Absorption spectrum of iron in the vacuum ultraviolet 2950 - 1588 angstrom

Absorption spectrum of iron in vacuum ultraviole

Reconstructing the global topology of the universe from the cosmic microwave background

If the universe is multiply-connected and sufficiently small, then the last scattering surface wraps around the universe and intersects itself. Each circle of intersection appears as two distinct circles on the microwave sky. The present article shows how to use the matched circles to explicitly reconstruct the global topology of space.Comment: 6 pages, 2 figures, IOP format. To be published in the proceedings of the Cleveland Cosmology and Topology Workshop 17-19 Oct 1997. Submitted to Class. Quant. Gra

Properties of cage rearrangements observed near the colloidal glass transition

We use confocal microscopy to study the motions of particles in concentrated colloidal systems. Near the glass transition, diffusive motion is inhibited, as particles spend time trapped in transient ``cages'' formed by neighboring particles. We measure the cage sizes and lifetimes, which respectively shrink and grow as the glass transition approaches. Cage rearrangements are more prevalent in regions with lower local concentrations and higher disorder. Neighboring rearranging particles typically move in parallel directions, although a nontrivial fraction move in anti-parallel directions, usually from pairs of particles with initial separations corresponding to the local maxima and minima of the pair correlation function $g(r)$, respectively.Comment: 5 pages, 4 figures; text & figures revised in v

On the geometric boundaries of hyperbolic 4-manifolds

We provide, for hyperbolic and flat 3-manifolds, obstructions to bounding hyperbolic 4-manifolds, thus resolving in the negative a question of Farrell and Zdravkovska.Comment: 8 pages. Published copy, also available at http://www.maths.warwick.ac.uk/gt/GTVol4/paper5.abs.htm

Circles in the Sky: Finding Topology with the Microwave Background Radiation

If the universe is finite and smaller than the distance to the surface of last scatter, then the signature of the topology of the universe is writ large on the microwave background sky. We show that the microwave background will be identified at the intersections of the surface of last scattering as seen by different ``copies'' of the observer. Since the surface of last scattering is a two-sphere, these intersections will be circles, regardless of the background geometry or topology. We therefore propose a statistic that is sensitive to all small, locally homogeneous topologies. Here, small means that the distance to the surface of last scatter is smaller than the ``topology scale'' of the universe.Comment: 14 pages, 10 figures, IOP format. This paper is a direct descendant of gr-qc/9602039. To appear in a special proceedings issue of Class. Quant. Grav. covering the Cleveland Topology & Cosmology Worksho

Attraction Between Like-Charged Walls: Short-Ranged Simulations Using Local Molecular Field Theory

Effective attraction between like-charged walls mediated by counterions is studied using local molecular field (LMF) theory. Monte Carlo simulations of the "mimic system'' given by LMF theory, with short-ranged "Coulomb core" interactions in an effective single particle potential incorporating a mean-field average of the long-ranged Coulomb interactions, provide a direct test of the theory, and are in excellent agreement with more complex simulations of the full Coulomb system by Moreira and Netz [Eur. Phys. J. E 8, 33 (2002)]. A simple, generally-applicable criterion to determine the consistency parameter sigma_{min} needed for accurate use of the LMF theory is presented

Description of the fluctuating colloid-polymer interface

To describe the full spectrum of surface fluctuations of the interface between phase-separated colloid-polymer mixtures from low scattering vector q (classical capillary wave theory) to high q (bulk-like fluctuations), one must take account of the interface's bending rigidity. We find that the bending rigidity is negative and that on approach to the critical point it vanishes proportionally to the interfacial tension. Both features are in agreement with Monte Carlo simulations.Comment: 5 pages, 3 figures, 1 table. Accepted for publication in Phys. Rev. Let

Spiral Evolution in a Confined Geometry

Supported nanoscale lead crystallites with a step emerging from a non-centered screw dislocation on the circular top facet were prepared by rapid cooling from just above the melting temperature. STM observations of the top facet show a nonuniform rotation rate and shape of the spiral step as the crystallite relaxes. These features can be accurately modeled using curvature driven dynamics, as in classical models of spiral growth, with boundary conditions fixing the dislocation core and regions of the step lying along the outer facet edge.Comment: 4 pages, 3 figures, to be published in Physical Review Letter

Derivation of quantitative management objectives for annual instream water temperatures in the Sabie River using a biological index

Adaptive management of river systems assumes uncertainty and makes provision for system variability. Inherent within this management approach is that perceived limits of 'acceptable' system variability are regarded not only as testable hypotheses, but also as playing a central role in maintaining biodiversity. While the Kruger National Park currently functions as a flagship conservation area in South Africa, projected increases in air temperatures as a consequence of global climate change present challenges in conserving this biodiversity inside the established land boundaries. Within the rivers of the Kruger National Park, a management goal of maintaining biodiversity requires a clearer understanding of system variability. One component of this is water temperature, an important water quality parameter defining the distribution patterns of aquatic organisms. In this study, Chiloglanis anoterus Crass (1960) (Pisces: Mochokidae) was selected as a biological indicator of changes in annual water temperatures within the Sabie River in the southern Kruger National Park. Relative abundances of C. anoterus were determined using standard electro-fishing surveys. The presence or absence of C. anoterus was linked to cumulative annual heat units using a logistic regression model, and a critical annual cumulative water temperature threshold estimated. A correlative relationship between this temperature threshold and a biological index using a C. anoterus condition factor provides river ecologists with a tool to assess ecologically significant warming trends in Sabie River water temperatures. A similar approach could be applied with relative ease to other Southern African river systems. Further testing of this hypothesis is suggested, as part of the adaptive management cycle

Segue Between Favorable and Unfavorable Solvation

Solvation of small and large clusters are studied by simulation, considering a range of solvent-solute attractive energy strengths. Over a wide range of conditions, both for solvation in the Lennard-Jones liquid and in the SPC model of water, it is shown that the mean solvent density varies linearly with changes in solvent-solute adhesion or attractive energy strength. This behavior is understood from the perspective of Weeks' theory of solvation [Ann. Rev. Phys. Chem. 2002, 53, 533] and supports theories based upon that perspective.Comment: 8 pages, 7 figure