• Journal of the Korean Chemical Society
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• v.29 no.4
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• pp.335-340
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• 1985

The crystal structure of ethylenediammonium bis (p-methylbenzenesulfonate) monohydrate, $C_2H_{10}N_{22}^{+2}{\cdot}(C_7O_3H_7S^-){\cdot}H_2O$ has been determined by X-ray diffraction techniques. The space group is P21, in 2 unit cell with a = 12.649 (2) ${\AA}$, b = 7.727 (1) ${\AA}$, c = 11.295 (2) ${\AA}$, ${\beta}$ =111.8(1)$^{\circ}$, and z = 2. The structure was solved by direct methods and refined to R = 0.060 for 1134 reflections measured with Mo-K${\alpha}$ radiation. Two p-methylbenzenesulfonates, fragment A and B, from a pair through the hydrogen bonds to the ethylenediammonium ion. The sulfonate group in the fragment B are disordered. There are six unique hydrogen bonds, of which four are between the ethylenediammonium ion and the sulfonate groups and remaining two involve the water molecule.

• The Journal of Advanced Prosthodontics
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• v.16 no.3
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• pp.163-173
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• 2024

PURPOSE. This study assessed the effect of storage time on chemical structure of a single-bottle and a two-bottle experimental ceramic primer and micro-shear bond strength (µSBS) of composite to ceramic. MATERIALS AND METHODS. This study was conducted on 60 sintered zirconia and 60 feldspathic porcelain blocks. Half of the specimens (n = 30) were subjected to surface treatment with the single-bottle Clearfil ceramic primer (n = 15) and two-bottle experimental primer (n = 15) after 24 hours. The remaining half received the same surface treatments after 6 months storage in distilled water. Composite cylinders were bonded to the ceramics, and they were then subjected to µSBS test. Also, the primers underwent Fourier-transform infrared spectroscopy (FTIR) after 24 hours and 6 months to assess their chemical structure. Data were analyzed with 3-way ANOVA and adjusted Bonferroni test (alpha = 0.05). RESULTS. The µSBS of both ceramics significantly decreased at 6 months in one-bottle ceramic primer group (P = .001), but it was not significantly different from the two-bottle experimental primer group (P = .635). FTIR showed hydrolysis of single-bottle primer, cleavage of silane and 10-MDP bonds, and formation of siloxane bonds after 6 months. CONCLUSION. Six months of storage caused significant degradation of single-bottle ceramic primer, and consequently had an adverse effect on µSBS.

• Textile Coloration and Finishing
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• v.21 no.5
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• pp.1-9
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• 2009

The feasibility of earthworm protease as a new cosmetic material for human hair care was investigated. The effectiveness of the earthworm protease treatment was assessed by thickness change of hairs, optical microscope examination, aminoacid analysis, surface morphology, angular resolution analysis through methylene blue staining method and tensile strength change. The protease treated hair became thinner and the soil on the surface removed in experimental groups unlike control group. Tensile strength decreased in experimental group in which the enzymes may decompose polypeptide bonds.

• Bulletin of the Korean Chemical Society
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• v.16 no.11
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• pp.1109-1112
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• 1995

Bis(silyl)alkylbenzenes such as bis(1-sila-sec-butyl)benzene (1) and 2-phenyl-1,3-disilapropane (2) were prepared in high yields by reduction of the corresponding chlorosilanes with LiAlH4. The dehydropolymerization of 1 and 2 was carried out with group 4 metallocene complexes generated in situ from Cp2MCl2/Red-Al and Cp2MCl2/n-BuLi (M=Ti, Hf), producing two phases of polymers. The TGA residue yields of the insoluble polymers were in the range of 64-74%. The molecular weights of the soluble polymers produced ranged from 700 to 5000 (Mw vs polystyrene) and from 500 to 900 (Mn vs polystyrene). The dehydropolymerization of 1 and 2 seemed to initially produce a low-molecular-weight polymer, which then underwent an extensive cross-linking reaction of backbone Si-H bonds, leading to an insoluble polymer.

• Journal of the Korean Chemical Society
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• v.33 no.6
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• pp.623-632
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• 1989

The positions and interaction energies of framework atoms and water molecules of $Mn^{2+}$-exchanged zeolite A were calculated using some potential energy functions and an optimization program. The sum of interaction energies of framework atoms in dehydrated $Mn_{4,5}Na_3-A$ was approximately the same as those of thermally stable $Ca^{2+}$-or $Mg^{2+}$-exchanged zeolite A. Since $Mn^{2+}$ ions can form good coordination bonds with framework oxygens even in dehydrated state, $Mn^{2+}$-exchanged zeolite A is considered to be thermally stable. The optimized positions of framework atoms and ions in this work are agreed well with the crystallographic data. Three groups of water molecules are found in hydrated $Mn^{2+}$-exchanged zeolite A; W(I) group of water molecules having only hydrogen bonds, W(II) group coordinated to $Na^+$ ion, and W(III) group coordinated to $Mn^{2+}$ ion. The average binding energy of each group of water molecules decrease in the order of W(III) > W(II) > W(I). The activation energies in the dehydration reaction of each group of water molecules increased in accordance with their binding energy.

• Journal of the Korean Chemical Society
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• v.29 no.1
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• pp.31-37
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• 1985

N-Acetyl-1-phenylalanyl-1-phenylalanine methyl ester (APhPhMe), N-acetyl-l-phenylalanine methyl ester (APhMe) and N-acetyl-1-phenylalanyl-1-alanine methyl ester (APhAlMe) were used as model compounds to investigate a protein denaturation under various temperatures and pressures. Overall, the solubility of APhPhMe in water increased with increasing pressure and that of APhMe decreased. However, the solubility of APhAlMe was nearly same. The values of volume change of APhPhMe were -0.9, -1.47, -1.09, -1.52 ml/mole at 20, 30, 40 and 50$^{\circ}C$, respectively, and those of APhMe were +6.0, +7.0, +7.5 ml/mole at 20, 30 and 40$^{\circ}C$, respectively. But those of APhAlMe were nearly zero at the measured temperature. The experimental result seems to be explained by the hydrophobic interaction and hydrogen bond of peptide bonds. In the compounds which have only peptide bonds and which have both a pretty large hydrophobic group and a peptide bond in the molecules, the hydrogen bond between peptide bonds is more dominant than the hydrophobic interaction. However, when the number of peptide bond and hydrophobic group increase simultaneously, the hydrophobic interaction seems to be more dominant.

• Restorative Dentistry and Endodontics
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• v.27 no.1
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• pp.16-23
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• 2002

Physical properties of composite resins such as strength, resistance to wear, discoloration, etc depend on the degree of conversion of the resin components. The purpose of this study was to evaluate the degree of conversion of the composite resins according to the thickness of tooth structure penetrated by light and applied light curing time. The coronal portions of extracted human teeth (one anterior tooth, three posterior tooth) was embedded by pink denture material. the mounted teeth were cut into three illumination sections (1mm thickness enamel section, 1mm thickness dentin section, 2mm thicknes dentin section) and one backing section with cutting wheel. Thin resin films were made by using 6kg pressure between slide glass during 5 minutes Thin resin film was light cured on coupled illumination section during 40sec, 80sec and 120sec. each illumination section was coupled as follows; no tooth structure(X), ename section(E), enamel section + 1mm dentin section(ED1), enamel section + 2mm dentin section(ED2), enamel section + 1mm dentin section + 2mm dentin section(EDD). To simulate the clinical situation more closely, thin resin films was cured against a backing section of tooth structure. The degree of conversion of carbon double bonds to single bonds in the resin films were examined by means of Fourier Transform Infrared Spectrometer. The results were obtained as follows ; 1 As curing time was increased, conversion rate was increased and as tooth thickness which was penetrated by curing light was increased, conversion rate was decreased. 2. At all tooth thickness groups, conversion rate between 80sec and 120sec was not significantly increased(P＞0.05). 3. At 40sec group and 80sec, conversion rate between no tooth structure(X) group and 1mm enamel section(E) group was not significantly decreased(P＞0.05). 4. At 80sec group and 120sec, conversion rate between 1mm enamel section(E) group and 1mm enamel section + 1mm dentin section(ED1) group was not significantly decreased(P＞0.05).

• Journal of the Korean Chemical Society
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• v.24 no.2
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• pp.121-128
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• 1980

Isonitrosobenzoylacetone is particularly interesting, as the isonitroso group has two potentially coordinating sites which can compete with the cabonyl groups in forming bonds with the metal ions. In this paper tris(isonitrosobenzoylacetonato)cobalt(III) and bis(isonitrosobenzoylacetonato)palladium(II) have been prepared, and their structures have been investigated. Spectroscopic studies lead to the conclusion that the both complexes do not contain an OH group in the chelated five-membered ring structure in which the ligand coordinates to metal through oxygen of the acetyl group and nitrogen of the isonitroso group. The coordination manner of this ligand is similar to that of isonitrosobenzoylacetone obtained by Patel and Haldar.

• The Journal of Korean Academy of Prosthodontics
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• v.41 no.5
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• pp.656-673
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• 2003

Statement of problem : Long-term exposure of dental porcelain to saliva during temporary cementation of a porcelain-fused to metal (PFM) restoration could affect mechanical strength of dental porcelain if the restoration is refired. Purpose : This work was performed to verify the effect of water on the mechanical strength in aged dental porcelain. Material and method : 63 specimens(Vintage Metalbond opaque and opal powder) were distributed to three experimental groups ; non-water immersed control, immersed and pedried, and immersed and non-predired groups. The changes in flexural strength and fracture toughness after specimen refiring related to Fourier Transform Infrared (FT-IR) spectroscopy. Results : 1. The FT-IR reflectances assigned to molecular bonds of $H_2O$ were noted as significantly different between the first-fired group and three refired groups and between two water-immersed groups and control group after refiring(p<0.05). They were also significantly different between predried group and non-predried group after refiring(p<0.05) 2. For opal specimens, FT-IR absorbances for hydrogen bond of $H_2O$ and silanols were significantly higher in non-predried group than in predreid group(p<0.05). 3 Predried opal group showed the highest mean flexural strength(p<0.05). Non-predried group indicated higher mean flexural strength than control group(p<0.05). 4. The mean fracture toughness for predired group was higher than non-predried group(p<0.05). 5. The difference of leucite crystal size is noted between control group and water-immersed, predried group in scanning electron microscopic study(${\times}10000$).

• Journal of Pharmaceutical Investigation
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• v.26 no.1
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• pp.55-59
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• 1996

The crystal structure of diflunisal, 2',4'-difluoro-4-hydroxy-3-biphenyl-carboxylic acid, was determined by single crystal X-ray diffraction technique. The compound was recrystallized from a mixture of acetone and water in monoclinic, space group C2/c, with $a\;=\;34.666(6),\;b\;=\;3.743(1),\;c\;=\;20.737(4)\;{\AA},\;{\beta}=\;110.57(2)^{\circ}$, and Z = 8. The calculated density is $1.324\;g/cm^3$. The structure was solved by the direct method and refined by full matrix least-squares procedure to the final R value of 0.045 for 1299 observed reflections. It was found that the molecules in the crystal are partially disordered, that is, the two equivalent conformers $(180^{\circ}$ rotated ones through C(1)-C(7)) are packed alternatively without regular symmetry or sequence. The two phenyl rings of the biphenyl group is tilted to each other by the dihedral angle of $43.3^{\circ}$. The carboxyl group at the salicylic moiety is just coplanar to the phenyl ring, and the planarity of this salicylic moiety is stabilized by an intramolecular hydrogen bond of O(3)-H(O3) O(2). The molecules are dimerized through the intermolecular hydrogen bonds at the carboxyl group in the crystal.