The Flattening of Globular Clusters

In the three nearest luminous galaxies, the Milky Way System, the Andromeda Galaxy and NGC 5128 the brightest globular clusters are rounder than the faintest ones. On the other hand (contrary to some previous results) the flattening of individual LMC clusters is found to be independent of their luminosities. This suggests the possibility that the relationship between the flattening and luminosity of clusters might depend on host galaxy luminosity. No significant differences are found between the intrinsic flattening distributions of Galactic old halo, Galactic young halo and Galactic bulge/disk clusters. Such a dependence might perhaps have been expected if tidal forces (which are largest at small Galactocentric distances) removed angular momentum from globular clusters. The preliminary conclusion by Norris that clusters with blue horizontal branches are more flattened than red HB clusters is not confirmed by the larger data base that is now available. In other words there is no evidence for the puzzling claimed correlation between the flattening and the horizontal branch morphology of Galactic globular clusters.Comment: 20 pages text + tables; 5 postscript figures. Astronomical Journal, in pres

Torsional rigidity for cylinders with a Brownian fracture

We obtain bounds for the expected loss of torsional rigidity of a cylinder $\Omega_L=(-L/2,L/2) \times \Omega\subset \R^3$ of length $L$ due to a Brownian fracture that starts at a random point in $\Omega_L,$ and runs until the first time it exits $\Omega_L$. These bounds are expressed in terms of the geometry of the cross-section $\Omega \subset \R^2$. It is shown that if $\Omega$ is a disc with radius $R$, then in the limit as $L \rightarrow \infty$ the expected loss of torsional rigidity equals $cR^5$ for some $c\in (0,\infty)$. We derive bounds for $c$ in terms of the expected Newtonian capacity of the trace of a Brownian path that starts at the centre of a ball in $\R^3$ with radius $1,$ and runs until the first time it exits this ball.Comment: 18 page

Preroughening transitions in a model for Si and Ge (001) type crystal surfaces

The uniaxial structure of Si and Ge (001) facets leads to nontrivial topological properties of steps and hence to interesting equilibrium phase transitions. The disordered flat phase and the preroughening transition can be stabilized without the need for step-step interactions. A model describing this is studied numerically by transfer matrix type finite-size-scaling of interface free energies. Its phase diagram contains a flat, rough, and disordered flat phase, separated by roughening and preroughening transition lines. Our estimate for the location of the multicritical point where the preroughening line merges with the roughening line, predicts that Si and Ge (001) undergo preroughening induced simultaneous deconstruction transitions.Comment: 13 pages, RevTex, 7 Postscript Figures, submitted to J. Phys.

A new tonometer based on the application of micro-mechanical sensors

An instrument for the measurement of intraocular pressure (IOP) is presented. It consists of a micromachined silicon sensor, which measures the diameter of a flattened part of the eye globe and simultaneously determines the smallest distance between the center of the sensor and the contour of this applanation. In the center of this applanation sensor a micro mechanical plunger is realized, which transfers the applied pressure to a separate force sensor. Preliminary results show that this sensor may improve the accuracy of Mackay-Marg-based electronic tonometer

Static Analysis of Functional Programs

In this paper, the static analysis of programs in the functional programming language Miranda* is described based on two graph models. A new control-flow graph model of Miranda definitions is presented, and a model with four classes of callgraphs. Standard software metrics are applicable to these models. A Miranda front end for Prometrix, ¿, a tool for the automated analysis of flowgraphs and callgraphs, has been developed. This front end produces the flowgraph and callgraph representations of Miranda programs. Some features of the metric analyser are illustrated with an example program. The tool provides a promising access to standard metrics on functional programs

Programmers' performance on structured versus nonstructured function definitions

A control-flow model for functional programs is used in an experimental comparison of the performance of programmers on structured versus nonstructured Miranda function definitions. The performance is taken as a measure of the comprehensibility of functional programs. The experimental set-up is similar to the Scanlan study (1989). However, in the present study, a two-factor repeated measures design is used in the statistical analysis. The control-flow model appears to be useful in the shaping of the experiment. A significantly better performance has been found for structured function definitions on both dependent variables: the time needed to answer questions about the function definitions and the proportion correct answers. Moreover, for structured function definitions, a counter-intuitive result has been obtained: there are significantly fewer errors in larger definitions than in smaller ones

Validation in the Software Metric Development Process

In this paper the validation of software metrics will be examined. Two approaches will be combined: representational measurement theory and a validation network scheme. The development process of a software metric will be described, together with validities for the three phases of the metric development process. Representation axioms from measurement theory are used both for the formal and empirical validation. The differentiation of validities according to these phases unifies several validation approaches found in the software metric's literature

Axiomatic Testing of Structure Metrics

Axiomatic testing of software metrics is described, based on axioms from representational measurement theory. In a case study, the axioms are given for the formal relational structure and the empirical relational structure. Two approaches to axiomatic testing are elaborated: deterministic testing and probabilistic testin

Bioenergy for Electricity Generation

Energy from biological materials addresses a number of key energy and environmental issues, including climate change, energy security, and replacement of carbon-intensive energy sources. This thesis assesses the feasibility of using three types of biological material for U.S. electricity generation: wood chips, biofuels, and organic waste. To evaluate economic feasibility, this paper examines system design, feedstock availability, and other advantages and disadvantages of alternative biological feedstocks. It also discusses three cost-benefit studies evaluating wood chips, biofuels, and waste-to-energy. This thesis recommends that the U.S. electricity sector consider investing in additional use of wood chips and organic waste and continue developing research for next-generation biofuel. Wood chips can cost less than heating oil. Municipal solid waste as a fuel could manage and reduce carbon. Although next-generation biofuels are more expensive in terms of capital and operating costs than conventional biofuel and fossil fuels, their use could mitigate food security and environmental concerns. All three technologies are used globally, proving technical feasibility. The availability of wood and waste in the U.S. offers another incentive for feedstock. Additional funding and research remain challenges for next-generation biofuel. Future research in bioenergy could include cost-benefit and carbon emission analyses that incorporate additional production pathways, comparisons to current renewable feedstocks, and recommended sites for the three technologies this paper addresses.Polymathic Scholar