Statically indeterminate stresses

Thesis (B.S.)--University of Illinois, 1908.Ms

Minimally Parametric Power Spectrum Reconstruction from the Lyman-alpha Forest

Current results from the Lyman alpha forest assume that the primordial power spectrum of density perturbations follows a simple power law form, with running. We present the first analysis of Lyman alpha data to study the effect of relaxing this strong assumption on primordial and astrophysical constraints. We perform a large suite of numerical simulations, using them to calibrate a minimally parametric framework for describing the power spectrum. Combined with cross-validation, a statistical technique which prevents over-fitting of the data, this framework allows us to reconstruct the power spectrum shape without strong prior assumptions. We find no evidence for deviation from scale-invariance; our analysis also shows that current Lyman alpha data do not have sufficient statistical power to robustly probe the shape of the power spectrum at these scales. In contrast, the ongoing Baryon Oscillation Sky Survey (BOSS) will be able to do so with high precision. Furthermore, this near-future data will be able to break degeneracies between the power spectrum shape and astrophysical parameters.Comment: 11 pages plus appendices, 8 figures. v2: matches version published in MNRAS. Some clarifications to discussion and exposition, updated reference

Probing Sub-parsec Structure in the Lyman Alpha Forest with Gravitational Microlensing

We present the results of microlens ray-tracing simulations showing the effect of absorbing material between a source quasar and a lensing galaxy in a gravitational lens system. We find that, in addition to brightness fluctuations due to microlensing, the strength of the absorption line relative to the continuum varies with time, with the properties of the variations depending on the structure of the absorbing material. We conclude that such variations will be measurable via UV spectroscopy of image A of the gravitationally lensed quasar Q2237+0305 if the Lyman Alpha clouds between the quasar and the lensing galaxy possess structure on scales smaller than $\sim 0.1$ pc. The time scale for the variations is on the order of order years to decades, although very short term variability can occur. While the Lyman alpha lines may not be accessible at all wavelengths, this approach is applicable to any absorption system, including metal lines.Comment: 8 pages, 11 figures, to appear in MNRAS (note resolution of some figures reduced due to size limitations

Ectopic Maxillary Canines:Segregation Analysis and a Twin Study

The etiology of ectopic canines is controversial, with opinion divided as to a genetic or environmental mechanism. This study addressed the hypothesis that genetic factors play a role in the etiology of ectopic maxillary canines. Sixty-three probands were identified, and information on the dental status of 395 relatives was determined. Pedigrees were constructed and the Relative Risk calculated. Complex segregation analysis was carried out by means of the Pedigree Analysis Package. The best mathematical model obtained was a single dominant gene with autosomal transmission, incomplete penetrance, and highly variable expression. Only two of seven pairs of monozygotic twins were concordant for ectopic canines. This is consistent with environmental or epigenetic variables affecting the phenotype. The low concordance rate is consistent with the low penetrance determined by the segregation analysis and further supports the existence of environmental factors.peer-reviewe

Internal Combustion Engine Bans and Global Oil Use

Automotive transport represents one of the highest contributing sources of oil use, local air pollution, and greenhouse gas emissions. Several countries, notably including several European countries and China, have proposed bans on the sale of automotive internal combustion engine (ICE) vehicles as a means to abate these negative effects from the sector. Some cities and regions have already instituted restrictions on ICE vehicles. Larger, national bans have been discussed as a policy to begin in 2040. We consider the literature on proposed policies to ban ICE vehicles and develop scenarios to estimate the potential impacts of these proposed bans, to contribute to a peaking in oil demand and eventual reductions in CO2 emissions. We find that national level ICE car bans in key markets such as China and Europe in 2040 could reduce oil use by five million barrels a day (b/d) by 2050, under five percent of projected global oil use. A global ban would eliminate three times that level of oil use but would likely take several decades for its full impact is realized. Our findings suggest that other supporting policies beyond the bans alone might be necessary to trigger more rapid changes in markets and purchase behavior

Sex, stress and sleep apnoea: decreased susceptibility to upper airway muscle dysfunction following intermittent hypoxia in females

Obstructive sleep apnoea syndrome (OSAS) is a devastating respiratory control disorder more common in men than women. The reasons for the sex difference in prevalence are multifactorial, but are partly attributable to protective effects of oestrogen. Indeed, OSAS prevalence increases in post-menopausal women. OSAS is characterized by repeated occlusions of the pharyngeal airway during sleep. Dysfunction of the upper airway muscles controlling airway calibre and collapsibility is implicated in the pathophysiology of OSAS, and sex differences in the neuro-mechanical control of upper airway patency are described. It is widely recognized that chronic intermittent hypoxia (CIH), a cardinal feature of OSAS due to recurrent apnoea, drives many of the morbid consequences characteristic of the disorder. In rodents, exposure to CIH-related redox stress causes upper airway muscle weakness and fatigue, associated with mitochondrial dysfunction. Of interest, in adults, there is female resilience to CIH-induced muscle dysfunction. Conversely, exposure to CIH in early life, results in upper airway muscle weakness equivalent between the two sexes at 3 and 6 weeks of age. Ovariectomy exacerbates the deleterious effects of exposure to CIH in adult female upper airway muscle, an effect partially restored by oestrogen replacement therapy. Intriguingly, female advantage intrinsic to upper airway muscle exists with evidence of substantially greater loss of performance in male muscle during acute exposure to severe hypoxic stress. Sex differences in upper airway muscle physiology may have relevance to human OSAS. The oestrogen–oestrogen receptor α axis represents a potential therapeutic target in OSAS, particularly in post-menopausal women

Evidence of scawtite and tilleyite formation at ambient conditions in hydrated Portland cement blended with freshly-precipitated nano-size calcium carbonate to reduce greenhouse gas emissions

Acknowledgements We thank CCM for its financial support of a PhD student ship tenable by LJM. Electron Microscopy was performed in the ACEMAC Facility at the University of Aberdeen by Mr. J. Still. Several of our group have contributed to discussion and provided samples, so thanks go to Wanawan Pragot and M. Ara Carballo-MeilanPeer reviewedPostprin

A New, Carbon-Negative Precipitated Calcium Carbonate Admixture (PCC-A) for Low Carbon Portland Cements

Funding: The first named author L.M., a PhD scholar at the University of Aberdeen working under the supervision of M.S.I. and F.P.G., is sponsored through a fully funded studentship by CCM (UK) Ltd. Acknowledgments: The cements used in this work were kindly provided by Hanson Cement UK. Electron Microscopy was performed in the ACEMAC Facility at the University of AberdeenPeer reviewedPublisher PD

Constraints on the Primordial Power Spectrum from High Resolution Lyman-alpha Forest Spectra and WMAP

The combined analysis of the cosmic microwave background on large scales and Lyman-alpha forest on small scales provides a sufficiently long lever arm to obtain strong constraints on the slope and curvature of the power spectrum of primordial density fluctuations. We present results from the combination of the first year WMAP data and the dark matter power spectrum inferred by Viel et al. (2004) for two different sets of high resolution and high signal-to-noise quasar absorption spectra: the Croft et al. (2002) sample with a median redshift z=2.72 and the LUQAS sample (Kim et al. 2004) with a median redshift z=2.125. The best fit value for the {\it rms} fluctuation amplitude of matter fluctuations is sigma_8 =0.94 +- 0.08 and n=0.99 +- 0.03, if we do not include running of the spectral index. The best fit model with a running spectral index has parameters n=0.959 +- 0.036 and n_run=-0.033 +- 0.025. The data is thus consistent with a scale-free primordial power spectrum with no running of the spectral index. We further include tensor modes and constrain the slow-roll parameters of inflation.Comment: 6 pages, 4 Figures, 1 Table. One figure added and second order extension of the standard slow-roll approximation included. Main results unchanged. MNRAS in pres