• Asia Marketing Journal
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• v.14 no.1
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• pp.83-98
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• 2012

In a market where new and used cars are competing with each other, we would run the risk of obtaining biased estimates of cross elasticity between them if we focus on only new cars or on only used cars. Unfortunately, most of previous studies on the automobile industry have focused on only new car models without taking into account the effect of used cars' pricing policy on new cars' market shares and vice versa, resulting in inadequate prediction of reactive pricing in response to competitors' rebate or price discount. However, there are some exceptions. Purohit (1992) and Sullivan (1990) looked into both new and used car markets at the same time to examine the effect of new car model launching on the used car prices. But their studies have some limitations in that they employed the average used car prices reported in NADA Used Car Guide instead of actual transaction prices. Some of the conflicting results may be due to this problem in the data. Park (1998) recognized this problem and used the actual prices in his study. His work is notable in that he investigated the qualitative effect of new car model launching on the pricing policy of the used car in terms of reinforcement of brand equity. The current work also used the actual price like Park (1998) but the quantitative aspect of competitive price promotion between new and used cars of the same model was explored. In this study, I develop a model that assumes that the cross elasticity between new and used cars of the same model is higher than those amongst new cars and used cars of the different model. Specifically, I apply the nested logit model that assumes the car model choice at the first stage and the choice between new and used cars at the second stage. This proposed model is compared to the IIA (Independence of Irrelevant Alternatives) model that assumes that there is no decision hierarchy but that new and used cars of the different model are all substitutable at the first stage. The data for this study are drawn from Power Information Network (PIN), an affiliate of J.D. Power and Associates. PIN collects sales transaction data from a sample of dealerships in the major metropolitan areas in the U.S. These are retail transactions, i.e., sales or leases to final consumers, excluding fleet sales and including both new car and used car sales. Each observation in the PIN database contains the transaction date, the manufacturer, model year, make, model, trim and other car information, the transaction price, consumer rebates, the interest rate, term, amount financed (when the vehicle is financed or leased), etc. I used data for the compact cars sold during the period January 2009- June 2009. The new and used cars of the top nine selling models are included in the study: Mazda 3, Honda Civic, Chevrolet Cobalt, Toyota Corolla, Hyundai Elantra, Ford Focus, Volkswagen Jetta, Nissan Sentra, and Kia Spectra. These models in the study accounted for 87% of category unit sales. Empirical application of the nested logit model showed that the proposed model outperformed the IIA (Independence of Irrelevant Alternatives) model in both calibration and holdout samples. The other comparison model that assumes choice between new and used cars at the first stage and car model choice at the second stage turned out to be mis-specfied since the dissimilarity parameter (i.e., inclusive or categroy value parameter) was estimated to be greater than 1. Post hoc analysis based on estimated parameters was conducted employing the modified Lanczo's iterative method. This method is intuitively appealing. For example, suppose a new car offers a certain amount of rebate and gains market share at first. In response to this rebate, a used car of the same model keeps decreasing price until it regains the lost market share to maintain the status quo. The new car settle down to a lowered market share due to the used car's reaction. The method enables us to find the amount of price discount to main the status quo and equilibrium market shares of the new and used cars. In the first simulation, I used Jetta as a focal brand to see how its new and used cars set prices, rebates or APR interactively assuming that reactive cars respond to price promotion to maintain the status quo. The simulation results showed that the IIA model underestimates cross elasticities, resulting in suggesting less aggressive used car price discount in response to new cars' rebate than the proposed nested logit model. In the second simulation, I used Elantra to reconfirm the result for Jetta and came to the same conclusion. In the third simulation, I had Corolla offer $1,000 rebate to see what could be the best response for Elantra's new and used cars. Interestingly, Elantra's used car could maintain the status quo by offering lower price discount ($160) than the new car ($205). In the future research, we might want to explore the plausibility of the alternative nested logit model. For example, the NUB model that assumes choice between new and used cars at the first stage and brand choice at the second stage could be a possibility even though it was rejected in the current study because of mis-specification (A dissimilarity parameter turned out to be higher than 1). The NUB model may have been rejected due to true mis-specification or data structure transmitted from a typical car dealership. In a typical car dealership, both new and used cars of the same model are displayed. Because of this fact, the BNU model that assumes brand choice at the first stage and choice between new and used cars at the second stage may have been favored in the current study since customers first choose a dealership (brand) then choose between new and used cars given this market environment. However, suppose there are dealerships that carry both new and used cars of various models, then the NUB model might fit the data as well as the BNU model. Which model is a better description of the data is an empirical question. In addition, it would be interesting to test a probabilistic mixture model of the BNU and NUB on a new data set.

• Korean Journal of Culture and Social Issue
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• v.12 no.5_spc
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• pp.81-98
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• 2006

The objective of this research is to do a cultural comparison on the daily lives of the children of Korea, Japan and China. To achieve this objective, the questionnares were distributed to the 2940 mothers of children from the ages of 3 to 6 in the countries of Korea, Japan and China. The target audience consisted of 941 mothers living in Seoul and Kyunggi area for Korea, 1007 mothers living in Tokyo for Japan, and 992 mothers living in Beijing for China. As a result of the research, we found out that firstly, although children in general got up anytime between 7:00am to 9:00am and went to bed between 8:00pm and 11:00pm, 61.5% of the Korean children went to bed after 10pm and 16.8% after 11pm. Besides that, we found that compared to 3.51% of Korean children who got up before 6am, 13.41% of Japanese children and 17.24% of Chinese children got up before 6:00am. So we could see that the Korean children got up later and went to bed later than their Japanese and Chinese counterpart. This pattern could also be seen in the average rising time and bed time. Korean children went to bed at 10:00pm and woke up at 7:75am whereas the Japanese children went to bed at 9:28pm and woke up at 7:39am, and the Chinese children went to bed at 9:05pm and woke up at 7:05am. The average sleeping hours for Japanese children was 10.12 hours, 9.50 hours for the Chinese and 9.75 hours for the Korean. As a result, we could see that the Korean children went to bed later, got up later and slept fewer hours than their Japanese and Chinese counterparts. Also, since the rising time and bedtime of the Korean children was later than those of the Chinese and Japanese counterparts, the former s' breakfast and dinner time was also much later. Secondly, we looked at the time children went off to and came back from institutes such as kindergarten and child care centers. The Chinese were earliest at going with average attendance at 7:83am, the Japanese came next at 8:59am and the Korean children were last at 8:90am, whereas the Japanese came first in coming back home at 3:36pm, Korean next at 3:91pm and the Chinese last at 5:46pm. Next when we looked at the hours spent at the kindergartens and child care centers, Japan spent 6.76 hours, Korea 7.01 hours and China spent the longest hours with 9.63 hours. Excluding China where all preschool institutes are centralized into kindergartens, we nest looked at time children went to and came back from the institutes as well as the time spent there. In the case of kindergarten, there was not much difference but in the case of child care centers, the Japanese children went to the child care centers mach earlier and came home later than the Korean children. Also, the time spent at the child care center was much longer for the Japanese than the Korean children. This fact coincides with the Korean mothers' number one wish to the kindergartens and child care centers i.e. for the institutes to prolong their school hours. Thus, the time spent at child care centers for Korea was 7.75 hours, 9.39 hours for Japan and 9.63 hours for China. The time for Korea was comparatively much shorter than that of Japan and China but if we consider the fact that 50% of the target audience was working mothers, we could easily presume that the working parents who usually use the child care centers would want the child care centers to prolong the hours looked after their children. Besides this, the next most wanted wish mothers have towards the child care centers and kindergartens was for those institutes to "look after their children when sick". This item showed high marks in all three countries, and the marks in Korea was especially higher when compared to Japan and China. Thirdly, we looked at the private extracurricular activities of the children. We found that 72.6% of the Korean children, 61.7% of the Japanese children, and 64.6% of the Chinese children were doing private extracurricular activities after attending kindergarten or day care centers. Amongst the private extracurricular activities done by Korean children, the most popular one was worksheet with 51.9% of the children doing it. Drawing (15.20%) and English (11.6%) came next. Swimming (21.95%) was the most popular activity for Japan, with English (17.48%), music (15,79%) and sports (14.70%) coming next. For China, art (30.95%) was first with English (22.08%) and music (19.96%) following next. All three countries had English as the most popular activity related to art and physical activities after school hours, but the rate for worksheet studies was much higher for Korea compared to Japan China. The reason Koreans universally use worksheet in because the parents who buy the worksheet are mothers who have easy access to advertisement or salespeople selling those products. The price is also relatively cheap, the worksheet helps the children to grow the basic learning ability in preparation for elementary school, and it is thought to help the children to build the habit of studying everyday. Not only that but it is estimated that the worksheet education is being conducted because parents can share the responsibility of the children's learning with the worksheet-teacher who make home visits. Looking at the expenses spent on private extracurricular activities as compared to income, we found that China spent 5% of income for activities outside of regular education, Korea 3% and Japan 2%. Fourthly, we looked at the amount of time children spent on using multimedia. The majority of the children in Korea, Japan and China watch television almost every day. In terms of video games, the Japanese children played the games the most, with Korea and China following next. The Korean children used the computer the most, with Japan and China next. The Korean children used about 21.17% of their daily time on computers which is much more than the Japanese who used 20.62% of their time 3 or 4 times a week, or the Chinese. The Chinese children were found to use considerably less time on multimedia compared to the Korean of Japanese.

• Clinical and Experimental Pediatrics
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• v.48 no.4
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• pp.395-400
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• 2005

Purpose :Rotavirus is one of the most important causes of nosocomial infections among children. The aim of this study is to determine the risk of nosocomial rotavirus infections and to evaluate the effectiveness of breast-feeding and probiotics in the prevention of nosocomial rotavirus infections. Methods : This study was carried out on admitted children without diarrhea between March 1, 2003 and February 29, 2004. Three hundred ninety patients aged 4 days to 13 years during this study were available. We examined the feces of all children for rotavirus by latex agglutination on admission, during hospital, and after discharge, to see whether they developed diarrhea or not. Results : Nosocomial rotavirus infections was significantly increased with children under 12 months of age(P=0.008). The monthly attack rate was great between December and March(P=0.046). Prolonged hospital stay was associated with an increased attack rate of nosocomial rotavirus infections (P=0.003). The risk of nosocomial rotavirus infections was not associated with the number of roommates and whether or not they were breast-fed or fed on probiotics. Conclusion : Nosocomial rotavirus infections are significantly more likely to occur in children under 12 months of age, admitted between December and March, and with prolonged hospital stays. Prompt identification and isolation of children with nosocomial rotavirus infections, even without diarrhea, may decrease rates of nosocomial rotavirus infections.

• Clinical and Experimental Pediatrics
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• v.50 no.1
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• pp.28-32
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• 2007

Purpose : Human angiotensin converting enzyme (ACE) gene shows an insertion/deletion polymorphism in 16 intron, and three genotypes are determined by whether a 287 bp fragment of the DNA is present or not; II, ID and DD genotype. DD genotype has been suggested as a risk factor of chronic nephrotic disease such as IgA nephropathy and diabetic nephropathy, various cardiovascular diseases and several other diseases. ACE activity increases in acute hepatitis, chronic persistent hepatitis, chronic active hepatitis and cirrhosis. On the other hand, patients with fatty livers have normal ACE activity. This study was designed to find out the relation between polymorphsims of the ACE genes and neonatal hyperbilirubinemia in Koreans. Methods : The genomic DNA was isolated from 110 full-term Korean neonates who had hyperbilirubinemia with no obvious causes (serum bilirubin$${\geq_-}12mg/dL$$) and 164 neonates of a control population (serum bilirubin <12 mg/dL). We performed polymerase chain reaction (PCR) to see the allele of the ACE gene. Electrophoresis was done in the PCR products in 1.5 percent agarose gel, and then DNA patterns were directly visualized under ethidium bromide staining. Results : ACE genotypes in the hyperbilirubinemia group are as follows; 26.36 percent for II, 53.64 percent for ID, 20.00 percent for DD, 0.532 for I allele and 0.468 for D allele. These distributions were not significantly different from those in the control group; 24.39 percent for II, 51.83 percent for DI, 23.78 percent for DD, 0.503 for I allele and 0.497 for D allele. Conclusion : In this study, ACE gene polymorphism was detected in the neonatal hyperbilirubinemia and control group. The most frequent genotype was ID. Our results indicate that the ACE gene polymorphism is not associated with the prevalence of neonatal hyperbilirubinemia in Koreans.

• Journal of Soil and Groundwater Environment
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• v.13 no.1
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• pp.77-91
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• 2008

In this study, we developed a technique of applying DRASTIC, which is the most widely used tool for estimation of groundwater vulnerability to the aqueous phase contaminant infiltrated from the surface, and a groundwater flow model jointly to assess groundwater contamination potential. The developed technique is then applied to Buyeo-eup area in Buyeo-gun, Chungcheongnam-do, Korea. The input thematic data of a depth to water required in DRASTIC model is known to be the most sensitive to the output while only a few observations at a few time schedules are generally available. To overcome this practical shortcoming, both steady-state and transient groundwater level distributions are simulated using a finite difference numerical model, MODFLOW. In the application for the assessment of groundwater vulnerability, it is found that the vulnerability results from the numerical simulation of a groundwater level is much more practical compared to cokriging methods. Those advantages are, first, the results from the simulation enable a practitioner to see the temporally comprehensive vulnerabilities. The second merit of the technique is that the method considers wide variety of engaging data such as field-observed hydrogeologic parameters as well as geographic relief. The depth to water generated through geostatistical methods in the conventional method is unable to incorporate temporally variable data, that is, the seasonal variation of a recharge rate. As a result, we found that the vulnerability out of both the geostatistical method and the steady-state groundwater flow simulation are in similar patterns. By applying the transient simulation results to DRASTIC model, we also found that the vulnerability shows sharp seasonal variation due to the change of groundwater recharge. The change of the vulnerability is found to be most peculiar during summer with the highest recharge rate and winter with the lowest. Our research indicates that numerical modeling can be a useful tool for temporal as well as spatial interpolation of the depth to water when the number of the observed data is inadequate for the vulnerability assessments through the conventional techniques.

• Journal of Korean Medical classics
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• v.22 no.1
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• pp.35-59
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• 2009

The acupuncture documentary characteristics of the "Chimgugapeulgyeong" can be summarized into 7 parts such as the following. 1. After Imeok(林億)'s revised edition of the "Gapeulgyeong(甲乙經)" was printed during the Song dynasty, there were no reprints during the Southern Song, Geum(金) and Won(元) eras, and the first printed edition that remains today is the 'Uihakyukgyeong edition[醫學六經本]' published by Omyeonhak(吳勉學) during the Mallyeok(萬曆) era of the Myeong(明) dynasty. This publication was put into the "Uitongjeongmaek(醫統正脈)" collection in the 29th year of the Manlleok(萬曆) era(1601). Most of the remaining copies have been restored during the Cheong dynasty at bookstores, and we can see that much was restored because of damage and missing characters. Also, the 'Namgyeokcho edition[藍格抄本]' and 'Yukgyeong edition[六經本]' of the Myeong dynasty do not come from the same original document, which allows the correction of the former in many places. However, this edition was not copied well, so the order of contents is different, and there are many mistakes. The 'Sagojeonseo edition[四庫全書本]' and the 'Gajeong edition[嘉靖本]', which Yeounsu(余云岫) quoted from, coincide with each other, making them worth much reference. So, the "Gapeulgyeong" and 'Yukgyeong edition' should be seen as the original, with the 'Myeongcho edition[明抄本]' as the main revision, and the 'Sago edition[四庫本]' as a reference edition. The so-called 'Chojeongtong edition(鈔正統本)' has many problems and marks of forgery, so therefore cannot be used in revising the "Gapeulgyeong" through comparison. 2. The table of contents[序例] in the front of the current edition was in the original edition and was not added by Imeok. The structure of sentences quoted by medical books before the Song dynasty coincide with this 'table of contents'. The "Gapeulgyeong" of the Song dynasty also coincide with the 'table of contents' but the edition remaining differs much from this 'table of contents' so it was edited or erased by people from future generations, especially after the Song dynasty. 3. The remaining edition of "Gapeulgyeong" consists of at least 4 parts. The original edited by Hwangbomil(皇甫謐), annotations added by medicinal practitioners before the Song dynasty, Imeok's revisionary annotations during the Song dynasty, and annotations after the Song dynasty. 4. Expressions such as 'Somun says[素問曰]' 'Gugwon says[九卷曰]' and explanatory annotations like 'Hae says[解曰]' are old writings from the original text and were not added by someone later. 5. Almost all of the 'Double lined small letter annotations[雙行小字注文]' of the 'Yukgyoeng edition' was by people during the Song dynasty. 6. There are many omitted and wrong letters in the remaining edition and there are also many places where future generations edited and supplemented the text. The table of contents differ greatly from the original text. 7. The medical books that quote "Gapeulgyeong" a lot are "Cheongeumyobang(千金要方)", "Oedaebiyobang(外臺秘要方)", "Seongjaechongrok(聖濟總錄)", "Chimgujasaenggyeong(鍼灸資生經)", "Yuyusinseo(幼幼新書)", and "Uihakgangmok(醫學綱目)" and such. However, the method used in using the text differs between the medical books, so the quotation from the same book comes from a quotation used by a doctor from a different era in one("Cheongeumyobang"), or the quotation was taken from each medical book("Chimgujasaenggyeong") or the quotation was all taken from another book("Yuyusinseo"). The reason we need to know about this problem properly is because we must use medical books that quote the original text of the "Gapeulgyeong" when we are looking for text that we can use to revise through comparison.

• Journal of Chest Surgery
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• v.38 no.12 s.257
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• pp.821-827
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• 2005

Background: Hemodilution after priming of the cardiopulmonary bypass is known to increase the possibility of bleeding and homologous transfusion in adult cardiac surgery. We investigated the effects of retrograde autologous priming (RAP) to see whether it would decrease postoperative bleeding and homologous transfusion. Material and Method: We retrospectively reviewed 34 patients wpho underwent RAP and 46 patients who did not. Retrograde autologous priming consisted of arterial lire drainage, venous reservoir and oxygenator drainage and venous line drainage. We compared the amount of priming solution and RAP volume, perioperative hematocrit, postoperative bleeding and transfusion requirements in the two groups. Resuit: Mean withdrawal volume in RAP group was 613.5$\pm$160.6 mL and initial priming volume was 1381.9$\pm$37.2 mL. Hemoatocrits ($\%$) in RAP and control groups were 25.0$\pm$3.7 vs 20.9$\pm$3.6 (5 minutes after CPB), 25.9$\pm$3.7 vs 22.5$\pm$3.6 (30 minutes after CPB), 25.9$\pm$3.4 vs 23.8$\pm$2.8 (60 minutes after CPB), 31.9$\pm$3.9 vs 31.5$\pm$4.5 (postoperative 1 hour), 32.4$\pm$4.4 vs 32.1$\pm$4.5 (postoperative 6 hours), 33.4$\pm$5.0 vs 31.7$\pm$5.1 (postoperative 1 day)[repeated measures ANOVA, p < 0.05]. Chest tube drainages (mL) in the two groups were 357.2$\pm$177.1 vs 411.7$\pm$279.5 (postoperative 6 hours), 599.4$\pm$145.6 vs 678.8$\pm$256.4 (postoperative 24 hours)[t-test, p < 0.05]. Homologous transfusion was performed in 7 out of 34 patients in RAP group (20.6$\%$), and 16 out of 46 (34.8$\%$) in control group (p < 0.05). Conclusion: This study suggests that the effects of reducing the priming volume during cardiopulmonary bypass may result in lesser bleeding and homologous transfusion. Retrograde autologous priming would be used to reduce postoperative bleeding and chance of transfusion after adult cardiac surgery.

• Journal of Korean Home Economics Education Association
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• v.18 no.1 s.39
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• pp.49-64
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• 2006

The objective of this research is to see the current status of application and development of web contents data, and to suggest the way to improve the application and development of web contents data in home economics classes in middle schools. The respondents of the research were 312 middle school home economics teachers from all over the nation, and the tool was a questionnaire which consist of 22 questions about general status of the person who was answering and their recognitions and demands on the application and development of the web contents data. The major findings were as follows : 1) 88.5% of the sample responded that they accurately grasped a meaning of a class employing web contents data, and as for effects on preparation of professional study. 2) Most of the teachers were making good use of materials from the web in their classes. They responded that it maximized the efficiency of students' learning. Some didn't use the web contents in their classes. The reasons why the web contents data usage had been low were that the classrooms were not equipped properly (43.2%) and it took long time to create web contests (37.8%). 3) Kinds of web contents data that showed the most amount of usage were the presentations (48.4%), multi-media teaching materials(23.7%), and moving pictures(19.9%). 4) Teaches wanted to improve these particular materials among the web contents: family life and home, administration and environment of resources, and clothing preparation and administration. As for the lessons, teachers wanted developments of contents of lessons, generating motives, and evaluation to be by individual teachers or curriculum researchers' societies, and 30.8% were by Korea Education & Research Information Service (KERIS).

• Journal of Life Science
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• v.19 no.4
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• pp.423-428
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• 2009

Selenium was investigated using human origin preadipocytes to see whether it possesses preventive or therapeutic effects for obesity. Unveiling the potential of selenium in the reduction of adipogenesis can help predict the therapeutic capabilities of selenium in obesity. In the present study, the molecular mechanism of the inhibition of adipogenesis by selenium was explored to unravel the involvement of the AMP-activated protein kinase. There is emerging evidence that AMPK, a sensor of cellular energy status, is a possible molecular target of controlling adipocyte differentiation on the basis of discovery that AMPK is responsible for the major metabolic responses to exercise, and integration of nutritional and hormonal signals to modulate feeding behavior or energy expenditure in the hypothalamus. Treatment of selenium resulted in inhibition of the adipocyte differentiation process and induction of mature apoptosis in 3T3-L1 adipocytes. We hypothesized that selenium may exert anti-adipogenic potential though modulating AMPK. We have found that selenium significantly activated AMPK and phosphorylated its substrate acetyl-CoA carboxylase ($ACC-serine^{79}$) during the inhibitory process of adipocytes. Also, the inhibition process of adipocyte differentiation by selenium was comparable to either reveratrol or a synthetic AMPK activator, AICAR (5-aminoimidazole-4-carboxamide-1-${\beta}$-D-ribofuranoside). To evaluate the involvement of AMPK in anti-lipogensis, we applied AICAR and Compound C, an AMPK inhibitor, to 3T3-L1-adipocytes and found that AMPK is required for the adipocyte differentiation blocking process. These results suggest that selenium has a potential to control adipogenesis and that this effect is mediated by AMPK, an essential kinase for both inhibition of adipocyte differentiation and apoptosis of mature adipocytes.

• Journal of the Korean Academy of Child and Adolescent Psychiatry
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• v.9 no.2
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• pp.218-226
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• 1998

This study aims at investigating the effects of psychostimulant on functional cerebral localization during the attentional tasks in ADHD. Inclusional subjects were 13 boy between 6-12 years old who met the DSM-IV criteria for ADHD. In each patient, there was a drugfree period(without methyphenidate) and a drug-loaded period(with oral methylphenidate administration), and within each period there was a resting state and a stimulated state with TOVA. Comparisons were made by measuring the amplitudes of four bands(${\alpha}$, ${\beta}$, ${\delta}$, ${\theta}$) of quantitative EEG to see if there were any differences between the drug-free period(resting and stimulated) and the drug-loaded period(resting and stimulated). In the resting state, there was no difference between the drug-free and drug-loaded periods. In the stimulated state with TOVA, the presence of methylphenidate induced significant changes in the theta to beta ratio(${\theta}/{\beta}$) in the right frontal, right parieto-occipital, and left temporal-parietal areas in contrast to the drugf-ree period. These data suggest that methylphenidate shows electrophysiological influences on cerebral topographical activities during the attentional tasks in ADHD.