• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2000년도 추계학술대회 논문집
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• pp.55-61
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• 2000

Tungsten heavy metal is characterized bi a high density and novel combination of strength and ductility. Among them, 90W-7Ni-3Fe is used for applications, where the high specific weight of the material plays an important role. They are used as counterweights, rotating inertia members, as well as for defense purposes(kinetic energy penetrators, etc.). Because of these applications, it is essential to detemine the dynamic characteristics of tungsten alloy. In this paper, Explicit FEM(finite element method) is employed to investigate the dynamic characteristics of tungsten heavy metal under base of stress wave propagation theory for SHPB, and the model of specimen is divided into two parts to understand the phenomenon that stress wave penetrates through each tungsten base and matrix. This simulation results were compared to experimental one and through this program the dynamic stress-strain curve of tungsten heavy metal can be obtained using quasi static stress-strain curve of pure tungsten and matrix.

• 한국정밀공학회지
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• 제22권8호
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• pp.92-99
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• 2005

Tungsten heavy metal is characterized by a high density and novel combination of strength and ductility. Among them, 90W-7Ni-3Fe is used for applications, where the high specific weight of the material plays an important role. They are used as counterweights, rotating inertia members, as well as fur defense purposes(kinetic energy Penetrators, etc.). Because of these applications, it is essential to detemine the dynamic characteristics of tungsten alloy. In this paper, Explicit FEM(finite element method) is employed to investigate the dynamic characteristics of tungsten heavy metal under base of stress wave propagation theory for SHPB, and the model of specimen is divided into two parts to understand the phenomenon that stress wave penetrates through each tungsten base and matrix. This simulation results were compared to experimental one and through this program, the dynamic stress-strain curve of tungsten heavy metal can be obtained using quasi static stress-strain curve of pure tungsten and matrix.

• 한국작물학회:학술대회논문집
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• 한국작물학회 2017년도 9th Asian Crop Science Association conference
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• pp.24-24
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• 2017

Heavy metals at toxic levels have the capability to interact with several vital cellular biomolecules such as nuclear proteins and DNA, leading to oxidative stress in plants. The present study was performed to explore the metal tolerance mechanism in Sorghum seedling. Morpho-physiological and metal ions uptake changes were observed prominently in the seedlings when the plants were subjected to different concentrations of $CuSO_4$ and $CdCl_2$. The observed morphological changes revealed that the plants treated with Cu and Cd displayed dramatically altered shoot lengths, fresh weights, and relative water content. In addition, the concentration of Cu and Cd was markedly increased by treatment with Cu and Cd, and the amount of interacting ions taken up by the shoots and roots was significantly and directly correlated with the applied level of Cu and Cd. Using the 2-DE method, a total of 24 and 21 differentially expressed protein spots from sorghum leaves and roots respectively, 33 protein spots from sorghum leaves under Cd stress were analyzed using MALDI-TOF/TOF MS. However, the over-expression of GAPDH plays a significant role in assisting Sorghum bicolor to attenuate the adverse effects of oxidative stress caused by Cu, and the proteins involved in resistance to stress helped the sorghum plants to tolerate high levels of Cu. Significant changes were absorbed in the levels of proteins known to be involved in carbohydrate metabolism, transcriptional regulation, translation and stress responses. In addition, the up-regulation of glutathione S-transferase and cytochrome P450 may play a significant role in Cd-related toxicity and stress responses. The results obtained from the present study may provide insights into the tolerance mechanism of seedling leaves and roots in Sorghum under heavy metal stress.

• 한국식물학회:학술대회논문집
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• 한국식물학회 1999년도 춘계학술발표대회:발표논문요지록
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• pp.2-2
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• 1999

• 한국환경과학회지
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• 제24권12호
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• pp.1591-1600
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• 2015

The response of the freshwater microalga, Chlorella vulgaris, to heavy metal stress was examined based on chlorophyll fluorescence analysis to assess the toxic effects of heavy metals in freshwater ecosystems. When toxic effects were analyzed using regular chlorophyll fluorescence analysis, photosystem II activity($F_v/F_m$) decreased significantly when exposed to $Cu^{2+}$ and $Hg^{2+}$ for 12 h, and decreased in the order of $Hg^{2+}>Cu^{2+}>Cd^{2+}>Ni^{2+}$ when exposed for 24h. The effective photochemical quantum yield(${\phi}{\prime}_{PSII}$), chlorophyll fluorescence decrease ratio($R_{Fd}$), minimal fluorescence yield($F_o$), and non-photochemical quenching(NPQ), but not photochemical quenching(qP), responded sensitively to $Hg^{2+}$, $Cu^{2+}$, and $Cd^{2+}$. These results suggest that $F_v/F_m$, as well as ${\phi}{\prime}_{PSII}$, $R_{Fd}$, $F_o$, and NPQ could be used to assess the effects of heavy metal ions in freshwater ecosystems. However, because many types of heavy metal ions and toxic compounds co-occur under natural conditions, it is difficult to assess heavy metal toxicity in freshwater ecosystems. When Chlorella was exposed to heavy metal ions for 12 or 24h, $F_v/F_m$ and maximal fluorescence yield($F_m$) changed in response to $Hg^{2+}$ and $Cu^{2+}$ based on image analysis. However, assessing quantitatively the toxic effects of several heavy metal ions is challenging.

• Fisheries and Aquatic Sciences
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• 제20권7호
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• pp.9.1-9.13
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• 2017

Background: Metal-responsive transcription factor-1 (MTF-1) is a key transcriptional regulator playing crucial roles in metal homeostasis and cellular adaptation to diverse oxidative stresses. In order to understand cellular pathways associated with metal regulation and stress responses in Pacific abalone (Haliotis discus hannai), this study was aimed to isolate the genetic determinant of abalone MTF-1 and to examine its expression characteristics under basal and experimentally stimulated conditions. Results: The abalone MTF-1 shared conserved features in zinc-finger DNA binding domain with its orthologs; however, it represented a non-conservative shape in presumed transactivation domain region with the lack of typical motifs for nuclear export signal (NES) and Cys-cluster. Abalone MTF-1 promoter exhibited various transcription factor binding motifs that would be potentially related with metal regulation, stress responses, and development. The highest messenger RNA (mRNA) expression level of MTF-1 was observed in the testes, and MTF-1 transcripts were detected during the entire period of embryonic and early ontogenic developments. Abalone MTF-1 was found to be Cd inducible and highly modulated by heat shock treatment. Conclusion: Abalone MTF-1 possesses a non-consensus structure of activation domains and represents distinct features for its activation mechanism in response to metal overload and heat stress. The activation mechanism of abalone MTF-1 might include both indirect zinc sensing and direct de novo synthesis of transcripts. Taken together, results from this study could be a useful basis for future researches on stress physiology of this abalone species, particularly with regard to heavy metal detoxification and thermal adaptation.

• 한국환경독성학회:학술대회논문집
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• 한국환경독성학회 2006년도 춘계학술대회 논문집
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• pp.89-90
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• 2006

• Fisheries and Aquatic Sciences
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• 제12권3호
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• pp.179-184
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• 2009

Hemibarbus mylodon (Cypriniformes) is an endemic freshwater fish species in the Korean peninsula, for which urgent conservation efforts are needed. To understand their stress responses in relation to metal toxicity and thermal elevation, we performed a real-time RT-PCR-based expression assay of hepatic copper/zinc-superoxide dismutase (Cu/Zn-SOD), a key antioxidant enzyme, in response to experimental heavy metal exposure or heat treatment. The transcription of hepatic Cu/Zn-SOD was differentially modulated by acute exposure to Cu, cadmium (Cd), or Zn. Exposure to each metal at $5{\mu}M$ for 24 h revealed that Cu stimulated the mRNA expression of Cu/Zn-SOD to a greater extent than the other two heavy metals. The elevation in Cu/Zn-SOD transcripts in response to Cu exposure was dose-dependent (0.5 to $5{\mu}M$). Time course analysis of Cu/Zn-SOD expression in response to Cd exposure ($5{\mu}M$) revealed a transient pattern up to day 7. Exposure to thermal stress (an increase from 22 to $30^{\circ}C$ at a rate of $1^{\circ}C/h$ followed by $30^{\circ}C$ for 18 h) did not significantly alter SOD transcription, although heat shock protein 90 kDa (HSP90) transcription was positively correlated with an increase in temperature.

• Journal of Ginseng Research
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• 제45권2호
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• pp.218-227
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• 2021

Background: Panax ginseng is one of the most important medicinal plants and is usually harvested after 5 to 6 years of cultivation in Korea. Heavy metal (HM) exposure is a type of abiotic stress that can induce oxidative stress and decrease the quality of the ginseng crop. Siderophore-producing rhizobacteria (SPR) may be capable of bioremediating HM contamination. Methods: Several isolates from ginseng rhizosphere were evaluated by in vitro screening of their plant growth-promoting traits and HM resistance. Subsequently, in planta (pot tests) and in vitro (medium tests) were designed to investigate the SPR ability to reduce oxidative stress and enhance HM resistance in P. ginseng inoculated with the SPR candidate. Results: In vitro tests revealed that the siderophore-producing Mesorhizobium panacihumi DCY119^T had higher HM resistance than the other tested isolates and was selected as the SPR candidate. In the planta experiments, 2-year-old ginseng seedlings exposed to 25 mL (500 mM) Fe solution had lower biomass and higher reactive oxygen species level than control seedlings. In contrast, seedlings treated with 10⁸ CFU/mL DCY119^T for 10 minutes had higher biomass and higher levels of antioxidant genes and nonenzymatic antioxidant chemicals than untreated seedlings. When Fe concentration in the medium was increased, DCY119^T can produce siderophores and scavenge reactive oxygen species to reduce Fe toxicity in addition to providing indole-3-acetic acid to promote seedling growth, thereby conferring inoculated ginseng with HM resistance. Conclusions: It was confirmed that SPR DCY119^T can potentially be used for bioremediation of HM contamination.

• 한국동물학회:학술대회논문집
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• 한국동물학회 1995년도 한국생물과학협회 학술발표대회
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• pp.350-350
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• 1995

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