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EPJ B Highlight - How a molecular motor moves in a network

Ratchets transfer energy in a lattice arrangement. Credit: M. A. Taye

A new study determines the efficiency of a single-molecule heat engine by considering a series of ratchets that transfer energy along a network.

From internal combustion engines to household refrigerators, heat engines are a ubiquitous component of daily life. These machines convert heat into usable energy which can then be used to do work. Heat engines can be as small as a single molecule whose random movements exchange energy with the environment. But determining the efficiency of a molecular heat engine is no simple task. In a study published in EPJ B, Mesfin Asfaw Taye, of West Los Angeles College, California, USA now calculates the performance of a molecular heat engine in terms of a series of molecular ratchets that transfer energy, step-wise, in one direction. He shows and discusses how to manipulate such a system for transporting a particle along a complex path.

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EPJ E Highlight - Exploring the elasticity of colloidal suspensions

Particles in a colloidal suspension.
Author: Zephyris, CC BY-SA 3.0 https://creativecommons.org/ licenses/by-sa/3.0, via Wikimedia Commons

Experiments reveal that under the right conditions, the elasticity of colloidal suspensions will peak at a certain value, which depends both on the deformation applied to the material and the strength of attraction between its solid particles.

The behaviours of colloidal materials – where tiny solid particles are suspended in fluid – depend strongly on how the particles interact with each other. Through new research published in EPJ E, a team led by Pascal Hébraud at the University of Strasbourg, France, show how under certain conditions, the elasticity of silica-based colloids subjected to oscillating flows will peak at a certain value. Their discovery could lead to improved techniques for manipulating the behaviour of colloidal materials, used in fields as wide-ranging as materials science, food technology, construction, and nanotechnology.

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EPJ B Highlight - Calculating thermal properties from phonon behaviours

Calculating phonon dispersions in ScAgC

A new study determines the thermal properties of advanced solid materials, based on first-principles calculations of quantum vibrations.

As the energy demands of our modern world continue to grow, there is a crucial need to understand how heat flows through the materials we use to build our technology. Through new research published in EPJ B, Vinod Solet and Sudhir Pandey at the Indian Institute of Technology Mandi have accurately estimated the thermal properties of a particularly promising alloy, based on first-principles calculations of phonons. Composed of scandium (Sc), silver (Ag), and carbon (C), this alloy could soon become a key component of devices which convert heat into electricity, while its low reflectivity and strong photon absorption would make it especially well-suited for highly efficient solar cells.

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EPJ D Highlight - Looking deeper into violent neutron star collisions to find the origins of heavy elements

An illustration of a kilonova the collision of neutron stars generating conditions extreme enough to forge the Universe’s heavy elements. Credit: Robin Dienel/The Carnegie Institution for ScienceContact

The gold that makes up your most precious jewellery may have been forged in a violent cosmic collision millions or billions of light years away between two neutron stars. New research seeks to better understand this process.

There is only a single confirmed site in the Universe capable of generating conditions extreme enough to initiate the production process for many of the heaviest elements in the Universe, including gold, platinum, uranium – neutron star mergers. These mergers are the only event observed to-date that can produce the incredible densities and temperatures needed to power the rapid neutron capture process.

In a new paper in EPJ D, Andrey Bondarev, a postdoc researcher at Helmholtz Institute Jena, James Gillanders a postdoc researcher in Rome, and their colleagues examine the spectra from the kilonova AT2017gfo to investigate the presence of forged tin, by looking for spectral features caused by its forbidden transitions.

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EPJ E Highlight - Measuring nanocomposite structures with neutron and x-ray scattering

Simulating diversity in nanoparticle sizes

Experiments with state-of-the-art scattering instruments reveal an absence of specific patterns in the x-rays scattered by nanocomposite materials. With the help of advanced simulation techniques, a new study suggests that attractive interactions between nanoparticles with diverse shapes and sizes are most likely responsible for this behaviour.

Small-angle scattering of x-rays and neutrons is a useful tool for studying molecular and nanoparticle structures. So far, however, experiments have revealed a surprising lack of nanoparticle structure in certain nanocomposite materials – whose molecular skeletons are reinforced with nanoparticles previously treated with polymer adsorption. In a new approach detailed in EPJ E, Anne-Caroline Genix and Julian Oberdisse at the University of Montpellier, France, show that these patterns can only be produced through attractive interactions between nanoparticles with a diverse array of shapes and sizes. The duo’s results highlight the rapidly improving capabilities of small-angle scattering instruments, and could also help researchers to improve their techniques for studying nanocomposites – with applications in areas including miniaturised electronics, biological tissue engineering, and strong, lightweight materials for aircraft.

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EPJ D Topical Issue: Precision Physics of Simple Atomic Systems

Guest Editors: Krzysztof Pachucki, Thomas Udem, Wim Ubachs, Paolo Crivelli & Stefan Ulmer

This EPJD special issue dedicated to the field of precision physics of simple atomic systems includes several important peer-reviewed contributions, presented on the 11th edition of the PSAS conference —initially planned to take place in May 2020 in Wuhan, China (only to be rescheduled 2 years later, in May 2022, due to the COVID-19 pandemic, in Warsaw, Poland).

The aim of the PSAS conference is to gather scientists from all over the world working on precise calculations and measurements, with the goal to test fundamental physics, to verify laws of physics, and to determine fundamental constants. Correspondingly, a mix of theoretical, numerical and experimental works spanning the fields of spectroscopy of atomic and molecular hydrogen, QED of few-electron bound systems, exotic atoms and ions, searches for BSM physics with atoms and antimatter, clocks, measurements of g-2 and alpha, originating from several of the major groups in this field, are reported here, making the current collection of interest for both the younger generation entering this research field and experts for efficient access on recent developments.

All articles are available here and are freely accessible until 29 August 2023. For further information read the Editorial.

EPJ D Highlight - Testing a perfect absorber metamaterial

The schematic picture of a proposed perfect absorber metamaterial

The proposed metamaterial could have a wide range of applications, from sensing to stealth technology

Metamaterials are a type of artificial material which, as the prefix “meta” – meaning in Greek “after” or “beyond” – indicates, demonstrate electromagnetic properties and other characteristics not found in nature.

As a result of these characteristics, including negative refraction and perfect lensing and cloaking, which arise from the lattice design composition of these substances rather than the materials that actually comprise them, metamaterials have become a hot research topic.

In particular, materials scientists are actively hunting for metamaterials that are “perfect absorbers” of electromagnetic radiation with controllable resonance characteristics that lead to their wide usage in applications as varied as solar cells, thermal radiation imaging, sensing technology, and even stealth technology.

In a new paper in EPJ D, Shahzad Anwar, a researcher at the Department of Physics, Islamia College Peshawar, Pakistan, and his colleagues document the proposed design of a triple-band perfect metamaterial absorber. The new metamaterial could have applications in sensors, filters, and in stealth technology.

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EPJ D Highlight - A broader approach to quantum walks

Simulating an evolving quantum system

Quantum walks have been widely studied for their ability to simulate real physical phenomena. Physicists previously studied two distinct types of quantum walk, but so far, they haven’t widely considered how their mathematical descriptions could be linked. Through new research published in EPJ D, a pair of physicists in France: Nicolas Jolly at ENS de Lyon, and Giuseppe Di Molfetta at Aix-Marseille University, show how ‘discrete-‘ and ‘continuous-time’ quantum walks can be described using more general mathematical language. Their results could allow researchers to simulate an even broader range of phenomena using quantum walks.

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EPJ E Highlight - Steering ‘microswimmers’ through choppy waters

A diagram of microswimmers immersed in a non-steady flow following five possible navigation strategies. Credit: J. Bec (2023)

New research looks at navigation strategies for deformable microswimmers in a viscous fluid faced with drifts, strains, and other deformations.

A deformable microswimmer is a small-scale organism or artificial structure that uses sinusoidal body undulations to propel itself through a fluid environment.

The term applies to organisms like bacteria which navigate through fluids using whip-like tails called flagella, sperm cells propelling themselves through the female reproductive system, and even nematodes, tiny worms that move through water or soil with undulations. Microswimmers can also describe tiny microrobots constructed from soft-materials designed to respond to stimuli and perform tasks like drug delivery on a micro-scale.

That means the study of microswimmers has applications in a vast array of scientific fields, from biology to fundamental physics to nanorobotics.

In a new paper in EPJ E by Jérémie Bec, a researcher at CNRS and Centre Inria d’Université Côte d’Azur and his colleagues attempt to find an optimal navigation policy for microswimmers, crucial for enhancing their performance, functionality, and versatility for applications such as targeted drug delivery.

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EPJ H Highlight - Is the end of the “particle era” of physics upon us?

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The completed standard model of particle physics. What shape will physics beyond this model take? Credit: Daniel Dominguez/CERN

New research looks at the potential for new discoveries in particle physics

The discovery of the Higgs Boson in 2012 represented a major turning point for particle physics marking the completion of what is known as the standard model of particle physics. Yet, the standard model can’t answer every question in physics, thus, since this discovery at the Large Hadron Collider (LHC) physicists have searched for physics beyond the standard model and to determine what shape future physics will take.

A new paper in EPJ H: Historical Perspectives on Contemporary Physics by Robert Harlander and Jean-Philippe Martinez of the Institute for Theoretical Particle Physics and Cosmology, RWTH Aachen University, Germany, and Gregor Schiemann from the Faculty of Humanities and Cultural Studies, Bergische Universität Wuppertal, Germany, considers the idea that particle physics may be on the verge of a new era of discovery and understanding in particle physics. The paper also considers the implications of the many possible scenarios for the future of high-energy physics.

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