• 한국균학회소식:학술대회논문집
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• 2015.05a
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• pp.54-54
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• 2015

Crops lack genetic resistance to most necrotrophic soil-borne pathogens and parasitic nematodes that are ubiquitous in agroecosystems worldwide. To overcome this disadvantage, plants recruit and nurture specific group of antagonistic microorganisms from the soil microbiome to defend their roots against pathogens and other pests. The best example of this microbe-based defense of roots is observed in disease-suppressive soils in which the suppressiveness is induced by continuously growing crops that are susceptible to a pathogen. Suppressive soils occur globally yet the microbial basis of most is still poorly described. Fusarium wilt, caused by Fusarium oxysporum f. sp. fragariae is a major disease of strawberry and is naturally suppressed in Korean fields that have undergone continuous strawberry monoculture. Here we show that members of the genus Streptomyces are the specific bacterial components of the microbiome responsible for the suppressiveness that controls Fusarium wilt of strawberry. Furthermore, genome sequencing revealed that Streptomyces griseus, which produces a novel thiopetide antibiotic, is the principal species involved in the suppressiveness. Finally, chemical-genetic studies demonstrated that S. griseus antagonizes F. oxysporum by interfering with fungal cell wall synthesis. An attack by F. oxysporum initiates a defensive "cry for help" by strawberry root and the mustering of microbial defenses led by Streptomyces. These results provide a model for future studies to elucidate the basis of microbially-based defense systems and soil suppressiveness from the field to the molecular level.

• Proceedings of the Korean Society of Plant Pathology Conference
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• 2003.10a
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• pp.81.1-81
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• 2003

Although plants have evolved to possess various defense mechanisms from local biotic and abiotic stressors, most of yield loss is caused by theses stressors. Recent studies have revealed that several different stress responsive reactions are inter-networking. Therefore, the identification and dissection of stress responsive genes is an essential and first step towards understanding of the global defense mechanism in response to various stressors. For this purpose, we applied cDNA microarray analysis, because it has powerful ability to monitor the global gene expression in a specific situation. To date, more than 10,000 non-redundant genes were identified from seven different cDNA libraries and deposited in our EST database (http://plant.pdrs.re.kr/ks200201/pepper.html). For this study, we have built 5K cDNA microarray containing 4,685 unigene clones from three different cDNA libraries. Monitoring of gene expression profiles of hot pepper interactions with biotic stress, abiotic stresses and chemical treatments will be presented. Although this work shows expression profiling at the sub-genomic level, this could be a good starting point to understand the complexity of global defense mechanism in hot pepper.

• The Plant Pathology Journal
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• v.21 no.3
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• pp.288-292
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• 2005

Pathogenesis-related protein-1a (PR-1a) is strongly induced in tobacco plants by pathogen attack, exogenous salicylic acid (SA) application and by other developmental processes. In order to develop a rapid screening system for the selection of plant defense-inducing compounds originated from various sources, we have transformed tobacco Samsun NN plants with a chimeric construct consisting of GUS $(\beta-glucuronidase)$. In the $T_1$ generation, three transgenic lines having stable GUS expression were selected for further promoter analysis. Using GUS histochemical assay, we observed strong GUS induction driven by PR-1a promoter in PR1a-GUS transgenic tobacco leaves in response to the exogenous application of SA or benzol (1,2,3) thiadiazole-7-carbothioic acid S-methyl ester (BTH), a SA­derivative compound. In addition, GUS expression was maintained locally or systemically in PR1a-GUS transgenic line $\#5\;T_2$ generation) until after 3 days when they were treated with same chemicals. Our results suggested that the PR1a-GUS reporter gene system in tobacco plants may be applicable for the large-scale screening of defense-inducing substances.

• Journal of Powder Materials
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• v.25 no.2
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• pp.109-119
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• 2018

The objective of this study is to reveal the sintering mechanism of mixed Ti-6Al-4V powders considering the densification and the homogenization between Ti and Al/V particles. It is found that the addition of master alloy particles into Ti enhances densification by the migration of Al into the Ti matrix prior to the self-diffusion of Ti. However, as Ti particles become coarser, sintering of the powders appears to be retarded due to slower inter-diffusion of the particles due to the reduced surface energies of Ti. Such phenomena are confirmed by a series of dilatometry tests and microstructural analyses in respect to the sintering temperature. Furthermore, the results are also consistent with the predicted activation energies for sintering. The energies are found to have decreased from 299.35 to $135.48kJ{\cdot}mol^{-1}$ by adding the Al/V particles because the activation energy for the diffusion of Al in ${\alpha}-Ti$ ($77kJ{\cdot}mol^{-1}$) is much lower than that of the self-diffusion of ${\alpha}-Ti$. The coarser Ti powders increase the energies from 135.48 to $181.16kJ{\cdot}mol^{-1}$ because the specific surface areas of Ti decrease.

• Mycobiology
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• v.45 no.4
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• pp.409-420
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• 2017

Foliar sprays of three plant resistance inducers, including chitosan (CH), potassium sorbate (PS) ($C_6H_7kO_2$), and potassium bicarbonates (PB) ($KHCO_3$), were used for resistance inducing against Erysiphe cichoracearum DC (powdery mildew) infecting okra plants. Experiments under green house and field conditions showed that, the powdery mildew disease severity was significantly reduced with all tested treatments of CH, PS, and PB in comparison with untreated control. CH at 0.5% and 0.75% (w/v) plus PS at 1.0% and 2.0% and/or PB at 2.0% or 3.0% recorded as the most effective treatments. Moreover, the highest values of vegetative studies and yield were observed with such treatments. CH and potassium salts treatments reflected many compounds of defense singles which leading to the activation power defense system in okra plant. The highest records of reduction in powdery mildew were accompanied with increasing in total phenolic, protein content and increased the activity of polyphenol oxidase, peroxidase, chitinase, and ${\beta}$-1,3-glucanase in okra plants. Meanwhile, single treatments of CH, PS, and PB at high concentration (0.75%, 2.0%, and/or 3.0%) caused considerable effects. Therefore, application of CH and potassium salts as natural and chemical inducers by foliar methods can be used to control of powdery mildew disease at early stages of growth and led to a maximum fruit yield in okra plants.

• Journal of Powder Materials
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• v.26 no.4
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• pp.311-318
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• 2019

The objective of this study is to investigate the influence of powder shape and densification mechanism on the microstructure and mechanical properties of Ti-6Al-4V components. BE powders are uniaxially and isostatically pressed, and PA ones are injection molded because of their high strengths. The isostatically compacted samples exhibit a density of 80%, which is higher than those of other samples, because hydrostatic compression can lead to higher strain hardening. Owing to the higher green density, the density of BE-CS (97%) is found to be as high as that of other samples (BE-DS (95%) and P-S (94%)). Furthermore, we have found that BE powders can be consolidated by sintering densification and chemical homogenization, whereas PA ones can be consolidated only by simple densification. After sintering, BE-CS and P-S are hot isostatically pressed and BE-DS is hot forged to remove residual pores in the sintered samples. Apparent microstructural evolution is not observed in BE-CSH and P-SH. Moreover, BE-DSF exhibits significantly fine grains and high density of low-angle grain boundaries. Thus, these microstructures provide Ti-6Al-4V components with enhanced mechanical properties (tensile strength of 1179 MPa).

• The Plant Pathology Journal
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• v.37 no.4
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• pp.356-364
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• 2021

This study was to investigate defense mechanisms on cassava induced by salicylic acid formulation (SA) against anthracnose disease. Our results indicated that the SA could reduce anthracnose severity in cassava plants up to 33.3% under the greenhouse condition. The 𝛽-1,3-glucanase and chitinase enzyme activities were significantly increased at 24 hours after inoculation (HAI) and decrease at 48 HAI after Colletotrichum gloeosporioides challenge inoculation, respectively, for cassava treated with SA formulation. Synchrotron radiation-based Fourier-transform infrared microspectroscopy spectra revealed changes of the C=H stretching vibration (3,000-2,800 cm^-1), pectin (1,740-1,700 cm^-1), amide I protein (1,700-1,600 cm^-1), amide II protein (1,600-1,500 cm^-1), lignin (1,515 cm^-1) as well as mainly C-O-C of polysaccharides (1,300-1,100 cm^-1) in the leaf epidermal and mesophyll tissues treated with SA formulations, compared to those treated with fungicide carbendazim and distilled water after the challenged inoculation with C. gloeosporioides. The results indicate that biochemical changes in cassava leaf treated with SA played an important role in the enhancement of structural and chemical defense mechanisms leading to reduced anthracnose severity.

• Journal of the Korean Society of Propulsion Engineers
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• v.27 no.1
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• pp.9-16
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• 2023

This paper investigated the method to predict a thermal response of internal insulation in a solid rocket motor considering both thermal decomposition and ablation. Changes in properties due to the thermal decomposition, swelling of char layer and movement of decomposition gases inside the material were considered during a modeling. And radiative/convective heat flux from the exhaust gas were applied as boundary conditions, while the chemical ablation of the material surface is modeled with algebraic equations. Test SRM with thermocouples was solved for a validation purpose. The results showed that predicted temperatures have identical trends and values compared to the experimental values. And an error of predicted thermal destruction depth was around 0.1 mm.

• Korean Chemical Engineering Research
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• v.52 no.2
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• pp.209-213
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• 2014

A graft copolymer of poly(vinyl chloride)-g-poly(oxyethylene methacrylate) (PVC-g-POEM) was synthesized via atom transfer radical polymerization (ATRP) and used as a structure-directing agent to prepare $Al@Fe_2O_3$ core-shell nanocomposites through a sol-gel process. The amphiphilic property of PVC-g-POEM allows for good dispersion of Al particles and leads to specific interaction with iron ethoxide, a precursor of $Fe_2O_3$. Secondary bonding interaction in the sol-gel composites was characterized by Fourier transform-infrared (FT-IR) spectroscopy. The well-organized morphology of $Al@Fe_2O_3$ core-shell nanocomposites was observed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Energy dispersive X-ray (EDX) and X-ray diffraction (XRD) were used to analyze the elemental composition and crystallization structure of the composites.

• CELLMED
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• v.6 no.4
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• pp.22.1-22.19
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• 2016

The biologically active compounds derived from different natural organisms such as animals, plants, and microorganisms like algae, fungi, bacteria and merine organisms. These natural compounds possess diverse biological activities like anthelmintic, antibacterial, antifungal, antimalarial, antiprotozoal, antituberculosis, and antiviral activities. These biological active compounds were acted by variety of molecular targets and thus may potentially contribute to several pharmacological classes. The synthesis of natural products and their analogues provides effect of structural modifications on the parent compounds which may be useful in the discovery of potential new drug molecules with different biological activities. Natural organisms have developed complex chemical defense systems by repelling or killing predators, such as insects, microorganisms, animals etc. These defense systems have the ability to produce large numbers of diverse compounds which can be used as new drugs. Thus, research on natural products for novel therapeutic agents with broad spectrum activities and will continue to provide important new drug molecules.