• Journal of the Korean Academy of Child and Adolescent Psychiatry
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• v.15 no.2
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• pp.160-167
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• 2004

Objectives : There have been very few studies on the compliance of methylphenidate-immediate releasing form(MPH-IR), which is the most frequently used drug in Korea, in Attention Deficit Hyperactivity Disorder(ADHD). This study was conducted to investigate the compliance rate and the related factors in the one year pharmacotherapy process via OPD for children with ADHD. Method : Total 100 ADHD patients were selected randomly among patients who have been treated with MPH-IR from September in 2002 to December in 2002. All the selected patients were diagnosed with DSM-IV-ADHD criteria and fulfilled the inclusion criteria. In March, 2003(at the time of 6 month treatment), all the patients and parents received the questionnaire for the compliance and satisfaction for MPH-IR treatment. In October 2003(at time of 1 year treatment), we, investigators evaluated the socio-demographic variables, developmental data, medical data, family data, comorbid disorders, treatment variables, and compliance rate. Through these very comprehensive data, The compliance rate at the time of mean 1 year treatment and the related factors were investigated. Result : 1) In the questionnaire for compliance and satisfaction for MPND treatment, the 60% of respondents(parents) reported more than moderate degree of satisfaction in the effectiveness of MPND. Their compliance rate for the morning prescription was 81%, but the rate of afternoon prescription was 43%. 2) In the evaluation at the time of 1 year treatment(October 2003), the 38% of parents were dropped out from the OPD treatment. The mean compliance rate for the 1 year treatment was 62%. the 38% of parents were dropped out from the OPD treatment. The mean compliance rate for the 1year treatment was 62%. 3) Compared with the noncompliant group(drop-out group), compliant group showed higher total, verbal and performance IQ scores. In the treatment variables, higher reposponder rate(clinician rating), higher medication dosage and more compliance rate in afternoon prescription were found in the compliant group compared with the noncompliant group. There were no statistical differences in the demographic variables(age, sex, SES, parental education level), medical data, developmental profiles and academic function. Conclusion : To our knowledge, this is the first report about the compliance rate of the MPH-IR treatment for the children with ADHD. The compliance rate at the time of mean 1year treatment was 62%, which was comparable with other studies performed in foreign countries, especially States. In this study, the compliance related factors were IQ score, clinical treatment response, dosage of MPH-IR, and early compliance for the afternoon prescription. These results suggest that clinician plan the strategies for the promotion of the early compliance for the after prescription and enhancement of overall treatment response.

• Journal of Chest Surgery
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• v.38 no.5 s.250
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• pp.349-356
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• 2005

Background: Arterial conduits using in coronary artery bypass grafting (CABG) have been known a great long term patency rates, and improved short and long term clinical outcomes. It has been reported that Off pump CABG has better clinical results than CABG using cardiopulmonary bypass. To evaluate the advantage of arterial conduits over venous conduits and to avoid the adverse effects of cardiopulmonary bypass, we performed total arterial Off pump CABG. Material and Method: From January 2001 to October 2004, Off pump CABG using only arterial conduits was performed on 325 patients with a mean age of $59.3\pm11.9$ years ($36\~83$). Mean ejection fraction was $55.4\pm14.0\%\;(15\~86).$ Angiography showed left main disease or triple-vessel disease in $81.9\%$ of the patients. Indications of using arterial conduits was stenosis $\ge50\%$ of left anterior descending artery, stenosis $\ge80\%$ of branches of left circumflex artery, and stenosis $\ge90\%$ of right coronary artery and its branches. Multi-slice computed tomography was performed on 194 patients to evaluate the short term patency rates. Result: A total of 928 distal anastomoses were performed and the average anastomoses per a patient were $2.86\pm0.78$. There was 1 operative mortality. Postoperative complications were mediastinitis in 6 patients ($1.8\%$), renal failure in 4 patients ($1.2\%$), perioperative myocardial infarction in 3 patients ($0.9\%$), reoperation for bleeding in 3 patients ($0.9\%$). There was no postoperative stroke. Patency rate of arterial conduits was $99.3\%$ (581/585). There were 4 stenoses or competitive flows in 2 radial arteries and 2 right internal mammary arteries. Conclusion: Total arterial Off pump CABG appears to be safe, showing a low surgical mortality and morbidity and excellent short term patency rates of arterial conduits.

• Journal of Distribution Research
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• v.17 no.3
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• pp.25-57
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• 2012

This study identified motives for writing apparel product reviews in online stores, and determined what motives increase the behavior of writing reviews. It also classified store customers based on the type of writing motives, and clarified the characteristics of internet purchase behavior and of a demographic profile. Data were collected from 252 females aged 20s' and 30s' who have experience of reading and writing reviews on online shopping. The five types of writing motives were altruistic information sharing, remedying of a grievance and vengeance, economic incentives, helping new product development, and the expression of satisfaction feelings. Among five motives, altruistic information sharing, economic incentives, and helping new product development stimulate writing reviews. Store customers who write reviews were classified into three groups based on their writing motive types: Other consumer advocates(29.8%), self-interested shoppers(40.5%) and shoppers with moderate motives(29.8%). There were significant differences among three groups in writing behavior (the frequency of writing reviews, writing intent of reviews, duration of writing reviews, and frequency of online shopping) and age. Based on results, managerial implications were suggested. Long Abstract : The purpose of present study is to identify the types of writing motives on online shopping, and to clarify the motives affecting the behavior of writing reviews. This study also classifies online shoppers based on the motive types, and identifies the characteristics of the classified groups in terms of writing behavior, frequency of online shopping, and demographics. Use and Gratification Theory was adopted in this study. Qualitative research (focus group interview) and quantitative research were used. Korean women(20 to 39 years old) who reported experience with purchasing clothing online, and reading and writing reviews were selected as samples(n=252). Most of the respondents were relatively young (20-34yrs., 86.1%,), single (61.1%), employed(61.1%) and residents living in big cities(50.9%). About 69.8% of respondents read and 40.5% write apparel reviews frequently or very frequently. 24.6% of the respondents indicated an "average" in their writing frequency. Based on the qualitative result of focus group interviews and previous studies on motives for online community activities, measurement items of motives for writing after-purchase reviews were developed. All items were used a five-point Likert scale with endpoints 1 (strongly disagree) and 5 (strongly agree). The degree of writing behavior was measured by items concerning experience of writing reviews, frequency of writing reviews, amount of writing reviews, and intention of writing reviews. A five-point scale(strongly disagree-strongly agree) was employed. SPSS 18.0 was used for exploratory factor analysis, K-means cluster analysis, one-way ANOVA(Scheffe test) and ${\chi}^2$-test. Confirmatory factor analysis and path model analysis were conducted by AMOS 18.0. By conducting principal components factor analysis (varimax rotation, extracting factors with eigenvalues above 1.0) on the measurement items, five factors were identified: Altruistic information sharing, remedying of a grievance and vengeance, economic incentives, helping new product development, and expression of satisfaction feelings(see Table 1). The measurement model including these final items was analyzed by confirmatory factor analysis. The measurement model had good fit indices(GFI=.918, AGFI=.884, RMR=.070, RMSEA=.054, TLI=.941) except for the probability value associated with the ${\chi}^2$ test(${\chi}^2$=189.078, df=109, p=.00). Convergent validities of all variables were confirmed using composite reliability. All SMC values were found to be lower than AVEs confirming discriminant validity. The path model's goodness-of-fit was greater than the recommended limits based on several indices(GFI=.905, AGFI=.872, RMR=.070, RMSEA=.052, TLI=.935; ${\chi}^2$=260.433, df=155, p=.00). Table 2 shows that motives of altruistic information sharing, economic incentives and helping new product development significantly increased the degree of writing product reviews of online shopping. In particular, the effect of altruistic information sharing and pursuit of economic incentives on the behavior of writing reviews were larger than the effect of helping new product development. As shown in table 3, online store shoppers were classified into three groups: Other consumer advocates (29.8%), self-interested shoppers (40.5%), and moderate shoppers (29.8%). There were significant differences among the three groups in the degree of writing reviews (experience of writing reviews, frequency of writing reviews, amount of writing reviews, intention of writing reviews, and duration of writing reviews, frequency of online shopping) and age. For five aspects of writing behavior, the group of other consumer advocates who is mainly comprised of 20s had higher scores than the other two groups. There were not any significant differences between self-interested group and moderate group regarding writing behavior and demographics.

• Journal of the Korean Geographical Society
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• v.31 no.3
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• pp.447-468
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• 1996

The peat layer was deposited on the abandoned channel of incised meander of River Banbyuncheon with 7 meter thickness on Youngyang basin. The late Quaternary environmental change on the study area was discussed based on pollen anaalysis and radiocarbon-dating from this peat. The swamp which was caused to sediment the peat, was produced by which the fan debris from the adjacent slope damed the waterflow on the abandoned channel. The peat layer contains continuous vegetational history from 60,000y.B.P. to Recent. The peat deposit was divided into two layers by the organic thin sand horizon, which was sedimented at one time and made unconformity between the lower decomposed compact peat layers and the upper fresh fiberous peat layer. As the result of the pollen analysis, both peat layers from the two boring sites, Profile YY1 and Profile YY2 were divided into five Pollenzones(Pollenzone I, II, III, IV and V) and 12 Subzones which were mainly corresponded by the AP (Arboreal Pollen)-Dominance. The two profiles have some differences on the sedimentary facies and on the pollen composition as well. Therefore these were in common with the Pollenone III, however the Pollenzone I and II existed only on the Profile YY1 and the Pollenzone IV and V existed only on the Profile YY2. The lower layer containing the Pollenzone I, II and III revealed vegetational records of Pleistocene, which was characterized as tundra-like landscape and thin forested landscapes. It represented the NAP (Non-Arboreal Pollen)-period with a plenty of Artemisia sp., Sanguisorba sp., Umbelliferae, Gramineae and Cyperaceae. However a relatively high proportion of the boreal trees with Picea sp., Pinus sp. and Betula sp. as AP was observed in the lower layer. The upper layer contained the Pollenzone IVb and V and vegetational history in Holocene which was characterized by thick forested landscape with rich tree pollen. It represented AP-period with plenty of Pinus sp. and Quercus sp. as temperate trees. The temperature fluctuation supposed from the vegetational records is as follows; the Pollenzone I(Betula-Dominance, about 57,000y.B.P.) represents relatively cold period. The Pollenzone II(EMW-Domi-nance, 57,000-43,000y.B.P.)represents relatively warm period. This period is supposed to be Interstadial, the transi-tional stage from Alt- to Mittel Wurm. The Pollenzone III(Butula-, Pinus- and Picea-Dominace in turns, 43,000-15,000y.B.P.) reproesents cold period which had been built from Mittel-to Jung Wurm. Especially the Subzone IIId represents the coldest period throughout the Pollenzone III. It is corresponds to Wurm Glacial Maximu. It is supposed that the mean temperature in July of this period was coller about 10${^\circ}$C than present. The Pollenzone IV and V represent the vegetational history of Holocene. Tilia, Quercus and Pinus were dominant in turns during this period. Subzone IVb and Pollenzone I and II at east coastal plain of Korean penninsula reported by JO(1979).

• Journal of Chest Surgery
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• v.37 no.8
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• pp.632-643
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• 2004

Background: The Histidine-Tryptophan-Ketoglutarate (HTK) solution has been shown to provide the excellent myocardial protection as a cardioplegia. The HTK solution has relatively low potassium as an arresting agent of myocardium, and low sodium content, and high. concentration of histidine biological buffer which confer a buffering capacity superior to that of blood.. Since HTK solution has an excellent myocardial protective ability, it is reported to protect myocardium from ischemia for a considerable time (120 minutes) with the single infusion of HTK solution as a cardioplegia. The purpose of this study is to evaluate the cardioprotective effect of HTK solution on myocardium when the ischemia is. exceeding 120 minutes at two different temperature (10 to 12$^{\circ}C$, 22 to 24$^{\circ}C$) using the Langendorff apparatus, Material and Method: Hearts from Sprague-Dawley rat, weighing 300 to 340 g, were perfused with Krebs-Henseleit solution at a perfusion pressure of 100 cm $H_2O$. After the stabilization, the heart rate, left ventricular developed pressure (LVDP), and coronary flow were measured. Single dose of HTK solution was infused into the ascending aorta of isolated rat heart and hearts were preserved at four different conditions. In group 1 (n=10), hearts were preserved at deep hypothermia (10∼12$^{\circ}C$) for 2 hours, in group 2 (n=10), hearts were preserved at moderate hypothermia (22∼24$^{\circ}C$) for 2 hours, in group 3 (n=10), hearts were preserved at deep hypothermia for 3 hours, and in group 4 (n=10), hearts were preserved at moderate hypothermia for 3 hours. After the completion of the preservation, the heart rate, left ventricular developed pressure, and coronary flow were measured at 15 minutes, 30 minutes, and 45 minutes after the initiation of reperfusion to assess the cardiac function. Biopsies were also done and mitochondrial scores were counted in two cases of each group for ultrastructural assessment. Result: The present study showed that the change of heart rate was not different between group 1 and group 2, and group 1 and group 3. The heart rate was significantly decreased at 15 minutes in group 4 compared to that of group 1 (p<0.05 by ANCOVA). The heart rate was recovered at 30 minutes and 45 minutes in group 4 with no significant difference compared to that of group 1. The decrease of LVDP was significant at 15 minutes, 30 minutes and 45 minutes in group 4 compared to that of group 1 (p < 0.001 by ANCOVA). Coronary flow was significantly decreased at 15 minutes, 30 minutes, and 45 minutes in group 4 compared to that of group 1 (p < 0.001 by ANCOVA). In ultrastructural assessment, the mean myocardial mitochondrial scores in group 1, group 2, group 3, and group 4 were 1.02$\pm$0.29, 1.52$\pm$0.26, 1.56$\pm$0.45, 2.22$\pm$0.44 respectively. Conclusion: The HTK solution provided excellent myocardial protection regardless of myocardial temperature for 2 hours. But, when ischemic time exceeded 2 hours, the myocardial hemodynamic function and ultrastructural changes were significantly deteriorated at moderate hypotherma (22∼ 24$^{\circ}C$). This indicates that it is recommended to decrease myocardial temperature when myocardial ischemic time exceeds 2 hours with single infusion of HTK solution as a cardioplegia.

• Journal of Chest Surgery
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• v.39 no.2 s.259
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• pp.106-110
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• 2006

Background: Bronchioloalveolar carcinoma (BAC) is an uncommon primary malignancy of the lung, and it accounts for $2{\~}14\%$ of all pulmonary malignancies. According to World Health Organization (WHO) categorisation, BAC is a subtype of adenocarcinoma. The current definition of BAC includes the following: malignant neoplasms of the lung that have no evidence of extrathoracic primary adenocarcinoma, an absence of a central bronchogenic source, a peripheral parenchymal location, and neoplastic cells growing along the alveolar septa. Previous reports had demonstrated a better prognosis following surgery for patients affected by BAC than those affected by other type of non-small cell lung cancer (NSCLC). We aim to analyse Asan Medical Center experiences of BAC. Material and Method: Between 1990 and 2002, 31 patients were received operations for BAC. We analyse retrosepectively sex, age, disease location, preoperative clinical stage, postoperative pathologic stage & complications, survival according to medical record. Result: There were 12 men and 19 women, the average age was 61.09$\pm$10.63 ($31{\~}79$) years. Tumor locations were 7 in RUL, 1 in RML, 4 in RLL, 8 in LUL, 11 in LLL. Operations were 28 lobectomies, 2 pneumonectomies. Postoperative pathologic stage were 12 T1N0M0, 15 T2N0M0, 1 T1N1M0, 1 T1N2M0, 1 T2N2M0, 1 T1N0M1. Mortality were 4 cases ($12.9\%$) and there were no early mortality. Cancer free death was 1 cases, other 3 were cancer related deaths. All of them were affected by distal metastasis and received chemotherapy and each metastatic locations were right rib, brain, and both lung field. The average follow up periods were 50.87$\pm$24.77 months. The overall 3, 5-year survival rate among all patients was $97.1\%,\;83.7\%$, stage I patients overall 2, 5year survival rate was $96.3\%$. The overall disease free 1, 2, 5-year survival rate among all patients was $100\%,\;90\%,\;76\%$ and 2, 5-year survival rate in cases of stage I was $96.4\%,\;90.6\%$. 7 cases ($22.58\%$) were chemotherapies, 1 case ($3.22\%$) was radiation therapy, and 2 cases ($6.45\%$) were chemoradiation therapies. Metastatic locations were 3 cases in lung, 1 case in bone, 1 cases in brain. Conclusion: BAC has a favourable survival and low recurrence rate compare with reported other NSCLC after operative resections.

• Tuberculosis and Respiratory Diseases
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• v.45 no.4
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• pp.723-735
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• 1998

Background : Vitamin C has been reported to have a role in the decrease of airway hyperresponsiveness in animal models. This data is based on some metabolic actions of vitamin C, such as promotion of histamine degradation, producing more $PGE_2$ than $PGF_{2\alpha}$ in cyclooxygenase pathway, decrease of smooth muscle contraction, and acting as reducing agent of oxidant. It has been also known that heavy smokers have lower blood levels of vitamin C than nonsmokers and this deficiency in heavy smokers have been explained by several mechanisms, such as increased oxidation by oxidants and free radicals, increased biosynthesis of catecholamine and serotonin released by nicotine, and inadequate dietary intake. In this study, We attempted to assess effect of vitamin C on bronchial hyperresponsiveness in heavy smokers who have bronchial hyperresponsiveness and role of vitamin C on bronchial hyperresponsiveness. Method: To assess acute effect of vitamin C on airway hyperresponsiveness, blood sample for vitamin C level and spirometry, methacholine challenge test were done in 17 smokers and 8 nonsmokers, and one hour after oral administration of vitamin C 3 g, blood sample for vitamin C level and spirometry, methacholine challenge test were repeated. To assess chronic effect of vitamin C on airway hyperresponsiveness, after daily administration of vitamin C 1 g for one week in 17 smokers, blood sample for vitamin C level and spirometry, methacholine challenge test were done. To assess role of vitamin C, after oral administration of vitamin C 3 g plus indomethacin 100 mg in 12 of 15 smokers who were reactive to methacholine challenge test, spirometry and methacholine challenge test were done and after oral intake of indomethacin 100 mg in 12 smokers who were reactive to methacholine challenge test, spirometry and methacholine challenge test were repeated. Result: There were no significant differences in whole blood vitamin C levels between smokers($1.17{\pm}0.22$ mg/dL) and nonsmcikers($1.14{\pm}0.19$ mg/dL) (p>0.05). Fifteen of the 17 smokers(88.2%) were reactive to methacholine challenge test and 10 of the 15 smokers who were reactive to methacholine challenge test were less than 8 mg/dL in $PC_{20}FEV-2$, and 7 of the 8 nonsmokers(87.5%) were nonreactive to methacholine challenge test There were significant decrease in bronchial responsiveness after oral administration of vitamin C 3 g in 13 of the 15 smokers who were reactive to methacholine challenge test This significant decrease persisted with maintenance daily administration of 1 g for one week. $PC_{20}FEV-2$ were not correlated to vitamin C levels in smokers. After oral administration of indomethacin 100 mg, significant reduction of bronchial responsiveness that occured after oral administration of vitamin C 3 g in smokers were attenuated. Conclusion: Although there were no significant differences in whole blood vitamin C levels between smokers and nonsmokers. heavy smokers have significant increase in bronchial responsiveness than nonsmokers. This bronchial hyperresponsiveness of heavy smokers can be attenuated by vitamin C supplement. Disappearance of vitamin C effect by indomethacin supplement may suggest that vitamin C exert its effect via alteration of arachidonic acid metabolism.

• Tuberculosis and Respiratory Diseases
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• v.42 no.5
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• pp.646-653
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• 1995

Background: The confirmative diagnosis of pulmonary tuberculosis(Tb) can be made by the isolation of Mycobacterium Tuberculosis(MTb) in the culture of the sputum, respiratory secretions or tissues of the patients, but positive result could not always be obtained in pulmonary Tb cases. Although there are many indirect ways of the diagnosis of Tb, clinicians still experience the difficulty in the diagnosis of Tb because each method has its own limitation. Therefore development of a new diagnostic tool is clinically urgent. It was reported that silica cause some lysosomal enzymes to be released from macrophages in vitro and one of these enzymes is elevated in workers exposed to silica dust and in silicotic subjects. In pulmonary Tb, alveolar macrophages are known to be activated after ingestion of MTb. Activated macrophages can kill MTb through oxygen free radical species and digestive enzymes of lysosome. But if macrophages allow the bacilli to grow intracellularly, the macrophages will die finally and local lesion will enlarge. Then it is assumed that the lysosomal enzymes would be released from the dead macrophages. The goal of this investigation was to determine if there are differences in the plasma activities of lysosomal enzymes, ($\beta$-glucuronidase(GLU) and $\beta$-N-acetyl glucosaminidase(NAG), among the groups of active and inactive pulmonary Tb and healthy control, and to see if there is any possibility that the plasma activity of GLU and NAG can be used as diagnostic indicies of active pulmonary Tb. Methods: The plasma were obtained from 20 patients with bacteriologically proven active pulmonary Tb, 15 persons with inactive Tb and 20 normal controls. In 10 patients with active pulmonary Tb, serial samples after 2 months of anti-Tb medications were obtained. Plasma GLU and NAG activities were measured by the fluorometric methods using 4-methylumbelliferyl substrates. All data are expressed as the mean $\pm$ the standard error of the mean. Results: The activites of GLU and NAG in plasma of the patients with active Tb were $21.52{\pm}3.01$ and $325.4{\pm}23.37$(nmol product/h/ml of plasma), respectively. Those of inactive pulmonary Tb were $24.87{\pm}3.78$, $362.36{\pm}33.92$ and those of healthy control were $25.45{\pm}4.05$, $324.44{\pm}28.66$(nmol product/h/ml of plasma), respectively. There were no significant differences in the plasma activities of both enzymes among 3 groups. The plasma activities of GLU at 2 months after anti-Tb medications were increased($42.18{\pm}5.94$ nmol product/h/ml of plasma) in the patients with active pulmonary Tb compared with that at the diagnosis of Tb(P-value <0.05). Conclusion: The results of the present investigation suggest that the measurement of the plasma activities of GLU and NAG in the patients with active pulmonary Tb could not be a useful method for the diagnosis of active Tb. Further investigation is necessary to define the reasons why the plasma activities of the GLU was increased in the patients with active pulmonary Tb after Tb therapy.

• 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.

• Journal of Chest Surgery
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• v.38 no.2 s.247
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• pp.116-122
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• 2005

Background: Adverse effects of cardiopulmonary bypass can be avoided by 'Off-pump' coronary artery bypass (OPCAB) surgery. Recent studies have reported that OPCAB had the most beneficial impact on patients at highest risk by reducing bypass-related complications. The purpose of this study is to compare the outcome of OPCAB and conventional coronary artery bypass grafting (CCAB) in patients with poor left ventricular (LV) function. Material and Method: From March 1997 to February 2004, seventy five patients with left ventricular ejection fraction (LVEF) of $35\%$ or less underwent isolated coronary artery bypass grafting at our institute. Of these patients, 33 patients underwent OPCAB and 42 underwent CCAB. Preoperative risk factors, operative and postoperative outcomes, including LV functional change, were compared and analysed. Result: Patients undergoing CCAB were more likely to have unstable angina, three vessel disease and acute myocardial infarction among the preoperative factors. OPCAB group had significantly lower mean operation time, less numbers of total distal anastomoses per patient and less numbers of distal anastomoses per patient in the circumflex territory than the CCAB group. There was no difference between the groups in regard to in-hospital mortality $(OPCAB\; 9.1\%\;(n=3)\;Vs.\;CCAB\;9.5\%\;(n=4)),$ intubation time, the length of stay in intensive care unit and in hospital postoperatively. Postoperative complication occurred more in CCAB group but did not show statistical difference. On follow-up echocardiography, OPCAB group showed $9.1\%$ improvement in mean LVEF, 4.3 mm decrease in mean left ventricular end-diastolic dimension (LVEDD) and 4.2 mm decrease in mean left ventricular end-systolic dimension (LVESD). CCAB group showed $11.0\%$ improvement in mean LVEF, 5.1 mm decrease in mean LVEDD and 5.5 mm decrease in mean LVESD. But there was no statistically significant difference between the two groups. Conclusion: This study showed that LV function improves postoperatively in patients with severe ischemic LV dysfunction, but failed to show any difference in the degree of improvement between OPCAB and CCAB. In terms of operative mortality rate and LV functional recovery, the results of OPCAB were as good as those of CCAB in patients with poor LV function. But, OPCAB procedure was advantageous in shortening of operative time and in decrease of complications. We recommend OPCAB as the first surgical option for patients with severe LV dysfunction.