The Role of phenomenon-making activities in learning electromagnetism

학위논문(박사)--서울대학교 대학원 :과학교육과 물리전공,2002.Docto

무단변속기 발진클러치 시스템의 해석 및 제어

학위논문(석사)--서울대학교 대학원 :기계설계학과,1998.Maste

전기와 자기에 대한 중학생들의 개방적 탐구과정 분석

학위논문(석사)--서울대학교 대학원 :과학교육과 물리전공,1998.Maste

α-MSH 투여 시 immortalized sebocyt의 intracellular calcium 농도의 변화

Dept. of Medicine/석사[한글]여드름의 발병원인 중 가장 중요한 것이 피지선에서 분비되는 피지의 과분비로 알려져 있다. 현재까지 많은 연구에 의하여 피지 분비를 조절하는 인자는 androgen/estrogen, IGF/GF/insulin, PPAR, retinoid, melanocortin 등이 알려져 있다.여러 연구에서 stress와 관련된 피지분비증가와 관련된 기전으로 POMC에 의해서 생성된 ACTH 1-17, ACTH1-10, α-MSH 들이 분화된 sebocyte에 존재하는 MC5R에 결합하여 피지분비증가를 유발하는 것이 밝혀졌다. 또한 최근에 mouse MC5R gene을 주입하여 MC5R을 표현하는 HEK293 cell에서 melanocortin으로 MC5R를 activation 시켰을 때 intracellular calcium과 cAMP가 증가하는 것을 관찰하여 calcium ion이 피지분비증가와 피지세포분화의 신호전달 물질임을 제시하였다. 또 다른 최근 연구에서는 분화된 sebocyte에서만 MC5R가 발현되어 MC5R이 sebocyte differentiation marker라 하였으며 sebocyte 분화에 cAMP가 필요하다는 연구도 있었다실험을 통하여 differentiated SZ95 sebocyte에서 MC5R이 표현됨을 관찰하였고 α-MSH 투여에 의한 [Ca2+]i 증가는 PLC activation과 연관되어 endoplasmic reticulum 등에 저장된 Ca2+이 IP3-sensitive Ca2+ channel을 통해 분비되는 기전에 의해 이루어짐을 보여주었다. 또한 α-MSH과 testosterone을 혼합하여 SZ95 sebocyte에 투여하였을 때 각각의 투여 농도에 비례하여 피지생성이 증가함을 보여주었다. [영문]Excessive sebum secretion is known as the most important of the four traditional factors in the pathogenesis of acne. The five famous sebum controlling factors are androgen/estrogen, IGF/GF/insulin, PPAR, retinoid, and melanocortin; we focused on melanocortin, a stress related peptide.Many other studies have suggested the pathogenesis of stress induced sebum secretion, that is melanocortins, stress induced pituitary peptide hormones such as ACTH 1-17, ACTH1-10, α-MSH bind MC5R in differentiated sebocyte and it could stimulated sebocyte to secrete sebum. Recently, a study using HEK293 cells transfected with mouse MC5R showed that melanocortin peptides stimulated a rapid and transient increase in [Ca2+]i, and the increase in [Ca2+]i was of intracellular origin. Other recent studies showed that both human primary cultured sebocytes and immortalized human sebocytes have MC1R, but MC5R was only found in differentiated human primary cultured sebocytes.I proposed that differentiated immortalized human sebocyte could also have MC5R and the increase in [Ca2+]i could be a signaling molecule to increase sebum in immortalized human sebocytes (SZ95). Our results showed that differentiated SZ95 cells express MC5R, α-MSH increases in [Ca2+]i, the increase in [Ca2+]i were of intracellular origin, it might be mediated by inositol triphosphate pathway, and α-MSH stimulation increase sebum.ope

나노 구리 분말의 소결 과정에 대한 원자적 해석

MasterMolecular dynamics (MD) simulation of the sintering process for crystalline copper powders at the submicroscopic level has been performed to understand how nano-scale powders are processed. We used the embeddedatom method (EAM) to describe the interaction between Cu atoms. The amount of neck growth and shrinkage during sintering has been calculated in the simulation, which enables the extension of these results to understanding how the global physical properties are evolved during sintering. The simulation of the densification and grain growth during sintering has also been calculated, considering variations in temperature, pressure, particle size, and crystalline misalignment between adjacent particles. These computational experiences are expected to provide ways of setting the processing cycles and materials design applicable to nano-scale powders in terms of the densification and grain growth during sintering. In addition, it is expected that MD simulation will be a foundation for multi-scale modeling that spans from atomistic simulation to discrete element method (DEM) to finite element method(FEM) for sintering process