Phase diagram for a mixture of colloids and polymers with equal size

We present the phase diagram of a colloid-polymer mixture in which the radius a of the colloidal spheres is approximately the same as the radius R of a polymer coil (q=R/a1). A three-phase coexistence region is experimentally observed, previously only reported for colloid-polymer mixtures with smaller polymer chains (q0.6). A recently developed generalized free-volume theory (GFVT) for mixtures of hard spheres and non-adsorbing excluded-volume polymer chains gives a quantitative description of the phase diagram. Monte Carlo simulations also agree well with experimen

Synthesis and self-assembly of giant porphyrin discs

Contains fulltext : 13852.pdf (publisher's version ) (Open Access

Rigid sphere transport through a colloidal gas-liquid interface

In this paper we report on the gravity-driven transport of rigid spheres of various sizes through the fluid-fluid interface of a demixed colloid-polymer mixture. Three consecutive stages can be distinguished: (i) the sphere approaches the interface by sedimenting through the polymer-rich phase, (ii) it is subsequently transported to the colloid-rich phase and (iii) it moves away from the interface. The spheres are covered by a thin wetting film of the colloidrich phase, to which they are eventually transported. The ultralow interfacial tension in these phase-separating mixtures results in very small capillary forces so that the process takes place in the low Reynolds regime. Moreover, it enables the investigation of the role of capillary waves in the process. Depending on the Bond number, the ratio between gravitational force and capillary force acting on the sphere, different transport configurations are observed. At low Bond numbers, the drainage transport configuration, with a dominant capillary force, is encountered. At high Bond numbers, spheres are transported through the tailing configuration, with a dominant gravitational force. By varying the sphere diameter, we observe both transport configurations as well as a crossover regime in a single experimental system. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft

El Sistema electoral a Austràlia : convivència en la complexitat democràtica

L'objectiu d'aquestes pàgines és descriure el desenvolupament del sistema electoral a Austràlia des de la perspectiva que comporta tant la seva complexitat com flexibilitat. Una complexitat a què s'ha acostumat el ciutadà australià fruit de la naturalesa federal del país. En comptes que les modificacions en les regles del joc democràtic facin perillar la credibilitat del poder polític, Austràlia sempre ha conservat una ferma evolució política a partir dels eixos de buscar la millor representació ciutadana. Aquesta diversitat i sofisticació constant no han portat a la ciutadania a una desinhibició de les regles democràtiques, sinó que s'ha combinat amb una participació electoral obligada dels ciutadans que els implica directament amb el seu sistema polític

Morphology and kinetics of phase separating transparent xanthan – colloid mixtures

We present a study on the morphology and kinetics of depletion-induced phase separation in aqueous xanthan-colloid mixtures with light microscopy and small angle light scattering (SALS), using fluorinated colloids with a refractive index close to that of water to prevent complications of multiple scattering. Microscopy with the direction of observation perpendicular to gravity enabled us to observe the development of the microstructure during the entire phase separation process including the formation of a macroscopic interface. Bicontinuous structures typical of a spinodal decomposition mechanism were observed at early times. These structures coarsened in time until hydrodynamic flow resulted in lane formation. Close to the binodal, a nucleation-and-growth mechanism was observed with formation of droplets. The coarsening kinetics were studied in more detail with SALS and turbidity measurements. Above polysaccharide concentrations at which entanglements become dominant, a slower coarsening and macroscopic phase separation were found because of the high continuous phase viscosity

Achieving Self-Directed Integrated Cancer Aftercare (ASICA) in melanoma: protocol for a randomised patient-focused pilot trial of delivering the ASICA intervention as a means to earlier detection of recurrent and second primary melanoma.

BACKGROUND: Melanoma is common; 15,906 people in the UK were diagnosed with melanoma in 2015 and incidence has increased fivefold in 30 years. Melanoma affects old and young people, with poor prognosis once metastatic. UK guidelines recommend people treated for cutaneous melanoma receive extended outpatient, hospital follow up to detect recurrence or new primaries. Such follow up of the growing population of melanoma survivors is burdensome for both individuals and health services. Follow up is important since approximately 20% of patients with early-stage melanoma experience a recurrence and 4-8% develop a new primary; the risk of either is highest in the first 5 years. Achieving Self-directed Integrated Cancer Aftercare (ASICA) is a digital intervention to increase total-skin-self-examination (TSSE) by people treated for melanoma, with usual follow up. METHODS: We aim to recruit 240 adults with a previous first-stage 0-2C primary cutaneous melanoma, from secondary care in North-East Scotland and the East of England. Participants will be randomised to receive the ASICA intervention (a tablet-based digital intervention to prompt and support TSSE) or control group (treatment as usual). Patient-reported and clinical data will be collected at baseline, including the modified Melanoma Worry Scale (MWS), the Hospital Anxiety and Depression Scale (HADs), the EuroQoL 5-dimension 5-level questionnaire (EQ-5D-5 L), and questions about TSSE practice, intentions, self-efficacy and planning. Participants will be followed up by postal questionnaire at 3, 6 and 12 months following randomization, along with a 12-month review of clinical data. The primary timepoint for outcome analyses will be12 months after randomisation. DISCUSSION: If the ASICA intervention improves the practice of TSSE in those affected by melanoma, this may lead to improved psychological well-being and earlier detection of recurrent and new primary melanoma. This could impact both patients and National Health Service (NHS) resources. This study will determine if a full-scale randomised controlled trial can be undertaken in the UK NHS to provide the high-quality evidence needed to determine the effectiveness of the intervention. ASICA is a pilot study evaluating the effectiveness of the practice of digitally supported TSSE in those affected by melanoma. TRIAL REGISTRATION: Clinical Trials.gov, NCT03328247 . Registered on 1 November 2017

Lethal traffic jam

The antibiotics chloramphenicol and tetracycline were discovered in the late 1940s shortly after the introduction of penicillin (1). Elucidation of the structure of the ribosome (2, 3) revealed how they bind to this target structure and inhibit protein synthesis. On page 753 in this issue, van Stelten et al. (4) demonstrate another mode of action for these antibiotics, involving the destruction of a complex that allows proteins to be translocated across (or into) the bacterial membrane (5

Dynamics in Concentrated Colloidal Suspensions

This thesis reports results from a study of particle dynamics in colloidal glasses in the absence and presence of a gravitational field. It also investigates the reentrant glass transition. All the experimental results are obtained after a real space analysis using a confocal scanning laser microscopy as experimental technique that significantly widens the time window over which colloidal systems can be studied. A fluorescent recovery of bleached regions in concentrated suspensions of fluorescent colloidal hard spheres was followed in real space. This method provided data for mean squared particle displacements up to time scales that are three orders of magnitude beyond those available by present experimental techniques like dynamic or static light scattering. It was shown that, above the (hard sphere) glass transition density, particles move over distances on the order of their own diameter on time scales of 106 to 108 Brownian times. Moreover, the mean squared displacement, , showed power-law behavior over seven time (?) decades: ??^ (0.30?0.05). This behavior is different from earlier observations by dynamic light scattering. It was argued that these differences are caused by gravity effects. Further on, the influence of gravity on the long-time behavior of the mean squared displacement in glasses of colloidal hard spheres was studied. For the first time, a significant influence of gravity on the mean squared displacements of the particles was presented. In particular, the systems which are glasses under gravity (with a gravitational length on the order of tens of micrometers) showed anomalous diffusion over several decades in time if the gravitational length is increased by an order of magnitude. No influence of gravity was observed in systems below the glass transition density. It was shown that this behavior is caused by gravity dramatically accelerating aging in colloidal hard sphere glasses. This behavior explained the observation that colloidal hard sphere systems which are a glass on earth rapidly crystallize in space. A quantitative analysis of the structure and dynamics of concentrated suspensions of colloids in which the magnitude of the short range attractive potential was increased by adding non-adsorbing polymers was done. These systems undergo a reentrant glass transition upon increasing polymer concentration. The melting of the glass is accompanied by significant changes in the displacement distribution and its moments. However, no significant variations were detected in the shapes of the displacement distributions. Moreover, structural correlation functions and the magnitude of local density fluctuations did not vary significantly between the glass states and the fluid. The influence of gravity on long-time diffusion in glasses was also studied using a new experimental setup that allowed a real space determination of particle displacements in directions parallel and perpendicular to the gravity field. Dispersions of particles were prepared in different solvent combinations that provide different gravitational lengths. It was shown that the direction of the external gravitational field couples to the particle dynamics and influences the values of mean square particle displacements

The interface in demixed colloid-polymer systems: wetting, waves and droplets

Phase transitions in colloid-polymer mixtures have attracted a large amount of attention over the last 20 years (W. C. K. Poon, J. Phys.: Condens. Matter, 2002, 14, R859; R. Tuinier, J. Rieger and C. G. de Kruif, Adv. Colloid Interface Sci., 2003, 103, 1). By comparison, the interfacial tension between the coexisting phases has received little attention. Here, we show that the ultralow interfacial tension in fluid-fluid demixed colloid-polymer systems, which is roughly one million times smaller than in ordinary liquids, manifests itself in a wide variety of interface characteristics and processes. Discussed are the interfacial wetting behaviour close to a hard wall, the thermal capillary waves at the free interface and the process of droplet coalescence and breakup. These subjects can be studied in a single experiment by combining modern soft matter chemistry and laser scanning confocal microscopy. This combination allows a further exploration of a broad range of interface issues. © The Royal Society of Chemistry