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121.
Radical cyclization reactions of both aliphatic 1,3‐diones 1a and 1b and of cyclic 1,3‐diones 1c – 1e with 2‐thienyl‐ and 3‐thienyl‐substituted alkenes 2a – 2d in the presence of manganese(III) acetate were investigated. Thienyl‐substituted dihydrofurans 3 were obtained with moderate to high yields (Table 1–3). Also, the favorable effect of the thienyl substituent on the intermediate carbocation stability was evaluated by comparison with a phenyl substituent. 相似文献
122.
Soyoung E. Seo Emre H. Discekici Yuanyi Zhang Christopher M. Bates Craig J. Hawker 《Journal of polymer science. Part A, Polymer chemistry》2020,58(1):70-76
An open-to-air method for the efficient synthesis of surface-tethered polymer brushes based on photoinduced electron transfer-reversible addition-fragmentation chain transfer (PET-RAFT) polymerization is reported. Key to this approach is an enzyme-assisted strategy using glucose oxidase to facilitate the in situ removal of oxygen during the polymerization process. Control experiments in the absence of glucose oxidase confirm the importance of enzymatic deoxygenation for successful polymerization of a variety of acrylamide, methacrylate, and acrylate monomers. In accordance with controlled polymerization kinetics, a linear increase in brush height as a function of irradiation time for a range of light intensities is demonstrated. Importantly, the use of light to mediate growth and the inherent monomer versatility of PET-RAFT allow for the facile fabrication of well-defined polymer brushes under aqueous conditions. © 2019 Wiley Periodicals, Inc. J. Polym. Sci. 2020 , 58, 70–76 相似文献
123.
Emre Alkan 《Journal of Number Theory》2003,101(2):404-423
Let a(n) be the number of nonisomorphic abelian groups of order n. We obtain a short interval result for the local density of a(n). More generally, we get short interval version of results of Ivi? on the local density of prime independent multiplicative functions. Also we prove a short interval version of the theorem of Erdös and Szekeres on the summatory function of a(n) and the theorem of Greenberg and Newman on the enumeration of a certain type of finite solvable groups. 相似文献
124.
Emre Mengi 《Numerische Mathematik》2011,118(1):109-135
The Wilkinson distance of a matrix A is the two-norm of the smallest perturbation E so that A + E has a multiple eigenvalue. Malyshev derived a singular value optimization characterization for the Wilkinson distance. In
this work we generalize the definition of the Wilkinson distance as the two-norm of the smallest perturbation so that the
perturbed matrix has an eigenvalue of prespecified algebraic multiplicity. We provide a singular value characterization for
this generalized Wilkinson distance. Then we outline a numerical technique to solve the derived singular value optimization
problems. In particular the numerical technique is applicable to Malyshev’s formula to compute the Wilkinson distance as well
as to retrieve a nearest matrix with a multiple eigenvalue. 相似文献
125.
This paper presents the probabilistic analysis of concrete-faced rockfill (CFR) dams according to the Monte Carlo Simulation (MCS) results which are obtained through the Response Surface Method (RSM). ANSYS finite element program is used to get displacement and principal stress components. First of all, some parametric studies are performed according to the simple and representative finite element model of dam body to obtain the optimum approximate model. Secondly, a sensitivity analysis is performed to get the most effective parameters on dam response. Then, RSM is used to obtain the approximate function through the selected parameters. After the performed analyses, star experimental design with quadratic function without mixed terms according to the k = 1 is determined as the most appropriate model. Finally, dam-foundation-reservoir interaction finite element model is constituted and probabilistic analyses are performed with MCS using the selected parameters, sampling method, function and arbitrary factor under gravity load for empty and full reservoir conditions. Geometrically and materially nonlinearity are considered in the analysis of dam-foundation-reservoir interaction system. Reservoir water is modeled by fluid finite elements based on the Lagrangian approach. Structural connections are modeled as welded contact and friction contact based on Coulomb’s friction law. Probabilistic displacements and stresses are presented and compared with deterministic results. 相似文献
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127.
In this study, nonperipherally tetra‐substituted ( 2 ), peripherally tetra‐substituted ( 3 ), and peripherally octa‐substituted ( 4 ) zinc(II) phthalocyanines were synthesized as sensitizers for dye‐sensitized solar cells (DSSCs) in which 3‐pyridin‐3‐ylpropoxy substituent acts as anchoring unit to bind TiO2 surface. The optical results indicated that there is an interaction between the dyes and the TiO2 surface. The photovoltaic performances of the DSSCs based on these dyes were found to depend on both the position and number of the substituents. Despite the more red‐shifted absorption, the DSSC based on 2 showed the conversion efficiency of 0.68%, which is lower than 1.36% and 0.92% for 3 and 4 , respectively, under one sun (AM 1.5G). The vertical orientation of the dye on TiO2 surface could be the main reason for the higher photovoltaic performance of complex 3 , which is beneficial for not only injecting the electrons into the conduction band of TiO2 but also reducing the charge recombination. Overall, these results demonstrate that the peripherally tetra‐substituted 3‐pyridin‐3‐ylpropoxy zinc(II) phthalocyanine complex ( 3 ) as a sensitizer can more efficiently utilize the photons in the red/near‐infrared region with respect to the other complexes studied. 相似文献
128.
A new application of the Paul wavelet algorithm was presented to determine the refractive index dispersion of a dielectric film from transmittance spectrum in the visible and near infrared region. The developed algorithm was tested by simulated data and experimentally applied to a sample of mica. The obtained refractive index dispersion determined by the Paul wavelet algorithm was compared with the refractive index values determined by the envelope and fringe counting methods, and also with the established result. It was shown that the degree of the Paul wavelet has a major effect on the outcome of a refractive index determination. The noise immunity of the presented method was shown by the simulation study. 相似文献
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Valentin Dybbert Samuel Matthias Fehr Florian Klein Achim Schaadt Anke Hoffmann Elias Frei Emre Erdem Thilo Ludwig Harald Hillebrecht Ingo Krossing 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(37):13069-13073
The influence of a mild difluorine treatment on Cu/ZnO precatalysts for methanol synthesis was investigated. It led to the incorporation of 1.2…1.3±0.1 wt % fluoride into the material. Fluorination considerably increased the amount of ZnOx related defect sites on the catalysts and significantly increased the space‐time yields. Although the apparent activation energy EA,app for methanol formation from CO2 and H2 was almost unchanged, the EA,app for the reverse water‐gas shift (rWGS) reaction increased considerably. Overall, fluorination led to a significant gain in methanol selectivity and productivity. Apparently, also the quantity of active sites increased. 相似文献