Interesting paper newly relevant with DI and soot. If it has been posted before, I apologize.
http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.922.299&rep=rep1&type=pdf
http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.922.299&rep=rep1&type=pdf