• Korean Chemical Engineering Research
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• 제48권4호
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• pp.470-474
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• 2010

In this study, we presents a simple microfluidic approach for generating uniform Poly(ethylene glycol)(PEG) microfiber. Elongated flow pattern of monomer induced by sheath flow of immiscible oil as continuous phase is generated in Y-shape junction and in situ polymerization by UV exposure. For uniform microfiber, we investigate the optimized flow condition and draw phase diagram as function of Ca and Qd. At the region for stable elongated flow pattern, the microfiber generated in microfluidic chip is very uniform and highly reproducible. Importantly, the thickness of microfibers can be easily controlled by flow rate of continuous and disperse phase. We also demonstrate the feasibility for biological application as encapsulating FITC-BSA in PEG microfiber.

• Journal of Technologic Dentistry
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• 제42권2호
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• pp.65-71
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• 2020

Purpose: To know the transmittance of light when wearing shading goggles and to protect eyes from blue light emitted from dental scanner when using CAD/CAM works or inducing polymerization reactions of dental resin with curing unit and infrared light occurred when melting Dental precious metal and non-precious metal alloys. Methods: By measuring and comparing the average transmittances of blue light, visible light and infrared ight by using UV-Vis Spectrophotometer analysis measuring instrument, I compared 3 GREEN Color Goggles worn when casting Dental precious metal and non-precious metal alloys, and compared each of YELLOW, ORANGE Color Goggles worn when using Dental CAD/CAM scanners and Light Curing(LED) the Dental resin. Results: In blue light range, YELLOW Color Goggles are more effective than ORANGE Color Goggles. In infrared light range, No.12 Goggles are more effective than No.10 and No.11 Goggles. Conclusion: When wearing blue light shading goggles to avoid harmful blue light occurred in using dental scanner and curing light, and when wearing infrared light shading goggles to avoid harmful infrared light during casting, to avoid the Side Effects like transmittance rate of blue light and infrared light goggles becomes too high to block appropriate amount of harmful light or too low that causing lower image clarity.

• Polymer(Korea)
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• 제29권4호
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• pp.357-362
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• 2005

As a new class of electroluminescent (EL) polymers, PPV-based polymers containing sulfone group in the main chain were synthesized through Witting polymerization reaction to control n-conjugation length and energy levels for predictable light emission and enhanced device performance. These EL polymers showed good solubility in common organic solvents and high thermal stability with initial decomposition temperature of ca. $400^{circ}$ and glass transition temperature around $200^{circ}C$ Emission colors were tuned from green to deep blue by reducing ${\pi}$-conjugated length between sulfone groups. It was also noted from the cyclic voltammetry (CV) measurements and semiempirical calculations that sulfone group with high electron affinity effectively lowered HOMO-LUMO energy levels to enhance EL device performance.

• Polymer(Korea)
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• 제33권3호
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• pp.237-242
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• 2009

This study examined the transdermal delivery of alendronate across hairless mouse skin. The effects of iontophoresis, perforation with a microneedle, and a combination of a microneedle pretreatment and iontophoresis were evaluated in vitro test. Hydrogel patches were polymerized by UN polymerization to supply a hydrogel patch to the iontophoretic transdermal drug delivery system. The alendronate content in the iontophoretic delivery patch was $5.0\;mg/cm^3$. The amounts of alendronate that permeated across the hairless mouse skin when current densities of 0.25 and $0.50\;mA/cm^2$ were supplied to the iontophoretic alendronate patch were $0.80{\pm}0.03$ and $2.00{\pm}0.02{\mu}g$, respectively. After pretreatment with a microneedle, the amounts of alendronate that permeated across the hairless mouse skin increased to $70.65{\pm}0.37$ and $162.23{\pm}0.40{\mu}g$, respectively. The biocompatibility of the iontophoretic alendronate patch was examined according to the international standardization organization 10993.

• Journal of the Korean Wood Science and Technology
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• 제24권1호
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• pp.48-53
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• 1996

Brown rot fungus, Tyromyces palustris, has been reported to cause the loss of strength accelerated by oxalate, a non-enzymatic low molecular weight acid, with minute weight loss of decaying wood in early stage. The production of oxalate in relation to wood decaying and the presence of oxaloacetase. an oxalate producing enzyme, were identified during the process. Tyromyces palustris produced the largest amount of oxalate among brown rot fungi. In order to find out the cleavage of pulp fiber, we submerged pulp fiber in oxalate solution and the results showed that the number of short pulp fiber was highly increased, compared with control solution. The pH of decaying wood was decreased to 1.77 which was close to that of saturated oxalate solution, pH 1.2, Thus, the oxalate was thought to be accumulated in the decaying wood, The oxaloacetase which accelerates production of oxalate was derived from fungus, and the production of oxalate by the enzyme was determined by using on UV/Vis spectrophotometer. Therefore, the oxalate was found to be produced by oxaloacetase during decay. The oxalate may cause the acid-hydrolysis of cellulose and hemicellulose. The oxalate was thought to reduce the degree of polymerization and increase the enzyme activity, which resulted in rapid loss of strength in early stage-an identical feature of brown rot fungus.

• Korean Journal of Microbiology
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• 제36권4호
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• pp.306-311
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• 2000

Infection of Vero cells with herpes simplex virus type-1 (HSV-1) resulted in a series of changes in intra-cellular free calcium concentration $([Ca^{2+}]_i)$. A significant and maximal decrease $[Ca^{2+}]_i$ was observed at 4 hours postinfection (hr p.i.) in HSV-1-infected in Vero cells. Inactivation of HSV-1 with UV irradiation and heat treatment abolished HSV-1-induced decrease in $[Ca^{2+}]_i$ at 4 hr p.i. in Vero cells. And the degree of the decrease in $[Ca^{2+}]_i$ was dependent on the amount of input virus. Taxol, which stabilizes the polymerization of microtubule blocked HSV-1-induced decrease in $[Ca^{2+}]_i$ at 4 hr p.i., suggesting that microtubule may mediate the transport of HSV-1 nucleocapsid to the nucleus of infected cell. Treatment of HSV-1-infected Vero cells with metabolic inhibitors such as cycloheximide, cordycepin, or acyclovir partially reversed the decrease in $[Ca^{2+}]_i$ at 4 hr p.i.. Thus, it is suggested that HSV-1 induced decrease in $[Ca^{2+}]_i$ at 4 hr p.i. in Vero cells may play an important role in the multiplication of HSV-1.

• Korean Chemical Engineering Research
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• 제60권1호
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• pp.139-144
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• 2022

This study reports a microfluidic approach to produce monodisperse hydrogel microparticles in a simple and highly efficient manner. Specifically, we produce double emulsion drops with a thin oil shell surrounding an aqueous prepolymer solution, which is solidified via UV-induced free radical polymerization. When they are dispersed in an aqueous solution, the oil shell is dewetted due to the absence of surfactants, resulting in production of highly uniform hydrogel microparticles (C.V.=1%). Results show that production of monodisperse hydrogel microparticles with controllable size and composition can be achieved with minimal use of oil unlike water-in-oil (w/o) single emulsion-based approach. Furthermore, in-depth study of flow patterns in microfluidic device using a phase diagram exhibits a crucial relationship among relative flow rates while providing windows of readily controllable parameters for reliable manufacturing of hydrogel microparticles.

• Journal of Microbiology and Biotechnology
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• 제31권7호
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• pp.990-998
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• 2021

Melanin is a natural skin pigment produced by specialized cells called melanocytes via a multistage biochemical pathway known as melanogenesis, involving the oxidation and polymerization of tyrosine. Melanogenesis is initiated upon exposure to ultraviolet (UV) radiation, causing the skin to darken, which protects skin cells from UVB radiation damage. However, the abnormal accumulation of melanin may lead to the development of certain skin diseases, including skin cancer. In this study, the antioxidant and antimelanogenic activities of the cell-free supernatant (CFS) of twenty strains were evaluated. Based on the results of 60% 2,2-diphenyl-1-picrylhydrazyl scavenging activity, 21% 2,2'-azino-bis (3-ethylbenzthiazoline-6-sulfonic acid) scavenging capacity, and a 50% ascorbic acid equivalent ferric reducing antioxidant power value, Limosilactobacillus fermentum JNU532 was selected as the strain with the highest antioxidant potential. No cytotoxicity was observed in cells treated with the CFS of L. fermentum JNU532. Tyrosinase activity was reduced by 16.7% in CFS-treated B16F10 cells (but not in the cell-free system), with >23.2% reduction in melanin content upon treatment with the L. fermentum JNU532-derived CFS. The inhibitory effect of the L. fermentum JNU532-derived CFS on B16F10 cell melanogenesis pathways was investigated using quantitative reverse transcription polymerase chain reaction and western blotting. The inhibitory effects of the L. fermentum JNU532-derived CFS were mediated by inhibiting the transcription of TYR, TRP-1, TRP-2, and MITF and the protein expression of TYR, TRP-1, TRP-2, and MITF. Therefore, L. fermentum JNU532 may be considered a potentially useful, natural depigmentation agent.

• Membrane Journal
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• 제14권3호
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• pp.250-257
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• 2004

PEG(poly(ethylene glycol)) acrylate/PPG(poly(propylene glycol)) acrylate (PEG/PPG) was prepared using UV induced photopolymerization method to investigate gas permeation properties of the membrane. The effect of PPG content on the solubility, diffusivity, and permeability of $CO_2$, $O_2$, and $N_2$ in PEG/PPG membrane is reported at $25^{\circ}C$ and $35^{\circ}C$. PEG/PPG (9:1) membrane exhibits $CO_2$ permeability coefficient of 28.9 barrer and $CO_2$/$N_2$ pure gas selectivity of 57.9 at $25^{\circ}C$. Permeability coefficient of increased with increasing with PPG content in the membrane. PEG/PPG (5:5) membrane shows $CO_2$ permeability coefficient of 78.9 barrer and $CO_2$/$N_2$ pure gas selectivity of 33.2 at $25^{\circ}C$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 한국전기전자재료학회 2009년도 하계학술대회 논문집
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• pp.269-270
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• 2009

The biased vertical alignment (BVA) liquid crystal (LC) mode shows a has a distinct advantage of lower manufacture cost due to the elimination of a lithographic process step to form either ITO-patterning or protrusions on the color-filter substrates. However, those devices have complex voltage conditions which is the respective induce voltage on common electrode, pixel electrode and bias electrode when positive and negative frame. In order to overcome the complex voltage condition, the pretilt angles is controlled by photo polymerization of the UV-curable reactive mesogen (RM). According to our studies, voltages to the cell are critical to achieve an optimized surface-modified quality BVA (Q-BVA) mode which provides the well defined reorientation of the LCs with respect to an electric field.