• Bulletin of the Korean Chemical Society
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• v.7 no.5
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• pp.331-334
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• 1986

The crystal structure of thiamin tetrahydrofurfuryl disulfide, one of the ring-opened derivatives of thiamin, has been determined by the X-ray diffraction methods. The crystal is monoclinic with cell dimensions of a = 8.704 (1), b = 11.207 (2), c = 21.260 (3) ${\AA}$ and ${\beta}$ = 92.44 (2)$^{circ}$, space group P2$_{1}$/c and Z = 4. The structure was solved by direct methods and refined to R = 0.076 for 1252 observed reflections measured on a diffractometer. The molecule assumes a folded conformation in which the pyrimidine and the tetrahydrofurfuryl rings are on the same side of the ethylenic plane. The pyrimidinyl, N-formyl and ethylenic planes are mutually perpendicular to each other and the N(3)-C(4) bond retains a single bond character. The structure is stabilized by an intramolecular N(4'${\alpha})-H{\cdots}O(2{\alpha}$) hydrogen bond. The molecules are connected via N(4'${\alpha}$)-H{\cdots}(N3')$ and O(5${\gamma})-H{\cdots}(N1')$ hydrogen bonds, forming a two-dimensional hydrogen-bonding network. The tetrahydrofurfuryl ring is dynamically disordered. The overall conformation as well as the packing mode is very similar to that of thiamin propyl disulfide.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 2000.06a
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• pp.59-64
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• 2000

Silicon nitride ceramics with various α/β phase ratio were fabricated by controlling sintering conditions of PECS process. Mechanical properties varied systematically with α/β ratio. Young's modulus and hardness increased with α-Si₃N₄ volume fraction, and fracture strength and toughness increased with β-Si₃N₄ content.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 2000.06a
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• pp.151-163
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• 2000

A polymerized organic-inorganic complexation route is introduced for the synthesis of oxide ceramic powders. Polyvinyl alcohol was used as the organic carrier for precursor ceramic gel. Porous and soft powders, which have a high specific surface area, were obtained after calcinating the aerated precursors. The PVA content and its degree of polymerization had a significant influence on the homogeneity of the final powder. In particular, attrition milling process with the porous powder resulted in ultra-fine particles. In the case of the preparation of cordierite powder, nano-size powder, which has a high specific surface area of 181 ㎡/g, was obtained by the milling process. The complexation route was also applied to the synthesis of unstable phase in room temperature like beta-cristobalite, high temperature form of silica.

• Korean Journal of Pharmacognosy
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• v.8 no.3
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• pp.95-101
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• 1977

Substance A, white prismatic crystal, mp $134{\sim}135,\;C_{29}H_{50}O$, substance B, white needle crystal, mp $131{\sim}132^{\circ},\;C_{17}H_{28}O_4$ and substance C colorless oils, bp $84{\sim}85,\;C_{15}H_{24}O$ were isolated from the underground portion of Valeriana fauriei var. dasycarpa $H_{ARA}$(Valerianaceae) according to Thies method. Substance A was confirmed as known sterol, ${\beta}-sitosterol$ by chemical and spectral discussions. Substance B was estimated as hitherto unknown sesquiterpenoid, 11-acetoxylhydroxyvaleranone by chemical and spectral discussions. Substance C was proposed as hitherto unknown sesquiterpenoid 1, 4-dimethyl-7-isopropenyl 4, 5, 6, 8, 9, 10-hexahydroazulene-1-ol by chemical and spectral discussions, and the general biogenetic considerations.

• Journal of the Korean Chemical Society
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• v.16 no.1
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• pp.6-12
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• 1972

The crystal structure of monoethanolamine hydrochloride is triclinic P1 with two formula units in a cell of dimensions a = $4.42\pm0.02$, b = $7.44\pm0.02$, c = $7.48\pm0.02$, $\alpha$ = $102.4\pm0.3$, $\beta$ = $91.1\pm0.3$, $\gamma$ = $77.2\pm0.3^{\circ}.$ The configuration of monoethanolamine is a gauche form with dihedral angle, $90^{\circ}$. The nitrogen atom forms four hydrogen bonds, three to Cl- ions(3.15, 3.24, $3.28\AA)$ and one to a hydroxyl group of another molecule (N${\cdot}{\cdot}{\cdot}$O, $2.90{\AA})$. The oxygen also forms two such bonds, one to a Cl- ion $(3.14\AA)$, one to an amine group of another molecule (O${\cdot}{\cdot}{\cdot}$N, $2.90{\AA}).$ Molecules are linked into two-dimensional network by hydrogen bonds.

• Journal of Korea Foundry Society
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• v.12 no.3
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• pp.203-209
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• 1992

Directional solidification of Al-Ti peritetic alloys was carried out using Upward Continuous Casting Process. The morphology of a solid-liquid interface and solidification microstructures were investigated under various crystal growing conditions. The experimental results were compared with those attained by the Bridgman method. The cell spacing of the Al-Ti peritetic alloys and the primary dendrite arm spacing of the Al-Ti peritetic alloys decreased with an increase in pulling speed. The primary ${\beta}$ phase of the Al-Cr and Al-Ti peritectic alloys did not appear in solidification microstructures because of the depleted solute contents in the melt ahead of the solid-liquid interface.

• Korean Journal of Pharmacognosy
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• v.27 no.3
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• pp.207-211
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• 1996

Cumambrin A has been isolated from the dried flowers of Chrysanthemum boreale Makino. The complete $^1H$ and $^{13}C$ NMR assignment of cumambrin A was achieved from two-dimensional $^1H$-$^1H$ COSY and $^{13}C$-$^1H$ COSY spectra with the aid of homonuclear and heteronuclear double resonance experiments. The its structure has been verified by single crystal X-ray diffraction.

• YAKHAK HOEJI
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• v.30 no.2
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• pp.73-78
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• 1986

Peucedanum terebinthaceum Fischer (Umbelliferae) known as "Gi Reum Na Mool" in Korea and used for the treatment of cough, phlegm, headache and common cold etc. The substances were isolated from the fruits of Peucedanum terebinthaceum and identified by UV, GLC, IR, NMR, Mass spectra and physico-chemical tests. The steroidal compounds from the fruits were identified as $\beta$-sitosterol (tR 33.01 min.) and stigmasterol (tR 28.87 min.) by GLC. Substance I (colorless prismatic crystal, $C_{19}H_{20}O_5$, mp $110~111^{\circ}$) was identified as decursin which is one of the pyranocoumarin. Hydrolysis of substance I with 5%-potassium hydroxide produced decursinol. Acetylation of decursinot gave its monoacetate, white needles, $C_{16}H_{16}O_5$. Substance II(light yellowish white needle crystal, $C_9H_6O_3$, mp $227~228^{\circ}$) was proved to be umbelliferone. Substance I, decursin, was isolated for the first time from the fruits of Peucedanum spp. (Umbelliferae).

• Archives of Pharmacal Research
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• v.11 no.1
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• pp.74-79
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• 1988

Crystals of tolazamide, $C_{14}H_{21}N_3O_3S$, are triclinic space group $P{\bar{1}}$ with cell dimensions of a = 6.355 (2), b = 9.223 (2), c = 13.510 (3) A, ${\alpha}\;=\;101.04\;(8),\;{\beta}=92.80(5),\;{\gamma}\;=\;85.72\;(6)^{\circ}$ and Z = 2. Intensities were collected on an automated four-circle diffractometer using graphite-monochromated Cu K ${\alpha}$ radiations. The structure was solved by direct method and refined by full-matrix least-squares to an R factor of 0.058 for 1184 observed reflections. The molecules are dimerized by the $N-H{\cdots}O$ hydrogen bonds. There are only van der Waals interactions between these molecular dimers.

• Bulletin of the Korean Chemical Society
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• v.25 no.8
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• pp.1207-1210
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• 2004

Holmium $\beta$ -diketonate complexes, Ho(hfa)$_3$(tme), has been prepared and characterized by IR, TGA, MS, and single-crystal X-ray analyses. This complex is air- and moisture-stable and most importantly has good volatility and thermal stability. Holmium atom binds to nine oxygen atoms, contributed by six oxygen atoms of three hfa ligands and three oxygen atoms of the tme ligand. The coordination polyhedron of Ho can be described as a distorted tricapped trigonal prism. Crystal data for $Ho(hfa)_3(tme)$; orthorhombic $P2_12_12_1$, a = 15.415(4), b = 13.17(2), c = 17.291(3) $\AA$, V = 3496(1) ${\AA}^3$.