Extrinsic versus intrinsic diameter for Riemannian filling-discs and van Kampen diagrams

The diameter of a disc filling a loop in the universal covering of a Riemannian manifold may be measured extrinsically using the distance function on the ambient space or intrinsically using the induced length metric on the disc. Correspondingly, the diameter of a van Kampen diagram filling a word that represents the identity in a finitely presented group can either be measured intrinsically its 1-skeleton or extrinsically in the Cayley graph of the group. We construct the first examples of closed manifolds and finitely presented groups for which this choice -- intrinsic versus extrinsic -- gives rise to qualitatively different min-diameter filling functions.Comment: 44 pages, 12 figures, to appear in the Journal of Differential Geometr

The absence of efficient dual pairs of spanning trees in planar graphs

A spanning tree T in a finite planar connected graph G determines a dual spanning tree T* in the dual graph G such that T and T* do not intersect. We show that it is not always possible to find T in G, such that the diameters of T and T* are both within a uniform multiplicative constant (independent of G) of the diameters of their ambient graphs.Comment: 7 pages, 3 figure

Visitors' Interpretive Strategies at Wolverhampton Art Gallery

Making Meaning in Art Museums is one of two research projects on the theme of art museums and interpretive communities. The first was published as Making Meaning 1:Visitors' Interpretive Strategies at Wolverhampton Art Gallery (RCMG 2001). Making Meaning in Art Museums 2 is the second of two research projects on the theme of art museums and interpretive communities. The Long Gallery at the Nottingham Castle Museum and Art Gallery was selected as the research site for this second study. Both studies have explored the ways in which visitors talked about their experience of a visit to the art museum-both what they said about the paintings and the whole of the visit.The research questions on which this project is based are: What interpretive strategies and repertories are deployed by art museum visitors? Can distinct interpretive communities be identified? What are the implications for the communication policies within art museums? This research is an ethnographic study, using qualitative methods.This research project was funded through a grant from the Arts and Humanities Research Boar

Evaluation of the SPAR thermal analyzer on the CYBER-203 computer

The use of the CYBER 203 vector computer for thermal analysis is investigated. Strengths of the CYBER 203 include the ability to perform, in vector mode using a 64 bit word, 50 million floating point operations per second (MFLOPS) for addition and subtraction, 25 MFLOPS for multiplication and 12.5 MFLOPS for division. The speed of scalar operation is comparable to that of a CDC 7600 and is some 2 to 3 times faster than Langley's CYBER 175s. The CYBER 203 has 1,048,576 64-bit words of real memory with an 80 nanosecond (nsec) access time. Memory is bit addressable and provides single error correction, double error detection (SECDED) capability. The virtual memory capability handles data in either 512 or 65,536 word pages. The machine has 256 registers with a 40 nsec access time. The weaknesses of the CYBER 203 include the amount of vector operation overhead and some data storage limitations. In vector operations there is a considerable amount of time before a single result is produced so that vector calculation speed is slower than scalar operation for short vectors

Spectral irradiance of total and spectral energy standards

Spectral irradiance measurements of tungsten and carbon filament lamps for energy standards and accuracy limits used in space simulator