Delamination and Wrinkling of Flexible Conductive Polymer Thin Films

Polymer based conductive and transparent thin films are an important class of functional materials at the heart of flexible organic electronic devices. These flexible films are prone to degradation and to mechanical instability leading to the formation of blisters, wrinkles, and cracks. This is detrimental to their use especially in the case of multilayer devices. Here, it is shown that a simple water or solvent drop deposited on such films gives rise to a buckling instability and the formation of several folds due to the tendency of these films to swell in contact with the solvent. A phase diagram of the instability portraying its domain of existence, and thus the means to inhibit it, is proposed. By depositing drops on such films and observing the instability, material parameters such as the elastic modulus of the thin films or their energy of adhesion to the substrate can be estimated reliably. Further, the instability can be harnessed to pattern surfaces at low cost giving rise to percolated and more conductive pathways in the conductive polymer films under scrutiny.     

Vaccenic acid metabolism in the liver of rat and bovine

Hepatic metabolism of vaccenic acid (VA), especially its conversion into CLA, was studied in the bovine (ruminant species that synthesizes CLA) and in the rat (model for nonruminant) by using the in vitro technique of liver explants. Liver tissue samples were collected from fed animals (5 male Wistar rats and 5 Charolais steers) and incubated at 37°C for 17 h under an atmosphere of 95% O₂/5% CO₂ in medium supplemented with 0.75 mM of FA mixture and with 55 μM [1-¹⁴C]VA. VA uptake was about sixfold lower in bovine than in rat liver slices (P<0.01). For both species, VA that was oxidized to partial oxidation products represented about 20% of VA incorporated by cells. The chemical structure of VA was not modified in bovine liver cells, whereas in rat liver cells, 3.2% of VA was converted into 16∶0 and only 0.33% into CLA. The extent of esterification of VA was similar for both animal species (70–80% of incorporated VA). Secretion of VA as part of VLDL particles was very low and similar in rat and bovine liver (around 0.07% of incorporated VA). In conclusion, characteristics of the hepatic metabolism of VA were similar for rat and bovine animals, the liver not being involved in tissue VA conversion into CLA in spite of its high capacity for FA desaturation especially in the rat. This indicates that endogenous synthesis of CLA should take place exclusively in peripheral tissues.     

Photoluminescence properties of La2O3 methane coupling catalysts

La₂O₃ catalysts prepared at 923 K (La₂O₃-LT) and 1073 K (La₂O₃-HT) exhibit different photoluminescence properties due to notably different concentrations of ions in position of low coordination at the surface or coordinatively unsaturated surface sites (cus). The catalyst which exhibits the higher yields of photoluminescence due to the higher concentration of cus corresponds to the one which gives the higher C₂₊ selectivity in the oxidative methane coupling reaction. On leave of absence from Laboratoire de Réactivité de Surface, Université Pierre et Marie Curie, URA 1106-CNRS, 75252 Paris Cedex, France.     

The Yeoh model applied to the modeling of large deformation contact/impact problems

The present paper is devoted to the modeling of finite deformations of hyperelastic bodies described by the Yeoh model under contact/impact conditions. A total Lagrangian formulation is adopted to describe the geometrically nonlinear behavior. A first order algorithm is applied to integrate the equations of motion. For the finite element implementation, an explicit expression of the tangent operator is derived. Two numerical examples are presented to show the applicability of the developed approach.     

Revalorization of glycerol: Comestible oil from biodiesel synthesis

High dependence on fossil fuel has caused increase of carbon dioxide concentration in the atmosphere. The actual political trends are towards an increased use of renewable fuels from agricultural origin. One of the main products of the European biorefineries is biodiesel. The main reaction involved in biodiesel synthesis produces a large amount of glycerol as by-product. Two aspects are arising in this respect: the glycerol obtained as residue and the food conversion to fuel. This paper deals with the revalorization of the residual glycerol stream to obtain triacetin (glyceryl triacetate), the lightest comestible oil. The application of glycerol as raw material to produce triacetin is not new. The goal of this paper is to check the feasibility of this transformation in an efficient integrated continuous process which is suitable for processing high quantities of glycerol. A kinetic model was determined experimentally for the production of triacetin from glycerol and acetic acid in the absence of catalyst. The results showed that by process integration of the reaction and distillation in the same unit (reactive distillation), a more sustainable process can be developed. The proposed configuration output is checked by rigorous simulation.     

Discussion of Nonconventional Effects in Solid-State Sintering of Cemented Carbides

WC–Co materials are usually produced through a powder metallurgy route, including a liquid-phase sintering step in the 1350°–1450°C temperature range. However, it is well established that a large part of sintering already occurs in the solid-state for micrometer or submicrometer WC particles. Solid-state spreading of the Co-rich binder phase and local rearrangement of WC particles are responsible for the compact densification. But important issues still remain unexplained. First, densification by pure rearrangement should stop at a critical packing fraction of the WC refractory phase. Second, a strong influence of the C/W ratio on the spreading and sintering kinetics is observed experimentally. Both these effects are discussed in this paper, based on experimental dilatometric results, microstructural investigations by SEM and transmission electron microscopy, and considerations about interfacial energies in the system.     

Two-dimensional interaction of oxidic corium with concretes: The VULCANO VB test series

Three two-dimensional Molten Core–Concrete Interaction tests have been conducted in the VULCANO facility with prototypic oxidic corium. The major finding is that for the two tests with silica-rich concrete, the ablation was anisotropic while it was isotropic for limestone-rich concrete. The cause of this behaviour is not yet well understood.Post Test Examinations have indicated that for the silica-rich concrete, the corium melt mixed specifically with mortar, while, for limestone-rich concretes, the analysed samples were in accordance with a corium–concrete mixing. The experimental results are described and compared to numerical codes. Separate Effect Tests with Artificial Concretes and prototypic corium are proposed to understand the phenomena governing the ablation geometry.     

Assessment of ignition hazard in turbulent flammable gas mixers combining a Lagrangian approach and large eddy simulation

In this article, a Lagrangian approach is adopted to assess both mixing efficiency and ignition hazard of fuel/oxygen flammable gas mixing in a jets-in-cross-flow configuration. Large eddy simulation is used to provide the unsteady fields of turbulent gas mixing. To achieve statistical reliability of the fluid dynamics field, such as velocity, pressure, temperature, and chemical composition, a large number of Lagrangian markers are dumped into the inlet streams of the mixer and their trajectories are determined during the numerical simulation. Those trajectories are stored in a file processed afterward to build up the probability density functions of the fuel molar fraction of Lagrangian markers gauging both mixer efficiency and safety. Flammability limits provided by H.F. Coward and G.W. Jones [U.S. Bur. Mines Bull. 503 (1952)] and autoignition delays from a detailed kinetics scheme are required to define the hazard range. Processing the marker trajectory file allows the calculation of relevant Lagrangian properties such as (i) the critical residence time in flammability areas for the ignition case and (ii) the marker Damköhler number for the autoignition case, both including the subgrid turbulence effects. The latter are accounted for by assuming a presumed beta shape for the large eddy probability density function of subgrid fluctuations of mixture fraction. Analysis of all marker trajectories leads to a computation of global probability density functions of Lagrangian properties that characterize mixer safety.     

Survival kinetics of Ephestia kuehniella eggs during 46–75 °C heat treatment

The effect of heat treatment on the survival of Ephestia kuehniella eggs was examined. Samples of 60 eggs were immersed in hot water at constant temperature in the 46–75 °C range for 5–1200 s. Following heat treatment and cooling, the eggs were stored at 24 ± 1 °C in a growth chamber for 7 days before survival evaluation. Statistical analysis of the data demonstrated that the thermal survival kinetics were best represented by a first-order reaction. The rate constant had an Arrhenius-type dependence over the 54–75 °C temperature range. Kinetic parameters were estimated by non-linear regression. The activation energy (E_a) and rate constant (k_ref) at the reference temperature (T_ref = 64.8 °C), were determined as 102.2 ± 6.2 kJ mol⁻¹ and 0.061 ± 0.003 s⁻¹, respectively, over the 54–75 °C temperature range. A 0.01% survival rate was obtained after 50 s at 75 °C. The data at temperatures below 50 °C were not in accordance with those at higher temperatures. Above this temperature, mortality was likely due to physiological disorders, as noted on a DSC thermogram.