Rational's experience using Ada for very large systems

The experience using the Rational Environment has confirmed the advantages forseen when the project was started. Interactive syntatic and semantic information makes a tremendous difference in the ease of constructing programs and making changes to them. The ability to follow semantic references makes it easier to understand exisiting programs and the impact of changes. The integrated debugger makes it much easier to find bugs and test fixes quickly. Taken together, these facilites have helped greatly in reducing the impact of ongoing maintenance of the ability to produce a new code. Similar improvements are anticipated as the same level of integration and interactivity are achieved for configuration management and version control. The environment has also proven useful in introducing personnel to the project and existing personnel to new parts of the system. Personnel benefit from the assistance with syntax and semantics; everyone benefits from the ability to traverse and understand the structure of unfamiliar software. It is often possible for someone completely unfamiliar with a body of code to use these facilities, to understand it well enough to successfully with a body of code to use these facilities to understand it well enough to successfully diagnose and fix bugs in a matter of minutes

Calculation involving hydrogen-hydrogen(2) collisional cooling processes for use in astrophysics

This thesis will calculate the H-H2 cooling processes used in astrophysics. Cooling is critical to the formation of the first objects formed in the early universe, and other diverse phenomenon of interest to astrophysics. For instance, in order to collapse into objects, the gravitational potential energy of primordial density fluctuations must be radiated away. The most abundant element in the universe is hydrogen, and cooling processes involving hydrogen are important in several contexts. To calculate the cooling, the cross section for collisional excitation at constant energy were integrated over a Maxwellian velocity distribution to determine a rate coefficient. Then the equilibrium level populations will be solved for a given temperature and H density. Finally, the cooling and spectra are calculated from these equilibrium populations

A Study of the Effects of Pair Production and Axionlike Particle Oscillations on Very High Energy Gamma Rays from the Crab Pulsar

Pulsars are highly-magnetized rapidly-rotating neutron stars that emit energy throughout the electromagnetic spectrum. Despite decades of study, the emission mechanisms of pulsars are not well understood. New observations at the highest energy end of the spectrum can provide strong constraints on theoretical models of pulsar emission. The strong magnetic fields of pulsar magnetospheres accelerate charged particles to relativistic energies and these particles emit very high energy (VHE; E \u3e 100 GeV) gamma rays. In addition to creating conditions to emit gamma rays, the magnetic fields are powerful enough to attenuate gamma rays through pair production. The attenuation of gamma rays limits the photon energies that may escape the magnetosphere, unless an additional physical process decreases the opacity of the magnetosphere to these photons. The interaction of axions or axionlike particles (ALPs) with magnetic fields is one such process. Some extensions of the Standard Model suggest the existence of axions, which are light pseudoscalar bosons with a two-photon coupling. As a result of this coupling photon-ALP oscillations can occur in the strong fields of a pulsar magnetosphere. For typical parameters of pulsar magnetospheres, VHE photons fall within the strong mixing-regime for oscillations when the axion mass is 10−3 eV \u3c ma \u3c 10 eV and the axion-photon coupling constant is 10−11 \u3c gaγ \u3c 10−6 . Axion-photon oscillations within the inner magnetosphere would decrease its opacity as axions would propagate unimpeded by pair attenuation. In this dissertation, the VHE photon emission and propagation from pulsars is studied in detail. New observations and analysis of the Crab pulsar from the VERITAS experiment are presented which extend the Crab spectrum to higher energies. The magnetospheres of pulsars are simulated using a retarded vacuum dipole solution for the magnetic field. VHE photon emission and propagation is studied using a Monte Carlo method. The emission regions are defined using the slot gap and outer gap models. The effects of pair production and axion-photon mixing are considered and light curves and spectra are produced to illustrate the influence of both processes on the observations of pulsars. For some geometries, VHE photons are heavily attenuated by pair production. Axion-photon mixing is shown to reduce the opacity of pulsar magnetospheres allowing a larger fraction of VHE photons to survive propagation. However, we find that the inclusion of QED effects on the effective photon mass limit the conversion probability over much of the region where strong pair attenuation is expected

Quantum mechanical hydrogen-hydrogen collisional cross section calculation for astrophysics

The purpose of this work is to perform a quantum mechanical calculation of the collisional state-to-state cross sections for H-H2 required for astrophysical modeling. Previous quantum and semi-classical cooling rates computed from cross sections have shown unexplained discrepancies. This attempts to clarify the situation and provide reliable cross sections to the astrophysical community. As a side benefit of this calculation geometric phase effects in the H-H2 collision dynamics are investigated at higher energies than previously attempted. Cooling is critical to the formation of the first objects formed in the early universe, and other diverse phenomenon of interest to astrophysics. For instance, in order to collapse into objects, the gravitational potential energy of primordial density fluctuations must be radiated away. The most abundant element in the universe is hydrogen, and cooling processes involving hydrogen are important in several contexts

Colonic Protein Fermentation and Promotion of Colon Carcinogenesis by Thermolyzed Casein

Thermolyzed casein is known to promote the growth of aberrant crypt foci (ACF) and colon cancer when it is fed to rats that have been initiated with azoxymethane. We speculated that the promotion was a consequence of increased colonic protein fermentation (i.e., that the thermolysis of the casein decreases its digestibility, increases the amount of protein reaching the colon, and increases colonic protein fermentation and that the potentially toxic products of this fermentation promote colon carcinogenesis). We found that the thermolysis of casein reduces its digestibility and increases colonic protein fermentation, as assessed by fecal ammonium and urinary phenol, cresol, and indol-3-ol. Thermolysis of two other proteins, soy and egg white protein, also increases colonic protein fermentation with increased fecal ammonia and urinary phenols, and thermolysis of all three proteins increases the levels of ammonia and butyric, valeric, and i-valeric acids in the cecal contents. We found, however, that the increased protein fermentation observed with thermolysis is not associated with pro-motion of colon carcinogenesis. With casein, the kinetics of protein fermentation with increasing thermolysis time are clearly different from the kinetics of promotion of ACF growth. The formation of the fermentation products was highest when the protein was thermolyzed for one hour, whereas promotion was highest for protein that had been thermolyzed for two or more hours. With soy and egg white, thermolysis increased colonic protein fermentation but did not promote colon carcinogenesis. Thus, although thermolysis of dietary casein increases colonic protein fermentation, products of this fermentation do not appear to be responsible for the promotion of colon carcinogenesis. Indeed, the results suggest that protein fermentation products do not play an important role in colon cancer promotion

Ripley

A text written for the magazine of feminism and contemporary art, SALT. Ripley concerns the experience of installing two works by Eva Hesse, Hang-Up and Accretion, for the first major exhibition of her work in Europe. The show opened at the Whitechapel Art Gallery on May 3, 1979, the same day that Margaret Thatcher was first elected Prime Minister. The text weaves personal experience, Hesse's writings, feminist socialist theory, the politics of separatism and references to the popular culture of the time using language that consciously acknowledges feminism's critique of the implicitly patriarchal nature of then current forms of address

Fata Morgana [catalogue essay]

Essay for the catalogue accompanying the exhibition Intreccio Mirage by Milly Thompson at 43 Inverness Street, London, February 27 - April 27, 2013. In making the work for Intreccio Mirage, one reference point for Thompson was Jeff Koons's basketball works and the analysis of them in my book One Ball Total Equilibrium Tank. The essay responds to the critique of consumerism and media prescriptions on bodily form, and to the forceful assertion of female desire expressed in Thompson's work

Imi Knoebel: Paint Project

Essay for the publication Imi Knoebel, published following Knoebel's major retrospective, Imi Knoebel: Works 1966-2014, at Kunstmuseum, Wolfsburg, October 26, 2014 - February 15, 2015 to accompany the exhibition of Knoebel's work at White Cube, London, July 15 - September 13, 2015. This essay on Knoebel's work follows an earlier text on Blinky Palermo, Knoebel's close friend and contemporary studying under Joseph Beuys at the Kunstakademie, Düsseldorf in the 1960s. The Palermo essay was published in Transmission: Speaking and Listening, volume 2, Sheffield Hallam University, 2003, and a review of Knoebel's exhibition Primary Structures 1966/2006 at the Henry Moore Foundation, Leeds, published in Artforum