Aspects of parabolic motion of MHD fluid flow past a vertical porous plate with cross-diffusion effects

In the presence of Soret and Dufour effects, a numerical analysis is performed for an unstable magnetohydrodynamics convective flow of parabolic motion with variable temperature and concentration. The finite-difference method is used to solve the set of nondimensional governing equations with boundary conditions numerically. Graphs are used to investigate the effect of various physical characteristics on flow quantities. Variations in skin friction, Nusselt number, and Sherwood number are also examined using tables for physical curiosity. This study is unique in that it takes into account changeable temperature as well as concentration with Soret and Dufour effects. The magnetic parameter, Prandtl number, heat source, radiation parameter, Schmidt number, and chemical reaction parameter show a significant increase in skin friction, whereas the Grashof number, modified Grashof number, permeability parameter, radiation absorption parameter, Dufour number, and Soret number show the opposite trend. As the Soret number rises, the concentration rises as well, whereas the opposite is true for the Schmidt number and the chemical reaction parameter. The current study is highly supported by previously published data that have been verified.     

Interference cancellation enhancement through generalized widely linear equalization in QAM systems

In this paper, we introduce a generalized widely linear (WL) equalizer for quadrature amplitude modulation (QAM) systems with single/multiple antennas. In our proposed implementation, the WL receiver first separates the in-phase (I) and quadrature (Q) parts of the complex-valued baseband received signal and jointly filters the two branches for signal detection. Infinite length WL minimum mean-square error (WL-MMSE) linear, and WL decision-feedback-equalizer (WL-DFE) settings are derived and performance is analyzed in co-channel interference limited channels. It is shown that, in frequency selective Rayleigh fading channels, the interference cancellation (IC) gain depends mainly on the rank (r) of the interference correlation matrix (ICM) which is defined as the covariance of the vector-valued signal which consists of the real and imaginary parts of the noise-plus-interference signal collected at multiple antenna branches. Assuming that the DFE feedback path is error free, we show that a WL QAM receiver with N antennas exhibits full IC capability (that is complete interference removal) when the ICM is rank deficient i.e., when: r ≪ 2N. This condition implies that a WL-DFE receiver can reject any combination of M1 pulse-amplitude-modulation (PAM) and M2 QAM interferers satisfying the constraint: M1 + 2M2 ≪ 2N. Simulation results show that, in the presence of PAM-type interference, the gain of WL-DFE is reduced by decision feedback errors while the IC benefit of WL-MMSE is limited by the noise enhancement problem. Nevertheless, the proposed receivers are shown to be useful in cellular systems that employ a combination of PAM and QAM schemes.     

Studies on the hydrolysis of urea for production of ammonia and modeling for flow characterization in presence of stirring in a batch reactor using computational fluid dynamics

Ammonia is a highly volatile noxious material with adverse physiological effects, which becomes intolerable even at very low concentrations and presents substantial environmental and operating hazards and risk. But ammonia has long been known to be useful in the treatment of flue gases from the fossil fuel combustion process, such as in industrial furnaces, incinerators and coal-fired electric power generating plants. The present study is concerned with the methods and means to safely produce relatively small amount (i.e., up to 50 kg/hour) of ammonia. Current study involves experimental investigation for hydrolysis of urea for production of ammonia in a batch reactor at different temperature ranging from 110 °C to 180 °C against different initial feed concentration (10, 20, and 30 wt%) with different stirring speed ranging from 400 rpm to 1,400 rpm. Three-dimensional geometry and meshing of reactor is created in Gambit, a preprocessor of the commercial software, Fluent, for hydrodynamic study.     

Iontophoresis of amoxicillin and cefuroxime: rapid therapeutic concentrations in skin

Context: Amoxicillin (AMX) and cefuroxime (CFX) are antibiotics used often to treat skin bacterial infections. Typically, high oral doses are required to achieve minimum inhibitory concentration (MIC) at the site of infection that may affect only a very small area of skin.

Objectives: To lower side effects and increase therapeutic effectiveness, the percutaneous absorption and retention of AMX and CFX administered by iontophoresis was investigated in a rabbit model by measuring dermis concentrations via microdialysis.

Methods: Iontophoresis was performed using a stainless steel electrode and a non-woven polypropylene pad. The cartridge pad was soaked with a solution of AMX in glycerin or of CFX in glycerin/water (60:40). Constant current density of 0, 100, 200 or 300?µA/cm² was applied for 60?min.

Results: For AMX, therapeutically effective skin concentrations were detected immediately after the application of electrical current for any of the current density tested and remained above it for at least 2?h from the end of iontophoresis. For CFX, skin concentrations rose above MIC only at the higher current densities and fell below the MIC by the end of the experiment.

Conclusion: Iontophoresis is a promising method to obtain a fast and sustained concentration of AMX and CFX in skin.     

Nanostructured manganese oxide–chitosan-based cholesterol sensor

Manganese oxide nano-rod (nano-MnO₂) was prepared by simple oxidation method. To fabricate nanocomposite film (nano-MnO₂/CT) onto glassy carbon electrode (GCE), nano-MnO₂ was homogeneously dispersed in chitosan (CT). Cholesterol oxidase (ChOx) was immobilized onto nano-MnO₂/CT by physisorption. Modified electrode was characterized by Fourier transform infrared, X-ray diffraction, cyclic voltammetry, scanning electron microscopy, transmission electron microscopy, and electrochemical impedance spectroscopy techniques. Prepared ChOx/nano-MnO₂/CT/GCE bioelectrode exhibited 0.03–11.66 mM linearity and 2.07 × 10^?3 mM limit of detection for cholesterol. Biosensing characteristics of modified bioelectrode were superior than other electrodes modified with metal oxide nanoparticles, reported in the literature.     

Direct synthesis of nanocrystalline silver from the reaction between silver carboxylates and n-trioctylphosphine

Neat n-Trioctylphosphine (TOP) has been used for the first ever time for reduction of silver nitrate and silver carboxylates (citrate, oleate, and myristate) under mild thermal reaction conditions. UV-visible absorption measurements of re-dispersible silver particles that were obtained by reduction of silver myristrate (product-IV) and silver nitrate (product-I) showed surface plasmon resonance absorption peak at 400 nm. The powder XRD pattern of fcc zero-valent silver resulted in diameters in the range of about 25-30 nm. TEM analysis showed particle diameter similar to that was observed by the XRD. FTIR spectroscopy revealed that the organics from the carboxylate group are retained by the nano-particles in case of product-IV however, presence of TOP is observed in product-I. It is found that when silver nitrate is reduced by TOP, spherical silver nano-particles with poor redispersity are formed but extended heating results in formation of long silver rods of micrometer size however, the re-dispersible nano-particles are easily formed when silver carboxylates are reduced by TOP.     

Finite element prediction of material removal rate due to traveling wire electrochemical spark machining

Manufacturing engineers are facing new challenges during machining of electrically nonconducting or partially conducting materials such as glass, quartz, ceramics, and composites. Traveling wire electrochemical spark machining (TW-ECSM), a largely unknown technology, has been applied successfully for cutting these types of materials. However, hardly any theoretical work has been reported related to machining performance of TW-ECSM process. The present work is an attempt in this direction. In the present work, a 3-D finite element transient thermal model has been developed to estimate the temperature field and material removal rate (MRR) due to Gaussian distributed input heat flux of a spark during TW-ECSM. First, the developed code calculates the temperature field in the workpiece and then MRR is calculated using this temperature field. The calculated MRR has been compared with the experimental MRR for verifying the approach. Computational experiments have been performed for the determination of energy partition and spark radius of a single spark. The effects of various process parameters such as energy partition, duty factor, spark radius, and ejection efficiency on MRR have been reported. It has been found that MRR increases with increase in energy partition, duty factor, and ejection efficiency but decreases with increase in spark radius.     

Synthesis of nano-particles of anatase-TiO2 and preparation of its optically transparent film in PVA

Anatase-TiO₂ nano-particles have been synthesized by using long-carbon chain carboxylic acid and titanium tetrachloride (TiCl₄). As-prepared powder has been calcined at 500 °C to obtain highly crystalline TiO₂. Broad X-ray diffraction (XRD) pattern of as-prepared as well as calcined powder showed all prominent peaks for tetragonal crystal structure representing anatase-TiO₂. The particle diameter by applying Scherrer formula was found to be about 20 nm. It was possible to load as-prepared particles in poly vinyl alcohol (PVA) for optical studies. Optically transparent film showed sharp absorption band for TiO₂ nano-particles at ∼ 300 nm. Photoluminescence (PL) studies of the solution showed emission wavelength at about 330 nm. Transmission electron microscopy (TEM) and selected area electron diffraction (SAED) revealed that the particles in the film have uniform distribution and even for the powder no agglomeration was observed. Thermal analysis (TGA) showed that the stability of host polymer is enhanced. FTIR spectra showed presence of carboxylate functional group in the powder.     

Identification of optimal rate-enhanced silver ELP processes for silver–ceramic composite membrane fabrication

This work targets the identification of optimal rate-enhancement technique for the electroless fabrication of silver–ceramic porous membranes. The membranes were fabricated with porous ceramic supports of 4.5?µm and porosity of 19.3% and with alternate electroless plating (ELP) processes including conventional (CEP), sonication (SOEP), and surfactant (SIEP) plating baths. The alternate processes were evaluated based on the process (conversion, plating efficiency (η), average plating rate) and membrane characteristics (percent pore densification (PPD), metal loading index (MLI)), and their combinations (η/(MLI.PPD)). Among alternate processes, SOEP has been evaluated to be the best to yield silver–ceramic membranes.