473 research outputs found
Ătude de ligands reposant sur des ylures de N-iminoimidazolium
Nous allons nous intĂ©resser dans cet ouvrage Ă lâutilisation dâylures de N-iminoimidazolium comme proligands NHC (carbĂšne N-hĂ©tĂ©rocyclique) anionique en catalyse organomĂ©tallique. Lâintroduction
rapporte tout dâabord les propriĂ©tĂ©s importantes des NHCs. Suite Ă la preuve de concept rapportĂ©e par le
groupe du professeur Charette en 2006, une premiÚre famille reposant sur des ylures de Nacyliminoimidazolium (famille des acyles) a été rapportée par le groupe Legault en 2013.
Une nouvelle famille de pro-ligands reposant sur des ylures de N-sulfonyliminoimidazolium (familles
des sulfonyles) a Ă©tĂ© synthĂ©tisĂ©e. Des complexes dâallylpalladium(II) supportant des ligands de la famille
des acyles et de la famille des sulfonyles ont été synthétisés. Il a été démontré que les ligands issus de la
famille des acyles ont permis la formation de complexes de type chélate. Les complexes issus de la famille des sulfonyles ont délivré uniquement des complexes oligomériques ainsi que des complexes
hétéropolymétalliques. Le chapitre 1 rapporte ces résultats.
Ayant formĂ© divers complexes dâallylpalladium(II) prĂ©sentant des propriĂ©tĂ©s structurelles bien distinctes,
nous avons proposĂ© dâĂ©tudier la rĂ©activitĂ© de ces diffĂ©rents complexes dans des rĂ©actions classiques de la chimie du palladium que sont la rĂ©action de Suzuki-Miyaura et la rĂ©action Tsuji-Trost. Le chapitre 2
rapporte ces résultats. Ces études de réactivité ont permis une plus grande compréhension du
comportement des complexes en catalyse.
Lâintroduction dâune unitĂ© NHC anionique sur un mĂ©tal a ouvert la porte Ă une grande gamme de
rĂ©activitĂ© intĂ©ressante, notamment les rĂ©actions par emprunt dâhydrogĂšne. La rĂ©action dâintĂ©rĂȘt
considĂ©rĂ©e exploitant lâemprunt dâhydrogĂšne a Ă©tĂ© la rĂ©action dâalkylation dâamines par des alcools. Ainsi
une librairie de complexes dâiridium(III) comportant des ligands de la famille des acyles et de la famille
des sulfonyles a Ă©tĂ© crĂ©Ă©e pour ĂȘtre Ă©valuĂ©e comme catalyseurs efficaces dans la rĂ©action dâalkylation
dâamines par transfert dâhydrogĂšne. Ainsi une mĂ©thodologie permettant la formation dâamines
substituĂ©es dans dâexcellents rendements a Ă©tĂ© rapportĂ©e. Dans un but Ă©cologique, un procĂ©dĂ© permettant la rĂ©action dans un mĂ©dium aqueux a aussi Ă©tĂ© proposĂ©. Les rĂ©sultats de cette Ă©tude sont rapportĂ©s dans le chapitre 3.
Devant le potentiel des complexes rapportés à transférer de façon formelle une molécule de dihydrogÚne,
diffĂ©rents tests ont Ă©tĂ© effectuĂ©s, notamment lâisomĂ©risation dâalcool allylique par emprunt dâhydrogĂšne.
Au cours de ces tests, un intermĂ©diaire Ă©nolate dâirididum a Ă©tĂ© observĂ©. Notre Ă©tude sâest alors portĂ©e
sur le piĂ©geage de cet Ă©nolate dâiridium par des dĂ©rivĂ©s dâiode(III) hypervalent permettant la formation
régiosélective de cétone alpha-substituées. Les résultats sont rapportés au chapitre 4
A simple and efficient feedback control strategy for wastewater denitrification
Due to severe mathematical modeling and calibration difficulties open-loop
feedforward control is mainly employed today for wastewater denitrification,
which is a key ecological issue. In order to improve the resulting poor
performances a new model-free control setting and its corresponding
"intelligent" controller are introduced. The pitfall of regulating two output
variables via a single input variable is overcome by introducing also an
open-loop knowledge-based control deduced from the plant behavior. Several
convincing computer simulations are presented and discussed.Comment: IFAC 2017 World Congress, Toulouse, Franc
NickelâNHC-Catalyzed Cross-Coupling of 2-Methylsulfanylbenzofurans with Alkyl Grignard Reagents
NiCl2(PPh3)(IPr) catalyzes cross-coupling reactions of 2-methylsulfanylbenzofurans with alkyl Grignard reagents. Other nickel complexes such as NiCl2(dppe) failed to catalyze the same reaction. The alkylation is applicable to the synthesis of a couple of protein tyrosine phosphatase inhibitors, 3-(4-biphenylyl)-2-alkylbenzofurans
Laser-doppler Acoustic Probing of Granular Media with Varying Water Levels
International audienceLaboratory physical modelling and non-contacting ultrasonic techniques are frequently proposed to tackle theoretical and method- ological issues related to geophysical prospecting. We used an innovative experimental set-up to perform laser-Doppler acoustic probing of granular materials with varying water levels to target near-surface hydrogeological applications. The preliminary results presented here show a clear influence of the water level on both first arrival times and dispersion of guided waves, and significant differences in terms of amplitudes. They validate the use of such approach to benchmark recently developed methods for water saturation detection in hydrogeophysics
Whole-genome, deep pyrosequencing analysis of a duck influenza A virus evolution in swine cells.
We studied the sub-population level evolution of a duck influenza A virus isolate during passage in swine tracheal cells. The complete genomes of the A/mallard/Netherlands/10-Nmkt/1999 strain and its swine cell-passaged descendent were analysed by 454 pyrosequencing with coverage depth ranging from several hundred to several thousand reads at any point. This allowed characterization of defined minority sub-populations of gene segments 2, 3, 4, 5, 7, and 8 present in the original isolate. These minority sub-populations ranged between 9.5% (for segment 2) and 46% (for segment 4) of their respective gene segments in the parental stock. They were likely contributed by one or more viruses circulating within the same area, at the same period and in the same or a sympatric host species. The minority sub-populations of segments 3, 4, and 5 became extinct upon viral passage in swine cells, whereas the minority sub-populations of segments 2, 7 and 8 completely replaced their majority counterparts. The swine cell-passaged virus was therefore a three-segment reassortant and also harboured point mutations in segments 3 and 4. The passaged virus was more homogenous than the parental stock, with only 17 minority single nucleotide polymorphisms present above 5% frequency across the whole genome. Though limited here to one sample, this deep sequencing approach highlights the evolutionary versatility of influenza viruses whereby they exploit their genetic diversity, predilection for mixed infection and reassortment to adapt to a new host environmental niche.This work was supported by a grant from DEFRA and HEFCE under the Veterinary Training and Research Initiative to the Cambridge Infectious Diseases Consortium (VB, LT), BBSRC grants BB/H014306/1 and BB/G00479X/1 (LT), and the French Ministry of Agriculture, INRA and the French Région Midi-Pyrénées (GC, J-LG, VB).This is the accepted version of the original version available at: http://dx.doi.org/10.1016/j.meegid.2013.04.03
Multichannel speech separation with recurrent neural networks from high-order ambisonics recordings
International audienceWe present a source separation system for high-order ambisonics (HOA) contents. We derive a multichannel spatial filter from a mask estimated by a long short-term memory (LSTM) recurrent neural network. We combine one channel of the mixture with the outputs of basic HOA beamformers as inputs to the LSTM, assuming that we know the directions of arrival of the directional sources. In our experiments, the speech of interest can be corrupted either by diffuse noise or by an equally loud competing speaker. We show that adding as input the output of the beamformer steered toward the competing speech in addition to that of the beamformer steered toward the target speech brings significant improvements in terms of word error rate
CRNN-based joint azimuth and elevation localization with the Ambisonics intensity vector
International audienceWe present a source localization system for first-order Ambisonics (FOA) contents based on a stacked convolutional and recurrent neural network (CRNN). We propose to use as input to the CRNN the FOA acoustic intensity vector, which is easy to compute and closely linked to the sound direction of arrival (DoA). The system estimates the DoA of a point source in both azimuth and elevation. We conduct an experimental evaluation in configurations including reverberation, noise, and various speaker w.r.t. microphone orientations. The results show that the proposed architecture and input allow the network to return accurate location estimates in realistic conditions compared to another recent CRNN-based system
ConseqĂŒĂšncies de la biodegradabilitat de la matĂšria orgĂ nica en les propietats fĂsiques i quĂmiques dels substrats
L'Ășs de nous materials de naturalesa orgĂ nica provinents de l'agricultura, de la indĂșstria i d'unes altres activitats humanes en la preparaciĂł de substrats per al cultiu de plantes fora del sĂČl natural requereix el coneixement de llur bioestabilitat, ja que aquesta propietat determina la variaciĂł de les caracterĂstiques fĂsiques i quĂmiques dels substrats en el decurs del temps. En una recerca conjunta duta a terme pels dos grups de recerca pertanyents als departaments de referĂšncia de l'INRA a França i de l'IRTA a Catalunya, s'ha estudiat la bioestabilitat de sis materials orgĂ nics: torba d'esfagne, compost d'escorça de pi, compost de residus verds de jardineria, compost de residus de bosc, fibra de coco i compost de fems de vacum, i alhora de set barreges binĂ ries formulades amb les matĂšries abans esmentades. Al mateix temps s'han estudiat els efectes de la bioestabilitat en la variaciĂł de les propietats fĂsiques i quĂmiques de tots els substrats.Considerant els Ăndexs de bioestabilitat respectius, les matĂšries primeres s'han classificat en tres grups: han resultat materials molt estables la fibra de coco, el compost d'escorça de pi i el compost de residus de jardineria; s'ha provat que sĂłn materials estables la torba d'esfagne i el compost de residus forestals; i, finalment, el compost de fems de vacum presenta una bioestabilitat moderada. S'hi mostra que, considerant els materials estudiats, la variaciĂł relativa de certes propietats fĂsiques, com ara l'aigua disponible i l'aigua difĂcilment disponible, i tambĂ© la de certes propietats quĂmiques, com la capacitat de bescanvi catiĂČnic, es correlacionen linealment, amb significaciĂł estadĂstica, amb l'Ăndex de bioestabilitat dels substrats estudiats en les dues localitzacions experimentals. Considerant nomĂ©s les matĂšries primeres, la regressiĂł lineal entre llur capacitat d'aireaciĂł i llur Ăndex de bioestabilitat presenta un coeficient de correlaciĂł tambĂ© estadĂsticament significatiu. Per contra, l'Ăndex de bioestabilEl uso de nuevos materiales de naturaleza orgĂĄnica procedentes de la agricultura, de la industria y de otras actividades humanas en la preparaciĂłn de sustratos para el cultivo de plantas fuera del suelo natural requiere el conocimiento de su bioestabilidad, ya que esta propiedad determina la variaciĂłn de las caracterĂsticas fĂsicas y quĂmicas de los sustratos en el transcurso del tiempo. En una investigaciĂłn conjunta realizada por los dos grupos de investigaciĂłn que pertenecen a los departamentos de referencia del INRA, en Francia, y del IRTA, en Catalunya, se ha estudiado la bioestabilidad de seis materiales orgĂĄnicos: turba de esfagno, compost de corteza de pino, compost de residuos verdes de jardinerĂa, compost de residuos de bosque, fibra de coco y compost de estiĂ©rcol de bovino. TambiĂ©n se ha estudiado este parĂĄmetro sobre siete mezclas binarias formuladas con las primeras materias antes citadas. Igualmente, se han estudiado los efectos de la bioestabilidad en la variaciĂłn de las propiedades fĂsicas y quĂmicas de todos los sustratos. Considerando los respectivos Ăndices de bioestabilidad, las primeras materias se han clasificado en tres grupos: materiales muy estables han resulta-do ser la fibra de coco, el compost de corteza de pino y el compost de residuos de jardinerĂa; materiales estables se ha probado que lo son la turba de esfagno y el compost de residuos forestales. Finalmente, el compost de estiĂ©rcol de bovino presenta una bioestabilidad moderada. Se muestra que, considerando los materiales estudiados, la variaciĂłn relativa de ciertas propiedades fĂsicas, como por ejemplo el agua disponible y el agua difĂcilmente disponible, y tambiĂ©n la de ciertas propiedades quĂmicas, como la capacidad de intercambio catiĂłnico, se correlacionan linealmente, con significaciĂłn estadĂstica, con el Ăndice de bioestabilidad de los sustratos estudiados en las dos localizaciones experimentales. Considerando sĂłlo las primeras materias, la regresiĂłn lineal entre su capacidad
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