Over the last decade, an increasing number of studies have used lake sediment DNA to trace past landscape changes, agricultural activities or human presence. However, the processes responsible for ...lake sediment formation and sediment properties might affect DNA records via taphonomic and analytical processes. It is crucial to understand these processes to ensure reliable interpretations for "palaeo" studies. Here, we combined plant and mammal DNA metabarcoding analyses with sedimentological and geochemical analyses from three lake-catchment systems that are characterised by different erosion dynamics. The new insights derived from this approach elucidate and assess issues relating to DNA sources and transfer processes. The sources of eroded materials strongly affect the "catchment-DNA" concentration in the sediments. For instance, erosion of upper organic and organo-mineral soil horizons provides a higher amount of plant DNA in lake sediments than deep horizons, bare soils or glacial flours. Moreover, high erosion rates, along with a well-developed hydrographic network, are proposed as factors positively affecting the representation of the catchment flora. The development of open and agricultural landscapes, which favour the erosion, could thus bias the reconstructed landscape trajectory but help the record of these human activities. Regarding domestic animals, pastoral practices and animal behaviour might affect their DNA record because they control the type of source of DNA ("point" vs. "diffuse").
Prompt-gamma emission detection is a promising technique for hadrontherapy monitoring purposes. In this regard, obtaining prompt-gamma yields that can be used to develop monitoring systems based on ...this principle is of utmost importance since any camera design must cope with the available signal. Herein, a comprehensive study of the data from ten single-slit experiments is presented, five consisting in the irradiation of either PMMA or water targets with lower and higher energy carbon ions, and another five experiments using PMMA targets and proton beams. Analysis techniques such as background subtraction methods, geometrical normalization, and systematic uncertainty estimation were applied to the data in order to obtain absolute prompt-gamma yields in units of prompt-gamma counts per incident ion, unit of field of view, and unit of solid angle. At the entrance of a PMMA target, where the contribution of secondary nuclear reactions is negligible, prompt-gamma counts per incident ion, per millimetre and per steradian equal to (124 ± 0.7stat ± 30sys) × 10(-6) for 95 MeV u(-1) carbon ions, (79 ± 2stat ± 23sys) × 10(-6) for 310 MeV u(-1) carbon ions, and (16 ± 0.07stat ± 1sys) × 10(-6) for 160 MeV protons were found for prompt gammas with energies higher than 1 MeV. This shows a factor 5 between the yields of two different ions species with the same range in water (160 MeV protons and 310 MeV u(-1) carbon ions). The target composition was also found to influence the prompt-gamma yield since, for 300/310 MeV u(-1) carbon ions, a 42% greater yield ((112 ± 1stat ± 22sys) × 10(-6) counts ion(-1) mm(-1) sr(-1)) was obtained with a water target compared to a PMMA one.
For real-time monitoring of the longitudinal position of the Bragg-peak during an ion therapy treatment, a novel non-invasive technique has been recently proposed that exploits the detection of ...prompt γ-rays issued from nuclear fragmentation. Two series of experiments have been performed at the GANIL and GSI facilities with 95 and 305 MeV/u ¹²C⁶⁺ ion beams stopped in PMMA and water phantoms. In both experiments, a clear correlation was obtained between the carbon ion range and the prompt photon profile. Additionally, an extensive study has been performed to investigate whether a prompt neutron component may be correlated with the carbon ion range. No such correlation was found. The present paper demonstrates that a collimated set-up can be used to detect single photons by means of time-of-flight measurements, at those high energies typical for ion therapy. Moreover, the applicability of the technique both at cyclotron and at synchrotron facilities is shown. It is concluded that the detected photon count rates provide sufficiently high statistics to allow real-time control of the longitudinal position of the Bragg-peak under clinical conditions.
Chronologies of lake-sediment records covering the last centuries to millennia are usually based on both short-lived radionuclides and radiocarbon dating. However, beyond the range of short-lived ...radionuclides, age model accuracy often suffers from large radiocarbon uncertainties. For high-altitude records, this issue is even more prominent as terrestrial plant fragments for radiocarbon dating are often lacking due to the sparse vegetation in such environments. In this study, we evaluate the potential of the geomagnetic field secular variations as a complementary tool to establish more robust age–depth relationships. Our palaeomagnetic study, applied to five high-altitude lakes from the western European Alps, first shows that recent unconsolidated sediments can carry stable remanent magnetization. The analysis of the magnetic parameters indicates that low-coercivity pseudo-single domain magnetite grains carry the natural magnetization. Nevertheless, the quality of palaeomagnetic secular variation records varies from one lake to another. This quality can be illustrated through the calculation of the declination/inclination maximum angular variations and their comparison to the expected value. Compared with available models, the declination variations are usually too large and the inclination too high. We discuss the validity of palaeosecular variation (PSV) of the Earth’s magnetic field regarding rock magnetism, magnetization processes and possible deformation during coring. From a magnetic point of view, the quality of data is variable, but the characteristic remanent magnetization direction is consistent at site level between neighbouring lakes and with the reference curve, suggesting that geomagnetic field secular variations are approximately recorded. Finally, we attempt to correlate the declination/inclination variations of the characteristic remanent magnetization measured in the five records to the reference geomagnetic model to provide additional chronological markers for age–depth modelling. These stratigraphic chrono-markers appear in systematic agreement with our previous chronological data and enable a reduction of dating uncertainties up to 30% when including these chrono-markers in the age–depth modelling. This agreement supports the interpretation that PSV may have been recorded more or less accurately depending on the studied lake. Therefore, coupled with a comprehensive understanding through other analysis (sedimentology, dating, geochemistry), PSV can be used to improve the age models in the more favourable cases.
Monte Carlo simulations based on the Geant4 toolkit (version 9.1) were performed to study the emission of secondary prompt-gamma rays produced by nuclear reactions during carbon ion-beam therapy. ...These simulations were performed along with an experimental program and instrumentation developments which aim at designing a prompt-gamma ray device for real-time control of hadrontherapy. The objective of the present study is twofold: firstly, to present the features of the prompt-gamma radiation in the case of carbon ion irradiation; secondly, to simulate the experimental setup and to compare measured and simulated counting rates corresponding to four different experiments. For each experiment, we found that simulations overestimate prompt-gamma ray detection yields by a factor of 12. Uncertainties in fragmentation cross sections and binary cascade model cannot explain such discrepancies. The so-called "photon evaporation" model is therefore questionable and its modification is currently in progress.
This paper gives a short review of the past and recent activities of the Atomic Collisions in Solids Lyon-group, in collaboration with other groups, in the field of high energy channelling. The ...ion-channelling programme was performed at GANIL-Caen and at GSI-Darmstadt. The electron-channelling programme started at ALS-Saclay for relativistic incident energies and was then extended to SPS-CERN for ultra-relativistic energies. The last part of this paper presents the electron-channelling experiments performed originally at ALS-Saclay, then at BTF-Frascati and more recently at LS-Saga, in order to observe the electron “internal clock” predicted in 1924 by L. de Broglie.
Uncovering anthropogenic and environmental drivers behind past biological change requires integrated analyses of long-term records from a diversity of disciplines. We applied an interdisciplinary ...approach exploring effects of human land-use and environmental changes on vegetation dynamics at Lake Ljøgottjern in southeastern Norway during the Holocene. Combined analysis of pollen and sedimentary ancient DNA (sedaDNA) metabarcoding of the sedimentary sequence of the lake describes the vegetation dynamics at different scales, and establishes a timeline for pastoral farming activities. We integrate this reconstruction with geochemical analysis of the sediments, climate data, archaeological evidence of local human settlement and regional human population dynamics.
Our data covering the last 10,000 years reveals consistent vegetation signals from pollen and sedaDNA indicating periods of deforestation connected to cultivation, matching the archaeological evidence. Multivariate analysis integrating the environmental data from geochemical and archaeological reconstructions with the vegetation composition indicates that the vegetation dynamics at Lake Ljøgottjern were primarily related to natural processes from the base of the core (in ca. 8000 BCE, Mesolithic) up to the Early Iron Age (ca. 500 BCE–550 CE), when agricultural activities in the region intensified. The pollen signal reflects the establishment of a Bronze Age (ca. 1800–500 BCE) farm in the area, while subsequent intensification of pollen concentrations of cultivated plants combined with the first sedaDNA signals of cultivation and pastoralism are consistent with evidence of the establishment of farming closer to the lake at around 300 BCE. These signals also correspond to the intensification of agriculture in southeastern Norway in the first centuries of the Early Iron Age. Applying an interdisciplinary approach allows us to reconstruct anthropogenic and environmental dynamics, and untangle effects of human land-use and environmental changes on vegetation dynamics in southeastern Norway during the Holocene.
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•Integration of pollen, sedaDNA, geochemical, archaeological and climate data.•Natural processes drove vegetation succession at Lake Ljøgottjern until Early Iron Age.•Matching pollen and sedaDNA records show rapid intensification of agropastoralism•Deviations between pollen and sedaDNA reflect distance to farms since the Bronze Age.•Major plant community shift coincided with growing human population in Early Iron Age.
It is proposed to build a national centre for light-ion hadrontherapy in France, located in Lyon in the Rhône-Alpes region. Under the auspices of University Claude Bernard Lyon-1 and with the support ...of a research contract between Rhône-Alpes region and the Minister of Research, a design has been elaborated. This paper reviews the medical and technical characteristics of the project, called ETOILE (Espace de Traitement Oncologique par Ions Légers dans le cadre Européen). The research programs associated with ETOILE concern mainly the tracking of moving organs, the design of an in-beam PET detector, the simulation of the interaction of carbon ions with tissues and radiobiological studies on the radiosensitivity and tolerance of normal tissues and on the radioresistance of tumours. The capital cost needed to realize ETOILE is about 90 M€. We expect a definitive decision to build ETOILE at the end of 2004. In that case the centre will treat its first patients in 2009. A routine flux of 1000 patients per year will be reached after 3 years with an operation cost of 15 M€.
We initiated studies on the mechanisms of cell death in head and neck squamous cell carcinoma cell lines (HNSCC) since recent clinical trials have shown that local treatment of HNSCC by carbon ...hadrontherapy is less efficient than it is in other radioresistant cancers.
Two p53-mutated HNSCC cell lines displaying opposite radiosensitivity were used. Different types of cell death were determined after exposure to carbon ions (33.6 and 184 keV/microm) or X-rays.
Exposure to radiation with high linear energy transfer (LET) induced clonogenic cell death for SCC61 (radiosensitive) and SQ20B (radioresistant) cells, the latter systematically showing less sensitivity. Activation of an early p53-independent apoptotic process occurred in SCC61 cells after both types of irradiation, which increased with time, dose and LET. In contrast, SQ20B cells underwent G2/M arrest associated with Chk1 activation and Cdc2 phosphorylation. This inhibition was transient after X-rays, compared with a more prolonged and LET-dependent accumulation after carbon irradiation. After release, a LET-dependent increase of polyploid and multinucleated cells, both typical signs of mitotic catastrophe, was identified. However, a subpopulation of SQ20B cells was able to escape mitotic catastrophe and continue to proliferate.
High LET irradiation induced distinct types of cell death in HNSCC cell lines and showed an increased effectiveness compared with X-rays. However, the reproliferation of SQ20B may explain the potential locoregional recurrence observed among some HNSCC patients treated by hadrontherapy. An adjuvant treatment forcing the tumor cells to enter apoptosis may therefore be necessary to improve the outcome of radiotherapy.
To establish the radiobiologic parameters of head-and-neck squamous cell carcinomas (HNSCC) in response to ion irradiation with various linear energy transfer (LET) values and to evaluate the ...relevance of the local effect model (LEM) in HNSCC.
Cell survival curves were established in radiosensitive SCC61 and radioresistant SQ20B cell lines irradiated with 33.6 and 184 keV/n carbon, 302 keV/n argon, and X-rays. The results of ion experiments were confronted to LEM predictions.
The relative biologic efficiency ranged from 1.5 to 4.2 for SCC61 and 2.1 to 2.8 for SQ20B cells. Fixing an arbitrary D(0) parameter, which characterized survival to X-ray at high doses (>10 Gy), gave unsatisfying LEM predictions for both cell lines. For D(0) = 10 Gy, the error on survival fraction at 2 Gy amounted to a factor of 10 for 184 keV/n carbon in SCC61 cells. We showed that the slope (s(max)) of the survival curve at high doses was much more reliable than D(0). Fitting s(max) to 2.5 Gy(-1) gave better predictions for both cell lines. Nevertheless, LEM could not predict the responses to fast and slow ions with the same accuracy.
The LEM could predict the main trends of these experimental data with correct orders of magnitude while s(max) was optimized. Thus the efficiency of carbon ions cannot be simply extracted from the clinical response of a patient to X-rays. LEM should help to optimize planning for hadrontherapy if a set of experimental data is available for high-LET radiations in various types of tumors.
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