Vessel walls mechanical models

The mechanism for heat transfer includes the following steps (1) conduction in the catalyst particle (2) convection from the particle to the gas phase (3) conduction at contact points between particles (4) convection between the gas and vessel wall (5) radiation heat transfer between the particles, the gas, and the vessel wall (6) conduction in the wall and (7) convection to the coolant. There are a number of ways, through reactor models, that these steps are correlated to provide design and analysis estimates and criteria for preventing runaway in exothermic reactors. 

Rote et al. (1993, 1994) used a carotid thrombosis model in dogs. A calibrated electromagnetic flow meter was placed on each common carotid artery proximal to both the point of insertion of an intravascular electrode and a mechanical constrictor. The external constrictor was adjusted with a screw until the pulsatile flow pattern decreased by 25 % without altering the mean blood flow. Electrolytic injury to the intimal surface was accomplished with the use of an intravascular electrode composed of a Teflon-insulated silver-coated copper wire connected to the positive pole of a 9-V nickel-cadmium battery in series with a 250000 ohm variable resistor. The cathode was connected to a subcutaneous site. Injury was initiated in the right carotid artery by application of a 150 xA continuous pulse anodal direct current to the intimal surface of the vessel for a maximum duration of 3 h or for 30 min beyond the time of complete vessel occlusion as determined by the blood flow recording. Upon completion of the study on the right carotid, the procedure for induction of vessel wall injury was repeated on the left carotid artery after administration of the test drug. 

In conclusion, this section has highlighted the potential pathogenic contribution of blood neutrophils to the CNS injury that accompanies the ischaemia-reperfusion injury of stroke. From experimental models of this disorder, it appears that the second wave of tissue damage is induced either by neutrophil-mediated vasoocclusion or by the infiltration of neutrophils into the ischaemic tissue with concomitant release of lytic factors. Antagonising both neutrophil attachment to endothelium and the transendothelial migration of these cells at the level of the blood-brain barrier is likely to be of clinical benefit to cerebral ischaemia-reperfusion injury. Consequently, it is anticipated that a further unravelling of the mechanisms that promote neutrophil interaction with cerebral vessel walls will lead to the introduction of a more specific therapeutic intervention for the treatment of stroke. 

It is fair to say that there is no universal agreement between those who champion either Bayesian or conventional probability theory. Indeed, as a bystander, one can find it interesting to watch the tussle. Conventional probability theory is very successful at modeling situations with large numbers of random events (e.g., the pressure in a vessel resulting fi om gas molecules colliding with the vessel walls). Indeed, statistical mechanics is based on conventional probability theory. On the other hand, Bayesian approaches seem to be more successful when the number of random events is smaller, and where there is insufficient information available. 

Purely electrical models of the heart are only a start. Combined electromechanical finite-element models of the heart take into account the close relationship that exists between the electrical and mechanical properties of individual heart cells. The mechanical operation of the heart is also influenced by the fluid-structure interactions between the blood and the blood vessels, heart walls, and valves. All of these interactions would need to be included in a complete description of heart contraction. 

Other problems may arise if the modeler s objective is to explain or predict the results of an "applications level" experiment (one involving a relatively complex system) that is carried out in the field or, more commonly, the laboratory. First, the conditions assumed to prevail in the experiment may not be the actual ones. For example, the experiment may be thought to be a closed system, when in fact there is loss or gain of volatiles such as carbon dioxide. For another, the walls of the experimental vessel may be thought to be not a factor in the course of reaction when in fact they are via such mechanisms as diffusive absorption or corrosion. 

Regirer S.A. and Shadrina N. A simple model of a vessel with a wall sensitive to mechanical stimuli. Biophysics 47 845 50,2002. 

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