• Journal of Magnetics
• /
• 제2권4호
• /
• pp.126-129
• /
• 1997

We have studied magnetostructural phase transitions in the perovskite-type layered structure compound (C18H37NH3)2 MnCl4 by means of electron paramagnetic resonance (EPR) and superconducting quantum interference device (SQUID) measurements. Distinct slopes were observed in the linear temperature dependences of the Mn++ EPR linewidth in the low and high temperature phases. Besides, linewidth anomalies at the transition temperatures sensitively reflect the magnetic changes arising from the MnCl6 octahedra.

• 한국생물물리학회:학술대회논문집
• /
• 한국생물물리학회 1999년도 학술발표회 진행표 및 논문초록
• /
• pp.44-44
• /
• 1999

Yeast cytochrome c peroxidase (CcP) was cloned and overexpressed in E. coli, and purified by a Ni$^{2＋}$-affinity column. HoloCcP was obtained by reconstituting apoCcP with Mn$^{3+}$-protoporphyrin IX (MnPP). Electron paramagnetic resonance (EPR) spectra of spin-labeled holoCcP showed a slightly more immobilized signal than spin-labeled apoCcP.(omitted)

• Journal of Magnetics
• /
• 제5권1호
• /
• pp.9-12
• /
• 2000

Electron spin resonance and magnetization measurements were carried out on $La_0.7Ca_0.3MnO_3$ in the ferromagnetic as well as paramagnetic phases. Evidence of an inhomogeneous magnetic structure, consisting of ferro-magnetic microregions embedded in an antiferromagnetic matrix near $T_c$, as well as similar local magnetic structures above and below $T_c$, were found.

• 한국자기공명학회논문지
• /
• 제12권2호
• /
• pp.103-110
• /
• 2008

Spin Hamiltonian for the paramagnetic center with a three-fold symmetry and high spin ($S{\geq}2$) multiplicity should contain the fourth order zero-field splitting (ZFS) terms. Electron magnetic resonance transition lines of the center with S = 5/2 are expected to split in a pair when the magnetic field is applied off the principal axes of ZFS, while they are superimposed when the magnetic field is applied parallel to the principal axes of ZFS. In this study we report that the transition lines of $Mn^{2+}$ centers at the three-fold symmetric sites in $LiNbO_3$, chemically equivalent but physically different, split in two due to the nonzero fourth order ZFS term.

• 한국자기공명학회논문지
• /
• 제5권1호
• /
• pp.13-18
• /
• 2001

Natural alpha radiation produced a stable defect center to certain minerals. Electron Paramagnetic Resonance(EPR) spectroscopy is a powerful tool f3r quantifying this defect center. EPR method has been applied to trace alpha-radiation effect around the uranium ore deposit. The results show that EPR technique can be used to measure rapidly and nondestructively the defect center produced by natural alpha radiation. In general, a good correlation was achieved between defect center concentration and actinide elements(U, Th). These results imply that the concentration of defect center is dependent on the alpha radiation dose over long time scale.

• 한국자기공명학회:학술대회논문집
• /
• 한국자기공명학회 2002년도 International Symposium on Magnetic Resonance
• /
• pp.72-72
• /
• 2002

In most traditional sorption study in environmental conditions, experimental sorption data have been measured and interpreted by empirical ways such as partition coefficient and sorption isotherms. A mechanistic understanding of heavy metal interactions with various minerals (metal oxides, clay minerals) in aqueous medium is required to describe the behavior of radioactive metal ions in the environment. Various spectroscopic methods provide direct or indirect information on sorption mechanisms involved. We applied EPR (Electron Paramagnetic Resonance) spectroscopy to investigate the nature of metal ion sorption at water/mineral interfaces using Cu(II) as a spin probe. The major sorbed species and their motional state was identified by their EPR spectra. They showed distinct signals due to their strength of binding, local structure and motional state. The EPR results together with macroscopic sorption data show that sorption involved at least three different mechanisms depending on chemical environments (1).

• Journal of Magnetics
• /
• 제17권4호
• /
• pp.251-254
• /
• 2012

The electron paramagnetic resonance (EPR) of the $Eu^{2+}$ ion in $SrCl_2$:Eu single crystal has been investigated using an X-band spectrometer. The angular dependence of magnetic resonance positions for the $Eu^{2+}$ impurity ion in the crystallographic aa-plane is analyzed with effective spin-Hamiltonian. The EPR spectra of the isolated $Eu^{2+}$ center merged to each other. The hyperfine splitting of the isolated $Eu^{2+}$ center due to the $^{151}Eu$ nucleus is approximately 35 G. Three kinds of $Eu^{2+}$ centers except the isolated $Eu^{2+}$ center, $Eu^{2+}$ pairs, $Eu^{2+}$ triples, and other $Eu^{2+}$ clusters, are split from the fitting of the integrated experimental spectrum with the Gaussian curve. The calculated spectroscopic splitting parameters of the $Eu^{2+}$ pairs, $Eu^{2+}$ triples, and other $Eu^{2+}$ clusters in $SrCl_2$:Eu crystal are $g_1$ = 2.06, $g_2$ = 1.94, and $g_3$ = 1.93, respectively.

• 한국자기공명학회논문지
• /
• 제12권1호
• /
• pp.26-32
• /
• 2008

We report on the ferromagnetic characteristics of $Zn_{1-x}Mn_xO$ films (x = 0.3) prepared by sol-gel method on the silicon and (0001) ${\alpha}-Al_2O_3$ substrates at the annealing temperature of 700$^{\circ}C$. Magnetic measurements show that Curie temperature ($T_C$) and the coercive field ($H_C$) for the film on the silicon are about 32 K and about 275 Oe, while those for that on the sapphire are about 32 K and 425 Oe, respectively. Energy dispersive spectroscopy and transmission electron microscopy measurements suggest that ferromagnetic precipitates originated by manganese oxide compound formed at the interfaces of the both substrates may be responsible for the observed ferromagnetic behavior of the films. Electron paramagnetic resonance study of the powders up to the concentration of x=0.15 supports the result.

• 한국해양바이오학회지
• /
• 제1권4호
• /
• pp.252-259
• /
• 2006

본 실험은 electron spin/paramagnetic resonance(ESR/EPR)를 이용하여 기존의 DPPH free radical 소거 활성을 측정하였고, 이를 해조류 유래 천연자원으로부터 새로운 항산화물질을 탐색하는데 적용해 보았다. 연구 결과, 녹조류 추출물에서는 참홑파래, 납작파래 및 청각의 고온 메탄올 추출물에서만 약간의 라디칼 소거활성을 나타내었고, 이 외의 추출물에서는 소거활성이 거의 보이지 않았다. 갈조류는 총 71개의 추출물 중 37개의 추출물에서 80% 이상의 소거율을 보여 아주 우수한 항산화 물질을 가진 family로 여겨지며, 특히 모자반류 (Sargassum spp.)는 수용성과 메탄올, 고온과 상온의 모든 추출물에서 높은 라디칼 소거 활성을 보여 앞으로의 신소재 물질 후보로 선별되었다. 홍조류에서는 수용성보다는 메탄올 추출물에서 대체적으로 높은 소거활성이 검색되어, 나중에는 유기용매 분획물을 제조하여 라디칼 소거능을 측정 할 수 있을 것이다. 이처럼 해조류는 라키칼 소거 능력을 가지는 성분을 여러 형태로 다량으로 함유 하고 있는 것으로 사료 되며 앞으로의 연구에 기대가치를 더해 줄 것으로 사료된다.

• Preventive Nutrition and Food Science
• /
• 제14권3호
• /
• pp.188-194
• /
• 2009

In this study, we evaluated the phytochemical compositions of the fruits of the pear cactus, mulberry, and Korean black raspberry to determine how they related to antioxidant capacity. Specifically, the total soluble polyphenol, flavonoid and anthocyanin contents were determined, and the phenolic compounds were evaluated by HPLC. In addition, the antioxidant capacity was evaluated by electron paramagnetic resonance (EPR), SOD-like activity and nitrate scavenging activity. Korean black raspberry was found to have the highest level of phytochemicals, followed by mulberry and pear cactus (p<0.05). Furthermore, EPR revealed that Korean black raspberry extract (100 ${\mu}g$/mL) removed 78.6% of the superoxide radicals in a xanthin-xanthin oxidase. Additionally, when the removal of hydroxyl radicals was evaluated, the extract of pear cactus showed 50% scavenging activity at 1000 ${\mu}g$/mL. Korean black raspberry extract showed the highest SOD-like activity, which was 44% (p<0.05). Finally, the nitrate scavenging activity of both extracts of mulberry and Korean black raspberry were found to be 93%, while that of the pear cactus was 63% at pH 1.2 (p<0.05).