In this study, the transport equation for scalar iso-surface area density ($\varSigma$) in a turbulent, temporally developing mixing layer is examined. Exploring the spatial and temporal evolution of the terms in the $\varSigma$ transport equation is vital to improving our understanding of turbulent flows characterized by distinct interfaces, e.g. the flame surface or the turbulent/non-turbulent interface. Previous work reported by the authors identified that $\varSigma$ exhibits self-similar behaviour consistent with the development of the temporal mixing layer (Blakeley et al., J. Fluid Mech., vol. 951, 2022, A44). Accordingly, each of the terms in the $\varSigma$ transport equation is found to behave in a self-similar manner, though there are notable differences in the self-similar behaviours for each term. Based on the results presented herein, it is suggested that the rate of change of $\varSigma$ ($\partial \varSigma /\partial t$) and the advection term scale with $h\lambda _\varPhi /\Delta U$, where $h$ is the width of the mixing layer, $\lambda _\varPhi$ is the scalar Taylor length scale and $\Delta U$ is the velocity difference. The production and destruction terms are found to scale with an additional factor $({Re}\,Sc)^{1/2}$. In contrast, the molecular diffusion term is found to scale with a factor $({Re}\,Sc)^{-1/2}$ compared to $\partial \varSigma /\partial t$. Importantly, it is found that the difference between the production and destruction terms, or net surface ‘stretch’, scales with the same factor as $\partial \varSigma /\partial t$ and the advection term, which may have a significant impact on how the evolution of $\varSigma$ is understood and modelled in turbulent flows.

Lithic technologies dominate understanding of early humans, yet natural processes can fracture rock in ways that resemble artefacts made by Homo sapiens and other primates. Differentiating between fractures made by natural processes and primates is important for assessing the validity of early and controversial archaeological sites. Rather than depend on expert authority or intuition, the authors propose a null model of conchoidally fractured Antarctic rocks. As no primates have ever occupied the continent, Antarctica offers a laboratory for generating samples that could only have been naturally fractured. Examples that resemble artefacts produced by primates illustrate the potential of ‘archaeological’ research in Antarctica for the evaluation of hominin sites worldwide.

A principal topic of interest and importance in stably stratified flows is how turbulence irreversibly mixes the ambient density field. Because the density field is coupled dynamically to the velocity field through the stable stratification, this mixing affects the overall flow dynamics, and its accurate parameterisation has become a ‘grand challenge’ in environmental fluid mechanics (Dauxois et al., Phys. Rev. Fluids, vol. 6, issue 2, 2021, 020501). In order to better understand the detailed kinematics of mixing in a stably stratified fluid, Jiang et al. (2022) perform experiments using a unique laboratory facility, capable of generating controllable stratified shear flows, and providing almost instantaneous density and three-component velocity measurements on a high-resolution, three-dimensional grid. Using three-dimensional data sets from the experiments, they employ the rortex–shear decomposition to identify the morphology of instantaneous rortices in the flow fields, leading to the interpretation of the motion of the rortices and ultimately to how the rortices cause irreversible mixing of the density field. This marks one of the first studies where, in a laboratory setting, full use has been made of somewhat high-resolution, three-dimensional near-instantaneous measurements; it demonstrates what can be accomplished in the laboratory, setting a new standard for future experiments.

Understanding the behaviour of scalar isosurfaces in a turbulent flow is of particular interest for many problems in turbulent mixing that contain sharp interfaces between regions of the flow. Common examples include combustion, where the chemical reactions occur in thin regions within the flow, and the turbulent/non-turbulent interface in shear flows, where a thin region separates the rotational, turbulent motions from the irrotational, non-turbulent background. Recent advances in computing technology allow for in-depth analysis of these interface problems that are difficult to quantify in a laboratory setting. In this paper, the results of a direct numerical simulation of a passive scalar $\varPhi$ evolving on a turbulent, temporally developing mixing layer are described. A novel approach has been taken to calculate the surface area of individual scalar isosurfaces, $A_{iso}$, throughout the simulation, as well as the mean isosurface area density, $\varSigma$, as a function of the cross-stream direction and time. A notable finding is that the profiles of $\varSigma$ develop in a self-similar manner when scaled by the Taylor scale of the scalar field, $\lambda _\phi$. Remarkably, the scaling appears to hold for a wide range of isovalues. A rough scaling argument based on the formal definition of $\varSigma$ and properties of a temporal mixing layer is presented which also exposes a dependence on $\lambda _\phi$. Based on these results, a possible scaling for the isosurface area is presented as $A_{iso}/A_0 \sim (Re \, Sc)^{1/2}$, where $Re$ and $Sc$ are local Reynolds and Schmidt numbers, respectively.

We introduce a new holdings-based procedure to identify whether a mutual fund has a benchmark discrepancy, which we define as a benchmark other than the prospectus benchmark best matching a fund’s investment strategy. We find that funds with a benchmark discrepancy tend to be riskier than their prospectus benchmarks indicate. As a result, the funds on average outperform their prospectus benchmarks, before further risk adjustments, despite underperforming the benchmarks that best match their portfolios.

In-situ transmission electron microscopy (TEM) provides an avenue to explore time-dependent nanoscale material changes induced by a wide range of environmental conditions that govern material performance and degradation. The In-situ Ion Irradiation TEM (I3TEM) at Sandia National Laboratories is a JEOL 2100 microscope that has been highly modified with an array of hardware and software that makes it particularly well suited to explore fundamental mechanisms that arise from coupled extreme conditions. Examples pertaining to multibeam ion irradiation, rapid thermal cycling, and nanomechanical testing on the I3TEM are highlighted, along with prospective advancements in the field of in-situ microscopy.

Gravitational waves from coalescing neutron stars encode information about nuclear matter at extreme densities, inaccessible by laboratory experiments. The late inspiral is influenced by the presence of tides, which depend on the neutron star equation of state. Neutron star mergers are expected to often produce rapidly rotating remnant neutron stars that emit gravitational waves. These will provide clues to the extremely hot post-merger environment. This signature of nuclear matter in gravitational waves contains most information in the 2–4 kHz frequency band, which is outside of the most sensitive band of current detectors. We present the design concept and science case for a Neutron Star Extreme Matter Observatory (NEMO): a gravitational-wave interferometer optimised to study nuclear physics with merging neutron stars. The concept uses high-circulating laser power, quantum squeezing, and a detector topology specifically designed to achieve the high-frequency sensitivity necessary to probe nuclear matter using gravitational waves. Above 1 kHz, the proposed strain sensitivity is comparable to full third-generation detectors at a fraction of the cost. Such sensitivity changes expected event rates for detection of post-merger remnants from approximately one per few decades with two A+ detectors to a few per year and potentially allow for the first gravitational-wave observations of supernovae, isolated neutron stars, and other exotica.

Fig. 1

[Improvement in daily accessible risk assessments]

We show enhanced patient safety through a quality improvement methodology project in an intensive psychiatric care unit of a psychiatric hospital in southwest of Scotland. This is a project as part of the national patient safety programme in mental health. The Scottish Patient Safety Programme for Mental Health aims to systematically reduce harm experienced by people using mental health services in Scotland, by supporting frontline staff to test, gather real-time data and reliably implement interventions, before spreading across their catchment area.

Multidisciplinary staff worked together in improving recording of daily electronic and paper based risk assessments from a baseline of 20% to nearly 100% over a sixth month period. We expect better quality risk management by readily accessible risk assessments and safe practise through enhanced safety perception by the patients as well as staff. Patient and staff safety perception tools were designed to measure impact of improvement in risk management. We have seen drop in the number of critical incidents and challenging situations requiring restraint following coordinated approach to risk assessment and easy access to key information. We have been successful as the frontline staff became part of the process of change and this has enabled sustained improvement.

Turbulent structures in stably stratified shear layers are studied with direct numerical simulation. Flow visualization confirms the existence of hairpin vortices and highly elongated structures with positive and negative velocity fluctuations, whose streamwise lengths divided by the layer thickness are $O(10^{0})$ and $O(10^{1})$, respectively. The flow at the wavelength related to these structures makes a large contribution to turbulent kinetic energy. These structures become prominent in late time, but with small buoyancy Reynolds numbers indicating suppression of turbulent mixing. Active turbulent mixing associated with the hairpin vortices, however, does occur. The structures and the vertical profile of the integral shear parameter show connections between stable stratified shear layers and wall-bounded shear flows.

A 2018 workshop on the White Mountain Apache Tribe lands in Arizona examined ways to enhance investigations into cultural property crime (CPC) through applications of rapidly evolving methods from archaeological science. CPC (also looting, graverobbing) refers to unauthorized damage, removal, or trafficking in materials possessing blends of communal, aesthetic, and scientific values. The Fort Apache workshop integrated four generally partitioned domains of CPC expertise: (1) theories of perpetrators’ motivations and methods; (2) recommended practice in sustaining public and community opposition to CPC; (3) tactics and strategies for documenting, investigating, and prosecuting CPC; and (4) forensic sedimentology—uses of biophysical sciences to link sediments from implicated persons and objects to crime scenes. Forensic sedimentology served as the touchstone for dialogues among experts in criminology, archaeological sciences, law enforcement, and heritage stewardship. Field visits to CPC crime scenes and workshop deliberations identified pathways toward integrating CPC theory and practice with forensic sedimentology’s potent battery of analytic methods.

Introduction: Improving public access and training for epinephrine auto-injectors (EAIs) can reduce time to initial treatment in anaphylaxis. Effective use of EAIs by the public requires bystanders to respond in a timely and proficient manner. We wished to examine optimal methods for assessing effective training and skill retention for public use of EAIs, including the use of microskills lists. Methods: In this prospective, stratified randomized study, 154 participants at 15 sites receiving installation of public EAIs were randomized to one of three experimental education interventions: A) didactic poster (POS) teaching; B) poster with video teaching (VID), and C) Poster, video, and simulation training (SIM). Participants were tested by participation in a standardized simulated anaphylaxis scenario at 0-months, immediately following training, and again at follow-up at 3 months. Participants’ responses were videoed and assessed by two blinded raters using microksills checklists. The microskills lists were derived from the best available evidence and interprofessional process mapping using a skills trainer. The interobserver reliability was assessed for each item in a 14 step microskill checklist composed of 3-point and 5-point Likert scale questions around EpiPen use, expressed as Kappa Values. Results: Overall there was poor agreement between the two raters. Being composed or panicked had the highest level of agreement K = 0.7, but a result that did not reach statistical significance (substantial agreement, p = 0.06) calling for EMS support has the second highest level of agreement, K = 0.6 (moderate agreement, p = 0.01), the remainder of the items had very low to moderate agreement with a Kappa value range of -103 to 0.48. Conclusion: Although microskills chesklists have been shown to identify areas where learners and interprofessional teams require deliberate practice, these results support previously published evidence that the use of microskills checklists to assess skills has poor reproducibility. Performance will be further assessed in this study using global rating scales, which have shown higher levels of agreement in other studies.

Implementation of a novel experimental approach using a bright source of narrowband x-ray emission has enabled the production of a photoionized argon plasma of relevance to astrophysical modelling codes such as Cloudy. We present results showing that the photoionization parameter ζ = 4πF/ne generated using the VULCAN laser was ≈ 50 erg cm s−1, higher than those obtained previously with more powerful facilities. Comparison of our argon emission-line spectra in the 4.15 - 4.25 Å range at varying initial gas pressures with predictions from the Cloudy code and a simple time-dependent code are also presented. Finally we briefly discuss how this proof-of-principle experiment may be scaled to larger facilities such as ORION to produce the closest laboratory analogue to a photoionized plasma.

Nuclear wastes generated from reprocessing of used nuclear fuel tend to contain a large fraction of rare earth (RE, e.g., Nd3+), transition (TM, e.g., Mo6+, Zr4+), alkali (A, e.g., Cs+), and alkaline earth cations (AE, e.g., Ba2+, Sr2+). Various strategies have been considered for immobilizing such waste streams, varying from nominally crystal-free glass to glass-ceramic to multi-phase ceramic waste forms. For glass and glass-ceramic waste forms, the added glass-forming system is generally alkali-alkaline earth-aluminoborosilicate (i.e., Na-Ca-Al-B-Si oxide). In a US-UK collaborative project, summarized here, we investigated the glass structure and crystallization dependence on compositional changes in simulated nuclear waste glasses and glass-ceramics. Compositions ranged in complexity from five – to – eight oxides. Specifically, the roles of Mo and rare earths are investigated, since a proposed glass-ceramic waste form contains crystalline phases such as powellite [(AE,A,RE)MoO4] and oxyapatite [(RE,AE,A)10Si6O26], and the precipitation of molybdenum phases is known to be affected by the rare earth concentration in the glass. Additionally, the effects of other chemical additions have been systematically investigated, including Zr, Ru, P, and Ti. A series of studies were also undertaken to ascertain the effect of the RE size on glass structure and on partitioning to crystal phases, investigating similarities and differences in glasses containing single RE oxides of Sc, Y, La, Ce, Nd, Sm, Er, Yb, or Lu. Finally, the effect of charge compensation was investigated by considering not only the commonly assessed peralkaline glass but also metaluminous and peraluminous compositions. Glass structure and crystallization studies were conducted by spectroscopic methods (i.e., Raman, X-ray absorption, nuclear magnetic resonance (NMR), optical absorption, photoluminescence, photoluminescence excitation, X-ray photoelectron spectroscopy), microscopy (i.e., scanning electron microscopy, transmission electron microscopy, electron probe microanalysis), scattering (i.e., X-ray and neutron diffraction, small angle measurements), and physical characterization (i.e., differential thermal analysis, liquidus, viscosity, density). This paper will give an overview of the research program and some example unpublished results on glass-ceramic crystallization kinetics, microstructure, and Raman spectra, as well as some examples of the effects of rare earths on the absorption, luminescence, and NMR spectra of starting glasses. The formal collaboration described here has resulted in the generation of a large number of results, some of which are still in the process of being published as separate studies.

We report on direct numerical simulations of the decay of initially isotropic, homogeneous turbulence subject to the application of stable density stratification. Flows were simulated for three different initial Reynolds numbers, but for the same initial Froude number. We find that the flows pass through three different dynamical regimes as they decay, depending on the local values of the Froude number and activity parameter. These regimes are analogous to those seen in the experimental study of Spedding (J. Fluid Mech., vol. 337, 1997, pp. 283–301) for the wake of a sphere. The flows initially decay with little influence of stratification, up to approximately one buoyancy period, when the local Froude number has dropped below 1. At this point the flows have adjusted to the density stratification, and, if the activity parameter is large enough, begin to decay at a slower rate and spread horizontally at a faster rate, consistent with the predictions of Davidson (J. Fluid Mech., vol. 663, 2010, pp. 268–292) and the scaling arguments of Billant & Chomaz (Phys. Fluids, vol. 13, 2001, pp. 1645–1651). We refer to this second regime as the stratified turbulence regime. As the flows continue to decay, ultimately the activity parameter drops below approximately 1 as viscous effects begin to dominate. In this regime, the flows have become quasi-horizontal, and approximately obey the scaling arguments of Godoy-Diana et al. (J. Fluid Mech., vol. 504, 2004, pp. 229–238).

Within the NHS health check (NHSHC) programme, there is evidence of marked inconsistencies and challenges in practice-level self-reporting of uptake. Consequently, we explored the perceptions of those involved in commissioning of NHSHC to better understand the implications for local and national monitoring and evaluation of programme uptake. Semi-structured, one-to-one, telephone interviews (n=15) were conducted with NHSHC commissioners and leads, and were analysed using inductive thematic analysis. NHSHC data were often collected from practices using online extraction systems but many still relied on self-reported data. Performance targets and indicators used to monitor and feedback to general practices varied between localities. Participants reported a number of issues when collecting and reporting data for NHSHC, namely because of opportunistic checks. Owing to the perceived inaccuracies in reporting, there was concern about the credibility and relevance of national uptake figures. The general practice extraction service will be important to fully understand uptake of NHSHC.

Localized turbulence bounded by non-turbulent flow in a uniformly stratified environment is studied with direct numerical simulations of stably stratified shear layers. Of particular interest is the turbulent/non-turbulent interfacial (TNTI) layer, which is detected by identifying the turbulent region in terms of its potential vorticity. Fluid near the outer edge of the turbulent region gains potential vorticity and becomes turbulent by diffusion arising from both viscous and molecular effects. The flow properties near the TNTI layer change depending on the buoyancy Reynolds number near the interface, $Re_{bI}$. The TNTI layer thickness is approximately 13 times the Kolmogorov length scale for large $Re_{bI}$ ($Re_{bI}\gtrsim 30$), consistent with non-stratified flows, whereas it is almost equal to the vertical length scale of the stratified flow, $l_{vI}=l_{hI}Re^{-1/2}$ (here $l_{hI}$ is the horizontal length scale near the TNTI layer, and $Re$ is the Reynolds number), in the low-$Re_{bI}$ regime ($Re_{bI}\lesssim 2$). Turbulent fluid is vertically transported towards the TNTI layer when $Re_{bI}$ is large, sustaining the thin TNTI layer with large buoyancy frequency and mean shear. This sharpening effect is weakened as $Re_{bI}$ decreases and eventually becomes negligible for very low $Re_{bI}$. Overturning motions occur near the TNTI layer for large $Re_{bI}$. The dependence on buoyancy Reynolds number is related to the value of $Re_{bI}$ near the TNTI layer, which is smaller than the value deep inside the turbulent core region. An imprint of the internal gravity waves propagating in the non-turbulent region is found for vorticity within the TNTI layer, inferring an interaction between turbulence and internal gravity waves. The wave energy flux causes a net loss of the kinetic energy in the turbulent core region bounded to the TNTI layer, and the amount of kinetic energy extracted from the turbulent region by internal gravity waves is comparable to the amount dissipated in the turbulent region.