• Journal of Applied Biological Chemistry
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• v.62 no.4
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• pp.407-415
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• 2019

The biological half-life of pesticides applied on crops is the key indicator for ensuring the safety of agricultural products. The biological half-life is affected by the several factors like growing conditions of the crop, climate, application method, and physicochemical properties of pesticides. In this study, the biological half-life was calculated and the degradation rates of six triazole fungicides sprayed on perilla leaves were evaluated. Moreover, the statistical analysis confirmed the correlation between the biological half-life and physicochemical properties of six triazole pesticides. The recoveries of the six pesticides were between 84.8-104.9%, which satisfied the residual pesticide analysis criteria. The biological half-life of six pesticides sprayed on perilla leaves, calculated using the first-order kinetics model, ranged between 6.4-15.1 days. When the biological half-life and the physicochemical properties were correlated using the principal component analysis: pKa and Log P, the biological half-life was found to be affected by PC1. The correlation coefficient between biological half-life and physicochemical properties (pKa), calculated by Spearman rank-order correlation, was R² = -0.928 (p <0.01). Biological half-life has been shown to correlate with pKa. In conclusion, it can be used as a database for the relationship between biological half-life and physicochemical properties and will contribute to ensure safe supply of agricultural products.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.220-220
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• 2006

Rheological and electrical properties of the polycarbonate (PC) / multi-walled carbon nanotube (MWNT) were studied. The MWNT was funtoinalized by treating with the hydrogen peroxide ($H_{2}O_{2}$). The electrical conductivity showed higher value for the PC/MWNT ($H_{2}O_{2}$ treated, freeze drying) composites compared that of the PC/MWNT ($H_{2}O_{2}$ treated, thermal drying) composites. From the results of the morphological, rheological, and electrical properties of the PC/MWNT composites, it is suggested that the electrical and rheological properties of the PC/MWNT composites are affected by the MWNT-MWNT network structure which is related with the MWNT morphologies such as the degree of aggregation and aspect ratio of the MWNT.

• Korea-Australia Rheology Journal
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• v.14 no.1
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• pp.11-16
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• 2002

Cephalosporium acremonium is a filamentous microorganism producing cephalosporin C. The morphological differentiation of C. acremonium in submerged culture is closely related with the rheological properties of culture broth and production of cephalosporin C. In this study, the rheological and morphological properties of culture broth of C. acremonium were investigated. In the seed broths of shake-flask and fermenter culture, the Herschel-Berkley equation was in excellent agreement with experimental results in the whole range of shear rate. In the seed broths of shake-flask culture, morphological differentiation into arthrospores affected to changes of apparent viscosity. But results in the fermenter culture, morphological factors such as mean hyphal thickness and the number of tips gave more effect on changes of apparent vitacosity than differentiation into arthrospores. Overall, it suggested that the morphological parameters measured by image analysis can be used as a good parameter to indicate the rheological properties of culture broth of C. acremonium M25.

• Macromolecular Research
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• v.14 no.4
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• pp.456-460
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• 2006

The electrical, morphological, and mechanical properties of poly carbonate (PC)/multi-walled carbon nan-otube (MWNT) composites were studied by electrical conductivity, electromagnetic interference shielding efficiency (EMI SE), scanning electron microscopy, and tensile strength measurements. In the electrical property analysis of the PC/MWNT composites, the percolation threshold of the PC/MWNT composites was observed between 1.5 and 2.5 wt% MWNT content. From the electrical conductivity and EMI SE studies, the theoretical values of the EMI SE were in good agreement with the experimental values of the EMI SE. From the morphology of the PC/MWNT composites, it was observed that MWNT is dispersed homogenously in the PC matrix. From the electrical conductivity and morphological studies, it was suggested that the percolation threshold of the PC/MWNT composites is related with the morphological results in that MWNT is apparently interconnected to form an electrical pathway. The mechanical properties of the PC/MWNT composites peaked at the MWNT content of 2.5 wt%.

• Macromolecular Research
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• v.15 no.6
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• pp.520-526
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• 2007

The effects of poly($({\varepsilon}$-caprolactone) (PCL) on poly(acrylonitrile-butadiene-styrene) (ABS) and polycarbonate (PC) blends were studied. Blends of ABS/PC (70/30, wt%) with PCL as a compatibilizer were prepared by a twin screw extruder. From the glass transition temperature $(T_g)$ results of the ABS/PC blends with PCL, the $T_g$(PC) of the ABS/PC (70/30) blends decreased with increasing PCL content. From the results of the morphology of the ABS/PC (70/30) blends with PCL, the phase separation between the ABS and PC phases became less significant after adding PCL in the ABS/PC blends. In addition, the morphological studies of the ABS/PC blends etched by NaOH indicated that the shape of the droplet was changed from regular round to irregular round by adding PCL in the ABS/PC blends. These results for the mechanical properties of the ABS/PC blends with PCL indicated that the tensile, flexural and impact strengths of the ABS/PC (70/30) blends peaked at a PCL content of 0.5 phr. From the results for the rheological properties of the ABS/PC (70/30) blends with PCL content, the storage modulus, loss modulus and complex viscosity increased at PCL content up to 5 phr. From the above results of the $T_g$, mechanical properties, morphology and complex viscosity of the ABS/PC blends with PCL, it was concluded that the compatibility was increased with PCL addition in the ABS/PC (70/30, wt%) blends and that the optimum concentration of PCL as a compatibilizer is 0.5 phr.

• Proceedings of the Korean Society of Rheology Conference
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• 2006.06a
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• pp.61-64
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• 2006

Soft materials, such as polymer solutions, gels and filamentous protein materials in cells, show complicated behavior due to their complex structures and dynamics with multiple characteristic time and length scales. Several complementary techniques have been developed to measure viscoelastic of soft materials. Especially, particle tracking microrheology, using the Brownian motion of particles in a medium to get rheological properties, has recently been improved both theoretically and experimentally. Compared to other conventional methods, video particle tracking microrheology has some advantages such as small sample volume, detecting spatial variation of local rheological properties, and less damage to sample materials. With these advantages, microrheology is more suitable to measure the properties of complex materials than other mechanical rheometries.

• Journal of Microbiology and Biotechnology
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• v.31 no.8
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• pp.1060-1068
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• 2021

Community-associated Methicillin-Resistant Staphylococcus aureus (CA-MRSA) is notorious as a leading cause of soft tissue infections. Despite several studies on the Agr regulator, the mechanisms of action of Agr on the virulence factors in different strains are still unknown. To reveal the role of Agr in different CA-MRSA, we investigated the LACΔagr mutant and the MW2Δagr mutant by comparing LAC (USA300), MW2 (USA400), and Δagr mutants. The changes of Δagr mutants in sensitivity to oxacillin and several virulence factors such as biofilm formation, pigmentation, motility, and membrane properties were monitored. LACΔagr and MW2Δagr mutants showed different oxacillin sensitivity and biofilm formation compared to the LAC and MW2 strains. Regardless of the strain, the motility was reduced in Δagr mutants. And there was an increase in the long chain fatty acid in phospholipid fatty acid composition of Δagr mutants. Other properties such as biofilm formation, pigmentation, motility, and membrane properties were different in both Δagr mutants. The Agr regulator may have a common role like the control of motility and straindependent roles such as antibiotic resistance, biofilm formation, change of membrane, and pigment production. It does not seem easy to control all MRSA by targeting the Agr regulator only as it showed strain-dependent behaviors.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.246-246
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• 2006

Ionic polymer-metal composite (IPMC) soaked with various ionic liquids was prepared by using polystyrene sulfonic acid-grafted poly(vinylidene fluoride-co-hexafluoropropylene) as ion-exchange membrane (IEM). The prepared IPMCs were effectively deformed three times larger and actuated for 300 times longer than those of Nafion with water at the same applied conditions. The experimental results indicated than the increase in the bending capability can be caused by the increase in the improved properties of the IEMs and ionic liquids such as uptake content and ionic conductivity. And air-operating stability of the IPMCs is appreciably governed by various physical and electrochemical properties of soaked solvents in IEMs.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.367-367
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• 2006

With poly (ethylene-co-methacrylic acid) ionomer (i.e. Surlyn) as a compatibilizer, PP/organoclay (Cloisite(R)20A) nanocomposites were prepared via melt compounding in a co-rotating twin-screw extruder. For comparison, the widely used PP-g-MA was also used as a reference. The content of organoclay was fixed at 5phr based on the total weight of polymer resins. The structures of nanocomposites were characterized by XRD, rheometry in small amplitude oscillatory shear, SEM, and TEM, respectively. It was found that PP/Surlyn/OMMT nanocomposites displayed higher intercalation degree and better dispersion effect than the corresponding PP/PP-g-MA/OMMT counterpart. Additionally, their mechanical properties and wettability were measured.

• Journal of Forest and Environmental Science
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• v.30 no.4
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• pp.370-377
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• 2014

There are very few studies about soil chemical and biological properties under tropical dry evergreen forest Coromandel Coast, India. The present study was conducted in six tropical dry evergreen forests sites such as Oorani, Puthupet, Vadaagram, Kotthatai, Sendrakillai and Palvathunnan. We measured the quantity of soil chemical, biological properties and selected soil microorganisms for investigating the impacts of soil microbial populations on soil chemical and biological properties. The result showed that total N, P, Ca, S, Fe, Mn, Cu, Co, exchangeable K, Olson P, extractable Ca and phosphobacterial population were higher in the soil from Kothattai forest site. Organic carbon, total Mg, extractable Na, soil respiration, ${\beta}$-glucosidase activity, bacterial population, fungi population and actinomycetes population were higher in the soil from Palvathunn forest site. Total K, $NH_4{^+}$-N, $NO_3{^-}$-N, exchangeable K, extractable Ca, extractable Na, azotobacter population, bacillus population and rhizobacteria population were higher in the soil from Sendrakillai. Beijerinckia population, rhizobacteria and soluble sodium were higher in Puthupet forest soil. Total Si, total Na and exchangeable K were higher in soil from Oorani forest site. Total Mo and exchangeable K were higher in the soil from Vadaagaram forest site. The results showed that organic carbon, total N, $NH_4{^+}$-N, $NO_3{^-}$-N, extractable P, extractable Ca, soil respiration and ${\beta}$-glucosidase were significantly correlated with soil microbial populations. Therefore soil microorganisms are important factor for maintaining soil quality in tropical dry evergreen forest.