Ferrofluid Impregnation Efficiency and Its Spatial Variability in Natural and Synthetic Porous Media: Implications for Magnetic Pore Fabric Studies

Transport in Porous Media - Magnetic pore fabrics (MPF) are an efficient way to characterize pore space anisotropy, i.e., the average pore shape and orientation. They are determined by impregnating...     

Interpolation categories for homology theories

For a homological functor from a triangulated category to an abelian category satisfying some technical assumptions, we construct a tower of interpolation categories. These are categories over which the functor factorizes and which capture more and more information according to the injective dimension of the images of the functor. The categories are obtained by using truncated versions of resolution model structures. Examples of functors fitting in our framework are given by every generalized homology theory represented by a ring spectrum satisfying the Adams-Atiyah condition. The constructions are closely related to the modified Adams spectral sequence and give a very conceptual approach to the associated moduli problem and obstruction theory. As an application, we establish an isomorphism between certain E(n)-local Picard groups and some Ext-groups.     

Kristallstrukturen von Kalium- und Silbercyanamidonitrat

Pseudoelement Compounds. XV Crystal Structure Analysis of Potassium and Silver Cyanamidonitrate The crystal structures of potassium and silver cyanamidonitrate are reported. In both the potassium and the silver salt metal anion contacts via the atoms cyano-N, amide-N and oxygen are observed. The structural parameters of the ion [NO₂NCN]^– are only slightly influenced by the different environments (potassium, silver). K[NO₂NCN] forms a coordination lattice in which the nearest neighbours of the potassium ion are nine N and O atoms belonging to seven different anions. Ag[NO₂NCN] has a layer structure; the silver atoms are arranged in zickzack chains running perpendicular to the layers with an Ag–Ag distance of 3.169(1) Å.     

Formation of highly ordered and orientated gold islands: effect of immersion time on the molecular adlayer structure of pentafluorobenzenethiols (PFBT) SAMs on Au(111)

Self-assembled monolayers (SAMs) of pentafluorobenzenethiol (PFBT) on Au(111) substrates, prepared with different immersion times (ITs) at room temperature, were studied using scanning tunneling microscopy (STM) and infrared reflection-absorption spectroscopy (IRRAS). In the present study, the focus was on several important points of interest in the field of SAMs. First, the gold islands formed upon adsorption of PFBT molecules on the gold surface were monitored at different ITs in terms of their size, density, and shape. After short ITs (5 to 30 min), small gold islands with rounded shape were formed. These gold islands were arranged in a rather regular fashion and found to be quite mobile under the influence of the STM-tip during the scanning. When the IT was increased to 16 h, the results revealed the formation of highly ordered and orientated gold islands with very unusual shapes with straight edges meeting at 60° or 120° running preferentially along the [11(-)0] substrate directions. The density of the gold islands was found to decrease with increasing IT until they almost disappeared from the SAMs prepared after 190 h of IT. On top of the gold islands, the PFBT molecules were found to adopt the closely packed (10√3 × 2) structure. Second, a number of structural defects such as disordered regions at the domain boundaries and dark row(s) of molecules within the ordered domains of the PFBT SAMs were observed at different ITs. The SAMs prepared after 190 h of IT were found to be free of these defects. Third, at low and moderate ITs, a variation in the PFBT molecular contrast was observed. This contrast variation was found to depend mainly on the tunneling parameters. Finally, our results revealed that the organization process of PFBT SAMs is IT-dependent. Consequently, a series of structural phases, namely, α, β, γ, δ, and ε were found. The α-, β-, γ-, and δ-phases were typically accompanied by the ε-phase that appeared on top of gold islands. With increasing IT, the α→β→ γ→δ→ε phase transitions took place. The resulting ε-phase, which covered the entire gold surface after 190 h of IT, yielded well-ordered self-assembled monolayers with large domains having a (10√3 × 2) superlattice structure.