• Journal of Food Hygiene and Safety
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• v.31 no.6
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• pp.432-438
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• 2016

Ethoxyquin (EQ, 1,2-dihydro-6-ethoxy-2,2,4-trimethyl-quinoline) is quinoline-based antioxidant used in the animal feed and food industry to protect the raw materials and final products against oxidation. In recent years the use of synthetic antioxidants in fishmeal ingredients carry-over to farmed fish fillets has received increasing attention in food safety. This study was conducted to develop an analytical method to determine EQ in aquatic products. The analytes were confirmed and quantified via liquid chromatography-tandem mass spectrometry (LC-MS/MS) in the positive ion mode using multiple reaction monitoring (MRM). The sample was extracted with 1 N HCl (in case of flatfish extracted with 1 N HCl containing 10% acetonitrile). Then, solid phase extraction (SPE) was used for the cleanup. Standard calibration curves presented linearity with the correlation coefficient ($r^2$) > 0.99, analyzed at 0.005-0.2 mg/kg concentration. The developed method was validated according to the Codex Alimentarius Commission (CAC) guideline. The limits of quantitation for EQ were 0.01 mg/kg. Average recoveries ranged from 81.3% to 107%. The repeatability of measurements, expressed as the coefficient of variation (CV, %), was below 10%. The analytical method was characterized with high accuracy and acceptable sensitivity to meet CODEX guideline requirements and would be applicable to analyze the EQ residue in aquatic products.

• Knowledge Management Research
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• v.22 no.3
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• pp.173-199
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• 2021

As the use of smart devices such as smartphones and tablets has become common, the time to start using smart devices is getting earlier, such as using smart devices from the age of one. Also, the use of smart devices by infants and toddlers is continuously increasing. Smart devices have become convenient means of acquiring pleasure and knowledge, but the side effects of addiction and overdependence are becoming issues as much as the benefits of smart devices. This study pays attention to young children's overdependence on smart devices, and focuses on the aspects of parents' perception, control, and observational behavior about smart devices, which can have a profound effect on young children. This study examines how young children's overdependence on smart devices can consequently affect children's characteristics in terms of activity, emotional sensitivity, and social aspects. In particular, this study attempts to explore that the factors influencing children's overdependence on smart devices and the results can vary depending on the moderating variables (parents' control method for children's smart device use, supervision method, and type of contents mainly used). Based on the findings, this study can provide guidelines and implications for parents on how to effectively use smart devices for their young children.

• Journal of the korean academy of Pediatric Dentistry
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• v.27 no.1
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• pp.169-179
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• 2000

The purpose of this study is to develop the system which convert the optical difference of teeth texture between intact enamel and incipient caries lesion into shade difference by laser fluorescence and to develop new and simple caries activity test using laser fluorescence. The experimental design of this study consists of three parts. In first part, a new method for the in vitro assessment of changes in initial enamel caries lesion of Bovine teeth using laser fluorescence is tested. In second part, in vivo assessment undertaken. Number of teeth which showed incipient carious lesion on buccal surface examined by laser fluorescence was compared with the caries activity test of $Cariescreen^{(R)}$ test and other oral environmental test of dDfFtT. In third part, new caries activity test measured by laser fluorescence was developed on the basis of above results and evaluated the sensitivity, specificity, and diagnostic power. Optical density measured by laser fluorescence was increased as increasing the depth of incipient carious lesion and showed high correlation$(\gamma=0.7015)$ with lesion depth. Optical density showed direct proportion to lesion depth. Linear equation was obtained between the optical density and the lesion depth by regression analysis. The result of caries activity test with laser fluorescence showed high correlation with those of $Cariescreen^{(R)}$ test and dDfFtT examination. Caries activity test with laser fluorescence showed 48% of sensitivity, 52% of specificity, and 45% of diagnostic power on the basis of dDfFtT examination, and also showed 48% of sensitivity, 51% of specificity, and 36% of diagnostic power on the basis of $Cariescreen^{(R)}$ test. In regard above result, caries activity test with laser fluorescence considered to be reliable for caries activity test compared with other oral environmental test. and it was also considered to be practical because it would be simple, inexpensive, and time saving method.

• Transactions of the Korean Society of Automotive Engineers
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• v.15 no.2
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• pp.50-57
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• 2007

Shocks are excited by impulsive forces and cause discomfort in vehicles. Current standards define means of evaluating shocks and predicting their discomfort, but the methods are based on research with a restricted range of shocks. This experimental study was designed to investigate the discomfort of seated subjects exposed to a wide range of vertical shocks. Shocks were produced from the responses of one degree-of-freedom models, with 16 natural frequencies (from 0.5 to 16 Hz) and four damping ratios (0.05 0.1, 0.2 and 0.4), to a hanning-windowed half-sine force inputs. Each type of shock was presented at five vibration dose values in the range $0.35\;ms^{-1.75}$ to $2.89\;ms^{-1.75}$. Fifteen subjects used magnitude estimation method to judge the discomfort of all shocks. The exponent in Stevens' power law, indicating the rate of growth in discomfort with shock magnitude, decreased with increasing fundamental frequency of the shocks. At all magnitudes, the equivalent comfort contours showed greatest sensitivity to shocks having fundamental frequencies in the range 4 to 12.5 Hz. At low magnitudes the variations in discomfort with the shock fundamental frequency were similar to the frequency weighting $W_b$ in BS 6841, but low frequency high magnitudes shocks produced greater discomfort than predicted by this weighting. At some frequencies, for the same unweighted vibration dose value, there were small but significant differences in discomfort caused by shocks having different damping ratios. The rate of increase in discomfort with increasing shock magnitude depends on the fundamental frequency of the shock. In consequence, the frequency-dependence of discomfort produced by vertical shocks depends on shock magnitude. For shocks of low and moderate discomfort, the current methods seem reasonable, but the response to higher magnitude shocks needs further investigation.

• Journal of Physiology & Pathology in Korean Medicine
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• v.26 no.3
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• pp.399-407
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• 2012

To evaluate age and gender differences in the relation of cardiovascular risk factors, cognitive impairment, and subclinical carotid atherosclerosis from aged people using by a cross sectional method. Sixty-nine healthy elders living in the community who had not previously undergone carotid ultrasonography were included. We conducted life style surveys, and cognitive function tests including Korean-mini-mental state examination (K-MMSE) and clinical dementia rating-Korean. Various biomarkers from blood were assessed; fasting insulin-like growth factor-1, lipid-profile, high sensitivity C-reactive protein, total homocysteine, glucose, insulin, Homeostasis model assessment (HOMA) for insulin resistance index, vitamin B12, and folate level. Carotid intima-media thickness (C-IMT), and plaques were measured using carotid ultrasonography and aortic ultrasonography, a valid index of atherosclerosis. For the elderly subjects (aged 65-82 years), cognition impairment was more prevalent in females while subclinical atherosclerosis was more prevalentin males. Increased C-IMT has been kept in males, and C-IMT shows increasing trend and the peak at about 80 year-old in females with increasing age. The significant correlations between C-IMT and many vascular risk factors including age, triglyceride, abnormal homocysteinein male, and K-MMSE, insulin, HOMA index and abnormal aortic ultrasonography in female were different in each gender, with the exception of homocysteine (p<0.05). This data suggests that there were differences of age and gender characteristics in terms of subclinical atherosclerosis, cognitive impairment and vascular risk factors in community-living elders. Further larger and longitudinal studies across entire age are required to better understand the effects of risk factors on subclinical atherosclerosis.

• Tuberculosis and Respiratory Diseases
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• v.68 no.3
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• pp.146-154
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• 2010

Background: The increasing incidence of multidrug-resistant tuberculosis (MDR-TB) and extensively drug-resistant tuberculosis (XDR-TB) has become a serious worldwide problem. However, there is insufficient data regarding the current status of MDR-TB and XDR-TB in Korea. This study examined the recent status of MDR- and XDR-TB using the data from 7 laboratories, in which almost all drug susceptibility tests (DST) for Mycobacterium tuberculosis were performed. Methods: The patients' identification data and DST results were collected from all 7 laboratories from 2001 to 2006 and the number of patients with MDR-TB and XDR-TB were calculated. Results: The number of DSTs was 140,638 for 6 years with an increasing incidence each year (p<0.001). The number of DST with MDR results was 18,510 and personal identifying information was obtained in 16,640 (89.9%) tests. The number of MDR-TB patients from 2001 to 2006 was 2,329, 2,496, 2,374, 2,300, 2,354, and 2,178, respectively, when counting the duplications in a year as one patient. The number of MDR-TB patients when counting the duplications in 6 years as one patient was 2,281, 1,977, 1,620, 1,446, 1,512, and 1,373, respectively. When the same method was adopted, the number of XDR-TB patients was 191, 238, 282, 260, 272, and 264, respectively, and 189, 150, 130, 90, 122, and 110 patients, respectively. Conclusion: Despite the national efforts to control TB, there are still a large number of MDR- and XDR-TB patients in Korea.

• Journal of the Korean Geotechnical Society
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• v.38 no.11
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• pp.107-118
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• 2022

The social need for stable hydrogen storage technologies that respond to the increasing demand for hydrogen energy is increasing. Among them, underground hydrogen storage is recognized as the most economical and reasonable storage method because of its vast hydrogen storage capacity. In Korea, low-depth hydrogen storage using artificial protective structures is being considered. Further, establishing corresponding safety standards and ground stability evaluation is becoming essential. This study evaluated the hydro-mechanical behavior of the ground during a hydrogen gas leak from a low-depth underground hydrogen storage facility through the HM coupled analysis model. The predictive reliability of the simulation model was verified through benchmark experiments. A parameter study was performed using a metamodel to analyze the sensitivity of factors affecting the surface uplift caused by the upward infiltration of high-pressure hydrogen gas. Accordingly, it was confirmed that the elastic modulus of the ground was the largest. The simulation results are considered to be valuable primary data for evaluating the complex analysis of hydrogen gas explosions as well as hydrogen gas leaks in the future.

• Journal of Chest Surgery
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• v.43 no.4
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• pp.345-355
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• 2010

Background: Extracellular and intracellular pH ($pH_o$ and $pH_i$), which can be changed in various pathological conditions such as hypoxia, affects vascular contractility. To elucidate the mechanism to alter vascular contractility by pH, the effects of pH on reactivity to vasocontracting agents, intracellular $Ca^{2+}$ influx, and $Ca^{2+}$ sensitivity in vascular smooth muscle were examined. Material and Method: Isometric contractions in rat superior mesenteric arteries (SMA) were observed. Intracellular $Ca^{2+}$ concentration ($[Ca^{2+}]_i$) was recorded by microfluorometer using Fura-2/acetoxylmethyl ester in muscle cells. $pH_o$ was increased from 7.4 to 7.8 or decreased to 6.9 or 6.4. $pH_i$ was decreased by applying $NH_4^+$ or propionic acid or modulated by changing $pH_o$ after increasing membrane permeability using $\beta$-escin. Result: Decreases in $pH_o$ from 7.4 to 6.9 or 6.4 shifted concentration-response curve by norepinephrine (NE) or serotonin (SE) to the right and significantly increased half maximal effective concentration (EC50) to NE or SE. Increase in $pH_o$ from 7.4 to 7.8 shifted concentration-response curve by norepinephrine (NE) or serotonin (SE) to the left and significantly reduced EC50 to NE or SE. NE increased $[Ca^{2+}]_i$ in cultured smooth muscle cells from SMA and the increased $[Ca^{2+}]_i$ was reduced by decreases in $pH_o$. NE-induced contraction was inhibited by $NH_4^+$, whereas the resting tension was increased by $NH_4^+$ or propionic acid. When the cell membrane of SMA was permeabilized using ${\beta}$-escin, SMA was contracted by increasing extracellular $Ca^{2+}$ concentration from 0 to $10{\mu}M$ and the magnitude of contraction was decreased by a decrease in $pH_o$ and vice versa. Conclusion: From these results, it can be concluded that a decrease in $pH_o$ might inhibit vascular contraction by reducing the reactivity of vascular smooth muscle to vasoactive agents, $Ca^{2+}$ influx and the sensitivity of vascular smooth muscle to $Ca^{2+}$.

• Journal of Trauma and Injury
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• v.20 no.2
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• pp.57-64
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• 2007

Purpose: Clinically, acute respiratory distress syndrome (ARDS) occurs within 72 hours after acute exposure of risk factors. Because of its high fatality rate once ARDS progresses, early detection and management are essential to reduce the mortality rate. Accordingly, studies on early changes of ARDS were started, and serum ferritin, as well the as injury severity score (ISS), which has been addressed in previous studies, thought to be an early predictive indicator for ARDSMethods: From March 2003 to March 2005, we investigated 50 trauma patients who were admitted to the intensive care unit in Dongguk University Medical Center, Gyeongju. The patients were characterized according to age, sex, ISS, onset of ARDS, time onset of ARDS, serum ferritin level (posttraumatic $1^{st}\;&\;2^{nd}$ day), amount of transfused blood, and death. Abdominal computed topography was performed as an early diagnostic tool to evaluate the onset of ARDS according to its diagnostic criteria. The serum ferritin was measured by using a $VIDAS^{(R)}$ Ferritin (bioMeriux, Marcy-1' Etoile, France) kit with an enzyme-linked fluorescent assay method. For statistical analysis, Windows SPSS 13.0 and MedCalc were used to confirm the probability of obtaining a predictive measure from the receiver operating characteristics (ROC) curve. Results: The ISS varied from 14 to 66 (mean: 33.8) whereas the onset of ARDS could be predicted with the score above 30 (sensitivity: 90.0%, specificity: 60.0%, p<0.05). On the posttraumatic $1^{st}$ day, the serum ferritin levels were measured to be from 31 mg/dL to 1,200 mg/dL (mean: 456 mg/dL), and the onset of ARDS could be predicted when the value was over 340 mg/dL (sensitivity: 80.0%, specificity: 65.0%, p<0.05). On the posttraumatic $2^{nd}$ day, the serum ferritin levels were measured to be from 73 mg/dL to 1,200 mg/dL (mean: 404 mg/dL), and the onset of ARDS could be predicted when the value was over 627 mg/dL (sensitivity: 60.0%, specificity: 92.5%, p<0.05). The serum ferritin levels and the ISS were significantly higher on the posttraumatic $1^{st}$ and $2^{nd}$ day in the ARDS group, suggesting that they are suitable indices predicting the onset of ARDS, however relationship between the serum ferritin levels and the ISS was not statistically significant. Conclusion: In this study, we discovered increasing serum ferritin levels in multiple- trauma patients on the posttraumatic $1^{st}$ & $2^{nd}$ day and concluded that both the serum ferritin level and the ISS were good predictors of ARDS. Although they do not show statistically significant relationship to each other, they can be used as independent predictive measures for ARDS. Since ARDS causes high mortality, further studies, including the types of surgery and the methods of anesthesia on a large number of patients are essential to predict the chance of ARDS earlier and to reduce the incidence of death.

• Journal of the Korean Society for Marine Environment & Energy
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• v.17 no.2
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• pp.153-165
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• 2014

Carbon dioxide capture and storage (CCS) technology is recognizing one of method responding the climate change with reduction of carbon dioxide in atmosphere. In Korea, due to its geological characteristics, sub-seabed geological $CO_2$ storage is regarded as more practical approach than on-land storage under the goal of its deployment. However, concerns on potential $CO_2$ leakage and relevant acidification issue in the marine environment can be an important subject in recently increasing sub-seabed geological $CO_2$ storage sites. In the present study effect data from literatures were collected in order to conduct an effect assessment of elevated $CO_2$ levels in marine environments using a species sensitivity distribution (SSD) various marine organisms such as microbe, crustacean, echinoderm, mollusc and fish. Results from literatures using domestic species were compared to those from foreign literatures to evaluate the reliability of the effect levels of each biological group and end-point. Ecological effect guidelines through estimating level of pH variation (${\delta}pH$) to adversely affect 5 and 50% of tested organisms, HC5 and HC50, were determined using SSD of marine organisms exposed to the $CO_2$-induced acidification. Estimated HC5 as ${\delta}pH$ of 0.137 can be used as only interim quality guideline possibly with adequate assessment factor. In the future, the current interim guideline as HC5 of ${\delta}pH$ in this study will look forward to compensate with supplement of ecotoxicological data reflecting various trophic levels and indigenous species.