Persistence of the Jahn–Teller distortion of Mo5+ in double perovskites : a structural study of Ba2NdMoO6 and the effect of chemical doping in Ba2Nd1xYxMoO6

The cation ordered perovskites Ba2NdMoO6 and Ba2Nd1-xYxMoO6 have been structurally characterised by a combination of neutron and X-ray powder diffraction. Ba2NdMoO6 retains the tetragonal room temperature structure on cooling to 150 K[: I4/m; a = 5.98555(5)Å, c = 8.59510(10) Å] although the MoO6 octahedra distort with an elongation of two, trans Mo-O bonds. Neutron diffraction data collected at T ≤ 130 K show that this compound has undergone a structural distortion to a triclinic space group, although the MoO6 octahedra do not distort any further on cooling below this temperature [at 130 K: ; 5.97625(14) Å, 5.9804(2) Å, 8.59650(13) Å, 89.876(2) °, 89.921(3) °, 89.994(2) °]. The room temperature tetragonal space group symmetry of Ba2NdMoO6 is preserved in the series Ba2Nd1-xYxMoO6 up to composition 0.35 ≤x< 0.5. The lattice parameters converge as the value of x increases until cubic symmetry is reached for the composition for Ba2Nd0.5Y0.5MoO6 [ ;a = 8.4529(3) Å]. Magnetic susceptibility measurements show that all of these compounds display the Curie-Weiss behaviour associated with a fully localised electronic systems. The paramagnetic moments show good agreement with those anticipated to arise from the spin-only contribution from Mo5+ (S=1/2, µso = 1.73 µB) and the moment of 3.62 µB associated with the spin-orbit coupling of the 4I9/2 ground state of Nd3+. For x≤0.125 this series shows a magnetic transition in the range 10 to 15 K indicative of a distortion of the MoO6 octahedra in these compounds that is similar to Ba2NdMoO6

Algorithms for Highly Symmetric Linear and Integer Programs

This paper deals with exploiting symmetry for solving linear and integer programming problems. Basic properties of linear representations of finite groups can be used to reduce symmetric linear programming to solving linear programs of lower dimension. Combining this approach with knowledge of the geometry of feasible integer solutions yields an algorithm for solving highly symmetric integer linear programs which only takes time which is linear in the number of constraints and quadratic in the dimension.Comment: 21 pages, 1 figure; some references and further comments added, title slightly change

Positive Affect and Physical Activity: Testing Effects on Goal Setting, Activation, Prioritization, and Attainment

Objective: The present research tested whether incidental positive affect promotes pursuit of physical activity goals. Four key features of goal pursuit were examined – setting physical activity goals (Study 1), goal activation (Study 2), and goal prioritization and goal attainment (Study 3). Design: Participants (Ns = 80, 81, and 59, in Studies 1–3, respectively) were randomized to positive affect (joy, hope) or neutral affect (control) conditions in each study. Main Outcome Measures: Questionnaire measures of goal level, goal commitment, and means selection (Study 1); a lexical decision task indexed goal activation (Study 2), a choice task captured goal prioritization and MET minutes quantified goal attainment (Study 3). Results: Study 1 showed that positive affect led to a greater number of intended physical activities, and that joy engendered greater willingness to try activities. In Study 2, a positive affect induction led to heightened activation of the physical activity goal compared to the control condition. The joy induction in Study 3 led to greater physical activity, and a trend towards greater goal prioritization. Conclusion: These findings suggest that positive affect enhances the pursuit of physical activity goals. Implications for health behavior theories and interventions are outlined

The impact of positive affect on health cognitions and behaviours: a meta-analysis of the experimental evidence

Several reviews suggest that positive affect is associated with improved longevity, fewer physical symptoms, and biological indicators of good health. It is possible that positive affect could influence these outcomes by promoting healthful cognitions and behaviours. The present review identified conceptual pathways from positive affect to health cognitions and behaviour, and used random effects meta-analysis to quantify the impact of positive affect inductions (versus neutral affect conditions) on these outcomes. Literature searches located 54 independent tests that could be included in the review. Across all studies, the findings revealed no reliable effects on intentions (d+ = −.12, 95% CI = −.32 to.08, k = 15) or behaviour (d+ =.15, 95% CI = −.03 to.33, k = 23). There were four reliable effects involving specific cognitions and behaviours, but little clear evidence for generalised benefits or adverse effects of positive emotions on health-related cognitions or actions. Conclusions must be cautious given the paucity of tests available for analysis. The review offers suggestions about research designs that might profitably be deployed in future studies, and calls for additional tests of the impact of discrete positive emotions on health cognitions and behaviour

Performance of a Neutron Polarimeter to Measure the Electric Form Factor of the Neutron

This research was sponsored by the National Science Foundation Grant NSF PHY-931478

Implementing evidence-based recommended practices for the management of patients with mild traumatic brain injuries in Australian emergency care departments: study protocol for a cluster randomised controlled trial

Background: Mild head injuries commonly present to emergency departments. The challenges facing clinicians in emergency departments include identifying which patients have traumatic brain injury, and which patients can safely be sent home. Traumatic brain injuries may exist with subtle symptoms or signs, but can still lead to adverse outcomes. Despite the existence of several high quality clinical practice guidelines, internationally and in Australia, research shows inconsistent implementation of these recommendations. The aim of this trial is to test the effectiveness of a targeted, theory- and evidence-informed implementation intervention to increase the uptake of three key clinical recommendations regarding the emergency department management of adult patients (18 years of age or older) who present following mild head injuries (concussion), compared with passive dissemination of these recommendations. The primary objective is to establish whether the intervention is effective in increasing the percentage of patients for which appropriate post-traumatic amnesia screening is performed. Methods/design: The design of this study is a cluster randomised trial. We aim to include 34 Australian 24-hour emergency departments, which will be randomised to an intervention or control group. Control group departments will receive a copy of the most recent Australian evidence-based clinical practice guideline on the acute management of patients with mild head injuries. The intervention group will receive an implementation intervention based on an analysis of influencing factors, which include local stakeholder meetings, identification of nursing and medical opinion leaders in each site, a train-the-trainer day and standardised education and interactive workshops delivered by the opinion leaders during a 3 month period of time. Clinical practice outcomes will be collected retrospectively from medical records by independent chart auditors over the 2 month period following intervention delivery (patient level outcomes). In consenting hospitals, eligible patients will be recruited for a follow-up telephone interview conducted by trained researchers. A cost-effectiveness analysis and process evaluation using mixed-methods will be conducted. Sample size calculations are based on including 30 patients on average per department. Outcome assessors will be blinded to group allocation

Curved Tails in Polymerization-Based Bacterial Motility

The curved actin ``comet-tail'' of the bacterium Listeria monocytogenes is a visually striking signature of actin polymerization-based motility. Similar actin tails are associated with Shigella flexneri, spotted-fever Rickettsiae, the Vaccinia virus, and vesicles and microspheres in related in vitro systems. We show that the torque required to produce the curvature in the tail can arise from randomly placed actin filaments pushing the bacterium or particle. We find that the curvature magnitude determines the number of actively pushing filaments, independent of viscosity and of the molecular details of force generation. The variation of the curvature with time can be used to infer the dynamics of actin filaments at the bacterial surface.Comment: 8 pages, 2 figures, Latex2

Dislocation interactions during low-temperature plasticity of olivine and their impact on the evolution of lithospheric strength

The strength of the lithosphere is typically modelled based on constitutive equations for steady-state flow. However, strain hardening may cause significant evolution of strength in the colder load-bearing portion of the lithosphere. Recent rheological data from low-temperature deformation experiments on olivine suggest that strain hardening occurs due to the presence of temperature-independent back stresses generated by long-range elastic interactions among dislocations. These interpretations provided the basis for a flow law that incorporates hardening by the development of back stress. Here, we test this dislocation-interaction hypothesis by examining the microstructures of olivine samples deformed plastically at room temperature either in a deformation-DIA apparatus at differential stresses of ≤4.3GPa or in a nanoindenter at applied contact stresses of ≥10.2GPa. High-angular resolution electron backscatter diffraction maps reveal the presence of geometrically necessary dislocations with densities commonly above 1014m−2 and intragranular heterogeneities in residual stress on the order of 1 GPa in both sets of samples. Scanning transmission electron micrographs reveal straight dislocations aligned in slip bands and interacting with dislocations of other types that act as obstacles. The resulting accumulations of dislocations in their slip planes, and associated stress heterogeneities, are consistent with strain hardening resulting from long-range back-stresses acting among dislocations and thereby support the form of the flow law for low-temperature plasticity. Based on these observations, we predict that back stresses among dislocations will impart significant mechanical anisotropy to deformed lithosphere by enhancing or reducing the effective stress. Therefore, strain history, with associated microstructural and micromechanical evolution, is an important consideration for models of lithospheric strength. The microstructural observations also provide new criteria for identifying the operation of back-stress induced strain hardening in natural samples and therefore provide a means to test the applicability of the flow law for low-temperature plasticity.This research was supported by Natural Environment Research Council grants NE/M000966/1 to LNH, AJW, and DW and 1710DG008/JC4 to LNH and AJW; European Plate Observing System Transnational Access grant EPOS-TNA-MSL 2018-022 to LNH; Advanced Photon Source General User Proposal 55176 to LNH, DLG, and WBD; and National Science Foundation Awards EAR-1361319 to WBD, EAR-1625032 to JMW, and EAR-1806791 to KMK