• Advances in nano research
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• 제13권4호
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• pp.325-339
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• 2022

Endophytes ascertain a symbiotic relationship with plants as promoters of growth, defense mechanism etc. This study is a first report to screen the endophytic population in Waltheria indica, a tropical medicinal plant. 5 bacterial and 3 fungal strains in leaves, 3 bacterial and 1 yeast species in stems were differentiated morphologically and identified by biochemical and molecular methods. The phylogenetic tree of the isolated endophytes was constructed using MEGA X. Silver nanoparticles were biosynthesized from a rare endophytic bacterium Cupriavidus metallidurans isolated from the leaf of W. indica. The formation of silver nanoparticles was confirmed by UV-Visible spectrophotometer that evidenced a strong absorption band at 408.5 nm of UV-Visible range with crystalline nature and average particle size of 16.4 nm by Particle size analyzer. The Fourier Transform Infra-Red spectrum displayed the presence of various functional groups that stabilized the nanoparticles. X-ray diffraction peaks were conferred to face centered cubic structure. Transmission Electron Microscope and Scanning Electron Microscope revealed the spherical-shaped, polycrystalline nature with the presence of elemental silver analyzed by Energy Dispersive of X-Ray spectrum. Selected area electron diffraction also confirmed the orientation of AgNPs at 111, 200, 220, 311 planes similar to X-ray diffraction analysis. The synthesized nanoparticles are evaluated for antimicrobial activity against 7 bacterial and 3 fungal pathogens. A good zone of inhibition was observed against pathogenic bacteria than fungal pathogens. Thus the study could hold a key aspect in drug discovery research and other pharmacological conducts of human clinical conditions.

• 한국결정학회:학술대회논문집
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• 한국결정학회 2003년도 춘계학술연구발표회
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• pp.8-8
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• 2003

Electron-phonon interaction plays a significant role in forming of colossal magnetoresistance effect (CMR). Polaron formation was observed by neutron diffraction and by extended X-ray absorption fine structure (EXAFS) analysis. Local probe as given by the EXAFS is a useful method to study the polaronic charge and its dependence on temperature and ions size. Here we present the EXAFS study of polaronic charge in La/sub 0.7/Ca/sub 0.3-X/Ba/sub X/MnO₃ compositions. The single phase La/sub 0.7/Ca/sub 0.3-X/Ba/sub X/MnO₃ manganites (x=0; 0.03; 0.06, ..., 0.3) were prepared by ceramic technology [1]. The Curie temperature was determined by extrapolation of the temperature dependence of the magnetization (down to zero magnetization). EXAFS experiments were carried out at the 7C EC beam line of the Pohang Light Source (PLS) in Korea. The atomic pair distribution functions (PDF) were obtained by re-regularization method [2] from filtered spectra. The PDF for the x=0.3 sample showed a single peak function and for x=0.0, 0.03, 0.06, 0.09, 0.12 compositions were asymmetric in agreement with a small Jahn-Teller elongation of two (short and long) bonds of the MnO/sub 6/ octahedron. Dispersion, σ/sub Min-O//sup 2/, and asymmetry, σ/sub Min-O//sup 3/, of the Mn-O bond distances varied significantly with x and showed a maximums at x=0.09. The maximum of σ/sub Min-O//sup 2/ is caused by increase of dynamic rms displacements of the Mn-O distances near the T/sub C/. The observed x dependence of σ/sub Min-O//sup 3/ reflects the reduction of charge carriers mobility at approaching to T/sub C/ from low as well as high temperatures.

• 한국표면공학회지
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• 제42권4호
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• pp.161-168
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• 2009

Effects of TiN/Ti multilayer coating on the Ti-30Ta-xZr alloy surface were studied by using various experiments. The Ti-30Ta containing Zr (5, 10 and 15 wt%) were melted 10 times to improve chemical homogeneity by using a vacuum furnace. And then samples were homogenized for 24 hrs at $1000^{\circ}C$. The specimens were prepared for TiN/Ti coating by cutting and polishing. The prepared specimens were coated with TiN/Ti multilayers by using DC magnetron sputtering method. The analyses of coated surface and coated layer were carried out by field emission scanning electron microscope(FE-SEM), EDX, and X-ray diffractometer(XRD). From the microstructure and XRD analysis of Ti-30Ta-xZr alloys, The equiaxed structure was changed to needle-like structure with increasing Zr content. And $\alpha$-peak and elastic modulus increased as Zr content increased. The $\alpha$ and $\beta$ phase predominantly were found in the specimen containing high Zr content. According to the analysis of TiN/Ti coating layer, the surface defects and structures of Ti-30Ta-xZr were covered with TiN/Ti coating layer and surface roughness decreased.

• 한국세라믹학회지
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• 제42권9호
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• pp.602-606
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• 2005

[ $LiCoO_{2}$ ] is the most common cathode electrode materials in Lithium-ion batteries. $LiCo_{0.97}Mg_{0.03}O_2$ was synthesized by the solid-state reaction method. We investigated crystal structures, electrical conductivities and electrochemical properties. The crystal structure of $LiCo_{0.97}Mg_{0.03}O_2$ was analyzed by X-ray powder diffraction and Rietveld refinement. The material showed a single phase of a layered structure with the space group R-3m. The lattice parameter(a, c) of $LiCo_{0.97}Mg_{0.03}O_2$ was larger than that of $LiCoO_2$. The electrical conductivity of sintered samples was measured by the Van der Pauw method. The electrical conductivities of $LiCoO_2$ and $LiCo_{0.97}Mg_{0.03}O_2$ were $2.11{\times}10^{-4}\;S/cm$ and $2.41{\times}10^{-1}\;S/cm$ at room temperature, respectively. On the basis of the Hall effect analysis, the increase in electrical conductivities of $LiCo_{0.97}Mg_{0.03}O_2$ is believed due to the increased carrier concentrations, while the carrier mobility was almost invariant. The electrochemical performance was investigated by coin cell test. $LiCo_{0.97}Mg_{0.03}O_2$ showed improved cycling performance as compared with $LiCoO_2$.

• Korean Chemical Engineering Research
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• 제46권3호
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• pp.529-534
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• 2008

생체복합재료인 참굴 (Crassostrea gigas) 패각은 생성되는 형태에 따라 정상패각과 재생패각으로 구분되었다. 산과 알칼리를 이용한 탈 석회화과정 및 단백질제거반응을 통해 재생패각 내에서 얻어진 유기막이 키틴 특성을 가지고 있음을 FT-IR (Fourier transform infrared spectrometer)과 XRD (X-ray Diffractometer)를 통해 확인하였다. 불용성단백질의 함량은 정상패각이 재생패각과 비교하여 두배 이상 이었던 반면 수용성단백질 2차구조는 재생패각의 경우 random과 같은 불규칙구조가 많은 부분을 차지하고 있음을 확인할 수 있었다. 수용성단백질의 아미노산 조성과 단백질 2차구조분석을 통해 재생패각의 탄산칼슘 합성전략을 분자수준에서 논의하였고 재생패각 형성과 관련된 생광물화 전략이 패각의 재료학적 특성에 미치는 결과로써 해석되었다.

• 공업화학
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• 제32권5호
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• pp.504-508
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• 2021

본 연구에서는 게스트 분자(guest molecule)의 특성이 고분자/베타-사이클로덱스트린(beta-cyclodextrin) 포접화합물(inclusion compound)로 이루어진 고분자 필름의 구조 및 물성에 미치는 영향에 대해서 고찰하고자 한다. 본 연구에서 사용된 게스트 분자는 미백 효과를 지니는 것으로 알려진 3가지로 하이드로퀴논(hydroquinone, HQ), 알부틴(arbutin, AB), 그리고 트랜액사믹 애시드(tranexamic acid, TA)이다. 먼저, 베타-사이클로덱스트린과 게스트 분자 간의 포접화합물의 성공적인 형성과 이를 포함하는 고분자 필름의 제조여부를 라만(Raman) 분광학으로 확인하였다. 포접화합물을 포함하는 고분자 필름의 구조 및 물성은 엑스선 회절법(X-ray diffraction)과 주사열용량법 및 열중량추적법 같은 열분석법으로 고찰하였다. 그 결과, 트랜액사믹 애시드의 영향이 다른 분자의 영향과 비교하여 상당히 상이하였음을 관찰할 수 있었다. 이러한 경향은 간단한 분자 시뮬레이션 기법으로 재검증하였다. 본 연구는 포접화합물을 형성하는 게스트 분자들의 상이한 영향에 대한 체계적인 접근을 통한 실험적 검증의 사례로 향후 관련 연구에 중요한 정보를 제공할 것으로 기대된다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 추계학술대회 논문집
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• pp.25-25
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• 2009

Zinc Oxide (ZnO) nanorod were grown on Si wafer by a thermal evaporation method at various temperatures. And their structure and optical properties were measured using Photoluminescence(PL), Scanning electron microscopy(SEM), and X-ray diffraction(XRD) analysis.

• Bulletin of the Korean Chemical Society
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• 제25권2호
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• pp.304-306
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• 2004

• Journal of Pharmaceutical Investigation
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• 제39권2호
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• pp.117-120
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• 2009

Two crystal forms of ziprasidone have been isolated by recrystallization from different organic solvents and characterized by differential scanning calorimetry, powder X-ray diffractometry and thermogravimetric analysis. It was confirmed that Form 2 has the same crystal structure as Form 1.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 2002년도 추계학술발표회요약집
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• pp.319.2-319
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• 2002

Synchrotron-based X-ray absorption spectroscopy has been applied to determine the changes in bulk oxidation state of uranium oxides in molten salt. From an analysis of XANES data, one can determine the cahnges in bulk oxidation-state of U compounds in salts(LiCl/KCl). XAFS spectroscpy is a powerful tool for probing the changes in valence state and structure of uranium compounds in colten salt as well as in noncrystalline form and doped in other matrices.