Browsing by Author "Kumar, Devendra"
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PublicationArticle An Extension of Exponentiated Gamma Distribution: A New Regression Model with Application(Pleiades Publishing, 2022) Kumar, Devendra; Sharma, Vikas KumarAbstract: In this paper, we introduce a two parameter extension of exponentiated gamma distribution. We explicitly derive the closed form expressions of the moments, mode and quantiles of the proposed distribution. L-moments and coefficients of skewness and kurtosis are obtained using the quantile function. Other important properties including identifiability, entropy, stochastic orderings, stress-strength reliability and differential equations associated with the distribution are also discussed. We briefly describe different estimation procedures namely, the method of maximum likelihood estimation, moment estimation, maximum product of spacings estimation, ordinary and weighted least squares estimation, and Cramér–von-Mises estimation along with an extensive simulation study for comparing their performance. An application of modeling trees growth data is presented to show the adequacy of the proposed distribution over the distributions existing in the literature. A parametric regression model based on the proposed distribution is introduced and used to establish a regression model for the volume, diameter and height of the trees. © 2022, Pleiades Publishing, Ltd.PublicationBook Analytical Impedance Spectroscopy: Basics and Applications(CRC Press, 2023) Pandey, Lakshman; Kumar, Devendra; Parkash, Om; Pandey, ShukdevThis book introduces the subject of impedance spectroscopy starting from fundamentals through to latest applications in areas such as ceramics, piezoelectric, sensors, agriculture, food quality control, medical diagnostics, cancer research, and so forth. Within the ambit of impedance spectroscopy, plots simulated for useful equivalent circuit models, design of sample holder, necessary precautions to be taken during measurement are described. It further discusses development of softwares for analysis of experimental data and choice of the most appropriate equivalent circuit model. All the materials are supported by problems, answers, appendices and references. Features: Includes fundamentals, equivalent circuit modeling and analysis of data related to impedance spectroscopy. Presents experimental measurements in a nuts-and-bolts approach. Includes derivation of expressions for some selected models and values of immittance functions as frequency of measurements tend to zero and to infinity. Provides clear recipe for beginners for proceeding toward developing equivalent circuit models. Describes computer program for complex nonlinear least squares fitting with example of program IMPSPEC.BAS This book is aimed at senior undergraduate/graduate students and researchers in materials engineering, mechanical engineering, electrical engineering, chemical engineering, biomedical engineering, construction engineering, physics, chemistry, medical diagnostics, agriculture and dairy. © 2024 Lakshman Pandey, Devendra Kumar, Om Parkash and Shukdev Pandey.PublicationConference paper ANOMALOUS DIELECTRIC BEHAVIOUR IN PbO-BaO-TiO//2-B//2O//3-SiO//2 GLASSES.(Indian Ceramic Soc, 1986) Kumar, Devendra; Parkash, Om; Pandey, Lakshman; Rajgopalan, R.Glass ceramics in this system show ferroelectric behaviour due to crystallisation of either BaTiO//3 or PbTiO//3 microcrystalline phase in the glass. The dielectric behaviour has been studied as a function of temperature at different frequencies. These glasses show a relatively high dielectric constant which increases slowly up to the glass transition temperature and thereafter it increases sharply showing an anomalous dielectric peak at around 680 K. The dielectrically soft local atomic configuration of randomly distorted TiO//6 octahedra remain identifiable in the glassy matrix. Strong dipolar forces between these units are responsible for the ferroelectric - paraelectric phase transition leading to an anomalous peak in dielectric constant versus temperature curve. The increase in dielectric constant is attributed to glass softening.PublicationReview Biomolecular basis of matrix metallo proteinase-9 activity(Future Medicine Ltd., 2018) Swetha, Rayala; Gayen, Chandrim; Kumar, Devendra; Singh, Tryambak Deo; Modi, Gyan; Singh, Sushil KumarMatrix metalloproteinases (MMPs) are structurally related endopeptidases. They are also known as metzincins due to their interaction with zinc ion of the conserved methionine (Met) at the active site. MMPs play an important role in physiological and signaling processes of wound healing, bone resorption and angiogenesis. The structure of MMPs consists of signal peptide, propeptide, catalytic domain, hinge region and hemopexin-like domain. MMP-9 shares high structural and functional similarities with MMP-2, therefore designing selective MMP-9 inhibitors (MMPIs) is challenging. The selectivity can be achieved by targeting S2 subsite of MMP-9 that is having difference with MMP-2. Further, targeting its exosite and protein disulfide isomerase may also provide selective MMPIs. The review highlights the molecular features and basis of MMP-9 enzyme action. The MMPIs reported in the recent years have also been included. © 2018 2018 Newlands Press.PublicationArticle Centella asiatica Alleviates AlCl3-induced Cognitive Impairment, Oxidative Stress, and Neurodegeneration by Modulating Cholinergic Activity and Oxidative Burden in Rat Brain(Springer, 2022) Firdaus, Zeba; Kumar, Devendra; Singh, Sushil Kumar; Singh, Tryambak DeoAluminum (Al) is linked to the development of many neurological disorders such as Alzheimer’s disease (AD), Parkinson’s disease, and autism. Centella asiatica (CA) is a regenerating herb traditionally used to stimulate memory. This study was designed to assess the neuroprotective role of ethanolic extract of CA (CAE) in AlCl3-induced neurological conditions in rats. Adult rats were chronically treated with AlCl3 (100 mg/kg b.w./day) for 60 days to establish the dementia model, and co-administration of CAE was evaluated for its ability to attenuate the toxic effect of AlCl3. CAE was given orally at a dose of 150 and 300 mg/kg b.w./day, for 60 days. The behavioral performances of rats were tested through Y-maze and open field tests. Lipid peroxidation, superoxide dismutase, and catalase activity were evaluated to measure oxidative stress; and acetylcholinesterase (AChE) activity was assessed to evaluate cholinergic dysfunction in the rat brain. H&E staining was used to assess structural abnormalities in the cortex and hippocampus. The result showed that AlCl3 induces cognitive dysfunction (impaired learning and memory, anxiety, diminished locomotor activity), oxidative stress, cholinergic impairment, and histopathological alteration in the rat brain. Co-administration of CAE with AlCl3 markedly protects the brain from AlCl3-induced cognitive dysfunction, oxidative stress, AChE activity, and cytoarchitectural alterations. Furthermore, 15 days CAE treatment after 45 days AlCl3 administration markedly ameliorates the AlCl3-induced neurotoxicity indicating its potential for therapeutic use. Graphical abstract: [Figure not available: see fulltext.] © 2021, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.PublicationErratum Corrigendum to “Preparation, characterization and electrical properties of alkali metal ions doped co-polymers based on TBF” [Mater. Sci. Eng. B 262 (2020) 114687](S092151072030194X)(10.1016/j.mseb.2020.114687)(Elsevier Ltd, 2021) Tiwari, Rudramani; Sonker, Ekta; Kumar, Devendra; Kumar, Krishna; Adhikary, Pubali; Krishnamoorthi, S.The authors regret to inform that in our published manuscript unfortunately we forgot to acknowledge one funding agency i.e. Council of Scientific and Industrial Research, New Delhi, India, which provides stipend to one of the author (First Author) Rudramani Tiwari. So we need to include “Rudramani Tiwari is grateful to Council of Scientific and Industrial Research (09/013(0874)/2019-EMR-I), New Delhi, India, for the financial support” in the Acknowledgement section. © 2020 Elsevier B.V.PublicationArticle DC conduction behaviour of niobium doped barium stannate(2005) Singh, Prabhakar; Parkash, Om; Kumar, DevendraA few compositions with x ≤ 0.100 in the system BaSn1-x NbxO3 have been synthesized by solid-state ceramic method. All these are found to be single phase having cubic structure similar to BaSnO3. Electrical resistivity decreases with increasing niobium concentration up to x = 0.010 and thereafter it increases rapidly for the compositions with x = 0.050 and 0.100. This has been explained in terms of the change in charge compensation behaviour beyond x = 0.010. Measurement of Seebeck coefficient as a function of temperature shows that electrons are the majority charge carriers in compositions with x ≤ 0.010 while compositions with x > 0.010, exhibit p-type conductivity showing that holes are the majority charge carriers. © 2005 Springer Science + Business Media, Inc.PublicationArticle Design, synthesis, characterization, and molecular modeling studies of novel oxadiazole derivatives of nipecotic acid as potential anticonvulsant and antidepressant agents(Birkhauser Boston, 2018) Singh, Ravi Bhushan; Singh, Gireesh Kumar; Chaturvedi, Krishna; Kumar, Devendra; Singh, Sushil Kumar; Zaman, Md. KamaruzA series of fifteen novel nipecotic acid 1,3,4-oxadiazole hybrids were synthesized with the intent to improve the lipophilicity of nipecotic acid and its penetration through the blood—brain barrier (BBB). The structures of the compounds were established by FT-IR, 1H-NMR, 13C-NMR, and elemental analysis. The effect of the synthesized compounds was assessed on motor coordination using the rotarod test in mice. Anticonvulsant activity was evaluated using the subcutaneous pentylenetetrazol (scPTZ) test in mice. Five compounds (5d, 5e, 5g, 5m, and 5o) exhibited significant protection against scPTZ-induced seizures. None of the compounds produced any disruption in motor coordination as observed in the rota-rod test, nor did they elevate the serum levels of biochemical markers related to hepatic and renal toxicity, affirming their relative safety. The derivatives also exhibited significant antidepressant activity, devoid of serotonergic augmentation as assessed using the despair swim test, 5-hydroxytryptophan (5-HTP)-induced head twitch test and learned helplessness test. In in silico docking studies on a homology model on target GABA transporter 1 (GAT1) protein and the most active compound 5e helped to identify critical enzyme-ligand interactions leading to the inhibition of the GAT1 transporter. © 2017, Springer Science+Business Media, LLC.PublicationArticle Development of Na+ ion conducting solid biopolymer electrolytes based on Na-CMC-SPA hydrogel(Elsevier Ltd, 2023) Kumar Verma, Dipendra; Tiwari, Rudramani; Kumar, Devendra; Yadav, Shashikant; Parwati, Km; Adhikary, Pubali; Krishnamoorthi, S.Solid polymer electrolytes based on biopolymers are green and environment-friendly materials. Here, solid biopolymer electrolyte (SBPE) hydrogel based on carboxymethyl cellulose is introduced for Na+ ion-based energy storage material. The synthesized SBPE material is biodegradable and shows excellent strength with good flexibility and high elasticity. SBPE-2 has compact packing with inner porous morphology which is helpful in ionic conduction inside the matrix. The ionic conductivity of electrolyte material was recorded in the range of 10-5 S/cm at room temperature and 10-4 S/cm at higher temperatures (>40 °C). The ionic transference number is found to be > 96% in 510 sec. LSV measurements confirm that the SBPEs material can be used in device fabrication up to 2.3 V. These properties of electrolytes make them a promising material for application in energy storage devices. © 2023 Elsevier B.V.PublicationArticle Dielectric and microstructural behaviour of BaTiO3 sintered in the presence of a crystallizable glass(Kluwer Academic Publishers, 1989) Kumar, Devendra; Sakharkar, P.K.; Parkash, Om; Pandey, Lakshman[No abstract available]PublicationArticle Dielectric and microstructural behaviour of strontium titanate borosilicate glass ceramic system(Springer India, 1995) Thakur, O.P.; Kumar, Devendra; Parkash, O.M.; Pandey, Lakshman65(SrO·TiO2)-35(2SiO2·B2O3) wt% glass was synthesized. Differential thermal analysis study shows one exothermic peak which shifts towards higher temperature with increasing heating rate. Glass ceramics prepared by controlled crystallization of strontium titanate borosilicate glass produce uniform distribution of crystallites in a glassy matrix. Attempt was made to crystallize strontium titanate phase in this glass ceramic. Different phases precipitated out during ceramization have been identified by X-ray diffraction. It appears that due to high reactivity of SrO with B2O3, strontium borate crystallizes as principal phase followed by TiO2 (rutile) and Sr3Ti2O7 phases. Dielectric constant of these glass ceramics was observed to be more or less temperature independent over wide range of temperatures with low values of dielectric constant and dissipation factor. © 1995 The Indian Academy of Sciences.PublicationArticle Dielectric behaviour of glasses and glass ceramics in the system BaO-PbO-TiO2-B2O3-SiO2(Springer India, 1987) Mandal, R.K.; Prasad, Ch. Durga; Parkash, O.M.; Kumar, DevendraGlasses with varying molar ratios of PbO/BaO in the system BaO-PbO-TiO2-B2O3-SiO2 were prepared keeping (BaO + PbO)/TiO2 ratio equal to one. The glasses were ceramized by two-stage heat treatment. X-ray diffraction indicates that PbTiO3 crystallizes in lead-rich glasses while BaTiO3 precipitates in barium-rich compositions. Solid solution (Ba, Pb)TiO3 does not seem to crystallize over the entire range of compositions. Simultaneous presence of PbO and BaO in the initial glass composition reduces the yield of ferroelectric phase. Dielectric properties have been interpreted in terms of microstructural features. © 1987 Indian Academy of Sciences.PublicationArticle Dielectric properties of the system Ca1 -x La x Ti1 -x Co x O3(Springer India, 1988) Durga Prasad, Ch; Tewari, H.S.; Kumar, Devendra; Parkash, OmDielectric behaviour of samples of the system Ca1 -x La x Ti1 -x Co x O3 with x ≤ 0·20 has been studied in the temperature range 300-525 K as a function of frequency. The strong dispersion of e{open} and D observed in these materials indicate the significant contribution of interfacial polarisation to the observed dielectric properties. The interfacial polarisation arises due to the presence of microscopic chemical heterogeneities arising out of the slow diffusion-controlled solid state sintering process used for their preparation. © 1988 the Indian Academy of Sciences.PublicationArticle Dielectric relaxation in valence compensated solid solution Sr0.65La0.35Ti0.65Co0.35O3(IOP, 2000) Dwivedi, R.K.; Kumar, Devendra; Parkash, OmThe valence compensated solid solution Sr0.65La0.35Ti0.65Co0.35O3 has been found to exhibit dielectric relaxor behaviour with a very high value of the dielectric constant. In the present investigation, this composition has been prepared using different processing parameters and routes, viz (a) solid-state sintering at 1350 °C followed by furnace cooling, (b) sintering at 1350 °C followed by annealing at 1000 °C, (c) sintering the sample prepared by the sol-gel route at 1100 °C and (d) sintering the powder prepared by the solid-state ceramic route at 1350 °C with 1 wt% SiO2 as a sintering aid. The dielectric characteristics were measured in the temperature range 300-500 K and frequency range 0.1 kHz-1 MHz. The dielectric characteristics of this composition are greatly influenced by processing parameters and routes. The dielectric relaxation in these materials was studied using impedance and modulus spectroscopic techniques.PublicationArticle Dual mode (upconversion and downshifting) behavior of Ho3+/Yb3+/Bi3+ co-doped YTaO4 phosphor and its application as a security ink(Elsevier Ltd, 2020) Roy, Abhishek; Dwivedi, Abhishek; Mishra, H.; Kumar, Devendra; Rai, S.B.The Ho3+/Yb3+ co-doped YTaO4 phosphor has been synthesized in absence and presence of Bi3+ ion using high temperature solid state reaction method. X-ray diffraction (XRD) patterns confirm the pure phase formation of the synthesized materials. The vibrational behavior of the samples is studied by Fourier Transform Infrared (FTIR) spectroscopy, which suggests the phonon frequency of the material about 625 cm−1. The direct optical band gap of the synthesized phosphor has been calculated using UV–Vis absorption spectrum and the value is found to be 4.80 eV. However, the value of band gap is reduced in presence of Bi3+ ions (4.26 eV). Ho3+/Yb3+ co-doped YTaO4 phosphor shows intense green and weak red upconversion emissions on 980 nm excitation. Ho3+/Yb3+ co-doped YTaO4 phosphor sample also shows intense green and weak red emissions on 450 nm excitation. The downshifting emission is enhanced two to three times in presence of Bi3+ due to metal to metal charge transfer self activation of the host. However, the UC emission intensity almost remains unchanged even in presence of Bi3+. Bi3+ ion also shows an intense broad blue emission on UV excitation. The Ho3+/Yb3+ co-doped YTaO4 phosphor sample has been used for security ink applications in green region via 980 nm excitations and in blue region in presence of Bi3+ via UV (365 nm) excitation. Thus, the dual mode emission of this phosphor is applicable for security ink applications in two different regions. This material also permits one to get an intense tunable radiation from 350 to 650 nm on excitation with 342 nm. There are very few dye lasers, which emit intense tunable radiation in this wavelength region in such a wide wavelength range. © 2019 Elsevier B.V.PublicationArticle Effect of a chelating agent at different pH on the spectroscopic and structural properties of microwave derived hydroxyapatite nanoparticles: A bone mimetic material(Royal Society of Chemistry, 2016) Mishra, Vijay Kumar; Bhattacharjee, Birendra Nath; Kumar, Devendra; Rai, Shyam Bahadur; Parkash, OmIn the present investigation, the effect of a capping agent (EDTA) and pH on the optical and structural characteristics of HAp nanoparticles (NPs) has been studied. Six samples of HAp were synthesized under six different chemical conditions. The HAp specimens were prepared via a microwave irradiation technique (MWIT) in the presence and absence of EDTA at three different pH values 9, 11 and 13. All the samples were calcined at 900 °C. HAp NPs with different sizes and shapes were found to be developed. X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques were employed to determine the crystal structure, crystallite size and bonding parameters of the resulting HAp. The SEM measurements revealed the formation of the different morphologies of the HAp NPs under different physico-chemical conditions. Electron microscopies revealed that the particle size of the samples was in the range of ∼10-200 nm. The TEM results were in good agreement with the SEM results. The study revealed the vital role of the chelating agent (EDTA) in the formation of the pure phase HAp nanostructures. EDTA assisted the formation of needle-like nanorods of HAP and prevented agglomeration. EDTA also prevented carbonate impurities. Carbonate impurities, probably from the atmosphere, were observed in the HAp samples formed without EDTA. Despite the effect of EDTA, the pH of the solution also played a key role in deciding the final morphology of the HAp nanostructures. The samples were also characterized spectroscopically using Fourier transform infrared (FT-IR) spectroscopy and Raman techniques to understand the molecular interactions. The application of laser induced breakdown spectroscopy (LIBS) detected the presence of N and further confirmed the formation of the HAp powders. © 2016 The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.PublicationArticle Effect of annealing on nanoparticles of hydroxyapatite synthesized via microwave irradiation: Structural and spectroscopic studies(Elsevier Ltd, 2014) Mishra, Vijay K.; Rai, Shyam B.; Asthana, Birendra P.; Parkash, Om; Kumar, DevendraNanostrips of hydroxyapatite [Ca10 (PO4)6(OH) 2: (HAp)] were synthesized by microwave irradiation using ethylene diamine tetra-acetic acid (EDTA) as a complexing reagent. Precursor of hydroxyapatite obtained by microwave irradiation was subjected to thermogravimetric and differential thermal analysis (TG-DTA). The precursor was calcined at different temperatures viz. 600, 800, 900 and 1000 °C. Crystal structure, microstructures, and nature of bonding of resulting hydroxyapatite were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), FT-IR and Raman spectroscopy techniques. Scanning electron micrographs revealed formation of beautiful nanostrips of HAp in HAp precursor. These nanostrips were stable upto 600 °C as observed in the SEM image of HAp calcined at 600 °C. The width of nanostrips was estimated to be ∼100 nm. As the calcination temperature was increased the surface morphology of the powder changed from strip-like nanostructure to capsule-like nanostructure. Micrographs of the powder samples calcined at 900 and 1000 °C show clearly nanocapsules having diameter around 200 nm. Crystallite size of the precursor and calcined powders estimated by Sherrer's formula agreed with the particle size of corresponding powders determined from SEM micrographs. FT-IR and Raman spectra of HAp powders obtained after calcinations at 600, 800, 900 and 1000 °C further confirmed the formation of pure HAp nanoparticles. © 2014 Elsevier Ltd and Techna Group S.r.l. All rights reserved.PublicationArticle Effect of crystallization temperature on luminescence behaviour of Er-Yb: SrO·TiO2 borosilicate glass(2013) Maheshwari, Aditya; Rai, Shyam Bahadur; Parkash, Om; Kumar, DevendraSystematic investigation over Er3+/Yb3+ doped SrO·TiO2 borosilicate glass ceramics has been carried out to study the change in crystallization and luminescence behaviour with heat treatment temperatures. Nano-crystalline phases Sr3Ti 2O7 and Ti10O19 were present in glass ceramics with heat treatment temperature 950 °C. Scanning electron microscope images showed that Sr3Ti2O7 particles (smaller) were distributed homogeneously and Ti10O 19 particles (bigger) were embedded at some places. Intensity of upconversion emission with excitation radiation 976 nm in crystalline glass ceramic was many times that of glass. Energy transfer and excited state absorption, mechanisms, responsible for upconversion, were studied through power log dependence. © 2013 Elsevier B.V. All rights reserved.PublicationArticle Effect of dispersion of metallic tin and silicon carbide on the ionic conductivity of B2O3Li2OLiCl glasses(1987) Parkash, Om; Kumar, Devendra; Gupta, AnjuB2O3Li2OLiCl glasses containing varying amounts of fine dispersion of silicon carbide and tin particulates have been prepared. Microstructural studies have been carried out using scanning electron microscope. Electrical conductivity measurements in the temperature range 300-575 K show that initially the conductivity increases with addition of dispersoid when the dispersed particles are uniformly distributed in the glassy matrix. Further addition of these in the glass leads to their agglomeration and the ionic conductivity decreases. This enhancement of ionic conductivity is similar to that of polycrystalline dispersed solid electrolytes. © 1987.PublicationArticle Effect of Hall current on the magnetohydrodynamic free convective flow between vertical walls with induced magnetic field(Springer Verlag, 2018) Kumar, Dileep; Singh, A.K.; Kumar, DevendraThe present work shows the effects of the Hall current as well as of the induced magnetic field on the fully developed free convective flow of a viscous incompressible and electrically conducting fluid between two non-conducting vertical walls. The basic non-dimensional governing equations, such as momentum, thermal energy and generalized Ohm’s law, have been solved analytically by using the suitable non-dimensional variables and parameters. After obtaining the exact solution of velocity, induced magnetic field and temperature field, we investigate the effects of the Hall current and of the Hartmann number on the primary and secondary components of velocity, induced magnetic field, induced current density, skin friction and mass flow rate of the fluid by using figures and tables. It is found that, as the Hall current increases, both components of the velocity increase while both components of the induced magnetic field and induced current density decrease. © 2018, Società Italiana di Fisica and Springer-Verlag GmbH Germany, part of Springer Nature.
