• Journal of Life Science
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• v.28 no.8
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• pp.931-937
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• 2018

Triptolide is a compound found in Tripterygium wilfordii and reported to have an anti-inflammatory and anti-oxidant activities. A previous study shows that the dietary supplementation with triptolide increases resistance to environmental stressors, including oxidative stress, heat shock, and ultraviolet irradiation, and extends lifespan in C. elegans. Here, we investigated the underlying mechanisms involved in the lifespan-extending effect of triptolide. The effect of triptolide on age-related diseases, such as diabetes mellitus and Alzheimer's disease, was also examined using animal disease models. The longevity phenotype conferred by triptolide was not observed in the eat-2 mutant, a well-known genetic model of dietary restriction, while there was an additional lifespan extension with triptolide in age-1 and clk-1 mutants. The long lifespan of age-1 mutant is resulted from a reduced insulin/IGF-1-like signaling and the clk-1 mutant lives longer than wild-type due to dysfunction of mitochondrial electron transport chain reaction. The effect of dietary restriction using bacterial dilution on lifespan also overlapped with that of triptolide. The toxicity of high glucose diet or transgenic human amyloid beta gene was significantly suppressed by the supplementation with triptolide. These findings suggest that triptolide can mimic the effect of dietary restriction on lifespan and onset of age-related diseases. We conclude that triptolide can be a strong candidate for the development of dietary restriction mimetics.

• Journal of the Microelectronics and Packaging Society
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• v.11 no.3 s.32
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• pp.37-45
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• 2004

Electroless Ni(P) has been widely used for under bump metallization (UBM) of flip chip and surface finish layer in microelectronic packaging because of its excellent solderability, corrosion resistance, uniformity, selective deposition without photo-lithography, and also good diffusion barrier. However, the brittle fracture at solder joints and the spatting of intermetallic compound (IMC) associated with electroless Ni(P) are critical issues for its successful applications. In the present study, the mechanism of IMC spatting and microstructure change of the Ni(P) film were investigated with varying P content in the Ni(P) film (4.6,9, and $13 wt.\%$P). A reaction between Sn penetrated through the channels among $Ni_3Sn_4$ IMCs and the P-rich layer ($Ni_3P$) of the Ni(P) film formed a $Ni_3SnP$ layer. Thickening of the $Ni_3SnP$ layer led to $Ni_3Sn_4$ spatting. After $Ni_3Sn_4$ spatting, the Ni(P) film directly contacted the molten solder and the $Ni_3P$ phase further transformed into a $Ni_2P$ phase. During the crystallization process, some cracks formed in the Ni(P) film to release tensile stress accumulated from volume shrinkage of the film.

• Journal of Life Science
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• v.16 no.3 s.76
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• pp.454-458
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• 2006

HSF1 is the heat shock transcription factor in Saccharomyces cerevisiae. S. cerevisiae KNU5377 can ferment at high temperature such as $40^{\b{o}}C$. We have been the subjects of intense study because Hsf1p mediates gene expression not only to heat shock, but to a variety of cellular and environmental stress challenges. Basing these facts, we firstly tried to construct the hsf1 gene-deleted mutant. PCR-method for fast production of gene disruption cassette was introduced in a thermotolerant yeast S. cerevisiae KNU5377, which allowed the addition of short flanking homology region as short as 45 bp suffice to mediate homologous recombination to kanMX module. Such a cassette is composed of linking genomic DNA of target gene to the selectable marker kanMX4 that confers geneticin (G418) resistance in yeast. That module is extensively used for PCR-based gene replacement of target gene in the laboratory strains. We describe here the generation of hsf1 gene disruption construction using PCR product of selectable marker with primers that provide homology to the hsf1 gene following separation of haploid strain in wild type yeast S. cerevisiae KNU5377. Yeast deletion overview containing replace cassette module, deletion mutant construction and strain confirmation in this study used Saccharomyces Genome Deletion Project (http:://www-sequence.standard.edu/group/yeast_deletion_project). This mutant by genetic manipulation of wild type yeast KNU5377 strain will provide a good system for analyzing the research of the molecular biology underlying their physiology and metabolic process under fermentation and improvement of their fermentative properties.

• Journal of the Korea Concrete Institute
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• v.23 no.2
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• pp.135-144
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• 2011

Recently, researches about fiber reinforced polymer (FRP) which has excellent durability, corrosion resistance, and tensile strength as a substitution material to steel tendon have been actively pursued. This study is performed to examine FRP tendon used prestressed beam's safety under service load. The specimen was a prestressed concrete beam with internal bonded FRP tendon. In order to compare the member fatigue capacity, a control specimen of a prestressed concrete beam with ordinary steel tendon was tested. A fatigue load was applied at a load range of 60%, 70%, and 80% of the 40% ultimate load, which was obtained though a static test. The fatigue load was applied as a 1~3 Hz sine wave with 4 point loading setup. Fatigue load with maximum 1 million cycles was applied. The specimen applied with a load ranging between 40~60% did not show a fatigue failure until 1 million cycles. However, it was found that horizontal cracks in the direction of tendons were found and bond force between the tendon and concrete was degraded as the load cycles increased. This fatigue study showed that the prestressed concrete beam using FRP tendon was safe under a fatigue load within a service load range. Fatigue strength of the specimen with FRP and steel tendon after 1 million cycles was 69.2% and 59.8% of the prestressed concrete beam's static strength, respectively.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.7 no.1
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• pp.93-101
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• 1987

Residual stresses have remained around welding areas of a steel structure member after welding operation. The major causes to occur these residual stresses are the local heat due to a welding, the heat stresses due to a irregular and rapid cooling condition, the material and rigidity of a steel structure. Ultimatly, these residual stresses have been known to decrease a brittle fracture strength, a fatigue strength, a buckling strength, dynamic properties, and the corrosion resistance of the material. This paper deals with the residual stresses on a steel structure member through experimental studies. SWS 58 plates were welded by the method of X-groove type. These plates were layed on the heat treatment at four different temperatures; $350^{\circ}C$, $500^{\circ}C$, $650^{\circ}C$ and $800^{\circ}C$. The resulting residual Stresses were measured by hole drilling method, and the followings were obtained. The residual stresses on the vicinity of a welding point were relieved most effectively at the temperature of $650^{\circ}C$, and these stresses relieved completly when the ratio of a hole diamerter to a hole depth became unity. Hardness test shows that the higher value of hardness at the heat affected zone dropped to belower as the temperature went up from $350^{\circ}C$ to $800^{\circ}C$. The Welding input heats have not influenced the magnitude of residual stresses at the input heat range between above and below one forth than standard.

• Journal of Animal Science and Technology
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• v.62 no.4
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• pp.504-520
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• 2020

Proliferation of shrubs at the expense of native forage in pastures has been associated with large changes in dry-matter intake and dietary components for grazing ruminants. These changes can also affect the animals' physiology and metabolism. However, little information is available concerning the effect of pastoral-shrub grazing on the rumen bacterial community. To explore rumen bacteria composition in grazing yaks and the response of rumen bacteria to increasing shrub coverage in alpine meadows, 48 yak steers were randomly assigned to four pastures with shrub coverage of 0%, 5.4%, 11.3%, and 20.1% (referred as control, low, middle, and high, respectively), and ruminal fluid was collected from four yaks from each pasture group after 85 days. Rumen fermentation products were measured and microbiota composition determined using Ion S5™ XL sequencing of the 16S rRNA gene. Principal coordinates analysis (PCoA) and similarity analysis indicated that the degree of shrub coverage correlated with altered rumen bacterial composition of yaks grazing in alpine shrub meadows. At the phyla level, the relative abundance of Firmicutes in rumen increased with increasing shrub coverage, whereas the proportions of Bacteroidetes, Cyanobacteria and Verrucomicrobia decreased. Yaks grazing in the high shrub-coverage pasture had decreased species of the genus Prevotellaceae UCG-001, Lachnospiraceae XPB1014 group, Lachnospiraceae AC2044 group, Lachnospiraceae FCS020 group and Fretibacterium, but increased species of Christensenellaceae R-7 group, Ruminococcaceae NK4A214 group, Ruminococcus 1, Ruminococcaceae UCG-002, Ruminococcaceae UCG-005 and Lachnospiraceae UCG-008. These variations can enhance the animals' utilization efficiencies of cellulose and hemicellulose from native forage. Meanwhile, yaks grazed in the high shrub-coverage pasture had increased concentrations of ammonia nitrogen (NH₃-N) and branched-chain volatile fatty acids (isobutyrate and isovalerate) in rumen compared with yaks grazing in the pasture without shrubs. These results indicate that yaks grazing in a high shrub-coverage pasture may have improved dietary energy utilization and enhanced resistance to cold stress during the winter. Our findings provide evidence for the influence of shrub coverage on the rumen bacterial community of yaks grazing in alpine meadows as well as insights into the sustainable production of grazing yaks on lands with increasing shrub coverage on the Qinghai-Tibet Plateau.

• Korean Journal of Food Science and Technology
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• v.37 no.3
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• pp.456-464
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• 2005

Antimicrobial drug-resistance is natural response to antimicrobial stress based on selection, which weakens chemotherapy effect. Introduction of large numbers of chemotherapeutic agents to clinical practice has generated strains of microorganisms that survive and multiply in vivo with high-drug concentrations. Methicillin-resistant Staphylococcus aureus (MRSA), bacteria found in normal daily life, can be easily ingested through milk vegetables, and meats, etc. MRSA emerged in many port of the world, increasing complex clinical problems. Therefore, new agents are needed to treat MRSA. Glycyrrhiza uralensis was extracted using 80% MeOH to investigate its antimicrobial activity against MRSA stains KCCM 11812, 40510, and 40512 through bacterial measurement, disc diffusion, and O.D. methods, MIC values, MRSA gene expression investigation, and scanning electron microscope observation. Results revealed MecA, Mecl, MecRI, and FemA were the most highly manifested MRSA genes. Methanolic extract of G. uralensis significantly inhibited MRSA and thus could be used in development of antibacteria.

• Journal of Korean Society of Steel Construction
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• v.19 no.6
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• pp.737-749
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• 2007

Flexural design of double composite box girder over the interior pier for three-span continuous bridge was performed by the LRFD method. The maximum span length of the continuous bridge ranged from 80m to 120m and the relative ratio of the span length was assumed to be 1:1.25:1. The girder section was designed for the strength limit state and service limit state with additional design check for constructibility. Before the bottom concrete and compression flange showed a complete composite action, the buckling of lower compression flange was checked. The flexural stiffness and flexural resistance characteristics for the section and for the constituent members such as tension flange, compression flange, and web were analyzed for different thicknesses of the bottom concrete on top of the compression flange. The effect of the distribution ratio of steel between the top and bottom flanges was investigated by analyzing ductility behavior and stress distribution through the girder's depth for several different relative area ratios of steel between the top and bottom flanges. It was found that a total amount of 15% of steel can be saved by applying the double composite system compared with that of the conventional composite system.

• Microbiology and Biotechnology Letters
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• v.36 no.4
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• pp.268-275
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• 2008

In order to develop the multi-functional rhizobacteria that can exert positive effect on the growth of plants growing in the coastal sand dune located along East Coast of Korea, rhizospheral bacteria of 11 different plants from this area were isolated 1,330 rhizobacteria. Among these, 23 strains were able to produce auxin and had spectrum of antagonism toward various phytopathogenic microbes. To know the mechanism of this antifungal activity, these 23 strains were subjected to further analyses; 19 strains of these produced siderophore as determined by color reaction on CAS-blue plate, 4 strains produced antifungal cellulase as judged by color change on CMC-Congo red plate, 17 strains were able to utilized insoluble phosphate salts, also determined by clear zone formation on PVK medium. Identification of the strain was assigned to all 23 strains by l6s rDNA sequence analysed, and all were identified to be in the genus of Bacillus and Pseudomonas. One strain of these, denoted Pseudomonas fluorescens IB4-14, showed ACC deaminase activity which is known to be involved in the resistance of environmental stress such as salt and drought. Also, P. fluorescens IB4-l4 showed the germination stimulation and roots growth promoting activity on the in vivo assay of Lysimachia mauritiana Lam. (spoonleaf yellow loosestrife).

• The Korean Journal of Pharmacology
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• v.31 no.3
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• pp.323-331
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• 1995

Monocyte/macrophage infiltration is the well known initial features associated with the development of glomerular disease including non-immune mediated nephropathy. Tumor necrosis factor ${\alpha}(TNF{\alpha})$, a cytokine produced primarily by monocyte/macrophage, exhibits similar effects as observed at the initial stages and during the progression of glomerular injury. Because the mesangial cells are target cells for glomerular injury, the present study examined the effect of $TNF{\alpha}$ on glomerular mesangial cell membrane lipid peroxidation as an index of cytotoxicity attributing to $TNF{\alpha}$. Primary culture of rat mesangial cell was established by incubation of glomeruli isolated from male Sprague-Dawley rat kidneys utilizing a standard sieving method. The levels of lipid peroxides in the mesangial cells were quantitated by malondialdehyde- thiobarbituric acid adduct formation. During an 8 hour incubation at $37^{\circ}C$, $TNF{\alpha}$ at 10 to 10,000 units/ml increased the levels of lipid peroxides dose dependently. Western blot analysis demonstrated that a short thermal stress induced heat shock response and the synthesis of heat shock protein 70(hsp70) in this mesangial cells. Further, this induction of hsp 70 prevented increase of lipid peroxides in the mesangial cells exposed to $TNF{\alpha}$. These data suggest that $TNF{\alpha}-induced$ lipid peroxidation in the mesangial cells may have pathophysiological relevance to glomerular injury and prior induction of heat shock response may play a role in the cellular resistance against $TNF{\alpha}-induced$ glomerular injury.