Investigating Analytical and Numerical Methods to Predict Satellite Orbits Using Two-Line Element Sets

As Low Earth Orbit (LEO) contains an ever-increasing number of objects, the prediction of future object positions must be precise in order to avoid collisions. Object positions are distributed in two-line element (TLE) sets and are generated using the analytical propagator known as Simplified General Perturbations 4 (SGP4). However, a numerical integrator called Special Perturbations (SP) provides an alternative approach to TLE generation and propagation. In this thesis, TLE accuracy was determined with both models, and the length of time that a single element set can provide valid information was also established. With two-line element sets as data, comparisons were made between the numerical integrator and the analytical model for objects in LEO, particularly the Hubble Space Telescope (HST). The results obtained indicated that the propagated position error using SGP4 remained within 1 km of the expected position during a 7 day period from the epoch of the initial element set. Additionally, the majority of comparisons between SGP4 and SP resulted in a higher error while using the numerical integrator, although some comparisons showed a lower propagated position error with SP. This final result shows a potential for SP to provide more accurate position information than SGP4 in future research

Preparing to Take the Field: A Temporal Exploration of Stress, Emotion, and Coping in Elite Cricket

The purpose of this study was to explore the stress, emotion, and coping (SEC) experiences of elite cricketers leading up to and on the day of their first competitive fixture of the season. Four elite male cricketers (M = 21.25, SD = 1.5) completed Stress and Emotion Diaries (SEDs) for the 7-day period leading up to and on the day of their first competitive fixture of the season. We then interviewed the cricketers to explore the content of the SEDs in more detail. We used semistructured interviews to glean insight into the stressors, cognitions, emotions, coping strategies, and behaviors. Inductive and deductive content data analysis provided a holistic and temporal exploration of the SEC process underpinned by the cognitive-motivational-relational theory of emotions (Lazarus, 1999). The results highlighted the ongoing and continuous nature of the SEC process while illustrating the coping strategies the cricketers used leading up to and on the day of competition

Can ABC be Used for Model Selection?

Over the past ten years, Approximate Bayesian Computation (ABC) has become hugely popular to estimate the parameters of a model when the likelihood function cannot be computed in a reasonable amount of time. ABC can in principle be used also to perform Bayesian model comparison, but this raises the question of which summary statistic should be used for such applications. Here we present a general method for constructing a summary statistic that is sufficient for the model choice problem. We apply this construction to models from the exponential family. Unfortunately, in more complex models, our construct often results in statistics with too high dimensionality to use in ABC. We therefore discuss the possibility of applying ABC with non-sufficient statistics

The association of preoperative cardiac stress testing with 30-day death and myocardial infarction among patients undergoing kidney transplantation

BACKGROUND:Although periodic cardiac stress testing is commonly used to screen patients on the waiting list for kidney transplantation for ischemic heart disease, there is little evidence to support this practice. We hypothesized that cardiac stress testing in the 18 months prior to kidney transplantation would not reduce postoperative death, total myocardial infarction (MI) or fatal MI. METHODS:Using the United States Renal Data System, we identified ESRD patients ≥40 years old with primary Medicare insurance who received their first kidney transplant between 7/1/2006 and 11/31/2013. Propensity matching created a 1:1 matched sample of patients with and without stress testing in the 18 months prior to kidney transplantation. The outcomes of interest were death, total (fatal and nonfatal) MI or fatal MI within 30 days of kidney transplantation. RESULTS:In the propensity-matched cohort of 17,304 patients, death within 30 days occurred in 72 of 8,652 (0.83%) patients who underwent stress testing and in 65 of 8,652 (0.75%) patients who did not (OR 1.07; 95% CI: 0.79-1.45; P = 0.66). MI within 30 days occurred in 339 (3.9%) patients who had a stress test and in 333 (3.8%) patients who did not (OR 1.03; 95% CI: 0.89-1.21; P = 0.68). Fatal MI occurred in 17 (0.20%) patients who underwent stress testing and 15 (0.17%) patients who did not (OR 0.97; 95% CI: 0.71-1.32; P = 0.84). CONCLUSION:Stress testing in the 18 months prior to kidney transplantation is not associated with a reduction in death, total MI or fatal MI within 30 days of kidney transplantation

10 Years of Cap and Trade: A Comprehensive Review of the Regional Greenhouse Gas Initiative

The Regional Greenhouse Gas Initiative was the first greenhouse gas-focused cap-and-trade program in the United States. Encompassing nine states in the northeast region of the country, the program covers carbon dioxide emissions from large-scale fossil-based electric power generators. Over the course of the last decade, the Initiative has helped make substantial progress in reducing emissions and changing the generation portfolio in the region, as seen in data from governments, independent system operators, and RGGI itself. It has helped to encourage the reduction of coal and petroleum as sources of electric generation, while encouraging the adoption of renewable generation, and collectively reducing emissions among RGGI states by over 22%, far exceeding the rest of the nation. While RGGI has been a major factor in emissions reduction and the shifts in the region’s generation portfolio, it is not likely the only reason. Other factors, including the cost of energy, Renewable Portfolio Standards, and the potential for emissions leakage, all have had an impact on sources of electric generation and emissions reduction. Ultimately, the Initiative has been successful in its goal of reducing greenhouse gas emissions and improving the region’s generation portfolio. While not without its drawbacks, including the overallocation of carbon allowances, and the potential for leakage, the program does have the potential for long-term improvement by expanding sector coverage and eliminating sources of leakage

Homophobia and heterosexism

“Homophobia” is a widely understood term referring to antihomosexual attitudes and practices, but terms such as “homophobia,” “heterosexism,” and “heteronormativity” point to different ideas of what “homosexual” means, and where opposition to same-sex relations originates. Gayle Rubin, relying on structural anthropology, proposes that it arises as a disciplinary mechanism used by men to exercise control over women’s reproductive power in families. Gender panic theory focuses particularly on how defensiveness against losing male status and privilege generates homophobia. Sociohistorical theories examine how homophobia increases or decreases according to the symbolic placement of lesbian, gay, bisexual, and transgender people in the social status system. In the early twenty-first century, contradictory trends have led to improved citizenship rights for LGBT people in some countries, while others have reinforced or increased state and social violence against their LGBT populations

Use of positive selection methods for discovery and improvement of nitroreductase enzymes for cancer gene therapy

Bacterial nitroreductases are members of a diverse family of oxidoreductase enzymes that are capable of activating nitroaromatic compounds, including anticancer prodrugs such as CB 1954 and PR-104A. This capability is useful in the anti-cancer gene therapy strategy known as gene-directed enzyme prodrug therapy (GDEPT), which involves the killing of tumour cells through activation of an inert prodrug to its cytotoxic form, following selective delivery of a genetically encoded prodrug-converting enzyme to cancerous tissues. A key limitation in nitroreductase-based GDEPT has been the inability to rapidly and non-invasively determine vector localisation and gene delivery prior to systemic administration of prodrug. To address this we have developed dual-purpose nitroreductases that exhibit the ability to efficiently activate both GDEPT prodrugs and next-generation radioisotope-labelled PET imaging probes, in a manner that renders the probes temporarily cell-entrapped for detection using a PET scanner. This capability places greater control of the therapy in the hands of the clinician, and will facilitate clinical development of this treatment. One key focus has been the engineering of more efficient enzymes using both random and targeted mutagenesis strategies. A complementary strategy has been the discovery of novel nitroreductases through the screening of metagenomic fragments of DNA from the unculturable bacteria present in New Zealand soil. To enable efficient screening of these libraries, we have developed an array of genetic and biochemical tools for the rapid selection of active nitroreductases. Here we have investigated the effectiveness of these different approaches for improving nitroreductase activity, and demonstrate their utility in improving activity with specific target substrates including next- generation prodrugs and PET imaging probes

Ultrastructure of Zebra Fish Dorsal Aortic Cells

Expression of vascular smooth muscle cell (VSMC) markers such as serum response factor (SRF) is complicated in zebrafish because of the ill-defined histology of the dorsal aorta and the presence of perivascular pigment. We report the ultrastructure of aortic cells in 7-day, 1-month, and 3-month-old zebrafish and provide clear evidence for the presence of perivascular melanocytes harboring an abundance of melanin. In 7-day-old larvae, endothelial cells (EC) and synthetic mural cells that display little evidence of VSMC differentiation comprise the dorsal aorta. The latter mural cells appear to fully differentiate into VSMC by 1 month of age. In 3-month-old adult zebrafish, EC exhibit greater differentiation as evidenced by the accumulation of electron-dense bodies having a diameter of approximately 200 nm. Adult zebrafish aortae also exhibit at least one clear layer of VSMC with the characteristic array of membrane-associated dense plaques, myofilament bundles, and a basement membrane. Subjacent to VSMC are collagen-producing adventitial fibroblasts and melanocytes. These studies indicate that fully differentiated VSMC occur only after day 7 in zebrafish and that such cells are arranged in at least one lamellar unit circumscribing the endothelium. These findings provide new data about the timing and accumulation of VSMC around the zebrafish aorta, which will be useful in phenotyping mutant zebrafish that exhibit defects in blood circulation