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S. Das,S. Sanyal,P. Halder,A. Varma,Y. Ravi Kumar,S. Mandal 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.8
In this study, the oxidation response of a T91 steel in dry air environment has been investigated by performing cyclic oxidationtests at 873, 973 and 1073 K for a total duration of 1000 h with intermediate intervals. The temperature range for thisstudy is chosen to be higher than the operating temperature range of the alloy to accelerate the oxidation kinetics. Developinga comprehensive understanding of the mechanisms and kinetics involved at such accelerated oxidation environmentswould help to formulate better strategies for countering oxidation related failure events. The results of this study showedthat the oxidation rate is greatly influenced by temperature as well as exposure time, and follows a near-parabolic rate law. Characterization of the oxide scales revealed formation of dual oxide layers where the inner layer is primarily rich in Feand Cr, and the outer layer in Fe only. At 1073 K, formation of cracks can be observed in the oxide scales after 24 h, whichbecame more severe after 1000 h. The oxidation kinetics, when fitted to an Arrhenius type equation, can be associated withactivation energy (Q) and parabolic rate constant (kp) values. The Q values lie within 104–109 kJ/mol, whereas the kp valuesincrease with temperature due to increase in the reaction rate. The kinetic equation developed based on the Q and kp valuescan be used to predict the thickness (inner, outer and overall) of the oxide scales in T91 steel at any temperature and timewithin the studied ranges.
Vijay D. Chavada,Nejal M. Bhatt,Mallika Sanyal,Pranav S. Shrivastav 한국공업화학회 2020 Journal of Industrial and Engineering Chemistry Vol.84 No.-
In the present work, a simple approach for colorimetric determination of allopurinol and its majormetabolite oxypurinol is presented using gold nanoparticles as a probe. Gold nanoparticles weresynthesized using the citrate reduction method and then functionalized using melamine (mel-AuNPs). The nanoparticles were characterized using UV–vis spectrophotometry, dynamic light scattering andtransmission electron microscopy. The bare AuNPs capped with citrate anions (cit-AuNPs) gave a linearresponse towards allopurinol and oxypurinol within the range 0.20–40.0 mM and 0.25–25.0 mMrespectively; however the melamine functionality on the AuNPs exhibited specific response foroxypurinol from 0.10 to 15.0 mM. This enabled development of a simple approach for the quantitation ofthe metabolite using mel-AuNPs, while the quantitation of allopurinol was carried out using theregression parameters of cit-AuNPs and the calculated amount of metabolite. For method optimizationparameters such as the pH, incubation time and effect of ionic strength of the medium which can causeaggregation of nanoparticles were studied. The methodology was found to yield reliable results asevident from the validation results. The application of the method is demonstrated by analyzingallopurinol from tablet formulations and the drug and its metabolite from spiked plasma samples.
P.K.Das,G.D.V. Pandiyan,P.R.Ghosh,B.C.Das,S. Sanyal 대한수의학회 2005 Journal of Veterinary Science Vol.6 No.4
Unilateral adrenalectomy was performed in six black Bengal goat (Capra hircus) to study electrocardiograph in connection with mineral metabolism with special reference to sodium and potassium and some other factors of physiological importance. The parameters were studied at every 12 hrs interval upto 120 hrs and 24 hrs interval from 120 to 240 hrs. Physiological parameters, like body weight and rectal temperature, changed non-significantly (p < 0.05) after adrenalectomy. Among minerals, plasma sodium (p < 0.01) and plasma potassium (p < 0.05) concentration were changed significantly between hours leaving impression in ECG as widening of QRS complex and peaked T wave with increased amplitude found after unilateral adrenalectomy. Heart rate also increased significantly (p < 0.01) between hours.