出版者・発行元：Plos One  

Making data FAIR—findable, accessible, interoperable, reproducible—has become the recurring theme behind many research data management efforts. dtool is a lightweight data management tool that packages metadata with immutable data to promote accessibility, interoperability, and reproducibility. Each dataset is self-contained and does not require metadata to be stored in a centralised system. This decentralised approach means that finding datasets can be difficult. dtool’s lookup server, short dserver, as defined by a REST API, makes dtool datasets findable, hence rendering the dtool ecosystem fit for a FAIR data management world. Its simplicity, modularity, accessibility and standardisation via API distinguish dtool and dserver from other solutions and enable it to serve as a common denominator for cross-disciplinary research data management. The dtool ecosystem bridges the gap between standardisation-free data management by individuals and FAIR platform solutions with rigid metadata requirements.

DOI： 10.1371/journal.pone.0306100

Open Access

Scopus

出版者・発行元：Journal of Chemical Physics  

We use molecular dynamics simulations to study the frictional response of monolayers of the anionic surfactant sodium dodecyl sulfate and hemicylindrical aggregates physisorbed on gold. Our simulations of a sliding spherical asperity reveal the following two friction regimes: at low loads, the films show Amonton's friction with a friction force that rises linearly with normal load, and at high loads, the friction force is independent of the load as long as no direct solid-solid contact occurs. The transition between these two regimes happens when a single molecular layer is confined in the gap between the sliding bodies. The friction force at high loads on a monolayer rises monotonically with film density and drops slightly with the transition to hemicylindrical aggregates. This monotonous increase of friction force is compatible with a traditional plowing model of sliding friction. At low loads, the friction coefficient reaches a minimum at the intermediate surface concentrations. We attribute this behavior to a competition between adhesive forces, repulsion of the compressed film, and the onset of plowing.

DOI： 10.1063/5.0153397

Open Access

Scopus

出版者・発行元：Tribology Letters  

We study the frictional response of water-lubricated gold electrodes subject to an electrostatic potential difference using molecular dynamics simulations. Contrary to previous studies on electrotunable lubrication that were carried out by fixing the charges, our simulations keep electrodes at fixed electrostatic potential using a variable charge method. For pure water and NaCl solutions, viscosity is independent of the polarization of the electrodes, but wall slip depends on the potential difference. Our findings are in agreement with previous analytical theories of how wall slip is affected by interatomic interactions. The simulations shed light on the role of electrode polarization for wall slip and illustrate a mechanism for controlling friction and nanoscale flow in simple aqueous lubricants.

DOI： 10.1007/s11249-020-01395-6

Open Access

Scopus

出版者・発行元：Mikrosystemtechnik Kongress 2021 Mikroelektronik Mikrosystemtechnik Und Ihre Anwendungen Innovative Produkte Fur Zukunftsfahige Markte Proceedings  

A widespread technology for analysing solid surfaces is atomic force microscopy, whose probes can operate in aqueous environment. In electrolytes, applied potential differences lead to a potential-specific double layer structure. We investigate the impact of probe geometry on the ionic charge distributions within a confined electrolyte. We obtain the equilibrium distributions of cations and anions by solving the static Poisson-Nernst-Planck equations. To illuminate the relationship between probe geometry and ion distributions, we investigate three specific geometries: a paraboloid probe and an extruded parabolic probe above a planar electrode, and a reference system of two opposing planar electrodes without any protruding probe geometry. Within those three geometries, we solve Poisson‘s equation coupled to the Nernst-Planck equations capturing drift and diffusion of an arbitrary number of ion species by means of the classical Finite Element Method (FEM). Our calculations show that the systems of parabolic or paraboloid probe geometry assume a near-electroneutral plateau between substrate and probe apex for our choice of parameters. This agrees well with expectations based on the classical double layer model at a plate capacitor. Parabola and paraboloid show a potential offset between their respective plateaus. The higher the reference concentration the broader the electroneutral plateau. Reducing this concentration, we observe the point of geometry-induced divergence from one-dimensional behaviour to move towards the planar electrode. By finding geometry-induced differences in behaviour, we have reached a better understanding of how the shape of probe tips can manipulate the electrochemical double layer structure between substrate and probe in atomic force microscopy systems. Within the investigated parameter space, the geometry of the probe tip has a non-negligible influence. When comparing a rotational symmetry with an axial symmetry, the potential difference between an electroneutral point and the substrate is lower for the former case.

Scopus