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Non-smooth variational regularization for processing manifold-valued data [article]

Martin Holler, Andreas Weinmann
2019 arXiv   pre-print
Many methods for processing scalar and vector valued images, volumes and other data in the context of inverse problems are based on variational formulations. Such formulations require appropriate regularization functionals that model expected properties of the object to reconstruct. Prominent examples of regularization functionals in a vector-space context are the total variation (TV) and the Mumford-Shah functional, as well as higher-order schemes such as total generalized variation models.
more » ... ven by applications where the signals or data live in nonlinear manifolds, there has been quite some interest in developing analogous methods for nonlinear, manifold-valued data recently. In this chapter, we consider various variational regularization methods for manifold-valued data. In particular, we consider TV minimization as well as higher order models such as total generalized variation (TGV). Also, we discuss (discrete) Mumford-Shah models and related methods for piecewise constant data. We develop discrete energies for denoising and report on algorithmic approaches to minimize them. Further, we also deal with the extension of such methods to incorporate indirect measurement terms, thus addressing the inverse problem setup. Finally, we discuss wavelet sparse regularization for manifold-valued data.
arXiv:1909.08921v1 fatcat:dz6qdvkhibbrhjbjmnh3ryvko4

Implementing Rlwe-Based Schemes Using An Rsa Co-Processor

Martin R. Albrecht, Christian Hanser, Andrea Höller, Thomas Pöppelmann, Fernando Virdia, Andreas Wallner
2018 Zenodo  
We repurpose existing RSA/ECC co-processors for (ideal) lattice-based cryptography by exploiting the availability of fast long integer multiplication. Such co-processors are deployed in smart cards in passports and identity cards, secured microcontrollers and hardware security modules (HSM). In particular, we demonstrate an implementation of a variant of the Module-LWE-based Kyber Key Encapsulation Mechanism (KEM) that is tailored for optimal performance on a commercially available smart card
more » ... ip (SLE 78). To benefit from the RSA/ECC co-processor we use Kronecker substitution in combination with schoolbook and Karatsuba polynomial multiplication. Moreover, we speed-up symmetric operations in our Kyber variant using the AES co-processor to implement a PRNG and a SHA-256 co-processor to realise hash functions. This allows us to execute CCA-secure Kyber768 key generation in 79.6ms, encapsulation in 102.4 ms and decapsulation in 132.7 ms.
doi:10.5281/zenodo.1486565 fatcat:vuj3jabg75b3dnqtn72wpv5pwe

Fuzzing with Code Fragments

Christian Holler, Kim Herzig, Andreas Zeller
2012 USENIX Security Symposium  
. * At the time of this study, Christan Holler was writing his master thesis at Saarland University. He is now employed at Mozilla.  ... 
dblp:conf/uss/HollerHZ12 fatcat:dawrgvj2fvfglhlsudlyoim7vi

DP, NP, or neither? Contours of an unresolved debate

Andreas Blümel, Anke Holler
2021 Glossa  
Glossa's Special Collection New perspectives on the NP/DP debate brings together syntactic analyses of various phenomena of complex nominals, shedding light on the central problem of their syntactic category label. In this paper, we survey arguments and analyses offered in the Special Collection, classifying their underlying assumptions and highlighting their relevance to syntactic theory more generally.
doi:10.16995/glossa.8326 fatcat:p7m7wtjo4nflpjuw5jaynsakai

Effects of intermittent theta burst stimulation on spasticity after spinal cord injury

Raffaele Nardone, Patrick B. Langthaler, Andrea Orioli, Peter Höller, Yvonne Höller, Vanessa N. Frey, Francesco Brigo, Eugen Trinka
2017 Restorative Neurology and Neuroscience  
Purpose: Spasticity is a common disorder in patients with spinal cord injury (SCI). The aim of this study was to investigate whether intermittent theta burst stimulation (iTBS), a safe, non-invasive and well-tolerated protocol of excitatory repetitive transcranial magnetic stimulation (rTMS), is effective in modulating spasticity in SCI patients. Methods: In this randomized, double-blind, crossover, sham-controlled study, ten subjects with incomplete cervical or thoracic SCI received 10 days of
more » ... daily sessions of real or sham iTBS. The H/M amplitude ratio of the Soleus H reflex, the amplitude of the motor evoked potentials (MEPs) at rest and during background contraction, as well as Modified Ashworth Scale (MAS) and the Spinal Cord Injury Assessment Tool for Spasticity (SCAT) were compared before and after the stimulation protocols. Results: Patients receiving real iTBS showed significant increased resting and active MEPs amplitude and a significant reduction of the H/M amplitude ratio. In these patients also the MAS and SCAT scores were significantly reduced after treatment. These changes persisted up to 1 week after the end of the iTBS treatment, and were not observed under the sham-TBS condition. Conclusion: These findings suggest that iTBS may be a promising therapeutic tool for the spasticity in SCI patients.
doi:10.3233/rnn-160701 pmid:28598858 fatcat:dg6pbcgqmzc4rgcloqbguxnzli

HD-EEG Based Classification of Motor-Imagery Related Activity in Patients With Spinal Cord Injury

Yvonne Höller, Aljoscha Thomschewski, Andreas Uhl, Arne C. Bathke, Raffaele Nardone, Stefan Leis, Eugen Trinka, Peter Höller
2018 Frontiers in Neurology  
Brain computer interfaces (BCIs) are thought to revolutionize rehabilitation after SCI, e.g., by controlling neuroprostheses, exoskeletons, functional electrical stimulation, or a combination of these components. However, most BCI research was performed in healthy volunteers and it is unknown whether these results can be translated to patients with spinal cord injury because of neuroplasticity. We sought to examine whether high-density EEG (HD-EEG) could improve the performance of motor-imagery
more » ... classification in patients with SCI. We recorded HD-EEG with 256 channels in 22 healthy controls and 7 patients with 14 recordings (4 patients had more than one recording) in an event related design. Participants were instructed acoustically to either imagine, execute, or observe foot and hand movements, or to rest. We calculated Fast Fourier Transform (FFT) and full frequency directed transfer function (ffDTF) for each condition and classified conditions pairwise with support vector machines when using only 2 channels over the sensorimotor area, full 10-20 montage, high-density montage of the sensorimotor cortex, and full HD-montage. Classification accuracies were comparable between patients and controls, with an advantage for controls for classifications that involved the foot movement condition. Full montages led to better results for both groups (p < 0.001), and classification accuracies were higher for FFT than for ffDTF (p < 0.001), for which the feature vector might be too long. However, full-montage 10-20 montage was comparable to high-density configurations. Motor-imagery driven control of neuroprostheses or BCI systems may perform as well in patients as in healthy volunteers with adequate technical configuration. We suggest the use of a whole-head montage and analysis of a broad frequency range.
doi:10.3389/fneur.2018.00955 pmid:30510537 pmcid:PMC6252382 fatcat:qej6ginexfcfvdh5cid647obee

A Note on the Regularity of Images Generated by Convolutional Neural Networks [article]

Andreas Habring, Martin Holler
2022 arXiv   pre-print
The regularity of images generated by convolutional neural networks, such as the U-net, generative adversarial networks, or the deep image prior, is analyzed. In a resolution-independent, infinite dimensional setting, it is shown that such images, represented as functions, are always continuous and, in some circumstances, even continuously differentiable, contradicting the widely accepted modeling of sharp edges in images via jump discontinuities. While such statements require an infinite
more » ... ional setting, the connection to (discretized) neural networks used in practice is made by considering the limit as the resolution approaches infinity. As practical consequence, the results of this paper suggest to refrain from basic L2 regularization of network weights in case of images being the network output.
arXiv:2204.10588v1 fatcat:y6znpawgm5apbeauct6dc5oegq

Endoscope Distortion Correction Does Not (Easily) Improve Mucosa-Based Classification of Celiac Disease [chapter]

Jutta Hämmerle-Uhl, Yvonne Höller, Andreas Uhl, Andreas Vécsei
2012 Lecture Notes in Computer Science  
Distortion correction is applied to endoscopic duodenal imagery to improve automated classification of celiac disease affected mucosa patches. In a set of six edge-and shape-related feature extraction techniques, only a single one is able to consistently benefit from distortion correction, while for others, even a decrease of classification accuracy is observed. Different types of distortion correction do not lead to significantly different behaviour in the observed application scenario.
doi:10.1007/978-3-642-33454-2_71 fatcat:zwyspuhaabdkbb7xntnffxibe4

A Generative Variational Model for Inverse Problems in Imaging [article]

Andreas Habring, Martin Holler
2021 arXiv   pre-print
This paper is concerned with the development, analysis and numerical realization of a novel variational model for the regularization of inverse problems in imaging. The proposed model is inspired by the architecture of generative convolutional neural networks; it aims to generate the unknown from variables in a latent space via multi-layer convolutions and non-linear penalties, and penalizes an associated cost. In contrast to conventional neural-network-based approaches, however, the
more » ... kernels are learned directly from the measured data such that no training is required. The present work provides a mathematical analysis of the proposed model in a function space setting, including proofs for regularity and existence/stability of solutions, and convergence for vanishing noise. Moreover, in a discretized setting, a numerical algorithm for solving various types of inverse problems with the proposed model is derived. Numerical results are provided for applications in inpainting, denoising, deblurring under noise, super-resolution and JPEG decompression with multiple test images.
arXiv:2104.12630v2 fatcat:zl3tzrqp2nbdzar6zd2ejg3zou

Self-assembly of highly luminescent heteronuclear coordination cages

Andrea Schmidt, Manuela Hollering, Jiaying Han, Angela Casini, Fritz E. Kühn
2016 Dalton Transactions  
A promising approach is described to enhance the luminescence of palladium(ii) cages resulting in one of the highest fluorescence qunatum yields for metallosupramolecular complexes.
doi:10.1039/c6dt02708c pmid:27436541 fatcat:r763ik2wujdznl52tvtbxf4uwm

Technical comparison of four different extracorporeal photopheresis systems

Andreas Brosig, Viola Hähnel, Evelyn Orsó, Daniel Wolff, Ernst Holler, Norbert Ahrens
2016 Transfusion  
doi:10.1111/trf.13728 pmid:27456672 fatcat:tgoaxvrqmnhn3kq2rmolzqb7fm

Abatacept as salvage therapy in chronic graft-versus-host disease—a retrospective analysis

Tobias Wertheimer, Marius Dohse, Gabriel Afram, Daniela Weber, Martin Heidenreich, Barbara Holler, Anna-Sophia Kattner, Andreas Neubauer, Stephan Mielke, Per Ljungman, Ernst Holler, Wolfgang Herr (+4 others)
2021 Annals of Hematology  
Wolff D, Gerbitz A, Ayuk F, Kiani A, Hildebrandt GC, Vogelsang GB, Elad S, Lawitschka A, Socie G, Pavletic SZ, Holler E, Greinix H (2010 Dec) Consensus conference on clinical practice in chronic Declarations  ... 
doi:10.1007/s00277-021-04434-x pmid:33515310 fatcat:enaa2axrgbfxrdunstbblnnddq

FAS Ligand, Bcl-2, Granulocyte Colony-Stimulating Factor, and p38 Mitogen-Activated Protein Kinase

Andreas Villunger, Lorraine A. O'Reilly, Nils Holler, Jerry Adams, Andreas Strasser
2000 Journal of Experimental Medicine  
The short life span of granulocytes, which limits many inflammatory responses, is thought to be influenced by the Bcl-2 protein family, death receptors such as CD95 (Fas/APO-1), stress-activated protein kinases such as p38 mitogen-activated protein kinase (MAPK), and proinflammatory cytokines like granulocyte colony-stimulating factor (G-CSF). To clarify the roles of these various regulators in granulocyte survival, we have investigated the spontaneous apoptosis of granulocytes in culture and
more » ... at induced by Fas ligand or chemotherapeutic drugs, using cells from normal, CD95-deficient lpr , or vav-bcl-2 transgenic mice. CD95-induced apoptosis, which required receptor aggregation by recombinant Fas ligand or the membrane-bound ligand, was unaffected by G-CSF treatment or Bcl-2 overexpression. Conversely, spontaneous and drug-induced apoptosis occurred normally in lpr granulocytes but were suppressed by G-CSF treatment or Bcl-2 overexpression. Although activation of p38 MAPK has been implicated in granulocyte death, their apoptosis actually was markedly accelerated by specific inhibitors of this kinase. These results suggest that G-CSF promotes granulocyte survival largely through the Bcl-2-controlled pathway, whereas CD95 regulates a distinct pathway to apoptosis that is not required for either their spontaneous or drug-induced death. Moreover, p38 MAPK signaling contributes to granulocyte survival rather than their apoptosis.
doi:10.1084/jem.192.5.647 pmid:10974031 pmcid:PMC2193264 fatcat:tchrq62aenbhzirj4jxrz6lquy

Predicting vulnerable software components

Stephan Neuhaus, Thomas Zimmermann, Christian Holler, Andreas Zeller
2007 Proceedings of the 14th ACM conference on Computer and communications security - CCS '07  
Where do most vulnerabilities occur in software? Our Vulture tool automatically mines existing vulnerability databases and version archives to map past vulnerabilities to components. The resulting ranking of the most vulnerable components is a perfect base for further investigations on what makes components vulnerable. In an investigation of the Mozilla vulnerability history, we surprisingly found that components that had a single vulnerability in the past were generally not likely to have
more » ... er vulnerabilities. However, components that had similar imports or function calls were likely to be vulnerable. Based on this observation, we were able to extend Vulture by a simple predictor that correctly predicts about half of all vulnerable components, and about two thirds of all predictions are correct. This allows developers and project managers to focus their their efforts where it is needed most: "We should look at nsXPInstallManager because it is likely to contain yet unknown vulnerabilities."
doi:10.1145/1315245.1315311 dblp:conf/ccs/NeuhausZHZ07 fatcat:5ofehv7eprhdnlylkuivdksgwm

Constructing Shape Spaces from a Topological Perspective [chapter]

Christoph Hofer, Roland Kwitt, Marc Niethammer, Yvonne Höller, Eugen Trinka, Andreas Uhl
2017 Lecture Notes in Computer Science  
We consider the task of constructing (metric) shape space(s) from a topological perspective. In particular, we present a generic construction scheme and demonstrate how to apply this scheme when shape is interpreted as the differences that remain after factoring out translation, scaling and rotation. This is achieved by leveraging a recently proposed injective functional transform of 2D/3D (binary) objects, based on persistent homology. The resulting shape space is then equipped with a
more » ... y measure that is (1) by design robust to noise and (2) fulfills all metric axioms. From a practical point of view, analyses of object shape can then be carried out directly on segmented objects obtained from some imaging modality without any preprocessing, such as alignment, smoothing, or landmark selection. We demonstrate the utility of the approach on the problem of distinguishing segmented hippocampi from normal controls vs. patients with Alzheimer's disease in a challenging setup where volume changes are no longer discriminative.
doi:10.1007/978-3-319-59050-9_9 fatcat:bkig67kpvnfsdhknfcryocdw3e
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