Extensive research on students’ understanding of science has documented persistent shortfalls at all ages. One way to account for students’ difficulties is to consider the particular challenges posed by individual science concepts. This article offers an alternative view. We argue that students’ difficulties in large part reflect unfamiliarity with a small number of causal modeling styles chara...

Deep-water drilling in the Gulf of Mexico could resume within weeks under a policy by the US government, which has come under increasing criticism from the oil industry and politicians in the region over the impact of the drilling halt and worries from scientists that the full impact has not yet been assessed. Oil and gas exploration in the gulf’s deep waters has been stopped since May, when Ob...

whether fasting and changes in diet might be changing leptin levels, thus altering the function of T cells. The implication of this new work is that leptin drives the activity of pro-inflammatory, self-reactive T cells, and that starvation, which reduces leptin production, changes the pattern of cytokines generated and the disease-inducing potential of the T cells. So, the authors show that ins...

Most of the alarming data about temperature rises as a result of likely climate change have come from high latitudes and altitudes. There appears growing evidence that glaciers and ice sheets are melting rapidly. The latest evidence comes from comparisons of pictures in the Andes reported last month which show that the Upsala glacier in Argentina has melted substantially, creating a lake where ...

It is proved that a triangulation of a polyhedron can always be transformed into any other triangulation of the polyhedron using only elementary moves. One consequence is that an additive function (valuation) defined only on simplices may always be extended to an additive function on all polyhedra. 2000 AMS subject classification: 52B45; 52A38; 57Q15;