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Quantized topological invariants characterizing topological phases in quasi-1D materials are usually considered only on the basis of spatial inversion parity eigenvalues. However, symmetry of quasi-1D systems is far more complex and their complete topological characterisation can be obtained only on the basis of elementary band representations (EBRs) for the relevant symmetry groups. We derive complete sets of inequivalent EBRs for line groups (LG), the symmetry groups of all quasi-1D systems with either translational or helical periodicity. Besides, we determine also EBRs for double-LGs, accounting for spin degree of freedom. In order to illustrate applicability of the results obtained, we analyze electronic-band topology of a chiral single-wall carbon nanotube, using EBRs for relevant (double)-LG and discuss Su-Schrieffer–Heeger model from EBR-perspective. [ABSTRACT FROM AUTHOR]

Quasi one-dimensional systems, including bio-polymers, nanotubes, nanowires, etc., are in focus of material science and technology for more than two decades. Using recently found quasi one-dimensional conformation classes, which are elementary building blocks of all quasi one-dimensional crystals, we make symmetry based study of their diffraction patterns. In particular, we single out the features distinguishing between the classes, thus enabling to characterize each of them. It turns out that this analysis suffices to find out chiral indices of carbon nanotubes. [ABSTRACT FROM AUTHOR]

Phonon of the single-wall MS2 (M = Mo,W) nanotubes with diameters up to 50 nm are systematically calculated using the full symmetry implemented valence-force-field model. Infrared and Raman active modes are singled out by the symmetry, and their applications in the experimental sample characterization are discussed. Raman measurement of the multiwall tubes and bulk has been performed. Obtained results are interpreted by simple coupled-spring like model concerning the same symmetry modes of walls. [ABSTRACT FROM AUTHOR]

The symmetry of single-wall carbon and inorganic tubes is reviewed. For the carbon nanotubes it is used to get the full set of quantum numbers, in the efficient precision (combined density functional and tight-binding methods) calculation of electronic bands and their complete assignation, to obtain the selection rules for optical transitions and the momenta matrix elements for the Bloch eigen-states. The optical characteristics are thoroughly found, and discussed. [ABSTRACT FROM AUTHOR]

The friction between the walls of multi-wall carbon nanotubes is shown to be extremely low in general, with important details related to the specific choice of the walls. This is governed by a simple expression revealing that the phenomenon is a profound consequence of the specific symmetry breaking: super-slippery sliding of the incommensurate walls is a Goldstone mode. Three universal principles of tribology, offering a recipe for lubricant selection are emphasized. [ABSTRACT FROM AUTHOR]

More than fifteen years have passed since the first report of experimental evidence of regularly coiled carbon nanotubes, but, the structure, formation mechanism and theoretical aspects of these nanotubes still remain unresolved. We propose model of hexagonal, helically coiled single wall carbon nanotubes, determine their line group symmetry and calculate electronic band structure of the relaxed configurations by means of fully symmetry adopted density functional tight binding method implemented into the POLSym code. Electrical properties of the straight and coiled carbon nanotubes of different chiralities are compared and analyzed. [ABSTRACT FROM AUTHOR]

We present a symmetry based analysis of diffraction intensities of transition metal dichalcogenide nanotubes. Obtained results point out specific features of the intensity distribution that are related to group parameters. It is possible to read out all the group parameters from diffraction patterns, and therefore to characterize nanotube, since symmetry group uniquely determines the chiralty indices. [ABSTRACT FROM AUTHOR]

Stone-Wales defect in graphene is a bond rotation transforming four adjacent hexagons into the pentaheptite ornament with two pentagons and two heptagons. There are two types of pentaheptite lattices, i.e., hexagonal and rectangular. Each of them can be rolled up to get pentaheptite nanotubes, analogously to the conventional carbon nanotubes obtained by rolling of the graphene. Using full symmetry of these nanotubes, stable configuration is found by numerical density functional theory-based relaxation with initial purely folded configurations. Pentaheptite tubes are less stable than the conventional ones; however, the transition can be induced by an external mechanical stress. New tubes have different electrical properties, most of them being conducting with considerable Fermi level density of states. These properties are exploited to propose electromechanical nanoswitch. [ABSTRACT FROM AUTHOR]

In this paper, a signal conditioner intended for use in variable impedance sensors is presented. First, an inductive linear displacement sensor design is described, and the signal conditioner discrete realization is presented. Second, based on this system's requirements, the integrated conditioner is proposed. The conditioner comprises an amplifier, a tunable band-pass filter, and a precision high-frequency AC-DC converter. It is designed in a low-cost AMS 0.35 µm CMOS process. The presented conditioner measures the sensor's impedance magnitude by using a simplified variation of the sensor voltage and current vector measurement. It can be used for the real-time measurement of fast sensors, having small output impedance. The post-layout simulation results show that the integrated conditioner has an inductance measurement range from 10 nH to 550 nH with a nonlinearity of 1.2%. The operating frequency in this case was 8 MHz, but the circuit can be easily adjusted to different operating frequencies (due to the tunable filter). The designed IC area is 500 × 330 μm 2 , and the total power consumption is 93.8 mW.

This work presents a novel approach towards integrating electronic components with textiles, by successfully creating a fully textile-based element that is capable of detecting applied forces by variation in its resistance value. The fabrication of the device consists of a specialized siliconized conductive fabric, which is placed above and below a layer of switch fabric, which acts as a force sensor. In this paper, the effects of three different geometries are observed, as well as the washability of the device, along with tension testing. Μoreover, the device behavior is simulated as well as applied in a real-life scenario. The proposed element demonstrates a good dynamic range, high repeatability and stability, and minimal impact of washing, creating a great candidate for integration in e-textiles., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2024 The Authors.)

Considered are 80 sets of layer groups, each set consisting of four groups: ordinary single and double, and grey single and double layer groups. The structural properties of layer groups (factorization into cyclic subgroups and the existence of grading according to the sequence of halving subgroups) enable efficient symbolic computation (by the POLSym code) of the relevant properties, real and complex irreducible and allowed (half-)integer (co-)representations in particular. This task includes, as the first step, classification of the irreducible domains based on the group action in the Brillouin zone combined with torus topology. Also, the band (co-)representations induced from the irreducible (co-)representations of Wyckoff-position stabilizers (site-symmetry groups) are decomposed into the irreducible components. These, and other layer group symmetry related theoretical data relevant for physics, layered materials in particular, are tabulated and made available through the web site https://nanolab.group/layer/.

Symmetry indicates that low energy spectra of materials could be richer than well-known Dirac, semi-Dirac, or quadratic, hosting some unusual quasiparticles. Performing the systematic study of exact forms of low energy effective Hamiltonians and dispersions in high-symmetry points with fourfold degeneracy of bands, we found new, previously unreported dispersion, which we named poppy flower (PF) after its shape. This massless fermion exists in non-magnetic two-dimensional (2D) crystals with spin-orbit coupling (SOC), which are invariant under one of the proposed ten noncentrosymmetric layer groups. We suggest real three-dimensional (3D) layered materials suitable for exfoliation, having layers that belong to these symmetry groups as candidates for realization of PF fermions. In 2D systems without spin-orbit interaction, fortune teller (FT)-like fermions were theoretically predicted, and afterward experimentally verified in the electronic structure of surface layer of silicon. Herein, we show that such fermions can also be hosted in 2D crystals with SOC, invariant under additional two noncentrosymmetric layer groups. This prediction is confirmed by density functional based calculation: layered BiIO 4 , which has been synthesized already as a 3D crystal, exfoliates to stable monolayer with symmetry pb 2 1 a , and FT fermion is observed in the band structure. Analytically calculated density of states (DOS) of the PF shows semimetallic characteristic, in contrast to metallic nature of FT having non-zero DOS at the bands contact energy. We indicate possibilities for symmetry breaking patterns which correspond to the robustness of the proposed dispersions as well as to the transition from Dirac centrosymmetric semimetal to PF., (© 2020 IOP Publishing Ltd.)

Spin line groups describe the symmetries of spin arrangements in quasi-one-dimensional systems. These groups are derived for the first family of line groups. Among them, magnetic groups are singled out as a special case. Spin arrangements generated by the derived groups are first discussed for single-orbit systems and then the conclusions are extended to multi-orbit cases. The results are illustrated by the examples of a CuO2 zigzag chain, a (13)C nanotube and the hexaferrite Ba2Mg2Fe12O22. Applications to neutron diffraction and classical ground-state determination are indicated.

Background/aim: Children and adolescents who enter a child welfare system are at higher risk of suffering from mental disorders, physical health, and/or social and educational problems than the general population of the same age is. This study was organized with the aim to evaluate the general characteristics of quality of life (QOL) in children and adolescents living in residential and foster care in Serbia., Methods: Two hundred and sixteen children and adolescents, aged 8-18 years, from residential and foster care and 238 children and adolescents from the general population participated in the study. QOL was assessed using the Pediatric Quality of Life Inventory (PedsQL) - Serbian version. Three groups were created: residential care group (RCG), foster care group (FCG), and control group (children and adolescents from biological families - CG). Descriptive data were calculated for all questionnaires' scores, while t-test and ANOVA were used to compare them., Results: The mean value of the total PedsQL was lower in the RCG, 67.47 +/- 17.75, than in the FCG and the CG, 88.33 +/- 11.27 and 80.74 +/- 11.23, respectively. Additionally, the RCG reported lower all PedsQL Scale scores, but the lowest value was for the psychosocial domain. These differences were statistically significant (F value ranged from 17.3 to 49.89, p < 0.000). However, only the scores of the RCG were statistically different from the FCG and the CG, while the differences between the FCG and the CG were statistically insignificant (p > 0.05)., Conclusion: Children and adolescents living in residential care have significantly poorer QOL than those living in foster care or in biological families. On the other side, QOL in children and adolescents from foster care is similar to the one of those living in biological families.

Purpose: The aim of this study was to evaluate the general measurement properties of the Serbian version of the Pediatric Quality of Life Inventory™ Version 4.0 Generic Core Scales (PedsQL™) self-report versions for children and adolescents (8-18 years)., Methods: The PedsQL™ was completed by 238 children and adolescents. The version was descriptively analyzed first. Afterward, internal consistency and construct and convergent validity were analyzed using the classic test theory psychometrical procedures., Results: The PedsQL™ scale score means ranged 70.65-88.34, with the total score was 80.74. Scale internal consistency reliability determined by Cronbach's coefficient was above 0.7 for all except the School, 0.65, and Emotional Functioning Scale, 0.69. The statistics assessing the adequacy of the model in confirmatory factor analysis revealed poor model fit for the current structure of the PedsQL™. Finally, the PedsQL™ total and psychosocial health showed convincing negative correlations with emotional and conduct problems, hyperactivity/inattention, and peer relationship problems., Conclusions: The Serbian PedsQL™ scales have appropriate internal consistency reliability, sufficient for group evaluations, and good convergent validity against psychological constructs. However, there are problems regarding its current construct validity (factorial validity).

The full geometrical symmetry groups of zinc oxide nanowires, nanotubes, nanosprings and nanorings are found and some physical properties which can be deduced from the symmetry are discussed: conserved quantum numbers and band degeneracies; dynamical representations, Raman and infrared active modes; piezoelectric tensor.

Nanotubes have become attractive subjects in solid-state physics owing to their potential applications in nanotechnology. Their symmetry is one of the important tools in theoretical investigations. Here a review is presented of the symmetry groups of the single-wall nano- and microtubes considered in literature: BN, GaN, MS2, C, BC3, BC2N.