• Journal of Microbiology and Biotechnology
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• v.28 no.1
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• pp.77-86
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• 2018

The human pathogen and food spoiler Bacillus cereus can form biofilms that act as a persistent source of contamination, which is of public health concern. This study aimed to understand how the source of isolation might affect the behavior of biofilm formation. Biofilm formation abilities of 56 strains of B. cereus isolated from different environments, including human food poisoning, farm, and food, were determined. Crystal violet assay results revealed significant (p < 0.05) differences in biofilm formation abilities among the strains isolated from different sources only at an early stage of incubation. However, strain origin showed no impact on later stage of biofilm formation. Next, correlation of the group of isolates on the basis of their biofilm-forming abilities with the number of sessile cells, sporulation, and extracellular polymeric substance (EPS) formation was determined. The number of sessile cells and spores in biofilms was greatly influenced by the groups of isolates that formed dense, moderate, and weak biofilms. The contribution of extracellular DNA and/or proteins to EPS formation was also positively correlated with biofilm formation abilities. Our results that the source of isolation had significant impact on biofilm formation might provide important information to develop strategies to control B. cereus biofilm formation.

• Korean Journal of Materials Research
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• v.19 no.2
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• pp.115-118
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• 2009

The use of dolomite refractories has increased during the past several years in the manufacturing of clean steel during the stainless steelmaking process. However, at the same time, the use of dolomite refractories has led to what is known as the skull formation. In the present work, to understand the skull formation, the wetting characteristics of dolomite substrates by liquid Fe-19wt%Cr-10wt%Ni alloys in various oxygen partial pressures were initially investigated at 1753K using the sessile drop technique. For comparison, the wetting characteristics of alumina substrates were investigated with the same technique. It was found that the wetting index, (1+$cos{\theta}$), of dolomite is approximately 40% higher compared to those of alumina. In addition, the oxygen partial pressure to generate the surface oxide, which may capture the liquid metal on the refractory surface, for dolomite is much lower than that for alumina. From this study, it was concluded that the use of dolomite is much more closely associated with the skull formation compared to the use of alumina due to the stronger wettability and the surface oxide formation at a lower oxygen partial pressure of dolomite.

• Animal cells and systems
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• v.3 no.4
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• pp.359-363
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• 1999

Urochordates, the most primitive group in phylum Chordata, are mostly sessile as adults although some are free living. Presently, the ancestral stock of urochordates as weir as chordates has been the focus of interest and two conflicting hypotheses have been presented. A free swimming ancestor is one and a sessile, filter feeding ancestor is the other. To clarify the phylogenetic relationships within the urochordates, 22 urochordates and five others as outgroups were used. And we applied neighbor joining, maximum likelihood, and maximum parsimony methods to partial 18S rDNA sequences. The inferred phylogeny in all analyses indicates that order Aplousobranchia of class Ascidiacea appears to be the most ancestral group among urochordates. But it is not clear for the low bootstrap value. The remaining two orders of ascidians, Phlebobranchia and Stolidobranchia, form monophyletic groups respectively, which are well supported by high bootstrap values. These two orders are closer to classes of Thaliacea and Appendicularia than to the Aplousobranchia. While class Appendicularia is strongly supported by the monophyletic group, the phylogenetic position of class Thaliacea is unclear in this study.

• Korean Journal of Metals and Materials
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• v.47 no.6
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• pp.383-390
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• 2009

The effects that processing atmospheres and alloy composition have on the wetting characteristics of Al-Mg alloys on the $SiO_{2}$ substrate were investigated by measuring the wetting angles. It was observed that the wetting behavior of the Al-Mg alloys on the $SiO_{2}$ substrate vary depending on the Mg content of the alloys and atmospheres. The results showed that the contact angle decreases with increasing Mg content, angle is generally larger in the $N_{2}$ atmosphere than in the Ar atmosphere. We discussed the validity of the results obtained from the wetting test on the basis of recent theories and the results observed from the actual penetration tests.

• ALGAE
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• v.36 no.3
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• pp.155-163
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• 2021

The crustose brown algal genus Endoplura has been known as a monotypic genus characterized by its intercalary plurangial reproductive structures composed of 2-4 separate parallel filaments terminated by 2-5 sterile cells and by containing several to many chloroplasts per cell. In this study, Endoplura jejuensis sp. nov. and E. koreana sp. nov. from Korea are newly described based on molecular and morphological analyses. Our phylogenetic analyses of the rbcL gene reveal that E. jejuensis sp. nov. and E. koreana sp. nov. are placed in the same clade with "E. aurea" from Japan with a strong bootstrap supporting value. E. jejuensis is characterized by small and light to dark brown crustose thalli of less than 1 cm diameter, tufts of hairs arising from the basal disc, plurangia composed mostly of two separate parallel reproductive filaments terminated by 2-4 sterile cells, and sessile unangia each with a single paraphysis. E. koreana is distinguished by olive or yellowish-brown crustose thalli of up to 3 cm diameter, tufts of hairs arising from the basal disc, and apical parts of erect filaments, plurangia with 2-5 separate reproductive filaments terminated by 2-8 sterile cells, and sessile unangia with 1-2 paraphyses. Our studies also show that "E. aurea" specimens from Japan may be recognized to be a different species from other Endoplura species.

• Journal of ILASS-Korea
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• v.26 no.2
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• pp.88-95
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• 2021

This study aims to investigate the influence of the droplet volume on the evaporation characteristics of the sessile droplet. In particular, the effect of the free convection in the vapor domain on the evaporation rate was analyzed through the numerical simulation. The commercial code of the ANSYS Fluent (V.2020 R2) was used to simulate the heat transfer in the liquid-vapor domain. Moreover, we used the diffusion model to estimate the evaporation rate for the different droplet volume under the room temperature. It was found that the evaporation rate significantly increases with the droplet volume because of the larger surface area for the mass transfer. Also, the effect of free convection on the evaporation rate becomes significant with an increment of droplet volume owing to the increase in the droplet radius corresponding to the characteristic length of the free convection.

• Journal of the Korean Wood Science and Technology
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• v.47 no.4
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• pp.408-417
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• 2019

Non-destructive test techniques are becoming increasingly important for assessment and maintenance. These techniques are very useful for assessment of materials such as wood, whose performance can vary considerably depending on the conditions of use. It is possible to estimate some mechanical properties of a material by determining the movement of energy through the material with the help of these techniques. In this study, it was investigated whether the wood material could be tested nondestructively by the heat energy produced by a source. The correlations between the thermal conductivity and mechanical properties of Scots pine (Pinus sylvestris L.) and sessile oak (Quercus petraea L.) woods were investigated. The thermal conductivity (TC), density, modulus of rupture (MOR), compression strength (CS), and modulus of elasticity (MOE) values of samples were measured according to the related standards and these values were correlated with each other. The linear and multiple regression tests were employed to determine the correlation between thermal conductivity and mechanical properties. The results showed that there is a very strong correlation between thermal conductivity and both density and MOR values. However, the correlations between TC and both MOE and CS were moderate. The results of this study suggest that the thermal conductivity value can be used to estimate the density and some mechanical properties of wood.

• Journal of Plant Biotechnology
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• v.44 no.1
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• pp.42-48
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• 2017

This study was conducted to establish the optimal condition for in vitro propagation of Disporum sessile. In the experiments with different kinds of media (MS, B5 and WPM) and explant types for shoot induction and elongation, the highest number of shoot inductions (2.5/explant) was shown when the axillary bud explants were cultured on MS medium without plant growth regulators (PGRs). The best shoot elongation (7.2 cm) was also obtained when the apical buds were cultured on MS medium. The effect of BA pulse treatments with in vitro shoots was also examined. The highest in shoot induction (2.29/explant) and elongation (7.28 cm) was observed when the shoots from axillary buds were cultured on the media without PGRs. However, it decreased with increasing duration of BA pulse-treatment. The highest rooting rate (100%) and number of root inductions (21.3/explant) were achieved with 1.0 mg/L indole-3-butyric acid (IBA) treatment, whereas no differences were observed by different shoot types. The regenerated in vitro plantlets were hardened and successfully established in soil.

• The Korean Journal of Mycology
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• v.20 no.4
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• pp.281-284
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• 1992

Two interesting new hyphomycetes collected on rachis of an unidentified palm (Palmao) from Malayasia are described and their taxonomy is discussed in this paper. One of them is unique in producing basauxic conidiophores from conidiophore mother cells that are sessile, simple, cylindrical or cupulate, and solitary, gangliar, acrogenous, dry phragmoconidia. It is classified in a new genus Basauxia, as a new species, B. pulchra. The other hyphomycete is also unique in producing characteristic solitary, eight-celled, eight-armed gangliar conidia on simple conidiophores. A new genus, Ashtaangam is proposed for it in which it is placed as a new species, A. sundaram.

• Journal of the Korea Concrete Institute
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• v.16 no.5 s.83
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• pp.591-596
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• 2004

In order to evaluate the applicability of steel slag aggregates for tetrapod concrete, the properties of concrete as structural material were investigated. The biochemical research of marine concrete using steel slag aggregates was also carried out. The tested concrete properties are slump, ai content, compressive strength, splitting tensile strength, elastic modulus, carbonation, hydration heat, freezing and thawing, sulfate attack, drying shrinkage, etc. The biochemical experiments are carried to research the propagation and reproduction of seaweeds and survival of bottom dwelling species. According to this experiment results, the steel slag aggregate content did not have a significant effect on compressive strength, splitting tensile strength and elastic modulus. The durability of concrete was not influenced by the steel slag aggregate content. From the biochemical research, steel slag aggregate can be evaluated as the material that is ideally suited for promoting propagation and reproduction of seaweeds and sessile benthos.