• Polymer(Korea)
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• v.33 no.5
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• pp.435-440
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• 2009

Thermal degradation behavior of CR (chloroprene) -modified NR (natural rubber) compounds, having different sulfur/accelerator compositions, was studied by non-isothermal TGA method. Data were analyzed using both Kissinger and Flynn-Wall-Ozawa analysis to assess the activation energies. Activation energy obtained from Kissinger analysis was $147.0{\pm}2.0$ kJ/mol for all samples, showing little effect of sulfur/accelerator composition changes in the samples. On the other hand, activation energy from Flynn-Wall-Ozawa analysis exhibited much variations with conversion, showing average value of $211.6{\pm}19.0$ kJ/mol. From the results, it was considered that whole thermal degradation processes of the samples were composed of complex multiple step processes, of which reaction mechanisms were different from each other.

• Journal of Periodontal and Implant Science
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• v.35 no.1
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• pp.21-30
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• 2005

Matrix metalloproteinases (MMPs) are a family of host-derived proteolytic enzymes and implicated in the remodeling and degradation of extracellular matrix under both physiological and pathological conditions. Connective tissue degradation in periodontal diseases is thought to be due to excessive MMP activities over their specific inhibitors. The effects of lipopolysaccharide (LPS) from Prevotella intermedia, one of the major putative pathogens of periodontitis, on the expression of mRNA for MMPs and tissue inhibitors of metalloproteinases (TIMPs) in human gingival and periodontal ligament fibroblasts were examined by reverse transcriptase-polymerase chain reaction (RT-PCR). The expression of mRNAs encoding MMP-1, -2, -3, -10, and -14 was increased in human gingival fibroblasts treated with p. intermedia LPS, whereas MMP-11 and TIMP-2 mRNA expression was decreased in these cells stimulated with LPS. P. intermedia LPS increased the MMP-1, -2, -10, -11, and -14 mRNA expression and decreased TIMP-1 and -2 mRNA expression in human periodontal ligament fibroblasts. These findings imply that P. intermedia LPS may play an important role in the connective tissue degradation in periodontitis.

• Journal of Life Science
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• v.21 no.11
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• pp.1511-1517
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• 2011

We isolated a potent phenanthrene-degrading bacterium from oil-contaminated soils of Suzhou, China, and assessed the potential use of these bacteria for bioremediation of soils contaminated by polycyclic aromatic hydrocarbons (PAHs) in a microcosm. Based on 16S rDNA sequencing, we identified this bacteria as Sphigobacterium sp. SW-09. By PCR amplification, we also identified catechol 2,3-dioxygenase genes (nahH genes) mediating PAH degradation. Staphylococcus sp. KW-07, which has been identified in our previous study, showed potential for use in bioremediation of oil-contaminated soils. In this experiment, we compared the rate of phenanthrene-degradation between Staphylococcus sp. KW-07 and Sphingobacterium sp. SW-09 in a microcosm condition. Newly isolated Sphingobacterium sp. SW-09 showed a higher phenanthrene-degradation rate than that of Staphylococcus sp. KW-07 in soil microcosms. Together, our results suggest that the Sphingobacterim sp. SW-09 strain isolated from the Suzhou area may also be useful in bioremediation of PAH-contaminated soils.

• Archives of Pharmacal Research
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• v.24 no.2
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• pp.144-149
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• 2001

N-acetylsphingosine (C2-ceramide) is a synthetic water-soluble ceramide mimicking the activity of natural ceramides. By fixing chiral conformation on carbon numbers 2 and 3 in the ceramide structure, four chiral C2-ceramides naming d-erythro-, I-erythro-, d-threo-and 1-three C2-ceramide were synthesized. We have investigated the chiral effects of these C2-ceramides on the sphingolipid metabolism, particularly on both the sphingolipid bio- synthetic pathway and on the degradation pathway. In both HL-60 and U937 cells, the chiral C2-ceramide ($10{\mu}\textrm{m}$) showed sphingosine accumulation monitored fluoromatrically by a high performance liquid chromatographic separation of the sphingoid bases. Most importantly, in HL-60 cells, l-erythro C2-ceramide induced a 50 fold increase in sphingosine as compared to the control, while l-threo C2-ceramide exhibited a minimal 7-fold in-crease. In contrast, sphinganine, another sphingoid base, showed less accumulation by any chiral C2-ceramide tested under the same conditions. These results suggested that chiral C2-ceramide primarilyacts on the sphingolipid degradation pathway rather than on the sphingolipid biosynthetic route. The strong $C_0/G_1$ phase arrest in the cell cycle by treatment of I-erythro C2-ceramide indicates that the blockade of the sphingolipid degradation pathway might be concomitantly involved in the dysfunction of the cell cycle. On the other hand, the fact that all chiral C2-ceramides tested failed to inhibit the activity of sphingosine kinase acting on the removal of sphingosine by producing sphingosine-1 -phosphate demonstrates that chiral C2- ceramides may increase sphingosine by activating various ceramidases by which natural ceramides are divided into sphingosine and free fatty acids. However, the precise steps involved in this interaction are still unknown.

• Journal of Microbiology and Biotechnology
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• v.27 no.9
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• pp.1670-1680
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• 2017

Lignocellulose, composed mostly of cellulose, hemicellulose, and lignin generated through secondary growth of woody plant, is considered as promising resources for biofuel. In order to use lignocellulose as a biofuel, biodegradation besides high-cost chemical treatments were applied, but knowledge on the decomposition of lignocellulose occurring in a natural environment is insufficient. We analyzed the 16S rRNA gene and metagenome to understand how the lignocellulose is decomposed naturally in decayed Torreya nucifera (L) of Bija forest (Bijarim) in Gotjawal, an ecologically distinct environment. A total of 464,360 reads were obtained from 16S rRNA gene sequencing, representing diverse phyla; Proteobacteria (51%), Bacteroidetes (11%) and Actinobacteria (10%). The metagenome analysis using single molecules real-time sequencing revealed that the assembled contigs determined originated from Proteobacteria (58%) and Actinobacteria (10.3%). Carbohydrate Active enZYmes (CAZy)- and Protein families (Pfam)-based analysis showed that Proteobacteria was involved in degrading whole lignocellulose, and Actinobacteria played a role only in a part of hemicellulose degradation. Combining these results, it suggested that Proteobacteria and Actinobacteria had selective biodegradation potential for different lignocellulose substrates. Thus, it is considered that understanding of the systemic microbial degradation pathways may be a useful strategy for recycle of lignocellulosic biomass, and the microbial enzymes in Bija forest can be useful natural resources in industrial processes.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.7
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• pp.2661-2669
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• 2010

In this study, a finite element formulation based first-order shear deformation theory is developed for non-linear behaviors of laminated composite plates containing matrix cracking. The multi-directional stiffness degradation is developed for adopting the stiffness variation induced from matrix cracking, which is proposed by Duan and Yao. The matrix cracking can be expressed in terms of the variation of material properties, such as Young's modulus, shear modulus and Possion ratio of plates, and sequently it is possible to predict the variation of the local stiffness. Using the assumed natural strain method, the present shell element generates neither membrane nor shear locking behavior. Numerical examples demonstrate that the present element behaves quite satisfactorily either for the linear or geometrical nonlinear analysis of laminated composite plates. The results of laminated composite plates with matrix cracking may be the benchmark test for the non-linear analysis of damaged laminated composite plates.

• Journal of the Korean Wood Science and Technology
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• v.31 no.4
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• pp.71-80
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• 2003

The lignin degrading fungi were isolated from decayed woods and fruiting bodies gathered in forest area. Lignin degradation ability was investigated by Klason lignin of microbial treated pine wood. Among selected fungi, CJ-6 had 49.48% Klason lignin loss which was greater than 40.58% shown by Trametes versicolor that it is known as a typical lignin degrading fungus. Also, the biodegradation process and morphological features of degraded pine wood by selected fungi were observed with the scanning electron microscope. At the stage of 20 days incubation, mycelia invasion was observed without any failure of wood structure. At 60 days, wood decay was gone in some degree and one part of tracheid and ray wall was destroyed. At 100 days, tracheid wall was severely destroyed, and distinction between ray cell was difficult as cell wall was decayed much.

• Journal of Microbiology and Biotechnology
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• v.13 no.5
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• pp.731-737
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• 2003

Mucinase complex from V. parahaemolyticus ATCC 17802 was purified 6-fold with 0.4% yield by two sequential steps of Q-Sepharose and Superdex 200HR column chromatographies. Partially purified mucinase complex showed at least 8 times higher mucin-degrading activity than the culture filtrates. The mucinase complex also showed gelatin-and-casein-hydrolyzing activities, which demonstrates that the protein is a complex compound containing several proteases. The optimum pH and temperature of partially purified mucinase complex for mucin degradation was 8.0 and $35^{\circ}C$, respectively. The partially purified mucinase complex showed high cytotoxic activity on vero cells when examined by MTT assay and microscopic observations. Cytotoxicity was significantly increased in proportion to the concentration of the mucinase complex. Mouse experiments revealed that the jejunum, ileum. and large intestinal tissues were damaged by the injection of the mucinase complex. In particular, the reduction of the goblet cells in the large intestine was remarkable. Collectively, these data suggest that the mucinase complex partially purified from V. parahaemolyticus ATCC 17802 contributes to the adhesion and invasion of V. parahaemolyticus into the host intestinal tract.

• Solar Energy
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• v.16 no.2
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• pp.15-37
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• 1996

Most of the world's energy demand is met by fossil fuels, mainly petroleum and natural gas. Even though their production is not keeping up with the demand, there are many options before us-solar energy in its direct and indirect forms, nuclear breeders, thermonuclear power, geothermal energy, synthetic fluid fuels, and hydrogen as energy carrier to complement the nonfossil energy sources. But, before these energy alternatives can be utilized, in most cases, it is necessary to conduct extensive research and development work. In order to solve global energy and environmental issues, it is very important to develop and install energy supply systems which utilizes natural energy. The installation of these systems brings the following merits from the viewpoints of energy saving or environmental protection-(a) the positive use of natural energy reduces fossil fuel consumption; and (b) it also prevents environmental degradation. In this paper, the types of natural energy considered is confined to the solar, wind, hydraulic, geothermal and ocean-wave energy. And, the objective of the paper is to describe the state of the art of natural energy and future utilization prospect of them.

• Journal of Korea Foresty Energy
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• v.22 no.3
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• pp.43-48
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• 2003

Black liquor staining for the development of natural color of bleached Hanji caused problems of discoloration and degradation. This study was carried out not only to complement these problems but also to develop natural dyeing method that was similar to the color of unbleached Hanji, through the dyeing of rice straw extractives. The dyeing properties of Hanji were influenced more by dyestuffs extraction method than extraction and dyeing time. Dyeing ability of hot water extractives was superior to cold-water extractives. Without the relation to the time of extraction and dyeing, the color of Hanji dyeing hot water extractives were similar to the control, and the color of Hanji dyed for 45 min with hot water extractives that extracted for 120 min, were almost same as the control. As natural dyestuffs, hot water extractives of rice straw showed that excellent dyeing ability for the development of various natural colors similar to unbleached Hanjis.