HWE(Hot Wall Epitaxy)에 의한 ZnIn_2S_4 박막 성장과 광전도 특성

홍광준,이관교,정준우,정경아,방진주,장현규,문종대,김혜숙 조선대학교 기초과학연구소 1999 自然科學硏究 Vol.22 No.1

HWE 방법에 의해 ZnIn_2S_4 박막을 Si(00) 기판 위에 성장시켰다. 증발원과 기판의 온도를 각각 610℃, 450℃로 하여 성장시킨 ZnIn_2S_4 박막의 이중 결정 X-선 요동곡선(DCRC)의 반폭치(FWHM)값이 245 arcsec로 가장 작았다. Van der Pauw 방법으로 Hall 효과를 측정하여 운반자농도의 1n n 대 1/T에서 구한 활성화에너지는 0.17eV로 측정되었다. Hall 이동도의 온도 의존성은 30K에서 100K까지는 불순물산란에 기인하고, 100K에서 293K까지는 격자산란에 기인한것으로 고찰되었다. 광전도셀의 특성으로 spectral response, 최대 허용소비전력(MAPD), 광전류와 암전류(pc/dc)의 비 및 응답시간을 측정하였다. S 증기분위기에서 열처리한 광전도 셀의 경우, 감도(??)는 0.99, pc/dc은 1.37x10^7, 그리고 최대 허용소비전력(MAPD)은 336mW, 오름시간(rise time)은 9ms, 내림시간(decay time)은 9.8ms로 가장 좋은 광전도 특성을 얻었다. The ZnIn_2S_4 thin films were grown on the Si(100) wafers by a hot wall epitaxy method(HWE). The source and substrate temperature are 610℃ and 450℃ respectively. The crystalline structure of epilayers was investigated by double crystal X-ray diffraction(DCXD). Hall effect on the sample was measured by the van der Pauw method and studied on the carrier density and mobility dependence on temperature. From Hall data, the mobility was increased in the temperature range 30K to 100K by impurity scattering and decreased in the temperature range 100K to 293K by the lattice scattering. In order to explore the applicability as a photoconductive cell, we measured the sensitivity(??), the ratio of photocurrent to darkcurrent(pc/dc), maximum allowable power dissipation(MAPD), spectral response and response time. The results indicated that the photoconductive characteristic were the best for the samples annealed in S vapor compare with in Zn, In, air and vacuum vapour. Then we obtained the sensitivity of 0.99, the value of pc/dc of 1.37x10^7, the MAPD of 336mW, and the rise and decay time of 9ms and 9.8ms, respectively.

유우개량을 위한 유단백질의 유전적 다형에 관한 연구 Ⅰ. αS1 - Casein 및 K - Casein 의 유전적 변이체

한상기(Sang K . Han),이기만(Khy M . Lee),정의용(Eui Y . Chung),장경진(Kyung J . Jang) 한국축산학회 1984 한국축산학회지 Vol.26 No.3

Genetic variants of αs₁-casein (αs₁-Cn) and K-casein (k-Cn) in milk proteins from 138 individual Holstein cattle in Korea were investigated by means of strach-gel-urea electrophoresis and the appearance of phenotypes, gene frequencies and genetic similarities were compared with those of foreign Holstein and of her breeds. The results are summarized as follows: 1. The milk proteins in cattle were controlled by codominant autosomal allelic genes of 9αs₁-Cn^A and αs₁-Cn^B(2 types), and K-Cn^A and K-Cn^B (2 types). 2. The distribution of phenotypes in each milk protein loci was αs₁-Cn BB 124, BC 14; K-Cn AA 76 Ab 49, BB 13. The number of phenotypes coxesponded closely to expectation of Hardy-Weinberg equilibrium (αs₁-Cn:0.7 $gt;P$gt;0.5, k-Cn;0.7$gt;P$gt;0.5). 3. Gene frequencies for genetic variants of the milk protein loci were analyzed. By the predominant allele in αs₁-Cn was αs₁-Cn B with a frequency of 0.949, whereas αs₁-CnC was in low gene frequency (0.051). Among the two alleles for K-Cn, K-Cn A gene showed to occur in high frequency (0.728). However, the Kin B was in low gene frequency (0.272).

Synthesis and Thermoelectric Properties of Ce1−z Pr z Fe4−x Co x Sb12 Skutterudites

Song, K. M.,Shin, D. K.,Jang, K. W.,Choi, S. M.,Lee, S.,Seo, W. S.,Kim, I. H. Springer Science + Business Media 2017 Journal of electronic materials Vol.46 No.5

<P>p-Type Ce1-z Pr (z) Fe4-x Co (x) Sb-12 skutterudites were prepared by encapsulated melting, quenching, annealing, and hot pressing. While the skutterudite phase was successfully synthesized, a small amount of the secondary phase (FeSb2) was observed. According to the scanning electron microscope analysis, (Ce,Pr)Sb-2 phases were also observed for Co-substituted specimens (x = 0.5). The electrical conductivity decreased with increasing temperature, implying a degenerate semiconductor behavior, and also decreased with increasing Co contents. All specimens showed p-type characteristics having positive signs of the Hall coefficient and the Seebeck coefficient. The Seebeck coefficient increased with increasing temperature and reached a maximum value at 823 K. The power factor (PF) increased with decreasing Co content and Ce0.75Pr0.25 Fe4Sb12 showed a peak value of PF = 3.2 mW m(-1) K-2 at 823 K. The electronic thermal conductivity decreased with increasing Co contents and the lattice thermal conductivity decreased with decreasing Ce and Co contents at high temperature. The thermal conductivity increased at temperatures above 623 K due to bipolar conduction. The dimensionless figurea of pound merit (ZT) showed a maximum value of ZT = 0.84 at 823 K for Ce0.25Pr0.75Fe4Sb12.</P>

Runx3 is required for the differentiation of lung epithelial cells and suppression of lung cancer

Lee, K-S,Lee, Y-S,Lee, J-M,Ito, K,Cinghu, S,Kim, J-H,Jang, J-W,Li, Y-H,Goh, Y-M,Chi, X-Z,Wee, H,Lee, H-W,Hosoya, A,Chung, J-H,Jang, J-J,Kundu, J K,Surh, Y-J,Kim, W-J,Ito, Y,Jung, H-S,Bae, S-C Macmillan Publishers Limited 2010 Oncogene Vol.29 No.23

Human lung adenocarcinoma, the most prevalent form of lung cancer, is characterized by many molecular abnormalities. K-ras mutations are associated with the initiation of lung adenocarcinomas, but K-ras-independent mechanisms may also initiate lung tumors. Here, we find that the runt-related transcription factor Runx3 is essential for normal murine lung development and is a tumor suppressor that prevents lung adenocarcinoma. Runx3−/− mice, which die soon after birth, exhibit alveolar hyperplasia. Importantly, Runx3−/− bronchioli exhibit impaired differentiation, as evidenced by the accumulation of epithelial cells containing specific markers for both alveolar (that is SP-B) and bronchiolar (that is CC10) lineages. Runx3−/− epithelial cells also express Bmi1, which supports self-renewal of stem cells. Lung adenomas spontaneously develop in aging Runx3+/− mice (∼18 months after birth) and invariably exhibit reduced levels of Runx3. As K-ras mutations are very rare in these adenomas, Runx3+/− mice provide an animal model for lung tumorigenesis that recapitulates the preneoplastic stage of human lung adenocarcinoma development, which is independent of K-Ras mutation. We conclude that Runx3 is essential for lung epithelial cell differentiation, and that downregulation of Runx3 is causally linked to the preneoplastic stage of lung adenocarcinoma.

The Phase-Shift Method for the Langmuir Adsorption Isotherms of Electroadsorbed Hydrogens for the Cathodic H₂ Evolution Reactions at the Poly-Pt Electrode Interfaces

천장호,전상규,이재항,Chun, Jang H.,Jeon, Sang K.,Lee, Jae H. The Korean Electrochemical Society 2002 한국전기화학회지 Vol.5 No.3

순환전압전류 및 교류임피던스 기법을 이용하여 다결정 Pt/0.5M $H_2SO_4$ 및 0.5M LiOH수용액 계면에서 저전위 수소흡착(UPD H) 과 전위 수소흡착(OPD H)에 관한 Langmuir 흡착등온식 $({\theta}\;vs.\;E)$ 을 연구조사 하였다. 계면에서 치적중간주파수일 때 위상이동$(0^{\circ}{\leq}{-\phi}{\leq}90^{\circ})$ 거동은 표면피복율$(1{\geq}{\theta}{\geq}0)$ 거동에 정확하게 상응한다. 위상이 동 방법 즉 최적중간주파수일 때 위상이동 변화$({-\phi}\;vs.\;E)$는 계면에서 음극 $H_2$ 발생 반응에 관한 UPD H와 OPDH의 Langmuir흡착등온식을 결정할 수 있는 새로운 전기화학적 방법으로 사용할 수 있다 다결정 Pt/0.5M $H_2SO_4$ 수용액 계면에서 OPD H의 흡착평형상수(K)와 표준자유에너지$({\Delta}G_{ads})$는 각각 $2.1\times10^{-4}$와 21.0kJ/mol 이다. 다결정 Pt/0.5M LiOH 수용액 계면에서 K는 음전위(E)에 따라 2.7 (UPD H)에서 $6.2\times10^{-6}$ (OPD H) 또는 $6.2\times10^{-6}$(OPD H)에서 2.7 (UPD H)로 전이한다. 유사하게 ${\Delta}G_{ads}$는 E에 따라 -2.5kJ/mol (UPD H)에서 29.7kJ/mol (OPD H)또는 29.7kJ/mol (OPD H)에서 -2.5kJ/mol (UPD H)로 전이한다. K와 ${\Delta}G_{ads}$의 전이는 다결정 Pt전극 표면의 상이한 UPD H와 OPD H의 흡착부위에 기인한다. 다결정 Pt전극 계면에서 UPD H와 OPD H는 음극 $H_2$ 발생 반응에 따른 순차적 과정이 아니라, 수소 흡착부위 자체에 따른 독립적 과정이다. UPD H와 OPD H의 기준은 음극 $H_2$발생 반응과 전위가 아니라, 수소 흡착부위와 과정이다. 수용액에서 음극 $H_2$발생 반응에는 다결정 Pt선 전극이 단결정 Pt(100)원반 전극보다 더 효율적이고 유용하다 위상이동 방법은 열역학적 방법과 상충적이 아니라, 보완적이다. The Langmuir adsorption isotherms of the under-potentially deposited hydrogen (UPD H) and the over-potentially deposited hydrogen (OPD H) at the poly-Pt/0.5M $H_2SO_4$ and 0.5 M LiOH aqueous electrolyte interfaces have been studied using cyclic voltammetric and ac impedance techniques. The behavior of the phase shift $(0^{\circ}{\leq}{-\phi}{\leq}90^{\circ})$ for the optimum intermediate frequency corresponds well to that of the fractional surface coverage $(1{\geq}{\theta}{\geq}0)$ at the interfaces. The phase-shift method, i.e., the phase-shift profile $({-\phi}\;vs.\;E)$ for the optimum intermediate frequency, can be used as a new electrochemical method to determine the Langmuir adsorption isotherms $({\theta}\;vs.\;E)$ of the UPD H and the OPD H for the cathodic $H_2$ evolution reactions at the interfaces. At the poly-Pt/0.5M $H_2SO_4$ aqueous electrolyte interface, the equilibrium constant (K) and the standard free energy $({\Delta}G_{ads})$ of the OPD H are $2.1\times10^{-4}$ and 21.0kJ/mol, respectively. At the poly-Pt/0.5M LiOH aqueous electrolyte interface, K transits from 2.7(UPD H) to $6.2\times10^{-6}$ (OPD H) depending on the cathode potential (E) and vice versa. Similarly, ${\Delta}G_{ads}$ transits from -2.5kJ/mol (UPD H) to 29.7kJ/mol (OPD H) depending on I and vice versa. The transition of K and ${\Delta}G_{ads}$ is attributed to the two distinct adsorption sites of the UPD H and the OPD H on the poly-Pt surface. The UPD H and the OPD H on the poly-Pt surface are the independent processes depending on the H adsorption sites themselves rather than the sequential processes for the cathodic $H_2$ evolution reactions. The criterion of the UPD H and the OPD H is the H adsorption sites and processes rather than the $H_2$ evolution reactions and potentials. The poly-Pt wire electrode is more efficient and useful than the Pt(100) disc electrode for the cathodic $H_2$ evolution reactions in the aqueous electrolytes. The phase-shift method is well complementary to the thermodynamic method rather than conflicting.

Role of conserved Met112 residue in the catalytic activity and stability of ketosteroid isomerase

Cha, H.J.,Jang, D.S.,Jeong, J.H.,Hong, B.H.,Yun, Y.S.,Shin, E.J.,Choi, K.Y. Elsevier Science 2016 Biochimica et biophysica acta. Proteins and proteo Vol.1864 No.10

<P>Ketosteroid isomerase (3-oxosteroid Delta(5)-Delta(4)-isomerase, KSI) from Pseudomonas putida catalyzes allylic rearrangement of the 5,6-double bond of Delta(5)-3-ketosteroid to 4,5-position by stereospecific intramolecular transfer of a proton. The active site of KSI is formed by several hydrophobic residues and three catalytic residues (Tyr14, Asp38, and Asp99). In this study, we investigated the role of a hydrophobic Met112 residue near the active site in the catalysis, steroid binding, and stability of KSI. Replacing Met112 with alanine (yields M112A) or leucine (M112L) decreased the k(cat) by 20- and 4-fold, respectively. Compared with the wild type (WT), M112A and M112L KSIs showed increased K-D values for equilenin, an intermediate analogue; these changes suggest that loss of packing at position 112 might lead to unfavorable steroid binding, thereby resulting in decreased catalytic activity. Furthermore, M112A and M112L mutations reduced melting temperature (T-m) by 6.4 degrees C and 2.5 degrees C, respectively. These changes suggest that favorable packing in the core is important for the maintenance of stability in KSI. The M112K mutation decreased k(cat) by 2000-fold, compared with the WT. In M112K KSI structure, a new salt bridge was formed between Asp38 and Lys112. This bridge could change the electrostatic potential of Asp38, and thereby contribute to the decreased catalytic activity. The M112K mutation also decreased the stability by reducing T-m by 4.1 degrees C. Our data suggest that the Met112 residue may contribute to the catalytic activity and stability of KSI by providing favorable hydrophobic environments and compact packing in the catalytic core. (C) 2016 Published by Elsevier B.V.</P>

Inconel 718 상향 엔드밀링시 절삭력에 미치는 공구형상오차

이영문,양승한,장승일,백승기,김선일 한국공작기계학회 2002 한국공작기계학회 춘계학술대회논문집 Vol.2002 No.-

In end milling process, the undeformed chip section area and cutting forces vary periodically with phase change of the tool. However, the real undeformed chip section area deviates from the geometrically ideal one owing to cutter runout and tool shape error. In this study, a method of estimating the real undeformed chip section area which reflects cutter runout and tool shape error was presented during up-end milling of Inconel 718 using measured cutting forces. The specific cutting resistance, K_(r) and K_(t) are defined as the radial and tangential cutting forces divided by the modified chip section area. Both of K_(r) and K_(t) values become smaller as the helix angle increases from 30° to 40°. Whereas they become larger as the helix angle increases from 40° to 50°. On the other hand, the K_(r) and K_(t) values show a tendency to decrease with increase of the modified chip section area and this tendency becomes distinct with smaller helix angle.

Telomere length, TERT and shelterin complex proteins in hepatocellular carcinomas expressing ''stemness''-related markers

Kim, H.,Yoo, J.E.,Cho, J.Y.,Oh, B.K.,Yoon, Y.S.,Han, H.S.,Lee, H.S.,Jang, J.J.,Jeong, S.H.,Kim, J.W.,Park, Y.N. Elsevier Science Publishers 2013 Journal of hepatology Vol.59 No.4

Background & Aims: Hepatocellular carcinomas (HCCs) expressing ''stemness''-related markers have been associated with aggressive biological behavior and poor prognosis. We examined the relationship between ''stemness''-related protein expression and telomere length, hTERT and shelterin complex protein expression and chromosomal instability. Methods: Quantitative fluorescent in situ hybridization for telomere length, immunohistochemistry for K19, EpCAM, CD133, c-kit, HepPar1, hTERT, TRF1, TRF2, POT1, RAP1 and TPP1, and TUNEL assay were performed in 137 HCCs, and array comparative genomic hybridization was performed with 24 HCCs. Results: Telomeres were significantly longer in HCCs expressing ''stemness''-related proteins (K19: p<0.001, EpCAM: p=0.002, CD133: p=0.002). On analyzing different tumor cells within EpCAM-expressing HCCs, EpCAM-positive tumor cells showed longer telomeres (1.329+/-0.246) compared to EpCAM-negative tumor cells (0.996+/-0.381) within the same HCCs (p=0.031). Telomeres were significantly longer in HCCs expressing hTERT (p=0.048) and RAP1 proteins (p=0.031). K19-expressing HCCs expressed hTERT (p=0.002), TRF2 (p=0.001) and TPP1 (p=0.013) more frequently compared to K19-negative HCCs. EpCAM-positivity was associated with more frequent hTERT (p=0.028), TPP1 (p=0.017), TRF2 (p=0.027) and POT1 (p=0.004) expression. Copy number alterations were more frequent in K19 and EpCAM-expressing HCCs compared to HCCs without these markers (K19: p=0.038, EpCAM: p=0.009). HCCs with longer telomeres were associated with a shorter overall (p=0.019) and disease-free survivals (p=0.049), and decreased disease-free survivals were seen in TRF2-positive HCCs (p=0.018). Conclusions: HCCs expressing ''stemness''-related proteins are characterized by increased telomere length, increased expression of hTERT and shelterin complex proteins, and increased chromosomal instability compared to conventional HCCs. Longer telomeres and TRF2 expression in HCCs are associated with poor patient outcomes.

InAs 양자점의 크기에 따른 분광학적 특성

권영수(Y. S. Kwon),임재영(J. Y. Leem),이철로(C. R. Lee),노삼규(S. K. Noh),유연희(Y. H. Ryu),최정우(J. W. Choe),김성만(S. M. Kim),이욱현(U. H. Lee),류동현(D. H. Ryu),이동한(D. H. Lee),박장환(Jang-Hwan Park) 한국진공학회(ASCT) 1999 Applied Science and Convergence Technology Vol.8 No.4(1)

MBE(Molecular Beam Epitaxy) 방법으로 InAS 양자점의 크기를 달리하여 성장한 lnAs 양자점의 구조적 특성과 분광학적 특성을 조사하였다. 구조적 특성은 AFM(Atomic Force Microscopy)으로 하였으며, 광학적 특성은 PL(Photoluminescence)로 수행하였다. AFM 측정결과 양자점의 밀도는 2 ML에서 최대 값인 1.1×10¹¹/㎠이다. 양자점의 크기가 증가함에 따라 PL 피크는 적색편이를 하고 있었다. 발광피크의 온도의존성을 조사한 결과 온도의 증가에 따라 발광피크는 낮은 에너지로 이동하였으며, 20 K에서 180 K 구간에서는 발광피크의 FWHM(Full Width at Half Maximum) 값은 감소하였으며, 180 K 이상의 온도에서는 온도의 증가에 따라 FWHM도 증가하였다. 한편 Arrehenius-type function으로 구한 활성화 에너지는 InAs 양자점의 크기가 증가함에 따라 증가하였다. We present Photoluminescence (PL) and Atomic Force Microscopy (AFM) image on InAs quantum dots (QDs) having different size which grown by Molecular Beam Epitaxy (MBE). For different size QDs, analysis of the AFM profiles show that the density of QDs was the maximum value (1.1×10¹¹/㎠) at 2.0 ML. In the PL spectra of QDs, it is found that the peak energy decreases with increasing dot size due to the effect of quantum confinement. Temperature dependence of PL intensities show that the PL is quenching and Red shift as the temperature increase. The FWHM range of 20 K~80 K is narrowing with increasing temperature. When temperature is over 180 K, the line-width starts to increase with increasing temperature. At last, temperature dependence of the integrated intensities were fit using the Arrehenius-type function for the activation energy. Fit value of the activation energy was increased with increasing QDs-size.

Nitrogen solubility in liquid Fe-C alloys

Jang, J.-M.,Seo, S.-H.,Jiang, M.,Paek, M.-K.,Wang, X.,Pak, J.-J. Iron and Steel Institute of Japan 2014 ISIJ international Vol.54 No.1

The nitrogen solubility in liquid Fe-C alloys containing carbon up to 5.2 mass% has been measured under reduced nitrogen partial pressures in the temperature range of 1 773-1 873 K. Previous studies on the C-N interaction in liquid iron have shown marked disagreement on its temperature dependency and the order of interaction. By the gas-liquid metal equilibration technique using a high frequency induction furnace with an accurate temperature measurement, precise nitrogen solubility data were obtained. The interaction between carbon and nitrogen in liquid iron has been expressed in terms of the first- and second-order interaction parameters. No temperature dependence of these values was observed in the temperature range from 1 773 to 1 873 K.logf(N)(C) = 08[%C]+0.014[%C](2)(1.14 <= mass% C <= 4.95 at 1 773 K, 0 <= mass% C <= 5.2 at 1 823-1 873 K)