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21.
22.
Hamid?Mofakham Rahim?Ghadari Ahmad?ShaabaniEmail author Milad?Pedarpour Sabrieh?Ghasemi 《Journal of the Iranian Chemical Society》2013,10(2):307-317
In this work, functionalized pyrimidine-2,4-dione-, benzo[g]-, and dihydropyrano[2,3-g]chromene derivatives have been synthesized via a Michael addition of 2-hydroxy-1,4-naphthoquinone or 2,5-dihydroxy-1,4-benzoquinone to the Knoevenagel condensation product of an aldehyde with Meldrum’s acid, dimedone or barbituric acid in the presence of a catalytic amount of l-proline under refluxing conditions in water in good to excellent yields. 相似文献
23.
Dadan Hermawan Izdiani Mohd Yatim Khaulah Ab Rahim Mohd Marsin Sanagi Wan Aini Wan Ibrahim Hassan Y. Aboul-Enein 《Chromatographia》2013,76(21-22):1527-1536
A simple solid phase extraction (SPE) method coupled with high performance liquid chromatography (HPLC) using UV detector and microemulsion electrokinetic chromatography (MEEKC) has been developed and compared for the quantitative determination of miconazole nitrate in pharmaceutical formulation. For HPLC method, two parameters were optimized, namely, the wavelength and the mobile phases. The optimized condition was at the 225 nm wavelength and the mobile phase of ACN:MeOH (90:10 v/v). There are seven MEEKC parameters that were optimized, in this research, which were applied to voltage, temperature, wavelength, sodium dodecyl sulfate (SDS) concentration, buffer pH, buffer concentration and butan-1-ol concentration. The optimum MEEKC condition was obtained using 86.35 % (w/w) 2.5 mM borate buffer pH 9, 0.25 % (w/w) SDS, 0.8 % (w/w) ethyl acetate, 6.6 % w/w butan-1-ol and 6.0 % (w/w) acetonitrile. The combination of SPE using a diol column with HPLC–UV and the MEEKC methods were successfully applied for the determination of miconazole nitrate in a pharmaceutical formulation with the recovery percentage of 98.35 and 92.50 %, respectively. 相似文献
24.
An extremely efficient heterogeneous protocol is reported for the one-pot, three-component synthesis of a series of dihydropyrimidinones (DHPMs) in the presence of ZnO nanoparticles in water as a green solvent. The ZnO nanoparticles exhibited excellent catalytic activity and the proposed methodology is capable of providing the desired products in good yields (65–94%) within short reaction times. After the reaction course, ZnO nanoparticles can be recycled and reused without any apparent loss of activity, which makes this ecofriendly process cost-effective. 相似文献
25.
Oleg Tkachenko Abdur Rahim Andrey Baraban Ruslan Sukhov Inna Khristenko Yoshitaka Gushikem Yuriy Kholin 《Journal of Sol-Gel Science and Technology》2013,66(1):145-154
A sol–gel based hybrid process was developed by manipulating different techniques in sol–gel process to synthesize γ-alumina and (CuO, CuO + ZnO) doped γ-alumina spherical particles. Catalysts having spherical geometry have an important advantage over powders or pellets which are impervious to fluids, when packed in a reactor. Boehmite sol was used as alumina precursor for synthesizing porous γ-alumina and doped materials. γ-alumina particles having 5 wt% CuO, 4 wt% CuO + 1 wt% ZnO, 3 wt% CuO + 2 wt% ZnO and 2 wt% CuO + 3 wt% ZnO were prepared by adding required amounts of Cu(NO3)2 and Zn(NO3)2 solutions prior to gelation of the sol. Methanol dehydration studies were carried out by employing these synthesized catalysts. Hundred percent conversion of methanol to dimethyl ether was observed with (4 wt% CuO + 1 wt% ZnO)-γ-alumina and (5 wt% CuO)-γ-alumina microspheres at 325 and 350 °C, respectively. 相似文献
26.
27.
This paper proves that a difference field (E, ) admits quantifierelimination if and only if E is an algebraically closed field,and is an integer power of the Frobenius automorphism. 1991Mathematics Subject Classification 03C60, 12H10. 相似文献
28.
Majid M. Heravi Samaheh Sadjadi Sodeh Sadjadi Hossein A. Oskooie Rahim Hekmat Shoar Fatemeh F. Bamoharram 《中国化学会会志》2009,56(2):246-250
Silica‐supported Preyssler nanoparticles (H14[NaP5W30O110])/SiO2 are used as a new and recyclable catalyst for the preparation of 1,3‐diaryl‐5‐spirohexahydropyrimidines via a one‐pot condensation of anilines, formaldehyde, and cyclohexanone. 相似文献
29.
This paper describes a new structure of left-handed metamaterial (LHM) based on parametric studies using Computer Simulation
Technology (CST) software. The LHM structure is a combination of the modified square rectangular split ring (MSRR) and the
capacitance loaded strip (CLS). In this paper, the parametric studies are used to see the effect of frequency and the negative
value range of permeability (μ
r
) and permittivity (ε
r
) toward changes of LHM parameters. The changes in the dimension of MSSR and CLS affect the S
11 and S
21 of the LHM structure which will affect the values of permeability and permittivity. The values of permeability and permittivity
were extracted from the reflection and transmission coefficient data. The studies proved that the LHM structure can be designed
within the frequency range of interest. 相似文献
30.
In this study, the Bonner sphere spectrometer (BSS) used for measurement of neutron spectra based a BF3 long counter. The most important problem for this system was a high count of scattered neutrons. This spectrometer was established
by designed a new shadow cone with a smaller length and improved attenuation coefficient. Because of shortening the length
of the shadow cone, distance of source and center of the sphere was decreased. Furthermore, external part of the thermal detector
was covered with a suitable layer to reduce the contribution count of scattering neutrons. Experimental results show that
BSS system with BF3 long cylindrical counter, applying the proper developments, can be used in neutron fluence spectrometry. 相似文献