News

EPJ A Highlight - Towards the solution of the “hyperon puzzle”

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Neutron star’s mass-radius relation with and without hyperons. Masses of the pulsars PSR J0348+0432 and PSR J0740+6620 are shown with their observation uncertainties.

The possible presence of strange matter in the core of neutron stars has given rise to the so-called hyperon puzzle: hyperonic degrees of freedom are energetically allowed in the extreme density conditions believed to exist in the core of Neutron Stars, but hyperons reduce the internal pressure of the star, which then cannot compensate the gravitational field to sustain the most massive compact stars observed.

This work reports on the effect of three-body interactions when including a Lambda hyperon on the properties of hyper-nuclei and Neutron Stars. State-of-the-art three-body chiral effective interactions are introduced in a microscopic Brueckner-Hartree-Fock calculation.

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EPJ Plus Focus Point: Past and Present: Recent Advances in the Investigation of Ancient Materials by Means of Scientific Instrumental Techniques

This Focus Point introduces selected papers from the contributions presented at the 10th Congress of Italian Association of Archaeometry (AIAr) held in Turin (Italy) in February 2018, where a large parterre of Italian as well as International researchers shared their experiences on new and more consolidated analytical approaches on archaeological and artistic materials.

Different topics were addressed in the realm of cultural heritage, from characterisation and diagnostics to bioarchaeology and man-environment interaction. A strong focus was put on the comparison between non-invasive/non-destructive and micro-invasive methods in the study of different categories of objects, evaluating the pros and cons of each approach. Also a growing interest, accompanied by increasing technological skills, was registered for monitoring of environmental conditions to which the archaeological and artistic patrimony is subjected.

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EPJ B Highlight - Better studying superconductivity in single-layer graphene

Charge carriers in graphene influence superconductivity. By CORE-Materials licensed under CC BY-SA 2.0

An existing technique is better suited to describing superconductivity in pure, single-layer graphene than current methods.

Made up of 2D sheets of carbon atoms arranged in honeycomb lattices, graphene has been intensively studied in recent years. As well as the material’s diverse structural properties, physicists have paid particular attention to the intriguing dynamics of the charge carriers its many variants can contain. The mathematical techniques used to study these physical processes have proved useful so far, but they have had limited success in explaining graphene’s ‘critical temperature’ of superconductivity, below which its’ electrical resistance drops to zero. In a new study published in EPJ B, Jacques Tempere and colleagues at the University of Antwerp in Belgium demonstrate that an existing technique is better suited for probing superconductivity in pure, single-layer graphene than previously thought.

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EPJ D Highlight - Proton-hydrogen collision model could impact fusion research

Models could aid nuclear fusion projects. IAEA Imagebank [CC BY-SA 2.0 (https://creativecommons.org/ licenses/by-sa/2.0)]

A new theoretical model predicts how protons will collide with hydrogen atoms which have been excited to higher energy levels, over a wide range of impact energies

The motions of plasmas may be notoriously difficult to model, but they can be better understood by analysing what happens when protons are scattered by atoms of hydrogen. In itself, this property is characterised by the size of a particular area surrounding the atom, known as its ‘cross section’. In new research published in EPJ D, Anthony Leung and Tom Kirchner at York University in Canada used new techniques to calculate the cross sections of atoms which have been excited to higher energy levels. They analysed the behaviour over a wide range of impact energies.

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EPJ Plus Focus Point: Fractional Differential Equations in Physics: Recent Advantages and Future Direction

The Focus Point on “Fractional Differential Equations in Physics: Recent Advantages and Future Direction” presents some of the multiple open research directions within the dynamical field of fractional calculus and its applications. Traditional viewpoints together with fractional calculus models and techniques are used to provide the readers with a full picture of how dynamic and useful fractional calculus ideas are in treating the dynamics of complex phenomena arising from science and engineering. We hope that the research articles of this Focus Point will motivate young researchers to apply their original ideas for solving the multiple open problems within fractional calculus.

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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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Editors-in-Chief
Pere Roca i Cabarrocas and Daniel Lincot
ISSN: 2105-0716 (Electronic Edition)

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