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121.
Abdelhamid Meziani 《Proceedings of the American Mathematical Society》1996,124(9):2767-2772
We prove that a nondegenerate CR structure with signature
at and with first integrals satisfying
at and with first integrals satisfying
is realizable if and only if an action of the group leaves invariant a one-dimensional subbundle of the structure bundle.
122.
Treatment of 1-phenyl-2-bromo-2-arylhydrazonoethanone (VII) with sodium etiolates of 2,4-pentanedione, 1-phenyl-1,3-butanedione, dibenzoylmethane, ethyl benzoylacetate, acetoaceta-nilide, and of benzoylacetanilide in ethanol afforded the substituted pyrazoles, VIII-XIII, respectively. The results show that VII, unlike 1-phenyl-2-bromo-2-hydroximinoethanone (V), is not easily deprotonated by carbanions; and that its reactions with β-diketones, β-keto esters, and β-keto amides follow one and the same mechanism. The structures of the products (VIII-XIII) were inferred from their elemental analyses and spectral data. 相似文献
123.
Pascale Hazot Thierry Delair Christian Pichot Jean-Paul Chapel Abdelhamid Elaissari 《Comptes Rendus Chimie》2003,6(11-12):1417-1424
Thermally-sensitive crosslinked submicronic particles were prepared by an emulsion/precipitation process of N-ethylmethacrylamide (NEMAM), using potassium persulphate as initiator and four different crosslinkers; ethylene glycol dimethacrylate (EGDMA), 1,3-butanediol dimethacrylate (1,3-BDDMA), 1,4-butanediol dimethacrylate (1,4-BDDMA) and tetraethylene glycol dimethacrylate (TEGDMA). At first, polymerization kinetics was studied by NMR, revealing the negligible effect of the crosslinker nature. On the contrary, the water-soluble polymer amounts, the final hydrodynamic particle size, the swelling ability, the electrokinetic properties were found to be dependent upon the nature of crosslinker. The final latexes were found to be narrowly size distributed irrespective of the crosslinker agent’s chemical nature. In this study, the water solubility of the cross-linker was reported to be an important criterion, but other factors, such as diffusion and reactivity, have to be taken into consideration. To cite this article: P. Hazot et al., C. R. Chimie 6 (2003). 相似文献
124.
Bessueille F Pla-Roca M Mills CA Martinez E Samitier J Errachid A 《Langmuir : the ACS journal of surfaces and colloids》2005,21(26):12060-12063
A technique for microcontact printing of thiols in liquid media is presented. Elastomeric poly(dimethyl siloxane) stamps are used to pattern gold surfaces with thiol-based self-assembled monolayers. The liquid (water in this case) has been used as an incompressible support and, advantageously, also acts as a medium in which alkylthiol ink molecules are poorly miscible. Consequently, we have been able to produce patterned thiol monolayers using stamps with aspect ratios unsuitable for conventional microcontact printing (i.e., 15:1) and present evidence to suggest that it is possible to use stamps with aspect ratios of up to 100:1. 相似文献
125.
Andrea M. Santos Abdelhamid Elaïssari José M. G. Martinho Christian Pichot 《Colloid and polymer science》2004,282(7):661-669
Poly(methyl methacrylate) (PMMA)-based latex particles bearing carboxylic groups at the surface were prepared via emulsion polymerization. The polymerization recipe and process were optimized in order to target monodisperse particles with diameters around 100 nm. The polymerizations were performed using 4,4-azobis(4-cyanopentanoic) acid (ACPA) as initiator and sodium dodecyl sulphate (SDS) as surfactant. The polymerization conversion was determined by both gas chromatography and gravimetry. The final latexes were characterized with respect to particle size, size distribution, surface charge density, electrokinetic properties (i.e. electrophoretic mobility vs pH and ionic strength) and colloidal stability (i.e. coagulation rate constants vs pH and stability factor vs ionic strength). 相似文献
126.
Neila Najai LabidI Abdelhamid Ghorbel Didier Tichit Gérard Delahay 《Reaction Kinetics and Catalysis Letters》2006,88(2):261-268
Summary Calcined CoMgAl LDHs and a Co-impregnated LDH were characterized by XRD, N2 physisorption, TPR and ICP elemental analysis, then tested in the selective catalytic reduction (SCR) of NO with ammonia.
Cobalt deposited by impregnation on LDH leads to the more active and selective catalyst. On this type of catalyst nearly 80%
of conversion and selectivity to N2 were reached at 578 K with a volume space velocity of 2200 h-1. 相似文献
127.
H. Schweighardt J. Böhm A. M. Abdelhamid J. Leibetseder M. Schuh E. Glawischnig 《Chromatographia》1980,13(7):447-450
Summary HPLC procedures for analyses of the fusariotoxins zearalenone and vomitoxin in individual food- and feedstuffs as well as in mixed feed are described. Zearalenone is separated on a column with polar stationary phase (25 cm × 4.6 mm i.d., particle size 7 m), eluted with a chloroform-isooctane (75/25, v/v)+1.5% methanol mixture and detected fluorometrically. The quantitative determination was possible in all analyzed samples with a detection limit of 2g/kg with 70–80% recovery. Vomitoxin is fractionated by HPLC (C
18
1
column, 25 cm×4 mm i.d., 5 m particle size) with water-methanol (60/40, v/v) mobile phase and determined by combining GLC or TLC with UV detection. The detection limit in mixed feed with interfering substances was 25 g/kg (recovery 25–35%). The separation by HPLC makes preparation of pure vomitoxin possible. The described methods are fast, simple and low cost and are suitable for routine analyses. 相似文献
128.
Imene Mejri Mohamed Kadri Younes Abdelhamid Ghorbel 《Journal of Sol-Gel Science and Technology》2006,40(1):3-8
Aerogel and xerogel sulphated zirconia with defined atomic ratio S/Zr = 0.5 and molar hydrolysis ratio h = nH2O/nZrO2 = 3 show different textural and structural properties after calcination at high temperatures. The aerogel obtained just after
solvent evacuation develops only the tetragonal phase, whereas the xerogel dried in an oven is amorphous. Heating to a temperature
above 833 K, leads to transition of the tetragonal phase to the monoclinic one for the two solids, due to sulphur loss but
the tetragonal phase remains stable for the aerogel . Raman, Infrared and XPS spectroscopies show that the loss of the sulphur
at high temperatures seems to be easier for the xerogel than for the aerogel. 相似文献
129.
Duangporn?Polpanich Pramuan?TangboriboonratEmail author Abdelhamid?Ela?ssari 《Colloid and polymer science》2005,284(2):183-191
Poly(styrene-co-acrylic acid) (St/AA) latices were prepared by using a batch soap-free emulsion copolymerisation in non-buffered medium. Polymerisation kinetics, followed by gravimetric method, revealed that increasing AA comonomer concentration was directly proportional to the copolymerisation rate, while adding AA comonomer caused a strong decrease of particle size of final St/AA latex particle without affecting the size distribution. Transmission electron microscopy indicated that the particles were monodispersed and spherical in shape irrespective of AA amount used in the investigated range. The colloidal stability of the latices was increased upon increasing the AA concentration; owing to the electrosteric stabilisation originated from AA-rich layer on the particle surface. In addition, electrophoretic mobility of formed particles versus polymerisation conversion exhibited the constancy of the surface charge density during the polymerisation process and was inferred for discussion of the polymerisation mechanism of this system. 相似文献
130.
Hamdi M. Hassaneen Abdou O. Abdelhamid Abdelgawad A. Fahmi Ahmad S. Shawali 《Journal of heterocyclic chemistry》1985,22(2):395-400
Bromination of 1-arylsulfonyl-1,2-propanedione-1-aryl-hydrazones 7 in a mixture of acetic acid and acetic anhydride in the presence of sodium acetate gave N-aryl-C-arylsulfonylformohydrazidoyl bromides 5. Treatment of 5 with dibenzoylmethane, acetylacetone, ethyl acetoacetate and ethyl benzoylacetate in ethanol in the presence of sodium ethoxide yielded the pyrazole derivatives 8-11 , respectively. Reaction of 5 with potassium thiocyanate afforded the thiadiazoline derivative 14. The bromides 5 also react with nucleophiles such as morpholine, piperidine, phenoxide, thiophenoxide and benzenesulfinate anions to give the corresponding substitution products 19-23 , respectively. The structures of the products 8-23 were assigned and confirmed on the basis of their spectral and elemental analyses, their chemical behaviour and alternate synthesis wherever possible. 相似文献