2,807 research outputs found
Continuity of the Explosive Percolation Transition
The explosive percolation problem on the complete graph is investigated via
extensive numerical simulations. We obtain the cluster-size distribution at the
moment when the cluster size heterogeneity becomes maximum. The distribution is
found to be well described by the power-law form with the decay exponent , followed by a hump. We then use the finite-size scaling method to
make all the distributions at various system sizes up to collapse
perfectly onto a scaling curve characterized solely by the single exponent
. We also observe that the instant of that collapse converges to a
well-defined percolation threshold from below as . Based on
these observations, we show that the explosive percolation transition in the
model should be continuous, contrary to the widely-spread belief of its
discontinuity.Comment: Some corrections during the revie
Scaling of cluster heterogeneity in percolation transitions
We investigate a critical scaling law for the cluster heterogeneity in
site and bond percolations in -dimensional lattices with . The
cluster heterogeneity is defined as the number of distinct cluster sizes. As an
occupation probability increases, the cluster size distribution evolves
from a monodisperse distribution to a polydisperse one in the subcritical
phase, and back to a monodisperse one in the supercritical phase. We show
analytically that diverges algebraically approaching the percolation
critical point as with the critical exponent
associated with the characteristic cluster size. Interestingly, its
finite-size-scaling behavior is governed by a new exponent where is the fractal dimension of the critical percolating
cluster and is the correlation length exponent. The corresponding scaling
variable defines a singular path to the critical point. All results are
confirmed by numerical simulations.Comment: 4 pages, 4 figure
Inelastic scattering in a monolayer graphene sheet; a weak-localization study
Charge carriers in a graphene sheet, a single layer of graphite, exhibit much
distinctive characteristics to those in other two-dimensional electronic
systems because of their chiral nature. In this report, we focus on the
observation of weak localization in a graphene sheet exfoliated from a piece of
natural graphite and nano-patterned into a Hall-bar geometry. Much stronger
chiral-symmetry-breaking elastic intervalley scattering in our graphene sheet
restores the conventional weak localization. The resulting carrier-density and
temperature dependence of the phase coherence length reveal that the
electron-electron interaction including a direct Coulomb interaction is the
main inelastic scattering factor while electron-hole puddles enhance the
inelastic scattering near the Dirac point.Comment: 12 pages, 3 figures, submitted to PR
Automatic 3D Registration of Dental CBCT and Face Scan Data using 2D Projection images
This paper presents a fully automatic registration method of dental cone-beam
computed tomography (CBCT) and face scan data. It can be used for a digital
platform of 3D jaw-teeth-face models in a variety of applications, including 3D
digital treatment planning and orthognathic surgery. Difficulties in accurately
merging facial scans and CBCT images are due to the different image acquisition
methods and limited area of correspondence between the two facial surfaces. In
addition, it is difficult to use machine learning techniques because they use
face-related 3D medical data with radiation exposure, which are difficult to
obtain for training. The proposed method addresses these problems by reusing an
existing machine-learning-based 2D landmark detection algorithm in an
open-source library and developing a novel mathematical algorithm that
identifies paired 3D landmarks from knowledge of the corresponding 2D
landmarks. A main contribution of this study is that the proposed method does
not require annotated training data of facial landmarks because it uses a
pre-trained facial landmark detection algorithm that is known to be robust and
generalized to various 2D face image models. Note that this reduces a 3D
landmark detection problem to a 2D problem of identifying the corresponding
landmarks on two 2D projection images generated from two different projection
angles. Here, the 3D landmarks for registration were selected from the
sub-surfaces with the least geometric change under the CBCT and face scan
environments. For the final fine-tuning of the registration, the Iterative
Closest Point method was applied, which utilizes geometrical information around
the 3D landmarks. The experimental results show that the proposed method
achieved an averaged surface distance error of 0.74 mm for three pairs of CBCT
and face scan datasets.Comment: 8 pages, 6 figures, 2 table
Development of a Perirenal Hematoma after Hula-Hooping
The development of a perirenal hematoma is rare and primarily the result of trauma, malignancy, or a connective tissue disease. Infrequently, a continuous or even mild trauma can cause a perirenal hematoma. Here, we report a case involving the development of a perirenal hematoma after excessive hula-hooping in the absence of a major trauma history
Elevated intracellular cAMP exacerbates vulnerability to oxidative stress in optic nerve head astrocytes.
Glaucoma is characterized by a progressive loss of retinal ganglion cells and their axons, but the underlying biological basis for the accompanying neurodegeneration is not known. Accumulating evidence indicates that structural and functional abnormalities of astrocytes within the optic nerve head (ONH) have a role. However, whether the activation of cyclic adenosine 3',5'-monophosphate (cAMP) signaling pathway is associated with astrocyte dysfunction in the ONH remains unknown. We report here that the cAMP/protein kinase A (PKA) pathway is critical to ONH astrocyte dysfunction, leading to caspase-3 activation and cell death via the AKT/Bim/Bax signaling pathway. Furthermore, elevated intracellular cAMP exacerbates vulnerability to oxidative stress in ONH astrocytes, and this may contribute to axonal damage in glaucomatous neurodegeneration. Inhibition of intracellular cAMP/PKA signaling activation protects ONH astrocytes by increasing AKT phosphorylation against oxidative stress. These results strongly indicate that activation of cAMP/PKA pathway has an important role in astrocyte dysfunction, and suggest that modulating cAMP/PKA pathway has therapeutic potential for glaucomatous ONH degeneration
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