Sea ice thickness and iceberg distribution in the Southern Ocean

The sea ice thickness distribution, represented by the probability density function (PDF), is critical to Earth's climate system and knowledge of the distribution in the Antarctic is limited. A novel methodology, using an acoustic Doppler current profiler, was developed to measure sea ice draft based on measurements taken from Autosub (an autonomous underwater vehicle). The PDF has been derived for three missions undertaken in the eastern Amundsen Sea during March 2003. The PDFs for all missions were found to have a single mode although there is evidence for variability in mean thickness along the ice front, as the most western mission has a lower mean draft. Geostatistical analyses of the data have allowed the derivation of PDFs to account for the spatial sampling. A factor on the thickness of ice measured is the presence of icebergs within a study region. This thesis reports on work carried out to investigate whether a correction to the sea ice thickness PDF can be made to account for icebergs and over what scale(s) this correction is valid. To answer this question data from Autosub and satellite images were used to investigate whether icebergs were randomly distributed both in open ocean and within sea ice. In conclusion, it was found that icebergs do cluster on the scale of typical Autosub missions (~few km). However, there are differences between icebergs in sea ice compared with open water. Therefore, icebergs should be accounted for in the sea ice thickness PDF

Improved GNSS-R bi-static altimetry and independent digital elevation models of Greenland and Antarctica from TechDemoSat-1

Improved digital elevation models (DEMs) of the Antarctic and Greenland ice sheets are presented, which have been derived from Global Navigation Satellite Systems-Reflectometry (GNSS-R). This builds on a previous study (Cartwright et al., 2018) using GNSS-R to derive an Antarctic DEM but uses improved processing and an additional 13 months of measurements, totalling 46 months of data from the UK TechDemoSat-1 satellite. A median bias of under 10 m and root-mean-square errors (RMSEs) of under 53 m for the Antarctic and 166 m for Greenland are obtained, as compared to existing DEMs. The results represent, compared to the earlier study, a halving of the median bias to 9 m, an improvement in coverage of 18 %, and a 4 times higher spatial resolution (now gridded at 25 km). In addition, these are the first published satellite altimetry measurements of the region surrounding the South Pole. Comparisons south of 88∘ S yield RMSEs of less than 33 m when compared to NASA's Operation IceBridge measurements. Differences between DEMs are explored, the limitations of the technique are noted, and the future potential of GNSS-R for glacial ice studies is discussed

Specification-Based Task Orchestration for Multi-Robot Aerial Teams

As humans begin working more frequently in environments with multi-agent systems, they are presented with challenges on how to control these systems in an intuitive manner. Current approaches tend to limit either the interaction ability of the user or limit the expressive capacity of instructions given to the robots. Applications that utilize temporal logics provide a human-readable syntax for systems that ensures formal guarantees for specification completion. By providing a modality for global task specification, we seek to reduce cognitive load and allow for high-level objectives to be communicated to a multi-agent system. In addition to this, we also seek to expand the capabilities of swarms to understand desired actions via interpretable commands retrieved from a human. In this thesis, we first present a method for specification-based control of a quadrotor. We utilize quadrotors as a highly agile and maneuverable application platform that has a wide variety of uses in complex problem domains. Leveraging specification-based control allows us to formulate a specification-based planning framework that will be utilized throughout the thesis. We then present methods for creating systems which allows us to provide task decomposition, allocation and planning for a team of quadrotors defined as task orchestration of multi-robot systems. Next, the task allocation portion of the task orchestration work is extended in the online case by considering cost agnostic sampling of trajectories from an online optimization problem. Then, we will introduce learning techniques where temporal logic specifications are learned and generated from a set of user given traces. Finally, we will conclude this thesis by presenting an extension to the Robotarium through hardware and software modifications that provides remote users access to control aerial swarms.Ph.D

Characteristics of hypervelocity impact craters on LDEF experiment S1003 and implications of small particle impacts on reflective surfaces

The Ion Beam textured and coated surfaces EXperiment (IBEX), designated S1003, was flown on LDEF at a location 98 deg in a north facing direction relative to the ram direction. Thirty-six diverse materials were exposed to the micrometeoroid (and some debris) environment for 5.8 years. Optical property measurements indicated no changes for almost all of the materials except S-13G, Kapton, and Kapton-coated surfaces, and these changes can be explained by other environmental effects. From the predicted micrometeoroid flux of NASA SP-8013, no significant changes in optical properties of the surfaces due to micrometeoroids were expected. There were hypervelocity impacts on the various diverse materials flown on IBEX, and the characteristics of these craters were documented using scanning electron microscopy (SEM). The S1003 alumigold-coated aluminum cover tray was sectioned into 2 cm x 2 cm pieces for crater documentation. The flux curve generated from this crater data fits well between the 1969 micrometeoroid model and the Kessler debris model for particles less than 10(exp -9) gm which were corrected for the S1003 positions (98 deg to ram). As the particle mass increases, the S1003 impact data is greater than that predicted by even the debris model. This, however, is consistent with data taken on intercostal F07 by the Micrometeoroid/Debris Special Investigating Group (M/D SIG). The mirrored surface micrometeoroid detector flown on IBEX showed no change in solar reflectance and corroborated the S1003 flux curve, as well as results of this surface flown on SERT 2 and OSO 3 for as long as 21 years

Assessing the potential impact of environmental land management schemes on emergent infection disease risks

Financial incentives are provided by governments to encourage the plantation of new woodland to increase habitat, biodiversity, carbon sequestration, and other economic benefits for landowners. Whilst these are largely positive effects, it is worth considering that greater biodiversity and presence of wildlife species in proximity to agricultural holdings may pose a risk of disease transmission between wildlife and livestock. Wildlife transmission and the provision of a reservoir for infectious disease is particularly important in the transmission dynamics of bovine tuberculosis. In this paper we develop an economic model for changing land use due to forestry subsidies. We use this asses the impact on wild deer populations in the newly created woodland areas and the emergent infectious disease risk arising from the proximity of new and existing wild deer populations and existing cattle holdings. We consider an area in the South-West of Scotland, having existing woodland, deer populations, and extensive and diverse cattle farm holdings. In this area we find that, with a varying level of subsidy and plausible new woodland creation, the contact risk between areas of wild deer and cattle increases between 26% and 35% over the contact risk present with zero subsidy. This model provides a foundation for extending to larger regions and for examining potential risk mitigation strategies, for example the targeting of subsidy in low risk areas or provisioning for buffer zones between woodland and agricultural holdings

A Mammalian Homolog of Drosophila melanogaster Transcriptional Coactivator Intersex Is a Subunit of the Mammalian Mediator Complex

The multiprotein Mediator complex is a coactivator required for transcriptional activation of RNA polymerase II transcribed genes by DNA binding transcription factors. We previously partially purified a Med8-containing Mediator complex from rat liver nuclei (Brower, C. S., Sato, S., Tomomori-Sato, C., Kamura, T., Pause, A., Stearman, R., Klausner, R. D., Malik, S., Lane, W. S., Sorokina, I., Roeder, R. G., Conaway, J. W., and Conaway, R. C. (2002) Proc. Natl. Acad. Sci. U. S. A. 99, 10353–10358). Analysis of proteins present in the most highly enriched Mediator fractions by tandem mass spectrometry led to the identification of several new mammalian Mediator subunits, as well as several potential Mediator subunits. Here we identify one of these proteins, encoded by the previously uncharacterized AK000411 open reading frame, as a new subunit of the mammalian Mediator complex. The AK000411 protein, which we designate hIntersex (human Intersex), shares significant sequence similarity with the Drosophila melanogaster intersex protein, which has functional properties expected of a transcriptional coactivator specific for the Drosophila doublesex transactivator. In addition, we show that hIntersex assembles into a subcomplex with Mediator subunits p28b and TRFP. Taken together, our findings identify a new subunit of the mammalian Mediator and shed new light on the architecture of the mammalian Mediator complex

Modelling plausible scenarios for the Omicron SARS-CoV-2 variant from early-stage surveillance

In this paper we used an adapted version of an existing simulation model of SARS-CoV-2 transmission in Scotland to investigate the rise of the Omicron variant of concern, in order to evaluate plausible scenarios for transmission advantage and vaccine immune escape relative to the Delta variant. We also explored possible outcomes of different levels of imposed non-pharmaceutical intervention. The initial results of these scenarios were used to inform the Scottish Government in the early outbreak stages of the Omicron variant. We use an explicitly spatial agent-based simulation model combined with spatially fine-grained COVID-19 observation data from Public Health Scotland. Using the model with parameters fit over the Delta variant epidemic, some initial assumptions about Omicron transmission advantage and vaccine escape, and a simple growth rate fitting procedure, we were able to capture the initial outbreak dynamics for Omicron. We also find the modelled dynamics hold up to retrospective scrutiny. We found that the modelled imposition of extra non-pharmaceutical interventions planned by the Scottish Government at the time would likely have little effect in light of the transmission advantage held by the Omicron variant and the fact that the planned interventions would have occurred too late in the outbreak's trajectory. Finally, we found that any assumptions made about the projected distribution of vaccines in the model population had little bearing on the outcome, in terms of outbreak size and timing, rather that the detailed landscape of immunity prior to the outbreak was of far greater importance

Sea ice detection using GNSS‐R data from TechDemoSat‐1

A new method for the detection of sea ice using GNSS‐R (Global Navigation Satellite Systems Reflectometry) is presented and applied to 33 months of data from the U.K. TechDemoSat‐1 mission. This method of sea ice detection shows the potential for a future GNSS‐R polar mission, attaining an agreement of over 98% and 96% in the Antarctic and Arctic, respectively, when compared to the European Space Agency's Climate Change Initiative sea ice concentration product. The algorithm uses a combination of two parameters derived from the delay‐Doppler Maps to quantify the spread of power in delay and Doppler. Application of thresholds then allows sea ice to be distinguished from open water. Differences between the TechDemoSat‐1 sea ice detection and comparison data sets are explored. The results provide information on the seasonal and multiyear changes in sea ice distribution of the Arctic and Antarctic. Future potential and applications of this technique are discussed

Stabilized Singlets in Supergravity as a Source of the mu-parameter

Within the context of supergravity-coupled supersymmetry, fields which are gauge and global singlets are usually considered anathema. Their vacuum expectation values are shifted by quadratically divergent tadpole diagrams which are cutoff at the Planck scale, destabilizing the classical potential and driving the singlet field to large values. We demonstrate a new and generic mechanism which stabilizes the singlet in the presence of an extended gauge symmetry. Such a symmetry will be broken down to the Standard Model by the supergravity interactions near the scale of spontaneous supersymmetry-breaking in the hidden-sector (about 10^{10-11} GeV). The resulting singlet expectation value is stabilized and naturally of order the gravitino mass, providing therefore a weak-scale mass for the Higgs fields of the supersymmetric Standard Model (a "mu-parameter"). The resulting low-energy theory is the minimal supersymmetric Standard Model, with all new fields decoupling at the intermediate scale.Comment: 9 pages, LaTe

Money, Well-Being, and Loss Aversion: Does an Income Loss Have a Greater Effect on Well-Being Than an Equivalent Income Gain?

Higher income is associated with greater well-being, but do income gains and losses affect well-being differently? Loss aversion, whereby losses loom larger than gains, is typically examined in relation to decisions about anticipated outcomes. Here, using subjective-well-being data from Germany (N = 28,723) and the United Kingdom (N = 20,570), we found that losses in income have a larger effect on well-being than equivalent income gains and that this effect is not explained by diminishing marginal benefits of income to well-being. Our findings show that loss aversion applies to experienced losses, challenging suggestions that loss aversion is only an affective-forecasting error. By failing to account for loss aversion, longitudinal studies of the relationship between income and well-being may have overestimated the positive effect of income on well-being. Moreover, societal well-being might best be served by small and stable income increases, even if such stability impairs long-term income growth