Synthesis of phenanthro[a] phenazine derivatives: a novel ring structure forming discotic liquid crystals

Phenanthro[a] phenazine, a new heterocyclic ring structure of both biological and physical interest, has been prepared by coupling 1,2-phenylenediamine with triphenylene-1,2-diquinone derivatives in high yields. 2,3,6,7,10-Penta-alkoxyphenanthro[a] phenazines are mesogenic over a broad temperature range. These novel unsymmetrical, coloured, polar, heteroaromatic discotic mesogens are potential candidates for the study of conducting, photoconducting, electroluminescence, photorefrective, etc. properties.     

Peristaltic flow of MHD Jeffrey fluid through finite length cylindrical tube

The present investigation studies the peristaltic flow of the Jeffrey fluid through a tube of finite length. The fluid is electrically conducting in the presence of an applied magnetic field. Analysis is carried out under the assumption of long wavelength and low Reynolds number approximations. Expressions of the pressure gradient, volume flow rate, average volume flow rate, and local wall shear stress are obtained. The effects of relaxation time, retardation time, Hartman number on pressure, local wall she...     

Benchmarking and scaling studies of pseudospectral code Tarang for turbulence simulations

Tarang is a general-purpose pseudospectral parallel code for simulating flows involving fluids, magnetohydrodynamics, and Rayleigh–Bénard convection in turbulence and instability regimes. In this paper we present code validation and benchmarking results of Tarang. We performed our simulations on 1024³, 2048³, and 4096³ grids using the HPC system of IIT Kanpur and Shaheen of KAUST. We observe good ‘weak’ and ‘strong’ scaling for Tarang on these systems.     

Molecular and impedance spectroscopy of Na 2 Mo 2 O 7 ceramics

The fine (i.e. 38 nm) powder of polycrystalline Na₂Mo₂O₇ was prepared by the high-temperature solid-state reaction technique. The formation of the compound in orthorhombic system is confirmed by preliminary structural analysis using X-ray diffraction (XRD) data. Spectroscopic studies of the compound have been carried out by vibration spectroscopy (Raman/FTIR) to understand its molecular structure at microscopic level. The complex impedance spectroscopy (CIS) technique has been used to study the electrical properties of the material as a function of frequency (10²–10⁶ Hz) at different temperatures (23–450^°C), and also to investigate the fundamental mechanism involved in the material. Impedance analysis also indicates that below 300^°C, the electrical conduction in the material is due to grain interior only. At and above 325^°C, the contribution of grain boundary is clearly evident. The electrical processes in the material are found to be temperature-dependent and are due to the relaxation phenomena in it. A frequency-dependent maximum of the imaginary electrical impedance is found to obey the Vogel–Fulcher law.     

DOES WATER DISINFECTANT PLAY A SUPPORTIVE ROLE IN THE SPREAD OF INFECTIOUS DISEASE? A MATHEMATICAL STUDY

The waterborne diseases cause millions of deaths across the globe. It was a preconceived notion since years that ingestion of contaminated water is the only possible way for the spread of waterborne infectious diseases. But some recent studies have shown that waterborne disease can also spread as a result of human to human transmission. The use of disinfectants is a common practice to prevent a waterborne disease. We assume that the inclusion of the disinfectant, although helpful in prevention of disease, caused negative effect on individuals. In this paper, a nonlinear mathematical model has been proposed to analyze the negative effects caused by disinfectant of water on individuals. Our study shows that if the mixing of disinfectant has not been performed in a controlled manner, then it results in an increase in human to human transmission of disease. The equilibrium and stability analysis have been performed to study the nature of the model system. An extensive numerical experiment has been performed to support the analytical findings.     

An algorithm for calculating the chemical potential in associating and reacting fluids

We present a Monte Carlo algorithm to determine the chemical potential of associating and reacting fluids. The algorithm is based on the fact that the chemical potential of a component is the same in the monomer (unbonded) state as in any bonded state. We demonstrate that the chemical potential of the unbonded specie can be calculated at relatively low cost and with high accuracy. The algorithm is applicable to both homogeneous as well as inhomogeneous systems. We compare the results of the presented algorithm against the findings of Widom's single stage particle insertion method for four commonly encountered inhomogeneous systems of associating fluids in phase equilibria studies. The constancy of the chemical potential throughout an inhomogeneous system under equilibrium is used as an independent test of the algorithm. The uncertainty in chemical potential values over the system for the cases studied was on an average 30 times smaller in the new algorithm, with at least 5 times fewer insertions than in the traditional Widom's method.     

Dynamic imaging and hydrodynamics study of high velocity, laser-accelerated thin foil targets using multiframe optical shadowgraphy

The main aim of the study of thin target foil–laser interaction experiments is to understand the physics of hydrodynamics of the foil acceleration, which is highly relevant to inertial confinement fusion (ICF). This paper discusses a simple, inexpensive multiframe optical shadowgraphy diagnostics developed for dynamic imaging of high velocity laser-accelerated target foils of different thicknesses. The diagnostic has a spatial and temporal resolution of 12 μm and 500 ps respectively in the measurements. The target velocity is in the range of 10⁶–10⁷ cm/s. Hydrodynamic efficiency of such targets was measured by energy balance experiments together with the measurement of kinetic energy of the laser-driven targets. Effect of target foil thickness on the hydrodynamics of aluminum foils was studied for determining the optimum conditions for obtaining a directed kinetic energy transfer of the accelerated foil. The diagnostics has also been successfully used to study ablatively accelerated targets of other novel materials.     

Oscillating two-stream instability of laser wakefield-driven plasma wave

The laser wakefield-driven plasma wave in a low-density plasma is seen to be susceptible to the oscillating two-stream instability (OTSI). The plasma wave couples to two short wavelength plasma wave sidebands. The pump plasma wave and sidebands exert a ponderomotive force on the electrons driving a low-frequency quasimode. The electron density perturbation associated with this mode couples with the pump-driven electron oscillatory velocity to produce nonlinear currents driving the sidebands. At large pump amplitude, the instability grows faster than the ion plasma frequency and ions do not play a significant role. The growth rate of the quasimode, at large pump amplitude scales faster than linear. The growth rate is maximum for an optimum wave number of the quasimode and also increases with pump amplitude. Nonlocal effects, however reduce the growth rate by about half.     

Physical hydrodynamic propulsion model study on creeping viscous flow through a ciliated porous tube

The present investigation focusses on a mathematical study of creeping viscous flow induced by metachronal wave propagation in a horizontal ciliated tube containing porous media. Creeping flow limitations are imposed, i.e. inertial forces are small compared to viscous forces and therefore a very low Reynolds number (Re ? 1) is taken into account. The wavelength of metachronal wave is also considered to be very large for cilia movement. The physical problem is linearized and exact solutions are developed for the differential equation problem. Mathematica software is used to compute and illustrate numerical results. The influence of slip parameter and Darcy number on velocity profile, pressure gradient and trapping of bolus are discussed with the aid of graphs. It is found that with increasing magnitude of the slip parameter, the trapped bolus inside the streamlines increases in size. The study is relevant to biological propulsion of medical micromachines in drug delivery.     

Preliminary communication First example of a functionalized triphenylene discotic trimer: molecular engineering of advanced materials

A new type of functionalized discotic oligomer system has been realized whose molecular architecture consists of a trisubstituted benzene as central core and three nitro-functionalized triphenylenes as regional cores. These regional cores are linked to the central core via ether linkages through an alkyl chain spacer. Polarizing microscopy and calorimetric measurements reveal the existence of a monotropic columnar mesophase in this novel functionalized oligomer. The product does not crystallize at room temperature over a long period (c. five months) or on cooling to 50 C. The corresponding unfunctionalized trimer is not liquid crystalline. The dipolar interaction of nitro groups is probably responsible for the induction of mesogenicity. The introduction of functionality into liquid crystal oligomers permits the variation of their properties on a wide scale and opens the route to new synthetic supramolecular systems for various device applications.