• Korean Chemical Engineering Research
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• v.54 no.4
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• pp.510-518
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• 2016

Ethyl cellulose-g-poly(ethylene glycol) (EP) was synthesized by esterification of carboxylic acid functionalized methoxy polyethylene glycol (MPEG-COOH) with ethyl cellulose (EC) in order to develop a hydrophilic substrate for thin-film composite (TFC) membrane in a forward osmosis (FO) system. A porous EP substrate, fabricated by a non-solvent induced phase separation method, was found to be more hydrophilic than the EC substrate due to the presence of polyethylene glycol (PEG) side chains in the EP. Since the EP substrate exhibits smaller water contact angles and higher porosity, the structural parameter (S) of TFC-EP is smaller than that of TFC-EC, indicating that internal concentration polarization (ICP) within porous substrates can occur less when TFC-EP is used as a membrane. For example, the water flux value of the TFC-EP is 15.7 LMH, whereas the water flux value of the TFC-EC is only 6.6 LMH. Therefore, we strongly believe that the TFC-EP could be a promising candidate with good FO performances.

• Membrane Journal
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• v.4 no.3
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• pp.152-162
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• 1994

The photodegradation efficiency of formic acid on $TiO_2$ photocatalytic membranes was investigated. A new titania membrane reactors for purification of water combining microfiltration with photocatalytic degradation of organic compounds were developed. Titania membrane tubes(average pore size of $0.2\mu m$) were prepared by the slip casting, and porous thin films of $TiO_2$ were formed on the tube surface by the sol-gel process to increase the surface area, and consequently to increase photodegradation efficiency of organic compounds. The UV light with the wavelength of 365 nm was used as a light source for photocatalytic reactions. The photodegradation efficiency of the organic compounds was strongly dependent on the flux of the solution, the microstructure of the membrane (sol pH), and the amount of $O_2$ supplied. The effects of the primary oxidant such as $H_2O_2$ and dopants such as $Nb_2O_5$ on the photodegradation efficiency were also investigated. The results showed that more than 80% of formic acid could be degraded using membrane coated with a $TiO_2$ sol of pH 1.45. The photodegradation efficiency could be improved by about 20% when adding $H_2O_2$ in feed solution or doping $TiO_2$ membranes with $Fe_2O_3$.

• Nutritional Sciences
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• v.5 no.2
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• pp.68-74
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• 2002

Studies of the relationship between the composition of serum fatty acids and blood pressure are complex and controversial. Fatty acids, important constituents of biological membranes, could potentially affect vasoreactivities including blood pressure. In this study the compositions of fatty acids in serum phospholipids were compared between three types of hypertensive subjects (men, pre-menopausal women, and post-menopausal women) and their respective nrmotensive controls. Serum lipids were extracted and phospholipids were separated by thin layer chromatography. The percentage of palmitic acid (16 : 0) in serum phospholipids was significantly higher and the percentage of stearic acid (18 : 0) was significantly lower in all three hypertensive groups, compared with their corresponding control groups. Only in the group of post-menopausal women, palmitic acid was closely associated wish increases in both systolic (SBP) and diastolic blood pressure (DBP), while stearic acid was associated with decreases in both SBP and DBP. The polyunsaturated fatty acids in serum phospholipids behaved differently from saturated fatty acids. The ratios of products / precursor fatty acids, such as $\sumLCPUFA\omega6/18 : 2\omega$6, 20 : 4$\omega$6/18 : 2$\omega$6, ∑LCPUFA$\omega$3/18 : 3$\omega$3 and 22 : 6$\omega$3/20 : 5$\omega$3, were all clearly associated with both SBP and DBP in hypertensive, post-menopausal women. Desaturation and elongation in fatty acid metabolism could affect the bioavailability of eicosanoid precursors. Changes in the constituent fatty acids of phospholipids and eicosanoid precursors may also influence fluidity, ionic transport, hormone receptors and enzyme activities in biological membranes. In conclusion, both systolic and diastolic blood pressure in post-menopausal women was positively associated with the level of palmitic acid, and negatively associated with the level of stearic acid, in serum phospholipids. The relationships between serum phospholipid-$\omega$6 and $\omega$3 series fatty acids and blood pressure in women, especially in post-menopausal women, require further investigation by taking into consideration hormonal status and eicosanoid metabolism. Funker study is needed to determine the value of dietary manipulation of fatty acid constituents of serum phospholipids, relating to hypertension in women.

• Korean Chemical Engineering Research
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• v.43 no.1
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• pp.118-124
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• 2005

In this study, a novel deposition method of Pt catalysts onto Nafion membranes modified with polypyrrole (PPy) has been proposed for PEMFC application. The PPy/Nafion composite membranes were fabricated by chemical polymerization of pyrrole using $FeCl_3$ and $Na_2S_2O_8$ as initiator. The proton conductivity and water uptake of the chemically prepared PPy/Nafion composites were investigated. The ionic conductivity and water uptake of PPy/Nafion composite membrane prepared with $Na_2S_2O_8$ were decreased with polymerization time of pyrrole. In the case of $FeCl_3$, the ionic conductivity was almost retained and the water uptake was decreased with polymerization time of pyrrole. When the Pt particle was deposited on PPy/Nafion composites membrane by chemical reduction of $H_2PtCl_6$, the Pt loading on Nafion membrane was enhanced by polypyrrole due to electronic conduction property. The performance evaluation with membrane electrode assembly composed of Pt/PPy/Nafion composite and diffusion electrode was carried out using a single cell. As a result of fuel cell test, current density of $569mA/cm^2$ at 0.3 V has been obtained for MEA contained with Pt/PPy/Nafion composite. This study shows that direct deposition of Pt catalysts on Nafion impregnated polypyrrole is a promising method to prepare thin catalyst layer for the PEMFC.

• Membrane Journal
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• v.32 no.5
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• pp.292-303
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• 2022

An eco-friendly energy conversion device without the emission of pollutants has gained much attention due to the rapid use of fossil fuels inducing carbon dioxide emissions ever since the first industrial revolution in the 18th century. Polymer electrolyte membrane fuel cells (PEMFCs) that can produce water during the reaction without the emission of carbon dioxide are promising devices for automotive and residential applications. As a key component of PEMFCs, polymer electrolyte membranes (PEMs) need to have high proton conductivity and physicochemical stability during the operation. Currently, perfluorinated sulfonic acid-based PEMs (PFSA-PEMs) have been commercialized and utilized in PEMFC systems. Although the PFSA-PEMs are found to meet these criteria, there is an ongoing need to improve these further, to be useful in practical PEMFC operation. In addition, the well-known drawbacks of PFSA-PEMs including low glass transition temperature and high gas crossover need to be improved. Therefore, this review focused on recent trends in the development of high-performance PFSA-PEMs in three different ways. First, control of the side chain of PFSA copolymers can effectively improve the proton conductivity and thermal stability by increasing the ion exchange capacity and polymer crystallinity. Second, the development of composite-type PFSA-PEMs is an effective way to improve proton conductivity and physical stability by incorporating organic/inorganic additives. Finally, the incorporation of porous substrates is also a promising way to develop a thin pore-filling membrane showing low membrane resistance and outstanding durability.

• Applied Microscopy
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• v.10 no.1_2
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• pp.7-17
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• 1980

Electron microscope radioautography introduced by Liquier-Milward (1956) is now used routinely in many laboratories. Most of the technical difficulties in specimen preparation have been overcome. This method is modified from loop method for improvement of EM radioautographic techniques. The advantages of this method are: 1. the use of single specimens on small corks and of a large wire loop, allows the experimenter to avoid the blemishes in the membrane; 2. the surfactant dioctyl sodium sulphosuccinate is added to diluted ILford L4, thus greatly prolonging the period of time over which good emulsion layers can be made; 3. corks can be handled in perspex holder which allows about 20 specimens to be developed simultaneously. The steps of the method comprise: 1. Cut ribbons of ultrathin sections of silver interference colour 2. Pick them up on formvar-coated 200 mesh grids 3. Prestaining of tissues 4. Coat the specimens with a thin layer of carbon by evaporation (30-60A) 5. Mount the specimens on corks (about 1cm apical diameter) using double-sided scotch tape 6. Emulsion coating; a. Take a 250m1 beaker, place it on the pan of a sliding weight balance and weigh it. Add 10 grams extra to the beam. Add pieces of ILford L4 emulsion to the beaker until the balance is swinging freely. Add the 20ml of distilled water that was previously measured out. b. Surfactant dioctyl sodium sulphosuccinate is added to diluted ILford L4. 7. Prepare a series of membranes of gelled emulsion with the wire loop and apply one to each cork-borne specimen. 8. Put the specimens away to expose by pushing the corks into short length of PVC tubing, each tube having a small hole in the side 9. Place the tubes in small boxes together with silica gel. 10. Exposure 11. Developer - Kodak Microdol X for 3 minutes 12. Fixer - A perspex holder can be manufactured which allows 20 specimens to be developed simultaneously. 12. Fixer - 30% sodium thiosulfate for 10 minutes 13. Examination with Siemens Elmiskop 1A electron microscope

• Membrane Journal
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• v.14 no.3
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• pp.207-217
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• 2004

In this study, we prepared nanofiltration membrane by applying the interfacial polymerization method as a way of manufacturing composite membranes. We have examined the effects of various preparation factors such as monomer concentration and composition, thermal curing condition, post treatment condition. In addition to preparation conditions, we also monitored the effects of operation conditions such as feed solution concentration and operation pressure on the permeation properties of the resulting nanofiltration membrane. We intended to increase the permeation rate of nanofiltration membrane by the enlargement of effective surface area using additives during interfacial polymerization step. With increasing the monomer concentration, membrane permeation rate are decreased with maintaining almost constant rejection. With respect to curing condition, with increasing the curing temperature both permeation rate and rejection are decreased. With increasing the ratio of MPD in amino monomer composition, permeation rate decreased drastically with high rejection. With increasing the feed solution concentration, both permeation rate and rejection decreased. Both permeation rates and rejection increased with increasing the operating pressure. Nanofiltration membrane have higher surface roughness with increasing additive concentration in the case of using MPD contained amine composition than using piperazine alone. Permeation rates are much lower than the nanofiltration membrane prepared by piperazine.

• Geomechanics and Engineering
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• v.16 no.4
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• pp.385-397
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• 2018

This study evaluates the interfacial properties of composite specimens consisting of shotcrete and sprayed waterproofing membrane. Two different membrane prototypes were first produced and tested for their waterproofing ability. Then composite specimens were prepared and their interfacial properties assessed in direct shear and uniaxial compression tests. The direct shear test showed the peak shear strength and shear stiffness of the composites' interface decreased as the membrane layer became thicker. The shear stiffness, a key input parameter for numerical analysis, was estimated to be 0.32-1.74 GPa/m. Shear stress transfer at the interface between the shotcrete and membrane clearly emerged when measuring peak shear strengths (1-3 MPa) under given normal stress conditions of 0.3-1.5 MPa. The failure mechanism was predominantly shear failure at the interface in most composite specimens, and shear failure in the membranes. The uniaxial compression test yielded normal stiffness values for the composite specimens of 5-24 GPa/m. The composite specimens appeared to fail by the compressive force forming transverse tension cracks, mainly around the shotcrete surface perpendicular to the membrane layer. Even though the composite specimens had strength and stiffness values sufficient for shear stress transfer at the interfaces of the two shotcrete layers and the membrane, the sprayed waterproofing membrane should be as thin as possible whilst ensuring waterproofing so as to obtain higher strength and stiffness at the interface.

• The Journal of Korean Academy of Prosthodontics
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• v.34 no.1
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• pp.187-200
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• 1996

After loss of tooth, initial healing process is critical to preserve residual alveolar process. This study was conducted to compare the effect of hydroxylapatite particle synthetic graft and guided tissue regeneration procedure on healing of extraction wounds in 5 mongrel dogs. To investigate the maturity of bone and velocity of bone heating, bone-labeled tracers were used. After 16 weeks healing period, dogs were sacrificed. The specimens were treated with Villanueva bone stain. Fluorescence microscopy and polarized microscopy were performed to exam the pattern of bone formation in the extraction socket. The results were following ; 1. Pattern of bone regeneration in the group of hydroxylapatie graft and the group of membrane protection after hydroxylapatite graft was following ; bone regeneration was slow, regenerated bone was immature, and thickness of cortical layer was thin compare to that of untreated control group. 2. Cortical layers in membrane protected group were somewhat thicker but less condense to that of untreated control group. 3. Infiltration of inflammation cells were found in the groups using hydroxylapatite graft and membrane. We concluded that grafting of replamineform hydroxylapatite particles into the extraction socket delayed healing of the wound and disturbed the formation of cortical bone at the roof of extraction socket. The placement of expanded polytetrafluoroethylene membranes on the extraction socket promotes the bone regeneration. But newly formed bone in cortical layer consists of the cortico-cancellous bone in comparison with the cortical bone of the control group.

• Journal of Periodontal and Implant Science
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• v.30 no.3
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• pp.527-538
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• 2000

Several extraction cases with advanced bone loss as a result of periodontal disease, root or labial bone fracture, extensive caries, and periapical lesions occur esthetic, functional problems and severe bone loss. Therefore, to treat these cases used several surgical methods and socket preservation among this therapies have been evaluated simple, effective and good prognosis in the implant placement. Socket preservation therapy have been used with barrier membranes or/and graft materials. Deproteinized bovine bone mineral have been evaluated ideal grafting materials. Recently, calcium-phosphate thin film coated bovine bone powders were developed in our country, but the study for these material wasn't reported. When two types of xenograft materials were implanted in extraction sockets of Beagle dogs, the effects of these were analyzed after 4 weeks and 8 weeks histological views. The results of this study were as follows. 1. In control groups, 4 weeks after implantation, the extraction sockets were filled with connective tissue which has dilated vessels and epithelial growth. And after 8 weeks, irregular connective bundles were observed. But new bone formation was not seen. 2. In Bio-Oss groups, epithelial growth was not seen and bone powder was covered with connective tissue fiber. New bone formation was found around the interproximal bone. There was no special change seen after 8 weeks, connective tissue fibers became more regular, and bone growth near bone powder was not made well. 3. In Ca-P BBP groups, epithelial cells didn't grow in the extraction sockets, there was a lot of new bone made around the bone powder after 8 weeks, new bone around bone powder was replaced with mature bone. It is thought that bone powder grafting into the extraction sockets is very useful for conservation of ridge, and Ca-P BBP is more effective in bone formation than Bio-Oss.