RESUMO
This paper examines the impact of meteorological conditions on the propagation of vehicular noise from urban freeways. A parabolic equation model coupled to an analytical Green's function solution close to the source field is used to compute the refracted sound field up to half a mile from the freeway to predict the noise exposure of residential areas nearby. The model was used in conjunction with meteorological and sound-level measurements taken at two freeway sites over the course of four days in Phoenix, AZ. From the data collected, three test cases of varying levels of atmospheric stratification and wind shear are presented and discussed. The model demonstrates that atmospheric effects are able to raise sound levels by 10-20 dB at significant distances away from the highway, causing violations of acceptable limits imposed by the Federal Highway Administration in residential areas that are normally in compliance.
RESUMO
Tall fescue (Festuca arundinacea Shreb) hay from a source known to cause "fescue foot" in grazing cattle was extracted with 80% ethanol. The ethanolic extract was further refined and fractionated into cation,nion, and neutral f fractions by ion-exchange chromatography. The cation fraction was partitioned with alkaline-chloroform to give chloroform-extractable cation and residual cation fractions. All fractions plus the crude ethanolic extract were assayed for toxic activity by intraperitoneal injection into 12 calves (weighting 152.4 to 241.3 kg each) over a 14-day period. Clinical signs of fescue foot were observed on the 5th day in calves given the anion and crude ethanolic extracts. Lameness, swelling, and reddening of the rear coronary bands, discoloration of the tip of the tail, and other signs of fescue foot were seen. Microscopically, coronary bands and tail tips of affected calves had blood vessels with thick walls and small lumens.
