Fixed and Distributed Gene Expression Time Delays in Reaction-Diffusion Systems.

Time delays, modelling the process of intracellular gene expression, have been shown to have important impacts on the dynamics of pattern formation in reaction-diffusion systems. In particular, past work has shown that such time delays can shrink the Turing space, thereby inhibiting patterns from forming across large ranges of parameters. Such delays can also increase the time taken for pattern formation even when Turing instabilities occur.

Osteoporosis and amenorrhea in young women.

Bone density of the radius was measured using both standard photon absorptiometry and X-ray computed tomography (CT) scanning, and of the femur using CT, in 21 young women with amenorrhea and estrogen deficiency due to hyperprolactinemia, 8 due to ovarian failure or weight loss, 17 postmenopausal women with bone fractures presumed to be due to osteoporosis, and 36 young normal controls. Bone density in the postmenopausal women was reduced by 18-20% in the radius and 11% in the femur (p less than 0.001).

An evaluation of the Meditech M250 and a comparison with other CT scanners.

The Meditech M250 computerised tomography (CT) machine was evaluated during the first half of 1984. Measurements were made of noise, modulation transfer function, slice width, radiation dose profile, uniformity and linearity of CT number, effective photon energy and parameters relating to machine specification, such as pixel size and scan time. All breakdowns were logged to indicate machine reliability.