O-free polyacrylonitrile doping to improve the J_c(B) and H_c2 of MgB₂ wires

Hwang, S.M.,Sung, K.,Choi, J.H.,Kim, W.,Joo, J.,Lim, J.H.,Kim, C.J.,Park, Y.S.,Kim, D.H. North-Holland 2010 Physica. C, Superconductivity Vol.470 No.20

We selected polyacrylonitrile (PAN, -[C<SUB>3</SUB>H<SUB>3</SUB>N]-) as an O-free organic dopant and fabricated C-doped MgB<SUB>2</SUB> wires by in situ and powder-in-tube techniques. 0-5 wt.% PAN powders were uniformly mixed with B powder using a liquid mixing method. The precursor powders were mixed with Mg powder, filled into Fe tubes, and then drawn into wires. Sintering was performed at 900<SUP>o</SUP>C for 1h in a flowing Ar gas. The PAN doping decreased the critical temperature (T<SUB>c</SUB>) and a-axis lattice parameter, but significantly improved the critical current density (J<SUB>c</SUB>) in high fields, upper critical field (H<SUB>c2</SUB>), and irreversibility field (H<SUB>irr</SUB>) performances. These results are attributed to the replacement of B sites with C by the PAN doping. Furthermore, as expected, the MgO amount did not increase as the doping content increased. The J<SUB>c</SUB> of the PAN-doped MgB<SUB>2</SUB> wires was more than one order of magnitude higher than that of the undoped MgB<SUB>2</SUB> wire at 5K and 6.6T (1.46-3.82kA/cm<SUP>2</SUP> vs. 0.11kA/cm<SUP>2</SUP>).

Improvement of high-field J_c of MgB₂ wires by polymethyl-methacrylate doping

Park, G.C.,Hwang, S.M.,Lee, C.M.,Choi, J.H.,Joo, J.,Lim, J.H.,Kang, W.N.,Kim, C.J. North-Holland 2010 Physica. C, Superconductivity Vol.470 No.suppl1

We applied polymethyl-methacrylate (PMMA) as a new doping material for MgB<SUB>2</SUB> and fabricated C-doped MgB<SUB>2</SUB> wires by in situ powder-in-tube (PIT) process. With increasing PMMA doping level, the transition temperature (T<SUB>c</SUB>) decreased and the MgO content increased, whereas the magnetic field dependence of the critical current density (J<SUB>c</SUB>) weakened. The MgB<SUB>2</SUB> wires doped with 3-10wt.% PMMA showed significantly higher J<SUB>c</SUB> by more than one order of magnitude than that of the undoped wire at 5K and 6.6T. These results confirmed the potential of PMMA as a promising material for the effective substitution of B by C in MgB<SUB>2</SUB>.

Fabrication of ex situ processed MgB₂ wires using nano carbon doped powder

Lee, C.M.,Park, J.H.,Hwang, S.M.,Lim, J.H.,Joo, J.,Kang, W.N.,Kim, C.J. North-Holland 2009 Physica. C, Superconductivity Vol.469 No.15

We fabricated ex situ MgB<SUB>2</SUB> wires using C-doped MgB<SUB>2</SUB> powder as a precursor in order to improve the core density of the wires and their C doping content. The C-doped powder was prepared with Mg, B, and nano carbon (NC) powders by the in situ technique and then MgB<SUB>2-x</SUB>C<SUB>x</SUB> (x=0, 0.01, and 0.03) wires were fabricated by the ex situ technique using the powder-in-tube method. The phase formation, lattice change, and microstructure were characterized and correlated with the T<SUB>c</SUB> and J<SUB>c</SUB> variations. We observed that the ex situ wire had a higher core density than the in situ wire, however its morphology consisted of agglomerated particles, indicating that sintering and grain growth did not occur completely, even though the sintering was conducted at high temperature (1000<SUP>o</SUP>C). As the C content increased, T<SUB>c</SUB> decreased, while the decrease of J<SUB>c</SUB> with increasing magnetic field became smaller. The J<SUB>c</SUB> of MgB<SUB>1.97</SUB>C<SUB>0.03</SUB> wire made by the ex situ technique was 3.34kA/cm<SUP>2</SUP> at 6.6T and 5K which is comparable to that of the in situ wire (4.81kA/cm<SUP>2</SUP> at 6.6T and 5K).

Novel dentin phosphoprotein frameshift mutations in dentinogenesis imperfecta type II

Lee, K‐,E,Kang, H‐,Y,Lee, S‐,K,Yoo, S‐,H,Lee, J‐,C,Hwang, Y‐,H,Nam, KH,Kim, J‐,S,Park, J‐,C,Kim, J‐,W Blackwell Publishing Ltd 2011 Clinical genetics Vol.79 No.4

<P>Lee K‐E, Kang H‐Y, Lee S‐K, Yoo S‐H, Lee J‐C, Hwang Y‐H, Nam KH, Kim J‐S, Park J‐C, Kim J‐W. Novel dentin phosphoprotein frameshift mutations in dentinogenesis imperfecta type II.</P><P>The dentin sialophosphoprotein (<I>DSPP</I>) gene encodes the most abundant non‐collagenous protein in tooth dentin and DSPP protein is cleaved into several segments including the highly phosphorylated dentin phosphoprotein (DPP). Mutations in the <I>DSPP</I> gene have been solely related to non‐syndromic form of hereditary dentin defects. We recruited three Korean families with dentinogenesis imperfecta (DGI) type II and sequenced the exons and exon–intron boundaries of the <I>DSPP</I> gene based on the candidate gene approach. Direct sequencing of PCR products and allele‐specific cloning of the highly repetitive exon 5 revealed novel single base pair (bp) deletional mutations (c.2688delT and c.3560delG) introducing hydrophobic amino acids in the hydrophilic repeat domain of the DPP coding region. All affected members of the three families showed exceptionally rapid pulp chambers obliteration, even before tooth eruption. Individuals with the c.3560delG mutation showed only mild, yellowish tooth discoloration, in contrast to the affected individuals from two families with c.2688delT mutation. We believe that these results will help us to understand the molecular pathogenesis of DGI type II as well as the normal process of dentin biomineralization.</P>

The C₃H-type zinc finger protein GDS1/C3H42 is a nuclear-speckle-localized protein that is essential for normal growth and development in Arabidopsis

Kim, D.W.,Jeon, S.J.,Hwang, S.M.,Hong, J.C.,Bahk, J.D. Elsevier Scientific Publishers Ireland Ltd 2016 Plant science Vol.250 No.-

<P>Eukaryotic C3H-type zinc finger proteins (Znfs) comprise a large family of regulatory proteins involved in many aspects of plant stress response, growth and development. However, compared to mammalian, only a few plant Znfs have been functionally characterized. Here, T-DNA inserted gdsl (growth, development and splicing 1) mutant, displayed abnormal growth throughout the lifecycle owing to the reduction of cell size and number. Inverse PCR analysis revealed that the abnormal growth was caused by the disruption of At3g47120, which encodes a C3H42 protein belonging to the C-X-7-C-X-5-C-X-3-H class of the Znf family. GDS1 was ubiquitously transcribed, but shows high levels of expression in young seedling and unexpanded new leaves. In gdsl, the transcripts of many growth- and development-related genes were down-regulated, and the auxin response was dramatically reduced. A fluorescence-based assay revealed that the GDS1 protein was localized to the nucleus, prominently in the speckle compartments. Its arginine/serine dipeptide-rich-like (RS-like) domain was essential for nuclear localization. In addition, the SRI, SRm102 and U1-70K components of the U1 spliceosome interacted with GDS1 in the nuclear speckle compartments. Taken together, these suggest that GDS1, a nuclear-speckle-associated Znf, might play a significant role in splicing during plant growth and development. (C) 2016 Elsevier Ireland Ltd. All rights reserved.</P>

Study on the improved J_c(B) performance of polyacrylic acid-doped MgB₂ bulks

Hwang, S.M.,Lee, C.M.,Lee, S.M.,Sung, K.,Joo, J.,Lim, J.H.,Kang, W.N.,Kim, C.J. North-Holland 2010 Physica. C, Superconductivity Vol.470 No.suppl1

We fabricated polyacrylic acid (PAA)-doped MgB<SUB>2</SUB> bulks by wet mixing and in situ reaction process and studied the relationships between the phase formation, lattice change, microstructure, and critical properties according to the PAA doping level. The PAA doping increased the MgO amount and grain boundary area but decreased the a-axis lattice constant and critical temperature (T<SUB>c</SUB>), which is indicative of the substitution of B sites by C in MgB<SUB>2</SUB>. Furthermore, the critical current density (J<SUB>c</SUB>) at high magnetic fields improved with the increasing PAA content to 5.99kA/cm<SUP>2</SUP> for the 7wt% PAA-doped sample, which was about 6-fold higher than that of the pure sample at 5K and 6.6T. This improvement was mainly attributed to the C substitution and the fine grain size due to PAA doping, suggesting that PAA is an effective dopant in improving J<SUB>c</SUB>(B) performance of MgB<SUB>2</SUB>.

<i>Rhodococcus aerolatus</i> sp. nov., isolated from subarctic rainwater

Hwang, C. Y.,Lee, I.,Cho, Y.,Lee, Y. M.,Baek, K.,Jung, Y.-J.,Yang, Y. Y.,Lee, T.,Rhee, T. S.,Lee, H. K. International Union of Microbiological Societies 2015 International journal of systematic and evolutiona Vol.65 No.2

<P>A Gram-stain-positive, rod-shaped and non-motile strain, designated PAMC 27367<SUP>T</SUP>, was isolated from rainwater collected on the Bering Sea. Analysis of the 16S rRNA gene sequence of the strain showed an affiliation with the genus <I>Rhodococcus</I>. Phylogenetic analyses revealed that strain PAMC 27367<SUP>T</SUP> formed a robust clade with the type strains of <I>Rhodococcus rhodnii</I>, <I>Rhodococcus aetherivorans</I> and <I>Rhodococcus ruber</I> with 16S rRNA gene sequence similarities of 96.3 %, 95.8 % and 95.5 %, respectively. Cells of the strain grew optimally at 25 °C and at pH 6.5–7.0 in the presence of 0–2 % (w/v) sea salts. The major polar lipids were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, phosphatidylinositol, phosphatidylinositol mannoside and three unknown phospholipids. The major cellular fatty acids (>10 %) were iso-C<SUB>16 : 0</SUB>, C<SUB>17 : 1</SUB>ω8<I>c</I> and 10-methyl C<SUB>17 : 0</SUB>. Cell wall analysis showed that strain PAMC 27367<SUP>T</SUP> contained <I>meso</I>-diaminopimelic acid. The genomic DNA G+C content was 77.1 mol%. Based on the phylogenetic, chemotaxonomic and phenotypic data presented here, we propose a novel species with the name <I>Rhodococcus</I> <I>aerolatus</I> sp. nov., with PAMC 27367<SUP>T</SUP> ( = KCTC 29240<SUP>T</SUP> = JCM 19485<SUP>T</SUP>) as the type strain.</P>

A peroxisome proliferator-activated receptor gamma agonist attenuates neurological deficits following spinal cord ischemia in rats

Kim, H.,Hwang, J.,Park, S.,Nahm, S.F.,Min, S.,Lim, C.,Park, K.,Han, S. C.V. Mosby Co 2014 Journal of Vascular Surgery Vol.59 No.4

Objective: Neuroprotective effects of the peroxisome proliferator-activated receptor gamma (PPARγ) agonist in cerebral ischemia have been reported, but the effect of a PPARγ agonist on spinal cord ischemia has not been investigated. The objective of this study was to investigate the effect of a PPARγ agonist on spinal cord ischemia. Pioglitazone, a PPARγ agonist, was administered in a rat model of spinal cord ischemia, and the extent of neurological damage and histological alterations were assessed. Methods: Forty-five rats were randomly enrolled into one of the three groups: (1) pioglitazone group (group PIO): rats were treated with pioglitazone 24 hours before ischemia; (2) control group (group C): rats were treated with the same volume of saline 24 hours before ischemia; and (3) sham group (group sham): rats were treated with the same volume of saline 24 hours before the sham surgery. Spinal cord ischemia was induced using a balloon-tipped catheter placed on the proximal descending aorta. Neurologic function was assessed using the motor deficit index (0 = normal, 6 = complete paralysis) during the 48 hours after reperfusion. Histological and biochemical evaluations were then performed. Results: Compared with group C, group PIO presented with lower motor deficit index 48 hours after reperfusion (5.0 [4.0-6.0] vs 3.0 [2.0-3.0]; group C vs group PIO, respectively; P < .001). Group PIO presented with a higher number of normal motor neurons (10.7 [8.1-11.9] vs 14.7 [14.0-15.3]; group C vs group PIO, respectively; P = .009) and a smaller area of infarcts (48.4% [46.3%-54.0%] vs 16.8% [11.5%-18.3%]; group C vs group PIO, respectively; P = .009) when compared with group C. The degree of inflammatory reactions, assessed by microglia activities, was significantly reduced in group PIO. Oxidative stress level, assessed using malonydialdehyde assay, was significantly reduced in group PIO relative to group C (192.21% [173.5%-206.4%] of sham vs 141.1% [131.7%-152.1%] of sham; group C vs group PIO, respectively; P = .007). The sham group exhibited no abnormality upon neurological or histological examination. Conclusions: PPARγ agonist pioglitazone pretreatment significantly reduces infarct volume and attenuates neurological deficits following spinal cord ischemia. The possible mechanism of neuroprotection by PPARγ agonist may involve modulation of inflammatory reaction and oxidative stress.

Purification and characterization of a novel peptide with inhibitory effects on colitis induced mice by dextran sulfate sodium from enzymatic hydrolysates of Crassostrea gigas

Hwang, J.W.,Lee, S.J.,Kim, Y.S.,Kim, E.K.,Ahn, C.B.,Jeon, Y.J.,Moon, S.H.,Jeon, B.T.,Park, P.J. Academic Press 2012 Fish & Shellfish Immunology Vol.33 No.4

The anti-inflammatory activity of purified peptides from Crassostrea gigas (C. gigas) hydrolysates was studied. To prepare hydrolysates from C. gigas, we used eight different proteinases and the anti-inflammatory activities were determined using a nitric oxide (NO) assay in RAW264.7 cells. Among the hydrolysates, Protamex hydrolysates showed the highest anti-inflammatory activity. We separated and purified the total hydrolysate using an ultrafiltration membrane system and consecutive chromatographic methods. Finally, we obtained a peptide with the following sequence: Gln-Cys-Gln-Cys-Ala-Val-Glu-Gly-Gly-Leu at N-terminal position. The anti-inflammatory peptide purified from C. gigas inhibited NO production by 72.2% compared to the lipopolysaccharide (LPS) treated group. In addition, the Protamex hydrolysates from C. gigas showed decreased serum IgE levels and increased spleen CD4<SUP>+</SUP>/CD8<SUP>+</SUP> levels on dextran sulfate sodium (DSS) induced colitis in mice. These results suggest the peptide and hydrolysate from C. gigas possess potent anti-inflammatory effect.

Development of carbon-doped ex situ MgB₂ wire by mechanical alloying

Hwang, S.M.,Choi, J.H.,Park, E.C.,Lim, J.H.,Joo, J.,Kang, W.N.,Kim, C.J. North-Holland 2009 Physica. C, Superconductivity Vol.469 No.15

Carbon-doped ex situ MgB<SUB>2</SUB> wires were fabricated using a mechanical alloying (MA) method and the effect of the milling time on the phase formation, lattice change, and critical properties was investigated. The precursor powder was prepared with a mixture of MgB<SUB>2</SUB> and 1at% carbon black (CB) powder by mechanical alloying for 0-100h. The MA process effectively decreased the powder size and increased the structural disorder of the powders, while it did not provide the incorporation of C in the MgB<SUB>2</SUB> powders. On the other hand, C doping occurred successfully in the MA-treated wires after sintering. The addition of CB and the MA process improved the J<SUB>c</SUB>(B) and flux pinning force. These improvements are related to the combined effects of the smaller grains, more severe structural disorder, and higher level of CB doping by the MA process.