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51.
Mihaela RomanBruno Andrioletti Marc Lemaire Jean-Marie BernardJohannes Schwartz Philippe Barbeau 《Tetrahedron》2011,67(7):1506-1510
Using HMDS as catalyst for the trimerization of isocyanates presents many advantages as the expected isocyanurate is not contaminated by the catalyst or other side-products resulting from its degradation. In addition, HMDS presents a low toxicity, and is compatible with industrial applications. This article describes the hexamethyldisilazane (HMDS)-catalyzed trimerization of octylisocyanate. Experimental investigations and mechanistic considerations indicate that the true catalyst of the trimerization is trimethylsilyloctylamine, which results from the preliminary condensation of HMDS with octylisocyanate. 相似文献
52.
Thalladi VR Schwartz A Phend JN Hutchinson JW Whitesides GM 《Journal of the American Chemical Society》2002,124(33):9912-9917
A new physical model based on mesoscale self-assembly is developed to simulate indentation fracture in crystalline materials. Millimeter-scale hexagonal objects exhibiting atom-like potential functions were designed and allowed to self-assemble into two-dimensional (2D) aggregates at the interface between water and perfluorodecalin. Indentation experiments were performed on these aggregates, and the stresses and strains involved in these processes were evaluated. The stress field in the aggregates was analyzed theoretically using the 2D elastic Hertz solution. Comparison of the experimental results with theoretical analysis revealed that fracture develops in regions subjected to high shear stress and some, albeit low, tensile stress. The potential for the broader application of the model is illustrated using indentation of assemblies with point defects and adatoms introduced at predetermined locations, and using a two-phase aggregate simulating a compliant film on a stiff substrate. 相似文献
53.
We show that perturbative high scale unification and a solution to the hierarchy problem are possible with extra dimensions in the context of the warped geometry of 5D anti-de Sitter space ( AdS(5)). This is possible because the couplings for bulk gauge bosons run logarithmically below the AdS(5) curvature scale. The calculation is done in five dimensions, rather than in the effective theory, which is strongly coupled above the TeV scale. 相似文献
54.
C Savariaux P Perrier J P Orliaguet J L Schwartz 《The Journal of the Acoustical Society of America》1999,106(1):381-393
A perceptual analysis of the French vowel [u] produced by 10 speakers under normal and perturbed conditions (Savariaux et al., 1995) is presented which aims at characterizing in the perceptual domain the task of a speaker for this vowel, and, then, at understanding the strategies developed by the speakers to deal with the lip perturbation. Identification and rating tests showed that the French [u] is perceptually fairly well described in the [F1, (F2-F0)] plane, and that the parameter (((F2-F0) + F1)/2) (all frequencies in bark) provides a good overall correlate of the "grave" feature classically used to describe the vowel [u] in all languages. This permitted reanalysis of the behavior of the speakers during the perturbation experiment. Three of them succeed in producing a good [u] in spite of the lip tube, thanks to a combination of limited changes on F1 and (F2-F0), but without producing the strong backward movement of the tongue, which would be necessary to keep the [F1,F2] pattern close to the one measured in normal speech. The only speaker who strongly moved his tongue back and maintained F1 and F2 at low values did not produce a perceptually well-rated [u], but additional tests demonstrate that this gesture allowed him to preserve the most important phonetic features of the French [u], which is primarily a back and rounded vowel. It is concluded that speech production is clearly guided by perceptual requirements, and that the speakers have a good representation of them, even if they are not all able to meet them in perturbed conditions. 相似文献
55.
The preparation of macrocyclic thiolactones by condensation of diacyl chlorides with siladithianes is described. 相似文献
56.
Wilfried Heller Ellen Shirley E. Schwartz 《Journal of Polymer Science.Polymer Physics》1972,10(10):1903-1915
The theory of an interferometric method for determining partial specific volumes of macromolecules is briefly reviewed. The experimental technique developed in this laboratory is described. Detailed results are given on the partial specific volume of ovalbumin in aqueous solution and its dependence on pH and KCl concentration. The results are compared, as far as possible, with dilatometric results obtained in another laboratory. The contribution of a change in partial specific volume of the macromolecules and in the partial specific volume of the water associated with them to the results is analyzed, and the scope of a possible complication due to changes in molecular polarizability is pointed out. 相似文献
57.
Zirconium or aluminum O-enolates undergo selenenylation with PhSeBr to give α-(phenylselenenyl) ketones in good to excellent yield. 相似文献
58.
We have numerically solved the microscopic equations of Golub for the space and time variations of the order parameter, supercurrent, and normal current within a current biased short superconducting weak link. Two limiting cases are considered. We also use a perturbation method to solve for the I–V characteristics of a weak link, and show that they are cosistent with experiment. 相似文献
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