Browsing by Author "Preeti Lahiri"

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Amyloid, cholinesterase, melatonin, and metals and their roles in aging and neurodegenerative diseases
(Blackwell Publishing Inc., 2005) Debomoy K. Lahiri; De-Mao Chen; Preeti Lahiri; Steve Bondy; Nigel H. Greig
The aging brain shows selective neurochemical changes involving several neural cell populations. Increased brain metal levels have been associated with normal aging and a variety of diseases, including Alzheimer's disease (AD). Melatonin levels are decreased in aging, particularly in AD subjects. The loss of melatonin, which is synthesized by the pineal gland, together with the degeneration of cholinergic neurons of the basal forebrain and the deposition of aggregated proteins, such as the amyloid β peptides (Aβ), are believed to contribute to the development of cognitive symptoms of dementia. Aging and its variants, such as AD, should be viewed as the result of multiple "hits," including alterations in the levels of Aβ, metals, cholinesterase enzymes, and neuronal gene expression. Herein, we present evidence in support of this theory, based on several studies. We discuss melatonin's neuroprotective function, which plays an important role in aging, prolongation of life span, and health in the aged individual. It interacts with metals and, in some cases, neutralizes their toxic effects. Dietary supplementation of melatonin restores its age-related loss. In mice, an elevated brain melatonin significantly reduced levels of potentially toxic Aβ peptides. Thus, compensation of melatonin loss in aging by dietary supplementation could well be beneficial in terms of reducing metal-induced toxicity, lipid peroxidation, and losses in cholinergic signaling. We propose that certain cholinesterase inhibitors and the NMDA partial antagonist memantine, which are FDA-approved drugs for AD and useful to boost central nervous system functioning, can be made more effective by their combination with melatonin or other neuroprotectants. Herein, we highlight studies elucidating the role of the amyloid pathway, metals, melatonin, and the cholinergic system in the context of aging and AD. Finally, melatonin is present in edible plants and walnuts, and consuming foodstuffs containing melatonin would be beneficial by enhancing the antioxidative capacity of the organisms. © 2005 New York Academy of Sciences.
Melatonin, metals, and gene expression: Implications in aging and neurodegenerative disorders
(New York Academy of Sciences, 2004) Debomoy K. Lahiri; Demao Chen; Preeti Lahiri; Jack T. Rogers; Nigel H. Greig; Stephen Bondy
Melatonin is a hormone secreted by the pineal gland, mostly in the dark period of the light/dark cycle, with corresponding fluctuations reflected in the plasma melatonin levels. This hormone plays a critical role in the regulation of various neural and endocrine processes that are synchronized with daily change in photoperiod. Abnormal melatonin levels are associated with metabolic disturbances and other disorders. Melatonin potentially plays an important role in aging, prolongation of life span, and health in the aged individual. It may exert a beneficial action on neurodegenerative conditions in those with debilitating diseases. It interacts with metals and, in some cases, neutralizes their toxic effects. Levels of melatonin decrease with aging in mice. Its dietary supplementation has recently been shown to result in a significant rise in levels of endogenous melatonin in serum as well as all other tissue samples tested. The effects of dietary melatonin have been studied in the brain of mice with regard to nitric oxide synthase, synaptic proteins, and amyloid β peptides (Aβ), which are involved in amyloid deposition and plaque formation in Alzheimer's disease (AD). Melatonin supplementation has no significant effect on cerebral cortical levels of nitric oxide synthase or synaptic proteins, such as synaptophysin and SNAP-25. Notably, however, elevated brain melatonin levels resulted in a significant reduction in levels of toxic cortical Aβ of both 40- and 42-aminoacid forms. Taken together, these results suggest that dietary melatonin supplementation may slow the neurodegenerative changes associated with brain aging and that the depletion of melatonin in the brain of aging mice may, in part, account for this adverse change. ©2004 New York Academy of Sciences.
Physico-chemical properties and catalytic activities of the spinel series MnxFe3-xO4 towards peroxide decomposition
(1995) Preeti Lahiri; Susanta K. Sengupta
Samples of the spinel series, MnxFe3-xO4 (O ≤ x ≤ 3), have been synthesized by the hydroxide coprecipitation technique and characterised by chemical analysis; XRD and SEM techniques, and measurements of their BET specific surface areas, saturation magnetisations and electrical resistivities. The specimens with values of x ≤ 1.5 are single-phase cubic spinels and those with x > 1.5 are two-phase cubic and tetragonal spinels. The relative catalytic activities of the specimens towards the decomposition of H2O2 in both alkaline and neutral media, measured on the basis of the energies of activation, a microstructure-independent parameter, and the rate constants normalised to unit BET surface area, a microstructure normalised parameter, follow the order, (given as values of x) 1.45 > 2.5 ≈ 2.0 > 1.0 > 1.2 > 0.8 > 0.5. All the MnxFe3-xO4 prepared specimens are potential substitutes for CoFe2O4, the high-performance catalyst for the decomposition of H2O2; the specimen with x = 1.45 is the most powerful and is significantly more active than CoFe2O4. The activity appears to depend on the availability and efficacy of redox conversion of redox conversion of MnII centres in the sublattices of the MnxFe3-xO4 catalysts.
Spectroscopic, Magnetic and Morphological studies of MgFe2O4 Nanopowder; [Спектроскопічні, магнітні та морфологічні дослідження нанопорошку MgFe2O4]
(Precarpathian National University, 2023) Farhana Naaz; Preeti Lahiri; Chanda Kumari; Hemant Kumar Dubey
Spinel type nano ferrite compound MgFe2O4 was synthesized through sol gel technique using metal nitrates as precursors. The phase composition, morphology and elemental analysis of magnesium ferrite (MgFe2O4) were performed by X-ray diffraction, fourier transform infrared, atomic force microscopy, energy dispersive x-ray and scanning electron microscopy, analyses. The sample's X-ray diffraction pattern verifies the existence of single phase material, with the size of its crystallites estimated to be 39.9 nm. Fourier transform infrared examination supported metal-oxygen vibrations corresponding to tetrahedral and octahedral sites, respectively. From scanning electron microscopy image, grain size obtained about 97.7 nm. Raman spectra of the sample shows five Raman active modes (A1g + Eg + 3F2g), which is compatible with the spinel structure. Magnetic measurement study at room temperature shows a hysteresis loop behaviour with a low saturation magnetization value, 27.192 emu g-1 and a small coercivity value. The optical band gap determined using UV-visible transmittance spectra. Additionally, X-ray photoelectron spectroscopy are used to confirm oxidation states and explore the chemical composition of the sample. © The Author(s) 2023.
Structural and magnetic properties of MgFe2O4 nanopowder synthesized via co-precipitation route
(Springer Nature, 2020) Farhana Naaz; Hemant Kumar Dubey; Chanda Kumari; Preeti Lahiri
Mg ferrite was successfully synthesized by adopting a simple co-precipitation route. A physical property of Mg ferrite has been investigated employing XRD, FTIR, SEM, EDS, AFM and Raman spectroscopic techniques. The XRD results indicated the formation of single phase spinel ferrite with crystalline size of 36 nm. FTIR results confrmed ferrite tetrahedral (580 cm−1) and octahedral sites (430 cm−1) metal oxygen vibrations. The Raman result revealed the well defined Raman active modes of synthesized sample. Scanning electron microscopic (SEM) studies revealed nano crystalline nature of the sample. An elemental composition of the sample was studied by energy dispersive spectroscopy (EDS). Crystallite size, X-ray density, hopping length, and magnetic properties of the product are also reported. AFM provides surface roughness. The magnetic hysteresis curves clearly indicate the soft nature of the prepared nanoferrite. The Raman spectra shows five Raman active modes (A1g + Eg + 3F2g) which are expected in the spinel structure and Raman spectra has a very good agreement with reported data. Various magnetic parameters such as saturation magnetization (Ms), and remanence (Mr) and coerciviy (Hc) are obtained from the hysteresis loops. © 2020, Springer Nature Switzerland AG.
Structural and optical properties of nanosized Co substituted Ni ferrites by coprecipitation method
(Taylor and Francis Ltd., 2020) Chanda Kumari; Hemant Kumar Dubey; Farhana Naaz; Preeti Lahiri
Nano crystalline powder of Co–Ni ferrites compounds having the chemical formula Ni1-xCoxFe2O4 with x = 0.0, 0.25, 0.5, 0.75 and 1.0 were prepared by co-precipitation method. The nanoparticles were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and Scanning Electron Microscopic (SEM) techniques. XRD studies confirmed the formation of single phase spinel structure with space group of (Formula presented.). Debye-Scherrer method was applied to determine average crystallite size and the value was found to be in the range of 23–66 nm. Elemental composition characterizations of the prepared samples were performed by Energy Dispersive Spectroscopy (EDS) which shows the presence of Ni, Co, Fe and O. The optical band gap (Eg) of Ni–Co ferrite samples was determined by means of UV–visible spectra. The optical band gap of the prepared samples have been calculated using Tauc plots and have been found to decrease with increase in Co2+ content from 3.66 to 3.58 eV. © 2020, © 2020 Informa UK Limited, trading as Taylor & Francis Group.
Structural investigations on nickel substituted zinc magnesium ferrites nanoparticles formed via co-precipitation method
(Elsevier B.V., 2024) Farhana Naaz; Preeti Lahiri; Vijay Kumar Mishra; Hemant Kumar Dubey; Pankaj Kumar Tripathi; Ehsan Shakerzadeh
The present study provides a comprehensive structural investigation on Mg0.5Zn0.5−xNixFe2O4 nano-ferrites. Nano-crystalline Mg0.5Zn0.5−xNixFe2O4 (x = 0.0,0.1,0.2,0.3,0.4) powder samples were synthesized using co-precipitation process followed by calcinations at 600 °C for 6 h. The purity and phase of thus prepared samples were confirmed using X-ray Diffraction, Atomic Force Microscopy and X-ray Photoelectron Spectroscopy techniques. The average crystallite size, determined using the Debye-Scherrer method, was estimated to be between 17 and 26 nm. The average particle size ranged from 26.9 nm to 13.1 nm. It was evident that as the nickel concentration increases in Mg-Zn-Ni ferrite, the average grain size decreases from 26.1 nm to 10.9 nm, indicating denser samples with higher nickel concentrations. The ferrites were found to be porous and at the nanoscale, with sizes less than 30 nm. Raman studies supported the presence of iron-oxide phases, confirming the spinel structure with tetrahedrally and octahedrally occupied iron sites. The low coercivity (Hc) values observed in the hysteresis loops indicate soft magnetic characteristics for all samples. This is advantageous for applications in recording heads, inductor and transformer cores, magnetic shielding, the high-frequency range, particularly in deflection yoke rings, microwave devices, and drug delivery. © 2024 Elsevier B.V.
Synthesis and Characterization of Nickel-Based Cobalt Ferrite Nanopowder
(Wiley-VCH Verlag, 2019) Chanda Kumari; Preeti Lahiri
In the present investigation, nickel-substituted cobalt ferrite (Ni0.5Co0.5Fe2O4) nanoparticles are synthesized using chemical co-precipitation method. Sodium hydroxide (NaOH) base is used as precipitant. The formation of single-phase cubic structure and the average crystalline sizes are evaluated by X-ray diffraction technique. The microstructural features is examined by scanning electron microscopy. The high- and low-frequency absorption bands (600–400 cm−1) of Ni0.5Co0.5Fe2O4 are investigated using Fourier-transform infrared spectroscopy analysis. © 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Synthesis of nanosized cadmium ferrite and assaying its magnetic and dielectric properties by analytical and physical techniques
(Carl Hanser Verlag, 2020) Hemant Kumar Dubey; Preeti Lahiri
Our goal is to investigate the physical, magnetic and dielectric properties of cadmium ferrite nanoparticles. Here we report the synthesis of nanosized cadmium ferrite (CdFe2O4) spinel ferrite by the sol-gel process using citric acid as a complexing agent. We assessed the properties of nano-CdFe2O4 by a variety of analytical and physical techniques. X-ray diffraction and Fourier transform infrared spectroscopy were performed to confirm spinel phase formation. Surface morphology images and compositional features were obtained using electron microscopy and other imaging techniques. Transmission electron microscopy analysis revealed the formation of nanoparticles with an average particle size of 40 nm. The magnetic properties were characterized by a highly sensitive magnetometer system (SQUID VSM) at room temperature revealing that the sintered sample of cadmium ferrite nanoparticles is ferromagnetic. We also studied dielectric behavior of the sintered pellet of the sample. We determined the frequency dependence of the dielectric permittivity, the loss factor and the impedance of the samples in the frequency range from 100 Hz to 20 MHz, at temperatures from 308-428 K at an interval of 40°C. The dielectric behavior of ferrites is explained by the interface polarization, arising from the heterogeneous nature of its structure. Further research, both in terms of the preparation and characterization of ferrites, is warranted to better understand the nature and application of ferrites. © 2020 Carl Hanser Verlag GmbH & Co. KG.
Synthesis, Structural, and Magnetic Properties of Mn0.5Zn0.5Fe2O4 Nanoparticles by Sol–Gel Route
(Wiley-VCH Verlag, 2019) Hemant Kumar Dubey; Preeti Lahiri
In this work, the cubic spinel manganese-zinc ferrite nanoparticle is synthesized by the sol–gel auto combustion method. It is the simple chemical route and low-cost method for the formation of manganese zinc ferrite nanoparticles. Structural and morphological studies of the synthesized manganese-zinc ferrite nanoparticles are done by X-ray diffraction, Fourier transform infrared spectroscopy (FTIR), and scanning electron microsccopy (SEM). The X-ray diffraction results indicate that the ferrite sample has a cubic spinel type structure with Fd3m space group. The average crystallite size of the synthesized manganese zinc ferrite nanoparticles is found to be 34 nm as determined by Debye–Scherrer equation. Two well-known absorption bands at 467 and 558 cm−1, in FTIR spectroscopy data also confirm the cubic spinel structure in the prepared samples. Morphological studies by SEM exposed formation of largely agglomerated and well-defined nanoparticles of the sample. From the magnetization data, parameters like magnetization, coercivity, remanance magnetization, and squareness ratio are calculated. © 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Synthesis, structural, dielectric and magnetic properties of Cd2+ based Mn nanosized ferrites
(Taylor and Francis Ltd., 2021) Hemant Kumar Dubey; Preeti Lahiri
Cadmium-substituted manganese ferrite nanoparticles with the general formula Mn1‒xCdxFe2O4(x = 0.0, 0.2, 0.4, 0.6, 0.8) were synthesised by the citrate‒gel auto combustion method. X-ray diffraction patterns revealed formation of a cubic phase spinel structure with (Formula presented.) space group. FT-IR confirms stretching vibration of tetrahedral and octahedral interstitial sites in the spinel lattice. Microstructural features observed by scanning electron microscopy (SEM) demonstrate that agglomerated particles were formed with an increase in average grain size according to Cd2+ content. Elemental composition features and particle size of samples were examined by energy dispersive spectroscopy (EDX) and Transmission electron microscopy (TEM). The magnetic properties characterised by the highly sensitive magnetometer system (SQUID VSM) at room temperature revealed ferromagnetism in all the samples. The values of dielectric permittivity (Formula presented.) and tangent loss ((Formula presented.)) decreased exponentially at low frequencies and were in accordance with the Maxwell–Wagner model and Koop’s theory. © 2020 Informa UK Limited, trading as Taylor & Francis Group.
The effect of dysprosium on nickel–cadmium spinel ferrites
(Taylor and Francis Ltd., 2021) Hemant Kumar Dubey; Preeti Lahiri
In the present work, Ni0.6Cd0.4Dy x Fe2-xO4 (x = 0.0, 0.05, 0.10, 0.15, 0.20) nanoparticles (NPs) were synthesized by using sol–gel method. X-ray diffraction (XRD) patterns confirmed that the pure and dysprosium substituted Ni–Cd ferrites are in single-phase spinel structures, while a trace of DyFeO3 appears as a minor phase for higher concentrations (x = 0.10, 0.15 and 0.20). The Debye–Scherrer’s method and Williamson–Hall (W-H) method were used to evaluate the crystallite sizes and lattice strain. Scanning electron microscope (SEM) images show that reduction of grain size with Dy3+ content. Elemental composition features of samples were examined by Energy-dispersive X-ray spectroscopy (EDS). The average particles size estimated from transmission electron microscopy (TEM) analysis is in good agreement with results obtained from XRD. The results showed that saturation magnetization (M s) decreases and coercivity (H c) increases with an increase in Dy3+ concentrations. The dielectric constant was found to decrease with increasing Dy content in Ni–Cd ferrites. © 2021 Informa UK Limited, trading as Taylor & Francis Group.