• Microbiology and Biotechnology Letters
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• v.33 no.1
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• pp.29-34
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• 2005

Lipase-producing bacteria (S3) were isolated from intertidal flat at Saemanguem. A isolated strain was identified as Psychrobacter species by physiological and fermentational characterization as well as 16S rRNA analysis. The strain was then named as Psychrobacter sp. S3. P. sp. S3 grew most rapidly at $30^{\circ}C$, but grew well even at $10^{\circ}C$ and its lipase activity was most high when cultivated at $20^{\circ}C$. Lipase S3 had optimum temperature of $30^{\circ}C$ for the hydrolysis of p-nitrophenyl caproate and had more than $80^{\circ}C$ activity even at $10^{\circ}C$. The activation energy was calculated to be 1.5 kcal/mol, which showed that it was a typical cold-adapted enzyme. It was an alkaline enzyme with optimum pH of $9.0\~9.5$. It could hydrolyze various length of triglycerides. Among them, it hydrolyzed most rapidly $C_4,\;C_{14},\; C_{16}-length$ triglycerides. When added to tributyrin-agarose gel, lipase S3 hydrolyzed tributyrin most rapidly at 30 and $40^{\circ}C$, but it could hydrolyze well even at $4^{\circ}C$.

• Journal of the Korean Ceramic Society
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• v.31 no.12
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• pp.1417-1422
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• 1994

Effect of MgO, CaSO4, and CaF2 addition on the formation of clinker minerals in portland cement have been investigated by measuring the amounts of free-CaO and C3S in the fired specimens and analyzing the Mg and S concentration in C3S and C2S. It was found that CaSO4 inhibited C3S formation but MgO addition offset this effect of CaSO4. MgO addition also enhanced the mineralizing effect of CaSO4+CaF2, resulting in the acceleration of C3S formation. It was suggested that Mg might inhibit the formation of sulphate compounds rim around C2S and thus C2S+CaOlongrightarrowC3S reaction was facilitated.

• Cement Symposium
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• no.25
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• pp.36-40
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• 1997

• Journal of the Korean Ceramic Society
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• v.25 no.3
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• pp.207-216
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• 1988

Effect of $SO_3$ on the formation of $C_3S$ and its properties were investigated through studies for diffusion of reacting component, the size variation of $C_3S$ and compositional change of the phases in the clinker. When less than 2.0% of $SO_3$ was added to the clinker composition, the formation of $C_3S$ was enhanced, however, addition of more than 2.0% of $SO_3$ rather restrained the reaction remarkably. The diffusion coefficient of Si into the melt was about $3.6~4.2{\times}10^{-7}Cm^2$/sec and it was slightly decreased with the amount of $SO_3$. The crystal size of $C_3S$ formed in the clinker was grown gradually according to the amount of $SO_3$, when more than 1.0% of $SO_3$ was added. With increasing of $SO_3$ content in the clinker composition of CaO and decreasing of $SiO_2$ were found in the melt of the clinker. Consequently, it is considered that the decreasing of $C_3S$ formation is caused by dissolution and transportation of CaO component into liquid phase is interrupted.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2019.11a
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• pp.170-171
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• 2019

When the cement paste in concrete is exposed to high temperatures, the mechanical performance decreases due to a series of reactions inside the cement. In this study, we investigated the change of nanostructure of $C_3S$ when $C_3S$ was exposed to high temperature using pair distribution function (PDF) based on high energy X-ray scattering. As a result of X-ray diffraction, there was no significant difference when $C_3S$ was heated at $300^{\circ}C$, but most of $Ca(OH)_2$ was decomposed into CaO at $500^{\circ}C$. In addition, it was confirmed that CaO is dominant in the nanostructure when $C_3S$ is heated to $500^{\circ}C$.

• Journal of the Korean Ceramic Society
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• v.40 no.9
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• pp.859-866
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• 2003

When calcium sulfoaluminate-based expansive cement was hydrated, ettringite and monosulfate were mainly formed. The crack of hardened cement was prevented by compensating drying shrinkage due to formation of the above hydrates. In order to study the hydration properties of calcium sulfoaluminate-based expanding cement, 3CaOㆍ3Al$_2$O$_3$ㆍCaSO$_4$(C$_4$A$_3$S) was prepared by chemical synthesis, and then the hydration of $C_4$A$_3$S-Ca(OH)$_2$-CaSO$_4$.$2H_2O$-C$_3$A system_was characterized. Good $C_4$A$_3$S phase was prepared at $1300^{\circ}C$ by chemical synthesis, and the main hydration product of $C_4$A$_3$S-Ca(OH)$_2$-CaSO$_4$.2$H_2O$ system was ettringite. In the case of hydration $C_4$A$_3$S-Ca(OH)$_2$-CaSO$_4$ㆍ 2$H_2O$-C$_3$A system, ettringite was formed in the early period and it was transformed into monosulfate while consumed gypsum.

• Journal of the Korean Chemical Society
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• v.40 no.4
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• pp.219-228
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• 1996

An ab initio molecular orbital method has been applied to investigation of molecular properties and equilibrium geometries for hexahydroxybenzene triscarbonate (C9O9) and its analogous cyclic compounds (C9S9, C9O6S3, C9O3S6). In these works, the optimized geometry of each compound has been obtained at HF and MP2 levels. These results have shown that the optimized geometries of these compounds prefer D3h planar structure to C3v bowl structure. Calculations of harmonic vibrational frequencies have been also carried out at HF/3-21G* level to analyze normal modes of these compounds. Bonding characters of these compounds are studied by Mulliken and natural populations obtained at HF/6-31G* level. We have also studied the structures and the populations of C6O6 and C6S6 at HF and MP2 levels which are obtained by pyrolyses of C9O9 and analogous compounds. In addition, the single point calculations have been performed to predict the approximate energy barrier for pyrolysis of each compound.

• Journal of the Korean Ceramic Society
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• v.30 no.1
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• pp.7-16
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• 1993

Effect of sulfate on the reactionof C3S formation in presence of clinker melt and its appearance in clinker were investigated, using (NH4)2SO4 and CaSO4 as sulfate sources. When (NH4)2SO4 and CaSO4 were added, both showed the similar results, 1.0wt% of sulfate could promoted the reaction of C3S formation, however for its content of more than 2.0wt%, the formation of C3S was prevented. Residual limit of sulfate to C3S formation is about 1.4wt%. Appearances of sulfate were C4A3l and CaSO4 in interstitial phase. For the addition of (NH4)2SO4 or CaSO4 of 20wt%~4.0wt%, C3S grains showed the hypertrophic growth. We might consider that, because sulfate reduced the surface tension and viscosity of the clinker melt, C3S crystals were precipitated below 140$0^{\circ}C$, and the crystlas of C3S were coalesced and linked in the same crystallographical direction with increasing temperature becuase of their rapid growth rate.

• Journal of the Korean Mathematical Society
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• v.34 no.2
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• pp.321-336
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• 1997

Let S be the Ricci curvature of an n-dimensional compact minimal totally real submanifold M of a quaternion projective space $HP^n (c)$ of quaternion sectional curvature c. We proved that if $S \leq \frac{16}{3(n -2)}c$, then either $S \equiv \frac{4}{n - 1}c$ (i.e. M is totally geodesic or $S \equiv \frac{16}{3(n - 2)}c$. All compact minimal totally real submanifolds of $HP^n (c)$ satisfy in $S \equiv \frac{16}{3(n - 2)}c$ are determined.

• Journal of dental hygiene science
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• v.22 no.3
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• pp.156-163
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• 2022

Background: This study attempted to apply resin infiltrant (RI) as a method to maintain the effect of tooth bleaching treatment and compared it with fluoride varnish (FV) or artificial saliva to evaluate the effect. Methods: Sixty healthy lozenge specimens were classified into five groups. Group 1 was the negative control group, and discoloration was induced after artificial saliva treatment of the tooth specimen (G1_S+C). Group 2 was a positive control group, in which pigmentation was induced after bleaching treatment and artificial saliva treatment (G2 _B+S+C). Coloration was induced in group 3 (experimental group 1) after bleaching treatment and artificial saliva treatment, followed by application of fluorine varnish (G3_B+FV+S+C). Coloration was induced in Group 4 (experimental group 2) after applying RI after bleaching treatment and artificial saliva treatment (G4_B+RI+S+C). Pigmentation was induced in group 5 (experimental group 3) after bleaching treatment and artificial saliva treatment, followed by acid treatment (etching) and treatment with RI (G5_B+E+RI+S+C). Coffee and wine were used to induce discoloration. The lightness value (L^*) of the CIE L^*a^*b^* color system was obtained by image analysis. Kruskal-Wallis H analysis was performed for the mean difference in L^* values by group. Results: When coloration was induced with coffee, there was no significant difference in L^* value between artificial saliva (G2 _B+S+C), FV (G3_B+FV+S+C), and RI (G4_B+RI+S+C, G5_B+E+RI+S+C) groups. There was no significant difference in L^* values between the artificial saliva (G2 _B+S+C), FV (G3_B+FV+S+C), and RI (G4_B+RI+S+C, G5_B+E+RI+S+C) groups, even in the case of wine induced coloration. Conclusion: It was confirmed that artificial saliva or RI treatment had similar effects to the FV previously used to maintain the effect of tooth bleaching treatment.