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Background: We aim to describe the health-related quality of life of informal carers and their experiences of primary care. Methods: Responses from the 2011-12 English General Practice Patient Survey, including 195,364 informal carers, were analysed using mixed effect logistic regressions controlling for age, gender, ethnicity and social deprivation to describe carer health-related quality of life (mobility, self-care, usual activities, pain, and anxiety/depression, measured using EQ-5D) and primary care experience (access, continuity and communication). Results: Informal carers reported poorer health-related quality of life than non-carers of similar age, gender, ethnicity and social deprivation. Increasing caring commitment was associated with worse EQ-5D scores, with carers of 50+ hours a week scoring 0.05 points lower than non-carers (95 % CI 0.05 to 0.04), equivalent to 18 fewer days of full health annually. Considering each domain of EQ-5D separately, carers of 50+ hours/week were more likely to report pain OR = 1.53 (1.50-1.57), p < 0.0001, and anxiety/depression OR = 1.69 (1.66-1.73), p < 0.0001, than non-carers. Younger carers scored lower on EQ-5D than non-carer peers but the converse was true among over-85s. In the most deprived areas carers reported the equivalent of 37 fewer days of full health annually than carers in the most affluent areas. On average, carers reported poorer patient experiences in all areas of primary care than non-carers (odds ratios 0.84-0.97), with this difference being most marked in the domain of access. Conclusions: Informal carers experience a double disadvantage of poorer health-related quality of life and poorer patient experience in primary care. We find no evidence for health benefits of caregiving. We recommend physicians identify and treat carer health problems, including pain and anxiety/depression, particularly among young, deprived and high time-commitment carers. Improving patient experience for carers, including access to primary care, should be a priority. [ABSTRACT FROM AUTHOR]

We present a new, high-speed technique to track the three-dimensional translation and rotation of non-spherical colloidal particles. We capture digital holograms of micrometer-scale silica rods and sub-micrometer-scale Janus particles freely diffusing in water, and then fit numerical scattering models based on the discrete dipole approximation to the measured holograms. This inverse-scattering approach allows us to extract the position and orientation of the particles as a function of time, along with static parameters including the size, shape, and refractive index. The best-fit sizes and refractive indices of both particles agree well with expected values. The technique is able to track the center of mass of the rod to a precision of 35 nm and its orientation to a precision of 1.5°, comparable to or better than the precision of other 3D diffusion measurements on non-spherical particles. Furthermore, the measured translational and rotational diffusion coefficients for the silica rods agree with hydrodynamic predictions for a spherocylinder to within 0.3%. We also show that although the Janus particles have only weak optical asymmetry, the technique can track their 2D translation and azimuthal rotation over a depth of field of several micrometers, yielding independent measurements of the effective hydrodynamic radius that agree to within 0.2%. The internal and external consistency of these measurements validate the technique. Because the discrete dipole approximation can model scattering from arbitrarily shaped particles, our technique could be used in a range of applications, including particle tracking, microrheology, and fundamental studies of colloidal self-assembly or microbial motion., Engineering and Applied Sciences, Physics

Fitting scattering solutions to time series of digital holograms is a precise way to measure three-dimensional dynamics of microscale objects such as colloidal particles. However, this inverse-problem approach is computationally expensive. We show that the computational time can be reduced by an order of magnitude or more by fitting to a random subset of the pixels in a hologram. We demonstrate our algorithm on experimentally measured holograms of micrometer-scale colloidal particles, and we show that 20-fold increases in speed, relative to fitting full frames, can be attained while introducing errors in the particle positions of 10 nm or less. The method is straightforward to implement and works for any scattering model. It also enables a parallelization strategy wherein random-subset fitting is used to quickly determine initial guesses that are subsequently used to fit full frames in parallel. This approach may prove particularly useful for studying rare events, such as nucleation, that can only be captured with high frame rates over long times., Engineering and Applied Sciences, Physics

Digital holographic microscopy is a fast three-dimensional (3D) imaging tool with many applications in soft matter physics. Recent studies have shown that electromagnetic scattering solutions can be fit to digital holograms to obtain the 3D positions of isolated colloidal spheres with nanometer precision and millisecond temporal resolution. Here we describe the results of new techniques that extend the range of systems that can be studied with fitting. We show that an exact multisphere superposition scattering solution can fit holograms of colloidal clusters containing up to six spheres. We also introduce an approximate and computationally simpler solution, Mie superposition, that is valid for multiple spheres spaced several wavelengths or more from one another. We show that this method can be used to analyze holograms of several spheres on an emulsion droplet, and we give a quantitative criterion for assessing its validity., Engineering and Applied Sciences

The energetics and assembly pathways of small clusters may yield insights into processes occurring at the earliest stages of nucleation. We use a model system consisting of micrometer-sized, spherical colloidal particles to study the structure and dynamics of small clusters, where the number of particles is small (N ≤ 10). The particles interact through a short-range depletion attraction with a depth of a few kBT. We describe two methods to form colloidal clusters, one based on isolating the particles in microwells and another based on directly assembling clusters in the gas phase using optical tweezers. We use the first technique to obtain ensemble-averaged probabilities of cluster structures as a function of N. These experiments show that clusters with symmetries compatible with crystalline order are rarely formed under equilibrium conditions. We use the second technique to study the dynamics of the clusters, and in particular how they transition between free-energy minima. To monitor the clusters we use a fast three-dimensional imaging technique, digital holographic microscopy, that can resolve the positions of each particle in the cluster with 30–45 nm precision on millisecond timescales. The real-space measurements allow us to obtain estimates for the lifetimes of the energy minima and the transition states. It is not yet clear whether the observed dynamics are relevant for small nuclei, which may not have sufficient time to transition between states before other particles or clusters attach to them. However, the measurements do provide some glimpses into how systems containing a small number of particles traverse their free-energy landscape., Engineering and Applied Sciences