Compost Amendments on Urban Soils vs. Water Retention

This study was undertaken to investigate the impact of compost on urban soils’ ability to retain water. Data from past studies led to the development of the hypothesis that compost will increase soil’s water-holding capacity up to a certain point, but, if too much compost is present, the soil will become hydrophobic. To test this hypothesis, four treatments were chosen in the form of compost layers of increasing thicknesses (0-inch compost layer, 1-inch compost layer, 2-inch compost layer, 3-inch compost layer), and three repetitions of each treatment were randomly assigned to twelve planting plots of equal size. Kale seeds were planted evenly in each plot and were tended as needed and watered consistently for the duration of two thirty-day trials. Soil moisture, temperature, and conductivity were measured with a soil probe twice weekly throughout the trials. The data showed an inverse relationship between compost and soil moisture: Soil moisture decreased as compost thickness increased. The same trend was seen between conductivity and compost. Temperature was not impacted by compost. This data led to a rejection of the hypothesis that compost increases soil’s water-holding capacity up to a certain limit. These unexpected results could be attributed to the shallow soil measurements achieved by the probe. In future research, a different method should be used to measure soil moisture in order to determine the characteristics of the soil below the compost layer. This study revealed implications for plants of different rooting lengths and provided insight for future designs of urban soil research projects

Cosmic String Radiation with Adaptive Mesh Refinement

Cosmic strings are a fundamental feature of many physically-motivated field theories which inevitably form in the early Universe, as a result of a symmetry breaking phase transition. An important example is the Peccei-Quinn mechanism, from which strings emerge as a potential source of dark matter axions. They are also a strong source of gravitational wave (GW) emission, with the potential for detection by the Laser Interferometer Gravitational-Wave Observatory (LIGO) and other GW experiments. The nonlinear evolution of cosmic strings has been extensively studied using large-scale numerical simulations. However, the vast difference in scale between a typical string width and the string curvature poses a significant computational challenge. This is usually addressed by approximating the string to have either zero or fixed comoving width, resulting in inconsistencies in predictions between different methods. One technique that can address this issue is adaptive mesh refinement (AMR), which allows the resolution of the numerical grid to adapt to the scale of the features of interest in the simulation. This thesis uses GRChombo, a sophisticated code originally designed for numerical relativity, to perform the first AMR simulations of global cosmic strings. We also present our numerical contributions to GRChombo as a core developer, including novel diagnostic tools and performance enhancement. We perform a detailed quantitative investigation of single sinusoidally displaced string configurations, comparing oscillating string trajectories with a backreaction model accounting for radiation energy losses. We conclude that analytic radiation modelling in the thin-string (Nambu-Goto) limit provides the appropriate picture for cosmological evolution. We also investigate the resulting massless (Goldstone boson or axion) and massive (Higgs) radiation signals, using quantitative diagnostic tools to determine their eigenmode decomposition. We find that the massless quadrupole is dominant and massive radiation is strongly suppressed with increasing mass, with a complex wavepacket structure that is sensitive to numerical resolution. String network configurations are also simulated, with advanced visualisation of radiation used to reveal new qualitative phenomena as strings reconnect and small loops decay. The thesis concludes with the cosmological implications of this work, considering dark matter axions radiated by cosmic strings and the outlook for gravitational wave signatures

Immunodiffusion and immunoelectrophoretic studies on Trypanosoma lewisi (Kent) during the course of an infection in the albino rat, Rattus rattus

Immunoelectrophoresis revealed an antigen-antibody response between 4 day metabolic products and 8, 12 and 16 day sera and between 4 day trypanosomal extract and 16 day serum. Metabolic products from trypanosomes incubated at room temperature do not appear to be antigenic. The limitations of immunodiffusion are discussed in reference to the results. It is suggested that some of the antibodies to metabolic products may be of the precipitating type while others are not. Since a faint reaction also occurred between 4 day trypanosomal extract and 16 day serum, it may be concluded that metabolic products contribute to only a portion of the antibody response of the rat and are by no means the exclusive agents. They possibly work in conjunction with other metabolics within or on the surface of the trypanosome

Resonance line-profile calculations based on hydrodynamical models of cataclysmic variable winds

We present synthetic line profiles as predicted by the models of 2-D line- driven disk winds due to Proga, Stone & Drew. We compare the model line profiles with HST observations of the cataclysmic variable IX Vel. The model wind consists of a slow outflow that is bounded on the polar side by a fast stream. We find that these two components of the wind produce distinct spectral features. The fast stream produces profiles which show features consistent with observations. These include the appearance of the P-Cygni shape for a range of inclinations, the location of the maximum depth of the absorption component at velocities less than the terminal velocity, and the transition from absorption to emission with increasing inclination. However the model profiles have too little absorption or emission equivalent width. This quantitative difference between our models and observations is not a surprise because the line-driven wind models predict a mass loss rate that is lower than the rate required by the observations. We note that the model profiles exhibit a double-humped structure near the line center which is not echoed in observations. We identify this structure with a non-negligible redshifted absorption which is formed in the slow component of the wind where the rotational velocity dominates over expansion velocity. We conclude that the next generation of disk wind models, developed for application to CVs, needs to yield stronger wind driving out to larger disk radii than do the present models.Comment: LaTeX, 19 pages, to appear in Ap

The effect of green waste composting on the concentration and composition of ambient bioaerosols

The emission and dispersal of bioaerosols from commercial composting facilities has become an issue of increasing concern over the past decade, as historical evidence links bioaerosol exposure to negative human health impacts. As a result, recommended concentrations and risk assessment limits were imposed in 2001. However, more recent research has suggested that these limits may be exceeded under certain circumstances. For example, underestimation of bioaerosol concentrations may occur through „snapshot‟ sampling, and the use of methods that may reduce culturability of bioaerosols. This study aimed to address several gaps in knowledge, including quantification of bioaerosol concentrations downwind from sites, analysis of the effect that operational and environmental influences have on emission and downwind concentrations, and investigation of methods for the enumeration of non-culturable bioaerosols. The concentrations of bioaerosols upwind, on-site and downwind from two open-air green waste windrow composting facilities were enumerated in extensive detail, producing the first detailed and validated database of bioaerosol concentrations at green-waste composting facilities. The effects of composting processing activities, season, and meteorological conditions on concentrations were also investigated utilising this dataset. Results from these studies suggested that bioaerosols are able to disperse in elevated concentrations to distances beyond the 250 m risk assessment limit. Downwind peaks in concentration were directly linked to compost processing activities on-site, with the risk of sensitive receptor exposure to bioaerosols during non-operational hours minimal. Further, it was found that patterns in downwind concentrations of bioaerosols are likely to be governed by buoyancy effects, as a second peak in concentrations was found at 100-150m downwind. This finding was further supported through the use of a novel direct counting method. Finally, molecular methods allowed the composition of bioaerosols emitted from composting to be determined and showed that composting significantly alters the aerobiotic community at distances downwind. The methods investigated provide the potential for detailed, continuous measurements of bioaerosols, alongside identification of potentially pathogenic microorganisms, and could ultimately lead to source apportionment of bioaerosols.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Tailoring seed oil composition in the real world: optimising omega-3 long chain polyunsaturated fatty acid accumulation in transgenic Camelina sativa

There is considerable interest in the de novo production of omega-3 long chain polyunsaturated fatty acids such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), not least of all given the importance of these fatty acids in both aquaculture and human nutrition. Previously we have demonstrated the feasibility of using metabolic engineering in transgenic plants (Camelina sativa) to modify the seed oil composition to now include EPA and/or DHA. In this study, we further tailored the seed oil profile to reduce the omega-6 content, and evaluated the performance of such GM plants under field conditions (i.e. environmental releases), in terms of agronomic performance and also the lipidomic profile of seed oil. We used MALDI- mass spectrometry imaging to identify discrete tissue-types in the seed in which these non-native fatty acids preferentially accumulated. Collectively, these data provide new insights into the complexity of plant lipid metabolism and the challenges associated with predictive manipulation of these pathways. However, this study identified the likely dispensable nature of a Δ12-desturase activity in our omega-3 metabolic engineering rationales for Camelina

Where to start? The Irish Emergency Department Antimicrobial Discharge (EDAD) study:a multicentre, prospective cohort analysis

Objectives: To determine the percentage of patients across Ireland who are discharged from the Emergency Department (ED) with an antimicrobial prescription, the indication, classification of infections, and guideline compliance. To identify potential areas for antimicrobial stewardship (AMS) interventions in the ED. Patients and methods: A multicentre, prospective cohort analysis study in EDs across eight hospitals in Ireland. At each site, patients aged 1 month and older who presented to the ED and were discharged directly from the ED were included. A random selection of records of patients discharged from the ED were reviewed until a minimum of 30 records with an infection diagnosis resulting in an antibiotic prescription were obtained per hospital. The number of patient discharges with no antibiotic prescriptions were included to calculate the denominator. The indication, infection classification and guideline compliance data were collected on the 30 prescriptions in the participating hospitals. Results: A total of 2619 patient records were reviewed. Of these, 249 (9.5%) patients were discharged with antimicrobial prescriptions from the ED. Most (158; 63%) were classified as probable bacterial infection, 21 (8%) as probable viral, and 18 (7%) had no documented evidence of infection. Three indications accounted for 73% of antimicrobial prescriptions: skin/soft tissue infection; ear, nose and throat infection; and urinary tract infection. Overall guideline compliance was 64%. Conclusions: Several areas for AMS interventions to optimize antimicrobial prescribing in the ED were identified, including targeted local and national guideline reviews, delayed prescribing, improved point-of-care testing and prescriber and patient education