Hall current effects on MHD flow of chemically reacting fluid through a porous medium with heat source

We considered the magnetohydrodynamic (MHD) free convective flow of an incompressible electrically conducting viscous fluid past an infinite vertical permeable porous plate with a uniform transverse magnetic field, heat source and chemical reaction in a rotating frame taking Hall current effects into account. The momentum equations for the fluid flow during absorbent medium are controlled by the Brinkman model. Through the undisturbed state, both the plate and fluid are in a rigid body rotation by the uniform angular velocity perpendicular to an infinite vertical plate. The perpendicular surface is subject to the homogeneous invariable suction at a right angle to it and the heat on the surface varies about a non-zero unvarying average whereas the warmth of complimentary flow is invariable. The systematic solutions of the velocity, temperature, and concentration distributions are acquired systematically by utilizing the perturbation method. The velocity expressions consist of steady-state and fluctuating situations. It is revealed that the steady part of the velocity field has a three-layer characteristic while the oscillatory part of the fluid field exhibits a multi-layer characteristic. The influence of various governing flow parameters on the velocity, temperature, and concentration are analyzed graphically. We also discuss computational results for the skin friction, Nusselt number, and Sherwood number in the tabular forms.     

Radiation-absorption,chemical reaction,Hall and ion slip impacts on magnetohydrodynamic free convective flow over semi-infinite moving absorbent surface

The investigation of radiation-absorption,chemical reaction,Hall and ion-slip impacts on unsteady MHD free convective laminar flow of an incompressible viscous,electrically conducting and heat generation/absorbing fluid enclosed with a semi-infinite porous plate within a rotating frame has been premeditated.The plate is assumed to be moving with a constant velocity in the direction of fluid movement.A uniform transverse magnetic field is applied at right angles to the porous surface,which is absorbing the fluid with a suction velocity changing with time.The non-dimensional governing equations for present inves-tigation are solved analytically making use of two term harmonic and non-harmonic functions.The graphical results of velocity,temperature and concentration distributions on the analytical solutions are displayed and discussed with reference to pertinent parameters.It is found that the velocity profiles decreased with an increasing in Hartmann number,rotation parameter,the Schmidt number,heat source parameter,while it increased due to an increase in permeability parameter,radiation-absorption param-eter,Hall and ion slip parameters.However,the temperature profile is an increasing function of radiation-absorption parameter,whereas an increase in chemical reaction parameter,the Schmidt num-ber Sc or frequency of oscillations decrease the temperature profile on cooling.Also,it is found that the concentration profile is decreased with an escalating in the Schmidt number or the chemical reaction parameter.     

Effect of HNT on the Microstructure,Thermal and Mechanical Properties of Al/FA<Subscript>CS</Subscript>-HNT Composites Produced by GPI

To develop an optimised manufacturing method of fly ash-reinforced metal matrix composites, the preliminary tests were performed on the cenospheres selected from fly ash (FA_CS) with halloysite nanotubes (HNTs) addition. The preform made out of FA_CS with and without the addition of HNT (with 5 and 10 wt.%) has been infiltrated by the pure aluminium (Al) via adapted gas pressure infiltration process. This paper reveals the influence of HNT addition on the microstructure (analysis was done by computed tomography and scanning electron microscopy combined with energy-dispersive x-ray spectroscopy), thermal properties (thermal expansion coefficient, thermal conductivity and specific heat) and the mechanical properties (hardness and compression test) of manufactured composites. The analysis of structure-property relationships for Al/FA_CS-HNT composites produced shows that the addition of 5 wt.% of HNT to FA_CS preform contributes to receiving of the best mechanical and structural properties of investigated composites.     

Principal component analysis of measured quantities during degradation of hydroperoxides in oxidized vegetable oils

Decomposition of hydroperoxides in sunflower oil under strictly oxygen-free conditions was followed by measuring peroxide values against time, absorbance values at 232 and 268 nm, para-anisidine values, and by quantitative analyses of volatile products using various additives. The results were arranged in a matrix form and subjected to principal component analysis. Three principal components explained 89–97% of the total variance in the data. The measured quantities and the effect of additives were closely related. Characteristic plots showed similarities among the measured quantities (loading plots) and among the additives (score plots). Initial decomposition rate of hydroperoxides and the amount of volatile products formed were similar to each other. The outliers, the absorbance values, were similar to each other but carried independent information from the other quantities. Para-anisidine value (PAV) was a unique parameter. Since PAV behaved differently during the course of hydroperoxide degradation, it served as a kinetic indicator. Most additives were similar in their effects on the mentioned quantities, but two outliers were also observed. Rotation of the principal component axes did not change the dominant patterns observed. The investigations clearly showed which variables were worth measuring to evaluate different additives.     

The incorporation of mono- and bi-functionalized multiwall carbon nanotubes in organic photovoltaic cells

We have successfully prepared mono- and bi-functionalized multiwall carbon nanotubes (MWCNT) with thiophene, amine and thiophene-amine groups. The dispersion of nanotubes has been enhanced and stable optimized dispersions in organic solvents were obtained. These functionalized nanotubes have been successfully incorporated into bulk heterojunction (BHJ) organic photovoltaic (OPV) cells with a poly (3-hexyl thiophene) (P3HT) and [6, 6]-phenyl-C(61)-butyric acid methyl ester (PCBM) photoactive blended layer. The incorporation of MWCNT with different functional groups, in the active layer, results in different cell performance with respect to a reference cell. A maximum power conversion efficiency of 2.5% is achieved with the inclusion of thiophene functionalized nanotubes. This improvement in the device performance is attributed to an extension of the exciton dissociation volume and charge transport properties through the nanotube percolation network in P3HT/CNT, PCBM/CNT or both phases. This is believed to be due to more efficient dispersion of the functionalized nanotubes within the photoactive composite layer.     

Preparation of sorbitol-based polyurethanes and their semiinterpenetrating polymer networks

Sorbitol is a useful agro-based substance that is inexpensive and commercially available. In the interest of adding value to bio-based raw materials, we have synthesized polyurethanes from sorbitol and toluene-2,4-diisocyanate (TDI) through both conventional heat and microwave processes. Relative to conventional heat, the microwave process achieved the same reaction at a faster rate, thereby saving time and energy. The nature of the resulting polyurethane products depended on the stoichiometry of the reaction. At increasing TDI levels, a viscous liquid, a soft gel, or a hard thermoset could be obtained. The polymers were fully characterized with ¹³C-NMR, Fourier transform infrared, size exclusion chromatography, and thermogravimetric analysis. The polyurethanes obtained near the gel point could be used to make semiinterpenetrating polymer networks (semi-IPNs) with a second polymer, thereby imparting some of the properties of the second polymer onto the sorbitol-based polyurethane. For illustration, the sorbitol-based polyurethane semi-IPNs were made in combination with poly(vinyl pyrrolidone) and poly(lactic acid). © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47602.     

Evaluation of the pore morphology formation of the Freeze Foaming process by in situ computed tomography

The so-called Freeze Foaming method aims at manufacturing ceramic cellular scaffolds for diverse applications. One application is dedicated to potential bone replacement material featuring open, micro and interconnected porosity. However, the main challenges of this foaming method is to achieve a homogeneous pore morphology. In a current project, the authors throw light on the bubble/pore and strut formation of this process by in situ computed tomography. This allows for evaluating varying process parameter’s effects on the growth of the ceramic foam during the foaming process. As first result and basis for CT analysis, a stable and reproducible model suspension was developed which resulted in reproducible foam structures. In dependence of selected process parameters like pressure reduction rate or air content in the ceramic suspension resulting Freeze Foams became adjustable with regard to their pore morphology. Pore size and distribution data as well as the porosity were characterized and evaluated accordingly.     

Rheum rhaponticum Root Extract Improves Vasomotor Menopausal Symptoms and Estrogen-Regulated Targets in Ovariectomized Rat Model

Ovarian insufficiency and ovariectomy are characterized by deregulated heat loss mechanisms. Unlike hormone therapy, ERr 731 (a standardized botanical extract of Siberian rhubarb Rheum rhaponticum L. high in rhaponticin) acts like a selective estrogen receptor modulator for ERβ receptors and may offer a higher degree of safety while maintaining the desired efficacy profile. In this study, we examined the relationship between oral administration of ERr 731 and the underlying components of skin vasomotion responses in an ovariectomized (OVX) rat model. ERr 731 dose-dependently reduced tail skin temperature (T_skin) values by an average of 1 °C. The rapid onset of this effect was observed in 1 and 3 mg/kg/day ERr 731 groups as early as day 2 of administration, and remained in place for the duration of the treatment (2 weeks). Substituting ERr 731 after E₂ withdrawal helped maintain body temperature similarly to E₂ alone, suggesting the usefulness of ERr 731 for replacing existing hormonal therapy in humans. ERr 731 also acted as a highly selective agonist for ERβ in the hypothalamus of OVX rats, as well as in ERα/β cell-based reporter assays. These data validate the OVX/T_skin rat model as a suitable screening platform to evaluate botanical and pharmaceutical treatments of menopause, while providing further evidence for the efficacy of ERr 731 towards alleviating vasomotor menopausal symptoms and improving wellbeing during the menopausal transition.     

Dispersion of chitosan on perlite for enhancement of copper(II) adsorption capacity

Chitosan coated perlite beads were prepared by drop-wise addition of slurry, made of chitosan dissolved in oxalic acid and perlite, to an alkaline bath (0.7 M NaOH). The beads that contained 32% chitosan enhanced the accessibility of OH and amine groups present in chitosan for adsorption of copper ions. The experiments using Cu(II) ions were carried out in the concentration range of 50-4100 mg/L (0.78-64.1 mmol/L). Adsorption capacity for Cu(II) was pH dependent and a maximum uptake of 104 mg/g of beads (325 mg/g of chitosan) was obtained at pH 4.5 when its equilibrium concentration in the solution was 812.5 mg/L at 298 K. The XPS and TEM data suggested that copper was mainly adsorbed as Cu(II) and was attached to amine groups. The adsorption data could be fitted to one-site Langmuir adsorption model. Anions in the solution had minimal effect on Cu(II) adsorption by chitosan coated perlite beads. EDTA was used effectively for the regeneration of the bed. The diffusion coefficient of Cu(II) onto chitosan coated beads was calculated from the breakthrough curve and was found to be 2.02 x 10(-8) cm(2)/s.     

Biosorption mechanism of nine different heavy metals onto biomatrix from rice husk

A biomatrix was prepared from rice husk, a lignocellulosic waste from agro-industry, for the removal of several heavy metals as a function of pH and metal concentrations in single and mixed solutions. The biomatrix was characterized using scanning electron microscope and Fourier transform infrared spectroscopy, which indicated the presence of several functional groups for binding metal ions. Different experimental approaches were applied to show mechanistic aspects, especially the role of calcium and magnesium present in the biomatrix in ion exchange mechanism. The ultimate maximum adsorption capacity obtained from the Langmuir isotherm increases in the order (mmol/g): Ni (0.094), Zn (0.124), Cd (0.149), Mn (0.151), Co (0.162), Cu (0.172), Hg (0.18) and Pb (0.28). The sorption of Cr(III) onto biomatrix at pH 2 was 1.0 mmol/g. Speciation of chromium, cadmium and mercury loaded on the biomatrix was determined by X-ray photoelectron spectroscopy. The biomatrix has adsorption capacity comparable or greater to other reported sorbents.