The effect of cation order on the elasticity of omphacite from atomistic calculations

Omphacite, a clinopyroxene mineral with two distinct crystallographic sites, M1 and M2, and composition intermediate between diopside and jadeite, is abundant throughout the Earth's upper mantle, and is the dominant mineral in subducted oceanic crust. Unlike the end-members, omphacite exists in two distinct phases, a P2/n ordered phase at low temperature and a high-temperature C2/c disordered phase. The crystal structure and full elastic constants tensor of ordered P2/n omphacite have been calculated to 15 GPa using plane-wave density functional theory. Our results show that several of the elastic constants, notably C11, C12, and C13 deviate from linear- mixing between diopside and jadeite. The anisotropy of omphacite decreases with increasing pressure and, at 10 GPa, is lower than that of either diopside or jadeite. The effect of cation disorder is investigated through force-field calculations of the elastic constants of Special Quasirandom Structures supercells with simulated disorder over the M2 sites only, and over both cation sites. These show that cation order influences the elasticity, with some components displaying particular sensitivity to order on a specific cation site. C11, C12, and C66 are sensitive to disorder on M1, while C22 is softened substantially by disorder on M2, but insensitive to disorder on M1. This shows that the elasticity of omphacite is sensitive to the degree of disorder, and hence the temperature. We expect these results to be relevant to other minerals with order-disorder phase transitions, implying that care must be taken when considering the effects of composition on seismic anisotropy

The compressibility and high pressure structure of diopside from first principles simulation

The structure of diopside (CaMgSi2O6) has been calculated at pressures between 0 and 25 GPa using the planewaves and pseudopotentials approach to density functional theory. After applying a pressure correction of 4.66 GPa to allow for the under-binding usually associated with the generalized gradient approximation, cell parameters are in good agreement with experiment. Fitting to the third-order Birch-Murnaghan equation of state yields values of 122 GPa and 4.7 for the bulk modulus and its pressure derivative. In addition to cell parameters, our calculations provide all atomic positional parameters to pressures considerably beyond those currently available from experiment. We have analyzed these data in terms of polyhedral rigidity and regularity and find that the most compressible Ca polyhedron becomes markedly less anisotropic above 10 GPa

Practice Makes Imperfect: Restorative Effects of Sleep on Motor Learning

Emerging evidence suggests that sleep plays a key role in procedural learning, particularly in the continued development of motor skill learning following initial acquisition. We argue that a detailed examination of the time course of performance across sleep on the finger-tapping task, established as the paradigm for studying the effect of sleep on motor learning, will help distinguish a restorative role of sleep in motor skill learning from a proactive one. Healthy subjects rehearsed for 12 trials and, following a night of sleep, were tested. Early training rapidly improved speed as well as accuracy on pre-sleep training. Additional rehearsal caused a marked slow-down in further improvement or partial reversal in performance to observed levels below theoretical upper limits derived on the basis of early pre-sleep rehearsal. This decrement in learning efficacy does not occur always, but if and only if it does, overnight sleep has an effect in fully or partly restoring the efficacy and actual performance to the optimal theoretically achieveable level. Our findings re-interpret the sleep-dependent memory enhancement in motor learning reported in the literature as a restoration of fatigued circuitry specialized for the skill. In providing restitution to the fatigued brain, sleep eliminates the rehearsal-induced synaptic fatigue of the circuitry specialized for the task and restores the benefit of early pre-sleep rehearsal. The present findings lend support to the notion that latent sleep-dependent enhancement of performance is a behavioral expression of the brain's restitution in sleep

Full STEAM ahead: a manifesto for integrating arts pedagogics in to STEM education

This paper sets out to challenge the common pedagogies found in STEM education with a particular focus on engineering. The dominant engineering pedagogy remains “chalk and talk”; despite research evidence that demonstrates its ineffectiveness. The paper argues that there is a potential confusion in engineering education around the role of active learning approaches, and that the adoption of these approaches may be limited as a result of this confusion, combined with a degree of disciplinary egocentrism. The paper presents examples of engineering and “engineering like” projects that demonstrate the effectiveness of adopting pedagogies and delivery methods more usually attributed to the liberal arts such as studio based learning. The paper concludes with some suggestions about how best to create a fertile environment from which inquiry based learning can emerge as well as a reflection on whether the only real limitation on cultivating such approaches is the disciplinary egocentrism of traditional engineering educators

Evaluating the Liverpool Care Pathway for care of the terminally ill in rural Australia

© 2015, Springer-Verlag Berlin Heidelberg. Purpose: This study evaluates a pilot implementation of the Liverpool Care Pathway (LCP), a clinical tool used to guide the care of dying patients in the last days of life, on the end-of-life care for dying patients in three regions in rural Australia. Methods: The LCP was implemented at 13 participating sites: nine hospitals (general wards), one community-based palliative care service, and three in-hospital palliative care units. To evaluate the implementation of the LCP, 415 eligible patient records were examined: 223 pre-implementation and 192 post-implementation (116 on the LCP and 76 receiving usual care). The primary analysis compared all patients pre-implementation of the LCP versus all patients post-implementation. Results: Increases were found post-implementation for communication with other health professionals and with patients or family (pre-69 %, post-87 %; p ≤ 0.000), use of palliative medications (pre-87 %, post-98 %; p ≤ 0.000) and frequency of symptom assessments (pre-66 %, post-82 %; p ≤ 0.000). Fewer blood and radiological investigations were conducted and venous access devices used in the post-implementation groups than in the pre-implementation period. Conclusions: This study suggests that when rigorously implemented, the LCP improves important components of end-of-life care for dying patients and their families

Substitution of Ti3+ and Ti4+ in hibonite (CaAl12O19)

The structures of eight synthetic samples of hibonite, with variable Ti oxidation state and Ti concentration (2.4–15.9 wt% TiO2) that span the range reported for natural hibonite found in meteorites, were determined by Rietveld refinements of neutron powder diffraction data. Ti3+ was found to exclusively occupy the octahedral face-sharing M4 site irrespective of the presence or absence of Ti4+. Ti4+ partitions between the trigonal bipyramidal M2 site and the M4 site. The ratio (Ti4+ on M2):(Ti4+ on M4) appears to be constant for all the samples, with an average of 0.18(2) irrespective of the concentrations of Ti3+ and Ti4+. These substitutional sites were shown to be the most stable configurations for Ti in hibonite from calculations using density functional theory, although the predicted preference of Ti4+ for M4 over M2 is not as strong as is observed. This is attributed to the different Ti contents of the experimental and calculated structures and suggests that the Ti site occupancies might change between these concentrations. Furthermore, it is shown that Ti has a preference to occupy neighboring M4 sites such that Ti-Ti interactions occur with stabilization energies of 83 kJ/mol for Ti3+-Ti3+ and at least 15 kJ/mol for Ti4+-Ti4+. Features in optical spectroscopy and electron spin resonance data from meteoritic and synthetic hibonites that have been used to infer Ti3+/Ti4+ are shown to actually derive from these Ti-Ti interactions. The amount of Ti4+ in hibonite can be determined from the unit-cell parameters if ∑Ti is determined independently. Ti3+/Ti4+ in hibonite may record the oxygen fugacity (fO2) of the early solar nebula, however, the existence of Ti3+-Ti3+ and Ti4+-Ti4+ interactions and the potential for Ti4+-Ti3+ interactions need to be considered when interpreting spectroscopic data in terms of Ti valence state and fO2. Hibonite as a single-mineral oxybarometer must be used with caution due to the potential role of crystal chemistry (including Ti-Ti interactions) to stabilize Ti oxidation states independently of fO2

Phosphoinositide 3-kinase: a critical signalling event in pulmonary cells.

Phosphoinositide 3-kinases (PI-3Ks) are enzymes that generate lipid second messenger molecules, resulting in the activation of multiple intracellular signalling cascades. These events regulate a broad array of cellular responses including survival, activation, differentiation and proliferation and are now recognised to have a key role in a number of physiological and pathophysiological processes in the lung. PI-3Ks contribute to the pathogenesis of asthma by influencing the proliferation of airways smooth muscle and the recruitment of eosinophils, and affect the balance between the harmful and protective responses in pulmonary inflammation and infection by the modulation of granulocyte recruitment, activation and apoptosis. In addition they also seem to exert a critical influence on the malignant phenotype of small cell lung cancer. PI-3K isoforms and their downstream targets thus provide novel therapeutic targets for intervention in a broad spectrum of respiratory diseases.RIGHTS : This article is licensed under the BioMed Central licence at http://www.biomedcentral.com/about/license which is similar to the 'Creative Commons Attribution Licence'. In brief you may : copy, distribute, and display the work; make derivative works; or make commercial use of the work - under the following conditions: the original author must be given credit; for any reuse or distribution, it must be made clear to others what the license terms of this work are