• Journal of Environmental Science International
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• v.14 no.6
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• pp.525-532
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• 2005

Polyelectrolyte titration, which was called colloid titration is based on the stoichiometric reaction between oppositely charged polyelectrolytes, This can be used, for instance, to determine the charge density of a cationic polyelectrolyte, using an anionic polyelectrolyte of known charge density, such as potassium polyvinyl sulfate (PPVS). The technique requires a suitable method of end-point detection and there are several possibilities. In this work, two methods have been investigated: visual titrimetry based on the color change of a cationic dye (o-toluidine blue, o-Tb) and spectrophotometry based on the absorbance change corresponding to the color change of the same dye. These have been applied to several cationic polyelectrolytes with different charge density and molecular weight. In all cases, the cationic charge was due to quaternary nitrogen groups. In the case of cationic dye, it was shown that the sharpness depends on the charge density of cationic polyelectrolyte. With the polyelectrolytes of lower charge density, the binding to PPVS is weaker and binding of the dye to PPVS can occur before all of the polyelectrolyte charge has been neutralized. However, by carrying out titrations at several polyelectrolyte concentrations, good linear relationships were found, from which reliable charge density values could be derived. Effects of pH and ionic strength were also briefly investigated. For cationic polyelectrolytes (copolymers of acrylamide and dimethylaminoethy] acrylate), there was some loss of charge at higher pH values, probably as a result of hydrolysis. Increasing ionic strength causes a less distinct color change of o-Tb, as a result of weaker electrostatic interactions.

• Journal of the Korean Ceramic Society
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• v.52 no.5
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• pp.366-373
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• 2015

Sol-gel binder was prepared by hydrolysis and condensation reaction using boehmite sol and methyltrimethoxysilane as a function of aging-time. The coating slurry was composed of a plate-shape alumina in the sol-gel binder for the EPD process, in which particles dispersed in the slurry were deposited on the electrode under an electric field due to the surface charge. We studied the effects of three parameters: the content of boehmite, the aging time, and the applied voltage, on the physical, thermal, and electrical properties of the hybrid composite films by EPD. The amount of boehmite was 10 ~ 20 wt% and the aging time was 0.5 ~ 72, with a fixed amount of plate-shape alumina of 10 wt%. The condition of applied voltage was 5 ~ 30 V with a distance of 2 cm between the electrode during the EPD process. We confirmed that a structure of hybrid composite films of well-ordered plate alumina was deposited on the substrate when the film was prepared using a sol-gel binder composed of 15 wt% boehmite with 1 hr aging time and EPD at 10 V. The process shows a weight loss of 7% at $500^{\circ}C$ in TGA and a breakdown voltage of 8 kV at $87{\mu}m$.

• Journal of the Microelectronics and Packaging Society
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• v.17 no.1
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• pp.41-46
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• 2010

The interfacial adhesion strengths between screen-printed Ag film and epoxy resin-coated polyimide were evaluated by $180^{\circ}$ peel test method. Measured peel strength value was initially around $164.0{\pm}24.4J/m^2$, while the heat treatment during 24h at $120^{\circ}C$ increase peel strength up to $220.8{\pm}19.2J/m^2$. $85^{\circ}C/85%$ RH temperature/humidity treatment decrease peel strength to $84.1{\pm}50.8J/m^2$, which seems to be attributed to hydrolysis bonding reaction mechanism between metal and adhesive epoxy resin coating layer.

• KSBB Journal
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• v.15 no.1
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• pp.35-41
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• 2000

We tried to prepare encapsulated whole cell cyclodextrin glucanotransferase(CGTase) in order to produce glycosyl-xylitol using xylitol as glucosyl acceptor. The organic nitrogen source was more effective for the production of CGTase from Bacillus macerans IFO 3490 than the inorganic one. Most of the CGTase which had been produced during cultivation was excreted to the growth medium. B. macerans cells inocculated in the capsule failed to grow to the high cell density. Adsorbents such as activated charcoal, Sephadex and Amberite resins could not adsorb efficiently the CGTase from the broth solution. We obtained successfully the encapsulated whole cell CGTase by immobilizing the concentrated broth solution in the calcium alginate capsules. The encapsulated whole cell CGTase carried out the transglycosylation reaction which converts xylitol into glucosyl-xylitol using dextrin as glucosyl donor.

• Current Photovoltaic Research
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• v.3 no.1
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• pp.5-9
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• 2015

Absorption and luminescence characteristics of disperse red-19 (DR-19) and $TiO_2$ composite have been investigated with various poling electric field strengths. Two step synthetic processes were employed to employ the DR-19 to the $TiO_2$ sol-gel. Firstly, urethane bond formation between DR-19 (-OH) and 3-isocyanatopropyl triethoxysilane (ICPTES, -N=C=O) performed (ICPDR) prior incorporation to the $TiO_2$ sol-gel. Secondary, the hydrolysis of the ethoxy group from the ICPTES and condensation reaction between silanol groups from ICPTES and $TiO_2$ sol-gel were performed. The ICPDR and $TiO_2$ sol-gel ($DRTiO_2$) were mixed and stirred for several days. The composite was coated to the ITO coated glass substrate. Corona poling were performed before drying the composite with various electric field strengths. The absorption intensity decreased with the increase of the poling field strength, which resulted in the increase of poling efficiency. The photoluminescence also decreased as the poling field strength increased. There is long luminescence tail for the poled $DRTiO_2$ film compared with unpoled $DRTiO_2$ film. The luminescence long tail indicates that the self-trapped excitons and polarons were generated when the $DRTiO_2$ film was poled with electric field.

• Microbiology and Biotechnology Letters
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• v.40 no.1
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• pp.17-22
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• 2012

A bacterial strain was isolated from homemade Cheongkookjang as a producer of the ${\beta}$-galactosidase, capable of hydrolyzing lactose to liberate galactose and glucose residues. The isolate YB-1105 has been identified as Bacillus licheniformis on the basis of its 16S rDNA sequence, morphology and biochemical properties. ${\beta}$-Galactosidase activity was detected in both the culture supernatant and the cell extract of B. licheniformis YB-1105. The enzymes of both fractions demonstrated maximum activity for hydrolysis of para-nitrophenyl-${\beta}$-D-galactopyranoside (pNP-${\beta}Gal$) under identical reaction conditions of pH 6.5 and $50^{\circ}C$. However, ${\beta}$-galactosidase activity from the culture filtrate was affected more than that from the cell free extract at acidic pHs and high temperatures. The hydrolyzing activity of both ${\beta}$-galactosidases for pNP-${\beta}Gal$ was dramatically decreased by the addition of low concentrations of galactose, but was only marginally decreased by high concentrations of glucose or mannose.

• Microbiology and Biotechnology Letters
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• v.42 no.2
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• pp.177-183
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• 2014

Recently, many biofuels and chemicals converted from renewable resources have been introduced into chemical industries. Sargassum fulvellum is a brown macro-algae, which is found on the seashores of Korea and Japan. In this work, the production of total reducing sugar and levulinic acid from S. fulvellum, using dilute-acid catalyzed hydrothermal hydrolysis and statistical methodology, was investigated. As a result, 15.28 g/l total reducing sugar was obtained under the optimized conditions of $160.1^{\circ}C$, 1.0% sulfuric acid, in 20.2 min. Furthermore, 2.65 g/l levulinic acid was obtained at $189.5^{\circ}C$, 2.93% sulfuric acid, in 48.8 min.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.37-37
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• 2010

Silicate-silsesquioxane or siloxane-silsesquioxane hybrid thin films are strong candidates as matrix materials for ultra low dielectric constant (low-k) thin films. We synthesized the silicate-silsesquioxane hybrid resins from tetraethoxyorthosilicate (TEOS) and methyltrimethoxysilane (MTMS) through hydrolysis and condensation polymerization by changing their molar ratios ([TEOS]:[MTMS] = 7:3, 5:5, and 3:7), spin-coating on Si(100) wafers. In the case of [TEOS]:[MTMS] 7:3, the dielectric permittivity value of the resultant thin film was measured at 4.30, exceeding that of the thermal oxide (3.9). This high value was thought to be due to Si-OH groups inside the film and more extensive studies were performed in terms of electronic, ionic, and orientational polarizations using Debye equation. The relationship between the mechanical properties and the synthetic conditions of the silicate-silsesquioxane precursors was also investigated. The synthetic conditions of the low-k films have to be chosen to meet both the low orientational polarization and high mechanical properties requirements. In addition, we have investigated a new solution-based approach to the synthesis of semiconducting chalcogenide films for use in thin-film transistor (TFT) devices, in an attempt to develop a simple and robust solution process for the synthesis of inorganic semiconductors. Our material design strategy is to use a sol-gel reaction to carry out the deposition of a spin-coated CdS film, which can then be converted to a xerogel material. These devices were found to exhibit n-channel TFT characteristics with an excellent field-effect mobility (a saturation mobility of ${\sim}\;48\;cm^2V^{-1}s^{-1}$) and low voltage operation (< 5 V). These results show that these semiconducting thin film materials can be used in low-cost and high-performance printable electronics.

• Toxicological Research
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• v.14 no.4
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• pp.525-533
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• 1998

The covalent interactions of toluenediisocyanate (TDI) with macromolecules were investigated both in vitro and in vivo. In vitro incubations of 2,4- and 2,6-TDI with DNA or proteins resulted in dose-dependent formation of TDI-protein and TDI-DNA adducts. TDI-treated DNA was highly resistant to enzymatic digestion and thermal hydrolysis, but was readily hydrolyzed under acidic conditions by releasing its corresponding toluenediamine (TDA), suggesting that TDI caused the crosslinking of DNA. Reaction of TDI with albumin and globin resulted in the formation of several adducts, and some adducts were formed in blood of TDI-treated rats in a dose-dependent fashion. Administration of TDI to rats resulted also in a dose-dependent binding of TDI to hepatic tissue. Levels of TDI-albumin adducts were 10 times higher than those of TDI-globin adducts; the biological half lives of TDI-albumin and TDI-globin adducts were 1.2 and 12.5 days, respectively. Globin adducts were detected up to 28 days after the treatment. Hepatic TDI protein adducts were persistent for a substantial period whereas the levels of hepatic TDI-DNA adduct were decreased rapidly. These results indicate that the isocyanato group of TDI is not readily hydrolyzed under physiological conditions, is transported to other organs, and is bound to DNA and/or proteins without further metabolic activation. As the adducted products degrade in the body, TDA is released and introduced to the liver. TDA may additionally bind to hepatic tissue after metabolic activation. Thus, the toxic effect of TDI exposure is considered to persist during the lifetime of the adducted biological macromolecules.

• Korean Journal of Food Science and Technology
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• v.28 no.1
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• pp.146-151
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• 1996

For the purpose of production of oligosaccharides from alginates, a bacterium was isolated from seaweed, and then an enzyme which degraded alginates was obtained from the bacterium. A specific activity of the enzyme was shown in G-rich block and Na-alginate (Wako Co.) as a result of reaction between the enzyme and six types of alginates (G-rich block, M-rich block and 4 commercial Na-alginate). Degradation products were prepared from the Na-alginate (Wako Co.) by the enzyme. The oligosaccharides were fractioned by Sephadex G-25 and Bio-gel P-2 and identified on a thin layer chromatography (TLC). Degree of polymerization (DP) of the oligosaccharides was shown from 2.6 to 7.5.