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Big data analytics and ‘Silk Road’ heritage in Inner Asia: Directions and discrepancies
No full textInternational audienceToday, “Silk Road” stands as a most enduring and extensive geospatial initiativefor aggregating and scaling data across vast regions. For over a century and a half,it has driven the pursuit and study of connectivities across Eurasia. This articleexamines the formation and implications of a rapidly expanding “Silk Road”datascape transformed by the proliferation of big data analytics and artificialintelligence. It assesses “Silk Road” as a unique milieu of knowledge production,intricately linked to Inner Asia’s growing concern with the hegemony andsecurity of data as both “commodity” and “discourse.” The impact of policiesand strategies shaping data provenance, governance, ethics, and infrastructureon empirical research is evaluated within the context of the broader academicdiscourse on the efficacy of big data, particularly in the domains of archaeologyand cultural heritage
Isostructural Phase Transition of Fe<sub>2</sub>O<sub>3</sub> under Laser Shock Compression
No full textInternational audienceWe present in-situ x-ray diffraction and velocity measurements of FeO under laser shock compression at pressures between 38-116 GPa. None of the phases reported by static compression studies were observed. Instead, we observed an isostructural phase transition from -FeO to a new -FeO phase at a pressure of 50-62 GPa. The -FeO phase differs from -FeO by an 11% volume drop and a different unit cell compressibility. We further observed a two-wave structure in the velocity profile, which can be related to an intermediate regime where both and phases coexist. Density functional theory calculations with a Hubbard parameter indicate that the observed unit cell volume drop can be associated with a spin transition following a magnetic collapse
Motor recovery through perineuronal net modulation in a Parkinson’s disease mouse model
No full textInternational audiencePerineuronal nets are specialized extracellular matrix structures forming preferentially around parvalbumin interneurons to regulate plasticity. While cortical perineuronal nets have been implicated in sensory plasticity and memory modulation, perineuronal nets of the primary motor cortex have been largely overlooked. We found that transient reduction of primary motor cortex perineuronal nets by ChABC treatment in otherwise healthy adult mice resulted in temporary deficits in motor function. In a mouse model of Parkinson's disease based on unilateral 6-hydroxydopamine lesions of the midbrain, perineuronal net levels were decreased in both primary motor cortex hemispheres 2 weeks post-lesion, yet returned to baseline within 5 weeks. We discovered that subsequent transient reduction of primary motor cortex perineuronal nets through ChABC treatment could unlock motor recovery when coupled with motor stimulation. This recovery was associated with a bilateral increase in perineuronal-net-enwrapped parvalbumin interneurons and a rebalancing of parvalbumin cell soma excitatory synaptic markers. These findings reveal distinct roles of perineuronal net plasticity – first in response to the initial midbrain lesion and then during rescue after ChABC treatment – suggesting that primary motor cortex perineuronal nets play a nuanced role in regulating motor function. This duality positions perineuronal nets as potential therapeutic targets for motor rehabilitation strategies in Parkinson's disease
Electron-magnon dynamics triggered by an ultrashort laser pulse: A real-time dual GW study
No full textInternational audienceUltrafast irradiation of correlated electronic systems triggers complex dynamics involving quasi-particle excitations, doublons, charge carriers, and spin fluctuations. To describe these effects, we develop an efficient non-equilibrium approach, dubbed D-, that enables a self-consistent treatment of local correlations within dynamical mean-field theory (DMFT) and spatial charge and spin fluctuations, that are accounted for simultaneously within a diagrammatic framework. The method is formulated in the real-time domain and provides direct access to single- and two-particle momentum- and energy-dependent response functions without the need for analytical continuation, which is required in Matsubara frequency-based approaches. We apply the D- method to investigate the dynamics of a photo-excited extended Hubbard model, the minimal system that simultaneously hosts strong charge and spin fluctuations. Focusing on the challenging parameter regime near the Mott transition, we demonstrate that correlated metals and narrow-gap Mott insulators undergo distinct thermalization processes involving complex energy transfer between single-particle and collective electronic excitations
Superconductivity of Bad Fermions: Origin of Two Gaps in HTSC Cuprates
No full textInternational audienceWe investigate the spectral properties of the doped Hubbard model with parameters typical for high-temperature cuprate superconductors. Our approach is based on a novel strong-coupling Green's function expansion around a reference system -- the exactly solvable undoped particle-hole symmetric Hubbard lattice -- that possesses a large antiferromagnetic Mott-Hubbard-Slater gap in the electron spectrum. The electron spectral function in the case of a large next-nearest-neighbor hopping , which is characteristic of the family of cuprates, reveals a strongly renormalized flat band feature with a pseudogap around the antinodal point. The superconducting response of this system to a small -like external field exhibits a very unusual form. It features a pseudogap at the antinodal point in the normal part of the Nambu Green's function, related to a ``bad-fermion'' behavior in a normal phase, as well as a -wave-like structure in the anomalous (Gorkov's) Green's function, with zero response at the nodal point of the Brillouin zone. Remarkably, we find that the anomalous part of the response deviates essentially from the simplest form in momentum space. Specifically, its extrema are shifted away from the and points due to suppression of the response by the pseudogap. The observed two-gap structure of the electron spectra in a generic strong-coupling model of cuprates can serve as a basis for phenomenological treatment of different physical properties of high-temperature superconductors within two-fluid model
Libraries of the Mind
No full textInternational audienceErich Auerbach wrote his classic work Mimesis, a history of narrative from Homer to Proust, based largely on his memory of past reading. Having left his physical library behind when he fled to Istanbul to escape the Nazis, he was forced to rely on the invisible library of his mind. Each of us has such a library—if not as extensive as Auerbach’s—even if we are unaware of it. In this erudite and provocative book, William Marx explores our invisible libraries—how we build them and how we should expand them. Libraries, Marx tells us, are mental realities, and, conversely, our minds are libraries. We never read books apart from other texts. We take them from mental shelves filled with a variety of works that help us understand what we are reading. And yet the libraries in our mind are not always what they should be. The selection on our mental shelves—often referred to as canon, heritage, patrimony, or tradition—needs to be modified and expanded. Our intangible libraries should incorporate what Marx calls the dark matter of literature: the works that have been lost, that exist only in fragments, that have been repurposed by their authors, or were never written in the first place. Marx suggests methods for recovering this missing literature, but he also warns us that adding new titles to our libraries is not enough. We must also adopt a new attitude, one that honors the diversity and otherness of literary works. We must shed our preconceptions and build within ourselves a mental world library
Stepwise molecular specification of excitatory synapse diversity onto cerebellar Purkinje cells
No full textInternational audienceBrain function relies on the generation of a large variety of morphologically and functionally diverse, but specific, neuronal synapses. Here we show that, in mice, the initial formation of synapses on cerebellar Purkinje cells involves a presynaptic protein-CBLN1, a member of the C1q protein family-that is secreted by all types of excitatory inputs. The molecular program then evolves only in one of the Purkinje cell inputs, the inferior olivary neurons, with the additional expression of the presynaptic secreted proteins C1QL1, CRTAC1 and LGI2. These molecules work in concert to specify the mature connectivity pattern on the Purkinje cell target. These results show that some inputs actively and gradually specify their synaptic molecular identity, while others rely on the 'original molecular code'. Thus, the molecular specification of excitatory synapses, crucial for proper circuit function, is acquired in a stepwise manner during mouse postnatal development and obeys input-specific rules