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1.
The allomerization of chlorophyll b in methanol produced 132(S)-hydroxy-10-methoxychlorophyll b in a yield of ca. 8%. The formation of this allomer was totally unexpected, as 10-substituted chlorophylls have never been reported before. The structure of the new chlorophyll b derivative was determined on the basis of UV/Vis, FAB-MS, 1H NMR and 2D ROESY NMR spectra. This letter focuses on the NMR analysis. 相似文献
2.
The regio- and stereospecific glycosylation of 8,3′,5′-trideuterodaidzein 1 with α-acetobromoglucose to provide 8,3′,5′-trideuterodaidzein-7-O-β-glucopyranoside 2 is presented. 相似文献
3.
We present a mathematical model and its numerical implementation for the analysis of the interaction of spatially partially coherent electromagnetic fields with micro- and nanostructured objects. The model is based on the decomposition of the incident field into a set of fully coherent but mutually uncorrelated elementary field modes, and the use of the Fourier Modal Method (FMM) with the S-matrix propagation algorithm. We apply the model to studies of the excitation of surface plasmons in thin metallic slabs, nanowires, and resonant structures. We demonstrate, e.g., that the plasmon excitation efficiency is not essentially affected by the degree of spatial coherence. However, certain plasmon interference effects can be efficiently smoothed out by using illumination with reduced coherence. 相似文献
4.
5.
G. Cilpa M. T. Hyvönen A. Koivuniemi M.‐L. Riekkola 《Journal of computational chemistry》2010,31(8):1670-1680
Chondroitin‐6‐sulfate (C6S) is a glycosaminoglycan (GAG) constituent in the extracellular matrix, which participates actively in crucial biological processes, as well as in various pathological conditions, such as atherosclerosis and cancer. Molecular interactions involving the C6S chain are therefore of considerable interest. A computational model for atomistic simulation was built. This work describes the design and validation of a force field for a C6S dodecasaccharide chain. The results of an extensive molecular dynamics simulation performed with the new force field provide a novel insight into the structure and dynamics of the C6S chain. The intramolecular H‐bonds in the disaccharide linkage region are suggested to play a major role in determining the chain structural dynamics. Moreover, the unravelling of an additional H‐bond involving the sulfate groups in C6S is interesting as changes in sulfation have been claimed to be an important factor in several diseases. The force field will prove useful for future studies of crucial interactions between C6S and various nanoassemblies. It can also be used as a basis for modeling of other GAGs. © 2010 Wiley Periodicals, Inc. J Comput Chem, 2010 相似文献
6.
Martin Hanke Nuutti Hyvönen Manfred Lehn Stefanie Reusswig 《BIT Numerical Mathematics》2008,48(2):245-264
We investigate the inverse source problem of electrostatics in a bounded and convex domain with compactly supported source.
We try to extract all information about the unknown source support from the given Cauchy data of the associated potential,
adopting by this previous work of Kusiak and Sylvester to the case of electrostatics. We introduce, and for the unit disk
we also compute numerically, what we call the discoidal source support, i.e., the smallest set made up by the intersection of disks within the domain, which carries a source compatible with the
given data.
AMS subject classification (2000) 35R30, 65N21 相似文献
7.
Mehdi Jonoobi Jalaluddin Harun Aji P. Mathew Mohd Zobir B. Hussein Kristiina Oksman 《Cellulose (London, England)》2010,17(2):299-307
The aim of this study was to develop cellulose nanofibers with hydrophobic surface characteristics using chemical modification.
Kenaf fibers were modified using acetic anhydride and cellulose nanofibers were isolated from the acetylated kenaf using mechanical
isolation methods. Fourier transform infrared spectroscopy (FTIR) indicated acetylation of the hydroxyl groups of cellulose.
The study of the dispersion demonstrated that acetylated cellulose nanofibers formed stable, well-dispersed suspensions in
both acetone and ethanol. The contact angle measurements showed that the surface characteristics of nanofibers were changed
from hydrophilic to more hydrophobic when acetylated. The microscopy study showed that the acetylation caused a swelling of
the kenaf fiber cell wall and that the diameters of isolated nanofibers were between 5 and 50 nm. X-ray analysis showed that
the acetylation process reduced the crystallinity of the fibers, whereas mechanical isolation increased it. The method used
provides a novel processing route for producing cellulose nanofibers with hydrophobic surfaces. 相似文献
8.
In this paper we give bounds for polynomials of operators. These bounds are robust in low rank perturbations. This problem is encountered in the study of the convergence of Krylov methods. The central idea here is to view the resolvent as a meromorphic function. 相似文献
9.
We introduce a mass‐flux‐based inlet boundary condition for the lattice‐Boltzmann method. The proposed boundary condition requires minimal amount of boundary data, it produces a steady‐state velocity field which is accurate close to the inlet even for arbitrary inlet geometries, and yet it is simple to implement. We demonstrate its capability for both simple and complex inlet geometries by numerical experiments. For simple inlet geometries, we show that the boundary condition provides very accurate inlet velocities when Re?1. Even with moderate Reynolds number, the inlet velocities are accurate for practical purposes. Furthermore, the potential of our boundary condition to produce inlet velocities which convincingly adapt to complex inlet geometries is highlighted with two specific examples. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
10.
A simple method for preparing redispersible nanofibers from sugar beet residue and their use as a well-dispersed reinforcement for a polyvinyl alcohol (PVA) matrix is reported. It is known that the redispersion of dried cellulose nanofibers is difficult because of the formation of strong hydrogen bonds between the nanofibers. The results show that the properties of the initial sugar beet nanofiber suspension can be recovered without the use of chemical modification or additives with higher pectin and hemicellulose content. Undried and redispersed nanofibers with and without pectin were used as nanocomposite reinforcement with PVA. The redispersed nanofibers were as good reinforcements as the undried nanofibers. The tensile strength and elastic modulus of the nanocomposites with the redispersed sugar beet nanofibers were as good as those of the nanocomposites with undried nanofibers. Interestingly, the nanofiber dispersion in the PVA matrix was better when sugar beet nanofibers containing pectin and hemicellulose were used as reinforcements. 相似文献