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排序方式: 共有813条查询结果,搜索用时 15 毫秒
741.
Sabino Veintemillas-Verdaguer Yann Leconte Rocío Costo Oscar Bomati-Miguel Brigitte Bouchet-Fabre M. Puerto Morales Pierre Bonville Sandra Pérez-Rial Ignacio Rodriguez Nathalie Herlin-Boime 《Journal of magnetism and magnetic materials》2007
Magnetic composites of Fe-based nanoparticles encapsulated in carbon/silica (C/SiO2@Fe) or carbon (C@Fe) matrices were prepared by laser-induced pyrolysis of aerosols. The powders were dispersed in aqueous solutions at pH 7 resulting in biocompatible colloidal dispersions with a high resistance to biodegradation. Structural and magnetic properties and the suitability of aqueous dispersions as contrast agent for MRI were analyzed. The results of these characterizations and the NMR relaxivity data are very encouraging for application of laser pyrolysis products in the field of living tissues. 相似文献
742.
Jan Hegewald Jürgen Pionteck Liane Häußler Hartmut Komber Brigitte Voit 《Journal of polymer science. Part A, Polymer chemistry》2009,47(15):3845-3859
Monoamino‐terminated and monocarboxylic acid‐terminated polystyrenes containing active halogenated end groups were prepared by atom transfer radical polymerization (ATRP) using the so‐called initiator method and protective group chemistry. α‐Chloropropionates were synthesized and utilized as initiators containing the tert‐butoxycarbonyl (t‐BOC)‐protected amino and the tert‐butyl (t‐Bu)‐protected carboxylic acid function, respectively. Optimum polymerization conditions were attained using CuCl/N,N,N′,N′′,N′′‐pentamethyldiethylenetriamine (PMDETA) as catalyst and 10 vol % n‐butanol as homogenizing agent at 110 °C. However, targeting larger quantities an alternative route was established employing 50 vol % N,N‐dimethylformamide (DMF). Subsequent hydrolysis of the ω‐tert‐butoxycarbonyl polystyrenes afforded well‐defined polymers with quantitative deprotection of the functional groups. Comparatively, thermolytic cleavage of the protective sites was studied. 1H NMR verified the quantitative removal of the t‐BOC‐protecting groups. Furthermore, the resulting α‐amino‐ω‐chloro polystyrenes were reacted with Sanger reagent to confirm the existence of the thereby converted primary amino groups. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3845–3859, 2009 相似文献
743.
744.
Recently, interest in steel alloyed with∼1% Al increased. These materials are expected to show a higher resistance against
oxidation at high temperatures which will improve their performance when used as high-speed-steels. Furthermore, efforts have
been made to combine the advantages of Al-steels with those of powder-metallurgic methods like hotisostatic-pressing (hip).
This should result in a better macro- and microscopic homogeneity of the distribution of all compounds, yielding less waste-production
and a longer life-time of products.
In order to gain deeper insights in the process of “hipping” of the considered material and to see the distribution of both
main as well as trace components, 2D and 3D-SIMS measurements of the material were performed before and after having undergone
the hip process.
The measurements showed enrichments of Na, K, Mg, Ca, and S at the particle boundaries before as well as after the hip-process.
In the hipped material, the enrichments are significantly stronger in the spatial domains in-between larger particles. They
also reveal, that the concentration of C is not equal in all particles and that the particles are covered with an Al2O3-layer which is not dispersed by the hip-process. There were also found small (∼50–100 nm) nitride-precipitates before as
well as after the hip-process. 相似文献
745.
This work deals with the chemical grafting of a styrene maleic anhydride copolymer on the surface of a previously hydrolyzed polyethylene terephthalate (PET) film 12 μm thick via covalent bond. Two different ways are studied. The first one involves an activation of the hydrolyzed PET by the triethylamine before the grafting step. In the second one, the copolymer reacts with the 4-dimethylaminopyridine in order to form maleinyl pyridinium salt which reacts with alcohol function of the hydrolyzed PET. Characterization and quantification of the grafting are performed by Fourier transform infrared spectroscopy. Factorial experiment designs are used to optimize the process and to estimate experimental parameters effects. The opportunity to associate the chemical process to a cold remote nitrogen plasma one is also examined. 相似文献
746.
Rishikesh M. Sawant Rupa R. Sawant Evin Gultepe Dattatri Nagesha Brigitte Papahadjopoulos-Sternberg Srinivas Sridhar Vladimir P. Torchilin 《Journal of nanoparticle research》2009,11(7):1777-1785
Stable 30–50 nm polymeric polyethylene glycol–phosphatidylethanolamine (PEG–PE)-based micelles entrapping superparamagnetic iron oxide nanoparticles (SPION) have been prepared. At similar concentrations of SPION, the SPION-micelles had significantly better magnetic resonance imaging (MRI) T2 relaxation signal compared to ‘plain’ SPION. Freeze-fracture electron microscopy confirmed SPION entrapment in the lipid core of the PEG–PE micelles. To enhance the targeting capability of these micelles, their surface was modified with the cancer cell-specific anti-nucleosome monoclonal antibody 2C5 (mAb 2C5). Such mAb 2C5-SPION immunomicelles demonstrated specific binding with cancer cells in vitro and were able to bring more SPION to the cancer cells thus demonstrating the potential to be used as targeted MRI contrast agents for tumor imaging. 相似文献
747.
Laurence Borgs Pierre Beukelaers Renaud Vandenbosch Laurent Nguyen Gustave Moonen Pierre Maquet Urs Albrecht Shibeshih Belachew Brigitte Malgrange 《BMC neuroscience》2009,10(1):30
Background
Newborn granule neurons are generated from proliferating neural stem/progenitor cells and integrated into mature synaptic networks in the adult dentate gyrus of the hippocampus. Since light/dark variations of the mitotic index and DNA synthesis occur in many tissues, we wanted to unravel the role of the clock-controlled Period2 gene (mPer2) in timing cell cycle kinetics and neurogenesis in the adult DG. 相似文献748.
749.
Based on geometrical data of porous components obtained by computer tomography, a micromechanical unit cell model is proposed to predict the influence of porosity on mechanical properties of high performance cast alloys. Simulations of uniaxial loaded periodic unit cells are compared to experimental data of tensile tests on porous materials. In this way a relationship between some significant geometrical data of the pores and the macroscopic material parameters is obtained. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
750.
Senta Reichelt Lothar Jakisch Frank Simon Karina Grundke Klaus-Jochen Eichhorn Brigitte Voit 《Macromolecular Symposia》2007,254(1):240-247
Summary: Stable thin films of a hyperbranched aromatic-aliphatic OH-terminated polyester (POH) were prepared on silicon substrates. We report on grafting-to processes using macromolecular (PGMA) and bifunctional low-molecular weight coupling agents (BOX). An appropriate annealing procedure was developed for the covalent immobilization. The HBP films were characterized with spectroscopic ellipsometry, drop shape analysis (DSA), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and electrokinetic measurements. The immobilized films have an uniform surface morphology and are slightly hydrophilic (θa = 79°). The grafting process did not influence the chemical composition and the surface properties, which is important for the further application as functional layers in aqueous media. 相似文献