Results regarding the pebbling number of various graphs are presented. We say a graph is of Class 0 if its pebbling number equals the number of its vertices. For diameter d we conjecture that every graph of su cient connectivity is of Class 0. We verify the conjecture for d = 2 by characterizing those diameter two graphs of Class 0, extending results of Pachter, Snevily and Voxman. In fact we u...

We survey results on the pebbling numbers of graphs as well as their historical connection with a number-theoretic question of Erdős and Lemke. We also present new results on two probabilistic pebbling considerations, first the random graph threshold for the property that the pebbling number of a graph equals its number of vertices, and second the pebbling threshold function for various natural...

Traditionally, models of complexity used in psychology have been based on probabilistic and algorithmic paradigms. While these models have inspired a great deal of research, they are generally opaque about the relationship between complexity and the cost of information processing. We argue that the psychological complexity is easily defined and quantified in terms of change and support this arg...

Cilia that sense orests of cilia wave fluids in desired directions. But recent excitement about primary cilia—which are unique in occurring at just one copy per cell— has focused on their possible signal trans-duction abilities. Now, on page 811, Iomini et al. have rediscovered primary cilia on endothelial cells and found that the growth of these cilia responds to outside signals. Buried in pap...