Hepatic Cellular Distribution of Silica Nanoparticles by Surface Energy Modification

Lee, A-Rang,Nam, Kibeom,Lee, Byeong Jun,Lee, Seoung-Woo,Baek, Su-Min,Bang, Jun-Sun,Choi, Seong-Kyoon,Park, Sang-Joon,Kim, Tae-Hwan,Jeong, Kyu-Shik,Lee, Dong Yun,Park, Jin-Kyu MDPI AG 2019 INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES Vol.20 No.15

<P>The cellular distribution of silica nanoparticles (NPs) in the liver is not well understood. Targeting specific cells is one of the most important issues in NP-based drug delivery to improve delivery efficacy. In this context, the present study analyzed the relative cellular distribution pattern of silica NPs in the liver, and the effect of surface energy modification on NPs. Hydrophobic NP surface modification enhanced NP delivery to the liver and liver sinusoid fFendothelial cells (LSECs). Conversely, hydrophilic NP surface modification was commensurate with targeting hepatic stellate cells (HSCs) rather than other cell types. There was no notable difference in NP delivery to Kupffer cells or hepatocytes, regardless of hydrophilic or hydrophobic NP surface modification, suggesting that both the targeting of hepatocytes and evasion of phagocytosis by Kupffer cells are not associated with surface energy modification of silica NPs. This study provides useful information to target specific cell types using silica NPs, as well as to understand the relationship between NP surface energy and the NP distribution pattern in the liver, thereby helping to establish strategies for cell targeting using various NPs.</P>

Comparison of Preanalytical Sample Stability between Serum and Ethylenediaminetetraacetic Acid Plasma for the Measurement of Biological Analytes

Jiwon Lee,Kibeom Jeon,Taekha Lee,Jisoo Lee,Miyoung Kim,Han-Sung Kim,Young Kyung Lee,Hee Jung Kang 대한임상검사정도관리협회 2020 Journal of Laboratory Medicine And Quality Assuran Vol.42 No.3

Background: In this study, we aim to examine the effects of pre-analytical factors such as specimen type (serum or plasma), collection and storage conditions, and time, on the results of chemiluminescence immunoassay. Methods: Blood samples were collected from 10 individuals and aliquoted into two sets of K3-ethylenediaminetetraacetic acid (EDTA) and serumseparating tubes (SST) each, for plasma and serum collection, respectively. For all the samples, one set of tubes was centrifuged within 1 hour and other set was centrifuged after 4 hours, followed by cell separation. Chemiluminescence assay was performed for adrenocorticotropic hormone (ACTH), parathyroid hormone (PTH), osteocalcin, C-telopeptide, and insulin at 0, 6, 24, and 48 hours after centrifugation; all the samples were assayed in duplicate. The samples were stored at 4℃ before the assay. Results: The results obtained showed that the levels detected in plasmas were more consistent and stable as compared to serum. After a 6-hour storage at 4℃, a significant decrease was observed in the levels of ACTH and osteocalcin in plasma and serum; whereas, PTH and C-telopeptide levels were stable in plasma but decreased significantly in serum. Insulin levels in serum showed a decrease after a 6-hour storage while the levels in plasma were found to be stable until 24-hour storage. Serum samples separated after 4 hours showed a significant decrease in all hormone levels, while C-telopeptide and insulin levels were stable in plasma samples separated after 4 hours. Conclusions: The results were found to be more stable in plasma samples from K3-EDTA tubes as compared to serum samples from SST in the measurement of unstable biological analytes. These results suggest that K3- EDTA tubes are preferable in the specimen collection for assaying biological analytes.

Using Experts Among Users for Novel Movie Recommendations

Kibeom Lee,Kyogu Lee 한국정보과학회 2013 Journal of Computing Science and Engineering Vol.7 No.1

The introduction of recommender systems to existing online services is now practically inevitable, with the increasing number of items and users on online services. Popular recommender systems have successfully implemented satisfactory systems, which are usually based on collaborative filtering. However, collaborative filtering-based recommenders suffer from well-known problems, such as popularity bias, and the cold-start problem. In this paper, we propose an innovative collaborative-filtering based recommender system, which uses the concepts of Experts and Novices to create finegrained recommendations that focus on being novel, while being kept relevant. Experts and Novices are defined using pre-made clusters of similar items, and the distribution of users’ ratings among these clusters. Thus, in order to generate recommendations, the experts are found dynamically depending on the seed items of the novice. The proposed recommender system was built using the MovieLens 1 M dataset, and evaluated with novelty metrics. Results show that the proposed system outperforms matrix factorization methods according to discovery-based novelty metrics, and can be a solution to popularity bias and the cold-start problem, while still retaining collaborative filtering.

Using Experts Among Users for Novel Movie Recommendations

Lee, Kibeom,Lee, Kyogu Korean Institute of Information Scientists and Eng 2013 Journal of Computing Science and Engineering Vol.7 No.1

The introduction of recommender systems to existing online services is now practically inevitable, with the increasing number of items and users on online services. Popular recommender systems have successfully implemented satisfactory systems, which are usually based on collaborative filtering. However, collaborative filtering-based recommenders suffer from well-known problems, such as popularity bias, and the cold-start problem. In this paper, we propose an innovative collaborative-filtering based recommender system, which uses the concepts of Experts and Novices to create fine-grained recommendations that focus on being novel, while being kept relevant. Experts and Novices are defined using pre-made clusters of similar items, and the distribution of users' ratings among these clusters. Thus, in order to generate recommendations, the experts are found dynamically depending on the seed items of the novice. The proposed recommender system was built using the MovieLens 1 M dataset, and evaluated with novelty metrics. Results show that the proposed system outperforms matrix factorization methods according to discovery-based novelty metrics, and can be a solution to popularity bias and the cold-start problem, while still retaining collaborative filtering.

Longitudinal and Lateral Integrated Safe Trajectory Planning of Autonomous Vehicle via Friction Limit

Kibeom. Lee,Dongsuk. Kum 제어로봇시스템학회 2020 제어로봇시스템학회 국제학술대회 논문집 Vol.2020 No.10

Due to the development of advanced driver assistance systems (ADAS) and autonomous vehicle (AV) technology, various path planning algorithms are being developed. However, most path planning algorithms operate in general and safety scenarios, and in emergency scenarios, the autonomous emergency brake (AEB) and autonomous emergency steering (AES) systems are operated limitedly. In an emergency situation in which the vehicle dynamic characteristics changed, planning a safe trajectory that can be safely tracking in necessary. In this study, a safe trajectory planning method in which the vehicle does not lose stability by using combined longitudinal and lateral acceleration vectors is proposed. The combined acceleration vector is limited by friction limit. The proposed trajectory planning algorithm is evaluated by simulation in a single obstacle scenario through comparison with existing AEB and AES algorithms. The simulation results show the proposed algorithm generates only safe trajectory that guarantee the vehicle stability, excluding dangerous trajectories when the AEB and AES algorithms operated.

Using Dynamically Promoted Experts for Music Recommendation

Lee, Kibeom,Lee, Kyogu IEEE 2014 IEEE transactions on multimedia Vol.16 No.5

<P>Recommender systems have become an invaluable asset to online services with the ever-growing number of items and users. Most systems focused on recommendation accuracy, predicting likable items for each user. Such methods tend to generate popular and safe recommendations, but fail to introduce users to potentially risky, yet novel items that could help in increasing the variety of items consumed by the users. This is known as popularity bias, which is predominant in methods that adopt collaborative filtering. Recently, however, recommenders have started to improve their methods to generate lists that encompass diverse items that are both accurate and novel through specific novelty-driven algorithms or hybrid recommender systems. In this paper, we propose a recommender system that uses the concepts of Experts to find both novel and relevant recommendations. By analyzing the ratings of the users, the algorithm promotes special Experts from the user population to create novel recommendations for a target user. Thus, different users are promoted dynamically to Experts depending on who the recommendations are for. The system used data collected from Last.fm and was evaluated with several metrics. Results show that the proposed system outperforms matrix factorization methods in finding novel items and performs on par in finding simultaneously novel and relevant items. This system can also provide a means to popularity bias while preserving the advantages of collaborative filtering.</P>

Improving Diversity of Radio Playlists with the Aid of Recommender Systems

Kibeom Lee(이기범),Ziwon Hyung(형지원),Namjun Kang(강남준),Kyogu Lee(이교구) 한국방송학회 2014 한국방송학회 학술대회 논문집 Vol.2014 No.4

다중 목표 강화학습에서 불균형 문제를 위한 균등 샘플링 방법

김기범(Kibeom Kim),이민후(Min Whoo Lee),이민수(Minsu Lee),장병탁(Byoung-Tak Zhang) 한국정보과학회 2022 한국정보과학회 학술발표논문집 Vol.2022 No.06

해양경계획정에 적용할 수 있는 ‘3단계 방법론’에 대한 비판적 소고

이기범(Lee Kibeom) 대한국제법학회 2020 國際法學會論叢 Vol.65 No.2

2009년 ICJ의 Black Sea (Romania v. Ukraine) 사건이 소위 ‘3단계 방법론’을 확립한 이후 3단계 방법론은 해양경계획정을 수행하는 국제재판소의 표준적 방법론으로 자리를 잡았다. 배타적 경제수역 또는 대륙붕의 경계획정을 규율하는 법적 구속력 있는 규칙은 유엔해양법협약 제74조 제1항 또는 제83조 제1항에 규정되어 있는 것처럼 그리고 국제관습법상으로도 ‘형평한 해결의 도달’이다. 이와 같이 모호한 법 규칙을 적용하기 위해 국제재판소가 확립한 3단계 방법론은 객관성 또는 예측가능성을 담보한다는 차원에서 찬사를 받고 있다. 그럼에도 3단계 방법론은 내재적으로 한계를 지니고 있다. 제1단계에서는 잠정적인 등거리선을 설정할 때 필요한 기점들이 주관적으로 선택될 수 있다는 것이 가장 큰 문제이다. 이는 등거리 방법 자체가 객관적이라 해도 등거리 방법의 ‘적용’은 주관적일 수 있다는 것을 의미한다. 관련 사정들이 제2단계에서만 그 역할을 수행할 수 있는 것처럼 보이는 것도 문제라 지적할 수 있다. 하지만 제1단계에서 관련 사정들의 존재 때문에 잠정적인 등거리선이 아닌 잠정적인 이등분선이 설정될 수도 있는 것처럼 관련 사정들이 반드시 제2단계에서만 고려되지는 않는다. 그리고 ‘불균형성 점검’, 즉 제3단계는 그 존재 의의부터 의심받고 있다. 오늘 현재까지 그 어떤 국제재판소 판례도 제3단계에서 제1단계와 제2단계를 통해 그려진 경계선을 이동시킨 적이 없기 때문이다. 이와 같은 내재적 한계를 고려했을 때 3단계 방법론은 ‘방법론’으로서의 의의만 가질뿐 3단계 방법론이 그 이상의 함의를 포함하고 있다고 보기 어렵다. 즉, 3단계 방법론이 적용되어 투명성과 해양경계획정 과정의 예측가능성이 확보되거나 제고된다 하여 해양경계획정의 궁극적 목표인 형평한 해결의 도달이 자동적으로 이루어지는 것은 아니다. 만약 3단계 방법론이 아닌 다른 방법론을 원용하여 해양경계획정의 목표인 형평한 해결의 도달이 이루어질 수 있다면 이는 3단계 방법론을 맹목적으로 고수할 필요가 없다는 것을 의미한다. 결국 여전히 해양경계획정을 지배하는 개념은 각 해양경계획정 사건마다 제각각인 ‘관련 사정들’이다. 따라서 3단계 방법론이라는 단계적 방법론의 고수가 형평한 해결의 도달을 어렵게 한다면 해당 해양경계획정 사건만의 관련 사정들을 고려하여 적절한 다른 방법론을 원용하는 것이 국제재판소가 취할 수 있는 가장 바람직한 태도가 될 것이다. Since the 2009 Black Sea (Romania v. Ukraine) case of the International Court of Justice (ICJ), the so-called ‘three-stage methodology’ has been employed as the ‘standard’ methodology by international courts and tribunals dealing with maritime boundary delimitation. The binding rule governing the delimitation of the exclusive economic zone or the continental shelf is the ‘achievement of an equitable solution’, as stipulated in Article 74(1) or 83(1) of the United Nations Convention on the Law of the Sea (UNCLOS) and recognized as part of customary international law by the ICJ. The three-stage methodology has been established to apply this open-textured rule in a given delimitation case, and the methodology is often complimented because it seems to assure not only objectivity but also predictability in applying the rule. Nevertheless, the three-stage methodology has its limitations. Firstly, it is, at the first stage, possible to subjectively select base points necessary to construct a provisional equidistance line. This means that the ‘application’ of the equidistance method would be subjective although the method in itself is objective. Secondly, within the framework of the three-stage methodology, relevant circumstances seem to take up their position only at the second stage. However, because of the existence of relevant circumstances, a provisional bisector line could be drawn at the ‘first’ stage, instead of a provisional equidistance line. Thirdly, it is questionable whether or not the third stage conducting the disproportionality test is a necessary step in maritime boundary delimitation. The reason for this is that any delimitation lines constructed through the first and second stages have not been adjusted at the third stage since the Black Sea (Romania v. Ukraine) case. Taking into account the limitations of the three-stage methodology described above, the methodology has to be regarded as a ‘just’ methodology. Moreover, transparency and the predictability of the delimitation process as a whole enhanced through the three-stage methodology do not automatically lead to the achievement of an equitable solution. If another methodology produces an equitable solution in a specific delimitation case, it could be employed, instead of the three-stage methodology. In fact, the concept of ‘relevant circumstances’ predominates the process of delimiting maritime boundaries for the achievement of an equitable solution. It is, therefore, desirable for international courts and tribunals to adopt an appropriate methodology taking into consideration relevant circumstances in a given delimitation case, without the need to only adhere to the employment of the three-stage methodology.

경계미획정 수역을 규율하는 국제법적 체제에 관한 비판적 소고 - 유엔해양법협약 제74조 제3항 및 제83조 제3항에 관한 논의를 중심으로 -

이기범(Lee, Kibeom) 대한국제법학회 2019 國際法學會論叢 Vol.64 No.3

분쟁당사국들 간 경계미획정 수역을 규율하기 위해 유엔해양법협약 제74조 제3항 및 제83조 제3항은 하나의 법적 체제를 제공하고 있다. 제74조 제3항 및 제83조 제3항에는 두 가지 의무가 규정되어 있는데, ‘실질적인 잠정약정 체결 의무’와 ‘위태롭게 하거나 방해하지 않을 의무’이다. 하지만 실질적인 잠정약정 체결 의무는 행위의 의무에 불과하기 때문에 반드시 실질적인 잠정약정을 도출하는 결과로 이어지지는 않는다. 그리고 (실질적인 잠정약정 체결 여부에 관계없이 존재하는) 위태롭게 하거나 방해하지 않을 의무는 일방분쟁당사국의 어떤 특정 활동이 이 의무 위반인지 아닌지를 판단할 수 있는 구체적인 기준을 제공하지 못하고 있다. 이는 두 가지 의무가 경계미획정 수역을 규율하기에는 한계를 내포하고 있다는 의미이다. 2007년 가이아나-수리남 사건에서 중재재판소가 언급함으로써 지난 10년 간 관심의 주제가 되었던 ‘항구적인 물리적 변화’를 가져오는지 여부 등의 기준은 사실 위태롭게 하거나 방해하지 않을 의무 위반 여부를 판단할 수 있는 기준이라 인정하기 어렵다. 가이아나-수리남 사건에서 중재재판소조차 항구적인 물리적 변화를 가져오는지 여부 등을 위태롭게 하거나 방해하지 않을 의무 위반 여부를 판단할 수 있는 절대적인 기준으로 생각하지 않았다. 단지 항구적인 물리적 변화를 가져오는지 여부와 같은 잠정조치 명령을 내리기 위한 다소 엄격한 기준이 위태롭게 하거나 방해하지 않을 의무 위반 여부라는 더 낮은 기준을 쉽게 충족시킬 수 있다는 차원에서 하나의 예시로 제시되었을 뿐이다. 이는 항구적인 물리적 변화를 가져오지 않는 어떤 특정 활동도 위태롭게 하거나 방해하지 않을 의무 위반에 해당할 수 있다는 것을 의미하는 것이다. 그리고 항구적인 물리적 변화를 가져오는지 여부와 마찬가지로 신의성실 의무 또는 개연성 검토도 위태롭게 하거나 방해하지 않을 의무 위반 여부를 판단할 수 있는 기준이라 보기 어렵다. 그런데 유엔해양법협약 제74조 제3항 및 제83조 제3항이 일방 분쟁당사국의 어떤 특정활동이 위태롭게 하거나 방해하지 않을 의무 위반인지 여부를 판단할 수 있는 정교한 법적체제를 제공하지 못하고 있는 현실은 오히려 분쟁당사국들에게 활동의 자유를 제공하지 못할 가능성을 높인다. 해양과학조사 또는 탄성파 탐사와 같이 항구적인 물리적 변화를 가져오지 않는 활동도 경우에 따라서는 위태롭게 하거나 방해하지 않을 의무 위반에 해당할 수 있기 때문이다. 이와 같은 법적 체제의 한계는 현 유엔해양법협약 체제 내에서 경계미획정 수역 문제가 잠정약정 체결 더 나아가 최종적인 해양경계획정 합의로만 해결될 수 있을 것이라는 결론으로 이어진다. Articles 74(3) and 83(3) of the United Nations Convention on the Law of the Sea (UNCLOS) set up the legal regime to govern undelimited maritime areas. These impose two obligations: the obligation to enter into provisional arrangements of a practical nature and the obligation not to jeopardize or hamper the reaching of the final agreement. However, provisional arrangements of a practical nature are not necessarily made because the obligation to enter into provisional arrangements of a practical nature is merely the obligation of conduct. Moreover, international courts and tribunals have not developed objective criteria to determine whether a unilateral activity conducted by a State is in violation of the obligation not to jeopardize or hamper the reaching of the final agreement or not. For these reasons, the two obligations cannot govern undelimited maritime areas effectively. In the 2007 Guyana-Suriname case, the Arbitral Tribunal illustrated the concept of “activities of the kind that lead to a permanent physical change.” However, the concept cannot play a key role in determining whether the obligation not to jeopardize or hamper the reaching of the final agreement has been breached or not. In fact, even the Tribunal did not regard the concept as the sole criterion to determine whether the obligation not to jeopardize or hamper the reaching of the final agreement has been violated or not. It mentioned that “[a]ctivities that would meet the standard required for the indication of interim measures, in other words, activities that would justify the use of an exceptional power due to their potential to cause irreparable prejudice, would easily meet the lower threshold of hampering or jeopardizing the reaching of a final agreement.” This means that even activities of the kind which ‘do not’ lead to a permanent physical change could result in the alleged violation of the obligation under Articles 74(3) and 83(3) of the UNCLOS in a given case. Furthermore, good faith or the plausibility test also lacks criteria to determine whether the obligation not to jeopardize or hamper the reaching of the final agreement has been breached or not. Such a drawback found in Articles 74(3) and 83(3) of the UNCLOS could lead to the restriction of freedom of the States concerned. As the case may be, maritime scientific research or seismic exploration, which does not lead to a permanent physical change, could also violate the obligation not to jeopardize or hamper the reaching of the final agreement. Ultimately, limitations on the legal regime governing undelimited maritime areas set up by the UNCLOS have to be overcome throughout the making of provisional arrangements of a practical nature or the reaching of the final agreement.