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JPC – Journal of Planar Chromatography – Modern TLC - A simple and precise high-performance thin-layer chromatographic (HPTLC) method has been established for simultaneous analysis of... 相似文献
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In this work, we investigate existence and uniqueness of solutions for a class of nonlinear multi-point boundary value problems for fractional differential equations. Our analysis relies on the Schauder fixed point theorem and the Banach contraction principle. 相似文献
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Rapid preparative isolation of erythrocentaurin from Enicostemma littorale by medium‐pressure liquid chromatography,its estimation by high‐pressure thin‐layer chromatography,and its α‐amylase inhibitory activity 下载免费PDF全文
Naila Hassan Javed Ahamad Saima Amin Mohd Mujeeb Showkat R. Mir 《Journal of separation science》2015,38(4):592-598
Erythrocentaurin is a relatively simple natural product present among the members of Gentianaceae. A preparative method for the isolation of erythrocentaurin from the ethyl acetate fraction of Enicostemma littorale using medium‐pressure liquid chromatography has been reported. The method consisted of a simple step gradient from 10 to 20% ethyl acetate in n‐hexane. Using a 70 × 460 mm Si60 column, this method is capable of processing 20 g of material in <3 h (purity ≈ 97%). The recovery of erythrocentaurin was 87.77%. Estimation of erythrocentaurin in extracts and fractions based on high‐pressure thin‐layer chromatography was carried out on silica gel 60 F254 plates with toluene/ethyl acetate/formic acid (80:18:2 v/v/v) as the mobile phase. The densitometric analysis was performed at 230 nm. A well‐separated compact band of erythrocentaurin appeared at Rf 0.54 ± 0.04. The analytical method showed good linearity in the concentration range of 200–1500 ng/band with a correlation coefficient of 0.99417. The limits of detection and quantification were found to be ≈60 and ≈180 ng/band, respectively. Erythrocentaurin exhibited a concentration‐dependent α‐amylase inhibition (IC50 1.67 ± 0.28 mg/mL). The outcome of the study should be considered for pharmacokinetic and biotransformation studies involving E. littorale. 相似文献
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Khan M Brunklaus G Enkelmann V Spiess HW 《Journal of the American Chemical Society》2008,130(5):1741-1748
13C-CPMAS and other solid-state NMR methods have been applied to monitor the solid-state reactions of trans-cinnamic acid derivatives, which are the pioneer and model compounds in the field of topochemistry previously studied by X-ray diffraction, AFM, and vibrational spectroscopy. Single-crystal X-ray analyses of photoirradiated alpha-trans-cinnamic acid where the monomers are arranged in a head-to-tail manner have revealed the formation of a centrosymmetric alpha-truxillic acid photodimer. For a centrosymmetric dimer, however, two cyclobutane carbon signals and one carbonyl carbon signal were expected apart from other aromatic carbon signals. Instead, four cyclobutane and two carbonyl carbon signals were observed suggesting the formation of a non-centrosymmetric photodimer. Removing hydrogen bonds from the system by esterfication of alpha-truxillic acid yield a centrosymmetric photodimer. Careful analysis of the obtained products via solid-state NMR clearly showed that the observed peak splittings in the 13C-CPMAS spectra did not originate from packing effects but rather result from asymmetric hydrogen bonds distorting the local symmetry. Further evidence of this rather dynamic hydrogen-bonding stems from high-temperature X-ray data revealing that only the joint approach of both X-ray analysis and solid-state NMR at similar temperatures allows for the successful characterization of dynamic processes occurring in topochemical reactions, thus, providing detailed insight into the reaction mechanism of organic solid-state transformations. 相似文献
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I. I. Fishchuk A. Kadashchuk S. V. Novikov Mujeeb Ullah J. Genoe N. S. Sariciftci 《Molecular Crystals and Liquid Crystals》2014,589(1):18-28
We report on the influence of the lateral electric field on the charge mobility in organic field-effect transistors (OFET) based on C60 films with multigrain morphology. The experimental data were quantitatively described using a recent analytical model by accounting for the strong local electric fields in a multigrain transistor channel and for the energy correlation effects. To rationalize the presence of a correlated disorder in a non-polar C60 material, we show that randomly oriented permanent dipoles in organic gate dielectric layers can generate a significant dipolar disorder in an adjacent nonpolar semiconductor layer. 相似文献
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Syed Farooq Adil Mohamed E. Assal Mohammed Rafi Shaik Mufsir Kuniyil Azhar Hashmi Mujeeb Khan Aslam Khan Muhammad Nawaz Tahir Abdulrahman Al-Warthan Mohammed Rafiq H. Siddiqui 《应用有机金属化学》2020,34(8):e5718
Graphene–metal nanocomposites have been found to remarkably enhance the catalytic performance of metal nanoparticle-based catalysts. In continuation of our previous report, in which highly reduced graphene oxide (HRG)-based nanocomposites were synthesized and evaluated, we present nanocomposites of graphene oxide (GRO) and ZnO nanoparticle-doped MnCO3 ([ZnO–MnCO3/(1%)GRO]) synthesized via a facile, straightforward co-precipitation technique. Interestingly, it was noticed that the incorporation of GRO in the catalytic system could noticeably improve the catalytic efficiency compared to a catalyst (ZnO–MnCO3) without GRO, for aerial oxidation of benzyl alcohol (BzOH) employing O2 as a nature-friendly oxidant under base-free conditions. The impacts of various reaction factors were thoroughly explored to optimize reaction conditions using oxidation of BzOH to benzaldehyde (BzH) as a model substrate. The catalysts were characterized using X-ray diffraction, thermogravimetric analysis, Fourier transform infrared spectroscopy, field-emission scanning electron microscopy, Energy dispersive X-ray spectroscopy (EDX), Brunauer-Emmett-Teller (BET), and Raman spectroscopy. The (1%)ZnO–MnCO3/(1%)GRO exhibited significant specific activity (67 mmol.g−1.hr−1) with full convversion of BzOH and >99% BzH selectivity within just 6 min. The catalytic efficiency of the (1%)ZnO–MnCO3/(1%)GRO nanocomposite was significantly better than the (1%)ZnO–MnCO3/(1%)HRG and (1%)ZnO–MnCO3 catalysts, presumably due to the existence of oxygen-possessing groups on the GRO surface and as well as a very high surface area that could have been instrumental in uniformly dispersing the active sites of the catalyst, i.e., ZnO–MnCO3. Under optimum circumstances, various kinds of alcohols were selectively transformed to respective carbonyls with full convertibility over the (1%)ZnO–MnCO3/(1%)GRO catalyst. Furthermore, the highly effective (1%)ZnO–MnCO3/(1%)GRO catalyst could be successfully reused and recycled over five consecutive runs with a marginal reduction in its performance and selectivity. 相似文献
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In this article, Haar wavelets have been employed to obtain solutions of boundary value problems for linear fractional partial differential equations. The differential equations are reduced to Sylvester matrix equations. The algorithm is novel in the sense that it effectively incorporates the aperiodic boundary conditions. Several examples with numerical simulations are provided to illustrate the simplicity and effectiveness of the method. 相似文献
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Usmani Zeba Mujeeb Mohd Qadir Abdul Aqil Mohd Mir Showkat Rasool Ahmad Aftab Ahmad Varish Warsi Musarrat H. Usmani Zakiya 《平面色谱法杂志一现代薄层色谱法》2020,33(6):587-597
JPC – Journal of Planar Chromatography – Modern TLC - In the present work, a simple, rapid, reliable and accessible high-performance thin-layer chromatography (HPTLC) technique has been... 相似文献