• Journal of the Korean Ceramic Society
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• v.35 no.11
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• pp.1212-1221
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• 1998

• Journal of Oral Medicine and Pain
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• v.20 no.1
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• pp.7-18
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• 1995

The Purpose of this article is to describe the biochemical properties and biological functions of several salivary proteins that possess the unusual properties of inhibiting spontaneous and secondary precipitation of calcium phosphate. This function is very important since human salivary secretion is supersaturated with respect to calcium phosphate. Biological function of statherin, proline rich protein (PRP) and histidine rich protein (HRP) is to inhibit precipitation of calcium phosphate in salivary glands, in the oral fluids, and onto tooth surfaces. The resulting supersaturated state of the salivary secretions contributes a protective and reparative environment which is important for the integrity of the tooth. Beneficial consequences of salivary supersaturation with respect to calcium phosphate are selectively expressed in the oral cavity- that is, protection is provided for the dental enamel-while undesirable consequences, for example, precipitation of calcium phosphates in the salivary glands and onto the teeth do not occur. Purification and structural characteristics of these proteins as well as clinical significance of functions of each protein will be discussed.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2004.09a
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• pp.219-222
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• 2004

Removal characteristics of Mn and Co was studied from the contaminated solutions via surface reaction with various calcium carbonate (calcite). Synthetic calcium carbonates which has different surface morphology as well as surface areas were prepared by a spontaneous precipitation method and used. Mn and Co removal behavior by the different solid surface demonstrate characteristic sorption behaviors depend on the type of calcite used, such as surface area or surface morphology. Calcium carbonate crystals (mostly calcite) which exhibit complicated surface morphology (c-type) shows strong sorption affinity for Mn and Co removal via sorption than on the a-type or b-type calcite crystals of less complicated surfaces. The applicability of two kinetic models, the pseudo-first-order kinetic equation and the Elovich kinetic model was examined on these sorption behavior. Elovich kinetic model was found more suitable to explain the very early stage adsorption kinetics, while the pseudo-first-order kinetic equation was successfully fitted for the adsorption kinetics after 50 hours.

• Journal of the Korean Ceramic Society
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• v.37 no.5
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• pp.473-478
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• 2000

The TiO2 powder with the values of the large specific surface area more than 150$m^2$/g has been prepared with the homogeneous precipitation process below 5$0^{\circ}C$ and its formation mechanism was investigated using the SEM, TEM and Raman Spectroscopy. With the spontaneous hydrolysis of aqueous TiOCl2 solutions, all the precipitates were fully and homogeneously crystallized with the rutile TiO2 phase simply by heating, which as transformed to the anatase TiO2 phase as increasing the addition of SO42- ions to the aqueous TiOCl2 solution. The precipitates were formed with spherical secondary particles which consisted of acicular, spherical and mixed primary particles corresponding to the rutile, anatase and mixed phases, respectively. It can be thought that the formation and phase determination of crystalline TiO2 powders even at ambient temperature would be related with the existence of the capillary force. This force might be varied depending on the shape change of the primary particles.

• Pediatric Gastroenterology, Hepatology & Nutrition
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• v.2 no.2
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• pp.262-266
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• 1999

Obstruction of the extrahepatic bile ducts is the most common cause of conjugated hyperbilirubinemia in early infancy. More than 90% of such obstructive lesions are accounted for by extrahepatic biliary atresia. A rare lesion is obstruction of the common duct by impacted, thickened secretions and bile. Bile plug syndrome is defined as extrahepatic obstruction of the bile ducts by bile sludge in term infants without anatomic abnormalities, congenital chemical defects of bile, or hepatocellular lesions. Obstruction of extrahepatic ducts by plugs of biliary material apperas to be due to the inspissation and precipitation of bile and mucus within the lumen of the ducts. Cholestasis and precipitation of bile develop in association with abnormal composition of bile in cystic fibrosis, hepatocellular damage, prolonged erythroblastic jaundice, altered biliary dynamics with total parenteral nutrition, gut dysfunction, diuretic therapy, exchange transfusions and perinatal hemolysis. In those cases, the term inspissated bile syndrome is used. The clinical and laboratory findings in bile plug syndrome are identical to those observed in biliary atresia and choledochal cyst. The diagnosis can be suspected based on the findings of clinical and laboratory examinations together with hepatobiliary imaging, ultrasonography, radionuclide scan and liver biopsy. We experienced a case of spontaneous resolution of bile plug syndrome in a 4-year-old girl. We report this case with brief review related literatures.

• Advances in environmental research
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• v.2 no.1
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• pp.35-49
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• 2013

Research work on removal of fluoride from water, referred to as water defluoridation, has resulted into the development of a number of technologies over the years but they suffer from either cost or efficiency drawbacks. In this work, enhancement effects of phosphate and silicate on defluoridation of water by low-cost Plaster of Paris (calcined gypsum) were studied. To our knowledge, the influence of silicate on defluoridation was not reported. It was claimed, that the presence of some ions in the treated water samples, was decreasing the fluoride removal since these ions compete the fluoride ions on occupying the available adsorption sites, however, phosphate and silicate ions, from its sodium slats, have enhanced the fluoride % removal, hence, precipitation of calcium-fluoro compounds of these ions can be suggested. Percentage removal of $F^-$ by neat Plaster is 48%, the electrical conductance (EC) curve shows the typical curve of Plaster setting which begins at 20 min and finished at 30 min. The addition of phosphate and silicate ions enhances the removal of fluoride to high extent > 90%. Thermodynamics parameters showed spontaneous fluoride removal by neat Plaster and Plaster-silicate system. The percentage removal with time showed second-order reaction kinetics.

• Journal of the Mineralogical Society of Korea
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• v.17 no.1
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• pp.11-21
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• 2004

Crystallization of CaC $O_3$ from the solutions of various degrees of supersaturation was carried out by a spontaneous precipitation method. The solution was kept at $25^{\circ}C$ and pH 6.9∼8.8. The solution compositions were varied in two ways: (1) The total carbonate, [C $O_3$]$_{Τ}$, to total calcium. [Ca]$_{Τ}$, ratios vary as ; [C $O_3$]$_{Τ}$/[Ca]$_{Τ}$ >1. [C $O_3$]$_{Τ}$/[Ca]$_{Τ}$=1, and [C $O_3$]$_{Τ}$/[Ca]$_{Τ}$<1. (2) The total calcium concentration, [Ca]$_{Τ}$, held at 0.02 mo1/d $m^3$, 0.2 mo1/d $m^3$, and 0.4 mo1/d $m^3$. We found that the CaC $O_3$ phase crystallized from the solutions of [C $O_3$]$_{Τ}$/[Ca]$_{Τ}$ $\geq$ 1 was mostly calcite with less than 1% of vaterite, while the CaC $O_3$ crystals precipitated from low carbonate concentration toward calcium concentration, [C $O_3$]$_{Τ}$/[Ca]$_{Τ}$ < 1, were dominated by vaterite crystals. It appears that the polymorph of CaC $O_3$ precipitate was mainly controlled not by the calcium concentration but by the carbonate concentration during the spontaneous precipitation. Also, we found that the surface roughness of vaterite increased with decreasing carbonate concentration from 0.8 or 0.5 of [C $O_3$]$_{Τ}$/[Ca]$_{Τ}$ ratios and the surface area of vaterite increased from 5.64∼7.34 $\mu\textrm{m}$ to 8.39∼10.3 $\mu\textrm{m}$.

• Restorative Dentistry and Endodontics
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• v.19 no.1
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• pp.27-44
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• 1994

The purpose of this study was to determine the effects of pH, temperature and time on the synthesis of hydroxyapatite(HAP) by spontaneous precipitation under relatively physiologic condition. Specimens were obtained from aqueous system with various pH, temperature and experimental time. Chemical composition, crystallographic structure and crystallinity of the synthetic HAP were evaluated by Infrared spectroscopy and powdered X-ray diffraction method. The following results were obtained. 1. No precipitate was obtained under pH 5.5. 2. All the specimens were concluded as HAP except one that was obtained under the condition of pH 6.5, $25^{\circ}C$ and 1 day. It was concluded as dicalcium phosphate dihydrate(DCPD). 3. The crystallinity of HAP was enhanced by increases in pH, temperature and time of the preparation. But, the crystallinity of the synthetic HAP was lower than that of the mineral HAP. 4. Intermediates such as DCPD and octacalcium phosphate were formed on the process of the synthesis of HAP.

• Membrane Journal
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• v.29 no.1
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• pp.61-65
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• 2019

Anisotropic particles have been issued in various fields due to their unique physical properties. Herein, a novel dynamic phase separation method (DPS) is introduced to fabricate anisotropic acorn-like nanoparticles. DPS consists of two dynamic conditions; solvent evaporation and nonsolvent induced precipitation. The bottom layer is controlled by feeding the water as a non-solvent diluent, and the phase separation of the upper layer relies on the diffusion and evaporation of a volatile good solvent. At this condition, the acorn-like particles were fabricated. Under a closed box filled with water (spontaneous phase separation), monodisperse polystyrene (PS) particles were synthesized. At the coexistence between DPS and spontaneous phase separation, the sizes of cap and particle were changed. Also, the volume of PS solutions influences on the particle shape. Since the unique structures could be utilized into various applications, if advanced techniques such as membrane-based controlled water feeding is developed, monodisperse acorn-like particles could be tuned.

• Journal of the Korean Chemical Society
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• v.54 no.1
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• pp.125-130
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• 2010

In the present work, we have investigated the adsorption efficiency of carbon/iron oxide nanocomposite towards removal of hazardous brilliant green (BG) from aqueous solutions. Carbon/iron oxide nanocomposite was prepared by chemical precipitation and thermal treatment of carbon with ferric nitrate at $750^{\circ}C$. The resulting material was thoroughly characterized by TEM, XRD and TGA. The adsorption studies of BG onto nanocomposite were performed using kinetic and thermodynamic parameters. The adsorption kinetics shows that pseudo-second-order rate equation was fitted better than pseudo-first-order rate equation. The experimental data were analyzed by the Langmuir and Freundlich adsorption isotherms. Equilibrium data was fitted well to the Langmuir model with maximum monolayer adsorption capacity of 64.1 mg/g. The thermodynamic parameters were also deduced for the adsorption of BG onto nanocomposite and the adsorption was found to be spontaneous and endothermic.