Physical constraints during Snowball Earth drive the evolution of multicellularity.

Molecular and fossil evidence suggests that complex eukaryotic multicellularity evolved during the late Neoproterozoic era, coincident with Snowball Earth glaciations, where ice sheets covered most of the globe. During this period, environmental conditions-such as seawater temperature and the availability of photosynthetically active light in the oceans-likely changed dramatically. Such changes would have had significant effects on both resource availability and optimal phenotypes.

An anomalous bond angle in 116H2. Theoretical evidence for supervalent hybridization.

The electronic structure and geometry of the superheavy group VI molecule (116)H(2) are examined and compared to those of the lighter group analogues H(2)O-PoH(2). The spin-orbit interaction is found to lengthen the (116)-H bond and more importantly lead to a modest but significant H-(116)-H bond angle increase. It is suggested that the latter is the result of a rehybridization of the valence 7p orbitals with a "supervalent" 8s orbital of element 116.

Regional changes in hemodynamics and cardiac myocyte size in rats with aortocaval fistulas. 1. Developing and established hypertrophy.

The effects of a large arteriovenous fistula on left and right ventricular hemodynamics and cardiac myocyte size were examined in adult rats at 1 week and 1 month after surgery. Cardiac output, left ventricular function, and right ventricular function were evaluated before obtaining isolated myocytes for cell size measurements. Average heart weight increased 35% at 1 week and 86% at 1 month in rats with fistulas.