No abstract

The objectives of this study were to evaluate the myogenic behavior of blood vessels and their interaction within the coronary arterial tree and to evaluate the possible role of the myogenic response in autoregulation. The model consists of 10 compartments in series, each representing a class of vessel sizes. Diameter and resistance in each class are determined by their value at full dilation (d(p,) R(p)) and by the myogenic response. Three distributions of R(p) and three distributions of myogenic strength, M(i) (slope of pressure-diameter curve, range -0.05 to -0.4%/mmHg) were evaluated (9 cases). It was found that larger vessels attenuate the myogenic activity of smaller vessels and that myogenic responsiveness is sufficient to achieve autoregulation. When M(i) has a maximum in vessels of 84 microm, the maximum effect of perfusion pressure on active diameter occurs in vessels between 123 and 181 microm, depending on the distribution of R(p). Distribution of resistance and control mechanisms in the coronary arterial tree are important for interpretation of individual vessel responses as observed in vivo.

No abstract

The tunnel-in-the-sky display is a possible candidate to become the primary flight display of future aircraft cockpits. To understand pilot manual control behaviour with a perspective tunnel display, and to incorporate this understanding in display design, it is essential to investigate the manner in which pilots use the spatial information conveyed by the display. A theoretical information-centered analysis has been conducted to study the effectiveness of the optical cues mediated by the display in straight tunnel sections. This analysis revealed that in straight tunnel sections the gradients of perspective and compression, in conjunction with novel concepts as the infinity point and the pseudo-horizons, are extremely useful in understanding pilot behaviour. An experiment provided substantial evidence for the pre-experimental analysis following the information-centered approach.