| 1. |
- Falster, Daniel, et al.
(författare)
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AusTraits, a curated plant trait database for the Australian flora
- 2021
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Ingår i: Scientific Data. - : Nature Portfolio. - 2052-4463. ; 8:1
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Tidskriftsartikel (refereegranskat)abstract
- We introduce the AusTraits database - a compilation of values of plant traits for taxa in the Australian flora (hereafter AusTraits). AusTraits synthesises data on 448 traits across 28,640 taxa from field campaigns, published literature, taxonomic monographs, and individual taxon descriptions. Traits vary in scope from physiological measures of performance (e.g. photosynthetic gas exchange, water-use efficiency) to morphological attributes (e.g. leaf area, seed mass, plant height) which link to aspects of ecological variation. AusTraits contains curated and harmonised individual- and species-level measurements coupled to, where available, contextual information on site properties and experimental conditions. This article provides information on version 3.0.2 of AusTraits which contains data for 997,808 trait-by-taxon combinations. We envision AusTraits as an ongoing collaborative initiative for easily archiving and sharing trait data, which also provides a template for other national or regional initiatives globally to fill persistent gaps in trait knowledge.
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| 2. |
- Tapia-Ruiz, Nuria, et al.
(författare)
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2021 roadmap for sodium-ion batteries
- 2021
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Ingår i: Journal of Physics. - : Institute of Physics Publishing (IOPP). - 2515-7655. ; 3:3
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Tidskriftsartikel (refereegranskat)abstract
- Increasing concerns regarding the sustainability of lithium sources, due to their limited availability and consequent expected price increase, have raised awareness of the importance of developing alternative energy-storage candidates that can sustain the ever-growing energy demand. Furthermore, limitations on the availability of the transition metals used in the manufacturing of cathode materials, together with questionable mining practices, are driving development towards more sustainable elements. Given the uniformly high abundance and cost-effectiveness of sodium, as well as its very suitable redox potential (close to that of lithium), sodium-ion battery technology offers tremendous potential to be a counterpart to lithium-ion batteries (LIBs) in different application scenarios, such as stationary energy storage and low-cost vehicles. This potential is reflected by the major investments that are being made by industry in a wide variety of markets and in diverse material combinations. Despite the associated advantages of being a drop-in replacement for LIBs, there are remarkable differences in the physicochemical properties between sodium and lithium that give rise to different behaviours, for example, different coordination preferences in compounds, desolvation energies, or solubility of the solid-electrolyte interphase inorganic salt components. This demands a more detailed study of the underlying physical and chemical processes occurring in sodium-ion batteries and allows great scope for groundbreaking advances in the field, from lab-scale to scale-up. This roadmap provides an extensive review by experts in academia and industry of the current state of the art in 2021 and the different research directions and strategies currently underway to improve the performance of sodium-ion batteries. The aim is to provide an opinion with respect to the current challenges and opportunities, from the fundamental properties to the practical applications of this technology.
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| 3. |
- Beam, Christopher R., et al.
(författare)
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Estimating Likelihood of Dementia in the Absence of Diagnostic Data : A Latent Dementia Index in 10 Genetically Informed Studies
- 2022
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Ingår i: Journal of Alzheimer's Disease. - : IOS Press. - 1387-2877 .- 1875-8908. ; 90:3, s. 1187-1201
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Epidemiological research on dementia is hampered by differences across studies in how dementia is classified, especially where clinical diagnoses of dementia may not be available. OBJECTIVE: We apply structural equation modeling to estimate dementia likelihood across heterogeneous samples within a multi-study consortium and use the twin design of the sample to validate the results. METHODS: Using 10 twin studies, we implement a latent variable approach that aligns different tests available in each study to assess cognitive, memory, and functional ability. The model separates general cognitive ability from components indicative of dementia. We examine the validity of this continuous latent dementia index (LDI). We then identify cut-off points along the LDI distributions in each study and align them across studies to distinguish individuals with and without probable dementia. Finally, we validate the LDI by determining its heritability and estimating genetic and environmental correlations between the LDI and clinically diagnosed dementia where available. RESULTS: Results indicate that coordinated estimation of LDI across 10 studies has validity against clinically diagnosed dementia. The LDI can be fit to heterogeneous sets of memory, other cognitive, and functional ability variables to extract a score reflective of likelihood of dementia that can be interpreted similarly across studies despite diverse study designs and sampling characteristics. Finally, the same genetic sources of variance strongly contribute to both the LDI and clinical diagnosis. CONCLUSION: This latent dementia indicator approach may serve as a model for other research consortia confronted with similar data integration challenges.
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| 4. |
- Weston, S., et al.
(författare)
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On More than Two Decades of Celestial Reference Frame VLBI Observations in the Deep South: IVS-CRDS (1995 - 2021)
- 2023
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Ingår i: Publications Astronomical Society of Australia. - 1448-6083 .- 1323-3580. ; 40
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Tidskriftsartikel (refereegranskat)abstract
- The International VLBI Service for Geodesy & Astrometry (IVS) regularly provides high-quality data to produce Earth Orientation Parameters (EOP), and for the maintenance and realization of the International Terrestrial and Celestial Reference Frames, ITRF and ICRF. The first iteration of the celestial reference frame (CRF) at radio wavelengths, the ICRF1, was adopted by the International Astronomical Union (IAU) in 1997 to replace the FK5 optical frame. Soon after, the IVS began official operations and in 2009 there was a significant increase in data sufficient to warrant a second iteration of the CRF, ICRF2. The most recent ICRF3, was adopted by the IAU in 2018. However, due to the geographic distribution of observing stations being concentrated in the Northern hemisphere, CRFs are generally weaker in the South due to there being fewer Southern Hemisphere observations. To increase the Southern Hemisphere observations, and the density, precision of the sources, a series of deep South observing sessions was initiated in 1995. This initiative in 2004 became the IVS Celestial Reference Frame Deep South (IVS-CRDS) observing program. This paper covers the evolution of the CRDS observing program for the period 1995 to 2021, details the data products and results, and concludes with a summary of upcoming improvements to this ongoing project.
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| 5. |
- Zhu, Jiazheng, et al.
(författare)
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SN 2017egm : A Helium-rich Superluminous Supernova with Multiple Bumps in the Light Curves
- 2023
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Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 949:1
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Tidskriftsartikel (refereegranskat)abstract
- When discovered, SN 2017egm was the closest (redshift z = 0.03) hydrogen-poor superluminous supernova (SLSN-I) and a rare case that exploded in a massive and metal-rich galaxy. Thus, it has since been extensively observed and studied. We report spectroscopic data showing strong emission at around He i lambda 10830 and four He i absorption lines in the optical. Consequently, we classify SN 2017egm as a member of an emerging population of helium-rich SLSNe-I (i.e., SLSNe-Ib). We also present our late-time photometric observations. By combining them with archival data, we analyze high-cadence ultraviolet, optical, and near-infrared light curves spanning from early pre-peak (similar to-20 days) to late phases (similar to+300 days). We obtain its most complete bolometric light curve, in which multiple bumps are identified. None of the previously proposed models can satisfactorily explain all main light-curve features, while multiple interactions between the ejecta and circumstellar material (CSM) may explain the undulating features. The prominent infrared excess with a blackbody luminosity of 10(7)-10(8) L (circle dot) detected in SN 2017egm could originate from the emission of either an echo of a pre-existing dust shell or newly formed dust, offering an additional piece of evidence supporting the ejecta-CSM interaction model. Moreover, our analysis of deep Chandra observations yields the tightest-ever constraint on the X-ray emission of an SLSN-I, amounting to an X-ray-to-optical luminosity ratio less than or similar to 10(-3) at late phases (similar to 100-200 days), which could help explore its close environment and central engine.
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| 6. |
- Beaumont, Robin N, et al.
(författare)
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Genome-wide association study of placental weight identifies distinct and shared genetic influences between placental and fetal growth.
- 2023
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Ingår i: Nature genetics. - 1546-1718 .- 1061-4036. ; 55:11, s. 1807-19
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Tidskriftsartikel (refereegranskat)abstract
- A well-functioning placenta is essential for fetal and maternal health throughout pregnancy. Using placental weight as a proxy for placental growth, we report genome-wide association analyses in the fetal (n=65,405), maternal (n=61,228) and paternal (n=52,392) genomes, yielding 40 independent association signals. Twenty-six signals are classified as fetal, four maternal and three fetal and maternal. A maternal parent-of-origin effect is seen near KCNQ1. Genetic correlation and colocalization analyses reveal overlap with birth weight genetics, but 12 loci are classified as predominantly or only affecting placental weight, with connections to placental development and morphology, and transport of antibodies and amino acids. Mendelian randomization analyses indicate that fetal genetically mediated higher placental weight is causally associated with preeclampsia risk and shorter gestational duration. Moreover, these analyses support the role of fetal insulin in regulating placental weight, providing a key link between fetal and placental growth.
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| 7. |
- Matthews, James H., et al.
(författare)
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How Do Magnetic Field Models Affect Astrophysical Limits on Light Axion-like Particles? An X-Ray Case Study with NGC 1275
- 2022
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 930:1
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Tidskriftsartikel (refereegranskat)abstract
- Axion-like particles (ALPs) are a well-motivated extension to the standard model of particle physics, and X-ray observations of cluster-hosted AGN currently place the most stringent constraints on the ALP coupling to electromagnetism, gaγ, for very light ALPs (ma ≲ 10−11 eV). We revisit limits obtained by Reynolds et al. using Chandra X-ray grating spectroscopy of NGC 1275, the central AGN in the Perseus cluster, examining the impact of the X-ray spectral model and magnetic field model. We also present a new publicly available code, ALPro, which we use to solve the ALP propagation problem. We discuss evidence for turbulent magnetic fields in Perseus and show that it can be important to resolve the magnetic field structure on scales below the coherence length. We reanalyze the NGC 1275 X-ray spectra using an improved data reduction and baseline spectral model. We find the limits are insensitive to whether a partially covering absorber is used in the fits. At low ma (ma ≲ 10−13 eV), we find marginally weaker limits on gaγ (by 0.1–0.3 dex) with different magnetic field models, compared to Model B from Reynolds et al. (2020). A Gaussian random field (GRF) model designed to mimic ∼50 kpc scale coherent structures also results in only slightly weaker limits. We conclude that the existing Model B limits are robust assuming that βpl ≈ 100, and are insensitive to whether cell-based or GRF methods are used. However, astrophysical uncertainties regarding the strength and structure of cluster magnetic fields persist, motivating high-sensitivity RM observations and tighter constraints on the radial profile of βpl.
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| 8. |
- Reynolds, Christopher S., et al.
(författare)
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Astrophysical Limits on Very Light Axion-like Particles from Chandra Grating Spectroscopy of NGC 1275
- 2020
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 890:1
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Tidskriftsartikel (refereegranskat)abstract
- Axions/axion-like particles (ALPs) are a well-motivated extension of the Standard Model and are generic within String Theory. The X-ray transparency of the intracluster medium (ICM) in galaxy clusters is a powerful probe of light ALPs (with mass <10(-11)eV); as X-ray photons from an embedded or background source propagate through the magnetized ICM, they may undergo energy-dependent quantum mechanical conversion into ALPs (and vice versa), imprinting distortions on the X-ray spectrum. We present Chandra data for the active galactic nucleus NGC 1275 at the center of the Perseus cluster. Employing a 490 ks High Energy Transmission Gratings exposure, we obtain a high-quality 1-9 keV spectrum free from photon pileup and ICM contamination. Apart from iron-band features, the spectrum is described by a power-law continuum, with any spectral distortions at the <3% level. We compute photon survival probabilities as a function of ALP mass m(a) and ALP-photon coupling constant g(alpha gamma) for an ensemble of ICM magnetic field models, and then use the NGC 1275 spectrum to constrain the (m(a), g(alpha gamma))-plane. Marginalizing over magnetic field realizations, the 99.7% credible region limits the ALP-photon coupling to G(alpha gamma) < 6 - 8 x 10(-13) GeV-1 (depending upon magnetic field model) for masses m(a) < 1 x 10(-12) eV. These are the most stringent limit to date on g(alpha gamma) for these light ALPs, and have already reached the sensitivity limits of next-generation helioscopes and light-shining-through-wall experiments. We highlight the potential of these studies with the next-generation X-ray observatories Athena and Lynx, but note the critical importance of advances in relative calibration of these future X-ray spectrometers.
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| 9. |
- Sisk-Reynés, Júlia, et al.
(författare)
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New constraints on light axion-like particles using Chandra transmission grating spectroscopy of the powerful cluster-hosted quasar H1821+643
- 2022
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 510:1, s. 1264-1277
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Tidskriftsartikel (refereegranskat)abstract
- Axion-like particles (ALPs) are predicted by several Beyond the Standard Model theories, in particular, string theory. In the presence of an external magnetic field perpendicular to the direction of propagation, ALPs can couple to photons. Therefore, if an X-ray source is viewed through a magnetized plasma, such as a luminous quasar in a galaxy cluster, we may expect spectral distortions that are well described by photon–ALP oscillations. We present a 571 ks combined high- and low-energy transmission grating Chandra observation of the powerful radio-quiet quasar H1821+643, hosted by a cool-core cluster at redshift 0.3. The spectrum is well described by a double power-law continuum and broad+narrow iron line emission typical of type-1 active galactic nuclei (AGNs), with remaining spectral features <2.5 per cent<2.5 per cent. Using a cell-based approach to describe the turbulent cluster magnetic field, we compare our spectrum with photon–ALP mixing curves for 500 field realizations, assuming that the thermal-to-magnetic pressure ratio β remains constant up to the virial radius. At 99.7 per cent99.7 per cent credibility and taking β = 100, we exclude all couplings gaγ > 6.3 × 10−13 GeV−1 for most ALP masses <10−12 eV. Our results are moderately more sensitive to constraining ALPs than the best previous result from Chandra observations of the Perseus cluster, albeit with a less constrained field model. We reflect on the promising future of ALP studies with bright AGNs embedded in rich clusters, especially with the upcoming Athena mission.
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| 10. |
- Sisk-Reynés, Júlia, et al.
(författare)
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Physics Beyond the Standard Model with Future X-Ray Observatories : Projected Constraints on Very-light Axion-like Particles with Athena and AXIS
- 2023
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Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 951:1
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Tidskriftsartikel (refereegranskat)abstract
- Axion-like particles (ALPs) are well-motivated extensions of the Standard Model of Particle Physics and a generic prediction of some string theories. X-ray observations of bright active galactic nuclei (AGNs) hosted by rich clusters of galaxies are excellent probes of very-light ALPs, with masses . We evaluate the potential of future X-ray observatories, particularly Athena and the proposed AXIS, to constrain ALPs via observations of cluster-hosted AGNs, taking NGC 1275 in the Perseus cluster as our exemplar. Assuming perfect knowledge of the instrument calibration, we show that a modest exposure (200 ks) of NGC 1275 by Athena permits us to exclude all photon–ALP couplings gaγ > 6.3 × 10−14 GeV−1 at the 95% confidence level, as previously shown by Conlon et al., representing a factor of 10 improvement over current limits. We then proceed to assess the impact of realistic calibration uncertainties on the Athena projection by applying a standard Cash likelihood procedure, showing the projected constraints on gaγ weaken by a factor of 10 (back to the current most sensitive constraints). However, we show how the use of a deep neural network can disentangle the energy-dependent features induced by instrumental miscalibration and those induced by photon–ALP mixing, allowing us to recover most of the sensitivity to the ALP physics. In our explicit demonstration, the machine learning applied allows us to exclude gaγ > 2.0 × 10−13 GeV−1, complementing the projected constraints of next-generation ALP dark matter birefringent cavity searches for very-light ALPs. Finally, we show that a 200 ks AXIS/on-axis observation of NGC 1275 will tighten the current best constraints on very-light ALPs by a factor of 3.
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