• 한국자기공명학회논문지
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• 제19권3호
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• pp.119-123
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• 2015

The thermodynamic properties and structural geometry of $KMgCl_3{\cdot}6H_2O$ were investigated using thermogravimetric analysis, differential scanning calorimetry, and nuclear magnetic resonance. The initial mass loss occurs around 351 K ($=T_d$), which is interpreted as the onset of partial thermal decomposition. Phase transition temperatures were found at 435 K ($=T_{C1}$) and 481 K ($=T_{C2}$). The temperature dependences of the spin-lattice relaxation time $T_1$ for the $^1H$ nucleus changes abruptly near $T_{C1}$. These changes are associated with changes in the geometry of the arrangement of octahedral water molecules.

• 한국자기공명학회논문지
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• 제19권1호
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• pp.18-22
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• 2015

The structural geometry of $[N(CH_3)_4]_2CdCl_4$ in a hexagonal phase is studied by $^1H$ MAS NMR, $^{13}C$ CP/MAS NMR, and $^{14}N$ NMR. The changes in the chemical shifts for $^{13}C$ and $^{14}N$ in the hexagonal phase are explained by the structural geometry. In addition, the temperature dependencies of the spin-lattice relaxation time in the rotating frame $T_{1{\rho}}$ for $^1H$ MAS NMR and $^{13}C$ CP/MAS NMR are measured.

• Journal of Magnetics
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• 제5권3호
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• pp.73-75
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• 2000

Undoped and Cr-doped samples of electrooptic material KTiOPO$_4$ were studied by $^{31}$P nuclear magnetic resonance (NMR). Spin-lattice relaxation time ($T_1$) measurements manifested phase transition behaviors that are attributed to changes in the dominant charge carriers in different temperature ranges.

• 한국자기공명학회논문지
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• 제18권1호
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• pp.41-46
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• 2014

In order to obtain information on the structural geometry of $NH_4HSeO_4$ near the phase transition temperature, the spectrum and spin-lattice relaxation time in the rotating frame $T_{1{\rho}}$ for the ammonium and hydrogen-bond protons were investigated through $^1H$ MAS NMR. $T_{1{\rho}}$ for the hydrogen-bond protons abruptly decreased at high temperature and it is associated with the change in the structural geometry in $O-H{\cdots}O$ bonds. This mobility of the hydrogen-bond protons may be the main reason for the high conductivity.

• 한국자기공명학회논문지
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• 제11권2호
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• pp.64-72
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• 2007

[ $^1H$ ] 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.

• 한국자기공명학회논문지
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• 제17권2호
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• pp.98-104
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• 2013

The ERETIC (Electronic REference To access In vivo Concentrations)2 method is a new qNMR experimental technique to measure analytes based on the signal of the reference compound without additional hardware equipment. In this study, ERETIC2 method was validated, and we sought to identify whether it would be possible to apply this method to a specific compound analysis of metabolites in plant. The $90^{\circ}$ pulse value (P1) and spin-lattice relaxation time ($T_1$) of each compound were measured for ERETIC2. The $9^1H$ of 3-(trimethylsilyl) propionic-2,2,3,3-$d_4$ acid (TSP) was used as a reference peak for ERETIC 2, and then, a suitable solvent and pulse sequence for each compound were selected. Under the NOESY-presat sequence, the relative accuracy error for quantitative analyses of primary metabolites was within the range of 5%, with the exception of glucose, which showed ${\geq}$ 55% error due to saturation. It showed excellent results for the quantification of glucose by using a $30^{\circ}$ pulse sequence, which did not suppress the water peak. In addition, the quantitative accuracy for secondary metabolites was extremely accurate, with an error ${\leq}$5% when considering the purity of the standard sample. The ERETIC2 method showed outstanding linearity, precision, and accuracy.