We survey known results and propose open problems on the biplanar crossing number. We study biplanar crossing numbers of speci c families of graphs, in particular, of complete bipartite graphs. We nd a few particular exact values and give general lower and upper bounds for the biplanar crossing number. We nd the exact biplanar crossing number of K5;q for every q.

The syntactic structure of a sentence can be modelled as a tree, where vertices correspond to words and edges indicate syntactic dependencies. It has been claimed recurrently that the number of edge crossings in real sentences is small. However, a baseline or null hypothesis has been lacking. Here we quantify the amount of crossings of real sentences and compare it to the predictions of a serie...

In Crossing the Quality Chasm: A New Health System for the 21st Century, the Institute of Medicine proposes 6 specific aims to improve the quality of care in the United States.1 These specific aims are to provide care that is safe, effective, timely, efficient, equitable, and patient centered. Of these goals, patient-centered care has received the least attention from both the scientific commun...