Multimodal Dispersion of Nanoparticles: A Comprehensive Evaluation of Size Distribution with 9 Size Measurement Methods

Purpose : Evaluation of particle size distribution (PSD) of multimodal dispersion of nanoparticles is a difficult task due to inherent limitations of size measurement methods. The present work reports the evaluation of PSD of a dispersion of poly(isobutylcyanoacrylate) nanoparticles decorated with dextran known as multimodal and developed as nanomedecine. Methods : The nine methods used were classified as batch particle i.e. Static Light Scattering (SLS) and Dynamic Light Scattering (DLS), single particle i.e. Electron Microscopy (EM), Atomic Force Microscopy (AFM), Tunable Resistive Pulse Sensing (TRPS) and Nanoparticle Tracking Analysis (NTA) and separative particle i.e. Asymmetrical Flow Field- Flow Fractionation coupled with DLS (AsFlFFF) size measurement methods. Results : The multimodal dispersion was identified using AFM, TRPS and NTA and results were consistent with those provided with the method based on a separation step prior to on-line size measurements. None of the light scattering batch methods could reveal the complexity of the PSD of the dispersion. Conclusions : Difference between PSD obtained from all size measurement methods tested suggested that study of the PSD of multimodal dispersion required to analyze samples by at least one of the single size particle measurement method or a method that uses a separation step prior PSD measurement

Accompagner le personnel enseignant dans les choix d’utilisation d’une ressource technopédagogique : Un questionnement technopédagogique utile à l’intégration des technologies en enseignement dans les programmes d’études au collégial

À l’heure où la pertinence de l’intégration des TIC en éducation n’est plus à démontrer, la difficulté de faire valoir ces technologies auprès du personnel enseignant demeure un constat fréquent. Cette réticence à les inclure dans l’axe enseignement-apprentissage prend différentes formes, la première étant l’impression d’une inefficacité pédagogique. En effet, malgré l’existence d’outils technopédagogiques novateurs, ces derniers sont encore peu utilisés, l’enseignement magistral demeurant encore la méthode privilégiée. Or, innover signifie être en rupture avec des habitudes, avec des modèles bien ancrés et éprouvés. Par conséquent, comment favoriser cette rupture avec l’approche traditionnelle dominante auprès des enseignantes et enseignants ? L’expérimentation que nous avons réalisée auprès de trois groupes de participants composés d’enseignants et de conseillers pédagogiques de l’ordre collégial* dont cet article rend compte, nous permet de proposer une façon d’y arriver en stimulant un questionnement intégrant les dimensions liées aux connaissances disciplinaires et à la pédagogie, à l’instar du cadre de référence appelé le TPaCK (Mishra et Koehler, 2006). Les collectes de données se sont déroulées en juin 2013 et en février 2014. Grâce à cet exercice, un répertoire de ressources numériques technopédagogiques a non seulement été créé, mais la pertinence d’un outil réflexif favorisant l’identification et l’intégration des technologies dans l’enseignement a également été évaluée. L’analyse des scénarios identifiés a permis de tirer quelques constats et recommandations permettant d’optimiser l’utilisation du TPaCK.* L’ordre collégial au Québec fait partie, au même titre que l’ordre universitaire, de l’enseignement supérieur et correspond à la dernière ou aux deux années de lycée français et à une année préuniversitaire.At a time when the relevance of ICT integration in education is well established, there remains the difficulty of promoting such technologies among teachers. This reluctance on the teachers’ part to include these technologies in the teaching-learning continuum takes various forms, beginning with their impression of its being an ineffective pedagogy. Indeed, despite the existence of innovative pedagogical tools promoting digital education, these tools are still little used, and lectures remain the preferred method of instruction. Innovation means breaking with habits and with well-entrenched, proven models. Consequently, how can this change be promoted among teachers? The experimentation we carried out with three groups of participants composed of college-level teachers and pedagogical counsellors [1] on which this article reports, enables us to propose a solution by integrating into their questioning the didactic and pedagogical dimensions, as in the TPACK framework (Mishra and Koehler, 2006). Data collection took place in June 2013 and February 2014.This exercise not only helped create a directory of techno-pedagogical resources, it also allowed for the evaluation of a reflective tool that promotes the identification and integration of technologies in teaching. The analysis of the resources identified gave rise to some observations and recommendations for optimizing the use of TPACK

Phytostabilisation d'un site pollué par les éléments traces : opération pilote et pérennité du traitement

National audienceGrâce à l'utilisation combinée de plantes et d'agents immobilisants, la phytostabilisation assistée limite les risques associés à un sol contaminé en réduisant la biodisponibilité des polluants. Le rôle des plantes est de réduire le lessivage et l'érosion. En Europe et dans le monde, de nombreux sites ont déjà été phytostabilisés avec succès. Cependant, peu de projets de phytostabilisation associent une surface et une durée d'expérimentation suffisantes pour établir l'efficacité sur le long terme et en conditions réelles d'une telle pratique pour la gestion d'un site pollué. La nécessité de conduire des opérations pilotes sur une longue durée a été ainsi mise en avant par la communauté scientifique. L'objectif de ce projet mené sur un dispositif pilote mis en place en 2002 est d'estimer l'efficacité dans le temps d'une phytostabilisation assistée appliquée à un sédiment pollué par les éléments traces (Cd, Zn, Pb, Cu, As). Les paramètres suivis dans cette étude sont liés aux plantes initialement semées, aux espèces végétales venues spontanément coloniser le dispositif, aux agents immobilisants utilisés et aux caractéristiques physico-agronomiques de la matrice polluée. Une synthèse des résultats obtenus sur 7 années de suivi sera présentée lors du colloque

Molecular cloning, characterization, genomic organization and promoter analysis of the α1,6-fucosyltransferase gene (fut8) expressed in the rat hybridoma cell line YB2/0

<p>Abstract</p> <p>Background</p> <p>The rat hybridoma cell line YB2/0 appears a good candidate for the large-scale production of low fucose recombinant mAbs due to its lower expression of <it>fut8 </it>gene than other commonly used rodent cell lines. However, important variations of the fucose content of recombinant mAbs are observed in production culture conditions. To improve our knowledge on the YB2/0 fucosylation capacity, we have cloned and characterized the rat <it>fut8 </it>gene.</p> <p>Results</p> <p>The cDNAs encoding the rat α1,6-fucosyltransferase (FucT VIII) were cloned from YB2/0 cells by polymerase chain reaction-based and 5' RNA-Ligase-Mediated RACE methods. The cDNAs contain an open reading frame of 1728 bp encoding a 575 amino acid sequence showing 94% and 88% identity to human and pig orthologs, respectively. The recombinant protein expressed in COS-7 cells exhibits a α1,6-fucosyltransferase activity toward human asialo-agalacto-apotransferrin. The rat <it>fut8 </it>gene is located on chromosome 6 q and spans over 140 kbp. It contains 9 coding exons and four 5'-untranslated exons. FISH analysis shows a heterogeneous copy number of <it>fut8 </it>in YB2/0 nuclei with 2.8 ± 1.4 mean copy number. The YB2/0 <it>fut8 </it>gene is expressed as two main transcripts that differ in the first untranslated exon by the usage of distinct promoters and alternative splicing. Luciferase assays allow defining the minimal promoting regions governing the initiation of the two transcripts, which are differentially expressed in YB2/0 as shown by duplex Taqman QPCR analysis. Bioinformatics analysis of the minimal promoter regions upstream exons E-2 and E-3, governing the transcription of T1 and T2 transcripts, respectively, evidenced several consensus sequences for potential transcriptional repressors. Transient transfections of Rat2 cells with transcription factor expression vectors allowed identifying KLF15 as a putative repressor of T1 transcript in Rat2 cells.</p> <p>Conclusion</p> <p>Altogether, these data contribute to a better knowledge of <it>fut8 </it>expression in YB2/0 that will be useful to better control the fucosylation of recombinant mAbs produced in these cells.</p

Mineralogical and isotopic record of biotic and abiotic diagenesis of the Callovian-Oxfordian clayey formation of Bure (France)

International audienceThe Callovian-Oxfordian (COx) clayey unit is being studied in the Eastern part of the Paris Basin at depths between 400 and 500 m depth to assess of its suitability for nuclear waste disposal. The present study combines new mineralogical and isotopic data to describe the sedimentary history of the COx unit. Petrologic study provided evidence of the following diagenetic mineral sequence: (1) framboidal pyrite and micritic calcite, (2) iron-rich euhedral carbonates (ankerite, sideroplesite) and glauconite (3) limpid calcite and dolomite and celestite infilling residual porosity in bioclasts and cracks, (4) chalcedony, (5) quartz/calcite. Pyrite in bioturbations shows a wide range of δ34S (−38‰ to +34.5‰), providing evidence of bacterial sulphate reduction processes in changing sedimentation conditions. The most negative values (−38‰ to −22‰), measured in the lower part of the COx unit indicate precipitation of pyrite in a marine environment with a continuous sulphate supply. The most positive pyrite δ34S values (−14‰ up to +34.5‰) in the upper part of the COx unit indicate pyrite precipitation in a closed system. Celestite δ34S values reflect the last evolutionary stage of the system when bacterial activity ended; however its deposition cannot be possible without sulphate supply due to carbonate bioclast dissolution. The 87Sr/86Sr ratio of celestite (0.706872-0.707040) is consistent with deposition from Jurassic marine-derived waters. Carbon and oxygen isotopic compositions of bulk calcite and dolomite are consistent with marine carbonates. Siderite, only present in the maximum clay zone, has chemical composition and δ18O consistent with a marine environment. Its δ13C is however lower than those of marine carbonates, suggesting a contribution of 13C-depleted carbon from degradation of organic matter. δ18O values of diagenetic chalcedony range between +27‰ and +31‰, suggesting precipitation from marine-derived pore waters. Late calcite crosscutting a vein filled with chalcedony and celestite, and late euhedral quartz in a limestone from the top of the formation have lower δ18O values (not, vert, similar+19‰), suggesting that they precipitated from meteoric fluids, isotopically close to present-day pore waters of the formation. Finally, the study illustrates the transition from very active, biotic diagenesis to abiotic diagenesis. This transition appears to be driven by compaction of the sediment, which inhibited movement of bacterial cells by reduction of porosity and pore sizes, rather than a lack of inorganic carbon or sulphates

Transgenic apple plants overexpressing the chalcone 3-hydroxylase gene of Cosmos sulphureus show increased levels of 3-hydroxyphloridzin and reduced susceptibility to apple scab and fire blight

Main conclusionOverexpression of chalcone-3-hydroxylase provokes increased accumulation of 3-hydroxyphloridzin inMalus. Decreased flavonoid concentrations but unchanged flavonoid class composition were observed. The increased 3-hydroxyphlorizin contents correlate well with reduced susceptibility to fire blight and scab.The involvement of dihydrochalcones in the apple defence mechanism against pathogens is discussed but unknown biosynthetic steps in their formation hamper studies on their physiological relevance. The formation of 3-hydroxyphloretin is one of the gaps in the pathway. Polyphenol oxidases and cytochrome P450 dependent enzymes could be involved. Hydroxylation of phloretin in position 3 has high similarity to the B-ring hydroxylation of flavonoids catalysed by the well-known flavonoid 3′-hydroxylase (F3′H). Using recombinant F3′H and chalcone 3-hydroxylase (CH3H) from Cosmos sulphureus we show that F3′H and CH3H accept phloretin to some extent but higher conversion rates are obtained with CH3H. To test whether CH3H catalyzes the hydroxylation of dihydrochalcones in planta and if this could be of physiological relevance, we created transgenic apple trees harbouring CH3H from C. sulphureus. The three transgenic lines obtained showed lower polyphenol concentrations but no shift between the main polyphenol classes dihydrochalcones, flavonols, hydroxycinnamic acids and flavan 3-ols. Increase of 3-hydroxyphloridzin within the dihydrochalcones and of epicatechin/catechin within soluble flavan 3-ols were observed. Decreased activity of dihydroflavonol 4-reductase and chalcone synthase/chalcone isomerase could partially explain the lower polyphenol concentrations. In comparison to the parent line, the transgenic CH3H-lines showed a lower disease susceptibility to fire blight and apple scab that correlated with the increased 3-hydroxyphlorizin contents.Austrian Sci-ence Fund (FWF

Etude biochimique et immunochimique de la stimulation des peptidases de la bordure en brosse entérocytaire par un régime hyperprotéique

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