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ABSTRACT: This study investigated the potential adverse effects of amitraz on the initiation and maintenance of pregnancy in Sprague-Dawley rats as well as its effects on embryo-fetal development after maternal exposure during the entire pregnancy period. Amitraz was administered to pregnant rats by gavage from days 1 to 19 of gestation at dose levels of 0, 3, 10, and 30 mg/kg/day. All dams underwent a caesarean section on day 20 of gestation and their fetuses were examined for any external, visceral, and skeletal abnormalities. At 30 mg/kg, maternal toxicity manifested as an increase in the incidence of abnormal clinical signs and a lower body weight gain and food intake. Developmental toxicity included an increase in the fetal death rate, a decrease in the litter size, and a reduction in the fetal body weight. In addition, there was an increase in the incidence of fetal external, visceral, and skeletal abnormalities. At 10 mg/kg, maternal toxicity observed included a decrease in the body weight gain and a decrease in food intake. In addition, minimal developmental toxicity, including a decrease in the fetal body weight, an increase in the visceral and skeletal aberrations, and a delay in fetal ossification. There were no signs of either maternal toxicity or developmental toxicity at 3 mg/kg. These results show that amitraz administered during the entire pregnancy period in rats is embryotoxic and teratogenic at the maternally toxic dose (i.e., 30 mg/kg/day) and is minimally embryotoxic at a minimally maternally toxic dose (i.e., 10 mg/kg/day). Under these experimental conditions, the no-observed-adverse-effect level of amitraz for both dams and embryo-fetal development is estimated to be 3 mg/kg/day.
Archives of Environmental Contamination and Toxicology 02/2007; 52(1):137-44. · 1.93 Impact Factor
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ABSTRACT: This study was carried out to investigate the potential subchronic inhalation toxicity of dimethyl disulfide (DMDS) via whole-body exposure in F344 rats. Groups of 10 rats of each sex were exposed to DMDS vapor by whole-body exposure at concentrations of 0, 5, 25, or 125 ppm for 6 h/day, 5 days/wk for 13 wk. All the rats were sacrificed at the end of treatment period. During the test period, clinical signs, mortality, body weights, food consumption, ophthalmoscopy, urinalysis, hematology, serum biochemistry, gross findings, organ weights, and histopathology were examined. At 25 ppm, a decrease in the body weight gain, food intake, aspartate aminotransferase (AST), alanine aminotransferase (ALT), and blood urea nitrogen (BUN) was observed in the males, but not in the females. However, at 125 ppm, a decrease in the body weight gain, food intake, and thymus weight and an increase in the weights of adrenal glands were observed in both genders. Serum biochemical investigations revealed a decrease in the AST, ALT, BUN, creatine phosphokinase (CPK), and triglyceride levels and an increase in the glucose level. In contrast, no treatment-related effects were observed in the 5 ppm group. The toxic potency of DMDS was slightly higher in males than that in females. In these experimental conditions, the target organ was not determined in rats. The no-observed-adverse-effect concentration (NOAEC) was found to be 5 ppm, 6 h/day for male rats and 25 ppm, 6 h/day for female rats.
Inhalation Toxicology 06/2006; 18(5):395-403. · 1.92 Impact Factor
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ABSTRACT: Gas/steam combined cycle has already become a well-known and substantial technology for power gener-ation due to its numerous advantages including high efficiency and low environmental emission. Many studies have been carried out for better performance and safe and reliable operation of combined-cycle power plants. A power plant is basically operated on its design conditions. However, it also operates on the so called off-design conditions due to the variation in a power load, process requirements, or operating mode. Therefore, the transient behavior of the system should be well-known for the safe operation and reliable control. In this study, dynamic simulation is performed to analyze the transient behavior of a combined-cycle power plant. Each component of the power plant system is mathematically modeled and then integrated into the unsteady form of conservation equations. Transient behavior was simulated when rapid changes and periodic oscillations of the gas turbine load are imposed. Time delay characteristic caused by the thermal and fluid damping is analyzed and overall time-response of the combined power plant system is shown.
Energy 01/2002; 27:1085-1098. · 3.49 Impact Factor
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ABSTRACT: An analytical characterization of the heat transfer in an oscillating flow through a porous medium is presented in this work. Based on a two-equation model, two important dimensionless parameters are identified as the ratio of the thermal capacities between the solid and fluid phases and the ratio of the interstitial heat conductance between the phases to the fluid thermal capacity. The analytic solutions are obtained for both the fluid and solid temperature variations, and the heat transfer characteristics between the phases are classified into four regimes. In addition, a criterion for the validity of the local thermal equilibrium is suggested in a simple form as the ratio of the two time scales intrinsically involved in any transient heat transfer in porous media, namely the time scale relevant to the thermal inertia of porous media and the time scale pertinent to the transient variation of the boundary condition.
International Journal of Heat and Mass Transfer.
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ABSTRACT: Gas/steam combined cycle has already become a well-known and substantial technology for power generation due to its numerous advantages including high efficiency and low environmental emission. Many studies have been carried out for better performance and safe and reliable operation of combined-cycle power plants. A power plant is basically operated on its design conditions. However, it also operates on the so called off-design conditions due to the variation in a power load, process requirements, or operating mode. Therefore, the transient behavior of the system should be well-known for the safe operation and reliable control. In this study, dynamic simulation is performed to analyze the transient behavior of a combined-cycle power plant. Each component of the power plant system is mathematically modeled and then integrated into the unsteady form of conservation equations. Transient behavior was simulated when rapid changes and periodic oscillations of the gas turbine load are imposed. Time delay characteristic caused by the thermal and fluid damping is analyzed and overall time-response of the combined power plant system is shown.
Energy.
