• Structural Engineering and Mechanics
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• v.64 no.2
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• pp.243-257
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• 2017

Investigating the properties and durability of high-strength concrete exposed to sulfuric acid attack for the purpose of its application in structures exposed to this acid is of outmost importance. In this research, the resistance and durability of high-strength concrete containing macro-polymeric or steel fibers together with the pozzolans of silica fume or nano-silica against sulfuric acid attack are explored. To accomplish this goal, in total, 108 high-strength concrete specimens were made with 9 different mix designs containing macro-polymeric and steel fibers at the volume fractions of 0.5, 0.75, and 1.0%, as well as the pozzolans of silica fume and nano-silica with the replacement levels of 10 and 2%, respectively. After placing the specimens inside a 5% sulfuric acid solution in the periods of 7, 21, and 63 days of immersion, the effect of adding the fibers and pozzolans on the compressive properties, ultrasonic pulse velocity (UPV), and weight loss of high-strength concrete was investigated and the respective results were compared with those of the reference specimens. The obtained results suggest the dependency of the resistance and durability loss of high-strength concrete against sulfuric acid attack to the properties of fibers as well as their fraction in concrete volume. Moreover, compared with using nano-silica, using silica fume in the fibrous concrete mix leads to more durable specimens against sulfuric acid attack. Finally, an optimum solution for the design parameters where the crushing load of high-strength fibrous concrete is maximized was found using response surface method (RSM).

• Journal of the Korean Ceramic Society
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• v.31 no.11
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• pp.1378-1386
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• 1994

The characteristic of calcined BaTiO3 powder and sintered PTC ceramics was investigated varing with calcination temperature and time of BaTiO(C2O4)2.4H2O synthesized from BaCl2.2H2O, TiCl4, oxalic acid and ethanol by oxalic acid method. When the particle size was less than 0.1 ${\mu}{\textrm}{m}$ by controlling calcination temperature and time, the resistance at room temperature was measured very high (above M{{{{ OMEGA }}). However, when the calcined particle sizes ranged from 0.2 to 0.3 ${\mu}{\textrm}{m}$, the resistance was 100 {{{{ OMEGA }} (After sintering, the grain size was 10~30 ${\mu}{\textrm}{m}$ homogeneously with the addition of dopant in sintering, the resistivity, resistance, $\alpha$ value and jumped to were 110{{{{ OMEGA }}.cm, 24$^{\circ}C$/% and 106{{{{ OMEGA }}, respectively.

• Corrosion Science and Technology
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• v.3 no.5
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• pp.194-197
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• 2004

The corrosion resistance of several kind of ME (Metal Evaporated) tape has been investigated both in mild sulfuric acid solution and NaCl solution by electrochemical impedance spectroscopy. It was found that the degradation of ME tapes was accelerated with increasing the concentration of sulfuric acid. There was no significant change in corrosion resistance when the concentration of NaCl was under 3.5 wt%. However, the impedance value decreased when the concentration of NaCl was up to 10 wt%. The degradation of backside of ME tapes was also investigated by AC impedance measurements. The results showed that the impedance behavior of backside plastic film changed with the concentration of sulfuric acid even at the beginning of immersion, implying the changing of the permeability for the backside of ME tapes. It was also found that the corrosion resistance of DVC (Digital Video Cassette) ME tape was better that that of Hi-8mm ME tapes in sulfuric acid solutions. Also, the backside of DVC ME tape showed better water resistance than that of Hi8 ME tapes.

• Journal of Microbiology
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• v.43 no.5
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• pp.391-397
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• 2005

Escherichia coli is a common inhabitant of the intestinal tracts of animals and humans. The intestines of animals also represent an ideal environment for the selection and transfer of antimicrobial resistance genes. The aim of this study was to investigate the resistance of E. coli isolated from chicken fecal samples to fluoroquinolones and to analyze the characterization of mutations in its gyrA and parC gene related resistance. One hundred and twenty-eight E. coil isolates showed a high resistance to ciprofloxacin (CIP; $60.2\%$), enrofloxacin (ENO; $73.4\%$) and norfloxacin (NOR; $60.2\%$). Missense mutation in gyrA was only found in the amino acid codons of Ser-83 or Asp-87. A high percentage of isolates ($60.2\%$) showed mutations at both amino acid codons. Missense mutation in parC was found in the amino acid codon of Ser-80 or Glu-84, and seven isolates showed mutations at both amino acid codons. Isolates with a single mutation in gyrA showed minimal inhibitory concentrations (MIC) for CIP (${\le}0.5\;to\;0.75{\mu}g/ml$), ENO (1 to $4{\mu}g/ml$) and NOR (0.75 to $4{\mu}g/ml$). These MIC were level compared to isolates with two mutations, one in gyrA and one in parC, and three mutations, one in gyrA and two in parC (CIP, ${\le}0.5\;to\;3{\mu}g/ml;\;ENO,\;2\;to\;32<{\mu}g/ml;\;NOR,\;1.5\;to\;6\;{\mu}g/ml$). However, the isolates with two mutation in gyrA regardless of whether there was a mutation in parC showed high MIC for the three fluoroquinolones (CIP, 0.75 to $32{\le}{\mu}g/ml;\;ENO,\;3\;to\;32{\le}{\mu}g/ml;\;NOR,\;3\;to\;32{\le}{\mu}g/ml$). Interestingly, although the E. coil used in this study was isolated from normal flora of chicken, not clinical specimens, a high percentage of isolates showed resistance to fluoroquinolones and possessed mutations at gyrA and parC associated with fluoroquinolone resistance.

• KSBB Journal
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• v.32 no.2
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• pp.153-159
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• 2017

The purpose of this study was to investigate the probiotic properties of lactic acid bacterial strains isolated from human feces. The properties were tested on the basis of guideline for probiotic selection protocol such as tolerance for acid or bile salt, autoaggregation, antibiotic resistance, and antimicrobial activity. Total 25 lactic acid bacteria were isolated from human feces, and their antibacterial activity was tested against Staphylococcus aureus, Escherichia coli, E. coli O157:H7, Vibrio parahaemolyticus, V. alginolyticus using an agar diffusion assay. Among them, 4 selected strains were identified by analysis of their 16S rRNA, as Lactobacillus rhamnosus MG316, L. acidophilus MG501, L. reuteri MG505, and L. gasseri MG570. Results show that resistance to low pH and bile salts. Also, the selected strains were resistant to bile acid up to 3% and their autoaggregation rates were as high as 60%. All strains tested were resistance to nalidixic acid and kanamycin.

• Journal of the Korean Ceramic Society
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• v.44 no.11
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• pp.633-638
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• 2007

The setting time of alkali activated slag cement tends to be much faster than ordinary Portland cement, and its compressive strength had been higher from the 1 day but became lower than that of the cement on the 28 days. According to the results of the surface observation, weight loss, compressed strength, and erosion depth tests on the sulphuric acid solution. It has been drawn that alkali activated slag cement has a higher sulphate resistance than ordinary Portland cement, and in particular, the alkali activated slag cement added 5 wt% alumina cement has little deterioration on the sulphuric acid solution. The reason why the alkali activated slag cement has higher sulphate resistance than other hardened cement pastes is that it has no $Ca(OH)_2$ reactive to sulphate ion, and there is little $CaSO_4{\cdot}2H_2O$ production causing volume expansion, unlike other pastes. And it is supposed that $Al(OH)_3$ hydrates with high sulphate resistance, which is produced by adding the alumina cement increases the sulfate resistance.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.54 no.5
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• pp.733-741
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• 2021

Jeju island is the largest island of South Korea, and has a relatively warm climate due to its geographical characteristics. These features have fostered development of various fermented foods distinct to Jeju island. Therefore, the functional activity of the lactic acid bacteria (LAB) isolated from the Jeju region's traditional fermented foods, including Kimchi and Jeotgal was characterized in this study. Fifteen strains were isolated from 6 types of fermented food. These strains include Enterococcus spp., Lactoplantibacillus spp., and Weisella spp. Several experiments were carried out to assess functional characteristics including acid resistance, bile resistance, hemolysis, DPPH and ABTS radical scavenging activity, and cholesterol-lowering activity. Three isolated strains (J-4, J-6 and J-10) exhibited high acid resistance, while the other 3 isolates (J-1, J-4 and J-6) showed high bile salt resistance. The strains displayed varied DPPH and ABTS radical scavenging activity: 71.14-86.42% among the first 3 strains, and 50.11-75.11% among the remaining 3 strains. Cholesterol-lowering activities were in the range 15.74-82.90% for all isolated strains. In conclusion, these studies suggest that isolated LAB strains from Jeju island traditional fermented foods possess the potential for broader application in the food industry.

• Mycobiology
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• v.33 no.1
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• pp.35-40
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• 2005

Selected isolates of Pseudomonas fluorescens (Pf4-92 and PfRsC5) and P. aeruginosa (PaRsG18 and PaRsG27) were examined for growth promotion and induced systemic resistance against Fusarium wilt of chickpea. Significant increase in plant height was observed in Pseudomonas treated plants. However, plant growth was inhibited when isolates of Pseudomonas were used in combination with Fusarium oxysporum f. sp. ciceri (FocRs1). It was also observed that the Pseudomonas spp. was colonized in root of chickpea and significantly suppressed the disease in greenhouse condition. Rock wool bioassay technique was used to study the effect of iron availability on the induction of systemic resistance to Fusarium wilt of chickpea mediated by the Pseudomonas spp. All the isolates of Pseudomonas spp. showed greater disease control in the induced systemic resistance (ISR) bioassay when iron availability in the nutrient solution was low. High performance liquid chromatography (HPLC) analysis indicated that an the bacterial isolates produced more salicylic acid (SA) at low iron ($10\;{\mu}M$ EDDHA) than high iron availability ($10\;{\mu}Fe^{3+}$ EDDHA). Except PaRsG27, all the three isolates produced more pseudobactin at low iron than high iron availability.

• Magazine of the Korean Society of Agricultural Engineers
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• v.45 no.7
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• pp.27-37
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• 2003

This study was performed to examine the flowing ability and filling ability of polypropylene fiber reinforced high performance concrete. The slump flow was decreased with increasing the polypropylene fiber content, rapidly. At the box-type filling ability, the difference of box height was increased with increasing the fiber content and the box-type passing ability was closed in fiber content 1 %. The final flowing distance of L-type was decreased with increasing the fiber content. Also, it was decreased above 0.75% of polypropylene fiber content, rapidly. The filling ability of L-type was badly showed above polypropylene fiber content 0.75%. Also, the compressive strength was decreased with increasing the fiber content, but the flexural strength was shown higher than that of the concrete without fiber. At the impact resistance, drop numbers for reaching in final fracture were increased with increasing the fiber content. Also, the drop numbers for reaching initial fracture of 1mm were increased with increasing the fiber content. At the acid resistance, the percent of original mass was decreased with increasing the fiber content.

• Journal of Yeungnam Medical Science
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• v.34 no.1
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• pp.19-28
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• 2017

The incidence of type 2 diabetes mellitus and insulin resistance is growing rapidly. Multiple organs including the liver, skeletal muscle and adipose tissue control insulin sensitivity coordinately, but the mechanism of skeletal muscle insulin resistance has not yet been fully elucidated. However, there is a growing body of evidence that lipotoxicity induced by mitochondrial dysfunction in skeletal muscle is an important mediator of insulin resistance. However, some recent findings suggest that skeletal mitochondrial dysfunction generated by genetic manipulation is not always correlated with insulin resistance in animal models. A high fat diet can provoke insulin resistance despite a coordinate increase in skeletal muscle mitochondria, which implies that mitochondrial dysfunction is not mandatory in insulin resistance. Furthermore, incomplete fatty acid oxidation by excessive nutrition supply compared to mitochondrial demand can induce insulin resistance without preceding impairment of mitochondrial function. Taken together we suggested that skeletal muscle mitochondrial overloading, not mitochondrial dysfunction, plays a pivotal role in insulin resistance.