308 research outputs found
Recovery from radiation and chemically induced premutational damage
The question of recovery from radiation and chemically induced premutational damage is discussed in relation to the nature of the primary genetic damage at the molecular level, and also in relation to factors which influence the recovery process
Commissioning Carillon Music: A Guide to Getting Started
An open-access guide for individuals interested in commissioning new carillon music.https://deepblue.lib.umich.edu/bitstream/2027.42/156042/1/GCNA-Franco-Committee-Guide-to-Commissioning-2020.pdfDescription of GCNA-Franco-Committee-Guide-to-Commissioning-2020.pdf : Main articl
Simulating full-sky interferometric observations
Aperture array interferometers, such as that proposed for the Square
Kilometre Array (SKA), will see the entire sky, hence the standard approach to
simulating visibilities will not be applicable since it relies on a tangent
plane approximation that is valid only for small fields of view. We derive
interferometric formulations in real, spherical harmonic and wavelet space that
include contributions over the entire sky and do not rely on any tangent plane
approximations. A fast wavelet method is developed to simulate the visibilities
observed by an interferometer in the full-sky setting. Computing visibilities
using the fast wavelet method adapts to the sparse representation of the
primary beam and sky intensity in the wavelet basis. Consequently, the fast
wavelet method exhibits superior computational complexity to the real and
spherical harmonic space methods and may be performed at substantially lower
computational cost, while introducing only negligible error to simulated
visibilities. Low-resolution interferometric observations are simulated using
all of the methods to compare their performance, demonstrating that the fast
wavelet method is approximately three times faster that the other methods for
these low-resolution simulations. The computational burden of the real and
spherical harmonic space methods renders these techniques computationally
infeasible for higher resolution simulations. High-resolution interferometric
observations are simulated using the fast wavelet method only, demonstrating
and validating the application of this method to realistic simulations. The
fast wavelet method is estimated to provide a greater than ten-fold reduction
in execution time compared to the other methods for these high-resolution
simulations.Comment: 16 pages, 9 figures, replaced to match version accepted by MNRAS
(major additions to previous version including new fast wavelet method
Unimodular Supergravity
We present the locally supersymmetric formulation of unimodular gravity
theory in D (1\le D \le 11) dimensions, namely supergravity theory with the
metric tensor whose determinant is constrained to be unity. In such a
formulation, the usual fine-tuning of cosmological constant is no longer
needed, but its value is understood as an initial condition. Moreover, the
zero-ness of the cosmological constant is concluded as the most probable
configuration, based on the effective vacuum functional. We also show that the
closure of supersymmetry gauge algebra is consistent with the unimodular
condition on the metric.Comment: 15 pages, latex, new section 7, two new paragraphs in Introduction
and Conclusion
All-sky convolution for polarimetry experiments
We discuss all-sky convolution of the instrument beam with the sky signal in
polarimetry experiments, such as the Planck mission which will map the
temperature anisotropy and polarization of the cosmic microwave background
(CMB). To account properly for stray light (from e.g. the galaxy, sun, and
planets) in the far side-lobes of such an experiment, it is necessary to
perform the beam convolution over the full sky. We discuss this process in
multipole space for an arbitrary beam response, fully including the effects of
beam asymmetry and cross-polarization. The form of the convolution in multipole
space is such that the Wandelt-Gorski fast technique for all-sky convolution of
scalar signals (e.g. temperature) can be applied with little modification. We
further show that for the special case of a pure co-polarized, axisymmetric
beam the effect of the convolution can be described by spin-weighted window
functions. In the limits of a small angle beam and large Legendre multipoles,
the spin-weight 2 window function for the linear polarization reduces to the
usual scalar window function used in previous analyses of beam effects in CMB
polarimetry experiments. While we focus on the example of polarimetry
experiments in the context of CMB studies, we emphasise that the formalism we
develop is applicable to anisotropic filtering of arbitrary tensor fields on
the sphere.Comment: 8 pages, 1 figure; Minor changes to match version accepted by Phys.
Rev.
Superextendons with a modified measure
For superstrings, the consequences of replacing the measure of integration
in the Polyakov's action by where is
a density built out of degrees of freedom independent of the metric
defined in the string are studied. As in Siegel reformulation of
the Green Schwarz formalism the Wess-Zumino term is the square of
supersymmetric currents. As opposed to the Siegel case, the compensating fields
needed for this do not enter into the action just as in a total derivative.
They instead play a crucial role to make up a consistent dynamics. The string
tension appears as an integration constant of the equations of motion. The
generalization to higher dimensional extended objects is also studied using in
this case the Bergshoeff and Sezgin formalism with the associated additional
fields, which again are dynamically relevant unlike the standard formulation.
Also unlike the standard formulation, there is no need of a cosmological term
on the world brane.Comment: typos corrected, references adde
Prospective multicentre study of indications for surgery in patients with idiopathic acute pancreatitis following endoscopic ultrasonography (PICUS)
Background:Cholecystectomy in patients with idiopathic acute pancreatitis (IAP) is controversial. A randomized trial found cholecystectomy to reduce the recurrence rate of IAP but did not include preoperative endoscopic ultrasonography (EUS). As EUS is effective in detecting gallstone disease, cholecystectomy may be indicated only in patients with gallstone disease. This study aimed to determine the diagnostic value of EUS in patients with IAP, and the rate of recurrent pancreatitis in patients in whom EUS could not determine the aetiology (EUS-negative IAP).Methods:This prospective multicentre cohort study included patients with a first episode of IAP who underwent outpatient EUS. The primary outcome was detection of aetiology by EUS. Secondary outcomes included adverse events after EUS, recurrence of pancreatitis, and quality of life during 1-year follow-up.Results:After screening 957 consecutive patients with acute pancreatitis from 24 centres, 105 patients with IAP were included and underwent EUS. In 34 patients (32 per cent), EUS detected an aetiology: (micro)lithiasis and biliary sludge (23.8 per cent), chronic pancreatitis (6.7 per cent), and neoplasms (2.9 per cent); 2 of the latter patients underwent pancreatoduodenectomy. During 1-year follow-up, the pancreatitis recurrence rate was 17 per cent (12 of 71) among patients with EUS-negative IAP versus 6 per cent (2 of 34) among those with positive EUS. Recurrent pancreatitis was associated with poorer quality of life.Conclusion:EUS detected an aetiology in a one-third of patients with a first episode of IAP, requiring mostly cholecystectomy or pancreatoduodenectomy. The role of cholecystectomy in patients with EUS-negative IAP remains uncertain and warrants further study
A computed tomography-based spatial reference for pedicle screw placement in adolescent idiopathic scoliosis
Study design: Cross-sectional. Objectives: To determine semiautomatically the 3D position of the pedicle axis in operative adolescent idiopathic scoliosis (AIS) patients relative to the operating table and the lamina, as orientation for pedicle screw placement for better understanding and reference of spine surgeons. Summary of background data: Pedicle morphology is well described as the angle between the convex and concave pedicle. However, the pedicle angle as relative to the neutral anterior–posterior axis or to an easy-to-use intravertebral landmark, remained unknown. Methods: The pedicles of the apex and two adjacent vertebrae cranial and caudal to the apex of 86 right-sided primary thoracic AIS curves were evaluated using semiautomatic 3D software on high-resolution CT scans, in the same prone position as during surgery. Pedicle vectors were obtained and calculated as transverse and sagittal angles, as relative to the neutral axis (corresponding with an axis perpendicular to the operating table) and to an axis perpendicular to the lamina. Results: At the apex, the mean convex and concave transverse pedicle angles were 14.3º (95% confidence interval [95% CI]: 12.0–16.6) and 30.4º (95% CI: 28.1–32.8) to the right. The angles decreased toward the adjacent levels cranial and caudal to the apex (p < 0.001) and linearly increased with a higher Cobb angle (r ≥ 0.472; p < 0.001). The mean transverse pedicle–lamina angles, sagittal pedicle angles and the sagittal pedicle–lamina angles differed along the curve as well (p < 0.001). Conclusions: Pedicle angulation differs between convex and concave and depends on the position of the vertebra relative to the apex, as well as the curve severity. The transverse and sagittal pedicle angles, as relative to the operating table and laminae, could provide useful reference for better understanding of the distorted 3D morphology, and the angles, as given in this study, could serve as an approximate guideline for the expected direction of the pedicle screw. Level of evidence: Level IV
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