New skyrmions in the attractive Hubbard model with broken SO(4) symmetry

The coexistence of superconducting and charge-density-wave order in the half-filled attractive Hubbard model is interpreted as a consequence of the pseudospin SU(2) symmetry spontaneously broken to a `hidden' subgroup U(1). By topological arguments we show that there must exist new skyrmion textures associated with this symmetry breakdown. This fact is illustrated via a non-linear $\sigma$-model. Unlike the spin textures previously known in an antiferromagnetic background, doping the model away from half-filling leads the new skyrmions to unwrap.Comment: 10 pages, 1 table, final version to be published in Phys. Lett.

LensMEM: A Gravitational Lens Inversion Algorithm Using the Maximum Entropy Method

We present a new algorithm for inverting poorly resolved gravitational lens systems using the maximum entropy method (MEM). We test the method with simulations and then apply it to an 8 GHz VLA map of the radio ring lens MG1654+134. We model the lens as a singular isothermal sphere embedded in an external shear field and find the critical radius of the lens is b=0\parcs9820, the dimensionless shear is $\gamma=0.0771$, and the position angle of the shear is \theta=100\pdeg8. These results are consistent with the results obtained by Kochanek (1995) using a complementary inversion algorithm based on Clean.Comment: 27 pages, uuencoded, gzip compressed postscrip

Employee share options and the equity-liability distinction: a way forward?

This paper explores the distinction between ‘equity’ and ‘liabilities’ in financial reporting in order to assess the merits of the current system of accounting for share-based payment transactions. It applies an interpretive methodology. Data were collected from a series of interviews with purposefully selected experts. Criticisms of and support for the current accounting regime are interpretively analysed and used to identify key themes or principles for evaluating the merits of three models proposed in the academic literature: the strict liability, narrow equity and ownership-settlement models. The study finds that the strict liability approach remains supported on the grounds that it provides decisionuseful information with which users are familiar. The other models are rejected as they are perceived as diminishing the usefulness of financial reporting. The study also identifies support for an obligation-centric approach, not fully developed in the literature, which may require detailed consideration by standard-setters. Overall, these findings will be useful for both practitioners and academics grappling with the difficulty of defining ‘equity’ and ‘liabilities’. In addition, the research makes a valuable contribution by addressing the need for interpretive-inspired financial reporting research. To the best of the author’s knowledge, this thesis is also the first South African study to investigate the appropriate classification criteria for instruments such as share-based payments and provide normative recommendations for the International Accounting Standards Board

The effectiveness of cannabidiol for anxiety and understanding patterns of and motivations for consumption of cannabidiol products in the UK

Part one of this project is a systematic review evaluating the effectiveness of cannabidiol (CBD) on anxiety. Included studies evaluate the experience of CBD on anxiety, in varying populations, as well as with individuals who are classified as experiencing anxiety disorders. Measures of anxiety include questionnaires or biomarkers (e.g., heart rate, blood pressure). Part two, an empirical paper, is an explorative study that involved UK-based participants completing an online survey. The primary aims of the study are to understand consumption patterns of CBD, factors influencing decisions to use CBD-products, attitudes towards health treatments and to also explore the impacts of perceived expectancy and beliefs of CBD-products. The study compares attitudes about CBD and health treatment behaviour amongst CBD users and non-CBD users. Statistical analysis includes mean comparisons and regression analysis. Part three evaluates and reflects on the process of parts one and two. Common themes emerge when personal beliefs made it uncomfortable completing the research. Furthermore, researcher inexperience led to some difficulties in the completion of all parts of the research

Streamlining Patient\u27s Wishes: Analyzing Improvements for the Implementation of Advance Directives

The purpose of this study was to complete a review of literature and determine methods providers can use to increase the implementation rates of advance directives (ADs). A growing elderly population coupled with an increase in chronic disease is making the implementation of advance directives more important than ever, yet the percentage of completed advance directives continues to be poor. Utilizing a review of evidence-based research, barriers to implementation were identified. This includes communication, timing and setting, appropriate end-of-life care and utilization of Provider Order for Life Sustaining Treatment (POLST) to provide a detailed format therefore lessening miscommunication. A pamphlet was designed to provide this information in a quick and easy-to-read format for providers and other healthcare staff. The pamphlet was well received by the participants and most agreed that this is an important topic to address with all patients. As a result of this project, the process of educating patients on ADs will be improved and the process of communication between all members of the healthcare team can be more efficien

Forest height inventory from airborne Synthetic Aperture Radar

This study assesses the capabilities of commercially available airborne short wavelength Synthetic Aperture Radar (SAR) Interferometry (JnSAR) for retrieving individual tree and forest stand height. Individual tree and stand heights are of importance to the forest industry for a number of reasons. Tree height is a key variable for calculating the amount of wood volume in a tree stem, as well as for predictions of amount of timber for extraction. Forest stand height is an important indicator of standing biomass for management purposes as well as for the assessment of carbon storage. Height is also an important ecological parameter in its own right, and an important input parameter for line-of-site analysis. Remote sensing offers an alternative to destructive measurements for accurate, rapid and cost effective technique without user subjectivity. SAR provides the potential for direct height measurement over large areas, and can operate independently of lighting or weather conditions, which often restricts the use of other remote sensing techniques.In this study, tree height is estimated by subtracting a ground surface elevation model (a UK Ordnance Survey DEM, OSDE M , or a Digital Terrain Model, DTM, from commercial Intermap Technologies) from a Digital Surface Model, DSM, (from Intermap Technologies) and the results are then compared to field measurements of tree and stand heights. The accuracy of Intermap Technologies ST AR-3i InSAR DEM products are initially compared to national elevation data sets. Over various ground types, it was concluded that, within the test areas, over non-vegetated ground the mean difference between the DTM and OSDEM was l.38m RMSE with a l.05m Standard Deviation (SD), and this is within Intermap's stated accuracies. Over forested ground the mean difference was 13.5lm RMSE (2.2lm SD). This vegetation bias was primarily due to limitations of the interpolation procedure used to determine the DTM from the DSM.Subsequently, the use of two airborne InSAR data sets is assessed for top height retrieval as an operational product, as well as a precursor and supplement to satellite data. Firstly, X-band data from Intermap are used to retrieve homogenous plantation top height over four UK study sites using the difference between the DSM and OSDEM with mean underestimations of 33.48% (6.99m mean difference). When assessed for single species, the DSM-OSDEM procedure gave height underestimations of 18-24% for Sitka spruce and 40% for Scots pine, indicating a dependency on canopy structure. Correcting retrieved height based on linear regression with ground reference data is shown to improve height estimation; as such, applying a generic correction to retrieved heights from all four UK study sites improves overall accuracy to 16.77% (3.12m mean difference). For trees greater than 18m measured height, the accuracy is increased to 12.27% (0.92m mean difference).Secondly, X-band data are also used to retrieve tree total height over two heterogeneous woodland areas in Belize and the UK. In Glen Affric, UK, height retrieval using the X-band DSM-OSDEM procedure for individual trees produce mean underestimation of 94.87% (6.08m mean difference). In Belize, height retrieval using the X-band DSM-DEM procedure for individual trees produces a mean underestimation of 74.71% (6.85m mean difference). For the Belize test site, height retrieval using JPL Airsar C-band DSM-DEM procedure for individual trees produces retrieved heights with a mean underestimation of 55.97% (4.79m mean difference). The primary cause of error is that layover effects due to SAR geometry may result in the retrieved height from a specific image coordinate not representing the same geographical position as the measured height.Relationships between radar retrieved height and forest parameters such as stocking density and tree height and radar dependent properties such as slope and edge effects are presented as possible explanations for variations across the collected data. Supporting work using a simple coherent interferometric scattering model is also used to characterise and explain the effects on tree height retrieval due to variations in slope, number density, stand height and forest edges.The results indicate that top height retrieval over homogenous forest stands is feasible with similar accuracies to those found with other remote sensing techniques and ground survey. Individual tree location assessment does not appear to be a suitable technique for assessing height retrieval in heterogeneous environments, and further investigations are required to determine a more suitable approach. This new data set therefore potentially allows a rapid and timely management tool for use in cost-effective sustainable forest management and related applications

The ecological baseline of select endorheic ephemeral pans in an arid African savanna

A research report submitted to the Faculty of Science, School of Animal, Plant and Environmental Sciences in partial fulfilment of the requirements for the degree of Master of Science, University of the Witwatersrand. Johannesburg, May 2018.The mosaic of nutrient-rich hot spots in nutrient-poor savannas is of importance to the functioning of these ecosystems. In the Lephalale plains there are the many ephemeral pan wetlands that have received limited scientific attention and are now under threat from mining in the area. The aim of this study was to gain some insight into the ecological baseline of these systems to possibly inform future studies and management approaches. Pans near the small town of Steenbokpan, Limpopo Province, South Africa were sampled in the summer rainfall season along a transect including three ‘hydro-ecological’ zones being the wetland centre (A), the pan ‘riparian-like’ area (B) and the surrounding representative terrestrial savanna habitat (C). The data gathered included vegetation species composition, tree density, physiochemical characteristics of the top (0- 30cm) and subsoils (30-60 cm) and pan water quality. The non-wetland areas were characterised mostly by forbs such as Limeum and Indigofera species and some hardy grasses including Tragus and Aristida species where more palatable grasses such as Panicum and Digitaria were present only under trees and shrubs. The pans (Zone A) were characterised by wetland grasses, Leptochloa fusca and Echinochloa colona, and had no woody species. Tree density around the pans (Zone B) was greater than the surrounding savanna vegetation (Zone C) and this habitat was characterised by a dominance in fine-leafed Acacia species. This was in contrast to the terrestrial areas that were largely dominated by broad leafed tree and shrub species (Combretum and Grewia sp.). The change from a broad-leaf to fine-leaf dominated habitat is generally associated with a change from nutrient-poor to nutrient-rich soils, which was confirmed in this study. All soil nutrients including key elements and base cations increased significantly from the broadleafed, through fine-leafed savanna and into the wetland soils. The nutrients showed a positive relationship with clay content, increasing from an average of 13% in the dry soils to 34% in the wetland soils. The water holding capacity too was significantly correlated with clay content, thus supporting the hydrological study gradient along which sampling was carried out. Water chemistry results showed the pans to be largely fresh with some high metal concentrations. Overall, the results show that these pans are much higher in soil nutrients and differ in species composition and structure from the surrounding nutrient-poor savanna. This highlights the very important functional role that these pans play in this arid environment with respect to biodiversity and nutrient dynamics. The nutritious Acacia-dominated (nutrient-rich) patches around the pans, as well as the palatable wetland grasses in the pan, will likely result in these habitats being favourable forage sites for game, especially given that these pans will likely be critical water sources for all fauna in the area. These pans are therefore critical habitats to take into account for management interventions as they will be the first to show sign of degradation. Furthermore, these wetlands and enriched savanna patches likely increase heterogeneity and biodiversity and should be priority monitoring sites for managers and targeted for conservation protection as they play a disproportionately large role in the ecological functioning of this landscape. This research has therefore shown that these pans should be highlighted as important in this ecosystem and further research would be able to enhance the understanding of their importance and sensitivity.LG201