Nonlinear Inversion from Partial EIT Data: Computational Experiments

Electrical impedance tomography (EIT) is a non-invasive imaging method in which an unknown physical body is probed with electric currents applied on the boundary, and the internal conductivity distribution is recovered from the measured boundary voltage data. The reconstruction task is a nonlinear and ill-posed inverse problem, whose solution calls for special regularized algorithms, such as D-bar methods which are based on complex geometrical optics solutions (CGOs). In many applications of EIT, such as monitoring the heart and lungs of unconscious intensive care patients or locating the focus of an epileptic seizure, data acquisition on the entire boundary of the body is impractical, restricting the boundary area available for EIT measurements. An extension of the D-bar method to the case when data is collected only on a subset of the boundary is studied by computational simulation. The approach is based on solving a boundary integral equation for the traces of the CGOs using localized basis functions (Haar wavelets). The numerical evidence suggests that the D-bar method can be applied to partial-boundary data in dimension two and that the traces of the partial data CGOs approximate the full data CGO solutions on the available portion of the boundary, for the necessary small $k$ frequencies.Comment: 24 pages, 12 figure

Incorporating a Spatial Prior into Nonlinear D-Bar EIT imaging for Complex Admittivities

Electrical Impedance Tomography (EIT) aims to recover the internal conductivity and permittivity distributions of a body from electrical measurements taken on electrodes on the surface of the body. The reconstruction task is a severely ill-posed nonlinear inverse problem that is highly sensitive to measurement noise and modeling errors. Regularized D-bar methods have shown great promise in producing noise-robust algorithms by employing a low-pass filtering of nonlinear (nonphysical) Fourier transform data specific to the EIT problem. Including prior data with the approximate locations of major organ boundaries in the scattering transform provides a means of extending the radius of the low-pass filter to include higher frequency components in the reconstruction, in particular, features that are known with high confidence. This information is additionally included in the system of D-bar equations with an independent regularization parameter from that of the extended scattering transform. In this paper, this approach is used in the 2-D D-bar method for admittivity (conductivity as well as permittivity) EIT imaging. Noise-robust reconstructions are presented for simulated EIT data on chest-shaped phantoms with a simulated pneumothorax and pleural effusion. No assumption of the pathology is used in the construction of the prior, yet the method still produces significant enhancements of the underlying pathology (pneumothorax or pleural effusion) even in the presence of strong noise.Comment: 18 pages, 10 figure

Social protest in three novels of Carlos Fuentes

Carlos Fuentes is one of Mexico\u27 s current fiction writers and to many he is controversial in that he delves into several of Mexico\u27s great preoccupations: the Revolution, the search for lo mexicano and the future for this growing country. This thesis is an endeavor to expose and explain Fuentes\u27 views on these and other social topics as seen in three of his novels: La region mas transparents, La guerte de Artemio Crux, and Cambio de piel

Direct D-bar reconstruction algorithm for complex admittivities in W2,∞(Ω) for the 2-D EIT problem, A

2012 Summer.Includes bibliographical references.Electrical Impedance Tomography (EIT) is a fairly new, portable, relatively inexpensive, imaging system that requires no ionizing radiation. Electrodes are placed at the surface of a body and low frequency, low amplitude current is applied on the electrodes, and the resulting voltage value on each electrode is measured. By applying a basis of current patterns, one can obtain sufficient information to recover the complex admittivity distribution of the region in the plane of the electrodes. In 2000, Elisa Francini presented a nearly constructive proof that was the first approach using D-bar methods to solve the full nonlinear problem for twice-differentiable conductivities and permittivities. In this thesis the necessary formulas to turn her proof into a direct D-bar reconstruction algorithm that solves the full nonlinear admittivity problem in 2-D are described. Reconstructions for simulated Finite Element data for circular and non-circular domains are presented

Improving Minors\u27 Access to Treatment for Opioid Use Disorder: A Policy Analysis

As the opioid epidemic continues to have devastating effects on our communities, medications to treat opioid use disorder (MOUDs) are severely underutilized especially for adolescents. Unlike adults, minors need parental approval before obtaining MOUDs presenting a key barrier to timely treatment. Being able to treat adolescents as soon as they are ready is critically important for people with OUD, and while cost and other barriers have been addressed in the literature, there is a paucity on how parental consent affects the accessibility of treatment. This paper aims to explore a potential policy in California that addresses the lack of access for adolescents. A health policy analysis format was used to compare and assess each policy option through a criteria of feasibility, effectiveness, relevance, and impact. Peer-reviewed articles and public health data was utilized for this analysis. After a comparison of two policy options, the more favorable option was a revision to California’s minor consent laws to allow providers to confidentially treat addicted youth, 16 and older, with buprenorphine. This analysis showed how this policy will likely be more effective in narrowing the treatment gap among older adolescents. Recommendations, implications and potential limitations were also discussed

Preliminary investigation into the development of an electronic forage budget and land condition application, for use on existing hand-held devices, for the northern grazing industry

Within this project Agri-Science Queensland (DAF) and Meat and Livestock Australia conducted a preliminary investigation into the viability, likely uptake and benefits of developing an ‘app’ (a software application hosted on a smart phone) to assist northern Australian graziers with their land condition monitoring and forage budgeting. Undertaking regular land condition assessments and forage budgets to match pasture supply to animal demand is considered part of best-practice management for graziers in northern Australia. Undertaking these management tasks, however, is often complex and requires a number of steps, both in the paddock and the office along with supporting tools and learnt skills to reach the end points; “what is the current condition of my pastures” and “how long will this feed last given the stock in the paddock”. A specifically designed app for a smart phone or tablet was proposed as a potential solution to increase the adoption of these management practices amongst graziers. Three tasks were undertaken concurrently as part of the investigation; a review of literature, a survey of graziers and advisors in northern Australia, and consultation with software developers to scope the technical feasibility of developing the proposed app. The review of literature considered the evolution of hand-held decision support tools, a comparison of operating platforms and ‘smart’ devices for the task, and currently available agricultural apps and their uptake. A survey of northern Australian graziers and advisors sought views from industry what would be the likely benefit and uptake of this proposed app. The survey found that 76% of respondents thought this 'app' would be either useful or very useful for the grazing industry generally. Around 74% and 73% of respondents respectively said the app would increase the number or frequency of forage budgets and land condition assessments undertaken. Approximately 80% of respondents said the app would help them get started on forage budgeting and land condition assessments if they did not currently undertake these practices already. There are no technical constraints to developing the desired app and development costs were investigated. If development of an app proceeds, it will be important to provide a strong extension framework to support its piloting and promotion

Demonstrating recovery of pasture productivity, Mulga Lands - Bollon, South West Queensland

Pasture recovery PDS, Mulga lands