• Clean Technology
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• v.22 no.4
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• pp.250-257
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• 2016

As an attempt to replacing petroleum-based chemicals with bio-based ones, synthesis of furfural from biomass-derived xylose attracts much attention in recent days. Conventionally, furfural from xylose has been produced via the utilization of highly corrosive, toxic, and environmentally unfriendly mineral acids such as sulfuric acid or hydrochloric acid. In this study, microwave-assisted biphasic reaction process in the presence of novel bio-based heterogeneous acid catalysts was developed for the eco-benign and effective synthesis of furfural from xylose. The microwave was irradiated for reaction acceleration and a biphasic system consisting of $H_2O$ : MIBK (1 : 2) was designed for continuous extraction of furfural into the organic phase in order to reduce the undesired side products formed by decomposition/condensation/oligomerization in the acidic aqueous phase. Moreover, sulfonated amorphous carbonaceous materials were prepared from wood powder, the most abundant lignocellulosic biomass. The prepared catalysts were characterized by FT-IR, XPS, BET, elemental analysis and they were used as bio-based heterogeneous acid catalysts for the dehydration of xylose into furfural more effectively. For further optimization, the effect of temperature, reaction time, water/organic solvent ratio, and substrate/catalyst ratio on the xylose conversion and furfural yield were investigated and 100% conversion of xylose and 74% yield of furfural was achieved within 5 h at $180^{\circ}C$. The bio-based heterogeneous acid catalysts could be used three times without any significant loss of activity. This greener protocol provides highly selective conversion of xylose to furfural as well as facile isolation of product and bio-based heterogeneous acid catalysts can alternate the environmentally-burdened mineral acids.

• Tribology and Lubricants
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• v.31 no.6
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• pp.308-315
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• 2015

In the tribological performance of materials, a textured surface reduces the friction coefficient and wear. This study investigates the effects of a pattern of 300 µm dimples in a hexagonal array on the tribological characteristics. Previous studies investigated 200 µm dimples by using a similar material and method. There are three frictional conditions based on the Stribeck curve: boundary friction, mixed friction, and fluid friction. In this experiment, we investigated the frictional characteristics by conducting frictional tests at sliding speeds ranging from 9.6 rpm to 143.3 rpm and a normal load ranging from 13.6 N to 92 N. We used a photolithography method to create dimples for surface texturing. We used five specimens with different dimple densities 10%, 15%, 20%, 25%, and 30% in this study. The dimple density on the surface area is one of the important factors affecting the friction characteristics. The duty number graph indicates a fully developed fluid friction regime. Fluid friction occurs at a velocity of 28.7-143.3 rpm. We observed the best performance at a dimple density of 10% and a dimple diameter of 300 µm in the hexagonal array, the lowest friction coefficient at 0.0037 with 9.6 rpm 9.6N load, and the maximum friction coefficient at 0.0267 with 143.3 rpm 92N load.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.45 no.1
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• pp.27-36
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• 2019

Soybean (Glycine max), as one of the foods with high plant proteins, contains a large amount of bioactive compounds and known to be effective in cardiovascular disease and obesity as well as in improving skin condition. The purpose of this study was to investigate the anti-photoaging effects of soybean fermented with Lactobacillus Rhamnosus ($Bio-Peptone^{(R)}$) by assessment of cytotoxicity against UVB, collagen synthesis after UVB-irradiation, tyrosinase activity, and melanin synthesis. Results showed that $Bio-Peptone^{(R)}$ protected skin fibroblasts against UVB-induced cytotoxicity and increased type I collagen synthesis. Furthermore, $Bio-Peptone^{(R)}$ significantly inhibited tyrosinase activity and reduced melanin contents. This study suggests that $Bio-Peptone^{(R)}$ has protective effects against UVB-induced skin damage. Thus, it is concluded that $Bio-Peptone^{(R)}$ is able to prevent skin damage against UVB and thus acts as anti-photoaging materials by protecting skin forming wrinkles and skin pigments.

• Journal of the Korean Chemical Society
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• v.37 no.5
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• pp.477-482
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• 1993

The determination of trace level mercury in bio-materials has been investigated by the square wave anodic stripping voltammetry (ASV)-technique at glassy carbon electrode. Prior to analysis, the bio-materials were digested with HNO3/H2SO4 mixture and KMnO4 was added to complete the oxidation. The detection limit of the mercury varied greatly with deposition time, deposition potential, pH and stirring rate. When deposition is carried out for 240 sec with 400 rpm stirring at -1.0 volts vs. Ag/AgCl, the detection limit was below $0.5\;ppb\;(2.5{\times}10^{-9} M)$. The method is recommended for trace level mercury analysis of biomaterials because this procedure is time saving and has higher sensitivity.

• International Journal of Industrial Entomology and Biomaterials
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• v.26 no.2
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• pp.81-88
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• 2013

Wet-spun silk fibers have attracted the attention of many researchers because of 1) the unique properties of silk as a biomaterial, including good biocompatibility and cyto-compatability and 2) the various methods available to control the structure and properties of the fiber. Cellulose nanofibrils (CNFs) have typically been used as a reinforcing material for natural and synthetic polymers. In this study, CNF-embedded silk fibroin (SF) nanocomposite fibers were prepared for the first time. The effects of CNF content on the rheology of the dope solution and the characteristics of wet-spun CNF/SF composite fibers were also examined. A 5% SF formic acid solution that contained no CNFs showed nearly Newtonian fluid behavior, with slight shear thinning. However, after the addition of 1% CNFs, the viscosity of the dope solution increased significantly, and apparent shear thinning was observed. The maximum draw ratio of the CNF/SF composite fibers decreased as the CNF content increased. Interestingly, the crystallinity index for the silk in the CNF/SF fibers was sequentially reduced as the CNF content was increased. This phenomenon may be due to the fact that the CNFs prevent ${\beta}$-sheet crystallization of the SF by elimination of formic acid from the dope solution during the coagulation process. The CNF/SF composite fibers displayed a relatively smooth surface with stripes, at low magnification (${\times}500$). However, a rugged nanoscale surface was observed at high magnification (${\times}10,000$), and the surface roughness increased with the CNF content.

• Journal of Adhesion and Interface
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• v.10 no.2
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• pp.84-89
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• 2009

The objective of this research was to investigate the curing behavior and adhesion performance of urea-melamine-formaldehyde (UMF) resin for the four types of UMF-1, UMF-2, UMF-3, and UMF-4 which synthesized by the staged addition of melamine. Also, various network structures of these resin types were discussed based on their different curing behavior and adhesion performance. The curing behavior was evaluated by DMTA and thermal stability was checked by TGA. Adhesion performance was evaluated by dry and wet shear strengths and the pH value of each cured resin was checked to see its effect on the adhesion performance. The results indicated that the UMF-1 resin type by the addition of melamine initially with the urea and formaldehyde at the same F/(U+M) rate showed the lowest thermal stability, rigidity (${\Delta}E^{\prime}$), temperature of tan ${\delta}$ maximum ($T_{tan}\;_{\delta}$), and wet shear strength, and pH value of cured resin. In wet shear strength, however, the UMF-4 resin type appears to be slightly higher than UMF-1 resin type.

• Journal of Periodontal and Implant Science
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• v.33 no.3
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• pp.533-542
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• 2003

The purpose of this study is to evaluate histologic result of bone substituting material on defects followed tooth extraction. We compare the histologic findings control, DFDBA, Bio-Oss(R), and $Regenafil^{TM}$, Briefly, mandibular premolar teeth were extracted available for bone filling. All alveolar sites were checked after extraction and thoroughly debrided with a dental curet to remove the periodontal ligament. Extraction sites were prepared dehiscence on buccal side 7mm height from alveolar crest. The graft materials were filled into the extraction socket and dehiscenc defects. The animals were sacrificed 12 weeks after implantation. Both treated and control mandibular sites were histologically evaluated with light microscopy. Histologic observation at 12 weeks revealed that control and experimental sites were healed uneventfully and directly apposed to new bone without any adverse tissue reaction. DFDBA and Bio-Ossn(R)sites maintain width of alveolar crest but were not fully resorbed. $Regenafil^{TM}$ sites also maintain width and particles were resorbed more than other graft materials. From this results, it was suggested that $Regenafil^{TM}$ is promising boen substituting materials maintaining the width of alveolar crest and height follewed tooth extraction.

• Journal of fish pathology
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• v.24 no.3
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• pp.279-287
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• 2011

Transcriptional response patterns of mud loach (Misgurnus mizolepis; Cypriniformes) hepcidin, a potential ortholog to human hamp1, in response to experimental challenges with non-pathogenic and pathogenic bacterial species were analyzed based on the semi-quantitative reverse transcription-PCR assay. Mud loach hepcidin transcripts were much more preferentially induced by pathogenic bacterial species (Edwardsiella tarda and Vibrio anguillarum) causing apparent pathological symptoms than by non-pathogenic species (Escherichia coli and Bacillus thuringiensis) displaying neither clinical signs nor mortality. However in overall, the induced amounts of hepcidin transcripts were positively related with the number of bacterial cells delivered in both pathogenic and non-pathogenic bacterial species. Inducibility of hepcidin transcripts were variable among three tissues examined (liver, kidney and spleen) in which kidney and spleen were more responsive to the bacterial challenge than liver. Time course expression patterns of hepcidin mRNAs after challenge were different between groups challenged with pathogenic and non-pathogenic species, although the overall pattern of hepcidin expression was in accordance with that generally observed in battery genes appeared during early phase of inflammation. Fish challenged with E. coli (non-pathogenic) showed the significant induction of hepcidin transcripts within 24 hr post injection (hpi) but the level was rapidly declined to the basal level either at 48 or 96 hpi. On the other hand, hepcidin transcript levels in E. tarda (pathogenic)-challenged fish were continuously elevated until 48 hpi, then downregulated at 96 hpi, although the level at 96 hpi was still significantly higher than control level observed in non-challenged fish. This expression pattern was consistent in all the three tissues examined. Taken together, our data indicate that hepcidin is tightly in relation with pathological and/or inflammation status during bacterial challenge, consequently providing useful basis to extend knowledge on the host defensive roles of hepcidin under infectious conditions in bony fish.

• The Plant Pathology Journal
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• v.17 no.5
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• pp.281-289
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• 2001

We analyzed 88 strains of Gibberella fujikuroi (Analmorph: Fusarium section Liseola) from maize in Korea for mating population, mating type, fumonisin production vegetative compatibility, and random amplified polymorphic DNA (RAPD) patterns. We found 50 strains that were MATA-2, 22 that were MATA-1, 1 that was MATD-1, and 15 that were not reproducibly fertile with any of the mating type testers. Of the 50 MATA-2, 15 were female fertile, while 10 of the 22 MATA-1 strains were female fertile. A total of 1,138 nitrate non-utilizing (nit) mutants were recovered from a total of 88 strains. These strains were grouped into 39 vegetative compatability groups (VCGs) by demonstrating heterokaryosis between nit mutants. A single maize ear could be infected by more than one VCG of F. moniliforme. RAPD analysis measured genetic diversity among 63 strains of F. moniliforme. Several VCGs were distinguished by RAPD fingerprinting patterns. Most strains produced significant levels of fumonisins. However, 6 MATA-2 strains from a single VCG produced higher levels of fumonisin $\textrm{B}_3$ than that of fumonisin $\textrm{B}_1$ or $\textrm{B}_2$. From these data, we concluded that most Korean strains of F. moniliforme associated with maize belonged to mating population A and produced significant levels of fumonisins. Futhermore, RAPD analysis could differentiate strains associated with different VCGs.

• Journal of the Korean Wood Science and Technology
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• v.42 no.1
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• pp.13-19
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• 2014

Three heat-treatment schedules were applied to $90{\times}90mm$ dimension square lumber of Pinus koraiensis, one of major domestic species, and their colors and physical properties were investigated for obtaining an optimum schedule. Each square lumber was heat-treated three times. The temperatures of $170^{\circ}C$ and $190^{\circ}C$, and the time of 9 hours and 13 hours were used for the first heat-treatment. The schedule of $190^{\circ}C$ and 7 hours were used for the next two heat-treatments. The averages of brightness $L^*$ decreased linearly as the heat-treatment repeated and its standard deviations also decreased slightly. While the averages of color difference ${\Delta}E^*$ increased linearly as the heat-treatment repeated and its standard deviations also increased slightly. The average compressive strength of the heat-treated specimen was higher than that of the control by 9%, which deviates from previous reports. ASE and WPG of the heat-treated specimens were measured to confirm that heat-treatment improved dimensional stability significantly.