Influence of biological and ecological factors on the bioaccumulation of polybrominated diphenyl ethers in aquatic food webs from French estuaries

Previous studies have shown the worldwide presence of six congeners of polybrominated diphenyl ethers (PBDEs) in marine biota (BDE-28, -47, -99, -100, -153 and -154). The objective of the present study was to document their presence, their level and their transfer in the food web of two major estuaries in France, the Loire and the Seine. PBDEs were quantified in eight principal species from the Loire, representing primary consumers (the bivalve Scrobicularia plana), omnivores (the worm Nereis diversicolor, the shrimps Crangon crangon, Palaemon elegans and Palaemon serratus, the flatfish Platichthys flesus and Solea solea) and supercarnivores (the eel Anguilla anguilla). In the Seine, only worms, bivalves, sole and eels have been studied. Parameters, which can interfere with the interpretation of contamination data (organ distribution, influence of weight or size of specimens, lipid richness, intrinsic variability), have been examined. BDE-47 was the predominant congener in all biota. Higher contamination was observed in most of the species collected from the Seine, in agreement with the higher human presence and economic activity in the Seine than in the Loire basin. PBDEs have been shown to biomagnify in both of the studied estuarine food webs. However, assessment of PBDE transfer from seafood products exposed to contaminants in the Seine estuary showed that human daily intake is far below the no observed adverse effect levels.     

Polypyrrole material for the electrostatic discharge sensitivity mitigation of Al/SnO2 energetic composites

Nanothermites are composite energetic materials made of fuel and oxidizer nanoparticles characterized by impressive exothermic reactions (highly flame temperatures and impressive heat combustion releases). However, nanothermites suffer from their high electrostatic discharge (ESD) sensitivity that may be at the origin of accidental ignitions during handling. The present study deals with the use of doped-polypyrrole conducting polymer in aluminum/tin (IV) oxide energetic formulation (Al/SnO₂). X-ray diffraction, Fourier transforms infrared spectroscopy, scanning electron microscopy, conductivity measurements, sensitivities and combustion tests were implemented to characterize the polypyrrole-doped Al/SnO₂ energetic composite. The results revealed a significant gradual ESD desensitization of the nanothermite (<0.14 mJ to 246.40 mJ) as a function of the doped-polypyrrole amount (0 to 15 wt%). The reactive properties of the polypyrrole-enriched Al/SnO₂ nanothermite were verified and an acceptable reactive behavior was claimed. The successful adding of doped-polypyrrole conducting polymer within energetic nanocomposites is reported for the first time.     

Liquid crystal crown ether derived from cyclic tetramer of epichlorohydrin

Summary A liquid crystal crown ether is obtained by chemical modification of the cyclic tetramer derived from epichlorohydrin with sodium 4-cyano-4′-biphenoxide. The crown ether exhibits a nematic mesophase and a high glass transition temperature.     

Amorphous Ge‐Sb‐Se thin films fabricated by co‐sputtering: Properties and photosensitivity

Amorphous Ge–Sb–Se thin films were fabricated by a rf‐magnetron co‐sputtering technique employing the following cathodes: GeSe₂, Sb₂Se₃, and Ge₂₈Sb₁₂Se₆₀. The influence of the composition, determined by energy‐dispersive X‐ray spectroscopy, on the optical properties was studied. Optical properties were analyzed based on variable angle spectroscopic ellipsometry and UV‐Vis‐NIR spectrophotometry. The results show that the optical bandgap range 1.35‐2.08 eV with corresponding refractive index ranging from 3.33 to 2.36 can be reliably covered. Furthermore, morphological and topographical properties of selenide‐sputtered films studied by scanning electron microscopy and atomic force microscopy showed a good quality of fabricated films. In addition, structure of the films was controlled using Raman scattering spectroscopy. Finally, irreversible photoinduced changes by means of change in optical bandgap energy and refractive index of co‐sputtered films were studied revealing the photobleaching effect in Ge‐rich films when irradiated by near‐bandgap light under Ar atmosphere. The photobleaching effect tends to decrease with increasing antimony content.     

X‐ray photoelectron spectroscopy analysis of Ge–Sb–Se pulsed laser deposited thin films

Pulsed laser deposition was used to prepare amorphous thin films from (GeSe₂)_100?x(Sb₂Se₃)_x system (x = 0, 5, 10, 20, 30, 40, 50, and 60). From a wide variety of chalcogenide glass‐forming systems, Ge–Sb–Se one, especially in thin films form, already proved to offer a great potential for photonic devices such as chemical sensors. This system has a large glass‐forming region which gives the possibility to adjust the chemical composition of the glasses according to required physical characteristics. The chemical composition of fabricated thin films was analyzed via X‐ray photoelectron spectroscopy (XPS) and compared to energy dispersive spectroscopy (EDS) data. The results of both techniques agree well: a small deficiency in chalcogen element and an excess of antimony was found. The structure of as‐deposited thin films has been investigated by XPS. The presence of the two main structural units, [GeSe₄] and [SbSe₃] proposed by Raman scattering spectroscopy data analysis, was confirmed by XPS. Moreover, XPS core level spectra analysis revealed the presence of M–M bonds (M = Ge, Sb) in (Ge,Sb)–Ge–(Se)₃ and (Ge,Sb)–Sb–(Se)₂ entities that could correspond to Ge‐based tetrahedra and Sb‐based pyramids where one of its Se atoms at corners is substituted by Ge or Sb ones. The content of depicted M–M bonds tends to increase with introduction of antimony in the amorphous network of as‐deposited thin films from x = 0 to x = 40 and then it decreases. XPS analysis of as‐deposited thin films shows also the presence of the (Ge,Sb)–Se–(Ge,Sb) and Se–Se–(Ge,Sb) entities.     

Making the Impossible Possible

This paper introduces new techniques and correct complexity analyses for impossible differential cryptanalysis, a powerful block cipher attack. We show how the key schedule of a cipher impacts an impossible differential attack, and we provide a new formula for the time complexity analysis that takes this parameter into account. Further, we show, for the first time, that the technique of multiple differentials can be applied to impossible differential attacks. Then, we demonstrate how this technique can be combined in practice with multiple impossible differentials or with the so-called state-test technique. To support our proposal, we implemented the above techniques on small-scale ciphers and verified their efficiency and accuracy in practice. We apply our techniques to the cryptanalysis of ciphers including AES-128, CRYPTON-128, ARIA-128, CLEFIA-128, Camellia-256 and LBlock. All of our attacks significantly improve previous impossible differential attacks and generally achieve the best memory complexity among all previous attacks against these ciphers.     

Ribbon-like Foldamers for Cellular Uptake and Drug Delivery

Different intracellular delivery systems of bioactive compounds have been developed, including cell-penetrating peptides. Although usually nontoxic and biocompatible, these vectors share some of the general drawbacks of peptides, notably low bioavailability and susceptibility to protease degradation, that limit their use. Herein, the conversion of short peptide sequences into poly-α-amino-γ-lactam foldamers that adopt a ribbon-like structure is investigated. This template is used to distribute critical cationic and/or hydrophobic groups on both sides of the backbone, leading to potent short, cell-permeable foldamers with a low positive-charge content. The lead compound showed dramatically improved protease resistance and was able to efficiently deliver a biologically relevant cargo inside cells. This study provided a simple strategy to convert short peptide sequences into efficient protease-resistant cell-penetrating foldamers.     

Allelochemicals of Pinus halepensis as Drivers of Biodiversity in Mediterranean Open Mosaic Habitats During the Colonization Stage of Secondary Succession

The Mediterranean region is recognized as a global biodiversity hotspot. However, over the last 50 years or so, the cessation of traditional farming has given way to strong afforestation at the expense of open habitats. Pinus halepensis Miller, known to synthesize a wide range of secondary metabolites, is a pioneer expansionist species colonizing abandoned agricultural land that present high species richness. Here, laboratory bioassays were used to study the potential impact of P. halepensis on plant diversity through allelopathy, and the role of microorganisms in these interactions. Germination and growth of 12 target species naturally present in fallow farmlands were tested according to concentration of aqueous extracts obtained from shoots of young pines (aged about 5 years), with or without the presence of soil microorganisms (autoclaved or natural soil). Under the highest concentrations and autoclaved soil, more than 80 % of target species were germination and/or growth-inhibited, and only two species were non-sensitive. Under more natural conditions (lower extracts concentrations and natural soil with microorganisms), only 50 % of species were still inhibited, one was non-sensitive, and five were stimulated. Thus, microorganisms alter the expression of allelochemicals released into the ecosystem, which highlights their key role in chemical plant-plant interactions. The results of allelopathic experiments conducted in the lab are consistent with the community patterns observed in the field. These findings suggest that allelopathy is likely to shape vegetation composition and participate to the control of biodiversity in Mediterranean open mosaic habitats.