School of Geography, Earth and Atmospheric Sciences - Research Publications
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ItemThe paradox of illicit economies: survival, resilience, and the limits of development and drug policy orthodoxy(Taylor and Francis Group, 2020)The illicit drug crops opium and coca are conventionally regarded as sources of instability, an ‘evil’ that breeds fragility and violence. Fragile states are supposed to be most vulnerable to their production and consequent harms. Yet by looking into the local contexts of the world’s leading opium and coca producers – Afghanistan, Myanmar, Colombia and Bolivia – these illicit crops are found to also be sources of stability, even drivers of economic growth. They enable marginalized communities and territories abandoned by the state to be reinserted into national and global markets. Within so-called ‘fragile’ and conflict-affected areas are displaced and dispossessed households adopting innovative and unorthodox strategies for coping and survival in changing and insecure environments. This paper maps out an approach, useful for examining the resilience that has emerged amidst violence and uncertainty in illicit-crop-producing territories, and which can hopefully tackle the continuing disconnect between drugs and development policy.
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ItemUn atto d’amore: Manifesto Open Access per la libertà, l’integrità e la creatività nelle scienze umane e nelle scienze sociali interpretative(Italian Society of Cultural Anthropology (SIAC)., 2020-12-31)Labour of Love: An Open Access Manifesto for Freedom, Integrity, and Creativity in the Humanities and Interpretive Social Sciences, is the result of an LSE Research Infrastructure and Investment–funded workshop entitled Academic Freedom, Academic Integrity and Open Access in the Social Sciences, organised by Andrea E. Pia and held at the London School of Economics on September 9, 2019.
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ItemEarly human occupation of southeastern Australia: New insights from 40Ar/39Ar dating of young volcanoes(GEOLOGICAL SOC AMER, INC, 2020-04-01)Abstract In Australia, the onset of human occupation (≥65 ka?) and dispersion across the continent are the subjects of intense debate and are critical to understanding global human migration routes. New-generation multi-collector mass spectrometers capable of high-precision 40Ar/39Ar dating of young (<500 ka) samples provide unprecedented opportunities to improve temporal constraints of archaeological events. In southeastern Australia, a novel approach to improving understanding of occupation involves dating key volcanic eruptions in the region, referenced to stone artifacts and Aboriginal oral traditions. The current study focuses on two monogenetic volcanoes in the Newer Volcanic Province of southeastern Australia: Budj Bim (previously Mount Eccles) and Tower Hill. Budj Bim and its surrounding lava landforms are of great cultural significance and feature prominently in the oral traditions of the Gunditjmara people. Tower Hill is of archaeological significance due to the occurrence of a stone tool beneath tephra. 40Ar/39Ar eruption ages of 36.9 ± 3.1 ka (95% confidence interval) and 36.8 ± 3.8 ka (2σ) were determined for the Budj Bim and Tower Hill volcanic complexes, respectively. The Tower Hill eruption age is a minimum age constraint for human presence in Victoria, consistent with published optically stimulated luminescence and 14C age constraints for the earliest known occupation sites in Tasmania, New South Wales, and South Australia. If aspects of oral traditions pertaining to Budj Bim or its surrounding lava landforms reflect volcanic activity, this could be interpreted as evidence for these being some of the oldest oral traditions in existence.
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ItemCorrigendum to "Ultra-high precision 40Ar/39Ar ages for Fish Canyon Tuff and Alder Creek Rhyolite sanidine: New dating standards required? (vol 121, pg 229, 2013)"(Elsevier, 2020-03-15)The authors regret that typographical and calculation errors occurred in Table 1, Table DR1 and Appendix A in the manuscript. Most relate to inconsistent propagation of uncertainty levels (i.e. 2σ vs 1σ uncertainties) associated with the J-values reported for FCTs and ACRs aliquots in Table DR1 and typographical errors in the J-values reported for aliquots FC3/AC3 and FC4/AC4. Corrected versions of Table 1, Figs. 3 and 4, and Appendix A are shown below. These errors do not affect the conclusions of the original paper and we summarise the resulting changes to the abstract, Sections 4.2 and 5, and Appendix A below. Correct J-values for aliquots FC3/AC3 and FC4/AC4 in Table DR1 are 0.0025205 ± 0.0000025 (0.098%; 2σ) and 0.0025295 ± 0.0000023 (0.091%; 2σ), respectively. We calculate revised eruption ages of 28.08 ± 0.04 Ma (2σ) for FCT and 1.181 ± 0.002 Ma (2σ) for ACR, relative to the astronomically calibrated age of A1 Tephra sanidine, Crete [Rivera et al. (2011) Earth Planet Sci. Lett. 311, 420–426]. R-values [Formula presented], based on mean fusion or total-gas results for the six irradiated aliquots (Table 1), range from 0.041638 ± 0.000031 (0.07%) to 0.041840 ± 0.000122 (0.29%), with a weighted mean value of 0.041680 ± 0.000050 (0.10%) (Table 1). The authors would like to apologize for any inconvenience these errors may have caused.
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ItemCorrigendum to "Astronomical calibration of 40Ar/39Ar reference minerals using high precision, multi-collector (ARGUSVI) mass spectrometry (vol 196, pg 351, 2017)"(PERGAMON-ELSEVIER SCIENCE LTD, 2020-03-15)The authors regret that typographical and calculation errors occurred in Table 1 and some related figures. Corrected versions of Table 1, Figs. 4–6 are reproduced below. These errors do not affect the conclusions of the original paper and we summarise the main changes to Section 4 below. We calculate revised and values of 0.041692 ± 0.000024 (0.058%) and 0.16989 ± 0.00015 (0.087%), respectively. The former value is indistinguishable from the average value of 0.041680 ± 0.000050 (0.096%) reported by Phillips and Matchan (2013) [Geochim. Cosmochim. Acta 121, 229–239]. Other corrections in Table 1 relate to typographical errors and inconsistent propagation of uncertainty levels (2σ vs 1σ uncertainties) associated with some mean and plateau ages. The authors would like to apologize for any inconvenience these errors may have caused.
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ItemInvesting in social housing during a pandemic( 2020)Australia needs a National Housing Strategy, as well as consistent funding and policy mechanisms, to reverse our long-term declines in social housing.
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ItemPathways to Agricultural Skill Development in the Indian Himalayas(SAGE PUBLICATIONS INDIA PVT LTD, 2020-08-27)Policymakers and practitioners in the field of skill development often carry individualist and narrowly instrumental understandings of the reasons people enrol in their programmes. This article argues that people in the Global South seek to develop skills for a range of reasons, many of which are strongly influenced by their social environment and factors outside of their control. It presents the findings of a study involving surveys and semi-structured interviews with 53 trainees enrolled in agricultural skill development programmes in the state of Himachal Pradesh in the Indian Himalayas. Trainees’ responses were analysed to determine common ‘pathways’ to agricultural skill development programmes. Seven major pathways were identified: supporting one’s family; adopting commercial approaches to agriculture; managing a transition to agriculture after working in other sectors; gaining new knowledge; contributing to society; working from home; and developing a fallback option while seeking other work. These pathways were highly inflected by gender, age and caste. It is suggested that agricultural skill development practitioners will benefit from working with these pathways rather than assuming trainees carry more economistic motivations, but also from being critically aware of how the social factors that impinge on trainees’ pathways are influenced by local power structures.
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ItemA single-column extraction chemistry for isotope dilution U-Pb dating of carbonate(ELSEVIER, 2020-01-05)U-Pb dating can provide age constraints on carbonate minerals from a wide range of geological settings. A major practical limitation, however, is the need for rapid and efficient extraction of Pb and U from large numbers of typically low-Pb (≤10 ng/g) calcite samples, while maintaining low blanks (∼10 pg Pb) and high Pb-U yields and purity. Here we describe a well-tested ion exchange procedure able to extract Pb and U from large (up to 200 mg) calcite samples using a single pass over a mini-column filled with small (∼0.1 ml) volumes of AG1-X8 anion exchange and Eichrom TRU-resins. This ‘stacked resin’ technique halves the time spent on elemental extractions and provides MC-ICPMS-ready Pb and U fractions in a single day. The method results in considerable savings in laboratory time and allows higher sample throughput, without negative impacts on data quality. It is ideally suited for high-precision U-Pb dating of speleothems where large numbers of samples need to be processed, but it is equally adaptable to calcites from other settings. While not explored as part of this work, the stacked resin technique should also be applicable to other carbonates (dolomite, ankerite, siderite).
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ItemStructure of the bacterial ribosome at 2 Å resolution.(eLife Sciences Publications, Ltd, 2020-09-14)Using cryo-electron microscopy (cryo-EM), we determined the structure of the Escherichia coli 70S ribosome with a global resolution of 2.0 Å. The maps reveal unambiguous positioning of protein and RNA residues, their detailed chemical interactions, and chemical modifications. Notable features include the first examples of isopeptide and thioamide backbone substitutions in ribosomal proteins, the former likely conserved in all domains of life. The maps also reveal extensive solvation of the small (30S) ribosomal subunit, and interactions with A-site and P-site tRNAs, mRNA, and the antibiotic paromomycin. The maps and models of the bacterial ribosome presented here now allow a deeper phylogenetic analysis of ribosomal components including structural conservation to the level of solvation. The high quality of the maps should enable future structural analyses of the chemical basis for translation and aid the development of robust tools for cryo-EM structure modeling and refinement.
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ItemConsistent Metagenome-Derived Metrics Verify and Delineate Bacterial Species Boundaries.(American Society for Microbiology, 2020-01-14)Longstanding questions relate to the existence of naturally distinct bacterial species and genetic approaches to distinguish them. Bacterial genomes in public databases form distinct groups, but these databases are subject to isolation and deposition biases. To avoid these biases, we compared 5,203 bacterial genomes from 1,457 environmental metagenomic samples to test for distinct clouds of diversity and evaluated metrics that could be used to define the species boundary. Bacterial genomes from the human gut, soil, and the ocean all exhibited gaps in whole-genome average nucleotide identities (ANI) near the previously suggested species threshold of 95% ANI. While genome-wide ratios of nonsynonymous and synonymous nucleotide differences (dN/dS) decrease until ANI values approach ∼98%, two methods for estimating homologous recombination approached zero at ∼95% ANI, supporting breakdown of recombination due to sequence divergence as a species-forming force. We evaluated 107 genome-based metrics for their ability to distinguish species when full genomes are not recovered. Full-length 16S rRNA genes were least useful, in part because they were underrecovered from metagenomes. However, many ribosomal proteins displayed both high metagenomic recoverability and species discrimination power. Taken together, our results verify the existence of sequence-discrete microbial species in metagenome-derived genomes and highlight the usefulness of ribosomal genes for gene-level species discrimination.IMPORTANCE There is controversy about whether bacterial diversity is clustered into distinct species groups or exists as a continuum. To address this issue, we analyzed bacterial genome databases and reports from several previous large-scale environment studies and identified clear discrete groups of species-level bacterial diversity in all cases. Genetic analysis further revealed that quasi-sexual reproduction via horizontal gene transfer is likely a key evolutionary force that maintains bacterial species integrity. We next benchmarked over 100 metrics to distinguish these bacterial species from each other and identified several genes encoding ribosomal proteins with high species discrimination power. Overall, the results from this study provide best practices for bacterial species delineation based on genome content and insight into the nature of bacterial species population genetics.
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