The Medusa Algorithm for Polynomial Matings

The Medusa algorithm takes as input two postcritically finite quadratic polynomials and outputs the quadratic rational map which is the mating of the two polynomials (if it exists). Specifically, the output is a sequence of approximations for the parameters of the rational map, as well as an image of its Julia set. Whether these approximations converge is answered using Thurston's topological characterization of rational maps. This algorithm was designed by John Hamal Hubbard, and implemented in 1998 by Christian Henriksen and REU students David Farris, and Kuon Ju Liu. In this paper we describe the algorithm and its implementation, discuss some output from the program (including many pictures) and related questions. Specifically, we include images and a discussion for some shared matings, Lattes examples, and tuning sequences of matings.Comment: 25 pages, many figures, submitte

Free-space propagation of high dimensional structured optical fields in an urban environment

Spatially structured optical fields have been used to enhance the functionality of a wide variety of systems that use light for sensing or information transfer. As higher-dimensional modes become a solution of choice in optical systems, it is important to develop channel models that suitably predict the effect of atmospheric turbulence on these modes. We investigate the propagation of a set of orthogonal spatial modes across a free-space channel between two buildings separated by 1.6 km. Given the circular geometry of a common optical lens, the orthogonal mode set we choose to implement is that described by the Laguerre-Gaussian (LG) field equations. Our study focuses on the preservation of phase purity, which is vital for spatial multiplexing and any system requiring full quantumstate tomography. We present experimental data for the modal degradation in a real urban environment and draw a comparison to recognized theoretical predictions of the link. Our findings indicate that adaptations to channel models are required to simulate the effects of atmospheric turbulence placed on high-dimensional structured modes that propagate over a long distance. Our study indicates that with mitigation of vortex splitting, potentially through precorrection techniques, one could overcome the challenges in a real point-to-point free-space channel in an urban environment

Cattle Egret Bubulcus ibis interactions with large mammals in the Tarangire-Manyara Ecosystem, Northern Tanzania

While Cattle Egrets Bubulcus ibis are globally widespread, their ecology is not fully understood. Surveys of the species were undertaken in November 2012, and April 2013, in Lake Manyara National Park, Manyara Ranch, and outside the two protected areas. We investigated the effects of host identity, habitat type and host animal behaviour on Cattle Egret numbers and distribution. Cattle Egrets associated more with grazers than with mixed-feeders or browsers, and chose large-bodied animals over small-bodied ones. They preferred wetland and grassland, over bushland. These findings underscore the importance of wetland management and the maintenance of healthy grasslands for the future of Cattle Egrets. Declines in large-bodied mammal species are likely to negatively affect them

The importance of understanding Indigenous employment in the Indigenous business sector

Indigenous employment has been the subject of numerous policies in Australia, with governments aiming to increase the workforce participation rate amongst Indigenous people in recent years. Indigenous-owned businesses, formally defined as businesses that are at least 50% Indigenous-owned, have been demonstrated in previous research to maintain substantially higher levels of proportional Indigenous employment than non-Indigenous businesses. This suggests that Indigenous-owned businesses maintain work environments that are more supportive of and conducive to Indigenous employment, meriting the influence of Indigenous-owned businesses' workplace practices in future Indigenous employment policy design. Using administrative data from two Indigenous business registries (Black Business Finder and Supply Nation), this paper provides an updated empirical analysis of the Indigenous business sector. This paper demonstrates that Indigenous-owned businesses of all sizes, industries, locations and profit statuses consistently average proportional Indigenous employment rates higher than the Indigenous proportional population. Of all the people employed in Supply Nation-listed businesses, over 35% are Indigenous. The potential impact of the Indigenous Procurement Policy is illustrated by differentials in the size of businesses and their capacity to employ Indigenous staff. This paper provides analysis of the Indigenous business sector that can inform future policy direction for both Indigenous employment and Indigenous business policies. © 2023 The Authors. Australian Journal of Social Issues published by John Wiley & Sons Australia, Ltd on behalf of Australian Social Policy Association

Renewable Electric Energy Integration: Quantifying the Value of Design of Markets for International Transmission Capacity

Integrating large quantities of supply-driven renewable electricity generation remains a political and operational challenge. One of the main obstacles in Europe to installing at least 200 GWs of power from variable renewable sources is how to deal with the insufficient network capacity and the congestion that will result from new flow patterns. We model the current methodology for controlling congestion at international borders and compare its results, under varying penetrations of wind power, with a model that simulates an integrated European network that utilises nodal/localised marginal pricing. The nodal pricing simulations illustrate that congestion - and price - patterns vary considerably between wind scenarios and within countries, and that a nodal price regime could make fuller use of existing EU network capacity, introducing substantial operational cost savings and reducing marginal power prices in the majority of European countries.Power market design, renewable power integration, congestion management, transmission economics

Illicit Methylphenidate Use in an Undergraduate Student Sample: Prevalence and Risk Factors

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/90236/1/phco.23.5.609.32210.pd