Neuro-mechanical entrainment in a bipedal robotic walking platform

In this study, we investigated the use of van der Pol oscillators in a 4-dof embodied bipedal robotic platform for the purposes of planar walking. The oscillator controlled the hip and knee joints of the robot and was capable of generating waveforms with the correct frequency and phase so as to entrain with the mechanical system. Lowering its oscillation frequency resulted in an increase to the walking pace, indicating exploitation of the global natural dynamics. This is verified by its operation in absence of entrainment, where faster limb motion results in a slower overall walking pace

Oligomeric Gold−Thiolate Units Define the Properties of the Molecular Junction between Gold and Benzene Dithiols

Understanding the structure and conductance of the molecular junction between benzene dithiolates (BDT) and gold electrodes has posed a classic unsolved problem for high-level theoretical work for over a decade. Recent breakthroughs for the gold−thiolate interface in thiolate-passivated gold clusters and in Au(111)/self-assembled monolayers (SAMs) motivated us to reanalyze the properties of Au−BDT−Au junctions. We show that distinct molecular Au(SR)₂ and Au₂(SR)₃ units, which are known to exist at the nanoparticle−thiolate and Au−SAM interfaces, define the properties of the electrode−molecule junction. These units can form multiple contacts. The junction can be stretched by more than 1 nm whereby alternating gold−thiolate chains are spontaneously formed in ab initio molecular dynamics simulations. The calculated conductance values for the BDT junctions agree with a wide range of reported experimental data. Our results give a solid ground for further theoretical studies of molecular junctions between gold and a wide variety of organic molecules containing dithiols

Silver-Stabilized Guanine Duplex: Structural and Optical Properties

Recent experimental duplexes of DNA stabilized by Ag cations, pairing homostrands of guanine–guanine, cytosine–cytosine, adenine–thymine, and thymine–thymine, display much higher stability than the Watson–Crick paired DNA duplexes; these broaden the range of applications for DNA nanotechnology. Here we focus on silver-stabilized guanine duplexes in water. Using hybrid quantum mechanics/molecular mechanics simulations, we propose an atomic structure for the Ag⁺-mediated guanine duplex with two nucleobases per strand, G₂–Ag₂⁺–G₂. We then compare experimental and time-dependent density functional theory-simulated electronic circular dichroism (ECD) spectra to validate our results. Both experimental and simulated ECD share two negative peaks around 220 and 280 nm, with no positive signal in the measured wavelength range. We found that the left- or right-handed disposition of bases in the structure has a decisive effect on the signs of the ECD. We conclude that G₂–Ag₂⁺–G₂ is left-hand-oriented, and extrapolation of this orientation to longer strands gives rise to a left-hand-oriented parallel helix stabilized by interplanar H bonds