• Journal of dental hygiene science
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• v.12 no.3
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• pp.253-258
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• 2012

Dental amalgam is an alloy composed of a mixture of approximately equal parts of elemental liquid mercury and an alloy powder. Amalgam has been the most popular and effective restorative material used in dentistry. Despite the long history and popularity of dental amalgam as a restorative material, there have been periodic concerns regarding the potential adverse health effects arising from exposure to mercury in amalgam. Since children are more at risk for mercury toxicity, we aimed to assess the association between dental amalgam filling and urinary mercury concentration in children. 581 of elementary school children in grades 1st4th were conveniently recruited from two schools located in Daegu city, Korea. To obtain dental caries experience states, oral examination were conducted using the full term for DFS index, number of amalgam filling surfaces and the type of filling materials. A questionnaire was used to collect information about general characteristics and the frequencies of tooth brushing, gum chewing and fish/seafood consumption. The statistical analysis was done using the SPSS 18.0 program. The mean urinary mercury concentration in children having more surfaces was highest. As a results Urinary mercury concentration of children who have 79 teeth of amalgam filling and more than 10 is higher than without amalgam filling. The number of amalgam filling surface is closely related with urinary mercury concentration.

• Polymer(Korea)
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• v.30 no.6
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• pp.556-562
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• 2006

Quarternized poly(4-vinyl pyridine)s have been prepared by the reaction of poly (4-vinyl pyridine)s (Mw=50 kg/mol and 200 kg/mol) and alkylating agents varying the carbon numbers of the alkyl groups (m):dimethyl sulfate (m=1) as well as bromoalkane (m= 5, 8, 12, 16, and 22) was used as an alkylating agent. The degree of alkylation was determined by using an elemental analysis and NMR spectroscopy. As a result, polyelectrolytes were obtained by the almost full alkylation of poly (4-vinyl pyridine)s. The critical aggregation concentration (CAC) was determined by measuring the change of turbidity occurred by addition of sodium dodecyl sulfate (SDS) into aqueous solution of quarternized poly-(4-vinyl pyridine)s, and the dependence of molecular weight of polymer, the length of N-alkyl group and concentration of NaCl upon CAC was investigated. As a result, as the molecular weight or the length of alkyl group was increased, less amount of SDS Gould induce the aggregation.

• Journal of Life Science
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• v.27 no.4
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• pp.435-441
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• 2017

Perchlorate ($ClO_4^-$) is an emerging contaminant detected in soil, groundwater, and surface water. Previous study revealed bacterial community in the enrichment culture tdegraded perchlorate using elemental sulfur as an electron donor. Quantitative and qualitative molecular methods were employed in this study to investigate archaeal community in the enrichment culture. Real-time qPCR showed that archaeal 16S rRNA gene copy number in the culture was about 1.5% of bacterial 16S rRNA gene copy number. This suggested that less archaea were adapted to the environment of the enrichment culture and bacteria were dominant. DGGE banding pattern revealed that archaeal community profile of the enrichment culture was different from that of the activated sludge used as an inoculum for the enrichment culture. The most dominant DGGE band of the enrichment culture was affiliated with Methanococci. Further research is necessary to investigate metabolic role of the dominant archaeal population to better understand microbial community in the perchlorate-reducing enrichment culture.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.10
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• pp.1038-1045
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• 2006

A series of experiments was conducted to test the compatibilities of two different techniques to determine elemental concentrations by INAA and ICP-MS based on both the NIST SRM 2783(air particulate on filter media) and the field samples for PM10. For NIST SRM the results of INAA were more accurate and precise for all target elements than those of ICP-MS. The comparative data set for PM10 samples collected in an industrial complex area showed that mean of concentration ratio, derived for the two different methods such as C(INNA/ICP-MS), were distinguished from each other: (1) Ba, Cu, K Mg, Na, and Sb: $0.9{\sim}1.1$; (2) Al, Co, Fe, and Mn: $0.8{\sim}1.2$; and (3) Se, Ti, and Zn: >1.3. When the results obtained from both methods were evaluated in terms of regression analysis, paired t-test, and Wilcoxon signed-rank test, the results of many elements determined from PM10 samples(such as Al, Ba, Co, Cu, Fe, K, Mn, Nd, and Sb) exhibited a fairly good agreement between the two methods, despite a wide range of variation.

• Journal of the Korean Applied Science and Technology
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• v.33 no.1
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• pp.51-57
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• 2016

In this study, we synthesized reactive surfactant which have functional radical group for effective chemical reaction. Reactive surfactant have been synthesized using synthesis of polyoxyethylene lauryl ether(POE 23) which is nonionic surfactant and methacrylic acid, acrylic acid. benzene was used as the solvent, p-TsOH was used as the catalyst. synthesized surfactant was confirmed by FT-IR, $^1H$-NMR spectra, and elemental analysis. Evaluation of physical properties was measured HLB, cloud point, surface tension, the critical micelle concentration, emulsifying power. HLB number was evaluated 11.62 to 12.09 range. The Critical Micelle Concentration(cmc) values evaluated was $1{\times}10^{-4}{\sim}5{\times}10^{-4}mol/L$ by surface tension method. The cloud point was $35^{\circ}C$, $39^{\circ}C$ each. The emulsifymvcqa ing properties of the synthesized surfactants was lower than polyoxyethylene lauryl ether. In addition, soybean oil was better than benzene. The experimental results confirmed the ester bond, the yield of 93.27%, 94.49% was found.

• Journal of the Korean Chemical Society
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• v.35 no.4
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• pp.379-388
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• 1991

We synthesized the binuclear Tetradentate Schiff base cobalt (II) complexes; [Co(II)$_2$(SMPD)$_2$(L)$_2$] and [Co(II)$_2$(SPPD)$_2$(L)$_2$] (where, SMPD: N,N'-bis(salicylaldehyde)-m-phenylenediimine, SPPD: N,N'-bis(salicylaldehyde)-p-phenylenediimine, L: Py, DMSO and DMF). We identified the binuclear structure of these complexes by elemental analysis, IR-spectrum, and T. G. A. According to the results of cyclic voltammetry and DPP measurements in aprotic solvents containing 0.1M TEAP as supporting electrolyte, it was found that diffusionally controlled redox process of two step for one electron was reversible or quasi reversible process in 0.1M TEAP-pyridine and 0.1M TEAP-DMSO solution at mononuclear complexes; [Co(II)(SOPD)(L)$_2$]. But, we knew that diffusionally controlled reduction processes of four steps with one electron for binuclear [Co(II)$_2$(SMPD)$_2$(L)$_2$] and [Co(II)$_2$(SPPD)$_2$(L)$_2$] complexes was Co(III)$_2\;{\longrightarrow^e}$ Co(III)Co(II) ${\longrightarrow^e}$ Co(II)$_2\;{\longrightarrow^e}$ Co(II)Co(I) ${\longrightarrow^e}$ Co(I)$_2$ in aprotic solvents.

• The Journal of Korean Academy of Prosthodontics
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• v.43 no.2
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• pp.264-279
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• 2005

Statement of problem. Intraoral corrosion not only affects the esthetic and function of metallic dental restoration, but also has biologic consequences as well. Therefore, corrosion is considered a primary factor when choosing the dental alloy and laboratory technique. Purpose. The objective of this study was to compare the effects of solder and laser weld on corrosion Material and methods. Test specimens were made of 2 types of gold alloys, Co-Cr and Ni-Cr alloy and fabricated 3 methods, respectively: as cast, solder, and laser weld. For the analysis of corroding properties, potentiodynamic polarization test and immersion test conducted. The potentiodynamic polarization scan curve were recorded in 0.9% NaCl solution(pH 7) using Potentiostat/Galyanostat Model 273A. All specimens were exposed to 0.9% NaCl solution(pH 2.3) during 14 days. Elemental release into corrosive solution was measured by atomic emission spectrometry Differences in corrosion potential and mass release were determined using ANOVA. Results and conclusion. Through analyses of the data, following results were obtained. 1. In Pontor MPF and Wiron 99, corrosion potential of the solder group was statistically lower than as cast and laser weld group (p<0.05) , but there was no difference between corrosion potential of solder group and laser weld group in Pontor MPF and no differences between as cast and laser weld group (p>0.05). In Jel-Bios 10 and Wirobond, there was no difference of corrosion potential according to joining methods(p>0.05). 2. In all tested alloys, the amount of released metallic ion was greatest in the solder group(p<0.05). There was no difference between as cast group and laser weld group in Jel-Bios 10 and Wirobond(p>0.05). 3. In scanning electron microscopic examination. except soldered Wiron 99 specimens, it is impossible to discriminate the corrosive property of solder and laser weld. 4. Under the this experimental circumstances, laser weld appears superior to the solder when corrosion is considered.

• Journal of the Korean Chemical Society
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• v.36 no.3
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• pp.428-441
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• 1992

We synthesized a series of binuclear pentadentate Schiff base complexes such as $Co(Ⅱ)_2$ (BSPP)($H_2O)_2$, $Co(Ⅱ)_2$ (BSPD)($H_2O)_2$, $Mn(Ⅱ)_2$ (BSPP)($H_2O)_2$ and $Mn(Ⅱ)_2$ (BSPD)($H_2O)_2$, mononuclear pentadentate Schiff base complexes such as Co(Ⅱ)(BSP)($H_2O)$ and Mn(Ⅱ)(BSP)($H_2O)$. The composition of these complexes identified by IR, UV-visible spectrum, T.G.A., DSC, and elemental analysis. The electrochemical redox processes have been examined by cyclic voltammetry and differential pulse polarography with glassy carbon electrode in 0.1M TEAP-Py(-DMSO and -DMF) as a supporting electrolyte solution. As a result of electrochemical measurements, the reduction processes for pentadentate binuclear Schiff base cobalt(Ⅱ) and manganese(Ⅱ) complexes occurred to four steps in $M(Ⅲ)_2$ / $Mn(Ⅱ)_2$ and $Mn(Ⅱ)_2$ / $M(Ⅰ)_2$ (M; Co, Mn) two processes through each two reduction steps with one electron, by contrast, the mononuclear pentadentate Schiff base cobalt(Ⅱ) and manganese(Ⅱ) complexes occurred to two steps in M(Ⅲ) / M(Ⅱ) and M(Ⅱ) / M(Ⅰ) (M; Co, Mn) two processes with one electron reduction steps.

• Journal of the Korean Chemical Society
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• v.36 no.6
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• pp.872-878
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• 1992

Some vanadium(III) complexes have been prepared by the reaction of VCl3${\cdot}$3MeCN with ligands and characterized by elemental analysis, 1H-NMR, infrared and UV-Visible spectroscopy. 3,5-lutidine(lutd), 8-hydroxyquinoline(oxine), 1,2-phenylenediamine(phda), ethylenediamine(en), and sym-diphenylethylenediamine(dpen) were chosen as coordinating ligands. ${\nu}$(V-Cl) of lutidine complex occurs at 418 $cm^{-1}$ and the other complexes (oxine, phda, en, dpen) occur at 337∼347 $cm^{-1}$. The value of ${\nu}$(V-Cl) indicates that the former complex has trigonal bipyramid structure and the latter complexes have octahedral structure. The ${\nu}$(C${\equiv}$N) of acetonitrile in oxine and phda complexes are characteristically shifted to about 70 $cm^{-1}$ higher frequency compared with that of free ligand (2260 $cm^{-1}$). The ${\delta}$(C${\equiv}$N) is also shifted to about 60 $cm^{-1}$ higher frequency compared with that of free ligand (377 $cm^{-1}$). Finally each vanadium(III) complex showed the following formulation; [$VCl_3(lutd)_2$], [$VCl(oxine)_2$MeCN]$Cl_2$, [$VCl(phda)_2$MeCN]$Cl_2$, [$VCl_2(en)_2$]Cl, [$VCl_2(dpen)_2$]Cl.

• Journal of the Korean Chemical Society
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• v.39 no.12
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• pp.940-945
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• 1995

The SS-epm(N,N '-bis-[2(S)-pyrrolidinylmethyl]ethane-1,2-diamine) ligand having stereospecificity has been prepared and reacted with $CoCl_2{\cdot}6H_2O$ or trans-$[Co(pyridine)_4Cl_2]Cl.$ The resultants are green crystals, both of which are identified to be trans-$[Co(SS-epm)Cl_2]_2(COCl_4)$ by elemental analysis and absorption spectra. CD spectrum of trans complex shows negative (-) cotton effect at long wavelength due to the vicinal effect of the stereospecifically chelated ligands. The conformation of SS-epm in trans complex is ${\delta}{\lambda}{\delta}$(SRRS) for each of the five membered chelated ring. $Co(II)Cl_4^{2-}$ as counter ion plays an importance role in the ionic association of the formation of trans complex with SS-epm. Furthermore, according to orientation of secondary amine, total strain energy on each isomers was calculated by molecular mechanics (MM) to verify structural characterization and spectral data.