Methods for interpreting and understanding deep neural networks

Montavon, Gré,goire,Samek, Wojciech,Mü,ller, Klaus-Robert Elsevier 2018 Digital signal processing Vol.73 No.-

<P><B>Abstract</B></P> <P>This paper provides an entry point to the problem of interpreting a deep neural network model and explaining its predictions. It is based on a tutorial given at ICASSP 2017. As a tutorial paper, the set of methods covered here is not exhaustive, but sufficiently representative to discuss a number of questions in interpretability, technical challenges, and possible applications. The second part of the tutorial focuses on the recently proposed layer-wise relevance propagation (LRP) technique, for which we provide theory, recommendations, and tricks, to make most efficient use of it on real data.</P>

A discontinuous Galerkin method for elliptic interface problems with application to electroporation

Guyomarc'h, Gré,gory,Lee, Chang-Ock,Jeon, Kiwan John Wiley Sons, Ltd. 2009 Communications in numerical methods in engineering Vol.25 No.10

<P>We solve elliptic interface problems using a discontinuous Galerkin (DG) method, for which discontinuities in the solution and in its normal derivatives are prescribed on an interface inside the domain. Standard ways to solve interface problems with finite element methods consist in enforcing the prescribed discontinuity of the solution in the finite element space. Here, we show that the DG method provides a natural framework to enforce both discontinuities weakly in the DG formulation, provided the triangulation of the domain is fitted to the interface. The resulting discretization leads to a symmetric system that can be efficiently solved with standard algorithms. The method is shown to be optimally convergent in the L<SUP>2</SUP>-norm. We apply our method to the numerical study of electroporation, a widely used medical technique with applications to gene therapy and cancer treatment. Mathematical models of electroporation involve elliptic problems with dynamic interface conditions. We discretize such problems into a sequence of elliptic interface problems that can be solved by our method. We obtain numerical results that agree with known exact solutions. Copyright © 2008 John Wiley & Sons, Ltd.</P>

Molecular Cosensitization for Efficient Panchromatic Dye-Sensitized Solar Cells

Cid, Juan-Jos&eacute,Yum, Jun-Ho,Jang, Song-Rim,Nazeeruddin, Mohammad K.,Martí,nez-Ferrero, Eugenia,Palomares, Emilio,Ko, Jaejung,Grä,tzel, Michael,Torres, Tomá,s WILEY-VCH Verlag 2007 Angewandte Chemie Vol.46 No.44

<B>Graphic Abstract</B> <P>Dyeing together: An efficient panchromatic dye-sensitized solar cell is constructed by using a “molecular cocktail” composed of an organic dye and a zinc phthalocyanine (see picture). The use of multiple, complementary dyes (cosensitization) is an important step towards solar cells that operate across the full spectrum of solar irradiation. <img src='wiley_img/14337851-2007-46-44-ANIE200703106-content.gif' alt='wiley_img/14337851-2007-46-44-ANIE200703106-content'> </P>

Explaining nonlinear classification decisions with deep Taylor decomposition

Montavon, Gré,goire,Lapuschkin, Sebastian,Binder, Alexander,Samek, Wojciech,Mü,ller, Klaus-Robert Elsevier 2017 Pattern recognition Vol.65 No.-

<P><B>Abstract</B></P> <P>Nonlinear methods such as Deep Neural Networks (DNNs) are the gold standard for various challenging machine learning problems such as image recognition. Although these methods perform impressively well, they have a significant disadvantage, the lack of transparency, limiting the interpretability of the solution and thus the scope of application in practice. Especially DNNs act as black boxes due to their multilayer nonlinear structure. In this paper we introduce a novel methodology for interpreting generic multilayer neural networks by decomposing the network classification decision into contributions of its input elements. Although our focus is on image classification, the method is applicable to a broad set of input data, learning tasks and network architectures. Our method called deep Taylor decomposition efficiently utilizes the structure of the network by backpropagating the explanations from the output to the input layer. We evaluate the proposed method empirically on the MNIST and ILSVRC data sets.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A novel method to explain nonlinear classification decisions in terms of input variables is introduced. </LI> <LI> The method is based on Taylor expansions and decomposes the output of a deep neural network in terms of input variables. </LI> <LI> The resulting deep Taylor decomposition can be applied directly to existing neural networks without retraining. </LI> <LI> The method is tested on two large-scale neural networks for image classification: BVLC CaffeNet and GoogleNet. </LI> </UL> </P>

Carboxyethynyl Anchoring Ligands: A Means to Improving the Efficiency of Phthalocyanine‐Sensitized Solar Cells

Ragoussi, Maria‐,Eleni,Cid, Juan‐,Jos&eacute,Yum, Jun‐,Ho,de ,la ,Torre, Gema,Di ,Censo, Davide,Grä,tzel, Michael,Nazeeruddin, Mohammad K.,Torres, Tomá,s WILEY‐VCH Verlag 2012 Angewandte Chemie Vol.124 No.18

<P><B>Starre π‐konjugierte Brücken</B> wie die Ethinylgruppe sind geeignet, um das π‐System eines Phthalocyanins effektiv an das Leitungsband von TiO<SUB>2</SUB> zu koppeln. Eine Reihe von Zinkphthalocyanin‐Photosensibilisatoren mit Carboxyethinyl‐Ankergruppen wurde synthetisiert. Solarzellen, die mit der gezeigten Verbindung sensibilisiert wurden, zeigten Wirkungsgrade von 5.5 % und 6.1 % unter 100 (1 sun) bzw. 9.5 mW cm<SUP>−2</SUP>.</P>

Role of radiotherapy fractionation in head and neck cancers (MARCH): an updated meta-analysis

Lacas, Benjamin,Bourhis, Jean,Overgaard, Jens,Zhang, Qiang,Gré,goire, Vincent,Nankivell, Matthew,Zackrisson, Bjö,rn,Szutkowski, Zbigniew,Suwiń,ski, Rafał,Poulsen, Michael,O'Sullivan, Br Elsevier 2017 The Lancet. Oncology Vol.18 No.9

<P><B>Summary</B></P> <P><B>Background</B></P> <P>The Meta-Analysis of Radiotherapy in squamous cell Carcinomas of Head and neck (MARCH) showed that altered fractionation radiotherapy is associated with improved overall and progression-free survival compared with conventional radiotherapy, with hyperfractionated radiotherapy showing the greatest benefit. This update aims to confirm and explain the superiority of hyperfractionated radiotherapy over other altered fractionation radiotherapy regimens and to assess the benefit of altered fractionation within the context of concomitant chemotherapy with the inclusion of new trials.</P> <P><B>Methods</B></P> <P>For this updated meta-analysis, we searched bibliography databases, trials registries, and meeting proceedings for published or unpublished randomised trials done between Jan 1, 2009, and July 15, 2015, comparing primary or postoperative conventional fractionation radiotherapy versus altered fractionation radiotherapy (comparison 1) or conventional fractionation radiotherapy plus concomitant chemotherapy versus altered fractionation radiotherapy alone (comparison 2). Eligible trials had to start randomisation on or after Jan 1, 1970, and completed accrual before Dec 31, 2010; had to have been randomised in a way that precluded prior knowledge of treatment assignment; and had to include patients with non-metastatic squamous cell carcinoma of the oral cavity, oropharynx, hypopharynx, or larynx undergoing first-line curative treatment. Trials including a non-conventional radiotherapy control group, investigating hypofractionated radiotherapy, or including mostly nasopharyngeal carcinomas were excluded. Trials were grouped in three types of altered fractionation: hyperfractionated, moderately accelerated, and very accelerated. Individual patient data were collected and combined with a fixed-effects model based on the intention-to-treat principle. The primary endpoint was overall survival.</P> <P><B>Findings</B></P> <P>Comparison 1 (conventional fractionation radiotherapy <I>vs</I> altered fractionation radiotherapy) included 33 trials and 11 423 patients. Altered fractionation radiotherapy was associated with a significant benefit on overall survival (hazard ratio [HR] 0·94, 95% CI 0·90–0·98; p=0·0033), with an absolute difference at 5 years of 3·1% (95% CI 1·3–4·9) and at 10 years of 1·2% (−0·8 to 3·2). We found a significant interaction (p=0·051) between type of fractionation and treatment effect, the overall survival benefit being restricted to the hyperfractionated group (HR 0·83, 0·74–0·92), with absolute differences at 5 years of 8·1% (3·4 to 12·8) and at 10 years of 3·9% (−0·6 to 8·4). Comparison 2 (conventional fractionation radiotherapy plus concomitant chemotherapy versus altered fractionation radiotherapy alone) included five trials and 986 patients. Overall survival was significantly worse with altered fractionation radiotherapy compared with concomitant chemoradiotherapy (HR 1·22, 1·05–1·42; p=0·0098), with absolute differences at 5 years of −5·8% (−11·9 to 0·3) and at 10 years of −5·1% (−13·0 to 2·8).</P> <P><B>Interpretation</B></P> <P>This update confirms, with more patients and a longer follow-up than the first version of MARCH, that hyperfractionated radiotherapy is, along with concomitant chemoradiotherapy, a standard of care for the treatment of locally advanced head and neck squamous cell cancers. The comparison between hyperfractionated radiotherapy and concomitant chemoradiotherapy remains to be specifically tested.</P> <P><B>Funding</B></P> <P>Institut National du Cancer; and Ligue Nationale Contre le Cancer.</P>

Integrated cladding-pumped multicore few-mode erbium-doped fibre amplifier for space-division-multiplexed communications

Chen, H.,Jin, C.,Huang, B.,Fontaine, N. K.,Ryf, R.,Shang, K.,Gré,goire, N.,Morency, S.,Essiambre, R.-J.,Li, G.,Messaddeq, Y.,LaRochelle, S. Nature Publishing Group 2016 Nature photonics Vol.10 No.8

Space-division multiplexing (SDM), whereby multiple spatial channels in multimode and multicore optical fibres are used to increase the total transmission capacity per fibre, is being investigated to avert a data capacity crunch and reduce the cost per transmitted bit. With the number of channels employed in SDM transmission experiments continuing to rise, there is a requirement for integrated SDM components that are scalable. Here, we demonstrate a cladding-pumped SDM erbium-doped fibre amplifier (EDFA) that consists of six uncoupled multimode erbium-doped cores. Each core supports three spatial modes, which enables the EDFA to amplify a total of 18 spatial channels (six cores × three modes) simultaneously with a single pump diode and a complexity similar to a single-mode EDFA. The amplifier delivers >20 dBm total output power per core and <7 dB noise figure over the C-band. This cladding-pumped EDFA enables combined space-division and wavelength-division multiplexed transmission over multiple multimode fibre spans.

Effect of anchoring groups in zinc phthalocyanine on the dye-sensitized solar cell performance and stability

Garcí,a-Iglesias, Miguel,Yum, Jun-Ho,Humphry-Baker, Robin,Zakeeruddin, Shaik M.,P&eacute,chy, Peter,Vá,zquez, Purificació,n,Palomares, Emilio,Grä,tzel, Michael,Nazeeruddin, Moham Royal Society of Chemistry 2011 Chemical science Vol.2 No.6

<P>We have designed and developed an unsymmetrical zinc phthalocyanine (TT9) sensitizer that consists of three <I>tert</I>-butyl and two carboxylic acid groups that act as “<I>push</I>” and “<I>pull</I>”, respectively. The two carboxylic acid groups graft the sensitizer onto the semiconductor surface resulting in enhanced stability under heat and light compared to the similar unsymmetrical zinc phthalocyanine (TT1) sensitizer that consists of three <I>tert</I>-butyl and only one carboxylic acid groups. The solar cells containing the TT9 and TT1 sensitizers with non-volatile electrolyte were subjected to light soaking conditions at 60 °C. Under these conditions, the short circuit current of the TT1 sensitized solar cell after 1000 h decreases to half of its initial value where as the TT9 sensitized solar cell remained the same demonstrating the influence of number of anchoring groups on the stability of zinc phthalocyanine sensitized solar cells.</P> <P>Graphic Abstract</P><P>Phthalocyanine TT9 (red) grafts onto the semiconductor surface resulting in enhanced stability compared to TT1 (black). <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c0sc00602e'> </P>