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1.
Hydrogels of N‐vinylimidazole (VI) and sodium styrenesulfonate (SSS) were synthesized in aqueous solution by radical crosslinking copolymerization with N,N′‐methylene‐bis(acrylamide) as crosslinker. Swelling in several saline solutions was measured for hydrogel samples synthesized with different comonomer concentrations (CT = 10, 25, or 40%) and with SSS mole fractions covering a broad range (fSSS = 0–0.7), while the crosslinker ratio was 2 wt % in all cases. The degree of swelling in aqueous solution with a specific ionic strength (μ), plotted versus the SSS composition of the feed, shows a minimum for any set of samples synthesized with a fixed CT. The dependence of swelling on μ shows both polyelectrolyte (fSSS beyond the minimum) and antipolyelectrolyte behaviors (in the low fSSS limit). It was found that the nonGaussian factor of the crosslinking density and the polymer‐solvent interaction parameter increase with fSSS for any CT. Moreover, in the low fSSS limit, the osmotic swelling pressure is governed not only by the ionic contribution, but also by the polymer‐solvent mixing and, the concentration of mobile counterions inside the gel is not proportional to the net fixed charge but to the addition of cationic and anionic side groups, what discards the formation of ionic pairs. The antipolyelectrolyte effect is interpreted as due to the increasing protonation of VI as μ goes up. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1683–1693, 2007 相似文献
2.
B. Boutevin G. Falgayrettes Y. Hervaud Y. Piétrasanta 《European Polymer Journal》1984,20(11):1067-1072
Recovered polyethylene is used with polyethylene waxes as a new binder for mineral granules. This binder is characterized and optimized mainly on a rheological basis. Its fluid index (I.F.), molecular distribution and crystallinity are especially studied. Its rheograms and tensile properties are compared with those of industrial polyethylene (I.F. = 250). The dimensional shrinkages of such binders during cooling from 190° to ambient temperature are measured. 相似文献
3.
Methyl methacrylate and butyl methacrylate were polymerized in oil-in-water microemulsions that were stabilized by sodium dodecyl sulphate (SDS). A poly(N-acetylethylenimine) (PNAEI) macromer was also included in the recipe, as a cosurfactant and a comonomer. Polymerizations were initiated by UV-irradiation. The average diameters of latex particles, obtained by STM, were in the range of 17-200 nm. The experimental data evidenced that the particle size was mainly dependent on the SDS/PNAEI ratio. Polymerization yields were around 75-85%. The synthesized copolymers have viscosity average molecular weights in the range of 2.1-2.4×106 and glass transition temperatures of 38.0-43.5°C, lower than those obtained without using PNAEI. The investigation by means of FTIR and 1H-NMR techniques revealed that PNAEI was incorporated into the nanoparticles. 相似文献
4.
A. Bączyński A. Kossakowski T. Marszałek 《Zeitschrift für Physik B Condensed Matter》1977,26(1):93-95
The expression for losses due to triplet states in dye laser considered as a six-level system is given. It is shown that triplet losses depend on pumping parameters and photon number. Depending on molecular and cavity parameters two different behaviours of dye lasers are expected. Physical conditions are discussed in which triplet losses as well as photon number undergo a jump at the threshold. 相似文献
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The Debye potentials are generalized to the case of electromagnetic fields in spherically gyrotropic media. A medium is called spherically gyrotropic if it is locally gyrotropic with the distinguished axis having a radial direction determined by a central point. Expressions for electromagnetic fields in terms of the generalized potentials are presented and the system of differential equations for the potentials is derived. The results are summarized in the form of a theorem. Basic facts about the Debye potentials in isotropic media are recalled. 相似文献
8.
Summary Conditions have been established for identification and quantification of cefuroxime axetil and cefuroxime by thin-layer chromatography and densitometry. Good separation of these compounds was achieved on silica gel by use of chloroform–ethyl acetate–glacial acetic acid–water, 4:4:4:1 (v/v), as mobile phase. UV densitometry was used to detect spots on chromatograms. Under these conditions the limits of detection for cefuroxime axetil and cefuroxime were 40 ng and 30 ng, respectively. Recoveries of cefuroxime axetil and cefuroxime were 99.93% and 97.94%, respectively. 相似文献
9.
We propose a model for the production of extra (additional) lepton pairs in deep inelastic lepton-hadron scattering, e+e– annihilation and large pT processes. Extra lepton pairs are supposed to be originated by annihilations of quarks and antiquarks created during the space-time evolution of quark initiated jets. This mechanism yields predominantly dileptons with rather low masses. Predictions following from the model are compared with the recent data on trimuon production in neutrino-nucleon interactions. It is also suggested that internal hard processes can lead to dileptons with both small and large masses. The latter mechanism has rather small cross section but it is particularly interesting from the point of view of the simple quark-parton model.Dedicated to Academician Václav Votruba on the occasion of his seventieth birthday. 相似文献
10.
Marcin Feldo Magdalena Wjciak Aleksandra Ziemlewska Sawomir Dresler Ireneusz Sowa 《Molecules (Basel, Switzerland)》2022,27(13)
Diosmin is widely used as a venoactive drug in the pharmacological treatment of chronic venous disorders. It exerts a strong protective effect on blood vessels via an increase in the elasticity of vessel walls and reduces the permeability of capillary walls, thereby producing an anti-edematous effect. In this paper, we investigated the effectiveness of diosmin and diosmetin in modulating the level of proinflammatory factors in human skin fibroblasts treated with lipopolysaccharide (LPS). Two variants of the experiments were performed: the flavonoid was added 2 h prior to or 24 h after LPS stimulation. Our study revealed that both flavonoids reduced the levels of IL-6 and Il-1β as well as COX-2 and PGE2 but had no impact on IL-10. However, the addition of the compounds prior to the LPS addition was more effective. Moreover, diosmetin modulated the proinflammatory factors more strongly than diosmin. Our investigations also showed that both flavonoids were potent inhibitors of elastase and collagenase activity, and no differences between the glycoside and aglycone forms were observed. 相似文献