Planar Ribbon Research Articles

Varying Structure‐Directing Anions in Uranyl Ion Complexes with Ni(2,2′ : 6′,2′′‐terpyridine‐4′‐carboxylate)2

Abstract2,2′ : 6′,2“‐Terpyridine‐4′‐carboxylic acid (tpycH) reacts with uranyl cations under solvo‐hydrothermal conditions to give [UO2(tpyc)2] ⋅ 2H2O (1), a monoperiodic polymer different from that previously reported. In the additional presence of NiII cations, the Ni(tpyc)2 “expanded ligand” is formed and the structure of its complexes with the uranyl cation depends on the additional anions present. [(UO2)2F4(H2O)2Ni(tpyc)2] ⋅ 2H2O (2) and [UO2(mds)(H2O)Ni(tpyc)2] (3), where mds2− is methanedisulfonate, are monoperiodic polymers in which the fluoride anions are bridging and the mds2− anions chelating. [(UO2)4(NO3)2(H2O)4Ni5(tpyc)10](CF3SO3)4(NO3)2 ⋅ 7H2O (4) crystallizes as a wide and nearly planar monoperiodic ribbon. [(UO2)2(NO3)2(chdc)Ni(tpyc)2] ⋅ chdcH2 ⋅ 2CH3CN (5), where chdc2− is trans‐1,4‐cyclohexanedicarboxylate, is a monoperiodic chain including both bridging Ni(tpyc)2 and chdc2− ligands, the chains being further assembled into layers through hydrogen bonding to bridging chdcH2 molecules. Finally, [UO2Ni2(tpyc)4](I3)2 (6) crystallizes as a diperiodic network with sql topology. These results point to the possibility of modulating the structure of cationic uranyl ion complexes with Ni(tpyc)2 through addition of a wide range of bonding or non‐bonding anions.

Tuning structural preference of negatively charged B16 by ionically or covalently interacting with alkali and coinage metals

The planar ribbon form is the lowest-energy structure of the neutral and negatively charged B16 clusters, especially planar B162− with ten delocalized π electrons is viewed as an all-boron naphthalene, whereas the doped B16TM− by transition metals unexpectedly exhibit the high coordinated TM-centered tubular structures. We found herein a totally different picture in B16M−/B16TM− (M = Li, Na, K; TM = Ag, Au) doped by s-block metals (being isoelectronic to B162−) relative to the reported B16-based clusters. A new quasi-planar trapezoid structure is predicted to be a global minimum, where B16TM− (TM = Ag, Au) presents chemistry similar to that of hydrogen in its bonding to boron. The chemical bonding and structural integrity of the quasi-planar trapezoid structure is not altered significantly in B16M−, suggesting its stability and viability as a promising building block for boron-assembled nanomaterials.

The effect of deviations from precise [001] tensile direction on creep of Ni-base single crystal superalloys

Low temperature (1023 K) high stress (800 MPa) tensile creep behavior of the superalloy single crystal ERBO-1 (CMSX-4 type) is investigated. Three loading directions are compared: precise [001] and 15 ° deviations from [001] towards [111] and [011]. It is found that creep rates ε˙ scale as ε˙[001]→[111]>ε˙[001]>ε˙[001]→[011]already in the early stages of creep (ε≤1%), where dislocation network formation and planar fault intersections cannot rationalize the observed rate effects. An analysis based on Peach-Köhler force calculations suggests, that fast creep rates are observed, when dislocations from two octahedral systems, which are required to react and form the leading part of a planar fault ribbon in the γ’-phase, experience similar driving forces. Creep data, micromechanical calculations and TEM results are in good qualitative agreement. From a technological point of view, the results show that while 15 ° deviations from [001] towards [011] can be tolerated, deviations towards [111] must be avoided.

Impact of angular irradiance distributions on coupling gains and energy yield of cell interconnection designs in silicon solar modules in tracking and fixed systems

Cell interconnector designs such as light redirecting films (LRFs) and various geometric ribbon layouts are all aimed at improving the performance of crystalline silicon solar modules. However, due to the usually specular reflecting surface, the angular-dependent module performance, which is typically quantified with an incidence angle modifier, depends on the rotation of the module. We find that typical power measurements under standard test conditions at 1000 W m−2 and 25 °C cell temperature are not suited to identify the best performing design in real-world conditions. In this work, we therefore determine the optimum ribbon geometry based on its simulated energy yield in common installation configurations for solar modules based on industry-standard full and half-cut solar cells. We compare the effects of planar, triangular, LRFs, pentagonal and wire ribbon geometries, as well as fixed optimal inclination, building-integrated (façade), and single-axis tracking installation scenarios of modules in portrait and landscape orientation. Energy yield gains of 1.8% can be achieved for full cell modules with LRFs or pentagonal ribbons in single-axis tracking installation compared to a reference module with five planar ribbons. Critically, we find that changing the module orientation to landscape reduces this energy yield gain by nearly 50% for the modules with LRFs. This directional dependence is significantly reduced with the pentagonal ribbon structure. The installation scenario can have a similarly dramatic impact. The expectation of power gains for certain designs inferred from standard test conditions may not only show significantly lower gains in annual energy yield, but may even lead to yield losses, especially for building-integrated photovoltaic systems. For a typical full-cell module, for example, we have found that LRFs perform 2.5% better than standard planar ribbons under standard test conditions but can result in a 0.2% lower annual yield in a façade installation. Therefore, to fully evaluate the effectiveness of a specific ribbon design, the annual energy yield must consider the angular irradiance distribution and weather conditions at a specific location, the installation scenario, and the module orientation.

Multi-beam OCT imaging based on an integrated, free-space interferometer

While it is a common practice to increase the speed of swept-source optical coherence tomography (OCT) systems by using a high-speed source, this approach may not always be optimal. Parallelization in the form of multiple imaging beams is an alternative approach, but scalable and low-loss multi-beam OCT architectures are needed to capitalize on its advantages. In this study, we demonstrate an eight-beam OCT system using an interferometer architecture comprising planar lightwave circuits (PLC) splitters, V-groove assemblies (VGA), and optical ribbon fibers. We achieved an excess loss and heterodyne efficiency on each channel that was close to that of single-beam systems. In vivo structural imaging of a human finger and OCT angiography imaging of a mouse ear was performed to demonstrate the imaging performance of the system. This work provides further evidence supporting multi-beam architectures as a viable strategy for increasing OCT imaging speed.

How Nanoscale Dislocation Reactions Govern Low- Temperature and High-Stress Creep of Ni-Base Single Crystal Superalloys

The present work investigates γ-channel dislocation reactions, which govern low-temperature (T = 750 °C) and high-stress (resolved shear stress: 300 MPa) creep of Ni-base single crystal superalloys (SX). It is well known that two dislocation families with different b-vectors are required to form planar faults, which can shear the ordered γ’-phase. However, so far, no direct mechanical and microstructural evidence has been presented which clearly proves the importance of these reactions. In the mechanical part of the present work, we perform shear creep tests and we compare the deformation behavior of two macroscopic crystallographic shear systems [ 01 1 ¯ ] ( 111 ) and [ 11 2 ¯ ] ( 111 ) . These two shear systems share the same glide plane but differ in loading direction. The [ 11 2 ¯ ] ( 111 ) shear system, where the two dislocation families required to form a planar fault ribbon experience the same resolved shear stresses, deforms significantly faster than the [ 01 1 ¯ ] ( 111 ) shear system, where only one of the two required dislocation families is strongly promoted. Diffraction contrast transmission electron microscopy (TEM) analysis identifies the dislocation reactions, which rationalize this macroscopic behavior.

Planar polymers under cylindrical confinement: geometrical approach

We show that the cylindrical confinement of a planar ribbon gives rise to the formation of stationary helical shapes, previously observed in molecular dynamics simulation studies of some planar polymers inside nanotubes. In the limit of small twisting deformations, we notice that a confined ribbon describes identical equilibrium configurations of an elastic rod on the plane. Also, every locally planar strip adsorbed on a cylinder is forced to follow a helical envelope, as its length increases. We also determine the forces and torques that sustain each ribbon equilibrium configuration through the equilibrium geometry and the confinement surface parameters.

Geometry-dependent stretchability and stiffness of ribbon kirigami based on large curvature curved beam model

This paper lays stress on the normalized stiffness and stretchability of planar ribbon kirigami. A dimensionless analytical model is proposed based on plane strain beam theory, in which the large curvature curved beam (LCCB) model is considered. The tensile experiments and simulations are performed and compared to validate the analytical model based on four dimensionless parameters. It is found that not all kirigami-based design is conducive to the enhancement of normalized stretchability. Remarkable long arm effect can enhance the normalized stretchability or reduce the normalized stiffness by several orders of magnitude. Finally, an optimization method is used to obtain the maximum normalized stretchability. The results in this paper can be used to guide the kirigami design in future application.

Coordination polymers of CdII and PbII with croconate show remarkable differences in coordination patterns: a structural and spectroscopic study.

The croconate dianion is a highly versatile ligand with two tautomeric forms making it useful for building large superstructures in the solid state. The single-crystal X-ray structures of PbII- and CdII-croconate coordination polymers, namely catena-poly[[[diaqualead(II)]-μ-croconato-κ4O1,O2:O3,O4] monohydrate], {[Pb(C5O5)(H2O)2]·H2O}n, 1, and catena-poly[[triaquacadmium(II)]-μ-croconato-κ4O1,O2:O3,O4], [Cd(C5O5)(H2O)3]n, 2, have been determined. Both polymers form one-dimensional (1D) structures; 1 is a nonplanar 1D zigzag coordination polymer extended along the crystallographic b axis, whereas 2 is a planar 1D ribbon parallel to the [101] direction. In 2, three H2O molecules are coordinated directly to the metal atom, while in 1, only two H2O molecules are directly coordinated to the metal atom. A third interstitial H2O molecule is involved in hydrogen bonding with O atoms of the croconate ligands of an adjacent layer and other H2O molecules, resulting in stacked double layers parallel to the [105] plane. Solid-state FT-IR and solution UV-Vis spectra also substantiate the croconate coordination.

Dual plasmonically tunable slow light based on plasmon-induced transparency in planar graphene ribbon metamaterials.

We propose a simulated terahertz design based on planar graphene ribbons. With numerical simulation, we can achieve a very obvious dual plasmon-induced transparency phenomenon through the destructive interference in this structure. Moreover, due to the simple design of this structure and the complete continuous graphene ribbons, the Fermi level of graphene can be regulated by voltage. Thus, the dual plasmon-induced transparency phenomenon can be easily tuned in the numerical simulation. Further structural analysis shows that the two graphene chips on the side of the graphene ribbons play a crucial role in the dual plasmon-induced transparency phenomenon. As the length of the two chips is close, the dual plasmon-induced transparency phenomenon gradually becomes a single plasmon-induced transparency phenomenon. The theoretical analysis of this structure shows that this system has a very high group index, and its maximum value is 800, which is far greater than that of other types of slow light devices. This work may open up a new way for designing tunable terahertz graphene-based devices and slow light devices.

The Bernardi Process and Torsor Structures on Spanning Trees

Let G be a ribbon graph, i.e., a connected finite graph G together with a cyclic ordering of the edges around each vertex. By adapting a construction due to O. Bernardi, we associate to any pair (v,e) consisting of a vertex v and an edge e adjacent to v a bijection between spanning trees of G and elements of the set Pic^g(G) of degree g divisor classes on G, where g is the genus of G. Using the natural action of the Picard group Pic^0(G) on Pic^g(G), we show that the Bernardi bijection gives rise to a simply transitive action \beta_v of Pic^0(G) on the set of spanning trees which does not depend on the choice of e. A plane graph has a natural ribbon structure (coming from the counterclockwise orientation of the plane), and in this case we show that \beta_v is independent of v as well. Thus for plane graphs, the set of spanning trees is naturally a torsor for the Picard group. Conversely, we show that if \beta_v is independent of v then G together with its ribbon structure is planar. We also show that the natural action of Pic^0(G) on spanning trees of a plane graph is compatible with planar duality. These findings are formally quite similar to results of Holroyd et al. and Chan-Church-Grochow, who used rotor-routing to construct an action r_v of Pic^0(G) on the spanning trees of a ribbon graph G, which they show is independent of v if and only if G is planar. It is therefore natural to ask how the two constructions are related. We prove that \beta_v = r_v for all vertices v of G when G is a planar ribbon graph, i.e. the two torsor structures (Bernardi and rotor-routing) on the set of spanning trees coincide. In particular, it follows that the rotor-routing torsor is compatible with planar duality. We conjecture that for every non-planar ribbon graph G, there exists a vertex v with \beta_v \neq r_v.

Zigzag double-chain C–Be nanoribbon featuring planar pentacoordinate carbons and ribbon aromaticity

Opening of a Be–Be edge stabilizes the planar pentacoordinate carbons (ppCs) in a nanoribbon geometrically.

Spontaneous Capture of Carbohydrate Guests through Folding and Zipping of Self‐Assembled Ribbons

AbstractOne of the great challenges in molecular self‐assembly is how to confer self‐folding and closing characteristics on flat two‐dimensional structures in response to external triggers. Herein, we report a planar ribbon assembly that folds into closed tubules in response to fructose. The ribbons, ≈28 nm wide and 3.5 nm thick, consist of 8 laterally‐associated elementary fibrils in which disc‐shaped macrocycle amphiphiles are stacked along their axis. Upon addition of fructose, these flat structures spontaneously fold into closed tubules, with an outer diameter of ≈8 nm, through zipping of the two sides of the ribbons. Notably, the folding and then zipping of the flat ribbons is accompanied by spontaneous capture of the fructose molecules inside the tubular cavities.

Spontaneous Capture of Carbohydrate Guests through Folding and Zipping of Self-Assembled Ribbons.

One of the great challenges in molecular self-assembly is how to confer self-folding and closing characteristics on flat two-dimensional structures in response to external triggers. Herein, we report a planar ribbon assembly that folds into closed tubules in response to fructose. The ribbons, ≈28 nm wide and 3.5 nm thick, consist of 8 laterally-associated elementary fibrils in which disc-shaped macrocycle amphiphiles are stacked along their axis. Upon addition of fructose, these flat structures spontaneously fold into closed tubules, with an outer diameter of ≈8 nm, through zipping of the two sides of the ribbons. Notably, the folding and then zipping of the flat ribbons is accompanied by spontaneous capture of the fructose molecules inside the tubular cavities.

Sandpiles, Spanning Trees, and Plane Duality

Let $G$ be a connected, loopless multigraph. The sandpile group of $G$ is a finite abelian group associated to $G$ whose order is equal to the number of spanning trees in $G$. Holroyd et al. used a dynamical process on graphs called rotor-routing to define a simply transitive action of the sandpile group of $G$ on its set of spanning trees. Their definition depends on two pieces of auxiliary data: a choice of a ribbon graph structure on $G$, and a choice of a root vertex. Chan, Church, and Grochow showed that if $G$ is a planar ribbon graph, it has a canonical rotor-routing action associated to it; i.e., the rotor-routing action is actually independent of the choice of root vertex. It is well known that the spanning trees of a planar graph $G$ are in canonical bijection with those of its planar dual $G^*$, and furthermore that the sandpile groups of $G$ and $G^*$ are isomorphic. Thus, one can ask: are the two rotor-routing actions, of the sandpile group of $G$ on its spanning trees, and of the sandpile group of $G^*$ on its spanning trees, compatible under plane duality? In this paper, we give an affirmative answer to this question, which had been conjectured by Baker.

(S) 2-phenyl-2-(p-tolylsulfonylamino)acetic acid. Structure, acidity and its alkali carboxylates

The structure and the preferred conformers of (S) 2-phenyl-2-(p-tolylsulfonylamino)acetic acid (1) are reported. Compound 1 is a derivative of the unnatural aminoacid the (S) phenyl glycine. The X-ray diffraction analyses of the complexes of 1 with water, methanol, pyridine and its own anion are discussed. In order to add information about the acidity of the COOH and NH protons in compound 1, its pKa in DMSO and those of N-benzyl-p-tolylsulfonamide and (S) N-methylbenzyl-p-tolylsulfonamide were determined by cyclic voltammetry. Data improved the scarce information about pKa in DMSO values of sulfonamides.The products of the reactions of compound 1 with one and two equivalents of LiOH, NaOH and KOH in methanol were analyzed. Crystals of the lithium (2) and sodium (3) carboxylates and the dipotassium sulfonylamide acetate (7) were obtained, they are coordination polymers. In compound 2, the lithium is bound to four oxygen atoms with short bond lengths. The coordination of the lithium atom to two carboxylates gives an infinite ribbon by formation of fused six membered rings. In the crystal of compound 3, two pentacoordinated sodium atoms are bridged by three oxygen atoms, one from a water molecule and two from DMSO. The short distance between the sodium atoms (3.123Å), implies a metal–metal interaction. The sodium couples are linked by two carboxylate groups, forming a planar ribbon of fused twelve membered rings. A notable discovery was a water molecule quenched in the middle of the ring, with a tetra coordinated oxygen atom in a square planar geometry. In compound 7, the carboxylate and the amide are bound to heptacoordinated potassium atoms. The 2D polymer of 7 has a sandwich structure, with the carboxylate and potassium atoms in the inner layer covered by the aromatic rings.

Superconductivity at 4.4 K in Ba2Bi3

We report on the superconductivity in Ba2Bi3, which contains planar anionic Bi ribbon nets with four- and three-bonded Bi separated by cationic Ba layers. A nearly single-phase sample is synthesized by reacting Ba and Bi powders at 800 °C under a pressure of 1 GPa. The temperature-dependent resistivity ρ(T) shows metallic behavior with a residual resistivity ratio of 27.3 and indicates a sharp superconducting transition at 4.4 K. The magnetic susceptibility has a large diamagnetic transition at a similar temperature. From the analysis of ρ(T), the Debye temperature ΘD and electron−phonon coupling constant λe − p are derived as 75.9 K and 1.0, respectively, indicating that Ba2Bi3 is a superconductor in the strong-coupling regime. Ba2Bi3 is a type-II superconductor with an estimated upper critical field Hc2(0) of about 1.23 T. For increasing pressures up to 1.5 GPa, Tc linearly decreases with a slope of −0.56 K GPa−1.

Rotor-Routing and Spanning Trees on Planar Graphs

The sandpile group Pic^0(G) of a finite graph G is a discrete analogue of the Jacobian of a Riemann surface which was rediscovered several times in the contexts of arithmetic geometry, self-organized criticality, random walks, and algorithms. Given a ribbon graph G, Holroyd et al. used the "rotor-routing" model to define a free and transitive action of Pic^0(G) on the set of spanning trees of G. However, their construction depends a priori on a choice of basepoint vertex. Ellenberg asked whether this action does in fact depend on the choice of basepoint. We answer this question by proving that the action of Pic^0(G) is independent of the basepoint if and only if G is a planar ribbon graph.

Coulomb drag between in-plane graphene double ribbons and the impact of the dielectric constant

With recent developments in the search for novel device ideas, understanding electron-electron interaction in low dimensional systems is of particular interest. Coulomb drag measurements can provide critical insights in this context. In this article, we present a novel planar graphene double ribbon structure that shows for the first time that Coulomb drag is observable in two adjacent monolayer ribbons in the same plane at room temperature. Moreover, our planar devices enable experimentally study of the impact of the dielectric constant on Coulomb drag which is difficult to explore in the typically used double layer graphene structures. Our experimental findings indicate in particular that the drag resistance is proportional to the dielectric constant (e) and does not, as recently reported, show an increasing trend of interaction strength for small e-values. In fact, we find that the drag resistance follows approximately an e 1.2-dependence. The exponent of “1.2” is consistent with the theory considering the carrier concentration in our samples, and positions our results in between the weak and strong coupling limits.

A Renormalizable 4-Dimensional Tensor Field Theory

We prove that an integrated version of the Gurau colored tensor model supplemented with the usual Bosonic propagator on U(1)4 is renormalizable to all orders in perturbation theory. The model is of the type expected for quantization of space-time in 4D Euclidean gravity and is the first example of a renormalizable model of this kind. Its vertex and propagator are four-stranded like in 4D group field theories, but without gauge averaging on the strands. Surprisingly perhaps, the model is of the $${\phi^6}$$ rather than of the $${\phi^4}$$ type, since two different $${\phi^6}$$ -type interactions are log-divergent, i.e. marginal in the renormalization group sense. The renormalization proof relies on a multiscale analysis. It identifies all divergent graphs through a power counting theorem. These divergent graphs have internal and external structure of a particular kind called melonic. Melonic graphs dominate the 1/N expansion of colored tensor models and generalize the planar ribbon graphs of matrix models. A new locality principle is established for this category of graphs which allows to renormalize their divergences through counterterms of the form of the bare Lagrangian interactions. The model also has an unexpected anomalous log-divergent $${(\int \phi^2)^2}$$ term, which can be interpreted as the generation of a scalar matter field out of pure gravity.