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This paper reports the synthesis and study of new pH-sensitive DB24C8-based [2]rotaxane molecular shuttles that contain within their axle the following four potential sites of interaction for the DB24C8: ammonium, amine, Weinreb amide and ketone. At the protonated state, the DB24C8 lied around the best ammonium site. After either deprotonation or deprotonation-then-carbamoylation of the ammonium, different localizations of the DB24C8 were noticed, depending on both the number and nature of the secondary stations and steric restriction. Unexpectedly, the results indicated that Weinreb amide was not a proper secondary molecular station for the DB24C8. Nevertheless, via its methoxy side-chain, it slowed down the shuttling of the macrocycle along the threaded axle, therefore partitioning the [2]rotaxane into two translational isomers on the NMR time scale. Regarding the ketone, it was successfully utilized as a secondary molecular station and its weak affinity for the DB24C8 was similar to that of a secondary amine.

The wrapping of an aromatic oligoamide helix around an active ester-containing [2]rotaxane enforced the sliding and the sequestration of the surrounding macrocycle around a part of the axle for which it has no formal affinity. The foldamer-mediated compartmentalization of the [2]rotaxane shuttle was subsequently used to prepare an improbable rotaxane.

In the last decade, the freshwater amphipod Gammarus fossarum proved to be a promising sentinel species in active biomonitoring programs to assess the effects of environmental contamination on non-target organisms. In many vertebrates, xenobiotics cause deregulation of the retinoids (RETs) metabolism implicated in many crucial biological functions. The retinoid system, known in the crustaceans, is yet to be explored in G. fossarum. Therefore, we studied the implication of all­-trans­ retinoic acid (atRA) in the reproduction (embryo, oocyte, and juvenile production) and development (success and delay of moulting) by exposing G. fossarum females to atRA and citral (CIT), a known inhibitor of RA synthesis to simulate an excess or a deficiency of RA, respectively. In parallel, we monitored the effects of methoprene (MET) and glyphosate (GLY), two pesticides suspected to interfere with atRA metabolism and signalling and frequently found in water systems. After 14 days of exposure, atRA, CIT, and MET reduced the number of oocytes, whereas only MET caused a reduced number of embryos. After 44 days, MET and GLY showed a tendency to decrease juvenile production. The duration of the moulting cycle increased following the exposures to atRA and MET, while the treatment with CIT caused a typical endocrine disruptive inverted U-shaped curve. The exposure to GLY led to increased duration of the moulting cycle at the lowest concentrations and lowered moulting success at the highest concentration tested. This study highlights for the first time the implication of RA in the oogenesis and moulting of G. fossarum and suggests that it may be a potential mediator of MET-induced effects on these processes. This study adds to the comprehension of the reproductive and developmental control in G. fossarum and opens new research avenues to study the effects of xenobiotics on the RET system in this sentinel species. Ultimately, our study will drive the development of RET-based biomarkers for non-target aquatic invertebrates exposed to xenobiotics.

The design and synthesis of a novel rotaxane/foldaxane hybrid architecture is reported. The winding of an aromatic oligoamide helix host around a dumbbell-shaped thread-like guest, or axle, already surrounded by a macrocycle was evidenced by NMR spectroscopy and X-ray crystallography. The process proved to depend on the position of the macrocycle along the axle and the associated steric hindrance. The macrocycle thus behaves as a switchable shield that modulates the affinity of the helix for the axle. Reciprocally, the foldamer helix acts as a supramolecular auxiliary that compartmentalizes the axle. In some cases, the macrocycle is forced to move along the axle to allow the foldamer to reach its best recognition site.

La rationalité de l’enfant constitue sans aucun doute l’un des thèmes les plus fondamentaux en philosophie de l’éducation : des multiples conceptions qui en ont été proposées au fil de l’histoire, elle s’articule tantôt à une activité éducative qui vise la manifestation, par l’élève, d’une attitude précise au regard d’une réalité elle-même rationnelle, tantôt à une forme idéale de faculté psychique à faire surgir (ou ressurgir) par l’éducation. Toutefois, peu importe l’acception privilégiée par les rationalistes antiques, modernes ou contemporains, il apparaît que l’enfant demeure toujours, au sein de cette tradition philosophique, un être inachevé, incomplet, déficient : dès lors, comment penser le problème que semble représenter l’enfance chez les plus importants penseurs de la raison? Et, ultimement, la tradition rationaliste se présente-t-elle comme une tradition de l’oubli et de la négation infantiles? Telles sont les questions auxquelles tente de répondre le présent texte.

Although not often encountered, cyclic interlocked molecules are appealing molecular targets because of their restrained tridimensional structure which is related to both the cyclic and interlocked shapes. Interlocked molecules such as rotaxane building blocks may be good candidates for post-synthetic intramolecular cyclization if the preservation of the mechanical bond ensures the interlocked architecture throughout the reaction. This is obviously the case if the modification does not involve the cleavage of either the macrocycle's main chain or the encircled part of the axle. However, among the post-synthetic reactions, the chemical linkage between two reactive sites belonging to embedded elements of rotaxanes still consists of an underexploited route to interlocked cyclic molecules. This Review lists the rare examples of macrocyclization through chemical connection between reactive sites belonging to a surrounding macrocycle and/or an encircled axle of interlocked rotaxanes.

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Several strategies have been successfully utilized so far in order to obtain a wide range of interlocked molecules. However, some interlocked compounds are still not obtained directly and/or efficiently from non-interlocked components because the requisites for self-assembly cannot be always enforced. To circumvent such a synthetic problem, the strategy that consists in synthesizing an isolable and storable interlocked building block in a step that precedes its modifications is an appealing chemical route to more sophisticated interlocked molecules. Synthetic opportunities and challenges are closely linked to the fact that the mechanical bond might tremendously affect the reactivity of a function of the encircled axle, while the interlocked architecture need to be preserved during the synthesis. Hence, the mechanical bond plays a fundamental role in the strategy employed. This review focuses on the challenging post-synthetic modifications of interlocked molecules, sometimes through the cleavage of the axle's main chain, and always with the conservation of the mechanical bond.

Over the last decade, the persistent dwindling of the populations of honey bees has become a growing concern. While this phenomenon is partly attributed to neonicotinoids (NEOCs), chronic exposures to these insecticides at environmentally-relevant concentrations are needed to fully estimate their implications. In this study, honey bees were orally exposed for 10 days to low field-realistic concentrations of NEOCs known for their effects on the cholinergic system (imidacloprid – IMI or thiamethoxam – THM). Selected biomarkers were measured such as acetylcholinesterase (AChE) activity, lipid peroxidation (LPO), α-tocopherol as well as several forms of vitamin A (retinoids) and carotenoids. Bees exposed to IMI showed lower levels of two carotenoids (α-carotene and α-cryptoxanthin) and α-tocopherol. The THM exposure increased the oxidized vitamin A metabolites in bees conjointly with the LPO. These results could be the consequence of a pro-oxidant effect of NEOCs and were observed at levels where no effects were recorded for AChE activity. This study reveals that exposure to low levels of NEOCs alters the carotenoid-retinoid system in honey bees. This would merit further investigation as these compounds are important in various aspects of bees’ health. Overall, this study contributes to the development of biomonitoring tools for the health of bees and other pollinators.

Several hypotheses have been proposed to explain the abnormally high mortality rate observed in bee populations in Europe and North America. While studies based on the effects of pesticides are paramount, the metals present in agroecosystems are often overlooked. Sources of metals are linked to the nature of soils and to agricultural practices, namely the use of natural or chemical nutrients as well as residual materials from waste-water treatment sludge. The aim of this study was to investigate the effects of metals on honey bees exposed for 10 days to environmentally realistic concentrations of Al, Pb and Cd (dissolved in syrup). The monitoring of syrup consumption combined with the quantification of metals in bees revealed the following order for metal bioconcentration ratios: Cd > Pb > Al. Alpha-tocopherol, metallothionein-like proteins (MTLPs) and lipid peroxidation were quantified. When bees were exposed to increasing amounts of Cd, a marked augmentation of MTLPs levels was found. Lead (Pb) and Cd caused an increase in α-tocopherol content, while alteration of lipid peroxidation was observed only with Al exposure. These findings raise concerns about the bioavailability and the additional threat posed by metals for pollinators in agricultural areas while providing new insights for potential use of the honey bee as a sentinel species for metal exposure.

L’arrivée des neurosciences en éducation suscite de vives réactions : si certains en accueillent la venue à bras ouverts, d’autres se montrent beaucoup plus réfractaires. Cet article propose une réflexion sur le sujet, s’inspirant des parallèles entre ce débat et la querelle du positivisme (Positivismusstreit), discussion épistémologique marquante du XXe siècle. Cette réflexion s’articule en trois temps : nous circonscrivons d’abord les postures dominantes structurant le débat concernant l’introduction des neurosciences en éducation ; ensuite, nous retraçons les grandes lignes de la querelle positiviste qui opposa Adorno et Habermas contre Popper et Albert, similaires au débat actuel ; enfin, nous tentons de voir si une conciliation n’est pas possible entre les postures antagonistes empruntées dans ces querelles. Ce faisant, nous espérons alimenter la réflexion en envisageant de nouveaux points de départ desquels pourraient s’inspirer une prolongation du présent débat. The introduction of neurosciences in education gives rise to animated reactions. As some embrace the arrival of such science with open arms, others tend to be more skeptical. This article submits fundemental thoughts regarding this debate, inspired by its parallels with the positivism dispute, one of the most important epistemological debates of the 20th century. This paper is divided in three distinct sections : first, we present the principal epistemological postures at the heart of the actual debate regarding the introduction of neurosciences in education ; we then retrace the most notable aspects of the positivism dispute which opposed Adorno and Habermas to Popper and Albert, and its similarities with the present debate. Finally, we propose a way by which we could continue the actual debate, starting from a more constructive perspective.

Predicting fluid-structure interaction phenomena is an ongoing challenge in numerical simulations. While we look for fast algorithms to solve the equations, some problems need a high accuracy in order to correctly predict results. Hence, controlling every aspect of the algorithm gives the possibility to optimise specific parts, potentially leading to greater accuracy. Developing such a numerical methodology can be achieved on an open source software such as OpenFOAM.

In hydraulic turbines, cavitation has unwanted consequences such as vibrations, noise, or material degradation. Thus, developping a method which can anticipate this phenomenon with good accuracy is vital from the designer’s perspective. This work aims at predicting two aspects of cavitation erosion: determining areas most endangered, and quantifying cavitation erosion in a relative way.

Structural reactive material (SRM) is consolidated from a fine granular mixture of reactive materials towards the mixture theoretical maximum density with little porosity, thus bearing both high energy density and mechanical strength. A reactive hot spot concept was investigated for fine fragmentation of a SRM solid under explosive loading to augment air blast through rapid reaction of fine SRM fragments. In this concept, micro‐sized reactive materials were distributed in a fuel‐rich SRM solid, such as MoO3 particles consolidated in a particulate aluminum base in 10Al+MoO3. Intermetallic reactions of micro‐sized MoO3 and nearby Al under explosive loading created heat and gas products to form microscale hot spots that initiated local fractures leading to fine fragments of the rest of Al. The SRM solid was made of a thick‐walled cylindrical casing, containing a high explosive in a detonation pressure range of 25–34 GPa with a casing‐to‐explosive mass ratio of 1.78. Experiments in a cylindrical chamber demonstrated the presence of a large amount of fine SRM fragments, whose reaction promptly after detonation significantly enhanced the primary and near field blast wave, as compared to the results from a baseline pure Al‐cased charge, thus indicating the feasibility of the concept.

A concept of reactive hot spots intruded in a thick, structural reactive material casing was investigated to generate fine fragments for efficient energy release from casing material under explosive loading. This was achieved through distributing micro MoO3 particles into a granular Al casing, made by hot isostatic pressing, in a fuel-rich ratio of 10Al+MoO3. Reaction of Al and MoO3 during casing primary or secondary fragmentation creates heat and gas products to form micro-scale hot spots, whose expansion initiates local fractures leading to fine fragments of the rest of Al. Explosion experiments, using a 4.4 cm diameter cased charge with a casing-to-explosive mass ratio of 1.78 in a 2.1 m3 cylindrical chamber, demonstrated the presence of fine fragments and more efficient fragment combustion to augment air blast, as compared to a baseline pure Al-cased charge, thus indicating the feasibility of the concept., Conference of the American Physical Society Topical Group on Shock Compression of Condensed Matter, 14-19 June 2015, Tampa Bay, Florida, USA, Series: AIP Conference Proceedings; no. 1793

This paper addresses an important issue for the practical application of lithium ion batteries in PHEV. More specifically, preliminary research results on the coating of separators, welding of battery tabs, and fabrication and surface featuring of anodic and cathodic current collectors are presented. These developments aim at improving the power performance, reliability, and safety of lithium ion batteries., 216th ECS Meeting, October 4-9, 2009, Vienna, Austria

The present work assesses the potential of three-dimensional porous titanium scaffolds produced by a novel powder metallurgy process for applications in bone engineering through in vitro experimentation. Mouse MC3T3-E1 pre-osteoblasts were used to investigate the proliferation (DNA content), differentiation (alkaline phosphatase activity and osteocalcin release) and mineralisation (calcium content) processes of cells on titanium scaffolds with average pore sizes ranging from 336 to 557 microm, using mirror-polished titanium as reference material. Scanning electron microscopy was employed to qualitatively corroborate the results. Cells proliferate on all materials before reaching a plateau at day 9, with proliferation rates being significantly higher on foams (ranging from 123 to 163 percent per day) than on the reference material (80% per day). Alkaline phosphatase activity is also significantly elevated on porous scaffolds following the proliferation stage. However, cells on polished titanium exhibit greater osteocalcin release toward the end of the differentiation process, resulting in earlier mineralisation of the extracellular matrix. Nevertheless, the calcium content is similar on all materials at the end of the experimental period. Average pore size of the porous structures does not have a major effect on cells as determined by the various analyses, affecting only the proliferation stage. Thus, the microstructured titanium scaffolds direct the behaviour of pre-osteoblasts toward a mature state capable of mineralising the extracellular matrix.

A technique has been recently developed to produce foamed metallic structures from dry powder blends containing a metallic powder, a polymeric binder, and a foaming agent. The blend is molded and heat-treated to foam and consolidate the material. The final properties may be tailored by varying the sintering temperature. Microstructure, chemical composition, and properties of nickel (Ni) foams sintered at different temperature are presented and discussed. The resulting material has an open cell microstructure with three levels of porosity. This structure leads to materials having low density (∼ 90% porosity) and high specific surface area. The specific surface area is reduced and the mechanical strength is increased when the sintering temperature increases.

This article presents the mechanical behavior of porous NiTi in the context of biomedical applications related to bone prostheses. To produce the porous metallic material, a novel technique consisting of mixing prealloyed NiTi powder with a polymer powder and a foaming agent has been used. This method permits control of the size of pores and the porosity level. For the present study, pores similar to those found in bones (400 to 500 μm) were obtained with a total porosity of the specimens varying from 50 to 70 pct. The compression mechanical testing carried out on small cylindrical specimens revealed shape memory deformation recovery up to 6.4 pct, while the superelastic behavior resulted in a reversible deformation up to 7.7 pct. By varying the amount of porosity, it was possible to obtain Young’s moduli in the range of 2.6 to 4.6 GPa, which is similar to the modulus of cancellous (spongy) human bone.

Titanium foam, prepared by using a patented powder-metallurgy–based process involving a powder blend that was molded, foamed, and sintered using a three-step thermal treatment, was deoxidized in a molten CaCl2 bath. The polarization experiments were carried out by cathodically polarizing the foam (working electrode) against a counter (graphite) electrode. Under constant potential (polarization) mode, the dominant mechanism of deoxidation was the ionization of oxygen, present in the foam, and its subsequent discharge, as CO2/CO, at the anode surface. More than ∼85 pct oxygen could be effectively removed by carrying out the electro-deoxidation experiments in fresh and pre-electrolyzed melt(s) at an electrolyte temperature of 950 °C. Scanning electron microscopy–energy dispersive X-ray (SEM-EDX) detection of the deoxidized foams did not show a presence of any inclusion(s) or secondary phase(s).

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Electrochemical impedance spectroscopy has been revealed to be a useful tool to evaluate the exposed surface area and consequently to evaluate the corrosion behavior of titanium foams intended for biomedical applications.In order to find the most accurate corrosion assessment, a new equivalent circuit involving a porous model in series with a double TiO 2 layer model was proposed to fit the experimental data. Although seldom used in the literature, such technique could be useful for the characterization of porous media. Determining corrosion potentials and current densities, the titanium foams have revealed to be slightly more resistant to corrosion in simulated body fluid solutions at 37°C under static mode (no stress applied to the samples) compared to dense and polished titanium. The best titanium foams exibited penetration rates around 0.07 μm yr - 1 . Cyclic voltammetry experiments have shown that the titanium oxide layer stability was not affected by the fabrication process of the foams.

207th Meeting of the Electrochemical Society, May 15-20, 2005, Québec City, Québec, Canada

Porous metallic scaffolds have recently gained recognition as a promising avenue toward the regeneration of damaged bone structures. Interest in these materials resides in their ability to guide bone growth by presenting a favorable structure for cellular adhesion and three-dimensional proliferation. A powder metallurgy process to fabricate titanium foams with favorable microstructural parameters for applications in bone engineering has recently been developed. This study assesses the potential of this novel material for applications as an osteoconductive scaffold through in vitro characterization of early cellular interactions with titanium foams having pore sizes ranging from 167 to 500 µm. The foams exhibit no cytotoxic effects on J774 mouse macrophages while favoring adhesion and proliferation of MC3T3-E1 pre-osteoblasts. Three-dimensional morphology assumed by these cells on porous titanium suggests that the microstructure of the foams is biomimetic., Symposium W: Biological and Bioinspired Materials and Devices, April 13-16, 2004, San Francisco, CA, USA, Series: MRS Online Proceedings Library; no. 823

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