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.

Reinforced matrices for pin-amalgam restorations reduce microleakage.

The considerable decrease in microkeakage in the compound-reinforced restorations may be due to the tighter fit of the matrix band at the gingival wall of the preparation, which allows better condensation and marginal sealing of the restoration. The compound prevents lateral migration of the band during condensation pressures.

The effect of deviations from stereotyped expectations upon attitudes toward older persons.

Subjects read an interview in which either a 36-year-old or a 76-year-old widow talked about her life and discussed how she had spent the previous day; they then recorded their impressions of the woman and rated her on a number of scales. Contrary to expectations, subjects rated the older woman significantly more favorably than the younger woman, even when her behavior corresponded to negative stereotypes of older person. Evidence from subjects' written impressions and spontaneous comments indicated that an older person who is alert, interesting, and involved is perceived as deviating from stereotyped expectations and is evaluated more positively than a younger person who exhibits these same characteristics.

NRL-ATM extreme ultraviolet solar image TV monitor flown on Skylab.

An instrument for recording extreme ultraviolet television images of the sun was flown in the Apollo Telescope Mount on Skylab. Solar radiation in the 171-630 A wavelength range, defined by the transmission band of three thin-film aluminum filters, was focused onto a p-quaterphenyl photon conversion layer by a platinum-coated mirror at normal incidence. The conversion layer was attached to the faceplate of a low light level SEC vidicon.

The influence of proximal retention grooves on the retention and resistance of class II preparations for amalgams.

The addition of proximal retention grooves to various designs of the Class II cavity preparation considerably improves the retention and resistance characteristics of amalgam restorations. The incorporation of proximal grooves should reduce the necessity for gross outline form as a means of gaining adequate retention adn resistance in the Class II preparation.