• The korean journal of orthodontics
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• v.43 no.1
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• pp.23-28
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• 2013

Objective: The purpose of this study was to evaluate the effect of casein phosphopeptide amorphous calcium phosphate (CPP-ACP) on the shear bond strength (SBS) of brackets bonded to non-demineralized teeth with either phosphoric acid etching or self-etching primer. Methods: Sixty human premolars were randomly assigned to 1 of 4 treatment groups (n = 15 each): phosphoric acid etching (group 1); self-etching primer (group 2); CPP-ACP for 2 weeks + phosphoric acid etching (group 3), and CPP-ACP for 2 weeks + self-etching primer (group 4). After bonding of the maxillary premolar metal brackets, specimens were subjected to shear forces in a testing machine. Scanning electron microscopy was used to observe etching patterns on the enamel surfaces of all teeth. A 2-way analysis of variance was used to test for effects of CPP-ACP and etching system on SBS. Results: Significantly higher mean SBSs were observed in groups subjected to phosphoric acid etching (i.e., groups 1 and 3; p < 0.05). On the other hand, SBSs did not appear to be influenced by CPP-ACP (i.e., groups 3 and 4; p > 0.05). We observed a uniform and clear etched pattern on the enamel surface of the phosphoric acid etching groups. Conclusions: CPP-ACP does not significantly affect the SBS of orthodontic brackets bonded to non-demineralized teeth, regardless of which adhesive method is used to bond the brackets.

• Journal of Microbiology and Biotechnology
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• v.12 no.2
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• pp.189-195
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• 2002

Using Streptomyces sp. YU100 isolated from Korean soil, the fermentative production of phospholipase D was attempted along with its purification and characterization studies. When different carbon and nitrogen sources were supplemented in the culture medium, glucose and yeast extract were found to be the best. By varying the concentration of nutrients and calcium carbonate, the optimal culture medium was determined as 2.0% glucose, 1.5% yeast extract, 0.5% tryptone 0.3% calcium carbonate. During cultivation, the strain secreted most of the phospholipase D in the early stage of growth within 24 h. The phospholipase D produced in the culture broth exhibited hydrolytic activity as well as transphosphatidylation activity on lecithin (phosphatidylcholine). In particular, the culture broth showed 8.7 units/ml of hydrolytic activity when cultivated at $28^{\circ}C$ for 1.5 days. The phospholipase D was purified using 80% ammonium sulfate precipitation and DEAE-Sepharose CL-6B column chromatography, which produced a major band of 57 kDa on a 10% SDS-polyacrylamide gel with purity higher than 80%. The enzyme showed an optimal pH of 7 in hydrolytic reaction, and at pH 4 in a transphosphatidylation reaction. The enzyme activity increased until the reaction temperature was elevated to $60^{\circ}C$. The enzyme was relatively stable at high temperatures and neutral pH, but significantly unstable in the alkaline range. Among the detergents tested as emulsifiers of phospholipids, the highest enzyme activity was observed when 1.5% Triton X-100 was employed. However, no inhibitory effect by metal ions was detected. Under optimized reaction conditions, the purified enzyme not only completely decomposed PC to phosphatidic acid within 1 h, but also exhibited higher than 80% conversion rate of PC to PS by transphosphatidylation within 4 h.

• Resources Recycling
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• v.21 no.6
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• pp.32-38
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• 2012

In this study, direct reduction of $ZrO_2$ using liquid calcium was investigated. The influence of molar ratio of Ca and $ZrO_2$, reaction time and temperature on the reduction behavior of $ZrO_2$ was studied. Experiments were conducted in a closed stainless steel chamber under Ar atmosphere during 5 to 60 minutes. Most of the $ZrO_2$ was reduced to Zr in 5 minutes at 1223 K and 3 Ca/$ZrO_2$ molar ratio. The minimum oxygen content in reduced metal Zr was obtained about 0.66 wt% at 1373 K after 30 minutes and 4 Ca/$ZrO_2$ molar ratio. The morphology of zirconium powder obtained was highly affected by the reaction temperature and reaction time.

• Journal of the Korean Recycled Construction Resources Institute
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• v.7 no.3
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• pp.262-270
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• 2019

Ferronickel slag, which is an industrial byproduct, is activated by mechanochemical reaction as a nonferrous metal and can be used as an admixture. Therefore, ferronickel slag is used as a substitute resource of admixture. In this study, to evaluate the effect of mixed of ferronickel slag powder and admixture, a mortar using a mixture of ferronickel slag powder, quicklime, gypsum and calcium chloride was fabricated by vibrated and rolled manufacturing method. Strength were evaluated by flexural and compressive strength tests, and durability was evaluated by performing chlorine ion penetration resistance and chemical resistance test. When the substitution ratio of ferronickel slag powder is constant, it is considered that the mixed use of quicklime, gypsum and calcium chloride as admixtures increases the performance.

• BMB Reports
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• v.40 no.3
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• pp.315-324
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• 2007

The novel $\alpha$-amylase purified from locally isolated strain, Bacillus sp. KR-8104, (KRA) (Enzyme Microb Technol; 2005; 36: 666-671) is active in a wide range of pH. The enzyme maximum activity is at pH 4.0 and it retains 90% of activity at pH 3.5. The irreversible thermoinactivation patterns of KRA and the enzyme activity are not changed in the presence and absence of $Ca^{2+}$ and EDTA. Therefore, KRA acts as a $Ca^{2+}$-independent enzyme. Based on circular dichroism (CD) data from thermal unfolding of the enzyme recorded at 222 nm, addition of $Ca^{2+}$ and EDTA similar to its irreversible thermoinactivation, does not influence the thermal denaturation of the enzyme and its Tm. The amino acid sequence of KRA was obtained from the nucleotide sequencing of PCR products of encoding gene. The deduced amino acid sequence of the enzyme revealed a very high sequence homology to Bacillus amyloliquefaciens (BAA) (85% identity, 90% similarity) and Bacillus licheniformis $\alpha$-amylases (BLA) (81% identity, 88% similarity). To elucidate and understand these characteristics of the $\alpha$-amylase, a model of 3D structure of KRA was constructed using the crystal structure of the mutant of BLA as the platform and refined with a molecular dynamics (MD) simulation program. Interestingly enough, there is only one amino acid substitution for KRA in comparison with BLA and BAA in the region involved in the calcium-binding sites. On the other hand, there are many amino acid differences between BLA and KRA at the interface of A and B domains and around the metal triad and active site area. These alterations could have a role in stabilizing the native structure of the loop in the active site cleft and maintenance and stabilization of the putative metal triad-binding site. The amino acid differences at the active site cleft and around the catalytic residues might affect their pKa values and consequently shift its pH profile. In addition, the intrinsic fluorescence intensity of the enzyme at 350 nm does not show considerable change at pH 3.5-7.0.

• Journal of Mushroom
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• v.19 no.1
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• pp.51-55
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• 2021

The mineral contents of domestic and Chinese Sarcodon aspratus were analyzed for comparing the differences in the mineral contents according to the production sites. The mineral contents of 10 domestic and 10 Chinese S. aspratus were analyzed by using an atomic absorption spectrophotometer and an inductively coupled plasma mass spectrometer. The sodium, magnesium, potassium, and calcium contents of domestic S. aspratus were 170.3±44.0 mg/kg, 81.3±20.8 mg/kg, 1,123.8±274.3 mg/kg, and 12.1±4.1 mg/kg, respectively, while those of Chinese S. aspratus were 112.2±40.8 mg/kg, 297.8±20.9 mg/kg, 10,938.4±2,914.1 mg/kg, and 52.5±27.7 mg/kg, respectively. There were no significant differences in the micro mineral contents and hazardous heavy metal contents between domestic and Chinese S. aspratus, while there was a significant difference in the macro mineral contents between domestic and Chinese S. aspratus. Thus, the comparative analyses of the sodium, magnesium, potassium, and calcium contents of many domestic and Chinese S. aspratus are required to determine their production sites in the future.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.12
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• pp.1249-1256
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• 2005

This study was performed to investigate the efficiency of the corrosion prevention in the simulated distribution system using CCPP(Calcium Carbonate Precipitation Potential) as the anti-corrosive index by adjusting pH, total dissolved solids, alkalinity and calcium hardness in the water treatment pilot process. The materials of the simulated distribution system(SDS) were equiped with same materials of real field water distribution system. CCPP concentrations controlled by $Ca(OH)_2$, $CO_2$ gas and $Na_2CO_3$ in the simulated distribution system and uncontrolled by the chemicals in the general water distribution system were average 0.61 mg/L and -7.77 mg/L. The concentrations of heavy metals like Fe, Zn, Cu ions in effluent water of the simulated distribution system controlled with water quality were decreased rather than the general water distribution system uncontrolled with water quality. In simulated distribution system(SDS), corrosion prevention film formed by CCPP control was observed that scale was come into forming six months later and it was formed into density as time goes on. We were analyzed XRD(X-ray diffraction) for investigating component of crystal compounds and structure for galvanized steel pipe(15 mm). Finding on analysis, scale was compounded to $Zn_4CO_3(OH)_6{\cdot}H_2O$ (Zinc Carbonate Hydroxide Hydrate) after ten months late, and it was compounded on $CaCO_3$(Calcium Carbonate) and $ZnCO_3$(Smithsonite) after nineteen months later.

• Journal of the Korean Society for Marine Environment & Energy
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• v.19 no.1
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• pp.18-24
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• 2016

Mineral carbonation is a technology for permanently storing carbon dioxide by reacting with metal oxides containing calcium and magnesium. In this study, we used sea water and alkaline industrial by-product such as paper sludge ash (PSA) for the storage of carbon dioxide through direct carbonation. We found the optimum conditions of both sea water content (mixing ratio of sea water and PSA) and reaction time required in the direct carbonation through various experiments using sea water and PSA. In addition, we compared the amounts of carbon dioxide storage with the cases when sea water and ultra-pure water were separately used as solvents in the direct carbonation with PSA. The amount of carbon dioxide storage was calculated by using both solid weight increase through the carbonation reaction and the contents of carbonate salts from thermal gravimetric analysis. PSA particle used in this study contained 67.2% of calcium. The optimum sea water content and reaction time in the carbonation reaction using sea water and PSA were 5 mL/g and 2 hours, respectively, under the conditions of 0.05 L/min flow rate of carbon dioxide injected at $25^{\circ}C$ and 1 atm. The amounts of carbon dioxide stored when sea water and ultra-pure water were separately used as solvents in the direct carbonation with PSA were 113 and $101kg\;CO_2/(ton\;PSA)$, respectively. The solid obtained through the carbonation reaction using sea water and PSA was composed of mainly calcium carbonate in the form of calcite and a small amount of magnesium carbonate. The solid obtained by using ultra-pure water, also, was found to be carbonate salt in the form of calcite.

• Korean Journal of Soil Science and Fertilizer
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• v.14 no.4
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• pp.242-249
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• 1982

Effects of lime and ameliolating materials on decreasing available soil cadmium were studied, applying the amendments to Cd pre-and post-treated soils. Soil sttreated with Cd were placed in pots and kept under field moisture condition, summer through winter in 1981. The results of soil analysis made 40 to 60 days after the Cd treatment are as follows ; 1. Greater amount of Cd was extracted by 0.1N-HCl or 2% Citric acid than N-AcNH4 solution. More Cd was dissoluted by 0.1-HCl than 2% Citric acid. No Cd was extracted by pure water. Showing a wide variance in the amount of extractable Cd among treatments (amendments), the $N-AcNH_4$ solution seemed to be the most effective extracting solution of available soil cadmium. 2. Calcium hydroxide was the most effective materials in reducing $N-AcNH_4$ extractable Cd, followed by calcium carbonate and calcium silicate. 3. Superphosphate is also effective in reducing exchangeable cadmium. The reduction seemed to be attributed to the precipitation of cadmium phosphate. 4. The exchangeable cadmium by $N-AcNH_4$ was large in the soil pH range of 6.0 and 6.5, and it decreased as the soil pH became far apart from these values. The decrese of exchangeable Cd at low pH seemed to be related to the increase of $Mn^{+{+}}$ and that at the high pH to the precipitation as Cd-hydroxide.

• Polymer(Korea)
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• v.28 no.5
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• pp.397-403
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• 2004

The sulfonated PET-g-GMA ion-exchange fine fibers were synthesized by UV radiation-induced graft copolymerization using a photoinitiator, and their chemical structure and adsorption properties were investigated. The optimum values for synthetic conditions - UV intensity, reaction time, and reaction temperature were 450 W, 60 min, and $40^{\circ}C$, respectively. Maximum values of the degree of sulfonation and ion exchange capacity were 8.12 mmol/g and 3.25 meq/g, respectively. Tensile strength of sulfonated PET-g-GMA fine ion exchange fibers was lower than that of PET trunk polymer as the grafting reaction rates increased. It was shown that as for the adsorption rate of $Ca^{2+}$ and $Mg^{2+}$ by the sulfonated PET-g-GMA fine ion exchange fibers, magnesium ion is slower than calcium ion in the solution. However, in the mixture of the calcium and magnesium ions, the adsorption rate of calcium ion was much slower than that of magnesium ion.