Hardening of Bi-Te based alloys by dispersing B₄C nanoparticles

Jung, S.J.,Park, S.Y.,Kim, B.K.,Kwon, B.,Kim, S.K.,Park, H.H.,Kim, D.I.,Kim, J.Y.,Hyun, D.B.,Kim, J.S.,Baek, S.H. Elsevier Science 2015 Acta materialia Vol.97 No.-

Thermoelectric devices have attracted a great attention for renewable energy harvesters and solid-state coolers. For practical applications, the mechanical properties of thermoelectric materials become critical for the device reliability, a persistent performance with a long time and high operation cycles. Bi-Te based single-crystals, mostly used in commercial thermoelectric devices, are intrinsically brittle with weak van der Waals bonding, often leading to device failures such as crack and debonding during fabrication and operation. Thus, it is highly desirable to enhance the mechanical property of Bi-Te based alloys as well as the thermoelectric property. Here, we investigate the effect of B<SUB>4</SUB>C nanoparticles (less than 0.5wt%) dispersed in p-type Bi<SUB>0.4</SUB>Sb<SUB>1.6</SUB>Te<SUB>3</SUB> matrix on the mechanical properties. X-ray diffraction (XRD) result confirms that B<SUB>4</SUB>C-dispersed Bi<SUB>0.4</SUB>Sb<SUB>1.6</SUB>Te<SUB>3</SUB> has a single phase. We observe that the grain size of Bi<SUB>0.4</SUB>Sb<SUB>1.6</SUB>Te<SUB>3</SUB> becomes decreased with the B<SUB>4</SUB>C nanoparticle concentration by electron backscatter diffraction (EBSD) technique. Hardness, Young's modulus, and flexural strength of B<SUB>4</SUB>C-dispersed Bi<SUB>0.4</SUB>Sb<SUB>1.6</SUB>Te<SUB>3</SUB> are enhanced, compared to the B<SUB>4</SUB>C-free Bi<SUB>0.4</SUB>Sb<SUB>1.6</SUB>Te<SUB>3</SUB> polycrystals. On the other hand, the thermoelectric figure-of-merit of B<SUB>4</SUB>C-dispersed Bi<SUB>0.4</SUB>Sb<SUB>1.6</SUB>Te<SUB>3</SUB> is almost identical to that of the pure Bi<SUB>0.4</SUB>Sb<SUB>1.6</SUB>Te<SUB>3</SUB>. Such enhancements of the mechanical properties of the B<SUB>4</SUB>C-dispersed Bi<SUB>0.4</SUB>Sb<SUB>1.6</SUB>Te<SUB>3</SUB> are attributed to the grain boundary hardening and second-phase hardening. Beyond thermoelectric materials, our result implies that the grain refinement by nanoparticle dispersion is a simple and promising way to strengthen the mechanical properties of other brittle materials with layered structure.

Study on the HDDR Characteristics of the Nd-Fe(-Co)-B(-Ga-Zr)-type Alloys

S. W. Shon,H. W. Kwon,D. I. Kang,Yoon. B. Kim,W. Y. Jeung 한국자기학회 1999 Journal of Magnetics Vol.4 No.4

The HDDR characteristics of the Nd-Fe-B-type isotropic and anisotropic HDDR alloys were investigated using three types of alloys: alloy A (Nd_(12.6)Fe_(81.4)B_6), alloy B (Nd_(l2.6)Fe_(81.3)B_6Zr_(0.l)), and alloy C (Nd_(12.6)Fe_(68.8)CO_(11.5)B_6Ga_(1.0)Zr_(0.1)). The alloy A is featured with the isotropic HDDR character, while alloy Band C are featured with the anisotropic HDDR character. Hydrogenation and disproportionation characteristics of the alloys were examined using DTA under hydrogen gas. Recombination characteristics of the alloys were examined by observing the coercivity variation as a function of recombination time. The present study revealed that the alloy C exhibits slightly higher hydrogenation and disproportionation temperatures compared to the alloy A and B. Recombination of the anisotropic alloy Band C takes place more rapidly with respect to the isotropic alloy A. The intrinsic coercivities of the recombined materials rapidly increased with increasing the recombination time and then showed a peak, after which the coercivities decreased gradually. The degraded coercivity was, however, recovered significantly on prolonged recombination treatment. Compared with the isotropic HDDR alloy A the anisotropic HDDR alloy B and C are notable for their greater recovery of coercivity. The significant recovery of coercivity was accounted for in terms of the development of well-defined smooth grain boundary between the recombined grains on prolonged recombination.

B-containing nanomaterial synthesis when a combustion wave moves within a packed bed of solid particles

Nersisyan, H.,Lee, T.H.,Yoo, B.U.,Kwon, S.C.,Suh, H.,Kim, J.G.,Lee, J.H. Elsevier [etc.] 2016 Combustion and Flame Vol.172 No.-

This study deals with combustion behavior of B<SUB>2</SUB>O<SUB>3</SUB>/Mg/NH<SUB>4</SUB>Cl/C complex systems for the synthesis of amorphous boron (B), boron carbide (B<SUB>4</SUB>C), and boron nitride (BN) nanostructures. The raw mixtures used in the experiments were prepared on the base of a B<SUB>2</SUB>O<SUB>3</SUB>-Mg precursor mixture, which is sufficiently exothermic to maintain a self-propagating regime of the combustion reaction. Thermodynamic analysis of the combustion temperatures and experimental validation indicate that the 1000-1500<SUP>o</SUP>C temperature range is very effective for synthesizing the nanostructures of B, B<SUB>4</SUB>C, and BN. It was found that B-containing functional nanostructures are mainly spherical nanoparticles (B) or nanosheets (B<SUB>4</SUB>C, BN). The phase composition and microstructural characteristics of the final products were evaluated based on the combustion temperature and solid/liquid phase changes.

Selective novel inverse agonists for human GPR43 augment GLP-1 secretion

Park, B.O.,Kim, S.H.,Kong, G.Y.,Kim, D.H.,Kwon, M.S.,Lee, S.U.,Kim, M.O.,Cho, S.,Lee, S.,Lee, H.J.,Han, S.B.,Kwak, Y.S.,Lee, S.B.,Kim, S. North-Holland ; Elsevier Science Ltd 2016 european journal of pharmacology Vol.771 No.-

<P>GPR43/Free Fatty Acid Receptor 2 (FFAR2) is known to be activated by short-chain fatty acids and be coupled to G(i), and G(q), family of heterotrimeric G proteins. GPR43 is mainly expressed in neutrophils, adipocytes and enteroendocrine cells, implicated to be involved in inflammation, obesity and type 2 diabetes. However, several groups have reported the contradictory data about the physiological functions of GPR43, so that its roles in vivo remain unclear. Here, we demonstrate that a novel compound of pyrimidinecarboxamide class named as BTI-A-404 is a selective and potent competitive inverse agonist of human GPR43, but not the murine ortholog. Through structure-activity relationship (SAR), we also found active compound named as BTI-A-292. These regulators increased the cyclic AMP level and reduced acetate-induced cytoplasmic Ca2+ level. Furthermore, we show that they modulated the downstream signaling pathways of GPR43, such as ERK, p38 MAPK, and NF-kappa B. It was surprising that two compounds augmented the secretion of glucagon-like peptide 1 (GLP-1) in NCI-H716 cell line. Collectively, these novel and specific competitive inhibitors regulate all aspects of GPR43 signaling and the results underscore the therapeutic potential of them. (C) 2015 Elsevier B.V. All rights reserved.</P>

20대 성인의 페이스북 이용행태에 따른 사회비교 경향성, 우울,자아존중감

김지원,남궁빈,안해정,권햇살,한예슬,허진성,김고은,김수진,김미혜,이수인 이화여자대학교 간호과학대학 2015 이화간호학회지 Vol.- No.49

Purpose: The purpose of this study was to explore the differences among social comparison orientation, depression, and self-esteem by patterns of using Facebook among Facebook users’ in their 20s. Methods: The participants in this descriptive study were 332 Facebook users in their 20s. Data collection took place between August 21 and 27, 2014. Questionnaires were the Iowa–Netherlands Comparison Orientation Measure (revised), Center for Epidemiologic Studies Depression Scale, and Rosenberg Self-Esteem Scale. Data were statistically analyzed using t-tests and ANOVAs. Result: Each mean score of social comparison, depression, and self-esteem was 26.04±6.82, 31.39±8.99 and 38.05±6.19. Significant differences emerged between the degree of social comparison and the following Facebook usage variables: average single-connection time to Facebook (F=3.570, p=.007) and self-evaluation of Facebook usage behavior (F=6.203, p<.001). Conclusion: The results of this study suggested that Facebook users in their 20s who access Facebook for long periods and assess themselves as using it more often had a high score of comparison orientation. This result can be used in Nursing by developing the theoretical basis for education and campaign related to Facebook usage. In-depth studies are needed for research on the effect social comparison has on Facebook users and relationships between social comparison and emotions.

Achaete-scute complex homologue 2 accelerates the development of Sjogren's syndrome-like disease in the NOD/ShiLtJ mouse

Kim, S.M.,Kwon, J.E.,Park, J.S.,Seo, H.B.,Jung, K.A.,Moon, Y.M.,Lee, J.,Kwok, S.K.,Cho, M.L.,Park, S.H. Elsevier/North-Holland Biomedical Press 2017 Immunology letters Vol.190 No.-

Achaete-scute complex homologue 2 (Ascl2) has been reported to induce the differentiation and activation of follicular helper T (T<SUB>FH</SUB>) cells, which are essential for development of Sjogren's syndrome (SS). This study examined whether Ascl2 plays a role in the development of SS. NOD/ShiLtJ mice were injected with an Ascl2-overexpression vector, and the infiltration of lymphocytes into salivary and lacrimal glands was assessed. The expression of inflammatory cytokines and chemoattractants for T or B cells was measured. The activation of T<SUB>FH</SUB> cells was assessed using a specific marker of T<SUB>FH</SUB> cells. Ascl2 level was also measured in SS patients. Overexpression of Ascl2 increased the expression of C-X-C chemokine receptor type 5 (CXCR5) in both salivary and lacrimal glands (p<0.0001). Overexpression of Ascl2 also increased the expression of proinflammatory cytokines and chemoattractants including interleukin 6 (IL-6), tumor necrosis factor-α, IL-8, programmed cell death 1 (PD-1), IL-21, and B-cell lymphoma 6 (Bcl-6). Overexpression of Ascl2 increased the populations of CD4<SUP>+</SUP>CXCR5<SUP>+</SUP>, CD4<SUP>+</SUP>ICOS<SUP>+</SUP>, and CD4<SUP>+</SUP>PD-1<SUP>+</SUP> cells. The Ascl2 level was higher in peripheral blood mononuclear cells from SS patients compared with those from healthy controls. Our findings suggest that Ascl2 may play a role in the development and progression of SS and may be a therapeutic target in the treatment of SS.

Control of electrical properties and gate bias stress stability in solution-processed a-IZO TFTs by Zr doping

Choi, W.S.,Jo, H.,Kwon, M.S.,Jung, B.J. Elsevier 2014 CURRENT APPLIED PHYSICS Vol.14 No.12

Zr-doped indium zinc oxide (IZO) thin film transistors (TFTs) are fabricated via a solution process with different Zr doping ratios. The addition of Zr suppressed the carrier concentration in the IZO films, which was confirmed by Hall Effect measurements. As the amount of Zr was increased in the oxide active layer of TFTs, the subthreshold swing (S.S) reduced, the ON/OFF ratio improved, and the threshold voltage (V<SUB>th</SUB>) shifted positively. Moreover, the starting points of the ON state for TFTs near the point zero gate voltage could be controlled by the addition of Zr. The 0.3% Zr-doped IZO TFT exhibited a high saturation mobility of 7.0 cm<SUP>2</SUP> V<SUP>-1</SUP> s<SUP>-1</SUP>, ON/OFF ratio of 2.6 x 10<SUP>6</SUP> and S.S of 0.57 V/decade compared the IZO TFT with 10.1 cm<SUP>2</SUP> V<SUP>-1</SUP> s<SUP>-1</SUP>, 1.7 x 10<SUP>6</SUP> and 0.75 V/decade. The Zr effect of the gate bias stability was examined. Zr-doped IZO TFTs were relatively unstable under a positive bias stress (PBS), whereas they showed good stability at a negative bias stress (NBS). The gate bias stability of the oxide TFTs were compared with the extracted parameters through a stretched-exponential equation. The characteristic trapping time under NBS of 0.3% Zr-doped IZO TFTs was improved from 8.3 x 10<SUP>4</SUP> s for the IZO TFT to 3.1 x 10<SUP>5</SUP> s.

Early Regulation of Viral Infection Reduces Inflammation and Rescues Mx-positive Mice from Lethal avian Influenza Infection

Song, M.S.,Cho, Y.H.,Park, S.J.,Pascua, P.N.Q.,Baek, Y.H.,Kwon, H.I.,Lee, O.J.,Kong, B.W.,Kim, H.,Shin, E.C.,Kim, C.J.,Choi, Y.K. American Association of Pathologists and Bacteriol 2013 The American journal of pathology Vol.182 No.4

Differing sensitivity of influenza A viruses to antiviral effects of the Myxovirus resistance (Mx) protein implies varying global gene expression profiles in the host. The role of Mx protein during lethal avian influenza (AI) virus infection was examined using Mx1-deficient C57BL/6 (B6-Mx1<SUP>-/-</SUP>) and congenic Mx1-expressing (B6-Mx1<SUP>+/+</SUP>) mice infected with a virulent, mouse-adapted avian H5N2 Ab/Korea/ma81/07 (Av/ma81) virus. After infection, B6-Mx1<SUP>+/+</SUP> mice were completely protected from lethal AI-induced mortality, and exhibited attenuated clinical disease and reduced viral titers and pathology in the lungs, compared with B6-Mx1<SUP>-/-</SUP> mice. Transcriptional profiling of lung tissues revealed that most of the genes up-regulated after infection are involved in activation of the immune response and host defense. Notably, more abundant and sustained expression of cytokine/chemokine genes was observed up to 3 dpi in B6-Mx1<SUP>-/-</SUP> mice, and this was associated with excessive induction of cytokines and chemokines. Consequently, massive infiltration of macrophages/monocytes and granulocytes into lung resulted in severe viral pneumonia and potentially contributed to decreased survival of B6-Mx1<SUP>-/-</SUP> mice. Taken together, our data show that dysregulated gene transcriptional activity corresponded to persistent induction of cytokine/chemokines and recruitment of cytokine-producing cells that promote inflammation in B6-Mx1<SUP>-/-</SUP> mouse lungs. Thus, we provide additional evidence of the interplay of genetic, molecular, and cellular correlates governed by the Mx1 protein that critically determine disease outcome during lethal AI virus infection.

CK2α/CSNK2A1 Phosphorylates SIRT6 and Is Involved in the Progression of Breast Carcinoma and Predicts Shorter Survival of Diagnosed Patients

Bae, J.S.,Park, S.H.,Jamiyandorj, U.,Kim, K.M.,Noh, S.J.,Kim, J.R.,Park, H.J.,Kwon, K.S.,Jung, S.H.,Park, H.S.,Park, B.H.,Lee, H.,Moon, W.S.,Sylvester, K.G.,Jang, K.Y. American Association of Pathologists and Bacteriol 2016 The American journal of pathology Vol.186 No.12

<P>Recently, the roles of sirtuins (SIRTs) in tumorigenesis have been of interest to oncologists, and protein kinase CK2 alpha 1 (CSNK2A1) has been shown to be involved in tumorigenesis by phosphorylating various proteins, including SIRT1. Therefore, we evaluated the roles of CSNK2A1, SIRT6, and phosphorylated SIRT6 and their relationships in breast carcinoma. Nuclear expression of CSNK2A1 and SIRT6 predicted shorter overall survival and relapse-free survival by multivariate analysis. Inhibition of CSNK2A1 decreased the proliferative and invasive activity of cancer cells. In addition, CSNK2A1 was bound to SIRT6 and phosphorylated SIRT6; evidence for this is provided from immunofluorescence staining, co-immunoprecipitation of CSNK2A1 and SIRT6, a glutathione S-transferase pull-down assay, an in vitro kinase assay, and transfection of mutant CSNK2A1. Knockdown of SIRT6 decreased the proliferation and invasiveness of cancer cells. Overexpression of SIRT6 increased proliferation, but mutation at the Ser338 phosphorylation site of SIRT6 inhibited the proliferation of MCF7 cells. Moreover, both knockdown of SIRT6 and a mutation at the phosphorylation site of SIRT6 decreased expression of matrix metallopeptidase 9, beta-catenin, cyclin D1, and NF-kappa B. Especially, SIRT6 expression was associated with the nuclear localization of B-catenin. This study demonstrates that CSNK2A1 and SIRT6 are indicators of poor prognosis for breast carcinomas and that CSNK2A1-mediated phosphorylation of SIRT6 might be involved in the progression of breast carcinoma.</P>

Caspase-3 activation as a key factor for HBx-transformed cell death

Kim, A.,Kwon, O. S.,Kim, S. O.,He, L.,Bae, E. Y.,Lee, M. S.,Jeong, S. J.,Shim, J. H.,Yoon, D. Y.,Kim, C. H.,Moon, A.,Kim, K. E.,Ahn, J. S.,Kim, B. Y. Blackwell Publishing Ltd 2008 Cell proliferation Vol.41 No.5

<P>Abstract. </P><P><I>Objectives</I>: Nuclear factor-kappa B (NF-&kgr;B) activation has been associated with the tumorigenic growth of hepatitis B virus X protein (HBx)-transformed cells. This study was aimed to find a key target for treatment of HBx-mediated cancers. <I>Materials and methods</I>: NF-&kgr;B activation, endoplasmic reticulum-stress (ER-stress), caspase-3 activation, and cell proliferation were evaluated after Chang/HBx cells permanently expressing HBx viral protein were treated with inhibitors of NF-&kgr;B, proteasome and DNA topoisomerase. <I>Results</I>: Inhibition of NF-&kgr;B transcriptional activity by transient transfection with mutant plasmids encoding Akt1 and glycogen synthase kinase-3&bgr; (GSK-3&bgr;), or by treatment with chemical inhibitors, wortmannin and LY294002, showed little effect on the survival of Chang/HBx cells. Furthermore, I&kgr;Bα (S32/36A) mutant plasmid or other NF-&kgr;B inhibitors, 1-pyrrolidinecarbonidithioic acid and sulphasalazine, were also shown to have little effect on the cell proliferation. By contrast, proteasome inhibitor-1 (Pro1) and MG132 enhanced the HBx-induced ER-stress response and the subsequent activation of caspase-12, -9 and -3 and reduced cell proliferation. Camptothecin (CPT), however, triggered activation of caspase-3 without induction of caspase-12, and reduced cell proliferation. In addition, CPT-induced cell death was reversed by pre-treatment with z-DEVD, a caspase-3-specific inhibitor. <I>Conclusions</I>: Detailed exploitation of the regulators of caspase-3 activation could open the gate for finding an efficient target for development of anticancer therapeutics against HBx-transformed hepatocellular carcinoma.</P>