45,582 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)
Beam-Energy and System-Size Dependence of Dynamical Net Charge Fluctuations
We present measurements of net charge fluctuations in collisions at
19.6, 62.4, 130, and 200 GeV, collisions at
62.4, 200 GeV, and collisions at 200
GeV using the net charge dynamical fluctuations measure . The
dynamical fluctuations are non-zero at all energies and exhibit a rather modest
dependence on beam energy. We find that at a given energy and collision system,
net charge dynamical fluctuations violate scaling, but display
approximate scaling. We observe strong dependence of dynamical
fluctuations on the azimuthal angular range and pseudorapidity widths.Comment: 4 pages, 4 figures, presented at the 19th International Conference on
Ultra-Relativistic Nucleus-Nucleus Collisions, "Quark Matter 2008", Jaipur,
India, February 4-10, 200
Elliptic flow of the dilute Fermi gas: From kinetics to hydrodynamics
We use the Boltzmann equation in the relaxation time approximation to study
the expansion of a dilute Fermi gas at unitarity. We focus, in particular, on
the approach to the hydrodynamic limit. Our main finding are: i) In the regime
that has been studied experimentally hydrodynamic effects beyond the
Navier-Stokes approximation are small, ii) mean field corrections to the
Boltzmann equation are not important, iii) experimental data imply that
freezeout occurs very late, that means that the relaxation time remains smaller
than the expansion time during the entire evolution of the system, iv) the
experimental results also imply that the bulk viscosity is significantly
smaller than the shear viscosity of the system.Comment: 18 pages, 6 figure
Results on the nucleon spin structure
SMC performed an investigation of the spin structure of the nucleon by
measuring deep inelastic scattering of polarised muons off polarised protons
and deuterons. A summary of the results for spin structure functions and sum
rules is given.Comment: 8 pages, LaTeX, Talk given at the Workshop on "Symmetry and Spin -
PRAHA98", Prag, September 1998. Proceedings to be published by Czech. Journ.
Phy
STUDIES ON ABLATION OF OBJECTS TRAVERSING AN ATMOSPHERE
Ablation-type thermal protection of objects traversing an atmosphere - earth and mar
Stopping and Baryon Transport in Heavy Ion Reactions
In this report I will give an experimental overview on nuclear stopping in
hadron collisions, and relate observations to understanding of baryon
transport. Baryon number transport is not only evidenced via net-proton
distributions but also by the enhancement of strange baryons near mid-rapidity.
Although the focus is on high-energy data obtained from pp and heavy ions from
RHIC, relevant data from SPS and ISR will be considered. A discussion how the
available data at higher energy relates and gives information on baryon
junction, quark-diquark breaking will be made.Comment: 8 pages, 7 figures. Invited plenary talk for the 5'th international
conference on Physics and Astrophysics of Quark Gluon Plasma, February 8-12,
2005, Salt Lake City, Kolkata, Indi
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
Coarsening of "clouds" and dynamic scaling in a far-from-equilibrium model system
A two-dimensional lattice gas of two species, driven in opposite directions
by an external force, undergoes a jamming transition if the filling fraction is
sufficiently high. Using Monte Carlo simulations, we investigate the growth of
these jams ("clouds"), as the system approaches a non-equilibrium steady state
from a disordered initial state. We monitor the dynamic structure factor
and find that the component exhibits dynamic scaling, of
the form . Over a significant range
of times, we observe excellent data collapse with and .
The effects of varying filling fraction and driving force are discussed
Fluctuations and Correlations in STAR
The study of correlations and fluctuations can provide evidence for the
production of the quark-gluon plasma (QGP) in relativistic heavy ion
collisions. Various theories predict that the production of a QGP phase in
relativistic heavy ion collisions could produce significant event-by-event
correlations and fluctuations in, transverse momentum, multiplicity, etc. Some
of the recent results using STAR at RHIC will be presented along with results
from other experiments at RHIC. The focus is on forward-backward multiplicity
correlations, balance function, charge and transverse momentum fluctuations,
and correlations.Comment: 6 pages, 13 figures, Invited talk at QNP06, Madrid, Spain,June 200
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