Imaging internal flows in a drying sessile polymer dispersion drop using Spectral Radar Optical Coherence Tomography (SR-OCT)

In this work, we present the visualization of the internal flows in a drying sessile polymer dispersion drop on hydrophilic and hydrophobic surfaces with Spectral Radar Optical Coherence Tomography (SR-OCT).We have found that surface features such as the initial contact angle and pinning of the contact line, play a crucial role on the flow direction and final shape of the dried drop. Moreover, imaging through selection of vertical slices using optical coherence tomography offers a feasible alternative compared to imaging through selection of narrow horizontal slices using confocal microscopy for turbid, barely transparent fluids

The four leading arms of the Magellanic Cloud system

The Magellanic Cloud System (MCS) interacts via tidal and drag forces with the Milky Way galaxy. Using the Parkes Galactic All-Sky Survey (GASS) of atomic hydrogen we explore the role of drag on the evolution of the so-called Leading Arm (LA). We present a new image recognition algorithm that allows us to differentiate features within a 3-D data cube (longitude, latitude, radial velocity) and to parameterize individual coherent structures. We compiled an HI object catalog of LA objects within an area of 70 degr x 85 degr (1.6 sr) of the LA region. This catalog comprises information of location, column density, line width, shape and asymmetries of the individual LA objects above the 4-sigma threshold of Delta T_b simeq 200 mK. We present evidence of a fourth arm segment (LA4). For all LA objects we find an inverse correlation of velocities v_GSR in Galactic Standard of Rest frame with Magellanic longitude. High-mass objects tend to have higher radial velocities than low-mass ones. About 1/4 of all LA objects can be characterized as head-tail (HT) structures. Using image recognition with objective criteria, it is feasible to isolate most of LA emission from the diffuse Milky Way HI gas. Some blended gas components (we estimate 5%) escape detection, but we find a total gas content of the LA that is about 50% higher than previously assumed. These methods allow the deceleration of the LA clouds to be traced towards the Milky Way disk by drag forces. The derived velocity gradient strongly supports the assumption that the whole LA originates entirely in the Large Magellanic Cloud (LMC). LA4 is observed opposite to LA1, and we propose that both arms are related, spanning about 52kpc in space. HT structures trace drag forces even at tens of kpc altitudes above the Milky Way disk.Comment: 12 pages, 7 figures, 2 tables, accepted for publication Astronomy & Astrophysics 201

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

Wechselwirkung von funktionellen Amphiphilen Polymeren mit Modellmembranen

SIGLEAvailable from TIB Hannover: MA 6599 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman