Browsing by Author "Bhat, K., U."

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    Biosynthesis of copper nanoparticles using copper-resistant Bacillus cereus, a soil isolate
    (2016) Tiwari, M.; Jain, P.; Chandrashekhar, Hariharapura, R.; Narayanan, K.; Bhat, K., U.; Udupa, N.; Rao, J.V.
    Microorganisms are useful systems for the production of biocompatible metal nanoparticles. Copper, an essential element of life, has good therapeutic potential. However, copper lacks suitable form for effective in vivo delivery, which has diminished its applicability. In this study, we produced biosynthesized copper nanoparticles (BCuNps) using a copper-resistant bacterial isolate from copper mine. The organism was able to tolerate >10 mM of copper and when analysed by 16S rRNA technique, showed 100% similarity with Bacillus cereus. BCuNps, produced by this microorganism, in cell-free filtrate, were characterized for surface plasmon resonance (SPR), particle's characteristics, spectroscopic properties and morphology. SPR peaks for BCuNps were recorded between 570 620 and 350 370 nm. BCuNps characteristics, namely particle size distribution, polydispersity index and zeta potential were found to be 11 33 nm, 0.433 and (?) 19.6 mV, respectively. Scanning electron microscope (SEM), transmission electron microscope (TEM) and atomic force microscope (AFM) analyses confirmed the uniform morphology; X-ray diffraction (XRD) spectrum revealed the crystalline nature; and Fourier transform infrared (FTIR) spectrum disclosed the presence of protein with BCuNps. A comparative evaluation of BCuNps with copper sulphate to determine their antimicrobial and cell toxicity levels was undertaken. BCuNps showed better antimicrobial effect and found to be safer against normal cell lines, such as HaCat, Vero and hFOB, than the copper sulphate control. 2016 Elsevier Ltd
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    Improved fatigue crack growth resistance by retrogression and re-aging heat treatment in 7010 aluminum alloy
    (2019) Nandana, M.S.; Bhat, K., U.; Manjunatha, C.M.
    Aircraft grade 7010 aluminum alloy was heat treated to two different conditions: (1) standard peak aging (T6) and (2) retrogression and re-aging (RRA). The microstructures of these alloys were characterized by using transmission electron microscope. Fatigue crack growth rate (FCGR) tests were conducted using standard compact tension specimens, following ASTM standards. Tests were conducted at various stress ratios, R ranging from 0.1 to 0.7. The RRA-treated alloy was observed to contain coarsened ?? (MgZn2) precipitates with higher inter-particle spacing when compared with T6-treated alloy. The grain boundary precipitates (GBPs) were also coarsened and discontinuous in RRA-treated alloy as compared with continuous GBPs in T6 condition. The FCGR was lower and ?Kth was higher in RRA-treated alloy compared with T6-treated alloy at all the stress ratios investigated. Improved fatigue crack growth resistance in RRA-treated alloy was correlated to the modified microstructure and enhanced crack closure levels. 2018 Wiley Publishing Ltd.