• Title/Summary/Keyword: Outcome analysis

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Clinical Characteristics, Prognostic Factors and Influence of Prophylaxis in Children with Pneumocystis jirovecii Pneumonia (소아 주폐포자충 폐렴의 임상양상, 위험인자 및 예방요법의 효과 연구)

  • Kim, Seohee;Yoo, Reenar;Sung, Hungseop;Lee, Jina
    • Pediatric Infection and Vaccine
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    • v.23 no.1
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    • pp.31-39
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    • 2016
  • Purpose: The aim of this study was to investigate the prognostic factors for Pneumocystis jirovecii pneumonia (PCP) and to evaluate the influence of PCP prophylaxis in pediatric patients. Methods: From January 2002 to April 2015, patients aged <18 years with a diagnosis of confirmed PCP at our institute were reviewed retrospectively. Clinical characteristics and outcomes were compared according to the groups with or without PCP prophylaxis. Risk factors associated with PCP-related death were analyzed by logistic regression analysis. Results: During study period, a total of 24 patients were diagnosed with PCP by immunofluorescence assay and/or PCR. The median age of the patients was 5 years (range, 3 months-18 years) and 23 (96%) had immunocompromised conditions including hematologic disorders with or without hematopoietic stem cell transplantation (n=15), solid organ transplantation (n=4), and primary immune deficiency (n=4). Most common presenting symptoms were tachypnea and cough (92%, each). At the time of diagnosis, 79% (19/24) and 25% (6/24) suffered from respiratory failure and multi-organ dysfunction syndrome (MODS), respectively. Mechanical ventilation was required in 8 (33%) patients and 5 (21%) patients died of PCP. Multivariate analysis showed that MODS at initial presentation was an indicator of poor prognosis (OR, 17.1 [95% CI 1.13-257.67]; P=0.04). Compared to the patients without PCP prophylaxis, the frequency of MODS at diagnosis, need for mechanical ventilation and length of hospital days were significantly less common in the children who received PCP prophylaxis. Conclusions: MODS at presentation was a significant predictor for poor outcome and PCP prophylaxis could alleviate the clinical courses of pediatric PCP. Prospective study will be mandatory to determine the risk factors for development and deterioration of PCP in children.

Clinical Analysis and Surgical Results of Skull Base Meningiomas (뇌기저부 수막종의 임상분석 및 수술성적)

  • Kim, Young Wook;Jung, Shin;Kim, Jae Sung;Lee, Jung Kil;Kim, Tae Sun;Kim, Jae Hyoo;Kim, Soo Han;Kang, Sam Suk;Lee, Je Hyuk
    • Journal of Korean Neurosurgical Society
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    • v.29 no.11
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    • pp.1437-1444
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    • 2000
  • Objectives : Traditionally intracranial meningiomas are regarded as benign and curable tumors. About half of all intracranial meningiomas locate in the skull base region. However, surgical removal of these tumors may be challenging and require special considerations. Here general aspects of skull base meningiomas including clinical presentation, surgical approaches, complications and their recurrence rate are discussed based on our experiences. Methods : A retrospective analysis of 61 consecutive patients with skull base meningioma among 210 patients of meningioma between 1989 and 1998 were done. Results : There were 41 women and 20 men ranging from 13 to 74 years(mean 52 years). These tumors were divided into seven categories according to location : olfactory groove(n=9), sphenoid ridge(n=16), cavernous sinus(n =2), tuberculum sellae(n=8), tentorium(n=13), cerebellopontine angle(n=12), and foramen magnum meningiomas (n=1). Surgical approaches were selected on the basis of the tumor attachment, size and extension on preoperative radiologic findings. Total removal(Simpson grade I and II) was achieved in 50 cases(82%), and subtotal removal (Simpson grade III) in 11 patients(18%). According to WHO classification, there were 52 of cases of benign meningioma( 86%), 6 atypical cases(10%), and 3 malignant cases(5%). The most common postoperative complications were CSF leakage(23.0%) and cranial nerve injury(8.2%). Three patient died related with tumor(one was due to surgical complication and the other two due to recurrence) but three patients died from other systemic causes. Mean follow-up period was 51.7 months after surgery. Recurrence occurred in six patients(10.9%) ; three with tentorial meningioma, two with sphenoid ridge, and one in cerebellopontine angle. Conclusion : With advances in neuroradiology and microsurgical techniques, the surgical outcome of miningiomas has been markedly improved with acceptable morbidity and mortality rates. Overall, our surgical results of skull base meningiomas is comparable to other reports. Therefore, with the appropriate operative strategy and techniques, these tumors can be completely removed and good surgical results can be expected.

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Human Resource Management Policy for University Faculty enhancing University-Industry Cooperation (산업현장친화형 대학교원 인사제도의 방향)

  • Jang, Seungkwon;Choi, Jong-In;Hong, Kilpyo
    • Asia-Pacific Journal of Business Venturing and Entrepreneurship
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    • v.8 no.4
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    • pp.95-109
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    • 2013
  • The practices and processes of HRM (Human Resource Management) for university faculty in Korea depend heavily on assessment of research and teaching rather than the UIC (University-Industry Cooperation) performance. In this regard, HRM of Korean universities is said to be far distant from UIC. Although policy initiatives by the Korean government, notably the MoE (Ministry of Education) have implemented in most universities, the desirable level of UIC could not be achieved yet. Moreover, the very notion of 'university' in Korea is much more to do with 'pure' education and research institution than with 'applied' and 'vocational' purpose. Considering upon HRM practices and organizational culture, for enhancing UIC in Korea, the government's policy should be linked to alter deep-rooted university culture. So the aims of the research are to describe the current state of HRM in Korean and foreign universities; to find out the critical factors of UIC in Korean universities; to analyze the gaps between university research and industrial commercialization based on a conceptual framework, the 'valley of the death'; and to recommend HRM policies fostering UIC for the MoE. For achieving these objectives, we deploy multiple methodologies, namely, in-depth interview, literature survey, and statistical data analysis with regard to UIC. Analyzing the data we have collected, the present research sheds light on all aspects of HRM processes and UICs. And the main policy implication is restricted to the Korean universities, even if we have collected and analyzed foreign universities, notably universities in the USA. The research findings are mainly two folds. Firstly, the HRM practices among Korean universities are very similar due to the legally institutionalized framework and the government's regulations. Secondly, the difficulties of UIC can be explained by notion of the 'valley of death' ways in which both parties of university and industry are looking for different purposes and directions. In order to overcome the gap in the valley of death, the HRM policy is better to be considered as leverage. Finally, the policy recommendations are as follows. Firstly, various kinds of UIC programs are able to enhance the performances of not only UIC, but also education and research outcome. Secondly, fostering organizational climate and culture for UIC, employing various UIC programs, and hiring industry-experienced faculty are all very important for enhancing the high performance of university. We recommend the HRM policies fostering UIC by means of indirect way rather than funding directly for university. The HRM policy of indirect support is more likely to have long-term effectiveness while the government's direct intervention to UIC will have likely short-term effectiveness as the previous policy initiatives have shown. The MEST's policy means of indirect support might vary from financial incentives to the universities practicing HRM for UIC voluntarily, to information disclosure for UIC. The benefits of the present research can be found in suggesting HRM policy for UIC, highlighting the significance of industry-experienced faculty for UIC, and providing statistical analysis and evidences of UIC in Korean universities.

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The Influence of Online Social Networking on Individual Virtual Competence and Task Performance in Organizations (온라인 네트워킹 활동이 가상협업 역량 및 업무성과에 미치는 영향)

  • Suh, A-Young;Shin, Kyung-Shik
    • Asia pacific journal of information systems
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    • v.22 no.2
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    • pp.39-69
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    • 2012
  • With the advent of communication technologies including electronic collaborative tools and conferencing systems provided over the Internet, virtual collaboration is becoming increasingly common in organizations. Virtual collaboration refers to an environment in which the people working together are interdependent in their tasks, share responsibility for outcomes, are geographically dispersed, and rely on mediated rather than face-to face, communication to produce an outcome. Research suggests that new sets of individual skill, knowledge, and ability (SKAs) are required to perform effectively in today's virtualized workplace, which is labeled as individual virtual competence. It is also argued that use of online social networking sites may influence not only individuals' daily lives but also their capability to manage their work-related relationships in organizations, which in turn leads to better performance. The existing research regarding (1) the relationship between virtual competence and task performance and (2) the relationship between online networking and task performance has been conducted based on different theoretical perspectives so that little is known about how online social networking and virtual competence interplay to predict individuals' task performance. To fill this gap, this study raises the following research questions: (1) What is the individual virtual competence required for better adjustment to the virtual collaboration environment? (2) How does online networking via diverse social network service sites influence individuals' task performance in organizations? (3) How do the joint effects of individual virtual competence and online networking influence task performance? To address these research questions, we first draw on the prior literature and derive four dimensions of individual virtual competence that are related with an individual's self-concept, knowledge and ability. Computer self-efficacy is defined as the extent to which an individual beliefs in his or her ability to use computer technology broadly. Remotework self-efficacy is defined as the extent to which an individual beliefs in his or her ability to work and perform joint tasks with others in virtual settings. Virtual media skill is defined as the degree of confidence of individuals to function in their work role without face-to-face interactions. Virtual social skill is an individual's skill level in using technologies to communicate in virtual settings to their full potential. It should be noted that the concept of virtual social skill is different from the self-efficacy and captures an individual's cognition-based ability to build social relationships with others in virtual settings. Next, we discuss how online networking influences both individual virtual competence and task performance based on the social network theory and the social learning theory. We argue that online networking may enhance individuals' capability in expanding their social networks with low costs. We also argue that online networking may enable individuals to learn the necessary skills regarding how they use technological functions, communicate with others, and share information and make social relations using the technical functions provided by electronic media, consequently increasing individual virtual competence. To examine the relationships among online networking, virtual competence, and task performance, we developed research models (the mediation, interaction, and additive models, respectively) by integrating the social network theory and the social learning theory. Using data from 112 employees of a virtualized company, we tested the proposed research models. The results of analysis partly support the mediation model in that online social networking positively influences individuals' computer self-efficacy, virtual social skill, and virtual media skill, which are key predictors of individuals' task performance. Furthermore, the results of the analysis partly support the interaction model in that the level of remotework self-efficacy moderates the relationship between online social networking and task performance. The results paint a picture of people adjusting to virtual collaboration that constrains and enables their task performance. This study contributes to research and practice. First, we suggest a shift of research focus to the individual level when examining virtual phenomena and theorize that online social networking can enhance individual virtual competence in some aspects. Second, we replicate and advance the prior competence literature by linking each component of virtual competence and objective task performance. The results of this study provide useful insights into how human resource responsibilities assess employees' weakness and strength when they organize virtualized groups or projects. Furthermore, it provides managers with insights into the kinds of development or training programs that they can engage in with their employees to advance their ability to undertake virtual work.

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Preliminary Environmental Impact Assessments on Fish Compositions and the Ecological Health of Jeokbyeok River on the Road Construction of Muju-Geumsan Region (무주-금산간 도로건설에 따른 적벽강의 어류 종 조성 분석 및 생태건강도 사전환경성평가)

  • Lee, Sang-Jae;Park, Hee-Sung;An, Kwang-Guk
    • Journal of Environmental Impact Assessment
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    • v.26 no.1
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    • pp.27-43
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    • 2017
  • The objectives of the study were to evaluate fish compositions, endangered species, community structure, physical habitat, and general water quality for a preliminary environmental impact assessment of Jeokbyeok River on the road construction between two regions. Total number of species and total number of individuals, based on CPUE, were 23 and 1186, respectively. The endangered species (I, II) as the legal protection species were Pseudopungtungia nigra (79 samples) Gobiobotia brevibarba) (5) Gobiobotia macrocephala (2), indicating a requiring of endangered species conservation. In the meantime, exotic species and ecological disturbing species such as Micropterus salmoides and Lepomis macrochirus, were not present, indicating a well conserved area. According to fish community analysis, values of species diversity index were high (range: 0.788 - 1.030), and the dominance index were low (range: 0.097 - 0.183), indicating that the fish community in this area was maintained well without high dominacne by specific species. Also, fish analysis on tolerance guilds and trophic guilds showed that the proportions of sensitive species were largely exceeded the proportions of the tolerant species, while the proportions of insectivore species were largely exceeded the proportions of the omnivore species. This outcome suggests that the ecosystem was well maintained in terms of tolerance and trophic compositions (food chain). Ecological health, based on the multi-metric fish model of Fish Assessment Integrity (FAI), reflected those fish conditions. In other words, values of FAI model averaged 82.4, which means a "good condition" in the criteria of ecological health by the Minstry of Environment, Korea. In addition, general water quality and physical habitat analyses showed that the system was in good condition. Under these conditions, if the road constructions between the two regions happen in the future, inorganic suspended solids may increase in the waterbody, and this may result in indirect or direct influences on the physical habitats and food chain as well as fish compositions, so the ecological protections and prevention strategy from the soil erosion are required in the system.

A Study on the Persons Enjoying the Landscape of Daegodea in Hamyang and Space Hegemony through Analysis of Poetry and Letters Carved on the Rocks (시문과 바위글씨로 본 함양 대고대(大孤臺)의 경관 향유자와 장소패권(場所覇權))

  • Rho, Jae-Hyun;Lee, Jung-Han
    • Journal of the Korean Institute of Traditional Landscape Architecture
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    • v.32 no.1
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    • pp.10-21
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    • 2014
  • This study focuses on the landscape of Daegodae(大孤臺), a prominent rock placed at the side of Namgae Stream in Hamyang, and the person who enjoy the landscape. Through the analysis of the letters such as names carved on the rocks based on ancient poetry and stone walls, the study examines the characteristics of the landscape and the space of Daegodae and the phase of hegemony to enjoy the landscape and space. The result of this study is as follow.2) There are 5 Seowon(書院: lecture halls) nearby Daegodae identified in the ancient map has 5 auditoriums nearby, and three-dimensional volume and eccentricity of the Daegodae is impressive. Daegodae, named by Noh Jin(1518~1578) in 16th century, was used in a variety of ways, including viewing, game, recreation, and meeting, by the staff of the lecture halls including Namgae Seowon(南溪書院), as a result of analyzing the ancient document Go-dae-il-Loc(孤臺日錄) written by Jung Kyung-Woon(鄭慶雲: 1556~?). The structure of Daegodae is that there is Chunggeunchung(淸近亭) on the rock face of the top and Sanangjae(山仰齋) to the west around the memorial stone for Yang Hee(梁喜: 1515~1581). The upper part of the foundation of Daegodae with 11m high and $10m^2$ wide to the east and west was widely used for lecturing and poetry reading. To the north and west of the foundation were the writing of Kim Jeong-Hee(金正喜: 1786~1856) with the words 'Seoksong Chusa(石松 秋史)' carved on the rock and the remains of a dead tree that is presumed to have been called as 'Seoksong'. They are the landscapes that further enhance the history and authenticity of this place. The two kinds of letters carved on the rock 'Daegodae Gaeeunseo(大高臺 介隱書)' and 'Mukheon JungGeunSang(鄭近相: 1893~1934)' were recorded each by Jung Jae-Gi(1811~1879) and his grandson Jung Geun-Sang, which are, as the outcome of exclusive space possession and space hegemony, the signatures indicating that they were the persons who enjoyed this place during the late Joseon and Japanese colonial era. In other words, Daegodae had some implied meaning of preoccupancy of the place as Gujolyangseonsengjangguso since the middle of Joseon, and the place was passed down as a buddhism lecturing and memorial venue called "Dungbukganghoiso Cheonryungjaeseonhyunjangguso" after going through the space hegemony of Jung Jae-Gi and Jung Geun-Sang during the late Joseon and Japanese colonial era each, Nevertheless, a number of letters carved on the rock identified also imply that 'Hadong Jung(河東鄭氏)' and 'Pungcheon Noh(豊川盧氏)' were those who enjoyed the landscape of Daegodae and the center of the space hegemony. The "letters carved on the rock of Daegudae" is another case of cultural landscape and traditional gardening space that serves as the representation of the will of enjoying the landscape in this place and the history of space hegemony.

Clinicopathologic Characteristics and Prognoses for Multicentric Occurrence and Intrahepatic Metastasis in Synchronous Multinodular Hepatocellular Carcinoma Patients

  • Li, Shi-Lai;Su, Ming;Peng, Tao;Xiao, Kai-Yin;Shang, Li-Ming;Xu, Bang-Hao;Su, Zhi-Xiong;Ye, Xin-Ping;Peng, Ning;Qin, Quan-Lin;Chen, De-Feng;Chen, Jie;Li, Le-Qun
    • Asian Pacific Journal of Cancer Prevention
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    • v.14 no.1
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    • pp.217-223
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    • 2013
  • Background: Hepatocellular carcinoma (HCC) is one of the most common cancers worldwide, and the outcomes for patients are still poor. It is important to determine the original type of synchronous multinodular HCC for preoperative assessment and the choice of treatment therapy as well as for the prediction of prognosis after treatment. Aims: To analyze clinicopathologic characteristics and prognoses in patients with multicentric occurrence (MO) and intrahepatic metastasis (IM) of synchronous multinodular hepatocellular carcinoma (HCC). Methods: The study group comprised 42 multinodular HCC patients with a total of 112 nodules. The control group comprised 20 HCC patients with 16 single nodular HCC cases and 4 HCC cases with a portal vein tumor emboli. The mitochondrial DNA (mtDNA) D-loop region was sequenced, and the patients of the study group were categorized as MO or IM based on the sequence variations. Univariate and multivariate analyses were used to determine the important clinicopathologic characteristics in the two groups. Results: In the study group, 20 cases were categorized as MO, and 22 as IM, whereas all 20 cases in the control group were characterized as IM. Several factors significantly differed between the IM and MO patients, including hepatitis B e antigen (HBeAg), cumulative tumor size, tumor nodule location, cirrhosis, portal vein and/or microvascular tumor embolus and the histological grade of the primary nodule. Multivariate analysis further demonstrated that cirrhosis and portal vein and/or microvascular tumor thrombus were independent factors differentiating between IM and MO patients. The tumor-free survival time of the MO subjects was significantly longer than that of the IM subjects ($25.7{\pm}4.8$ months vs. $8.9{\pm}3.1$ months, p=0.017). Similarly, the overall survival time of the MO subjects was longer ($31.6{\pm}5.3$ months vs. $15.4{\pm}3.4$ months, p=0.024). The multivariate analysis further demonstrated that the original type (p=0.035) and Child-Pugh grade (p<0.001) were independent predictors of tumor-free survival time. Cirrhosis (p=0.011), original type (p=0.034) and Child-Pugh grade (p<0.001) were independent predictors of overall survival time. Conclusions: HBeAg, cumulative tumor size, tumor nodule location, cirrhosis, portal vein and/or microvascular tumor embolus and histological grade of the primary nodule are important factors for differentiating IM and MO. MO HCC patients might have a favorable outcome compared with IM patients.

Clinical Analysis of the Acute Respiratory Distress Syndrome after Thoracotomy (개흉술 후 발생하는 급성 호흡부전 증후군에 대한 임상적 고찰)

  • 이용직;박승일;제형곤;박창률;김동관;주석중;김용희;손광현
    • Journal of Chest Surgery
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    • v.35 no.9
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    • pp.653-658
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    • 2002
  • The cause and clinical course of the postoperative ARDS is, as of yet, not very well understood. The current study is a review of our experience on patients with ARDS after thoracotomy. Material and Method: Between Jan. 1996 to Aug. 2001, a retrospective analysis was conducted on 32 post-thoracotomy ARDS patients among 4018 patients receiving thoracotomy inclusive of thoracoscopic surgery. Result: The incidence of ARDS after pneumonectomy cases was 5.3%(13/245), 1.3% after lobectomy(9/ 710), and 4.4% after esophageal surgery(10/226). Of the 32 ARDS patients, 31 had malignant disease. The remaining 1 patient had aspergillosis. In the majority, the cause of ARDS was unknown. The average onset was on the 7.4th postoperative day. In 10 cases, the initial lesion was in the right lower lung field(31.2%), in the left lower lung field in 9(28.1%), and in both lower lung fields in 12(37.5%) cases. In all, the initial lesion was in the lower lung fields in 96.9% of the cases(31/32). There was a significant relationship between the development of ARDS and intraoperative I/O balance. The overall mortality rate was 65.6%(21/32). In the earlier period of the study(1996-Jun, 1998) the mortality rate was 100%, but in the latter period(July, 1998-Aug, 2001) it was significantly reduced to 47.6%: Conclusion: The current data showed a higher incidence of postoperative ARDS in patients with malignant disease and in those receiving extensive lymph node dissection with either lobectomy or pneumonectomy, and also in patients receiving esophageal surgery. In addition, introperative fluid overload was also associated with an increased incidence of ARDS. Treatment outcome could be improved with prone positioning and NO gas inhalation.

Surgical Option for Sufficient Safety Margine in Locally Advanced Type II Cardia Cancer - Left Colon Interposition (국소 진행된 Type II 분문부 선암의 절제연 확보를 위한 수술 방법: 좌측 대장 간치술)

  • Yoon, Ho Young;Kim, Hyoung-Il;Lee, Sang Hoon;Kim, Choong Bai
    • Journal of Gastric Cancer
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    • v.8 no.2
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    • pp.97-103
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    • 2008
  • Purpose: Radical surgery is the standard therapy for patients with resectable cardia cancer. In the case of type II disease with esophageal invasion, a transhiatal extended radical total gastrectomy is needed or a gastroesophagectomy through an abdomino-thoracotomy, depending on the extent of the esophageal invasion. We analyzed the indications and outcome of left colon interposition as an esophageal substitution. Materials and Methods: Between 1 January 1994 and 31 December 2006, 10 patients underwent left colon interposition after gastroesophagectomy through an abdomino-thoracotomy or the tanshiatal approach for type II cardia cancer at the Department of surgery, Yonsei University College of Medicine. The outcomes of these patients were reviewed and compared, with those who underwent a Roux-en-Y, by gender and age matched analysis, retrospectively. Results: There were nine males and one female with a mean age of 52.5 (range, 16~72). The operation time was $449.00{\pm}87.39minutes$. The mean distance between the proximal resection margin and the cancer was $6.56{\pm}3.65cm$; the maximum size of the tumor was $9.90{\pm}3.97cm$. These measures differed significantly from patients who underwent Roux-en-Y. The patients had a double primary cancer in the cardia and esophagus. There were no events of colon necrosis. However, a pneumothorax occurred in one patient (10%) and a proximal anastomotic stricture occurred in one patient. There were no reports of heartburn, regurgitation, thoracic or epigastric fullness, and one patient even gained weight, 16 kg. Conclusion: Colon interposition after esophagogastrectomy was safe and effective and should be considered as an additional surgical option for locally advanced type II cardia cancer patients with esophageal invasion.

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Technical Efficiency in Korea: Interindustry Determinants and Dynamic Stability (기술적(技術的) 효율성(效率性)의 결정요인(決定要因)과 동태적(動態的) 변화(變化))

  • Yoo, Seong-min
    • KDI Journal of Economic Policy
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    • v.12 no.4
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    • pp.21-46
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    • 1990
  • This paper, a sequel to Yoo and Lee (1990), attempts to investigate the interindustry determinants of technical efficiency in Korea's manufacturing industries, and also to conduct an exploratory analysis on the stability of technical efficiency over time. The hypotheses set forth in this paper are most found in the existing literature on technical efficiency. They are, however, revised and shed a new light upon, whenever possible, to accommodate any Korea-specific conditions. The set of regressors used in the cross-sectional analysis are chosen and the hypotheses are posed in such a way that our result can be made comparable to those of similar studies conducted for the U.S. and Japan by Caves and Barton (1990) and Uekusa and Torii (1987), respectively. It is interesting to observe a certain degree of similarity as well as differentiation between the cross-section evidence on Korea's manufacturing industries and that on the U.S. and Japanese industries. As for the similarities, we can find positive and significant effects on technical efficiency of relative size of production and the extent of specialization in production, and negative and significant effect of the variations in capital-labor ratio within industries. The curvature influence of concentration ratio on technical efficiency is also confirmed in the Korean case. There are differences, too. We cannot find any significant effects of capital vintage, R&D and foreign competition on technical efficiency, all of which were shown to be robust determinants of technical efficiency in the U.S. case. We note, however, that the variables measuring capital vintage effect, R&D and the degree of foreign competition in Korean markets are suspected to suffer from serious measurement errors incurred in data collection and/or conversion of industrial classification system into the KSIC (Korea Standard Industrial Classification) system. Thus, we are reluctant to accept the findings on the effects of these variables as definitive conclusions on Korea's industrial organization. Another finding that interests us is that the cross-industry evidence becomes consistently strong when we use the efficiency estimates based on gross output instead of value added, which provides us with an ex post empirical criterion to choose an output measure between the two in estimating the production frontier. We also conduct exploratory analyses on the stability of the estimates of technical efficiency in Korea's manufacturing industries. Though the method of testing stability employed in this paper is never a complete one, we cannot find strong evidence that our efficiency estimates are stable over time. The outcome is both surprising and disappointing. We can also show that the instability of technical efficiency over time is partly explained by the way we constructed our measures of technical efficiency. To the extent that our efficiency estimates depend on the shape of the empirical distribution of plants in the input-output space, any movements of the production frontier over time are not reflected in the estimates, and possibilities exist of associating a higher level of technical efficiency with a downward movement of the production frontier over time, and so on. Thus, we find that efficiency measures that take into account not only the distributional changes, but also the shifts of the production frontier over time, increase the extent of stability, and are more appropriate for use in a dynamic context. The remaining portion of the instability of technical efficiency over time is not explained satisfactorily in this paper, and future research should address this question.

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