3,558 research outputs found
Fast and Accurate Lung Tumor Spotting and Segmentation for Boundary Delineation on CT Slices In A Coarse-To-Fine Framework
Label noise and class imbalance are two of the critical challenges when training image-based deep neural networks, especially in the biomedical image processing domain. Our work focuses on how to address the two challenges effectively and accurately in the task of lesion segmentation from biomedical/medical images. To address the pixel-level label noise problem, we propose an advanced transfer training and learning approach with a detailed DICOM pre-processing method. To address the tumor/non-tumor class imbalance problem, we exploit a self-adaptive fully convolutional neural network with an automated weight distribution mechanism to spot the Radiomics lung tumor regions accurately. Furthermore, an improved conditional random field method is employed to obtain sophisticated lung tumor contour delineation and segmentation. Finally, our approach has been evaluated using several well-known evaluation metrics on the Lung Tumor segmentation dataset used in the 2018 IEEE VIP-CUP Challenge. Experimental results show that our weakly supervised learning algorithm outperforms other deep models and state-of-the-art approache
Activation of Notch signalling by soluble Dll4 decreases vascular permeability via a cAMP/PKA-dependent pathway
© 2019 the American Physiological Society. The Notch ligand delta-like ligand 4 (Dll4), upregulated by VEGF, is a key regulator of vessel morphogenesis and function, controlling tip and stalk cell selection during sprouting angiogenesis. Inhibition of Dll4 results in hypersprouting, nonfunctional, poorly perfused vessels, suggesting a role for Dll4 in the formation of mature, reactive, functional vessels, with low permeability and able to restrict fluid and solute exchange. We tested the hypothesis that Dll4 controls transvascular fluid exchange. A recombinant protein expressing only the extracellular portion of Dll4 [soluble Dll4 (sDll4)] induced Notch signaling in endothelial cells (ECs), resulting in increased expression of vascular-endothelial cadherin, but not the tight junctional protein zonula occludens 1, at intercellular junctions. sDll4 decreased the permeability of FITC-labeled albumin across EC monolayers, and this effect was abrogated by coculture with the γ-secretase inhibitor N-[N-(3,5-difluorophenacetyl)-L-alanyl]-S-phenylglycine t-butyl ester. One of the known molecular effectors responsible for strengthening EC-EC contacts is PKA, so we tested the effect of modulation of PKA on the sDll4-mediated reduction of permeability. Inhibition of PKA reversed the sDll4-mediated reduction in permeability and reduced expression of the Notch target gene Hey1. Knockdown of PKA reduced sDLL4-mediated vascular-endothelial cadherin junctional expression. sDll4 also caused a significant decrease in the hydraulic conductivity of rat mesenteric microvessels in vivo. This reduction was abolished upon coperfusion with the PKA inhibitor H89 dihydrochloride. These results indicate that Dll4 signaling through Notch activation acts through a cAMP/PKA pathway upon intercellular adherens junctions, but not tight junctions, to regulate endothelial barrier function. NEW & NOTEWORTHY Notch signaling reduces vascular permeability through stimulation of cAMP-dependent protein kinase A
Phase Diagram of the Two-Channel Kondo Lattice
The phase diagram of the two-channel Kondo lattice model is examined with a
Quantum Monte Carlo simulation in the limit of infinite dimensions.
Commensurate (and incommensurate) antiferromagnetic and superconducting states
are found. The antiferromagnetic transition is very weak and continuous;
whereas the superconducting transition is discontinuous to an odd-frequency
channel-singlet and spin-singlet pairing state.Comment: 5 pages, LaTeX and 4 PS figures (see also cond-mat/9609146 and
cond-mat/9605109
Range of the t--J model parameters for CuO plane: experimental data constraints
The t-J model effective hopping integral is determined from the three-band
Hubbard model for the charge carriers in CuO plane. For this purpose the
values of the superexchange constant and the charge-transfer gap
are calculated in the framework of the three-band model. Fitting values of
and to the experimental data allows to narrow the uncertainty region
of the three-band model parameters. As a result, the ratio of the t-J
model is fixed in the range for holes and for
electrons. Formation of the Frenkel exciton is justified and the main features
of the charge-transfer spectrum are correctly described in the framework of
this approach.Comment: 20pp., REVTEX 3.0, (11 figures), report 66
Riemannian Sparse Coding for Positive Definite Matrices
International audienceInspired by the great success of sparse coding for vector valued data, our goal is to represent symmetric positive definite (SPD) data matrices as sparse linear combinations of atoms from a dictionary, where each atom itself is an SPD matrix. Since SPD matrices follow a non-Euclidean (in fact a Riemannian) geometry, existing sparse coding techniques for Euclidean data cannot be directly extended. Prior works have approached this problem by defining a sparse coding loss function using either extrinsic similarity measures (such as the log-Euclidean distance) or kernelized variants of statistical measures (such as the Stein divergence, Jeffrey's divergence, etc.). In contrast, we propose to use the intrinsic Riemannian distance on the manifold of SPD matrices. Our main contribution is a novel mathematical model for sparse coding of SPD matrices; we also present a computationally simple algorithm for optimizing our model. Experiments on several computer vision datasets showcase superior classification and retrieval performance compared with state-of-the-art approaches
Weight bases of Gelfand-Tsetlin type for representations of classical Lie algebras
This paper completes a series devoted to explicit constructions of
finite-dimensional irreducible representations of the classical Lie algebras.
Here the case of odd orthogonal Lie algebras (of type B) is considered (two
previous papers dealt with C and D types). A weight basis for each
representation of the Lie algebra o(2n+1) is constructed. The basis vectors are
parametrized by Gelfand--Tsetlin-type patterns. Explicit formulas for the
matrix elements of generators of o(2n+1) in this basis are given. The
construction is based on the representation theory of the Yangians. A similar
approach is applied to the A type case where the well-known formulas due to
Gelfand and Tsetlin are reproduced.Comment: 29 pages, Late
Anderson-localization versus delocalization of interacting fermions in one dimension
Using the density matrix renormalization group algorithm, we investigate the
lattice model for spinless fermions in one dimension in the presence of a
strong interaction and disorder. The phase sensitivity of the ground state
energy is determined with high accuracy for systems up to a size of 60 lattice
constants. This quantity is found to be log-normally distributed. The
fluctuations grow algebraically with system size with a universal exponent of
~2/3 in the localized region of the phase diagram. Surprizingly, we find, for
an attractive interaction, a delocalized phase of finite extension. The
boundary of this delocalized phase is determined.Comment: 5 pages, 6 figures, revte
Numerical Renormalization Group Study of Kondo Effect in Unconventional Superconductors
Orbital degrees of freedom of a Cooper pair play an important role in the
unconventional superconductivity. To elucidate the orbital effect in the Kondo
problem, we investigated a single magnetic impurity coupled to Cooper pairs
with a () symmetry using the numerical
renormalization group method. It is found that the ground state is always a
spin doublet. The analytical solution for the strong coupling limit explicitly
shows that the orbital dynamics of the Cooper pair generates the spin 1/2 of
the ground state.Comment: 4 pages, 2 figures, JPSJ.sty, to be published in J. Phys. Soc. Jpn.
70 (2001) No. 1
Crossover between Fermi Liquid and non-Fermi Liquid in Orbitally Degenerate Kondo Systems
Entanglement of spin and orbital Kondo effect is investigated on the basis of
a Kondo-type exchange model with twofold orbital degeneracy. By using Wilson's
numerical renormalization-group method, we examine dynamical and thermal
properties respecting the difference in time-reversal property of multipole
operators. In the presence of particle-hole symmetry, the model has a new
non-Fermi-liquid fixed point with a fractional entropy. The spectral intensity
of the quadrupole susceptibility diverges in the zero-frequency limit, while
the dipole susceptibility shows a Fermi-liquid-like behavior. This is
understood by mapping to the two-channel Kondo model, in which the dipole
moment is mapped onto the operators with the scaling dimension ,
while the quadrupole moment onto the operators with another scaling dimension
. Even for a fairly particle-hole asymmetric case with the
Fermi-liquid ground state, the non-Fermi-liquid behavior has significant
influences in electric and thermal properties.Comment: 7 pages, 9 figures, to appear in J. Phys Soc. Jpn. Vol. 68 No. 12,
title changed and some corrections mad
A new non-Fermi liquid fixed point
We study a new exchange interaction in which the conduction electrons with
pseudo spin interact with the impurity spin . Due to the
overscreening of the impurity spin by higher conduction electron spin, a new
non-trivial intermediate coupling strength fixed point is realized. Using the
numerical renormalization group (NRG), we show that the low-energy spectra are
described by a non-Fermi liquid excitation spectrum. A conformal field theory
analysis is compared with NRG results and excellent agreement is obtained.
Using the double fusion rule to generate the operator spectrum with the
conformal theory, we find that the specific heat coefficient and magnetic
susceptibility will diverge as , that the scaling dimension of an
applied magnetic field is , and that exchange anisotropy is always
relevant. We discuss the possible relevance of our work to two-level system
Kondo materials and dilute cerium alloys, and we point out a paradox in
understanding the Bethe-Ansatz solutions to the multichannel Kondo model.Comment: Revised. 20 page
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