• Journal of the Korean Chemical Society
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• v.38 no.2
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• pp.169-173
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• 1994

The previously reported cytotoxic metabolites, against the KB cell line, xestoquinone, halenaquinol sulfate and $halenaquinol^{5,6}$ were isolated from the unidentified sponge collected in October 1992, Manado Bay, Sulawesi in Indonesia. Their structure were elucidated by $^1H-,\;^{13}C$-NMR, $^1H-,\;^{13}C$(1 bond) Heteronuclear Multiple Quantum Coherence Spectroscopy$(HMQC)^1$, $^1H-,\;^{13}C$C(2 and 3 bond) Heteronuclear multiple Bond Correlation Spectroscopy$(HMBC)^2$, Electron Impact Mass Spectroscopy(EI ms), Ultraviolet Spectroscopy(UV), and Infrared Spectroscopy(IR)

• Bulletin of the Korean Chemical Society
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• v.20 no.4
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• pp.445-450
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• 1999

Molecular dynamics (MD) simulation of non-rigid H-Y zeolite framework are performed at 298.15 and 5.0 K. Usual bond stretching, bond angle bending, torsional rotational, and non-bonded Lennard-Jones and electrostatic interactions are considered as intraframework interaction potentials. Calculated atomic parameters are in good agreement with the experiment, which indicates the successful reproduction of the framework structure and its motion. Both calculated bond lengths and bond angles are also in good agreement with the experiment except generally for a little longer bond lengths and a little smaller T-O-H bond angles. The calculated overall site occupation of HI keeps the order O(2) > O(3) > O(4) > O(t) at 298.15 K, which is very different from the experimental prediction, O(l) > O(3) > O(2) at 5 K. Calculated IR spectra of the H-Y zeolite framework show that most of the main peaks of the O-H bonds are in the broad region 3700-5000 cm-1 and that the O-T stretching bands appeared in 0-2000 cm-1 and at 2700 cm-1

• Journal of the Korean Chemical Society
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• v.63 no.4
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• pp.237-245
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• 2019

Hydrogen bihalide anions, $XHX^-$ (X = F, Cl, and Br) have been studied by high level ab initio methods to determine the molecular structure, vibrational frequencies, and energetics of the anions. All bihalide anions are found to be of linear and symmetric structures, and the calculated bond lengths are consistent with experimental data. The harmonic frequencies exhibit large deviations from the experimental frequencies, suggesting the vibrations of these anions are very anharmonic. Two different approaches, the VSCF and VPT2 methods, are employed to calculate the anharmonic frequencies, and the results are compared with the experimental frequencies. While the ${\nu}_1$ and ${\nu}_2$ frequencies are in reasonable agreement with the experimental values, the ${\nu}_3$ and ${\nu}_1+{\nu}_3$ frequencies still exhibit large deviations. The hydrogen-bond energies and enthalpies are calculated at various levels including the W1BD and G4 composite methods. The hydrogen-bond enthalpies calculated are in good agreement with the experimental values.

• Journal of the Korea institute for structural maintenance and inspection
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• v.6 no.1
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• pp.103-109
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• 2002

Reinforced concrete structure resist to external load caused by integration of steel bar and concrete and this integration is obtained from bond stress between steel bar and concrete. Researches of bond stress between steel bar and concrete have been performed by many researcher, but existent researches of bond stress are concerned with compression strength of well cured concrete and insufficient study of bond stress according to early material. The secure regular strength of concrete in early age is caused by rapid velocity of early hardening process, but questionable bond stress in early age is proportion to strength of that. So this study performed experiments to compare bond stress according to material age and compression strength. The result is showed that bonding strength in early material age compare the ratio of concrete compression strength with the ratio of maximum bond stress the later inferior on the former.

• Land and Housing Review
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• v.3 no.4
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• pp.333-341
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• 2012

The financial resources for public land banking enacted by Public Land Banking Act (2009) are LH (Korea Land and Housing Corporation) contributions, LH Bond, Land Bank revenues, etc. But, in real, the efficient funding resource is mainly LH bond. In these days, LH has experienced deep financial distress, and difficulties in issuing it's bond. Therefore, Land Banking project also has been inactivated because of poor financial resources. As Land Banking project depending its financial resources mainly on LH Bond does not have financial sustainability, it is necessary to reform the fundamental funding structure. This is the starting point for the topic of this paper. This paper suggests to reform the funding structure, and to introduce Land Bank Bond guaranteed by Government, and also to modify the accounting method of Land Bank to separate the Land Bank accounts with LH accounts. The funding structure reform can be summarized as follows; In early stage of the Land Banking project, sufficient government support by guaranteeing the Land Bank Bond is necessary. Gradually, the portion of LH's contribution can be increased in company with LH's financial distress being solved and administration being normalized. When the project reached on the stage of maturity, cash inflows by selling the reserved land can exceed the cash outflows for reserve new land. To introduce the Land Bank Bond guaranteed by government, the Public Land Banking Act (2009) should be revised. Along with this, to modify the accounting method of Land Bank, the rule for public enterprise accounting system must be partially revised.

• Journal of the korean academy of Pediatric Dentistry
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• v.25 no.1
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• pp.76-92
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• 1998

The purpose of this study was to evaluate the possible efficacy of Nd-YAG laser as a dentin conditioner by observing the laser irradiation dentin surface under scanning electron micrograph and measuring shear bond strength of restored light-cured glass ionomer mold. Fifty intact premolars were prepared for shear bond strength tests. The teeth were randomly divided into five groups as follows; Group I. no treatment Group II. 10% poly acrylic acid, 20 sec Group III. laser treatment 2 w, 20 Hz, 2 sec Group IV. laser treatment 2 w, 20 Hz, 5 sec Group V. laser treatment 2 w, 20 Hz, 10 sec Samples of each group were restored with light-cured glass ionomer cement after dentin conditioning and then measuring the shear bond strength of each specimen were measured using universal testing machine. Additional ten premolars were prepared for SEM analysis The result from the this study can be summarized as follows. 1. Shear bond strength of polyacrylic acid-treated group (II) was significantly higher than other groups (p<0.05). 2. No statistically significant difference could be found between three laser-treated groups (III, IV, V) in shear bond strength(p>0.05) 3. According to the result of observation under SEM, Polyacrylic acid was shown to have removed the smear layer effectively and opened the dentinal tubules, whereas the laser has produced the irregular surface mainly composed of melted and fused structure. The microcracks found in laser-treated groups increased in number with irradiation time and formed the regular mesh-type in 10 sec-irradiation group. 4. The ultrastructural change of dentin surface created by laser irradiation was found to the improper for bonding of the glass ionomer restorative materials. And the lower shear bond strength of laser irradiated group might have been due to the failure to form the suit able dentin surface for the glass ionomer to penetrated into and form the proper micromechanical retention.

• 한국생물공학회:학술대회논문집
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• 2001.11a
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• pp.886-889
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• 2001

C-terminus specific immobilization often results in a increased structural stability resistant to various denaturation factors. In order to elucidate the immobilization effect on the c-terminus in molecular level, we made over 200 protein data set from Protein Data Bank(PDB), analyzed c-terminus structure of each protein, and investigated the structural relationship with the stabilizing factors such as hydrogen bond, ion pairs, cation pi, disulfide bond, solvation free energy, surface area, flexibility and so on.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.185-188
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• 2002

An abrasive vitreous bonded solid mass having a vitrified abrasive structure comprising diamond grains which are held by an in inorganic bonding agent, the vitrified diamond wheel is impregnated with a composition which comprises a thermosetting synthetic resin and a surfactant. The vitrified diamond wheel is manufactured by preparing the composition including the resin and the surfactant, impregnating the abrasive structure with the composition, and curing the composition. The diamond wheel newly developed showed excellent performance in grinding carbide.

• Journal of the Korean Ceramic Society
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• v.23 no.5
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• pp.25-34
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• 1986

This study was to refined the crystal structure of solid solution to determine the position and amount of Al in diopside and to relate crystal structure changes and properties of solid solution. Single crystals of the solid solution in the system CaO.MgO.$2 SiO_2-Al_2O_3$ were made from the melt with slow cooling and used to refine the structure. The following were obtained. 1. Tetrahedra rotated around axis parallel to the direction which the angle 03-03-03 became small. 2. Tetrahedron became large and regular. Average T-O bond distance increased 0.53 percent. 3. M1 octahedron became small and average M1-O bond distance decreased 1.1 percent. 4, M2 polyhedron became small and average M2-O bond distance decreased 0.37 percent Polythedron was affected not so much compared with any cation site. 5. Distance between metal ions distances between T and oxygens which were coordinated with M2 and meighboring tetrahedron distances between M2 and oxygens which coordinated with M1 and M2 were not changed almost. 6. $Al^{3+}$ substituted 4Mg^{2+}$ and $Si^{4+}$

• 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.