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111.
112.
Paul R. Carlier Weldon W.-F. Lam Nan Chi Wan Ian D. Williams 《Angewandte Chemie (International ed. in English)》1998,37(16):2252-2254
Deracemization , the conversion of a racemic mixture into an enantiomerically enriched material, is achieved with the retro-aldol reaction of rac- 1 in the presence of lithium (−)-ephedrinate [Eq. (1)]. Remarkably, two stereogenic centers are simultaneously deracemized. This reaction shows that efficient thermodynamic control of the enantioselectivity of aldol reactions is possible 相似文献
113.
114.
Many synthetic methods exist for dibenzoquinoxalines but only a few for dibenzophenazines and their aza derivatives and even less are ‘green’. Some dibenzophenazines and dibenzopyridoquinoxaline have been efficiently obtained with good to excellent yield by a very simple method which does not require use of solvent or catalyst. Solid phase synthesis using co-grinding presents thus many advantages in developing greener synthetic organic pathways. 相似文献
115.
Guillaume Carlier Lina Mallozzi 《Journal of Mathematical Analysis and Applications》2018,457(2):1218-1231
We consider a bilevel optimization framework corresponding to a monopoly spatial pricing problem: the price for a set of given facilities maximizes the profit (upper level problem) taking into account that the demand is determined by consumers' cost minimization (lower level problem). In our model, both transportation costs and congestion costs are considered, and the lower level problem is solved via partial transport mass theory. The partial transport aspect of the problem comes from the fact that each consumer has the possibility to remain out of the market. We also generalize the model and our variational analysis to the stochastic case where utility involves a random term. 相似文献
116.
This paper introduces a subgradient descent algorithm to compute a Riemannian metric that minimizes an energy involving geodesic
distances. The heart of the method is the Subgradient Marching Algorithm to compute the derivative of the geodesic distance
with respect to the metric. The geodesic distance being a concave function of the metric, this algorithm computes an element
of the subgradient in O(N
2 log(N)) operations on a discrete grid of N points. It performs a front propagation that computes a subgradient of a discrete geodesic distance. We show applications
to landscape modeling and to traffic congestion. Both applications require the maximization of geodesic distances under convex
constraints, and are solved by subgradient descent computed with our Subgradient Marching. We also show application to the
inversion of travel time tomography, where the recovered metric is the local minimum of a non-convex variational problem involving
geodesic distances. 相似文献
117.
This work investigated the ability of several kinds of molecules to mediate the melt functionalization of polypropylene. N-Bromosuccinimide, nitroxides, iniferters, thiols and RAFT chain transfer agents were tested as potential mediators. The grafting of maleic anhydride onto polypropylene was carried out with and without mediator and the grafted polymers are discussed in terms of graft content, graft structure and molecular weights. 相似文献
118.
Frouin F Duteil S Lesage D Carlier PG Herment A Leroy-Willig A 《Magnetic resonance imaging》2006,24(7):941-951
Arterial spin labeling (ASL) perfusion measurements allow the follow-up of muscle perfusion with high temporal resolution during a stress test. Automated image processing is proposed to estimate perfusion maps from ASL images. It is based on two successive analyses: at first, automated rejection of the image pairs between which a large displacement is detected is performed, followed by factor analysis of the dynamic data and cluster analysis to classify pixels with large signal variation characteristic of vessels. Then, after masking these "vascular" pixels, factor analysis and cluster analysis are further applied to separate the different muscles between low or high perfusion increase, yielding a functional map of the leg. Data from 10 subjects (five normal volunteers and five elite sportsmen) had been analyzed. Resulting time perfusion curves from a region of interest (ROI) in active muscles show a good accordance whether extracted with automated processing or with manual processing. This method of functional segmentation allows automated suppression of vessels and fast visualization of muscles with high, medium or low perfusion, without any a priori knowledge. 相似文献
119.
Simon Sieber Aurlien Carlier Markus Neuburger Giselher Grabenweger Leo Eberl Karl Gademann 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2015,127(27):8079-8081
The new C7N aminocyclitol kirkamide ( 1 ) was isolated from leaf nodules of the plant Psychotria kirkii by using a genome‐driven 1H NMR‐guided fractionation approach. The structure and absolute configuration were elucidated by HRMS, NMR, and single‐crystal X‐ray crystallography. An enantioselective total synthesis was developed, which delivered kirkamide ( 1 ) on a gram scale in 11 steps and features a Ferrier carbocyclization and a Pd‐mediated hydroxymethylation. We propose that kirkamide is synthesized by Candidatus Burkholderia kirkii, the obligate leaf symbiont of Psychotria kirkii. Kirkamide ( 1 ) was shown to be toxic to aquatic arthropods and insects, thus suggesting that bacterial secondary metabolites play a protective role in the Psychotria/Burkholderia leaf nodule symbiosis. 相似文献
120.
Carlier D Cheng JH Berthelot R Guignard M Yoncheva M Stoyanova R Hwang BJ Delmas C 《Dalton transactions (Cambridge, England : 2003)》2011,40(36):9306-9312
Manganese substituted sodium cobaltate, Na(2/3)Co(2/3)Mn(1/3)O(2), with a layered hexagonal structure (P2-type) was obtained by a co-precipitation method followed by a heat treatment at 950 °C. Powder X-ray diffraction analysis revealed that the phase is pure in the absence of long-range ordering of Co and Mn ions in the slab or Na(+) and vacancy in the interslab space. The oxidation states of the transition metal ions were studied by magnetic susceptibility measurements, electron paramagnetic resonance (ESR) and (23)Na magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy. The charge compensation is achieved by the stabilization of low-spin Co(3+) and Mn(4+) ions. The capability of Na(2/3)Co(2/3)Mn(1/3)O(2) to intercalate and deintercalate Na(+) reversibly was tested in electrochemical sodium cells. It appears that the P2 structure is maintained during cycling, the cell parameter evolution versus the sodium amount is given. From the features of the cycling curve the formation of an ordered phase for the Na(0.5)Co(2/3)Mn(1/3)O(2) composition is expected. 相似文献