Enhancement of the Raman Scattering Intensity in Folded Bilayer Graphene

윤두희,정현식,최진식,박배호 한국물리학회 2012 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.60 No.8

We found Raman scattering enhancement of the Raman G band in folded bilayer graphene. Its Raman intensity is more than 40 times greater than that of AB stacked Bernal bilayer graphene. The enhancement is interpreted as being caused by resonant Raman scattering via the π2* and the π1* states in the modified electronic band structure of the folded bilayer graphene. This enhancement of the Raman G band is a critical indicator of the strength of the coupling between the upper and the lower graphene sheets.

추계학술대회 : 일반 포스터 ; 자외선 B가 무모생쥐의 피부 장벽대 기능에 미치는 영향

윤두희,김형옥,김태윤,김정원 대한피부과학회 1995 대한피부과학회 학술발표대회집 Vol.47 No.2

춘계학술대회 : 포스타 연제 ; 사마귀양 각화이상종 1예

윤두희,허동,김태윤,김형옥,김정원 대한피부과학회 1993 대한피부과학회 학술발표대회집 Vol.45 No.1

GPS 수신기를 이용한 전리층 시간지연 측정 및 L1/L2 오차의 추정

윤두희,기창돈 한국항공우주학회 1997 한국항공우주학회 학술발표회 논문집 Vol.- No.-

의사위성을 이용한 실시간 실내 이동체 위치 파악 시스템 개발

윤두희,전해영,기창돈 한국항공우주학회 2000 한국항공우주학회 학술발표회 논문집 Vol.- No.-

전리층 지연 및 대류층 지연 모델을 이용한 실시간 보정위성항법시스템(SNUDGPS) 개발

윤두희,기창돈 한국항공우주학회 1999 한국항공우주학회 학술발표회 논문집 Vol.- No.-

LPCLysophosphatidylcholine suppresses apoptosis and induces neurite outgrowth in PC12 cells through activation of phospholipase D2

윤두희,전은수,성상민,류성호,김재호 생화학분자생물학회 2006 Experimental and molecular medicine Vol.38 No.4

Lysophosphatidylcholine (LPC) is a bioactive lipid generated by phospholipase A2-mediated hydro - lysis of phosphatidylcholine. In the present study, we demonstrate that LPC stimulates phospholipase D2 (PLD2) activity in rat pheochromocytoma PC12 cells. Serum deprivation induced cell death of PC12 cells, as demonstrated by decreased viability, DNA frag - mentation, and increased sub-G1 fraction of cell cycle. LPC treatment protected PC12 cells partially from the cell death and induced neurite outgrowth of the cells. Overexpression of PLD2 drastically en - hanced the LPC-induced inhibition of apoptosis and neuritogenesis. Pretreatment of the cells with 1-butanol, a PLD inhibitor, completely abrogated the LPC-induced inhibition of apoptosis and neurite outgrowth in PC12 cells overexpressing PLD2. These results indicate that LPC possesses the neurotrophic effects, such as anti-apoptosis and neurite outgrowth, through activation of PLD2.

Variations in the Raman Spectrum as a Function of the Number of Graphene Layers

윤두희,문혜림,Jin Sik Choi,Jung Ae Choi,박배호,정현식 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.55 No.3

We studied variations in the Raman spectrum as a function of the number of graphene layers by using micro-Raman spectroscopy and atomic force microscopy (AFM). The sample preparation was done by micromechanical cleaving of natural graphite on an 300 nm layer. The Raman G band (1580 ), band (2450 ) and 2D band (2700 ) varied as functions of the number of graphene layers. The Raman 2D band was especially sensitive to the number of graphene layers. These features are related to the electronic band structure of graphene. Moreover, areas of different numbers of graphene layers were clearly identified using spatially-resolved micro-Raman imaging spectroscopy.

자외선 B가 무모생쥐의 피부 장벽대 기능에 미치는 영향 - 경피적 수분소실과 피부각질층 지질의 변화 -

윤두희,김형옥,김태윤,김정원,송계용 ( Dou Hee Yoon,Hyung Ok Kim,Tae Yoon Kim,Chung Won Kim,Kyae Yong Song ) 대한피부과학회 1995 대한피부과학회지 Vol.33 No.4

피부 각질층은 피부의 가장 바깥층으로 포유동물에서 외부의 유해 자극으로 부터 자신을 보호하고 외부 물질의 피부 흡수 조절과 건조한 주위환경으로 포피에서의 과도한 수분증발을 방지하는 등 매우 중요한 기능을 담당한다. 각질층 지질이 피부장벽대(skin barrier function)의 주 역할인 각질층내 수분 유지기능(water holding function)과 함께 외부 수분 유입에 대한 투과 장벽대(water permeability barrier)등의 중요한 역할을 함이 알려져 있다. 이런 각질층 지질은 ceramide가 80%인 sphingolipid와 유리 지방산(free fatty acid) 및 콜레스테롤(cholesterol)이 주인 중성 지질(neutral lipid)등이 대부분이며, 각질화가 진행될수록 그 양의 증가를 보이는 sphingolipid와 유리 지방산(free fatty acid) 및 콜레스테롤(cholesterol)이 주인 중성 지질(neutral lipid)등이 대부분이며, 각질화가 진행될수록 그 양의 증가를 보이는 sphingolipid 계열의 지질들이 강력한 수소 결합력을 가져 수분 유지기능에 가장 중요한 역할을 한다. 자외선 조사는 피부의 물리적 생화학적 성상의 변화를 초래하여 홍반의 발생, 상피세포의 증식, 과색소 침착, DNA 손상, 각종 효소와 단백질의 활성 내지는 비활성, 유리 산소(oxygen radical)의 형성과 Vitamin-D_3합성 등이 있다. 자외선 조사후의 각질층 지질의 변화는 각 보고자의 실험 대상, 자외선 조사의 차이와 지질 분석의 방법에 따라서 다른 결과를 나타내기도 하였다. 본 실험에서 저자들은 정상 피부에 자극 반응을 일으키지 않는 저용량(suberythemal dose, SED)과 자극을 일으키기 시작하는 최소 홍반량(minimal srythemal dose, MED)의 자외선 B를 1주에 이틀간격으로 3회씩 3주간 반복조사함으로써 지속적인 자외선의 조사가 피부 장벽대에 시간대별로 미치는 영향과 고용량의 자외선 B를 일시에 조사하여 피부 장벽대에 손상을 입힌 후와 그 회복과정에서의 피부장벽대의 변화를 시간대별로 evaporimeter를 이용한 transepidermal water loss(TEWL)의 측정과 high performance thin layer chromatography(HPTLC)의 방법으로 각질층 지질 분석을 통하여 자외선 B가 피부 장벽대에 미치는 영향을 알아보고자 본 연구를 시도하였다. Background:Stratum corneum lipids serve as a water retainer as well as permeability barrier by forming a multi-lamellae structure in the stratum corneum. The major constituent of these lipids, ceramides, have been shown to be predominantly associated with both functions. Objective:Exposure of human epidermis to ultraviolet(UV) irradiation leads to changes in the physiologic and biochemical features of the skin. In order to investigate the effect of UVB irradiation on the skin barrier function in hairless mice, transepidermal water loss(TEWL) and lipid composition of stratum corneum were evaluated in hairless mice. Methods:Hairless mice were irradiated 3 times weekly for 3 weeks with suberythemal dose(0.6MED, Group Ⅰ) and minimal erythemal dose(MED, Group Ⅱ) of UVB. The mice of Group Ⅲ recieved high dose of UVB(3MED) on the back in a single exposure. The control was Group Ⅳ. TEWL measured by evaporimeter and lipid composition of stratum corneum appraised by high performance thin layer chromatography(HPTLC) were evaluated weekly for 3 weeks. Results: 1. Each time it was measured, the values of TEWL in group Ⅰ were lower than group Ⅳ, but the difference was not significant. The peak value of REWL in group Ⅱ was 8.2±1.56 g/㎠/h on the 7th day. The increase in TEWL was markedly significant at this point(P<0.001). Although the values of TEWL on the 14th and 21th day in group Ⅱ increased compared with those of the control group, the significance of the values decreased(P<0.05). 2. The peak value of TEWL in group Ⅲ was 9.88±1.13 g/㎠/h on the 2nd day, showed a markedly significant increase compared with that of the control group(P<0.001). The values of TEWL decreased to the level of the control group on the 14th day. 3. The lipid(cholesterol sulface, ceramide and neutral lipid) and total lipid mass in group Ⅰ were insignificantly larger than that of the group Ⅳ measured each time. On the 7th and 14th day, the amount of each three lipid and total lipid mass significantly increased(<0.05), furthermore the total lipid mass increased pronouncedly(P<0.01) in group Ⅱ. 4. The amount of the 3 kinds of lipid and total lipid mass in group Ⅲ significantly increased compared with those of the control group on the 2nd day(P<0.05). After the 7th day, no significant difference of the lipid mass except neutral lipid compared with that of the control group was seen. Comparing the 2nd and 14th day, there was a significant decrease in the amount of ceramide and total lipid mass(P<0.05). comclusion:These results suggest that considerable amount of UVB irradiation given in single or repeated exposure causes the disruption of skin barrier function, but a compensatory increase of skin lipid, sepecially ceramide, protects it from further damage and also improves skin barrier function.(Kor J Dermatol 1995;33(4):669∼678)

그래핀의 라만분광분석

윤두희,정현식 한국물리학회 2010 새물리 Vol.60 No.3

Graphene is a single atomic layer of carbon atoms, corresponding to a layer in a graphite crystal. Its many peculiar physical properties have recently attracted much interest. In graphene research. Raman spectroscopy is used not only as an indispensible characterization tool to measure the number of layers in a sample and to identify single-layer graphene positively, but also as a probe to investigate its mechanical, electrical, and optical properties. In this review,important recent results in Raman spectroscopic studies of graphene are reviewed. 흑연을 이루는 탄소원자의 한 층을 분리한 것에 해당하는 그래핀은 그특이한 물리적 특성 때문에 많은 연구의 대상이 되고 있다. 그래핀의연구에 있어서 라만분광분석은 그래핀 층수를 판별하고 단일층 그래핀을확인하는 중요한 분석도구로 활용될 뿐만 아니라, 그래핀의 기계적,전자적, 광학적 특성을 조사하는 도구로서도 중요한 역할을 하고 있다. 이 총설논문에서는 그래핀의 라만분광분석과 관련된 중요한 연구결과들을소개한다.