• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.30 no.5
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• pp.368-379
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• 2004

Distraction osteogenesis is a biologic process of new bone formation between the surfaces of bone segments that are gradually separated by incremental traction. Distraction osteogenesis is clinically applied as a new treatment modality of mandibular hypoplasia or bony defect area in maxillofacial area by many studies of distraction devices and method. But disadvantage of distraction osteogenesis shows unfavorably long consolidation period and relapse tendency. Therefore. this experiment was designed to investigate the effectiveness of combined application of distraction and compression force for improving of bone quality and shortening of treatment period during distraction osteogenesis. Twenty-one Sprague-Dawley rats with $300{\sim}350gm$ were used. These were divided into two group as distraction group and combination group was applied with compression force in the consolidation period. The rat were sacrificed for gross finding, radiographic and histologic findings. at 2, 4 weeks after distraction. The result were follow : 1. On radiographic finding, all experimental groups appeared more radiopacity than control groups both at 2, 4 weeks after distraction. 2. On histologic finding, trabeculae of bone and mature lamellar bone were showed increasingly in experimental group. Ossification occured rapidly. From this study, we may suggest that compression force application in consolidation period during distraction osteogenesis can be useful method improve bone quality and to shorten the treatment period. But more experimental and clinical studis are necessitated on effects of compression force application during distraction osteogenesis.

• The Korean Journal of Zoology
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• v.29 no.2
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• pp.121-140
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• 1986

The spermiogenesis of Cipangopaludina chinensis malleata began with the changes of nucleus and cytoplasm. The chromatin in the nucleus began to stack and condense around perinuclear envelope. Axonema (doublet microtubules of 9+2) appeared in the cytoplasm. After this process, the cytoplasm was protruded and the bell-shaped nucleus was located on protruding part of it. The electron dense masses were distributed throughout cytoplasm and lysed or secreted by exocytosis of lysosomal vacuoles. Especially, some mitochondria were migrated by the doublet microtubules of axonema toward nucleus. The axoneme was enclosed by electron dense materials after exocytosis of unnecessary materials for the tail formation. The electron dense masses were released and migrated into the each part through microtubules or axonemal doublet microtubules as the granular particles. These granular particles were containing glycogen. Ultimately, the condensed head developed into helical and neck region into cylindrical shape respectively. The mitochondria which have regular lamellar layers at cross axis became to middle piece, and then spermatozoon was completely matured. Thus, these phenomena showed special processes in spermiogenesis, those were as follows; chromatin in the head was condensed, the head was changed into helical shape, and cytoplasmic materials are migrated and transferred into the each part in the tail by mitochondria and microtubules.

• Archives of Plastic Surgery
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• v.33 no.5
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• pp.601-605
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• 2006

Purpose: Large skin defect by various causes, should be covered by autologous skin graft. But, the donor site of autologous skin graft is limited and leaves permanent donor scar and contracture. There have been our trial to engineer artificial skin using allogenic dermis (AlloDerm) with basement membrane. Methods: Dermal and epidermal layer were separated by immersing in dipase solution for 30 minutes, and the separated layers were treated with 0.05% trypsin for 10 minutes. And then each layer was cultivated to fibroblasts and keratinocytes on a culture medium. Fibroblasts were first penetrated into basement membrane of allogenic dermis facing down, then allogenic dermis was flipped over to face up and keratinocytes were transplanted to allogenic dermis. Results: Observing artificial skin fabricated in vitro, we found following: 1) The artificial skin opened in air for 5 days formed epidermal layer. In dermal layer, fibroblast was distributed evenly among all. 2) The artificial skin opened in air for 30 days formed thicker and thicker, and it formed basement membrane, spinous and granular layers. PAS stain to confirm existence of basement membrane showed positive reaction. 3) Cytokeratin 10 stain to confirm the formation of epidermal layer showed positive reaction. 4) The formation of thick keratin, lamellar body and desmosome similar to human skin were observed in result of an electron micrograph. Conclusion: As a result of research, the structure seen in normal skin such as rete ridge, is found in reproduced artificial skin. This type of artificial skin can be used as a useful model for investigating skin disease and for clinical application also.

• Environmental Analysis Health and Toxicology
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• v.22 no.1 s.56
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• pp.83-90
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• 2007

This study was investigated the effort of growth and gonadal development in olive flounder, Paralichthys olivaceus exposed to PCBs Effluent Allowance Concentration, 3.0 ppb in Korea. Total length, body weight and weight gam of fish were no significant differences between two treatments (control: T.L.-110.0 mm, T.W.-9.61 g: treatment: T.L.-112.8 mm, T.W.-9.68 g), however, weight gain of fish unexposed to PCBs wat observed to increase gradually from 100 days after hatching (30 days after treatment). In the indifferentiated gonad to the juvenile stage, the differentiation of the ovary occured at 60 days after hatching (20 days after treatment) and that of the testis occured at 70 days after hatching (30 days after treatment) in two groups. In the ovary, the oogonia and ovarian lamellar appeared 130 days after hatching (50 days after treatment). The spermatogonia and resticular lobule of the testis were observed at 130 days after hatching (50 days after treatment). Testicular cyst appeared 140 days after hatching (60 days After treatment). There was no difference on the development of ovary and testis. There was no obvious difference of sex ratios. Therefore, These results considerate that PCBs have any effect for growth and gonadal development, but a little act for early growth in olive flounder.

• Journal of fish pathology
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• v.19 no.3
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• pp.277-284
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• 2006

Application of wood vinegar in fish farms has been used for the disinfection of pathogenic microorganisms and the treatment of infectious diseases. This study was performed to know the acute toxicity of wood vinegar to carp Cyprinus carpio, flounder Paralichyhus olivaceus, rock fish Sebastes schlegeli and black sea bream Pagrus major. The 24 hr, 48 hr and 96 hr LC50 respectively were: carp 1243, 1143 and 1016 ppm; flounder 1397, 1253 and 1226 ppm; rock fish 1058, 993 and 967 ppm; and black sea bream 650, 616 and 596 ppm. Death and survival of fish exposed to lethal concentrations of wood vinegar were apparently related to massive necrosis, fusion and epithelial lifting of gill lamellar epithelium, suggesting the osmotic imbalance and lack of oxygen uptake.

• Journal of the Korean Society for Heat Treatment
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• v.27 no.1
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• pp.15-22
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• 2014

This study is to investigate the phase changes and cold workability after isothermal transformation at $780^{\circ}C$ by using the high temperature gas nitrided (HTGN) STS 430 ferritic stainless steel specimens. The phase diagram of STS 430 steel obtained by calculation showed that the phase appeared at $1100^{\circ}C$ showed as ${\alpha}+{\gamma}{\rightarrow}{\gamma}{\rightarrow}{\gamma}+Cr_2N{\rightarrow}{\gamma}+Cr_2N+CrN$ with increasing nitrogen concentration. Also, the transformation of ${\gamma}{\rightarrow}Cr_2N$ during heat treatment isothermally at $780^{\circ}C$, nitrogen pearlite with lamellar type was fully formed at the nitrogen permated surface layer for 10 hrs. However, this transformation was not completed for 1 hr, resulting nitrogen pearlite plus martensite. The cold rolled specimen of isothermally transformed at $780^{\circ}C$ for 10 hrs after high temperature gas nitriding decreased the layer thickness of nitrogen pearlite inducing the deformation of hard $Cr_2N$ phase. the dissolution rate of $Cr_2N$ phase increased rapidly with increasing cold rolling ratio. Specimens with the microstructure of nitrogen pearlite (isothermally transformed at $780^{\circ}C$ for 10 hrs) were possible to cold rolling without crack formation. However, the mixed structures of nitrogen pearlite + martensite (isothermally transformed at $780^{\circ}C$ for 1 hr) were impossible to cold deformation without cracking.

• Journal of Powder Materials
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• v.26 no.6
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• pp.471-476
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• 2019

Additively manufactured metallic components contain high surface roughness values, which lead to unsatisfactory high cycle fatigue resistance. In this study, high cycle fatigue properties of selective laser melted Ti-6Al-4V alloy are investigated and the effect of dry-electropolishing, which does not cause weight loss, on the fatigue resistance is also examined. To reduce the internal defect in the as-built Ti-6Al-4V, first, hot isostatic pressing (HIP) is conducted. Then, to improve the mechanical properties, solution treatment and aging are also implemented. Selective laser melting (SLM)-built Ti64 shows a primary α and secondary α+β lamellar structure. The sizes of secondary α and β are approximately 2 ㎛ and 100 nm, respectively. On the other hand, surface roughness Ra values of before and after dry-electropolishing are 6.21 ㎛ and 3.15 ㎛, respectively. This means that dry-electropolishing is effective in decreasing the surface roughness of selective laser melted Ti-6Al-4V alloy. The comparison of high cycle fatigue properties between before and after dry-electropolished samples shows that reduced surface roughness improves the fatigue limit from 150 MPa to 170 MPa. Correlations between surface roughness and high cycle fatigue properties are also discussed based on these findings.

• Journal of Pharmaceutical Investigation
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• v.32 no.3
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• pp.165-172
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• 2002

Injectable gel composed of egg phosphatidylcholine (egg PC), hyaluronate (HA) and water was formulated for local drug delivery. The lamellar liquid crystalline structure of the egg PC/water system did not change by adding HA in the formulation. However, egg PC/HA/water gel was more resistant to erosion than the egg PC/water gel. The egg PC/HA/water and egg PC/water gels containing model drugs, tetracycline and sudan IV were prepared to perform in vitro and in vivo drug release experiments. In vitro release of tetracycline was sustained in the gel type formulations. The release rate of hydrophobic sudan IV was extremely slow. More than 99% of sudan IV remained inside the gel after 5 days. In vivo release of drugs from the air pouch model in Balb/c mice shows that lipophilic sudan IV remained for more than 10 days whereas tetracycline remained for 1 day in the pouch. The compatibility of the gels was also examined by histopathology. The gels did not cause any adverse inflammatory effect in the air pouch.

• Journal of Powder Materials
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• v.23 no.3
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• pp.207-212
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• 2016

In this study, Fe-Cu-Ni-Mo-C low alloy steel powder is consolidated by spark plasma sintering (SPS) process. The internal structure and the surface fracture behavior are studied using field-emission scanning electron microscopy and optical microscopy techniques. The bulk samples are polished and etched in order to observe the internal structure. The sample sintered at $900^{\circ}C$ with holding time of 10 minutes achieves nearly full density of 98.9% while the density of the as-received conventionally sintered product is 90.3%. The fracture microstructures indicate that the sample prepared at $900^{\circ}C$ by the SPS process is hard to break out because of the presence of both grain boundaries and internal particle fractures. Moreover, the lamellar pearlite structure is also observed in this sample. The samples sintered at 1000 and $1100^{\circ}C$ exhibit a large number of tiny particles and pores due to the melting of Cu and aggregation of the alloy elements during the SPS process. The highest hardness value of 296.52 HV is observed for the sample sintered at $900^{\circ}C$ with holding time of 10 minutes.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.46 no.6
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• pp.923-929
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• 2013

Black seabream juveniles Acanthopagrus schlegelii held at $20^{\circ}C$ were exposed to formalin at concentrations of 50 to 400 ppm, and tolerance values were determined by calculating median lethal concentration values (LC50) through probit analysis. The 12-, 24, 48, 72- and 96-h LC50 values for formalin were 297, 233, 171, 162 and 157 ppm, respectively. The histological effects of formalin on gill and liver tissues in this fish were determined. No histological effects were observed in the control group. The intensity of cell damage increased with the concentration of, and duration of exposure to, formalin. Hyperplasia, separation and epithelial necrosis, epithelial lifting, lamellar synechiae and collapsed lamellae were observed in gill tissues exposed to formalin. Hepatic lesions in liver tissues of fishes exposed to formalin were characterized by cloudy swelling of hepatocytes, necrosis, cytoplasmic vacuolization, deposition of pigments, spongiosis hepatis, nuclear hypertrophy, dilation of sinusoids and bile stagnation. The LC50 values and histological results obtained in this study will aid in designing treatment regimens to minimize toxic side effects and increase efficacy.