Identical Rings Research Articles

Stimuli Induced Reversible Switching Between a Self-Assembled 2-Catenane and the Constituent Coordination Rings.

A pair of comparable sized C-shaped bis-monodentate ligands (L1 and L22+) and a linear bis-monodentate ligand (L3) complementing to the terminal-lengths of the C-shaped ligands have been identified. One-pot combination of cis-Pd(tmeda)2+, L1 and L3 (2 : 1 : 1 ratio) in water resulted an octa-cationic 2-catenane, [Pd2(tmeda)2(L1)(L3)]2 8+ in which two identical tetra-cationic macromonocyclic coordination rings are interlocked; however, a guest bound coordination ring was formed in presence of a selected di-anionic guest. Complexation of cis-Pd(tmeda)2+ with a mixture of L22+ and L3 (2 : 1 : 1 ratio) in water resulted the hexa-cationic macromonocyclic coordination ring, [Pd2(tmeda)2(L2)(L3)]6+ whereas a guest bound coordination ring was formed in the presence of the di-anionic guest. Addition of the guest to the preformed octa-cationic catenane caused ring separation to favour the guest-bound ring. This guest bound ring could be reverted to the 2-catenane by sequestering the bound guest using the relatively electron deficient hexa-cationic coordination ring. Thus, a design principle for reversible switching between a 2-catenane and the constituent macromonocyclic-rings using anion-binding/-sequestering as the core concept has been established.

Wide Frequency Multiphase Oscillator Designed by Coupling Two Identical Ring Voltage Controlled Oscillators

ABSTRACTThis work presents a novel wide tuning range ring voltage controlled oscillator (RVCO) designed to generate six‐phase signals. The proposed circuit is realized by coupling two identical three‐stage single‐ended inverter‐based RVCOs. The coupling network injects the common mode signals from one RVCO to the other one and vice versa in a cross‐connected manner. Three‐stage RVCOs used for coupling have been configured by modifying the conventional current‐starved RVCO. The proposed six‐phase RVCO is optimized using an improved version of non‐dominated Sorting Genetic Algorithm III (NSGAIII). In this algorithm, the sigma scaling method is used to control selection pressure and enhance the algorithm's performance. The proposed RVCO oscillates at 3.46 GHz. It can operate from 970 MHz to 4 GHz with a supply voltage of 1.5 V, demonstrating a wide frequency tuning range of 120%. Additionally, another six‐phase oscillator is proposed, achieved by capacitively coupling two identical three‐stage RVCOs. Both proposed oscillators are designed in TSMC 0.18 μm CMOS technology.

High-Pressure Rate Rules for Ether Alkylperoxy Radical Isomerization.

The first isomerization reaction of an alkylperoxy (RO2) radical holds significant importance in low-temperature oxidation, as it governs the branching ratios of the hydroperoxyalkyl (QOOH) radicals, which influence the competition between the chain-propagation and chain-branching reactions. In this study, we systematically calculated high-pressure rate rules for the RO2 isomerization reaction of monoethers, exploring 5-, 6-, 7-, and 8-membered ring transition states. Primary, secondary, and tertiary carbon sites, where both the abstracting peroxy group and the abstracted hydrogen are located, were considered, with particular emphasis on distinguishing between secondary carbons adjacent (alpha) and nonadjacent to the ether functional group. Using the G4//B3LYP/6-311++G(2df,2pd) level of theory and the transition state theory, we estimated the rate constants and the Arrhenius coefficient for over 120 possible isomerization reactions. We examined the effect of ring size and ring atoms, revealing that 6- and 7-membered ring isomerizations were generally the fastest. The impact of the ether functional group on transition states was investigated by comparing reactions with identical ring size, peroxy, and radical positions, but with the ether functional group positioned either outside (i.e., out) or inside (i.e., in) the transition state ring, leading to differences in the rate constants. When comparing to analogous alkane rate constants, differences of up to an order of magnitude were observed, underscoring the need for caution when assigning rate rules by analogy. We applied our rate constants in the di-iso-butyl ether kinetic model and evaluated their influence on low-temperature chemistry finding that they altered the branching ratios by up to a factor of 9, highlighting the significance of site-specific rate constants for more accurate low-temperature modeling.

Bonding and antibonding electromagnetic coupling in two interacting toroidal metamolecules

The existence of a toroidal-like eigenmode and its electromagnetic coupling in a system of dielectric particles are studied. A constituent structure (metamolecule) is made of a ring consisting of the radial arrangement of several vertically standing dielectric disks (meta-atoms). In the eigenstate of the given metamolecule, the second-order term related to the exact electric dipole in the multipole decomposition is much greater than the first-order term. This eigenstate is defined as a toroidal-like mode. Then, the characteristics of a system (metamacromolecule) composed of two identical rings are studied in both eigen- and excited states to reveal the peculiarities of the toroidal-like mode coupling. Similar to the well-known electric dipole-dipole and magnetic dipole-dipole interactions, the interaction of toroidal-like modes also appears in symmetric (bonding) and antisymmetric (antibonding) forms. Their excitation in the metamacromolecule depends on the propagation direction and polarization of the irradiating wave. The manifestation of toroidal-like mode coupling is confirmed by checking the extinction cross section and near-field distributions obtained from the full-wave numerical simulation and microwave experiment. A clear understanding of the nature of toroidicity is important from the fundamental physics perspective and practical implementation of metamaterials operated in such exotic states. Published by the American Physical Society 2024

Some Aspects of the Effects of Dry Friction Discontinuities on the Behaviour of Dynamic Systems

Most studies in the literature consider the value of the coefficient of dynamic friction to be constant. We studied the evolution of a dynamic system when the coefficient of friction results in different values depending on the contact surfaces. A system with four balls fixed on an aluminium plate was driven with constant velocity into motion on the coaxial races of two identical outer bearing rings. The assembly presents a motion with periodic variable amplitude between two extremes, a fact that suggests the presence of a periodical excitation. The test was repeated, but this time, new bodies were used, which were two identical bodies made of two balls rigidised via a short cylindrical rod. When the rings were driven into rotational motion, the two bodies performed different motions; if the bodies were inter-changed, the differences between the motions remained. The rings were analysed, and a small region on the race of one ring was observed, where the roughness was considerably greater than the rest of the surface. Then, a mathematical model for the dynamic system with different friction coefficients was proposed and solved. This model is capable of simulating different situations, such as oscillatory motion and circular motion, with or without separation of the contacting bodies. Here, we present a dynamic model with Hertzian contact points in the presence of dry friction, with the coefficient of friction changing suddenly on the contacting surfaces.

Study on the Conductivity Effect on the Characteristics of a Wideband Printed Dipole Antenna Implemented with Silver Nanoparticle Ink

This study examined a flexible composite wideband dipole antenna implemented with conductive silver nanoparticle ink having different conductivities. Two identical split ring resonators (SRRs) were designed to encompass each arm of a dipole element, and each dipole arm and its coupled SRR were printed on the top and bottom sides of a dielectric substrate. The overall dimensions of the compact antenna were 10 mm × 74.8 mm × 0.254 mm (0.053λo × 0.399λo × 0.0014λo at 1.6 GHz). The characteristics of the antenna with different conductivities were numerically investigated and experimentally confirmed. Our investigation aimed to ascertain the proposed antenna's response to different conductivity values and to determine the range of conductivity values that generates major changes in the antenna's performance characteristics in terms of impedance bandwidth, gain, and radiation efficiency. At conductivity values less than approximately 6.0 × 104 S/m, the number of generated resonances changed from three to two, and the antenna experienced a nearly 3-dB gain reduction when the conductivity approached 5.8 × 104 S/m.

CFZA camera: a high-resolution lensless imaging technique based on compound Fresnel zone aperture.

In lensless imaging using a Fresnel zone aperture (FZA), it is generally believed that the resolution is limited by the outermost ring breadth of the FZA. The limitation has the potential to be broken according to the multi-order property of binary FZAs. In this Letter, we propose to use a high-order component of the FZA as the point spread function (PSF) to develop a high-order transfer function backpropagation (HBP) algorithm to enhance the resolution. The proportion of high-order diffraction energy is low, leading to severe defocus noise in the reconstructed image. To address this issue, we propose a Compound FZA (CFZA), which merges two partial FZAs operating at different orders as the mask to strike a balance between the noise and resolution. Experimental results verify that the CFZA-based camera has a resolution that is double that of a traditional FZA-based camera with an identical outer ring breadth and can be reconstructed with high quality by a single HBP without calibration. Our method offers a cost-effective solution for achieving high-resolution imaging, expanding the potential applications of FZA-based lensless imaging in a variety of areas.

Design, Synthesis, and Biological Evaluation of Anti-prostate Cancer Agent

In search of more effective chemotherapeutics for the treatment of castration-resistant prostate cancer. The 1,3- thiazolidine-2,4-diones possess a wide diversity of important biochemical effects and interesting pharmacological properties. 1,9-diarylnona-1,3,6,8-tetraen-5-ones bearing two identical terminal heteroaromatic rings have been successfully synthesized through Wittig reaction followed by Horner-Wadsworth-Emmons reaction. The cell proliferation assay was employed to assess their anti-proliferative effects toward both androgen-sensitive and androgen-insensitive human prostate cancer cell lines. curcumin in inhibiting prostate cancer cell proliferation. It can be concluded from our data that 1,9-diarylnona-1,3,6,8-tetraen-5-one can serve as a new potential scaffold for the development of anti-prostate cancer agents.

Miniaturized Dual-Band SIW-Based Bandpass Filters Using Open-Loop Ring Resonators

This article presents two novel architectures of dual-band substrate-integrated waveguide (SIW) bandpass filters (BPFs). Initially, two identical open-loop ring resonators (OLRRs) were coupled face-to-face on the top of the SIW cavity to realize a dual-band single-pole BPF. To obtain two-pole dual-band characteristics, two OLRRs resonant units were assembled horizontally within the top metal layer of the SIW, which is a technique used for the first time in the literature. For demonstration purposes, two types of SIW filters loaded with OLRRs were designed and fabricated. The proposed filters feature an extremely compact size, a low insertion loss, and good selectivity. The single- and two-pole filters have an overall size of 0.012λg2 and 0.041λg2, respectively. The simulated and measured circuit responses are in good agreement.

Emergence and evolution of unusual inhomogeneous limit cycles displacing hyperchaos in three quorum-sensing coupled identical ring oscillators

We demonstrate that strongly asymmetric limit cycles can be observed in the system of three identical ring oscillators (3-gene networks known as Repressilators) globally coupled by signal molecule diffusion added to the model in a way like the known bacterial “quorum-sensing” mechanism. These cycles are stable over a wide interval of the coupling strengths where they expel the dominant hyperchaotic regime existing in three Repressilators in very large areas of parameters. The bifurcations of the inhomogeneous limit cycle, with a high-amplitude orbit for one oscillator and two low-amplitude identical orbits for the other two, are traced. Bifurcation analysis reveals an unusual cascade of bifurcations ended in the appearance of a new limit cycle with splitted (slightly nonidentical) low-amplitude orbits. Both cycles lose stability giving birth inhomogeneous chaos in the small parameter interval. Hyperchaos dominates in the parameter plane around the “island” with inhomogeneous limit cycles, and this accounts for very long hyper chaotic transients when the system is returning to stable asymmetric cycles after their perturbations. In turn, it is the cycles that contribute the asymmetric and often rather long pieces in hyperchaotic trajectories. The presented cycles differ from the known asymmetric attractors: inhomogeneous limit cycles born from “oscillation death” and the cycles observing in “smallest chimeras”.

Nonperturbative approach to magnetic response of an isolated nanoring in a strongly anharmonic confinement

It is a huge challenge in both classical and quantum physics to solve analytically the equation of motion in a strongly anharmonic confinement. For an isolated nanoring, we propose a continuous and bounded potential model, which patches up the disadvantages of the usual square-well and parabolic potentials. A fully nonlinear and nonperturbative approach is developed to solve analytically the equation of motion, from which various frequency shifts and dynamic displacements are exactly derived by an order-by-order self-consistent method. A series of new energy levels and new energy states are found, indicating an alternative magnetic response mechanism. In nominally identical rings, especially, we observe a diamagnetic-paramagnetic transition in the period-halving Φ0/2-current with Φ0 the flux quantum and a large increase in the Φ0-current at least one order of magnitude, which explain well the experimental observations. This work opens a new way to solve the strong or weak nonlinear problems.

NO2 Sensor Based on Faraday Rotation Spectroscopy Using Ring Array Permanent Magnets.

Faraday rotation spectroscopy (FRS) exploits the magneto-optical effect to achieve highly selective and sensitive detection of paramagnetic molecules. Usually, a solenoid coil is used to provide a longitudinal magnetic field to produce the magneto-optical effect. However, such a method has the disadvantages of excessive power consumption and susceptibility to electromagnetic interference. In the present work, a novel FRS approach based on a combination of a neodymium iron boron permanent magnet ring array and a Herriott multipass absorption cell is proposed. A longitudinal magnetic field was generated by using 14 identical neodymium iron boron permanent magnet rings combined in a non-equidistant form according to their magnetic field's spatial distribution characteristics. The average magnetic field strength within a length of 380 mm was 346 gauss. A quantum cascade laser was used to target the optimum 441 ← 440 Q-branch nitrogen dioxide transition at 1613.25 cm-1 (6.2 μm) with an optical power of 40 mW. Coupling to a Herriott multipass absorption cell, a minimum detection limit of 0.4 ppb was achieved with an integration time of 70 s. The low-power FRS nitrogen dioxide sensor proposed in this work is expected to be developed into a robust field-deployable environment monitoring system.

CRBFT: An Optimized Blockchain Algorithm for Edge-Based IoT System

In this article, a credit identity ring optimization blockchain algorithm (CRBFT) based on practical Byzantine fault tolerance (PBFT) is proposed to address the security problem for the network of Internet of Things (IoT). The contributions of this work are given as follows. First, combined with the edge computing architecture, CRBFT introduces the improved credit grading protocol and the improved ring signature scheme into the blockchain network, rewards or punishes the nodes through their behavior, changes the way of selecting the primary node, and ensures that the identity of the primary node will not be disclosed, so as to prevent the primary node from adaptive attack by Byzantine nodes, improve the reliability of the nodes participating in the consensus, and enhance the security of the system. Second, in order to reduce the communication traffic among nodes, CRBFT optimizes the consensus protocol, which not only reduces the time complexity of the traffic in the consensus stage from O ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${n}^{{2}}$ </tex-math></inline-formula> ) to O ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${n}$ </tex-math></inline-formula> ) but also improves the consensus efficiency of the system while ensuring the system security. Finally, CRBFT aims to measure the performance of CRBFT. This article is simulated and tested in three aspects: throughput (transactions per second), consistency delay, and communication overhead. Performance evaluation shows that CRBFT achieves lower communication overhead than PBFT. When the number of nodes is the same, CRBFT can obtain higher TPS and lower consistency delay. The results show that compared with PBFT, CRBFT can provide very competitive results.

Crystal Engineering of Ionic Cocrystals Sustained by Azolium···Azole Heterosynthons.

Crystal engineering of multi-component molecular crystals, cocrystals, is a subject of growing interest, thanks in part to the potential utility of pharmaceutical cocrystals as drug substances with improved properties. Whereas molecular cocrystals (MCCs) are quite well studied from a design perspective, ionic cocrystals (ICCs) remain relatively underexplored despite there being several recently FDA-approved drug products based upon ICCs. Successful cocrystal design strategies typically depend on strong and directional noncovalent interactions between coformers, as exemplified by hydrogen bonds. Understanding of the hierarchy of such interactions is key to successful outcomes in cocrystal design. We herein address the crystal engineering of ICCs comprising azole functional groups, particularly imidazoles and triazoles, which are commonly encountered in biologically active molecules. Specifically, azoles were studied for their propensity to serve as coformers with strong organic (trifluoroacetic acid and p-toluenesulfonic acid) and inorganic (hydrochloric acid, hydrobromic acid and nitric acid) acids to gain insight into the hierarchy of NH+···N (azolium-azole) supramolecular heterosynthons. Accordingly, we combined data mining of the Cambridge Structural Database (CSD) with the structural characterization of 16 new ICCs (11 imidazoles, 4 triazoles, one imidazole-triazole). Analysis of the new ICCs and 66 relevant hits archived in the CSD revealed that supramolecular synthons between identical azole rings (A+B-A) are much more commonly encountered, 71, than supramolecular synthons between different azole rings (A+B-C), 11. The average NH+···N distance found in the new ICCs reported herein is 2.697(3) Å and binding energy calculations suggested that hydrogen bond strengths range from 31-46 kJ mol-1. The azolium-triazole ICC (A+B-C) was obtained via mechanochemistry and differed from the other ICCs studied as there was no NH+···N hydrogen bonding. That the CNC angles in imidazoles and 1,2,4-triazoles are sensitive to protonation, the cationic forms having larger (approximately 4.4 degrees) values than comparable neutral rings, was used as a parameter to distinguish between protonated and neutral azole rings. Our results indicate that ICCs based upon azolium-azole supramolecular heterosynthons are viable targets, which has implications for the development of new azole drug substances with improved properties.

Metasurface around the side surface of an optical fiber for light focusing.

Optical fibers integrated with metasurfaces have drawn tremendous interest in recent years due to the great potential for revolutionizing and functionalizing traditional optics. However, in most cases, metasurfaces have been placed on the fiber end-facet where the area is quite limited. Here, by dressing a series of identical dielectric rings around the side surface of the microfiber and adjusting their positions along the microfiber axis, we extracted guided waves into free-space radiation with continuously controllable phase shift and achieved circular-arc-shaped line focusing. We demonstrated that the off-fiber foci could be rotated around the fiber axis by tuning the polarization of the guided waves. In addition, we demonstrated that the shape of the focus could be further tuned by introducing symmetry breaking into the dielectric rings. Our study provides a new dimension for the design of optical fiber devices decorated with metasurfaces.

Buckling resistance of the cylindrical shells with two secondary stiffening rings under external pressure

The common way to amplify strength and stiffness of the tank wall is to use the stiffening rings. These stiffening rings can be classified as the primary and secondary stiffening rings (PSRs and SSRs). PSR is placed around the top of the tank shell and it assists to avoid ovalization at the top when the open-top tank is exposed to the external pressure. PSR having small dimensions may be used for fixed roof tanks since the roof system attached to the top of the cylindrical shell provides a natural restraint at this location. On the other hand, one or more SSRs may be required to preclude local buckling in both fixed and open-top cylindrical steel tanks (CSTs) which are exposed to external pressure. The requirements of single secondary stiffening ring have been investigated in detail in previous studies. However, in same cases, a single SSR does not provide sufficient resistance to maintain stability over the entire shell height. Thus, buckling capacity of the CSTs with two identical secondary stiffening rings have been explored in this present work. Pursuant to this aim, the requirements for stiffness of the SSRs which are given in terms of minimum second moment of area (SMA) were evaluated by performing Linear Elastic Bifurcation Analysis (LBA) of CSTs under uniform external pressure. Analysis results show that minimum SMA expression proposed by Blackler underestimates critical buckling value for the tanks, having especially low height-to-diameter ratios and low radius-to-thickness ratios. Furthermore, to trace strength reduction in the tank due to geometrical imperfections, Geometrically Nonlinear Analysis including Imperfections (GNIA) was performed. Analysis findings affirm that thin-walled structures are very sensitive to geometrical imperfections.

Design and fabrication of a terahertz dual-plane hologram and extended-depth-of-focus diffractive lens

This work discusses the design and fabrication of a dual-plane terahertz (THz) hologram and an extended-depth-of-focus THz diffractive lens. The dual-plane THz hologram consists of 50 × 50 diffractive optical elements with identical element pixel size 1×1 mm, and the extended-depth-of-focus THz diffractive lens is designed with 25 concentric rings with identical ring width of 1 mm, resulting in same device dimension 50 mm × 50 mm. The height of the hologram pixels and concentric rings of the diffractive lens are optimized by nonlinear optimization algorithms with scalar diffraction theory based on Ray-Sommerfeld diffraction equation. Finite-Difference Time-Domain (FDTD) simulation results agree with optimization results obtained from the scalar diffraction theory for both the THz hologram and the THz diffractive lens. The demonstrated experimental results show that the proposed THz hologram and THz diffractive lens can generate the desired diffraction patterns. These diffractive structures have the potential to be applied in areas such as THz imaging, data storage, and displays.

Synchronization of Traveling Waves in Memristively Coupled Ensembles of FitzHugh–Nagumo Neurons With Periodic Boundary Conditions

Synchronization of traveling waves in two rings of FitzHugh–Nagumo neurons is studied. Coupling between neurons within each ring is dissipative, while one between rings is memristive. Complete synchronization of waves in identical rings in the presence of an initial phase shift between wave processes and partial synchronization of waves in the case of different coupling strengths inside the rings are considered. The influence of the initial states of memristive coupling on the synchronization of wave processes in the case of memristors with an infinitely long memory and with the forgetting effect is investigated.

Design of triangular shaped slotted patch antennas for both wideband and multiband applications

In this article two fractal geometry-based slotted patch antennas are designed to achieve wideband response with multiband characteristics and reduced cross polarized radiation in both E- and H-plane for all the resonating bands. The proposed antennas are fed with microstrip line feeding formed on a FR4 substrate of size 0.25𝜆0 × 0.25𝜆0 × 0.02𝜆0 mm3 and loaded with a partial ground plane at the bottom of the substrate. HFSS is used to design and simulate both the antennas. Wideband behavior and impedance matching of Antenna-1 are improved by optimizing the factor of iteration and length of the ground plane. Due to addition of 3 identical split ring resonators (SRR) with the antenna geometry leads to achieve multiband response in Antenna-2. The dimensions of the SRR connectors and feedline have been optimized through parametric analysis to match the impedance properly at all the three resonating bands. It has been found that simulated and measurement results of both the antennas are properly matched.

Phase‐shifted metasurface design for pseudo‐nondiffractive beam deflection

A transmission phase-shifted metasurface (PSM) array has been proposed for non-diffractive beam deflection. A PSM element consists of two identical semicircular rings and an I-shaped structure, which is symmetrically printed on both sides of the F4B substrate. According to the geometric optics, the phase distribution on the metasurface can be obtained. To achieve the desired phase distribution, the metasurface elements rotated at different angles are rearranged, since the phase of the transmitted wave is manipulated by rotating the metasurface element. Then, the standard horn is used to produce the sphere wave across the proposed metasurface array for the non-diffractive beam deflection. Simulated (measured) results show that the inclined non-diffractive beam can be generated at a tilted angle of 35° (34.9°) with a maximum non-diffractive distance of 100 mm (97.5 mm) at 10 GHz. The proposed metasurface array has the advantages of non-diffractive beam deflection, low sidelobes and miniaturisation.