• Economic and Environmental Geology
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• v.5 no.4
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• pp.187-209
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• 1972

Drilling position is one of the most important factors affecting on the blasting effects. There has been many reports on several blasting factors of burn-cut by Messrs. Brown and Cook, but in this study the author tried to compare drilling positions of burn-cut to pyramid-cut, and also to correlate burn-cut effects of drilling patterns, not being dealt by Prof. Ito in his theory, which emphasized on dynamical stress analysis between explosion and free face. According to former theories, there break out additional tensile stress reflected at the free face supplemented to primary compressive stress on the blasting with one-free-face. But with these experimented new drilling patterns of burn-cut, more free faces and nearer distance of each drilling holes make blasting effects greater than any other methods. To promote the above explosive effect rationary, it has to be considered two important categories under-mentioned. First, unloaded hole in the key holes should be drilled in wider diameter possibly so that it breaks out greater stress relief. Second, key holes possibly should have closer distances each other to result clean blasting. These two important factors derived from experiments with, theories of that the larger the dia of the unloaded hole, it can be allowed wider secondary free faces and closes distances of each holes make more developed stress relief, between loaded and unloaded holes. It was suggested that most ideal distance between holes is about 4 clearance in U. S. A., but the author, according to the experiments, it results that the less distance allow, the more effective blasting with increased broken rock volume and longer drifted length can be accomplished. Developed large hole burn-cut method aimed to increase drifting length technically under the above considerations, and progressive success resulted to achieve maximum 7 blasting cycles per day with 3.1m drifting length per cycle. This achievement originated high-speed-drifting works, and it was also proven that application of Metallic AN-FO on large hole burn-cut method overcomes resistance of one-free-face. AN-FO which was favored with low price and safety handling is the mixture of the fertilizer or industrial Ammonium-Nitrate and fuel oil, and it is also experienced that it shows insensible property before the initiation, but once it is initiated by the booster, it has equal explosive power of Ammonium Nitrate Explosives (ANE). There was many reports about AN-FO. On AN-FO mixing ratio, according to these experiments, prowdered AN-FO, 93.5 : 6.5 and prilled AN-FO 94 : 6, are the best ratios. Detonation, shock, and friction sensities are all more insensitive than any other explosives. Residual gas is not toxic, too. On initation and propagation of the detonation test, prilled AN-FO is more effective than powered AN-FO. AN-FO has the best explosion power at 7 days elapsed after it has mixed. While AN-FO was used at open pit in past years prior to other conditions, the author developed new improved explosives, Metallic AN-FO and Underwater explosive, based on the experiments of these fundmental characteristics by study on its usage utilizing AN-FO. Metallic AN-FO is the mixture of AN-FO and Al, Fe-Si powder, and Underwater explosive is made from usual explosive and AN-FO. The explanations about them are described in the other paper. In this study, it is confirmed that the blasting effects of utilizing AN-FO explosives are very good.

• Journal of the Korean Society of Food Science and Nutrition
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• v.34 no.1
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• pp.42-56
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• 2005

Hyperlipidemia is one of the risk factors for coronary artery disease. Despite of epidemiological evidence that tea consumption is associated with the reduced risk of coronary heart disease, experimental studies designed to show that drinking tea affects blood lipid concentration or oxidative stress have been unsuccessful. The purpose of this study was to investigate whether functional tea (three servings/day) supplement with medical nutrition therapy (MNT) lead to a beneficial outcomes in mildly hyperlipidemic adults. From February to October, 2003, the 43 hyperlipidemic (23 men, 20 women) subjects (total cholesterol$\geq$200 mg/dL or triglyceride$\geq$150 mg/dL) admitted to K Medical Center were studied. Subjects were randomly divided into 3 groups; placebo tea (PT), half dose of functional tea (HFT), full dose of functional tea (FFT). During 12 weeks of study period, the subjects were given placebo or functional tea daily with MNT. Anthropometric measurements, blood chemical analysis including lipid levels, total superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) levels, and dietary assessment were carried out at the beginning and end of experiment. The effects of functional tea were compared with the placebo in randomized clinical trial study. The placebo was prepared to match with the functional tea in color and taste. After the 12 weeks of MNT, the subjects had regular and balanced meal pattern. Consumption of foods high in cholesterol and saturated fat, salty foods, fried foods, and instant foods decreased significantly in all three groups (p<0.05). Intake of energy and cholesterol also decreased (p<0.05). Drinking three servings per day (390 mL/day) of functional tea significantly reduced the levels of blood triglyceride (HFT, 42.5%; FFT, 29.4%), total cholesterol (HFT, 8.5%; FFT, 13.7%), and atherogenic index (HFT, 14.6%; FFT, 21.7%). Whereas no changes were found in the LDL-, HDL-cholesterollevels, and LDL/HDL ratio. Plasma homocysteine (Hcy) concentration decreased significantly (p<0.05) in functional tea groups (HFT, 14.9%; FFT, 14.1%). SOD increased significantly (p<0.05) in HFT (8.3%). GSH-Px increased significantly (p<0.05) in FFT (12.8%). In conclusion, the MNT improved the dietary habits, in addition, functional tea supplement decreased blood lipid levels and Hcy, and increased SOD and GSH-Px levels. These results indicate that functional tea consumption may decrease the risk of cardiovascular disease via improving blood lipid levels and antioxidant status.

• Clinical and Experimental Pediatrics
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• v.49 no.12
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• pp.1329-1339
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• 2006

Purpose : Failure of hematopoietic stem cell transplantation(HSCT) may be encountered in practice because of either relapse of the malignancy or dysfunction of the graft. Second HSCT may be the only option for some patients whose initial HSCT failed. Methods : From May, 1991 to December, 2004, 115 HSCTs were performed at the Pediatric Blood & Marrow Transplantation Center, Chonnam National University. This study was a retrospective analysis of the medical records of 15 patients who received the second HSCT after initial graft. Results : Among eight patients with nonmalignant diseases, two patients underwent the second HSCT because of primary graft failure and five because of late graft rejection. The remaining Fanconi anemia patient was re-transplanted due to development of AML. Two patients died and one experienced primary graft failure, but is still alive. The Kaplan-Meier 5-year overall survival rate was 75 percent and the disease free survival rate was 62.5 percent in nonmalignant diseases. All malignant patients underwent second transplants because of relapses. Four died of relapse and one of treatment-related complications. The Kaplan-Meier 2-year overall and event free survival rate was 28.6 percent each in malignant diseases. Conclusion : Second HSCT for graft dysfunction of nonmalignant disease seems to be feasible and should be considered as a standard practice. The relapse of malignant diseases remains a big obstacle even after the second HSCT, although a small portion of patients might be salvaged. Further investigation of novel therapeutic strategies, as well an the understanding of the biology should be explored.

• Journal of the Korean Geographical Society
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• v.29 no.1
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• pp.84-104
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• 1994

The migration of population into the city has been on the increase according as Korea has been industrialized repidly since the 1960's. And there is a steady decrease in rural population. Thus lack of the number of the students forced many elementary Schools to be abolished. The aim of this study is to grasp the abolition types and the regional characteristics with the subject region of Chungbuk province. From the viewpoint of the increasing abolition of the elementary schools, I think it is very important to understand how the elementary schools have been abolished so far and predict how the subject region will have been changed in geography. Data for this study are based on Annual Establishment-Abolition Situation of the Schools published by Chungbuk office of Education in 1992, and many Kinds of the statistical reports, and the interview with the related. The results are as follows: 1. By examining the change of the number of the elementary schools and students in Chnugbuk, the numder of the students had also decreased since 1969 and was less than the half in 1990. As the number of the schools began to decrease ten years later than the students began to, the abolition of the elementary schools has started in reality from 1980's. 2. The 72 elementary schools were aboilshed between 1980 and 1992: the principal school is 9.7%, the branch school is 90.3%. The most fifteen schools are abolished in Yongdong-county and Chechon-county, and the least one school is abolished in Chechon-city and Okchon-county, and there is no abolition in Chongju-city and Chungju-city: According to the type of the abolition process, the least seven principal schools are abolished, and the principal school is reorganized as a branch school and twenty eight branch schools are abolished, and the most thirty seven branch schools are abolished. 3. When special change of the abolition is classified into the first perio (1980-1986) and the second period (1987-1992), in the first period the principal and branch schools were abolished and they are 13.9% of total abolition. The abolition out of them by building a dam is 60%. The principal schools in the submerged area though they have many students, were abolished. In the second period sixty two branch schools are abolished and they are 86.1% of total abolition. The most fifteen schools are abolished in Yongdong-county, thirteen in Chechon-county, seven in Tanyang-county, six in Chongwon-county, five in Chungwon-county and Koesan-county. Unlike the first period, the schools were abolished in this period because the number of students was so small. In this period sixty branch schools were abolished. All the students in the abolished schools except six schools transfered to the principal schools. The 58 school authorities help the students attend school by bus or support the expenses for attending school after that. 4. The abolition types of city, county and myon are classified into five types by the number of the abolished schools. The most forty nine abolished schools in type II are 68.1 of the total abolition. The least three abolished ones in type I are 12.5%. Considering the relation between the abolition type ane the number of schools and students, the number of the schools, increased in type I, II, III, V except IV from 1980 and then have decreased by abolition since 1980, while the more students decreased than they did in 1970 and the more the abolished school increases, the less the students decreases. The average students per school decreased in every abolition type and the most students decreased in type IV. 5. Considering the relation between the abolition type and the regional characteristics, most abolished schools were located between 100m and 300m above the sea level and it is 71% of the total abolition. The region without the abolition is high in the ratio of the cultivate land, ratio of rice field, and the part-time farmer, but the region with many abolition is low in the ratio of cultivated land. As for the manufacturing there are the most city, county and myon in the abolition type in Youngdong-county and Chechon-county where the manufacturing ratio of employing is low but Chongju-city without the abolition is a region where the manufacturing ratio is high. Consequently the development of the manufacturing causes the population to emigation out and the decrease of the population leads the transport is difficult of access, the facilities sold after being abolished are not being used in many ways. 7. Take an example of Youndong-county where the most schools were abolished, I have examined the school district and the population characteristics of the abolition. Though there were more villages, households, populations in the region that is higher than low above the sea level, the schools were abolished. Therefore we know that above the sea level had a great effect on the abolition. As a result of the regional analysis of the abolition, many schools were abolished by the artificial buildings such as a dam in the early 1980's but the schools in the late 1980's were abolished ten years later after the students decreased. More schools were abolished in the region where the manufacturing industry didn't develop. And the higher the school position was above the sea level, the sooner the school was abolished. It is also proved that both the beautiful natural scenery and accessibility are the important factor in using the abolished facilities practically.

• The Korean Journal of Nuclear Medicine Technology
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• v.13 no.1
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• pp.77-81
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• 2009

Purpose: The PET of the PET/CT (Positron Emission Tomography/Computed Tomography) quantitatively shows the biological and chemical information of the body, but has limitation of presenting the clear anatomic structure. Thus combining the PET with CT, it is not only possible to offer the higher resolution but also effectively shorten the scanning time and reduce the noises by using CT data in attenuation correction. And because, at the CT scanning, the contrast media makes it easy to determine a exact range of the lesion and distinguish the normal organs, there is a certain increase in the use of it. However, in the case of using the contrast media, it affects semi-quantitative measures of the PET/CT images. In this study, therefore, we will be to establish the reliability of the SUV (Standardized Uptake Value) with CT data correction so that it can help more accurate diagnosis. Materials and Methods: In this experiment, a total of 30 people are targeted - age range: from 27 to 72, average age : 49.6 - and DSTe (General Electric Healthcare, Milwaukee, MI, USA) is used for equipment. $^{18}F$- FDG 370~555 MBq is injected into the subjects depending on their weight and, after about 60 minutes of their stable position, a whole-body scan is taken. The CT scan is set to 140 kV and 210 mA, and the injected amount of the contrast media is 2 cc per 1 kg of the patients' weight. With the raw data from the scan, we obtain a image showing the effect of the contrast media through the attenuation correction by both of the corrected and uncorrected CT data. Then we mark out ROI (Region of Interest) in each area to measure SUV and analyze the difference. Results: According to the analysis, the SUV is decreased in the liver and heart which have more bloodstream than the others, because of the contrast media correction. On the other hand, there is no difference in the lungs. Conclusions: Whereas the CT scan images with the contrast media from the PET/CT increase the contrast of the targeted region for the test so that it can improve efficiency of diagnosis, there occurred an increase of SUV, a semi-quantitative analytical method. In this research, we measure the variation of SUV through the correction of the influence of contrast media and compare the differences. As we revise the SUV which is increasing in the image with attenuation correction by using contrast media, we can expect anatomical images of high-resolution. Furthermore, it is considered that through this trusted semi-quantitative method, it will definitely enhance the diagnostic value.

• Journal of Aquaculture
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• v.19 no.2
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• pp.84-89
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• 2006

Effect of dietary inclusion of various sources of green tea on growth, immune system and challenging test of juvenile olive flounder Paralichthys olivaceus was investigated. Five experimental diets with triplicates were prepared: control, raw leaves, dry leaves, by-product and extract. Twenty five (an initial body weight of 52.5 g) were randomly distributed into 15 of 180 L flow-through tanks. Nutrient requirements of the experimental diets satisfied growth of juvenile olive flounder. The feeding trial lasted for 7 weeks. After 7-week feeding trial, blood were sampled from three randomly chosen fish for serum analysis of Iysozyme and bactericidal activity, and ten fish were infected with Edwardsiella tarda for challenging test from each tank. Weight gain (g/fish) of fish fed the diet containing extract and control diet was significantly higher than that of fish fed the other diets. Feed efficiency ratio for fish fed the diet containing extract and control diet was significantly higher than that for fish fed the diets containing raw leaves and by-product, but not significantly different from that for fish fed the diet containing dry leaves. Serum Iysozyme activity (units/ml) of fish fed the diets containing dry leaves and extract was significantly higher than that of fish fed the diets containing raw leaves and by-product, but not significantly different from that of fish fed the control diet. Serum bactericidal activity (${\times}10^6$ bacteria/ml) of fish fed the diet containing dry leaves and extract was significantly lower than that of fish fed the diets containing raw leaves, by-product and control diet in 3 hour. However, serum bactericidal activity of fish fed the diet containing extract was significantly lower than that of fish fed the other diets in 6 hour. And serum bacterial activity was low in fish fed the diets containing dry and raw leaves, by-product, and control in 6 hour in order. Accumulative mortality (%) of fish fed the control diet was low compared to that of fish fed the diets containing raw leaves and by-product, but high compared to that of fish fed the diets containing dry leaves and extract although no significant difference was found among treatments. In considering above results, dietary inclusion of extract and dry leaves of green tea seemed to be highly effective to improve immune system and endurance against E. tarda infection of juvenile olive flounder.

• Journal of Intelligence and Information Systems
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• v.26 no.3
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• pp.51-69
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• 2020

Now, it is a stylized fact that a small number of technology firms such as Apple, Alphabet, Microsoft, Amazon, Facebook and a few others have become larger and dominant players in an industry. Coupled with the rise of these leading firms, we have also observed that a large number of young firms have become an acquisition target in their early IPO stages. This indeed results in a sharp decline in the number of new entries in public exchanges although a series of policy reforms have been promulgated to foster competition through an increase in new entries. Given the observed industry trend in recent decades, a number of studies have reported increased concentration in most developed countries. However, it is less understood as to what caused an increase in industry concentration. In this paper, we uncover the mechanisms by which industries have become concentrated over the last decades by tracing the changes in industry concentration associated with a firm's status change in its early IPO stages. To this end, we put emphasis on the case in which firms are acquired shortly after they went public. Especially, with the transition to digital-based economies, it is imperative for incumbent firms to adapt and keep pace with new ICT and related intelligent systems. For instance, after the acquisition of a young firm equipped with AI-based solutions, an incumbent firm may better respond to a change in customer taste and preference by integrating acquired AI solutions and analytics skills into multiple business processes. Accordingly, it is not unusual for young ICT firms become an attractive acquisition target. To examine the role of M&As involved with young firms in reshaping the level of industry concentration, we identify a firm's status in early post-IPO stages over the sample periods spanning from 1990 to 2016 as follows: i) being delisted, ii) being standalone firms and iii) being acquired. According to our analysis, firms that have conducted IPO since 2000s have been acquired by incumbent firms at a relatively quicker time than those that did IPO in previous generations. We also show a greater acquisition rate for IPO firms in the ICT sector compared with their counterparts in other sectors. Our results based on multinomial logit models suggest that a large number of IPO firms have been acquired in their early post-IPO lives despite their financial soundness. Specifically, we show that IPO firms are likely to be acquired rather than be delisted due to financial distress in early IPO stages when they are more profitable, more mature or less leveraged. For those IPO firms with venture capital backup have also become an acquisition target more frequently. As a larger number of firms are acquired shortly after their IPO, our results show increased concentration. While providing limited evidence on the impact of large incumbent firms in explaining the change in industry concentration, our results show that the large firms' effect on industry concentration are pronounced in the ICT sector. This result possibly captures the current trend that a few tech giants such as Alphabet, Apple and Facebook continue to increase their market share. In addition, compared with the acquisitions of non-ICT firms, the concentration impact of IPO firms in early stages becomes larger when ICT firms are acquired as a target. Our study makes new contributions. To our best knowledge, this is one of a few studies that link a firm's post-IPO status to associated changes in industry concentration. Although some studies have addressed concentration issues, their primary focus was on market power or proprietary software. Contrast to earlier studies, we are able to uncover the mechanism by which industries have become concentrated by placing emphasis on M&As involving young IPO firms. Interestingly, the concentration impact of IPO firm acquisitions are magnified when a large incumbent firms are involved as an acquirer. This leads us to infer the underlying reasons as to why industries have become more concentrated with a favor of large firms in recent decades. Overall, our study sheds new light on the literature by providing a plausible explanation as to why industries have become concentrated.

• Tuberculosis and Respiratory Diseases
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• v.44 no.4
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• pp.729-741
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• 1997

Background : We have recently reported that airway epithelial cells can produce RANTES and IL-8 in response to the stimulation of tubercle bacilli suggesting a certain role of airway epithelial cells in the pathogenesis of pulmonary tuberculosis. The pathogenesis of tuberculosis is determined by several factors including phagocytosis, immunological response of host, and virulence of tubercle bacilli. Interestingly, there have been reports suggesting that difference in immunological response of host according to the virulence of tubercle bacilli may be related with the pathogenesis of tuberculosis. We, therefore, studied the expressions and productions of RANTES and IL-8 in airway epithelial cells in response to tubercle bacilli(H37Rv, virulent strain and H37Ra, avirulent strain), in order to elucidate the possible pathophysiology of pulmonary tuberculosis. Methods : Peripheral blood monocytes were isolated from normal volunteers. Peripheral blood monocytes (PBM) were stimulated with LPS($10{\mu}g/ml$), H37Rv, or H37Ra($5{\times}10^5$ bacilli/well) along with normal control for 24 hours. A549 cells were stimulated with supernatants of cultured PBM for 24 hours. ELISA kit was used for the measurement of $TNF{\alpha}$ and IL-$1{\beta}$ production in supernatants of cultured PBM and for the measurement of RANTES and IL-8 in supernatants of cultured A549 cells. Northern blot analysis was used for the measurement of RANTES and IL-8 mRNA expression in cultured A549 cells. Results : $TNF{\alpha}$ and IL-$1{\beta}$ productions were increased in cultured PBM stimulated with LPS or tubercle bacilli(H37Rv or H37Ra) compared with the control. There was, however, no difference in $TNF{\alpha}$ and IL-$1{\beta}$ production between cultured PBM stimulated with H37Rv and H37Ra. RANTES and IL-8 expressions and productions were also increased in cultured A549 cells stimulated with LPS or tubercle bacilli compared with the control. RANTES and IL-8 mRNA expressions were significantly increased in cultured A549 cells stimulated with H37Ra-conditioned media(CM) compared with A549 cells stimulated with H37Rv-CM (p<0.05). However, there was no difference in RANTES and IL-8 productions between A549 cells stimulated with H37Rv-CM and H37Ra-CM. Conclusion : Airway epithelial cells can produce the potent chemokines such as RANTES and IL-8, in response to the stimulation of tubercle bacilli. These results suggest that airway epithelial cells may play a certain role in the pathogenesis of pulmonary tuberculosis. However, the role of airway epithelial cells in the pathogenesis of tuberculosis according to the virulence of tubercle bacilli was not clear in this study.

• Korea journal of population studies
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• v.11 no.2
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• pp.54-66
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• 1988

I. Introduction Since the 1970's drug abuse among young people has increasingly become a social problem in Korea. In the 1980's, drug abuse, especially glue sniffing, has become the cause of many unfortunated incidents resulting in harm to others as well as the abusers themselves. Taking into consideration of the seriousness of this problem, the Republic of Korea National Red Cross initiated a nation-wide research programme, to understand the present situation and to raise the level of public awareness. The goal of this research was to begin a nation - wide campaign against drug abuse. The research team was composed of the Advisary Committee members and the staff of the Youth Department of the Republic of Korea National Red Cross. The data were collected in February 1988 with the collaboration of the staff and volunteers in the local Chapters. The respondents were allocated nation-wide by the quota sampling method. The questionnaires were distributed to the respondents in three groups :2, 700 to junior and senior high school students, 605 to working youths, and 916 to delinquent youths. A total of 4, 221 questionnaires were collected. II. Characteristics of the Respondents The respondents in each group were selected evenly from rural and urban areas. The general characteristics of the respondents can be described as follow: in case of students, the proportions between male and female respondents, and between senior high school and junior high school students were almost evenly distributed. In case of working youths, the proportion of females (80.5%) was higher than those of the students and the delinquents groups. Delinquent youths were defined as those currently being under custody of the centers for juvenile delinquents. Of this number, 38.8% and 68.2% were junior and senior high school drop-outs respectively. The majority of them (92.6%) were male. As for the family background of the respondents, the proportion of those residing in poverty - stricken areas, and the proportion of those from broken families were higher in case of working youths and delinquent youths than those in case of students. III. Present Patterns of Drug Abuse The following summarizes the presents of drug abuse, as tabulated from the results of the survey. 1. Smoking The percentage of youths who smoke was 36% in the student group, 32% m the working youths group, and 94.4% in the delinquent youths group. 2. Alcohol 50.3% of students, 71.6% of working youths, and 93.3% of delinquent youths has experienced drinking alcohol beverages. 3. Tonic: non - alcoholic, caffeinated beverages popular in Korea and Japan The percentage of those who have used tonic at least once was over 90% in all of the three groups. 4. Sedative About 70% of each group has used sedative with the proportion of working youths use higher than those in other groups. 5. Stimulants Those who have used stimulants comprised around 15% in each group. 6. Tranquilizers Somewhat less than 5% of students and working youths, and 28% of delinquent youths, have used tranquilizers. 7. Hypnotics The users of hypnotics amounted to 0.4% of students, 2.6% of working youths and 7.1% of delinquent youths. 8. Marihuana Those who have used marihuana indicated 0.7% of students, 0.8% of working youths, and 13% of delinquent youths. 9. Glue-sniffing The percentage of glue-sniffing was 3.7%, 5% in the students group and in the youths group respectively, but the proportion was unusually high, at 40.7% in the delinquent youths group. From the results of the survey the present situation of drug abuse in Korea can be summarized as follows: 1. A high percentage of Korean youths have experienced smoking cigarettes and drinking alcoholic beverages. 2. Tonics (non - alcoholic, caffeinated beverages), antipyretic analgesics and stimulants quite regularly used. 3. Tranquilizers, hypnotics, marihuana and glue-sniffing are more widely used among delinquent youths than the other youths. From this fact, there exists a correlation between drug abuse and juvenile delinquency. IV. Time-series Analysis of the First Experience of Drug Abuse and Deviant Behaviour The respoundents were asked when they were first exposed to drugs and when they committed deviant acts. By calculating the average age of each experience, the following pattern was found (See Figure 1). Youths are first exposed to drugs by abuse of tonic(non - alcoholic, caffeinated beverages). At the age of 13, they amoke cigarettes, the use of antipyretic analgesics begins at 14 year old, while at the age of 15, they use tranquilizers, and at 16 hynotics. The period of drug abuse which starts from drinking caffeinated beverages and smoking cigarettes and ends in the use of hypnotics takes about three years. During this period, other delinquent behaviours begin to surface, that is, at the age of 13 when smoking cigarettes begins, the delinquent behaviour pattern starts with truancy. Next, they start taking money from others by using physical force. Prior to the age of 15, they are suspended from school, become hostile to adults, begin running away from home, and start using stimulants and alcohol. Soon they become involved even in glue-sniffing and in the use of marihuana. At the age of 15, they begin to see adult videos and carry weapons. Sexual promiscuity and usage of tranquilizers follows the viewing of adult videos. Consequently, by the time they reach the age of 16, they visit drinking establishments, and are picked up by police for committing delinquent acts. And finally, they come to use hypnotic - type drugs. From the above descriptions, drug abuse can be assumed to have a close correlation with delinquent behaviour. V. Social Factors Related to Drug Abuse As for the Korean youths, glue-sniffing is found to he related to aggressive delinquency, in such cases as run - aways, being picked up by the police, and taking money by force. Smoking cigarettes and drinking alcohol is found to be related to seeing adult videos and visiting drinking establishments. Hypnotics and marihuana were found to be representive of drugs which are related to degenerational delinquency, irrespective of social delinquency. The social factors connected with these drug abuse are as follows: 1. Individual factors Male students were more heavily involved in the usage of drug than females. Youths who do not attend church were more likely to be involved in drugs than those who attend. 2. Family factors The youths who were displeased with their mothers smoking and those who thought their parents did not love each other, or those whose parents had used drugs without prescription, were more likely to he drug users. 3. School factors Those youths who found school life boring, were unsuccessful in their studies, spend most of their time with friends, feel their teachers smoke too much, those who had a positive perception of their teachers smoking were likely to he drug users. To sum up, drug abusers depend on the influence of their parents, teachers and peers. IV. Reasons for Drug Abuse Korean students have mainly used drugs to release stress (42.8%), to stay awake (19.7%), and because of the easy accessibility of drugs( 16.6%). Other reasons are due to their ignorance of the side effects of the drugs (3.6%), natural curiosity (4.2%), and to increase strength(3.O%). From the above facts, the major reasons for drug abuse among Korean youths are to release stress and to stay awake in order to prepare exams. Furthermore, since drugs are readily available, we can conclude that drug abuse is caused by the school system(such as entrance exams) in Korea. VII. Conclusion Drug usage among Korean youths are relatively less common than those of western youths. In some cases, such as, glue-sniffing and use of stimulants, the pattern of drug abuse is found. Moreover, early drug abuse is evident, and it has a close connection with deviant behaviour, resulting in juvenile delinquency. Drug abuse cannot be attributed to any one social factor. Specifically, drug abuse depends on parents, peers, teachers and other members of the community, and also is influenced by social institutions such as the entrance exam system. Every person and organization concerned with youth must participate collectively in restraining drug abuse. Finally, it is suggested that social agencial working for youth welfare should make every effort to tackle this serious problem confronted by the Korean youths today.

• Clinical and Experimental Pediatrics
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• v.50 no.6
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• pp.556-564
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• 2007

Purpose : We hypothesized that the persisting bronchial hyperresponsiveness (BHR) of adolescents with asthma remission may be controlled mainly by genetic factors, and the BHR of symptomatic asthma by airway inflammation. ${\beta}_2$-adrenoceptor gene is considered to be a candidate gene in the development of BHR. Thus, ${\beta}_2$-adrenoceptor gene polymorphism may be associated with the BHR of adolescents with asthma remission, but not with the BHR of symptomatic asthma. To evaluate this hypothesis, ${\beta}_2$-adrenoceptor gene polymorphism at 2 sites (Arg16-Gly, Gln27-Glu) were examined. Methods : Two hundred two adolescents with BHR ($PC_{20}<18\;mg/mL$) and long term remission (neither asthma-related symptoms nor medication during the previous 2 years) of their asthma (remission group), 182 adolescents with symptomatic asthma (symptomatic group), and 200 healthy adolescents (control group) were studied. Asthma phenotypes were determined using methacholine bronchial provocation test and skin prick test. Genotypes of ${\beta}_2$-adrenoceptor polymorphism were evaluated by PCR-based methods. Results : Gly/Gly allele and Gly16-Gln27 haplotype were more prevalent in the remission group than in the control group (P=0.01, P=0.02), although there was no difference between the symptomatic group and the control group. In the remission group, there was significant difference in geometric mean of $PC_{20}$ among the 3 groups subdivided by the number of Gly16-Gln27 haplotype, showing that the Gly16-Gln27 haplotype was positively associated with BHR. However, no association was found between Gly16-Gln27 haplotype and BHR in the symptomatic group. Conclusion : This study demonstrates that ${\beta}_2$-adrenoceptor polymorphism at amino acid 16 and 27 was associated with BHR persisting in adolescents with asthma remission.