• Journal of the Korean Chemical Society
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• v.17 no.2
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• pp.95-104
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• 1973

Ground electronic structures and SNreactivities of a series of alkylchlorides (methyl,ethyl, iso-propyl, trans n-butyl, sec-butyl, tert-butylchloride) have been studied using approximate $({\sigma}-MO)$ method, such as EHT and CNDO/2. It was found that CNDO/2 gives better results for the systems such as alkylchlorides whose structural differences are not remarkable, in comparison with EHT method. According to CNDO/2 results, calculated dipole moments for alkylchlorides are slightly higher than observed values, showing the order of primary < secondary < tertiary alkylchlorides. It was also found that highest occupied(HO) MO's are completely or nearly degenerate, and show relatively weak $\pi$-antibonding nature between$\alpha$-carbon and Cl atoms. Furthermore, the electrons in this MO are largely confined to Cl atom, and hence these behaves as likely as p-lone pair electrons of Cl atom. On the contrary, lowest unoccupied (LU) MO's show strong $\sigma$-antibonding nature between $\alpha$-carbon and Cl atoms whose electron clouds are directed along the C-Cl axis. It has been discussed that the$S_N2$ reactivities of alkylchlorides may largely be controlled by ${\sigma}^{\ast}$ LUMO, and the antibonding strength between $\alpha$-carbon and Cl atoms in this MO may become the measure of $S_N2$reactivity. The relationship between $S_N2$reactivity and C-Cl bond polarizability has also been discussed. It has been suggested that the unique structure factors determining $S_N1$reactivities may be $\pi$-antibonding strength between $\alpha$-carbon and Cl atoms in HOMO and C-Cl bond strength in ground state.

• Journal of Life Science
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• v.25 no.6
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• pp.680-685
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• 2015

Previously, cellulase and xylanase producing microorganism, Bacillus subtilis NC1, was isolated from soil. Based on the 16S rRNA gene sequence and API 50 CHL test the strain was identified as Bacillus subtilis, and named as B. subtilis NC1. We cloned and sequenced the genes for cellulase and xylanase. Plus, the deduced amino acid sequences from the genes of cellulase and xylanase were determined and were also identified as glycosyl hydrolases family (GH) 5 and 30, respectively. In this study to optimize the medium parameters for cellulase production by B. subtilis NC1 the RSM (response surface methodology) based on CCD (central composite design) model was performed. Three factors, tryptone, yeast extract, and NaCl, for N or C source were investigated. The cellulase activity was measured with a carboxylmethyl cellulose (CMC) plate and the 3,5-dinitrosalicylic acid (DNS) methods. The coefficient of determination (R²) for the model was 0.960, and the probability value (p=0.0001) of the regression model was highly significant. Based on the RSM, the optimum conditions for cellulase production by B. subtilis NC1 were predicted to be tryptone of 2.5%, yeast extract of 0.5%, and NaCl of 1.0%. Through the model verification, cellulase activity of Bacillus subtilis NC1 increased from 0.5 to 0.62 U/ml (24%) compared to the original medium.

• Korean Journal of Food Science and Technology
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• v.28 no.3
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• pp.411-416
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• 1996

Supercritical fluid extraction of ${\beta}$-carotene from carrot was optimized to maximize ${\beta}$-carotene (Y) extraction yield. A central composite design involving extraction pressure ($X_1$ 200-,100 bar), temperature ($X_2,\;35-51^{\circ}C$) and time ($X_1$$ 60-200min) was used. Three independent factors ($X_1,\;X_2,\;X_3$) were chosen to determine their effects on the various responses and the function was expressed in terms of a quadratic polynomial equation,$Y={\beta}_0+{\beta}_1X_1+{\beta}_2X_2+{\beta}_3X_3+{\beta}_11X_12+{\beta}_22X_3^2+{\beta}_-12X_1X_2+{\beta}_12X_1X_2+{\beta}_13X_1X_3+{\beta}_23X_2X_3,$ which measures the linear, quadratic and interaction effects. Extraction yields of ${\beta}$-carotene were affected by pressure, time and temperature in the decreasing order, and linear effect of tenter point (${\beta}_11$) and pressure (${\beta}_1$) were significant at a level of 0.001(${\alpha}$). Based on the analysis of variance, the model fitted for ${\beta}_11$-carotene (Y) was significant at 5% confidence level and the coefficient of determination was 0.938. According to the response surface of ${\beta}$-carotene by cannoical analysis, the stationary point for quantitatively dependent variable (Y) was found to be the maximum point for extraction yield. Response area for ${\beta}$-carotene (Y) in terms of interesting region was estimated over $10,611{\mu}g$ Per 100 g raw carrot under extraction.

• Journal of the Korean Society of Food Science and Nutrition
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• v.13 no.2
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• pp.215-221
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• 1984

To investigate stability for the quality of selected ginseng products, their sorption properties were clarified in red ginseng extract(RGEP), and red ginseng extract powder(RGEP), and red ginseng extract tea(RGET). Simultaneously, the BET monolayer value of each product was determined in order to inquire out the possibility of establishment as a criterion for the optimum moisture content of the ginseng products. Based on the BET monolayer moisture level of spray dried RGEP which ranged from 4.08 to 4.65%, it would be desirable to establish the optimum moisture content of the products at 4.4${\pm}$0.3%. This is 1.3 to 1.9% lower than the criter on, "less than 6.0%". The optimum moisture level for RGET of which monolayer value ranged 0.93 to 1.37% would be 1.2${\pm}$0.17%. In this case, the maximum permissible limit of moisture content could presumably be raised up to 1.37% in place of current criterion, "less than l.2%". From the results of a study on the growth of molds, the optimum moisture content for RGE assumed to be extended up to 40.0${\pm}$1.07 despite 36.0${\pm}$1.0% of the present criterion. On the other hand, a storage study under the maltreated condition, $48{\pm}2^{\circ}C$ 75%RH, was also carried out in order to make it clear whether the BET monolayer values were able to be used as indices for optimum moisture level of the products. In all samples tested adsorption occurred at even higher levels of moisture than the monolayer values. However, since there are many other possible factors affecting the quality of products the optimum moisture content is preferable to be reduced to the monolayer value. As a result, it was proved that the optimum level of moisture for both RGEP and RGET could be established by the monolayer values.

• Journal of Bio-Environment Control
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• v.20 no.4
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• pp.247-252
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• 2011

Electrical conductivity, drainage, and irrigation amount of nutrient solution are important factors for determination of the mixing ratio of fresh and reused nutrient solutions in closed-loop soilless culture. Generally a fixed mixing ratio is applied in commercial scale greenhouses using solar radiation-based irrigation system. Although it ensures continuous supply of fresh nutrient solution in the mixing process, occasional discharge of the drainage is inevitably required. This study was conducted to compare the nutrient replenishing effect under different mixing processes and to investigate appropriate mixing process. For this experiment, a fixed mixing ratio (FR), modifiable mixing ratio (MR), and open-loop (OP) as control were applied. Mixing ratio was determined by a set value of EC for dilution of collected drainage in FR and the set values of 1.0 and $2.0dS{\cdot}m^{-1}$ were used as treatments (FR 1.0 and FR 2.0), respectively. In MR, mixing ratio was determined based on EC and volume of drainage within irrigation volume per event. The volume of drainage stored in the drainage tank tended to increase in FR 1.0. Although such trend was not observed in FR 2.0 and MR, the volume of drainage stored in MR was lower than that in FR 2.0. The ion balance of $Mg^{2+}:K^+:Ca^{2+}$ or $SO^{2-}_4:NO^-_3:PO^{3-}_4$ in the drainage and reused nutrient solution changed within a narrow range regardless of treatment.

• Journal of the Korean Institute of Navigation
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• v.4 no.2
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• pp.45-79
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• 1980

The aim of this paper is to analyze the mechanics of price formation in the tramp shipping. For the purpose of this study, the main characteristics of tramp freight rates and the market is examined, and a brief examination of the nature ofthe costs of operation is given which are essential for the understanding of the functioning of shipping firms as well as for the understanding of developments in the tramp freight market. The demand and supply relationships in the market is also analysed in detail. Tramp shipping is an industry that has a market which functions under conditions that are not dissimilar to the theoretical model of perfect competition. However, it does notmean that tramp shipping market is a perfectly competitive market. It is apparent that this realworld competitive system has its imperfections, which means that the market for tramp shipping is near to being a perfectly competitive market on an internaitonal scale and it is freight are therefore subjext to the laws of supply and demand. In theory, the minimum freight rate in the short term is that at which the lowest cost vessels will lay-up in preference to operating, and is equal to the variable costs minus lay-up costs; and this would imply that in all times except those of full employment for ships there is a tendency for newer low-cost, and, probably, faster vessels to be driving the older high-cost vessels in the breaker's yards. In this case, shipowners may be reluctant to lay-up their ships becasue of obligations to crews, or because they would lose credibility with shippers or financiers, or simply because of lost prestige. Mainly, however, the decision is made on strictly economic grounds. When, for example, the total operating costs minus the likely freight earnings are greater than the cost of taking the ship out of service, maintaining it, and recommissioning it, then a ship may be considered for laying-up; shipowners will, in other words, run the ships at freight earnings below operating costs by as much as the cost of laying them up. As described above, the freight rates fixed on the tramp shipping market are subject to the laws of supply and demand. In other words, the basic properties of supply and demand are of significance so far as price or rate fluctuations in the tramp freight market are concerned. In connection with the same of the demand for tramp shipping services, the following points should be brone in mind: (a) That the magnitude of demand for sea transport of dry cargoes in general and for tramp shipping services in particular is increasing in the long run. (b) That owning to external factors, the demand for tramp shipping services is capable of varying sharphy at a given going of time. (c) The demad for the industry's services tends to be price inelastic in the short run. On the other hand the demand for the services offered by the individual shipping firm tends as a rule to be infinitely price elastic. In the meantime, the properties of the supply of the tramp shipping facilities are that it cannot expand or contract in the short run. Also, that in the long run there is a time-lag between entrepreneurs' decision to expand their fleets and the actual time of delivery of the new vessels. Thus, supply is inelastic and not capable of responding to demand and price changes at a given period of time. In conclusion, it can be safely stated that short-run changes in freight rates are a direct result of variations in the magnitude of demand for tramp shipping facilities, whilest the average level of freight rates is brought down to relatively low levels over prolonged periods of time.

• Journal of the Korean Institute of Landscape Architecture
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• v.46 no.4
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• pp.21-35
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• 2018

In recent years, there has been a tendency to reuse 'landscapes of memory,' including industrial heritages, modern cultural heritages, and post-industrial parks, as public spaces in many cities. Among the various types of landscapes, 'modern historic landscapes', which were formed in the 19th and 20th centuries, are landscapes where the debate between conservation and removal is most frequent, according to the change of evaluation and recognition of modern history. This study examines conflicts between conservation and removal around modern historic landscapes and explores the value judgment criteria and the process of formation of those landscapes, as highlighted in the case of the demolition controversy of the old Japanese general government building in Seoul, which was dismantled in 1995. First, this study reviews newspaper articles, television news and debate programs from 1980-1999 and some articles related to the controversy of the Japanese general government building. Then it draws the following six factors as the main issues of the demolition controversy of the building: symbolic location, discoveries and responses of new historical facts, reaction and intervention of a related country, financial conditions, function and usage of the landscape, changes of urban, historical and architectural policies. Based on these issues, this study examines the conflicts between symbolic values that play an important role in the formation of modern historic landscapes and determines conservation or removal, and the utility of functional values that solve the problems and respond to criticisms that arise in the process of forming the modern historic landscape. Especially, it is noted that the most important factor that makes the decision is the symbolic values, although the determination of the conservation or removal of modern historic landscapes has changed according to changes in historical perceptions of modern history. Today, the modern historic landscape is an important site for urban design, and still has historical issues to be agreed upon and addressed. Thi study has contemporary significance from the point that it divides the many values of modern historic landscapes into symbolic values and functional values, evaluates these, and reviews the background social context.

• The Korean Journal of Nuclear Medicine
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• v.34 no.4
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• pp.294-302
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• 2000

Purpose: To investigate the mechanisms related to F-18-FDG uptake by tumors, F-18-FDG accumulation was compared with glucose transporter-1 (Glut-1) expression and hexokinase activity in various human cancer cell lines. Materials and Methods: Human colon cancer (SNU-C2A, SNU-C4, SNU-C5), hepatocellular carcinoma (SNU-387, SNU-423, SNU-449), lung cancer (NCI-H522, NCI-H358, NCI-H1299), uterine cervical cancer (HeLa, HeLa 229, HeLa S3) and brain tumor (A172, Hs 683) cell lines were used. After 24 hr incubation of $5{\times}10^5$ cells, 37 kBq F-18-FDG was added and the uptake by cells at 10 min was measured using a gamma counter. Hexokinase activity was measured by continuous spectrophotometric rate determination. To measure mitochondrial hexokinase activity, mitochondrial fraction was separated by a high speed centrifuge. Immunohistochemical staining of Glut-1 was performed, and graded as 0, 1, 2, or 3 according to expression. Results: There was difference among F-18-FDG uptake, total and mitochondrial hexokinase activity, and Glut-1 expression with different cancer cell lines. The correlations of F-18-FDG with total hexokinase and mitochondrial hexokinase activity were low (r=0.27 and 0.26, respectively). Glut-1 expression showed a good correlation with F-18-FDG uptake (p=0.81, p=0.0015). Previously, we reported no correlation of F-18-FDG uptake with hexokinase activity in colon cancer cell lines. Thus, when colon cancer cells were excluded, F-18-FDG uptake showed higher correlation with total hexokinase and mitochondrial hexokinase activity (r=0.81, p=0.0027 and r=0.81, p=0.0049, respectively). Conclusion: Both Glut-1 expression and hexokinase activity were contributing factors related to F-18-FDG accumulation in human cancer cell lines. The relative contribution of Glut-1 expression and hexokinase activity, however, was different among different cancer cell types.

• Journal of Bio-Environment Control
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• v.28 no.4
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• pp.286-292
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• 2019

This study aimed to investigate the suitable of layer on growth of six baby leaf vegetables using existing facilities and equipment in rice seedling nursery. Three kinds of Lactuca(lettuce 'Jinppallola' and 'Romain white', and indian lettuce), two of Brassica(tatsoi and red tatsoi) and amaranth were used as the materials. After sowing, the rice seedling tray was placed in multi bench system($L120{\times}W60{\times}H195cm$, 10th floor), which were low(1st) layer above 15cm, middle(4th) layer above 115cm and high(7th) layer above 175cm apart from ground. Irrigation was sprayed 2~3 times a day using a automatic irrigation system. The growth characteristics and leaf color were investigated when leaf vegetables were reached the optimum size(within 10cm of plant height). During the culture periods(29th Jun.~31th Jul. 2017), daytime average temperature was $27.4{\sim}28.3^{\circ}C$ regardless of layers but solar irradiance was higher in the high-layer than low and middle-layer of 37% and 22%, respectively. The leaf length, leaf width and number of leaves in middle and high-layer have a tendency to increase but, fresh weight was different according to the layer. When the correlation between accumulation radiation and growth was analyzed, all of growth factor of Amaranth showed a high correlation and other cultivars showed correlation with each growth factors. As a result, It is suitable that amaranth and red tatsoi for high-layer, Indian lettuce and tatsoi for middle and high-layer and 'Romain white' for middle-layer. The growth of red lettuce 'Jinppallola' was good at low layer, but leaf color expression was poor. So the high layer is suitable for 'Jinppallola'.

• Food Engineering Progress
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• v.15 no.4
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• pp.388-397
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• 2011

The purpose of this study was to determine the optimum ethanol extraction conditions for maximum extraction of functional components such as ferulic acid, oryzanol, and toopherol from black rice bran using Response Surface Methodology (RSM). A central composite design was applied to investigate the effects of the independent variables of solvent ratio ($X_{1}$), extraction temperature ($X_{2}$) and extraction time ($X_{3}$) on the dependent variables such as total phenol components ($Y_{1}$), total flavonoids compounds ($Y_{2}$), electron donating ability ($Y_{3}$), $\gamma$-oryzanol ($Y_{4}$), ferulic acid ($Y_{5}$) and $\alpha$-toopherol components ($Y_{6}$). ANOVA results showed that coefficients of determination (R-square) of estimated models for dependent variables ranged from 0.8939 to 0.9470. It was found that solvent ratio and extraction temperature were the main effective factors in this extraction proess. Particularly, the extraction efficiency of ferulic acid, $\gamma$-oryzanol and $\alpha$-toopherol components were significantly affected by extraction temperature. As a result, optimum extraction conditions were 20.35 mL/g of solvent ratio, 79.4$^{\circ}C$ of extraction temperature and 2.88 hr of extraction time. Predicted values at the optimized conditions were acceptable when compared with experimental values.