Deformation of the contact line around spherical particles bound at anisotropic fluid interfaces

When a particle adsorbs at a liquid interface, the 3-phase contact line geometry depends on the shape of the particle and of the liquid interface. The shape of the contact line is the key to controlling capillary forces among particles, and is therefore a useful means to direct assembly of interfacial particles. We measured the shape of the contact line around millimeter-sized PDMS-coated glass spheres at water/air interfaces with anisotropic shapes. We studied the advancing and receding conditions separately. We focused on interfaces with a cylindrical shape, where the predominant deformation of the meniscus and the contact line both have quadrupolar cos(2ϕ) symmetry. We related the measured magnitude of the quadrupolar deformation to the applied vertical force on the sphere and the interface's deviatoric curvature, D0. For modest curvature (D0 < 0.1 × sphere radius), our results agree with the theoretical prediction for free particles. At higher curvature, the measurements exceed the theory. The theory appears to apply even when there is contact-angle hysteresis, as long as the measured contact angle is used rather than the equilibrium (Young-Dupré) angle. The magnitude of the quadrupolar deformation depends on the applied force. Together, these results show the range of validity of the theory

Effects of antiplatelet therapy on stroke risk by brain imaging features of intracerebral haemorrhage and cerebral small vessel diseases: subgroup analyses of the RESTART randomised, open-label trial

Background Findings from the RESTART trial suggest that starting antiplatelet therapy might reduce the risk of recurrent symptomatic intracerebral haemorrhage compared with avoiding antiplatelet therapy. Brain imaging features of intracerebral haemorrhage and cerebral small vessel diseases (such as cerebral microbleeds) are associated with greater risks of recurrent intracerebral haemorrhage. We did subgroup analyses of the RESTART trial to explore whether these brain imaging features modify the effects of antiplatelet therapy

Effects of fluoxetine on functional outcomes after acute stroke (FOCUS): a pragmatic, double-blind, randomised, controlled trial

Background Results of small trials indicate that fluoxetine might improve functional outcomes after stroke. The FOCUS trial aimed to provide a precise estimate of these effects. Methods FOCUS was a pragmatic, multicentre, parallel group, double-blind, randomised, placebo-controlled trial done at 103 hospitals in the UK. Patients were eligible if they were aged 18 years or older, had a clinical stroke diagnosis, were enrolled and randomly assigned between 2 days and 15 days after onset, and had focal neurological deficits. Patients were randomly allocated fluoxetine 20 mg or matching placebo orally once daily for 6 months via a web-based system by use of a minimisation algorithm. The primary outcome was functional status, measured with the modified Rankin Scale (mRS), at 6 months. Patients, carers, health-care staff, and the trial team were masked to treatment allocation. Functional status was assessed at 6 months and 12 months after randomisation. Patients were analysed according to their treatment allocation. This trial is registered with the ISRCTN registry, number ISRCTN83290762. Findings Between Sept 10, 2012, and March 31, 2017, 3127 patients were recruited. 1564 patients were allocated fluoxetine and 1563 allocated placebo. mRS data at 6 months were available for 1553 (99·3%) patients in each treatment group. The distribution across mRS categories at 6 months was similar in the fluoxetine and placebo groups (common odds ratio adjusted for minimisation variables 0·951 [95% CI 0·839–1·079]; p=0·439). Patients allocated fluoxetine were less likely than those allocated placebo to develop new depression by 6 months (210 [13·43%] patients vs 269 [17·21%]; difference 3·78% [95% CI 1·26–6·30]; p=0·0033), but they had more bone fractures (45 [2·88%] vs 23 [1·47%]; difference 1·41% [95% CI 0·38–2·43]; p=0·0070). There were no significant differences in any other event at 6 or 12 months. Interpretation Fluoxetine 20 mg given daily for 6 months after acute stroke does not seem to improve functional outcomes. Although the treatment reduced the occurrence of depression, it increased the frequency of bone fractures. These results do not support the routine use of fluoxetine either for the prevention of post-stroke depression or to promote recovery of function. Funding UK Stroke Association and NIHR Health Technology Assessment Programme

Evolution of Hierarchical Structures in Polyelectrolyte–Micelle Coacervates

We investigated the temperature-induced liquid–liquid phase separation (coacervation) of polyelectrolyte (PE)–micelle systems and the structure of the resultant coacervates. Dynamic light scattering, small angle neutron scattering and cryo-transmission electron microscopy (DLS, SANS, Cryo-TEM) were used to examine the evolution of complex structure up to the point of temperature-induced coacervation and beyond. Three diffusional modes, seen in the single phase samples and in the coexisting coacervated supernatant phases were attributed respectively to free micelles, PE–micelle complexes, and aggregates thereof. They corresponded to SANS Guinier region slopes yielding Rg [similar] 4 nm (micelles) and Rg [similar] 50 nm (unresolved complexes and aggregates). Cryo-TEM images of coacervates indicated how these subunits are organized within dense and dilute coacervate domains at larger length scales. Taken together, these results are understood to arise from the requirements of overall charge neutralization, and ion-pairing and counterion release during coacervation. We conclude that a polyelectrolyte:micelle system at incipient coacervation with charge stoichiometry ([+]/[−] \u3e 1) donates excess polycations to other complexes in solution. In the coacervate, a similar disproportionation but at different length scales ejects excess polycations and their counterions into dilute domains. In both phases, association and desolvation are driven by counterion release, enhanced chain configurational entropy, and ion-pairing. These enthalpic and entropic forces operating in both phases could explain the structural similarities between soluble aggregates and coacervate dense domains

Change of Line Tension in Phase-Separated Vesicles upon Protein Binding

We measured the effect of a model membrane-binding protein on line tension and morphology of phase-separated lipid-bilayer vesicles. We studied giant unilamellar vesicles composed of a cholesterol/dioleoylphosphatidylcholine/palmitoylsphingomyelin mixture and a controlled mole fraction of a Ni-chelating lipid. These vesicles exhibited two coexisting fluid-phase domains at room temperature. Owing to the line tension, σ, between the two phases, the boundary between them was pulled like a purse string so that the smaller domain formed a bud. While observing the vesicles in a microscope, histidine-tagged green fluorescent protein was added, which bound to the Ni-chelating lipid. As protein bound, the vesicle shape changed and the length of the phase boundary increased. The change in morphology was attributed to a reduction of σ between the two phases because of preferential accumulation of histidine-tagged green fluorescent protein–Ni-chelating lipid clusters at the domain boundary. Greater reductions of σ were found in samples with higher concentrations of Ni-chelating lipid; this trend provided an estimate of the binding energy at the boundary, approximately <i>k</i>_B<i>T</i>. The results show how domain boundaries can lead to an accumulation of membrane-binding proteins at their boundaries and, in turn, how proteins can alter line tension and vesicle morphology