Effect of silicon infiltration on the bend and tensile strength of 2D cross-ply carbon-carbon composites are studied. It is observed that bend strength higher than tensile strength in both types of composite is due to the different mode of fracture and loading direction. After silicon infiltrations bend and tensile strength suddenly decreases of carbon-carbon composites. This is due to the fact that, after silicon infiltration, silicon in the immediate vicinity of carbon forms the strong bond between carbon and silicon by formation silicon carbide and un-reacted silicon as free silicon. Therefore, these composites consist of three components carbon, silicon carbide and silicon. Due to mismatch between these three components secondary cracks developed and these cracks propagate from 90˚ oriented plies to 0˚ oriented plies by damaging the fibers (i.e., in-situ fiber damages). Hence, secondary cracks and in-situ fiber damages are responsible for degradation of mechanical properties of carbon-carbon composites after silicon infiltration which is revealed by microstructure investigation study by scanning electron microscope.

Performance of carbon-carbon composites is known to be influenced by the fibre matrix interactions. The present investigation was undertaken to ascertain the development of microstructure in such composites when carbon fibres possessing different surface energies (T-300, HM-35, P120 and Dialed 1370) and pitch matrices with different characteristics (Coal tar pitch SP110℃ and mesophase pitch SP285℃) are used as precursor materials. These composites were subjected to two different heat treatment temperatures of 1000℃ and 2600℃. Quite interesting changes in the crystalline parameters as well as the matrix microstructure are observed and attempt has been made to correlate these observations with the fibre matrix interactions.

Molecular genetic markers were genotyped used to detect chromosomal regions which contain economically important traits such as growth traits in pigs. Three generation resource population was constructed from a cross between the Korean native boars and Landrace sows. A total of 193 F2 animals from intercross of F1 were produced. Phenotypic data on 7 traits, birth weight, body weight at 3, 5, 12, 30 weeks of age, live empty weight were collected for F2 animals. Animals including grandparents (F0), parents (F1), offspring (F2) were genotyped for 194 microsatellite markers covering from chromosome 1 to 18. Quantitative trait locus analyses were performed using interval mapping by regression under line-cross model. To characterize presence of imprinting, genetic full model in which dominance, additive and imprinting effect were included was fitted in this analysis. Significance thresholds were determined by permutation test. Using imprinting full model, four QTL with expression of imprinted effect were detected at 5% chromosome-wide significance level for growth traits on chromosome 1, 5, 7, 13, 14, and 16.

This study was carried out to evaluate the effects of glucose and sodium phosphate on in vitro development of porcine oocytes matured and fertilized in vitro. When the culture medium was supplemented with various concentrations of glucose, the higher proportions (23 and 26%) of oocytes developed to morular or blastocyst stages were at the concentrations of 2.78 and 5.56 mM than 0 (9%; P<0.05) and 11.12 mM (18%). In experiment to evaluate effect of sodium phosphate during in vitro development of porcine oocytes, a significantly (P<0.05) higher proportions of embryos developed to morular or blastocyst stages was obtained with sodium phosphateof 0.28 (25%) and 0.53 (27％) mM than 0 (15%), 1.05 (19%) and 2.10 (10%) mM. On the other hand, when oocytes were cultured in medium with (0.53 mM) sodium phosphate, the proportions of developed embryos were significantly (P<0.05) higher in medium without (29%) that than with (14%) 5.56 mM glucose. However, a higher proportion of embryos developed to morular or blastocyst stages were obtained in medium with (23%) that than without (8%) glucose (P<0.05). The minimum essential medium (MEM) added to the culture medium were higher regardless of presence of sodium phosphate and glucose on the development of embryos. Although sodium phosphate and glucose could support morular and blastocyst development to a limited extend (10∼24%), significantly higher proportion (36%) at morular or blastocyst stages was obtained by MEM adding in the medium with sodium phosphate and glucose. These results suggest that the early development of in vitro fertilized porcine oocytes can be maintained efficiently by glucose and sodium phosphate when they were cultured in medium with MEM.

Silver nitrate (AgNO3) powder was mixed into a reformed pitch precursor. Then, the silver-containing pitch was melt spun to form round and "C" shape fibers. A wire mesh was inserted prior to the nozzle to improve the spinnability of the silvercontaining precursor pitch. Silver particles in the carbon fibers (CFs) were detected by XRD and TEM. These tests showed that silver particles were uniformly distributed and the total amount of silver remained constant during stabilization and carbonization. Next, the silver-containing CFs were activated by steam diluted in nitrogen gas. Silver particles accelerated the activation rate, but the specific surface areas of the silver-containing ACFs were similar to those of non-silver containing ACFs at the same burn-off levels. The specific surface area of the C-shaped activated carbon fibers was larger than that of the round activated carbon fibers. The likely reason is that the surface area of a C-shaped CF is about two times larger than that of a round CF when equivalent cross-sectional areas are compared. A small amount of silver particles in the periphery of the CFs was removed during the activation, but the remainder of silver was stayed within the ACFs.

The purpose of this study was to investigate the development of bovine nuclear transfer (NT) embryos cultured in serum-free conditions. Bovine NT embryos cultured in various culture conditions were compared blastocyst development, total cell number and apoptosis using TUNEL assay. In experiment 1, blastocyst rates of NT embryos were significantly higher (P<0.01) in FBS (22.0％) and BSA (26.6％) groups than in PVA (6.3％) group. Total cell number was significantly higher in FBS (78.4±19.4) and BSA (90.9±29.1) groups than in PVA group (46.0±0.0). Apoptotic cell number was significantly fewer in FBS (3.1±1.4) and BSA (1.7±1.4) groups than in PVA group (7.0±20.0) However, all of results were not different between the FBS and BSA group. In experiment 2, blastocyst rates of NT embryos were significantly higher (P<0.05) in fatty acid free-BSA (FAF-BSA) group (26.8％) than in fraction V-BSA group (11.2％). Total cell number were somewhat higher in FAF-BSA group (89.8±30.7) than in fraction V-BSA group (88.1±19.3). Apoptotic cell number were somewhat fewer in FAF-BSA (1.7±1.5) group than in fraction V-BSA group (4.2±2.9). These findings suggest that serum free condition were effective for the in vitro development of bovine NT embryos. Therefore, we concluded that fatty acid free-BSA has beneficial effect in development bovine NT embryos and can be use as a serum substitute.

This study was carried out to investigate the effect of cysteamine addition during in vitro maturation, fertilization and culture of porcine oocytes. Oocytes were matured for the first 22 h in mTCM -199 media supplemented with or without 150 μM cysteamine. They then were matured for an additional 22 h in mTCM-199 media without hormones supplemented with or without 150 μM cysteamine. When cumulus-oocyte complexes (COCs) were matured in the mTCM-199 media supplemented with cysteamine, the rates of GVBD and maturation (metaphase Ⅱ) were enhanced as compared to the media without the addition of cysteamine. Also, when COCs were matured in the mTCM-199 media supplemented with cysteamine, the rates of sperm penetration, male pronucleus formation, cleavage and blastocyst formation after in vitro fertilization were enhanced as compared to the media without the addition of cysteamine. In conclusion, it was suggested that oocytes matured for the first 22 h in mTCM-199 media supplemented with 150 μM cysteamine increased the rates of metaphase Ⅱ, sperm penetration, male pronucleus and blastocyst formation were higher as compared to the media without addition of cysteamine.