• Journal of the Korean Chemical Society
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• v.65 no.1
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• pp.9-14
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• 2021

In this study, the DFT calculation was performed using the B3LYP/6-31G(d,p) basis sets for the reaction process in which phenanthrene decomposes due to the chain reaction of two OH radicals on phenanthrene in the gaseous state of 298 K at 1 atm. As a result of the calculation, even when two OH radicals act on phenanthrene in a chain, the reaction for producing phenanthren-9-ol is predicted to be more advantageous than the reaction for producing phenanthren-1-ol. On the other hand, it was predicted that the OH addition process at room temperature would be advantageous for the priority of the OH addition and H abstraction process.

• Journal of Korean Society of Water and Wastewater
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• v.35 no.1
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• pp.27-37
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• 2021

Tetracycline is one of the most commonly used as antibiotics for the livestock industry and it is still widely used nowadays. Tetracycline and its metabolites are excreted with excrement, which is difficult to completely removed with conventional sewage treatment, therefore it is apprehended that the tetracycline-resistant bacteria occurs. In this study, the oxidant named ferrate(VI) was used to degrade the tetracycline and investigate the reaction between ferrate(VI) and tetracycline under various aqueous conditions. The highest degradation efficiency of tetracycline occurred in basic condition (pH 10.1 ± 0.1) because of the pKa values of tetracycline and ferrate(VI). The results also showed the effect of water temperature on the degradation of tetracycline was not significant. In addition, the dosage of ferrate(VI) was higher, the degradation of tetracycline and the self-degradation of ferrate(VI) also higher, finally the efficiency of ferrate(VI) was lower. The results said that the various mechanisms effects the reaction of ferrate(VI) oxidation, it required the consideration of the characteristics of the target compound for optimal degradation efficiency. Additionally, intermediate products were detected with LC/MS/MS and three degradation pathways were proposed.

• Applied Chemistry for Engineering
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• v.18 no.2
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• pp.136-141
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• 2007

The decomposition of chlorinated methanes including $CCl_4$, $CCl_3H$, and $CCl_2H_2$ was carried out using a thermal plasma process and the characteristics of the process were investigated. The thermal equilibrium composition was analyzed with temperature by Fcatsage program. The decomposition rates at various process parameters including the concentration of reactants, flow rate of carrier gas, and quenching rate, were evaluated, where sufficiently high conversion over 92% was achieved. The generation of main products was strongly influenced by the reaction atmosphere; carbon, chlorine, and hydrogen chloride at neutral condition; carbon dioxide, chlorine, and hydrogen chloride at oxidative condition. The decomposition mechanism was speculated considering the results from Factsage and the identification of generated radicals and ionic species. The main decomposition pathways were found to be dissociative electron attachment and oxidative by radicals formed in a plasma state.

• Korean Journal of Environmental Biology
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• v.40 no.3
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• pp.255-266
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• 2022

In crustaceans, molting is regulated by interactions between ecdysteroid and juvenile hormone (JH) signaling pathway-related genes. Unlike the ecdysteroid signaling pathway, little information on the role of JH signaling pathway-related genes in molting is available in zooplanktonic crustaceans. In this study, three genes (juvenile hormone acid O-methyltransferase (JHAMT), methoprene-tolerant (Met), and juvenile hormone epoxide hydrolase (JHEH)) which are involved in the synthesis, receptor-binding, and degradation of JH were identified using sequence and phylogenetic analysis in the brackish water flea, Diaphanosoma celebensis. Transcriptional changes in these genes during the molting cycle in D. celebensis were analyzed. Sequence and phylogenetic analysis revealed that these putative proteins may be functionally conserved along with those of insects and other crustaceans. In addition, the expression of the three genes was correlated with the molting cycle of D. celebensis, indicating that these genes may be involved in the synthesis and degradation of JH, resulting in normal molting. This study will provide information for a better understanding of the role of JH signaling pathway-related genes during the molting process in Cladocera.

• Journal of the Korean Chemical Society
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• v.44 no.4
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• pp.328-336
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• 2000

The pulsed-delayed extraction (PDE) in linear time-of-flight mass spectrometer(TOF MS) is characterized on the enhancement of resolution, mass-depth of focus and effect of instrumentahan 2000. The ion signals separate isotopically by up to molecular weight of 2500 in instrumental broadening of 5 ns, which is a good agreement with calculation. The fragmentation paths of PPG can be sug-gested by the isotopica distributions of fragment series produced when PPG desorbed from graphite surface.

• Applied Biological Chemistry
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• v.25 no.3
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• pp.126-134
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• 1982

When $^{14}C-2$, 6-Diethylaniline (2, 6-DEA) was incubated aerobically in soil, $^{14}CO_2$ evolved from non-sterile soil A and B was 6.5 and 10.1%, respectively, in the 21st week. Methanol could extract 3.1 and 13.5% of the radioactivity from soil A and B, respectively, 2, 6-Diethylacetanilide was detected as a degradation product in soil. Chaetomium globosum produced 2, 6-diethyl-p-benzoquinone as a degradation product in pure culture. A possible pathway was proposed to include p-hydroxylation of 2, 6-DEA, formation of quinoneimine, and the subsequent hydrolysis with the release of ammonia.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.2A
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• pp.119-127
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• 2012

In this paper a super-resolution time delay estimation algorithm is developed for real-time locating systems (RTLSs) that employ a direct-sequence spread spectrum technique, along with its performance analysis in multipath environments. The classical correlation method provides relatively good performance in line-of-sight (LOS) environments but its performance seriously degrades in multipath environments, especially when signals are spaced closer than a PN chip. Therefore we shall develop a super-resolution time delay estimation algorithm that may estimate the time delays of multipath signals even in closely spaced multipath environments using the MUSIC algorithm for direction-of-arrival estimation and analyze its performance by applying the algorithm to the ISO/IEC 24730-2.1 RTLS system. 

• Analytical Science and Technology
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• v.27 no.6
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• pp.292-299
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• 2014

Iopromide is an X-ray contrast agent that has been detected frequently with high concentration level in surface waters. Structural characterization of degradation products and measurement of degradation efficiency of iopromide by an electron beam irradiation were performed. For the fortified sample with iopromide, electron beam irradiation (UELV-10-10S, klysotrn, 10 MeV, 1 mA and 10 kW) was performed. The chemical structures of I_D_665 and I_D_663, which are degradation products of iopromide, were proposed by interpretation of mass spectra and chromatograms by LC/ESI-MS/MS. The mass fragmentation pathways of mass spectra in tandem mass spectrometry were also proposed. Iopromide was degraded 30.5~98.4% at dose of 0.3~5 kGy, and 97.8~30% in the concentration range $0.5{\sim}100{\mu}g/kg$ at electron beam dose of 0.3 kGy, respectively. Thus, increased degradation efficiency of iopromide by electron beam irradiation was observed with a higher dose of electron beam and lower concentration.

• KSBB Journal
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• v.18 no.3
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• pp.239-242
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• 2003

To develop a nicotine-degrading material (NDM), the natural herbal extract was studied. For the in vitro verification, the herbal extract was mixed into the dilute nicotine solution and the ability of NDM to degrade nicotine into cotinine was measured spectrophotometically. In the in vivo study, the rats in experimental and control groups were orally fed with the herbal extract and water, respectively, for 2 weeks. And then, 3 ㎎/㎏ nicotine was administered to both groups by intraperitoneal injection. In results, the ability of NDM to degrade nicotine into cotinine was shown 2.5 fold higher after 90 min reaction in comparison with the control group. In addition, a decrease of 33% in nicotine concentration and a increase of 57% in cotinine concentration were shown in rat blood. Therefore, NDM was shown to be effective in the conversion of nicotine into cotinine.

• Clean Technology
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• v.16 no.3
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• pp.198-205
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• 2010

Two sets of thermal reaction experiment for chlorinated hydrocarbons were performed using an isothermal tubular-flow reactor in order to investigate thermal decomposition, including product distribution of chlorinated hydrocarbons. The effects of $H_2$ or Ar as the reaction atmosphere on the thermal decomposition and product distribution for dichloromethane($CH_2Cl_2$) was examined. The experimental results showed that higher conversion of $CH_2Cl_2$ was obtained under $H_2$ atmosphere than under Ar atmosphere. This phenomenon indicates that reactive-gas $H_2$ reaction atmosphere was found to accelerate $CH_2Cl_2$ decomposition. The $H_2$ plays a key role in acceleration of $CH_2Cl_2$ decomposition and formation of dechlorinated light hydrocarbons, while reducing PAH and soot formation through hydrodechlorination process. It was also observed that $CH_3Cl,\;CH_4,\;C_2H_6,\;C_2H_4$ and HCl in $CH_2Cl_2/H_2$ reaction system were the major products with some minor products including chloroethylenes. The $CH_2Cl_2$/Ar reaction system gives poor carbon material balance above reaction temperature of $750^{\circ}C$. Chloroethylenes and soot were found to be the major products and small amounts of $CH_3Cl$ and $C_2H_2$ were formed above $750^{\circ}C$ in $CH_2Cl_2$/Ar. The thermal decomposition reactions of chloroform($CHCl_3$) with argon reaction atmosphere in the absence or the presence of $CH_4$ were carried out using the same tubular flow reactor. The slower $CH_3Cl$ decay occurred when $CH_4$ was added to $CH_3Cl$/Ar reaction system. This is because :$CCl_2$ diradicals that had been produced from $CHCl_3$ unimolecular dissociation reacted with $CH_4$. It appears that the added $CH_4$ worked as the :$CCl_2$ scavenger in the $CHCl_3$ decomposition process. The product distributions for $CHCl_3$ pyrolysis under argon bath gas were distinctly different for the two cases: one with $CH_4$ and the other without $CH_4$. The important pyrolytic reaction pathways to describe the important features of reagent decay and intermediate product distributions, based upon thermochemistry and kinetic principles, were proposed in this study.