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Physics, Volume 3, Issue 1 (March 2021) – 12 articles

Cover Story (view full-size image): In 1950, Alan M. Turing wondered if brain networks operate under a critical regimen, referring to the neuron’s sensitivity to receive activity and then propagate it. Ordered or silent systems poorly propagate information, whereas highly sensitive systems exhibit overactivation that does not allow dynamic pattern recovery. In contrast, many biological systems, including brain networks, share intermediate or critical stability properties, displaying a broad dynamic repertoire, memory, and robustness. Moreover, the metabolic cost could shape the brain network dynamics during biological evolution. We show that critical neural dynamics exhibits minimum metabolic consumption and global communication, outperforming highly sensitive and ordered systems. View this paper.
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Article
A Hidden Anomaly in the Binary Mixture Natural Convection Subject to Flux Boundary Conditions
Physics 2021, 3(1), 144-159; https://0-doi-org.brum.beds.ac.uk/10.3390/physics3010012 - 23 Mar 2021
Viewed by 475
Abstract
The problem of natural convection in a binary mixture subject to realistic boundary conditions of imposed zero mass flux on the solid walls shows solutions that might lead to unrealistic negative values of the mass fraction (or solute concentration). This anomaly is being [...] Read more.
The problem of natural convection in a binary mixture subject to realistic boundary conditions of imposed zero mass flux on the solid walls shows solutions that might lead to unrealistic negative values of the mass fraction (or solute concentration). This anomaly is being investigated in this paper, and a possible way of addressing it is suggested via a mass-fraction-dependent thermodiffusion coefficient that can have negative values in regions of low mass fractions. Full article
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Article
Sensitivity of Solid-Scintillator Detectors to Dark Matter
Physics 2021, 3(1), 128-143; https://0-doi-org.brum.beds.ac.uk/10.3390/physics3010011 - 22 Mar 2021
Viewed by 656
Abstract
This paper shortly reviews the sensitivities that can be achieved to unambiguously point out the presence of a signal of Galactic origin in dark matter experiments with solid-scintillator detectors. Examples of the experimental sensitivities obtained by exploiting the annual and diurnal modulation signatures [...] Read more.
This paper shortly reviews the sensitivities that can be achieved to unambiguously point out the presence of a signal of Galactic origin in dark matter experiments with solid-scintillator detectors. Examples of the experimental sensitivities obtained by exploiting the annual and diurnal modulation signatures are reported with particular regard to the investigations performed in the framework of the DAMA Collaboration. The directionality approach in solid scintillators is also presented and, in particular, the perspectives of the ADAMO project are discussed. Full article
(This article belongs to the Special Issue Radiation Spectroscopy with Solid Scintillators for Rare Events)
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Article
Comparison of Main Covid-19 Outbreaks and Interpretation Based on Age Differences
Physics 2021, 3(1), 119-127; https://0-doi-org.brum.beds.ac.uk/10.3390/physics3010010 - 16 Mar 2021
Viewed by 539
Abstract
The main scope of this study is a critical comparison of data coming from different regions in the world, where significant outbreaks of the Covid-19 pandemic took place, accounting for age differences among the considered samples. Scaling laws are derived, driving interpretations of [...] Read more.
The main scope of this study is a critical comparison of data coming from different regions in the world, where significant outbreaks of the Covid-19 pandemic took place, accounting for age differences among the considered samples. Scaling laws are derived, driving interpretations of the death toll in the analyzed clusters. Full article
(This article belongs to the Special Issue Physics Methods in Coronavirus Pandemic Analysis)
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Review
Enriched Crystal Scintillators for 2β Experiments
Physics 2021, 3(1), 103-118; https://0-doi-org.brum.beds.ac.uk/10.3390/physics3010009 - 09 Mar 2021
Cited by 1 | Viewed by 685
Abstract
The investigation of 2β decay is an important issue in modern physics, allowing the test of the Standard Model of elementary particles and the study of the nature and properties of neutrinos. The crystal scintillators, especially made of isotopically-enriched materials, are powerful detectors [...] Read more.
The investigation of 2β decay is an important issue in modern physics, allowing the test of the Standard Model of elementary particles and the study of the nature and properties of neutrinos. The crystal scintillators, especially made of isotopically-enriched materials, are powerful detectors for 2β decay experiments thanks to the high radiopurity level and the possibility to realize the calorimetric “source = detector” approach with a high detection efficiency. For the moment, the 2ν2β processes have been observed at the level of 1019–1024 years with enriched crystals; the sensitivity to the 0ν mode have reached the level of 1024–1026 years in some decay channels for different nuclides allowing one to calculate the upper limits on the effective mass of the Majorana neutrino at the level of 0.1–0.6 eV. The paper is intended to be a review on the latest results to investigate 2β processes with crystal scintillators enriched in 48Ca, 106Cd, and 116Cd. Full article
(This article belongs to the Special Issue Radiation Spectroscopy with Solid Scintillators for Rare Events)
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Article
Simulation of Spatial Spread of the COVID-19 Pandemic on the Basis of the Kinetic-Advection Model
Physics 2021, 3(1), 85-102; https://0-doi-org.brum.beds.ac.uk/10.3390/physics3010008 - 18 Feb 2021
Cited by 1 | Viewed by 781
Abstract
A new two-parameter kinetic equation model is proposed to describe the spatial spread of the virus in the current pandemic COVID-19. The migration of infection carriers from certain foci inherent in some countries is considered. The one-dimensional model is applied to three countries: [...] Read more.
A new two-parameter kinetic equation model is proposed to describe the spatial spread of the virus in the current pandemic COVID-19. The migration of infection carriers from certain foci inherent in some countries is considered. The one-dimensional model is applied to three countries: Russia, Italy, and Chile. Both their geographical location and their particular shape stretching in the direction from the centers of infection (Moscow, Lombardy, and Santiago, respectively) make it possible to use such an approximation. The dynamic density of the infected is studied. Two parameters of the model are derived from known data. The first is the value of the average spreading rate associated with the transfer of infected persons in transport vehicles. The second is the frequency of the decrease in numbers of the infected as they move around the country, associated with the arrival of passengers at their destination. An analytical solution is obtained. Simple numerical methods are also used to perform a series of calculations. Calculations us to make some predictions, for example, about the time of recovery in Russia, if the beginning of recovery in Moscow is known. Full article
(This article belongs to the Special Issue Physics Methods in Coronavirus Pandemic Analysis)
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Review
Material Screening with Mass Spectrometry
Physics 2021, 3(1), 71-84; https://0-doi-org.brum.beds.ac.uk/10.3390/physics3010007 - 15 Feb 2021
Cited by 1 | Viewed by 785
Abstract
Inductively coupled plasma mass spectrometry is a powerful analytical technique. Because of its sensitivity, accuracy, multielement capability, high throughput, rapid analysis times and low detection limits, it is able to determine simultaneously long-lived radionuclides at trace and ultra-trace levels as well as isotope [...] Read more.
Inductively coupled plasma mass spectrometry is a powerful analytical technique. Because of its sensitivity, accuracy, multielement capability, high throughput, rapid analysis times and low detection limits, it is able to determine simultaneously long-lived radionuclides at trace and ultra-trace levels as well as isotope ratios. It has been increasingly applied in the framework of rare events experiments like those investigating the nature of dark matter and neutrinos, where the screening and selection of extremely radiopure materials for the experimental apparatus is crucial. Here, the inductively coupled plasma mass spectrometry (ICP-MS) measurements of the chemical purity of a Cs2HfCl6 crystal scintillator used to study α decay of naturally occurring Hf isotopes and its own raw materials are reported. Moreover, in the framework of the GERDA/LEGEND experiment, an overview of the ICP-MS results to monitor the recycling process of enriched germanium scraps is shown. Significant outcomes, such as low detection limits despite the small amount of sample to analyze and fast ICP-MS results, have been achieved in response to the challenges required by modern low background experiments. Full article
(This article belongs to the Special Issue Radiation Spectroscopy with Solid Scintillators for Rare Events)
Article
Relativistic Ermakov–Milne–Pinney Systems and First Integrals
Physics 2021, 3(1), 59-70; https://0-doi-org.brum.beds.ac.uk/10.3390/physics3010006 - 12 Feb 2021
Viewed by 617
Abstract
The Ermakov–Milne–Pinney equation is ubiquitous in many areas of physics that have an explicit time-dependence, including quantum systems with time-dependent Hamiltonian, cosmology, time-dependent harmonic oscillators, accelerator dynamics, etc. The Eliezer and Gray physical interpretation of the Ermakov–Lewis invariant is applied as a guiding [...] Read more.
The Ermakov–Milne–Pinney equation is ubiquitous in many areas of physics that have an explicit time-dependence, including quantum systems with time-dependent Hamiltonian, cosmology, time-dependent harmonic oscillators, accelerator dynamics, etc. The Eliezer and Gray physical interpretation of the Ermakov–Lewis invariant is applied as a guiding principle for the derivation of the special relativistic analog of the Ermakov–Milne–Pinney equation and associated first integral. The special relativistic extension of the Ray–Reid system and invariant is obtained. General properties of the relativistic Ermakov–Milne–Pinney are analyzed. The conservative case of the relativistic Ermakov–Milne–Pinney equation is described in terms of a pseudo-potential, reducing the problem to an effective Newtonian form. The non-relativistic limit is considered to be well. A relativistic nonlinear superposition law for relativistic Ermakov systems is identified. The generalized Ermakov–Milne–Pinney equation has additional nonlinearities, due to the relativistic effects. Full article
(This article belongs to the Section Classical Physics)
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Article
Critical Neural Networks Minimize Metabolic Cost
Physics 2021, 3(1), 42-58; https://0-doi-org.brum.beds.ac.uk/10.3390/physics3010005 - 10 Feb 2021
Viewed by 1304
Abstract
Brain dynamics show a rich spatiotemporal behavior whose stability is neither ordered nor chaotic, indicating that neural networks operate at intermediate stability regimes including critical dynamics represented by a negative power-law distribution of avalanche sizes with exponent α=1.5. However, it is unknown which stability regimen allows global and local information transmission with reduced metabolic costs, which are measured in terms of synaptic potentials and action potentials. In this work, using a hierarchical neuron model with rich-club organization, we measure the average number of action potentials required to activate n different neurons (avalanche size). Besides, we develop a mathematical formula to represent the metabolic synaptic potential cost. We develop simulations variating the synaptic amplitude, synaptic time course (ms), and hub excitatory/inhibitory ratio. We compare different dynamic regimes in terms of avalanche sizes vs. metabolic cost. We also implement the dynamic model in a Drosophila and Erdos–Renyi networks to computer dynamics and metabolic costs. The results show that the synaptic amplitude and time course play a key role in information propagation. They can drive the system from subcritical to supercritical regimes. The later result promotes the coexistence of critical regimes with a wide range of excitation/inhibition hub ratios. Moreover, subcritical or silent regimes minimize metabolic cost for local avalanche sizes, whereas critical and intermediate stability regimes show the best compromise between information propagation and reduced metabolic consumption, also minimizing metabolic cost for a wide range of avalanche sizes. Full article
(This article belongs to the Section Life Physics)
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Article
Scattering on Quasi-Spherical Black-Holes: Features and Beyond
Physics 2021, 3(1), 17-41; https://0-doi-org.brum.beds.ac.uk/10.3390/physics3010004 - 28 Jan 2021
Viewed by 877
Abstract
Recent developments in the gravitational waves interferometry require more pertinent theoretical models of gravitational waves generation and propagation. Untouched possible mechanisms of spin-2 spacetime perturbations production, we will consider their subsequent scattering on other black holes (BHs). Specifically, we consider a generalization of [...] Read more.
Recent developments in the gravitational waves interferometry require more pertinent theoretical models of gravitational waves generation and propagation. Untouched possible mechanisms of spin-2 spacetime perturbations production, we will consider their subsequent scattering on other black holes (BHs). Specifically, we consider a generalization of the Regge-Wheeler-Zerilli equations for the case of distorted BHs (BHs surrounded with matter) in Minkowski and Anti-de Sitter spacetimes, the metric potential of which obeys the Liouville equation. We establish significant differences in scattering characteristics of waves of different spins and angular momenta, including the gravitational waves, caused by losing the spherical symmetry of their propagation background. In particular, we demonstrate the strong impact of the background geometry deformation on the grey-body factors, hence on the absorption cross-sections of scattering waves, and explore the issue of stability of the background geometry upon changing the deformation degree parameters. Full article
(This article belongs to the Special Issue Beyond the Standard Models of Physics and Cosmology)
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Communication
Emergence of Many Mini-Circles from a Coffee Suspension with Mechanical Rotation
Physics 2021, 3(1), 8-16; https://0-doi-org.brum.beds.ac.uk/10.3390/physics3010003 - 22 Jan 2021
Viewed by 979
Abstract
Drying of an aqueous suspension containing fine granules leads to the formation of a circular pattern, i.e., the coffee-ring effect. Here, we report the effect of mechanical rotation with drying of an aqueous suspension containing a large amount of granular particles as in [...] Read more.
Drying of an aqueous suspension containing fine granules leads to the formation of a circular pattern, i.e., the coffee-ring effect. Here, we report the effect of mechanical rotation with drying of an aqueous suspension containing a large amount of granular particles as in the Turkish coffee. It was found that wavy fragmented stripes, or a “waggly pattern”, appear in the early stage of the drying process and a “polka-dot pattern” with many small circles is generated in the late stage. We discuss the mechanism of these patterns in terms of the kinetic effect on micro phase-segregation. We suggest that the waggly pattern is induced through a mechanism similar to spinodal decomposition, whereas polka-dot formation is accompanied by the enhanced segregation of a water-rich phase under mechanical rotation. Full article
(This article belongs to the Special Issue Dedication to Professor Michael Tribelsky: 50 Years in Physics)
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Editorial
Acknowledgment to Reviewers of Physics in 2020
Physics 2021, 3(1), 6-7; https://0-doi-org.brum.beds.ac.uk/10.3390/physics3010002 - 21 Jan 2021
Viewed by 637
Abstract
Peer review is the driving force of journal development, and reviewers are gatekeepers who ensure that Physics maintains its standards for the high quality of its published papers [...] Full article
Addendum
Addendum: Babic, S., et al. Self-Inductance of the Circular Coils of the Rectangular Cross-Section with the Radial and Azimuthal Current Densities. Physics 2020, 2, 352–367
Physics 2021, 3(1), 1-5; https://0-doi-org.brum.beds.ac.uk/10.3390/physics3010001 - 18 Jan 2021
Cited by 1 | Viewed by 591
(This article belongs to the Section Applied Physics)
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