Effect of simulated microgravity on aged pea seed vigour and related physiological properties.

We used simulated microgravity to treat aged pea seeds, in order to observe its effect on seed vigour and related physiological properties. The result shows that microgravity obviously promotes the germination rate, vitality index, germination index, and keeps the activity of protective enzyme, with conductivity and the content of MDA decreased. These effects gradually disappeared for a certain period after the microgravity administration.

[A digital simulation study on the effect of change in cardiovascular system parameters on the pulse waveform of the radial artery].

OBJECTIVE: To understand the effect of the change in cardiovascular system parameters on the pressure pulse waveform of the radial artery. METHOD: A previously developed cardiovascular system mathematical model was used in this simulation study. The parameters used were heart rate, ventricular contractility, arterial compliance, peripheral resistance and blood viscosity. RESULT: The change in each parameter would influence the pulse waveform. Most of the influences were in agreement with the results of clinical observations reported in the literature. However, several new phenomena were observed. The effect of change in single parameter on the pulse waveform was different for different combinations of other parameter values. CONCLUSION: It is suggested that the model is useful in studying the relationship between cardiovascular system parameters and pulse waveform of the radial artery.

Wall shear stress distribution in a model human aortic arch: assessment by an electrochemical technique.

Wall shear stress (WSS) distribution in a human aortic arch model is studied using 130 cathode electrodes flush-mounted on the model walls. Flow visualizations are made in a transparent geometry model to identify the regions of fluid mechanical interests, e.g. regions of flow separation, eddy formation and flow stagnancy. The 130 electrodes are strategically positioned in the arch based on information obtained from the flow visualizations. The measured data indicate that the aortic arch may be categorized into eight regions: three along the inner wall of the arch (A,B,C); and five near the outer wall (D,E,F,G,H). (1) The regions of low WSS are distributed along the inner wall of the ascending aorta A; the inner wall of the descending aorta C; and the upstream inner wall of the innominate and the common carotid branchings F. (2) The high WSS regions are distributed along the outer wall of the arch E; and the inner wall in the arch opposite to the left subclavian branching B. (3) In certain regions, high and low WSS may be found next to each other (e.g. G and H) without a definable boundary in between; and (4) as the Reynolds number increases, the areas of low WSS decrease, while the high WSS areas increase with no obvious change in magnitude of the stress along the inner wall of the arch. At the branchings, the WSS distribution is not affected by the Reynolds number within the range of observations. The measured WSS distribution is compared with Rodkiewicz's map of early atherosclerotic lesions in the aortic arch of cholesterol fed rabbits.