Change of electrical properties of (K_0.5Na_0.5) (Mn_0.005Nb_0.995)O₃ thin films induced by gamma-ray irradiation

Kim, B.H.,Yang, S.A.,Kang, S.W.,Choi, G.P.,Cho, S.Y.,Han, J.K.,Lee, G.J.,Lee, M.K.,Seog, H.J.,Kim, I.W.,Bu, S.D. Elsevier 2016 CURRENT APPLIED PHYSICS Vol.16 No.5

<P>We investigated the effects of gamma-ray (gamma) irradiation on the electrical properties of (K0.5Na0.5) (Mn0.005Nb0.995)O-3 (KNMN) thin films. The KNMN thin films were prepared on Pt/Ti/SiO2/Si substrate using a chemical solution deposition method through a spin-coating process and were subject to gamma radiation at various total doses from 0 to 3000 kGy. The structural properties as well as the ferroelectric and dielectric properties of the prepared films were examined before and after gamma irradiation. We found that their crystalline quality did not vary significantly with an increase in the total dose. It was also observed that the remnant polarization value of the films decreased by similar to 10%, but the films maintained ferroelectricity even after irradiation up to 3000 kGy. In addition, the dielectric constant of the films decreased with the total dose. The observed variation of the electrical properties on the total dose might be mainly associated with the mobile defects in Mn-doped KNN thin films such oxygen vacancy and the stored energy gained from gamma-rays. (C) 2016 Elsevier B.V. All rights reserved.</P>

Chlorogenic acid ameliorates brain damage and edema by inhibiting matrix metalloproteinase-2 and 9 in a rat model of focal cerebral ischemia

Lee, K.,Lee, J.S.,Jang, H.J.,Kim, S.M.,Chang, M.S.,Park, S.H.,Kim, K.S.,Bae, J.,Park, J.W.,Lee, B.,Choi, H.Y.,Jeong, C.H.,Bu, Y. North-Holland ; Elsevier Science Ltd 2012 european journal of pharmacology Vol.689 No.1

Chlorogenic acid (CGA) has been reported to have various beneficial effects on the cardiovascular and central nervous systems. The purpose of the current study was to investigate whether CGA has protective effects against cerebral ischemia and whether these effects are due to modification of brain edema-related vascular factors. In a rat model of transient middle cerebral artery occlusion (MCAo, 2h of occlusion followed by 22h of reperfusion), we measured infarct volume and performed behavioral test to evaluate the effects of CGA on brain damage and sensory-motor functional deficits. Brain water content and Evans blue extravasation were measured to evaluate brain edema and blood brain barrier (BBB) damage. Lipid peroxidation (LPO) and the expressions and activities of matrix metalloproteinase (MMP)-2 and MMP-9 were measured to investigate the mechanisms of action. Intraperitoneal injection of CGA (3, 10, and 30mg/kg) at 0h and 2h after MCAo dose-dependently reduced infarct volume and sensory-motor functional deficits. It also reduced brain water content and Evans blue extravasation. Mechanistically, CGA reduced LPO and MMPs expressions and activities. These results suggest that CGA reduces brain damage, BBB damage and brain edema by radical scavenging activity and the inhibitory effects on MMP-2 and MMP-9.

Development of the 3.7 GHz LHCD System on HL-2A

B. Lu,M. Huang,H. Zeng,X. Y. Bai,X. H. Mao,Z. H. Lu,J. Liang,Z. H. Kang,M. W. Wang,K. Feng,H. Wang,C. Wang,J. Q. Wang,S. Wei,T. Yao,Y. N. Bu,J. Feng,G. Y. Cheng,S. D. Song,D. H. Xia,J. Rao 한국물리학회 2014 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.65 No.8

A 2 MW-3.7 GHz lower hybrid current drive (LHCD) system is under development for physicsexperiments on the HL-2A device. The RF Power is generated by four TH2103A klystron amplifiersand propagates in the TE10 mode through WR284 waveguides. The transmission lines with a lengthof 20 m to 30 m are pressurized with 2 bars of nitrogen to decrease the possibility of arcing. Thelauncher, based on the passive-active multi-junction (PAM) concept, has been developed and iscurrently being realized. It was designed for a power spectrum peaked at Nk = 2.75 with goodcoupling properties over a wide range of plasma parameters. The four klystrons are fed by ahigh-voltage power supply (HVPS) based on the pulse step modulation (PSM) concept with a fastswitch-off time of less than ten μs. This system is expected to be in operation within 1 years and willexplore many international thermonuclear experimental reactor (ITER) related LH experiments inthe following years.

The effects of the phase structure of the polymorphic phase boundary on the piezoelectric properties of (K,Na)NbO₃-based ceramics

Yang, S.A.,Kim, B.H.,Lee, M.K.,Bu, S.D.,Lee, G.J. Elsevier 2016 CURRENT APPLIED PHYSICS Vol.16 No.5

<P>We report the effects of the phase, i.e., the rhombohedral (R), orthorhombic (O) and tetragonal (T) phase, within a polymorphic phase boundary on the piezoelectric properties of (K,Na)NbO3 ceramics doped with Bi(Na,K,Li)ZrO3 and (Bi,Na)TiO3. For the R-O-T phase boundary, the formation of an R-T phase boundary by O phase shrinkage is clearly beneficial to enhance the piezoelectric performance, whereas the enrichment of the T phase in the R-T phase boundary negatively affects the piezoelectric activity. Electrical poling in relation to the piezoelectric property strongly depends on the nature of the phase boundary, requiring the optimization of temperatures corresponding to the R-T phase boundary without the O phase. (C) 2016 Elsevier B.V. All rights reserved.</P>

Effect of Silicon Supplementation on Bone Status in Ovariectomized Rats Under Calcium-Replete Condition

Bu, S. Y.,Kim, M. H.,Choi, M. K. Humana Press 2016 Biological trace element research Vol.171 No.1

<P>Previous studies have suggested that silicon (Si) had positive effects on bone, but such benefits from Si may be dependent on calcium status. Also, several biochemical roles of Si in osteoblastic mineralization, the regulation of gene expression related to bone matrix synthesis, and the decrease in reactive oxygen species and pro-inflammatory mediators were reported, but these effects were mostly shown in cell culture studies. Hence, we tested the effect of Si supplementation on bone status and the gene expression related to bone metabolism and inflammatory mediators in young estrogen-deficient rats under calcium-replete condition (0.5 % diet). Results showed that 15-week supplementation of both high and very high doses of Si (0.025 and 0.075 % diet, respectively) could not restore the ovariectomy (OVX)-induced decrease of bone mineral density (BMD) of vertebrae, femur, and tibia. Also, several bone biochemical markers (ALP, osteocalcin, CTx) and mRNA expression of COL-I, RANKL, IL-6, and TNF-alpha in femur metaphysis were not significantly changed by Si in OVX rats. However, a very high dose (0.075 %) of Si supplementation significantly increased OPG expression and decreased the ratio of RANKL/OPG in mRNA expression comparable to that of sham-control animals. Taken together, Si supplementation did not increase BMD under calcium-replete condition but the decrease in the ratio of RANKL/OPG expression to the normal level suggests the possibility of a bone health benefit of Si in estrogen deficiency-induced bone loss.</P>

Column Chromatography 에 의한 바르비탈류 분리 정량법에 관한 연구

정인명,심수일,최광식,전성환,고미혜,부인향 한국약제학회 1979 Journal of Pharmaceutical Investigation Vol.9 No.4

The analytical method of phenobarbital and mephobarbital in the pharmaceutical preparation were investigated by the partition chromatographic method. The influence of 13 kinds of excipients and various kinds of ingredients such as 8 kinds of antipyretics and 5 kinds of antacids on the partition chromatographic analysis of phenobarbital and mephobarbital in the preparation were investigated. The results were not affected by materials with the exception of caffeine, aspirin and sulpyrin.

Self-organized Pattern Formations from Two-length-scale Repulsive Interactions

권희영,S. S. Hong,K. M. Bu,H. S. Jung,C. Won 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.1

We investigated the self-organized pattern formations of particle clusters generated from two length scale isotropic repulsive interactions by using off-axis Monte-Carlo simulations. Increasing the density of particles, we obtained the conditions for the formation of long-range ordered structures such as chain structures, hexagonally arranged droplets, and aligned stripes. We studied the properties of the spontaneously ordered phases and the critical conditions of their phase transitions for various length ratios of the two-length-scale repulsive interactions. Our simulation results show that the ratio between the two length scales is an essential parameter for determining not only the critical conditions of the phase transitions but also the existence of long-range ordered structures. In particular, the transition phase behaviors become complicated when the ratio is small, and the system exhibits alternating droplet and stripe structures as the density changes.

Pivotal role of the RanBP9-cofilin pathway in Aβ-induced apoptosis and neurodegeneration

Woo, J A,Jung, A R,Lakshmana, M K,Bedrossian, A,Lim, Y,Bu, J H,Park, S A,Koo, E H,Mook-Jung, I,Kang, D E Macmillan Publishers Limited 2012 CELL DEATH AND DIFFERENTIATION Vol.19 No.9

Neurodegeneration associated with amyloid β (Aβ) peptide accumulation, synaptic loss, neuroinflammation, tauopathy, and memory impairments encompass the pathophysiological features of Alzheimer's disease (AD). We previously reported that the scaffolding protein RanBP9, which is overall increased in brains of AD patients, simultaneously promotes Aβ generation and focal adhesion disruption by accelerating the endocytosis of amyloid precursor protein (APP) and β1-integrin, respectively. Here, we show that RanBP9 protein levels are increased by fourfold in FAD mutant APP transgenic mice. Accordingly, RanBP9 transgenic mice demonstrate significantly increased synapse loss, neurodegeneration, gliosis, and spatial memory deficits. RanBP9 overexpression promotes apoptosis and potentiates Aβ-induced neurotoxicity independent of its capacity to promote Aβ generation. Conversely, RanBP9 reduction by siRNA or gene dosage mitigates Aβ-induced neurotoxicity. Importantly, RanBP9 activates/dephosphorylates cofilin, a key regulator of actin dynamics and mitochondria-mediated apoptosis, and siRNA knockdown of cofilin abolishes both Aβ and RanBP9-induced apoptosis. These findings implicate the RanBP9–cofilin pathway as critical therapeutic targets not only for stemming Aβ generation but also antagonizing Aβ-induced neurotoxicity.

Gamma-ray irradiation effects on electrical properties of bismuth layer-structured ferroelectric ceramics

Cho, S.Y.,Choi, G.P.,Kim, E.Y.,Lee, G.J.,Lee, M.K.,Bu, S.D. Elsevier 2017 CERAMICS INTERNATIONAL Vol.43 No.17

<P><B>Abstract</B></P> <P>In this study, we prepared the bismuth layer-structured ferroelectric (BLSF)-type Bi<SUB>4</SUB>Ti<SUB>3</SUB>O<SUB>12</SUB> (BiT), Bi<SUB>3.25</SUB>La<SUB>0.75</SUB>Ti<SUB>3</SUB>O<SUB>12</SUB> (BLaT), and Bi<SUB>3.1</SUB>Nd<SUB>0.9</SUB>Ti<SUB>3</SUB>O<SUB>12</SUB> (BNdT) ceramics using the solid-state reaction method. The prepared ceramics were irradiated at room temperature by using a <SUP>60</SUP>Co gamma-ray source in a dose range of 0–3000kGy with a dose rate of 10kGy/h to compare the structure and electrical properties of the irradiated ceramics. The X-ray diffraction analysis shows that the BLSF structure was well formed in all ceramics without a secondary phase. There was no structural change such as grain size change and secondary phase formation despite the cumulative gamma-ray dose of 3000kGy. A comparison of the electrical properties with gamma-ray irradiation shows that the BiT ceramics exhibits a larger reduction ratio compared to the BLaT and BNdT ceramics. The rate of change of the remnant polarization (2<I>P</I> <SUB>r</SUB>) value with the gamma-ray irradiation doses was − 14.2%, − 8%, and − 3.4% in BiT, BLaT, and BNdT ceramics, respectively, at a cumulative gamma-ray dose of up to 3000kGy. Furthermore, the dielectric relaxation phenomenon in BiT ceramics at low frequency was observed when gamma rays of 1000kGy or more were irradiated. Based on these results, in this study, we investigated the structure and electrical properties of BLSF ceramics with gamma-ray irradiation.</P>

Effects of excess Bi₂O₃ on grain orientation and electrical properties of CaBi₄Ti₄O₁₅ ceramics

Cho, S.Y.,Choi, G.P.,Jeon, D.H.,Johnson, T.A.,Lee, M.K.,Lee, G.J.,Bu, S.D. Elsevier 2015 CURRENT APPLIED PHYSICS Vol.15 No.11

A CaBi<SUB>4</SUB>Ti<SUB>4</SUB>O<SUB>15</SUB> (CBTO) ceramic in which the Bi<SUB>2</SUB>O<SUB>3</SUB> concentration was controlled from 0 to 10 wt% was fabricated using a solid-state reaction method. Structural analysis by field-emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD) indicated differences in the preferred grain orientation and size of the plate-like grains according to the Bi<SUB>2</SUB>O<SUB>3</SUB> concentration. The orientation of plate-like grains was also found to vary with the Bi<SUB>2</SUB>O<SUB>3</SUB> concentration. There was no noticeable change trend of dielectric properties with different Bi<SUB>2</SUB>O<SUB>3</SUB> concentrations. Relatively low dielectric constants (about 135) were exhibited by the CBTO ceramic with 1 wt% Bi<SUB>2</SUB>O<SUB>3</SUB> and CBTO ceramic with 10 wt% Bi<SUB>2</SUB>O<SUB>3</SUB> only, and similar values (about 150) were exhibited by the other ceramics. The dielectric loss exhibited a low value in the range of 0.01-0.09 for all samples (frequency range of 1-100 kHz). Regarding the ratio changes of the piezoelectric coefficient (d<SUB>33</SUB>) and the ratio of a-axis orientation of plate-like grains, the trends of these two values were shown to be similar. These results suggest that the addition of Bi<SUB>2</SUB>O<SUB>3</SUB> greatly influences the microstructure of CBTO ceramics, including the grain size and orientation of plate-like grains. In particular, the change in the preferred grain orientation is closely related to the change in the piezoelectric properties.