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Hourglasses measure time because the discharge rate of dry sand is constant. Here Koivisto et al. show that when such a system contains water there is a surge in discharge because the fluid drains faster than the grains, which might help us understand the transport of grains in silos.
Mechanical properties of living organisms are determined by intra- and extra-cellular biopolymer networks. Here, the authors show how the mechanics of polyisocyanopeptide hydrogels, mimicking biopolymers, can be readily manipulated by introducing a second polymer network.
Glial scars are thought to provide a biochemical and mechanical barrier to neuronal regeneration post-injury, but the mechanical properties of the scars have not been studied in detail. Here the authors perform atomic force microscopy measurements of glial scars from the injured rat cortex and spinal cord, and find that brain tissue softens in response to the injury.
The fabrication of emulsion droplets stabilized by solid particles adsorbed on the interface is restricted to delicate interfacial conditions. Here, Kim et al. show a general approach to prepare them using the depletion interaction, modified by soluble polymers, between particles and emulsions.
Crushing a brittle porous medium such as a box of cereal causes the grains to break up and rearrange themselves. A lattice spring model based on simple physical assumptions gives rise to behaviours that are complex enough to reproduce diverse compaction patterns.
You can run across a swimming pool filled with a mixture of cornflour and water, but you sink if you stand still. Conventional understanding of this phenomenon is now being turned on its head. See Letter p.205
The cytoplasm of living cells responds to deformation in much the same way as a water-filled sponge does. This behaviour, although intuitive, is connected to long-standing and unsolved fundamental questions in cell mechanics.
Experiments have shown that the physical characteristics of the matrix surrounding a stem cell can affect its behaviour. This picture gets further complicated by studies of stem cells and their differentiated counterparts that show that the cells' own softness also has a clear role in how they respond to stress.