Journal Articles
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Item Development of a Spectrophotometric Biphasic Assay for the Estimation of mPEG-maleimide in Thiol PEGylation Reaction Mixtures(Taylor and Francis Ltd. michael.wagreich@univie.ac.at, 2016) Nanda, P.; JagadeeshBabu, P.E.; Gupta, P.; Prasad, A.G.Methoxy(polyethylene glycol)-maleimide (mPEG-mal) is a PEG derivative used for thiol PEGylation of protein molecules and finds application in drug delivery studies. The maleimide group undergoes degradation in aqueous media, resulting in the difficult quantitative analysis of mPEG-mal. Routinely employed methods for separation and estimation of mPEG-mal include tedious chromatographic methods like ion exchange, high-performance liquid chromatography with refractive index detector and techniques like mass spectrometry and proton nuclear magnetic resonance. We present a direct and reproducible spectrophotometric method to quantify free and protein bound mPEG-mal in thiol PEGylation reaction mixtures. This method is based on the partitioning of a PEG bound chromophore between an aqueous ammonium isoferrothiocyanate phase to a chloroform phase in the presence of mPEG-mal. Several important parameters influencing the partitioning and stability of the chromophore, volume ratios of liquid phases, ethylenediaminetetraacetic acid concentration in the reaction mixture, mixing time, and chlorinated solvents used for partitioning have been studied. © 2016, Copyright © Taylor & Francis Group, LLC.Item Performance of eco-friendly mortar mixes against aggressive environments(Techno-Press info@techno-press.com, 2020) Saha, S.; C, C.; Gupta, P.Past research efforts already established geopolymer as an environment-friendly alternative binder system for ordinary Portland cement (OPC) and recycled aggregate is also one of the promising alternative for natural aggregates. In this study, an effort was made to produce eco-friendly mortar mixes using geopolymer as binder and recycled fine aggregate (RFA) partially and study the resistance ability of these mortar mixes against the aggressive environments. To form the geopolymer binder, 70% fly ash, 30% ground granulated blast furnace slag (GGBS) and alkaline solution comprising of sodium silicate solution and 14M sodium hydroxide solution with a ratio of 1.5 were used. The ratio of alkaline liquid to binder (AL/B) was also considered as 0.4 and 0.6. In order to determine the resistance ability against aggressive environmental conditions, acid attack test, sulphate attack test and rapid chloride permeability test were conducted. Change in mass, change in compressive strength of the specimens after the immersion in acid/sulphate solution for a period of 28, 56, 90 and 120 days has been presented and discussed in this study. Results indicated that the incorporation of RFA leads to the reduction in compressive strength. Even though strength reduction was observed, eco-friendly mortar mixes containing geopolymer as binder and RFA as fine aggregate performed better when it was produced with AL/B ratio of 0.6. © 2020 Techno-Press, Ltd.Item Evaluation of a comprehensive non-toxic, biodegradable and sustainable cutting fluid developed from coconut oil(SAGE Publications Ltd, 2021) Suvin, P.S.; Gupta, P.; Horng, J.-H.; Kailas, S.V.The evolution in development of cutting fluid from petroleum based products have brought about remarkable changes to the present and growing machining industry. Most of the cutting fluids are made of mineral base oils which are toxic, non-biodegradable and unsustainable. A major issue lies in their inappropriate disposal which results in surface water and groundwater contamination and consequently, agricultural products and food contamination. Hence, the objective of this study is to develop an alternative, sustainable, non- toxic and completely bio-degradable cutting fluid to replace the mineral oil based cutting fluid. A Green cutting fluid [GCF] was prepared by combining nontoxic emulsifiers and natural additives. GCF meets many of the characteristic specifications of commercial formulations with the added advantage that it is eco-friendly. Toxicity test for cutting fluids has been carried out using fish toxicity test (OECD -203). The GCF with green additives has an LC50 value ?1064 mg/L. Commercial cutting fluid (CCF) has an LC50 value less than 100 mg/L These tests show that commercial cutting fluids are highly toxic, while the GCF can be considered as non-toxic. Biodegradability test was done using BOD-COD technique and found GCF as biodegradable and CCF as non-biodegradable. The ASTM D4627 corrosion tests infer that the GCF with grade 3 has better anticorrosive characteristics when compared to grade 4 of most CCF samples tested this could be possibly by the effect of natural additives in GCF. Drilling experiments were carried out to evaluate the machining performance of cutting fluids. Results from the drilling tests comparing the axial force/cutting force and torque showed that the performance of the GCF was comparable to that of the CCFs. Nevertheless, GCF formulation with non- toxic emulsifiers and natural additives is a good basis for further development and use of non-toxic tribological products. © IMechE 2020.Item Acoustic fluid–structure study of 2D cavity with composite curved flexible walls using graphene platelets reinforcement by higher-order finite element approach(Elsevier Ltd, 2021) Jeyaraj, J.; Gupta, P.; Vasudevan, V.; Polit, O.; Manickam, G.In the present study, acousto-vibration analysis of 2D fluid-filled cavities/tanks having flat and curved flexible walls is made using a trigonometric function based shear deformable theory and the Helmholtz wave model for fluid domain. The governing equation formed here is solved through higher-order finite element approach. The walls are modeled by C1 continuous 3-noded beam element and the fluid is idealized using an eight-noded quadrilateral element. Structural and coupled frequencies are evaluated for fluid-filled cavities with rigid/flexible vertical walls along with flat/curved beam on top. The sound pressure level is also predicted in the fluid domain due to a steady-state mechanical harmonic load on the top of the cavity. This investigation is conducted for metallic cavities and then extended to graphene platelets reinforced cavity. The effect of degree of fluid–structure coupling is examined assuming different fluid domains. Considering a wide range of cavity geometry and material parameters such as thickness ratio, curved beam angle, graded porosity and graphene platelets, porosity coefficient, loading of GPL, fluid medium, a comprehensive investigation is depicted to highlight their impacts on vibro-acoustic nature of fluid-filled cavities. It is observed that the dynamic characteristics of rigid and flexible wall cavities are significantly different from each other. © 2021 Elsevier LtdItem A low loss hexagonal six-port optical circulator using silicon photonic crystal(Springer, 2023) Sangeetha, S.; Vani, D.; Gupta, P.; Krishnan, P.A 6-port optical circulator using silicon photonic crystals has been designed and proposed in this paper as an essential component of an optical communication system. The proposed 6-port circulator has greater isolation values between the input and isolated ports and lower insertion loss values between the input and output ports. The proposed circulator achieves maximum isolation of 38.7 dB and minimum insertion loss of 0.0029 dB. The proposed designs are extremely useful in the telecommunications industry, wavelength division multiplexing and photonic integrated circuits applications due to their low insertion and high isolations. © 2023, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.Item High figure-of-merit in Zn, Sb co-doped Mg2Si0.3Sn0.7 alloy through simultaneous optimization of electrical and thermal transports(Elsevier Ltd, 2025) Sarkar, P.; Gupta, P.; Shenoy, U.S.; Singh, S.; Kundu, S.; Kumawat, N.; Kedia, D.K.; Bhat, D.K.; Bhattacharya, S.; Singh, A.The derivatives of Mg2Si have recently attracted wide attention as promising thermoelectric materials due to earth abundant and environment friendly low-cost constituents. The main challenge in optimizing the thermoelectric figure of merit ZT, is the low electrical and high thermal conductivities of Mg2Si. The present study demonstrates high ZT of ?1.55 at 673 K in Mg2Si0.3Sn0.7 through simultaneous optimization of electrical and thermal transport through Sb and Zn co-doping. The ultra-low deformation and alloy scattering potentials in Sb and Zn co-doped samples helps in maintaining record high Hall mobility ?70–90 cm2/V.s. The doping induced pudding mold band structure with hyperconvergence in conduction band balances high Seebeck coefficient and high electrical conductivity. The point defects and dislocations created by doping helps in lowering of lattice thermal conductivity as well. The uni-leg power generator fabricated using optimized Mg1.96Zn0.04(Si0.3Sn0.7)0.98Sb0.02 exhibits a record efficiency of ?9.5 % at ?T ? 329 K. © 2025