• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2006년도 춘계학술대회 논문집
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• pp.57-58
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• 2006

The effects of lowering ECAP temperature during ECAP process and Post-ECAP annealing on microstructure, texture and mechanical properties of the AZ31 alloys have been investigated in the present study. The as-extruded materials were ECAP processed to 2 passes at 553K prior to subsequent pressing up to 6 passes at 523K or 493K. When this method of lowering ECAP temperature during ECAP was used, the rods could be successfully deformed up to 6 passes without any surface cracking. Grain refinement during ECAP process at 553K might have helped the material to endure further straining at lower deformation temperatures probably by increasing the strain accommodation effect by grain boundary sliding, causing stress relaxation. Texture modification during ECAP has a great influence on the strength of Mg alloys because HCP metals have limited number of slip systems. As slip is most prone to take place on basal planes in Mg at room temperature, the rotation of high fraction of basal planes to the directions favorable for slip as in ECAP decreases the yield stress appreciably. The strength of AZ31 Mg alloys increases with decrease of grain size if the texture is constant though ECAP deformation history is different. A standard positive strength dependence on the grain size for Mg alloys with the similar texture (Fig. 1) supports that the softening of ECAPed Mg alloys (a negative slope) typically observed despite the significant grain refinement is due to the texture modification where the rotation of basal planes occurs towards the orientation for easier slip. It could be predicted that if the original fiber texture is restored after ECAP treatment yielding marked grain refinement, yield stress as high as 500 MPa will be obtained at the grain size of ${\sim}1{\mu}m$. Differential speed rolling (DSR) with a high speed ratio between the upper and lower rolls was applied to alter the microstructure and texture of the AZ31 sheets. Significant grain refinement took place during the rolling owing to introduction of large shear deformation. Grain size as small as $1.4{\mu}m$ could be obtained at 423K after DSR. There was a good correlation between the (0002) pole intensity and tensile elongation. This result indicates that tensile ductility improvement in the asymmetrically rolled AZ31 Mg alloys is closely related to the weakening of basal texture during DSR. Further basal texture weakening occurred during annealing after DSR. According to Hall-Petch relation shown in Fig. 1, the strength of the asymmetrically rolled AZ31 is lower than that of the symmetrically rolled one when compared at the same grain size. This result was attributed to weakening of fiber texture during DSR. The DSRed AZ31, however, shows higher strength than the ECAPed AZ31 where texture has been completely replaced by a new texture associated with high Schmid factors.

• 한국해양생명과학회지
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• 제5권2호
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• pp.64-71
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• 2020

홍조류 참풀가사리(Gloiopeltis tenax)는 중국과 일본에서 경제적으로 유용한 종으로 알려져 있으며 이것은 예로부터 접착제나 식용 등으로 이용되었다. 실험에 사용된 재료는 전북 부안군 변산면 격포리에서 채집한 성숙한 사분포자체로부터 사분포자를 방출 받은 후 배양하여 형성된 반상근을 대량으로 확보하였다. 이를 해부현미경 하에서 4등분하여 재생과 생장 과정을 추적하였다. 절단된 반상근을 각 조건별로 배양하였고 광주기는 16:8 h L:D이며 온도조건은 10, 15, 20, 25℃이고 광도조건은 30, 85 µmol photons m^-2s^-1이다. 4등분된 반상근은 타원형으로 생장하다가 원주상의 직립 축을 형성하였다. 반상근의 크기는 배양 12주 후, 광도 85 µmol photons m^-2s^-1의 15℃ 온도에서 9.61±3.59 mm²로 최대였다. 평균 상대생장률은 광도 85 µmol photons m^-2s^-1의 15℃ 온도에서 5.15±0.80 %day-1으로 최대 생장률을 나타내었고 10℃ 온도에서 3.15±0.94 %day^-1으로 최저 생장률을 나타냈으며 통계적으로 유의한 차이를 보였다(p < 0.05). 결론적으로 참풀가사리의 반상근을 이용한 방법이 효과적인 양식 방법임이 확인되었다.

• 치과방사선
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• 제13권1호
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• pp.29-73
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• 1983

The age related changes in the life cycle of the progenitor cell population of murine oral epithelia was studied. Using radioautographic methods which have been adopted in previous cell cycle studies, the age-related changes of different phases in renewing cells of the palatal, buccal and lingual mucosae were determined. The results confirm published findings on cell cycle changes of epithelia with aging and illustrated further that mitotic phase which has hither to been considered stationary, also changes with aging. The major parts revealed by this study are as follows: 1) The basal progenitor cells in different regions of oral mucosa have different generation times. 2) The basal cell cycle time increases as a function of aging and the region most affected by aging appears to be the epithelium of the cheek. 3) The phases of the cell cycle affected by the process of aging are in increasing order of magnitude: M-, S- and G₁-phase. 4) The age elated change in the number of DNA synthesizing basal progenitor cells occurs at two age periods. Between 1 and 12 months of life it decreases, while from 12 to 20 months it increases.

• Applied Microscopy
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• 제27권4호
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• pp.391-402
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• 1997

본 연구는 고단백뇨를 보이는 신장질환모델마우스(FGS/Kist mouse)의 사구체에 대한 미세구조학적 변화를 관찰하고자 수행하였다. 전반적으로 사구체내의 모세혈관은 주변부의 혈관사이세포(mesangial cell) 부위의 확장으로 인하여 관강이 좁아져 있었으며 관강내에는 점액양 물질들이 흔히 관찰되었다. 또한 사구체바닥판(basal lamina)이 모세혈관 사이의 공간쪽으로 돌출되어져 있는 소견들도 볼 수 있었다. 혈관사이세포 부위에는 주변부와 뚜렷이 구분되는 전자밀도가 높은 물질들이 많이 차여져 있었다. 한편, 사구체바닥판에 인접하여 존재하고 있는 발세포들(podocytes)은 세포질내 많은 공포들이 관찰되었고, 발세포들이 내고 있는 발세포발(foot process)들은 서로 융합되거나 소실되어 매우 불규칙적인 소견을 보였다.

• The Korean Journal of Physiology
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• 제11권2호
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• pp.57-61
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• 1977

Two methods have been widely used for measuring basal metabolic rates (BMR), Douglas-Scholander (open circuit) and Sanborn-Metabulator (closed circuit ) methods. The latter has been used more by clinicians, since the Process is simple. But it is not as accurate as the Douglas-Scholander method. We measured the BMR of 938 healthy individuals who were selected at random, using a Douglas-Scholander method. The lowest value of the 6 measurments in three days was taken from each subject in the basal state. A single determination of BMR also was made with the Metabulator for 684 individuals. We applied both methods for 13 subjects among them who have same physical conditions. The results obtained were as follows: 1. The mean value of BMR with the Metabulator is significantly higher than Douglas-Scholander method by 9.2%. 2. The Metabulator can be used for measuring BMR, since the normal value is generally less than 15% of BMR. But one may considered that there is likely errors about 10% in Metabulator method.

• Food Science and Biotechnology
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• 제15권4호
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• pp.635-638
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• 2006

The effects of raw and processed small black soybean powders on dietary fiber content and gastrointestinal function in rats were investigated. The crude oil, protein, and ash contents of raw small black soybean powder were not significantly different from those of processed small black soybean powders. The germination process increased soluble and insoluble dietary fiber contents significantly, as compared to raw small black soybean powder. The germinated small black soybean powder diet led to a significantly different food intake than the basal diet in both normal and loperamide-induced constipated rats. The body weight gains of the experimental groups, however, were not significantly different from that of the basal diet groups for both the normal and loperamide-induced rats. The gastrointestinal transit times and fecal weights for normal and loperamide-induced rats consuming the processed small black soybean powder diet were significantly different from those on a basal diet. These results suggest that the processes of cooking and germinating the small black soybean might contribute to acceleration of fecal excretion in both experimental normal and constipation model rats.

• 자원환경지질
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• 제22권1호
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• pp.65-80
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• 1989

Strongly weathered granitic rocks are widely distributed in the south-eastern part of the Ganghwa island. Kaolinite developed during intense weathering on this granitic rocks have been studied mineralogically and chemically. Various weathering indexes were ca1culated on the basis of oxide. Those indexes are slightly varied with depth. It shows that the percentages of $Al_2O_3$ increase but that of $CaO+Na_2O+K_2O$ decrease as the weathering progress. These results indicate that day minerals, mainly kaolinite with the appreciable amount of halloysite, were formed by the weathering of feldspars in the granitic rocks. X-ray diffraction, differential thermal analysis, infrared spectrometry and electron microscopy were used to characterize and estimate crystallinity of the kaolinite. Generally, Kaolinite shows a less sharp basal reflection and relatively low dehydroxylation temperature, indicating disordered kaolinite. They usually occur aggregates as a vermicular kaolinites showing loose basal plane stacking arrangement.

• 한국해양생명과학회지
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• 제6권1호
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• pp.23-30
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• 2021

북방전복 Haliotis discus hannai 웅성생식세포의 분화과정과 정자의 형태를 미세구조적으로 기재하였다. 정자의 분화과정은 정원세포기, 정모세포기, 정세포기 및 정자기의 4단계로 구분하였다. 정원세포기에서 정모세포기로의 분화과정은 형태학적 변화가 크지 않았다. 그러나 정자변태과정 동안 염색질 응축, 핵의 형태 변화, 첨체와 중편 및 편모 형성 등의 급격한 형태학적 변화를 나타냈다. 북방전복의 정자는 두부, 중편 및 미부로 구성되며, 두부의 길이는 약 5.3 ㎛로 전자밀도가 높은 핵과 총알형의 첨체로 이루어져 있었다. 중편은 기저체와 미토콘드리아로 구성되어 있었으며, 기저체를 중심으로 5개의 미토콘드리아가 한 층으로 배열되어 있었다. 미부의 횡단면은 "9+2"의 미세소관 구조를 보였다. 이러한 형태 및 구조적 특징은 북방전복의 정자는 원시형(primitive type) 정자임을 보여주는 결과이다.

• 치과방사선
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• 제24권1호
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• pp.67-77
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• 1994

The purpose of this study was to investigate the irradiatiion effects on the capillary and endothelial cell in the submandibular gland. Sprague-Dawley strain male rats were singly irradiated to their neck region with the dose of 5Gy by 6MV X-irradiation and sacrificed on the 6 hours, 12 hours, 1, 3, 7, and 14days after irradiation. The authors observed the histological changes of the capillary at H & E and PAS staining under a light microscope, and also observed the ultrastructural changes of the endothelial cell using a transmission electron microscope. The obtaining results were as follows: 1. In the light microscopic examination, the capillary density was slightly increased on the 1day after irradiation, and increased until the 7 days after irradiatiion. After then, capillary density was apparently decreased. 2. The reaction to PAS staining at acinar cells was decreased on the 6 hours after irradiation, and recovered on the 7days after irradiation. But reaction was decreased on the 14days after irradiation agan, after then, gradually recovered with days. 3. In the transmission electron microscopic examination, mild proliferation of cytoplasmic process of the endothelial cell and reduction in luminal size were observed just after irradiation. After then, nuclear degeneration, marked proliferation of cytoplasmic process, thickened basal lamina, and numerous cytoplasmic vesicles were observed on the 1day after irradiation. These changes were recovered to normal on the 14days after 5Gy group, but not with 10Gy irradiation group. And destruction of endothelial cell and loss of basal lamina were not observed in both groups. 4. From the above results, reduction in luminal size, proliferation of cytoplasmic process and thickening of basal lamina were observed as the irradiation effects on the capillary and endothelial cell of the submandibular gland. And also, these changes may induce increase in capillary number and endothelial permeability by means of increase of cytoplasmic vesicle formation. The changes appeared earlier and more prominent in 10Gy irradiated group than in 5Gy irradiated group.

• 치과방사선
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• 제25권1호
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• pp.71-87
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• 1995

The purpose of this study was to investigate the early irradiation changes on the ultrastructure of the capillary endothelial cell in the rat submandibular glands. For the study, 110 Sprague-Dawley strain male rats were singly irradiated to their neck regions with the doses of 2Gy, 5Gy, and 10Gy by 6MV X -irradiation, and sacrificed on the 3 hours, 6 hours, 12 hours, 1 day, 3 days, 7 days, and 14 days after irradiation. The authors observed the histologic and ultrastructural changes of the capillary endothelial cell using the light and electron microscopes. The results were as follows: I. In the light microscopic examination, the capillary dilation was observed on the 6 hours group and the capillary density was slightly increased on the 12 hours group after 2Gy and 5Gy irradiation. And luminal size and capillary density were decreased on the 3 days and the 7 days groups after irradiation, after then, they were recovered. But capillary density was still decreased on the 14 days group after 10Gy irradiation. 2. In the transmission electron microscopic examination, the mild proliferation of cytoplasmic process of the endothelial cell and reduction in luminal size were observed on the 3 hours group after irradiation. After then, endothelial swelling, marked proliferation of cytoplasmic process, thickened basal lamina, and numerous pinocytotic vesicles were observed after the 1 day group after irradiation. Thickened basal lamina and numerous pinocytotic vesicles were still observed until the 7 days group after irradiation. These changes were recovered to normal on the 14 days group after 2Gy and 5Gy irradiation, but not after 10Gy irradiation. 3. In the scanning electron microscopic examination, the dilation of conduits and constriction, and meandering were observed on the 1 day group after 10Gy irradiation. These changes were observed with increased coarseness of the surface of the vascular resin casting on the 3 days group after irradiation. 4. From the above results, endothelial swelling, proliferation of cytoplasmic process, and thickening of the basal lamina appeared before the 6 hours group after irradiation. And these changes may also induce the increase of the capillary number and luminal size, after then, capillary permeability was increased via the increase of the number of pinocytotic vesicles. The changes were observed earlier and more apparent with the increase of the irradiation doses under the dose of 10Gy irradiation.