Experiments Relevant to the Development of Laser Interferometric Gravitational Wave Detectors

The development of gravitational wave detectors has been in progress for approximately twenty-five years. As yet there has been no clear evidence for the successful detection of such propagating fluctuations in the curvature of spacetime, but the prospects seem good that detectors of sufficient sensitivity to detect gravitational waves of astrophysical origin can be constructed in the near future. The most promising form of detector is the long baseline laser interferometer, and prototypes are being developed at a number of sites around the world. A 10 metre prototype is currently being developed in Glasgow. This thesis is an account of work based on the Glasgow prototype. After an elementary introduction to the theoretical foundations of gravitational waves, various sources of gravitational radiation, the nature of their emitted signal and their strengths are considered. Suitable detectors and their possible sensitivities are reviewed. Noise sources which could limit the sensitivity of laser interferometer detectors and the constraints which these place on the design of the detector are discussed. Since the test masses in an interferometer detector must be freely suspended as pendulums, yet their orientation must be accurately controlled to maintain correct alignment of the optical cavities forming the interferometer, an active orientation control system was developed and installed on the Glasgow prototype. This system provides a high degree of positional and angular stabilisation at low frequencies while leaving the test mass essentially free at high frequencies. Some of the potential limitations and noise sources are noted and their magnitudes calculated. A digital recording system was designed and used to record data from the prototype detector at Glasgow. The effects of the detector's response are analysed and techniques to recover the gravitational wave signal from the recorded data are described. The analysis of some data recorded with this system is then reported. The pulse statistics of the interferometer are analysed and the implications for searches for millisecond pulses of gravitational waves are discussed. The results of a search for periodic signals in the detector output are presented. Various sources of contamination which may be present in the detector output are identified, limitations of the recorded data are noted, and techniques which may be used to reduce the importance of these effects are described

A Survey of Housing Equity Withdrawal and Injection in Australia

Over the past decade or so, aggregate data suggest a trend increase in housing equity withdrawal in Australia, potentially stimulating household spending. However, there has been little disaggregated information on how equity is being withdrawn and injected, the characteristics of households altering housing equity, and how funds from withdrawn equity are being used. This paper uses a survey of 4 500 households commissioned by the Reserve Bank of Australia (RBA) to address these questions. The results suggest that, during 2004, the most common method of withdrawing equity was for a household to increase the level of debt secured against a property they already owned. In contrast, most of the value of equity withdrawn was associated with property transactions, with the typical property transaction resulting in a net equity withdrawal. Turnover in the property market is therefore likely to be an important driver of cycles in aggregate housing equity withdrawal. Bivariate and logit analysis suggests a significant life-cycle influence, with the bulk of equity withdrawal being undertaken by older households, while younger households typically inject, primarily through mortgage repayments or deposits for property purchase. Finally, the results suggest that the bulk of the value of withdrawn equity was used to increase non-housing assets, although a significant proportion of households used the funds for consumption expenditure.housing equity withdrawal; housing turnover; household debt

Imagine a world without borders: an immunologist's thoughts on Brexit.

Science is a truly global enterprise and the opposite of nationalism. In light of the British referendum and the decision to leave the EU, we can look to southern Italy for two lessons to see where the decision could lead us. [Image: see text]This is the final version of the article. It first appeared from Wiley via http://dx.doi.org/10.15252/embr.20164301

Lignin Formation and the Effects of Gravity: A New Approach

Two aspects of considerable importance in the enigmatic processes associated with lignification have made excellent progress. The first is that, even in a microgravity environment, compression wood formation, and hence altered lignin deposition, can be induced upon mechanically bending the stems of woody gymnosperms. It now needs to be established if an organism reorientating its woody stem tissue will generate this tissue in microgravity, in the absence of externally applied pressure. If it does not, then gravity has no effect on its formation, and instead it results from alterations in the stress gradient experienced by the organism impacted. The second area of progress involves establishing how the biochemical pathway to lignin is regulated, particularly with respect to selective monolignol biosynthesis. This is an important question since individual monomer deposition occurs in a temporally and spatially specific manner. In this regard, the elusive metabolic switch between E-p-coumaryl alcohol and E-coniferyl alcohol synthesis has been detected, the significance of which now needs to be defined at the enzyme and gene level. Switching between monolignol synthesis is important, since it is viewed to be a consequence of different perceptions by plants in the gravitational load experienced, and thus in the control of the type of lignification response. Additional experiments also revealed the rate-limiting processes involved in monolignol synthesis, and suggest that a biological system (involving metabolite concentrations, as well as enzymatic and gene (in)activation processes) is involved, rather than a single rate-limiting step

Plant metabolism and cell wall formation in space (microgravity) and on Earth

Variations in cell wall chemistry provide vascular plants with the ability to withstand gravitational forces, as well as providing facile mechanisms for correctional responses to various gravitational stimuli, e.g., in reaction wood formation. A principal focus of our current research is to precisely and systematically dissect the essentially unknown mechanism(s) of vascular plant cell wall assembly, particularly with respect to formation of its phenolic constituents, i.e., lignins and suberins, and how gravity impacts upon these processes. Formation of these phenolic polymers is of particular interest, since it appears that elaboration of their biochemical pathways was essential for successful land adaptation. By extrapolation, we are also greatly intrigued as to how the microgravity environment impacts upon 'normal' cell wall assembly mechanisms/metabolism