Search results for "Hexagonal crystal system"
showing 9 items of 39 documents
Detecting Crystalline Nonequilibrium Phases on the Nanometer Scale
2012
The use of Automated electron Diffraction Tomography (ADT) is presented as a novel approach for crystallization studies at the nanometer scale for nonequilibrium phases. Here, ADT was applied to elucidate the structural identity of the recently reported hexagonal morphology of caffeine crystals, which grow only on specific surfaces. Caffeine was crystallized from solution on a specially treated TEM carbon grid. The analysis of ADT data revealed that the lattice parameters of these hexagons match those of the high temperature α- form of caffeine. Furthermore, it was observed that in this hexagonal morphology, the α-form remained stable for a prolonged period of time. The stabilization of hex…
Intranukleäre virusähnliche Partikeln in einem Mammakarzinom
1969
By electron microscopic examination of a solid, chiefly scirrhous mammary cancer, 3 kinds of unusual nuclear inclusions were found: (a) Electron dense particles of a 54–80 nm diameter, whose outlines appear mainly hexagonal, which points at an icosahedral structure, (b) Clusters of granules with a diameter of 200–300a, respectively 300–400a, at whose circumference the larger particles appear, (c) Bundles of filaments in close association and continuous with the granules. In all 3 nuclear inclusions there are subunits of 40–45a. The comparison between these results and experiments published suggest that these nuclear inclusions are (a) virus particles, (b) virus at an early stage of developm…
Two-dimensional mobile breather scattering in a hexagonal crystal lattice.
2021
We describe the full two-dimensional scattering of long-lived breathers in a model hexagonal lattice of atoms. The chosen system, representing an idealized model of mica, combines a Lennard-Jones interatomic potential with an “egg-box” harmonic potential well surface. We investigate the dependence of breather properties on the ratio of the well depths associated with the interaction and on-site potentials. High values of this ratio lead to large spatial displacements in adjacent chains of atoms and thus enhance the two-dimensional character of the quasi-one-dimensional breather solutions. This effect is further investigated during breather-breather collisions by following the constrained en…
Polymorphic domains in monolayers of isomeric triple-chain phospholipids
1991
Monolayers of two isomeric branched chain phosphatidyl cholines at the air/water interface have been studied by means of fluorescence microscopy. The lipids differ in the position of the branched chain at the glycerol backbone and carry three chains per headgroup of almost equal length. Most qualitative features of the compression isotherms are similar except a difference of 4 A2/molecule in the minimum molecular area at high lateral pressures. This indicates a more condensed solid phase of compound C2 and is also reflected in the shapes of domains observed in the LE/LC phase coexistence range: domains with sharp edges and a mostly hexagonal shape are formed. On the other hand, the compound…
Linked Analysis of Large Cooperative, Allosteric Systems: The Case of the Giant HBL Hemoglobins
2008
Homotropic and heterotropic allosteric interactions are important mechanisms that regulate protein function. These mechanisms depend on the ability of oligomeric protein complexes to adopt different conformations and to transmit conformation-linked signals from one subunit of the complex to the neighboring ones. An important step in understanding the regulation of protein function is to identify and characterize the conformations available to the protein complex. This task becomes increasingly challenging with increasing numbers of interacting binding sites. However, a large number of interacting binding sites allows for high homotropic interactions (cooperativity) and thus represents the m…
Analysis of the railway network operations safety, with of different obstacles along the route, by the study of Buffon-Laplace type problems: the cas…
2016
In this paper we use an approach based on a Buffon-Laplace type problem for an irregular hexagonal lattice and obstacles to study some problems about analysis of the railway network operations safety in the presence of different obstacles on the route.
Preparation of thin films of the heavy fermion superconductor UNi2Al3
2004
Abstract Thin films of the heavy fermion superconductor UNi 2 Al 3 were prepared by coevaporation of the elementary components in an MBE-system. We obtained textured (1 0 0)-oriented films of this hexagonal compound depositing on Al 2 O 3 substrates. Epitaxial growth was observed on (1 1 2)-oriented orthorhombical YAlO 3 substrates. However, due to pronounced strain the UNi 2 Al 3 (1 0 0)-axis is shortened by ≈2%. No superconductivity of the films was observed which can be associated with the high impurity concentration deduced from R ( T ) and XRD investigations.
A new tool for evaluating and/or selecting analytical methods: Summarizing the information in a hexagon
2019
Abstract A quantitative evaluation tool is proposed, which aims to assess optimal selection or/and testing of analytical methods. Objective criteria related to analytical performance, sustainability, environmental impact and economic cost are evaluated through the definition of penalty points divided into five different blocks, namely, figures of merit, toxicity and safety, residues, carbon footprint and economic cost. For each block, the overall qualification is scaled from 0 to 4 and it is depicted on a regular hexagonal pictogram that allows a user friendly comparison of analytical procedures. The present evaluation tool aims to be a guideline for evaluating and/or selecting analytical p…
Hexagonal nanosheets from the exfoliation of Ni2+-Fe3+ LDHs: a route towards layered multifunctional materials
2010
Here we report the synthesis of a crystalline micrometric-sized hexagonal-shaped Ni2+-Fe3+ LDH by following a modified homogeneous precipitation method. The exfoliation of the material in formamide leads to stable suspensions of hexagonal nanometric sheets, which have been extensively characterized. Our data confirm that the intrinsic properties of the bulk material are retained by these segregated nanosheets, thus opening the door for their use in the development of layered multifunctional materials.