Portail HAL du Collège de France
Not a member yet
22122 research outputs found
Sort by
Investigating galactic fountains in M101: Insights from UV emission, ionised gas, and neutral gas
No full textInternational audienceSpiral galaxy disks are thought to exist in a quasi-stationary state, between fresh gas accretion from cosmic filaments and disk star formation, self-regulated through massive-star feedback. Our goal here is to quantify these feedback processes and probe their efficiency. While star formation can be traced at 10 Myr time-scales through H α emission, the signature of OB stars, and at 100 Myr scale with UV emission, the gas surface density is traced by H I emission for the atomic phase. We chose to investigate feedback processes using fountain effects in M101, a nearby well-observed face-on galaxy. Face-on studies are complementary to the more frequent edge-on observations of these fountains in the literature. We use high-resolution data from THINGS for the H I emission, GALEX for UV, and SITELLE-SIGNALS for the H α tracer. We identified 20 new H I holes, in addition to the 52 holes found in 1993. We study in more detail the nine holes satisfying strong criteria to be true fountain effects, compute their physical properties, and derive their energy balance. Only one small H I hole still contains H α and young stars inside, while the largest hole of 2.4 kpc and the oldest age (94 Myr) is deprived of H α and UV. For face-on disks, the possibility to study simultaneously the H I shell morphology, the stellar association, and kinematic evidence is of primordial importance. In M101, we quantified how stellar feedback is responsible for carving the observed cavities in the atomic gas disk, and how it can expel neutral gas above the disk, which is then unavailable for star formation during up to 100 Myr
Towards a Josephson element using aluminum junctions with well-transmitted channels
No full textInternational audienceWe introduce a novel method for fabricating all-aluminum Josephson junctions with highly transmitted conduction channels. Such properties are typically associated with structures requiring intricate fabrication processes, such as atomic contacts or hybrid junctions based on semiconducting nanowires and 2D materials. In contrast, our approach relies solely on standard nanofabrication techniques. The resulting devices exhibit a key signature of high-transmission junctions - Multiple Andreev Reflections (MAR) - in their current-voltage characteristics. Furthermore, we propose a straightforward superconducting circuit design based on these junctions, enabling the implementation of a parity-protected qubit
Bullae from the Main Tell: Documents of Umma’s Administration in the Early Old Babylonian Period, by N. A. Al-Mutawalli, K. S. Ismael, and W. Sallaberger, with a contribution by A. Otto. Cuneiform Texts from the Iraqi Excavations at Umma (Jokha) 3. Wiesbaden: Harrassowitz, 2024. 348 + viii pp. Paperback and e-book, €98
No full textInternational audienc
Evolution, structure and function of L-cysteine desulfidase, an enzyme involved in sulfur metabolism in the methanogenic archeon Methanococcus maripaludis
No full textInternational audienceThe biosynthesis of sulfur-containing molecules, which play essential roles in cell metabolism, often relies on enzymes that mobilize sulfur from cysteine. The function of such enzyme, L-cysteine desulfidase CyuA, which catalyzes L-cysteine decomposition to pyruvate, ammonia, and hydrogen sulfide, remains incompletely understood. Here, we used phylogenetic, genetic, biochemical, spectroscopic, and structural approaches to connect molecular structure to cellular physiology and evolutionary history and elucidate CyuA’s role in sulfur metabolism. We found that Methanococcales and several other archaeal lineages acquired CyuA via horizontal gene transfer from bacteria. In Methanococcus maripaludis , CyuA (MmCyuA) stimulates growth in sulfide-rich conditions and enables slow growth with cysteine as the sole sulfur source. Crystallographic and biochemical data reveal that MmCyuA binds a [4Fe-4S] cluster coordinated by three conserved cysteines; the fourth ligand is a nonconserved cysteine in the wild-type enzyme but is replaced by glycerol or ethylene glycol in a variant. These results enabled modeling of the enzyme–substrate complex, allowing us to propose a detailed mechanism for L-cysteine desulfuration by CyuA, potentially involving a transient [4Fe-5S] species to transfer sulfur from cysteine to various [4Fe-4S]-dependent tRNA sulfuration enzymes. These findings advance understanding of sulfur activation and trafficking related to biosynthetic pathways leading to sulfur-containing compounds
Expansion of forest cover and coeval shifts in Later Stone Age land-use at Taforalt and Rhafas Caves, Morocco, as inferred from carbon isotopes in ungulate tooth enamel
No full textInternational audienceLater Stone Age (Iberomaurusian) hunter-gatherer groups in northwestern Africa appear to have experienced a major reorganization of land-use strategies and settlement dynamics around 15–13 cal ka BP, which broadly corresponds to the globally recognized Greenland Interstadial 1 (Bølling-Allerød) climate interval. However, our understanding of the local impacts of this interval on environments in Morocco is incomplete, as is our understanding of the strength of the relationship, if any, between paleoenvironmental change and human behavior in the Moroccan Later Stone Age. This paper reconstructs changes through time in local forest canopy cover during the Later Stone Age around the archaeological cave sites of Taforalt and Rhafas (northeastern Morocco), using stable isotopes of carbon in ungulate tooth enamel. Results indicate a close link between tree cover expansion during Greenland Interstadial 1 and changes in land-use behaviors, which at Taforalt included the exploitation of storable oak and pine-derived plant foods and greater intensity of site occupation. High local productivity of nut-bearing trees paired with regional increases in human population densities likely contributed to greater intensity of occupations at Taforalt and Rhafas during Greenland Interstadial 1
Заостровье-2. Могильник римского времени в Северной Самбии
No full textInternational audienceВ монографии публикуются результаты комплексного исследования грунто-вого могильника римского времени Заостровье-2 (7) / Шлакалькен-2 (4), принадлежавшего западным балтам (эстиям). Памятник исследован Институтом археологии АН в ходе спасательных раскопок в Зеленоградском районе алининградскойобласти в 2010–2011 гг. При изучении материалов могильника были привлечены и архивные данные о немецких раскопках этого памятника Шлакалькен-2 (4) в XIX в. На основе анализа погребальных комплексов выявлены особенности погребального обряда и материальной культуры древних эстиев, получены палеоантропоогические и археозоологические данные, предложены исторические выводы
Analysis of Polycerate Mutants Reveals the Evolutionary Co-option of HOXD1 to Determine the Number and Topology of Horns in Bovidae
No full textInternational audienceIn the course of evolution, pecorans (i.e. higher ruminants) developed a remarkable diversity of osseous cranial appendages, collectively referred to as ‘headgear’, which likely share the same origin and genetic basis. However, the nature and function of the genetic determinants underlying their number and position remain elusive. Jacob and other rare populations of sheep and goats, are characterized by polyceraty, the presence of more than two horns. Here, we characterize distinct POLYCERATE alleles in each species, both associated with defective HOXD1 function. We show that haploinsufficiency at this locus results in the splitting of horn bud primordia, likely following the abnormal extension of an initial morphogenetic field. These results highlight the key role played by this gene in headgear patterning and illustrate the evolutionary co-option of a gene involved in the early development of bilateria to properly fix the position and number of these distinctive organs of Bovidae
Postnatal Development of Perivascular Astrocytic Processes and Detection of Local mRNA and Translation
No full textInternational audienc
Insights into the charge compensation mechanism at graphene-polydopamine electrode in the presence of various alkali metal cations
No full textInternational audienceUnderstanding the ion transfer dynamics at the electrode/electrolyte interface is crucial for optimizing the performance of supercapacitors. Here, the interfacial behavior of electrochemically reduced graphene oxide modified with polydopamine electrode in various alkali metal sulfate aqueous electrolytes (Li 2 SO 4 , Na 2 SO 4 , and K 2 SO 4 ) was investigated. Using a combination of electrochemical quartz crystal microbalance and advanced electrogravimetric tool (ac-electrogravimetry), the impact of polydopamine on ion desolvation and transport kinetics was elucidated. Our results reveal that the polydopamine allows to homogenize the dynamic behavior of different cations, leading to uniform and efficient ion transfer irrespective of ion size. Hydrated cations, desolvated cations, and water molecules simultaneously are implied to the charge compensation process, as water which plays a dominant role. This study underscores the potential of bio-inspired surface modification strategies for advancing high-performance energy storage materials
Nernst effect and its thickness dependence in superconducting NbN films
No full textInternational audienceSuperconducting thin films and layered crystals display a Nernst signal generated by short-lived Cooper pairs above their critical temperature. Several experimental studies have broadly verified the standard theory invoking Gaussian fluctuations of a two-dimensional (2D) superconducting order parameter. Here, we present a study of the Nernst effect in granular NbN thin films with a thickness varying from 4 to 30 nm, exceeding the short superconducting coherence length and putting the system in the three-dimensional (3D) limit. We find that the nernst conductivity decreases linearly with reduced temperature (αxy ∝ T −Tc Tc ), but the amplitude of αxy scales with thickness. While the temperature dependence corresponds to what is expected in a 2D picture, scaling with thickness corresponds to a 3D picture. We argue that this behavior indicates a 2 + 1D situation, in which the relevant coherence length along the thickness of the film has no temperature dependence. We find no visible discontinuity in the temperature dependence of the Nernst conductivity across Tc. Explaining how the response of the superconducting vortices evolves to the one above the critical temperature of short-lived Cooper pairs emerges as a challenge to the theory