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991.
E. H. El‐Mossalamy 《应用聚合物科学杂志》2004,93(2):942-947
Oligomeric polyester, namely poly(tetramethylene asparate) (PTMA), was synthesized From D ,L ‐aspartic acid and 1,4‐butanediol by a melt codensation technique. Polyester–metal complexes were synthesized by the reaction of PTMA with hydrated acetates of Fe(III), Pd(IV), and UO2(II) in DMSO. The polyester–metal complexes were characterized by elemental analysis, UV–Vis, IR spectral studies, magnetic susceptibility measurements and 1H‐NMR. Mossbauer spectra of mixed samples of Pd‐PTMA and Fe(II)‐PTMA with a ratio of 1 : 2 mol showed the iron(III) oxide formed in early stages of the decomposition at 250°C is mainly fine‐grained and as the temperature is increased, well‐crystalline hematic is formed. Above 250°C, the Mossbauer spectrum showed the typical six‐line pattern of magnetically oriented Fe(III) oxide, but at 800°C, the spectrum showed quadrupole interaction characteristic of PdFe2O4 spinel. The metal ions were found to be six—coordinated with two water molecules as additional ligands besides oxygen and nitrogen atoms of polyester repeating units. Thermogravimetric analysis (DTA‐TG) showed that co‐ordination polymers are thermally more stable than polyester; the activation parameters for both decomposition steps were calculated and discussed. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 942–947, 2004 相似文献
992.
ET‐g‐PAAc membranes were obtained by radiation grafting of acrylic acid onto poly(tetrafluoroethylene–ethylene) copolymer films using a mutual technique. The ion selectivity of the grafted membranes was determined toward K+, Ag+, Hg2+, Co2+, and Cu2+ in a mixed aqueous solution. The ion‐exchange capacity of the grafted membranes was measured by back titration and atomic absorption spectroscopy. The Hg2+ ion content of the membrane was more than that of either the K+ or Ag+ ions. The presence of metal ions in the membranes was studied by infrared and energy‐dispersive spectroscopy measurements. Scanning electron microscopy of the grafted and metal‐treated grafted membranes showed modification of the morphology of the surface due to the adsorption of K+ and Ag+ ions. No change was observed for the surface of the membrane that was treated with Hg2+ ions. The thermal stability of different membranes was improved more with Ag+ and Hg2+ ions than with K+ ions. It was found that the modified grafted membranes possessed good hydrophilicity, which may make them promising candidates for practical applications, such as for cation‐exchange membranes in the recovery of metals from an aqueous solution. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2692–2698, 2002 相似文献
993.
El‐Refaie Kenawy Fouad I. Abdel‐Hay Lamies Shahada Abd El‐Raheem R. El‐Shanshoury Mohamed H. El‐Newehy 《应用聚合物科学杂志》2006,102(5):4780-4790
New bactericidal polyamides with quaternary ammonium or phosphonium salts were prepared, and their antimicrobial activities were explored. The polyamides were synthesized by the polycondensation of diethyl‐l‐tartrate or chloromethylated diethyl‐l‐tartrate with ethylenediamine in dry absolute ethanol. The polyamides were modified to yield polymers with either quaternary ammonium or phosphonium salts. The polymers were characterized with elemental microanalysis and 1H‐NMR and IR spectra. The antimicrobial activity of the polymers bearing onium salts was studied against Gram‐negative bacteria (Escherichia coli, Pseudomones aeruginosa, Shigella sp., and Salmonella typhae), Gram‐positive bacteria (Bacillus subtilis and Bacillus cereus), and a fungus (Trichophytum rubrum) by the cut‐plug and viable‐cell‐count methods. Although all the polymers showed high antibacterial activity, some had no antifungal activity. The tributyl phosphonium salt of the polyamide was more effective against both Gram‐negative and Gram‐positive bacteria than the triethyl ammonium and triphenyl phosphonium salts of the polyamide. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4780–4790, 2006 相似文献
994.
Jiansheng Tang Tianhua Ding Eric S. Daniels Victoria L. Dimonie Andrew Klein Mohamed S. El‐Aasser 《应用聚合物科学杂志》2003,88(1):30-41
The design of a semicontinuous emulsion polymerization process, primarily based on theoretical calculations, has been carried out with the objective of achieving overall independent control over the latex particle size, the monodispersity in the particle size distribution, the homogeneous copolymer composition, the concentration of functional groups (e.g., carboxyl groups), and the glass‐transition temperature with n‐butyl methacrylate/n‐butyl acrylate/methacrylic acid as a model system. The surfactant coverage on the latex particles is very important for maintaining a constant particle number throughout the feed process, and this results in the formation of monodisperse latex particles. A model has been set up to calculate the surfactant coverage from the monomer feed rate, surfactant feed rate, desired solid content, and particle size. This model also leads to an equation correlating the polymerization rate to the instantaneous conversion of the monomer or comonomer mixture. This equation can be used to determine the maximum polymerization rate, only below or at which monomer‐starved conditions can be achieved. The maximum polymerization rate provides guidance for selecting the monomer feed rate in the semicontinuous emulsion polymerization process. The glass‐transition temperature of the resulting carboxylated poly(n‐butyl methacrylate‐co‐n‐butyl acrylate) copolymer can be adjusted through variations in the compositions of the copolymers with the linear Pochan equation. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 30–41, 2003 相似文献
995.
Farid El‐Tantawy 《应用聚合物科学杂志》2005,98(5):2226-2235
Swelling of polymer composites in solvents has become one of the major problems in the use of polymer composites exposed to petroleum products. As a possible solution to the problem, this experimental study was conducted to examine the potential application of TiB2 ceramic in butyl rubber (IIR) composites. The effect of TiB2 content on the curing kinetics of IIR composites was studied using a torque rheometer technique. The effect of TiB2 on the network structure was investigated in terms of the crosslinking density, interparticle distance between conducting particles, surface tension, glass transition temperature, degree of crystallinity, scanning electron microscopy, and X‐ray analysis. Moreover, the effect of TiB2 content on the molecular transport of solvent (kerosene) was examined by means of degree of swelling, solvent interaction parameters, volume fraction of rubber, interparticle distance after swelling, penetration rate of solvent, mean diffusion coefficient, cohesive energy density of polymer, standard entropy, standard enthalpy, and standard free energy of IIR composites. It was ascertained that with increasing TiB2 content the degree of swelling shifts to a lower value. The main reason was interpreted as the introduction of good interface adhesion of TiB2 with rubber matrix, which tends to block the diffusion of solvent molecules. The effect of TiB2 content on hardness, tensile strength, Young's modules, and elongation at break is discussed. An apparent steady‐state creep of butyl rubber IIR/TiB2 composites is evident under different constant stresses at room temperature. The strain rate of steady‐state creep showed a dependence on stress and TiB2 volume fraction. The stress sensitivity parameter, viscosity coefficient, and activation volume for samples loaded with different content of TiB2 were estimated. It is apparent that these new composites should be very useful for solvent permeation resistance at high TiB2 loading level with good mechanical properties. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 2226–2235, 2005 相似文献
996.
Mustapha El HANINE ;Elhassane ABDELMOUNIM ;Rachid HADDADI ;Abdelaziz BELAGUID 《计算机技术与应用:英文》2014,(2):98-104
The most common noises in ECG (electrocardiogram) signal processing are BW (baseline wandering) and the 50 or 60 Hz PLI (power line interferences). In order to remove these two major source of noises, we have used the recent powerful DWT (discrete wavelet transform) signal processing in ECG signals which are obtained from MIT-BIH Arrhythmia Database. The results indicate that DWT is a good method for filtering noises without changing the morphology of ECG, and can be applied to all types of ECG signals, whether normal or presenting arrhythmias. 相似文献
997.
Dounia El Hamrani Amandine Chepied William Même Marc Mesnil Norah Defamie Sandra Même 《Magma (New York, N.Y.)》2018,31(4):565-576
Objective
Using non-invasive magnetic resonance (MR) techniques and a histological approach, we assessed the outcomes of perinatal exposure at a low dose of 3,3′-DCBPA (2-chloro-4-[1-(3-chloro-4-hydroxyphenyl)-1-methylethyl]phenol) and/or 3,5-DCBPA (2,6-dichloro-4-[1-(4-hydroxyphenyl)-1-methylethyl]phenol) on mice livers.Materials and methods
Fertilized female Swiss mice were injected intraperitoneally during gestation and lactation with either vehicle control, 20 μg/kg/day of BPA, 3,5-DCBPA, 3,3′-DCBPA or a mixture (mix-DCBPA). Complementary methods were used to evaluate, in male and female pups, (1) liver structure by texture analysis of images obtained through MR imaging (MRI) and histology, (2) hepatic lipid composition through in vivo 1H MR spectroscopy (1H MRS).Results
Principal component analysis of texture parameters showed no structural modification of the liver with BPA and DCBPA treatments. Accordingly, no hepatic microvesicular steatosis was observed through hematoxylin–eosin staining. Compared to control, MRS revealed no difference in lipid composition for BPA, 3,5-DCBPA or 3,3′-DCBPA groups. However, MRS detected a significant increase in the mix-DCBPA groups for the saturated component of fatty acids (FA), total unsaturated FA bond index and polyunsaturated FA bond index.Conclusion
Prior to any structural changes, polyunsaturated fatty acids significantly increased in young male and female mice exposed perinatally at a low dose to a mixture of dichlorinated BPA.998.
D. El Hellani A. El Hajjaji R. Ceschi 《International Journal of Adaptive Control and Signal Processing》2018,32(8):1191-1205
This paper presents a novel design approach for the finite frequency (FF) H∞ filtering problem for discrete‐time state‐delayed systems with quantized measurements. The system state and output are assumed affected by FF external noises. Attention is focused on the design of a stable filter that guarantees the stability and a prescribed ?2 gain performance level for the filtering error system in the FF domain of input noises. Sufficient conditions for the solvability of this problem are developed by choosing an appropriate Lyapunov‐Krasovskii functional based on the delay partitioning technique and using the FF ?2 gain definition combined with the generalized S‐procedure. Then, by means of Finsler's lemma, the derived conditions are linearized and additional slack variables are further introduced to more flexible result. Final filter design conditions are consequently established in terms of linear matrix inequalities in three different frequency ranges, ie, low‐, middle‐ and high‐frequency range. Finally, a simulation example is presented to illustrate the effectiveness and the merits of the proposed approach. 相似文献
999.
Maria Leżańska Andrzej Olejniczak Jerzy P. Łukaszewicz 《Journal of Porous Materials》2018,25(6):1633-1648
Nitrogen-containing mesoporous carbons with the use of colloidal silica spheres of (14 nm) and chitosan as a carbon precursor were obtained. A removal of such small template particles from carbonized silica–chitosan composite is difficult and HF with a minimum concentration of 15 wt% should be used. By varying the silica-to-chitosan ratio, the porous characteristic of products is controlled. The modification by ZnCl2 with a molar Zn-to-C (in chitosan mass) ratio of ‘6’ results in the development of microporosity; however it is accompanied by a significant reduction of mesopore volume (Vmes). The addition of ZnCl2 in a ratio of ‘5.25’ and pH adjustment to 5.8 increase the volumes of micropores, small mesopores, BET surface area to 1975 m2/g, and preserve Vmes of 4.15 cm3/g. The novelty of the presented strategy is the creation of microporosity in the hard-templated materials by incorporating ZnCl2 into the mixture of Ludox HS-40 template and chitosan precursor, as well as the investigation on how the pH of synthesis influences the final porosity. The pH of a silica–chitosan–zinc solution, equal to 3.9, provides some coordination of Zn2+ by –OH and –NH2 groups, whereas pH adjustment to 5.8 results in the precipitation of a new template—Zn(OH)2. 相似文献
1000.
Synthesis,Characterization, and Applications of Some New Trimeric‐Type Cationic Surfactants 下载免费PDF全文
Waleed A. El‐Said Ahmed S. Moharram Essam M. Hussein Ahmed M. El‐Khawaga 《Journal of surfactants and detergents》2018,21(3):343-353
In recent years, trimeric surfactants have created excitement in the surfactant field because of their properties, which have been found to be better than monomeric or dimeric homologues. Only a limited number of trimeric surfactants have been synthesized and studied so far, probably owing to the difficulty in synthesis. In this article, we synthesized some novel star‐shaped trimeric cationic surfactants based on the alkylation of the 3 hydroxyl groups of the phloroglucinol nuclei as a core (i.e., spacer) with 3 dodecyl or 3 octyl groups (as tails) for the surfactant. The chemical structures were confirmed by nuclear magnetic resonance, Fourier transform infrared, mass spectrometry, and elemental analysis; also the critical micelle concentration was determined by electrical conductivity measurements. These surfactants were used in the synthesis of mesoporous silica nanoparticles by the sol–gel method. The silica particles shape and size were determined using field emission scanning electron microscopy and high‐resolution transmission electron microscopy images. Furthermore, the corrosion inhibitor capability of these surfactants was investigated by monitoring the corrosion rate of iron sheets in 0.5 M hydrochloric acid in the presence and in the absence of different surfactants at 45°C based on the weight loss method. We have used cetyltrimethylammonium bromide (CTAB) as a positive control, the obtained results showed a high inhibition efficiency at very low concentrations, and the prepared trimeric surfactants exhibited a higher anticorrosion efficiency than the CTAB surfactants. 相似文献