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Dielectric study of neutral and charged hydrogels during the swelling process

Dielectric spectroscopy measurements of conductivity were applied for understanding the change in the internal morphology of the neutral and permanently charged polyacrylamide (PAAm) hydrogels during the swelling process. For the first time four distinct peaks (each corresponding to a different swelling stage) in the conductivity of the neutral gel were observed during the swelling of this gel. These peaks are related to the distribution of dense polymer regions (they are defined as the "blobs") appearing in a microstructure of the given PAAm gel having at least four average sizes. For the charged gel the heterogeneity decreases due to the internal electric field of the charged sites. Thus, this characteristic behavior in the conductivity becomes almost negligible for the gel charged with permanent S O3- groups. It seems this fact causes considerable decrease in amplitude of the peaks and overall decrease the conductivity during the whole swelling process especially at high frequencies. The new theory of dielectric relaxation based on the fractional kinetics containing the complex power-law exponents was used for verifying these swelling processes and received an excellent confirmation in description of the real part of the complex conductivity Re [ (ω)] by the fitting function that follows from the suggested theory. The calculated power-law exponents describe the behavior of Re [ (ω,m m0)] in the available frequency range (30 Hz-13 MHz) and for all values of the relative masses (volumes) measured in the process of the experiment. The excellent coincidence between the new theory and measured data gives a possibility to suggest more reliable physical picture of the swelling process that takes place in neutral/charged gels. © 2006 American Institute of Physics

Dielectric study of neutral and charged hydrogels during the swelling process

Dielectric spectroscopy measurements of conductivity were applied for understanding the change in the internal morphology of the neutral and permanently charged polyacrylamide (PAAm) hydrogels during the swelling process. For the first time four distinct peaks (each corresponding to a different swelling stage) in the conductivity of the neutral gel were observed during the swelling of this gel. These peaks are related to the distribution of dense polymer regions (they are defined as the "blobs") appearing in a microstructure of the given PAAm gel having at least four average sizes. For the charged gel the heterogeneity decreases due to the internal electric field of the charged sites. Thus, this characteristic behavior in the conductivity becomes almost negligible for the gel charged with permanent S O3- groups. It seems this fact causes considerable decrease in amplitude of the peaks and overall decrease the conductivity during the whole swelling process especially at high frequencies. The new theory of dielectric relaxation based on the fractional kinetics containing the complex power-law exponents was used for verifying these swelling processes and received an excellent confirmation in description of the real part of the complex conductivity Re [ (ω)] by the fitting function that follows from the suggested theory. The calculated power-law exponents describe the behavior of Re [ (ω,m m0)] in the available frequency range (30 Hz-13 MHz) and for all values of the relative masses (volumes) measured in the process of the experiment. The excellent coincidence between the new theory and measured data gives a possibility to suggest more reliable physical picture of the swelling process that takes place in neutral/charged gels. © 2006 American Institute of Physics

Dielectric study of neutral and charged hydrogels during the swelling process

Dielectric spectroscopy measurements of conductivity were applied for understanding the change in the internal morphology of the neutral and permanently charged polyacrylamide (PAAm) hydrogels during the swelling process. For the first time four distinct peaks (each corresponding to a different swelling stage) in the conductivity of the neutral gel were observed during the swelling of this gel. These peaks are related to the distribution of dense polymer regions (they are defined as the "blobs") appearing in a microstructure of the given PAAm gel having at least four average sizes. For the charged gel the heterogeneity decreases due to the internal electric field of the charged sites. Thus, this characteristic behavior in the conductivity becomes almost negligible for the gel charged with permanent S O3- groups. It seems this fact causes considerable decrease in amplitude of the peaks and overall decrease the conductivity during the whole swelling process especially at high frequencies. The new theory of dielectric relaxation based on the fractional kinetics containing the complex power-law exponents was used for verifying these swelling processes and received an excellent confirmation in description of the real part of the complex conductivity Re [ (ω)] by the fitting function that follows from the suggested theory. The calculated power-law exponents describe the behavior of Re [ (ω,m m0)] in the available frequency range (30 Hz-13 MHz) and for all values of the relative masses (volumes) measured in the process of the experiment. The excellent coincidence between the new theory and measured data gives a possibility to suggest more reliable physical picture of the swelling process that takes place in neutral/charged gels. © 2006 American Institute of Physics

The protective effect of thymoquinone on ethanol-induced acute gastric damage in the rat

Previous studies have indicated a pivotal role of reactive oxygen species in the pathomechanism of gastric ulcer. Recent studies demonstrated that thymoquinone (TQ) had an antioxidant effect on injuries caused by various toxic agents in different experimental models. The present study was planned to test whether TQ, the main constituent of the volatile oil of Nigella sativa seeds, was capable to exert beneficial effects on acute gastric ulcer model in rats. We examined antiulcerative and antioxidant effects of TQ on ethanol (EtOH)-induced gastric lesions in rats. The data we collected showed that gastric ulcer caused by absolute EtOH induction resulted in an increase in lipid peroxidation, represented by malondialdehyde level as well as by superoxide dismutase level, an antioxidant enzyme, whereas it resulted in a decrease in glutathione content in rat stomach tissue. Thymoquinone (20 mg/kg) administration reduced the ulcer index and the malondialdehyde level, and reversed the glutathione depletion. However, it did not statistically change the high superoxide dismutase activity induced by EtOH. These results suggest that TQ could inhibit the development of EtOH-induced gastric ulcer, and gastroprotective action of TQ might be in part dependent on its antioxidant property. © 2005 Elsevier Inc. All rights reserved.Support from the Research Foundation of the Zonguldak Karaelmas University is appreciated. This study was presented at the fifth International Congress of Turkish Society of Toxicology, 2003, Antalya, Turkey

Biphasic (Janus), Core–Shell and Functionalized Magnetic Polymer Particles: A Route of Synthesis to Application

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