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.

Classical sea-ice models in climate model resolution do not resolve the small-scale physics of sea ice. New methods to address this problem include modifications to established viscous-plastic (VP) rheology models, sub-gridscale parameterizations or new rheologies such as the Maxwell elasto-brittle (MEB) rheology. Here, we investigate differences in gridscale dynamics simulated by the VP and MEB models, their dependency on tunable model parameters and their response to added stochastic perturbations of material parameters in a new implementation in the Massachusetts Institute of Technology general circulation model. Idealized simulations are used to demonstrate that material parameters can be tuned so that both VP and MEB rheologies lead to similar cohesive stress states, arching behaviour and heterogeneity in the deformation fields. As expected, simulations with MEB rheology generally show more heterogeneity than the VP model as measured by the number of simulated linear kinematic features (LKFs). For both rheologies, the cohesion determines the emergence of LKFs. Introducing gridscale heterogeneity by random model parameter perturbation, however, leads to a larger increase of LKF numbers in the VP simulations than in the MEB simulations and similar heterogeneity between VP and MEB models.

Declining labor force participation of older men throughout the 20th century and recent increases in participation have generated substantial interest in understanding the effect of public pensions on retirement. The National Bureau of Economic Research's International Social Security (ISS) Project, a long-term collaboration among researchers in a dozen developed countries, has explored this and related questions. The project employs a harmonized approach to conduct within-country analyses that are combined for meaningful cross-country comparisons. The key lesson is that the choices of policy makers affect the incentive to work at older ages and these incentives have important effects on retirement behavior.

Cremation graves appear in different forms and shapes, from urns to simple pits and from single to plural graves. The challenging nature of highly fragmented cremated human remains renders the identification of multiple individuals within the same cremation grave rather complex. Osteological analyses alone are often insufficient to detect the presence of bone fragments from different individuals as they are small and diagnostic elements are often missing, although, detection of nonadult bone fragments within adult bone assemblages (or the other way around) points to the presence of at least two individuals—one adult and one nonadult—within the same grave. The combination of osteological analyses, radiocarbon dating, and strontium isotope ratios has proven to be particularly powerful. At different Belgian Metal Age sites, this novel multi-disciplinary approach enabled to identify the presence of bone fragments belonging to up to three different individuals within the same cremation grave who were cremated up to several centuries apart. Whether the presence of these two or three individuals in the same grave is intentional (e.g. curation) or not requires more in-depth analyses. This study shows the high level of complexity of cremation burial (intentionally or not) and shows the necessity to carry out all analytical measurements (i.e. radiocarbon dating, infrared, elemental and isotope analyses) on the same bone fragment to ensure the results are related to the same individual.

The rapid growth of cultural evolutionary science, its expansion into numerous fields, its use of diverse methods, and several conceptual problems have outpaced corollary developments in theory and philosophy of science. This has led to concern, exemplified in results from a recent survey conducted with members of the Cultural Evolution Society, that the field lacks ‘knowledge synthesis’, is poorly supported by ‘theory’, has an ambiguous relation to biological evolution and uses key terms (e.g. ‘culture’, ‘social learning’, ‘cumulative culture’) in ways that hamper operationalization in models, experiments and field studies. Although numerous review papers in the field represent and categorize its empirical findings, the field's theoretical challenges receive less critical attention even though challenges of a theoretical or conceptual nature underlie most of the problems identified by Cultural Evolution Society members. Guided by the heterogeneous ‘grand challenges’ emergent in this survey, this paper restates those challenges and adopts an organizational style requisite to discussion of them. The paper's goal is to contribute to increasing conceptual clarity and theoretical discernment around the most pressing challenges facing the field of cultural evolutionary science. It will be of most interest to cultural evolutionary scientists, theoreticians, philosophers of science and interdisciplinary researchers.

The Final Neolithic and the Bronze Age (3000–800 BC) are periods of great transformations in the communities inhabiting the area of modern-day Belgium, as testified by archaeological evidence showing an increasing complexity in social structure, technological transformations, and large-scale contacts. By combining 599 available radiocarbon dates with 88 new 14C dates from 23 from funerary sites, this paper uses kernel density estimates to model the temporality in the use of inhumation vs. cremation burials, cremation deposits in barrows vs. flat graves, and cremation grave types. Additionally, by including 78 dates from settlements, changes in population dynamics were reconstructed. The results suggest a phase of demographic contraction around ca. 2200–1800 BC highlighted by a lack of dates from both settlements and funerary contexts, followed by an increase in the Middle Bronze Age, with the coexistence of cremation deposits in barrows and, in a lower number, in flat graves. At the end of the 14th–13th century BC, an episode of cultural change with the almost generalized use of flat graves over barrows is observed. Regional differentiations in the funerary practices and the simultaneous use of different grave types characterize the Late Bronze Age.

We prove a double commutant theorem for separable subalgebras of a wide class of corona C*-algebras, largely resolving a problem posed by Pedersen in 1988. Double commutant theorems originated with von Neumann, whose seminal result evolved into an entire field now called von Neumann algebra theory. Voiculescu later proved a C*-algebraic double commutant theorem for subalgebras of the Calkin algebra. We prove a similar result for subalgebras of a much more general class of so-called corona C*-algebras.

We demonstrate how exact structures can be placed on the additive category of right operator modules over an operator algebra in order to discuss global dimension for operator algebras. The properties of the Haagerup tensor product play a decisive role in this.

Spectral-broadening of the APOLLON PW-class laser pulses using a thin-film compression technique within the long-focal-area interaction chamber of the APOLLON laser facility is reported, demonstrating the delivery of the full energy pulse to the target interaction area. The laser pulse at 7 J passing through large aperture, thin glass wafers is spectrally broadened to a bandwidth that is compatible with a 15-fs pulse, indicating also the possibility to achieve sub-10-fs pulses using 14 J. Placing the post-compressor near the interaction makes for an economical method to produce the shortest pulses by limiting the need for high damage, broadband optics close to the final target rather than throughout the entire laser transport system.

Antarctica's ice shelves modulate the grounded ice flow, and weakening of ice shelves due to climate forcing will decrease their ‘buttressing’ effect, causing a response in the grounded ice. While the processes governing ice-shelf weakening are complex, uncertainties in the response of the grounded ice sheet are also difficult to assess. The Antarctic BUttressing Model Intercomparison Project (ABUMIP) compares ice-sheet model responses to decrease in buttressing by investigating the ‘end-member’ scenario of total and sustained loss of ice shelves. Although unrealistic, this scenario enables gauging the sensitivity of an ensemble of 15 ice-sheet models to a total loss of buttressing, hence exhibiting the full potential of marine ice-sheet instability. All models predict that this scenario leads to multi-metre (1–12 m) sea-level rise over 500 years from present day. West Antarctic ice sheet collapse alone leads to a 1.91–5.08 m sea-level rise due to the marine ice-sheet instability. Mass loss rates are a strong function of the sliding/friction law, with plastic laws cause a further destabilization of the Aurora and Wilkes Subglacial Basins, East Antarctica. Improvements to marine ice-sheet models have greatly reduced variability between modelled ice-sheet responses to extreme ice-shelf loss, e.g. compared to the SeaRISE assessments.

The adoption of a new funerary ritual with all its social and cognitive meanings is of great importance to understanding social transformations of past societies. The first known occurrence of cremation in the territory corresponding to modern Belgium dates back to the Mesolithic period. From the end of the Neolithic onward, the practice of cremation was characterized by periods in which this rite was predominant and periods of contractions, defined by a decrease in the use of this funerary ritual. This paper aims to quantify such phenomenon for the first time by modeling discontinuities in burial practices through kernel density analysis of 1428 radiocarbon (14C) dates from 311 archaeological sites located in Belgium from the Mesolithic to the Middle Ages. Despite possible taphonomic and sampling biases, the results highlight the existence of periods with a large uptake of cremation rite followed by periods of contractions; such discontinuities took place in correlation with changes in the socio-economical structure of local communities, as, for example, during the later Middle Bronze Age and at the end of the Roman Period.

Donald J. Trump won the 2016 US presidential election with fewer popular votes than Hillary R. Clinton. This is the fourth time this has happened, the others being 1876, 1888, and 2000. In earlier work, we analyzed these elections (and others) and showed how the electoral winner can often depend on the size of the US House of Representatives. This work was inspired by Neubauer and Zeitlin (2003, 721–5) in their paper, “Outcomes of Presidential Elections and the House Size.” A sufficiently larger House would have given electoral victories to the popular vote winner in both 1876 and 2000. An exception is the election of 1888. We show that Trump’s victory in 2016 is like Harrison’s in 1888 and unlike Hayes’s in 1876 and Bush’s in 2000. This article updates our previous work to include the 2016 election. It also draws attention to some of the anomalous behavior that can arise under the Electoral College.

Ten ice-sheet models are used to study sensitivity of the Greenland and Antarctic ice sheets to prescribed changes of surface mass balance, sub-ice-shelf melting and basal sliding. Results exhibit a large range in projected contributions to sea-level change. In most cases, the ice volume above flotation lost is linearly dependent on the strength of the forcing. Combinations of forcings can be closely approximated by linearly summing the contributions from single forcing experiments, suggesting that nonlinear feedbacks are modest. Our models indicate that Greenland is more sensitive than Antarctica to likely atmospheric changes in temperature and precipitation, while Antarctica is more sensitive to increased ice-shelf basal melting. An experiment approximating the Intergovernmental Panel on Climate Change’s RCP8.5 scenario produces additional first-century contributions to sea level of 22.3 and 8.1 cm from Greenland and Antarctica, respectively, with a range among models of 62 and 14 cm, respectively. By 200 years, projections increase to 53.2 and 26.7 cm, respectively, with ranges of 79 and 43 cm. Linear interpolation of the sensitivity results closely approximates these projections, revealing the relative contributions of the individual forcings on the combined volume change and suggesting that total ice-sheet response to complicated forcings over 200 years can be linearized.

Predictions of marine ice-sheet behaviour require models able to simulate grounding-line migration. We present results of an intercomparison experiment for plan-view marine ice-sheet models. Verification is effected by comparison with approximate analytical solutions for flux across the grounding line using simplified geometrical configurations (no lateral variations, no buttressing effects from lateral drag). Perturbation experiments specifying spatial variation in basal sliding parameters permitted the evolution of curved grounding lines, generating buttressing effects. The experiments showed regions of compression and extensional flow across the grounding line, thereby invalidating the boundary layer theory. Steady-state grounding-line positions were found to be dependent on the level of physical model approximation. Resolving grounding lines requires inclusion of membrane stresses, a sufficiently small grid size (<500 m), or subgrid interpolation of the grounding line. The latter still requires nominal grid sizes of <5 km. For larger grid spacings, appropriate parameterizations for ice flux may be imposed at the grounding line, but the short-time transient behaviour is then incorrect and different from models that do not incorporate grounding-line parameterizations. The numerical error associated with predicting grounding-line motion can be reduced significantly below the errors associated with parameter ignorance and uncertainties in future scenarios.

The objective of the Apollon 10 PW project is the generation of 10 PW peak power pulses of 15 fs at $1~\text{shot}~\text{min}^{-1}$. In this paper a brief update on the current status of the Apollon project is presented, followed by a more detailed presentation of our experimental and theoretical investigations of the temporal characteristics of the laser. More specifically the design considerations as well as the technological and physical limitations to achieve the intended pulse duration and contrast are discussed.

The etiology of Alzheimer disease (AD) remains unknown. The hypothesis of genetic factors playing a role in the causation of the disease, at least in its familial form, has been borne out by results showing linkage in several early-onset AD families to a locus on the proximal part of the long arm of chromosome 21. Linkage was not detected in several other families using the same markers. The metabolism of neurofilaments is perturbed in AD, as indicated by the presence of neurofilament epitopes in neurofibrillary tangles, as well as by the severe reduction of the expression of the gene for the light neurofilament subunit in AD brain. To detect a possible anomaly that might relate to the disease, we have searched for an association between the genes for the light subunit and the heavy subunit of the neurofilament triplet, and AD. Genotypes for restriction fragment length polymorphisms (RFLP) at each of the two loci were determined for an AD group and a control group. Allelic frequencies at a Taql-defined RFLP for the gene for the light neurofilament subunit were 0.70 for the 3.7 kb allele and 0.30 for the 2.9 kb allele. Hindi detected an RFLP for the heavy neurofilament subunit gene with frequencies of 0.31 for the 18.0 kb allele and 0.69 for the 6.8 kb allele. Frequencies were found to be similar in the two groups for both light and heavy neurofilament subunit loci. Although it cannot be excluded that mutations at other sites of the neurofilament genes are relevant to AD, the data reported here do not support an association between these genes and the disease.

The objective of the Apollon project is the generation of 10 PW peak power pulses of 15 fs at 1 shot/minute. In this paper the Apollon facility design, the technological challenges and the current progress of the project will be presented.