Aspects of mirrors and suspensions for advanced gravitational wave detectors

Gravitational waves were first predicted by Albert Einstein's Theory of general relativity, published in 1916. These waves are perturbations in the curvature of space-time. Indirect evidence of their existence has been obtained via observations of binary pulsar system inspirals by Hulse and Taylor. Research is now focussed on achieving direct detection of gravitational waves, giving a new way of observing astronoomical events in the universe. Gravitational waves are quadrupole in nature, causing tidal strains in space. The weak nature of gravity means that the magnitude of these strains is very small. Only astronomical scale sources are likely to produce waves of sufficient amplitude to be detected on Earth. In the frequency band of a few Hz to a few kHz, the expected strain amplitude for violent sources is of the order of 10[superscript -22]. Detection is most likely to be achieved using long baseline interferometer detectors. Currently several such detectors are in operation worldwide, including the GEO600 detector, built in a collaboration involving the Institute for Gravitational Research at the University of Glasgow, the Albert Einstein Institute (Hannover and Golm), and the University of Cardiff. In America the LIGO detector network has three large interferometric detectors - two of 4 km arm length and one with 2 km arms. In Italy a European collaboration has constructed the 3 km VIRGO detector. Currently GEO600 and LIGO have undertaken 5 data taking science runs with the most recent year long run, also involving VIRGO, concluding in November 2007. No detections have yet been confirmed, but analysis on the results of the most recent GEO600/LIGO/VIRGO run is ongoing. These detectors are now operating at, or close to their design sensitivities, so research is focussed on reduction of various noise sources by upgrading of the detectors. One important noise source is thermal noise (both Brownian and thermo-elastic) - a limiting factor at midband frequencies. Reduction of mechanical loss in mirrors and their suspensions will help lessen the impact of thermal noise in future detectors. The research detailed in this thesis was aimed at reducing thermal noise. In particular, it covers work undertaken to investigate the mechanical loss of suspension ribbons and fibres, test mass mirror coatings and also diffractive surfaces on test masses to evaluate their suitability for employment in future advanced gravitational wave detectors. Upgrade of LIGO to "Advanced LIGO" will aim to reduce thermal noise by implementing mirror suspension techniques pioneered in GEO600. Specifically, it was initially proposed that test masses be suspended from silica ribbon fibres, a key choice that will be re-evaluated in this thesis. Ribbons (or fibres) will be fabricated by a CO[subscript 2] laser pulling machine being developed in Glasgow, with control programming being undertaken by the author. Characterising the dimensions, strength and vertical bounce frequencies of the ribbons is important to confirm their suitability for use in detector mirror suspensions. A dimensional characterisation machine was constructed to measure the ribbon's cross sectional dimensions, with emphasis being placed on achieving high resolution in the ribbon neck regions, where the most bending occurs. Also, a bounce testing machine was constructed to experimentally measure the ribbon's vertical bounce frequency. Finally a proof load test was constructed to verify that ribbons could support the required weight. Results showed that ribbons could be fabricated successfully with the required strength and bounce frequency, though shaping of the cross section still requires further research to achieve the optimum. In a pendulum system most of the energy is stored as gravitational potential energy rather than bending energy of the suspension fibres or ribbons. Thus the effective loss of the suspension fibres/ribbons is reduced or "diluted" and thermal noise is lower than may be naively expected. Dilution of the mechanical loss of the pendulum suspensions was investigated using finite element modelling. Methods for importing data from the dimensional characterisation machine were developed, and it was observed that the dilution resulting from ribbon suspensions was not as high as had been initially expected, with bending in the neck region of the ribbon being seen to significantly reduce dilution. It was observed that the rectangular ribbons had inferior dilution to equivalent cross section circular fibres for necks of the length typically being produced. A typical 7.5 mm necked ribbon was seen to have a dilution 1.5 times lower than an equivalent fibre, despite the ribbons having 3.3 times greater dilution with no necks. Ribbons were only seen to have this superior dilution for very short necks. Bending in the necks resulted in an increased amount of bending strain energy occurring which caused the lower dilution factors. Additionally, bending occurring in the ears that join the fibres or ribbons to the masses was seen to further reduce the dilution. In the light of low dilution factors, reduction (ideally nulling) of thermoelastic noise was studied. Reduction in thermal noise in this way is proposed through the use of tapered fibres, which showed that a lower overall noise level than that from the baseline ribbons planned for Advanced LIGO can be achieved, despite lower dilution factors. In the light of this work tapered fibres have now been adopted as the baseling for Advanced LIGO. Measurement of test mass mirror samples showed that the mechanical loss of mirror coatings can be significantly reduced by doping the high refractive index layer, with reduction up to a factor of 2.5 in measured mechanical loss observed, when compared to equivalent undoped coatings. In order to perform these measurements an interferometric read out system was constructed. Future detectors will use higher laser powers which may cause thermal distortions in transmissive optical components. Use of all reflective components may be required to reduce this problem, possibly via diffractive mirrors. Measurements were undertaken on samples to discover if introducing a diffraction grating to an optic's surface increased the mechanical loss. However, the grating was not seen to do this, and also did not increase the mechanical loss of an optical coating applied on top of its surface, which verified that diffractive optics are viable for use in future detectors

Educational Research - Two Paradigms : Two Epistemologies

Put simply, educational research is the systematic study of educational problems and practices. Its basic purposes would at least be seen to cover such things as evaluating new and existing policies, programmes, curricula and practices; strengthening the information base underlying educational planning, the formulation of educational policy and the design of educational programmes; increasing the problem solving capacity of education systems, institutions and teachers; increasing knowledge and understanding of educational problems and processes; and raising questions concerning assumptions and identifying weaknesses. Research into these problems and practices has commonly been designed and structured so as to lay claim to \u27scientific\u27 respectability (Brim: 1974). This claim remains a constant theme throughout the literature concerning education and in the normal parlance and value judgements made by educators. However, it has also been a feature of educational research that many of its practitioners have confused academic excellence and scholarly endeavour with the requirement to become as \u27scientific\u27 as possible in their research designs. This is in spite of the now recognised triviality and irrelevance of much of the so called \u27scientific\u27 research undertaken by postgraduate students

The Validity of Automatic Methods for Estimating Skeletal Age in Young Athletes:A Comparison of the BAUSport Ultrasound System and BoneXpert with the Radiographic method of Fels.

This study examined the validity of two automated methods (BAUSport, BoneXpert software using Fels, Greulich-Pyle, Tanner-Whithouse III protocols) for estimating skeletal age (SA) in young athletes in comparison to a reference standard (Fels). 85 male and female athletes, nine to seventeen years of age, from multiple sports were assessed for SA as part of an annual medical and health screening programme. Intra-class correlations demonstrated high degrees of association between the automatic methods for estimating SA (BAUSport r =.98; BoneXpert r =.96-.99) and the discrepancy between SA and chronological age (SA-CA) (BAUSport r =.93; BoneXpert r =.88-.97), with the reference standard. Concordance analyses for the categorisation of participants as early, on-time and late maturing also demonstrated substantial levels of agreement for both methods (BAUSport Kappa = .71; BoneXpert Fels Kappa = .63) with the reference standard. Bland-Altman plots comparing the automatic methods with the reference standard identified statistically significant fixed biases, ranging in magnitude from small to large. Collectively, these results suggest that BoneXpert and BAUSport can provide comparable estimates of SA and SA-CA in young athletes relative to the Fels method. Biases in the estimation of SA should, however, be considered and the automatic methods should be implemented as part of a comprehensive growth and maturity screening protocol. The non-invasive nature of the BAUSport method affords particular advantages (no radiation exposure, portability) in contexts where the regular estimation of SA is recommended

The Validity of Automatic Methods for Estimating Skeletal Age in Young Athletes:A Comparison of the BAUSport Ultrasound System and BoneXpert with the Radiographic method of Fels.

This study examined the validity of two automated methods (BAUSport, BoneXpert software using Fels, Greulich-Pyle, Tanner-Whithouse III protocols) for estimating skeletal age (SA) in young athletes in comparison to a reference standard (Fels). 85 male and female athletes, nine to seventeen years of age, from multiple sports were assessed for SA as part of an annual medical and health screening programme. Intra-class correlations demonstrated high degrees of association between the automatic methods for estimating SA (BAUSport r =.98; BoneXpert r =.96-.99) and the discrepancy between SA and chronological age (SA-CA) (BAUSport r =.93; BoneXpert r =.88-.97), with the reference standard. Concordance analyses for the categorisation of participants as early, on-time and late maturing also demonstrated substantial levels of agreement for both methods (BAUSport Kappa = .71; BoneXpert Fels Kappa = .63) with the reference standard. Bland-Altman plots comparing the automatic methods with the reference standard identified statistically significant fixed biases, ranging in magnitude from small to large. Collectively, these results suggest that BoneXpert and BAUSport can provide comparable estimates of SA and SA-CA in young athletes relative to the Fels method. Biases in the estimation of SA should, however, be considered and the automatic methods should be implemented as part of a comprehensive growth and maturity screening protocol. The non-invasive nature of the BAUSport method affords particular advantages (no radiation exposure, portability) in contexts where the regular estimation of SA is recommended

Improved fused silica fibres for the advanced LIGO monolithic suspensions

To further increase the sensitivity of the advanced LIGO (aLIGO) gravitational wave detectors, two major upgrades of the monolithic fused silica suspension are considered: a higher stress in the suspension fibres and a longer final suspension stage. One of the challenges for this upgrade will be producing thinner and longer fibres that can hold the test mass safely. We demonstrate that laser power fluctuations during the fibre fabrication process can produce diameter variations and potentially weak fibres. We present a laser intensity stabilisation technology for fused silica fibre fabrication using a camera system to monitor heating. Fibres fabricated with this new technique showed a 34% decrease in the interquartile range of measured breaking stress, which indicates that the application of intensity stabilisation technology can improve the statistical strength of fused silica fibres by tightening the spread of values. As the aLIGO detectors upgrade plan (A+) proposes to use thinner fibres, it is essential to enhance the performance of fused silica fibres

The Development of the Role of Inspectors of Schools in the Education Department of South Australia: 1875 to 1970

The purpose of this study is to examine the development of the role of the inspectors of schools in the Education Department of South Australia from the assent to the 1875 Education Act to 1970, the year of appointment of A.W. Jones as Director-General of Education. The first inspector of schools was appointed in South Australia in 1851 with an ill-defined role given to him by the Governor. In fact, Dr. William Wyatt, who was not a teacher, was left to determine his own role, except that he was not to interfere with the religious feelings and prejudices of this generally dissenting and voluntaryist Colony of free settlers. ... This study shows that the value for money aspect of the role of the inspectors of schools was always present, but that the values sought changed over the period; different aspects of the multi-faceted role were to the fore or in the background at different times; and the role changed from mainly regulatory to mainly developmental as the teachers and, indeed, as the inspectors were better educated and better prepared for their tasks. The study also indicates that the clash between the advisory and the assessing role was greatest when trust between teachers and the administration was at a low ebb, for instance, when in 1913 the inspectors reacted badly to the transfer of their examining and promoting of pupils to head teachers and when in the 1940s the administration promoted teachers without regard to promotion lists. Such situations were brought about by an amalgam of personalities, social, economic and political conditions and the educational thinking of the time

Bio-Banding in Youth Sports::Background, Concept and Application

Inter-individual differences in size, maturity status, function, and behavior among youth of the same chronological age (CA) have long been a concern in grouping for sport. Bio-banding is a recent attempt to accommodate maturity-associated variation among youth in sport. The historical basis of the concept of maturity-matching and its relevance to youth sport, and bio-banding as currently applied are reviewed. Maturity matching in sport has often been noted but has not been systematically applied. Bio-banding is a recent iteration of maturity matching for grouping youth athletes into ‘bands’ or groups based on characteristic(s) other than CA. The percentage of predicted young adult height at the time of observation is the estimate of maturity status of choice. Several applications of bio-banding in youth soccer have indicated positive responses from players and coaches. Bio-banding reduces, but does not eliminate, maturity-associated variation. The potential utility of bio-banding for appropriate training loads, injury prevention, and fitness assessment merits closer attention, specifically during the interval of pubertal growth. The currently used height prediction equation requires further evaluation

Burden of disease from inadequate water, sanitation and hygiene in low- and middle-income settings: a retrospective analysis of data from 145 countries

objective To estimate the burden of diarrhoeal diseases from exposure to inadequate water, sanitation and hand hygiene in low- and middle-income settings and provide an overview of the impact on other diseases. methods For estimating the impact of water, sanitation and hygiene on diarrhoea, we selected exposure levels with both sufficient global exposure data and a matching exposure-risk relationship. Global exposure data were estimated for the year 2012, and risk estimates were taken from the most recent systematic analyses. We estimated attributable deaths and disability-adjusted life years (DALYs) by country, age and sex for inadequate water, sanitation and hand hygiene separately, and as a cluster of risk factors. Uncertainty estimates were computed on the basis of uncertainty surrounding exposure estimates and relative risks. results In 2012, 502 000 diarrhoea deaths were estimated to be caused by inadequate drinking water and 280 000 deaths by inadequate sanitation. The most likely estimate of disease burden from inadequate hand hygiene amounts to 297 000 deaths. In total, 842 000 diarrhoea deaths are estimated to be caused by this cluster of risk factors, which amounts to 1.5% of the total disease burden and 58% of diarrhoeal diseases. In children under 5 years old, 361 000 deaths could be prevented, representing 5.5% of deaths in that age group. conclusions This estimate confirms the importance of improving water and sanitation in low- and middle-income settings for the prevention of diarrhoeal disease burden. It also underscores the need for better data on exposure and risk reductions that can be achieved with provision of reliable piped water, community sewage with treatment and hand hygiene

The PHASES Differential Astrometry Data Archive. V. Candidate Substellar Companions to Binary Systems

The Palomar High-precision Astrometric Search for Exoplanet Systems monitored 51 subarcsecond binary systems to evaluate whether tertiary companions as small as Jovian planets orbited either the primary or secondary stars, perturbing their otherwise smooth Keplerian motions. Six binaries are presented that show evidence of substellar companions orbiting either the primary or secondary star. Of these six systems, the likelihoods of two of the detected perturbations to represent real objects are considered to be "high confidence", while the remaining four systems are less certain and will require continued observations for confirmation.Comment: 16 Pages, Accepted to A