Also see:Mapping the Chemical Composition of Porous Graphene-Polymer Multilayers: Detection of Individual Flakes by Peak Force Atomic Force Microscopy and X-ray Photoelectron Spectroscopy.
We demonstrate that the chemical composition of porous graphene-polymer multilayers can be mapped by synchrotron radiation-based X-ray photoelectron spectroscopy (SR-XPS) in combination with atomic force microscopy (AFM) imaging. It is shown that the surface sensitivity of AFM, depending on the material contrast of the sample, can be tailored by a slight variation of the nominal exposure of a sample to X-ray radiation. It is shown that by using a special in situ cleaning procedure, the AFM-XPS analysis is not limited by irreversible charging effects and can be performed without significant degradation of the initial topography of the sample. However, some sample degradation after prolonged XPS measurements is observed, and it is demonstrated that a specific structural feature (bromine in the top layer), necessary to establish the chemical contrast for the chemical analysis, is not affected by this degradation. AFM-XPS measurements are performed on two-dimensional nanostructures with an edge length of more than 3 μm (single graphene and polystyrene multilayer flakes), and the chemical contrast as well as the topography of the samples is compared. The same samples are characterized by scanning electron microscopy. It is shown that graphene multilayers with a stack structure are composed of individual flakes, which are detached from the substrate upon X-ray exposure. By monitoring the thickness of the individual flakes as a function of the nominal X-ray exposure of the substrate, it is found that the edges of the flakes are preferential sites for X-ray-induced cleavage, whereas the brominated top layer is not affected by the cleavage. These results demonstrate that the chemical contrast of graphene-polymer multilayers is capable of providing a unique, structural-sensitive, mapping of the sample.Effect of inflammatory mediators on blood flow and microcirculation of colonic mucosa.
Colonic mucosal microcirculation is regulated by neurogenic mechanisms, locally released transmitters, and hemodynamic factors. The aim of this study was to investigate the effect of tumor necrosis factor (TNF), histamine, serotonin, bradykinin, and substance P on mucosal blood flow and microcirculation in the colon. Luminal perfusion was be359ba680
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