- Published on 02 December 2019
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.
EPJ Plus Focus Point: Fractional Differential Equations in Physics: Recent Advantages and Future Direction
- Published on 20 November 2019
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.
EPJ A Highlight - Confirming the validity of the Silver-Blaze property for QCD at finite chemical potential
- Published on 06 November 2019
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.
- Published on 24 October 2019
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.
- Published on 24 October 2019
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.
- Published on 23 October 2019
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.
- Published on 22 October 2019
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.
- Published on 21 October 2019
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.
- Published on 16 October 2019
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.
- Published on 09 October 2019
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.