The motion of a drop in a rigid surface

The assumptions of a region of slip near a moving contact line (to remove the force singularity) and a constant contact angle are used to obtain the equation for the shape of a thin drop of liquid resting on a rigid plane. Three asymptotic expansions are matched together to obtain an expression for the rate at which the drop spreads. Some cases of sliding motion are also examined. Although the technique is presented here for thin drops only, it can also be applied to drops of arbitrary size

Free surface flows with large slopes: beyond lubrication theory

The description of free surface flows can often be simplified to thin film (or lubrication) equations, when the slopes of the liquid-gas interface are small. Here we present a long wavelength theory that remains fully quantitative for steep interface slopes, by expanding about Stokes flow in a wedge. For small capillary numbers, the variations of the interface slope are slow and can be treated perturbatively. This geometry occurs naturally for flows with contact lines: we quantify the difference with ordinary lubrication theory through a numerical example and analytically recover the full Cox-Voinov asymptotic solution.Comment: 4 pages, 3 figure

Hydrodynamic theory of de-wetting

A prototypical problem in the study of wetting phenomena is that of a solid plunging into or being withdrawn from a liquid bath. In the latter, de-wetting case, a critical speed exists above which a stationary contact line is no longer sustainable and a liquid film is being deposited on the solid. Demonstrating this behavior to be a hydrodynamic instability close to the contact line, we provide the first theoretical explanation of a classical prediction due to Derjaguin and Levi: instability occurs when the outer, static meniscus approaches the shape corresponding to a perfectly wetting fluid

Innovating for improved healthcare: Sociotechnical and innovation systems perspectives and lessons from the NHS

Healthcare systems with limited resources face rising demand pressures. Healthcare decision-makers increasingly recognise the potential of innovation to help respond to this challenge and to support high-quality care. However, comprehensive and actionable evidence on how to realise this potential is lacking. We adopt sociotechnical systems and innovation systems theoretical perspectives to examine conditions that can support and sustain innovating healthcare systems. We use primary data focussing on England (with 670 contributions over time) and triangulate findings against globally-relevant literature. We discuss the complexity of factors influencing an innovating healthcare system’s ability to support the development and uptake of innovations and share practical learning about changes in policy, culture, and behaviour that could support system improvement. Three themes are examined in detail: skills, capabilities, and leadership; motivations and accountabilities; and collaboration and coordination. We also contribute to advancing applications of sociotechnical systems thinking to major societal transformation challenges

Take the sex out of STI screening! Views of young women on implementing chlamydia screening in General Practice

<p>Abstract</p> <p>Background</p> <p>Australia is developing a chlamydia screening program. This study aimed to determine the attitudes of young women to the introduction of chlamydia screening in Australian General Practice.</p> <p>Methods</p> <p>In-depth face-to-face interviews with 24 young women from across Victoria, Australia, attending a randomly selected sample of general practices.</p> <p>Results</p> <p>Young women reported that they would accept age-based screening for chlamydia in general practice, during both sexual-health and non-sexual-health related consultations. Trust in their general practitioner (GP) was reported to be a major factor in the acceptability of chlamydia screening. The women felt chlamydia screening should be offered to <it>all </it>young women rather than targeted at "high risk" women based on sexual history and they particularly emphasised the importance of normalising chlamydia screening. The women reported that they did not want to be asked to provide a sexual history as part of being asked to have a chlamydia test. Some reported that they would lie if asked how many partners they had had</p> <p>Conclusion</p> <p>Women do not want a sexual history taken when being asked to have a chlamydia test while attending a general practitioner. They prefer the offer of chlamydia screening to be based on age rather than assessment of sexual risk. Chlamydia screening needs to be normalised and destigmatised.</p

Disjoining Potential and Spreading of Thin Liquid Layers in the Diffuse Interface Model Coupled to Hydrodynamics

The hydrodynamic phase field model is applied to the problem of film spreading on a solid surface. The disjoining potential, responsible for modification of the fluid properties near a three-phase contact line, is computed from the solvability conditions of the density field equation with appropriate boundary conditions imposed on the solid support. The equation describing the motion of a spreading film are derived in the lubrication approximation. In the case of quasi-equilibrium spreading, is shown that the correct sharp-interface limit is obtained, and sample solutions are obtained by numerical integration. It is further shown that evaporation or condensation may strongly affect the dynamics near the contact line, and accounting for kinetic retardation of the interphase transport is necessary to build up a consistent theory.Comment: 14 pages, 5 figures, to appear in PR

Defect chaos and bursts: Hexagonal rotating convection and the complex Ginzburg-Landau equation

We employ numerical computations of the full Navier-Stokes equations to investigate non-Boussinesq convection in a rotating system using water as the working fluid. We identify two regimes. For weak non- Boussinesq effects the Hopf bifurcation from steady to oscillating (whirling) hexagons is supercritical and typical states exhibit defect chaos that is systematically described by the cubic complex Ginzburg-Landau equation. For stronger non-Boussinesq effects the Hopf bifurcation becomes subcritical and the oscil- lations exhibit localized chaotic bursting, which is modeled by a quintic complex Ginzburg-Landau equation

Asymptotic theory for a moving droplet driven by a wettability gradient

An asymptotic theory is developed for a moving drop driven by a wettability gradient. We distinguish the mesoscale where an exact solution is known for the properly simplified problem. This solution is matched at both -- the advancing and the receding side -- to respective solutions of the problem on the microscale. On the microscale the velocity of movement is used as the small parameter of an asymptotic expansion. Matching gives the droplet shape, velocity of movement as a function of the imposed wettability gradient and droplet volume.Comment: 8 fig

Telling partners about chlamydia: how acceptable are the new technologies?

BACKGROUND Partner notification is accepted as a vital component in the control of chlamydia. However, in reality, many sexual partners of individuals diagnosed with chlamydia are never informed of their risk. The newer technologies of email and SMS have been used as a means of improving partner notification rates. This study explored the use and acceptability of different partner notification methods to help inform the development of strategies and resources to increase the number of partners notified. METHODS Semi-structured telephone interviews were conducted with 40 people who were recently diagnosed with chlamydia from three sexual health centres and two general practices across three Australian jurisdictions. RESULTS Most participants chose to contact their partners either in person (56%) or by phone (44%). Only 17% chose email or SMS. Participants viewed face-to-face as the "gold standard" in partner notification because it demonstrated caring, respect and courage. Telephone contact, while considered insensitive by some, was often valued because it was quick, convenient and less confronting. Email was often seen as less personal while SMS was generally considered the least acceptable method for telling partners. There was also concern that emails and SMS could be misunderstood, not taken seriously or shown to others. Despite these, email and SMS were seen to be appropriate and useful in some circumstances. Letters, both from the patients or from their doctor, were viewed more favourably but were seldom used. CONCLUSION These findings suggest that many people diagnosed with chlamydia are reluctant to use the new technologies for partner notification, except in specific circumstances, and our efforts in developing partner notification resources may best be focused on giving patients the skills and confidence for personal interaction.The study was funded by the Australian Federal Government Department of Health and Ageing Chlamydia Pilot Program of Targeted Grants

Understanding the confluence of injury and obesity in a Grade 2 obesity and above population

Objective: Obesity and injury are major inter-related public health challenges. The objective of this study was to explore the perceptions of injury in people with severe obesity. Methods: A cross-sectional design was employed to capture injury perception and lifestyle habits via questionnaires. Weight (kg) and height (m) were measured by clinicians for patients attending a weight loss group program. Univariate, chi-square, ANOVA and ordinal regression analyses were undertaken. Results: There were 292 participants (67.1% female), mean age 49.3 years and Body Mass Index 47.2 kg/m2 (range 30.7–91.9 kg/m2). Concern about having an injury was found in 83%, and 74.2% thought that weight would increase the likelihood of injury. A greater concern of being injured at baseline was associated with less weight loss at eight weeks (F=3.567; p=0.03). Depression, anxiety and sleepiness score were higher in those who reported greater ‘Concern about having an injury’. Conclusions: People with obesity fear injury and falling, which limits their willingness to exercise. Anxiety symptoms appear to exacerbate this connection. Implications for public health: In individuals with obesity, anxiety, sleepiness and depression are associated with a fear of being injured. Addressing fear and reducing anxiety may decrease barriers to participating in physical activity