Remote sensing of the magnetic moment of uranus: predictions for voyager

Power is supplied to a planet's magnetosphere from the kinetic energy of planetary spin and the energy flux of the impinging solar wind. A fraction of this power is available to drive numerous observable phenomena, such as polar auroras and planetary radio emissions. In this report our present understanding of these power transfer mechanisms is applied to Uranus to make specific predictions of the detectability of radio and auroral emissions by the planetary radio astronomy (PRA) and ultraviolet spectrometer (UVS) instruments aboard the Voyager spacecraft before its encounter with Uranus at the end of January 1986. The power available for these two phenomena is (among other factors) a function of the magnetic moment of Uranus. The date of earliest detectability also depends on whether the predominant power source for the magnetosphere is planetary spin or solar wind. The magnetic moment of Uranus is derived for each power source as a function of the date of first detection of radio emissions by the PRA instrument or auroral emissions by the UVS instrument. If we accept the interpretation of ultraviolet observations now available from the Earth-orbiting International Ultraviolet Explorer satellite, Uranus has a surface magnetic field of at least 0.6 gauss, and more probably several gauss, making it the largest or second-largest planetary magnetic field in the solar system.     

Protein displacement by DExH/D "RNA helicases" without duplex unwinding

Members of the DExH/D superfamily of nucleic acid-activated nucleotide triphosphatases are essential for virtually all aspects of RNA metabolism, including pre-messenger RNA splicing, RNA interference, translation, and nucleocytoplasmic trafficking. Physiological substrates for these enzymes are thought to be regions of double-stranded RNA, because several DExH/D proteins catalyze strand separation in vitro. These "RNA helicases" can also disrupt RNA-protein interactions, but it is unclear whether this activity is coupled to duplex unwinding. Here we demonstrate that two unrelated DExH/D proteins catalyze protein displacement independently of duplex unwinding. Therefore, the essential functions of DExH/D proteins are not confined to RNA duplexes but can be exerted on a wide range of ribonucleoprotein substrates.     

Scent organ development in creatonotos moths: regulation by pyrrolizidine alkaloids

7-Hydroxy-6,7-dihydro-5H-pyrolizine-1-carboxaldehyde is the major volatile component of the scent organs in males of two species of Creatonotos (Lepidoptera, Arctiidae). The biosynthesis of this presumed pheromone depends on the presence of pyrrolizidine alkaloids in plants that are ingested by the larvae. In addition, these secondary plant substances control the morphogenesis of the scent organs. This morphogenetic effect of an alkaloid has not been observed previously.     

Tidal vertical migration: an endogenous rhythm in estuarine crab larvae

Field-caught larvae of the estuarine crab Rhithropanopeus harrisii have a tidal rhythm of vertical migration when maintained in constant conditions. Laboratory-reared larvae do not show this rhythm. Endogenous tidal vertical migrations aid the retention of these planktonic larvae in estuaries near the parent populations.     

Fire history and climate change in giant sequoia groves

Fire scars in giant sequoia [Sequoiadendron giganteum (Lindley) Buchholz] were used to reconstruct the spatial and temporal pattern of surface fires that burned episodically through five groves during the past 2000 years. Comparisons with independent dendroclimatic reconstructions indicate that regionally synchronous fire occurrence was inversely related to yearly fluctuations in precipitation and directly related to decadal-to-centennial variations in temperature. Frequent small fires occurred during a warm period from about A.D. 1000 to 1300, and less frequent but more widespread fires occurred during cooler periods from about A.D. 500 to 1000 and after A.D. 1300. Regionally synchronous fire histories demonstrate the importance of climate in maintaining nonequilibrium conditions.     

Shatter cones at sierra madera, Texas

Shatter cones abound in the central uplift of Sierra Madera and they occur as far as 6.5 kilometers from the center. Apical angles average near 90 degrees. Whole cones and full cones represented by diversely oriented cone segments in any structural block show relatively uniform orientations of axes and a dominant direction of point. The cones predate faulting and folding in the central uplift, and, when beds are restored to horizontal, most cones point inward and upward, a pattern that supports the hypothesis of an impact origin.