42 research outputs found
Diazadimethano[8]circulene: Synthesis, structure, properties, and isolation of stable radical cation
No full textHetero[8]circulenes have emerged as novel heteroatom-doped polycyclic aromatic hydrocarbons whose properties depend on the constituent aromatic units. Herein we report a C-doped variant, diazadimethano[8]circulene 3, in which two diphenylcyclopentadiene units are installed into the core of [8]circulene that may prevent effective conjugation. The structure of 3 has been revealed to have two longer C–C bonds in the central eight-membered ring, while the absorption and emission profiles are quite similar to those of tetraaza[8]circulene. Stable radical cation 3⁺ was easily obtained by facile oxidation of 3. X-ray diffraction analysis of 3⁺ showed a slipped dimer arrangement with negligible intermolecular interaction. Interestingly, the lowest-energy absorption of 3⁺ reaches around 2500 nm, while that of 3 is 447 nm
GREEMA: Proposal and Experimental Verification of Growing Robot by Eating Environmental MAterial for Landslide Disaster
No full textIn areas that are inaccessible to humans, such as the lunar surface and
landslide sites, there is a need for multiple autonomous mobile robot systems
that can replace human workers. In particular, at landslide sites such as river
channel blockages, robots are required to remove water and sediment from the
site as soon as possible. Conventionally, several construction machines have
been deployed to the site for civil engineering work. However, because of the
large size and weight of conventional construction equipment, it is difficult
to move multiple units of construction equipment to the site, resulting in
significant transportation costs and time. To solve such problems, this study
proposes a novel growing robot by eating environmental material called GREEMA,
which is lightweight and compact during transportation, but can function by
eating on environmental materials once it arrives at the site. GREEMA actively
takes in environmental materials such as water and sediment, uses them as its
structure, and removes them by moving itself. In this paper, we developed and
experimentally verified two types of GREEMAs. First, we developed a fin-type
swimming robot that passively takes water into its body using a water-absorbing
polymer and forms a body to express its swimming function. Second, we
constructed an arm-type robot that eats soil to increase the rigidity of its
body. We discuss the results of these two experiments from the viewpoint of
Explicit-Implicit control and describe the design theory of GREEMA
Exploration of sheepdog controller for sheep flock navigation based on the model derived from a real shepherding
No full textBIORO
Scholl Reaction of ortho-Phenylene-Bridged Cyclic Pyrrole-Thiophene Hybrid Hexamer
No full textThe Scholl reaction of ortho-phenylene-bridged cyclic pyrrole-thiophene hybrid hexamer gave cyclophane-type [5]heterohelicene exclusively in 45% yield. The structure was unambiguously revealed by X-ray diffraction analysis. This helicenophane-type compound showed sharp absorption and fluorescence spectra, reflecting its rigid structure. The reaction path was analyzed on the basis of DFT calculations, and it was found that the formation of the [5]helicene-dimer is thermodynamically favored and further oxidation is prohibited due to the increased strain energy
Efficient and facile synthesis of cyanohydrin carbonate promoted by γ-alumina
No full textA variety of cyanohydrin carbonates were readily prepared by the reaction of aldehydes with cyanoformate under the influence of γ-alumina using a convenient one-pot procedure.</p
Fold‐in Synthesis of a Pentabenzopentaaza[10]circulene
No full textA pentabenzopentaaza[10]circulene has been synthesized as the largest fully conjugated hetero[n]circulene via a fold-in oxidative fusion reaction of an ortho-phenylene-bridged cyclic pyrrole pentamer. This circulene takes a saddle-distorted structure with bond lengths of the central ten-membered-ring in the range of 1.455–1.493 Å. Relatively broad absorption and fluorescence spectra were observed, which reflects its flexible structure, in accordance with the low-temperature NMR spectra and theoretical calculations. The energy barrier for saddle-to-saddle interconversion was estimated to be quite small (≈3 kcal mol⁻¹)
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Author Correction: Vulnerability to collapse of coral reef ecosystems in the Western Indian Ocean
No full textCorrection to: Nature Sustainability https://doi.org/10.1038/s41893-021-00817-0, published online 6 December 2021.This paper was originally published under the standard Springer Nature license (© The Author(s), under exclusive licence to Springer Nature America, Inc.). It is now available as an open-access paper under a Creative Commons Attribution 4.0 International license, © The Author(s). The error has been corrected in the HTML and PDF versions of the article
Mathematical Modeling of a Quasi-passive Dynamic Walker with Whole-body Tensile Connections
No full textHumans have whole-body viscoelastic connections called anatomy trains (ATs), which include multiple muscles and connective tissues. ATs are expected to realize coordinated motion in passive dynamic walkers with a large number of joints. However, the details of how the coordinated motion is realized are not fully understood. In this paper, we propose a mathematical model of a quasi-passive dynamic walker with whole-body viscoelastic connections inspired by the AT theory, and investigate how the connections improve the walking performance in numerical simulation. We introduced a tension transmission line that connects from the foot to the head, modeled after one of human ATs, the superficial back line (SBL), into the mathematical model of a conventional passive walker. The important features of this whole-body line are that the tension transmission function of the line can be instantly switched on/off by a controller that contracts and relaxes the line, and that the line in a contracted state mechanically interacts with the whole-body joints, depending on the spring constant of the line and the posture of the whole body. The simulation results indicate that the walking performance, i.e., the step count, can be improved under the specific combinations of the spring constant and the on/off timing of the whole-body line. These results suggest a method for tuning the SBL to improve the step count, based on the step count and how posture is disrupted. By accumulating insights through both simulations using this mathematical model and experiments with physical robots, while cross-referencing these approaches, it is anticipated that this will eventually contribute to theoretical analysis in the future
