• Korean Journal of Pharmacognosy
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• v.45 no.2
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• pp.101-106
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• 2014

Marine-derived microbes have yielded a variety of metabolites so far. In the course of the project to find metabolites from marine microbes, an isolate of Penicillium glabrum (SF 5317) was selected for chemical investigation. A large scale culture of this strain in PDA media was extracted with an organic solvent and the extract was subjected to a serious of chromatography, which led to six metabolites. Their chemical structures were elucidated as sulochrin (1), questin (2), questinol (3), ergosterol (4), 3-methyldesmethoxyyangonin (5), and hydroxysulochrin (6) on the basis of spectroscopic data. To the best of our knowledge, this is the second isolation of compounds 5 and 6 in nature and especially 6 is isolated from Penicillium sp. for the first time.

• Bulletin of the Korean Chemical Society
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• v.35 no.1
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• pp.69-75
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• 2014

Accurate analysis of fly ash particles is not trivial because of complex nature in physical and chemical properties. SPLITT fractionation (SF) was employed to fractionate the fly ash particles into subpopulations in large quantities. Then the SF-fractions were analyzed by the steric mode of sedimentation field-flow fractionation (Sd/StFFF) for size analysis. The SF-fractions were also analyzed by ICP-OES. The results showed that the fly ash is mainly composed of Fe, Ca, Mg and Mn. No particular trends were observed between the particle size and the concentrations of Fe, Ca, Mg, while Mn, Cu and Zn were in higher concentrations in smaller particles. Sample preparation procedures were established, where the fly ash particles were sieved to remove large contaminants, and then washed with acetone to remove organics on the surface of particles. The sample preparation and analysis methods developed in this study could be applied to other environmental particles.

• Elastomers and Composites
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• v.38 no.2
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• pp.167-174
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• 2003

Thermoplastic vulcanizates (TPV) or dynamic vulcanizates are thermoplastic elastomers produced by simultaneous mixing and crosslinking of a rubber and a thermoplastic. The objective of the present work is to investigate the effects of different types of peroxides as curing agents on the properties of PP/EPDM TPVs. The mechanical properties change significantly with the chemical nature of the peroxides and the extent of crosslinking at a fixed PP/EPDM blend ratio. The tensile strength of the TPVs obtained with the various peroxides can be related to the solubility parameters of the polymers and of the peroxides. The Young's modulus of the peroxide-cured TPVs can be correlated with the delta torque values of equivalent thermoset EPDM vulcanizates, corresponding to the crosslinking efficiencies of the peroxides.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.11
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• pp.46-52
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• 2004

CMP (Chemical-Mechanical Polishing) is a process in which both chemical and mechanical mechanisms act simultaneously to produce the planarized wafer. CMP process is an extensive usage and continuing high growth rates in the semiconductor industry. The understanding of the process, however, is much slower. The nature of material removal from the wafer is still undefined and ambiguous. Material removal rate according to the slurry flow rate is also undefined and ambiguous. Thus, in this study, the basic mechanism of material removal rate as slurry flow rate is defined in terms of energy supply and energy loss.

• Bulletin of the Korean Chemical Society
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• v.15 no.11
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• pp.949-953
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• 1994

In oxides characterized by the $K_2NiF_4-type$ structure, the low-spin${\to}$high-spin transition of trivalent cobalt ion was studied in function of the nature of competing bonds in the perovskite-plane and along the c-axis. Using Slichter and Drickamer's model the calculated values of parameters characterizing such a transition are correlated with the covalency of competing bonds along the c-axis of the $K_2NiF_4$-structure and the local structural distortion of the $(CoO_6)$ octahedron.

• Bulletin of the Korean Chemical Society
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• v.9 no.5
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• pp.280-282
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• 1988

The structural, electrical and magnetic properties were investigated for the high-Tc superconductor $YBa_2Cu_3O_{7-x}$, where x was 0.13. The results of temperature dependence of the resistivity and the magnetization in $YBa_2Cu_3O_{6.87}$ whose structure and phase are confirmed by arialysis of X-ray powder diffraction pattern have been reported. A very sharp superconductivity transition appears at 92K in the specimen whose chemical composition is determined from redox titration, strongly suggesting that this specimen consists of a single-phase superconductor. From the results of X-ray diffraction analysis, magnetization curves, levitation and resistance measurements, it is suggested that the observed superconductivity is bulk property in nature and that the $YBa_2Cu_3O_{6.87}$ phase is responsible for the superconductivity of the present reproducible specimen.

• Bulletin of the Korean Chemical Society
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• v.9 no.6
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• pp.365-368
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• 1988

Coordination chemistry of organotin(IV) dithiocarbamate complexes has been examined in terms of far infrared and $^{119}Sn$-NMR spectroscopies. Although the Sn-S stretching vibrational bands of the complex could not be correlated with the bonding nature of the dithiocarbamate ligand, $^{119}Sn$ chemical shifts were sensitive enough to distinguish clearly the coordination number of tin, and as such the bonding mode of the dithiocarbamate ligand could be indentified to be monodentate or bidentate. Thus the $^{119}Sn$-NMR study on new cyclohexyltin(IV) dithiocarbamate complexes along with the known complexes suggests that the bonding mode of the dithiocarbamate ligands and the consequent coordination number of tin are determined mainly by the inductive effects of the organic groups attached to the tin atom.

• Journal of Microbiology and Biotechnology
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• v.31 no.4
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• pp.493-500
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• 2021

Endophytic fungi are symbiotically related to plants and spend most of their life cycle within them. In nature, they have a crucial role in plant micro-ecosystem. They are harnessed for their bioactive compounds to counter human health problems and diseases. Endophytic Diaporthe sp. is a widely distributed fungal genus that has garnered much interest within the scientific community. A substantial number of secondary metabolites have been detected from Diaporthe sp. inhabited in various plants. As such, this minireview highlights the potential of Diaporthe sp. as a rich source of bioactive compounds by emphasizing on their diverse chemical entities and potent biological properties. The bioactive compounds produced are of significant importance to act as new lead compounds for drug discovery and development.

• Fibers and Polymers
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• v.7 no.2
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• pp.129-138
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• 2006

Using a strain-controlled rheometer, the steady shear flow properties of aqueous xanthan gum solutions of different concentrations were measured over a wide range of shear rates. In this article, both the shear rate and concentration dependencies of steady shear flow behavior are reported from the experimentally obtained data. The viscous behavior is quantitatively discussed using a well-known power law type flow equation with a special emphasis on its importance in industrial processing and actual usage. In addition, several inelastic-viscoplastic flow models including a yield stress parameter are employed to make a quantitative evaluation of the steady shear flow behavior, and then the applicability of these models is also examined in detail. Finally, the elastic nature is explained with a brief comment on its practical significance. Main results obtained from this study can be summarized as follows: (1) Concentrated xanthan gum solutions exhibit a finite magnitude of yield stress. This may come from the fact that a large number of hydrogen bonds in the helix structure result in a stable configuration that can show a resistance to flow. (2) Concentrated xanthan gum solutions show a marked non-Newtonian shear-thinning behavior which is well described by a power law flow equation and may be interpreted in terms of the conformational status of the polymer molecules under the influence of shear flow. This rheological feature enhances sensory qualities in food, pharmaceutical, and cosmetic products and guarantees a high degree of mix ability, pumpability, and pourability during their processing and/or actual use. (3) The Herschel-Bulkley, Mizrahi-Berk, and Heinz-Casson models are all applicable and have equivalent ability to describe the steady shear flow behavior of concentrated xanthan gum solutions, whereas both the Bingham and Casson models do not give a good applicability. (4) Concentrated xanthan gum solutions exhibit a quite important elastic flow behavior which acts as a significant factor for many industrial applications such as food, pharmaceutical, and cosmetic manufacturing processes.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.5B no.2
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• pp.118-122
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• 2005

Electro-chemo-mechanical devices or artificial muscles based on conducting polymers (CP) are presented as bilayers, CP/adhesive polymer, or as triple layers, CP/adhesive polymer/CP. Those soft and wet materials, working in aqueous solutions of a salt, mimic the composition of most organs from animals. Under electrochemical control, so working as new electrical machines, they produce continuous, reverse and elegant bending movements, mimicking those produce by animal muscles. By means of the current a perfect controls of the movement rate is attained giving soft and continuous movements. Muscles able to sense the chemical and mechanical conditions of work or muscle having tactile sense, as will be presented here, are being developed. All of them are founded on the non-stoichiometric nature of the soft and wet materials.