• 한국자기학회지
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• 제23권6호
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• pp.188-192
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• 2013

수직 자기기록 매체로 알려진 CoPt 자성막을 전기도금법으로 제작하여 자기상호작용이 활성화 부피와 면적에 미치는 영향을 조사하였다. 모든 시료의 상호작용 기구는 쌍극자 상호작용이었으며, 낮은 전류밀도에서 제작한 시료일수록 두께가 두꺼울수록 상호작용 세기가 증가하였다. 한편 활성화 부피는 낮은 전류밀도에서 제작한 시료가 더 컸으나 두께에 따른 증감현상은 뚜렷하지 않았다. 그러나 활성화 면적은 상호작용의 세기가 강할수록 전류밀도가 낮을수록 감소하는 경향을 보였다.

• 한국자기공명학회논문지
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• 제19권3호
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• pp.137-142
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• 2015

NMR-based structural studies on membrane proteins are appreciated quite challenging due to various reasons, generally including the narrow dispersion of NMR spectra, the severe peak broadening, and the lack of long range NOEs. In spite of the poor biophysical properties, structural studies on membrane proteins have got to go on, considering their functional importance in biological systems. In this review, we provide a simple overview of the techniques generally used in structural studies of membrane proteins by solution NMR, with experimental examples of a helical membrane protein, caveolin 3. Detergent screening is usually employed as the first step and the selection of appropriate detergent is the most important for successful approach to membrane proteins. Various tools can then be applied as specialized NMR techniques in solution that include sample deteuration, amino-acid selective isotope labeling, residual dipolar coupling, and paramagnetic relaxation enhancement.

• 대한화학회지
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• 제26권1호
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• pp.24-30
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• 1982

란탄족 화합물인 Ln$(fod)_3$ (Ln = Pr, Nd, Eu 및 Yb)를 사용하여 contact-only (COM) 및 dipolar-only (DOM) 2성분계 혼합물을 만든 후 기질인 4-picoline의 $F_i$ 및 $G_i$값을 핵자기공명 이동으로 부터 측정하였다. 그 결과 Pr$(fod)_3$ 및 Eu$(fod)_3$의 혼합물인 COM 1 및 DOM 1으로 얻은 값들을 단일 Ln$(fod)_3$로 얻은 값들과 잘 일치하였다. 그러나 $(fod)_3$ 및 Yb$(fod)_3$의 혼합물인 COM 2 및 DOM 2로 얻을 값들을 단일 Ln$(fod)_3$로 얻은 값들과 상당한 오차를 나타내었다. 그 오차는 이테르븀(Yb) 착물에 기인하는 것으로 추정되었다.

• 대한화학회지
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• 제41권4호
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• pp.198-204
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• 1997

N-(2,4-dinitrophenyl)benzhydrazonyl bromide 유도체들의 가수분해 반응속도상수를 20$^{\circ}C$의 수용액에서 자외선 분광광도법으로 측정하여 넓은 pH 범위에서의 반응속도식을 구하였다. 반응속도식, 용매효과, 치환기 효과, 염효과, 열역학적 활성화 파라미터 등의 결과로부터 가수분해 반응메카니즘을 제안하였다. 즉, pH 3.0에서는 carbonium ion 중간체를 거쳐 SN1 반응에 의해 진행되며, pH 10.0에서는 1,3-dipolar 반응 메카니즘 또는 SN2 반응에 의해 진행됨을 제안하였다.

• Bulletin of the Korean Chemical Society
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• 제27권11호
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• pp.1752-1756
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• 2006

This study explores and interprets in a new way the complex solvent and the temperature dependence of the NMR shifts for the N-$CH_2$ protons in tris(N,N-diethyldithiocarbamato) iron(III) in acetone, benzene, carbon disulfide, chloroform, dimethylformamide and pyridine. The NMR shifts are interpreted in terms of the Fermi contact interaction and the dipolar term from the multipole expansion of the interaction of the electron orbital angular momentum and the electron spin dipolar-nuclear spin angular momentum. This analysis yields a direct measure of the effect of the solvent system on the environment of the transition metal ion. The results are analysed in terms of the crystal field environment of the transition metal ion with contributions from (a) the dithiocarbamate ligand (b) the solvent molecules and (c) the interaction of the effective dipole moment of the polar solvent molecule with the transition metal ion complex.

• 전력전자학회논문지
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• 제19권4호
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• pp.376-382
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• 2014

This paper proposes the pulse width modulation (PWM) control strategy for low-speed operation in the three-level neutral-point-clamped (NPC) inverters based on the bootstrap gate drive circuit. As a purpose of the cost reduction, several papers have paid attention to the bootstrap circuit applied to the three-level NPC inverter. However, the bootstrap gate driver IC cannot generate the gate signal to the IGBT for low-speed operation, because the bootstrap capacitor voltage decreases under the threshold level. For low-speed operation, the dipolar and partial-dipolar modulations can be the effective solution. However, these modulations have drawbacks in terms of the switching loss and THD. Therefore, this paper proposes the PWM control strategy to operate the inverter at low-speed and to minimize the switching loss and harmonics. The experimental results are presented to verify the validity on the proposed method.

• Bulletin of the Korean Chemical Society
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• 제15권7호
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• pp.553-559
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• 1994

Dynamics of $CH_2CI$ group in ${\alpha},2,6$-trichlorotoluene dissolved in $CDCl_3$ was studied by observing various relaxation modes for $^{13}C$ under proton undecoupled condition. Partially relaxed $^{13}C$ spectra were obtained at $34^{\circ}C$ as a function of evolution time after applying various designed pulse sequences to this $AX_2$ spin system. It was found that nonlinear regression analysis of the relaxation data for these magnetization modes could provide the information about dipolar and spin-rotational auto-correlation and cross-correlation spectral densities for fluctuation of the $^{13}C-^1H$ internuclear vector in $CH_2Cl$ group. The results show that the effect of cross-correlation is comparable in magnitude to that of auto-correlation and the relaxation in this spin system is dominated by dipolar mechanism rather than spin-rotational one. From the resulting spectral density data we could calculate the bond angle ${\angle}HCH\;(105.1$^{\circ}$) and elements of the rotational diffusion tensor for $CH_2Cl$ group.

• Bulletin of the Korean Chemical Society
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• 제31권3호
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• pp.694-696
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• 2010

• Journal of Astronomy and Space Sciences
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• 제30권3호
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• pp.153-158
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• 2013

In this review paper we explain the following gamma-ray emission features from the millisecond pulsars. (1) Why is the dipolar field of millisecond pulsars so weak but the magnetic pair creation process may still be able to control the size of the outergap? (2) A sub-GeV pulse component could occur in the vicinity of the radio pulse of millisecond pulsars. (3) Orbital modulated gamma-rays should exist in the black widow systems for large viewing angle.

• Bulletin of the Korean Chemical Society
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• 제33권8호
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• pp.2703-2706
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• 2012

New C60 fullerenes derivatives [G1]-C60 (1) and [G2]-C60 (2) comprising of phenylenevinylene bridges and phenylquinoline peripheral surface groups were synthesized by 1,3-dipolar cycloaddition reaction of fullerene C60 with azomethine ylide in situ generated from [Gx]-CHO dendrons (x = 1 and 2) and sarcosine.