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991.
Sebastian Mendrek Aleksandra Mendrek Hans‐Jürgen Adler Wojciech Walach Andrzej Dworak Dirk Kuckling 《Journal of polymer science. Part A, Polymer chemistry》2008,46(7):2488-2499
New, water soluble poly(glycidol) (PGl) macroinitiators for atom transfer radical polymerization (ATRP) were synthesized. This new class of macroinitiators were prepared in a three‐step process. First, series of well‐defined ω‐hydroxyl functional poly(glycidol acetal)s with different molecular weights was synthesized via anionic polymerization followed by quantitative termination of anionically growing active sites. End capping was achieved by treatment of living chain ends with water. The living nature of the system and termination reaction is discussed. In the second stage, monofunctional poly(glycidol acetal)s were functionalized by esterification with 2‐chloropropionyl chloride. Finally, selective deprotection (hydrolysis) of acetal protective groups was performed. As simultaneous partial cleavage of ester bond of attached ATRP moieties was unavoidable, the final functionality of macroinitiator calculated from 1H NMR varied in the range 85–95%. The obtained (2‐chloropropionyl) poly(glycidol) macroinitiator with DP = 55 and 90% functionality was successfully used in ATRP polymerization of N‐isopropylacrylamide (NIPAAm) at room temperature in the DMF/water mixture. Linear block copolymers with relatively narrow molecular weight distribution and controlled composition were obtained and characterized with 1H NMR and SEC‐MALLS measurements. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2488–2499, 2008 相似文献
992.
993.
We have investigated the dynamics of adiabatic electron transfer reactions at metal electrodes using a Hamiltonian suggested by Schmickler (J. Electroanal. Chem., 204 (1986) 31). We show that in the adiabatic limit the problem reduces to that of dynamics of a single variable, the shift of the ionic orbital caused by its interaction with the solvent. This variable is identified as the reaction co-ordinate for the problem and we show that in certain limits, it obeys a non-linear Volterra type integral equation, with a stochastic inhomogeneous term. For an inhomogenous term with the autocorrelation function decaying exponentially, this may be converted into a differential equation for Brownian motion. This equation can be analysed to obtain the rate, through the associated Fokker-Planck equation. The rate so obtained, has a correction to the pre-exponential factor obtained by Schmickler. A possible extension to inner sphere reactions is also discussed. 相似文献
994.
N. Erdmann V. Sebastian V.N. Fedoseyev M. Hannawald G. Huber T. Kautzsch K.-L. Kratz V.I. Mishin M. Nunnemann G. Passler N. Trautmann 《Applied physics. B, Lasers and optics》1998,66(4):431-433
1 =228.8 nm). Laser light with an average power of 2 mW was obtained after frequency tripling and was successfully used for
RIS test measurements on cadmium with a time-of-flight mass spectrometer. The eight stable Cd isotopes could be identified
unambiguously.
Received: 6 October 1997 相似文献
995.
We consider the exact null controllability problem for the semi- linear heat equation with dissipative nonlinearity in a bounded domain of Rn . The main result of the article asserts that if the nonlinearity is even mildly superlinear, then global null controllability in an arbitrarily short time fails; instead we provide sharp estimates for the controllability time in terms of the size of the initial data. 相似文献
996.
997.
998.
Sebastian Reich 《BIT Numerical Mathematics》1996,36(1):122-134
Recent observations [5] indicate that energy-momentum methods might be better suited for the numerical integration of highly oscillatory Hamiltonian systems than implicit symplectic methods. However, the popular energy-momentum method, suggested in [3], achieves conservation of energy by a global scaling of the force field. This leads to an undesirable coupling of all degrees of freedom that is not present in the original problem formulation. We suggest enhancing this energy-momentum method by splitting the force field and using separate adjustment factors for each force. In case that the potential energy function can be split into a strong and a weak part, we also show how to combine an energy conserving discretization of the strong forces with a symplectic discretization of the weak contributions. We demonstrate the numerical properties of our method by simulating particles that interact through Lennard-Jones potentials and by integrating the Sine-Gordon equation.This work was partly supported by NIH Grant P41RR05969, DOE/NSF Grant DE-FG02-91-ER25099/DMS-9304268, and NSF GCAG/HPCC ASC-9318159. 相似文献
999.
Dirichlet integrals and the associated Dirichlet statistical densities are widely used in various areas. Generalizations of
Dirichlet integrals and Dirichlet models to matrix-variate cases, when the matrices are real symmetric positive definite or
hermitian positive definite, are available [4]. Real scalar variables case of the Dirichlet models are generalized in various
directions. One such generalization of the type-2 or inverted Dirichlet is looked into in this article. Matrix-variate analogue,
when the matrices are hermitian positive definite, are worked out along with some properties which are mathematically and
statistically interesting. 相似文献
1000.
Wavelength stabilized 980 nm uncooled pump laser modules for erbium-doped fiber amplifiers 总被引:2,自引:0,他引:2
Tomas Pliska Sebastian Arlt Rainer Bttig Tim Kellner Isabella Jung Nicolai Matuschek Pascal Mauron Bernd Mayer Stefan Mohrdiek Jürgen Müller Susanne Pawlik Hans-Ulrich Pfeiffer Berthold Schmidt Boris Sverdlov Stefan Teodoropol Jrg Troger Bernd Valk Christoph Harder 《Optics and Lasers in Engineering》2005,43(3-5):271
We review the development of wavelength stabilized 980 nm pump laser modules without active temperature stabilization for applications in erbium-doped fiber amplifiers. Operation over a wide temperature range with an output power exceeding 400 mW at an ambient temperature of 70°C is demonstrated. The overall reliability of uncooled modules is estimated to be well below 500 FIT at all operating conditions. Such devices are made possible by continuous development and steady improvement of the pump laser chip, the optimization of the fiber Bragg grating stabilization scheme, careful design of the module package, and extended reliability analysis on the basis of stress tests as well as field data. 相似文献