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.
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.
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.
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.
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.
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.
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.
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.
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: