49,112 research outputs found
Spring-Charged Particles Model to Improved Shape Recovery:An Application for X-Ray Spinal Segmentation
Deformable models are widely used in medical image segmentation methods, to find not only single but also multiple objects within an image. They have the ability to follow the contours of an object of interest, define the boundary of ROI (Region Of Interest) and improve shape recovery. However, these methods still have limitations in cases of low image quality or clutter. This paper presents a new deformable model, the Spring-Charged Particles Model (SCPM). It simulates the movement of positively charged particles connected by springs, attracted towards the contour of objects of interest which is charged negatively, according to the gradient-magnitude image. Springs prevent the particles from moving away and keep the particles at appropriate distances without reducing their flexibility. SCPM was tested on simple shape images and on frontal X-ray images of scoliosis patients. Artificial noise was added to the simple images to examine the robustness of the method. Several configurations of springs and positively charged-particles were evaluated by determining the best spinal segmentation result. The performance of SCPM was compared to the Charged Fluid Model (CFM), Active Contours, and a convolutional neural network (CNN) with U-Net architecture to measure its ability for determining the curvature of the spinal column from frontal X-Ray images. The results show that SCPM is better at segmenting the spine and determining its curvature, as indicated by the highest Area Score value of 0.837, and the lowest standard deviation value of 0.028
The Higgs Seesaw Induced Neutrino Masses and Dark Matter
In this paper we propose a possible explanation of the active neutrino
Majorana masses with the TeV scale new physics which also provide a dark matter
candidate. We extend the Standard Model (SM) with a local U(1)' symmetry and
introduce a seesaw relation for the vacuum expectation values (VEVs) of the
exotic scalar singlets, which break the U(1)' spontaneously. The larger VEV is
responsible for generating the Dirac mass term of the heavy neutrinos, while
the smaller for the Majorana mass term. As a result active neutrino masses are
generated via the modified inverse seesaw mechanism. The lightest of the new
fermion singlets, which are introduced to cancel the U(1)' anomalies, can be a
stable particle with ultra flavor symmetry and thus a plausible dark matter
candidate. We explore the parameter space with constraints from the dark matter
relic abundance and dark matter direct detection.Comment: 14 pages, 4 figure
Constraints on composite Dirac neutrinos from observations of galaxy clusters
Recently, to explain the origin of neutrino masses a model based on confining
some hidden fermionic bound states into right-handed chiral neutrinos has been
proposed. One of the consequences of condensing the hidden sector fields in
this model is the presence of sterile composite Dirac neutrinos of keV mass,
which can form viable warm dark matter particles. We have analyzed constraints
on this model from the observations of satellite based telescopes to detect the
sterile neutrinos in clusters of galaxies.Comment: 17 pages, 2 figures, minor modifications, a reference is added, this
manuscript is published in Physics Letters
Effects of non-Hermitian perturbations on Weyl Hamiltonians with arbitrary topological charges
We provide a systematic study of non-Hermitian topologically charged systems.
Starting from a Hermitian Hamiltonian supporting Weyl points with arbitrary
topological charge, adding a non-Hermitian perturbation transforms the Weyl
points to one-dimensional exceptional contours. We analytical prove that the
topological charge is preserved on the exceptional contours. In contrast to
Hermitian systems, the addition of gain and loss allows for a new class of
topological phase transition: when two oppositely charged exceptional contours
touch, the topological charge can dissipate without opening a gap. These
effects can be demonstrated in realistic photonics and acoustics systems.Comment: 11 pages, 9 figure
On Using Physical Analogies for Feature and Shape Extraction in Computer Vision
There is a rich literature of approaches to image feature extraction in computer vision. Many sophisticated approaches exist for low- and high-level feature extraction but can be complex to implement with parameter choice guided by experimentation, but impeded by speed of computation. We have developed new ways to extract features based on notional use of physical paradigms, with parameterisation that is more familiar to a scientifically-trained user, aiming to make best use of computational resource. We describe how analogies based on gravitational force can be used for low-level analysis, whilst analogies of water flow and heat can be deployed to achieve high-level smooth shape detection. These new approaches to arbitrary shape extraction are compared with standard state-of-art approaches by curve evolution. There is no comparator operator to our use of gravitational force. We also aim to show that the implementation is consistent with the original motivations for these techniques and so contend that the exploration of physical paradigms offers a promising new avenue for new approaches to feature extraction in computer vision
Heavy Neutrinos and Lepton Flavour Violation in Left-Right Symmetric Models at the LHC
We discuss lepton flavour violating processes induced in the production and
decay of heavy right-handed neutrinos at the LHC. Such particles appear in
left-right symmetrical extensions of the Standard Model as the messengers of
neutrino mass generation, and can have masses at the TeV scale. We determine
the expected sensitivity on the right-handed neutrino mixing matrix, as well as
on the right-handed gauge boson and heavy neutrino masses. By comparing the
sensitivity of the LHC with that of searches for low energy LFV processes, we
identify favourable areas of the parameter space to explore the complementarity
between LFV at low and high energies.Comment: 34 pages, 16 figures, PRD versio
Inclusive Displaced Vertex Searches for Heavy Neutral Leptons at the LHC
The inclusion of heavy neutral leptons to the Standard Model particle content
could provide solutions to many open questions in particle physics and
cosmology. The modification of the charged and neutral currents from
active-sterile mixing of neutral leptons can provide novel signatures in
Standard Model processes. We revisit the displaced vertex signature that could
occur in collisions at the LHC via the decay of heavy neutral leptons with
masses of a few GeV emphasizing the implications of flavor, kinematics,
inclusive production and number of these extra neutral fermions. We study in
particular the implication on the parameter space sensitivity when all mixings
to active flavors are taken into account. We also discuss alternative cases
where the new particles are produced in a boosted regime.Comment: 24 pages, 10 figures. Extended analysis. Published versio
- …