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581.
Laboratory investigations of the potential use of dried biomasses of Rhizopus stolonifer, Fusarium sp., Geotrichum sp., and Aspergillus fumigatus as biosorbents for the removal of bromophenol blue (BPB) dye from aqueous solutions were conducted. Kinetics studies indicated
that the BPB dye uptake processes can be well described by the pseudo-second-order model. The fungal biomasses exhibited the
highest dye biosorption at pH 2.0. The Langmuir adsorption model appears to fit the dye biosorption better than the Freundlich
model, with maximum dye uptake capacities ranging from 526 to 1111 mg/g, depending on the biomass used. 相似文献
582.
Zouari N Sayari A Miled N Verger R Gargouri Y 《Colloids and surfaces. B, Biointerfaces》2006,49(1):8-14
Using the classical emulsified system and the monomolecular film technique, we compared the interfacial properties of the scorpion digestive lipase (SDL) with those of higher animals'. In the absence of bile slats, SDL does not hydrolyse efficiently pure tributyrin, as well as dicaprin films maintained at low surface pressure. The preincubation of bile salts with tributyrin seems to be a better substrate for SDL than the pure tributyrin. A kinetic study on the surface pressure dependency, stereospecificity and regioselectivity of SDL was performed using monomolecular films of either three dicaprin isomers or three pairs of didecanoyl-deoxyamino-O-methyl glycerol enantiomers (DDG) containing a single hydrolysable decanoyl ester bond. With all diacylglycerol isomers, SDL has a surface pressure threshold of about 15 m Nm(-1), below which enzymatic activity is undetectable. SDL seems to prefer vicinal ester groups of the diacylglycerol isomers, with preference for sn-1 position at both 15 and 23 m Nm(-1). Furthermore, the maximum SDL activity is measured with DDG having a primary ester bond (1,3DDG, SII). This shows that SDL has a preference for the sn-1 position of this diacylglycerol analogue. Moreover, this was in line with the fact that SDL is inactive on sn-2 position of both DDG isomers and a triacylglycerol. With diacylglycerol analogue isomers, SDL shows a preference for distal isomers contrary to what has been observed with diacylglycerol isomers. SDL interacts with egg-phosphatidyl choline (egg-PC) monomolecular films. The critical surface pressure value (13 m Nm(-1)) is comparable to those of pancreatic lipases. 相似文献
583.
Kamal A. Kandeel Ahmed S. A. Youssef Wael S. I. Abou‐Elmagd Ahmed I. Hashem 《Journal of heterocyclic chemistry》2006,43(4):957-962
Ring closure of 2‐N‐benzylamino‐3‐aroylpropionic acids ( 3 ) with acetic anhydride afforded 3‐N‐benzylamino‐5‐aryl‐2(3H)‐furanones ( 4 ). The reaction of the furanones ( 4 ) with benzylamine in benzene was found to be time dependent. Thus refluxing the reaction mixture for 1 h only afforded the open‐chain amides ( 5a‐c ). When the reaction was conducted for 3 h the 2(3H)‐pyrrolones ( 6 ) were obtained. Hydrazine hydrate affected ring opening of the furanones to give the hydrazides ( 5d‐f ). Also, semicarbazide converted ( 4 ) into the corresponding semicarbazide derivatives ( 5g‐i ). The hydrazides ( 5d‐f ) were reacted with benzoyl chloride to give the corresponding diaroylhydrazines ( 5j‐l ). The open‐chain derivatives ( 5 ) were converted into a variety of heterocycles: isothiazolones ( 7 ), dihydropyridazinones ( 8 ), 1,3,4‐oxadiazoles ( 9 ) and 1,2,4‐triazole derivatives ( 10 ) via cyclization reactions. 相似文献
584.
Maher Kammoun Imed Koubaa Yassine Ben Ali Raoudha Jarraya Youssef Gargouri Mohamed Damak Sofiane Bezzine 《Applied biochemistry and biotechnology》2010,162(3):662-670
The aim of the present work was to evaluate the anti-inflammatory properties of Cynara cardunculus L. (Asteraceae) during its growth using various solvents such as n-hexane, dichloromethane, acetone, and methanol for air-dried leaves and stems. The anti-inflammatory activities of crude
extracts were evaluated by measuring the inhibition potency of mammalian non-pancreatic phospholipases A2 (hG-IIA). The methanol
and acetone extracts of leaves harvested in February exhibit potent inhibition of hG-IIA (IC50 = 50 and 70 μg/ml, respectively). However, the acetone extract of stems harvested in December inhibits the hG-IIA with a
lower IC50 around 130 μg/ml. Fractionation on silica gel and hydrophobic gel of the methanol extract of leaves harvested in February
increases the inhibitory effect, and the IC50 reached 10 μg/ml. 相似文献
585.
Existence results for periodic solutions of integro-dynamic equations on time scales 总被引:1,自引:0,他引:1
Using the topological degree method and Schaefer’s fixed point theorem, we deduce the existence of periodic solutions of nonlinear
system of integro-dynamic equations on periodic time scales. Furthermore, we provide several applications to scalar equations,
in which we develop a time scale analog of Lyapunov’s direct method and prove an analog of Sobolev’s inequality on time scales
to arrive at a priori bound on all periodic solutions. Therefore, we improve and generalize the corresponding results in Burton
et al. (Ann Mat Pura Appl 161:271–283, 1992)
相似文献
586.
An implicit multilevel finite volume solver on adaptively refined quadtree meshes is presented for the solution of steady state flow problems. The nonlinear problem arising from the implicit time discretization is solved by an adaptive FAS multigrid method. Local grid adaptation is performed by means of a multiscale-based strategy. For this purpose data of the flow field are decomposed into coarse grid information and a sequence of detail coefficients that describe the difference between two refinement levels and reveal insight into the local regularity behavior of the solution. Here wavelet techniques are employed for the multiscale analysis. The key idea of the present work is to use the transfer operators of the multiscale analysis for the prolongation and restriction operator in the FAS cycle. The efficiency of the solver is investigated by means of an inviscid 2D flow over a bump. 相似文献
587.
588.
Carina Sinclér Delfino Michel Nicolau Youssef Fábio Barbosa De Souza Rodivan Braz Míriam Lacalle Turbino 《Optik》2012,123(3):263-267
The objective of this study was to compare the microhardness of two resin composites (microhybrid and nanoparticles). Light activation was performed with argon ion laser 1.56 J (L) and halogen light 2.6 J (H) was used as control. Measurements were taken on the irradiated surfaces and those opposite them, at thicknesses of 1, 2 and 3 mm. To evaluate the quality of polymerization, the percentages of maximum hardness were calculated (PMH). For statistical analysis the ANOVA and Tukey tests were used (p ≤ 0.05). To microhybrid was shown that the hardness with laser was inferior to the hardness achieved with halogen light, for both the 1 mm and 2 mm. The nanoparticles polymerized with laser, presented lower hardness even on the irradiated surface, than the same surface light activated with halogen light. The microhybrid attained a minimum PMH of 80% up to the thickness of 2 mm with halogen light, and with laser, only up to 1 mm. The nanoparticles attained a minimum PMH of 80% up to 3 mm thickness with halogen light and with laser this minimum was not obtained at any thickness. Based on these results, it could be concluded that light activation with argon ion laser is contra-indicated for the studied nanoparticles. 相似文献
589.
Youssef AO 《Journal of fluorescence》2012,22(3):827-834
A new, simple, sensitive and selective spectrofluorimetric method for the determination of Hydrochlorothiazide was developed
in acetonitrile at pH 6.2. The Hydrochlorothiazide can remarkably enhance the luminescence intensity of the Tb3+ ion doped in sol–gel matrix at λex = 370 nm. The intensity of the emission band of Tb3+ ion doped in sol–gel matrix was increased due to the energy transfer from the triplet excited state of Hydrochlorothiazide
to (5D4) excited energy state of Tb3 ion. The enhancement of the emission band of Tb3+ ion doped in sol–gel matrix at (5D4→7 F5) 545 nm was directly proportion to the concentration of Hydrochlorothiazide with a dynamic ranges of 5.0 × 10−10—5.0 × 10−6 mol L−1 and detection limit of 2.2 × 10−11 mol L−1. 相似文献
590.
Stephen E. Bechtel Nivine T. Youssef M. Gregory Forest Hong Zhou Kurt W. Koelling 《Rheologica Acta》2001,40(4):373-383
A model for oscillating free surface jet flow of a fluid from an elliptical orifice, together with experimental measurements,
can be exploited to characterize the elongational viscosity of non-Newtonian inelastic fluids. The oscillating jet flow is
predominantly elongational, with a small strain that oscillates rapidly between large and zero strain rates. We find that
to reproduce the experimentally observed steady oscillating jet flow in model simulations, the assumed form of the non-Newtonian
viscosity as a function of strain rate must have zero gradient, i.e., be Newtonian, at zero strain rate (a behavior exhibited,
in general, by real inelastic fluids). We demonstrate that the Cross, Carreau, Prandtl-Eyring, and Powell-Eyring forms, although
they have finite viscosity at zero strain rate, have either nonzero or even unbounded gradient at zero, and hence are unable
to model oscillating jet behavior. We propose a new non-Newtonian viscous form which has all of the desirable features of
existing forms (high and low strain rate plateaus, with adjustable location and steepness of the transition) and the additional
feature of Newtonian behavior at low strain rates.
Received: 7 February 2000 Accepted: 31 October 2000 相似文献