The effects of Polychlorinated biphenyls(PCBs) on the Mammalian Cells

Youm, Jeong-Won Graduate School of Education Sookmyung Women's Uni 2005 국내석사

Apoptotic cell death is an active progress, which is a critical feature of the regulated development of multicelluar organism. Polychlorinated biphenyls (PCBs) is a group of persistent, widely dispersed environmental pollutants and shows their toxic effects including neurotoxicity, hepatotoxicity, carcinogenicity, immunotoxicity and cardiotoxicity. These toxicities depend on the chemical structure of congeners. As the usage of PCB increased, various effects of PCB on human and animals should be continuously searched. It was investigated that the cellular signaling mechanisms of PCB-induced apoptosis in diverse organ cells. As diverse organ cells treated with Aroclor 1254, one of the most widely used PCB, in the time- and dose-dependent manner was decreased cell viability significantly. By exposure of the Aroclor 1254 induced DNA fragmentation, a hall mark of Apoptosis. In monocytic cells, the Aroclor 1254-induced apoptosis was associated with the proteolytic cleavage of specific target protein such as poly (ADP-ribose) polymerase (PARP), suggesting the possible involvement of caspase. Polychlorinated biphenyls (PCBs)는 전세계적으로 광범위하게 오염되어 있는 환경오염물질로서 이중에는 신경독성물질, 간독성물질, 발암물질, 면역독성물질 등 여러가지 독성물질이 존재하는 것으로 알려져 있다. PCBs의 사용량이 늘어나는 만큼이나 실제 인간을 비롯한 동물에게 미치는 PCBs의 다양한 독성효과를 규명하고자 하는 노력은 지속적으로 수행되어져야 한다. 따라서 이 연구에서는 PCB가 어떻게 포유류 세포에 영향을 미치는지를 조사하였다. 아울러 세포 사멸(Apoptosis)은 다핵세포 생명체의 성장조절에 있어서 중요한 과정이므로 다양한 organ cells에서 PCB가 일으키는 apoptosis의 cellular signaling mechanism을 조사하여 보았다. 여러 가지 기관세포를 가지고 PCBs mixture인 Aroclor 1254의 독성효과를 관찰하고 세포 사멸(Apoptosis)를 유발함을 확인하였다. Aroclor 1254는 각각의 기관세포에서 viability를 감소시키며 특히 embryonic kidney T cell과 monocytic cell에서는 PCBs에 대해 가장 sensitive한 반응을 보였다. 그리고 Aroclor 1254는 각각의 기관세포에서 형태를 변화시켜 DNA fragmentation을 유발함을 확인하였다. 또한 monocytic cell에서는 Caspase3의 기질인 poly (ADP-ribose) polymerases (PARP) 분해를 유도하였다. 이 결과 Aroclor 1254가 각 기관세포에 사멸(apoptosis)를 유발함을 의미하며 monocytic cell에서의 사멸(apoptosis)는 caspase의 작용이 관여되어 있음을 제시하는 결과이다.

Controllability problems for abstract fuzzy differential equations in credibility space

Youm Hae eun The graduate school of Dong-A University 2013 국내박사

Freedom of the press in South Korea, 1945-1983 : a sociopolitical and legal perspective

Youm, Kyu Ho Southern Illinois University 1985 국내박사

Freedom of the press in South Korea, 1945-1983 : a sociopolitical and legal perspective

Youm, Kyu Ho University microfilms international 1989 국내박사

Freedom of the press in South Korea, 1945-83 : a sociopolitical and legal perspective

Youm, Kyu Ho U.M.I 1989 국내박사

Experimental study of hafnium oxide-based CMOS-compatible devices enabling low power operation

Youm, Gisu Sungkyunkwan University 2022 국내석사

As Moore's Law has been threatened since it faced the problem of energy consumption, many efforts have been made from a device perspective to exceed the physical limitations of traditional devices. Hafnium oxide (HfO2) is one of the most promising materials for new-generation devices because of its CMOS-compatible. CMOS compatibility of HfO2 enables improved data processing capabilities and reduced power consumption through minimal fabrication process changes. In this study, two different CMOS-compatible applications using HfO2 thin film are demonstrated. Firstly, we fabricated a HfO2-based threshold switching device for selector of one-selector-one-resistor (1S1R) cross-point memory and atomic threshold switching field-effect-transistor (ATSFET). Secondly, a one-transistor-one-capacitor negative differential transconductance (1T1C NDT) circuit is investigated with a Hf0.5Zr0.5O2-based ferroelectric capacitor. NDT can be used for multi-valued logic (MVL) devices capable of handling three or more logical states. 무어의 법칙에 따라 금속-산화물-반도체 전계 효과 트랜지스터는 지속적으로 발전을 거듭해왔지만, 최근 발열 및 터널링 문제에 봉착하며 한계에 다다르고 있다. 이 한계를 돌파하기 위해 다양한 차세대 소자가 제안되었고, 그 중 특히 하프늄 옥사이드 (HfO2)를 이용한 소자들은 CMOS 호환성이 매우 좋아 경제적 관점에서 특별히 각광받고 있다. 이 연구에서는 HfO2를 이용한 두 가지 차세대 소자를 제안한다. 먼저, of one-selector-one-resistor (1S1R) cross-point memory 또는 atomic threshold switching field-effect-transistor (ATSFET)에서 누설 전류를 억제할 수 있는 HfO2 기반의 Threshold switching 소자가 연구되었다. 이 소자는 매우 낮은 누설 전류와 steep한 switching 특성을 가진다. HfO2의 ALD 증착 온도를 최적화하여 TS device의 문턱전압 감소와 안정성 확보를 위해서. 두번째로, HfO2에 어닐링과 같은 열 공정과 도핑을 통해 얻은 Ferroelectric 특성을 이용하여 one-transistor-one-capacitor negative differential transconductance (1T1C NDT)회로가 구현되었다. Hf0.5Zr0.5O2 기반의 ferroelectric capacitor를 MOSFET의 게이트 상단에 연결하여 얻어진 NDT 효과는 multi-valued logic (MVL) 소자로서 두 개 이상의 로직 상태를 표현하는 데에 사용될 수 있다.

Discrete Element Modeling of Geosynthetic Reinforcement in Pavement Overlays

Youm, Hyeseon North Carolina State University 2012 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

Reflective cracking is one of the most serious problems in AC overlays. The application of geosynthetics in pavement rehabilitation has been considered to strengthen pavement and extend its service life, with one of the effects being the mitigation of reflective cracking. There is a major gap in the understanding of the contributing mechanisms of geosynthetics in overlays under applied loading conditions. To quantify the benefits of geosynthetics in pavement overlay for reducing or retarding reflective cracking, a better understanding of the contributing mechanisms is needed. The discrete element method (DEM) is the most suitable for capturing the particle-level behavior of complex systems such as reinforced overlays with geosynthetics. A DEM fracture model based on field scale is used for model calibration, and reflective cracking is analyzed and compared with field data with respect to both overlay thickness and geosynthetic properties, with and without reinforcement. Based on model calibration, the current research uses the discrete element method to quantify the mechanisms that govern the response of reinforced overlays with geosynthetics under different loading conditions (e.g., constant loading, constant loading rate, and dynamic wheel loading). The DEM pavement model is developed and analysis is conducted under constant loading. Analyses of displacement of overlay on top of asphalt concrete, as well as strain and stress distributions, are performed both with and without reinforcement. In addition, the stress and porosity contours of the overlay are displayed in order to enable visual evaluation. To evaluate the effects of geosynthetics, the following factors are investigated without and with reinforcement: i) effect of an initial crack on overlay (including geosynthetic properties, geosynthetic locations and aggregate distribution), ii) effect of existing pavement conditions (PCC properties, PCC crack widths), and iii) effect of overlay thickness. In addition, DEM pavement modeling is conducted under a constant loading rate of y-velocity equals 0.7 mm/s. This study includes the comparisons of maximum stress and maximum strain observed from 5 different measurement circles at a local level, and macro and micro cracks are displayed in order to enable visual comparison of reflective cracking. Finally, moving wheel load tests, as one of the different loading conditions for unreinforced and reinforced overlays, are conducted by using a DEM model. The effect of wheel movement from the left to the right side of the overlay is examined only once because of the issue of computational time. Stress and strain are monitored from measurement circles at 5 different positions along the moving wheel. The results obtained under different loading conditions clearly indicate that geosynthetic reinforcement provides significant benefit in reducing/retarding reflective cracking by reducing stress and strain. Reinforcement at one-third of depth is most effective, and increasing overlay thickness also has a strong effect on decreasing stress and strain.

Freedom of the press in South Korea, 1945-1983: a sociopolitical and legal perspective

Youm, Kyu Ho University microfilms international a bell and how 1985 국내박사

The effect of relationship type on reasoning strategies for systems understanding

Youm, Julie H Columbia University 2010 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

This study investigates whether explicit training and attention to functional relationships can improve the reasoning and understanding about complex physical systems better than training and attention to causal relationships alone. Functional relationships describe the nature or function of change between two objects and are considered dynamic, complex counterparts to simple, static causal relationships. The causal models of physical systems that are developed in one's mind are critical in allowing for the generation of predictions and explanations of a system's behavior. However, learners often do not account for the complex nature of causality in their causal models, likely due to their limited perceptions of causality itself (Chi, 2000; Grotzer, 2003; Wilensky & Resnick, 1999). To address these limitations, a focus on functional relationships is proposed as an instructional approach to engage learners in an active perspective and evoke fluid views of system interactions to better enable mental simulation and mental model development (Tsuei, 2004; Chan & Black, 2006). In this study, participants were randomly assigned to either the Functional group, who received training on functional relationships, the Causal group, who received training on causal relationships, or to a non-treatment control group. They then learned about a system selected for the study by reading an article and constructing relationships, or taking notes in the control group. Participants were asked in written posttests and structured interviews about their understanding of the systems and the strategies used in constructing relationships or taking notes. A list of representative strategies including mental simulation, looking for definitions, and considering the ability to manipulate objects was identified after reviewing the interview transcripts. Findings suggest that functional relationships engage different reasoning strategies than causal relationships when learning about complex systems, specifically those that are considered to elicit dynamic thinking. Though causal models of systems may be more salient for learners, an emphasis on functional relationships appears to be a more effective means to promote robust reasoning about a system. The positive findings from this study provide educators a revised perspective from which to present information to students, specifically, to stimulate functional reasoning when designing materials on complex topics.

(A)mineralogical and physiochemical study of the Dunjun Gold-Silver Mine

Youm, Seung-Jun Korea Univ. 1988 국내석사