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991.
Khan SB Afza N Malik A Azhar-Ul-Haq Perveen S Ahmad I Ejaz A Choudhary MI 《Natural product research》2006,20(4):335-339
A new flavonol glycoside (1) has been isolated from the ethyl acetate soluble fraction of Amberboa ramosa and assigned the structure 5,7,4'-trihydroxy-3,8-dimethoxylflavone 5-O-beta-D-gluco-pyranoside (1). In addition, 6,4'-dihydroxy-3,5,7-trimethoxyflavone (2), 5,7-dihydroxy-4'-methoxyflavone (3) and (23R)-5alpha-cycloart-24-ene-3beta,21,23-triol (4) have also been reported for the first time from this species. The structures were deduced on the basis of 1D and 2D NMR techniques. The compounds 1-3 displayed weak to moderate inhibition against the xanthine oxidase enzyme. 相似文献
992.
Esa Toukoniitty Päivi Mäki-Arvela Ahmad Kalantar Neyestanaki Ensio Laine Jyri-Pekka Mikkola Tapio Salmi Dmitry Yu. Murzin 《Reaction Kinetics and Catalysis Letters》2001,73(1):3-11
In the presence of ultrasound both the initial hydrogenation rate of 1-phenyl-1,2- propanedione and the enantiomeric excess of the main product, i.e. (R)-1-hydroxy- 1-phenylpropanone, increased by 75 % and 52 % in toluene, respectively, as compared to the silent hydrogenation. 相似文献
993.
Iraj Mohammadpoor-Baltork Ahmad R. Khosropour Seyedeh F. Hojati 《Monatshefte für Chemie / Chemical Monthly》2007,138(7):663-667
Summary. A series of benzoxazoles, benzothiazoles, benzimidazoles, and oxazolo[4,5-b]pyridines was efficiently synthesized from the reactions of o-aminophenols, o-aminothiophenol, o-phenylenediamines, and 2-amino-3-hydroxypyridine with orthoesters in the presence of catalytic amounts of Bi(III) salts,
such as Bi(TFA)3, Bi(OTf)3, and BiOClO4 · xH2O under solvent-free conditions. The remarkable features of this new protocol are high conversion, very short reaction times,
cleaner reaction profiles under solvent-free conditions, straightforward procedure, and use of relatively non-toxic catalysts. 相似文献
994.
995.
Ahmad J Rusumdar A. Abuthalib Vaka Murali Mohan C. Srinivasa Kumar V. Sujatha P. Rajendra Prasad 《Experimental Thermal and Fluid Science》2009,33(5):791-796
The hydrodynamics and energy consumption have been studied in a cold flow, bubbling and turbulent, pressurized gas–liquid–solid three-phase fluidized bed (0.15 m ID × 1 m height) with concurrent gas–liquid up flow is proposed with the intention of increasing the gas hold up. The hydrodynamic behaviour is described and characterised by some specific gas and liquid velocities. Particles are easily fluidized and can be uniformly distributed over the whole height of the column. The effect of parameters like liquid flow rate, gas flow rate, particle loading, particle size, and solid density on gas hold up and effect of gas flow rate, solid density and particle size on solid hold up, energy consumption and minimum fluidization velocity has been studied. At the elevated pressures a superior method for better prediction of minimum fluidization velocity and terminal settling velocities has been adopted. The results have been interpreted with Bernoulli’s theorem and Richardson–Zaki equation. Based on the assumption of the gas and liquid as a pretend fluid, a simplification has been made to predict the particle terminal settling velocities. The Richardson–Zaki parameter n′ was compared with Renzo’s results. A correlation has been proposed with the experimental results for the three-phase fluidization. 相似文献
996.
The phenomenon of slip is known to strongly influence the performance of centrifugal pumps. In the present work, the slip phenomenon at the impeller outlet is studied experimentally for five industrial pumps at different flow rates and the slip factor is estimated for each of these cases. Theoretical slip factors are calculated using several existing methods taking into consideration the main geometric parameters of the impeller. Then the experimental slip factors are compared with the calculated theoretical values.It was observed that in the design-point condition of the pumps, the experimental values are in a good agreement with the theoretical values. However, there are significant disagreements between the theoretical and experimental values at off-design regiments. The difference is more apparent at low flow rates. It is also found that the slip factor depends on the impeller-outlet velocity profile. By defining a flow distortion coefficient, a correlation is derived for evaluating the slip-factor value for off-design conditions.Finally, a slip factor table is provided to calculate the slip factor in centrifugal pumps, using the geometry of impeller. 相似文献
997.
Ahmad Shaabani Abbas Rahmati Elham Farhangi Ali Hossein Rezayan 《Monatshefte für Chemie / Chemical Monthly》2007,35(1):615-618
A novel class of 3,4-dihydrobenzimidazo[2,1-b]quinazolin-1(2H)-ones was synthesized in very short reaction times with good yields in the presence of 3-butyl-1-methyl imidazolium bromide
as a room temperature ionic liquid at 120°C. The ionic liquid can be recycled for subsequent reactions without any loss of
efficiency. 相似文献
998.
JPC – Journal of Planar Chromatography – Modern TLC - Rapid separation of p-hydroxybenzoic acid from methyl p-hydroxy-benzoate, ethyl p-hydroxybenzoate, propyl p-hydroxybenzoate,... 相似文献
999.
1000.
H. Ahmad M. S. Rahman M. A. J. Miah A. M. I. Ali 《Colloid and polymer science》2001,279(10):1039-1043
A series of poly(methyl methacrylate)/poly(methyl methacrylate-acrylamide) composite polymer particles was prepared with
varying proportions of acrylamide in the copolymer shell layer. Adsorption behaviors of some biomolecules and specific activity
of adsorbed trypsin were studied. The hydrophobic interaction between the composite polymer particle surfaces and biomolecules
decreased with increasing acrylamide content.
Received: 7 February 2001 Accepted: 16 May 2001 相似文献