RESUMEN
The crack self-healing behavior of high-performance steel-fiber reinforced cement composites (HPSFRCs) was investigated. High-strength deformed steel fibers were employed in a high strength mortar with very fine silica sand to decreasing the crack width by generating higher interfacial bond strength. The width of micro-cracks, strongly affected by the type of fiber and sand, clearly produced the effects on the self-healing behavior. The use of fine silica sand in HPSFRCs with high strength deformed steel fibers successfully led to rapid healing owing to very fine cracks with width less than 20 µm. The use of very fine silica sand instead of normal sand produced 17%-19% higher tensile strength and 51%-58% smaller width of micro-cracks.
RESUMEN
We have recently reported that the fluoroquinolone antibacterial DW-116 induces a significant developmental toxicity in rat. The present study was conducted to better understand the teratogenic effects of DW-116 at several developmental toxic doses in rats. DW-116 was orally administered to pregnant rats from gestational day (GD) 6 through 16 at dose levels of 0, 320, 400, and 500 mg/kg/day. All dams were subjected to caesarean section on GD 20 and their fetuses were examined for external, visceral, and skeletal abnormalities. At above 400 mg/kg, severe decreases in maternal body weight gain, food consumption, litter size, fetal weight and placental weight, and severe increases in resorption rate and fetal morphological alterations were observed. At 320 mg/kg, mild decreases in maternal body weight gain, food consumption, fetal weight and placental weight, and mild increases in fetal variations and retardations were observed. These results suggest that DW-116 is embryotoxic at above 320 mg/kg/day and is embryolethal and teratogenic at above 400 mg/kg in pregnant rats and that DW-116 is a selective developmental toxicant in rat conceptuses.