Rim instability in dewetting of thin polymer films

Understanding flow properties at the solid/liquid interface is important for numerous of technological applications in nanotechnology and microfluidic. The strong scientific interest in the field of thin liquid films led to new conclusions on the impact of hydrodynamic slippage on the dewetting dynamics and on the shape of the rim growing at the three phase contact line. This work consists of verifying the validity of these findings at late stage of dewetting, i.e. while the rim instability develops, and of drawing new conclusions linking interactions at interfaces with the later instability. In a first part, a qualitative analysis demonstrates a rim instability decomposed into several regimes, while fingering solely develops with flows with strong interfacial slip length. A closer look of the instability at nanometric resolution evidences the onset of a second flow varying with slippage but also with viscosity. We finally propose a new method to determine to what extent hydrodynamic slippage interferes flow properties in the rim.Das Verständnis der Fließeigenschaften an der Fest/flüssig-Grenzfläche ist wichtig für viele technische Anwendungen in der Nanotechnologie und Mikrofluidik. Das starke wissenschaftliche Interesse im Bereich der d¨unnen Filmen f¨uhrte zu neuen Erkenntnissen, wie sich hydrodynamisches Rutschen auf die Form eines sich von der Drei-Phasenkontaktlinie eintwickeknden Randwulstes auswirkt. Diese Arbeit verifiziert diese Ergebnisse in einen späten Stadium der Entnetzung, d.h. während sich die Randwulstinstabilität entwickelt. Sie zieht neue Schlussfolgerungen indem sie die Wechselwirkungen an der Grenzfläche mit denen der späteren Instabilität verknüpft. Zunächst demonstriert eine qualitative Analyse des Randwulstinstabilität, dass diese sich im verschiedene Regime einteilen lässt. Die Fingerstrukturen entwickeln sich im dabei ausschließlich unter Einfluss von starken Rutschen an der Grenzfläche. Ein genauer Blick auf die Instabilität zeigt, dass auf die nanometerskalar das Einsetzen eines zweiten Flussen nicht nur durch Rutschen sondern auch durch die Viscosität beeinflusst wird. Schließlich wird eine neue Methode zur Bestimmung inwiefern hydrodynamisches Rutschen auf den Fluss im Randwulst Einfluss nimmt, vorgeschlagen

Influence of slip on the Rayleigh-Plateau rim instability in dewetting viscous films

A dewetting viscous film develops a characteristic fluid rim at its receding edge due to mass conservation. In the course of the dewetting process the rim becomes unstable via an instability of Rayleigh-Plateau type. An important difference exists between this classic instability of a liquid column and the rim instability in the thin film as the growth of the rim is continuously fueled by the receding film. We explain how the development and macroscopic morphology of the rim instability are controlled by the slip of the film on the substrate. A single thin-film model captures quantitatively the characteristics of the evolution of the rim observed in our experiments

Influence of slip on the Rayleigh--Plateau rim instability in dewetting viscous films

A dewetting viscous film develops a characteristic fluid rim at its receding edge due to mass conservation. In the course of the dewetting process the rim becomes unstable via an instability of Rayleigh-Plateau type. An important difference exists between this classic instability of a liquid column and the rim instability in the thin film as the growth of the rim is continuously fueled by the receding film. We explain how the development and macroscopic morphology of the rim instability are controlled by the slip of the film on the substrate. A single thin-film model captures quantitatively the characteristics of the evolution of the rim observed in our experiments

Predictive modeling of glass quenching for tableware products

In glassware markets related to tableware, for which Arc is one of the world leaders, the increased requirement of customer specifications and quality of production, but also of energy efficiency and limiting the environmental impact, requires increased control and finer and more in-depth knowledge of processes, going from the molten glass inside the furnaces to the final product. Glass tempering is an important part of the global process and has been deployed for many years in the glass industry. It generates compressive stress fields on the surface which greatly improve the mechanical strength properties of the products. The addition, or superimposition of these compressive stresses on the surface makes them more resistant to mechanical shocks, but also to thermal shocks.Modeling and numerical simulations are powerful tools allowing a better understanding and analysis, to be able to improve the process and quality of the produced item. To be predictive with a sufficient accuracy to achieve these goals, the modeling of the thermal tempering must integrate several key factors: (i) the item's geometry (highly three-dimensional for tableware industry products) and the thickness distributions, (ii) cooling systems representative of real conditions, (iii) a good knowledge of physical and physico-chemical parameters of the glass, over the entire temperature range concerned by thermal tempering

Structure and Dynamics of an Intrinsically Disordered Protein Region That Partially Folds upon Binding by Chemical-Exchange NMR

International audienceMany intrinsically disordered proteins (IDPs) and protein regions (IDRs) engage in transient, yet specific, interactions with a variety of protein partners. Often, if not always, interactions with a protein partner lead to partial folding of the IDR. Characterizing the conformational space of such complexes is challenging: in solution-­‐state NMR, signals of the IDR in the interacting region become broad, weak and often invisible; while X-­‐ray crystallography only provides information on fully ordered regions. There is thus a need for a simple method to characterize both fully and partially ordered regions in the bound state of IDPs. Here, we introduce an approach based on monitoring chemical ex-­‐ change by NMR to investigate the state of an IDR that folds upon binding through the observation of the free state of the protein. Structural constraints for the bound state are obtained from chemical shifts and site-­‐specific dynamics of the bound state are characterized by relaxation rates. The conformation of the interacting part of the IDR was determined and subsequently docked onto the structure of the folded partner. We apply the method to investigate the interaction between the disordered C-­‐terminal region of Artemis and the DNA binding domain of Ligase IV. We show that we can accurately reproduce the structure of the core of the complex determined by X-­‐ray crystallography and identify a broader interface. The method is widely applicable to the biophysical investigation of complexes of disordered proteins and folded proteins

Peptidoglycan potentiates the membrane disrupting effect of the carboxyamidated form of DMS-DA6, a Gram-positive selective antimicrobial peptide isolated from Pachymedusa dacnicolor skin.

The occurrence of nosocomial infections has been on the rise for the past twenty years. Notably, infections caused by the Gram-positive bacteria Staphylococcus aureus represent a major clinical problem, as an increase in antibiotic multi-resistant strains has accompanied this rise. There is thus a crucial need to find and characterize new antibiotics against Gram-positive bacteria, and against antibiotic-resistant strains in general. We identified a new dermaseptin, DMS-DA6, produced by the skin of the Mexican frog Pachymedusa dacnicolor, with specific antibacterial activity against Gram-positive bacteria. This peptide is particularly effective against two multiple drug-resistant strains Enterococcus faecium BM4147 and Staphylococcus aureus DAR5829, and has no hemolytic activity. DMS-DA6 is naturally produced with the C-terminal carboxyl group in either the free or amide forms. By using Gram-positive model membranes and different experimental approaches, we showed that both forms of the peptide adopt an α-helical fold and have the same ability to insert into, and to disorganize a membrane composed of anionic lipids. However, the bactericidal capacity of DMS-DA6-NH2 was consistently more potent than that of DMS-DA6-OH. Remarkably, rather than resulting from the interaction with the negatively charged lipids of the membrane, or from a more stable conformation towards proteolysis, the increased capacity to permeabilize the membrane of Gram-positive bacteria of the carboxyamidated form of DMS-DA6 was found to result from its enhanced ability to interact with peptidoglycan