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The feasibility of close coupling techniques for bifurcation processes is investigated using a simple model. Density contours and a flux map illustrate the bifurcation process. The relevance of this study to the theory of three-dimensional chemical reactions is discussed. 相似文献
44.
An atomistic mechanism has been derived for the initial stages of the adsorption reaction for metal-nitride atomic layer deposition (ALD) from alkylamido organometallic precursors of Ti and Zr on alkyltrichorosilane-based self-assembled monolayers (SAMs). The effect of altering the terminal functional group on the SAM (including -OH, -NH2, -SH, and -NH(CH3)) has been investigated using the density functional theory and the MP2 perturbation theory. Reactions on amine-terminated SAMs proceed through the formation of a dative-bond complex with an activation barrier of 16-20 kcal/mol. In contrast, thiol-terminated SAMs form weak hydrogen-bonded intermediates with activation barriers between 7 and 10 kcal/mol. The deposition of Ti organometallic precursors on hydroxyl-terminated SAMs proceeds through the formation of stronger hydrogen-bonded complexes with barriers of 7 kcal/mol. Zr-based precursors form dative-bonded adducts with near barrierless transitions. This variety allows us to select a kinetically favorable substrate for a chosen precursor. The predicted order of reactivity of differently terminated SAMs and the temperature dependence of the initial reaction probability have been confirmed for Ti-based precursors by recent experimental results. We predict that the replacement of methyl groups by trifluoromethyl groups on the SAM backbone decreases the activation barrier for amine-terminated SAMs by 5 kcal/mol. This opens a route to alter the native reactivities of a given SAM termination, in this case making amine termination energetically viable. The surface distribution of SAM molecules has a strong effect on the adsorption kinetics of Ti-based precursors. Unimolecular side decomposition reactions were found to be kinetically competitive with adsorption at 400 K. 相似文献
45.
Mester Z Willie S Yang L Sturgeon R Caruso JA Fernández ML Fodor P Goldschmidt RJ Goenaga-Infante H Lobinski R Maxwell P McSheehy S Polatajko A Sadi BB Sanz-Medel A Scriver C Szpunar J Wahlen R Wolf W 《Analytical and bioanalytical chemistry》2006,385(1):168-180
A new selenized yeast reference material (SELM-1) produced by the Institute for National Measurement Standards, National Research
Council of Canada (INMS, NRC) certified for total selenium (2,059±64 mg kg−1), methionine (Met, 5,758±277 mg kg−1) and selenomethionine (SeMet, 3,431±157 mg kg−1) content is described. The ±value represents an expanded uncertainty with a coverage factor of 2. SeMet and Met amount contents
were established following a methanesulfonic acid digestion of the yeast using GC-MS and LC-MS quantitation. Isotope dilution
(ID) calibration was used for both compounds, using 13C-labelled SeMet and Met. Total Se was determined after complete microwave acid digestion based on ID ICP-MS using a 82Se spike or ICP-OES spectrometry using external calibration. An international intercomparison exercise was piloted by NRC
to assess the state-of-the-art of measurement of selenomethione in SELM-1. Determination of total Se and methionine was also
attempted. Seven laboratories submitted results (2 National Metrology Institutes (NMIs) and 5 university/government laboratories).
For SeMet, ten independent mean values were generated. Various acid digestion and enzymatic procedures followed by LC ICP-MS,
LC AFS or GC-MS quantitation were used. Four values were based on species-specific ID calibration, one on non-species-specific
ID with the remainder using standard addition (SA) or external calibration (EC). For total selenium, laboratories employed
various acid digestion procedures followed by ICP-MS, AFS or GC-MS quantitation. Four laboratories employed ID calibration,
the remaining used SA or EC. A total of seven independent results were submitted. Results for methionine were reported by
only three laboratories, all of which used various acid digestion protocols combined with determination by GC-MS and LC UV.
The majority of participants submitted values within the certified range for SeMet and total Se, whereas the intercomparison
was judged unsuccessful for Met because only two external laboratories provided values, both of which were outside the certified
range. 相似文献
46.
Michaux C Charlier P Frère JM Wouters J 《Journal of the American Chemical Society》2005,127(10):3262-3263
BRL 42715, C6-(N1-methyl-1,2,3-triazolylmethylene)penem, is an active-site-directed inactivator of bacterial beta-lactamases. The crystal structure of Enterobacter cloacae 908R class C beta-lactamase in complex with BRL 42715, docking, and energy minimization studies explain stereoselectivity of the binding of C6-(heterocyclic methylene)penems against class C beta-lactamase. 相似文献
47.
Zhang Q Prins P Jones SC Barlow S Kondo T An Z Siebbeles LD Marder SR 《Organic letters》2005,7(22):5019-5022
[structure: see text] The first fluorine-substituted hexabenzocoronene has been synthesized and is much more readily reduced than its nonfluorinated analogues. Thin films of this material show columnar order at room temperature, and the charge-carrier mobility measured by the pulse-radiolysis time-resolved microwave conductivity technique is comparable to that of other hexabenzocoronene materials. 相似文献
48.
Summary Some compactness results in the space of Bochner integrable functions in Banach spaces and in the space of integrably bounded multifunction with non empty convex weakly compact values are presented. Applications to minimization problems are given.
Pour terminer, nous remercions M.Valadier qui a lu attentivement ce papier. 相似文献
Pour terminer, nous remercions M.Valadier qui a lu attentivement ce papier. 相似文献
49.
50.
Edmundo J.S.G. Azevedo Lélio Q. Lobo Lionel A.K. Staveley Paulette Clancy 《Fluid Phase Equilibria》1982,9(3):267-277
The heat of mixing of liquid argon (component 1) and liquid carbon monoxide has been measured by direct calorimetry for several mixtures of composition ranging from x1 ? 0.2 to x1 ? 0.8 at 85.79 K. At this temperature HE is positive and an almost parabolic function of mole fraction, with a maximum value of HE = 95.9 J mol?1 at x1 = 0.569.The experimental results are compared with those derived from the Gibbons-Rigby equation of state, and from conformal solution theory. 相似文献