The role of the GI radiographer: A UK perspective

Context: Since the 1990s radiographers in the United Kingdom have expanded their role in gastrointestinal (GI) radiology, first by performing double-contrast barium enema (DCBE) examinations independently and later by interpreting and reporting the results of these exams. Objective: This article will trace the evolution of GI radiographers in the United Kingdom, evaluate their success and explore how the U.K. experience could apply to American radiologist assistants. Methods: The authors surveyed the professional literature to determine the historical context in which GI radiographers emerged and assess how their performance on DCBE exams compares with radiologists’ performance. Results: DCBE exams performed by GI radiographers have been shown to be efficient, cost effective and safe. In addition, GI radiographers have helped reduce waiting and turnaround times for DCBE exams. Summary: The success of GI radiographers in the United Kingdom offers assurance that radiologist assistants can benefit American patients, radiologists and radiologic technologists

Age of the Rotoehu Ash. Comment.

Suggests that the article by Whitehead & Ditchburn (1994), although presenting useful new data on 230Th/232Th analyses, is flawed and misleading in suggesting that the Rotoiti Tephra is considerably younger than c. 50 ka

Unsteady turbulent buoyant plumes

We model the unsteady evolution of turbulent buoyant plumes following temporal changes to the source conditions. The integral model is derived from radial integration of the governing equations expressing the conservation of mass, axial momentum and buoyancy. The non-uniform radial profiles of the axial velocity and density deficit in the plume are explicitly described by shape factors in the integral equations; the commonly-assumed top-hat profiles lead to shape factors equal to unity. The resultant model is hyperbolic when the momentum shape factor, determined from the radial profile of the mean axial velocity, differs from unity. The solutions of the model when source conditions are maintained at constant values retain the form of the well-established steady plume solutions. We demonstrate that the inclusion of a momentum shape factor that differs from unity leads to a well-posed integral model. Therefore, our model does not exhibit the mathematical pathologies that appear in previously proposed unsteady integral models of turbulent plumes. A stability threshold for the value of the shape factor is identified, resulting in a range of its values where the amplitude of small perturbations to the steady solutions decay with distance from the source. The hyperbolic character of the system allows the formation of discontinuities in the fields describing the plume properties during the unsteady evolution. We compute numerical solutions to illustrate the transient development following an abrupt change in the source conditions. The adjustment to the new source conditions occurs through the propagation of a pulse of fluid through the plume. The dynamics of this pulse are described by a similarity solution and, by constructing this new similarity solution, we identify three regimes in which the evolution of the transient pulse following adjustment of the source qualitatively differ.Comment: 41 pages, 16 figures, under consideration for publication in Journal of Fluid Mechanic

Single-Step Quantum Search Using Problem Structure

The structure of satisfiability problems is used to improve search algorithms for quantum computers and reduce their required coherence times by using only a single coherent evaluation of problem properties. The structure of random k-SAT allows determining the asymptotic average behavior of these algorithms, showing they improve on quantum algorithms, such as amplitude amplification, that ignore detailed problem structure but remain exponential for hard problem instances. Compared to good classical methods, the algorithm performs better, on average, for weakly and highly constrained problems but worse for hard cases. The analytic techniques introduced here also apply to other quantum algorithms, supplementing the limited evaluation possible with classical simulations and showing how quantum computing can use ensemble properties of NP search problems.Comment: 39 pages, 12 figures. Revision describes further improvement with multiple steps (section 7). See also http://www.parc.xerox.com/dynamics/www/quantum.htm

Parent materials of Yellow-brown loams in the Waikato-Coromandel district.

The yellow-brown loams of the Waikato-Coromandel region are derived from weathered airfall volcanic materials. These materials may be either direct airfall deposits, or erosion products of these deposits, described as reworked ash in some publications. In the erosion products small amounts of other rocks may be included in the parent materials, and these additions may modify to a slight degree the chemical and physical properties of the soil as a yellow-brown loam. In larger amounts these additions result in the formation of intergrades to yellow-brown earths or gley soils

¹⁴C dating of modern marine and estuarine shellfish

We measured the ¹⁴C content of 36 living marine molluscs from Tairua Harbour and the rocky coast on the Coromandel Peninsula of New Zealand. We identified species suitable for radiocarbon dating and show that the open marine intertidal zone is enriched in ¹⁴C compared to the open marine subtidal zone or estuary. We also found a uniform ¹⁴C distribution in the Tairua Harbour, by analyzing samples of the estuarine bivalveAustrovenus stutchburyi collected up to 5 km from the harbor entrance