Enhancement of dielectric and electro-optical parameters of a newly prepared ferroelectric liquid crystal mixture by dispersing nano-sized copper oxide

ABSTRACT

Here, we present the effect of copper (II) oxide nanoparticles (nCuO) on dielectric and electro-optical parameters of a newly prepared ferroelectric liquid crystal (FLC) mixture, namely W302. The FLC mixture, comprising of pyrimidine compounds, was characterised through dielectric spectroscopy, differential scanning calorimetry (DSC), polarising optical microscopy (POM) and other electro-optical methods. The material parameters such as spontaneous polarisation, rotational viscosity, response time and tilt angle of W302 were found to be 14 nC/cm², 240 mPa.s, 150 µs and 28^?, respectively. The phase transition temperatures of W302 were observed through DSC and further confirmed by the dependence of dielectric loss factor in homogeneously aligned FLC sample with temperature. We also demonstrate the observance of a low-frequency dielectric relaxation mode due to the unwinding of the helix, called as partially unwound helical mode (p-UHM) along with Goldstone mode. The behaviour of p-UHM has been systematically studied with temperature and applied bias field. Further, dispersion of nCuO into host W302 has shown a significant increase in dielectric permittivity. Also, the p-UHM relaxation peak in the dielectric regime has disappeared with the incorporation of nCuO. These studies would be useful to fabricate better electro-optical devices for display, switching and beam steering applications. The formulation and characterization of a ferroelectric liquid crystal (FLC) mixture W302 composed of pyrimidine compounds is presented. Then, we observed the effect of copper (II) oxide nanoparticles (nCuO) on dielectric and electro-optical parameters of a newly prepared and characterized FLC mixture.     

Green synthesis and characterizations of Nickel oxide nanoparticles using leaf extract of Rhamnus virgata and their potential biological applications

In the present report, Nickel oxide nanoparticles (NiONPs) were synthesized using Rhamnus virgata (Roxb.) (Family: Rhamnaceae) as a potential stabilizing, reducing and chelating agent. The formation, morphology, structure and other physicochemical properties of resulting NiONPs were characterized by Ultra violet spectroscopy, X‐ray diffraction (XRD), Fourier Transform Infrared analysis (FTIR), Scanning electron microscopy (SEM), Energy‐dispersive‐spectroscopy (EDS), Transmission electron microscopy (TEM), Raman spectroscopy and dynamic light scattering (DLS). Detailed in vitro biological activities revealed significant therapeutic potential for NiONPs. The antimicrobial efficacy of biogenic NiONPs was demonstrated against five different gram positive and gram negative bacterial strains. Klebsiella pneumoniae and Pseudomonas aeruginosa (MIC: 125 μg/mL) were found to be the least susceptible and Bacillus subtilis (MIC: 31.25 μg/mL) was found to be the most susceptible strain to NiONPs. Biogenic NiONPs were reported to be highly potent against HepG2 cells (IC₅₀: 29.68 μg/ml). Moderate antileishmanial activity against Leishmania tropica (KMH₂₃) promastigotes (IC₅₀: 10.62 μg/ml) and amastigotes (IC₅₀: 27.58 μg/ml) cultures are reported. The cytotoxic activity was studied using brine shrimps and their IC₅₀ value was recorded as 43.73 μg/ml. For toxicological assessment, NiONPs were found compatible towards human RBCs (IC₅₀: > 200 μg/ml) and macrophages (IC₅₀: > 200 μg/ml), deeming particles safe for various applications in nanomedicines. Moderate antioxidant activities: total antioxidant capacity (TAC) (51.43%), 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) activity (70.36%) and total reducing power (TRP) (45%) are reported for NiONPs. In addition, protein kinase and alpha amylase inhibition assays were also performed. Our results concluded that Rhamnus virgata synthesized NiONPs could find important biomedical applications with low cytotoxicity to normal cells.     

Performance evaluation of praseodymium doped fiber amplifiers

Optical Review - In this paper, we report the performance evaluation of praseodymium doped fiber amplifier (PDFA) operating in 1.25–1.35 μm band of wavelengths based on...     

Thermal decomposition of model compound of algal biomass

This contribution investigates thermal decomposition of leucine, as a representative model compound for amino acids in algal biomass. We map out potential energy surface for a wide array of unimolecular and self-condensation reactions operating in the decomposition of leucine. Decarboxylation and dehydration of leucine ensues by eliminating CO₂ and –OH, respectively, from the –COOH group attached to the α-carbon. The molecular channel for deamination involves cleavage of NH₂ from α-carbon of leucine. The activation energies for direct elimination of CO₂, NH₃, and H₂O from a leucine molecule lie within 20.7 kJ/mol of each other. Activation energies for these decomposition pathways reside below the bond dissociation enthalpy of H–C(α) of 323.1 kJ/mol. The decarboxylation, deamination, and dehydration pathways, via radical-prompted pathways, systematically require lower energy barriers, in reference to closed-shell reaction corridors. Detailed computations at the CBS-QB3 level provide the Arrhenius rate parameters for the unimolecular and bimolecular reactions, and standard enthalpies of formation, standard entropies, and heat capacities for all the products and intermediates. A kinetic analysis of gas-phase reactions, within the context of a plug-flow reactor model, accounts qualitatively for the formation of major products observed experimentally in the thermal degradation of the condensed-phase leucine. Among notable N-containing species, the model predicts the prevailing of NH₃ over HCN and HNCO, in addition to corresponding appreciable concentrations of amines, imines, and nitriles. Our detailed kinetic investigation illustrates a negligible contribution of the self-condensation reactions of leucine in the gas phase.     

Determination of trace amounts of chromium (VI) by flow injection analysis with chemiluminescence detection

A new sensitive chemiluminescence (CL) method combined with continuous flow injection analysis is described for the determination of Cr(VI). Strong CL signals were generated by Cr(VI)-catalysed oxidation of gallic acid in the presence of potassium permanganate and hydrogen peroxide. Effects of reagent concentrations, temperature, pH, flow rates, mixing coil length and mixing flow sequences on the chemiluminescence intensity were studied. Under the optimised experimental conditions, the relationship between the logarithm of concentration (log?C) of Cr(VI) and the logarithm of intensity (log?I) is linear over the range of 2?×?10^?11 – 5?×?10^?4?mol?L^?1, with the detection limit (3σ) of 4?×?10^?12?mol?L^?1. Relative standard deviation of ten measurements of 1?×?10^?9?mol?L^?1 Cr(VI) is 1.7%. This flow injection analysis (FIA) system proved to be able to analyse up to 40 samples h^?1. Effects of various interferences possibly present in the water samples were investigated. Most cations and anions, as well as organic compounds, did not interfere with the determination of Cr(VI) in water samples. The experimental results obtained for chromium in reference materials were also in good agreement with the certified values.     

A study of heat and mass transfer of Non-Newtonian fluid with surface chemical reaction

Considering the significance of non-Newtonian fluid usage in manufacturing such as molten plastics, polymeric materials, pulps, and so on, significant efforts have been made to investigate the phenomenon of non-Newtonian fluids. In this article the influences of heat and mass transfer on non-Newtonian Walter's B fluid flow over uppermost catalytic surface of a paraboloid is encountered. An elasticity of the fluid layer is considered in the freestream together with heat source/sink and has the tendency to cause heat flow in the fluid saturated domain. The flow problem of two-dimensional Walter's B fluid is represented using Law of conservation of mass, momentum, heat, and concentration along with thermal and solutal chemical reactive boundary conditions. The governing equations are non-linear partial differential equation and are non-dimensionalized by employing stream function and similarity transformation. The final dimensionless equations yielded are coupled non-linear ordinary differential equations. Furthermore, shooting technique along with RK-4th order method is used to get the numerical results. Graphs and tables are modeled by using MATLAB software to check the effects of Walter's B parameter, Chemical reaction parameter and Thickness parameter on temperature, velocity, and concentration profiles. Tabular analysis shows the results of some physical parameters like skin friction coefficient, Nusselt number and Sherwood number due to the variation of Walter's B parameter, thickness parameter and chemical reactive parameter.     

Biomedical Applications of Scutellaria edelbergii Rech. f.: In Vitro and In Vivo Approach

In the current study, in vitro antimicrobial and antioxidant activities and in vivo anti-inflammatory and analgesic activities of Scutellaria edelbergii Rech. f. (crude extract and subfractions, i.e., n-hexane, ethyl acetate (EtOAc), chloroform, n-butanol (n-BuOH) and aqueous) were explored. Initially, extraction and fractionation of the selected medicinal plant were carried out, followed by phytochemical qualitative tests, which were mostly positive for all the extracts. EtOAc fraction possessed a significant amount of phenolic (79.2 ± 0.30 mg GAE/g) and flavonoid (84.0 ± 0.39 mg QE/g) content. The EtOAc fraction of S. edelbergii exhibited appreciable antibacterial activity against Gram-negative (Escherichia coli and Klebsiella pneumoniae) strains and significant zones of inhibition were observed against Gram-positive bacterial strains (Bacillus subtilis and Staphylococcus aureus). However, it was found inactive against Candida Albicans and Fusarium oxysporum fungal strains. The chloroform fraction was the most effective with an IC₅₀ value of 172 and 74 µg/mL against DPPH (1,1-Diphenyl-2-picryl-hydrazyl) and ABTS assays, in comparison with standard ascorbic acid 59 and 63 µg/mL, respectively. Moreover, the EtOAc fraction displayed significant in vivo anti-inflammatory activity (54%) using carrageenan-induced assay and significant (55%) in vivo analgesic activity using acetic acid-induced writing assay. In addition, nine known compounds, ursolic acid (UA), ovaul (OV), oleanolic acid (OA), β-sitosterol (BS), micromeric acid (MA), taraxasterol acetate (TA), 5,3′,4′-trihydroxy-7-methoxy flavone (FL-1), 5,7,4′-trihydroxy-6,3′-dimiethoxyflavone (FL-2) and 7-methoxy catechin (FL-3), were isolated from methanolic extract of S. edelbergii. These constituents have never been obtained from this source. The structures of all the isolated constituents were elucidated by spectroscopic means. In conclusion, the EtOAc fraction and all other fractions of S. edelbergii, in general, displayed a significant role as antibacterial, free radical scavenger, anti-inflammatory and analgesic agents which may be due to the presence of these constituents and other flavonoids.     

Form Factor of Proton Predicted Using the Data of ppbar Elastic Scattering at $$\boldsymbol{\sqrt{s}=1.96}$$ eV

Physics of Atomic Nuclei - Based on the behavior of elastic scattering of proton and anti-proton at $$\sqrt{s}=1.96$$ TeV for squared four-momentum transfer $$0.26<{-}t<1.2($$ GeV...     

On the room-temperature ferromagnetism in (ZnO)0.98(MnO2)0.02

Room-temperature ferromagnetism (RTFM) is investigated in the polycrystalline bulk (ZnO)_0.98(MnO₂)_0.02 samples prepared by a modified solid-state sintering route. Successive sintering of a sample was carried out in air at different temperatures in the range of 400-1000 °C. The study of magnetization and phase-investigation in the sample was carried out after each sintering step. The progressive suppression of impurities and the consequent reduction in RTFM is clearly observed in the samples with increase in the sintering temperature up to 800 °C. The subsequent successive sintering of the (ZnO)_0.98(MnO₂)_0.02 sample up to 1000 °C yields fully paramagnetic sample exhibiting wurtzite structure. The studies support the conjecture (Kundaliya et al., Nat. Mater. 3 (2004) 709 [18]) that RTFM in this system has an origin related to a randomly distributed impurity phase produced by local dissolution of ZnO and MnO₂.