• Journal of The Korean Society of Clinical Toxicology
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• v.14 no.2
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• pp.122-128
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• 2016

Purpose: This study was conducted to describe the characteristics of patients with carbon monoxide (CO) poisoning. Methods: We retrospectively surveyed data from the Emergency Department based Injury In-depth Surveillance of 20 hospitals (2011-2014). We included patients whose mechanism of injury was acute CO poisoning caused by inhalation of gases from charcoal or briquettes. We surveyed the annual frequency, gender, age, result of emergency treatment, rate of intensive care unit (ICU) admission, result of admission, association with alcohol, and place of accident. We also surveyed the cause and experience of past suicide attempts by intentional poisoning. Results: A total of 3,405 patients were included (2,015 (59.2%) and 1,390 (40.8%) males and females, respectively) with a mean age of $39.83{\pm}18.51$ year old. The results revealed that the annual frequency of CO poisoning had increased and the frequency of unintentional CO poisoning was higher than that of intentional CO poisoning in January, February and December. The mean age of intentional CO poisoning was younger than that of unintentional CO poisoning ($38.41{\pm}13.03$ vs $40.95{\pm}21.83$) (p<0.001). The rates of discharge against medical advice (DAMA), ICU care and alcohol association for intentional CO poisoning were higher than for unintentional CO poisoning (36.4% vs 14.0%, 17.8% vs 4.7%, 45.2% vs 5.6%) (p<0.001). The most common place of CO poisoning was in one's residence. Conclusion: The annual frequency of total CO poisoning has increased, and unintentional CO poisoning showed seasonal variation. DAMA, ICU care, and alcohol association of intentional CO poisoning were higher than those of unintentional CO poisoning.

• Reproductive and Developmental Biology
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• v.33 no.2
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• pp.99-105
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• 2009

Curcumin is a major active component of the food flovour tumeric. It has been used for the treatment of many diseases such as inflammatory and infectious diseases, cancer and other disease due to its antioxidant properties. Curcumin is a powerful scavenger of many free radicals such as superoxide anion, hydroxyl radical and nitric oxide. The objective of this study was to investigate the antioxidative effects of curcumin against hydrogen peroxide on semen quality during in vitro storage of boar semen. The sperm treated with different concentration of curcumin (1, 5 and 10 ${\mu}M$) in the presence or absence of hydrogen peroxide (250 ${\mu}M\;H_2O_2$) were incubated for 3, 6 and 9 hr at $37^{\circ}C$ and analyzed sperm characteristics such as motility, membrane integrity (MI), lipid peroxidation (LPO), reactive oxygen species (ROS) and DNA fragmentation (DF). The sperm motility and MI in $H_2O_2$ treated group ($47.8%{\pm}6.8$ and $24.8%{\pm}2.2$) were significantly decreased when compare to curcumin treated group ($79.8%{\pm}2.7$ and $34.6%{\pm}1.0$, respectively) irrespective of incubation periods(p<0.05). The LPO of spermatozoal plasma membrane was measured by thiobarbituric acid (TBA) reactions for malondialdehyde (MDA), MDA level in control ($11.6{\pm}0.6\;nmol/L{\times}10^6$) and curcumin groups ($10.7{\pm}0.3\;nmol/L{\times}10^6$) were lower than those of curcumin plus $H_2O_2$ ($17.1{\pm}0.8\;nmol/L{\times}10^6$) or $H_2O_2$ group ($22.5{\pm}1.9\;nmol/L{\times}10^6$) from 3 to 9 hr incubation periods. The DF by sperm chromatin dispersion (SCD) test and ROS production measured by 2',7'-dichlorofluorescein (DCF) fluorescence intensity were no significantly difference through all experimental groups (p>0.05). Correlation among evaluation methods for sperm quality, motility vs MI and DF vs ROS was positively correlated while motility vs DF and ROS vs LPO were negatively correlated in all treatment groups. These results demonstrate that curcumin can effectively improve the sperm quality during in vitro storage of boar semen through its hydrogen peroxide scavenging mechanism as an antioxidant.

• Bulletin of the Korean Chemical Society
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• v.35 no.1
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• pp.225-230
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• 2014

A kinetic study on nucleophilic substitution reactions of 4-nitrophenyl X-substituted-benzoates (7a-i) with EtOK in anhydrous ethanol at $25.0{\pm}0.1^{\circ}C$ is reported. The plots of pseudo-first-order rate constants ($k_{obsd}$) vs. [EtOK] curve upward. Dissection of $k_{obsd}$ into the second-order rate constants for the reactions with the dissociated $EtO^-$ and ion-paired EtOK (i.e., $k_{EtO^-}$ and $k_{EtOK}$, respectively) has revealed that the ion-paired EtOK is more reactive than the dissociated $EtO^-$. Hammett plots for the reactions of 7a-i with the dissociated $EtO^-$ and ion-paired EtOK exhibit excellent linear correlations with ${\rho}_X$ = 3.00 and 2.47, respectively. The reactions have been suggested to proceed through a stepwise mechanism in which departure of the leaving-group occurs after the RDS. The correlation of the $k_{EtOK}/k_{EtO^-}$ ratio with the ${\sigma}_X$ constants exhibits excellent linearity with a slope of -0.53. It is concluded that the ion-paired EtOK catalyzes the reaction by increasing the electrophilicity of the reaction center rather than by enhancing the nucleofugality of the leaving group.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.18 no.1
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• pp.10-14
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• 2008

We synthesized GaN nanowires with high quality using the vapor phase epitaxy technique. The GaN nanowires were obtained at a temperature of $950^{\circ}C$. The Ar and $NH_3$ flow rates were 1000 sccm and 50 sccm, respectively. The shape of the GaN nanowires was confirmed through FESEM analysis. We were able to conclude that the GaN nanowires synthesized via vapor-solid (VLS) mechanism when the source was closed to the substrate. On the other side, the VS mechanism changed to vapor-liquid-solid (VLS) as the source and the substrate became more distant. Therefore, we can suggest that the large amount of Ga source from initial growth interrupt the role of catalyst on the substrate.

• Bulletin of the Korean Chemical Society
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• v.30 no.12
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• pp.2913-2917
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• 2009

Second-order rate constants (k$_{Nu–}$) have been measured for nucleophilic substitution reactions of Y-substituted phenyl benzoates (1a-i) with butane-2,3-dione monoximate ($Ox^-\;an\;\alpha$-nucleophile) and Z-substituted phenoxides in 80 mol% H$_2$O/20 mol% DMSO at 25.0${\pm}$0.1$^{\circ}C$. Hammett plots correlated with ${\sigma}^o$ and ${\sigma}^-$ constants for reactions of 1a-h with Ox$^–$ exhibit many scattered points. In contrast, the Yukawa-Tsuno plot results in a good linear correlation with ${\rho}_Y$ = 2.20 and r = 0.45, indicating that expulsion of the leaving group occurs in the rate-determining step (RDS). A stepwise mechanism with expulsion of the leaving-group being the RDS has been excluded, since Y-substituted phenoxides are less basic and better nucleofuges than Ox$^–$. Thus, the reactions have been concluded to proceed through a concerted mechanism. Ox$^–$ is over 10$^2$ times more reactive than its reference nucleophile, 4-chlorophenoxide (4-ClPhO$^–$). One might suggest that stabilization of the transition-state (TS) through intramolecular general acid/base catalysis is responsible for the ${\alpha}$-effect since such general acid/base catalysis is not possible for the corresponding reactions with 4-ClPhO$^–$. However, destabilization of the ground-state (GS) of Ox$^–$ has been concluded to be mainly responsible for the ${\alpha}$-effect found in this study on the basis of the fact that the magnitude of the ${\alpha}$-effect is independent of the nature of the substituent Y.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.11a
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• pp.122-122
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• 2003

In recent years, there has been increasing interest in quasi one-dimensional nanostructural systems, because of their numerous potential applications in various areas, such as materials sciences, electronics, optics, magnetism and energy storage. Specifically, zinc oxide (ZnO) is recognized as one of the most promising oxide semiconductor materials, because of its good optical, electrical, and piezoelectrical properties. The ZnO nanorods were synthesized using vapor-solid (VS) mechanism on soda lime glass substrate without the presence of metal catalyst. ZnO nanorods were prepared thermal evaporation of a Zn powder at 500. As-fabricated ZnO nanorods had an average diameter and length of 40nm and 3$\mu\textrm{m}$. Transmission electron microscopy revealed that the ZnO nanorods were single crystalline with the growth direction perpendicular to the (101) lattice plane. The influences of reaction time on the formation of the ZnO nanorods were investigated. The Photoluminescence measurements showed that the ZnO nanorods had a strong ultraviolet emission at around 380nm and a green emission at around 500nm.

• Journal of Microbiology and Biotechnology
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• v.13 no.3
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• pp.332-337
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• 2003

Enzyme kinetics data play a vital role in the design of reactors and control of processes. In the present study, kinetic studies on pectinases were carried out. Partially purified polymethylgalacturonase (PMG) and polygalacturonase (PG) were the two pectinases studied. The plot of initial rate vs. initial substrate concentration did not follow the conventional Michaelis-Menten kinetics, but substrate inhibition was observed. For PMG, maximum rate was attained at an initial pectin concentration of 3 g/l, whereas maximum rate was attained when the initial substrate concentration of 2.5 g/l of polygalacturonic acid for PG I and PG II. The kinetic data were fitted to five different kinetic models to explain the substrate inhibition effect. Among the five models tested, the combined mechanism of protective diffusion limitation of both high and inhibitory substrate concentrations (semi-empirical model) explained the inhibition data with 96-99% confidence interval.

• Tribology and Lubricants
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• v.8 no.1
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• pp.63-69
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• 1992

In order to gain better understanding of wear behaviors of TiN-coated boron cast iron, tests and analyses were conducted with block-on disc type tribometer. TiN layer of thickness $2 \mu m$ and $4 \mu m$, coated by cathodic arc evaporation process, were experimentally investigated with the variation of applied load and sliding speed under dry sliding condition. Wear characteristics were expressed in terms of the three-dimentional wear map as well as the wear rate vs sliding speed and load. Comparisons of wear and friction characteristics between coated cast irons and uncoated cast irns were also made. Wear mechanism of TiN layer was explained in view of surface interaction between the mating surfaces. The thicker coating exhibited higher hardness and adhesion strength. the significance of stresses at the surface and in the subsurface was briefly discussed in relation to the wear behavior.

• Journal of the Korean Ceramic Society
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• v.18 no.1
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• pp.35-40
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• 1981

The kinetics of the dehydration of Ha-dong kaolin was studied isothermally at various temperatures. Dehydration rate was measured by thermogravimetry method in the temperature range of 440~50$0^{\circ}C$ and the particle size range of 170~325mesh. The general equation f($\alpha$)=kt, where $\alpha$ is the fraction reacted in the time and the function f($\alpha$) depends on the reaction mechanism, was applied to this reaction. The function, f($\alpha$) was obtained by application of reduced-time plot and plot of lnln (1-$\alpha$) vs. ln (time), and expressed as (1-$\alpha$) ln (1-$\alpha$)+$\alpha$=kt. The dehydration followed the diffusion-controlled reaction model and gave activation energy of 30Kcal/mole.

• Journal of the Korean Chemical Society
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• v.15 no.6
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• pp.324-329
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• 1971

In order to evaluate the mechanism of electrolytic oxidation of iodate and to determine the optimum conditions for the electrolysis, studies were made using the cells without diaphragm and the lead peroxide anode. Results are summarized as followings: 1) Current density vs. anode potential curve by lead peroxide electrode had the different limiting current densities from platinum electrode and was more positive than platinum electrode. 2) Additions of potassium bichromate in the electrolyte contribute to maintain high current efficiency. 3) In the acid and alkaline regions, the current efficiencies decreased by reduction of iodate and discharge of hydroxyl ion, so maximum current efficiency was shown at pH 7. 4) Higher current density lowered the current efficiency in the region of 60-80% conversion of iodate. 5) Influence of the conversion on current efficiency in the region of 60-80% conversion of iodate.