53,954 research outputs found
Predictions for the fracture toughness of cancellous bone of fracture neck of femur patients
Current protocol in determining if a patient is osteoporotic and their fracture risk is based on dual energy X-ray absorptiometry (DXA). DXA gives an indication of their bone mineral density (BMD) which is the product of both the porosity and density of the mineralized bone tissue; this is usually taken at the hip. The DXA results are assessed using the fracture risk assessment tool as recommended by the World Health Organization. While this provides valuable data on a person’s fracture risk advancements in medical imagining technology enables development of more robust and accurate risk assessment tools. In order to develop such tools in vitro analysis of bone is required to assess the morphological properties of bone osteoporotic bone tissue and how these pertain to the fracture toughness (Kcmax) of the tissue.Support was provided by the EPSRC (EP/K020196: Point-ofCare High Accuracy Fracture Risk Prediction), the UK Department of Transport under the BOSCOS (Bone Scanning for Occupant Safety) project, and approved by Gloucester and Cheltenham NHS Trust hospitals under ethical consent (BOSCOS – Mr. Curwen CI REC ref 01/179G)
Etching of High Purity Zinc
A method of etching high purity zinc to reveal various etch figures on {101¯0} planes is presented in this
paper. Etch figures are formed by polishing in a dichromic acid solution after the introduction of mercury
to the crystal surface. No measurable aging time is required to form etch figures at newly formed dislocation
sites when mercury is on the surface prior to deformation. The mercury concentrates at the sites
where etch figures form and may be removed by vacuum distillation and chemical polishing before it appreciably
affects the purity of the bulk of the crystal
Dislocations and etch figures in high purity zinc
A method of etching high purity zinc single crystals to reveal various etch figures on {1010} planes is presented in the preceding paper. The procedure involves the introduction of mercury to the crystal surface prior to a chemical polish with dichromic acid. The mercury was found to be concentrated at the etch figures. This paper presents the results of several experiments which support the conclusion that there exists a one-to-one correspondence between etch figures and dislocations. Some observations of slip on (0001) basal planes and {1212} pyramidal planes, and of twinning in zinc are also presented
Orientation Dependence of a Dislocation Etch for Zinc
The dislocation etch for (101-[bar]0] surfaces of zinc reported by Brandt, Adams, and Vreeland have been further explored. Additional surface orientations have been found where dislocation etching takes place. These orientations cover an area located between 3 degrees and 12.2 degrees to the [0001], and the area is symmetric about that axis. Attempts to produce dislocation etching on within 2 degrees of (0001) were generally unsuccessful. This is in contrast to etching of many crystals which takes place only within a few degrees of a low index plane
The Invincible (1758) site: an integrated geophysical assessment
Chirp sub-bottom profiler and repeat sidescan sonar imaging of the Invincible wreck site (1758) in the Solent (U.K.), interpretation, and implications for management of the site
A Review and Outlook for the Removal of Radon-Generated Po-210 Surface Contamination
The next generation low-background detectors operating deep underground aim
for unprecedented low levels of radioactive backgrounds. The deposition and
presence of radon progeny on detector surfaces is an added source of energetic
background events. In addition to limiting the detector material's radon
exposure in order to reduce potential surface backgrounds, it is just as
important to clean surfaces to remove inevitable contamination. Such studies of
radon progeny removal have generally found that a form of etching is effective
at removing some of the progeny (Bi and Pb), however more aggressive
techniques, including electropolishing, have been shown to effectively remove
the Po atoms. In the absence of an aggressive etch, a significant fraction of
the Po atoms are believed to either remain behind within the surface or
redeposit from the etching solution back onto the surface. We explore the
chemical nature of the aqueous Po ions and the effect of the oxidation state of
Po to maximize the Po ions remaining in the etching solution of contaminated Cu
surfaces. We present a review of the previous studies of surface radon progeny
removal and our findings on the role of oxidizing agents and a cell potential
in the preparation of a clean etching technique.Comment: Proceedings of the Low Radioactivity Techniques (LRT) 2017, Seoul,
South Korea, May 24-26, 201
General bounds on the Wilson-Dirac operator
Lower bounds on the magnitude of the spectrum of the Hermitian Wilson-Dirac
operator H(m) have previously been derived for 0<m<2 when the lattice gauge
field satisfies a certain smoothness condition. In this paper lower bounds are
derived for 2p-2<m<2p for general p=1,2,...,d where d is the spacetime
dimension. The bounds can alternatively be viewed as localisation bounds on the
real spectrum of the usual Wilson-Dirac operator. They are needed for the
rigorous evaluation of the classical continuum limit of the axial anomaly and
index of the overlap Dirac operator at general values of m, and provide
information on the topological phase structure of overlap fermions. They are
also useful for understanding the instanton size-dependence of the real
spectrum of the Wilson-Dirac operator in an instanton background.Comment: 26 pages, 2 figures. v3: Completely rewritten with new material and
new title; to appear in Phys.Rev.
A Study of Educational Simulations Part I - Engagement and Learning
Interactive computer simulations with complex representations and sophisticated graphics are a relatively new addition to the classroom, and research in this area is limited. We have conducted over 200 individual student interviews during which the students described what they were thinking as they interacted with simulations. These interviews were conducted as part of the research and design of simulations for the Physics Education Technology (PhET) project. PhET is an ongoing project that has developed over 60 simulations for use in teaching physics, chemistry, and physical science. These interviews are a rich source of information about how students interact with computer simulations and what makes an educationally effective simulation. We have observed that simulations can be highly engaging and educationally effective, but only if the student's interaction with the simulation is directed by the student's own questioning. Here we describe our design process, what features are effective for engaging students in educationally productive interactions and the underlying principles which support our empirically developed guidelines. In a companion paper we describe in detail the design features used to create an intuitive simulation for students to use
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