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Conflicts are represented in a cognitive space to reconcile domain-general and domain-specific cognitive control
No full textCognitive control resolves conflict between task-relevant and -irrelevant information to enable goal-directed behavior. As conflict can arise from different sources (e.g., sensory input, internal representations), how a finite set of cognitive control processes can effectively address huge array of conflict remains a major challenge. We hypothesize that different conflict can be parameterized and represented as distinct points in a (low-dimensional) cognitive space, which can then be resolved by a limited set of cognitive control processes working along the dimensions. To test this hypothesis, we designed a task with five types of conflict that could be conceptually parameterized along one dimension. Over two experiments, both human performance and fMRI activity patterns in the right dorsolateral prefrontal (dlPFC) support that different types of conflict are organized in a cognitive space. The findings suggest that cognitive space can be a dimension reduction tool to effectively organize neural representations of conflict for cognitive control
Primate-conserved Carbonic Anhydrase IV and murine-restricted Ly6c1 are new targets for crossing the blood-brain barrier
No full textThe blood-brain barrier (BBB) presents a major challenge to delivering large molecules to study and treat the central nervous system (CNS). This is due in part to the scarcity of effective targets for BBB crossing, the identification of which is the crucial first step of drug development. Here, we leveraged a panel of adeno-associated viruses (AAVs) previously identified through directed evolution for improved BBB transport to reverse engineer protein targets for enhanced BBB crossing. We identify both murine-restricted Ly6c1 and primate-conserved carbonic anhydrase IV (Car4; CA4) as novel receptors for crossing the BBB. We demonstrate how these receptors can unlock new experimental and computational target-focused engineering strategies by creating the enhanced Ly6c1-binding vector AAV-PHP.eC and by applying AlphaFold2-enabled in silico methods to rank capsids against identified receptors and generate capsid-receptor binding models. Here, with Car4, we add a completely new receptor to the very short list currently available for crossing the BBB in humans and, with Ly6c1, we validate a pipeline for receptor-targeted engineering. The identification of Car4/CA4 and structural insights from computational modeling provide new paths toward human brain-penetrant chemicals (drugs) and biologicals (including gene delivery)
TOI-4562b: A Highly Eccentric Temperate Jupiter Analog Orbiting a Young Field Star
No full textWe report the discovery of TOI-4562b (TIC-349576261), a Jovian planet orbiting a young F7V-type star, younger than the Praesepe/Hyades clusters (<700 Myr). This planet stands out because of its unusually long orbital period for transiting planets with known masses (P_(orb) = 225.11781_(-0.00022)^(+0.00025) days) and because it has a substantial eccentricity (e = 0.76_(-0.02)^(+0.02)). The location of TOI-4562 near the southern continuous viewing zone of TESS allowed observations throughout 25 sectors, enabling an unambiguous period measurement from TESS alone. Alongside the four available TESS transits, we performed follow-up photometry using the South African Astronomical Observatory node of the Las Cumbres Observatory and spectroscopy with the CHIRON spectrograph on the 1.5 m SMARTS telescope. We measure a radius of 1.118_(+0.013)^(-0.014) R_J and a mass of 2.30_(-0.47)^(+0.48) M_J for TOI-4562b. The radius of the planet is consistent with contraction models describing the early evolution of the size of giant planets. We detect tentative transit timing variations at the ∼20 minutes level from five transit events, favoring the presence of a companion that could explain the dynamical history of this system if confirmed by future follow-up observations. With its current orbital configuration, tidal timescales are too long for TOI-4562b to become a hot Jupiter via high-eccentricity migration though it is not excluded that interactions with the possible companion could modify TOI-4562b's eccentricity and trigger circularization. The characterization of more such young systems is essential to set constraints on models describing giant-planet evolution
Laboratory measurements of anhydrous minerals mixed with hyperfine hydrated minerals to support interpretation of infrared reflectance observations of planetary surfaces
No full textIdentification of water in our Solar System is a key point to understanding the formation and evolution of planetary bodies as well as for astrobiological studies. Scientists identified hydrated minerals as a prime source of H₂O in our Solar System. Minerals such as clays, serpentines and other phyllosilicates were discovered by orbiter and lander spacecraft and ground observations on a large variety of rocky surfaces from Mars to small asteroids using InfraRed (IR) spectroscopy as primary technique. It has already been observed that in the presence of large amounts of hydrated minerals in mixtures with anhydrous minerals, the IR spectra can be dominated by the features of hydrated minerals. However, it is still poorly studied how the IR spectra change in presence of different grain size of the two components.
The goal of this study was to investigate the infrared spectroscopic features of anhydrous mineral spectra in presence of low amounts of small grain size hydrated hyperfine particles. We prepared several mixtures using 1 wt% and 5 wt% of very small grain size (< 10 μm) hydrated minerals and 95 wt% and 99 wt% of larger grain size (200–500 μm) anhydrous minerals. We measured the IR reflectance spectrum of these mixtures in the range 8000–400 cm⁻¹ (1.25–25 μm). Results presented here show how the presence of a very limited amount of hydrated minerals with grain size one order of magnitude smaller than the anhydrous component is sufficient to change the IR spectrum, especially in the Near-InfraRed (NIR) region where some of the major hydrated features manifest. On the contrary, the Mid-InfraRed (MIR) part of the spectrum (also identified as thermal infrared) is definitely less affected and anhydrous mineral features continue to be dominant with slight modifications. This result is of pivotal importance for correctly interpreting the IR reflectance observations of planetary bodies such as Mars or asteroids where a mixing of anhydrous and hydrated minerals can be observed. The presence of strong spectroscopic features due to hydrated minerals can be misinterpreted as a large abundance of this material instead of a spectroscopic effect
PHANGS–JWST First Results: The Influence of Stellar Clusters on Polycyclic Aromatic Hydrocarbons in Nearby Galaxies
No full textWe present a comparison of theoretical predictions of dust continuum and polycyclic aromatic hydrocarbon (PAH) emission with new JWST observations in three nearby galaxies: NGC 628, NGC 1365, and NGC 7496. Our analysis focuses on a total of 1063 compact stellar clusters and 2654 stellar associations previously characterized by the Hubble Space Telescope in the three galaxies. We find that the distributions and trends in the observed PAH-focused infrared colors generally agree with theoretical expectations, and that the bulk of the observations is more aligned with models of larger, ionized PAHs. These JWST data usher in a new era of probing interstellar dust and studying how the intense radiation fields near stellar clusters and associations play a role in shaping the physical properties of PAHs
Ultracool dwarfs in Gaia DR3
No full textContext. Previous Gaia data releases offered the opportunity to uncover ultracool dwarfs (UCDs) through astrometric, rather than purely photometric, selection. The most recent, the third data release (DR3), offers in addition the opportunity to use low-resolution spectra to refine and widen the selection.
Aims. In this work we use the Gaia DR3 set of UCD candidates and complement the Gaia spectrophotometry with additional photometry in order to characterise the global properties of the set. This includes the inference of the distances, their locus in the Gaia colour-absolute magnitude diagram, and the (biased through selection) luminosity function at the faint end of the main sequence. We study the overall changes in the Gaia RP spectra as a function of spectral type. We study the UCDs in binary systems, we attempt to identify low-mass members of nearby young associations, star-forming regions, and clusters, and we analyse their variability properties.
Methods. We used a forward model and the Bayesian inference framework to produce posterior probabilities for the distribution parameters and a calibration of the colour index as a function of the absolute magnitude in the form of a Gaussian process. Additionally, we applied the hierarchical mode association clustering (HMAC) unsupervised classification algorithm for the detection and characterisation of overdensities in the space of celestial coordinates, projected velocities, and parallaxes.
Results. We detect 57 young, kinematically homogeneous groups, some of which are identified as well-known star-forming regions, associations, and clusters of different ages. We find that the primary members of the 880 binary systems with a UCD belong to the thin and thick disc components of the Milky Way. We identify 1109 variable UCDs using the variability tables in the Gaia archive, 728 of which belong to the star-forming regions defined by HMAC. We define two groups of variable UCDs with extreme bright or faint outliers.
Conclusions. The set of sources identified as UCDs in the Gaia archive contains a wealth of information that will require focused follow-up studies and observations. It will help advance our understanding of the nature of the faint end of the main sequence and the stellar-substellar transition
Development of a Mg/O ReaxFF Potential to describe the Passivation Processes in Magnesium‐Ion Batteries
No full textOne of the key challenges preventing the breakthrough of magnesium-ion batteries (MIB) is the formation of a passivating boundary layer at the Mg anode. To describe the initial steps of Mg anode degradation by O2 impurities, we have developed a Mg/O ReaxFF reactive force field description capable of accurately modeling the bulk, surface, adsorption, and diffusion properties of both metallic Mg and the salt MgO. We show that O2 immediately dissociates upon first contact with the Mg anode (modeled as Mg(0001), Mg(10m10)A, and Mg(10m11)), heating the surface to several 1000 K. The high temperature assists the further oxidation and forms a rocksalt interphase intersected by several grain boundaries. Among the Mg surface terminations, Mg(10m10)A is the most reactive, forming an MgO layer with a thickness of up to 25 Å. We also demonstrate the recrystallization of an amorphous MgO particle, which is obtained performing grand-canonical Monte Carlo simulations, into the rocksalt structure by thermal annealing at elevated temperatures. Our force field can be used to model the ongoing reactions in Mg-air batteries and constitutes an important step towards modeling the solid--electrolyte interface formation at the Mg anode
Wavelet-based resolvent analysis for statistically-stationary and temporally-evolving flows
No full textThis work introduces a formulation of resolvent analysis that uses wavelet transforms rather than Fourier transforms in time. This allows resolvent analysis to be extended to turbulent flows with non-stationary means in addition to statistically-stationary flows. The optimal resolvent modes for this formulation correspond to the potentially time-transient structures that are most amplified by the linearized Navier-Stokes operator. We validate this methodology for turbulent channel flow and show that the wavelet-based and Fourier-based resolvent analyses are equivalent for statistically-stationary flows. We then apply the wavelet-based resolvent analysis to study the transient growth mechanism in the buffer layer of a turbulent channel flow by windowing the resolvent operator in time and frequency. The method is also applied to temporally-evolving parallel shear flows such as an oscillating boundary layer and three-dimensional channel flow, in which a lateral pressure gradient perturbs a fully-developed turbulent flow in a channel
Measurements of Hypersonic Double Cone Flows with Shock Wave/Boundary Layer Interactions in the X3 Expansion Tunnel
No full textThis paper presents the results from a series of hypersonic double cone experiments, conducted in the X3 expansion tunnel at the University of Queensland (UQ). The model was previously used and produced at California Institute of Technology (Caltech) and is a scaled model of the double cone model used by the Calspan-University of Buffalo Research Center (CUBRC). The data presented is a full transient set of surface heat flux, and surface pressure measurements along the axial length of the model as well as a full suite of tunnel data. These aim to help characterize the flow over the geometry by providing surface conditions, an accurate location of the boundary layer separation, the flow reattachment points and the general structure of the shockwave boundary layer interaction. The geometry of the X3 facility is also provided to give a more complete picture of the test conditions, an important consideration for numerical models. The outcome of this paper is to provide the most detailed experimental data to date and improve validation attempts of existing non-equilibrium thermochemistry codes
Testing the Radio-selection Method of Dual Active Galactic Nuclei in the Stripe 82 Field
No full textWe test the merger-induced dual active galactic nuclei (dAGNs) paradigm using a sample of 35 radio galaxy pairs from the Sloan Digital Sky Survey Stripe 82 field. Using Keck optical spectroscopy, we confirm 21 pairs have consistent redshifts, constituting kinematic pairs; the remaining 14 pairs are line-of-sight projections. We classify the optical spectral signatures via emission line ratios, equivalent widths, and excess of radio power above star formation predicted outputs. We find six galaxies are classified as LINERs and seven are AGN/starburst composites. Most of the LINERs are retired galaxies, while the composites likely have AGN contribution. All of the kinematic pairs exhibit radio power more than 10× above the level expected from just star formation, suggestive of a radio AGN contribution. We also analyze high-resolution (0.″3) imaging at 6 GHz from the NSF’s Karl G. Jansky Very Large Array for 17 of the kinematic pairs. We find six pairs (two new, four previously known) host two separate radio cores, confirming their status as dAGNs. The remaining 11 pairs contain single AGNs, with most exhibiting prominent jets/lobes overlapping their companion. Our final census indicates a dAGN duty cycle slightly higher than predictions of purely stochastic fueling, although a larger sample (potentially culled from VLASS) is needed to fully address the dAGN fraction. We conclude that while dAGNs in the Stripe 82 field are rare, the merger process plays some role in their triggering and it facilitates low to moderate levels of accretion