Search

Isothermal kinetics of the exchange of absorbed water in a silica hydrogel (SH) with ethanol was examined. The isothermal kinetic curves of absorbed water exchange with ethanol were measured at the temperatures: T = = 297, 306 and 316 K. The rate of the exchange was analysed as a function of time. The possibility of mathematical description of the kinetics of exchange by the Brouers and Sotolongo-Costa’s (BS) fractal’s kinetics model was examined. Parameter values (n, τ, β) of the model and their changes with temperature were calculated. By applying the method of Ozao, it was determined that the rate limiting step of the process of exchange was the rate of exchange of the absorbed water with ethanol. Values of the fractal dimension of the SH-ethanol interphase were calculated. The dependences of the effective time-dependent rate coefficient, activation energy and pre-exponential factor on time and degree of exchange were calculated and discussed. The proposed model of the mechanism of the exchange of absorbed water with ethanol was discussed.

The isothermal kinetics of the exchange of absorbed water in calcium alginate hydrogels with ethanol was investigated. The isothermal kinetic curves were measured within the temperature range from 297 to 316 K. By the application of differential isoconversional methods, it was found that the process of exchange of water absorbed in calcium alginate hydrogel with ethanol has a unique rate determining step (a single step process). Using the model fitting method, it was determined that the kinetics of the exchange can be mathematically described with the kinetic model of the first-order chemical reaction. The values of the kinetic parameters of water exchange: the rate constants (km), energy of activation (Ea = 18.0 kJ∙mol–1), and the pre-exponential factor (ln[A/min–1] = 4.0) were calculated. By using Eyring's equation, the values of thermodynamics parameters: standard enthalpy of activation (ΔH*), standard entropy of activation (ΔS*), and Gibbs energy of activation (ΔG*) were calculated. It was found that the rate of rearrangements of the bound water around hydrophilic groups of a polymeric network has a dominant effect on the kinetics of the exchange of the absorbed water with ethanol. The mechanism of the exchange of adsorbed water with ethanol was suggested. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. 172015]

The effect of operating parameters such as reaction mixture inlet pressure p1 (101.3–1013.2 kPa), methanol to oil molar ratio M1 (3–12), the concentration of catalyst Cc (0.0–1.0 wt%), temperature T (25–50 °C) and the number of passes of the reaction mixture through the venturi type hydrodynamic cavitation reactor n (1–12) on alkali-catalyzed transesterification of sunflower oil with methanol assisted by hydrodynamic cavitation (ACTC) on the value of the degree of triglyceride conversion (DTC) was investigated. ACTC was performed by the venturi-type hydrodynamic cavitation reactor (VCR) of our construction. It was found that the values of DTC increase with the increase in p1, M1, Cc, and n, and decrease with the increase in T. Cavitation yield (CY) values were calculated. The ACTC was proved to be the simplest, fastest, and most highly energy-efficient current technology for the production of biodiesel. [ABSTRACT FROM AUTHOR]

Haptoglobin (Hp) is a hemoglobin-binding protein that prevents free hemoglobin-induced tissue oxidative damage. In streptozotocin-induced diabetic rats, the initial elevation of Hp expression in the serum and liver tends to decrease with diabetes progression, contributing to increased oxidative stress. Glucose toxicity and diabetic complications are closely related to increased modification of nucleocytoplasmic proteins by O-linked-N-acetylglucosamine (O-GlcNAc). We examined the contribution of O-GlcNAcylation of NF-κB p65 to changes in liver Hp expression in diabetic rats. WGA-affinity chromatography revealed a progressive increase in O-GlcNAcylation in nuclear NF-κB p65 during eight weeks of diabetes. DNA-affinity chromatography followed by immunoblot analysis revealed that decreased Hp expression at 4 and 8 weeks of diabetes was accompanied by the absence of Hp gene hormone-responsive element (HRE) occupancy with NF-κB p65, low occupancy with glucocorticoid receptor (GR), and almost no changes in STAT3 occupancy compared to 2 weeks, when Hp expression was highest. Coimmunoprecipitation experiments indicate that these events were the result of impaired NF-κB p65/STAT3 and GR/STAT3 interactions. Results suggest that the attenuation of Hp expression associated with diabetes was at least in part the result of O-GlcNAcylation of NF-κB p65, which prevents the formation of an effective transcription initiation complex on the Hp gene promoter. [ABSTRACT FROM AUTHOR]

Previously, we described the link between C-X-C motif chemokine 12 (Cxcl12) gene induction and DNA hypomethylation in the absence of poly(ADP-ribose) polymerase 1 (PARP-1). We have now firmly established that demethylation is the primary cause of gene induction on the basis of Cxcl12 gene upregulation upon treatment with the demethylating agent 5-azacytidine (5-aza). Since the demethylation state of Cxcl12 is favored by PARP-1 absence, we investigated the presence of ten-eleven translocation (TET) proteins on the Cxcl12 promoter in order to corroborate the relationship between the demethylation process and increased gene expression that occurs in the absence of PARP-1. Analysis was performed on the promoter region within CpG islands of Cxcl12 from control mouse embryonic fibroblasts (NIH3T3) and PARP-1 knock-out mouse embryonic fibroblasts (PARP1-/-). The lack of PARP-1 increased the abundance of TET2 on the Cxcl12 promoter, suggesting that TET-mediated demethylation provoked by the absence of PARP-1 could account for the observed increased expression of this chemokine. Deciphering the regulation of DNA (de)methylation factors that control Cxcl12 expression may provide an additional therapeutic approach in pharmacological interventions where gene switching on or off based on targeted stimulation or inhibition is necessary. [ABSTRACT FROM AUTHOR]

Copyright of Military Technical Courier / Vojnotehnicki Glasnik is the property of Military Technical Courier / Vojnotehnicki Glasnik and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The kinetics of the alkali-catalyzed transesterification of sunflower oil with methanol in the presence of co-solvent (TSMPC) were investigated. The kinetics curves of the alkali-catalyzed TSMPC, in the temperature range of 26°C–55°C, were measured for conventional heating (CH) and microwave heating with controlled cooling. The results showed that for both heating modes, the kinetics of the alkali-catalyzed TSMPC reaction can be described with the kinetic model of the pseudo first-order reaction with respect to the concentration of the triglycerides. The values of apparent reaction rate constants, activation energies, and pre-exponential factors are also calculated. The existence of a linear correlation (compensation effect) between the values of apparent kinetic parameters determined for CH and microwave heating with controlled cooling conditions is established. The results confirmed that the increase in the transesterification rate in the microwave heating with controlled cooling conditions is not caused by overheating nor by the existence of hotspots. The model of mechanism of the impact of microwave heating on the kinetics of transesterification is hereby proposed.