• Korean Journal of Materials Research
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• v.11 no.2
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• pp.137-145
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• 2001

A new process, gelcasting in aqueous medium, to fabricate complex-shaped ceramic core has investigated. The ceramic slurry, mixture of fused silica powder and additives such as zircon and cordierite, was electrosterically stabilizes. The slip was prepared by ball milling of polydispered ceramic suspension with monomer, dimer and dispersant. The rheological behavior of slip was evaluated by viscosity measurement. It was found that the high solid loading of polydispersed ceramic slip, which has low viscosity of 50vol%, is possible to obtained. The viscosity of the slip was significantly dependent upon the amount of polymer dispersant and the formulation of monomer and dimer. The green bodies were fabricated through casting and gelation at room temperature followed by drying at $25^{\circ}C$ for 48hrs under relative humidity of 80~85%. Crack-free green body was successfully fabricated through the above process.

• Journal of Electrochemical Science and Technology
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• v.12 no.2
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• pp.204-211
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• 2021

We report, synthesis of high surface area composite carbon aerogel using additive based polymerization technique by incorporating graphitic porous carbon as additive. This additive was separately prepared using sol-gel polymerization of resorcinol-furfuraldehyde in iso-propyl alcohol medium at much above the routine gelation temperature to yield porous carbon (CA-IPA) having graphitic layered morphology. CA-IPA exhibited a unique combination of meso-pore dominated surface area (~ 700 m²/g) and good conductivity of ~ 300 S/m. The composite carbon aerogel (CCA) was synthesized by traditional aqueous medium based resorcinol-formaldehyde gelation with CA-IPA as additive. The presence of CA-IPA favored enhanced meso-porosity as well as contributed to improvement in bulk conductivity. Based on the surface area characteristics, CCA-8 composition having 8% additive was found to be optimum. It showed specific surface area of ~ 2056 m²/g, mesopore area of 827 m²/g and electrical conductivity of 180 S/m. The electrode formed with CCA-8 showed improved electrochemical behavior, with specific capacitance of 148 F/g & ESR < 1 Ω, making it a better choice as super capacitor for energy storage applications.

• The Journal of Korean Academy of Prosthodontics
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• v.58 no.1
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• pp.23-29
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• 2020

Purpose: The purpose of this retrospective study was to evaluate the method using the S-reamer and gel-type graft material by the success rate and survival rate. Materials and methods: Implantation period was from 2008 to 2014, Follow check up year is 2019. There were 59 patients and 117 implants. All implants were placed in the posterior maxilla with the sinus lift. The patients population consisted of 34 men and 25 women, ranging from 19 to 75 years. The residual bone heights were from 1 mm to 6 mm. Sinus was perforated with S-reamer without membrane tearing and gel type bone graft material was used for membrane lifting and filling the space. all implants were placed simultaneously. Panoramic X-ray was taken. After 5 - 6 months healing period, final prostheses were restored. After more 5-years implant surgery, Panoramic X-ray was obtained and X-ray analysis and clinical examination were performed. Success criteria was referred to a Buser's success critera. All implants were classified to success implant, survival implant, failed implant. A success implant was satisfying success criteria, a survival implant was a implant that was acute infection with suppuration and bone loss, a failed implant was a implant that was mobile, removed. Results: Five implants were removed, and 4 implants had infected with bone loss. Survival rate was 95.7% and success rate was 92.3%. Conclusion: This retrospective study presented that this method with S-reamer and gel-type graft material was a successful treatment without membrane tear in the condition of 1-6 mm residual bone height.

• Applied Biological Chemistry
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• v.49 no.3
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• pp.170-174
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• 2006

For the purpose of developing a high quality agricultural microbial inoculant, methods and materials for improving encapsulation were investigated. Preparation of capsule was conducted by improving extrusion system with micro-nozzle and peristaltic pump. The sodium alginate was selected because of its cheapness, stability of cells, and gel formation ability. The yields, physical properties and gel formation abilities of extractable alginate from sea tangle were investigated by hot water extractable and alkali soluble methods. The extraction yields of hot water extractable alginate (HWEA) and alkali soluble alginate (ASA) from sea tangle were 8 and 20%, respectively. The HWEA was almost not viscous even in 1.5% of the sample solution, whereas the ASA was very highly viscous in above 3% sample solution. The gel formation ability of each samples varied from 1.5% to 5% and the ASA showed a good gel formation ability at 3% solution as commercial alginate (CA). The soil microbial inoculant, Bacillus thuringiensis, Bacillus subtilis, Lactobacillus plantarum and Geotrichum candidum encapsulated sodium alginate with starch and zeolite for stabilizer. The survivability of encapsulated soil microbial inoculant using alginate without stabilizer appeared to be 66, 52, 70 and 50%, respectively. Inclusion of starch and zeolite with alginate bead increased viabilities in Bacillus sp. and Geotrichum candidum by 81-83% and 89%, respectively.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.5 no.1
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• pp.104-118
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• 1995

This study was performed to evaluate factors affecting desorption of organic solvents collected on charcoal tube and to find out the optimum condition. Desorption efficiency for polar analytes was improved when several polar desorption solvents such as methanol, dimethylformamide(DMF), 2-(2-butoxyethoxy)ethanol were added to carbon disulfide($CS_2$). The best improvement was achieved when 10% dimethylformamide(DMF) in $CS_2$ was used as desorption solvent. During storage of polar analytes, recovery was greatly reduced. Especially, the recovery of cyclohexanone was decreased to 18.1 % after a month storage at $34^{\circ}C$. After two weeks storage, recovery of polar analytes was sharply decreased. Water adsorbed on charcoal interfered the recovery of polar analytes but didn't interfere that one of nonpolar solvent, toluene. When 10% DMF in $CS_2$ was used as desorption solvent, the effect of water on recovery was decreased, comparing with Desorption efficiency increased when analyte loading increased, and usage of 10% DMF in $CS_2$ decreased the loading effect. Increasing volume of desorption solvent was not effective to improve desorption efficiency of analytes when 10% DMF was used. Continuous shaking and sonication is not helpful to increase the desorption efficiency of analytes except cyclohexanone using 10% DMF. When silica gel used as adsorbent, methanol was better desorbent than dimethylsulfoxide. Analytes adsorbed on silica gel showed high recovery in low concentration and less affected by humidity. On the basis of this study, the following conclusions have been drawn. To improve the recovery of polar organic materials in air samples, it is necessary to analyze samples as soon as possible after they were collected. Otherwise, samples must be stored at low temperature. Using two components of desorption solvents, such as 10% DMF in $CS_2$, the effects of loading and humidity decreased for polar analytes such as methyl ethyl ketone and methyl isobutyl ketone. When work place has high humidity with low concentration of polar organic solvents, silica gel can be used as adsorbent, because it produces quantitative recovery for polar analytes at this condition. But it should be noted that high humidity makes breakthrough easy in silica gel samples.

• The Korean Journal of Urological Oncology
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• 제15권3호
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• pp.178-186
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• 2017

Purpose: Poloxamer 407 (P407) thermo-sensitive hydrogel formulations were developed to enhance the retention time in the urinary bladder after intravesical instillation. Materials and Methods: P407 hydrogels (P407Gels) containing 0.2 w/w% fluorescein isothiocyanate dextran (FD, MW 4 kDa) as a fluorescent probe were prepared by the cold method with different concentrations of the polymer (20, 25, and 30 w/w%). The gel-forming capacities were characterized in terms of gelation temperature (G-Temp), gelation time (G-Time), and gel duration (G-Dur). Homogenous dispersion of the probe throughout the hydrogel was observed by using fluorescence microscopy. The in vitro bladder simulation model was established to evaluate the retention and drug release properties. P407Gels in the solution state were administered to nude mice via urinary instillation, and the in vivo retention behavior of P407Gels was visualized by using an in vivo imaging system (IVIS). Results: P407Gels showed a thermo-reversible phase transition at $4^{\circ}C$ (refrigerated; sol) and $37^{\circ}C$ (body temperature; gel). The G-Temp, G-Time, and G-Dur of FD-free P407Gels were approximately $10^{\circ}C-20^{\circ}C$, 12-30 seconds, and 12-35 hours, respectively, and were not altered by the addition of FD. Fluorescence imaging showed that FD was spread homogenously in the gelled P407 solution. In a bladder simulation model, even after repeated periodic filling-emptying cycles, the hydrogel formulation displayed excellent retention with continuous release of the probe over 8 hours. The FD release from P407Gels and the erosion of the gel, both of which followed zero-order kinetics, had a linear relationship ($r^2=0.988$). IVIS demonstrated that the intravesical retention time of P407Gels was over 4 hours, which was longer than that of the FD solution (<1 hour), even though periodic urination occurred in the mice. Conclusions: FD release from P407Gels was erosion-controlled. P407Gels represent a promising system to enhance intravesical retention with extended drug delivery.

• Journal of dental hygiene science
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• v.23 no.4
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• pp.351-360
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• 2023

Background: The purpose of this study is to investigate the tooth whitening effect of Listerine Healthy White and provide effective management of extrinsic discoloration by comparing the whitening effects of existing whitening products. Methods: The included study four groups: those using whitening gel, whitening toothpaste, and Listerine Healthy White and a control using artificial saliva. Each group received 40 bovine tooth specimens, which were stained with commonly consumed tooth-coloring-inducing foods; black tea, black coffee, and instant noodles for 72 hours. The specimens were treated with tooth whitening materials for 5 weeks, after which the lightness (L^*) was measured weekly using a spectrophotometer. Results: There was a significant difference in lightness among the groups between the 1st and 5th week of treatment for all tooth-coloring-inducing foods (p<0.05). When comparing the changes in lightness values from before whitening to the 5th week of whitening for all tooth-coloring-inducing foods, the order of change was as follows: whitening gel, whitening toothpaste, Listerine Healthy White, and artificial saliva. Listerine Healthy White showed a significant whitening effect for all tooth-coloring-inducing foods (p<0.05). Particularly, changes in lightness values for specimens stained by black tea after 5 weeks of whitening were in the following order: whitening gel (21.72), whitening toothpaste (14.89), Listerine Healthy White (12.91), and artificial saliva (3.85). For specimens stained by black coffee, the changes in lightness values were in the following order: whitening gel (12.99), whitening toothpaste (9.66), Listerine Healthy White (7.91), and artificial saliva (3.12). Lastly, changes in lightness values for specimens stained by instant noodles were as follows: whitening gel (10.84), whitening toothpaste (9.85), Listerine Healthy White (7.71), and artificial saliva (2.61). Conclusion: Listerine Healthy White exhibits continuous whitening effects over time, and for consumers seeking convenient ways to achieve tooth whitening effects at home, consistent use of Listerine Healthy White is recommended.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.2A
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• pp.129-136
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• 2011

Recently studies on functional concrete with a photocatalytic material such as $TiO_2$ have actively been carried out in order to remove air pollutants. The absorbtion of $TiO_2$ from those studies is applied by it being directly mixed into concrete or by suspension coated on the surface. When it comes to the effectiveness, the former process is less than that of the latter compared with the $TiO_2$ use. As a result, the direct coating of $TiO_2$ on materials' surface is more used for effectiveness. The Surface spread of it needs to have a more than $400^{\circ}C$ heat treat done to stimulate the activation and adhesion of photocatalysis. Heat treat consequently leads hydration products in concrete to be dehydrated and shrunk and is the cause of cracking. The study produces $TiO_2$ used Sol-gel method which enables it to be coated with a low temperature treat, applies it to pearlite using Lightweight Aggregate Concrete fixed with a low temperature treat and evaluates the spread performance of it. In addition to this, the size of pearlite is divided into two types: One is 2.5 mm to 5.0 mm and the other is more than 5.0 mm for the benefit of finding out the removal characteristics of $CH_3CHO$ whether they are affected by pearlite size, mixing method and ratio with $TiO_2$ and elapsed time. The result of this experiment shows that although $TiO_2$ produced by Sol-gel method is treated with 120 temperature, it maintains a high spread rate on the XRF(X ray Florescence) quantitative analysis which ranks $TiO_2$ 38 percent, $SiO_2$ 29 percent and CaO 18 percent. In the size of perlite from 2.5 mm to 5.0 mm, the removal characteristic of $CH_3CHO$ from a low temperature heated Lightweight concrete appears 20 percent higher when $TiO_2$ with Sol-gel method is spreaded on the 7 percent of surface. In other words, the removal rate is 94 percent compared with the 72 percent where $TiO_2$ is mixed in 10 percent surface. In more than 5.0 mm sized perlite, the removal rate of $CH_3CHO$, when $TiO_2$ is mixed with 10 percent, is 69 percent, which is similar with that of the previous case. It suggests that the size of pearlite has little effects on the removal rate of $CH_3CHO$. In terms of Elapsed time, the removal characteristic seems apparent at the early stage, where the average removal rate for the first 10 hours takes up 84 percent compared with that of 20 hours.

• Radiation Oncology Journal
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• v.20 no.3
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• pp.264-273
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• 2002

Purpose : Three-dimensional radiation dosimetry using magnetic resonance imaging of polymer gel was recently introduced. This dosimetry system is based on radiation induced chain polymerization of acrylic monomers in a muscle equivalent gel and provide accurate 3 dimensional dose distribution. We planned this study to evaluate the clinical value of this 3-dimensional dosimetry. Materials and Methods: The polymer gel poured into a cylindrical glass flask and a spherical glass flask. The cylindrical test tubes were for dose response evaluation and the spherical flasks, which is comparable to the human head, were for isodose curves. T2 maps from MR images were calculated using software, IDL. Dose distributions have been displayed for dosimetry. The same spherical flask of gel and the same irradiation technique was used for film and TLD dosimetry and compared with each other. Results : The R2 of the gel respond linearly with radiation doses in the range of 2 to 15 Gy. The repeated dosimetry of spherical gel showed the same isodose curves. These isodose curves were identical to dose distributions from treatment planning system especially high dose range. In addition, the gel dosimetry system showed comparable or superior results with the film and TLD dosimetry. Conclusion : The 3-dimensional dosimetry for conformal radiation therapy using MRI of polymer gal showed stable and accurate results. Although more studies are needed for convenient clinical application, it appears to be a useful tool for conformal radiation therapy.

• Journal of Food Hygiene and Safety
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• v.27 no.3
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• pp.271-276
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• 2012

This study intented to standardize the method for total polysaccharide, which is a functional marker for aloe vera gel in Korea. We used four lyophilized raw materials and commercial aloe gel products, certified as Health Functional Food by Korea Food and Drug Administration, including powder, solution, jelly, tablet and capsule, to optimize the analytical condition of dialysis and phenol-sulfuric acid reaction in polysaccharide analysis. The optimal conditions for polysaccharide analysis included 1 L water for dialysis and change 3 times for 24hr against 25 mL prepared sample solution. Validation test showed lower than 5% of coefficient of variation(CV) in intra-, interday validation in lyophilized raw materials and 4 types of commercial products. In inter-person and inter-laboratory validation with 4 persons from 4 different laboratories, CV(%) were 5.50 and 6.64 respectively. The linearity of polysaccharide analysis was assessed using 5 serial concentration of lyophilized raw materials(0.1, 0.2, 0.3, 0.4, 0.5%(w/v)). The results showed $R^2{\geq}0.995$ of high linearity. In the commercial aloe vera gel products, the results of reproductivity showed lower than 7.08% and revealed that the standardized method from this study ensured high precision for polysaccharide analysis.