ESR dating of optically bleached quartz grains: assessing the impact of different experimental setups on dose evaluations

The samples used in the present study have been collected from Bizat Ruhama site with the support of Y. Zaidner, from the University of Haifa, Israel. V.G. research stay in the Australian Research Centre for Human Evolution at Griffith University was funded by a Jose Castillejo Mobility Fellowship CAS18/00285 from the Spanish Ministry of Science, Innovation and Universities. Aspects of this study have been funded by the Australian Research Council Future Fellowship grant FT150100215 granted to M.D.In recent years, our investigation has been centred on improving the reliability and accuracy of the ESR method applied to quartz grains. As part of this ongoing investigation, we present an intra-laboratory study to evaluate the impact of different experimental setups on the ESR measurement precision and dose evaluation for ESR dating of optically bleached quartz grains. Repeated measurements of quartz samples have been performed at CENIEH, Spain, using two different Bruker spectrometers (EMXmicro and Elexsys E500) and resonators (standard rectangular ER4102ST and cylindrical Super High QE cavities). Their performance in terms of sensitivity, measurement repeatability and dose determination are presented in this study. This intra-laboratory work has allowed to evaluate the robustness of our protocol for ESR dating of quartz grains and to study the potential impact of different experimental setups on dose evaluation, which is essential for future standardization of the ESR dating method. Our results indicate that all the different experimental setups provide comparable precision of the ESR intensity measurements. Moreover, all the ESR dose estimates are within 1-sigma error, suggesting that it is possible to compare results obtained by different laboratories when similar analytical procedures are followed. Finally, the higher sensitivity achieved by the SHQE resonator appears to be of particular interest when dealing with samples showing low ESR signal intensities.Spanish Government CAS18/00285Australian Research Council FT15010021

Deprotometalation-iodolysis and computed CH acidity of 1,2,3- and 1,2,4-triazoles. Application to the synthesis of resveratrol analogues

International audience1-Aryl- and 2-aryl-1,2,3-triazoles were synthesized by N-arylation of the corresponding azoles using aryl iodides. The deprotometalations of 1-phenyl-1,2,3-triazole and -1,2,4-triazole were performed using a 2,2,6,6-tetramethylpiperidino-based mixed lithium-zinc combination and occurred at the most acidic site, affording by iodolysis the 5-substituted derivatives. Dideprotonation was noted from 1-(2-thienyl)-1,2,4-triazole by increasing the amount of base. From 2-phenyl-1,2,3-triazoles, and in particular from 2-(4-trifluoromethoxy)phenyl-1,2,3-triazole, reactions at the 4 position of the triazolyl, but also ortho to the triazolyl on the phenyl group, were observed. The results were analyzed with the help of the CH acidities of the substrates, determined in THF solution using the DFT B3LYP method. 4-Iodo-2-phenyl-1,2,3-triazole and 4-iodo-2-(2-iodophenyl)-1,2,3-triazole were next involved in Suzuki coupling reactions to furnish the corresponding 4-arylated and 4,2’-diarylated derivatives. When evaluated for biological activities, the latter (which are resveratrol analogues) showed moderate antibacterial activity and promising antiproliferative effect against MDA-MB-231 cell line

Telematics Combined Actuarial Neural Networks for Cross-Sectional and Longitudinal Claim Count Data

We present novel cross-sectional and longitudinal claim count models for vehicle insurance built upon the Combined Actuarial Neural Network (CANN) framework proposed by Mario W\"uthrich and Michael Merz. The CANN approach combines a classical actuarial model, such as a generalized linear model, with a neural network. This blending of models results in a two-component model comprising a classical regression model and a neural network part. The CANN model leverages the strengths of both components, providing a solid foundation and interpretability from the classical model while harnessing the flexibility and capacity to capture intricate relationships and interactions offered by the neural network. In our proposed models, we use well-known log-linear claim count regression models for the classical regression part and a multilayer perceptron (MLP) for the neural network part. The MLP part is used to process telematics car driving data given as a vector characterizing the driving behavior of each insured driver. In addition to the Poisson and negative binomial distributions for cross-sectional data, we propose a procedure for training our CANN model with a multivariate negative binomial (MVNB) specification. By doing so, we introduce a longitudinal model that accounts for the dependence between contracts from the same insured. Our results reveal that the CANN models exhibit superior performance compared to log-linear models that rely on manually engineered telematics features.Comment: 30 pages, 10 tables, 6 figure

On the impact of micro-CT scanning on radiocarbon dating of fossil material: A cautionary note for the palaeoanthropological community and beyond

In this study, we investigate the impact of X-rays produced by conventional mCT instruments on fossil materials dated by radiocarbon. Our results clearly show a decrease on the collagen preservation in fossil and modern bones and teeth, and therefore on the radiocarbon analytical results (in particular, the collagen yield and, possibly, stable isotope composition), after mCT scanning. In other words, all the samples analysed here have experienced a noticeable radiation damage, regardless of their nature (bone and dental tissue) and age (modern and fossil). Given these observations, a prudent approach would be for radiocarbon laboratories to expect lower collagen yields for samples that have been previously mCT scanned and ensure appropriately sized standards are processed alongside these samples. Additionally, samples with originally low collagen yields might become unsuitable for radiocarbon dating after mCT or at least show a yield lower than the usual minimum cut-off value. In this case, it might be viable to extend the collagen yield quality assurance parameter for mCT scanned bones and teeth and instead focus on the C:N ratio as the most appropriate indicator of collagen quality, although we cannot exclude that the latter may also be impacted by X-ray exposure. Further investigations on a larger set of samples are required to confirm these first observations. Nevertheless, in the light of these results, we can reasonably conclude by recommending caution regarding the systematic and unlimited use of mCT scanning in palaeoanthropology or in other related disciplines involving fossil material

Revealing the pace of river landscape evolution during the Quaternary: recent developments in numerical dating methods

During the last twenty years, several technical developments have considerably intensified the use of numerical dating methods for the Quaternary. The study of fluvial archives has greatly benefited from these enhancements, opening new dating horizons for a range of archives at distinct time scales and thereby providing new insights into previously unanswered questions. In this contribution, we separately present the state of the art of five numerical dating methods that are frequently used in the fluvial context: radiocarbon, Luminescence, Electron Spin Resonance (ESR), 230Th/U and terrestrial cosmogenic nuclides (TCN) dating. We focus on the major recent developments for each technique that are most relevant for new dating applications in diverse fluvial environments and on explaining these for non-specialists. Therefore, essential information and precautions about sampling strategies in the field and/or laboratory procedures are provided. For each method, new and important implications for chronological reconstructions of Quaternary fluvial landscapes are discussed and, where necessary, exemplified by key case studies. A clear statement of the current technical limitations of these methods is included and forthcoming developments, which might possibly open new horizons for dating fluvial archives in the near future, are summarised

To what extent do field conditions affect gamma dose rate determination using portable gamma spectrometry?

Field gamma spectrometry is a widely used approach for determining in situ gamma dose rates in dosimetric (i.e., electron spin resonance and luminescence) dating applications. In comparison with laboratory-based determinations, in situ radioactivity measurements typically provide more representative gamma dose rate evaluations for heterogeneous sedimentary environments. However, it is often not possible to perform in situ gamma spectrometry measurements under carefully controlled conditions that are directly comparable to those originally used for equipment calibration. In this study, we use Geant4 Monte Carlo simulations to model gamma spectrometry measurements under a range of field conditions, and examine the relative impacts of the following parameters on dose rate determination using the threshold calibration approach: (i) geometry and depth of the measurement hole in which the probe is inserted, (ii) nature of the sediment or rock materials and their water content, (iii) geometry of the radiation environment surrounding the measurement hole, i.e. closed and partially closed sites (e.g., caves, trenches) versus open-air sites (e.g. plain field excavations, cliff or cutting exposures). Our results show that some differences in calibration and field measurement configurations can significantly bias in situ gamma dose rate determinations. Variations in the depth of probe holes can result in underestimations of infinite matrix gamma dose rates by 5% for a 30 cm-deep hole to 58% for measurements made against sediment surfaces (i.e., 2π geometry). Use of hole shapes that do not match those of the probe can lead to underestimations of infinite matrix dose rates by up to 4%, with these biasing effects becoming more significant for shallow holes. External gamma radiation originating from, and backscattered against, structures in the surrounding environment can contribute significantly to gamma dose rates measured using shallow probe holes. The nature of the mineral materials can have a small effect on the measured gamma dose rate (equivalent to infinite matrix dose rate biases of a few percent), mostly due to differences in the density of different materials. Measurements performed in materials with high water contents can be affected by small gamma dose rate overestimations due to differences in water attenuation factors of centimetre-scale objects such as gamma spectrometer probes and those of relevance for dating smaller objects such as sediment grains. These problems can be resolved by using specific correction factors, by including additional uncertainties during dose rate determination, or by performing in situ measurements at different depths for the same location