24,295 research outputs found
Soyoung Yoon, piano, Wednesday, July 11, 2007
No full textIn partial fulfillment of the requirements for the degree of Artist Diplom
원자로 가압용기로부터 고압용융물 방출에 관한 실험 및 이론적 연구
No full text학위논문(박사) - 한국과학기술원 : 원자력공학과, 1992.2, [ xvi, 191 p. ]A High Pressure Melt Ejection (HPME) is one of the most important phenomena relevant to Direct Containment Heating(DCH) which could lead to an early containment failure in a severa accident of PWRs. Dispersal of core debris following a postulated high pressure failure of PWR reactor vessel has been investigated by experimental works and one-dimensional computer modeling to find the relation between the fraction of melt simulant retained in the cavity and the reactor vessel initial conditions as well as to examine the hydrodynamic processes in a reactor cavity geometry. Simulated HPME experiments have been performed with two small-scale (1/25-th and 1/41-st) transparent reactor cavity models of the Young-Gwang unit 1\&2. Wood``s metal and water have been used as melt sumulants while high pressure nitrogen and carbon dioxide have been used as driver gases to simulate the blowdown steam and gas from the breach of the reactor pressure vessel. The high speed movies of the transient tests showed that no fraction of the melt simulant exits the cavity model via the vertical cavity tunnel under its own momentum, and that the discharged simulant from the pressure vessel exits the reactor cavity model during the gas blowdown. The principal removal mechanism seemed to be a combined mechanism of film entrainment and particle levitation due to the driving force of the blowdown gas. Experimental data for the fraction of melt simulant retained in the cavity model () during a postulated scenario of the HPME from PWR pressure vessels have been obtained as a function of various test parameters. These data have been used to develop a correlation for that fits all the data (a total of 313 data points) within the standard deviation of 0.054 by means of dimensional analysis and nonlinear least squares optimization technique. The basic effects of important parameters used to describe the HPME accident sequence on the are determined based on the correlation obtained he...한국과학기술원 : 원자력공학과
Spin-Orbit and Electron Correlation Effects on the Structure of EF(3) (E = I, At, and Element 117)
No full textStructures and vibrational frequencies of group 17 fluorides EF3 (E = I, At, and element 117) are calculated at the density functional theory (DFT) level of theory using relativistic effective core potentials (RECPs) with and without spin-orbit terms in order to investigate the effects of spin-orbit interactions and electron correlations on the structures and vibrational frequencies of EF3. Various tests imply that spin-orbit and electron correlation effects estimated presently from Hartree-Fock (HF) and DFT calculations with RECPs with and without spin-orbit terms are quite reasonable. Spin-orbit and electron correlation effects generally increase bond lengths and/or angles in both C-2v and D-3h structures. For IF3, the C-2v structure is a global minimum, and the D-3h structure is a second-order saddle point in both HF and DFT calculations with and without spin-orbit interactions. Spin-orbit effects for IF3 are negligible in comparison to electron correlation effects. The D-3h global minimum is the only minimum structure for (117)F-3 in all RECP calculations, and the C-2v structure is neither a local minimum nor a saddle point. In the case of AtF3, the C-2v structure is found to be a local minimum in all RECP calculations without spin-orbit terms, and the D-3v structure becomes a local minimum at the DFT level of theory with and without spin-orbit interactions. In the HF calculation with spin-orbit terms, the D-3h structure of AtF3 is a second-order saddle point. AtF3 is a borderline case between the valence-shell-electron-pair-repulsion (VSEPR) structure of IF3 and the non-VSEPR structure of (117)F-3. Relativistic effects, including scalar relativistic and spin-orbit effects, and electron correlation effects together or separately stabilize the D-3h structures more than the C-2v structures. As a result, one may suggest that the VSEPR predictions agree very well with the structures optimized by the nonrelativistic HF level of theory even for heavy-atom molecules but not so well with those from more elaborate theoretical methods. Vibrational frequencies of AtF3 and (117)F-3 are modified substantially and nonadditively by spin-orbit and electron correlation contributions. This is one of those rare cases for which vibrational frequencies of the closed-shell molecules are significantly affected by spin-orbit interactions. Spin-orbit interactions decrease all vibrational frequencies of EF3 molecules considered
AUTOMATIC CLOSED EYE CORRECTION
No full textRCV lab members have been supported by National Strategic R&D
Program for Industrial Technology and the Global Research Network
program (No. D00096(100363)) of National Research Foundation
of Korea. Kuk-Jin Yoon thanks the financial support of the
MKE(The Ministry of Knowledge Economy), Korea, under the
ITRC (Information Technology Research Center) support program
supervised by the IITA (Institute for Information Technology Advancement)
(IITA-2009-(C1090-0902-0017))
Spin–orbit coupling and electron correlation in relativistic configuration interaction and coupled-cluster methods
No full textWe studied convergence characteristics of relativistic effective core potential (RECP) based configuration interaction (CI) and coupled-cluster (CC) schemes in terms of spin-orbit coupling and electron correlation. The relativistic correlated methods can be divided into Kramers restricted (KR) and spin-orbit (SO) methods which differ by the stage of spin-orbit treatment: the KR method employs two-component Kramers restricted Hartree-Fock (HF) spinors as the one-electron basis in which spin-orbit coupling is included, whereas the SO method is based on one-component molecular orbitals generated from scalar relativistic HF and the spin-orbit interaction is then entered in post-HF step. The KR method is usually superior to the SO method for molecules containing heavy elements since spin-orbit coupling is included from the HF step. A performance calibration of the SO method against the KR method is performed by computations of the ground state energies and equilibrium bond lengths of MH (M = Tl, Pb, Bi, Po, and At). Spin-orbit coupling of each molecule was systematically increased by adjusting the spin-orbit operator of RECP to investigate its impact on the SO method. Although KRCI and SOCI converged to the same full-CI limit, for the strong spin-orbit coupling SOCI required higher levels of correlation compared to KRCI to account for the orbital relaxation effect. SOCC, in contrast, was able to recover both spin-orbit interaction and electron correlation in CC steps regardless of the spin-orbit strength, implying that SOCC could be the reliable and efficient relativistic ab initio method for moderate sized molecules containing heavy elements. (C) 2011 Elsevier B.V. All rights reserved
Studies on the Mechanism of Polyamine-and Prothrombin kringle-2-induced Degeneration of Neuron and Microglia
No full text학위논문(박사)--아주대학교 일반대학원 :의학과,2010. 8퇴행성 뇌 질환의 주요원인은 신경세포 사멸이라 할 수 있다. 따라서 신경세포 사멸의 기전을 밝히는 것은 뇌 질환의 과정을 이해하고 중재하는 하는 방법을 가능하게 할 것이다.
뇌의 염증반응은 퇴행성 뇌 질환의 발병에 관여하는 것으로 알려져 있다. 뇌의 면역세포로 잘 알려진 신경교세포인마이크로글리아는 염증 매개물질들을 생성하는데 이러한 염증매개물질들은신경세포사멸의 한 원인으로 작용하고 있다. 또한 뇌의 생체항상성을유지하기 위해서는 활성화된 신경교세포는 항 염증반응 사이토카인 (antiinflammatory cytokine)들에 의해 제어되어야 한다. 따라서 본 연구는 파 킨 슨 병 에 서 일 어 나 는 도 파 민 신 경 세 포 사 멸 기 전 연 구 와 더 불 어 활성화된 신경교세포 가 신경세포 사멸 및 사멸방지에 관련된 작용 기전을조사하였다.
최근연구결과에 의하면 p o l y am i n e 은 신경세포 사멸을 유발시킨다고 알려졌다. 체내 또는 시험관내의 사멸은 polyamine 의 생합성 효 소 인 o r n i t h i n e d e c a r b o x y l a s e ( O D C ) 의 반 응 억 제 제 인 α-difluoromethylornithine (DFMO)의 처리에 의해 보호되는 것을 관찰하였다. TRPV1 길항제인 capsazepine (CZP)에 의하여 6-OHDA 와 polyamine 에 의한 도파민 신경세포의 손상이 억제되는 것을 보아, TRPV1 활 성 이 도 파 민 신 경 세 포 독 성 에 관 여 하 는 확 인 할 수 있 었 다 .
또 한 중뇌신경세포 배양에 DFMO 를 전 처리한 후 6-OHDA 를 처리 하였을 때6-OHDA 만 처리한 경우와 다르게 인산화된 Akt 의 증가와 caspase-3 의 억 제 를 w e s t e r n b l o t 으 로 확 인 하 였 다 .
이 실 험 결 과 로 중 뇌 신경세포배양에서 도파민 신경세포의 신경독성에 관여하는 6-OHDApo l y a m i n e s - T R P V 1 간 신호전 달 체계 를 처 음으로 확인하였다.
프로쓰롬빈 크링글-2 는 염증을 유발시킬 수 있는 물질로 뇌의 면역반응에 관여하는 마이크로글리아를 활성화 시켜 염증매개물질들을 유발시킨다고 알려졌다. 프로쓰롬빈 크링를-2 의 증가는 주로 혈장내 프로쓰롬빈으로부터 나오지만 여러 보고들에 의하면 뇌에서도 프로쓰롬빈의 전사체가 발현 되어지고 손상이 일어났을 때 쓰롬빈의 양이 증가하는 것처럼 프로쓰롬빈 크링를-2 의 생성이 증가된다고 볼 수 있다.
프로쓰롬빈 크링를-2 을해마대뇌피질에 주입하였을 때 강한 마이크로글리아의 활성화를 면역화학염색법을 통해 관찰할 수 있었고, 활성화된 마이크로글리아에서 염증반응을 유발시킬 수 있는 물질들의 발현을 관찰할 수 있었다.
또한 프로쓰롬빈 크링글-2 에 의해서 NADPH oxidase의 구성요소 (p47 ^(phox),
p67^(phox))의 발현이 증가되고, p67^(phox)가 마이크로글리아에 위치하고, NADPH
oxidase의 활성화에 필요한 p67^(phox)의 세포질로부터 세포막으로의 이동을 관찰하였다. 프로쓰롬빈 크링글-2 에 의한 활성산소의 생성을 대뇌피질에서 관찰하였다. 이런 일련의 과정을 통해 만들어진 활성산소에 의해서 단백질의산화와 신경세포의 사멸이 유발된다는 것을 NADPH oxidase저해제, 항산화제를 사용하여 검증할 수 있었다. 이 결과를 통해 프로쓰롬빈 크링글-2 에 의한 신경세포사멸은 마이크로글리아의 활성화에 의한
세포독성을 유발시킬 수 있는 물질의 생성증가와 세포변성을 일으키는 활성산소의 생성을 통해 일어난다는 것을 확인하였다.
따라서, 과도한 마이크로글리아와 NADPH oxidase활성화를 저해하면 산화적 염증반응을
통해 일어나는 세포사멸을 억제할 수 있을 것이다.
과도하게 활성화된 마이크로글리아의 염증반응을 조절하는 기전은 매우 중요하고 필요하다.
뇌의 염증반응을 조절하는 중요한 기전 중의 하나는 활성화된마이크로글리아의 사멸이다. 프로쓰롬빈 크링글-2 에 의해 활성화된마이크로글리아에 Interleukin-13 이나 Interleukin-4 를 같이 처리하였을때 8 일째 마이크로글리아의 사멸을 관찰하였다. 흥미롭게도 프로쓰롬빈크링글-2 를 단독 처리하였을 때 보다 Interleukin-13 이나 Interleukin-4 를 프로쓰롬빈 크링글-2 와 함께 처리 하였을때 활성산소가 더 증가되는것을 확인하였다.
게다가 Interleukin-13 이나 Interleukin-4 가 증가시킨활성산소는 NADPH oxidase 의 반응억제제인 apocynin 에 의해 감소되는것을 확인하였다.
Interleukin-13 이나 Interleukin-4 에 의한 마이크로글리아의 사멸은 NADPH oxidase 의 저해제와 항산화제 에 의해감소되는 것을 관찰하였다. 프로쓰롬빈 크링글-2 와 Interleukin-13 이나Interleukin-4 를 같이 처리하였을 때 Cyclooxygenase-2 (COX-2) 가
증가하였다.
NADPH oxidase 의 저해제와 항산화제 에 의해 Interleukin-13 이나 Interleukin-4 에 의해 증가된 COX-2 의 증가는 감소되었다.
COX-2 저해제를 처리하였때 Interleukin-13 이나 Interleukin-4 에 의한 마이크로글리아의 사멸이 감소되는 것을 관찰하였다.I. INTRODUCTION 1
II. MATERIALS AND METHODS 16
A. METHODS 16
1. Sterotaxic surgery and drug injection 16
2. Tissue preparation and immunohistochemistry 16
3. Double-immunofluorescence staining 18
4. Live and dead assay 19
5. MTT Reduction Assay 19
6. TdT-mediated dUTP Nick-EnD Labeling (TUNEL) assay 20
7. Immunocytochemistry 20
8. Reverse transcription-polymerase chain reaction (RT-PCR) 21
9. Western blot analysis 21
10. In situ detection of O2- and O2- -derived oxidants 23
11. Detection of protein oxidation 24
12. Measurement of ROS Generation 25
13. Primary culture of cortical neuron, drug treatement, and assessment neuronal cell death 25
14. Primary culture of dopaminergic neuron, drug treatement, and assessment neuronal cell death 26
15. Cortical Microglia Cultures 27
16. Co-cultures of microglia and neurons 27
17. ODC enzyme activity assay 28
18. Dopamine (DA) uptake assay 28
19. Measurement of the densities of the immunoblot bands 29
20. Determination of NO 29
21. Quantification of TNF- Release 29
22. Statistical analysis 29
III. RESULTS 30
PART I. DFMO, Ornithine Decarboxylase Inhibitor, Prevents 6- hydroxydopamine-Induced Neurotoxicity in Rat Mesencephalic Dopaminergic Neuron 30
1. Polyamine depletion protects on 6-OHDA-induced neurotoxicity of dopainergic neurons in neuron-enriched mesencephalic culture 30
2. ODC activity in neuron-enriched mesencephalic culture exposed to 6-hydroxydopamine (6-OHDA) 34
3. Spermidine and Spermine induces neurotoxicity of dopaminergic neurons in neuron-enriched mesencephalic culture 36
4. Polyamines and 6-OHDA induces loss of dopaminergic neurons through TRPV1 in neuron-enriched mesencephalic culture 38
5. Effects of DFMO on the phosphorylation of AKT and activation of caspase-3 in neuron-enriched mesencephalic culture exposed to 6-OHDA 40
6. Depletion of Polyamines rescue dopaminergic neurons in the SN from 6-OHDA-induced neurotoxicity in vivo 42
PART II. Prothrombin kringle-2-induced oxidative stress contributes to the death of cortical neurons in vivo and in vitro:Role of microglial NADPH oxidase. 45
1. pKr-2 induces microglial activation and proinflammatory cytokines in the cortex in vivo 45
2. pKr-2 stimulates NADPH oxidase-mediated production of ROS by activated microglia in the cortex 51
3. NADPH oxidase contributes to pKr-2-induced neurodegeneration in the cortex in vivo 56
4. pKr-2 induces cortical neuron death in co-cultures of neuron and microglia.58
PART III. IL-13/IL-4 regulate oxidative stress via activation of NADPH oxidase and cell death of microglia in Prothrombin kringle-2-treated microglia culture 61
1. IL-13/IL-4 induced cell death of cultured rat microglia 61
2. Interleukin-13/-4 enhances the NADPH Oxidase-Mediated Production of ROS in pKr-2 treated microglia cultures 64
3. NADPH oxidase contributes to IL-13/IL-4-induced death of activated microglia In vitro 66
4. Interleukin-13/-4-enhanced COX-2 contributes to microglia cell death mediated by the NADPH oxidase-mediated production of ROS 69
IV.DISCUSSION 72
V.CONCLUSION 87
REFERENCES 88
국문요약 141MasterNeural cell death is the defining feature of all neurodegenerative diseases and is the underlying cause of many functional deficits. Clarifying the mechanism of cell death in the nervous system is essential to understand disease pathology and to devise effective treatment strategies. Increasing evidence has linked chronic inflammation to a number of neurodegenerative disorders including Alzheimer’s disease (AD), Parkinson’s disease (PD). In the central nervous system, microglia, the resident innate immune cells play major role in inflammatory process. Microglia may directly toxic to neurons by releasing various substances such as inflammatory cytokines. Thus, it is pathophysiologically important to understand how the extent and duration of brain inflammation is controlled in vivo. In addition to down-regulation of inflammatory mediators, the extent and duration of inflammation in the CNS may be controlled by the removal of activated microglia. Therefore, this study shows the degeneration mechanism of dopaminergic neuron and the rolls of activated microglia to provocation or prevention of neuronal cell death.
Recently polyamines have been also implicated in cell death. I examined whether polyamines, endogenous ligand for transient receptor potential vanilloid 1 (TRPV1), could mediate 6-hydroxydopamine (6-OHDA)-induced Mesencephalic Dopaminergic (DA) Neurons In vivo and In Vitro. Intranigral injection of the 6-OHDA into the rat brain, or treatment of rat mesencephalic cultures with 6-OHDA, resulted in cell death of dopaminergic (DA) neurons, as visualized by immunocytochemistry. This in vivo and in vitro effect was prevented by the -difluoromethylornithine (DFMO), an inhibitor of polyamines biosynthesizing enzyme ornithine decarboxylase (ODC), suggesting the direct involvement of Polyamines in neurotoxicity. TRPV1 antagonist capsazepine (CZP) reversed 6-OHDA-or polyamines-induced loss of DA neurons in vivo and in vitro, indicating TRPV1-mediated neurotoxicity. Western blot analysis also showed that pretreatment with DFMO reversed 6-OHDA-induced downregulation of phosphorylated Akt and upregulation of cleaved caspase-3 in mesencephalic cultures. This result is the first to show that 6-OHDA-polyamines-TRPV1 signaling pathway exerts neurotoxicity on dopaminergic neurons in vivo and in vitro. Prothrombin kringle-2 acts as an proinflammtory agent that activates microglia to release pro-inflammatory mediators. Intracortical injection of pKr-2 caused significant loss of cortical neurons in vivo after seven days, as evident from Nissl staining and immunohistochemical analysis using the neuronal-specific nuclear protein (NeuN) antibody. In parallel, pKr-2-activated microglia and ROS production were observed in rat cortex displaying degeneration of cortical neurons. Reverse transcription-PCR at various time points after pKr-2 administration disclosed early and transient expression of inducible nitric oxide synthase (iNOS) and proinflammatory cytokines, such as interleukin 1β (IL-1β). Co-localization of iNOS, IL-1β, and TNF-α within microglia was evident with double-label immunohistochemistry. Additionally, pKr-2 induced upregulation of cytosolic components of NADPH oxidase (p67phox), translocation of cytosolic p67phox protein to the membrane, and p67phox expression in microglia in the cortex in vivo, signifying NADPH oxidase activation. The pKr-2-induced oxidation of proteins and loss of cortical neurons were partially inhibited by DPI, an NADPH oxidase inhibitor, and trolox, an antioxidant. Consistent with my hypothesis, following treatment with pKr-2 in vitro, neurotoxicity was detected exclusively in co-cultures of cortical neurons and microglia, but not in microglia-free neuron-enriched cortical cultures, indicating that microglia are required for pKr-2 neurotoxicity. My results strongly suggest that pKr-2 as an endogenous compound participates in cortical neuron death through microglial NADPH oxidase-mediated oxidative stress. Therefore, inhibition of microglial NADPH oxidase activation may offer prospective clinical therapeutic benefit for neuroinflammation-related neurodegenerative disorders. How to minimize brain inflammation is pathophysiologically important, since inflammation induced by microglial activation can exacerbate brain damage. Thus, Death of activated microglia could act as a critical mechanism for the resolution of brain inflammation. Microglia cell death was detected at eight days after co-treatment of pKr-2 with IL-13/IL-4 in vitro. This cell death assessed by live and dead assay, TUNEL and MTT assay. Interestingly, superoxide assay, WST-1 show significantly increased reactive oxygen species (ROS) in combination of pKr-2 and IL-13 or IL-4 treated microglia. Additionally, the IL-13/IL-4-enhanced ROS were partially inhibited by an NADPH oxidase inhibitor. The IL-13/IL-4 induced cell death of microglia were partially inhibited by an NADPH oxidase inhibitor and by an antioxidant. Therefore, I hypothesized that the effects of IL-13/IL-4 and NADPH oxidase-derived ROS production may be linked to death of activated microglia. Moreover, Western blot analysis show significantly increased Cyclooxygenase-2 (COX-2) expression in combination of pKr-2 and IL-13 or IL-4 treated microglia. The IL-13/IL-4-enhanced COX-2 expression were partially inhibited by an NADPH oxidase inhibitor and an antioxidant. Additional studies demonstrated that microglia cell death was reversed by treatment with NADPH oxidase inhibitor, antioxidant, and COX-2 inhibitor. To my knowledge, This result is the first to demonstrate that IL-13/IL-4 induced cell death of pKr-2 activated microglia is mediated by oxidative stress and COX-2 through NADPH oxidase
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