296 research outputs found
Arthroscopic Iliac Crest Bone Graft Augmentation Using All-Suture Anchors for Shoulder Instability Caused by Glenoid Bone Loss.
Augmentation of the anterior glenoid with bone graft is an established treatment for recurrent anterior instability due to critical glenoid bone loss. Both open and arthroscopic techniques have been described. Fixation with metal screws through an open approach is the most common technique, but the risk of metal screw-related complications remains a concern. A variety of arthroscopic techniques using suspensory fixation or suture anchors have been described in the literature. However, they all require a posterior incision to insert a targeting device or to manage sutures. We describe a technique for arthroscopic bone grafting of the anterior glenoid via a purely anterior approach with 2 linked knotless suture anchors, thereby avoiding posterior suture management and glenoid metalwork complications
Micro-fading spectrometry: investigating the wavelength specificity of fading
A modified microfading spectrometer incorporating a linear variable filter is used to investigate the wavelength dependence of fading of traditional watercolour pigments, dosimeters and fading standards at a higher spectral resolution and/or sampling than had previously been attempted. While the wavelength dependence of photochemical damage was largely found to correlate well with the absorption spectra of each material, exceptions were found in the case of Prussian blue and Prussian green pigments (the latter includes Prussian blue), for which an anti-correlation between the spectral colour change and the absorption spectrum was found
Universal neural field computation
Turing machines and G\"odel numbers are important pillars of the theory of
computation. Thus, any computational architecture needs to show how it could
relate to Turing machines and how stable implementations of Turing computation
are possible. In this chapter, we implement universal Turing computation in a
neural field environment. To this end, we employ the canonical symbologram
representation of a Turing machine obtained from a G\"odel encoding of its
symbolic repertoire and generalized shifts. The resulting nonlinear dynamical
automaton (NDA) is a piecewise affine-linear map acting on the unit square that
is partitioned into rectangular domains. Instead of looking at point dynamics
in phase space, we then consider functional dynamics of probability
distributions functions (p.d.f.s) over phase space. This is generally described
by a Frobenius-Perron integral transformation that can be regarded as a neural
field equation over the unit square as feature space of a dynamic field theory
(DFT). Solving the Frobenius-Perron equation yields that uniform p.d.f.s with
rectangular support are mapped onto uniform p.d.f.s with rectangular support,
again. We call the resulting representation \emph{dynamic field automaton}.Comment: 21 pages; 6 figures. arXiv admin note: text overlap with
arXiv:1204.546
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CT methods for measuring glenoid bone loss are inaccurate, and not reproducible or interchangeable.
AIMS: Glenoid bone loss is a significant problem in the management of shoulder instability. The threshold at which the bone loss is considered "critical" requiring bony reconstruction has steadily dropped and is now approximately 15%. This necessitates accurate measurement in order that the correct operation is performed. CT scanning is the most commonly used modality and there are a number of techniques described to measure the bone loss however few have been validated. The aim of this study was to assess the accuracy of the most commonly used techniques for measuring glenoid bone loss on CT. METHODS: Anatomically accurate models with known glenoid diameter and degree of bone loss were used to determine the mathematical and statistical accuracy of six of the most commonly described techniques (relative diameter, linear ipsilateral circle of best fit (COBF), linear contralateral COBF, Pico, Sugaya, and circle line methods). The models were prepared at 13.8%, 17.6%, and 22.9% bone loss. Sequential CT scans were taken and randomized. Blinded reviewers made repeated measurements using the different techniques with a threshold for theoretical bone grafting set at 15%. RESULTS: At 13.8%, only the Pico technique measured under the threshold. At 17.6% and 22.9% bone loss all techniques measured above the threshold. The Pico technique was 97.1% accurate, but had a high false-negative rate and poor sensitivity underestimating the need for grafting. The Sugaya technique had 100% specificity but 25% of the measurements were incorrectly above the threshold. A contralateral COBF underestimates the area by 16% and the diameter by 5 to 7%. CONCLUSION: No one method stands out as being truly accurate and clinicians need to be aware of the limitations of their chosen technique. They are not interchangeable, and caution must be used when reading the literature as comparisons are not reliable
Constraints on the Ultra High Energy Photon flux using inclined showers from the Haverah Park array
We describe a method to analyse inclined air showers produced by ultra high
energy cosmic rays using an analytical description of the muon densities. We
report the results obtained using data from inclined events
(60^{\circ}<\theta<80^{\circ}) recorded by the Haverah Park shower detector for
energies above 10^19 eV. Using mass independent knowledge of the UHECR spectrum
obtained from vertical air shower measurements and comparing the expected
horizontal shower rate to the reported measurements we show that above 10^19 eV
less than 48 % of the primary cosmic rays can be photons at the 95 % confidence
level and above 4 X 10^19 eV less than 50 % of the cosmic rays can be photonic
at the same confidence level. These limits place important constraints on some
models of the origin of ultra high-energy cosmic rays.Comment: 45 pages, 25 figure
Neutrino Detection with Inclined Air Showers
The possibilities of detecting high energy neutrinos through inclined showers
produced in the atmosphere are addressed with an emphasis on the detection of
air showers by arrays of particle detectors. Rates of inclined showers produced
by both down-going neutrino interactions and by up-coming decays from
earth-skimming neutrinos as a function of shower energy are calculated with
analytical methods using two sample neutrino fluxes with different spectral
indices. The relative contributions from different flavors and charged, neutral
current and resonant interactions are compared for down-going neutrinos
interacting in the atmosphere. No detailed description of detectors is
attempted but rough energy thresholds are implemented to establish the ranges
of energies which are more suitable for neutrino detection through inclined
showers. Down-going and up-coming rates are compared.Comment: Submitted to New Journal of Physic
âFilipâ or flop? Managing public relations and the Latin American reaction to the 1966 FIFA World Cup
The 1966 FIFA World Cup has become part of the iconography of its hosts and champions, England. Extant literature has tended to focus on the cultural and symbolic legacy of the tournament, or engaged with diplomatic relations between Britain and North Korea. Contrastingly, we use archival sources from footballing and government institutions to explore the less studied topic of how the tournament was reported and perceived in Latin America, where England had commercial interests and influence, but where there were allegations that FIFA, the FA and even the UK government manipulated the tournament to the advantage of England and other European teams. We provide fresh perspectives on the social and cultural significance of the 1966 FIFA World Cup by analysing how the tournamentâs organizers attempted to manage the situation and resulting negative public relations, and how 1966 fits within longer-term footballing and diplomatic relations between England and Latin America
The Sheaf-Theoretic Structure Of Non-Locality and Contextuality
We use the mathematical language of sheaf theory to give a unified treatment
of non-locality and contextuality, in a setting which generalizes the familiar
probability tables used in non-locality theory to arbitrary measurement covers;
this includes Kochen-Specker configurations and more. We show that
contextuality, and non-locality as a special case, correspond exactly to
obstructions to the existence of global sections. We describe a linear
algebraic approach to computing these obstructions, which allows a systematic
treatment of arguments for non-locality and contextuality. We distinguish a
proper hierarchy of strengths of no-go theorems, and show that three leading
examples --- due to Bell, Hardy, and Greenberger, Horne and Zeilinger,
respectively --- occupy successively higher levels of this hierarchy. A general
correspondence is shown between the existence of local hidden-variable
realizations using negative probabilities, and no-signalling; this is based on
a result showing that the linear subspaces generated by the non-contextual and
no-signalling models, over an arbitrary measurement cover, coincide. Maximal
non-locality is generalized to maximal contextuality, and characterized in
purely qualitative terms, as the non-existence of global sections in the
support. A general setting is developed for Kochen-Specker type results, as
generic, model-independent proofs of maximal contextuality, and a new
combinatorial condition is given, which generalizes the `parity proofs'
commonly found in the literature. We also show how our abstract setting can be
represented in quantum mechanics. This leads to a strengthening of the usual
no-signalling theorem, which shows that quantum mechanics obeys no-signalling
for arbitrary families of commuting observables, not just those represented on
different factors of a tensor product.Comment: 33 pages. Extensively revised, new results included. Published in New
Journal of Physic
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