A bioavailable strontium isoscape for Western Europe: A machine learning approach

Strontium isotope ratios (87Sr/86Sr) are gaining considerable interest as a geolocation tool and are now widely applied in archaeology, ecology, and forensic research. However, their application for provenance requires the development of baseline models predicting surficial 87Sr/86Sr variations (“isoscapes”). A variety of empirically-based and process-based models have been proposed to build terrestrial 87Sr/86Sr isoscapes but, in their current forms, those models are not mature enough to be integrated with continuous-probability surface models used in geographic assignment. In this study, we aim to overcome those limitations and to predict 87Sr/86Sr variations across Western Europe by combining process-based models and a series of remote-sensing geospatial products into a regression framework. We find that random forest regression significantly outperforms other commonly used regression and interpolation methods, and efficiently predicts the multi-scale patterning of 87Sr/86Sr variations by accounting for geological, geomorphological and atmospheric controls. Random forest regression also provides an easily interpretable and flexible framework to integrate different types of environmental auxiliary variables required to model the multi-scale patterning of 87Sr/86Sr variability. The method is transferable to different scales and resolutions and can be applied to the large collection of geospatial data available at local and global levels. The isoscape generated in this study provides the most accurate 87Sr/86Sr predictions in bioavailable strontium for Western Europe (R2 = 0.58 and RMSE = 0.0023) to date, as well as a conservative estimate of spatial uncertainty by applying quantile regression forest. We anticipate that the method presented in this study combined with the growing numbers of bioavailable 87Sr/86Sr data and satellite geospatial products will extend the applicability of the 87Sr/86Sr geo-profiling tool in provenance applications

Weak magnetism and non-Fermi liquids near heavy-fermion critical points

This paper is concerned with the weak-moment magnetism in heavy-fermion materials and its relation to the non-Fermi liquid physics observed near the transition to the Fermi liquid. We explore the hypothesis that the primary fluctuations responsible for the non-Fermi liquid physics are those associated with the destruction of the large Fermi surface of the Fermi liquid. Magnetism is suggested to be a low-energy instability of the resulting small Fermi surface state. A concrete realization of this picture is provided by a fractionalized Fermi liquid state which has a small Fermi surface of conduction electrons, but also has other exotic excitations with interactions described by a gauge theory in its deconfined phase. Of particular interest is a three-dimensional fractionalized Fermi liquid with a spinon Fermi surface and a U(1) gauge structure. A direct second-order transition from this state to the conventional Fermi liquid is possible and involves a jump in the electron Fermi surface volume. The critical point displays non-Fermi liquid behavior. A magnetic phase may develop from a spin density wave instability of the spinon Fermi surface. This exotic magnetic metal may have a weak ordered moment although the local moments do not participate in the Fermi surface. Experimental signatures of this phase and implications for heavy-fermion systems are discussed.Comment: 20 pages, 8 figures; (v2) includes expanded discussion and solution of quantum Boltzmann equatio

Orbital-selective Mott transitions: Heavy fermions and beyond

Quantum phase transitions in metals are often accompanied by violations of Fermi liquid behavior in the quantum critical regime. Particularly fascinating are transitions beyond the Landau-Ginzburg-Wilson concept of a local order parameter. The breakdown of the Kondo effect in heavy-fermion metals constitutes a prime example of such a transition. Here, the strongly correlated f electrons become localized and disappear from the Fermi surface, implying that the transition is equivalent to an orbital-selective Mott transition, as has been discussed for multi-band transition-metal oxides. In this article, available theoretical descriptions for orbital-selective Mott transitions will be reviewed, with an emphasis on conceptual aspects like the distinction between different low-temperature phases and the structure of the global phase diagram. Selected results for quantum critical properties will be listed as well. Finally, a brief overview is given on experiments which have been interpreted in terms of orbital-selective Mott physics.Comment: 29 pages, 4 figs, mini-review prepared for a special issue of JLT

An assessment of procedures to remove exogenous Sr before 87Sr/86Sr analysis of wet archaeological wool textiles

Strontium isotope analysis (87Sr/86Sr) has been employed as a provenancing tool for archaeological wool textiles. To date, the effect of post-depositional (soil burial environment) contamination on keratin samples, which contain ∼ppm concentrations of Sr, has not been rigorously investigated. We compared published methods for removing exogenous Sr from keratinous textiles, using either: (1) compressed N2 gas, (2) HF(aq) solution (with and without a strong oxidising agent to remove dyestuff) or (3) organic solvents. 87Sr/86Sr ratios and Sr contents were determined in undyed and madder-dyed/alum-mordanted moieties of the same wool textile, buried for up to three years in contrasting environments (marine sediment/fenland bog), and two archaeological textiles recovered in Iceland (one typical and one atypical of local manufacture). Undyed experimental samples had low Sr contents (0.07–0.29 ppm) that were increased by both dyeing (0.14–8.92 ppm) and soil burial (0.11–15.01 ppm). The efficacy of Sr removal was: HF(aq) + oxidising agent > organic solvents > HF(aq) > compressed N2. Unburied samples showed little variation in 87Sr/86Sr ratio between cleaning methods (0.00006–0.00035); buried samples showed greater variation (0.00257–0.00713). Archaeological samples showed Sr contents greater than experimental soil burials (1–118 ppm), and 87Sr/86Sr values consistent with Icelandic groundwater (0.70357–0.70540). No cleaning methods retrieved original (unburied and undyed) 87Sr/86Sr ratios except treatment with compressed N2 in undyed samples. Exogenous Sr from the short term soil burial environment is probably mostly present as particulates. We conclude that 87Sr/86Sr ratios of archaeological wool textiles recovered from wet burial environments do not accurately reflect wool provenance even after cleaning with the methods investigated

TIMS analysis of neodymium isotopes in human tooth enamel using 1013 Ω amplifiers

Human provenance studies employing isotope analysis are essential in archaeological and forensic sciences but current applications provide limited spatial resolution. This study reports on the potential of neodymium isotope composition (143Nd/144Nd) to improve human provenancing capabilities. Human tissues contain very low (100 pg of Nd, by thermal ionization mass spectrometry (TIMS) using 1013 Ω resistors. Neodymium concentrations in enamel from third molars of modern Dutch residents range between 0.1-21.0 ppb (n = 23). The 143Nd/144Nd values for Amsterdam (0.51204-0.51259, n = 12) and Rotterdam (0.51187-0.51239, n = 8) are significantly different (P value = 0.02), demonstrating the potential of neodymium isotope composition to provide improved spatial resolution. Further assessment of Nd composition in enamel of residents from other geological contexts is required to better understand the human provenance capabilities of neodymium

Delivery of care to diabetic patients with foot ulcers in daily practice: results of the Eurodiale Study, a prospective cohort study

Aims To determine current management and to identify patient-related factors and barriers that influence management strategies in diabetic foot disease. Methods The Eurodiale Study is a prospective cohort study of 1232 consecutive individuals presenting with a new diabetic foot ulcer in 14 centres across Europe. We determined the use of management strategies: referral, use of offloading, vascular imaging and revascularization. Results Twenty-seven percent of the patients had been treated for > 3 months before referral to a foot clinic. This varied considerably between countries (6-55%). At study entry, 77% of the patients had no or inadequate offloading. During follow-up, casting was used in 35% (0-68%) of the plantar fore- or midfoot ulcers. Predictors of use of casting were male gender, large ulcer size and being employed. Vascular imaging was performed in 56% (14-86%) of patients with severe limb ischaemia; revascularization was performed in 43%. Predictors of use of vascular imaging were the presence of infection and ischaemic rest pain. Conclusion Treatment of many patients is not in line with current guidelines and there are large differences between countries and centres. Our data suggest that current guidelines are too general and that healthcare organizational barriers and personal beliefs result in underuse of recommended therapies. Action should be undertaken to overcome these barriers and to guarantee the delivery of optimal care for the many individuals with diabetic foot disease

Health-Related Quality of Life Predicts Major Amputation and Death, but Not Healing, in People With Diabetes Presenting With Foot Ulcers: The Eurodiale Study

OBJECTIVE Low health-related quality of life (HRQoL) has been consistently reported to be associated with poor prognosis for a variety of health outcomes in various settings. We aimed to evaluate whether HRQoL in patients presenting with new diabetic foot ulcers (DFUs) has prognostic significance for ulcer healing, major amputation, and death.RESEARCH DESIGN AND METHODSWe followed 1,088 patients with new DFUs presenting for treatment at one of the 14 centers in 10 European countries participating in the Eurodiale (European Study Group on Diabetes and the Lower Extremity) study, prospectively until healing (76.9%), major amputation (4.6%), or death (6.4%) up to a maximum of 1 year. At baseline, patient and ulcer characteristics were recorded as well as EQ-5D, a standardized instrument consisting of five domains and a visual analog scale for use as a measure of HRQoL. The prognostic influence of the EQ-5D domains was evaluated in multivariable Cox regression analyses on the time-to-event data, adjusting for baseline clinical characteristics of the ulcer and comorbidities.RESULTSWhile predictive effects of HRQoL, adjusted for possible confounders, were absent for healing, decreased HRQoL, especially in the physical domains, was statistically significant for major amputation (mobility, self-care, usual activities) and death (self-care, usual activities, pain/discomfort).CONCLUSIONSLow HRQoL appears to be predictive for major amputation and death, but high HRQoL does not increase healing. Future studies into the influence of HRQoL on ulcer outcome are important in attempts to decrease treatment failure and mortality

Optimal organization of health care in diabetic foot disease: Introduction to the Eurodiale study

This article describes the rationale and protocol of a large data collection study in patients with new diabetic foot ulcers by the Eurodiale study group, a consortium of centers of expertise in the field of diabetic foot disease within Europe. This study is a multicenter, observational, prospective data collection study. Its main aim is to determine the major factors determining clinical outcome and outcome in terms of health-related quality of life and health care consumption. Between September 1, 2003, and October 1, 2004, in 14 European centers, all consecutive patients with diabetes and a new foot ulcer were included in the study and followed until the end point or for a maximum of 1 year. End points were healing of the foot, major amputation, or death. Data were collected on patient, foot, and ulcer characteristics and on diagnostic and management procedures. Furthermore, data were collected on health care organization, quality of life, and resource use. A total of 1232 patients were included in the study. Sixty-three percent of the patients were referred by their general practitioner or were self-referrals. Twenty-seven percent of the patients were admitted at the time of inclusion; 1088 patients were followed until the end point. "Optimal Organization of Health Care in Diabetic Foot Disease" is one of the first large multicenter studies in the field of diabetic foot disease on clinical presentation, clinical outcome, quality of life, resource utilization, and health care organization and their interrelationships. These data will provide us with new insights that enable us to improve care for these patients and guide the development of new studies in this area. The results of this study are the subject of a separate presentation. © 2007 Sage Publications