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排序方式: 共有229条查询结果,搜索用时 15 毫秒
191.
Alain Cimetière Damien Halm Jean-Jacques Marigo Estelle Molines 《Comptes Rendus Mecanique》2003,331(4):291-294
A thermodynamic framework is introduced for damage models. This framework, which consists in adding internal variables called complementary variables, lies within the framework of standard materials whose convex domain of admissible forces does not depend on the present state of internal variables. Thus its advantages are kept. Marigo's model is put back in this framework and another example combining isotropic and kinematic hardening is given. To cite this article: A. Cimetière et al., C. R. Mecanique 331 (2003). 相似文献
192.
A. von Homeyer D.-O. Krentz W.-M. Kulicke D. Lerche 《Colloid and polymer science》1999,277(7):637-645
The flocculation of sewage sludge with poly(diallyldimethylammonium chloride) (PDADMAC) as well as cationic, poly[acrylamide-co-(N,N,N-trimethylammoniumethylacrylate chloride)] (PTAC), and anionic acrylamide copolymers, poly(acrylamide-co-acrylate) (PAAM/AA), was investigated by using a new method to evaluate the velocity of centrifugal separation and the packing
behaviour of the sediments. By means of a centrifugation analyser with an optoelectronic measuring system the position of
the centrate/sediment interface of the conditioned suspensions can be determined as a function of the separation time, which
allows the polyelectrolyte dosage to be optimized for various rotational speeds. At high centrifugal accelerations it was
found that using the anionic polyelectrolyte PAAM/AA does not result in better dewatering performance, whereas both polycations
recorded high degrees of separation. Furthermore, the measurements with the high-molar-mass PTAC indicate a high resistance
to centrifugation which correlates with floc stability. In contrast, addition of the low-molar-mass PDADMAC gives more fragile
flocs, leading to faster collapse of the sludge cake in the compression zone of the centrifuge at lower gravitational forces.
These experimental findings agree well with the much higher filtration capacity of sludges conditioned with PTAC which was
measured by means of a pressure filtration device. Comparisons of the optimum polyelectrolyte concentrations obtained by pressure
filtration or centrifugation at low gravitational forces with the zeta potential of the flocculated particles appear to be
consistent with bridge formation for PTAC and with the charge patch mechanism for PDADMAC. The centrifugation experiments
at high centrifugal accelerations show an optimum separation efficiency at relatively low degrees of coverage and a high level
of agreement with the large-scale process.
Received: 24 November 1998 Accepted in revised form: 12 February 1999 相似文献
193.
194.
Dr. Aurélien Herbinski Dr. Estelle Illous Dr. Estelle Métay Jesus F. Ontiveros Prof. Jean-Marie Aubry Prof. Marc Lemaire 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(28):e202200274
New alkyl ether carboxylates with a glyceryl spacer instead of ethylene glycol units have been synthesised using environmentally friendly methodology. A cascade synthesis of acetalisation and hydrogenolysis was developed to obtain products containing an alkyl chain linked to a glycerol unit bearing a polar carboxylate head. These products were methylated by using trimethyl phosphate to observe the influence of a free or methoxylated alcohol on the physicochemical properties. Finally, saponification gave the carboxylate anionic group of the new hydrotropes. Studying the amphiphilicity, the tolerance to sodium and calcium ions, and the solubilising power of these bio-based ionic/nonionic hydrotropes has shown that they exhibit significantly improved application properties compared to similar petro-based hydrotropes. 相似文献
195.
196.
Chemically and Electrochemically Triggered Assembly of Viologen Radicals: Towards Multiaddressable Molecular Switches 下载免费PDF全文
Christophe Kahlfuss Dr. Estelle Métay Marie‐Christine Duclos Prof. Marc Lemaire Prof. Anne Milet Prof. Eric Saint‐Aman Dr. Christophe Bucher 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(5):2090-2106
We have established that bipyridinium radicals can be reversibly π‐dimerized under the combined effects of chemical (proton transfer) and electrochemical (electron transfer) stimuli. Our investigations also led to the discovery that a bis‐pyridinyl appended calixarene intermediate is involved in a fully reversible redox‐triggered σ‐dimerization process. The structure of the most stable intramolecular σ‐dimer was provided by computational chemistry and its complete conversion into a noncovalent π‐dimer could be triggered chemically by addition of protons, leading to the formation of protonated cation radicals. Theoretical data collected with the N‐methylated and N‐protonated π‐dimers also support the existence of multivariant orientations in π‐bonded dimers of viologen cation‐radicals. 相似文献
197.
This account will discuss the advances performed in our group on direct arylation of heterocyclic systems regarded as critical scaffolds of pharmaceutical industries due to their wide-ranging biological and therapeutical properties. Applications to larger molecules devoted to pharmaceutical, material or agrochemical industries should bring significant improvement, getting rid of the preliminary step of prefunctionalization. 相似文献
198.
199.
Negative electrospray ionization mass spectrometry: a method for sequencing and determining linkage position in oligosaccharides from branched hemicelluloses 下载免费PDF全文
Bernard Quéméner Jacqueline Vigouroux Estelle Rathahao Jean Claude Tabet Aleksandra Dimitrijevic Marc Lahaye 《Journal of mass spectrometry : JMS》2015,50(1):247-264
Xyloglucans of apple, tomato, bilberry and tamarind were hydrolyzed by commercial endo β‐1‐4‐D‐endoglucanase. The xylo‐gluco‐oligosaccharides (XylGos) released were separated on CarboPac PA 200 column in less than 15 min, and, after purification, they were structurally characterized by negative electrospray ionization mass spectrometry using a quadrupole time‐of‐flight (ESI‐Q‐TOF), a hybrid linear ion trap (LTQ)/Orbitrap and a hybrid quadrupole Fourier transform ion cyclotron resonance (FT‐ICR) mass spectrometers. In order to corroborate the fragmentation routes observed on XylGos, some commercial galacto‐manno‐oligosaccharides (GalMOs) and glucurono‐xylo‐oligosaccharides were also studied. The fragmentation pathways of the ionized GalMos were similar to those of XylGos ones. The product ion spectra were mainly characterized by prominent double cleavage (D) ions corresponding to the entire inner side chains. The directed fragmentation from the reducing end to the other end was observed for the main glycosylated backbone but also for the side‐chains, allowing their complete sequencing. Relevant cross‐ring cleavage ions from 0,2Xj ‐type revealed to be diagnostic of the 1‐2‐linked‐ glycosyl units from XylGos together with the 1‐2‐linked glucuronic acid unit from glucuronoxylans. Resonant activation in the LTQ Orbitrap allowed not only determining the type of all linkages but also the O‐acetyl group location on fucosylated side‐chains. Moreover, the fragmentation of the different side chains using the MSn capabilities of the LTQ/Orbitrap analyzer also allowed differentiating terminal arabinosyl and xylosyl substituents inside S and U side‐chains of XylGos, respectively. The CID spectra obtained were very informative for distinction of isomeric structures differing only in their substitution pattern. These features together makes the fragmentation in negative ionization mode a relevant and powerful technique useful to highlight the subtle structural changes generally observed during the development of plant organs such as during fruit ripening and for the screening of cell wall mutants with altered hemicellulose structure. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
200.
Estelle Piquer Marie-Catherine Charrier-Mojtabi Mejdi Azaiez Abdelkader Mojtabi 《Comptes Rendus Mecanique》2005,333(2):179-186
This Note deals with mixed convection in binary fluid with Soret effect in a rectangular duct heated from below. In particular, we study the transition towards transverse 2D rolls appearing at low Reynolds and Rayleigh numbers. The linear stability analysis of Poiseuille flow, with linearly stratified temperature and concentration fields, shows the influence of the separation ratio on the critical Rayleigh number at the transition towards the transversal 2D convective patterns. It highlights the presence, at low Reynolds numbers, of propagating transverse rolls in the downwards as well as in the upwards direction. Finally, we point out that, under these conditions, the propagating frequency of the rolls is the sum of two well defined frequencies: the first related to the Reynolds, the second to the separation ratio. To cite this article: E. Piquer et al., C. R. Mecanique 333 (2005). 相似文献