Cosmic Ray Rejection by Linear Filtering of Single Images

We present a convolution-based algorithm for finding cosmic rays in single well-sampled astronomical images. The spatial filter used is the point spread function (approximated by a Gaussian) minus a scaled delta function, and cosmic rays are identified by thresholding the filtered image. This filter searches for features with significant power at spatial frequencies too high for legitimate objects. Noise properties of the filtered image are readily calculated, which allows us to compute the probability of rejecting a pixel not contaminated by a cosmic ray (the false alarm probability). We demonstrate that the false alarm probability for a pixel containing object flux will never exceed the corresponding probability for a blank sky pixel, provided we choose the convolution kernel appropriately. This allows confident rejection of cosmic rays superposed on real objects. Identification of multiple-pixel cosmic ray hits can be enhanced by running the algorithm iteratively, replacing flagged pixels with the background level at each iteration.Comment: Accepted for publication in PASP (May 2000 issue). An iraf script implementing the algorithm is available from the author, or from http://sol.stsci.edu/~rhoads/ . 16 pages including 3 figures. Uses AASTeX aaspp4 styl

Consequences of Fine-Tuning for Fifth Force Searches

Light bosonic fields mediate long range forces between objects. If these fields have self-interactions, i.e., non-quadratic terms in the potential, the experimental constraints on such forces can be drastically altered due to a screening (chameleon) or enhancement effect. We explore how technically natural values for such self-interaction coupling constants modify the existing constraints. We point out that assuming the existence of these natural interactions leads to new constraints, contrary to the usual expectation that screening leads to gaps in coverage. We discuss how screening can turn fundamentally equivalence principle (EP)-preserving forces into EP-violating ones. This means that when natural screening is present, searches for EP violation can be used to constrain EP-preserving forces. We show how this effect enables the recently discovered stellar triple system \textit{PSR J0337$+$1715} to place a powerful constraint on EP-preserving fifth forces. Finally, we demonstrate that technically natural cubic self-interactions modify the vacuum structure of the scalar potential, leading to new constraints from spontaneous and induced vacuum decay.Comment: 36 pages, 9 figures -- v3 reflects version published in JHE

Tonal prisms: iterated quantization in chromatic tonality and Ravel's 'Ondine'

The mathematics of second-order maximal evenness has far-reaching potential for application in music analysis. One of its assets is its foundation in an inherently continuous conception of pitch, a feature it shares with voice-leading geometries. This paper reformulates second-order maximal evenness as iterated quantization in voice-leading spaces, discusses the implications of viewing diatonic triads as second-order maximally even sets for the understanding of nineteenth-century modulatory schemes, and applies a second-order maximally even derivation of acoustic collections in an in-depth analysis of Ravel's ‘Ondine’. In the interaction between these two very different applications, the paper generalizes the concepts and analytical methods associated with iterated quantization and also pursues a broader argument about the mutual dependence of mathematical music theory and music analysis.Accepted manuscrip

Study of cryogenic fluid mixing techniques. Volume 1 - Large-scale experimental mixing investigations and liquid-oxygen mixer design Final report

Large-scale experimental liquid hydrogen mixing and liquid oxygen mixer desig

The momentum spectrum of nuclear active particles in the cosmic radiation

This thesis describes studies of nuclear active particles (NAPs) in the cosmic radiation over the momentum range 1-30 GeV/c. Both unaccompanied particles and NAPs in extensive air showers (EAS) are studied near sea level at Durham using an air-gap magnet spectrograph in conjunction with a neutron monitor. Details are given of the design of the spectrograph, neutron monitor and associated equipment as used for measurements on unaccompanied NAPs (Chapter 2), and the techniques used for derivation of the momentum spectra from the basic data are described in Chapter 3. The results, in the form of momentum spectra of unaccompanied protons and negative pions, and the limited analysis of NAPs in EAS are presented in Chapter 4 where they are compared with the results of other workers. Measurements of the momentum of NAPs in EAS were found to be difficult and the data are mainly concerned with the response of the neutron monitor to EAS. A model of the propagation of cosmic rays through the atmosphere, which was mainly intended for predictions of the properties of large EAS, is described and used to predict the momentum spectra of unaccompanied particles at sea level. The results of this prediction are compared with the experimental data (Chapter 5) and the results of other model predictions (Chapter 6). It is shown that no single model, when combined with a reasonable spectrum of primary cosmic rays, can adequately explain all the data on unaccompanied particles at sea level. It is also shown that the spectra of high energy protons and pions are likely to be the sea level measurements which are most sensitive to the form of the primary cosmic ray spectrum