• Applied Chemistry for Engineering
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• v.27 no.3
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• pp.285-290
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• 2016

To improve properties of epoxy composites, surfaces of the illite and carbon nanotube (CNT) were treated by fluorine gas. The fluorinated illite and CNT were then characterized by X-ray photoelectron microscopy (XPS) and the mechanical and thermal properties of their composites were evaluated. The tensile and impact strengths and thermal stability of the composites increased upto about 59%, 18% and 124%, respectively compared to those of the neat epoxy. Improvements of mechanical and thermal properties in the composites were attributed that the fluorination of illite and carbon nanotube helps to enhance the dispersion in epoxy resin and interfacial interaction between them.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.4 no.2
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• pp.157-168
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• 1994

The surface morphology, electrical properties, and optical properties of textured $SnO_2(:F)$ films according to deposition parameters such as HF and $H_2O$ content was studies. The electron concentration, resistivity, and mobility was $3{\Times}10^{20}/cm^3$, $7{\Times}10^4~9{\Times}10^4{Omega}cm$ and $18~25cm^2/V.sec$, respectively, when HF bubbling rate over 0.9 slm. The surface morphology was sharp edged pyramid shape without bubbling $H_2O$ but changed to round edged hemispherical shape when $H_2O$ was added.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.6
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• pp.571-575
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• 2005

In order to improve the efficiency of dye-sensitized solar cell (DSSC), $TiO_2$ electrode screen-printed on transparent conducting oxide (TCO) substrate was sintered in variation with different temperature$(350\;to\;550^{\circ}C)$. $TiO_2$ electrode on fluorine doped tin oxide (FTO) glass was assembled with Pt counter electrode on FTO glass. I-V properties of DSSCs were measured under solar simulator. Also, effect of sintering temperature on surface morphology of $TiO_2$ films was investigated to understand correlation between its surface morphology and sintering temperature. Such surface morphology was observed by atomic force microscopy (AFM). Below sintering temperature of $500^{\circ}C$, efficiency of DSSCs was relatively lower due to lower open circuit voltage. Oppositely, above sintering temperature of $500^{\circ}C$, efficiency of DSSCs was relatively higher due to higher open circuit voltage. In both cases, lower fill factor (FF) was observed. However, at sintering temperature of $500^{\circ}C$, both efficiency and fill factor of DSSCs were mutually complementary, enhancing highest fill factor and efficiency. Such results can be explained in comparison of surface morphology with schematic diagram of energy states on the $TiO_2$ electrode surface. Consequently, it was considered that optimum sintering temperature of a-terpinol included $TiO_2$ paste is at $500^{\circ}C$.

• Research in Community and Public Health Nursing
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• v.15 no.4
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• pp.618-627
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• 2004

Purpose: To investigate the dental health status of kindergarten children according to their oral health behavior. Method: The subjects were 172 kindergarten children aged 5. A structured questionnaire was used for dental health behavior and oral health status were examined by dentist and bacteria in salivary. Result: 1. Mean score of oral health behavior of children was 4.69 points (SD1.65) with the highest score being 13. No significant differences were observed according to sex, except using tooth paste. A total 71.5% of subjects brushed their tooth twice a day, 9.9% of them once a day, 18.6% of them three times a day, 19.2% of children brushed their teeth after breakfast and lunch, 89.5% of then after dinner, 5.8% of them before going to bed, 18.6% of children brushed correctly, 79.7% of them used tooth paste with fluorine, 3.5% of them regularly examined oral cavity, 84.4% of them took cariogenic food without any restrain, 67.1% of them were observed with oral cavity by their mother. 2. Streptococcus mutans and lactobacilli in the saliva was $3.66({\times}106CFU/m{\ell})\;and\;1.05({\times}103CFU/m{\ell})$, respectively. No significant differences were observed according to sex, while lactobacilli were significantly lower in those children who had regular dental examinations. 3. The index of plaque was 1.56 and the boys were significantly higher than the girls. The mean dft was 4.99. No significant differences were observed according to sex, while the children whose oral cavity was observed regular were significantly lower than those who were not observed. Conclusion: As a whole the practice of oral health behavior of the kindergarten children was poor, and regular dental examinations and oral cavity observations affect their dental health status. These results suggest that intensive dental health education was needed not only for the pre-school children but also their parents and teachers.

• The Korean Journal of Nuclear Medicine
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• v.37 no.5
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• pp.331-335
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• 2003

Purpose: Accurate assessment of the lesion after treatment of patients with bone lymphoma is difficult. In this patient who demonstrated complete remission after chemotherapy, the regions of fluorine-18 fluorodeoxyglucose $(^{18}FFDG)PET$ uptake diminished more rapidly fellowing therapy, indicating a complete response at much earlier stage than did Magnetic Resonance Imaging (MRI) or CT based findings. With the conventional methods, such as MRI and CT, It was difficult to assess whether the residual tumor tissue was viable or not. Decision to complete response is very important in patients with lymphoma to plan the further treatment. We experienced a patient with primary lymphoma of bone who revealed complete response to chemotherapy on $^{18}FFDGPET$ while CT showed persistent destructive bone lesion. Thus, $^{18}FFDGPET$ study after therapy may be superior to CT in the evaluation of response to treatment in primary lymphoma of bone.

• The Korean Journal of Nuclear Medicine
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• v.33 no.6
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• pp.527-536
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• 1999

Purpose: Radiotracers that bind to the central benzodiazepine receptor are useful for the investigation of various neurological and psychiatric diseases. [C-11]Flumazenil, a benzodiazepine antagonist, is the most widely used radioligand for central benzodiazepine receptor imaging by PET. We synthesized 3-(2-[F-18]fluoro)flumazenil, a new fluorine-18 ($t_{1/2}$= 110 min) labeled analogue of benzodiazepine receptor imaging agent, and evaluated in vivo for biodistribution in mice. Materials and Methods: Flumazenil (Ro 15-1788) was synthesized by a modification of the reported method. Precursor of 3-(2-[F-18]fluoro)flumazenil, the tosylated flumazenil derivative was prepared by the tosylation of the ethyl ester by ditosylethane. [F-18] labeling of tosyl substitued flumazenil precursor was performed by adding F-18 ion at $85^{\circ}C$ in the hot ceil for 20 min. The reaction mixture was trapped by C18 cartridge, washed with 10% ethanol, and eluted by 40% ethanol. Bidistribution in mice was determined after intravenous injection. Results: The total chemical yield of tosylated flumazenil derivative was ${\sim}40%$. The efficiency of labeling 3-(2-[F-18]fluoro)flumazenil was 66% with a total synthesis time of 50 min. Brain uptakes of 3-(2-[F-18]fluoro)flumazenil at 10, 30, 60 min after injection, were $2.5{\pm}0.37,\;2.2{\pm}0.26,\;2.1{\pm}0.11$ and blood activities were $3.7{\pm}0.43,\;3.3{\pm}0.07,\;3.3{\pm}0.09%ID/g$, respectively. Conclusion: We synthesized a tosylated flumazenil derivative which was successfully labeled with no-carrier-added F-18 by nucleophilic substitution.

• The Korean Journal of Nuclear Medicine Technology
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• v.14 no.2
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• pp.104-109
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• 2010

Purpose: $[^{18}F]$Fallypride plays an effective radiotracer for the study of dopamine $D_2/D_3$ receptor occupancy, neuropsychiatric disorders and aging in humans. This tracer has the potential for clinical use, but automated labeling efficiency showed low radiochemical yields about 5~20% with relatively long labelling time of fluorine-18. In present study, we describe an improved automatic synthesis of [$^{18}F$]Fallypride using different base concentration for routine clinical use. Materials and Methods: Fully automated synthetic process of [$^{18}F$]Fallypride was perform using the TracerLab $FX_{FN}$ synthesizer under various labeling conditions and tosyl-fallypride was used as a precursor. [$^{18}F$]Fluoride was extracted with various concentration of $K_{2.2.2.}/K_2CO_3$ from $^{18}O$-enriched water trapped on the ion exchange cartridge. After azeotropic drying, the labeling reaction proceeded in $CH_3CN$ at $100^{\circ}C$ for 10 or 30 min. The reaction mixture was purified by reverse phase HPLC and collected organic solution was exchanged by tc-18 Sep-Pak for the clinically available solution. Results: The optimal labeling condition of [$^{18}F$]Fallypride in the automatic production was that 2 mg of tosyl-fallypride in acetonitrile (1 mL) was incubated at $100^{\circ}C$ for 10 min with $K_{2.2.2.}/K_2CO_3$ (11/0.8 mg). [$^{18}F$]Fallypride was obtained with high radiochemical yield about $66{\pm}1.4%$ (decay-corrected, n=28) within $51{\pm}1.2$ min including HPLC purification and solid-phase purification for the final formulation. Conclusion: [$^{18}F$]Fallypride was prepared with a significantly improved radiochemical yield with high specific activity and shorten synthetic time. In addition, this automated procedure provides the high reproducibility with no synthesis failures (n=28).

• The Korean Journal of Nuclear Medicine Technology
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• v.22 no.1
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• pp.51-54
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• 2018

Purpose $^{18}F-THK5351$ is the newly developed PET probe for tau imaging in alzheimer's disease. The purpose of study was to establish the automated production of $^{18}F-THK5351$ on a commercial module. Materials and Methods Two different approaches were evaluated for the synthesis of $^{18}F-THK5351$. The first approach (method I) included the nucleophilic $^{18}F$-fluorination of the tosylate precursor, subsequently followed by pre-HPLC purification of crude reaction mixture with SPE cartridge. In the second approach (method II), the crude reaction mixture was directly introduced to a semi-preparative HPLC without SPE purification. The radiosynthesis of $^{18}F-THK5351$ was performed on a commercial GE $TRACERlab^{TM}$ $FX-_{FN}$ module. Quality control of $^{18}F-THK5351$ was carried out to meet the criteria guidelined in USP for PET radiopharmaceuticals. Results The overall radiochemical yield of method I was $23.8{\pm}1.9%$ (n=4) as the decay-corrected yield (end of synthesis, EOS) and the total synthesis time was $75{\pm}3min$. The radiochemical yield of method II was $31.9{\pm}6.7%$ (decay-corrected, n=10) and the total preparation time was $70{\pm}2min$. The radiochemical purity was>98%. Conclusion This study shows that method II provides higher radiochemical yield and shorter production time compared to the pre-SPE purification described in method I. The $^{18}F-THK5351$ synthesis by method II will be ideal for routine clinical application, considering short physical half-life of fluorine-18 ($t_{1/2}=110min$).

• The Korean Journal of Nuclear Medicine Technology
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• v.15 no.1
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• pp.86-89
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• 2011

Purpose: The KOTRON-13 cyclotron was developed in South Korea and was introduced to regional cyclotron centers to produce short-lifetime medical radioisotopes. However, this cyclotron has limited capacity to produce carbon-11 isotope so far. We herein study how to develop and optimize an effective carbon-11 target system in the KOTRON-13 cyclotron by changing cooling system, combing with fluorine-18 target and evaluating beam currents. Materials and Method: To develop the optimal carbon-11 target and an effective cooling system, we designed the carbon-11 target system by Stopping and Range of Ions in Matter (SRIM) simulation program and considered the cavity pressure during irradiation at target grid. In this investigation, we evaluated the yield of carbon-11 production at different beam currents and the stability of the operation of the KOTRON-13 cyclotron. Results: The production of carbon-11 was enhanced from about 1.700 mCi ($50{\mu}A$) to 2,000 mCi ($60{\mu}A$) on the carbon-11 target which developed by seoul national university bundang hospital (SNUBH) and Samyoung Unitech. Additionally, the cooling condition was showed stable to produce carbon-11 under high beam current. Conclude: The carbon-11 target system of the KOTRON-13 cyclotron was successfully developed and improved carbon-11 production. Consequently, the operation of carbon-11 target system was highly effective and stable compare with other commercial cyclotrons. Our results are believed that this optimal carbon-11 target system will be helpful for the routine carbon-11 production in the KOTRON-13 cyclotron.

• Nuclear Medicine and Molecular Imaging
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• v.40 no.5
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• pp.263-270
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• 2006

Purpose: Several radioisotope-labeled thymidine derivatives such as $[^{11}C]$thymidine was developed to demonstrate cell proliferation in tumor. But it is difficult to track metabolism with $[^{11}C]$thymidine due to rapid in vivo degradation and its short physical half-life. 3'-$[^{18}F]$fluoro-3'-deoxythymidine ($[^{18}F]$FLT) was reported to have the longer half life of fluorine-18 and the lack of metabolic degradation in vivo. Here, we described the synthesis of the 3'-$[^{18}F]$fluoro-3'-deoxythymidine ($[^{18}F]$FLT) and compared with $([^{18}F]FET)\;and\;([^{18}F]FDG)$ in cultured 9L cell and obtained the biodistribution and PET image in 9L tumor hearing rats. Material and Methods: For the synthesis of $[^{18}F]$FLT, 3-N-tert-butoxycarbonyl-(5'-O-(4,4'-dimet hoxytriphenylmethyl)-2'-deoxy-3'-O-(4-nitrobenzenesulfonyl)-${\beta}$-D-threopentofuranosyl)thymine was used as a FLT precursor, on which the tert-butyloxycarbonyl group was introduced to protect N3-position and nitrobenzenesulfonyl group. Radiolabeling of nosyl substitued precursor with $^{18}F$ was performed in acetonitrile at $120^{\circ}C$ and deproteced with 0.5 N HCI. The cell uptake was measured in cultured 9L glioma cell. The biodistribution was evaluated in 9L tumor bearing rats after intravenous injection at 10 min, 30 min, 60 min and 120 min and obtained PET image 60 minutes after injection. Results: The radiochemical yield was about 20-30% and radiochemical purity was more than 95% after HPLC purification. Cellular uptake of $[^{18}F]$FLT was increased as time elapsed. At 120 min post-injection, the ratios of tumor/blood, tumor/muscle and tumor/brain were $1.61{\pm}0.34,\;1.70{\pm}0.30\;and\;9.33{\pm}2.22$, respectively. The 9L tumor was well visualized at 60 min post injection in PET image. Conclusion: The uptake of $[^{18}F]$FLT in tumor was higher than in normal brain and PET image of $[^{18}F]$FLT was acceptable. These results suggest the possibility of $[^{18}F]$FLT at an imaging agent for brain tumor.