Approximate Bayesian inference for doubly robust estimation

Doubly robust estimators are typically constructed by combining outcome regression and propensity score models to satisfy moment restrictions that ensure consistent estimation of causal quantities provided at least one of the component models is correctly specified. Standard Bayesian methods are difficult to apply because restricted moment models do not imply fully specified likelihood functions. This paper proposes a Bayesian bootstrap approach to derive approximate posterior predictive distributions that are doubly robust for estimation of causal quantities. Simulations show that the approach performs well under various sources of misspecification of the outcome regression or propensity score models. The estimator is applied in a case study of the effect of area deprivation on the incidence of child pedestrian casualties in British cities

The Immigration Bill's proposals for young migrants in care will lead to a constitutional mess in Scottish policy-making

The focus of this post is about what it means for young migrants in Scotland and more broadly what it suggests about the ability of Westminster legislation to have primacy over Scottish policy and practice

Anticrossing of spin-split subbands in quasi-one-dimensional wires

In quantum Hall systems, both anticrossings and magnetic phase transitions can occur when opposite-spin Landau levels coincide. Our results indicate that both processes are also possible in quasi-1D quantum wires in an in-plane B field, B-parallel to. Crossings of opposite-spin 1D subbands resemble magnetic phase transitions at zero dc source-drain bias, but display anticrossings at high dc bias. Our data also imply that the well-known 0.7 structure may evolve into a spin-hybridized state in finite dc bias

Time, timing, talking and training : findings from an exploratory action research study to improve quality of end of life care for minority ethnic kidney patients

Background. With an ageing and increasingly diverse population at risk from rising levels of obesity, diabetes and cardiovascular disease, including kidney complications, there is a need to provide quality care at all stages in the care pathway including at the end of life and to all patients. Aim. This study purposively explored South Asian patients' experiences of kidney end of life care to understand how services can be delivered in a way that meets diverse patient needs. Methods. Within an action research design 14 focus groups (45 care providers) of kidney care providers discussed the recruitment and analysis of individual interviews with 16 South Asian kidney patients (eight men, eight women). Emergent themes from the focus groups were analysed thematically. The research took place at four UK centres providing kidney care to diverse populations: West London, Luton, Leicester and Bradford. Results. Key themes related to time and the timing of discussions about end of life care and the factors that place limitations on patients and providers in talking about end of life care. Lack of time and confidence of nurses in areas of kidney care, individual attitudes and workforce composition influence whether and how patients have access to end of life care through kidney services. Conclusion. Training, team work and time to discuss overarching issues (including timing and communication about end of life) with colleagues could support service providers to facilitate access and delivery of end of life care to this group of patients.Peer reviewedFinal Published versio

Interaction effects at crossings of spin-polarized one-dimensional subbands

We report conductance measurements of ballistic one-dimensional (1D) wires defined in GaAs/AlGaAs heterostructures in an in-plane magnetic field, B. When the Zeeman energy is equal to the 1D subband energy spacing, the spin-split subband Nup arrow intersects (N+1)down arrow, where N is the index of the spin-degenerate 1D subband. At the crossing of N=1up arrow and N=2down arrow subbands, there is a spontaneous splitting giving rise to an additional conductance structure evolving from the 1.5(2e(2)/h) plateau. With further increase in B, the structure develops into a plateau and lowers to 2e(2)/h. With increasing temperature and magnetic field the structure shows characteristics of the 0.7 structure. Our results suggest that at low densities a spontaneous spin splitting occurs whenever two 1D subbands of opposite spins cross

The early-type dwarf galaxy population of the Centaurus cluster

We present a photometric study of the early-type dwarf galaxy population of the Centaurus cluster, aiming at investigating the galaxy luminosity function (LF) and galaxy scaling relations down to the regime of galaxies with M_V~-10 mag. On deep VLT/FORS1 V- and I-band images of the central part of the cluster, we identify cluster dwarf-galaxy candidates using both morphological and surface brightness selection criteria. Photometric and structural parameters of the candidates are derived from analysis of their surface brightness profiles. Fundamental scaling relations, such as the colour-magnitude and the magnitude-surface brightness relation, are used to distinguish the cluster from the background. We find a flat LF with a slope of \alpha = -1.14 \pm 0.12 for M_V>-14 mag, when fitting a power law to the completeness-corrected galaxy number counts. When plotting the central surface brightness of a Sersic model vs. the galaxy magnitude, we find a continuous relation for magnitudes -20<M_V<-10 mag, with only the brightest core galaxies deviating from this relation, in agreement with previous studies of other clusters. In a size-luminosity diagram of early-type galaxies from a range of environments, we observe that R_eff slowly decreases with decreasing luminosity for -21<M_V<-13 mag and decreases more rapidly at fainter magnitudes. This trend continues to the ultra-faint Local Group dwarf galaxies (M_V~-4 mag). The continuous central surface brightness vs. absolute magnitude relation and the smooth relation in the size-luminosity diagram over a wide range of magnitudes are consistent with the interpretation of dwarf galaxies and more massive elliptical galaxies being one family of objects with gradually changing structural properties. The most massive core galaxies and the rare cE galaxies are the only exceptions.Comment: 14 pages, 10 figures, 4 tables, accepted for publication in A&

Fractionation of potentially toxic elements in urban soils from five European cities by means of a harmonised sequential extraction procedure

The revised (four-step) BCR sequential extraction procedure has been applied to fractionate the chromium, copper, iron, manganese, nickel, lead and zinc contents in urban soil samples from public-access areas in five European cities. A preliminary inter-laboratory comparison was conducted and showed that data obtained by different laboratories participating in the study were sufficiently harmonious for comparisons to be made between cities and land types (e.g. parks, roadside, riverbanks, etc.). Analyte recoveries by sequential extraction, with respect to direct aqua regia digestion, were generally acceptable (100 ± 15%). Iron, nickel and, at most sites, chromium were found mainly in association with the residual phase of the soil matrix. Copper was present in the reducible, oxidisable and residual fractions, whilst zinc was found in all four sequential extracts. Manganese was strongly associated with reducible material as, in some cities, was lead. This is of concern because high lead concentrations were present in some soils (>500 mg kg−1) and the potential exists for remobilisation under reducing conditions. As would be expected, extractable metal contents were generally highest in older, more heavily industrialised cities. Copper, lead and zinc showed marked (and often correlated) variations in concentrations between sites within the same city whereas manganese and, especially, iron, did not. No overall relationships were, however, found between analyte concentrations and land use, nor between analyte partitioning and land use