• Applied Chemistry for Engineering
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• v.7 no.6
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• pp.1156-1163
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• 1996

This study is related to the investigation of the characteristics of quaternary ammonium salt catalyst on the addition reaction of carbon dioxide and glycidyl methacrylate(GMA) to form(2-oxo-1,3-dioxolane-4-yl)methacrylate(DOMA). Among the salts tested, the ones with higher alkyl chain length and with more nucleophilic counter anion showed a higher catalytic activity. Mixed catalysts of NaI and 18-crown-6 showed a good yield of DOMA, but when they are used alone, they showed no catalytic activity. The DOMA monomer was obtained in low polar solvents, while poly(DOMA) could be directly synthesized in aprotic dipolar solvents. Kinetic studies carried out by measuring $CO_2$ pressure in a high pressure batch reactor showed that the reaction rate was first order to the concentration of GMA and $CO_2$ respectively. The rate constant(k) was 0.56L/mol hr and Henry's constant(H') of $CO_2$ in diglyme at $80^{\circ}C$ was $6.5{\times}10^{-4}mol/L{\cdot}kPa$.

• Applied Chemistry for Engineering
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• v.5 no.4
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• pp.698-705
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• 1994

The basic medium oil modified alkyd resin was synthesized from linseed oil fatty acid(LOFA), phthalic anhydride(PAA), maleic anhydride(MA) and trimethylol propane(TMP) by condensation polymerization at $230^{\circ}C$. MA/TMPTA modified water-reducible alkyd resins were synthesized with TMPTA graft copolymerization onto the basic resin at $180^{\circ}C$. Acid value of the resin was controlled by the addition amount of MA and N,N-dimethylethanol amine(DMEA) was used as a neutralizing agent to prepare of the water-reducible alkyd resin. The effect of TMPTA on the graft copolymerization of the resin was studied by measuring molecular weight glass transition temperature(Tg), viscosity, graft efficiency, and gel contents of melanin cured film. Heat resistance, UV resistance and water resistance of cured film of MA/TMPTA modified resin was compared to those of TMA/TMPTA modified alkyd resin. The molecular weight, viscosity gel contents and graft efficiency of water reducible alkyd resin were increased according to the TMPTA graft copolymerization, but Tg was decreased. The viscosity was lower when the solid contents reached 40% than that of 30% content and also and also became lower with the extent of neutralization ratio, The heat resistance, UV resistance and water resistance of the MA/TMPTA modified alkyd resis were better than those of TMA/TMPTA modified alkyd resin but the storage stability of the TMA/TMPTA alkyd resis was better than that of MA/TMPTA modified alkyd resin.

• Korean Journal of Food Science and Technology
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• v.35 no.3
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• pp.373-378
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• 2003

This research was conducted to investigate the possibilities of usage of rose (Rosa hybrida L. cv. Mary Devor) by examining th antioxidative and antimicrobial activities of extracts with various levels of ethanol concentrates. Proximate composition, dietary fiber, and flavonoids contents were analyzed, and total antioxidant status and yield ratios of extraction of rose were measured. The rose extracts were extracted in different level of ethanol concentrates (0, 75, 85, 95%), and peroxide value, acid value, and TBA value were investigated in different level of concentrates of extracts added and time duration of storage. The results were as follows; derivation period from measuring peroxide value showed that the rose (Petal & Calyces) extract-added group showed longer derivation period than the control group, tocopherol-added, or BHT-added groups, and it proved to be a highly effective antioxidant as a result. It showed the longest derivation period especially when 85% ethanol extract was added with concentration of 0.05%. For the acid values and TBA values of the extract added oil, the rose extract-added group and BHT-added group showed lower values than the control group and tocopherol-added group as th length of time for storage becomes longer. In fact, the rose extracts suggested the possibility to be used as a natural antioxidants as it showed high antioxidative effect similar to BHT. Overall, the rose extracts from each solvent showed high antimicrobial effects against Escherichia coli, Salmonella typhimurium, Staphylococcus aureus than control group. Especially, 85% ethanol extract showed significantly high antimicrobial effect against Escherichia coli.

• The Journal of Korean Academy of Prosthodontics
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• v.43 no.1
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• pp.78-94
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• 2005

Purpose. The purpose of this study was to compare the effects of various surface treatments by measuring resonance frequency and histomorphometric analyses. Material and methods. In 5 adult dogs, the mandibular premolar were extracted. Six months later, 30 screw titanium implants (Dentium Co., Seoul, Korea) 6mm in length and 3.4mm in diameter, were placed in the mandibles of 5 dogs. Implants were divided into five groups following to surface treatment methods ; Group 1 is machined controls, Group 2 is sandblasted with large grit and acid-etched (SLA), Group 3 is anodized (Autoelectric Co., Korea, 660Hz, Duty10), Group 4 is hydroxyapatite(HA) coated by ion beam assisted deposition(E-beam), Group 5 is hydroxyapatite(HA) coated with Sol-gel coating process. Resonance frequency was measured implant placement immediately, and 3, 6 weeks and 10 weeks of healing perods. With the animal subject's sacrifice 10 weeks after implantation, implants were removed on bloc and histologic and computer-based histomorphometric analyses were performed. Histomorphometric analysis involved quantification of the entire bone to metal contact around the implants. Statistical analyses were performed using the SPSS for Windows (ver. 9.0 SPSS Inc.) Statistical differences were considered significant at P<0.05. Results. The results were as follows : 1) In five groups, mean value of resonance frequency analysis(RFA) were highest in group 5 (Sol-gel implant) at implantation and those of group 4 (E-beam)was highest at 10 weeks . but there was no correlation between surface treatments and RFA. 2) In all surface treatment groups, the RFA values of implants decreased until 3 weeks and increased to 10 weeks. 3) The percentage of direct bone-to-implant contact (BIC) had statistical significance between five groups in cancellous bone, (P<0.05) the percentage of bone density inside the thread had no statistical significance between five groups. (P>0.05) 4) There was a significant difference between cortical bone and cancellous bone in BIC. (P<0.05) and bone density. (P<0.05) 5) There was a correlation between the RFA value of implants at 10 weeks and BIC in cancellous bone, and between the RFA value of implants at 10 weeks and bone density in cortical bone. (P<0.05). Conclusions. These results indicate that surface treatment does not affect the implant stability in case of good bone quality.

• Journal of the korean academy of Pediatric Dentistry
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• v.45 no.1
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• pp.65-74
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• 2018

The aim of this study was to obtain the traceability of the software used to analyze lateral cephalometry and to calculate the uncertainty of the measurements. Furthermore, this study aimed to provide a basis for obtaining standard references for measurement values for orthodontic treatment in children. Cephalometric data were collected from 100 children diagnosed with class I malocclusion between the ages 6 to 13 years who visited the pediatric dentist at Seoul National University Dental Hospital. To ensure traceability, a phantom device was created. Correction values were calculated by measuring the length and angle of the phantom device using the software. Type A uncertainty was calculated by obtaining the standard deviation of cephalometric measurements of 100 persons and the standard error of repeated measurements. Determination of the type B uncertainty was induced by minimum resolution and the position of the head. Using these, the combined standard uncertainty was obtained and the expanded uncertainty was calculated. The results of this study confirm that the currently used software has high accuracy and reliability. Furthermore, the uncertainty of orthodontic measurements in Korean children aged 6 to 13 years was calculated, and distribution range for class I malocclusion with 95% confidence interval was suggested.

• Journal of the East Asian Society of Dietary Life
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• v.15 no.4
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• pp.386-396
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• 2005

The effects of spirulina-added salad dressing on lipid profiles and antioxidant biomarkers such as total glutathionine, TBARS value, carbonyl value, GPx, GR, SOD and paraoxonase activity in plasma or liver of mice were evaluated Sixteen male ICR mice weighing 20$\pm$2 g were divided into two groups and fed low fat ($5\%$ fat) diet (low fat control: LFC) and low fat control plus dressing diet (LFD) for eight weeks. Body weight, tissue weights of liver, heart and kidney, and the distribution of body fat deposition were not significantly different between two groups. Also, the profile of TG, TC, LDL and HDL cholesterol were similar between two groups. The DNA damage was determined using the comet assay (single cell gel assay) with alkaline electrophoresis and quantified by measuring tail length (TL). Spirulina salad dressing consumption resulted in significant decrease in lymphocyte DNA damage expressed by TL (LFC: $28.8{\mu}m$, LFD: $20.3{\mu}m$). Additionally, salad dressing consumption for 8 wks decreased the lipid peroxidation assayed by TBARS to $12.6\%$ compared with the control. The levels of antioxidant vitamins such as $\beta$-carotene were significantly higher in plasma of LFD group than those in LFC group based on HPLC method This study shows that spirulina-added salad dressing exerts degenerative disease-protective effects on oxidative DNA damage and lipid peroxidation possibly via a free radical levels.

• Journal of the Korean Chemical Society
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• v.60 no.3
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• pp.181-186
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• 2016

The hydrophilic ophthalmic lens with addition of 2-hydroxyethyl acrylate (HEA), 2-hydroxyethyl methacrylate (HEMA), hydroxypropyl methacrylate (HPMA) and Ag nanoparticles were manufactured. And also, the cross-linker ethylene glycol dimethacrylate (EGDMA) and the initiator azobisisobutyronitrile (AIBN) were used for polymerization. The polymerization of the hydrogel lens material was conducted through thermal polymerization in 100 ℃ for 1h. The optical and physical characteristics of hydrogel lens were evaluated by measuring water content, refractive index and optical transmittance. The water content of sample containing HEA, HEMA and HPMA was in the average of 82.12%, 37.06% and 21.57%, respectively. And also, refractive index of the sample containing HEA, HEMA and HPMA was in the average of 1.3540, 1.4330 and 1.4649, respectively. In case of the optical properties of the sample, the results showed that the near-UV transmittance was 82.67%, 80.32% and 79.83%, and the visible transmittance was 89.72%, 88.24% and 86.89%, respectively. And also, optical transmittance of the sample containing Ag nanoparticles showed that the near-UV transmittance of 10.59% and visible transmittance of 43.74% were obtained. From the results, the molecular length influenced on the water content and refractive index of the polymerized material.

• The Korean Journal of Pain
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• v.8 no.2
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• pp.298-303
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• 1995

We have inserted epidural catheter for single or continuous injection of a drug for epidural analgesia. It is important to localize the tip of epidural catheter in appropriate site to acquire the most effective analgesia. In epidural block, we observed course and location of the tip of epidural catheter. Subject: 70 patients were divided into group I(non-injection of saline group during catheter insertion) and group II(injection group during catheter insertion). Group I included cervical(n=20), thoracic(n=10), and lumbar(n=20) epidural group. Group II, cervical(n=10), and lumbar(n=10) epidural group. Method: 19G FlexTip $Plus^{TM}$ Epidural Catheter ($Arrow^{(R)}$) was inserted 10cm cephaladly in epidural space with(group II) or without(group I) saline flushing. We observed course and location of the tip of epidural catheter by C-arm image intensifier during injection of contrast media ($Omnipaque^{(R)}$). Result: In group I, the number of tips of epidural catheters located within 2 cm from inserted site were: cervical 14/20(70%), thoracic 2/10(20%). lumbar 16/20(80%). In thoracic epidural blocks, tips of epidural catheters were more cephaladly located than with cervical and lumbar epidural blocks. With cervical epidural blocks, the number of tips of epidural catheters located within 2 cm from insertion site were less in group II than group I (20% vs. 70%). But no significant differences were noted between group I and group II with lumbar epidural block(90% vs. 80%). The number of tips of epidural catheters located around a predicted site were: cervical 2/20(10%), thoracic 4/10(40%), lumbar 0/20(0%) in group I, and cervical 2/10(20%), lumbar 1/10(10%) in group II. Conclusion: It was impossible to predict the exact location of tips of epidural catheters by measuring the inserted length without epidurogram. With many cases, tips of epidural catheters were located around the insertion site in lumbar epidural blocks, and in some cases around the predicted site in thoracic epidural blocks. The results suggests that epidural block should be done at a point near the required band of analgesia.

• Restorative Dentistry and Endodontics
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• v.24 no.4
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• pp.578-584
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• 1999

The purpose of this experiment was to determine: (1) the safe automatic apical reverse setting that prevents overinstrumentation of the root canal, using Tri Auto ZX$^{(R)}$ and (2) the effect of various irrigant on such instrumentation. The instrumentation was carried out with the automatic apical reverse setting of 0.5, 1.0, 1.5, and 2.0. The root canal irrigants used in usual manner were normal saline(0.9%), NaOCl(2.5%), and RC Prep$^{(R)}$. For each reverse setting and each irrigant, ten teeth were used with the total of 120 teeth. The distance between the file tip and the apical constriction was determined by stereomicroscope using the point that the file began to rotate in reverse direction. When the reverse setting mode was set to 0.5, 18 of 30 were overinstrumented. If these were discriminated by irrigant, 10 of 6 with 0.9% saline, 10 of 6 with NaOCl, and 10 of 6 with RC Prep$^{(R)}$ has the file tip located 0.57${\pm}$0.30mm, 0.73${\pm}$0.39mm, and 0.26${\pm}$0.25mm beyond the apical constriction respectively. In 1.0 setting 15 of 29 were over the apical constriction, and the distribution was 6 in saline, 5 in NaOCl, and 4 in RC Prep$^{(R)}$. The mean distance over the apical constriction was 0.28${\pm}$0.13mm with saline, 0.75${\pm}$0.61mm with NaOCl, and 0.25${\pm}$0.17mm with RC Prep$^{(R)}$. When the autoatic reverse mode was set to 1.5, and 2.0, 5, and 1 teeth were found to be overinstrumented in respective settings. But there were large variations in overinstrumented distances when an attempt was made to compare the effect of irrigants on this overinstrumentations and they were meaningless for the small sample size. When all of the autoreverse setting were combined to compare the number of overinstrumented teeth with each irrigant, there were no significant differences (14 for normal saline, 12 for NaOCl, 13 for RC Prep$^{(R)}$). When 0.5 or 1.0 automatic apical reverse setting mode was used the Tri Auto ZX$^{(R)}$ in clinical application, the possibility of overinstrumentation beyond the apical constriction exists in 55.9% of cases. Therefore 1.5 or 2.0 setting is safer for the preparation inside the canal but this type setting needs additional apical hand preparation of the root canal because the accuracy is lower than 0.5 or 1.0 setting.

• Bulletin of the Society of Naval Architects of Korea
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• v.27 no.4
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• pp.58-66
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• 1990

A series of test was performed measuring the failure strength and failure mode of Gr/Pi, $[0^{\circ}/45^{\circ}/90^{\circ}/-45^{\circ}]_s$ laminate containing a single pin loaded hole. The finite element method is applied to calculate the stress distribution in the laminates, then the failure load and the failure mode were predicted by means of the characteristic length. 12 different geometric variations were developed to analyze the effects of the ratio of specimen width to hole diameter (W/d) and ratio of edge distance to hole diameter (L/d). X-Ray of NDE methods were utilized in finding out the initial defects, damage and the fracture mechanism, and SEM(Scanning Electron Microscopes) was used the evaluation of the fracture mechanism and crack propagation around hole under tension pin loading. $[0^{\circ}/45^{\circ}/90^{\circ}/-45^{\circ}]_s$ laminate are found to be most sensitive to W/d but not so influenced by L/d. The failure mode and tensile strength predicted by the model show agreement with experiment data for pin loading bolted jointed test except range of $L/d{\leqq}3$.