Pour une sémiosis du devenir photographique : du régime chimique au régime numérique

International audienc

Biologically-inspired training of spiking recurrent neural networks with neuromorphic hardware

Recurrent spiking neural networks (SNNs) are inspired by the working principles of biological nervous systems that offer unique temporal dynamics and event-based processing. Recently, the error backpropagation through time (BPTT) algorithm has been successfully employed to train SNNs offline, with comparable performance to artificial neural networks (ANNs) on complex tasks. However, BPTT has severe limitations for online learning scenarios of SNNs where the network is required to simultaneously process and learn from incoming data. Specifically, as BPTT separates the inference and update phases, it would require to store all neuronal states for calculating the weight updates backwards in time. To address these fundamental issues, alternative credit assignment schemes are required. Within this context, neuromorphic hardware (NMHW) implementations of SNNs can greatly benefit from in-memory computing (IMC) concepts that follow the brain-inspired collocation of memory and processing, further enhancing their energy efficiency. In this work, we utilize a biologically-inspired local and online training algorithm compatible with IMC, which approximates BPTT, e-prop, and present an approach to support both inference and training of a recurrent SNN using NMHW. To do so, we embed the SNN weights on an in-memory computing NMHW with phase-change memory (PCM) devices and integrate it into a hardware-in-the-loop training setup. We develop our approach with respect to limited precision and imperfections of the analog devices using a PCM-based simulation framework and a NMHW consisting of in-memory computing cores fabricated in 14nm CMOS technology with 256×256 PCM crossbar arrays. We demonstrate that our approach is robust even to 4-bit precision and achieves competitive performance to a floating-point 32-bit realization, while simultaneously equipping the SNN with online training capabilities and exploiting the acceleration benefits of NMHW

A standardized procedure to obtain mesenchymal stem/stromal cells from minimally manipulated dental pulp and Wharton’s jelly samples

Transplantation of mesenchymal stem/stromal cells (MSCs) has emerged as an effective method to treat diseased or damaged organs and tissues, and hundreds of clinical trials using MSCs are currently under way to demonstrate the validity of such a therapeutic approach. However, most MSCs used for clinical trials are prepared in research laboratories with insufficient manufacturing quality control.In particular, laboratories lack standardized procedures for in vitro isolation of MSCs from tissue samples, resulting in heterogeneous populations of cells and variable experimental and clinical results. MSCs are now referred to as Human Cellular Tissue-based Products or Advanced Therapy Medicinal Products, and guidelines from the American Code of Federal Regulation of the Food and Drug Administration (21 CFR Part 1271) and from the European Medicines Agency (European Directive 1394/2007) define requirements for appropriate production of these cells. These guidelines, commonly called “Good Manufacturing Practices” (GMP), include recommendations about laboratory cell culture procedures to ensure optimal reproducibility, efficacy and safety of the final medicinal product. In particular, the Food and Drug Administration divides ex vivo cultured cells into “minimally” and “more than minimally” manipulated samples, in function of the use or not of procedures “that might alter the biological features of the cells”. Today, minimal manipulation conditions have not been defined for the collection and isolation of MSCs (Torre et al. 2015)(Ducret et al. 2015).Most if not all culture protocols that have been reported so far are unsatisfactory, because of the use of xeno- or allogeneic cell culture media, enzymatic treatment and long-term cell amplification that are known to alter the quality of MSCs. The aim of this study was to describe a standardized procedure for recovering MSCs with minimal handling from two promising sources, the dental pulp (DP) and the Wharton’s jelly (WJ) of the umbilical cord. The quality and homogeneity of the expanded cell populations were assessed by using flow cytometry with criteria that go beyond the International Society of Cellular Therapy (ISCT) guidelines for MSC characterization

Immunophenotyping Reveals the Diversity of Human Dental Pulp Mesenchymal Stromal Cells In vivo and Their Evolution upon In vitro Amplification

International audienceMesenchymal stromal/stem cells (MSCs) from human dental pulp (DP) can be expanded in vitro for cell-based and regenerative dentistry therapeutic purposes. However, their heterogeneity may be a hurdle to the achievement of reproducible and predictable therapeutic outcomes. To get a better knowledge about this heterogeneity, we designed a flow cytometric strategy to analyze the phenotype of DP cells in vivo and upon in vitro expansion with stem cell markers. We focused on the CD31 − cell population to exclude endothelial and leukocytic cells. Results showed that the in vivo CD31 − DP cell population contained 1.4% of CD56 + , 1.5% of CD146 + , 2.4% of CD271 + and 6.3% of MSCA-1 + cells but very few Stro-1 + cells (≤1%). CD56 + , CD146 + , CD271 + , and MSCA-1 + cell subpopulations expressed various levels of these markers. CD146 + MSCA-1 + , CD271 + MSCA-1 + , and CD146 + CD271 + cells were the most abundant DP-MSC populations. Analysis of DP-MSCs expanded in vitro with a medicinal manufacturing approach showed that CD146 was expressed by about 50% of CD56 + , CD271 + , MSCA-1 + , and Stro-1 + cells, and MSCA-1 by 15-30% of CD56 + , CD146 + , CD271 + , and Stro-1 + cells. These ratios remained stable with passages. CD271 and Stro-1 were expressed by <1% of the expanded cell populations. Interestingly, the percentage of CD56 + cells strongly increased from P1 (25%) to P4 (80%) both in all sub-populations studied. CD146 + CD56 + , MSCA-1 + CD56 + , and CD146 + MSCA-1 + cells were the most abundant DP-MSCs at the end of P4. These results established that DP-MSCs constitute a heterogeneous mixture of cells in pulp tissue in vivo and in culture, and that their phenotype is modified upon in vitro expansion. Further studies are needed to determine whether co-expression of specific MSC markers confers DP cells specific properties that could be used for the regeneration of human tissues, including the dental pulp, with standardized cell-based medicinal products

A practical review on linear and nonlinear global approaches to flow instabilities

This paper aims at reviewing linear and nonlinear approaches to study the stability offluid flows. We provide a concise but self-contained exposition of the main concepts andspecific numerical methods designed for global stability studies, including the classicallinear stability analysis, the adjoint-based sensitivity, and the most recent nonlineardevelopments. Regarding numerical implementation, a number of ideas making resolu-tion particularly efficient are discussed, including mesh adaptation, simple shift-invertstrategy instead of the classical Arnoldi algorithm, and a simplification of the recent non-linear self-consistent (SC) approach proposed by Manticˇ-Lugo et al. (2014, “Self-Consistent Mean Flow Description of the Nonlinear Saturation of the Vortex Shedding inthe Cylinder Wake,” Phys. Rev. Lett., 113(8), p. 084501). An open-source software imple-menting all the concepts discussed in this paper is provided. The software is demon-strated for the reference case of the two-dimensional (2D) flow around a circularcylinder, in both incompressible and compressible cases, but is easily customizable to avariety of other flow configurations or flow equations

Genome wide SNP comparative analysis between EGFR and KRAS mutated NSCLC and characterization of two models of oncogenic cooperation in non-small cell lung carcinoma

<p>Abstract</p> <p>Background</p> <p>Lung cancer with EGFR mutation was shown to be a specific clinical entity. In order to better understand the biology behind this disease we used a genome wide characterization of loss of heterozygosity and amplification by Single Nucleotide Polymorphism (SNP) Array analysis to point out chromosome segments linked to <it>EGFR </it>mutations. To do so, we compared genetic profiles between <it>EGFR </it>mutated adenocarcinomas (ADC) and <it>KRAS </it>mutated ADC from 24 women with localized lung cancer.</p> <p>Results</p> <p>Patterns of alterations were different between <it>EGFR </it>and <it>KRAS </it>mutated tumors and specific chromosomes alterations were linked to the <it>EGFR </it>mutated group. Indeed chromosome regions 14q21.3 (p = 0.027), 7p21.3-p21.2 (p = 0.032), 7p21.3 (p = 0.042) and 7p21.2-7p15.3 (p = 0.043) were found significantly amplified in EGFR mutated tumors. Within those regions 3 genes are of special interest <it>ITGB8</it>, <it>HDAC9 </it>and <it>TWIST1</it>. Moreover, homozygous deletions at <it>CDKN2A </it>and LOH at <it>RB1 </it>were identified in <it>EGFR </it>mutated tumors. We therefore tested the existence of a link between EGFR mutation, CDKN2A homozygous deletion and cyclin amplification in a larger series of tumors. Indeed, in a series of non-small-cell lung carcinoma (n = 98) we showed that homozygous deletions at <it>CDKN2A </it>were linked to <it>EGFR </it>mutations and absence of smoking whereas cyclin amplifications (<it>CCNE1 </it>and <it>CCND1</it>) were associated to <it>TP53 </it>mutations and smoking habit.</p> <p>Conclusion</p> <p>All together, our results show that genome wide patterns of alteration differ between <it>EGFR </it>and <it>KRAS </it>mutated lung ADC, describe two models of oncogenic cooperation involving either <it>EGFR </it>mutation and <it>CDKN2A </it>deletion or cyclin amplification and <it>TP53 </it>inactivating mutations and identified new chromosome regions at 7p and 14q associated to EGFR mutations in lung cancer.</p

NeuroBench:A Framework for Benchmarking Neuromorphic Computing Algorithms and Systems

Neuromorphic computing shows promise for advancing computing efficiency and capabilities of AI applications using brain-inspired principles. However, the neuromorphic research field currently lacks standardized benchmarks, making it difficult to accurately measure technological advancements, compare performance with conventional methods, and identify promising future research directions. Prior neuromorphic computing benchmark efforts have not seen widespread adoption due to a lack of inclusive, actionable, and iterative benchmark design and guidelines. To address these shortcomings, we present NeuroBench: a benchmark framework for neuromorphic computing algorithms and systems. NeuroBench is a collaboratively-designed effort from an open community of nearly 100 co-authors across over 50 institutions in industry and academia, aiming to provide a representative structure for standardizing the evaluation of neuromorphic approaches. The NeuroBench framework introduces a common set of tools and systematic methodology for inclusive benchmark measurement, delivering an objective reference framework for quantifying neuromorphic approaches in both hardware-independent (algorithm track) and hardware-dependent (system track) settings. In this article, we present initial performance baselines across various model architectures on the algorithm track and outline the system track benchmark tasks and guidelines. NeuroBench is intended to continually expand its benchmarks and features to foster and track the progress made by the research community

COVID-19 symptoms at hospital admission vary with age and sex: results from the ISARIC prospective multinational observational study

Background: The ISARIC prospective multinational observational study is the largest cohort of hospitalized patients with COVID-19. We present relationships of age, sex, and nationality to presenting symptoms. Methods: International, prospective observational study of 60 109 hospitalized symptomatic patients with laboratory-confirmed COVID-19 recruited from 43 countries between 30 January and 3 August 2020. Logistic regression was performed to evaluate relationships of age and sex to published COVID-19 case definitions and the most commonly reported symptoms. Results: ‘Typical’ symptoms of fever (69%), cough (68%) and shortness of breath (66%) were the most commonly reported. 92% of patients experienced at least one of these. Prevalence of typical symptoms was greatest in 30- to 60-year-olds (respectively 80, 79, 69%; at least one 95%). They were reported less frequently in children (≤ 18 years: 69, 48, 23; 85%), older adults (≥ 70 years: 61, 62, 65; 90%), and women (66, 66, 64; 90%; vs. men 71, 70, 67; 93%, each P &lt; 0.001). The most common atypical presentations under 60 years of age were nausea and vomiting and abdominal pain, and over 60 years was confusion. Regression models showed significant differences in symptoms with sex, age and country. Interpretation: This international collaboration has allowed us to report reliable symptom data from the largest cohort of patients admitted to hospital with COVID-19. Adults over 60 and children admitted to hospital with COVID-19 are less likely to present with typical symptoms. Nausea and vomiting are common atypical presentations under 30 years. Confusion is a frequent atypical presentation of COVID-19 in adults over 60 years. Women are less likely to experience typical symptoms than men

Image on display : the representations of AFP's photographic pictures on digital social networks

Le cliché d’une « barquette de frites nappées de chocolat », un « coucher de soleil » aux couleurs saturées près de Puerto Natales au Chili… Cette thèse a pour objectif d’étudier la représentation des photographies exposées par l’Agence France-Presse sur les « réseaux sociaux » – Instagram, Facebook, Twitter et Tumblr en têtes –, à l’aune d’une réflexion sur les transformations et les mutations des pratiques photojournalistiques en régime « numérique ». L’étude se divise en deux axes : une approche sémiotique d’abord, qui permet de comprendre de quelle manière le discours photojournalistique déploie les conditions formelles et médiatiques qui président à la fixation de la croyance, et articulent des normes et des attentes sur le statut de vérité du monde présenté par ces images ; une approche généalogique ensuite, qui étudie les conditions selon lesquelles les photographies de presse sont exposées. En réinterrogeant le concept de banalité, en lui redonnant son sens premier, ce deuxième axe développe une réflexion sur la complexité de la médiation « numérique », entre le pouvoir de réquisition des « industries du passage » d’un côté, et l’adaptation du discours informationnel de l’AFP de l’autre. À partir d’un point de vue nettement interdisciplinaire, la thèse prouve ici qu’il est possible de comprendre la médiation « numérique » comme la corrélation expressive entre l’économie d’un dispositif et le développement de formes de vies iconiques singulières.A picture of « French fries coated with chocolate », a « sunset » picturing saturated colours near Puerto Natales, Chili… This PhD thesis studies the representation of pictures posted on « Social Networks » by the Agence France-Presse – mainly Instagram, Facebook, Twitter and Tumblr – and examines the transformations and mutations of photojournalism through “digitization”. This work is structured around two axes. A semiotics approach allows first to understand how photojournalistic contents play on faith and belief in the media; these contents and pictures play on the norms and expectations linked to the representations of truth. We then studied the representation of press photography through a genealogical approach; interrogating the notion of banalité, this approach underlines the complexity of “digital” mediations. These mediations are caught between the requisitioning power of “industries du passage” and the adaptation of AFP’s informative speech. The interdisciplinary and integrative approach offered in this PhD allows to prove that digital mediations are only understandable as the correlation between an economy of devices and the development of unusual iconic lives