Origin of the R(15 × 3) surface reconstruction of carburized W(110) - revisited

Kim, Jihyun,Shin, Eun-Ha,Seo, J.,Kim, H.,Rojas, G.,Chen, X.,Enders, A.,Kim, Hanchul,Kim, J.-S. Elsevier 2019 Surface science Vol.682 No.-

<P><B>Abstract</B></P> <P>The identification of the surface atomic structure having a <I>large</I> unit cell remains a major challenge, while this surface structure is the starting point for templated growth on it. The atomic structure of the carbon-induced R(15 × 3)-W(110) is investigated by scanning tunneling microscopy (STM) operated around 80 K in near-contact mode, combined with the first-principles calculations. It is shown that the R(15 × 3) reconstruction results from the moiré pattern, which a W-C bilayer of <I>α</I>-W<SUB>2</SUB>C(0001) forms with the W(110) substrate, confirming an earlier prediction by Bauer et al. Besides the moiré pattern, the present structure contains the surface lattice deformation, the main ingredient of the other model, and provides a comprehensive picture, well reconciling the two previous models.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Near-contact mode operation of STM reveals the atomic structure of the R(15 x 3) reconstruction. </LI> <LI> The atomic structure is formed of W-C bi-layer of alpha tungsten carbide on W(110) with their relative azimuthal orientation clearly identified. </LI> <LI> The first principles calculation based on the atomic structure well reproduces the STM images as well as the XPS spectra for the reconstructed system. </LI> <LI> The atomic structure shows strong surface corrugation well reconciling with the other model attributing the reconstruction to the surface modification. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Water-induced point defects on the dimerized Si(001) surface

Hanchul Kim,Sang-Yong Yu,Ja-Yong Koo 한국진공학회 2008 한국진공학회 학술발표회초록집 Vol.2008 No.8

Surface reconstruction and magnetic phase of the FePt thin films on Pt (110) substrate

Hanchul Kim,Miyoung Kim 한국자기학회 2016 한국자기학회 학술연구발표회 논문개요집 Vol.2016 No.11

Missing row and surface relaxation induced ferromagnetic phase stabilization of Fe(x)Pt(1−x) (110) surface alloy: First-principles calculation

Kim, Miyoung,Kim, Hanchul American Institute of Physics 2009 JOURNAL OF APPLIED PHYSICS - Vol.105 No.7

<P>The structural properties and magnetic phase stability of Fe(x)Pt(1-x) alloys in L1(2) crystal structure in bulk as well as thin film on Pt (110) substrate are studied by means of the highly precise full-potential linearized augmented plane-wave method within generalized gradient approximation. The antiferromagnetic (AFM) phase is found to be preferred over the ferromagnetic (FM) phase for FePt3 bulk alloy in agreement with experiment while FexPt(1-x), where x=0.25 and 0.5 with a film thickness smaller than 0.5 nm, favor the FM phase. The total energy calculation assuming pseudomorphic strain reveals that the AFM preference for bulk is maintained in wide range of tetragonal distortion up to the value of 22% reached by the surface relaxation of thin film, implying that the magnetic configuration change from AFM to FM at the thin film surface is originated in rather complex surface effects beyond the structural relaxation. The FM preference of thin film is predicted to fast suppress as the film thickness increases and finally the AFM preference is recovered for the film thickness of five atomic layers. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3057775]</P>

Abinitio Investigation on the Magnetic Phase Stability of the FePt Surface

Miyoung Kim,Hanchul Kim 한국자기학회 2015 한국자기학회 학술연구발표회 논문개요집 Vol.2015 No.11

Extraction and Mixing Effects of Grape(Campbell) Seed Oil

Kang, HanChul,, Min, Young Kyoo,, Hwang, Jong Tag,Kim , Si Dong,Kim, Tae Su 한국농화학회 1999 Applied Biological Chemistry (Appl Biol Chem) Vol.42 No.4

Grape seed oil was extracted using different preparatory treatments as follows: (1) grinding, (2) grinding and roasting, (3) grinding and wet- roasting, (4) grinding, roasting, and wet-roasting, and (5) grinding, wet-roasting, and wet-roasting. The highest antioxidant activity was obtained from the sample with the method (2). Initial states of oxidation were similar except method (1) that showed more oxidized state, being P.O.V.8. Acid values were observed in the range from 1.42 to 1.89. The lowest acid value was found as 1.42 in method (1) and those of others were somewhat higher, indicating that heating process of roasting produced some free fatty acids. From the results of sensory evaluation, the best odor and taste were obtained from the methods (2) and (3). Repetitive procedure of wet-roasting, like method 5, caused some loss of flavor components and decrease in the sensory evaluation score. Addition of grape seed oil (method 2) to soybean and perilla oil at the level of 20% retained considerable antioxidant activities as much as 4.3 and 5 times, respectively, than 100% soybean or perilla oil stored for 12 weeks. When soybean or perilla oil was mixed with 20% grape seed oils, P.O.V. decreased to half of that of unmixed oils.

Shockwave-induced deformation of organic particles during laser shockwave cleaning

Hoon Kim, Tae,Cho, Hanchul,Busnaina, Ahmed,Park, Jin-Goo,Kim, Dongsik American Institute of Physics 2013 JOURNAL OF APPLIED PHYSICS - Vol.114 No.6

Development and Characterization of Double-Contact Triboelectric Nanogenerator with Improved Energy Harvesting Performance

김기용(Giyong Kim),김진아(Jinah Kim),무하메드 우스만 자베이드(Muhammad Usman Javaid),조한철(Hanchul Cho),김성열(Sung Yeol Kim),박진형(Jinhyoung Park) Korean Society for Precision Engineering 2021 한국정밀공학회지 Vol.38 No.4

Cation composition effects on electronic structures of In-Sn-Zn-O amorphous semiconductors

Noh, Ji-Young,Kim, Hanchul,Nahm, Ho-Hyun,Kim, Yong-Sung,Hwan Kim, Dae,Ahn, Byung-Du,Lim, Jun-Hyung,Hee Kim, Gun,Lee, Je-Hun,Song, Junho American Institute of Physics 2013 JOURNAL OF APPLIED PHYSICS - Vol.113 No.18

허혈성 전처치(Ischemic Preconditioning)에 의한 심근보호 효과와 Protein Kinase C 활성과의 관계에 관한 연구

김한철,김호덕 동국대학교 경주대학 2000 東國論集 Vol.19 No.-

연구배경 : 짧은 기간 동안 허혈-재관류로 전처치(ischemic precon-ditioning, IP)하면 후속되는 보다 긴 기간 동안의 허혈에도 불구하고 재관류시 심근의 수축기능이 증가되며 심근괴사범위도 줄어드는 등의 심근보호효과가 있는 것으로 알려져 있다. 최근에는 protein kinase C(PCK), 특히 동종효소중 α나 ε 등의 활성화로 IP효과가 나타날 것이라는 실험결과들이 제시되고 있으나 논란이 많다. 본 연구에서는 적출 토끼 심장을 이용하여 PKC활성촉진제(phorbol ester, PMA, 0.01 nM) 또는 억제제(calphostin C, 200 nM)를 투여한 후 심근세포내의 PKC활성도를 정량분석하고 PKC 동종효소의 발현을 관찰하여 이들이 IP효과와 어떤 관계가 있는가를 알아보고자 하였다. 연구방법 : Langendorff방법에 따라 관류하여 baseline이 유지되면 전체 허혈(5분)-재관류(10분) 1회 실시로 IP를 유도하고 45분 동안 전체허혈후 120분 동안 재관류하였다 (IP군, n=18). 허혈 대조군(n=16)에서는 IP없이 45분 동안 전체허혈후 120분 동안 재관류를 실시하였다. PMA투여군(n=19)에서는 baseline후 5분 동안 PMA를 투여한 후 10분 동안 washout하고 45분 동안 허혈을 실실한 후 120분 동안 재관류하였으며, calphostin C투여군(n=15)에서는 IP 5분전부터 IP기간중에 calphostin C를 투여하고 45분 동안 허혈, 120분 동안 재관류를 실시하였다. 모든 실험 종료후 또는 IP만 실시, IP후 45분 동안 허혈만 실시, PMA투여직후의 좌심실 심근조직에서 심근세포 세포질 및 세포막 PKC 분획을 PKC-specific peptide와 32P-γ-ATP incorporation으로 활성도를 측정하였으며 동종효소의 발현정도는 Western blot으로 비교하였다. 허혈후 재관류 기간 동안 좌심실 기능, 관혈류 등을 측정하였으며 심근괴사 크기는 1% tetrazolium으로 염색하여 형태계측하였다. 좌심실기능과 형태계측으로 얻은 측정치 및 PKC활성도는 모두 통계학적으로 검정하였다. 결과 : 1) 좌심실기능 : 45분 동안 허혈후 LVDP(LV developed pressure)는 재관류 시간 경과에 따라 증가하였으나 대부분에서 재관류후 45분경 부터는 서서히 감소하는 경향을 나타내었으며 허혈 대조군을 포함한 다른 실험군에 비하여 특히 IP군에서 유의한 증가를 볼 수 있었다 (p<0.01). dP/dt의 최대값(dP/dtmax)은 LVDP와 같이 재관류 시간 경과에 따라 증가하였으나 모든 군에서 재관류후 45분 경부터는 일정히 유지되는 경향을 나타내었다. 특히 calphostin C 투여군에서 가장 낮았으며 허혈 대조군을 포함한 다른 실험군에 비하여 IP군에서는 유의한 증가를 볼 수 있었다 (p<0.01). 심박동수는 모든 실험군에서 재관류후 10분경부터 기준선에 접근하여 유지되는 경향을 나타내었으나 실험군 사이에서 유의한 차이는 나타나지 않았다. LVEDP(LV end-diastolic pressure)는 재관류 초기에는 상승하였다가 시간이 경과할수록 서서히 감소하는 경향을 나타내었다. IP군과 PMA투여군 사이에서는 유의한 차이가 없었으나 IP군과 PMA 투여군은 허혈 대조군, calphostin C 투여군에 비하여 재관류후 30분부터 90분 사이에서 LVEDP의 상승폭이 현저히 낮았다 (p<0.05). 2) 관혈류 : 관혈류량은 재관류 시작후 증가하여 허혈 대조군이나 IP군에서는 비교적 일정한 값으로 유지되었으나 다른 실험군 에서는 감소하는 경향을 나타내었다. 특히 IP군에서는 다른 실험군보다 관혈류의 현저한 증가를 볼 수 있었으며 calphostin C 투여군에서는 가장 낮은 값을 나타내었다 (p<0.01). 3) PKC 변화 : 기준선의 세포질분획 및 세포막분획의 PKC활성도는 각각 7307.71±310.55, 1834.18±20.98 p㏖/g tissue 이었다. 허혈 대조군에서 세포질분획 및 세포막분획의 PKC활성도는 각각 7666.95±393.57, 1854±80.46 p㏖/g tissue 였으며, IP군에서는 각각 5980.40±205.32, 3994.77±140.26 p㏖/g tissue, calphostin C 투여군에서는 각각 7219.06±259.89, 2026.12±49.06 p㏖/g tissue 이었다. 따라서 IP를 시행하거나 PMA를 투여하면 세포질분획의 PKC 활성도는 각각 기준선 값의 82%, 76% 까지 유의하게 감소하였으며(p<0.05) 세포막분획의 활성도는 각각 기준선 값의 218%, 272% 까지 유의한 증가를 나타내었다 (p<0.01). 그러나 calphostin C를 투여하면 이상과 같은 PKC활성도의 감소나 증가는 소실되었다. 이와 함께 IP군이나 PMA 투여군에서 45분 동안 허혈 기간중에 PKC-α 및 ε 동종효소의 세포질분획과 세포막분획은 각각 감소하거나 증가함을 Western blot으로 확인할 수 있었다. 이러한 결과는 IP를 실시하면 세포질 PKC가 활성화되어 세포막으로 이동함을 나타내는 것이다. 4) 심근괴사 크기 : 심근괴사 크기는 허혈 대조군, IP군, PMA 투여군, calphostin C 투여군에서 각각 37.7±2.4. 20.3±1.2, 10.0±2.1, 33.7±1.8%로 IP군과 PMA 투여군에서 괴사크기의 유의한 감소를 볼 수 있었으며 특히 PMA 투여군에서 현저히 감소하였으나 (p<0.01) calphostin C투여로 소실되었다. 결론 : 이상으로 적출 관류 토끼 심장에서도 IP를 실시할 경우 후속된 장시간 동안의 허혈에 대하여 좌심실기능 증가, 심근경색범위 한정 등의 보호효과가 있고 이상의 심근보호효과는 PKC-α, ε, 특히 ε의 세포막분획 PKC 활성화와 밀접한 관계가 있을 것으로 생각된다. Background : It has been demonstrated that brief period of ischemia and reperfusion (ischemic preconditioning, IP) enhances recovery of post-ischemic contractile dysfunction and reduces incidences of reperfusion-induced arrhythmia or infarct size after a prolonged ischemia. A lot of mechanisms have been proposed. however, controversies still remain. Recent studies suggested that IP triggers selective activation of protein kinase C (PKC) isozymes. In the present study, the author tested this hypothesis with PKC activator, phorbol ester (PMA, 0.01 nM) or inhibitor (calphostin C, 200 mM) to measure the left ventricular function, infarct size, and PKC activity as well as the expression of PKC isozymes. Methods and Results : Hearts isolated from New Zealand White rabbits (1.5-2.0 ㎏ body weight) were perfused with Tyrode solution by Langendorff technique. After stabilization of baseline hemodynamics, the hearts were subjected to 45 min global ischemia followed by 120 min reperfusion with IP (IP group, n=18) or without IP (ischemic control group, n=16). IP was induced by single episode of 5 min global ischemia and 10 min reperfusion. In the PMA-treated group (n=19), the heart was subjected to perfusion with Tyrode solution containing PMA for 5 min after stabilization of the baseline, washing out (for 10 min with normal perfusion), and 45 min ischemia and 120 min reperfusion ; in the Calphostin C-treated preconditioned group (n=15), calphostin was given for 15 min from 5 min before IP regimen. Left ventricular function including developed pressure (LVDP), dP/dt, heart rate, left ventricular end-diastolic pressure (LVEDP) and coronary flow (CF) was measured. Myocardial cytosolic and membrane PKC activities were measured by 32P-γ-ATP incorporation into PKC-specific pepetide : PKC isozymes were analyzed by Western blot with monoclonal antibodies. Iinfarct size was determined by staining with TTC (tetrazolium salt) and planimetry. Data were analyzed by one-way analysis of variance (ANOVA) and Tukey's post-hoc test. In comparison with the ischemic control group, IP significantly increased the recovery of the left ventricular function including left ventricular developed pressure, contractility, and coronary flow, and lowered the increase of the left ventricular end-diastolic pressure (p<0.05). However, enhancement of the functional recovery disappeared by calphostin or PMA treatment. Cytosolic PKC activity was decreased to 82-76% in the IP and PMA-treated group (p<0.05) ; membrane PKC activity was increased to 218-272% (p<0.01), However, both fraction of PKC activity was not changed in the calphostin C-treated preconditioned group. In addition, Western blot revealed that PKC-α and ε, especially ε, were selectively translocated during subsequent sustained ischemia after IP or PMA administration. IP and PMA also reduced infarct size (frim 38 to 10-20%, 0<0.05). However, calphostin C blocked infarct reduction effect of IP. Conclusion : These results indicate that in isolated Langendorff-perfused rabbit heart model, IP (induced by single episode of 5-minute global ischemia and 10-minute reperfusion) could improve post-ischemic contractile dysfunction (after 45-minute global ischemia), as well as it has an infarct size-limiting effect ; these cardioprotective effect of IP may be related, at least in part, to trigger selective activation of PKC isozyme, especially ε isotype.