Editor’s Choice Articles

Editor’s Choice articles are based on recommendations by the scientific editors of MDPI journals from around the world. Editors select a small number of articles recently published in the journal that they believe will be particularly interesting to readers, or important in the respective research area. The aim is to provide a snapshot of some of the most exciting work published in the various research areas of the journal.

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14 pages, 9517 KiB  
Article
A Family of 1D Chaotic Maps without Equilibria
by Marcin Lawnik, Lazaros Moysis and Christos Volos
Symmetry 2023, 15(7), 1311; https://doi.org/10.3390/sym15071311 - 27 Jun 2023
Cited by 4 | Viewed by 1132
Abstract
In this work, a family of piecewise chaotic maps is proposed. This family of maps is parameterized by the nonlinear functions used for each piece of the mapping, which can be either symmetric or non-symmetric. Applying a constraint on the shape of each [...] Read more.
In this work, a family of piecewise chaotic maps is proposed. This family of maps is parameterized by the nonlinear functions used for each piece of the mapping, which can be either symmetric or non-symmetric. Applying a constraint on the shape of each piece, the generated maps have no equilibria and can showcase chaotic behavior. This family thus belongs to the category of systems with hidden attractors. Numerous examples of chaotic maps are provided, showcasing fractal-like, symmetrical patterns at the interchange between chaotic and non-chaotic behavior. Moreover, the application of the proposed maps to a pseudorandom bit generator is successfully performed. Full article
(This article belongs to the Special Issue Symmetry in Nonlinear Dynamics and Chaos II)
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17 pages, 1204 KiB  
Article
Influence of Magnetic Field and Porous Medium on the Steady State and Flow Resistance of Second Grade Fluids over an Infinite Plate
by Constantin Fetecau and Costică Moroşanu
Symmetry 2023, 15(6), 1269; https://doi.org/10.3390/sym15061269 - 16 Jun 2023
Cited by 3 | Viewed by 869
Abstract
The main purpose of this work is to completely solve two motion problems of some differential type fluids when velocity or shear stress is given on the boundary. In order to do that, isothermal MHD motions of incompressible second grade fluids over an [...] Read more.
The main purpose of this work is to completely solve two motion problems of some differential type fluids when velocity or shear stress is given on the boundary. In order to do that, isothermal MHD motions of incompressible second grade fluids over an infinite flat plate are analytically investigated when porous effects are taken into consideration. The fluid motion is due to the plate moving in its plane with an arbitrary time-dependent velocity or applying a time-dependent shear stress to the fluid. Closed-form expressions are established both for the dimensionless velocity and shear stress fields and the Darcy’s resistance corresponding to the first motion. The dimensionless shear stress corresponding to the second motion has been immediately obtained using a perfect symmetry between the governing equations of velocity and the non-trivial shear stress. Furthermore, the obtained results provide the first exact general solutions for MHD motions of second grade fluids through porous media. Finally, for illustration, as well as for their use in engineering applications, the starting and/or steady state solutions of some problems with technical relevance are provided, and the validation of the results is graphically proved. The influence of magnetic field and porous medium on the steady state and the flow resistance of fluid are graphically underlined and discussed. It was found that the flow resistance of the fluid declines or increases in the presence of a magnetic field or porous medium, respectively. In addition, the steady state is obtained earlier in the presence of a magnetic field or porous medium. Full article
(This article belongs to the Section Mathematics)
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19 pages, 7215 KiB  
Article
Myrtenal and Myrtanal as Auxiliaries in the Synthesis of Some C,P-Stereogenic Hydroxyphosphine Oxides and Hydroxyphosphine-Boranes Possessing up to Four Contiguous Centers of Chirality
by K. Michał Pietrusiewicz, Anna E. Kozioł, Hanna Małuszyńska and Sylwia Sowa
Symmetry 2023, 15(6), 1172; https://doi.org/10.3390/sym15061172 - 30 May 2023
Cited by 1 | Viewed by 1170
Abstract
1,4- and 1,2-additons of secondary phosphine oxides to (1R)-myrtenal and (1S)-myrtanal were evaluated as potential routes to P,C-stereogenic phosphine oxides bearing additional hydroxyl or aldehyde functions. 1,4-Additions of racemic secondary phosphine oxides to (1R)-myrtenal were found to [...] Read more.
1,4- and 1,2-additons of secondary phosphine oxides to (1R)-myrtenal and (1S)-myrtanal were evaluated as potential routes to P,C-stereogenic phosphine oxides bearing additional hydroxyl or aldehyde functions. 1,4-Additions of racemic secondary phosphine oxides to (1R)-myrtenal were found to offer moderate to good stereoselectivity which shows some promise for utility in kinetic resolution processes, especially at lower conversions. In case of 1,2-additions making the process doubly asymmetric by using an enantiomerically pure secondary phosphine oxide as substrate turned out to be practical. The stereochemical course of the addition reactions under study is presented. The P-resolved 1,2-addition products were demonstrated to undergo facile reduction by BH3 at room temperature leading to the formation of the corresponding α-hydroxyphosphine-boranes with clean inversion of configuration at the P-centre. All P,C-stereogenic phosphine oxides and boranes that were isolated in the form of a single diastereoisomer were assigned their absolute configurations by means of X-ray crystallography and/or 2D NMR spectral techniques. Full article
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26 pages, 16642 KiB  
Article
A Deep Learning Approach to Extracting Nuclear Matter Properties from Neutron Star Observations
by Plamen G. Krastev
Symmetry 2023, 15(5), 1123; https://doi.org/10.3390/sym15051123 - 20 May 2023
Cited by 11 | Viewed by 1367
Abstract
Understanding the equation of state of dense neutron-rich matter remains a major challenge in modern physics and astrophysics. Neutron star observations from electromagnetic and gravitational wave spectra provide critical insights into the behavior of dense neutron-rich matter. The next generation of telescopes and [...] Read more.
Understanding the equation of state of dense neutron-rich matter remains a major challenge in modern physics and astrophysics. Neutron star observations from electromagnetic and gravitational wave spectra provide critical insights into the behavior of dense neutron-rich matter. The next generation of telescopes and gravitational wave detectors will offer even more detailed neutron-star observations. Employing deep learning techniques to map neutron star mass and radius observations to the equation of state allows for its accurate and reliable determination. This work demonstrates the feasibility of using deep learning to extract the equation of state directly from observations of neutron stars, and to also obtain related nuclear matter properties such as the slope, curvature, and skewness of nuclear symmetry energy at saturation density. Most importantly, it shows that this deep learning approach is able to reconstruct realistic equations of state and deduce realistic nuclear matter properties. This highlights the potential of artificial neural networks in providing a reliable and efficient means to extract crucial information about the equation of state and related properties of dense neutron-rich matter in the era of multi-messenger astrophysics. Full article
(This article belongs to the Special Issue Symmetries and Ultra Dense Matter of Compact Stars)
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19 pages, 2058 KiB  
Article
Privacy-Preserving Medical Data-Sharing System with Symmetric Encryption Based on Blockchain
by Mingqi Hu, Yanli Ren and Cien Chen
Symmetry 2023, 15(5), 1010; https://doi.org/10.3390/sym15051010 - 30 Apr 2023
Cited by 1 | Viewed by 1538
Abstract
Nowadays, data between hospitals are usually not interoperable, which brings great inconvenience to medical data sharing and patients’ medical treatment. In addition, patients do not want their medical data to be leaked during the sharing process. Researchers have employed blockchain to build data-sharing [...] Read more.
Nowadays, data between hospitals are usually not interoperable, which brings great inconvenience to medical data sharing and patients’ medical treatment. In addition, patients do not want their medical data to be leaked during the sharing process. Researchers have employed blockchain to build data-sharing systems to address these issues. However, current systems do not restrict the power of participants, nor do they prevent visitors from sharing the obtained data to unauthorized parties. To address these issues, we propose a private data-sharing system with symmetric encryption for the medical industry that implements power restriction and access control, and prevents the leakage of private data. To be specific, firstly, symmetric encryption algorithm is utilized to encrypt medical data to protect the privacy of data owner. Secondly, our proposed system is built on a new blockchain framework, in which only visitors with permission can access the medical data. Thirdly, we employ chameleon signature to prevent visitors from sharing data with other parties without permission. Finally, we make the power of participants in the system revocable to prevent them from abusing their power. Our proposed system has been proven to be secure through security analysis and can protect the privacy of patients. In addition, the experimental results show that our system has excellent performance in terms of time overhead compared to other systems. Full article
(This article belongs to the Special Issue Symmetry and Asymmetry in Cryptography and Outsourcing Computation)
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12 pages, 6811 KiB  
Article
Building an Equation of State Density Ladder
by Marc Salinas and Jorge Piekarewicz
Symmetry 2023, 15(5), 994; https://doi.org/10.3390/sym15050994 - 27 Apr 2023
Cited by 4 | Viewed by 905
Abstract
The confluence of major theoretical, experimental, and observational advances are providing a unique perspective on the equation of state of dense neutron-rich matter—particularly its symmetry energy—and its imprint on the mass-radius relation for neutron stars. In this contribution, we organize these developments in [...] Read more.
The confluence of major theoretical, experimental, and observational advances are providing a unique perspective on the equation of state of dense neutron-rich matter—particularly its symmetry energy—and its imprint on the mass-radius relation for neutron stars. In this contribution, we organize these developments in an equation of the state density ladder. Of particular relevance to this discussion are the impact of the various rungs on the equation of state and the identification of possible discrepancies among the various methods. A preliminary analysis identifies possible tension between laboratory measurements and gravitational-wave detections that could indicate the emergence of a phase transition in the stellar core. Full article
(This article belongs to the Special Issue Symmetries and Ultra Dense Matter of Compact Stars)
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18 pages, 324 KiB  
Article
Expansion-Free Dissipative Fluid Spheres: Analytical Solutions
by Luis Herrera, Alicia Di Prisco and Justo Ospino
Symmetry 2023, 15(3), 754; https://doi.org/10.3390/sym15030754 - 19 Mar 2023
Cited by 8 | Viewed by 941
Abstract
We search for exact analytical solutions of spherically symmetric dissipative fluid distributions satisfying the vanishing expansion condition (vanishing expansion scalar Θ). To accomplish this, we shall impose additional restrictions allowing integration of the field equations. The solutions are analyzed, and possible applications [...] Read more.
We search for exact analytical solutions of spherically symmetric dissipative fluid distributions satisfying the vanishing expansion condition (vanishing expansion scalar Θ). To accomplish this, we shall impose additional restrictions allowing integration of the field equations. The solutions are analyzed, and possible applications to astrophysical scenarios as well as alternative approaches to obtaining new solutions are discussed. Full article
(This article belongs to the Special Issue Symmetry in Cosmology and Gravity: Topic and Advance)
30 pages, 3480 KiB  
Review
Chiral Restoration of Nucleons in Neutron Star Matter: Studies Based on a Parity Doublet Model
by Takuya Minamikawa, Bikai Gao, Toru Kojo and Masayasu Harada
Symmetry 2023, 15(3), 745; https://doi.org/10.3390/sym15030745 - 17 Mar 2023
Cited by 9 | Viewed by 3186
Abstract
We review the chiral variant and invariant components of nucleon masses and the consequence of their existence on the chiral restoration in extreme conditions, particularly in neutron star matter. We consider a model of linear realization of chiral symmetry with the nucleon parity [...] Read more.
We review the chiral variant and invariant components of nucleon masses and the consequence of their existence on the chiral restoration in extreme conditions, particularly in neutron star matter. We consider a model of linear realization of chiral symmetry with the nucleon parity doublet structure that permits the chiral invariant mass, m0, for positive and negative parity nucleons. The nuclear matter is constructed with the parity doublet nucleon model coupled to scalar fields σ, vector fields (ω,ρ), and mesons with strangeness through the U(1)A anomaly. In models with a large m0, the nucleon mass is insensitive to the medium, and the nuclear saturation properties can be reproduced without demanding strong couplings of the nucleons to the scalar fields σ and vector fields ω. We confront the resulting nuclear equations of state with nuclear constraints and neutron star observations and delineate the chiral invariant mass and effective interactions. To further examine the nuclear equations of state beyond the saturation density, we supplement quark models to set the boundary conditions from the high-density side. The quark models are constrained by the two-solar-mass conditions, and such constraints are transferred to nuclear models through the causality and thermodynamic stability conditions. We also calculate various condensates and the matter composition from nuclear to quark matter in a unified matter by constructing a generating functional that interpolates the nuclear and quark matter with external fields. Two types of chiral restoration are discussed: one due to the positive scalar charges of nucleons and the other triggered by the evolution of the Dirac sea. We found that the U(1)A anomaly softens equations of state from low to high density. Full article
(This article belongs to the Special Issue Symmetries and Ultra Dense Matter of Compact Stars)
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27 pages, 13869 KiB  
Article
Chaotification of 1D Maps by Multiple Remainder Operator Additions—Application to B-Spline Curve Encryption
by Lazaros Moysis, Marcin Lawnik, Ioannis P. Antoniades, Ioannis Kafetzis, Murilo S. Baptista and Christos Volos
Symmetry 2023, 15(3), 726; https://doi.org/10.3390/sym15030726 - 14 Mar 2023
Cited by 4 | Viewed by 1301
Abstract
In this work, a chaotification technique is proposed for increasing the complexity of chaotic maps. The technique consists of adding the remainder of multiple scalings of the map’s value for the next iteration, so that the most- and least-significant digits are combined. By [...] Read more.
In this work, a chaotification technique is proposed for increasing the complexity of chaotic maps. The technique consists of adding the remainder of multiple scalings of the map’s value for the next iteration, so that the most- and least-significant digits are combined. By appropriate parameter tuning, the resulting map can achieve a higher Lyapunov exponent value, a result that was first proven theoretically and then showcased through numerical simulations for a collection of chaotic maps. As a proposed application of the transformed maps, the encryption of B-spline curves and patches was considered. The symmetric encryption consisted of two steps: a shuffling of the control point coordinates and an additive modulation. A transformed chaotic map was utilised to perform both steps. The resulting ciphertext curves and patches were visually unrecognisable compared to the plaintext ones and performed well on several statistical tests. The proposed work gives an insight into the potential of the remainder operator for chaotification, as well as the chaos-based encryption of curves and computer graphics. Full article
(This article belongs to the Special Issue Symmetry in Nonlinear Dynamics and Chaos II)
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28 pages, 825 KiB  
Article
Near-Miss Symmetric Polyhedral Cages
by Bernard M. A. G. Piette and Árpad Lukács
Symmetry 2023, 15(3), 717; https://doi.org/10.3390/sym15030717 - 13 Mar 2023
Cited by 2 | Viewed by 1692
Abstract
Following the experimental discovery of several nearly symmetric protein cages, we define the concept of homogeneous symmetric congruent equivalent near-miss polyhedral cages made out of P-gons. We use group theory to parameterize the possible configurations and we minimize the irregularity of the P-gons [...] Read more.
Following the experimental discovery of several nearly symmetric protein cages, we define the concept of homogeneous symmetric congruent equivalent near-miss polyhedral cages made out of P-gons. We use group theory to parameterize the possible configurations and we minimize the irregularity of the P-gons numerically to construct all such polyhedral cages for P=6 to P=20 with deformation of up to 10%. Full article
(This article belongs to the Section Mathematics)
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17 pages, 3212 KiB  
Article
Classification of Blood Rheological Models through an Idealized Symmetrical Bifurcation
by Konstantinos Tzirakis, Yiannis Kamarianakis, Nikolaos Kontopodis and Christos V. Ioannou
Symmetry 2023, 15(3), 630; https://doi.org/10.3390/sym15030630 - 02 Mar 2023
Cited by 5 | Viewed by 1902
Abstract
The assumed rheological behavior of blood influences the hemodynamic characteristics of numerical blood flow simulations. Until now, alternative rheological specifications have been utilized, with uncertain implications for the results obtained. This work aims to group sixteen blood rheological models in homogeneous clusters, by [...] Read more.
The assumed rheological behavior of blood influences the hemodynamic characteristics of numerical blood flow simulations. Until now, alternative rheological specifications have been utilized, with uncertain implications for the results obtained. This work aims to group sixteen blood rheological models in homogeneous clusters, by exploiting data generated from numerical simulations on an idealized symmetrical arterial bifurcation. Blood flow is assumed to be pulsatile and is simulated using a commercial finite volume solver. An appropriate mesh convergence study is performed, and all results are collected at three different time instants throughout the cardiac cycle: at peak systole, early diastole, and late diastole. Six hemodynamic variables are computed: the time average wall shear stress, oscillatory shear index, relative residence time, global and local non-Newtonian importance factor, and non-Newtonian effect factor. The resulting data are analyzed using hierarchical agglomerative clustering algorithms, which constitute typical unsupervised classification methods. Interestingly, the rheological models can be partitioned into three homogeneous groups, whereas three specifications appear as outliers which do not belong in any partition. Our findings suggest that models which are defined in a similar manner from a mathematical perspective may behave substantially differently in terms of the data they produce. On the other hand, models characterized by different mathematical formulations may belong to the same statistical group (cluster) and can thus be considered interchangeably. Full article
(This article belongs to the Special Issue Biology and Symmetry/Asymmetry:Feature Papers 2022)
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15 pages, 313 KiB  
Article
The η-Anti-Hermitian Solution to a System of Constrained Matrix Equations over the Generalized Segre Quaternion Algebra
by Bai-Ying Ren, Qing-Wen Wang and Xue-Ying Chen
Symmetry 2023, 15(3), 592; https://doi.org/10.3390/sym15030592 - 24 Feb 2023
Cited by 9 | Viewed by 1057
Abstract
In this paper, we propose three real representations of a generalized Segre quaternion matrix. We establish necessary and sufficient conditions for the existence of the η-anti-Hermitian solution to a system of constrained matrix equations over the generalized Segre quaternion algebra. We also [...] Read more.
In this paper, we propose three real representations of a generalized Segre quaternion matrix. We establish necessary and sufficient conditions for the existence of the η-anti-Hermitian solution to a system of constrained matrix equations over the generalized Segre quaternion algebra. We also obtain the expression of the general η-anti-Hermitian solution to the system when it is solvable. Finally, we provide a numerical example to verify the main results of this paper. Full article
(This article belongs to the Section Mathematics)
16 pages, 2144 KiB  
Article
Intermolecular Interactions in Binary and Ternary Solutions of a Zwitterionic Compound Studied by Solvatochromism
by Dana Ortansa Dorohoi, Dorina Emilia Creanga and Dan Gheorghe Dimitriu
Symmetry 2023, 15(2), 563; https://doi.org/10.3390/sym15020563 - 20 Feb 2023
Viewed by 1139
Abstract
The 1-dithiocarboxy-2-ethoxy-1-(isoquinolin-2-yl)-2-oxoethan-1-ylid (iQTCY) zwitterionic molecule has been studied by computational and spectral means in order to establish some of its structural parameters in the ground electronic state as well as the nature and the strength of its universal and specific interactions with different [...] Read more.
The 1-dithiocarboxy-2-ethoxy-1-(isoquinolin-2-yl)-2-oxoethan-1-ylid (iQTCY) zwitterionic molecule has been studied by computational and spectral means in order to establish some of its structural parameters in the ground electronic state as well as the nature and the strength of its universal and specific interactions with different solvents. The prevalence of the orientation–induction interactions in the diluted solutions of iQTCY in aprotic solvents and the additional specific interactions by hydrogen bonds (HB) in the protic solvents were demonstrated. Three theoretical models were comparatively used to estimate the composition of the first solvation shell of the iQTCY molecule in ternary solutions. The difference between the interaction energies in molecular pairs solute–solvent was computed based on the statistical cell model of ternary solutions of iQTCY in mixtures of water–ethanol and water–methanol. Using the electro-optical parameters computed by the quantum-mechanical technique and the results of the solvatochromic study, the excited state dipole moment of iQTCY was estimated within the limit of the variational method applicable to molecules that show only an absorption electronic spectrum. Full article
(This article belongs to the Collection Feature Papers in Chemistry)
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22 pages, 1233 KiB  
Article
Detecting Heavy Neutral SUSY Higgs Bosons Decaying to Sparticles at the High-Luminosity LHC
by Howard Baer, Vernon Barger, Xerxes Tata and Kairui Zhang
Symmetry 2023, 15(2), 548; https://doi.org/10.3390/sym15020548 - 18 Feb 2023
Cited by 4 | Viewed by 1228
Abstract
In supersymmetry (SUSY) models with low electroweak naturalness (natSUSY), which have been suggested to be the most likely version of SUSY to emerge from the string landscape, higgsinos are expected at the few hundred GeV scale, whilst electroweak gauginos inhabit the TeV scale. [...] Read more.
In supersymmetry (SUSY) models with low electroweak naturalness (natSUSY), which have been suggested to be the most likely version of SUSY to emerge from the string landscape, higgsinos are expected at the few hundred GeV scale, whilst electroweak gauginos inhabit the TeV scale. For TeV-scale heavy neutral SUSY Higgs bosons H and A, as currently required by LHC searches, the dominant decay modes of H,A are gaugino plus higgsino provided these decays are kinematically open. The light higgsinos decay to soft particles, so are largely invisible, whilst the gauginos decay to W, Z or h plus missing transverse energy (ET). Thus, we examine the viability of H,AW+ET, Z+ET and h+ET signatures at the high luminosity LHC (HL-LHC) in light of large standard model (SM) backgrounds from (mainly) tt¯, VV and Vh production (where V=W,Z). We also examine whether these signal channels can be enhanced over backgrounds by requiring the presence of an additional soft lepton from the decays of the light higgsinos. We find significant regions in the vicinity of mA12 TeV of the mA vs. tanβ plane, which can be probed at the high luminosity LHC, using these dominant signatures by HL-LHC at 5σ and at the 95% confidence level (CL). Full article
(This article belongs to the Special Issue Supersymmetry with Higgs Bosons Research)
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10 pages, 2168 KiB  
Article
A Study on the Intersection of Ground Reaction Forces during Overground Walking in Down Syndrome: Effects of the Pathology and Left–Right Asymmetry
by Johanna Vielemeyer, Cristina Sole, Manuela Galli, Matteo Zago, Roy Müller and Claudia Condoluci
Symmetry 2023, 15(2), 544; https://doi.org/10.3390/sym15020544 - 17 Feb 2023
Cited by 3 | Viewed by 2332
Abstract
Motor dysfunctions in patients with Down Syndrome (DS) result in poor locomotion and an altered gait phenotype, characterized by compromised stability management and frequent bilateral asymmetries. Directing ground reaction forces to a point above the center of mass, referred to as the virtual [...] Read more.
Motor dysfunctions in patients with Down Syndrome (DS) result in poor locomotion and an altered gait phenotype, characterized by compromised stability management and frequent bilateral asymmetries. Directing ground reaction forces to a point above the center of mass, referred to as the virtual pivot point (VPP), is one means of maintaining stability during walking. This cross-sectional observational study compared the dynamic gait function of 33 individuals with DS (mean age: 17.7 ± 6.4 years, 13 females) to a group of 36 healthy controls (mean age: 15.5 ± 6.1 years, 15 females), using the concept of the VPP. Results showed that the VPP was located more anteriorly in individuals with DS compared to healthy controls, with no differences in the variability (R2) or symmetry of VPP coordinates. This anterior VPP position is likely due to the larger hip moments observed in patients with DS during the propulsive phase of stance. High R2 values in DS suggest that the VPP is strongly related to dynamic stability during walking. Full article
(This article belongs to the Special Issue Biology and Symmetry/Asymmetry:Feature Papers 2022)
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13 pages, 6325 KiB  
Article
Electrochemical Studies of Azulene Modified Electrodes
by Veronica Anăstăsoaie, Ovidiu Teodor Matica, Cecilia Lete, Raluca Isopescu, Vesna Miskovic-Stankovic and Eleonora-Mihaela Ungureanu
Symmetry 2023, 15(2), 514; https://doi.org/10.3390/sym15020514 - 15 Feb 2023
Cited by 1 | Viewed by 1421
Abstract
Previous studies performed on 2-(azulen-1-yldiazenyl)-5-phenyl-1,3,4-thiadiazole (T) showed that T is a ligand with complexing properties towards heavy metals (HMs) in solution and can be attached to electrode surfaces. Films of T were deposited on glassy carbon to obtain chemically modified electrodes [...] Read more.
Previous studies performed on 2-(azulen-1-yldiazenyl)-5-phenyl-1,3,4-thiadiazole (T) showed that T is a ligand with complexing properties towards heavy metals (HMs) in solution and can be attached to electrode surfaces. Films of T were deposited on glassy carbon to obtain chemically modified electrodes (T-CMEs), either through scanning or using controlled potential electrolysis in tetrabutylammonium perchlorate in acetonitrile. They were investigated using cyclic voltammetry (CV), differential pulse voltammetry (DPV), electrochemical impedance spectroscopy (EIS), and spectroelectrochemistry. All methods provided evidence for showing the formation of insulating films, with properties depending on their electropolymerization potential. CV and EIS studies of T-CMEs in tetrabutylammonium perchlorate in acetonitrile as supporting electrolyte, and in the presence of a ferrocene redox probe resulted in a thickness of ~10 µm, an active surface area about 6 times higher than the geometrical one, and conductivity of about 10−6 S/cm. This characterization performed using voltammetric techniques reveals the symmetry of the reversible anodic and cathodic redox CV peaks for the polymer, while spectroelectrochemistry shows the intensification of the charge transport process through polarons, due to the anodic polarization of the film. Full article
(This article belongs to the Section Chemistry: Symmetry/Asymmetry)
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20 pages, 905 KiB  
Article
Collective Excitation in High-Energy Nuclear Collisions—In Memory of Professor Lianshou Liu
by Huan Zhong Huang, Feng Liu, Xiaofeng Luo, Shusu Shi, Fuqiang Wang and Nu Xu
Symmetry 2023, 15(2), 499; https://doi.org/10.3390/sym15020499 - 13 Feb 2023
Cited by 3 | Viewed by 1350
Abstract
We celebrate the legacies of our friend and mentor Professor Lianshou Liu who was one of the pioneers for the phenomenology of multi-particle interactions and initiated the physics of relativistic heavy-ion collisions in China. In this article, we discuss some of the recent [...] Read more.
We celebrate the legacies of our friend and mentor Professor Lianshou Liu who was one of the pioneers for the phenomenology of multi-particle interactions and initiated the physics of relativistic heavy-ion collisions in China. In this article, we discuss some of the recent exciting experimental observations on the collective phenomena including collectivity, chirality, criticality, strangeness production, and thermal equilibrium in high-energy nuclear collisions. Future directions, especially the physics at high baryon density, will be discussed with a focus on the first-order phase boundary and hyperon–nucleon interactions. Full article
(This article belongs to the Special Issue Heavy-Ion Collisions and Multiparticle Production)
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19 pages, 2126 KiB  
Article
Metamaterial with Tunable Positive and Negative Hygrothermal Expansion Inspired by a Four-Fold Symmetrical Islamic Motif
by Teik-Cheng Lim
Symmetry 2023, 15(2), 462; https://doi.org/10.3390/sym15020462 - 09 Feb 2023
Cited by 3 | Viewed by 1365
Abstract
A metamaterial with controllable positive and negative thermal and hygroscopic expansions is investigated herein by inspiration from a range of Islamic geometric patterns. Constructing from eight pairs of pin-jointed Y-elements, each unit cell manifests eight rhombi that are arranged circumferentially, thereby manifesting four [...] Read more.
A metamaterial with controllable positive and negative thermal and hygroscopic expansions is investigated herein by inspiration from a range of Islamic geometric patterns. Constructing from eight pairs of pin-jointed Y-elements, each unit cell manifests eight rhombi that are arranged circumferentially, thereby manifesting four axes of symmetry. By attachment of bimaterial spiral springs of contrasting expansion coefficients to the far arms of the paired Y-elements, a change in the environment’s thermal or hygroscopic condition alters the offset angle of the paired Y-elements such that the unit cell of the metamaterial ranges from the eight-pointed star to the regular octagon. The effective coefficient of thermal expansion (CTE) and the coefficient of moisture expansion (CME) of this metamaterial were developed for small and large changes in environmental fluctuations using infinitesimal and finite models, respectively. Generated data indicates that the sign and magnitude of the effective thermal and hygroscopic expansion coefficients can be controlled by geometrical descriptors of the bimaterial spiral spring—such as its coil number and the ratio of its mean radius to its thickness—as well as the properties of the bimaterial’s layers such as their expansion coefficients, Young’s moduli and, in the case of effective hygroscopic expansion, their relative absorptivity. The obtained results suggest that the proposed metamaterial can be designed to perform as highly sensitive thermal and/or moisture sensors, as well as other functional materials or devices that take advantage of environmental changes as stimuli. Full article
(This article belongs to the Special Issue Materials Science and Symmetry)
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21 pages, 380 KiB  
Article
Potentials from the Polynomial Solutions of the Confluent Heun Equation
by Géza Lévai
Symmetry 2023, 15(2), 461; https://doi.org/10.3390/sym15020461 - 09 Feb 2023
Cited by 4 | Viewed by 1634
Abstract
Polynomial solutions of the confluent Heun differential equation (CHE) are derived by identifying conditions under which the infinite power series expansions around the z=0 singular point can be terminated. Assuming a specific structure of the expansion coefficients, these conditions lead to [...] Read more.
Polynomial solutions of the confluent Heun differential equation (CHE) are derived by identifying conditions under which the infinite power series expansions around the z=0 singular point can be terminated. Assuming a specific structure of the expansion coefficients, these conditions lead to four non-trivial polynomials that can be expressed as special cases of the confluent Heun function Hc(p,β,γ,δ,σ;z). One of these recovers the generalized Laguerre polynomials LN(α), and another one the rationally extended X1 type Laguerre polynomials L^N(α). The two remaining solutions represent previously unknown polynomials that do not form an orthogonal set and exhibit features characteristic of semi-classical orthogonal polynomials. A standard method of generating exactly solvable potentials in the one-dimensional Schrödinger equation is applied to the CHE, and all known potentials with solutions expressed in terms of the generalized Laguerre polynomials within, or outside the Natanzon confluent potential class, are recovered. It is also found that the potentials generated from the two new polynomial systems necessarily depend on the N quantum number. General considerations on the application of the Heun type differential differential equations within the present framework are also discussed. Full article
20 pages, 355 KiB  
Article
Gravity as a Quantum Field Theory
by Roberto Percacci
Symmetry 2023, 15(2), 449; https://doi.org/10.3390/sym15020449 - 08 Feb 2023
Cited by 5 | Viewed by 2479
Abstract
Classical gravity is understood as the geometry of spacetime, and it seems very different from the other known interactions. In this review, I will instead stress the analogies: Like strong interactions, the low energy effective field theory of gravity is related to a [...] Read more.
Classical gravity is understood as the geometry of spacetime, and it seems very different from the other known interactions. In this review, I will instead stress the analogies: Like strong interactions, the low energy effective field theory of gravity is related to a nonlinearly realized symmetry, and like electroweak interactions, it is a gauge theory in Higgs phase, with a massive connection. I will also discuss the possibility of finding a UV complete quantum field theoretic description of all interactions. Full article
33 pages, 11453 KiB  
Review
Nonextensive Footprints in Dissipative and Conservative Dynamical Systems
by Antonio Rodríguez, Alessandro Pluchino, Ugur Tirnakli, Andrea Rapisarda and Constantino Tsallis
Symmetry 2023, 15(2), 444; https://doi.org/10.3390/sym15020444 - 07 Feb 2023
Cited by 3 | Viewed by 1352
Abstract
Despite its centennial successes in describing physical systems at thermal equilibrium, Boltzmann–Gibbs (BG) statistical mechanics have exhibited, in the last several decades, several flaws in addressing out-of-equilibrium dynamics of many nonlinear complex systems. In such circumstances, it has been shown that an appropriate [...] Read more.
Despite its centennial successes in describing physical systems at thermal equilibrium, Boltzmann–Gibbs (BG) statistical mechanics have exhibited, in the last several decades, several flaws in addressing out-of-equilibrium dynamics of many nonlinear complex systems. In such circumstances, it has been shown that an appropriate generalization of the BG theory, known as nonextensive statistical mechanics and based on nonadditive entropies, is able to satisfactorily handle wide classes of anomalous emerging features and violations of standard equilibrium prescriptions, such as ergodicity, mixing, breakdown of the symmetry of homogeneous occupancy of phase space, and related features. In the present study, we review various important results of nonextensive statistical mechanics for dissipative and conservative dynamical systems. In particular, we discuss applications to both discrete-time systems with a few degrees of freedom and continuous-time ones with many degrees of freedom, as well as to asymptotically scale-free networks and systems with diverse dimensionalities and ranges of interactions, of either classical or quantum nature. Full article
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22 pages, 3802 KiB  
Article
Making and Breaking—Insight into the Symmetry of Salen Analogues
by Katarzyna M. Krupka, Sylwia Banach, Michał Pocheć, Jarosław J. Panek and Aneta Jezierska
Symmetry 2023, 15(2), 424; https://doi.org/10.3390/sym15020424 - 05 Feb 2023
Cited by 1 | Viewed by 1780
Abstract
This study focuses on selected members of the general salen-analogues family possessing two O-H⋯N hydrogen bonds, namely three isomers of N,N’-bis(salicylidene)-X-phenylenediamine, denoted as ortho, meta and para. Two of the isomers are not planar in the published crystal [...] Read more.
This study focuses on selected members of the general salen-analogues family possessing two O-H⋯N hydrogen bonds, namely three isomers of N,N’-bis(salicylidene)-X-phenylenediamine, denoted as ortho, meta and para. Two of the isomers are not planar in the published crystal structures. The current study tackles the problem of symmetry and interactions within the molecules, as well as in the crystal lattice. The aromaticity of the phenyl rings is evaluated using the Harmonic Oscillator Model of Aromaticity (HOMA) index. Intra- and inter-molecular non-covalent interactions are studied via Hirshfeld surface analysis, Independent Gradient Model (IGM), Quantum Theory of Atoms in Molecules (QTAIM), Non-Covalent Interaction (NCI) index, Electron Localisation Function (ELF), Core-Valence Bifurcation (CVB) index and Symmetry-Adapted Perturbation Theory (SAPT). Density Functional Theory (DFT) simulations were carried out in vacuo and with solvent reaction field based on Polarisable Continuum Model (IEF-PCM formulation) at the ωB97XD/6-311+G(2d,2p) level. Crystal structure analyses were performed for the data reported previously in the literature. The obtained results demonstrate that the three isomers differ greatly in their structural properties (molecular symmetry is broken for the ortho and meta isomers in the solid state) and ability to form intermolecular interactions, while retaining overall similar physico-chemical characteristics, e.g., aromaticity of the phenyl rings. It was found that the presence of the polar solvent does not significantly affect the structure of the studied compounds. An application of the Hirshfeld surface analysis revealed the nature of the non-covalent interactions present in the investigated crystals. The SAPT results showed that the stability of the dimers extracted from the crystals of the Schiff base derivatives arises from electrostatics and dispersion. Full article
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35 pages, 542 KiB  
Article
More Insights into Symmetries in Multisymplectic Field Theories
by Arnoldo Guerra IV and Narciso Román-Roy
Symmetry 2023, 15(2), 390; https://doi.org/10.3390/sym15020390 - 01 Feb 2023
Cited by 4 | Viewed by 885
Abstract
This work provides a general overview for the treatment of symmetries in classical field theories and (pre)multisymplectic geometry. The geometric characteristics of the relation between how symmetries are interpreted in theoretical physics and in the geometric formulation of these theories are clarified. Finally, [...] Read more.
This work provides a general overview for the treatment of symmetries in classical field theories and (pre)multisymplectic geometry. The geometric characteristics of the relation between how symmetries are interpreted in theoretical physics and in the geometric formulation of these theories are clarified. Finally, a general discussion is given on the structure of symmetries in the presence of constraints appearing in singular field theories. Symmetries of some typical theories in theoretical physics are analyzed through the construction of the relevant multimomentum maps which are the conserved quantities (by Noether’s theorem) on the (pre)multisymplectic phase spaces. Full article
(This article belongs to the Special Issue Symmetry in Geometric Mechanics and Mathematical Physics)
12 pages, 3207 KiB  
Article
Synthesis and Spectroscopic Properties of Selected Acrylic and Methacrylic Derivatives of 2-Mercaptobenzothiazole
by Janina Kabatc-Borcz, Przemysław Czeleń and Agnieszka Skotnicka
Symmetry 2023, 15(2), 370; https://doi.org/10.3390/sym15020370 - 30 Jan 2023
Cited by 1 | Viewed by 1066
Abstract
One of the most basic properties of chemical compounds is structural symmetry or asymmetry. This property can be considered at different levels of structural organization. The physical, chemical, biological, and technological properties of organic compounds depend on their chemical structure and are systematically [...] Read more.
One of the most basic properties of chemical compounds is structural symmetry or asymmetry. This property can be considered at different levels of structural organization. The physical, chemical, biological, and technological properties of organic compounds depend on their chemical structure and are systematically related to it. The presented paper is focused on the synthesis and study of the spectroscopic properties of selected photoinitiators from the acrylate and methacrylate derivatives of 2-(benzothiazolylthio)ethyl. The indicated compounds can find potential application in medicine. The 2-(benzothiazolylthio)ethyl acrylate and methacrylate derivatives were characterized using infrared spectroscopy (IR) and nuclear magnetic resonance (NMR) spectroscopy. Their spectroscopic properties were determined on the basis of UV–Vis spectra. The calculated DFT energies and Frontier Molecular Orbitals calculations of the studied compounds were proved to be consistent with the experimental observations. The results have showed that the introduction of the ethoxy substituent increases the reactivity of the compounds and results in the slight bathochromic shift (~19 nm) of the absorption spectra maxima. Full article
(This article belongs to the Section Chemistry: Symmetry/Asymmetry)
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21 pages, 2060 KiB  
Article
On Analogies in Proton-Transfers for Pyrimidine Bases in the Gas Phase (Apolar Environment)—Cytosine Versus Isocytosine
by Ewa D. Raczyńska
Symmetry 2023, 15(2), 342; https://doi.org/10.3390/sym15020342 - 26 Jan 2023
Cited by 3 | Viewed by 888
Abstract
Inter- and intra-molecular proton-transfers between functional groups in nucleobases play a principal role in their interactions (pairing) in nucleic acids. Although prototropic rearrangements (intramolecular proton-transfers) for neutral pyrimidine bases are well documented, they have not always been considered for their protonated and deprotonated [...] Read more.
Inter- and intra-molecular proton-transfers between functional groups in nucleobases play a principal role in their interactions (pairing) in nucleic acids. Although prototropic rearrangements (intramolecular proton-transfers) for neutral pyrimidine bases are well documented, they have not always been considered for their protonated and deprotonated forms. The complete isomeric mixtures in acid-base equilibria and in acidity–basicity parameters have not yet been examined. Taking into account the lack of literature and data, research into the question of prototropy for the ionic (protonated and deprotonated) forms has been undertaken in this work. For the purposes of this investigation, two isomeric pyrimidine bases (C—cytosine and iC—isocytosine) were chosen. They exhibit analogous (symmetrical) general acid-base equilibria (intermolecular proton-transfers). Being similar polyfunctional tautomeric systems, C and iC possess two labile protons and five conjugated tautomeric sites. However, positions of exo groups are different. Consequently, structural conversions such as prototropy, rotational, and geometrical isomerism of exo groups (=O/−OH and =NH/−NH2) and their intramolecular interactions with endo groups (=N−/>NH) possible in neutral C and iC and in their ionic forms lead to some differences in compositions of isomeric mixtures. By application of quantum–chemical methods to the isolated (in vacuo) species, stability of all possible neutral and ionic isomers has been examined and the candidate isomers selected. The complete isomeric mixtures have been considered for the first time for di-deprotonated, mono-deprotonated, mono-protonated, and di-protonated forms. Protonation–deprotonation reactions have been analyzed in the gas phase that models non-polar environment. The gas-phase microscopic (kinetic) and macroscopic (thermodynamic) acidity–basicity parameters have been estimated for each step of acid-base equilibria. When proceeding from di-anion to di-cation in four steps of protonation–deprotonation reaction, the macroscopic proton affinities for C and iC differ by less than 10 kcal mol−1. Their DFT-calculated values are as follows: 451 and 457, 340 and 339, 228 and 224, and 100 and 104 kcal mol−1, respectively. Differences between the microscopic proton affinities for analogous isomers of C and iC seem to be larger for the exo than endo groups. Owing to variations of relative stabilities for neutral and ionic isomers, in some cases they are even larger than 10 kcal mol−1. Full article
(This article belongs to the Special Issue Symmetry in Acid-Base Chemistry II)
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20 pages, 756 KiB  
Article
Popcorn Transitions and Approach to Conformality in Homogeneous Holographic Nuclear Matter
by Jesús Cruz Rojas, Tuna Demircik and Matti Järvinen
Symmetry 2023, 15(2), 331; https://doi.org/10.3390/sym15020331 - 25 Jan 2023
Cited by 9 | Viewed by 1867
Abstract
We study cold and dense nuclear matter by using the gauge/gravity duality. To this end, we use the Witten–Sakai–Sugimoto model and the V-QCD models with an approach where the nuclear matter is taken to be spatially homogeneous. We focus on the “popcorn” transitions, [...] Read more.
We study cold and dense nuclear matter by using the gauge/gravity duality. To this end, we use the Witten–Sakai–Sugimoto model and the V-QCD models with an approach where the nuclear matter is taken to be spatially homogeneous. We focus on the “popcorn” transitions, which are phase transitions in the nuclear matter phases induced by changes in the layer structure of the configuration on the gravity side. We demonstrate that the equation of state for the homogeneous nuclear matter becomes approximately conformal at high densities, and compare our results to other approaches. Full article
(This article belongs to the Special Issue Symmetries and Ultra Dense Matter of Compact Stars)
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23 pages, 1063 KiB  
Article
Jacobi and Lyapunov Stability Analysis of Circular Geodesics around a Spherically Symmetric Dilaton Black Hole
by Cristina Blaga, Paul Blaga and Tiberiu Harko
Symmetry 2023, 15(2), 329; https://doi.org/10.3390/sym15020329 - 24 Jan 2023
Cited by 5 | Viewed by 1211
Abstract
We analyze the stability of the geodesic curves in the geometry of the Gibbons–Maeda–Garfinkle–Horowitz–Strominger black hole, describing the space time of a charged black hole in the low energy limit of the string theory. The stability analysis is performed by using both the [...] Read more.
We analyze the stability of the geodesic curves in the geometry of the Gibbons–Maeda–Garfinkle–Horowitz–Strominger black hole, describing the space time of a charged black hole in the low energy limit of the string theory. The stability analysis is performed by using both the linear (Lyapunov) stability method, as well as the notion of Jacobi stability, based on the Kosambi–Cartan–Chern theory. Brief reviews of the two stability methods are also presented. After obtaining the geodesic equations in spherical symmetry, we reformulate them as a two-dimensional dynamic system. The Jacobi stability analysis of the geodesic equations is performed by considering the important geometric invariants that can be used for the description of this system (the nonlinear and the Berwald connections), as well as the deviation curvature tensor, respectively. The characteristic values of the deviation curvature tensor are specifically calculated, as given by the second derivative of effective potential of the geodesic motion. The Lyapunov stability analysis leads to the same results. Hence, we can conclude that, in the particular case of the geodesic motion on circular orbits in the Gibbons–Maeda–Garfinkle–Horowitz–Strominger, the Lyapunov and the Jacobi stability analysis gives equivalent results. Full article
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10 pages, 1961 KiB  
Article
A New Program to Estimate the Parameters of Preston’s Equation, a General Formula for Describing the Egg Shape of Birds
by Peijian Shi, Lin Wang, Brady K. Quinn and Johan Gielis
Symmetry 2023, 15(1), 231; https://doi.org/10.3390/sym15010231 - 13 Jan 2023
Cited by 5 | Viewed by 1713
Abstract
Preston’s equation is a general model describing the egg shape of birds. The parameters of Preston’s equation are usually estimated after re-expressing it as the Todd-Smart equation and scaling the egg’s actual length to two. This method assumes that the straight line through [...] Read more.
Preston’s equation is a general model describing the egg shape of birds. The parameters of Preston’s equation are usually estimated after re-expressing it as the Todd-Smart equation and scaling the egg’s actual length to two. This method assumes that the straight line through the two points on an egg’s profile separated by the maximum distance (i.e., the longest axis of an egg’s profile) is the mid-line. It hypothesizes that the photographed egg’s profile is perfectly bilaterally symmetrical, which seldom holds true because of photographic errors and placement errors. The existing parameter estimation method for Preston’s equation considers an angle of deviation for the longest axis of an egg’s profile from the mid-line, which decreases prediction errors to a certain degree. Nevertheless, this method cannot provide an accurate estimate of the coordinates of the egg’s center, and it leads to sub-optimal parameter estimation. Thus, it is better to account for the possible asymmetry between the two sides of an egg’s profile along its mid-line when fitting egg-shape data. In this paper, we propose a method based on the optimization algorithm (optimPE) to fit egg-shape data and better estimate the parameters of Preston’s equation by automatically searching for the optimal mid-line of an egg’s profile and testing its validity using profiles of 59 bird eggs spanning a wide range of existing egg shapes. We further compared this method with the existing one based on multiple linear regression (lmPE). This study demonstrated the ability of the optimPE method to estimate numerical values of the parameters of Preston’s equation and provide the theoretical egg length (i.e., the distance between two ends of the mid-line of an egg’s profile) and the egg’s maximum breadth. This provides a valuable approach for comparing egg shapes among conspecifics or across different species, or even different classes (e.g., birds and reptiles), in future investigations. Full article
(This article belongs to the Section Life Sciences)
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12 pages, 698 KiB  
Article
Nanoscale Bending Dynamics in Mixed-Chain Lipid Membranes
by Elizabeth G. Kelley, Moritz P. K. Frewein, Orsolya Czakkel and Michihiro Nagao
Symmetry 2023, 15(1), 191; https://doi.org/10.3390/sym15010191 - 09 Jan 2023
Cited by 2 | Viewed by 1533
Abstract
Lipids that have two tails of different lengths are found throughout biomembranes in nature, yet the effects of this asymmetry on the membrane properties are not well understood, especially when it comes to the membrane dynamics. Here we study the nanoscale bending fluctuations [...] Read more.
Lipids that have two tails of different lengths are found throughout biomembranes in nature, yet the effects of this asymmetry on the membrane properties are not well understood, especially when it comes to the membrane dynamics. Here we study the nanoscale bending fluctuations in model mixed-chain 14:0–18:0 PC (MSPC) and 18:0–14:0 PC (SMPC) lipid bilayers using neutron spin echo (NSE) spectroscopy. We find that despite the partial interdigitation that is known to persist in the fluid phase of these membranes, the collective fluctuations are enhanced on timescales of tens of nanoseconds, and the chain-asymmetric lipid bilayers are softer than an analogous chain-symmetric lipid bilayer with the same average number of carbons in the acyl tails, di-16:0 PC (DPPC). Quantitative comparison of the NSE results suggests that the enhanced bending fluctuations at the nanosecond timescales are consistent with experimental and computational studies that showed the compressibility moduli of chain-asymmetric lipid membranes are 20% to 40% lower than chain-symmetric lipid membranes. These studies add to growing evidence that the partial interdigitation in mixed-chain lipid membranes is highly dynamic in the fluid phase and impacts membrane dynamic processes from the molecular to mesoscopic length scales without significantly changing the bilayer thickness or area per lipid. Full article
(This article belongs to the Special Issue Symmetric and Asymmetric Cellular Membranes)
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34 pages, 2488 KiB  
Review
The Proxy-SU(3) Symmetry in Atomic Nuclei
by Dennis Bonatsos, Andriana Martinou, Spyridon Kosmas Peroulis, Theodoros John Mertzimekis and Nikolay Minkov
Symmetry 2023, 15(1), 169; https://doi.org/10.3390/sym15010169 - 06 Jan 2023
Cited by 9 | Viewed by 7155
Abstract
The microscopic origins and the current predictions of the proxy-SU(3) symmetry model of atomic nuclei were reviewed. Beginning with experimental evidence for the special roles played by nucleon pairs with maximal spatial overlap, the proxy-SU(3) approximation scheme is introduced; its validity is demonstrated [...] Read more.
The microscopic origins and the current predictions of the proxy-SU(3) symmetry model of atomic nuclei were reviewed. Beginning with experimental evidence for the special roles played by nucleon pairs with maximal spatial overlap, the proxy-SU(3) approximation scheme is introduced; its validity is demonstrated through Nilsson model calculations and its connection to the spherical shell model. The major role played by the highest weight-irreducible representations of SU(3) in shaping up the nuclear properties is pointed out, resulting in parameter-free predictions of the collective variables β and γ for even–even nuclei in the explanation of the dominance of prolate over oblate shapes in the ground states of even–even nuclei, in the prediction of a shape/phase transition from prolate to oblate shapes below closed shells, and in the prediction of specific islands on the nuclear chart in which shape coexistence is confined. Further developments within the proxy-SU(3) scheme are outlined. Full article
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18 pages, 2415 KiB  
Article
A Symmetry In-between the Shapes, Shells, and Clusters of Nuclei
by József Cseh, Gábor Riczu and Judit Darai
Symmetry 2023, 15(1), 115; https://doi.org/10.3390/sym15010115 - 31 Dec 2022
Cited by 6 | Viewed by 1380
Abstract
The multiconfigurational dynamical symmetry (MUSY) connects the shell, collective, and cluster models of atomic nuclei for the case of multi-shell excitations. Therefore, it can give a unified description of various phenomena. The shape isomers are obtained from the investigation of the stability and [...] Read more.
The multiconfigurational dynamical symmetry (MUSY) connects the shell, collective, and cluster models of atomic nuclei for the case of multi-shell excitations. Therefore, it can give a unified description of various phenomena. The shape isomers are obtained from the investigation of the stability and consistency of the symmetry, and selection rules connect them to the possible cluster configurations and the related reaction channels. A simple, dynamically symmetric Hamiltonian turns out to be able to provide a unified description of the gross features of spectra of different regions of excitation energy and deformation. Some predictions of MUSY have been justified by experimental observations. Full article
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11 pages, 2622 KiB  
Article
Symmetrization of Mechanical Response in Fibrous Metamaterials through Micro-Shear Deformability
by Mario Spagnuolo
Symmetry 2022, 14(12), 2660; https://doi.org/10.3390/sym14122660 - 16 Dec 2022
Cited by 4 | Viewed by 1077
Abstract
The basic concept of this study consists of the investigation of symmetrization of the mechanical response in extension and compression for fibrous metamaterials endowed with a symmetric microstructure relative to the axial direction. It is known that generally, this response is non-symmetric due [...] Read more.
The basic concept of this study consists of the investigation of symmetrization of the mechanical response in extension and compression for fibrous metamaterials endowed with a symmetric microstructure relative to the axial direction. It is known that generally, this response is non-symmetric due to the different deformation mechanisms activated in the two tests. If a further deformation mechanism based on the micro-shearing of connective elements is taken into account, the global mechanical response is observed to be symmetric for given sets of stiffnesses. The studied problem is addressed with the help of numerical simulations. Full article
(This article belongs to the Special Issue Recent Advances in the Study of Symmetry and Continuum Mechanics II)
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19 pages, 711 KiB  
Article
SDSM: Secure Data Sharing for Multilevel Partnerships in IoT Based Supply Chain
by Chuntang Yu, Yongzhao Zhan and Muhammad Sohail
Symmetry 2022, 14(12), 2656; https://doi.org/10.3390/sym14122656 - 15 Dec 2022
Cited by 7 | Viewed by 1621
Abstract
Symmetric encryption algorithms enable rapid encryption of data in IoT based supply chains, which helps to alleviate the concerns of supply chain participants about privacy disclosure when sharing data. However, in supply chain management where multilevel partnerships exist universally, a pure symmetric encryption [...] Read more.
Symmetric encryption algorithms enable rapid encryption of data in IoT based supply chains, which helps to alleviate the concerns of supply chain participants about privacy disclosure when sharing data. However, in supply chain management where multilevel partnerships exist universally, a pure symmetric encryption scheme cannot provide efficient data sharing and fine-grained access control. To overcome these problems, this paper proposes a secure data sharing scheme (SDSM) for IoT based supply chains by combining blockchain and ciphertext-based attribute cryptography. This scheme supports the enforcement of fine-grained access control for different levels of partnerships. In addition, to identify partnerships, we propose a metric based on the historical transaction facts on the blockchain, where the level of partnerships among participants is automatically calculated by smart contracts. Finally, we introduce personalized attributes of participants in the ciphertext-based attribute encryption algorithm to support the construction of access policies that include partnerships, allowing for more fine-grained access control. Security analyses and simulation experiments show that our proposed scheme is secure, effective, and practical. Full article
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58 pages, 2239 KiB  
Review
Dynamic Load Balancing Techniques in the IoT: A Review
by Dimitris Kanellopoulos and Varun Kumar Sharma
Symmetry 2022, 14(12), 2554; https://doi.org/10.3390/sym14122554 - 02 Dec 2022
Cited by 13 | Viewed by 5810
Abstract
The Internet of things (IoT) extends the Internet space by allowing smart things to sense and/or interact with the physical environment and communicate with other physical objects (or things) around us. In IoT, sensors, actuators, smart devices, cameras, protocols, and cloud services are [...] Read more.
The Internet of things (IoT) extends the Internet space by allowing smart things to sense and/or interact with the physical environment and communicate with other physical objects (or things) around us. In IoT, sensors, actuators, smart devices, cameras, protocols, and cloud services are used to support many intelligent applications such as environmental monitoring, traffic monitoring, remote monitoring of patients, security surveillance, and smart home automation. To optimize the usage of an IoT network, certain challenges must be addressed such as energy constraints, scalability, reliability, heterogeneity, security, privacy, routing, quality of service (QoS), and congestion. To avoid congestion in IoT, efficient load balancing (LB) is needed for distributing traffic loads among different routes. To this end, this survey presents the IoT architectures and the networking paradigms (i.e., edge–fog–cloud paradigms) adopted in these architectures. Then, it analyzes and compares previous related surveys on LB in the IoT. It reviews and classifies dynamic LB techniques in the IoT for cloud and edge/fog networks. Lastly, it presents some lessons learned and open research issues. Full article
(This article belongs to the Special Issue Advances in Electrical Engineering, Computing, and Symmetry)
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21 pages, 2952 KiB  
Article
Fractional Stefan Problem Solving by the Alternating Phase Truncation Method
by Agata Chmielowska and Damian Słota
Symmetry 2022, 14(11), 2287; https://doi.org/10.3390/sym14112287 - 01 Nov 2022
Cited by 4 | Viewed by 1246
Abstract
The aim of this paper is the adaptation of the alternating phase truncation (APT) method for solving the two-phase time-fractional Stefan problem. The aim was to determine the approximate temperature distribution in the domain with the moving boundary between the solid and the [...] Read more.
The aim of this paper is the adaptation of the alternating phase truncation (APT) method for solving the two-phase time-fractional Stefan problem. The aim was to determine the approximate temperature distribution in the domain with the moving boundary between the solid and the liquid phase. The adaptation of the APT method is a kind of method that allows us to consider the enthalpy distribution instead of the temperature distribution in the domain. The method consists of reducing the whole considered domain to liquid phase by adding sufficient heat at each point of the solid and then, after solving the heat equation transformed to the enthalpy form in the obtained region, subtracting the heat that has been added. Next the whole domain is reduced to the solid phase by subtracting the sufficient heat from each point of the liquid. The heat equation is solved in the obtained region and, after that, the heat that had been subtracted is added at the proper points. The steps of the APT method were adapted to solve the equations with the fractional derivatives. The paper includes numerical examples illustrating the application of the described method. Full article
(This article belongs to the Special Issue Trends in Fractional Modelling in Science and Innovative Technologies)
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13 pages, 508 KiB  
Article
Pseudo-Conformal Sound Speed in the Core of Compact Stars
by Mannque Rho
Symmetry 2022, 14(10), 2154; https://doi.org/10.3390/sym14102154 - 14 Oct 2022
Cited by 9 | Viewed by 1035
Abstract
By implementing the putative “hadron-quark continuity” conjectured in QCD in terms of skyrmion-half-skyrmion topological change in an effective field theory for dense matter, we argue that (quasi-)baryons could “masquerade” deconfined quarks in the interior of compact stars. We interpret this phenomenon as a [...] Read more.
By implementing the putative “hadron-quark continuity” conjectured in QCD in terms of skyrmion-half-skyrmion topological change in an effective field theory for dense matter, we argue that (quasi-)baryons could “masquerade” deconfined quarks in the interior of compact stars. We interpret this phenomenon as a consequence of possible interplay between hidden scale symmetry and hidden local symmetry at high density. A surprising spin-off of the emerging symmetry that we call “pseudo-conformality” is that the long-standing puzzle of the quenched gA1 in nuclei can be given a simple resolution by the way the hidden symmetries impact nuclear dynamics at low density. Full article
(This article belongs to the Special Issue Symmetries and Ultra Dense Matter of Compact Stars)
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12 pages, 8582 KiB  
Article
Design and Robustness Evaluation of Valley Topological Elastic Wave Propagation in a Thin Plate with Phononic Structure
by Motoki Kataoka, Masaaki Misawa and Kenji Tsuruta
Symmetry 2022, 14(10), 2133; https://doi.org/10.3390/sym14102133 - 13 Oct 2022
Cited by 5 | Viewed by 1822
Abstract
Based on the concept of band topology in phonon dispersion, we designed a topological phononic crystal in a thin plate for developing an efficient elastic waveguide. Despite that various topological phononic structures have been actively proposed, a quantitative design strategy of the phononic [...] Read more.
Based on the concept of band topology in phonon dispersion, we designed a topological phononic crystal in a thin plate for developing an efficient elastic waveguide. Despite that various topological phononic structures have been actively proposed, a quantitative design strategy of the phononic band and its robustness assessment in an elastic regime are still missing, hampering the realization of topological acoustic devices. We adopted a snowflake-like structure for the crystal unit cell and determined the optimal structure that exhibited the topological phase transition of the planar phononic crystal by changing the unit cell structure. The bandgap width could be adjusted by varying the length of the snow-side branch, and a topological phase transition occurred in the unit cell structure with threefold rotational symmetry. Elastic waveguides based on edge modes appearing at interfaces between crystals with different band topologies were designed, and their transmission efficiencies were evaluated numerically and experimentally. The results demonstrate the robustness of the elastic wave propagation in thin plates. Moreover, we experimentally estimated the backscattering length, which measures the robustness of the topologically protected propagating states against structural inhomogeneities. The results quantitatively indicated that degradation of the immunization against the backscattering occurs predominantly at the corners in the waveguides, indicating that the edge mode observed is a relatively weak topological state. Full article
(This article belongs to the Section Physics)
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23 pages, 1790 KiB  
Article
Prospects for Heavy Neutral SUSY HIGGS Scalars in the hMSSM and Natural SUSY at LHC Upgrades
by Howard Baer, Vernon Barger, Xerxes Tata and Kairui Zhang
Symmetry 2022, 14(10), 2061; https://doi.org/10.3390/sym14102061 - 03 Oct 2022
Cited by 9 | Viewed by 1046
Abstract
We examine production and decay of heavy neutral SUSY Higgs bosons ppH,Aττ¯ within the hMSSM and compare against a perhaps more plausible natural supersymmetry scenario dubbed mh125(nat) which allows [...] Read more.
We examine production and decay of heavy neutral SUSY Higgs bosons ppH,Aττ¯ within the hMSSM and compare against a perhaps more plausible natural supersymmetry scenario dubbed mh125(nat) which allows for a natural explanation for mweakmW,Z,h100 GeV while maintaining mh125 GeV. We evaluate signal against various Standard Model backgrounds from γ,Zττ¯, tt¯ and vector boson pair production VV. We combine the transverse mass method for back-to-back (BtB) taus along with the ditau mass peak mττ method for acollinear taus as our signal channels. This technique ultimately gives a boost to the signal significance over the standard technique of using just the BtB signal channel. We evaluate both the 95% CL exclusion and 5σ discovery reach in the mA vs. tanβ plane for present LHC with 139 fb−1, Run 3 with 300 fb−1 and high luminosity LHC (HL-LHC) with 3000 fb−1 of integrated luminosity. For tanβ=10, the exclusion limits range up to mA1, 1.1 and 1.4 TeV, respectively. These may be compared to the range of mA values gleaned from a statistical analysis of the string landscape wherein mA can range up to 8 TeV. Full article
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26 pages, 7028 KiB  
Article
A Triple-Structure Network Model Based upon MobileNet V1 and Multi-Loss Function for Facial Expression Recognition
by Baojin Han, Min Hu, Xiaohua Wang and Fuji Ren
Symmetry 2022, 14(10), 2055; https://doi.org/10.3390/sym14102055 - 02 Oct 2022
Cited by 5 | Viewed by 2551
Abstract
Existing facial expression recognition methods have some drawbacks. For example, it becomes difficult for network learning on cross-dataset facial expressions, multi-region learning on an image did not extract the overall image information, and a frequency multiplication network did not take into account the [...] Read more.
Existing facial expression recognition methods have some drawbacks. For example, it becomes difficult for network learning on cross-dataset facial expressions, multi-region learning on an image did not extract the overall image information, and a frequency multiplication network did not take into account the inter-class and intra-class features in image classification. In order to deal with the above problems, in our current research, we raise a symmetric mode to extract the inter-class features and intra-class diversity features, and then propose a triple-structure network model based upon MobileNet V1, which is trained via a new multi-branch loss function. Such a proposed network consists of triple structures, viz., a global branch network, an attention mechanism branch network, and a diversified feature learning branch network. To begin with, the global branch network is used to extract the global features of the facial expression images. Furthermore, an attention mechanism branch network concentrates to extract inter-class features. In addition, the diversified feature learning branch network is utilized to extract intra-class diverse features. The network training is performed by using multiple loss functions to decrease intra-class differences and inter-class similarities. Finally, through ablation experiments and visualization, the intrinsic mechanism of our triple-structure network model is proved to be very reasonable. Experiments on the KDEF, MMI, and CK+ datasets show that the accuracy of facial expression recognition using the proposed model is 1.224%, 13.051%, and 3.085% higher than that using MC-loss (VGG16), respectively. In addition, related comparison tests and analyses proved that our raised triple-structure network model reaches better performance than dozens of state-of-the-art methods. Full article
(This article belongs to the Special Issue Symmetry/Asymmetry and Fuzzy Systems)
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27 pages, 10857 KiB  
Article
Influence of Centrifugal Buoyancy in Thermal Convection within a Rotating Spherical Shell
by Hidemoto Satake and Toshio Tagawa
Symmetry 2022, 14(10), 2021; https://doi.org/10.3390/sym14102021 - 26 Sep 2022
Cited by 2 | Viewed by 2056
Abstract
The dynamo action, which is of importance in the study of the geomagnetism mechanism, is considered to be caused by the convection structure formed inside a rotating spherical shell. This convection structure elongated in the rotation axis is generated by the action of [...] Read more.
The dynamo action, which is of importance in the study of the geomagnetism mechanism, is considered to be caused by the convection structure formed inside a rotating spherical shell. This convection structure elongated in the rotation axis is generated by the action of both heat and rotation on the fluid inside a spherical shell. In this study, we analyzed thermal convection in such a rotating spherical shell and attempted to understand the phenomenon of this convective structure. It is known that each value of the Prandtl number, the Ekman number and the Rayleigh number and their balance are important for the generation of such convective structure. We fixed these three parameters and considered the effect of centrifugal buoyancy as the Froude number additionally. To investigate how the effects of centrifugal buoyancy affect the convective structure, we carried out both three-dimensional numerical simulations and linear stability analyses. In particular, we focused on the transition from axisymmetric flow to non-axisymmetric flow having wavenumbers in the toroidal direction and investigated both growth rate and phase velocity of the disturbance. It was found that axisymmetric flow tends to be maintained as the effect of centrifugal buoyancy increases. Full article
(This article belongs to the Special Issue Symmetry in Fluid Flow II)
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