First principles calculations of the Shift Current Bulk Photovoltaic Effect in Ferroelectrics

We calculate the bulk photovoltaic response of the ferroelectrics BaTiO$_3$ and PbTiO$_3$ from first principles by applying "shift current" theory to the electronic structure from density functional theory. The first principles results for BaTiO$_3$ reproduce eperimental photocurrent direction and magnitude as a function of light frequency, as well as the dependence of current on light polarization, demonstrating that shift current is the dominant mechanism of the bulk photovoltaic effect in BaTiO$_3$. Additionally, we analyze the relationship between response and material properties in detail. The photocurrent does not depend simply or strongly on the magnitude of material polarization, as has been previously assumed; instead, electronic states with delocalized, covalent bonding that is highly asymmetric along the current direction are required for strong shift current enhancements. The complexity of the response dependence on both external and material parameters suggests applications not only in solar energy conversion, but to photocatalysis and sensor and switch type devices as well.Comment: First submitted April 2011, submitted PRL July 201

Circulation changes and teleconnections between glacial advances on the west coast of New Zealand and extended spells of drought years in South Africa

Twentieth century changes in the terminal position of the Franz Josef Glacier on the west coast of New Zealand are compared with an area‐averaged mean annual rainfall series for the summer rainfall region of South Africa. Distinctive teleconnections are evident in an out‐of‐phase relationship between the two series, each of which exhibits an oscillation of 18–20 years. Periods of glacial advance are shown to coincide with extended dry spells in South Africa, when drought years are prevalent. Reconstructed pressure anomaly fields are presented for periods of advance and recession of the glacier and for the inter‐decadal wet and dry spells in South Africa. In both cases major regional atmospheric circulation adjustments take place in a quasi‐regular fashion over time to produce an enhancement in westerly airflow during the periods of drought in Africa and glacial advance on the west coast of New Zealand. Extended wet periods and glacial recession are likewise shown to be associated with an enhancement of easterly components of the circulation. Changes in precipitation, temperature and moisture transport are examined and associations with the Southern Oscillation Index are investigated. Franz Josef glacial advances are shown to occur 4–5 years after the onset of enhanced south‐westerly airflow on to the west coast of New Zealand. Advances occur on average 4 years after the onset of extended dry spells in South Africa. Similar atmospheric circulation anomalies in the respective sectors of the Southern Hemisphere and adjustments in the locations of the positions of the ridges in standing wave three are responsible for this correspondence

Scale in education research: towards a multi-scale methodology

This article explores some theoretical and methodological problems concerned with scale in education research through a critique of a recent mixed-method project. The project was framed by scale metaphors drawn from the physical and earth sciences and I consider how recent thinking around scale, for example in ecosystems and human geography might offer helpful points and angles of view on the challenges of thinking spatially in education research. Working between the spatial metaphors of ecology scholars and the critiques of the human geographers, for example the hypercomplex social space in Lefebvre’s political-economic thinking and the fluid, simultaneous, multiple spatialities of Massey’s post-structuralism, I problematize space and scale in education research. Interweaving these geographical ideas with Giddens’ structuration and Bourdieu’s theory of practice, both of which employed what might be termed scale-bridging to challenge social science’s entrenched paradigms, leads me to reconsider what is possible and desirable in the study of education systems. Following the spatial turn in the social sciences generally, there is an outstanding need to theorise multi-scale methodology for education research

The impact of research on policy: a case of qualifications reform

The relationship between research and policymaking has been discussed repeatedly. However, the debate tends to be in general, abstract terms or from a macro-economic perspective with any examples described in a fairly cursory way. Despite the inherent complexity of the research-policy interface, analyses tend to homogenize ‘research’ and ‘policy’ as coherent entities with discussions often focusing on products (research and policies) rather than on the relationships between producers (researchers and policy makers). Here we take one piece of research on qualifications that has influenced policy rhetoric over the last 5 years. We trace the career of the research from its production in the late 1990s in order to understand the conditions of its dormancy, reemergence and use over the ensuing years. The paper serves to document the case, which is important in its own right, but also proposes a typology of ways in which research gets adopted and adapted into policy

Studying advanced mathematics in England: findings from a survey of student choices and attitudes

The UK Government has set a goal that the ‘vast majority’ of students in England will be studying mathematics to 18 by the end of the decade. The policy levers for achieving this goal include new Core Maths qualifications, designed for over 200,000 students who have achieved good grades at the age of 16 but then opt out of advanced or A-level mathematics. This paper reports findings from a cluster-sampled survey of over ten thousand 17-year-olds in England in 2015. Participants’ views on post-16 mathematics are presented and discussed. The main finding is that they are strongly opposed to the idea of compulsory mathematical study, but are less antithetical to being encouraged to study mathematics beyond 16. We consider how attitudes vary by gender, prior attainment, study patterns and future aspirations. The paper considers the implications of these findings in the current policy landscape

A vertical profile of PM10 dust concentrations measured during a regional dust event identified by MODIS Terra, western Queensland, Australia

Accurate determination of the spatiotemporal properties of dust plumes and their dust concentrations is essential for calibration of satellite products and the initialization and validation of numerical models that simulate the physical properties and affects of dust events. In this paper, we present a 500 m vertical profile of PM10 dust concentrations measured during a regional dust event in western Queensland, Australia. PM10 dust concentrations within the haze were found to be >20 times background ambient values and decreased with height following an exponential function. We apply an over-land algorithm to MODIS Terra satellite images of the dust haze to enhance its visual appearance against the bright land surface and define its size. In conjunction with the measured attenuation of dust concentrations with height we calculate the PM10 dust load of the plume to be ∼60% of that which would have been calculated assuming a constant dust concentration up to the dust ceiling height. Results extend previous findings from tower-based studies made close to the surface and confirm that atmospheric dust concentrations decrease rapidly with increasing height, thereby enabling more accurate calculation of atmospheric dust loads during synoptic-scale dust outbreaks

Promoting Functional Health in Midlife and Old Age: Long-Term Protective Effects of Control Beliefs, Social Support, and Physical Exercise

Previous studies have examined physical risk factors in relation to functional health, but less work has focused on the protective role of psychological and social factors. We examined the individual and joint protective contribution of control beliefs, social support and physical exercise to changes in functional health, beyond the influence of health status and physical risk factors in middle-aged and older adults. Given that functional health typically declines throughout adulthood, it is important to identify modifiable factors that can be implemented to maintain functioning, improve quality of life, and reduce disability.We conducted a national longitudinal study, Midlife in the United States (MIDUS), with assessments in 1995-1996 and 2004-2006, and 3,626 community-residing adults, aged 32 to 84, were included in the analyses. Functional health (Physical Functioning subscale of the SF-36) and protective factors were measured at both occasions. While controlling for socio-demographic, health status, and physical risk factors (large waist circumference, smoking, and alcohol or drug problems), a composite of the three protective variables (control beliefs, social support, and physical exercise) at Time 1 was significantly related to functional health change. The more of these factors at Time 1, the better the health maintenance over 10 years. Among middle-aged and older adults, declines in health were significantly reduced with an increased number of protective factors.Age-related declines in health were reduced among those with more protective factors up to a decade earlier in life. Modifiable psychological, social, and physical protective factors, individually and in the aggregate, are associated with maintenance of functional health, beyond the damaging effects of physical risk factors. The results are encouraging for the prospect of developing interventions to promote functional health and for reducing public health expenditures for physical disability in later life