• The Korean Journal of Ceramics
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• v.5 no.2
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• pp.178-182
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• 1999

Simple binary $Na_2S-SiO_2$ oxysulfide glasses were prepared by a conventional melt-quench method in order to investigate the role of sulfur in glass structure and the electronic state. By X-ray photoelectron spectroscopy(XPS) measurement, S2p binding energy of the glass was observed at approximately 161eV which was close to that of ionic $S^{2-}$. The coordinating state around silicon atoms were investigated by ${29}^Si$ MAS-NMR measurement. The chemical shift observed from NMR supported that sulfur atom was joined to a silicon atom by substituting for an oxygen atom and was present as a non-bridging sulfide ion in low alkali content. On the other hand, it could be presumed that a portion of sulfur anions existed in an isolated state from the glass-network frame at high alkali content. The state of these sulfurs was also studied by Raman spectroscopy in detail.

• Restorative Dentistry and Endodontics
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• v.43 no.2
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• pp.20.1-20.9
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• 2018

Objectives: The aim of this in vitro study was to evaluate the bond strength of 2 universal adhesives used in different application modes to bleached enamel. Materials and Methods: Extracted 160 sound human incisors were used for the study. Teeth were divided into 4 treatment groups: No treatment, 35% hydrogen peroxide, 16% carbamid peroxide, 7.5% carbamid peroxide. After bleaching treatments, groups were divided into subgroups according to the adhesive systems used and application modes (n = 10): 1) Single Bond Universal, etch and rinse mode; 2) Single Bond Universal, self-etch mode; 3) Gluma Universal, etch and rinse mode; 4) Gluma Universal, self-etch mode. After adhesive procedures nanohybrid composite resin cylinders were bonded to the enamel surfaces. All specimens were subjected to shear bond strength (SBS) test after thermocycling. Data were analyzed using a 3-way analysis of variance (ANOVA) and Tukey post hoc test. Results: No significant difference were found among bleaching groups (35% hydrogen peroxide, 16% carbamid peroxide, 7.5% carbamid peroxide, and no treatment groups) in the mean SBS values. There was also no difference in SBS values between Single Bond Universal and Gluma Universal at same application modes, whereas self-etch mode showed significantly lower SBS values than etch and rinse mode (p < 0.05). Conclusions: The bonding performance of the universal adhesives was enhanced with the etch and rinse mode application to bleached enamel and non-bleached enamel.

• Journal of the Korean institute of surface engineering
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• v.26 no.3
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• pp.149-157
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• 1993

In the study of TAB(Tape Automated Bonding)technologies, Cu-Cr sputtered seed layer has been used to improve the adhesion between Polyimide and Cu film and electrical properties. But the Cu electrodeposit on Cu-Cr film had poor adhesion or powder-like form due to the surface Cr oxides on the Cu-Cr film. By means of activating the Cu-Cr film with the oxalic acid and phosphoric acid, the Cu film with the improved adhesion could be coated on the Cu-Cr sputtered film in CuSO4 solution. The etching rate was compared with increasing the Cr content of the sputtered Cu-Cr film, and anodic polarization curve in FeCl3 solution was investigated. With increasing the Cr content, the etching rate was reduced. The clean etching cross section could be obtained with increasing the concentration of FeCl3 solution. But above the 13 w/o Cr content, Cu-Cr sputtered film could not bed etched cleanly only with FeCl3 solution and additives were needed.

• Bulletin of the Korean Chemical Society
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• v.10 no.1
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• pp.72-74
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• 1989

Aminolysis of various carboxyl-containing ester substrates by triamines was kinetically studied in dimethyl sulfoxide (DMSO) in the presence of p-toluenesulfonic acid (TSA) or in the presence of sulfuric acid and potassium iodide (KI). In the presence of TSA or KI, the pseudo-first-order rate constants ($k_o$) were proportional to the total amine concentration ($N_o$). This stands in marked contrast with the corresponding reactions carried out with sulfuric acid added as the sole additive, in which saturation kinetic behavior of ko with respect to No was manifested. This indicates that complex formation between the ester substrate and the amine is greatly suppressed by the addition of TSA or KI. The second-order rate constants obtained in the presence of TSA or KI were substantially greater than those measured in the absence of any additive. These kinetic features were explained in terms of tight interaction between the protonated amines with I- or TSA-. Thus, the results were related to the hydrogen bonding that involves DMSO, bisulfate ion, I-, TSA-, and the protonated forms of triamines.

• Bulletin of the Korean Chemical Society
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• v.4 no.2
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• pp.79-83
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• 1983

The structure of thiamphenicol, one of the congeners of chloramphenicol which is a well-known antibiotic, has been determined by single crystal x-ray diffraction techniques. The crystal structure was determined using diffractometer data obtained by the $2{\theta}:{\omega}$ scan technique with $MoK{\alpha}$ radiation from a crystal having space group symmetry $P2_{1}2_{1}2_{1}$, and unit cell parameters a = 5.779, b = 15.292 and c = 17.322 ${\AA}$ . The structure was solved by direct methods and refined by least squares to an R = 0.070 for the 2116 reflections. The overall V-shaped conformation of thiamphenicol revealed in this study is consistent with those from the crystallographic studies and the proposed models from the theoretical and nmr studies of chloramphenicol. However there is no intramolecular hydrogen bond and the propanediol moiety is fully extended in the thiamphenicol molecule, while the crystal structures of chloramphenicol show the existence of the hydrogen bond between the two hydroxyl groups of the propanediol moiety forming an acyclic ring. All of the thiamphenicol molecules in the crystal are linked by a threedimensional hydrogen bonding network.

• Bulletin of the Korean Chemical Society
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• v.1 no.1
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• pp.10-17
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• 1980

Penicillin amidohydrolase was partially purified from the fermented broth of Bacillus megaterium, and was immobilized on nylon fiber. The surface area of nylon fiber was increased by roughening it with fine sand and activated by acid treatment. The free amino groups on the nylon fiber exposed by such treatment were then utilized to immobilize the penicillin amidase. Enzymatic properties of penicillin amidohydrolase immobilized on the nylon fiber by covalent bonding and cross linking with glutaraldehyde were studied and compared with those of soluble enzyme. The optimal pH and temperature profile of immobilized enzyme showed only slightly broader peaks, and the values of kinetic constants, $K_m$, $K_{ia}$, and $K_{ip}$, of the immobilized enzyme are only slightly greater than those of the soluble enzyme. These results suggest that the mass transfer effect on the reaction rate for the penicillin amidase immobilized on nylon fiber is not so significant as the enzyme immobilized on some other support material like bentonite. The experimental results of batch reaction agreed well with the results of computer simulation for both the immobilized and soluble enzyme systems, confirming the validity of the rate equation derived which was based on the combined double inhibition by two reaction products.

• Nuclear Engineering and Technology
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• v.34 no.2
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• pp.142-145
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• 2002

CaSO$_4$:Dy thermoluminescence dosimeter (TLD) is widely used as a personal or environmental dosimeter because of its high sensitivity to radiation. There are many methods to make pellets from the TL phosphorss[l-5]. Sintered pellets were made from a mixture of CaSO$_4$:Dy phosphor and Teflon powder is the most common method. But this method has disadvantage that CaSO$_4$:Dy pellet does not have very high sensitivity because of large amounts of Teflon in Pellets. This Paper described development of a new type of CaSO$_4$:Dy pellets by using P- compounds as a bonding material (KCT-300), and compared the TL sensitivity with that of the commercialized Teledyne CaSO$_4$: Dy pellets. Sensitivity of a new developed KCT-300 shows about 6 times than Teledyne ones, and can be used to measure very low radiation dose.

• Journal of Korean Society on Water Environment
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• v.27 no.4
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• pp.486-490
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• 2011

As(V) adsorption on aluminum oxide powder which was recycled from industrial wastes containing aluminum hydroxide was evaluated. Aluminum oxide powder in this study was prepared by calcinating aluminum hydroxide wastes at$550^{\circ}C$. Spectroscopic analysis indicated that the aluminum hydroxide wastes were changed to aluminum oxide by calcination. Arsenic adsorption isotherm was conducted with variation of ionic strength and multiple-ion systems using Ca(II) and Cu(II). As(V) removal showed typical anionic adsorption characteristics that the removal efficiency decreased with increasing pH in single As(V) system as well as in binary and ternary system. More than 80% of As(V) at an initial concentration of $5{\times}10^{-5}$ M was removed from aluminum oxide powder in As(V) single system. The effect of ionic strength on As(V) adsorption was negligible, which indicated the strong bonding between aluminum oxide powder and As(V). The removal efficiency of As(V) was higher in a binary system with Cu(II) than in a binary system with Ca(II).

• 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.

• Elastomers and Composites
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• v.57 no.4
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• pp.197-204
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• 2022

Recently, the demand has increased for protective clothing materials capable of shielding the wearer from bullets, fragment bullets, knives, and swords. It is therefore necessary to develop light and soft protective clothing materials with excellent wearability and mobility. To this end, research is being conducted on hybrid design methods for various highly functional materials, such as carbon nanotube (CNT) sheets, which are well known for their low weight and excellent strength. In this study, a hybrid protective material using CNT sheets was developed and its performance was evaluated. The material design incorporated a bonding method that used a binder for interlayer combination between the CNT sheets. Four types of binders were selected according to their characteristics and impregnated within CNT sheets, followed by further combination with aramid fabric to produce the hybrid protective material. After applying the binder, the tensile strength increased significantly, especially with the phenoxy binder, which has rigid characteristics. However, as the molecular weight of the phenoxy binder increased, the adhesive force and strength decreased. On the other hand, when a 25% lightweight-design and high-molecular-weight phenoxy binder were applied, the backface signature (BFS) decreased by 6.2 mm. When the CNT sheet was placed in the middle of the aramid fabric, the BFS was the lowest. In a stab resistance test, the penetration depth was the largest when the CNT sheet was in the middle layer. As the binder was applied, the stab resistance improvement against the P1 blade was most effective.