The extended finite element method with new crack-tip enrichment functions for an interface crack between two dissimilar piezoelectric materials

This paper studies the static fracture problems of an interface crack in linear piezoelectric bimaterial by means of the extended finite element method (X-FEM) with new crack-tip enrichment functions. In the X-FEM, crack modeling is facilitated by adding a discontinuous function and crack-tip asymptotic functions to the classical finite element approximation within the framework of the partition of unity. In this work, the coupled effects of an elastic field and an electric field in piezoelectricity are considered. Corresponding to the two classes of singularities of the aforementioned interface crack problem, namely, E class and class, two classes of crack-tip enrichment functions are newly derived, and the former that exhibits oscillating feature at the crack tip is numerically investigated. Computation of the fracture parameter, i.e., the J-integral, using the domain form of the contour integral, is presented. Excellent accuracy of the proposed formulation is demonstrated on benchmark interface crack problems through comparisons with analytical solutions and numerical results obtained by the classical FEM. Moreover, it is shown that the geometrical enrichment combining the mesh with local refinement is substantially better in terms of accuracy and efficiency.postprin

Semaphorin3A, associated with perineuronal nets, regulates the development of the maturation of the central vestibular circuitry

Poster Presentation - Theme 5: NeuroscienceDuring the formative period of neural circuits, perineuronal nets (PN) are established to restrict plasticity of the circuit. The role of PN in vestibular plasticity can be tested by studying the emergence of negative geotaxis with postnatal maturation of the vestibular circuitry for gravity detection. Using rats as model, we observed that negative geotaxis was mature by postnatal day (P) 9, in correlation with consolidation of PN around GABAergic neurons …postprin

Robust Multi-Image HDR Reconstruction for the Modulo Camera

Photographing scenes with high dynamic range (HDR) poses great challenges to consumer cameras with their limited sensor bit depth. To address this, Zhao et al. recently proposed a novel sensor concept - the modulo camera - which captures the least significant bits of the recorded scene instead of going into saturation. Similar to conventional pipelines, HDR images can be reconstructed from multiple exposures, but significantly fewer images are needed than with a typical saturating sensor. While the concept is appealing, we show that the original reconstruction approach assumes noise-free measurements and quickly breaks down otherwise. To address this, we propose a novel reconstruction algorithm that is robust to image noise and produces significantly fewer artifacts. We theoretically analyze correctness as well as limitations, and show that our approach significantly outperforms the baseline on real data.Comment: to appear at the 39th German Conference on Pattern Recognition (GCPR) 201

Perineuronal chondroitin sulfates and semaphorin 3A regulate postnatal maturation of the vestibular circuit for gravity detection

Conference Theme: The Extracellular Matrix NichePoster Presentation: abstract no. P30Perineuronal chondroitin sulfate proteoglycan networks are implicated in restricting plasticity of the mature CNS. Less is known of the impact of ligands associated with the perineuronal network (PN) in the formative period of neural circuits. The emergence of negative geotaxis with postnatal maturation of the vestibular circuitry for gravity detection offers a behavioral readout in tests for roles of the PN and associated ligands in vestibular plasticity. Using postnatal rats as model, we found that negative geotaxis was mature by postnatal day (P) 9, in correlation with ...postprin

Nonlocal homogenization for nonlinear metamaterials

©2016 American Physical Society. We present a consistent theoretical approach for calculating effective nonlinear susceptibilities of metamaterials taking into account both frequency and spatial dispersion. Employing the discrete dipole model, we demonstrate that effects of spatial dispersion become especially pronounced in the vicinity of effective permittivity resonance where nonlinear susceptibilities reach their maxima. In that case spatial dispersion may enable simultaneous generation of two harmonic signals with the same frequency and polarization but different wave vectors. We also prove that the derived expressions for nonlinear susceptibilities transform into the known form when spatial dispersion effects are negligible. In addition to revealing new physical phenomena, our results provide useful theoretical tools for analyzing resonant nonlinear metamaterials

The role of proheparanase in synaptic plasticity at the hippocampus

Abstract no. P-110Perineuronal heparan sulfate (HS) moieties are implicated in the modulation of neurotransmission by controlling the functional properties of AMPA-type glutamate receptors. We hypothesize that neuronal mechanisms modulate peri-synaptic HS level, thereby regulating synaptic strength and plasticity. To address this, basal synaptic strength and long-term changes in synaptic efficacy in the Schaffer collateral pathway of the rat hippocampus were assessed in relation to strategies that perturb peri-synaptic HS. In hippocampal slices, heparitinase treatment led to dose-dependent attenuation of long-term potentiation (LTP) in correlation with loss of perineuronal HS …postprin

Regulatory role of proheparanase with peri-synaptic heparan sulfate proteoglycan and AMPA-type glutamate receptor in synaptic plasticity

Poster Presentation: P59AMPA-type glutamate receptors (AMPAR) govern excitatory synaptic transmission. Perineuronal heparan sulfates (HS) have been implicated in controlling the open-state of AMPAR. Our finding of neuronal heparanase expression in adult rats led us to test (1) if neuronal heparanase is secreted and (2) if the secreted form acts on perineuronal HS to modulate synaptic plasticity. Neuronal secretion of heparanase was triggered by phorbol ester of rat hippocampal neurons in culture. Western blot analysis of the secreted product revealed enzymatically inactive proheparanase, but not the enzymatically active heparanase. Synaptosomes prepared from phorbol ester-treated rat cortexslices showed enrichment in proheparanase; co-immunoprecipitation studies further showed association of AMPAR subunits (GluA1 and GluA2/3) with both syndecan-3 (a transmembrane HS-proteoglycan) and proheparanase, suggesting their partnership in the peri-synaptic environment. Treatment of hippocampal neurons in culture with recombinant proheparanase triggered internalization of proheparanase, perineuronal HS-proteoglycans and AMPARs, suggesting their clustering as a functional complex. Heparitinase pre-treatment of hippocampal neuron cultures reduced proheparanase-induced internalization of AMPARs, suggesting that the HS moiety is critical for effecting the partnership. Treatment of hippocampal slices with recombinant proheparanase resulted in down-regulation of both basal synaptic strength and LTP at Schaffer collateral synapses. These results reveal a novel role of neuronal proheparanase in resetting AMPAR and perineuronal HS levels at the synapse and thus the modulation of synaptic plasticity.postprin

Asymptotic behaviour of estimators of the parameters of nearly unstable INAR(1) models

A sequence of first-order integer-valued autoregressive type (INAR(1)) processes is investigated, where the autoregressive type coefficients converge to 1. It is shown that the limiting distribution of the joint conditional least squares estimators for this coefficient and for the mean of the innovation is normal. Consequences for sequences of Galton{Watson branching processes with unobservable immigration, where the mean of the offspring distribution converges to 1 (which is the critical value), are discussed

Confluent Orthogonal Drawings of Syntax Diagrams

We provide a pipeline for generating syntax diagrams (also called railroad diagrams) from context free grammars. Syntax diagrams are a graphical representation of a context free language, which we formalize abstractly as a set of mutually recursive nondeterministic finite automata and draw by combining elements from the confluent drawing, layered drawing, and smooth orthogonal drawing styles. Within our pipeline we introduce several heuristics that modify the grammar but preserve the language, improving the aesthetics of the final drawing.Comment: GD 201

Class mutation operators for C++ object-oriented systems

Mutation testing is a fault injection testing technique around which a great variety of studies and tools for different programming languages have been developed. Nevertheless, the mutation testing research with respect to C++ is pending. This paper proposes a set of class mutation operators related to this language and its particular object-oriented (OO) features. In addition, an implementation technique to apply mutation testing based on the traversal of the abstract syntax tree (AST) is presented. Finally, an experiment is conducted to study the operator behaviour with different C++ programs, suggesting their usefulness in the creation of complete test suites. The analysis includes a Web service (WS) library, one of the domains where this technique can prove useful, considering its challenging testing phase and that C++ is still a reference language for critical distributed systems WS