• Bulletin of the Korean Chemical Society
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• v.25 no.7
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• pp.1041-1045
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• 2004

Kinetic studies of the pyridinolysis $(XC_5H_4N)$ of aryl dithiomethylacetates $(CH_3CH_2C(=S)SC_6H_4Z,\;1)$ are carried out in acetonitrile at $60.0^{\circ}C$. A biphasic Bronsted plot is obtained with a change in slope from a large $({\beta}X\;{\cong}\;0.8)$ to a small $({\beta}X\;{\cong}\;0.2)$ value at $pK_a^{\circ}$ = 5.2, which is attributed to a change in the rate limiting step from breakdown to formation of a zwitterionic tetrahedral intermediate, $T^{\pm}$, in reaction path as the basicity of the pyridine nucleophile increases. This mechanism is supported by the change of the cross-interaction constant ${\rho}xz$ from a large positive ( ${\rho}xz$ = +1.36) for the weakly basic pyridines to a small negative ( ${\rho}_xz$ = -0.22) value for the strongly basic pyridines. The magnitudes of ${\rho}z$ and activation parameters are also consistent with the proposed mechanism.

• KIISE Transactions on Computing Practices
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• v.22 no.1
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• pp.26-31
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• 2016

Migrim(Migration enhanced Grid Middleware) is a communication middleware between embedded devices and multiple servers. In traditional client-server communication, users' requests are sent to and processed by a designated server even though the server may suffer from a heavy load. In addition, the designated server may not have proper information to process the user's request correctly. Proposed connection migration mechanism and transaction migration mechanism are designed to improve the performance and accuracy of request processing. The connection migration is a procedure for delegating a connection to another server, which results in a well-distributed balancing of load among the servers. The transaction migration is a procedure for delegating a transaction to another server, and improves the accuracy of response.

• Applied Biological Chemistry
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• v.44 no.1
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• pp.1-6
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• 2001

To elucidate the apoptosis mechanism of Trichoplusia ni cell, fundamental studies for apoptosis induction and suppression were performed. Hygromycin B, a known inducer of apoptosis, started the inhibition of T. ni cell growth at $200\;{\mu}/ml$ concentration. Furthermore, at $400\;{\mu}/ml$ concentration, DNA fragmentation was detected on day 2 of incubation. Although both dexamethasone and sodium butyrate inhibited T. ni cell growth, DNA fragmentation was not detected by both treatments. Also, when apoptosis induced T. ni cells with $200\;{\mu}/ml$ hygromycin B were treated with caspase inhibitor (Ac-DEVD-CHO), the apoptotsis was suppressed by 36%. In addition, N-acetylcysteine, another apoptosis repressor, also inhibited the apoptosis of T. ni cells. In order to express the anti-apoptosis gene (bcl-2), T. ni cells were transiently transformed with bcl-2 and its expression was confirmed by western blot analysis. These results showed the potential of developing new insect cell lines with suppressed apoptosis.

• Journal of the Korean Society of Industry Convergence
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• v.5 no.1
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• pp.39-43
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• 2002

In present much CMOS devices used in VLSI circuit and Logic circuit. With increasing a number of device in VLSI, the confidence becomes more serious. This paper describe the mechanism of breakdown on CMOS, especially n-MOS, based on Hydro Dynamic model with device self-heating. Additionally, illustrate the CMOS latch-up characteristics on simplified device structure on this paper.

• Journal of Power System Engineering
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• v.7 no.1
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• pp.68-73
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• 2003

The purpose of this study is to develop a new proportional pressure reducing valve and to verify the validity of a new mechanism with pressure control pin. The dynamic characteristics of the object pressure reducing valve was studied by numerical analysis of the mathematical model. Also, static and dynamic characteristics of the new pressure control valve were tested with a testing system based on the test standard.

• KSBB Journal
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• v.16 no.5
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• pp.486-492
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• 2001

The antimutagenic mechanism of the fraction III(RG III)separated from the water extract of Rehmannia glutionosa was investigated by Escherichia. coli GW and B/r strains. RG-III treatment did not affect the ${\beta}$-galactosidase activity E. coli GW-1060, 1106, 1107 and 1105. These results indicated that RG-III did not induce RecA protein amplification and did not also prevent the proteolytic cleavage of LexA. The bio-antimutagenicity and survival effect of RG-III on 4-nitroquinoline 1-oxide(4NQO), N-methyl-N-nitor-N\`-nitrosoguanidine(MNING) were investigate by E. coli B/r strains with have different pathway of DNA repai. RG-III slightly increased the survival of 4NQO-treated WP2, WP2s, WP67, CM561, CM611 cells, but the reactivation of survival cannot ve explained by the repair mode. RG-III caused the decrease of mutagenicity and lethality treated with MNNG in ZA159 despite of the increase in WP2, WP2s, WP67, CW561, CM611. Compared with bio-antimutagenic effects of RG-III on 4NQO, greatly increased antimutagenic effects of RG-III were observed with all the E. coli B/r strains tested, but less active in ZA159. These results suggest that RG-III was identified as a blocking agent for preventing the 4NQO induced mutagenesis, and may act as chl-products.

• Natural Product Sciences
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• v.12 no.1
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• pp.14-18
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• 2006

The effect(s) of the volatile oil (VO) of Nigella sativa and its two components, ${\alpha}-pinene$ and ${\rho}-cymene$ on body temperature of male and female conscious mice were studied. Further investigations to delineate the mechanism(s) of action of the observed effect(s) by using various blockers involved in the central regulation of body temperature were made. VO and ${\alpha}-pinene$ caused significant reductions in rectal body temperature at is and 30 minute after treatment. ${\rho}-cymene$ had negligible effect on body temperature of mice. Cyproheptadine inhibited VO and ${\alpha}-pinene-induced$ hypothermia significantly. Nalbuphine inhibited ${\alpha}-pinene-induced$ hypothermia significantly but did not affect VO-induced hypothermia. Droperidol potentiated VO and ${\alpha}-pinene-induced$ hypothermia to a non-significant level; whereas atropine potentiated VO-induced hypothermia non-significantly. The study confirms further the role of serotoninergic receptors in the mechanism(s) of the observed pharmacological effects of the VO of Nigella sativa. It also indicated a possible role of opioid receptors in ${\alpha}-pinene-induced$ hypothermia.

• Journal of the Korean Chemical Society
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• v.30 no.3
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• pp.301-306
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• 1986

The rate constants for the solvolysis reactions of p-methoxybenzylchloride in ethanol-water mixtures were determined at 2$^{\circ}$ and 10$^{\circ}C$ up to 1600bar. Rates of reaction were increased with increasing temperature and pressure, and decreased with increasing solvent composition of ethanol mole fraction. From the rate constants, the values of the activation parameters (${{\Delta}V_o}^{\neq},\;{\Delta}{\beta}^{\neq},\;{\Delta}H^{\neq},\;and\;{\Delta}S^{\neq}$) were evaluated. The values of ${{\Delta}V_o}^{\neq}$ and ${\Delta}{\beta}^{\neq}$ exhibit the extremum behavior at about 0.30 mole fraction of ethanol. This behavior is discussed in terms of solvent structure variation. From these results, it could be postulated that the reaction proceeds through $S_N1$ mechanism.

• Journal of Korean Society for Atmospheric Environment
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• v.13 no.2
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• pp.161-170
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• 1997

The concentrations of dimethylsulfide (DMS) were determined using samples collected from a station located at Kosan, Cheju Island during two field campaigns held in December 1996 and January 1997. The atmospheric DMS concentrations measured at 6-hr intervals during the entire campaign periods, after excluding a few extreme values, spanned in the range of 14 to 410 pptv with mean and 1 SD value of 127 $\pm$ 94 pptv (N=42). Between two month periods during which the field campaigns were conducted, a notable reduction in DMS levels was observed which was comparable to the dramatic shift in air temperature. A considerable difference was also noted in DMS levels, when data were grouped by day/night basis. The cause of unexpected, high day-to-night DMS ratios is best explained in terms of high efficiency of daytime source processes relative to low efficiency of nighttime sink processes due to the characteristics of the study location. The surface water DMS of the study site, although scarcely measured, also behaved similarly to its atmospheric counterpart with its range from 0.3 to 19 nM (N=11). When correlation analysis was conducted between the atmospheric DMS concentration and other concurrently determined parameters, significant correlations were observed from most basic meteorological parameters such as windspeed, relative humidy, and air temperature. However, the existence of "not-so-strong" correlations between air temperature and DMS concentrations relative to other ones indicated that the effect of temperature on DMS behavior must be reflected in more complicated manners at the study site. The sea-to-air flux of DMS was approximated through an application of the mass-balance flux calculation method of Wylie and de Mora (1996) under the assumption that sink mechanism within the marine boundary layer is in steady-state condition with its counterpart, source mechanism. Based on this estimation method, we reached a conclusion that oceanic DMS emitted from the southwest sea of the Korean Peninsula can amount to approximately 9 $\sim$ 36 Gg S $yr^{-1}$.$yr^{-1}$.

• Transactions of Materials Processing
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• v.20 no.7
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• pp.479-484
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• 2011

Dry sliding wear behavior of AISI 52100 steel that has a pearlite or bainite microstructure was characterized to explore the effect of microstructure on the wear of the steel. Isothermal heat treatments were employed to obtain the different microstructures. Pin-on-disk type wear tests of the steel disk were performed at loads of 25~125N in air against an alumina ball. Sliding speed and wear distance used were 0.1m/sec and 300m, respectively. Worn surfaces, wear debris and cross-sections of the worn surfaces were examined with SEM to investigate the wear mechanism of the steel. Hardness of the steel was also evaluated. Wear rate of the steel was correlated with the hardness and the microstructure. On the whole, wear resistance increased with an increase in hardness. However, the pearlite microstructure showed superior wear resistance as compared to the bainite microstructure with a similar hardness. The effect of the microstructure on the wear rate was attributed to the morphological differences of the carbide in the microstructure, which was found to have a significant effect on strain hardening during the wear.