• Korean Journal of Weed Science
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• v.12 no.1
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• pp.61-69
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• 1992

Weed control in mid season of rice fields was systemized earlier in Korea than in Western Europe or China. The most representative method was pull out the weeds by hand followed by 'Seojibeob'(鋤地法 : method of hoeing) after draining. It was practiced 3 to 4 times to do extensively. Also, the purposes of transplanting arid direct seeding in rows were to manage weed problems effectively, which means that the development of cultural techniques is closely related to 'Seojibeob'(鋤地法). From the 17th century, techniques of deep plowing(because of principal : 'Simkyonginu'(深耨易耕 : Deep plowing make easy to hoe) and 'Hwanubeob'(火耨法 : derived from 'Hwakyong soonubeob) for effective weed management of waste lands were newly adopted and spreaded due to the situations ant that time. Thus, the practice of large-scale farming resulted from the adaptation of the techniques and methods described above. In the 18th to 19th century, the cultural methods, not much different from 'Seojibeob', were changed and the number of weeding was decreased. Especially, the techniques of dry seeding of rice were practiced by originating the ideal 'Seojibeob', in which water availability was improved in northern drought areas and also weed problems were easily managed. In addition, intensively large-scale farming showed weed management problems, so that 'Cheonilrok'(千一錄) by Woo Ha-young described the techniques of 'Banjongbeob'(反種法) or 'Hwanubeob' and in the end of the Chosun dynasty extensively large-scale farming was practiced by putting intensive and extensive techniques together. As the results, agricuitural productivity of Korea was increased 5 times by that time.

• Korean journal of applied entomology
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• v.26 no.4 s.73
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• pp.221-228
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• 1987

The optimum temperature range for conidial germination of Pyriculacia oryzae on a slide glass was $26{\sim}30^{\circ}C$, at which at least four hours of leaf wetness period was required to germinate. Conidial germination was significantly reduced under dry conditions (relative humidity<85%) at $34^{\circ}C$ but not at lower temperature (18, 22, 26, $30^{\circ}C$). Number of lesions developed were greater at $26^{\circ}C$ than at other temperature tested. The average leaf wetness period required for production of a lesion per plant was 22 hours at $18^{\circ}C$, 16 hours at $22^{\circ}C$, 10 hours at $26^{\circ}C$, and 8 hours at $30^{\circ}C$. Less than one lesion per plant occurred at $34^{\circ}C$ even under 24 hours of leaf wetness period. The time period between inoculation and lesion appearance was $7{\sim}8$ days at $18^{\circ}C$, $4{\sim}5$ days at $22^{\circ}C$ and $26^{\circ}C$, and $3{\sim}4$ days at $30^{\circ}C$. The time period required for lesion appearance after inoculation was not affected by leaf wetness period and relative humidity. Lesion length increased most rapidly at $30^{\circ}C$ during the first four days after lesion appearance. Thereater, the rate of increase in lesion length was geratest at $26^{\circ}C$. The average increment of lesion length per day when relative humidity was greater than 90% was 0.7mm at $18^{\circ}C\;and\;22^{\circ}C$, 1mm at $26^{\circ}C$, and 0.8mm at $30^{\circ}C$. When relative humidity was less than 85%, the increments of lesion length per day were approximately $50{\sim}60%$ of those under humid conditions (relative humidity>90%) at all temperature regimes except $30^{\circ}C$. Relative humidity did not significantly affected lesion length at $30^{\circ}C$.

• Korean Journal of Ichthyology
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• v.18 no.4
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• pp.311-318
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• 2006

Ultrastructure of germ cells, the cyst epithelial cells and interstitial cells during spermatogenesis of the stone flounder, Kareius bicoloratus (Pleuronectidae) sampled on the west coast of Korea were investigated by electron microscopic observations. In the primary spermatocyte, the synaptonemal complexes appear in the zygotene stage of the prophase during maturation division. In the growing testis, especially, the interstitial cells (Leydig cells) appear near the primary, secondary spermatocytes and spermatids. Well-developed interstitial cells (steroid hormone secreting cells) which are located in the interlobular space in growing testis have three morphological characteristics of a vesicular nucleus, mitochondria with tubular cristae and smooth endoplasmic reticulum. During spermatogenesis, the primary and secondary spermatocytes attach to the cyst epithelial cell (Sertoli cell) having an elongated ovoid or triangular nucleus and several mitochondria in the cytoplasm. In the growing testis, lipid droplets, the mitochondrial rosettes and glycogen particles appear in the cytoplasm of the cyst epithelial cells near the secondary spermatocytes and spermatids. Particularly, the mitochondria, endoplasmic reticulum, little lipid droplets and the large amount of glycogen particles are present in the cytoplasm of the cyst epithelial cell in the late growing testis. In the late stage of spermiogenesis, the proximal centriole is joined to the nuclear envelope, the distal centriole forms the basal body of the flagellum and gives rise to the axial filament of the flagellum. No acrosome of the sperm is formed as seen in other teleost fish. The head of the spermatozoon is approximately $3{\mu}m$ in length and its tail is about $30{\mu}m$ in length. The axoneme of the tail flagellum of the spermatozoon consists of nine outer doublet microtubules at the periphery and two centrial singlet microtubules at the center. The spermatozoon of this species has two axonemal lateral fins. Especially, the cyst epithelial cells which located near groups of gametes in the various stages, show three functions: nutrition, phagocytosis and steroidogenesis. Especially, the nuclei of cyst epithelial cells in the recovery stage of the testicular developmental stages appear to be irregular in shape after spermiation. Of three functions of the cyst epithelial cell, several characteristics of phagocytosis are showed in the cytoplasm of the cyst epithelial cells in the recovery stage of the testicular developmental stages. At this stage, therefore, it is assumed that the cyst epithelial cells are involved in degeneration and resorption of undischarged germ cells after spermiation.

• Progress in Medical Physics
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• v.18 no.1
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• pp.48-54
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• 2007

This study is to develope a phantom for MOSFET (Metal Oxide Semiconductors Field Effect Transistors) dosimetry and compare the dosimetric properties of standard MOSFET and microMOSFET with the phantom. In this study, the developed phantom have two shape: one is the shape of semi-sphere with 10cm diameters and the other one is the flat slab of $30{\times}30cm$with 1 cm thickness. The slab phantom was used for calibration and characterization measurements of reproducibility, linearity and dose rate dependency. The semi-sphere phantom was used for angular and directional dependence on the types of MOSFETs. The measurements were conducted under $10{\times}10cm^2$ fields at 100cm SSD with 6MV photon of Clinac (21EX, Varian, USA). For calibration and reproducibility, five standard MOSFETS and microMOSFETs were repeatedly Irradiated by 200cGy five times. The average calibration factor was a range of $1.09{\pm}0.01{\sim}1.12{\pm}0.02mV/cGy$ for standard MOSFETS and $2.81{\pm}0.03{\sim}2.85{\pm}0.04 mV/cGy$ for microMOSFETs. The response of reproducibility in the two types of MOSFETS was found to be maximum 2% variation. Dose linearity was evaluated In the range of 5 to 600 cGy and showed good linear response with $R^2$ value of 0.997 and 0.999. The dose rate dependence of standard MOSFET and microMOSFET was within 1% for 200 cGy from 100 to 500MU/min. For linearity, reproducibility and calibration factor, two types of MOSFETS showed similar results. On the other hand, the standard MOSFET and microMOSFET were found to be remarkable difference in angular and directional dependence. The measured angular dependence of standard MOSFET and microMOSFET was also found to be the variation of 13%, 10% and standard deviation of ${\pm}4.4%,\;{\pm}2.1%$. The directional dependence was found to be the variation of 5%, 2% and standard deviation of ${\pm}2.1%,\;{\pm}1.5%$. Therefore, dose verification of radiation therapy used multidirectional X-ray beam treatments allows for better the use of microMOSFET which has a reduced angular and directional dependence than that of standard MOSFET.

• Journal of Life Science
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• v.20 no.2
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• pp.237-244
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• 2010

Five mold strains - Mucor racemousus, Rhizopus oryzae, Aspergillus oryzae, Aspergillus kawachii, and Monascus purpureus - were used for the fermentation of both freeze-dried and air-dried silkworm powders. The concentrations of proteins and minerals, electrophoretical protein patterns, fatty acid composition and the activities of fibrinolytic and antioxidation with freeze-dried silkworm (FDSW) or air-dried silkworm powders (ADSW) fermented by the five molds were investigated. The concentrations of major minerals in fermented FDSW and ADSW powders were K by 72.0-76.3 and 77.1-78.9 ppm, Mg by 29.6-49.7 and 44.3-58.7 ppm, Ca by 1.9-14.9 and 9.8-21.6 ppm and Zn by 0.64-0.70 and 4.17-4.52 ppm, respectively. Major fatty acids in fermented FDSW and ADSW powders were linolenic acid, oleic acid, and palmitic acid. There were slightly varietal differences in electrophoretical protein patterns when total protein patterns of fermented FDSW and ADSW powders were analyzed by native-and SDS-polyacrylamide gel electrophoresis (PAGE). DPPH radical scavenging activity was slightly stronger in fermented ADSW powders than that in fermented FDSW. Fibriolytic activity was only detected in the FDSW fermented by Aspergillus kawachi and Monascus purpureus. These results may provide the basic data to understand the biological activities and chemical characteristics of silkworm fermented by mold, which can be used for the development of functional foods.

• Journal of Korean Home Economics Education Association
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• v.32 no.2
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• pp.43-58
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• 2020

This study was conducted to investigate adolescents' food purchasing attitudes and related factors in the aim of improving youth's ability to purchase food properly and providing basic data on educational program development regarding dietary life. Total 476 adolescents residing in Daegu area participated in this study, and followings are the summary of the results. In terms of concerns in food purchasing, adolescents put priority in order of price(3.81±0.64), taste(3.70±0.72), safety(3.52±0.78), health(2.93±0.92). With respect to food purchasing attitudes, a significant differences were found in economic concern(p<.05) by gender and by the amount of allowance; preference(p<.01) and safety(p<.01) by school year. The analysis of environmental factors affecting food purchasing attitudes revealed that adolescents were most influenced by their parents(3.44±0.62) in food purchasing, whereas friends' influences(2.43±0.60) were relatively low. Regarding the effect of environmental factors on food purchasing, significant differences were found in parents(p<.05) and brands(p<.05) by gender; friends(p<.01) and parents(p<.05) by school year; friends(p<.01) by the amount of allowance. Food purchasing attitudes represented positive correlation with parents, advertisements and brands(p<.001). In addition, regression analysis showed that parents and advertisements affect adolescents' food purchasing. Conclusively, adolescents appear to prioritize price and taste, and they were influenced most by their parents when purchasing food. Therefore, parents, serving as a consumer role model, should instruct their children to learn considerate attitude in food purchasing.

• The Korean Journal of Ecology
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• v.28 no.3
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• pp.149-156
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• 2005

This study was conducted to elucidate the relationship between the aboveground vegetation structure and fine roots of the topsoil (<15m), and thereafter to obtain the regression models for the estimation of the fine roots of the topsoil using the aboveground vegetation values in the burned forest areas, Korea. The FRT (fine roots of the top soil) as well as the aboveground vegetation structure showed spatial variation in the earlier successional stages after forest fire. The fine roots (<2 mm) of the topsoil in the earlier successional stages than the first 3 year after forest fire showed the range from 3 to 166 g $DM/m^2$. The FRT in the naturally regenerated sites and planted sites after forest fire was closely correlated with the vegetation indices, especially lvc, representing the development status of the aboveground vegetation. The FRT in the terrace seeding work sites after forest fire was closely correlated with year elapsed after terrace seeding work. The FRT in the terrace seeding work sites showed the much higher values because of the vigorous growth of grass species than the other sites. In the naturally regenerated sites, the FRT showed the parabola form according to the increment of aboveground vegetation value (Ivc). Although the aboveground vegetation value (Ivc) showed a tendency to increase logarithmically during the secondary succession after forest fire, the estimated fine roots of the topsoil was depicted the parabola form showing the gradual increment until the first 15 years and slight decrease thereafter. Decrease of FRT in the later successional stage showing the high vegetation value may be caused by increment of the woody species contribution to the vegetation value (Ivc). Our results represented that the aboveground vegetation value (Ivc) can be used to the estimation of the fine roots of the topsoil in burned forest areas.

• Tuberculosis and Respiratory Diseases
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• v.67 no.2
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• pp.88-94
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• 2009

Background: From November 2006, The national health insurance system in the Republic of Korea began to cover prescribed long-term oxygen therapy (LTOT) in patients with chronic respiratory insufficiency. This study examined the current status of LTOT after national health insurance coverage. Methods: Between November 1, 2006 and June 30, 2008, the medical records of patients who were prescribed LTOT by chest physicians were reviewed. The data was collected from 13 university hospitals. Results: 197 patients (131 male and 66 female) were prescribed LTOT. The mean age was 64.3${\pm}$13.0 years. The most common underlying disease was chronic obstructive pulmonary disease (n=103, 52.3%). Chest physicians prescribed LTOT using arterial blood gas analysis or a pulse oxymeter (74.6%), symptoms (14%), or a pulmonary function test (11.2%). The mean oxygen flow rate was 1.56${\pm}$0.68 L/min at rest, 2.08${\pm}$0.91 L/min during exercise or 1.51${\pm}$0.75 L/min during sleep. Most patients (98.3%) used oxygen concentrators. Only 19% of patients used ambulatory oxygen supplies. The oxygen saturation before and after LTOT was 83.18${\pm}$10.48% and 91.64${\pm}$7.1%, respectively. After LTOT, dyspnea improved in 81.2% of patients. The mean duration of LTOT was 16.85${\pm}$6.71 hours/day. The rental cost for the oxygen concentrator and related electricity charges were 48,414${\pm}$15,618 won/month and 40,352${\pm}$36,815 won/month, respectively. Approximately 75% of patients had a regular visit by the company. 5.8% of patients had personal pulse oxymetry. 54.9% of patients had their oxygen saturation checked on each visit hospital. 8% of patients were current smokers. The most common complaint with LTOT was the limitation of daily activity (53%). The most common complaint with oxygen concentrators was noise (41%). Conclusion: The patients showed good compliance with LTOT. However, only a few patients used an ambulatory oxygen device or had their oxygen saturation measured.

• Journal of the Korean Society of Food Science and Nutrition
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• v.42 no.2
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• pp.268-277
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• 2013

This study investigates the effects of accumulated levels of heavy metals and nutrients of cultivated soybean plant tissues, after the continuous application of sewage sludge (SS) and industrial sludge (IS). SS and IS were applied to soybean plants at loading of 0, 11.25, 22.50, and 45.00 Mg/ha, and the contents of heavy metals (Cd, Pb, Ni, Cu, and Zn), proteins, and amino acids in the cultivated soybean plants were measured. The Cd content in the soybean was 0.02~0.05 mg/kg, which is within the safety level set in the standard, and that of Pb was 0.02~0.15 mg/kg, which is also within the safety level except for IS 45 Mg/ha. The soybean harvest quantity was higher in the treatment groups than the control group in the first year. However, in the second year, SS had lower harvest and IS had the same level or a decreasing tendency, compared with the control group. In the first year, the content of amino acid which followed handling of SS was increased in the sludge groups more than in the control group in the case of glutamate. However, the influence of continuous application was increased in the sludge groups in the case of amino acids of 12 types. In conclusions, the accumulation in soybean of heavy metals by sludge treatment is not a problem, but the decreased yields needs to be considered. In addition, the most appropriate level of sludge treatment was 11.25 Mg/ha.

• KDI Journal of Economic Policy
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• v.31 no.2
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• pp.127-153
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• 2009

There is a growing concern about potential harmful effect of second-hand or environmental tobacco smoking. As a result, smoking bans in workplace become more prevalent worldwide. In Korea, workplace smoking ban policy become more restrictive in 2003 when National health enhancing law was amended. The new law requires all office buildings larger than 3,000 square meters (multi-purpose buildings larger than 2,000 square meters) should be smoke free. Therefore, a lot of indoor office became non smoking area. Previous studies in other counties often found contradicting answers for the effects of workplace smoking ban on smoking behavior. In addition, there was no study in Korea yet that examines the causal impacts of smoking ban on smoking behavior. The situation in Korea might be different from other countries. Using 2001 and 2005 Korea National Health and Nutrition surveys which are representative for population in Korea we try to examine the impacts of law change on current smoker and cigarettes smoked per day. The amended law impacted the whole country at the same time and there was a declining trend in smoking rate even before the legislation update. So, the challenge here is to tease out the true impact only. We compare indoor working occupations which are constrained by the law change with outdoor working occupations which are less impacted. Since the data has been collected before (2001) and after (2005) the law change for treated (indoor working occupations) and control (outdoor working occupations) groups we will use difference in difference method. We restrict our sample to working age (between 20 and 65) since these are the relevant population by the workplace smoking ban policy. We also restrict the sample to indoor occupations (executive or administrative and administrative support) and outdoor occupations (sales and low skilled worker) after dropping unemployed and someone working for military since it is not clear whether these occupations are treated group or control group. This classification was supported when we examined the answers for workplace smoking ban policy existing only in 2005 survey. Sixty eight percent of indoor occupations reported having an office smoking ban policy compared to forty percent of outdoor occupation answering workplace smoking ban policy. The estimated impacts on current smoker are 4.1 percentage point decline and cigarettes per day show statistically significant decline of 2.5 cigarettes per day. Taking into account consumption of average sixteen cigarettes per day among smokers it is sixteen percent decline in smoking rate which is substantial. We tested robustness using the same sample across two surveys and also using tobit model. Our results are robust against both concerns. It is possible that our measure of treated and control group have measurement error which will lead to attenuation bias. However, we are finding statistically significant impacts which might be a lower bound of the true estimates. The magnitude of our finding is not much different from previous finding of significant impacts. For cigarettes per day previous estimates varied from 1.37 to 3.9 and for current smoker it showed between 1%p and 7.8%p.