• 한국전기전자재료학회논문지
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• 제36권4호
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• pp.413-417
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• 2023

Gallium Oxide (Ga₂O₃) is preferred as a material for next generation power semiconductors. The Ga₂O₃ should solve the disadvantages of low thermal resistance characteristics and difficulty in forming an inversion layer through p-type ion implantation. However, Ga₂O₃ is difficult to inject p-type ions, so it is being studied in a heterojunction structure using p-type oxides, such as NiO, SnO, and Cu₂O. Research the lateral-type FET structure of NiO/Ga₂O₃ heterojunction under the Gate contact using the Sentaurus TCAD simulation. At this time, the VG-ID and VD-ID curves were identified by the thickness of the Epi-region (channel) and the doping concentration of NiO of 1×10¹⁷ to 1×10¹⁹ cm-3. The increase in Epi region thickness has a lower threshold voltage from -4.4 V to -9.3 V at I_D = 1×10^-8 mA/mm, as current does not flow only when the depletion of the PN junction extends to the Epi/Sub interface. As an increase of NiO doping concentration, increases the depletion area in Ga₂O₃ region and a high electric field distribution on PN junction, and thus the breakdown voltage increases from 512 V to 636 V at I_D =1×10^-3 A/mm.

• 대한화학회지
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• 제59권3호
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• pp.215-224
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• 2015

Unsymmetrical tetradentate Schiff base N-(2-hydroxy-5-methylacetophenone)-N'-(2-hydroxy acetophenone) ethylene diamine (H₂L) and its complexes with Cr(III), Mn(II), Fe(III), Co(II), Ni(II) and Cu(II) have been synthesized and characterized by elemental analyses, magnetic susceptibility measurements, IR, electronic spectra and thermogravimetric analyses. ¹H, ¹³C-NMR and FAB Mass spectra of ligand clearly indicate the presence of OH and azomethine groups. Elemental analyses of the complexes indicate that the metal to ligand ratio is 1:1 in all complexes. Infrared spectra of complexes indicate a dibasic quadridentate nature of the ligand and its coordination to metal ions through phenolic oxygen and azomethine nitrogen atoms. The thermal behavior of these complexes showed the loss of lattice water in the first step followed by decomposition of the ligand in subsequent steps. The thermal data have also been analyzed for the kinetic parameters by using Horowitz-Metzger method. The dependence of the electrical conductivity on the temperature has been studied over the temperature range 313-403 K and the complexes are found to show semiconducting behavior. XRD and SEM images of some representative complexes have been recorded. The antimicrobial activity of the ligand and its complexes has been screened against various microorganisms and all of them were found to be active against the test organisms. The Fe(III) and Ni(II) complex have been tested for the catalytic oxidation of styrene.

• Journal of Microbiology and Biotechnology
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• 제25권8호
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• pp.1281-1290
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• 2015

Thermolysin and its homologs are a group of metalloproteases that have been widely used in both therapeutic and biotechnological applications. We here report the identification and characterization of a novel thermolysin-like protease, BtsTLP1, from insect pathogen Bacillus thuringiensis serovar Sichuansis strain MC28. BtsTLP1 is extracellularly produced in Bacillus subtilis, and the active protein was purified via successive chromatographic steps. The mature form of BtsTLP1 has a molecule mass of 35.6 kDa as determined by mass spectrometry analyses. The biochemical characterization indicates that BtsTLP1 has an apparent K_m value of 1.57 mg/ml for azocasein and is active between 20℃ and 80℃. Unlike other reported neutral gram-positive thermolysin homologs with optimal pH around 7, BtsTLP1 exhibits an alkaline pH optimum around 10. The activity of BtsTLP1 is strongly inhibited by EDTA and a group of specific divalent ions, with Zn²⁺ and Cu²⁺ showing particular effects in promoting the enzyme autolysis. Furthermore, our data also indicate that BtsTLP1 has potential in cleaning applications.

• Korean Chemical Engineering Research
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• 제58권1호
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• pp.29-35
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• 2020

본 연구에서는 경피흡수가 잘 안되는 주름개선 펩티드인 GHK, GHK-Cu, Pal-GHK에 대하여 세포투과 펩티드인 알르기닌 올리고머(tetra-D-arginine, R4)와 hexa-D-arginine, R6)를 첨가한 후 경피 투과도를 측정하여 그 결과를 다음 6가지 경우로 분석하였다. 첫번째로 주름개선 펩티드만 함유한 경우는 구리이온(Cu₂⁺)과 팔미트산이 경피 투과율을 증진시키는 것을 알 수 있다. 두번째로, GHK에 알르기닌 올리고머(R4, R6)를 첨가한 경우는 알르기닌 올리고머(R4, R6)가 경피 투과율을 증가시켰으며, R4에서 더 좋은 경피 투과율 증가를 나타났다. 세번째로, GHK-Cu에 R4, R6를 첨가한 경우는 경피 투과율 증가가 나타났으며, R6 < R4 경피 투과율 순서로 나타났다. 네번째로 Pal-GHK에 R4, R6를 첨가한 경우에도 경피 투과율 증가가 나타났으며, R6 < R4 경피 투과율 순서로 나타났다. 다섯번 째로, R4를 GHK, GHK-Cu, Pal-GHK에 첨가한 경우에는 GHK+R4 < GHK-Cu+R4 < Pal-GHK+R4 순서로 경피 투과율 증가가 나타났다. 마지막으로 R6를 GHK, GHK-Cu, Pal-GHK에 첨가한 경우에는 GHK+R4 < GHK-Cu+R4 < Pal-GHK+R4 순서로 경피 투과율 증가가 나타났다. 이를 통하여 주름 개선 펩티드인 GHK, GHK-Cu, Pal-GHK의 피부 투과를 증가를 위한 최적의 조건을 제시하여 그 효능을 극대화할 수 있는 방안을 제시함으로써 주름 개선 기능성 화장품에서의 폭넓은 활용과 응용을 제안하고자 한다.

• 한국방사선학회논문지
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• 제9권5호
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• pp.295-300
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• 2015

현재 우리나라는 포항방사광가속기와 국립암센터의 양성자 치료용 가속기와 경주 양성자 가속기가 운영되고 있고 중이온 가속기, 4세대 방사광가속기 등 대형가속기 시설이 건설 중에 있다. 이들 시설에서 고에너지로 가속된 입사입자는 표적물질과 상호작용 후 2차 중성자를 발생시키고, 이 중성자는 가속기 구조물 및 주변 콘크리트, 토양, 지하수 등을 방사화 시킨다. 따라서 이러한 가속기 시설의 안전적 측면을 고려할 때 방사화를 일으키는 중성자의 차폐가 중요하다. 본 연구는 차폐해석에 사용되는 몬테카를로 코드 중 MCNPX를 이용하여 $^{12}C$ beam빔과 표적물질(Cu)과의 상호작용 후 생성되는 중성자를 계산하고, 그 중성자의 철 차폐체와 콘크리트 차폐체의 두께별 투과 후 스펙트럼을 MCNPX의 JENDL/HE 07과 la150을 이용해 비교하여 계산하였다. 빔의 방향과 차폐체의 종류 및 두께에 따라 그 결과를 실험값과 비교하여 검증함으로써 핵자료의 특성을 확인하였으며 향후 대형가속기시설의 선량평가용 기반기술로 활용하고자 하였다.

• Biotechnology and Bioprocess Engineering:BBE
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• 제5권5호
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• pp.366-371
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• 2000

The aim of this study was to investigate the efficiency of the pentagalloic acid compound in inhibiting the metal ions and cell lines that mediate in low density lipoprotein (LDL) oxidation. Pentagalloic acid prolonged the lag time preceeding the onset of conjugated diene formation. In chemically induced LDL oxidation by Cu$^2$(sup)+ plus hydrogen peroxide or peroxyl radical generated by 2, 2-azo-vis (2-amidino propane) hydrochloride (AAPH), pentagalloic acid inhibited LDL oxidation as monitored by measuring the thiobarbituric acid reactive substances(TBARS), malondialdehyde(MDA), and gel electrophoretic mobility. The physiological relevance of the antioxidative activity was validated at the cellular level where pentagalloic acid inhibited mouse macrophage J774 and endothelial cell-mediated LDL oxidation. When compared with several other antioxidants, pentagalloic acid showed a much higher ability than naturally occuring antioxidants, ${\alpha}$-tocopherol and ascorbic acid, and the synthetic antioxidant, probucol.

• 청정기술
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• 제22권3호
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• pp.175-180
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• 2016

본 연구에서는, 저온 및 약산성 조건에서 높은 활성을 보이는 티로시나아제인 tyrosinase-CNK의 반응 안정성을 조사하였다. Tyrosinase-CNK는 지금까지 알려진 중온성(mesophilic) 및 호열성(thermophilic) 환경 유래의 티로시나아제 보다는 열 안정성이 낮았으나 0 ℃에서 효소 안정성이 매우 뛰어났고, 반복적인 동결-해동(freeze-thaw) 과정에서도 효소 활성을 안정적으로 유지하였다. 또한, 물과 ethanol 및 acetonitrile이 혼합된 유기용매 환경에서 초기 상대 활성 값의 변화가 관찰되었으나 유기용매 농도의 증가로 인한 추가적인 활성 저하를 유발하지 않고 활성을 일정하게 유지하였다. 한편, 효소 반응의 염(salt)에 대한 저해는 chaotropic 특성이 많이 나타나는 염일수록 적게 나타났다. 결과적으로, tyrosinase-CNK는 통상의 티로시나아제를 이용하여 반응을 수행하기 어려운 환경에서도 원하지 않는 반응을 억제하고 효소 불활성화를 최소화면서 반응을 촉매할 것으로 기대된다.

• Journal of Microbiology and Biotechnology
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• 제30권5호
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• pp.689-699
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• 2020

Brevibacillus brevis GZDF3 is a gram-positive, plant growth-promoting rhizosphere bacterium (PGPR) isolated from the rhizosphere soil of Pinellia ternata (an important herb in traditional Chinese medicine). The GZDF3 strain produces certain active compounds, such as siderophores, which are the final metabolite products of non-ribosomal peptide synthetase (NRPS) and independent non-ribosomal peptide synthetase (NIS) activity. With the present study, we attempted to investigate the siderophore production characteristics and conditions of Bacillus sp. GZDF3. The antibacterial activity of the siderophores on pathogenic fungi was also investigated. Optimal conditions for the synthesis of siderophores were determined by single factor method, using sucrose 15 g/l, asparagine 2 g/l, 32℃, and 48 h. The optimized sucrose asparagine medium significantly increased the production of siderophores, from 27.09% to 54.99%. Moreover, the effects of different kinds of metal ions on siderophore production were explored here. We found that Fe³⁺ and Cu²⁺ significantly inhibited the synthesis of siderophores. The preliminary separation and purification of siderophores by immobilized-metal affinity chromatography (IMAC) provides strong antibacterial activity against Candida albicans. The synergistic effect of siderophores and amphotericin B was also demonstrated. Our results have shown that the GZDF3 strain could produce a large amount of siderophores with strong antagonistic activity, which is helpful in the development of new biological control agents.

• Carbon letters
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• 제18권
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• pp.49-55
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• 2016

Refuse-derived fuel (RDF) produced using municipal solid waste was pyrolyzed to produce RDF char. For the first time, the RDF char was used to remove aqueous copper, a representative heavy metal water pollutant. Activation of the RDF char using steam and KOH treatments was performed to change the specific surface area, pore volume, and the metal cation quantity of the char. N₂ sorption, Inductively Coupled Plasma-Atomic Emission Spectrometer (ICP-AES), and Fourier transform infrared spectroscopy were used to characterize the char. The optimum pH for copper removal was shown to be 5.5, and the steam-treated char displayed the best copper removal capability. Ion exchange between copper ions and alkali/alkaline metal cations was the most important mechanism of copper removal by RDF char, followed by adsorption on functional groups existing on the char surface. The copper adsorption behavior was represented well by a pseudo-second-order kinetics model and the Langmuir isotherm. The maximum copper removal capacity was determined to be 38.17 mg/g, which is larger than those of other low-cost char adsorbents reported previously.

• 한국환경보건학회:학술대회논문집
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• 한국환경보건학회 2003년도 Challenges and Achievements in Environmental Health
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• pp.177-180
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• 2003

A glassy carbon electrode(GCE) modified with nafion-DTPA-glycerol was used for the highly selective and sensitive determination of a trace amount of Cu$\^$2+/. Various experimental parameters, which influenced the response of nafion-DTPA-glycerol modified electrode to Cu$\^$2+/, were optimized. The copper(II) was accumulated on the electrode surface by the formation of the complex in an open circuit, and the resulting surface was characterized by medium exchange, electrochemical reduction, and differential pulse voltammetry, A linear range was obtained in the concentration range 1.0${\times}$10$\^$-8/M∼1.0${\times}$10$\^$-6/M Cu(II) with 7 min preconcentration. Further, when an approximate amount of lead(II) is added to the test solution, nafion-DTPA-glycerol modified glassy carbon electrode has a dynamic range of 2 orders magnitude(1.0${\times}$10$\^$-9/M∼1.0${\times}$10$\^$-7/M). The detection limit(3 $\sigma$) was as low as 5.0${\times}$10$\^$-6/M(0.032ppb). The interferences from other metal ions could be reduced by adding KCN into the sample solutions. This method was applied to the determination of coppe,(II) in certified reference material(3.23${\times}$10$\^$-7/M, 21ppb), sea water(9.50${\times}$10/sup-7/M, 60ppb). The result agrees satisfactorily with the value measured by Korea Research Institute of Standard and Science.