Portail HAL du Collège de France
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Nam qui fuimus Occidentales, nunc facti sumus Orientales. Baldwin of Boulogne: to conquer and rule
No full textInternational audienceA careful reading of the sources relating to the seizure of power by Baldwin of Boulogne in Edessa, and to his role in the delay of the Holy Fire at Easter 1101 in Jerusalem, makes it possible to reassess various historiographical trends in the foundation of the crusader states including the concepts of Latinisation and cultural transfer. The strategy followed by Baldwin in Edessa and then in Jerusalem reveals his rapid understanding of Middle Eastern society. Rather than seeing the Franks as Westerners who recently arrived in the region, these two episodes allow us to consider them from the perspective of the Christian groups in the Middle East. Far from being newcomers for the Byzantine Greeks, the Melkites or the Armenians, the new settlers came in the wake of the Frankish mercenaries recruited for a century by the basileus, or of the 'trouble-shooters' studied by Shepard. This inquiry will re-situate the Franks as part of the diverse and fragmented society of the Middle East. In so doing, this article aims to contribute to decolonising and deorientalising the study of the foundation of the crusader states.</div
The fountain of the luminous infrared galaxy Zw049.057 as traced by its OH megamaser
No full textInternational audienceHigh-resolution ( [10 ‑ 35 pc]) e-MERLIN (λ6 ‑ 18 cm) and ( [6.5 pc]) ALMA (λ1.1 mm) observations have been used to image OH (hydroxyl) and H2CO (formaldehyde) megamaser emission, and HCN 3 → 2 emission toward the nuclear (< 100 pc) region of the luminous infrared galaxy Zw049.057. Zw049.057 hosts a compact obscured nucleus (CON), and thus represents a class of galaxies that are often associated with inflow and outflow motions. Formaldehyde megamaser emission has been detected toward the nuclear region, ≲30 pc (), and traces a structure along the disk major axis. OH megamaser (OHM) emission has been detected along the minor axis of the disk, ∼30 pc () from the nucleus, where it exhibits a velocity gradient with extrema of ‑20 km s‑1 southeast (SE) of the disk and ‑110 km s‑1 northwest (NW) of the disk. HCN 3 → 2 emission reveals extended emission, along the disk minor axis out to ∼60 pc (). Analysis of the minor axis HCN emission reveals high-velocity features extending out to 600 km s‑1, redshifted on the SE side and blueshifted on the NW side. We propose that the high-velocity HCN emission traces a fast (> 250 km s‑1) and collimated outflow that is enveloped by a wide-angle and slow (∼50 km s‑1) outflow that is traced by the OHM emission. Analysis of the outflow kinematics suggests that the slow wide-angle outflow will not reach escape velocity and will instead fall back to the galaxy disk, evolving as a so-called fountain flow, while the fast collimated outflow traced by HCN emission will likely escape the nuclear region. We suggest that the absence of OHM emission in the nuclear region is due to high densities there. Even though OHMs associated with outflows are an exception to conventional OHM emission, we expect them to be common in CON sources that host both OHM and H2CO megamasers
Higher COVID-19 pneumonia risk associated with anti-IFN-α than with anti-IFN-ω auto-Abs in children
No full textInternational audienceWe found that 19 (10.4%) of 183 unvaccinated children hospitalized for COVID-19 pneumonia had autoantibodies (auto-Abs) neutralizing type I IFNs (IFN-α2 in 10 patients: IFN-α2 only in three, IFN-α2 plus IFN-ω in five, and IFN-α2, IFN-ω plus IFN-β in two; IFN-ω only in nine patients). Seven children (3.8%) had Abs neutralizing at least 10 ng/ml of one IFN, whereas the other 12 (6.6%) had Abs neutralizing only 100 pg/ml. The auto-Abs neutralized both unglycosylated and glycosylated IFNs. We also detected auto-Abs neutralizing 100 pg/ml IFN-α2 in 4 of 2,267 uninfected children (0.2%) and auto-Abs neutralizing IFN-ω in 45 children (2%). The odds ratios (ORs) for life-threatening COVID-19 pneumonia were, therefore, higher for auto-Abs neutralizing IFN-α2 only (OR [95% CI] = 67.6 [5.7–9,196.6]) than for auto-Abs neutralizing IFN-ω only (OR [95% CI] = 2.6 [1.2–5.3]). ORs were also higher for auto-Abs neutralizing high concentrations (OR [95% CI] = 12.9 [4.6–35.9]) than for those neutralizing low concentrations (OR [95% CI] = 5.5 [3.1–9.6]) of IFN-ω and/or IFN-α2
Breakdown of Linear Spin-Wave Theory in a Non-Hermitian Quantum Spin Chain
No full text17 pages, 15 figuresInternational audienceWe present the spin-wave theory of the excitation spectrum and quench dynamics of the non-Hermitian transverse-field Ising model. The complex excitation spectrum is obtained for a generic hypercubic lattice using the linear approximation of the Holstein-Primakoff transformation together with the complex bosonic Bogolyubov transformation. In the one-dimensional case, our result compares very well with the exact quasiparticle dispersion relation obtained via a fermionic representation of the problem, at least in the regime of large dissipation and transverse field. When applied to the quench dynamics we show however that the linear spin-wave approximation breaks down and the bosonic theory is plagued by a divergence at finite times. We understand the origin of this instability using a single mode approximation. While limited to short times, we show that this approach allows us to characterize the dynamics arising from the quench of the dissipative term and the structure of the Lieb-Robinson light-cone of the propagation quantum correlations. Furthermore, for the one-dimensional case, the linear spin-wave dynamics shows good agreement with the exact fermionic solution, both for the local magnetization and the spin-spin correlations
PML Nuclear bodies: the cancer connection and beyond
No full textInternational audiencePromyelocytic leukemia (PML) nuclear bodies, membrane-less organelles in the nucleus, play a crucial role in cellular homeostasis. These dynamic structures result from the assembly of scaffolding PML proteins and various partners. Recent crystal structure analyses revealed essential self-interacting domains, while liquid–liquid phase separation contributes to their formation. PML bodies orchestrate post-translational modifications, particularly stress-induced SUMOylation, impacting target protein functions. Serving as hubs in multiple signaling pathways, they influence cellular processes like senescence. Dysregulation of PML expression contributes to diseases, including cancer, highlighting their significance. Therapeutically, PML bodies are promising targets, exemplified by successful acute promyelocytic leukemia treatment with arsenic trioxide and retinoic acid restoring PML bodies. Understanding their functions illuminates both normal and pathological cellular physiology, guiding potential therapies. This review explores recent advancements in PML body biogenesis, biochemical activity, and their evolving biological roles
Innovation and inequalities
No full textInternational audienceInnovation is a key source of sustainable growth, but it can affect inequalities in many ways—increasing some inequalities and decreasing others. The impact of any particular innovation on inequalities will depend importantly on who controls the property rights to exploit the innovation and what they decide to do with it. The introduction of an innovation can affect the power of different actors in a market, the way markets work, and the returns to different attributes of actors in the market. All of these factors and more will influence how innovation affects inequalities. We would like policy to encourage innovation while making sure that yesterday's innovators do not use their rents to deter innovation by new entrants, thereby eventually undermining productivity growth and social mobility, and increasing inequalities. This requires a combination of regulation, progressive taxation, and enlightened competition policy
Photoredox-and Piezo-Catalysed Access to Complex Trifluoromethylated Polycyclic Structures from Ynamides
No full textInternational audienceRadical cyclization cascades triggered by a trifluoromethyl radical represent a valuable tool for accessing highly complex and biologically relevant scaffolds. Herein, we introduce a strategy employing ynamides as pivotal functions for the diastereoselective synthesis of lactam polycyclic compounds incorporating a trifluoromethyl group. Using photoredox conditions, this cascade featuring notably a 1,5 hydrogen atom transfer proceeds with high efficiency and diastereoselectivity. Additionally, a mechanoredox approach utilizing piezocatalysis proved to be competent in providing the same highly functionalized polycyclic products
Many-Body Open Quantum Systems
No full textLecture Notes, 185 pages, 40 figureThese Lecture Notes discuss the recent theoretical advances in the understanding of open quantum many-body physics in platforms where both dissipative and coherent processes can be tuned and controlled to a high degree. We start by reviewing the theoretical frameworks and methods used to describe and tackle open quantum many-body systems. We then discuss the use of dissipative processes to engineer many-body stationary states with desired properties and the emergence of dissipative phase transitions arising out of the competition between coherent evolution and dissipation. We review the dynamics of open quantum many body systems in the presence of correlated many-body dissipative processes, such as heating and many-body losses. Finally we provide a different perspective on open quantum many-body systems by looking at stochastic quantum trajectories, relevant for the case in which the environment represents a monitoring device, and the associated measurement-induced phase transitions
Many-Body Dephasing by Hole Motion in a Spin-Orbit-Coupled Mott Insulator
No full textWe use Ramsey interferometry to study spin dynamics in the strongly interacting regime of spin-orbit-coupled quantum gases in one-dimensional optical lattices. We observe an intrinsic many-body dephasing mechanism immune to spin-echo in two-component Mott insulators. We ascribe the dephasing to the motion of hole-like defects in an otherwise inert Mott insulator, the spinless nature of the holes explaining the ineffectiveness of spin echo to restore it. We show that a model of spin-orbit-coupled hardcore bosons can explain quantitatively our experimental observations
Experimental and computational aspects of molecular frustrated Lewis pairs for CO2 hydrogenation: en route for heterogeneous systems?
No full textInternational audienceCatalysis plays a crucial role in advancing sustainability. The unique reactivity of frustrated Lewis pairs (FLPs) is driving an ever-growing interest in the transition metal-free transformation of small molecules like CO2 into valuable products. In this area, there is a recent growing incentive to heterogenize molecular FLPs into porous solids, merging the benefits of homogeneous and heterogeneous catalysis -high activity, selectivity, and recyclability. Despite the progress, challenges remain in preventing deactivation, poisoning, and simplifying catalyst-product separation. This review explores the expanding field of FLPs in catalysis, covering existing molecular FLPs for CO2 hydrogenation and recent efforts to design heterogeneous porous systems from both experimental and theoretical perspectives. Section 2 discusses experimental examples of CO2 hydrogenation by molecular FLPs, starting with stoichiometric reactions and advancing to catalytic ones. It then examines attempts to immobilize FLPs in porous matrices, including siliceous solids, metal-organic frameworks (MOFs), covalent organic frameworks, and disordered polymers, highlighting current limitations and challenges. Section 3 then reviews computational studies on the mechanistic details of CO2 hydrogenation, focusing on H2 splitting and hydride/proton transfer steps, summarizing efforts to establish structure-activity relationships. It also covers the computational aspects on grafting FLPs inside MOFs. Finally, Section 4 summarizes the main design principles established so far, while addressing the complexities of translating computational approaches into the experimental realm, particularly in heterogeneous systems. This section underscores the need to strengthen the dialogue between theoretical and experimental approaches in this field