Über Nitrophtalaldehydsäuren

Ohne Zusammenfassung     

Geometrical vs. Fortuin–Kasteleyn clusters in the two-dimensional q-state Potts model

The tricritical behavior of the two-dimensional q-state Potts model with vacancies for 0q4 is argued to be encoded in the fractal structure of the geometrical spin clusters of the pure model. The known close connection between the critical properties of the pure model and the tricritical properties of the diluted model is shown to be reflected in an intimate relation between Fortuin–Kasteleyn and geometrical clusters: the same transformation mapping the two critical regimes onto each other also maps the two cluster types onto each other. The map conserves the central charge, so that both cluster types are in the same universality class. The geometrical picture is supported by a Monte Carlo simulation of the high-temperature representation of the Ising model (q=2) in which closed graph configurations are generated by means of a Metropolis update algorithm involving single plaquettes.     

Use of sensitivity as a function of fluorescent x-ray energy in energy-dispersive x-ray spectrometry

The approximate linear relationship between the logarithm of the sensitivity and the logarithm of the energy of the observed characteristic x-ray emission is used to show the relative retention of elements during fusion with lithium tetraborate to form fused pellets, and the relative recovery of elements by preconcentration methods. Elements with atomic numbers ranging from 20 to 33 were investigated in fused pellets and/or filtered precipitated samples. Linear or nearly linear curves with slopes ranging from near two for infinitely thin samples to near six for infinitely thick samples are predicted if certain conditions of x-ray excitation are met.     

Untersuchungen über die Veresterung unsymmetrischer zwei- und mehrbasischer Säuren

Monatshefte für Chemie - Chemical Monthly -     

Implementation of proficiency testing schemes for a limited number of participants

A metrological background for the selection and use of proficiency testing (PT) schemes for a limited number N of laboratories-participants (less than 20–30) is discussed. The following basic scenarios are taken into account: (1) adequate matrix certified reference materials (CRM) or in-house reference materials (IHRM) with traceable property values are available for PT use as test items; (2) no appropriate matrix CRM is available, but a CRM or IHRM with traceable property values can be applied as a spike or similar; (3) only an IHRM with limited traceability is available. The discussion also considers the effect of a limited population of PT participants N _p on statistical assessment of the PT results for a given sample of N responses from this population. When N _p is finite and the sample fraction N/N _p is not negligible, a correction to the statistical parameters may be necessary. Scores suitable for laboratory performance assessment in such PT schemes are compared. Presented at the 3rd International Conference on Metrology, November 2006, Tel Aviv, Israel.     

Anomalous ion accelerated bulk diffusion of interstitial nitrogen

Interstitial N diffusion under low energy (approximately 700 eV) Ar+ bombardment at 673 K in ion beam nitrided austenitic stainless steel is investigated. Ar+ ion bombardment increases the N mobility in depths far beyond the ion penetration depth, resulting in an increased broadening of the N depth profile as a function of Ar+ flux. This effect cannot be explained by any established mechanism of radiation-enhanced diffusion. An explanation based on quasiparticle-enhanced mobility is proposed.     

Indefinite damping in mechanical systems and gyroscopic stabilization

This paper deals with gyroscopic stabilization of the unstable system Mẍ + Dẋ + Kx = 0, with positive definite mass and stiffness matrices M and K, respectively, and an indefinite damping matrix D. The main question is for which skew-symmetric matrices G the system Mẍ + (D + G)ẋ + Kx = 0 can become stable? After investigating special cases we find an appropriate solution of the Lyapunov matrix equation for the general case. Examples show the deviation of the stability limit found by the Lyapunov method from the exact value.      

Preconcentration of trace elements on oxine cellulose

Summary X-ray Diffraction Analysis of Corrosion Products on Electrochemically Polarized Copper Surface An investigation was undertaken to examine the feasibility of X-ray diffractometry for the identification and characterization of corrosion products formed, electrochemically, on copper surface in various aqueous media. The removal of the products from the metal surface was useful in overcoming serious interferences from the intense diffraction lines of copper and was most satisfactory for the identification of common film components such as cuprous oxide, cuprous chloride and cupric oxide. In addition, the results obtained for the surface film components by slow scan linear (or potentiodynamic) polarization agreed favourably with the X-ray diffraction analysis. The influence of the solution pH and temperature on the nature of the corrosion products was evident on the results obtained by both techniques. The dominance of cuprous oxide as the major film component at the low solution pH and of cupric oxide as the predominant species at the higher solution pH and higher temperature were also confirmed by both results.Work undertaken while at the School of Applied Chemistry, Western Australian Institute of Technology, W. A. 6102 (Australia).