This study examined cannabis use motives in individuals with anxiety disorders and compared motives between infrequent and frequent cannabis users. It was hypothesised that coping motives would be endorsed at a significantly higher rate than other motives, and that frequent cannabis users would endorse coping motives significantly more than infrequent users. Participants were 144 adults seeking clinical services for anxiety disorders who reported using cannabis. Cannabis use was categorized by infrequent (n = 54) and frequent (n = 90) use. Anxiety symptoms were assessed and deemed clinically significant. Participants completed measures of cannabis use motives, cannabis use patterns, and cannabis use disorder symptoms, cross-sectionally. Cannabis use motives were examined for the entire sample and compared between frequent and infrequent users. In general, cannabis users endorsed coping (i.e., use for managing distress) and enhancement (i.e., use for fun, pleasant feeling, or the high) motives at equal rates (p = .265) and more than other motives (p < .001). Frequent users reported using cannabis for coping and expansion motives (i.e., use to change one's thinking) significantly more than infrequent users. These results indicate that individuals with anxiety disorders use cannabis for various reasons, some of which may not be directly related to their mental health symptoms. Future research is needed to compare motives for cannabis use in those with anxiety disorders, other mental health populations, and the general population, as well as examine motives for cannabis use within specific anxiety disorders.

Experiments are performed in a Mach-6 shock tunnel to examine the laminar-to-turbulent transition process associated with a sudden increase in surface angle on a slender body. A cone/flare geometry with a 5$^\circ$ frustum and compression angles ranging from 5$^\circ$ to 15$^\circ$ allow a range of mean flow configurations, spanning an attached shock-wave/boundary-layer interaction to a fully separated one; the unit Reynolds number of the flow is also varied to modify the state of incoming second-mode boundary-layer disturbances. Ultra-high-speed schlieren visualizations provide a global picture of the flow development, supplemented by high-frequency surface pressure measurements. For the 5$^\circ$ compression, the unsteady flow field is dominated by the second-mode waves, whose breakdown to turbulence is generally accelerated (compared with the straight-cone configuration) by encountering the angle change. As the compression angle is increased to induce separation, lower-frequency disturbances appear along the separated shear layer that exhibit much larger amplification rates than the incoming second-mode waves; the latter effectively freeze in amplitude downstream of the separation point before rapidly breaking down upon reattachment. The shear-layer disturbances become dominant at the largest compression angle tested. Radiation of disturbance energy to the external flow is consistently observed: this generally occurs along mean flow features (flare, separation or reattachment shocks) for the second-mode disturbances and spontaneously for the shear-layer waves. The combined application of spectral proper orthogonal decomposition and a global bispectral analysis allows the identification of important unsteady flow structures and the association of these with prominent nonlinear interactions in the various configurations.

MeerTime is a five-year Large Survey Project to time pulsars with MeerKAT, the 64-dish South African precursor to the Square Kilometre Array. The science goals for the programme include timing millisecond pulsar (MSPs) to high precision ( ${<} 1 \unicode{x03BC} \mathrm{s}$ ) to study the Galactic MSP population and to contribute to global efforts to detect nanohertz gravitational waves with the International Pulsar Timing Array (IPTA). In order to plan for the remainder of the programme and to use the allocated time most efficiently, we have conducted an initial census with the MeerKAT ‘L-band’ receiver of 189 MSPs visible to MeerKAT and here present their dispersion measures, polarisation profiles, polarisation fractions, rotation measures, flux density measurements, spectral indices, and timing potential. As all of these observations are taken with the same instrument (which uses coherent dedispersion, interferometric polarisation calibration techniques, and a uniform flux scale), they present an excellent resource for population studies. We used wideband pulse portraits as timing standards for each MSP and demonstrated that the MeerTime Pulsar Timing Array (MPTA) can already contribute significantly to the IPTA as it currently achieves better than $1\,\unicode{x03BC}\mathrm{s}$ timing accuracy on 89 MSPs (observed with fortnightly cadence). By the conclusion of the initial five-year MeerTime programme in 2024 July, the MPTA will be extremely significant in global efforts to detect the gravitational wave background with a contribution to the detection statistic comparable to other long-standing timing programmes.

This article documents the transition from the Late Classic to Postclassic periods at Río Amarillo, a hinterland outpost of the Copan polity, and at an associated residential group, Site 5, in the Río Amarillo East Pocket of the Copan Valley. Late Classic period evidence indicates that the site of Río Amarillo operated as an administrative center for the Copan polity with the likely objective of increased agricultural production for the burgeoning population in the Copan Pocket. In the Terminal Classic period, Río Amarillo shared the fate of Copan, with evidence indicating it was burned and sacked. However, unlike the Copan Pocket, many residential groups remained occupied during the Early Postclassic. Here we focus on Site 5. An unbroken occupation from the Late Classic through to the end of the Early Postclassic period, as this site provides a window into an existence without the requirements of tribute given to their western neighbor. We hypothesize that the smaller settlement size and higher amount of rainfall in this valley pocket, as well as a richer and more diversified environment, were important factors in the survival of some of its population.

Wetland sediments are valuable archives of environmental change but can be challenging to date. Terrestrial macrofossils are often sparse, resulting in radiocarbon (14C) dating of less desirable organic fractions. An alternative approach for capturing changes in atmospheric 14C is the use of terrestrial microfossils. We 14C date pollen microfossils from two Australian wetland sediment sequences and compare these to ages from other sediment fractions (n = 56). For the Holocene Lake Werri Berri record, pollen 14C ages are consistent with 14C ages on bulk sediment and humic acids (n = 14), whilst Stable Polycyclic Aromatic Carbon (SPAC) 14C ages (n = 4) are significantly younger. For Welsby Lagoon, pollen concentrate 14C ages (n = 21) provide a stratigraphically coherent sequence back to 50 ka BP. 14C ages from humic acid and >100 µm fractions (n = 13) are inconsistent, and often substantially younger than pollen ages. Our comparison of Bayesian age-depth models, developed in Oxcal, Bacon and Undatable, highlight the strengths and weaknesses of the different programs for straightforward and more complex chrono-stratigraphic records. All models display broad similarities but differences in modeled age-uncertainty, particularly when age constraints are sparse. Intensive dating of wetland sequences improves the identification of outliers and generation of robust age models, regardless of program used.

Cross-species evidence suggests that the ability to exert control over a stressor is a key dimension of stress exposure that may sensitize frontostriatal-amygdala circuitry to promote more adaptive responses to subsequent stressors. The present study examined neural correlates of stressor controllability in young adults. Participants (N = 56; M age = 23.74, range = 18–30 years) completed either the controllable or uncontrollable stress condition of the first of two novel stressor controllability tasks during functional magnetic resonance imaging (fMRI) acquisition. Participants in the uncontrollable stress condition were yoked to age- and sex-matched participants in the controllable stress condition. All participants were subsequently exposed to uncontrollable stress in the second task, which is the focus of fMRI analyses reported here. A whole-brain searchlight classification analysis revealed that patterns of activity in the right dorsal anterior insula (dAI) during subsequent exposure to uncontrollable stress could be used to classify participants' initial exposure to either controllable or uncontrollable stress with a peak of 73% accuracy. Previous experience of exerting control over a stressor may change the computations performed within the right dAI during subsequent stress exposure, shedding further light on the neural underpinnings of stressor controllability.

An experimental campaign was conducted to examine the impact of an abrupt change in surface geometry on hypersonic boundary-layer instability waves. The primary test configuration consisted of a $5^{\circ }$ half-angle, nominally sharp cone with a $15^{\circ }$ half-angle flare attachment. Tests were conducted at Mach 6 with the unit Reynolds number varying from $3.0\times 10^6$ to $4.9\times 10^6\ \textrm {m}^{-1}$. The $10^{\circ }$ compression was sufficient to create a small separation region at the cone–flare junction at these conditions. Ultra-high-speed schlieren (822 kHz) revealed the propagation of second-mode disturbances with frequencies between 200 and 300 kHz within the upstream boundary layer; when these reached the separation region, radiation of disturbance energy along the separation shock was observed. Tests conducted at low unit Reynolds numbers demonstrated inhibited instability growth (compared to the straight-cone case) through the separation region and the development of low-frequency (${\sim }75\ \textrm {kHz}$) instabilities within the separated shear layer. At higher Reynolds numbers, however, the corner interaction was found to cause rapid breakdown near reattachment, leading to earlier transition than for a straight cone. Analysis of the schlieren images using spectral proper orthogonal decomposition provided a global picture of the structure and development of the second-mode and shear-generated instabilities.

Debate about the nature of climate and the magnitude of ecological change across Australia during the last glacial maximum (LGM; 26.5–19 ka) persists despite considerable research into the late Pleistocene. This is partly due to a lack of detailed paleoenvironmental records and reliable chronological frameworks. Geochemical and geochronological analyses of a 60 ka sedimentary record from Brown Lake, subtropical Queensland, are presented and considered in the context of climate-controlled environmental change. Optically stimulated luminescence dating of dune crests adjacent to prominent wetlands across North Stradbroke Island (Minjerribah) returned a mean age of 119.9 ± 10.6 ka; indicating relative dune stability soon after formation in Marine Isotope Stage 5. Synthesis of wetland sediment geochemistry across the island was used to identify dust accumulation and applied as an aridification proxy over the last glacial-interglacial cycle. A positive trend of dust deposition from ca. 50 ka was found with highest influx occurring leading into the LGM. Complexities of comparing sedimentary records and the need for robust age models are highlighted with local variation influencing the accumulation of exogenic material. An inter-site comparison suggests enhanced moisture stress regionally during the last glaciation and throughout the LGM, returning to a more positive moisture balance ca. 8 ka.