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排序方式: 共有417条查询结果,搜索用时 15 毫秒
411.
Olga Varghese 《Discrete Mathematics》2019,342(7):2100-2105
Graph products of groups and Coxeter groups are defined via vertex-edge-labeled graphs. We show that if the graph has a special shape, then the corresponding group is coherent, i.e. every finitely generated subgroup is finitely presented. 相似文献
412.
JPC – Journal of Planar Chromatography – Modern TLC - This paper describes a validated high-performance thin-layer chromatography (HPTLC) method for the simultaneous determination of... 相似文献
413.
This paper describes two simple, specific, accurate, and precise methods for estimation of olopatadine hydrochloride (OLO) in tablet dosage form. The first method is a stability-indicating isocratic RP-HPLC method. The analysis is performed on an RP-18 column using 0.1% orthophosphoric acid (adjusted to pH 4.5 with triethylamine)-acetonitrile (75 + 25, v/v) mobile phase at a flow rate of 1 mL/min. Paracetamol (PAR) was selected as the internal standard. Retention times of OLO and PAR were 11.30 +/- 0.02 and 4.70 +/- 0.03 min, respectively. For the HPTLC method, precoated silica gel 60 F254 aluminum sheets were used as the stationary phase; the mobile phase was methanol-chloroform-ammonia (8 + 2 + 0.1, v/v/v). The detection of the analyte band was carried out at 301 nm, and its Rf value was 0.46 +/- 0.03. The analytical methods were validated according to International Conference on Harmonization guidelines. Linear regression analysis data for the calibration plots showed a good linear relationship between response and concentration in the range of 0.1-1 microg/mL and 0.1-0.9 microg/band for HPLC and HPTLC, respectively. 相似文献
414.
C. Yohannan Panicker Hema Tresa Varghese L. Ushakumary 《Journal of Raman spectroscopy : JRS》2009,40(12):2023-2030
The IR and Raman spectra of ethyl salicylate were recorded and analyzed. The surface enhanced Raman scattering (SERS) spectrum was recorded in a silver colloid. The vibrational wavenumbers of the compound have been computed using the Hartree‐Fock/6‐31G* basis. The direction of charge transfer contribution to SERS has been discussed from the frontier orbital theory. The presence of methyl modes in the SERS spectrum indicates the nearness of the methyl group to the metal surface and the presence of ring vibrations and out‐of‐plane ring modes in the SERS spectrum suggests a flat orientation of the molecule on the silver surface. The first hyperpolarizability is calculated and the calculated molecular geometry has been compared with the reported similar structures. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
415.
L. Ushakumari Hema Tresa Varghese C. Yohannan Panicker Tugba Ertan Ilkay Yildiz 《Journal of Raman spectroscopy : JRS》2008,39(12):1832-1839
Fourier transform infrared (FT‐IR) and FT‐Raman spectra of 4‐fluoro‐N‐(2‐hydroxy‐4‐nitrophenyl)benzamide were recorded and analyzed. The vibrational wavenumbers and corresponding vibrational assignments were examined theoretically using the Gaussian03 set of quantum chemistry codes. The red‐shift of the NH‐stretching wavenumber in the infrared (IR) spectrum from the computed wavenumber indicates the weakening of the NH bond resulting in proton transfer to the neighboring oxygen atom. The simultaneous IR and Raman activation of the CO‐stretching mode gives the charge transfer interaction through a π‐conjugated path. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
416.
417.
Rajnikant V.K. Gupta M.B. Deshmukh B. Varghese Dinesh 《Crystal Research and Technology》2001,36(12):1451-1456
The crystal structure of methyl‐3, 4‐dihydro‐3‐(p‐methylphenyl)‐4‐oxo‐2‐quinazolinyl thiopropionate (C19H18N2O3S) has been determined by X‐ray diffraction methods. The compound crystallizes in the triclinic space group P with unit cell parameters: a = 9.094(2), b = 9.428(3), c = 10.612(3) Å, α = 94.55(3), β = 95.44(2), γ = 106.75(3)° and Z = 2. The structure has been refined to an R‐value of 0.054 for 2533 observed reflections [Fo > 4σ(Fo)]. The quinazoline moiety and the methyl substituted phenyl ring is almost planar. The dihedral angle between these two moieties is 84.96(8)° . The crystal structure is stabilized by an intermolecular C‐H … O interaction. 相似文献