• Journal of the Korean Society of Food Science and Nutrition
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• v.24 no.2
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• pp.202-207
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• 1995

The effects of lipoxygenase, linoleic acid, tocopherol and pH on the co-oxidation of $\beta$-carotene in the aqueous system were studied. It showed that the co-oxidation of $\beta$-carotene was noticeable at both pH 7.4 and 9.0. As the concentraitons of linoleic acid and $\beta$-carotene increased, the rate of oxidation of $\beta$-carotene tended to be increased. However, $\alpha$- and $\delta$-tocopherol retarded the co-oxidation of $\beta$-carotene. As the concentrations of tocopherols increased, $\beta$-carotene was more stabilized, generally. But low concentration of $\alpha$-tocopherol(10-4M) acted more effective antioxidant than high concentration of it(10-3M) at pH 7.4. The antioxidant effect of tocopherol greatly depended on pH ; it was outstanding at pH 7.4.

• Bulletin of the Korean Chemical Society
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• v.13 no.6
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• pp.680-683
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• 1992

The electrochemistry of benzidine and hydrazobenzene was studied in water-acetonitrile mixed solutions at various pHs and the results are reported. The cyclic voltammetric peak for the oxidation of benzidine shows a pH dependency of -62 mV/pH in the pH range of 0-3.5, no pH dependency between pH values of 3.5 and about 10.5, and of about -50 mV/pH between pH=10.50 and 14.0, indicating that oxidation mechanisms differ depending on the pH of the medium. However, the CV peak for the hydrazobenzene oxidation is shown to be independent of pH of the medium, suggesting that the proton is not involved in the rate limiting step of the electrochemical oxidation of hydrazobenzene to azobenzene. Results of in situ spectroelectrochemical experiments indicate that the oxidation products obtained during the oxidation of benzidine and hydrazobenzene depend on the result of dynamic equilibria taking place at various pHs.

• Journal of Nutrition and Health
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• v.44 no.6
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• pp.507-517
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• 2011

The purpose of this study was to investigate the effects of gender on the thermic effect of food and substrate oxidation rate during 5 hours after a mixed meal. Twenty healthy college students (10 males and 10 females) aged 20-26 years participated in this study. The energy contents of the experimental diets were 775 kcal and 627 kcal for males and females respectively, which were 30% of individual energy requirements and were composed of 65/15/20% as the proportion of carbohydrate/protein/fat. Resting and postprandial energy expenditure and substrate oxidation rates were measured with indirect calorimetry in the fasting state and every 30 min for 5 hours after meal consumption. Thermic effects of food expressed as ${\Delta}AUC$ and TEF% were not significantly different between males and females. However, TEF% adjusted for body weight and fat-free mass in males (0.095% and 0.120%) were significantly lower than those in females (0.152% and 0.213%)(p < 0.05). The total amount of carbohydrate oxidized was significantly lower in males than that in females (58.6 vs. 86.6 mg/kcal energy intake/5 h, p < 0.05). In contrast, the total amount of fat oxidized was significantly higher in males than that in females after the meal (32.9 vs. 17.2 mg/kcal energy intake/5 h, p < 0.01). These results indicate that gender affects the thermic effects of food and the substrate oxidation rate after a meal. The results show that males use relatively less carbohydrate and more fat as an energy source after a meal than that of females.

• Nutrition Research and Practice
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• v.8 no.1
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• pp.59-65
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• 2014

There is currently no reference for intake of lysine for Chinese people; therefore, the present study was conducted to determine the lysine requirement of Chinese young male adults on a habitual Chinese mixed diet based on the modified indicator amino acid oxidation method. Seven young men with a mean age of $23.7{\pm}2.2$ years that were healthy based on questionnaire, physical examinations and screening tests were evaluated. Subjects were evaluated over five consecutive 7 day periods, during which time they were administered decreasing amounts of lysine via the diet (65, 55, 45, 35, $25mg{\cdot}kg^{-1}{\cdot}d^{-1}$). Subjects were allowed to adapt from day 1 to 6 and the isotopes were measured on day 7 in each period. The subjects' body weights, body compositions and plasma proteins were also examined during the study. Amino acid kinetics were measured based on the indicator amino acid oxidation technique using the $^{13}CO_2$ release rate and phenylalanine oxidation rate to estimate lysine requirements. Body weights, body compositions, and plasma proteins of subjects did not change significantly relative to those at baseline. The mean and the upper 95% CI of lysine requirements of Chinese habitual diets were determined to be 58.41 and $70.09mg{\cdot}kg^{-1}{\cdot}d^{-1}$, respectively, based on the $^{13}CO_2$ release rate and 54.28 and $65.14mg{\cdot}kg^{-1}{\cdot}d^{-1}$, respectively, based on the phenylalanine oxidation rate.

• Bulletin of the Korean Chemical Society
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• v.35 no.5
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• pp.1385-1390
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• 2014

Hydrofluoroethers (HFEs) are developed as a suitable for the replacement of environmentally hazardous CFCs and are termed as third generation refrigerants. One of the major products of decomposition of HFEs in the atmosphere is a fluoroester. The present study relates to the OH and Cl initiated oxidation of $CF_3C(O)OCH_2CF_3$ formed from the oxidation of HFE-356mff. The latter is used as a solvent in the industry and reaches the atmosphere without any degradation. Kinetics of the titled molecule has been studied at MPWB1K/6-31+G(d,p) level of theory. Single point energy calculations have been made at G2(MP2) level of theory and barrier heights are determined. The rate constants are calculated using canonical transition state theory. Tunnelling correction are made using one-dimensional Eckart potential barrier. The rate constant calculated during the present study are compared with the experimental values determined using relative rate method and FTIR detection technique.

• Journal of Environmental Health Sciences
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• v.30 no.2
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• pp.133-139
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• 2004

The objective of this study was to investigate the destruction efficiency and to determine the fundamental parameters of oxidation kinetics under the supercritical water(SCW) condition. Target material was cephradine, toxic and antibiotic material, in the pharmaceutical wastewater. For this purpose, the effect of reaction temperature and oxidant were investigated on the destruction efficiency of cephradine. And the oxidation kinetics of cephradine was derived by using a empirical power-law model. The experiment was carried out in a cylindrical batch reactor made of Hastelloy C-276 which was endurable high temperature and pressure. The destruction efficiency of cephradine increased with increment of the temperature and reaction time. Also the type of oxidants was effected and oxidants(Air and $H_2O$$_2$) were enhanced the destruction efficiency. The global oxidation kinetics for cephradine has led to two rate expressions according to type of oxidant. - In the presence of air oxidant: Rate=k. $e^{-Ea}$RT/(Ceph.)$^{1.0}$ ( $O_2$)$^{0.51}$$\pm$0.05(k=3.27${\times}$$10^{5}$ sec. Ea=63.25 kJ/mole) - In the presence of $H_2O$$_2$ oxidant : Rate=kㆍ $e^{-Ea}$RT/(Ceph.)$^{1.0}$ ($H_2O$$_2$)$^{0.62}$$\pm$0.02(k=2.76${\times}$$10^4$/sec. Ea=47.65 kJ/mole)ole))

• Corrosion Science and Technology
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• v.4 no.4
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• pp.136-139
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• 2005

The effect of oxidation and hot corrosion on the solid particle erosion was investigated for hot-pressed silicon nitride using as-polished, pre-oxidized and pre-corroded specimens by molten sodium sulfates. Erosion tests were performed at 22, 500 and $900^{\circ}C$ using angular silicon carbide particles of mean diameter $100{\mu}m$. Experimental results show that solid particle erosion rate of silicon nitride increases with increasing temperature for as-polished or pre-oxidized specimens in consistent with the prediction of a theoretical model. Erosion rate of pre-oxidized specimens is lower than that of as-polished specimens at $22^{\circ}C$, but it is higher at $900^{\circ}C$. Lower erosion rate at $22^{\circ}C$ in the pre-oxidized specimens is attributed due to the blunting of surface flaws, and the higher erosion rate at $900^{\circ}C$ is due to brittle lateral cracking. Erosion rate of pre-corroded specimens decreases with increasing temperature. Less erosion at $900^{\circ}C$ than at $22^{\circ}C$ is associated with the liquid corrosion products sealing off pores at $900^{\circ}C$ and the absence of inter-granular crack propagation observed at $22^{\circ}C$.

• Journal of the Korean Society of Industry Convergence
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• v.15 no.3
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• pp.71-77
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• 2012

This study gives the optimal reaction conditions, reaction mechanisms, reaction rates leaded from the oxidation of phenol by electron beam accelerator and ozone used for recent water treatment. It gives the new possibility of water treatment process to effectively manage industrial sewage containing toxic organic compounds and biological refractory materials. The high decomposition of phenol was observed at the low dose rate, but at this low dose rate, the reaction time was lengthened. So we must find out the optimal dose rate to promote high oxidation of reactants. The reason why the TOC value of aqueous solution wasn't decreased at the low dose was that there were a lot of low molecular organic acids as an intermediates such as formic acid or glyoxalic acid. In order to use both electron beam accelerator and biological treatment for high concentration refractory organic compounds, biological treatment is needed when low molecular organic compounds exist abundantly in sewage. In this experiment, the condition of making a lot of organic acids is from 5 kGy into 20 kGy dose. Decomposition rate of phenol by electron beam accelerator was first order reaction up to 300ppm phenol solution on the basic of TOC value and also showed first order reaction by using both air and ozone as an oxidants.

• The Korean Journal of Ceramics
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• v.5 no.2
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• pp.155-161
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• 1999

The tribological behaviour of monolithic SiC as well as SiC-TiC and SiC-TiC-$TiB_2$ particulate composite materials has been investigated in unlubricated oscillating sliding tests against $Al_2O_3$ at temperature in the range from room temperature up to $600^{\circ}C$. At temperatures below $600^{\circ}C$ the wear rate of the systems with the composite materials was up to 20 times lower than the wear of the $Al_2O_3$/SiC system and was dominated by the oxidation of the titanium phases. At $600^{\circ}C$ the oxidation rate of the TiC and -TEX>$TiB_2$ grains becomes predominant resulting in an enhanced wear rate of the composite rate of the TiC and TiB2 grains becomes predominant resulting in an enhanced wear rate of the composite materials. The coefficient of friction shows similar values for all materials of investigation, increasing from 0.25…0.3 at room temperature to 0.7…0.8 $600^{\circ}C$. The wear of the $Al_2O_3$/SiC system is mainly abrasive at temperatures above room temperature and is characterised by an enhanced wear of the alumina ball at $600^{\circ}C$.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.6 no.2
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• pp.185-193
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• 1996

$2.5^{\circ}\;and\;5^{\circ}$ tilted (100) Si wafer were oxidized in dry oxygen, and the differences in thermal oxidation behavior and oxidation induced stacking faults (OSF) between specimens were investigated. Ellipsometer measurements of the oxide thickness produced by oxidation in dry oxygen from 900 to $1200^{\circ}C$ showed that the oxidation rates of the tilted (100) Si were more rapid than those of the (100) Si and the differences between them decreased as the oxidation temperature increased. The activation energies based on the parabolic rate constant, B for (100) Si, $2.5^{\circ}$ off (100) Si and $5^{\circ}$ off (100) Si were 27.3, 25.9, 27.6 kcal/mol and those on the linear rate constant, B/A were 58.6, 56.6, 57.6 kcal/mol, respectively. Also, considerable decrease in the density of oxidation induced stacking faults for the $5^{\circ}$ off (100) Si was observed through optical microscopy after preferentially etching off the oxide layer, and the angle of stacking faults were changed with tilted angles.