Transient-field strength measurements for52Cr traversing Fe hosts at high velocity and polarization transfer mechanisms

Transient-field strengths were measured for⁵²Cr ions traversing polarized Fe hosts at velocities up to 12υ₀ (12υ₀ =c/137 = Bohr velocity). The results are compared with predictions of various transient-field parametrizations and discussed in terms of possible mechanisms by which polarization might be transferred from the Fe host to inner vacancies of the moving Cr ions. Theg-factor of the first 2⁺ state of⁵²Cr was also measured by the transient-field technique and found to be in accord with shell model calculations.     

Diffusive motion of iron microcrystals studied by Mössbauer spectroscopy

A new model is presented which explains well the dramatic decrease of the Mössbauer line intensities with raising temperatures for freely dispersed iron microscrystals. In contrast to other theories which consider mainly vibration to be responsible we discuss here the decrease in terms of large amplitude diffusive rotational or translational jumps of the particles. Such diffusive jumps lead — in agreement with the observation — to a strong reduction of the Mössbauer-intensity without broadening the line width in a noticeable way. The typical potential well for a diffusing particle in an equilibrium position is derived quantitatively to be 13 meV. The model might be important also for a new understanding of the dynamics of catalytic clusters either in contact with each other or with larger solid surfaces.Part of this work was supported by the DFG Sonderforschungsbereich 306, Konstanz     

Network externalities in a dynamic monopoly

We reconsider the role of network externalities in a dynamic spatial monopoly where the firm must invest in order to accumulate capacity, while consumers may have either linear or quadratic preferences. We (1) characterise saddle point equilibria, (2) prove that the extent of market coverage is increasing in the network effect and (3) unlike the existing static literature on the same problem, the monopolist may not make introductory price offers. Then, we briefly deal with the socially optimal solution, showing that, in general, a planner would serve more consumers than a profit-seeking monopolist.      

Corn stover fractions and bioenergy

Information is presented on structure, composition, and response to enzymes of corn stover related to barriers for bioconversion to ethanol. Aromatic compounds occurred in most tissue cell walls. Ferulic acid esterase treatment before cellulase treatment significantly improved dry weight loss and release of phenolic acids and sugars in most fractions over cellulase alone. Leaf fractions were considerably higher in dry weight loss and released sugars with esterase treatment, but stem pith cells gave up the most phenolic acids. Results help identify plant fractions more appropriate for coproducts and bioconversion and those more suitable as residues for soil erosion control.     

Laser-induced breakdown threshold and fracture versus the nanostructure of two-phase glass

The radiation hardness and mechanical strength of single-and two-phase glasses are studied for the case when nanosecond laser pulses (λ= 1.06 μm, τ_0.5 ≈ 12.5 ns) are focused inside the material. Laser interferometry is applied to measure the displacement of the free surface, find optical breakage thresholds, and carry out the fractographic analysis of damaged regions. It is shown that breakdown channels and damage regions develop in a nonlinear manner according to optical breakdown mechanisms, changing each other with an increase in the laser energy. The strength of the two-phase glass is found to be more than four times that of the single-phase glass, although their elastic properties differ insignificantly. Such a considerable difference in the hardness of these materials with chemically similar constitutents is attributed to the presence of the double-lattice nanometer-scale structure of the two-phase glass.     

Near field imaging in microwave regime using double layer split-ring resonator based metamaterial

A planar metamaterial structure consisting of two layers of split-ring resonator (SRR) arrays is demonstrated to form the image of a point source with subwavelength resolution. The source frequency is swept through the resonance gap of the metamaterial layers and the lateral field intensity distribution is recorded on the transmission side of the metamaterial. When the source is tuned to the resonance frequency of SRRs, the metamaterial acts as a high permeability medium and a distinct image with subwavelength resolution in the lateral direction is obtained. Increasing the distance between the individual SRR layers reduces the interlayer coupling, and the intensity and spatial resolution of the image decrease rapidly.     

Visualization of industrial engineering data in Augmented Reality

This paper presents an innovative application of Augmented Reality (AR) techniques in the field of industrial engineering in which the user explores data from numerical simulations or the results of measurements and experiments, superimposed to the real object that they refer to. The user observes the object through a tablet PC, used as a video see-through handheld display. Data are visualized superimposed to the real object that represents a spatial reference relative to which the user can refer to, so the exploration is more natural compared to a traditional visualization software. Moreover, we have developed a new framework, called VTK4AR, that provides a set of useful software classes for the rapid development of AR applications for scientific visualization. VTK4AR is built on top of VTK (an open source API for scientific visualization), so it will be possible to employ a wide range of visualization techniques in many application fields, and moreover, it is possible to interactively manipulate data-sets in order to achieve a more effective way of visualization.     

Thermal treatment on composite γ-zirconium phosphate-silica

The prepared amorphous γ-ZrP\SiO₂ composite had a complicated composition, since a part of γ-ZrP is converted to α-form during the exfoliation of it. The γ-ZrP\SiO₂ composite have specific surface area of 421 m²g^–1. The acidic P–OH groups of the lamellae species placed on the surface (it is ≈1.0 meq g^–1), do not destroy until the temperature of 1030 K. During the thermal treatment the total mass loss of 7.79% was found. This value corresponds to 0.42 mole of H₂O per molecule unit. The water loss process was found very slow, because of the placing of bilamellar species in the composite.     

Variation of supramolecular structure of heat-resistant polyimide films during thermal treatment

Variation of the supramolecular structure of heat-resistant polymide films in the course of high-temperature treatment was studied by X-ray diffraction analysis and NMR spectroscopy in solids.