2018 Impact factor 1.000
Historical Perspectives on Contemporary Physics

EPJ E Highlight - Shocking embryonic limbs into shape

Mechanism of formation of an early vertebrate embryo. Each of the rings of cells in the round blastula (shown in colours) forms into a different part of the embryo or placenta.

Electrical stimulation of early chicken embryos has shed light on the process through which the limbs of all vertebrates are formed.

Every vertebrate, whatever its eventual form, starts embryonic life in the same way – as a hollow ball or disc of cells called a blastula. In theory, knowing the mechanism through which the blastula is formed into the shape of an animal could help correct defects and even, one day, regenerate body parts. But evolution and genetics are of little help in understanding this process. Now, however, Vincent Fleury and Ameya Vaishnavi Murukutla from Université Paris Diderot, Paris, France have used experiments with chicken embryos to propose a mechanism for vertebrate limb formation. These findings have been published in the journal EPJ E.

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EPJ E Topical review - Liquid-liquid criticality in the dielectric constant and refractive index: A perspective

The critical region in the phase diagram of condensed matter systems such as fluids or fluid mixtures is characterized by the anomalous behaviour of specific thermodynamic properties. In a new review article published in EPJE, Patricia Losada-Pérez (Department of Physics, Université Libre de Bruxelles) describes recent progress in the understanding of the behaviour of two intimately related properties, the dielectric constant ε and the refractive index n, when approaching the liquid-liquid critical point in binary liquid mixtures.

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EPJ E Highlight - Optimising structures within complex arrangements of bubbles

Optimising an arrangement of five bubbles.

Computer simulations reveal how groups of bubbles with two different areas can be optimised to minimise the lengths of the edges at which they touch, potentially allowing for stronger, cheaper structures which emulate bubbly foams.

While structures which emulate foam-like arrangements of bubbles are lightweight and cheap to build, they are also remarkably stable. The bubbles which cover the iconic Beijing Aquatics Centre, for example, each have the same volume, but are arranged in a way which minimises the total area of the structure – optimising the building’s construction. The mathematics underlying this behaviour is now well understood, but if the areas of the bubbles are not equal, the situation becomes more complicated. Ultimately, this makes it harder to make general statements about how the total surface area or, in 2D, edge length, or ‘perimeter’, can be minimised to optimise structural stability. In new research published in EPJ E, Francis Headley and Simon Cox at Aberystwyth University in the UK explore how different numbers of 2D bubbles of two different areas can be arranged within circular discs, in ways which minimise their perimeters.

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EPJ E Highlight - Improving heat recycling with the thermodiffusion effect

Recycling heat using falling films.

Numerical simulations of the thermodiffusion effect within falling film absorbers reveal that thin films composed of liquid mixtures with negative thermodiffusion coefficients enhance the efficiency of heat recycling

Absorption heat transformers can effectively reuse the waste heat generated in various industries. In these devices, specialised liquids form thin films as they flow downward due to gravity. These liquid films can absorb vapour, and the heat is then extracted by a coolant so that it can be used in future processes. So far, however, there has been little research into how the performance of these films is influenced by the thermodiffusion effect – a behaviour seen in mixtures, where different types of mixture respond differently to the same temperature gradient. In a study recently published in EPJ E, researchers from the Fluid Mechanics group at Mondragon University and Tecnalia in Spain, led by M. M. Bou-Ali at Mondragon University, pooled their expertise in transport phenomena and absorption technology. Together, they explored for the first time the influence of the thermodiffusion property on the absorption, temperature and concentration profiles of falling films.

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EPJ E Colloquium - European Space Agency experiments on thermodiffusion of fluid mixtures in space

Diffusive processes are ubiquitous in daily life and in natural processes, playing a key role in the transformation and mixing of fluid mixtures, and there is considerable scientific and industrial interest in such mixing processes. One consequence of diffusion is the development of non-equilibrium fluctuations in liquid mixtures, particularly when fluids are exposed to a thermal gradient. This is easier to observe in weightlessness, as gravity dampens this phenomenon on Earth especially for large fluctuations.

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EPJE Topical Review: Lattice Boltzmann methods and active fluids

Active fluids are living matter or biologically inspired systems, consisting of self-propelled units that burn stored or ambient energy and turn it into work, eventually giving rise to systematic movement. In a new Topical Review paper published in EPJE, authors from groups in Bari (University of Bari, INFN, and the Istituto Applicazioni Calcolo, CNR) and the Center for Life Nano Science, La Sapienza, Rome describe the use of Lattice Boltzmann Methods (LBM) in the study of large scale properties of active fluids.

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EPJ E Highlight - No assumptions needed to simulate petroleum reservoirs

Modelling reservoirs: easier than we thought? https://commons.wikimedia.org/wiki/ File:Contour_map_software_screen_ snapshot_of_isopach_map_for_ 8500ft_deep_OIL_reservoir_with_ a_Fault_line.jpg

Hydrocarbons trapped within porous media are easier to model with computer simulations than researchers previously assumed – a discovery that opens up new possibilities for thermodynamics research.

Hidden deep below our feet, petroleum reservoirs are made up of hydrocarbons like oil and natural gas, stored within porous rock. These systems are particularly interesting to physicists, as they clearly show how temperature gradients between different regions affect the gradients of fluid pressures and compositions. However, because these reservoirs are so hard to access, researchers can only model them using data from a few sparse points, meaning many of their properties can only be guessed at. In a new study published in EPJ E, physicists from France and Vietnam, led by Guillaume Galliero at the University of Pau, have found that this guesswork actually isn’t necessary. They show that if the right choices are made when constructing models, no assumptions are needed in order to calculate the impact of temperature gradients on pressure and composition gradients.

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EPJ E Highlight - Dowsing for electric fields in liquid crystals

Following the change in orientation of the molecules in the dowser texture yields a shape that resembles the wooden dowsing rods used in previous centuries to locate groundwater. Left: © Pawel Pieranski, Right: https://en.wikipedia.org/wiki/ Dowsing#/media/File: 18th_century_dowser.jpg

The orientation of the ordered molecules that make up nematic liquid crystals can change under electric fields, and can be used to detect subtle electrical effects.

You may not know it, but you probably spend several hours a day looking at nematic liquid crystals; they are used in virtually every smartphone, computer and TV screen. They are liquids composed of elongated molecules, which in some situations can be oriented in a curious way termed the 'dowser texture', which is sensitive to external conditions. Physicists Pawel Pieranski of the Universite Paris-Sud, Paris, France and Maria Helena Godinho of Universidade Nova de Lisboa, Lisbon, Portugal have now published a paper in EPJ E that shows that the dowser texture responds to electric fields in different ways in different nematic materials.

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EPJ E Highlight - Collagen fibres grow like a sunflower

Phyllotactic pattern with concentric circles.

A new study suggests the pattern of fibres in tissues is similar to the petals of a flower

Collagen fibrils are a major component of the connective tissues found throughout the animal kingdom. The cable-like assemblies of long biological molecules combine to form tissues as varied as skin, corneas, tendons or bones. The development of these complex tissues is the subject of a variety of research efforts, focusing on the steps involved and the respective contributions of genetics and physical chemistry to their development. Now, two researchers at the Universite Paris-sud in Orsay, France, have shed new light on how complex collagen fibrils form. In a new study published in EPJ E, the authors focus on one of the hierarchical steps, in which molecules spontaneously associate in long and dense axisymmetric fibres, known as type I collagen fibrils.

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EPJ E Highlight - How red blood cells behave in crowded vessels

Red blood cells flowing through a blood vessel. https://pixabay.com/illustrations/blood-cells-red-medical-medicine-1813410/

A new model of red blood flowing through narrow capillaries shows that the cells change shape and alignment, allowing plasma to flow down the sides

Blood consists of a suspension of cells and other components in plasma, including red blood cells, which give it its red colour. When blood flows through the narrowest vessels in the body, known as the capillaries, the interactions between the cells become much more important. In a new study published in EPJ E, a team of researchers led by Ignacio Pagonabarraga from the University of Barcelona, Spain, has now developed a mathematical model of how red blood cells flow in narrow, crowded vessels. This could help design more precise methods for intravenous drug delivery, as well as 'microfluidic chips' incorporating artificial capillaries, which could offer faster, simpler and more precise blood-based diagnoses.

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Managing Editors
W. Beiglböck and F. Guerra
ISSN (Print Edition): 2102-6459
ISSN (Electronic Edition): 2102-6467

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