Current in-service inspections of austenitic stainless steel and dissimilar metal welds in light water nuclear power plants

A tendency towards growing requirements for the inspection of austenitic piping can be observed in several countries. In Germany the revised KTA rule demands the UT inspection of austenitic and dissimilar metal welds in piping with diameters of 200 mm or more.On the basis of experience gained from austenitic piping with integranular stress corrosion cracking (IGSCC), longitudinal waves and mode conversion techniques are used. Depending on the geometry, material and grain orientation, spurious signals can be observed which require additional evaluation or analysis measurements.A promising new technique is based on horizontally polarized shear (SH) waves generated by electromagnetic acoustic transducers (EMATs). Investigations in the laboratory and field inspections showed that SH waves are well suited for the detection of longitudinal flaws, especially where the weld can be examined from one side only.For the complete solution of a given inspection problem SH waves can be combined with well-known standard techniques in order to provide redundant information for the characterization and sizing of indications.The investigation of possibilities of SH waves showed that the problem of cast austenitic steel inspection might not be solved using this technique. However, measurements using low frequency UT transducers showed promising results.     

Directional reflectance properties determined by analysis of airborne multispectral scanner data and atmospheric correction

Directional reflectance properties of natural surfaces are very important in the interpretation of remotely sensed data. The analysis of multispectral scanner data shows a distinct dependence on scan angle, wavelength (0.4–1.1 μm), and classes (e.g., bare soil, vegetation). This relationship can be described by polynomials determined by regression methods. Atmospheric effects are computed with a simple model by parametrization of the multiple scattered skylight. The model permits a quick and sufficient estimation of the airlight, depending on the data collection conditions. Comparisons of the scanner data with the corresponding model yield the following results: The differences between airborne and ground measurements are due to atmospheric effects. The directional variation in brightness is mainly caused by the object itself with the exception of short wavelengths and/or a very low albedo. The hue shift of vegetation is essentially produced by the object and modified by the atmosphere. Taking into account the directional reflectance properties in a direction-dependent classification procedure results in an improvement of up to 20% in comparison with algorithms used so far. Quantitative relationships between ground measurements and radiation measurements by airborne sensors including atmospheric effects can be determined with the proposed methods.     

Beanspruchungsverhalten von PVD-CrN Beschichtungen auf Leichtmetallwerkstoffen

Behaviour of light metals with PVD-CrN coatings using different test methods The application of thin hard coatings on machining tools, e.g. drilling tools is state of the art. The increase of lifetime of coated Tools compared to uncoated tools is well known. [1]. In this context ?separation of functions”? is an often used phrase, by meaning the separation of functions of the volume and the surface of materials. Going one step forward, from the point of view of tribology or corrosion this means, you have ?only”? to protect the surface by using a ?good”? coating without looking at the material underneath. In the past the influence of substrate materials or the optimization of the system (substrate-coating) was not the main aim of PVD development. Looking at substrate and coating as a system is especially necessary, if the differences of the properties of substrate and coating are large (e.g. hard coating – light metals). This paper shows different aspect of the tribological and electrochemical characterization of PVD coated light metals (CrN coating).     

Prion proteins as memory molecules: an hypothesis

Prions are infectious agents widely implicated in a variety of mammalian neurodegenerative diseases generally referred to as transmissible spongiform encephalopathies. Their infectivity is primarily associated with an aberrant conformation of a host-encoded protein, the prion protein, induced by the prion itself in an autocatalytic reaction. The physiological function of this protein is not known. In this paper we suggest that alternative conformations of the prion protein, other than its pathological scrapie state, exist and that the self-sustaining autocatalytic propagation of these states underlies its normal cellular function. In kinetic model calculations we show that the prion protein may constitute a bi-stable molecular switch that can structurally encode and stably store information. A number of cases of prion involvement in normal cellular function and ample molecular detail of pathological prion propagation are cited and correlated to substantiate the implications of this tenet. Our contention is that the prion hypothesis should be extended to a wide variety of physiological processes. We propose that prion proteins are stable determinants of phenotype, operating in diverse functions possibly including memory.     

Raltitrexed (Tomudex): an alternative drug for patients with colorectal cancer and 5-fluorouracil associated cardiotoxicity

Two patients with proven 5-fluorouracil (5-FU)-associated cardiotoxicity were treated with the specific thymidylate synthase inhibitor raltitrexed safely, without evidence of cardiotoxicity. Raltitrexed might be an alternative for patients with advanced colorectal cancer and 5-FU-associated cardiotoxicity. 5-FU cardiotoxicity is not due to the antineoplastic mechanisms via thymidilate synthase.     

Structure prediction of subtilisin BPN' mutants using molecular dynamics methods

In this paper we describe the achievements and pitfalls encounteredin doing structure predictions of protein mutants using moleculardynamics simulation techniques in which properties of atomsare slowly changed as a function of time. Basically the methodconsists of a thermodynamic integration (slow growth) calculationused for free energy determination, but aimed at structure prediction;this allows for a fast determination of the mutant structure.We compared the calculated structure of the mutants Met222Ala,Met222Phe and Met222Gln of subtilisin BPN' with the respectiveX-ray structures and found good agreement between predictedand X-ray structure. The conformation of the residue subjectto the mutation is relatively easy to predict and is mainlydetermined by packing criteria. When the side chain has polargroups its exact orientation may pose problems; long-range Coulombinteractions may generate a polarization feedback involvingsystem relaxation times beyond the simulation time. Changesinduced in the environment are harder to predict using thismethod. In particular, rearrangement of the hydration structurewas difficult to predict correctly, probably because of thelong relaxation times. In all conversions made the changes observedin the environment were found to be history-dependent and inparticular the hydrogen bonding patterns provided evidence formetastable substates. In all cases the structure predicted wascompared with available kinetic data and the reduced activitycould be explained in terms of changes in the configurationof the active site.     

Hard coatings on light-metal components under mechanical surface loading

In this work the behaviour of hard coated light-metal components was investigated when they are mechanically loaded. Three lightmetal alloys, Ti-6Al-4V, AlSi7Mg and AlMgSi0.5 and 100Cr6 steel (as a reference material) were coated by two different physical vapour deposition processes: radio frequency magnetron sputtering and electron beam evaporation. The coating materials utilised were CrN and TiN. Standard test methods with different loading conditions were used to evaluate the substrate/coating-combinations: the hardness test (applying a static normal load), the scratch test (applying a combination of a static normal and a static tangential force) and the impact test (applying a dynamic normal load). It was observed that the load support of coated materials depends on the loading conditions. The coated aluminium alloys showed poor load support under all loading test conditions but produced a higher surface hardness than uncoated steel. Coated Ti-6Al-4V showed very good load support properties, similar to coated steel. All coated light-metal substrates demonstrated significant improvement in load support behaviour with an increase in coating thickness. The results of the scratch test, which is commonly used to asses adhesion properties of thin coatings, showed an immediate indenter-breakthrough on the aluminium alloy substrates, but causing no coating delamination. Due to this behaviour, the scratch test is not suitable to evaluate adhesion properties on coated soft light-metals. Yet the impact test allowed assessment of coating delamination on the aluminium alloys, proving its usefulness for adhesion measurement even on soft substrates. The study indicates that substitution of steel with coated lightmetal alloys is a viable proposition for certain applications.     

Spannungsrißbildung und Spannungsrißkorrosion bei Kunststoffen

Environmental stress cracking and stress-corrosion cracking in plastics Plastics are being used to an increasing extent in fields which have hitherto been the reserve of other, usually metallic, materials. Owing to their good processability and chemical resistance, plastics engineering materials are for example employed for vessels, pipes, valves and fittings, blowers, pumps and gear wheels. In these applications they are not only exposed to liquid media but, are also subjected to occasional or continuous mechanical stress. The trouble is that there are media to which plastics in the stress-free state are absolutely immune, but that, when tensile stresses are present, cracking may occur; this phenomenon is called environmental stress cracking. It is therefore necessary for the design engineer both to know whether the medium to be handled causes environmental stress cracking, and to be familiar with the other properties of the material. The following article describes the most important methods of detecting environmental stress cracking and the most important media which cause this form of cracking in common plastics materials.