In this paper, a two-phase model of air shock wave induced by rock-fall was described. The model was made up of the uniform motion phase (velocity was close to 0 m·s-1) and the acceleration movement phase. The uniform motion phase was determined by experience, meanwhile the acceleration movement phase was derived by the theoretical analysis.A series of experiments were performed to verify the t...

Little is known about the effects of hyperoxia on the cerebral circulation of human infants. Using duplex Doppler we measured the changes in cerebral blood flow velocity in a group of full term (n = 15) and premature infants (n = 17, median gestational age 31 weeks) in response to a transient threefold increase in oxygen tension. Measurements of blood gas tensions as well as blood pressure and ...

We previously reported that the probability of an older adult recovering from a forward trip and using a "lowering" strategy increases with decreased walking velocity and faster response time. To determine the within-subject interaction of these variables we asked three questions: (1) Is the body orientation at the time that the recovery foot is lowered to the ground ("tilt angle") critical for...

At least 280 000 hip fractures occur annually in the U.S. at an estimated cost of $9 billion. While over 90 percent of these are caused by falls, only about 2 percent of all falls result in hip fracture. Evidence suggests that the most important determinants of hip fracture risk during a fall are the body's impact velocity and configuration. Accordingly, protective responses for reducing impact...

Atmospheric ammonia concentrations were measured during fall 2001, winter, spring, and summer 2002 over natural surfaces in North Carolina where animal farms and waste storage and treatment lagoons (which are known to emit ammonia) at two heights (2 and 6m) above the surface employing an arrangement of two Thermo Environmental Instruments, Inc. Model 17C chemiluminescent nitrogen oxides (NOX)–a...