Editor's Choice Articles

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

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Article
Crystal Structure of Chiral Drug Prenalterol and Its Precursor Prone to Spontaneous Resolution
Symmetry 2022, 14(6), 1150; https://doi.org/10.3390/sym14061150 - 02 Jun 2022
Cited by 1 | Viewed by 770
Abstract
Due to the chiral uniformity of proteins and carbohydrates, the basic building blocks of living matter, the mirror symmetry characteristics of drugs are of exceptional importance for medicinal chemistry. In this work, we present a new synthesis of the mono-enantiomeric chiral drug prenalterol [...] Read more.
Due to the chiral uniformity of proteins and carbohydrates, the basic building blocks of living matter, the mirror symmetry characteristics of drugs are of exceptional importance for medicinal chemistry. In this work, we present a new synthesis of the mono-enantiomeric chiral drug prenalterol 1 based on the symmetry-breaking phenomenon, namely, the spontaneous resolution of 4-hydroxyphenyl glycerol ether 2. The single crystal X-ray diffraction method was used to investigate both rac- and (S)-1 as well as (R)-2. A feature of the main crystal-forming supramolecular motif (SMM) for diol 2 is the participation of three different molecules representing different types of hydroxyl groups in the formation of its repeating unit. The type of prenalterol SMM, as in the case of the related drugs propranolol 3 and pindolol 4, appears to be a chirality driven property, and is dictated by the enantiomeric composition of the crystals. In single-enantiomeric forms, infinite one-dimensional chains are realized, organized around helical axes, while in racemates, zero-dimensional cycles are realized, organized around inversion symmetry elements. The results obtained again demonstrate the influence of the chiral polarization of a substance not only on the general (selection of a space group), but also on particular characteristics of matter crystal organization, namely selection of a specific SMM. Full article
(This article belongs to the Special Issue Symmetry and Asymmetry in Medicinal Chemistry)
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Article
MCD and Induced CD of a Tetraphenoxyperylene-Based Dye in Chiral Solvents: An Experimental and Computational Study
Symmetry 2022, 14(6), 1108; https://doi.org/10.3390/sym14061108 - 28 May 2022
Cited by 1 | Viewed by 888
Abstract
The magnetic circular dichroism (MCD) spectrum of N,N′-bis(2,6-diisopropylphenyl)-1,6,7,12-tetraphenoxyperylene-3,4:9,10-tetracarboxydiimide, also known as Lumogen Red 300 or ROT-300, has been recorded both in achiral and chiral solvents. The induced CD spectra in chiral solvents have, similarly, been recorded. A discussion of the spectroscopic response, both [...] Read more.
The magnetic circular dichroism (MCD) spectrum of N,N′-bis(2,6-diisopropylphenyl)-1,6,7,12-tetraphenoxyperylene-3,4:9,10-tetracarboxydiimide, also known as Lumogen Red 300 or ROT-300, has been recorded both in achiral and chiral solvents. The induced CD spectra in chiral solvents have, similarly, been recorded. A discussion of the spectroscopic response, both in CD and in MCD experiments, is presented in this paper. Both types of spectra have been predicted most satisfactorily by DFT calculations; the CD spectra were obtained by assuming the prevalence of one “enantiomeric” conformer and the same set of conformers could also be used for MCD, since “enantiomeric” structures present identically in MCD spectra. Full article
(This article belongs to the Special Issue Asymmetric Molecules and Chirality Recognition)
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Article
Design of a New Dimension-Changeable Hyperchaotic Model Based on Discrete Memristor
Symmetry 2022, 14(5), 1019; https://doi.org/10.3390/sym14051019 - 17 May 2022
Cited by 5 | Viewed by 765
Abstract
The application of a memristor in chaotic circuits is increasingly becoming a popular research topic. The influence of a memristor on the dynamics of chaotic systems is worthy of further exploration. In this paper, a multi-dimensional closed-loop coupling model based on a Logistic [...] Read more.
The application of a memristor in chaotic circuits is increasingly becoming a popular research topic. The influence of a memristor on the dynamics of chaotic systems is worthy of further exploration. In this paper, a multi-dimensional closed-loop coupling model based on a Logistic map and Sine map (CLS) is proposed. The new chaotic model is constructed by cascade operation in which the output of the Logistic map is used as the input of the Sine map. Additionally, the one-dimensional map is extended to any dimension through the coupling modulation. In order to further increase the complexity and stability of CLS, the discrete memristor model is introduced to construct a discrete memristor-based coupling model with a Logistic map and a Sine map (MCLS). By analyzing the Lyapunov exponents, bifurcation diagram, complexity, and the 0–1 test result, the comparison result between CLS and MCLS is obtained. The dynamics performance analysis shows that the Lyapunov exponents and bifurcation diagrams present symmetrical distribution with variations of some parameters. The MCLS has parameters whose values can be set in a wider range and can generate more complex and more stable chaotic sequences. It proves that the proposed discrete memristor-based closed-loop coupling model can produce any higher dimension hyperchaotic system and the discrete memristor model can effectively improve the performance of discrete chaotic map and make this hyperchaotic system more stable. Full article
(This article belongs to the Special Issue Discrete and Continuous Memristive Nonlinear Systems and Symmetry)
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Article
Asymmetry in Muscle Strength, Dynamic Balance, and Range of Motion in Adult Symptomatic Hip Dysplasia
Symmetry 2022, 14(4), 748; https://doi.org/10.3390/sym14040748 - 05 Apr 2022
Cited by 3 | Viewed by 997
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
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Article
From Memristor-Modeled Jerk System to the Nonlinear Systems with Memristor
Symmetry 2022, 14(4), 659; https://doi.org/10.3390/sym14040659 - 24 Mar 2022
Cited by 7 | Viewed by 1160
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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Article
Evolution of Microstructure, Texture and Corrosion Properties of Additively Manufactured AlSi10Mg Alloy Subjected to Equal Channel Angular Pressing (ECAP)
Symmetry 2022, 14(4), 674; https://doi.org/10.3390/sym14040674 - 24 Mar 2022
Cited by 2 | Viewed by 1103
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 Ecorr and lower Icorr 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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Article
Symmetry Constraints on Spin Order Transfer in Parahydrogen-Induced Polarization (PHIP)
Symmetry 2022, 14(3), 530; https://doi.org/10.3390/sym14030530 - 04 Mar 2022
Cited by 1 | Viewed by 1286
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 ~1.27N 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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Article
Neutron Stars with Baryon Number Violation, Probing Dark Sectors
Symmetry 2022, 14(3), 518; https://doi.org/10.3390/sym14030518 - 02 Mar 2022
Cited by 11 | Viewed by 1657
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
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Article
Some Results in the Theory of a Cosserat Thermoelastic Body with Microtemperatures and Inner Structure
Symmetry 2022, 14(3), 511; https://doi.org/10.3390/sym14030511 - 02 Mar 2022
Cited by 3 | Viewed by 1256
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 Special Issue Symmetry in Applied Continuous Mechanics 2022)
Article
Improved Search for Neutron to Mirror-Neutron Oscillations in the Presence of Mirror Magnetic Fields with a Dedicated Apparatus at the PSI UCN Source
Symmetry 2022, 14(3), 503; https://doi.org/10.3390/sym14030503 - 01 Mar 2022
Cited by 11 | Viewed by 1581
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 nn 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 (τnn). 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 τnn/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
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Article
A Search for Cosmic Ray Bursts at 0.1 PeV with a Small Air Shower Array
Symmetry 2022, 14(3), 501; https://doi.org/10.3390/sym14030501 - 01 Mar 2022
Cited by 5 | Viewed by 1606
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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Article
A Search for Neutron to Mirror Neutron Oscillation Using Neutron Electric Dipole Moment Measurements
Symmetry 2022, 14(3), 487; https://doi.org/10.3390/sym14030487 - 28 Feb 2022
Cited by 6 | Viewed by 1143
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 (nn) oscillation. Consequently, there were many experiments that have searched for nn 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 nn oscillation. All the previous efforts searched for nn 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, nn 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 nn oscillation. After compensating for the systematic effects that affect the ratio of precession frequencies of ultracold neutrons and cohabiting 199Hg-atoms, chief among which was due to their motion in non-uniform magnetic field, we constrained any further perturbations due to nn oscillation. We thereby provide a lower limit on the nn oscillation time constant of τnn/|cos(β)|>5.7s,0.36T<B<1.01T (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 0.36T<B<0.40T. Full article
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Article
Infrasonic, Acoustic and Seismic Waves Produced by the Axion Quark Nuggets
Symmetry 2022, 14(3), 459; https://doi.org/10.3390/sym14030459 - 24 Feb 2022
Cited by 6 | Viewed by 839
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 ν5 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 ν5 Hz and overpressure δp0.3 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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Article
Attaching Onto or Inserting Into an Intramolecular Hydrogen Bond: Exploring and Controlling a Chirality-Dependent Dilemma for Alcohols
Symmetry 2022, 14(2), 357; https://doi.org/10.3390/sym14020357 - 11 Feb 2022
Cited by 2 | Viewed by 989
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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Article
Bayesian Interval Estimation for the Two-Parameter Exponential Distribution Based on the Right Type II Censored Sample
Symmetry 2022, 14(2), 352; https://doi.org/10.3390/sym14020352 - 10 Feb 2022
Cited by 3 | Viewed by 686
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
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Article
Interface Asymmetry Induced and Surface Pressure Controlled Valence Tautomerism in Monolayers of bis-Phthalocyaninates of Lanthanides
Symmetry 2022, 14(2), 340; https://doi.org/10.3390/sym14020340 - 07 Feb 2022
Cited by 2 | Viewed by 767
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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Article
The Cosmological Constant as Event Horizon
Symmetry 2022, 14(2), 300; https://doi.org/10.3390/sym14020300 - 01 Feb 2022
Cited by 8 | Viewed by 865
Abstract
General Relativity allows for a cosmological constant (Λ) which has inspired models of cosmic Inflation and Dark Energy. We show instead that rΛ=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 rΛ=3/Λ corresponds to an event horizon: a causal boundary term in the action. Our Universe is expanding inside its Schwarzschild radius rS=rΛ=2GM, 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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Article
Transient Propagation of Spherical Waves in Porous Material: Application of Fractional Calculus
Symmetry 2022, 14(2), 233; https://doi.org/10.3390/sym14020233 - 25 Jan 2022
Cited by 5 | Viewed by 1291
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
Article
Neutron-Mirror Neutron Oscillations in Absorbing Matter
Symmetry 2022, 14(2), 230; https://doi.org/10.3390/sym14020230 - 25 Jan 2022
Cited by 7 | Viewed by 1252
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 nn 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 nn system in a cold neutron beam passing through dense absorbing materials in connection to the possible regeneration type of experiments, where the effect of nnn transformation can be observed. Full article
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Article
Notes on Confinement on R3 × S1: From Yang–Mills, Super-Yang–Mills, and QCD (adj) to QCD(F)
Symmetry 2022, 14(1), 180; https://doi.org/10.3390/sym14010180 - 17 Jan 2022
Cited by 9 | Viewed by 929
Abstract
This is a pedagogical introduction to the physics of confinement on R3×S1, using SU(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 R3×S1, using SU(2) Yang–Mills with massive or massless adjoint fermions as the prime example; we also add fundamental flavours to conclude. The small-S1 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 R3. Moving on to R3×S1, 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 S1 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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Article
Intelligent System for Estimation of the Spatial Position of Apples Based on YOLOv3 and Real Sense Depth Camera D415
Symmetry 2022, 14(1), 148; https://doi.org/10.3390/sym14010148 - 13 Jan 2022
Cited by 19 | Viewed by 1571
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 Special Issue Mathematical Modelling in Science and Engineering)
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Article
Energetic and Geometric Characteristics of Substituents, Part 3: The Case of NO2 and NH2 Groups in Their Mono-Substituted Derivatives of Six-Membered Heterocycles
Symmetry 2022, 14(1), 145; https://doi.org/10.3390/sym14010145 - 12 Jan 2022
Cited by 1 | Viewed by 725
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 (Erel) 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 Erel 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
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Article
Analysis of Electro-Optical Behavior in Liquid Crystal Cells with Asymmetric Anchoring Strength
Symmetry 2022, 14(1), 85; https://doi.org/10.3390/sym14010085 - 06 Jan 2022
Cited by 1 | Viewed by 1163
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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Article
Homochiral or Heterochiral: A Systematic Study of Threonine Clusters Using a FT ICR Mass Spectrometer
Symmetry 2022, 14(1), 86; https://doi.org/10.3390/sym14010086 - 06 Jan 2022
Cited by 2 | Viewed by 618
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 [Thrn+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 [Thrn+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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Article
A 3D Agent-Based Model of Lung Fibrosis
Symmetry 2022, 14(1), 90; https://doi.org/10.3390/sym14010090 - 06 Jan 2022
Cited by 2 | Viewed by 1584
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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Article
On the Unique Solvability of Incomplete Cauchy Type Problems for a Class of Multi-Term Equations with the Riemann–Liouville Derivatives
Symmetry 2022, 14(1), 75; https://doi.org/10.3390/sym14010075 - 05 Jan 2022
Cited by 5 | Viewed by 562
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
Article
Best Dominants and Subordinants for Certain Sandwich-Type Theorems
Symmetry 2022, 14(1), 62; https://doi.org/10.3390/sym14010062 - 03 Jan 2022
Cited by 3 | Viewed by 533
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)
Article
Energetic Particle Superdiffusion in Solar System Plasmas: Which Fractional Transport Equation?
Symmetry 2021, 13(12), 2368; https://doi.org/10.3390/sym13122368 - 08 Dec 2021
Cited by 3 | Viewed by 2093
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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Communication
2-Pyridylselenenyl versus 2-Pyridyltellurenyl Halides: Symmetrical Chalcogen Bonding in the Solid State and Reactivity towards Nitriles
Symmetry 2021, 13(12), 2350; https://doi.org/10.3390/sym13122350 - 07 Dec 2021
Cited by 7 | Viewed by 1665
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 Special Issue Symmetry in Quantum and Computational Chemistry)
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Article
New Light H± Discovery Channels at the LHC
Symmetry 2021, 13(12), 2319; https://doi.org/10.3390/sym13122319 - 04 Dec 2021
Cited by 5 | Viewed by 1037
Abstract
A light charged Higgs boson has been searched for at the Large Hadron Collider (LHC) via top (anti)quark decay, i.e., tbH+, 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., tbH+, if kinematically allowed. In this contribution, we propose new channels for light charged Higgs boson searches via the pair productions ppH±h/A and ppH+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±W±h and/or H±W±A. We demonstrate that such production and decay channels can yield substantial alternative discovery channels for H± 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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Article
On the Semi-Analytical Solutions in Hydrodynamics of Ideal Fluid Flows Governed by Large-Scale Coherent Structures of Spiral-Type
Symmetry 2021, 13(12), 2307; https://doi.org/10.3390/sym13122307 - 03 Dec 2021
Cited by 3 | Viewed by 895
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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Article
On the Fekete–Szegö Problem for Meromorphic Functions Associated with p,q-Wright Type Hypergeometric Function
Symmetry 2021, 13(11), 2143; https://doi.org/10.3390/sym13112143 - 10 Nov 2021
Cited by 11 | Viewed by 1112
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)
Article
Asymmetry of Plant Cell Divisions under Salt Stress
Symmetry 2021, 13(10), 1811; https://doi.org/10.3390/sym13101811 - 28 Sep 2021
Cited by 5 | Viewed by 1333
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
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Article
Brain Symmetry Analysis during the Use of a BCI Based on Motor Imagery for the Control of a Lower-Limb Exoskeleton
Symmetry 2021, 13(9), 1746; https://doi.org/10.3390/sym13091746 - 19 Sep 2021
Cited by 5 | Viewed by 2067
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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Article
Quadratic Stabilization of Linear Uncertain Positive Discrete-Time Systems
Symmetry 2021, 13(9), 1725; https://doi.org/10.3390/sym13091725 - 17 Sep 2021
Cited by 5 | Viewed by 857
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)
Article
Gravitational Decoupling in Higher Order Theories
Symmetry 2021, 13(9), 1598; https://doi.org/10.3390/sym13091598 - 31 Aug 2021
Cited by 6 | Viewed by 1247
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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Article
Null Homology Groups and Stable Currents in Warped Product Submanifolds of Euclidean Spaces
Symmetry 2021, 13(9), 1587; https://doi.org/10.3390/sym13091587 - 28 Aug 2021
Cited by 6 | Viewed by 1089
Abstract
In this paper, we prove that, for compact warped product submanifolds Mn in an Euclidean space En+k, there are no stable p-currents, homology groups are vanishing, and M3 is homotopic to the Euclidean sphere S3 [...] Read more.
In this paper, we prove that, for compact warped product submanifolds Mn in an Euclidean space En+k, there are no stable p-currents, homology groups are vanishing, and M3 is homotopic to the Euclidean sphere S3 under various extrinsic restrictions, involving the eigenvalue of the warped function, integral Ricci curvature, and the Hessian tensor. The results in this paper can be considered an extension of Xin’s work in the framework of a compact warped product submanifold, when the base manifold is minimal in ambient manifolds. Full article
Article
On Special Differential Subordinations Using Fractional Integral of Sălăgean and Ruscheweyh Operators
Symmetry 2021, 13(9), 1553; https://doi.org/10.3390/sym13091553 - 24 Aug 2021
Cited by 11 | Viewed by 1057
Abstract
In the present paper, a new operator denoted by DzλLαn is defined by using the fractional integral of Sălăgean and Ruscheweyh operators. By means of the newly obtained operator, the subclass [...] Read more.
In the present paper, a new operator denoted by DzλLαn is defined by using the fractional integral of Sălăgean and Ruscheweyh operators. By means of the newly obtained operator, the subclass Snδ,α,λ of analytic functions in the unit disc is introduced, and various properties and characteristics of this class are derived by applying techniques specific to the differential subordination concept. By studying the operator DzλLαn, some interesting differential subordinations are also given. Full article
(This article belongs to the Special Issue Symmetry in Functional Equations and Analytic Inequalities II)
Article
Neurofunctional Symmetries and Asymmetries during Voluntary out-of- and within-Body Vivid Imagery Concurrent with Orienting Attention and Visuospatial Detection
Symmetry 2021, 13(8), 1549; https://doi.org/10.3390/sym13081549 - 23 Aug 2021
Cited by 2 | Viewed by 2299
Abstract
We explored whether two visual mental imagery experiences may be differentiated by electroencephalographic (EEG) and performance interactions with concurrent orienting external attention (OEA) to stimulus location and subsequent visuospatial detection. We measured within-subject (N = 10) event-related potential (ERP) changes during out-of-body imagery [...] Read more.
We explored whether two visual mental imagery experiences may be differentiated by electroencephalographic (EEG) and performance interactions with concurrent orienting external attention (OEA) to stimulus location and subsequent visuospatial detection. We measured within-subject (N = 10) event-related potential (ERP) changes during out-of-body imagery (OBI)—vivid imagery of a vertical line outside of the head/body—and within-body imagery (WBI)—vivid imagery of the line within one’s own head. Furthermore, we measured ERP changes and line offset Vernier acuity (hyperacuity) performance concurrent with those imagery, compared to baseline detection without imagery. Relative to OEA baseline, OBI yielded larger N200 and P300, whereas WBI yielded larger P50, P100, N400, and P800. Additionally, hyperacuity dropped significantly when concurrent with both imagery types. Partial least squares analysis combined behavioural performance, ERPs, and/or event-related EEG band power (ERBP). For both imagery types, hyperacuity reduction correlated with opposite frontal and occipital ERP amplitude and polarity changes. Furthermore, ERP modulation and ERBP synchronizations for all EEG frequencies correlated inversely with hyperacuity. Dipole Source Localization Analysis revealed unique generators in the left middle temporal gyrus (WBI) and in the right frontal middle gyrus (OBI), whereas the common generators were in the left precuneus and middle occipital cortex (cuneus). Imagery experiences, we conclude, can be identified by symmetric and asymmetric combined neurophysiological-behavioural patterns in interactions with the width of attentional focus. Full article
(This article belongs to the Special Issue Symmetry and Asymmetry in Brain Behavior and Perception II)
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Article
Individual Laterality in Ghost Crabs (Ocypode saratan) Influences Burrowing Behavior
Symmetry 2021, 13(8), 1512; https://doi.org/10.3390/sym13081512 - 17 Aug 2021
Cited by 4 | Viewed by 1468
Abstract
Behavioral handedness is known to enhance an individual’s handling capabilities. However, the ecological advantages in brachyuran crustaceans remain unclear, despite the Ocypode species having been studied extensively. Thus, in this study, we analyzed the laterality of the endemic Red Sea ghost crab on [...] Read more.
Behavioral handedness is known to enhance an individual’s handling capabilities. However, the ecological advantages in brachyuran crustaceans remain unclear, despite the Ocypode species having been studied extensively. Thus, in this study, we analyzed the laterality of the endemic Red Sea ghost crab on one beach in Eilat, Israel. We successfully documented the laterality of the large cheliped in 125 crabs; in 60 (48.0%), the right cheliped was larger, and in 64 (51.2%), the left. We also observed temporal segregation between the right- and left-clawed crabs. The right-handed crabs start activity just after sunrise, while left-handed crabs appear ca. 40 min after it. Similarly, temporal segregations were also observed in the evening. The right-clawed crab activity peaked ca. 20 min before sunset, while the left-clawed crabs were active uniformly. Additionally, burrow entrances corresponded to the larger cheliped of the resident individual and is probably a self-defense-related behavior. We conclude that cheliped laterality in O. saratan populations should be considered as a bimodal trait, where left- and right-handedness is not under natural selection pressure. Full article
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Article
New Conservation Laws and Exact Cosmological Solutions in Brans–Dicke Cosmology with an Extra Scalar Field
Symmetry 2021, 13(8), 1364; https://doi.org/10.3390/sym13081364 - 27 Jul 2021
Cited by 5 | Viewed by 1479
Abstract
The derivation of conservation laws and invariant functions is an essential procedure for the investigation of nonlinear dynamical systems. In this study, we consider a two-field cosmological model with scalar fields defined in the Jordan frame. In particular, we consider a Brans–Dicke scalar [...] Read more.
The derivation of conservation laws and invariant functions is an essential procedure for the investigation of nonlinear dynamical systems. In this study, we consider a two-field cosmological model with scalar fields defined in the Jordan frame. In particular, we consider a Brans–Dicke scalar field theory and for the second scalar field we consider a quintessence scalar field minimally coupled to gravity. For this cosmological model, we apply for the first time a new technique for the derivation of conservation laws without the application of variational symmetries. The results are applied for the derivation of new exact solutions. The stability properties of the scaling solutions are investigated and criteria for the nature of the second field according to the stability of these solutions are determined. Full article
(This article belongs to the Special Issue Symmetry and Integrability in Natural Sciences)
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Article
Feature Ranking and Differential Evolution for Feature Selection in Brushless DC Motor Fault Diagnosis
Symmetry 2021, 13(7), 1291; https://doi.org/10.3390/sym13071291 - 18 Jul 2021
Cited by 7 | Viewed by 1593
Abstract
A fault diagnosis system with the ability to recognize many different faults obviously has a certain complexity. Therefore, improving the performance of similar systems has attracted much research interest. This article proposes a system of feature ranking and differential evolution for feature selection [...] Read more.
A fault diagnosis system with the ability to recognize many different faults obviously has a certain complexity. Therefore, improving the performance of similar systems has attracted much research interest. This article proposes a system of feature ranking and differential evolution for feature selection in BLDC fault diagnosis. First, this study used the Hilbert–Huang transform (HHT) to extract the features of four different types of brushless DC motor Hall signal. When there is a fault, the symmetry of the Hall signal will be influenced. Second, we used feature selection based on a distance discriminant (FSDD) to calculate the feature factors which base on the category separability of features to select the features which have a positive correlation with the types. The features were entered sequentially into the two supervised classifiers: backpropagation neural network (BPNN) and linear discriminant analysis (LDA), and the identification results were then evaluated. The feature input for the classifier was derived from the FSDD, and then we optimized the feature rank using differential evolution (DE). Finally, the results were verified from the BLDC motor’s operating environment simulation with the same features by adding appropriate signal-to-noise ratio magnitudes. The identification system obtained an accuracy rate of 96% when there were 14 features. Additionally, the experimental results show that the proposed system has a robust anti-noise ability, and the accuracy rate is 92.04%, even when 20 dB of white Gaussian noise is added to the signal. Moreover, compared with the systems established from the discrete wavelet transform (DWT) and a variety of classifiers, our proposed system has a higher accuracy with fewer features. Full article
(This article belongs to the Special Issue Complex Systems and Its Applications)
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Article
Building a Fuzzy Classifier Based on Whale Optimization Algorithm to Detect Network Intrusions
Symmetry 2021, 13(7), 1211; https://doi.org/10.3390/sym13071211 - 06 Jul 2021
Cited by 7 | Viewed by 1545
Abstract
The quantity of network attacks and the harm from them is constantly increasing, so the detection of these attacks is an urgent task in the information security field. In this paper, we investigate an approach to building intrusion detection systems using a classifier [...] Read more.
The quantity of network attacks and the harm from them is constantly increasing, so the detection of these attacks is an urgent task in the information security field. In this paper, we investigate an approach to building intrusion detection systems using a classifier based on fuzzy rules. The process of creating a fuzzy classifier based on a given set of input and output data can be presented as a solution to the problems of clustering, informative features selection, and the parameters of the rule antecedents optimization. To solve these problems, the whale optimization algorithm is used. The performance of algorithms for constructing a fuzzy classifier based on this metaheuristic is estimated using the KDD Cup 1999 intrusion detection dataset. On average, the resulting classifiers have a type I error of 0.92% and a type II error of 1.07%. The obtained results are also compared with the results of other classifiers. The comparison shows the competitiveness of the proposed method. Full article
(This article belongs to the Special Issue Information Technologies and Electronics Ⅱ)
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Article
Symmetric Ground States for Doubly Nonlocal Equations with Mass Constraint
Symmetry 2021, 13(7), 1199; https://doi.org/10.3390/sym13071199 - 02 Jul 2021
Cited by 5 | Viewed by 1356
Abstract
We prove the existence of a spherically symmetric solution for a Schrödinger equation with a nonlocal nonlinearity of Choquard type. This term is assumed to be subcritical and satisfy almost optimal assumptions. The mass of of the solution, described by its norm in [...] Read more.
We prove the existence of a spherically symmetric solution for a Schrödinger equation with a nonlocal nonlinearity of Choquard type. This term is assumed to be subcritical and satisfy almost optimal assumptions. The mass of of the solution, described by its norm in the Lebesgue space, is prescribed in advance. The approach to this constrained problem relies on a Lagrange formulation and new deformation arguments. In addition, we prove that the obtained solution is also a ground state, which means that it realizes minimal energy among all the possible solutions to the problem. Full article
(This article belongs to the Special Issue Recent Advance in Mathematical Physics)
Article
Use of the Molecular Dynamics Method to Investigate the Stability of α-α-Corner Structural Motifs in Proteins
Symmetry 2021, 13(7), 1193; https://doi.org/10.3390/sym13071193 - 02 Jul 2021
Cited by 4 | Viewed by 1593
Abstract
This study investigated the stability of structural motifs via molecular dynamics, using α-α-corners as an example. A molecular dynamics experiment was performed on a sample of α-α-corners selected by the authors from the PDB database. For the first time during a molecular dynamics [...] Read more.
This study investigated the stability of structural motifs via molecular dynamics, using α-α-corners as an example. A molecular dynamics experiment was performed on a sample of α-α-corners selected by the authors from the PDB database. For the first time during a molecular dynamics experiment, we investigated the characteristics of structural motifs by describing their geometry, including the interplanar distance, area of polygon of the helices projections intersection, and torsion angles between axes of helices in helical pairs. The torsion angles for the constriction amino acids in the equilibrium portion of the molecular dynamics trajectory were analyzed. Using the molecular dynamics method, α-α-corners were found to be autonomous structures that are stable in aquatic environments. Full article
(This article belongs to the Special Issue Medicinal Chemistry: Topics and Advances)
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