Summary
Background: The burden on caregivers providing support to atrial fibrillation (AF) patients has not been evaluated.
Objective: To examine the interrelationship between unpaid caregiver, ...patient and thromboprophylaxis characteristics and caregiver burden in AF.
Methods: We conducted a cross‐sectional survey study of AF patient‐caregiver dyads recruited from cardiology clinics at an urban teaching hospital. Eligible patients had a diagnosis of AF, received thromboprophylaxis to prevent stroke, lived in the community and had an adult, unpaid, English‐speaking caregiver. Hierarchical multivariate regression was used to evaluate the association between caregiver, patient and thromboprophylaxis characteristics and caregiver burden as measured by the ‘Caregiver Reaction Assessment’ (CRA).
Results: Eighty patient‐caregiver dyads were surveyed. The mean ± standard deviation scores for each CRA domain were ‘Disrupted schedule’ (2.4 ± 1.0), ‘Financial problems’ (2.1 ± 0.8), ‘Lack of family support’ (1.9 ± 0.7), ‘Health problems’ (1.9 ± 0.7) and ‘Self‐esteem’ (0.9 ± 0.5). Significantly greater caregiver burden due to ‘Disrupted schedule’ was seen in those spending > 4 h/week providing care and when caring for frail, sick or disabled patients, with higher CHADS2 scores and requiring help with their medications. ‘Financial problems’ burden scores were significantly associated with caring for frail patients and those requiring more frequent office follow‐up. ‘Lack of family support’ scores were inversely associated with having somebody else to help provide care and increased as patients CHADS2 score increased. Lower ‘Health problem’ burden scores were associated with female gender and higher scores with the need to spend > 4 h/week providing care.
Conclusion: The greatest burden to caregivers of AF patients occurs due to schedule disruption.
► The flow of a gravity-driven thin liquid film over topography is explored. ► The focus is the interplay between inertia and an applied normal electric field. ► Results are presented for flow over ...both two- and three-dimensional topography. ► Electric fields are able to suppress the free-surface capillary waves that arise. ► Explanation is based on competition between capillary pressure and Maxwell stress.
The flow of a gravity-driven thin liquid film over a substrate containing topography, in the presence of a normal electric field, is investigated. The liquid is assumed to be a perfect conductor and the air above it a perfect dielectric. Of particular interest is the interplay between inertia, for finite values of the Reynolds number, Re, and electric field strength, expressed in terms of the Weber number, We, on the resultant free-surface disturbance away from planarity. The hydrodynamics of the film are modelled via a depth-averaged form of the Navier–Stokes equations which is coupled to a Fourier series separable solution of Laplace’s equation for the electric potential: detailed steady-state solutions of the coupled equation set are obtained numerically.
The case of two-dimensional flow over different forms of discrete and periodically varying spanwise topography is explored. In the case of the familiar free-surface capillary peaks and depressions that arise for steep topography, and become more pronounced with increasing Re, greater electric field strength affects them differently. In particular, it is found that for topography heights commensurate with the long-wave approximation: (i) the capillary ridge associated with a step-down topography at first increases before decreasing, both monotonically, with increasing We and (ii) the free-surface hump which arises at a step-up topography continues to increase monotonically with increasing We, the increase achieved being smaller the larger the value of Re.
A series of results for the more practically relevant problem of three-dimensional film flow over substrate containing a localised square trench topography is provided. These exhibit behaviour and features consistent with those observed for two-dimensional flow, in that as We is increased the primary free-surface capillary ridges and depressions are at first enhanced, with a corresponding narrowing, before becoming suppressed. In addition, it is found that, while the well-known horse-shoe shaped disturbance characteristic of such flows continues to persist with increasing Re in the absence of an electric field, when the latter is present and We increased in value the associated comet tail disappears as does the related downstream surge. The phenomenon is explained with reference to the competition between the corresponding capillary pressure and Maxwell stress distributions.
We study the influence of an undulated bottom profile on steady two-dimensional gravity driven film flows of a Newtonian fluid. Traditional approaches towards this topic are based on lubrication ...approximation, on special perturbation methods or on numerics. However, lubrication approximation and perturbation methods deliver acceptable results only within their range of validity. Especially if the bottom is strongly undulated, conventional analytical methods fail. Neither can the classical separation solution of the biharmonic equation in terms of an infinite series be applied because of massive convergence problems if the waviness exceeds a limit. In this paper we present an analytical method based on a representation of the solution of Stokes equations in terms of holomorphic functions. Applying the complex function theory, convergence problems are avoided and the problem is reduced to solving ordinary differential equations and integral equations at the boundaries only. Our calculations show the creation, formation and evolution of vortices if waviness and film thickness exceed critical values. A detailed parameter study on size and strength of the vortices is shown. Moreover, we present a quantitative study on the effect of the vortices on the flow rate. Our calculations show very good agreement with experimental results. PUBLICATION ABSTRACT
An elegant four-dimensional Lorentz-invariant first-integral of the energy–momentum equations for viscous flow, comprised of a single tensor equation, is derived assuming a flat space–time and that ...the energy–momentum tensor is symmetric. It represents a generalisation of corresponding Galilei-invariant theory associated with the classical incompressible Navier–Stokes equations, with the key features that the first-integral: (i) while taking the same form, overcomes the incompressibility constraint associated with its two- and three-dimensional incompressible Navier–Stokes counterparts; (ii) does not depend at outset on the constitutive fluid relationship forming the energy–momentum tensor. Starting from the resulting first integral: (iii) a rigorous asymptotic analysis shows that it reduces to one representing unsteady compressible viscous flow, from which the corresponding classical Galilei-invariant field equations are recovered; (iv) its use as a solid platform from which to solve viscous flow problems is demonstrated by applying the new general theory to the case of propagating acoustic waves, with and without viscous damping, and is shown to recover the well-known classical expressions for sound speed and damping rate consistent with those available in the open literature, derived previously as solutions of the linearised Navier–Stokes equations.
It is widely accepted that for bodies in turbulent flows a reduction of skin friction can be reached if the surface of the body is provided with small ridges aligned in the local flow direction. This ...surprising and counterintuitive phenomenon is called the shark-skin effect, motivated from the dermal surface morphology of sharks. In the present article we examine the possibility of resistance reduction due to a rippled surface topography in Stokes flow. We especially analyse the influence of wall riblets perpendicular to the flow direction on the mean transport velocity in gravity-driven creeping film flows following the idea that eddies generated in the valleys of the riblets act like fluid roller bearings and hence may reduce drag. Using a theoretical treatment of the Stokes equations with complex function theory, parameter studies with varying flow rate, bottom amplitude and bottom shape are presented. For the given bottom shapes the maximum enhancement of transport velocity is found by optimising the film thickness.
A general rule is derived for the free surface profile of a gravity-driven fluid film on an inclined wall as it flows over a local irregularity, or obstacle, in the present case a trench. Starting ...from an exact analytical solution of Stokes' equations, based on complex function theory, it is proved that the integral of the free surface profile, from its planer asymptotic equilibrium level, vanishes. This general analytical result, which is valid for arbitrary wall irregularities where the spatial extension is small compared to an intrinsic length, is not only an interesting feature in itself but also provides a useful check of the accuracy of numerical schemes that are used to solve such problems. PUBLICATION ABSTRACT
Heat transfer in a plane laminar shear flow configuration consisting of two infinitely long plates orientated parallel to each other is investigated theoretically. The upper plate, which is planar, ...drives the flow; the lower one, which is fixed, has a regular sinusoidally varying profile. A closed form analytical solution for velocity, based on lubrication theory, together with a semi-analytic one for temperature, from application of Ritz’s direct method, is derived for creeping flow. In addition, detailed numerical solutions are obtained from a finite element formulation of the weak form of the governing equations for mass, momentum and energy (temperature) conservation, enabling the effects of inertia to be explored. It is shown that changes in the mean plate separation, that is the geometry, and the level of inertia present affect the local hydrodynamic flow structure in the form of kinematically and inertially induced eddies, respectively. These in turn impact on the local “laminar thermal mixing”, and consequently enhance the global heat transfer. Results are reported for a wide range of Peclét, Reynolds and Nusselt numbers with agreement between the two methods of solution, for the case of creeping flow, found to be extremely good. The key flow features that emerge are
(i)
For creeping flow and varying Peclét number, the thermal field is asymmetric for all values of the Peclét number other than the limiting conditions of zero and infinity, at which extremes the corresponding thermal field is symmetric. In the limit of infinite Peclét number the eddy becomes a basin of fluid at uniform temperature.
(ii)
Global heat transfer in the case of creeping flow, expressed in terms of the Nusselt number, for a given Peclét number increases as the mean plate separation decreases, that is as the local kinematically induced eddy structure becomes more pronounced.
(iii)
There exists a subtle interplay between variations in the mean plate separation and the level of inertia imposed, in that both influence the presence or otherwise of eddies. Starting from a creeping flow condition the introduction of inertia can in addition both enlarge and skew an existing eddy. When this information is condensed to a series of Nusselt number curves the indication is that it should be possible, from a practical standpoint, to find a critical mean plate separation, for a given Peclét number, for which local inertially influenced eddy effects on the global heat transfer are at a minimum.
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