A sample of 18 286 radio-loud active galactic nuclei (AGN) is presented, constructed by combining the seventh data release of the Sloan Digital Sky Survey with the NRAO (National Radio Astronomy ...Observatory) VLA (Very Large Array) Sky Survey (NVSS) and the Faint Images of the Radio Sky at Twenty centimetres (FIRST) survey. Using this sample, the differences between radio galaxies of 'high-excitation' ('quasar-mode'; hereafer HERG) and 'low-excitation' ('radio-mode'; LERG) are investigated. A primary difference between the two radio source classes is the distinct nature of the Eddington-scaled accretion rate on to their central black holes: HERGs typically have accretion rates between one per cent and 10 per cent of their Eddington rate, whereas LERGs predominately accrete at a rate below one per cent Eddington. This is consistent with models whereby the population dichotomy is caused by a switch between radiatively efficient and radiatively inefficient accretion modes at low accretion rates. Local radio luminosity functions are derived separately for the two populations, for the first time, showing that although LERGs dominate at low radio luminosity and HERGs begin to take over at L
1.4 GHz∼ 1026 W Hz−1, examples of both classes are found at all radio luminosities. Using the V/V
max test it is shown that the two populations show differential cosmic evolution at fixed radio luminosity: HERGs evolve strongly at all radio luminosities, while LERGs show weak or no evolution. This suggests that the luminosity dependence of the evolution previously seen in the radio luminosity function is driven, at least in part, by the changing relative contributions of these two populations with luminosity. The host galaxies of the radio sources are also distinct: HERGs are typically of lower stellar mass, with lower black hole masses, bluer colours, lower concentration indices and less pronounced 4000 Å breaks indicating younger stellar populations. Even if samples are matched in radio luminosity and stellar and black hole masses, significant differences still remain between the accretion rates, stellar populations and structural properties of the host galaxies of the two radio source classes. These results offer strong support to the developing picture of radio-loud AGN in which HERGs are fuelled at high rates through radiatively efficient standard accretion discs by cold gas, perhaps brought in through mergers and interactions, while LERGs are fuelled via radiatively inefficient flows at low accretion rates. In this picture, the gas supplying the LERGs is frequently associated with the hot X-ray haloes surrounding massive galaxies, groups and clusters, as part of a radio-AGN feedback loop.
High levels of penetrating cryoprotectants (CPAs) can eliminate ice formation during cryopreservation of cells, tissues, and organs to cryogenic temperatures. But CPAs become increasingly toxic as ...concentration increases. Many strategies have been attempted to overcome the problem of eliminating ice while minimizing toxicity, such as attempting to optimize cooling and warming rates, or attempting to optimize time of adding individual CPAs during cooling. Because strategies currently used are not adequate, CPA toxicity remains the greatest obstacle to cryopreservation. CPA toxicity stands in the way of cryogenic cryopreservation of human organs, a procedure that has the potential to save many lives. This review attempts to describe what is known about CPA toxicity, theories of CPA toxicity, and strategies to reduce CPA toxicity. Critical analysis and suggestions are also included.
The development of facile and versatile strategies for thin-film and particle engineering is of immense scientific interest. However, few methods can conformally coat substrates of different ...composition, size, shape, and structure. We report the one-step coating of various interfaces using coordination complexes of natural polyphenols and Fe(III) ions. Film formation is initiated by the adsorption of the polyphenol and directed by pH-dependent, multivalent coordination bonding. Aqueous deposition is performed on a range of planar as well as inorganic, organic, and biological particle templates, demonstrating an extremely rapid technique for producing structurally diverse, thin films and capsules that can disassemble. The ease, low cost, and scalability of the assembly process, combined with pH responsiveness and negligible cytotoxicity, makes these films potential candidates for biomedical and environmental applications.
The effect of extracellular polymeric substances (EPS) on the meso-scale physical structure and hydraulic resistance of membrane biofilms during gravity driven membrane (GDM) filtration was ...investigated. Biofilms were developed on the surface of ultrafiltration membranes during dead-end filtration at ultra-low pressure (70 mbar). Biofilm EPS composition (total protein, polysaccharide and eDNA) was manipulated by growing biofilms under contrasting nutrient conditions. Nutrient conditions consisted of (i) a nutrient enriched condition with a nutrient ratio of 100:30:10 (C: N: P), (ii) a phosphorus limitation (C: N: P ratio: 100:30:0), and (iii) a nitrogen limitation (C: N: P ratio: 100:0:10). The structure of the biofilm was characterised at meso-scale using Optical Coherence Tomography (OCT). Biofilm composition was analysed with respect to total organic carbon, total cellular mass and extracellular concentrations of proteins, polysaccharides, and eDNA. 2D-confocal Raman mapping was used to characterise the functional group composition and micro-scale distribution of the biofilms EPS. Our study reveals that the composition of the EPS matrix can determine the meso-scale physical structure of membrane biofilms and in turn its hydraulic resistance. Biofilms grown under P limiting conditions were characterised by dense and homogeneous physical structures with high concentrations of polysaccharides and eDNA. Biofilm grown under nutrient enriched or N limiting conditions were characterised by heterogeneous physical structures with lower concentrations of polysaccharides and eDNA. For P limiting biofilms, 2D-confocal Raman microscopy revealed a homogeneous spatial distribution of anionic functional groups in homogeneous biofilm structures with higher polysaccharide and eDNA concentrations. This study links EPS composition, physical structure and hydraulic resistance of membrane biofilms, with practical relevance for the hydraulic performances of GDM ultrafiltration.
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•Hydraulic resistance of biofilms formed during GDM filtration was studied.•Influent composition determined EPS chemical composition.•Resulting EPS compositions were linked to distinct physical structures.•Hydraulic resistance was dependent on biofilm thickness and density.
We present a study of the prevalence of optical and radio nuclear activity with respect to the environment and interactions in a sample of the Sloan Digital Sky Survey (SDSS) galaxies. The aim is to ...determine the independent effects of distinct aspects of source environment on the triggering of different types of nuclear activity. We defined a local density parameter and a tidal force estimator and used a cluster richness estimator from the literature to trace different aspects of environment and interaction. The possible correlations between the environmental parameters were removed using a principal component analysis. By far, the strongest trend found for the active galactic nuclei (AGN) fractions, of all AGN types, is with galaxy mass. We therefore applied a stratified statistical method that takes into account the effect of possible confounding factors like the galaxy mass. We found that (at fixed mass) the prevalence of optical AGN is a factor of 2-3 lower in the densest environments, but increases by a factor of ∼2 in the presence of strong one-on-one interactions. These effects are even more pronounced for star-forming nuclei. The importance of galaxy interactions decreases from star-forming nuclei to Seyferts to low-ionization nuclear emission-line regions to passive galaxies, in accordance with previous suggestions of an evolutionary time-sequence. The fraction of radio AGN increases very strongly (by nearly an order of magnitude) towards denser environments, and is also enhanced by galaxy interactions. Overall, the results agree with a scenario in which the mechanisms of accretion into the black hole are determined by the presence and nature of a supply of gas, which in turn is controlled by the local density of galaxies and their interactions. A plentiful cold gas supply is required to trigger star formation, optical AGN and radiatively efficient radio AGN. This is less common in the cold-gas-poor environments of groups and clusters, but is enhanced by one-on-one interactions which result in the flow of gas into nuclear regions; these two factors compete against each other. In the denser environments where cold gas is rare, cooling hot gas can supply the nucleus at a sufficient rate to fuel low-luminosity radiatively inefficient radio AGN. However, the increased prevalence of these AGN in interacting galaxies suggests that this is not the only mechanism by which radiatively inefficient AGN can be triggered.
We investigate the evolution of the H β + O iii and O ii luminosity functions from z ∼ 0.8 to ∼5 in four redshift slices per emission line using data from the High-z Emission Line Survey (HiZELS). ...This is the first time that the H β + O iii and O ii luminosity functions have been studied at these redshifts in a self-consistent analysis. This is also the largest sample of O ii and H β + O iii emitters (3475 and 3298 emitters, respectively) in this redshift range, with large comoving volumes ∼1 × 106 Mpc−3 in two independent volumes (COSMOS and UDS), greatly reducing the effects of cosmic variance. The emitters were selected by a combination of photometric redshift and colour–colour selections, as well as spectroscopic follow-up, including recent spectroscopic observations using DEIMOS and MOSFIRE on the Keck Telescopes and FMOS on Subaru. We find a strong increase in L
⋆ and a decrease in ϕ⋆ for both H β + O iii and O ii emitters. We derive the O ii star formation history of the Universe since z ∼ 5 and find that the cosmic star formation rate density (SFRD) rises from z ∼ 5 to ∼3 and then drops towards z ∼ 0. We also find that our star formation history is able to reproduce the evolution of the stellar mass density up to z ∼ 5 based only on a single tracer of star formation. When comparing the H β + O iii SFRDs to the O ii and H α SFRD measurements in the literature, we find that there is a remarkable agreement, suggesting that the H β + O iii sample is dominated by star-forming galaxies at high-z rather than AGNs.
Abstract
We present a study of the low-frequency radio properties of star-forming (SF) galaxies and active galactic nuclei (AGNs) up to redshift z = 2.5. The new spectral window probed by the Low ...Frequency Array (LOFAR) allows us to reconstruct the radio continuum emission from 150 MHz to 1.4 GHz to an unprecedented depth for a radio-selected sample of 1542 galaxies in ∼ 7 deg2 of the LOFAR Boötes field. Using the extensive multiwavelength data set available in Boötes and detailed modelling of the far-infrared to ultraviolet spectral energy distribution (SED), we are able to separate the star formation (N = 758) and the AGN (N = 784) dominated populations. We study the shape of the radio SEDs and their evolution across cosmic time and find significant differences in the spectral curvature between the SF galaxy and AGN populations. While the radio spectra of SF galaxies exhibit a weak but statistically significant flattening, AGN SEDs show a clear trend to become steeper towards lower frequencies. No evolution of the spectral curvature as a function of redshift is found for SF galaxies or AGNs. We investigate the redshift evolution of the infrared–radio correlation for SF galaxies and find that the ratio of total infrared to 1.4-GHz radio luminosities decreases with increasing redshift: q
1.4 GHz = (2.45 ± 0.04) (1 + z)−0.15 ± 0.03. Similarly, q
150 MHz shows a redshift evolution following q
150 GHz = (1.72 ± 0.04) (1 + z)−0.22 ± 0.05. Calibration of the 150 MHz radio luminosity as a star formation rate tracer suggests that a single power-law extrapolation from q
1.4 GHz is not an accurate approximation at all redshifts.
Abstract
We present the results of the first, deep Atacama Large Millimeter Array (ALMA) imaging covering the full ≃4.5 arcmin2 of the Hubble Ultra Deep Field (HUDF) imaged with Wide Field Camera ...3/IR on HST. Using a 45-pointing mosaic, we have obtained a homogeneous 1.3-mm image reaching σ1.3 ≃ 35 μJy, at a resolution of ≃0.7 arcsec. From an initial list of ≃50 > 3.5σ peaks, a rigorous analysis confirms 16 sources with S
1.3 > 120 μJy. All of these have secure galaxy counterparts with robust redshifts (〈z〉 = 2.15). Due to the unparalleled supporting data, the physical properties of the ALMA sources are well constrained, including their stellar masses (M
*) and UV+FIR star formation rates (SFR). Our results show that stellar mass is the best predictor of SFR in the high-redshift Universe; indeed at z ≥ 2 our ALMA sample contains seven of the nine galaxies in the HUDF with M
* ≥ 2 × 1010 M⊙, and we detect only one galaxy at z > 3.5, reflecting the rapid drop-off of high-mass galaxies with increasing redshift. The detections, coupled with stacking, allow us to probe the redshift/mass distribution of the 1.3-mm background down to S
1.3 ≃ 10 μJy. We find strong evidence for a steep star-forming ‘main sequence’ at z ≃ 2, with SFR ∝M
* and a mean specific SFR ≃ 2.2 Gyr−1. Moreover, we find that ≃85 per cent of total star formation at z ≃ 2 is enshrouded in dust, with ≃65 per cent of all star formation at this epoch occurring in high-mass galaxies (M
* > 2 × 1010 M⊙), for which the average obscured:unobscured SF ratio is ≃200. Finally, we revisit the cosmic evolution of SFR density; we find this peaks at z ≃ 2.5, and that the star-forming Universe transits from primarily unobscured to primarily obscured at z ≃ 4.
There is some evidence that increased maternal intake of omega-3 (n-3) long-chain polyunsaturated fatty acids (LC-PUFAs) during pregnancy may reduce the incidence of immunoglobulin E (IgE)-mediated ...allergic disease.
We aimed to evaluate prenatal n-3 LC-PUFA dietary exposure in observational studies and n-3 LC-PUFA supplementation in randomized controlled trials (RCTs) on outcomes of IgE-mediated allergic disease.
We conducted searches of the Cochrane Central Register of Controlled Trials, PubMed, Ovid MEDLINE, EMBASE, CINAHL, SCOPUS, and Web of Science to 30 July 2015. We included prospective cohort studies that showed an association between maternal fish or n-3 LC-PUFA intake during pregnancy and RCTs with a prenatal intervention to modify maternal n-3 LC-PUFA intake and outcomes of allergic disease (eczema, rhino-conjunctivitis, asthma) or sensitization in the offspring.
A total of 13 publications from 10 prospective cohort studies and 7 publications representing 5 unique RCTs were included. Three RCTs were combined in a meta-analysis for selected outcomes. Nine of 13 observational study publications and 5 of 7 publications from RCTs found a protective association between increased prenatal n-3 LC-PUFA or fish intake and incidence of allergic disease symptoms in the child. Meta-analysis was limited because of the heterogeneity of the RCTs. Pooled results showed a significant reduction in the incidence of "atopic eczema," "any positive SPT skin-prick test," "sensitization to egg," and "sensitization to any food" in the first 12 mo of life RRs (95% CIs): 0.53 (0.35, 0.81), P = 0.004; 0.68 (0.52-0.89), P = 0.006; 0.55 (0.39-0.76), P = 0.0004; and 0.59 (0.46, 0.76), P < 0.0001, respectively.
Our systematic review and meta-analysis was suggestive of benefits of increased n-3 LC-PUFAs in the maternal diet and outcomes of childhood allergic disease. However, due to the inconsistency in results, the hypothesis linking maternal n-3 LC-PUFA intake to childhood allergic disease cannot unequivocally be confirmed or rejected.
Abstract
We present dynamical measurements for 586 Hα-detected star-forming galaxies from the KMOS (K-band Multi-Object Spectrograph) Redshift One Spectroscopic Survey (KROSS). The sample represents ...typical star-forming galaxies at this redshift (z = 0.6–1.0), with a median star formation rate of ≈7 M⊙ yr−1 and a stellar mass range of log (M⋆M⊙) ≈ 9–11. We find that the rotation velocity–stellar mass relationship (the inverse of the Tully–Fisher relationship) for our rotationally dominated sources (vC/σ0 > 1) has a consistent slope and normalization as that observed for z = 0 discs. In contrast, the specific angular momentum (j⋆; angular momentum divided by stellar mass) is ≈0.2–0.3 dex lower on average compared to z = 0 discs. The specific angular momentum scales as $j_{\rm s}\propto M_{\star }^{0.6\pm 0.2}$, consistent with that expected for dark matter (i.e. $j_{\rm DM}\propto M_{\rm DM}^{2/3}$). We find that z ≈ 0.9 star-forming galaxies have decreasing specific angular momentum with increasing Sérsic index. Visually, the sources with the highest specific angular momentum, for a given mass, have the most disc-dominated morphologies. This implies that an angular momentum–mass–morphology relationship, similar to that observed in local massive galaxies, is already in place by z ≈ 1.
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