Autocatalytic binary polymer model (Vol. 45 No.5-6)

Template directed replication of information in polymers is at the essence of living beings, and is believed to be a cornerstone of life's origin. Using a binary polymer model, where polymers act as templates for their autocatalytic replication, we analyze the chemical reaction network in which replicators serve as reactants of each other and compete for common resources. The involved random ligation, degradation and autocatalytic replication reactions are shown in figure (a). Our idealized model demonstrates how autocatalysis in such a molecular ecology completely alters the qualitative and quantitative system dynamics in counter-intuitive ways. We demonstrate analytically that the system features a stationary state where the concentration of polymers does not decrease with length. Numerical simulations reveal a strong intrinsic selection mechanism that favors the appearance of few population structures with highly ordered sequence patterns when starting from a pool of monomers. An example of such a cooperative structure is shown in figure (b). This selection mechanism is due to symmetries in the underlying reaction network, and we discuss how these intrinsically selected species might be in line or in conflict with other prebiotic selection mechanisms.

S. Tanaka, H. Fellermann and S. Rasmussen, "Structure and selection in an autocatalytic binary polymer model", EPL, 107, 28004 (2014)
[Abstract]

Automated symmetry adaption in nuclear many-body theory (Vol. 52, No. 1)

The extreme cost of solving the A-nucleon Schrödinger equation can be minimised by leveraging rotational symmetry and, thus, enable the computation of observables in heavy nuclei and/or with high precision.

The associated reduction process, which amounts to re-expressing the working equations in terms of rotationally-invariant objects, requires lengthy symbolic manipulations of elaborate algebraic identities.

For the first time, this involved process is automated by a powerful graph-theory-based tool, the AMC code, which condenses months of error-prone derivations into a simple computational task performed within seconds.

The AMC program tightens the gap for a full automation of the many-body workflow, thereby lowering the time required to build and test novel quantum many-body formalisms.

A. Tichai, R. Wirth, J. Ripoche and T. Duguet, Symmetry reduction of tensor networks in manybody theory, Eur. Phys. J. A 56, 272 (2020)
[Abstract]

Avoiding environmental losses in quantum information systems (Vol. 51, No. 5)

Through new techniques for generating ‘exceptional points’ in quantum information systems, researchers have minimised the transitions through which they lose information to their surrounding environments.

Recently, researchers have begun to exploit the effects of quantum mechanics to process information in some fascinating new ways. One of the main challenges faced by these efforts is that systems can easily lose their quantum information as they interact with particles in their surrounding environments.

To understand this behaviour, researchers in the past have used advanced models to observe how systems can spontaneously evolve into different states over time – losing their quantum information in the process. We have discovered how robust initial states can be prepared in quantum information systems, avoiding any unwanted transitions extensive time periods.

R Ramírez, M Reboiro , D Tielas, Exceptional Points from the Hamiltonian of a hybrid physical system: Squeezing and anti-Squeezing, Eur. Phys. J. D 74, 193 (2020)
[Abstract]

Back to basics with thermoelectric power (Vol. 47 No. 3)

New study highlights the role of electron diffusivity when turning waste heat into electricity

Many phenomena in physics, though well-known, are not necessarily widely understood. That’s the case with thermoelectricity, which harnesses waste heat by coupling heat flux and electric current. However, understanding such phenomena is important in order to leave the door open for discovering novel manifestations of them. Thus, even today, physicists working in the area of thermoelectricity continue to ask fundamental questions about the underlying physical process. For example, in a recent study, the authors questioned the nature of the force that puts electrons to work when a temperature difference is applied across a thermoelectric material. Now, they have published a study showing that the force that puts electrons to work to harness the waste heat is linked to the ability of electrons to diffuse through the material. Potential applications in the field of electrical power production from waste heat include thermoelectric devices designed to boost power over a range spanning ten orders of magnitude: typically from microwatts to several kilowatts.

Y. Apertet, H. Ouerdane, C. Goupil and Ph. Lecoeur, A note on the electrochemical nature of thermoelectric power, Eur. Phys. J. Plus 131, 76 (2016)
[Abstract]

Bacteria-inspired motility could power a new generation of mini-robots (Vol. 50, No. 1)

Physicists develop a model to explain how deforming a helix could generate additional locomotion for some microorganisms and mini-robots

Many microorganisms rely on helices to move. For example, some bacteria rotate a helical tail, called a flagellar filament, for thrust and deform these tails during rotation. In addition, some types of bacteria, named Spirochaetes, rely on the deformation of a helical body for their motion. To better understand such locomotion mechanisms, scientists have created mathematical models of mini-robots with helical structures, referred to as swimmers. In a study published recently, the authors identify the factors enhancing the agility of deforming helix swimmers. They examine what happens when these swimmers placed in a fluid uniformly change the radius, the helical pitch and the wavelength of the helix across their body. They identify swimming strokes that allow rotation and motion in a given direction and thus explain how the helix’s deformation influences the direction in which the swimmers move.

L. Koens, H. Zhang, M. Moeller, A. Mourran, and E. Lauga, The swimming of a deforming helix, Eur. Phys. J. E 41, 119 (2018)
[Abstract]

Balancing renewable energy costs (Vol. 45 No.5-6)

Simulating the cost of generating a combination of electricity sources while accounting for the fluctuating nature of energy production and demand provides tools to optimise such energy mix.

Increasing reliance on renewable energies is the way to achieve greater CO₂ emission sustainability and energy independence. Yet, because such energies are only available intermittently and energy cannot be stored easily, most countries aim to combine several energy sources. Now, in a new study, the authors have come up with an open source simulation method to calculate the actual cost of relying on a combination of electricity sources. They demonstrate that cost is not directly proportional to the demand level. Although recognised as crude by its creator, this method can be tailored to account for the public’s interest—and not solely economic performance—when optimising the energy mix.

B. Bonin, H. Safa, A. Laureau, E. Merle-Lucotte, J. Miss and Y. Richet, “MIXOPTIM: a tool for the evaluation and the optimization of the electricity mix in a territory”, Eur. Phys. J. Plus, 129, 198 (2014)
[Abstract]

Best tactical approach to handling patients with simultaneous parasitic and HIV infection (Vol. 48, No. 5-6)

New mathematical model for cryptosporidiosis - HIV co-infection explores their synergistic relationship in connection with prevention and treatment

One of the most common waterborne diseases worldwide is cryptosporidiosis, a parasitic disease affecting the small intestine and possibly our airways. It is a common cause of diarrhoea in HIV-positive patients, who are known to have lower immunity. Now the authors have developed a new model and numerical simulations to determine the optimal combination of prevention and treatment strategies for controlling both diseases in patients who have been co-infected. Their results, recently published, show a positive impact on the treatment and prevention for cryptosporidiosis alone, for HIV-AIDS alone, or for both together. They found that cryptosporidiosis preventions and treatment alone had no significant impact on reducing HIV-AIDS-related problems. By contrast, the prevention and treatment strategy for HIV-AIDS had a significant positive impact on the co-infected patients. Finally, applying both strategies at the same time resulted in reduction in all cases.

K.O. Okosun, M.A. Khan, E. Bonyah and S.T. Ogunlade, On the dynamics of HIV-AIDS and cryptosporidiosis, Eur. Phys. J. Plus 132, 363 (2017)
[Abstract]

Better chemo drug adsorption onto targeted delivery capsules (Vol. 49 No.5-6)

New study demonstrates adsorption of chemotherapy drugs onto active carbon delivery capsule can be enhanced with aluminium atom inclusions

The efficacy of chemotherapy treatment depends on how effectively it reaches cancerous cells. Increasing targeted delivery could mean decreasing side effects. Scientists are enhancing methods of selectively transmitting active chemotherapy agents and reducing their toxicity by encapsulating chemo drugs into active carbon used as the targeted delivery device. In a new study published recently, the authors have demonstrated that adding minute amounts of aluminium atoms onto activated carbon atoms helps increase the adsorption onto the delivery carbon capsule of a standard chemotherapy drug, called 5-Fluorouracil (5-FU). This drug is typically used for stomach, colorectal, neck and head cancer treatments. This model could lead to more effective and convenient cancer treatments with fewer side effects by encapsulating the chemo drug into the active carbon, so that it can be taken orally.

G. Román, E. Noseda Grau, A. Diaz Compañy, G. Brizuela, A. Juan, and S. Simonetti, A first-principles study of pristine and Al-doped activated carbon interacting with 5-Fluorouracil anticancer drug, Eur. Phys. J. E 41, 107 (2018)
[Abstract]

Better defining the signals left by as-yet-undefined dark matter at the LHC (Vol. 47 No. 5-6)

New theoretical models that better describe the interaction between dark matter and ordinary particles advance the quest for dark matter

In the quest for dark matter, physicists rely on particle colliders such as the LHC in CERN, located near Geneva, Switzerland. The trouble is: physicists still don't know exactly what dark matter is. Indeed, they can only see its effect in the form of gravity. Until now, theoretical physicists have used models based on a simple, abstract description of the interaction between dark matter and ordinary particles, such as the Effective Field Theories (EFTs). However, until we observe dark matter, it is impossible to know whether or not these models neglect some key signals. Now, the high energy physics community has come together to develop a set of simplified models, which retain the elegance of EFT-style models yet provide a better description of the signals of dark matter, at the LHC. These developments are described in a review published by the authors.

A. De Simone and T. Jacques, Simplified models vs. effective field theory approaches in dark matter searches, Eur. Phys. J. C 76, 367 (2016)
[Abstract]

Better material insights with gentle e-beams (Vol. 47 No. 5-6)

Great potential for a new, more accurate, tool for using electron collisions to probe matter

There are several ways to change a molecule, chemically or physically. One way is to heat it; another is to bombard it with light particles, or photons. A lesser known method relies on electron collision, or e-beam technology, which is becoming increasingly popular in industry. In a review outlining new research avenues based on electron scattering, the authors explain the subtle intricacies of the extremely brief electron-molecule encounter, in particular with gentle, i.e., very low energy electrons. In this paper, which was recently published, the authors describe how the use of very low energy electrons and a number of other performance criteria, make the approach with the so-called Fribourg instrument a more appealing candidate than previously available tools used to study electron collisions. One of the potential applications of this approach is in the quest to find a replacement for a molecule called sulfur hexafluoride (SF6), a greenhouse gas stored in high voltage electricity distributing devices, such as switches and transformers. Electron collision could help identify a more suitable gas.

M. Allan, K. Regeta, J. D. Gorfinkiel, Z. Mašín, S. Grimme and C. Bannwarth, Recent research directions in Fribourg: nuclear dynamics in resonances revealed by 2-dimensional EEL spectra, electron collisions with ionic liquids and electronic excitation of pyrimidine, Eur. Phys. J. D 70, 123 (2016)
[Abstract]

Better safeguards for sensitive information (Vol. 50, No. 2)

Study improves the lower boundary and secret key capacity of an encryption channel

The secure encryption of information units based on a method called quantum key distribution (QKD) involves distributing secret keys between two parties—namely, Alice, the sender, and Bob, the receiver—by using quantum systems as information carriers. However, the most advanced quantum technology, QKD, is currently limited by the channel's capacity to send or share secret bits. In a recent study the authors show how to better approach the secret key capacity by improving the channel's lower boundary. They focus on a particular type of channel, called the noisy thermal amplifier channel, where the input signals are amplified together with noise induced by the thermal environment. The authors calculate the highest-known amount of secret information units, or bits, that Alice and Bob can share via such a channel. This is done by injecting controlled noise—made up of well-defined thermal agitation—into the detection apparatuses. By optimising over this noise, they improve the lower boundary of the capacity in the amplifier channel. The authors also confirm that the distribution of secret keys over this channel may occur at higher rates than the transmission of quantum information itself.

G. Wang, C. Ottaviani, H. Guo, and S. Pirandola, Improving the lower bound to the secret-key capacity of the thermal amplifier channel, Eur. Phys. J. D 73, 17 (2019)
[Abstract]

Biological rhythms—what sets their amplitude? (Vol. 49, No. 2)

Living organisms rely on internal biological timers to ensure their proper development and functioning during adult life; examples are the formation of repetitive embryonic patterns or the entrainment of activity cycles to the day-night cycle. Such timers are typically embodied as biochemical oscillators, i.e., genetic regulatory networks that generate oscillations in the concentration of gene products within cells via a delayed negative feedback. Theoretical descriptions of these oscillators often rely on nonlinear rate equations that describe how the interactions between different gene products can give rise to stable limit-cycle oscillations. For a large class of such models, we here derive a method to construct analytical bounds for the minima and maxima of the oscillations, one of their functional key features besides their period. Numerical simulations of different example systems show that the oscillations saturate the bounds as the feedback delay becomes large. The results shed light on which details of the nonlinear feedback are responsible for constraining the oscillation amplitude and can be readily generalised to similar oscillator systems.

D. J. Jörg, Amplitude bounds for for biochemical oscillators, EPL 119, 58004 (2017)
[Abstract]

Bose condensation gives new insight into turbulent advection (Vol. 41, No. 6)

Bose-like condensation of Lagrangian particles and higher-order statistics in passive scalar turbulent advection
T. Dombre, EPL, 91, 54002 (2010)
[Abstract]