A key component of the flexibility and complexity of the brain is its ability to dynamically adapt its functional network structure between integrated and segregated brain states depending on the ...demands of different cognitive tasks. Integrated states are prevalent when performing tasks of high complexity, such as maintaining items in working memory, consistent with models of a global workspace architecture. Recent work has suggested that the balance between integration and segregation is under the control of ascending neuromodulatory systems, such as the noradrenergic system, via changes in neural gain (in terms of the amplification and non-linearity in stimulus-response transfer function of brain regions). In a previous large-scale nonlinear oscillator model of neuronal network dynamics, we showed that manipulating neural gain parameters led to a 'critical' transition in phase synchrony that was associated with a shift from segregated to integrated topology, thus confirming our original prediction. In this study, we advance these results by demonstrating that the gain-mediated phase transition is characterized by a shift in the underlying dynamics of neural information processing. Specifically, the dynamics of the subcritical (segregated) regime are dominated by information storage, whereas the supercritical (integrated) regime is associated with increased information transfer (measured via transfer entropy). Operating near to the critical regime with respect to modulating neural gain parameters would thus appear to provide computational advantages, offering flexibility in the information processing that can be performed with only subtle changes in gain control. Our results thus link studies of whole-brain network topology and the ascending arousal system with information processing dynamics, and suggest that the constraints imposed by the ascending arousal system constrain low-dimensional modes of information processing within the brain.
WR 112 is a dust-forming carbon-rich Wolf-Rayet (WC) binary with a dusty circumstellar nebula that exhibits a complex asymmetric morphology, which traces the orbital motion and dust formation in the ...colliding winds of the central binary. Unraveling the complicated circumstellar dust emission around WR 112 therefore provides an opportunity to understand the dust formation process in colliding-wind WC binaries. In this work, we present a multi-epoch analysis of the circumstellar dust around WR 112 using seven high spatial resolution (FWHM ∼ 0 3-0 4) N-band (λ ∼ 12 m) imaging observations spanning almost 20 yr and that includes images obtained from Subaru/COMICS in 2019 October. In contrast to previous interpretations of a face-on spiral morphology, we observe clear evidence of proper motion of the circumstellar dust around WR 112 consistent with a nearly edge-on spiral with a θs = 55° half-opening angle and a ∼20 yr period. The revised near edge-on geometry of WR 112 reconciles previous observations of highly variable nonthermal radio emission that was inconsistent with a face-on geometry. We estimate a revised distance to WR 112 of kpc based on the observed dust expansion rate and a spectroscopically derived WC terminal wind velocity of km s−1. With the newly derived WR 112 parameters, we fit optically thin dust spectral energy distribution models and determine a dust production rate of M yr−1, which demonstrates that WR 112 is one of the most prolific dust-making WC systems known.
Abstract We present infrared aperture-masking interferometry (AMI) observations of newly formed dust from the colliding winds of the massive binary Wolf–Rayet system WR 137 with JWST using the Near ...Infrared Imager and Slitless Spectrograph (NIRISS). NIRISS AMI observations of WR 137 and a point-spread function calibrator star, HD 228337, were taken using the F380M and F480M filters in 2022 July and August as part of the Director’s Discretionary Early Release Science program #1349. Interferometric observables (squared visibilities and closure phases) from the WR 137 “interferogram” were extracted and calibrated using three independent software tools: ImPlaneIA, AMICAL, and SAMpip. The analysis of the calibrated observables yielded consistent values except for slightly discrepant closure phases measured by ImPlaneIA. Based on all three sets of calibrated observables, images were reconstructed using three independent software tools: BSMEM, IRBis, and SQUEEZE. All reconstructed image combinations generated consistent images in both F380M and F480M filters. The reconstructed images of WR 137 reveal a bright central core with a ∼300 mas linear filament extending to the northwest. A geometric colliding-wind model with dust production constrained to the orbital plane of the binary system and enhanced as the system approaches periapsis provided a general agreement with the interferometric observables and reconstructed images. Based on a colliding-wind dust condensation analysis, we suggest that dust formation within the orbital plane of WR 137 is induced by enhanced equatorial mass loss from the rapidly rotating O9 companion star, whose axis of rotation is aligned with that of the orbit.
Abstract
Wolf-Rayet (WR) 140 is the archetypal periodic dust-forming colliding-wind binary that hosts a carbon-rich WR (WC) star and an O-star companion with an orbital period of 7.93 yr and an ...orbital eccentricity of 0.9. Throughout the past few decades, multiple dust-formation episodes from WR 140 have been observed that are linked to the binary orbit and occur near the time of periastron passage. Given its predictable dust-formation episodes, WR 140 presents an ideal astrophysical laboratory to investigate the formation and evolution of dust in the hostile environment around a massive binary system. In this paper, we present near- and mid-infrared (IR) spectroscopic and imaging observations of WR 140 with Subaru/SCExAO+CHARIS, Keck/NIRC2+PyWFS, and Subaru/Cooled Mid-Infrared Camera and Spectrograph taken between 2020 June and September that resolve the circumstellar dust emission linked to its most recent dust-formation episode in 2016 December. Our spectral energy distribution analysis of WR 140's resolved circumstellar dust emission reveals the presence of a hot (
T
d
∼ 1000 K) near-IR dust component that is co-spatial with the previously known and cooler (
T
d
∼ 500 K) mid-IR dust component composed of 300–500 Å sized dust grains. We attribute the hot near-IR dust emission to the presence of nano-sized (nanodust) grains and suggest they were formed from grain–grain collisions or the rotational disruption of the larger grain size population by radiative torques in the strong radiation field from the central binary. Lastly, we speculate on the astrophysical implications of nanodust formation around colliding-wind WC binaries, which may present an early source of carbonaceous nanodust in the interstellar medium.
Extremely low currents synthesis of molecular sieve films by controlling the interfacial microenvironment with catalytic efficiency of 105 is explored.
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•Extremely low currents applied ...for the synthesis of AEL molecular sieve films.•Water and ionic liquid cation are linked by hydrogen bonding in microenvironment.•The catalytic efficiency in the synthesis is defined as high as 105.
Minimizing electric currents in the electrosynthesis of molecular sieve films is critically challenging. Herein we demonstrate the electric currents can be significantly minimized to catalyze AEL molecular sieve films nucleation in ionic liquids by the control of interfacial microenvironment. In the local microenvironment, the nucleation promoter of water and structure directing agents of ionic liquids are believed to be linked via hydrogen bonding in the electrical double layer, thus lowering the currents to 10e-8 A. The corresponding catalytic efficiency reaches up to as high as 105. This study sheds lights on manipulating the local chemical domain in the interfacial structure using extremely low currents for the synthesis chemistry.
Electronic waste leads to a waste of resources and is a source of environmental pollution. The effective recovery of electronic waste is an urgent sustainability challenge. From the perspective of ...retailers, this paper constructs a retail sales strategy model under three strategies: a cash incentive, price preference incentive, and price discount incentive. By comparing the relationships among retailer benefits, incentive utility and incentive capital investment under these three incentive strategies, the model determines the optimal incentive strategies. This research shows: (1) When the incentive utility value is below the cross point, the price discount incentive strategy could earn a retailer the maximum profit. When the incentive utility value increases up to the cross point, the cash incentive strategy could earn a retailer the maximum profit; (2) The price discount incentive strategy is the optimal choice for retailers, and retailers can obtain the largest net profit at the same incentive cost; (3) The cash incentive strategy is less attractive because it creates biggest variability in net profit.
Abstract
The Wolf–Rayet (WR) binary system WR140 is a close (0.9–16.7 mas; ref.
1
) binary star consisting of an O5 primary and WC7 companion
2
and is known as the archetype of episodic ...dust-producing WRs. Dust in WR binaries is known to form in a confined stream originating from the collision of the two stellar winds, with orbital motion of the binary sculpting the large-scale dust structure into arcs as dust is swept radially outwards. It is understood that sensitive conditions required for dust production in WR140 are only met around periastron when the two stars are sufficiently close
2–4
. Here we present multiepoch imagery of the circumstellar dust shell of WR140. We constructed geometric models that closely trace the expansion of the intricately structured dust plume, showing that complex effects induced by orbital modulation may result in a ‘Goldilocks zone’ for dust production. We find that the expansion of the dust plume cannot be reproduced under the assumption of a simple uniform-speed outflow, finding instead the dust to be accelerating. This constitutes a direct kinematic record of dust motion under acceleration by radiation pressure and further highlights the complexity of the physical conditions in colliding-wind binaries.
Perovskite oxides are considered as highly active electrodes for reversible solid oxide cells (RSOCs), which show high conversion efficiency in power-fuel and fuel-power modes. In this work, ...La0.6A0.4Co0.2Fe0.8O3 (A = Sr, Ca, Ba) oxides are synthesized as bifunctional electrodes for RSOCs. Among them, La0.6Ca0.4Co0.2Fe0.8O3 (LCCF) exhibits the best redox performance, which makes it have the highest catalytic activity not only for the oxygen reduction reaction (ORR) but also for the hydrogen oxidation reaction (HOR). This is mainly because LCCF has the highest oxygen vacancy concentration, which promotes the HOR and ORR. In addition, for HOR and ORR processes on LCCF-based equivalent symmetrical cells, the rate-determining steps (RDSs) are the charge transfer reaction and the reduction of O to O–, respectively. When LCCF is used as the electrode material, an RSOC displays the highest discharge/electrolytic water performance in reversible operation conditions. When the fuel gas is H2/H2O, the maximum power density of the LCCF-based cell can reach 271.1 mW cm–2 at 700 °C and the current density of LCCF-based cell reaches −400.2 mA cm–2 at 700 °C and 1.3 V.
ABSTRACT
Constraining the vertical and radial structure of debris discs is crucial to understanding their formation, evolution, and dynamics. To measure both the radial and vertical structure, a disc ...must be sufficiently inclined. However, if a disc is too close to edge-on, deprojecting its emission becomes non-trivial. In this paper we show how Frankenstein, a non-parametric tool to extract the radial brightness profile of circumstellar discs, can be used to deproject their emission at any inclination as long as they are optically thin and axisymmetric. Furthermore, we extend Frankenstein to account for the vertical thickness of an optically thin disc (H(r)) and show how it can be constrained by sampling its posterior probability distribution and assuming a functional form (e.g. constant h = H/r), while fitting the radial profile non-parametrically. We use this new method to determine the radial and vertical structures of 16 highly inclined debris discs observed by ALMA. We find a wide range of vertical aspect ratios, h, ranging from 0.020 ± 0.002 (AU Mic) to 0.20 ± 0.03 (HD 110058), which are consistent with parametric models. We find a tentative correlation between h and the disc fractional width, as expected if wide discs were more stirred. Assuming discs are self-stirred, the thinnest discs would require the presence of at least 500-km-sized planetesimals. The thickest discs would likely require the presence of planets. We also recover previously inferred and new radial structures, including a potential gap in the radial distribution of HD 61005. Finally, our new extension of Frankenstein also allows constraining how h varies as a function of radius, which we test on 49 Ceti, finding that h is consistent with being constant.
ABSTRACT
Extrasolar analogues of the Solar System’s Kuiper belt offer unique constraints on outer planetary system architecture. Radial features such as the sharpness of disc edges and substructures ...such as gaps may be indicative of embedded planets within a disc. Vertically, the height of a disc can constrain the mass of embedded bodies. Edge-on debris discs offer a unique opportunity to simultaneously access the radial and vertical distribution of material; however, recovering either distribution in an unbiased way is challenging. In this study, we present a non-parametric method to recover the surface brightness profile (face-on surface brightness as a function of radius) and height profile (scale height as a function of radius) of azimuthally symmetric, edge-on debris discs. The method is primarily designed for observations at thermal emission wavelengths, but is also applicable to scattered light observations under the assumption of isotropic scattering. By removing assumptions on underlying functional forms, this algorithm provides more realistic constraints on disc structures. We also apply this technique to Atacama Large Millimeter/submillimeter Array observations of the AU Mic debris disc and derive a surface brightness profile consistent with estimates from parametric approaches, but with a more realistic range of possible models that is independent of parametrization assumptions. Our results are consistent with a uniform scale height of 0.8 au, but a scale height that increases linearly with radius is also possible.
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