Yoo-Keun Kim

A multicenter, randomized, placebo-controlled, double-blind phase II trial evaluating the optimal dose, efficacy and safety of LC 15-0444 in patients with type 2 diabetes

Aim: The objective of this study was to evaluate the optimal dose, efficacy and safety of a novel dipeptidyl peptidase‐4 (DPP‐IV) inhibitor, LC15‐0444, in Korean subjects with type 2 diabetes mellitus treated by diet and exercise.

Characteristics of Asian dust transport based on synoptic meteorological analysis over Korea.

Classification of synoptic patterns and their correlation with dust events over East Asia were performed by means of cluster analysis. The average linkage and K-means clustering techniques were used to identify two major weather types during Asian dust events (ADEs; total 26 ADEs with 47 dusty days) of six spring seasons from 1996 to 2001. The first weather type mainly influenced neighboring Asian countries and frequently occurred with ADEs (∼23% of ADE cases). It mostly occurred under a surface high (low)-pressure system over the west (east) of the Korean peninsula coupled with an upper-level trough and cutoff low passage over the center of the Korean peninsula. It showed strong advection in the middle/upper troposphere with both a high aerosol index and enhanced coarse particulate matter (PM) loading over Korea. In contrast, the second weather type was mostly associated with long distance or continental-scale transport and occurred less frequently with ADEs (∼15%). It appeared with an upper-level trough and a cutoff low vertically connected with a surface low system that was formed by a strong cyclonic vortex over the north of the Korean peninsula. There were weak advection, low aerosol index, and low coarse PM concentration over the Korean peninsula during the second weather type. In addition, it was found to be mostly associated with the trans-Pacific transport of Asian dust to the western coast of North America.

Comparison of outdoor and indoor mobile source-related volatile organic compounds between low- and high-floor apartments

The current study examined the hypothesis that there may be vertical variation in mobile source-related volatile organic compound (VOC) concentrations in high-rise apartment buildings. One hundred twelve homes in 56 high-rise apartment buildings with 10 or more stories participated in the study. Both the outdoor and the indoor air concentrations of three VOCs [methyl-tertiary butyl ether (MTBE), benzene, and toluene] were significantly higher for the low-floor apartments than for the high-floor apartments (P < 0.05). The median outdoor concentrations were 5.4, 6.8, and 29.1 microgram/m3, respectively, for the low-floor apartments, yet 4.4, 4.3, and 21.9 microgram/m3, respectively, for the high-floor apartments. Meanwhile, the median indoor concentrations were 6.3, 9.4, and 44.8 microgram/m3, respectively, for the low-floor apartments, yet 5.1, 7.6, and 38.8 microgram/m3, respectively, for the high-floor apartments. These findings indicate that residents of low-floor apartments are exposed to elevated residential levels of mobile source-related VOCs compared to high-floor apartment residents. The indoor concentrations of the target VOCs, except for MTBE, were significantly higher than the outdoor air concentrations for both the low and high floors (P < 0.05). Plus, the outdoor and indoor VOC concentrations were significantly different between the daytime and nighttime data sets for both low- and high-floor apartments, with a P value of less than or close to 0.05.

Surface Ozone Episode Due to Stratosphere-Troposphere Exchange and Free Troposphere-Boundary Layer Exchange in Busan During Asian Dust Events

The current paper reports on the enhancement of O, CO, NO, and aerosols during the Asian dust event that occurred over Korea on 1 May 1999. To confirm the origin and net flux of the O, CO, NO, and aerosols, the meteorological parameters of the weather conditions were investigated using Mesoscale Meteorological Model 5(MM5) and the TOMS total ozone and aerosol index, the back trajectory was identified using the Hybrid Single-Particle Lagrangian Integrated Trajectory Model(HYSPLIT), and the ozone and ozone precursor concentrations were determined using the Urban Ashed Model(UAM). In the presence of sufficiently large concentrations of NOx/, the oxidation of CO led to O formation with OH, HO, NO, and NO acting as catalysts. The sudden enhancement of O, CO, NO and aerosols was also found to be associated with a deepening cut-off low connected with a surface cyclone and surface anticyclone located to the south of Korea during the Asian dust event. The wave pattern of the upper trough/cut-off low and total ozone level remained stationary when they came into contact with a surface cyclone during the Asian dust event. A typical example of a stratosphere-troposphere exchange(STE) of ozone was demonstrated by tropopause folding due to the jet stream. As such, the secondary maxima of ozone above 80 ppbv that occurred at night in Busan, Korea on 1 May 2001 were considered to result from vertical mixing and advection from a free troposphere-boundary layer exchange in connection with an STE in the upper troposphere. Whereas the sudden enhancement of ozone above 100 ppbv during the day was explained by the catalytic reaction of ozone precursors and transport of ozone from a slow-moving anticyclone area that included a high level of ozone and its precursors coming from China to the south of Korea. The aerosols identified in the free troposphere over Busan, Korea on 1 May 1999 originated from the Taklamakan and Gobi deserts across the Yellow River. In particular, the 1000m profile indicated that the source of the air parcels was from an anticyclone located to the south of Korea. The net flux due to the first invasion of ozone between 0000 LST and 0600 LST on 1 May 1999 agreed with the observed ground-based background concentration of ozone. From 0600 LST to 1200 LST, the net flux of the second invasion of ozone was twice as much as the day before. In this case, a change in the horizontal wind direction may have been responsible for the ozone increase.

Elevated Ozone Layers over the Seoul Metropolitan Region in Korea: Evidence for Long-Range Ozone Transport from Eastern China and Its Contribution to Surface Concentrations

Abstract Elevated layers of high ozone concentration were observed over the Seoul metropolitan region (SMR) in Korea by ozonesonde measurements during 6–9 June 2003. An analysis of the synoptic-scale meteorological features and backward trajectories revealed that the layers were associated with the long-range transport of ozone from eastern China. Further examination of the long-range transport process responsible for the development of these layers was performed using the Community Multiscale Air Quality (CMAQ) model. CMAQ demonstrated that the upward mixing of ozone by convective activity in eastern China and subsequent horizontal transport aloft in the periphery of a slow-moving high pressure system led to the development of thick ozone layers over the SMR. Through comparative simulation studies, it was found that the surface ozone levels in the SMR can be significantly enhanced by the vertical down-mixing of ozone from the layer aloft with the growing mixed layer. On average, about 25% of the surface ...

Identification and Interpretation of Representative Ozone Distributions in Association with the Sea Breeze from Different Synoptic Winds over the Coastal Urban Area in Korea

Abstract To aid the studies of long-term impact assessment of cumulative ozone (O3) exposures, the representative 8-hr O3 pollution patterns have been identified over the Greater Seoul Area (GSA) in Korea. Principal component analysis and two-stage clustering techniques were used to identify the representative O3 patterns, and numerical and observational analyses were also used to interpret the identified horizontal distribution patterns. The results yielded three major O3 distribution patterns, and each of the three patterns was found to have strong correlations with local and synoptic meteorological conditions over the GSA. For example, pattern 1, accounting for 46% of O3 concentration distributions, mostly occurred under relatively weak westerly synoptic winds. The predominant features of this pattern were infrequent high O3 levels but a distinct gradient of O3 concentration from the western coastal area to the eastern inland area that was mainly induced by the local sea breeze. Pattern 2, accounting for 31% of O3 concentration distributions, was found with higher O3 levels in the western coastal area but lower in the eastern inland area. This is due to the modified sea breeze under the relatively stronger easterly opposing synoptic wind, affecting the high O3 occurrence in the western coastal area only. However, pattern 3, accounting for 21% of O3 concentration distributions, showed significantly higher O3 concentrations over the whole GSA mainly due to the retarded and slow-moving sea-breeze front under the weak opposing synoptic flow. Modeling study also indicated that local and synoptic meteorological processes play a major role in determining the high O3 concentration distribution patterns over the GSA.

High-resolution Simulation of Meteorological Fields over the Coastal Area with Urban Buildings

A meso-urban meteorological model (Urbanized MM5; uMM5) with urban canopy parameterization (UCP) was applied to the high-resolution simulation of meteorological fields in a complex coastal urban area and the assessment of urban impacts. Multi-scale simulations with the uMM5 in the innermost domain (1-km resolution) covering the Busan metropolitan region were performed during a typical sea breeze episode (4~8 August 2006) with detailed fine-resolution inputs (urban morphology, land-use/land-cover sub-grid distribution, and high-quality digital elevation model data sets). An additional simulation using the standard MM5 was also conducted to identify the effects of urban surface properties under urban meteorological conditions. Results showed that the uMM5 reproduced well the urban thermal and dynamic environment and captured well the observed feature of sea breeze. When comparison with simulations of the standard MM5, it was found that the uMM5 better reproduced urban impacts on temperature (especially at nighttime) and urban wind flows: roughness-induced deceleration and UHI (Urban Heat Island)-induced convergence.

Intercomparison of Wind and Air Temperature Fields of Meteorological Model for Forecasting Air Quality in Seoul Metropolitan Area

The MM5, RAMS and WRF, meteorological models have provided the dynamical parameters as inputs to air quality model. A major content of this study is that significant characteristics of three models for high-ozone occurrence analyze for surface wind and air temperature fields and compare with observation data in Seoul metropolitan area. An analysis of air temperature field revealed that location of core in high temperature of MM5 and WRF differed from that of RAMS. MM5 and WRF indicated high temperature in Seoul but RAMS represented it on the outskirts of Seoul. MM5 and WRF were underestimated maximum temperature during daytime but RAMS simulated similar value with observation data. Surface wind field with three models, it was shown many differences at horizontal distribution of wind direction. RAMS indicated weak wind speed in land and strong sea breeze at coastal areas than MM5 and WRF. However wind speed simulated by three model were overestimated during both daytime and nighttime.

Modeling of the Air Pollutant Recirculation using the MM5-CAMx on Ozone Episode in Greater Seoul Area during June, 2004

Recent evidence has demonstrated that the pollutant recirculation can play an important role in leading to high ozone concentrations. In this study, the MM5-CAMx air quality modeling system was applied to simulate the pollutant recirculation and identify the transport of pollution during the high event (the maximum of 195 ppb) observed in the Greater Seoul Area (GSA) on June in 2004. The results showed a weak northeasterly synoptic wind during the night and early morning moved the air parcels containing the locally emitted urban pollution to the coast, which contributed to enhance formation in the southwest part of the GSA. As the sea breeze developed and started to penetrate inland in the late afternoon, the rapid build-up of concentration was found in the southwest coastal area due to the recirculation of the polluted air loaded with high level . The simulated backward trajectories and observations at coastal sites confirmed the recirculation of pollutant with the late sea breeze is the dominant factor affecting the occurrence of high concentrations in the southwestern GSA.

Evaluation of Thermal Environments during the Heat Waves of Summer 2013 in Busan Metropolitan Area

Now a days, frequency of abnormally high temperatures like heat wave by global warming and climate change is increasing constantly and the number of patient with heat related illness are jumping rapidly. In this study, we chose the case day for the heat wave in Busan area(Busan and Yangsan), 2013 which it was the most hottest year during 21th century. And then, we analysed the weather condition using automatic synoptic observing system(ASOS) data. Also, four indices, heat index(HI), wet bulb globe temperature(WBGT), Man-ENvironment heat EXchange model(MENEX)’s results like Physiological subjective temperature(PST), Physiological strain(PhS), were calculated to evaluate the thermal comfort and stress quantitatively. However, thermal comfort was different as the each station and thermal comfort index during same time. Busan’s thermal indices (HI: hot, WBGT: sweltering, PST: very hot, PhS: very hot) indicated relatively higher than Yansan’s (HI: very hot, WBGT: sweltering, PST: very hot, PhS: sweltering). It shows that Busan near coast is relatively more comfortable than Yangsan located in inland.