• Journal of Korean Society of Environmental Engineers
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• v.27 no.7
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• pp.771-776
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• 2005

In recent days, there is much interest in the biocidal activity of silver since silver is known to be safe and effective as disinfectant and biocidal material against coliforms and viruses. In particular, nano silted silver particles which can be used as effective biocidal material received more attention. Accordingly, it is important to investigate antimicrobial activity and mechanism of nano sized silver particles prepared in a cost-effective manner. In this study, nano sized silver particles were prepared via photoreduction of a silver salt ($AgNO_3$) in the bulk phase of $PEO_{20}-PPO_{70}-PEO_{20}$ (Pluronic 123) block copolymer The antimicrobial efficacy of silver nano particles against E. coli was investigated and compared with that of silver ion as the concentration of silver nano particles, pH ($5.6{\sim}8.2$), temperature ($4^{\circ}C{\sim}35^{\circ}C$) varied in aqueous system. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) was used to examine the nature of damaged microorganism with nano sized silver particles and silver ion. This study showed that antimicrobial efficacy of silver nano particles was approximately one twentieth than that of silver ion. It was more biocidal at higher pH in contrast with silver ion. In addition, nano silver particles was demonstrated to disrupt the outer membrane of E. coli, subsequently causing their aggregation. On the other hand, silver ion diffused into the cell damaging the cytoplasmic membrane without disrupting the outer membrane of E. coli.

• YAKHAK HOEJI
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• v.60 no.1
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• pp.36-45
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• 2016

This study was aimed to enhance the percutaneous absorption of tizanidine hydrochloride (TZ) across Strat-M$^{TM}$ artificial membrane and excised hairless mouse skin using various vehicles and chemical permeation enhancers. Solubility studies were performed using hydrophilic and lipophilic vehicles. To initially evaluate vehicle effects on skin permeation, Strat-M$^{TM}$ membrane was adopted using Franz-type diffusion cells loaded with 0.4 mg donor dose. Effects of fatty acids on the permeation of TZ from PG and PGMC were compared, and the effects of various hydrophilic vehicles in the presence of linoleic acid were studied using excised hairless mouse skin specimens. The mean solubility (mg/ml) of TZ in hydrophilic vehicles was higher: water > PG > DMSO > ethanol > PEG 200 > NMP > PEG 300 > PEG 400 > DGME, and solubilities in lipophilic vehicles such as PGMC, PGMC, IPM, Captex 200 and Captex 300 were much less than 1.0 mg/ml. Permeation rates through StratTM membrane from pure vehicles were in the rank order: PGMC ${\geq}$ LBF > DMSO ${\geq}$ NMP ${\geq}$ PGML ${\geq}$ PG ${\geq}$ PEG 200 ${\geq}$ DGME ${\geq}$ EtOH. However, permeation rates of TZ through hairless mouse skin from pure vehicles were very low, although PG showed the highest flux ($1.66{\pm}0.28{\mu}g/cm^2{\cdot}hr$). Therefore, PG was selected in further studies. Addition of enhancers (3 v/v%) into PG markedly increased the flux (${\mu}g/cm^2{\cdot}hr$): oleyl alcohol ($14.9{\pm}3.1$) ${\geq}$ oleic acid ($14.5{\pm}1.6$) ${\geq}$ linoleic acid ($13.7{\pm}1.3$) > capric acid ($4.4{\pm}0.6$) > caprylic acid ($2.1{\pm}0.4$). Among hydrophilic vehicles with linoleic acid, PG and DMSO revealed relatively higher permeation for TZ. Increase of donor dose in PG resulted in dose-dependent permeation fluxes. These results suggest that permeation properties of TZ from nonaqueous solutions are markedly different between Strat-$M^{TM}$ membrane and excised hairless mouse skin, and transdermal delivery of TZ would be feasible with a combination of PG and enhancers.

• Applied Microscopy
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• v.29 no.1
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• pp.43-56
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• 1999

The relationship between intravascular erythroblasts and Kupffer cells in the human fetal liver from 11 to 20 week gestation was studied ultrastructurally. The walls of the developing sinusoids consisted of two cell types devoid of basal lamina, the nonfenestrasted endothelial cells and Kupffer cells. Kupffer cells examined were easily identified by their content of phagosmes and their morphological features, and partially proliferated by mitotic division which was different way of proliferation from adult. Some extruded nuclei of acidophilic erythroblasts were trapped within Kupffer cells which exhibited various stages of intracellular digestion of the nuclei. During high activity of human fetal hepatic erythropoiesis, Kupffer cells were found in association with developing erythrob-lasts, which was similar with erythroblastic islands. The developing erythroblasts were partially surrounded by multilaminated membrane system of the Kupffer cell consisting erythroblastic island, or in contact with Kupffer cell via cytoptasmic processes in the sinu-soidal lumen. The presence of these islands was confirmed by transmission and scanning electron microscopic study. The results demonstrate that Kupffer cells in fetal heaptic erythropoiesis phagocytized expelled nuclei and contributed to erythropoiesis mechanically and physiologically by the hypertrophy and the formation of erythroblastic islands.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.5
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• pp.1213-1218
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• 2013

In this study, Ga-doped ZnO (GZO) thin films were fabricated on transparent sapphire substrate by RF magnetron sputtering method and then investigated the effect of various substrate temperature on the electrical, optical properties and characteristic of crystallization of the GZO thin films. The electrical property indicated that the lowest resistivity ($4.18{\times}10^{-4}{\Omega}cm$), the highest carrier concentration ($6.77{\times}10^{20}cm^{-3}$) and Hall mobility ($22cm^2/Vs$) were obtained in the GZO thin film fabricated at $300^{\circ}C$. And for this condition, the highest c-axis orientation and (002) diffraction peak which exhibits a FWHM of $0.34^{\circ}$ were obtained. From the results of AFM measurements, it is known that the highest crystallinity is observed at $300^{\circ}C$. The transmittance spectrum in the visible range was approximately 80 % regardless of substrate temperature. The optical band-gap showed the blue-shift as increasing the substrate temperature to $300^{\circ}C$, and they are all larger than the band gap of bulk ZnO (3.3 eV). It can be explained by the Burstein-Moss effect.

• Membrane Journal
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• v.16 no.4
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• pp.241-251
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• 2006

In this study, crosslinked copolyimides with random (r-) and block (b-) structure were fabricated using N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonic acid and pentanediol as crosslinkers. Linear r- and b-sulfonated copolyimides were also fabricated for comparison. Ion exchange capacities of r- and b-copolyimides were very similar to each other owing to their strong dependence of sulfonic acid content. The physical crosslinking via dimerization of carboxylic acid groups induced a reduced average interchain distance in b-copolyimide without crosslinkers. Consequently, its water uptake and methanol permeability were lower than those of r-sulfonated copolyimides. Simultaneously, the reduced interchain distance increased the content of fixed-charged ions per unit volume. The high fixed-charged ion density contributed to an enhancement of proton conductivity In the b-sulfonated copolyimide. Crosslinking caused the reduction of average interchain distance between polymer chains irrespective of types of crosslinker and polymer structure, leading to low methanol permeability. On the contrary, their proton conductivity was improved owing to formation of effective hydrophilic channels responsible for proton conduction. In particular, this trend was observed in r-copolyimide containing a fixed charged ion.

• Journal of the Korea institute for structural maintenance and inspection
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• v.7 no.4
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• pp.99-107
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• 2003

Normally coating is used a method for protecting reinforced concrete. For this purpose, organic as well as inorganic coatings are used. The advantages of inorganic coatings are lower absorption of UV, non-burning etc. On the other hand, organic coatings have the advantage of low permeability of $CO_2$, $SO_2$ and water. Organic coatings provide better protection for reinforced concrete. However, in organic coatings such as epoxy, urethane and acryl, long-term adhesive strength is reduced and the formed membrane of those is blistered by various causes. Also when organic coatings are applied to the wet surface of concrete, they have a problem with adhesion. So, we developed coating material, WGS-Eco which was hybridized with polymer and cement based material to protect concrete structures and solve problems of organic coatings. This study was conducted an comparative evaluation on physical and durable performance of developed coating material and previously used coating materials. As a result, the performance of developed coating material was not inferior to organic coating materials. So, the developed coating material was considered as a suitable coating material which had advantages of inorganic and organic coatings for protecting concrete.

• Membrane Journal
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• v.29 no.2
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• pp.111-121
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• 2019

An organic citrate series draw solute was synthesized using diethyl malonate for forward osmosis. The structure of the final compound potassium pentane-1,3,3,5-tetracarboxylate was confirmed by $^1H-NMR$ and $^{13}C-NMR$ analysis. Osmotic pressure, solubility, water permeability and reverse salt flux were measured for the properties of the draw solute. Forward osmosis results showed that the draw solute exhibited higher water flux than other draw solutes of trisodium citrate and tripotassium citrate. Reverse salt flux of all the organic daw solutes was much lower than that of NaCl. The osmotic pressure of the synthesized draw solute was 25% lower than that of NaCl. The solubility of the draw solute was 317 g/ 100 g water, which is 8.8 times higher than that of NaCl. A commercialized nanofiltration membrane was used for the recovery of the draw solute. The draw solute could be effectively recovered at low pressure.

• Korean Journal of Food Science and Technology
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• v.12 no.1
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• pp.45-52
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• 1980

The nylon (poly 6, 10) microcapsules containing ${\beta}-galactosidase$ were obtained by the interfacial polymerization of 1, 6-diaminohexane and sebacoyl chloride with ${\beta}-galactosidase$ from Escherichia coli. They were generally spherical and had a mean diameter of $80{\mu}$ with 45 % of the activity recovery. In particular, there was no transport hamper of lactose through the membrane of microcapsules. The characteristics of the microencapsulated enzyme were similar to those of soluble enzyme optimal pHs, $7.0{\sim}7.2$ for the soluble and $7.3{\sim}7.5$ for the microencapsulated ; optimal temperatures, $50^{\circ}C$ for both ; apparent $K_m,\;3.33{\times}10^{-4}(on ONPG),$ $2.86{\times}10^{-3}$ M(on lactose) for the soluble and $5.28{\times}10^{-4}$ (on ONPG), $4.25{\times}10^{-3}$ M (on lactose) for the microencapsulated ; activation energies, 8.94 for the soluble and 9.78 Kcal/mole for the microencapsulated enzyme. Using this microencapsulated ${\beta}-galactosidase$, hydrolyses of lactose and milk lactose were carried out and 80 % of 5 % lactose solution and 70 % of lactose in skim milk were hydrolyzed in 40 hr at $27^{\circ}C$. The reusability and operational stability showed that the remaining activity was 50 % of the original activity after 5 runs and 120 hr of total operating time at $27^{\circ}C$.

• Membrane Journal
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• v.19 no.1
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• pp.7-18
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• 2009

In this study, we used the hybrid module that was composed of granular activated carbons (GAC) packing between module inside and outside of tubular ceramic microfiltration membrane for advanced drinking water treatment. Instead of natural organic matters (NOM) and fine inorganic particles in natural water source, modified solution was prepared with humic acid and kaolin. We were investigated effect of water-back-flushing time (BT) and water-back-flushing period (FT) to minimize membrane fouling and to enhance permeate flux (J) in the hybrid process, and tried to find the optimal operating conditions. As a result, resistance of membrane fouling ($R_f$) was slightly decreased according to increasing BT. Also, the shorter FT was the more effective to reduce $R_f$ and to enhance J because of frequent water-back-flushing. However, the optimal BT and FT conditions were 10 sec and 8 min respectively when operating costs were considered. Then, the optimal conditions derived from our experiments of modified solution were applied to lake water treatment. As a result, average treatment efficiencies of turbidity, $UV_{254}$ absorbance, and $COD_{Mn}$ were very high as 99.11%, 91.40% and 89.34%, respectively, but that of TDS was low as 30.05%.

• Membrane Journal
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• v.24 no.2
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• pp.123-135
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• 2014

The effects of pH, saturated oxygen, and back-flushing media were investigated in hybrid process of tubular ceramic microfiltration and $TiO_2$ photocatalyst-loaded PES (polyethersulfone) beads for advanced drinking water treatment, and compared results of water, nitrogen, or oxygen back-flushing in the viewpoints of membrane fouling resistance ($R_f$), permeate flux (J) and total treated water ($V_T$). $R_f$ decreased, and J and $V_T$ increased as decreasing pH. Turbidity treatment efficiencies were similar at water or nitrogen back-flushing independent of pH, but DOM (dissolved organic matter) treatment efficiency did not have a trend at water back-flushing. $R_f$ at NBF (no back-flushing) with SO (saturated oxygen) was the lower than that at NBF without SO. Also, the DOM treatment efficiency at NBF with SO was the lower than that at NBF without SO. It happened because OH radicals produced by reaction of SO and photocatalyst could dilute with water inside the module. The DOM treatment efficiency of gas back-flushing showed the larger than that of water back-flushing at back-flushig period 10 min. It proved that the adsorption or photo-oxidation of PES beads could be activated by the more effective bead-cleaning of gas back-flushing than water back-flushing.