Flexible Ring Research Articles

Synthesis and liquid crystal properties of benzoates containing 1,2,3-triazole

Two series of benzoates containing 1,2,3-triazole heterocyclic were prepared. The molecules containing alkyl chains of 12 ∼ 14 carbon atoms and with benzene ring as the central core show liquid crystal behaviors. After replacing benzene ring with cyclohexane, the compounds with short or long alkyl chains or ferrocene terminal group have no mesomorphic behavior. However, the compounds with medium length alkyl chain have lower melting point and wider mesomorphic domain than those with benzene ring as the central core containing the same length alkyl chain. This study adds new members to liquid crystal whose central core is a flexible ring.

Improved Design of Flange Mount Coaxial Connector With Low Passive Intermodulation Distortion

Imperfect electrical connections cause multiple problems in radio-frequency (RF) measurements, with passive intermodulation (PIM) being the most common one. This article proposes a new design approach to reduce the PIM distortion caused by the imperfect electrical connection in flange mount coaxial connectors. The proposed approach employs a flexible ring embedded in the outer conductor of the flange mount coaxial connector to improve the reliability of the metal electrical connection. A simulation model is further developed to analyze the effects of the embedded ring on the signal transmission performance. The effectiveness of the proposed approach is verified by experiments, demonstrating that the improved design can not only decrease the PIM level by up to 9 dB, but also show a good reliability and stability in the conditions requiring repeated connection and disconnection, and thus, this method has the potential for the application of all flange mount devices.

Programmable and scalable assembly of a flexible hexagonal DNA origami

Nanoscale structures demonstrate considerable potential utility in the construction of nanorobots, nanomachines, and many other devices. In this study, a hexagonal DNA origami ring was assembled and visualized via atomic force microscopy. The DNA origami shape could be programmed into either a hexagonal or linear shape with an open or folded pattern. The flexible origami was robust and switchable for dynamic pattern recognition. Its edges were folded by six bundles of DNA helices, which could be opened or folded in a honeycomb shape. Additionally, the edges were programmed into a concave-convex pattern, which enabled linkage between the origami and dipolymers. Furthermore, biotin-streptavidin labels were embedded at each edge for nanoscale calibration. The atomic force microscopy results demonstrated the stability and high-yield of the flexible DNA origami ring. The polymorphous nanostructure is useful for dynamic nano-construction and calibration of structural probes or sensors.

Turning ON/OFF the fluorescence of the ESIPT state by changing the hydrogen bond distance and orientation in quinoline–pyrazole derivatives

• Targeted modifications to the HB structure can induce different ESIPT activities. • The ISC process is responsible for the fluorescence quenching in QP1 and QP3. • The dark state of ESIPT was successfully lighted up in fused HB six-membered ring QP2. The excited-state intramolecular proton transfer (ESIPT) process is sometimes non-fluorescent owing to interference from other non-radiative processes. Thus, effectively lighting up the “invisible” ESIPT state is crucial. In this work, quinoline–pyrazole (QP) derivatives containing fused and non-fused aromatic frameworks (QP1, QP2, and QP3) were used as model compounds to explore the effects of hydrogen bond (HB) distance and orientation on ESIPT. Analysis of the electronic structures and HB interactions revealed that the HB in fused six-membered ring QP2 was significantly enhanced upon photoexcitation, which making the ESIPT process occur more readily. In contrast, the ESIPT process was less favorable for the more flexible non-fused six-membered ring in QP3 owing to HB weakening in the S 1 state. Furthermore, analysis of the potential energy curves indicated that the ESIPT fluorescence of QP1 and QP3 was quenched by intersystem crossing. Remarkably, the dark ESIPT state was successfully illuminated in QP2. Our findings demonstrate that targeted modifications to the molecular structure in the region of HBs can serve as a control knob to effectively regulate the ESIPT fluorescence, providing a route toward potential photoelectric applications.

DNA Conformation Dictates Strength and Flocculation in DNA-Microtubule Composites.

Polymer topology has been shown to play a key role in tuning the dynamics of complex fluids and gels. At the same time, polymer composites, ubiquitous in everyday life, have been shown to exhibit emergent desirable mechanical properties not attainable in single-species systems. Yet, how topology impacts the dynamics and structure of polymer composites remains poorly understood. Here, we create composites of rigid rods (microtubules) polymerized within entangled solutions of flexible linear and ring polymers (DNA) of equal length. We couple optical tweezers microrheology with confocal microscopy and scaled particle theory to show that composites with linear DNA exhibit a strongly nonmonotonic dependence of elasticity and stiffness on microtubule concentration due to depletion-driven polymerization and flocculation of microtubules. In contrast, composites containing ring DNA show a much more modest monotonic increase in elastic strength with microtubule concentration, which we demonstrate arises from the decreased conformational size and increased miscibility of rings.

Abstract 10378: A Novel Selectively Flexible Mitral Annuloplasty Ring Designed Based on Human Imaging with Superior Performance in Hemodynamics, Biomechanics, and Annular Dynamics - A Comprehensive Bench to in vivo Large Animal Analysis

Introduction: We designed a novel mitral annuloplasty ring based on healthy human imaging to allow for the mitral valve (MV) annular conformational changes while restricting the anteroposterior (AP) distance. The objectives were to evaluate ex vivo biomechanics of the novel ring and to validate the annular dynamics after ring implantation in vivo. Methods: Cardiac MRI exams were obtained for 3 healthy volunteers. The MV annulus was tracked (Fig. A-C). Based the imaging data, a novel ring was manufactured (Fig. D-F). An ex vivo annular dilation model of mitral regurgitation was used in a left heart simulator (Fig. G, H) to measure hemodynamics and chordal forces at dilated baseline and after repair using the novel, rigid, and flexible rings in 5 porcine MVs. Novel (n = 6) or rigid rings (n = 5) were implanted into male Dorset sheep. Pre- and post-operative cardiac MRI exams were analyzed. Results: Repair using the novel, rigid, and flexible ring reduced regurgitation fraction from 30.0 ± 5.8% at dilated baseline to 4.7 ± 2.7%, 2.4 ± 3.2%, and 17.8 ± 10.0% ( p < .0001, Fig. I-N ). Peak forces on the primary chordae decreased after ring annuloplasty repair ( p < .0001, Fig. O ). The novel ring also showed lower peak forces compared to the rigid ring (p = .03) in secondary chordae ( Fig. P ). MV annular motion was preserved in vivo using the novel ring but restricted to a planar geometry using the rigid ring ( Fig. Q-S ). Annular height to intercommissure ratio at midsystole were similar pre-repair (0.2 ± 0.1) and after novel ring repair (0.2 ± 0.0, p = .89). The variance of AP distance during the cardiac cycle was similar between the novel (0.4 ± 0.3) and rigid ring (0.5 ± 0.1, p = .58). Conclusions: This novel mitral annuloplasty ring demonstrated excellent capability in reducing AP dimension and repairing regurgitation with a superior chordal force profile while facilitating the annular flexible motion. Future studies will focus on evaluating repair durability and effect on left ventricular remodeling.

Compressive deformations of ring polymers in a confining channel

We used Langevin Dynamics Simulations to study compression and relaxation processes of confined ring polymers in a nanochannel by a sliding piston. Our findings show that ring polymers undergo a series of complex deformations in compression, dependent on the degree of confinement and the topological constrains: the weakly confined flexible ring is compressed into the condensed blobs, while the strongly confined semiflexible ring undergoes deformations from double helix to collapsed states, in order to reduce the bending energy. In the relaxation process, with the piston drawing back, the weakly confined ring relaxs to the initial states, while the strongly confined ring extends from the compacted states to the randomly folded states, due to the interpenetrated and self-entangled structures formed in the compression process. These findings are important to understand the complex deformations and relaxation of ring polymers in mechanical compression or driven transport arising from the geometric confinement.

Mitral valve repair for myxomatous mitral regurgitation; Respect or Resect

Background: The superiority of mitral repair using resection of the posterior leaflet versus neo-artificial chordea is still debatable. The objective of this study was to compare leaflet resection versus chordal replacement for mitral valve repair in patients with isolated myxomatous degeneration of the posterior mitral valve leaflet. 
 Methods: This study was conducted on 199 patients with severe symptomatic mitral regurgitation due to myxomatous mitral valve degeneration. Patients were grouped into two groups: Group (1): Respect technique which included 76 patients who had limited resection of the anterior leaflet, chordal transfer, and replacement of anterior leaflet chordae by polytetrafluoroethylene sutures, and placement of annuloplasty ring. Group (2): Resect technique included 123 patients where the operation was done by resecting the prolapsed mid scallop of the posterior leaflet and placement of flexible annuloplasty ring.
 Results: There was no difference between both groups regarding gender. Patients in the Respect group were younger (37 (25th- 75th percentiles: 29- 44) vs. 54 (48- 60) years, P<0.001). The minimally invasive approach was more commonly used in patients who had resection techniques (20 (26.32%) vs. 106 (86.18%); P<0.001). Ischemic (99 (95- 106) vs. 79 (75- 82); P<0.001) and cardiopulmonary bypass times (134.5 (130- 138.5) vs. 99 (97- 104) min; P<0.001) were higher in the Respect group. Blood loss was more in the Resect group (370 (305- 390) vs. 550 (490- 600) ml; P<0.001). There were no differences in the postoperative complications between groups. ICU stay was longer in patients in the Resect group (5 (5- 6) vs. 7 (6- 8) days; P<0.001). Mitral valve gradient after 12 months was significantly higher in the Resect group (3 (3- 3.5) vs. 4 (3- 5) mmHg; P<0.001). Mitral valve reoperation was required more in patients in the Respect group (5 (6.58%) vs. 1 (0.81%); P= 0.03).
 Conclusions: Both Respect and resect techniques for mitral valve repair had comparable outcomes and durability. The repair technique should be tailored according to the mitral valve pathology.

Simulation and experimental test of load-sharing behavior of planetary gear train with flexible ring gear

Simulation and experimental test of load-sharing behavior of planetary gear train with flexible ring gear

Rigid Ring Versus Flexible Band for Tricuspid Valve Repair in Patients Scheduled for Mitral Valve Surgery: A Prospective Randomised Study

Tricuspid valve repair for functional regurgitation is effectively performed with different annuloplasty devices. However, it remains unclear whether there are advantages associated with rigid rings compared to flexible bands. This prospective randomised study aimed to compare results of using a flexible band ring versus a rigid ring for functional tricuspid regurgitation in patients undergoing mitral valve surgery. A single-centre randomised study was designed to allocate patients with functional tricuspid regurgitation undergoing mitral valve surgery to be treated with a flexible band or rigid ring. These patients were analysed by echocardiographic follow-up. The primary outcome was freedom from recurrent tricuspid regurgitation at 12-months follow-up. Secondary outcomes were 30-day mortality, survival, freedom from tricuspid valve reoperation, right ventricular reverse remodelling, and rate of major adverse events. A total of 308 patients were allocated to receive concomitant tricuspid valve annuloplasty with the flexible band or rigid ring. There was no between-group difference in freedom from recurrent tricuspid regurgitation: 97.3% in Rigid group (95% CI, 93.0-98.8) and 96.2% in the Flexible group (95% CI, 92.0-98.5) at 12-months follow-up (log-rank, p=0.261). Early mortality, survival, freedom from tricuspid valve reoperation, and global right ventricle systolic function were also comparable in both groups of patients. However, the flexible band had advantage in restoring regional right ventricle function (Doppler-derived systolic velocities of the annulus [S], tricuspid annular plane systolic excursion) at 12-months follow-up. Both the rigid ring and flexible band offered acceptable outcomes for functional tricuspid regurgitation correction without significant differences, as assessed at 12-months follow-up.

Resonance modulation vibration mechanism of equally-spaced planetary gearbox with a localized fault on sun gear

The vibration signal of the planetary gearbox shows complicated modulation sidebands no matter the gear is normal or fault. It leads to a challenge in the fault diagnosis, especially for the localized faults which stimulate resonance modulation phenomena. To reveal the resonance modulation mechanism of sun gear’s localized fault, the vibration signal model is built based on the convolution of transient impact force and transfer function of the planetary gearbox. Three prominent transfer paths including modal parameters of the flexible ring gear or housing are involved to obtain resonance modulation sidebands. A projection function is used to model the time-varying direction of transient impact force. Resonance modulation sidebands of a single planet gear meshing is first deduced, and then the sidebands related to multiply planet gears meshing. The resonance modulation of localized fault on sun gear are concluded to be consist of three groups of sidebands. The proposed model is verified by the good consistency between simulation and experimental testing on a commodity planetary gearbox. It contributes an important and effective frequency indicator to confirm the condition of planetary gearboxes.

Atypical and Asymmetric 1,3-P,N Ligands: Synthesis, Coordination and Catalytic Performance of Cycloiminophosphanes.

Novel seven‐membered cyclic imine‐based 1,3‐P,N ligands were obtained by capturing a Beckmann nitrilium ion intermediate generated in situ from cyclohexanone with benzotriazole, and then displacing it by a secondary phosphane under triflic acid promotion. These “cycloiminophosphanes” possess flexible non‐isomerizable tetrahydroazepine rings with a high basicity; this sets them apart from previously reported iminophophanes. The donor strength of the ligands was investigated by using their P‐κ1‐ and P,N‐κ2‐tungsten(0) carbonyl complexes, by determining the IR frequency of the trans‐CO ligands. Complexes with [RhCp*Cl2]2 demonstrated the hemilability of the ligands, giving a dynamic equilibrium of κ1 and κ2 species; treatment with AgOTf gives full conversion to the κ2 complex. The potential for catalysis was shown in the RuII‐catalyzed, solvent‐free hydration of benzonitrile and the RuII‐ and IrI‐catalyzed transfer hydrogenation of cyclohexanone in isopropanol. Finally, to enable access to asymmetric catalysts, chiral cycloiminophosphanes were prepared from l‐menthone, as well as their P,N‐κ2‐RhIII and a P‐κ1‐RuII complexes.

Spin-States of Diastereomeric Iron(II) Complexes of 2,6-Bis(thiazolin-2-yl)pyridine (ThioPyBox) Ligands and a Comparison with the Corresponding PyBox Derivatives.

This report investigates homoleptic iron(II) complexes of thiazolinyl analogues of chiral PyBox tridentate ligands: 2,6-bis(4-phenyl-4,5-dihydrothiazol-2-yl)pyridine (L1Ph), 2,6-bis(4-isopropyl-4,5-dihydrothiazol-2-yl)pyridine (L1iPr), and 2,6-bis(4-tert-butyl-4,5-dihydrothiazol-2-yl)pyridine (L1t-Bu). Crystallographic data imply the larger and more flexible thiazolinyl rings reduce steric clashes between the R substituents in homochiral [Fe((R)-L1R)2]2+ or [Fe((S)-L1R)2]2+ (R = Ph, iPr, or t-Bu), compared to their PyBox (L2R) analogues. Conversely, the larger heterocyclic S atoms are in close contact with the R substituents in heterochiral [Fe((R)-L1Ph)((S)-L1Ph)]2+, giving it a more sterically hindered ligand environment than that in [Fe((R)-L2Ph)((S)-L2Ph)]2+ (L2Ph = 2,6-bis(4-phenyl-4,5-dihydrooxazol-2-yl)pyridine). Preformed [Fe((R)-L1Ph)((S)-L1Ph)]2+ and [Fe((R)-L1iPr)((S)-L1iPr)]2+ do not racemize by ligand redistribution in CD3CN solution, but homochiral [Fe(L1iPr)2]2+ and [Fe(L1t-Bu)2]2+ both undergo partial ligand displacement in that solvent. Homochiral [Fe(L1Ph)2]2+ and [Fe(L1iPr)2]2+ exhibit spin-crossover equilibria in CD3CN, centered at 344 ± 6 K and 277 ± 1 K respectively, while their heterochiral congeners are essentially low-spin within the liquid range of the solvent. These data imply that the diastereomers of [Fe(L1Ph)2]2+ and [Fe(L1iPr)2]2+ show a greater difference in their spin-state behaviors than was previous found for [Fe(L2Ph)2]2+. Gas-phase DFT calculations (B86PW91/def2-SVP) of the [Fe(L1R)2]2+ and [Fe(L2R)2]2+ complexes reproduce most of the observed trends, but they overstabilize the high-spin state of SCO-active [Fe(L1iPr)2]2+ by ca. 1.5 kcal mol-1. This might reflect the influence of intramolecular dispersion interactions on the spin states of these compounds. Attempts to model this with the dispersion-corrected functionals B97-D2 or PBE-D3 were less successful than our original protocol, confirming that the spin states of sterically hindered molecules are a challenging computational problem.

Vibratile Dihydrophenazines with Controllable Luminescence Enabled by Precise Regulation of π-Conjugated Wings

Vibratile Dihydrophenazines with Controllable Luminescence Enabled by Precise Regulation of π-Conjugated Wings

Virtual Generation of Flexible Ring Tire Models Using Finite Element Analysis: Application to Dynamic Cleat Simulations

ABSTRACT The main goal of this work is to investigate if finite element (FE) model techniques with special applications of material properties accurately estimate the parameters of flexible ring tire models. It is known that commercially available ring tire models are used as standard tools for simulating and predicting vehicle ride and durability, e.g., rigid ring MF-Swift [1] and flexible ring Flexible Structure Tire Model (FTire) [2–5]. Despite wide acceptance of these models, difficulty in model parameterization limits their application in the vehicle development process. For estimation of tire dynamic stiffnesses and inertial properties, rolling tire cleat test data are required for most ring models. Although this test method produces reliable models, the parameterization is not time and cost effective as it requires measurement and processing of cleat data at multiple speeds and loads and is prone to test rig dynamic compliance variations. This approach also limits the ability to evaluate tire performances during the virtual stages of tire design. The objective of this work is to develop virtual data using time and cost effective FE-based methods towards the estimation of flexible ring model parameters rather than relying on measured cleat data on physical tires. Commercial product ABAQUS is used for the FE simulations and FTire for tire flexible ring model simulations. Two FE modeling techniques are utilized in this work. Firstly, it is shown that the dynamic stiffness of a rolling tire can be estimated from a steady state eigensolution modal analysis of a static tire using material properties characterized for a rolling tire. Secondly, a method of separation of the sidewall from the tread band is developed for the estimation of mass and bending properties of the tread band. The estimated stiffnesses, inertias, and dimensions from the FE model results are converted into FTire model parameters. Finally, to validate the virtually generated FTire model, simulated dynamic cleat data response trends at multiple inflation pressures and velocities are compared with measurements. The virtual FE based techniques presented in this work can be applied to other ring based models as well.

Performance of a friction ring DVA for vibration control of a flywheel

A flexible ring DVA with friction contact interfaces (essentially a viscoelastic-friction DVA) is proposed to suppress vibration of a flywheel, two other cases are also studied, i.e., viscoelastic DVA and friction DVA. Based on an equivalent 3 degrees of freedom (DOFs) dynamic model, displacement response of the flywheel-DVA are obtained by using harmonic balance method (HBM). It is shown that all three types of DVA can suppress vibration of the flywheel effectively, bandwidth of the viscoelastic-friction DVA is enlarged due to the existence of friction interface. Performances of the DVA are evaluated by analyzing the displacement responses and forces (i.e., spring force, damping force and friction force). It is shown that the frequency corresponding to the turning point on the response curve is the critical frequency at which dynamic vibration absorption takes place, and it is also the frequency at which the friction force begins to take effect. In the process of emergence and disappearance of the dynamic vibration absorption, the friction force plays a role similar to a "switch"

Disturbance compensation of a multiaperture imaging system based on a coupling rotating prism using an improved model compensation control.

In this paper, a cascade double-loop control (DLC) combined with modeling compensation methods is proposed to improve the tracking precision of the multiaperture imaging system (MAIS). The application of the flexible thin-wall ring mechanism in the coupling rotating prism (CRP) system causes a series of tracking and pointing challenges. Disturbances such as friction, shaft deformation, and model perturbation significantly deteriorate the tracking and pointing accuracy of the CRP. Two different modeling compensation methods that are interfaced with classical DLC are proposed to guarantee the tracking precision of the MAIS. Moreover, the disturbance observation and compensation performance of two different modeling compensation methods are analyzed and compared. Finally, simulation and experiment results indicate that the proposed control methods, especially model compensation based on speed close-loop control, obtain the best performance for disturbance rejection in the MAIS.

Active resonance triboelectric nanogenerator for harvesting omnidirectional water-wave energy

<h2>Summary</h2> Water-wave energy, as one of the important renewable energies, is greatly difficult to efficiently harvest due to its characteristics of low frequency and randomly moving direction. Herein, we report an active resonance triboelectric nanogenerator (AR-TENG) system fabricated by using simple pendulum, tumbler, and flexible ring TENG, which can harvest omnidirectional and frequency varying water-wave energy through excellent structural design and resonance effect. Besides, thanks to the high-frequency damped motion of simple pendulum and tumbler, the high-frequency output generated by the AR-TENG system under the driving condition of low-frequency water wave can greatly improve the efficiency of wave energy harvesting. More importantly, based on the low damping coefficient, resonance effect, and elimination of water screening effect, the output performance of AR-TENG system in the water wave is closest to the simulated test. This work not only can realize the omnidirectional water-wave energy harvesting by TENG but also provide a method for large-scale blue energy harvesting.

Tire dimensionless numbers for analysis of tire characteristics and intelligent tire signals

It is essential to understand and analyze the characteristics of the tire. This paper focuses on analyzing tire characteristics using intelligent tires based on physical tire models. The flexible ring tire model has been selected as the tire model. The flexible ring tire model is analyzed and simplified based on modal analysis. Four tire dimensionless numbers have been proposed to represent tire characteristics using the Buckingham theorem. Tire dimensionless numbers were estimated using intelligent tire sensor signals. The estimation algorithm was designed based on the standing wave characteristics of the tire. The proposed estimation algorithm has been validated through experiments on various tire conditions. The physical correlation between the estimated tire dimensionless numbers and the tire state dimensionless numbers were analyzed. The experimental results verify the physical meaning and estimation performance of the proposed tire dimensionless numbers.

Multiscale Approaches for Confined Ring Polymer Solutions.

We apply a hierarchy of multiscale modeling approaches to investigate the structure of ring polymer solutions under planar confinement. In particular, we employ both monomer-resolved (MR-DFT) and a coarse-grained (CG-DFT) density functional theories for fully flexible ring polymers, with the former based on a flexible tangent hard-sphere model and the latter based on an effective soft-colloid representation, to elucidate the ring polymer organization within slits of variable width in different concentration regimes. The predicted monomer and polymer center-of-mass densities in confinement, as well as the surface tension at the solution-wall interface, are compared to explicit molecular dynamics (MD) simulations. The approaches yield quantitative (MR-DFT) or semiquantitative (CG-DFT) agreement with MD. In addition, we provide a systematic comparison between confined linear and ring polymer solutions. When compared to their linear counterparts, the rings are found to feature a higher propensity to structure in confinement that translates into a distinct shape of the depletion potentials between two walls immersed into a polymer solution. The depletion potentials that we extract from CG-DFT and MR-DFT are in semiquantitative agreement with each other. Overall, we find consistency among all approaches as regards the shapes, trends, and qualitative characteristics of density profiles and depletion potentials induced on hard walls by linear and cyclic polymers.