DRAC:Dose Rate and Age Calculator for trapped charge dating

Accurate calculation of the environmental radiation dose rate (Ḋ) is an essential part of trapped charge dating methods, such as luminescence and electron spin resonance dating. Although the calculation of Ḋ is not mathematically complex, the incorporation of multiple variables and the propagation of uncertainties can be challenging. The Dose Rate and Age Calculator (DRAC) is an open access, web-based program which enables rapid Ḋ calculation for trapped charge dating applications. Users can select from recently published attenuation and conversion factors to make mathematically robust, reproducible Ḋ calculations. Comparison of DRAC calculated Ḋ values against the published Ḋ determinations of 422 samples from 32 studies results in a reproducibility ratio of 1.01 ± 0.05. It is anticipated that DRAC will facilitate easier inter-laboratory comparisons and will provide greater transparency for Ḋ calculations. DRAC will be updated to reflect the latest advances in Ḋ calculation and is freely accessible at www.aber.ac.uk/alrl/drac. The code for DRAC is available from github at https://github.com/DRAC-calculator/DRAC-calculator

The aggradation of alluvial fans in response to monsoon variability over the last 400 ka in the Hajar Mountains, south-east Arabia

The preservation and interpretation of past external forcings within sedimentary archives can be complicated. Marine proxy records show that, throughout the Mid-Late Quaternary, monsoon rainfall in south-east Arabia has varied at precessional timescales (∼ 23 ka). By contrast, terrestrial environmental records from the region, such as speleothems and palaeolake sequences, generally only capture rainfall variability at eccentricity (∼ 100 ka) timescales and geomorphological archives rarely record events over multiple glacial cycles. Previous work has suggested that the alluvial fan systems of the Hajar Mountains record aggradation coincident with precessional peaks because of more northerly Indian Ocean Summer Monsoon (IOSM) rainfall, relative to present. However, the alluvial record is complex: there is a growing body of ‘anomalous’ aggradation age data from periods of precessional minima and it is spatially uneven, mainly being derived from fans at either the northern- or southern-most extents of the western side of the mountains. We present optically stimulated luminescence (OSL) ages of alluvial aggradation from new sites in the central portion of the western and eastern sides of the Hajar mountains. Sedimentary units that show evidence of more sustained flow conditions, such as coarse conglomerate deposition and the development of thick floodplain deposits, typically date to periods of higher IOSM rainfall at precessional timescales. Sites where there is evidence of deposition under more ephemeral flow conditions, like today, yield ages corresponding to precessional minima. We synthesise these data with similarly interpreted alluvial and lacustrine deposits from across the region, employing a hierarchical clustering approach to generate clusters of ages representing periods of increased hydrological activity. This objective approach to regional chronological data suggests that ten periods of more sustained hydrological activity are evidenced across the Hajar region, broadly aligning to precessional and eccentricity peaks over the last 400 ka. These clusters show that Hajar fans predominately aggrade because of increasing rainfall over their catchments, with the central ages of clusters often aligning with the onset of precessional forcing. Hajar alluvial systems preserve important records of Quaternary climate variability over long timescales in an arid region where terrestrial records are scarce due to preservation issues

Re‐analysis of late Quaternary dust mass accumulation rates in Serbia using new luminescence chronology for loess–palaeosol sequence at Surduk

Despite numerous palaeoenvironmental investigations of loess–palaeosol sequences across the Carpathian Basin, well‐dated high‐resolution records are scarce. This paper presents a new high‐resolution chronology for the loess‐palaeosol sequence at Surduk (Serbia), based on optically stimulated luminescence (quartz) and post‐infrared infrared stimulated luminescence (polymineral) dating. The presented record spans 53–19 ka, with primary loess deposition occurring after 52±2 ka, and differs from previously published chronologies that relied on less precise and now superseded dating protocols. Based on the new chronology, mass accumulation rates (MAR s) for Surduk were constructed and compared with sites in the Carpathian Basin. The results demonstrate that accumulation periods across this area are not consistent in timing or rates. The high‐resolution dating strategy identifies a disturbance in sediment deposition that occurred after 45±2 ka and implies that site contains a hiatus. Finally, we show samples that failed routine dose recovery and preheat plateau tests, and had low fast ratios. Supported by bulk sample geochemical analysis it is proposed that a potential abrupt source shift, during the Last Glacial Maximum, may be the cause of the anomalous luminescence behaviour

Luminescence Dating in Fluvial Settings: Overcoming the Challenge of Partial Bleaching

Optically stimulated luminescence (OSL) dating is a versatile technique that utilises the two most ubiquitous minerals on Earth (quartz or K-feldspar) for constraining the timing of sediment deposition. It has provided accurate ages in agreement with independent age control in many fluvial settings, but is often characterised by partial bleaching of individual grains. Partial bleaching can occur where sunlight exposure is limited and so only a portion of the grains in the sample was exposed to sunlight prior to burial, especially in sediment-laden, turbulent or deep water columns. OSL analysis on multiple grains can provide accurate ages for partially bleached sediments where the OSL signal intensity is dominated by a single brighter grain, but will overestimate the age where the OSL signal intensity is equally as bright (often typical of K-feldspar) or as dim (sometimes typical of quartz). In such settings, it is important to identify partial bleaching and the minimum dose population, preferably by analysing single grains, and applying the appropriate statistical age model to the dose population obtained for each sample. To determine accurate OSL ages using these age models, it is important to quantify the amount of scatter (or overdispersion) in the well-bleached part of the partially bleached dose distribution, which can vary between sediment samples depending upon the bedrock sources and transport histories of grains. Here, we discuss how the effects of partial bleaching can be easily identified and overcome to determine accurate ages. This discussion will therefore focus entirely on the burial dose determination for OSL dating, rather than the dose-rate, as only the burial doses are impacted by the effects of partial bleaching

Genome-wide association study of germline variants and breast cancer-specific mortality.

BackgroundWe examined the associations between germline variants and breast cancer mortality using a large meta-analysis of women of European ancestry.MethodsMeta-analyses included summary estimates based on Cox models of twelve datasets using ~10.4 million variants for 96,661 women with breast cancer and 7697 events (breast cancer-specific deaths). Oestrogen receptor (ER)-specific analyses were based on 64,171 ER-positive (4116) and 16,172 ER-negative (2125) patients. We evaluated the probability of a signal to be a true positive using the Bayesian false discovery probability (BFDP).ResultsWe did not find any variant associated with breast cancer-specific mortality at P < 5 × 10-8. For ER-positive disease, the most significantly associated variant was chr7:rs4717568 (BFDP = 7%, P = 1.28 × 10-7, hazard ratio [HR] = 0.88, 95% confidence interval [CI] = 0.84-0.92); the closest gene is AUTS2. For ER-negative disease, the most significant variant was chr7:rs67918676 (BFDP = 11%, P = 1.38 × 10-7, HR = 1.27, 95% CI = 1.16-1.39); located within a long intergenic non-coding RNA gene (AC004009.3), close to the HOXA gene cluster.ConclusionsWe uncovered germline variants on chromosome 7 at BFDP < 15% close to genes for which there is biological evidence related to breast cancer outcome. However, the paucity of variants associated with mortality at genome-wide significance underpins the challenge in providing genetic-based individualised prognostic information for breast cancer patients

Genome-wide association study of germline variants and breast cancer-specific mortality

BACKGROUND: We examined the associations between germline variants and breast cancer mortality using a large meta-analysis of women of European ancestry. METHODS: Meta-analyses included summary estimates based on Cox models of twelve datasets using ~10

Increasing frailty is associated with higher prevalence and reduced recognition of delirium in older hospitalised inpatients: results of a multi-centre study

Purpose: Delirium is a neuropsychiatric disorder delineated by an acute change in cognition, attention, and consciousness. It is common, particularly in older adults, but poorly recognised. Frailty is the accumulation of deficits conferring an increased risk of adverse outcomes. We set out to determine how severity of frailty, as measured using the CFS, affected delirium rates, and recognition in hospitalised older people in the United Kingdom. Methods: Adults over 65 years were included in an observational multi-centre audit across UK hospitals, two prospective rounds, and one retrospective note review. Clinical Frailty Scale (CFS), delirium status, and 30-day outcomes were recorded. Results: The overall prevalence of delirium was 16.3% (483). Patients with delirium were more frail than patients without delirium (median CFS 6 vs 4). The risk of delirium was greater with increasing frailty [OR 2.9 (1.8–4.6) in CFS 4 vs 1–3; OR 12.4 (6.2–24.5) in CFS 8 vs 1–3]. Higher CFS was associated with reduced recognition of delirium (OR of 0.7 (0.3–1.9) in CFS 4 compared to 0.2 (0.1–0.7) in CFS 8). These risks were both independent of age and dementia. Conclusion: We have demonstrated an incremental increase in risk of delirium with increasing frailty. This has important clinical implications, suggesting that frailty may provide a more nuanced measure of vulnerability to delirium and poor outcomes. However, the most frail patients are least likely to have their delirium diagnosed and there is a significant lack of research into the underlying pathophysiology of both of these common geriatric syndromes

Holocene dune activity in the Thar Desert, India

The Thar Desert dune system in north-west India and eastern Pakistan provides a rich archive of past environmental, geomorphological and climatic change. Much of the knowledge about the timing of dune accumulation in the Thar stems from scattered and sporadic records, based on older luminescence dating protocols. If the Thar dune record is to be incorporated within a growing multiproxy framework of past climate and environmental dynamics, it is necessary to generate a systematic record of the timing of dunefield accumulation. From this, relationships to climate and other drivers of dune activity may then be better established. To this end, an intensive programme of field sampling and optically stimulated luminescence (OSL) dating was carried out from a dunefield in the east-central Thar Desert. This study presents the first detailed Holocene dune accumulation history from the region, and sheds light on the development of the multi-generational parabolic dune systems. In contrast to previously published work, we identify the importance of the Holocene and the last millennium as periods with a number of preserved accumulation phases. OSL ages suggest that accumulation was persistent during the early and mid-Holocene (within 11.7-5.5 ka), late Holocene (2-1 ka), as well as two major phases in the last millennium (600 – 200 a and within the last 70 a). Potential drivers of dune mobility in the last century include a strong anthropogenic dimension. Rapid net accumulation is recorded in the last 70 years, with rates varying between 2 and 5 m/year, in an environment where agricultural pressures have increased dramatically with the advent of irrigation schemes expanding into dunefield areas.</p