Survival analysis of germination data in response to temperature for Ornithopus species and other temperate pasture legumes.

Cool temperatures can limit productivity of temperate grazing systems as poor pasture growth rates in winter create feed shortages for livestock. Ornithopus spp. (serradella) are broadly adapted annual pasture legumes that produce high-quality forage in soil types considered marginal for other temperate legume species. However, serradella establishment is perceived to be difficult in cool-season environments. We used survival analysis to compare germination rate and seedling emergence for two serradella species (yellow serradella and French serradella) against three reference species (Medicago sativa, M. polymorpha and Trifolium subterraneum ) in four temperature treatments (10/5, 15/10, 20/15 and 25/20°C; max/min). We also compared shoot relative growth rate and photosynthetic rate at 15/10°C (cool) and 23/18°C (warm). Cool temperatures (10/5, 15/10°C) did not slow germination rates for serradella relative to the reference species, but warm temperatures (20/15, 25/20°C) delayed emergence and reduced post-emergent shoot growth rates. Once established, Ornithopus spp. had similar mean photosynthetic rates and stomatal conductance at cool temperatures to the reference species. We conclude that, contrary to common perception, cool temperatures did not adversely influence germination, emergence, or early growth of Ornithopus spp. relative to the reference species.

The chaotic obliquity of Mars.

Numerical integration of the rotation of Mars shows that the obliquity of Mars undergoes large chaotic variations. These variations occur as the system evolves in the chaotic zone associated with a secular spin-orbit resonance.

Numerical evidence that the motion of pluto is chaotic.

The Digital Orrery has been used to perform an integration of the motion of the outer planets for 845 million years. This integration indicates that the long-term motion of the planet Pluto is chaotic. Nearby trajectories diverge exponentially with an e-folding time of only about 20 million years.

Chaotic evolution of the solar system.

The evolution of the entire planetary system has been numerically integrated for a time span of nearly 100 million years. This calculation confirms that the evolution of the solar system as a whole is chaotic, with a time scale of exponential divergence of about 4 million years. Additional numerical experiments indicate that the Jovian planet subsystem is chaotic, although some small variations in the model can yield quasiperiodic motion. The motion of Pluto is independently and robustly chaotic.

Simple Dynamical Models of Neptune's Great Dark Spot.

The large amplitude oscillations of the shape of Neptune's Great Dark Spot are well reproduced by simple dynamical models of an isolated vortex embedded in a background shear flow. From the time series of the aspect ratio and inclination of the vortex values are estimated for the background shear and the mean vorticity of the Great Dark Spot, and a lower bound is placed on the value of the Rossby deformation radius. These models imply the existence of a planetary-scale zone of deterministic chaotic advection in the atmosphere of Neptune.

Studies on the pathogenesis of hemorrhagic enteritis of turkeys.

The infectivity of turkey hemorrhagic enteritis (HE) virus was studied in poults with no detectable maternal antibody and in turkeys bursectomized or injected with killed-virus preparations. Poults less than three weeks old were not infected by hemorrhagic enteritis virus, and survivors were susceptible to challenge at the age of eight weeks. Three- and four-week-old poults were susceptible to HE, and survivors resisted challenge. Bursectomy partially interfered with the immune response but did not alter the course of the disease, and survivors were resistant to challenge. Injections of spleen suspension containing 1% formalin produced antibody in only two of six turkeys. Three of the four poults without detectable antibody resisted challenge.

Cassini observes the active south pole of Enceladus.

Cassini has identified a geologically active province at the south pole of Saturn's moon Enceladus. In images acquired by the Imaging Science Subsystem (ISS), this region is circumscribed by a chain of folded ridges and troughs at approximately 55 degrees S latitude. The terrain southward of this boundary is distinguished by its albedo and color contrasts, elevated temperatures, extreme geologic youth, and narrow tectonic rifts that exhibit coarse-grained ice and coincide with the hottest temperatures measured in the region. Jets of fine icy particles that supply Saturn's E ring emanate from this province, carried aloft by water vapor probably venting from subsurface reservoirs of liquid water. The shape of Enceladus suggests a possible intense heating epoch in the past by capture into a 1:4 secondary spin/orbit resonance.