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The Tape Reconfiguration Problem and Its Consequences for Dominating Set Reconfiguration
No full textInternational audienceA dominating set of a graph G = (V,E) is a set of vertices D ⊆ V whose closed neighborhood is V, i.e., N[D] = V. We view a dominating set as a collection of tokens placed on the vertices of D. In the token sliding variant of the Dominating Set Reconfiguration problem (TS-DSR), we seek to transform a source dominating set into a target dominating set in G by sliding tokens along edges, and while maintaining a dominating set all along the transformation. TS-DSR is known to be PSPACE-complete even restricted to graphs of pathwidth w, for some non-explicit constant w and to be XL-complete parameterized by the size k of the solution. The first contribution of this article consists in using a novel approach to provide the first explicit constant for which the TS-DSR problem is PSPACE-complete, a question that was left open in the literature. From a parameterized complexity perspective, the token jumping variant of DSR, i.e., where tokens can jump to arbitrary vertices, is known to be FPT when parameterized by the size of the dominating sets on nowhere dense classes of graphs. But, in contrast, no non-trivial result was known about TS-DSR. We prove that DSR is actually much harder in the sliding model since it is XL-complete when restricted to bounded pathwidth graphs and even when parameterized by k plus the feedback vertex set number of the graph. This gives, for the first time, a difference of behavior between the complexity under token sliding and token jumping for some problem on graphs of bounded treewidth. All our results are obtained using a brand new method, based on the hardness of the so-called Tape Reconfiguration problem, a problem we believe to be of independent interest. We complement these hardness results with a positive result showing that DSR (parameterized by k) in the sliding model is FPT on planar graphs, also answering an open problem from the literature
Climate Change: What is Computing’s Responsibility?
No full textManifestoThis Manifesto was produced from the Perspectives Workshop 25122 entitled "Climate Change: What is Computing’s Responsibility?" held March 16-19, 2025 at Schloss Dagstuhl, Germany. The Workshop provided a forum for world-leading computer scientists and expert consultants on environmental policy and sustainable transition to engage in a critical and urgent conversation about computing’s responsibilities in addressing climate change - or more aptly, climate crisis. The resulting Manifesto outlines commitments and directions for future action which, if adopted as a basis for more responsible computing practices, will help ensure that these technologies do not threaten the long-term habitability of the planet. We preface our Manifesto with a recognition that humanity is on a path that is not in agreement with international global warming targets and explore how computing technologies are currently hastening the overshoot of these boundaries. We critically assess the vaunted potential for harnessing computing technologies for the mitigation of global warming, agreeing that, under current circumstances, computing is contributing to negative environmental impacts in other sectors. Computing primarily improves efficiency and reduces costs which leads to more consumption and more negative environmental impact. Relying solely on efficiency gains in computing has thus far proven to be insufficient to curb global greenhouse gas emissions. Therefore, computing’s purpose within a strategy for tackling climate change must be reimagined. Our recommendations cover changes that need to be urgently made to the design priorities of computing technologies, but also speak to the more systemic shift in mindset, with sustainability and human rights providing a necessary moral foundation for developing the kinds of computing technologies most needed by society. We also stress the importance of digital policy that accounts for both the direct material impacts of computing and the detrimental indirect impacts arising from computing-enabled efficiencies, and the role of computing professionals in informing policy making
Use of Hospital‐at‐Home Services for Injectable Chemotherapy for Patients With Multiple Myeloma in France in 2019 and 2020: A Real‐World Nationwide Study Based on the French Hospital Discharge Database
No full textInternational audienceBackground Some injectable medicines introduced recently allow patients with multiple myeloma (MM) to receive their chemotherapy at home. This study aimed at describing adult patients with MM receiving injectable chemotherapy via hospital‐at‐home (HAH) services and outpatient hospital units (OHUs) in metropolitan France in 2019 and 2020, analyzing the factors influencing HAH use, and evaluating the geographic variations and the evolution over time of HAH use by these patients during the study period. Methods Real‐world data from the French Hospital Discharge Database (PMSI) were analyzed. Results In total, 2169/9278 patients (23.4%) received at least one HAH chemotherapy injection. These patients were diagnosed more recently (mean ± standard deviation = 25.1 ± 19.6 vs. 31.6 ± 21.8 months), and lived in larger and wealthier cities (59,000 vs. 41,000 inhabitants; €23,300 ± €5300 vs. €21,700 ± €4100) and closer to their follow‐up hospital (18.7 ± 18.4 vs. 31.3 ± 31.2 km) than patients exclusively treated in OHUs ( p < 0.001). Receiving bortezomib and carfilzomib, and the first chemotherapy dose in 2020, were the most significant factors associated with HAH use (odds ratio [95% confidence interval]: 6.12 [5.40–6.96], 2.01 [1.69‐2.39], and 1.81 [1.57–2.09], respectively, p < 0.001). HAH use increased between 2019 and 2020 (patients, +23%; administrative departments, +25%), likely related to the COVID‐19 pandemic. However, HAH use remained limited overall and exhibited inter‐regional variability. Infection‐related hospitalizations remained stable. Conclusions Receiving chemotherapy injections at home is feasible and safe, but further development and equitable access are essential to enhance patients’ quality of life and reduce costs
Implémentation d'un algorithme de Schwarz en décomposition de domaine et couplage
No full textThree test cases for Schwarz domain decomposition and coupling algorithm implementation
Atténuer la congestion du stockage partagé grâce à la théorie du contrôle
No full textInternational audienceEfficient data access in High-Performance Computing (HPC) systems is essential to the performance of intensive computing tasks. Traditional optimizations of the I/O stack aim to improve peak performance but are often workload specific and require deep expertise, making them difficult to generalize or re-use. In shared HPC environments, resource congestion can lead to unpredictable performance, causing slowdowns and timeouts. To address these challenges, we propose a self-adaptive approach based on Control Theory to dynamically regulate client-side I/O rates. Our approach leverages a small set of runtime system load metrics to reduce congestion and enhance performance stability. We implement a controller in a multi-node cluster and evaluate it on a real testbed under a representative workload. Experimental results demonstrate that our method effectively mitigates I/O congestion, reducing total runtime by up to 20% and lowering tail latency, while maintaining stable performance.L'accès efficace aux données dans les systèmes de calcul haute performance (HPC) est essentiel à l'exécution de tâches de calcul intensives. Les optimisations traditionnelles de la stack I/O visent à améliorer les performances de pointe, mais sont souvent spécifiques à une charge de travail et nécessitent une expertise pointue, ce qui les rend difficiles à généraliser ou à réutiliser. Dans les environnements HPC partagés, la congestion des ressources peut entraîner des performances imprévisibles, provoquant des ralentissements et des délais d'attente. Pour relever ces défis, nous proposons une approche auto-adaptative basée sur la théorie du contrôle afin de réguler dynamiquement les débits des I/Os côté client. Notre approche exploite un petit ensemble de métriques de charge système en temps réel pour réduire la congestion et améliorer la stabilité des performances. Nous avons implémenté un contrôleur dans un cluster multi-nœuds et l'avons évalué sur un banc d'essai réel sous une charge de travail représentative. Les résultats expérimentaux démontrent que notre méthode atténue efficacement la congestion des I/Os, réduisant le temps d'exécution total jusqu'à 20 % et la latence de queue, tout en maintenant des performances stables
CD206+CD14− Skin-Resident Macrophages and DC–T Cell Clusters Are Spatial Features Characterizing Nonrelapsing Cutaneous Squamous Cell Carcinoma
No full textInternational audienceCurrent histopathologic classifications do not reliably distinguish patients with primary cutaneous squamous cell carcinomas (cSCC) at risk of relapse from those with nonrelapsing tumors. This underscores the need for molecular signatures capable of stratifying patients during primary tumor resection. In this study, we used high-dimensional imaging mass cytometry and a 39-antibody panel to define the immune landscape of 20 primary cSCC with distinct clinical outcomes, four relapsing cSCC, and their perilesional skins. Computational analysis of spatially resolved single-cell data from 47 imaging mass cytometry images identified 12 immune-cell subsets that discriminated primary cSCC from perilesional skin. Regulatory T cells, cytotoxic CD8+ T lymphocytes, and tumor-associated macrophages and neutrophils characterized tumors, whereas Langerhans cells and skin-resident macrophages defined perilesional skin. Skin-resident macrophages were characterized by the expression of CD206, CD11c, and HLA-DR and the absence of CD14. These cells infiltrated tumors from nonrelapsing patients more efficiently. We found a higher density of proliferating, mature, and cytotoxic cells within this macrophage subset, consistent with the absence of relapse. Spectral flow cytometry analysis on fresh tumor biopsies revealed that the skin-resident macrophages had phagocytic properties, suggesting a role in tumor antigen processing. Additionally, neighborhood profiling revealed that DC-LAMP+ dendritic cells were in close proximity with helper and cytotoxic T lymphocytes in primary cSCC from patients without relapse, indicative of active adaptive immunity. Our findings identify phagocytic skin-resident macrophages and dendritic cell–T cell clusters as features differentiating nonrelapsing cSCC from primary cSCC at risk of relapse. These data have the potential to guide the identification of prognostic biomarkers for cSCC
Humoral immune response to Covid-19 vaccination in patients with cancer – Results from the ANRS0001S COV-POPART study
No full textInternational audienceBackground: Patients with cancer, whose immune responses to vaccines are commonly weaker than those of the general population, are recommended a booster dose after two initial doses of Covid-19 vaccine. Our objective was to compare the humoral immunogenicity of Covid-19 vaccines in patients with cancer compared to healthy adults (control group) after primary vaccine series and after a booster dose.Methods: We included participants aged ≤75 and vaccinated with two doses in the primary vaccine series and a booster, from the French national prospective Covid-19 vaccine cohort study (ANRS0001S COV-POPART) and excluded those with SARS-CoV-2 infection. Percentage of responders, geometric mean titers (GMT) of anti-SARS-CoV-2 IgG antibodies (ELISA) and specific neutralizing antibodies against original strain, Delta and Omicron variants of concern, were estimated one month after the primary vaccine series, then one month and six months after a booster dose.Results: We included 183 patients with cancer and 1173 controls. The most frequent cancers were breast (37.2 %) and lung cancer (17.5 %). Patients with cancer were older and had lower anti-Spike IgG levels after the primary vaccine series (GMT = 132.4 vs 332.7 BAU/mL, P < 0.0001), but they developed similar response at one month (GMT = 2146.1 vs 1841.3 BAU/mL], P = 0.16) and six months after booster (602.0 vs 574.4 BAU/mL, P = 0.80). Neutralizing antibodies levels confirmed these results.Conclusion: Patients with cancer have comparable response rates to controls one month and six months after a booster dose. Our results support the benefit of a booster dose in patients with cancer
L2 -Stability of explicit Runge-Kutta methods with supg stabilization for transient transport problems
No full textWe analyze the approximation of linear transport problems using continuous finite elements in space with SUPG stabilization and explicit Runge-Kutta (ERK) schemes in time. We establish stability for ERK3 and ERK4 schemes in the L2-norm augmented by the mesh-dependent weighted advective derivative induced by the SUPG stabilization. We provide two proofs. The first proof hinges on the stability of Taylor polynomials and covers both ERK3 and ERK4 schemes. The second proof uses more classical energy arguments and covers only ERK3 schemes. This second proof is presented to provide a more direct connection to previous work in the literature. We present numerical experiments illustrating the theoretical findings, including a Fourier analysis in 1D and the approximation of smooth solutions and solutions in BV in 2D. Finally, we briefly discuss the parabolic setting within an implicit-explicit (IMEX) approach, where the diffusion step does not involve the SUPG stabilization. We establish the stability of a simple IMEX scheme in the same norm as above, where a stable ERK scheme is followed by one implicit diffusive step
Couplage sismo-électrique dynamique : des modèles fréquentiels aux modèles temporels
No full textThis thesis deals with the mathematical modelling of seismo-electric effects which occur in porous media comprised of charged fluid within an oppositely-charged solid matrix. As such, the medium is neutral at a macroscopic scale, but relative displacements between the solid and fluid induce electrical currents (displacement of charges). Seismic waves propagating in these media induce local fluid flow, hence charge displacements, leading to the creation of electromagnetic waves. Mathematically, this is modelled by Biot's equations of poro-elasticity coupled to Maxwell's equations. The coupling theory derived by S. Pride in 1994 is carried out in frequency domain, and the coupling quantities (coupling coefficient and dynamic permeability) depend on the frequency, in a manner that leads to difficulties in time domain. By interpreting these parameters as symbols of pseudo-differential operators that are global in time, it becomes clear that the model in time domain involves operators whose discretization will lead to very high computational cost. This explains why simulations carried out in time domain always involve a very low frequency model in which the frequency dependence of these parameters is masked.Two main developments are carried out. The first deals with the approximation of the frequency-dependent coupling operators, in order to obtain higher fidelity time domain seismo-electric equations, i.e. valid for a larger frequency range than the very low frequency approximations. This opens the perspective of using time domain equations in a laboratory scale. This thesis introduces several polynomial and rational approximation types and studies them numerically, leading to new time domain equations, which take into account the dynamic nature of the coupling. At low frequencies, local approximants such as Padé or Taylor (very low frequency) can be used. Global approximations --- Legendre and Chebyshev --- are used with high frequencies, or a wide frequency band. These approximations are tested numerically using analytical solutions to compute, as well as with a numerical code based on the hydridizable discontinuous Galerkin method in an HPC context.The second development deals with the mathematical analysis of Pride's equations in time domain with strong (bidirectional) coupling. Considering this bidirectional coupling introduces difficulties to show the well-posedness of the problem. As such, only one-way coupling has been considered to show well-posedness of the equations, that is electro-seismic coupling only. Two approaches are introduced in a low frequency approximation of the system. Firstly, an application of the Hille-Yosida Theorem to the full system. Secondly, we use a fixed-point technique, to show there exists a unique solution to the fully coupled system in a weak sense.Cette thèse s'intéresse à la modélisation mathématique des effets sismo-électriques qui se produisent dans des milieux poreux constitués de fluide chargé au sein d'une matrice solide de charge opposée. Ainsi, le milieu est neutre à l'échelle macroscopique, mais les déplacements relatifs entre le solide et le fluide induisent des courants électriques (déplacement de charges). Les ondes sismiques se propageant dans ces milieux induisent des écoulements locaux de fluide, donc des déplacements de charges, conduisant à la création d'ondes électromagnétiques. Mathématiquement, ceci est modélisé par les équations de poro-élasticité de Biot couplées aux équations de Maxwell. La théorie du couplage dérivée par S. Pride en 1994 est réalisée dans le domaine fréquentiel, et les paramètres de couplage (coefficient de couplage et perméabilité dynamique) dépendent de la fréquence, d'une manière qui induit de fortes difficultés en domaine temporel. En interprétant ces paramètres comme des symboles d'opérateurs pseudo-différentiels globaux en temps, on comprend que l'écriture du modèle dans le domaine temporel fait intervenir des opérateurs dont la discrétisation va générer de très lourds coûts de calcul. Cela explique pourquoi les simulations réalisées dans le domaine temporel impliquent toujours un modèle très basse fréquence dans lequel la dépendance en fréquence des paramètres est masquée. Deux développements principaux sont réalisés. Le premier s'intéresse à l'approximation des opérateurs de couplage dépendants de la fréquence, afin d'obtenir des équations sismo-électriques temporelles de plus grande fidélité, c'est-à-dire valable pour un régime de fréquence plus large que celui de la très basse fréquence. Cela ouvre ainsi la perspective d'utiliser des modèles en temps valide à l'échelle du laboratoire. Cette thèse introduit plusieurs types d'approximations polynomiales et rationnelles et les étudie numériquement, conduisant à de nouvelles équations temporelles, qui prennent en compte la nature dynamique du couplage. A basse fréquence, des approximants locaux tels que Padé ou Taylor (très basse fréquence) peuvent être utilisés. Des approximations globales --- de type Legendre et Chebyshev --- sont utilisées avec des fréquences élevées, ou une large bande de fréquence. Ces approximations sont testées numériquement en utilisant des solutions analytiques, ainsi qu'avec des solutions calculées avec le solveur basé sur une méthode de type Galerkine discontinu hybride (HDG) dans un contexte de calcul parallèle.Le deuxième développement concerne l'analyse mathématique du système d'équations de Pride dans le domaine temporel avec couplage fort (de Biot vers Marwell et de Maxwell vers Biot). Considérer ce couplage bidirectionnel introduit des difficultés pour prouver le caractère bien posé du problème. Ainsi, seules les équations couplées unidirectionnelles ont été démontrées comme étant bien posées, à savoir avec un couplage électro-sismique. Deux approches sont introduites. Premièrement, une application du théorème de Hille-Yosida au système entier en se plaçant dans une approximation basse fréquences du système. Deuxièmement, nous employons une technique de point fixe, afin de montrer qu'il existe une unique solution du système entièrement couplé au sens faible
