Theoretical study of reorientation and torque of liquid crystal molecules under influence of external electric field and experimentally generation of spatial optical soliton beam and getting a sharp switching in chiral nematic liquid crystal

Liquid crystals (LC) are anisotropic materials which experience a torque if an electric field is present. This field can be due to an external voltage or to the presence of a light beam. Reorientation due to light leads to non-linear behavior in the optical behavior. Due to this kind of nonlinearity therefore it is possible to generate optical spatial soliton beam in LC by bias voltage or without it and interestingly chiral nematic liquid crystals has a opportunity to generate spatial optical solitons without the need for a bias voltage. In this paper we also demonstrate that a sharp switching of the helix structure occurs when the spatial soliton is launched in the middle of two regions where soliton generation is favorable. Due to the optical nonlinearity, the helical structure becomes asymmetric and a sharp switching in one direction can be obtained. Moreover, in this paper, the torque and reorientation of the liquid crystal and the change in angular momentum of the light are discussed.     

Thermally Stimulated Depolarization Current and Thermal Analysis Studies of Gamma Irradiated Lithium‐Salt/Polymer Electrolyte Blends

Thermally stimulated depolarization current (TSDC) and thermal analysis studies of gamma irradiated LiOH/PVA blends were done. To study the mechanisms of conduction and TSDC in poly(vinyl alcohol) (PVA) and LiOH/PVA blends, short circuit TSDC at a polarizing temperature 353 K with a polarizing field of 3 kV cm^?1 have been analyzed in the temperature range 300–410 K. Two peaks are evident from the global TSDC measurements on the pure PVA homopolymer. Meanwhile, in all blended samples; there is only one broad peak with a shoulder on the high temperature side due to the relaxation of the poly‐blend system. The temperature dependence, 300–408 K, of the current density (J) for pure PVA and its blended samples has been studied. It was observed that J values increase dramatically with increasing temperature (in the low temperature region from 300–340 K) owing to the formation of local ordered regions in the otherwise disordered amorphous matrix of PVA. Further increase in the temperature caused a marginal increase in J values. The temperature dependence of the specific heat for all samples was measured. A linear increase of C _p was observed with an increase in temperature, which is ascribed to the increase in lattice vibration of linear macromolecules and consequently, increases in the number of internal degree of freedom of phonons.     

Phytochemical and in vitro screening of some Ficus and Morus spp. for hypolipidaemic and antioxidant activities and in vivo assessment of Ficus mysorensis (Roth)

Phytochemical screening of air-dried leaves and fruit juice of certain Ficus and Morus spp. have been studied. In an in?vitro study, the ethanol and hexane extracts of the investigated plants were evaluated against hyperlipidaemia by estimating the rate limiting enzyme of cholesterol biothenysis; β-hydroxy-β-methylglutaryl coenzyme A reductase (HMG-CoA reductase). The antioxidant activity was evaluated by reduction of DPPH(-) free radical. Extra phytochemical screening of Ficus extracts was undertaken, which recorded potent hypolipidaemic and antioxidant activities. The more pronounced extract, Ficus mysorensis (hexane extract), was evaluated in?vivo by estimation of the lipid profile and certain antioxidant parameters in hypercholesterolemic rats. The hexane fraction was chromatographed and six isolated compounds were identified. Furthermore, its saponifiable fraction was identified by a MS/MS technique. In conclusion, F. mysorensis recorded hypolipidaemic and antioxidant effects. Detailed studies of the isolated compounds must be undertaken for an evaluation against hypercholesterolemia and free radical elevation.     

Phytochemical screening of Nepeta cataria extracts and their in vitro inhibitory effects on free radicals and carbohydrate-metabolising enzymes

This research was performed to investigate in?vitro the biological activities of successive as well as 70% ethanol extracts of Nepeta cataria on some biochemical parameters including oxidative markers and carbohydrate-hydrolysing enzyme activities (α-amylase, β-galactosidase and α-glucosidase). Powdered N. cataria and its successive extracts were screened for their phytochemical constituents. Tests for tannins, carbohydrates, glycosides and flavonoids were positive in ethanolic extract, but those for steroids and terpenoids were positive in petroleum ether and chloroform extracts. Also, different extracts were chromatographically investigated. The results obtained demonstrated that different successive extracts of N. cataria exhibited an inhibitory effect on oxidative stress indices and carbohydrate-hydrolysing enzymes. It is observed that 70% ethanol, petroleum ether and chloroform extracts showed, respectively, the most potent inhibitory activities, while ethyl acetate and ethanol successive extracts appeared with moderate or low reducing activities.     

Impact of γ-rays on constructional,optical and thermal behavior of alkaline and non alkaline low density polyethylene

ABSTRACT

In this study, we investigated the graft copolymerization of methyl methacrylate (MMA) onto low-density polyethylene (LDPE) in the presence of aniline as an inhibitor by gamma radiation. An alkaline treatment was carried out for the prepared graft copolymer. The structural properties of the prepared samples were examined via X-ray diffraction (XRD) and scanning electron microscopy (SEM). The XRD peaks were slightly shifted, indicating an interaction between MMA and the polyethylene matrix. The morphology of the samples confirmed the homogenous grafted phase scattered onto the LDPE surface. Analysis of the absorption spectra indicated an allowed indirect transition mechanism. The Urbach energy (E_U) results showed that the value of the E_U for grafted LDPE was found to be higher than that of pure LDPE—up to 15?kGy irradiation dose, although this value decreases upon grafting. However, the value of the E_U for alkaline-treated grafted films decreases systematically by increasing the degree of grafting. The thermogravimetric analysis (TGA) of the sample indicated that the thermal stability of LDPE samples is significantly changed by grafting MMA onto it. Horowitz and Metzger's models were utilized to measure the activation energy of the thermal decomposition of all samples.     

A homotopy analysis solution to large deformation of beams under static arbitrary distributed load

In this article, homotopy analysis method (HAM) is employed to investigate non-linear large deformation of Euler–Bernoulli beams subjected to an arbitrary distributed load. Constitutive equations of the problem are obtained. It is assumed that the length of the beam remains constant after applying external loads. Different auxiliary parameters and functions of the HAM and the extra auxiliary parameter, which is applied to initial guess of the solution, are employed to procure better convergence rate of the solution. The results of the solution are obtained for two different examples including constant cross sectional beam subjected to constant distributed load and periodic distributed load. Special base functions, orthogonal polynomials e.g. Chebyshev expansion, are employed as a tool to improve the convergence of the solution. The general solution, presented in this paper, can be used to attain the solution of the beam under arbitrary distributed load and flexural stiffness. Ultimately, it is shown that small deformation theory overestimates different quantities such as bending moment, shear force, etc. for large deflection of the beams in comparison with large deformation theory. Finally, it is concluded that solution of small deformation theory is far from reality for large deflection of straight Euler–Bernoulli beams.     

Renormalization Group Study of the Mixed Spin-1 and Spin-3/2 Blume-Emery-Griffiths Model with Attractive Biquadratic Coupling

The mixed spin-1 and spin-3/2 Blume-Emery-Griffiths model with attractive biquadratic coupling is investigated in the framework of the Migdal-Kadanoff Renormalization Group method. By changing the ratio R > 0 of biquadratic and bilinear exchange interactions and according to the different values of crystal field interactions, we have determined six main types of phase diagrams. The full flow in the parameters space of the Hamiltonian was established and the fixed points obtained are drawn up in a table. In addition, we have determined the eigenvalues of the transformation of the group in the vicinity of the critical points. Finally, the introduction of a positive biquadratic interaction was discussed.

     

Experimental study of liquid-crystal alignment on a surface relief grating

In this experimental work, photofabrication of a surface relief grating (SRG) on poly[(methyl-methacrylate)-co-(DR1 methacrylate)] copolymer was used align liquid-crystal molecules in parallel. The interference pattern of circularly polarized Ar⁺ laser beams was used for this purpose, and the dynamic diffraction efficiency of the grating was measured at the same time. Then, the polymeric layers aligned by SRG were used to fabricate a homogeneous aligned liquid-crystal cell. The SRG-induced optical anisotropy of the empty cell and the cell filled with the well-known 5CB nematic liquid crystal was investigated by polarizing microscopy. In addition, the SRG-induced dichroism was studied by polarized UV-Vis spectrophotometry. Finally, the SRG-induced dichroism and optical anisotropy were compared for four different incidence angles. This alignment technique could have useful applications in in-plane switching LC displays.     

Electrochemical and structural study of neodymium nickelate thick film deposited by spin coating on an oxyapatite electrolyte

The electrochemical characteristics of an Nd₂NiO₄ cathode, synthesized using the citric acid-nitrate combustion method and symmetrically deposited by spin coating on both surfaces of an La_9.33Si_5.3Al_0.7O_25.65 (LSAO) electrolyte, were studied using AC impedance spectroscopy. It was found that, varying the temperature (600 to 850 °C) and the oxygen partial pressure (0.2–10^?7 atm), the impedance characteristics of the electrode could be determined by three different processes. Said processes were ionic conduction in the electrode bulk, interfacial charge transfer, and gas-phase diffusion, all of which are based on the temperature and oxygen partial pressure dependence on the polarization resistance, which is associated with each individual processes as well as on the corresponding capacitance values.     

An experimental investigation of polyacrylamide and sulfonated polyacrylamides based gels crosslinked with cr(III)-acetate for water shutoff in fractured oil reservoirs

Abstract

Water injection as one of the most efficient and worldwide extensively employed approach in homogenous oil reservoirs suffers from early water breakthrough time as well as low oil sweep efficiency values in fractured oil reservoirs. This study investigates the potential application of Cr(III)-acetate based gel polymer system in a typical water injection process using one fractured micromodel. For this purpose, three sulfonated polyacrylamides, different in solfunation degree, and one hydrolyzed polyacrylamide were studied regarding gelation time, gel strength and stability to find the optimized conditions in terms of polymer type and concentration, and polymer/Cr(III)-acetate ratio, which were subsequently used for one dynamic test. Results illustrated the optimized conditions as AN 105 polymer with concentration of 5000?ppm and polymer/Cr(III) ratio of 5. Moreover, results showed that implementing such gel system yields an increased oil recovery value of 24.46% OOIP at 1.55 PV and delays the breakthrough time from 0.47 PV to 0.51 PV.