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491.
Maarten Goesten Dr. Eli Stavitski Dr. Evgeny A. Pidko Canan Gücüyener Bart Boshuizen Dr. Steven N. Ehrlich Prof. Emiel J. M. Hensen Prof. Freek Kapteijn Dr. Jorge Gascon 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(24):7809-7816
We present an in situ small‐ and wide‐angle X‐ray scattering (SAXS/WAXS) and quick‐scanning extended X‐ray absorption fine‐structure (QEXAFS) spectroscopy study on the crystallization of the metal–organic framework ZIF‐7. In combination with DFT calculations, the self‐assembly and growth of ZIF‐7 microrods together with the chemical function of the crystal growth modulator (diethylamine) are revealed at all relevant length scales, from the atomic to the full crystal size. 相似文献
492.
We consider a free boundary problem for a system of two semilinear parabolic equations. The system represents a simple model of granuloma, a collection of immune cells and bacteria filling a 3-dimensional domain Ω(t) which varies in time. We prove the existence of stationary spherical solutions and study their linear asymptotic stability as time increases to infinity. 相似文献
493.
Łukasz Klapiszewski Jakub Zdarta Tomasz Szatkowski Marcin Wysokowski Magdalena Nowacka Karolina Szwarc-Rzepka Przemysław Bartczak Katarzyna Siwińska-Stefańska Hermann Ehrlich Teofil Jesionowski 《Central European Journal of Chemistry》2014,12(6):719-735
The research reported here concerns the synthesis, characterization and potential applications of silica/lignosulfonate hybrid materials. Three types of silica were used (Aerosil®200, Syloid®244 and hydrated silica), along with magnesium lignosulfonate. The effectiveness of the hybrid material synthesis methodology was confirmed indirectly, using Fourier transform infrared spectroscopy, elemental and colorimetric analysis. Dispersive-morphological analysis indicates that the products with the best properties were obtained using 10 parts by weight of magnesium lignosulfonate per 100 parts of Syloid®244 silica. The relatively high thermal stability recorded for the majority of the synthesized products indicates the potential use of this kind of a material as a polymer filler. Results indicating the high electrokinetic stability of the materials are also of great importance. Additionally, the very good porous structure properties indicate the potential use of silica/lignosulfonate systems as biosorbents of hazardous metal ions and harmful organic compounds. 相似文献
494.
Ehrlich G Hassfeld J Eggert U Kalesse M 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(7):2232-2247
Tedanolide, which was isolated by Schmitz in 1984 from the marine sponge Tedania ignis, is a highly cytotoxic macrolide leading to strong growth inhibition of P338 tumor cells in bioassays. A unique structural feature of the known tedanolides is the primary hydroxyl group incorporated in the macrolactone. This unusual motif for macrolactones originated from PKS biosynthesis might arise through lactonizations others than those derived by the thioesterase reaction. First experimental data that support this hypothesis and reflect the inherent preference of PKS-induced macrolactonization were obtained during this synthesis. The inherent preference for the formation of a 14-membered macrocyclization is discussed together with the pivotal steps in the synthesis. 相似文献
495.
We consider a free boundary problem for a system of partial differential equations, which arises in a model of tumor growth. For any positive number there exists a radially symmetric stationary solution with free boundary . The system depends on a positive parameter , and for a sequence of values there also exist branches of symmetric-breaking stationary solutions, parameterized by , small, which bifurcate from these values. In particular, for near the free boundary has the form where is the spherical harmonic of mode . It was recently proved by the authors that the stationary solution is asymptotically stable for any , but linearly unstable if , where if and if ; . In this paper we prove that for each of the stationary solutions which bifurcates from is linearly stable if and linearly unstable if . We also prove, for , that the point is a Hopf bifurcation, in the sense that the linearized time-dependent problem has a family of solutions which are asymptotically periodic in .
496.
Dr. Nina Diaz Dr. Mingzhao Zhu Dr. Gunnar Ehrlich Ulrike Eggert Yazh Muthukumar Dr. Florenz Sasse Prof. Dr. Markus Kalesse 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(16):4946-4952
The improved synthesis of the antitumor compound (+)‐tedanolide is described through an aldol coupling of bis‐ketone 7 . This modification shortens the synthetic steps in the endgame and provides rapid access to this biologically important natural product. Additionally, it serves as a probe in order to unravel the conformational effects that impede or enable its successful synthesis. Having this way access to des‐epoxy‐tedanolide, its biological characterization surprisingly unravelled the mode of action to resemble candidaspongiolide rather than deoxytedanolide. 相似文献
497.
Many electrophoresis-based DNA sequencing and genotyping microdevices rely on field-driven effects to load and preconcentrate the sample. A quantitative model is developed for a broad class of electrophoresis-based microfabricated sample injectors. Quantitative predictions of DNA preconcentration are compared with experimental data and are shown to qualitatively reproduce the detailed time-evolving sample distribution in the injector. The model provides practical guidance on device and protocol design, in order to optimize this critical aspect of microfluidic devices. 相似文献
498.
We consider a time-dependent free boundary problem with radially symmetric initial data: σt − Δσ + σ = 0 if and σ(r,0)=σ0(r) in {r < R(0)} where R(0) is given. This is a model for tumor growth, with nutrient concentration (or tumor cells density) σ(r,t) and proliferation rate then there exists a unique stationary solution (σS(r), RS), where RS depends only on the number . We prove that there exists a number μ*, such that if μ < μ* . . . then the stationary solution is stable with respect to non-radially symmetric perturbations, whereas if μ > μ* then the stationary solution is unstable. 相似文献