Extragalactic Peaked-Spectrum Radio Sources at Low-Frequencies are Young Radio Galaxies

© 2022 Dementia and Geriatric Cognitive Disorders. All rights reserved. This is an Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0).We present a sample of 373 peaked-spectrum (PS) sources with spectral peaks around 150 MHz, selected using a subset of the two LOw Frequency ARray (LOFAR) all-sky surveys, the LOFAR Two Meter Sky Survey and the LOFAR LBA Sky Survey. These LOFAR surveys are the most sensitive low-frequency widefield surveys to date, allowing us to select low-luminosity peaked-spectrum sources. Our sample increases the number of known PS sources in our survey area by a factor 50. The 5 GHz luminosity distribution of our PS sample shows we sample the lowest luminosity PS sources to date by nearly an order of magnitude. Since high-frequency gigahertz-peaked spectrum sources and compact steep-spectrum sources are hypothesised to be the precursors to large radio galaxies, we investigate whether this is also the case for our sample of low-frequency PS sources. Using optical line emission criteria, we find that our PS sources are predominately high-excitation radio galaxies instead of low-excitation radio galaxies, corresponding to a quickly evolving population. We compute the radio source counts of our PS sample, and find they are scaled down by a factor of ≈40 compared to a general sample of radio-loud active galactic nuclei (AGN). This implies that the lifetimes of PS sources are 40 times shorter than large-scale radio galaxies if their luminosity functions are identical. To investigate this, we compute the first radio luminosity function for a homogeneously selected PS sample. We find that for 144 MHz luminosities ≳1025 W Hz-1, the PS luminosity function has the same shape as an unresolved radio-loud AGN population, but shifted down by a factor of ≈-pagination10. We interpret this as strong evidence that these high-luminosity PS sources evolve into large-scale radio-loud AGN. For local low-luminosity PS sources, there is a surplus of PS sources, which we hypothesise to be the addition of frustrated PS sources that do not evolve into large-scale AGN.Peer reviewe

Genotoxic mixtures and dissimilar action: Concepts for prediction and assessment

This article has been made available through the Brunel Open Access Publishing Fund. This article is distributed under the terms of the creative commons Attribution license which permits any use, distribution, and reproduction in any medium, provided the original author(s)and the source are credited.Combinations of genotoxic agents have frequently been assessed without clear assumptions regarding their expected (additive) mixture effects, often leading to claims of synergisms that might in fact be compatible with additivity. We have shown earlier that the combined effects of chemicals, which induce micronuclei (MN) in the cytokinesis-block micronucleus assay in Chinese hamster ovary-K1 cells by a similar mechanism, were additive according to the concept of concentration addition (CA). Here, we extended these studies and investigated for the first time whether valid additivity expectations can be formulated for MN-inducing chemicals that operate through a variety of mechanisms, including aneugens and clastogens (DNA cross-linkers, topoisomerase II inhibitors, minor groove binders). We expected that their effects should follow the additivity principles of independent action (IA). With two mixtures, one composed of various aneugens (colchicine, flubendazole, vinblastine sulphate, griseofulvin, paclitaxel), and another composed of aneugens and clastogens (flubendazole, doxorubicin, etoposide, melphalan and mitomycin C), we observed mixture effects that fell between the additivity predictions derived from CA and IA. We achieved better agreement between observation and prediction by grouping the chemicals into common assessment groups and using hybrid CA/IA prediction models. The combined effects of four dissimilarly acting compounds (flubendazole, paclitaxel, doxorubicin and melphalan) also fell within CA and IA. Two binary mixtures (flubendazole/paclitaxel and flubendazole/doxorubicin) showed effects in reasonable agreement with IA additivity. Our studies provide a systematic basis for the investigation of mixtures that affect endpoints of relevance to genotoxicity and show that their effects are largely additive.UK Food Standards Agenc

Dispelling urban myths about default uncertainty factors in chemical risk assessment - Sufficient protection against mixture effects?

© 2013 Martin et al.; licensee BioMed Central LtdThis article has been made available through the Brunel Open Access Publishing Fund.Assessing the detrimental health effects of chemicals requires the extrapolation of experimental data in animals to human populations. This is achieved by applying a default uncertainty factor of 100 to doses not found to be associated with observable effects in laboratory animals. It is commonly assumed that the toxicokinetic and toxicodynamic sub-components of this default uncertainty factor represent worst-case scenarios and that the multiplication of those components yields conservative estimates of safe levels for humans. It is sometimes claimed that this conservatism also offers adequate protection from mixture effects. By analysing the evolution of uncertainty factors from a historical perspective, we expose that the default factor and its sub-components are intended to represent adequate rather than worst-case scenarios. The intention of using assessment factors for mixture effects was abandoned thirty years ago. It is also often ignored that the conservatism (or otherwise) of uncertainty factors can only be considered in relation to a defined level of protection. A protection equivalent to an effect magnitude of 0.001-0.0001% over background incidence is generally considered acceptable. However, it is impossible to say whether this level of protection is in fact realised with the tolerable doses that are derived by employing uncertainty factors. Accordingly, it is difficult to assess whether uncertainty factors overestimate or underestimate the sensitivity differences in human populations. It is also often not appreciated that the outcome of probabilistic approaches to the multiplication of sub-factors is dependent on the choice of probability distributions. Therefore, the idea that default uncertainty factors are overly conservative worst-case scenarios which can account both for the lack of statistical power in animal experiments and protect against potential mixture effects is ill-founded. We contend that precautionary regulation should provide an incentive to generate better data and recommend adopting a pragmatic, but scientifically better founded approach to mixture risk assessment. © 2013 Martin et al.; licensee BioMed Central Ltd.Oak Foundatio

Dutch dairy farmers' perspectives on culling reasons and strategies

Since the abolishment of the milk quota system in Europe in 2014 and the introduction of environmental policies such as the phosphate rights system in the Netherlands, the reasons for culling dairy cows might have changed. The aim of this study was to determine the culling reasons for dairy cattle and to identify farmers' culling strategies and their intentions regarding the alteration of indicated culling strategies. To this end, an online questionnaire was distributed among dairy farmers nationally that resulted in 207 responses. Results showed that the most frequent culling reasons were related to problems with reproduction, udder, and hoof health. Primiparous cows were primarily culled for miscellaneous reasons such as injury, reproduction failure, and low milk yield. Multiparous cows were culled predominantly for reproduction failure, udder health and hoof health reasons. Most respondents indicated that they consider formulating a culling strategy, based on certain rules of thumb regarding the most common reasons for culling. Most farmers also reported that culling decisions on their farms were perceived to be unavoidable, though reproductive culling decisions are primarily voluntary. Most respondents stated that they intended to reduce the culling rate for better economic gain did not intend to alter the amount of replacement stock reared. The applied rules of thumb regarding culling strategies do not seem to have changed since the policy changes in dairy farming. The question remains whether farmers' rules of thumb might have made them unaware of the actual economic consequences of their culling strategies under the altered situation

Early-life antibiotic use and risk of asthma and eczema:results of a discordant twin study

RATIONALE: Early-life antibiotic use has been associated with development of atopic diseases, but the aetiology remains unclear. To elucidate aetiology, we used a discordant twin design to control for genetic and environmental confounding. METHODS: We conducted a retrospective cohort study in twins (3-10 years) from the Netherlands Twin Register (NTR, n=34 352) and a replication study at age 9 in the Childhood and Adolescent Twin Study in Sweden (CATSS, n=7906). Antibiotic use was recorded at 0-2 years. Doctor diagnosed asthma and eczema were reported by parents when children were 3-12 years in both cohorts. Individuals were included in unmatched analyses and in co-twin control analyses with disease discordant twin pairs. RESULTS: Early-life antibiotic use was associated with increased risk of asthma (NTR OR 1.34 95%CI 1.28-1.41; CATSS 1.45 95%CI 1.34-1.56) and eczema (NTR OR 1.08 95%CI 1.03-1.13; CATSS 1.07 95%CI 1.01-1.14) in unmatched analyses. Co-twin analyses in mono- and dizygotic twin pairs showed similar results for asthma (NTR 1.54 95%CI 1.20-1.98 and CATSS 2.00 95%CI 1.28-3.13), but opposing results for eczema in NTR (0.99 95%CI 0.80-1.25) and CATSS (1.67 95%CI 1.12-2.49). The risk of asthma increased for antibiotics prescribed for respiratory infections (CATSS 1.45 95%CI 1.34-1.56), but not for antibiotics commonly used for urinary tract/skin infections (CATSS 1.02 95%CI 0.88-1.17). CONCLUSION: Children exposed to early-life antibiotic use, particularly prescribed for respiratory infections, may be at higher risk of asthma. This risk can still be observed, when correcting for genetic and environmental factors. Our results could not elucidate whether the relationship between early-life antibiotic use and eczema is confounded by familial and genetic factors