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51.
Kokalj A Bonini N de Gironcoli S Sbraccia C Fratesi G Baroni S 《Journal of the American Chemical Society》2006,128(38):12448-12454
The issue of tuning the relative height of the first two dehydrogenation barriers of methane (CH(4) --> CH(3) + H and CH(3) --> CH(2) + H) is addressed using density-functional theory. It is shown that the combination of a very active reaction center-such as Rh-with a more inert substrate-such as Cu(111)-may hinder the second dehydrogenation step with respect to the first, thus resulting in the reverse of the natural order of the two barriers' heights. 相似文献
52.
Benedetta Marmiroli Fernando Cacho‐Nerin Barbara Sartori Javier Pérez Heinz Amenitsch 《Journal of synchrotron radiation》2014,21(1):193-202
Liquid jets are of interest, both for their industrial relevance and for scientific applications (more important, in particular for X‐rays, after the advent of free‐electron lasers that require liquid jets as sample carrier). Instability mechanisms have been described theoretically and by numerical simulation, but confirmed by few experimental techniques. In fact, these are mainly based on cameras, which is limited by the imaging resolution, and on light scattering, which is hindered by absorption, reflection, Mie scattering and multiple scattering due to complex air/liquid interfaces during jet break‐up. In this communication it is demonstrated that synchrotron small‐angle X‐ray scattering (SAXS) can give quantitative information on liquid jet dynamics at the nanoscale, by detecting time‐dependent morphology and break‐up length. Jets ejected from circular tubes of different diameters (100–450 µm) and speeds (0.7–21 m s?1) have been explored to cover the Rayleigh and first wind‐induced regimes. Various solvents (water, ethanol, 2‐propanol) and their mixtures have been examined. The determination of the liquid jet behaviour becomes essential, as it provides background data in subsequent studies of chemical and biological reactions using SAXS or X‐ray diffraction based on synchrotron radiation and free‐electron lasers. 相似文献
53.
C Albrecht L Shi JM Pérez M van Gastel S Schwieger F Neese R Streubel 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(32):9780-9783
Phosphaalkenes: Deoxygenation of oxaphosphirane complexes 1 and 2 by using Ti(III) complexes gave mixtures of E/Z phosphaalkene complexes 3?a,?b and 4?a,?b. Theoretical calculations of deoxygenation pathways of 1 revealed that the final products are obtained via intermediate 5 providing the final products by reaction with a second [TiCpCl(2) ] unit and C?O bond cleavage. 相似文献
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57.
Validation of a high-performance liquid chromatographic-radioimmunoassay method for the determination of lacidipine in plasma. 总被引:2,自引:0,他引:2
M Pellegatti S Braggio S Sartori F Franceschetti G F Bolelli 《Journal of chromatography. A》1992,573(1):105-111
A sensitive and reproducible method for the determination of lacidipine, a new potent antihypertensive dihydropyridine, is reported. The method involves solid-phase extraction, reversed-phase high-performance liquid chromatography and radioimmunoassay of the collected fraction. The assay provides a limit of detection of 20 pg/ml of plasma, allowing the determination of trough (24 h) plasma concentrations. The method is suitable for pharmacokinetic studies in man. 相似文献
58.
We present two convergence theorems for Hamilton-Jacobi equations and we apply them to the convergence of approximations and perturbations of optimal control problems and of two-players zero-sum differential games. One of our results is, for instance, the following. LetT andT
h be the minimal time functions to reach the origin of two control systemsy = f(y, a) andy = f
h
(y, a), both locally controllable in the origin, and letK be any compact set of points controllable to the origin. If f
h –f Ch, then |T(x) – T
h
(x)| C
K
h
, for all x K, where is the exponent of Hölder continuity ofT(x). 相似文献
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60.
Nicolas DesroyRémi Le Roux Phannarath PhansavathLucia Chiummiento Carlo Bonini Jean-Pierre Genêt 《Tetrahedron letters》2003,44(9):1763-1766
The stereocontrolled synthesis of a C15C24 fragment of dolabelides is reported. The C19 and C21 hydroxyl-bearing stereocenters were installed using ruthenium-mediated asymmetric hydrogenations of cyclic hemiketal 4 and β-keto ester 7. The C25C30 portion of dolabelides was prepared as well by ring opening of chiral epoxy alcohol 12 to set up the C27 stereogenic center. 相似文献