• Journal of The Korean Astronomical Society
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• v.11 no.1
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• pp.1-30
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• 1978

The four dimensional classification of globular dusters with the parameters, Z, Y, age and HB type is presented defining two new parameters. $(B-V)_{1/2}\;and\;S_{3/2}$ which are shown to be tightly correlated with Kinman's spectral types and the helium abundances obtained from the R-method, respectively. The Z- and Y- abundances are derived from $(B-V)_{1/2}\;and\;S_{3/2}$, respectively, and the latter parameters determine the age class of clusters with help of Dickens' HB type, which is a function of Z. Y and age. For the examined forty two globular clusters the computed range at Z and Y are $1.5{\times}10^{-4}{\leq}Z{\leq}4.5{\times}10^{-2}\;and\;0.23<Y{\leq}0.41$. The age difference between the oldest (HB type 1) and the youngest (HB type 7) clusters is roughly estimated to be $2-4{\times}10^9$ years. Using these four parameters the known anomalous C-M diagrams seem to be reasonably interpreted without taking into account some complicate parameters such as unusually overabundant heavy elements, mass loss and mass spread, etc. The four dimensional scheme strongly suggests the slow successive collapses of the proto-Galaxy rather than a single fast collapse, and by this slow collapse model the inversion of chemical abundance gradient in the Galaxy can be explained. It is also shown that the clump position along the RGB near the HB level removes down to the fainter magnitude as the Z(Y)- abundance increases (decreases).

• Journal of Environmental Health Sciences
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• v.49 no.4
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• pp.218-227
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• 2023

Background: Since 2019, the Ministry of Environment has implemented a seasonal fine dust management system from December to March, targeting high PM_2.5 levels with the aim of reducing PM_2.5 concentrations and protecting public health. The focus of improving the seasonal management system lies in the atmospheric PM_2.5 levels. Considering the primary goal of protecting public health, it is necessary to analyze the policy effects from an exposure perspective rather than a concentration-based approach. Objectives: This study aims to quantitatively assess the improvement of indoor PM_2.5 levels and the health impacts of the seasonal management system by comparing the periods before and during its implementation in residential environments. Methods: PM_2.5 concentrations within residential environments in a metropolitan area were measured using an optical particle counter (IAQ-C7, K-weather, Ltd, Korea) at one-minute intervals during the pre-implementation period (November 21~25, 2022) and during the implementation period (December 19~23, 2022). Based on the measured PM_2.5 concentrations, a quantitative evaluation of cancer and mortality risks was conducted according to age and gender. Results: The results of comparing indoor and outdoor PM_2.5 concentrations before and during the implementation of the seasonal management system showed a decrease of approximately 56.6% and 47.9%, respectively. Health risk assessments revealed that both the safety-limit-based and safety-target-based Hazard Quotients (HQ) exceeded the threshold of 0.1 for children under 19 years of age, both before and after the implementation. The mortality risk decreased by approximately 47.9% after the implementation, with children aged 0-9 showing the highest mortality risk at 0.9%. Conclusions: The findings of this study confirmed the positive health impacts of the seasonal management system across all age groups, particularly children under 19 who are more vulnerable to fine dust exposure.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2004.09a
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• pp.138-141
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• 2004

The environmental tracers tritium/helium-3 (3H/3He) and chlorofluorocarbons (CFCs) were investigated in ground water from Jeju Island, Korea, a basaltic volcanic island. The apparent 3H/3He and CFC-12 ages were in relatively good agreement in samples with low concentrations of terrigenic He. Ground water mixing was evaluated by comparing 3H and CFC-12 concentrations with mixing models, which distinguished old water with negligible 3H and CFC-12, young water with piston flow, and binary mixtures of the two end members. The ground water CFC-12 age is much older in water from wells completed in confined zones of the hydro-volcanic Seoguipo formation in coastal areas than in water from the basaltic aquifer. Comparison of major element concentrations in ground water with the CFC-12 age shows that nitrate contamination processes contribute more solutes in young water than are derived from water-rock interactions in non-contaminated old water. Chemical evolution of ground water resulting from silicate weathering in basaltic rocks reaches the zeolite-smectite phase boundary. The calcite saturation state of ground water increased with the CFC-12 apparent (piston flow) age. In agricultural areas, the temporal trend of nitrate concentration in ground water was consistent with the known history of chemical fertilizer use on Jeju Island, but the response of nitrate concentration in ground water to nitrogen inputs follows an approximate 10-year delay. Based on mass balance calculations, it was estimated that about 40% of the nitrogen applied by fertilizers reached the water table and contaminated ground water resources when the fertilizer use was at the highest level.

• Journal of Food Hygiene and Safety
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• v.30 no.2
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• pp.210-216
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• 2015

This study was investigated about the antibacterial effects of aqueous garlic extract (AGE) against Escherichia coli O157:H7 (E. coli O157:H7), Salmonella typhimurium (S. typhimurium) and Staphylococcus aureus (S. aureus). The minimum inhibitory concentration (MIC) of AGE against E. coli O157:H7, S. typhimurium, and S. aureus was 24, 48 and 24 mg/mL, respectively. In addition, the minimum bactericidal concentration (MBC) of AGE against E. coli O157:H7, S. typhimurium, and S. aureus was all of 96 mg/mL. The growth of E. coli O157:H7 was significantly inhibited at the concentration of AGE 24 mg/mL at 24 hr post-incubation (p < 0.01), but that of S. aureus was not significantly inhibited at the same concentration. However, the growth of S. aureus at the concentration of AGE 96 mg/mL was significantly inhibited at 24 hr post-incubation compared to that of untreated bacteria (p < 0.01). At the concentration of AGE 48 (p < 0.05) and 96 mg/mL (p < 0.001), the growth of S. typhimurim was significantly inhibited at 24 hr after incubation compared to that of untreated bacteria. With the results of this study, AGE can be used as alternative to antibiotics and chemical food preservatives.

• Investigative Magnetic Resonance Imaging
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• v.16 no.1
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• pp.16-24
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• 2012

Purpose : The purpose of this study was to determine whether there is a significant correlation between vertebral marrow fat fraction measured using Dixon quantitative chemical shift MRI (QCSI) and BMD on dual-energy X-ray absorptiometry (DXA). Materials and Methods: This retrospective study included 68 healthy individuals [mean age, 50.7 years; range, 25-76; male/female (M/F) = 36/32] who underwent DXA of the L-spine and whole body MRI including QCSI of the L-spine and chemical shift MRI of the liver. The enrolled individuals were divided into subgroups according to sex and T-score [i.e., normal bone density (M/F=27/23) and osteopenia (M/F=9/9)]. Vertebral marrow (Dixon QCSI, TR/TE 10.2/4.8 ms) and hepatic fat fractions (chemical shift technique, TR/TE 110/4.9 and 2.2 ms) were calculated on MRI. We evaluated whether there were significant differences in age, body mass index (BMI), vertebral marrow fat fraction, or hepatic fat fraction among the subgroups. Whether or not the participant had reached menopause was also evaluated in females. The correlations among variables (i.e., age, BMI, vertebral marrow and hepatic fat fractions, BMD) were evaluated using Spearman's correlation method. Results: There were no significant differences in age, BMI, or vertebral marrow and hepatic fat fractions between the two male subgroups (normal bone density vs. osteopenia). In female subjects, mean age in the osteopenic subgroup was greater than that in the normal subgroup (p=0.01). Presence of menopause was more common in the osteopenic subgroup [77.8% (7/9)] than the normal subgroup [26.1% (6/23), p<0.05]. The other variables showed no significant difference between female subgroups. The only significant correlation with marrow fat fraction after partial correlation analysis was that with age in the female subjects (r=0.43, p<0.05). Conclusion: The vertebral marrow fat fraction calculated using the Dixon QCSI does not precisely reflect the mild decrease in BMD for either sex.

• Journal of the Korea Institute of Building Construction
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• v.14 no.2
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• pp.170-176
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• 2014

This study examined the effect of chemical attack on the stress-strain relationship of alkali-activated Hwangtoh concrete. Water-to-binder ratio and air content were selected as mixture parameters. The stress-strain relationship of concrete was measured at chemical immersion times of 0, 7, 28, 56, and 91 days from an age of 28 days. Based on the test results, the reduction in compressive strength of alkali-activated hwangtoh concrete owing to chemical attack was formulated. In sddition the present study demonstrated that the stress-strain behavior of concrete under chemical attack is significantly dependent on the air content and chemical immersion time, indicating the rate of decrease of modulus of elasticity was greater than that of compressive strength at the same immersion time. As a result, the stress-strain behavior of concrete under chemical attack was significantly inconsistent with the conventional models specified in the CEB-FIP provision.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.38 no.1
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• pp.44-49
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• 2012

Introduction: Sialolithes are initiated by localized deposition of calcified material in the salivary glands. And that may even cause various symptom especially swelling and pain. This study purposes to collect statistical data of sialolithiasis for clinical analysis. Materials and Methods: Among forty seven patients who have visited Seoul National University Dental Hospital during 2004-2009, patients' age, sex, location and size of stone, radiodensity of stone, symptom, surgical procedure were investigated. Statistical correlation between size, location, symptom was evaluated. Chemical composition was analyzed for 3 sialolithes. Results: The average age was 41.4 years. Sialolithiasis had slight female predilection (57.4%). Most cases occurred in the submandibular glands (91.5%). And most cases had radiopaque features (95.8%). The average size was 7.17 mm. The most frequent location of the stones were the duct orifice and the submandibular gland hilum (16 cases in each), followed by the middle part of the duct (n=8), the intraglandular area (n=4), and the proximal part of the duct (n=3). Eleven cases were asymptomatic. Thirty six cases had complaints of pain, swelling, hardness, and decrease in saliva flow (multiple symptoms). Various methods of surgery was performed. Two cases were self-removed. Thirty seven cases underwent procedure involving stone removal alone. Six cases underwent gland extirpation, and two cases underwent ductoplasty. Conclusion: There was no statistical correlation between size, location, and symptoms. Sialolith was composed of Ca (58.5-69.3%), P (30.7-35.7%), organic material, and trace inorganic material.

• Journal of the Korean Chemical Society
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• v.36 no.5
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• pp.727-737
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• 1992

The water chemical characteristics and age dating of springwater in Cheju island had been investigated. C_1, C_4, C_7, C_9 springwaters were not affected by seawater intrusion by TDS and electrical conductivity, relationship of Cl and tritium, Cl and HCO_3 ratio, and total hardness and pseudo hardness. In this case only C_7 springwater was evaluated tasty and healthy mineral springwater by Hahimoto's Mineral Balance Index. On the basis of the mean tritium content of rainfalls and springwater, the average residence time of it, were calculated. Considering the hydrogeologic and hydrochemical condition, completely mixed model seems to be very fit. It was obtained the result that C_9 group springwater (C_{10}, C_{12}, C_{14}) was 1.2 months, C_7 springwater was 5.6 months, and deep groundwater C_{17} was 4 years.

• Journal of Plant Biology
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• v.12 no.1
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• pp.7-14
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• 1969

Korea has a lots of margin for security of farm land from her coastal region. The area of saline soil may be reached about 10% of present farm land if the reclamation works are finished. This paper was conducted as a part of studying the possibilities of desalination of saline soil through the experiment of some halophytes. The halophytes in this works were Salicornia herbacea L., Suaeda glauca Bunge, chenopodium acuminatum Willd, and Scirpus triquerter L. Of the above halophytes, Salicornia was proved the most effective plant for desalination of saline soil referring to the following results; 1) The seasonal uptake of chloride by Salicornia was the highest of all. However, the general tendencies of all plants showed a decrease on August. 2) Salinity of soil showed the lowest value on the site where Salicornia was grwon densely. Comparing the other sites grouped by age of saline soil with the above site, the salinity of rice-paddy (10 years after reclamation) is similar to those of the site wehre Salicornia were as well as the 50 cm below the surface soil. 3) The maximum water holding capacity of surface soil appeared in the site of Salicornia, but in 50 cm below the surface, the maximum water holding capacity are almost on equat terms having no connection with the age of saline soil. Soil pH, other chemical compositions such as organic matter, magnesium, potassium, phosphorous, and nitrate were determined to elucidate the relationship between the changes of soil properties and chemical uptakes by certain halophytes. It is assumed that the above chemical compositions are frequently affected by the factors such as coastal circulation of salts, exchangeable base, microbial growth, climatic conditions, and irrigation of water.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.33 no.4
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• pp.502-516
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• 2023

Objectives: The purpose of this study was to investigate occupational exposure to chemical and health status of foreign workers in Korea. Methods: The data were collected from survey of general characteristics, job-related characteristics, work environment-related characteristics of 180 foreign workers who have been working at manufacturing industries in Korea in 2022. The data were analyzed using Rex. Results: Among the 180 participants, men accounted for more than women by 71.7% (129 people). Most of them are Vietnamese or Filipino and most of them graduated from high school. 116 of all participants are exposed to chemicals at work. The most prevalence rate of subject's health problems were backache (61.0%), headache (53.9%), fatigue (68.0%). Controlling for age, the number of physical health problems experienced in the last year was associated with BMI (r=0.184, p=0.049), and the number of mental health problems experienced in the past year (r=0.056, p<0.001) and all showed significant positive (+) correlations. The number of chemical products handled under age control showed a significant negative (-) correlation with working hours (r=0.207, p=0.027) and BMI (r=0.214, p=0.022) and showed a significant positive (+) correlation. Conclusions: The results of this study provided the latest update on the health status of foreign workers in Korea. It is also the first survey to attempt to assess the exposure of foreign workers to chemicals.