Grundsätzliche Überlegungen zur Entstehung der Kristallseigerung und der eutektischen Zweitphasenausscheidung in Dreistoffsystemen

Erörterung über den Erstarrungsablauf und über die Ausscheidung zweier eutektischer Verbindungen in Dreistofflegierungen anhand eines angenommenen Zustandsschaubildes. Quantitative Darstellung von Rechenergebnissen über die Kristallseigerung primärer Mischkristalle bei veränderten Gesamtlegierungsgehalten mit Aussagen über den Legierungseinfluß auf die Kristallseigerung. Angaben über die Zusammenhänge zwischen Zustandsschaubild, Verteilungskoeffizient und Kristallseigerung. Behandlung des Mechanismus für eine Zweitphasenausscheidung. Hinweise auf die praktische Bedeutung der seigerungsbedingten Schmelzpunkterniedrigung.     

Testing colour fading of cotton fabrics by activated oxygen bleach-ontaining detergent an interlaboratory trial

A single diagnostic wash test to identify coloured cotton fabrics susceptible to activated oxygen bleach was subjected to an interlaboratory trial (ring test). The results from the trial are described and a procedure developed for use as a British Standard is outlined.     

Pancreatic colon stenoses

Benign colonic stenosis may be caused by pancreatitis. Colonic obstruction arising during the acute stage of pancreatitis is mostly found to be reversible. Persistant colonic stenosis after acute or relapsing pancreatitis may point to an adjacent abscess. Two patients with pancreatitic colonic stenosis illustrate those different courses of the disease.     

The colour fastness of dyed fabrics to activated oxygen bleach-containing detergents: an international interlaboratory trial

The UK-TO single wash test procedure, developed to be diagnostic of the oxidative bleach response of dyed articles to repeated washing in activated oxygen bleach-containing detergents, has been subjected to extensive interlaboratory trials. The results indicate that both its repeatability and reproducibility are fully acceptable for the purpose of interlaboratory comparisons.     

Modeling of SCC initiation and propagation mechanisms in BWR environments

During operation of mainly BWRs’ (Boiling Water Reactors) excursions from recommended water chemistries may provide favorite conditions for stress corrosion cracking (SCC). Maximum levels for chloride and sulfate ion contents for avoiding local corrosion are therefore given in respective water specifications. In a previously published deterministic 288 °C – corrosion model for Nickel as a main alloying element of BWR components it was demonstrated that, as a theoretically worst case, bulk water chloride levels as low as 30 ppb provide local chloride ion accumulation, dissolution of passivating nickel oxide and precipitation of nickel chlorides followed by subsequent local acidification. In an extension of the above model to SCC the following work shows that, in a first step, local anodic path corrosion with subsequent oxide breakdown, chloride salt formation and acidification at 288 °C would establish local cathodic reduction of accumulated hydrogen ions inside the crack tip fluid. In a second step, local hydrogen reduction charges and increasing local crack tip strains from increasing crack lengths at given global stresses are time stepwise calculated and related to experimentally determined crack critical cathodic hydrogen charges and fracture strains taken from small scale SSRT tensile tests pieces. As a result, at local hydrogen equilibrium potentials higher than those of nickel in the crack tip solution, hydrogen ion reduction initiates hydrogen crack propagation that is enhanced with increasing global stresses. In accordance with respective experimental literature data it is shown that decreasing chloride and increasing pH levels of the primary bulk water at 288 °C reduce the total crack propagation rates including anodic path corrosion as well as hydrogen cracking. It is also demonstrated that crack propagation rates can be significantly suppressed by hydrogen water chemistry (HWC) that leads to reduction of bulk surface corrosion potentials. As a conclusion the extended SSC-model for nickel supplies quantitative insight into the frequently controversially discussed high temperature SCC mechanisms of a basic alloying element of BWR components.     

Characterization of the Suillus grevillei Quinone Synthetase GreA Supports a Nonribosomal Code for Aromatic α-Keto Acids

The gene greA was cloned from the genome of the basidiomycete Suillus grevillei. It encodes a monomodular natural product biosynthesis protein composed of three domains for adenylation, thiolation, and thioesterase and, hence, is reminiscent of a nonribosomal peptide synthetase (NRPS). GreA was biochemically characterized in vitro. It was identified as atromentin synthetase and therefore represents one of only a limited number of biochemically characterized NRPS-like enzymes which accept an aromatic α-keto acid. Specificity-conferring amino acid residues-collectively referred to as the nonribosomal code-were predicted for the primary sequence of the GreA adenylation domain and were an unprecedented combination for aromatic α-keto acids. Plausible support for this new code came from in silico simulation of the adenylation domain structure. According to the model, the predicted residues line the active site and, therefore, very likely contribute to substrate specificity.     

Concept and procedure of the IRC test for assessing hydrogen assisted weld cracking

The self restraining Instrumented Restraint Cracking (IRC)-test enables the determination of weld joint reaction forces and -moments responsible for hydrogen assisted cracking. With help of continuous measurements during cooling of the weld, the effects of crack inducing parameters can be detected in detail. The IRC-test can be applied to procedure development and procedure qualification welding, making use of current fabrication practice at restraint intensities of the to-be-fabricated structure. It is easy to carry out and the results are quickly at hand.