• Korean Journal of Weed Science
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• v.15 no.1
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• pp.73-84
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• 1995

Four malformin A's produced by Aspergillus niger van Tiegh. were separated by HPLC equipped with $C_{18}$ reversed-phase column and subjected to structural determination. Amino acid analyses and mass spectra data of the compounds indicate that they structurally resemble the cyclic pentapeptide malformin $A_1$. Their structures were deduced by two dimensional NMR and MS/MS experiments as cyclo-D-Cys-D-Cys-L-Val-D-Leu-L-Ile for $A_1$, cyclo-D-Cys-D-Cys-L-Val-D-Leu-L-Val for $A_2$, cyclo-D-Cys-D-Cys-L-Val-D-Leu-L-Leu for $A_3$, and cyclo-D-Cys-D-Cys-L-Val-D-Ile-L-Val for $A_4$. Among the mal-formin A's, the structure of $A_3$ was identical to that of malformin C, which was produced by A. niger strain AN-1. All the malformin A's caused severe curvatures of corn(Zea mays L.) roots and the activities of the malformin A's with molecular weight 529 were greater than those with molecular weight 515. Malformin $A_1$ caused the corn root curvature by 83% at a concentration of $0.25{\mu}M$. In the mung bean(Phaseolus aureus Roxb.) hypercotyl segment test, however, the molecular weight of malformin A's was not a factor influencing the physiological activities. Malformin $A_1$ stimulated the growth of mung bean hypercotyles by 165% at a $0.1{\mu}M$ concentration.

• Journal of Food Hygiene and Safety
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• v.13 no.2
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• pp.164-170
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• 1998

In this study a commercial fermented milk produced in Korea and a Lactobacillus strain used for the product (L. casei) were found to affect mold growth and inhibit aflatoxin production by Aspergillus parasiticus ATCC 15517. Aflatoxins were determined using an HPLC system that consisted of a $C_{18}$ column and a fluorescence detector. When the fermented milk was added to the yeast-extract broth the levels of aflatoxin $B_{1}\;and\;G_{1}$ significantly decreased by 48.6~58.1% and 29.8~34.2%, respectively (p$B_{1}\;and\;G_{1}$ were found in comparison with the control (monoculture). L. casei was found to be very inhibitory to the growth of A. parasiticus for 5 days, but no significant difference of mycelial weight was observed between the mixed culture and control at the end of incubation. The pH values of the culture broth in mixed culture were observed to be significantly lower than those in monoculture (p

• Applied Chemistry for Engineering
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• v.18 no.6
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• pp.643-649
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• 2007

Lipase-catalyzed esterification of structural butanol isomers and n-butyric acid was investigated in supercritical carbon dioxide. The experiments were performed in a high pressure cell for 5 hrs with a stirring rate of 150 rpm at 323.15 K and 130 bar. The Candida Antarctica lipase B (CALB) was used in whole system as a catalyst. The experimental results were analyzed by GC-FID using a INNOWax capillary column. The conversion yield and the tendency of the esterification in supercritical carbon dioxide were compared with estimated results by molecular dynamics simulation. Based on the Ping-Pong Bi-Bi mechanism with competitive inhibition, each step of the reaction was optimized; using this result the transition state was predicted. Conformational preference of isomers was also analyzed using molecular dynamics simulations. This kind of approach will be further extended to the prediction of enzyme-catalyzed reactions using computers.

• Korean Journal of Environmental Agriculture
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• v.12 no.3
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• pp.209-218
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• 1993

The behaviour of insectcide ethoprophos (O-ethyl S,S-propyl phosphorodithioate) in soil was investigated. In a laboratory study, the degradation of ethoprophos in soil followed first-order reaction kinetics. The half-life of the insecticide in the soil incubated with 10, 18 and $25^{\circ}C$ was 12.4, 5.5 and 2.5 days, respectively. Arrhenius activation energy was 73.8 KJ/mole. The half-life was 46.4, 17.6 and 6.9 day in the soil with 7, 14 and 19% of soil water content, respectively. The moisture dependence B value in empirical equation was 1.67. The adsorption isotherm for ethoprophos in the soil agreed with freundlich equation. The adsorption distribution coefficient (Kd) was 0.27. In a field study prepared in autumn with undisturbed soil column in a mini-lysimeter system, ethoprophos residues were largely distributed in the top $0{\sim}2cm$ soil layer and moved down to the top 6cm soil layer. Persistence of ethoprophos in field soil was correlated with variation in weather pattern during the period of experiments. The half-life of ethoprophos treated at March and October was about 17 and 5 days, respectively. The ethoprophos woil was degraded up to 90% at 37day after the both treatment. In persistence and mobility of ethoprophos in field soil, the observed data were reasonably corresponded with predicted data by some computer model of pesticide behaviour.

• Korean Chemical Engineering Research
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• v.50 no.1
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• pp.155-161
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• 2012

A dynamic biofilter model was suggested to integrate the effect of biofilter-medium adsorption capacity on the removal efficiency of volatile organic compound (VOC) contained in waste air. In particular, the suggested biofilter model is composed of four components such as biofilm, gas phase, sorption volume and adsorption phase and is capable of predicting the unsteady behavior of biofilter-operation. The process-lumping model previously suggested was limited in the application for the treatment of waste air since it was derived under the assumption that the adsorbed amount of VOC equilibrated with biofilter-media would be proportional to the concentration of dissolved VOC in the sorption volume of biofilter-media. Therefore a Freundlich adsorption isotherm was integrated into a robust biofilter process-lumping model applicable to a wide range of VOC concentration. The values of model parameters related to biofilter-medium adsorption were obtained from the dynamic adsorption column experiments in the preceding article and literature survey. Furthermore a separate biofilter experiment was conducted to treat waste air containing ethanol and the experimental result was compared with the model predictions with various values of Thiele modulus (${\phi}$). The obtained value of Thiele modulus (${\phi}$) was close to 0.03.

• Solar Energy
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• v.15 no.3
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• pp.3-14
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• 1995

The Direct Contact heat Exchanger(DCHX) has been widely studied in the chemical industry for many years due to its inherent simplicity as a counter-current divice for heat and mass transfer. In many solar systems, the DCHX unit can be combined with the thermal storage unit, or alternatively, it can be used separately from the storage unit, much like an external(to storage) closed heat exchanger system. In the present work, the spray column type of direct contact heat exchangers are studied extensively to harness the solar energy for hot water and spaced heating. Some of the major considerations that are involved in the design of heat exchangers in this study are that : working fluid is a hydrocaabon(such as Texaterm) or water which is either lighter or heavier than storage medium. The experimental data have revealed some interesting characteristics concerning the application of DCHXs for solar energy utilization. These experiments are carried out in the line of solar heating system, major results are as follows : 1) the flow and aspect of working fluid drop for maxium heat transfer 2) efficiency and volumetric heat transfer coefficient of D.C.H.X with a heavier working fluid are higher than those of D.C.H.X with a lighter working fluid.

• Journal of the Korean Chemical Society
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• v.43 no.4
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• pp.438-446
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• 1999

The optimum analytical method of aldehydes, ozone by-products, was established by reverse phase liquid chromatography. Six aldehydes including formaldehyde, acetaldehyde, acrolein, propionaldehyde, butylaldehyde and benzaldehyde, and one ketone including acetone were selected as aldehyde test samples through preliminary experiments. Such analytical conditions as the pH of citrate buffer solution, reaction temperature, reaction time, and concentration of DNPH, the component and composition of desorption solvent were optimized. As the result, pH 3.0 of citrate buffer solution, 40$^{\circ}C$ of reaction temperature, 15 minutes of reaction time, and 0.012% of DNPH concentration were chosen as optimum conditions. Aldehydes-DNPH derivatives in water were concentrated on $C_18$ Sep-Pak cartridge and followed by elution of their derivatives fraction with THF/ACN(70/30) mixture, and showed recoveries of the range from 87 to 107%. Separation condition on Nova-Pak $C_18$ column with low pressure gradient elution from ACN/MeOH/water(30/10/60) of an initial condition to 80% ACN of a final condition was found to give a good resolution within 20 minutes of run time. 86% to 103% of recovery for aldehydes using this method was similar to that for aldehyde using EPA Method 554 which is ranged from 84% to 103%.

• The KIPS Transactions:PartD
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• v.14D no.2
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• pp.157-168
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• 2007

For effective analyses in various business applications, OLAP(On-Line Analytical Processing) systems represent the multidimensional data as the horizontal format of tables whose columns are corresponding to values of dimension attributes. Because the traditional RDBMSs have the limitation on the maximum number of attributes in table columns(MS SQLServer and Oracle permit each table to have up to 1,024 columns), horizontal tables cannot be directly stored into relational database systems. In this paper, we propose various efficient optimization strategies in transforming horizontal queries to equivalent vertical queries. To achieve this goral, we first store a horizontal table using an equivalent vertical table, and then develop various query transformation rules for horizontal table queries using the PIVOT operator. In particular, we propose various alternative query transformation rules for the basic relational operators, selection, projection, and join. Here, we note that the transformed queries can be executed in several ways, and their execution times will differ from each other. Thus, we propose various optimization strategies that transform the horizontal queries to the equivalent vertical queries when using the PIVOT operator. Finally, we evaluate these methods through extensive experiments and identify the optimal transformation strategy when using the PIVOT operator.

• The Korea Journal of Herbology
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• v.25 no.2
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• pp.129-136
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• 2010

Objective : Sinapis alba L. (SA) is a korean traditional herbal medicine that is usually used to prevent or treat inflammatory diseases, such as respiratory infection and rheumatoid arthritis. However, the effects of SA supplementation in vitro on serum antibody levels, splenocyte and peritoneal macrophage immune responses have not yet been determined. In this study, we examined the effect of SA on the production of Th1/Th2 cytokines. Methods : Splenocytes were isolated from naive C57BL/6 mice. Cells were enriched for CD4+ cell populations by first staining the cells with anti-CD4 (BD PharMingen, Calif, USA). CD4+ T cells were selected on a (CS) column, and the flow-through was collected as CD4+ T cells. Isolated cells were activated by overnight incubation on 24-well plates coated with $1{\mu}g/mL$ anti-CD3, $1{\mu}g/mL$ anti-CD28 and with SA ($100{\mu}g/mL$). Primary macrophages were collected from the peritoneal cavities of mice (8-week-old female C57BL/6). The peritoneal macrophages were washed and plated with RPMI-1640 overnight for the experiments. After 48-hours cultures, samples were centrifuged at 2000 rpm for 10 minutes, and the supernatants were stored at $-80^{\circ}C$. Mouse IL-4, IFN-$\gamma$ and TNF-$\alpha$ were quantified using ELISA kits (BioSource International, Camarillo, Calif, USA) according to the manufacturer's protocols. Results : SA at 100ug/ml decreased the generation of Th1 cytokine (IFN-$\gamma$) by 0.5-fold. However, SA has no effect on Th2 (IL-4) production. Conclusions : These results suggest that SA may play an important role in the control of T-cell-mediated autoimmunity by down-regulation of Th1 cytokine (especially IFN-$\gamma$, TNF-$\alpha$). These data may contribute to the design of new immunomodulating treatments for a group of autoimmune diseases.

• Korean Journal of Agricultural Science
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• v.22 no.1
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• pp.82-95
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• 1995

These experiments were carried out to isolate SIgA from human and bovine milk. The immunochemical properties of SIgA from human and bovine milk were examined by Gel filtration, DEAE and SDS-PAGE. Double Immunodiffusion, and Immunoelectrophoresis. The results obtained are as follows: 1. Human SIgA was purified from colostrum of Korean women by repeated gel filtration on Sephadex G-200 and Sepharose 6B, but bovine SigA was not cleary purified from bovine colostrum of Holstein cows by anion exchange chromatography using DEAE-Sephadex A-50 and gel filtration on Sephadex G-200 and Sepharose 6B. 2. The immunochemical properties of fractions from gel filtration on the Sephadex G-200 and Sepharose 6B column as assessed by Immunoelectrophoresis and double Immunodiffusion to identify the presence of IgM in first peak fraction, and the presence of pure SIgA in second peak fraction. However, Bovine SigA rich fraction from bovine colostrum of Holstein cows contained a large amount of $IgG_1$-dimer in addition to SIgA. 3. The fragments of reduced bovine colostrum SIgA rich fraction were estimated to have molecular weights of secretory component, heavy chain and light chain (75,000-80,000, 50,000-60,000, 25,000-27,000 daltons) by SDS-PAGE, respectively. Those were similar to the molecular weight of reduced SIgA from human milk.