Proceedings

EPJ E Highlight - Speed-dependent attraction governs what goes on at the heart of midge swarms

Trajectories of individual midges within a swarm recorded using high-speed cameras.

New study reveals swarm cohesion stems from an adaptive behaviour, where the faster individual midges fly, the stronger the gravitational-like force they experience

Ever wondered what makes the collective behaviour in insect swarms possible? Andy Reynolds from Rothamsted Research, UK, and colleagues at Stanford University, California, USA, modelled the effect of the attraction force, which resembles Newton’s gravity force, acting towards the centre of a midge swarm to give cohesion to their group movement. In a recent study published in EPJ E, their model reveals that the gravity-like attraction towards the heart of the swarm increases with an individual’s flight speed. The authors confirmed the existence of such an attractive force with experimental data.

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EPJ E Highlight - Molecular scale transporter with a twist, powered by liquid crystal defects

Twisting effect, called chirogyral, dictated by the handedness of the fibre in a vertical magnetic field.

Delivery of biochemical substances is now possible using a novel application of liquid crystal defects, forming a loop enclosing the substance travelling alongside twisted fibres

Defects that break the symmetry of otherwise orderly material are called topological defects. In solid crystals, they are called dislocations because they interrupt the regularly structured atom lattice. In contrast, topological defects called disclinations take the form of loops in liquid crystal of the nematic variety, whose elongated molecules look like a shoal of fish. New experiments supported by a theoretical model show how defects forming loops around twisted plastic fibres dipped in liquid crystal could be used for the transport of biochemical substances, when controlled by electric and magnetic fields. Published in EPJ E, these findings - achieved by Mallory Dazza from the Ecole normale supérieure Cachan, France, and colleagues - have potential applications in electro-optical micromechanical and microfluidic systems.

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EPJ E Review - Water and ionic liquids. Two very different solvents, two intriguing behaviours when nanoconfined

Confinement of liquids at the nanoscale gives rise to intriguing new chemical and physical behaviours and structures. Scientists are studying the phenomenon also because of its relevance to molecular biology (permeability of ion channels and protein stability), chemical engineering (nano-fluidic devices and molecular sieves) and geology (transport through porous rocks).

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EPJ E Highlight - Nanoparticles hitchhiking their way along strands of hair

Corrugated hair surface.

Massaging hair can help more quickly deliver nanoparticle-based treatment to the roots

In shampoo ads, hair always looks like a shiny, smooth surface. But for physicists peering into microscopes, the hair surface looks much more rugged, as it is made of saw-tooth, ratchet-like scales. In a new theoretical study published in EPJ E, Matthias Radtke and Roland Netz have demonstrated that massaging hair can help to apply drug treatment - encapsulated in nanoparticles trapped in the channels formed around individual hairs - to the hair roots. This is because the oscillatory movement of the massaging directs the way these particles are transported.

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EPJ E Highlight - How water can split into two liquids below zero

Representation of the diamond lattices formed by the particle studied.

Theoretical possibility of the coexistence of dual liquid states of matter in sub-zero water due to the origami-like stacking behaviour of microscale moleculesy

Did you know that water can still remain liquid below zero degrees Celsius? It is called supercooled water and is present in refrigerators. At even smaller temperatures, supercooled water could exist as a cocktail of two distinct liquids. Unfortunately, the presence of ice often prevents us from observing this phenomenon. So physicists had the idea of replicating the tetrahedral shape of water molecules - using DNA as a scaffold to create tetrahedral molecules - and thus removing the interference of ice formation. This approach allowed Simone Ciarella from the University of Rome, Italy, and his colleagues to confirm that, in theory, a dual liquid phase is possible in sub-zero water and any other liquids made of tetrahedral molecules. These results have been published in EPJ E. It is a great tale of how the underlying microscopic shape determines the overall macroscopic form.

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EPJ E Colloquium: Non-local fluctuation phenomena in liquids

Fluids in non-equilibrium steady states exhibit long-range fluctuations which extend over the entire system. They can be described by non-equilibrium thermodynamics and fluctuating hydrodynamics that assume local equilibrium for the thermophysical properties as a function of space and time.

The experimental evidence for the consistency between this assumption of local equilibrium in the equations and the non-local fluctuation phenomena observed is reviewed in this EPJ E colloquium paper

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EPJ E Highlight - Physicists reveal cocktails with Dr Jekyll and Mr Hyde features

False colour image of the long-range concentration fluctuations arising in a critical binary mixture.

Study explains how long-range effects in two-liquid cocktails have a bearing on the diffusion of their molecules, resulting in the coexistence of different characteristics within the same fluid

Disturbing a mix of two liquids can yield some surprising effects. For example, if one portion of the mixture is brought to a different composition, it starts a process called diffusion, which continues until the liquid mix reverts to the resting point, which physicists refer to as equilibrium. Understanding the underlying physical phenomenon matters because diffusion is ubiquitous in physical and biological processes, such as the transport of nutrients within our cells. Now, an Italian team of physicists has found that two-liquid cocktails display long-range correlations, both at equilibrium and when disturbed. This means that large regions with slightly different physical properties coexist within the same fluid. Outside the equilibrium condition, the authors explain, this is due to the coupling between the difference in concentration between different portions of the liquid and spontaneous fluctuations, which are also observed when the mix is at equilibrium. These findings have been published in EPJ E as part of the Topical Issue "Non-isothermal transport in complex fluids" by Fabio Giavazzi from the University of Milan, Italy, and colleagues. They imply that the long-range effects, observed when the mixture is not at equilibrium, need to be taken into account as an additional contribution to the effects observed when the mixture is at equilibrium, so as to understand the diffusion mechanisms.

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EPJ E Colloquium: Self-consistent field theory of multicomponent wormlike-copolymer melts

A linear, a 3-arm star, and a sidechain copolymer segment.

The self-consistent field theory (FCFT) is a convenient theoretical tool to describe the ordered structures of copolymer melts. It supports the current understanding of many polymeric systems. In a new EPJ E Colloquium Ying Jiang and colleagues showcase the versatility and power of the wormlike-chain formalism for calculating the microphase-separated crystallographic structures of multi-component wormlike polymers.

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EPJ E Review - Watching crystals grow

Ice nucleus forming in supercooled liquid water
© Philipp Geiger

Crystallization, a typical self-organization process during which a disordered state spontaneously transforms into an ordered one, a crystal, usually proceeds by nucleation and growth. In the initial stages of the transformation, a localized nucleus of the new phase forms due to a random fluctuation. Most of these small nuclei disappear after a short time, but in some rare cases a crystalline embryo may reach a critical size, after which further growth becomes thermodynamically favorable and the entire system is converted into the new phase.

In this EPJ E review paper, Jungblut and Dellago discuss several theoretical concepts and computational methods to better understand crystallization. More specifically, they address the rare event problem arising in the simulation of nucleation processes, and explain how to calculate nucleation rates accurately. Particular emphasis is placed on discussing statistical tools to analyze crystallization trajectories and identify the transition mechanism.

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EPJ E Highlight - Asymmetrical magnetic microbeads transform into micro-robots

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Transformation of particle clusters while exposed to an oscillating external magnetic field.

Thanks to the ordering effects of two-faced magnetic beads, they can be turned into useful tools controlled by a changing external magnetic field

Janus was a Roman god with two distinct faces. Thousands of years later, he inspired material scientists working on asymmetrical microscopic spheres - with both a magnetic and a non-magnetic half - called Janus particles. Instead of behaving like normal magnetic beads, with opposite poles attracting, Janus particle assemblies look as if poles of the same type attract each other. A new study reveals that the dynamics of such assemblies can be predicted by modelling the interaction of only two particles and simply taking into account their magnetic asymmetry. These findings were recently published in EPJ E by Gabi Steinbach from the Chemnitz University of Technology, Germany, and colleagues at the Helmholtz-Zentrum Dresden-Rossendorf. It is part of a topical issue entitled "Nonequilibrium Collective Dynamics in Condensed and Biological Matter." The observed effects were exploited in a lab-on-a-chip application in which microscopic systems perform tasks in response to a changing external magnetic field.

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In 2012 we organized the International Conference on Nuclear Structure and Related Topics (NSRT12). Among several offers for publishing the Proceedings we have chosen the open-access journal EPJ Web of Conferences and have not been disappointed. Since this was our first experience with the on-line publication we had many questions to the editorial staff and several times changed our mind. And always we got prompt, exhaustive and patient answers and instructions. We were fully satisfied with the final quality of publication when it has appeared on the website. So our experience in collaboration with the journal is encouraging without any doubts.

Prof. Andrej I. Vdovin, Joint Institute for Nuclear Research, Russia
Member of the Organizing Committee NSRT12, EPJ Web of Conferences vol.38, 2012

ISSN: 2100-014X (Electronic Edition)

© EDP Sciences

Conference announcements

POSMOL 2017

Magnetic Island, Queensland, Australia, 22-24 July 2017