The Middle Mississippian component at Aztalan was a mixed, Late Woodland / Mississippian occupation sited within a heavily fortified habitation and mound center that is located on a tributary of the Rock River in Wisconsin. It represents the northernmost large Cahokian-related village recorded. The Oneota Lake Koshkonong Locality of the Rock River drainage is located approximately 20 km south of Aztalan, and it consists of a 25 km2 area along the northwest shore with a small cluster of habitation settlements. Sixty-eight radiocarbon measurements have been obtained from Aztalan, and 52 from Oneota settlements in the Lake Koshkonong Locality. We discuss how to best interpret this dataset, and we use Bayesian chronological modeling to analyze these dates. The results suggest that (1) Aztalan's Late Woodland (Kekoskee phase) occupation began in the AD 900s or early AD 1000s, (2) Aztalan's Mississippian occupation ceased in the AD 1200s, (3) Oneota occupations at Lake Koshkonong began after AD 1050 and were established by the AD 1200s, and (4) Oneota occupations at Lake Koshkonong continued after Aztalan's Mississippian abandonment until at least the late AD 1300s. Additionally, the results demonstrate that Aztalan was fortified with a palisade with bastions for much of the Mississippian occupation, suggesting a contested presence in a multiethnic landscape.

Laser–plasma interaction (LPI) at intensities $10^{15}{-}10^{16}~\text{W}\cdot \text{cm}^{-2}$ is dominated by parametric instabilities which can be responsible for a significant amount of non-collisional absorption and generate large fluxes of high-energy nonthermal electrons. Such a regime is of paramount importance for inertial confinement fusion (ICF) and in particular for the shock ignition scheme. In this paper we report on an experiment carried out at the Prague Asterix Laser System (PALS) facility to investigate the extent and time history of stimulated Raman scattering (SRS) and two-plasmon decay (TPD) instabilities, driven by the interaction of an infrared laser pulse at an intensity ${\sim}1.2\times 10^{16}~\text{W}\cdot \text{cm}^{-2}$ with a ${\sim}100~\unicode[STIX]{x03BC}\text{m}$ scalelength plasma produced from irradiation of a flat plastic target. The laser pulse duration (300 ps) and the high value of plasma temperature (${\sim}4~\text{keV}$) expected from hydrodynamic simulations make these results interesting for a deeper understanding of LPI in shock ignition conditions. Experimental results show that absolute TPD/SRS, driven at a quarter of the critical density, and convective SRS, driven at lower plasma densities, are well separated in time, with absolute instabilities driven at early times of interaction and convective backward SRS emerging at the laser peak and persisting all over the tail of the pulse. Side-scattering SRS, driven at low plasma densities, is also clearly observed. Experimental results are compared to fully kinetic large-scale, two-dimensional simulations. Particle-in-cell results, beyond reproducing the framework delineated by the experimental measurements, reveal the importance of filamentation instability in ruling the onset of SRS and stimulated Brillouin scattering instabilities and confirm the crucial role of collisionless absorption in the LPI energy balance.

Geophysical survey and excavations from 2010–2016 at Lawrenz Gun Club (11CS4), a late pre-Columbian village located in the central Illinois River valley in Illinois, identified 10 mounds, a central plaza, and dozens of structures enclosed within a stout 10 hectare bastioned palisade. Nineteen radiocarbon (14C) measurements were taken from single entities of wood charcoal, short-lived plants, and animal bones. A site chronology has been constructed using a Bayesian approach that considers the stratigraphic contexts and feature formation processes. The village was host to hundreds of years of continuous human activity during the Mississippi Period. Mississippian activity at the site is estimated to have begun in cal AD 990–1165 (95% probability), ended in cal AD 1295–1450 (95% probability), and lasted 150–420 yr (95% probability) in the primary Bayesian model with similar results obtained in two alternative models. The palisade is estimated to have been constructed in cal AD 1150–1230 (95% probability) and was continuously repaired and rebuilt for 15–125 yr (95% probability), probably for 40–85 yr (68% probability). Comparison to other studies demonstrates that the bastioned palisade at Lawrenz was one of the earliest constructed in the midcontinental United States.

This study provides an assessment of the temporal changes in ΔR, which is the local deviation from the global surface water marine reservoir effect (MRE), in the Point Barrow area of the Alaskan Arctic, a coastal archaeological area that has experienced severe erosion accelerated by global warming. A total of 26 samples were submitted for radiocarbon (14C) dating from eight secure Thule (AD 1000–1750) archaeological contexts, and specifically from archaeological features with paired processed seal and caribou bones that had been frozen in situ. This new approach towards ΔR estimation provides a best-fit local correction for the 14C dating of human populations by focusing on the marine mammal (seals) predominantly consumed by the Thule (Coltrain et al. 2016). The weighted-mean ΔR value on these pairs is 450 ± 84 yr, which is about 50 years less than the weighted-mean (506 ± 69 yr) for the Point Barrow area calculated through 14C measurements from four known-age bivalves collected in AD 1913 (McNeely et al. 2006). The effects of using this new ΔR value for calibration was assessed through the Bayesian chronological modeling of 54 14C measurements from samples of human skeletons interred in the Nuvuk cemetery at Point Barrow, the largest ancient cemetery in northwest Alaska and traditionally thought to date to the Thule and earlier Birnirk (AD 500–1000) periods.

This paper provides a summary of recent research connected with the shock ignition (SI) concept of the inertial confinement fusion which was carried out at PALS. In the experiments, Cu planar targets coated with a thin CH layer were used. Two-beam irradiation experiment was applied to investigate the effect of preliminary produced plasma to shock-wave generation. The 1ω or 3ω main beam with a high intensity >1015 W/cm2 generates shock wave, while the other 1ω beam with the intensity below 1014 W/cm2 creates CH pre-plasma simulating the pre-compressed plasma related to SI. Influence of laser wavelength on absorbed energy transfer to shock wave was studied by means of femtosecond interferometry and measuring the crater volume. To characterize the hot electron and ion emission, two-dimensional (2D) Kα-imaging of Cu plasma and grid collector measurements were used. In single 1ω beam experiments energy transport by fast electrons produced by resonant absorption made a significant contribution to shock-wave pressure. However, two-beam experiments with 1ω main beam show that the pre-plasma is strongly degrading the scalelength which leads to decreasing the fast electron energy contribution to shock pressure. In both the single 3ω beam experiments and the two-beam experiments with the 3ω main beam, do not show any clear influence of fast electron transport on shock-wave pressure. The non-monotonic behavior of the scalelength at changing the laser beam focal radius in both presence and absence of pre-plasma reflects the competition of plasma motion and electron heat conduction under the conditions of one-dimensional and 2D plasma expansion at large and small focal radii, respectively.

The originally published version of this article (Hamilton and Krus, 2017) listed the incorrect article type. The correct article type for this article is “Forum.”

Bayesian chronological modeling is used to investigate the chronology for a large-scale human depopulation event during the Mississippian period (AD 1000–1600) known as the Vacant Quarter phenomenon. The Middle Cumberland region (MCR) of Tennessee is within the Vacant Quarter area, and six villages from the final phase of Mississippian activity in the MCR have been subjected to radiocarbon dating. Complete radiocarbon datasets from these sites are presented within an interpretative Bayesian statistical framework. The results provide a unique history of each settlement and demonstrate that Mississippian occupations at each site likely terminated in the mid- to late fifteenth and possibly early sixteenth centuries AD, which is 50 to 100 years later than the most recent estimate for the timing of the Vacant Quarter. Mississippian abandonment in the MCR was relatively quick, likely occurring over less than a century. The exact reasons for abandonment are not entirely clear but appear to be linked to climate change. A radiocarbon simulation experiment indicates that future robust radiocarbon dating with well-selected samples could greatly improve the chronological precision for this late Mississippian activity. More broadly, this example demonstrates that model building with radiocarbon simulations can be used to address regional-scale chronological issues within the American Southeast and beyond.

We review the history of Bayesian chronological modeling in archaeology and demonstrate that there has been a surge over the past several years in American archaeological applications. Most of these applications have been performed by archaeologists who are self-taught in this method because formal training opportunities in Bayesian chronological modeling are infrequently provided. We define and address misconceptions about Bayesian chronological modeling that we have encountered in conversations with colleagues and in anonymous reviews, some of which have been expressed in the published literature. Objectivity and scientific rigor is inherent in the Bayesian chronological modeling process. Each stage of this process is described in detail, and we present examples of this process in practice. Our concluding discussion focuses on the potential that Bayesian chronological modeling has for enhancing understandings of important topics.

Excavations from 2009–2010 in Armadale, Isle of Skye, Scotland, encountered a burial site with seven cists, pits containing cremation burials, a kerbed cairn, and a small stone and post circle. Twenty-one radiocarbon measurements were taken from single entities of wood charcoal, carbonized residue on pottery, and cremated human bone. A site chronology has been constructed using a Bayesian approach that considers the stratigraphic contexts and feature formation processes. The site was host to thousands of years of discontinuous human activity beginning with little understood Mesolithic and Neolithic components. Modeling estimates that mortuary activity at the site began in the Early Bronze Age in 2220–1985 cal BC (95% probability) and to have ended in 1880–1660 cal BC (95% probability). The span of activity during this burial component is estimated to be 140–520 yr (95% probability) in the primary Bayesian model and 50–470 yr (95% probability) in an alternative model. These modeling results demonstrate that human burial at Armadale was an infrequent event and further suggest that the memory of the location and social role of Armadale as a burial ground persisted throughout much of the Early Bronze Age.

Bayesian chronological modeling is used to investigate the chronology of bastioned palisades during the precolumbian period in the Midwestern and Southeastern United States. Nine precolumbian settlements in the Midwest and Southeast with bastioned palisades have been subject to scientific dating (Angel Mounds, Annis Village, Aztalan, Cahokia Mounds, Etowah, Kincaid Mounds, Jonathan Creek, Moundville, and Southwind). Complete radiocarbon datasets from these sites are presented within an interpretative Bayesian statistical framework. The results provide a glimpse into the history of Mississippi period (A.D. 1000–1700) fortifications with bastions and indicate that the analyzed fortifications were built and maintained predominantly in A.D. 1200–1400. This finding suggests a greater institutionalized role for defense and warfare in post-A.D. 1200 Mississippian societies. Additionally, modeling results further indicate that the investigated Mississippian centers continued to maintain fortifications for generations after their construction.

Radiocarbon results from houses, pits, and burials at the SunWatch site, Dayton, Ohio, are presented within an interpretative Bayesian statistical framework. The primary model incorporates dates from archaeological features in an unordered phase and uses charcoal outlier modeling (Bronk Ramsey 2009b) to account for issues of wood charcoal 14C dates predating their context. The results of the primary model estimate occupation lasted for 1–245 yr (95% probability), starting in cal AD 1175–1385 (95% probability) and ending in cal AD 1330–1470 (95% probability). An alternative model was created by placing the 14C dates into two unordered phases corresponding with horizontal stratigraphic relationships or distinct groups of artifacts thought to be temporally diagnostic. The results of the alternative model further suggest that there is some temporal separation between Group 1 and Group 2, which seems more likely in the event of a multicomponent occupation. Overall, the modeling results provide chronology estimates for SunWatch that are more accurate and precise than that provided in earlier studies. While it is difficult to determine with certainty if SunWatch had a single-component or multicomponent occupation, it is clear that SunWatch's occupation lasted until the second half of the AD 1300s.

Strongly radiative shocks are characterized by an ionization front induced by the shock wave. The role played together by opacity and geometry is critical for the physics of these shock waves. Moreover, radiation is an obvious way of probing these shock waves, either by self-emission or by probe absorption. These aspects will be illustrated by recent experimental results obtained at the iodine PALS (Prague Asterix Laser System) facility.