Stress corrosion cracking of Al-Mg-Zn-Cu alloys after precompression

Stress corrosion cracking (SCC) experiments have been carried out on double-cantilever-beam (DCB) specimens of 7017-T651 aluminium alloy. The specimens were first subjected to a known compressive load which caused plastic deformation at the notch tip. On unloading, this region developed a residual tensile stress field and on subsequent exposure to moist air at 40° C (95% relative humidity, r.h.), intergranular cracks formed. These cracks grew at a decelerating rate until they stopped. The final crack length increased with the value of the initial compressive preload, provided this was below the value for general yielding of the alloy. Electron fractography has been used to correlate changes in surface morphology with crack growth rate. It was found that ductile tearing of the notch tip may occur during unloading when the compression exceeds — 30kN. The practical importance of these results is outlined.     

The theory of equivalence of Pfaffian systems and input systems under feedback

The Theory of equivalence of exterior differential systems is applied to study canonical forms under feedback for nonlinear systems in differential equation, state-space forms.Supported by Ames Research Center (NASA), Grant NSG-2404, U.S. Army Research Office. Contract #IL161102BH57-03 MATH, NSF MCS8003227.     

The crystalline qualities of silicon layers formed by solid phase epitaxial growth

The quality of epitaxial Si layers grown by solid phase reactions was studied by MeV ⁴He backscattering spectrometry and transmission electron microscopy. The grown layers are essentially epitaxial with the underlying Si crystals. Defects in the grown layers are mainly twins, i.e. primary twins in the layers grown during the initial stage of growth and additional secondary twins in the layers grown during the later stages. The amount of Pd trapped in the grown layers is strongly temperature dependent, with an activation energy of 1.8 eV. However, the size of the Pd inclusions is temperature insensitive.     

9,12,15-octadecatrien-6-ynoic acid,new acetylenic acid from mosses

Lipids of the moss,Ceratodon purpureus, yield up to 25% of an acetylenic acid which was identified as allcis-9,12,15-octadecatrien-6-ynoic acid. The methyl ester of this acid was isolated in 95% purity by gas liquid chromatography. Mass spectroscopy provided the mol wt and confirmed methyl stearate as product of hydrogenation. Ozonization indicated a triple bond in position 6 and a double bond in position 15. UV and IR spectra showedcis-double bonds, no conjugation, and notrans-double bonds. The Raman spectrum provided direct evidence for the triple bond and confirmed the presence of double bonds and the absence of conjugation. The ratio of intensities indicated 1 triple bond/3 double bonds. 9,12,15-Octadecatrien-6-ynoic acid has not previously been isolated from biological materials. It was found only in the triglycerides ofCeratodon purpureus and several other mosses. In contrast to arachidonic and eicosapentaenoic acids, the acetylenic acid seems to be restricted to few moss genera.     

Reaktionen zwischen feuerfesten Stoffen des Systems SiO2–Al2O3 und manganhaltigen Eisenschmelzen

Laboratoriumsuntersuchungen über das Verhalten von Schamotte-, Mullit-, Sillimanit- und Bauxitsteinen in Eisenschmelzen mit Mangangehalten bis zu 2% bei 1600°C. Beschreibung des Ablaufes der Reaktionen zwischen Schmelze und Stein, Untersuchung der Eigenschaften der Reaktionsprodukte sowie Ermittlung des Einflusses von Silizium und Aluminium auf die Reaktionen. Vergleich mit Ergebnissen aus Betriebsuntersuchungen und Folgerungen aus den Versuchsergebnissen für Beiriebsverhältnisse.     

Elektrophoretische Differenzierung hitzedenaturierter und eisgelagerter Fischproteine

Zusammenfassung Eine Natrium-dodecylsulfat(SDS)-Lösung mit Mercapto-ethanol in Tris-Borat-Puffer pH 8.9 löst bei Raumtemperatur alle Fischproteine, auch die von gekochten Proben. Die Trennung durch Polyacrylamidgel(PAG)-Elektrophorese in Gegenwart von SDS ergibt trotz verschiedener Vorbehandlung artencharakteristische Pherogramme, vor allem im Bereich der sarkoplasmatischen Proteine. Die PAG-Focussierung der SDS-extrahierten Proteine gelingt nach Fällung von überschüssigem SDS und Trennung in PAG unter Zugabe von Harnstoff und Tetramethylharnstoff im pH-Bereich von 2–11. Dabei wird das artenspezifische Muster überlagert von einer Veränderung, die z. T. die fortschreitende Autolyse etc. während der Lagerung widerspiegelt.

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Evaluation of fish proteins by electrophoretic methods after boiling and after storage on ice

Summary All proteins from fish including boiled samples can be dissolved at room temperature in Tris-borate-buffer pH 8.9 containing 2% Sodiumdodecylsulfate (SDS) and 1% mercapto-ethanol. The separation is carried out in polyacrylamidegels (PAG) by SDS-electrophoresis, showing a species-specific pattern even for the heated samples. Focussing in PAG after removing SDS by precipitation and separation in the presence of urea and tetramethyl-urea between pH 2 and 11 showed species-specificity and a shift of protein bands which partially mirrored the increasing autolysis and degradation of the samples during storage.

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Verwendete Abkürzungen PAA Polyacrylamid - PAGE Polyacrylamidgelelektrophorese - PAGIF Polyacrylamidgelisoelektrische Focussierung - SDS Natrium(Sodium)-dodecylsulfat - ME 2-Mercapto-ethanol - Tris Tris-(hydroxymethyl)aminomethan - kD Kilo-Dalton (Einheit für scheinbares Molekular-Gewicht)     

Psychological,social and cognitive characteristics of high-risk drivers: A pilot study

A battery of short tests was administered to 30 young drivers who reported being involved in three or more accidents during the past three years and to 30 drivers who had no accident history but were matched for age, sex and exposure to driving. The high accident group scored higher on measures of personal maladjustment, social maladjustment, and to a lesser extent on measures of impulsivity and information processing deficiency. A discriminant function based on data for 46 drivers in the original sample was able to predict at 86% accuracy the group membership for seven additional high accident drivers and seven matched controls on the basis of the test scores. Implications for a theory of human accident involvement were discussed.     

Verwendung von Ersatzkörnungen und Wirkradien bei Untersuchungen der Reduzierbarkeit von Eisenerzen

Ermittlung von Ersatzkörnungen von Erzen mit Hilfe einer Körnungsaustauschgleichung. Vergleich der Ergebnisse nach diesem Verfahren mit Versuchsergebnissen. Verbesserung der Aussagegenauigkeit durch Einführen von Wirkradien. Ableitung von Gleichungen zur Ermittlung der Wirkradien aus der Siebkorngröße und dem Kornvolumen.