We present a new stellar feedback model that reproduces superbubbles. Superbubbles from clustered young stars evolve quite differently to individual supernovae and are substantially more efficient at ...generating gas motions. The essential new components of the model are thermal conduction, subgrid evaporation and a subgrid multiphase treatment for cases where the simulation mass resolution is insufficient to model the early stages of the superbubble. The multiphase stage is short compared to superbubble lifetimes. Thermal conduction physically regulates the hot gas mass without requiring a free parameter. Accurately following the hot component naturally avoids overcooling. Prior approaches tend to heat too much mass, leaving the hot interstellar medium (ISM) below 106 K and susceptible to rapid cooling unless ad hoc fixes were used. The hot phase also allows feedback energy to correctly accumulate from multiple, clustered sources, including stellar winds and supernovae. We employ high-resolution simulations of a single star cluster to show the model is insensitive to numerical resolution, unresolved ISM structure and suppression of conduction by magnetic fields. We also simulate a Milky Way analogue and a dwarf galaxy. Both galaxies show regulated star formation and produce strong outflows.
Nuclear factor erythroid 2-related factor 2 (Nrf2) is ubiquitously expressed in most eukaryotic cells and functions to induce a broad range of cellular defenses against exogenous and endogenous ...stresses, including oxidants, xenobiotics, and excessive nutrient/metabolite supply. Because the production and fate of stem cells are often modulated by cellular redox and metabolic homeostasis, important roles of Nrf2 have emerged in the regulation of stem cell quiescence, survival, self-renewal, proliferation, senescence, and differentiation. In a rapidly advancing field, this review summarizes Nrf2 signaling in the context of stem cell state and function and provides a rationale for Nrf2 as a therapeutic target in stem cell-based regenerative medicine.
As a cellular metabolic and stress sensor, the transcription factor Nrf2 is a pivotal regulator of stem cell self-renewal, proliferation, and differentiation.Nrf2 displays cell type-specific and/or stage-dependent impact on stem cell biology in response to various environmental cues.Nrf2 modulates PSCs through the regulation of pluripotency factors, metabolism, redox homeostasis, and cellular stress responses.Nrf2 maintain ASCs self-renewal, quiescence, and regenerative capacity while protecting against ASC depletion in response to stress and aging.
Motor cortex (M1) lesions result in motor impairments, yet how M1 contributes to the control of movement remains controversial. To investigate the role of M1 in sensory guided motor coordination, we ...trained mice to navigate a virtual corridor using a spherical treadmill. This task required directional adjustments through spontaneous turning, while unexpected visual offset perturbations prompted induced turning. We found that M1 is essential for execution and learning of this visually guided task. Turn-selective layer 2/3 and layer 5 pyramidal tract (PT) neuron activation was shaped differentially with learning but scaled linearly with turn acceleration during spontaneous turns. During induced turns, however, layer 2/3 neurons were activated independent of behavioral response, while PT neurons still encoded behavioral response magnitude. Our results are consistent with a role of M1 in the detection of sensory perturbations that result in deviations from intended motor state and the initiation of an appropriate corrective response.
•Motor cortex (M1) is necessary for the motor response to an unexpected perturbation•M1 is not necessary when the same movement is carried out spontaneously•Layer 2/3 neurons are differentially activated by unexpected visual perturbations•Activity in layer 5 PT neurons correlates with behavioral responses
The role of motor cortex in movement control is controversial. Heindorf et al. demonstrate that motor cortex mediates corrective behavioral responses to unexpected visual perturbations, paralleled by layer-specific cortical responses distinct from the ones during the same movement without perturbation.
Abstract
Recent photometric detections of extreme (
z
> 10) redshift galaxies from the JWST have been shown to be in strong tension with existing simulation models for galaxy formation and in the ...most acute case, in tension with ΛCDM itself. These results, however, all rest on the confirmation of these distances by spectroscopy. Recently, the JADES survey has detected the most distant galaxies with spectroscopically confirmed redshifts, with four galaxies found with redshifts between
z
= 10.38 and
z
= 13.2. In this Letter, we compare simulation predictions from four large cosmological volumes and two zoom-in protoclusters with the JADES observations to determine whether these spectroscopically confirmed galaxy detections are in tension with existing models for galaxy formation or with ΛCDM more broadly. We find that existing models for cosmological galaxy formation can generally reproduce the observations for JADES in terms of galaxy stellar masses, star formation rates, and the number density of galaxies at
z
> 10.
Prediction errors are differences between expected and actual sensory input and are thought to be key computational signals that drive learning related plasticity. One way that prediction errors ...could drive learning is by activating neuromodulatory systems to gate plasticity. The catecholaminergic locus coeruleus (LC) is a major neuromodulatory system involved in neuronal plasticity in the cortex. Using two-photon calcium imaging in mice exploring a virtual environment, we found that the activity of LC axons in the cortex correlated with the magnitude of unsigned visuomotor prediction errors. LC response profiles were similar in both motor and visual cortical areas, indicating that LC axons broadcast prediction errors throughout the dorsal cortex. While imaging calcium activity in layer 2/3 of the primary visual cortex, we found that optogenetic stimulation of LC axons facilitated learning of a stimulus-specific suppression of visual responses during locomotion. This plasticity - induced by minutes of LC stimulation - recapitulated the effect of visuomotor learning on a scale that is normally observed during visuomotor development across days. We conclude that prediction errors drive LC activity, and that LC activity facilitates sensorimotor plasticity in the cortex, consistent with a role in modulating learning rates.
Roots promote the formation of slow‐cycling soil carbon (C), yet we have a limited understanding of the magnitude and controls on this flux. We hypothesised arbuscular mycorrhizal (AM)‐ and ...ectomycorrhizal (ECM)‐associated trees would exhibit differences in root‐derived C accumulation in the soil, and that much of this C would be transferred into mineral‐associated pools. We installed δ13C‐enriched ingrowth cores across mycorrhizal gradients in six Eastern U.S. forests (n = 54 plots). Overall, root‐derived C was 54% greater in AM versus ECM‐dominated plots. This resulted in nearly twice as much root‐derived C in putatively slow‐cycling mineral‐associated pools in AM compared to ECM plots. Given that our estimates of root‐derived inputs were often equal to or greater than leaf litter inputs, our results suggest that variation in root‐derived soil C accumulation due to tree mycorrhizal dominance may be a key control of soil C dynamics in forests.
Plant carbon (C) inputs to soils represent a major ecosystem C flux, with belowground inputs disproportionately important for soil C accumulation. Here we demonstrate both the impressive magnitude of root‐derived C accumulation in soils as well as how plant mycorrhizal association can drive variation in soil C dynamics through differences in belowground C supply. Across six temperate U.S. forests, we find greater root‐derived C accumulation in forest plots dominated by arbuscular mycorrhizal (AM)‐associated trees compared to plots dominated by ectomycorrhizal (ECM)‐associated trees.
We explore the regulation of star formation in star-forming galaxies through a suite of high-resolution isolated galaxy simulations. We use the smoothed particle hydrodynamics code gasoline, ...including photoelectric heating and metal cooling, which produces a multi-phase interstellar medium (ISM). We show that representative star formation and feedback sub-grid models naturally lead to a weak, sub-linear dependence between the amount of star formation and changes to star formation parameters. We incorporate these sub-grid models into an equilibrium pressure-driven regulation framework. We show that the sub-linear scaling arises as a consequence of the non-linear relationship between scaleheight and the effective pressure generated by stellar feedback. Thus, simulated star formation regulation is sensitive to how well vertical structure in the ISM is resolved. Full galaxy discs experience density waves which drive locally time-dependent star formation. We develop a simple time-dependent, pressure-driven model that reproduces the response extremely well.
Homeostatic regulation has been shown to restore cortical activity in vivo following sensory deprivation, but it is unclear whether this recovery is uniform across all cells or specific to a subset ...of the network. To address this issue, we used chronic calcium imaging in behaving adult mice to examine the activity of individual excitatory and inhibitory neurons in the same region of the layer 2/3 monocular visual cortex following enucleation. We found that only a fraction of excitatory neurons homeostatically recover activity after deprivation and inhibitory neurons show no recovery. Prior to deprivation, excitatory cells that did recover were more likely to have significantly correlated activity with other recovering excitatory neurons, thus forming a subnetwork of recovering neurons. These network level changes are accompanied by a reduction in synaptic inhibition onto all excitatory neurons, suggesting that both synaptic mechanisms and subnetwork activity are important for homeostatic recovery of activity after deprivation.
•In adult cortex, a subset of excitatory neurons recover activity after enucleation•Inhibitory neurons do not homeostatically recover activity over 72 hr•Excitatory neurons recover in subnetwork specific manner•Recovery of activity is facilitated by reduced synaptic inhibition
Barnes et al. examine homeostatic recovery of activity of individual excitatory and inhibitory neurons in the adult cortex following enucleation. A fraction of excitatory neurons recover activity, in a subnetwork specific manner, but inhibitory cells do not recover activity over 72 hr.
Chaos and variance in galaxy formation Keller, B W; Wadsley, J W; Wang, L ...
Monthly notices of the Royal Astronomical Society,
01/2019, Letnik:
482, Številka:
2
Journal Article
PDF
