• Journal of the Korean Chemical Society
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• v.48 no.6
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• pp.561-567
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• 2004

The influence of ultrasound frequency, dissolved gases, and initial concentration on the decomposition of sodium dodecylbenzene sulfonate(DBS) aqueous solution was investigated using ultrasound generator with 200 W ultrasound power. The decomposition rates at three frequencies(50, 200, and 600 kHz) examined under argon atmosphere were highest at 200 kHz. The highest observed decomposition rate at 200 kHz occurred in the presence of oxygen followed by air and argon, helium, and nitrogen. The effect of initial concentration of DBS on the ultrasonic decomposition was decreased with increasing initial concentration and would depend upon the formation of micelle in aqueous solution. It appears that the ultrasound frequency, dissolved gases, and initial concentration play an important role on the sonolysis of DBS. Sonolysis of DBS mainly take place at the interfacial region of cavitation bubbles by both OH radical attack and pyrolysis to alkyl chain, aromatic ring, and headgroup.

• Journal of the Korean Chemical Society
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• v.39 no.6
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• pp.453-458
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• 1995

We have applied Pb2+ to the structural analysis of 5S rRNA from Pseudomonas alcaligenes. The mode of Pb2+-induced clevage on 5S rRNA has shown several specific features which may be utilized for the examination of tertiary structure of 5S rRNA: Pb2+ does not attack the stable helical stems; single stranded regions or bulges are attacked in variable susceptibilities depending on the positions of the sequences or the bases on the molecule; unstable helical region d is not attacked at all; only 3' sided strand of unstable helical stem C is weakly attacked, leaving 5' sided strand unattacked. Based on the Pb2+ cleavage properties and the structural analysis of Xanthomonas celebensis 5S rRNA, we have proposed a working hypothesis for the tertiary interactions in 5S rRNA.

• Journal of the Korean Chemical Society
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• v.57 no.6
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• pp.703-711
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• 2013

In the present investigation, kinetic studies of oxidation of formic acid with and without catalyst and promoter in aqueous acid media were studied under the pseudo-first order conditions [formic acid]T ${\gg}[Cr(VI)]_T$ at room temperature. In the 1,10-phenanthroline (phen) promoted path, the cationic Cr(VI) phen complex is the main active oxidant species undergoes a nucleophilic attack by the substrate to form a ternary complex which subsequently experiences a redox decomposition through several steps leading to the products $CO_2$ and $H_2$ along with the Cr(III) phen complex. The anionic surfactant (i.e., sodium dodecyl sulfate, SDS) and neutral surfactant (i.e., Triton X-100, TX-100) act as catalyst and the reaction undergo simultaneously in both aqueous and micellar phase with an enhanced rate of oxidation in the micellar phase. Whereas the cationic surfactant (i.e., N-cetyl pyridinium chloride, CPC) acts as an inhibitor restricts the reaction to aqueous phase. The observed net enhancement of rate effects has been explained by considering the hydrophobic and electrostatic interaction between the surfactants and reactants. The neutral surfactant TX-100 has been observed as the suitable micellar catalyst for the phen promoted chromic acid oxidation of formic acid.

• Journal of the Korean Chemical Society
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• v.28 no.5
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• pp.328-334
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• 1984

A series of phenyl N-benzenesulfonylchloroformimidate derivatives (p-H, p-Cl, p-CH3 & p-OCH3) were prepared and the hydrolysis of these compounds were studied kinetically at various pH by UV spectrophotometry in 1 ; 4 dioxane-water at $25^{\circ}C$. Hammett ${\rho}$ values measured at pH 5.0 (${\rho}$ = -0.45) and pH 10.0 (${\rho}$ = 0.40) indicate that the reaction proceeds via an azocarbonium ion intermediate in the acidic medium, whereas, it involves direct attack by hydroxide ion on the azomethine carbon atom occurs under the basic medium. The formation of stabilized azocarbonium ion species at pH 5.0 is also consistent with the large solvent effect(m = 1.3-1.5 & n = 5.0-5.5). On the basis of these findings, we may concluded that the hydrolysis of phenyl N-benzenesulfonylchloroformimidate derivatives proceeds by $SN_1$ below pH 8.0, however, above pH 10.0, the hydrolysis proceeds through $SN_2$ and in the range of pH 8.0-10.0, these two reactions occur competitively.

• Journal of the Korean Wood Science and Technology
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• v.41 no.6
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• pp.559-565
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• 2013

This study evaluated the ability of white and brown rot fungi to decompose fire retardant-treated wood by measuring mass loss. Anti efficacy of FRT against sapstain and mold fungi was evaluated. Wood was treated with liquid sodium silicate and boric acid, ammonium borate, di-ammonium phosphate. Retardant treated wood was then subjected to fungal decay resistance tests performed according to KS standard method using a brown-rot fungus, Fomitopsis palustris and white rot fungus Trametes versicolor. Aspergillus niger, Penicillium funiculosum, Rhizopus nigricans, Aureobasidium pullulans, Tricoderma virede fungi were used anti-sapstain and mold test. Boron and phosphorus chemicals used in this study increased the resistance of fire retardant treated wood against both fungal attack. Anti mold and sapstain efficacy of the fire retardant treated wood was excellent but there were difference depend on mold. After the liquid sodium silicate treatment, the second chemical treatment process could lead chemical fixation into wood, which effects decay resistance.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.5
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• pp.87-92
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• 2019

This study is the analysis of causes of printed circuit board (PCB) in collective protection equipment failure and quality improvement. The equipment is a component of the weapon system currently in operation and serves to defend against enemy chemical and biological attack as well as heating and cooling functions. However, during operation in the military, fans of condensate assembly failed to operate. The cause of the failure is the burning of PCB. It was found that the parts were heated according to the continuous cooling operation under the high temperature environmental conditions. Accordingly, the electronic components exposed to high temperature were deteriorated and destroyed. To solve this problem, PCB apply to heatsink. The performance test of improved PCB has been completed. Futhermore system compatibility, positive pressure maintenance and noise test were performed. This improvement confirmed that no faults have occurred in PCB so far. Therefore, the quality of the equipment has improved.

• 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.

• The Plant Pathology Journal
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• v.34 no.1
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• pp.35-43
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• 2018

Root-knot nematodes (Meloidogyne spp.) are parasites that attack many field crops and orchard trees, and affect both the quantity and quality of the products. A root-colonizing bacterium, Pseudomonas chlororaphis O6, possesses beneficial traits including strong nematicidal activity. To determine the molecular mechanisms involved in the nematicidal activity of P. chlororaphis O6, we constructed two mutants; one lacking hydrogen cyanide production, and a second lacking an insecticidal toxin, FitD. Root drenching with wild-type P. chlororaphis O6 cells caused juvenile mortality in vitro and in planta. Efficacy was not altered in the fitD mutant compared to the wild-type but was reduced in both bioassays for the mutant lacking hydrogen cyanide production. The reduced number of galls on tomato plants caused by the wild-type strain was comparable to that of a standard chemical nematicide. These findings suggest that hydrogen cyanide-producing root colonizers, such as P. chlororaphis O6, could be formulated as "green" nematicides that are compatible with many crops and offer agricultural sustainability.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.43 no.2 s.344
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• pp.13-17
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• 2006

Pentacene channel for organic thin film transistor was deposited on the SiOC film by thermal evaporation. The growth of pentacene is related with the Diels-Alder reaction and the nucleophilic reaction by the thermal induction. The surface is an important factor to control the recursive Diels-Alder reaction for growing of pentacene on SiOC far The terminal C=C double bond of pentacene molecule was broken easily as a result of attack of the nucleophilic reagents on the surface of SiOC film. The nucleophilic reaction can be accelerated by increasing temperature on surface, and it maks pentacene to grow hardly on the SiOC film with a flow rate ratio of $O_2/(BTMSM+O_2)=0.5$ due to its inorganic property. The nucleophlic reaction mechanism is $SN_2(bimolecular nucleophilic substitution)$ type.

• Journal of Sensor Science and Technology
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• v.16 no.2
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• pp.97-103
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• 2007

Crystallized carbon nitride film that has many stable physical and/or chemical properties has been expected potentially by a new electrical material. However, one of the most significant problems degrading the quality of carbon nitride films is an existence of N-H and C-H bonds from the deposition environment. The possibility of these reactions with hydroxyl group in carbon nitride films, caused by a hydrogen attack, was suggested and proved in our previous reports that this undesired effect could be applied for fabricating micro-humidity sensors. In this study, MIS capacitor and MIM capacitor with $5{\mu}m{\times}5{\mu}m$ meshes were fabricated. As an insulator, carbon nitride film was deposited on a $Si_{3}N_{4}/SiO_{2}/Si$ substrate using reactive magnetron sputtering system, and its dielectric constant, C-V characteristics and humidity sensing properties were investigated. The fabricated humidity sensors showed a linearity in the humidity range of 0 %RH to 80 %RH. These results reveal that MIS and MIM $CN_{X}$ capacitive humidity sensors can be used for Si based micro-humidity sensors.