Symmetry

21 pages, 844 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Structural Brain Asymmetries for Language: A Comparative Approach across Primates

by Yannick Becker and Adrien Meguerditchian

Symmetry 2022, 14(5), 876; https://doi.org/10.3390/sym14050876 - 25 Apr 2022

Cited by 13 | Viewed by 10314

Humans are the only species that can speak. Nonhuman primates, however, share some ‘domain-general’ cognitive properties that are essential to language processes. Whether these shared cognitive properties between humans and nonhuman primates are the results of a continuous evolution [homologies] or of a [...] Read more.

Humans are the only species that can speak. Nonhuman primates, however, share some ‘domain-general’ cognitive properties that are essential to language processes. Whether these shared cognitive properties between humans and nonhuman primates are the results of a continuous evolution [homologies] or of a convergent evolution [analogies] remain difficult to demonstrate. However, comparing their respective underlying structure—the brain—to determinate their similarity or their divergence across species is critical to help increase the probability of either of the two hypotheses, respectively. Key areas associated with language processes are the Planum Temporale, Broca’s Area, the Arcuate Fasciculus, Cingulate Sulcus, The Insula, Superior Temporal Sulcus, the Inferior Parietal lobe, and the Central Sulcus. These structures share a fundamental feature: They are functionally and structurally specialised to one hemisphere. Interestingly, several nonhuman primate species, such as chimpanzees and baboons, show human-like structural brain asymmetries for areas homologous to key language regions. The question then arises: for what function did these asymmetries arise in non-linguistic primates, if not for language per se? In an attempt to provide some answers, we review the literature on the lateralisation of the gestural communication system, which may represent the missing behavioural link to brain asymmetries for language area’s homologues in our common ancestor. Full article

(This article belongs to the Special Issue Cognitive and Neurophysiological Models of Brain Asymmetry)

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76 pages, 4149 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Cerebral Polymorphisms for Lateralisation: Modelling the Genetic and Phenotypic Architectures of Multiple Functional Modules

by Chris McManus

Symmetry 2022, 14(4), 814; https://doi.org/10.3390/sym14040814 - 14 Apr 2022

Cited by 28 | Viewed by 15989

Abstract

Recent fMRI and fTCD studies have found that functional modules for aspects of language, praxis, and visuo-spatial functioning, while typically left, left and right hemispheric respectively, frequently show atypical lateralisation. Studies with increasing numbers of modules and participants are finding increasing numbers of [...] Read more.

Recent fMRI and fTCD studies have found that functional modules for aspects of language, praxis, and visuo-spatial functioning, while typically left, left and right hemispheric respectively, frequently show atypical lateralisation. Studies with increasing numbers of modules and participants are finding increasing numbers of module combinations, which here are termed cerebral polymorphisms—qualitatively different lateral organisations of cognitive functions. Polymorphisms are more frequent in left-handers than right-handers, but it is far from the case that right-handers all show the lateral organisation of modules described in introductory textbooks. In computational terms, this paper extends the original, monogenic McManus DC (dextral-chance) model of handedness and language dominance to multiple functional modules, and to a polygenic DC model compatible with the molecular genetics of handedness, and with the biology of visceral asymmetries found in primary ciliary dyskinesia. Distributions of cerebral polymorphisms are calculated for families and twins, and consequences and implications of cerebral polymorphisms are explored for explaining aphasia due to cerebral damage, as well as possible talents and deficits arising from atypical inter- and intra-hemispheric modular connections. The model is set in the broader context of the testing of psychological theories, of issues of laterality measurement, of mutation-selection balance, and the evolution of brain and visceral asymmetries. Full article

(This article belongs to the Special Issue Cognitive and Neurophysiological Models of Brain Asymmetry)

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49 pages, 14068 KiB

Open AccessEditor’s ChoiceReview

Overview: State-of-the-Art in the Energy Harvesting Based on Piezoelectric Devices for Last Decade

by Ivan A. Parinov and Alexander V. Cherpakov

Symmetry 2022, 14(4), 765; https://doi.org/10.3390/sym14040765 - 7 Apr 2022

Cited by 29 | Viewed by 7060

Abstract

Technologies of energy harvesting have been developed intensively since the beginning of the twenty-first century, presenting themselves as alternatives to traditional energy sources (for instance, batteries) for small-dimensional and low-power electronics. Batteries have numerous shortcomings connected, for example, with restricted service life and [...] Read more.

Technologies of energy harvesting have been developed intensively since the beginning of the twenty-first century, presenting themselves as alternatives to traditional energy sources (for instance, batteries) for small-dimensional and low-power electronics. Batteries have numerous shortcomings connected, for example, with restricted service life and the necessity of periodic recharging/replacement that create significant problems for portative and remote devices and for power equipment. Environmental energy covers solar, thermal, and oscillation energy. By this, the vibration energy exists continuously around us due to the operation of numerous artificial structures and mechanisms. Different materials (including piezoelectrics) and conversion mechanisms can transform oscillation energy into electrical energy for use in many devices of energy harvesting. Piezoelectric transducers possessing electric mechanical coupling and demonstrating a high density of power in comparison with electromagnetic and electrostatic sensors are broadly applied for the generation of energy from different oscillation energy sources. For the last decade, novel piezoelectric materials, transformation mechanisms, electrical circuits, and experimental and theoretical approaches with results of computer simulation have been developed for improving different piezoelectric devices of energy harvesting. This overview presents results, obtained in the area of piezoelectric energy harvesting for the last decade, including a wide spectrum of experimental, analytical, and computer simulation investigations. Full article

(This article belongs to the Special Issue Advances in Energy Harvesting, Metamaterials, and Their Integrated Multifunctional Systems)

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10 pages, 1040 KiB

Open AccessEditor’s ChoiceArticle

Asymmetry in Muscle Strength, Dynamic Balance, and Range of Motion in Adult Symptomatic Hip Dysplasia

by Haifang Wang, Hailong Yu, Yonghwan Kim and Tingting Chen

Symmetry 2022, 14(4), 748; https://doi.org/10.3390/sym14040748 - 5 Apr 2022

Cited by 7 | Viewed by 4464

Abstract

Hip dysplasia (HD) is a typical developmental abnormality of the hip joint, and discomfort is often found in adulthood. This study compared patients with symptomatic HD in muscle strength, dynamic balance, and range of motion (ROM) with healthy individuals. Patients included those who [...] Read more.

Hip dysplasia (HD) is a typical developmental abnormality of the hip joint, and discomfort is often found in adulthood. This study compared patients with symptomatic HD in muscle strength, dynamic balance, and range of motion (ROM) with healthy individuals. Patients included those who complained of unilateral pain although the lateral center edge angle (LCEA) exhibited bilateral abnormality. Participants (n = 95; men: 46, women: 49) were divided into symptomatic and asymptomatic sides, and a healthy group without a history of hip joint disease (n = 70; men: 30, women: 40) was compared. Hip flexion, extension, abduction, and adduction were performed at an angular velocity of 30°/s using an isokinetic strength test device. The Y-balance test was conducted to measure dynamic balance, and ROM was measured using an electronic goniometer to evaluate flexion, extension, adduction, abduction, and internal and external rotations. In addition, the pain visual analog scale (VAS) and hip and groin outcome scale (HAGOS), a subjective evaluation of the hip joint, were evaluated. ROM (flexion, abduction, internal rotation, and external rotation) was significantly decreased in the HD symptomatic sides of men and women compared to those of the healthy group and the asymptomatic side, and the dynamic balance, flexion, and abduction muscle strength were also lower on the symptomatic sides. Although the LCEA of the HD asymptomatic side was lower than that of the healthy group, there were no significant differences in VAS, flexion, extension, abduction ROM, and extension strength compared to those of healthy individuals. In conclusion, patients with HD were mostly bilateral, and on the symptomatic side, there was a decrease in ROM, dynamic balance, and muscle strength; however, on the asymptomatic side, the function was relatively close to normal. Full article

(This article belongs to the Special Issue Asymmetric and Symmetric Study in Clinical Rehabilitation, Exercise Science, Clinical Biomechanics, and Biomedical Engineering: Technologies, Advances, and Applications)

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15 pages, 365 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Spectrum of Primordial Gravitational Waves in Modified Gravities: A Short Overview

by Sergei D. Odintsov, Vasilis K. Oikonomou and Ratbay Myrzakulov

Symmetry 2022, 14(4), 729; https://doi.org/10.3390/sym14040729 - 3 Apr 2022

Cited by 59 | Viewed by 4274

Abstract

In this work, we shall exhaustively study the effects of modified gravity on the energy spectrum of the primordial gravitational waves background. S. Weinberg has also produced significant works related to the primordial gravitational waves, with the most important one being the effects [...] Read more.

In this work, we shall exhaustively study the effects of modified gravity on the energy spectrum of the primordial gravitational waves background. S. Weinberg has also produced significant works related to the primordial gravitational waves, with the most important one being the effects of neutrinos on primordial gravitational waves. With this short review, our main aim is to gather all the necessary information for studying the effects of modified gravity on primordial gravitational waves in a concrete and quantitative way and in a single paper. After reviewing all the necessary techniques for extracting the general relativistic energy spectrum, and how to obtain, in a WKB way, the modified gravity damping or amplifying factor, we concentrate on specific forms of modified gravity of interest. The most important parameter involved for the calculation of the effects of modified gravity on the energy spectrum is the parameter

a_{M}

, which we calculate for the cases of

f (R, ϕ)

gravity, Chern–Simons-corrected

f (R, ϕ)

gravity, Einstein–Gauss–Bonnet-corrected

f (R, ϕ)

gravity, and higher derivative extended Einstein–Gauss–Bonnet-corrected

f (R, ϕ)

gravity. The exact form of

a_{M}

is presented explicitly for the first time in the literature. With regard to Einstein–Gauss–Bonnet-corrected

f (R, ϕ)

gravity, and higher derivative extended Einstein–Gauss–Bonnet-corrected

f (R, ϕ)

gravity theories, we focus on the case in which the gravitational wave propagating speed is equal to that of light in a vacuum. We provide expressions for

a_{M}

expressed in terms of the cosmic time and in terms of the redshift, which can be used directly for the numerical calculation of the effect of modified gravity on the primordial gravitational wave energy spectrum. Full article

(This article belongs to the Special Issue Fundamental Aspects of Theoretical Physics - Memorial Issue for Prof. Dr. Weinberg)

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13 pages, 3012 KiB

Open AccessFeature PaperEditor’s ChoiceReview

How Symmetry Influences the Dissociation of Protonated Cyclic Peptides

by Ariel F. Pérez-Mellor, Riccardo Spezia and Anne Zehnacker

Symmetry 2022, 14(4), 679; https://doi.org/10.3390/sym14040679 - 25 Mar 2022

Cited by 5 | Viewed by 3422

Abstract

Protonated cyclic dipeptides undergo collision-induced dissociation, and this reaction mechanism strongly depends on the symmetry and the nature of the residues. We review the main dissociation mechanism for a series of cyclic dipeptides, obtained through chemical dynamics simulations. The systems range from the [...] Read more.

Protonated cyclic dipeptides undergo collision-induced dissociation, and this reaction mechanism strongly depends on the symmetry and the nature of the residues. We review the main dissociation mechanism for a series of cyclic dipeptides, obtained through chemical dynamics simulations. The systems range from the symmetrical cyclo-(glycyl-glycyl), with two possible symmetrical protonation sites located on the peptide ring, to cyclo-(tyrosyl-prolyl), where the symmetry of protonation sites on the peptide ring is broken by the dissimilar nature of the different residues. Finally, cyclo-(phenylalanyl-histidyl) shows a completely asymmetric situation, with the proton located on one of the dipeptide side chains, which explains the peculiar fragmentation mechanism induced by shuttling the proton, whose efficiency is strongly dependent on the relative chirality of the residues. Full article

(This article belongs to the Special Issue Asymmetric Molecules and Chirality Recognition)

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15 pages, 2266 KiB

Open AccessEditor’s ChoiceArticle

From Memristor-Modeled Jerk System to the Nonlinear Systems with Memristor

by Xianming Wu, Shaobo He, Weijie Tan and Huihai Wang

Symmetry 2022, 14(4), 659; https://doi.org/10.3390/sym14040659 - 24 Mar 2022

Cited by 10 | Viewed by 3102

Abstract

Based on the proposed generalized memristor, a new jerk system is proposed. The complex dynamics of the system are investigated by means of bifurcation diagrams, Lyapunov exponents, and MSampEn, and rich dynamics are observed. Moreover, the circuits of the generalized memristor and the [...] Read more.

Based on the proposed generalized memristor, a new jerk system is proposed. The complex dynamics of the system are investigated by means of bifurcation diagrams, Lyapunov exponents, and MSampEn, and rich dynamics are observed. Moreover, the circuits of the generalized memristor and the jerk system are physically implemented in the hardware level. The experimental results show that the memristor circuit can generate “8”-shaped pinched hysteresis loops, and the observed attractors match well with the numerical simulations results. In this paper, we summarize nonlinear systems with memristors in the references. It indicates that there are two symmetry methods to find a memristor model in nonlinear systems. However, some of them cannot be realized using the memristor devices, although a memristor model can be found. For example, the famous Lorenz system contains a memristor function, but it cannot be realized using the memristor device. The principles regarding whether nonlinear systems with a memristor function can be realized using a memristor device are discussed. Full article

(This article belongs to the Special Issue Discrete and Continuous Memristive Nonlinear Systems and Symmetry)

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19 pages, 9170 KiB

Open AccessEditor’s ChoiceArticle

Evolution of Microstructure, Texture and Corrosion Properties of Additively Manufactured AlSi10Mg Alloy Subjected to Equal Channel Angular Pressing (ECAP)

by Przemysław Snopiński, Anna Woźniak, Dariusz Łukowiec, Krzysztof Matus, Tomasz Tański, Stanislav Rusz and Ondřej Hilšer

Symmetry 2022, 14(4), 674; https://doi.org/10.3390/sym14040674 - 24 Mar 2022

Cited by 17 | Viewed by 3532

Abstract

In the selective laser melting process (SLM), the region irradiated by the laser beam is melted and quickly solidified, forming solidification lines (laser scan tracks) with symmetrical shapes. Because of the unique (rapid) crystallization conditions, the subgrain structures, typically observed inside these solidification [...] Read more.

In the selective laser melting process (SLM), the region irradiated by the laser beam is melted and quickly solidified, forming solidification lines (laser scan tracks) with symmetrical shapes. Because of the unique (rapid) crystallization conditions, the subgrain structures, typically observed inside these solidification lines, could also have variable geometric symmetrical patterns, e.g., cellular, pentagonal, or hexagonal cellular. The existence of such distinctive microstructures in SLM-made alloys has a significant impact on their superior mechanical and corrosion properties. Thus, any modification of this symmetrical microstructure (due to post-processing) can degrade or improve the properties of SLM-fabricated alloys. This study presents the experimental results on the effects of heat treatment and ECAP on microstructure modification and corrosion behavior of SLM-fabricated AlSi10Mg alloy. Light microscopy, scanning electron microscopy (SEM), electron backscattered diffraction (EBSD), and X-ray diffraction (XRD) were used for microstructural analysis. The corrosion properties of the given samples were determined using open-circuit potential (OCP), potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS) techniques. EBSD observations showed that the imposed strain resulted in an obvious reduction in grain size to ~1.42 µm and ~0.24 µm after the first and second ECAP passes, respectively. Electrochemical tests revealed that the corrosion resistance of the ECAP-processed AlSi10Mg alloy improved significantly, which was confirmed by a nobler E_corr and lower I_corr values, and higher polarization resistance. The final results indicated that the strain-induced crystalline defects provided more nucleation sites for the formation of a denser and thicker oxide film, thus enhancing the corrosion resistance of the AlSi10Mg alloy. Full article

(This article belongs to the Special Issue Advances in Materials Science with Symmetry/Asymmetry)

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27 pages, 17811 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Symmetry Constraints on Spin Order Transfer in Parahydrogen-Induced Polarization (PHIP)

by Andrey N. Pravdivtsev, Danila A. Barskiy, Jan-Bernd Hövener and Igor V. Koptyug

Symmetry 2022, 14(3), 530; https://doi.org/10.3390/sym14030530 - 4 Mar 2022

Cited by 11 | Viewed by 4310

Abstract

It is well known that the association of parahydrogen (pH₂) with an unsaturated molecule or a transient metalorganic complex can enhance the intensity of NMR signals; the effect is known as parahydrogen-induced polarization (PHIP). During recent decades, numerous methods were proposed [...] Read more.

It is well known that the association of parahydrogen (pH₂) with an unsaturated molecule or a transient metalorganic complex can enhance the intensity of NMR signals; the effect is known as parahydrogen-induced polarization (PHIP). During recent decades, numerous methods were proposed for converting pH₂-derived nuclear spin order to the observable magnetization of protons or other nuclei of interest, usually ¹³C or ¹⁵N. Here, we analyze the constraints imposed by the topological symmetry of the spin systems on the amplitude of transferred polarization. We find that in asymmetric systems, heteronuclei can be polarized to 100%. However, the amplitude drops to 75% in A₂BX systems and further to 50% in A₃B₂X systems. The latter case is of primary importance for biological applications of PHIP using sidearm hydrogenation (PHIP-SAH). If the polarization is transferred to the same type of nuclei, i.e., ¹H, symmetry constraints impose significant boundaries on the spin-order distribution. For AB, A₂B, A₃B, A₂B₂, AA’(AA’) systems, the maximum average polarization for each spin is 100%, 50%, 33.3%, 25%, and 0, respectively, (where A and B (or A’) came from pH₂). Remarkably, if the polarization of all spins in a molecule is summed up, the total polarization grows asymptotically with ~1.27

\sqrt{N}

and can exceed 2 in the absence of symmetry constraints (where

N

is the number of spins). We also discuss the effect of dipole–dipole-induced pH₂ spin-order distribution in heterogeneous catalysis or nematic liquid crystals. Practical examples from the literature illustrate our theoretical analysis. Full article

(This article belongs to the Special Issue Symmetry Principles in the Nuclear Magnetic Resonance)

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13 pages, 289 KiB

Open AccessEditor’s ChoiceArticle

Some Results in the Theory of a Cosserat Thermoelastic Body with Microtemperatures and Inner Structure

by Marin Marin, Sorin Vlase, Eduard M. Craciun, Nicolae Pop and Ioan Tuns

Symmetry 2022, 14(3), 511; https://doi.org/10.3390/sym14030511 - 2 Mar 2022

Cited by 6 | Viewed by 2844

Abstract

This study is concerned with the theory of Cosserat thermoelastic media, whose micro-particles possess microtemperatures. The mixed initial boundary value problem considered in this context is transformed in a temporally evolutionary equation on a Hilbert space. Using some results from the theory of [...] Read more.

This study is concerned with the theory of Cosserat thermoelastic media, whose micro-particles possess microtemperatures. The mixed initial boundary value problem considered in this context is transformed in a temporally evolutionary equation on a Hilbert space. Using some results from the theory of semigroups, the existence and uniqueness of solution is proved. In the same manner, it approached the continuous dependence of the solution upon initial data and loads. From what we have studied, neither on the internet nor in the databases, we have not found qualitative issues addressed regarding the mixed problem in the context of the theory of thermoelasticity of Cosserat environments, in which the contribution of inner structure and microtemperatures are taken into account. Full article

(This article belongs to the Section Mathematics)

62 pages, 6768 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Neutron Stars with Baryon Number Violation, Probing Dark Sectors

by Jeffrey M. Berryman, Susan Gardner and Mohammadreza Zakeri

Symmetry 2022, 14(3), 518; https://doi.org/10.3390/sym14030518 - 2 Mar 2022

Cited by 31 | Viewed by 8909

Abstract

The neutron lifetime anomaly has been used to motivate the introduction of new physics with hidden-sector particles coupled to baryon number, and on which neutron stars provide powerful constraints. Although the neutron lifetime anomaly may eventually prove to be of mundane origin, we [...] Read more.

The neutron lifetime anomaly has been used to motivate the introduction of new physics with hidden-sector particles coupled to baryon number, and on which neutron stars provide powerful constraints. Although the neutron lifetime anomaly may eventually prove to be of mundane origin, we use it as motivation for a broader review of the ways that baryon number violation, be it real or apparent, and dark sectors can intertwine and how neutron star observables, both present and future, can constrain them. Full article

(This article belongs to the Special Issue The Neutron Physics - Dark Matter Connection: Bridge Through the Baryon Symmetry Violation)

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10 pages, 1365 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

A Search for Cosmic Ray Bursts at 0.1 PeV with a Small Air Shower Array

by Roger Clay, Jassimar Singh, Piotr Homola, Olaf Bar, Dmitry Beznosko, Apoorva Bhatt, Gopal Bhatta, Łukasz Bibrzycki, Nikolay Budnev, David E. Alvarez-Castillo, Niraj Dhital, Alan R. Duffy, Michał Frontczak, Dariusz Góra, Alok C. Gupta, Bartosz Łozowski, Mikhail V. Medvedev, Justyna Mędrala, Justyna Miszczyk, Michał Niedźwiecki, Marcin Piekarczyk, Krzysztof Rzecki, Jilberto Zamora-Saa, Katarzyna Smelcerz, Karel Smolek, Tomasz Sośnicki, Jaroslaw Stasielak, Sławomir Stuglik, Oleksandr Sushchov, Arman Tursunov and Tadeusz Wibig Show full author list Hide full author list

Symmetry 2022, 14(3), 501; https://doi.org/10.3390/sym14030501 - 1 Mar 2022

Cited by 8 | Viewed by 3688

Abstract

The Cosmic Ray Extremely Distributed Observatory (CREDO) pursues a global research strategy dedicated to the search for correlated cosmic rays, so-called Cosmic Ray Ensembles (CRE). Its general approach to CRE detection does not involve any a priori considerations, and its search strategy encompasses [...] Read more.

The Cosmic Ray Extremely Distributed Observatory (CREDO) pursues a global research strategy dedicated to the search for correlated cosmic rays, so-called Cosmic Ray Ensembles (CRE). Its general approach to CRE detection does not involve any a priori considerations, and its search strategy encompasses both spatial and temporal correlations, on different scales. Here we search for time clustering of the cosmic ray events collected with a small sea-level extensive air shower array at the University of Adelaide. The array consists of seven one-square-metre scintillators enclosing an area of 10 m × 19 m. It has a threshold energy ~0.1 PeV, and records cosmic ray showers at a rate of ~6 mHz. We have examined event arrival times over a period of over 2.5 years in two equipment configurations (without and with GPS timing), recording ~300 k events and ~100 k events. We determined the event time spacing distributions between individual events and the distributions of time periods which contained specific numbers of multiple events. We find that the overall time distributions are as expected for random events. The distribution which was chosen a priori for particular study was for time periods covering five events (four spacings). Overall, these distributions fit closely with expectation, but there are two outliers of short burst periods in data for each configuration. One of these outliers contains eight events within 48 s. The physical characteristics of the array will be discussed together with the analysis procedure, including a comparison between the observed time distributions and expectation based on randomly arriving events. Full article

(This article belongs to the Special Issue Symmetry in Cosmic Ray Detections)

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22 pages, 6035 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Improved Search for Neutron to Mirror-Neutron Oscillations in the Presence of Mirror Magnetic Fields with a Dedicated Apparatus at the PSI UCN Source

by Nicholas J. Ayres, Zurab Berezhiani, Riccardo Biondi, Georg Bison, Kazimierz Bodek, Vira Bondar, Pin-Jung Chiu, Manfred Daum, Reza Tavakoli Dinani, Cornelis B. Doorenbos, Solange Emmenegger, Klaus Kirch, Victoria Kletzl, Jochen Krempel, Bernhard Lauss, Duarte Pais, Ingo Rienäcker, Dieter Ries, Nicola Rossi, Dagmara Rozpedzik, Philipp Schmidt-Wellenburg, Kazuo S. Tanaka, Jacek Zejma, Nathalie Ziehl and Geza Zsigmond Show full author list Hide full author list

Symmetry 2022, 14(3), 503; https://doi.org/10.3390/sym14030503 - 1 Mar 2022

Cited by 22 | Viewed by 7252

Abstract

While the international nEDM collaboration at the Paul Scherrer Institut (PSI) took data in 2017 that covered a considerable fraction of the parameter space of claimed potential signals of hypothetical neutron (n) to mirror-neutron (

n^{'}

) transitions, it could [...] Read more.

While the international nEDM collaboration at the Paul Scherrer Institut (PSI) took data in 2017 that covered a considerable fraction of the parameter space of claimed potential signals of hypothetical neutron (n) to mirror-neutron (

n^{'}

) transitions, it could not test all claimed signal regions at various mirror magnetic fields. Therefore, a new study of

n - n^{'}

oscillations using stored ultracold neutrons (UCNs) is underway at PSI, considerably expanding the reach in parameter space of mirror magnetic fields (

B^{'}

) and oscillation time constants (

τ_{n n^{'}}

). The new apparatus is designed to test for the anomalous loss of stored ultracold neutrons as a function of an applied magnetic field. The experiment is distinguished from its predecessors by its very large storage vessel (1.47 m³), enhancing its statistical sensitivity. In a test experiment in 2020 we have demonstrated the capabilities of our apparatus. However, the full analysis of our recent data is still pending. Based on already demonstrated performance, we will reach sensitivity to oscillation times

τ_{n n^{'}} / \sqrt{cos (β)}

well above a hundred seconds, with

β

being the angle between

B^{'}

and the applied magnetic field B. The scan of B will allow the finding or the comprehensive exclusion of potential signals reported in the analysis of previous experiments and suggested to be consistent with neutron to mirror-neutron oscillations. Full article

(This article belongs to the Special Issue The Neutron Physics - Dark Matter Connection: Bridge Through the Baryon Symmetry Violation)

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14 pages, 1441 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

A Search for Neutron to Mirror Neutron Oscillation Using Neutron Electric Dipole Moment Measurements

by Prajwal Mohanmurthy, Albert R. Young, Jeff A. Winger and Geza Zsigmond

Symmetry 2022, 14(3), 487; https://doi.org/10.3390/sym14030487 - 28 Feb 2022

Cited by 9 | Viewed by 3307

Abstract

Baryon number violation is a key ingredient of baryogenesis. It has been hypothesized that there could also be a parity-conjugated copy of the standard model particles, called mirror particles. The existence of such a mirror universe has specific testable implications, especially in the [...] Read more.

Baryon number violation is a key ingredient of baryogenesis. It has been hypothesized that there could also be a parity-conjugated copy of the standard model particles, called mirror particles. The existence of such a mirror universe has specific testable implications, especially in the domain of neutral particle oscillation, viz. the baryon number violating neutron to mirror-neutron (

n - n^{'}

) oscillation. Consequently, there were many experiments that have searched for

n - n^{'}

oscillation, and imposed constraints upon the parameters that describe it. Recently, further analysis on some of these results have identified anomalies which could point to the detection of

n - n^{'}

oscillation. All the previous efforts searched for

n - n^{'}

oscillation by comparing the relative number of ultracold neutrons that survive after a period of storage for one or both of the two cases: (i) comparison of zero applied magnetic field to a non-zero applied magnetic field, and (ii) comparison where the orientation of the applied magnetic field was reversed. However,

n - n^{'}

oscillations also lead to variations in the precession frequency of polarized neutrons upon flipping the direction of the applied magnetic field. Precession frequencies are measured, very precisely, by experiments searching for the electric dipole moment. For the first time, we used the data from the latest search for the neutron electric dipole moment to constrain

n - n^{'}

oscillation. After compensating for the systematic effects that affect the ratio of precession frequencies of ultracold neutrons and cohabiting

^{199}

Hg-atoms, chief among which was due to their motion in non-uniform magnetic field, we constrained any further perturbations due to

n - n^{'}

oscillation. We thereby provide a lower limit on the

n - n^{'}

oscillation time constant of

τ_{n n^{'}} / \sqrt{| cos (β) |} > 5.7 s, 0.36 T^{'} < B^{'} < 1.01 T^{'}

(95% C.L.), where

β

is the angle between the applied magnetic field and the ambient mirror magnetic field. This constraint is the best available in the range of

0.36 T^{'} < B^{'} < 0.40 T^{'}

. Full article

(This article belongs to the Special Issue The Neutron Physics - Dark Matter Connection: Bridge Through the Baryon Symmetry Violation)

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13 pages, 1022 KiB

Open AccessEditor’s ChoiceSystematic Review

Genetic Factors That Affect Asymmetric Mandibular Growth—A Systematic Review

by Alicja Babczyńska, Beata Kawala and Michał Sarul

Symmetry 2022, 14(3), 490; https://doi.org/10.3390/sym14030490 - 28 Feb 2022

Cited by 10 | Viewed by 4734

Abstract

Facial asymmetry is a feature that occurs to a greater or lesser extent in the general population. As its severity is usually slight, facial asymmetry may not be noticeable to the patient. However, there are cases when severe facial asymmetry not only affects [...] Read more.

Facial asymmetry is a feature that occurs to a greater or lesser extent in the general population. As its severity is usually slight, facial asymmetry may not be noticeable to the patient. However, there are cases when severe facial asymmetry not only affects the facial aesthetics by distorting facial proportions, but also contributes to problems related to the function of the stomatognathic system. The nodal signalling pathway appears to be of particular importance in the process of mandibular asymmetry, as it affects not only structures formed from the first pharyngeal arch, but also other organs, such as the heart and lungs. Following the evaluation of the available literature, the inheritance of mandibular asymmetry is a very complex and multifactorial process, and the genes whose altered expression appears to be a more important potential aetiological factor for asymmetry include PITX2, ACTN3, ENPP1 and ESR1. This systematic review attempts to systematise the available literature concerning the impact of signalling pathway disruption, including the disruption of the nodal signalling pathway, on the development of mandibular asymmetry. Full article

(This article belongs to the Special Issue Dentofacial Asymmetry — Challenges and Perspectives)

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23 pages, 1034 KiB

Open AccessEditor’s ChoiceArticle

Infrasonic, Acoustic and Seismic Waves Produced by the Axion Quark Nuggets

by Dmitry Budker, Victor V. Flambaum and Ariel Zhitnitsky

Symmetry 2022, 14(3), 459; https://doi.org/10.3390/sym14030459 - 24 Feb 2022

Cited by 28 | Viewed by 2905

Abstract

We advocate the idea that Axion Quark Nuggets (AQN) hitting the Earth can be detected by analysing the infrasound, acoustic, and seismic waves which always accompany their passage in the atmosphere and underground. Our estimates for the infrasonic frequency

ν ≃ 5

Hz [...] Read more.

We advocate the idea that Axion Quark Nuggets (AQN) hitting the Earth can be detected by analysing the infrasound, acoustic, and seismic waves which always accompany their passage in the atmosphere and underground. Our estimates for the infrasonic frequency

ν ≃ 5

Hz and overpressure

δ p \sim 0.3

Pa for relatively large size dark matter (DM) nuggets suggest that sensitivity of presently available instruments is already sufficient to detect very intense (but very rare) events today with existing technology. A study of much more frequent but less intense events requires a new type of instrument. We propose a detection strategy for a systematic study to search for such relatively weak and frequent events by using distributed acoustic sensing and briefly mention other possible detection methods. Full article

(This article belongs to the Special Issue The Dark Universe: The Harbinger of a Major Discovery)

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48 pages, 2788 KiB

Open AccessEditor’s ChoiceReview

Chirality in Organic and Mineral Systems: A Review of Reactivity and Alteration Processes Relevant to Prebiotic Chemistry and Life Detection Missions

by Carina Lee, Jessica M. Weber, Laura E. Rodriguez, Rachel Y. Sheppard, Laura M. Barge, Eve L. Berger and Aaron S. Burton

Symmetry 2022, 14(3), 460; https://doi.org/10.3390/sym14030460 - 24 Feb 2022

Cited by 22 | Viewed by 16704

Abstract

Chirality is a central feature in the evolution of biological systems, but the reason for biology’s strong preference for specific chiralities of amino acids, sugars, and other molecules remains a controversial and unanswered question in origins of life research. Biological polymers tend toward [...] Read more.

Chirality is a central feature in the evolution of biological systems, but the reason for biology’s strong preference for specific chiralities of amino acids, sugars, and other molecules remains a controversial and unanswered question in origins of life research. Biological polymers tend toward homochiral systems, which favor the incorporation of a single enantiomer (molecules with a specific chiral configuration) over the other. There have been numerous investigations into the processes that preferentially enrich one enantiomer to understand the evolution of an early, racemic, prebiotic organic world. Chirality can also be a property of minerals; their interaction with chiral organics is important for assessing how post-depositional alteration processes could affect the stereochemical configuration of simple and complex organic molecules. In this paper, we review the properties of organic compounds and minerals as well as the physical, chemical, and geological processes that affect organic and mineral chirality during the preservation and detection of organic compounds. We provide perspectives and discussions on the reactions and analytical techniques that can be performed in the laboratory, and comment on the state of knowledge of flight-capable technologies in current and future planetary missions, with a focus on organics analysis and life detection. Full article

(This article belongs to the Section Chemistry: Symmetry/Asymmetry)

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26 pages, 18774 KiB

Open AccessEditor’s ChoiceReview

Lamellar Tetragonal Symmetry of Amphiphilic Thermotropic Ionic Liquid Crystals in the Framework of Other Closely Related Highly Ordered Structures

by Michael Arkas, Marilina Douloudi, Michail Vardavoulias and Theodora Katsika

Symmetry 2022, 14(2), 394; https://doi.org/10.3390/sym14020394 - 16 Feb 2022

Cited by 4 | Viewed by 3877

Abstract

An overview of the chemical compounds forming the rare smectic T phases is presented with references to the historical context. Thermodynamics (transition temperatures, enthalpies) along with the factors (stereochemical constraints, electrostatic interactions, aliphatic chain stacking, intermolecular forces) contributing to the adoption of tetragonal [...] Read more.

An overview of the chemical compounds forming the rare smectic T phases is presented with references to the historical context. Thermodynamics (transition temperatures, enthalpies) along with the factors (stereochemical constraints, electrostatic interactions, aliphatic chain stacking, intermolecular forces) contributing to the adoption of tetragonal scaffolds are also discussed. Characteristic optical microscopy textures and X-ray diffraction patterns are presented. In parallel, a comparison of the geometrical parameters such as distances between atoms, molecular areas, volumes, and lattice parameters with the closest two-dimensional and three-dimensional organizations, is performed. Full article

(This article belongs to the Collection Feature Papers in Chemistry)

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19 pages, 1220 KiB

Open AccessEditor’s ChoiceArticle

Attaching Onto or Inserting Into an Intramolecular Hydrogen Bond: Exploring and Controlling a Chirality-Dependent Dilemma for Alcohols

by Manuel Lange, Elisabeth Sennert and Martin A. Suhm

Symmetry 2022, 14(2), 357; https://doi.org/10.3390/sym14020357 - 11 Feb 2022

Cited by 5 | Viewed by 2999

Abstract

Prereactive complexes in noncovalent organocatalysis are sensitive to the relative chirality of the binding partners and to hydrogen bond isomerism. Both effects are present when a transiently chiral alcohol docks on a chiral

α

-hydroxy ester, turning such 1:1 complexes into elementary, non-reactive [...] Read more.

Prereactive complexes in noncovalent organocatalysis are sensitive to the relative chirality of the binding partners and to hydrogen bond isomerism. Both effects are present when a transiently chiral alcohol docks on a chiral

α

-hydroxy ester, turning such 1:1 complexes into elementary, non-reactive model systems for chirality induction in the gas phase. With the help of linear infrared and Raman spectroscopy in supersonic jet expansions, conformational preferences are investigated for benzyl alcohol in combination with methyl lactate, also exploring p-chlorination of the alcohol and the achiral homolog methyl glycolate to identify potential London dispersion and chirality effects on the energy sequence. Three of the four combinations prefer barrierless complexation via the hydroxy group of the ester (association). In contrast, the lightest complex predominantly shows insertion into the intramolecular hydrogen bond, such as the analogous lactate and glycolate complexes of methanol. The experimental findings are rationalized with computations, and a uniform helicality induction in the alcohol by the lactate is predicted, independent of insertion into or association with the internal lactate hydrogen bond. p-chlorination of benzyl alcohol has a stabilizing effect on association because the insertion motif prevents a close contact between the chlorine and the hydroxy ester. After simple anharmonicity and substitution corrections, the B3LYP-D3 approach offers a fairly systematic description of the known spectroscopic data on alcohol complexes with

α

-hydroxy esters. Full article

(This article belongs to the Special Issue Asymmetric Molecules and Chirality Recognition)

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10 pages, 855 KiB

Open AccessEditor’s ChoiceArticle

Bayesian Interval Estimation for the Two-Parameter Exponential Distribution Based on the Right Type II Censored Sample

by Shu-Fei Wu

Symmetry 2022, 14(2), 352; https://doi.org/10.3390/sym14020352 - 10 Feb 2022

Cited by 7 | Viewed by 2776

Abstract

The Bayesian interval estimation of the scale parameter for two-parameter exponential distribution is proposed based on the right type II censored sample. Under this type of censoring, two methods of Bayesian joint confidence region of the two parameters are also proposed. The simulation [...] Read more.

The Bayesian interval estimation of the scale parameter for two-parameter exponential distribution is proposed based on the right type II censored sample. Under this type of censoring, two methods of Bayesian joint confidence region of the two parameters are also proposed. The simulation results show that the Bayesian method has a higher coverage probability than the existing method, so the Bayesian method is recommended for use. This research is related to the topic of asymmetrical probability distributions and applications across disciplines. The predictive interval of the future observation based on the right type II censored sample is also provided. One biometrical example is given to illustrate the proposed methods for the Bayesian interval estimations and prediction interval. Full article

(This article belongs to the Special Issue Skewed (Asymmetrical) Probability Distributions and Applications across Disciplines II)

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15 pages, 2620 KiB

Open AccessEditor’s ChoiceArticle

Interface Asymmetry Induced and Surface Pressure Controlled Valence Tautomerism in Monolayers of bis-Phthalocyaninates of Lanthanides

by Daria S. Kutsybala, Alexander V. Shokurov, Alexander G. Martynov, Alexey V. Yagodin, Vladimir V. Arslanov, Yulia G. Gorbunova and Sofiya L. Selektor

Symmetry 2022, 14(2), 340; https://doi.org/10.3390/sym14020340 - 7 Feb 2022

Cited by 7 | Viewed by 2446

Abstract

Supramolecular systems based on transition metal complexes capable of reversible redox isomerization due to intramolecular electron transfer are one of the most interesting objects from the viewpoint of molecular switches’ design. In the present work, a comparative analysis of valence transformation of lanthanide [...] Read more.

Supramolecular systems based on transition metal complexes capable of reversible redox isomerization due to intramolecular electron transfer are one of the most interesting objects from the viewpoint of molecular switches’ design. In the present work, a comparative analysis of valence transformation of lanthanide complexes (Sm, Er, Tm and Yb) with donor-substituted bis-phthalocyaninates occurring during the formation and compression–extension of Langmuir monolayers was carried out using data of UV–Vis–NIR spectroscopy. It is shown that the numerical values of the Q-band positions in the absorption spectra for the extended monolayers of the complexes under study depend linearly on the ionic radius of the metal center, if the metals have an oxidation state of +2. This makes it possible to draw a direct analogy between the behavior of the studied compounds and analogous europium and cerium complexes, for which direct evidence of the valence tautomerism in such planar systems was obtained earlier. This led to the conclusion that the intramolecular electron transfer from the phthalocyanine ligand to the central metal ion [Ln³⁺(R₄Pc²⁻)(R₄Pc^•−)]⁰→[Ln²⁺(R₄Pc^•−)₂]⁰ occurs when solutions of donor-substituted bis-phthalocyaninates of samarium, erbium, thulium, and ytterbium are deposited onto the water subphase, and the reverse redox-isomeric transition is observed in most cases when the monolayer is compressed to high surface pressures. The first of these switches is related to the asymmetry of the air/water interface, and the second one is controlled by the lateral compression–expansion of the monolayer. It has been demonstrated that when bis-phthalocyanine monolayers of lanthanides with variable valence are transferred to solid substrates, the valence state of the metal center, and consequently, the redox-isomeric state of the complex, do not change. This means that we are able to form films with a predetermined state of the complex. Note that the redox-isomeric state of complexes should affect the entire range of physicochemical properties of such films. Full article

(This article belongs to the Special Issue Spin Crossover and Valence Tautomerism: Symmetry Aspects)

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53 pages, 2604 KiB

Open AccessEditor’s ChoiceReview

Low-Energy Interactions of Mesons with Participation of the First Radially Excited States in U(3) × U(3) NJL Model

by Mikhail Konstantinovich Volkov, Aleksey Aleksandrovich Pivovarov and Kanat Nurlan

Symmetry 2022, 14(2), 308; https://doi.org/10.3390/sym14020308 - 2 Feb 2022

Cited by 14 | Viewed by 2653

Abstract

The

U (3) \times U (3)

chiral symmetric NJL model describing pseudoscalar, vector, and axial-vector mesons in both the ground state and first radially excited states is shortly presented in this review. In this model, it is possible to [...] Read more.

The

U (3) \times U (3)

chiral symmetric NJL model describing pseudoscalar, vector, and axial-vector mesons in both the ground state and first radially excited states is shortly presented in this review. In this model, it is possible to describe a large number of low-energy interactions of mesons,

τ

lepton decays into mesons, and processes of meson production in electron–positron annihilations in satisfactory agreement with the experiments. In describing a number of processes, it turned out to be necessary to take into account the interactions of mesons in the final state. Full article

(This article belongs to the Special Issue Symmetry in Quantum Field Theory, Critical Behavior Theory and Stochastic Dynamics)

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27 pages, 5203 KiB

Open AccessEditor’s ChoiceReview

Functional Chirality: From Small Molecules to Supramolecular Assemblies

by Alaa Adawy

Symmetry 2022, 14(2), 292; https://doi.org/10.3390/sym14020292 - 1 Feb 2022

Cited by 25 | Viewed by 10037

Abstract

Many structures in nature look symmetric, but this is not completely accurate, because absolute symmetry is close to death. Chirality (handedness) is one form of living asymmetry. Chirality has been extensively investigated at different levels. Many rules were coined in attempts made for [...] Read more.

Many structures in nature look symmetric, but this is not completely accurate, because absolute symmetry is close to death. Chirality (handedness) is one form of living asymmetry. Chirality has been extensively investigated at different levels. Many rules were coined in attempts made for many decades to have control over the selection of handedness that seems to easily occur in nature. It is certain that if good control is realized on chirality, the roads will be ultimately open towards numerous developments in pharmaceutical, technological, and industrial applications. This tutorial review presents a report on chirality from single molecules to supramolecular assemblies. The realized functions are still in their infancy and have been scarcely converted into actual applications. This review provides an overview for starters in the chirality field of research on concepts, common methodologies, and outstanding accomplishments. It starts with an introductory section on the definitions and classifications of chirality at the different levels of molecular complexity, followed by highlighting the importance of chirality in biological systems and the different means of realizing chirality and its inversion in solid and solution-based systems at molecular and supramolecular levels. Chirality-relevant important findings and (bio-)technological applications are also reported accordingly. Full article

(This article belongs to the Section Chemistry: Symmetry/Asymmetry)

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8 pages, 499 KiB

Open AccessEditor’s ChoiceArticle

The Cosmological Constant as Event Horizon

by Enrique Gaztanaga

Symmetry 2022, 14(2), 300; https://doi.org/10.3390/sym14020300 - 1 Feb 2022

Cited by 12 | Viewed by 4971

Abstract

General Relativity allows for a cosmological constant (

Λ

) which has inspired models of cosmic Inflation and Dark Energy. We show instead that

r_{Λ} = \sqrt{3 / Λ}

corresponds to an event horizon: a causal boundary term in the action. Our [...] Read more.

General Relativity allows for a cosmological constant (

Λ

) which has inspired models of cosmic Inflation and Dark Energy. We show instead that

r_{Λ} = \sqrt{3 / Λ}

corresponds to an event horizon: a causal boundary term in the action. Our Universe is expanding inside its Schwarzschild radius

r_{S} = r_{Λ} = 2 G M

, which could have originated from a uniform free falling cloud of mass M that collapsed as a Black Hole (BH) 25 Gyrs ago. Such a BH Universe allows for large-scale structure formation without the need of Inflation or Dark Energy. Full article

(This article belongs to the Special Issue Fundamental Constants in Cosmology)

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11 pages, 628 KiB

Open AccessEditor’s ChoiceSystematic Review

A Systematic Review of Non-Pharmacological Interventions to Improve Gait Asymmetries in Neurological Populations

by Krista G. Meder, Chanel T. LoJacono and Christopher K. Rhea

Symmetry 2022, 14(2), 281; https://doi.org/10.3390/sym14020281 - 30 Jan 2022

Cited by 11 | Viewed by 4409

Abstract

Gait asymmetries are commonly observed in neurological populations and linked to decreased gait velocity, balance decrements, increased fall risk, and heightened metabolic cost. Interventions designed to improve gait asymmetries have varying methods and results. The purpose of this systematic review was to investigate [...] Read more.

Gait asymmetries are commonly observed in neurological populations and linked to decreased gait velocity, balance decrements, increased fall risk, and heightened metabolic cost. Interventions designed to improve gait asymmetries have varying methods and results. The purpose of this systematic review was to investigate non-pharmacological interventions to improve gait asymmetries in neurological populations. Keyword searches were conducted using PubMed, CINAHL, and Academic Search Complete. The search yielded 14 studies for inclusion. Gait was assessed using 3D motion capture systems (n = 7), pressure-sensitive mats (e.g., GAITRite; n = 5), and positional sensors (n = 2). The gait variables most commonly analyzed for asymmetry were step length (n = 11), stance time (n = 9), and swing time (n = 5). Interventions to improve gait asymmetries predominantly used gait training techniques via a split-belt treadmill (n = 6), followed by insoles/orthoses (n = 3). The literature suggests that a wide range of methods can be used to improve spatiotemporal asymmetries. However, future research should further examine kinematic and kinetic gait asymmetries. Additionally, researchers should explore the necessary frequency and duration of various intervention strategies to achieve the greatest improvement in gait asymmetries, and to determine the best symmetry equation for quantifying gait asymmetries. Full article

(This article belongs to the Special Issue Symmetry and Asymmetry in Sport Sciences)

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14 pages, 569 KiB

Open AccessEditor’s ChoiceArticle

Improving the Statistical Qualities of Pseudo Random Number Generators

by Rafael Álvarez, Francisco Martínez and Antonio Zamora

Symmetry 2022, 14(2), 269; https://doi.org/10.3390/sym14020269 - 29 Jan 2022

Cited by 8 | Viewed by 3422

Abstract

Pseudo random and true random sequence generators are important components in many scientific and technical fields, playing a fundamental role in the application of the Monte Carlo methods and stochastic simulation. Unfortunately, the quality of the sequences produced by these generators are not [...] Read more.

Pseudo random and true random sequence generators are important components in many scientific and technical fields, playing a fundamental role in the application of the Monte Carlo methods and stochastic simulation. Unfortunately, the quality of the sequences produced by these generators are not always ideal in terms of randomness for many applications. We present a new nonlinear filter design that improves the output sequences of common pseudo random generators in terms of statistical randomness. Taking inspiration from techniques employed in symmetric ciphers, it is based on four seed-dependent substitution boxes, an evolving internal state register, and the combination of different types of operations with the aim of diffusing nonrandom patterns in the input sequence. For statistical analysis we employ a custom initial battery of tests and well-regarded comprehensive packages such as TestU01 and PractRand. Analysis results show that our proposal achieves excellent randomness characteristics and can even transform nonrandom sources (such as a simple counter generator) into perfectly usable pseudo random sequences. Furthermore, performance is excellent while storage consumption is moderate, enabling its implementation in embedded or low power computational platforms. Full article

(This article belongs to the Section Computer)

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13 pages, 567 KiB

Open AccessEditor’s ChoiceArticle

Neutron-Mirror Neutron Oscillations in Absorbing Matter

by Yuri Kamyshkov, James Ternullo, Louis Varriano and Zurab Berezhiani

Symmetry 2022, 14(2), 230; https://doi.org/10.3390/sym14020230 - 25 Jan 2022

Cited by 10 | Viewed by 3261

Abstract

The possibility that a neutron can be transformed to a hidden sector particle remains intriguingly open. Proposed theoretical models conjecture that the hidden sector can be represented by a mirror sector, and the neutron n can oscillate into its sterile mirror twin [...] Read more.

The possibility that a neutron can be transformed to a hidden sector particle remains intriguingly open. Proposed theoretical models conjecture that the hidden sector can be represented by a mirror sector, and the neutron n can oscillate into its sterile mirror twin

n^{'}

, exactly or nearly degenerate in mass with n. Oscillations

n - n^{'}

can take place in vacuum or in an environment containing regular matter and a magnetic field, in which only the neutron will be subject to interactions with the environment. We describe the propagation of the oscillating

n - n^{'}

system in a cold neutron beam passing through dense absorbing materials in connection to the possible regeneration type of experiments, where the effect of

n \to n^{'} \to n

transformation can be observed. Full article

(This article belongs to the Special Issue The Neutron Physics - Dark Matter Connection: Bridge Through the Baryon Symmetry Violation)

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12 pages, 322 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Transient Propagation of Spherical Waves in Porous Material: Application of Fractional Calculus

by Zine El Abiddine Fellah, Mohamed Fellah, Rémi Roncen, Nicholas O. Ongwen, Erick Ogam and Claude Depollier

Symmetry 2022, 14(2), 233; https://doi.org/10.3390/sym14020233 - 25 Jan 2022

Cited by 7 | Viewed by 3306

Abstract

A fractional-order wave equation is established and solved for a space of three dimensions using spherical coordinates. An equivalent fluid model is used in which the acoustic wave propagates only in the fluid saturating the porous medium; this model is a special case [...] Read more.

A fractional-order wave equation is established and solved for a space of three dimensions using spherical coordinates. An equivalent fluid model is used in which the acoustic wave propagates only in the fluid saturating the porous medium; this model is a special case of Biot’s theory obtained by the symmetry of the Lagrangian (invariance by translation and rotation). The basic solution of the wave equation is obtained in the time domain by analytically calculating Green’s function of the porous medium and using the properties of the Laplace transforms. Fractional derivatives are used to describe, in the time domain, the fluid–structure interactions, which are of the inertial, viscous, and thermal kind. The solution to the fractional-order wave equation represents the radiation field in the porous medium emitted by a point source. An important result obtained in this study is that the solution of the fractional equation is expressed by recurrence relations that are the consequence of the modified Bessel function of the third kind, which represents a physical solution of the wave equation. This theoretical work with analytical results opens up prospects for the resolution of forward and inverse problems allowing the characterization of a porous medium using spherical waves. Full article

(This article belongs to the Special Issue Symmetries of Difference Equations, Special Functions and Orthogonal Polynomials)

22 pages, 9091 KiB

Open AccessEditor’s ChoiceArticle

A Motion Planning Method for Automated Vehicles in Dynamic Traffic Scenarios

by Bo Peng, Dexin Yu, Huxing Zhou, Xue Xiao and Chen Xie

Symmetry 2022, 14(2), 208; https://doi.org/10.3390/sym14020208 - 21 Jan 2022

Cited by 16 | Viewed by 6960

Abstract

We propose a motion planning method for automated vehicles (AVs) to complete driving tasks in dynamic traffic scenes. The proposed method aims to generate motion trajectories for an AV after obtaining the surrounding dynamic information and making a preliminary driving decision. The method [...] Read more.

We propose a motion planning method for automated vehicles (AVs) to complete driving tasks in dynamic traffic scenes. The proposed method aims to generate motion trajectories for an AV after obtaining the surrounding dynamic information and making a preliminary driving decision. The method generates a reference line by interpolating the original waypoints and generates optional trajectories with costs in a prediction interval containing three dimensions (lateral distance, time, and velocity) in the Frenet frame, and filters the optimal trajectory by a series of threshold checks. When calculating the feasibility of optional trajectories, the cost of all optional trajectories after removing obstacle interference shows obvious axisymmetric regularity concerning the reference line. Based on this regularity, we apply the constrained Simulated Annealing Algorithm (SAA) to improve the process of searching for the optimal trajectories. Experiments in three different simulated driving scenarios (speed maintaining, lane changing, and car following) show that the proposed method can efficiently generate safe and comfortable motion trajectories for AVs in dynamic environments. Compared with the method of traversing sampling points in discrete space, the improved motion planning method saves 70.23% of the computation time, and overcomes the limitation of the spatial sampling interval. Full article

(This article belongs to the Section Engineering and Materials)

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109 pages, 4632 KiB

Open AccessEditor’s ChoiceArticle

Notes on Confinement on R³ × S¹: From Yang–Mills, Super-Yang–Mills, and QCD (adj) to QCD(F)

by Erich Poppitz

Symmetry 2022, 14(1), 180; https://doi.org/10.3390/sym14010180 - 17 Jan 2022

Cited by 19 | Viewed by 4663

Abstract

This is a pedagogical introduction to the physics of confinement on

R^{3} \times S^{1}

, using

S U (2)

Yang–Mills with massive or massless adjoint fermions as the prime example; we also add fundamental flavours to conclude. The small- [...] Read more.

This is a pedagogical introduction to the physics of confinement on

R^{3} \times S^{1}

, using

S U (2)

Yang–Mills with massive or massless adjoint fermions as the prime example; we also add fundamental flavours to conclude. The small-

S^{1}

limit is remarkable, allowing for controlled semiclassical determination of the nonperturbative physics in these, mostly non-supersymmetric, theories. We begin by reviewing the Polyakov confinement mechanism on

R^{3}

. Moving on to

R^{3} \times S^{1}

, we show how introducing adjoint fermions stabilizes center symmetry, leading to abelianization and semiclassical calculability. We explain how monopole–instantons and twisted monopole–instantons arise. We describe the role of various novel topological excitations in extending Polyakov’s confinement to the locally four-dimensional case, discuss the nature of the confining string, and the

θ

-angle dependence. We study the global symmetry realization and, when available, present evidence for the absence of phase transitions as a function of the

S^{1}

size. As our aim is not to cover all work on the subject, but to prepare the interested reader for its study, we also include brief descriptions of topics not covered in detail: the necessity for analytic continuation of path integrals, the study of more general theories, and the ’t Hooft anomalies involving higher-form symmetries. Full article

(This article belongs to the Special Issue New Applications of Symmetry in Lattice Field Theory)

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14 pages, 4052 KiB

Open AccessEditor’s ChoiceArticle

Intelligent System for Estimation of the Spatial Position of Apples Based on YOLOv3 and Real Sense Depth Camera D415

by Nikita Andriyanov, Ilshat Khasanshin, Daniil Utkin, Timur Gataullin, Stefan Ignar, Vyacheslav Shumaev and Vladimir Soloviev

Symmetry 2022, 14(1), 148; https://doi.org/10.3390/sym14010148 - 13 Jan 2022

Cited by 71 | Viewed by 10164

Abstract

Despite the great possibilities of modern neural network architectures concerning the problems of object detection and recognition, the output of such models is the local (pixel) coordinates of objects bounding boxes in the image and their predicted classes. However, in several practical tasks, [...] Read more.

Despite the great possibilities of modern neural network architectures concerning the problems of object detection and recognition, the output of such models is the local (pixel) coordinates of objects bounding boxes in the image and their predicted classes. However, in several practical tasks, it is necessary to obtain more complete information about the object from the image. In particular, for robotic apple picking, it is necessary to clearly understand where and how much to move the grabber. To determine the real position of the apple relative to the source of image registration, it is proposed to use the Intel Real Sense depth camera and aggregate information from its depth and brightness channels. The apples detection is carried out using the YOLOv3 architecture; then, based on the distance to the object and its localization in the image, the relative distances are calculated for all coordinates. In this case, to determine the coordinates of apples, a transition to a symmetric coordinate system takes place by means of simple linear transformations. Estimating the position in a symmetric coordinate system allows estimating not only the magnitude of the shift but also the location of the object relative to the camera. The proposed approach makes it possible to obtain position estimates with high accuracy. The approximate root mean square error is 7–12 mm, depending on the range and axis. As for precision and recall metrics, the first is 100% and the second is 90%. Full article

(This article belongs to the Section Mathematics)

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19 pages, 6924 KiB

Open AccessEditor’s ChoiceArticle

Energetic and Geometric Characteristics of Substituents, Part 3: The Case of NO₂ and NH₂ Groups in Their Mono-Substituted Derivatives of Six-Membered Heterocycles

by Paweł A. Wieczorkiewicz, Halina Szatylowicz and Tadeusz M. Krygowski

Symmetry 2022, 14(1), 145; https://doi.org/10.3390/sym14010145 - 12 Jan 2022

Cited by 3 | Viewed by 2744

Abstract

Substituted heterocyclic arenes play important roles in biochemistry, catalysis, and in the design of functional materials. Exemplary six-membered heteroaromatic molecules, that differ from benzene by inclusion of one heteroatom, are pyridine, phosphorine, arsabenzene, and borabenzene. This theoretical study concerns the influence of the [...] Read more.

Substituted heterocyclic arenes play important roles in biochemistry, catalysis, and in the design of functional materials. Exemplary six-membered heteroaromatic molecules, that differ from benzene by inclusion of one heteroatom, are pyridine, phosphorine, arsabenzene, and borabenzene. This theoretical study concerns the influence of the heteroatom present in these molecules on the properties of substituents of two types: electron-donating (ED) NH₂ group and electron-accepting (EA) NO₂ group, attached at the 2-, 3-, or 4-position. The effect is evaluated by the energy of interaction (E_rel) between the substituent and the substituted system and electronic properties of the substituents described by the charge of the substituent active region (cSAR) index. In addition, several geometric descriptors of the substituent and heteroaromatic ring, as well as changes in the aromaticity, are considered. The latter are assessed using the Electron Density of Delocalized Bonds (EDDBs) property of delocalized π electrons. The obtained results show that the electronegativity (EN) of the heteroatom has a profound effect on the EA/ED properties of the substituents. This effect is also reflected in the geometry of studied molecules. The E_rel parameter indicates that the relative stability of the molecules is highly related to the electronic interactions between the substituent and the heteroarene. This especially applies to the enhancement or weakening of π-resonance due to the EN of the heteroatom. Additionally, in the 2-heteroarene derivatives, specific through-space ortho interactions contribute to the heteroatom effects. Full article

(This article belongs to the Special Issue Exploring Inter- and Intramolecular Interactions as Building Blocks of Larger Systems)

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33 pages, 1668 KiB

Open AccessEditor’s ChoiceReview

Limb Preference in Animals: New Insights into the Evolution of Manual Laterality in Hominids

by Grégoire Boulinguez-Ambroise, Juliette Aychet and Emmanuelle Pouydebat

Symmetry 2022, 14(1), 96; https://doi.org/10.3390/sym14010096 - 7 Jan 2022

Cited by 15 | Viewed by 6841

Abstract

Until the 1990s, the notion of brain lateralization—the division of labor between the two hemispheres—and its more visible behavioral manifestation, handedness, remained fiercely defined as a human specific trait. Since then, many studies have evidenced lateralized functions in a wide range of species, [...] Read more.

Until the 1990s, the notion of brain lateralization—the division of labor between the two hemispheres—and its more visible behavioral manifestation, handedness, remained fiercely defined as a human specific trait. Since then, many studies have evidenced lateralized functions in a wide range of species, including both vertebrates and invertebrates. In this review, we highlight the great contribution of comparative research to the understanding of human handedness’ evolutionary and developmental pathways, by distinguishing animal forelimb asymmetries for functionally different actions—i.e., potentially depending on different hemispheric specializations. Firstly, lateralization for the manipulation of inanimate objects has been associated with genetic and ontogenetic factors, with specific brain regions’ activity, and with morphological limb specializations. These could have emerged under selective pressures notably related to the animal locomotion and social styles. Secondly, lateralization for actions directed to living targets (to self or conspecifics) seems to be in relationship with the brain lateralization for emotion processing. Thirdly, findings on primates’ hand preferences for communicative gestures accounts for a link between gestural laterality and a left-hemispheric specialization for intentional communication and language. Throughout this review, we highlight the value of functional neuroimaging and developmental approaches to shed light on the mechanisms underlying human handedness. Full article

(This article belongs to the Special Issue Symmetry in Human Evolution, from Biology to Behaviours)

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8 pages, 2022 KiB

Open AccessEditor’s ChoiceArticle

Analysis of Electro-Optical Behavior in Liquid Crystal Cells with Asymmetric Anchoring Strength

by Rumiko Yamaguchi

Symmetry 2022, 14(1), 85; https://doi.org/10.3390/sym14010085 - 6 Jan 2022

Cited by 11 | Viewed by 4157

Abstract

Liquid crystal director distributions have been numerically analyzed between asymmetric anchoring surfaces, that is, infinitely strong and very weak anchoring strength interfaces. In a hybrid aligned nematic (HAN) cell and a twisted nematic (TN) cell, HAN and TN orientations turn to a homogeneous [...] Read more.

Liquid crystal director distributions have been numerically analyzed between asymmetric anchoring surfaces, that is, infinitely strong and very weak anchoring strength interfaces. In a hybrid aligned nematic (HAN) cell and a twisted nematic (TN) cell, HAN and TN orientations turn to a homogeneous orientation when the weak anchoring strength is lower than a critical one. Relationships between the anchoring strength and elastic constants of the liquid crystal were analyzed to be of a quasi-homogeneous orientation. The quasi-homogeneous orientation returned to the original HAN and TN orientations under voltage application. Low-driving electro-optical properties with no threshold voltage can be obtained in a quasi-homogeneous HAN cell. A unique voltage–transmission curve of 0–100–0% appeared in a quasi-homogeneous TN cell between the crossed polarizers. Full article

(This article belongs to the Special Issue Symmetry and Liquid Crystals)

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8 pages, 1907 KiB

Open AccessEditor’s ChoiceArticle

Homochiral or Heterochiral: A Systematic Study of Threonine Clusters Using a FT ICR Mass Spectrometer

by Luyang Jiao, Mengying Du, Yameng Hou, Yuan Ma and Xianglei Kong

Symmetry 2022, 14(1), 86; https://doi.org/10.3390/sym14010086 - 6 Jan 2022

Cited by 2 | Viewed by 2267

Abstract

The strong chiral preferences of some magic clusters of amino acids have attracted continually increasing interests due to their unique structures, properties and possible roles in homochirogenesis. However, how chirality can influence the generation and stability of cluster ions in a wild range [...] Read more.

The strong chiral preferences of some magic clusters of amino acids have attracted continually increasing interests due to their unique structures, properties and possible roles in homochirogenesis. However, how chirality can influence the generation and stability of cluster ions in a wild range of cluster sizes is still unknown for most amino acids. In this study, the preference for threonine clusters to form homochiral and heterochiral complex ions has been investigated by electrospray ionization (ESI) mass spectrometry. Abundant cluster [Thr_n+mH]^m+ ions (7 ≤ n ≤ 78, 1 ≤ m ≤ 5) have been observed for both samples of enantiopure (100% L) and racemic (50:50 L:D) threonine solutions. Further analyses of the spectra show that the [Thr₁₄+2H]²⁺ ion is characterized by its most outstanding homochiral preference, and [Thr₇+H]⁺ and [Thr₈+H]⁺ ions also clearly exhibit their homochiral preferences. Although most of the triply charged clusters (20 ≤ n ≤ 36) are characterized by heterochiral preferences, the quadruply charged [Thr_n+4H]⁴⁺ ions (40 ≤ n ≤ 59) have no obvious chiral preference in general. On the other hand, a weak homochiral preference exists for most of the quintuply charged ions observed in the experiment. Full article

(This article belongs to the Special Issue Chiral Molecules: Properties, Synthesis and Analysis)

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21 pages, 3956 KiB

Open AccessEditor’s ChoiceArticle

A 3D Agent-Based Model of Lung Fibrosis

by Nicolò Cogno, Roman Bauer and Marco Durante

Symmetry 2022, 14(1), 90; https://doi.org/10.3390/sym14010090 - 6 Jan 2022

Cited by 6 | Viewed by 4922

Abstract

Understanding the pathophysiology of lung fibrosis is of paramount importance to elaborate targeted and effective therapies. As it onsets, the randomly accumulating extracellular matrix (ECM) breaks the symmetry of the branching lung structure. Interestingly, similar pathways have been reported for both idiopathic pulmonary [...] Read more.

Understanding the pathophysiology of lung fibrosis is of paramount importance to elaborate targeted and effective therapies. As it onsets, the randomly accumulating extracellular matrix (ECM) breaks the symmetry of the branching lung structure. Interestingly, similar pathways have been reported for both idiopathic pulmonary fibrosis and radiation-induced lung fibrosis (RILF). Individuals suffering from the disease, the worldwide incidence of which is growing, have poor prognosis and a short mean survival time. In this context, mathematical and computational models have the potential to shed light on key underlying pathological mechanisms, shorten the time needed for clinical trials, parallelize hypotheses testing, and improve personalized drug development. Agent-based modeling (ABM) has proven to be a reliable and versatile simulation tool, whose features make it a good candidate for recapitulating emergent behaviors in heterogeneous systems, such as those found at multiple scales in the human body. In this paper, we detail the implementation of a 3D agent-based model of lung fibrosis using a novel simulation platform, namely, BioDynaMo, and prove that it can qualitatively and quantitatively reproduce published results. Furthermore, we provide additional insights on late-fibrosis patterns through ECM density distribution histograms. The model recapitulates key intercellular mechanisms, while cell numbers and types are embodied by alveolar segments that act as agents and are spatially arranged by a custom algorithm. Finally, our model may hold potential for future applications in the context of lung disorders, ranging from RILF (by implementing radiation-induced cell damage mechanisms) to COVID-19 and inflammatory diseases (such as asthma or chronic obstructive pulmonary disease). Full article

(This article belongs to the Special Issue Networks in Cancer: From Symmetry Breaking to Targeted Therapy)

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15 pages, 573 KiB

Open AccessEditor’s ChoiceReview

Time-like Proton Form Factors with Initial State Radiation Technique

by Dexu Lin, Alaa Dbeyssi and Frank Maas

Symmetry 2022, 14(1), 91; https://doi.org/10.3390/sym14010091 - 6 Jan 2022

Cited by 6 | Viewed by 2589

Abstract

Electromagnetic form factors are fundamental quantities describing the internal structure of hadrons. They can be measured with scattering processes in the space-like region and annihilation processes in the time-like region. The two regions are connected by crossing symmetry. The measurements of the proton [...] Read more.

Electromagnetic form factors are fundamental quantities describing the internal structure of hadrons. They can be measured with scattering processes in the space-like region and annihilation processes in the time-like region. The two regions are connected by crossing symmetry. The measurements of the proton electromagnetic form factors in the time-like region using the initial state radiation technique are reviewed. Recent experimental studies have shown that initial state radiation processes at high luminosity electron-positron colliders can be effectively used to probe the electromagnetic structure of hadrons. The BABAR experiment at the B-factory PEP-II in Stanford and the BESIII experiment at BEPCII (an electron positron collider in the

τ

-charm mass region) in Beijing have measured the time-like form factors of the proton using the initial state radiation process

e^{+} e^{-} \to p \bar{p} γ

. The two kinematical regions where the photon is emitted from the initial state at small and large polar angles have been investigated. In the first case, the photon is in the region not covered by the detector acceptance and is not detected. The Born cross section and the proton effective form factor have been measured over a wide and continuous range of the the momentum transfer squared

q^{2}

from the threshold up to 42 (GeV/c)

^{2}

. The ratio of electric and magnetic form factors of the proton has been also determined. In this report, the theoretical aspect and the experimental studies of the initial state radiation process

e^{+} e^{-} \to p \bar{p} γ

are described. The measurements of the Born cross section and the proton form factors obtained in these analyses near the threshold region and in the relatively large

q^{2}

region are examined. The experimental results are compared to the predictions from theory and models. Their impact on our understanding of the nucleon structure is discussed. Full article

(This article belongs to the Special Issue Baryon Structure: Form Factors and Polarization)

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16 pages, 328 KiB

Open AccessEditor’s ChoiceArticle

On the Unique Solvability of Incomplete Cauchy Type Problems for a Class of Multi-Term Equations with the Riemann–Liouville Derivatives

by Vladimir E. Fedorov, Wei-Shih Du and Mikhail M. Turov

Symmetry 2022, 14(1), 75; https://doi.org/10.3390/sym14010075 - 5 Jan 2022

Cited by 13 | Viewed by 1905

Abstract

Incomplete Cauchy-type problems are considered for linear multi-term equations solved with respect to the highest derivative in Banach spaces with fractional Riemann–Liouville derivatives and with linear closed operators at them. Some new existence and uniqueness theorems for solutions are presented explicitly and the [...] Read more.

Incomplete Cauchy-type problems are considered for linear multi-term equations solved with respect to the highest derivative in Banach spaces with fractional Riemann–Liouville derivatives and with linear closed operators at them. Some new existence and uniqueness theorems for solutions are presented explicitly and the analyticity of the solutions of the homogeneous equations are also shown. The asymmetry of the Cauchy-type problem under study is expressed in the presence of a so-called defect, which shows the number of lower-order initial conditions that should not be set when setting the problem. As applications, our abstract results are used in the study of a class of initial-boundary value problems for multi-term equations with Riemann–Liouville derivatives in time and with polynomials of a self-adjoint elliptic differential operator with respect to spatial variables. Full article

(This article belongs to the Special Issue Symmetry and Asymmetry in Fixed Point Theory and Computational Analysis)

12 pages, 274 KiB

Open AccessEditor’s ChoiceArticle

Best Dominants and Subordinants for Certain Sandwich-Type Theorems

by Adriana Cătaş, Emilia Borşa and Loredana Iambor

Symmetry 2022, 14(1), 62; https://doi.org/10.3390/sym14010062 - 3 Jan 2022

Cited by 3 | Viewed by 1931

Abstract

In this paper, we aim to present a survey on subordination and superordination theorems related to the class of analytic functions defined in a symmetric domain, which is the open unit disc. The results were deduced by making use of a new differential [...] Read more.

In this paper, we aim to present a survey on subordination and superordination theorems related to the class of analytic functions defined in a symmetric domain, which is the open unit disc. The results were deduced by making use of a new differential operator. We present two properties of this operator from which we constructed the final results. Moreover, based on the obtained outcomes, we give two sandwich-type theorems. Some interesting further consequences are also taken into consideration. Full article

(This article belongs to the Special Issue Symmetry in Functional Equations and Analytic Inequalities II)

9 pages, 314 KiB

Open AccessEditor’s ChoiceArticle

Energetic Particle Superdiffusion in Solar System Plasmas: Which Fractional Transport Equation?

by Gaetano Zimbardo, Francesco Malara and Silvia Perri

Symmetry 2021, 13(12), 2368; https://doi.org/10.3390/sym13122368 - 8 Dec 2021

Cited by 6 | Viewed by 3412

Abstract

Superdiffusive transport of energetic particles in the solar system and in other plasma environments is often inferred; while this can be described in terms of Lévy walks, a corresponding transport differential equation still calls for investigation. Here, we propose that superdiffusive transport can [...] Read more.

Superdiffusive transport of energetic particles in the solar system and in other plasma environments is often inferred; while this can be described in terms of Lévy walks, a corresponding transport differential equation still calls for investigation. Here, we propose that superdiffusive transport can be described by means of a transport equation for pitch-angle scattering where the time derivative is fractional rather than integer. We show that this simply leads to superdiffusion in the direction parallel to the magnetic field, and we discuss some advantages with respect to approaches based on transport equations with symmetric spatial fractional derivates. Full article

(This article belongs to the Special Issue Solar Physics and Plasma Physics: Topics and Advances)

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11 pages, 5229 KiB

Open AccessEditor’s ChoiceCommunication

2-Pyridylselenenyl versus 2-Pyridyltellurenyl Halides: Symmetrical Chalcogen Bonding in the Solid State and Reactivity towards Nitriles

by Ivan V. Buslov, Alexander S. Novikov, Victor N. Khrustalev, Mariya V. Grudova, Alexey S. Kubasov, Zhanna V. Matsulevich, Alexander V. Borisov, Julia M. Lukiyanova, Maria M. Grishina, Anatoly A. Kirichuk, Tatiyana V. Serebryanskaya, Andreii S. Kritchenkov and Alexander G. Tskhovrebov

Symmetry 2021, 13(12), 2350; https://doi.org/10.3390/sym13122350 - 7 Dec 2021

Cited by 19 | Viewed by 4567

Abstract

The synthesis of 2-pyridyltellurenyl bromide via Br₂ oxidative cleavage of the Te–Te bond of dipyridylditelluride is reported. Single-crystal X-ray diffraction analysis of 2-pyridyltellurenyl bromide demonstrated that the Te atom of 2-pyridyltellurenyl bromide was involved in four different noncovalent contacts: Te⋯Te interactions, two [...] Read more.

The synthesis of 2-pyridyltellurenyl bromide via Br₂ oxidative cleavage of the Te–Te bond of dipyridylditelluride is reported. Single-crystal X-ray diffraction analysis of 2-pyridyltellurenyl bromide demonstrated that the Te atom of 2-pyridyltellurenyl bromide was involved in four different noncovalent contacts: Te⋯Te interactions, two Te⋯Br ChB, and one Te⋯N ChB contact forming 3D supramolecular symmetrical framework. In contrast to 2-pyridylselenenyl halides, the Te congener does not react with nitriles furnishing cyclization products. 2-Pyridylselenenyl chloride was demonstrated to easily form the corresponding adduct with benzonitrile. The cyclization product was studied by the single-crystal X-ray diffraction analysis, which revealed that in contrast to earlier studied cationic 1,2,4-selenadiazoles, here we observed that the adduct with benzonitrile formed supramolecular dimers via Se⋯Se interactions in the solid state, which were never observed before for 1,2,4-selenadiazoles. Full article

(This article belongs to the Section Chemistry: Symmetry/Asymmetry)

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6 pages, 683 KiB

Open AccessEditor’s ChoiceArticle

New Light H^± Discovery Channels at the LHC

by Abdesslam Arhrib, Rachid Benbrik, Mohamed Krab, Bouzid Manaut, Stefano Moretti, Yan Wang and Qi-Shu Yan

Symmetry 2021, 13(12), 2319; https://doi.org/10.3390/sym13122319 - 4 Dec 2021

Cited by 12 | Viewed by 2356

Abstract

A light charged Higgs boson has been searched for at the Large Hadron Collider (LHC) via top (anti)quark decay, i.e.,

t \to b H^{+}

, if kinematically allowed. In this contribution, we propose new channels for light charged Higgs boson searches via [...] Read more.

A light charged Higgs boson has been searched for at the Large Hadron Collider (LHC) via top (anti)quark decay, i.e.,

t \to b H^{+}

, if kinematically allowed. In this contribution, we propose new channels for light charged Higgs boson searches via the pair productions

p p \to H^{\pm} h / A

and

p p \to H^{+} H^{-}

at the LHC in the context of the Two-Higgs Doublet Model (2HDM) Type-I. By focusing on a case where the heavy H state is the Standard Model (SM)-like one already observed, we investigate the production of the aforementioned charged Higgs bosons and their bosonic decay channels, namely,

H^{\pm} \to W^{\pm} h

and/or

H^{\pm} \to W^{\pm} A

. We demonstrate that such production and decay channels can yield substantial alternative discovery channels for

H^{\pm}

bosons at the LHC. Finally, we propose eight benchmark points (BPs) to motivate the search for such signatures. Full article

(This article belongs to the Special Issue Symmetry, Collider Phenomenology and High Energy Physics)

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15 pages, 5719 KiB

Open AccessEditor’s ChoiceArticle

On the Semi-Analytical Solutions in Hydrodynamics of Ideal Fluid Flows Governed by Large-Scale Coherent Structures of Spiral-Type

by Sergey V. Ershkov, Alla Rachinskaya, Evgenii Yu. Prosviryakov and Roman V. Shamin

Symmetry 2021, 13(12), 2307; https://doi.org/10.3390/sym13122307 - 3 Dec 2021

Cited by 5 | Viewed by 2400

Abstract

We have presented here a clearly formulated algorithm or semi-analytical solving procedure for obtaining or tracing approximate hydrodynamical fields of flows (and thus, videlicet, their trajectories) for ideal incompressible fluids governed by external large-scale coherent structures of spiral-type, which can be [...] Read more.

We have presented here a clearly formulated algorithm or semi-analytical solving procedure for obtaining or tracing approximate hydrodynamical fields of flows (and thus, videlicet, their trajectories) for ideal incompressible fluids governed by external large-scale coherent structures of spiral-type, which can be recognized as special invariant at symmetry reduction. Examples of such structures are widely presented in nature in “wind-water-coastline” interactions during a long-time period. Our suggested mathematical approach has obvious practical meaning as tracing process of formation of the paths or trajectories for material flows of fallout descending near ocean coastlines which are forming its geometry or bottom surface of the ocean. In our presentation, we explore (as first approximation) the case of non-stationary flows of Euler equations for incompressible fluids, which should conserve the Bernoulli-function as being invariant for the aforementioned system. The current research assumes approximated solution (with numerical findings), which stems from presenting the Euler equations in a special form with a partial type of approximated components of vortex field in a fluid. Conditions and restrictions for the existence of the 2D and 3D non-stationary solutions of the aforementioned type have been formulated as well. Full article

(This article belongs to the Special Issue Applied Mathematics and Fluid Dynamics)

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10 pages, 249 KiB

Open AccessEditor’s ChoiceReview

Chaos in the Real World: Recent Applications to Communications, Computing, Distributed Sensing, Robotic Motion, Bio-Impedance Modelling and Encryption Systems

by Giuseppe Grassi

Symmetry 2021, 13(11), 2151; https://doi.org/10.3390/sym13112151 - 11 Nov 2021

Cited by 41 | Viewed by 4135

Abstract

Most of the papers published so far in literature have focused on the theoretical phenomena underlying the formation of chaos, rather than on the investigation of potential applications of chaos to the real world. This paper aims to bridge the gap between chaos [...] Read more.

Most of the papers published so far in literature have focused on the theoretical phenomena underlying the formation of chaos, rather than on the investigation of potential applications of chaos to the real world. This paper aims to bridge the gap between chaos theory and chaos applications by presenting a survey of very recent applications of chaos. In particular, the manuscript covers the last three years by describing different applications of chaos as reported in the literature published during the years 2018 to 2020, including the matter related to the symmetry properties of chaotic systems. The topics covered herein include applications of chaos to communications, to distributed sensing, to robotic motion, to bio-impedance modelling, to hardware implementation of encryption systems, to computing and to random number generation. Full article

(This article belongs to the Special Issue Chaotic Systems and Nonlinear Dynamics)

16 pages, 310 KiB

Open AccessEditor’s ChoiceArticle

On the Fekete–Szegö Problem for Meromorphic Functions Associated with p,q-Wright Type Hypergeometric Function

by Adriana Cătaş

Symmetry 2021, 13(11), 2143; https://doi.org/10.3390/sym13112143 - 10 Nov 2021

Cited by 19 | Viewed by 2344

Abstract

Making use of a post-quantum derivative operator, we define two classes of meromorphic analytic functions. For the considered family of functions, we aim to investigate the sharp bounds’ values in the case of the Fekete–Szegö problem. The study of the well-known Fekete–Szegö functional [...] Read more.

Making use of a post-quantum derivative operator, we define two classes of meromorphic analytic functions. For the considered family of functions, we aim to investigate the sharp bounds’ values in the case of the Fekete–Szegö problem. The study of the well-known Fekete–Szegö functional in the post-quantum calculus case for meromorphic functions provides new outcomes for research in the field. With the extended

p, q

-operator, we establish certain inequalities’ relations concerning meromorphic functions. In the final part of the paper, a new

p, q

-analogue of the q-Wright type hypergeometric function is introduced. This function generalizes the classical and symmetrical Gauss hypergeometric function. All the obtained results are sharp. Full article

(This article belongs to the Special Issue Functional Equations and Inequalities 2021)

17 pages, 4728 KiB

Open AccessEditor’s ChoiceReview

On the Question of Stepwise [4+2] Cycloaddition Reactions and Their Stereochemical Aspects

by Radomir Jasiński

Symmetry 2021, 13(10), 1911; https://doi.org/10.3390/sym13101911 - 11 Oct 2021

Cited by 40 | Viewed by 6293

Abstract

Even at the end of the twentieth century, the view of the one-step [4+2] cycloaddition (Diels-Alder) reaction mechanism was widely accepted as the only possible one, regardless of the nature of the reaction components. Much has changed in the way these reactions are [...] Read more.

Even at the end of the twentieth century, the view of the one-step [4+2] cycloaddition (Diels-Alder) reaction mechanism was widely accepted as the only possible one, regardless of the nature of the reaction components. Much has changed in the way these reactions are perceived since then. In particular, multi-step mechanisms with zwitterionic or diradical intermediates have been proposed for a number of processes. This review provided a critical analysis of such cases. Full article

(This article belongs to the Special Issue Regio- and Stereoselectivity in Cycloaddition Reactions)

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31 pages, 17655 KiB

Open AccessEditor’s ChoiceArticle

Asymmetry of Plant Cell Divisions under Salt Stress

by Ekaterina N. Baranova and Alexander A. Gulevich

Symmetry 2021, 13(10), 1811; https://doi.org/10.3390/sym13101811 - 28 Sep 2021

Cited by 19 | Viewed by 4779

Abstract

Salt stress causes several damaging effects in plant cells. These commonly observed effects are the results of oxidative, osmotic, and toxic stresses. To ensure normal growth and development of tissues, the cellular compartments of multicellular plants have a unique system that provides the [...] Read more.

Salt stress causes several damaging effects in plant cells. These commonly observed effects are the results of oxidative, osmotic, and toxic stresses. To ensure normal growth and development of tissues, the cellular compartments of multicellular plants have a unique system that provides the specified parameters of growth and differentiation. The cell shape and the direction of division support the steady development of the organism, the habit, and the typical shape of the organs and the whole plant. When dividing, daughter cells evenly or unevenly distribute the components of cytoplasm. Factors such as impaired osmotic regulation, exposure to toxic compounds, and imbalance in the antioxidant system cause disorders associated with the moving of organelles, distribution transformations of the endoplasmic reticulum, and the vacuolar compartment. In some cases, one can observe a different degree of plasmolysis manifestation, local changes in the density of cytoplasm. Together, these processes can cause disturbances in the direction of cell division, the formation of a phragmoplast, the formation of nuclei of daughter cells, and a violation of their fine structural organization. These processes are often accompanied by significant damage to the cytoskeleton, the formation of nonspecific structures formed by proteins of the cytoskeleton. The consequences of these processes can lead to the death of some cells or to a significant change in their morphology and properties, deformation of newly formed tissues and organs, and changes in the plant phenotype. Thus, as a result of significant violations of the cytoskeleton, causing critical destabilization of the symmetric distribution of the cell content, disturbances in the distribution of chromosomes, especially in polyploid cells, may occur, resulting in the appearance of micronuclei. Hence, the asymmetry of a certain component of the plant cell is a marker of susceptibility to abiotic damage. Full article

(This article belongs to the Special Issue Molecular Mechanisms Regulating Asymmetry in Crop Plants Embryogenesis and Growth)

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14 pages, 7386 KiB

Open AccessEditor’s ChoiceArticle

Brain Symmetry Analysis during the Use of a BCI Based on Motor Imagery for the Control of a Lower-Limb Exoskeleton

by Laura Ferrero, Mario Ortiz, Vicente Quiles, Eduardo Iáñez, José A. Flores and José M. Azorín

Symmetry 2021, 13(9), 1746; https://doi.org/10.3390/sym13091746 - 19 Sep 2021

Cited by 13 | Viewed by 4178

Abstract

Brain–Computer Interfaces (BCI) are systems that allow external devices to be controlled by means of brain activity. There are different such technologies, and electroencephalography (EEG) is an example. One of the most common EEG control methods is based on detecting changes in sensorimotor [...] Read more.

Brain–Computer Interfaces (BCI) are systems that allow external devices to be controlled by means of brain activity. There are different such technologies, and electroencephalography (EEG) is an example. One of the most common EEG control methods is based on detecting changes in sensorimotor rhythms (SMRs) during motor imagery (MI). The aim of this study was to assess the laterality of cortical function when performing MI of the lower limb. Brain signals from five subjects were analyzed in two conditions, during exoskeleton-assisted gait and while static. Three different EEG electrode configurations were evaluated: covering both hemispheres, covering the non-dominant hemisphere and covering the dominant hemisphere. In addition, the evolution of performance and laterality with practice was assessed. Although sightly superior results were achieved with information from all electrodes, differences between electrode configurations were not statistically significant. Regarding the evolution during the experimental sessions, the performance of the BCI generally evolved positively the higher the experience was. Full article

(This article belongs to the Special Issue Neuroscience, Neurophysiology and Asymmetry)

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20 pages, 355 KiB

Open AccessEditor’s ChoiceArticle

Quadratic Stabilization of Linear Uncertain Positive Discrete-Time Systems

by Dušan Krokavec and Anna Filasová

Symmetry 2021, 13(9), 1725; https://doi.org/10.3390/sym13091725 - 17 Sep 2021

Cited by 7 | Viewed by 2178

Abstract

The paper provides extended methods for control linear positive discrete-time systems that are subject to parameter uncertainties, reflecting structural system parameter constraints and positive system properties when solving the problem of system quadratic stability. By using an extension of the Lyapunov approach, system [...] Read more.

The paper provides extended methods for control linear positive discrete-time systems that are subject to parameter uncertainties, reflecting structural system parameter constraints and positive system properties when solving the problem of system quadratic stability. By using an extension of the Lyapunov approach, system quadratic stability is presented to become apparent in pre-existing positivity constraints in the design of feedback control. The approach prefers constraints representation in the form of linear matrix inequalities, reflects the diagonal stabilization principle in order to apply to positive systems the idea of matrix parameter positivity, applies observer-based linear state control to assert closed-loop system quadratic stability and projects design conditions, allowing minimization of an undesirable impact on matching parameter uncertainties. The method is utilised in numerical examples to illustrate the technique when applying the above strategy. Full article

(This article belongs to the Special Issue Symmetry in Dynamic Systems)

16 pages, 730 KiB

Open AccessEditor’s ChoiceArticle

Gravitational Decoupling in Higher Order Theories

by Joseph Sultana

Symmetry 2021, 13(9), 1598; https://doi.org/10.3390/sym13091598 - 31 Aug 2021

Cited by 22 | Viewed by 3226

Abstract

Gravitational decoupling via the Minimal Geometric Deformation (MGD) approach has been used extensively in General Relativity (GR), mainly as a simple method for generating exact anisotropic solutions from perfect fluid seed solutions. Recently this method has also been used to generate exact spherically [...] Read more.

Gravitational decoupling via the Minimal Geometric Deformation (MGD) approach has been used extensively in General Relativity (GR), mainly as a simple method for generating exact anisotropic solutions from perfect fluid seed solutions. Recently this method has also been used to generate exact spherically symmetric solutions of the Einstein-scalar system from the Schwarzschild vacuum metric. This was then used to investigate the effect of scalar fields on the Schwarzschild black hole solution. We show that this method can be extended to higher order theories. In particular, we consider fourth order Einstein–Weyl gravity, and in this case by using the Schwarzschild metric as a seed solution to the associated vacuum field equations, we apply the MGD method to generate a solution to the Einstein–Weyl scalar theory representing a hairy black hole solution. This solution is expressed in terms of a series using the Homotopy Analysis Method (HAM). Full article

(This article belongs to the Special Issue Physics and Mathematics of the Dark Universe)

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