- Published on 09 April 2019
A new study explores how the characteristics of aromaticity affect the process of Auger decay
When an electron from one of the lower energy levels in an atom is knocked out of the atom, it creates a space which can be filled by one of the higher-energy electrons, also releasing excess energy. This energy is released in an electron called an Auger electron - and produces an effect known as Auger decay. Now, Guoke Zhao from Tsinghua University in Beijing, China and colleagues at Sorbonne University in Paris, France have studied the Auger effect in four hydrocarbon molecules: benzene, cyclohexane, hexatriene and hexadiene. These molecules were chosen because they exhibit different characteristics of aromaticity. The authors found that molecules containing pi bonds have a lower threshold for Auger decay.
- Published on 03 April 2019
Magnetic hyperthermia is still a highly experimental cancer treatment, but new research shows that the therapy is tunable
Unfortunately, cancer isn’t simply a single disease, and some types, like pancreas, brain or liver tumours, are still difficult to treat with chemotherapy, radiation therapy or surgery, leading to low survival rates for patients. Thankfully, new therapies are emerging, like therapeutic hyperthermia, which heats tumours by firing nanoparticles into tumour cells. In a new study published in EPJ B, Angl Apostolova from the University of Architecture, Civil Engineering and Geodesy in Sofia, Bulgaria and colleagues show that tumour cells’ specific absorption rate of destructive heat depends on the diameter of the nanoparticles and the composition of the magnetic material used to deliver the heat to the tumour.
- Published on 03 April 2019
Using computational models to investigate how liquid drops behave on surfaces
Whether we're aware of it or not, in day-to-day life we often witness an intriguing phenomenon: the breakup of jets of liquid into chains of droplets. It happens when it rains, for example, and it is important for inkjet printers. However, little is known about what happens when a liquid jet, also known as a liquid filament, breaks up on top of a substrate. According to a new study, the presence of a nearby surface changes the way the filament breaks up into smaller droplets. In a new paper published by Andrew Dziedzic at the New Jersey Institute of Technology in Newark, New Jersey, USA, and colleagues in EPJ E, computer simulations are used to show that a filament is more likely to break up near a surface.
- Published on 02 April 2019
New model improves our understanding of energy transfer in radiotherapy treatment plans by replacing 50-year-old parameters with more complex ones
Particle beam therapy is increasingly being used to treat many types of cancer. It consists in subjecting tumours to beams of high-energy charged particles such as protons. Although more targeted than conventional radiotherapy using X-rays, this approach still damages surrounding normal tissue. To design the optimum treatment plan for each patient, it is essential to know the energy of the beam and its effect on tumour and normal tissue alike. In a recent study published in EPJ D, a group of researchers led by Ramin Abolfath at the University of Texas MD Anderson Cancer Center, Houston, Texas, USA, put forward a new mathematical model outlining the effects of these beam therapies on patients' tissues, based on new, more complex, parameters. Using these new models, clinicians should be able to predict the effect of proton beams on normal and tumour tissue more precisely, allowing them to prepare more effective treatment plans.
EPJ B Colloquium - Cooperative magnetic phenomena in artificial spin systems: spin liquids, Coulomb phase and fragmentation of magnetism
- Published on 28 March 2019
Two-dimensional arrays of interacting magnetic nanostructures offer a remarkable playground for simulating, experimentally, lattice spin models. Initially designed to capture the low-energy physics of highly frustrated magnets, they quickly became a lab-on-chip platform to investigate cooperative magnetic phenomena often associated with classical frustrated magnetism.
This Colloquium paper from Nicolas Rougemaille and Benjamin Canals at the Institut NEEL (Univ. Grenoble, CNRS, France) reviews the many-body physics which can be visualized, directly in real space, through the magnetic imaging of artificial arrays of magnetic nanostructures. Particular attention is paid to classical spin liquid states, magnetic Coulomb phases and magnetic moment fragmentation. Other phenomena, such as complex magnetic ordering, charge crystallization and monopole-like excitations, are also described in light of the recent advances in the field.
- Published on 27 March 2019
A liquid-lithium target (LiLiT) bombarded by a 1.5 mA, 1.92 MeV proton beam from the SARAF superconducting linac acts as a ~30 keV quasi-Maxwellian neutron source via the 7Li(p,n) reaction with the highest intensity (5×1010 neutrons/s) available todate. We activate samples relevant to stellar nucleosynthesis by slow neutron capture (s-process). Activation products are detected by α, β or γ spectrometry or by direct atom counting (accelerator mass spectrometry, atom-trap trace analysis). The neutron capture cross sections, corrected for systematic effects using detailed simulations of neutron production and transport, lead to experimental astrophysical Maxwellian averaged cross sections (MACS). A parallel effort to develop a LiLiT-based neutron source for cancer therapy is ongoing, taking advantage of the neutron spectrum suitability for Boron Neutron Capture Therapy (BNCT) and the high neutron yield available.
Michael Paul et al. (2019), Reactions along the astrophysical s-process path and prospects for neutron radiotherapy with the Liquid-Lithium Target (LiLiT) at the Soreq Applied Research Accelerator Facility (SARAF), Eur. Phys. J. A 55: 44, DOI 10.1140/epja/i2019-12723-5
- Published on 27 March 2019
A comparison of two models for stock market prediction shows clear differences in their accuracy, depending on the length of the forecasting period
Understanding stock market returns hinges on understanding their volatility. Two simple but competing models have been dominant for decades: the Heston model, introduced in 1993, and the multiplicative model, which dates back to 1990. American physicists recently compared the two models by applying them to the United States stock market and using historical data from two indexes: the S&P500 and Dow Jones Industrial Average. In a study published in EPJ B, Rostislav Serota and colleagues from the University of Cincinnati, OH, USA, demonstrate the clear differences between the two models. Simply put, the Heston model is better for predicting long-time accumulations of stock returns, while the multiplicative model is better suited to predicting daily or several-day returns.
- Published on 26 March 2019
A new research paper finds the high-energy physics concept of 'un-naturalness' may be applicable to the study of turbulence or that of strongly correlated systems of elementary particles
Many scientists have been disappointed that no new elementary particles have been discovered at CERN's Large Hadron Collider in the wake of the Higgs boson discovery in 2012. The no-show of elusive particles that had previously been predicted by theory is only one example of a 'hole' that has recently appeared in the concept of Naturalness in theoretical physics. In simple terms, the concept states that physical parameters should depend roughly equally on all the terms used to calculate them, in terms of proportion. Sauro Succi, a theoretical physicist at the Fondazione Istituto Italiano di Tecnologia in Rome, Italy, has now published an intriguing essay in the journal EPJ Plus in which he argues that several common natural phenomena do not operate under ‘Naturalness' at all. Rather, they can only be explained using parameters with widely separated numerical values.
- Published on 26 March 2019
An invention from the 1950s is still being used today
What do televisions and space exploration have in common? No, we’re not talking about a cheesy physics joke; rather, this is the story of an often-overlooked piece of equipment that deserves a place in the annals of telecommunication history. Some would argue that the traveling-wave tube (TWT) has not received the recognition it deserves when it comes to the history of space travel and communications – until now. A group of researchers based at the Aix-Marseille Université in France has published a review looking into the history of TWTs, recently published in EPJ H.
- Published on 20 March 2019
Metashells can adapt their wave-bending behaviour based on the characteristics of the material they contain
A chameleon can flexibly change its colour to match its surroundings. And a similar phenomenon can now be seen in a new class of smart materials called metamaterials. The trouble is that these metamaterials lack the ability to respond to nearby objects due to their physical characteristics. To remedy this shortcoming, Chinese physicists have developed so-called 'metashells': hollow shells made of metamaterials and capable of carrying materials in their core. The advantage is that their physical characteristics, such as permittivity - the extent to which a material can store charge within an electrical field - change with the electromagnetic properties of the material they contain. In a recent theoretical study published in EPJ B, Liujun Xu and Jiping Huang from Fudan University in Shanghai, China, describe how they have developed an entire class of these chameleon-like metashells.