6,183 research outputs found
Structured learning of assignment models for neuron reconstruction to minimize topological errors
© 20xx IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.Structured learning provides a powerful framework for empirical risk minimization on the predictions of
structured models. It allows end-to-end learning of model parameters to minimize an application specific loss function. This framework is particularly well suited for discrete optimization models that are used for neuron reconstruction from anisotropic electron microscopy (EM) volumes. However, current methods are still learning unary potentials by training a classifier that is agnostic about the model it is used in. We believe the reason for that lies in the difficulties of (1) finding a representative training sample, and (2) designing an application specific loss function that captures the quality of a proposed solution. In this paper, we show how to find a representative training sample from human generated ground truth, and propose a loss function that is suitable to minimize topological errors in the reconstruction. We compare different training methods on two challenging EM-datasets. Our structured learning approach shows consistently higher reconstruction accuracy than other current learning methods.Peer ReviewedPostprint (author's final draft
Anharmonic Self-Energy of Phonons: Ab Initio Calculations and Neutron Spin Echo Measurements
We have calculated (ab initio) and measured (by spin-echo techniques) the
anharmonic self-energy of phonons at the X-point of the Brillouin zone for
isotopically pure germanium. The real part agrees with former, less accurate,
high temperature data obtained by inelastic neutron scattering on natural
germanium. For the imaginary part our results provide evidence that transverse
acoustic phonons at the X-point are very long lived at low temperatures, i.e.
their probability of decay approaches zero, as a consequence of an unusual
decay mechanism allowed by energy conservation.Comment: 8 pages, 2 figures, pdf fil
Raman scattering study of electron-doped PrCaFeAs superconductors
Temperature-dependent polarized Raman spectra of electron-doped
superconducting PrCaFeAs () single crystals
are reported. All four allowed by symmetry even-parity phonons are identified.
Phonon mode of B symmetry at 222 cm, which is associated with the
c-axis motion of Fe ions, is found to exhibit an anomalous frequency hardening
at low temperatures, that signals non-vanishing electron-phonon coupling in the
superconducting state and implies that the superconducting gap magnitude
meV.Comment: 4 pages, 3 figure
Holographic energy density, dark energy sound speed, and tensions in cosmological parameters: and
Interesting discrepancies in cosmological parameters are challenging the
success of the CDM model. Direct measurements of the Hubble constant
using Cepheid variables and supernovae turn out to be higher than
inferred from the Cosmic Microwave Background (CMB). Weak galaxy lensing
surveys consistently report values of the strength of matter clustering
lower than values derived from the CMB in the context of
CDM. In this paper we address these discrepancies in cosmological
parameters by considering Dark Energy (DE) as a fluid with evolving equation of
state , constant sound speed squared
, and vanishing anisotropic stress . Our
is derived from the Holographic Principle and can
consecutively exhibit radiation-like, matter-like, and DE-like behaviour, thus
affecting the sound horizon and the comoving angular diameter distance, hence
. Here we show DE sound speed plays a part in the matter clustering
behaviour through its effect on the evolution of the gravitational potential.
We compute cosmological constraints using several data set combinations
including primary CMB, CMB lensing, redshift-space-distortions, local
distance-ladder, supernovae, and baryon acoustic oscillations. In our analysis
we marginalise over and find
is excluded at . For our baseline
result including the whole data set we found and in good
agreement (within ) with low redshift probes. Our constraint
for the baryon energy density is however in
tension with BBN constraints. We conclude evolving DE also having non-standard
clustering properties [e.g., ] might be relevant
for the solution of current discrepancies in cosmological parameters.Comment: 28 pages, 12 figures, 3 tables. References adde
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