Thermodynamic Assessment of the Silver–Oxygen System

An assessment of the silver–oxygen system has been made, and a consistent set of thermodynamic parameters has been optimized. The calculated thermodynamic properties and phase relations are in good agreement with the experimental data. Ag₂O is the only phase that is commonly found within the system. In air, it decomposes to silver and oxygen gas at 420 K. There is a eutectic between silver and Ag₂O at a temperature of 804 K, an oxygen partial pressure ( P _O2) of 526 bar (5.26 × 10⁷ Pa), and an oxygen mole fraction in the liquid phase of 0.25. Uncertainties remain on the Ag₂O liquidus for P _O2 > 10⁸ Pa. An ionic two-sublattice model has been used to describe the liquid phase. This work is part of a study of interactions between compounds from the bismuth-strontium-calcium-copper-oxygen system and silver.     

Analytical approaches to improved characterization of substitution in hydroxypropyl cellulose

Chemical characterization of cellulose derivatives is of high importance as it provides information about the often inhomogeneous substitution that may seriously affect the properties of these polymers in various applications. A detailed mapping of the chemical structure of these derivatives requires several advanced techniques to be employed. In this study, the average substitution and the substitution heterogeneity in two hydroxypropyl cellulose (HPC) samples from different suppliers were studied by means of NMR spectroscopy, MALDI-TOF MS, and HPAEC-PAD. (1)H and (13)C NMR provided information on the molar substitution, a parameter that could be analyzed by MALDI-TOF MS as well. In addition, the latter technique was used for determination of the distribution of the number of hydroxypropyl groups per glucose unit present in the two polymers. The heterogeneity of the substitution was studied by determining the amount of unsubstituted glucose units in the HPC samples, which was accomplished by HPAEC-PAD analysis. The results obtained suggest that the two HPC samples differ in both hydroxypropoxy content and distribution of the hydroxypropyl groups. Further, the benefits and importance of employing several analytical methods when investigating the cellulose ether substitution are demonstrated, as each method provides different kinds of information on the chemical content.     

Absorption of Di- and triglycerides by intestinal slices in vitro

The uptake by hamster intestinal rings of labeled 1,3-diolein and triolein in bile salt emulsions was studied. About 6% of triolein was taken up from emulsions containing glycerides and fatty acid in 6 mM sodium taurodeoxycholate. Lesser uptake was noted when triolein was emulsified with lecithin, cholesterol and bile salt; lowest uptake (3%) was observed from triolein-lecithincholesterol emulsions prepared without bile salt. Absorption of 1,3-diolein from bile salt emulsion was greater and acylation to triglyceride was observed. Diglycerides and triglycerides in small quantity may be absorbed intact from a micellar phase.     

Effects of plasma treatment on mechanical properties of rubber/cellulose fibre composites

Natural rubber materials reinforced with cellulose fibres have been studied with respect to crosslink density, tensile strength and stress relaxation. The fibres have been grafted with butadiene or divinylbenzene by plasma treatment. Chemiluminescence analysis was used to indicate the grafting on the surface of the cellulose fibres and also to estimate the effect of the plasma on the cellulose fibres. The results indicate the possibility of obtaining a surface layer on the fibres, which is a conceivable way of improving the mechanical properties of rubber composites.     

Radiation crosslinking of polyethylene with electron beam at different temperatures

The effect of temperature over the range ?196 to 150°C on the crosslinking of polyethylenes irradiated by electron beam has been investigated on the basis of gel content determination and Fourier transform infra-red (FTIR) spectroscopy. The crosslinking efficiency increases significantly with increasing irradiation does and at elevated irradiation temperature. The crosslinking rates of high density polyethylene (HDPE) and low density polyethylene (LDPE) samples above the melting point (T_M) are much higher than those below T_m. The FTIR data give positive evidence: (i) that trans-vinylene double bonds in cross linked HDPE and LDPE samples increase with increasing irradiation dose temperature (ii) that vinyl double bonds in HDPE decrease rapidly with increasing irradiation dose and temperature, and (iii) vinylidene groups in LDPE decrease slowly with increasing temperature at the lower dose and are almost independent of the irradiation temperature at above room temperature and the higher dose of more than 100 kGy. Gas bubbles are observed in LDPE samples irradiated at 100 and 150°C with high dose (200 to 250 kGy). The size of the bubbles increases gradually at high temperatures.     

Mass spectrometric determination of positions of double bonds in polyunsaturated fatty acid pyrrolidides

Low resolution mass spectra of pyrrolidides of isomeric octadecadienoic acids and other polyunsaturated straight chain fatty acids are presented and discussed. The spectra of the pyrrolidides contain mainly ions from the polar part of the molecule and give spectra that are specific for each isomer. The interpretation follows, in most cases, the rule developed for monounsaturated fatty acid pyrrolidides.     

The effect of prandtl number on conjugate heat transfer from rectangular fins

The problem of conjugate heat transfer from rectangular fins is treated numerically. Results are provided for the three Prandtl numbers (three fluids) 0.021, 0.7 and 5.0 and convection - conduction parameters meters in the range of 0 ≤ √Re k_fL/k_sb = CCP ≤ 5. The results indicated great effects of both CCP and Pr. Comparisons with the simple conventional fin theory show that concerning the fin efficiency, the simple theory yields acceptable results while the temperature variation and local heat flux distributions are not correctly predicted.     

Effects of dietary phenolic compounds on tocopherol, cholesterol, and fatty acids in rats

The effects of the phenolic compounds butylated hydroxytoluene (BHT), sesamin (S), curcumin (CU), and ferulic acid (FA) on plasma, liver, and lung concentrations of α- and γ-tocopherols (T), on plasma and liver cholesterol, and on the fatty acid composition of liver lipids were studied in male Sprague-Dawley rats. Test compounds were given to rats ad libitum for 4 wk at 4 g/kg diet, in a diet low but adequate in vitamin E (36 mg/kg of γ-T and 25 mg/kg of α-T) and containing 2 g/kg of cholesterol. BHT significantly reduced feed intake (P<0.05) and body weight and increased feed conversion ratio; S and BHT caused a significant enlargement of the liver (P<0.001), whereas CU and FA did not affect any of these parameters. The amount of liver lipids was significantly lowered by BHT (P<0.01) while the other substances reduced liver lipid concentrations but not significantly. Regarding effects on tocopherol levels, (i) feeding of BHT resulted in a significant elevation (P<0.001) of α-T in plasma, liver, and lung, while γ-T values remained unchanged; (ii) rats provided with the S diet had substantially higher γ-T levels (P<0.001) in plasma, liver, and lung, whereas α-T levels were not affected; (iii) administration of CU raised the concentration of α-T in the lung (P<0.01) but did not affect the plasma or liver values of any of the tocopherols; and (iv) FA had no effect on the levels of either homolog in the plasma, liver, or lung. The level of an unknown substance in the liver was significantly reduced by dietary BHT (P<0.001). BHT was the only compound that tended to increase total cholesterol (TC) in plasma, due to an elevation of cholesterol in the very low density lipoprotein + low density lipoprotein (VLDL+LDL) fraction. S and FA tended to lower plasma total and VLDL+LDL cholesterol concentrations, but the effect for CU was statistically significant (P<0.05). FA increased plasma high density lipoprotein cholesterol while the other compounds reduced it numerially, but not significantly. BHT, CU, and S reduced cholesterol levels in the liver TC (P<0.001) and percentages of TC in liver lipids (P<0.05). With regard to the fatty acid composition of liver lipids, S increased the n-6/n-3 and the 18∶3/20∶5 polyunsaturated fatty acids (PUFA) ratios, and BHT lowered total monounsaturated fatty acids and increased total PUFA (n−6+n−3). The effects of CU and FA on fatty acids were not highly significant. These results suggest some in vivo interactions between these phenolic compounds and tocopherols that may increase the bioavailability of vitamin E and decrease cholesterol in rats.