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.     

Chemical and structural modifications of laser treated iron surfaces: investigation of laser processing parameters

This study focuses on the chemical, morphological and structural characterization of iron surfaces treated by laser in ambient air. Incorporation of nitrogen over a 1–2 μm thickness (10–30 at.% at the profile maximum) and superficial oxidation on 200–400 nm depth have been evidenced by nuclear reaction analyses. X-ray diffraction at grazing incidence has shown the formation of FeO and Fe₃O₄ oxide phases as well as γ-Fe(N), and ε-Fe_xN for a sufficiently high amount of nitrogen incorporated. Treatments performed with different laser beams indicate that the parameter playing the major role in surface modification processes is the wavelength. Nitrogen incorporation has been found to occur via the interaction of reactive N, present in the laser-induced plasma, and the iron molten bath. The nitriding process is promoted in the IR wavelength range. Oxidation takes place by chemical reaction during the cooling step, and is furthered in the case of UV treatment.     

Application of the multicanonical multigrid Monte Carlo method to the two-dimensional φ4: Autocorrelations and interface tension: Autocorrelations and interface tension

We discuss the recently proposed multicanonical multigrid Monte Carlo method and apply it to the scalar ⁴ on a square lattice. To investigate the peformance of the new algorithm at the field-driven first-order phase transitions between the two ordered phases we carefully analyze the autocorrelations of the Monte Carlo process. Compared with standard mlticanonical simulations a real-time improvement of about one order of magnitude is established. The interface tension between the two ordered phases is extracted from highstatistics histograms of the magnetization applying histogram reweighting techniques.     

Traceable property values of in-house reference materials

The traceability of in-house reference materials (IHRM) is discussed. It is shown that a systematic error in results of a measured value, specific to a measurement method or to a laboratory developing an IHRM, can be overcome if a comparative approach to IHRM characterization is used. A traceability chain of the value carried by the IHRM to the value carried by the reference material with higher metrological status and sufficiently similar matrix (for example, a certified reference material – CRM according to ISO Guide 30) is helpful in such a case. The chain is realized when the IHRM samples are analysed simultaneously with the CRM samples under the same conditions. This and other traceability chains necessary for the IHRM development are examined as the measurement information sources.     

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.     

Über Diacetine und andere Glycerinabkömmlinge

Ohne Zusammenfassung     

Quantifying the measurement uncertainty of results from environmental analytical methods

The Eurachem–CITAC Guide Quantifying Uncertainty in Analytical Measurement was put into practice in a public laboratory devoted to environmental analytical measurements. In doing so due regard was given to the provisions of ISO 17025 and an attempt was made to base the entire estimation of measurement uncertainty on available data from the literature or from previously performed validation studies. Most environmental analytical procedures laid down in national or international standards are the result of cooperative efforts and put into effect as part of a compromise between all parties involved, public and private, that also encompasses environmental standards and statutory limits. Central to many procedures is the focus on the measurement of environmental effects rather than on individual chemical species. In this situation it is particularly important to understand the measurement process well enough to produce a realistic uncertainty statement. Environmental analytical methods will be examined as far as necessary, but reference will also be made to analytical methods in general and to physical measurement methods where appropriate. This paper describes ways and means of quantifying uncertainty for frequently practised methods of environmental analysis. It will be shown that operationally defined measurands are no obstacle to the estimation process as described in the Eurachem/CITAC Guide if it is accepted that the dominating component of uncertainty comes from the actual practice of the method as a reproducibility standard deviation.