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1.
Vishal Sipani Ann Kirsch Alec B. Scranton 《Journal of polymer science. Part A, Polymer chemistry》2004,42(17):4409-4416
The effective propagation rate constant (kp; averaged over all the propagating active centers) was characterized for solvent‐free cationic photopolymerizations of phenyl glycidyl ether over the entire range of conversions, including the high conversion regime in which mass transfer limitations become important. The profile for the kp as a function of conversion was found to exhibit a constant plateau value at low to intermediate conversions, followed by a monotonic increase above a threshold value of conversion. To explain this trend, it is proposed that at high conversion the diffusional mobility of the photoinitiator counterion is reduced whereas the mobility of the cationic active center remains high because of reactive diffusion. Therefore, with increasing conversion, the average distance between the active centers and counterions may increase, resulting in an increase in the propagation rate constant. The profiles for the kp values were investigated as a function of the temperature, photoinitiator anion, and photoinitiator concentration. As the photoinitiator concentration was increased, the plateau value of the effective propagation rate constant decreased whereas the threshold conversion increased. All of the experimental trends are consistent with the proposed increase in ion separation at high conversions. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4409–4416, 2004 相似文献
2.
Arno Jüschke Johannes Jahn Andreas Kirsch 《Computational Optimization and Applications》1997,7(3):261-276
In this paper we consider a special optimization problem withtwo objectives which arises in antenna theory. It is shown that thisabstract bicriterial optimization problem has at least one solution.Discretized versions of this problem are also discussed, and therelationships between these finite dimensional problems and the infinitedimensional problem are investigated. Moreover, we presentnumerical results for special parameters using a multiobjectiveoptimization method. 相似文献
3.
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5.
6.
We prove that the integrated density of states () for a potentialW
=V
per +V
has Lifshitz tails where Vper is a periodic potential with reflection symmetry andV
is a random potential, e.g., of the formV
=q
i
()f(x–i).research partially supported by DFG.research partially supported by USNSF under grant No. MCS-81-20833. 相似文献
7.
In the present paper, we discuss spectral properties of a periodic Schrödinger operator which is perturbed by randomly distributed impurities; such operators occur as simple models for crystals (or semi-conductors) with impurities. While the spectrum itself is independent of the concentrationp of impurities, for 0<p<1, we focus our attention on the limiting behavior of the integrated density of states
p
of the random Schrödinger operator, inside a spectral gap of the periodic operator, asp0. Denoting byU
0 the set of eigenvalues (in the gap) of the reference problem having precisely one impurity (located at the origin, say), we show that the integrated density of states concentrates around the points ofU
0, in the sense that
p
(U
) is of orderp, for any fixed -neighborhoodU
ofU
0, while
p
(K)C·p
2, for any compact subsetK of the gap which does not intersectU
.Research partially supported by Deutsche Forschungsgemeinschaft 相似文献
8.
Kirsch SF 《The Journal of organic chemistry》2005,70(24):10210-10212
[reaction: see text] IBX (o-iodoxybenzoic acid) is an excellent reagent for the alpha-hydroxylation of alpha-alkynyl carbonyl compounds without giving dehydrogenation products. The convenient procedure proves to be useful for the construction of a variety of tertiary alcohols (55-91%) under mildly acidic conditions. 相似文献
9.
The electron-diffraction data for cyclohexane and perdeuterated cyclohexane were analyzed and the results were compared. It was found that rg(C-C) = 1.535 Å (±0.002) for both compounds; rg (C-H) = 1.116 Å (±0.004) and rg(C-D) = 1.109 Å (±0.003). Observed hydrogen isotope effects in mean amplitudes agree very well with calculated ones. The C-C bond distance of cyclohexane is in good agreement with some of the previous studies, which is of importance in view of a recent scaling controversy involving this parameter. 相似文献
10.
Engel CK Pirard B Schimanski S Kirsch R Habermann J Klingler O Schlotte V Weithmann KU Wendt KU 《Chemistry & biology》2005,12(2):181-189
Inhibitors for matrix metalloproteinases (MMPs) are under investigation for the treatment of cancer, arthritis, and cardiovascular disease. Here, we report a class of highly selective MMP-13 inhibitors (pyrimidine dicarboxamides) that exhibit no detectable activity against other MMPs. The high-resolution X-ray structures of three molecules of this series bound to MMP-13 reveal a novel binding mode characterized by the absence of interactions between the inhibitors and the catalytic zinc. The inhibitors bind in the S1' pocket and extend into an additional S1' side pocket, which is unique to MMP-13. We analyze the determinants for selectivity and describe the rational design of improved compounds with low nanomolar affinity. 相似文献