• KOREAN JOURNAL OF CROP SCIENCE
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• v.68 no.3
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• pp.207-215
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• 2023

This study was compared the soil environment and growth and yield of onion (Allium cepa L.) treated with non-mulching (NM) and mulching polyethylene film (PEF) and two biodegradable films (BFI and BFII) commonly used in farmhouses. Visual observation confirmed the degradation of BFI and BFII films after 150 days after tansplanting (DAT). BFII increased light penetration into the films and reduced the weight maintenace after 180 DAT, with a high decompostion at 30 days after soil tilling. Soil moisture contents much fluctuated between -14 kP and - 0 kPa in NM plots, increasing the minimum soil temperature of BFI plots. Mulching treatments decreased soil organic matter contents but did not subtantially increase soil mineral nutrients, soil bulk density, and number of bacteria compared to those of NM plots. Onion root growth was increased by PEF and BFI treatments at an early growth stage, 60 DAT, with the most remarkable stem extension observed for PEF and BFI treatments after 150 DAT. PEF and BFI treatments increased the bulb's diameter, length, weight, and lodging at 180 DAT. BFI treatments exhibited a high portion of the "very large" category producing with 55.3 tons ha^-1 based on the classification into bulb size, followed by PE (49.3 tons), NM (9.4 tons), and BFII treatments (2.7 tons) at 230 DAT.

• Journal of radiological science and technology
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• v.21 no.1
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• pp.79-87
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• 1998

The total-bodies of 10 week-old Sprague-Dawley rats were irradiated with single doses 4.5 and 7.5 Gy, respectively. The effects on plasma and sciatic nerve platelet-derived growth factor(PDGF) concentrations and sciatic nerve PDGF ${\alpha}$ -and ${\beta}$ -receptors densities were examined up to 10 days post-treatment. There was no consistent significant variation in the plasma and sciatic nerve PDGF concentrations in time over the period of study between 4.5 and 7.5 Gy groups. Plasma PDGF concentrations were significantly reduced to 58% of control values between 5 and 10 days with 4.5 Gy and to 51% of control values as percentage of control values between 5 and 10 days with 7.5 Gy after irradiation, respectively(p<0.05). Sciatic nerve PDGF concentrations were increased to 118% of control values at 1 day with 4.5 Gy and to 130% of control values at 1 day with 7.5 Gy after irradiation, respectively(p>0.05). After irradiation, the levels of PDGF ${\alpha}$ -receptor protein density were reduced to 33% of control values at 2 days with 4.5 Gy and to 50% at 2 days with 7.5 Gy, while the levels of PDGF ${\beta}$-receptor protein density were reduced to maximally 26% of control values at 2 days with 4.5 Gy and to 27% at 2 days with 7.5 Gy, respectively, but both initial decreased levels of those were increased subsequently after 2 days following irradiation. These results suggest that the radiation-induced alteration of plasma and sciatic nerve PDGF concentrations, and sciatic nerve PDGF ${\alpha}$ -and ${\beta}$ -receptors densities may be involved in the pathogenesis of bone marrow stem cell and peripheral neuron damages.

• Korean Journal of Soil Science and Fertilizer
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• v.22 no.3
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• pp.197-204
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• 1989

To evaluate the effect of soil improvement on the chemical properties and corn silage yield, this experiment was carried out in the newly-reclaimed sloped land. Corn (Suwon 19) was cultivated under the six different treatments including integrated improvement plot at Songjeong loam, 20 percent slope, from 1985 to 1987 and various soil chemical properties and silage yield were investigated. pH of topsoil was above 5.0 except for control and phosphate plot, but lime and integrated improvement plots were above 5.0 in subsoil. The contents of organic matter of topsoil were above 2.0% except control and subsoiling plot. Except control, the range of cation exchange capacity was 7.4-7.8 me/100g in topsoil, 7.0-7.7 me/100g in subsoil. Soil bacteria density of root zone was the highest in integrated improvement than the other treatments, and it was higher at the harvesting stage than the heading stage. Mean density of microorganism was $61.3{\times}10^5$ in bacteria, $21.5{\times}10^4$ in fungi and actinomycetes was B/F ratio was 28.5 and B/A ratio was 2.9. Vertical root distribution of total and 10cm depth below was more in the integrated improvement and subsoi ling plot than the other plots. Total nitrogen (T-N) content was higher in integrated improvement plot, and phosphate content of leaves was higher in compost and integrated improvement plot, but stem and grain were not different. Potassium content of the plant was higher in integra ted improvement plot. Correlation between dry matter yield and T-N was more significant than the other elements. And the contents of phosphate, calcium and magnesium were significant at 5%, but potassium was not.

• Journal of Korean Society of Forest Science
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• v.87 no.3
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• pp.328-333
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• 1998

To obtain basic information for establishing a pest control strategy for insect pest management system, changes in the population densities of the black-tipped sawfly(Acantholyda posticalis posticalis Matsumura) and damage patterns in tree growth were investigated in national forests in Hoigok-ri, Kapyung-gun, Kyunggi-do, where the pest control measures were taken. The results obtained were as follows ; 1. The larval density in the soil of the forests where the insecticides were applied have been kept below economic threshold for about 7 years. The density was the highest in the middle of slopes and similar to the level of the early stage of the insect outbreak. 2. After the pest control by insecticides, reduction in tree height and diameter growth lasted for 2-3 years in trees defoliated by over 70%. 3. The diameter growth of the trees damaged by black-tipped sawfly recovered faster in upper stem than in the lower. 4. volume growth of the trees defoliated over 70% by the insect decreased for three to four years. The volume loss of trees defoliated by 70% and 90% was 19.6% and 54.0%, respectively. 5. Maintaining the rate of defoliation below 50%, which is the economic threshold, by chemical control measures had an effect of reducing the tree volume loss by $40m^2/ha$ as compared with a stand defoliated by 90%.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.21 no.1
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• pp.35-40
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• 2015

Effect of packaging and storage methods for enhancing the shelf life and improving the postharvest quality of lettuce (Lactuca sativa L.) was studied during high temperature period. Lettuces were packed using four packaging and storage types: (A) plastic box container (control); (B) plastic box container covered with high density polyethylene (HDPE) film; (C) plastic box container with lettuce wrapped in linear low-density polyethylene (LLD-PE) film; and (D) plastic box container with lettuce with its stem. The quality parameters, such as fresh weight loss, SPAD value, and appearance of lettuce were investigated. The lettuce wrapped with LLD-PE film inside the plastic box container showed the lowest weight loss, highest SPAD value and best appearance compared to those exposed to the other packaging and storage methods during the three-week storage at $2^{\circ}C$. The results indicate that the marketability of lettuce can be optimized if proper packaging and storing is adopted. Prolonging the freshness even on low temperature storage will increase the potential of its sale ability in the domestic market even during summer season.

• Journal of the Korean Institute of Landscape Architecture
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• v.48 no.4
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• pp.1-7
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• 2020

This study quantified annual uptake and storage of carbon by urban greenspace in institutional lands and suggested improvement of greenspace structures to enhance carbon reduction effects. The study selected a total of five study cities including Seoul, Daejeon, Daegu, Chuncheon, and Suncheon, based on areal size and nationwide distribution. Horizontal and vertical greenspace structures were field-surveyed, after institutional greenspace lots were selected using a systematic random sampling method on aerial photographs of the study cities. Annual uptake and storage of carbon by woody plants were computed applying quantitative models of each species developed for urban landscape trees and shrubs. Tree density and stem diameter (at breast height) in institutional lands averaged 1.4±0.1 trees/100 ㎡ and 14.9±0.2 cm across the study cities, respectively. Of the total planted area, the ratio of single-layered planting only with trees, shrubs, or grass was higher than that of multi-layered structures. Annual uptake and storage of carbon per unit area by woody plants averaged 0.65±0.04 t/ha/yr and 7.37±0.47 t/ha, which were lower than those for other greenspace types at home and abroad. This lower carbon reduction was attributed to lower density and smaller size of trees planted in institutional lands studied. Nevertheless, the greenspace in institutional lands annually offset carbon emissions from institutional electricity use by 0.6 (Seoul)~1.9% (Chuncheon). Tree planting in potential planting spaces was estimated to sequester additionally about 18% of the existing annual carbon uptake. Enhancing carbon reduction effects requires active tree planting in the potential spaces, multi-layered/clustered planting composed of the upper trees, middle trees and lower shrubs, planting of tree species with greater carbon uptake capacity, and avoidance of the topiary tree maintenance. This study was focused on finding out greenspace structures and carbon offset levels in institutional lands on which little had been known.

• Journal of Korean Society of Forest Science
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• v.110 no.3
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• pp.341-354
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• 2021

A large part of Gapyeong is occupied by Korean pine (Pinus koraiensis) and Japanese larch (Larix kaempferi) plantations. Abies holophylla stands are scattered throughout Gapyeong, but little information on their distribution is available. This study explored the potential of succession from planted species to native A. holophylla in plantations. Trees were inventoried and regeneration of A. holoplhylla and stand management history were examined in Korean pine, Japanese larch, and A. holophylla-dominated stands. The importance percentage of A. holophylla was the highest among species with a range of 36.1% to 79.1% in all stands and the density of A. holophylla in understory (DBH <2 cm or <1.3 m height) ranged from 50 to 5,820 trees ha^-1. Non-metric multidimensional scaling classified stands into four types, AN, AP, AM, and P. The AN type showed a reverse J-shape DBH distribution, which was similar to that in natural A. holophylla stands. Both AP and AM types included Korean pine plantations with A. holophylla seed trees within stands. For AP, A. holophylla competed with planted species in overstory and deciduous broadleaved species in understory. The AM type was once thinned from below, thus stem density in the mid DBH classes was lower than upper or lower DBH classes. The P type consisted of plantations without A. holophylla seed trees. However, understory regeneration of A. holophylla was abundant through seed supply from A. holophylla in adjacent stands. Plantations with A. holophylla seed trees within or in adjacent stands showed vigorous natural regeneration of A. holophylla, highlighting the potential for succession from planted species to native A. holophylla in the Gapyeong area. Further studies can help develop techniques to restore plantations to native species-dominated natural stands using ecological succession.

• Korean Journal of Environmental Agriculture
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• v.29 no.1
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• pp.54-60
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• 2010

We have researched the changes in nutrient content in each phase of fermentation in crops treated with liquefied pig fertilizer, and have determined the best method for applying livestock excrement to cultured crops. In the execution of this experiment, rice was cultivated to full maturity at a paddy field in Jeollabuk-Do Agriculture Research and Extension Services(Jeon-buk series) from 2007 to 2008. The rice plant nitrogen absorption quantity change, according to the growth stages of the cultivated rice, was 20.3% in the rice treated with the liquid pig manure and 22.2% the chemical fertilizer at highest congelation. The chemical fertilizer showed a higher absorption quantity than the liquid manure compost. The nitrogen density at highest congelation was 1.5% in the chemical fertilizer, and 1.8% in the pig manure liquid compost not a significant difference. The stem height at harvest time was 73.8 cm in the crops treated with the liquid pig manure compost. Those treated with the chemical fertilizer, yielded a height of 4.2 cm less than the crops treated with the liquid pig manure compost. The yield was 507 kg/10a in the liquid pig manure compost treated rice, compared with the chemical fertilizer, which showed a value of 1.2% lower. The protein content was 6.3% in the rice treated with the chemical fertilizer, but 6.4% in the rice treated with the liquid pig manure compost. This is not a significant difference. However, the lodging rice plant treated with the chemical fertilizer control showed a protein content of 6.8%, which was even higher than the normal rice. The head rice ratio in the brown rice and the polished rice ended up to be lower in the crop treated with the liquid pig manure than that treated with the chemical fertilizer, Quality, the palatability value, was similar in both groups. The above result indicate that, the effect of liquid pig manure compost corresponds to the effect of chemical fertilizer, when each are scattered uniformly.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.29 no.4
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• pp.279-288
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• 2007

In the present study, we focused on stem cells in the dental papilla of the tooth germ. The tooth germ, sometimes called the tooth bud, is the primordial structure from which a tooth is formed. The tooth germ consists of the enamel organ, the dental papilla, and the dental follicle. The dental papilla lies below a cellular aggregation of the enamel organ. Mesenchymal cells within the dental papilla are responsible for formation of dentin and pulp of a tooth. Tooth germ disappears as a tooth is formed, but that of a third molar stays in the jawbone of a human until the age of 10 to 16, because third molars grow slowly. Impacted third molar tooth germs from young adults are sometimes extracted for orthodontic treatment. In the present study, we evaluated the osteogenic activity and mineralization of cultured human dental papilla-derived cells. Dental papillas were harvested from mandible during surgical extraction of lower impacted third molar from 3 patients aged 13-15 years. After passage 3, the dental papilla-derived cells were trypsinized and subsequently suspended in the osteogenic induction DMEM medium supplemented with 10% fetal bovine serum, 50 g/ml L-ascorbic acid 2-phosphate, 10 nM dexamethasone and 10 mM -glycerophosphate at a density of $1\;{\times}10^6\;cells/dish$ in a 100-mm culture dish. The dental papilla-derived cells were then cultured for 6 weeks and the medium was changes every 3 days during the incubation period. Dental papilla-derived cells showed positive alkaline phosphatase (ALP) staining during 42 days of culture period. The formation of ALP stain showed its maximal manifestation at day 7 of culture period, then decreased in intensity during the culture period. ALP mRNA level was largely elevated at 1 weeks and gradually decreased with culture time. Osteocalcin mRNA expression appeared at day 14 in culture, after that its expression continuously increased in a time-dependent manner up to day 28. The expression remained constant thereafter. Runx2 expression appeared at day 7 with no detection thereafter. Von Kossa-positive mineralization nodules were first present at day 14 in culture followed by an increased number of positive nodules during the entire duration of the culture period. Osteocalcin secretion was detectable in the culture medium from 1 week. The secretion of osteocalcin from dental papilla-derived cells into the medium greatly increased after 3 weeks although it showed a shallow increase by then. In conclusion, our study showed that cultured human dental papilla-derived cells differentiated into active osteoblastic cells that were involved in synthesis of bone matrix and the subsequent mineralization of the matrix.

• Composites Research
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• v.12 no.4
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• pp.71-78
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• 1999

To determine the effect of chemical structure of linear amine curing agents on thermal and mechanical properties, standard epoxy resin DGEBA was cured with diaminodiphenyl methane (DDM), diaminodiphenyl sulphone (DDS) in a stoichiometrically equivalent ratio. From this work, the effect of aromatic amine curing agents. In contrast, the results show that the DGEBA/DDS cure system having the sulfone structure between the benzene rings had higher values in the conversion of epoxide, density, shrinkage (%), glass transition temperature, tensile modulus and strength, flexural modulus and strength than the DGEBA/DDM cure system having methylene structure between the benzene rings, whereas the DGEBA/DDM cure system presented higher values in the maximum exothermic temperature, thermal expansion coefficient, and thermal stability. These results are caused by the relative effects of sulfone group having strong electronegativity and methylene group having (+) repulsive property and stem from the effect of the conversion ratio of epoxide group. The result of fractography shows that the each grain size of the DDM/DGEBA system with feather-like structure is larger than that of the DDS/DGEBA system.