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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.
[ $^1H$ ] Nuclear Magnetic Resonance Study of Ferroelectric $(NH_4)_3H(SO_4)_2$
Choi, S.H.,Han, K.S.,Kwon, S.K.,Nam, S.K.,Choi, H.H.,Lee, Moo-Hee,Lim, Ae-Ran Korean Magnetic Resonance Society 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 $(NH_4)_3H(SO_4)_2$. 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 $T_1$ for ammonium and hydrogen-bond protons are similar in the whole range of temperature. $T_1$ of $^1H$ NMR shows a gradual decrease down to 120 K and starts to steeply increase below 100 K. Then $T_1$ shows abrupt decrease below 70 K with a sharp minimum at 63 K, where the ferroelectric transition occurs. This temperature dependence of spectrum and $T_1$ clearly prove that the large change in the dynamics of hydrogen bond network is associated with the ferroelectric phase transition at 63 K.
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.
Kim, Y.I.,Park, S.J.,Kwon, H.I.,Kim, E.H.,Si, Y.J.,Jeong, J.H.,Lee, I.W.,Nguyen, H.D.,Kwon, J.J.,Choi, W.S.,Song, M.S.,Kim, C.J.,Choi, Y.K. Elsevier Science 2017 INFECTION GENETICS AND EVOLUTION Vol.53 No.-
<P>During the outbreaks of highly pathogenic avian influenza (HPAI) H5N6 viruses in 2016 in South Korea, novel H5N8 viruses were also isolated from migratory birds. Phylogenetic analysis revealed that the HA gene of these H5N8 viruses belonged to clade 2.3.4.4, similarly to recent H5Nx viruses, and originated from A/Brk/Korea/Gochang1/14(H5N8), a minor lineage of H5N8 that appeared in 2014 and then disappeared. At least four reassortment events occurred with different subtypes (H5N8, H7N7, H3N8 and H10N7) and a chicken challenge study revealed that they were classified as HPAI viruses according to OIE criteria. (C) 2017 Elsevier B.V. All rights reserved.</P>
Lee, J.H.,Pascua, P.N.Q.,Decano, A.G.,Kim, S.M.,Park, S.J.,Kwon, H.I.,Kim, E.H.,Kim, Y.I.,Kim, H.,Kim, S.Y.,Song, M.S.,Jang, H.K.,Park, B.K.,Choi, Y.K. Elsevier Science 2015 INFECTION GENETICS AND EVOLUTION Vol.34 No.-
In 2011-2012, contemporary North American-like H3N2 swine influenza viruses (SIVs) possessing the 2009 pandemic H1N1 matrix gene (H3N2pM-like virus) were detected in domestic pigs of South Korea where H1N2 SIV strains are endemic. More recently, we isolated novel reassortant H1N2 SIVs bearing the Eurasian avian-like swine H1-like hemagglutinin and Korean swine H1N2-like neuraminidase in the internal gene backbone of the H3N2pM-like virus. In the present study, we clearly provide evidence on the genetic origins of the novel H1N2 SIVs virus through genetic and phylogenetic analyses. In vitro studies demonstrated that, in comparison with a pre-existing 2012 Korean H1N2 SIV [A/swine/Korea/CY03-1½012 (CY03-1½012)], the 2013 novel reassortant H1N2 isolate [A/swine/Korea/CY0423/2013 (CY0423-12/2013)] replicated more efficiently in differentiated primary human bronchial epithelial cells. The CY0423-12/2013 virus induced higher viral titers than the CY03-1½012 virus in the lungs and nasal turbinates of infected mice and nasal wash samples of ferrets. Moreover, the 2013 H1N2 reassortant, but not the intact 2012 H1N2 virus, was transmissible to naive contact ferrets via respiratory-droplets. Noting that the viral precursors have the ability to infect humans, our findings highlight the potential threat of a novel reassortant H1N2 SIV to public health and underscore the need to further strengthen influenza surveillance strategies worldwide, including swine populations.
최병희(B. H. Choi),조예찬(Y. C. Jo),박정현(J. H. Park),최성운(S. W. Choi),조상훈(S. H. Cho),김바다(B. D. Kim),박기협(K. H. Park),김주호(J. H. Kim),이대엽(D. Lee) 유공압건설기계학회 2023 유공압건설기계학회 학술대회논문집 Vol.2023 No.5
In many equipment, including construction machinery that operates with hydraulic oil, it is very important to solve the problem of the generation of fine particles in the hydraulic circuit and the inability to use the equipment due to causes such as damage of parts and repair. In this study, as a base study to solve these problems, a study that can detect the color change of hydraulic oil due to particles mixed in hydraulic oil in real time using machine learning was conducted. Using the k-NN classification algorithm, the color change of hydraulic oil is classified into ten classes so that the color can be recognized in real time. It is planned to carry out the development of the sensor system in the following study.
대장 선종과 암의 동시성 병변에서 K-ras 유전자의 돌연변이 및 k-Ras, p16, Cyclin D1과 p53 단백질의 발현
오용열 ( Y. L. Oh ),전훈재 ( H. J. Chun ),박동규 ( D. K. Park ),박재홍 ( J. H. Park ),박철희 ( C. H. Park ),진윤태 ( Y. T. Jeen ),이홍식 ( H. S. Lee ),이상우 ( S. W. Lee ),엄순호 ( S. H. Um ),최재현 ( J. H. Choi ),김창덕 ( C. D. Kim 대한소화기학회 2002 대한소화기학회 춘계학술대회 Vol.2002 No.-
<Background> The colorectal adenoma-carcinoma sequence represents a well-known paradigm for the sequential development of cancer driven by the accumulation of genomic defects, Although the colorectal adenoma-carcinoma sequence is well established, the stu
Choi, B.Y.,Yun, S.T.,Kim, K.H.,Choi, H.S.,Chae, G.T.,Lee, P.K. Elsevier 2014 Journal of geochemical exploration Vol.144 No.1
Naturally outflowing CO<SUB>2</SUB>-rich springs are a natural analogue of the seepage of sequestered CO<SUB>2</SUB> in geological storage sites. In Kangwon district of South Korea, two hydrochemically different types of CO<SUB>2</SUB>-rich springs (i.e., Ca-HCO<SUB>3</SUB>-type and Na-HCO<SUB>3</SUB>-type) occur together in a granitic terrain. Hydrochemical and water-isotope data (i.e., δ<SUP>18</SUP>O-δD and tritium) show that Na-HCO<SUB>3</SUB>-type springs have experienced significant silicate weathering processes over a long residence time at depths, while Ca-HCO<SUB>3</SUB>-type springs were formed by the mixing of Na-HCO<SUB>3</SUB>-type springs with shallow groundwater during ascent. In this study, diverse geochemical models including mixing, ion exchange and reaction path were investigated to verify the geochemical processes accounting for the occurrence of two contrasting types of CO<SUB>2</SUB>-rich springs. The mixing and ion exchange models reveal that Ca-HCO<SUB>3</SUB>-type springs are well explained by reverse cation exchange occurring during the mixing of Na-HCO<SUB>3</SUB>-type springs with shallow groundwater. The Na-HCO<SUB>3</SUB>-type springs are well explained by the reaction path modeling including the dissolution of silicate minerals (plagioclase, K-feldspar and biotite) and the precipitation of secondary minerals (calcite, kaolinite, muscovite and Mg-beidellite), implying that dissolved carbon is sequestered by calcite precipitation (i.e., mineral trapping). However, the concentrations of K in our modeling results are far below those of K observed in Na-HCO<SUB>3</SUB>-type springs, because of the precipitation of muscovite considered in the model, suggesting the partial disequilibrium state of the aquifer during the hydrolysis of K-feldspar under high P<SUB>CO'2</SUB> conditions. This result implies that to better predict long-term CO<SUB>2</SUB>-water-rock interactions in a geological storage site with abundant K-feldspar, the secondary K-bearing minerals should be carefully predicted, because a target aquifer can be far from chemical equilibrium during the storage period. This study shows that geochemical modeling can be effectively used to predict the hydrochemical changes of groundwater during long-term CO<SUB>2</SUB>-water-rock interactions and subsequent leakage toward surface in K-feldspar rich aquifer, although it should be included in a fully coupled computational approach between fluid flow, heat transfer and reactive mass transport processes in the future research.
Choi, K.Y.,Kim, S.H.,Choi, C.,Jung, M.H.,Wang, X.F.,Chen, X.H.,Noh, J.D.,Lee, S.I. North-Holland 2010 Physica. C, Superconductivity Vol.470 No.suppl1
To clarify the gap structure of the iron-pnictide superconductors, we synthesized optimally doped single crystals of BaFe<SUB>1.8</SUB>Co<SUB>0.2</SUB>As<SUB>2</SUB>, which had a critical temperature, T<SUB>c</SUB>, of 23.6K. The initial M-H curve was used to find the lower critical field, H<SUB>c1</SUB>. The full range of the temperature dependence of H<SUB>c1</SUB> was explained by using a two S-wave gap symmetry. We estimate the two gap as Δ<SUB>1</SUB>(0)=1.64+/-0.2meV for the small gap and Δ<SUB>2</SUB>(0)=6.20+/-0.2meV for the large gap.