About EPJ

The European Physical Journal (EPJ) is a series of peer-reviewed journals covering the whole spectrum of physics and related interdisciplinary subjects. EPJ is committed to high scientific quality in publishing and is indexed in all main citation databases.


EPJ A Highlight - Modern three-body forces make neutron stars collapse
Friday, 08 August 2014 09:38
Density profile of the collapsed state of 10000 neutrons in the X-Y-plane along the symmetry axis Z=0 (schematic illustration). Polarized neutrons, which interact through incorrect three-body forces, concentrate in small spheres separated by 0.9 fermi. © Dmitry K. Gridnev et al.

Nuclear systems ranging from light nuclei to massive neutron stars can be well described by nucleons interacting through two-body and three-body forces. From electrostatics we know that two identical uniformly charged spheres repel at any distance but the repulsion disappears when the spheres completely overlap. Similarly, in some modern expressions of nuclear three-body force it is assumed that the nuclear repulsion between the three nucleons is zero when they occupy the same position in space.

EPJ B Highlight - Nano-pea pod model widens applications
Thursday, 31 July 2014 16:30
The dependence of the continuous spectrum on the connecting wires’ length. © Eremin et al.

A new theoretical model outlines the conditions under which a novel nanostructure, such as the nano-pea pod, can exhibit localised electrons for electronics applications

Periodic chain-like nanostructures are widely used in nanoelectronics. Typically, chain elements include the likes of quantum rings, quantum dots, or quantum graphs. Such a structure enables electrons to move along the chain, in theory, indefinitely. The trouble is that some applications require localised electrons - these are no longer in a continuous energy spectrum but in a discrete energy spectrum, instead. Now, a new study by Russian scientists identifies ways of disturbing the periodicity of a model nanostructure to obtain the desired discrete spectrum with localised electrons. These findings have been published in EPJ B by Dr. Eremin from the Mordovian State University, in Saransk, Russia and colleagues.

EPJ B Highlight - Inter-dependent networks stress test
Thursday, 31 July 2014 16:00
Impact of network topologies. © Fu et al.

A new study relies on a complex systems modelling approach, known as graph theory, to analyze inter-dependent physical or social networks and improve their reliability in the event of failure

Energy production systems are good examples of complex systems. Their infrastructure equipment requires ancillary sub-systems structured like a network - including water for cooling, transport to supply fuel, and ICT systems for control and management. Every step in the network chain is interconnected with a wider network and they are all mutually dependent. A team of UK-based scientists has studied various aspects of inter-network dependencies, not previously explored. The findings have been published in EPJ B by Gaihua Fu from Newcastle University, UK, and colleagues. These findings could have implications for maximising the reliability of such networks when facing natural and man-made hazards.

EPJ D Highlight - Water window imaging opportunity
Thursday, 31 July 2014 15:36
Time-frequency analysis of dipole acceleration extracted from the numerical simulations performed in argon, for three different regimes of laser intensity. © Pérez-Hernández et al.

A new theoretical study elucidates mechanisms that could help in producing coherent radiations, and could ultimately help to achieve high-contrast images of biological samples

Ever heard of the water window? It consists of radiations in the 3.3 to 4.4 nanometre range, which are not absorbed by the water in biological tissues. New theoretical findings predict a novel way of achieving coherent radiations within the water window. These could be the basis of an optimal technique to obtain a high-contrast image of the biological samples or to be used in high-precision spectroscopy. Now, a new theoretical study identifies the physical mechanism needed to efficiently generate the harmonic radiations - which are multiples of an incoming laser’s frequency - at high laser intensities that occur beyond the saturation threshold of atoms and molecules. These findings, aimed at improving conventional methods of coherent radiation production to reach the water window, were recently published in the EPJ D by José Pérez-Hernández from the Centre for Pulsated Laser, CLPU, in Salamanca, Spain, and colleagues.

EPJ Quantum Technology Highlight - Quantum simulators explained
Friday, 25 July 2014 11:33
A quantum simulator can then loosely be considered to be a simulator for the system of interest. © Johnson et al.

Everything you ever wanted to know about quantum simulators has been summed up in a new review from EPJ Quantum Technology

As part of a new Thematic Series on Quantum Simulations, the open access journal EPJ Quantum Technology has just published an overview of what a quantum simulator is, namely: a device that actively uses quantum effects to answer questions on model systems. This review, published by Tomi Johnson and colleagues from the Centre for Quantum Technologies in Singapore and the University of Oxford, UK, outlines various approaches used in quantum simulators.

EPJ E Highlight - Optimum inertial self-propulsion design for snowman-like nanorobot
Tuesday, 22 July 2014 11:56
Streamlines, velocity field, and magnitude of the share of the propelling flow attributed to the low level inertial force, in the case of touching spheres. © Nadal et al.

A new study investigates the effects of small but finite inertia on the propulsion of micro and nano-scale swimming machines that could have implications for biomedical applications

Scale plays a major role in locomotion. Swimming microorganisms, such as bacteria and spermatozoa, are subjected to relatively small inertial forces compared to the viscous forces exerted by the surrounding fluid. Such low-level inertia makes self-propulsion a major challenge. Now, scientists have found that the direction of propulsion made possible by such inertia is opposite to that induced by a viscoelastic fluid. These findings have been published in EPJ E by François Nadal from the Alternative Energies and Atomic Energy Commission (CEA), in Le Barp, France, and colleagues. This study could help optimise the design of self-propelled micro- and nanoscale artificial swimming machines to improve their mobility in medical applications.

EPJ D Colloquium - One Hundred Years of the Franck-Hertz Experiment
Monday, 21 July 2014 00:00
Schematic representation of the Franck-Hertz experiment © Robson et al.

The seminal 1914 experiment of James Franck and Gustav Hertz provided a graphic demonstration of the quantisation properties of atoms, and thereby laid the foundations of modern atomic physics. This EPJ D colloquium revisits the experiment on the occasion of its Centenary and compares the traditional and modern interpretations, as well as highlighting the link between microscopic processes, which are governed by the laws of quantum mechanics, and macroscopic phenomena, as observed in the laboratory.

EPJ D Topical Review - Gas breakdown and secondary electron yields
Thursday, 17 July 2014 00:00
Paschen curves for molecular gases © Marić et al.

In this EPJ D topical review, the authors present a systematic study of gas breakdown potentials. An analysis of the key elementary processes involved in low-current low-pressure discharges is given, with the aim of illustrating how such discharges are used to determine swarm parameters and how such data may be applied to the modeling of discharges.

EPJ B Highlight - Unleashing the power of quantum dot triplets
Tuesday, 08 July 2014 13:35
Triple quantum dot system. © S. B. Tooski et al.

Another step towards faster computers relies on three coherently coupled quantum dots used as quantum information units, which could ultimately enhance quantum computers’ speed

Quantum computers have yet to materialise. Yet, scientists are making progress in devising suitable means of making such computers faster. One such approach relies on quantum dots—a kind of artificial atom, easily controlled by applying an electric field. A new study demonstrates that changing the coupling of three coherently coupled quantum dots (TQDs) with electrical impulses can help better control them. This has implications, for example, should TQDs be used as quantum information units, which would produce faster quantum computers due to the fact that they would be operated through electrical impulses. These findings have been published in EPJ B by Sahib Babaee Tooski and colleagues affiliated with both the Institute of Molecular Physics at the Polish Academy of Sciences, in Poznan, Poland, the University of Ljubljana and the Jožef Stefan Institute in Slovenia.

EPJ B Colloquium - Next generation interatomic potentials for condensed matter systems
Tuesday, 08 July 2014 00:00
A small two-dimensional feed-forward Neural Network containing a single hidden layer. © Handley et al.

More efficient computational methods are urgently needed to capture condensed matter systems in simulations. Electronic structure methods, such as density-functional theory (DFT), usually provide a good compromise between accuracy and efficiency, but they demand much computational power. For this reason, they are only applicable to small systems containing a few hundred atoms at most. Conversely, many interesting phenomena involve much larger systems comprising thousands of atoms or more. Considerable effort has been invested in the development of potentials that enable simulations to run on larger system and for longer times. Typically these potentials are based on physically-motivated functional forms. Therefore, while they perform very well for the specific applications for which they have been designed, they cannot easily be transferred from one system to another. Moreover, their numerical accuracy is restricted by the intrinsic limitations of the imposed functional forms. In this EPJ B Colloquium, Handley and Behler survey several novel types of potentials emerged in recent years, which are not based on physical considerations.

EPJ E Highlight - Refined biological evolution model
Monday, 07 July 2014 14:53
Artistic impression symbolising population evolution. © elly99 | istockphoto.com

A new study accounts for species interactions, and adds a layer of complexity to previous minimalists models

Models for the evolution of life are now being developed to try and clarify the long-term dynamics of an evolving system of species. Specifically, a recent model proposed by Petri Kärenlampi from the University of Eastern Finland in Joensuu accounts for species interactions with various degrees of symmetry, connectivity, and species abundance. This is an improvement on previous, simpler models, which apply random fitness levels to species. The findings published in EPJ E demonstrate that the resulting replicator ecosystems do not appear to be a self-organised critical model, unlike the so-called Bak-Sneppen model; a reference in the field. The reasons for this discrepancy are not yet known.

EPJ D Highlight - Ultra-cold atom transport made simple
Monday, 30 June 2014 00:00
Figure 1.a. from the original paper Caption: “Schematic representation of the physical system consisting of a ring trap and two dipole waveguides for injecting neutral atoms into, extracting them from, and velocity filtering them in the ring waveguide.” © Loiko et al.

New study provides proof of the validity of a filtering device for ultra-cold neutral atoms based on tunnelling

Techniques for controlling ultra-cold atoms travelling in ring traps currently represent an important research area in physics. A new study published in EPJ D gives a proof of principle, confirmed by numerical simulations, of the applicability to ultra-cold atoms of a very efficient and robust transport technique called spatial adiabatic passage (SAP). Yu Loiko from the University of Barcelona, Spain, and colleagues have, for the first time, applied SAP to inject, extract, and filter the velocity of neutral atoms from and into a ring trap. Such traps are key to improving our understanding of phenomena involving ultra-cold atoms, which are relevant to high-precision applications such as atom optics, quantum metrology, quantum computation, and quantum simulation.

EPJ D Highlight - Improving tumour radiation therapy: when basic ions break DNA down
Monday, 30 June 2014 00:00
Figure 2 from the original paper Caption: “Power spectral density spectrum of a protonated DNA strand.” © Piekarczyk et al.

A new study relevant for cancer radiation therapy shows that DNA building blocks are susceptible to fragmentation on contact with the full range of ions from alkaline element species

Scientists now have a better understanding of how short DNA strands decompose in microseconds. A European team found new fragmentation pathways that occur universally when DNA strands are exposed to metal ions from a family of alkaline and alkaline earth elements. These ions tend to replace protons in the DNA backbone and at the same time induce a reactive conformation leading more readily to fragmentation. These finding have been published by Andreas Piekarczyk, from the University of Iceland, and colleagues in a study in EPJ D. They could contribute to optimising cancerous tumour therapy through a greater understanding of how radiation and its by-products, reactive intermediate particles, interact with complex DNA structures.

Ludwik Leibler awarded the EPJE Pierre-Gilles De Gennes Lecture Prize for 2014
Monday, 23 June 2014 00:00
Ludwik Leibler awarded the EPJE Pierre-Gilles De Gennes Lecture Prize for 2014. © CNRS Photothèque / Cyril FRESILLON
Ludwik Leibler awarded the EPJE Pierre-Gilles De Gennes Lecture Prize for 2014. © CNRS Photothèque / Cyril FRESILLON

The journal EPJE – Soft Matter and Biological Physics is pleased to honour Ludwik Leibler with the 2014 EPJE Pierre-Gilles De Gennes Lecture prize. Leibler is researcher at CNRS and Adjunct Professor at ESPCI ParisTech where he directs the Laboratory for Soft Matter and Chemistry. The Editors of the journal nominated him for his seminal contributions to polymer physics and the revolutionary polymeric materials, self-healing elastomers and vitrimers that he invented. This is the 4th edition of this prestigious prize, named after the Nobel laureate who founded EPJE. The prize consist of 1000 Euros and a plenary lecture that will be introduced by Daan Frenkel, co-Editor-in-Chief of EPJE. The EPJE Pierre-Gilles de Gennes lecture will be delivered July 22nd in Lisbon, during the 9th Liquid Matter conference of the European Physical Society.

EPJ D Highlight - Deeper insights into protein folding
Thursday, 19 June 2014 13:01
Figure 2 (a) from the original paper Caption: “Structure of staphylococcal nuclease.” © Yakubovich et al.

Physicists have published a new theoretical foundation explaining the mechanism of protein folding and unfolding in water

Investigating the structure and dynamics of so-called Meso-Bio-Nano (MBN) systems—micron-sized biological or nanotechnology entities—is a rapidly expanding field of science. Now, scientists Alexander Yakubovich and Andrey Solov'yov from MBN Research Centre in Frankfurt, Germany, have produced a new theoretical study of a protein macromolecules changing from a coil structural conformation to a globular one. Their statistic mechanics model, just published in EPJ D, describes the thermodynamic properties of real proteins in an aqueous environment, using a minimal number of free physical parameters.

EPJ B Highlight - Ti-V alloys’ superconductivity: inherent, not accidental
Thursday, 12 June 2014 14:50
The variation of the superconducting transition temperature (Tc) as a function of vanadium concentration along with the binary phase information for the quenched Ti-V alloys. © Matin et al.

All of the Ti-V alloys could display a relatively high superconducting transition temperature, as it is their unusual physical properties that influence this property, unlike previously thought

Physicists from India have shed new light on a long-unanswered question related to superconductivity in so-called transition metal binary alloys. The team revealed that the local magnetic fluctuations, or spin fluctuations, an intrinsic property of Titanium-Vanadium (Ti-V) alloys, influences superconductivity in a way that is more widespread than previously thought. They found that it is the competition between these local magnetic fluctuations and the interaction between electrons and collective excitations, referred to as phonons, which determine the superconductivity. Dr. Matin, from the Raja Ramanna Center for Advanced Technology, Indore, India, and colleagues published their findings in a study in EPJ B

EPJ B Highlight - Market crashes are anomalous features in the financial data fractal landscape
Saturday, 07 June 2014 18:28
Graph of the normalised empirically found distribution of the American Dow Jones Industrial Average index, DJIA (red squares), and European Euro Stoxx 50 (blue circles) index data with prices recorded every minute data along with the Standard Normal curve for comparison. © Green et al.

Analysing the adequation of financial data structure with its expected fractal scaling could help early detection of extreme financial events because these represent a scaling irregularity

Due to their previously discovered fractal nature, financial data patterns are self-similar when scaling up. New research shows that the most extreme events in financial data dynamics—reflected in very large price moves—are incompatible with multi-fractal scaling. These findings have been published in EPJ B by physicist Elena Green from the National University of Ireland, Maynooth, Ireland and colleagues. Understanding the multi-fractal structure of financially sound markets could, ultimately, help in identifying structural signs of impending extreme events.

EPJ E Highlight - Horizontal levitation: the ultimate solution to particle separation
Saturday, 07 June 2014 17:50
Forces acting on glass particles in a magnetic field. © Liu et al.

Separating particles from the liquid they are in can now be done with a new concept, based on horizontal deflection during particle levitation for the separation of minerals and particles.

Magnetic separators exploit the difference in magnetic properties between minerals, for example when separating magnetite from quartz. But this exercise becomes considerably more complex when the particles are not magnetic. In the wake of previous particle levitation experiments under high-power magnetic fields, a new study reveals that particles are deflected away from the magnet’s round-shaped bore centre in a horizontal direction. Previous studies had observed the vertical levitation of the particles. These findings are presented by Shixiao Liu from the Faculty of Engineering, University of Nottingham, UK and colleagues, in a paper recently published in EPJ E, and could led to a new concept in particles and minerals separation technologies.

EPJ E Highlight - Elucidating optimal biological tissue shape during growth
Wednesday, 28 May 2014 09:35
Friction-dominated growth. © Blanch-Mercader et al.

A new study investigates the role of cells’ alignment in shaping biological tissue, as cell division provides dynamic evolution during tissue growth.

A team of European scientists has now extended a previous biophysical model to investigate elongated growth within biological tissues to describing the evolution over time of the shape of a fruit fly’s wing. They found the aspect ratio of the typical biological shapes may exhibit a maximum at finite time and then decrease. For sufficiently large tissues, the shape is expected to approach that of a disk or sphere. These findings have been reported by Carles Blanch-Mercader from the University of Barcelona, Spain, and colleagues, in a paper published in EPJ E. They provide a more general classification than previously available of the different types of morphologies a tissue can be expected to attain, depending on its initial size and its physical properties.

EPJ Techniques and Instrumentation – A new Open-Access Journal
Friday, 16 May 2014 08:04

The publishers are pleased to announce the publication of the first articles in the latest EPJ open-access journal – EPJ Techniques and Instrumentation.

EPJ Techniques and Instrumentation focuses on the design, implementation, and application of new techniques in all areas of the physical and applied sciences.

EPJ B Highlight - Particles near absolute zero do not break the laws of physics after all
Tuesday, 06 May 2014 22:06
A free particle strongly coupled to a heat bath. © Adamietz et al.

A change of models demystifies anomalous particle behaviour at very low temperatures, confirming that the third law of thermodynamics cannot be violated

In theory, the laws of physics are absolute. However, when it comes to the laws of thermodynamics—the science that studies how heat and temperature relate to energy—there are times where they no longer seem to apply. In a paper recently published in EPJ B, Robert Adamietz from the University of Augsburg, Germany, and colleagues have demonstrated that a theoretical model of the environment’s influence on a particle does not violate the third law of thermodynamics, despite appearances to the contrary. These findings are relevant for systems at the micro or nanometer scale that are difficult to decouple from the heat or the quantum effects exerted by their environment.

EPJ E Highlight - Stability lost as supernovae explode
Tuesday, 29 April 2014 11:42
Early stage supernovae can be modelled as dynamic systems abruptly losing stability. © Imag'In Pyrénées/Fotolia

A new model accounting for the loss of stability occurring at the very start of supernova explosions sheds some new light on this phenomenon, opening up potential broader applications

Exploding supernovae are a phenomenon that is still not fully understood. The trouble is that the state of nuclear matter in stars cannot be reproduced on Earth. In a recent paper published in EPJ E, Yves Pomeau from the University of Arizona, USA, and his French colleagues from the CNRS provide a new model of supernovae represented as dynamical systems subject to a loss of stability, just before they explode. Because similar stability losses also occur in dynamical systems in nature, this model could be used to predict natural catastrophes before they happen. Previous studies of the creeping of soft solids, earthquakes, and sleep-wake transitions have already confirmed the validity of this approach.

EPJ A Highlight – COMPASS: Radiative widths of the a2(1320) and π2(1670) mesons
Tuesday, 29 April 2014 10:04
Intensity of the 2-+ partial-wave in π^- γ→π^- π^- π^+, interpreted as radiative width of the π2(1670).

Radiative transitions are among the most important and insightful processes for the investigation of atomic, nuclear and hadronic systems. They reveal the electromagnetic substructure of the involved particles. The a2(1320) meson is known since the 1980s to decay radiatively with a branching of about 0.3% into a pion and a photon. Theoretically this can be linked, for example through the vector meson dominance model, to the main hadronic decay channels.

EPJ B Highlight - Nanoscale heat flow predictions
Tuesday, 22 April 2014 12:02
Snapshot of the final configuration of a nc-Si sample. © Melis et al.

A new study predicts that heat flow in novel nanomaterials could contribute to creating environmentally friendly and cost-effective nanometric-scale energy devices

Physicists are now designing novel materials with physical properties tailored to meet specific energy consumption needs. Before these so-called materials-by-design can be applied, it is essential to understand their characteristics, such as heat flow. Now, a team of Italian physicists has developed a predictive theoretical model for heat flux in these materials, using atom-scale calculations. These findings, published in EPJ B by Claudio Melis and colleagues from the University of Cagliary, Italy, could have implications for optimising the thermal budget of nanoelectronic devices—which means they could help dissipate the total amount of thermal energy generated by electron currents—or in the production of energy through thermoelectric effects in novel nanomaterials.

EPJ B Highlight - Grasp of SQUIDs dynamics facilitates eavesdropping
Tuesday, 08 April 2014 09:29
Average voltage output of a DC SQUID under varying conditions. © Berggren et al.

Latest theoretical advances pertaining to the dynamics of highly sensitive magnetometers could find military applications in low-noise amplifiers and sensitive antennas

Theoretical physicists are currently exploring the dynamics of a very unusual kind of device called a SQUID. This Superconducting Quantum Interference Device is a highly sensitive magnetometer used to measure extremely subtle magnetic fields. It is made of two thin regions of insulating material that separate two superconductors – referred to as Josephson junctions – placed in parallel into a ring of superconducting material. In a study published in EPJ B, US scientists have focused on finding an analytical approximation to the theoretical equations that govern the dynamics of an array of SQUIDs. This work was performed by Susan Berggren from the US Navy research lab, SPAWAR Systems Center Pacific, in San Diego, CA, USA and Antonio Palacios San Diego State University. Its applications are mainly in the military sector, including SQUID array-based low-noise amplifiers and antennas.

EPJ E - Andreas Bausch, the new biological physics EiC
Monday, 07 April 2014 16:01

This month EPJE welcomes Andreas Bausch, who takes over from Frank Jülicher, as Editor in Chief for biological physics in EPJ E – Soft Matter and Biological Physics. In his lab, Bausch applies new experimental tools of soft condensed matter physics to living cells and bio-mimetic model systems. This is his vision for biological physics within EPJE in the years to come:

EPJ B Highlight - Graphene nanoribbons as electronic switches
Monday, 31 March 2014 12:32
© Credit: Dmitry Knorre/Fotolia

A new theoretical study shows the conductivity conditions under which graphene nanoribbons can become switches in externally controlled electronic devices

One of graphene’s most sought after properties is its high conductivity. Argentinian and Brazilian physicists have now successfully calculated the conditions of the transport, or conductance mechanisms, in graphene nanoribbons. The results, recently published in a paper in EPJ B, yield a clearer theoretical understanding of conductivity in graphene samples of finite size, which have applications in externally controlled electronic devices.

EPJ E Highlight - Making the most of carbon nanotube-liquid crystal combos
Wednesday, 26 March 2014 09:28
Dispersed multi-wall carbon nanotubes on a glass surface. © Yakemseva et al.

A better understanding of the physical response of combination materials made of nanotubes with ferroelectric liquid crystals could soon open the door to applications as sensors or switches

Dispersions of carbon nanotubes with liquid crystals have attracted much interest because they pave the way for creating new materials with added functionalities. Now, a study published in EPJ E by Marina Yakemseva and colleagues at the Nanomaterials Research Institute in Ivanovo, Russia, focuses on the influence of temperature and nanotube concentration on the physical properties of such combined materials. These findings could have implications for optimising these combinations for non-display applications, such as sensors or externally stimulated switches, and novel materials that are responsive to electric, magnetic, mechanical or even optical fields.

EPJ E Topical Review: Foaming experiments on the ISS
Monday, 24 March 2014 15:38

Foams and foaming processes pose interesting questions for both fundamental research and practical applications. Although foams are a familiar thing, both in our everyday lives and in industry, many aspects of foam physics and chemistry still remain unclear.

This EPJ E paper comprehensively reviews the studies of foams under microgravity, including studies conducted in parabolic flights, in sounding rockets and in the International Space Station.

EPJ D Highlight - Plasma tool for destroying cancer cells
Tuesday, 11 March 2014 14:05
The plasma discharged used to study DNA at ambient air conditions. © Han et al.

Inducing biological tissue damage with an atmospheric pressure plasma source could open the door to many applications in medicine

Plasma medicine is a new and rapidly developing area of medical technology. Specifically, understanding the interaction of so-called atmospheric pressure plasma jets with biological tissues could help use them in medical practice. Under the supervision of Sylwia Ptasinska from the University of Notre Dame, in Indiana, USA, Xu Han and colleagues conducted a quantitative and qualitative study of the different types of DNA damage induced by atmospheric pressure plasma exposure, in a paper published in EPJ D as part of a special issue on nanoscale insights into Ion Beam Cancer Therapy. This approach, they hope, could ultimately lead to devising alternative tools for cancer therapy as well as applications in hospital hygiene, dental care, skin diseases, antifungal care, chronic wounds and cosmetics treatments.

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