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81.
Soleyman Hosseinzadeh Younes Saadat Samira Abdolbaghi Faramarz Afshar-Taromi Alireza Hosseinzadeh 《Colloid Journal》2014,76(1):104-112
In this work, seeded dispersion polymerization of styrene was carried out in the presence of various types of seed particles. We found that in the case of polystyrene and poly(methyl methacrylate) seeds, the shape of the resulting particles remained spherical. For styrene/poly(nbutyl methacrylate) (PnBMA) and styrene/poly(lauryl methacrylate) seeding particles, raspberry like particles were produced along with those of occluded morphology. We studied the effects of various polymerization factors such as concentrations of a stabilizer, an initiator, and a monomer, a weight ratio of methanol to water, a type of initiator, weight ratio of styrene to Pn-BMA seed particles, and polymerization temperature on the formation of these raspberry-like particles. The experimental results showed that the increase of concentrations of the initiator and the stabilizer as well as that of methanol favors the formation of such particles by increasing their surface roughness. An increase of the temperature of polymerization had the same effect on the morphology of resulting product. We hypothesized that the nucleation and growth of specifically fine-structured polystyrene domains on the surface of the Pn-BMA particles guides the formation of non-linear morphology during seeded polymerization in colloidal solution. 相似文献
82.
Abdul-Latif Hamdan Walid Medawar Abbas Younes Hala Bikhazi Nabil Fuleihan 《Journal of voice》2005,19(2):290-295
Because respiration is part of the well-coordinated process necessary for phonation, this study was conducted with the purpose of analyzing the effect of chronic hemodialysis on voice characteristics of patients with chronic renal failure. A total of 57 patients were recruited for the study, including 31 males and 26 females ranging in age from 16 to 85 years. Patients underwent evaluation of their voice directly before and after hemodialysis using the Kay Elemetric VISI Pitch (Model 330; Kay Elemetric Corporation, Lincoln Park, New Jersey). The vocal acoustic parameters studied include habitual pitch, pitch range, relative average perturbation, shimmer, noise-to-harmonic ratio, voice turbulence index, maximum phonation time, and voice energy. The data were analyzed using the paired t-test for the total sample and the nonparametric test for the female and male subgroups. The total sample analysis showed a statistically significant increase in the habitual pitch after the hemodialyis (p < 0.05), with a borderline increase in the pitch range and maximum phonation time (p < 0.10). In the female group, there was a statistically significant increase in the habitual pitch and a borderline increase in the relative average perturbation. In the male group, there was a significant increase in the habitual pitch with a borderline increase in maximum phonation time. Discussion of the after-mentioned results is presented. 相似文献
83.
By using the electronic wave functions obtained from an ab initio calculation, including the spin‐orbit coupling, the electronic transition moments have been investigated for two bound states of symmetry Ω = 1/2 and Ω = 3/2 of the molecular ion KRb+. Based on a canonical functions approach for the determination of the vibrational wave functions, the matrix elements have been calculated for the bound states considered for v = 0, 10, 20 with v′‐ v = 0, 1, 2, …, 6; by using the same canonical approach, the eigenvalues and abscissas of the corresponding turning points (rmin and rmax) have been investigated for these states that obtained from a theoretical ab initio calculation up to v = 105. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2005 相似文献
84.
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
85.
4‐Bromo‐1‐phenyl‐3,5‐pyrazolidinedione 2 reacted with different nucleophilic reagents to give the corresponding 4‐substituted derivatives 3–8 . The cyclized compounds 9–11 were achieved on refluxing compounds 3 , 4 or 6a in glacial acetic acid or diphenyl ether. 4,4‐Dibromo‐1‐phenyl‐3,5‐pyrazolidinedione 12 reacted with the proper bidentates to give the corresponding spiro 3,5‐pyrazolidinediones 13–15 , respectively. The 4‐aralkylidine derivatives 16a‐c , were subjected to Mannich reaction to give Mannich bases 17a‐c‐22a‐c , respectively. 4‐(p‐Methylphenylaminomethylidine)‐1‐phenyl‐3,5‐pyrazolidinedione 23 or 4‐(p‐methylphenylazo)‐1‐phenyl‐3,5‐pyrazolidinedione 29 were prepared and reacted with active nitriles, cyclic ketones and N,S‐acetals to give pyrano[2,3‐c]pyrazole, pyrazolo[4′,3′:5,6]pyrano[2,3‐c]pyrazole, spiropyrazole‐4,3′‐pyrazole and spiropyrazole‐4,3′‐[1,2,4]triazolane derivatives 24–34 , respectively. 相似文献
86.
Gaël Poirier Younes Messaddeq Marcel Poulain 《Journal of solid state chemistry》2005,178(5):1533-1538
Transparent glasses were synthesized in the NaPO3-BaF2-WO3 ternary system and several structural characterizations were performed by X-ray absorption spectroscopy (XANES) at the tungsten LI and LIII absorption edges and by Raman spectroscopy. Special attention was paid to the coordination state of tungsten atoms in the vitreous network.XANES investigations showed that tungsten atoms are only six-fold coordinated (octahedra WO6) and that these glasses are free of tungstate tetrahedra (WO4).In addition, Raman spectroscopy allowed to identify a break in the linear phosphate chains as the amount of WO3 increases and the formation of P-O-W bonds in the vitreous network indicating the modifier behavior of WO6 octahedra in the glass network. Based on XANES data, we suggested a new attribution of several Raman absorption bands which allowed to identify the presence of W-O− and WO terminal bonds and a progressive apparition of W-O-W bridging bonds for the most WO3 concentrated samples (?30% molar) due to the formation of WO6 clusters. 相似文献
87.
Knoevenagel reactions involving carbonyl compounds and active methylene derivatives have been studied in the presence of alumina, KSF and K10 montmorillonites. With addition of water the ester group undergoes hydrolysis. A route is disclosed for the synthesis of coumarine compounds catalyzed by solid supports. 相似文献
88.
Sillen A Wieruszeski JM Leroy A Younes AB Landrieu I Lippens G 《Journal of the American Chemical Society》2005,127(29):10138-10139
HRMAS NMR of tau paired helical fragments assembled with heparin show an intensity decrease for those amino acids that are incorporated into the rigid core region, whereas the N-terminal amino acids maintain their full mobility. 相似文献
89.
Seyed Mohammad Seyed Khademi Mahmoud Tabrizchi Ursula Telgheder Younes Valadbeigi Vahideh Ilbeigi 《International Journal for Ion Mobility Spectrometry》2017,20(1-2):15-21
Methyl tertiary-butyl ether (MTBE) is an organic compound which is used as a gasoline additive. Contamination of ground and surface water can occur due to large scale use of MTBE and its high solubility in water. According to United State Environmental Protection Agency (USEPA), MTBE is a possible human carcinogen at high doses and its detection and measurement in the water is important as concerned about human health. In this work, ion mobility spectrometry (IMS) equipped with a corona discharge ionization source was used for determination of MTBE in drinking water. Both pure and aqueous solutions of MTBE were studied and their ion mobility spectra were obtained at different temperatures. Using a calibration curve for detection of MTBE in drinking water, a detection limit (LOD) of 1 mg/L was obtained by IMS. This work proved that, IMS with corona discharge can be used for fast and direct detection of MTBE in water sample without any sample preparation. 相似文献
90.
The amino acid ionic liquid tetrabutylammonium asparaginate (TBAAsp) was immobilized on titanomagnetite (Fe3?xTixO4) nanoparticles in a facile one‐pot process using an organosilane compound (TMSP) as spacer. The modified Fe3?xTixO4@TMSP@TBAAsp magnetic nanoparticles were characterized using Fourier transform spectroscopy, scanning electron microscopy, energy‐dispersive X‐ray spectroscopy, vibrating sample magnetometry and thermogravimetric analysis. The resulting analytical data clearly verified the successful immobilization of the ionic liquid on the magnetic substrate. The magnetic ionic liquid‐based nanoparticles exhibited high catalytic activity in the synthesis of 1,4‐dihydropyrano[2,3‐c]pyrazole derivatives via a one‐pot three‐component reaction under mild reaction conditions. The catalyst was easily recycled and reused for at least six runs without any considerable loss of activity. 相似文献