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  • Oxford University Press  (168,790)
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Years
  • 1
    Publication Date: 2020-01-31
    Description: Deep-towed geophysical surveys require precise knowledge of navigational parameters such as instrument position and orientation because navigational uncertainties reflect in the data and therefore in the inferred geophysical properties of the subseafloor. We address this issue for the case of electrical conductivity inferred from controlled source electromagnetic data. We show that the data error is laterally variable due to irregular motion during deep towing, but also due to lateral variations in conductivity, including those resulting from topography. To address this variability and quantify the data error prior to inversion, we propose a 2-D perturbation study. Our workflow enables stable and geologically reliable results for multicomponent and multifrequency inversions. An error estimation workflow is presented, which comprises the assessment of navigational uncertainties, perturbation of navigational parameters, and forward modelling of electric field amplitudes for a homogeneous and then a heterogeneous subseafloor conductivity model. Some navigational uncertainties are estimated from variations of direct measurements. Other navigational parameters required for inversion are derived from the measured quantities and their error is calculated by means of error propagation. Some navigational parameters show direct correlation with the measured electric fields. For example, the antenna dip correlates with the vertical electric field and the depth correlates with the horizontal electric field. For the perturbation study each standard deviation is added to the navigational parameters. Forward models are run for each perturbation. Amplitude deviations are summed in quadrature with the stacking error for a total, laterally varying, data error. The error estimation is repeated for a heterogeneous subseafloor model due to the large conductivity range (several orders of magnitude), which affects the forward model. The approach enables us to utilize data from several components (multiple electric fields, frequencies and receivers) in the inversion to constrain the final model and reduce ambiguity. The final model is geologically reasonable, in this case enabling the identification of conductive metal sulphide deposits on the seafloor.
    Type: Article , PeerReviewed
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  • 2
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    Oxford University Press
    Publication Date: 2020-03-12
    Description: Due to an exceptional variety of habitats, body plans, and lifestyles, crustaceans exhibit a wide array of mating systems. Some groups engage in simple, pure- search polygamous systems in which males usually search for receptive females. In other groups, males defend valuable resources to attract and/ or guard females to ensure paternity. Some species have developed highly complex systems of harem defense polygyny and monogamy, even cases of sub- and eusociality are reported. The expression of mating systems does not seem to be uniformly correlated to taxonomic affiliation, but is rather diverse within certain groups, suggesting that the evolution of mating systems is largely facilitated by the lifestyle of the species. Despite the broad range of mating systems in crustaceans, and although some groups have been studied comparably well, there remains a lack of knowledge about the behavioral and sexual biology of many species. In the light of the high diversity of lifestyles, mating systems, and habitats of certain groups, crustacean species would be ideal models to unravel the evolution of reproductive strategies and social behaviors.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Inbook , NonPeerReviewed
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  • 3
    Publication Date: 2020-04-23
    Description: Background: The giant squid (Architeuthis dux; Steenstrup, 1857) is an enigmatic giant mollusc with a circumglobal distribution in the deep ocean, except in the high Arctic and Antarctic waters. The elusiveness of the species makes it difficult to study. Thus, having a genome assembled for this deep-sea-dwelling species will allow several pending evolutionary questions to be unlocked. Findings: We present a draft genome assembly that includes 200 Gb of Illumina reads, 4 Gb of Moleculo synthetic long reads, and 108 Gb of Chicago libraries, with a final size matching the estimated genome size of 2.7 Gb, and a scaffold N50 of 4.8 Mb. We also present an alternative assembly including 27 Gb raw reads generated using the Pacific Biosciences platform. In addition, we sequenced the proteome of the same individual and RNA from 3 different tissue types from 3 other species of squid (Onychoteuthis banksii, Dosidicus gigas, and Sthenoteuthis oualaniensis) to assist genome annotation. We annotated 33,406 protein-coding genes supported by evidence, and the genome completeness estimated by BUSCO reached 92%. Repetitive regions cover 49.17% of the genome. Conclusions: This annotated draft genome of A. dux provides a critical resource to investigate the unique traits of this species, including its gigantism and key adaptations to deep-sea environments.
    Type: Article , PeerReviewed
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  • 4
    Publication Date: 2020-04-28
    Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Vallecillo-Viejo, I. C., Liscovitch-Brauer, N., Diaz Quiroz, J. F., Montiel-Gonzalez, Maria F., Nemes, Sonya E., Rangan, K. J., Levinson, S. R., Eisenberg, E., & Rosenthal, J. J. C. Spatially regulated editing of genetic information within a neuron. Nucleic Acids Research, (2020): gkaa172, doi: 10.1093/nar/gkaa172.
    Description: In eukaryotic cells, with the exception of the specialized genomes of mitochondria and plastids, all genetic information is sequestered within the nucleus. This arrangement imposes constraints on how the information can be tailored for different cellular regions, particularly in cells with complex morphologies like neurons. Although messenger RNAs (mRNAs), and the proteins that they encode, can be differentially sorted between cellular regions, the information itself does not change. RNA editing by adenosine deamination can alter the genome’s blueprint by recoding mRNAs; however, this process too is thought to be restricted to the nucleus. In this work, we show that ADAR2 (adenosine deaminase that acts on RNA), an RNA editing enzyme, is expressed outside of the nucleus in squid neurons. Furthermore, purified axoplasm exhibits adenosine-to-inosine activity and can specifically edit adenosines in a known substrate. Finally, a transcriptome-wide analysis of RNA editing reveals that tens of thousands of editing sites (〉70% of all sites) are edited more extensively in the squid giant axon than in its cell bodies. These results indicate that within a neuron RNA editing can recode genetic information in a region-specific manner.
    Description: National Science Foundation (NSF) [IOS1557748 to J.R.]; United States–Israel Binational Science Foundation [BSF2013094 to J.R. and E.E.]; The Grass Foundation grant in support of the Doryteuthis pealeii Genome Project, and a gift by Mr. Edward Owens. Funding for open access charge: United States–Israel Binational Science Foundation [BSF2013094].
    Repository Name: Woods Hole Open Access Server
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  • 5
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    Oxford University Press
    In:  Journal of Plankton Research, 42 (2). pp. 189-202.
    Publication Date: 2020-06-19
    Description: The copepod Acartia tonsa is a key component of a wide range of marine ecosystems, linking energy transfer from phytoplankton to higher trophic levels, and has a central role in productivity and biogeochemistry. The interaction of end-of-century global warming and ocean acidification scenarios with testing moderate temperature effects on a seminatural copepod community is needed to understand future community functioning. Here, we deployed a mesocosm experimental set-up with a full factorial design using two temperatures (13°C and 19°C) crossed with a pCO2 gradient ranging from ambient (550 μatm) to 3000 μatm. We used the natural bacteria, phyto- and microzooplankton species composition and biomass of the Kiel Bight and tested the response of A. tonsa development, carbon growth, mortality, size and condition. The tested traits were differently affected by the interaction of temperature and acidification. Ocean acidification increased development, carbon growth, size and mortality under the warming scenario of 19°C. At 13°C mortality rates decreased, while carbon growth, size and condition increased with acidification. We conclude from our experimental approach that a single species shows a variety of responses depending on the focal functional trait. Trait-specific mesozooplankton responses need to be further investigated and compared between geographical regions, seasons and taxonomic groups.
    Type: Article , PeerReviewed
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  • 6
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    Oxford University Press
    In:  FEMS Microbiology Ecology, 96 (5). fiaa075.
    Publication Date: 2020-06-19
    Type: Article , PeerReviewed
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  • 7
    Publication Date: 2020-07-01
    Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Johnson, W. M., Alexander, H., Bier, R. L., Miller, D. R., Muscarella, M. E., Pitz, K. J., & Smith, H. Auxotrophic interactions: A stabilizing attribute of aquatic microbial communities? FEMS Microbiology Ecology, (2020): fiaa115, doi: 10.1093/femsec/fiaa115.
    Description: Auxotrophy, or an organism's requirement for an exogenous source of an organic molecule, is widespread throughout species and ecosystems. Auxotrophy can result in obligate interactions between organisms, influencing ecosystem structure and community composition. We explore how auxotrophy-induced interactions between aquatic microorganisms affect microbial community structure and stability. While some studies have documented auxotrophy in aquatic microorganisms, these studies are not widespread, and we therefore do not know the full extent of auxotrophic interactions in aquatic environments. Current theoretical and experimental work suggests that auxotrophy links microbial community members through a complex web of metabolic dependencies. We discuss the proposed ways in which auxotrophy may enhance or undermine the stability of aquatic microbial communities, highlighting areas where our limited understanding of these interactions prevents us from being able to predict the ecological implications of auxotrophy. Finally, we examine an example of auxotrophy in harmful algal blooms to place this often theoretical discussion in a field context where auxotrophy may have implications for the development and robustness of algal bloom communities. We seek to draw attention to the relationship between auxotrophy and community stability in an effort to encourage further field and theoretical work that explores the underlying principles of microbial interactions.
    Description: This work was supported by the National Science Foundation [OCE-1356192].
    Keywords: auxotrophy ; microbial community stability ; microbial interactions ; aquatic
    Repository Name: Woods Hole Open Access Server
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  • 8
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    Oxford University Press
    In:  Journal Of Plankton Research, 42 (3). pp. 398-401.
    Publication Date: 2020-07-10
    Description: The present study quantified prey preferences by adult males and females of the mysid Mesopodopsis wooldridgei fed the calanoid copepods Pseudodiaptomus hessei and Paracartia longipatella at varying proportions. Both sexes of M. wooldridgei showed a lack of prey switching and a strong preference for the smaller, less active P. longipatella irrespective of density. Given a lack of low-density prey refuge, this finding may have important implications for the distribution of P. longipatella in estuaries along the eastern seaboard of South Africa. Results of the present study contribute to a growing body of literature that suggests that selective predation may play an important role in structuring plankton prey populations in shallow water ecosystems.
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  • 9
    Publication Date: 2020-07-14
    Description: The two toothed jaws of cichlid fishes provide textbook examples of convergent evolution. Tooth phenotypes such as enlarged molar-like teeth used to process hard-shelled molluscs have evolved numerous times independently during cichlid diversification. While the ecological benefit of molar-like teeth to crush prey is known, it is unclear whether the same molecular mechanisms underlie these convergent traits. To identify genes involved in the evolution and development of enlarged cichlid teeth, we performed RNA-seq on the serially homologous toothed oral and pharyngeal jaws as well as the fourth toothless gill arch of Astatoreochromis alluaudi. We identified 27 genes that are highly upregulated on both tooth-bearing jaws compared to the toothless gill arch. Most of these genes have never been reported to play a role in tooth formation. Two of these genes (unk, rpfA) are not found in other vertebrate genomes but are present in all cichlid genomes. They also cluster genomically with two other highly expressed tooth genes (odam, scpp5) that exhibit conserved expression during vertebrate odontogenesis. Unk and rpfA were confirmed via in situ hybridization to be expressed in developing teeth of Astatotilapia burtoni. We then examined expression of the cluster's four genes in six evolutionarily independent and phylogenetically disparate cichlid species pairs each with a large- and a small-toothed species. Odam and unk commonly and scpp5 and rpfA always showed higher expression in larger-toothed cichlid jaws. Convergent trophic adaptations across cichlid diversity are associated with the repeated developmental deployment of this genomic cluster containing conserved and novel cichlid-specific genes.
    Type: Article , PeerReviewed
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  • 10
    Publication Date: 2020-06-17
    Description: Petrological and geochemical (major element, trace element, Sr–Nd isotope) data for recent (〈5 kyr old) basalts that sporadically erupt on the western flank of Piton de la Fournaise (PdF), one of the most active volcanoes on Earth, allow the tracking of magma transfer and evolution from mantle to crustal depths. In the western peripheral area of PdF we document the broadly synchronous eruptions of (1) primitive olivine and olivine–clinopyroxene transitional basalts with tholeiitic affinity 30 that are closely associated in space with (2) transitional olivine basalts with alkaline affinity, and (3) hybrid lavas, intermediate between the ‘alkaline’ and the ‘tholeiitic’ end-members. The composition of the latter overlaps with that of the lavas frequently erupted from the conduit system feeding the main summit cone. AlphaMELTS modelling, and fluid inclusion and clinopyroxene barometry, constrain the conditions of magma storage at 10–30 km, and the ascent of magma from the upper 35 mantle to the shallow crustal plumbing system. Variable degrees of mantle melting, together with minor source heterogeneity and contamination with cumulate-derived partial melts, contribute to the diversity of PdF magmas. However, all these processes do not represent the dominant factors that produce the large variability we found in major element composition. Indeed, the composition of basalts erupted from PdF peripheral centers is strongly controlled by polybaric olivine–clinopyr- 40 oxene fractionation at pressures higher than 3 kbar. Crystal textures and geochemical modelling suggest that fast magma ascent is critical to prevent clinopyroxene dissolution. Conversely, longlasting magma stagnation promotes pyroxene resorption and magma differentiation. ‘Central’ eruptions occurring close to the PdF summit cone emit variably more evolved melts, which result from olivine–clinopyroxene–plagioclase differentiation at intermediate–shallow pressure (〈3 kbar and in most cases 〈1 kbar). Deep and extensive magma mixing before injection into the crustal magma conduit system, located below the summit region, results in the apparent homogeneity of basalts erupted from the central area. As regards ‘peripheral’ eruptions, deep-seated stagnation of basaltic melts and differentiation at the mantle–crust transition zone (c. 4 kbar) produces a range of 5 magma compositions. We demonstrate that rapid magma ascent from deep-seated reservoirs can bypass the central plumbing system. The eruptions of these magmas both in the central area and on the densely populated flanks have major consequences in terms of volcanic hazard at PdF.
    Description: Published
    Description: 1717–1752
    Description: 2V. Struttura e sistema di alimentazione dei vulcani
    Description: JCR Journal
    Keywords: transitional basalts ; clinopyroxene crystallization and resorption ; mantle–crust underplating
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 11
    Publication Date: 2020-08-12
    Description: Parasites are arguably among the strongest drivers of natural selection, constraining hosts to evolve resistance and tolerance mechanisms. Although, the genetic basis of adaptation to parasite infection has been widely studied, little is known about how epigenetic changes contribute to parasite resistance and eventually, adaptation. Here, we investigated the role of host DNA methylation modifications to respond to parasite infections. In a controlled infection experiment, we used the three-spined stickleback fish, a model species for host-parasite studies, and their nematode parasite Camallanus lacustris. We showed that the levels of DNA methylation are higher in infected fish. Results furthermore suggest correlations between DNA methylation and shifts in key fitness and immune traits between infected and control fish, including respiratory burst and functional trans-generational traits such as the concentration of motile sperm. We revealed that genes associated with metabolic, developmental and regulatory processes (cell death and apoptosis) were differentially methylated between infected and control fish. Interestingly, genes such as the neuropeptide FF receptor 2 and the integrin alpha 1 as well as molecular pathways including the Th1 and Th2 cell differentiation were hypermethylated in infected fish, suggesting parasite-mediated repression mechanisms of immune responses. Altogether, we demonstrate that parasite infection contributes to genome-wide DNA methylation modifications. Our study brings novel insights into the evolution of vertebrate immunity and suggests that epigenetic mechanisms are complementary to genetic responses against parasite-mediated selection.
    Type: Article , PeerReviewed
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  • 12
    Publication Date: 2020-04-07
    Description: Little is known about the mass–metallicity relation (MZR) in galaxies at cosmic dawn. Studying the first appearance of the MZR is one of the keys to understand the formation and evolution of the first galaxies. In order to lay the groundwork for upcoming observational campaigns, we analyse 290 galaxies in haloes spanning Mh = 109–1011 M⊙ selected from the FirstLight cosmological zoom simulations to predict the MZR at z = 5–8. Over this interval, the metallicity of FirstLight galaxies with stellar mass M* = 108 M⊙ declines by ≤0.2 dex. This contrasts with the observed tendency for metallicities to increase at lower redshifts, and reflects weakly evolving or even increasing gas fractions. We assess the use of the R3 strong-line diagnostic as a metallicity indicator, finding that it is informative for 12 + log (O/H) 〈 8 but saturates to R3 ≈ 3 at higher metallicities owing to a cancellation between enrichment and spectral softening. None the less, campaigns with JWST should be able to detect a clear trend between R3 and stellar mass for M* > 107.5 M⊙. We caution that, at fixed metallicity, galaxies with higher specific star formation show higher R3 owing to their more intense radiation fields, indicating a potential for selection biases.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
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  • 13
    Publication Date: 2020-06-04
    Description: Recent declines of macroalgal forests due to climate change imply that the aquaculture production of macroalgae may also be negatively affected by ocean warming. It has previously been shown that nutrient enrichment can offset the negative impact of warming on the survival and growth of the cultivated macroalga Undaria pinnatifida, although it can also increase the risk of herbivory by unrecognized mesograzers. Observations of several hundreds or thousands of the isopod Cymodocea japonica around U. pinnatifida cultivation ropes in autumn, prompted the analysis of their size-frequency distribution, relationship between body size and consumption rate, and combined effects of elevated temperature and nutrient enrichment on the consumption rate of the algae by the isopod in the current study. Although the body size of the isopods collected in autumn was smaller than those collected in winter and spring, the consumption rate of 600 small isopods was similar to the rate of a large individual. Additionally, the consumption rate doubled in response to an increase in temperature from 15 to 18°C and nutrient enrichment, and tripled with their combination. These results suggest that ocean warming combined with nutrient enrichment increase the risk of herbivory during U. pinnatifida cultivation, especially during isopod outbreak periods.
    Print ISSN: 1054-3139
    Electronic ISSN: 1095-9289
    Topics: Biology , Geosciences , Physics
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  • 14
    Publication Date: 2020-04-04
    Description: The observed rate of water production of comet 67P/Churyumov–Gerasimenko near its perihelion can be approximated by a very steep power function of the heliocentric distance. Widely used thermophysical models based on a static dust layer on top of the icy/refractory matrix are poorly consistent with these observations. We analyse published model results and demonstrate that thermophysical models with a uniform and static ice free layer do not reproduce the observed steep water production rates of 67P near perihelion. Based on transient thermal modeling we conclude that the accelerated gas activity can be explained assuming that the active area fraction near the south pole is increased. The deeper penetration of the heat wave during polar day (no sunset) can activate sublimation through thicker inert dust layers. This can also lead to removal of thicker dust layers and consequently to an expansion of the active area.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
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  • 15
    Publication Date: 2020-03-29
    Description: Observed temperatures of transiently accreting neutron stars in the quiescent state are generally believed to be supported by deep crustal heating, associated with non-equilibrium exothermic reactions in the crust. Traditionally, these reactions are studied by considering nuclear evolution governed by compression of the accreted matter. Here we show that this approach has a basic weakness, that is that in some regions of the inner crust the conservative forces, applied for matter components (nuclei and neutrons), are not in mechanical equilibrium. In principle the force balance can be restored by dissipative forces, however the required diffusion fluxes are of the same order as total baryon flux at Eddington accretion. We argue that redistribution of neutrons in the inner crust should be involved in realistic model of accreted crust.
    Print ISSN: 1745-3925
    Electronic ISSN: 1745-3933
    Topics: Physics
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  • 16
    Publication Date: 2020-04-04
    Description: We look at the contribution of different galaxy populations to the atomic hydrogen (H i) mass function (HIMF) and the H i density parameter, ΩH i, in the local Universe. Our analysis is based on a sample of 7857 H i selected galaxies selected from a volume common to the Sloan Digital Sky Survey (SDSS) and Arecibo Fast Legacy ALFA (40 per cent catalogue – α.40) surveys. We define different populations of galaxies in the colour (u − r)–magnitude (Mr) plane and compute the HIMF for each of them. Additionally we compute the HIMF for dark galaxies; these are undetected in SDSS and represent $sim 2{{ m per cent}}$ of the total sample. We find that the luminous red population dominates the total HIMF for $log _{10}(M_{ m{H,{small I}}}h^2_{70}/M_{odot }) ge 10.4$. The full red population – luminous and faint – represents about $sim 17{{ m per cent}}$ of the ΩH i budget, while that of the dark population is $sim 3{{ m per cent}}$. The HIMF about the knee, $log _{10}(M_{ m{H,{small I}}}h^2_{70}/M_{odot }) in [8,10.4]$, is dominated by the faint and luminous blue populations, the latter dominating at larger masses in this interval. Their total contribution to ΩH i is $sim 55!-!70{{ m per cent}}$, the variation depending on the definition of population. The dominant populations at the low-mass end, $log _{10}(M_{ m{H,{small I}}}h^2_{70}/M_{odot }) le 8.0$ are the faint blue and faint bluer populations, the latter’s dominance being sensitive to its definition. The full blue (blue–bluer luminous and faint) population represents $sim 80{{ m per cent}}$ of ΩH i. A bimodal HIMF suggested by our results is however not seen since the amplitude of the HIMF of the luminous red population is small compared to that of the luminous blue population.
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  • 17
    Publication Date: 2020-04-07
    Description: Cosmography becomes non-predictive when cosmic data span beyond the redshift limit z ≃ 1. This leads to a strong convergence issue that jeopardizes its viability. In this work, we critically compare the two main solutions of the convergence problem, i.e. the y-parametrizations of the redshift and the alternatives to Taylor expansions based on Padé series. In particular, among several possibilities, we consider two widely adopted parametrizations, namely y1 = 1−a and $y_2=arctan (a^{-1}-1)$, being a the scale factor of the Universe. We find that the y2-parametrization performs relatively better than the y1-parametrization over the whole redshift domain. Even though y2 overcomes the issues of y1, we get that the most viable approximations of the luminosity distance dL(z) are given in terms of Padé approximations. In order to check this result by means of cosmic data, we analyse the Padé approximations up to the fifth order, and compare these series with the corresponding y-variables of the same orders. We investigate two distinct domains involving Monte Carlo analysis on the Pantheon Superovae Ia data, H(z) and shift parameter measurements. We conclude that the (2,1) Padé approximation is statistically the optimal approach to explain low- and high-redshift data, together with the fifth-order y2-parametrization. At high redshifts, the (3,2) Padé approximation cannot be fully excluded, while the (2,2) Padé one is essentially ruled out.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
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  • 18
    Publication Date: 2020-04-04
    Description: Photospheric emission may originate from relativistic outflows in two qualitatively different regimes: last scattering of photons inside the outflow at the photospheric radius or radiative diffusion to the boundary of the outflow. In this work, the measurement of temperature and flux of the thermal component in the early afterglows of several gamma-ray bursts along with the total flux in the prompt phase is used to determine initial radii of the outflow as well as its Lorentz factors. Results indicate that in some cases the outflow has relatively low Lorentz factors (Γ 〈 10), favouring cocoon interpretation, while in other cases Lorentz factors are larger (Γ > 10), indicating diffusive photospheric origin of the thermal component, associated with an ultrarelativistic outflow.
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  • 19
    Publication Date: 2020-04-01
    Description: In volcanoes, topography, shallow heterogeneity and even shallow morphology can substantially modify seismic coda signals. Coda waves are an essential tool to monitor eruption dynamics and model volcanic structures jointly and independently from velocity anomalies: it is thus fundamental to test their spatial sensitivity to seismic path effects. Here, we apply the Multiple Lapse Time Window Analysis (MLTWA) to measure the relative importance of scattering attenuation vs absorption at Mount St Helens volcano before its 2004 eruption. The results show the characteristic dominance of scattering attenuation in volcanoes at lower frequencies (3–6 Hz), while absorption is the primary attenuation mechanism at 12 and 18 Hz. Scattering attenuation is similar but seismic absorption is one order of magnitude lower than at open-conduit volcanoes, like Etna and Kilauea, a typical behaviour of a (relatively) cool magmatic plumbing system. Still, the seismic albedo (measuring the ratio between seismic energy emitted and received from the area) is anomalously high (0.95) at 3 Hz. A radiative-transfer forward model of far- and near-field envelopes confirms this is due to strong near-receiver scattering enhancing anomalous phases in the intermediate and late coda across the 1980 debris avalanche and central crater. Only above this frequency and in the far-field diffusion onsets at late lapse times. The scattering and absorption parameters derived from MLTWA are used as inputs to construct 2-D frequency-dependent bulk sensitivity kernels for the S-wave coda in the multiple-scattering (using the Energy Transport Equations—ETE) and diffusive (AD, independent of MLTWA results) regimes. At 12 Hz, high coda-attenuation anomalies characterize the eastern side of the volcano using both kernels, in spatial correlation with low-velocity anomalies from literature. At 3 Hz, the anomalous albedo, the forward modelling, and the results of the tomographic imaging confirm that shallow heterogeneity beneath the extended 1980 debris-avalanche and crater enhance anomalous intermediate and late coda phases, mapping shallow geological contrasts. We remark the effect this may have on coda-dependent source inversion and tomography, currently used across the world to image and monitor volcanoes. At Mount St Helens, higher frequencies and deep borehole data are necessary to reconstruct deep volcanic structures with coda waves.
    Print ISSN: 0956-540X
    Electronic ISSN: 1365-246X
    Topics: Geosciences
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  • 20
    Publication Date: 2020-03-29
    Description: The orientations of faults activated relative to the local principal stress directions can provide insights into the role of pore pressure changes in induced earthquake sequences. Here, we examine the 2011 M 5.7 Prague earthquake sequence that was induced by nearby wastewater disposal. We estimate the local principal compressive stress direction near the rupture as inferred from shear wave splitting measurements at spatial resolutions as small as 750 m. We find that the dominant azimuth observed is parallel to previous estimates of the regional compressive stress with some secondary azimuths oriented subparallel to the strike of the major fault structures. From an extended catalogue, we map ten distinct fault segments activated during the sequence that exhibit a wide array of orientations. We assess whether the five near-vertical fault planes are optimally oriented to fail in the determined stress field. We find that only two of the fault planes, including the M   5.7 main shock fault, are optimally oriented. Both the M 4.8 foreshock and M   4.8 aftershock occur on fault planes that deviate 20–29° from the optimal orientation for slip. Our results confirm that induced event sequences can occur on faults not optimally oriented for failure in the local stress field. The results suggest elevated pore fluid pressures likely induced failure along several of the faults activated in the 2011 Prague sequence.
    Print ISSN: 0956-540X
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  • 21
    Publication Date: 2020-04-04
    Description: A very large dynamic range with simultaneous capture of both large and small scales in the simulations of cosmic structures is required for correct modelling of many cosmological phenomena, particularly at high redshift. This is not always available, or when it is, it makes such simulations very expensive. We present a novel subgrid method for modelling low-mass ($10^5, { m M}_odot le M_{ m halo}le 10^9, { m M}_odot$) haloes, which are otherwise unresolved in large-volume cosmological simulations limited in numerical resolution. In addition to the deterministic halo bias that captures the average property, we model its stochasticity that is correlated in time. We find that the instantaneous binned distribution of the number of haloes is well approximated by a lognormal distribution, with overall amplitude modulated by this ‘temporal correlation bias’. The robustness of our new scheme is tested against various statistical measures, and we find that temporally correlated stochasticity generates mock halo data that is significantly more reliable than that from temporally uncorrelated stochasticity. Our method can be applied for simulating processes that depend on both the small- and large-scale structures, especially for those that are sensitive to the evolution history of structure formation such as the process of cosmic reionization. As a sample application, we generate a mock distribution of medium-mass (108 ≤ M/M⊙ ≤ 109) haloes inside a 500 Mpc $, h^{-1}$, 3003 grid simulation box. This mock halo catalogue bears a reasonable statistical agreement with a halo catalogue from numerically resolved haloes in a smaller box, and therefore will allow a very self-consistent sets of cosmic reionization simulations in a box large enough to generate statistically reliable data.
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  • 22
    Publication Date: 2020-03-30
    Description: We present stellar metallicity measurements of more than 600 late-type stars in the central 10 pc of the Galactic Centre. Together with our previously published KMOS data, this data set allows us to investigate, for the first time, spatial variations of the nuclear star cluster’s metallicity distribution. Using the integral-field spectrograph KMOS (VLT), we observed almost half of the area enclosed by the nuclear star cluster’s effective radius. We extract spectra at medium spectral resolution and apply full spectral fitting utilizing the PHOENIX library of synthetic stellar spectra. The stellar metallicities range from [M/H] = −1.25 dex to [M/H] > +0.3 dex, with most of the stars having supersolar metallicity. We are able to measure an anisotropy of the stellar metallicity distribution. In the Galactic north, the portion of subsolar metallicity stars with [M/H] 〈 0.0 dex is more than twice as high as in the Galactic south. One possible explanation for different fractions of subsolar metallicity stars in different parts of the cluster is a recent merger event. We propose to test this hypothesis with high-resolution spectroscopy and by combining the metallicity information with kinematic data.
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  • 23
    Publication Date: 2020-01-01
    Description: Acute lymphoblastic leukemia (ALL) is one of the most common hematological malignancies in children. Recent studies suggest the involvement of multiple microRNAs in the tumorigenesis of various leukemias. However, until now, no comprehensive database exists for miRNAs and their cognate target genes involved specifically in ALL. Therefore, we developed ‘LeukmiR’ a dynamic database comprising in silico predicted microRNAs, and experimentally validated miRNAs along with the target genes they regulate in mouse and human. LeukmiR is a user-friendly platform with search strings for ALL-associated microRNAs, their sequences, description of target genes, their location on the chromosomes and the corresponding deregulated signaling pathways. For the user query, different search modules exist where either quick search can be carried out using any fuzzy term or by providing exact terms in specific modules. All entries for both human and mouse genomes can be retrieved through multiple options such as miRNA ID, their accession number, sequence, target genes, Ensemble-ID or Entrez-ID. User can also access miRNA: mRNA interaction networks in different signaling pathways, the genomic location of the targeted regions such as 3′UTR, 5′UTR and exons with their gene ontology and disease ontology information in both human and mouse systems. Herein, we also report 51 novel microRNAs which are not described earlier for ALL. Thus, LeukmiR database will be a valuable source of information for researchers to understand and investigate miRNAs and their targets with diagnostic and therapeutic potential in ALL. Database URL: http://tdb.ccmb.res.in/LeukmiR/
    Electronic ISSN: 1758-0463
    Topics: Biology
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  • 24
    Publication Date: 2020-01-01
    Description: The Symbiotic Genomes Database (SymGenDB; http://symbiogenomesdb.uv.es/) is a public resource of manually curated associations between organisms involved in symbiotic relationships, maintaining a catalog of completely sequenced/finished bacterial genomes exclusively. It originally consisted of three modules where users could search for the bacteria involved in a specific symbiotic relationship, their genomes and their genes (including their orthologs). In this update, we present an additional module that includes a representation of the metabolic network of each organism included in the database, as Directed Acyclic Graphs (MetaDAGs). This module provides unique opportunities to explore the metabolism of each individual organism and/or to evaluate the shared and joint metabolic capabilities of the organisms of the same genera included in our listing, allowing users to construct predictive analyses of metabolic associations and complementation between systems. We also report a ~25% increase in manually curated content in the database, i.e. bacterial genomes and their associations, with a final count of 2328 bacterial genomes associated to 498 hosts. We describe new querying possibilities for all the modules, as well as new display features for the MetaDAGs module, providing a relevant range of content and utility. This update continues to improve SymGenDB and can help elucidate the mechanisms by which organisms depend on each other.
    Electronic ISSN: 1758-0463
    Topics: Biology
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  • 25
    Publication Date: 2020-01-01
    Description: Heat shock proteins (Hsp) are among highly conserved proteins across all domains of life. Though originally discovered as a cellular response to stress, these proteins are also involved in a wide range of cellular functions such as protein refolding, protein trafficking and cellular signalling. A large number of potential Hsp modulators are under clinical trials against various human diseases. As the number of modulators targeting Hsps is growing, there is a need to develop a comprehensive knowledge repository of these findings which is largely scattered. We have thus developed a web-accessible database, HSPMdb, which is a first of its kind manually curated repository of experimentally validated Hsp modulators (activators and inhibitors). The data was collected from 176 research articles and current version of HSPMdb holds 10 223 entries of compounds that are known to modulate activities of five major Hsps (Hsp100, Hsp90, Hsp70, Hsp60 and Hsp40) originated from 15 different organisms (i.e. human, yeast, bacteria, virus, mouse, rat, bovine, porcine, canine, chicken, Trypanosoma brucei and Plasmodium falciparum). HSPMdb provides comprehensive information on biological activities as well as the chemical properties of Hsp modulators. The biological activities of modulators are presented as enzymatic activity and cellular activity. Under the enzymatic activity field, parameters such as IC50, EC50, DC50, Ki and KD have been provided. In the cellular activity field, complete information on cellular activities (percentage cell growth inhibition, EC50 and GI50), type of cell viability assays and cell line used has been provided. One of the important features of HSPMdb is that it allows users to screen whether or not their compound of interest has any similarity with the previously known Hsp modulators. We anticipate that HSPMdb would become a valuable resource for the broader scientific community working in the area of chaperone biology and protein misfolding diseases. HSPMdb is freely accessible at http://bioinfo.imtech.res.in/bvs/hspmdb/index.php
    Electronic ISSN: 1758-0463
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  • 26
    Publication Date: 2020-01-01
    Description: A gene regulatory process is the result of the concerted action of transcription factors, co-factors, regulatory non-coding RNAs (ncRNAs) and chromatin interactions. Therefore, the combination of protein–DNA, protein–protein, ncRNA–DNA, ncRNA–protein and DNA–DNA data in a single graph database offers new possibilities regarding generation of biological hypotheses. GREG (The Gene Regulation Graph Database) is an integrative database and web resource that allows the user to visualize and explore the network of all above-mentioned interactions for a query transcription factor, long non-coding RNA, genomic range or DNA annotation, as well as extracting node and interaction information, identifying connected nodes and performing advanced graphical queries directly on the regulatory network, in a simple and efficient way. In this article, we introduce GREG together with some application examples (including exploratory research of Nanog’s regulatory landscape and the etiology of chronic obstructive pulmonary disease), which we use as a demonstration of the advantages of using graph databases in biomedical research. Database URL: https://mora-lab.github.io/projects/greg.html, www.moralab.science/GREG/
    Electronic ISSN: 1758-0463
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  • 27
    Publication Date: 2020-04-09
    Description: We compare a sample of five high-resolution, high S/N  Ly α forest spectra of bright 6 〈 z 〈 ∼6.5 QSOs aimed at spectrally resolving the last remaining transmission spikes at z > 5 with those obtained from mock absorption spectra from the Sherwoodand Sherwood–Relics simulation suites of hydrodynamical simulations of the intergalactic medium (IGM). We use a profile-fitting procedure for the inverted transmitted flux, 1 − F, similar to the widely used Voigt profile fitting of the transmitted flux F at lower redshifts, to characterize the transmission spikes that probe predominately underdense regions of the IGM. We are able to reproduce the width and height distributions of the transmission spikes, both with optically thin simulations of the post-reionization Universe using a homogeneous UV background and full radiative transfer simulations of a late reionization model. We find that the width of the fitted components of the simulated transmission spikes is very sensitive to the instantaneous temperature of the reionized IGM. The internal structures of the spikes are more prominent in low temperature models of the IGM. The width distribution of the observed transmission spikes, which require high spectral resolution (≤ 8  km s−1) to be resolved, is reproduced for optically thin simulations with a temperature at mean density of T0 = (11 000 ± 1600, 10 500 ± 2100, 12 000 ± 2200) K at z = (5.4, 5.6, 5.8). This is weakly dependent on the slope of the temperature-density relation, which is favoured to be moderately steeper than isothermal. In the inhomogeneous, late reionization, full radiative transfer simulations where islands of neutral hydrogen persist to z ∼ 5.3, the width distribution of the observed transmission spikes is consistent with the range of T0 caused by spatial fluctuations in the temperature–density relation.
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  • 28
    Publication Date: 2020-04-07
    Description: We study the timing stability of three black widow pulsars (BWPs), both in terms of their long-term spin evolution and their shorter term orbital stability. The erratic timing behaviour and radio eclipses of the first two BWP systems discovered (PSRs B1957+20 and J2051−0827) were assumed to be representative for this class of pulsars. With several new black widow systems added to this population in the last decade, there are now several systems known that do not show these typical orbital variations or radio eclipses. We present timing solutions using 7–8 yr of observations from four of the European Pulsar Timing Array telescopes for PSRs J0023+0923, J2214+3000, and J2234+0944, and confirm that two of these systems do not show any significant orbital variability over our observing time span, both in terms of secular or orbital parameters. The third pulsar PSR J0023+0923 shows orbital variability and we discuss the implications for the timing solution. Our results from the long-term timing of these pulsars provide several new or improved parameters compared to earlier works. We discuss our results regarding the stability of these pulsars, and the stability of the class of BWPs in general, in the context of the binary parameters, and discuss the potential of the Roche lobe filling factor of the companion star being an indicator for stability of these systems.
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  • 29
    Publication Date: 2020-06-03
    Description: Europe has a history rich in examples of successful and problematic introductions of trees with a native origin outside of Europe (non-native trees, NNT). Many international legal frameworks such as treaties and conventions and also the European Union have responded to the global concern about potential negative impacts of NNT that may become invasive in natural ecosystems. It is, however, national and regional legislation in particular that affects current and future management decisions in the forest sector and shapes the landscapes of Europe. We identified all relevant legal instruments regulating NNT, the different legal approaches and the regulatory intensity in 40 European countries (no microstates). Information on hard and effective soft law instruments were collected by means of a targeted questionnaire and consultation of international and national legislation information systems and databases. In total, 335 relevant legal instruments were in place in June/July 2019 to regulate the use of NNT in the investigated 116 geopolitical legal units (countries as well as sub-national regions with their own legislation). Countries and regions were empirically categorized according to ad hoc-defined legislation indicators. These indicators pay respect to the general bans on the introduction of non-native species, the generally allowed and prohibited NNT, approval mechanisms and specific areas or cases where NNT are restricted or prohibited. Our study revealed a very diverse landscape of legal frameworks across Europe, with a large variety of approaches to regulating NNT being pursued and the intensity of restriction ranging from very few restrictions on species choice and plantation surface area to the complete banning of NNT from forests. The main conclusion is that there is a clear need for more co-ordinated, science-based policies both at the local and international levels to enhance the advantages of NNT and mitigate potential negative effects.
    Print ISSN: 0015-752X
    Electronic ISSN: 1464-3626
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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  • 30
    Publication Date: 2020-04-07
    Description: We analyse 16 failed filament eruptions observed near 24 solar cycle maximum from 2013 May to 2014 July. No significant rotation of filament spines is observed during the ascent in all studied failed eruptions, which does not support kink-instability mechanism of triggering the eruptions. We calculate potential magnetic field distributions in the corona above the initial locations of the filaments to study their height dependence. In seven events, the vertical profiles of the decay index n are monotonic. The other nine events occur in the regions with the switchback or saddle-like n-profiles. The direction of the horizontal field near the saddle bottom is turned through more than 100° relative its direction at the initial filament position, which reveals the quadrupolar magnetic configuration with null points in these regions. The eruptive filaments stop above the null points where the total Lorentz force is directed upward. The most reasonable force that can terminate filament ascending and balance the Lorentz force seems the gravity.
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  • 31
    Publication Date: 2020-04-25
    Description: The computational requirements posed by multi-dimensional simulations of type Ia supernovae make it difficult to incorporate complex nuclear networks to follow the release of nuclear energy along with the propagation of the flame. Instead, these codes usually model the flame and use simplified nuclear kinetics, with the goal of determining a sufficiently accurate rate of nuclear energy generation and, afterwards, post-processing the thermodynamic trajectories with a large nuclear network to obtain more reliable nuclear yields. In this work, I study the performance of simplified nuclear networks with respect to reproduction of the nuclear yields obtained with a one-dimensional supernova code equipped with a large nuclear network. I start by defining a strategy to follow the properties of matter in nuclear statistical equilibrium (NSE). I propose to use published tables of NSE properties, together with a careful interpolation routine. Short networks (iso7 and 13α) are able to give an accurate yield of 56Ni, after post-processing, but can fail by order of magnitude in predicting the ejected mass of even mildly abundant species (>10−3 M⊙). A network of 21 species reproduces the nucleosynthesis of the Chandrasekhar and sub-Chandrasekhar explosions studied here with average errors better than 20 per cent for the whole set of stable elements and isotopes followed in the models.
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  • 32
    Publication Date: 2020-04-13
    Description: Deep observation of the High Energy Stereoscopic System (HESS) on the most extended pulsar wind nebula HESS J1825−137 reveals an enhanced energy-dependent morphology, providing useful information on the particle transport mechanism in the nebula. We find that the energy-dependent morphology is consistent with a diffusion-dominated transport of electrons/positrons. It provides an alternative possible interpretation for the unusually large spatial extent (i.e. ${gtrsim} 100$ pc) of the nebula, which could then be attributed to the diffusion of escaping electrons/positrons from a compact plerion. The influence of various model parameters on the energy-dependent extent of the nebula is studied in the diffusion-dominated scenario. We also show that the energy-dependent morphology of the nebula may also be used to study the spin-down history of the pulsar.
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  • 33
    Publication Date: 2020-04-24
    Description: Interstellar dust is a significant component of matter in the galaxies. The dust owns its origin and reprocessing in a wide range of astrophysical environments. In order to understand the origin and evolution of the distinct types of interstellar dust grains, we have attempted a comprehensive correlated study of the thermodynamics condensation of dust grains in distinct stellar environments with the Galactic chemical evolution of the Milky Way Galaxy. The Galaxy is evolved in terms of elemental evolution resulting from stellar nucleosynthetic contributions of several generations of stars. Based on the elemental composition of the evolving Galaxy, the relative abundances of the major constituents of interstellar dust are assessed. The major aim is to redistribute the various condensable elements at any epoch during the evolution of the Galaxy into various grain constituents and understand their abundance evolution based on a mass-balance formalism. We also performed thermodynamical equilibrium condensation calculations to understand the stellar origin of various grain constituents that could carry the isotopic signatures of the various stellar nucleosynthetic sources. This is perhaps a novel attempt to estimate the bulk dust mass budget in the evolving Galaxy. The normalized mass of the Galactic dust is predicted to decrease with the increase in distance from the Galactic centre. It increases over time. The supernovae SNe Ia are predicted as the most prominent sources of Fe-dust mass, the supernova SN II+Ib/c produces oxides- and silicate-dust mass, and the AGB stars contribute to carbonaceous dust mass.
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  • 34
    Publication Date: 2020-04-14
    Description: We perform the calibration of the X-ray luminosity–mass scaling relation on a sample of 344 CODEX clusters with z 〈 0.66 using the dynamics of their member galaxies. Spectroscopic follow-up measurements have been obtained from the SPIDERS survey, leading to a sample of 6658 red member galaxies. We use the Jeans equation to calculate halo masses, assuming an NFW mass profile and analysing a broad range of anisotropy profiles. With a scaling relation of the form $L_{ m {X}} propto ext{A}_{ m {X}}M_{ ext{200c}}^{ ext{B}_{ m {X}}} E(z)^2 (1+z)^{gamma _{ m {X}}}$, we find best-fitting parameters $ ext{A}_{ m {X}}=0.62^{+0.05}_{-0.06} (pm 0.06) imes 10^{44}, mathrm{erg, s^{-1}}$, $ ext{B}_{ m {X}}=2.35^{+0.21}_{-0.18}(pm 0.09)$, $gamma _{ m {X}}=-2.77^{+1.06}_{-1.05}(pm 0.79)$, where we include systematic uncertainties in parentheses and for a pivot mass and redshift of $3 imes 10^{14}, mathrm{M}_odot$ and 0.16, respectively. We compare our constraints with previous results, and we combine our sample with the SPT SZE-selected cluster subsample observed with XMM–Newton  extending the validity of our results to a wider range of redshifts and cluster masses.
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  • 35
    Publication Date: 2020-04-09
    Description: Fast radio bursts (FRBs) are mysterious radio bursts with a time-scale of approximately milliseconds. Two populations of FRB, namely repeating and non-repeating FRBs, are observationally identified. However, the differences between these two and their origins are still cloaked in mystery. Here we show the time-integrated luminosity–duration (Lν–wint, rest) relations and luminosity functions (LFs) of repeating and non-repeating FRBs in the FRB Catalogue project. These two populations are obviously separated in the Lν-wint, rest plane with distinct LFs, i.e. repeating FRBs have relatively fainter Lν and longer wint, rest with a much lower LF. In contrast with non-repeating FRBs, repeating FRBs do not show any clear correlation between Lν and wint, rest. These results suggest essentially different physical origins of the two. The faint ends of the LFs of repeating and non-repeating FRBs are higher than volumetric occurrence rates of neutron star (NS) mergers and accretion-induced collapse (AIC) of white dwarfs (WDs), and are consistent with those of soft gamma-ray repeaters (SGRs), Type Ia supernovae (SNe Ia), magnetars, and WD mergers. This indicates two possibilities: either (i) faint non-repeating FRBs originate in NS mergers or AIC and are actually repeating during the lifetime of the progenitor, or (ii) faint non-repeating FRBs originate in any of SGRs, SNe Ia, magnetars, and WD mergers. The bright ends of LFs of repeating and non-repeating FRBs are lower than any candidates of progenitors, suggesting that bright FRBs are produced from a very small fraction of the progenitors regardless of the repetition. Otherwise, they might originate in unknown progenitors.
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  • 36
    Publication Date: 2020-04-07
    Description: The radial acceleration relation (RAR) shows a strong correlation between two accelerations associated with galaxy rotation curves. The relation between these accelerations is given by a non-linear function that depends on an acceleration scale a†. Some have interpreted this as an evidence for a gravity model, such as modified Newtonian dynamics (MOND), which posits a fundamental acceleration scale a0 common to all the galaxies. However, it was later shown, using Bayesian inference, that this seems not to be the case: the a0 credible intervals for individual galaxies were not found to be compatible among themselves. A test like the latter is a fundamental test for MOND as a theory for gravity, since it directly evaluates its basic assumption and this using the data that most favour MOND: galaxy rotation curves. Here we improve upon the previous analyses by introducing a more robust method to assess the compatibility between the credible intervals, in particular without Gaussian approximations. We directly estimate, using a Monte Carlo simulation, that the existence of a fundamental acceleration is incompatible with the data at more than 5σ. We also consider quality cuts in order to show that our results are robust against outliers. In conclusion, the new analysis further supports the claim that the acceleration scale found in the RAR is an emergent quantity.
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  • 37
    Publication Date: 2020-04-07
    Description: In 2011 December, PSR B054−69 experienced a spin-down rate transition (SRT), after which the spin-down power of the pulsar increased by $sim 36{{ m per cent}}$. About 1000 d after the SRT, the X-ray luminosity of the associated pulsar wind nebula (PWN) was found to brighten by $32pm 8{{ m per cent}}$. After the SRT, the braking index n of PSR B0540−69 changes from n = 2.12 to 0.03 and then keeps this value for about five years before rising to n = 0.9 in the following years. We find that most of the current models have difficulties in explaining the measured braking index. One exceptive model of the braking index evolution is the increasing dipole magnetic field of PSR B0540−69. We suggest that the field increase may result from some instabilities within the pulsar core that enhance the poloidal component at the price of toroidal component of the magnetic field. The increasing dipole magnetic field will result in the X-ray brightening of the PWN. We fit the PWN X-ray light curve by two models: one assumes a constant magnetic field within the PWN during the brightening and the other assumes an enhanced magnetic field proportional to the energy density of the PWN. It appears that the two models fit the data well, though the later model seems to fit the data a bit better. This provides marginal observational evidence that magnetic field in the PWN is generated by the termination shock. Future high-quality and high-cadence data are required to draw a solid conclusion.
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  • 38
    Publication Date: 2020-04-09
    Description: Conventional geophysical inversion techniques suffer from several limitations including computational cost, nonlinearity, non-uniqueness and dimensionality of the inverse problem. Successful inversion of geophysical data has been a major challenge for decades. Here, a novel approach based on deep learning (DL) inversion via convolutional neural network (CNN) is proposed to instantaneously estimate subsurface electrical conductivity (σ) layering from electromagnetic induction (EMI) data. In this respect, a fully convolutional network was trained on a large synthetic data set generated based on 1-D EMI forward model. The accuracy of the proposed approach was examined using several synthetic scenarios. Moreover, the trained network was used to find subsurface electromagnetic conductivity images (EMCIs) from EMI data measured along two transects from Chicken Creek catchment (Brandenburg, Germany). Dipole–dipole electrical resistivity tomography data were measured as well to obtain reference subsurface σ distributions down to a 6 m depth. The inversely estimated models were juxtaposed and compared with their counterparts obtained from a spatially constrained deterministic algorithm as a standard code. Theoretical simulations demonstrated a well performance of the algorithm even in the presence of noise in data. Moreover, application of the DL inversion for subsurface imaging from Chicken Creek catchment manifested the accuracy and robustness of the proposed approach for EMI inversion. This approach returns subsurface σ distribution directly from EMI data in a single step without any iterations. The proposed strategy simplifies considerably EMI inversion and allows for rapid and accurate estimation of subsurface EMCI from multiconfiguration EMI data.
    Print ISSN: 0956-540X
    Electronic ISSN: 1365-246X
    Topics: Geosciences
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  • 39
    Publication Date: 2020-04-17
    Description: Cosmic rays (CRs) and magnetic fields may be dynamically important in driving large-scale galactic outflows from rapidly star-forming galaxies. We construct two-dimensional axisymmetric models of the local starburst and superwind galaxy M82 using the CR propagation code galprop. Using prescribed gas density and magnetic field distributions, wind profiles, CR injection rates, and stellar radiation fields, we simultaneously fit both the integrated gamma-ray emission and the spatially resolved multifrequency radio emission extended along M82’s minor axis. We explore the resulting constraints on the gas density, magnetic field strength, CR energy density, and the assumed CR advection profile. In accord with earlier one-zone studies, we generically find low central CR pressures, strong secondary electron/positron production, and an important role for relativistic bremsstrahlung losses in shaping the synchrotron spectrum. We find that the relatively low central CR density produces CR pressure gradients that are weak compared to gravity, strongly limiting the role of CRs in driving M82’s fast and mass-loaded galactic outflow. Our models require strong magnetic fields and advection speeds of the order of ∼1000 km s−1 on kpc scales along the minor axis in order to reproduce the extended radio emission. Degeneracies between the controlling physical parameters of the model and caveats to these findings are discussed.
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  • 40
  • 41
    Publication Date: 2020-04-03
    Description: We present a new model for the cross-covariance between galaxy redshift-space distortions and peculiar velocities. We combine this with the autocovariance models of both probes in a fully self-consistent, maximum-likelihood method, allowing us to extract enhanced cosmological parameter constraints. When applying our method to the 6-degree Field Galaxy Survey (6dFGS), our constraint on the growth rate of structure is $fsigma _8 = 0.384 pm 0.052 m {(stat)} pm 0.061 m {(sys)}$ and our constraint for the redshift-space distortion parameter is $ eta = 0.289^{+0.044}_{-0.043} m {(stat)} pm 0.049 m {(sys)}$. We find that the statistical uncertainty for the growth rate of structure is reduced by 64 per cent when using the complete covariance model compared to the redshift-space distortion autocovariance model and 50 per cent when compared to using the peculiar-velocity autocovariance model. Our constraints are consistent with those from the literature on combining multiple tracers of large-scale structure, as well as those from other 6dFGS analyses. Our measurement is also consistent with the standard cosmological model.
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  • 42
    Publication Date: 2020-04-07
    Description: We report iron and titanium abundance measurements from high-resolution spectra in a volume-limited sample of 106 M0 and M0.5 dwarf stars. The sample includes stars north of the celestial equator and closer than 29 parsecs. The results imply that there is an M dwarf problem similar to the previously known G dwarf problem, in that the fraction of low-metallicity M dwarfs is not large enough to fit simple closed-box models of Galactic chemical evolution. This volume-limited sample avoids many of the statistical uncertainties present in a previous study using a brightness-limited sample of M dwarf stars.
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  • 43
    Publication Date: 2020-04-04
    Description: We present the discovery of ASASSN-18jd (AT 2018bcb), a luminous optical/ultraviolet(UV)/X-ray transient located in the nucleus of the galaxy 2MASX J22434289–1659083 at z = 0.1192. Over the year after discovery, Swift UltraViolet and Optical Telescope (UVOT) photometry shows the UV spectral energy distribution of the transient to be well modelled by a slowly shrinking blackbody with temperature $T sim 2.5 imes 10^{4} , { m K}$, a maximum observed luminosity of $L_{ m max} = 4.5^{+0.6}_{-0.3} imes 10^{44} , { m erg ,s}^{-1}$, and a radiated energy of $E = 9.6^{+1.1}_{-0.6} imes 10^{51} , { m erg}$. X-ray data from Swift X-Ray Telescope (XRT) and XMM–Newton show a transient, variable X-ray flux with blackbody and power-law components that fade by nearly an order of magnitude over the following year. Optical spectra show strong, roughly constant broad Balmer emission and transient features attributable to He ii, N iii–v, O iii, and coronal Fe. While ASASSN-18jd shares similarities with tidal disruption events (TDEs), it is also similar to the newly discovered nuclear transients seen in quiescent galaxies and faint active galactic nuclei (AGNs).
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  • 44
    Publication Date: 2020-03-28
    Description: The recent study of the SN 2013fs flash spectrum suggests an enormous explosion energy for SNe IIP, far beyond the possibilities of the neutrino mechanism. The issue of the explosion energy of SN 2013fs is revisited, making use of the effects of the early supernova interaction with the dense circumstellar shell. The velocity of the cold dense shell between reverse and forward shocks is inferred from the analysis of the broad He ii 4686 Å on day 2.4. This velocity, alongside other observables, provides us with an alternative energy estimate of ∼1.8 × 1051 erg for the preferred mass of ∼10 M⊙. The inferred value is within the range of neutrino-driven explosions.
    Print ISSN: 1745-3925
    Electronic ISSN: 1745-3933
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  • 45
    Publication Date: 2020-04-03
    Description: Highly accreting quasars are quite luminous in the X-ray and optical regimes; while, they tend to become radio quiet and have optically thin radio spectra. Among the known quasars, IRAS F11119+3257 is a supercritical accretion source because it has a bolometric luminosity slightly above the Eddington limit and extremely powerful X-ray outflows. To probe its radio structure, we investigated its radio spectrum between 0.15 and 96.15 GHz and performed very-long-baseline interferometric (VLBI) observations with the European VLBI Network (EVN) at 1.66 and 4.93 GHz. The deep EVN image at 1.66 GHz shows a two-sided jet with a projected separation about 200 pc and a very high flux density ratio of about 290. Together with the best-fitting value of the integrated spectral index of −1.31 ± 0.02 in the optically thin part, we infer that the approaching jet has an intrinsic speed at least 0.57 times of the light speed. This is a new record among the known all kinds of super-Eddington accreting sources and unlikely accelerated by the radiation pressure in a certain models. We propose a scenario in which IRAS F11119+3257 is an unusual compact symmetric object with a small jet viewing angle and a radio spectrum peaking at 0.53 ± 0.06 GHz mainly due to the synchrotron self-absorption.
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  • 46
    Publication Date: 2020-05-20
    Description: The interstellar medium (ISM) is typically a hostile environment: cold, dilute and irradiated. Nevertheless, it appears very fertile for molecules. The localized heating resulting from turbulence dissipation is a possible channel to produce and excite molecules. However, large-scale simulations cannot resolve the dissipative scales of the ISM. Here, we present two-dimensional small-scale simulations of decaying hydrodynamic turbulence using the chemses code, with fully resolved viscous dissipation, time-dependent heating, cooling, chemistry and excitation of a few rotational levels of H2. We show that molecules are produced and excited in the wake of strong dissipation ridges. We carefully identify shocks and we assess their statistics and contribution to the molecular yields and excitation. We find that the formation of molecules is strongly linked to increased density as a result of shock compression and to the opening of endothermic chemical routes because of higher temperatures. We identify a new channel for molecule production via H2 excitation, illustrated by CH+ yields in our simulations. Despite low temperatures and the absence of magnetic fields (favouring CH+ production through ion-neutral velocity drifts), the excitation of the first few rotational levels of H2 shrinks the energy gap to form CH+. The present study demonstrates how dissipative chemistry can be modelled by statistical collections of one-dimensional steady-state shocks. Thus, the excitation of higher J levels of H2 is likely to be a direct signature of turbulence dissipation, and an indirect probe for molecule formation. We hope these results will help to bring new tools and ideas for the interpretation of current observations of H2 rotational lines carried out using the Stratospheric Observatory for Infrared Astronomy (SOFIA), and pave the way for a better understanding of the high-resolution mapping of H2 emission by future instruments, such as theJames Webb Space Telescope and the Space Infrared Telescope for Cosmology and Astrophysics.
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  • 47
    Publication Date: 2020-04-07
    Description: We describe and test a new version of the adaptive mesh refinement cosmological code masclet. The new version of the code includes all the ingredients of its previous version plus a description of the evolution of the magnetic field under the approximation of the ideal magnetohydrodynamics (MHD). To preserve the divergence-free condition of MHD, the original divergence cleaning algorithm of Dedner et al. (2002) is implemented. We present a set of well-known 1D and 2D tests, such as several shock tube problems, the fast rotor, and the Orszag–Tang vortex. The performance of the code in all the tests is excellent with estimated median relative errors of ∇ · B in the 2D tests smaller than 5 × 10−5 for the fast rotor test, and 5 × 10−3 for the Orszag–Tang vortex. As an astrophysical application of the code, we present a simulation of a cosmological box of 40 comoving Mpc side length in which a primordial uniform comoving magnetic field of strength 0.1 nG is seeded. The simulation shows how the magnetic field is channelled along the filaments of gas and is concentrated and amplified within galaxy clusters. Comparison with the values expected from pure compression reveals an additional amplification of the magnetic field caused by turbulence in the central region of the cluster. Values of the order of ∼1µG are obtained in clusters at z ∼ 0 with median relative errors of ∇ · B below 0.4 per cent. The implications of a proper description of the dynamics of the magnetic field and their possible observational counterparts in future facilities are discussed.
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  • 48
    Publication Date: 2020-04-07
    Description: The oscillatory model of star formation in giant and dwarf galaxies have been studied through a dynamical open system. In addition to various dynamical processes involving fractional masses of hot, warm, and cold gases, the system is subjected to dissipative processes e.g. outflow from the gaseous component caused by supernovae explosion and subsequent ram pressure stripping within the oscillation period. This is more realistic than a previous model which was considered conservative. The present episodic model has been found to be unimodal in general contrary to discrete episodes of star formation of decreasing amplitudes as found for closed systems. The duty cycles under various parametric conditions derived, vary in the range (2.0–40.0) × 107 yr for giant galaxies contrary to longer time, for example 9.0 × 107–1.0 × 109 yr for dwarf galaxies. This might be due to the low production rate of supernova in dwarf galaxies which reduces the evaporation rate of cold gas into hot gas making cold gas available for continuing the cycle for a longer time. The duty cycles have increased in both cases compared to the previous model by an order of one for giant galaxies and order of two for dwarf galaxies depending on the degree of dissipation. This might be due to the unimodal pattern of star formation which prevails for longer time in the late phase of galaxy evolution. Under very special parametric conditions limit cycles may occur i.e. star formation in discrete episodes, may occur involving one or more stable attractors especially in early-type dwarf and giant galaxies. Tendency of formation of multiple attractors are more likely in early-type giant spiral galaxies when the rate of dissipation is very slow.
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  • 49
    Publication Date: 2020-04-02
    Description: We report the detection of the full orbital phase curve and occultation of the hot-Jupiter WASP-100b using TESS photometry. The phase curve is isolated by suppressing low-frequency stellar and instrumental modes using both a non-parametric harmonic notch filter (phasma) and semi-sector long polynomials. This yields a phase-curve signal of (73 ± 9) ppm amplitude, preferred over a null-model by ΔBIC = 25, indicating very strong evidence for an observed effect. We recover the occultation event with a suite of five temporally localized tools, including Gaussian processes and cosine filtering. This allows us to infer an occultation depth of (100 ± 14) ppm, with an additional ±16 ppm systematic error from the differences between methods. We regress a model including atmospheric reflection, emission, ellipsoidal variations, and Doppler beaming to the combined phase-curve and occultation data. This allows us to infer that WASP-100b has a geometric albedo of $A_g = 0.16^{+0.04}_{-0.03}$ in the TESS bandpass, with a maximum dayside brightness temperature of (2710 ± 100) K and a warm nightside temperature of $(2380^{+170}_{-200})$ K. Additionally, we find evidence that WASP-100b has a high thermal redistribution efficiency, manifesting as a substantial eastward hotspot offset of $(71^{+2}_{-4})^{circ }$. These results present the first measurement of a thermal phase shift among the phase curves observed by TESS so far, and challenge the predicted efficiency of heat transport in the atmospheres of ultra-hot-Jupiters.
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  • 50
    Publication Date: 2020-04-10
    Description: We observe damped temporal oscillations in the scale factor at a dominant frequency of ∼7 cycles/Hubble-time in the Pantheon compilation of 1048 Type Ia supernovae (SNe Ia). The residual oscillations observed in the Pantheon data closely match and reaffirm our initial observation of oscillations from earlier SNe data (primarily SNLS3 data of Conley 2011) at 2σ confidence. The nearly identical shapes in amplitude, frequency, phase, and damping constant makes it highly likely that the signal is real. Furthermore, two-thirds of the Pantheon SNe cover different portions of the sky compared with SNLS3 strengthening this conclusion. Our model describing the oscillation, presented in an earlier paper, is a simple scalar field harmonic oscillator coupled to the Lambda cold dark matter (ΛCDM) Friedmann equation, but carried into the present epoch. The scalar field energy density plays the role of the dark matter energy density in ΛCDM cosmology, fits well as an average, and closely matches the present dark matter density parameter, suggesting the oscillation plays a role in the dark matter sector. Temporal oscillations in the scale factor and its derivative, as described in this work, would also induce temporal oscillations of the Hubble parameter.
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  • 51
    Publication Date: 2020-04-02
    Description: We examine the rheology and thermal structure of the oceanic lithosphere, expressed in situ by plate flexure beneath the Hawaiian Ridge, where volcanoes of variable sizes have loaded seafloor of approximately the same age, and thus where the lithosphere is expected to have had an approximately uniform age-dependent thermal structure at the time of loading. Shipboard and satellite-derived gravity, as well as multibeam bathymetry data are used in models of plate flexure with curvature-dependent flexural rigidity, the strength of which is limited, in the shallow lithosphere, by brittle failure, and in the deeper lithosphere, by low-temperature plasticity (LTP). We compute relative likelihoods and posterior probabilities for four model parameters: average crustal density ρc, friction coefficient for brittle failure ${mu _f}$, a pre-exponential weakening factor F controlling the strength of LTP and lithospheric geotherm age t. Results show that if the lithosphere temperatures were as is expected for normal (t = ) 90-Myr-old seafloor at the time of volcano loading, the rheology must be significantly weaker than expected. Specifically, weak brittle strengths (μf ≤ 0.3) show relatively high probabilities for three of the six published LTP flow laws examined. Alternatively, moderate-to-large brittle strengths (μf ≥ 0.5) require all LTP flow laws to be substantially weakened with F = 102 to > 108 or, equivalently, activation energy reduced by 10–35 per cent. In contrast, if the lithosphere has been moderately reheated by the Hawaiian hotspot, represented by geotherms for t = 50–70 Myr, then the flow laws of Evans & Goetze, Raterron et al. and Krancj et al. require little or no weakening. Such modest thermal rejuvenation is allowed by heatflow constraints, supported by regional mantle seismic tomography imaging as well as compositions of mantle xenoliths, and reconciles previously noted discrepancies between the LTP strengths of lithosphere beneath Hawaii versus that entering the Pacific subduction zones.
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  • 52
    Publication Date: 2020-04-04
    Description: We compare the spectral energy distributions (SEDs) and inferred physical properties for simulated and observed galaxies at low redshift. We exploit UV-submillimetre mock fluxes of ∼7000 z = 0 galaxies from the EAGLE suite of cosmological simulations, derived using the radiative transfer code skirt. We compare these to ∼800 observed galaxies in the UV-submillimetre range, from the DustPedia sample of nearby galaxies. To derive global properties, we apply the SED fitting code cigale consistently to both data sets, using the same set of ∼80 million models. The results of this comparison reveal overall agreement between the simulations and observations, both in the SEDs and in the derived physical properties, with a number of discrepancies. The optical and far-infrared regimes, and the scaling relations based upon the global emission, diffuse dust, and stellar mass, show high levels of agreement. However, the mid-infrared fluxes of the EAGLE galaxies are overestimated while the far-UV domain is not attenuated enough, compared to the observations. We attribute these discrepancies to a combination of galaxy population differences between the samples and limitations in the subgrid treatment of star-forming regions in the EAGLE-skirt post-processing recipe. Our findings show the importance of detailed radiative transfer calculations and consistent comparison, and provide suggestions for improved numerical models.
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  • 53
    Publication Date: 2020-04-09
    Description: We present a sub-kpc resolved study of the interstellar medium properties in SDP.81, a $z$ = 3.042 strongly gravitationally lensed, dusty star-forming galaxy, based on high-resolution, multiband ALMA observations of the far-infrared (FIR) continuum, CO ladder, and the [C ii] line. Using a visibility-plane lens modelling code, we achieve a median source-plane resolution of ∼200 pc. We use photon-dominated region (PDR) models to infer the physical conditions – far-ultraviolet (FUV) field strength, density, and PDR surface temperature – of the star-forming gas on 200-pc scales, finding a FUV field strength of ∼103−104G0, gas density of ∼105 cm−3, and cloud surface temperatures up to 1500 K, similar to those in the Orion Trapezium region. The [C ii] emission is significantly more extended than that FIR continuum: ∼50 per cent of [C ii] emission arises outside the FIR-bright region. The resolved [C ii]/FIR ratio varies by almost 2 dex across the source, down to ∼2 × 10−4 in the star-forming clumps. The observed [C ii]/FIR deficit trend is consistent with thermal saturation of the C+ fine-structure-level occupancy at high gas temperatures. We make the source-plane reconstructions of all emission lines and continuum data publicly available.
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  • 54
    Publication Date: 2020-06-08
    Description: With ever-expanding marine aquaculture, calls for sustainable development become louder. The concept of aquaculture carrying capacity (CC) emerged 30 years ago to frame development, though so far, most studies have focused on the production and ecological components, leaving aside the social perspective. Often, estimations are carried out a posteriori, once aquaculture is already in place, hence ignoring relevant voices potentially opposing the onset of aquaculture implementation. We argue that CC should be multidimensional, iterative, inclusive, and just. Hence, the evaluative scope of CC needs to be broadened by moving from industry-driven, Western-based approaches towards an inclusive vision taking into consideration historical, cultural, and socio-economic concerns of all stakeholders of a given area. To this end, we suggest guidelines to frame a safe operating space for aquaculture based on a multi-criteria, multi-stakeholder approach, while embracing the social-ecological dynamics of aquaculture settings by applying an adaptive approach and acknowledging the critical role of place-based constraints. Rather than producing a box-checking exercise, CC approaches should proactively engage with aquaculture-produced outcomes at multiple scales, embracing complexity, and uncertainty. Scoping CC with the voices of all relevant societal groups, ideally before aquaculture implementation, provides the unique opportunity to jointly develop truly sustainable aquaculture.
    Print ISSN: 1054-3139
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    Topics: Biology , Geosciences , Physics
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  • 55
    Publication Date: 2020-01-01
    Description: Maximizing the impact and value of scientific research requires efficient knowledge distribution, which increasingly depends on the integration of standardized published data into online databases. To make data integration more comprehensive and efficient for fission yeast research, PomBase has pioneered a community curation effort that engages publication authors directly in FAIR-sharing of data representing detailed biological knowledge from hypothesis-driven experiments. Canto, an intuitive online curation tool that enables biologists to describe their detailed functional data using shared ontologies, forms the core of PomBase’s system. With 8 years’ experience, and as the author response rate reaches 50%, we review community curation progress and the insights we have gained from the project. We highlight incentives and nudges we deploy to maximize participation, and summarize project outcomes, which include increased knowledge integration and dissemination as well as the unanticipated added value arising from co-curation by publication authors and professional curators.
    Electronic ISSN: 1758-0463
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  • 56
    Publication Date: 2020-01-01
    Description: Macaques are the most widely used non-human primates in biomedical research. The genetic divergence between these animal models is responsible for their phenotypic differences in response to certain diseases. However, the macaque single nucleotide polymorphism resources mainly focused on rhesus macaque (Macaca mulatta), which hinders the broad research and biomedical application of other macaques. In order to overcome these limitations, we constructed a database named MACSNVdb that focuses on the interspecies genetic diversity among macaque genomes. MACSNVdb is a web-enabled database comprising ~74.51 million high-quality non-redundant single nucleotide variants (SNVs) identified among 20 macaque individuals from six species groups (muttla, fascicularis, sinica, arctoides, silenus, sylvanus). In addition to individual SNVs, MACSNVdb also allows users to browse and retrieve groups of user-defined SNVs. In particular, users can retrieve non-synonymous SNVs that may have deleterious effects on protein structure or function within macaque orthologs of human disease and drug-target genes. Besides position, alleles and flanking sequences, MACSNVdb integrated additional genomic information including SNV annotations and gene functional annotations. MACSNVdb will facilitate biomedical researchers to discover molecular mechanisms of diverse responses to diseases as well as primatologist to perform population genetic studies. We will continue updating MACSNVdb with newly available sequencing data and annotation to keep the resource up to date. Database URL: http://big.cdu.edu.cn/macsnvdb/
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  • 57
    Publication Date: 2020-03-29
    Description: Supernovae (SNe) generate hot gas in the interstellar medium (ISM), help setting the ISM structure, and support the driving of outflows. It is important to resolve the hot gas generation for galaxy formation simulations at solar mass and sub-parsec resolution that realize individual SN explosions with ambient densities varying by several orders of magnitude in a realistic multiphase ISM. We test resolution requirements by simulating SN blast waves at three metallicities (Z = 0.01, 0.1, and 1 Z⊙), six densities and their respective equilibrium chemical compositions (n = 0.001–100 cm−3), and four mass resolutions (0.1–100 M⊙), in three dimensions. We include non-equilibrium cooling and chemistry, a homogeneous interstellar radiation field, and shielding with a modern pressure–energy smoothed particle hydrodynamics method including isotropic thermal conduction and a meshless-finite-mass solver. We find stronger resolution requirements for chemistry and hot phase generation than for momentum generation. While at 10 M⊙ the radial momenta at the end of the Sedov phase start converging, the hot phase generation and chemistry require higher resolutions to represent the neutral-to-ionized hydrogen fraction at the end of the Sedov phase correctly. Thermal conduction typically reduces the hot phase by 0.2 dex and has little impact on the chemical composition. In general, our 1 and 0.1 M⊙ results agree well with previous numerical and analytic estimates. We conclude that for the thermal energy injection SN model presented here resolutions higher than 10 M⊙ are required to model the chemistry, momentum, and hot phase generation in the multiphase ISM.
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  • 58
    Publication Date: 2020-03-24
    Description: Using science verification observations obtained with ESPRESSO at the Very Large Telescope (VLT) in 4UT mode, we report the first bound on the carbon isotope ratio $ m ^{12}C/^{13}C$ of a quiescent, near-pristine damped Ly α (DLA) system at z = 2.34. We infer a limit $ m log_{10}, ^{12}C/^{13}C gt +0.37, (2sigma)$. We use the abundance pattern of this DLA, combined with a stochastic chemical enrichment model, to infer the properties of the enriching stars, finding the total gas mass of this system to be $log _{10}(M_{ m gas}/{ m M_{odot }})=6.3^{+1.4}_{-0.9}$ and the total stellar mass to be log10(M⋆/M⊙) = 4.8 ± 1.3. The current observations disfavour enrichment by metal-poor asymptotic giant branch (AGB) stars with masses $ m lt 2.4, M_{odot }$, limiting the epoch at which this DLA formed most of its enriching stars. Our modelling suggests that this DLA formed very few stars until $gtrsim 1$ Gyr after the cosmic reionization of hydrogen and, despite its very low metallicity ($sim 1/1000$ of solar), this DLA appears to have formed most of its stars in the past few hundred Myr. Combining the inferred star formation history with evidence that some of the most metal-poor DLAs display an elevated [C/O] ratio at redshift z ≲ 3, we suggest that very metal-poor DLAs may have been affected by reionization quenching. Finally, given the simplicity and quiescence of the absorption features associated with the DLA studied here, we use these ESPRESSO data to place a bound on the possible variability of the fine-structure constant, Δα/α = (−1.2 ± 1.1) × 10−5.
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  • 59
    Publication Date: 2020-03-24
    Description: The electron population inferred to be responsible for the mini-halo within the Ophiuchus galaxy cluster is a steep power law in energy with a slope of 3.8. This is substantially different to that predicted by dark matter (DM) annihilation models. In this work, we present a method of indirect comparison between the observed electron spectrum and that predicted for indirect DM emissions. This method utilizes differences in the consequences of a given electron distribution on the subsequent spectral features of synchrotron emissions. To fully exploit this difference, by leveraging the fact that the peak and cut-off synchrotron frequencies are substantially different to hard power-law cases for WIMP masses above ∼50 GeV, we find that we need μJy sensitivities at frequencies above 10 GHz while being sensitive to arcminute scales. We explore the extent to which this electron spectrum comparison can be validated with the up-coming next-generation Very Large Array (ngVLA) instrument. We show that, with the ngVLA, this method allows us to produce far stronger constraints than existing VLA data, indeed these exceed the Fermi-LAT dwarf searches in a wide variety of annihilation channels and for all studied magnetic field scenarios.
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  • 60
    Publication Date: 2020-03-28
    Description: We aim at analysis of kinematics of main-sequence stars from the GaiaDR2 and PMA catalogues as well as comparison of kinematic parameters derived from their proper motions. We decompose the stellar velocity field on to a set of vector spherical harmonics (VSH), and, using the relations between the decomposition coefficients and the Ogorodnikov–Milne (O–M) model parameters, calculate the latter. The method of VSH allowed to detect all systematic constituents present in the GaiaDR2 and PMA stellar velocity fields. We notice incompleteness of the O–M model, discuss the kinematic parameters derived within its framework, as well as significant decomposition coefficients that do not have analogues within this model. For separate analysis of the kinematic parameters in the Northern and Southern Galactic hemispheres, we apply the decomposition on to a set of zonal VSH (ZVSH). Modelling the stellar velocity field allowed to confirm the causes of some significant beyond-the-model harmonics. Based on stellar proper motions from the Gaia DR2 and PMA catalogues, we confirm the previous conclusion that the values of ω1 and $M^+_{23}$ O–M model parameters derived in the Northern and Southern Galactic hemispheres have opposite signs. This fact takes place due to a vertical gradient of the linear rotation velocity about the Galactic centre. We estimate influence of the vertical gradient on the value of solar velocity component Y⊙. We confirm that the beyond-the-model coefficients t211 and s310 are caused by the vertical gradient as well.
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  • 61
    Publication Date: 2020-03-24
    Description: M dwarf stars are currently the main targets in searches for potentially habitable planets. However, their winds have been suggested to be harmful to planetary atmospheres. Here, in order to better understand the winds of M dwarfs and also infer their physical properties, we perform a one-dimensional magnetohydrodynamic parametric study of winds of M dwarfs that are heated by current biases in planet dissipation of Alfvén waves. These waves are triggered by sub-surface convective motions and propagate along magnetic field lines. Here, we vary the magnetic field strength B0 and density ρ0 at the wind base (chromosphere), while keeping the same relative wave amplitude (0.1B0) and dissipation length-scale. Our simulations thus range from low plasma-β to high plasma-β (0.005–3.7). We find that our winds very quickly reach isothermal temperatures with mass-loss rates $skew{2}dot{M} propto ho _0^2$. We compare our results with Parker wind (PW) models and find that, in the high-β regime, both models agree. However, in the low-β regime, the PW underestimates the terminal velocity by around one order of magnitude and $skew{2}dot{M}$ by several orders of magnitude. We also find that M dwarfs could have chromospheres extending to 18 to 180 per cent of the stellar radius. We apply our model to the planet-hosting star GJ 436 and find, from X-ray observational constraints, $skew{2}dot{M}lt 7.6 imes 10^{-15}, { m M}_{odot }~ ext{yr}^{-1}$. This is in agreement with values derived from the Lyman-α transit of GJ 436b, indicating that spectroscopic planetary transits could be used as a way to study stellar wind properties.
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  • 62
    Publication Date: 2020-03-28
    Description: The cross-correlation of gravitational wave strain with upcoming galaxy surveys probes theories of gravity in a new way. This method enables testing the theory of gravity by combining the effects from both gravitational lensing of gravitational waves and the propagation of gravitational waves in space–time. We find that within 10 yr the combination of the Advanced LIGO (Laser Interferometer Gravitational-Wave Observatory) and VIRGO (Virgo interferometer) detector networks with planned galaxy surveys should detect weak gravitational lensing of gravitational waves in the low-redshift Universe (z 〈 0.5). With the next-generation gravitational wave experiments such as Voyager, LISA (Laser Interferometer Space Antenna), Cosmic Explorer, and the Einstein Telescope, we can extend this test of the theory of gravity to larger redshifts by exploiting the synergies between electromagnetic wave and gravitational wave probes.
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  • 63
    Publication Date: 2020-03-28
    Description: The Gravity Recovery and Climate Experiment (GRACE) satellite gravimetry observations have been widely used in the study of glaciers. However, there is still no detailed GRACE-based study of the glaciers over the Scandinavian Mountains (SCAMs), where the glaciers are debris-covered and the effects of glacial isostatic adjustment (GIA) are significant. In this paper, GRACE observations are combined with climate data to analyse interannual mass changes in glacier and lake areas over Scandinavia during the period from 2003 to 2016. An inversion algorithm, the constrained forward modelling method, is used to recover the signals of glaciers and lakes from GRACE observations. Our results show that the total glacier mass loss rate over Scandinavia is –1.0 ± 1.1 Gt yr–1 during our study period. We find that the glacier accumulation regime in different subregions of the SCAMs may be different. The glacier mass change in the central SCAMs tends to be mainly driven by precipitation. Two rapid transitions from dry/wet years to wet/dry years in the lake area in south Scandinavia are identified by multiple data. The transitions are likely caused by changes in atmospheric circulation, that is surface wind. The mass changes of Scandinavia can be primarily explained by the influence of winds. We find that the glacier area is controlled by both the northerly and southerly winds, while the lake area is mainly driven by the southerly winds. This discrepancy leads to the different mechanisms of mass change in glacier and lake areas. We also discuss the influence of GIA, and suggest that the GRACE-derived long-term hydrology trends over Scandinavia may be unreliable and need to be verified. Our study indicates that GRACE data have potential in detecting small-scale glacier changes.
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  • 64
    Publication Date: 2020-04-02
    Description: The natural remanent magnetization (NRM) of the ocean floor is carried by titanomagnetite grains that undergo low-temperature oxidation after initial cooling. Progressing oxidation is known to generate shrinkage cracks in grains larger than approximately 5 μm, and is suspected to control the long wavelength variation of NRM-intensity across the ocean floor. Here we develop a quantitative theory of single-phase oxidation and crack formation by solving the vacancy-diffusion equation that describes the oxidation process for spherical titanomagnetite particles, where the diffusion coefficient strongly decreases with vacancy concentration. The latter dependence has been experimentally demonstrated and is essential to explain the peculiarities of the observed variations of oxidation-degree with ocean-floor age. The calculated diffusion profiles provide the exact stress distributions inside oxidized titanomagnetite spheres, and predict a size limit for shrinkage-crack formation that agrees with microscopic observations of crack appearance in ocean-floor basalt samples. The new diffusion model provides a unified explanation of long-known experimental facts that (1) temperatures for the onset of low-temperature oxidation during laboratory heating are theoretically estimated as 200–400 ○C, depending on grain size and (2) that heating to 400–500 ○C is required to obtain a sufficiently high degree of oxidation z ≈ 0.8 for the development of high-temperature exsolution lamellae. Calculations for ocean-floor conditions quantitatively suggest that a rapid decrease of NRM intensity during the first 40 ka results from a deflection of magnetization by strong stresses that emerge in titanomagnetite grains of subcritical sizes, and randomization of domain-state by crack formation in larger grains.
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  • 65
    Publication Date: 2020-04-02
    Description: The impact of the Zeeman effect on the Λ-doublet spectra of diatomic radicals is analysed from the point of view of a possible cosmological variation of the proton-to-electron mass ratio, μ. The actual model calculations performed for the 2Π3/2 and 2Π1/2 states of 16OH reveal that the Λ-doublet energy levels of diatomic radicals can be tuned to degeneracy by means of the Zeeman effect using realistic magnetic fields. Tuning this degeneracy allows for a dramatic enhancement of the relative mass sensitivity coefficients of the corresponding transitions and for a substantial reduction of their Doppler broadening. Moreover, unlike their field-free counterparts associated with the degeneracies arising due to the A ∼ 4B situations (A and B being the spin–orbit and rotation constant, respectively), the electric dipole allowed e ↔f Zeeman-tuned transitions exhibit favourable intensities, thus evidencing their promising potential.
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  • 66
    Publication Date: 2020-04-02
    Description: We analyse the physical properties of a large, homogeneously selected sample of ALMA-located sub-millimetre galaxies (SMGs). This survey, AS2UDS, identified 707 SMGs across the ∼1 deg2 field, including ∼17 per cent, which are undetected at K ≳ 25.7 mag. We interpret their ultraviolet-to-radio data using magphys and determine a median redshift of z = 2.61 ± 0.08 (1σ range of z = 1.8–3.4) with just ∼6 per cent at z > 4. Our survey provides a sample of massive dusty galaxies at z ≳ 1, with median dust and stellar masses of Md = (6.8 ± 0.3) × 108 M⊙ (thus, gas masses of ∼1011 M⊙) and M* = (1.26 ± 0.05) × 1011 M⊙. We find no evolution in dust temperature at a constant far-infrared luminosity across z ∼ 1.5–4. The gas mass function of our sample increases to z ∼ 2–3 and then declines at z > 3. The space density and masses of SMGs suggest that almost all galaxies with M* ≳ 3 × 1011 M⊙ have passed through an SMG-like phase. The redshift distribution is well fit by a model combining evolution of the gas fraction in haloes with the growth of halo mass past a critical threshold of Mh ∼ 6 × 1012 M⊙, thus SMGs may represent the highly efficient collapse of gas-rich massive haloes. We show that SMGs are broadly consistent with simple homologous systems in the far-infrared, consistent with a centrally illuminated starburst. Our study provides strong support for an evolutionary link between the active, gas-rich SMG population at z > 1 and the formation of massive, bulge-dominated galaxies across the history of the Universe.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
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  • 67
    Publication Date: 2020-04-02
    Description: Ram-pressure stripping (RPS) is a well observed phenomenon of massive spiral galaxies passing through the hot intracluster medium (ICM) of galaxy clusters. For dwarf galaxies (DGs) within a cluster, the transformation from gaseous to gas-poor systems by RPS is not easily observed and must happen in the outskirts of clusters. In a few objects in close by galaxy clusters and the field, RPS has been observed. Since cluster early-type DGs also show a large variety of internal structures (unexpected central gas reservoirs, blue stellar cores, composite radial stellar profiles), we aim in this study to investigate how ram pressure (RP) affects the interstellar gas content and therefore the star formation (SF) activity. Using a series of numerical simulations, we quantify the dependence of the stripped-off gas on the velocity of the infalling DGs and on the ambient ICM density. We demonstrated that SF can be either suppressed or triggered by RP depending on the ICM density and the DGs mass. Under some conditions, RP can compress the gas, so that it is unexpectedly retained in the central DG region and forms stars. When gas clouds are still bound against stripping but lifted from a thin disc and fall back, their new stars form an ellipsoidal (young) stellar population already with a larger velocity dispersion without the necessity of harassment. Most spectacularly, star clusters can form downstream in stripped-off massive gas clouds in the case of strong RP. We compare our results to observations.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
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  • 68
    Publication Date: 2020-03-24
    Description: The recent discovery of high-redshift dusty galaxies implies a rapid dust enrichment of their interstellar medium (ISM). To interpret these observations, we run a cosmological simulation in a 30 h−1 cMpc/size volume down to z ≈ 4. We use the hydrodynamical code dustygadget, which accounts for the production of dust by stellar populations and its evolution in the ISM. We find that the cosmic dust density parameter (Ωd) is mainly driven by stellar dust at z ≳ 10, so that mass- and metallicity-dependent yields are required to assess the dust content in the first galaxies. At z ≲ 9, the growth of grains in the ISM of evolved systems [log(M⋆/M⊙) > 8.5] significantly increases their dust mass, in agreement with observations in the redshift range 4 ≲ z 〈 8. Our simulation shows that the variety of high-redshift galaxies observed with the Atacama Large Millimeter Array can naturally be accounted for by modelling the grain growth time-scale as a function of the physical conditions in the gas cold phase. In addition, the trends of dust-to-metal and dust-to-gas (${cal D}$) ratios are compatible with the available data. A qualitative investigation of the inhomogeneous dust distribution in a representative massive halo at z ≈ 4 shows that dust is found from the central galaxy up to the closest satellites along polluted filaments with $ m log({cal D}) le -2.4$, but sharply declines at distances d ≳ 30 kpc along many lines of sight, where $ m log({cal D}) lesssim -4.0$.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
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  • 69
    Publication Date: 2020-03-24
    Description: We provide constraints on fast radio burst (FRB) models by careful considerations of radiation forces associated with these powerful transients. We find that the induced Compton scatterings of the coherent radiation by electrons/positrons accelerate particles to very large Lorentz factors (LFs) in and around the source of this radiation. This severely restricts those models for FRBs that invoke relativistic shocks and maser-type instabilities at distances less than about 1013 cm of the neutron star. Radiation travelling upstream, in these models, forces particles to move away from the shock with an LF larger than the LF of the shock front. This suspends the photon generation process after it has been operating for less than ∼0.1 ms (observer frame duration). We show that masers operating in shocks at distances larger than 1013 cm cannot simultaneously account for the burst duration of 1 ms or more and the observed ∼GHz frequencies of FRBs without requiring an excessive energy budget (>1046 erg); the energy is not calculated by imposing any efficiency consideration, or other details, for the maser mechanism, but is entirely the result of ensuring that particle acceleration by induced Compton forces upstream of the shock front does not choke off the maser process. For the source to operate more or less continuously for a few ms, it should be embedded in a strong magnetic field – cyclotron frequency ≫ wave frequency – so that radiation forces do not disperse the plasma and shut off the engine.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
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