• Applied Microscopy
• /
• v.26 no.4
• /
• pp.389-399
• /
• 1996

In order to understand the morphological differences between two different organic loadings by its upstream, and to compare with other algal groups with references, the fine structure of blue-green algae, Microcystis aeruginosa Kitzing, taken from two branches, Tongbok and Bosung stream of Lake Chuam, Korea pennisula was examined. It showed extinct differences in most physicochemical factors between both branches, except water temperature and pH values. The concentrations of total phosphorus in Tongbok branch were twice as those of Bosung. M. aeruginosa cells were enumerated totally $1.2X10^4cells/ml$ and these individuals in branch of Tongbok were close to two times as much as Bosung. In light and electron microscopy, natural M. aeruginosa colonies formed irregular shape and non-directional array in amorphous matrix. They were consisted of many kinds of cells, youngs or olds in cell division, solitary, and various size of cells. Each cell ranged from 2.61 to $5.40{\mu}m$ in diameter, and averaged as $3.54{\pm}0.19{\mu}m$. In cytoplasm, they contained a number of inclusions in various size, shape and appearances. Among them, polyhedral bodies or carboxysomes, a structured granules, photosynthetic lamellae or thylakoids, and gas vacuoles were prominent and easy to recognize. Although it was failed to find the definable morphological variations in the ultrastructure of M. aeruginosa in terms of algal habitual environments, some useful characters were founded, outer layer of cell wall, polyhedral bodies and gas vacuoles, in blue-green algal classification and taxonomy.

• Korean Journal of Materials Research
• /
• v.18 no.6
• /
• pp.339-346
• /
• 2008

Single-crystal $ZnIn_2S_4$ layers were grown on a thoroughly etched semi-insulating GaAs (100) substrate at $450^{\circ}C$ with a hot wall epitaxy (HWE) system by evaporating a $ZnIn_2S_4$ source at $610^{\circ}C$. The crystalline structures of the single-crystal thin films were investigated via the photoluminescence (PL) and Double-crystal X-ray rocking curve (DCRC). The temperature dependence of the energy band gap of the $ZnIn_2S_4$ obtained from the absorption spectra was well described by Varshni's relationship, $E_g(T)=2.9514\;eV-(7.24{\times}10^{-4}\;eV/K)T2/(T＋489K)$. After the as-grown $ZnIn_2S_4$ single-crystal thin films was annealed in Zn-, S-, and In-atmospheres, the origin-of-point defects of the $ZnIn_2S_4$ single-crystal thin films were investigated via the photoluminescence (PL) at 10 K. The native defects of $V_{Zn}$, $V_S$, $Zn_{int}$, and $S_{int}$ obtained from the PL measurements were classified as donor or acceptor types. Additionally, it was concluded that a heat treatment in an S-atmosphere converted $ZnIn_2S_4$ single crystal thin films into optical p-type films. Moreover, it was confirmed that In in $ZnIn_2S_4$/GaAs did not form a native defects, as In in $ZnIn_2S_4$ single-crystal thin films existed in the form of stable bonds.

• Applied Biological Chemistry
• /
• v.50 no.2
• /
• pp.87-94
• /
• 2007

A bacterium which has high enzymatic activities such as amylase, cellulase and protease was isolated from Korean traditional soybean food, doenjang. The isolated bacterium was identified to Bacillus subtilis HS25 by the test of morphological and biochemical properties according to Bergey's Manual of Systematic Bacteriology and API 50 CHL kit, and by the 16S rDNA sequence. The isolated B. subtilis HS25 had a potent antibacterial activity against food born causative or pathogenic bacteria. B. subtilis HS25 is endospore forming cell and contained flagella and abundant viscous material at the out layer of cell wall. It was rod type bacterium $(0.5{\sim}0.8{\times}3{\sim}5{\mu}m)$ having biochemical characteristics such as gram staining(+), catalase(+), oxidase(-) and hydrolysis of esculin(+). The optimal medium compositions for production of antibacterial substance in the B. subtilis HS25 were 1% of soluble starch, 0.5% of yeast extract, 0.5% of peptone and 0.05% of MgCl$_2{\cdot}6H_{2}O$. The optimum temperature and pH of the growth of the B. subtilis HS25 was 35$^{\circ}C$ and pH 7.5, respectively. The antibacterial activity was more high in neutral to a little alkaline pH (6.5-10.5) than in acidic pH. The optimal shaking speed to grow and to produce antibacterial substance of the B. subtilis HS25 was 160${\sim}$200 rpm. The optimal culture time for antibacterial activities of the bacterium were shown to be in the range of 12-36 hr.

• Journal of Korean Society of Environmental Engineers
• /
• v.31 no.10
• /
• pp.901-908
• /
• 2009

We examine the processing method of the food wastewater to direct spray at living waste incinerator. The demoscale stoker system is used as a incineration facility. The results show that it brings effect on the reduction of nitrogen oxide ($NO_x$) concentration as well as the ammonia ($NH_3$) amount in SNCR (selective non-catalytic reduction) by the incineration of food wastewater which is containing a plentiful ammoniac nitrogen ($NH_3$-N). Furthermore, the stability of incineration facility and the extension of operation period is actualized as a improvement of clogging phenomenon on outer wall of water pipe as the 870~$950^{\circ}C$ maintain of exit temperature in a second combustor by spray of the food wastewater. The 26 items of air pollution matter of nitrogen oxide ($NO_x$), sulfur oxide ($SO_x$) and dioxin etc. are measured. The results show that it is under the value of allowable exhaust standard.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.35 no.4
• /
• pp.342-347
• /
• 2002

Ciliates have the possibility of a new live food in marine finfish culture because of their wide range of body size, thin tell wall, show motility, and fast reproduction rate. In this research, six species of ciliates were isolated from south coast and salt pond in Korea. The fitness of these species as a live food was evaluated in terms of size, motility, suspensibility and cell density. As the result, Euplotes sp. (K-1) was found suitable to be a new live food which might substitute rotifers, Brachionus plintilis and B. rotundiformis in fish larvae culture. The modified $F{\emptyset}yn's$ Erdschreiberd media, MErds-2 with the addition of glycine, glucose and yeast extract increased six times higher growth rate of Euplotes sp. (K-1) than the basic F$\emptyset$yn's Erdschreiberd media. The optimum water temperature, pH and light intensity for this ciliates were $22.5^{\circ}C$, 8 and 2,000 lux, respectively, and its culture environmental range was relatively wide, On the other hand, this ciliate fed baker's yeast, Saccharomyces cererisiae grew up to 1,240 inds./mL with the inocula of 100 inds./mL within 7 days. The results of the study showed that Euplotes sp. (K-1) has a potential to be utilized as a new live food in fish larvae culture.

• Restorative Dentistry and Endodontics
• /
• v.25 no.3
• /
• pp.435-445
• /
• 2000

The purpose of this study was to compare the leakage of four different obturation techniques in conjunction with immediate apical barrier of ${\beta}$-tricalcium phosphate(TCP) in teeth with open apex. Eighty single-rooted human premolar teeth were prepared and sectioned horizontally, so maximum diameter in apex was 4mm. Apical defects that were similar to open apex, were created with #1/2 round bur and SF104R bur. The apical foramen were opened to a size 80 file extended 3mm beyond the apex. The teeth were placed into the oasis block soaked saline to simulate periapical tissue often associated with pulpless teeth and received apical barriers consisting of TCP followed by obturation using lateral condensation technique, vertical condensation technique, continuous wave technique and thermoplasticized gutta-percha injection technique. Two unobturated teeth served as positive and negative controls. Teeth were immersed in resorcinol-formaldehyde resin for S days at $4^{\circ}C$, and the resin was allowed to polymerize completely for 4 days at room temperature. Teeth were then sectioned horizontally at 1.5mm(level 1), 2.5mm(level 2) and 3.5mm(level 3) from the apex, and examined under a stereomicroscope at ${\times}40$ magnification. The photographs were taken at ${\times}40$ magnification of the filling in each level and scanned. The leakage length in tooth/resin interface was measured at each of the three levels. Each ratio of leakage was obtained by calculating the ratio of the leakage length of canal wall infiltrated with resin to the total length of the canal and was analyzed statistically(One-way ANOVA and Scheffe test). The result were as follows : 1. At the level 1, there was the least leakage in the thermoplasticized gutta-percha injection technique group(group 4), but there was statistically significant(p<0.05). 2. At the level 2, there was the least leakage in the thermoplasticized gutta-percha injection technique group(group 4), and the most leakage in the continuous wave technique group(group 3). There was statistically significant difference between the thermoplasticized gutta-percha injection technique group and the continuous wave technique group(p<0.05). 3. At the level 3, there was the least leakage in the thermoplasticized gutta-percha injection technique group(group 4), but there were no statistically significant differences between other groups(p>0.05). These results suggest that thermoplasticized gutta-percha injection technique which had 1mm apical gutta-percha matrix after the formation of TCP apical barrier, can demonstrate favorable apical sealing.

• Korean Chemical Engineering Research
• /
• v.51 no.4
• /
• pp.443-454
• /
• 2013

Various metal ions (transition and base metals) incorporated MCM-41 catalysts can be synthesized using colloidal and soluble silica with non-sodium involved process. Transition metal ion-typically $V^{5+}$, $Co^{2+}$, and $Ni^{2+}$-incorporated MCM-41 catalysts were synthesized by isomorphous substitution of Si ions in the framework. Each incorporated metal ion created a single species in the silica framework, single-site solid catalyst, showing a substantial stability in reduction and catalytic activity. Radius of pore curvature effect was investigated with Co-MCM-41 by temperature programmed reduction (TPR). The size of metallic Co clusters, sub-nanometer, could be controlled by a proper reduction treatment of Co-MCM-41 having different pore size and the initial pH adjustment of the Co-MCM-41 synthesis solution. These small metallic clusters showed a high stability under a harsh reaction condition without serious migration, resulting from a direct anchoring of small metallic clusters to the partially or unreduced metal ions on the surface. After a complete reduction, partial occlusion of the metallic cluster surface by amorphous silica stabilized the particles against aggregations. As a probe reaction of particle size sensitivity, carbon single wall nanotubes (SWNT) were synthesized using Co-MCM-41. A metallic cluster stability test was performed by CO methanation using Co- and Ni-MCM-41. Methanol and methane partial oxidations were carried out with V-MCM-41, and the radius of pore curvature effect on the catalytic activity was investigated.

• Journal of the Korean Vacuum Society
• /
• v.20 no.2
• /
• pp.155-163
• /
• 2011

Carbon nanotubes (CNT) have been attracted much attention since they have been expected to be used in various areas by virtue of their outstanding physical, electrical, and chemical properties. In order to make full use of their prominent electric conductivity in some areas such as electron emission sources, device interconnects, and electrodes in energy storage devices, direct growth of CNT with vertical alignment is definitely beneficial issue because they can maintain mechanical stability and high conductivity at the interface between substrates. Here, we report direct growth of vertically aligned CNT (VCNT) on Cu foils using thermal chemical vapor deposition and characterize the field emission property of the VCNT. The VCNT's height was controlled by changing the growth temperature, growth time, and catalytic layer thickness. Optimum growth condition was found to be $800^{\circ}C$ for 20 min with acetylene and hydrogen mixtures on Fe catalytic layer of 1 nm thick. The diameter of VCNT grown was smaller than that of usual multi walled CNT. Based on the result of field emission characterization, we concluded that the VCNT on Cu foils can be useful in various potential applications where high conductivity through the interface between CNT and substrate is required.

• Korean Journal of Microbiology
• /
• v.27 no.4
• /
• pp.357-365
• /
• 1989

Induction conditions for autolysis and autoplast formation of thermophilic Clostridium thermohydrosulfuricum were studied. The cells in the initial exponential growth phase were well autolysed in Tris-HCl buffer or inorganic buffers containing univalents, such as $K^{+}$ and $Na^{+}$ , and chemicals such as cysteine-HCl, sorbitol and glycerol. Meanwhile, autolysis induction was slightly inhibited by divalents, such as $Mg^{2+}, Mn^{2+}, Ca^{2+}, Ni^{2+}$, and strongly by divalents, such as $Fe^{2+}, Cu^{2+}$ and citric acid. The autolysis was stimulated when the cells were grown in the medium containing ampicillin that inhibites cell wall synthesis, meanwhile, it was slightly inhibited by nucleic acids and protein synthesis inhibitors. The optimal pH and temperature for the induction of autolysis were 7.5 and $60^{\circ}C$, respectively. On the other hand, the cells were autoplasted without lysozyme treatment during autolysis due to the stabilization of protoplasmic membrane in the presence of divalents such as $Mg^{2+}, Mn^{2+}, Ca^{2+}, Ni^{2+}$. Autoplast formation was mostly induced at $37^{\circ}C$ in 50mM Tris-HCl buffer (pH 7.5) containing 20 mM $MgCl^{2}$ and 0.3 M glycerol, and in the late exponential growth phase growing cell.

• Korean Chemical Engineering Research
• /
• v.56 no.2
• /
• pp.229-239
• /
• 2018

The purpose of this study was to effectively produce the biosugar from cell wall of lipid extracted microalgae (LEA) by using microwave-assisted pretreatment without enzymatic hydrolysis process. Response surface methodology (RSM) was applied to optimization of microwave-assisted pretreatment conditions for the production of biosugar based on enzyme-free process from LEA. Microwave power (198~702 W), extraction time (39~241 sec), and sulfuric acid (0~1.0 mol) were used as independent variables for central composite design (CCD) in order to predict optimum pretreatment conditions. It was noted that the pretreatment variables that affect the production of glucose (C6) and xylose (C5) significantly have been identified as the microwave power and extraction time. Additionally, the increase in microwave power and time had led to an increase in biosugar production. The superimposed contour plot for maximizing dependent variables showed the maximum C6 (hexose) and C5 (pentose) yields of 92.7 and 74.5% were estimated by the predicted model under pretreatment condition of 700 w, 185.7 sec, and 0.48 mol, and the yields of C6 and C5 were confirmed as 94.2 and 71.8% by experimental validation, respectively. This study showed that microwave-assisted pretreatment under low temperature below $100^{\circ}C$ with short pretreatment time was verified to be an effective enzyme free pretreatment process for the production of biosugar from LEA compared to conventional pretreatment methods.