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A Study on Manufacturing Technique and Alloy Characteristics of Bronze Mirrors from Jeollanam-do Region in the Three Kingdoms Period (전남지역 출토 삼국시대 청동거울의 합금 특성과 제작 방법 고찰)

  • Lee, Eun Ji
    • Journal of Conservation Science
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    • v.37 no.6
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    • pp.767-777
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    • 2021
  • This study analyzed the microstructures and chemical composition of three samples of bronze mirrors excavated in the Jeollanam-do region, particularly Goheung and Damyang. Under x-ray irradiation, the analysis results confirmed the broken parts and pores caused by cracks, casting, and corrosion. Major and minor elemental analysis were performed on three mirrors by Scanning electron microscopy (SEM) with Energy dispersive x-ray spectrometry (EDS) and Inductively coupled plasma mass spe ctrome try (ICP-MS). The re sult shows that the bronze mirrors containe d Cu-Sn-Pb alloys. Alpha phase and eutectic phase were observed in the microstructure, confirming that the casting was performed without additional heat treatment. Notably, Three bronze mirrors were made early Three Kingdoms period in Korea.

Effect of Zn/Al Cation Ratio on Corrosion Inhibition Capabilities of Hydrotalcites Containing Benzoate Against Carbon Steel

  • Thu Thuy, Pham;Anh Son, Nguyen;Thu Thuy, Thai;Gia Vu, Pham;Ngoc Bach, Ta;Thuy Duong, Nguyen;To Thi Xuan, Hang
    • Corrosion Science and Technology
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    • v.21 no.6
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    • pp.434-444
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    • 2022
  • Corrosion inhibitors based on Zn-Al hydrotalcites containing benzoate (ZnAlHB) with different molar ratios of Zn/Al were prepared with a co-precipitation process. Compositions and structures of the resulting hydrotalcites were studied with suitable spectroscopic methods such as inductively coupled plasma mass spectrometry (ICP-MS), ultraviolet-visible spectrophotometry (UV-Vis), scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and surface zeta potential measurements, respectively. Results of physico-chemical studies showed that crystallite sizes, compositions of products, and surface electrical properties were significantly changed when the molar ratio of Zn/Al was increased. The release of benzoate from hydrotalcites also differed slightly among samples. Anticorrosion abilities of hydrotalcites intercalated with benzoate at a concentration of 3 g/L on carbon steel were analyzed using electrochemical impedance spectroscopy (EIS), polarization curve, energy-dispersive X-ray spectroscopy (EDX), and SEM. Corrosion inhibition abilities of benzoate modified hydrotalcites in 0.1 M NaCl showed an upward trend with increasing Zn/Al ratio. The reason for the dependence of corrosion resistance on the Zn/Al ratio was discussed, including changes in the microstructure of hydrotalcites such as crystal size, density, uniformity, and formation of ZnO.

In Silico Analysis and Biochemical Characterization of Streptomyces PET Hydrolase with Bis(2-Hydroxyethyl) Terephthalate Biodegradation Activity

  • Gobinda Thapa;So-Ra Han;Prakash Paudel;Min-Su Kim;Young-Soo Hong;Tae-Jin Oh
    • Journal of Microbiology and Biotechnology
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    • v.34 no.9
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    • pp.1836-1847
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    • 2024
  • Polyethylene terephthalate (PET), one of the most widely used plastics in the world, causes serious environmental problems. Recently, scientists have been focused on the enzymatic degradation of PET, an environmentally friendly method that offers an attractive approach to the degradation and recycling of PET. In this work, PET hydrolase from Streptomyces sp. W2061 was biochemically characterized, and the biodegradation of PET was performed using the PET model substrate bis (2-hydroxyethyl terephthalate) (BHET). PET hydrolase has an isoelectric point of 5.84, and a molecular mass of about 50.31 kDa. The optimum pH and temperature were 7.0 and 40℃, respectively. LC-MS analysis of the enzymatic products showed that the PET hydrolase successfully degraded a single ester bond of BHET, leading to the formation of MHET. Furthermore, in silico characterization of the PET hydrolase protein sequence and its predicted three-dimensional structure was designed and compared with the well-characterized IsPETase from Ideonella sakaiensis. The structural analysis showed that the (Gly-x1-Ser-x2-Gly) serine hydrolase motif and the catalytic triad (Ser, Asp, and His) were conserved in all sequences. In addition, we integrated molecular dynamics (MD) simulations to analyze the variation in the structural stability of the PET hydrolase in the absence and presence of BHET. These simulations showed the formation of a stable complex between the PET hydrolase and BHET. To the best of our knowledge, this is the first study on Streptomyces sp. W2061 to investigate the BHET degradation activity of PET hydrolase, which has potential application in the biodegradation of plastics in the environment.

Influence of Heat Treatment on Transformation Characteristics and Shape Recovery in Fe-X%/Mn-5Cr-5Co-4Si Alloy Ribbons (Fe-X%Mn-5Cr-5Co-4Si 합금 리본의 변태특성 및 형상기억능에 미치는 열처리 영향)

  • Kang, H.W.;Jee, K.K.;Jang, W.Y.;Kang, J.W.
    • Journal of the Korean Society for Heat Treatment
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    • v.14 no.3
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    • pp.160-166
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    • 2001
  • The change of ribbon geometry, microstructure and shape recovery with Mn contents, wheel speed and various annealing temperature have been studied in Fe-X%Mn-5Cr-5Co-4Si (X%=15, 20, 24) shape memory alloy (SMA) ribbons rapidly solidfied by single roll chill-block melt-spinning process. The thickness and width of melt-spun ribbons are reduced, results in refining and uniformalizing grains with increasing wheel speed. In the ribbons melt-spun at a wheel speed of 15m/sec, both ${\varepsilon}$ and ${\alpha}^{\prime}$martensites are formed in ribbon 1 (15.5wt%Mn), while only ${\varepsilon}$ martensite is revealed in ribbon 2 (20.2wt%Mn) and ribbon 3 (23.5wt%Mn). The volume fraction of ${\varepsilon}$ martensite is decreased with increasing Mn contents, and those of ${\varepsilon}$ as well ${\alpha}^{\prime}$martensites are increased due to thermal stress relief and grain growth with increasing annealing temperature. Ms temperatures of the ribbons 1, 2 and 3 are fallen with increasing Mn contents. $M_s$ temperatures of the ribbons 1, 2 and 3 annealed at $300^{\circ}C$ for 3 min are risen abruptly, but are nearly constant even at higher annealing temperature, i.e., 400, 500 and $600^{\circ}C$ for 3 min. Shape recovery of the ribbons 1, 2 and 3 increased 30%, 52% and 69% with Mn contents, respectively. Shape recovery of ribbon 1 (15.5wt%Mn) formed ${\varepsilon}$ and ${\alpha}^{\prime}$martensites decreased because of the presence of ${\alpha}^{\prime}$martensite but those of ribbon 2 (20.2wt%Mn) and ribbon 3 (23.5wt%Mn) formed ${\varepsilon}$ martensite increased with increasing annealing temperature.

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Antioxidant Activities and Inhibitory Effect on Oxidative DNA Damage of Nelumbinis Semen Extracts (연자육 추출물의 항산화 및 산화적 DNA 손상억제 활성)

  • Park, Jae-Ho;Lee, Byung-Gu;Byun, Gwang-In;Kim, Do-Wan
    • The Korea Journal of Herbology
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    • v.25 no.4
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    • pp.55-59
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    • 2010
  • Objective : This study was conducted to investigate the antioxidant activity and inhibitory effect on oxidative DNA damage of Nelumbinis Semen Extracts Methods : Nelumbins semen were extracted with hot-water and ethylacetate (EtOAC). The 1,1-diphenyl-2-picrylhydrazyl (DPPH) and hydroxyl radical scavenging assay and $Fe^{2+}$ chelating assay were performed for antioxidative effect and ${\phi}X$-174 RF I DNA cleavage assay and intracellular DNA damage assay were used for inhibitory effect on intracellular DNA damage. Results : In DPPH, Hydroxyl radical scavenging activity and $Fe^{2+}$ chelating activity of EtOAC extracts were 96.22%, 53.53%, 64.72%, while those of hot-water extracts were 20.86%, 10.72%, 29.74% at $200{\mu}g/m{\ell}$, respectively. In ${\phi}X$-174 RF I plasmid DNA cleavage assay, the protective effects of EtOAC and hot-water extracts against oxidative DNA damage were 76% and 6% at $200{\mu}g/m{\ell}$, respectively. Conclusion : These results indicated that the seed extracts of Nelumbo nucifera can be used as a natural antioxidants, which effectively inhibits the oxidative DNA damage.

Electrochemical Behaviors of Pt-Ru Catalysts on the Surface Treated Mesoporous Carbon Supports for Direct Methanol Fuel Cells (직접메탄올 연료전지용 표면처리된 중형기공 탄소지지체에 담지된 백금-루테늄 촉매의 전기화학적 거동)

  • Kim, Byung-Ju;Seo, Min-Kang;Choi, Kyeong-Eun;Park, Soo-Jin
    • Applied Chemistry for Engineering
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    • v.22 no.2
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    • pp.167-172
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    • 2011
  • In this work, the effect of surface treatment on mesoporous carbons (MCs) supports was investigated by analyzing surface functional groups. MCs were prepared by a conventional templating method using mesoporous silica (SBA-15) for using catalyst supports in direct methanol fuel cells (DMFCs). The MCs were treated with different phosphoric acid ($H_3PO_4$) concentrations i.e., 0, 1, 3, 4, and 5 M at 343 K for 6 h. And then Pt-Ru was deposited onto surface treated MCs (H-MCs) by chemical reduction method. The characteristics of Pt-Ru catalysts deposited onto H-MCs were determined by specific surface area and pore size analyzer, X-ray diffraction, X-ray photoelectron, transmission electron microscopy, and inductive coupled plasma-mass spectrometer. The electrochemical properties of Pt-Ru/H-MCs catalysts were also analyzed by cyclic voltammetry experiments. From the results of surface analysis, an oxygen functional group was introduced to the surface of carbon supports. From the results, the H4M-MCs carbon supports surface treated with 4 M $H_3PO_4$ led to uniform dispersion of Pt-Ru onto H4M-MCs, resulting in enhancing the electro-catalytic activity of Pt-Ru catalysts.

Analysis of Image Distortion on Magnetic Resonance Diffusion Weighted Imaging

  • Cho, Ah Rang;Lee, Hae Kag;Yoo, Heung Joon;Park, Cheol-Soo
    • Journal of Magnetics
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    • v.20 no.4
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    • pp.381-386
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    • 2015
  • The purpose of this study is to improve diagnostic efficiency of clinical study by setting up guidelines for more precise examination with a comparative analysis of signal intensity and image distortion depending on the location of X axial of object when performing magnetic resonance diffusion weighted imaging (MR DWI) examination. We arranged the self-produced phantom with a 45 mm of interval from the core of 44 regent bottles that have a 16 mm of external diameter and 55 mm of height, and were placed in 4 rows and 11 columns in an acrylic box. We also filled up water and margarine to portrait the fat. We used 3T Skyra and 18 Channel Body array coil. We also obtained the coronal image with the direction of RL (right to left) by using scan slice thinkness 3 mm, slice gap: 0mm, field of view (FOV): $450{\times}450mm^2$, repetition time (TR): 5000 ms, echo time (TE): 73/118 ms, Matrix: $126{\times}126$, slice number: 15, scan time: 9 min 45sec, number of excitations (NEX): 3, phase encoding as a diffusion-weighted imaging parameter. In order to scan, we set b-value to $0s/mm^2$, $400s/mm^2$, and $1,400s/mm^2$, and obtained T2 fat saturation image. Then we did a comparative analysis on the differences between image distortion and signal intensity depending on the location of X axial based on iso-center of patient's table. We used "Image J" as a comparative analysis programme, and used SPSS v18.0 as a statistic programme. There was not much difference between image distortion and signal intensity on fat and water from T2 fat saturation image. But, the average value depends on the location of X axial was statistically significant (p < 0.05). From DWI image, when b-value was 0 and 400, there was no significant difference up to $2^{nd}$ columns right to left from the core of patient's table, however, there was a decline in signal intensity and image distortion from the $3^{rd}$ columns and they started to decrease rapidly at the $4^{th}$ columns. When b-value was 1,400, there was not much difference between the $1^{st}$ row right to left from the core of patient's table, however, image distortion started to appear from the $2^{nd}$ columns with no change in signal intensity, the signal was getting decreased from the $3^{rd}$ columns, and both signal intensity and image distortion started to get decreased rapidly. At this moment, the reagent bottles from outside out of 11 reagent bottles were not verified from the image, and only 9 reagent bottles were verified. However, it was not possible to verify anything from the $5^{th}$ columns. But, the average value depends on the location of X axial was statistically significant. On T2 FS image, there was a significant decline in image distortion and signal intensity over 180mm from the core of patient's table. On diffusion-weighted image, there was a significant decline in image distortion and signal intensity over 90 mm, and they became unverifiable over 180 mm. Therefore, we should make an image that has a diagnostic value from examinations that are hard to locate patient's position.

Mineralogical, Micro-textural, and Geochemical Characteristics for the Carbonate Rocks of the Lower Makgol Formation in Seokgaejae Section (석개재 지역 하부 막골층 탄산염암의 광물조성, 미세구조 및 지화학적 특성)

  • Park, Chaewon;Kim, Ha;Song, Yungoo
    • Economic and Environmental Geology
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    • v.51 no.4
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    • pp.323-343
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    • 2018
  • This study defines the mineralogical, micro-textural and geochemical characteristics for the carbonate rocks and discusses the fluids that have affected the depositional environment of the Lower Makgol Formation in Seokgaejae section. Based on analysis of X-ray Diffraction (XRD), Scanning Electron Microscope-Energy Dispersive X-ray Spectrometry (SEM-EDS), Electron Probe Micro Analyzer-Wavelength Dispersive X-ray Spectrometry (EPMA-WDS) and Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS), carbonate miorofacies in the basal and the lower members of the Makgol Formation are distinguished and classified into four types. Type 1 dolomite (xenotopic interlocking texture) and Type 2 dolomite (idiotopic interlocking texture) have relatively high Mg/Ca ratio, flat REE pattern, low Fe and Mn. Extensively interlocking textures in these dolomites indicate constant supply of Mg ion from hypersaline brine. Type 3 and Type 4 dolomite (scattered and loosely-aggregated texture) have relatively moderate Mg/Ca ratio, MREE enriched pattern, low to high Fe and Mn. These partial dolomitization indicate limited supply of Mg ion under the influx of meteoric water with seawater. Also, the evidence of Fe-bearing minerals, recrystallization and relatively high Fe and Mn in Type 4 indicates the influence of secondary diagenetic fluids under suboxic conditions. Integrating geochemical data with mineralogical and micro-textural evidence, the discrepancy between the basal and the lower members of the Makgol Formation indicates different sedimentary environment. It suggest that hypersaline brine have an influence on the basal member, while mixing meteoric water with seawater have an effect on the lower member of the Makgol Formation.

Synthesis and thermal decomposition of $Zn[BH_4]_2$ ($Zn[BH_4]_2$ 분말의 합성과 열분해 특성)

  • Jeon, Eun;Cho, Young-Whan
    • Journal of Hydrogen and New Energy
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    • v.16 no.3
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    • pp.262-268
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    • 2005
  • [ $Zn(BH_4)_2$ ](8.4 wt% theoretical hydrogen storage capacity powders have been successfully synthesized by mechanochemical reaction from mixtures of $ZnCl_2$ and $NaBH_4$ powders in a 1:2 molar ratio in different times. $$ZnCl_2+2NaBH_4{\rightarrow}Zn(BH_4)_2+2NaCl$$ (1) $Zn(BH_4)_2$ powders were characterized by X-ray diffractometry(XRD), and Furier Transform Infrared spectrometry(FT-IR). The thermal stabilities of $Zn(BH_4)_2$ powders were studied by Differential scanning calorimetry(DSC), Thermogravimetry analysis(TGA), and Mass spectrometry(MS). $Zn(BH_4)_2$ can be tested for hydrogen evolution without further purification. The reaction to yield hydrogen is irreversible, the other products being compounds of Zn, and borane. $Zn(BH_4)_2$ thermally decomposes to release borane and hydrogen gas between about 85 and 150$^{\circ}C$.

Effects of Abeliophyllum distichum Nakai Flower Extracts on Antioxidative Activities and Inhibition of DNA Damage

  • Ahn, Joungjwa;Park, Jae Ho
    • Korean Journal of Plant Resources
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    • v.26 no.3
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    • pp.355-361
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    • 2013
  • The present study attempts to evaluate antioxidant activities of extracts from Abeliophyllum distichum. Nakai flower. The samples were collected in Jangyyeon-myeon, Goesan-gun, Korea and extracted with either hot-water or ethyl acetate (EtOAC). In DPPH, hydroxyl radical scavenging activity and $Fe^{2+}$ chelating activity of EtOAC extracts were 93.41%, 98.43%, and 7.38%, while those of hot-water extracts were 86.93%, 41.33% and 47.68% at 200 ${\mu}g/ml$, respectively. In ${\varphi}X$-174 RF I plasmid DNA cleavage assay, the protective effects of EtOAC and hot-water extracts against oxidative DNA damage were 82% and 17% at 200 ${\mu}g/ml$, respectively. Both extracts showed the protective effect of DNA migration by oxidative stress in intracellular DNA migration assay. Both extracts had no cytotoxity in NIH3T3 cells. Several polyphenolic compounds were identified such as 2-methoxy-benzoic acid, vanillic acid, phytol and pulegone by GC/MS. These results indicated that extracts of Abeliophyllum distichum Nakai flower showed antioxidant activities and protective activities against oxidative DNA damage and showed the possibility to be used as an effective natural antioxidants.