Radio observations of the planetary nebula around the OH/IR star OH 354.88-0.54 (V1018 Sco)

We present radio observations of the unique, recently formed, planetary nebula (PN) associated with a very long-period OH/IR variable star V1018 Sco that is unequivocally still in its asymptotic giant branch phase. Two regions within the optical nebula are clearly detected in non-thermal radio continuum emission, with radio spectral indices comparable to those seen in colliding-wind Wolf–Rayet binaries. We suggest that these represent shocked interactions between the hot, fast stellar wind and the cold nebular shell that represents the PN's slow wind moving away from the central star. This same interface produces both synchrotron radio continuum and the optical PN emission. The fast wind is neither spherical in geometry nor aligned with any obvious optical or radio axis. We also report the detection of transient H₂O maser emission in this nebula.     

A Critical Review of Sun-Space Physics

The Sun and the heliosphere form a single dynamical system, driven by the convection in the Sun and the magnetic fields generated by that convection. The magnetic fields are the primary channel for producing the high temperatures and high velocities that extend outward to form the heliosphere. The essential point is that, while the general picture seems to be reasonable, several important steps in the process are not understood, and several concepts commonly employed in explanation are false physics. These scientific gaps should not be forgotten in the rush to pursue new and exotic discoveries. This revised version was published online in July 2006 with corrections to the Cover Date.     

Solar Activity and Classical Physics

1 INTRODUCTION The Sun is close enough to observe in some detail, and it shows that a star is more than the traditional stable self-gravitating thermonuclear body established half a celltury ago. For the fact is that out of sight beneath the visible surface the outward flow of heat from the thermonuclear core drives hydrodynamics that generates magnetic fields. It is the complicated dynamics of those magnetic fields that produces the modern mysteries of the active Sun. The…     

The instability of strong magnetic fields in stellar interiors

There has been discussion of the possibility of resolving the solar neutrino dilemma with a sufficiently strong magnetic field (5×10⁸ G) in the solar interior to relieve the gas pressure by some ten percent or more. We examine the time in which magnetic buoyancy will bring a strong field to the surface and find it to be less than 10⁸ yr. We see no possibility for retaining a suitably strong magnetic field in the solar interior.     

TERRESTRIAL VERTEBRATES AND VEGETATION STRUCTURE IN THE WESTERN UNITED STATES

Terrestrial vertebrates in the western United States are functionally linked to environmental settings, as revealed by principal components analyses. Species number in five major vertebrate feeding guilds increases as vegetation structure becomes more complex and environmental conditions become more varied, and as evolutionary history has promoted species richness. Two other major vertebrate feeding guilds increase with temperature and evolutionary factors. Results support the view of animals as adapted parts of deterministic environmental systems, although complete explanations of species distributions require consideration of evolutionary history and stochastic processes.     

Isostatic compensation on a continental scale: local versus regional mechanisms

Summary. Using the techniques of linear and quadratic programming, it can be shown that the isostatic response function for the continental United States, computed by Lewis & Dorman (1970), is incompatible with any local compensation model that involves only negative density contrasts beneath topographic loads. We interpret the need for positive densities as indicating that compensation is regional rather than local. The regional compensation model that we investigate treats the outer shell of the Earth as a thin elastic plate, floating on the surface of a liquid. The response of such a model can be inverted to yield the absolute density gradient in the plate, provided the flexural rigidity of the plate and the density contrast between mantle and topography are specified.
If only positive density gradients are allowed, such a regional model fits the United States response data provided the flexural rigidity of the plate lies between 10²¹ and 10²² N m. The fit of the model is insensitive to the mantle/ load density contrast, but certain bounds on the density structure can be established if the model is assumed correct. In particular, the maximum density increase within the plate at depths greater than 34 kin must not exceed 470 kg m⁻³; this can be regarded as an upper bound on the density contrast at the Mohorovicic discontinuity.
The permitted values of the flexural rigidity correspond to plate thicknesses in the range 5–10 km, yet deformations at depths greater than 20 km are indicated by other geophysical data. We conclude that the plate cannot be perfectly elastic; its effective elastic moduli must be much smaller than the seismically determined values. Estimates of the stress-differences produced in the earth by topographic loads, that use the elastic plate model, together with seismically determined elastic parameters, will be too large by a factor of four or more.     

Nitrogen mineralization across an atmospheric nitrogen deposition gradient in Southern California deserts

Dry nitrogen deposition is common in arid ecosystems near urban and agricultural centers, yet its impacts on natural environments are relatively understudied. We examined the effects of N deposition on soil N mineralization across a depositional gradient at Joshua Tree National Park. We hypothesized that N deposition affects N mineralization by promoting exotic grass invasion and increasing soil carbon and nitrogen. These relationships were tested through a laboratory incubation on soils collected from sixteen sites where atmospheric N, soil characteristics, and annual vegetation were measured. Mineralization parameters modeled using the Gompertz model were compared to soil C, soil N, estimated soil N from deposition, and percent cover of exotic and native annuals. Calculated soil N from deposition was directly correlated with measured soil C and N and decreasing C:N ratios, which were associated with increased total amounts of mineralized N. However, no effects of soil C or N, and thus N deposition, were observed on mineralization rates. Exotic grasses, but not native forbs or total annual cover, increased with soil C, soil N, and total mineralized N, suggesting that exotic grasses and N deposition are correlated and associated with increasing total C and N in the interspace soils at polluted locations.     

Tangential discontinuities and the optical analogy for stationary fields IV. High speed fluid sheets

Abstract

It was shown in the previous paper that a sufficiently strong pressure maximum applied to an equilibrium flux surface, by the fields on either side of the surface, produces a gap in the flux surface. The fields on either side make contact through the gap to produce a surface of tangential discontinuity (current sheet). It is shown in the present paper that there is a high speed sheet of fluid and field sliding over the surface of discontinuity when the applied pressure moves slowly across the flux surface. Conditions in the active X-ray corona of the sun suggest that such sheets are generally present, with velocities of the order of 10² km/sec, but with thicknesses too small to be observed. More substantial high speed sheets of fluid may occur in solar flares.