• Korean Journal of Environmental Agriculture
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• v.33 no.4
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• pp.231-238
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• 2014

BACKGROUND: Biochar (BC) has a great potential for enhancing soil fertility and carbon sequestration while facilitating beneficial waste disposition. Therefore, it is essential to assess and mitigate any inadvertent consequences associated with soil biochar amendment. Earthworm activity is very vital in the soil system, yet there are a limited number of studies that have examined their impact resulting from biochar application to soil. METHODS AND RESULTS: In this study, the survival, growth, reproductive tests, and oxidative DNA damage tests (measured by 8-hydroxydeoxyguanosine (8-OHdG) and catalase (CAT) activities) to assess the potential toxicity to earthworm Eisenia fetida in artificial soil amended with BCs were investigated. The BCs derived from perilla meal, sesame meal, and pumpkin seed were pyrolyzed at 300 and $550^{\circ}C$, and then amended with soil at a rate of 5%. All the earthworms survived, but lost weight compared to control soil after 28 day incubation period. Moreover, the BC-amended soils did not significantly affect the cocoon numbers of earthworms. Slightly higher concentrations of 8-OHdG and CAT were observed in earthworms present in BC-treated soil than those in control soil. Furthermore, the 8-OHdG concentrations in the soil amended with BC produced at $550^{\circ}C$ were greater than those at $300^{\circ}C$, and it slightly decreased as the incubation time increased. CONCLUSION: These observations could be due to higher contents of toxic metal(loid)s and also higher pH in BCs pyrolyzed at $550^{\circ}C$ than $300^{\circ}C$. While BC is efficiently being used in agricultural fields, this study suggests that it is required to assess the unintended negative impacts of BC on soil ecosystems.

• Korean Journal of Plant Tissue Culture
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• v.22 no.5
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• pp.267-271
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• 1995

To improve regeneration efficiency of Brassica campestris ssp. pekinensis (chinese cabbage) in vitro, the effect of ehtylene inhibitors [AgNO$_3$ and silver thiosulfate (STS)] and optimal age of explantse were investigated. On the effect of ethylene inhibitors either 100 $\mu$M of AgNO$_3$ or 5 $\mu$M of STS enhanced shoot regeneration from cotyledons when it was added in basal shoot induction media(MS salts, B5 vitamine, sucrose 2%, BA 2.0mg/L, NAA 1.0mg/L). But at higher concentrations, AgNO$_3$ induced abnormal shoots, and STS greatly reduced regeneration frequency. On the other hand, the maximum regeneration rate was obtained from the cotyledons taken from 3-day old seedlings. However there was no distinctive effect among the containers used for cultivation. The most optimal condition of root induction was a minimal Murashige and Skoog media containing 0.1 mg/L NAA. In order to induce bolting and flowering from in vitro regenerated chinese cabbage, the plant were healed at 4$^{\circ}C$ for weeks in a cold chamber. When they were planted in pots, the plane produced phenotipically normal flowers and seeds. The overall results suggest that ethylene inhibitors promote regeneration of shoot from cotyledons of chinese cabbage without alleviating fertility.

• Journal of Korean Society on Water Environment
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• v.24 no.2
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• pp.185-194
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• 2008

There is increased soil erosion potential at highland agricultural crop fields because of its topographic characteristics and site-specific agricultural management practices performed at these areas. The agricultural upland fields are usually located at the sloping areas, resulting in higher soil loss, pesticides, and nutrients in case of torrential rainfall events or typhoon, such as 2002 Rusa and 2003 MaeMi. At the highland agricultural fields, the soil reconditioning have been performed every year to decrease damage by continuous cropping and pests. Also it has been done to increase crop productivity and soil fertility. The increased amounts of soil used for soil reconditioning are increasing over the years, causing significant impacts on water quality at the receiving water bodies. In this study, the field investigation was done to check soil reconditioning status for potato, carrot, and cabbage at the Doam-dam watershed. With these data obtained from the field investigation, the Soil and Water Assesment Tool (SWAT) model was used to simulate the soil loss reduction with environment-friendly and agronomically enough soil reconditioning. The average soil reconditioning depth for potato was 34.3 cm, 48.3 cm for carrot, and 31.2 cm for cabbage at the Doam-dam watershed. These data were used for SWAT model runs. Before the SWAT simulation, the SWAT ArcView GIS Patch, developed by the Kangwon National University, was applied because of proper simulation of soil erosion and sediment yield at the sloping watershed, such as the Doam-dam watershed. With this patch applied, the Coefficient of Determination ($R^2$) value was 0.85 and the Nash-Sutcliffe Model Efficiency (EI) was 0.75 for flow calibration. The $R^2$ value was 0.87 and the EI was 0.85 for flow validation. For sediment simulation, the $R^2$ value was 0.91 and the EI was 0.70, indicating the SWAT model predicts the soil erosion processes and sediment yield at the Doam-dam watershed. With the calibrated and validated SWAT for the Doam-dam watershed, the soil erosion reduction was investigated for potato, carrot, and cabbage. For potato, around 19.3 cm of soil were over applied to the agricultural field, causing 146% of more soil erosion rate, approximately 33.3 cm, causing 146% of more soil erosion for carrot, and approximately 16.2 cm, causing 44% of more soil erosion. The results obtained in this study showed that excessive soil reconditioning are performed at the highland agricultural fields, causing severe muddy water issues and water quality degradation at the Doam-water watershed. The results can be used to develop soil reconditioning standard policy for various crops at the highland agricultural fields, without causing problems agronomically and environmentally.

• Journal of Embryo Transfer
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• v.19 no.1
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• pp.53-59
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• 2004

The environmental impact of nutrient waste from agriculture has become an area of concern as ways to produce more food and of offspring. In dairy cattle, as the genetic capacity for milk production has increased, decreased fertility has become a severe problem by feeding high dietary protein, resulting in high concentration of blood urea nitrogen (BUN). There are numerous reports on BUN which is associated with reduced conception rates and closely related to body condition score (BCS) in lactating cattle, but not in Korean native cattle. This study was therefore performed to investigate the relation of BUN to both BCS and conception rates in Korean cattle. A total of 400 female Korean cattle (2∼5 years) in Daewanryong were used for this experiment. Feeding condition divided into two groups depending on grazing and darn feeding period. In grazing period, the mixture of Timothy, Orchard grass and Tall fescue, and concentrates (2.5 kg/day) was fed whereas hay (6.5 kg/day) and corn silage (20 kg/day) were fed while barn feeding period. Average BUN concentration at grazing and barn feeding were 7.39$\pm$2.65 mg/㎗ and 12.36$\pm$2.92 mg/㎗, respectively. During grazing period, high rates of pregnancy showed at 4∼8 mg/㎗ BUN concentration. In barn feeding period, 66%, of cattle were in pregnant at 8∼l4 mg/㎗ BUN concentration. The BCS for obtaining high rate of pregnancy raged at 2.5∼3.5. However, BUN did not directly relate to BCS in Korean cattle.

• Journal of the Korean Society of School Health
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• v.12 no.1
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• pp.97-107
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• 1999

The purpose of the study was to ascertain the trends of future circumstances in primary education along with population change. These trends, which are subject to change in population and structure, have a great impact on the size and characteristics of primary school-aged children. Accordingly, it is imperative for the government to plan for future conditions involving primary education. The major findings of the study were as follows: 1. In the long-term primary school children aged 6-11, which accounted for 17.7% of the total population in 1970, will decline to 8.6% by the year 2000, 6.9% in 2020 and 6.4% in 2030. This drastic reduction in fertility rate is a direct result of pressure by the government to control population. 2. In 1996, the total number of classes in primary schools rose to 106,594. In the future, these numbers will actually decline. By 2003 the total number of classes will peak at 142,605, but until then drop off to 112,288 by 2030-a decrease of over 6,000. 3. The actual number of primary schools in 1997 totaled 5,721. This figure will reach its highest peak, 5,942, in 2003, but it is expected decrease later after declining by 1,263, it will bottom out at 4,679 in 2003. 4. The number of teachers at primary schools increased from 101,095 in 1970, 119, 064 in 1980, 136,800 in 1990 to 138,369 in 1995. Accordingly this means that the ratio of students to teaching staff changed for the better. By the year 2005, if teachers of specialty subjects (music, art, English, physical education) are assigned to every primary school with over 18 classrooms and the number of students per class is 30, it should improve educational surroundings. This is because it is expected that the population of primary school children will continue to grow until 2003 and then decrease. Thus, there is a need to maintain the number of primary school teachers between the years 2003 and 2030 so that the ratio of students to teachers will be reduced to 1/20.25. In considering factors related to migration which influence conditions of education, it is evident that changes have already begun. In the suburbs of Seoul, population shifts are causing overcrowding in classrooms. The government believes it would be inefficient to invest in education because fluctuating migration figures make it impossible. Accordingly, we have to be concerned about stabilizing the population throughout the entire country.

• Korean Journal of Soil Science and Fertilizer
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• v.30 no.4
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• pp.334-340
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• 1997

It was proven that rice straw can serve can serve as a good support medium for trickling filter with livestock wastewater treatment. The efficiency of removal of removal of environmentally undesirable components from the wastewater by the straw medium was no less inferior to other commonly used support materials. The treated straw was also proven to be a source of abundant plant nutrients. The growth of orchard grass was enhanced greatly by the application of large quantity of the support medium. A maximum yield of dry matter was obtained at the rate of 40 ton/ha. Inorganic NPK elements as background fertilizers were highly recommended for better development in an early stage of growth. The nutritional status of the soil was very much improved by the addition of the medium in terms of exchangeable cations(K, Ca, Mg and Na), available phosphate, and organic matter contents. Nutrient uptake by orchard grass such as N, P and cations was enhanced by rice straw medium treatment and that was proportional to the levels of treatment.

• Journal of The Korean Society of Grassland and Forage Science
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• v.28 no.3
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• pp.237-244
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• 2008

This study was conducted to investigate the effects of the cropping system of forage crops and application of cattle slurry on productivity of forage crops and soil fertility. The field experiments were conducted on the silt clay loam at Gongiam, Kwangju, Kyung-gi province in Korea for two years. This study was arranged in split plot design with three replicates. Main plots were the cropping systems, such as single crop and mixed crops. Subplots were the application rate of cattle slurry, such as 0, 150 and 300 kg N/ha. The yields of dry matter (DM) and nitrogen (N) were hardly influenced by the cropping system, whereas DM and N yields enhanced as increasing the rates of cattle slurry application (p<0.05). The contents of crude protein (CP) and total digestible nutrients (TDN) were hardly influenced by the cropping system, whereas CP content increased as increasing the rates of cattle slurry application (p<0.05). TDN was not differentially influenced by cattle slurry application. Neutral detergent fiber (NDF) and acid detergent fiber (ADF) contents were hardly influenced by the cropping system and application of cattle slurry. Organic matter (OM) content in soil samples collected at the end of the experiment were remarkably higher than those in the beginning of the experiment. The OM content of soil was significantly increased by application of cattle slurry (p<0.05).

• Reproductive and Developmental Biology
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• v.33 no.1
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• pp.35-40
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• 2009

The objectives of this study was to evaluate the efficiency of the bacteria eliminated sperm by percoll gradient method on sperm quality and embryo cleavage in vitro in pig. The semen of miniature pig collected by gloved-hand method pre-warmed ($37^{\circ}C$) in thermos bottle, and separated by 65% percoll. Analysis of sperm ability was estimated by examining viability, capacitation and acrosome reaction using chlortetracycline (CTC) and the abnormality. Also, fertility of sperm was monitored with cleavage rate of embryo after IVF using separated and un-separated sperm by percoll. The result, viability of separated sperm was significantly(p<0.05) higher($83.6{\pm}$2.0 vs $59.0{\pm}4.4%$) than un-separated sperm. The results of CTC analysis showed the percentage of F- and B-patterned separated sperm was higher in separated that than un-separated sperm. On the contrary, the percentage of AR-patterned form unseparaed sperm was significantly(p<0.05) higher($13.6{\pm}0.8$ vs $8.1{\pm}0.6%$) than separated sperm. Also, abnormality of un-separated sperm was significantly(p<0.05) higher($2.2{\pm}0.4$ vs $16.8{\pm}2.8%$) than separated sperm. However, the cleavage rates of embryo using separated sperm by percoll and un-separated sperm had not significantly difference on 2 cell stage(9.25 vs 11.88%), 4 cell stage(26.76 vs 24.51%) and >4 cell stage(63.99 vs 63.61%) at 48h of IVF. Therefore, the sperm separated by percoll method showed improvement in sperm quality than un-separated sperm in miniature pig.

• Clinical and Experimental Reproductive Medicine
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• v.32 no.4
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• pp.301-314
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• 2005

Objective: Rebamipide is a propionic acid derivative that has an action of the inhibition of superoxide production and removal of hydroxyl radical with the sperm incubation and cryopreservation. In the present study, to investigate whether rebamipide is useful to treat male infertility and sterility, the author observed the antioxidative effects in patient with male infertility and also examined its absorption and distribution in rat genital organ. Methods: To measure the distribution of rebamipide in reproductive organ in the rat, carbon indicated rebamipide, $^{14}C-OPC-12759$, was orally administered to 10 Spraque-Dawley rats and its organ concentration in serum, liver, kidney, stomach, duodenum, colon, urinary bladder, seminal vesicle, epididymis and testicle were measured each time after 0.5, 1, 2, 4, 8 and 24 hours by using HPLC fluorescent method. The concentrations in semen were measured by HPLC fluorescent method in a sample of 50 infertile males who took 900 mg of rebamipide daily for 3 months. To measure the antioxidative effect and fertility rate for 3 months, each month before and after the treatment, sperm motility, vitality, the oxygen free radical formation, level of peroxidation, fetilizing capacity of semen sample which were obtained from infertile male patients by masturbation after at least 48 hours abstinence were analyzed by computer assisted semen analyzer, eosin-nigrosin stain, chemiluminescence, thiobarbituric acid method and hypo-osmotic swelling test. Simultaneously in a sample that wanted baby, both pregnancy and delivery were researched. Results: The $^{14}C-OPC-12759$ concentration in the body of white rats was highest in gastrointestinal organ like stomach, smal intestine and duodenum and followed by genital organ like seminal vesicle, testis and epididymis. The rebamipide concentration in semen of infertile males was $220.77{\pm}327.84ng/mL$ (SD) which showed a large deviation but it was higher than serum which was $126{\pm}76ng/mL$ (SD). In the infertile males, after the treatment with rebamipide, the level of seminal reactive oxygen species (ROS) and lipid peroxidation have significantly decreased in duration of the treatment (p<0.05) and sperm vitality and fertilizing capacity except sperm motility significantly improved on post treatment of 2~3 months (p<0.05). Out of the 41 cases who hoped for pregnancy, 15 cases (36.6%) became pregnant and 12 cases had childbrith, 2 cases had miscarriage and one case is ongoing. The side effect was observed in 1 case (2%) which experienced diarrhea but it was lost spontaneously. Conclusions: We conclude from this study that rebamipide showed relatively high tendancy of absorption and excretion in the genital organ. In infertile males who had elevated ROS in semen, by specifically inhibiting the cell damage from the antioxidation, a way to preserve sperm motility, vitality and fertilizing capacity was confirmed.

• Journal of Labour Economics
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• v.42 no.4
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• pp.1-29
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• 2019

This study estimates how changes in the female (aged 25 to 54) labor force participation rate (LFPR) following the historical experiences of the US and Japan would alter the future trend of the female economically active population by 2065, compared to the case in which the LFPR as of 2018 will remain unchanged. According to the results, the female labor force aged 25 to 54 will increase by 14% (about 797,000) and 15% (about 831,000), respectively, by 2042 if the female LFPR should change following the past trends of the US and Japan. In particular, the increase in the labor force is expected to be pronounced among females aged 30 to 44 who currently suffer high rates of job severance. The results of this study strengthen the prediction that the on-going population changes will not reduce much the overall economically active population in the near future. The result of a simulation based on the historical experiences of Japan suggests that, as least in the near future, policy efforts to encourage female labor supply will be more effective in alleviating the potential labor-market impacts of population changes, compared to policies aiming at increasing old-age employment.