Octagonal Arrangement Research Articles

Numerical analysis of microstructured optical fibers based on flint glass for ultra-high nonlinearity, low loss, and broadband dispersion compensation across telecom bands

This research investigates the potential of flint glass as a foundational material for photonic crystal configurations designed to achieve high nonlinear coefficients across various communication wavelengths. We explore dispersion management within telecom bands using flint glass-based micro-structured optical fibers, employing numerical analysis via the finite element method to assess optical properties. In this study, three different basic MOF structures (hexagonal, square, and octagonal) were created using flint glass background material rather of the commonly utilized fused silica material, and the numerically was assessed in contrast to prior studies and designs. Among the configurations studied, the octagonal arrangement (FGO-MOF) excels in dispersion compensation, achieving −136.6 ps/(nm.km) at 1.55 µm. Conversely, the hexagonal air hole ring cladding design (FGH-MOF) displays higher nonlinearity (770.5 W−1.km−1), a smaller effective area (1.115 µm2), and a high numerical aperture (0.6378). In contrast, the square air hole ring cladding optical fiber (FGS-MOF) exhibits low confinement loss (6.309 × 10−7 dB/cm) at 1.55 µm but with comparatively less favorable optical properties. Our study demonstrates that the hexagonal microstructured optical fiber with flint glass (FGH-MOF) offers superior performance in dispersion compensation, nonlinearity, and low loss within telecom bands. This finding suggests promising applications in high-bit-rate communication systems, biomedical sensing, and supercontinuum generation, presenting exciting avenues for further research and practical implementation.

Nano-onions based on chitosan: Production and characterization

This work presents the morphology and characterization of chitosan nanoparticles crosslinked with lecithin in the form of nano-onions obtained by an easy, economical, and possibly scalable method from a polymeric precursor known as chitosan. The creation of new products by using shrimp waste is a fundamental factor in avoiding water pollution. These materials have a positive impact as they add value to waste, and they provide the opportunity to decrease pollution. Chitosan nano-onions were synthesized by an environmentally friendly, easy, and inexpensive method using chitosan as a natural source. Chitosan nano-onions (CSNO) were characterized by using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), dynamic light scattering (DLS) and specific surface area (SSA). The nano-onions characterization obtained by FTIR shows the presence of carbonyl groups at a wavenumber of 1752.12 cm–1, while the phosphate groups attributed to lecithin are observed at 1156.88 cm–1. XRD analysis confirmed an amorphous structure, while SEM images presented a globular morphology with concave surfaces. TEM analysis showed that the nano-onions are congregated in a unique structure that includes nanotubes. The CSNO average diameter by DLS was 442.5 nm with an octagonal arrangement, and a polydispersity index (PDI) of 0.532 and 31.9 mV. The average size of CSNO, the PDI, and the value of zeta potential were indicators of a stable dispersion with a specific superficial area measured by the Brunauer-Emmett-Teller (BET) method of 1.4 m2 g–1. The results of the chitosan-lecithin nano-onions characterization indicate changes in the surface of the material with a larger total surface area and pore structure, compared to that of pure chitosan. According to the results of the CHNO characterization, they could be used as adsorbents for contaminants and they also have a potential application in the biomedical area, mainly as drug encapsulation material.

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Three dimensional flow over elliptic cylinders arrays in octagonal arrangement

A numerical study of flow characteristics around eight elliptic cross-section cylinders in an octagonal configuration is presented. The axis ratio of elliptic cylinder is taken as 1:2. Three spacings between the cylinders (0.07 m, 0.14 m and 0.2 m), two angles of attack (α=0° and α=15°) and two Reynolds numbers (Re=4060 and Re=45800) are considered to investigate the parametric influences. The flow is modelled using three-dimensional large eddy simulation. Simulations are performed by utilizing ANSYS Fluent software. The results comprise of flow patterns and force coefficients (drag and lift). It is seen that both the drag and lift forces acting on the cylinders vary with the spacings values, angle of attack and Reynolds numbers. The lift force peaks at α=15° and Reynolds number 45800. The drag force on the upstream cylinder reaches its peak at α=0° and Reynolds number 4060. It is observed that the drag on the upstream cylinders decreases as the value of the Reynolds number increases. Contours of velocity and subgrid turbulent viscosity are also presented. Moreover, it is concluded from the present study that the effect of change in the Reynolds number on flow characteristics is more significant as compared to the change in the spacing between the cylinders.

Extracellular Matrix Alignment Directs Provisional Matrix Assembly and Three Dimensional Fibrous Tissue Closure.

Gap closure is a dynamic process in wound healing, in which a wound contracts and a provisional matrix is laid down, to restore structural integrity to injured tissues. The efficiency of wound closure has been found to depend on the shape of a wound, and this shape dependence has been echoed in various in vitro studies. While wound shape itself appears to contribute to this effect, it remains unclear whether the alignment of the surrounding extracellular matrix (ECM) may also contribute. In this study, we investigate the role both wound curvature and ECM alignment have on gap closure in a 3D culture model of fibrous tissue. Using microfabricated flexible micropillars positioned in rectangular and octagonal arrangements, seeded 3T3 fibroblasts embedded in a collagen matrix formed microtissues with different ECM alignments. Wounding these microtissues with a microsurgical knife resulted in wounds with different shapes and curvatures that closed at different rates. Observing different regions around the wounds, we noted local wound curvature did not impact the rate of production of provisional fibronectin matrix assembled by the fibroblasts. Instead, the rate of provisional matrix assembly was lowest emerging from regions of high fibronectin alignment and highest in the areas of low matrix alignment. Our data suggest that the underlying ECM structure affects the shape of the wound as well as the ability of fibroblasts to build provisional matrix, an important step in the process of tissue closure and restoration of tissue architecture. The study highlights an important interplay between ECM alignment, wound shape, and tissue healing that has not been previously recognized and may inform approaches to engineer tissues. Impact statement Current models of tissue growth have identified a role for curvature in driving provisional matrix assembly. However, most tissue repair occurs in fibrous tissues with different levels of extracellular matrix (ECM) alignment. Here, we show how this underlying ECM alignment may affect the ability of fibroblasts to build new provisional matrix, with implications for in vivo wound healing and providing insight for engineering of new tissues.

Wave-Driven Assembly of Quasiperiodic Patterns of Particles.

We theoretically show that a superposition of plane waves causes small (compared to the wavelength) particles dispersed in a fluid to assemble in quasiperiodic two or three-dimensional patterns. We experimentally demonstrate this theory by using ultrasound waves to assemble quasiperiodic patterns of carbon nanoparticles in water using an octagonal arrangement of ultrasound transducers, and we document good agreement between theory and experiments. The theory also applies to obtaining quasiperiodic patterns in other situations where particles move with linear waves, such as optical lattices.

Long-term tracking of circumpolar cyclones on Jupiter from polar observations with JunoCam

We use observations from the JunoCam instrument on the Juno spacecraft to map the polar regions of Jupiter between 2016 and 2018. These polar maps track the long-term evolution of the pentagonal and octagonal structures of circumpolar cyclones (CPCs). The south-polar pentagonal and north-polar octagonal arrangements of the CPCs have remained largely stable over the last 2 years of observation. The morphologies of individual cyclones also remain largely stable for 1–2 years, although some changes are observed, so that the location of each CPC is uniquely identifiable. At both north and south poles, individual cyclones move around the center to a limited extent, and there is a gap of variable width between one pair of south polar CPCs. Measurements at consecutive closest approaches (perijoves, 53 days apart) show small movements of individual cyclones both eastward and westward. However, the south-polar CPCs have a long-term systematic westward drift rate of 1.5 ± 0.2° per orbit or 0.040 ± 0.005 m/s, whereas north polar CPCs do not show a consistent drift in longitude. Around the perimeter of the southern pentagon, we detect no rapid jet in short-term animations, and we provide evidence that anticyclonic white ovals may have a range of longitudinal drifts between −44 and +15° per orbit (+1.8 to −0.7 m/s). Measurement of the angular velocities within the cyclones shows increasing angular velocity with decreasing radius, except in the inner bright cloud deck of one class of northern CPCs, which are inferred to have smaller or even negative angular velocities very near the center. Tangential wind velocities within the cyclones range up to 100 m/s (and even >100 m/s in the southern polar cyclone) and are maximal between radii of ~900–1600 km. Overall, we find that the behavior of the polar cyclones constellations compares well to vortex crystal theory, even though the theory does not include anticyclonic vorticity.

Clues to basis of exploratory behaviour of theC. eleganssnout from head somatotropy

Wave propagation during locomotory movements of Caenorhabditis elegans is constrained to a single dorso/ventral plane. By contrast, the tip of the head (snout) can make rapid exploratory movements in all directions relative to the body axis. These extra degrees of freedom are probably important for animals to seek and identify desirable passages in the interstices of the three-dimensional matrix of soil particles, their usual habitat. The differences in degrees of freedom of movement between snout and body are reflected in the innervation of the musculature. Along the length of the body, the two quadrants of dorsal muscle receive common innervation as do the two quadrants of ventral muscle. By contrast, muscles in the snout have an octagonal arrangement of innervation. It is likely that the exploratory behaviour of the snout is mediated by octant-specific motor and sensory neurons, together with their associated interneurons. The well-defined anatomical structure and neural circuitry of the snout together with behavioural observations should facilitate the implementation of models of the neural basis of exploratory movements, which could lead to an understanding of the basis of this relatively complex behaviour, a behaviour that has similarities to foraging in some vertebrates.This article is part of a discussion meeting issue 'Connectome to behaviour: modelling C. elegans at cellular resolution'.

Low-temperature behaviour of K2Sc[Si2O6]F: determination of the lock-in phase and its relationships with fresnoite- and melilite-type compounds.

K2Sc[Si2O6]F exhibits, at room temperature, a (3 + 2)-dimensional incommensurately modulated structure [a = 8.9878 (1), c = 8.2694 (2) Å, V = 668.01 (2) Å3; superspace group P42/mnm(α,α,0)000s(-α,α,0)0000] with modulation wavevectors q1 = 0.2982 (4)(a* + b*) and q2 = 0.2982 (4)(-a* + b*). Its low-temperature behaviour has been studied by single-crystal X-ray diffraction. Down to 45 K, the irrational component α of the modulation wavevectors is quite constant varying from 0.2982 (4) (RT), through 0.2955 (8) (120 K), 0.297 (1) (90 K), 0.298 (1) (75 K), to 0.299 (1) (45 K). At 25 K it approaches the commensurate value of one-third [i.e. 0.332 (3)]: thus indicating that the incommensurate-commensurate phase transition takes place between 45 K and 25 K. The commensurate lock-in phase of K2Sc[Si2O6]F has been solved and refined with a 3 × 3 × 1 supercell compared with the tetragonal incommensurately modulated structure stable at room temperature. This corresponds to a 3 × 1 × 3 supercell in the pseudo-orthorhombic monoclinic setting of the low-temperature structure, space group P2/m, with lattice parameters a = 26.786 (3), b = 8.245 (2) c = 26.824 (3) Å, β = 90.00 (1)°. The structure is a mixed tetrahedral-octahedral framework composed of chains of [ScO4F2] octahedra that are interconnected by [Si4O12] rings with K atoms in fourfold to ninefold coordination. Distorted [ScO4F2] octahedra are connected to distorted Si tetrahedra to form octagonal arrangements closely resembling those observed in the incommensurate structure of fresnoite- and melilite-type compounds.

Parallel imaging in non-bijective, curvilinear magnetic field gradients: a concept study

ObjectivesThe paper presents a novel and more generalized concept for spatial encoding by non-unidirectional, non- bijective spatial encoding magnetic fields (SEMs). In combination with parallel local receiver coils these fields allow one to overcome the current limitations of neuronal nerve stimulation. Additionally the geometry of such fields can be adapted to anatomy.Materials and methodsAs an example of such a parallel imaging technique using localized gradients (PatLoc)- system, we present a polar gradient system consisting of 2 × 8 rectangular current loops in octagonal arrangement, which generates a radial magnetic field gradient. By inverting the direction of current in alternating loops, a near sinusoidal field variation in the circumferential direction is produced. Ambiguities in spatial assignment are resolved by use of multiple receiver coils and parallel reconstruction. Simulations demonstrate the potential advantages and limitations of this approach.Results and conclusionsThe exact behaviour of PatLoc fields with respect to peripheral nerve stimulation needs to be tested in practice. Based on geometrical considerations SEMs of radial geometry allow for about three times faster gradient switching compared to conventional head gradient inserts and even more compared to whole body gradients. The strong nonlinear geometry of the fields needs to be considered for practical applications.

Diisopropylammonium 3,5,6-trichloropyridin-2-olate

In the title salt, C6H16N+·C5HCl3NO−, the cation links to the anion, which is almost planar, through an N—H⋯O hydrogen bond. Inter­molecular hydrogen bonds link two cations and two anions into a centrosymmetric cluster. The atoms involved in the hydrogen bonding form a planar octa­gonal arrangement in the crystal structure.

Temperature dependence of the modulation wavelength in Co-åkermanite

Two-dimensional modulation in synthetic Co-åkermanite, Ca2CoSi2O7, has been precisely studied using synchrotron X-ray diffraction methods in the temperature range between 180 and 523 K to determine the temperature dependence of q (the magnitude of the primary wavevectors of modulation waves). Three kinds of plateau-like regions are observed for q ∼ 2/7, 3/10 and 4/13 in addition to the low-temperature commensurate phase (q = 1/3). Using a simulation method we were able to generate nearly commensurate structures. The most probable structure of incommensurate Co-åkermanite is octagonal arrangements of the bundles along the c-axis, which are composed of four CaO6 arrays and a central array of CoO4 tetrahedra.

メリライト族鉱物のインコメンシュレート構造における大規模規則性とその温度変化

The structures of the melilite (three compounds) have been determined in the range from room temperature up to 773 K. The structures of incommensurate (IC) phase are characterized by bundles of four arrays of the six-coordinated Ca polyhedra with T 1 tetrahedra along the c-axis. The IC phases undergo the phase transition into the normal phases at elevated temperatures. The change of the modulated structure has been clarified by construction of the structures using the desired q-values and the modulation amplitudes determined at 293 K. The change of IC structures is characterized by variable distribution of bundle and octagonal arrangements of them. Large-scale regularities with sizes much larger than the modulation wavelength are also formed in the structures. The structure of commensurate phase of Ca2CoSi2O7 has been determined based on the results of simulation.

Variation of large-scale regularity in modulated structures of Ca2CoSi2O7 studied by a simulation method.

The period of two-dimensional modulation in Ca2CoSi2O7 varies with temperature (q = 0.285-1/3). The change in the modulated structure with the variation of q has been clarified by the construction of the structures using various q values and the modulation amplitudes determined at 293 K [q = 0.2913 (1), tetragonal]. The features of the modulated structures are characterized by the formation of CaO6 polyhedra and the variable distribution of bundles along the c-axis, composed of four arrays of CaO6 polyhedra and an array of CoO4 tetrahedra. The formation of octagonal arrangements of the bundles is a typical feature of the structures in the incommensurate phase. Large-scale regularities with sizes much larger than the modulation wavelength are also formed in the structures.

Attachment in an interpersonal context.

Attachment theory is essentially a child-centred theory which is not readily adaptable to the relating of adults. Dependence is proposed as the adult equivalent of attachment. Both attachment and dependence have both a closeness-seeking component and an upwardly directed component. From this observation emerges a theory of relating constructed around a horizontal axis concerning closeness seeking versus distance seeking and a vertical axis concerning upwardly directed behaviour versus downwardly directed behaviour. By the insertion of four intermediate positions, an octagonal arrangement of relating objectives is created which resembles the interpersonal circle. The theory differs from orthodox interpersonal theory in the clear distinction which is drawn between positive relating and negative relating. Three classes of negative relating are described. As in attachment theory, continuities are established between the relating of animals and the relating of humans. It is tentatively shown how the 10 DSM-IV personality disorders might be accommodated within the structure of the octagon. Psychotherapy based upon interpersonal theory is described. Two instruments for measuring negative relating are described: the Person's Relating to Others Questionnaire, which is a general measure of relating, and the Couple's Relating to Each Other Questionnaire, which measures specifically interrelating within couples. The usefulness of these in measuring change in psychotherapy is illustrated.