P A College of Engineering

Abstract: Over the past several years, although the resolution, signal-to-noise ratio and acquisition speed of magnetic resonance imaging (MRI) technology have been increased, MR images are still affected by artifacts and noise. A tradeoff between noise reduction and the preservation of actual detail features has to be made in the way that enhances the diagnostically relevant image content. Therefore, noise reduction is still a difficult task. A variety of techniques have been presented in the literature on denoising MR images and each technique has its own assumptions, advantages and limitations. The purpose of this paper is to present a survey of the published literature in dealing with denoising methods in MR images. After a brief introduction about magnetic resonance imaging and the characteristics of noise in MRI, the popular approaches are classified into different groups and an overview of various methods is provided. The denoising method's advantages and limitations are also discussed.

Abstract: The synthesis, crystal growth and non-linear optical (NLO) property of new chalcone derivatives are reported. 4-Propyloxy and 4-butoxy benzaldehydes were made to under go Claisen–Schmidt condensation with 4-methoxy, 4-nitro and 4-phenoxy acetophenones to form corresponding chalcones. The newly synthesized compounds were characterized by analytical and spectral data. The Second harmonic generation (SHG) efficiency of these compounds was measured by powder technique using Nd:YAG laser. Among tested compounds three chalcones showed NLO property. The chalcone 1-(4-methoxyphenyl)-3-(4-propyloxy phenyl)-2-propen-1-one exhibited SHG conversion efficiency 2.7 times that of urea. The bulk crystal of 1-(4-methoxyphenyl)-3-(4-butoxyphenyl)-2-propen-1-one (crystal size 65×28×15 mm 3 ) was grown by slow-evaporation technique from acetone. Microhardness of the crystal was tested by Vicker's microhardness method.

Abstract: Synthesis of a series of 7-arylidene-6-(2,4-dichlorophenyl)-3-aryloxymethyl/anilinomethyl-1,2,4-triazolo[3,4-b]-1,3,4-thiadiazines (3) by the condensation of 3-aryl-1-(2,4-dichloro-5-fluorophenyl)-2-bromo-propen-1-one (1) and 4-amino-5-mercapto-3-aryloxymethyl/anilinomethyl-1,2,4-triazoles (2) is described. The newly synthesized compounds were characterized by elemental analysis IR, 1H NMR and mass spectral data. These compounds were tested for their antimicrobial activities against Escherichia coli, Staphylococcus aureus (Smith), Psuedomonas aeruginosa (Gessard), Bacillus subtilis and Candida albicans. Some of the newly synthesized compounds were also screened for their anticancer activity. Among them compounds 3m, 3o, 3q showed in vitro anticancer activity.

Abstract: The 2-hydroxy-5-(1,3-thiazol-5-yl) benzamide (4a), 5-(2-amino-1, 3-thiazol-5-yl)-2-hydroxy benzamide (4b), 2-hydroxy-5-(2-alkyl-1,3-Thiazol-5-yl) benzamide (4c and 4d), 5-{2-[(N-substituted aryl)amino]-1,3-thiazol-5-yl}2-hydroxy benzamides (6a–j) were prepared by reacting 5-(bromoacetyl) salicylamide (2) with thiourea, thioformamide, thioalkylamide (3c–d) and substituted thioureas (5a–j) in absolute ethanol. These compounds were converted to 5-(2-substituted–1,3-thiazol-5-yl)-2-alkoxybenzamides and 5-(2-N-(substituted aryl)-1,3-thiazol-5-yl)-2-alkoxy benzamides (8a–g) by reacting with n-alkylbromides (7a–b) in presence of a base. The newly synthesized compounds were characterized by IR, 1H-NMR and mass spectral data. Compounds were also screened for their antifungal activity.

Abstract: Two bis-chalcone derivatives, 1,5-[di(4-methoxyphenyl)]penta-1,4-dien-3-one and 1,5-[di(4-chlorophenyl)]penta-1,4-dien-3-one were synthesized. Their SHG conversion efficiencies are reported to be 6.0 and 5.0 times that of urea and hyper polarizabilities are 9.9×10−30 and 10.2×10−30 esu, respectively. The third-order nonlinear optical properties in PMMA matrix were studied by Z-scan technique using 7 ns laser pulses at 532 nm. The nonlinear refractive index γ, nonlinear absorption coefficient β, magnitude of effective third order susceptibility χ(3) and the coupling factor ρ have been investigated. The values obtained are of the order of 10−14 cm2/W, 1.2 cm/GW, 10−14 esu and 0.2, respectively, which are comparable with the values obtained in stilbazoleum like dyes. The experimental investigation also shows that they are very interesting optical limiting materials and their optical limiting behaviour is mainly due to two photon absorption phenomenon.