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EPJ B Highlight - Examining heat transfer in granular materials

Heat transfer via gas and water capillaries

Heat transfer through granular materials in a humid atmosphere occurs mainly through the air in the case of larger particles, and via water capillary bridges for smaller particles.

Granular materials contain large numbers of small, discrete particles, which collectively behave like uniform media. Their thermal conductivity is crucial to understanding their overall behaviour – but so far, researchers haven’t considered how this value is affected by the surface roughness of their constituent particles. Through new analysis published in EPJ B, Bo Persson at the Peter Grünberg Institute, part of the Jülich Research Centre in Germany, has discovered that when this roughness is considered, thermal conductivity in granular materials is heavily influenced by particle sizes. These findings could help physicists to better describe a wide array of granular materials: from sand and snow, to piles of rice, coffee beans, and fertilizer.

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EPJ Plus Highlight - Building a computer with a single atom

How small can a computer get? As small as an atom new research suggests. Credit: Robert Lea (created with Canva)

New research opens the horizons regarding what a “computer” can be and how small a computational unit can get

Considering a “computer” as anything that processes information by taking an input and producing an output leads to the obvious questions, what kind of objects could perform computations? And how small can a computer be? As transistors approach the limit of miniaturisation, these questions are more than mere curiosities, their answers could form the basis of a new computing paradigm.

In a new paper in EPJ Plus by Tulane University, New Orleans, Louisiana, researcher Gerard McCaul, and his co-authors demonstrate that even one of the more basic constituents of matter — atoms — can act as a reservoir for computing where all input-output processing is optical.

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EPJ E Highlight - Shear ultrasound shaking lowers friction between solids

Measuring responses to shear ultrasound vibrations

A simple new experiment shows how tiny ultrasound shaking at the interfaces between two objects will lower the friction between them – and in some cases, can induce sudden, large jerky motions

When high-frequency shaking occurs at an interface between two solids, recent experiments have revealed that the frictional forces between the objects can be weakened. Through a simple new experiment detailed in EPJ E, Julien Léopoldès at Université Gustave Eiffel, Marne la Vallée (formerly at ESPCI Paris) has discovered that mechanical vibrations also enhance structural aging in these systems, and can sometimes trigger sudden, jerking motions. The results could lead to a better understanding of how buildings are weakened by ambient vibrations, and may also help geologists to draw new insights into the mechanisms responsible for triggering earthquakes and landslides.

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EPJA Topical Collection: CompOSE: a repository for Neutron Star Equations of State and Transport Properties

Guest Editors: Danai Antonopoulou, Enrico Bozzo, Chikako Ishizuka, Ian Jones, Micaela Oertel, Constança Providencia, Laura Tolos and Stefan Typel

The CompOSE Topical Collection is a compendium of several works on neutron star equations of state (EoS) and transport properties related to the online repository CompOSE (CompStar Online Supernovae Equations of State).

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EPJ D Highlight - Atoms slow down more within colder blackbody radiation

The blackbody radiation curve. https://en.wikipedia.org/wiki/Black-body_radiation#/media/ File:Black_body.svg

New analysis shows that atoms will encounter high frictional forces in the presence of blackbody radiation at lower temperatures. Accounting for this effect could help researchers to improve the accuracy of high-precision experiments.

Blackbody radiation (BBR) contains electromagnetic waves with characteristic spectra, which changes shape depending on the temperature of the body. When moving atoms encounter these fields, they experience a repulsive force which slows down their movement towards the source of the radiation. Through new analysis published in EPJ D, Vipul Badhan and colleagues at Guru Nanak Dev University, India, show that the influence of this ‘blackbody friction force’ (BBFF) is particularly strong at lower temperatures.

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EPJ H Highlight - Quarks and gluons: The JADE experiment at DESY

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Illustration of an electron-positron annihilation event recorded with the JADE detector. The emergence of a separate, third “jet” of particle tracks from the central annihilation point was the first indicator for the existence of gluons. Credit: DESY.

A new paper in EPJ H describes the JADE experiment at DESY in Hamburg, in which high-energy electron-positron collisions led to the discovery of the particle that holds quarks together to form protons and neutrons: the gluon.

The DESY research centre in Hamburg has been at the centre of German physical science research since the 1960s, leading to important discoveries about the fundamental structure of matter. One experiment at DESY, known as JADE, recorded data on electron-positron collisions between 1979 and 1986. Siggi Bethke from the Max Planck Institute of Physics in Munich and Albrecht Wagner from DESY have now reviewed the history of JADE in the journal EPJ H: Historical Perspectives on Contemporary Physics.

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EPJ B Highlight - Finely-tuned quantum dots enhance nonlinear optics

Quantum dot with a spherical impurity

Quantum dots with finely-tuned spherical defects could display advanced ‘nonlinear’ optical properties, new calculations have suggested. Adjusting the sizes of these defects could enable researchers to tightly control the brightness and frequency of the light they produce when illuminated.

Quantum dots are semiconductor particles measuring just a few nanometres across, which are now widely studied for their intriguing electrical and optical properties. Through new research published in EPJ B, Kobra Hasanirokh at Azarbaijan Shahid Madani University in Iran, together with Luay Hashem Abbud at Al-Mustaqbal University College, Iraq, show how quantum dots containing spherical defects can significantly enhance their nonlinear optical properties. By fine-tuning these defects, researchers could tightly control the frequency and brightness of the light emitted by quantum dots.

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EPJ H Highlight - Mid-twentieth-century physics in the home of Galileo

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Credit: Department of Physics and Astronomy, Scientific and Technological Hub, University of Florence.

Breakthroughs made at the Institute of Physics near Florence before 1950 include Fermi statistics and the first electronic coincidence circuits

Florence was a flourishing centre for fundamental physics research throughout most of the twentieth century. Roberto Casalbuoni, Daniele Dominici and Massimo Mazzoni – all physicists currently working there – have reviewed the history of the city’s Institute of Physics for the journal EPJ H: Historical Perspectives on Contemporary Physics, concentrating on the important decades of the 1920s to 1960s.

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EPJ D Topical review - Theory and molecular simulations of plasma sputtering, transport and deposition processes

One shot atomistic simulations of sputtering deposition

A new Topical Review published in EPJD provides an overview of the basic theory of sputtering with recent models, focussing in particular on sputtered atom energy distribution functions. Models such as Monte-Carlo, kinetic Monte-Carlo, and classical Molecular Dynamics simulations are presented due to their ability to describe the various processes involved in sputtering, transport and deposition processes.

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EPJ E Highlight - Machine learning could help kites and gliders to harvest wind energy

Powering a ship with a kite

Using trial-and-error, machine learning algorithms could enable flying wind harvesters to dynamically adjust their orientations, allowing them to account for unpredictable turbulence and improve their performances.

Airborne wind energy (AWE) is a lightweight technology which uses flying devices including kites and gliders to harvest power from the atmosphere. To maximise the energy they extract, these devices need to precisely control their orientations to account for turbulence in Earth’s atmosphere. Through new research published in EPJ E, Antonio Celani and colleagues at the Abdus Salam International Center for Theoretical Physics, Italy, demonstrate how a Reinforcement Learning algorithm could significantly boost the ability of AWE devices to account for turbulence.

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Editors-in-Chief
B. Fraboni and G. García López
Thank you very much for your assistance and quick and excellent handling of the manuscript.

Jakub Bielecki, Institute of Nuclear Physics, Polish Academy of Sciences, Krakow, Poland

ISSN: 2190-5444 (Electronic Edition)

© Società Italiana di Fisica and
Springer-Verlag