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Persistence is the remnant signal that plagues HgCdTe infrared detectors used for astronomy applications after a bright illumination. Briefly, any perturbation on these detectors generates a nonlinear signal with higher amplitude than a dark current and lasts for hours. The traditional hypothesis used to explain this phenomenon is based on trapping/emission processes from deep-level defects in the space charge region (SCR) of the diode. Inspired by deep-level transient spectroscopy formalism, we have developed an analytical model describing the trap emission current from the SCR of the photodiode. We also take into account the intrinsic non-linearity of the source follower per detector ROIC architecture. Compared to data obtained on detectors built in-house at CEA-LETI, the model allows the estimation that a trap density on the order of the residual doping is enough to explain the persistence amplitude. A graded trap density in the SCR is in addition necessary to explain the persistence measurement as a function of the stress amplitude. Limits of the model are also underlined in the case of higher persistence amplitude. In this case, trap density should be close to the doping. This implies that N doping of the diode would be compensated, which is an extreme scenario out of the scope of this model.

This study deals with the nonlinear cyclo-geostrophic adjustment of a circular density front in a two-layer fluid. Laboratory experiments have been performed to investigate the dynamical evolution of a fixed volume of buoyant water, initially confined within a bottomless cylinder, which is quickly released in a dense rotating fluid. This configuration corresponds to a rapid input of potential energy in a geostrophic fluid layer and reproduces some dynamical processes which occur during oceanic upwelling or stratospheric warming events. We focus our efforts on the visualization techniques in order to have simultaneous and independent measurements of both the horizontal velocity field and the vertical density field. We thus obtained, for the first time, quantitative measurements of the potential vorticity and the flow balance after a geostrophic adjustment process. The density profile of the mean adjusted state observed in the experiment is in good agreement with the prediction of the standard adjustment theory based on Lagrangian conservation of potential vorticity except in the frontal region. There, strong three-dimensional motions (plume structures, shocks and rapid transient instabilities) take place during the early stage of adjustment. These transient three-dimensional motions could dissipate up to 50% of the initial energy of the system, especially when the size of the initial density anomaly is close to or larger than the deformation radius. Therefore, it significantly changes the velocity and the energy budget predicted by the standard Rossby adjustment. Both the kinetic energy of the mean adjusted state and the energy transferred to inertia–gravity wave modes are reduced by these transient dissipative processes.

Abstract Resource‐limited ecosystems, such as drylands, can exhibit self‐organized spatial patterns. Theory suggests that changes in these patterns can inform about the ecosystem degradation level. While the current theory is expected to work well when following a given site in time, we still lack ways of comparing different field sites using static observations of vegetation spatial structure. Such methods would be crucial to pinpoint the least fragile ecosystem areas from observation of spatial structure. Here, we tackle these limitations using an inverse‐modelling approach relying on Approximate Bayesian Computing, which uses a snapshot of the spatial structure of ecosystems characterized by so‐called irregular patterns and estimates a distance to its desertification point regardless of whether it is reached via progressive or sudden degradation. The approach allows us to comparably rank sites according to their distance to their desertification point (i.e. their resilience). We validated the approach on simulated landscapes from different models, showing that the approach performs well at ranking all landscapes. We applied the approach to a global dryland dataset and investigated the drivers of the estimated distances to desertification. We emphasized a possible application of our approach by combining these distances to desertification with aridity projections to illustrate the possibility of integrating our approach into the risk assessment of drylands. This made it possible to pinpoint the least resilient sites among those studied, therefore, paving the way for a risk‐assessment method for spatially organized ecosystems. Our inverse‐modelling approach can be extended to other ecosystems and other types of spatial patterns (e.g. periodic patterns). By allowing linking spatial structure and ecosystem resilience, it offers a promising development toward comparing and ranking sites of self‐organized ecosystems from a single snapshot of their spatial structure.

Astrometry, one of the oldest branches of astronomy, has been revolutionized by missions like Hipparcos and especially Gaia, which mapped billions of stars with extraordinary precision. However, challenges such as detecting Earth-like exoplanets in nearby habitable zones and probing the influence of dark matter in galactic environments require sub-microarcsecond accuracy. With a 6--8 meter large-aperture telescope operating across at visible wavelengths, the Habitable Worlds Observatory by NASA can combine astrometry and direct imaging to detect rocky exoplanets within 10 parsecs and study their atmospheres. We consider here the scientific requirements and present a concept for a dedicated astrometric instrument on HWO. It is capable to produce diffraction-limited images of large fields, achieving a point-spread function (PSF) precision of 20 milliarcseconds. Equipped with a detector calibration system, HWO can perform high precision astrometry, and, detect and measure the orbit of Earth-mass planets in the habitable zone of Nearby Solar-type stars. HWO can dramatically improve current constraints on the self- interaction cross-section of heavy dark matter particles (WIMPs) and on the masses of ultra-high dark matter particles, through the study of stellar motions in galactic environments. The visible channel of the instrument features a large CMOS-based focal plane with stitched pixel arrays, enabling a large field of view. The ``Detector Calibration Unit'' system uses interferometric laser fringes to calibrate pixel positions. Using differential astrometry and pointed observations with a stable telescope design enables extended integration times, enhancing sensitivity to sub-microarcsecond precision for detecting exoplanets and studying dark matter through stellar motion.

SPHERE+ is a proposed upgrade of the SPHERE instrument at the VLT, which is intended to boost the current performances of detection and characterization for exoplanets and disks. SPHERE+ will also serve as a demonstrator for the future planet finder (PCS) of the European ELT. The main science drivers for SPHERE+ are 1/ to access the bulk of the young giant planet population down to the snow line (\\(3-10\\) au), to bridge the gap with complementary techniques (radial velocity, astrometry); 2/ to observe fainter and redder targets in the youngest (\\(1-10\\)\\,Myr) associations compared to those observed with SPHERE to directly study the formation of giant planets in their birth environment; 3/ to improve the level of characterization of exoplanetary atmospheres by increasing the spectral resolution in order to break degeneracies in giant planet atmosphere models. Achieving these objectives requires to increase the bandwidth of the xAO system (from \\(\\sim\\)1 to 3\\,kHz) as well as the sensitivity in the infrared (2 to 3\\,mag). These features will be brought by a second stage AO system optimized in the infrared with a pyramid wavefront sensor. As a new science instrument, a medium resolution integral field spectrograph will provide a spectral resolution from 1000 to 5000 in the J and H bands. This paper gives an overview of the science drivers, requirements and key instrumental trade-off that were done for SPHERE+ to reach the final selected baseline concept.

Three new cyanido-bridged heterometallic ReIVNin and ReIVCu one-dimensional systems were synthesized and extensively characterized both structurally and magnetically. Single-crystal X-ray diffraction analysis revealed that these compounds display a common topology, with chains composed of alternating [RetVc14（CN）2]2- and [Mn（cyclam）]2＋ （M = Ni in 1, Cu in 2） or [Cull（N,N＇-dimethylcyclam）]2＋ （in 3） building units. Two different chain orientations with a tilt angle of ca. 51° to 55° are present in the crystal packing of these compounds. The magnetic susceptibility measurements suggest the presence of intrachain ferromagnetic interactions between the S = 3/2 ReTM centers and the 3d metal ions： S = 1 Ni1I or S = 1/2 CuII. At low temperature, a three-dimensional ordered magnetic phase induced by interchain antiferromagnetic interactions （antiferromagnetic for 1 and 2; canted antiferromagnetic for 3） is detected for the three compounds.

In vertebrates, motor control relies on cholinergic neurons in the spinal cord that have been extensively studied over the past hundred years, yet the full heterogeneity of these neurons and their different functional roles in the adult remain to be defined. Here, we develop a targeted single nuclear RNA sequencing approach and use it to identify an array of cholinergic interneurons, visceral and skeletal motor neurons. Our data expose markers for distinguishing these classes of cholinergic neurons and their rich diversity. Specifically, visceral motor neurons, which provide autonomic control, can be divided into more than a dozen transcriptomic classes with anatomically restricted localization along the spinal cord. The complexity of the skeletal motor neurons is also reflected in our analysis with alpha, gamma, and a third subtype, possibly corresponding to the elusive beta motor neurons, clearly distinguished. In combination, our data provide a comprehensive transcriptomic description of this important population of neurons that control many aspects of physiology and movement and encompass the cellular substrates for debilitating degenerative disorders. The full heterogeneity and different functional roles of cholinergic neurons in the adult spinal cord remain to be defined. Here the authors develop a targeted single nuclear RNA sequencing approach and use it to identify an array of cholinergic interneurons, as well as visceral and skeletal motor neurons.

The perspective that behavior is often driven by unconscious determinants has become widespread in social psychology. Bargh, Chen, and Burrows' (1996) famous study, in which participants unwittingly exposed to the stereotype of age walked slower when exiting the laboratory, was instrumental in defining this perspective. Here, we present two experiments aimed at replicating the original study. Despite the use of automated timing methods and a larger sample, our first experiment failed to show priming. Our second experiment was aimed at manipulating the beliefs of the experimenters: Half were led to think that participants would walk slower when primed congruently, and the other half was led to expect the opposite. Strikingly, we obtained a walking speed effect, but only when experimenters believed participants would indeed walk slower. This suggests that both priming and experimenters' expectations are instrumental in explaining the walking speed effect. Further, debriefing was suggestive of awareness of the primes. We conclude that unconscious behavioral priming is real, while real, involves mechanisms different from those typically assumed to cause the effect.

Amilra Prasanna (AP) de Silva talks to Nature Chemistry about his path in chemistry, from photochemistry to sodium sensors to logic gates, through connections between people and between two places that share more than it may seem, Sri Lanka and Northern Ireland.