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Electron dynamics induced by circularly polarized laser pulses in <i>Im-3m</i> H<sub>3</sub>S in the superconducting pressure regime
No full textWe investigated crystalline Im-3m H3S at 200 GPa, a pressure regime where H3S is generally considered to be an exotic superconductor. Simulated circularly polarized 10 femtosecond (fs) laser pulses were applied and we quantified the effects on the electron dynamics during the application of “pump” and candidate “probe” laser pulses to discover optimal “probe” laser pulses. This is undertaken for the first application of Next Generation Quantum Theory of Atoms in Molecules (NG-QTAIM) using the Hessian of the “spin-up” and “spin-down” contributions to the total electronic charge density ρ(r). The optimal “probe” pulse was found to possess a peak electric field E = 10.0 × 10−4 a.u. compared with the “pump” pulse of E = 200.0 × 10−4 a.u. Separately considering the spin-up and spin-down contributions doubles the values of the chirality-helicity Chelicity function relative to that of the total charge density contribution for the H-H bonding for the application of the “pump” laser pulse. Within the NG-QTAIM interpretation, a combination of highly responsive and coherent behaviors is associated with superconductivity. These behaviors were discovered from the very high values of the Chelicity function, near-linear scaling of the bond-flexing F and bond-chirality C values with peak E-field and all instances of the H-H bonding possessing R electronic chirality assignments. The “pump” pulse was found to magnify the effects associated with superconductivity within the NG-QTAIM interpretation. Future applications are discussed including chiral spin selective phenomena and exotic high temperature superconductivity where phonons do not play a significant role
A surprisingly effective way to save the capercaillie:keep its predators well-fed – new research
No full textFinite Froude and Rossby number baroclinic vortex pairs
No full textWe study the evolution of baroclinically-unstable pairs of opposite-signed vortices in a three-dimensional, continuously-stratified, rotating fluid at finite Froude and Rossby numbers. We explore how ageostophic motions affect the evolution of the vortex pairs, in particular the dynamical asymmetry these motions induce in their evolution. To set the stage, we first consider the quasi-geostrophic limit of vanishingly-small Froude and Rossby numbers, conducting a linear stability analysis of two equal-volume, vertically aligned, equal-and-opposite uniform potential vorticity vortices lying at different depths. We also briefly address their nonlinear evolution. In the quasi-geostrophic limit, there is no dynamical asymmetry: cyclonic and anticyclonic vortices (hereafter “cyclones” and “anticyclones”) are identical apart from their sense of rotation. Next, the evolution of equivalent (in isopycnal coordinates) vortex pairs, at finite Froude and Rossby number is explored. In this case, an cyclone/anticyclone asymmetry arises in the evolution of the vortex pair, due to ageostrophic effects. We show that the anticyclone typically deforms less than the cyclone. Moreover, increasing the Froude and Rossby numbers tends to favour baroclinic instabilities with lower azimuthal wavenumbers. The origin of this asymmetry is traced to two contributing factors. First, the displacement of isopycnals means that two vortices, identical in isopycnal coordinates, enclose different volumes, the anticyclone being larger. Second, ageotrophic effects intensify the anticyclone relative to the cyclone. The combination of the two effects implies that the evolution of the baroclinic pair of vortices is dominated by the anticyclone
Factors influencing UK arthroplasty surgeons' decision-making between total and medial unicompartmental knee surgery:A vignette-based behavioural experiment
No full textPURPOSE: Surgical options for end-stage knee osteoarthritis (OA) include total and medial unicompartmental knee replacement (TKR and UKR). Deciding which surgery to perform is complex and ill-defined, yet it has important implications for patients and the health service. The study aimed to identify clinical and surgeon factors predicting surgeons' preferences.METHODS: Based on a preliminary survey of 162 UK surgeons, we identified clinical features frequently considered when deciding between TKR and UKR. By systematically varying patient age, obesity, site of pain, anaesthetic risk and anterior cruciate ligament (ACL) integrity, we constructed 32 clinical vignettes. We used these in a new survey, where surgeons indicated which surgery they would recommend on an 11-point rating scale with end points anchored at 'definitely TKR' and 'definitely medial UKR'. Data were analysed with mixed-effects linear regressions.RESULTS: Eighty-three UK arthroplasty surgeons completed the vignettes. Preference for UKR over TKR was significantly lower for patients over 50 years (b = -0.57 [-0.82 to -0.33], p < 0.001) with abnormal ACL (b = -1.93 [-2.17 to -1.68], p < 0.001) and severe systemic disease (b = -0.46 [-0.70 to -0.21], p < 0.001). Obesity was a weak and unreliable predictor, and we did not detect any influence of site of pain. The surgeons' habitual practice (proportion of UKRs over all knee replacements performed in a typical year) was the second strongest predictor after ACL (b = 1.26 [0.54-1.99], p = 0.001).CONCLUSIONS: ACL integrity was the most important determinant of surgeons' preferences between TKR and UKR. Their habitual practice was also a strong predictor, outweighing most clinical factors in the vignettes.LEVEL OF EVIDENCE: Level II, prospective cohort study.</p
Periglacial slope processes, landforms and deposits
No full textOn soil-mantled slopes in periglacial environments, mass movement results from solifluction, active-layer failure and permafrost creep. Solifluction has four components. Of these, needle-ice creep and frost creep result from uplift of soil during freezing and deposition farther downslope during thaw; gelifluction and plug-like deformation are caused by development of elevated pore-water pressures due to thaw of ice lenses. Active-layer failures occur when above-hydrostatic pore-water pressures at the base of the active layer cause it to rupture from the underlying permafrost. Permafrost creep occurs in ice-rich permafrozen sediments. Collectively these processes have produced a range of landforms, structures and distinctive deposits, including solifluction sheets, terraces and lobes, gelifluctate (head) deposits, stratified slope deposits, periglacial shears and cambered caprocks
Ion-rich acceleration during an eruptive flux rope event in a multiple null-point configuration
No full textWe report on the γ-ray emission above 100 MeV from the GOES M3.3 flare SOL2012-06-03. The hard X-ray (HXR) and microwave emissions have typical time profiles with a fast rise to a well-defined peak followed by a slower decay. The >100 MeV emission during the prompt phase displayed a double-peaked temporal structure with the first peak following the HXR and microwaves, and the second one, about 3 times stronger, occurring 17 ± 2 s later. The time profiles seem to indicate two separate acceleration mechanisms at work, where the second γ-ray peak reveals a potentially pure or at least largely dominant ion acceleration. The Atmospheric Imaging Assembly imaging shows a bright elliptical ribbon and a transient brightening in the northwestern (NW) region. Nonlinear force-free extrapolations at the time of the impulsive peaks show closed field lines connecting the NW region to the southeastern part of the ribbon, and the magnetic topology revealed clusters of nulls. These observations suggest a spine-and-fan geometry, and based on these observations, we interpret the second γ-ray peak as being due to the predominant acceleration of ions in a region with multiple null points. The >100 MeV emission from this flare also exhibits a delayed phase with an exponential decay of roughly 350 s. We find that the delayed emission is consistent with ions being trapped in a closed flux tube with gradual escape via their loss cone to the chromosphere
Barriers and facilitators to digital technology application for antimicrobial resistance surveillance:a co-produced qualitative synthesis
No full textThe systematic collection, analysis, and interpretation of antimicrobial resistance (AMR) data are imperative to quantify the AMR burden, monitor and identify emerging AMR, and inform global, international, and national health strategies and guidelines. Despite ongoing global efforts to improve surveillance capacities across Nigeria and other African countries, laboratory information management systems (LIMS) that could improve data quality, and completeness remain underutilized. We used a participatory research approach, drawing on the unique experiences of various stakeholders, such as data analysts, laboratory scientists, infection prevention and control specialists, medical doctors, and representatives from the National Coordinating Center in Nigeria. Over two phases of evidence synthesis, involving in-depth interviews and a participatory co-design workshop, we sought to understand the experiences of key stakeholders in using the LIMS tool, WHONET, for AMR surveillance, and co-develop solutions and priorities to address the challenges they experience. We identified a complex interplay of systemic/political factors and structural/user-related factors that influence the use of WHONET as a LIMS. Key areas for intervention identified by stakeholders include addressing infrastructural deficits, enhancing stakeholder engagement, and improving the perceived usefulness of the system, as well as the need for management support. Stakeholders also identified 18 potential solutions to tackle key challenges, ten of which require low effort and have a high influence on LIMS use behaviors. Our study highlights the multifaceted challenges affecting the effective utilization of WHONET for AMR surveillance in Nigeria. The co-developed solutions provide a roadmap for targeted interventions to strengthen AMR surveillance capacity and inform evidence-based public health strategies
Applying a unified framework to compare taxonomic, functional and phylogenetic diversity in Holocene pollen records
No full text1. Biodiversity is multifaceted, encompassing taxonomic, phylogenetic and functional dimensions of biological variation. Long‐term studies which compare these dimensions across a range of environments elucidate ecosystem dynamics and responses to environmental change. A recently developed quantitative framework allows measurement of taxonomic, phylogenetic and functional diversity in equivalent, abundance‐sensitive units, so that these three dimensions of diversity can be directly compared. This framework has been implemented for both alpha diversity (iNEXT.3D) and beta diversity (iNEXT.Beta3D). 2. We adapt this framework for application to pollen records, a major source of data on long‐term ecological change. To the best of our knowledge, this is the first application of the new framework to pollen records. We used the framework to compare dimensions of diversity during shifts in woodland extent and composition in northern Scotland, focusing on two sites with contrasting climatic and vegetation histories. These records capture responses to c. 8000 years of climatic and land‐use change. 3. We found that despite persistent woodland cover, the less exposed site exhibits large variations in taxonomic, phylogenetic and functional diversity and composition, including a decline across all dimensions of diversity since 1200 cal year BP. Since around 7500 cal year BP, the exposed site shows more stable biodiversity across all three dimensions. We attribute these differing dynamics to habitat heterogeneity at the less exposed site and slow ecological processes (e.g. peat expansion and regeneration failure in trees) at the exposed site. The results show that diversity responses to changing or persistent woodland cover varied across the three dimensions of diversity and also for rare, abundant and dominant groups. These responses are not detected through conventional analyses of taxonomic richness. 4. Synthesis. Evaluating long‐term diversity patterns in an integrated framework allows direct comparison of taxonomic, functional and phylogenetic diversity patterns, and generates insights of potential relevance to ecosystem management. Across multiple dimensions, changes in diversity and composition are evident despite woodland persistence, and long‐term site‐specific ecological processes strongly influence diversity dynamics. By applying the framework to pollen data, and demonstrating that this yields insights into long‐term diversity change, our work supports broader application of this method to palaeoecological records
