Volume 74, Issue 3

Copper-containing nanoparticles in a high-pressure polyethylene matrix were prepared by thermal decomposition of copper acetate. An electron microscopic study of the morphology and an X-ray diffraction analysis of the phase composition of a nanocomposite were carried out. It was shown that the dispersed phase essentially consisted of metallic copper nanoparticles with a size of 33.94 nm.

A new method of quantitative estimation of the exchange constants of magnetisations between different states by means of cross peaks on a T 1 – T 2 topogram obtained from stimulated echo experiments for nuclear quadrupole and nuclear magnetic resonances is proposed.

The topic of this article is “research of accidents induced by supersonic electric spark discharges in water”. Experiments referring to such accidents were published by Urutskoev et al. in 2000 and Urutskoev in 2004. According to Urutskoev these spark discharges should be accompanied by the emission of a new kind of particles, namely leptonic magnetic monopoles, predicted by Lochak in 1985. Later, Lochak considered these monopoles as excited neutrinos. Both Lochak and Urutskoev supposed that these particles can influence weak decays and nuclear transmutations and that by catalysis the monopole effect can be amplified, leading to macroscopic effects, i.e. accidents. Spark discharges in water are connected with CP-symmetry-breaking, forcing the introduction of an extended standard model described in previous papers. There also, a mechanism of the catalytic effect was discussed, which is further studied in this article. For the selected unstable nuclear element Mn2551${}_{25}^{51}\text{Mn}$, the effect is demonstrated and numerically evaluated. A simple non-relativistic nuclear state description is applied for these low-energy processes. The extension of these calculations to other unstable nuclei requires higher calculational effort and is not done in this paper. However, the extraordinarily strong catalytic power of the monopoles revealed by the numerical calculation of the above example suggests looking for macroscopic effects of monopoles as an explanation for accidents, for instance, the catastrophe of Chernobyl, which has been the origin of monopole research. A short review of the corresponding experimental observations connected with this accident is also given in this article.

The existence of the subsonic dynamic potential for a test charge in extremely dense quantum plasmas is pointed out for the first time. The dispersion equation of ion acoustic wave in relativistic plasmas is derived by using the quantum hydrodynamic model. The relativistic electrons obey Fermi statistics, whereas the ions are taken classically. The standard model of wake potential is hereafter applied for the derivation of dynamic potential of the test particle. A usual supersonic potential is found suppressed. However, the oscillatory subsonic wake potential does exist in small length scales. The analytical results are applied in different regions by taking the range of magnetic field as well as the electron number density. It is found that the dynamic potential exists only when v t < C s , showing the presence of subsonic wake potential contrary to the usual supersonic condition v t > C s . Here v t is the test particle speed and C s is the acoustic speed defined by the Fermi temperature of the electrons. This work is significant in order to describe the structure formation in the astrophysical environment and laboratory dense plasmas.

In this work, the streamline topologies and their bifurcations for peristaltic transport of shear-thinning and shear-thickening fluids characterised by power-law model are analysed. The flow is assumed in a two-dimensional symmetric channel. The analytical solution is obtained in a wave frame of reference under low Reynolds number and long wavelength approximations. To study the streamline topologies, a system of non-linear autonomous differential equations is formed and the method of dynamical system is employed to investigate the bifurcations and their changes. Three different types of flow situations occur: backward flow, trapping and augmented flow. The conversions of backward flow to trapping and then trapping to augmented flow correspond to bifurcations. The stability and nature of bifurcations and their topological changes are explained graphically. For this purpose, a global bifurcation diagram is constructed. The backward flow and trapping regions are significantly affected by fluid behaviour index. In fact, the trapping region expands and the backward region shrinks by increasing the fluid behaviour index. Theoretical results are verified by comparing them with the experimental data, which is available in the literature.

The dissipative propagation due to the dust viscosity of dust nonlinear shock acoustic wave in a collisionless, unmagnetised, oppositely charged viscous dusty plasma with trapped ion has been examined using parameters related to mesosphere and magnetosphere of Jupiter. The modified dissipative Korteweg de Vries–Burgers equation describes the model and solves according to different physical dissipation conditions. The physical effects of two dusty kinematic viscosity coefficients and positively charged dust grains on the shock properties are investigated.

An exact solution for mixed convection flow with temperature-dependent viscosity in a vertical channel subject to wall asymmetric heating and concentration is obtained. The momentum, concentration, and energy equations governing the flow configuration are derived and solved exactly by incorporating the variable viscosity term, which is assumed to exponentially decrease/increase with temperature difference into the momentum equation. The roles of governing parameters are depicted with the aid of tables and line graphs. Results show that buoyancy ratio parameter can bring about the occurrence of flow reversal at the walls. It is also found that heat transfer, total species rate, skin friction, and reverse flow occurrence are enhanced in the presence of temperature-dependent viscosity.

New material conservation laws and conserved quantities are derived for the helically symmetric flows of an inviscid compressible gas and an ideal incompressible fluid with variable density ρ(x,t)$\rho(\mathbf{x},\;t)$.

In this work different shapes of carbon nanofibers (CNFs) were successfully synthesised on a treated commercial steel substrate by catalytic chemical vapour deposition (CCVD) utilising ethanol at 700 °C. The formation of the nanofibers with average diameter of 200–400 nm was confirmed via X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy. The BET surface area, pore volume and pore size of the obtained CNFs were sequentially: 182 m 2 /g, 10.5 cm 3 /g and 103.3 Å as determined by nitrogen adsorption analysis. The influence of the surface treatment on the size and shape of CNFs was investigated and the results indicated a positive correlation that can be employed to tailor CNFs of desired morphology. Accordingly, a growth mechanism due to the deposition of carbonaceous materials on large size nanoparticles was proposed. As the CCVD is a facile and economical route for CNFs synthesis, thus, it can be efficiently adopted for the growth of CNFs on pretreated steel substrates as proved by this study.

Hierarchical bismuth vanadate (BiVO 4 ) nano-knitted hollow cages have been synthesized by simple hydrothermal method and characterized by scanning electron microscopy, x-ray diffraction, energy-dispersive x-ray spectrometer, Fourier transform infrared, UV-Vis, and Raman. The photodegradation efficiency of BiVO 4 nanocage for universally used methylene blue dye. The BiVO 4 hollow nanostructure demonstrated better photocatalytic competence in dye degradation as compared to the commercial TiO 2 powders (P25). The excellent dye degradation can be certified to the high crystallisation of monoclinic BiVO 4 and hollow nanostructure, which leads to high surface area and small bandgap energy of 2.44 eV.

A complete formula consisting of the static factor stemming from lattice thermal expansion and the dynamic factor owing to electron-phonon interaction is employed to investigate the thermal shift at near and higher than room temperature for the 7 D 0 ⟶ 5 F 0 fluorescence line in strontium tetraborate (SrB 4 O 7 ):Sm 2+ crystal. The static factor is gained in terms of the pressure dependence of the fluorescence line. With the aid of an approximate processing, the static parameter A (characterising the static factor) and the electron-phonon coupling parameter α ’ (characterising the dynamic factor) are estimated even if there is no observed thermal shift curve from low temperature (<30 K) to near and higher than room temperature. The static factor and dynamic one in SrB 4 O 7 :Sm 2+ crystal give rise to the thermal blue shift and red shift, respectively, and the total or observed thermal shift is due to the emulation between the two factors. The static factor in shift direction is contrary to and in magnitude is slightly greater than the dynamic one for the 7 D 0 ⟶ 5 F 0 line in SrB 4 O 7 :Sm 2+ crystal. Thus, the observed very small thermal blue shift (which is not explained up to now) for the studied line in SrB 4 O 7 :Sm 2+ crystal is rationally explained.