Thank you. These matrices cover wide spectrum of domains (such as structural engineering, computational fluid dynamics, model reduction, electromagnetics and so forth). They are available as a public data set on Amazon cloud: http://aws.amazon.com/datasets/2379?_encoding=UTF8&jiveR...

As for not connected dots - it might be a bug in my transformation code, but more likely they are just isolated components of the graph. E.g. http://www.yasiv.com/graphs#HB/bcsstm26 - big bang :)