• Advances in nano research
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• v.16 no.4
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• pp.353-363
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• 2024

The incorporation of nanoplatelets in composite and polymeric materials represents a recent and innovative approach, holding substantial promise for diverse property enhancements. This study focuses on the application of nanocomposites in the production of sports equipment, particularly soccer balls, aiming to bridge the gap between theoretical advancements and practical implications. Addressing the longstanding challenge of suboptimal interaction between carbon nanofillers and epoxy resin in epoxy composites, this research pioneers inventive solutions. Furthermore, the investigation extends into unexplored territory, examining the integration of glass fiber/epoxy composites with nanoparticles. The incorporation of nanomaterials, specifically expanded graphite and graphene, at a concentration of 25.0% by weight in both the epoxy structure and the composite with glass fibers demonstrates a marked increase in impact resistance compared to their nanomaterial-free counterparts. The research transcends laboratory experiments to explore the practical applications of nanocomposites in the design and production of sports equipment, with a particular emphasis on soccer balls. Analytical techniques such as infrared spectroscopy and scanning electron microscopy are employed to scrutinize the surface chemical structure and morphology of the epoxy nanocomposites. Additionally, an in-depth examination of the thermal, mechanical, viscoelastic, and conductive properties of these materials is conducted. Noteworthy findings include the efficacy of surface modification of carbon nanotubes in preventing accumulation and enhancing their distribution within the epoxy matrix. This optimization results in improved interfacial interactions, heightened thermal stability, superior mechanical properties, and enhanced electrical conductivity in the nanocomposite.

• Management & Information Systems Review
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• v.39 no.2
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• pp.145-162
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• 2020

This study examines problems with using the conventional analytic hierarchy process (AHP) method and proposes a method of weight adjustment as a modification of AHP. AHP is a method for transforming complex decision problems into a hierarchal structure, which is composed of elements in the upper and lower levels and then using pairwise comparisons to evaluate these elements and subsequently to obtain their relative weights. The elements' relative importance is reliable if the elements in the lower hierarchical levels (sub factors) that comprise each element in the upper hierarchical level (primary factor) are equal in number. In other words, if the number of sub factors is different for each primary factor, a serious error is expected as a result. Therefore, this study proposes a modification of AHP that can avoid such an error when AHP is used. Specifically, an error that arises from different number of sub factors (matrix size) can be overcome by making the number of sub factors identical for each primary factor. The resulting model has been validated through the applications in different AHP hierarchical structures.

• Korean Chemical Engineering Research
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• v.54 no.3
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• pp.410-418
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• 2016

In this study, we prepared electrically conducting composites using epoxy resin of diglycidyl ether of bisphenol A (DGEBA) as a matrix, triethylenetetramine (TETA) as a hardener and nickel powder or multi-walled carbon nanotubes (MWCNTs) grafted with $-NH_2$ groups (MWCNT-$NH_2$) as electrically conducting fillers. Electrical conductivity of composite films were measured by coating on the slide glass with a doctor blade. We measured modification reactions of MWCNT and reaction of MWCNT-$NH_2$ with DGEBA epoxy resin by fourier transform infrared spectrometer (FTIR), thermogravimetric analyzer (TGA) and elemental analyzer (EA). Morphology of composites was investigated by scanning electron microscope (SEM) and sheet resistances of composites were measured by 4-point probe. We found $(9.87{\pm}1.09){\times}10^4{\Omega}/sq$ of sheet resistance for epoxy composite containing both 40 wt% nickel powder and 0.5 wt% of MWCNT-$NH_2$ as fillers, equivalent to epoxy composite containing 53.3 wt% nickel powder only as a filler.

• Archives of Plastic Surgery
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• v.33 no.1
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• pp.46-52
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• 2006

High-density micromass culture was needed to take three dimensions culture with ASCs(adipose derived stromal cells) and chondrogenesis. However, the synthetic polymer has hydrophobic character and low affinity to cells and other biomolecules. Therefore, the surface modification without changes of physical and chemical properties is necessary for more suitable condition to cells and biomolecules. This study was performed to investigate the effect of surface modification of poly (lactic-co-glycolic acid)(PLGA) scaffold by plasma treatment (P(+)) on the adhesion, proliferation and chondrogenesis of ASCs, and not plasma treatment (P(-)). ASCs were isolated from human subcutaneous adipose tissue obtained by lipectomy and liposuction. At 1 hour 30 minutes and 3days after cell seeding onto the P(-) group and the P(+) group, total DNA amount of attached and proliferated ASCs markedly increased in the P(+) group (p < 0.05). The changes of the actin under confocal microscope were done for evaluation of cellular affinity, at 1 hour 30 minutes, the shape of the cells was spherical form in all group. At 3rd day, the shape of the cells was fiber network form and finely arranged in P(+) group rather than in P(-) group. RT-PCR analysis of cartilage-specific type II collagen and link protein were expressed in 1, 2 weeks of induction. Amount of Glycoaminoglycan (GAG) markedly increased in P(+) group(p < 0.05). In a week, extracellular matrix was not observed in the Alcian blue and Safranin O staining. However in 2 weeks, it was observed that sulfated proteoglycan increased in P(+) group rather than in P(-) group. In conclusion, we recognized that plasma treatment of PLGA scaffold could increase the hydrophilic property of cells, and provide suitable environment for high-density micromass culture to chondrogenesis

• KSBB Journal
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• v.21 no.2
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• pp.133-139
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• 2006

In 'solid-phase' PEGylation, the conjugation reaction occurs as the proteins are attached to a solid matrix, and thus it can have distinct advantages over the conventional, solution-phase process. We report a case study: rhIFN-${\alpha}$-2a was first adsorbed to cation exchange resin and then N-terminally PEGylated by aldehyde mPEG of 5, 10, and 20 kD through reductive alkylation. After the PEGylation, salt gradient elution efficiently recovered the mono-PEGylate in a purified form from the unwanted species such as unmodified IFN, unreacted PEG, and others. The mono-PEGylation and its purification were integrated in a single chromatographic step. Depending on the molecular weight of the mPEG aldehyde used, the mono-PEGylation yield ranged 50-64%. We could overcome the major problems of random, or uncontrollable, multi-PEGylation and the post-PEGylation purification difficulties associated with the solution-phase process. N-terminal sequencing and MALDI-TOF MS confirmed that a PEG molecule was conjugated only to the N-terminus. Compared with the unmodified IFN, the mono-PEGylate showed the reduced anti-viral activity as measured by the cell proliferation assay. The bioactivity was reduced more as the higher molecular weight PEG was conjugated. Immunoreactivity, evaluated indirectly by antibody binding activity using a surface plasmon resonance biosensor, also decreased. Nevertheless, trypsin resistance as well as thermal stability was considerably improved.

• Korean Chemical Engineering Research
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• v.51 no.3
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• pp.388-393
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• 2013

The study was focused to evaluate the possibility for combination membrane of bacterial cellulose (BC) and graphene with high electrical properties. BC with natural polymer matrix was known to have strong physical strength. For the combination of graphene with BC, the surface of graphene was modified with oxygen plasma by changing strength and time of radio waves in room temperature. Water contact angle of modified graphene grew smaller from $130^{\circ}$ to $12^{\circ}$. XPS analysis showed that oxygen content after treatment increased from 2.99 to 10.98%. Damage degree of graphene was examined from $I_D/I_G$ ratio of Raman analysis. $I_D/I_G$ ratio of non-treated graphene (NTG) was 0.11, and 0.36 to 0.43 in plasma treated graphene (PTG), increasing structural defects of PTG. XRD analysis of PTG membrane with BC was $2{\theta}$ same to BC only, indicating chemically combined membrane. In FT-IR analysis, 1,000 to 1,300 $cm^{-1}$ (C=O) peak indicating oxygen radicals in PTG membrane had formed was larger than NTG membrane. The results suggest that BC as an alternation of plastic material for graphene combination has a possibility in some degree on the part like transparent conductive films.

• Journal of Nutrition and Health
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• v.31 no.3
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• pp.253-262
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• 1998

This study was performed to investigated the effect of dietary fat sources on renal senescence in aged rats. Seventeen month old male Sprague-Dawley rats were divided into 3 groups according to urinary protein excretion. Four month old rats were used as a control group. The rats were fed one of three different experimental diets ; 20% beef tallow, 20% corn oil 20% fish oil diet. They were fed experimental diets ad libitum for 16 weeks . The results are summarized as follows. Serum lipid concentrations were higher in aged rats than in control rats, with the beef tallow group showing the highest level, followed by the corn oil and fish oil groups. Old rats showed higher HDL and lower LDL levels than the control groups. Age and dietary fat had no effect on VLDL. GFR for the both age groups were increased with experimental period with the beef tallow group showing the highest value. Urinary protein excretion was also increased with experimental period in both age groups. There was a large increase in urinary protein in old rats that were fed beef tallow and corn oil, but not in old rats fed fish oil. On the contrary , the effect of dietary fat on urinary protein was not found in control groups. There was individual susceptibility in the effect of dietary fat on urinary protein. Old rats fed beef tallow with high initial urinary protein showed highest increase, but , the change was not significant in rats with a low initial value . It was also found that the increase was kept low in rats of the fish oil group with high initial urinary protein. The corn oil group showed in between values. There were no differences in urine and renal tissue concentrations of TXB2 . Aged rats showed a tendency of having higher urinary PGE2 excretion and lower renal cortex content. Since higher PGE2 excretion was reported to be associated with decreased renal function, this might suggest that the aged rats show renal function reduction. Light microscopic examination showed that glomerular segmental sclerosis, mesangial matrix expansion and tubular atrophy were more frequently present in aged rats, and that these changes were more significant in the beef tallow group, followed by corn oil and fish oil groups. The percentage of urinary protein excretion was increased in aged rats in association with increased glomerular sclerosis and mesangial matrix . This change could be partly due to a change in eicosanoids metabolism . Therefore, modification of dietary fat could affect the eicosanoids metabolism in kidney and renal senescence.

• Journal of Nutrition and Health
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• v.42 no.6
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• pp.505-515
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• 2009

Collagen is the major matrix protein in dermis and consists of proline and lysine, which are hydroxylated by prolyl hydroxylase (PH) and lysyl hydroxylase (LH) with cofactors such as vitamin C, oxygen, iron (Fe$^{2+}$), ketoglutarate and silicon. The collagen degradation is regulated by matrix metalloproteinase-1 (MMP-1), of which is the major collagen-degrading proteinase whereas tissue inhibitors of metalloproteinase-1 (TIMP-1) bind to MMP-1 thereby inhibiting MMP-1 activity. In this study, we investigated the effects of vitamin C, silicon and iron on mRNA, protein expressions of PH, LH, MMP-1 and TIMP-1. The physiological concentrations of vitamin C (0-100 $\mu$M), silicon (0-50 $\mu$M) and iron (Fe$^{2+}$：0-50 $\mu$M) were treated to human dermal fibroblast cells (HS27 cells) for 3 or 5days. The expression level of mRNA and protein was increased in not only PH but also LH when cells were incubated with vitamin C. A similar increase in LH mRNA or protein expression occurred when cells were incubated with silicon. Our results suggest that treatment of vitamin C and silicon increased mRNA and protein expression of PH and LH in human dermal fibroblast.

• Membrane Journal
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• v.24 no.4
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• pp.301-310
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• 2014

In this study, the silica nanoparticles were considerably chosen to improve a dimensional stability, proton transport and electrochemical performance of the resulting inorganic-organic nanocomposite membranes. For this purpose, hydrophobic silica (Aerosil$^{(R)}$ 812, Degussa) and hydrophilic silica (Aerosil$^{(R)}$ 380, Degussa) nanoparticles were, respectively, introduced into a Sulfonated poly(arylene ether sulfone) (SPAES) polymer matrix. The $SiO_2$ particles are evenly dispersed in a SPAES matrix by the aid of a non-ionic surfactant (Pluronics$^{(R)}$ L64). A $SiO_2$ content plays an important role in membrane microstructures and membrane properties such as proton conductivity and water uptake. Therefore, to study nanocomposite membranes with excessive amount of silica, the content of silica nanoparticles were increased up to 5 wt%. Interestingly, a hydrophobic $SiO_2$ containing nanocomposite membrane showed better electrochemical performance (29% higher than pristine SPAES) despite of low proton conductivity due to its adhesive properties with a catalyst layer in a single cell test. All the silica-SPAES membranes exhibited better performance than a pristine SPAES membrane.

• Elastomers and Composites
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• v.46 no.3
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• pp.195-203
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• 2011

Eco-friendly materials or bio-composites were made with poly(lactic acid) (PLA) as matrix polymer and kenaf fibers as filler. Also, acetylated kenaf fibers and compatibilizer were adopted in order to improve the interfacial adhesion between fiber and polymer. In this study, the effect of chemical modification and compatibilizer on the mechanical-viscoelastic and morphology properties of the bio-composites was discussed. The hydrophobic fibers by acetylation were known to show better interfacial bonding with the matrix polymer and resulted in improved performance and morphology. Viscoelastic property and glass transition temperature, however, were not nearly enhanced.