• 한국자기공명학회논문지
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• 제22권4호
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• pp.107-114
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• 2018

In this exploration, the nuclear magnetic resonance of the $^{207}Pb$ nucleus in $PbWO_4:Mn^{2+}$ and $PbWO_4:Dy^{3+}$ Single Crystals using FT-NMR spectrometer is investigated. The line width of the resonance line for the $^{207}Pb$ nucleus decreases as temperature increases due to motional narrowing. The chemical shift of $^{207}Pb$ NMR spectra also increases as temperature decreases for both crystals. The spinlattice relaxation times $T_1$ of $^{39}K$ nucleus were calculated as a function of temperature (180 K~400 K). The $T_1$ of $^{207}Pb$ nucleus decreases as temperature increases. The dominant relaxation mechanism at the studied temperature range can be deduced as the Raman process, which is the coupling between lattice vibrations and the nuclear spins. This deduction is substantiated by the fact that the nuclear spin-lattice relaxation rate $1/T_1$ of the $^{207}Pb$ nucleus in $PbWO_4:Mn^{2+}$ and $PbWO_4:Dy^{3+}$ single crystal is proportional to $T^2$, or temperature squared. The activation energies for the $^{207}Pb$ nucleus in $PbWO_4:Mn^{2+}$ and $PbWO_4:Dy^{3+}$ single crystals are $E_a=49{\pm}1meV$ and $E_a=47{\pm}2meV$, respectively.

• Journal of Ceramic Processing Research
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• 제20권6호
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• pp.589-596
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• 2019

Pigments with minute particle sizes, such as carbon black (CB) and pigment red 48:2 (P.R.48:2), are the most important types of pigment and have been widely used in many industrial applications. However, minute particles have large surface areas, high oil absorption and low surface energy. They therefore tend to be repellent to the vehicle and lose stability, resulting in significant increases in viscosity or reaggregation in the vehicle. Therefore, finding the best way to improve the dispersion properties of minute particle size pigments presents a major technical challenge. In this study, minute particle types of CB and P.R.48:2 were treated with nitrogen gas plasma generated via radio frequency-plasma enhanced chemical vapor deposition (RF-PECVD) to increase the dispersion properties of minute particles in deionized (DI) water. The morphologies and particle sizes of untreated and plasma treated particles were evaluated using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The average distributions of particle size were measured using a laser particle sizer. Fourier transform infrared spectroscopy was carried out on the samples to identify changes in molecular interactions during plasma processing. The results of our analysis indicate that N2 plasma treatment is an effective method for improving the dispersibility of minute particles of pigment in DI water.

• Medical Lasers
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• 제10권1호
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• pp.22-30
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• 2021

Background and Objectives Ocular alkali burns cause severe damage to the ocular tissues and vision loss. Solcoseryl is a standardized calf blood extract that normalizes the metabolic disturbance and aids in maintaining the chemical and hormonal balance and has been used to treat burns in various tissues. This study examined the effects of Solcoseryl on a rat corneal alkali burn model. Materials and Methods Twenty rats were assigned randomly to four equal groups, including alkali burn, hyaluronic acid, Solcoseryl eyedrop, and Solcoseryl gel. A corneal alkali burn was induced by a NaOH-soaked paper disc. The treatments were given twice a day, every day. The wound area was measured after 24 and 48 hours, and the degree of neovascularization and corneal opacity were scored every week. The rats were sacrificed after three weeks for immunohistochemistry (IHC) to compare the level of inflammatory cytokines, IL-1β, IL-6, and TNF-α. The thickness of the retinal layers was compared to observe any changes in the retina. Results The use of Solcoseryl on corneal alkali burn accelerated wound healing with less neovascularization, greater opacity, and less cataract. IHC showed that the inflammation of the cornea was controlled by both the hyaluronic acid and Solcoseryl treatments. On the other hand, the inflammation had spread to the retina. When the dosage forms were compared, eyedrops were more effective on corneal inflammation, while the gel-type had a greater effect on retinal inflammation. Conclusion Solcoseryl was effective in accelerating the wound healing rate on a corneal alkali burn but could not prevent the spread of inflammation from the cornea to the retina. Eyedrops were more effective on inflammation in the cornea, and the gel was more effective in the retina.

• 한국표면공학회지
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• 제56권3호
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• pp.208-218
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• 2023

Photocatalysts are advanced materials which accelerate the photoreaction by providing ordinary reactions with other pathways. The catalysts have various advantages, such as low-cost, low operating temperature and pressure, and long-term use. They are applied to environmental and energy field, including the air and water purification, water splitting for hydrogen production, sterilization and self-cleaning surfaces. However, commercial photocatalysts only absorb ultraviolet light between 100 and 400 nm of wavelength which comprises only 5% in sunlight due to the wide band gap. In addition, rapid recombination of electron-hole pairs reduces the photocatalytic performance. Recently, studies on blackening photocatalysts by laser, thermal, and plasma treatments have been conducted to enhance the absorption of visible light and photocatalytic activity. The disordered structures could yield mid-gap states and vacancies could cause charge carrier trapping. Herein, liquid phase plasma (LPP) is adopted to synthesize Ag-doped black ZnO for the utilization of visible-light. The physical and chemical characteristics of the synthesized photocatalysts are analyzed by SEM/EDS, XRD, XPS and the optical properties of them are investigated using UV/Vis DRS and PL analyses. Lastly, the photocatalytic activity was evaluated using methylene blue as a pollutant.

• 대한화학회지
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• 제48권4호
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• pp.351-357
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• 2004

의료용 구리증기 레이저 개발의 일환으로 관통형 속 빈 음극관 글로우 방전(seethrough Hollow Cathode Glow Discharge; st-HCGD)을 이용하여 Cu 510.6 nm 방출선의 세기 증가를 조사하였다. 높은 전류에서도 매우 안정한 플라스마가 생성될 수 있도록 여러 가지 요인들 - 작동 전압 및 전류, 음극관의 길이와 내경 및 내부 형태, 음극관의 sputtering range 등 - 에 따른 최적조건을 찾는 실험을 수행하였다. 그 결과, 최종적으로 디자인된 글로우 방전셀에서는 앞선 여러 가지 실험으로 최적화된 조건을 적용하였다. 이들 최적화된 조건으로는 방전셀 내부에 아르곤 가스를 100 SCCM(standard cubic centimeter)으로 일정하게 흘려주었을 때의 방전셀 압력은 2.3 Torr 이며, 방전 전압 및 전류는 600 V, 700 mA(420 W), 음극관의 형태는 4-11-4 mm, 음극관의 길이는 40 mm 등이다. 한편, 700 mA 이상의 고전류에서 녹은 구리 음극관을 관찰함으로써 음극 sputtering으로 인한 플라스마의 온도가 최소 $1,000{\circ}C$ 이상에 이르렀음을 확인할 수 있었다(구리의 녹는점, $1084{\circ}C$).

• 대한화장품학회지
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• 제34권4호
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• pp.311-316
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• 2008

본 연구에서는 모발의 내부 및 외부구조에 자외선이 미치는 영향에 관하여 조사를 수행하였다. 자외선이 조사된 모발의 형태학적 및 화학적 구조의 변화를 알아보기 위해 주사전자현미경(SEM), 투과전자현미경(TEM), 공초점레이져주사현미경(CLSM) 등을 사용하였다. SEM상에서 자외선이 조사된 모발은 자외선에 의한 화학적 산화반응에 의한 표면이 거칠고 부풀어진 형태를 보였다. 이황화결합(disulfide bond)의 산화에 의한 시스테인산(cysteic acid)의 분해로 팽윤부위가 관찰되었다. 또한 자외선 조사에 의해 표면색의 변화를 나타내었다. TEM 분석결과 버진헤어(virgin hair)의 경우에는 매끄러운 표면구조를 나타내었지만, 자외선 조사모발에 있어서는 거칠고 모수질층이 갈라진 형태를 보여주었다. 모피질층에 존재하는 멜라닌 입자의 크기가 감소하고 소실되는 것이 관찰 되었다. CLSM에 의해 3차원적 구조의 입체영상을 얻을 수 있었으며, 광학분할에 의한 버진헤어는 강한 형광을 나타내었지만, 자외선 조사모발은 낮은 형광을 보여주었다. 이는 버진헤어의 경우 자동형광을 나타낼 수 있는 방향족 아미노산이 많이 존재하는데 비해 자외선 조사모발은 방향족 아미노산이 파괴되어 낮게 나온 것으로 여겨진다.

• Bulletin of the Korean Chemical Society
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• 제35권11호
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• pp.3289-3293
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• 2014

Femtosecond laser ablation (fs LA) was used in this study to identify pollution by heavy metals and the distribution of elemental nutrients at different rice milling ratios. Polished rice (degrees of milling of 3, 5, 7, 9, and 11) was collected from major Korean supermarkets and one sample thereof was selected. An internal quality control experiment was conducted using a rice flour certified reference material from the Korea Research Institute of Standards and Science (KRISS CRM) for the evaluation of the efficacy. To assess the effectiveness of the analysis method, the reliability was validated using a food analysis performance assessment scheme (FAPAS), with chili powder serving as an external quality control. The results of the analysis of the inorganic elements Ti, Ca, Al, Fe and Mn in white and brown rice with degrees of milling of 3, 5, 7, 9 and 11 using ICP-MS, ICP-OES and AAS revealed contents of 0.40, 49.2, 2.43, 5.36 and 10.3 mg/kg in white rice and 0.59, 78.0, 7.52, 11.0 and 18.5 mg/kg in brown rice, respectively. Among the elements, there were remarkable differences in the measured contents. By comparing the contents of the elements at different degrees of milling, Ti, Co, As, Ca, Al, Cu, Fe, and Mn were determined to be distributed on the surface of the rice grains, whereas the contents of Cd and Pb increased toward the center of the rice grains, and Si was evenly distributed. After the quantitative analysis of rice samples polished to different degrees of milling, Ca and Al, which were contained in large amounts, and Si were analyzed with specificity by fs LA. The results show that Ca and Al were distributed in the rice husk (protective covering of rice) and Si was distributed in all parts of the rice.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
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• pp.330-332
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• 2013

소 분위기에서 플라즈마 표면 처리의 경우 기판 표면에 존재하는 수소와 탄소 유기물들이 산소와 반응하여 $H_2O$와 $CO_2$ 등으로 제거되며 표면에 오존 결합을 유도하여 표면 에너지를 증가시키는 것으로 알려져 있다. ZnO 나노구조물을 성장시키는 방법으로는 MOCVD (Metal-Organic Chemical Vapor Deposited), PLD (Pulsed Laser Deposition), VLS (Vapor-Liquid-Solid), Sputtering, 습식화학합성법(Wet Chemical Method) 방법 등이 있다. 그중에서도 습식화학합성법은 쉽게 구성요소를 제어할 수 있고, 저비용 공정과 낮은 온도에서 성장 가능하며 플렉서블 소자에도 적용이 가능하다. 그러므로 본 연구에서는 플라즈마 표면처리에 따라 표면에너지를 변화하여 습식화학합성법으로 성장시킨 ZnO nanorods의 밀도를 제어하고 photolithography 공정 없이 패터닝 가능성을 유 무를 판단하는 연구를 진행하였다. 기판은 Si wafer (100)를 사용하였으며 세척 후 표면에너지 증가를 위한 플라즈마 표면처리를 실시하였다. 분위기 가스는 Ar/$O_2$를 사용하였으며 입력전압 400 W에서 0, 5, 10, 15, 60초 동안 각각 실시하였다. ZnO nanorods의 seed layer를 도포하기 위하여 Zinc acetate dehydrate [Zn $(CH_3COO)_2{\cdot}2H_2O$, 0.03 M]를 ethanol 50 ml에 용해시킨 후 스핀코팅기를 이용하여 850 RPM, 15초로 5회 실시하였으며 $80^{\circ}C$에서 5분간 건조하였다. ZnO rods의 성장은 Zinc nitrate hexahydrate [$Zn(NO_3)_2{\cdot}6H_2O$, 0.025M], HMT [$C6H_{12}N_4$, 0.025M]를 deionized water 250 ml에 용해시켜 hotplate에 올리고 $300^{\circ}C$에서 녹인 후 $200^{\circ}C$에서 3시간 성장시켰다. ZnO nanorods의 성장 공정은(Fig. 1)과 같다. 먼저 플라즈마 처리한 시편의 표면에너지 측정을 위해 접촉각 측정 장치[KRUSS, DSA100]를 이용하였다. 그 결과 0, 5, 10, 15, 60 초로 플라즈마 표면 처리했던 시편이 각각 Fig. l, 2와 같이 $79^{\circ}$, $43^{\circ}$, $11^{\circ}$, $6^{\circ}$, $7.8^{\circ}$로 측정되었으며 이것을 각각 습식화학합성법으로 ZnO nanorods를 성장 시켰을 때 Fig. 3과 같이 밀도 차이를 확인할 수 있었다. 이러한 결과를 바탕으로 기판의 표면에너지를 제어하여 Fig. 4와 같이 나타나며 photolithography 공정없이 ZnO nanorods를 패터닝을 할 수 있었다. 본 연구에서는 플라즈마 표면 처리를 통하여 표면에너지의 변화를 제어함으로써 ZnO nanorods 성장의 밀도 차이를 나타냈었다. 이러한 저비용, 저온 공정으로 $O_2$, CO, $H_2$, $H_2O$와 같은 다양한 화학종에 반응하는 ZnO를 이용한 플렉시블 화학센서에 응용 및 사용될 수 있고, 플렉시블 디스플레이 및 3D 디스플레이 소자에 활용 가능하다.

• Bulletin of the Korean Chemical Society
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• 제34권8호
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• pp.2419-2424
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• 2013

Guanosine-5'-diphosphate 3'-diphosphate (ppGpp) serves as alarmone in bacterial stringent responses. In this study, an affinity column was constructed by immobilizing ppGpp to NHS-Sepharose for isolating ppGpp-binding proteins. A novel ppGpp-binding protein, YjgA, was isolated and characterized by MALDI-TOF MS (matrix-assisted laser desorption ionization-time-of-flight mass spectrometry) coupled with two-dimensional gel electrophoresis. YjgA and truncated forms of YjgA were cloned and over-expressed in BL21 (DE3). The binding affinity of YjgA to ppGpp was determined by equilibrium dialysis. The interaction of YjgA with ppGpp was very specific, considering that the dissociation constant of YjgA with ppGpp was measured as $5.2{\pm}2.0{\mu}M$, while the affinities to GTP and GDP were about 60 and 30 times weaker than ppGpp. Expression of yjgA gene in Escherichia coli K-12 MG1655 was examined by reverse transcription polymerase chain reaction (RT-PCR). RT-PCR results revealed that yjgA was expressed from early to late stationary phase. The yjgA deletion mutant exhibited decreased cell number at stationary phase compared to parent strain and the over-expression of YjgA increased the cell number. These results suggested that YjgA might stimulate cell division under stationary phase. In most prokaryotic genome, about half of the protein candidates are hypothetical, that are expected to be expressed but there is no experimental report on their functions. The approach utilized in this study may serve as an effective mean to probe the functions of hypothetical proteins.

• 청정기술
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• 제28권4호
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• pp.323-330
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• 2022

미세유체 종이-기반 분석 장치는 최근 현장 진단 및 환경 물질 감지를 포함한 다양한 적용가능성으로 주목을 받고 있다. 본 연구는 적은 비용과 간단한 검출 방법으로 중금속을 빠르게 검출할 수 있는 3D-μPAD를 제작하기 위해 PDMS 양면 인쇄 방법을 제안하였다. 3D-μPAD 디자인은 레이저 커팅으로 아크릴 스탬프에 적용할 수 있으며, 제작된 스탬프에 PDMS 고분자를 스핀 코팅 후 양면접촉인쇄 방식 도입을 통해 3차원 형태의 소수성 장벽 형성에 필요한 조건을 확인하였다. 구체적으로 소수성 장벽 형성 조건인 고분자 농도, 스핀 코팅 속도 및 접촉 시간에 따라 PDMS 소수성 장벽 면적과 친수성 채널의 면적 변화를 분석함으로써 3D-μPAD 제작 공정 조건 최적화를 수행하였다. 최적화된 μPAD로 니켈, 구리, 수은 이온, pH를 다양한 농도에서 검출하였고 이를 ImageJ 프로그램으로 분석하여 grayscale 값으로 정량화 하였다. 이를 통해 3D-μPAD를 제작함으로써 특별한 분석 기기 없이 다양한 중금속 비색 검출을 수행함으로써 조기진단 바이오 센서로의 응용 가능성을 증명하였다. 이 3D-μPAD는 휴대가 간편한 다중 금속이온 검출 바이오센서로서, 신속한 현장 모니터링이 가능하므로 개발도상국 같은 자원이 제한된 지역에서 유용하게 사용 가능하다.