가입비를 부과하는 양면시장에서 플랫폼 수익에 영향을 주는 주요인들에 대한 연구

학위논문 (석사)-- 서울대학교 대학원 : 경영학과, 2014. 2. 오정석.In many of two-sided market studies, network externality has been the most attention receiving variable. Li et al. suggested in their work that if platform does not differentiate itself enough, attempt to increase network externality could actually harm platforms profit. In this work, a model was designed to accommodate buyer side access fee, which was not considered in Li et al.s model. Examining newly constructed model, several implications are derived. There are difference makers in each of optimization casesalso no-difference makers. Moreover access fee differences cause uncertainties that are possible to control with platforms access fees for either seller or buyer. Furthermore the finding of common no-difference maker could free platforms from what these no-difference makers represent. Also application of the results to case of professional SNS shows access fee discount of certain platform could be an unnecessary discount. This paper contribute to two-sided market study by providing hints of where to allocate its resource and where not toalso gives shows how each of variables are related and even interacts (particularly seller side access fee and buyer side access fee). Furthermore, the study verifies result of Li et al.s study and shows their result might be lack of generality.1. Introduction 2. Literature Review 3. Model 4. Analysis and Results 4.1. Optimized to Seller Side Access Fee case one 4.2. Optimized to Seller Side Access Fee case two 4.3. Optimized to Buyer Side Access Fee case one 4.4. Optimized to Buyer Side Access Fee case two 4.5. Summary of Analysis 4.6. Case - Professional Social Network Services 5. Conclusion 5.1 Conclusion 5.2 Limitations and suggestions References Appendix 국문초록Maste

Repetitive short-course hepatic arterial infusion chemotherapy with high-dose 5-fluorouracil and cisplatin in patients with advanced hepatocellular carcinoma

BACKGROUND: Hepatic arterial infusion chemotherapy (HAIC) has often been selected as a therapeutic option for patients with advanced hepatocellular carcinoma (HCC). The objective of the current study was to evaluate the efficacy and safety of repetitive HAIC with high-dose 5-fluorouracil (5-FU) and cisplatin given for 3 days in patients with advanced HCC. METHODS: Between January 2001 and December 2004, a total of 41 patients with unresectable advanced HCC were enrolled. The patients underwent HAIC via the implantable port system with 5-FU (at a dose of 500 mg/m(2) on Days 1-3) and cisplatin (at a dose of 60 mg/m(2) on Day 2) every 4 weeks. Tumor response was assessed at the end of every 3 cycles. RESULTS: The median age of the patients was 53 years and 34 patients (82.9%) had evidence of portal vein thrombosis. In total, 230 cycles of HAIC were administered to the 41 patients, with a median of 6 cycles given (range, 1-14 cycles). Nine patients (22.0%) achieved a partial response and 14 patients (34.1%) had stable disease. The median time to disease progression and overall survival were 7.0 months and 12.0 months, respectively. The overall survival was found to be significantly longer in the successful disease control group (patients with a complete response, partial response, and stable disease) than in the disease progression group (median of 14.0 months vs 6.0 months; P < .001). Adverse reactions were tolerable and successfully managed with conservative treatment. CONCLUSIONS: HAIC with high-dose 5-FU and cisplatin given for 3 days achieved effective and safe results in patients with advanced HCC. Therefore, repetitive short-course HAIC with high-dose 5-FU and cisplatin may be useful as an alternative therapeutic option for patients with advanced HCC.ope

MDM2 and p53 polymorphisms are associated with the development of hepatocellular carcinoma in patients with chronic hepatitis B virus infection

A single-nucleotide polymorphism (SNP) in the promoter region of MDM2, SNP 309, is associated with hepatocellular carcinoma (HCC) in patients with chronic hepatitis C virus infection. The effect of p53 codon 72 polymorphism Arg72Pro on HCC risk remains inconsistent. This study evaluated the association of MDM2 and p53 polymorphisms with the presence and early onset of HCC in Korean patients with chronic hepatitis B virus (HBV) infection. In total, 583 consecutive patients with chronic HBV infection were classified according to the presence (n = 287) or absence (n = 296) of HCC. The MDM2 SNP 309 and p53 Arg72Pro were genotyped using restriction fragment length polymorphism method. The MDM2 G/G and p53 Pro/Pro genotypes were more frequent in HCC group than in non-HCC group (P < 0.001 and P = 0.004, respectively). Multivariate analysis for the presence of HCC revealed that the odds ratio (OR) for MDM2 G/G over T/T was 4.89 (P < 0.001) and that of p53 Pro/Pro over Arg/Arg was 3.03 (P = 0.006). Combined MDM2 G/G and p53 Pro/Pro had a synergistic effect on HCC risk, with an OR of 20.78 (P < 0.001). The mean age of tumor onset in patients with MDM2 G/G genotype was 50.9 years compared with 55.1 with T/T genotype (P = 0.018) and that with p53 Pro/Pro was 49.7 years compared with 52.9 with Arg/Arg (P = 0.040). Thus, MDM2 SNP 309 and p53 Arg72Pro are associated with the early development of HCC in Korean patients with chronic HBV infection.ope

Antifibrotic effects of magnesium lithospermate B on hepatic stellate cells and thioacetamide-induced cirrhotic rats.

Magnesium lithospermate B (MLB) is one of the major active components of Salvia miltiorrhizae. The anti-oxidative effects of Salvia miltiorrhizae have been previously reported. The aim of this study was to investigate the effect of purified MLB on hepatic fibrosis in rats and on the fibrogenic responses in hepatic stellate cells (HSCs). Hepatic fibrosis was induced in rats by intraperitoneal thioacetamide (TAA) injections over a period of 8 or 12 weeks. MLB was orally administered daily by gavage tube. Serum AST and ALT levels in TAA+ MLB group were significantly lower than those in TAA only group at week 8. Hepatic fibrosis was significantly attenuated in TAA+MLB group than in TAA only group at week 8 or 12. Activation of HSCs was also decreased in TAA+MLB group as compared to TAA only group. Hepatic mRNA expression of α-smooth muscle actin (α-SMA), TGF-β1, and collagen α1(I) was significantly decreased in TAA+MLB group as compared to TAA only group. Incubation with HSCs and MLB (>or=100 μM) for up to 48 h showed no cytotoxicity. MLB suppressed PDGF-induced HSC proliferation. MLB inhibited NF-ΚB transcriptional activation and monocyte chemotactic protein 1 (MCP-1) production in HSCs. MLB strongly suppressed H(2)O(2)-induced reactive oxygen species (ROS) generation in HSCs, and MLB inhibited type I collagen secretion in HSCs. We concluded that MLB has potent antifibrotic effect in TAA-treated cirrhotic rats, and inhibits fibrogenic responses in HSCs. These data suggest that MLB has potential as a novel therapy for hepatic fibrosis.ope

Marathon running may induce a temporary bone loss

This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (grant number 2015R1D1A1A09057878

맥진기(脈診機) 제작과 맥파(脈波) 분석

학위논문(석사)--서울대학교 대학원 :과학교육과 물리전공,2000.Maste

Cost-effectiveness analysis of low sulfur oil application for the air pollution abatement

환경관리학과/석사[한글] 産業과 　濟의 高度成長에 따른 産業體와 自動車等의 化石燃料使用增加와 더불어 最近 우리나라 主要都市의 大氣汚染度는 대부분 法的環境基準値를 넘어서 있다. 이에 環境과 大氣汚染에 關聯된 最近의 各種資料를 蒐集分析하여 우리나라에서 가장 效果的이고 實效性있는 大氣汚染防止對策으로 低流黃油對策이 實行되어질 경우 果와 費用에 關해 硏究해 본 結果는 다음과 같다. 1. 現在의 狀態로 全國에서 使用하는 輕油 및 B-C油의 硫黃含流量을 各各 60%씩 減少시킨 低硫黃油로 全量代替하여 供給할 경우 全國의 亞黃酸가스排出量은 約485, 서울市의 亞黃酸가스 排出量은 約40%가 減少하게 될 것으로 推計된다. 2. 서울市에서 前述한 低硫黃油對策을 實行할 경우 80年度의 年平均 亞黃酸가스汚染度였던 0.094ppm은 0.056ppm까지 減少시킬 수 있을 것으로 推計된다. 따라서 法的環境基準値를 推持하기 爲해서는 石炭使用量의 50%를 低硫黃輕油로 代替해야 할 것으로 推計된다. 3. 低硫黃油對策을 實行할 경우 每年 費用增加總額은 83年에 1,425.1億원, 84年에 1,423.9億원, 85年에 1,136億원, 86年에 1,396.9億원이 될 것으로 推算되었다. 特히, 우리나라 亞黃酸가스 全倍出量의 75%가 B-C油로부터 排出되어온 것으로 나타나, 現在 使用되고 있는 高硫黃B-C油의 低硫黃化는 더욱이 시급한 실정이라 하겠다. [영문] Recently, the air pollution in the main cities in Korea is over the legal envitonmental criteria,Especially sulfur dioxide pollution is serious because of growing usage of fossil fuel. About the low sulfur oil usage policy in Korea, the cost effectiveness analysis were performed with the various recent data related to air pollution. The results were as follows. 1. Low sulfur Bunker-C oil (1.6%S), and Light oil (0.4%S) are used instead of light oil (1.0%S) and Bunker-C oil (4.0%S), to reduce sulfur dioxide exhaust in Seoul and whole country at a rate of 40% and 48% respectively. 2. The low sulfur oil application would be conducted in Seoul, the Seoul ambient concentration of SO^^2 in 1980 would be 0.056ppm from 0.094ppm. To maintain an air quality standard of SO^^2 concentration in Seoul city, 25% of coal consumption has to be substituted for city gas or Liquified Natural Gas, or 50% of coal has to be substituted for low sulfur oil. 3. By the low sulfur oil application the annual amounts of cost would be estinated to increase 142.51 billion won in 1983, 142.39 billion won in 1984, 113.6 billion won in 1985, and 139.69 billion won in 1986. Since 75% of total sulfur dioxide exhaust in Korea from high sulfur B-C oil, it is required that convert policy to low sulfur B-C oil urgently.restrictio

혈압파형과 심박동 변이도를 이용한 심혈관 시스템에 관한 연구

Thesis(doctoral)--서울대학교 대학원 :물리학부,2005.Docto

사람 간성상세포주 및 백서에서 Magnesium lithospermate B의 항섬유화 효과

Dept. of Medicine/박사[한글] 간섬유화 현상은 간 조직에서 나타나는 상처치유 과정의 일종으로서 거듭되는 간조직의 손상과 재생과정을 통하여 간경변증이 발생되고 있다. 현재까지 수많은 항섬유화 치료가 시도되었으나 효과적인 항섬유화 약제로 사용되는 물질은 없다. 약초의 일종인 Salvia miltiorrhiza의 추출물은 페놀화합물로 구성되어 있으며 중국에서 혈관계통의 질환 치료에 널리 이용되고 있다. Salvia miltiorrhiza의 주요 성분중의 하나인 magnesium lithospermate B (LAB)는 항산화 효과로 신장보호 성질을 가지고 있다고 알려져 있다. 이에 저자는 사람 간성상세포주 및 백서에서 LAB의 항섬유화 효과를 알아보고자 하였다. 동물 간섬유화 모델은 thioacetamide (TAA) 랫드 모델을 사용하였다. 사람 간성상세포주는 정상 사람 간조직으로부터 간성상세포를 분리한 뒤에 레트로바이러스를 이용하여 불멸화시킨 human telomerase reverse transcriptase (hTERT) 간성상세포주를 사용하였다. 랫드는 각 군당 5마리씩 6개 군으로 분류하였다. 대조군 5마리, LAB투여군 5마리, TAA 투여군 10마리, TAA와 LAB 투여군 10마리로 하여 TAA 투여군 5마리와 TAA 및 LAB 동시 투여군 5마리는 8주에 희생하였으며 나머지는 12주에 희생하였다. 간조직을 Masson's trichrome 염색과 -smooth muscle actin ( -SMA) 면역화학 염색을 시행 후 컴퓨터 이미지 분석을 통하여 염색된 면적을 구하였다. 간 손상 정도를 측정하기 위하여 랫드 희생 시 수집한 혈액에서 aspartate aminotransferase (AST)와 alanine transferase (ALT)를 측정하였다. 역전사효소 중합효소연쇄반응을 이용하여 -SMA, transforming growth factor- (TGF- )와 type I collagen 1의 mRNA 수치를 상대적으로 측정하였다. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT)를 이용하여 LAB의 세포독성 및 세포 증식 억제 효과를 측정하였다. 과산화수소 처리 후 발생하는 세포 내 반응성 산소기 억제 효과를 측정하였으며 tumor necrosis factor- (TNF- )를 처리 후 nuclear factor- B (NF- B)의 전사 활성도의 억제 정도를 측정하였다. 간성상세포에서 분비한 I형 교원질 및 안지오텐신 II에 처리 후 extracellular signal-regulated kinases 1/2 (ERK 1/2)의 표현이 LAB에 의해 억제되는지 측정하였다. 면역화학염색 결과 TAA 단독 투여 군에 비하여 TAA와 LAB를 동시에 투여한 군의 염색된 면적이 유의하게 낮았다. 8주 TAA군에 비하여 8주 TAA와 LAB 동시 투여군에서 AST, ALT 모두 의미 있게 낮은 수치를 보였으나 12주 TAA군과 12주 TAA와 LAB 동시 투여군에서는 의미 있는 차이가 없었다. -SMA, TGF- 와 type I collagen 1의 상대적 mRNA 수치는 TAA군에 비해 TAA와 LAB 동시 투여군에서 유의하게 낮은 결과를 보였다. MTT를 이용한 간성상세포 독성 실험 결과 LAB 40 ?M까지는 세포 독성을 보이지 않았다. PDGF 및 LAB를 동시에 투여한 간성상세포는 PDGF 단독 투여한 세포에 비하여 증식이 억제되었다. 과산화수소로 자극하여 세포내 반응성 산소기를 측정한 결과 LAB로 전 처리한 간성상세포가 전 처리하지 않은 세포에 비하여 반응성 산소기가 의미있게 억제되는 소견을 보였다. TNF- 를 처리하였을 때 간성상세포에서 NF- B의 전사 활성도가 증가하였으며 LAB를 전 처리한 간성상세포에서는 NF- B의 전사 활성도가 의미 있게 감소함을 보였다. Western blot 결과 LAB를 처리한 간성상세포에서 분비한 I형 교원질의 양이 처리하지 않은 세포와 비교하여 적게 나타났다. 안지오텐신 II가 ERK 1/2의 인산화를 유도하였으며 LAB를 전처리한 간성상세포에서는 ERK 1/2의 표현이 감소되었다. LAB는 항산화 작용으로 ERK 경로 및 NF- B 신호전달체계 차단하여 사람 간성상세포 증식 및 교원질 생성을 억제하였으며 TAA로 유도한 랫드 간경변 모델에서 간섬유화 억제를 보였다. 결론적으로 사람 간성상세포주 및 랫드 간경변 모델에서 LAB의 항섬유화 효과를 확인하였다. [영문] Hepatic fibrosis refers to a wound-healing response to a variety of insults, ultimately leading to cirrhosis. Recently, magnesium lithospermate B (LAB), one of the major active components from Salvia miltiorrhizae, has been given attention for its anti-fibrogenic effects. The antifibrotic effect of LAB in an experimental rat model was demonstrated. The aim of this study was to elucidate the antifibrogenic mechanism of LAB. Sprague-Dawley rats were divided into 6 groups: the control group (n = 5), control + LAB group (n = 5), TAA 8-week group (n = 5), TAA + LAB 8-week group (n = 5), TAA 12-week group (n=5) and TAA + LAB 12-week group (n = 5). The serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) were tested. Masson's trichrome stain and α-smooth muscle actin ( -SMA) stain of liver sections were analyzed. The relative levels of mRNA expressions of -SMA, transforming growth factor- (TGF- ) and type I collagen 1 were measured using real-time PCR. The human hepatic stellate cell (HSC) line was used for in vitro analysis. Cell cytotoxicity and proliferation were evaluated. Intracellular reactive oxygen species (ROS) formation was measured using H2DCFDA labeling. Nuclear factor- B (NF- B) transcriptional activation induced by tumor necrosis factor- (TNF- ) was measured using luciferase activity after virus vector transfer. Secreted type I collagen expression and phospho-extracellular signal regulated kinase (ERK) was evaluated using Western blots. LAB attenuated fibrosis in liver sections. The serum levels of AST and ALT were significantly lower in the TAA + LAB 8-week group than in the TAA 8-week group. LAB significantly decreased the mRNA levels of -SMA, TGF- and type I collagen 1. LAB treatment up to 40 ?M did not show any discernable toxicity. Platelet-derived growth factor (PDGF)-induced proliferation of HSCs was suppressed by LAB. H2O2-induced ROS formation in HSCs was decreased by LAB. Western blot demonstrated that LAB decreased type I collagen secretion and phospho-ERK expression in HSCs. In conclusion, the results of this study suggest that LAB may attenuate the activation of human HSCs through antioxidant activity. LAB demonstrated an antifibrogenic effect on TAA-induced cirrhosis in Sprague-Dawley ratsope

단면형상이 불연속적으로 변하는 원형링의 진동에 관한 연구

Thesis (master`s)--서울대학교 대학원 :기계설계학과,2000.Maste