49,117 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)
Accelerated Overlap Fermions
Numerical evaluation of the overlap Dirac operator is difficult since it
contains the sign function of the Hermitian Wilson-Dirac
operator with a negative mass term. The problems are due to having
very small eigenvalues on the equilibrium background configurations generated
in current day Monte Carlo simulations. Since these are a consequence of the
lattice discretisation and do not occur in the continuum version of the
operator, we investigate in this paper to what extent the numerical evaluation
of the overlap can be accelerated by making the Wilson-Dirac operator more
continuum-like. Specifically, we study the effect of including the clover term
in the Wilson-Dirac operator and smearing the link variables in the irrelevant
terms. In doing so, we have obtained a factor of two speedup by moving from the
Wilson action to a FLIC (Fat Link Irrelevant Clover) action as the overlap
kernel.Comment: 15 pages, 6 figures; V2 contains major revision of the introduction
and motivation sections. Conclusion and results unchanged v2.1: formatting
chang
Further investigation of a contactless patient-electrode interface of an Electrical Impedance Mammography system
The Sussex Mk4 Electrical Impedance Mammography (EIM) system is a novel instrument, designed for the detection of early breast cancer, based upon Electrical Impedance Tomography (EIT). Many innovations in the field have been incorporated in the design improving both signal distribution and response. This paper investigates the behaviour of the contactless patient-electrode interface. The interface was studied in detail using phantom and healthy volunteer, in-vivo, data. Our findings show the necessity for the careful design of electrode enclosure so that the response of the system is not affected by the unpredictable positioning of the breast; it closely mimics those conditions seen when using the phantom. The paper includes a number of possible designs and their individual characteristics. In addition an explanation on the unanticipated effects and solutions for such are described. © 2010 IOP Publishing Ltd
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Interface Microstructures and Bond Formation in Ultrasonic Consolidation
The quality of ultrasonically consolidated parts critically depends on the bond quality
between individual metal foils. This necessitates a detailed understanding of interface
microstructures and ultrasonic bonding mechanism. There is a lack of information on interface
microstructures in ultrasonically consolidated parts as well as a lack of consensus on the
mechanism of metal ultrasonic welding, especially on matters such as plastic deformation and
recrystallization. In the current work, interface microstructures of an ultrasonically consolidated
multi-material Al 3003-Ni 201 sample were analyzed in detail using optical microscopy,
scanning electron microscopy, energy dispersive spectroscopy, and orientation imaging
microscopy. Based on the results of microstructural studies, the mechanism of metal ultrasonic
welding has been discussed. The reasons for formation of defects/unbonded regions in
ultrasonically consolidated parts have also been identified and discussedMechanical Engineerin
Brain computer interfaces: psychology and pragmatic perspectives for the future.
Whilst technologies, such as psychophysiological
measurements in general and electroencephalograms (EEG) in
particular, have been around and continually improving for many years, future technologies promise to revolutionise the emerging Information Society through the development of brain-computer interfaces and augmented cognition solutions. This paper explores critical psychological and pragmatic issues that must be understood before these technologies can deliver their potential well. Within the context of HCI, we examined a sample (n =105) BCI papers and found that the majority of research aimed to provide communication and control resources to people with
disabilities or with extreme task demands. However, the concepts of usability and accessibility, and respective findings from their substantial research literatures were rarely applied explicitly but referenced implicitly. While this suggests an increased awareness of these concepts and the related large research literatures, the task remains to sharpen these concepts and to articulate their obvious relevance to BCI work
Orbital Response of Evanescent Cooper Pairs in Paramagnetically Limited Al Films
We report a detailed study of the pairing resonance via tunneling density of
states in ultra-thin superconducting Al films in supercritical magnetic fields.
Particular emphasis is placed on effects of the perpendicular component of the
magnetic field on the resonance energy and magnitude. Though the resonance is
broadened and attenuated by as expected, its energy is shifted upward
linearly with . Extension of the original theory of the resonance to
include strong perpendicular fields shows that at sufficiently large
the overlap of the broadened resonance tail with the underlying degenerate
Fermi sea alters the spectral distribution of the resonance via the exclusion
principle. This leads to the shift of the the resonance feature to higher
energy.Comment: 8 pages, 4 figure
Pseudorapidity dependence of parton energy loss in relativistic heavy ion collisions
We analyze the recent data from the BRAHMS Collaboration on the
pseudorapidity dependence of nuclear modification factors in Au+Au collisions
at = 200 GeV by using the full three dimensional hydrodynamic
simulations for the density effects on parton energy loss. We first compute the
transverse spectra at and 2.2, and next take a ratio
, where is a nuclear
modification factor. It is shown that hydrodynamic components account for
at low and that quenched pQCD components lead
at high which are consistent with the data.
Strong suppression at is compatible with the parton energy loss in
the final state.Comment: 5 pages, 4 figures; one figure adde
Far-infrared vibrational properties of high-pressure-high-temperature C60 polymers and the C60 dimer
We report high-resolution far-infrared transmission measurements of the 2 + 2 cycloaddition C-60 dimer and two-dimensional rhombohedral and one-dimensional orthorhombic high-pressure high-temperature C60 polymers. In the spectral region investigated(20-650 cm(-1)), we see no low-energy interball modes, but symmetry breaking of the linked C-60 balls is evident in the complex spectrum of intramolecular modes. Experimental features suggest large splittings or frequency shifts of some IhC60-derived modes that are activated by symmetry reduction, implying that the balls are strongly distorted in these structures. We have calculated the vibrations of all three systems by first-principles quantum molecular dynamics and use them to assign the predominant IhC60 symmetries of observed modes. Pur calculations show unprecedentedly large downshifts of T-1u(2)-derived modes and extremely large splittings of other modes, both of which are consistent with the experimental spectra. For the rhombohedral and orthorhombic polymers, the T-1u(2)-derived mode that is polarized along the bonding direction is calculated to downshift below any T-1u(1)-derived modes. We also identify a previously unassigned feature near 610 cm(-1) in all three systems as a widely split or shifted mode derived from various silent IhC60 vibrations, confirming a strong perturbation model for these linked fullerene structures
Hyperspherical Harmonics, Separation of Variables and the Bethe Ansatz
The relation between solutions to Helmholtz's equation on the sphere
and the [{\gr sl}(2)]^n Gaudin spin chain is clarified. The joint
eigenfuctions of the Laplacian and a complete set of commuting second order
operators suggested by the --matrix approach to integrable systems, based on
the loop algebra \wt{sl}(2)_R, are found in terms of homogeneous polynomials
in the ambient space. The relation of this method of determining a basis of
harmonic functions on to the Bethe ansatz approach to integrable
systems is explained.Comment: 14 pgs, Plain Tex, preprint CRM--2174 (May, 1994
How important are next-to-leading order models in predicting strange particle spectra in p+p collisions at STAR ?
STAR has measured a variety of strange particle species in p + p collisions
at = 200 GeV. These high statistics data are ideal for comparing to
existing leading- and next-to-leading order perturbative QCD (pQCD) models.
Next-to-leading (NLO) models have been successful in describing inclusive
hadron production using parameterized fragmentation functions (FF) for quarks
and gluons. However, in order to describe identied strange particle spectra at
NLO, knowledge of flavor separated FF is essential. Such FF have recently been
parameterized using data by the OPAL experiment and allow for the first time to
perform NLO calculation for strange baryons. In fact, comparing the STAR Lambda
data with these calculations allow to put a constraint on the gluon
fragmentation function. We show that the Leading-order (LO) event generator
PYTHIA has to be tuned significantly to reproduce the STAR identified strange
particle data. In particular, it fails to describe the observed enhancement of
baryon-to-meson ratio at intermediate pT (2-6 GeV/c). In heavy-ion (HI)
collisions this observable has been extensively compared with models and shows
a strong dependency on collision centrality or parton density. In the HI
context the observed enhancement has been explained by recent approaches in
terms of parton coalescense and recombination models.Comment: 5 pages, HotQuarks 2006 conference proceeding
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