E.A. Mohamed

Study of the glassy magnetic behaviour and charge-ordering phase transitions in La0.75Ca0.25FeO3−δ perovskite

Abstract In this work, La0.75Ca0.25FeO3−δ perovskite sample was prepared by the coprecipitation method. The nanoparticle was found to crystallize in the orthorhombic (Pbnm) phase as confirmed by X-ray diffraction (XRD) and transmission electron microscopic (TEM). The oxygen non-stoichiometry (δ) and magnetic states of iron ions (three magnetic sextets and non-magnetic doublet) were investigated by Mössbauer spectroscopy at room temperature (RT). The shape of the magnetic hysteresis loop of the sample reveals the existence of a weak ferromagnetism at RT. The magnetization vs. temperature curves, measured in the 9 to 200 K range, showed that the sample exhibits two magnetic-phase transition temperatures at 29 K (Tg) and 120 K (TCO). The magnetization isotherms, M (H), around these magnetic-phase transition temperatures for the sample are analyzed.

Dielectric and Pyroelectric Properties of BaTiO3 Embedded in Li2B4O7 Glass Matrix

Glass sample with the composition 80 Li2B4O7–20 BaTiO3 (in mol%) was prepared by the conventional melt quenching technique. Amorphous and glassy characteristics of the sample were established via X-ray powder diffraction (XRD) and differential scanning calorimetry (DSC) respectively. The precipitated BaTiO3 nanocrystal phase embedded in the glass sample was identified by transmission electron microscopic (TEM) and infrared absorption spectroscopy. The phase transition (ferroelectric–paraelectric) in the present sample was established through the detailed studies of DSC, dielectric constant, dielectric loss, ac conductivity, dc conductivity and pyroelectric properties. The results demonstrate that the method presented may be an effective way to improvement of pyroelectric properties which is beneficial to the development of pyroelectric detectors.

Multiferroic and exchange bias in La0.85Sr0.15FeO3−δ perovskite nanoparticles

ABSTRACT Multiferroic and exchange bias was observed in La0.85Sr0.15FeO3−δ nanoparticles sample which was prepared by co-precipitation method. These nanoparticles have an average size of about 18.49 nm and orthorhombic phase (Pbnm) with small impurities. The anomalous peaks of the dielectric as a function of temperature indicate that the Neel temperature at TN = 321 K and a ferroelectric to paraelectric transition at TC = 555 K which confirmed by differential scanning calorimetric (DSC). The dielectric response at low frequency is dominated by Debye relaxation behaviour and the resonance behaviour is dominated above 1.7 GHz. Mössbauer spectrum revealed the presence of magnetic ordering temperature (TN) lies above room temperature (RT). Moreover, the oxygen deficient (δ = 0.038) was calculated from Mössbauer spectrum. The hysteresis loop (B-H) of the nanoparticle sample exhibits exchange bias as a result of the exchange coupling at the interface between the ferromagnetic surface with canted spins and the antiferromagnetic core of the particles.

Candesartan and epigallocatechin-3-gallate ameliorate gentamicin-induced renal damage in rats through p38-MAPK and NF-κB pathways: AHMED and MOHAMED

This study pointed to estimate the possible protective impacts of candesartan and/or epigallocatechin‐3‐gallate (EGCG) against gentamicin‐induced nephrotoxicity. The current work revealed that gentamicin significantly elevated relative kidney weight and the serum level of creatinine and urea. Also, renal level of malondialdehyde was significantly increased with a concurrent decrease in renal glutathione‐S‐transferase and superoxide dismutase activities. Moreover, renal levels of nuclear factor‐kappa B (NF‐κB) and p38 mitogen‐activated protein kinase (p38‐MAPK) were increased together with the elevation of tumor necrosis factor‐alpha and interleukin‐1 beta levels after gentamicin treatment. In addition, caspase‐3 expression was elevated, and histological examination revealed extreme alterations enlightening inflammation, degeneration, and necrosis. Pretreatments with candesartan and/or EGCG attenuated gentamicin‐induced nephrotoxicity. Importantly, the altered expression of p38‐MAPK and NF‐κB may play a significant role in the protective mechanisms exerted by candesartan and EGCG. Coadministration of candesartan and EGCG exhibited more profound response compared with the monotherapy.

Protective effect of irbesartan against doxorubicin-induced nephrotoxicity in rats: implication of AMPK, PI3K/Akt, and mTOR signaling pathways

Nephrotoxicity is one of the serious undesirable effects related to doxorubicin (DOX). Herein, we have investigated the potential protective effect of irbesartan (IRB) against chronic nephrotoxicity induced by DOX, and the implication of different mechanistic pathways underlying these effects. Rats were treated with either DOX (2.5 mg/kg i.p., 3 times/week) for 2 weeks, and (or) IRB (40 mg/kg, daily) for 3 weeks. IRB prohibited nephrotoxicity induced by DOX, which was evident by the increase in blood urea nitrogen and creatinine levels and histopathological changes. IRB improved DOX-induced alterations in oxidative status by diminishing lipid peroxidation and upregulating the antioxidant enzymes. Also, upon DOX treatment, the renal expression of tumor necrosis factor-α, interleukin-6, and caspase-3 were significantly increased; IRB diminished DOX-induced alterations in these parameters. Moreover, DOX significantly decreased the expression level of AMP-activated protein kinase (AMPK). Meanwhile, DOX induced activation of phosphatidylinositol 3-kinase (PI3K)/protein kinase B (Akt/PKB) and mammalian target of rapamycin (mTOR) pathways that cross talked with AMPK. On the contrary, IRB successfully counterbalanced all these effects. Collectively, these outcomes suggest that the modulation of AMPK, PI3K, Akt, and mTOR pathways plays a critical role in conferring the protective effects of IRB against DOX nephrotoxicity.