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排序方式: 共有275条查询结果,搜索用时 265 毫秒
91.
Jafar Abbasi Shiran Manouchehr Mamaghani Bohari M. Yamin Jalal Albadi Farhad Shirini 《合成通讯》2013,43(13):1520-1532
A convenient, one-pot, three-component regioselective synthesis of novel 2,2′-(1,4-phenylene)-bis-(3-aryl-2-substituted imino-4-aryl-3H-thiazole) derivatives from 1,4-phenylene diisothiocyanate, aryl amines, and various phenacyl bromide, and also the regioselective synthesis of 3-alkyl-2-(aryl imino)-4-cyclopropyl-5-(2′-fluorophenyl)-thiazole derivatives from alkylisothiocyanate, aryl amines, and 2-bromo-2-(2-fluorophenyl)-1-cyclopropylethanone in the presence of poly-4-vinyl pyridine as heterogenous basic catalyst are described. This efficient method produced the products at room temperature with excellent yields (82–96%). The structures of all products were characterized by spectral and elemental analyses. The antimicrobial activity of the synthesized compounds was evaluated against Salmonella enterica, Micrococcus luteus, Bacillus subtilis, and Pseudomonas aeruginosa. 相似文献
92.
A simple, efficient, and mild method for selective bromination of some activated aromatic compounds using potassium bromide in the presence of benzyltriphenylphosphonium peroxodisulfate in nonaqueous solution is reported. The results obtained revealed good to excellent selectivity between ortho and para positions of phenols and methoxyarenes. 相似文献
93.
CuO–CeO2 is reported as a highly efficient and green recyclable catalyst,for the multicomponent synthesis of 4H-benzo[b]pyran derivatives.The catalyst was synthesized by a co-precipitation method and characterized by XRD,BET specific surface area,ESEM and EDS analysis.This synthetic method provides several advantages such as simple work-up procedures,minimal amount of waste generated,short reaction time,and high yields of products. 相似文献
94.
Huda Abdullah Mohd Syafiq Zulfakar Wan Nasarudin Wan Jalal Mohammad Tariqul Islam Sahbudin Shaari 《Journal of Sol-Gel Science and Technology》2014,69(1):183-192
Zinc aluminate compounds have been dispersed in silica matrix prepared by sol-gel method with different compositions for (1 ? x)ZnAl2O4–xSiO2. Continuous stirring of ethylene glycol solution contained zinc nitrate, aluminium nitrate and silicon dioxide to produces gel precursor. Structural and morphological studies of (1 ? x)ZnAl2O4–xSiO2 thin films were examined by field emission scanning electron microscopy (FESEM) and X-ray diffractometer (XRD) analysis. The FESEM images showed the spherical structures with porosity for (1 ? x)ZnAl2O4–xSiO2 thin films. XRD analysis indicated that the crystallite size for (1 ? x)ZnAl2O4–xSiO2 increased from 39.79 to 44.34 nm. Fourier transform infra-red analysis showed that the existence of H2O molecules and the presence of nitrate group within the samples. Dielectric permittivity (ε r ) of (1 ? x)ZnAl2O4–xSiO2 samples were measured within frequency range from 1 Hz to 1 MHz. The dielectric permittivity, ε r decreased as frequency was applied to the sample. The performance of the patch antenna can be measured using return loss analysis. The highest result shows that the patch antenna resonated at frequency 3.46 GHz and gives ?14.25 dB return loss bandwidth. 相似文献
95.
Ahmed Jalal Uddin Norihiro Katayama Yutaka Ohkoshi Yasuo Gotoh Masanobu Nagura 《Journal of Polymer Science.Polymer Physics》2002,40(21):2449-2462
For monofilament biodegradable sutures fabricated from the L ‐lactide–ε‐caprolactone (75/25) copolymer [P(LLA/CL)], there have been some concerns regarding their mechanical properties, such as the knot‐pull strength and stiffness. This article demonstrates the further potentiality of these sutures through improvements in those properties. With the aim of diminishing the molecular orientation, particularly in the suture surface region, we adopted an expedient method to treat P(LLA/CL) sutures with an acetone/water mixture, using different times and time patterns. The changes in the molecular orientation distributions across the suture cross sections were characterized by the specific index of birefringence measured with an interference microscope. The crystal orientations, knot‐pull strengths, tensile strengths, and bending rigidity were measured. The conformational changes in suture breaking during knot‐pull tests were analyzed with high‐speed‐video observations. Morphological analyses of the fractural surfaces were performed with scanning electron microscopy. The knot‐pull strength tended to rise, in comparison with that of untreated samples, up to a certain treatment time and was accompanied by a minimal decrement of the tensile strength. The knot‐pull strength did not show an increasing trend with further treatment, whereas the tensile strength declined remarkably. The birefringence, crystal orientation, bending rigidity, fractured surface analysis, and high‐speed‐video observations revealed molecular disorientation mainly in the filament outer layers for that particular treatment causing the sutures to be considerably softer. The suture softness played a role in changing the deformation behavior of the knot when a load was applied and caused the knot‐pull strength to rise. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2449–2462, 2002 相似文献
96.
97.
Basic Ionic Liquid as Catalyst and Reaction Media for the One‐pot Three‐component Regioselective Synthesis of Various Thiazol‐2‐imine Derivatives
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Jafar Abbasi Shiran Asieh Yahyazadeh Bohari M. Yamin Manouchehr Mamaghani Jalal Albadi 《Journal of heterocyclic chemistry》2016,53(4):1009-1016
Thiazol‐2‐imine derivatives were synthesized in an easy and efficient route from the regioselective one‐pot three‐component reaction of aryl amine, alkylisothiocyanate, and various α‐haloketones in [omim][OH] basic ionic liquid. Recyclable reaction media, catalyst free, and short reaction times are the main advantages of this protocol. This method produces the products at room temperature in excellent yields (68–96%). Furthermore, the target compound 6b was determined by X‐ray crystallographic analysis. 相似文献
98.
Tahira?Batool Essam?A.?MakkyEmail author Muna?Jalal Mashitah?M.?Yusoff 《Applied biochemistry and biotechnology》2016,180(5):900-916
l-asparaginase (LA) catalyzes the degradation of asparagine, an essential amino acid for leukemic cells, into ammonia and aspartate. Owing to its ability to inhibit protein biosynthesis in lymphoblasts, LA is used to treat acute lymphoblastic leukemia (ALL). Different isozymes of this enzyme have been isolated from a wide range of organisms, including plants and terrestrial and marine microorganisms. Pieces of information about the three-dimensional structure of l-asparaginase from Escherichia coli and Erwinia sp. have identified residues that are essential for catalytic activity. This review catalogues the major sources of l-asparaginase, the methods of its production through the solid state (SSF) and submerged (SmF) fermentation, purification, and characterization as well as its biological roles. In the same breath, this article explores both the past and present applications of this important enzyme and discusses its future prospects. 相似文献
99.
Alizadeh MH Emampour JS Salimi AR Razavi H 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2007,66(4-5):1126-1132
Optimized geometries and vibrational frequencies were calculated for the hexamolybdoaluminate(III), [AlIII(OH)6Mo6O18]3-, Anderson-type heteropolyanion with the HF, B3LYP, B3PW91, B3P86 and B1LYP methods of theory using the LanL2DZ, SDD and combination of LanL2DZ with 6-31G (d, p) basis sets. The agreement between the optimized and experimental geometries was in the decreasing order: HF, B3P86, B3PW91, B1LYP and B3LYP. The calculated frequencies by the B3LYP have the smallest mean root mean square (RMS) error. The effect of the basis set on the calculated bond lengths and frequencies by the density functional calculations (DFT) methods was minor. The agreement between the previously reported IR and Raman spectra and the calculated values is, in general, good. 相似文献
100.
In this study, a new way of understanding the shear-thickening phenomenon in self-assembled solutions is introduced. The near-
and out-of-equilibrium behavior is investigated in four aqueous micellar solutions containing surfactants of the same family:
the alkyltrimethylammonium bromide mixed with an ionic salt at equimolar concentration. Thus, the four molecules of surfactants
have the same polar head but different aliphatic chain length containing 12, 14, 16, and 18 carbon atoms. In aqueous solutions,
the attractive forces between the surfactant molecules depend on the length of the aliphatic chain, thus, varying this parameter
will have a definite influence on the aggregation number, the shape and dimension of the micelles. According to our results,
the evolution of the low shear viscosity is affected by the chain length. The rheometric measurements performed in steady
and time-dependent flows show that the emergence, the range, and the amplitude of the shear thickening also depend on this
parameter. However, in the domain of high shear rates, after reaching the maximum of viscosity, all flow curves superimpose
irrespective of the chain length. The rheo-optic measurements confirm the apparition of the shear-induced structure (SIS);
this new phase is locally oriented and the chain length affects strongly the micelles orientation and the birefringence intensity.
These results undoubtedly demonstrate that the chain length plays an important role in the behavior near equilibrium and under
shear flow of the micellar systems.
Paper presented at the third Annual European Rheology Conference (AERC 2006) on April 27–29, 2006, Crete, Greece. 相似文献