Progress report on the ultra heavy cosmic ray experiment (AO178)

The Ultra Heavy Cosmic Ray Experiment (UHCRE) is based on a modular array of 192 side-viewing solid state nuclear track detector stacks. These stacks were mounted in sets of four in 48 pressure vessels employing sixteen peripheral Long Duration Exposure Facility (LDEF) trays. The extended duration of the LDEF mission has resulted in a greatly enhanced scientific yield from the UHCRE. The geometry factor for high energy cosmic ray nuclei, allowing for Earth shadowing, was 30 sq m-sr, giving a total exposure factor of 170 sq m-sr-y at an orbital inclination of 28.4 degrees. Scanning results indicate that about 3000 cosmic ray nuclei in the charge region with Z greater than 65 were collected. This sample is more than ten times the current world data in the field (taken to be the data set from the HEAO-3 mission plus that from the Ariel-6 mission) and is sufficient to provide the world's first statistically significant sample of actinide (Z greater than 88) cosmic rays. Results to date are presented including details of ultra-heavy cosmic ray nuclei, analysis of pre-flight and post-flight calibration events and details of track response in the context of detector temperature history. The integrated effect of all temperature and age related latent track variations cause a maximum charge shift of +/- 0.8 e for uranium and +/- 0.6 e for the platinum-lead group. The precision of charge assignment as a function of energy is derived and evidence for remarkably good charge resolution achieved in the UHCRE is considered. Astrophysical implications of the UHCRE charge spectrum are discussed

The LDEF ultra heavy cosmic ray experiment

The LDEF Ultra Heavy Cosmic Ray Experiment (UHCRE) used 16 side viewing LDEF trays giving a total geometry factor for high energy cosmic rays of 30 sq m sr. The total exposure factor was 170 sq m sr y. The experiment is based on a modular array of 192 solid state nuclear track detector stacks, mounted in sets of four in 48 pressure vessels. The extended duration of the LDEF mission has resulted in a greatly enhanced potential scientific yield from the UHCRE. Initial scanning results indicate that at least 1800 cosmic ray nuclei with Z greater than 65 were collected, including the world's first statistically significant sample of actinides. Post flight work to date and the current status of the experiment are reviewed

Testing for Markovian Character and Modeling of Intermittency in Solar Wind Turbulence

We present results of statistical analysis of solar wind turbulence using an approach based on the theory of Markov processes. It is shown that the Chapman-Kolmogorov equation is approximately satisfied for the turbulent cascade. We evaluate the first two Kramers-Moyal coefficients from experimental data and show that the solution of the resulting Fokker-Planck equation agrees well with experimental probability distributions. Our results suggest the presence of a local transfer mechanism for magnetic field fluctuations in solar wind turbulence

Disorder Induced Quantum Phase Transition in Random-Exchange Spin-1/2 Chains

We investigate the effect of quenched bond-disorder on the anisotropic spin-1/2 (XXZ) chain as a model for disorder induced quantum phase transitions. We find non-universal behavior of the average correlation functions for weak disorder, followed by a quantum phase transition into a strongly disordered phase with only short-range xy-correlations. We find no evidence for the universal strong-disorder fixed point predicted by the real-space renormalization group, suggesting a qualitatively different view of the relationship between quantum fluctuations and disorder.Comment: 4 pages, 4 postscript figures, needs RevTeX

Damage and repair classification in reinforced concrete beams using frequency domain data

This research aims at developing a new vibration-based damage classification technique that can efficiently be applied to a real-time large data. Statistical pattern recognition paradigm is relevant to perform a reliable site-location damage diagnosis system. By adopting such paradigm, the finite element and other inverse models with their intensive computations, corrections and inherent inaccuracies can be avoided. In this research, a two-stage combination between principal component analysis and Karhunen-Loéve transformation (also known as canonical correlation analysis) was proposed as a statistical-based damage classification technique. Vibration measurements from frequency domain were tested as possible damage-sensitive features. The performance of the proposed system was tested and verified on real vibration measurements collected from five laboratory-scale reinforced concrete beams modelled with various ranges of defects. The results of the system helped in distinguishing between normal and damaged patterns in structural vibration data. Most importantly, the system further dissected reasonably each main damage group into subgroups according to their severity of damage. Its efficiency was conclusively proved on data from both frequency response functions and response-only functions. The outcomes of this two-stage system showed a realistic detection and classification and outperform results from the principal component analysis-only. The success of this classification model is substantially tenable because the observed clusters come from well-controlled and known state conditions

Evolving friendships and shifting ethical dilemmas: fieldworkers' experiences in a short term community based study in Kenya

Fieldworkers (FWs) are community members employed by research teams to support access to participants, address language barriers, and advise on culturally appropriate research conduct. The critical role that FWs play in studies, and the range of practical and ethical dilemmas associated with their involvement, is increasingly recognised. In this paper, we draw on qualitative observation and interview data collected alongside a six month basic science study which involved a team of FWs regularly visiting 47 participating households in their homes. The qualitative study documented how relationships between field workers and research participants were initiated, developed and evolved over the course of the study, the shifting dilemmas FWs faced and how they handled them. Even in this one case study, we see how the complex and evolving relationships between fieldworkers and study participants had important implications for consent processes, access to benefits and mutual understanding and trust. While the precise issues that FWs face are likely to depend on the type of research and the context in which that research is being conducted, we argue that appropriate support for field workers is a key requirement to strengthen ethical research practice and for the long term sustainability of research programmes

The use of high aspect ratio photoresist (SU-8) for super-hydrophobic pattern prototyping

In this work we present a reliable technique for the production of large areas of high aspect-ratio patterns and describe their use as model super-hydrophobic systems. The high thickness and straight sidewalls possible with SU-8 were used to generate dense patterns of small pillars. These photoresist patterns could be used directly, without the need for micromoulding. A method is given allowing resist thickness to be varied over a wide range and a bottom antireflective layer was used to simplify patterning on reflective substrates. This patterning technique allows rapid testing of wetting theories, as pattern size and depth can be varied simply and samples can be produced in sufficient numbers for laboratory use. We show how the static contact angle of water varies with pattern height for one sample-pattern and how static and dynamic contact angles vary with dimension using high aspect-ratio patterns