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Higher in the mountains: Dynamics of agro-pastoral practices in a low-latitude mountain system (Karkas Mountains, central Iran) during the Mediaeval Warm Period and the Little Ice Age
No full textInternational audienceLittle is known about the impact of the Mediaeval Warm Period (MWP: 950–1250 CE) and the Little Ice Age (LIA: 1250–1850 CE) on high-altitude agro-pastoral practices and the vertical mobility of human communities in the mountain regions of interior Southwest Asia. Although the area experienced significant socio-political changes during the last millennium, the socio-environmental interactions during these climatic periods remain poorly understood. This study presents a geochronologically well-constrained, multi-proxy geochemical and palaeoecological record from a high-altitude (2500 m) wetland in the Karkas Mountains, located on the central Iranian desert plateau. All proxies, including bioindicators (pollen, non-pollen palynomorphs, fossil insects) and sedimentological and geochemical data (X-ray fluorescence intensity variations, Isothermal Remanent Magnetization measurements, and lithological changes), reveal two contrasting patterns of hydroclimatic conditions and agro-pastoral practices during the MWP and the LIA. Pollen and non-pollen palynomorphs show that the MWP was characterised by intensive cereal cultivation (mainly wheat) and the establishment of permanent agricultural communities, while the LIA was characterised by intensified grazing pressure on montane steppe vegetation, suggesting a shift towards a more mobile pastoral lifestyle—one that persisted into the 20th century. Interestingly, this shift coincides with the Mongol invasion of the Iranian plateau. Variations in lithology, XRF intensities, magnetic field as well as the insect faunal assemblages further provide insights into the wetland hydrological variations and erosional episodes related to land-use and hydroclimatic changes during the MWP and LIA. Based on the Gahak wetland record and regional palaeoclimatic data, we conclude that the MWP in the mountainous areas of central Iran was marked by milder winters and possibly shorter summer droughts, in contrast to the LIA, which had harsher winters and longer-lasting snow cover. Results of the spectral analysis on Gahak record compared to well-known solar cycles, suggest that the climate of the central Iranian highlands is highly sensitive to the variations in solar irradiance. Our findings highlight the significant role of high-altitude agro-pastoral communities in supplying food to the lowland urban centres of mediaeval Persia, at least during the MWP. Although socio-political changes (e.g. Mongol invasion) could affect the mediaeval societies, the impact of climatic shifts on socio-economic changes should not be underestimate
Investigating the H I distribution and kinematics of ESO444-G084 and [KKS2000]23: New insights from the MHONGOOSE survey
No full textInternational audienceWe present the neutral atomic hydrogen (H I ) distribution, kinematics, mass modelling, and gravitational stability of the dwarf irregular galaxies ESO444–G084 and [KKS2000]23 using high spatial, spectral, and column density sensitivity data from the MeerKAT H I observations of nearby galactic objects: Observing Southern Emitters (MHONGOOSE) survey obtained with MeerKAT. ESO444–G084 exhibits centrally concentrated H I emission, while [KKS2000]23 has irregularly distributed high-density pockets. The total H I fluxes measured down to column density thresholds of 10 19 cm −2 and 10 18 cm −2 are nearly the same, suggesting that the increase in the H I diameter at lower column densities is primarily due to the larger beam size, and that no significant additional emission is detected. The total H I masses are (1.1±0.1)×10 8 M ⊙ for ESO444–G084 and (6.1±0.3)×10 8 M ⊙ for [KKS2000]23. We derived rotation curves using 3D kinematic modelling tools Python fully automated TiRiFiC (PyFAT) and tilted ring fitting code (TiRiFiC), which allow us to fully capture the gas kinematics. Both galaxies exhibit disk-like rotation, with ESO444–G084 showing a kinematic warp beyond ∼1.8 kpc. Its relatively fast-rising rotation curve suggests a more centrally concentrated dark matter distribution, whereas [KKS2000]23's more gradual rise indicates a more extended mass distribution. Mass modelling with an isothermal halo and stellar mass-to-light ratio ( M / L ) 3. μ m * =0.20 for ESO444–G084 and 0.18 for [KKS2000]23 yields physically consistent results. We further analyse disk stability using spatially resolved maps of the Toomre Q parameter and Σ gas /Σ crit , linking these with recent star formation traced by hydrogen-alpha (H α ) and far-ultraviolet (FUV) emission. ESO444–G084 supports localised star formation despite global stability, while [KKS2000]23 is gravitationally unstable yet lacks strong H α emission, suggesting that turbulence, gas depletion, or past feedback suppresses star formation. The absence of detectable inflows or outflows implies that internal processes regulate star formation. This study highlights the interplay between H I morphology, kinematics, dark matter distribution, and disk stability, demonstrating how internal mechanisms shape dwarf galaxy evolution
Li-Mg alloys as anode for Li batteries in liquid electrolytes: Preparation, shaping, characterization and parametric electrochemical study
No full textInternational audienceLithium-metal batteries offer significant energy density advantages over classical Li-ion technology but their practical implementation is hampered by the poor reversibility of the lithium deposition/stripping processes. To solve this issue, Li-Mg alloys have already been considered as possible alternative and are examined in greater details herein. Homogeneous Li-rich alloys (β-phase) with controlled composition (5–13 at.%Mg) were fabricated and electrochemically reacted with Li to explore the kinetics of the Li-driven β−α phase equilibrium. We showed that the (de)lithiation of the β-phase that occurs at ∼0 Volt vs Li+/Li°, and therefore the most interesting, is strongly limited with the early appearance of Mg-rich α-phase at higher voltages. We demonstrated that this β-domain can be largely extended by using moderate cycling temperature (40 °C), low current density, high initial Li/Mg ratio and rest sequences. Post-cycling observations reveal that repeated (de)alloyings proceed without dendritic growth but rather involve the continuous growth of a porous surface film at the expense of the dense Li-Mg alloy resulting in a sudden drop in capacity when the electrode is becoming completely porous. By limiting the capacity, it is possible to control the progression of this porous layer, improve the efficiency of the Li plating-stripping process, and thus achieve a thousand cycles (0.8 mA.cm-2, 0.8 mAh.cm-2). In full cells, better reversibility is spotted for LiFePO4/Li17Mg compared to LiFePO4/Li cells provided that cycling rate is not pushed over ∼1.2 mAh.cm-2. Overall, we hope these results will provide useful insights for the design of lithium alloy electrodes to improve lithium-metal batteries
New constraints on the values of the fundamental constants at a look-back time of 7.3 Gyr
No full textInternational audienceThe study of the redshifted spectral lines can provide a measure of the fundamental constants over large look-back times. Current grand unified theories predict an evolution in these and astronomical observations offer the only experimental measure of the values of the constants over large time scales. Of particular interest are the dimensionless constants; the fine structure constant (), the proton-electron mass ratio () and the proton g-factor (), since these do not require a `standard metre-stick'. Here we present a re-analysis of the 18-cm hydroxyl (OH) lines at , recently detected with the MeerKAT telescope, towards the radio source PKS 1830-211. Utilizing the previous constraint of , we obtain , and . These new constraints are consistent with no evolution over a look-back time of 7.3 Gyr and provide another valuable data point in the putative evolution in the constants
Oxytocin Gα signaling-induced amygdala astrocytes processes retraction shapes behavioral stress response
No full textAnticipated reactions to stressful situations are vital for the survival and well-being of organisms, and abnormal reactions are involved in stress-related disorders. The neuropeptide oxytocin is a key modulator ensuring well-adapted stress responses. Oxytocin acts on both neurons and astrocytes, but the molecular and cellular mechanisms mediating stress response remain poorly understood. Here, we focus on the amygdala, a crucial hub that integrates and processes sensory information through oxytocin- dependent mechanisms. Using an acute stress paradigm in mice, genetic and pharmacological manipulations combined with proteomic, morphological, electrophysiological and behavioral approaches, we reveal that oxytocinergic modulation of the freezing response to stress is mediated by transient Gαi-dependent retraction of astrocytic processes, followed by enhanced neuronal sensitivity to extracellular potassium in the amygdala. Our findings elucidate a pivotal role for astrocytes morphology- dependent modulation of brain circuits that is required for proper anticipated behavioral response to stressful situations
Multiply quantized vortex spectroscopy in a quantum fluid of light
No full textInternational audienceThe formation of quantized vortices is a unifying feature of quantum mechanical systems, making it a premier means for fundamental and comparative studies of different quantum fluids. Being excited states of motion, vortices are normally unstable towards relaxation into lower energy states. However, here we exploit the driven-dissipative nature of polaritonic fluids of light to create stationary, multiply charged vortices. We measure the spectrum of collective excitations and observe negative energy modes at the core and positive energy modes at large radii. Their coexistence at the same frequency normally causes the dynamical instability, but here intrinsic losses stabilize the system, allowing for phase pinning by the pump on macroscopic scales. We observe common features of quantized vortices in quantum fluids and other rotating geometries like astrophysical compact objects, opening the way to the study of universal amplification phenomena
