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EPJ B Colloquium - Particles, conformal invariance and criticality in pure and disordered systems
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- Published on 23 March 2021
The two-dimensional case occupies a special position in the theory of critical phenomena due to the exact results provided by lattice solutions and, directly in the continuum, by the infinite-dimensional character of the conformal algebra. However, some sectors of the theory, and most notably criticality in systems with quenched disorder and short range interactions, have appeared out of reach of exact methods and lacked the insight coming from analytical solutions.
EPJ Plus Focus Point on Cancer & HIV/AIDS Dynamics: From Optimality to Modelling
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- Published on 19 March 2021
This Focus Point covers twelve original papers obtained from advanced theoretical analysis, experimental, and numerical simulations in Cancer and HIV/AIDS research. Results include a randomized discrete logistic equation to describe the dynamics of breast tumor; a mathematical model of breast cancer involving a system of differential equations with piecewise constant arguments to analyze the tumor growth and chemotherapeutic treatment; a new stochastic HIV mathematical model; incorporation of the Beddington–DeAngelis incidence rate to a continuous-time HIV infection model with cure rate and full logistic proliferation; a model for the tumor and normal cell growth under the influence of carcinogenic agents, an immunomodulator and variable influx of immune cells; a within-host HIV dynamical model under the effect of cytotoxic T lymphocytes immune response; the study of the interaction between drug addiction and the contagion of HIV/AIDS; a system of fractional differential equations with delays and a new computational method based on hybrid functions and Legendre polynomials with application to immunodeficiency viruses systems; investigation of cervical cancer; an HIV/AIDS epidemic model under fractal-fractional-order derivatives; study of the dynamics of HIV-AIDS infection via a fractional order SICA system; and sufficient conditions for the stability of a system describing the growth of malignant tumors.
EPJ E Highlight - Modelling speed-ups in nutrient-seeking bacteria
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- Published on 17 March 2021
By considering how some bacteria will swim faster within higher nutrient concentrations, researchers have created a more accurate model of how these microbes search for nutrients
Many bacteria swim towards nutrients by rotating the helix-shaped flagella attached to their bodies. As they move, the cells can either ‘run’ in a straight line, or ‘tumble’ by varying the rotational directions of their flagella, causing their paths to randomly change course. Through a process named ‘chemotaxis,’ bacteria can decrease their rate of tumbling at higher concentrations of nutrients, while maintaining their swimming speeds. In more hospitable environments like the gut, this helps them to seek out nutrients more easily. However, in more nutrient-sparse environments, some species of bacteria will also perform ‘chemokinesis’: increasing their swim speeds as nutrient concentrations increase, without changing their tumbling rates. Through new research published in EPJ E, Theresa Jakuszeit and a team at the University of Cambridge led by Ottavio Croze produced a model which accurately accounts for the combined influences of these two motions.
EPJ C Highlight - Factoring in gravitomagnetism could do away with dark matter
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- Published on 04 March 2021
Models of galactic rotation curves built of a general relativistic framework could use gravitomagnetism to explain the effects of dark matter.
Observations of galactic rotation curves give one of the strongest lines of evidence pointing towards the existence of dark matter, a non-baryonic form of matter that makes up an estimated 85% of the matter in the observable Universe. Current assessments of galactic rotation curves are based upon a framework of Newtonian accounts of gravity, a new paper published in EPJ C, by Gerson Otto Ludwig, National Institute for Space Research, Brazil, suggests that if this is substituted with a general relativity-based model, the need to recourse to dark matter is relieved, replaced by the effects of gravitomagnetism.
EPJ B Highlight - Considering disorder and cooperative effects in photon escape rates from atomic gases
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- Published on 26 February 2021
Investigating more complex models of photon escape rates from cold atomic gases could help researchers learn more about light-matter interactions.
Whilst a great deal of research has studied the rates of photons escaping from cold atomic gases, these studies have used a scalar description of light leaving some of its properties untested. In a new paper published in EPJ B Louis Bellando, a post-doctoral researcher at LOMA, University of Bordeaux, France, and his coauthors—Aharon Gero and Eric Akkermans, Technion-Israel Institute of Technology, Israel, and Robin Kaiser, Université Côte d'Azur, France—aim to numerically investigative the roles of cooperative effects and disorder in photon escape rates from a cold atomic gas to construct a model that considers the vectorial nature of light. Thus, the study accounts for properties of light, previously neglected.
EPJ E Highlight - Using neutron scattering to better understand milk composition
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- Published on 19 February 2021
By using a more complex model for neutron scattering data, researchers can better understand the composition of materials such as milk.
Neutron scattering is a technique commonly used in physics and biology to understand the composition of complex multicomponent mixtures and is increasingly being used to study applied materials such as food. A new paper published in EPJ E by Gregory N Smith, Niels Bohr Institute, University of Copenhagen, Denmark, shows an example of neutron scattering in the area of food science. Smith uses neutron scattering to better investigate casein micelles in milk, with the aim of developing an approach for future research.
Smith, also a researcher at the ISIS Neutron and Muon Source in the UK, explains why better modelling of how neutrons are scattered by structures in colloid materials is important. “How well you can understand the structure of a system from scattering data depends on how good your model is, and the better and more realistic your model, the better your understanding,” the researcher says. “This is true for food as for any material. A better understanding of the structure of casein in milk can help better understand dairy products.”
EPJ D Highlight - Investigating dense plasmas with positron waves
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- Published on 19 February 2021
Astrophysical and lab-created plasmas under the influence of magnetic fields are the source of intense study. New research seeks to understand the dynamics of position waves travelling through these clouds of highly ionised gas.
The investigation of Electron-Positron-Ion (EPI) plasma — a fully ionised gas of electrons and positrons that includes astrophysical plasmas like solar winds — has attracted a great deal of attention over the last twenty years. A new study published in EPJ D by Garston Tiofack, Faculty of Sciences, University of Marousa, Cameroon, and colleagues, assesses the dynamics of positron acoustic waves (PAWS) in EPI plasmas whilst under the influence of magnetic fields, or magnetoplasmas.
EPJ C Highlight - Placing cosmological constraints on quantum gravity phenomenology
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- Published on 09 February 2021
Researchers have used cosmological data to place stringent new limits on a model which emerges in attempts to reconcile gravity with the principles of quantum mechanics.
A description of gravity compatible with the principles of quantum mechanics has long been a widely pursued goal in physics. Existing theories of this ‘quantum gravity’ often involve mathematical corrections to Heisenberg’s Uncertainty Principle (HUP), which quantifies the inherent limits in the accuracy of any quantum measurement. These corrections arise when gravitational interactions are considered, leading to a ‘Generalized Uncertainty Principle’ (GUP). Two specific GUP models are often used: the first modifies the HUP with a linear correction, while the second introduces a quadratic one. Through new research published in EPJ C, Serena Giardino and Vincenzo Salzano at the University of Szczecin in Poland have used well-established cosmological observations to place tighter constraints on the quadratic model, while discrediting the linear model.
EPJ B Highlight - Modelling the brain during pain processing
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- Published on 02 February 2021
Novel approaches in graph theory have enabled researchers to reveal the characteristic configurations of neurons which arise as our brains process pain
The many different sensations our bodies experience are accompanied by deeply complex exchanges of information within the brain, and the feeling of pain is no exception. So far, research has shown how pain intensity can be directly related to specific patterns of oscillation in brain activity, which are altered by the activation and deactivation of the ‘interneurons’ connecting different regions of the brain. However, it remains unclear how the process is affected by ‘inhibitory’ interneurons, which prevent chemical messages from passing between these regions. Through new research published in EPJ B, researchers led by Fernando Montani at Instituto de Física La Plata, Argentina, show that inhibitory interneurons make up 20% of the circuitry in the brain required for pain processing.
EPJ A Highlight - Paving the way for effective field theories
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- Published on 01 February 2021
A detailed analysis of theories which approximate the underlying properties of physical systems could lead to new advances in studies of low-energy nuclear processes
Over the past century, a wide variety of models have emerged to explain the complex behaviours which unfold within atomic nuclei at low energies. However, these theories bring up deep philosophical questions regarding their scientific value. Indeed, traditional epistemological tools have been rather elaborated to account for a unified and stabilised theory rather than to apprehend a plurality of models. Ideally, a theory is meant to be reductionist, unifying and fundamentalist. In view of the intrinsic limited precision of their prediction and of the difficulty in assessing a priori their range of applicability, as well as of their specific and disconnected character, traditional nuclear models are necessarily deficient when analysed by means of standard epistemological interpretative frameworks.
