The VMC survey - VIII : First results for anomalous Cepheids

The VISTA near-infrared YJKs survey of the Magellanic Clouds System (VMC, PI M.-R. L. Cioni) is collecting deep Ks-band time-series photometry of the pulsating variable stars hosted in the system formed by the two Magellanic Clouds and the Bridge connecting them. In this paper, we present for the first time Ks-band light curves for anomalous Cepheid (AC) variables. In particular, we have analysed a sample of 48 Large Magellanic Cloud ACs, for which identification and optical magnitudes were obtained from the OGLE III and IV catalogues. The VMC Ks-band light curves for ACs are well sampled, with the number of epochs ranging from 8 to 16, and allowing us to obtain very precise mean Ks magnitudes with errors on average of the order of 0.01 mag. The values were used to build the first period-luminosity and period-Wesenheit relations in the near-infrared for fundamental mode and first overtone ACs. At the same time we exploited the optical (V, I) OGLE data to build accurate period-luminosity, period-luminosity-colour and period-Wesenheit relations both for fundamental mode and first overtone ACs. For the first time, these relations were derived from a sample of pulsators which uniformly cover the whole AC instability strip. The application of the optical period-Wesenheit relation to a sample of dwarf galaxies hosting a significant population of ACs revealed that this relation is a valuable tool for deriving distances within the Local Group. Due to its lower dispersion, we expect the Ks period-Wesenheit relations first derived in this paper to represent a valuable tool for measuring accurate distances to galaxies hosting ACs when more data in near-infrared filters become available.Peer reviewe

Superspreading: Mechanisms and Molecular Design

The intriguing ability of certain surfactant molecules to drive the superspreading of liquids to complete wetting on hydrophobic substrates is central to numerous applications that range from coating flow technology to enhanced oil recovery. Despite significant experimental efforts, the precise mechanisms underlying superspreading remain unknown to date. Here, we isolate these mechanisms by analyzing coarse-grained molecular dynamics simulations of surfactant molecules of varying molecular architecture and substrate affinity. We observe that for superspreading to occur, two key conditions must be simultaneously satisfied: the adsorption of surfactants from the liquid–vapor surface onto the three-phase contact line augmented by local bilayer formation. Crucially, this must be coordinated with the rapid replenishment of liquid–vapor and solid–liquid interfaces with surfactants from the interior of the droplet. This article also highlights and explores the differences between superspreading and conventional surfactants, paving the way for the design of molecular architectures tailored specifically for applications that rely on the control of wetting

Zur Schlangenfauna S\ufcd-Kleinasiens, speziell des cilicischen Taurus

Volume: 83Start Page: 95End Page: 12

Voltage-induced spreading and superspreading of liquids

The ability to quickly spread a liquid across a surface and form a film is fundamental for a diverse range of technological processes, including printing, painting and spraying. We show that liquid dielectrophoresis or electrowetting can produce wetting on normally non-wetting surfaces, without needing modification of the surface topography or chemistry. Additionally, super-spreading can be achieved without needing surfactants in the liquid. We use a modified Hoffman-de Gennes law to predict three distinct spreading regimes: (i) exponential approach to an equilibrium shape, (ii) spreading to complete wetting obeying a Tanner’s law-type relationship, and (iii) superspreading towards a complete wetting film. We demonstrate quantitative experimental agreement with these predictions using dielectrophoresis induced spreading of stripes of 1,2 propylene glycol. Our findings show how the rate of spreading of a partial wetting system can be controlled using uniform and non-uniform electric fields and how to induce more rapid super-spreading using voltage control

Voltage-induced spreading and superspreading of liquids

The ability to quickly spread a liquid across a surface and form a film is fundamental for a diverse range of technological processes, including printing, painting and spraying. We show that liquid dielectrophoresis or electrowetting can produce wetting on normally non-wetting surfaces, without needing modification of the surface topography or chemistry. Additionally, super-spreading can be achieved without needing surfactants in the liquid. We use a modified Hoffman-de Gennes law to predict three distinct spreading regimes: (i) exponential approach to an equilibrium shape, (ii) spreading to complete wetting obeying a Tanner’s law-type relationship, and (iii) superspreading towards a complete wetting film. We demonstrate quantitative experimental agreement with these predictions using dielectrophoresis induced spreading of stripes of 1,2 propylene glycol. Our findings show how the rate of spreading of a partial wetting system can be controlled using uniform and non-uniform electric fields and how to induce more rapid super-spreading using voltage control