Recent changes to US research funding are having far-reaching consequences that imperil the integrity of science and the provision of care to vulnerable populations. Resisting these changes, the BJPsych Portfolio reaffirms its commitment to publishing mental science and advancing psychiatric knowledge that improves the mental health of one and all.

Aviation passenger screening has been used worldwide to mitigate the translocation risk of SARS-CoV-2. We present a model that evaluates factors in screening strategies used in air travel and assess their relative sensitivity and importance in identifying infectious passengers. We use adapted Monte Carlo simulations to produce hypothetical disease timelines for the Omicron variant of SARS-CoV-2 for travelling passengers. Screening strategy factors assessed include having one or two RT-PCR and/or antigen tests prior to departure and/or post-arrival, and quarantine length and compliance upon arrival. One or more post-arrival tests and high quarantine compliance were the most important factors in reducing pathogen translocation. Screening that combines quarantine and post-arrival testing can shorten the length of quarantine for travelers, and variability and mean testing sensitivity in post-arrival RT-PCR and antigen tests decrease and increase with the greater time between the first and second post-arrival test, respectively. This study provides insight into the role various screening strategy factors have in preventing the translocation of infectious diseases and a flexible framework adaptable to other existing or emerging diseases. Such findings may help in public health policy and decision-making in present and future evidence-based practices for passenger screening and pandemic preparedness.

Five international consensus statements on concussion in sports have been published. This commentary argues that there is a strong need for a new approach to them that foregrounds public health expertise and patient-centered guidance. Doing so will help players, parents and practitioners keep perspective about these potentially life-altering injuries especially when they recur.

Several grass and broadleaf weed species around the world have evolved multiple-herbicide resistance at alarmingly increasing rates. Research on the biochemical and molecular resistance mechanisms of multiple-resistant weed populations indicate a prevalence of herbicide metabolism catalyzed by enzyme systems such as cytochrome P450 monooxygenases and glutathione S-transferases and, to a lesser extent, by glucosyl transferases. A symposium was conducted to gain an understanding of the current state of research on metabolic resistance mechanisms in weed species that pose major management problems around the world. These topics, as well as future directions of investigations that were identified in the symposium, are summarized herein. In addition, the latest information on selected topics such as the role of safeners in inducing crop tolerance to herbicides, selectivity to clomazone, glyphosate metabolism in crops and weeds, and bioactivation of natural molecules is reviewed.

Sea-ice cores from 11 sites in McMurdo Sound, Antarctica, were collected in 1982 and their crystallography examined. All but one were first-year sea ice. The cores, approximately 2 m long, consisted typically of a thin layer of granular or snow ice (approximately 0.1 m) followed by columnar-grained ice in the top metre and platelet ice in the bottom metre. Salinity and temperature measurements are reported. The columnar-grained ice usually had a strong preferred c-axis orientation in the horizontal plane and also showed a change in this preferred direction with depth in the ice. The mean c-axis orientation, however, usually aligned well with measured or implied currents in the Sound. The platelets were usually aligned with c axis horizontal or close to horizontal, and did not exhibit as marked a preferred orientation as the columnar-grained ice.

We present a re-analysis of the results obtained from a series of measurements on freshwater and saline ice beams under various centrifugal accelerations. The data show a strong influence of beam size, brine volume and centrifugal acceleration on the elastic modulus of ice. The data suggest a transition brine volume at around 9%, which might occur close to the melting point, at which the elastic modulus of ice drops rapidly due to a possible change of brine-pocket structure. Furthermore, for brine volumes less than 9%, there is a negligible increase in the elastic modulus measured under high centrifugal acceleration, but for brine volumes more than 9% the increase is considerable, approaching that measured with freshwater ice. This may be due to necking of brine drainage channels just above the ice/water interface at high centrifugal acceleration. A model of sea ice was constructed based on existing theories of brine inclusions in sea ice, which satisfactorily predicts the observed trends.

Laboratory-grown single crystals, both pure and HF-doped, and pure polycrystals of ice, as well as natural, columnar-grained ice from the River St Lawrence, have been deformed in uniaxial compression at 77 K at strain-rates between 10-5 and 10-3 s-1. Brittle fracture was observed, with stress-strain curves similar to those found for rocks at room temperature. The first cracks appeared at low stresses, ≈0.3 MN m-2, in agreement with theory, but the failure or fracture stress was high ≈50 MN m-2. The ratio of experimental to theoretical strength was o.28. HF doping of the single crystals had no effect at this temperature.

Constant strain-rate compression tests on ice single crystals at temperatures between –20°C and -0.2°C are described. The power-law dependence of yield stress on strain-rate gives a value of n which varies from 1.95±0.04 at –0.2°C to 2.07±0.08 at –20°C. The activation energy of deformation varies with strain-rate, but a mean value of 70±2 kJ mol–1 is obtained, with no indication of any increase close to maleting point,as has been found polycrystalline ice. An apparent work-hardening effect, at strains greater than 15%, is explained as being due to bending of the crystal changing the orientation of the basal planes.

Uniaxial compressive creep tests on single crystals and polycrystals of ice at about -10°C under different hydrostatic pressures are described . After creeping under a constant load at atmospheric pressure for some hours, a hydrostatic pressure of the order of 35 MN m-2 was applied and the change in strain-rate was noted. Some hours later the hydrostatic pressure was removed and the test continued at atmospheric pressure. From these changes in strain-rate , an activation volume V was determined from the equation

where R is the gas constant, T is the absolute temperature, P is the hydrostatic pressure and τ is the superimposed uniaxial creep stress. V is negative if E increases with P.

For single crystals, which show an accelerating creep curve, that is the strain-rate increases continuously with time, no sensible activation volume was determined because the strain-rate increased both on the application of the hydrostatic pressure, and on its removal. For polycrystals, application of a hydrostatic pressure caused an increase in strain-rate which gave an activation volume of about - 10 cm3 mol-1. However, on removal of the pressure the strain-rate did not return to its original atmospheric-pressure value implying that steady-state creep had not been reached.

This value of activation volume is in general agreement with two previously published values for creep deformation, but is of opposite sign to the activation volume for dielectric relaxation. Further tests are in progress.

Untersteincr and Nye (1968) calculated the possible future movement of Berendon Glacier, B.C. These calculations are repeated using much improved data and a slightly different method for computing the datum state. The predictions that result are very similar to those found in the earlier work. It is concluded, however, from mass-balance data, that the chance of the glacier rising sufficiently in the next 25 years to be a danger to the mining installations situated near the snout of the glacier is much greater than was previously considered. The sensitivity of the theory to changes in input data is discussed.

The friction of pure ice against various materials was studied at the melting point by pulling plates of the materials of known roughness under a melting ice sample, which was loaded from above, and by maintaining a surrounding air temperature of +2°C (±1°C). Speed was varied over a wide range from 0.05 to 400 mm s−1.

Results for an aluminium sheet of roughness Ra = 0.84 μm, showed a maximum in friction coefficient of 0.04 at a speed of 16 mm s−1. Below this speed the friction coefficient dropped to 0.002 at 0.2 mm s −1 and results from different ice samples were very reproducible. Above 16 mm s−1, the friction coefficient initially dropped to about 0.002 at 100 mm s−1, and then increased again to 0.037 at 400 mm s−1. Results at speeds above 16 mm s−1 were much less reproducible than those at lower speeds. Results are given also for the friction of ice on Formica, acrylic, and copper plates.

The amount of meltwater produced during a test was measured by weighing an absorbent tissue before and after mopping-up the meltwater. The amount of meltwater was significantly more for aluminium than for Formica or acrylic, showing that the thermal conductivity of the slider was controlling the amount of meltwater. The amount was also a strong function of velocity.

Triaxial tests were carried out on randomly oriented, laboratory-made, polycrystalline ice, between strain-rates of 10–7 and 10–1 s–1 and with confining pressures from 0.1 to 85 MN m–2, at –11 ± 1°C. Below strain-rates of about 10–5 s–1 the confining pressure has little effect, but at higher strain-rates the confining pressure prevents cracking which allows the compressive strength to rise to a value greater than the unconfined compressive strength. At 1.4 ×10–2 s–1, the unconfined strength of 12 MN m–2 rises to 26 MN m–2 with a confining pressure of 25 MN m–2, before dropping slowly with greater confining pressures. Above 10–2 s–1 the unconfined strength decreases rapidly with increasing strain-rate, but the confined strength continues to increase. The dependence of strain rate on the maximum compressive stress is discussed.

Most non-linear fluids for which the appropriate measurements have been made exhibit non-zero and unequal normal stress differences in shearing flows. Power-law models such as Glen’s law cannot represent this phenomenon. The simplest constitutive equation that does embody normal stress effects defines the second-order fluid. An exact analytical solution for biaxial creep of such a fluid is fit to data from four tests on polycrystalline ice. The model gives an excellent representation of both primary and secondary creep. The fits provide values for the three material constants. These coefficients indicate positive first and second normal stress differences. One consequence is the prediction that a steady open-channel flow will exhibit a longitudinal free-surface depression of up to several meters for sufficiently thick ice on steep slopes. In addition, the compressive principal stress at the channel margin is decreased and the tensile principal stress is increased in magnitude over those predicted by models without normal stresses. The normal stresses thus favor the formation of crevasses. Furthermore, the angle these crevasses form with the channel margin is decreased.