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Effect of Al addition on corrosion behavior of high-purity Mg in terms of processing history

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Journal of Magnesium and Alloys 2023年第3期11卷 851-868页

作者： sang kyu woo Byeong-Chan Suh Ha Sik Kim Chang Dong Yim Helmholtz Zentrum Hereon Max-Planck-Straße 1Geesthacht D-21502Germany Korea Institute of Materials Science 797 Changwondae-roSeongsan-guChangwonGyeongnam 51508Republic of Korea University of Science and Technology 217 Gajeong-roYuseong-guDaejeon 34113Republic of Korea

In this study,the effects of Al addition on the corrosion behavior of pure Mg with controlled impurity contents were systematically analyzed according to the processing history.The results revealed that the corrosion behavior of high-purity Mg-Al alloys is strongly related to changes in the microstructure,including theβphase and Al-Mn or Al-Fe phases,and the protectiveness of the surface film according to the Al content and processing history.In the as-cast alloys,the corrosion rate increased due to the increase ofβphase as the Al content increased,but in the as-extruded alloys,the corrosion rate,which was high due to intermetallic compounds caused by impurities in the low Al alloy,decreased as the Al content increased,and then increased again.This is due to the combined effect of the increase of theβphase and decrease of the impurity effect,and the increase of the dissolved Al content.The results suggest that it is necessary to analyze the effect of alloying elements on the corrosion behavior of pure Mg with information concerning the impurity content and processing history.

关键词： Mg High purity Mg-Al alloys Processing history Micro-galvanic Surface film

Effects of Ca and Nd addition on plastic instability in extruded Mg-Mn alloy deformed under various conditions

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Journal of Magnesium and Alloys 2023年第2期11卷 543-552页

作者： sang kyu woo Risheng Pei Talal Al-Samman Dietmar Letzig sangbong Yi Institute of Materials and Process Design Helmholtz-Zentrum hereon21502 GeesthachtGermany Institut für Metallkunde und Materialphysik RWTH Aachen University52056 AachenGermany

Plastic instability, called Portevin-Le-Chatelier(PLC) effect, manifests itself as an unstable plastic flow during tensile tests of structural materials. This phenomenon has a strong influence on diverse properties, leading to unexpected vulnerabilities in the service environment.Among various magnesium-based alloys, PLC phenomenon is most prominently observed in the Mg-Mn-Nd alloy under elevated temperature and low strain rate conditions. An important aim of the study is to clarify and compare the significance of the RE and Ca addition, which are known to cause a formation of a largely weakened non-basal type texture, in the occurrence of plastic instability. Due to the PLC phenomenon, there is a risk of weakening texture and formability improvement by the addition of RE and Ca elements in Mg alloys. Based on the understanding of the role of Nd to the PLC phenomenon in Mg-Mn alloy identified in previous studies, the PLC characteristics according to alloying elements and deformation conditions were compared and analyzed. To identify the micromechanical mechanisms of the PLC phenomenon, varies in the microstructure and mechanical properties during deformation of Mg-Mn binary and Ca or Nd-containing Mg-Mn-based ternary alloys in various conditions were systemically analyzed. The addition of Ca did not show a marked PLC effect due to the formation of low number density Mn-Ca and Ca-Ca solute clusters and an unbalanced Mn:Ca ratio. In contrast, the addition of Nd leads to the formation of a higher number density of Nd-Nd and Mn-Nd solute clusters than that of Ca-Ca and Mn-Ca solute clusters of the Mg-Mn-Ca alloy, resulting in a stable solute-dislocation interaction atmosphere under specific ranges of deformation temperature and strain rate. The deformation in the regime of PLC phenomenon, results in a decrease in ductility and an increase in strength, despite deformation at elevated temperatures with maintaining the weakened texture.

关键词： Magnesium Plastic instability Portevin-Le Chatelier effect Solute cluster Neodymium Calcium

Synthesis of porous flower-like SnO_(2)/CdSnO_(3) microstructures with excellent sensing performances for volatile organic compounds

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Frontiers of Materials Science 2024年第1期18卷 45-57页

作者： Jie Wan Gang Wang Haibo Ren Jiarui Huang sang woo Joo School of Materials Science and Engineering Anhui Polytechnic UniversityWuhu 241000China Key Laboratory of Functional Molecular Solids of the Ministry of Education College of Chemistry and Materials ScienceAnhui Normal UniversityWuhu 241002China School of Mechanical Engineering Yeungnam UniversityGyeongsanGyeoungbuk 712749Republic of Korea

Porous flower-like SnO_(2)/CdSnO_(3) microstructures self-assembled by uniform nanosheets were synthesized using a hydrothermal process followed by calcination,and the sensing performance was measured when a gas sensor,based on such microstructures,was exposed to various volatile organic compound(VOC)gases.The response value was found to reach as high as 100.1 when the SnO_(2)/CdSnO_(3) sensor was used to detect 100 ppm formaldehyde gas,much larger than those of other tested VOC gases,indicating the high gas sensitivity possessed by this sensor especially in the detection of formaldehyde gas.Meanwhile,the response/recovery process was fast with the response time and recovery time of only 13 and 21 s,respectively.The excellent gas sensing performance derive from the advantages of SnO_(2)/CdSnO_(3),such as abundant n-n heterojunctions built at the interface,high available specific surface area,abundant porosity,large pore size,and rich reactive oxygen species,as well as joint effects arising from SnO_(2) and CdSnO_(3),suggesting that such porous flower-like SnO_(2)/CdSnO_(3) microstructures composed of nanosheets have a high potential for developing gas sensors.

关键词： SnO_(2)/CdSnO_(3) porous flower-like microstructure volatile organic gas sensingproperty gas sensor

MoP nanoparticles encapsulated in N-doped carbon nanotubes as sulfur host for advanced lithium-sulfur batteries

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Nano Research 2024年第4期17卷 2736-2745页

作者： Guozhi Wu Shanqing Li Zheng Chen Ajiao Sun Jie Yang sang woo Joo Jiarui Huang Key Laboratory of Functional Molecular Solids of the Ministry of Education Anhui Laboratory of Molecule-Based MaterialsCollege of Chemistry and Materials ScienceAnhui Normal UniversityWuhu 241002China Anhui Engineering Research Center of Highly Reactive Micro-Nano Powders School of Materials and Environmental engineeringChizhou UniversityChizhou 247000China School of Mechanical Engineering Yeungnam UniversityGyeongsanGyeongbuk 38541Republic of Korea

The low electrical conductivity of sulfur,strong volume expansion,shuttle effect,and sluggish redox reactions in Li-S batteries limit their practical application.MoP nanoparticles encapsulated in nitrogen-doped carbon nanotubes(MoP/NC NTs)were synthesized using MoO_(3) nanorods as templates via a polypyrrole coating,heat-carbonization,MoO_(3) partial reduction,ammonia washing,and phosphorization.The MoP/NC NTs had a hollow nanostructure with a high specific surface area,which can alleviate the volume expansion of the cathode and the shuttle effect of polysulfides.The encapsulated MoP nanoparticles can anchor the polysulfides and enhance the redox reaction kinetics.Thus,the MoP/NC NTs combined with sulfur(MoP/S/NC NTs)exhibited 440.8 mAh·g^(-1) over 500 cycles at 1.0 A·g^(-1) with a decay rate of 0.06%per cycle.The density functional theory calculations and X-ray photoelectron spectroscopy results confirmed that MoP/NC NTs could anchor polysulfides and alleviate the shuttle effect by chemical interactions.This study supplies a novel route to prepare nanoparticle-embedded in N-doped carbon nanotubes for advanced Li-S battery.

关键词： MoP N-doped carbon nanotube lithium-sulfur battery cathode

Tetramic acid-motif natural products from a marine fungus Tolypocladium cylindrosporum FB06 and their anti-Parkinson activities

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Marine Life Science & Technology 2024年第1期6卷 84-92页

作者： Yuna Jung Chaesun Kwon Taeyeon Kim Jin woo Lee Min-Kyoo Shin sang Hee Shim Natural Products Research Institute College of PharmacySeoul National UniversitySeoul 08826Republic of Korea College of Pharmacy and Research Institute of Pharmaceutical Sciences Seoul National UniversitySeoul 08826Republic of Korea College of Pharmacy Duksung Women’s UniversitySeoul 01369Republic of Korea

Tetramic acid-containing natural products are attracting significantly increasing attention from biologists and chemists due to their intriguing structures and biological activities.In the present study,two new tetramic acid alkaloids tolypyridone I(1)and tolypyridone J(2),together with five known ones(3–7),were isolated from cultures of a marine fungus Tolypocladium cylindrosporum FB06 isolate obtained from a marine sediment in Beaufort sea of North Alaska.Their structures were elucidated using 1D,2D NMR,and HRESIMS.Their configurations were established on the basis of 1H coupling constants,ROESY correlations and DP4 calculations.Compound 2 was isolated as mixtures of rotational isomers with C-3 to C-7 axis between 4-hydroxy-2-pyridone and 1-ethyl-3,5-dimethylcyclohexane,hindering rotation.In our unbiased screening to discover neuroprotective compounds in an in vitro Parkinson’s disease(PD)model,SH-SY5Y dopaminergic cells were treated with isolated compounds followed by treatment with 1-methyl-4-phenylpyridinium(MPP^(+)),a parkinsonian neurotoxin.Among tested compounds,F-14329(7)significantly protected cells from MPP^(+)-induced cytotoxicity.MPP^(+)-mediated cell death is known to be related to the regulation of Bcl-2 family proteins,specifically the down-regulation of anti-apoptotic Bcl-2 and the up-regulation of pro-apoptotic Bax levels.Treatment with 2 mmol/L of MPP^(+)for 24 h significantly reduced Bcl-2 levels compared to control treated with vehicle.However,treatment with F-14329(7)attenuated such reduction.This study demonstrates that tetramic acid-motif compounds could be potential lead compounds for treating PD.

关键词： Tolypocladium cylindrosporum Tetramic acid Tolypyridone Parkinson’s disease

Tailoring local structures of atomically dispersed copper sites for highly selective CO2 electroreduction

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Carbon Energy 2024年第4期6卷 79-90页

作者： kyung‐Jong Noh Byoung Joon Park Ying Wang Yejung Choi sang‐Hoon You Yong‐Tae Kim Kug‐Seung Lee Jeong woo Han Department of Chemical Engineering Pohang University of Science and Technology(POSTECH)PohangGyeongbukRepublic of Korea Department of Materials Science and Engineering Pohang University of Science and Technology(POSTECH)PohangGyeongbukRepublic of Korea Pohang Accelerator Laboratory(PAL) Beamline DivisionPohangGyeongbukRepublic of Korea

Atomically‐dispersed copper sites coordinated with nitrogen‐doped carbon(Cu–N–C)can provide novel possibilities to enable highly selective and active electrochemical CO_(2) reduction reactions.However,the construction of optimal local electronic structures for nitrogen‐coordinated Cu sites(Cu–N_(4))on carbon remains challenging.Here,we synthesized the Cu–N–C catalysts with atomically‐dispersed edge‐hosted Cu–N_(4) sites(Cu–N_(4)C_(8))located in a micropore between two graphitic sheets via a facile method to control the concentration of metal precursor.Edge‐hosted Cu–N_(4)C_(8) catalysts outperformed the previously reported M–N–C catalysts for CO_(2)‐to‐CO conversion,achieving a maximum CO Faradaic efficiency(FECO)of 96%,a CO current density of–8.97 mA cm–2 at–0.8 V versus reversible hydrogen electrode(RHE),and over FECO of 90%from–0.6 to–1.0 V versus RHE.Computational studies revealed that the micropore of the graphitic layer in edge‐hosted Cu–N_(4)C_(8) sites causes the d‐orbital energy level of the Cu atom to shift upward,which in return decreases the occupancy of antibonding states in the*COOH binding.This research suggests new insights into tailoring the locally coordinated structure of the electrocatalyst at the atomic scale to achieve highly selective electrocatalytic reactions.

关键词： atomic local structure density functional theory electrochemical CO_(2)reduction metal nitrogen‐doped carbon single‐atom catalyst

Potential reduction in carbon fixation capacity under climate change in a Pinus koraiensis forest

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Forest Ecosystems 2024年第2期11卷 152-161页

作者： Dong Kook woo Department of Civil Engineering Keimyung UniversityDaegu42601Republic of Korea

There has been an increasing recognition of the crucial role of forests, responsible for sequestering atmospheric CO_(2), as a moral imperative for mitigating the pace of climate change. The complexity of evaluating climate change impacts on forest carbon and water dynamics lies in the diverse acclimations of forests to changing environments. In this study, we assessed two of the most common acclimation traits, namely leaf area index and the maximum rate of carboxylation(V_(cmax)), to explore the potential acclimation pathways of Pinus koraiensis under climate change. We used a mechanistic and process-based ecohydrological model applied to a P. koraiensis forest in Mt. Taehwa, South Korea. We conducted numerical investigations into the impacts of(i) Shared Socioeconomic Pathways 2–4.5(SSP2-4.5) and 5–8.5(SSP5-8.5),(ii) elevated atmospheric CO_(2) and temperature, and(iii) acclimations of leaf area index and V_(cmax)on the carbon and water dynamics of P. koraiensis. We found that there was a reduction in net primary productivity(NPP) under the SSP2-4.5 scenario, but not under SSP5-8.5, compared to the baseline, due to an imbalance between increases in atmospheric CO_(2) and temperature. A decrease in leaf area index and an increase in V_(cmax)of P. koraiensis were expected if acclimations were made to reduce its leaf temperature. Under such acclimation pathways, it would be expected that the well-known CO_(2) fertilizer effects on NPP would be attenuated.

关键词： Climate change NEP Pinus koraiensis Warming Acclimation

Recent progress and future directions of the research on nanoplastic-induced neurotoxicity

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Neural Regeneration Research 2024年第2期19卷 331-335页

作者： Seung-woo Han Jinhee Choi Kwon-Yul Ryu Department of Life Science University of SeoulSeoulSouth Korea School of Environmental Engineering University of SeoulSeoulSouth Korea

Many types of plastic products,including polystyrene,have long been used in commercial and industrial applications.Microplastics and nanoplastics,plastic particles derived from these plastic products,are emerging as environmental pollutants that can pose health risks to a wide variety of living organisms,including humans.However,it is not well understood how microplastics and nanoplastics affect cellular functions and induce stress responses.Humans can be exposed to polystyrene-microplastics and polystyrene-nanoplastics through ingestion,inhalation,or skin contact.Most ingested plastics are excreted from the body,but inhaled plastics may accumulate in the lungs and can even reach the brain via the nose-to-brain route.Small-sized polystyrene-nanoplastics can enter cells by endocytosis,accumulate in the cytoplasm,and cause various cellular stresses,such as inflammation with increased pro-inflammatory cytokine production,oxidative stress with generation of reactive oxygen species,and mitochondrial dysfunction.They induce autophagy activation and autophagosome formation,but autophagic flux may be impaired due to lysosomal dysfunction.Unless permanently exposed to polystyrene-nanoplastics,they can be removed from cells by exocytosis and subsequently restore cellular function.However,neurons are very susceptible to this type of stress,thus even acute exposure can lead to neurodegeneration without recovery.This review focuses specifically on recent advances in research on polystyrene-nanoplastic-induced cytotoxicity and neurotoxicity.Furthermore,in this review,based on mechanistic studies of polystyrene-nanoplastics at the cellular level other than neurons,future directions for overcoming the negative effects of polystyrene-nanoplastics on neurons were suggested.

关键词： autophagy cellular stress cytotoxicity endocytosis exocytosis inflammation microplastics nanoplastics neurotoxicity oxidative stress polystyrene

Congestive ischemic colitis successfully treated with antiinflammatory therapy: A case report

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World Journal of Clinical Cases 2024年第1期12卷 142-147页

作者： Geon woo Lee Su Bum Park Department of Internal Medicine Pusan National University School of Medicine and Research Institute for Convergence of Biomedical Science and TechnologyPusan National University Yangsan HospitalYangsan 50612South Korea

BACKGROUND Congestive ischemic colitis is a rare subtype of ischemic colitis with an unknown pathophysiology.Excluding conservative management,such as fasting,no established treatment exists;therefore,surgical intervention should be considered in some cases if symptoms worsen.Current literature suggests that anti-inflam-matory agents may effectively treat congestive ischemic colitis.CASE SUMMARY We present the case of a 68-year-old female patient who underwent laparoscopic left hemicolectomy for transverse colon cancer 3 years ago.Postoperatively,follow-up included an annual colonoscopy and abdominal computed tomography(CT)at a local clinic.However,progressive erythema and edema of the sigmoid colon were observed 1 year postoperatively.Upon admission to our hospital,she complained of abdominal pain and diarrhea.Abdominal CT showed thickening of the sigmoid colon walls,and colonoscopy revealed erythema,edema,and multiple ulcers with exudate in the sigmoid colon.CT angiography showed engorgement of the sigmoid vasa recta without any vascular abnormalities.The diagnosis was congestive ischemic colitis,and we treated the patient with anti-inflammatory agents.After 2 mo of glucocorticoid therapy(20 mg once daily)and 7 mo of 5-aminosalicylate therapy(1 g twice daily),the ulcers completely healed.She has not experienced any recurrence for 2 years.CONCLUSION Anti-inflammatory therapy,specifically glucocorticoids and 5-aminosalicylate,has demonstrated promising efficacy and introduces potential novel treatment options for congestive ischemic colitis.

关键词： Ischemic colitis Glucocorticoids 5-aminosalicylate Colon cancer