• Applied Chemistry for Engineering
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• v.28 no.2
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• pp.153-157
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• 2017

Gel type internal electrolytes were synthesized by varying hydroxyethyl-cellulose (HEC) amounts and their durability and conductivity were measured. The ionic conductivity decreased as the content of HEC increased thus the internal electrolyte containing more than 12% of HEC could not be used as a reference electrode. Based on durability test results, as the HEC amount decreased carrier density resulting in increasing of the amount of KCl coming out of the porous membrane. Therefore in order to use long time at ballast water treatment systems, we selected 10% HEC for gel type internal electrolyte. The resolution test for total residual oxidants (TRO) was carried out using the TRO sensor and the gel type reference electrode made of 10% HEC. A 50 mV potential was applied to the TRO sensor for 30 sec and changes in the current were measured. It was confirmed that the TRO concentrations ranging from 0 to 15 mg/L could be separated at salinity conditions of 0.2~30 PSU. The results indicated that the TRO concentration at sea water and at fresh water was successfully measured by the TRO sensor constructed with the reference electrode using gel-type internal electrolyte of HEC.

• Journal of Korean Society for Atmospheric Environment
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• v.25 no.4
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• pp.275-288
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• 2009

The Korean government strengthened the environmental polices to manage and enhance Metropolitan Area air quality, and also has enforced "Special Act on Seoul Metropolitan Air Quality Improvement (SASMAQI)" issued in Dec. 2004. Recently government expanded the Seoul Metropolitan Air Quality Management District (SMAQMD) to the outskirts satellite cities of Seoul area through the "Revised Law Draft of SASMAQI". The SMAQMD has been alloted the allowable emission loads to the local governments on the basis of the carrying $PM_{10}$ capacity. However, in order to establish the effective air quality control strategy for $PM_{10}$, it is necessary to understand the corresponding sources which have a potential to directly impact ambient $PM_{10}$ concentration. To deal with the situations, many receptor methodologies have been developed to identify the origins of pollutants and to determine the contributions of sources of interests. The objective of this study was to extensively identify $PM_{10}$ sources and to estimate their contributions at the metropolitan area. $PM_{10}$ samples were simultaneously collected at the 3 semi-industrialized local cities in the Seoul metropolitan area such as Hwasung-si, Paju-si, and Icheon-si sites from April 15 to May 31, 2007. The samples collected on the teflon membrane filter by one $PM_{10}$ cyclone sampler were analyzed for trace metals and soluble ions and samples on the quartz fiber filter by another sampler were analyzed for OC and EC. Source apportionment study was then performed by using a positive matrix factorization (PMF) receptor model. A total of 6 sources were identified and their contributions were estimated in each monitoring site. Contribution results on Hwasung, Paju, and Icheon sites were as follows: 33%, 27%, and 27% from soil source, 26%, 26%, and 21% from secondary aerosol source, 11%, 11%, and 12% from biomass burning, 12%, 6%, and 5% from sea salt, 7%, 15%, and 19% from industrial related source, and finally 11%, 15%, and 16% from mobile and oil complex source, respectively. This study provides information on the major sources affecting air quality in the receptor sites and thus it will help to manage the ambient air quality in the metropolitan area by establishing reasonable control strategies, especially for the anthropogenic emission sources.

• Applied Chemistry for Engineering
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• v.10 no.3
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• pp.362-366
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• 1999

Membranes for biosensor were prepared from poly(vinyl chloride) (PVC)l derivatives using the solution casting method, and their gas permeabilities were studied. The polymer membranes dried slowly in air showed higher permeability coefficients than those dried in vacuum. The permeabilily coefficients of carboxylated poly(vinyl chloride) (CPVC) membranes for $O_2$ and $CO_2$ decreased as the pressure of the feed gas increased. The addition of dioctylphthalate (DOP) enhanced the permeation rates for $O_2$ and $CO_2$. For example, the permeability coefficients of CPVC membranes containing 30 wt. % DOP for $O_2$ and $CO_2$ at 100 psig were 2.03 and 0.96 Barrer, respectively, which were about 4~5 times higher than those of the membranes without DOP. Poly(vinyl chloride-co-vinyl acetate-co-vinyl alcohol) (Syn-PVCAcAl) obtained by hydrolysis of poly(vinyl chloride-co-vinyl acetate (PVCA) showed a higher permeability coefficient for $CO_2$ in the presence of DOP than that for commercial PVCAcAl, but did not show any significant difference in permeability for $O_2$.

• Applied Biological Chemistry
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• v.49 no.4
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• pp.315-321
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• 2006

Inhibitors of acetylcholinesterase(AchE), such as organophosphates and carbamates, interfere the action of AchE in nerve and may lead to a severe impairment of nerve functions or even death. Therefore, insect AchE is the biological target of predominant insecticides used in agriculture. Biosensors are sensitive and can be used as dispoisable sensors for environmental control. In recent years, the use of AchEs in biosensor technology has gained enormous attention, in particular with respect to insecticide detection. The principle of biosensors using AchE as a biological recognition element is based on the inhibition the catalytic activity by the agents to be detected. We here present a strip-type biosensor based on AchE inhibition. In this study, acetylcholinesterase and PVA-SbQ(polyvinyl alcohol functionalized with methyl pyridinium methyl sulfate) were co-immobilized on immobilone-P membranes. Immobilization of the enzymes showed a stability in 6 months without activity loss in $4^{\circ}C$ storage. Enzymes immobilized on surfaces of membrane responded to organophosphates and carbamate more sensitivitive than enzyme in solution. Organophosphates and carbamates concentrations could be detected by entrapped and surface immobilized enzymes, in 5 min. For chlorpyrifos, carbofuran, cabaryl, and methidathion, the detection limits of AChE-strip were similar to that of HPLC/GC method.

• Journal of Applied Biological Chemistry
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• v.60 no.3
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• pp.271-277
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• 2017

Ethyl formate has been used for the control of insect pests by fumigation. However, there were not many reports to show its target site of fumigant toxicity on insect pests since its first use in the agricultural industry. In the present study, we showed the presumable target sites of ethyl formate fumigation in insect pests using Myzus persicae nymphs. After ethyl formate fumigation, the nymphs of this species were collected and the changes at the biochemical and molecular level were determined. The activity of cytochrome c oxidase (COX) was approximately two-fold higher after ethyl formate fumigation. In addition, the expression levels of acetylcholinesterase (AChE) decreased gradually with increasing ethyl formate concentration. These two findings suggested that COX and AChE might be the major target sites of ethyl formate fumigation. In addition to these results, the analysis of lipid content using MALDI-TOF MS/MS identified 9 phospholipids differently generated 2-fold higher in the ethyl formate-treated nymphs than that in the control nymphs, thereby leading to changes in cell membrane composition in M. persicae nymphs. Therefore, the ethyl formate fumigation caused lethal effects on M. persicae nymphs by changing COX activity, AChE gene expression, and phospholipid production.

• Applied Chemistry for Engineering
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• v.19 no.2
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• pp.145-150
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• 2008

In this work we have studied the antifouling properties of the hydrophobic sol-gel modified sensing membrane and its optical properties for sensor application. E. coli JM109, B. cereus 318 and P. pastoris X-33 were cultivated in confocal cultivation dishes with glass surface, respectively. The glass surface was coated with the hydrophobic sol-gels prepared by the dimethoxy-dimethyl-silane (DiMe-DMOS) and tetramethyl-orthosilicate (TMOS). After cultivation, microorganisms adhered on the surface coated with sol-gels and glass surface were dyed by gram-staining method and the numbers of microorganisms were analyzed based on the image data of the scanning electronic microscope (SEM). A great number of microorganisms, about $2{\sim}3{\times}10^4/mm^2$, was adhered on the glass surfaces which no hydrophobic sol-gels were coated. But, the antifouling effect of the hydrophobic sol-gels was large, that microorganisms of less than $200{\sim}300/mm^2$ were adhered on the coated glass surface. The performance of the sensing membranes for detection of pH and dissolved oxygen was enhanced by recoating the light insulation layer prepared with the mixture of the hydrophobic sol-gel and graphite particles.

• Applied Chemistry for Engineering
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• v.18 no.5
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• pp.483-489
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• 2007

Polyaniline (PANI)/Polyimide (PI) membranes were prepared and the effects of PANI contents and doping on the structural properties and gas separation properties were studied. The polyamic acid (PAA) solution was prepared by the polycondensation reaction of 4,4'-(hexafluoroisopropylidene) diphthalic anhydride (6FDA) and 4,4'-oxydianiline (ODA) in 1-methyl-2-pyrrolydinone (NMP) solvent. The PANI/PI blends were obtained by mixing PAA solution and PANI solution, and were doped with 1 M aqueous HCl solution for 24 h. The structural characterizations of the as-cast and doped membranes were examined by FT-IR, XRD, and TGA. The gas permeation experiments with $H_2$, $CO_2$, $O_2$, $N_2$, and $CH_4$ were carried out by variable pressure method at $30^{\circ}C$ and 5 atm. For all gases tested, the permeability coefficients of the blends decreased with increasing PANI content and the magnitude of permeability was in the order of $H_2$ > $CO_2$ > $O_2$ > $N_2$ > $CH_4$. The permeability for PANI/PI membranes decreased after the doping process while the permselectivity increased. For $H_2/CH_4$ separation, the doped PANI/PI (75/25) membrane has a permselectivity of 991.

• Polymer(Korea)
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• v.35 no.1
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• pp.35-39
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• 2011

In this work, mesoporous carbons (CMK-3) were prepared by a conventional templating method using mesoporous silica (SBA-15) for using catalyst supports in polymer electrolyte membrane fuel cells (PEMFCs). The CMK-3 were chemically activated to obtain high surface area and small pore diameter with different potassium hydroxide (KOH) amounts, i.e., 0, 1, 3, and 4 g as an activating agent. And then Pt-Ru was deposited onto activated CMK-3 (K-CMK-3) by a chemical reduction method. The characteristics of Pt-Ru catalysts deposited onto K-CMK-3 were determined by surface area and pore size analysis, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and inductive coupled plasma-mass spectrometry (ICP-MS). The electrochemical properties of Pt-Ru/K-CMK-3 catalysts were also analyzed by cyclic voltammetry (CV). From the results, the K3g-CMK-3 carbon supports activated with 3 g KOH showed the highest specific surface areas. In addition, the K3g-CMK-3 led to uniform dispersion of Pt-Ru onto K-CMK-3, resulted in the enhancement of elelctro-catalystic activity of Pt-Ru catalysts.

• Polymer(Korea)
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• v.39 no.2
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• pp.338-345
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• 2015

Poly(phenylene oxide) (PPO) and polyether imide (PEI) were sulfonated and aminated to create sulfonated poly(phenylene oxide) (SPPO) and aminated polyether imide (APEI), respectively. Characterization of the SPPO and APEI were performed via measurements of FTIR, thermogravimetry (TGA), swelling degree, ion exchange capacity (IEC), and ion conductivity. Next, the surfaces of these membranes were modified by surface fluorination at room temperature. The surface fluorinated SPPO and APEI membranes underwent characterization again for the mentioned measurements to determine any differences. The 3 types of bi-polar membranes were prepared by varying the IEC of the APEI at a fixed SPPO IEC value, which were applied to the low and high NaCl concentration of feed solution at the different current density, respectively. The hypochlorite concentration derived from the surface fluorinated membranes was dependent on the IEC of the APEI and ranged from 491 to 692 ppm at $80mA/m^2$. At low current density of $5mA/m^2$, the hypochlorite concentrations ranged from 18 to 28 ppm for the 4 hrs surface fluorinated membranes and their durability increased greatly.

• Applied Biological Chemistry
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• v.42 no.1
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• pp.12-19
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• 1999

To improve biopolymer productivity and properties of Bacillus strains, protoplast fusion was performed between biopolymer producing Bacillus subtilis K-1 and lactose utilizing Bacillus coagulans. The results were as follows; Protoplasts mixed in fusion fluid containing 33% PEG 6000, 1% PVP and 10 mM $CaCl_2$ were reacted for 5 min at $37^{\circ}C$ and then centrifused protoplasts were directly overlaid on the selective media containing $100\;{\mu}g/ml$ antibiotics and incubated for 3 days. At this conditions, the frequency of protoplast fusion was generally in the range of $4.6{\times}10^{-5}\;to\;1.8{\times}10^{-7}$ in ratio. Segregation ratio was observed between 1 to 6% indicating genetic stability of all the fusants. Fusants growth were also observed on the media contained amino acid and antibiotics as required marked materials. DNA contents of the selected fusants were 1.6 to 2.7 times more than that of parent strains. With observation by TEM microscopy, spherical protoplasts were first released from the swollen parental cells and then contracted to fuse in the process of fusion. And fused cells were observed representative vesicle. Originally, the parental cells were observed as in the morphology of thick-walled and double membrane-surrounded rod shape with TEM microscopy.