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11.
Leonid S. Vasilev Aleksei B. Sheremetev Vladimir A. Dorokhov Kyrill Yu. Suponitsky 《Journal of heterocyclic chemistry》2007,44(4):843-847
Reaction of 6‐acetyl‐7‐aminofurazano[3,4‐b]pyridines with DMFDMA afforded N,N‐dimethylformamidines that were cyclized to the novel furazan‐fused [1,6]naphthyridine system by treatment with sodium methylate in good yield. The tricyclic system is characterized by X‐ray crystallography. 相似文献
12.
The VideoAFM provides a 1000 fold increase in image rate compared to conventional atomic force microscopes, giving nanometre resolution images of surfaces at a rate of 15 frames s(-1), which is approximately 1 million pixels s(-1). Images of high stiffness surfaces such as calibration grids are provided for the first time, and allow for a more rigorous examination of the meaning of the data obtained with the VideoAFM. Instrumental changes that could provide true topographic images are discussed. The advantages of a high speed scanning technique that is integrated within a conventional AFM are outlined. Particular emphasis is given to the capability to 'tile' images, and hence rapidly map large areas with nanometre resolution. It is found that the inherent increase in stability that comes from a high frame rate leads to the possibility of manually manipulating the sample while maintaining a sharp image, allowing real-time user interaction with the AFM. The possible application of the VideoAFM approach for the very rapid analysis of surface properties and, ultimately, surface chemistry is discussed and some possible routes are given. 相似文献
13.
The fluorescence intensity from a planar multilayered system with a chromophore separated from a gold film by a dielectric spacer is measured quantitatively. The direction of excitation and the spacer thickness are varied and the angular distribution of the emission is recorded as well as its polarization. The experimental data are compared to the predictions obtained from classical electromagnetic theory, taking into account the refractive indices of the layer system as well as the nonradiative decay rate and the relative orientation of absorption and emission dipole moments of the dye. Excellent agreement is found for a spacer thickness above 15 nm if proper values for these parameters are used. Samples with thinner spacer layers show significant deviations from classical theory. 相似文献
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Crystallography Reports - The morphology and anatomy of diamond crystals with tetragonal depressions on their surface have been studied. Based on the study of the interrelation between tetragonal... 相似文献
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Vasilev K Stefani FD Jacobsen V Knoll W Kreiter M 《The Journal of chemical physics》2004,120(14):6701-6704
The photobleaching of chromophores in front of a metal film is measured by recording the emitted fluorescence intensity from an ensemble of chromophores as a function of time. A strong dependence of the photostability on the distance from the metal surface is found. The experimental data are well described in a classical electromagnetic model with the additional assumption that photobleaching occurs at a constant rate from the excited state. The metal interface influences the photostability of the chromophores in two ways, first by altering the excitation rate by local enhancement of the electromagnetic field and second by altering the electromagnetic decay rate. 相似文献
18.
The growing demand for titanium-based implants and the subsequent rise in implant-associated infections necessitate novel developments in anti-infective technologies. Recent research has drawn inspiration from nature to solve this problem. The nanoscale topography observed on cicada and dragonfly wings serves as a blueprint for synthetic analogs which seek to kill bacteria on contact through mechanical forces. This type of interaction has been dubbed the mechano-bactericidal effect. Various techniques have been utilized to mimic and improve upon these natural bactericidal surfaces. Alkaline hydrothermal etching is a simple and cost-effective technique to fabricate nanoscale protrusions on titanium and its alloys. This review aims to consolidate the current knowledge surrounding how fabrication parameters lead to varying surface topographies on titanium substrates, and subsequently, how surface topography and bacterial characteristics affect bactericidal activity. The bactericidal mechanism of hydrothermally etched titanium is inferred from comparisons with similar mechano-bactericidal biomaterials. The hostility of hydrothermally etched titanium toward bacteria is discussed in contrast to the observed host cell compatibility. Last, suggestions are made for the standardization of terminology in this emerging field. 相似文献
19.
Mekenyan O Dimitrov S Dimitrova N Dimitrova G Pavlov T Chankov G Kotov S Vasilev K Vasilev R 《SAR and QSAR in environmental research》2006,17(1):107-120
The role of metabolism in prioritising chemicals according to their potential adverse health effects is extremely important given the fact that innocuous parents can be transformed into toxic metabolites. Our recent efforts in simulating metabolic activation of chemicals are reviewed in this work. The application of metabolic simulators to predict biodegradation (microbial degradation pathways), bioaccumulation (fish liver metabolism), skin sensitisation (skin metabolism), mutagenicity (rat liver S-9 metabolism) are discussed. The ability of OASIS approach to predict metabolism (toxicokinetics) and toxicity (toxicodynamics) of chemicals resulting from their metabolic activation in a single modelling platform is an important advantage of the method. It allows prioritisation of chemicals due to predicted toxicity of their metabolites. 相似文献
20.
V.S. Burakov N.V. Tarasenko M.I. Nedelko V.A. Kononov N.N. Vasilev S.N. Isakov 《Spectrochimica Acta Part B: Atomic Spectroscopy》2009
In the present work, a model of double pulse laser-induced breakdown spectroscopy (LIBS) spectrometer has been developed and results from two different applications of double pulse LIBS for solving the problems of environmental interest are presented. In one case, laser induced breakdown spectroscopy has been applied to the determination of heavy and toxic metals (lead) in soil samples. In the second case, laser induced breakdown spectroscopy was used in preliminary experiments for the detection of sulfur content in coal, and on the basis of spectral features, ways to improve the sensitivity of laser induced breakdown spectroscopy detection of sulfur are proposed. The detection limit for lead in soil was estimated to be approximately 20 ppm that is lower than the regulatory standards for the presence of lead in soil. 相似文献