332 research outputs found
Information-Theoretic Active Learning for Content-Based Image Retrieval
We propose Information-Theoretic Active Learning (ITAL), a novel batch-mode
active learning method for binary classification, and apply it for acquiring
meaningful user feedback in the context of content-based image retrieval.
Instead of combining different heuristics such as uncertainty, diversity, or
density, our method is based on maximizing the mutual information between the
predicted relevance of the images and the expected user feedback regarding the
selected batch. We propose suitable approximations to this computationally
demanding problem and also integrate an explicit model of user behavior that
accounts for possible incorrect labels and unnameable instances. Furthermore,
our approach does not only take the structure of the data but also the expected
model output change caused by the user feedback into account. In contrast to
other methods, ITAL turns out to be highly flexible and provides
state-of-the-art performance across various datasets, such as MIRFLICKR and
ImageNet.Comment: GCPR 2018 paper (14 pages text + 2 pages references + 6 pages
appendix
Subsequent cultivation of chondrocytes and mesenchymal stem cells on the devitalised tissue
The regeneration of cartilage lesions still represents a major challenge.
Cartilage has a tissue-specific architecture, complicating recreation by
synthetic biomaterials. A novel approach for reconstruction is the use of
devitalised cartilage. Treatment with high hydrostatic pressure (HHP) achieves
devitalisation while biomechanical properties are remained. Therefore, in the
present study, cartilage was devitalised using HHP treatment and the potential
for revitalisation with chondrocytes and mesenchymal stem cells (MSCs) was
investigated. The devitalisation of cartilage was performed by application of
480âMPa over 10âminutes. Effective cellular inactivation was demonstrated by
the trypan blue exclusion test and DNA quantification. Histology and electron
microscopy examinations showed undamaged cartilage structure after HHP
treatment. For revitalisation chondrocytes and MSCs were cultured on
devitalised cartilage without supplementation of chondrogenic growth factors.
Both chondrocytes and MSCs significantly increased expression of cartilage-
specific genes. ECM stainings showed neocartilage-like structure with positive
AZAN staining as well as collagen type II and aggrecan deposition after three
weeks of cultivation. Our results showed that HHP treatment caused
devitalisation of cartilage tissue. ECM proteins were not influenced, thus,
providing a scaffold for chondrogenic differentiation of MSCs and
chondrocytes. Therefore, using HHP-treated tissue might be a promising
approach for cartilage repair
Orbital electron capture by the nucleus
The theory of nuclear electron capture is reviewed in the light of current understanding of weak interactions. Experimental methods and results regarding capture probabilities, capture ratios, and EC/Beta(+) ratios are summarized. Radiative electron capture is discussed, including both theory and experiment. Atomic wave function overlap and electron exchange effects are covered, as are atomic transitions that accompany nuclear electron capture. Tables are provided to assist the reader in determining quantities of interest for specific cases
High-Dimensional Stochastic Design Optimization by Adaptive-Sparse Polynomial Dimensional Decomposition
This paper presents a novel adaptive-sparse polynomial dimensional
decomposition (PDD) method for stochastic design optimization of complex
systems. The method entails an adaptive-sparse PDD approximation of a
high-dimensional stochastic response for statistical moment and reliability
analyses; a novel integration of the adaptive-sparse PDD approximation and
score functions for estimating the first-order design sensitivities of the
statistical moments and failure probability; and standard gradient-based
optimization algorithms. New analytical formulae are presented for the design
sensitivities that are simultaneously determined along with the moments or the
failure probability. Numerical results stemming from mathematical functions
indicate that the new method provides more computationally efficient design
solutions than the existing methods. Finally, stochastic shape optimization of
a jet engine bracket with 79 variables was performed, demonstrating the power
of the new method to tackle practical engineering problems.Comment: 18 pages, 2 figures, to appear in Sparse Grids and
Applications--Stuttgart 2014, Lecture Notes in Computational Science and
Engineering 109, edited by J. Garcke and D. Pfl\"{u}ger, Springer
International Publishing, 201
Bayesian Analysis of the Polarization of Distant Radio Sources: Limits on Cosmological Birefringence
A recent study of the rotation of the plane of polarization of light from 160
cosmological sources claims to find significant evidence for cosmological
anisotropy. We point out methodological weaknesses of that study, and reanalyze
the same data using Bayesian methods that overcome these problems. We find that
the data always favor isotropic models for the distribution of observed
polarizations over counterparts that have a cosmological anisotropy of the type
advocated in the earlier study. Although anisotropic models are not completely
ruled out, the data put strong lower limits on the length scale (in
units of the Hubble length) associated with the anisotropy; the lower limits of
95% credible regions for lie between 0.43 and 0.62 in all anisotropic
models we studied, values several times larger than the best-fit value of
found in the earlier study. The length scale is not
constrained from above. The vast majority of sources in the data are at
distances closer than 0.4 Hubble lengths (corresponding to a redshift of
0.8); the results are thus consistent with there being no significant
anisotropy on the length scale probed by these data.Comment: 8 pages, 3 figures; submitted to Phys. Rev.
Overexpression of miRNA-25-3p inhibits Notch1 signaling and TGF-ÎČ-induced collagen expression in hepatic stellate cells
During chronic liver injury hepatic stellate cells (HSCs), the principal source of extracellular matrix in the fibrotic liver, transdifferentiate into pro-fibrotic myofibroblast-like cells - a process potentially regulated by microRNAs (miRNAs). Recently, we found serum miRNA-25-3p (miR-25) levels were upregulated in children with Cystic Fibrosis (CF) without liver disease, compared to children with CF-associated liver disease and healthy individuals. Here we examine the role of miR-25 in HSC biology. MiR-25 was detected in the human HSC cell line LX-2 and in primary murine HSCs, and increased with culture-induced activation. Transient overexpression of miR-25 inhibited TGF-ÎČ and its type 1 receptor (TGFBR1) mRNA expression, TGF-ÎČ-induced Smad2 phosphorylation and subsequent collagen1α1 induction in LX-2 cells. Pull-down experiments with biotinylated miR-25 revealed Notch signaling (co-)activators ADAM-17 and FKBP14 as miR-25 targets in HSCs. NanoString analysis confirmed miR-25 regulation of Notch- and Wnt-signaling pathways. Expression of Notch signaling pathway components and endogenous Notch1 signaling was downregulated in miR-25 overexpressing LX-2 cells, as were components of Wnt signaling such as Wnt5a. We propose that miR-25 acts as a negative feedback anti-fibrotic control during HSC activation by reducing the reactivity of HSCs to TGF-ÎČ-induced collagen expression and modulating the cross-talk between Notch, Wnt and TGF-ÎČ signaling
Chiral Symmetry and the Nucleon's Vector Strangeness Form Factors
The nucleon's strange-quark vector current form factors are studied from the
perspective of chiral symmetry. It is argued that chiral perturbation theory
cannot yield a prediction for the strangeness radius and magnetic moment.
Arrival at definite predictions requires the introduction of additional,
model-dependent assumptions which go beyond the framework of chiral
perturbation theory. A variety of such model predictions is surveyed, and the
credibility of each is evaluated. The most plausible prediction appears in a
model where the unknown chiral counterterms are identified with -channel
vector meson exchange amplitudes. The corresponding prediction for the mean
square Dirac strangeness radius is fm, which
would be observable in up-coming semileptonic determinations of the nucleon's
strangeness form factors.Comment: LaTex 31 pages, four figures available from authors
Latest Developments from the S-DALINAC*
The S-DALINAC is a 130 MeV superconducting recirculating electron accelerator serving several nuclear and radiation physics experiments as well as driving an infrared free-electron laser. A system of normal conducting rf resonators for noninvasive beam position and current measurement was established. For the measurement of gamma-radiation inside the accelerator cave a system of Compton diodes has been developed and tested. Detailed investigations of the transverse phasespace were carried out with a tomographical reconstruction method of optical transition radiation spots. The method can be applied also to non-Gaussian phasespace distributions. The results are in good accordance with simulations. To improve the quality factor of the superconducting 3 GHz cavities, an external 2K testcryostat was commissioned. The influence of electro-chemical polishing and magnetic shielding is currently under investigation. A digital rf-feedback-system for the accelerator cavities is being developed in order to improve the energy spread of the beam of the S-DALINAC. * Supported by the BMBF under contract no. 06 DA 820, the DFG under contract no. Ri 242/12-1 and -2 and the DFG Graduiertenkolleg 'Physik und Technik von Beschleunigern
Frequency and isostericity of RNA base pairs
Most of the hairpin, internal and junction loops that appear single-stranded in standard RNA secondary structures form recurrent 3D motifs, where non-WatsonâCrick base pairs play a central role. Non-WatsonâCrick base pairs also play crucial roles in tertiary contacts in structured RNA molecules. We previously classified RNA base pairs geometrically so as to group together those base pairs that are structurally similar (isosteric) and therefore able to substitute for each other by mutation without disrupting the 3D structure. Here, we introduce a quantitative measure of base pair isostericity, the IsoDiscrepancy Index (IDI), to more accurately determine which base pair substitutions can potentially occur in conserved motifs. We extract and classify base pairs from a reduced-redundancy set of RNA 3D structures from the Protein Data Bank (PDB) and calculate centroids (exemplars) for each base combination and geometric base pair type (family). We use the exemplars and IDI values to update our online Basepair Catalog and the Isostericity Matrices (IM) for each base pair family. From the database of base pairs observed in 3D structures we derive base pair occurrence frequencies for each of the 12 geometric base pair families. In order to improve the statistics from the 3D structures, we also derive base pair occurrence frequencies from rRNA sequence alignments
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