Assessment of the calibration of gamma spectrometry systems in forest environments

A Monte Carlo simulation was used to develop a model of the response of a portable gamma spectrometry system in forest environments. This model was used to evaluate any corrections needed to measurements of 137Cs activity per unit area calibrated assuming an open field geometry. These were shown to be less than 20% for most forest environments. The model was also used to assess the impact of activity in the canopy on ground level measurements. For similar activity per unit area in the lower parts of the canopy as on the ground, 10-25% of the ground based measurement would be due to activity in the canopy, depending on the depth profile in the soil. The model verifies that an optional collimator cap can assess activity in the canopy by repeat survey

Review of nuclear data for naturally occurring radionuclides applied to environmental applications

Accurate nuclear data, commonly using evaluated libraries, is essential in many applications, allowing confidence in derived parameters. An approach to assess the confidence with which these data can be used is proposed, not previously reported, comparing nuclear data presented by different evaluations. Variations between evaluations are used as an indication of potential inaccuracies in the nuclear data or evaluation procedure, and the relevant primary literature reviewed more fully. Applying this approach to naturally occurring radionuclides has identified eight radionuclides where the evaluations differ significantly. Where recommended data are supported by a single set of high precision measurements, independent verification of those measurements will increase confidence in the accuracy of the data (214Bi and 214Pb). Further measurements should be conducted where the decay schemes are incomplete ( 228Ac and 228Ra). For 40K, the mean beta energy in all the evaluations has been calculated using an incorrect shape factor, and log ft and branching ratios have been calculated using an inappropriate program. Precise measurements of beta spectra will allow the use of experimentally derived shape factors for the calculation of mean beta energies (40K and 210Bi). Parameters used for infinite matrix dose rate and geothermal heat production calculations have been derived for the data discussed here

Rapid 20th century warming reverses 900-year cooling in the Gulf of Maine

The Gulf of Maine, located in the western North Atlantic, has undergone recent, rapid ocean warming but the lack of long-term, instrumental records hampers the ability to put these significant hydrographic changes into context. Here we present multiple 300-year long geochemical records (oxygen, nitrogen, and previously published radiocarbon isotopes) measured in absolutely-dated Arctica islandica shells from the western Gulf of Maine. These records, in combination with climate model simulations, suggest that the Gulf of Maine underwent a long-term cooling over most of the last 1000 years, driven primarily by volcanic forcing and North Atlantic ocean dynamics. This cooling trend was reversed by warming beginning in the late 1800s, likely due to increased atmospheric greenhouse gas concentrations and changes in western North Atlantic circulation. The climate model simulations suggest that the warming over the last century was more rapid than almost any other 100-year period in the last 1000 years in the region

Luminescence dating of soils and sediments from Jerash, Jordan

The urban site of Jerash, Jordan is recognised as one of the great cities of the classical Middle East and has been the subject of ongoing systematic archaeological investigations since the 1920s. Its significance lies in its location on limestone geology in one of the more fertile areas of the Ajlun Highlands in northern Jordan with a good water supply, a number of springs and its central position in regional trade routes. The hinterland context of the city is yet to be considered and is a significant omission given the importance of water and its management together with the agricultural systems dependent on water in supporting urban development. Landscape chronologies are vital to the establishment of city and hinterland relationships and in this working papers we assess the value and significance of optically stimulated luminescence (OSL) measurement in this endeavour. Our findings so far suggest a measurement cluster range of ca. 480 BC – 250 BC in landscapes underlying the city and a dominant trend of sediments infilling the adjacent Wadi Suf between 640 ± 240 AD and 1400 ± 60 AD reflecting land management changes in a soil environment sensitive to degradation

Controls on luminescence signals in lake sediment cores:A study from Lake Suigetsu, Japan

The luminescence characteristics of sediments are driven by a range of environmental factors and can be used as indicators of both local and regional environmental shifts. Hence, rapid luminescence profiling techniques are increasingly employed during multiproxy analysis of sediment cores, overcoming the practical limitations of traditional (dating) methods. One emerging application of luminescence profiling is in the palaeoenvironmental investigation of lake cores. This study demonstrates the versatility of rapid core profiling using portable optically stimulated luminescence and laboratory profiling techniques for appraising the luminescence characteristics of the Lake Suigetsu (Japan) sediment cores. These techniques were employed across four key time periods, each selected for their unique environmental context and significance on either a local or global scale, in order to identify relationships between down-core luminescence and environmental change. We demonstrate that the luminescence characteristics of the cores are susceptible to a range of environmental perturbations and can therefore act as proxies of past change. Additionally, the quantification of these luminescence signals, alongside an assessment of dose rate variations down-core, supports the notion that future luminescence dating is feasible. The results of this analysis contribute to the wider understanding of the application of luminescence techniques – both profiling and dating – to lake sediment cores

Production of 40Ar by an overlooked mode of 40K decay with implications for K-Ar geochronology

The decay of 40K to the stable isotopes 40Ca and 40Ar is used as a measure of time for both the K-Ca and KAr geochronometers, the latter of which is most generally utilized by the variant 40Ar/ 39Ar system. The increasing precision of geochronology has forced practitioners to deal with the systematic uncertainties rooted in all radioisotope dating methods. A major component of these systematic uncertainties for the K-Ar and 40Ar/ 39Ar techniques is imprecisely determined decay constants and an incomplete knowledge of the decay scheme of 40K. Recent geochronology studies question whether 40K can decay to 40Ar via an electron capture directly to ground state (ECground), citing the lack of experimental verification as reasoning for its omission. In this study, we (1) provide a theoretical argument in favor of the presence of this decay mode and (2) evaluate the magnitude of this decay mode by calculating the electron capture to positron ratio (ECground/β+) and comparing calculated ratios to previously published calculations, which yield ECground/β+ between 150–212. We provide support for this calculation through comparison of the experimentally verified ECground/β+ ratio of 22Na with our calculation using the theory of β decay. When combined with measured values of β + and β − decay rates, the best estimate for the calculated ECground/β+ for 40K yields a partial decay constant for 40K direct to ground-state 40Ar of 11.6±1.5×10−13 a −1 (2σ). We calculate a partial decay constant of 40K to 40Ar of 0.592 ± 0.014 × 10−10 a −1 and a total decay constant of 5.475 ± 0.107 × 10−10 a −1 (2σ), and we conclude that although omission of this decay mode can be significant for K-Ar dating, it is minor for 40Ar/ 39Ar geochronology and is therefore unlikely to have significantly biased published measurements

A systematic multi-technique comparison of luminescence characteristics of two reference quartz samples

MB did the experiments using the equipment belonging to the Centre for Modern Interdisciplinary Technologies, Nicolaus Copernicus University in Torun, ul. Wilenska 4, 87–100 Torun, Poland (e-mail: [email protected]) and has been financed by the grant of the National Science Centre, Poland, No. 2018/31/B/ST10/03917.International audienceFurther developments in luminescence dating, dosimetry and temperature-sensing require a deep understanding of luminescence processes and their driving parameters. Natural quartz is one of the most widely used minerals for these purposes. Still, poor reproducibility of results often hampers comparability and credibility of findings in the literature. We identified the lack of suitable natural reference samples as a pivotal problem impeding significant progression. Ideally, basic investigations involve several laboratories working on well-characterised reference quartz samples with different characteristics. Investigations should include multiple complementing methods to analyse luminescence properties and mineralogical and geochemical composition.Here, we present such a multi-technique luminescence comparison of two natural quartz samples. Next to the recently introduced Fontainebleau (FB) reference quartz, we propose another reference sample derived from the ‘Silver Sands of Morar’ (lab code ‘MR’; Scotland, UK). Our experiments confirm that both quartz samples behave fundamentally different in terms of signal composition and sensitivity. The comparative characterisation of both samples targeted electron traps via thermoluminescence (TL) and optically stimulated luminescence (OSL) techniques and luminescence centres via radioluminescence and time-resolved OSL spectrometry. In summary, we conclude that all observed differences are likely the results of divergent defect concentrations rather than variances in defects' composition (nature). The measurement data of our study are accessible open-access for inspection by others

Rational solutions of the discrete time Toda lattice and the alternate discrete Painleve II equation

The Yablonskii-Vorob'ev polynomials $y_{n}(t)$, which are defined by a second order bilinear differential-difference equation, provide rational solutions of the Toda lattice. They are also polynomial tau-functions for the rational solutions of the second Painlev\'{e} equation ($P_{II}$). Here we define two-variable polynomials $Y_{n}(t,h)$ on a lattice with spacing $h$, by considering rational solutions of the discrete time Toda lattice as introduced by Suris. These polynomials are shown to have many properties that are analogous to those of the Yablonskii-Vorob'ev polynomials, to which they reduce when $h=0$. They also provide rational solutions for a particular discretisation of $P_{II}$, namely the so called {\it alternate discrete} $P_{II}$, and this connection leads to an expression in terms of the Umemura polynomials for the third Painlev\'{e} equation ($P_{III}$). It is shown that B\"{a}cklund transformation for the alternate discrete Painlev\'{e} equation is a symplectic map, and the shift in time is also symplectic. Finally we present a Lax pair for the alternate discrete $P_{II}$, which recovers Jimbo and Miwa's Lax pair for $P_{II}$ in the continuum limit $h\to 0$.Comment: 23 pages, IOP style. Title changed, and connection with Umemura polynomials adde

Spectators’ Negotiations of Risk, Masculinity and Performative Mobilities at the TT Races

This paper explores the particular assemblage of place, event and individual identity performances that occur each year in the Isle of Man in and through the TT (Tourist Trophy) motorcycle races. These road races are associated with a high degree of risk for the racers and the confluence of over 30,000 visitors and 10,000 motorcycles also presents potential risks for spectators and residents alike. Both motorcycling and risk-taking have been associated with particular forms of masculinity, notably hegemonic, working class and youthful masculinities. Using detailed surveys of spectators we argue that the TT races, while undoubtedly dominated by men and predicated on a cultural privileging of speed and skill, are grounded in varying combinations of determinate and reflexive attitudes to risk, reflecting the performance of a variety of gendered, ‘biker’ and wider identity-based positionalities. Findings also highlight a particular inter-relation of mobilities and place identities at the TT races and bring to light the highly significant and under-researched embodied, performative and emotional mobilities of spectators. The conceptual and methodological importance of (a) situated research of both mobilities and gender in specific place-temporalities and (b) wider surveys of motorcyclists to complement ethnographic studies of small cohorts are also stressed