• The Journal of Engineering Geology
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• v.33 no.4
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• pp.543-553
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• 2023

The current status of domestic a agalmatolite mines in South Korea was investigated with a view to establishing a stable supply of agalmatolite and managing its demand. Most mined agalmatolite deposits were formed through hydrothermal alteration of Mesozoic volcanic rocks. The physical characteristics of pyrophyllite, the main constituent mineral of agalmatolite, are as follows: specific gravity 2.65~2.90, hardness 1~2, density 1.60~1.80 g/cm³, refractoriness ≥29, and color white, gray, grayish white, grayish green, yellow, or yellowish green. Among the chemical components of domestic agalmatolite, SiO₂ and Al₂O₃ contents are respectively 58.2~67.2 and 23.1~28.8 wt.% for pyrophyllite, 49.2~72.6 and 16.5~31.0 wt.% for pyrophyllite + dickite, 45.1 and 23.3 wt.% for pyrophyllite + illite, 43.1~82.3 and 11.4~35.8 wt.% for illite, and 37.6~69.0 and 19.6~35.3 wt.% for dickite. Domestic agalmatolite mines are concentrated mainly in the southwest and southeast of the Korean Peninsula, with some occurring in the northeast. Twenty-one mines currently produce agalmatolite in South Korea, with reserves in the order of Jeonnam (45.6%) > Chungbuk (30.8%) > Gyeongnam (13.0%) > Gangwon (4.8%), and Gyeongbuk (4.8%). The top 10 agalmatolite-producing mines are in the order of the Central Resources Mine (37.9%) > Wando Mine (25.6%) > Naju Ceramic Mine (13.4%) > Cheongseok-Sajiwon Mine (5.4%) > Gyeongju Mine (5.0%) > Baekam Mine (5.0%) > Minkyung-Nohwado Mine (3.3%) > Bugok Mine (2.3%) > Jinhae Pylphin Mine (2.2%) > Bohae Mine. Agalmatolite has low thermal conductivity, thermal expansion, thermal deformation, and expansion coefficients, low bulk density, high heat and corrosion resistance, and high sterilization and insecticidal efficiency. Accordingly, it is used in fields such as refractory, ceramic, cement additive, sterilization, and insecticide manufacturing and in filling materials. Its scope of use is expanding to high-tech industries, such as water treatment ceramic membranes, diesel exhaust gas-reduction ceramic filters, glass fibers, and LCD panels.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.68 no.3
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• pp.188-196
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• 2023

Wheat (Triticum aestivum L.) is an important crop in Korea, with a per capita consumption of 31.6 kg in 2019. In the southern region, wheat is grown after paddy rice, and it is harvested during the rainy season in mid-June. This timing, in combination with high humidity and untimely rainfall, activates the enzyme alpha-amylase, which breaks down starch in the wheat grains. As a result, sprouted grains have lower quality and value for flour. However, seeds that absorb water before sprouting are expected to maintain better quality. The aim of the study was to identify the critical period during wheat maturation when rainfall has the greatest impact on grain quality, to prevent price declines due to quality deterioration. Two wheat cultivars, Jokyoung and Hwanggeumal, were grown in a speed breeding room, and artificial rainfall was applied at different times after heading (30, 35, 40, 45, 50, and 55 days). The proportion of vitreous grains decreased from 40 to 55 days after heading (DAH). Both cultivars had chalky grain sections from 35 DAH, with Hwanggeumal having a higher proportion of vitreous grains. Starch degradation was observed using FE-SEM (Field Emission Scanning Electron Microscope) at 40 DAH for Jokyoung and 50 DAH for Hwanggeumal. Color measurements indicated increased L and E values from 40 DAH, with rain treatment at 55 DAH leading to a significant increase in L values for both cultivars. Ash content increased at 45 DAH, whereas SDSS decreased at 35 DAH. Overall, grain quality from 40 DAH until harvest was found to be affected to the greatest extent by direct exposure of the spikes to moisture. Red wheat showed better quality than white wheat. These findings have implications for the cultivation of high-quality wheat and can guide future research efforts in this area.

• Korean Journal of Poultry Science
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• v.50 no.4
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• pp.293-301
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• 2023

This study aimed to investigate the effects of seasonal differences and crating densities on the behavior, surface temperature, and respiration rate of broilers during transportation. A total of 600 broilers aged 35 days were divided into 10 treatment groups based on five crating densities (10.3, 11.5, 12.8, 14.1, 15.4 birds/m²) with two seasons (i.e. summer and winter) to give six replicates. Broilers were allocated to the crates (1.00 m × 0.78 m × 0.26 m) in a randomized design. The transportation distance was 20 km for 40 minutes (average 30-50 km/h) during the early morning. The results revealed that standing behavior of broilers during transportation was shown more frequently (P<0.05) in winter. Moreover, sitting behavior was significantly shown (P<0.05) more at densities of 14.1 birds/m² and 15.4 birds/m² compared to other treatments. Standing behavior was significantly shown more (P<0.05) in winter and lower crating density. Changes in broilers surface temperature after transportation were higher (P<0.05) in summer. However, surface temperature after transportation was not affected (P>0.05) by crating density, and interaction between seasonal differences and crating density. Respiration rate was higher (P<0.05) in summer. But there were no effects (P>0.05) on respiration rate based on crating density, and interaction between seasonal differences and crating density. Based on the results of the present study, broilers transportation is recommended in winter rather than summer to minimize the climatic stress, but further research is required to identify proper crating densities to improve the broilers welfare during transportation.

• Journal of Life Science
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• v.33 no.12
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• pp.1002-1014
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• 2023

The root of Cirsium japonicum var. maackii (Maxim.) has long been used in traditional medicine to prevent the onset and progression of various diseases and has been reported to exert a wide range of physiological effects, including antioxidant activity. However, research on its effects on hepatocytes remains scarce. This study used the human hepatocellular carcinoma HepG2 cell line to investigate the antioxidant activity of ethanol extract of C. japonicum root (EECJ) on hepatocytes. Hydrogen peroxide (H₂O₂) was used to mimic oxidative stress. The results showed that EECJ significantly reverted the decrease in cell viability and suppressed the release of lactate dehydrogenase in HepG2 cells treated with H₂O₂. Moreover, an analysis of changes in cell morphology, flow cytometry, and microtubule-associated protein light chain 3 (LC3) expression showed that EECJ significantly inhibited HepG2 cell autophagy induced by H₂O₂. Furthermore, it attenuated H₂O₂-induced apoptosis and cell cycle disruption by blocking intracellular reactive oxygen species and mitochondrial superoxide production, indicating strong antioxidant activity. EECJ also restored the decreased levels of intracellular glutathione (GSH) and enhanced the expression and activity of superoxide dismutase and GSH peroxidase in H₂O₂-treated HepG2 cells. Although an analysis of the components contained in EECJ and in vivo validation using animal models are needed, these findings indicate that EECJ is a promising candidate for the prevention and treatment of oxidative stress-induced liver cell damage.

• Journal of Life Science
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• v.33 no.12
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• pp.1015-1024
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• 2023

Antibiotics have greatly contributed to the treatment and prevention of bacterial diseases in humans, animals, and fish. However, antibiotic misuse has led to the emergence and spread of multidrug-resistant bacteria. In addition to antibiotic discovery research, efforts are being made to combat such multidrug-resistant bacteria using antimicrobial agents, antioxidants, host immune enhancement, probiotics, and bacteriophages, as well as various symptomatic therapies. To discover novel bioactive compounds, it is crucial to adopt approaches that incorporate fresh ideas, new targets, innovative techniques, and untapped resources. Halophytes are plants that grow in high-salt soils and are known to adapt to salt-induced stress through unique metabolic processes that produce secondary metabolites. This study aimed to investigate the effects of extracts of halophytes native to Korea on oxidative stress and to determine whether they exert inhibitory activity against biofilms, which are major pathogenic factors of infectious bacteria. The Acinetobacter baumannii strain ATCC 17978, a representative drug-resistant bacterium, was used to measure anti-biofilm activity. The results showed that Aster spathulifolius, Carex kobomugi, Rosa rugosa, and Asparagus cochinchiensis exerted strong antioxidant and anti-biofilm effects without affecting bacterial growth itself. The halophytes used in this study are promising candidates for the development of pharmaceutical agents with antioxidant and antimicrobial properties.

• Korean Journal of Organic Agriculture
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• v.31 no.4
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• pp.453-460
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• 2023

This study was conducted to confirm the growth performance of Hanwoo steers according to the crude protein and calcium levels and their effects on carcass characteristics. The experiment consisted of a total of 4 groups: HPHC (CP 15%, Ca 1.2%), HPLC (CP 15%, Ca 0.6%), LPHC (CP 12.5%, Ca 1.2%), LPLC (CP 12.5%, Ca 0.6%). In the feeding trial, Hanwoo steers (650.8±16.27 kg, n = 32, 24 months of age) were divided into four feeding groups (n = 8 each) with the same initial body weight. Animals were fed with each rice straw and concentrate (1:9) until the late fattening stage. Growth performance was measured by daily weight gain, feed conversion rate, and final weight. Carcass characteristics were measured carcass weight, loin area, back-fat thickness and marbling score. There was no significant difference in growth performance and carcass characteristics among the treatment groups. However, the ratio of meat quality grade 1⁺ or higher was 76% in LPLC, which was higher than other treatments (HPHC, 63%; HPLC, 63% and LPHC, 50%). Therefore, reducing crude protein in the feed did not affect growth and carcass characteristics. In addition, calcium control in the late fattening stage did not affect growth performance. In LPLC, the ratio of meat quality 1⁺ or higher was the highest, so additional research on calcium control in feed is thought to be necessary. However, there was no significant difference in the relationship between protein and calcium levels in feed in all study results, so the influence of the two factors on each other is thought to be low.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
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• v.17 no.5
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• pp.81-94
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• 2022

This study analyzed the effect of the entrepreneurship planning course provided by an women's university in Seoul on the enhancement of the core competencies of entrepreneurship of university students. To this end, pre- and post-test of core entrepreneurship competency were conducted on 63 female university students (32 in experimental group, 31 in control group) and then the results were analyzed. The course in which the experimental group participated was a team-based project learning course and it required a team of three people to draw an entrepreneurship plan containing social problem solving as the final result. The course was operated for a total of 8 weeks. To measure the level of entrepreneurship core competency in the pre- and post- test, the survey tool that was developed by the Ministry of Education and Korea Entrepreneurship Foundation (2020) was used. This tool composed by 'value creation', 'challenge', 'self-directed', and 'group creativity' competencies. As analyses methods, i) covariance analysis was performed using the pretest as a covariate, and then a two-way ANOVA was performed with treatment (experimental group, control group) and time point (pre test, post test) as two independent variables. Results show while there was no significant difference between the experimental group and the control group in the value creation competency, it significantly contributed to the enhancement of challenge, self-directed, and collective creativity competencies. Based on these results, implications and limitations were discussed, followed by future research direction.

• Health Policy and Management
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• v.34 no.1
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• pp.38-47
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• 2024

Background: Korea's population of children and adolescents has decreased by 2.88 million over the past decade and is expected to decline further due to the unprecedented low birth rate. In the fee-for-service compensation system, the decline in the pediatric population relates directly to the profit decrease in the pediatric clinics. This study analyzed whether the worsening profits of pediatric clinics impacted their closure. Methods: We built annual data for pediatric and other department clinics (internal medicine, otolaryngology, and family medicine) using the status of medical institute and health insurance claims data from 2012 to 2022. Then, we analyzed whether institutional variables such as annual profit and regional variables (Herfindahl-Hirschman index, the number of clinics per 100,000, etc.) affected the closure of clinics. The methods used in this study are descriptive statistics and chi-square analysis. Odds ratios for each variable were estimated by generalized estimating equations (GEE). Results: The closure rate of pediatric clinics was 2.66%-7.04% in 2012-2022, which was consistently higher than those of internal medicine, otolaryngology, and family medicine clinics. The profit gap per institution between the pediatric and the other clinics grew from 126 million won in 2012 to 245 million won in 2019. In the GEE analysis, profit decrease compared to the previous year with lower profit was the main factor that increased the closure of pediatric and other department clinics. After adjusting profit-related variables, the decrease in the pediatric population itself did not relate to the closure of pediatric clinics. The number of pediatric clinics or monopolies also did not affect the closure of pediatric clinics. Conclusion: The worsening profit is the crucial factor for the closure of pediatric clinics, while the pediatric population is decreasing. For this reason, it is necessary to actively seek ways to maintain a stable treatment system for children and adolescents.

• Membrane Journal
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• v.34 no.1
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• pp.50-57
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• 2024

In this experiment, Pd-Ag-Cu membrane was manufactured using electroless plating on an α-Al₂O₃ support. Pd, Ag and Cu were each coated on the surface of the support through electroless plating and heat treatment was performed for 18 h at 500℃ in H₂ in the middle of electroless plating to form Pd alloy. The surface of the Pd-Ag-Cu membrane was observed through Scanning Electron Microscopy (SEM), and the thickness of the Pd membrane was measured to be 7.82 ㎛ and the thickness of the Pd-Ag-Cu membrane was measured to be 3.54 ㎛. Energy dispersive X-ray spectroscopy and X-ray diffraction analysis confirmed the formation of a Pd-Ag-Cu alloy with a composition of Pd-78wt%, Ag-8.81wt% and Cu-13.19wt%. The gas permeation experiment was conducted under the conditions of 350~450℃ and 1~4 bar in H₂ single gas and H₂/N₂ mixed gas. The maximum H₂ flux of the hydrogen separation membrane measured in H₂ single gas is 74.16 ml/cm²·min at 450℃ and 4 bar for the Pd membrane and 113.64 ml/cm²·min at 450℃ and 4 bar for the Pd-Ag-Cu membrane. In the case of the separation factor measured in H₂/N₂ mixed gas, separation factors of 2437 and 11032 were measured at 450℃ and 4 bar.

• Pediatric Infection and Vaccine
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• v.31 no.1
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• pp.75-82
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• 2024

Purpose: As the coronavirus disease 2019 (COVID-19) pandemic ended, the number of patients with respiratory syncytial virus (RSV) pneumonia increased during the spring/summer of 2022. This study aimed to analyze the clinical features and antibiotic usage of children hospitalized for RSV pneumonia in a recently established general hospital in Sejong city. Methods: In this retrospective review, we included inpatients of the Pediatric Department of Chungnam National University Sejong Hospital diagnosed with RSV pneumonia between March 2022 and April 2023. Patients were divided into 2 groups: with and without antibiotic treatment. Demographic data, initial presentations, and clinical courses were reviewed. Results: A total of 116 patients with RSV pneumonia were hospitalized during this period, of which 102 were analyzed, excluding 14 with underlying diseases or who did not fall within the definition of pneumonia. The median age was 17 months. Diagnoses of bacterial infections (acute otitis media and sinusitis) were documented in 9.8% of cases. Intravenous (IV) antibiotics were administered in 46% of cases. The group receiving IV antibiotics showed higher inflammatory levels (C-reactive protein; CRP), more infiltration on initial chest X-rays, and longer fever duration. There was no difference in the length of hospitalization between the groups with and without IV antibiotics. Conclusions: This study showed a tendency for the attending physician to prescribe IV antibiotics to patients with longer fever duration, pulmonary infiltrations on the initial chest X-ray, and higher CRP levels. However, given the high rate of IV antibiotic usage compared to previous studies, care should be taken in antibiotic use.