Lamination of polyethylene composite films by ultrasonic welding: Investigation of peel behavior and identification of optimum welding parameters

The lamination of different polyethylene (PE) composite films by ultrasonic welding to fabricate peelable seals that open at defined burst pressures is investigated. The sealing time, pressure, and amplitude were varied within the range of 100–400 ms, 50–250 kPa, and 12–24 µm, respectively. T‐peel tests and electron micrographs revealed four different peel regimes, depending on the parameter combination: (I) Interlaminar peeling at low‐peel strength with uniform peeling along a weakly bonded PE lamination layer; (II) transition tearing at intermediate peel strength showing areas of interlaminar peeling and translaminar tearing; (III) translaminar tearing at high‐peel strength showing tears through the entire film; and, (IV) undefined tearing at varying tear strength occurring when vibration effects during welding lead to insufficient contact of the films or high pressures lead to a displacement of PE. This study will allow the systematic adjustment of ultrasonic welding parameters for PE films. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40291.     

Reduction and functionalization of graphene oxide sheets using biomimetic dopamine derivatives in one step

An easy and environmentally friendly chemical method for the simultaneous reduction and noncovalent functionalization of graphene oxide (GO) using dopamine derivatives is described. The reaction takes place at room temperature under ultrasonication of an aqueous suspension of GO and a dopamine derivative. X-ray photoelectron spectroscopy, FT-IR spectroscopy, and cyclic voltammetry characterizations revealed that the resulting material consists of graphene functionalized with the dopamine derivative. This one-step protocol is applied for simultaneous reduction and functionalization of graphene oxide with a dopamine derivative bearing an azide function. The chemical reactivity of the azide function was demonstrated by a postfunctionalization with ethynylferrocene using the Cu(I) catalyzed 1,3-dipolar cyloaddition.     

Morphology and physico-chemical properties of Bacillus spores surrounded or not with an exosporium: Consequences on their ability to adhere to stainless steel

This study was designed to elucidate the influence of spore properties such as the presence of an exosporium, on their ability to adhere to materials. This analysis was performed on 17 strains belonging to the B. cereus group and to less related Bacillus species. We first demonstrated that spores of the B. cereus group, surrounded by an exosporium, differed in their morphological features such as exosporium size, number of appendages or hair-like nap length. We also found that the saccharidic composition of exosporium differed among strains, e.g. concerning a newly identified rhamnose derivative: the 2,4-O-dimethyl-rhamnose. Conversely, spores of distant Bacillus species shared morphological and physico-chemical properties with B. cereus spores. Some external features were also observed on these spores, such as a thin loose-fitting layer, whose nature is still to be determined, or a thick saccharidic layer (mainly composed of rhamnose and quinovose). The ability of spores to adhere to stainless steel varied among strains, those belonging to the B. cereus group generally being the most adherent. However, the presence of an exosporium is not sufficient to explain the ability of spores to adhere to inanimate surfaces. Indeed, when the 17 strains were compared, hydrophobicity and the number of appendages were the only significant adhesion parameters. Furthermore, the differences in spore adhesion observed within the B. cereus group were related to differences in the number of appendages, the exosporium length and to a lesser extent, the zeta potential.     

Electrical Conductivity of RuO2–Borosilicate Glasses: Effect of the Synthesis Route

Although glass–RuO₂ composites are well known for their particular electrical properties, the reasons for their very low percolation thresholds are still subject to debate. In this paper, a detailed study of the influence of various experimental parameters (temperature, RuO₂ content, stirring, etc.) on the electrical conductivity and, in particular, on the percolation threshold in borosilicate glass–RuO₂ composites is presented. This percolation threshold is shown to increase by a factor of two (from 0.6 to 1.2 vol%) when stirring is applied during synthesis and by more than a factor of three (>2.1 vol%) when a sol–gel route is used. Besides, the study of various synthesis temperatures reveals that the electronic part of the electrical conductivity is highly correlated to Ru solubility in the glass matrix. It can be concluded from these various experiments that both the presence of dissolved ruthenium in the glass matrix and the possibility of RuO₂ particles to rearrange in the melt in order to form kind of a network are necessary for a low percolation threshold.     

Definition of spacing constraints for the car sequencing problem

A car sequencing problem deals with the ordering of a list of vehicles to be produced on an assembly line so that the overall capacity of each work station is not exceeded. Some types of vehicles require several time-consuming operations to be done on a work station and will naturally overload that work station. Such vehicles are spaced out in the sequence, by means of a set of spacing constraints, in order to cope with the momentary increase of workload that they create. Two questions arise: which type of vehicles should be subject to the spacing constraints and by which distance should they be spaced out in the sequence. In practice as well as in the car sequencing literature, there does not exist a methodical way to answer the first question and the existing methods for the second one is no longer adequate due to the increased diversity of cars produced in an assembly line. In this paper, we propose two new methods to answer these questions with a special emphasis on the first one. The performance of the proposed methods is illustrated using a real case study.     

Modular inference of subprogram contracts for safety checking

Contracts expressed by logic formulas allow one to formally specify expected behavior of programs. But writing such specifications manually takes a significant amount of work, in particular for uninteresting contracts which only aim at avoiding run-time errors during the execution. Thus, for programs of large size, it is desirable to at least partially infer such contracts. We propose a method to infer contracts expressed as boolean combinations of linear equalities and inequalities by combining different kinds of static analyses: abstract interpretation, weakest precondition computation and quantifier elimination. An important originality of our approach is to proceed modularly, considering subprograms independently.     

Numerical modeling of polystyrene synthesis in coiled flow inverter

Recent studies show that microfluidic devices are gaining importance as micromixer in chemical and bio-chemical analysis systems. However, little attention has been paid to investigate chemical reactions such as polymerization reaction process in microreactors. In the present study, numerical modeling of the free-radical polymerization of styrene was carried out in novel coiled flow inverter (CFI) microreactor. The concept of CFI is based on the technique developed by Saxena and Nigam (AlChE J 30:363–368, 1984). This device is made up of helical coiled tube which is bent periodically to 90° at equidistant length. The CFD modeling for polymerization reaction taking place in coiled tube reactor was also performed in order to understand the influence of secondary flows on reactor performance for fluid flowing with very low flow rate. Its performance was compared with CFD results obtained in a straight tube reactor having identical length and operating under the same process conditions. The results showed that monomer conversion in the coiled tube reactor was higher than that of the straight tube reactor. Further work was carried out in the novel CFI reactor to study the effect of diffusion coefficient and number of bends on different parameters such as monomer conversion, number-average degree of polymerization (DP _n ), and polydispersity indexes (PDI). It was found that the performance of CFI as reactor increased when the diffusion coefficients of reactants was decreased. Thus, CFI was found to be an efficient microfluidic device for controlling the free-radical polymerization.     

Tumor Suppressive Role of miR-342-5p in Human Chondrosarcoma Cells and 3D Organoids

Chondrosarcomas are malignant bone tumors. Their abundant cartilage-like extracellular matrix and their hypoxic microenvironment contribute to their resistance to chemotherapy and radiotherapy, and no effective therapy is currently available. MicroRNAs (miRNAs) may be an interesting alternative in the development of therapeutic options. Here, for the first time in chondrosarcoma cells, we carried out high-throughput functional screening using impedancemetry, and identified five miRNAs with potential antiproliferative or chemosensitive effects on SW1353 chondrosarcoma cells. The cytotoxic effects of miR-342-5p and miR-491-5p were confirmed on three chondrosarcoma cell lines, using functional validation under normoxia and hypoxia. Both miRNAs induced apoptosis and miR-342-5p also induced autophagy. Western blots and luciferase reporter assays identified for the first time Bcl-2 as a direct target of miR-342-5p, and also Bcl-xL as a direct target of both miR-342-5p and miR-491-5p in chondrosarcoma cells. MiR-491-5p also inhibited EGFR expression. Finally, only miR-342-5p induced cell death on a relevant 3D chondrosarcoma organoid model under hypoxia that mimics the in vivo microenvironment. Altogether, our results revealed the tumor suppressive activity of miR-342-5p, and to a lesser extent of miR-491-5p, on chondrosarcoma lines. Through this study, we also confirmed the potential of Bcl-2 family members as therapeutic targets in chondrosarcomas.     

Analogue-driven bistable ferroelectric liquid crystals

This paper presents a new driving method allowing fast analogue light modulation with bistable ferroelectric liquid crystals (FLC). The method is evaluated using a functional virtual prototyping design flow. First, a surface stabilized binary FLC cell is modeled in VHDL-AMS language on the basis of well-known theories of FLC. Some physical and environmental phenomena are added (e.g. electronic behavior of the cell, temperature, etc.) in order to improve its reliability. Once the model is validated, a virtual prototype of a FLC pixel is performed by associating the model of the FLC cell and the model of an appropriate wave generator. Simulations show that our new driving method works, but with certain limitations. The most critical one seems to be the high temperature dependence of the pixel response.