ABSTRACT The main sequence (MS) of star-forming (SF) galaxies plays a fundamental role in driving galaxy evolution and our efforts to understand it. However, different studies find significant ...differences in the normalization, slope, and shape of the MS. These discrepancies arise mainly from the different selection criteria adopted to isolate SF galaxies, which may include or exclude galaxies with a specific star formation rate (SFR) substantially below the MS value. To obviate this limitation of all current criteria, we propose an objective definition of the MS that does not rely at all on a pre-selection of SF galaxies. Constructing the 3D SFR-mass-number plot, the MS is then defined as the ridge line of the SF peak, as illustrated with various figures. The advantages of such a definition are manifold. If generally adopted, it will facilitate the inter-comparison of results from different groups using the same SFR and stellar mass diagnostics, or it will highlight the relative systematics of different diagnostics. All of this could help to understand MS galaxies as systems in a quasi-steady state equilibrium and would also provide a more objective criterion for identifying quenching galaxies.
Disc growth and quenching Peng, Ying-jie; Renzini, Alvio
Monthly notices of the Royal Astronomical Society. Letters,
01/2020, Letnik:
491, Številka:
1
Journal Article
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ABSTRACT Based on well-established scaling relation for star-forming galaxies as a function of redshift, we argue that the implied growth by a large factor of their angular momentum requires that the ...angular momentum of the inflowing gas fuelling star formation and disc growth must also secularly increase. We then propose that star formation in discs can cease (quench) once the accreted material (mainly atomic hydrogen) comes in with excessive angular momentum for sustaining an adequate radial flow of cold, molecular gas. Existing observational evidence supporting this scenario is mentioned, together with some future observational studies that may validate (or invalidate) it.
Carotid bodies are the principal sensory organs for detecting changes in arterial blood oxygen concentration, and the carotid body chemoreflex is a major regulator of the sympathetic tone, blood ...pressure and breathing. Intermittent hypoxia is a hallmark manifestation of obstructive sleep apnoea (OSA), which is a widespread respiratory disorder. In the first part of this review, we discuss the role of carotid bodies in heightened sympathetic tone and hypertension in rodents treated with intermittent hypoxia, and the underlying cellular, molecular and epigenetic mechanisms. We also present evidence for hitherto‐uncharacterized role of carotid body afferents in triggering cellular and molecular changes induced by intermittent hypoxia. In the second part of the review, we present evidence for a contribution of a hypersensitive carotid body to OSA and potential therapeutic intervention to mitigate OSA in a murine model.
figure legend Hyperactive sympathetic nervous system (SNA) and hypertension are major comorbidities of obstructive sleep apnea (OSA). Intermittent hypoxia (IH) is a hallmark manifestation of OSA. First part of the review discuss the role of hyperactive CB in sympathetic activation and hypertension and underlying cellular and molecular mechanisms in rodents treated with IH (left panel). Second part of the review presents evidence for hyperactive CB as a cause of OSA in a murine model (right panel). Abbreviations: CSE, cystathionine‐gama‐lyase; HO2, hemeoxygease‐2; KO, knockout; ROS, reactive oxygen species.
We explore the basic parameters that drive the evolution of the fundamental properties of star-forming galaxies within the ‘gas regulator model’, or bathtub-model. From the five basic equations of ...the typical gas regulator model, we derive the general analytic form of the evolution of the key galaxy properties, i.e. gas mass, star formation rate (SFR), stellar mass, specific SFR (sSFR), gas fraction, gas phase metallicity and stellar metallicity, without assuming that galaxies live in the equilibrium state. We find that the timescale required to reach equilibrium, τeq, which is determined by the product of star formation efficiency ε and mass-loading factor λ, is the central parameter in the gas regulator model that is essentially in control of the evolution of all key galaxy properties. The scatters in most of the key scaling relations, such as the stellar mass–SFR relation and stellar mass–metallicity relation, are primarily governed by τeq. Most strikingly, the predicted sSFR evolution is controlled solely by τeq (apart from the cosmic time), independent of the gas inflow rate and of the individual values of ε and λ. Although the precise evolution of the sSFR depends on τeq, the sSFR history is largely insensitive to different values of τeq. The difference between the minimum and maximum sSFR at any epoch is less than a factor of 4 for any given values of τeq. The shape of the predicted sSFR history simply mimics that of the specific mass increase rate of the dark matter halos (sMIRDM) with the typical value of the sSFR around 2 × sMIRDM. We show that the predicted sSFR from the gas regulator model is in good agreement with the predictions from typical semi-analytic models (SAMs), but both are fundamentally different from the observed sSFR history. This clearly implies that some key process is missing in both typical SAMs and gas regulator model, and we hint at some possible culprit. We emphasize the critical role of τeq in controlling the evolution of the galaxy population, especially for gas rich low-mass galaxies and dwarf galaxies that are very unlikely to live around the equilibrium state at any epoch and this has been largely ignored in many similar studies.
Lightweight metal‐polymer composited foam has drawn considerable attention in fields of wearable electronics, acoustic and electromagnetic shielding, automotive and aerospace manufacturing, owing to ...its unique advantages like electrical conductivity and mechanical properties. Herein, a facile strategy is studied for one‐step fabrication of multifunctional liquid metal (LM) permeated expancel microspheres foam (EMLM foam) with controllable shape and size. Specifically, the formation process and mechanism of bicontinuous structure with polymer and liquid metal are explored by real‐time monitoring and finite element simulation. Both experimental and simulating results confirmed a stable 3D metal interconnected network that can be constructed with lower limit of LM (3 vol.%). In addition, based on the unique features of reversible rigidity control, lightweight, electrical conductivity, and mechanical stability, the EMLM foam can exhibit intelligent performance in tunable acoustic, energy absorption, and thermal driving repair. Combined with EMLM foam's facile preparation process and versatility, it can provide the remarkable opportunity to develop the lightweight intelligent devices.
An inside to outside strategy is proposed for one‐step fabrication of lightweight foam (density <0.3 g cm−3) with bicontinuous structure of polymer and metal. A stable conductive network with ultra‐low liquid metal content is constructed and the formation mechanism is studied in detail. The bicontinuous structure endows the foam with excellent reversible and controllable rigidity, lightweight, electrical conductivity, and mechanical stability.
Intermittent hypoxia (IH) is a hallmark manifestation of obstructive sleep apnea (OSA), a widespread disorder of breathing. This Review focuses on the role of hypoxia-inducible factors (HIFs) in ...hypertension, type 2 diabetes (T2D), and cognitive decline in experimental models of IH patterned after O2 profiles seen in OSA. IH increases HIF-1α and decreases HIF-2α protein levels. Dysregulated HIFs increase reactive oxygen species (ROS) through HIF-1-dependent activation of pro-oxidant enzyme genes in addition to reduced transcription of antioxidant genes by HIF-2. ROS in turn activate chemoreflex and suppress baroreflex, thereby stimulating the sympathetic nervous system and causing hypertension. We also discuss how increased ROS generation by HIF-1 contributes to IH-induced insulin resistance and T2D as well as disrupted NMDA receptor signaling in the hippocampus, resulting in cognitive decline.
Radiocesium remediation is desirable for ecological protection, human health and sustainable development of nuclear energy. Effective capture of Cs
from acidic solutions is still challenging, mainly ...due to the low stability of the adsorbing materials and the competitive adsorption of protons. Herein, the rapid and highly selective capture of Cs
from strongly acidic solutions is achieved by a robust K
-directed layered metal sulfide KInSnS
(InSnS-1) that exhibits excellent acid and radiation resistance. InSnS-1 possesses high adsorption capacity for Cs
and can serve as the stationary phase in ion exchange columns to effectively remove Cs
from neutral and acidic solutions. The adsorption of Cs
and H
O
is monitored by single-crystal structure analysis, and thus the underlying mechanism of selective Cs
capture from acidic solutions is elucidated at the molecular level.
The impact of missing data on quantitative research can be serious, leading to biased estimates of parameters, loss of information, decreased statistical power, increased standard errors, and ...weakened generalizability of findings. In this paper, we discussed and demonstrated three principled missing data methods: multiple imputation, full information maximum likelihood, and expectation-maximization algorithm, applied to a real-world data set. Results were contrasted with those obtained from the complete data set and from the listwise deletion method. The relative merits of each method are noted, along with common features they share. The paper concludes with an emphasis on the importance of statistical assumptions, and recommendations for researchers. Quality of research will be enhanced if (a) researchers explicitly acknowledge missing data problems and the conditions under which they occurred, (b) principled methods are employed to handle missing data, and (c) the appropriate treatment of missing data is incorporated into review standards of manuscripts submitted for publication.
Wheat plants are ubiquitously simultaneously exposed to salinity and limited iron availability caused by soil saline‐alkalisation. Through this study, we found that both low Fe and NaCl severely ...inhibited the growth of seminal roots in wheat seedlings; however, sufficient Fe caused greater growth cessation of seminal roots than low Fe under salt stress. Low Fe improved the root meristematic division activity, not altering the mature cell sizes compared with sufficient Fe under salt stress. Foliar Fe spray and split‐root experiments showed that low Fe‐alleviating the salinity‐induced growth cessation of seminal roots was dependent on local low Fe signals in the roots. Ionomics combined with TEM/X‐ray few differences in the root Na+ uptake and vacuolar Na+ sequestration between two Fe levels under salt stress. Phytohormone profiling and metabolomics revealed salinity‐induced overaccumulation of ACC/ethylene and tryptophan/auxin in the roots under sufficient Fe than under low Fe. Differential gene expression, pharmacological inhibitor addition and the root growth performance of transgenic wheat plants revealed that the rootward auxin efflux and was responsible for the low Fe‐mediated amelioration of the salinity‐induced growth cessation of seminal roots. Our findings will provide novel insights into the modulation of crop root growth under salt stress.
Summary statement
We found that low Fe ameliorated the salinity‐induced growth cessation of wheat seminal roots, and our findings will provide novel insights into the understanding of Fe involved nutrient interactions and the modulation of crop root growth under salt stress.
We explore the dependence of the galaxy mass-metallicity relation on environment in SDSS, in terms of both over-density and central/satellite dichotomy. We find that at a given stellar mass, there is ...a strong dependence of metallicity on over-density for star-forming satellites (i.e. all galaxies members of groups/clusters which are not centrals). High metallicity satellites reside, on average, in regions four times denser than the low metallicity ones. Instead, for star-forming centrals no correlation is found. Star-forming satellites at different stellar masses form a tight sequence in the average over-density - metallicity plane, which covers the entire observed range of metallicities and stellar masses. This remarkable result appears to imply that there exists a universal evolutionary path for all star-forming satellites, regardless of their stellar masses. The strong correlation between over-density and metallicity for star-forming satellites indicates that the gas inflow of satellite galaxies is progressively metal-enriched in denser regions. We interpret our results by employing the gas regulator model and find that the metallicity of the enriched inflow of star-forming satellite galaxies, Z
0, sat, strongly increases with increasing over-density. The derived Z
0, sat- overdensity relation is largely independent of stellar mass and can be well described by a simple power law. If the metallicity of the inflow of star-forming satellites can represent the metallicity of the IGM, then the implied metallicity of the IGM rises from ∼0.01 Z in the void-like environment to ∼0.3 Z in the cluster-like environment, in broad agreement with observations. We show that the observed metallicity difference between star-forming centrals and star-forming satellites becoming smaller towards high stellar masses can be simply explained by the mass-independent enriched inflow, without the need to involve any mass-dependent environmental effect on metallicity. Since satellite galaxies account for at least half of the galaxy population, our findings prompt for a revision of many galaxy evolutionary models, which generally assume pristine gas inflows.
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