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11.
12.
Thin films of polystyrene (PS), poly(methyl methacrylate) (PMMA) and polystyrene-polyacrylonitrile copolymer (PS-AN), containing various embedded transition-metal complexes, have been studied by FTIR microscopy. The spatial distributions of the transition-metal carbonyl complexes throughout the thin organic polymer films have been determined by a two-dimensional IR mapping procedure. The spectral variations observed in the distribution of the metal carbonyls throughout the different polymer films are discussed. The IR data show that the technique used to prepare the organometallic-embedded thin films (viz. freeze-drying of solutions followed by hot mechanical pressing of the residues) does in general lead to homogeneous films which may eventually find industrial application, e.g. as membrane sensors for small molecules. 相似文献
13.
Ian Kiming 《manuscripta mathematica》1995,87(1):101-129
For an imaginary quadratic fieldK we study the asymptotic behaviour (with respect top) of the number of integers inK with norm of the formk(p−k) for some 1≤k≤p−1, wherep is a prime number. The motivation for studying this problem is that it is known by recent results due to G. Frey and E. Kani
that knowledge of this asymptotic behaviour can lead to statements of existence of curves of genus 2 with elliptic differentials
in particular cases.
We give a general, and from one point of view complete, answer to this question on asymptotic behaviour. This answer is derived
from a theorem concerning the number of representations of a natural number by certain quaternary quadratic forms. This second
result may be of some independent interest because it can be seen as a generalisation of the classical theorem of Jacobi on
the number of representations of a natural number as a sum of 4 squares. 相似文献
14.
John M. Davis Ian A. Gravagne 《Journal of Mathematical Analysis and Applications》2007,332(2):1291-1307
In this work, we reexamine the time scale Laplace transform as defined by Bohner and Peterson [M. Bohner, A. Peterson, Dynamic Equations on Time Scales: An Introduction with Applications, Birkhäuser, Boston, 2001; M. Bohner, A. Peterson, Laplace transform and Z-transform: Unification and extension, Methods Appl. Anal. 9 (1) (2002) 155-162]. In particular, we give conditions on the class of functions which have a transform, develop an inversion formula for the transform, and further, we provide a convolution for the transform. The notion of convolution leads to considering its algebraic structure—in particular the existence of an identity element—motivating the development of the Dirac delta functional on time scales. Applications and examples of these concepts are given. 相似文献
15.
Christopher A. Luckhurst Ian Millichip Beth Parker James Reuberson Mark Furber 《Tetrahedron letters》2007,48(50):8878-8882
A one-pot reaction of carboxylic acids with sulfonamides to afford sulfonylureas is described. 相似文献
16.
Ian W. Roxburgh 《General Relativity and Gravitation》1991,23(9):1071-1080
In Finsler spaces the intervalds=F(x
i
,dx
i
) is an arbitrary function of the coordinatesx
i
and coordinate incrementsdx
i
withF homogeneous of degree one in thedx
i
. It is shown that for Riemannian spacesds
R
2=g
ij
dx
i
dx
i
which admit a non trivial covariantly constant tensorH
i
.(x
k
) there is an associated Finsler space with the same geodesic structure. The subset of such Finsler spaces withH
i
.(x
k
) a vector or second rank decomposable tensor is determined. 相似文献
17.
18.
19.
Michelle J. S. Spencer Andrew Hung Ian K. Snook Irene Yarovsky 《Surface science》2003,540(2-3):420-430
The adsorption of atomic S on the Fe(1 1 0) surface is examined using density functional theory (DFT). Three different adsorption sites are considered, including the atop, hollow and bridge sites and the S is adsorbed at a quarter monolayer coverage in a p(2 × 2) arrangement. The hollow site is found to be the most stable, followed by the bridge and atop sites. At all three sites, S adsorption results in relatively minor surface reconstruction, with the most significant being that for the hollow site, with lateral displacements of 0.09 Å. Comparisons between S-adsorbed and pure Fe surfaces revealed reductions in the magnetic moments of surface-layer Fe atoms in the vicinity of the S. At the hollow site, the presence of S causes an increase in the surface Fe d-orbital density of states between 4 and 5 eV. However, S adsorption has no significant effect on the structure and magnetic properties of the lower substrate layers. 相似文献
20.
Functionalised hydroxylamine derivatives of (S)-prolinol prepared by a Cope elimination have been found to undergo oxidation to the nitrone either in the presence of air or a catalytic quantity of TPAP. These undergo intramolecular cycloaddition to give tricyclic isoxazolidines with high diastereoselectivity. 相似文献