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51.
Chahrazed Gheffar Hung Le Thierry Jouenne Annick Schaumann Auriane Corbière David Vaudry Didier LeCerf Carole Karakasyan 《Particle & Particle Systems Characterization》2021,38(1):2000253
The formation of bacterial biofilms on material surfaces is a recurrent problem in public health. Antibacterial nanoparticles (NPs) are promising because pathogens have not yet developed resistance mechanisms and encapsulation of the drug can protect it from the surrounding medium and improve pharmacokinetics. Biocompatible and biodegradable particles of various sizes (nano- and micro-scale) based on poly(lactic-co-glycolic acid) (PLGA) are elaborated using a simple and free toxic nanoprecipitation process. Particles are poly(ethylene glycol) (PEG)-ylated in order to reduce unwanted interactions with biological fluids, or loaded with the large spectrum antibiotic ciprofloxacin (CIP). NPs are studied against Staphylococcus aureus in planktonic and biofilm modes. Empty NPs with smallest size (60 nm) are able to totally eradicate planktonic culture after 24 h, even in the presence of serum proteins. CIP-loaded NPs present slightly lower antimicrobial activity against planktonic microorganisms compared with the free antibiotic, due to progressive release of CIP over time. In biofilm mode, CIP-loaded NPs show a very good antibiofilm activity, much better than free CIP, thanks to NPs penetration within the polymer matrix and a consequent release of the antibiotic close to the embedded bacteria. The present results open the way for widespread applications of PLGA-NPs in the pharmaceutical or medical fields. 相似文献
52.
Yannick VianoDominique Bonhomme Annick Ortalo-MagnéOlivier P. Thomas Mohamed El HattabLouis Piovetti Yves BlacheGérald Culioli 《Tetrahedron letters》2011,52(9):1031-1035
A phytochemical investigation of a Mediterranean brown alga (Dictyota sp.) led to the isolation of a novel C40bis-diterpene, named dictyotadimer A. The chemical structure of this unusual dissymmetric dimer, characterized by a C-C linkage between two different xenicane units, was elucidated by 1D and 2D NMR analyses together with HR-ESI mass spectrometry. The relative configuration of the two diterpenoid components was determined by NOESY NMR correlations and molecular modeling. A plausible biogenetic pathway of dictyotadimer A was also proposed. 相似文献
53.
We present in this review a joint experimental and theoretical overview of the synthesis techniques and properties of boron-nitride (BN) and boron-carbonitride (BCN) nanotubes. While their tubular structure is similar to that of their carbon analogues, we show that their electronic properties are significantly different. BN tubes are wide band gap insulators while BCN systems can be semiconductors with a band gap in the visible range. 相似文献
54.
Annick Dion‐Fortier Alexia Gravel Cassandra Gurette Fanny Chevillot Sonia Blais Serge Auger Pierre Picard Pedro A. Segura 《Journal of mass spectrometry : JMS》2019,54(2):167-177
Laser‐diode thermal desorption (LDTD) is an ionization source usually coupled to triple quadrupole mass spectrometry (QqQMS) and specifically designed for laboratories requiring high‐throughput analysis. It has been observed that surface coatings on LDTD microwell plates can improve the sensitivity of the analysis of small polar molecules. The objective of the present study is to understand and quantify the effect of microwell surface coatings on signal intensity of small organic molecules of clinical, environmental, and forensic interest. Experiments showed that the peak areas of diclofenac, chloramphenicol, salicylic acid, and 11‐nor‐9‐carboxy‐Δ9‐tetrahydrocannabinol obtained by LDTD‐QqQMS increased by up to 3 orders of magnitude when using microwells coated with ethylenediaminetetraacetic acid (EDTA). Tests with different chelating agents and polytetrafluoroethylene as microwell surface coatings showed that nitrilotriacetic acid gave significantly higher peak areas for five out of the nine compounds that showed signal enhancement using chelating agents as coatings. Scanning electron microscopy studies of EDTA‐coated and uncoated microwells showed that analytes deposited in the former formed more uniform and thinner films than in the latter. The enhancement effect of surface coatings in LDTD‐QqQMS was explained mainly by the formation of homogenous and thinner layers of nanocrystals of analytes that are easier to desorb thermally than the layers formed when the analytes dry in direct contact with the bare stainless‐steel surface. Chemisorption of some analytes to the stainless‐steel surface of the microwell plate appeared to be a minor factor. Surface coatings widen the number of compounds analyzable by LDTD‐QqQMS and can also improve sensitivity and limits of detection. 相似文献
55.
Annick Van Put Akos Vertes Darek Wegrzynek Boris Treiger René Van Grieken 《Fresenius' Journal of Analytical Chemistry》1994,350(7-9):440-447
Morphological characterization of individual particle surfaces was explored by off-line image processing of data obtained by scanning electron microscope — microanalyzer. The fractal geometry was studied by two methods, the power spectrum and the variogram approach. Both methods were evaluated, theoretically by a series of numerically simulated surface profiles and experimentally on a set of pre-recorded secondary electron images of particle surfaces exposing characteristic textures. It was shown that the fractal approach could stand as a base of the methods enlarging the application of electron probe X-ray microanalyzers for individual particle characterization.Dedicated to Professor Dr. Dieter Klockow on the occasion of his 60th birthday
On leave from: State Pedagogical Institute, Kirovograd, Ukraine 相似文献
56.
During the past few years a number of reports have appeared, dealing with applications of the retro-Diels-Alder reaction, which now takes a place in the methodology of organic synthesis. An attempt is made here to summarize all the important work which has been done in this field from 1970 until the end of 1976. The accent will be the simplicity and broad variety of synthetic applications. 相似文献
57.
By seeking analogies in behavior between aliphatic and alicyclic carboxylic acids, it is possible to determine the sterically active sites of the latter. 相似文献
58.
59.
Jorge Nocedal Annick Sartenaer Ciyou Zhu 《Computational Optimization and Applications》2002,22(1):5-35
It is well known that the norm of the gradient may be unreliable as a stopping test in unconstrained optimization, and that it often exhibits oscillations in the course of the optimization. In this paper we present results descibing the properties of the gradient norm for the steepest descent method applied to quadratic objective functions. We also make some general observations that apply to nonlinear problems, relating the gradient norm, the objective function value, and the path generated by the iterates. 相似文献
60.
Characterization and event specific-detection by quantitative real-time PCR of T25 maize insert 总被引:10,自引:0,他引:10
Collonnier C Schattner A Berthier G Boyer F Coué-Philippe G Diolez A Duplan MN Fernandez S Kebdani N Kobilinsky A Romaniuk M de Beuckeleer M de Loose M Windels P Bertheau Y 《Journal of AOAC International》2005,88(2):536-546
T25 is one of the 4 maize transformation events from which commercial lines have so far been authorized in Europe. It was created by polyethylene glycol-mediated transformation using a construct bearing one copy of the synthetic pat gene associated with both promoter and terminator of the 35S ribosomal gene from cauliflower mosaic virus. In this article, we report the sequencing of the whole T25 insert and the characterization of its integration site by using a genome walking strategy. Our results confirmed that one intact copy of the initial construct had been integrated in the plant genome. They also revealed, at the 5' junction of the insert, the presence of a second truncated 35S promoter, probably resulting from rearrangements which may have occurred before or during integration of the plasmid DNA. The analysis of the junction fragments showed that the integration site of the insert presented high homologies with the Huck retrotransposon family. By using one primer annealing in the maize genome and the other in the 5' end of the integrated DNA, we developed a reliable event-specific detection system for T25 maize. To provide means to comply with the European regulation, a real-time PCR test was designed for specific quantitation of T25 event by using Taqman chemistry. 相似文献