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31.
C. Praveen 《Tetrahedron》2008,64(10):2369-2374
Pyridinium chlorochromate (PCC) supported on silica gel effects the oxidative cyclization of structurally diverse thiophenolic and phenolic Schiff's bases, thereby providing an efficient and convenient method for the synthesis of a library of 2-arylbenzothiazoles and 2-arylbenzoxazoles. 相似文献
32.
Lalit Giri Arun Kumar Jugran Amit Bahukhandi Praveen Dhyani Indra D. Bhatt Ranbeer Singh Rawal Shyamal Kumar Nandi Uppeandra Dhar 《Applied biochemistry and biotechnology》2017,181(1):267-282
Habenaria edgeworthii Hook. f. ex Collett is an important terrestrial orchid used in different Ayurvedic formulations. In the present study, variations among morphological, phytochemical and molecular markers were assessed. A significant difference was observed among populations using morphological traits. Inter-simple sequence repeat (ISSR) data revealed lower genetic diversity at population level (He = 0.207) as compared to species level (He = 0.334). Analysis of molecular variance (AMOVA) indicates 74 % variation among populations and 26 % within population. Tuber extracts showed significantly (p < 0.05) higher total phenolics and flavonoids among the populations. Antioxidant activity determined by 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical scavenging, 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging and ferric reducing antioxidant power (FRAP) assays exhibited considerable antioxidant potential. Furthermore, the associations between molecular and morphological and phytochemical attributes were studied using multiple regression analysis (MRA). Several ISSR fragments were associated with some morphological and phytochemical traits. These ISSR fragments can be useful for breeding programme of the species when no other genetic information, such as linkage maps and quantitative trait loci, is available. 相似文献
33.
Synthesis and photophysical studies of a simple and efficient dansyl-styrylquinoline conjugate (DansSQ) which shows excellent selectivity toward Fe2+ over other transition metal ions including Fe3+ are described. The fluorescent emission of DansSQ at 450 nm was enhanced upon addition of Fe2+ in the presence of common interfering metal ions in background. These studies suggest that DansSQ could be used as fluorescent sensor for Fe2+. 相似文献
34.
Choorikkat Ranjith K.K. Vijayan Vakayil K. Praveen N.S. Saleesh Kumar 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2010,75(5):1610-1616
In the present work an array of novel substituted 2H-chromen-2-one (coumarin) derivatives has been subjected to photophysical analysis. Though the influence of the electron-donating groups such as amino, substituted amino, hydroxyl, alkoxy groups, etc. at position 7 of the coumarin ring system has been extensively studied, the luminescent properties of the coumarin moieties with an acetoxy substituent have not been explored. Herein it is attempted to study the variation of fluorescence behavior of substituted coumarin derivatives with change of nature and position of the substituents on the 2H-chromen-2-one skeleton. Effect of a methyl substituent at position 4 which imposes abnormal photophysical behavior to the chromenone unit has also been briefly described. 相似文献
35.
Molly Megraw Praveen Sethupathy Kiranmai Gumireddy Shane T. Jensen Qihong Huang Artemis G. Hatzigeorgiou 《Theoretical chemistry accounts》2010,125(3-6):593-598
In this study, we investigate whether miRNAs located within “host” protein-coding genes may regulate the expression of their host genes. We find that 43 of 174 miRNAs encoded within RefSeq genes are predicted to target their host genes. Statistical analysis of this phenomenon suggests that gene auto-regulation via miRNAs may be under positive selective pressure. Our analysis also indicates that several of the 43 miRNAs have a much lower expectation of targeting their host genes by chance than others. Among these examples, we identify miR-128b:ARPP-21 (cyclic AMP-regulated phosphoprotein, 21 kD) as a case in which both the miRNA and the target site are also evolutionarily conserved. We provide experimental support for this miRNA:target interaction via reporter silencing assays, and present evidence that this isoform-specific gene auto-regulation has been preserved in vertebrate species in order to prevent detrimental consequences of ARPP-21 over-expression in brain. 相似文献
36.
K.L.N. Deepak R. Kuladeep V. Praveen Kumar S. Venugopal Rao D. Narayana Rao 《Optics Communications》2011,284(12):3074-9305
We report microfabrication of structures in bulk and thin films of polystyrene (PS) using femtosecond (fs) laser pulses. For the first time to our knowledge, we report emission from the fs laser modified regions of bulk and thin films of PS when excited at 458, 488, and 514 nm. Moreover, we report the existence of peroxide type free radicals, for the first time, in fs laser irradiated bulk PS. We observed the suppression of Raman modes in case of structures fabricated at higher energies and the same effect was noticed in central portion of the structures fabricated. No appreciable broadening was observed in the case of structures fabricated at low energies. Possible applications resulting from such structures are discussed briefly. 相似文献
37.
We investigate the effect of temperature on structure and dynamics of a colloidal glass created by tethering polymers to the surface of inorganic nanoparticles. Contrary to the conventional assumption, an increase in temperature slows down glassy dynamics of the material, yet causes no change in its static structure factor. We show that these findings can be explained within the soft glassy rheology framework if the noise temperature X of the glass phase is correlated with thermodynamic temperature. 相似文献
38.
39.
P. Lakshmi Praveen Ramakrishna D. S. Durga P. Ojha 《Molecular Crystals and Liquid Crystals》2017,643(1):76-82
In the present article, UV spectral characterization of a smectic-C liquid crystal 4,4′-bis(n-alkoxy)azoxybenzene (n = 14) (C40H66N2O3) has been carried out. Structure of the molecule has been optimized using the Density functional B3LYP with 6-31+G (d) basis set using crystallographic geometry as input. The absorption spectra have been estimated in the UV region by employing the DFT method, semiempirical CNDO/S and INDO/S parameterizations. The oscillator strength (f) and vertical transition energy (EV) have been reported corresponding to absorption wavelength (λmax). These values have been compared with the experimental value reported in the literature to offer theoretical support to the experimental value. Further, some electrochemical properties have been reported for the molecule. 相似文献
40.
High-purity Fe powder was mechanically milled under argon at ambient temperature using an SPEX 8000 mill. The local atomic and magnetic structure was studied using57Co/Fe Mössbauer and111In/Cd perturbed angular correlations (PAC) spectroscopies. After 32 hours of milling, X-ray diffraction revealed effective grain diameters of 18 nm and energy-dispersive X-ray analysis indicated a Cr impurity concentration of 5%, presumably introduced by mechanical attrition of steel ball bearings used for milling. In addition to a spectral component very similar to bulk iron metal, the Mössbauer spectra exhibited hyperfine field shifts attributed to the Cr impurities. PAC spectra on Fe milled for 5 h, with no contamination, exhibited two components: (1) A slightly broadened magnetic interaction attributed to interior, defect-free sites of In/Cd probes with a mean hyperfine field slightly greater than in macroscopic grains. The defect-free site fraction grew appreciably during milling, even though In is essentially insoluble in Fe. (2) An indistinct signal due to mixed magnetic and quadrupole interactions attributed to probes at surface or other defect sites. 相似文献