국제정치적 갈등이 남북한 경제에 미치는 영향: 주식 시장과 무역에 대한 분석

학위논문(박사)--서울대학교 대학원 :사회과학대학 경제학부,2020. 2. 김병연.본 논문은 국제정치적 갈등의 경제적 영향에 대해 남북한의 사례를 중심으로 살펴본다. 특히 북한 관련 리스크가 남한의 주식 시장에 미치는 영향과 경제 제재가 북한의 무역에 미치는 영향에 주목하였다. 전체 논문은 개별적인 소주제를 다루는 세 편의 실증 연구로 구성된다. 첫 번째 장에서는 남한의 기업 주가 수익률이 북한 리스크에 어떻게 반응하는지 분석한다. 이를 위해 남한 언론의 북한 관련 보도 자료를 사용하여 월별 북한 리스크 지수를 작성하였다. 이 지수는 남북 관계의 긴장이 확대되거나 완화되는 경우 언론보도에 등장할 것으로 기대되는 키워드를 포함한 기사의 빈도수를 바탕으로 산출된다. 1999~2018년의 언론 보도자료를 분석한 결과, 북한 발 리스크는 핵/미사일 실험, 군사도발 등 이벤트 시점에 급증하며, 반대로 정상회담, 6자 회담 등 대화의 시기에는 감소하는 것으로 나타났다. 기업 주가 수익률을 종속변수로 한 회귀 분석에서는 국내 투자자의 주식 보유 비율이 높은 기업일수록, 자산 규모가 크고 고정자산의 비중이 높은 기업일수록, 남북경협에 관여한 경험이 있는 기업일수록 북한 관련 리스크에 민감하게 반응하는 것으로 나타났다. 두 번째 장에서는 북한에 부과된 주요 경제 제재가 무역에 준 영향을 무역의 질적 측면을 중심으로 분석한다. 우선 1998~2018년의 북한-중국 간 무역을 외연적 확장 수준(extensive margin), 상대 가격(relative unit price), 물량(quantity)으로 분해하고, 이 중 무역의 질적 측면으로 볼 수 있는 외연적 확장 수준과 상대 가격 지수의 변화에 주목하였다. 이를 통해, 북한의 대중 수출이 지난 20년간 양적으로 성장하였을 뿐 질적으로는 정체되어 있거나 오히려 후퇴했다는 사실을 확인하였다. 회귀분석에서는 북한의 무역을 직접적으로 타격하고자 한 한국과 일본의 독자 제재 및 2017년 UN안보리에서 결의된 다자 제재를 핵심 설명 변수로 설정하였고, 분석 방법으로는 전기 종속 변수가 포함된 동적 패널 모형(dynamic panel model)을 사용하였다. 추정 결과, 2017년 UN의 제재가 북한의 대중 수출에서 품목의 외연적 확장 수준을 축소 시킨 것으로 나타났다. 또한 2003년 일본의 제재는 중국 수입 시장에서 북한 생산품의 상대 가격을 유의하게 하락시킨 것으로 추정되었다. 추가적인 회귀분석에 따르면, 이러한 상대 가격 하락은 북-중 간 가격 협상력의 차이에서 기인한다. 이 연구 결과는 북한에 대한 무역 제재가 다른 주요 교역국과의 거래 관계를 차단하고 중국에 대한 의존도를 지나치게 높이면서 암묵적 비용을 발생시키고 있음을 시사한다. 마지막 장에서는 남한의 5.24 조치를 회피하기 위한 북-중 간의 우회무역 규모를 추정하였다. 이 연구는 중국의 기업-품목 단위의 자료를 사용하여 현재까지 북-중 무역에 대한 연구 중 가장 미시적 수준의 실증분석 결과를 제시한다. 분석 방법은 이중 차분법(difference-in-difference estimation)을 사용하였으며, 대 남한 수출과 대 북한 수입이 동시에 발생한 기업-품목들을 처치그룹으로 설정하여 2010년 전후의 변화를 추정하였다. 분석 결과, 북한의 중국을 경유한 남한으로의 간접 수출은 2010년 5.24 조치 이후 유의하게 증가한 것으로 나타났다. 산업별로 나누어 보면, 이러한 우회 무역은 주로 의류 임가공 부문에 집중되어 있으며 그 규모는 제재 이후 북한의 대남 직접 수출 감소분의 25%에 달하는 것으로 추정되었다.This dissertation investigates the economic impacts of international conflict, focusing on the cases of the two Koreas. Specifically, it examines the effects of North Korea-related risks on the South Korean stock market and economic sanctions on North Korea's foreign trade. It consists of three empirical studies covering subtopics. The first chapter analyzes how South Korean stock returns respond to North Korea-related risk. To do this, a monthly index for geopolitical risk from North Korea is constructed using South Korean media coverage database. The index is based on the frequency of articles containing keywords that are likely to appear in the media when inter-Korean tensions escalate or ease. Analysis of the media coverage from 1999 to 2018 show that the geopolitical risk index sharply increases in the occurrences of nuclear tests, missile launches, and military confrontations, while decreases significantly at around the times of summit meetings and multilateral talks. In the regression analysis, it is found that geopolitical risk related to North Korea has more negative effects on stock returns of firms with a higher share of domestic investors, larger assets and a higher proportion of fixed assets. It is also found that stock prices of companies involved in inter-Korean economic cooperation exhibit a more sensitive response to the North Korea risk. Chapter Ⅱ explores the impact of economic sanctions on North Koreas foreign trade, focusing on the quality of trade. It decomposes the trade between North Korea and China into the extensive margin, relative unit price and quantity, over the periods 1998-2018. Then it estimates sanction-induced changes in the former two elements of North Koreas export to China. The decomposition results show that the growth of North Koreas export to China is mostly attributed to the growth in quantity rather than quality. In the regression analysis, sanctions imposed by South Korea, Japan and the United Nations Security Council (UNSC) are used as key treatments. It is found that the UN sanctions in 2017 reduce the extensive margin in North Korean exports, and Japanese sanctions in 2003 have lowered the relative prices of North Korean products in the Chinese import market. The price impacts of sanctions are found to be associated with the bargaining power of China over North Korea. The findings suggest that trade sanctions against North Korea have created implicit costs by preventing North Korea from trading with alternative partners and increasing reliance on China. The last chapter estimates the size of the transit trade between North Korea and China to circumvent the sanctions imposed by South Korea. It exploits firm-product level variations in Chinese trade data to present micro evidence of the sanction-bypassing trade. Specifically, the transit trade is identified only when a firm import a product from North Korea and export the same product to South Korea in the same period. The difference-in-difference estimation results show that indirect exports from North Korea to South Korea via China are increased significantly by the 5.24 measures in 2010. The increase in North Koreas indirect export of apparels, in particular, accounts for a 25% of the decrease in North Korea's direct exports to South Korea.Introduction 1 Chapter Ⅰ. Geopolitical Risk from North Korea and Stock Market Reaction 4 1. Introduction 4 2. Related Literature 6 2.1. News-based Uncertainty Index 6 2.2. The Effects of Geopolitical Risk from North Korea 7 3. Measuring Geopolitical Risk from North Korea 7 3.1. Definition and Scope of Geopolitical Risk 7 3.2. Data and Methodology 9 3.3. Evaluating the GPRNK Index 12 4. Geopolitical Risk and Firm-level Stock Returns 20 4.1. Empirical Framework 20 4.2. Data and Descriptive Statistics 23 4.3. Baseline Results 26 4.4. Robustness Check 32 5. Conclusion 40 Chapter Ⅱ. Decomposing North Koreas Trade with China and Revisiting Sanction Effects 41 1. Introduction 41 2. Decomposing North Koreas Trade with China 46 2.1. Data 47 2.2. Methodology 50 2.3. Decomposition Results 52 3. Panel Regression Analysis 59 3.1. Empirical Framework 59 3.2. Baseline Results 63 3.3. Possible Channels 66 3.4. Robustness Check 71 4. Conclusion 73 Chapter Ⅲ. The Role of Chinese firms in Bypassing Sanctions on North Korea 75 1. Introduction 75 2. Data 78 2.1. Chinese Custom Trade Data 78 2.2. Stylized Facts 81 3. Empirical Strategy 83 4. Regression Results 86 4.1. North Koreas Indirect Exports via China 86 4.2. The Effects of Sanctions on the Indirect Exports 90 5. Conclusion 93 Concluding Remarks 95 References 98 Appendices 107 A1. Supplementary Materials for Chapter 1 107 A2. Supplementary Materials for Chapter Ⅱ 117 A3. Supplementary Materials for Chapter Ⅲ 121Docto

리만다양체 상의 비모수적 차원축소방법론

학위논문(박사) -- 서울대학교대학원 : 자연과학대학 통계학과, 2022. 8. 오희석.Over the decades, parametric dimension reduction methods have been actively developed for non-Euclidean data analysis. Examples include Fletcher et al., 2004; Huckemann et al., 2010; Jung et al., 2011; Jung et al., 2012; Zhang et al., 2013. Sometimes the methods are not enough to capture the structure of data. This dissertation presents newly developed nonparametric dimension reductions for data observed on manifold, resulting in more flexible fits. More precisely, the main focus is on the generalizations of principal curves into Riemannian manifold. The principal curve is considered as a nonlinear generalization of principal component analysis (PCA). The dissertation consists of four main parts as follows. First, the approach given in Chapter 3 lie in the same lines of Hastie (1984) and Hastie and Stuetzle (1989) that introduced the definition of original principal curve on Euclidean space. The main contributions of this study can be summarized as follows: (a) We propose both extrinsic and intrinsic approaches to form principal curves on spheres. (b) We establish the stationarity of the proposed principal curves on spheres. (c) In extensive numerical studies, we show the usefulness of the proposed method through real seismological data and real Human motion capture data as well as simulated data on 2-sphere, 4-sphere. Secondly, As one of further work in the previous approach, a robust nonparametric dimension reduction is proposed. To this ends, absolute loss and Huber loss are used rather than L2 loss. The contributions of Chapter 4 can be summarized as follows: (a) We study robust principal curves on spheres that are resistant to outliers. Specifically, we propose absolute-type and Huber-type principal curves, which go through the median of data, to robustify the principal curves for a set of data which may contain outliers. (b) For a theoretical aspect, the stationarity of the robust principal curves is investigated. (c) We provide practical algorithms for implementing the proposed robust principal curves, which are computationally feasible and more convenient to implement. Thirdly, An R package 'spherepc' comprehensively providing dimension reduction methods on a sphere is introduced with details for possible reproducible research. To the best of our knowledge, no available R packages offer the methods of dimension reduction and principal curves on a sphere. The existing R packages providing principal curves, such as 'princurve' and 'LPCM', are available only on Euclidean space. In addition, most nonparametric dimension reduction methods on manifold involve somewhat complex intrinsic optimizations. The proposed R package 'spherepc' provides the state-of-the-art principal curve technique on the sphere and comprehensively collects and implements the existing techniques. Lastly, for an effective initial estimate of complex structured data on manifold, local principal geodesics are first provided and the method is applied to various simulated and real seismological data. For variance stabilization and theoretical investigations for the procedure, nextly, the focus is on the generalization of Kégl (1999); Kégl et al., (2000), which provided the new definition of principal curve on Euclidean space, into generic Riemannian manifolds. Theories including consistency and convergence rate of the procedure by means of empirical risk minimization principle, are further established on generic Riemannian manifolds. The consequences on the real data analysis and simulation study show the promising characteristics of the proposed approach.본 학위 논문은 다양체 자료의 변동성을 더욱 효과적으로 찾아내기 위해, 다양체 자료의 새로운 비모수적 차원축소방법론을 제시하였다. 구체적으로, 주곡선(principal curves) 방법을 일반적인 다양체 공간으로 확장하는 것이 주요 연구 주제이다. 주곡선은 주성분분석(PCA)의 비선형적 확장 중 하나이며, 본 학위논문은 크게 네 가지의 주제로 이루어져 있다. 첫 번째로, Hastie (1984), Hastie and Stuetzle (1989}의 방법을 임의의 차원의 구면으로 표준적인 방식으로 확장한다. 이 연구 주제의 공헌은 다음과 같다. (a) 임의의 차원의 구면에서 내재적, 외재적인 방식의 주곡선 방법을 각각 제안한다. (b) 본 방법의 이론적 성질(정상성)을 규명한다. (c) 지질학적 자료 및 인간 움직임 자료 등의 실제 자료와 2차원, 4차원 구면위의 시뮬레이션 자료에 본 방법을 적용하여, 그 유용성을 보인다. 두 번째로, 첫 번째 주제의 후속 연구 중 하나로서, 두꺼운 꼬리 분포를 가지는 자료에 대하여 강건한 비모수적 차원축소 방법을 제안한다. 이를 위해, L2 손실함수 대신에 L1 및 휴버(Huber) 손실함수를 활용한다. 이 연구 주제의 공헌은 다음과 같다. (a) 이상치에 민감하지 않은 강건화주곡선(robust principal curves)을 정의한다. 구체적으로, 자료의 기하적 중심점을 지나는 L1 및 휴버 손실함수에 대응되는 새로운 주곡선을 제안한다. (b) 이론적인 측면에서, 강건화주곡선의 정상성을 규명한다. (c) 강건화주곡선을 구현하기 위해 계산이 빠른 실용적인 알고리즘을 제안한다. 세 번째로, 기존의 차원축소방법 및 본 방법론을 제공하는 R 패키지를 구현하였으며 이를 다양한 예제 및 설명과 함께 소개한다. 본 방법론의 강점은 다양체 위에서의 복잡한 최적화 방정식을 풀지않고, 직관적인 방식으로 구현 가능하다는 점이다. R 패키지로 구현되어 제공된다는 점이 이를 방증하며, 본 학위 논문의 연구를 재현가능하게 만든다. 마지막으로, 보다 복잡한 구조를 가지는 다양체 자료의 구조를 추정하기위해, 국소주측지선분석(local principal geodesics) 방법을 우선 제안한다. 이 방법을 실제 지질학 자료 및 다양한 모의실험 자료에 적용하여 그 활용성을 보였다. 다음으로, 추정치의 분산안정화 및 이론적 정당화를 위하여 Kégl (1999), Kégl et al., (2000) 방법을 일반적인 리만다양체로 확장한다. 더 나아가, 방법론의 일치성, 수렴속도와 같은 점근적 성질을 비롯하여 비점근적 성질인 집중부등식(concentration inequality)을 통계적학습이론을 이용하여 규명한다.1 Introduction 1 2 Preliminaries 8 2.1 Principal curves 8 2.1 Riemannian manifolds and centrality on manifold 10 2.1 Principal curves on Riemannian manifolds 14 3 Spherical principal curves 15 3.1 Enhancement of principal circle for initialization 16 3.2 Proposed principal curves 25 3.3 Numerical experiments 34 3.4 Proofs 45 3.5 Concluding remarks 62 4 Robust spherical principal curves 64 4.1 The proposed robust principal curves 64 4.2 Stationarity of robust spherical principal curves 72 4.3 Numerical experiments 74 4.4 Summary and future work 80 5 spherepc: An R package for dimension reduction on a sphere 84 5.1 Existing methods 85 5.2 Spherical principal curves 91 5.3 Local principal geodesics 94 5.4 Application 99 5.5 Conclusion 101 6 Local principal curves on Riemannian manifolds 112 6.1 Preliminaries 116 6.2 Local principal geodesics 118 6.3 Local principal curves 125 6.4 Real data analysis 133 6.5 Further work 133 7 Conclusion 139 A. Appendix 141 A.1. Appendix for Chapter 3 141 A.2. Appendix for Chapter 4 145 A.3. Appendix for Chapter 6 152 Abstract in Korean 176 Acknowledgement in Korean 179박

Approximation algorithms for mobile multi-agent sensing problem

학위논문 (석사) -- 서울대학교 대학원 : 공과대학 산업공학과, 2020. 8. 문일경.Multi-agent systems are generally applicable in a wide diversity of domains, such as robot engineering, computer science, the military, and smart cities. In particular, the mobile multi-agent sensing problem can be defined as a problem of detecting events occurring in a large number of nodes using moving agents. In this thesis, we introduce a mobile multi-agent sensing problem and present a mathematical formulation. The model can be represented as a submodular maximization problem under a partition matroid constraint, which is NP-hard in general. The optimal solution of the model can be considered computationally intractable. Therefore, we propose two approximation algorithms based on the greedy approach, which are global greedy and sequential greedy algorithms, respectively. We present new approximation ratios of the sequential greedy algorithm and prove tightness of the ratios. Moreover, we show that the sequential greedy algorithm is competitive with the global greedy algorithm and has advantages of computation times. Finally, we demonstrate the performances of our results through numerical experiments.다중 에이전트 시스템은 일반적으로 로봇 공학, 컴퓨터 과학, 군사 및 스마트 도시와 같은 다양한 분야에 적용할 수 있다. 특히, 모바일 다중 에이전트 감지 문제는 움직이는 에이전트를 이용해 많은 수의 노드에서 발생하는 이벤트를 감지하는 문제로 정의할 수 있다. 본 논문에서는 모바일 다중 에이전트 감지 문제의 수학적 공식을 제안한다. 이 문제는 일반적으로 NP-난해 문제인 분할 매트로이드 제약 하에서 하위 모듈 함수의 최대화 문제로 표현할 수 있다. 문제의 최적해는 입력 데이터의 크기가 커질수록 보통 합리적인 시간 이내에 계산하기 어렵다. 따라서 본 논문에서는 탐욕적 접근 방식에 기초한 두 가지 근사 알고리즘 (전역 탐욕 알고리즘, 순차 탐욕 알고리즘)을 제안한다. 또한, 순차 탐욕 알고리즘의 새로운 근사 비율을 증명하고 근사 비율에 정확하게 일치하는 인스턴스를 제시한다. 또한, 수치 실험 결과로 순차 탐욕 알고리즘은 효과적인 해를 찾아줄 뿐 아니라, 전역 탐욕 알고리즘과 비교해 계산 시간의 이점을 가지고 있음을 확인한다.Chapter 1 Introduction 1 Chapter 2 Literature Review 4 Chapter 3 Problem statement 7 Chapter 4 Algorithms and approximation ratios 11 Chapter 5 Computational Experiments 22 Chapter 6 Conclusions 30 Bibliography 31 국문초록 40Maste

좁고 깊은 심층신경망의 뉴럴 탄젠트 커널 분석

학위논문(석사) -- 서울대학교대학원 : 자연과학대학 수리과학부, 2023. 8. Ernest K. Ryu.The tremendous recent progress in analyzing the training dynamics of over parameterized neural networks has primarily focused on wide networks and therefore does not sufficiently address the role of depth in deep learning. In this work, we present the first trainability guarantee of infinitely deep but narrow neural networks. We study the infinite-depth limit of a multilayer perceptron (MLP) with a specific initialization and establish a trainability guarantee using the NTK theory. We then extend the analysis to an infinitely deep convolutional neural network (CNN) and perform brief experiments.과매개화된 신경망의 훈련 역학을 분석하는 최근의 엄청난 발전은 주로 넓은 네트워크에 초점을 맞추었기 때문에 딥 러닝에서 깊이의 역할을 충분히 다루지 못 한다. 이 논문에서 우리는 무한히 깊지만 좁은 신경망의 훈련 가능성을 처음으로 보인다. 우리는 특정 초기화하에서 무한한 깊이의 다층 신경망을 연구하고 뉴럴 탄젠트커널 이론을 사용하여 학습 가능성울 보장한다. 그런 다음 분석을 무한히 깊은 합성곱 신경망으로 확장하고 간단한 실험을 수행한다.1 Introduction 2 1.1 Prior works 3 2 Preliminaries and Notations 5 2.1 Kernel gradient flow 6 2.2 Neural tangent kernel 7 3 NTK analysis of infinitely deep MLP 9 3.1 Initialization 10 3.1.1 Gradient flow and neural tangent kernel 11 3.2 Convergence in infinite-depth limit 13 3.3 Proof outline 15 4 NTK analysis of infinitely deep CNN 19 4.0.1 Initialization 20 4.0.2 Convergence in infinite-depth limit 22 5 Experiments 24 5.1 Convergence of the scaled NTK 24 5.2 Trainability of the deep narrow neural network 24 5.3 Accumulation of the layer-wise effect 26 6 Conclusion 27 7 Appendix 28 Bibliography 29 초 록 37 감사의 글 38석

Expression patterns of tenascin-N in the developing mandible

Previous studies have demonstrated that tenascin-N belongs to the family of tenascins, which are found in the extracellular matrix of various embryonic tissues, wounds, and tumors. Tenascin is expressed in the embryonic epithelium, including the neural epithelium from which neural crest cells emerge. However, the expression pattern and role of tenascin-N in the craniofacial region remains unknown. In this study, expression patterns of tenascin-N were confirmed in the mouse craniofacial region from embryonic day 12.5 (E12.5) to postnatal 11. In the diastema region, tenascin-N was strongly expressed in the mesenchyme from E12.5 to E14.5. Tenascin-N expression was also detected in the developing tooth germ. From the bell stage to the premature stage, tenascin- N was expressed in the odontoblasts and ameloblasts of the molar tooth germ, and the ameloblasts of the incisor tooth germ. These findings indicate that the spatial and temporal expression of tenascin-N might have a role in proper mouse craniofacial development, especially tooth developmentope

황해 연안 갯벌 퇴적환경내 유기탄소의 시공간 분포 및 거동특성 규명

학위논문(박사) -- 서울대학교대학원 : 자연과학대학 지구환경과학부, 2022. 8. 김종성.전 세계적으로 염습지, 맹그로브, 잘피를 포함한 블루카본 생태계는 지구온난화가 가속화되는 상황에서 높은 이산화탄소 흡수율로 기후 변화를 완화하는데 중요한 역할을 한다. 그러나 기존의 블루카본 생태계의 이산화탄소 흡수 능력에 대해 많은 연구가 진행되었으나, 잠재적 탄소흡수원인 갯벌의 탄소 저장 능력과 그 조절 요인에 대한 연구는 미비한 실정이다. 이에 본 연구에서는 황해 갯벌 퇴적물내 유기탄소의 시공간분포와 거동요인에 미치는 영향을 평가하였다. 첫째로, 한국 조간대 표층퇴적물내 총유기탄소의 시공간적 분포와 거동을 평가하였다. 조간대 환경의 대표성과 객관적 비교를 담보하기 위해 전형적 자연 갯벌 4개소와 닫힌 하구 1개소를 대상으로 2018년 1월부터 12월까지 월별 조사를 수행하였다. 조사 및 분석결과, 총 유기탄소 함량은 퇴적물 입자크기(입도)를 대변하는 니질 함량에 따라 결정됨이 확인되었다. 가로림만과 순천만 퇴적물은 저서미세조류 대발생에 기인하여 겨울철 총 유기탄소 함량이 높았고, 특히 δ13C 값이 크게 증가했다. 반면 낙동강 하구 퇴적물은 장마철(9–10월)에 육상으로부터의 담수방류 영향으로 인해 δ13C와 δ15N 값이 감소하는 것이 확인되었다. 둘째로, 한국 전 연안 갯벌 퇴적물내 유기탄소 저장량과 유기탄소 침적률의 산정을 위해 현장조사 자료와 원격탐사 기법을 활용하였다. 조사지역은 동서남해 7개 시도(경기, 충남, 전북, 전남, 경남, 경북, 강원) 내 21개 지역이었으며, 2017년부터 2020년까지 코어퇴적물을 분석하였고, 원격 탐사기법을 통해 갯벌의 퇴적물 성상과 면적을 산정하였다. 염생식물이 서식하는 염습지에서는 식물의 일차생산을 통한 높은 탄소고정 능력으로 인해, 비식생 갯벌보다 상대적으로 높은 유기탄소 저장량을 보였다. 현장조사 자료와 원격탐사 기법을 통해, 국가 수준에서 한국 전 연안의 조간대 갯벌의 총 유기탄소 저장량 및 연간 유기탄소 침적률을 산정하였다. 셋째로, 외래식물 갯끈풀과 토착식물 갈대, 칠면초가 유기탄소 증가에 미치는 영향을 비교하기 위해 염생식물 종별 유기탄소 저장량 증가율을 분석하였다. 중국 7개지역과 한국 12개지역을 대상으로, 각 지역의 염생식물이 서식하는 염습지와 비식생 갯벌에서 조사를 실시하였다. 외래식물 갯끈풀이 우점하는 중국 염습지가 토착식물 갈대와 칠면초가 우점하는 한국 염습지보다 높은 유기탄소 저장량을 보였다. 동일 기간 동안 갯끈풀의 유기탄소 저장량 증가율은 칠면초와 갈대에 비해 높았으며, 이는 상대적으로 높은 일차생산량과 지하부 뿌리 생물량으로 인한 것으로 나타났다. 또한 갯끈풀 서식지는 비식생 갯벌과 갈대 서식지에 비해 온실가스 배출, 대형저서동물 먹이망, 퇴적물 안정도, 탄소침적의 관점에서 이점이 있는 것으로 확인되었다. 끝으로, 대규모 현장조사를 통해 황해 전 연안 갯벌의 유기탄소 저장량과 유기탄소 침적률을 산정하였다. 조사지역은 중국 5개 시도(랴오닝성, 허베이성, 톈진시, 산둥성, 장쑤성)내 19개 지역, 한국 5개 시도(경기, 충남, 전북, 전남, 경남)내 18개 지역에서 코어퇴적물을 채집하였다. 분석결과, 양식장, 도시 및 산업단지로부터 강을 통한 유기물질의 유입이 유기탄소 침적에 기여하는 것이 확인되었다. 황해 갯벌 퇴적물내 유기탄소 함량은 퇴적물 입도와 염생식물의 유무에 따라 결정되는 것으로 나타났다. 단위면적당 유기탄소 저장량과 갯벌 면적자료를 기반으로 황해 전 연안 갯벌의 총 유기탄소 저장량 21–171 Tg C과 연간 유기탄소 침적률 0.08–0.61 Tg C yr-1; 0.29–2.24 Tg CO2 eq. yr-1을 추정하였다. 기존의 블루카본 생태계와 비교하였을 때 갯벌은 상대적은 낮은 단위면적당 유기탄소 저장량과 침적률을 보이나, 전 세계적으로 광활한 면적과 해당 서식지의 일차생산자인 저서미세조류를 고려할 때 갯벌도 또한 중요한 탄소흡수원임을 시사한다. 이상의 연구결과를 종합 요약하면, 황해 갯벌 퇴적물내 유기탄소 분포는 퇴적물 입도와 식생의 유무에 의해 가장 많은 영향을 받으며, 유기탄소 기원은 염생식물 종과 육상-해양기원 유기물 유입에 따라 변화되는 것이 확인되었다. 결과적으로, 본 연구는 황해 갯벌의 블루카본 잠재성과 이에 영향을 미치는 생태학적 특성에 대한 정보를 제공하며, 향후 황해 갯벌 퇴적물내 탄소순환 연구에 대한 중요한 기초자료로 활용될 수 있음을 시사한다.Recently, blue carbon ecosystems (BCEs), including salt marshes, mangrove forests, and seagrass meadows, have been highlighted for their capacity to fix high quantities of carbon under global warming. Although these conventional BCEs are widely studied for their role as highly efficient CO2 sinks, holistic data analysis of carbon sink capacity and its controlling factors remain limited in the tidal flat ecosystems of the Yellow Sea. Thus, the current study evaluated the spatiotemporal distribution and fate of sedimentary organic carbon of tidal flat ecosystems in the Yellow Sea. Sedimentary organic carbon in the surface sediments of typical intertidal areas were investigated to address year-round monthly distributions and site-specific sources. Target areas included four natural tidal flats (Ganghwa, Garolim, Sinan, and Suncheon) and one artificially closed estuary (Nakdong River) in South Korea during 2018. Among the parameters monitored, mud content was a key factor controlling organic matter content, across varying habitats, with significant positive correlations to total organic carbon (TOC). Elevated TOC content and heavier carbon stable isotope ratios (δ13C) in the sediments of Garolim and Suncheon from February to April of 2018 reflected microphybenthos blooms during winter, indicating a primary influence of marine sources. In comparison, δ13C and δ15N were depleted in the sediments of Nakdong River estuary during the flood season (September–October), indicating the direct influence of terrestrial organic input through freshwater discharge. To estimate current organic carbon stocks and sequestration rates in the coastal areas of the West Sea, South Sea, and East Sea of South Korea, field surveys were conducted over 4 years combined with remote sensing technology were conducted encompassing entire intertidal areas. Twenty-one intertidal flats were targeted across seven provinces (Gyeonggi, Chungnam, Jeonbuk, Jeonnam, Gyeongnam, Gyeongbuk, and Gangwon). Organic carbon stocks measured in salt marshes (i.e., upper intertidal zone) reflected the high carbon fixation capacity of halophytes through primary production. The texture of different sediments was classified based on remotely sensed imagery, and was confirmed to be closely correlated with field-based classification data. Using field and remote sensing results, total organic carbon stocks and sequestration rates were estimated in the tidal flats of South Korea. This investigation was conducted to address the effects of an invasive halophyte (i.e., Spartina alterniflora) on sedimentary organic carbon compared to native halophyte habitats (i.e., Suaeda japonica and Phragmites australis) in South Korea and China. Out of the two countries, salt marshes in China tended to have higher organic carbon stocks compared to those in Korea, which was attributed to different rates of increase in TOC by halophyte species. Spartina alterniflora contributed to higher carbon accumulation rates in sediments (3.4 times), through higher primary production and greater root biomass, compared to S. japonica (2.5 times) and P. australis (2.4 times) over the same period. In addition, compared to P. australis and bare tidal flats, S. alterniflora had advantages with respect to greenhouse gas emissions, the food web, sediment erodibility, and carbon burial. Finally, a large-scale investigation was conducted to demonstrate the distribution of total organic carbon stocks and sequestration rates of coastal sediments along the Yellow Sea. Riverine inputs of anthropogenic organic matter from aquaculture, municipal, and industrial areas contributed to the burial of sedimentary organic carbon. Out of the evaluated environmental parameters, sediment mud contents and halophytes were confirmed as key factors affecting organic carbon levels in coastal sediment. Based on the assimilated data, total organic carbon stocks (21–171 Tg C) and sequestration rates (0.08–0.61 Tg C yr-1; 0.29–2.24 Tg CO2 eq. yr-1) were evaluated in the Yellow Sea. Of note, tidal flats had relatively lower carbon stocks due to having lower net primary production (NPP) compared to conventional BCEs. Nevertheless, given the extensive areal coverage and microphytobenthos (MPB), tidal flats could be significant carbon sinks, and also terminal reservoirs of detritus organic matter from adjacent vegetated coastal ecosystems. Overall, the distribution of sedimentary organic carbon varied in the sediment mud content and vegetation of tidal flats in the Yellow Sea. Furthermore, the sources affecting the differences in its origin included halophyte species and terrestrial-marine inputs. In conclusion, the present study provides a relatively large-scale baseline on the carbon dynamics of coastal sediments along the Yellow Sea, contributing to the global database of “Blue Carbon” science.CHAPTER. 1. Introduction 1 1.1. Backgrounds 2 1.2. Objectives 8 CHAPTER. 2. Natural and anthropogenic signatures on sedimentary organic matters across varying intertidal habitats in the Korean waters 11 2.1. Introduction 12 2.2. Materials and methods 15 2.2.1. Study area 15 2.2.2. Sampling and laboratory analyses 18 2.2.3. Data analysis 21 2.3. Results and discussion 22 2.3.1. Spatiotemporal distributions of sedimentary organic matter 22 2.3.2. Effects of the mud contents on sedimentary TOC and TN 29 2.3.3. Effects of benthic microalgae on sedimentary TOC and TN 32 2.3.4. Site-specific variabilities in sources of sedimentary organic matters 36 2.3.5. Factors affecting complex dynamics of sedimentary organic matter 39 CHAPTER. 3. The first national scale evaluation of organic carbon stocks and sequestration rates of coastal sediments along the West Sea, South Sea, and East Sea of South Korea 42 3.1. Introduction 43 3.2. Materials and methods 46 3.2.1. Study area 46 3.2.2. Tidal flat delineation using remote sensing 58 3.2.3. Validation of sediment textural types using remote sensing 62 3.2.4. Sampling and laboratory analyses 63 3.2.5. Calculation of organic carbon stock 69 3.2.6. Calculation of organic carbon sequestration rate 73 3.2.7. Statistical analyses 74 3.3. Results and discussion 75 3.3.1. Spatiotemporal distribution of organic carbon stocks per unit area 75 3.3.2. Environmental factors affecting the complex dynamics of sedimentary organic carbon stocks 78 3.3.3. Effects of mud content and vegetation on sedimentary TOC 81 3.3.4. Validation of tidal flat areas and sediment textural types using remote sensing classification 86 3.3.5. Estimation of organic carbon stocks and sequestration rates in South Korea 90 CHAPTER. 4. The effect of exotic S. alterniflora invasion on sedimentary organic carbon across the coastal areas of the Yellow Sea 99 4.1. Introduction 100 4.2. Materials and methods 103 4.2.1. Data packages 103 4.2.2. Air temperature anomaly 105 4.2.3. Sedimentary organic carbon stocks per unit area 106 4.2.4. Benthic community after Spartina alterniflora eradication 109 4.2.5. CO2 and CH4 emissions 110 4.2.6. Relatively contribution of primary diet 111 4.2.7. Statistical analysis 112 4.3. Results and discussion 113 4.3.1. Elevated temperature affecting the spread of Spartina alterniflora in the Yellow Sea 113 4.3.2. Effects of Spartina alterniflora invasion on sedimentary organic carbon 117 4.3.3. Effect of eradication on Spartina alterniflora and macrobenthos community 124 4.3.4. Comparision of ecological functions between bare tidal flat, native Phragmites australis, and invasive Spartina alterniflora 127 CHAPTER. 5. Spatial variation of sedimentary organic carbon in the coastal areas of the Yellow Sea 135 5.1. Introduction 136 5.2. Materials and methods 138 5.2.1. Study area 138 5.2.2. Sampling and laboratory analyses 140 5.2.3. Data analyses 146 5.3. Results and discussion 147 5.3.1. Spatial distribution of organic carbon stocks per unit area 147 5.3.2. Environmental factors affecting the complex dynamics of sedimentary organic carbon stocks 149 5.3.3. Halophyte species-specific variability in the sources of sedimentary organic matter 151 5.3.4. Organic carbon stocks and carbon sequestration rates in the coastal areas of the Yellow Sea 153 CHAPTER. 6. Conclusions 157 6.1. Summary 158 6.2. Environmental implications and limitations 163 6.3. Future research directions 166 BIBLIOGRAPHY 169 ABSTRACT (IN KOREAN) 186박

Action of Actomyosin Contraction With Shh Modulation Drive Epithelial Folding in the Circumvallate Papilla

The mouse tongue possesses three types of gustatory papillae: large circumvallate papillae (CVP), foliate papillae (FOP) and fungiform papillae (FFP). Although CVP is the largest papilla and contain a high density of taste buds, little is known about CVP development. Their transition from placode to dome-shape is particularly ambiguous. Understanding this phase is crucial since dome-shaped morphology is essential for proper localization of the imminent nerve fibers and taste buds. Here, we report actomyosin-dependent apical and basal constriction of epithelial cells during dynamic epithelial folding. Furthermore, actomyosin-dependent basal constriction requires focal adhesion kinase to guide dome-shape formation. Sonic hedgehog (Shh) is closely associated with the differentiation or survival of the neurons in CVP ganglion and cytoskeletal alteration in trench epithelial cells which regulate CVP morphogenesis. Our results demonstrate the CVP morphogenesis mechanism from placode to dome-shape by actomyosin-dependent cell shape change and suggest roles that Shh may play in trench and stromal core formation during CVP development.ope

Runx3 regulates iron metabolism via modulation of BMP signalling

Objectives: Runx3, a member of the Runx family of transcription factors, has been studied as a tumour suppressor and key player of organ development. In a previous study, we reported differentiation failure and excessive angiogenesis in the liver of Runx3 knock-out (KO) mice. Here, we examined a function of the Runx3 in liver, especially in iron metabolism. Methods: We performed histological and immunohistological analyses of the Runx3 KO mouse liver. RNA-sequencing analyses were performed on primary hepatocytes isolated from Runx3 conditional KO (cKO) mice. The effect of Runx3 knock-down (KD) was also investigated using siRNA-mediated KD in functional human hepatocytes and human hepatocellular carcinoma cells. Result: We observed an iron-overloaded liver with decreased expression of hepcidin in Runx3 KO mice. Expression of BMP6, a regulator of hepcidin transcription, and activity of the BMP pathway were decreased in the liver tissue of Runx3 KO mice. Transcriptome analysis on primary hepatocytes isolated from Runx3 cKO mice also revealed that iron-induced increase in BMP6 was mediated by Runx3. Similar results were observed in Runx3 knock-down experiments using HepaRG cells and HepG2 cells. Finally, we showed that Runx3 enhanced the activity of the BMP6 promoter by responding to iron stimuli in the hepatocytes. Conclusion: In conclusion, we suggest that Runx3 plays important roles in iron metabolism of the liver through regulation of BMP signalling.ope

FGF10 Is Required for Circumvallate Papilla Morphogenesis by Maintaining Lgr5 Activity

Taste buds develop in different regions of the mammal oral cavity. Adult stem cells in various organs including the tongue papillae are marked by leucine-rich repeat-containing G protein-coupled receptor 5 (Lgr5) and its homolog, Lgr6. Recent studies have reported that adult taste stem/progenitor cells in circumvallate papilla (CVP) on the posterior tongue are Lgr5-positive. In this study, we confirm the Lgr5 expression pattern during CVP development. A previous study reported that mesenchymal Fgf10 is necessary for maintaining epithelial Lgr5-positive stem/progenitor cells. To confirm the interaction between Lgr5-positive CVP epithelium and mesenchymal factor FGF10, reverse recombination (180-degree) was performed after tongue epithelium detachment. FGF10 protein-soaked bead implantation was performed after reverse recombination to rescue CVP development. Moreover, we reduced mesenchymal Fgf10 by BIO and SU5402 treatment which disrupted CVP morphogenesis. This study suggests that the crosstalk between epithelial Lgr5 and mesenchymal Fgf10 plays a pivotal role in CVP epithelium invagination during mouse tongue CVP development by maintaining Lgr5-positive stem/progenitor cells.ope

Postoperative developed intra-abdominal desmoid tumor after surgical resection of gastrointestinal malignancy: A review of 10 cases

Purpose Desmoid tumors are locally aggressive tumors with no known potential for metastasis. They tend to recur even after complete excision. Sometimes it is not easy to differentiate between intra-abdominal desmoid and tumor recurrence, especially after gastrointestinal (GI) tumor resection. The current study aims to review the characteristics, management, and outcomes of patients with intra-abdominal desmoid tumor post GI resection. Methods During the period between 2007 and 2018, after a retrospective review of patients’ clinical data, 10 patients were finally included. Medical records were screened for demographic, clinical, pathological data, management strategy, postoperative morbidity, mortality, recurrence rate and follow-up. Results The study comprised 10 patients (8 males). The median age was 53.5 years (range, 35–68 years). Two patients diagnosed as familial adenomatous polyposis (FAP). All the patients underwent previous GI resection: three (30%) for colon cancer, three (30%) gastrectomy, two (20%) total proctocolectomy with ileal pouch-anal anastomosis (TPC+IPAA) for FAP, one (10%) low anterior resection (three rectal cancers) and one (10%) distal pancreatectomy. The tumor was found to be in bowel mesentery in eight cases (80%). The median tumor size was 5.3 cm (range, 2.6–19.0 cm). Six patients (60%) underwent open resection, while four patients (40%) underwent laparoscopic surgery. Complications occurred in five cases (50%) and ranged from Clavien-Dindo (II–III). The median follow-up period was 16.5 months (1.5–136.0 months) with recurrence in one case (10%). Pathology came out to be desmoid tumor fibromatosis in all cases. Conclusion When a mass develops after surgical resection for abdominal GI malignancy and tends to be large in size, located in the bowel mesentery and away from previous primary tumor site, most probably it is desmoid rather than tumor recurrence.ope