• Journal of the Korean Society for Heat Treatment
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• v.20 no.6
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• pp.293-298
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• 2007

Influences of aluminum carbide ($Al_4C_3$) addition on microstructure and damping capacity of Mg-3%Al casting alloy have been investigated based on experimental results of optical micrography, scanning electron microscopy with energy-dispersive spectrometry analysis and damping capacity measurement at RT. The addition of $Al_4C_3$ particles results in an efficient grain refinement. The damping capacity shows an increasing tendency with an increase in $Al_4C_3$ content. The damping value associated with $Al_4C_3$ particles is linearly dependent on the volume fraction of $Al_4C_3$ particles to the 2/3 power, $f_{2/3}$, which corresponds to the total surface area of the particles.

• The Korean Journal of Ecology
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• v.4 no.3_4
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• pp.114-123
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• 1981

Diurnal acid fluctuations, stomatal resistance, and morphology and anatomy were investigated in leaves and stems P. oleracea L. growing under the natural environmental condition. A CAM-like pattern of acid fluctuation was exhibited not in leaves of the young purslane but in its stems. Defoliated stems showed a decreased in diurnal changes of total acidity as compared with normal stems. Excised stems stored in continuous darkness exhibited diurnal acid rhythms, and they showed light deacidifications for three days. Kranz-type arrangement was observed in leaves, but not in stems. Micrography of cross sections of stems showed cells with relatively large vaculoles and a few chloroplasts. The number of stomata was 3,275cm-2 in leaves, while the stomata could not be observed in stems. Stomatal resistance was high at night and low in daytime in leaves of the young purslane, and the range of its value was 5~40 sec.$\textrm{cm}^{-1}$. But stomatal resistance in leaves of the water-stressed plant was comparratively high in day time, and its value was 30 sec.$\textrm{cm}^{-1}$. The result of these studies showed the possibility that the stem of P.oleracea L. possesses CAM under certain stressed conditions.

• Journal of the Korean Wood Science and Technology
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• v.40 no.4
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• pp.268-275
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• 2012

This study was carried out to understand the anatomical characteristics of Korean mistletoe (Viscum album var. coloratum) and host tree of Mongolian oak (Quercus mongolica) by the aid of light and scanning electron microscopy. The branch diameter of host tree at the parasitic part by mistletoe is larger than that of non-parasitic part. In the mistletoe, phloem consists of bast fiber and parenchyma cell and xylem is composed of fiber, ray and axial parenchyma cell, and vascular tracheid. The volume of ray parenchyma cell is higher than common wood species and is heterocellular made up of procumbent, upright, and square cells in the mistletoe. In the vascular tracheid of mistletoe, coarse spiral thickenings and bordered pit are present. Due to the insertion of the mistletoe haustorium, some deformed vessels but no tylosis are observed in the mistletoe. The shapes of mistletoe haustorium are sharp, and the destruction of the host tree cells due to the insertion of the mistletoe haustorium are not identified.

• Applied Microscopy
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• v.31 no.1
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• pp.59-70
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• 2001

The present study was to elucidate the cytochemical study on the cytochrome oxidase (CO) activity and myocardial adaptation to treadmill exercise in rat. The three month Sprague-Dowley male $(150{\pm}10g)$ were used in experimental animal. The experimental groups were divided into 2 groups: the normal sedentary group and the treadmill exercise group. On each 1st and 3rd day, 1st, 4th, 8th, and 12th experimental week four rats of each group were sacrificed for tests. The morphometrical measurements were used to evalute the change of heart weight, rate of myocardial fibers to capillaries, and cytochemical study of CO activities, using light and electron microscopy. The results were as follows: The heart weights were more increased in the treadmill exercise group than those of their sedentary group. The rate of myocardial fibers to capillaries were not changed in sedentary group, but those were significantly from 4th weeks in the treadmill exercise group. The CO activity was not changed in sedentary group, but increased in treadmill exercise group after 1 st week. I and III types of CO activity were increased In sedentary group, in contast to II and III types in treadmill exercise group on electron micrographic study. These results suggest that, the treadmill exercise-induced changes in CO activity and rate of myocardial fibers to capillaries appear to be related to exercise, and the adaptive response seems to occurs from 4th week of treadmill exercise.