M. Ayub

Phonons with orbital angular momentum

Ion accoustic waves or phonon modes are studied with orbital angular momentum (OAM) in an unmagnetized collissionless uniform plasma, whose constituents are the Boltzmann electrons and inertial ions. For this purpose, we have employed the fluid equations to obtain a paraxial equation in terms of ion density perturbations and discussed its Gaussian beam and Laguerre-Gauss (LG) beam solutions. Furthermore, an approximate solution for the electrostatic potential problem is presented, allowing to express the components of the electric field in terms of LG potential perturbations. The energy flux due to phonons is also calculated and the corresponding OAM is derived. Numerically, it is shown that the parameters such as azimuthal angle, radial and angular mode numbers, and beam waist, strongly modify the profiles of the phonon LG potential. The present results should be helpful in understanding the phonon mode excitations produced by Brillouin backscattering of laser beams in a uniform plasma.

Ion-acoustic vortices in inhomogeneous and dissipative electron-positron-ion quantum magnetoplasmas

Linear and nonlinear properties of quantum ion-acoustic waves are studied in a nonuniform, dissipative quantum plasma (composed of electrons, positrons, and ions) with sheared ion flow parallel to the ambient magnetic field, using the quantum hydrodynamic model. It is shown that the shear ion flow parallel to the external magnetic field can drive the quantum ion-acoustic wave unstable provided ∣S∣ky>kz. Stationary solutions of the nonlinear equations that govern the quantum ion-acoustic waves are also obtained. It is found that electrostatic monopolar, dipolar, and vortex street-type solutions can appear in such a plasma. It is observed that the inclusion of positron, quantum statistical, and Bohm potential terms significantly modifies the scale lengths of these nonlinear structures. The relevance of the present investigation with regard to the dense astrophysical environments is also pointed out.

Influence of acoustic dominant mode propagation in a trifurcated lined duct with different impedances

In this study, we analyzed the diffraction of the acoustic dominant mode in a parallel-plate trifurcated waveguide with normal impedance boundary conditions in the case where surface impedances of the upper and lower infinite plates are different from each other. The acoustic dominant mode is incident in a soft/hard semi-infinite duct located symmetrically in the infinite lined duct. The solution of the boundary value problem using Fourier transform leads to two simultaneous modified Wiener–Hopf equations that are uncoupled using the pole removal technique. Two infinite sets of unknown coefficients are involved in the solution, which satisfy two infinite systems of linear algebraic equations. These systems are solved numerically. The new kernel functions are factorized. Some graphical results showing the influence of sundry parameters of interest on the reflection coefficient are presented.

Electromagnetohydrodynamic nanofluid flow past a porous Riga plate containing gyrotactic microorganism

Here we have numerically examined the effects of EMHD in flow of nanofluid past a porous Riga surface with gyrotactic microorganism and nanoparticles. Modeling is presented via Grinberg term and a Lorentz force parallel to the wall of a Riga plate. The fluid is electrically conducting, and the Lorentz force decreases exponentially. Using shooting method, the obtained governing nonlinear coupled ODEs are solved. Physical impact of all the pertinent parameters are examined using graphs and tables. In particular, we discussed the behavior of temperature, velocity, motile microorganism density and nanoparticle concentration profile. Nusselt and Sherwood numbers are examined with the help of tables. This analysis motivates the recent researchers, and it provides a platform for further study on nanofluid flow with gyrotactic microorganism past a Riga plate. A comparison is also presented with previously published results as a special case of our study.

E-polarized plane wave diffraction by an impedance loaded parallel-plate waveguide located in cold plasma

The effects of wall impedances with cold plasma permittivity on an E-polarized electromagnetic signal propagating through a parallel-plate waveguide immersed in a cold plasma have been analyzed. The Helmholtz equation in cold plasma is derived from the model equations. The solution of the Helmholtz equation in cold plasma is determined by Wiener-Hopf technique. From the solution it is observed that the amplitude of the diffracted field decreases with increasing permittivity of the plasma (i.e., by decreasing electron number density (or plasma frequency) or by increasing ion number density). The work presented may be of great importance to quantify the effects of ionosphere plasma on the communicating signals between an Earth station and an artificial satellite in Earthʼs atmosphere.

Formation of tripolar vortices in toroidal ion-temperature-gradient driven modes in the presence of dust contamination

A system of nonlinear equations that governs the dynamics of toroidal-ion-temperature-gradient (TITG) driven modes in the presence of dust contamination is presented. In the linear limit, a local dispersion relation is derived and analyzed for a flat density profile case. In the nonlinear case, and by taking some specific profiles of equilibrium density, ion temperature, magnetic field, and sheared plasma flows, the stationary solutions of the nonlinear system can be represented in the form of a tripolar vortex solution. Numerical results obtained in the present study show that the inclusion of dust modifies the nonlinear vortical structures, and the amplitude of the normalized potential is found to be increased in the presence of negatively charged dust grains. The results of our present investigation would be useful to understand some linear as well as nonlinear properties of TITG modes in a dust-contaminated tokamak plasma.

Development and Quality Evaluation of RTS from Mandarin ( Citrus reticulata ) and Carrot Blend Flavored with Ginger Extract

The current investigation was carried out to prepare RTS beverage from Mandarin and carrot blend flavored with ginger extract. Five different formulations of Mandarin juice, carrot juice and ginger extract were used to prepare RTS beverage and quality was assess for a total period of 90 days. Physicochemical and sensory evaluation was carried out. The result of nutritional analysis showed that pH and TSS increase during storage while the declining trend in ascorbic acid content and titratable acidity increased during total period of storage. Sensory analysis showed that there was a declining trend in color, taste, flavor and overall acceptability. Among different treatments, T2 gives highest score for overall acceptability and could be recommended for large scale production in industries.

Inhibitory effect of ginger and turmeric on Rhizopus stolonifer growth on bread.

The inhibitory effect of ginger and turmeric was studied on the Rhizopus stolonifer growth on bread. Different ratios of ginger and turmeric were incorporated to bread dough formulation. The treatments were BG0 (control), BG1 (3% ginger), BG2 (4% ginger), BG3 (3% turmeric), BG4 (4% turmeric), BG5 (1.5% ginger + 1.5% turmeric) and BG6 (2% ginger + 2% turmeric). All the samples were analyzed physicochemically (moisture, ash, pH and water activity), microbiologically (colony count of Rhizopus stolonifer) and organoleptically (color, texture, flavor and overall acceptability). The results showed that overall moisture decreased (from 27.46 to 26.41), water activity aW (from 0.89 to 0.86), color (from 7.4 to 5.58), texture (from 6.94 to 5.34), flavor (from 7.75 to 5.54) and overall acceptability (from 7.38 to 5.48), while percent ash increased (from 0.84 to 0.86), pH (from 5.95 to 6.20) and microbial count of Rhizopus stolonifer (3.8×101 to 2×102). The highest mean value for ash was recorded for treatment BG4 (0.98), water activity in BG0 (0.91), moisture in BG0 (29.69), pH in BG4 (6.34) Microbial count in BG0 (1.5 × 102cfu/g), color in BG3 (6.98), texture in BG0 (7.04), flavor in BG0 (6.90) and overall acceptability in BG0 and BG3 (6.96). The overall results showed that BG3 gave the best inhibitory results against Rhizopus stolonifer as well as in physicochemical and sensory evaluation, while BG6 also presented better inhibitory results in microbial analysis but it was not satisfactory in terms of sensory characteristics.

Chaos in toroidal ion-temperature-gradient-driven modes in dust-contaminated magnetoplasma

A new set of nonlinear equations for toroidal ion-temperature-gradient-driven (ITGD) drift-dissipative waves is derived by using Braginskiis transport model of the ion dynamics and the Boltzmann distribution of electrons in the presence of negatively charged dust grains. The temporal behaviour of the nonlinear ITGD mode is found to be governed by three nonlinear equations for the amplitudes, which is a generalization of Lorenz- and Stenflo-type equations admitting chaotic trajectories. The linear stability analysis has been presented and stationary points for our generalized mode coupling equations are also derived.