• Bulletin of the Korean Chemical Society
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• 제22권5호
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• pp.527-530
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• 2001

• Journal of the Korean Physical Society
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• 제73권12호
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• pp.1884-1888
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• 2018

We have employed electron paramagnetic resonance spectroscopy and magnetization measurements in order to study the effect of Al-incorporation on the magnetic interactions in ZnO:Mn diluted magnetic semiconductors. Al-doping is shown to decrease the antiferromagnetic correlation and to increase the ferromagnetic interaction, which is attributed to the hydrogen-mediated ferromagnetic Mn complexes in our Mn-doped ZnO samples.

• Bulletin of the Korean Chemical Society
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• 제33권9호
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• pp.2981-2984
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• 2012

Active site mapping has been done for ${\Delta}^5$-3-ketosteroid isomerase (KSI) by analyses of paramagnetic effect on $^1H-^{15}N$ HSQC spectra using 4-hydroxyl-2,2,6,6-tetramethylpiperidinyl-1-oxy (HyTEMPO) and an intermediate analog (equilenin). Our result revealed that residues in hydrophobic cavity of KSI, particularly active site region, mainly experienced a high line-broadening effect of NMR signal with HyTEMPO, while they experienced full recovery of a lineshape upon the addition of equilenin. The mapped region was very similar to the active site of KSI as described by the crystal structure. These observations indicate that a combined use of paramagnetic reagent and substrate (or analog) could rapidly identify the residues in potential active site of KSI, and can be applied to the analysis of both active site and function in unknown protein.

• Bulletin of the Korean Chemical Society
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• 제20권7호
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• pp.796-800
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• 1999

Three anthrylazacrown ethers in which the anthracene fluorophore π system is separated from the electron donor atoms by one methylene group were synthesized, and their photophysical study was accomplished. These fluorescent compounds showed a maximum fluorescence intensity at pH=5 in aqueous solutions and a decrease in fluorescence intensity upon binding of paramagnetic metal cations (Mn 2+ (d 5 ), Co 2+ (d 7 ), Cu 2+ (d 9 )). The decrease in fluorescence intensity may be attributed to the paramagnetic effect of metal cations to deactivate the excited state by the nonradiative quenching process. The benzylic nitrogen was found to play an important role in changing fluorescence intensity. From the observed linear Stern-Volmer plot and the fluorescence lifetime independence of the presence of metal ions, it was inferred that the chelation enhanced fluorescence quenching (CHEQ) mechanism in the system is a ground state static quenching process. Enhanced fluorescence was also observed when an excess Na + ion was added to the quenched aqueous solution, and it was attributed to cation displacement of a complexed fluorescence quencher.

• 대한의용생체공학회:의공학회지
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• 제16권4호
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• pp.395-402
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• 1995

자기공명 영상 시스템에서 영상을 얻고자 하는 물체내의 자화율 차이는 복셀내의 스핀들의 위상을 변화시킨다. 또한 스핀들 상호간의 위상변화로 인하여 영상 신호는 감쇄된다. 이러한 신호 세기의 감쇄는 자기공명 영상분야에서 자화율 효과라 알려져 왔고 이런 효과를 억제시키거나 또는 이용하는 연구가 심도있게 논의되어왔다. 본 논문에서 자화율 효과로 인한 신호의 변화를 분석할 수 있는 새로운 스펙트럼 분해법과 영상법을 제안하였다. 그리고 자화율 스펙트럼 분해법을 위한 펄스시퀀스를 개발하였고, 이것을 상자성(paramagnetic) 성질 때문에 자화율 효과가 생기는 정맥영상에 적용하였다. 컴퓨터 모의 실험과 팬텀(phantom)을 대상으로 한 실험 결과로 스펙트럼 분해법의 타당성을 보였다.

• 한국연소학회지
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• 제17권1호
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• pp.58-65
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• 2012

The influence of magnetic field on propane and acetylene diffusion flames have been experimentally investigated using an electromagnetic system. Periodically induced magnetic field having various frequencies and duty ratios was established in square wave form. The maximum intensity and gradient of magnetic field were 1.3 T and 0.27 T/mm, respectively. The width of a propane flame was reduced up to 4.5% and the brightness was enhanced up to 25% when the magnetic field was induced. The soot emission from an acetylene flame was ceased when magnetic field was induced. The alteration of flow field, which is due to the paramagnetic characteristics of oxygen molecule, is most likely to be responsible for the change in flame size and brightness. The effect of magnetic field on diffusion flames, which competes with the gravitational effect, was more apparent from a smaller size flame. The magnetic field effect, therefore, could be important under microgravity conditions. Since the time required to alter the flow field must be finite, the magnetic field effect is likely to be less significant for a periodically oscillating magnetic field at a high frequency or having a small duty ratio.

• Journal of Korean Vacuum Science & Technology
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• 제6권4호
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• pp.153-157
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• 2002

The electronic structures of Gd$_{5}$Si$_2$Ge$_2$ compound, which has a giant magnetocaloric effect, in the monoclinic and orthorhombic phases were calculated using the tight-binding linear-muffin-tin-orbital method within the atomic-sphere approximation. The calculated total energies of the monoclinic and orthorhombic structures in the paramagnetic phase confirm that the orthorhombic structure is more stable than monoclinic structure. The density of states (DOS) at the Fermi level of the orthorhombic phase is higher than that of the monoclinic phase in the paramagnetic phase, fulfilling the Stoner criterion. The calculated charge density verified the breaking of Ge(Si)-Ge(Si) bonding in the basal plane upon the orthorhombic-monoclinic phase transition. The DOS curve fairly well reproduces the photoemission spectrum.m.

• 한국자기공명학회논문지
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• 제24권2호
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• pp.47-52
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• 2020

Liquid-liquid phase separation (LLPS) of biomolecules, a newly-found phase behavior of molecules in the liquid phase, has shown to its relationship to various biological function and misfolding diseases. Extensive studies have increasingly revealed a general mechanism of LLPS and characterized the liquid droplet; ho wever, intermolecular interactions of proteins and structural states of LLPS-inducing proteins inside of the droplet remain largely unknown. Solution NMR spectroscopy has emerged as a powerful approach as it provides invaluable information on protein intermolecular interactions and structures at the atomic and residue level. We herein comprehensively address useful techniques of solution NMR including the effect of paramagnetic relaxation enhancement for the study on the LLPS and droplet based on recent studies.

• Journal of Magnetics
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• 제19권2호
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• pp.116-120
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• 2014

The spin-lattice relaxation time, $T_1$, for $^{69}Ga$, $^{71}Ga$, and $^{75}As$ nuclei in GaAs:$Mn^{2+}$ single crystals was measured as a function of temperature. The values of $T_1$ for $^{69}Ga$, $^{71}Ga$, and $^{75}As$ nuclei were found to decrease with increasing temperature. The $T_1$ values in GaAs:$Mn^{2+}$ crystal are similar to those in pure GaAs crystal. The calculated activation energies for the $^{69}Ga$, $^{71}Ga$, and $^{75}As$ nuclei are 4.34, 4.07, and 3.99 kJ/mol. It turns out that the paramagnetic impurity effect of $Mn^{2+}$ ion doped in GaAs single crystal was not strong on the spin-lattice relaxation time.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2009년 추계학술대회논문집
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• pp.88-92
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• 2009

When exposed to uniform magnetic fields externally applied, paramagnetic particles acquire dipole moments and the induced moments interacting with each other lead to the formation of chainlike structures or clusters of particles aligned with the field direction. A direct simulation method, based on the Maxwell stress tensor and a fictitious domain method, is applied to solve flows with magnetic chains in simple shear flow. We assumed that the particles constituting the chains are paramagnetic, and inertia of both flow and magnetic particles is negligible. The numerical scheme enables us to take into account both hydrodynamic and magnetic interactions between particles in a fully coupled manner, enabling us to numerically visualize breakup and reformation of the chains by the combined effect of the external field and the shear flow. Simple shear flow with suspended magnetic chains is solved in a periodic domain for a given magnetic field. Dynamics of interacting magnetic chains is found to be significantly affected by a dimensionless parameter called the Mason number, the ratio of the viscous force to the magnetic force in the shear flow. The effect of particle area fraction on the chain dynamics is investigated as well.