28,052 research outputs found
Mocarts: a lightweight radiation transport simulator for easy handling of complex sensing geometries
In functional neuroimaging (fNIRS), elaborated sensing geometries pairing multiple light sources and detectors arranged over the tissue surface are needed. A variety of software tools for probing forward models of radiation transport in tissue exist, but their handling of sensing geometries and specification of complex tissue architectures is, most times, cumbersome. In this work, we introduce a lightweight simulator, Monte Carlo Radiation Transport Simulator (MOCARTS) that attends these demands for simplifying specification of tissue architectures and complex sensing geometries. An object-oriented architecture facilitates such goal. The simulator core is evolved from the Monte Carlo Multi-Layer (mcml) tool but extended to support multi-channel simulations. Verification against mcml yields negligible error (RMSE~4-10e-9) over a photon trajectory. Full simulations show concurrent validity of the proposed tool. Finally, the ability of the new software to simulate multi-channel sensing geometries and to define biological tissue models in an intuitive nested-hierarchy way are exemplified
Failure Analysis Following Osteochondroplasty for Hip Impingement in Osteoporotic and Non-Osteoporotic Bones
A Unique Resource for Solar Flare Diagnostic Studies: the SMM Bent Crystal Spectrometer
The {\em Bent Crystal Spectrometer}\/ (BCS) on the NASA {\em Solar Maximum
Mission}\/ spacecraft observed the X-ray spectra of numerous solar flares
during the periods 1980 February to November and 1984~--~1989. The instrument,
the first of its kind to use curved crystal technology, observed the resonance
lines of He-like Ca (\caxix) and Fe (\fexxv) and neighboring satellite lines,
allowing the study of the rapid evolution of flare plasma temperature,
turbulence, mass motions etc. To date there has not been a solar X-ray
spectrometer with comparable spectral and time resolution, while subsequent
solar cycles have delivered far fewer and less intense flares. The BCS data
archive thus offers an unparalleled resource for flare studies. A recent
re-assessment of the BCS calibration and its operations is extended here by
using data during a spacecraft scan in the course of a flare on 1980 November~6
that highlights small deformations in the crystal curvature of the important
channel~1 (viewing lines of \caxix\ and satellites). The results explain
long-standing anomalies in spectral line ratios which have been widely
discussed in the past. We also provide an in-flight estimation of the BCS
collimator field of view which improves the absolute intensity calibration of
the BCS. The BCS channel~1 background is shown to be entirely due to solar
continuum radiation, confirming earlier analyses implying a time-variable flare
abundance of Ca. We suggest that BCS high-resolution \caxix\ and \fexxv\ line
spectra be used as templates for the analysis of X-ray spectra of non-solar
sources.Comment: To be published, Astrophysical Journa
Dark spinor models in gravitation and cosmology
We introduce and carefully define an entire class of field theories based on
non-standard spinors. Their dominant interaction is via the gravitational field
which makes them naturally dark; we refer to them as Dark Spinors. We provide a
critical analysis of previous proposals for dark spinors noting that they
violate Lorentz invariance. As a working assumption we restrict our analysis to
non-standard spinors which preserve Lorentz invariance, whilst being non-local
and explicitly construct such a theory. We construct the complete
energy-momentum tensor and derive its components explicitly by assuming a
specific projection operator. It is natural to next consider dark spinors in a
cosmological setting. We find various interesting solutions where the spinor
field leads to slow roll and fast roll de Sitter solutions. We also analyse
models where the spinor is coupled conformally to gravity, and consider the
perturbations and stability of the spinor.Comment: 43 pages. Several new sections and details added. JHEP in prin
Delayed biliary duet obstruction after orthotopic liver transplantation
After orthotopic liver transplantation and biliary reconstruction by cholecystoduodenostomy, four of 40 patients developed delayed obstruction of the cystic duct. The recipients had the clinical syndrome of fulminating cholangitis with jaundice, fever, leukocytosis, toxemia, and bacteremia. All four patients died; of the four, two patients died despite late reoperation and re-establishment of bile drainage by choledochoenterostomy. In all four cases, a factor contributing to the biliary obstruction may have been infection of the extrahepatic biliary ducts with or without ulceration, and in three of the livers, there was evidence of infection of the ducts with CMV. If cholecystoduodenostomy is used in future cases, prompt re-exploration and conversion to choledochoenterostomy should be considered if the diagnosis of duct obstruction, cholangitis, and persistent bacteremia are made. © 1972
Vitamin A supplementation in Tanzania: the impact of a change in programmatic delivery strategy on coverage.
BACKGROUND\ud
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Efficient delivery strategies for health interventions are essential for high and sustainable coverage. We report impact of a change in programmatic delivery strategy from routine delivery through the Expanded Programme on Immunization (EPI+) approach to twice-yearly mass distribution campaigns on coverage of vitamin A supplementation in Tanzania\ud
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METHODS\ud
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We investigated disparities in age, sex, socio-economic status, nutritional status and maternal education within vitamin A coverage in children between 1 and 2 years of age from two independent household level child health surveys conducted (1) during a continuous universal targeting scheme based on routine EPI contacts for children aged 9, 15 and 21 months (1999); and (2) three years later after the introduction of twice-yearly vitamin A supplementation campaigns for children aged 6 months to 5 years, a 6-monthly universal targeting scheme (2002). A representative cluster sample of approximately 2,400 rural households was obtained from Rufiji, Morogoro Rural, Kilombero and Ulanga districts. A modular questionnaire about the health of all children under the age of five was administered to consenting heads of households and caretakers of children. Information on the use of child health interventions including vitamin A was asked.\ud
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RESULTS\ud
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Coverage of vitamin A supplementation among 1-2 year old children increased from 13% [95% CI 10-18%] in 1999 to 76% [95%CI 72-81%] in 2002. In 2002 knowledge of two or more child health danger signs was negatively associated with vitamin A supplementation coverage (80% versus 70%) (p = 0.04). Nevertheless, we did not find any disparities in coverage of vitamin A by district, gender, socio-economic status and DPT vaccinations.\ud
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CONCLUSION\ud
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Change in programmatic delivery of vitamin A supplementation was associated with a major improvement in coverage in Tanzania that was been sustained by repeated campaigns for at least three years. There is a need to monitor the effect of such campaigns on the routine health system and on equity of coverage. Documentation of vitamin A supplementation campaign contacts on routine maternal and child health cards would be a simple step to facilitate this monitoring
M2-M5 blackfold funnels
We analyze the basic M2-M5 intersection in the supergravity regime using the
blackfold approach. This approach allows us to recover the 1/4-BPS self-dual
string soliton solution of Howe, Lambert and West as a three-funnel solution of
an effective fivebrane worldvolume theory in a new regime, the regime of a
large number of M2 and M5 branes. In addition, it allows us to discuss finite
temperature effects for non-extremal self-dual string soliton solutions and
wormhole solutions interpolating between stacks of M5 and anti-M5 branes. The
purpose of this paper is to exhibit these solutions and their basic properties.Comment: 19 pages, 5 figures, harvmac; typo corrected in equation (3.19
Exact results for static and radiative fields of a quark in N=4 super Yang-Mills
In this work (which supersedes our previous preprint arXiv:1112.2345) we
determine the expectation value of the N=4$ SU(N) SYM Lagrangian density
operator in the presence of an infinitely heavy static particle in the
symmetric representation of SU(N), by means of a D3-brane probe computation.
The result that we obtain coincides with two previous computations of different
observables, up to kinematical factors. We argue that these agreements go
beyond the D-brane probe approximation, which leads us to propose an exact
formula for the expectation value of various operators. In particular, we
provide an expression for the total energy loss by radiation of a heavy
particle in the fundamental representation.Comment: 14 pages. This submission supersedes our previous preprint
arXiv:1112.2345. v2: numerical factors fixed, minor clarifications, added
reference
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