A persistent homology-based topological loss function for multi-class CNN segmentation of cardiac MRI

With respect to spatial overlap, CNN-based segmentation of short axis cardiovascular magnetic resonance (CMR) images has achieved a level of performance consistent with inter observer variation. However, conventional training procedures frequently depend on pixel-wise loss functions, limiting optimisation with respect to extended or global features. As a result, inferred segmentations can lack spatial coherence, including spurious connected components or holes. Such results are implausible, violating the anticipated topology of image segments, which is frequently known a priori. Addressing this challenge, published work has employed persistent homology, constructing topological loss functions for the evaluation of image segments against an explicit prior. Building a richer description of segmentation topology by considering all possible labels and label pairs, we extend these losses to the task of multi-class segmentation. These topological priors allow us to resolve all topological errors in a subset of 150 examples from the ACDC short axis CMR training data set, without sacrificing overlap performance.Comment: To be presented at the STACOM workshop at MICCAI 202

Advances and new applications using the acousto-optic effect in optical fibers

This work presents a short review of the current research on the acousto-optic mechanism applied to optical fibers. The role of the piezoelectric element and the acousto-optic modulator in the excitation of flexural and longitudinal acoustic modes in the frequency range up to 1.2 MHz is highlighted. A combination of the finite elements and the transfer matrix methods is used to simulate the interaction of the waves with Bragg and long period gratings. Results show a very good agreement with experimental data. Recent applications such as the writing of gratings under the acoustic excitation and a novel viscometer sensor based on the acousto-optic mechanism are discussed

Corrigendum Recrystallization of Cu In,Ga Se 2 thin films studied by X ray diffraction

Recrystallization is essential for the synthesis of the highest quality Cu In,Ga Se2 CIGSe thin films for solar cell applications. Here we present a real time study of the recrystallization of CIGSe thin films. We trigger the recrystallization by allowing diffusion of Cu into a Cu poor CIGSe film and use synchrotron based energy dispersive X ray diffraction to monitor this transition in real time. Additionally, we characterize the films by means of angle dispersive X ray diffraction. Before recrystallization, the X ray diffraction patterns exhibit a signature that does not correspond to the ideal chalcopyrite structure of CIGSe. This signature can be attributed to stacking faults within the bulk of the films by modeling diffraction patterns of faulted CIGSe with the software DIFFaX. It is detected at temperatures below 650 K and is absent at temperatures above 750 K, which indicates that the faults in question were annihilated in this temperature range. This process occurs after the incorporation of Cu into the Cu poor CIGSe lattice, which takes place in the 550 650 K temperature rang

Fiber-modes and fiber-anisotropy characterization using low-coherence interferometry

An optical low-coherence interferometry technique has been used to simultaneously resolve the mode profile and to measure the intermodal dispersion of guided modes of a few-mode fiber. Measurements are performed using short samples of fiber (about 50 cm). There is no need for a complex mode-conversion technique to reach a high interference visibility. Four LP mode groups of the few-mode fiber are resolved. Experimental results and numerical simulations show that the ellipticity of the fiber core leads to a distinct splitting of the degenerate high-order modes in group index. For the first time, to the best of our knowledge, it has been demonstrated that degenerate LP11 modes are much more sensitive to core shape variations than the fundamental modes and that intermodal dispersion of high-order degenerate modes can be used for characterizing the anisotropy of an optical waveguide