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EPJ A Highlight - Confirming the validity of the Silver-Blaze property for QCD at finite chemical potential

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Sketch of the QCD phase diagram in the temperature and baryon chemical potential plane.

The properties of the theory of strong interactions, QCD, at finite chemical potential are of great interest for at least two reasons: (i) model studies suggest a potentially rich landscape of different phases with highly interesting analogies to those found in solid state physics; (ii) the resulting thermodynamic properties have far reaching consequences for the physics of neutron stars and neutron star mergers.

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EPJ E Highlight - Mathematics reveals new insights into Marangoni flows

Impurity concentrations vary along temperature gradients.

New theoretical analysis describing the movements of impurity-laden, temperature-varying fluids at water-air interfaces better matches previous experimental observations

The Marangoni effect is a popular physics experiment. It is produced when an interface between water and air is heated in just one spot. Since this heat will radiate outwards, a temperature gradient is produced on the surface, causing the fluid to move through the radiation process of convection. When un-dissolvable impurities are introduced to this surface, they are immediately swept to the side of the water’s container. In turn, this creates a gradient in surface tension which causes the interface to become elastic. The structures of these flows have been well understood theoretically for over a century, but still don’t completely line up with experimental observations of the effect. In a new study published in EPJ E, Thomas Bickel at the University of Bordeaux in France has discovered new mathematical laws governing the properties of Marangoni flows.

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EPJ Plus Highlight - Science reveals improvements in Roman building techniques

The Atrium Vestae in Rome from https://commons.wikimedia.org/wiki/ File:House_of_the_Vestal_Virgins_ (Atrium_Vestae),_Upper_Via_Sacra, _Rome_(9114141425).jpg
Carole Raddato from Frankfurt, Germany [CC BY-SA 2.0 (https://creativecommons.org/ licenses/by-sa/2.0)]

A variety of scientific techniques have been combined to highlight improvements in the technologies employed by the Romans in successive modifications to the Atrium Vestae in Rome.

The Romans were some of the most sophisticated builders of the ancient world. Over the centuries, they adopted an increasingly advanced set of materials and technologies to create their famous structures. To distinguish the time periods over which these improvements took place, historians and archaeologists typically measure the colours, shapes and consistencies of the bricks and mortar used by the Romans, along with historical sources. In new research published in EPJ Plus, Francesca Rosi and colleagues at the Italian National Research Council improved on these techniques through scientific analysis of the materials used to build the Roman Forum’s Atrium Vestae. They found that successive phases of modification to the building saw improvements including higher quality raw materials, higher brick firing temperatures, and better ratios between carbonate and silicate building materials.

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EPJ E Highlight - Advanced cancer drug shrinks and intercalates DNA

Pixantrone thoroughly damages cancer cell DNA.

Experiments and statistical models reveal that the recently developed cancer drug Pixantrone forces itself inside the double helix structure of DNA molecules, then shrinks their backbones.

Because of the harmful side-effects of chemotherapy, and the increasing resistance to drugs found in many cancer cells, it is critical for researchers to continually search for new ways to update current cancer treatments. Recently, a drug named Pixantrone (PIX) was developed, which is far less damaging to the heart than previous, less advanced compounds. PIX is now used to treat cancers including non-Hodgkin’s lymphoma and leukaemia, but a detailed knowledge of the molecular processes it uses to destroy cancer cells has been lacking so far. In a new study published in EPJ E, Marcio Rocha and colleagues at the Federal University of Viçosa in Brazil uncovered the molecular mechanisms involved in PIX’s interactions with cancer DNA in precise detail. They found that the drug first forces itself between the strands of the DNA molecule’s double helix, prising them apart; then compacts the structures by partially neutralising their phosphate backbones.

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EPJ D Highlight - Retrieving physical properties from two-colour laser experiments

Extracting ionisation yields following ultrafast interactions.

Useful information about ultrafast light-matter interactions is buried deep in the signals produced by two-colour pump-probe experiments, and requires sophisticated techniques to disentangle it.

When photons of light interact with particles of matter, a diverse variety of physical processes can unfold in ultrafast timescales. To explore them, physicists currently use ‘two-colour pump-probe’ experiments, in which an ultrashort, infrared laser pulse is first fired at a material, causing its constituent electrons to move. After a controllable delay, this pulse is followed by a train of similarly short, extreme-ultraviolet pulses, ionising the material. By measuring the total ionisation following the pulses along with the resulting electron energy spectra, physicists can theoretically learn more about ultrafast, light-matter interactions. In new research published in EPJ D, an international team of physicists, led by Eric Suraud at the University of Toulouse, discovered that these signals are in fact dominated by the less interesting interplay between electrons and the initial infrared laser. They show that more useful information is buried deeper within these signals, and requires sophisticated techniques to disentangle it.

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EPJ E Highlight - Deflating beach balls and drug delivery

A shell buckles as its internal volume is gradually reduced.

The deflation of beach balls, squash balls and other common objects offers a good model for distortion in microscopic hollow spheres. This can help us understand the properties of some cells and, potentially, develop new drug delivery mechanisms.

Many natural microscopic objects – red blood cells and pollen grains, for example – take the form of distorted spheres. The distortions can be compared to those observed when a sphere is ‘deflated’; so that it steadily loses internal volume. Until now, most of the work done to understand the physics involved has been theoretical. Now, however, Gwennou Coupier and his colleagues at Grenoble Alps University, France have shown that macroscopic-level models of the properties of these tiny spheres agree very well with this theory. The new study, which has implications for targeted drug delivery, was recently published in EPJ E.

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EPJ B Highlight - Determining the shapes of atomic clusters

Defining the shapes of atomic clusters

By considering the crystal structures of atomic clusters in new ways, researchers may be able to better assess whether the groups have distinctive shapes, or whether they are amorphous.

Too large to be classed as molecules, but too small to be bulk solids, atomic clusters can range in size from a few dozen to several hundred atoms. The structures can be used for a diverse range of applications, which requires a detailed knowledge of their shapes. These are easy to describe using mathematics in some cases; while in others, their morphologies are far more irregular. However, current models typically ignore this level of detail; often defining clusters as simple ball-shaped structures. In research published in EPJ B, José M. Cabrera-Trujillo and colleagues at the Autonomous University of San Luis Potosí in Mexico propose a new method of identifying the morphologies of atomic clusters. They have now confirmed that the distinctive geometric shapes of some clusters, as well as the irregularity of amorphous structures, can be fully identified mathematically.

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EPJ D Highlight - Modelling ion beam therapy

https://commons.wikimedia.org/wiki/ File:Hadrontherapy.jpg Anna.puliaieva [CC BY-SA 4.0 (https://creativecommons.org/ licenses/by-sa/4.0)]

Recent analysis shows precisely how beams of charged particles transfer their energy to water, which has important implications for how these beams are targeted in ion beam cancer therapy.

Hadron beam therapy, which is often used to treat solid tumours, involves irradiating a tumour with a beam of high-energy charged particles, most often protons; these transfer their energy to the tumour cells, destroying them. It is important to understand the precise physics of this energy transfer so the tumour can be targeted precisely. Pablo de Vera of MBN Research Center, Frankfurt, Germany and co-workers in the Universities of Murcia and Alicante, Spain, have produced a consistent theoretical interpretation of the most accurate experimental measurements of ion beams energy deposition in liquid water jets, which is the most relevant substance for simulating interactions with human tissue. Their work is published in EPJ D.

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EPJ B Highlight - Fractal patterns in growing bacterial colonies

Simulated fractal patterns of bacterial colonies generated using different diffusion coefficients (X axis) and nutrient concentrations (Y axis)

A new agent-based computer modelling technique has been applied to the growth and sliding movement of colonies of bacteria

As many people will remember from school science classes, bacteria growing on solid surfaces form colonies that can be easily visible to the naked eye. Each of these is a complex biological system in its own right; colonies display collective behaviours that indicate a kind of 'social intelligence' and grow in fractal patterns that can resemble snowflakes. Despite this complexity, colony growth can be modelled using principles of basic physics. Lautaro Vassallo and his co-workers in Universidad Nacional de Mar del Plata, Argentina have modelled such growth using a novel method in which the behaviour of each of the bacteria is simulated separately. This work has now been published in the journal EPJ B.

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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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I choose EPJ Web of Conferences for our proceedings, following the suggestion of a close colleague. As it was anticipated to me, I found the EPJ Web of Conferences services highly professional and exceptionally efficient. The proceedings were nicely edited, published online and printed in the shortest time I could imagine, providing us continuous support and satisfying all our requirements. I strongly recommend EPJ Web of Conferences to any editor.

Dr. Enricco Bozzo, ISDC - Science data center for Astrophysics, Switzerland
Co-editor EPJ Web of Conferences vol. 64, 2014

ISSN: 2100-014X (Electronic Edition)

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