Dual solutions of mixed convective hybrid nanofluid flow over a shrinking cylinder placed in a porous medium.

Mixed convective hybrid nanofluid flow over a shrinking cylinder saturated in a porous medium is analyzed in the presence of magnetic field. The mathematical model of the present problem is formulated with constant thermophysical properties. The system of governing equations is reduced to ordinary differential equations utilizing appropriate similarity transformations. The resulting equations are solved by the implicit Runge-Kutta-Butcher procedure together with Nachtsheim-Swigert iteration scheme. The key findings are that the skin friction coefficient and the Nusselt number are substantially augmented with the increase in mixed convection parameter, Ri, magnetic field parameter, M, and porosity parameter, K. However, the boundary layer separation is delayed owing to the higher value of M, Ri, K, curvature parameter, γ, volume fractions of Al2O3 (φ1) and Cu (φ2). Moreover, the thermal boundary layer for the Cu-Al2O3/H2O hybrid nanofluid is wider in comparison with that for Cu-H2O and Al2O3-H2O nanofluid. On the other hand, the momentum boundary layer is thicker for 10 % of Al2O3 nanoparticle volume fraction and the reverse is seen for 10 % volume fraction of Cu nanoparticle.

Natural convective non-Newtonian nanofluid flow in a wavy-shaped enclosure with a heated elliptic obstacle.

A numerical investigation has been carried out in a wavy-shaped enclosure with an elliptical inner cylinder to find out the effect of an inclined magnetic field and a non-Newtonian nanofluid on fluid flow and heat transfer. Here, the dynamic viscosity and thermal conductivity of the nanofluid are also taken into account. These properties change with the temperature and nanoparticle volume fraction. The vertical walls of the enclosure are modeled through complex wavy geometries and are kept at a constant cold temperature. The inner elliptical cylinder is deemed to be heated and the horizontal walls are considered adiabatic. Temperature difference between the wavy walls and the hot cylinder leads to natural convective circulation flow inside the enclosure. The dimensionless set of the governing equations and associated boundary conditions are numerically simulated using the COMSOL Multiphysics software, which is based on finite element methods. Numerical analysis has been scrutinized for varying Rayleigh number (Ra), Hartmann number (Ha), magnetic field inclination angle (γ), rotation angle of the inner cylinder (ω), power-law index (n), and nanoparticle volume fraction (ϕ). The findings demonstrate that the solid volumetric concentration of nanoparticles diminishes the fluid movement at greater values of φ. The heat transfer rate decreases for larger nanoparticle volume fractions. The flow strength increases with an increasing Rayleigh number resulting in a best possible heat transfer. A higher Hartmann number diminishes the fluid flow but converse behavior is exhibited for magnetic field inclination angle (γ). The average Nusselt number (Nuavg) values are maximum for γ = 90°. The power-law index plays a significant role on the heat transfer rate, and results show that the shear-thinning liquid augments the average Nusselt number.

Viscoelastic hybrid nanofluid flow over a vertical plate with sinusoidal surface temperature variations.

Natural convection of a viscoelastic hybrid nanofluid along a vertically heated plate with sinusoidal surface temperature variations is investigated. The current investigation explores the non-similar boundary layer flow patterns and heat transfer of second-grade viscoelastic flow of hybrid nanofluid. Effects of magnetic field and thermal radiation are considered. The governing dimensional equations are converted into a non-dimensional form taking suitable transformations. Resulting equations are solved with the aid of finite difference method. It is discovered that the momentum boundary layer lessens while the thermal boundary layer grows for higher radiation parameters, surface temperature parameters, Eckert numbers, magnetic field parameters and amount of nanoparticles. For larger Deborah numbers (De1), shear stress (τ) and heat transfer rate (q) accelerate, but momentum and thermal boundary decline near the leading edge of the vertical plate. However, the effects of Deborah number (De2) show opposite results. Increase in magnetic field parameters causes a reduction in shear stress. The higher volume fraction of nanoparticles (φ1, φ2) enhances q as it was expected. Moreover, τ and q were increased with larger surface temperature parameters and decrease with higher Eckert numbers. This is because higher surface temperature boost up the fluid temperature, but higher Eckert numbers admit the fluid to spread over the surface. An increase in the amplitude of surface temperature oscillation enhances the shear stress and heat transfer rate.

Reduction of cadmium toxicity in wheat through plasma technology.

Cadmium (Cd) contamination in plant-derived food is a big concern. This study examines whether and how Ar/O2 and Ar/Air plasma techniques lead to Cd detoxification in wheat. Treatment with Ar/O2 and Ar/Air changed the seed surface and decreased the pH of seeds as well as the cultivation media. Generally, plants subjected to Cd treatment from seeds treated with Ar/O2and Ar/Air plasma showed considerable progress in morphology and total chlorophyll synthesis compared to Cd-treated wheat, suggesting that plasma technology is effective for Cd detoxification. Furthermore, Ar/O2 and Ar/Air plasma treated plants showed a significant decrease in root and shoot Cd concentration, which is consistent with the reduced expression of Cd transporters in the root (TaLCT1 and TaHMA2) compared with the plants not treated with plasma in response to Cd stress. This Cd inhibition is possibly accomplished by the decrease of pH reducing the bioavailability of Cd in the rhizosphere. These observations are in line with maintenance of total soluble protein along with reduced electrolyte leakage and cell death (%) in root and shoot due to Ar/O2 and Ar/Air treatments. Further, Cd-induced elevated H2O2 or oxidative damage in tissues was mainly diminished through the upregulation of antioxidant enzymes (SOD and CAT) and their corresponding genes (TaSOD and TaCAT) induced by Ar/O2 and Ar/Air plasma. Grafting results suggest that root originating nitric oxide signal possibly drives the mechanisms of Cd detoxification due to plasma treatment in wheat. These findings provide a novel and eco-friendly use of plasma technology for the mitigation of Cd toxicity in wheat plants.

Mechanisms and Signaling Associated with LPDBD Plasma Mediated Growth Improvement in Wheat.

This study investigates the effect and mechanisms of low pressure dielectric barrier discharge (LPDBD) produced with Ar/O2 and Ar/Air technique causing biological stimulation leading to improved germination and growth in wheat. Both plasma treatments caused rougher and chapped seed surface along with noticeable improvement in seed germination in wheat. Beside this, seed H2O2 concentration significantly increased compared to controls subjected to Ar/O2 and Ar/Air while this phenomenon was more pronounced due to Ar/Air plasma. Analysis of plants grown from the plasma treated seeds showed significant improvement in shoot characteristics, iron concentration, total soluble protein and sugar concentration in comparison with the controls more efficiently due to Ar/O2 plasma than that of Ar/Air. Further, none of the plasma treatments caused membrane damage or cell death in root and shoot of wheat. Interestingly, Ar/O2 treated plants showed a significant increase (2-fold) of H2O2 compared to controls in both root and shoot, while Ar/Air plasma caused no changes in H2O2. This phenomenon was supported by the biochemical and molecular evidence of SOD, APX and CAT in wheat plants. Plants derived from Ar/O2 treated seeds demonstrated a significant increase in SOD activity and TaSOD expression in roots of wheat, while APX and CAT activities along with TaCAT and TaAPX expression showed no significant changes. In contrast, Ar/Air plasma caused a significant increase only in APX activity in the shoot. This suggests that Ar/O2 plasma caused a slight induction in H2O2 accumulation without triggering the H2O2 scavengers (APX and CAT) and thus, efficiency affect growth and development in wheat plants. Further, grafting of control and Ar/O2 treated plants showed a significant increase in shoot biomass and H2O2 concentration in grafts having Ar/O2 rootstock regardless of the type scion attached to it. It indicates that signal driving Ar/O2 plasma mediated growth improvement in wheat is possibly originated in roots. Taken together, this paper delivers new insight into the mechanistic basis for growth improvement by LPDBD technique.