Volume 74, Issue 9

The electrical conductivity of molten ternary alkali carbonate eutectic, coexisting with MgO particles, has been investigated. The conductivity was measured by the AC impedance method. The apparent activation energy Δ E a increased with the MgO content. This fact can be attributed to the effect of the solid phase. The specific conductivity of those systems could not be described using the Maxwell model over the solvation process of the carbonate ions on the particles of the magnesium oxide.

By systematic Rayleigh–Ritz variation calculations, the energies are reported for the core-excited states 1 s 2s2 p 2 5 P and 1 s 2 p 3 5 S o in the Be-like isoelectronic sequence ( Z = 11–20). Energy corrections, including the restricted variational method, mass polarisation, and relativistic effect, are considered to improve the accuracy of energy. The oscillator strengths and transition wavelength between these states are also reported. Computational data on hyperfine structures presented in this paper are calculated for the first time.

A novel sucrose sensor based on graphene-coated optical fibre with waist-enlarged bitapers as Mach-Zehnder interferometer is proposed and demonstrated. The sensor is formed by arc fusion splicing a photonic crystal fibre (PCF) sandwiched between two single-mode fibres (SMFs). The intermodal interference is achieved by two waist-enlarged fibre tapers at the coupling points between the PCF and two SMFs. The result shows that the dips of transmission spectra exhibit blue shift with the concentration increase of the sucrose, and the sensor has a high linear response ( R 2 = 0.98233) to sucrose with an excellent sensitivity of 3.36 pm/ppm in the range of 0–230 ppm. Additionally, the surface adsorption mechanism is also discussed. Such easily fabricated, cost-effective and small volume fibre interferometer could be used for sucrose sensing applications.

Propagation and interaction of three solitons are studied within the framework of the Korteweg-de Vries (KdV) equation. The KdV equation is derived from an unmagnetised, collision-less dusty plasma containing cold inertial ions, stationary dusts with negative charge, and non-inertial kappa-distributed electrons, using the reductive perturbation technique (RPT). Adopting Hirota’s bilinear method, the three-soliton solution of the KdV equation is obtained and, as an elementary act of soliton turbulence, a study on the soliton interaction is presented. The concavity of the resulting pulse is studied at the strongest interaction point of three solitons. At the time of soliton interaction, the first- and second-order moments as well as the skewness and kurtosis of the wave field are calculated. The skewness and kurtosis decrease as a result of soliton interaction, whereas the first- and second-order moments remain invariant. Also, it is observed that the spectral index κ and the unperturbed dust-to-ion ratio μ have great influence on the skewness and kurtosis of the wave field.

The Riemann problem for a perfect fluid model with zero pressure is considered, where the external force is a given continuous function of time. All of exact solutions are given. In particular, a vacuum occurs in the solutions, although initial data stay far away from the vacuum. It is shown that a delta shock wave in which density and internal energy contain a Dirac delta function develops in the solutions. The position, velocity, and weights of the delta shock wave are presented explicitly. Moreover, all of the solutions are not self-similar because of the presence of the external force.

An investigation of magnetoacoustic nonlinear solitary and freak waves in a magnetised collisionless pair-ion plasma using two-dimensional magnetohydrodynamic model is presented. The reductive perturbation method is used to obtain the Kadomtsev–Petviashvili (KP) equation. The solitary wave solution of KP equation is examined. Further, on modulating KP equation, the nonlinear Schrödinger equation is derived with the help of appropriate transformation. The influence of various plasma parameters such as magnetic field strength, number density of ions, and temperature ratio of negative to positive ions, etc. on the propagation characteristics of solitary waves and first- as well as second-order magnetoacoustic freak waves in pair-ion plasma is examined.

In this article, we considered the evolutionary behaviour of one-dimensional shock waves propagating through a relaxing gas with dust particles in a duct with spatially varying cross section. We adopted the procedure based on the kinematics of a one-dimensional motion to derive an infinite hierarchy of transport equations, which describe the evolutionary behaviour of shock of arbitrary strength propagating through the medium. The first three truncation approximations are considered, and the results are compared with existing results in the absence of relaxation and dust particles. The effects of dust particles and relaxation are studied using numerical computations. The results are depicted for different values of dust and relaxation parameters.

We analyse the ping-pong (PP) protocol [K. Bostrom and T. Felbinger, Phys. Rev. Lett. 89 , 187902 (2002)] using different sets of partially entangled three-qubit states. Interestingly, our results show that the partially entangled nonorthogonal three-qubit states are more useful as resources in comparison to three-qubit maximally entangled Greenberger–Horne–Zeilinger (GHZ) states. The properties of orthogonal set of partially entangled states as resources for PP protocol, however, are similar to that of maximally entangled GHZ states – both the states are not preferable due to the vulnerability towards eavesdropping. On the other hand, partially entangled nonorthogonal basis set holds importance for transferring two-bit information, one each from a sender, to a single receiver. The protocol is further analysed for various eavesdropping attacks, and the results are compared with the use of two shared Bell pairs for two-bit information transfer. Surprisingly, the use of partially entangled nonorthogonal set of states is found to offer better qubit efficiency and increased security, as against the use of two separate maximally entangled Bell states with orthogonal basis. In addition, we also propose a mixed-state sharing protocol to further enhance the security of the PP protocol.

Copper tartrate crystals were grown by the gel growth method and characterised by energy-dispersive X-ray (EDAX), scanning electron microscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV-vis spectroscopy, Fourier transform infrared, photoluminescence (PL), electron paramagnetic resonance, and low-temperature magnetic studies in the temperature range 300–20 K. The XRD study confirmed the orthorhombic structure of the crystal and the XPS study established the Cu 2+ ions in the crystal. UV-vis study deduced the energy gap as 2.15 eV, confirming the semiconducting nature, and Urbach energy as 0.4686 eV. PL showed the presence of Cu 2+ vacancy-related defects. Low-temperature magnetic study confirmed the paramagnetic nature in the temperature range 300–77 K, and the crystal showed a weak ferromagnetic signal at 20 K, which is interesting. The magnetic field along with the low temperature caused an ordered spin orientation.

The electrical and photoelectric properties of GaS(Yb) monocrystal have been studied in the range of 100–300 K. It has been established that as the partial compensation of structure defects (V Ga ) occurs due to the inclusion of ytterbium dopant, the electroconductivity of GaS monocrystal decreases. The simultaneously occurrence of substitution (Yb Ga ) of cation vacancy – V Yb and Yb-Ga due to the formation of acceptor and donor type two charged local centers during the doping, leads to a self-compensating process. As a result, the specific resistance of the crystal increases, and thermal activation and extinction processes are observed in the temperature dependence of photoconductivity.

In the present work, perovskite oxides XReO 3 (X = Rb, Cs, Tl) have been reported using density functional theory (DFT) for structural, electronic, mechanical, elastic, and thermodynamic properties. Structural optimization has been carried out using local density approximation (LDA) and generalized gradient approximation (GGA) in the scheme of Perdew, Burke, and Ernzerhof. Electronic properties have been calculated using GGA, and all the three materials were found to have metallic nature. From the elastic constants, all the three compounds were found mechanically stable in cubic structure. Poisson’s ratio (ν), Cauchy’s pressure ( C 12 – C 44 ) and Pugh ratio ( B / G ) present the ductile nature of RbReO 3 and TlReO 3 , whereas CsReO 3 was found to establish a brittle nature. These compounds were found to have an elastically anisotropic nature. The calculated melting temperatures were found to be 2851 ± 300, 2814 ± 300, and 2924 ± 300 K, respectively, for XReO 3 (X = Rb, Cs, Tl). Using quasi-harmonic Debye approximation, we have calculated the pressure- and temperature-dependent variation in cell volume, bulk modulus, Debye temperature, and specific heat capacity.