• 대한치과보철학회지
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• 제43권2호
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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.

• 자원리싸이클링
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• 제26권6호
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• pp.84-90
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• 2017

저품위 동 함유 슬러지로부터 회수된 동 조금속을 황산구리 전해액에서 전해정련을 수행하여 고순도 동을 회수하고자 하였다. 유기첨가제 종류 및 농도에 따른 전해정련동 표면 형상 및 조도를 분석하였을 때, gelatin계 유기첨가제 5 ppm 및 thiol계 유기첨가제 5~10 ppm 혼합 조건에서 가장 우수한 표면 형상을 얻을 수 있었다. 건식환원공정을 통해 회수한 철(Fe), 니켈(Ni), 코발트(Co) 및 주석(Sn) 등의 불순물이 함유된 각 86.635, 94.969 및 99.917 wt.% 순도의 동 조금속을 사용하여 전해정련하였고, 순도 3N~4N급 전해정련동을 얻을 수 있었다. 동 조금속, 전해액, 전해정련동의 불순 원소 농도 및 동 순도 등의 분석을 통해, 순도 99.99 wt.% 이상 전해정련동을 회수할 수 있는 전해정련 공정시간 및 동 조금속 순도를 도출하였다.

• 한국식물학회:학술대회논문집
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• 한국식물학회 1987년도 식물생명공학 심포지움 논문집 Proceedings of Symposia on Plant Biotechnology
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• pp.133-148
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• 1987

Gibberellin(GA) 3-$\beta$ hydroxylation is very important for the shoot elogation in the higher plants, since only 3$\beta$-hydryoxylated GAs promote shoot elogation in several plants. Fluctuation of 3$\beta$-hydryoxylase activity was examined during seed maturation using two cultivars of , P. vulgaris, Kentucky Wonder (normal) and Masterpiece (dwarf). Very immature seeds of both cultivars contain high level of 3$\beta$-hydroxylase activity (per mg protein). Both cultivars showed maximum of enzyme activity (per seed) in the middle of their maturation process. Gibberellin 3$\beta$-hydroxylase catalyzing the hydroxylation of GA20 to GA1 was purified 313-fold from very early immature seeds of P. vulgaris. Crude soluble enzyme extracts were purified by 15% methanol precipitation, hydrophobic interaction chromatogrphy, DEAE ion exchange column chromatography and gel filtration HPLC. The 3$\beta$-hydroxylase activity was unstable and lost much of its activity duting the purification. The molecular weight of purified enzyme was extimated to be 42, 000 by gel filtration HPLC and SDS-PAGE. The enzyme exhibited maximum activity at pH 7.7. The Km values for [2.3-3H] GA20 and [2.3-3H]GA9 were 0.29 $\mu$M and 0.33 $\mu$M, respectively. The enzyme requires 2-oxoglutarate as a cosubstrate; the Km value for 2-oxoglutarate was 250 $\mu$M using 3H GA20 as a substrate. Fe2+ and ascorbate significantly activated the enzyme at all purification steps, while catalase and BSA activated the purified enzyme only. The enzyme was inhibited by divalent cations Mn2+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+ and Hg2+. Effects of several GAs and GA anaogues on the putrified 3$\beta$-hydroxylase were examined using [3H]GA9 and GA20 as a substrates. Among them, GA5, GA9, GA15, GA20 and GA44 inhibited the enzyme activity. [13C, 3H] GA20 was converted by the partially purified enzyme preparation to [13C, 3H]GA1, GA5 and GA6, which were identified by GC-MS, GA9 was converted only GA4, GA15 and GA44 were converted to GA37 and GA38, respectively. GA5 was epoxidized to GA6 by the preparation. This suggests that 3$\beta$-hydroxylation of GA20 and epoxidation of GA5 are catalyzed by the same enzyme in P, vulgaris.

• 접착 및 계면
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• 제2권3호
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• pp.9-15
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• 2001

표면 에너지가 낮아 접착이 어려운 EVA foam을 용해도 파라미터와 표면장력이 다른 용매로 표면처리하여 표면의 상태 변화를 SEM, 접촉각 측정 등으로 조사하였으며 표면의 변화가 접착력에 미치는 영향을 고찰하였다. Zismann plot에 의해 계산된 EVA foam의 임계표면장력 (${\gamma}_{c,0}$)은 27.08 dyne/cm이었다. 용매 처리에 의해 EVA foam 표면의 형태 및 임계포면장력이 변화하였으며 EVA foam의 팽윤도가 용해도 파라미터에 의해 영향을 받는 것에 비해 표면의 변화 정도는 용매의 표면장력에 더 크게 의존하였다. 표면의 변화는 용매의 표면장력 (${\gamma}_L$)이 EVA foam의 임계표면장력 보다 낮아 wetting이 잘될수록 커지는 것으로 나타났다. 용매 처리된 EVA foam을 접착한 결과 처리하지 않은 것에 비해 접착력이 600% 이상 크게 향상되었으며, ${\gamma}_c$가 프라이머의 ${\gamma}_{L,p}$에 근접하여 ${\gamma}_c/{\gamma}_{L,p}$가 1에 가까워질수록 접착력이 증가하였다.

• 한국환경보건학회지
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• 제44권1호
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• pp.55-62
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• 2018

Objectives: This study set out to measure the heavy metal concentrations in waste water produced in the casting pickling process at dental technical laboratories and examine the actual state of its treatment. Methods:The investigator measured the concentrations of each heavy metal at 55 dental technical laboratories using an inductively coupled plasma optical emission system. Results: The annual usage of electrolytes was under 10 L in 50 (90.9%), and was 10L or more in five (9.1%) laboratories. Among the laboratories, 15 (27.3%) commissioned the treatment of waste,12 (21.8%) treated the waste with general sewage,and 28 (50.9%) treated the waste in aseptic tank. The arithmetic $mean{\pm}standard$ deviation and the geometric mean of chrome(Cr) were $75.3{\pm}50.9$ and 58.3 mg/L; those of cobalt (Co) were $112.3{\pm}106.7$ and 66.1 mg/L; those of nickel (Ni) were $62.9{\pm}83.5$ and 8.9 mg/L; those of molybdenum (Mo) were $17.1{\pm}13.4$ and 12.0 mg/L; those of iron (Fe) were $31.5{\pm}44.1$ and 6.2 mg/L; those of lead (Pb) were $0.3{\pm}0.3$ and 0.3 mg/L; those of beryllium (Be) were $3.6{\pm}3.6$ and 2.0 mg/L. The hydrogen ion concentration was under pH 2 across all the samples. Conclusions: The findings show that the dental technical laboratories were not doing well with the separation, storage, collection, and treatment of the electrolytes they discarded, and that most of the electrolytes were introduced through the general sewage or aseptic tank. The causes of this include alack of perception among the practitioners at dental technical laboratories and contracted companies avoiding collection for economic reasons. There is a need for education to improve the perceptions of waste water treatment among the practitioners at dental technical laboratories. Environment-related departments should be stricter with legal applications in the central and local governments. It is also required to provide proper management of commissioned treatment.

• 한국환경보건학회지
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• 제44권1호
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• pp.63-75
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• 2018

Objectives: The aim of this research is to explore the total heavy metals from a coal-fired power plant burning bituminous coal with wood pellets due to the implementation of the Renewable Portfolio Standard policy (RPS, 10% of electricity from renewable energy resources by 2023). Methods: The research was carried out by collecting archival data and using the USEPA's AP-42 & EMEP/EEA compilation of emission factors for use in calculating emissions. The Monte Carlo method was also applied for carrying out the calculations of measurement uncertainty. Results: In this paper, the results are listed as follows. Sb was measured at 110 kg (2015) and calculated as 165 kg (2019) and 201 kg (2023). Cr was measured at 1,597 kg (2015) and calculated as 1,687 kg (2019) and 1,728 kg (2023). Cu was measured at 2,888 kg (2015) and calculated as 3,133 kg (2019) and 3,264 kg (2023). Pb was measured at 2,580 kg (2015) and calculated as 2,831 kg (2019) and 2,969 kg (2023). Mn was measured at 3,011 kg (2015) and calculated as 15,034 kg (2019) and 23,014 kg (2023). Hg was measured at 510 kg (2015) and calculated as 513 kg (2019) and 537 kg (2023). Ni was measured at 1,720 kg (2015) and calculated as 1,895 kg (2019) and 1,991 kg (2023). Zn was measured at 7,054 kg (2015) and calculated as 9,938 kg (2019) and 11,778 kg (2023). Se was measured at 7,988 kg (2015) and calculated as 7,663 kg (2019) and 7,351 kg (2023). Conclusion: This shows that most heavy metals would increase steadily from 2015 to 2023. However, Se would decrease by 7.9%. This analysis was conducted with EMEP/EEA's emission factors due to the limited emission factors in South Korea. Co-firewood pellets in coal-fired power plants cause the emission of heavy metals. For this reason, emission factors at air pollution control facilities would be presented and the replacement of wood pellets would be needed.

• Journal of Microbiology and Biotechnology
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• 제14권3호
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• pp.584-592
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• 2004

A thermostable $\beta$-glycosidase gene, tfi $\beta$-gly, was cloned from the genomic library of Thermus filiformis Wai33 A1. ifi $\beta$-gly consists of 1,296 bp nucleotide sequence and encodes a polypeptide of 431 amino acids. It shares a strong amino acid sequence similarity with the $\beta$-glycosidases from other Thermus spp. belonging to the glycosyl hydrolase family 1. In the present study, the enzyme was overexpressed in Escherichia coli BL21 (DE3) using the pET21b(+) vector system. The recombinant enzyme was purified to homogeneity by heat treatment and a $Ni^{2+}$-affinity chromatography. Polyacrylamide gel electrophoresis (PAGE) showed that the recombinant Tfi $\beta$-glycosidase was a monomeric form with molecular mass of 49 kDa. The temperature and pH range for optimal activity of the purified enzyme were 80- $90^{\circ}C$ and 5.0-6.0, respectively. Ninety-three percent of the enzyme activity was remained at $70^{\circ}C$ after 12 h, and its half-life at $80^{\circ}C$ was 6 h, indicating that Tfi $\beta$-glycosidase is highly thermostable. Based on its K_m$, or $K_{cat}K_m$, ratio, Tfi $\beta$-glycosidase appeared to have higher affinity for $\beta$-D-glucoside than for $\beta$-D-galactoside, however, $K_{cat} for \beta$-D-galactoside was much higher than that for $\beta$-D-glucoside. The activity for lactose hydrolysis was proportionally increased at $70^{\circ}C$ and pH 7.0 without substrate inhibition until reaching 250 mM lactose concentration. The specific activity of Tfi TEX>$\beta$-glycosidase on 138 mM lactose at $70{^\circ}C$ and pH 7.0 was 134.9 U/mg. Consequently, this newly cloned enzyme appears to have a valuable advantage of conducting biotechnological processes at elevated temperature during milk pasteurization in the production of low-lactose milk.

• 한국해양환경ㆍ에너지학회지
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• 제5권1호
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• pp.51-67
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• 2002

경기도 서해안의 발달된 조간대 지역에 건설된 인공 호수인 시화호와 피 주변 하천 표층수 중의 중금속 거동을 이해하기 위하여 1996년부터 1998년까지 연구를 수행하였다. 반월 및 시화 공단, 도시 통의 다양한 인위적 오염원으로부터 극심한 오염물질 유입에 의해서 시화호와 주변 하천들은 중금속으로 오염되어 있었다. 하천과 공단 토구에서 유출수중의 용존성 중금속 농도와 입자성 중금속 농축계수는 매우 높게 나타났으며, 시ㆍ공간적인 변화 역시 크게 나타났다. 담수화 기간중 시화호 표층수의 중금속 공간분포는 산업 폐수 및 도시 하수의 유입 뿐 아니라 다양한 생지화학적 요인에 영향을 많이 밭으며, 유통의 제한으로 물리적인 혼합은 크게 작용하지는 않았다 또한 시화호는 담수화 중에 주변 환경에 의하여 중금속이 다량 축적되는 것으로 판단되며, 지속적인 환경 개선책이 마련되어야 할 것이다.

• 한국미생물·생명공학회지
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• 제12권4호
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• pp.277-283
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• 1984

제방 효모로 부터 분리 정제한 adenylate kinase 는 한개의 기질에 의해 또 하나의 기질 결합을ADP생성 반응에서는 4배, AMP와 Mg·ATP 생성에서는 2배 촉진되었다. 기질 특이성에 있어서는 nucleotide monophosphale일 경우 dAMP만이 활성을 보여주었으며 nucleotide triphosphate일 경우 ATP이외 UTP, ITP, GTP의 순위로 활성이 높았다. AMP와 Mg·ATP가 기질일 경우 과잉의 AMP는 pH 7.2와 pH8.0에서는 Mg·ATP에 경쟁적으로 저해하였으며 pH가 높을수록 그 Ki정수는 낮았다. Phosphoenolpyruvate는 AMP에 대해 경쟁적 Mg·ATP에 대해서는 비 경쟁적 저해제 이었으며 Adenosine pentaphosphoadenosine은 모든 기질에 대해 경쟁적 저해제로 작용하였다. 제빵 효모로부터의 adenylate kinase는 아미노산 조성에 있어서 동물의 Mitochondria형에 가까우며 Ito등의 결과와 일치하지 않았다. 상기와 같은 효소학적 성질을 종합 고찰한 결과 효모 adenylate kinase는 동물의 Mitochondria형 효소로 분류할 수 있으며 효모 adenylate kinase에 있어 연구자 상호간의 차이점은 사용한 균주의 차이에 기인하는 것으로 생각된다.

• Restorative Dentistry and Endodontics
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• 제33권5호
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• pp.435-442
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• 2008

제2형의 근관형태를 갖는 치아에서 각각의 근관을 모두 근관장까지 확대한 경우, 여러 확대기구에 따른 최종근관장파일의 크기를 상호 비교하여 얼마나 많은 변화가 있었는지를 분석하고자 치근 우식이 없고 치근단공 형성이 완료되었으며 2개의 근관 입구에서 시작하여 하나의 치근단공을 갖는 제 2형의 근관형태를 보이는 상악 소구치, 상악 대구치의 근심협측 치근 및 하악 대구치의 근심 치근을 선택하여 확대기구에 따라 KF군, PT군, HS군, K3군으로 분류하고 치경부 조기 확대를 시행하였다. 초기근관장파일이 15번 크기인 치아를 각 군당 20개씩 무작위로 선택하였고, 모든 근관을 각 군에 해당되는 30번 크기의 파일까지 제조회사의 지시에 따라 확대를 시행한 후, 촉감과 universal testing machine을 이용하여 최종근관장파일의 크기를 결정하였다. 각 군의 최종근관장파일의 크기와 제거 시 요구되는 힘의 크기에 대한 유의성 검증은 one-way ANOVA를 이용하여 비교 분석하였으며, 사후검정은 Tukey HSD test를 이용하여 0.05의 유의수준에서 분석하였다. 본 연구의 결과 제2형의 근관형태를 갖는 치아의 근관확대 시, 모든 근관을 각각의 근관장으로 확대하는 방법은 확대에 마지막으로 이용된 기구의 크기보다 한, 두 단계 정도 증가된 최종근관장파일을 나타냈다. 그러므로 제2형 근관형태를 나타내는 치아의 근관치료 시 임상가들은 근관충전에 앞서 치근단 받침을 다시 확인하고 형성하는 과정이 필요하리라 사료된다.