Measurements of the Cosmological Evolution of Magnetic Fields with the Square Kilometre Array

We investigate the potential of the Square Kilometre Array (SKA) for measuring the magnetic fields in clusters of galaxies via Faraday rotation of background polarised sources. [...] We find that about 10 per cent of the sky is covered by a significant extragalactic Faraday screen. Most of it has rotation measures between 10 and 100 rad/m/m. We argue that the cluster centres should have up to about 5000 rad/m/m. We show that the proposed mid frequency aperture array of the SKA as well as the lowest band of the SKA dish array are well suited to make measurements for most of these rotation measure values, typically requiring a signal-to-noise of ten. We calculate the spacing of sources forming a grid for the purpose of measuring foreground rotation measures: it reaches a spacing of 36 arcsec for a 100 hour SKA observation per field. We also calculate the statistics for background RM measurements in clusters of galaxies. We find that a first phase of the SKA would allow us to take stacking experiments out to high redshifts (>1), and provide improved magnetic field structure measurements for individual nearby clusters. The full SKA aperture array would be able to make very detailed magnetic field structure measurements of clusters with more than 100 background sources per cluster up to a redshift of 0.5 and more than 1000 background sources per cluster for nearby clusters, and could for reasonable assumptions about future measurements of electron densities in high redshift clusters constrain the power law index for the magnetic field evolution to better than dm=0.4, if the magnetic field in clusters should follow B ~ (1+z)^m.Comment: 12 pages, 10 figures, 3 tables, accepted by MNRAS, minor correction to eq (5

Advanced nickel-cadmium batteries for geosynchronous spacecraft

A nickel cadmium battery was developed that can be operated at 80 percent depth of discharge in excess of 10 years in a geosynchronous orbit application, and has about a 30 percent weight savings per spacecraft over present nickel cadmium batteries when used with a 1000 watts eclipse load. The approach used in the development was to replace nylon separators with inert polymer impregnated zirconia, use electrochemically deposited plates in place of conventional chemically precipitated ones, and use an additive to extend negative plate lifetime. The design has undergone extensive testing using both engineering and protoflight cell configurations

The Changing Financial Structure of the U.S. Farm Sector

Agricultural Finance,

Recharacterization and the Nonhindrance of Creditors

Using a 1977 article by Robert Clark as the starting point, this article attempts to shed new light on the question of whether and when shareholder loans to her company should be either equitably subordinated or, as courts have done in a few recent cases, recharacterized as equity. In its emphasis on the particular issue of shareholder loans, the article has a narrower compass than Clark’s article, which uses a four-part typology to explore the relationship among fraudulent conveyance law, equitable subordination, veil piercing and dividend restrictions. But the article also expands Clark’s analysis in several respects. The most important adjustment involves the general Nonhindrance ideal, which we use to identify a crucially important form of interference with the rights of creditors that Clark does not himself consider directly. Part 1 of the article very briefly describes the 1939 Supreme Court case that served as a well-spring for equitable subordination doctrine in general, and for subordination of shareholder loans in particular. Part 2 then focuses on a series of recent decisions that have wrestled with the question whether shareholder loans should be recharacterized as equity contributions. Recharacterization doctrine is closely related to equitable subordination, but most courts view it as a separate development. Part 2 suggests that much of the confusion in the cases could be eliminated by disentangling two issues, whether the status of a loan is ambiguous (which raises issues of Truth, in terms of Clark’s typology) and whether it was likely to destroy value that would otherwise go to creditors (the Nonhindrance concern); and by distinguishing bankruptcy recharacterization from the tax characterization cases that seem to have spawned the new doctrine. Part 3 then concludes by briefly considering the German and Austrian approaches to these same issues, which focus on capitalization and creditworthiness. The most important, and initially counterintuitive, implication comes in Part 2: whereas US courts have treated security interests as a badge of legitimacy in assessing shareholder loans, secured loans are actually the most worrisome form of shareholder investment. These security interests, we argue, should be disallowed

Recharacterization and the Nonhindrance of Creditors

Using a 1977 article by Robert Clark as the starting point, this article attempts to shed new light on the question of whether and when shareholder loans to her company should be either equitably subordinated or, as courts have done in a few recent cases, recharacterized as equity. In its emphasis on the particular issue of shareholder loans, the article has a narrower compass than Clark’s article, which uses a four-part typology to explore the relationship among fraudulent conveyance law, equitable subordination, veil piercing and dividend restrictions. But the article also expands Clark’s analysis in several respects. The most important adjustment involves the general Nonhindrance ideal, which we use to identify a crucially important form of interference with the rights of creditors that Clark does not himself consider directly. Part 1 of the article very briefly describes the 1939 Supreme Court case that served as a well-spring for equitable subordination doctrine in general, and for subordination of shareholder loans in particular. Part 2 then focuses on a series of recent decisions that have wrestled with the question whether shareholder loans should be recharacterized as equity contributions. Recharacterization doctrine is closely related to equitable subordination, but most courts view it as a separate development. Part 2 suggests that much of the confusion in the cases could be eliminated by disentangling two issues, whether the status of a loan is ambiguous (which raises issues of Truth, in terms of Clark’s typology) and whether it was likely to destroy value that would otherwise go to creditors (the Nonhindrance concern); and by distinguishing bankruptcy recharacterization from the tax characterization cases that seem to have spawned the new doctrine. Part 3 then concludes by briefly considering the German and Austrian approaches to these same issues, which focus on capitalization and creditworthiness. The most important, and initially counterintuitive, implication comes in Part 2: whereas US courts have treated security interests as a badge of legitimacy in assessing shareholder loans, secured loans are actually the most worrisome form of shareholder investment. These security interests, we argue, should be disallowed

Titanium Aluminide Applications in the High Speed Civil Transport

It is projected that within the next two decades, overseas air travel will increase to over 600,000 passengers per day. The High Speed Civil Transport (HSCT) is a second-generation supersonic commercial aircraft proposed to meet this demand. The expected fleet of 500 to 1500 aircraft is required to meet EPA environmental goals; the HSCT propulsion system requires advanced technologies to reduce exhaust and noise pollution. A part of the resultant strategy for noise attenuation is the use of an extremely large exhaust nozzle. In the nozzle, several critical components are fabricated from titanium aluminide: the divergent nap uses wrought gamma; the nozzle sidewall is a hybrid fabrication of both wrought gamma face sheet and cast gamma substructure. This paper describes the HSCT program and the use of titanium aluminide for its components

The negative side of cohomology for Calabi-Yau categories

We study integer-graded cohomology rings defined over Calabi-Yau categories. We show that the cohomology in negative degree is a trivial extension of the cohomology ring in non-negative degree, provided the latter admits a regular sequence of central elements of length two. In particular, the product of elements of negative degrees are zero. As corollaries we apply this to Tate-Hochschild cohomology rings of symmetric algebras, and to Tate cohomology rings over group algebras. We also prove similar results for Tate cohomology rings over commutative local Gorenstein rings.Comment: 14 page

Reversible skew laurent polynomial rings and deformations of poisson automorphisms

A skew Laurent polynomial ring S = R[x(+/- 1); alpha] is reversible if it has a reversing automorphism, that is, an automorphism theta of period 2 that transposes x and x(-1) and restricts to an automorphism gamma of R with gamma = gamma(-1). We study invariants for reversing automorphisms and apply our methods to determine the rings of invariants of reversing automorphisms of the two most familiar examples of simple skew Laurent polynomial rings, namely a localization of the enveloping algebra of the two-dimensional non-abelian solvable Lie algebra and the coordinate ring of the quantum torus, both of which are deformations of Poisson algebras over the base field F. Their reversing automorphisms are deformations of Poisson automorphisms of those Poisson algebras. In each case, the ring of invariants of the Poisson automorphism is the coordinate ring B of a surface in F-3 and the ring of invariants S-theta of the reversing automorphism is a deformation of B and is a factor of a deformation of F[x(1), x(2), x(3)] for a Poisson bracket determined by the appropriate surface