Nanoscale simulation of crystal defects with application to mantle minerals

Minor and trace elements can influence the chemical and physical properties of the Earth's mantle, whether by forming separate minerals that can host trace elements at far higher concentrations than major mantle minerals, or by influencing physical properties of major minerals, for instance by enhancing diffusion or pinning topological defects. The present study uses atomistic computational modeling to investigate the properties of calcium phosphate minerals at mantle pressures, and to determine if cation vacancies can lubricate dislocation glide in mantle minerals. With their large, high-coordination cation sites, calcium phosphate minerals can potentially dissolve large quantities of incompatible elements, and may be an important mantle reservoirs for these elements. Quantum mechanical calculations are used to determine the variation of structure and properties of apatite, a common low-pressure phosphate, with the identity of its channel anion. The crystal structure and compressibility are both found to vary substantially with channel anion identity. Tuite, which forms by the breakdown of apatite at high pressure, may extend the phosphorous cycle beyond the stability field of apatite and into the lower mantle. DFT calculations are used to show that the pressure at which apatite decomposes to form tuite is sensitive to the identity of the channel anion. The calculated bulk moduli of the calcium-hosting sites in tuite are considerably lower than those of the M site in CaSiO3 perovskite (cpv). Atomistic calculations show that strontium and barium impurities partition strongly from cpv into tuite. The second part of this thesis considers the role that dislocations play in hosting vacancy-related defects, and influence that these segregated defects may have on the rheology of mantle minerals. Interatomic potentials are used to calculate energies for the segregation of bare and protonated cation defects to dislocation cores in MgO and forsterite. Vacancies segregate strongly to [100](010) and [001](010) dislocations in forsterite. [100](010) edge dislocations serve as particularly suitable hosts for vacancies on the M1 sub-lattice, while vacant M2 sites, which are energetically unfavorable in the unstrained bulk lattice are more common around [001](010) edge dislocations. Similarly, both {□Mg}″ and {2HMg}X defects segregate strongly to all of the major dislocation slip systems in MgO. For both minerals, cation vacancies will be far higher at dislocation core sites than in the unstrained lattice. Peierls-Nabarro calculations, parameterized using generalized stacking fault energies calculated using plane-wave density functional theory, show that protonated vacancies increase dislocation core widths and reduce the Peierls stresses in MgO. Bare Mg vacancies, especially those on the M2 sub-lattice, similarly reduce g-line energies and Peierls stresses for the dislocations in olivine. The magnitude of this decrease depends strongly on dislocation and the type of the lattice site (i.e. M1 or M2). Concentrations of vacancy related defects are likely to be elevated particularly in mantle wedge, due to the combination of oxidizing conditions and the availability of liquid water from dehydrating phases in the subducting slab, and changes in the olivine deformation fabric in these regions match those predicted in this study

North of Here: Imagining the Human and Other-Than-Human in Late-Upper Palaeolithic Britain

What were the cosmogonies, mythologies, rituals and ontological beliefs of the LateUpper Palaeolithic peoples who returned to the ‘British’ peninsula when the ice sheets began to retreat, some 15,000 years ago? More specifically, can we come to understand how they conceived of place, landscape and the natural world? Those working within the field of archaeology are rightly circumspect, but artistic practitioners, I suggest, are not bound in the same way by material evidence, and can consequently venture more freely. What, therefore, can speculative creative writing say about the deep past, and how can it bridge the gulf of time between us and our ancestral selves? North of Here is a ‘Creative Geographies: Writing Place’ project in the form of a long poem; a dialogic and visionary narrative that imbricates both ancient and contemporary ways of being. Drawing on environmental science, archaeology and the anthropology of circumpolar Indigenous cultures, it explores the human and other-thanhuman in terms of shared personhood, and the values of respect and reciprocity that govern non-hierarchical ‘social universes’. In particular, it examines consent-seeking and transgression in hunting, and the role of ‘special’ animals such as the bear in cosmogonic beliefs. This thesis will document the evolution of my interest in landscape and otherthan-human studies leading up to this PhD project. It will primarily contextualise the poem itself within anthropological and mythological literature, and therefore argue that the creative writer can meaningfully engage with cross-disciplinary subject matter. Moreover, in light of the so-called ‘creative turn’ in the humanities, it will suggest ways in which creative writers can contribute to interdisciplinary knowledge exchange

Asymptotic theory of microstructured surfaces: An asymptotic theory for waves guided by diffraction gratings or along microstructured surfaces

An effective surface equation, that encapsulates the detail of a microstructure, is developed to model microstructured surfaces. The equations deduced accurately reproduce a key feature of surface wave phenomena, created by periodic geometry, that are commonly called Rayleigh-Bloch waves, but which also go under other names such as Spoof Surface Plasmon Polaritons in photonics. Several illustrative examples are considered and it is shown that the theory extends to similar waves that propagate along gratings. Line source excitation is considered and an implicit long-scale wavelength is identified and compared to full numerical simulations. We also investigate non-periodic situations where a long-scale geometric variation in the structure is introduced and show that localised defect states emerge which the asymptotic theory explains

The influence of neighbourhoods and the social environment on sedentary behaviour in older adults in three prospective cohorts

Sedentary behaviour is an emerging risk factor for poor health. This study aimed to identify ecological determinants of sedentary behaviour, for which evidence is currently scarce. The analysed participants were community dwelling adults aged around 79, 83, and 64 years from, respectively, the Lothian Birth Cohort 1936 (n=271) and the 1930s (n=119) and 1950s (n=310) cohorts of the West of Scotland Twenty-07 study. The outcome measure, percentage of waking time spent sedentary (sedentary time), was measured using an activPAL activity monitor worn continuously for seven days. Potential determinants included objective and subjective neighbourhood measures such as natural space, crime, social cohesion and fear of crime. Other determinants included measures of social participation such as social support, social group membership and providing care. Results from multivariable regression analyses indicated that providing care was associated with reduced sedentary time in retired participants in all cohorts. Fear of crime and perceived absence of services were associated with increased sedentary time for retired 1950s cohort members. Higher crime rates were associated with increased sedentary time in all cohorts but this was not significant after adjustment for socio-demographic characteristics. Most other neighbourhood and social participation measures showed no association with sedentary time

Frailty predicts short-term incidence of future falls among British community-dwelling older people: a prospective cohort study nested within a randomised controlled trial

BACKGROUND: Although population-based studies have shown frailty predicted future falls, their follow-up periods were one year or longer and short-term fall risks associated with frailty are unknown. METHODS: A prospective cohort study nested within a randomised controlled trial was conducted to examine associations between frailty and short-term incident future falls among community-dwelling older people. Two hundred forty eight community-dwelling people > =65 years without history of > =three falls and allocated to a usual care arm of exercise intervention trial were prospectively monitored for falls over 24 weeks. Frailty index (FI) was constructed from 40 deficits at baseline. The future fall risks according to frailty status was examined using logistic regression models. RESULTS: Of 248 participants, 46 were classified as frail and 57 had one or more falls during follow-up. Both each 0.01 increase in FI and frailty defined as FI > =0.25 were significantly associated with higher risks of future falls in multivariate logistic regression models adjusted for age, gender and history of two falls in the previous year (odds ratio (OR) = 1.05, 95 % confidence interval (95 % CI) = 1.02-1.07, p < 0.001; OR = 3.04, 95 % CI = 1.53-6.02, p = 0.001, respectively). Receiver operating characteristic (ROC) curve analysis showed FI predicted future falls with fair accuracy with area under ROC curve of 0.62 (95 % CI = 0.53-0.71, p < 0.01). CONCLUSIONS: Frailty was a significant and independent predictor of short-term future falls among community-dwelling older people who had volunteered for a physical activity study. It is important for healthcare practitioners to recognise frailty as a risk factor of imminent future falling even in older people who appear to be ageing well

Cognitive ability does not predict objectively measured sedentary behaviour: evidence from three older cohorts

Higher cognitive ability is associated with being more physically active. Much less is known about the associations between cognitive ability and sedentary behavior. Ours is the first study to examine whether historic and contemporaneous cognitive ability predicts objectively measured sedentary behavior in older age. Participants were drawn from 3 cohorts (Lothian Birth Cohort, 1936 [LBC1936] [n = 271]; and 2 West of Scotland Twenty-07 cohorts: 1950s [n = 310] and 1930s [n = 119]). Regression models were used to assess the associations between a range of cognitive tests measured at different points in the life course, with sedentary behavior in older age recorded over 7 days. Prior simple reaction time (RT) was significantly related to later sedentary time in the youngest, Twenty-07 1950s cohort (p = .04). The relationship was nonsignificant after controlling for long-standing illness or employment status, or after correcting for multiple comparisons in the initial model. None of the cognitive measures were related to sedentary behavior in either of the 2 older cohorts (LBC1936, Twenty-07 1930s). There was no association between any of the cognitive tests and the number of sit-to-stand transitions in any of the 3 cohorts. The meta-analytic estimates for the measures of simple and choice RT that were identical in all cohorts (n = 700) were also not significant. In conclusion, we found no evidence that objectively measured sedentary time in older adults is associated with measures of cognitive ability at different time points in life, including cognitive change from childhood to older age

Biola Hour Highlights, 1974 - 07

If I Were the Devil by Paul Harvey I Pledge Allegiance by Red Skelton Communicating the Gospel by Al Sanders Last Days: Perilous Times by Al Sanders The Revelation of Jesus Christ by Lloyd Anderson Panel Discussions with Richard Chase, Charles Feinberg, and Samuel Sutherlandhttps://digitalcommons.biola.edu/bhhs/1006/thumbnail.jp

Biola Hour Highlights, 1974 - 07

If I Were the Devil by Paul Harvey I Pledge Allegiance by Red Skelton Communicating the Gospel by Al Sanders Last Days: Perilous Times by Al Sanders The Revelation of Jesus Christ by Lloyd Anderson Panel Discussions with Richard Chase, Charles Feinberg, and Samuel Sutherlandhttps://digitalcommons.biola.edu/bhhs/1006/thumbnail.jp

Patient-centred orientation of students from different healthcare disciplines, their understanding of the concept and factors influencing their development as patient-centred professionals: a mixed methods study

Background A patient-centred approach to care is increasingly the mandate for healthcare delivery. There is a need to explore how health professional students develop patient-centred attributes. This study aims to understand the extent of patient-centred orientations of health professional students, their perceptions and factors influencing their adoption of the approach. Methods The study used a cross-sectional, parallel mixed methods design combining a survey using the Patient-Practitioner Orientation Scale (PPOS) followed by focus groups with medical, nursing, physiotherapy and speech and language therapy students. Data included students’ age, gender, programme, and placements experienced. Pearson’s chi squared and the non-parametric equivalent Kruskal-Wallis H test were done to test for differences in demographics for appropriate variables. One-way ANOVA or Welch test was done to explore differences in PPOS scores. Regression analysis was done to test the influence of the demographic variables on PPOS scores. Data from focus groups were coded, categorised and organised under themes appropriate to the research aims. Results Of the 211 complete responses, significant differences were observed between medical and physiotherapy students in total PPOS scores, (MD -8.11 [95% CI -12.02 - 4.20] p = 0.000), Caring component (MD -4.44 [95% CI - 6.69, − 2.19] p = 0.000) and Sharing component (MD -3.67 [95% CI -6.12 -1.22] p = 0.001). The programme in which students were enrolled i.e. Medicine and SALT were the only indicators of higher PPOS total scores (F = 4.6 Df 10,69; p = 7.396e-06) and caring scores (F = 2.164 Df 10, 69 p = 0.022). Focus groups revealed that students perceived patient-centredness as holistic yet individualised care through establishing a partnership with patient. They identified that their student status, placement pressures, placement characteristics especially mentoring influenced their development of patient-centred attributes. Conclusion This study highlights the fact that the pressures of training in the National Health Service affects the development of students’ patient-centred orientation. There is a need for further work to explore aspects related to mentor training, for the development of patient-centred attributes, in a curricular framework structured on students’ needs from this study