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21.
22.
Eltayeb Fadul Arsalan Nizamani Saima Rasheed Achyut Adhikari Sammer Yousuf Shahida Parveen 《Natural product research》2020,34(17):2456-2464
AbstractA new sesquiterpene lactone geigerianoloide (1) and four known flavonoids axillarin (2), quercetin (3), 3-methoxy-5,7,3',4'-tetrahydroxy-flavone (4) and hispidulin (5) were isolated from Geigeria alata (DC) Oliv. & Hiern. (Asteraceae). Structures were deduced using 1H- and 13C- NMR spectroscopy, mass spectrometry, while the structure of compound 1 was also deduced using X-ray crystallography technique.Geigeria alata is traditionally used for diabetes, therefore compounds were tested for anti-glycation activity, in which compounds 2 and 3 showed potent activities (IC50 values of 246.97?±?0.83 and 262.37?±?0.22 µM, respectively) compared to IC50 value 294.50?±?1.5 µM of rutin. Moreover, compound 4 exhibited a comparable activity to rutin (IC50?=?293.28?±?1.34 µM). Compound 5 showed a weak activity.Compounds 2, 3, and 4 exhibited potent DPPH radical scavenging activity (IC50?=?0.1?±?0.00, 0.13?±?0.00 and 0.15?±?0.01 µM, respectively). Compounds 2, 3, and 4 demonstrated significant superoxide anion scavenging activity with IC50 values of 0.14?±?0.001, 0.17?±?0.00, and 0.11?±?0.006 µM, respectively. 相似文献
23.
In this communication we describe the design and synthesis of five new conjugated polymers (P1–P5) with various π-electron conjugation bridges. Their structures were established by FTIR, 1H NMR spectroscopy, elemental analysis. The molecular weights of the polymers were estimated by gel permeation chromatographic technique. Further, their electrochemical, linear and nonlinear optical properties were investigated. The electrochemical band gaps of P1–P5 were found to be 1.72–2.35 eV. Their third-order nonlinear optical activities were studied by open aperture Z-scan technique, using a Q-switched, frequency doubled Nd:YAG laser producing 7 nano second laser pulses at 532 nm. Z-scan results reveal that the polymers exhibit self-defocusing nonlinearity and their operating mechanism involves reverse saturable absorption. The polymers showed strong optical limiting behavior due to effective two-photon absorption (2PA) with 2PA coefficients of the order of 10?11 m/W, which is comparable to that of good optical limiting materials in the literature. 相似文献
24.
Josephson oscillation of a superfluid Fermi gas 总被引:1,自引:0,他引:1
S. K. Adhikari 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,47(3):413-419
Using the complete numerical solution of a time-dependent
three-dimensional mean-field model we
study the Josephson oscillation of a superfluid Fermi gas (SFG) at zero temperature formed in a combined axially-symmetric
harmonic plus one-dimensional periodic optical-lattice (OL) potentials after displacing the harmonic trap along the axial
OL
axis. We study the dependence of Josephson frequency on the strength of the OL potential. The Josephson frequency decreases
with increasing strength as found in the experiment of Cataliotti et al. [Science 293, 843 (2001)] for a Bose-Einstein condensate and of the experiment of Pezzè et al. [Phys. Rev. Lett. 93, 120401 (2004)] for an ideal Fermi gas. We demonstrate a
breakdown of Josephson oscillation in the SFG for a large displacement
of the harmonic trap. These features of Josephson oscillation of a SFG can be tested experimentally. 相似文献
25.
A simple method for the amperometric estimation of N-cyclohexyl-2-benzothiazole sulphenamide, N-dicyclohexyl-2-benzothiazole sulphenamide, 2-(morpholinothio)benzothiazole and N-tert.-butyl-2-benzothiazole sulphenamide is reported. The results are obtained within 5 min and are correct within +/- 2.0%. 相似文献
26.
27.
28.
Trinh An Huy Rameshwar Adhikari Thomas Lüpke Sven Henning Goerg H. Michler 《Journal of Polymer Science.Polymer Physics》2004,42(24):4478-4488
The orientation behavior of isotactic polypropylene (iPP) in α‐ and β‐crystal form was investigated by rheo‐optical Fourier transformed infrared (FTIR) spectroscopy. This method enabled quantification of the degree of orientation as a feature of structural changes during uniaxial elongation in not only the crystalline phase but also the amorphous one. Molecular orientation mechanisms can be successfully derived from experimental results. Generally, three mechanisms were detected for iPP: (1) interlamellar separation in the amorphous phase, (2) interlamellar slip and lamellar twisting at small elongations, and (3) intralamellar slip at high elongations. The third mechanism was favored by α‐PP, whereas β‐PP favored the second mechanism, which, in fact, was responsible for the different mechanical properties of both materials at the macroscopic level. On the other hand, crystallization conditions may have significantly affected the amorphous orientation. Nevertheless, for both iPP types the chains in the amorphous phase always oriented less than did those in the crystalline phase. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 4478–4488, 2004 相似文献
29.
Anwar Usman Ibrahim Abdul Razak Suchada Chantrapromma Hoong-Kun Fun Jayanta Kumar Ray Sujit Das Adhikari Bishnu Pada Datta 《Acta Crystallographica. Section C, Structural Chemistry》2001,57(12):1441-1442
In the title compound, C20H20FNO5S, the pyrrolidine ring adopts an envelope conformation. The fluorophenyl and thiophene rings are individually planar. The molecular and crystal structures are stabilized by intra- and intermolecular C—H⋯O interactions. 相似文献
30.
Medha Rele B. S. Patro S. Adhikari G. P. Kalena S. Chattopadhyay T. Mukherjee 《Journal of Chemical Sciences》2002,114(6):739-747
The free radical scavenging properties and possible antioxidant activity of 1,3-diphenylpropane-1,3-dione (1) are reported.
Pulse radiolysis technique was employed to study the one-electron oxidation of 1 with various radicals viz. CCl3O2
•, N3
• and•OH in homogeneous aqueous solution. All these radicals reacted with 1 under ambient conditions at almost diffusion controlled
rates producing transient species with an absorption maximum around 420 nm that decayed at first order rates. The transient
absorption peak was shifted in the case of CCl3OO• radical reaction with 1 due to change in the polarity of the medium. Formation of a stable product with a broad absorption
band starting from 400 nm and cut off at 230 nm was observed in the oxidation of 1 with•OH and•N3 radicals. In a biological system also, 1 showed significant inhibitory activity against Fe2+-mediatedlipidperoxidation. Based on these observations, a suitable mechanism for the oxidation of 1 has been proposed. 相似文献