Perfect Symmetry Research Articles

Neuro Postural Optimization Neuromodulation Treatment of Radio Electric Asymmetric Conveyer Technology on Stress and Quality of Life in Institutionalized Children in a Capital City of the Brazilian Amazon.

BackgroundThe deviation from perfect bilateral symmetry is defined as fluctuating asymmetry (FA) and is a common phenomenon among living organisms. This deviation from perfection is thought to reflect the environmental pressures experienced during development and, therefore, the FA represents an epigenetic measure of the environmental stress, which affects all living beings from conception, progressively affecting all aspects of life.Rinaldi and Fontani hypothesized that the FA morpho-functional changes are originated by an adaptive motor behavior determined by functional alterations in the cerebellum and neural circuits, not caused by a lesion, but induced by the experienced environmental stress. They identified in the asymmetric activation of symmetrical muscle groups, detectable even in healthy subjects, the expression of the dysfunctional adaptation state of the subject and named this clinical semeiotic phenomenon functional dysmetria (FD).On these premises, they developed the radio electric asymmetric conveyer (REAC) technology, a neuromodulation technology aimed at optimizing the best neuro-psycho-motor strategies in relation to environmental interaction. Neuro postural optimization (NPO) is a neurobiological stimulation treatment administered with the REAC technology and it has been specifically studied to treat the state of dysfunctional adaptation that is revealed through the presence of FD.AimThe purpose of this study was to verify whether a single administration of the REAC NPO treatment can trigger the improvement of the capacity of stress management and the quality of life in a population of children housed in a group home in Macapá, Brazil.Materials and methodsThe sample of this study consisted of nine children (six boys and three girls) in the age group of 6-11 years, which represented the totality of the children present in the structure. The children was investigated for the assessment of the presence of functional dysmetria and with the Pediatric Quality of Life Inventory TM 4.0 (PedsQL) before and one week after the administration of the REAC NPO.ResultsThe stable disappearance of FD was found in all children at follow-up. In addition, improvements were found in stress management and quality of life, in the physical, emotional, social, and scholastic aspects evaluated with PedsQL.ConclusionsIt was seen that the REAC NPO neurobiological modulation treatment induced the stable disappearance of FD and triggered the initial improvement of neurophysical aspects also in a population of children housed in a group home in the Amazon region of Macapá, Brazil.

Body Size and Symmetry Properties of Termite Soldiers Under Two Intraspecific Competition Scenarios

Single-piece nesting termites live and forage in the same piece of wood throughout their life, which limit their colony size. In certain species, more than one colony thrive in a given piece of wood (multicolonial substrate) and intraspecific competition become important in this limited resource, as has been reported in Zootermopsis nevadensis (Hagen, 1858) and Neotermes chilensis (Blattodea: Kalotermitidae) (Blanchard, 1851). The effects of such competition have been described mainly at population and colony levels rather than at the individual level. In eusocial insects such as termites, intraspecific competition constitutes a stress factor imposed to a colony as a whole and should also cause developmental instability in soldiers produced under such conditions. Investment in the production of soldiers involves a trade-off between colony maintenance costs and defense benefits. Hence, we hypothesize that body size and fluctuating asymmetry, two indicators of developmental instability, will increase when two or more colonies of N. chilensis share a piece of wood (high intraspecific competition scenario). Our results showed that soldiers developing in multicolonial substrates were indeed larger and more asymmetric than soldiers developing in unicolonial substrates. The large body size in a soldier could improve its chance to win a physical contest with a non-nestmate opponent; thus, despite the high cost to produce large soldiers in small colonies, larger soldier production could be an adaptative strategy to avoid being outcompeted. However, the effects of deviations from perfect symmetry on soldier performance are not clear.

Curtain of Glass – Textured by Stone

The new World Trade Center site was rebuilt after 9/11 comprising seven mayor skyscrapers around the memorial site and the 9/11 museum. Between WTC 2 and WTC 3, Santiago Calatrava’s Oculus Station spans its wings in the NY air while finally, the complex is completed by the “The Ronald O. Perelman Performing Arts Center”. This building sets a one-in-a-kind visual appearance to the area. Its four-sided, 42 m tall, even facade is made from 4736 equal-sized insulated glass panes. More specifically, the architectural vision is to create a marble stone front covered with glass which results in a stone-glass laminate as a part of an insulated glass unit. The marble shows a distinguished white face with crisp black veining. Each of the four elevations of the building impresses with a perfect symmetry and veins touching at the vertical center line. So, the design team at Josef Gartner was challenged to set-up a logistics chain from quarry in Portugal where the stone panels were cut and catalogued to glass production of laminated glass in France and IGUs in Germany and assembly of curtain wall mega-panels at Gartner in Germany up to the site in Lower Manhattan. Our in-house logistics concept, customized for this project, guarantees that each individual piece of stone finds its correct and unique spot defined by the architect on the 7,000 m2 surface – a large-scale game of “Matching Pairs”. The steel base building provides a cantilevering roof that holds 128 hot-rolled steel mullions. Each 36 m in length with one intermediate lateral support only. This allows the visitor to experience a clear and unobstructed view along the transom-free facade elements that carry the translucent stone-wall. During the day, it appears white from the outside and shines with an amber-glow during the night when the interior space is illuminated. We show the use of a novel stone-glass product that is exposed to a variety of requirements. The logistics chain is described from quarry to site making sure that the architectural and economical demand is met along the whole process. Finally, the team connects all branches in facade design using stone, aluminum, glass and architectural exposed structural steel assembled in one landmark project.

Color Variability Constrains Detection of Geometrically Perfect Mirror Symmetry

Symmetry in nature is a result of biological self-organization, driven by evolutionary processes. Detected by the visual systems of various species, from invertebrates to primates, symmetry determines survival relevant choice behaviors and supports adaptive function by reducing stimulus uncertainty. Symmetry also provides a major structural key to bio-inspired artificial vision and shape or movement simulations. In this psychophysical study, local variations in color covering the whole spectrum of visible wavelengths are compared to local variations in luminance contrast across an axis of geometrically perfect vertical mirror symmetry. The chromatic variations are found to delay response time to shape symmetry to a significantly larger extent than achromatic variations. This effect depends on the degree of variability, i.e., stimulus complexity. In both cases, we observe linear increase in response time as a function of local color variations across the vertical axis of symmetry. These results are directly explained by the difference in computational complexity between the two major (magnocellular vs. parvocellular) visual pathways involved in filtering the contrast (luminance vs. luminance and color) of the shapes. It is concluded that color variability across an axis of symmetry proves detrimental to the rapid detection of symmetry, and, presumably, other structural shape regularities. The results have implications for vision-inspired artificial intelligence and robotics exploiting functional principles of human vision for gesture and movement detection, or geometric shape simulation for recognition systems, where symmetry is often a critical property.

A CPW fed quad-port MIMO DRA for sub-6 GHz 5G applications

The present work investigates a novel four-port, multiple-input multiple-output (MIMO), single element dielectric resonator antenna (DRA) for sub-6 GHz band. The DRA is designed and fabricated into a symmetric cross shape and fed using a coplanar waveguide (CPW) feed. A single radiator with four ports is rarely found in the literature. The -10 dB impedance bandwidth covered by the antenna is from 5.52 GHz to 6.2 GHz (11.6%) which covers fifth generation (5G) new radio (NR) bands N47 and wireless local area network (WLAN) IEEE 802.11a band. The isolation between orthogonal ports is about 15 dB while the isolation between opposite ports is 12 dB. The radiation pattern of the proposed antenna is bidirectional due to the absence of a ground plane below the DRA. The orthogonal modes excited in the DRA are and through the four symmetrical CPW feeds. The simulated and measured results of the proposed design show that MIMO characteristics are achieved by pattern diversity between the ports. Due to the perfect symmetry of the design, the proposed work could be extended to MIMO array applications as well.

Long-Lasting Efficacy of Radio Electric Asymmetric Conveyer Neuromodulation Treatment on Functional Dysmetria, an Adaptive Motor Behavior.

BackgroundFluctuating asymmetry (FA) is widely defined as the deviation from perfect bilateral symmetry and is considered an epigenetic measure of environmental stress. Rinaldi and Fontani hypothesized that the FA morpho-functional changes originate from an adaptive motor behavior determined by functional alterations in the cerebellum and neural circuits, not caused by a lesion, but induced by environmental stress. They called this phenomenon functional dysmetria (FD). On this premise, they developed the radio electric asymmetric conveyer (REAC) technology, a neuromodulation technology aimed at optimizing the best neuro-psycho-motor strategies in relation to environmental interaction.AimsPrevious studies showed that specific REAC neuro postural optimization (NPO) treatment can induce stable FD recovery. This study aimed to verify the duration of the NPO effect in inducing the stable FD recovery over time.Materials and methodsData were retrospectively collected from a population of 29,794 subjects who underwent a specific semiological FD assessment and received the NPO treatment, regardless of the pathology referred.ResultsThe analysis of the data collected by the various participants in the study led us to ascertain the disappearance of FD in 100% of the cases treated, with a stability of the result detected up to 18 years after the single administration of the REAC NPO treatment.ConclusionsThe REAC NPO neurobiological modulation treatment consisting of a single administration surprisingly maintains a very long efficacy in the correction of FD. This effect can be explained as the long-lasting capacity of the NPO treatment to induce greater functional efficiency of the brain dynamics as proven in previous studies.

Quantum field theory for spin operator of the photon

All elementary particles in nature can be classified as fermions with half-integer spin and bosons with integer spin. Within quantum electrodynamics (QED), even though the spin of the Dirac particle is well defined, there exist open questions on the quantized description of spin of the gauge field particle -- the photon. Using quantum field theory, we discover the quantum operators for the spin angular momentum (SAM) $\boldsymbol{S}_{M}=(1/c)\int d^{3}x\boldsymbol{\pi}\times\boldsymbol{A}$ and orbital angular momentum (OAM) $\boldsymbol{L}_{M}=-(1/c)\int d^{3}x\pi^{\mu}\boldsymbol{x}\times\boldsymbol{\nabla}A_{\mu}$ of the photon, where $\pi^{\mu}$ is the conjugate canonical momentum of the gauge field $A^{\mu}$. We also reveal a perfect symmetry between the angular momentum commutation relations for Dirac fields and Maxwell fields. We derive the well-known OAM and SAM of classical electromagnetic fields from the above defined quantum operators. Our work shows that the spin and OAM operators commute which is important for simultaneously observing and separating the SAM and OAM. The correct commutation relations of orbital and spin angular momentum of the photon have applications in quantum optics, topological photonics as well as nanophotonics and can be extended in the future for the spin structure of nucleons.

Leaf size is more sensitive than leaf fluctuating asymmetry as an indicator of plant stress caused by simulated herbivory

Fluctuating asymmetry (FA), defined as small, random departures away from perfect symmetry, is frequently recommended as a sensitive and universal indicator of environmental stress imposed by both abiotic and biotic factors. However, the stress sensitivities of FA and of other morphological traits are rarely compared directly. Here, we tested the hypothesis that leaf FA, rather than leaf size, is more sensitive to simulated herbivory. We performed blind measurements of FA and length of the same leaves of juvenile mountain birches (Betula pubescens var. pumila) after removal of 0, 2, 4, 8 and 16% of their leaf area during five consequent years. The leaf length in defoliated birches was 88% of that in control birches, indicating that simulated herbivory was stressful for trees. By contrast, leaf FA did not differ significantly between defoliated and control birches, despite a sufficient (91%) power of statistical analysis. Thus, leaf size, rather than leaf FA, was a more sensitive indicator of stress. This low sensitivity of FA to stress, discovered with the use of blind methods, contrasts a large pool of earlier studies, many of which have been likely influences by confirmation bias. We urge the publication of ‘negative’ or inconclusive results which currently remain underreported due to publication bias.

Breakdown of the Weak-Coupling Limit in Quantum Annealing

Reverse annealing is a variant of quantum annealing, in which the system is prepared in a classical state, reverse-annealed to an inversion point, and then forward-annealed. We report on reverse annealing experiments using the D-Wave 2000Q device, with a focus on the $p=2$ $p$-spin problem, which undergoes a second order quantum phase transition with a gap that closes polynomially in the number of spins. We concentrate on the total and partial success probabilities, the latter being the probabilities of finding each of two degenerate ground states of all spins up or all spins down, the former being their sum. The empirical partial success probabilities exhibit a strong asymmetry between the two degenerate ground states, depending on the initial state of the reverse anneal. To explain these results, we perform open-system simulations using master equations in the limits of weak and strong coupling to the bath. The former, known as the adiabatic master equation (AME), with decoherence in the instantaneous energy eigenbasis, predicts perfect symmetry between the two degenerate ground states, thus failing to agree with the experiment. In contrast, the latter, known as the polaron transformed Redfield equation (PTRE), is in close agreement with experiment. Thus our results present a challenge to the sufficiency of the weak system-bath coupling limit in describing the dynamics of current experimental quantum annealers, at least for reverse annealing on timescales of a microsecond or longer.

Diagnostic and treatment alternatives for the correction of facial asymmetries: a literature review

Facial symmetry refers to a complete coincidence of each facial component on the sagittal plane, while asymmetry refers to the bilateral difference between these components. The presence of perfect bilateral symmetry is almost never present in human, so it is more common for individuals to predominate facial asymmetry. However, this condition can result from functional and esthetic problems. This research seeks to determine the alternatives, diagnosis and ideal treatment plan for the correction of each type of facial asymmetry through orthognathic surgery. For this purpose, a review of articles published between 2015 to date was carried out. Selecting those that were focused on describing or evaluating facial and dentofacial symmetry and asymmetry, type of diagnosis or treatment plan, including clinical cases. The Google search engine, SciELO and databases of medical interest, such as PubMed, PMC and Medigraphic were used. According to the research and treatments carried out during the last few years in the dental clinic, it has been proven that orthognathic treatment accompanied by previous planning is the best option for the management of skeletal facial asymmetries.

Are there correlations between the levels of fluctuating asymmetry in Pelophylax ridibundus (Anura: Ranidae) meristic morphological traits and morphological parameters used for assessing their physical fitness (health status)?

The degree of developmental stability of individuals and populations is most often estimated by their level of fluctuating asymmetry (FA) - the random deviations from perfect symmetry. In our previous work, we recorded high levels of FA (FAMI index: frequency of asymmetric manifestation of an individual) in Pelophylax ridibundus populations that inhabit biotopes at Sazliyka River, south Bulgaria with high levels of anthropogenic pollution (domestic sewage pollution). At the same time, in the biotopes located in the upper reaches of the river (less disrupted habitats), the populations showed low levels of FA. Currently, we present the results of the study of the values of several morphological parameters: snout-vent length (SVL), body weight (BW), and body condition factor (CF) in the same populations of P. ridibundus. In addition, we evaluate the correlation between the values of these morphological parameters and the values of fluctuating asymmetry (the FAMI index), using the Kendall rank correlation analysis. The analysis of the relationships between the parameters characterizing the physical fitness of frogs and the indicator of developmental stability - the FAMI index - did not establish statistically significant correlations in the analyses in the whole groups of P. ridibundus from each site and in the correlations between sexes. We believe that the approaches to the study of developmental stability (analysis of fluctuating asymmetry levels) and those related to the assessment of physical fitness (health status) of frogs should be applied independently of each other.

Perspective Slant Makes Symmetry Harder to Detect and Less Aesthetically Appealing

Abstract symmetric patterns are generally preferred to less regular patterns. Here, we studied 2D patterns presented as 2D images in the plane, and therefore producing a symmetric pattern on the retina, and the same patterns seen in perspective. This perspective transformation eliminates the presence of perfect symmetry in terms of retinotopic coordinates. Stimuli were abstract patterns of local coplanar elements, or irregular polygons. In both cases they can be understood as 2D patterns on a transparent glass pane. In the first study we found that perspective increased reaction time and errors in a classification task, even when the viewing angle was kept constant over many images. In a second study we tested a large sample (148 participants) and asked for a rating of beauty for the same images. In addition, we used the Cognitive Reflection Test (CRT) to test the hypothesis that people who tend to give the more immediate and intuitive answer would also show a stronger preference for the symmetry presented in the frontoparallel plane (in the image and on the retina). Preference for symmetry was confirmed, and there was a cost for perspective viewing. CRT scores were not related to preference, thus not supporting the hypothesis of a stronger preference for symmetry in the image when people follow a more immediate and intuitive gut response.

Facial asymmetry tracks genetic diversity among Gorilla subspecies.

Mountain gorillas are particularly inbred compared to other gorillas and even the most inbred human populations. As mountain gorilla skeletal material accumulated during the 1970s, researchers noted their pronounced facial asymmetry and hypothesized that it reflects a population-wide chewing side preference. However, asymmetry has also been linked to environmental and genetic stress in experimental models. Here, we examine facial asymmetry in 114 crania from three Gorilla subspecies using 3D geometric morphometrics. We measure fluctuating asymmetry (FA), defined as random deviations from perfect symmetry, and population-specific patterns of directional asymmetry (DA). Mountain gorillas, with a current population size of about 1000 individuals, have the highest degree of facial FA (explaining 17% of total facial shape variation), followed by Grauer gorillas (9%) and western lowland gorillas (6%), despite the latter experiencing the greatest ecological and dietary variability. DA, while significant in all three taxa, explains relatively less shape variation than FA does. Facial asymmetry correlates neither with tooth wear asymmetry nor increases with age in a mountain gorilla subsample, undermining the hypothesis that facial asymmetry is driven by chewing side preference. An examination of temporal trends shows that stress-induced developmental instability has increased over the last 100 years in these endangered apes.

Impact of Amplitude and Phase Imbalance on Dual Differential Fed Patch Antenna With High Isolation

In this paper, the impact of amplitude and phase imbalance on a proposed dual differential fed patch antenna is analyzed in the context of system effective reflection coefficient and axial ratio (AR). A single square patch with four ports is used as a solo radiating element and provides absolute symmetry at radiating. An in-depth analysis will be presented to understand the impact of external RF chain components on the performance of the proposed antenna. When fully differential excitations and perfect symmetry can be achieved, all six polarization states exhibit identical system effective reflection coefficients with close to ideal AR for CP. When phase imbalance and amplitude imbalance only exist in between the two differential pairs, the antenna system matching performance is found to be unchanged. In the presence of the feed network, circular polarization (CP) achieves a measured maximum AR of 0.49dB along the antenna pointing angle, while linear polarization (LP) has a measured maximum cross polarization of −30dB. This work monitors the beamwidth over which the AR can be kept below 1dB (BW-AR−1dB). Based on the optimization of phase imbalance, a novel BW-AR−1dB enhancement technique is introduced. Compared to the case with better AR at the main beam location, an improvement of 14. beamwidth is measured without significant degradation of AR. Isolation better than 40dB across an operating frequency of 9.27 – 9.4 GHz has been experimentally demonstrated for the proposed dual differential fed technique. The resulting antenna is compact and low profile which is an appealing candidate for phased array applications.

Effects of operating room layout and ventilation system on ultrafine particle transport and deposition

The main role of Heat Ventilation and Air Conditioning (HVAC) systems in Operating Rooms (ORs) is to ensure the desired thermo-hygrometric conditions and indoor air quality, minimizing the risk of air contamination. The main sources of contamination inside ORs, during surgical operations, are Colony-Forming Units (CFUs), fine particles and ultrafine particles (UFPs), which could cause surgical site infections or health issues for the medical staff. The present work aims at increasing the scientific knowledge concerning numerical modelling of the UFP transport and deposition in ORs, analysing the effectiveness of three different ventilation systems. A numerical methodology, validated in previous works, has been used to study UFP transport and deposition inside three actual ORs, two of them equipped with a Laminar AirFlow (LAF) system and one with a Turbulent Mixing Airflow (TMA) system. Both the LAF and the TMA systems effectively evacuate the UFPs, ensuring a particle deposition rate significantly lower than the evacuation rate. The installation of extraction grilles near the surgical table allows obtaining an improvement of UFP evacuation. Due to the not perfect symmetry of OR layouts and surgical wound position, a preferred way for UFP transport can be observed. The instrument table position should be chosen consequently, to reduce UFP, CFU and contaminant deposition. The UFP concentrations at surgical staff head height cannot be neglected for health-related risks.

Quantum phase transition revealed by the exceptional point in a Hopfield-Bogoliubov matrix

We use the exceptional point in Hopfield-Bogoliubov matrix to find the phase transition points in the bosonic system. In many previous jobs, the excitation energy vanished at the critical point. It can be stated equivalently that quantum critical point is obtained when the determinant of Hopfield-Bogoliubov matrix vanishes. We analytically obtain the Hopfield-Bogoliubov matrix corresponding to the general quadratic Hamiltonian. For single-mode system the appearance of the exceptional point in Hopfield-Bogoliubov matrix is equivalent to the disappearance of the determinant of Hopfield-Bogoliubov matrix. However, in multi-mode bosonic system, they are not equivalent except in some special cases. For example, in the case of perfect symmetry, that is, swapping any two subsystems and keeping the total Hamiltonian invariable, the exceptional point and the degenerate point coincide all the time when the phase transition occurs. When the exceptional point and the degenerate point do not coincide, we find a significant result. With the increase of two-photon driving intensity, the normal phase changes to the superradiant phase, then the superradiant phase changes to the normal phase, and finally the normal phase changes to the superradiant phase.

First-principles study of helium-vacancy complexes in Be12Ti

First-principles calculations have been conducted to study the stability of He-vacancy clusters and the trapping behavior of vacancies for He atoms in Be12Ti. We considered the various metastable microstructures of four types of He-vacancy clusters, and the most stable configurations were determined by the calculations of solution energy. Some He-vacancy clusters in Be12Ti have specific geometrical shape, and grow along specific crystal plane. For example, three types of He2V clusters (two He atoms trapped by vacancy) form dumbbell-shaped structure, three He atoms of He3V clusters (three He atoms trapped by vacancy) are located in the specific crystal plane. The solution energies of four types of clusters increase with the increase of number of He atoms, and the increasing rate is basically identical. The solution energies of HenVBe1 clusters are always the largest, and the solution energies of the HenVTi clusters are always the smallest, which mainly attribute to the larger vacancy volume and perfect spatial symmetry of Ti vacancies. The binding energies of a single He atom with HenV (n=0-3) clusters are all positive, and the segregation of He atoms on the inner surface of the vacancy is closer to the center of the vacancy, indicating that the He-vacancy has a stronger trapping ability for He atoms. The present research results provide a theoretical foundation of vacancy trapping mechanism for He atoms in Be12Ti, which is extremely important for the nucleation and growth mechanism of He bubbles in Be12Ti.

Asymmetry in sprinting: An insight into sub-10 and sub-11 s men and women sprinters.

We assessed sprint mechanical asymmetry in world-class competitors and evaluated whether inter-limb sex-based differences in sprinting mechanics exist. The eight finalists in the men's and women's 100m events at the 2017 IAAF World Championships were studied. Five high-speed cameras (150Hz) were used to capture two consecutive steps of the whole body between 47.0m and 55.5m from the start, while four additional cameras (250Hz) focussed on the lower extremities. A total of 33 spatio-temporal, touchdown and toe-off joint angles, and horizontal and vertical foot velocity parameters were extracted through three-dimensional analysis. Group mean asymmetry scores were assessed using the symmetry angle (SA) where scores of 0% and 100% represent perfect symmetry and perfect asymmetry, respectively. Although considered generally low (SA <3% for 22 out of 33 parameters), the magnitude of mechanical asymmetry varied widely between sprinters of the same sex. However, there was no mean SA scores difference between men and women for any stride mechanical parameters (all p≥0.064). Asymmetry scores were inconsistent between parameters and phases (touchdown vs toe-off instants), and sprinting mechanics were generally not related to asymmetry magnitudes. In summary, low to moderate asymmetry is a natural phenomenon in elite sprinting. Asymmetry was inconsistent between parameters and competitors during near maximum velocity running, yet mean values for a given parameter generally did not differ between sexes. Sprinters' performances were not related to their SA scores.

A study of transmission on cylindrical photonic quasicrystals

We study the transmittance spectra of light waves propagating on binary quasiperiodic cylindrical stackings. Such structures are called Cylindrical Photonic Quasicrystals (CPQs). In our model, Maxwell's equations are solved, and amplitudes of fields on distinct layers, for each generation of the cylindrical stackings, are linked through appropriate boundary conditions. Then, a transfer-matrix formalism is used to obtain the allowed and forbidden modes. We use both SiO 2 and TiO 2 as the binary components of the CPQs, and consider four distinct aperiodic stackings: Thue–Morse, Fibonacci, Octonacci, and Double–Period. Our results show that the transmission spectra for TE and TM waves, in all generations of the four sequences, did not present a perfect specular symmetry for both SiO 2 and TiO 2 . Also, we found that the transmission rates of the TE waves are higher than the ones of the TM waves. We also observed for Fibonacci and Octonacci CPQs that, for TM modes only, there exist refraction-index-independent bandgaps. • We analyze the reflection, transmission, and absorption spectra of electromagnetic waves. • The waves propagate in Cylindrical Photonic Quasicrystals (CPQs). • We consider four distinct CPQs: Fibonacci, Octonacci, Thue--Morse and Double-Period. • Our results show that the transmission spectra for TE and TM waves did not present a perfect specular symmetry. • We also observed for Fibonacci and Octonacci CPQs that two refraction-index-independent bandgaps exist for TM modes only.

Terahertz Broadband Absorber Based on a Combined Circular Disc Structure.

To solve the problem of complex structure and narrow absorption band of most of today′s terahertz absorbers, this paper proposes and utilizes the finite element (COMSOL) method to numerically simulate a broadband absorber based on a straightforward periodic structure consisting of a disk and concentric ring. The final results show that our designed absorber has an absorption rate of over 99% in the broadband range of 9.06 THz to 9.8 THz and an average of over 97.7% in the ultra-broadband range of 8.62 THz to 10 THz. The reason for the high absorption is explained by the depiction of the electric field on the absorber surface at different frequencies. In addition, the materials for the top pattern of the absorber are replaced by Cu, Ag, or Al, and the absorber still achieves perfect absorption with different metal materials. Due to the perfect symmetry of the absorber structure, the absorber is very polarization-insensitive. The overall design is simple, easy to process and production. Therefore, our research will offer great potential for applications in areas such as terahertz electromagnetic stealth, sensing, and thermal imaging.