- Published on 30 May 2018
Patchy particles is the name given to a large class of systems of mesoscopic particles characterized by a repulsive core and a discrete number of short-range and highly directional interaction sites. Numerical simulations have contributed significantly to our understanding of the behaviour of patchy particles, but, although simple in principle, advanced simulation techniques are often required to sample the low temperatures and long time-scales associated with their self-assembly behaviour.
In this EPJ E colloquium paper, Rovigatti et al. review the most popular simulation techniques that have been used to study patchy particles, with a special focus on Monte Carlo methods.
- Published on 23 May 2018
A new study shows how to couple highly accurate and simplified models of the same system to extract thermodynamics information using simulations
Computer simulations are used to understand the properties of soft matter - such as liquids, polymers and biomolecules like DNA - which are too complicated to be described by equations. They are often too expensive to simulate in full, given the intensive computational power required. Instead, a helpful strategy is to couple an accurate model - applied in the areas of the system that require greater attention - with a simpler, idealised model. In a recent paper published in EPJ E, Maziar Heidari, from the Max Planck Institute for Polymer Research, Mainz, Germany and colleagues make the accurate model in high-resolution coincide seamlessly with an exactly solvable representation at lower resolution.
- Published on 22 May 2018
A team in China has just calculated the size of scale-free and small-world networks
Networks are often described as trees with spanning branches. How the tree branches out depends on the logic behind the network’s expansion, such as random expansion. However, some aspects of such randomly expanding networks are invariant; in other words, they display the same characteristics, regardless of the network’s scale. As a result, the entire network has the same shape as one or more of its parts. In a new study published in EPJ B, Fei Ma from Northwest Normal University in Lanzhou, Gansu Province, China, anc colleagues calculate the total number of spanning trees in randomly expanding networks. This method can be applied to modelling scale-free network models, which, as it turns out, are characterised by small-world properties. This means, for instance, that members of the network only exhibit six degrees of separation, like most people in our society.
- Published on 16 May 2018
Revisiting the roots of a physics field known as computational statistical mechanics
It may sound like the stuff of fairy tales, but in the 1950s two numerical models initially developed as a pet project by physicists led to the birth of an entirely new field of physics: computational statistical mechanics. This story has recently appeared in a paper published in EPJ H, authored by Michel Mareschal, an Emeritus Professor of Physics at the Free University of Brussels, Belgium. The article outlines the long journey leading to the acceptance of such models - namely Monte Carlo and Molecular Dynamics simulations - as reliable evidence for describing matter. This happened at a time when the computing power required to run simulations was scarce. Today, these techniques are used by thousands of researchers to model the behaviour of materials, in contexts ranging from fusion to biological systems.
- Published on 15 May 2018
The field of experimental positronium physics has advanced significantly in the last few decades, with new areas of research driven by the development of techniques for trapping and manipulating positrons using Surko-type buffer gas traps. Large numbers of positrons (typically ≥106) accumulated in such a device may be ejected all at once, so as to generate an intense pulse.
- Published on 14 May 2018
New study outlines key factors affecting the transfer of molecules through biological channels
In our bodies, the transfer of genetic information, viral infections and protein trafficking, as well as the synthesis and the degradation of biomolecules, are all phenomena that require the transport of molecules through channels. Improving our control of these channels and the capacity of molecules to get across could have many potential applications in the fields of energy, biotechnology and medicine. These include ultra-fast DNA sequencing, detection of biological markers used in disease diagnostics, protein folding, high-resolution determination of the size of biological molecules or even the control of ion or biomolecule transport through the protein sensor. In a new study published in EPJ E, Manuela Pastoriza-Gallego from the University Paris-Seine, France, and colleagues have shown how to alter external factors, such as external voltage, to control the transport of a dextran sulfate molecule - a polyelectrolyte - through the nanopores of the aerolysin protein channel.
- Published on 03 May 2018
Improving the spatial compression of a mixed matter-antimatter trapped plasma brings us one step closer to grasping the acceleration of antimatter due to Earth’s gravity
An international team of physicists studying antimatter have now derived an improved way of spatially compressing a state of matter called non-neutral plasma, which is made up of a type of antimatter particles, called antiprotons, trapped together with matter particles, like electrons.
- Published on 27 April 2018
An open source software that is able to construct synthetic blood vessel networks in 3D, matching the properties observed in real tumor samples.
The tumor vasculature is a major target of anticancer therapies. Rieger, Fredrich and Welter at Saarland University, Germany have been pursuing a quantitative analysis of the physical determinants of vascularized tumors for several years . With the help of computer simulations they have been able to recapitulate the knowledge accrued from in vitro research of tumor spheroids, animal models and clinical studies and have re-created a vascularized tumor system in silico.
- Published on 27 April 2018
In an article just published in EPJ Data Science, Valentin Kassarnig, Sune Lehmann and Andreas Bjerre-Nielsen look into smartphone data of undergraduate students to assess factors influencing social behavior and educational performance.
(Guest post by Valentin Kassarnig, Sune Lehmann & Andreas Bjerre-Nielsen, originally published on the SpringerOpen blog)
- Published on 25 April 2018
Tuning the graphene embedded in a photonic crystal by varying the external temperature can transform it into a light-sensitive sensor
Graphene has many properties; it is e.g. an extremely good conductor. But it does not absorb light very well. To remedy this limiting aspect of what is an otherwise amazing material, physicists resort to embedding a sheet of graphene in a flat photonic crystal, which is excellent for controlling the flow of light. The combination endows graphene with substantially enhanced light-absorbing capabilities. In a new study published in EPJ B, Arezou Rashidi and Abdolrahman Namdar from the University of Tabriz, Iran demonstrate that, by altering the temperature in such a hybrid cavity structure, they can tune its capacity for optical absorption. They explain that it is the thermal expansion and thermo-optical effects which give the graphene these optical characteristics. Potential applications include light sensors, ultra-fast lasers, and systems capable of modulating incoming optical beams.