• Journal of Preventive Medicine and Public Health
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• v.39 no.4
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• pp.309-316
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• 2006

Objectives: Korean epidemiological studies have used reduced samples according to the subject's characteristics, such as the health services provided, the historical note with asthma, and age, to examine the acute effect of air pollution on asthma using the Korean National Health Insurance records. However, there have been few studies on whether the effects shown in these reduced samples are different from those of all samples. This study compared the effects of air pollution on asthma attacks in three reduced samples with those of entire samples. Methods: The air pollution data for $PM_{10},\;CO,\;SO_2,\;NO_2,\;and\;O_3$, and weather conditions including temperature, relative humidity, and air pressure in Seoul, 2002, were obtained from outdoor monitoring stations in Seoul. The emergency hospital visits with an asthma attack in Seoul, 2002 were extracted from the Korean National Health Insurance records. From these, the reduced samples were created by health service, historical notes with asthma, and age. A case-crossover design was adopted and the acute effects of air pollution on asthma were estimated after adjusting for weather, time trend, and seasonality. The model was applied to each reduced sample and the entire sample. Results: With respect to the health service, the effects on outpatients were similar to those for the total sample but were different for inpatients. These similar effect sizes were also observed in the reduced samples according to the historical note with asthma and age. The relative risks of $PM_{10},\;CO,\;SO_2,\;NO_2,\;and\;O_3$, among the reduced and entire samples were 1.03, 1.04-1.05, 1.02-1.03, 1.04-1.06, and 1.10-1.17, respectively. Conclusions: There was no clear evidence to show a difference between the reduced samples and the entire samples.

• The Korean Journal of Food And Nutrition
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• v.30 no.4
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• pp.735-741
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• 2017

This study was conducted to investigate if the supplement formula may improve alcohol metabolism in healthy adult men. In a double-blinded, randomized, crossover study, subjects were administrated yeast extract mixtures (YEM, n=15), Hovenia dulcis mixtures (HDM, n=15), placebo (PLA, n=15), and control (CON, n=15) in an oral dose followed by one week washout periods. At each visit (0, 1, 2, 3, 4 week), subjects drank 450 mL, 20.1 percent alcohol after administered mixtures. Blood was drawn periodically (0, 0.25, 0.5, 1, 2, 4, 6, 15 hours). Fifteen subjects completed the protocol and were included in the analysis. Plasma ethanol concentration was lower in YEM (10 percent) and the HDM (5 percent) groups. The area under the curves (AUC) and $C_{max}$ for plasma ethanol were significantly decreased only in the YEM group, when compared with the CON group. The AUC and $C_{max}$ for plasma acetaldehyde concentration were significantly decreased in the YEM (45 and 54 percent) and the HDM (35 and 53 percent) groups respectively, when compared with PLA (p<0.01). Together, these findings validate that YEM or HDM improved alcohol metabolism and hangover syndromes, leading to reduce alcohol concentration and acetaldehyde concentration without adverse effects.

• Clinical and Experimental Emergency Medicine
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• v.3 no.3
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• pp.148-157
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• 2016

Objective Our aim was to compare the compression quality, exercise intensity, and energy expenditure in 5-minute single-rescuer cardiopulmonary resuscitation (CPR) using 15:1 or 30:2 compression-to-ventilation (C:V) ratios or chest compression only (CCO). Methods This was a randomized, crossover manikin study. Medical students were randomized to perform either type of CPR and do the others with intervals of at least 1 day. We measured compression quality, ratings of perceived exertion (RPE) score, heart rate, maximal oxygen uptake, and energy expenditure during CPR. Results Forty-seven students were recruited. Mean compression rates did not differ between the 3 groups. However, the mean percentage of adequate compressions in the CCO group was significantly lower than that of the 15:1 or 30:2 group ($31.2{\pm}30.3%$ vs. $55.1{\pm}37.5%$ vs. $54.0{\pm}36.9%$, respectively; P<0.001) and the difference occurred within the first minute. The RPE score in each minute and heart rate change in the CCO group was significantly higher than those of the C:V ratio groups. There was no significant difference in maximal oxygen uptake between the 3 groups. Energy expenditure in the CCO group was relatively lower than that of the 2 C:V ratio groups. Conclusion CPR using a 15:1 C:V ratio may provide a compression quality and exercise intensity comparable to those obtained using a 30:2 C:V ratio. An earlier decrease in compression quality and increase in RPE and heart rate could be produced by CCO CPR compared with 15:1 or 30:2 C:V ratios with relatively lower oxygen uptake and energy expenditure.

• The Korean Journal of Emergency Medical Services
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• v.25 no.1
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• pp.23-36
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• 2021

Purpose: The purpose of this study was to determine how the use of level D personal protective equipment (PPE) and cardiopulmonary resuscitation (CPR) feedback equipment affects chest compression (CC). Furthermore, this study provides basic data for developing Korean CPR guidelines that can be applied to patients with suspected or confirmed COVID-19. Methods: This randomized, single-blinded, crossover simulation trial included 26 student paramedics who performed 2-minute chest compressions using three different methods: Method A involved performing traditional CC for two minutes without donning level D PPE, Method B involved performing CC while donning level D PPE, and Method C involved performing CC with a CPR feedback device while donning level D PPE. Results: The use of a CPR feedback device during the 2-minute CC increased the exercise intensity of the subjects, but donning level D PPE didn't affect the quality of CC and the exercise intensity. The results of methods A and B showed changes in the quality of compression 80 seconds after the start of CC. No significant changes occurred in 2-minute CC when using the CPR feedback device. Conclusion: Using a CPR feedback device could prevent deterioration in the quality of CC while donning level D PPE.

• The Korean Journal of Pain
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• v.35 no.3
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• pp.336-344
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• 2022

Background: The U.S. Food and Drug Administration has prohibited epidural steroid injection (ESI) with particulate steroids. Thus, this study aimed to compare the efficacy and safety of ESI with two nonparticulate steroids, dexamethasone and betamethasone. Methods: The eligible patients (n = 600) who received ESI (0 week) with dexamethasone (ESI-dexa) or betamethasone (ESI-beta) had follow-up visits at 2, 4, and 8 weeks with a phone interview at 12 weeks. The primary endpoint was the proportion of effective responders without pain or who were much improved at 2 weeks. The secondary endpoints were the proportion of crossover injections at 2 weeks; changes in the visual analog scale (VAS) and disability index scores at 2, 4, and 8 weeks; the number of additional ESIs in 12 weeks; the number of participants having spinal surgery, as well as the incidence of adverse events over the 12 weeks. Results: The proportion of effective responders at 2 weeks was not different between ESI-beta (72/216, 33.3%) and ESI-dexa (63/200, 31.5%; P = 0.670). Adverse events were more common with ESI-dexa (40/200, 20.0%) than with ESI-beta (24/216, 11.1%; P = 0.012). VAS scores decreased more with ESI-beta than with ESI-dexa at 2 weeks (difference, 0.35; P = 0.023) and 4 weeks (difference, 0.42; P = 0.011). The disability score improved significantly more with ESI-beta compared with ESI-dexa at 2 weeks (difference, 3.37; P = 0.009), 4 weeks (difference, 4.01; P = 0.002), and 8 weeks (difference, 3.54; P = 0.007). Conclusions: Betamethasone would be more appropriate for ESI.

• New Physics: Sae Mulli
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• v.68 no.12
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• pp.1302-1307
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• 2018

The crystallographic, electrical and magnetic behaviors of magnetite powder in the vicinity of its Verwey transition were investigated in this study. Magnetite was prepared by synthesizing a nanoparticle precursor and then annealing it at $800^{\circ}C$ for 1 h under a dynamic vacuum. Crystallographic and morphology analyses were done by using scanning electron microscope (SEM) and X-ray diffraction (XRD). The electrical and the magnetic properties were examined by using $M{\ddot{o}}ssbauer$ spectroscopy, vibrating sample magnetometer (VSM) and resistivity measurement. Both the magnetic moment and the resistivity showed discontinuous changes at the Verwey transition temperature ($T_V$). The temperature dependence of magnetic anisotropy constant showed a monotonic decrease with increasing temperature, with slight dip near $T_V$. $M{\ddot{o}}ssbauer$ spectra showed the superposition of two sextets, one from the tetrahedral (A) and the other from the octahedral (B) sites. The results revealed that identical charge states existed in the B site at temperatures both above and below $T_V$. A coordination crossover resulted in a transition from an inverse to a normal spinel at or close to $T_V$.

• Korean Chemical Engineering Research
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• v.61 no.1
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• pp.26-31
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• 2023

For durability improvement of polymer electrolyte membrane fuel cell (PEMFC) polymer membrane, accelerated durability evaluation methods that can evaluate durability in a short time have been researched and developed. However, the lifespan of fuel cells for large commercial vehicles such as trucks and buses is more than three times that of passenger cars, and the chemical accelerated stress test (AST) time is also longer, reaching 1,500 hours or more. Therefore, in this study, as a method to evaluate the chemical durability of a membrane within a short time, it was examined whether the durability could be predicted by the pristine membrane characteristics. Hydrogen crossover current density (HCCD) and short resistance (SR) were estimated as initial characteristics, and AST time was predicted through the Fenton experiment, which was possible as an out-of-cell experiment for 3 hours. As the HCCD and fluoride ion emission concentration increased, the AST time tended to be linearly shortened, but there was a deviation (R² ≒0.65). When the SR decreased, the AST time showed a linear increase, and the accuracy was high (R² =0.93), so the AST time could be predicted with the initial SR of the membrane.

• Korean Journal of Biological Psychiatry
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• v.19 no.4
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• pp.159-163
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• 2012

An appropriate research design for hypotheses and purposes leads to a good quality of research results. In this review article, we summarized the types of research methods and described the characteristics of clinical trials. Research designs are categorized into observational studies and experimental ones, depending on data collecting methods. In an observational study, there are cross-sectional, cohort and case-control studies. Parallel groups design and crossover trial studies are representative designs in a randomized controlled trial study, a kind of experimental study. Clinical researchers should understand the characteristics of clinical research designs including advantages and disadvantages and choose the suitable design according to their study purposes and the nature of collected data or subjects.

• Proceedings of the PSK Conference
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• 2002.10a
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• pp.420.1-420.1
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• 2002

The purposes of this study were to evaluate bioequivalence (BE) using In-transformed pharmacokinetic parameters obtained from two tiropramide HCI products and to develop the analytical methods for the quantitative determination of tiropramide in human serum. In addition. the in vitro dissolution profiles of the two tiropramide HCI products in various dissolution media: pH 1.2, 4.0. 6.8 and water (KP Ⅶ Apparatus II method) were assessed. BE was evaluated in 20 healthy male Korean volunteers in randomized crossover study. (omitted)

• Korean Chemical Engineering Research
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• v.55 no.3
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• pp.296-301
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• 2017

Recently, there are many efforts focused on development of more economical non-fluorinated membranes for PEMFCs (Proton Exchange Membrane Fuel Cells). In this study, sulfonated poly (ether ether ketone) (sPEEK) membrane reinforced with poly imide was made to enhance of membrane durability. In order to test durability of single (un-reinforced) membrane and reinforced membrane MEA (Membrane and Electrode Assembly), degradation accelerated stress test was used. Before and after degradation, I-V polarization curve, hydrogen crossover current, electrochemical surface area, membrane resistance and charge transfer resistance were measured. As a result of experiments, hydrogen crossover current of reinforced MEA was lower than that of single MEA, therefor durability of reinforced MEA was higher than that of single MEA. There was not especially short phenomena in reinforced MEA after degradation accelerated stress test.