368 research outputs found
The Political Economy of Autism
Autism is a global epidemic. An estimated 1 in 40 children in Australia, 1 in 64 children in the U.K., and 1 in 36 children in the U.S. have an autism spectrum disorder (ASD). This is an enormous increase from the first known autism prevalence study in the U.S. in 1970, that established an autism prevalence rate of less than 1 per 10,000. Several studies have shown that changes in diagnostic criteria account for only a small fraction of the increased prevalence. Families of children on the spectrum face extraordinary additional expenses and decreased earnings as one parent often becomes a caregiver. Autism cost the U.S. 1 trillion (3.6% of GDP) in 2025 (as a point of comparison, U.S. Defense Department spending is 3.1% of GDP). Over the last decade, several groups of leading epidemiologists, doctors, and public health experts have published consensus statements declaring that toxicants in the environment are contributing to the rising prevalence of neurodevelopmental disorders including autism. Beyond the consensus statements, a range of independent researchers have identified many additional factors that appear to increase autism risk. Given rising prevalence rates and the extraordinary impacts of ASD on individuals, families, and communities, what explains why public health authorities, thus far, have failed to ban or restrict toxicants that have been shown to increase autism risk? I argue that autism is not only a public health issue, it also represents a crisis of political economy. In this thesis I will show that: capitalism has transformed science and medicine from a focus on use values to a focus on exchange values; regulation is largely a reflection of political power not scientific evidence; and cultural and financial capture are blocking the sorts of regulatory responses that are necessary to stop the autism epidemic
Paper folding, Riemann surfaces, and convergence of pseudo-Anosov sequences
A method is presented for constructing closed surfaces out of Euclidean
polygons with infinitely many segment identifications along the boundary. The
metric on the quotient is identified. A sufficient condition is presented which
guarantees that the Euclidean structure on the polygons induces a unique
conformal structure on the quotient surface, making it into a closed Riemann
surface. In this case, a modulus of continuity for uniformizing coordinates is
found which depends only on the geometry of the polygons and on the
identifications. An application is presented in which a uniform modulus of
continuity is obtained for a family of pseudo-Anosov homeomorphisms, making it
possible to prove that they converge to a Teichm\"uller mapping on the Riemann
sphere.Comment: 75 pages, 18 figure
Determination of size, sex and maturity stage of free swimming catsharks using laser photogrammetry
Twin Studies: Research in Genes, Teeth and Faces
This volume is about an ongoing long-term research initiative led by researchers from the School of Dentistry at the University of Adelaide. The aim of this book is to provide an overview of the studies of the teeth and faces of Australian twins and their families that have extended over more than thirty years
Segmented nitinol guidewires with stiffness-matched connectors for cardiovascular magnetic resonance catheterization: preserved mechanical performance and freedom from heating.
BACKGROUND: Conventional guidewires are not suitable for use during cardiovascular magnetic resonance (CMR) catheterization. They employ metallic shafts for mechanical performance, but which are conductors subject to radiofrequency (RF) induced heating. To date, non-metallic CMR guidewire designs have provided inadequate mechanical support, trackability, and torquability. We propose a metallic guidewire for CMR that is by design intrinsically safe and that retains mechanical performance of commercial guidewires.
METHODS: The NHLBI passive guidewire is a 0.035 CMR-safe, segmented-core nitinol device constructed using short nitinol rod segments. The electrical length of each segment is less than one-quarter wavelength at 1.5 Tesla, which eliminates standing wave formation, and which therefore eliminates RF heating along the shaft. Each of the electrically insulated segments is connected with nitinol tubes for stiffness matching to assure uniform flexion. Iron oxide markers on the distal shaft impart conspicuity. Mechanical integrity was tested according to International Organization for Standardization (ISO) standards. CMR RF heating safety was tested in vitro in a phantom according to American Society for Testing and Materials (ASTM) F-2182 standard, and in vivo in seven swine. Results were compared with a high-performance commercial nitinol guidewire.
RESULTS: The NHLBI passive guidewire exhibited similar mechanical behavior to the commercial comparator. RF heating was reduced from 13 °C in the commercial guidewire to 1.2 °C in the NHLBI passive guidewire in vitro, using a flip angle of 75°. The maximum temperature increase was 1.1 ± 0.3 °C in vivo, using a flip angle of 45°. The guidewire was conspicuous during left heart catheterization in swine.
CONCLUSIONS: We describe a simple and intrinsically safe design of a metallic guidewire for CMR cardiovascular catheterization. The guidewire exhibits negligible heating at high flip angles in conformance with regulatory guidelines, yet mechanically resembles a high-performance commercial guidewire. Iron oxide markers along the length of the guidewire impart passive visibility during real-time CMR. Clinical translation is imminent
Spiral imaging with off-resonance reconstruction for MRI-guided cardiovascular catheterizations using commercial off-the-shelf nitinol guidewires
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