• Applied Chemistry for Engineering
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• v.3 no.4
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• pp.686-693
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• 1992

In order to investigate the mechanism of dissolutin of nickel from a matte composed essentially of heazlewoodite and ferronickel, the leaching in an aqueous solution of hydrochloric was carried out at $50-90^{\circ}C$, 0.5-3.ON HCl, and with the particle sizes between $100-160{\mu}m$ and $400-500{\mu}m$. The leaching rate of heazlewoodite was much rapider than that of ferronickel, and the two components were simultaneously dissolved with different reaction rates. Within the experimental range, NiS, an intermediate, was not formed. However a possibility to form a thin layer of NiS on particle surface upon saturating the reaction mixture with $H_2S$ was not excluded. At the initial stage, the activation energy was about 10 kcal/g mol. The reaction occurred at the particle surface, and consequently the particle size decreased with time. The rate of dissoultion for nickel was linearly proportional to the concentration of HCl up to 1.0N.

• Journal of the Korean Chemical Society
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• v.38 no.12
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• pp.915-920
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• 1994

The Menschutkin type reactions of substituted (Z)-benzyl (X)-arenesulfonates with substituted(Y)-pyridines were studied by the electroconductometric method in acetonitrile at $35\circC$. Hammett $\rho$ values were calculated by the second order rate constants for the reaction of substituted (Z)-benzyl (X)-arenesulfonates with substituted (Y)-pyridines. The negative $\rho_Y$ values meant positive charge development on the nitrogen of pyridine at transition state owing to the charge development on the oxygen atom of benzenesulfonate. And the negative $\rho_Z$ values meant positive charge development on the benzylic carbon. Application of the multi-Hammett interaction,│$\rho_YZ$│ > │$\rho_XY$│ > │$\rho_ZX$│, the Menschutkin type reaction of substituted benzyl arenesulfonates with substituted pyridines was shown to be dissociative $S_N2$ mechanism.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.1B
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• pp.8-19
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• 2010

In this paper, we propose the NCP (Network Control Platform)-based defense mechanism against DDoS (Distributed Denial of Service) attacks in order to guarantee the transmission of normal traffic and prevent the flood of abnormal traffic. We also define defense modules, the threshold and packet drop-rate used for the response against DDoS attacks. NCP analyzes whether DDoS attacks are occurred or not based on the flow and queue information collected from SR (Source Router) and VR (Victim Router). Attack packets are dopped according to drop rate decided from NCP. The performance is simulated using OPNET and evaluated in terms of the queue size of both SR and VR, the transmitted volumes of legitimate and attack packets at SR.

• Molecules and Cells
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• v.20 no.1
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• pp.127-135
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• 2005

The uptake of putrescine, spermidine and spermine by Fortner's hamster amelanocytic melanoma AMEL-3 cells was observed in this study to be time-dependent, temperature-sensitive, pH-dependent and saturable. Metabolic poisons nullified polyamine uptake, an indication that this is an energy-requiring mechanism. The presence of $Na^+$ ions was found to be requisite to full activity. Valinomycin, gramicidin, monensin and the calcium ionophore calcimycin were also observed to inhibit the process substantially. The transporter active site would seem to contain sulfhydryl groups. Other diamines and polyamine analogues, as well as cationic diamidines, suppressed putrescine uptake. The presence of the ornithine decarboxylase inhibitor DFMO in the culture medium induced putrescine inflows. Putrescine, in turn, induced the negative expression of the carrier, thus suggesting that this influx mechanism is governed by up/down regulation. The cationic diamidine CGP 40215A and its analogue CGP039937A competitively inhibited putrescine transport, with Ki values of 1.9 and $15{\mu}M$, respectively. The role of polyamine uptake in these cultures is discussed.

• Journal of the Korean Chemical Society
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• v.23 no.4
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• pp.243-247
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• 1979

Kinetics of the reaction of phenethyltosylate with substituted pyridines at 50, 60 and 70$^{\circ}C$ in acetonitrile were investigated by an electric conductivity method. The effects of substituents on the reaction of phenethyltosylate with pyridines were discussed. The rates of reaction were increased with electron donating power of substituents of pyridines. The isokinetic relationship was shown $E_{\alpha}$ and ${\Delta}S^{\neq}$, it's temperature was 240$^{\circ}$K. Bronsted plots were excellent linear except for 4-amino pyridine given by the following equation, logk=O. 22pKa-3.71 (r=O. 986). According to a plot of log k against Hammett substituent constants, the Iinearity was good except for bamino pyridine too, log k= -1.330${\sigma}$+0.08 (r= -0.987). In both cases, deviation of 4-amino pyridine from linearity was considered to solvent effect, resonance effect and ${\sigma}$ value itself. From all the above results, this reaction was found typical $S_N2$ reaction which the rates of reaction was determined by C…N bond formation at transition state.

• Electrical & Electronic Materials
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• v.11 no.10
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• pp.60-65
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• 1998

Deposition conditions, surface morphology, and electrical properties of polyamic acid alkylamine salts (PAAS) Langmuir-Blodgett(LB) films have been investigated through a study of surface pressure-area $\pi$-A isotherms, AFM (atomic force microscopy), and current-voltage characteristics. To obtain the optimum conditions of film deposition, the $\pi$-A isotherms were examined by varying temperature, barrier moving speed, dipping speed, spreading amount of solution etc. The Z-type LB films were made at the surface pressure of 5 mN m-1 and 25 mN m-1 for the AFM study; the former surface pressure forms the gas phase and the latter one forms the solid phase. The LB film made in the gas phase show domains with a size of about 200 A diameter and 70 A height. However, the LB films made in the solid phase show a very smooth surface with 2 A surface roughness. In the current-voltage characteristics measured along the perpendicular direction of the films, ohmic conduction has been observed below 105 V cm-1 and the calculated electrical conductivity is about 10-13 S cm-1. Nonohmic conduction has been observed above = 10-11 V cm and the conduction mechanism can be explained by the Schottky effect.

• Asian-Australasian Journal of Animal Sciences
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• v.14 no.8
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• pp.1085-1089
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• 2001

Metabolites, such as isopropyl alcohol (IPA) produced by rumen fermentation, were intravenously infused into a jugular vein of goats during feeding to explore the mechanism and roles of IPA in ruminating behavior (number of boli and ruminating time). Three female goats were confined in metabolism cages with a stanchion, The ruminating behavior measured by the number of ruminations, ruminating time, number of remastications, and remasticating time decreased (p<0,05) with intravenous IPA infusion. The IPA concentrations and VFA concentrations increased in the blood circulation. Our data suggest that sensitive receptors of rumination to IPA are more likely to be in an area such as the brain stem where they can respond to blood metabolite levels.

• Bulletin of the Korean Chemical Society
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• v.33 no.1
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• pp.204-208
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• 2012

A novel chemiluminescence (CL) flow injection method for the determination of balofloxacin is described. The method is based on the weak CL signal arising from the reaction of $KBrO_3$ with $Na_2S_2O_4$ in acidic medium being significantly enhanced by balofloxacin in the presence of europium (III) ion and sodium dodecyl benzene sulfonate (SDBS). The experimental conditions that affected CL intensity were carefully optimized and the CL reaction mechanism was briefly discussed. Under the optimum conditions, the relative CL intensity was proportional to the concentration of balofloxacin in the range of $7.0{\times}10^{-11}$ to $3.0{\times}10^{-7}g\;mL^{-1}$. The detection limit was $2.7{\times}10^{-11}g\;mL^{-1}$ and the relative standard deviation was 2.1% for $7.0{\times}10^{-10}g\;mL^{-1}$ balofloxacin (n = 13). The proposed method was successfully applied to the determination of balofloxacin in pharmaceutical formulations and biological fluids.

• Applied Chemistry for Engineering
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• v.5 no.2
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• pp.230-237
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• 1994

The reaction conversions of n-butyl acetate in the alkaline hydrolysis of n-butyl acetate by Aliquat 336 were measured in a flat agitator and a dispersion agitator. These measured data was used to analyze the complicated reaction mechanism of the liquid-liquid heterogeneous reaction by a phase transfer catalyst with a pseudo-first order reaction model, a interfacial reaction model and a bulk-body reaction model. The pseudo-firsts order reaction model and the interfacial reaction model could be explained by the experimental data from the dispersion agitator and the bulk-boby reaction model could be explained by those from the flat agitator and the reaction rate constants were $3.1{\times}10^{-4}$, $7.3{\times}10^{-4}$, $6.6m^3/kmol.s$ from these models at $25^{\circ}C$, respectively.

• The Korean Journal of Food And Nutrition
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• v.10 no.3
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• pp.407-413
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• 1997

The antimutagenic mechanism of cinnamaldeyde on mutagenesis induced by 4-nitroquinoline-1-oxide(4-NQO) and N-metyl-N'-nitro-N-nitrosoguanidine (MNNG) was investigated in various DNA repair-deficient strains, E. coli B/r and K-12 series. Cinnamaldehyde did not show any effects not only on the $\beta$-galactosidase activities of GW1060 and GW1103(recA441) which synthesizes $\beta$-galactosidase consitutively at 41$^{\circ}C$ but also on that of GW1107[lexA51 (Def)] in which the SOS response always occur. These results suggest that cinnamaldehyde dose not change the function of RecA which positively controls the SOS response as well as not acting as the repressor like LexA. In addition, no inhibitory effect of cinnamaldehyde was observed on the growth of Trp+ revertant and the delay of viable cell growth was also not found by adding cinnamaldehyde. Despite the decrease in the number of revertants, a significant increase in survival of 4-NQO treated cells was observed in E. coli WP2s(uvrA), ZA159($\Delta$uvrB) and TK603(uvrA). But these effects disappeared in excision-proficient strain WP2(uvrA+) and lexA-deficient strains(CM561 and CM611). The enhancement of survival was not found in WP67(uvrA polA) deficient in polymerase I which ligates the gap between complementary DNA. From the above results, we assume that cinnamaldehyde might show antimutagenic effect by enhancing an error-free recombinational repair system.