Volume 15 Issue 7, July 2019

The mechanics of many materials can be modelled by a network of balls connected by springs. A bottom-up approach based on differential geometry now captures changes in mechanics upon network growth or merger, going beyond the linear deformation regime.

A measurement based on quantum entanglement of the parameter describing the asymmetry of the Λ hyperon decay is inconsistent with the current world average. This shows that relying on previous measurements can be hazardous.

A variety of magnetic structures based around ferromagnetic spin spirals have been the topic of intense study over the past decade. The discovery of spin spirals that arise from antiferromagnetic order has just broadened the horizons for magnetic possibilities even further.

Experiments and simulations show that trains of droplets in microfluidic networks undergo synchronized oscillations, and that strategies to prevent these oscillations can help maintain uniform distribution of red blood cells in microcirculation.

An experimental study of living cells suggests that single myosin molecules are capable of generating unusually large forces. The observation is supported by a theoretical model — and demonstrates the complexity of in vivo force generation.

The decay asymmetry and helicity phase of polarized baryon–antibaryon pairs are measured at the BESIII experiment, testing charge–parity symmetry and revealing a discrepancy of the Λ → pπ⁻ decay asymmetry with respect to the current world average.

A feedback loop based on chaos control theory permits the generation of stable and coherent terahertz radiation from relativistic electron bunches in synchrotron light sources.

Single-particle resolved measurements in an ultracold-atom experiment reveal an intuitive picture of quantum correlations, providing strong constraints on the full density matrix of the two-particle system in the presence of interactions.

In acoustic metamaterials, unconventional chiral quasiparticles exhibit multifold band degeneracy points, each carrying non-zero topological charges, giving rise to the topologically protected negative surface refraction.

Magnetic textures known as skyrmions have gathered much attention in recent years. It is now shown that focused vector beams can also give rise to photonic skyrmion-like structures.

Structures containing multiple skyrmions inside a larger skyrmion—called skyrmion bags—are experimentally created in liquid crystals and theoretically predicted in magnetic materials. These may have applications in information storage technology.

A continuous version of the Maxwell demon is a machine that repeatedly monitors a system, but extracts work only on state change. Arbitrarily large quantities of work can thus be extracted, as demonstrated by DNA hairpin pulling experiments.

Following a closed evolution in the Hilbert space, the state vector of a quantum system accumulates a geometric phase factor. A series of weak measurements reveal the origin of this in the back-action of any quantum measurement.

Small-angle neutron scattering experiments of the layered antiferromagnet Ca₃Ru₂O₇ reveal a metamagnetic spin texture that is indicative of an extraordinary coexistence of spin orders belonging to different symmetries.

A phase transition often implies symmetry breaking in the system. However, an unconventional first-order phase transition is predicted, where higher-order symmetry than that of the underlying Hamiltonian emerges exactly at the phase boundary.

Simulations of a system comprising polymer rings with internal elasticity reveal a key role for deformation in controlling the microscopic dynamics of soft colloids.

High-resolution experiments attribute surprisingly large forces to the molecular motors helping a cell sense its surroundings. A two-state theory interprets the contractile properties of these motors as emergent features of their collective behaviour.

When a wound heals, different types of branched and bundled actin structure form, each designed to perform a specific function. Experiments and theory now suggest that the actin architecture depends on the stiffness of the cell’s surroundings.

Droplet sequences in microfluidic networks are shown to form trains that oscillate between branches of the network. Control of this effect suggests a mechanism by which red blood cells might avoid certain pathologies by minimizing oscillations.

A bottom-up mathematical approach provides a framework for the design of mechanical networks of two- or three-dimensional frames composed of freely rotating rods and springs that achieve any desired coordinate motion.

Imaginary numbers have a chequered history, and a sparse — if devoted — following. Abigail Klopper looks at why a concept as beautiful as i gets such a bad rap.