A phenomenological model for hydrocarbon high-temperature autoignition

A four-step phenomenological chemical–kinetic model is presented that is believed to apply to many aspects of combustion of most hydrocarbons at temperatures above about 1000 K. The mechanism involves chain initiation through reactive collision of fuel and oxidizer molecules, fuel consumption in a step that removes radicals, oxidizer consumption in a step that produces radicals and a chain termination step. An expression for the autoignition time is derived on the basis of this model and is applied to describe the ignition of propane–air mixtures and a few other hydrocarbons. It is shown that excellent agreement with ignition times obtained from detailed chemistry can be achieved by this model.     

Direct observation of macroscopic charge quantization

The circuit formed by a nanoscale tunnel junction in series with a capacitance and a voltage source is the building block of most multi-junction circuits of single electronics. The state of this single electron box is entirely determined by the numbern of extra electrons on the intermediate island electrode between the junction and the capacitance. We have fabricated such a system and measured the charge on the junction capacitance, which is directly related to the average value ofn, as a function of the bias voltage using a Fulton-Dolan electrometer. At low temperature, the junction charge followed thee-periodic sawtooth function expected from the theory of macroscopic charge quantization. Strikingly,e-periodic variations were also observed when the box was superconducting. The thermal rounding of the sawtooth function is well explained by a simple model, except at the lowest temperatures.