• Investigative Magnetic Resonance Imaging
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• 제5권1호
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• pp.33-37
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• 2001

목적 : 자성 자기공명조명제의 효율을 결정하는데는 상자성물질의 물분자 결합위치에 구속되어 있는 물분자와 자유 물분자사이의 물분자 교환율이 매우 중요한 역할을 담당한다. 따라서 본 연구에서는 $^{17}O-NMR$기법을 사용하여 현재 상용화 되어 있는 Gd 자기공명조영제 및 최근 간특이성 자기공명조영제로 제안되고 있는 Gd-EOB-DTPA의 물분자 교율을 측정하고자 하였다. 대상 및 방법 본 연구에 사용된 조영제는 Gd-DTPA, Gd-DTPA-BMA, Gd-DOTA, Gd-EOB-DTPA 이며 여기에 Isotech 사의 5% $^{17}O$로 치환된 증류수를 혼합하여 사용하였다. 결과적인 시료의 pH는 buffer용액을 사용하여 pH=7로 고정하였으며 다양한 온도에서 Bruker-600 (14.1 T, 81.3 MHz)모델의 NMR장비를 사용하여 측정하였다. 에코열 24개의 Carr-Purcell-Meiboom-Gill (CPMG) 펄스 시권스를 사용하여 $^{17}O$의 스핀-스핀 이완시간(T2)을 측정하고 이렇게 얻어진 T2 데이터는 최소자승법을 이용하여 Solomon-Bloembergen방정식에 fitting시켜서 최종적으로 각 조명제의 물분자 교환율을 계산하였다. 결과 : 측정된 각 조영제의 물분자 교환시간은 300k의 온도에서는 Gd-DTPA의 경우 0.427, Gd-DTPA-BMA의 경우 $1.99{\;}{\mu}s$, Gd-DOTA의 경우 $0.27{\;}{\mu}s$, Gd-EOB-DTPA의 경우 $0.11{\;}{\mu}s$로 나타났으며 이러한 물분자 교환시간은 온도에 따라 변화함을 알았다. 물분자 교환시간의 온도 의존성은 모든 조영제에서 지수함수의 형태로 나타났으나 조영제에 따라 온도가 올라감에 따라 물분자 교환시간이 감소하는 감소율에서는 차이를 나타내었다. 결론 : 상자성 조영제의 relaxation enhancement 기전을 이해하는데는 물분자 교환율에 대한 정보가 매우 중요하며 이러한 물분자 교환율을 정확히 측정하는데는 $^{17}O-NMR$기법이 매우 유용함을 알 수 있었다.

• 동의생리병리학회지
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• 제27권4호
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• pp.437-445
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• 2013

This study was investigated to evaluate the vasorelaxant effect of Rubus coreanus(RC) extract on contracted rabbit carotid artery and its mechanism. To study the effect of RC extract on contracted rabbit carotid arterial strips, arterial strips with intact or damaged endothelium were used for experiment using organ bath. The pre-contracted arterial strips with norepinephrine(NE) or potassium chloride(KCl) was treated with various concentrations of an extract of RC(0.01, 0.03, 0.1, 0.3 and 1.0 $mg/m{\ell}$). To determine the mechanisms of RC-induced vasorelaxant, RC extract was infused into contracted arterial rings which had been pretreated by indomethacin(IM), tetraethylammonium chloride(TEA), $N{\omega}$-nitro-L-arginine (L-NNA), methylene blue(MB). And calcium chloride(Ca) 1 mM was infused into precontracted arterial ring induced by NE or KCl after treatment of RC extract in $Ca^{2+}$-free krebs solution. Cytotoxic activity of RC extract on human umbilical vein endothelial cell(HUVEC) was measured by MTT assay, and nitric oxide(NO) prodution was measured by Griess reagent. RC extract revealed significant relaxation on NE-induced arterial contraction, but didn't relax on KCl-induced arterial contraction. RC extract also had an effective relaxation to the intact endothelium arterial ring, but not the damaged endothelium arterial ring. Treatment of IM, TEA, L-NNA, MB reduced the relaxation of RC extract. Pretreatment of RC extract inhibited the contraction by influx of extracellular $Ca^{2+}$ in contracted arterial ring induced by NE, but it didn't work the contraction by influx of extracellular $Ca^{2+}$ in contracted arterial ring induced by KCl in $Ca^{2+}$-free krebs solution. RC extract increased nitric oxide production on HUVEC. This study indicated that the relaxation effect of RC extract on contracted rabbit carotid artery is related with NO-cGMP pathway, EDHF, prostacyclin.

• Investigative Magnetic Resonance Imaging
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• 제6권1호
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• pp.35-40
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• 2002

목적 : 새로운 개념의 macromolecular MR 조영제를 개발하여 자기이완적 특성 및 조직특이성 조영제로서의 가능성을 탐색해 보고자 하였다. 대상 및 방법 : Phthalocyanine (PC)을 상자성 원소의 배위자로 선택하였다. 2.01g (5.2 mmol)의 Phthalocyanine을 0.37 g(1.4mmo1)의 Mn chloride와 $310^{\circ}C$에서 36시간동안 반응시킨 후 혼합물을 크로마토그래피(CHC13/CH3OH 98/2 v/v, Rf, 0.76)로 정제하여 1.04 g (46%)의 MnPC (분자량 2000)를 얻었다. 0.1 mM로 희석시킨 MnPC를 1.5T(64MHz) MR 장비를 이용하여 T1/T2 자기이완율을 측정하였다. MnPC의 MR 영상 특성을 알아보기위해 1.5T MRI에서 스핀반향 기법(TR/TE= 500/14 msec)과 경사에코 기법중 FLASH 기법(TR/TE=80/4 msec, flip angle=60)을 사용하여 매 10분 간격으로 최고 4시간까지 연속적으로 토끼의 간에서 영상을 획득하였다. 농도별 차이를 알아보기위해 MnPC를 20 mM, 50 mM, 100 mM로 희석하여 사용하였다. 결과 : MnPC의 1.5 T(64 MHz)에서의 자기이완율은 Rl : 7.28 $mM^{-1}S^{-1}$, R2=55.56 $mM^{-1}S^{-1}$으로 small molecular weight 조영제인 Gd-DTPA의 Rl(=4.8 $mM^{-1}S^{-1}$), R2(=5.2 $mM^{-1}S^{-1}$) 값과 비교할 때 T1/T2 자기이완율이 매우 컸다. 스핀반향과 FlASH 기법 모두에서 조영증강은 조영제 주사후 약 10분 정도에 최고치에 달한 후 약 2시간 정도까지 유지하였다. MnPC는 small molecular weight의 간특이성 조영제들인 Gd-EOB-DTPA, Gd-BOPTA 및 MnDPDP과 비교할 때 조명증강을 유지하는 시간이 훨씬 더 긴 특성을 보였다. MnPC는 시간 경과에 따라 담도로 배출되었다. 결론 : 새로운 종류의 macromolecular MR agent인 MnPC를 자체 개발하였고 자기이완율을 측정한 결과 T1/T2 효과가 기존의 small molecular Gd-chelate에 비해 매우 큼을 알 수 있었다. MnPC는 간세포에 흡수된 후 담도계로 배출되는 간특이성 조영제임을 확인하였다.

• Asian-Australasian Journal of Animal Sciences
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• 제16권12호
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• pp.1749-1754
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• 2003

The study was undertaken to see the effect of elevated feeding during pre-partum or pre- as well as post-partum period on the productive and reproductive performance of crossbred cows. The experiment lasted for 60 d pre-partum to 120 d post-partum. Eighteen dry pregnant crossbred cows divided into three equal groups were fed either as per NRC feeding standard (C) or 20% above NRC during 60 d pre-partum ($T_1$) or fed 20% above NRC during both 60 d pre-partum to 120 d post-partum ($T_2$) period. During prepartum period body weight gain was significantly ($p{\leq}0.05$) higher in $T_1$ and $T_2$ groups than that of control group. The animals fed at higher plane of nutrition ($T_1$ and $T_2$) took significantly lesser time for complete relaxation of pelvic muscles, act of calving and for expulsion of placenta than that of control group. Moreover, such cows delivered 2 to 3 kg heavier calves as compared to normal fed dams. During post-partum period, the average daily milk yield was significantly higher in $T_2$ group than that in $T_1$ and control groups. The peak yield was significantly higher in $T_2$ group, it took longer time to reach peak production but it was more persistent in this group as compared to $T_1$ and control groups. Average milk fat, solids-not-fat (SNF) and total solids were significantly higher in $T_1$ and $T_2$ groups as compared to control group. Body weight losses incurred during early lactation were not even compensated by end of 4th month of lactation in C and $T_1$ groups whereas the animals in $T_2$ group gained 2.0 kg. The 1st post-partum estrus and conception rate were better in high fed groups ($T_1$ and $T_2$) than that of control group. The returns over feed cost of milk production were higher in $T_2$ group followed by $T_1$ and control groups indicating the advantage of elevated feeding during pre- and post-partum periods.

• 한국자기공명학회논문지
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• 제6권2호
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• pp.132-141
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• 2002

$^1H$ nuclear magnetic resonance (NMR) relaxations have been investigated in ammonium sulfate $((NH_4)_2SO_4)$ power at temperatures ranging form 102 K to 440 K. There is a bottleneck in the spin-lattice relaxation between the nuclear spin system and the hindered rotation of ammonium ions, which is certified by measuring the relaxation according to the initial condition of the spin system. For temperatures below 318 K the $^1H$ spin-lattice relaxations have double-exponential behaviors with the exponent, n, having a value 2>n>1 initially and n=l after a long time. Above 318 K not only is the relaxation exponential initially with exponent n=1, but it is a single-exponential over the entire time, resulting in one $T_1$ value. The two types of $NH_4^+$ ions have different activation energies for hindered rotation, $E_a^1=0.27{\pm}0.02eV$ and $E_a^11=0.12{\pm}0.0eV$, in the ferroelectric phase.

• 한국재료학회지
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• 제8권2호
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• pp.95-98
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• 1998

완화형 강유전체인 0.9MPb*Mg$_{1}$3/Nb$_{2}$3/)O$_{3}$-0.1PbTiO$_{3}$에서 강유전-상유전 상전이에 수반되는 relaxation거동을 살펴보기위해 낮은 전계에서 측정된 유전특성과 높은 전계에서 측정된 전계유기 분극 거동 등을 조사하였다. -50-9$0^{\circ}C$의 상전이 온도범위에 걸쳐 1V/mm의 낮은 전계에서 측정된 유전특성의 온도의존성을 구하고 수 kVmm의 강전계하에서 발생된 분극의 온도의존성을 관찰하였다. 이 모든 결과들은 Vogel-Fulcher관계식에 비교적 정확하게 일치되었으며 그 결과 T$_{f}$ 는 294.6˚K로 나타났다. 본 연구결과를 통하여 Vogel-Fulcher관계식에 의한 주파수 의존성은 낮은 전계하에서의 유전특성 뿐 아니라 강전계하에서의 여러물성들도 동일하게 적용되는 것을 확인할 수 있었다.

• Advances in materials Research
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• 제2권1호
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• pp.1-13
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• 2013

Lead-free compound $(Na_{0.5}Bi_{0.5})(Zr_{0.75}Ti_{0.25})O_3$ was prepared using conventional ceramic technique at $1070^{\circ}C$/4h in air atmosphere. X-ray diffraction analysis showed the formation of single-phase orthorhombic structure. Permittivity data showed low temperature coefficient of capacitance ($T_{CC}{\approx}5%$) up to $100^{\circ}C$. Complex impedance studies indicated the presence of grain boundary effect, non-Debye type dielectric relaxation and evidences of a negative temperature coefficient of resistance. The ac conductivity data were used to evaluate the density of states at Fermi level and apparent activation energy of the compound.

• 음성과학
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• 제8권3호
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• pp.185-200
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• 2001

This study was designed to investigate the treatment, generalization, and maintenance effects of vocal relaxation treatment on compensatory articulation(i.e., glottalization of plosive sound) of three children with cleft palate. Multiple baseline design was applied to evaluate treatment, generalization, and maintenance effects. The targeted phonemes were ph/, th/, /t/ which Were frequently substituted by glottal stop sounds. The main component of the treatment program was vocal relaxation using humming and aspiration sound /h/. The following conclusions were deduced from the results: (1) the treatment program for compensatory articulation was effective in facilitating correct production of targeted phoneme and eliminating glottalization for all subjects, (2) the treatment effects on articulation accuracy were generalized to untreated phonemes (/c/, /c$c^{h}$/) for 2 subjects, (3) the treatment effects on decrease of glottalization were generalized to untreated phonemes for all subjects, and (4) the treatment effects were maintained for all subjects for 2 weeks after treatment was terminated.

• 한국진공학회지
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• 제21권4호
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• pp.219-224
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• 2012

태양광에 노출되어있는 동안 비정질실리콘 태양전지에서 일어나는 장시간 성능변화에 대해서 연구하였다. 그리고 결함밀도의 운동학 모형을 통해서 태양광으로 인한 태양전지 성능변화를 예측하였다. 특히, 전하운반자 수명이 결함밀도에 의해서 크게 영향을 받기 때문에 비정질실리콘 태양전지의 광유도 성능감소(light-induced degradation)가 확장지수함수 완화법칙(stretched-exponential relaxation)을 따르는 결함밀도에 의해서 물리적으로 설명된다. 그리고 확장지수함수 완화법칙과AMPS-1D 컴퓨터 프로그램의 모의실험에 의해서 비정질실리콘 태양전지의 광유도 성능감소를 계산했고, 모의실험의 결과를 옥외에 설치한 태양전지의 측정데이터에 비교하였다. 본 연구는 상온에서 다음과 같은 특성을 갖는 전형적인 비정질실리콘pin 태양전지에 대해서 모의실험을 진행했다: 두께${\approx}$300 nm, 내부전위${\approx}$1.05 V, 초기 결함밀도${\approx}5{\times}10^{15}cm^{-3}$, 초기 단락전류${\approx}15.8mA/cm^2$, 초기 채우기비율${\approx}0.691$, 초기 개방전압${\approx}0.865V$, 초기 변환효율${\approx}9.50%$.

• 한국초전도학회:학술대회논문집
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• 한국초전도학회 2000년도 High Temperature Superconductivity Vol.X
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• pp.107-110
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• 2000

($^{11}$B NMR measurements have been performed on single crystals of LuNi$_2$B$_2$C superconductor to investigate vortex lattice structures and dynamical behavior. The spectrum in the superconducting state is significantly broadened by local field inhomogeneity due to the vortex lattice and the peak point of the spectrum shifts toward low magnetic field due to the imperfect field penetration. The linewidth of the spectrum reflecting local field variation is much smaller than expected for conventional vortex lattices and shows peculiar increase at low temperature. Furthermore, the transverse relaxation rate, 1/T$_2$, probing the slow motion of vortices, exhibits a single peak as temperature decreases. These prominent results highlight significant fluctuation of vortices even for this low T$_c$, and nearly isotropic 3D superconductor.