Influence of Threshold Stress on the Estimation of the Weibull Statistics

The influence of threshold stress on the estimation of the Weibull statistics is discussed in terms of the Akaike information criterion. Numerical simulations show that, if sample data are limited in number and threshold stress is not too large, the two-parameter Weibull distribution is still a preferred choice. For example, the fit of strength data of glass and ceramics to the two- and three-parameter Weibull distributions is compared.     

Measurement of fat content of food with single-sided NMR

Fat content is one of the important parameters of quality control in many food products. Several techniques are used to determine the amount of fat in a given product. In this work, the applicability of a portable dedicated nuclear magnetic resonance (NMR) analyzer to measure the fat content in a packaged product without destruction of the material was examined. Two different low-field NMR methods, namely, a ratio method and a relaxation time method, were applied and discussed. The processed NMR signal was linearly correlated with the fat content obtained by reference methods. The linear correlation allowed the application of single-sided NMR for fat measurements. In memoriam     

A simple method for the objective characterisation of fabric softness. Part 1: Influence of bleaching,dyeing and crosslinking of wool*

A simple method for the characterisation of fabric softness using a conventional tensile tester and a special measurement device has been developed. The method is demonstrated to be especially useful in detecting changes in softness of a given substrate due to different treatments. The results obtained, particularly hysteresis at 75% of the maximum extension, provide a good correlation with subjective ranking for samples that are subjectively distinguishable; they also differentiate well between samples which seem subjectively indistinguishable. Screening tests were carried out, mainly on wool fabrics, to find the effect of different treatments such as oxidative (alkaline and acidic) and reductive (Blankit IN) bleaching, dyeing with acid and a 1:2 metal complex, chrome and (mono and bi)reactive dyes, the effect of the antisetting agent Basolan AS (BASF) and of crosslinking with Irgasol HTW (CGY) on fabric softness.     

Hochselektive Stofftrennungen mit Carriermembranen — Stand der Entwicklung und Erwartungen

Membrane processes are able to separate liquid mixtures as well as mixtures of gases or vapours according to the sizes, solubilities, rates of diffusion or charges of the components. A separation is also possible using membranes in which the transport is coupled to a specific chemical reaction between the permeand and the membrane (facilitated or carrier mediated transport). This paper discusses aspects related to carrier‐mediated separation processes such as the transport mechanisms, the choice of appropriate carriers, the incorporation of carriers in the polymeric membrane material, the coating of porous support membranes with thin selective layers of the carrier‐polymer and, finally, the choice of appropriate parameters for the separation process. The separation of gas mixtures by carrier‐membranes appears very promising from a technical point of view. Experimental membrane samples often show excellent separation factors, but they have not met the permeability requirements for an economic use so far.     

Iterative Antimicrobial Candidate Selection from Informed D‐/L‐Peptide Dimer Libraries

Growing resistance to antibiotics, as well as newly emerging pathogens, stimulate the investigation of antimicrobial peptides (AMPs) as therapeutic agents. Here, we report a new library design concept based on a stochastic distribution of natural AMP amino acid sequences onto half‐length synthetic peptides. For these compounds, a non‐natural motif of alternating D ‐ and L ‐backbone stereochemistry of the peptide chain predisposed for β‐helix formation was explored. Synthetic D ‐/L ‐peptides with permuted half‐length sequences were delineated from a full‐length starter sequence and covalently recombined to create two‐dimensional compound arrays for antibacterial screening. Using the natural AMP magainin as a seed sequence, we identified and iteratively optimized hit compounds showing high antimicrobial activity against Gram‐positive and Gram‐negative bacteria with low hemolytic activity. Cryo‐electron microscopy characterized the membrane‐associated mechanism of action of the new D ‐/L ‐peptide antibiotics.     

Entwicklung einer kontinuierlichen Mikrowellen‐Vakuumtrocknungsanlage mit hexagonalem Verfahrensraum

A continuous microwave vacuum drying processor with a hexagonal cross‐section of the cavity was constructed. Due to the geometry of the cavity and the continuous movement of the product, homogeneous microwave power absorption of the product can be favored. By the expansion and simultaneous dehydration of non‐expanded, starch‐based extrudates, the applicability of the constructed processor could be shown.     

In-Operation Monitoring of the Soot Load of Diesel Particulate Filters: Initial Tests

Diesel particulate filters (DPF) are indispensable parts of modern automotive exhaust gas aftertreatment systems due to the stringent emissions legislation. For a fuel-efficient control strategy, it would be beneficial to determine directly and in-operation their actual trapped soot mass. Two novel approaches—based on the electrical conductivity of trapped soot particles—emerged recently. By measuring the electrical resistance between different single walls inside the filter, the soot load is determined with local resolution. The microwave-based technique is a contactless approach that gives an integral value depending on the soot mass in the DPF. We present investigations on loading and regeneration of DPFs in a dynamometer test bench applying both methods. The results are compared with each other and correlated with the differential pressure and the soot mass. Especially the microwave-based technique has a potential for serial application.     

The Kinetics of the Thermal Decomposition of Thermoplastic Polyurethane Elastomers under Thermoplastic Processing Conditions

A theoretical approach to the kinetics of the thermal decomposition of molten thermoplastic polyurethane elastomers, under conditions of thermoplastic processing, is described. On the basis of these considerations, the thermal decomposition in different instruments (melt index analyser and measuring extruder) can be described quantitatively and the various results can be compared. As a result, identical conditions of decomposition of the melt can be defined accurately, thus opening up the possibility of combining experimental values from different instruments. The fundamental kinetic equation obtained for the kinetics of the thermal decomposition of thermoplastic polyurethanes describes the decomposition reaction and the reverse reaction (formation reaction) – which is dependent on the system of measurement and processing – as a function of the molar mass (end‐group concentration) of the original product, determined from the velocity constants for the decomposition reaction and back reaction. The consideration of the limiting value for t → ∞ is in agreement with the equilibrium constant. Consequently, the development of physical characteristic functions of thermoplastic polyurethane elastomers – independent of the system of measurement – is possible.

Experimental values and calculated curves for the thermal decomposition of PUR‐Et in a melt index analyser.     

Catalysis with Soluble Hybrids of Highly Branched Macromolecules with Palladium Nanoparticles in a Continuously Operated Membrane Reactor

The continuous recovery and recycling of soluble metal nanoparticles by means of ultrafiltration is described, employing hybrids of palladium nanoparticles with highly branched amphiphilic polyglycerol as a catalyst for cyclohexene hydrogenation as a model reaction. In a continuously operated membrane reactor a productivity of 29000 TO over 30 exchanged reactor volumes was observed for nanoparticles of 2.2 nm size, with a maximum rate of 1200 TO h⁻¹. Catalysis by soluble metal complexes can be excluded. After 30 hours of operation, some decrease in activity is observed which is due to deposition of palladium on the ultrafiltration membrane, however this material does not contribute to catalytic activity.