• Journal of the Korea institute for structural maintenance and inspection
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• v.9 no.3
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• pp.187-194
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• 2005

This paper deals with a waterproof and mechanical feature of concrete using an inorganic self waterproof agent. The waterproof agents having been used in our country were a membrane agent, penetration agent and an organic waterproof agent. However, these agents have a lot of problems such as losing the effect of waterproof in the environment of lots of water, the difficulty of dispersion. For the clear of problems of these water -proof agents, we used the inorganic waterproof agent. This agent was made from inorganic fluosilicate. Generally, a waterproof agent has been used only for the waterproof effect. In this paper, however through the some tests of concrete using the inorganic self waterproof agent, we recognized that the concrete using the agent is more excellent in some peculiar properties than general concrete's properties. In this paper, we performed compressive strength, permeability, pore volume test, etc. As a result, the concrete of using the agent is more excellent in economy, waterproof, compressive strength.

• Macromolecular Research
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• v.13 no.4
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• pp.314-320
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• 2005

Crosslinked poly(vinyl alcohol) (PVA) membranes were prepared at various crosslinking temperatures using poly(acrylic acid-co-maleic acid) (PAM) containing different PAM contents. The thermal properties of these PVA/PAM membranes prepared at various reaction temperatures were characterized using differential scanning calorimetry (DSC). The proton conductivity and methanol permeability of PVA/PAM membranes were then investigated as PAM content was varied from 3 to 13 wt%. It was found that the proton and methanol transport were dependent on PAM content in their function both as crosslinking agent and as donor of hydrophilic -COOH groups. Both these properties decreased monotonously with increasing PAM concentration. The proton conductivities of these PVA/PAM membranes were in the range from $10^{-3}\;to\;10^{-2}S/cm$ and the methanol permeabilities from $10^{-7}\;to\;10^{-6}cm^{2}/sec$. In addition, the effect of operating temperature up to $80^{\circ}C$ on ion conductivity was examined for three selected membranes: 7, 9 and 11 wt% PAM membranes. Ion conductivity increased with increasing operating temperature and showed and S/cm at $80^{\circ}C$, respectively. The effects of crosslinking and ionomer group concentration were also examined in terms of water content, ion exchange capacity (IEC), and fixed ion concentration. In addition, the number of water molecules per ionomer site was calculated using both water contents and IEC values. With overall consideration for all the properties measured in this study, $7{\sim}9\;wt%$ PAM membrane prepared at $140^{\circ}C$ exhibited the best performance. These characteristics of PVA/PAM membranes are desirable in applications related to the direct methanol fuel cell (DMFC).

• Journal of Life Science
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• v.31 no.11
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• pp.1004-1009
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• 2021

Angelica gigas Nakai (AGN) has been used in Korean herbal medicine for various pharmacological activities, such as to create antioxidant and skin whitening effects. Decursin and decursinol angelate of AGN extracts can be used as potential active drugs and cosmetic ingredients. This study investigated the possibility of topical delivery of AGN extracts using a manufactured emulsion system. Lotion was formulated by using Tefose^® and paraffin for the oil phase, Kolliphor RH 40 for the surfactant and solubilizing agent-which showed high solubility in water (0.82 mg/ml)-and a water phase with a carbomer. In vitro skin permeation of decursin and decursinol angelate was determined using a Strat-M^® membrane in Franz diffusion cells. Lotion samples as the experimental group (248.08±19.72 ug/cm²) significantly increased the permeation of decursin and decursinol angelate for up to 24 hr compared to the control group (119.18±19.23 ug/cm²). The permeability was also characterized by the flux (penetration rates) and Kp (permeability coefficient) values. The experimental group (17.20±1.23 ug/h/cm² and 5.73±1.39 cm/h^*10^-3) had higher flux and Kp than the control group (8.22±1.24 ug/h/cm² and 2.74±0.51 cm/h^*10^-3). Lotion with decursin and decursinol angelate of AGN extracts could be used for the topical application of drug and cosmetic products.

• Food Science and Preservation
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• v.11 no.3
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• pp.417-423
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• 2004

Botanical antimicrobial agent-grapefruit seed extract mixture (BAAG) have an unknown compounds which exhibit the antibiotic activities aganist microorganisms including bacteria and fungi. We have examined the effects of BAAG on the physiological function of Botrytis cinerea which was isolated from necrotic lesions of decayed fruits and vegetables such as cucumbers, grapes, tomatoes, and red peppers during storage. In the results of enzymatic activities related to the energetic metabolism there was no inhibitory effect of BAAG on the activities of several enzymes in vitro including glucose 6-phosphate dehydrogenase and malate dehydrogenase, while there was inhibitory effect of BAAG on the activities of hexokinase and succinate dehydrogenase. O-nitrophenyl-$\beta$-D-galactopyranoside(ONPG), the artificial substrate of $\beta$-galactosidase was hydrolyzed in the presence of BAAG, indicating that the membrane was pertubated by the BAAG. From the results we suggested that the antibiotic activity of BAAG is due to the change of membrane permeability of the cell. BAAG was fractionated and purified by silica gel and sephadex column chromatography. Among active fractions two peaks were identified as naringin and limonin when they were analyzed by by NMR and Fast atomic bombardment.

• 한국신재생에너지학회:학술대회논문집
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• 2006.11a
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• pp.348-351
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• 2006

Bipolar plate, which forms about 50% of the stack cost, is an important core part with polymer electrolyte membrane in PEMFC. Bipolar plates have been commonly fabricated from graphite meterial having high electrical conductivity and corrosion resistance. Lately, many researchers have concentrated their efforts on the development of metallic bipolar plate and stainless steel has been considered as a potential material for metallic bipolar plate because of its high strength, chemical stability, low gas permeability and applicability to mass production. However, it has been reported that its inadequate corrosion behavior under PEMFC environment lead to a deterioration of membrane by dissolved metal ions and an increase in contact resistance by the growth of passive film therefore, its corrosion resistance as well as contact resistance must be improved for bipolar plate application. In this work, several types of coating were applied to 316L and their electrical conductivity and corrosion resistance were evaluated In the simulated PEMFC environment. Application of coating gave rise to low interfacial contact resistances below $19m{\Omega}cm^2$ under the compress force of $150N/cm^2$. It also made the corrosion potential to shift in the posit ive direct ion by 0.3V or above and decreased the corrosion current from ca. $9{\mu}A/cm^2$ to ca. $0.5{\mu}A/cm^2$ in the mixed solution of $0.1N\;N_2SO_4$ and 2ppm HF A coat ing layer under potentiostatic control of 0.6V and $0.75V_{SCE}$ for 500 hours or longer showed some instabilities, however, no significant change in coat Ing layer were observed from Impedance data. In addition, the corrosion current maintained less than $1{\mu}A/cm^2$ for most of time for potentiostatic tests. It indicates that high electrical conductivity and corrosion resistance can be obtained by application of coatings in the present work.

• Korean Journal of Microbiology
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• v.51 no.4
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• pp.448-452
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• 2015

The bacterial strain that was isolated from chinese cabbage rhizosphere, showed inhibition of yeast growth. This strain was identified as Pseudomonas fluorescens BB2 by API 20NE test and 16S rRNA gene sequence analysis. P. fluorescens BB2 strain produced antibiotics against yeast as a secondary metabolite effectively when the culture was carried out in YM medium with 3% glucose at $20^{\circ}C$. The protein antibiotic of BB2 strain which was concentrated by ammonium sulfate precipitation and n-butanol extraction inhibited the growth of yeast with the minimal inhibitory concentration of $10{\mu}g/ml$ against Candida albicans KCTC 7965, and the growth of yeast was completely inhibited at $80{\mu}g/ml$. The hydrophilic fraction of n-butanol extraction inhibited the growth of Bacillus cereus ATCC 21366, showed orange halo on chrome azurol S plate, which means the fraction contained iron chelating siderophore. The results of crystal violet uptake through the cell membrane showed that membrane permeability was increased about 9% than control, when the concentration of hydrophobic antibiotic against yeast C. albicans was $60{\mu}g/ml$. As a result, the antibiotic produced by P. fluorescens BB2 against yeast Candida is considered antimicrobial peptide, and this is the first report in the genus Pseudomonas.

• Korean Journal of Food Science and Technology
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• v.27 no.6
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• pp.985-990
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• 1995

Grapefruit seed extracts(GFSE) have some unknown compounds which exhibit the antibiotic activities aganist microorganisms including bacteria and fungi. We have examined the effects of GFSE on the growth of Enterobacter pyrinus which was isolated from necrotic lesions of pear trees. During the cultivation, the growth of the bacteria was strongly inhibited at the low concentration(0.01%, w/w) of GFSE. Hydrophobic fraction extracted from GFSE by mixed solvents (chloroform : methanol : water, 1 : 2 : 0.8, v/v/v) had components which inhibited the growth of bacteria. There was, however, no inhibitory effect of GFSE on the activities of several enzymes including hexokinase, glucose 6-phosphate dehydrogenase, malate dehydrogenase and succinate dehydrogenase. $O-nitrophenyl-{\beta}-D-galactopyranoside(ONPG)$, the artificial substrate of ${\beta}-galactosidase$ was hydrolyzed in the presence of GFSE, indicating that the membrane was pertubated by the GFSE. From the results it was suggested that the antibiotic activity of GFSE is due to the change of membrane permeability of cell. GFSE was fractionated by high performance liquid chromatography equipped with $C_{18}$ reverse phase column. Among active fractions, three peaks were identified as 1-chloro-2-methyl-benzene (o-toluene), N,N-dimethyl-benzenemethaneamine, 1-[2-(2-ethylethoxy)ethoxy]-4- (1,1,3,3-tetramethyl)-bezene, respectively, while the other three remained unidentified.

• Journal of Korean Medicine Rehabilitation
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• v.25 no.2
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• pp.1-13
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• 2015

Objectives Methicillin-Resistant Staphylococcus aureus (MRSA) is a human pathogen and a major cause of hospital-acquired infections. New antibacterial agents that have not been compromised by bacterial resistance are needed to treat MRSA-related infections. In this study, we investigated the antimicrobial activity ofethanol extract of Haedokgeumhwa-san (HGH) which prescription is composed of korean medicine against MRSA. Methods The antibacterial activity of HGH extract was evaluated against MRSA strains by using the Disc diffusion method, broth microdilution method (minimal inhibitory concentration; MIC), checkerboard dilution test, and time-kill test; its mechanism of action was investigated by bacteriolysis, detergent or ATPase inhibitors. The checkerboard dilution test was used to examined synergistic effect of ampicillin, oxacillin, ciprofloxacin, vancomycin, gentamicin and norfloxacin in combination with HGH ethanol extract. A time-kill assay was performed a survival curve which was obtained by plotting viable colony counts depending on time on bacterial growth. Results The minimum inhibitory concentration (MIC) of ethanol extract (HGH) ranged from 1,000 to $2,000{\mu}g/mL$ against all the tested bacterial strains, respectively. We are able to confirm that HGH extract has potentially strong antibacterial activity. In the checkerboard dilution test, fractional inhibitory concentration index of HGH in combination with antibiotics indicated synergy or partial synergism against S. aureus. A time-kill study showed that the growth of the tested bacteria was considerably inhibited after 8 hr of treatment with the combination of HGH with selected antibiotics. For measurement of cell membrane permeability, HGH $250{\sim}1,000{\mu}g/mL$ along with concentration of Triton X-100 (TX) and Tris-(hydroxymethyl) aminomethane (Tris) were used. In the other hand, N,N-dicyclohexylcarbodimide (DCCD) and Sodium azide ($NaN_3$) was used as an inhibitor of ATPase. TX, Tris, DCCD and $NaN_3$ cooperation against S. aureus showed synergistic action. Accordingly, antimicrobial activity of HGH was affected by cell membrane and inhibitor of ATPase. Conclusions These results suggest that Haedokgeumhwa-san extract has antibacterial activity, and that HGH extract offers a potential as a natural antibiotic against MRSA.

• Korean Chemical Engineering Research
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• v.53 no.4
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• pp.407-411
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• 2015

Dense ceramic membranes have been prepared using the commercial perovsikite $Ba_{0.5}Sr_{0.5}Co_{0.8}Fe_{0.2}O_{3-{\delta}}$, powders synthesized by the solid state reaction method. The as-synthesized powders were compressed into disks with 1.0 mm of thickness and the disk was sintered at $1,100^{\circ}C$ for 2 hr. The oxygen permeation flux of $Ba_{0.5}Sr_{0.5}Co_{0.8}Fe_{0.2}O_{3-{\delta}}$ membrane increased with the increasing temperature and oxygen partial pressure. The activation energy for oxygen permeation was increased with the increasing oxygen partial pressure. Oxygen permeation flux at $950^{\circ}C$ were measured at various flow rates of feed and sweep gas. It has been demonstrated that oxygen permeability increased at elevated flow rates of both gases, but the sweep gas is more influential.

• Membrane Journal
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• v.15 no.3
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• pp.247-254
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• 2005

Chitosan film has potential applications in agriculture, food, and pharmacy. However, films made only from chitosan lack gas barrier and have poor mechanical properties. For enhanced gas barrier and mechanical properties, chitosan/clay nanocomposites have been prepared with montmorillonite (MMT) which is a layered structure of clays and chitosan. The cationic biopolymer, chitosan is intercalated into $Na^+-montmorillonite$ through cationic exchange and hydrogen bonding process. Diluted acetic acid is used as solvent f3r dissolving and dispersing chitosan. Chitosan was intercalated or exfoliated in MMT and it was confirmed by X-ray diffraction method. D-spacing of the characteristic peak from MMT plate in chitosan/clay nanocomposites was moved and diminished. The thermal stability and the mechanical properties of the nanocomposites are measured by TGA and Universal Testing Machine. Gas permeability through the chitosan/clay nanocomposites films decreased due to increased tortuosity made by intercalation of clay in chitosan.