Anthropogenic lead isotopes in Antarctica

We report the first measurements of Pb isotopes in Antarctic snow, which show that even recent snow containing 2.3 pg/g is highly polluted with anthropogenic Pb. This follows from a comparison of isotope abundances of Pb in surface snow and terrestrial dust extracted from ancient Antarctic ice (Dome C, depth 308 m, approximate age 7,500 a BP), the latter being distinctly more radiogenic. This result is independent of geochemical arguments based on measurements of Al, Na and SO_4. South America is suggested as a likely source of this anthropogenic Pb. The presence of significantly less radiogenic Pb in the snow adjacent to two Antarctic base stations indicates that there is contamination from station emissions, although emission from Australia is an alternative explanation for a site 33 km from Dumont d'Urville

Lead Isotopes and Selected Metals in Ice from Law Dome, Antarctica

The isotopic composition. of Pb and the concentrations of Pb, Ba and Bi were measured in selected ice-core samples from Law Dome, East Antarctica, to a depth of 1196 m. The range of concentrations found in decontaminated ice was 0.03-1.5 pg g-1 for Pb, 0.9-6.1 pg g-1 for Ba and 0.4-17 fg g-1 for Bi, excluding the deepest sample which contained ∼1 ppm of rock dust. The abundances of all four stable lead isotopes were measured and gave 206Pb/207Pb ratios ≤ ∼1.23. A value of 208Pb/207Pb = 2.78 was measured in the deepest sample and is consistent with reported Pb isotope ratios of Antarctic granulites. Although the element concentrations in some samples were lower than have been reported elsewhere, geochemical and isotopic evidence indicated that a number of samples were contaminated with Pb not present in the original ice. However, it appears that the technical skills now available are approaching the level where careful sample selection, decontamination and analysis can yield accurate results for the concentration and isotopic composition of Pb in Earth\u27s purest naturally occurring ice

HST Observations of Heavy Elements in Metal-Poor Galactic Halo Stars

We present new abundance determinations of neutron-capture elements Ge, Zr, Os, Ir, and Pt in a sample of 11 metal-poor (-3.1 <= [Fe/H] <= -1.6) Galactic halo giant stars, based on Hubble Space Telescope UV and Keck I optical high-resolution spectroscopy. The stellar sample is dominated by r-process-rich stars such as the well-studied CS 22892-052 and bd+173248, but also includes the r-process-poor, bright giant HD 122563. Our results demonstrate that abundances of the 3rd r-process peak elements Os, Ir and Pt in these metal-poor halo stars are very well-correlated among themselves, and with the abundances of the canonical r-process element Eu (determined in other studies), thus arguing for a common origin or site for r-process nucleosynthesis of heavier (Z>56) elements. However, the large (and correlated) scatters of [Eu,Os,Ir,Pt/Fe] suggests that the heaviest neutron-capture r-process elements are not formed in all supernovae. In contrast, the Ge abundances of all program stars track their Fe abundances, very well. An explosive process on iron-peak nuclei (e.g., the alpha-rich freeze-out in supernovae), rather than neutron capture, appears to have been the dominant synthesis mechanism for this element at low metallicities -- Ge abundances seem completely uncorrelated with Eu.Comment: 35 pages, 5 tables, 7 figures; To appear in the Astrophysical Journa

Learning object relationships which determine the outcome of actions

Peer reviewedPublisher PD

The Fine-structure Constant as a Probe of Chemical Evolution and AGB Nucleosynthesis in Damped Lyman-alpha Systems

Evidence from a large sample of quasar absorption-line spectra in damped Lyman-alpha systems has suggested a possible time variation of the fine structure constant alpha. The most statistically significant portion of this sample involves the comparison of Mg and Fe wavelength shifts using the many-multiplet (MM) method. However, the sensitivity of this method to the abundance of heavy isotopes, especially Mg, is enough to imitate an apparent variation in alpha in the redshift range 0.5 < z < 1.8. We implement recent yields of intermediate mass (IM) stars into a chemical evolution model and show that the ensuing isotope distribution of Mg can account for the observed variation in alpha provided the early IMF was particularly rich in intermediate mass stars (or the heavy Mg isotope yields from AGB stars are even higher than in present-day models). As such, these observations of quasar absorption spectra can be used to probe the nucleosynthetic history of low-metallicity damped Lyman-alpha systems in the redshift range 0.5 < z < 1.8. This analysis, in conjunction with other abundance measurements of low-metallicity systems, reinforces the mounting evidence that star formation at low metallicities may have been strongly influenced by a population of IM stars. Such IM stars have a significant influence on other abundances, particularly nitrogen. We constrain our models with independent measurements of N, Si, and Fe in damped Lyman-alpha systems as well as C/O in low-metallicity stars. In this way, we obtain consistent model parameters for this chemical-evolution interpretation of the MM method results.Comment: 38 pages, latex, 25 ps figures, as accepted in Ap

Beta decay of 115-In to the first excited level of 115-Sn: Potential outcome for neutrino mass

Recent observation of beta decay of 115-In to the first excited level of 115-Sn with an extremely low Q_beta value (Q_beta ~ 1 keV) could be used to set a limit on neutrino mass. To give restriction potentially competitive with those extracted from experiments with 3-H (~2 eV) and 187-Re (~15 eV), atomic mass difference between 115-In and 115-Sn and energy of the first 115-Sn level should be remeasured with higher accuracy (possibly of the order of ~1 eV).Comment: 9 pages, 3 figures; talk at the NANP'05 Conferenc

Detection of the Natural Alpha Decay of Tungsten

The natural alpha decay of 180W has been unambiguously detected for the first time. The alpha peak is found in a (gamma,beta and neutron)-free background spectrum. This has been achieved by the simultaneous measurement of phonon and light signals with the CRESST cryogenic detectors. A half-life of T1/2 = (1.8 +- 0.2) x 10^18 y and an energy release of Q = (2516.4 +- 1.1 (stat.) +- 1.2 (sys.)) keV have been measured. New limits are also set on the half-lives of the other naturally occurring tungsten isotopes.Comment: Submitted to Physical Review C Revised versio

Eye health and quality of life: an umbrella review protocol.

INTRODUCTION: Vision impairment and eye disease are major global health concerns and have been associated with increased morbidity and mortality, and lower quality of life. Quality of life, whether generic, vision-specific or disease-specific, is an important measure of the impact of eye health on people's daily activities, well-being and visual function, and is increasingly used to evaluate the impact of ophthalmic interventions and new devices. While many studies and reviews have examined the relationship between vision or eye health and quality of life across different contexts, there has yet to be a synthesis of the impact of vision impairment, eye disease and ophthalmic interventions on quality of life globally and across the lifespan. METHODS AND ANALYSIS: An umbrella review of systematic reviews will be conducted to address these two questions: (1) What is the association of vision impairment and eye disease with quality of life? (2) What is the impact of ophthalmic interventions on quality of life? A search of related literature will be performed on the 11 February 2020 in Medline Ovid, Embase.com, Cochrane Database of Systematic Reviews, Proquest Dissertations and Theses Global, and the grey literature, and repeated at the synthesis stage. Title/abstract and full-text screening, methodological quality assessment and data extraction will be conducted by reviewers working independently and in duplicate. Assessment of methodological quality and data extraction will be performed using Joanna Briggs Institute standard forms. Findings from the systematic reviews and their methodological quality will be summarised qualitatively in the text and using tables. ETHICS AND DISSEMINATION: No ethical approval is required. Results of this umbrella review will be published in a peer-reviewed journal and summarised in the Lancet Global Health Commission on Global Eye Health. TRIAL REGISTRATION NUMBER: This protocol was registered in the Open Science Framework Registries (https://osf.io/qhv9g/)

Multicenter, Prospective, Longitudinal Study of the Recurrence, Surgical Site Infection, and Quality of Life After Contaminated Ventral Hernia Repair Using Biosynthetic Absorbable Mesh: The COBRA Study

OBJECTIVE: The aim of the study was to evaluate biosynthetic absorbable mesh in single-staged contaminated (Centers for Disease Control class II and III) ventral hernia (CVH) repair over 24 months. BACKGROUND: CVH has an increased risk of postoperative infection. CVH repair with synthetic or biologic meshes has reported chronic biomaterial infections and high hernia recurrence rates. METHODS: Patients with a contaminated or clean-contaminated operative field and a hernia defect at least 9 cm had a biosynthetic mesh (open, sublay, retrorectus, or intraperitoneal) repair with fascial closure (n = 104). Endpoints included overall Kaplan-Meier estimates for hernia recurrence and postoperative wound infection rates at 24 months, and the EQ-5D and Short Form 12 Health Survey (SF-12). Analyses were conducted on the intent-to-treat population, and health outcome measures evaluated using paired t tests. RESULTS: Patients had a mean age of 58 years, body mass index of 28 kg/m, 77% had contaminated wounds, and 84% completed 24-months follow-up. Concomitant procedures included fistula takedown (n = 24) or removal of infected previously placed mesh (n = 29). Hernia recurrence rate was 17% (n = 16). At the time of CVH repair, intraperitoneal placement of the biosynthetic mesh significantly increased the risk of recurrences (P ≤ 0.04). Surgical site infections (19/104) led to higher risk of recurrence (P < 0.01). Mean 24-month EQ-5D (index and visual analogue) and SF-12 physical component and mental scores improved from baseline (P < 0.05). CONCLUSIONS: In this prospective longitudinal study, biosynthetic absorbable mesh showed efficacy in terms of long-term recurrence and quality of life for CVH repair patients and offers an alternative to biologic and permanent synthetic meshes in these complex situations

The roles and values of wild foods in agricultural systems

Almost every ecosystem has been amended so that plants and animals can be used as food, fibre, fodder, medicines, traps and weapons. Historically, wild plants and animals were sole dietary components for hunter–gatherer and forager cultures. Today, they remain key to many agricultural communities. The mean use of wild foods by agricultural and forager communities in 22 countries of Asia and Africa (36 studies) is 90–100 species per location. Aggregate country estimates can reach 300–800 species (e.g. India, Ethiopia, Kenya). The mean use of wild species is 120 per community for indigenous communities in both industrialized and developing countries. Many of these wild foods are actively managed, suggesting there is a false dichotomy around ideas of the agricultural and the wild: hunter–gatherers and foragers farm and manage their environments, and cultivators use many wild plants and animals. Yet, provision of and access to these sources of food may be declining as natural habitats come under increasing pressure from development, conservation-exclusions and agricultural expansion. Despite their value, wild foods are excluded from official statistics on economic values of natural resources. It is clear that wild plants and animals continue to form a significant proportion of the global food basket, and while a variety of social and ecological drivers are acting to reduce wild food use, their importance may be set to grow as pressures on agricultural productivity increase.</jats:p