1,675 research outputs found
Mesh-to-raster based non-rigid registration of multi-modal images
Region of interest (ROI) alignment in medical images plays a crucial role in
diagnostics, procedure planning, treatment, and follow-up. Frequently, a model
is represented as triangulated mesh while the patient data is provided from CAT
scanners as pixel or voxel data. Previously, we presented a 2D method for
curve-to-pixel registration. This paper contributes (i) a general
mesh-to-raster (M2R) framework to register ROIs in multi-modal images; (ii) a
3D surface-to-voxel application, and (iii) a comprehensive quantitative
evaluation in 2D using ground truth provided by the simultaneous truth and
performance level estimation (STAPLE) method. The registration is formulated as
a minimization problem where the objective consists of a data term, which
involves the signed distance function of the ROI from the reference image, and
a higher order elastic regularizer for the deformation. The evaluation is based
on quantitative light-induced fluoroscopy (QLF) and digital photography (DP) of
decalcified teeth. STAPLE is computed on 150 image pairs from 32 subjects, each
showing one corresponding tooth in both modalities. The ROI in each image is
manually marked by three experts (900 curves in total). In the QLF-DP setting,
our approach significantly outperforms the mutual information-based
registration algorithm implemented with the Insight Segmentation and
Registration Toolkit (ITK) and Elastix
Existence of Majorana fermions for M-branes wrapped in space and time
We show that it is possible to define Majorana (s)pinor fields on M-branes
which have been identified under the action of the antipodal map on the adS
factor of the throat geometry, or which have been wrapped on two-cycles of
arbitrary genus. This is an important consistency check, since it means that
one may still take the generators of supertranslations in superspace to
transform as Majorana fermions under the adjoint action of , even
though the antipodally identified M2-brane is {\it not} space-orientable. We
point out that similar conclusions hold for any p-branes which have the generic
(adS)(Sphere) throat geometry.Comment: 10 pages REVTe
SU(2) Lattice Gauge Theory with Logarithmic Action: Scaling and Universality
We investigate a version of SU(2) lattice gauge theory with a logarithmic
action. The model is found to exhibit confinement, contrary to previous claims
in the literature. Comparing ratios of physical quantities, like
, we find that the model belongs to the same universality
class as the standard SU(2) lattice gauge theory with Wilson action. Like the
positive plaquette model, the model with logarithmic action has a monotonic
-function, without the famous dip exhibited by the Wilson action. Short
distance dislocations affecting the definition of topology are slightly more
suppressed than for the positive plaquette model.Comment: 19 pages. Self-unwrapping compressed postscript fil
The Kinetic Basis of Morphogenesis
It has been shown recently (Shalygo, 2014) that stationary and dynamic
patterns can arise in the proposed one-component model of the analog
(continuous state) kinetic automaton, or kinon for short, defined as a
reflexive dynamical system with active transport. This paper presents
extensions of the model, which increase further its complexity and tunability,
and shows that the extended kinon model can produce spatio-temporal patterns
pertaining not only to pattern formation but also to morphogenesis in real
physical and biological systems. The possible applicability of the model to
morphogenetic engineering and swarm robotics is also discussed.Comment: 8 pages. Submitted to the 13th European Conference on Artificial Life
(ECAL-2015) on March 10, 2015. Accepted on April 28, 201
A comparison of updating algorithms for large N reduced models
We investigate Monte Carlo updating algorithms for simulating
Yang-Mills fields on a single-site lattice, such as for the Twisted
Eguchi-Kawai model (TEK). We show that performing only over-relaxation (OR)
updates of the gauge links is a valid simulation algorithm for the Fabricius
and Haan formulation of this model, and that this decorrelates observables
faster than using heat-bath updates. We consider two different methods of
implementing the OR update: either updating the whole matrix at once,
or iterating through subgroups of the matrix, we find the same
critical exponent in both cases, and only a slight difference between the two.Comment: 21 pages, 4 figure
Club guessing and the universal models
We survey the use of club guessing and other pcf constructs in the context of
showing that a given partially ordered class of objects does not have a
largest, or a universal element
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