• Applied Microscopy
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• v.31 no.4
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• pp.325-331
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• 2001

Integumentary structures of the stone flounder, Karefus bicoloratus were examined by means of the light and transmission electron microscopy. Stratified epidermal layer consists of supporting cells, unicellular glands and granular cells. The epidermal layer could be classified into superficial, intermediated and basal layer by morphology and structure of the supporting cells . The cytoplasm of supporting cells is divided into cortex and medullar part. In the cortex microfilaments are well developed. Mucous cells of unicellular gland were observed in the superficial and intermediated layer of the epidermis. The mucous materials were identified as glycoprotein of neutral and carboxylated mucosubstance by histochemical methods. Club cell has well developed smooth endoplasmic reticula and Golgi complex in the cytoplasm. Granular cells were observed in the intermediated and basal layer, and the cytoplasm is occupied with membrane-bounded granules of electron dense. Three types of pigment cells could be distinguished with electron density of cytoplasmic inclusions. Nerve myelins were observed near the pigment cells.

• Korean Journal of Ichthyology
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• v.23 no.3
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• pp.250-254
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• 2011

Modified organs for air respiration in Korean fish was reviewed in the following 6 Korean fishes: three mudskippers (Boleophthalmus pectinirostris, Periophthalmus modestus and P. magnuspinnatus), two mud loaches (Misgurnus mizolepis and M. anguillicaudatus), and a torrent catfish (Liobagrus mediadiposalis). Three mudskippers and a torrent catfish have a modified epidermis to in order to make up for the deficient oxygen supply. Their epidermis has abundant intraepithelial blood capillaries except dermal capillaries situated just beneath the stratum germinativum of the epidermis in B. pectinirostris. The epidermis was thick due to component of the following cells: two kinds of glands as a small mucous cells and a large club cells in L. mediadiposalis, voluminous cells (swollen cells) swollen by epidermal cells and a small mucous cells in B. pectinirostris, and only voluminous cells having no any glandular cells in P. modestus and P. magnuspinnatus. In Particular, the epidermis of the mudskippers appears to be a web-like structure due to the swollen epithelial cells. The dermal bulges are found in B. pectinirostris and they are situated at the skin covering the body, not appendage of all the fins and the sucking disc. Another modified organ in M. mizolepis and M. anguillicaudatus occurs in intestine and its mucosal epithelium has abundant blood capillaries.

• Structural Engineering and Mechanics
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• v.60 no.6
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• pp.939-952
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• 2016

A compression to tensile load transforming (CTT) device was developed to determine indirect tensile strength of concrete material. Before CTT test, Particle flow code was used for the determination of the standard dimension of physical samples. Four numerical models with different dimensions were made and were subjected to tensile loading. The geometry of the model with ideal failure pattern was selected for physical sample preparation. A concrete slab with dimensions of $15{\times}19{\times}6cm$ and a hole at its center was prepared and subjected to tensile loading using this special loading device. The ratio of hole diameter to sample width was 0.5. The samples were made from a mixture of water, fine sand and cement with a ratio of 1-0.5-1, respectively. A 30-ton hydraulic jack with a load cell applied compressive loading to CTT with the compressive pressure rate of 0.02 MPa per second. The compressive loading was converted to tensile stress on the sample because of the overall test design. A numerical modeling was also done to analyze the effect of the hole diameter on stress concentrations of the hole side along its horizontal axis to provide a suitable criterion for determining the real tensile strength of concrete. Concurrent with indirect tensile test, the Brazilian test was performed to compare the results from two methods and also to perform numerical calibration. The numerical modeling shows that the models have tensile failure in the sides of the hole along the horizontal axis before any failure under shear loading. Also the stress concentration at the edge of the hole was 1.4 times more than the applied stress registered by the machine. Experimental Results showed that, the indirect tensile strength was clearly lower than the Brazilian test strength.

• Korean Journal of Environmental Biology
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• v.32 no.4
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• pp.344-352
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• 2014

The aim of the present study was to assess the effects of ammonia on physiological responses in Korean rockfish (Sebastes schlegeli). Interestingly, no mortality were observed when the specimens ($301.1{\pm}8.0g$) were exposed to five levels of un-ionized ammonia ($NH_3$) (control, 1, 2, 4, $8mg\;L^{-1}$) for 3 hours. Furthermore, a significantly higher increase in gill $Na^+/K^+$-ATPase (NKA) pump activity with was detected due to the ammonia exposure. The activity of the fishes were found to be 4 and $8mg\;L^{-1}$ $NH_3$, which was significantly high compared to normal $1mg\;L^{-1}$ $NH_3$. Although ammonia exposure had no effect on plasma $Cl^-$, exposure to both 4 and $8mg\;L^{-1}$ $NH_3$, however it led to increase in the plasma $Na^+$, $K^+$ and osmolality levels. Also, prolong ammonia exposure cause increase of plasma cortisol and glucose levels. The increase in glucose was accompanied by an increase in cortisol. The fish exposed to 4 and $8mg\;L^{-1}$ $NH_3$ showed significantly higher hematocrit than control group than those exposed to 1 and $2mg\;L^{-1}$ $NH_3$. The intensity of cell damage increased with the increase concentration and exposure to ammonia. Furthermore, hyperplasia, separation and epithelial necrosis were also observed in gill tissues. Taken together, the results showed that direction of changes to the investigated parameters can be used to determine the physiological responses of Korean rockfish to ammonia.