Euclid in a Taxicab: Sparse Blind Deconvolution with Smoothed l1/l2 Regularization

The l1/l2 ratio regularization function has shown good performance for retrieving sparse signals in a number of recent works, in the context of blind deconvolution. Indeed, it benefits from a scale invariance property much desirable in the blind context. However, the l1/l2 function raises some difficulties when solving the nonconvex and nonsmooth minimization problems resulting from the use of such a penalty term in current restoration methods. In this paper, we propose a new penalty based on a smooth approximation to the l1/l2 function. In addition, we develop a proximal-based algorithm to solve variational problems involving this function and we derive theoretical convergence results. We demonstrate the effectiveness of our method through a comparison with a recent alternating optimization strategy dealing with the exact l1/l2 term, on an application to seismic data blind deconvolution.Comment: 5 page

PENDANTSS: PEnalized Norm-ratios Disentangling Additive Noise, Trend and Sparse Spikes

Denoising, detrending, deconvolution: usual restoration tasks, traditionally decoupled. Coupled formulations entail complex ill-posed inverse problems. We propose PENDANTSS for joint trend removal and blind deconvolution of sparse peak-like signals. It blends a parsimonious prior with the hypothesis that smooth trend and noise can somewhat be separated by low-pass filtering. We combine the generalized quasi-norm ratio SOOT/SPOQ sparse penalties $\ell_p/\ell_q$ with the BEADS ternary assisted source separation algorithm. This results in a both convergent and efficient tool, with a novel Trust-Region block alternating variable metric forward-backward approach. It outperforms comparable methods, when applied to typically peaked analytical chemistry signals. Reproducible code is provided

Stability theory for some scalar finite difference schemes : Validity of the modified equations approach

In this paper, we discuss some limitations of the modified equations approach as a tool for stability analysis for a class of explicit linear schemes to scalar partial derivative equations. We show that the infinite series obtained by Fourier transform of the modified equation is not always convergent and that in the case of divergence, it becomes unrelated to the scheme. Based on these results, we explain when the stability analysis of a given truncation of a modified equation may yield a reasonable estimation of a stability condition for the associated scheme. We illustrate our analysis by some examples of schemes namely for the heat equation and the transport equation.Comment: 13 pages, 2 figures, submitted as proceedings for CEMRACS 2019 summer schoo

Impact of cone-beam computed tomography for the identification and management of an oral portal of entry in patients with infective endocarditis. A Delphi study

Infective endocarditis (IE) is a rare and life-threatening disease. Cutaneous portal of entry (POE) is predominant for IE, but an oral POE is the second most frequent source. Thus looking for and treating an oral POE in IE patients is of critical importance in order to reduce the risk of IE relapse or recurrence. The objectives of this study were: 1) To reach a consensus on decision-making following the detection of an oral POE on cone-beam computed tomography (CBCT) while they were not identified using the current recommended approach in IE patients (oral examination and orthopantomogram: OPT). 2) To determine whether this consensus differs when regarding the microbiology of IE. Twenty oral or maxillofacial surgeons participated to this Delphi study. The questionnaire was based on five radiological cases (OPT and matching CBCT) with two scenarios according to the objectives of detecting oral POE in an IE patient (curative in case of oral causative microorganism, and preventive if not) and different therapeutic approaches (surgical or conservative treatment, no treatment) for each of them. Consensus was defined as an agreement rate of ?75%. The response rate was?85%. After four rounds, consensus was achieved for all proposals. CBCT changed the decision-making of experts in four cases. In one case, the decision was influenced by the IE microbiology toward a more radical approach in case of oral causative microorganism. In IE patients, CBCT changed markedly the decision-making of experts by eradicating more oral POE than when using OPT. This could reduce the risk of IE relapse and recurrence

D\'em\'elange, d\'econvolution et d\'ebruitage conjoints d'un mod\`ele convolutif parcimonieux avec d\'erive instrumentale, par p\'enalisation de rapports de normes ou quasi-normes liss\'ees (PENDANTSS)

Denoising, detrending, deconvolution: usual restoration tasks, traditionally decoupled. Coupled formulations entail complex ill-posed inverse problems. We propose PENDANTSS for joint trend removal and blind deconvolution of sparse peak-like signals. It blends a parsimonious prior with the hypothesis that smooth trend and noise can somewhat be separated by low-pass filtering. We combine the generalized pseudo-norm ratio SOOT/SPOQ sparse penalties $\ell_p/\ell_q$ with the BEADS ternary assisted source separation algorithm. This results in a both convergent and efficient tool, with a novel Trust-Region block alternating variable metric forward-backward approach. It outperforms comparable methods, when applied to typically peaked analytical chemistry signals. Reproducible code is provided: https://github.com/paulzhengfr/PENDANTSS.Comment: in French languag

Stability theory for some scalar finite difference schemes: validity of the modified equations approach*

In this paper, we discuss some limitations of the modified equations approach as a tool for stability analysis for a class of explicit linear schemes to scalar partial differential equations. We show that the infinite series obtained by Fourier transform of the modified equation is not always convergent and that in the case of divergence, it becomes unrelated to the scheme. Based on these results, we explain when the stability analysis of a given truncation of a modified equation may yield a reasonable estimation of a stability condition for the associated scheme. We illustrate our analysis by some examples of schemes namely for the heat equation and the transport equation

GPU-based Implementations of MM Algorithms. Application to Spectroscopy Signal Restoration

International audienceRestoration of analytical chemistry data from degraded physical acquisitions is an important task for chemists to obtain accurate component analysis and sound interpretation. The high-dimensional nature of these signals and the large amount of data to be processed call for fast and efficient reconstruction methods. Existing works have primarily relied on optimization algorithms to solve a penalized formulation. Although very powerful, such methods can be computationally heavy, and hyperparameter tuning can be a tedious task for non-experts. Another family of approaches explored recently consists in adopting deep learning to perform the signal recovery task in a supervised fashion. Although fast, thanks to their formulations amenable to GPU implementations, these methods usually need large annotated databases and are not explainable. In this work, we propose to combine the best of both worlds, by proposing unfolded Majorization-Minimization (MM) algorithms with the aim to reach fast and accurate methods for sparse spectroscopy signal restoration. Two state-of-the-art iterative MM algorithms are unfolded onto deep network architectures. This allows both the deployment of GPU-friendly tools for accelerated implementation, as well as the introduction of a supervised learning strategy for tuning automatically the regularization parameter. The effectiveness of our approach is demonstrated on the restoration of a large dataset of realistic mass spectrometry data

Formation of high-valent iron-oxo species in superoxide reductase: characterization by resonance Raman spectroscopy.

International audienceSuperoxide reductase (SOR), a non-heme mononuclear iron protein that is involved in superoxide detoxification in microorganisms, can be used as an unprecedented model to study the mechanisms of O2 activation and of the formation of high-valent iron-oxo species in metalloenzymes. By using resonance Raman spectroscopy, it was shown that the mutation of two residues in the second coordination sphere of the SOR iron active site, K48 and I118, led to the formation of a high-valent iron-oxo species when the mutant proteins were reacted with H2O2. These data demonstrate that these residues in the second coordination sphere tightly control the evolution and the cleavage of the O-O bond of the ferric iron hydroperoxide intermediate that is formed in the SOR active site

Case report: Parsonage-turner syndrome in a melanoma patient treated by BRAF/MEK inhibitors after immune checkpoint inhibitors

IntroductionCombination molecular BRAF/MEK inhibitors targeted therapy has been shown to improve overall survival in patients with BRAF V600 mutated unresectable or metastatic melanoma. Most patients treated with BRAF/MEK inhibitors will experience adverse events but neurological adverse events (nAEs) remain rare.Case reportA 42-year-old woman diagnosed with metastatic melanoma presented with an intense pain in the left shoulder 7 days after the beginning of encorafenib/binimetinib after immune checkpoint inhibitors (ICI) combination. No other triggering factors were identified. Electromyogram performed one month after the pain onset revealed a left brachial plexopathy suggestive of a Parsonage-Turner syndrome. The weakness slowly improved with intensive rehabilitation and targeted therapies were continued.ConclusionWe report the first case of Parsonage-Turner syndrome in a melanoma patient treated with encorafenib/binimetinib following checkpoint inhibitors combination.We cannot rule out the implication of ICI in the development of this syndrome but the rapid onset of the symptoms after the beginning of targeted therapies makes their involvment more likely.Given the increased use of BRAF/MEK inhibitors in managing of stage III and IV melanoma, as well as the development in stage II, clinicians should be aware of this potential side effect

Keratinocytic Malfunction as a Trigger for the Development of Solar Lentigines

Introduction: Solar lentigines (SL) affect chronically UV-radiated skin. Treatment is often refractory. Deeper knowledge on its pathogenesis might improve therapeutic effects. Material and Methods: Morphological characterization of 190 SL was performed and epidermal thickness, pigment distribution, dendricity, and cornification grade were measured. Immunoreactivity was investigated using Melan A, Tyrosinase, MITF, p53, and CD20, as well as Notch1 using immunofluorescence. Results: We found 2 groups of histological patterns, i.e., either acanthotic or atrophic epidermis. Lesions with basket-woven cornification and atrophic epidermis were observed in 6 out of 9 and 14 out of 16 cases from the face, respectively. Consistency of areas with a high pigmentation was observed in 96–97% of the cases. Hyperpigmentation grade and acanthosis or cornification disorders correlated positively in 88.5% of the cases. Overexpressed of p53 was found in 19 out of 20 lesions, presenting in a scattered distribution. A significant correlation of p53 and acanthosis (p = 0.003) and cornification grade (p = 0.0008) was observed. Notch1 was expressed in all SL, with the highest immunoreactivity in atrophic facial lesions. Lesions from the hands expressed Notch1 mainly in acanthotic areas with elongated rete ridges and less compact cornification. Discussion: We suggest that Notch1-dependent keratinocytic malfunction causes the development of SL. Consequently, hyperpigmentation would be a result and not the primary cause of the pathogenesis. Confirmation of these findings might have clinical implications as hitherto treatment has mainly focused on melanocytes and pigmentation and not on the proliferation/differentiation balance of keratinocytes