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      • KCI등재

        1H NMR Measurements of the Phase Transition of (NH₄)₃H(SO₄)₂ Single Crystals

        S. H. Choi,Moohee Lee,Ae Ran Lim,K. S. Han,S. K. Kwon,S. K. Nam 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.52 No.2

        $^1$H nuclear magnetic resonance (NMR) experiments have been performed in the temperature range of 30 -- 300 K at 7 T to investigate the phase-dependent nature of the dynamic network of hydrogen bonds in a ((NH₄)₃H(SO₄)₂ single crystal. The crystal has six phases, which are ferroelectric, antiferroelectric, incommensurate, antiferroelectric, ferroelastic, and superionic with the respective transition temperatures of 63, 133, 139, 256 and 413 K. The spin-lattice relaxation time, T₁, of ¹H NMR is similar for the ammonium protons and the hydrogen-bond protons over the entire range of experimental temperatures. The T₁, of ¹H NMR gradually decreases down to 120 K and starts to steeply increase below 100 K. Then, the T₁ shows an abrupt decrease below 68 K with a sharp minimum at 63 K, where the ferroelectric transition occurs. The ¹H NMR spectrum shifts to the high-frequency side at temperatures below 63 K due to the ferroelectric phase transition. This behavior of the T₁ and the spectrum confirms a dramatic change in the dynamics of hydrogen bonds associated with the ferroelectric phase transition at 63 K. $^1$H nuclear magnetic resonance (NMR) experiments have been performed in the temperature range of 30 -- 300 K at 7 T to investigate the phase-dependent nature of the dynamic network of hydrogen bonds in a ((NH₄)₃H(SO₄)₂ single crystal. The crystal has six phases, which are ferroelectric, antiferroelectric, incommensurate, antiferroelectric, ferroelastic, and superionic with the respective transition temperatures of 63, 133, 139, 256 and 413 K. The spin-lattice relaxation time, T₁, of ¹H NMR is similar for the ammonium protons and the hydrogen-bond protons over the entire range of experimental temperatures. The T₁, of ¹H NMR gradually decreases down to 120 K and starts to steeply increase below 100 K. Then, the T₁ shows an abrupt decrease below 68 K with a sharp minimum at 63 K, where the ferroelectric transition occurs. The ¹H NMR spectrum shifts to the high-frequency side at temperatures below 63 K due to the ferroelectric phase transition. This behavior of the T₁ and the spectrum confirms a dramatic change in the dynamics of hydrogen bonds associated with the ferroelectric phase transition at 63 K.

      • SCISCIESCOPUS

        Reactivities of organic isothiocyanates and thiocyanates toward dialkyl bis(phosphine) complexes of palladium(II) and platinum(II)

        Lee, S.G.,Choi, K.Y.,Kim, Y.J.,Park, S.,Lee, S.W. Pergamon Press 2015 Polyhedron Vol.85 No.-

        Room-temperature reactions of trans-[PdEt<SUB>2</SUB>L<SUB>2</SUB>] (L=PMe<SUB>3</SUB>, PEt<SUB>3</SUB>, PMe<SUB>2</SUB>Ph) with organic isothiocyanates [R-NCS; R=benzyl; CH(CH<SUB>3</SUB>)Ph, R-(-) and S-(+); indanyl, S-(+)] afforded the S,S-coordinated Pd(II) complexes [Pd(S<SUB>2</SUB>C?N-R)L<SUB>2</SUB>] containing a dithiocarbonimidato (S<SUB>2</SUB>C?N-R) group. Similar reactions involving allyl isothiocyanates produced the cationic η<SUP>3</SUP>-allyl Pd complex [Pd(η<SUP>3</SUP>-allyl)(PMe<SUB>3</SUB>)<SUB>2</SUB>]<SUP>+</SUP>(NCS)<SUP>-</SUP>. When [Pd(S<SUB>2</SUB>C?N-R)(PMe<SUB>3</SUB>)<SUB>2</SUB>] was treated with 1equiv of a chelating phosphine [L-L=depe (1,2-bis(diethylphosphino)ethane) and dmpe (1,2-bis(dimethylphosphino)ethane)], the corresponding complexes [Pd(S<SUB>2</SUB>C?N-R)(L-L)] were produced. Reactions of trans-[PdEt<SUB>2</SUB>L<SUB>2</SUB>] (L=PMe<SUB>3</SUB>, PMe<SUB>2</SUB>Ph) with organic thiocyanates (R-SCN; R=benzyl, Et) resulted in the formation of [Pd(CN)<SUB>2</SUB>L<SUB>2</SUB>] and an organic disulfide by S-C bond cleavage of R-SCN. However, similar reactions of the dimethyl analogs, trans-[PdMe<SUB>2</SUB>L<SUB>2</SUB>] (L=PMe<SUB>3</SUB>, PEt<SUB>3</SUB>), with benzyl thiocyanate afforded different products, [Pd(NCS)<SUB>2</SUB>L<SUB>2</SUB>] or [PdMe(NCS)L<SUB>2</SUB>]. Treating [Pt(styrene)(PMe<SUB>3</SUB>)<SUB>2</SUB>] with benzyl isothiocyanate gave the S-coordinated dithiocarbonimidato Pt(II) complex, [Pt(S<SUB>2</SUB>C?N-R)(Me<SUB>3</SUB>P)<SUB>2</SUB>] (R=benzyl). In contrast, cis-[PtEt<SUB>2</SUB>(PMe<SUB>3</SUB>)<SUB>2</SUB>] reacted with the isothiocyanate to afford the trialkyl Pt(IV) complex [PtEt<SUB>2</SUB>(SCN)(CH<SUB>2</SUB>Ph)(PMe<SUB>3</SUB>)<SUB>2</SUB>].

      • Diagnostic usefulness of a T cell-based assay for latent tuberculosis infection in kidney transplant candidates before transplantation

        Kim, S.-H.,Lee, S.-O.,Park, I.-A.,Park, S.J.,Choi, S.-H.,Kim, Y.S.,Woo, J.H.,Park, S.-K.,Park, J.S.,Kim, S.C.,Han, D.J. Blackwell Publishing Inc 2010 Transplant infectious disease Vol.12 No.2

        <P>S.-H. Kim, S.-O. Lee, I.-A. Park, S.J. Park, S.-H. Choi, Y.S. Kim, J.H. Woo, S.-K. Park, J.S. Park, S.C. Kim, D.J. Han. Diagnostic usefulness of a T cell-based assay for latent tuberculosis infection in kidney transplant candidates before transplantation.Transpl Infect Dis 2010: <B>12:</B> 113–119. All rights reserved</P><P>Background</P><P>The presence of latent tuberculosis (TB) infection (LTBI) should be evaluated before kidney transplantation. Although a new T cell-based assay for diagnosing LTBI gave promising results, this assay has not yet been compared with the tuberculin skin test (TST) for diagnosing LTBI in renal transplant candidates before transplantation.</P><P>Patients and methods</P><P>All adult patients admitted to a single institute for renal transplantation over a 1-year period were prospectively enrolled. A clinically predictive risk of LTBI was defined as: (i) recent close contact with a person with pulmonary TB; (ii) abnormal chest radiography; (iii) a history of untreated or inadequately treated TB; or (iv) a new infection (i.e., a recent conversion of TST).</P><P>Results</P><P>Of 209 renal recipients, 47 (22%) had a positive TST≥5 mm, 21 (10%) had a positive TST≥10 mm, 65 (30%) had a positive T-SPOT.<I>TB</I> test, and 25 (12%) had an indeterminate T-SPOT.<I>TB</I> test. The induration size of TST was significantly associated with a high positivity rate on T-SPOT.<I>TB</I> (<I>P</I><0.001). Agreement between T-SPOT.<I>TB</I> test and TST≥10 mm was fair (<I>k</I>=0.24, 95% confidence interval 0.11–0.36). However, neither univariate nor multivariate analysis showed any association between the clinical risk for LTBI and positivity on T-SPOT.<I>TB</I> or TST.</P><P>Conclusion</P><P>T-SPOT.<I>TB</I> test was more frequently positive than TST in renal transplant candidates. However, further longitudinal studies are awaited to determine whether the ability of T-SPOT.<I>TB</I> assay to detect LTBI in renal transplant recipients can better predict the development of TB than can TST after transplantation.</P>

      • SCISCIESCOPUS

        The prolyl isomerase Pin1 interacts with a ribosomal protein S6 kinase to enhance insulin-induced AP-1 activity and cellular transformation

        Lee, N. Y.,Choi, H.-K.,Shim, J.-H.,Kang, K.-W.,Dong, Z.,Choi, H. S. Oxford University Press 2009 Carcinogenesis Vol.30 No.4

        <P>Phosphorylation of proteins on serine or threonine residues that immediately precede proline (pSer/Thr-Pro) is specifically catalyzed by the peptidyl-prolyl cis-trans isomerase Pin1 and is a central signaling mechanism in cell proliferation and transformation. Although Pin1 is frequently overexpressed in hepatocellular carcinoma (HCC), the molecular mechanism of Pin1 in HCC has not been completely elucidated. Here, we show that Pin1 interacts with p70S6K in vitro and ex vivo. Overexpression of Pin1 resulted in enhanced p70S6K phosphorylation induced by insulin in SK-HEP-1 cells. In contrast, Pin1(-/-) mouse embryonic fibroblasts (MEFs) exhibited significantly decreased insulin-induced p70S6K phosphorylation compared with Pin1(+/+) MEFs. Furthermore, Pin1 enhanced the insulin-induced extracellular signal-regulated protein kinase (ERK)1/2 phosphorylation through its interaction with p70S6K, whereas the inhibition of p70S6K activity by rapamycin suppressed insulin-induced ERK1/2 phosphorylation in SK-HEP-1 cells. Hence, Pin1 affected activator protein-1 activity through p70S6K-ERK1/2 signaling in SK-HEP-1 cells. Most importantly, Pin1-overexpressing JB6 Cl41 cells enhanced neoplastic cell transformation promoted by insulin much more than green fluorescent protein-overexpressing JB6 Cl41 control cells. These results imply that Pin1 amplifies insulin signaling in hepatocarcinoma cells through its interaction with p70S6K, suggesting that Pin1 plays an important role in insulin-induced tumorigenesis and is a potential therapeutic target in hepatocarcinoma.</P>

      • KCI등재후보

        1H Nuclear Magnetic Resonance study of Ferroelectric (NH4)3H(SO4)2

        S. H. Choi,K. S. Han,S. K. Kwon,S. K. Nam,H. H. Choi,Moohee Lee,Ae Ran Lim 한국자기공명학회 2007 Journal of the Korean Magnetic Resonance Society Vol.11 No.2

        1H nuclear magnetic resonance (NMR) experiments have been performed at 30 - 300 K and 7 T to investigate dynamics of hydrogen bond network in the single crystal (NH4)3H(SO4)2. The two proton sites, ammonium proton and hydrogen-bond proton, are identified from the 1H NMR MAS spectrum at 340 K. As temperature decreases, the 1H NMR spectrum shifts to the higher frequency side with a larger linewidth. The spectrum at 65 K shows a distinctive change in line shape toward the ferroelectric transition at 63 K. The measured values of T1 for ammonium and hydrogen-bond protons are similar in the whole range of temperature. T1 of 1H NMR shows a gradual decrease down to 120 K and starts to steeply increase below 100 K. Then T1 shows abrupt decrease below 70 K with a sharp minimum at 63 K, where the ferroelectric transition occurs. This temperature dependence of spectrum and T1 clearly prove that the large change in the dynamics of hydrogen bond network is associated with the ferroelectric phase transition at 63 K.

      • K<sub>2</sub>WO<sub>4</sub> flux 에 의한 K<sub>2</sub>Oㆍ6TiO<sub>2</sub> whisker 의 합성

        이진식 ( J. S. Lee ),이상문 ( S. M. Lee ),이철태 ( C. T. Lee ),권긍택 ( K. T. Kohn ),김영명 ( Y. M. Kim ) 한국공업화학회 1993 한국공업화학회 연구논문 초록집 Vol.1993 No.0

        K<sub>2</sub>Oㆍ6TiO<sub>2</sub> whisker는 구조적인 특성 때문에 물리ㆍ화학적으로 매우 안정하며 보강재, 마찰재, 단열재 등의 많은 용도를 갖게된다. 특히 최근에는 석면이 발암물질로 인한 자동차 브레이크 마찰재료의 사용이 금지됨에 따라 K<sub>2</sub>Oㆍ6TiO<sub>2</sub> whisker는 이의 대체 섬유로서 주목을 받고 있다. 이러한 K<sub>2</sub>Oㆍ6TiO<sub>2</sub> whisker의 합성방법으로는 TiO<sub>2</sub>와 K<sub>2</sub>CO<sub>3</sub>의 화학양론적 조성의 혼합들을 설정온도에서 소성(calcination method)시키는 방법을 비롯하여 응용법(melting method), 수열법(hydrothermal method), 융제법(flux) 및 KDC법(kneading-drying-calcination method) 등의 방법이 있다. 그러나 수열법의 경우 양질의 whisker를 얻을 수 있으나 고압합성 이므로 위험하고 가격이 비싼 결점이 있으며 공업상 제조에 필요한 조건이 복잡하고 연속조작이 어려워 비현실적인 방법이다. 또한 서냉소성법의 경우 공정이 단순하며 공업화가 쉬우나 비교적 장섬유가 얻어지게 된다. 따라서 본 연구에서는 융제법을 이용하여 K<sub>2</sub>Oㆍ6TiO<sub>2</sub> whisker를 합성하였으며. 과거에 용제로 사용된 KC1-KF계. K<sub>2</sub>O-Na<sub>2</sub>O-B<sub>2</sub>O<sub>3</sub>계 등의 높은 volatility와 viscosity 그리고 낮은 solubility에 대한 문제점을 개선하기 위해 K<sub>2</sub>WO<sub>4</sub>를 flux로 선정하여 K<sub>2</sub>Oㆍ6TiO<sub>2</sub> whisker를 합성하였다.

      • 화학적 거세 및 갑상선 기능조절이 닭의 산육성 증진에 미치는 효과에 관한 연구

        이규승,김관영,권순기 忠南大學校 1971 論文集 Vol.10 No.-

        This experiment was conducted to improve the meat production and quality of cockerels by controling the function of thyroid and gonad with the hormone preparations. Three weeks old 180 Rhode island red cockerels were divided into six group : iodocasein treatment group, tapazol treatment group, D.E.S. treatment group, D.E.S.+iodocasein treatment group, D.E.S.+tapazol treatment group and control group. Each group was then divided into two groups of 4 weeks and 8 weeks after treatment, arranging the cockerels 15 each. Iodocasein of 0.25 per cent of the basal ration and tapazol in dose of 0.3 ㎎ per Kg of body weight were administered with the basal ration, and 0.75 ㎎ of D.E.S. was implanted subcutaneously at the head. Body weight was measured weekly to investigate the growth rate and daily gain. Sacrifice was done at the certain days after treatment, and carcass percentage and organ weight were observed. Histological observation on thyroid and gonad was conducted at the same time. The results obtained areas follows; 1. The body weight of D. E. S. group, Tap. group and D. E. S. +Tap. group at the end of experimental period were 1452.37±17.61g and 1473.53±16.18g respectively, showing the increasing significance with P<0.05 as compared with 1305.93±21.67g of control group. Iodo. group and D.E.S.+Iodo. group were lighter than control group, but no significance was recognized. 2. Daily gain and carcass percentage were changed as a similar tendency, showing the significance with P<0.05 after 4 weeks and no significance after 8 weeks. Generally high value was obtained in the group treated with D.E.S. and tapazol. 3. Among the meat compositions any marked difference was not recognized in moisture and crude ash cntents of the experimental groups. Crude protein contents were comparatively more in control group (19.87%) than in treatment groups. As compared with 3.39% of control group, crude fat contents of Tap. grop, D. E. S. group anud D. E. S. +Tap. group were 4.44%, 4.22% and 5.35% respectively. 4. Improved effects on feed convertion rate were obtained in the groups treated with D.E.S. and tapazol. D.E.S.+Tap. group was best : 2.61 on the mean. 5. Comb and wattle weights were changed as a similar tendency, showing the significance with p<0.01 after 4 and 8 weeks. Those of all treatment groups were lighter than of control group, particularly in the groups treated with D.E.S. they were atrophied extremely. 6. Generally weights of head, heart, spleen, gizzard and liver were in proportion to body weight. 7. Whole viscera weight showed the significance with p<0.01 among the treatment groups after 4 and 8 weeks. Those of the groups treated with tapazol and D.E.S. were heavier than of control group. 8. Cloacal thymus weight showed the significance with p<0.05. That of control group was heaviest, being heavier after 4 weeks than after 8 weeks. Meat production and quality cockerels was improved successively by decreasing more or less the function of thyroid and gonad with tapazol and D.E.S. treatment. Only use of tapazol or D.E.S. was fairly effective. Because the iodocasein administration caused the growth restraint and derease of fats, it was worthless for practical application.

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