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41.
Yvette Kosmann-Schwarzbach 《Letters in Mathematical Physics》1981,5(3):229-237
We offer a new geometric theory of Hamiltonian systems with an infinite number of degrees of freedom in which the Hamiltonian operators are nonlinear differential operators on fields. The Poisson bracket is carried into the vertical bracket by the mapping between functionals and Hamitonian operators which is established by a Hamiltonian structure. 相似文献
42.
43.
Summary To elucidate the mechanism of chiral recognition of cholic acid-based stationary phases, four new cholic acid derivatives,
with differently substituted carbamate or three acetoxy groups, were bonded to a hydrosilyl-modified silica gel. Their capacity
to discriminate between enantiomers was evaluated in normal-phase high-performance liquid chromatography. The results were
compared with those from equivalent separations on trihydroxy- and 3α-phenylcarbamate-substituted cholic acid-based bonded
phases. The influence of mobile phase composition of the separation of the enantiomers of amino alcohols was shown. Different
mechanisms of chiral discrimination are discussed, highlighting the influence of the nature of the carbamate on enantioselectivity. 相似文献
44.
Yvette Kosmann-Schwarzbach 《Bulletin of the Brazilian Mathematical Society》2011,42(4):625-649
We study Nijenhuis structures on Courant algebroids in terms of the canonical Poisson bracket on their symplectic realizations.
We prove that the Nijenhuis torsion of a skew-symmetric endomorphism N of a Courant algebroid is skewsymmetric if N
2 is proportional to the identity, and only in this case when the Courant algebroid is irreducible. We derive a necessary and
sufficient condition for a skewsymmetric endomorphism to give rise to a deformed Courant structure. In the case of the double
of a Lie bialgebroid (A, A*), given an endomorphism N of A that defines a skew-symmetric endomorphism N of the double of A, we prove that the torsion ofN is the sum of the torsion of N and that of the transpose of N. 相似文献
45.
Sanchari Bhattacharya Tzu-Chiao Chao Nethmi Ariyasinghe Yvette Ruiz Douglas Lake Robert Ros Alexandra Ros 《Analytical and bioanalytical chemistry》2014,406(7):1855-1865
The trapping or immobilization of individual cells at specific locations in microfluidic platforms is essential for single cell studies, especially those requiring cell stimulation and downstream analysis of cellular content. Selectivity for individual cell types is required when mixtures of cells are analyzed in heterogeneous and complex matrices, such as the selection of metastatic cells within blood samples. Here, we demonstrate a microfluidic device based on direct current (DC) insulator-based dielectrophoresis (iDEP) for selective trapping of single MCF-7 breast cancer cells from mixtures with both mammalian peripheral blood mononuclear cells (PBMC) as well MDA-MB-231 as a second breast cancer cell type. The microfluidic device has a teardrop iDEP design optimized for the selective capture of single cells based on their differential DEP behavior under DC conditions. Numerical simulations adapted to experimental device geometries and buffer conditions predicted the trapping condition in which the dielectrophoretic force overcomes electrokinetic forces for MCF-7 cells, whereas PBMCs were not trapped. Experimentally, selective trapping of viable MCF-7 cells in mixtures with PBMCs was demonstrated in good agreement with simulations. A similar approach was also executed to demonstrate the selective trapping of MCF-7 cells in a mixture with MDA-MB-231 cells, indicating the selectivity of the device for weakly invasive and highly invasive breast cancer cells. The DEP studies were complemented with cell viability tests indicating acceptable cell viability over the course of an iDEP trapping experiment. Figure
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46.
Jean-Claude Folest Jean-Marc Duprilot Jacques Perichon Yvette Robin Jacques Devynck 《Tetrahedron letters》1985,26(22):2633-2636
The carboxylation of benzylic and allylic chlorides by CO2 in tetrahydrofuran + hexamethylphosphoramide (40% – 60%) is electrocatalyzed by a cobalt Schiff-base complex Co(Salen). The reactions were performed by controlled-potential electrolysis at the RCo (Salen) reduction potential. The yield of the carboxylic acid formation has been calculated. 相似文献
47.
48.
Gerstenberger BS Lin J Mimieux YS Brown LE Oliver AG Konopelski JP 《Organic letters》2008,10(3):369-372
Decomposition of a diazo beta-ketoamide derived from N-trityl serine imidazolide and N-protected acetanilides provides, instead of the expected 3-acyloxindole product, an enantiomerically pure (EP) beta-lactam. The amino acid stereocenter is incorporated, the second chiral center is induced, and trityl protection of the beta-lactam ring is realized for the first time. The desired 3-acyloxindole is obtained from oxindole and Tr-Ser(OBn)-imidazole, the X-ray of which provides the first structural determination of an EP amino acid imidazolide. 相似文献
49.
Nano-LC-MS/MS for the monitoring of angiotensin IV in rat brain microdialysates: limitations and possibilities 总被引:1,自引:0,他引:1
Lanckmans K Stragier B Sarre S Smolders I Michotte Y 《Journal of separation science》2007,30(14):2217-2224
To broaden our knowledge about the central role of the angiotensin IV (Ang IV) peptide, we aimed to monitor its extracellular concentration in the brain using in vivo microdialysis. Ang IV was measured in the dialysates using a previously developed nano-LC-MS/MS assay with an LOD of 50 pM. Using this assay, baseline levels of Ang IV in dialysates from different brain structures were undetectable. However, immediately after microdialysis probe insertion, Ang IV could be detected in a concentration that varied between 120 and 187 pM. Using the zero-net-flux method, the extracellular levels of Ang IV in the striatum were estimated at 46 pM. These data may indicate that Ang IV is mainly present intracellularly. In addition, Ang IV was clearly measurable after striatal perfusion of Ang II. On the other hand, our nano-LC-MS/MS method was successful for the detection of Met-enkephalin and neurotensin in dialysates from the rat. In conclusion, the nano-LC-MS/MS method coupled with microdialysis is well suited to monitor the biologically significant conversion between Ang II and Ang IV in vivo, but physiological extracellular levels of Ang IV appear too low to be detected. 相似文献
50.
Gardner JY Brillhart DE Benjamin MM Dixon LG Mitchell LM Dimandja JM 《Journal of separation science》2011,34(2):176-185
The cellular fatty acid profiles of eight strains of Bacillus, Staphylococcus, and Enterobacteriacae (Escherichia coli and Salmonella) were analyzed by comprehensive two-dimensional gas chromatography/time-of-flight mass spectrometry. A novel template method was developed to standardize the raw two-dimensional gas chromatography retention data through the use of a chemical indexing mixture. Analyte retention coordinates were normalized in the primary dimension with respect to a series of n-alkanes (Kovats index) and in the secondary dimension with respect to a series of aromatic hydrocarbons (Lee index). Fatty acid profiles extracted from the templates were compared by multidimensional scaling and principal component analysis. Differences in the profiles of Gram-positive and Gram-negative bacteria were observed, and a series of heterogeneous mixtures comprising different fractions (containing one Gram-positive and one Gram-negative bacteria strain) were also distinguished from their homogeneous constituents. 相似文献