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This investigation involves the synthesis and study of dielectric, structural and impedance properties of polycrystalline Bi(Ni 2/5 Ti 2/5 Fe 1/5)O 3 (symbolized as BNTF) nano-ceramic. The BNTF polycrystalline sample was fabricated through the use of a conventional solid-state reaction route. X-ray structural examination reveals that the parent compound (i.e., BiFeO 3) crystallizes in the rhombohedral structure (space group-R3c) while that the BNTF compound crystallizes in orthorhombic symmetry. The substitution of NiTiO 3 into BiFeO 3 enhances various properties and reduces electrical leakage current. The average crystallite size is calculated to be 29 nm. The room temperature textures and surface morphologies of the specimen were verified by field-emission scanning electron microscope, and show uniform grains distribution on sample surfaces. Dielectric parameters (constant and tangent-loss) and impedance spectroscopy parameters of NiTiO 3 modified BiFeO 3 compound were investigated over a wide temperature range (25–500 °C) at different frequency (25 kHz-500 kHz), which offers several interesting features of BNTF material suitable for further device applications. [ABSTRACT FROM AUTHOR]

Abstract In this communication, studies of basic crystal structure, microstructure, dielectrics, impedance, conductivity, electric polarization and magnetization of an eco-friendly distorted perovskite Bi(Co 0.35 Ti 0.35 Fe 0.30)O 3 (abbreviate as BCTF70/30) have been reported. Analysis of crystal structure, phase formation and composition of the specimen, carried out through the powder X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDXS) techniques, confirms the formation of single-phase orthorhombic system at room temperature. The surface morphology of the compound, evaluated through the field emission scanning electron microscope, displayed the formation of high-density sample with uniform distributions of grains of varying dimensions. The phonon mode, intensity, location and width of the Raman peaks were analyzed using the Raman spectroscopy. The correlation between the frequency-temperature dielectric parameters, impedance parameters and electrical conductivity with structure-microstructure has been established. The influence of grain and grain boundary on the resistive and capacitive features has been examined through impedance spectroscopy formalism with an idealized simulated circuit. Studies of impedance spectroscopic show the semiconductor nature (i.e., negative temperature coefficient of resistance) and the non-Debye type relaxation. Polarization versus electric field analysis of BCTF70/30 sample displays enhanced value of remnant polarization as compared to that of BFO. The magnetic hysteresis loop analysis also exhibits significant improvement in the magnetization values of the compound. Accordingly, based on such enhancement of remnant polarization and magnetic parameters, we assumed that an eco-friendly material of BCTF70/30 could considered as promising material for some new electronic devices. [ABSTRACT FROM AUTHOR]

Neisseria gonorrhoeae is an obligate human pathogen and the causative agent of the sexually-transmitted disease gonorrhea. The control of this disease has been compromised by the increasing proportion of infections due to antibiotic-resistant strains, which are growing at an alarming rate. The MtrCDE tripartite multidrug efflux pump, belonging to the hydrophobic and amphiphilic efflux resistance-nodulation-cell division (HAE-RND) family, spans both the inner and outer membranes of N. gonorrhoeae and confers resistance to a variety of antibiotics and toxic compounds. We here report the crystal structure of the inner membrane MtrD multidrug efflux pump, which reveals a novel structural feature that is not found in other RND efflux pumps. [ABSTRACT FROM AUTHOR]

Active efflux of antimicrobial agents is one of the most important strategies used by bacteria to defend against antimicrobial factors present in their environment. Mediating many cases of antibiotic resistance are transmembrane efflux pumps, composed of one or more proteins. The Neisseria gonorrhoeae MtrCDE tripartite multidrug efflux pump, belonging to the hydrophobic and amphiphilic efflux resistance-nodulation-cell division (HAE-RND) family, spans both the inner and outer membranes of N. gonorrhoeae and confers resistance to a variety of antibiotics and toxic compounds. We here describe the crystal structure of N. gonorrhoeae MtrE, the outer membrane component of the MtrCDE tripartite multidrug efflux system. This trimeric MtrE channel forms a vertical tunnel extending down contiguously from the outer membrane surface to the periplasmic end, indicating that our structure of MtrE depicts an open conformational state of this channel. [ABSTRACT FROM AUTHOR]