Diffusiophoresis in non-adsorbing polymer solutions: the Asakura-Oosawa model and stratification in drying films

A colloidal particle placed in an inhomogeneous solution of smaller non-adsorbing polymers will move towards regions of lower polymer concentration, in order to reduce the free energy of the interface between the surface of the particle and the solution. This phenomenon is known as diffusiophoresis. Treating the polymer as penetrable hard spheres, as in the Asakura-Oosawa model, a simple analytic expression for the diffusiophoretic drift velocity can be obtained. In the context of drying films we show that diffusiophoresis by this mechanism can lead to stratification under easily accessible experimental conditions. By stratification we mean spontaneous formation of a layer of polymer on top of a layer of the colloid. Transposed to the case of binary colloidal mixtures, this offers an explanation for the stratification observed recently in these systems [A. Fortini et al, Phys. Rev. Lett. 116, 118301 (2016)]. Our results emphasise the importance of treating solvent dynamics explicitly in these problems, and caution against the neglect of hydrodynamic interactions or the use of implicit solvent models in which the absence of solvent backflow results in an unbalanced osmotic force which gives rise to large but unphysical effects.Comment: 11 pages, 6 figure

Space capsule ejection assembly Patent

Describing assembly for opening stabilizing and decelerating flaps of flight capsules used in space researc

Tutors as learners: overcoming barriers to learning ICT skills

This paper explores the use of ICT to provide distance training for UK Open University (OU) Associate lecturers (ALs) and identifies the range of outcomes and issues which emerged. There is an increasing demand from many of our students for the University to provide more facilities and functions (both administrative or course-related) online or by electronic mail. To this end the University has attempted to increase the awareness of these computing-related issues with ALs by offering various methods of increasing ICT skills. One programme involved a contingent of ALs participating in an online short course. This paper will summarise some of the qualitative feedback along with the quantitative results in order to establish whether this course did indeed assist in tutors gaining some new computing skills. Furthermore, tutors made many additional comments about the process of learning and the experience of being a learner. Many of the issues raised were found to be important when designing a programme of study for those who take courses as a form of staff development

21st Century emissions technology - a review

This article reviews the 21st Century Emissions Technology conference held by Institute of Mechanical Engineers (in December 2000) and summarises the latest developments in emissions control

On the electrical double layer contribution to the interfacial tension of protein crystals

We study the electrical double layer at the interface between a protein crystal and a salt solution or a dilute solution of protein, and estimate the double layer's contribution to the interfacial tension of this interface. This contribution is negative and decreases in magnitude with increasing salt concentration. We also consider briefly the interaction between a pair of protein surfaces.Comment: 6 pages, 3 figures, revtex

Observation and Modeling of Coronal "Moss" With the EUV Imaging Spectrometer on Hinode

Observations of transition region emission in solar active regions represent a powerful tool for determining the properties of hot coronal loops. In this Letter we present the analysis of new observations of active region moss taken with the Extreme Ultraviolet Imaging Spectrometer (EIS) on the \textit{Hinode} mission. We find that the intensities predicted by steady, uniformly heated loop models are too intense relative to the observations, consistent with previous work. To bring the model into agreement with the observations a filling factor of about 16% is required. Furthermore, our analysis indicates that the filling factor in the moss is nonuniform and varies inversely with the loop pressure

Hydrogen: tomorrow's fuel or just hot air? The Icelandic Experience

Hydrogen is once again in the limelight, with rising fuel prices, the search for fuels beyond petrol and diesel is being debated even more hotly. The European fuel cell bus trial has been extended by one year and there has been much talk about the potential for hydrogen powered vehicles working during the London Olympics. These would bring even more people into contact with future fuels on perhaps boats and buses. The Department for Transport (UK) has also announced a major call for more research on hydrogen, clearly indicating a focus on both vehicles and infrastructure. So what is all the hype about this fuel and what does it mean for transport engineers in general? This article tries to address some of those issues by trying to understand hydrogen, and then by looking at how the Icelanders have used this remarkable fuel. There may be some meaningful lessons for the UK and other countries interested in implementing hydrogen

Monolayers of 3He on the Surface of Bulk Superfluid 4He

We have used quantum evaporation to investigate the two-dimensional fermion system that forms at the free surface of (initially isotopically pure) 4He when small quantities of 3He are added to it. By measuring the first-arrival times of the evaporated atoms, we have determined that the 3He-3He potential in this system is V_3S/k_B=(0.23+/-0.02) K nm^2 (repulsive) and estimated a value of m_3S=(1.53+/-0.02)m_3 for the zero-coverage effective mass. We have also observed the predicted second layer-state which becomes occupied once the first layer-state density exceeds about 0.6 monolayers.Comment: 2 pages, 3 figures. Submitted to Proc. LT-22 (1999) to appear in Physica