Runway reaction

We note two important features on this graph. First, the transition from stable to potentially runway conditions increases dramatically with decreasing e, that is, increasing the reaction constant activation energy in the limit at e — 0 we have explosive conditions. Second, the transition from stable to potentially unstable reactions occurs when the dimensionless at 0 = 7 / 1. Furthermore, for 0 = 10-1 the reaction is stable with 0/(1 + 0) = 1 and for >10 there are is a significant increase (of the order of 104 to 1010) in the dimensionless heat-generation term, denoting the potential of unstable, runway reactions. 

Evidence consistent with this conclusion has been recently obtained by Pecina et al. (2003) in the genetically-engineered DAT knockdown mice, who carry a subtotal reduction in the expression of DAT which results in an increased steady-state level of extracellular DA (Pecina et al., 2003). Compared to the wild-type mice, the knockdown mice show faster running for food in a straight runway and an increased food intake, which results in an increased body weight. This increased motivation for food was not the result of increased rewarding properties of food as estimated from the hedonic reactions to intraoral infusion of sucrose. These studies therefore are consistent with the idea that sweet reward is independent from DA and that DA plays a role in the incentive, rather than the rewarding properties of food. 

Runway reaction caused by excess hydrogenation and polymerization reaction Cold box under slight positive nitrogen pressure... 

An actual test to depict thermal runway reactions is in the plots often referred to as Semenov plots, as drawn in Fig. 3. The curved line represents the heat generation due to an exothermic reaction with exponential function assuming Arrhenius law, while the straight lines represent the heat removal which is a linear function with Newton s law of cooling at different coolant temperatures. The temperature of the coolant can be sufficiently low (case of line B) or insufficiendy, like in case C where thermal control is not possible under any circumstances. Line B has one tangent... 

Urea is widely used as an airport runway deicer, as it is not corrosive to aircraft materials. However, urea is generally not considered to be a viable alternative deicing chemical for highway applications. Reported limitations include higher application rates, longer reaction times, effectiveness only at temperatures above -10°C, relatively high cost, and significant adverse effects on the environment. ... 

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