Electron Density of Polymeric Nanoparticles Determined by Image Processing of Transmission Electron Micrographs: Insights into Heavy Metal Staining Processes

A crucial parameter for the investigation of in particular low electron scattering materials by transmission electron microscopy is their ability to attenuate the electron beam and by this to generate appropriate contrast. Surprisingly little attempts have been devoted to at least qualitatively judge on this property of materials. Here an automated imaging analysis algorithm is introduced for the determination of a characteristic electron attenuation factor for homo‐ and (co)polymer nanoparticles which provides a means to access a measure for the contrast in a systematic study of the inherent contrast as well as of the contrast of the nanoparticles after staining procedures. The determination is based on similar imaging conditions for different nanoparticle systems, which enables a comparative approach. Additionally, based on the importance and versatility of osmium tetroxide staining, experiments are conducted elucidating the staining process of model nanoparticle systems bearing olefinic groups. The binding of osmium tetroxide in the environment of the nanoparticle is investigated by means of high‐resolution electrospray mass spectrometry.     

On types of growth for graph-different permutations

We consider an infinite graph G whose vertex set is the set of natural numbers and adjacency depends solely on the difference between vertices. We study the largest cardinality of a set of permutations of [n] any pair of which differ somewhere in a pair of adjacent vertices of G and determine it completely in an interesting special case. We give estimates for other cases and compare the results in case of complementary graphs. We also explore the close relationship between our problem and the concept of Shannon capacity “within a given type.”