Ion-acoustic solitary waves in e-p-i plasmas with (r,q)-distributed electrons and kappa-distributed positrons

In this paper, we have studied the propagation of non-linear ion-acoustic waves in a plasma comprising of (r, q) -distributed electrons and kappa-distributed positrons. We have investigated the effect of complete electron distribution profile on the propagation of small, as well as arbitrary, amplitude solitons (via pseudopotential technique) by using generalized (r, q) distribution, which exhibits a spiky and flat top nature at low energies and a super-thermal tail at high energies. Interestingly, for negative values of r , solitons are formed with both polarities, positive (compressive) and negative (rarefactive), separately within a small amplitude limit and exist simultaneously in an arbitrary amplitude limit. We also found that the propagation of solitons has been affected by the change in parameters r , q , positron concentration, and electron to positron temperature ratio. The results presented in this study add to the fundamental understanding of the complete profile of the electron distribution function, high- and low-energy parts, and in the formation of compressive and rarefactive small and finite amplitude solitons in both space and astrophysical plasmas.     

Flow and Transport Properties of Deforming Porous Media. II. Electrical Conductivity

In Part I of this series, we presented a new theoretical approach for computing the effective permeability of porous media that are under deformation by a hydrostatic pressure P. Beginning with the initial pore-size distribution (PSD) of a porous medium before deformation and given the Young’s modulus and Poisson’s ratio of its grains, the model used an extension of the Hertz–Mindlin theory of contact between grains to compute the new PSD that results from applying the pressure P to the medium and utilized the updated PSD in the effective-medium approximation (EMA) to estimate the effective permeability. In the present paper, we extend the theory in order to compute the electrical conductivity of the same porous media that are saturated by brine. We account for the possible contribution of surface conduction, in order to estimate the electrical conductivity of brine-saturated porous media. We then utilize the theory to update the PSD and, hence, the pore-conductance distribution, which is then used in the EMA to predict the pressure dependence of the electrical conductivity. Comparison between the predictions and experimental data for twenty-six sandstones indicates agreement between the two that ranges from excellent to good.

     

Correction to: Thermal performance enhancement of shell and helical coil heat exchanger using MWCNTs/water nanofluid

Journal of Thermal Analysis and Calorimetry -     

Hydroxypropylcellulose-aceclofenac conjugates: high covalent loading design, structure characterization, nano-assemblies and thermal kinetics

This article presents synthesis of novel macromolecular prodrugs of aceclofenac (an anti-inflammatory drug) onto hydroxypropylcellulose (HPC). The HPC-aceclofenac conjugates were prepared using an acylating agent 1,1′-carbonyldiimidazole (CDI) under homogenous reaction conditions. Aceclofenac was first activated by using CDI to form its N-acylimidazole. The N-acylimidazole of aceclofenac was then reacted with HPC polymer at 80 °C for 24 h. Highly pure prodrugs of aceclofenac were synthesized with a wide range of moderate to high degree of substitution (DS 0.41–2.12) as calculated by ¹H NMR spectroscopy. The UV spectroscopic analysis has also revealed that the active drug aceclofenac was found in different conjugates from 28 to 67 mg/100 mg of HPC-aceclofenac conjugates which are in good agreement with DS calculated by ¹H NMR spectroscopy. The gel permeation chromatography showed unimodal absorption that indicates no significant degradation in polymer chains during the reaction. The macromolecular prodrugs of aceclofenac were characterized using different spectroscopic and chromatographic techniques. The thermal analysis has revealed that HPC-aceclofenac conjugates (prodrugs) are 92 and 96 °C more stable than pure aceclofenac regarding their initial (Tdi) and maximum degradation temperatures (Tdm), respectively. The activation energy (Ea) and frequency factor (Z) of the degradation reactions were evaluated using Friedman, Broido and Chang methods. Degradation followed first order (n) kinetics. Transmission electron microscopy has revealed the formation of sponge like nano aggregates with population size distribution of around 80–150 nm.     

Entropy generation (irreversibility) associated with flow and heat transport mechanism in Sisko nanomaterial

Here a novel applications of entropy generation optimization is presented for nonlinear Sisko nanomaterial flow by rotating stretchable disk. Flow is examined in the absence of magnetohydrodynamics and Joule heating. Total irreversibility rate (entropy generation rate) is investigated for different flow parameters. Heat source/sink and viscous dissipation effects are considered. Impacts of Brownian motion and thermophoresis on irreversibility have been analyzed. Governing flow equations comprise momentum, energy and nanoparticle concentration. Von Karman's similarity variables are implemented for reduction of PDEs into ODEs. Homotopy analysis technique for series solutions is implemented. Attention is given to the irreversibility. The impacts of different flow parameters on velocity, nanoparticle concentration, temperature and irreversibility rate are graphically presented. From obtained results it is examined that irreversibility rate enhances for larger estimation of Brinkman number and diffusion. Furthermore it is also examined that temperature and nanoparticle concentration show contrast behavior through Prandtl number and Brownian motion.     

Experimental and Computational Studies on the CH Amination Mechanism of Tetrahydrocarbazoles via Hydroperoxides

The acid‐catalyzed reactions of photochemically generated tetrahydrocarbazole peroxides with anilines have been studied experimentally and computationally to identify the underlying reaction mechanism. The kinetic data indicate a reaction order of one in the hydroperoxide and zero in the aniline. Computational investigations using density functional theory support the experimental findings and predict an initial tautomerization between an imine and enamine substructure of the primarily generated tetrahydrocarbazole peroxide to be the rate controlling step. The enamine tautomer then loses hydrogen peroxide upon protonation, generating a stabilized allylic carbocation that is reversibly trapped by solvent or aniline to form the isolated products.     

12-Tungstophosphoric acid niched in Zr-based metal-organic framework: a stable and efficient catalyst for Friedel-Crafts acylation

Heteropoly acids(HPA) are well known for their versatile solid acid catalysis in diverse chemical reactions, however they suffer from low surface area(10 m~2/g) and leaching into the reactions media, which reduce their prospects as industrial catalyst.Herein, a novel hybrid material HPW@Zr-BTC,composed of 12-tungstophoric acid(HPW) and Zr~(Ⅳ)-benzene tri-carboxylate(Zr-BTC) metal-organic framework(MOF), was prepared via one-pot solvothermal method. Excellent HPW loading up to 32.3 wt% was achieved, and HPW@Zr-BTC composite proved to be highly stable, besides the crystalline morphology of Zr-BTC was intact. The catalytic activity of the hybrid composite was explored via Friedel-Crafts acylation of anisole with benzoyl chloride.The 28.2 wt% HPW@Zr-BTC showed excellent catalytic performance, with 99.4% anisole conversion and 97.6% yield(pmethoxybenzophenone) under solvent free conditions. Excellent retention of catalytic activity was achieved after at least five consecutive runs due to non-observable HPW leaching. The promising activity and stability of the catalyst forecasted its potential industrial applications.     

Synthesis of biologically active nickelocenyl–amino acid conjugates using 1,3-dipolar cycloaddition click reactions

Russian Journal of General Chemistry - Herein we present the study of synthesis of novel bio-organometallic conjugates using 1,3-dipolar cycloaddition click reactions. Amino acid azides such as...