• Journal of Sensor Science and Technology
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• v.17 no.5
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• pp.346-349
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• 2008

A metal-semiconductor-metal (MSM) ultraviolet (UV) photodetector (PD) is proposed as an effective UV sensing device for integration with a GaN n-channel MISFET on auto-doped p-type GaN grown on a silicon substrate. Due to the high hole barrier of the metal-p-GaN contact, the dark current density of the fabricated MSM PD was less than $3\;nA/cm^2$ at a bias of up to 5 V. Meanwhile, the UV/visible rejection ratio was 400 and the cutoff wavelength of the spectral responsivity was 365 nm. However, the UV/visible ratio was limited by the sub-bandgap response, which was attributed to defectrelated deep traps in the p-GaN layer of the MSM PD. In conclusion, an MSM PD has a high process compatibility with the n-channel GaN Schottky barrier MISFET fabrication process and epitaxy on a silicon substrate.

• Journal of Microbiology and Biotechnology
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• v.25 no.12
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• pp.2034-2042
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• 2015

A one-pot process of enzymatic synthesis of deoxythymidine-5'-triphosphate (5'-dTTP) employing whole cells of recombinant Escherichia coli coexpressing thymidylate kinase (TMKase) and acetate kinase (ACKase) was developed. Genes tmk and ack from E. coli were cloned and inserted into pET28a(+), and then transduced into E. coli BL21 (DE3) to form recombinant strain pTA in which TMKase and ACKase were simultaneously overexpressed. It was found that the relative residual specific activities of TMKase and ACKase, in pTA pretreated with 20 mM ethylene diamine tetraacetic acid (EDTA) at 25℃ for 30 min, were 94% and 96%, respectively. The yield of 5'-dTTP reached above 94% from 5 mM deoxythymidine 5'-monophosphate (5'-dTMP) and 15 mM acetyl phosphate catalyzed with intact cells of pTA pretreated with EDTA. The process was so effective that only 0.125 mM adenosine-5'-triphosphate was sufficient to deliver the phosphate group from acetyl phosphate to dTMP and dTDP.

• Journal of Korean Society on Water Environment
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• v.25 no.5
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• pp.758-763
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• 2009

This study presents the optimal conditions of zero-valent iron (ZVI) pretreatment for color removal from real dye wastewater. Removal of color by ZVI was strongly subject to the acidity of the wastewater buffering the pH increased after ZVI reduction. The real dye wastewater did not contain a sufficient amount of acidity and thus it was necessary to supplement acid to the dye wastewater before treatment. In continuous operation of iron column, the empty bed contact time (EBCT) and initial pH were varied to find the optimal conditions. A non-linear regression model fitted well the experimental result predicting that the optimal EBCT and pH for 80% removal efficiency was present in the range of 57~90 and 5~5.9, respectively. Color of column effluents could be further removed in the following biological oxidation step and the biodegradability of wastewater was also enhanced after iron pretreatment.

• Microbiology and Biotechnology Letters
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• v.16 no.4
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• pp.316-319
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• 1988

Pectate Lyase (PL) was cloned from alkali-tolerant Bacillus sp. YA-14 into Escherichia coli MB1000 by inserting HindIII-generated DNA fragment into the HindIII site of pBR322 and then screening recombinant transformant for the ability to hydrolyze sodium polypectate on agar plate, The recombinant plasmid, called pYPC29, was isolated, and the size of the cloned HindIII fragment was found to be 1.6 kb. The PL gene was stablely maintained and expressed efficiently in Escherichia coli. The Pt accumulated largely in the periplasmic space of Escherichia coli clones.

• Journal of Applied Biological Chemistry
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• v.43 no.4
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• pp.246-249
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• 2000

We investigated the production of chitin oligosaccharides using food grade papain. A solution of commercial food grade papain (FGP) was dialyzed for 12 h before measuring its chitinolytic activity. The effects of enzyme concentration, reaction temperature, and pH on the endochitinase and $\beta$-N-acetylglucosaminidase activities and the thermostability of these enzymes were investigated. In adddition, the reaction products were analyzed with gel filtration on a Bio-Gel P2. The endochitinase activity was twentyfold higher than that of $\beta$-N-acetylglucosaminidase. The optimal endochitinase activity was at pH 3.0, while the maximal $\beta$-N-acetylglucosaminidase activity was at pH 6.0. The reaction product consisted mainly of the dimer of N -acetylglucosamine, with a small amount of its trimer. Under the experimental conditions, $120{\mu}g$ of chitin oligomers were obtained with 1 mg of FGP protein after an incubation of 2 h.

• Korean Chemical Engineering Research
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• v.50 no.5
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• pp.923-928
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• 2012

Optimizing a water-phase suspending system is very important to manufacture high-quality suspension polymerized toners. Therefore, in this study, the effects of the molar ratio of calcium hydroxide ($CaOH_2$)/phosphoric acid ($H_3PO_4$)(Ca/P), which were used as inorganic suspending agents, and pH of the water-phase on the characteristics of styrene-based suspension polymerized toners were mainly investigated. At first, the water-phase was fixed to neutral condition (pH=7.5) and Ca/P molar ratio was changed from 1.5:1 to 1.76:1. As a result, an ideal calcium phosphate (hydroxyapatite) was prepared at the Ca/P molar ratio of 1.73:1 and polymerized toners prepared at this condition showed good particle size distribution, circularity and charging characteristic. Based on this result, Ca/P molar ratio was fixed to 1.73:1 and pH of the water-phase was changed to weak acidic (pH=5.5) and weak basic (pH=9.5) conditions. As a result, polymerized toners prepared under the weak acidic condition showed very good particle size distribution, circularity and charging characteristic along with excellent printing quality. High-quality suspension polymerized toners could be prepared via optimizing Ca/P molar ratio and pH of the water-phase.

• Journal of Korea Foundry Society
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• v.22 no.1
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• pp.42-48
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• 2002

Effects of coating treatment of metallic Cu, Ni-P film on $SiC_p$, for $SiC_p$/iron aluminide composites were studied. Porous hybrid preforms were fabricated by reactive sintering after mixing the coated $SiC_p$, Fe and Al powders. Then the final composites were manufactured by squeeze casting after pouring AC4C Al alloy melts in preforms. The change of reactive temperature, density, microstructure of the preforms and microstructure of the composites were investigated. The exprimental results were summarized as follows. The thickness of Cu and Ni-P metallic layer formed on $SiC_p$ by electroless plating method were about $0.5{\mu}m$ and coated uniformly. There was no remakable change in the ignition temperature with variation of the mixing ratio of Fe and Al powder while in the case of coated $SiC_p$ it was lower about $20^{\circ}C$ than in the non-coated $SiC_p$. The maximum reaction temperature increased with increasing Al contents, but decreased with increasing $SiC_p$ contents. Expansion ratio of preform after reactive sintering increased with amount of Cu coated $SiC_p$. In the case of Fe-70at.%Al, the expansion ratio was about 7% up to 8wt.% of $SiC_p$, addition but further addition of $SiC_p$, increased the ratio significantly. And in the case of Fe-50 and 60at.%Al, it was about 20% up to 16wt.% of $SiC_p$ addition and about 28% in 24wt.% of $SiC_p$, addition. The microstructures of compounds showed that the grains became finer as amount of $SiC_p$, and mixing ratio of iron powder increased and the shape of compounds was changed gradually from irregular to spheroidal.

• Journal of Biomedical Engineering Research
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• v.28 no.2
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• pp.250-257
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• 2007

Functional gastrointestinal disorders affect millions of people of all age regardless of race and sex. There are, however, rare diagnostic methods for the functional gastrointestinal disorders because functional disorders show no evidence of organic and physical causes. Our research group identified recently that the gastrointestinal tract well in the patients with the functional gastrointestinal disorders becomes more rigid than healthy people when palpating the abdominal regions overlaying the gastrointestinal tract. The aim is, therefore, to develop a diagnostic method for the functional gastrointestinal disorders based on quantitative measurement of the rigidity of the gastrointestinal tract well using ultrasound technique. For this purpose, a preliminary ultrasound diagnostic system was developed and verified through phantom tests. The system consisted of transmitter, ultrasonic transducer, receiver, TGC, and CPLD, and verified via a phantom test. For the phantom test, ten soft-tissue specimens were harvested from porcine. Five of them were then treated chemically to mimic a rigid condition of gastrointestinal tract well, which was induced by functional gastrointestinal disorders. Additionally, the specimens were tested mechanically to identify if the mimic was reasonable. The customized ultrasound system was finally verified through application to human subjects with/without functional gastrointestinal disorders(Normal and Patient Groups). It was identified from the mechanical test that the chemically treated specimens were more rigid than normalspecimen. This finding was favorably compared with the result obtained from the phantom test. The phantom test also showed that ultrasound system well described the specimen geometric characteristics and detected an alteration in the specimens. The maximum amplitude of the ultrasonic reflective signal in the rigid specimens $(0.2{\pm}0.1Vp-p)$ at the interface between the fat and muscle layers was explicitly higher than that in the normal specimens $(0.1{\pm}0.0Vp-p)$ (p<0.05). Clinical tests using our customized ultrasound system for human subject showed that the maximum amplitudes of the ultrasonic reflective signals nea. to the gastrointestinal tract well for the patient group$(2.6{\pm}0.3Vp-p)$ were generally higher than those in normal group$(0.1{\pm}0.2Vp-p)$ (p<0.05). These results suggest that newly designed diagnostic system based on ultrasound technique may diagnose enough the functional gastrointestinal disorders.

• Resources Recycling
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• v.16 no.4
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• pp.27-32
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• 2007

The characteristics of fluorine removal from wastewater have been investigated by precipitation method using calcium as a precipitant for the purpose of the reuse of treated wastewater. In the conditions of 10 mM of the initial concentration of fluorine and pH 4, the precipitation of fluorine was rapidly progressed within a few minutes after the precipitant was added and the precipitation of fluorine was observed to follow a second order reaction. Also, as the addition of precipitant was increased, the reaction rate constant of fluorine precipitation was found to rise. Postulating that the maximum fluorine removal was attained at pH 4, about 70% of fluorine was precipitated compared with the maximum removal when 10 times of equivalent amount of calcium was employed at pH 2 and the fluorine removal was about 96% compared with its maximum value at pH 3 under the same addition of precipitant. The fluorine precipitation reaction was found to be endothermic and the coexistence of $SiF_6{^{2-}}$ with fluorine resulted in its less removal. Finally, the isoelectric point of the precipitate was examined to be ca. pH 5.

• Biotechnology and Bioprocess Engineering:BBE
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• v.10 no.4
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• pp.367-371
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• 2005

About 3,000 bacterial colonies with esterase activities were isolated from soil samples by enrichment culture and halo-size on Luria broth-tributyrin (LT) plates. The colonies were assayed for esterase activity in microtiter plates using enantiomerically pure (R)- and (S)-2-phenylbutyric acid resorufin ester (2PB-O-res) as substrates. Two enantioselective strains (JH2 and JH13) were selected by the ratio of initial rate of hydrolysis of enantiomerically pure (R)- and (S)-2-PB-O-res. When cell pellets were used, both strains showed high apparent enantioselectivity ($E_{app}>100$) for (R)-2PB-O-res and were identified as Exiguobacterium acetylicum. The JH13 strain showed high esterase activity on p-nitrophenyl acetate (pNPA), but showed low lipase activity on p-nitrophenyl palmitate (pNPP). The esterase was located in the soluble fraction of the cell extract. The crude intracellular enzyme preparation was stable at a pH range from 6.0 to 11.0.