ANU Research Publications
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The Australian National University's Research Publications collection is an online location for collecting, preserving and disseminating the scholarly output of the University. This service allows members of the University to share their research with the wider community. ANU Open Research accepts journal articles, conference papers, book chapters, working or technical papers and other forms of scholarly communication.
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Item Embargo The GALAH+ survey: Third data release(Oxford University Press on behalf of Royal Astronomical Society, 2021) Buder, Sven; Sharma, Sanjib; Kos, J.; Amarsi, A. M.; Nordlander, Thomas; Lind, Karin; Martell, S. L.; Asplund, Martin; Bland-Hawthorn, Jonathan; Casey, Andrew; De Silva, Gayandhi M; D’Orazi, Valentina; Freeman, Kenneth; Hayden, Michael R.; Lewis, Geraint Francis; lin, jane; Schlesinger, Katharine; Simpson, Jeffrey D; Stello, Dennis; Zucker, Daniel; Casagrande, Luca; Da Costa, Gary; Nandakumar, Govind; Ting, Yuan-Sen; Zerjal, MarusaThe ensemble of chemical element abundance measurements for stars, along with precision distances and orbit properties, provides high-dimensional data to study the evolution of the Milky Way. With this third data release of the Galactic Archaeology with HERMES (GALAH) survey, we publish 678 423 spectra for 588 571 mostly nearby stars (81.2 per cent of stars are within <2 kpc), observed with the HERMES spectrograph at the Anglo-Australian Telescope. This release (hereafter GALAH+ DR3) includes all observations from GALAH Phase 1 (bright, main, and faint survey, 70 per cent), K2-HERMES (17 per cent), TESS-HERMES (5 per cent), and a subset of ancillary observations (8 per cent) including the bulge and >75 stellar clusters. We derive stellar parameters T-eff, logg, [Fe/H], v(mic), v(broad), and v(rad) using our modified version of the spectrum synthesis code Spectroscopy Made Easy (SME) and 1D MARCS model atmospheres. We break spectroscopic degeneracies in our spectrum analysis with astrometry from Gaia DR2 and photometry from 2MASS. We report abundance ratios [X/Fe] for 30 different elements (11 of which are based on non-LTE computations) covering five nucleosynthetic pathways. We describe validations for accuracy and precision, flagging of peculiar stars/measurements and recommendations for using our results. Our catalogue comprises 65 per cent dwarfs, 34 per cent giants, and 1 per cent other/unclassified stars. Based on unflagged chemical composition and age, we find 62 per cent young low-alpha, 9 per cent young high-alpha, 27 per cent old high-alpha, and 2 per cent stars with [Fe/H] <= -1. Based on kinematics, 4 per cent are halo stars. Several Value-Added-Catalogues, including stellar ages and dynamics, updated after Gaia eDR3, accompany this release and allow chrono-chemodynamic analyses, as we showcase.Item Embargo Direct zircon U-Pb evidence for pre-Himalayan HT metamorphism in the Higher Himalayan Crystallines, eastern Garhwal Himalaya, India(John Wiley & Sons Inc, 2022-01-02) Mohan, Shashank Prabha; Williams, Ian; Singh, SandeepThe high-grade Higher Himalayan Crystallines (HHC), located between the South Tibetan Detachment System and Main Central Thrust in the collision zone between the Indo-Australian and Eurasian plates, have been subject to at least four significant phases of deformation and metamorphism. The earliest of those significantly predates the Cenozoic continent-continent collision, but has been difficult to date isotopically because of later overprinting. Migmatitic paragneiss from the Badrinath Formation in the Dhauliganga Valley, northern Uttarakhand, some of the highest-grade rocks in the HHC, preserves direct evidence of mid-Ordovician metamorphism in the form of 465.8 +/- 6.4 Ma zircon overgrowths with extremely low Th/U (0.0038-0.0074). The overgrowths have formed on ca. 2.63-0.71 Ga detrital zircon cores and are themselves overgrown by two generations of Miocene metamorphic zircon with mean Pb/U ages of ca. 21.5 and 18.2 Ma. Monazite from the same sample has a mean Pb/Th age of 19.4 +/- 0.2 Ma. The oxygen isotopic compositions of the monazite (delta O-18: 7.69 +/- 0.08 parts per thousand) and youngest zircon overgrowths (delta O-18: 7.95 +/- 0.12, 8.24 +/- 0.09 parts per thousand) are consistent with mineral growth in a metasediment, but either of the two minerals did not grow in isotopic equilibrium with each other, or the original composition of the monazite has not been preserved. If the quartz (delta O-18: 13.29 +/- 0.11 parts per thousand) equilibrated with the youngest zircon and its composition has been preserved, then the last episode of zircon growth took place at low temperature, ca. 420 degrees C, after the migmatization. The protolith of the Badrinath migmatite was a Neoproterozoic or Early Palaeozoic metasediment partially melted (and probably migmatized) in the Middle Ordovician. The strong planar foliation currently present in the migmatite is probably the result of mid-crustal extrusional channel flow and HT decompressional partial melting in the Miocene.Item Embargo Quantifying the nature of ore-forming fluids in the Dalucao carbonatite-related REE deposit, Southwest China: implication for the transport and deposition of REEs(Springer Verlag, 2022-08) Zhang, Wei; Chen, Wei Terry; Mernagh, Terry; Zhou, LiCarbonatite-related rare earth element (REE) deposits are major hosts of REE resources. REE mineralization in these deposits is generally associated with hydrothermal systems at late stages of carbonatite evolution, but the nature of ore-forming fluids and their role in concentrating REEs are not well understood. In this study, we quantified the nature of ore-forming fluids by conducting a detailed investigation on the fluid inclusions of the Dalucao carbonatite–related REE deposit, Southwest China. Based on the phases present at room temperature, three types of fluid inclusions, namely, high-density, CO2-rich inclusions, solid-bearing brine inclusions, and aqueous liquid inclusions, have been distinguished in the deposit. High-resolution Raman mapping reveals that the daughter minerals in the earliest brine inclusions are dominantly composed of sulfate (average mass proportion of 92.3%) with minor chloride (3.1%), carbonate (4.4%), and silicate (0.2%). In addition, a Raman peak of SO42– has been detected in the liquid phase of the aqueous inclusions. These new results suggest that the early, high-temperature ore-forming fluids are unique for containing extremely high concentrations of sulfate. Such sulfate-rich fluids are confirmed to be responsible for transporting appreciable amounts of REEs in the forms of REE-sulfate complexes. We further propose that deposition of REE minerals was mainly triggered by decreasing temperatures, which, as a result, reduced the solubility of sulfate in the fluids. Our new findings highlight the fact that sulfate-rich fluids tend to be more common in carbonatite-related REE deposits and play key roles in REE mineralization.Publication Metadata only Algebraic Characterization of Fixed Modes in Decentralized Control(1981) Anderson, Brian D.O.; Clements, David J.Algebraic characterizations are presented for the existence of fixed modes of a linear closed-loop system with decentralized feedback control. The class of controllers for which fixed modes are present is extended beyond that currently known.Item Embargo First extragalactic measurement of the turbulence driving parameter: ALMA observations of the star-foing region N159E in the Large Magellanic Cloud(Oxford University Press on behalf of Royal Astronomical Society, 2021) Sharda, Piyush; Harimohan Menon, Shyam; Federrath, Christoph; Krumholz, Mark; Beattie, James; Jameson, K.; Tokuda, K.; Burkhart, Blakesley; Crocker, Roland; Law, Charles J.; Seta, Amit; Gaetz, Terrance, J.; Pingel, Nickolas; Seitenzahl, Ivo R; Sano, Hidetoshi; Fukui, YasuoStudying the driving modes of turbulence is important for characterizing the impact of turbulence in various astrophysical environments. The driving mode of turbulence is parametrized by b, which relates the width of the gas density PDF to the turbulent Mach number; b approximate to 1/3, 1, and 0.4 correspond to driving that is solenoidal, compressive, and a natural mixture of the two, respectively. In this work, we use high-resolution (sub-pc) ALMA (CO)-C-12 (J = 2-1), (CO)-C-13 (J = 2-1), and (CO)-O-18 (J = 2-1) observations of filamentary molecular clouds in the star-forming region N159E (the Papillon Nebula) in the Large Magellanic Cloud (LMC) to provide the first measurement of turbulence driving parameter in an extragalactic region. We use a non-local thermodynamic equilibrium (NLTE) analysis of the CO isotopologues to construct a gas density PDF, which we find to be largely lognormal in shape with some intermittent features indicating deviations from lognormality. We find that the width of the lognormal part of the density PDF is comparable to the supersonic turbulent Mach number, resulting in b approximate to 0.9. This implies that the driving mode of turbulence in N159E is primarily compressive. We speculate that the compressive turbulence could have been powered by gravo-turbulent fragmentation of the molecular gas, or due to compression powered by Hi flows that led to the development of the molecular filaments observed by ALMA in the region. Our analysis can be easily applied to study the nature of turbulence driving in resolved star-forming regions in the local as well as the high-redshift Universe.Item Embargo A radio polarization study of magnetic fields in the Small Magellanic Cloud(Oxford University Press on behalf of Royal Astronomical Society, 2022) Livingston, Jack; McClure-Griffiths, Naomi; Mao, S. A.; Ma, Yik Ki; Gaensler, B. M.; Heald, G; Seta, AmitObserving the magnetic fields of low-mass interacting galaxies tells us how they have evolved over cosmic time and their importance in galaxy evolution. We have measured the Faraday rotation of 80 extra-galactic radio sources behind the Small Magellanic Cloud (SMC) using the CSIRO Australia Telescope Compact Array (ATCA) with a frequency range of 1.4-3.0 GHz. Both the sensitivity of our observations and the source density are an order-of-magnitude improvement on previous Faraday rotation measurements of this galaxy. The SMC generally produces negative rotation measures after accounting for the Milky Way foreground contribution, indicating that it has a mean coherent line-of-sight magnetic field strength of -0.3 +/- 0.1 mu G, consistent with previous findings. We detect signatures of magnetic fields extending from the north and south of the Bar of the SMC. The random component of the SMC magnetic field has a strength of similar to 5 mu G with a characteristic size-scale of magneto-ionic turbulence <250 pc, making the SMC like other low-mass interacting galaxies. The magnetic fields of the SMC and Magellanic Bridge appear similar in direction and strength, hinting at a connection between the two fields as part of the hypothesized `pan-Magellanic' magnetic field.Item Embargo When did the initial mass function become bottom-heavy?(Oxford University Press on behalf of Royal Astronomical Society, 2022) Krumholz, Mark; Sharda, PiyushThe characteristic mass that sets the peak of the stellar initial mass function (IMF) is closely linked to the theodynamic behaviour of interstellar gas, which controls how gas fragments as it collapses under gravity. As the Universe has grown in metal abundance over cosmic time, this theodynamic behaviour has evolved from a primordial regime dominated by the competition between compressional heating and molecular hydrogen cooling to a modern regime where the dominant process in dense gas is protostellar radiation feedback, transmitted to the gas by dust-gas collisions. In this paper, we map out the primordial-to-modern transition by constructing a model for the theodynamics of collapsing, dusty gas clouds at a wide range of metallicities. We show the transition from the primordial regime to the modern regime begins at metallicity $ 10{-4}, {Z}$, passes through an inteediate stage where metal line cooling is dominant at $ 10{-3}, {Z_}$, and then transitions to the modern dust- and feedback-dominated regime at $ 10{-2}, {Z}$. In low pressure environments like the Milky Way, this transition is accompanied by a dramatic change in the characteristic stellar mass, from $50, {M}$ at $ 10{-6}, {Z_}$ to $0.3, {M}$ once radiation feedback begins to dominate, which marks the appearance of the modern bottom-heavy Milky Way IMF. In the high pressure environments typical of massive elliptical galaxies, the characteristic mass for the modern, dust-dominated regime falls to $0.1, {M_}$, thus providing an explanation for the more bottom-heavy IMF observed in these galaxies. We conclude that metallicity is a key driver of variations in the characteristic stellar mass, and by extension, the IMF.Item Embargo The role of the social determinants of health in outcomes of surgery for low back pain: A systematic review and narrative synthesis(Elsevier BV, 2022) Yap, Zen L.; Summers, Simon J.; Grant, Ashley, R.; Moseley, G. Lorimer; Karran, Emma L.BACKGROUND CONTEXT: Low back pain is a major cause of morbidity and disability worldwide and is responsible for vast societal impact. Rates of surgical intervention for lumbar spine disorders continue to rise but poor outcomes remain common. Understanding how the social determinants of health (SDH) influence spinal surgical outcomes stands to inform appropriately tailored care practices and lead to better patient outcomes. PURPOSE: To determine the relationships between the SDH and pain, opioid use, disability and work absenteeism following lumbar spine surgery. STUDY DESIGN: Systematic review and narrative synthesis. METHODS: We searched Embase, the Cochrane Library, Medline, and Web of Science from inception to April 21, 2020. Studies eligible for inclusion involved participants receiving lumbar spine surgery and investigated the relationship between at least one SDH and post-surgical pain, opioid use, disability or work absenteeism. We evaluated the risk of bias of included studies and used the PROGRESS-Plus framework to organize a narrative synthesis of findings. RESULTS: Relevant data was extracted from twenty-three studies involving 30,987 adults from 12 countries. A total of 107 relationships between the SDH and post-surgical outcomes were evaluated, 67 in multivariate analyses. Education was investigated in 23 analyses (14 studies): 70% revealed significant independent relationships between lower education and poorer outcomes. Socioeconomic status was investigated in nine analyses (four studies): 67% revealed independent relationships between lower socioeconomic status and poorer outcomes. Gender was investigated in 40 analyses (22 studies): indications that male versus female sex was associated with poorer outcomes were equivocal. Place of residence, race/ethnicity, and social capital were infrequently investigated. CONCLUSIONS: Low educational attainment and low-income status are clear independent contributors to poorer outcomes following lumbar spine surgery. Occupational factors and work context are likely to be influential. Further research is critical to guide best-practice spinal surgery through a health equity lens.Item Embargo Ventilation of the Southern Ocean Pycnocline(Annual Reviews Inc, 2022) Morrison, Adele; Waugh, D. W.; Hogg, Andy; Jones, Daniel C.; Abernathey, Ryan P.Ocean ventilation is the transfer of tracers and young water from the surface down into the ocean interior. The tracers that can be transported to depth include anthropogenic heat and carbon, both of which are critical to understanding future climate trajectories. Ventilation occurs in both high-and midlatitude regions, but it is the southern midlatitudes that are responsible for the largest fraction of anthropogenic heat and carbon uptake; such Southern Ocean ventilation is the focus of this review. Southern Ocean ventilation occurs through a chain of interconnected mechanisms, including the zonally averaged meridional overturning circulation, localized subduction, eddy-driven mixing along isopycnals, and lateral transport by subtropical gyres. To unravel the complex pathways of ventilation and reconcile conflicting results, here we assess the relative contribution of each of thesemechanisms, emphasizing the three-dimensional and temporally varying nature of the ventilation of the Southern Ocean pycnocline. We conclude that Southern Ocean ventilation depends on multiple processes and that simplified frameworks that explain ventilation changes through a single process are insufficient.Item Embargo Reinforcing managerial prerogative in the Australian Public Service during the COVID-19 pandemic(SAGE Publications, 2022) Roles, Cameron; Ananth, Sukanya; O’Donnell, MichaelOver several decades Liberal-National Governments have encouraged Australian Public Service (APS) employers to uphold managerial prerogative by offering individual employment arrangements to employees. During the period of the COVID-19 pandemic, the Morrison Liberal-National Government’s Workplace Bargaining Policy reinforced this agenda. In place of collective bargaining, APS agency heads were encouraged to determine pay rises and new employment conditions for employees using Section 24 of the Public Service Act (PS Act) 1999. Workplace determinations did not need to be negotiated with public sector unions and some 85,500 employees across 57 APS agencies, or approximately 63% of the APS workforce, had accepted pay increases via workplace determinations by 31 December 2020. The widespread adoption of workplace determinations in the APS poses significant challenges for public sector unions and for the future of APS collective bargaining. JEL Codes: J21, J45, J53, K31.Item Metadata only From stars to brains: Milestones in the planetary evolution of life and intelligence(Springer Cham, 2019) Glikson, AndrewThe permutation of basic atoms-nitrogen, hydrogen, oxygen, carbon and phosphorus?into the biomolecules DNA and RNA, subsequently evolved in cells and brains, defining the origin of life and intelligence, remains unexplained. Equally the origin of the genetic information and the intertwined nature of ‘hardware’ and ‘software’ involved in the evolution of bio-molecules and the cells are shrouded in mystery. This treatise aims at exploring individual and swarm behaviour patterns which potentially hint at as yet unknown biological principles. It reviews theories of evolution with perspectives from the earth sciences, commencing with the earliest observed records of life. This is followed by reviews and discussion of the building blocks of life, marine and terrestrial communities, the arthropods, birds and finally humans. It is suggested that, further to the mutation/natural selection processes established by Darwin and Wallace, an understanding of the evolution of intelligence remains little understood. A directionality of evolutionary trajectories is evident, not least the purposeful thinking process of humans as well as animals. It is not clear how directional intelligence, manifested for example by the collective intelligence of arthropod colonies, has evolved from mutation/natural selection processes. Potential clues for the understanding of life and evolution are provided by Aristotle’s dictum of “the whole being greater than the sum of the parts”, Niels Bohr’s principle of quantum complementarity and George Ellis’ theory of top-down causality. Inherent in the question of the origin of life is an anthropocentric bias, related to the self-referential Anthropic Principle and theological paradigms of man’s supposed dominion over all other species. The Anthropic Principle, however, should be capable of being circumvented using the scientific falsification method, assuming universal verified constants of physics. The phenomenon of the human mastery of fire and the splitting of the atom, leading to the seventh major mass extinction of species, remains incomprehensible.Item Open Access Algorithms for the Multiplication Table Problem(Walter de Gruyter GmbH & Co. KG, 2021) Brent, Richard; POMERANCE, CARL; Purdum, David; WEBSTER, JONATHANLet M(n) denote the number of distinct entries in the n×n multiplication table. The function M(n) has been studied by Erdős, Tenenbaum, Ford, and others, but the asymptotic behavior of M(n) as n → ∞ is not known precisely. Thus, there is some interest in algorithms for computing M(n) either exactly or approximately. We compare several algorithms for computing M(n) exactly, and give a new algorithm that has a subquadratic running time. We also present two Monte Carlo algorithms for approximate computation of M(n). We give the results of exact computations for values of n up to 230, and of Monte Carlo computations for n up to 2100,000,000, and compare our experimental results with Ford’s order-of-magnitude result.Item Embargo Ultraluminous high-redshift quasars from SkyMapper - II. New quasars and the bright end of the luminosity function(Oxford University Press, 2022-03-01) Onken, Christopher; Wolf, Christian; Bian, Fuyan; Fan, Xiaohui; Hon, Wei Jeat; Raithel, David; Tisserand, Patrick; Lai, SamuelWe search for ultraluminous Quasi-Stellar Objects (QSOs) at high redshift using photometry from the SkyMapper Southern Survey Data Release 3 (DR3), in combination with 2MASS, VHS DR6, VIKING DR5, AllWISE, and CatWISE2020, as well as parallaxes and proper motions from Gaia DR2 and eDR3. We report 142 newly discovered Southern QSOs at 3.8 < z < 5.5, of which 126 have M-145 < -27 AB mag and are found in a search area of 14 486 deg(2). This Southern sample, utilizing the Gaia astrometry to offset wider photometric colour criteria, achieves unprecedented completeness for an ultraluminous QSO search at high redshift. In combination with already known QSOs, we construct a sample that is >80 per cent complete for M-145 < -27.33 AB mag at z = 4.7 and for M-145 < -27.73 AB mag at z = 5.4. We derive the bright end of the QSO luminosity function at rest frame 145 nm for z = 4.7-5.4 and measure its slope to be beta = -3.60 +/- 0.37 and beta = -3.38 +/- 0.32 for two different estimates of the faint-end QSO density adopted from the literature. We also present the first z similar to 5 QSO luminosity function at rest frame 300 nm.Item Embargo Quokka: a code for two-moment AMR radiation hydrodynamics on GPUs(Oxford University Press, 2022) Wibking, Ben; Krumholz, MarkWe present quokka, a new subcycling-in-time, block-structured adaptive mesh refinement (AMR) radiation hydrodynamics (RHD) code optimized for graphics processing units (GPUs). quokka solves the equations of HD with the piecewise parabolic method (PPM) in a method-of-lines formulation, and handles radiative transfer via the variable Eddington tensor (VET) radiation moment equations with a local closure. We use the amrex library to handle the AM management. In order to maximize GPU performance, we combine explicit-in-time evolution of the radiation moment equations with the reduced speed-of-light approximation. We show results for a wide range of test problems for HD, radiation, and coupled RHD. On uniform grids in 3D on a single GPU, our code achieves >250 million hydrodynamic updates per second and almost 40 million radiation hydrodynamic updates per second. For RHD problems on uniform grids in 3D, our code scales from 4 to 256 GPUs with an efficiency of 76 per cent. The code is publicly released under an open-source license on GitHub.Item Embargo Fundamental stellar parameters of benchmark stars from CHARA interferometry: II. Dwarf stars(EDP Sciences, 2022) Karovicova, I.; White, T. R.; Nordlander, Thomas; Casagrande, Luca; Ireland, Michael; Huber, D.Context. Stellar models applied to large stellar surveys of the Milky Way need to be properly tested against a sample of stars with highly reliable fundamental stellar parameters. We have established a programme aiming to deliver such a sample of stars. Aims. Here we present new fundamental stellar parameters of nine dwarf stars that will be used as benchmark stars for large stellar surveys. One of these stars is the solar-twin 18 Sco, which is also one of the Gaia-ESO benchmarks. The goal is to reach a precision of 1% in effective temperature (Teff). This precision is important for accurate determinations of the full set of fundamental parameters and abundances of stars observed by the surveys. Methods. We observed HD 131156 (ζ Boo), HD 146233 (18 Sco), HD 152391, HD 173701, HD 185395 (θ Cyg), HD 186408 (16 Cyg A), HD 186427 (16 Cyg B), HD 190360, and HD 207978 (15 Peg) using the high angular resolution optical interferometric instrument PAVO at the CHARA Array. We derived limb-darkening corrections from 3D model atmospheres and determined Teff directly from the Stefan-Boltzmann relation, with an iterative procedure to interpolate over tables of bolometric corrections. Surface gravities were estimated from comparisons to Dartmouth stellar evolution model tracks. We collected spectroscopic observations from the ELODIE spectrograph and estimated metallicities ([Fe/H]) from a 1D non-local thermodynamic equilibrium (NLTE) abundance analysis of unblended lines of neutral and singly ionised iron. Results. For eight of the nine stars we measure the Teff ⪅ 1%, and for one star better than 2%. We determined the median uncertainties in log g and [Fe/H] as 0.015 dex and 0.05 dex, respectively. Conclusions. This study presents updated fundamental stellar parameters of nine dwarf stars that can be used as a new set of benchmarks. All the fundamental stellar parameters were based on consistently combining interferometric observations, 3D limb-darkening modelling, and spectroscopic analysis. The next paper in this series will extend our sample to giants in the metal-rich range.Item Embargo Feminist approaches to peace and conflict: International human rights law disappearing and re-emerging?(Routledge, 2021-03-12) Ogg, Kate; Craker, Louise; Väyrynen, Tarja; Parashar, Swati; Féron, Élise; Confortini, Catia CeciliaThis chapter examines the extent to which feminist legal scholars draw on International Human Rights Law (IHLR) in undertaking peace and conflict research. This is a significant question because in feminist scholarship IHRL is treated as harbouring international law’s emancipatory potential as well as reproducing the gendered nature of international law. Our analysis of the literature unearths three trends. In some literature, IHRL is seen as the central tool in addressing peace and conflict. Other feminist scholars take a more equivocal approach acknowledging IHRL’s flaws and biases but accepting it has some role to play. In research on Women, Peace and Security, references to IHRL are almost absent but there is an emerging trend to reconsider its relevance. We highlight new questions arising within and across these three approaches and identify methodological and theoretical innovations within feminist peace and conflict research that can be employed to address these issues for future research.Item Embargo Thresholds: First gradually, then suddenly?(Elsevier, 2022-06-09) Manderson, DesmondWriting in the context of proposal to expand the decriminalisation of illicit drugs in the Australian Capital Territory, Australia's smallest and most progressive jurisdiction, this article explores the key question of the use of quantitative thresholds to determine the level of drug use distinguishing personal use from trafficking. Recent literature demonstrates the use of quantitative thresholds has yielded highly divergent approaches in jurisdictions around the world. The literature also points to the underlying challenges involved in evaluating whether it is appropriate to employ quantitative figures to make that distinction, and if so how and to what ends. Harris (2011) goes so far as to describe ‘conviction by numbers’ as a ‘lazy shorthand’ that may exact an ‘immeasurable cost of injustice’ (3). Yet practices which do not rely on quantitative measures are at real risk of exacerbating discretionary judgments by police and prosecutors that may well result in discriminatory application of the laws. The basis on which the balance between these two countervailing considerations is struck in these discussions is not always clear. The paper focuses first on the merits of adopting an approach based on quantitative thresholds and argues that the implications of applying legally mandated drug quantities is in fact not as cut and dried as many authors have assumed. There is an important ‘middle way’ between the rote application of quantitative measures and their abandonment. This middle way has previously been ignored. The article then addresses exactly how and on what basis quantitative thresholds should be determined if they are to reflect and advance harm reduction principles. Finally, the paper considers and critiques arguments that quantitative thresholds should be set not only by reference to the consumption patterns of users but also in relation to the relative harm of particular substances. As a whole, the essay aims to contribute to a broader international literature on thresholds, a vexed question which matters not only in Canberra, but around the world.Item Embargo The effect of invasive fall armyworm abundance on native species depends on relative trophic level(Springer Verlag, 2023) Wu, Pengxiang; Shi, Kai; Zhang, Tianhao; Head, Megan; Zhang, RunzhiFall armyworm (FAW) has posed a significant threat to Chinese agriculture and native species since its presence was first reported in 2019. To better understand the impacts of FAW, however, information on how FAW abundance affects native abundance and communities and whether these effects are dependent on the trophic level of native species relative to FAW is needed. Here, we studied the direction, strength, and shape of the relationship between FAW abundance and responses of native abundance and community-level metrics (mean value of unit-scaled richness, diversity, and evenness). We then tested how relative trophic position influenced these relationships. Across 25 study sites in Yunnan province, we recorded FAW abundance ranging from 0 to 715 individuals per 2666.8 m2. Across this range, native abundance declined nonlinearly by 14.6%, on average, and community metrics declined linearly by 18.1%. For lower trophic levels, FAW caused a significant nonlinear decline in native abundance (20.7%) and community metrics (28.6%), with the greatest declines occurring at low FAW abundance. At the same trophic level, native abundance (9.1%) and community metrics (14.5%) declined nonlinearly and linearly, respectively. In contrast, FAW had no significant impact on native abundance or community metrics at higher trophic levels. At the community level, negative impacts were stronger for evenness and diversity than for richness. The results of our analyses suggest native responses to FAW invasion rely strongly on FAW abundance and trophic position. The FAW abundance–native response relationships reveal how FAW impacts may develop during the invasion process and when to best manage them.Item Embargo The role of the flavonoid pathway in Medicago truncatula in root nodule formation. A review(John Wiley & Sons, Inc., 2020) Mathesius, Ulrike; de Bruijn, Frans J.Flavonoids are plant secondary metabolites with a wide array of structures and functions. In legumes, their most prominent role is in the determination of host specificity through their recognition by rhizobial NodD transcription factors. Specific flavonoid recognition leads to expression of nod genes and production of Nod factors in rhizobia. In addition, flavonoids play a role in chemoattraction of rhizobia toward the root. Silencing of different branches of the flavonoid pathway in Medicago truncatula demonstrated that root flavonoids are essential for nodulation, and that flavones function as nod gene inducers. However, other flavonoids, including isoflavonoids and chalcones, act as nod gene inducers and suppressors in M. truncatula. Flavonoids are also essential in M. truncatula nodule development, likely through their action as auxin transport inhibitors. The induction of flavonoids controlling auxin transport in the root following rhizobial infection is under the control of cytokinin signaling. Flavonols are the most likely candidates controlling auxin transport during nodule development. However, the actual bioactive flavonoids remain to be identified.Item Open Access The nano- and meso-scale structure of amorphous calcium carbonate(Nature Publishing Group, 2022-04-27) Clark, Simon; Colas, Bruno; Jacob, Dorrit; Neuefeind, Joerg C.; Wang, Hsiu-Wen; Page, Katherine L.; Soper, A. K.; Schodder, Philipp I.; Duchstein, Patrick; Apeleo Zubiri, Benjamin; Yokosawa, TadahiroUnderstanding the underlying processes of biomineralization is crucial to a range of disciplines allowing us to quantify the effects of climate change on marine organisms, decipher the details of paleoclimate records and advance the development of biomimetic materials. Many biological minerals form via intermediate amorphous phases, which are hard to characterize due to their transient nature and a lack of long-range order. Here, using Monte Carlo simulations constrained by X-ray and neutron scattering data together with model building, we demonstrate a method for determining the structure of these intermediates with a study of amorphous calcium carbonate (ACC) which is a precursor in the bio-formation of crystalline calcium carbonates. We find that ACC consists of highly ordered anhydrous nano-domains of approx. 2 nm that can be described as nanocrystalline. These nano-domains are held together by an interstitial net-like matrix of water molecules which generate, on the mesoscale, a heterogeneous and gel-like structure of ACC. We probed the structural stability and dynamics of our model on the nanosecond timescale by molecular dynamics simulations. These simulations revealed a gel-like and glassy nature of ACC due to the water molecules and carbonate ions in the interstitial matrix featuring pronounced orientational and translational flexibility. This allows for viscous mobility with diffusion constants four to five orders of magnitude lower than those observed in solutions. Small and ultra-small angle neutron scattering indicates a hierarchically-ordered organization of ACC across length scales that allow us, based on our nano-domain model, to build a comprehensive picture of ACC formation by cluster assembly from solution. This contribution provides a new atomic-scale understanding of ACC and provides a framework for the general exploration of biomineralization and biomimetic processes.