Université Paris Dauphine-PSL
Recent publications
We study the Dirac Hamiltonian in dimension two with a mass term and a large momentum regularization and show that bulk-edge correspondence fails. Despite a well-defined bulk topological index (the Chern number), the number of edge modes depends on the boundary condition. The origin of this anomaly is rooted in the unbounded nature of the spectrum. It is detected with Levinson’s theorem from scattering theory and quantified via an anomalous winding number at infinite energy, dubbed ghost charge. First, we classify, up to equivalence, all self-adjoint boundary conditions, using Schubert cell decomposition of a Grassmannian. Then, we investigate which ones are anomalous. We expand the scattering amplitude near infinite energy, for which a dominant scale captures the asymptotic winding number. Remarkably, this can be achieved for every self-adjoint boundary condition, leading to an exhaustive anomaly classification. It shows that anomalies are ubiquitous and typical. Boundary conditions with a ghost charge of 2 are also revealed within the process.
Integrin clusters facilitate mechanical force transmission (mechanotransduction) and regulate biochemical signaling during cell adhesion. However, most studies have focused on rigid substrates. On fluid substrates like supported lipid bilayers (SLBs), integrin ligands are mobile, and adhesive complexes are traditionally thought unable to anchor for cell spreading. Here, we demonstrate that cells spread on SLBs coated with Invasin, a high-affinity integrin ligand. Unlike SLBs functionalized with RGD peptides, integrin clusters on Invasin-SLBs grow in size and complexity comparable to those on glass. While actomyosin contraction dominates adhesion maturation on stiff substrates, we find that on fluid SLBs, integrin mechanotransduction and cell spreading rely on dynein pulling forces along microtubules perpendicular to the membranes and microtubules pushing on adhesive complexes, respectively. These forces, potentially present on non-deformable surfaces, are revealed in fluid substrate systems. Supported by a theoretical model, our findings demonstrate a mechanical role for microtubules in integrin clustering.
Over the past few decades, diplomatic organizations have recruited increasing numbers of women as career diplomats. However, research in the fields of both expatriation and diplomacy emphasizes that transnational careers have been historically monopolized by men, that most “trailing spouses” are still women, and that men's transnational careers still take precedence in dual‐career couples. Our study uses the “gender turn” in diplomatic studies to better understand how gender disparities continue to structure diplomatic careers, even as more women take on primary roles in expatriation. We focus on international assignment practices that we redefine as “gendered diplomatic practices”. We present an original random sample of 300 male and 300 female French diplomats employed in 2015. We show that men cover 1.5 times more distance than women throughout their careers, and that they travel 1.3 times further for each international assignment. We also show that men spend 14 years abroad on average, 3 years more than women. In addition, women spend 1 year longer in each assignment to avoid frequent relocation. These gendered disparities hold for diplomats who access managerial positions. They underscore the necessity for ongoing research and efforts to address sex disparities in transnational careers and measure the gendering of diplomatic practices.
Most management and organization theories focus on the full existence and finitude of things. They deal with fullness and the full happening of things. Both organizing and managing mean fully producing something, doing something, or giving value to something. A good manager should follow what is happening and, even better, make things fully happen. But in everyday life, our managerial capitalism makes the world more and more impatient, problematic and incomplete, full of more and more holes, interruptions and voids that permeate experience. This is true both emotionally (as frustration), narratively (as cliffhangers and suspense) and materially (as creative destruction scars our earth). In this essay for ML's 55th anniversary, I argue for a process-oriented perspective on managerial emptiness and incompleteness based on three core interwoven negative processes - representation, narration and materialization. I explain how each of these processes contributes to a nexus of incompleting events at the heart of managerial processes. Paradoxically, I also suggest that different kinds of emptiness and incompleteness might be part of a more resonant experience of the world. Embracing patience, waiting, deep letting go, and the nuanced exploration of non-events within events could foster what Whitehead called a “culture of possibilities”. This perspective on possibilities - considering what might have been and what might yet be - could lead to a more harmonious relationship with nature. Finally, I encourage business schools and the corporate world to (un)learn nothingness and non-events in the context of the negative ontology discussed here. Keywords: Nothingness; Interruptions; Incompleting events; Non-events; Negative ontology; Culture of possibilities; Whitehead; Managerial education.
Synergistic drug combination screening is a promising strategy in drug discovery, but it involves navigating a costly and complex search space. While AI, particularly deep learning, has advanced synergy predictions, its effectiveness is limited by the low occurrence of synergistic drug pairs. Active learning, which integrates experimental testing into the learning process, has been proposed to address this challenge. In this work, we explore the key components of active learning to provide recommendations for its implementation. We find that molecular encoding has a limited impact on performance, while the cellular environment features significantly enhance predictions. Additionally, active learning can discover 60% of synergistic drug pairs with only exploring 10% of combinatorial space. The synergy yield ratio is observed to be even higher with smaller batch sizes, where dynamic tuning of the exploration-exploitation strategy can further enhance performance. The code can be found at https://github.com/LBiophyEvo/DrugSynergy
The eligibility criteria for social pension schemes in Africa hinder equitable and healthy aging. In 2019, women in 14 sub‐Saharan African countries had an average life expectancy of 67 years but a healthy life expectancy of only 57 years, leaving them 5 years in poor health before receiving a pension at age 62. Men had a similar situation—a life expectancy of 62 years and a healthy life expectancy of 53 years, spending 10 years in poor health before becoming eligible for pensions at age 63. Many men do not receive pensions due to early death. Delays and low pension payouts contribute to a 2.5% increase in the death rate from Alzheimer's disease and dementia. Highlights Eligibility criteria for social pension schemes in Africa hinder equitable and healthy aging. Delays and low pension payouts are associated with worsening death rates from dementia. Average health life expectancy for both genders should serve as a basis for initiating pension payouts.
The objective of this retrospective observational study was to estimate the prevalence of actinic keratosis (AK) in individuals aged ≥ 40 years in France, to describe the characteristics of affected patients, and to describe treatments. A representative panel of 20,000 households with ≥ 1 member aged ≥ 40 years were invited to participate. Participants who reported AK lesions diagnosed by a physician were eligible. The study questionnaire collected data on demographics, lesion characteristics, Fitzpatrick phototype, diagnosis, and treatments. In total, 15,246 questionnaires (78.5%) were returned and 639 responders were eligible. The adjusted prevalence of AK was 4.03% (95% CI: 3.73–4.35). Prevalence is probably underestimated due to data collection by self-report and low awareness of AK. 177 participants (27.7%) were aged < 65 years. AK was diagnosed by a dermatologist for 521 participants (81.6%). Some 200 participants (31.3%) had no lesions at the time of the survey and 243 (37.9%) had never been treated; 312 participants (78.6%) were prescribed physical treatment, principally cryotherapy; and 125 (31.5%) were prescribed topical treatment, principally 5-fluorouracil or imiquimod. In conclusion, improving diagnosis of AK in everyday clinical practice is important to ensure that all individuals with AK are treated optimally and encouraged to take sun protection measures to prevent progression to SCC.
Background Testing for COVID-19 has been strongly recommended for individuals experiencing COVID-19-like symptoms or those with a close relative who tested positive. In France, tests were free of charge until mid-October 2021 and became widely available after June 2020. Our main objective was to investigate whether access to COVID-19 testing in France was associated with socio-economic conditions, considering gender and ethno-racial status. Methods A random population-based cohort survey was conducted in France in May 2020 and November 2020, including 95,388 participants aged 18 and over. We used logistic regressions to identify how having been tested in 2020 was associated with socio-economic status and exposure factors among two groups of individuals. The first group consisted of individuals who had no close relative test positive but reported experiencing COVID-19-like symptoms, such as cough, fever, dyspnea, or sudden onset of ageusia, dysgeusia, or anosmia (N = 12,729). The second group included individuals, with or without symptoms, who reported that a close relative had tested positive for COVID-19 (N = 5,360). Findings In both groups, testing was more frequent among individuals living in urban areas. For individuals who had no close relative test positive but reported COVID-19-like symptoms, women were 1.04 (95%CI [1.01–1.06]) more likely than men to be tested, and testing decreased with age up to 35. Individuals holding a university degree were (1.08 [1.04–1.12]) more likely than those who only completed high school to be tested, as well as those in one of the three top income deciles with reference to the bottom decile (OR 1.07, [1.02–1.13] for the top decile). Ethno-racial status was not significantly associated with testing. For respondents who had a close relative test positive, testing was strongly associated with having experienced some symptoms, especially after September 1 (OR 1.34, 95%CI [1.30–1.39]). However, there was no link between testing and income, education, or ethno-racial status. Interpretation When an individual experiences symptoms but has no close relative who is positive, the motivation to test to avoid transmitting the virus to relatives by isolating oneself is particularly strong. This strategy makes sense when there are actual possibilities to isolate, which may explain why higher income and education positively impact the propensity to test. For individuals who had a close relative test positive, most socio-economic variables were no longer related to testing once infection risk was controlled for. The availability of tests at no cost is not sufficient in itself to eliminate socio-economic inequalities in testing.
Marine heatwaves are increasingly common due to human‐induced climate change. Under prolonged thermal stress on coral reefs, corals can undergo bleaching, leading to mass coral mortality and large‐scale changes in benthic community composition. While coral mortality has clear, negative impacts on the body condition and populations of coral‐dependent fish species, the mechanisms that drive these changes remain poorly resolved. Specifically, little is known about the effects of coral bleaching on (1) the nutritional quality of corals, (2) nutrient acquisition in coral‐feeding butterflyfishes and (3) fish dietary selectivity and potential supplementary consumption of non‐coral prey. Here, we evaluate the response of obligate coral‐feeding butterflyfishes to a mass coral bleaching event in French Polynesia, which resulted in high coral mortality and a 50% decline in obligate corallivore density. We examine benthic and butterflyfish community composition over two decades, including a mass bleaching event in 2019 and multiple prior disturbances. We couple these data with surveys of butterflyfish feeding selectivity, high‐resolution molecular assays of gut contents and nutrient acquisition before, during and after the bleaching event. Contrary to previous studies, obligate corallivores did not strongly alter their feeding preferences for different coral genera in response to bleaching. They did not increase their consumption of non‐corals in response to coral mortality, and hard corals continued to dominate their diets (>90%). Instead, butterflyfishes targeted partially bleached corals that were likely releasing nutrient‐rich mucus, and they avoided fully bleached and dead corals that were likely nutrient‐depleted. Moreover, after bleaching, butterflyfishes exhibit reduced nitrogen assimilation, indicating that coral stress may adversely impact butterflyfish nutrient acquisition. Coupled with the increasing frequency of recurrent bleaching events, severe, long‐term nutritional impacts of coral bleaching on butterflyfish populations may jeopardize the persistence of coral‐feeding fishes in the future.
Building a composite index (CI) is a task that requiring a series of decisions, the consequences of which will determine the scope of the tool. This is especially true for the very first steps of this construction: the definition of the theoretical framework and the selection of relevant indicators, usually referred to as the construction of the structure. However, the literature seems to focus more on the other aspects, quite often eluding those first steps or considering it a self‐evident process. How to ensure the soundness of those tools when the values that they convey are not even clearly expressed? How to ensure the completeness of the structure according to the reality that it ought to synthesise when it is a highly complex or abstract one? Each of these steps involves hypotheses and presuppositions that must be explained and evaluated with care. In this article, we seek to identify a coherent method that will allow us to build the structure of CI answering those demands. The construction of a composite indicator can be conceptualised as a multi‐criteria decision aiding problem (MCDA), given that it entails the aggregation of evaluations pertaining to distinct attributes. The MCDA is rich in structuring methodologies, such as Ralph Keeney's Value Focused Thinking (VFT) approach. Using a real‐life application, the construction of the Prison Life Index (PLI), we try to show the relevance of those primary hypotheses by displaying the structure of the index and summarising the stage of its construction. This adapted methodology can guide index builders in the determination of a structure that comprehensively fits its intended purpose and that is not overly dependent on available data. Our article endeavours to underscore the importance of the structuring phase, arguing that it should take priority according to the ethical and moral values of the decision‐maker. It should not be solely reliant on data availability, as it is the case with most composite indices. We demonstrate, through the implementation of the PLI structure developed using VFT, that it can achieve a high degree of conformity with internationally established standards pertaining to human rights. This approach not only facilitates a comprehensive understanding of the interconnections among various normative texts but also provides jurists with a visual representation of these relationships.
Live-cell microscopy routinely provides massive amounts of time-lapse images of complex cellular systems under various physiological or therapeutic conditions. However, this wealth of data remains difficult to interpret in terms of causal effects. Here, we describe CausalXtract, a flexible computational pipeline that discovers causal and possibly time-lagged effects from morphodynamic features and cell–cell interactions in live-cell imaging data. CausalXtract methodology combines network-based and information-based frameworks, which is shown to discover causal effects overlooked by classical Granger and Schreiber causality approaches. We showcase the use of CausalXtract to uncover novel causal effects in a tumor-on-chip cellular ecosystem under therapeutically relevant conditions. In particular, we find that cancer-associated fibroblasts directly inhibit cancer cell apoptosis, independently from anticancer treatment. CausalXtract uncovers also multiple antagonistic effects at different time delays. Hence, CausalXtract provides a unique computational tool to interpret live-cell imaging data for a range of fundamental and translational research applications.
Background The benefits and risks of extending anticoagulant treatment beyond the first 3 to 6 months in patients with venous thromboembolism (VTE) in clinical practice are not well understood. Methods ETNA-VTE Europe is a prospective, noninterventional, post-authorization study in unselected patients with VTE treated with edoxaban in eight European countries for up to 18 months. Recurrent VTE, major bleeding, and all-cause death were the primary study outcomes. Results The median age of the 2,644 patients was 65 years; 46.6% were female, and 22.8% had a history of VTE. The median treatment duration was 50.6 weeks (interquartile range: 23.4–77.7). VTE recurrence occurred in 100 patients (3.8% at an annual rate of 2.7%/year); 37 patients (1.4%) were on edoxaban at the time of the event, with a corresponding annualized rate of 1.6%/year. Major bleeding was experienced by 37 patients (1.4%) during edoxaban treatment, corresponding to an annualized rate of 1.5%/year. Overall, 95 patients died (3.6%; annualized rate 2.6%/year), with the majority for reasons other than VTE- and cardiovascular (CV)-related causes. Out of 15 deaths (1.9%; annualized rate 2.1%/year) that occurred during edoxaban treatment, 1 was related to VTE and 11 related to CV (annualized rate 0.0%/year and 0.5%/year). Conclusions ETNA-VTE Europe provides evidence for the real-world effectiveness of edoxaban treatment (up to 18 months) based on a low rate of VTE recurrence, all-cause death, and major bleeding, and is aligned with the results of the randomized clinical trial reassuring the use of edoxaban in the treatment of VTE in routine clinical practice.
We study the long-time behavior of solutions to a kinetic equation inspired by a model of sexual populations structured in phenotypes. The model features a nonlinear integral reproduction operator derived from the Fisher infinitesimal operator and a trait-dependent selection term. The reproduction operator describes here the inheritance of the mean parental traits to the offspring without variability. We show that, under assumptions on the growth of the selection rate, Dirac masses are stable around phenotypes for which the difference between the selection rate and its minimum value is less than 12\frac{1}{2}. Moreover, we prove the convergence in some Fourier-based distance of the centered and rescaled solution to a stationary profile under some conditions on the initial moments of the solution.
We study a generalization of the multi-marginal optimal transport problem, which has no fixed number of marginals N and is inspired of statistical mechanics. It consists in optimizing a linear combination of the costs for all the possible N’s, while fixing a certain linear combination of the corresponding marginals.
Marine protected areas (MPAs) are widely implemented tools for long‐term ocean conservation and resource management. Assessments of MPA performance have largely focused on specific ecosystems individually and have rarely evaluated performance across multiple ecosystems either in an individual MPA or across an MPA network. We evaluated the conservation performance of 59 MPAs in California's large MPA network, which encompasses 4 primary ecosystems (surf zone, kelp forest, shallow reef, deep reef) and 4 bioregions, and identified MPA attributes that best explain performance. Using a meta‐analytic framework, we evaluated the ability of MPAs to conserve fish biomass, richness, and diversity. At the scale of the network and for 3 of 4 regions, the biomass of species targeted by fishing was positively associated with the level of regulatory protection and was greater inside no‐take MPAs, whereas species not targeted by fishing had similar biomass in MPAs and areas open to fishing. In contrast, species richness and diversity were not as strongly enhanced by MPA protection. The key features of conservation effectiveness included MPA age, preimplementation fisheries pressure, and habitat diversity. Important drivers of MPA effectiveness for single MPAs were consistent across MPAs in the network, spanning regions and ecosystems. With international targets aimed at protecting 30% of the world's oceans by 2030, MPA design and assessment frameworks should consider conservation performance at multiple ecologically relevant scales, from individual MPAs to MPA networks.
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4,080 members
Thierry Kirat
  • Center for Interdisciplinary Research in the Social (IRISSO)
Béatrice Parguel
  • Dauphine Center for Management Research (DRM)
Maxime Chupin
  • Center for Research in Decision Mathematics
jean-François Chanlat
  • Management and Organization DRM UMR-CNRS 7088
Gabriella Pigozzi
  • Laboratory for Analysis and Modeling Systems for Decision Support (LAMSADE)
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