X-ray emulsion chambers (XRECs) at depths of more than 70 radiation length units is analyzed. Preliminary experimental data on the absorption of cosmic-ray hadrons in a two-storied XREC with a large air gap, exposed in the Tien Shan mountains, are presented. The chamber was designed to test the hypothesis that the main source of the excess of dark spots detected on X-ray films deep inside the XREC was substantial growth of the charmed-particle production cross section at energy E_lab ∼ 75 TeV. The experimental data obtained using a two-storied REC and in experiments with deep homogeneous XRECs are compared to the results from calculations using the FANSY 1.0 model. The comparison shows qualitative agreement between the experimental and the model data, assuming high values of the charmed-particle production cross section when E_lab ∼ 75 TeV in the forward kinematic region with x_F ≥ 0.1.

The properties of one-body and two-body density matrices of a nucleus as a nonrelativistic system are studied. Unlike the usual procedure applied in the theory of infinite systems, for a nucleus of A nucleons these quantities are determined as the expectation values of A-body multiplicative operators that depend on the relative coordinates and momenta (Jacobi variables) and affect the intrinsic wave functions. The translational invariance of these operators is thus ensured. An algebraic technique based on the Cartesian representation is developed for handling such operators. Within this technique, the coordinate and momentum operators are linear combinations of production and annihilation operators \(\hat \vec a^ + \) and \(\hat \vec a\) with commutation relations for bosons (oscillators). Each of the multiplicative operators reduces to the normally ordered product of two exponents, one of which depends on set \(\left\{ {\hat \vec a^ + } \right\}\) only and is located to the left of the second, which depends on \(\left\{ {\hat \vec a} \right\}\) only. This procedure offers a new view of the origin of the so-called Tassie–Barker factors and other model-independent results. In addition, the proposed method yields a fair description of the available experimental data and can easily be extended to investigate the role of short-range nucleon-nucleon correlations within these translationally invariant calculations of nucleon density and momentum distributions in light nuclei.

Known experimental and model-calculated data, along with independent calculations using the TALYS- and EMPIRE-codes, are compiled for the cross sections of reactions ¹⁴N(γ, 2n)¹²N, ¹⁴N(γ, 2p)¹²B, and ¹³C(γ, p)¹²B used in the photonuclear technique under development for the detection of hidden explosives. Indications of a substantial underestimate of model-calculated values, compared to the available measured results, are obtained.

Differential cross sections and longitudinal momentum distributions of observed particles are calculated for stripping reactions that result from diffractive interaction between halo nuclei and targets. The applicability of different analytic methods of calculation is considered. The advantages of an improved approximation of small target radius are demonstrated for valent halo nucleon absorption radii of 2–4 fm in describing momentum distributions in particular.

A physical picture of the origin of lepton mass is presented on the basis of the byuon theory (BT). The BT is the theory of the life of special unobservable discrete objects: byuons, from which the world surrounding us are formed (physical space; fundamental constants h, e, c; the mass of elementary particles; the four fundamental interactions; the predicted new force in nature, and so on). A key difference between this theory and current models of the classical and quantum field theories is that the potentials of physical fields acquire precise fixable, measurable values. The definition of byuon contains a new fundamental vector constant: the cosmological vector potential (A_g ≈ 1.95 × 10¹¹ G cm). The BT contains only three constants: \(\tilde x_0 \) ≈ 2.78 × 10^–33 cm, τ₀ ≈ 0.927 × 10^–43 s, and a modulus of A_g that allows us to obtain the masses of all known leptons and predict the mass of the next lepton (80.4 GeV).

Double polarization asymmetry D_p^(M) for the process of elastic electroweak scattering of the longitudinally polarized electrons by polarized proton target is considered with account of anapole G_1p and electric dipole moment (EDM) G_2p proton form factors. This asymmetry is only due to T-parity violating form factor G_2p, but does not directly depend on it, and having a significant value, allows to confirm the existence of the EDM of the proton.