Rhombic Configuration Research Articles

Synergistic global and local flexibilities in Zr-based metal-organic frameworks enable sequential sieving of hexane isomers.

Separating hexane isomers based on the branching degree is crucial for their efficient utilization in the petrochemical industry, yet remains challenging due to their similar properties. Here we report a temperature-responsive Zr-based metal-organic framework, Zr-fum-FA, capable of sequentially sieving linear, mono-, and di-branched hexane isomers. Notably, the pore structure of Zr-fum-FA dynamically transforms from segmented triangular channels to an integrated rhombic configuration as the temperature increases, leading to distinct sieving effects. At low temperatures, the narrow triangular pores allow the exclusive adsorption of n-hexane while excluding branched isomers. In contrast, the expanded rhombic pores at high temperatures enable the sieving of mono- and di-branched isomers. Mechanistic studies reveal that this unique dual-sieving behavior originates from the synergistic effects of the global framework flexibility and the local dynamics of pendent hydroxyl groups. Furthermore, we demonstrate the decoupling of global and local flexibilities via two strategies: incorporating steric hindrance to dampen the global framework dynamics and enhancing the metal node rigidity to limit the local vibrations. These findings not only provide a promising adsorbent for the challenging separation of hexane isomers but also offer rational design principles for harnessing flexibility in MOFs.

A New Structural Type of Bismuth(III) Dithiocarbamato-Chlorido Complexes: Preparation, Structural Organization, and Thermal Behavior of Binuclear Compounds [Bi2{S2CN(CH2)6}4(μ2-Cl)2] and [Bi2{S2CN(CH2)6}4(μ2-Cl)2]·2CH2Cl2

Heteroleptic compounds of bismuth(III) adopting a new binuclear structural type: hexamethylenedithiocarbamato(HmDtc)-chloride of [Bi2(S2CNHm)4(μ2-Cl)2] (I) and its solvated form [Bi2(S2CNHm)4(μ2-Cl)2]·2CH2Cl2 (II) have been isolated and studied by X-ray diffraction, IR spectroscopy, and simultaneous thermal analysis. Despite the identical chemical composition, the structure of binuclear molecules in I and II differs significantly. In the first case, the noncentrosymmetric molecule includes two nonequivalent moieties of [Bi(S2CNHm)2Cl], which are combined by μ2-Cl ligands to form the [Bi–(μ2-Cl)2–Bi] metallocycle in the butterfly conformation: Bi(1)–Bi(2) 4.0785(5) Å, Cl(1)–Cl(2) 3.936(2) Å. On the contrary, in the solvated form II, the complex is centrosymmetric and four-membered [Bi2Cl2] ring is stabilized in a rhombic configuration: Bi(1)–Bi(1)a 3.9592(9) Å and Cl(1)–Cl(1)a 4.540(4) Å. According to the microprobe method, the main residual substance after the thermolysis of the complexes is microcrystalline Bi2S3 with inclusions of metallic bismuth particles.

Comparison of the Effect of Rhombic and Inverted Triangle Configurations of Cannulated Screws on Internal Fixation of Nondisplaced Femoral Neck Fractures in Elderly Patients.

ObjectiveTo investigate whether four‐screw fixation in rhombic configuration could improve the clinical outcomes and decrease the complication rate compared with three‐screw fixation in inverted triangle configuration in elderly patients with nondisplaced femoral neck fractures.MethodFrom January 2018 to January 2019, 91 elderly patients with nondisplaced femoral neck fractures who were treated with a cannulated screw system were reviewed retrospectively. The inverted triangle configuration was applied in 51 patients and rhombic configuration in 40 patients. The demographic and perioperative information of the patients were extracted from medical records and surgical records. Variables including incision size, surgical blood loss, surgical time, fluoroscopy time, hospital stays, fracture union time, postoperative visual analogue scale (VAS) scores, and complications were compared between the two groups. Also, Harris hip score at the final follow‐up was used to evaluate the functional outcomes.ResultsAll patients were followed up from 24 to 36 months, with an average of 29.75 months. The average age of patients was 72.37 ± 7.16 years. No significant differences were found between the two groups with regard to patients' age, gender, affected side, Garden classification, Pauwels classification and comminution of posterior wall (P > 0.05). We found shorter incision size (P < 0.001), less blood loss (P = 0.020), less surgical time (P = 0.026), and shorter fluoroscopy time (P < 0.001) in inverted triangle configuration group. However, shorter hospital stays (P = 0.001) and fracture union time (P = 0.002) were found in the rhombic configuration group. The VAS scores were lower in the rhombic configuration group at the first (P < 0.001) and third months (P = 0.010), but no significant difference was found at the sixth month (P = 0.075). Meanwhile, the total complication rate was relatively lower in the rhombic configuration group compared to the inverted triangle configuration group (P = 0.041). Harris hip score presented no significant difference between the two groups at final follow‐up (P = 0.078). No wound infection or cortical perforation occurred in either group.ConclusionFour‐screw fixation in rhombic configuration was superior to three‐screw fixation in inverted triangle configuration in the treatment of nondisplaced femoral neck fractures in elderly patients in terms of less early postsurgical pain, shorter fracture union time, and lower complication rate.

A 60 GHz Rhombic Patch Array Antenna With High Gain, Low Sidelobe Level, and Reduced Array Area

This work designs a 60 GHz rhombic patch array antenna with high gain, low sidelobe level (SLL), and reduced array area. This antenna consists of eight linear serial arrays with varying number of patches. A slot-coupled center-fed structure of substrate-integrated waveguide (SIW) is designed to simplify the complex feed network required for direct excitation of planar arrays and reduce insertion loss. The rhombic configuration utilizes the quantity ratio of patches for equivalent taper excitation to reduce SLL, rather than the use of tapered width as in traditional designs, which can achieve high gain and avoid cumbersome resizing of patches and connecting lines. An array factor analysis method is proposed to predict the SLL of the antenna. To form a planar array and further reduce the H-plane SLL, a -25-dB Dolph-Chebyshev SIW feed network is constructed. The measured gain of the rhombic array antenna is 18.2 dBi, and the E-plane and H-plane SLLs are less than -20 dB and -25 dB, respectively. This work also simulates a reference uniformly excited high-gain 8&#x00D7;10 array antenna. Compared to this reference antenna, the proposed rhombic array antenna has similar simulated gain but much lower SLL and 23% smaller array area.

Theory of topological corner state laser in Kagome waveguide arrays

In comparison with conventional lasers, topological lasers are more robust and can be immune to disorder or defects if lasing occurs in topologically protected states. Previously reported topological lasers were almost exclusively based on the first-order photonic topological insulators. Here, we show that lasing can be achieved in the zero-dimensional corner state in a second-order photonic topological insulator, which is based on the Kagome waveguide array with a rhombic configuration. If gain is present in the corner of the structure, where the topological corner state resides, stable lasing in this state is achieved, with the lowest possible threshold, in the presence of uniform losses and two-photon absorption. When gain acts in other corners of the structure, lasing may occur in edge or bulk states, but it requires substantially larger thresholds, and transition to stable lasing occurs over much larger propagation distances, sometimes due to instabilities, which are absent for lasing in corner states. We find that increasing two-photon absorption generally plays strong stabilizing action for nonlinear lasing states. The transition to stable lasing stimulated by noisy inputs is illustrated. Our work demonstrates the realistic setting for corner state lasers based on higher-order topological insulators realized with waveguide arrays.

A novel auxetic honeycomb with enhanced in-plane stiffness and buckling strength

In the present work, a new design of honeycomb is proposed by embedding the rhombic configuration into the normal re-entrant hexagonal honeycomb (NRHH), in order to enhance the honeycomb’s in-plane mechanical properties. Both theoretical analysis and numerical simulations are employed to calculate the in-plane mechanical properties of the new honeycomb under uniaxial compression, including Young’s modulus, Poisson’s ratio and critical buckling strength. The results show that the new honeycomb can maintain auxetic performance, while both the in-plane Young’s modulus and the critical buckling strength are significantly improved compared to the NRHH. Comparisons between the present design and other exiting enhanced periodic topologies are also carried out. With respect to them, the present design features superior performances. For these outstanding properties, this layout may provide a new concept for the optimization and design of auxetic materials.

Geometry of Prismatic Tensegrity Constructions Composed of Three and Four-strut Cells

Abstract In the paper there is described geometry of double layer tensegrity constructions composed of prismatic cells with rhombic configuration of three or four strut bases so-called prismatic Tensegrity constructions. There are described bi-dimensional assemblies creating double layer grids of three or four-strut cells with a node-on-node junction. The grids can be planar, of one or two curvature constructions.

Phase matched second harmonic generation in planar two-dimensional photonic crystals

We report a detailed numerical study of phase matched second harmonic generation for narrow beams (of few wavelengths width) in quadratic nonlinear photonic crystals under realistic situations, i.e. considering the dispersion of real materials (in particular Al0.3Ga0.7As), considering experimentally convenient architecture (in particular the planar waveguiding structure) and considering different symmetries of the lattice (the square and rhombic symmetries). We find that in the case of the Al0.3Ga0.7As in planar structures, for the rhombic configuration of the photonic crystal the sign and modulus of the diffraction can be manipulated for the second harmonic wave whereas out-of-plane losses vanish for both fundamental and second harmonic waves, thus making the predicted structure interesting for experiments and applications.

Pseudo-Jahn-Teller origin of geometry and pseudorotations in second row tetra-atomic clusters X4 (X=Na,Mg,Al,Si,P,S)

Experimentally determined or ab initio calculated molecular geometries carry no information about their origin. Employing the Jahn-Teller (JT) vibronic coupling effects as the only source of instability and consequent distortions of high-symmetry molecular configurations, we have worked out a procedure that allows us to trace the origin of particular geometries and determine the detailed electronic mechanism of their formation. This procedure is illustrated by considering a series of X(4) clusters with X=Na, Mg, Al, Si, P, and S. It shows explicitly why Na(4), Si(4), and Al(4) have a rhombic geometry in the ground state, while Mg(4) and P(4) are tetrahedral, whereas S(4) is a trapezium. Even when the minimum-energy geometries are the same (as in the case of rhombic Na(4), Si(4), and Al(4)), the electronic mechanism of their formation is quite different. In particular, in Na(4) and Si(4) the rhombic minima are produced by a strong pseudo JT coupling between two excited states in the square-planar configuration (different in the two cases) that stabilizes one of them and makes it the ground state by rhombic distortions. The rhombic configuration of Al(4) is due to the pseudo JT effect in its ground-state square-planar configuration, and the trapezium in S(4) is formed by two pseudo JT couplings essentially involving excited states. In several cases this analysis shows also the tunneling paths between equivalent configurations.

Seismic Behavior of Short Coupling Beams with Different Reinforcement Layouts

This paper presents an experimental investigation on the seismic behavior of reinforced concrete coupling beams. The reinforcement layout and the loading history were the main variables of the tests. Fifteen short coupling beams with four different reinforcement arrangements were tested. They were subjected to monotonic and cyclic loading by a suitable experimental setup. All specimens were characterized by a shear span-depth ratio of 0.75. The reinforcement layouts consisted of a classical scheme, diagonal scheme without confining ties, diagonal scheme with confining ties, and inclined bars to form a rhombic configuration. Concrete compressive strengths of the specimens varied from 40 MPa to 54 MPa. Test results showed that the beams with diagonal or rhombic reinforcement layouts behaved better than beams with longitudinal arrangement of the steel bars. These results were produced by the different resisting truss mechanisms that were developed in the coupling beams after the first cracking. The differences in energy dissipation were negligible between the diagonal and rhombic layouts. The rhombic arrangement, however, was more advantageous in terms of rotational ductility capacity and decay in strength and stiffness of the beams. Moreover, cyclic tests demonstrated that the behavior of the rhombic layout was less affected by the different loading histories.

Occurrence of Magnesium Oxalate Crystals on Lesions Incited byMycena citricoloron Coffee

Scanning electron microscopy showed that these crystals exist singly or as aggregates. The single crystals exhibited rhombic configuration, and crystal aggregates were organized as druses or crystal conglomerates (…). It is postulated that magnesium oxalate crystals, which were absent in the control treatments, were formed in the infected tissue through sequestration of leaf magnesium by fungal oxalic acid

FIM Observation of Interactions between W Atoms on W Surfaces

Kinetics of rearrangement and self-diffusion of tungsten adatoms of field-evaporated (110) and (321) planes of tungsten were studied by a field ion microscope. A zigzag chain of dimers which was left on (110) plane by field evaporation at 140 K-RT was rearranged by heating at 270 K-300 K to form stable clusters with the rhombic configuration. Evidence of saturation in W-W bindings on (110) plane is presented. Terminal W-W bindings on dimers, trimers and longer atom-rows along the channels on (321) plane exhibited the short-ranged character. However, the interaction between adatoms across the channel was suggested to be long-ranged.