Caged Colloids

Colloidal microcontainers, such as hollow capsules and colloidosomes, have a range of applications, including drug delivery, energy storage, and artificial protocells. In this study, we present a versatile and scalable self-assembly approach for encapsulating cargo particles within well-defined porous membranes or cages. The encapsulation process involves camouflaging cargo within a liquid matrix that serves as a scaffold for satellite particles to form densely packed shells around. These satellites fuse to create self-standing cages, after which the liquid matrix is dissolved, trapping the cargo inside. By adjusting the fusion protocol, we can control the porosity of the cages at various length scales. We demonstrate the potential of this technique by employing functional cargo to showcase transmembrane transport phenomena, such as the delivery and active uptake of nanoparticles

Temperature-dependent internal friction of clay in a cylindrical heat source problem

peer reviewedThe effect of the temperature dependence of the internal friction angle is studied in a boundary value problem simulating the impact of a cylindrical heat source on the soil mass in which it is embedded. This follows a previous study which shows that such temperature dependence may substantially affect the interpretation of thermal failure in laboratory experiments. Even if the thermal increase of the internal friction is quite modest (less than 20% in terms of the critical state parameter, M), it affects quite significantly the effective stress path near the heat source. The effective stress path approaches the yield locus and the critical state at significantly higher principal stress difference values for the variable internal friction than for the M = const case. The 'mean effective stress distance from the critical state' is substantially reduced during heating, which in the case of small perturbations of any parameter may lead to potentially unstable or statically inadmissible behaviour. The solutions obtained allow one to identify zones of influence around the heat source of several variables of interest. The two fields most affected by the thermal sensitivity of M are that of the axial stress, dropping significantly near the heat source, and that of the appearance of the thermoplastic strain. Both zones of influence are reduced in size by almost half when the friction angle is increased by 20% over 70°. The presented results may be of relevance to the design of prototype in situ installations and their monitoring, and eventually of actual facilities for nuclear waste disposal

Effect of thermal variability of the internal friction in clay in a cylindrical thermo-mechanical problem

peer reviewe

Numerical and phenomenological study of desiccation of soil

Desiccation cracks are assumed to be the consequence of an excess of tensile stresses induced by shrinkage of the drying body with a constrained kinematics. Free and constrained desiccation shrinking tests on silt samples are compared and simulated using linear hygro-elasticity. The results reveal diverse patterns of stress depending on the external constraints and presence of moisture gradient. The linear hygro-elasticity captures well the drying process before the appearance of the cracks. For the tested material, the tensile axial stress at the first crack (w=24%) was estimated at about 3.7 kPa

Conservação e restauro de uma urna em vidro do século I d.C., encontrada em Mértola (Portugal)

International audienceThe evolution of capillary forces during evap-oration and the corresponding changes in the geometrical characteristics of liquid (water) bridges between two glass spheres with constant separation are examined experimen-tally. For comparison, the liquid bridges were also tested for mechanical extension (at constant volume). The obtained results reveal substantial differences between the evolution of capillary force due to evaporation and the evolution due to extension of the liquid bridges. During both evaporation and extension, the change of interparticle capillary forces consists in a force decrease to zero either gradually or via rupture of the bridge. At small separations between the grains (short & wide bridges) during evaporation and at large volumes during extension, there is a slight initial increase of force. During evaporation, the capillary force decreases slowly at the begin-ning of the process and quickly at the end of the process; during extension, the capillary force decreases quickly at the beginning and slowly at the end of the process. Rup-ture during evaporation of the bridges occurs most abruptly for bridges with wider separations (tall and thin), sometimes occurring after only 25 % of the water volume was evapo-rated. The evolution (pinning/depinning) of two geometri-cal characteristics of the bridge, the diameter of the three-phase contact line and the "apparent" contact angle at the solid/liquid/gas interface, seem to control the capillary force evolution. The findings are of relevance to the mechanics of unsaturated granular media in the final phase of drying

Colonization and community development of fish assemblages associated with estuarine artificial reefs

Despite the long history of the development of artificial structures in NSW estuaries there are no studies that provide any comprehensive scientific evaluation of post-deployment goals. We assessed the effectiveness of estuarine artificial reefs as a fisheries enhancement initiative; described the diversity and abundance of species associated with them, and detailed the patterns of colonization and community development associated with an artificial reef deployment in Lake Macquarie, a large coastal barrier lagoon on the southeast coast of Australia. Six artificial reefs (one artificial reef group), constructed from artificial reef units (Reef Balls®), were deployed in December 2005 and sampled six times per season over two years using baited remote underwater video (BRUV). Colonization of the artificial reef group was relatively rapid with the majority of species identified over the two-year study period observed within the first year post-deployment. Overall, 27 species from 17 families were identified. Key colonising species included Pelates sexlineatus (Terapontidae), Acanthopagrus australis (Sparidae), Pagrus auratus (Sparidae) and Rhabdosargus sarba (Sparidae). Species richness showed evidence of potential seasonal fluctuations, being higher in warm water months (Summer/Autumn), and lower in the colder water months (Winter/Spring), while species diversity increased significantly with reef age. Fish assemblage composition remained relatively stable after the first year of sampling, with few discernible patterns in assemblage structure evident after the first year. Distinct separation in reef age groupings was evident during the second year of sampling; a pattern primarily driven by a decrease in abundance of P. sexlineatus, a result of the isolated nature of the artificial reefs and the interrelated effects of density dependence and predation.A despeito da longa história do desenvolvimento de estruturas artificiais nos estuários de NSW, não existem estudos que apresentem uma avaliação global sobre os efeitos obtidos com o estabelecimento dessas estruturas. No presente trabalho abordamos a efetividade dos recifes artificiais estuarinos como iniciativa para aumento da pesca; descrevemos a diversidade e abundância das espécies a eles associadas; descrevemos os padrões de colonização e o desenvolvimento das comunidades associadas a um recife artificial colocado no Lago Macquaire, extensa lagoa de barreira situada na costa sudeste da Australia. Seis recifes artificiais (formando um único grupo), construídos a partir de unidades artificiais (Reef Balls®), foram lançados em Dezembro de 2005 e amostrados seis vezes a cada estação do ano, durante dois anos, utilizando video subaquático remoto (BRUV). A colonizaç��o dentro do grupo de recifes ocorreu de maneira relativamente rápida, sendo que a maioria das espécies identificadas nos dois anos de estudo foi observada durante o primeiro ano de amostragem. Um total de 27 espécies pertencentes a 17 famílias foram identificadas. As espécies chave do processo de colonização foram Pelates sexlineatus (Teraponidae), Acanthopagrus australis (Sparidae), Pagrus auratus (Sparidae) and Rhabdosargus sarba (Sparidea). A riqueza de espécies mostrou evidência de sazonalidade, enquanto a diversidade aumentou significativamente com o aumento da idade do recife. A composição da assembléia de peixes permaneceu relativamente estável após o primeiro ano de amostragem, com poucos padrões identificáveis relativos à estrutura. Durante o segundo ano tornou-se evidente a formação de grupos por idade, padrão primariamente ocasionado pelo decréscimo na abundância de P. sexlineatus; por sua vez este decréscimo mostrou ser resultado da natureza isolada do recife artificial e dos efeitos interdependentes de abundância e predação