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.
A new Colloquium paper published in EPJ B looks at ion irradiation techniques as a means to control the structure of nanoclusters and nanocrystals embedded in solid materials, such as silica or silicon.
Zero gravity experiments on the International Space Station shed some light on thermodiffusion effects, relevant to the oil and gas industry and global warming prevention processes
Thermodiffusion, also called the Soret effect, is a mechanism by which an imposed temperature difference establishes a concentration difference within a mixture. Two studies by Belgian scientists from the Free University of Brussels, recently published in EPJ E, provide a better understanding of such effects. They build on recent experimental results from the IVIDIL—Influence Vibration on Diffusion in Liquids—research project performed on the International Space Station under microgravity to avoid motion in the liquids.
A new theoretical study demonstrates for the first time that quantum holograms could be a candidate for becoming quantum information memory
Russian scientists have developed a theoretical model of quantum memory for light, adapting the concept of a hologram to a quantum system. These findings are included in study just published in EPJ D, by Anton Vetlugin and Ivan Sokolov from St. Petersburg State University in Russia. The authors demonstrate for the first time, that it is theoretically possible to retrieve, on demand, a given portion of the stored quantised light signal of a holographic image—set in a given direction in a given position in time sequence.
In this EPJ D colloquium paper, the authors review a cross-section of recent results relating to low-energy positron scattering from atomic targets, and present a comparison of the latest measurements and calculations for positron collisions with the noble gases, together with a brief update on the newest studies addressing other atomic targets. In particular, they provide an overview of the work that has been done in examining elastic scattering, positronium formation, direct and total ionisation, as well as total scattering, at typical energies ranging from 0.1 eV to a few hundred eV.
How does an electric (or magnetic) dipole behave in an electromagnetic field, when its velocity becomes comparable with the speed of light?
This problem has been solved for the first time in a paper recently published in EPJ Plus, where novel relativistic effects were found. In particular, it has been shown that the concept of “hidden” momentum of magnetic dipoles in an electric field, being disputable up to date, is strongly required to derive relativistically adequate solutions. Moreover, a novel concept of “latent” momentum of electric dipole should be also involved into the description of dipoles.
Simulating the cost of generating a combination of electricity sources while accounting for the fluctuating nature of energy production and demand provides tools to optimise such energy mix
Increasing reliance on renewable energies is the way to achieve greater CO2 emission sustainability and energy independence. Yet, because such energies are only available intermittently and energy cannot be stored easily, most countries aim to combine several energy sources. Now, in a new study in EPJ Plus, French scientists have come up with an open source simulation method to calculate the actual cost of relying on a combination of electricity sources. Bernard Bonin from the Atomic Energy Research Centre CEA Saclay, France, and colleagues demonstrate that cost is not directly proportional to the demand level. Although recognised as crude by its creator, this method can be tailored to account for the public’s interest—and not solely economic performance—when optimising the energy mix.
Improved theoretical model of photoabsorption of nitrous oxide matters because its by-product, nitric oxide, is involved in the catalytic destruction of stratospheric ozone
New theoretical physics models could help us better grasp the atmospheric chemistry of ozone depletion. Indeed, understanding photoabsorption of nitrous oxide (N2O)-- a process which involves the transfer of the energy of a photo to the molecule--matters because a small fraction of N2O reacts with oxygen atoms in the stratosphere to produce, among other things, nitric oxide (NO). The latter participates to the catalytic destruction of ozone (O3). Now, new theoretical work unveils the actual dynamic of the photoabsorption of nitrous oxide (N2O) molecules. These findings by Mohammad Noh Daud from the University of Malaya, Kuala Lumpur in Malaysia, have just been published in EPJ D. The work has led to new calculations of the probability of an absorption process taking place, also referred to as absorption cross section, which confirm experimental results.
Bohmian mechanics provides an explanation of quantum phenomena in terms of point particles guided by wave functions. This EPJ D review focuses on the formalism of non-relativistic Bohmian mechanics, rather than its interpretation, and although the Bohmian and standard quantum mechanical theories have different formalisms, they both yield exactly the same predictions for all phenomena.
Over the past 15 years, the density matrix renormalisation group (DMRG) has become increasingly important for ab initio quantum chemistry. Its underlying wavefunction ansatz, the matrix product state (MPS), is a low-rank decomposition of the full configuration interaction tensor. The virtual dimension of the MPS, viz. the rank of the decomposition, controls the size of the corner of the many-body Hilbert space that can be reached with the ansatz, and can be systematically increased until numerical convergence is reached. The MPS ansatz naturally captures exponentially decaying correlation functions, and the DMRG therefore works extremely well for noncritical one-dimensional systems.
New theoretical model of the effect of triangular defects in graphene provides numerical estimates of the resulting current rectification with potential applications in security screening.
Electronic transport in graphene contributes to its characteristics. Now, a Russian scientist is proposing a new theoretical approach to describe graphene with defects—in the form of artificial triangular holes—resulting in the rectification of the electric current within the material. Specifically, the study provides an analytical and numerical theory of the so-called ratchet effect —which results in a direct current under the action of an oscillating electric field, due to the skew scattering of electronic carriers by coherently oriented defects in the material. These findings are published in EPJ B by Sergei Koniakhin from the Ioffe Physical-Technical Institute and the Academic University - Nanotechnology Research and Education Centre, both affiliated with the Russian Academy of Sciences in St. Petersburg.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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
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.
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.