Browsing by Author "Vivek Kumar Sharma"

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A new topology for multilevel inverter
(Institute of Electrical and Electronics Engineers Inc., 2015) Vivek Kumar Sharma; Varun Anand; Gaurav Gupta; Vishakha Vaish
Single-Phase multilevel converters are suitable for medium power applications as photovoltaic systems and switched reluctance machines, whereas, three-phase inverters are widely used in industries for high power applications. A new single phase topology and its three-phase applications with reduced device count is proposed so that the complexity as well as the cost of the system gets reduced to a larger extent. A new control scheme known as, zero level control, is introduced to maintain the voltage of DC-link capacitors. Simulation results have also been presented to validate the proposed control scheme. © 2015 IEEE.
Algorithm for even power sharing using feed forward space vector modulation technique in multilevel inverter
(Institute of Electrical and Electronics Engineers Inc., 2015) Varun Anand; Vivek Kumar Sharma; Gaurav Gupta; Vishakha Vaish
Advances in multilevel inverter topologies has been comprehended by advent of newer control strategies. One such strategy is feed forward space vector modulation which can be applied on single phase multilevel inverters. The algorithm, being flexible in manipulation, can be easily implemented with a digital controller. This paper proposes a feed-forward space vector modulation method with equal power sharing. Simulation is carried out in MATLAB and experimental validation has been done for a particular load on a five-level topology to verify the concept. © 2015 IEEE.
Approximation of a Function f Belonging to Generalized Hölder Class of Order 0 < α ≤ 1 and Generalized Lipschitz class by Haar Wavelet Method
(Springer, 2020) Shyam Lal; Vivek Kumar Sharma
In this paper, the approximations of a function f of generalized Hölder class Hα(w)[0,1] and generalized Lipschitz class Lipα(s)[0,1] have been obtained by Haar wavelet method.Calculated approximations are best possible in wavelet analysis. © 2019, The National Academy of Sciences, India.
Approximation of a function f belonging to lipschitz class by legendre wavelet method
(Springer, 2019) Shyam Lal; Vivek Kumar Sharma
In this paper, the function of Lipschitz class and Legendre wavelet method are studied. Four new wavelet approximations of the function f belonging to Lipschitz class in norms ‖.‖1 and ‖.‖2 by Legendre wavelet method are estimated. The calculated wavelet approximations are best possible in wavelet analysis. © Springer Nature India Private Limited 2019.
APPROXIMATION OF A FUNCTION HAVING BOUNDED DERIVATIVES UPTO THE SECOND ORDER BY SINE-COSINE WAVELET EXPANSION AND ITS APPLICATIONS
(Poincare Publishers, 2023) Vivek Kumar Sharma; Virendra Sharma; Shyam Lal; H.M. Srivastava; Rakesh
In this paper, sine-cosine wavelet has been introduced and the approximation errors of the function f(t) whose first and second derivatives are bounded have been estimated using this wavelet and it is used to solve some linear differential equations. Solution obtained by this method is compared with Euler’s method and with exact solution. We observe that the solution obtained by this method is better than the solution given by the Euler’s method which shows the usefulness of this method. © Poincare Publishers.
Harnessing conformational changes in TAM for enhanced photophysical properties leading to biological applications
(Elsevier Ltd, 2025) Soumya Singh; Krishanu Bandyopadhyay; Vivek Kumar Sharma; Biplob Koch; Satyen Saha
Triarylmethanes (TAMs) are particularly notable for their medicinal potential and are being investigated for their structure, photophysical characteristics, and applications. However, the suboptimal photophysical properties of TAMs limit their practical applications, highlighting the need for further optimization. In light of this, the present study synthesizes flexible (F) and conformationally rigid xanthene (R) derivatives of TAM through Friedel-Crafts alkylation and investigated their photophysical properties. The investigation reveals the enhanced photophysical properties of R-derivative as compared to F-derivative. Additionally, the biological applications of R were examined including its interactions with CT-DNA, where it exhibited high binding affinity. Moreover, cytotoxicity assays performed on RAW 264.7 macrophage cell lines and HeLa cells (cervical cancer cell line) using Rhodamine B (RhB) as a standard showed low toxicity and similar biocompatibility. Furthermore, in vitro cellular imaging revealed that R exhibited significantly higher fluorescence intensity than RhB. The outcome of this study offers valuable insights paving the way for the broader use of TAM derivatives in therapeutic and diagnostic fields. © 2025 Elsevier Ltd
Isolation of cytotoxic cycloartane triterpenoids from Dysoxylum malabaricum
(Royal Society of Chemistry, 2024) Nivedita Bhardwaj; Vivek Kumar Sharma; Nancy Tripathi; Kavita Pimpre; Rajesh Sonti; G. Ravikanth; Biplob Koch; Shreyans K. Jain
New cycloartane triterpenoids (2-4) have been recently discovered in the bark of Dysoxylum malabaricum. The extraction process involved the utilization of a cytotoxic dichloromethane-methanol extract, which underwent meticulous bioassay-guided fractionation employing high-performance liquid chromatography. A strategic LCMS-DNP-based dereplication approach was used to target the new compounds. Subsequently, the isolated compounds were thoroughly characterized utilizing nuclear magnetic resonance (NMR) and high-resolution electrospray ionization mass spectrometry (HRESIMS) data, and their absolute configurations were ascertained through electronic circular dichroism (ECD) calculations. In the context of biological activity, the compounds were evaluated for their cytotoxic potential against a panel of breast cancer cell lines and human normal embryonic kidney cancer cells. 2 demonstrated remarkable cytotoxicity, exhibiting an IC50 value of 18 μM against the T-47D breast cancer cell line, concurrently eliciting apoptotic cell death. The findings of this study emphasize the substantial potential of 2 as a promising candidate for further development as an anti-cancer agent. © 2024 The Royal Society of Chemistry.
Shaping the gut microbiota by bioactive phytochemicals: An emerging approach for the prevention and treatment of human diseases
(Elsevier B.V., 2022) Surya Sudheer; Prateeksha Gangwar; Zeba Usmani; Minaxi Sharma; Vivek Kumar Sharma; Siva Sankar Sana; Fausto Almeida; Nawal Kishore Dubey; Dhananjaya Pratap Singh; Neeraj Dilbaghi; Hamid Reza Khayat Kashani; Vijai Kumar Gupta; Brahma Nand Singh; Maryam Khayatkashani; Seyed Mohammad Nabavi
The human digestive tract is the cottage to trillions of live microorganisms, which regulate health and illness. A healthy Gut Microbiota (GM) is necessary for preventing microbial growth, body growth, obesity, cancer, diabetes, and enhancing immunity. The equilibrium in GM's composition and the presence/absence of critical species enable specific responses to be essential for the host's better health condition. Research evidences revealed that the dietary plants and their bioactive phytochemicals (BPs) play an extensive and critical role in shaping the GM to get beneficial health effects. BPs are also known to improve gastrointestinal health and reduce the risk of several diseases by modulating GM-mediated cellular and molecular processes. Regular intake of BPs-rich vegetables, fruits, and herbal preparations promotes probiotic bacteria, including Bifidobacteria and Lactobacillus species, while inhibiting unwanted gut residents' development Escherichia coli, and Salmonella typhimurium etc. Upon consumption, BPs contact the GM that gets transformed before being absorbed from the gastrointestinal tract. Biotransformation of BPs by GM is linked with the enhancement of bioactivity/toxicity diminishment of the BPs compared to parental phytochemicals. Therefore, the current review focuses on the role of BPs in shaping GM for the prevention and treatment of human diseases. © 2021
Solution of Differential Equations by Using Legendre Wavelet Operational Matrix of Integration
(Springer, 2022) Vivek Kumar Sharma; Shyam Lal
In this paper, the operational matrix of integration using the Legendre wavelet has been introduced and it is used to solve different types of linear and non-linear differential equations. The solution obtained by the Legendre wavelet operational matrix of integration is compared with the exact solution to show the usefulness of the method. © 2022, The Author(s), under exclusive licence to Springer Nature India Private Limited.
Synthesis and anticancer evaluation of tri-n-butyltin complexes featuring azomethine- and diazenyl-functionalized benzoates with peripheral fluorine against MDA-MB-231 breast cancer cells
(Elsevier Inc., 2025) Tushar S. Basu Baul; Amon Das; Avishek Khatiwara; Vivek Kumar Sharma; Andrew Duthie; Biplob Koch; Sean R. Parkin
Five complexes, [n-Bu3Sn(HLH)] (1), [n-Bu3Sn(HL4-F)] (2), [n-Bu3Sn(HL2-CF3)] (3), [n-Bu3Sn(HL3-CF3)] (4) and [n-Bu3Sn(HL4-CF3)] (5), were synthesized by reacting the corresponding azomethine- and diazenyl-functionalized hydroxy-benzoic acid pro-ligands (H'HLH, H'HL4-F, H'HL2-CF3, H'HL3-CF3 and H'HL4-CF3) with (n-Bu3Sn)2O. Compounds 1–5 were thoroughly characterized by FT-IR and NMR (1H, 13C, and 119Sn) spectroscopy. Additionally, the molecular and crystal structures of compounds 2, 4 and 5, along with one of their pro-ligands (H'HL3-CF3), were determined by single-crystal X-ray diffraction analysis. The tri-n-butyltin(IV) complexes (2, 4, and 5) form mono-periodic chains in which the n-Bu3Sn groups are linked to the oxygen atoms of the benzoate ligand through one short and one long Sn-O bond. This arrangement results in a pentacoordinated tin center, exhibiting slightly distorted trans-Bu3SnO2 trigonal-bipyramidal geometries, as indicated by their τ5 parameters. The hydroxy H atom forms an intramolecular O–H···N hydrogen bond with the imine N-atom, as observed in the crystal structure of H'HL3-CF3. The 119Sn NMR spectra of compounds 1–5 showed a resonance at around +110 ppm, consistent with a tetrahedral geometry in solution. This suggests that the polymeric structures of complexes 2, 4, and 5 observed in the solid state dissociate upon dissolution. The in vitro cytotoxicity of the tri-n-butyl compounds 1–5 was assessed against MDA-MB-231 breast cancer cells. Compounds 1–5 showed potent cytotoxicity against MDA-MB-231 cells (IC50: 0.90–2.18 μM), with the fluorinated complex [n-Bu3Sn(HL4-F)] (2) being the most active (IC50 = 0.90 ± 0.05 μM). The proposed mechanism of action is discussed in light of findings from various biological assays. © 2025 Elsevier Inc.