• Corrosion Science and Technology
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• v.19 no.5
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• pp.239-249
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• 2020

The characteristics of cavitation-erosion damage with changes in the amplitude of 5052-O aluminum alloy for ships were investigated in a seawater environment. In the cavitation-erosion experiment, the cavitation environment was created using a vibration-generating device with a piezo-electric effect. The amplitudes of 5 ㎛, 10 ㎛, and 30 ㎛ were created by changing the geometric shape of the cavitation horn. The resistance characteristics of cavitation-erosion damage were evaluated by weight loss and pitting area. The damaged surface was analyzed using scanning electron microscopy (SEM) and 3D optical microscopy. As the amplitude increased, the amount of damage and the area of the damaged surface increased, and the damage was concentrated at the center and edge of the specimen. The pit was created after the initial incubation period with increasing experimental time, and then the pits were merged to grow and propagate into craters, and eventually, the surface was detached and damaged. The cavitation-erosion damage after 30 minutes with amplitude of 10 ㎛ and 30 ㎛ was 1.48 and 2.21 times compared to 5 ㎛, respectively.

• International Journal of Industrial Entomology and Biomaterials
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• v.30 no.2
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• pp.45-49
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• 2015

The giant mealworm beetle, Zophobas atratus (Coleoptera: Tenebrionidae), is reared for commercial purposes as a live feed for animals. In 2011, it was officially introduced in Korea, and since then it has been considered commercially important. This beetle is a good animal feed resource because of its high protein content with balanced nutrients. However, its life stage characteristics have not been clearly described, especially of the larval stage that can be used as commercial products. To this end, in our study, we determined the number of Z. atratus larval instars, and described their characteristics at each stage, providing basic information about this beetle. Z. atratus larvae required eight to nine d of incubation period before hatching. The first instar period comprised three to four d. There were relatively large variations in each instar period, except for the first instar. Before the adults emerged, most of the individuals passed through15 to 18 instars. The highest pupation rate, 25.71%, was observed in both 16th and 17th instars. Body length gradually increased with each successive instar and it reached its maximum at the 18th instar. The color of larvae was white at the first instar, and gradually turned brown after the second instar.

• Animal cells and systems
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• v.6 no.3
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• pp.227-232
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• 2002

GroESLx proteins of symbiotic X-bacteria were overproduced in Escherichia coli and their structural characteristics were assayed after simple purification. The GroESx and GroELx were heat-stable at 8$0^{\circ}C$ and 5$0^{\circ}C$, respectively. After heat-treatment, GroESx was purified by DEAE Sephadex A-50 chromatography and GroELx was purified by step- and linear sucrose density gradient ultracentrifugation. Molecular masses of GroESx and GroELx were 50-80 kDa and 800 kDa, respectively, as estimated by sucrose density gradient ultracentrifugation. In chemical cross-linking analysis, subunits of GroESx were mostly cross-linked by incubation for 3 h in 0.4% glutaralde-hyde and GroESx was found to be composed of homo-heptamer subunits. Those of GroELx were cross-linked within 10 min in 0.3% glutaraldehyde and GroELx was in two stacks of homo-heptamer subunits. On the other hand, GroESx and GroELx proteins in a solution could not be cross-linked even after incubation for 3 h in 0.5% glutaraldehyde. GroELx was stable at 4-37$^{\circ}C$. In the presence of both GroESx and ATP, GroELx$_{14}$ was stable at 37$^{\circ}C$ but not at 4$^{\circ}C$ or 24$^{\circ}C$. Thus, we confirmed the oligomeric properties of GroESx$_{7}$ and GroELx$_{14}$ and their stability to heat and in the interaction with GroESx.x.

• KSBB Journal
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• v.23 no.3
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• pp.251-256
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• 2008

The aim of this work was to investigate the fibrinolytic activity and characterization of Bacillus licheniformis HK-12, which produces the fibrinolytic enzyme excreted from naturally fermented Chungkook-Jang. Initially, the physiological and biochemical characteristics of strain HK-12 was examined. Both physiological analysis using BIOLOG system and phylogenetic analysis using 16S rRNA sequencing were performed to identify the strain, and the strain could be assigned to Bacillus licheniformis, designated as B. lichenformis HK-12, and registered in GenBank as [EU288193]. Phylogenetic analysis of B. licheniformis HK-12 was plotted based on 16S rRNA sequence comparisons. During the incubation period of B. licheniformis HK-12, the changes of bacterial growth, fibrinolytic activity, and pH were monitored. As the results, after 36 hours of incubation, the maximum fibinolytic activity was about 2.25 times than that of plasmin used as standard. Optimal conditions on the growth of B. licheniformis HK-12 associated with the fibrinolytic activity was initial pH 7.0 and 40$^{\circ}C$, respectively.

• Journal of Microbiology and Biotechnology
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• v.14 no.6
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• pp.1232-1238
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• 2004

To investigate the production and characteristics of thermostable levan sucrase from Rahnella aquatilis ATCC 33071, the levan sucrase gene from R. aquatilis was cloned and expressed in Escherichia coli without induction system. Expression of levansucrase gene in E. coli had no notable or detrimental effect on the growth of host strain, and the recombinant levan sucrase exhibited levan synthesis activity. Levansucrase was secreted to the periplasm in E. coli, and addition of $0.5\%$ glycine yielded further secretion of levansucrase to the growth medium and resulted in an increase of total levansucrase activity. Furthermore, the cellular levansucrase was evaluated for the production of levan by using toluene­permeabilized whole-cells. The levansucrase was thermostable at $37^{\circ}C$. The molecular size oflevan was $1{\times}\;10^{6}$ Da, as determined by HPLC, and the degree of polymerization of levan varied with incubation temperatures: Low incubation temperature was preferable for the production of high-molecular size levan. The present study demonstrated that the mass production of levan and levan oligosaccharides can be achieved by glycine supplementation to the growth medium or by toluene­permeabilized whole-cells.

• Asian-Australasian Journal of Animal Sciences
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• v.25 no.1
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• pp.86-91
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• 2012

An in vitro rumen batch culture study was completed to compare effects of common grasses, leguminous shrubs and non-leguminous shrubs used for livestock grazing in Australia and Ghana on $CH_4$ production and fermentation characteristics. Grass species included Andropodon gayanus, Brachiaria ruziziensis and Pennisetum purpureum. Leguminous shrub species included Cajanus cajan, Cratylia argentea, Gliricidia sepium, Leucaena leucocephala and Stylosanthes guianensis and non-leguminous shrub species included Annona senegalensis, Moringa oleifera, Securinega virosa and Vitellaria paradoxa. Leaves were harvested, dried at $55^{\circ}C$ and ground through a 1 mm screen. Serum bottles containing 500 mg of forage, modified McDougall's buffer and rumen fluid were incubated under anaerobic conditions at $39^{\circ}C$ for 24 h. Samples of each forage type were removed after 0, 2, 6, 12 and 24 h of incubation for determination of cumulative gas production. Methane production, ammonia concentration and proportions of VFA were measured at 24 h. Concentration of aNDF (g/kg DM) ranged from 671 to 713 (grasses), 377 to 590 (leguminous shrubs) and 288 to 517 (non-leguminous shrubs). After 24 h of in vitro incubation, cumulative gas, $CH_4$ production, ammonia concentration, proportion of propionate in VFA and IVDMD differed (p<0.05) within each forage type. B. ruziziensis and G. sepium produced the highest cumulative gas, IVDMD, total VFA, proportion of propionate in VFA and the lowest A:P ratios within their forage types. Consequently, these two species produced moderate $CH_4$ emissions without compromising digestion. Grazing of these two species may be a strategy to reduce $CH_4$ emissions however further assessment in in vivo trials and at different stages of maturity is recommended.

• Korean Journal of Soil Science and Fertilizer
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• v.49 no.6
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• pp.712-719
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• 2016

Understanding N mineralization dynamics in soil is essential for efficient nutrient management. An anaerobic incubation experiment was conducted to examine N mineralization potential and N mineralization rate of the organic amendments with different C:N ratio in paddy soil. Inorganic N in the soil sample was measured periodically under three temperature conditions ($20^{\circ}C$, $25^{\circ}C$, $30^{\circ}C$) for 90 days. N mineralization was accelerated as the temperature rises by approximately $10%^{\circ}C^{-1}$ in average. Negative correlation ($R^2=0.707$) was observed between soil inorganic N and C:N ratio, while total organic carbon extract ($R^2=0.947$) and microbial biomass C ($R^2=0.824$) in the soil were positively related to C:N ratio. Single exponential model was applied for quantitative evaluation of N mineralization process. Model parameter for N mineralization rate, k, increased in proportion to temperature. N mineralization potential, $N_p$, was very different depending on C:N ratio of organic input. $N_p$ value decreased as C:N ratio increased, ranged from $74.3mg\;kg^{-1}$ in a low C:N ratio (12.0 in hairy vetch) to $15.1mg\;kg^{-1}$ in a high C:N ratio (78.2 in rice straw). This result indicated that the amount of inorganic N available for crop uptake can be predicted by temperature and C:N ratio of organic amendment. Consequently, it is suggested that the amount of organic fertilizer application in paddy soil would be determined based on temperature observations and C:N ratio, which represent the decomposition characteristics of organic amendments.

• Proceedings of the Plant Resources Society of Korea Conference
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• 2018.10a
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• pp.88-88
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• 2018

In order to increase the germination speed and uniformity of tomato seeds, sonication and modified drum priming treatments were investigated to produce high quality seeds for export. Sonication treatment was performed for 5, 10 and 20minutes at an intensity of 5.2, 10.4 and 15.7kHz in water at $15^{\circ}C$. After sonication treatment, seeds were primed with water or 100mM $KNO_3$ for 4days. 40, 50 and 60% seed moisture content (SMC) of hydrated seeds were incubated for 60, 72 and 84h in a container with a relative humidity of 99% at 26rpm for a modified drum priming treatments. Germination speed were highly improved by sonication with osmotic priming. The seed treatment of osmotic priming or hydro priming after sonication or sonication without priming enhanced germination percentage (GP) on the $2^{rd}$day after sowing to 46%, 43% and 28%, respectively, while untreated seeds resulted in only 1% GP. These treatments also highly improved mean germination time (MGT) to 1.4, 1.8 and 2.6days, respectively, when compared to 3.5days MGT of untreated seeds. The modified drum priming treatment (72h incubation after 60% SMC hydration) significantly improved results of 74% GP(on the $3^{rd}$day after sowing), 2.6days MGT and $39%{\cdot}day^{-1}$ germination rate (GR), however, untreated seeds showed 19% GP, 4.1 MGT, and $25%{\cdot}day^{-1}$ GR. Although osmotic priming after sonication, hydro priming showed similar improved germination characteristics, however, modified drum priming is considered as an industrially promising treatment methods considering the shortening of the treatment period and environment-friendly aspects.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
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• v.10 no.1
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• pp.175-185
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• 2015

This article focuses on an analysis of entrepreneurship education programs at U.S. college and universities in order to determine distinctive features of those programs. To this end, we delved into the entrepreneurship programs including Martin Trust Center for MIT, Harvard University VIP program, Polsky Center of Chicago University and Stanford University program. By analyzing major roles, curriculums, and characteristics of the programs, three types of distinctive features emerged. The first feature is dynamic education-focused programs, which provide students with opportunities for applying what they have learned through startup competitions. The second is local-based programs, which take the lead in local startups by focusing on the local industry. The third is the programs with support and encouragement for startups. Based on the three types of features, we suggested critical factors for successful entrepreneurship education.

• Asian-Australasian Journal of Animal Sciences
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• v.24 no.4
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• pp.471-478
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• 2011

The objectives were to compare the ability of various rumen microbial fractions to reduce nitrate and to assess the effect of nitrate on in vitro fermentation characteristics. Physical and chemical methods were used to differentiate the rumen microbial population into the following fractions: whole rumen fluid (WRF), protozoa (Pr), bacteria (Ba), and fungi (Fu). The three nitrogen substrate treatments were as follows: no supplemental nitrogen source, nitrate or urea, with the latter two being isonitrogenous additions. The results showed that during 24 h incubation, WRF, Pr and Ba fractions had an ability to reduce nitrate, and the rate of nitrate disappearance for the Pr fraction was similar to the WRF fraction, while the Ba fraction needed an adaptation period of 12 h before rapid nitrate disappearance. The WRF fraction had the greatest methane ($CH_4$) production and the Pr fraction had the greatest prevailing $H_2$ concentration (p<0.05). Compared to the urea treatment, nitrate diminished net gas and $CH_4$ production during incubation (p<0.05), and ammonia-N ($NH_3$-N) concentration (p<0.01). Nitrate also increased acetate, decreased propionate and decreased butyrate molar proportions (p<0.05). The Pr fraction had the highest acetate to propionate ratio (p<0.05). The Pr fraction as well as the Ba fraction appears to have an important role in nitrate reduction. Nitrate did not consistently alter total VFA concentration, but it did shift the VFA profile to higher acetate, lower propionate and lower butyrate molar proportions, consistent with less $CH_4$ production by all microbial fractions.