Showing papers by "Nikesh A. Shah published in 2018"

Mechanism of Anti-bacterial Activity of Zinc Oxide Nanoparticle Against Carbapenem-Resistant Acinetobacter baumannii.

Abstract: Acinetobacter baumannii is a multi-drug resistant opportunistic pathogen, which causes respiratory and urinary tract infections. Its prevalence increases gradually in the clinical setup. Carbapenems (beta-lactam) are most effective antibiotics till now against A. baumannii, but the development of resistance against it may lead to high mortality. Therefore, it is of utmost importance to develop an alternative drug against A. baumannii. In the present study, we have synthesized ZnO nanoparticle (ZnO-NP) and characterized by X-ray diffraction, Fourier transform infrared (FTIR) spectroscopy and UV-Visible spectroscopy. Prepared ZnO-NPs have the size of 30 nm and have different characteristics of ZnO-NPs. Growth kinetics and disk diffusion assay showed that ZnO-NP demonstrated good antibacterial activity against carbapenem resistant A. baumannii. We have also investigated the mechanism of action of ZnO-NPs on the carbapenem resistant strain of A. baumannii. The proposed mechanism of action of ZnO involves the production of reactive oxygen species, which elevates membrane lipid peroxidation that causes membrane leakage of reducing sugars, DNA, proteins, and reduces cell viability. These results demonstrate that ZnO-NP could be developed as alternative therapeutics against A. baumannii.

An empirical model for magnetic field dependent resistivity and magnetoresistance in manganites: application on polycrystalline charge-ordered La0.4Gd0.1Ca0.5MnO3

Abstract: In this paper, we have investigated the electrical and magnetic response of a La0.4Gd0.1Ca0.5MnO3 polycrystalline sample. This sample seems to exhibit fascinating phenomena like charge ordering, magnetic phase separation, training effects and kinetic arrest. It also shows colossal values of negative magnetoresistance (∼91.7% at 96 K under 1 T applied magnetic field), which raises the possibility of using this sample for technological applications. We have also proposed, in this work, a new empirical model to describe the evolution of resistivity and magnetoresistance as a function of magnetic field. This model was successfully tested on the La0.4Gd0.1Ca0.5MnO3 sample in spite of its complicated magnetic behavior, which suggests the use of this model for other magnetic samples in order to check its validity.

Magnetoelectric properties of Co-doped BiFeO3 nanoparticles

Abstract: The magnetoelectric (ME) properties of sol–gel grown BiFe0.95Co0.05O3 (BFCO) nanoceramics, with different sizes, were investigated at room-temperature. X-ray diffraction (XRD) measurement was performed to investigate structural properties of the samples understudy. Magnetic field-dependent dielectric permittivity has been systematically investigated in the frequency range of 20 Hz to 1 MHz. To ensure the origin of magnetodielectric response, the magnetoimpedance (MI) spectroscopy was adopted using equivalent circuit model. The a.c. conductivity was found to obey the Jonscher’s universal power law. The modifications in spiral spin structure in the BFCO nanoparticles with size less than ∼62 nm significantly affect the ME coupling parameters.

Role of Gallium in the charge transport mechanisms for La0.67Ca0.33Mn1–xGaxO3 manganites

Abstract: In this communication, we report the results of the studies on structural, transport and magnetoresistance (MR) properties of nonmagnetic Ga – substituted La0.67Ca0.33Mn1–xGaxO3 (LCMGO) manganites synthesized using conventional ceramic route. Rietveld refined XRD patterns shows that all the samples possess single phasic nature without any detectable impurity. Resistivity behavior shows a systematic variation with Ga3+ – content (x) while metal to insulator transition temperature (TP) shifts towards lower temperature which has been discussed in the light of zener double exchange (ZDE) mechanism and magnetic lattice distortion due to nonmagnetic ion substitution. Observation of low temperature resistivity minima behavior has been explained in the context of electron – electron scattering mechanism. Various transport models and mechanisms have been employed to understand the charge transport in metallic and semiconducting regions of all LCMGO samples. Temperature and Field dependent MR studies reveal intrinsic and extrinsic MR contributions in presently studied LCMGO manganites.