• Journal of dental hygiene science
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• v.8 no.2
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• pp.89-96
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• 2008

Effects of sodium fluoride exposure on the amelogenesis during fetal formation were investigated using 11 days rat incisor of control group and two experimental groups. According to results of morphological analysis using an electron microscope, enamel organ in the rat incisor consisted of presecretory, secretory, and maturation zone, especially maturation zone had ruffle-ended ameloblasts (rAB) that additionally supply inorganic ions and smooth-ended ameloblasts (sAB) that remove water and organic compounds. Such a histological composition was same in fetal and adult rats. According to experimental results using calcein (green fluorescence) in order to reveal the modulation cycle of ameloblast, modulation cycle of experimental group decreased on an average one time than control group, as increase of density of sodium fluoride indicated that thickness of smooth-ended ameloblast decreased. Also ratio of thickness on sagittal total length of sAB increased than rAB in experimental groups than control group. In total length of teeth, an injected 100 ppm sodium fluoride group was similar control group but as injected 200 ppm group became short. In experimental group, thickness of sAB and rAB became narrow to the tip of cutting edge. According to concentration of sodium fluoride grows, the modulation cycle and total length of teeth were decreased, finally it prevented teeth growth.

• Journal of dental hygiene science
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• v.16 no.4
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• pp.272-283
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• 2016

This study compared and analyzed the occluding effects of fluoride compounds and desensitizers, which are commonly used in dental clinics, on dentinal tubules. This study also evaluated the persistence of the active ingredients over time by performing toothbrushing with an electric toothbrush. Thirty-five molar teeth, which had been extracted within the past 3 months from healthy people without tooth decays, amalgam fillings, or dental crowns, were divided into 4 pieces each. Of these, 135 teeth pieces were used as study specimens. These specimens were divided into a control group, an untreated group, and 5 experimental groups (acidulated fluoride gel, fluoride varnish, Gluma, Super Seal, and SE-Bond). The specimens were then subjected to toothbrushing equivalent to 1 week (140 times), 2 weeks (280 times), and 4 weeks (560 times), and the occluding effects on dentinal tubules in 3 regions of each specimen were examined under a scanning electron microscope. The fluoride varnish treated group showed the highest degree of dentinal tubule occlusion effects during the first, second, and fourth weeks of toothbrushing, with the SE-Bond treated group showing the second highest degree and the Gluma treated group showing the lowest degree. After 4 weeks of toothbrushing, the Gluma treated group and the Super Seal treated group showed the lowest degrees of dentinal tubule occlusion effects. In summary, the fluoride varnish treated group and the SE-Bond treated group displayed higher occlusion effects even after 4 weeks of treatment than did the other experimental groups. Therefore, it is the authors' belief that fluoride varnish and SE-Bond are effective for treating dentinal hyperesthesia.

• Bulletin of the Korean Chemical Society
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• v.32 no.spc8
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• pp.3022-3030
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• 2011

Since the discovery of the fact that compounds bearing a vinylic fluoride moiety often exhibit remarkable biological activities such as enzyme inhibitors, many synthetic methods for fluorine-substituted vinylic compounds have been developed. The synthesis of selectively fluorinated building blocks, such as arylsubstituted fluoro-alkenes, also has become an area of interest in recent years. Herein we describe a novel and practical method for the synthesis of 1,1-difluoro- and 1-fluoroalkenes starting from easily accessible trifluoroacetophenone derivatives. Various 1,1-difluoro- and 1-fluoroalkenes were prepared by the reaction of the corresponding tosyl hydrazones that were derived from trifluoroacetophenone derivatives by treating with alkyl or aryllithium reagents via addition-elimination and single electron transfer (SET) mechanism.

• YAKHAK HOEJI
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• v.43 no.5
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• pp.566-571
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• 1999

(1H-1,2,4-Triazolyl) methy-4-(sub). phenyl-5-methyl-1,3-dioxolan-2-yliden (3) derivatives were synthesized and tested for their antifungal activities. The designed compounds with a 1,2,4-triazolylmethyl group at the 4-position of 1,3-dioxolan-2-yliden moiety were synthesized by reaction of difluorinated olefins(2) with (2R, 3R)-2-(2,4-dihalophenyl)-1-(1H-1,2,4-triazol-l-yl) butane-2,3-diol (1). These compounds were tested for in vitro antifungal activities against 16 fungi species. The MIC values were determined by the micro broth dilution method. In general, 1,3-dioxolan-2-yliden derivatives showed antifungal activities in vitro. Among them, (4R, 5R)-4-(2,4-difluorophenyl)-5-methyl-2-[1-(3,4-methylenedioxypheny)meth-ylidene)-1,3-dioxolon-4-yl(1H-1,2,4-triazollyl)methane showed superior antifungal activities to fluconazol and ketoconazol.

• Korean Journal of Environmental Biology
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• v.21 no.2
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• pp.158-163
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• 2003

This study was conducted te evaluate the effect of organotin compounds on rotifer(Brachionus plicatilis), which is important as food organism of aqua-cultured fish and shellfish. To evaluate the texicities of tributyltin compounds such as tributyltin chloride (TBTC), tributyltin oxide (TBTO), tributyltin acetate (TBTA) and tributyltin benzoate (TBTB), and triphenyltin compounds such as triphenyltin chloride (TPTC), triphenyltin fluoride (TPTF), triphenyltin hydroxide (TPTB), the survival rates of rotifer exposed to these compounds were measured as the 96 hr-$LC_{50}$. Exposed concentrations Were from 0.5 to 8 bbp depending on compounds. Based on 96 hr-$LC_{50}$ Value, the Order of toxicity in TBTs was TBTA(1.1 ppb)>TBTC (2.0)>TBTB (3.3)>TBTO(5.6), and that in TPTs was TPTF (1.0)$\geq$TPTC(1.1)>TPTH(1.6). Triphenyltin compounds were slightly higher toxic than tributyltins. The toxicity is likely to depend on alkyl or aryl group other than halogen or the other substituted radicals.

• Membrane and Water Treatment
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• v.11 no.2
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• pp.159-166
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• 2020

In this study, the performance and antifouling properties of polysulfone (PSf) and polyvinylidene fluoride/polyvinylpyrrolidone (PVDF/PVP) membranes in a membrane bioreactor (MBR) were investigated. The membranes were prepared via phase inversion method, and then characterized by a set of analyses including contact angle, porosity and water flux and applied in a lab-scale MBR system. Soluble microbial product (SMP), extracellular polymeric substance (EPS), FTIR, gel permission chromatography (GPC) and particle size distribution (PSD) analyses were also carried out for MBR system. The results showed that the MBR with PSf membrane had higher hydrophobic organic compounds which resulted in formation of larger flocs in MBR. However, in this MBR had high compressibility coefficient of cake layer was higher (n=0.91) compared to MBR with PVDF/PVP membrane (n=0.8); hence, the fouling was more profound. GPC analysis revealed that compounds with molecular weight lower than 2 kDa are more formed on PSf membrane more than PVDF/PVP membrane. The results of FTIR analysis confirmed the presence of polysaccharide and protein compounds on the cake layer of both membranes which was in good agreement with EPS analysis. In addition, the results showed that their concentration was higher for the cake on PSf membrane.

• Journal of Korean Society on Water Environment
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• v.28 no.1
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• pp.148-156
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• 2012

In this research, the application of carbon nanotubes (CNTs) modified PVDF (polyvinylidene fluoride) membrane was tested as a simply and beginning attempt to overcome membrane fouling because CNTs importantly affect the transport of natural organic matter (NOM). Suwannee River fulvic acid (SRFA) as the representative of NOM was selected and its sorption results with single-walled CNT (SWCNT), multi-walled CNT (MWCNT), and oxidized MWCNT (O-MWCNT) were obtained through the batch experiment. SRFA sorption isotherms had a strong nonlinearity and its sorption capacity followed the order O-MWCNT < MWCNT < SWCNT. The adsorbed mass of SRFA on each CNT decreased as a function of pH due to their charge repulsion. For the CNT-PVDF membrane filtration experiments, the suspended CNT solution (10 mg/40 mL) was incorporated into $0.45{\mu}m$-PVDF membrane and 5 mg/L of SRFA solution was monitored using UV detector connected with high pressure pump after passing through CNT-PVDF membrane. The SRFA removal efficiency by MWCNT-PVDF membrane was the strongest among other modified membranes. This suggests that the CNT modified microfiltration (MF) membrane might effectively and selectively apply to treat the contaminated water including organic compounds in the presence of NOM.

• Journal of the Microelectronics and Packaging Society
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• v.8 no.3
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• pp.63-67
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• 2001

Up to now, most studies about Pt-etching have been focused on physical sputtering mechanism with Cl-based plasma, while only a limited results are available for etching characteristics with fluorine-based plasma. In this study, etch characteristics of Pt thin film with $Cl_2$/Ar and $SF_{6}$/Ar Ar gas chemistries have been studied with ECR plasma etching system. It is confirmed that $SF_{6}$/Ar Ar plasma chemistry could make volatile etch-products through the reaction with Pt thin film. Also the improvement in etch rate, etch profile and surface roughness is obtained due to the formation of volatile platinum fluoride compounds.

• Journal of the Korean Society of Safety
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• v.11 no.3
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• pp.126-136
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• 1996

Synthesis of perfluoromethanesulfonyl fluoride(PFMSF) which is a valuable precursor of perfluoro-chemicals such as surface modifier and fine chemicals was studied by electrochemical fluorination (ECF). In order to determine the termination of preelectrolysis, it was carried to monitor the variation of current during preelectrolysis by means of constant cell voltage operation. In a batch cell, chronopotentiometric electrolysis and various chemical analysis such as GC, GC/MS and If were used to understand the potential change of electrode and synthesis and control of hazardous gases products. Termination of preelectrolysis was determinated by measurement the current and/or detection of $F_2$ gas generation. And during the preelectrolysis, an amount of generated $OF_2$ was shown that a lot of moisture was absorbed from air when a cell was filled with anhydrous hydrogen fluoride( AHF ). Above 4V cell voltage, $F_2$ gas was generated and acted on any form of fluorinating agents. In the ECF of MSC (methane sulfonyl chloride) by constant current operation, the potential of anode was intimately relation with generation of $SO_2F_2$. Exchange of Cl to F was dominatly occured in a initial stage. There were various gaseous products including PFMSF as main product and $C_4$ compounds.

• Journal of the korean academy of Pediatric Dentistry
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• v.47 no.4
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• pp.406-415
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• 2020

Silver diamine fluoride (SDF) is an effective and efficient agent for arresting dental caries. It can be useful in treating children with behavioral or medical limitations. The purpose of this study was to evaluate the antimicrobial effect of SDF by using salivary biofilm. Pellicle-like saliva coated structure was prepared by using unstimulated saliva. For developing cariogenic biofilm, Streptococcus mutans was added to the mixture of pooled saliva and inoculated into a saliva coated glass or chamber. SDF was applied to cariogenic biofilm to evaluate the antimicrobial effect of SDF. As time passed, total bacteria and S. mutans were reduced after application of SDF (p < 0.000). Confocal laser scanning microscope also showed the increment of the ratio of dead cell. As a result of experiment using enamel and dentin of primary teeth, it was confirmed that the growth of cariogenic biofilm was inhibited when the SDF was treated (p = 0.029 each). This study showed excellent anti-microbial effect of SDF. And anti-caries effect in clinical practice can be expected.