Concentric Circular Structures Research Articles

A 4-port flexible MIMO antenna with isolation enhancement for wireless IoT applications

This paper presents a conformal, miniaturized, and geometrically simple monopole antenna designed for Vehicle–to–Everything (V2X) communications. The antenna consists of a flexible substrate, radiating patch, ground, and metallic stubs. Meandered lines are added to the U-shaped radiator to achieve the required bandwidth of the antenna. The antenna has |S11|< −10 dB magnitude from 5.06 to 7.24 GHz, attaining a peak low magnitude of–68 dB. The antenna is configured into a 4-port Multiple–Input–Multiple–Output (MIMO) setup to minimize the mutual coupling between its elements. The proposed flexible MIMO antenna offers bandwidth from 5.37 to 7.34 GHz and a peak moderate gain of 4.63 dBi with omnidirectional stable radiation patterns. To improve the mutual coupling, two hollow concentric circular structures, in combination with a pair of stub networks are integrated between the elements of the MIMO system. The transmission coefficient and surface current analysis confirm the effectiveness of the decoupling structure. The presented MIMO antenna is characterized by high isolation, a low envelope correlation coefficient (ECC), and high diversity gain, suitable for V2X MIMO communication scenarios.

High-directivity far-field radiation of quantum dot-based single-photon emitter coupled to polymeric circular waveguide resonant grating

Solid-state single-photon emitters (SPEs) commonly encounter the limitation of quasi-omnidirectional radiation patterns, which poses challenges in utilizing their emission with conventional optical instruments. In this study, we demonstrate the tailoring of the far-field radiation patterns of SPEs based on colloidal quantum dots (QDs), both theoretically and experimentally, by employing a polymer-based dielectric antenna. We introduce a simple and cost-effective technique, namely low one-photon absorption direct laser writing, to achieve precise coupling of a QD into an all-polymer circular waveguide resonance grating. By optimizing the geometry parameters of the structure using 3D finite-difference time-domain simulations, resonance at the emission wavelength of QDs is achieved in the direction perpendicular to the substrate, resulting in photon streams with remarkably high directivity on both sides of the grating. Theoretical calculations predict beam divergence values below 2°, while experimental measurements using back focal plane imaging yield divergence angles of approximately 8°. Our study contributes to the evaluation of concentric circular grating structures employing low refractive index polymer materials, thereby expanding the possibilities for their application.

Effect of graphene-oxide-modified osteon-like concentric microgrooved surface on the osteoclastic differentiation of macrophages.

This study aimed to investigate the effect of new biomimetic micro/nano surfaces on the osteoclastic differentiation of RAW264.7 macrophages by simulating natural osteons for the design of concentric circular structures and modifying graphene oxide (GO). The groups were divided into smooth titanium surface group (SS), concentric microgrooved titanium surface group (CMS), and microgroove modified with GO group (GO-CMS). The physicochemical properties of the material surfaces were studied using scanning electron microscopy (SEM), contact-angle measurement, atomic force microscopy, X-ray photoelectron spectroscopy analysis, and Raman spectroscopy. The effect of the modified material surface on the cell biological behavior of RAW264.7 was investigated by cell-activity assay, SEM, and laser confocal microscopy. The effect on the osteoclastic differentiation of macrophages was investiga-ted by tartrate-resistant acid phosphatase (TRAP) immunofluorescence staining and quantitative real-time polymerase chain reaction (qRT-PCR) experiments. Macrophages were arranged in concentric circles along the microgrooves, and after modification with GO, the oxygen-containing groups on the surface of the material increased and hydrophilicity increased. Osteoclasts in the GO-CMS group were small in size and number and had the lowest TRAP expression. Although it promoted the proliferation of macrophages in the GO-CMS group, the expression of osteoclastic differentiation-related genes was lower than that in the SS group, and the difference was statistically significant (P<0.05). Concentric circular microgrooves restricted the fusion of osteoclasts and the formation of sealing zones. Osteomimetic concentric microgrooves modified with GO inhibited the osteoclastic differentiation of RAW 264.7 macrophages.

Analytical Solution for Wave Diffraction by a Concentric Three-Cylinder System near a Vertical Wall

In this study, a semi-analytical model was developed to study wave diffraction around a concentric three-cylinder system near a wall based on linear potential theory. As a critical element, the target problem is transformed into bidirectional incident wave diffraction around two concentric structures based on the image principle and an analytical solution is obtained through eigenfunction expansion combined with a matching technique and Graf’s addition theorem. The validity of the proposed model was verified by comparing its results to known values. Parametric studies on porosity, annular spacing, incident angle, space between the structure and wall, and water depth were performed. The hydrodynamic loads and free-surface elevations in the system were calculated and compared to those reported in existing works on impermeable and permeable cylinders near a wall. The results indicate that the wave loads and run-ups on the exterior cylinder increase significantly based on the existence of the wall. However, based on the presence of an exterior porous protective structure, a significantly reduced influence of the wall on the interior cylinder can be observed. Considering the widespread use of concentric circular structures in ocean engineering, it is essential to conduct study on the hydrodynamic performance of concentric systems near walls, which can provide useful information for the design of marine structures.

MSE-based analysis of circular grating self-images for testing beam collimation.

Mean square error (MSE) is used to detect variations in the period between a pair of self-images formed at two different Talbot planes of a circular grating (CG) using a beam splitter in a conventional collimation testing setup. By varying the position of the collimator with respect to the point source, the collimation state of the input beam is varied and the computed MSEs are analyzed to deduce the collimation state. The minimum value of the MSE indicates beam collimation. For equal sized images, the MSE relates to the sum of the squared difference between spatially correspondent pixel values of the images. Since comparison of the spatial information takes place at the pixels' level, any small spatial shift between patterns of the two self-images due to collimation error is detected with precision. The CG, comprising concentric circular structures, offers added advantage in terms of error-free alignment, which otherwise is error prone and cumbersome with widely used linear gratings. It is well known that self-images formed with circular grating have good fidelity with less optical distortions and irregularities, especially at distant Talbot planes. Also, the self-images formed with circular gratings are less affected by lens aberrations, tilts, misalignments, etc. Higher sensitivity in beam collimation is achievable, as self-images of a CG can be recorded at widely separated Talbot planes, and analyzed using an algorithm which is more responsive toward any minute difference between them. The suggested method is promising for a quick collimation setting with good accuracy and enhanced sensitivity.

Concentric Structures and Hydrothermal Venting in the Western Desert, Egypt

Large-scale concentric structures are enigmatic geological features observed on the Earth surface and on other planetary bodies. Their formation has been attributed to several processes. Here we describe for the first time the results of mapping and characterization of ∼100 large concentric circular structures found in Early Cenomanian argillaceous strata of the Bahariya depression (Egyptian Western Desert). The geological processes that lead to the formation of these features have remained so far elusive. We investigate the concentric structures with a multidisciplinary approach combining field observations, statistical analysis, soil-flux gas measurements and laboratory analyses of rock samples. The whole depression is dissected by the ∼90 km long N60°E-striking dextral strike-slip Bahariya fault. Effusive lavas and shallow intrusions crop out in the down faulted blocks. The mapped circular structures increase in number approaching the fault zone. These features are up to 10 m high and 625 m wide, have a morphology similar in shape to impact craters with steeper external flanks and a gently dipping internal subsided zone. Halite-cemented brecciated sediments from different geological units have been sampled in the central part of the concentric circular structures implying a subsurface mechanism involved in their formation. Petrography analyses revealed also the presence of high- and low-temperature minerals (e.g., Ba-K-feldspars and ferroaluminoceladonite) suggesting former phases of hydrothermal circulation. Soil-gas flux profiles (CO₂ and CH₄) reveal a modest CO₂ increase when crossing the central part of the circular structures inferring enhanced permeability. Field and laboratory data are consistent with a scenario envisaging a diffused and vigorous hydrothermal venting. The proposed scenario includes multiple phases where several geological elements and processes interact. The Bahariya fault, which activity initiated during the Late Cretaceous, provided pathways for Miocene magma ascent toward the surface and for the development of a network of subsurface intrusions in the organic-rich sedimentary rocks of the Bahariya Formation. The interaction of the igneous intrusions with carbon-rich sedimentary deposits produced overpressured fluids, causing the formation of sparse hydrothermal vents at the surface. The elongation of the main axis of the vents and the deformed structures located within the strike-slip zone suggest that faulting controlled the emplacement and the final shape of some of the hydrothermal vents. We speculate that this system may represent a palaeo sediment-hosted hydrothermal system and could be related to the opening of the Red Sea.

Solvent induced nanostructure formation in polymer thin films: The impact of oxidation and solvent

Polystyrene (PS) films, upon deep UV exposure, readily formed nanostructures when soaking in a solvent. In this study, we provide compelling evidence confirming the critical roles of oxidation and solvent for the nanostructure formation. When the irradiation was carried out in argon, no structure could be generated on the films. Solvent is another critical parameter. Ordered concentric circular structures formed when the UV-irradiated PS films were soaked in an aromatic solvent such as toluene, benzene, and xylene. Addition of n-heptane to toluene reduced the size of the circles. The concentric circular structures disappeared when 0.1% methanol was added to the soaking solvent toluene. X-ray photoelectron spectroscopy (XPS) showed that the percentage of O-containing products decreased with increasing amount of added methanol, indicating that the polar solvent prevented the structure formation by removing the oxidation products from the films.

Laser-induced circular nanostructures in fused silica assisted by a self-assembling chromium layer

Nanostructures have a widespread field of applications and are of growing industrial importance. However, the economic fabrication of nanostructures poses a critical challenge. In this work, a fundamental research of a laser-induced surface nanostructuring of fused silica using the dynamic self-assembling structure formation in metal layers is presented. This method may offer promising opportunities for nanostructuring of dielectrics. This new approach is demonstrated by the formation of randomly distributed concentric nanostructures into fused silica. The irradiation of chromium-covered fused silica samples with a KrF excimer laser results in melting, partial ablation, restructuring, and resolidification of both the metal layer and the dielectric surface. In this way, concentric circular structures into the dielectric were formed with dimensions that can be controlled by the laser fluence Φ and by the pulse number N. The distance of the concentric rings increases with increasing laser fluence. The experimental results were compared with simulated structure dimensions taking into account the heat equation and the Navier–Stokes equation. Despite the currently applied decoupled approach for the simulations, i.e. separating the heat equation and the fluid flow, a good agreement of simulation results with experimental data was achieved.

Clinical analysis of 42 cases of chronic expanding intracerebral hematoma

To summarize our own experiences of managing chronic expanding intracerebral hematoma (CEICH) and discuss its diagnosis and treatment. The courses of CEICH, clinical and imaging features, intraoperative findings, pathological examinations and follow-up outcomes were reviewed retrospectively. The relevant literatures were reviewed simultaneously. The course of CEICHs ranged from 22 days to 10 years. Twenty-three cases (54.8%) were misdiagnosed as cystic gliomas, cystic gliomas, brain cysticercoses, brain abscesses and tumor strokes, etc. The misdiagnostic rate had decreased to 19.0% since June 1997. Thirty-eight patients underwent surgical operations and 4 had puncture drainage of hematoma. There was no operative death. Thirty-three cases achieved an excellent recovery and 9 cases had varying degrees of nervous dysfunctions. The follow-up period was 1-21 years. One patient had recurrence after 10 years. Among the cases of multiple CEICH, two lesions underwent no surgical treatment. One increased obviously after 7 years and another disappeared. The following five points may be used as the diagnostic criteria of CEICH: (1) intracerebral cystic space-occupying lesions on brain images; (2) circular or circle-like enhancement around lesions; (3) a mixed signal of concentric circular lamellar structures on MRI T1WI; (4) abnormal vascular lesions on CTA, MRA or DSA; (5) clinical signs and symptoms of slow progress of intracranial pressure. CEICHs with clinical symptoms of local mass effect shall be obliterated surgically. The abnormal tissues in cyst wall of hematoma should be resected. Small hematomas (< 2 cm) may be followed up.

Evidence for pervasive mud volcanism in Acidalia Planitia, Mars

We have mapped 18,000+ circular mounds in a portion of southern Acidalia Planitia using their sizes, shapes, and responses in Nighttime IR. We estimate that 40,000+ of these features could occur in the area, with a distribution generally corresponding to the southern half of the proposed Acidalia impact basin. The mounds have average diameters of about 1 km and relief up to 180 m and most overlie units mapped as Early Amazonian. High resolution images of mound surfaces show relatively smooth veneers, apron-like extensions onto the plains, moats, and concentric circular crestal structures. Some images show lobate and flow-like features associated with the mounds. Albedo of the mounds is generally higher than that of the surrounding plains. Visible and near-infrared spectra suggest that the mounds and plains have subtle mineralogical differences, with the mounds having enhanced coatings or possibly greater quantities of crystalline ferric oxides. Multiple analogs for these structures were assessed in light of new orbital data and regional mapping. Mud volcanism is the closest terrestrial analogy, though the process in Acidalia would have had distinctly martian attributes. This interpretation is supported by the geologic setting of the Acidalia which sits at the distal end of the Chryse–Acidalia embayment into which large quantities of sediments were deposited through the Hesperian outflow channels. In its distal position, Acidalia would have been a depocenter for accumulation of mud and fluids from outflow sedimentation. Thus, the profusion of mounds in Acidalia is likely to be a consequence of this basin’s unique geologic setting. Basinwide mud eruption may be attributable to overpressure (developed in response to rapid outflow deposition) perhaps aided by regional triggers for fluid expulsion related to events such as tectonic or hydrothermal pulses, destabilization of clathrates, or sublimation of a frozen body of water. Significant release of gas may have been involved, and the extensive mud volcanism could have created long-lived conduits for upwelling groundwaters, providing potential habitats for an in situ microbiota. Mud volcanism transports minimally-altered materials from depth to the surface, and mud volcanoes in Acidalia, therefore, could provide access to samples from deep zones that would otherwise be inaccessible. Since the distal setting of Acidalia also would favor concentration and preservation of potentially-present organic materials, samples brought to the surface by mud volcanism could include biosignatures of possible past or even present life. Accordingly, the mounds of Acidalia may offer a new class of exploration target.

Regular arrangement of wall polymers in staphylococci.

Concentric circular structures were observed on the newly exposed surface of the wall of Staphylococcus epidermidis and on its isolated cross-wall. These structures were removed by treatment with trichloroacetic acid. Chemical analysis revealed that after treatment with trichloroacetic acid most of the wall phosphorus was extracted but more than half of the N-acetylglucosamine remained associated with the wall. These observations suggest that polysaccharides are likely to be arranged circularly on the surface of the wall.