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Ah Young Lee,Bo Ra Hwang,Myoung Hee Lee,Sanghyun Lee,Eun Ju Cho 대한지역사회영양학회 2016 Nutrition Research and Practice Vol.10 No.3
BACKGROUND/OBJECTIVES: The accumulation of amyloid-β (Aβ) in the brain is a hallmark of Alzheimer’s disease (AD) and plays a key role in cognitive dysfunction. Perilla frutescens var. japonica extract (PFE) and its major compound, rosmarinic acid (RA), have shown antioxidant and anti-inflammatory activities. We investigated whether administration of PFE and RA contributes to cognitive improvement in an Aβ25-35-injected mouse model. MATERIALS/METHODS: Male ICR mice were intracerebroventricularly injected with aggregated Aβ25-35 to induce AD. Aβ25-35-injected mice were fed PFE (50 mg/kg/day) or RA (0.25 mg/kg/day) for 14 days and examined for learning and memory ability through the T-maze, object recognition, and Morris water maze test. RESULTS: Our present study demonstrated that PFE and RA administration significantly enhanced cognition function and object discrimination, which were impaired by Aβ25-35, in the T-maze and object recognition tests, respectively. In addition, oral administration of PFE and RA decreased the time to reach the platform and increased the number of crossings over the removed platform when compared with the Aβ25-35-induced control group in the Morris water maze test. Furthermore, PFE and RA significantly decreased the levels of nitric oxide (NO) and malondialdehyde (MDA) in the brain, kidney, and liver. In particular, PFE markedly attenuated oxidative stress by inhibiting production of NO and MDA in the Aβ25-35-injected mouse brain. CONCLUSIONS: These results suggest that PFE and its active compound RA have beneficial effects on cognitive improvement and may help prevent AD induced by Aβ.
The Magnetic Behaviors of Spin-Glass <tex> $\hbox{FeGa}_{2}\hbox{O}_{4}$</tex> System
Bo Ra Myoung,Seung Kyu Han,Sam Jin Kim,Chul Sung Kim IEEE 2012 IEEE transactions on magnetics Vol.48 No.4
<P>We present the investigation of magnetic properties of spin-glass FeGa<SUB>2</SUB>O<SUB>4</SUB> system. From X-ray diffraction patterns of FeGa<SUB>2</SUB>O<SUB>4</SUB>, refined with Rietveld's refinement method, its structure is determined to be cubic spinel with space group Fd - 3m and the lattice parameter of α<SUB>0</SUB> = 8.385 Å. From temperature-dependent magnetization curves under 1000 Oe, the Neel temperature is found to be T<SUB>N</SUB> = 14 K, which coincides with the value obtained from the Mossbauer spectrum. The freezing temperature T<SUB>f</SUB> of the sample shifts to higher temperature with increasing frequency, as seen in conventional metallic spin glasses. Also, we have determined the small activation energy, E<SUB>a</SUB> of 1.04266 × 10<SUP>-4</SUP> meV from Arrhenius law v = v<SUB>0</SUB> exp(-E<SUB>n</SUB>/k<SUB>B</SUB>T<SUB>f</SUB>), where k<SUB>B</SUB> is Boltzmann constant, and E<SUB>a</SUB> is activation energy. The Mossbauer spectrum at 4.2 K shows severely distorted 8-line shape coming from frozen spin-disorder state and an incommensurate spin structure, as in spin glasses. The change in the electric quadrupole shift above T<SUB>f</SUB> is caused by the presence of the maximum electric dipole interaction among frozen disordered spins around T<SUB>f</SUB> as in spin-glass material, and charge re-distribution from spin-relocation arising above T<SUB>N</SUB>.</P>
Myoung, Bo Ra,Lim, Jung Tae,Kim, Chul Sung North-Holland Pub. Co 2017 Journal of magnetism and magnetic materials Vol.438 No.-
<P><B>Abstract</B></P> <P>We have studied crystal and magnetic properties of chalcogenides FeGa<SUB>2</SUB>S<SUB>4</SUB> and FeIn<SUB>2</SUB>S<SUB>4</SUB> with X-ray diffractometer (XRD), magnetic property measurement system (MPMS), magnetometer, physical property measurement system (PPMS), and Mössbauer spectrometer. The crystal structure has 2-dimension triangular lattice structure with <I>P-</I>3<I>m</I>1 of FeGa<SUB>2</SUB>S<SUB>4</SUB>, while FeIn<SUB>2</SUB>S<SUB>4</SUB> has inverse spinel with space group <I>Fd</I>3<I>m</I>. The AC magnetic susceptibility measurements show that FeGa<SUB>2</SUB>S<SUB>4</SUB> is an insulating spin glass material, exhibiting geometrical frustration, unlike in the antiferromagnetic [AFM] metallic spin glass FeIn<SUB>2</SUB>S<SUB>4</SUB>. From hysteresis (M-H) curves at 4.2K, FeGa<SUB>2</SUB>S<SUB>4</SUB> has spin-flop behavior with an angle of 120° of triangle, as against linear slope of FeIn<SUB>2</SUB>S<SUB>4</SUB> due to anti-parallel spin. The gap energy by splitting of <SUP>5</SUP> <I>T</I> <SUB>2g</SUB>, <I>Δ</I> <SUB>1</SUB> and electric quadrupole splitting Δ<I>E</I> <SUB>Q</SUB> of FeIn<SUB>2</SUB>S<SUB>4</SUB> are much higher than that of FeGa<SUB>2</SUB>S<SUB>4</SUB> at 4.2K because FeGa<SUB>2</SUB>S<SUB>4</SUB> is geometrically frustrated magnet having degenerate ground state at low temperature.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We have investigated the magnetic properties of FeIn<SUB>2</SUB>S<SUB>4</SUB> and FeGa<SUB>2</SUB>S<SUB>4</SUB>. </LI> <LI> FeGa<SUB>2</SUB>S<SUB>4</SUB> has incommensurate spin-fluctuation, whereas FeIn<SUB>2</SUB>S<SUB>4</SUB> appears to have AFM spin structure. </LI> <LI> The gap energy, <I>Δ</I> <SUB>1</SUB> of 5<I>T</I> <SUB>2g</SUB> band on crystal field in FeIn<SUB>2</SUB>S<SUB>4</SUB> is 1.350meV, which is much higher than <I>Δ</I> <SUB>1</SUB> =0.197meV of FeGa<SUB>2</SUB>S<SUB>4</SUB> at 4.2K, since FeGa<SUB>2</SUB>S<SUB>4</SUB> has the degenerate ground state energy with spin-ordering by an angle of 120° of triangle as a geometrically frustrated magnet at low temperature. </LI> </UL> </P>
Evidence of Spin Reorientation by Mössbauer Analysis
Bo Ra Myoung,Sam Jin Kim,Chul Sung Kim 한국자기학회 2014 Journal of Magnetics Vol.19 No.2
We report the crystallographic and magnetic properties of Ni0.3Fe0.7Ga₂S₄ by means of X-ray diffractometer (XRD), a superconducting quantum interference device (SQUID) magnetometer, and a Mossbauer spectroscopy. In particular, Ni0.3Fe0.7Ga₂S₄ was studied by Mossbauer analysis for evidence of spin reorientation. The chalcogenide material Ni0.3Fe0.7Ga₂S₄ was fabricated by a direct reaction method. XRD analysis confirmed that Ni0.3Fe0.7Ga₂S₄ has a 2-dimension (2-D) triangular lattice structure, with space group P-3m1. The Mossbauer spectra of Ni0.3Fe0.7Ga₂S₄ at spectra at various temperatures from 4.2 to 300 K showed that the spectrum at 4.2 K has a severely distorted 8-line shape, as spin liquid. Electric quadrupole splitting, EQ has anomalous twopoints of temperature dependence of EQ curve as freezing temperature, Tf = 11 K, and Neel temperature, TN = 26 K. This suggests that there appears to be a slowly-fluctuating “spin gel” state between Tf and TN, caused by non-paramagnetic spin state below TN. This comes from charge re-distribution due to spin-orientation above Tf, and TN, due to the changing EQ at various temperatures. Isomer shift value (0.7 mm/s ≤ δ ≤ 0.9 mm/s) shows that the charge states are ferrous (Fe<SUP>2+</SUP>), for all temperature range. The Debye temperature for the octahedral site was found to be ΘD = 260 K.
Crystallographic and M?ssbauer Studies for Ni0.9957Fe0.01Ga2S4
Bo Ra Myoung,Chul Sung Kim,Sam Jin Kim 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.52 No.6
Ni0.9957Fe0.0₁Ga₂S₄ was fabricated by using a solid-state method with high-purity elements of Fe, Ni, Ga and S. The structure of the sample was examined with an X-ray diffractometer (XRD) and analyzed by using the Rietveld refinement. The crystal structure of the Ni0.9957Fe0.0₁Ga₂S₄ was determined to be a trigonal structure of P-3m1 with lattice constants a_0 = 3.629 A, b0 = 3.629 Aand c0 = 11.996 A. The Mossbauer spectra of Ni0.9957Fe0.0₁Ga₂S₄ were recorded at various temperatures ranging from 4.2 to 300 K. The magnetic hyperfine field and the electric quadrupole interactions at 4.2 K were fitted, yielding the following results: Hhf = 112.7 kOe, △EQ = 1.374 mm/s, θ = 48.0˚ Φ =0.0˚, η = 0.5 and R = 1.8. The charge state of Fe ions is ferrous Fe²+ as characterized by an isomer shift of δ = 0.653 mm/s at 300 K. The Mossbauer spectra show a large quadrupole interaction in Ni0.9957Fe0.0₁Ga₂S₄. Ni0.9957Fe0.0₁Ga₂S₄ was fabricated by using a solid-state method with high-purity elements of Fe, Ni, Ga and S. The structure of the sample was examined with an X-ray diffractometer (XRD) and analyzed by using the Rietveld refinement. The crystal structure of the Ni0.9957Fe0.0₁Ga₂S₄ was determined to be a trigonal structure of P-3m1 with lattice constants a_0 = 3.629 A, b0 = 3.629 Aand c0 = 11.996 A. The Mossbauer spectra of Ni0.9957Fe0.0₁Ga₂S₄ were recorded at various temperatures ranging from 4.2 to 300 K. The magnetic hyperfine field and the electric quadrupole interactions at 4.2 K were fitted, yielding the following results: Hhf = 112.7 kOe, △EQ = 1.374 mm/s, θ = 48.0˚ Φ =0.0˚, η = 0.5 and R = 1.8. The charge state of Fe ions is ferrous Fe²+ as characterized by an isomer shift of δ = 0.653 mm/s at 300 K. The Mossbauer spectra show a large quadrupole interaction in Ni0.9957Fe0.0₁Ga₂S₄.