• Applied Chemistry for Engineering
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• v.4 no.2
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• pp.318-323
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• 1993

Pentachloroethane($CHCl_2CCl_3$) was synthesized and reacted with hydrogen fluoride using antimony pentahalide catalyst($SbCl_xF_y$) in order to manufacture HCFC-123$(CF_3CHCl_2)$, a potential CFC-11$(CFCl_3$) substitute candidate. Products analyses showed the fluorination proceeds through fluorine-chlorine exchanges between $HF/SbCl_xF_y$ and $SbCl_xF_y/CCl_3CHCl_2$ respectively. The degree of fluorination of $CCl_3$ group in pentachloroethane was greatly affected on the reaction temperature, but the effect of catalyst concentration was relatively small. Mechanistic study was also performed to elucidate the pathway to the formation of side-products such as $CCl_3CFCl_2$, $CFCl_2CFCl_2$ and $CF_2ClCFCl_2$.

• Korean Journal of Veterinary Research
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• v.30 no.4
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• pp.487-497
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• 1990

This study was carried out to observe in vitro effect of praziquantel on the tegumental changes of Heterophyopsis continua with scanning electron microscope. Metacercariae were collected from the perch, Lateolabrax japonicus, by artificial digestion technique and fed to 2-week old chickens. Adult worms were recovered from small intestine of chickens 8 days after infection. For working solutions, praziquantel was diluted with TC199 medium at concentration of 0.01, 0.1. 1 and $10{\mu}g/ml$. To each petri dish containing 10ml of solution, 5~10 worms were introduced and incubated at $37^{\circ}C$. For the scanning electron microscopy(SEM), the worms were fixed in cold 2.5% glutaraldehyde, dehydrated in a series of graded ethanol and freeze-dried. Dried specimen was mounted on stub and coated with gold and observed in an SEM. The results were as follows: 1. Severe tegumental alterations were recognized by scanning electron microscope. Bleb formation of tegument was observed in 5 minute group and most pronounced on anterior tegument of worms. The number and size of blebs increased as incubation time prolonged. 2. The surface destruction was more pronounced at ventral margin between the oral and the ventral suckers. 3. The sensory papillae were slightly affected, but destruction of tegumental spine was not recognized. 4. The effect of praziquantel on the worm was found dependent on the concentration and incubation time, however, the effect was more dependent upon the incubation time.

• Journal of the Economic Geographical Society of Korea
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• v.17 no.1
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• pp.178-199
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• 2014

This study aims to understand regional specificity and its impact on the IT service industry in Fairfax County. Fairfax County primarily specializes in the IT service in the United States, and it has cultivated a resilient and unique industrial environment. Business-related initiatives by the federal government have resulted in the influx and expansion of IT service firms, the formation of new small firms, the abundance of skilled workers, and the growth of the IT services related with the federal procurement market, though the government policies do not explicitly intend to affect the industrial path in Fairfax County. Meanwhile, local institutions have provided various programs and services for both incumbent firms and potential entrants, and have recently focused on the accumulation and leverage of relational assets among economic actors through a variety of networking venues.

• Bulletin of the Korean Chemical Society
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• v.17 no.9
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• pp.802-807
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• 1996

Second-order rate constants have been measured spectrophotometrically for the reactions of aryl benzoates (X-C6H4CO2C6H4-Y) with EtO-, Z-C6H4O- and Z-C6H4C(Me)=NO- in absolute ethanol at 25.0 ℃. All the reactions have been performed in the presence of excess 18-crown-6 ether in order to eliminate the catalytic effect shown by alkali metal ion. A good Hammett correlation has been obtained with a large ρ- value (-1.96) when σ- (Z) constant was used for the reaction of p-nitrophenyl benzoate (PNPB) with Z-C6H4O-. Surprisingly, the one for the reaction of PNPB with Z-C6H4C(Me)=NO- gives a small but definitely positive ρ- value (＋0.09). However, for reactions of C6H5CO2C6H4-Y with EtO-, correlation of log k with σ- (Y) constant gives very poor Hammett correlation. A significantly improved linearity has been obtained when σ0 (Y) constant was used, indicating that the leaving group departure is little advanced at the TS of the RDS. For reactions of X-C6H4CO2C6H4-4-NO2 with EtO-, C6H5O- and C6H5C(Me)=NO-, correlations of log k with σ (X) constants for all the three nucleophile systems give good linearity with large positive ρ values, e.g. 2.95, 2.81 and 3.06 for EtO-, C6H5O- and C6H5C(Me)=NO-, respectively. The large ρ values clearly suggest that the present reaction proceeds via a stepwise mechanism in which the formation of the addition intermediate is the RDS.

• Journal of Ginseng Research
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• v.46 no.3
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• pp.444-453
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• 2022

Background: Compound K (CK) is among the protopanaxadiol (PPD)-type ginsenoside group, which produces multiple pharmacological effects. Herein, we examined the effects of CK on muscle atrophy under hyperlipidemic conditions along with its pro-myogenic effects. Further, the molecular pathways underlying the effects of CK on skeletal muscle have been justified. Methods: C2C12 myotubes were treated with palmitate and CK. C2C12 myoblasts were differentiated using CK for 4-5 days. For the in vivo experiments, CK was administered to mice fed on a high-fat diet for 8 weeks. The protein expression levels were analyzed using western blotting analysis. Target protein suppression was performed using small interfering (si) RNA transfection. Histological examination was performed using Jenner-Giemsa and H&E staining techniques. Results: CK treatment attenuated ER stress markers, such as eIF2a phosphorylation and CHOP expression and impaired myotube formation in palmitate-treated C2C12 myotubes and skeletal muscle of mice fed on HFD. CK treatment augmented AMPK along with autophagy markers in skeletal muscle cells in vitro and in vivo experiments. AMPK siRNA or 3-MA, an autophagy inhibitor, abrogated the impacts of CK in C2C12 myotubes. CK treatment augmented p38 and Akt phosphorylation, leading to an enhancement of C2C12 myogenesis. However, AMPK siRNA abolished the effects of CK in C2C12 myoblasts. Conclusion: These findings denote that CK prevents lipid-induced skeletal muscle apoptosis via AMPK/autophagy-mediated attenuation of ER stress and induction of myoblast differentiation. Therefore, we may suggest the use of CK as a potential therapeutic approach for treating muscle-wasting conditions associated with obesity.

• Communications of Mathematical Education
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• v.38 no.1
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• pp.69-92
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• 2024

This study analyzed students' mathematical noticing in high school sequence classes based on students' two perceptions of sequence. Specifically, mathematical noticing was analyzed in four aspects: center of focus, focusing interaction, task features, and nature of mathematics activities, and the following results were obtained. First of all, the change pattern of central of focus could not be uniquely described by any one component among 'focusing interaction', 'task features', and 'the nature of mathematical activities'. Next, the interactions between the components of mathematical noticing were identified, and the teacher's individual feedback during small group activities influenced the formation of the center of focus. Finally, students showed two different modes of reasoning even within the same classroom, that is, focusing interaction, task features, and nature of mathematics activities that resulted in the same focus. It is hoped that this study will serve as a catalyst for more active research on students' understanding of sequence.

• Microbiology and Biotechnology Letters
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• v.47 no.1
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• pp.164-171
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• 2019

Radiation therapy has many side effects, such as digestive mucosal ulcers, without regard to its efficacy. The purpose of this study is to address an alternative method to replace the limitation of radiation therapy using radiomimetic microbial ribotoxins. In the evaluation of cancer therapy, we analyzed the formation of colorectal cancer (CRC) cell spheroids, which can take into account the heterogeneous cellular constitution, tumor stem cells, and the surrounding microenvironment. Ribotoxic stress interfered with the spheroid structure composed of relatively small clusters. Spheroids under ribotoxic stress were structurally sparse and their shrinkage was very slow. In the control group, the clusters of strongly aggregated cells were resistant to physical stress, but the ribotoxic stress-exposed spheroids were easily broken up by the physical stress. Moreover, the ribosome-insulted CRC cells slowly migrated to form clusters and the cell-cell junctional points in the ribosome-insulted spheroids were rarer than those in the control CRC spheroid. Moreover, levels of the cell-to-cell junctional protein E-cadherin were suppressed by ribotoxic stress in both allograft and xenograft spheroids. In conclusion, the radiomimetic microbial ribotoxins induced structural defects in CRC cell spheroids via retardation of migration and cell-cell junction in the formation of three-dimensional structures, and provides a basis for the mechanism of pharmacological radiomimetic anticancer actions as an alternate to radiotherapy against cancer.

• Economic and Environmental Geology
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• v.50 no.5
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• pp.325-340
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• 2017

The Seongdo Pb-Zn deposit, located in the northwestern part of the Ogcheon Metamorphic Belt, consists of skarn ore replacing limestone within the Hwajeonri Formation of Ogcheon Group and hydrothermal vein ore filling the fracture of host rock. Skarn minerals comprise mostly hedenbergitic pyroxene, garnet displaying oscillatory zonal texture composed of grossular and andradite, and a small amount of wollastonite, tremolite, and epidote, indicating reducing condition of formation. Ore minerals of skarn ore include sphalerite and galena with a small amount of pyrite, pyrrhotite, and chalcopyrite. In hydrothermal vein ore, arsenopyrite, sphalerite, chalcopyrite, and pyrite occur with a small amount of galena, native Bi, and stannite. Chemical compositions of sphalerite vary from 17.4 mole% FeS in average for dark grey sphalerite, 3.6 mole% for reddish brown sphalerite in skarn ore, and to 10.3 mole% FeS in hydrothermal vein ore. In comparison with representative metallic deposits in South Korea on the FeS-MnS-CdS diagram, skarn and hydrothermal vein ore plot close to the field of Pb-Zn deposits and Au-Ag deposits, respectively. Arsenic contents of arsenopyrite in hydrothermal vein ore decrease from 31.93~33.00 at.% in early stage to 29.58~30.21 at.% in middle stage, and their corresponding mineralizing temperature and sulfur fugacity are $441{\sim}490^{\circ}C$, $10^{-6}{\sim}10^{-4.5}atm$. and $330{\sim}364^{\circ}C$, <$10^{-8}atm$. respectively. Phase equilibrium temperatures calculated from Fe and Zn contents for coexisting sphalerite and stannite in hydrothermal vein are $236{\sim}254^{\circ}C$. Sulfur isotope compositions are 5.4~7.2‰ for skarn ore and 5.4~8.4‰ for hydrothermal vein ore, being similar or slightly higher to magmatic sulfur, suggesting that ore sulfur was mostly of magmatic origin with partial derivation from host rocks. However, much higher sulfur isotope equilibrium temperatures of $549^{\circ}C$와 $487^{\circ}C$, respectively for skarn ore and hydrothermal ore, than those estimated from phase equilibria imply that isotopic equilibrium has not been fully established.

• Korean Journal of Oriental Medicine
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• v.17 no.2
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• pp.1-15
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• 2011

In the latter half of the Joseon(朝鮮) Dynasty, the medical world was encountering a great change. It is said that a large stream between the first half and the latter half of the Joseon Dynasty was a qualitative transition from official relationships to private relationships, that is, from adjustments by governmental power to contractual relationships between individuals. Doctors who can be said to be the core of the medical world became to be left in severer competition. The fact that the number of people engaged in medical practice increased to the extent that doctors had to compete with each other implies that not only demand for medical care was increasing but also that medical care was becoming social service that must be shared by all people in the Joseon Dynasty rather than by small numbers of men of power. Anyway, it seems like that, in the competition that was becoming fiercer, they tried to establish their authority in diverse methods unlike before. As an authority to determine the social positions of doctors in the latter half of the Joseon Dynasty, the government was still occupying an important position, but doctors tried to show off their medical techniques utilizing excellent teachers or books. Meanwhile, they were making efforts to improve treating skills and thereby they were contributing to the development of medical techniques although they were sometimes criticised because of radical treatment or fierce drugs. In this process, it seems like that some doctors made efforts to establish the social meaning of medicine and their identity. In the short dialogue with Hong Yangho(洪良浩), Cho Gwangil(趙光一) was presenting the image of doctors as active and subjective beings. Pointing out the fact that in the society where feudal position systems were still impregnable, even the Confucian scholars who could be considered as a leading group could not but be passive in front of the sovereign power, he emphasized the fact that doctors could practice treatment as they liked. In that he re-discovered the meaning of treating people's diseases as a professional intellectual and that he was forming a subjective sense that medical techniques are active self expression, it can be carefully said that Cho Gwangil was obtaining his identity as a doctor. In the society in the Joseon Dynasty where the position systems were still valid and the value system under Neo-confucianism(性理學) supporting the system was impregnable, this change can be thought to be small yet quite meaningful.

• Korean Journal of Culture and Social Issue
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• v.20 no.4
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• pp.469-491
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• 2014

The purpose of this research is to examine the factors influencing on worker's job-satisfaction analyzing the influence of emotional support from fellow workers, resiliency of self-efficacy, stress and job-performance. A total of 456 completed questionnaire, consisted of small business workers 253 (male 89, female 164) and middle school teachers 203 (male 44, female 159). The questionnaire showed relatively high reliability, with Cronbach α ranging from .83 to .91. The results of the path analysis and effect analysis showed very similar pattern in the group of small business workers and middle school teachers. Based on the path analysis, emotional support from fellow workers had a positive influence on the workers resiliency of self-efficacy. Consequently, the enhanced resiliency of self-efficacy increased the job-performance, however decreased the stress, which in turn contributed to increase the job-satisfaction significantly. Based on the effect analysis, resiliency of self-efficacy showed the most big size of positive total effect to worker's job-satisfaction, followed by job-performance and emotional support. On the other hand, stress showed negative effect on job-satisfaction.