Linking Group Research Articles

Symmetry Detection and Topological Synthesis of Mechanisms of Powertrains

The function of vehicle powertrains (including hybrid powertrains) is to transmit power from the power source (engine or electric machine) to driving wheels. The planetary gear train (PGT) is a core structure of mechanisms of powertrains. The detection of topological symmetry is helpful for improving the efficiency of mechanism design. In this paper, we present a fully automatic and reliable method for detecting symmetry of plane kinematic chains and extend this method to symmetry detection and the topological design of mechanisms of powertrains. First, the topological model and adjacency matrix are introduced to represent various kinds of plane kinematic chains. Then, the moment matrix of the kinematic chain is established to obtain link groups, based on which we propose an algorithm to generate the unique numerical code of each link and precisely detect the symmetry. Our method is applied to synthesize different kinds of plane kinematic chains and mechanisms, which can improve the design efficiency of mechanisms of powertrains and other mechanical devices.

The stationarity control of the average links for the Hebb complex dynamical network via external stimulus signals

The model of complex dynamical network (CDN) can be represented as the mathematic graph, in which some characteristics may emerge from the dynamic nodes group (NG) and links group (LG). This paper primarily focuses on the feature appearing from the dynamic links. The average link weight (ALW), as a novel quantitative index to describe the characteristic of dynamic links is introduced. Inspired by the Hebb’s neuroscience theory, the Hebb complex dynamical network (HCDN) is constructed. The ALW of the HCDN can track a given target via external stimulus signals with adaptive amplifiers’ proportional coefficients. In other words, the stationary network implies the ALW is a constant in time. Finally, two simulation examples are performed to validate the proposed adaptive update law’s effectiveness.

Star-type melamine based conjugated carboxy functionalized porphyrin trimer for DSSCs: An efficient approach to clean, aggregation free and true energy generation

A novel, π-conjugated melamine-based trimeric porphyrin dye with serving nine carboxylate linker groups has been prepared to use as a panchromatic dye for application in dye-sensitized solar cells (DSSCs). The star-shaped trimer was characterized by using Proton Nuclear Magnetic Resonance (NMR) Spectroscopy, Carbon Nuclear Magnetic Resonance Spectroscopy (CMR), Fourier Transformed Infrared Spectroscopy (FT-IR), UV-VIS Absorption Spectroscopy, Thermo-gravimetric analysis (TGA), Cyclic Voltammetry (CV) and Electrochemical Impedance Studies (EIS). CV studies revealed frontiers energy levels at −5.654 (HOMO) and −3.879 eV (LUMO) versus vacuum. The optical band gap evolved via absorption spectra measurements was found to be 1.49 eV. A planar perfect conjugation among three porphyrins sets up multiple push-pull communication and lowers the bandgap, while nine carboxylate linkers cover-up TiO2 surface effectively leading to better electronic dynamics. The DSSC set up using iodide-based redox couples forms a simple, stable, additive-free, truly energy generating device with 7.1% conversion efficiency, the highest among trimeric porphyrin category.

Comparison of three zinc binding groups for HDAC inhibitors – A potency, selectivity and enzymatic kinetics study

Hydroxamic acid and benzamide are the most commonly used zinc binding group (ZBG) for HDAC inhibitors both in clinic and pre-clinic. Recently, we discovered several analogs of new type HDAC inhibitors with hydrazide as ZBG. Representative compounds displayed high potency, class I HDAC selectivity and excellent pharmacokinetics profile. In this research, we synthesize tool compounds 4 and 6 by modifying the hydroxamic acid of SAHA with benzamide and hydrazide, respectively, and compare the potency, isoform selectivity, binding profile and enzymatic kinetics for the hydroxamate, benzamide and hydrazide-based inhibitors. It is well known that SAHA with hydroxamic acid is a pan-HDAC inhibitor with competitive binding and fast-on/fast-off profile. Compound 6 is a slow-binding class I selective inhibitor with mixed (competitive and non-competitive) binding mode, which is the same as the hydrazide inhibitors in our previous study. Compound 4 is a class I selective, fast-on/fast-off inhibitor with competitive binding mode to HDAC1/2/3, which is different with published benzamide MS275 and 106. Therefore, the kinetics profile of benzamide is not only due to the ZBG, but also rely on the cap and linker groups. To the best of our knowledge, this is the first report to compare the enzymatic profile of three promising ZBGs of HDAC inhibitors.

Self-Assembly of Alkylamido Isophthalic Acids toward the Design of a Supergelator: Phase-Selective Gelation and Dye Adsorption.

A new series of 5-alkylamido isophthalic acid (ISA) derivatives with varying single and twin alkyl chain lengths were designed and synthesized as potential supramolecular organogelators. 5-alkylamido ISAs with linear or branched alkyl tail-groups of different lengths were effective gelators for low polarity solvents. In particular, among the presented series, a derivative with a branched, 24 carbon atom tail-group behaves as a “supergelator” with up to twenty organic solvents forming gels that are highly stable over time. The gelation behavior was analyzed using Hansen solubility parameters, and the thermal stability and viscoelastic properties of select gels were characterized. Microscopy, spectroscopy, powder X-ray diffraction, and computer modeling studies were consistent with a hierarchical self-assembly process involving the formation of cyclic H-bonded hexamers via the ISA carboxylic acid groups, which stack into elementary fibers stabilized by H-bonding of the amide linker groups and π–π stacking of the aromatic groups. These new nanomaterials exhibited potential for the phase-selective gelation of oil from oil–water mixtures and dye uptake from contaminated water. The work expands upon the design and synthesis of supramolecular self-assembled nanomaterials and their application in water purification/remediation.

Toward High-Performance CO2 -to-C2 Electroreduction via Linker Tuning on MOF-Derived Catalysts.

Copper (Cu)-based metal-organic frameworks (MOFs) and MOF-derived catalysts are well studied for electroreduction of carbon dioxide (CO2 ); however, the effects of organic linkers for the selectivity of CO2 reduction are still unrevealed. Here, a series of Cu-based MOF-derived catalysts is investigated with different organic linkers appended, named X-Cu-BDC (BDC=1,4-benzenedicarboxylic acid, X=NH2 , OH, H, F, and 2F). It is found that the linkers affect the faradaic efficiency (FE) for C2 products with an order of NH2 <OH<bare Cu-BDC<F<2F, thus tuning the FEC2 :FEC1 ratios from 0.6 to 3.8. As a result, the highest C2 FE of ≈63% at a current density of 150mAcm-2 on 2F-Cu-BDC derived catalyst is achieved. Using operando Raman measurements, it is revealed that the MOF derives to Cu2 O during eCO2 RR but organic linkers are stable. The fluorine group in organic linker can promote the H2 O dissociation to *H species, further facilitating the hydrogenation of *CO to *CHO that helps CC coupling.

Formation and Evolution of Metallocene Single-Molecule Circuits with Direct Gold-π Links.

Single-molecule circuits with group 8 metallocenes are formed without additional linker groups in scanning tunneling microscope-based break junction (STMBJ) measurements at cryogenic and room-temperature conditions with gold (Au) electrodes. We investigate the nature of this direct gold-π binding motif and its effect on molecular conductance and persistence characteristics during junction evolution. The measurement technique under cryogenic conditions tracks molecular plateaus through the full cycle of extension and compression. Analysis reveals that junction persistence when the metal electrodes are pushed together correlates with whether electrodes are locally sharp or blunt, suggesting distinct scenarios for metallocene junction formation and evolution. The top and bottom surfaces of the "barrel"-shaped metallocenes present the electron-rich π system of cyclopentadienyl rings, which interacts with the gold electrodes in two distinct ways. An undercoordinated gold atom on a sharp tip forms a donor-acceptor bond to a specific carbon atom in the ring. However, a small, flat patch on a dull tip can bind more strongly to the ring as a whole through van der Waals interactions. Density functional theory (DFT)-based calculations of model electrode structures provide an atomic-scale picture of these scenarios, demonstrating the role of these bonding motifs during junction evolution and showing that the conductance is relatively independent of tip atomic-scale structure. The nonspecific interaction of the cyclopentadienyl rings with the electrodes enables extended conductance plateaus, a mechanism distinct from that identified for the more commonly studied, rod-shaped organic molecular wires.

The Core‐Shell Magnetic Mesoporous Microspheres Immobilized NHC‐Palladacycles: An Efficient and Recyclable Catalyst for Suzuki‐Miyaura Cross‐Coupling of Pharmaceutical Synthesis

AbstractThe core‐shell magnetic mesoporous microspheres immobilized NHC‐palladacycles (NHC=N‐heterocyclic carbene) catalyst with constrained aliphatic linker group (Fe3O4@mSiO2@NHC−Pd) were readily prepared by the well‐designed method, which showed higher palladium loading (0.20 mmol g−1) and higher catalytic activity than the non‐mesoporous catalysts (Fe3O4@SiO2@NHC−Pd) prepared by the same process in the Suzuki‐Miyaura cross‐coupling reactions of aryl chlorides and aryl boronic acids. Herein, Fe3O4@mSiO2@NHC−Pd could be used 12 times without significant activity loss, and no palladium leakage was detected in both the product and catalytic residue, highlighting the efficiency of our strategy for immobilizing the catalyst. Remarkably, this approach allows the synthesis of important drug intermediates 2‐aryl‐4‐aminoquinazolines and o‐tolylbenzonitrile (OTBN).

Fine-tuning of pore-space-partitioned metal-organic frameworks for efficient C2H2/C2H4 and C2H2/CO2 separation

Acetylene (C2H2) and ethylene (C2H4) both are important chemical raw materials and energy fuel gasses. But the effective removement of trace C2H2 from C2H4 and the purification of C2H2 from carbon dioxide (CO2) are particularly challenging in the petrochemical industry. As a class of porous physical adsorbent, metal-organic frameworks (MOFs) have exhibited great success in separation and purification of light hydrocarbon gas. Herein, we rationally designed four novel MOFs by the strategy of pore space partition (PSP) via introducing triangular tri(pyridin-4-yl)-amine (TPA) into the 1D hexagonal channels of acs-type parent skeleton. By modulating the functional groups of linear dicarboxylate linkers for the parent skeleton, a series of isoreticular PSP-MOFs (SNNU-278−281) were successfully obtained. The synergistic effects of suitable pore size and Lewis basic functional groups make these MOFs ideal C2H2 adsorbents. The gas adsorption experimental results show that all MOFs have excellent C2H2 uptakes. Specially, SNNU-278 demonstrates a high C2H2 uptake of 149.7 cm3/g at 273 K and 1 atm. Meanwhile, SNNU-278−281 MOFs also show extremely great C2H2 separation from CO2 and C2H4. The optimized SNNU-281 with high-density hydroxy groups exhibits extraordinary C2H2/CO2 and C2H2/C2H4 dynamic breakthrough interval times up to 31 min/g and 17 min/g under 298 K and 1 bar.

Substantiations of the beginnings of a unified theory of planetary gears

Multi-satellite planetary mechanisms are analyzed. A new approach to the creation of planetary gearboxes on the principle of L. V. Assur's mechanisms is proposed, according to which the satellites add a group of links of zero mobility to the kinematic chain. Schemes of patented multi-satellite planetary gears are shown. The basis for the development of a new theory of design and manufacture of planetary gearboxes is presented. Keywords: planetary gear, satellite, multi-satellite transmission, uniform load distribution, gear transmission. tmmiok@yandex.ru, tmmiok@yandex.ru

Functionalized Homologues and Positional Isomers of Rabbit 15- Lipoxygenase RS75091 Inhibitor.

RS75091 is a cinnamic acid derivative that has been used for the crystallization of the rabbit ALOX15-inhibitor complex. The atomic coordinates of the resolved ALOX15- inhibitor complex were later on used to define the binding sites of other mammalian lipoxygenase orthologs, for which no direct structural data with ligand has been reported so far. The putative binding pocket of the human ALOX5 was reconstructed on the basis of its structural alignment with rabbit ALOX15-RS75091 inhibitor. However, considering the possible conformational changes the enzyme may undergo in solution, it remains unclear whether the existing models adequately mirror the architecture of ALOX5 active site. In this study, we prepared a series of RS75091 derivatives using a Sonogashira coupling reaction of regioisomeric bromocinnamates with protected acetylenic alcohols and tested their inhibitory properties on rabbit ALOX15. A bulky pentafluorophenyl moiety linked to either ortho- or metha-ethynylcinnamates via aliphatic spacer does not significantly impair the inhibitory properties of RS75091. Hydroxylated 2- and 3-alkynylcinnamates may be suitable candidates for incorporation of an aromatic linker group like tetrafluorophenylazides for photoaffinity labeling assays.

Tertiary amine-bisquaternary ammonium functionalized polyacrylonitrile fiber for catalytic synthesis of pyran-annulated heterocycles

Polyacrylonitrile fiber supported bisquaternary ammonium salts with varying interchain quaternary ammonium (QA) to tertiary amine (TA) ratio, counter ions and linker groups were prepared and characterized by TGA, FTIR, XPS, XRD, SEM, EA and water contact angle. The functionalized fibers were used to catalyze three-component reaction (3CR) and tandem deacetalization-3CR for the synthesis of pyrano[4,3-b]pyrans, pyrano[3,2-c]chromenes and pyrano[3,2-c]quinolines in ethanol-water mixture. Under varying reaction conditions such as time, temperature, catalyst amount and solvents, the catalytic ability of the prepared fiber catalyst was investigated. Under the optimum conditions, the bisquaternary ammonium fiber with acetate counter ion and an interchain QA to TA ratio of 1:1 (PANBQAcF) showed the best catalytic activity among the prepared fiber catalysts, and it can be used for 10 runs consecutively with only a slight depreciation in catalytic activity. Interestingly, PANBQAcF can efficiently catalyze tandem deacetalization-Knoevenagel reaction and the relevant novel tandem deacetalization-3CRs for the synthesis of pyran-annulated heterocycles. In the tandem deacetalization reactions, the acetate ion plays an important role of facilitating proton transfer, which makes PANBQAcF a cooperative and reusable heterogeneous catalyst.

Reversible Dissociation for Effective Storage of Diborane Gas within the UiO-66-NH2 Metal-Organic Framework.

There is an acute need for materials that can store the toxic and highly reactive diborane gas at room temperature. In this work, the interfacial chemistry leading to safe and reversible storage of diborane (B2H6) in the UiO-66-NH2 metal-organic framework (MOF) was investigated via in situ transmission infrared (IR) spectroscopy, temperature-programmed desorption (TPD), and electronic structure calculations. The infrared spectrum of B2H6 adsorbed within UiO-66-NH2 indicates hydrogen bonding with the μ3-OH groups of the MOF nodes and chemisorption at the -NH2 groups of the MOF linkers. The conversion of physisorbed to chemisorbed diborane, as observed through a spectroscopically unique intermediate species, occurred over a broad temperature regime from 80 to 410 K. During B2H6-TPD studies, both the weakly and strongly bound species were found to desorb exclusively as molecular B2H6. Infrared spectroscopic studies, performed during diborane adsorption and reaction, combined with electronic structure calculations, revealed that chemisorption occurred via a reversible dissociation reaction involving a "half-open" B2H6 intermediate and resulted in the formation of two NH2-bound BH3 units, which leave the MOF as B2H6 via recombinative desorption. The close spacing of -NH2 groups in the UiO-66-NH2 MOF is key to enabling high-temperature chemisorptive storage of B2H6, and the spatial arrangement of the amine groups has a significant effect on the dissociation energy profile. This work demonstrates that reversible dissociation of B2H6 on precisely engineered, nucleophile-rich materials represents a promising pathway to diborane stabilization and long-term storage.

Ligand Defect Density Regulation in Metal-Organic Frameworks by Functional Group Engineering on Linkers.

Defects in solid materials vitally determine their physicochemical properties; however, facile regulation of the defect density is still a challenge. Herein, we demonstrate that the ligand defect density of metal-organic frameworks (MOFs) with a UiO-66 structural prototype is precisely regulated by tuning the linker groups (X = OMe, Me, H, F). Detailed analyses reveal that the ligand defect concentration is positively correlated with the electronegativity of linker groups, and Ce-UiO-66-F, constructed by F-containing ligands and Ce-oxo nodes, possesses the superior ligand defect density (>25%) and identifiable irregular periodicity. The increase in ligand defect density results in the reduction of the valence state and the coordination number of Ce sites in Ce-UiO-66-X, and this merit further validates the relationship between the defective structure and catalytic performance of CO2 cycloaddition reaction. This facile, efficient, and reliable strategy may also be applicable to precisely constructing the defect density of porous materials in the future.

Slopes and signatures of links

We define the slope of a colored link in an integral homology sphere, associated to admissible characters on the link group. Away from a certain singular locus, the slope is a rational function which can be regarded as a multivariate generalization of the Kojima--Yamasaki $\eta$-function. It is the ratio of two Conway potentials, provided that the latter makes sense; otherwise, it is a new invariant. The slope is responsible for an extra correction term in the signature formula for the splice of two links, in the previously open exceptional case where both characters are admissible. Using a similar construction for a special class of tangles, we formulate generalized skein relations for the signature.

Anchored complexes of rhodium and iridium for the hydrogenation of alkynes and olefins with parahydrogen

Iridium and rhodium complexes anchored on silica gel surface via NH2–(CH2)3– and P(Ph)2–(CH2)2– linker groups achieve high (∼9%) efficiency in pairwise addition of parahydrogen to unsaturated gaseous substrates in heterogeneous hydrogenation processes.

Robust QoT Assured Resource Allocation in Shared Backup Path Protection Based EONs

Survivability is mission-critical for elastic optical networks (EONs) as they are expected to carry an enormous amount of data. In this paper, we consider the problem of designing shared backup path protection (SBPP) based EON that facilitates the minimum quality-of-transmission (QoT) assured allocation against physical layer impairments (PLIs) under any single link/shared risk link group (SRLG) failure for static and dynamic traffic scenarios. In general, the effect of PLIs on lightpath varies based on the location of failure of a link as it introduces different active working and backup paths. To address these issues in the design of SBPP EON, we formulate a mixed integer linear programming (MILP) based robust optimization framework for static traffic with the objective of minimizing overall fragmentation. In this process, we use the efficient robust bitloading technique for spectrum allocation where each frequency slot of a request is assigned with different modulation format. In addition, we propose novel SBPP-impairment aware (SBPP-IA) algorithm considering the limitations of MILP for larger networks. For this purpose, we introduce a novel sorting technique named most congested working-least congested backup first (MCW-LCBF) to sort the given set of requests. Next, we employ our SBPP-IA algorithm for dynamic traffic scenario and compare it with existing algorithms in terms of different QoT parameters. Further, we guarantee the QoT of existing requests while allocating each new request without reserving any margin. We demonstrated through simulations that our study provides 33.94-41.02% more QoT guaranteed requests compared to existing ones at 70 Tbps traffic load.

Virtually symmetric representations and marked Gauss diagrams

In this paper, we define the notion of a virtually symmetric representation of representations of virtual braid groups and prove that many known representations are equivalent to virtually symmetric. Using one such representation, we define the notion of virtual link groups which is an extension of virtual link groups defined by Kauffman. Moreover, we introduce the concept of marked Gauss diagrams as a generalisation of Gauss diagrams and their interpretation in terms of knot-like diagrams. We extend the definition of virtual link groups to marked Gauss diagrams and define their peripheral structure. We define Cm-groups and prove that every group presented by a 1-irreducible C1-presentation of deficiency 1 or 2 can be realised as the group of a marked Gauss diagram.

Augmentations and link group representations

We construct the augmentation representation. It is a representation of the fundamental group of the link complement associated to an augmentation of the framed cord algebra. This construction connects representations of two link invariants of different types. We also study properties of the augmentation representation.

Discovery of phenyl-linked symmetric small molecules as inhibitors of the programmed cell death-1/programmed cell death-ligand 1 interaction.

Programmed cell death-1/programmed cell death ligand 1 (PD-1/PD-L1) is one of the most promising targets in the field of immune checkpoint blockade therapy. Beginning with our exploration of linkers and structure-activity relationship research, we found that the aromatic ring could replace the linker and aryl group to maintain the satisfactory activity of classic triaryl scaffold inhibitor. Based on previous studies, we designed and synthesized a series of C2-symmetric phenyl-linked compounds, and further tail optimization afforded the inhibitors, which displayed promising inhibitory activity against the PD-1/PD-L1 interaction with IC50 value at the single nanomolar range (C13-C15). Further cell-based PD-1/PD-L1 blockade bioassays indicated that these C2-symmetric molecules could significantly inhibit the PD-1/PD-L1 interaction at the cellular level and restore T cells' immune function at the safety concentrations. The discovery of these phenyl-linked symmetric small molecules showed the potential of simplified-linker and C2-symmetric strategy and provided a basis for developing symmetric small molecule inhibitors of PD-1/PD-L1 interaction. Moreover, C13 and C15 performed stable binding modes to PD-L1 dimeric after computational docking and dynamic simulation, which may serve as a good starting point for further development.