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Aluminium
Terms modified by Aluminium Selected AbstractsPseudomonas fluorescens orchestrates a fine metabolic-balancing act to counter aluminium toxicityENVIRONMENTAL MICROBIOLOGY, Issue 6 2010Joseph Lemire Summary Aluminium (Al), an environmental toxin, is known to disrupt cellular functions by perturbing iron (Fe) homeostasis. However, Fe is essential for such metabolic processes as the tricarboxylic acid (TCA) cycle and oxidative phosphorylation, the two pivotal networks that mediate ATP production during aerobiosis. To counter the Fe conundrum induced by Al toxicity, Pseudomonas fluorescens utilizes isocitrate lyase and isocitrate dehydrogenase-NADP dependent to metabolize citrate when confronted with an ineffective aconitase provoked by Al stress. By invoking fumarase C, a hydratase devoid of Fe, this microbe is able to generate essential metabolites. To compensate for the severely diminished enzymes like Complex I, Complex II and Complex IV, the upregulation of a H2O-generating NADH oxidase enables the metabolism of citrate, the sole carbon source via a modified TCA cycle. The overexpression of succinyl-CoA synthetase affords an effective route to ATP production by substrate-level phosphorylation in the absence of O2. This fine metabolic balance enables P. fluorescens to survive the dearth of bioavailable Fe triggered by an Al environment, a feature that may have potential applications in bioremediation technologies. [source] Incorporation of Aluminium and Iron into the Zeolite MCM-58EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 6 2005Gabriela Ko Abstract The hydrothermal synthesis of zeolite MCM-58 is investigated with N -benzylquinuclidinium bromide as a structure-directing agent in order to isomorphously substitute aluminium or iron for silicon. Al-MCM-58 was synthesised in a wide range of nSi/nAl ratios (from 19 to 56), and Fe-MCM-58 was successfully prepared in a narrower range of nSi/nFe ratios (from 18 to 36). The obtained products were characterised by XRD, SEM, 27Al MAS NMR, 29Si MAS NMR, FTIR, and ESR spectroscopy. Two different calcination procedures, viz. in a stream of nitrogen and air or in a stream of ammonia, were used in order to modify the acid sites in the zeolite. FTIR spectroscopy before and after the adsorption of [D3]acetonitrile and pyridine was employed to determine the concentration and type of the acid sites. The acid forms of Al(Fe)-MCM-58 are characterised by the vibrations of bridging Si,OH,Al(Fe) groups at 3628 cm,1 and 3564 cm,1 (Al-MCM-58) or 3646 cm,1 and 3520 cm,1 (Fe-MCM-58). The acid sites of both zeolites Al-MCM-58 and Fe-MCM-58 are accessible for [D3]acetonitrile and pyridine, and all materials contain substantial numbers of Lewis sites (Al-MCM-58: 50,% of the total acid sites; Fe-MCM-58: 90,%) over the whole range of nSi/nAl (nSi/nFe) ratios studied. Only a small increase in the concentration of Brønsted acid sites was achieved after calcination of the as-synthesised samples in a flow of ammonia. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Transformation of haematite and Al-poor goethite to Al-rich goethite and associated yellowing in a ferralitic clay soil profile of the middle Amazon Basin (Manaus, Brazil)EUROPEAN JOURNAL OF SOIL SCIENCE, Issue 5 2005E. Fritsch Summary The red and yellow colours of ferralitic soils in the tropics have for long intrigued pedologists. We have investigated the upward yellowing in a 10-m thick profile representative of the Ferralsols of the plateaux of the Manaus region of Brazil. We determined changes in the nature and crystal chemistry of their Fe oxides by optical and Mössbauer spectroscopy as well as Rietveld refinement of X-ray diffraction patterns. We attribute the upward yellowing of the soil to a progressive transformation of the Fe oxides at nearly invariant iron contents. Aluminium in contrast is strongly mobilized in the uppermost clay-depleted topsoil where there is preferential dissolution of kaolinite and crystallization of gibbsite. Haematite decreases from 35 to 10% of the Fe oxides from the bottom to the top of the profile and the particles become smaller (75,10 nm). Its Al for Fe-substitution remains almost unchanged (10,15 mol %). The average Al-substitution rate of goethite increases from 25 to 33 mol %, and its mean crystal diameter remains in the range 20,40 nm. The proportion of Al-rich goethite (33 mol %) increases at the expense of less Al-substituted Fe oxides (haematite and goethite). This conversion with restricted transfer of iron means that the amount of Al stored in Fe oxides gradually increases. Kaolinite, haematite and Al-poor goethite are thus witnesses of earlier stages of ferralitization of the soil. In contrast, Al-rich goethite and gibbsite initiate the alitization (or bauxitization) of the soil. They correspond to the last generation of soil minerals, which most likely reflects the present-day weathering conditions. The progressive replacement of kaolinite, haematite and Al-poor goethite by new generations of Al-rich goethite and gibbsite attests to greater activities of water and aluminium and smaller activity of aqueous silica in the topsoil than in the subsoil. We interpret this as a consequence of longer periods of wetting in the topsoil that could result from soil aging, more humid climate or both. [source] Process Shrinkage and Accuracy during Indirect Laser Sintering of Aluminium,ADVANCED ENGINEERING MATERIALS, Issue 4 2006B. Sercombe In this paper we have investigated the shrinkage and accuracy of indirect selective laser sintered aluminium. The majority of the ,1.2-1.4% linear shrinkage occurs during the infiltration of the skeleton structure. By optimising scale and offset parameters during selective laser sintering of the preforms, accuracy similar to that of casting processes can be achieved. [source] Enhanced Strength and Ductility in Ultrafine-Grained Aluminium Produced by Accumulative Roll Bonding,ADVANCED ENGINEERING MATERIALS, Issue 9 2004H.W. Höppel Due to a printing error in the Adv. Eng. Mater. 2004, 6, issue 4, this article, originally published on pages 219,222, had to be reprinted. Now the correct references are given to allow all readers the correct access to the literature. The editorial team apologizes for any inconveniences this may have caused. [source] The influence of porosity on the fatigue strength of high-pressure die cast aluminiumFATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 5 2006J. LINDER ABSTRACT Aluminium is a lightweight material with high strength and good corrosion resistance among other beneficial properties. Thanks to these properties, aluminium is more extensively used in the vehicle industry. High-pressure die casting of aluminium is a manufacturing process that makes it possible to attain complex, multi-functional components with near-net shape. However, there is one disadvantage of such castings, that is, the presence of various defects such as porosity and its effect on mechanical properties. The aim of this work was to investigate the influence of porosity on the fatigue strength of high-pressure die cast aluminium. The objective was to derive the influence of defect size with respect to the fatigue load, and to generate a model for fatigue life in terms of a Kitagawa diagram. The aluminium alloy used in this study is comparable to AlSi9Cu3. Specimens were examined in X-ray prior to fatigue loading and classified with respect to porosity level and eventually fatigue tested in bending at the load ratio, R, equal to ,1. Two different specimen types with a stress concentration factor of 1.05 and 2.25 have been tested. It has been shown that the fatigue strength decreases by up to 25% as the amount of porosity of the specimen is increased. The results further showed that the influence of defects was less for the specimen type with the higher stress concentration. This is believed to be an effect of a smaller volume being exposed to the maximum stress for this specimen type. A Kitagawa diagram was constructed on the basis of the test results and fracture mechanics calculations. A value of 1.4 Mpa m1/2 was used for the so-called stress intensity threshold range. This analysis predicts that defects larger than 0.06 mm2 will reduce the fatigue strength at 5 × 106 cycles for the aluminium AlSi9Cu3 material tested. [source] Incidence of Phytophthora species in oak forests in Austria and their possible involvement in oak declineFOREST PATHOLOGY, Issue 3 2003Y. Balci Summary A survey on the occurrence of Phytophthora species in oak ecosystems in Austria was conducted from April to May 1999 and in June 2000. The investigations were carried out at 35 study sites distributed throughout the zone of oak forests in eastern Austria. Four oak species, including Quercus robur, Q. petraea, Q. cerris and Q. pubescens were considered in the survey. Rhizosphere soil samples were taken from sample trees, which consisted of healthy and declining trees as indicated by their crown transparency. Young oak leaflets were used as baits to recover Phytophthora species. The assemblage of Phytophthora spp. detected in Austrian oak forests consisted of five species, including Phytophthora quercina, P. citricola, P. gonapodyides, P. europaea and P. syringae. P. quercina and P. citricola were isolated from 11 and seven sites, respectively, and were thus the most common and most widely distributed species. The three other species were recovered only sporadically. P. citricola could be separated into two morphologically and genetically well-characterized types (A and B). Phytophthora species, in particular the common P. quercina and P. citricola occurred on sites showing a wide variety of soil types, soil textures and moisture classes. There was mild evidence for connection between deteriorating crown status and the presence of Phytophthora spp. Furthermore, significant differences in contents of magnesium, as well as calcium, aluminium, nitrogen and carbon at different soil depths (0,10, 10,20 and 20,40 cm) were detected between Phytophthora -infested and Phytophthora -free sites. The results of the present study provide circumstantial evidence that Phytophthora species are involved in oak decline at certain sites in Austria. Résumé Une prospection des espèces de Phytophthora dans les écosystèmes de chênaie a été réalisée en Autriche en avril-mai 1999 et en juin 2000. Les recherches ont été conduites dans 35 sites répartis dans l'ensemble des chênaies de l'est de l'Autriche. Quatre espèces de chênes ont été prises en considération: Quercus robur, Q. petraea, Q. cerris et Q. pubescens. Des échantillons de sol rhizosphérique ont été prélevés au pied d'arbres sains ou dépérissants, jugés d'après la transparence de leur houppier. De jeunes feuilles de chênes ont été utilisées comme piège. Les Phytophthora spp. détectés dans les chênaies autrichiennes appartenaient à cinq espèces : P. quercina, P. citricola, P. gonapodyides, P. europaea et P. syringae. Phytophthora quercina et P. citricola ont été isolés dans 11 et 7 sites respectivement; ils étaient les plus fréquents et les plus largement répandus. Les trois autres espèces n'ont été trouvées que sporadiquement. Chez P. citricola, deux types (A et B) ont pu être distingués, morphologiquement et génétiquement différents. Les espèces de Phytophthora, en particulier P. quercina et P. citricola,étaient présents dans des sites très variés pour les types de sol, leur texture et l'humidité. Phythophthora spp. tendaient àêtre plus fréquemment présents en lien avec la détérioration des houppiers. Par ailleurs, des différences significatives ont été trouvées entre les sites avec ou sans Phytophthora, pour les teneurs en magnésium ainsi qu'en calcium, aluminium, azote et carbone à différentes profondeurs du sol (0,10, 10,20 et 20,40 cm). Les résultats montrent que des espèces de Phytophthora sont impliquées dans le dépérissement des chênes dans certains sites en Autriche. Zusammenfassung Im Rahmen einer breit angelegten Erhebung wurde im April und Mai 1999 sowie im Juni 2000 das Auftreten von Phytophthora -Arten in Eichenwaldökosystemen in Österreich untersucht. Die Erhebungen wurden an 35 Standorten durchgeführt, die über das gesamte natürliche Eichenwaldvorkommen in Ostösterreich verteilt waren. In die Untersuchung wurden die vier Eichenarten Quercus robur, Q. petraea, Q. cerris und Q. pubescens einbezogen. Von jeder , anhand ihres Kronenzustands als gesund bzw. krank eingestuften , Eiche wurden Bodenproben entnommen und aus diesen mittels ,Eichenblatt'-Ködermethode die Phytophthora -Arten isoliert. Das Spektrum der in Österreich isolierten Phytophthora -Arten umfasste die 5 Arten Phytophthora quercina, P. citricola, P. gonapodyides, P. europaea und P. syringae. P. quercina und P. citricola wurden von 11 bzw. 7 der untersuchten Standorte isoliert und waren somit die häufigsten und am weitesten verbreiteten Arten. Die drei anderen Phytophthora -Arten traten hingegen nur sporadisch auf. Innerhalb von P. citricola konnten anhand morphologischer und genetischer Merkmale 2 Typen (Typ A und Typ B) unterschieden werden. Phytophthora -Arten, insbesondere die häufig nachgewiesenen Arten P. quercina und P. citricola wurden an Standorten mit den unterschiedlichsten Bodentypen, -textur und -feuchteklassen nachgewissen. Es wurde ein schwach signifikanter Zusammenhang zwischen dem sich verschlechternden Kronenzustand und dem Vorhandensein von Phytophthora nachgewissen. Darüber hinaus unterschieden sich Phytophthora -infizierte und Phytophthora -freie Standorte in verschiedenen Bodentiefen (0,10, 10,20 und 20,40 cm) signifikant in ihren Magnesium, Kalzium, Aluminium, Stickstoff und Kohlenstoff-Gehalten. Die Ergebnisse der vorliegenden Studie lassen den Schluss zu, dass Phytophthora -Arten an einigen Untersuchungsstandorten in Österreich am Eichensterben beteiligt sind. [source] Concentration of aluminium in breast cyst fluids collected from women affected by gross cystic breast diseaseJOURNAL OF APPLIED TOXICOLOGY, Issue 1 2009Ferdinando Mannello Abstract Gross cystic breast disease (GCBD) is the most common benign breast disorder, but the molecular basis of cyst formation remains to be identified. If the use of aluminium-based antiperspirant salts is involved in the etiology of gross breast cyst formation, it might be expected that aluminium would be at elevated levels in human breast cyst fluid (BCF). Aluminium was measured by ICP-MS in 48 samples of BCF, 30 samples of human blood serum and 45 samples of human breast milk at different stages of lactation (colostrum, intermediate, mature). The median level of aluminium in apocrine type I BCF (n = 27, 150 µg l,1) was significantly higher than in transudative type II BCF (n = 21, 32 µg l,1; P <0.0001). By comparison, aluminium measurements gave a median concentration of 6 µg l,1 in human serum and 25 µg l,1 in human breast milk, with no difference between colostrum, intermediate and mature milk. Levels of aluminium were significantly higher in both types of BCF than in human serum (P <0.0001). However when compared with human breast milk, aluminium levels were only significantly higher in apocrine type I BCF (P <0.0001) and not in transudative type II BCF (P = 0.152). It remains to be identified why such high levels of aluminium were found in the apocrine type I BCF and from where the aluminium originated. However, if aluminium-based antiperspirants are found to be the source and to play any causal role in development of breast cysts, then it might become possible to prevent this common breast disorder. Copyright © 2008 John Wiley & Sons, Ltd. [source] Laser-MIG-Hybridfügen von Aluminium-Stahl LeichtbaustrukturenLASER TECHNIK JOURNAL, Issue 4 2007Neues Fügeverfahren verspricht Effizienzgewinn Im Fahrzeugbau wird derzeit der Einsatz von hybriden Strukturelementen aus artungleichen Werkstoffen intensiv diskutiert. Ziel ist es dabei, Gewichtsreduktionen zu erreichen und gleichzeitig die mechanischen Eigenschaften zu erhalten oder zu verbessern. Das Fügen von Aluminium- mit Stahl-Legierungen ist dabei besonders interessant für den Fahrzeugbau, aber auch für den Schiffbau. [source] Novel Nanosized Aluminium Carboxylates: Synthesis, Characterization and Use as Nanofillers for Protective Polymeric CoatingsMACROMOLECULAR MATERIALS & ENGINEERING, Issue 1 2007Hans-Jürgen Gläsel Abstract A mixture of novel aluminium carboxylate nanoparticles and aluminium hydroxide ultrafine powder was prepared via precipitation reaction between Al(2-PrO)3 and maleic acid. In this mixture both free primary particles occur (mean geometrical size around 40 nm) together with a secondary agglomerated particle fraction of sizes in the low micrometer region. However, centrifugation processes allowed for the removal of the latter and resulted in the formation of size stable nanopowders. Up to 30 wt.-% of these particles were incorporated into acrylate matrices resulting in low-viscosity formulations with [,],<,1,000 mPa,·,s, which allowed for roller application and even spray coating of these nanocomposites at room temperature. Radiation curing of such coatings was accomplished via UV irradiation. In comparison to the corresponding SiO2 -based nanocomposites and carboxylate alumoxane fillers, the cured coatings revealed significantly improved surface mechanical properties. [source] A new austenitic alumina forming alloy: an aluminium-coated FeNi32Cr20MATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 6 2008H. Hattendorf Abstract The FeCrAl alloys owe their low oxidation rate to the formation of a slow growing , -aluminium oxide scale. Therefore they are used, for example, as a substrate material in metal-supported automotive catalytic converters. Increasing exhaust gas temperatures mean that, in addition to the oxidation properties, high temperature mechanical properties should also be improved. Compared to the ferritic FeCrAl alloys, austenitic alloys possess the required high mechanical strength at higher temperatures. However for most commercially available materials the oxidation resistance is not sufficient due to a low aluminium content. High aluminium contents are avoided in austenitic alloys, since they cause severe workability problems, even at aluminium contents, which are below the necessary amount to get a pure alumina scale. The newly developed material Nicrofer 3220 PAl (coated FeNiCrAl) consists of an austenitic FeNi32Cr20 alloy coated with aluminium on both sides. It combines the outstanding oxidation resistance of an alumina forming FeCrAl alloy with the advantage of the high temperature strength of an austenitic alloy. Additionally the oxidation is even lower than the oxidation of the commercial grade Aluchrom YHf (FeCr20Al6),conventional homogenous FeCrAl. Aluminium coated FeNiCrAl can easily be formed into its final shape. Prior to service, an in situ heat treatment is recommended in order to optimize the properties. [source] Impedance measurements on oxide films on aluminium obtained by pulsed tensionsMATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 1 2003K. Belmokre Anodisation; Elektrochemische Impedanzspektroskopie (EIS); pulsierende Spannung; Alterung von Oxidfilmen Abstract We have performed this study on oxide films sealed or not in boiling water. The films are first obtained on type 1050 A aluminium substrat by pulsed tensions anodizing technique, in a sulfuric acid solution. Afterwards the, Electrochemical Impedance Spectroscopy (EIS) is employed to appreciate the films behaviour in a neutral solution of 3.5% K2SO4, in which the interface processes interest only the ageing phenomenon of the oxide films and not their corrosion. We have also attempted a correlation between pulse parameters of anodization and the electrical parameters characterizing these films. The sealing influence on ageing has been studied as well. For all films, ageing is appreciated using impedance diagrams evolution versus time. The results show: , the existence of two capacitive loops confirming the presence of two oxide layers characteristic of oxide films obtained in a sulfuric acid medium. The first loop, at high frequencies, is related to the external porous layer and the second one, at lower freqencies, is related to the internal barrier layer. , the thickness of the barrier layer varies between 25 and 40 nm in relation with the electrical pulse parameters. , the sealing acts favorably against anodic oxide films ageing. Impedanzmessungen an durch pulsierende Spannung erzeugten Oxidfilmen auf Aluminium Die vorliegenden Untersuchungen wurden an versiegelten und nicht versiegelten Oxidfilmen in kochendem Wasser durchgeführt. Die Filme wurden zuerst auf Aluminiumsubstrat des Typs 1050A durch anodische Technik mit pulsierender Spannung in einer Schwefelsäurelösung erzeugt. Anschließend wurde die elektrochemische Impedanzspektroskopie eingesetzt, um das Filmverhalten in einer neutralen 3,5% K2SO4 -Lösung zu beurteilen, wobei bezüglich der Grenzflächenprozesse nur das Alterungsphänomen der Oxidfilme und nicht ihr Korrosionsverhalten interessierte. Es wurde versucht, eine Korrelation zwischen den Pulsparametern der Anodisierung und den elektrischen Parametern, die diese Filme charakterisieren, zu finden. Ebenfalls wurde der Versiegelungseinfluss auf die Alterung untersucht. Für alle Filme wurde die Alterung mit Hilfe der Entwicklung von Impedanzdiagrammen über die Zeit beurteilt. Die Ergebnisse zeigen: , die Existenz von zwei kapazitiven Schleifen, die die Anwesenheit von zwei Oxidschichten bestätigen, was charakteristisch ist für Oxidfilme, die in einer Schwefelsäurelösung erzeugt wurden. Die erste Schleife, bei hohen Frequenzen, bezieht sich auf die äußere poröse Schicht und die zweite, bei niedrigeren Frequenzen, bezieht sich auf die innere Barriereschicht , die Dicke der Barriereschicht variiert zwischen 25 und 40 nm, abhängig von den elektrischen Pulsparametern , die Versiegelung wirkt günstig gegenüber der Alterung des anodischen Oxidfilms. [source] Theoretical and experimental analysis of plastic response of isotropic circular plates subjected to underwater explosion loadingMATERIALWISSENSCHAFT UND WERKSTOFFTECHNIK, Issue 2 2008J. Z. Ashani Abstract Dynamic response analysis of structures subjected to underwater explosion (UndEx) loading has been always an interesting field of study for ship designers and metal forming specialists. Understanding the deformation and rupture mechanism of simple structures plays an important role in successful designing of a reliable structure under this kind of loading. In this paper, first the major parameters of the UndEx phenomenon (peak overpressure, impulse per unit area, dimensionless damage parameter ,, etc.) are discussed and determined by means of available experimental relations mostly offered by R. Cole. After that, the maximum deflection of a fully clamped circular plate has been calculated using a theoretical procedure assuming two different conditions: (1) neglecting the effect of strain rate, (2) considering the strain rate sensitivity of the material. Some experiments have been conducted on 5010 aluminum circular plates, using C4 as explosive. In order to simulate reality, a fixture was designed so that the plates are loaded in air-backed condition. Plates were fixed on top of the fixture, so the fully clamped condition which was assumed as the boundary condition was achieved. The test specimens were measured, not only their maximum deflection but also their thickness at different radii were determined. The results are compared to experimental-based predictions offered by Nurick and Rajendran who has conducted similar experiments. The results show reasonable agreement with theoretical predictions, especially when strain rate effects are considered. In addition, two new material constants (D, q) for this special aluminum alloy are introduced. Theoretische und experimentelle Analyse der plastischen Umformung isotroper kreisförmiger Platten bei Unterwasser-Explosionsbelastung Die Analyse der dynamischen Reaktion einer Struktur bei einer Explosionsbelastung unter dem Wasser ist für die Konstrukteure von Schiffen und Umformspezialisten eine interessante Forschungsaufgabe. Das Verständnis der Umformung und der Bruchmechanismen einfacher Strukturen spielt eine wichtige Rolle im erfolgreichen Konstruieren einer festen Struktur gegen diese Belastungsart. In diesem Beitrag werden erstens die Hauptparameter der Explosionserscheinung unter Wasser (maximaler Druck, Impulse per Flächeneinheit, dimensionsloser zerstörender Parameter usw.) dargestellt und zweitens durch die vorhandenen Methoden, die überwiegend von R. Cole vorliegen, berechnet. Danach ist die maximale Durchbiegung einer ganz gespannten kreisförmigen Platte durch eine analytische Methode in zwei Formen bestimmt worden: (1) Vernachlässigung der Dehnungsgeschwindigkeit, (2) Berücksichtigung der Dehnungsgeschwindigkeitsempfindlichkeit des Werkstoffes. Einige Untersuchungen wurden an kreisförmigen Platten aus Aluminium 5010 mittels Sprengstoff C4 durchgeführt. Zur Praxissimulation wurde die Spannvorrichtung so konstruiert, so dass die Platten Luft-gepuffert belastet wurden. Die Platten wurden oben auf der Spannvorrichtung vollständig eingespannt, um Grenzbedingungen zu erhalten. Bei den Proben wurde nicht nur die maximale Durchbiegung sondern auch die Dicke in verschiedenen Radien ermittelt. Die Ergebnisse wurden mit den experimentellen Abschätzungen von Nurick und Rajendran, die ähnliche Versuche durchgeführt haben, verglichen. Die Ergebnisse zeigen eine gute Übereinstimmung mit den theoretischen Abschätzungen, insbesondere bei Betrachtung der Dehngeschwindigkeit. Zusätzlich wurden für diese spezielle Aluminiumlegierung zwei neue Materialkonstanten (D, q) eingeführt. [source] Fortschritte beim Rührreibschweißen von Aluminium, Magnesium und StahlMATERIALWISSENSCHAFT UND WERKSTOFFTECHNIK, Issue 9 2006S. Sheikhi Dr.-Ing. Friction Stir Welding; Aluminium; Magnesium; Steel; Tailored welded blanks Abstract Das Rührreibschweißen (Friction Stir Welding (FSW)) stellt einen innovativen Schweißprozess zum Fügen von Leichtmetallen insbesondere von Aluminiumlegierungen dar. Die Herstellung von Aluminiumverbindungen mit konventionellen Schmelzschweißverfahren erfüllt nicht immer und nicht bei jeder Legierung die von der Industrie gestellten Qualitätsanforderungen. Das Rührreibschweißen stellt eine Alternative zu den Schmelzschweißverfahren dar. Die entstehenden Schweißnähte weisen gute mechanische Eigenschaften auf, das Verfahren ist robust und seine Reproduzierbarkeit sehr gut. Im Rahmen dieser Arbeit wird der Einsatz des Rührreibschweißens zum Fügen von Aluminium- und Magnesiumlegierungen erläutert. Dabei werden artgleiche und artungleiche Verbindungen und deren mechanische Eigenschaften beschrieben. Das Rührreibschweißen von Stahl mit seinen besonderen Anforderungen an das Schweißwerkzeug wird ebenfalls vorgestellt. Progresses on the friction stir welding of aluminium, magnesium and steel Friction Stir Welding (FSW) represents an innovative welding process for joining light metal, especially, aluminium and its alloys. Friction Stir Welding offers an attractive alternative to conventional fusion welding processes because of the excellent properties (particularly ductility), reproducibility, robustness, and surface finish obtained with the process. Within the scope of this work the Friction Stir Welding-Process with its possible joint configurations is explained. The focus of this work concentrates on weldability studies concerning cladded aluminium alloys, aluminium cast alloys, aluminium tailored welded blanks both from similar and dissimilar joints produced in aluminium, magnesium and steel. The mechanical properties of the welded samples will be discussed. [source] Aluminium per se and in the anti-acid drug sucralfate promotes sensitization via the oral routeALLERGY, Issue 6 2009R. Brunner Background:, Aluminium (ALUM) is used as experimental and clinical adjuvant for parenteral vaccine formulation. It is also contained in anti-acid drugs like sucralfate (SUC). These anti-acids have been shown to cause sensitization to food proteins via elevation of the gastric pH. The aim of this study was to assess the oral adjuvant properties of ALUM, alone or contained in SUC, in a BALB/c mouse model. Methods:, Mice were fed SUC plus ovalbumin (OVA) and compared with groups where ALUM or proton pump inhibitors (PPI) were applied as adjuvants. The humoral and cellular immune responses were assessed on antigen-specific antibody and cytokine levels. The in vivo relevance was investigated in skin tests. Results:, The highest OVA-specific immunoglobulin G1 (IgG1) and IgE antibody levels were found in mice fed with OVA/SUC, followed by OVA/ALUM-treated animals, indicating a T helper 2 (Th2) shift in both groups. Antibody levels in other groups revealed lower (OVA/PPI-group) or baseline levels (control groups). Positive skin tests confirmed an allergic response in anti-acid or adjuvant-treated animals. Conclusions:, Our data show for the first time that ALUM acts as a Th2-adjuvant via the oral route. This suggests that orally applied SUC leads to an enhanced risk for food allergy, not only by inhibiting peptic digestion but also by acting as a Th2-adjuvant by its ALUM content. [source] Cytological and enzymatic responses to aluminium stress in root tips of Norway spruce seedlingsNEW PHYTOLOGIST, Issue 3 2004Nina Elisabeth Nagy Summary ,,Aluminium (Al) stress reduces plant growth. However, some species such as Norway spruce (Picea abies) seem to tolerate high Al concentrations. The aim of this study was to investigate characteristics possibly involved in Al tolerance in Norway spruce seedlings. ,,Seedlings (10-d-old) were exposed to Al3+ concentrations of 0.5 and 5 mm for up to 168 h. The effect of Al stress on root growth, cell morphology and Al distribution, callose production, and peroxidase and chitinase activity was analysed. ,,Root growth decreased after 1 d and 2 d with 5 and 0.5 mm Al, respectively. Callose concentration increased strongly after 6 h treatment with 5 mm Al. The activity of many peroxidase and chitinase isoforms decreased after 1,24 h exposure of both treatments. Several isoforms increased after 48,168 h exposure to 5 mm Al. ,,We postulate that, with external Al concentrations 0.5 mm or lower, an increased production above constitutive levels of peroxidase or chitinase is not required for Al tolerance in young Norway spruce seedlings. High constitutive levels of peroxidase and chitinase in this species may be part of this Al tolerance. [source] Pressurised partnership: a case of perishable compromise in contested terrainNEW TECHNOLOGY, WORK AND EMPLOYMENT, Issue 3 2008Jean Jenkins This paper analyses the life cycle of a partnership agreement in the context of managerially driven changes to work organisation at an aluminium manufacturing plant (Aluminium) located in South Wales, UK. The paper highlights the contingent, context-specific nature of workplace partnerships and their limited influence and vulnerability to the operation of the market. [source] Packaging materials for fermented milk: effects of material crystallinity and polarity on food qualityPACKAGING TECHNOLOGY AND SCIENCE, Issue 3 2001S. E. A. Jansson Abstract The ability of a packaging material to protect the food product and extend its shelf-life depends on several material properties. In this work the effects of material crystallinity and polarity on the quality of fermented milk were studied. The fermented milk is a high-quality Swedish product, similar to yoghurt. The quality of the food product was determined as a function of storage time by containing the liquid in pouches of different materials. The material crystallinity was varied by using very low-density polyethylene, high-density polyethylene and aluminium laminate as packaging materials. Aluminium was used on account of its ,100%' gas-tightness. The polarity was varied by comparing an aliphatic polyketone with polyethylene of similar crystallinity. The carbon dioxide (CO2) and oxygen (O2) contents in the headspace of the pouches were determined. The food quality was determined by measuring whey syneresis, viscosity and the content of desired Bifidobacteria, as well as of undesired yeast and mould. A trained taste panel determined the degree of acidity and of the sparkling taste. It was found that the content of CO2 increased and that of O2 decreased in the pouches with increasing degree of crystallinity and increasing polarity. The sparkling taste of fermented milk was a clear function of the headspace CO2 content. The data presented here could thus be used to ,design' a package for a desired sparkling taste of the fermented milk by selecting a certain material crystallinity. Whey syneresis, viscosity and content of Bifidobacteria were found to be independent of pouch material. While the degree of whey syneresis and the viscosity increased with increasing storage time, the content of Bifidobacteria slowly decreased. The content of yeast and mould in the liquid was below the existing limit values for foodstuffs. The degrees of acidity and sparkling taste were highest for the liquids contained in aluminium and polyketone pouches, although the differences in acidulous taste between the various pouch materials were small. Copyright © 2001 John Wiley & Sons, Ltd. [source] Spatial coordination of aluminium uptake, production of reactive oxygen species, callose production and wall rigidification in maize rootsPLANT CELL & ENVIRONMENT, Issue 7 2006D. L. JONES ABSTRACT Aluminium (Al) toxicity associated with acid soils represents one of the biggest limitations to crop production worldwide. Although Al specifically inhibits the elongation of root cells, the exact mechanism by which this growth reduction occurs remains controversial. The aim of this study was to investigate the spatial and temporal dynamics of Al migration into roots of maize (Zea mays L.) and the production of the stress response compound callose. Using the Al-specific fluorescent probe morin, we demonstrate the gradual penetration of Al into roots. Al readily accumulates in the root's epidermal and outer cortical cell layers but does not readily penetrate into the inner cortex. After prolonged exposure times (12,24 h), Al had entered all areas of the root apex. The spatial and temporal accumulation of Al within the root is similarly matched by the production of the cell wall polymer callose, which is also highly localized to the epidermis and outer cortical region. Exposure to Al induced the rapid production of reactive oxygen species and induced a significant rigidification of the cell wall. Our results suggest that Al-induced root inhibition in maize occurs by rigidification of the epidermal layers. [source] Atmospheric Pressure Plasma Deposition of Adhesion Promotion Layers on AluminiumPLASMA PROCESSES AND POLYMERS, Issue S1 2009Philipp Bringmann Abstract The paper presents investigations on the deposition of plasma polymerised films at atmospheric pressure as a pretreatment for painting and adhesive bonding of aircraft aluminium structures. Two different plasma jet sources are employed, one based on a controlled arc discharge and air as process gas, and another based on a dielectric barrier discharge (DBD) and He as plasma gas. The organosilicon precursors HMDSO, TEOS and OMCTS are used with both plasma sources. Deposition in the arc discharge plasma jet leads to almost carbon-free silica coatings, whereas coatings deposited with the DBD jet source contain a high amount of carbon, varying with precursor type. The obtained results of corrosion investigations and adhesion tests are promising, as some representative aircraft industry requirements could be achieved. However, the investigations show a strong dependency on the used precursor and type of polymer (paint or adhesive) applied on the plasma polymerised film. [source] Detonation and Blast Wave Characteristics of Nitromethane Mixed with Particles of an Aluminium,Magnesium AlloyPROPELLANTS, EXPLOSIVES, PYROTECHNICS, Issue 2 2010Waldemar Abstract Investigation of detonation parameters, blast wave characteristics and quasi-static pressures (QSPs) for the mixtures of nitromethane and particles of an aluminium and magnesium (Al3Mg4) alloy was carried out. The mixtures of gelled nitromethane containing 15,60,wt.-% AlMg alloy were tested. Detonation velocity and Gurney energy were determined. Parameters of blast waves produced by charges of the investigated explosives were measured. QSP measurements were conducted in a steel chamber of 0.15,m3 volume filled with air. Thermochemical and gasdynamical calculations were also performed. The degree of combustion of the metallic addition with the gaseous products during detonation and expansion is discussed. [source] Perturbations produced by electrospray ionization mass spectrometry in the speciation of aluminium(III)/1,6-dimethyl-4-hydroxy-3-pyridinecarboxylate aqueous solutionsRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 7 2010Valerio B. Di Marco Electrospray ionization mass spectrometry (ESI-MS) is very often employed to study metal/ligand equilibria in aqueous solution. However, the ionization process can introduce perturbations which affect the speciation results in an unpredictable way. It is necessary to identify these perturbations in order to correctly interpret the ESI-MS speciation results. Aluminium(III)/1,6-dimethyl-4-hydroxy-3-pyridinecarboxylate (DQ716) aqueous solutions at various pH were analysed by ESI-MS, and speciation results were compared with those obtained by equilibrium techniques. Differences observed were both qualitative and quantitative. The ESI-MS spectral changes due to different settings of the following instrumental parameters were analyzed: the solution flow rate (FS), the nebulizer gas flow rate (FG), the potential applied at the entrance capillary (EC), and the temperature of the drying gas (TG). The effects produced by FS and EC on the spectra strongly suggest the key role of surface activity in determining the relative fraction of the ions reaching the detector. The experimental effects of FS and TG were interpreted considering the presence of at least two reactions in the gas phase and a dimerization occurring in the droplets. These perturbations cannot be generalized because they appear to be chemical system-related and instrument-dependent. Therefore, the identification of perturbations is a required task for any metal-ligand equilibrium study performed by ESI-MS. Our results indicate that perturbations can be identified by evaluating the effects produced in the spectra by a change of instrumental parameters. Copyright © 2010 John Wiley & Sons, Ltd. [source] Direct Synthesis of 1,4-Disubstituted-5-alumino-1,2,3-triazoles: Copper-Catalyzed Cycloaddition of Organic Azides and Mixed Aluminum Acetylides,ANGEWANDTE CHEMIE, Issue 14 2010Yuhan Zhou Dr. Aluminium ,klickt" mit: Aluminotriazole resultieren aus einer vollständig chemo- und regioselektiven kupferkatalysierten Cycloaddition von organischen Aziden mit gemischten Aluminiumacetyliden. Die Kohlenstoff-Aluminium-Bindung steht anschließend für Reaktionen mit verschiedenen Elektrophilen bereit. [source] Radical Cyclization of , -Bromo Aluminum Acetals: An Easy Approach to , -Lactols,ANGEWANDTE CHEMIE, Issue 50 2009Anne Boussonnière Ringe um Aluminium: Ein effizientes Verfahren zur Radikalcyclisierung von , -Bromestern ist die hier beschriebene Reduktion der Ester mit DIBAL-H bei niedriger Temperatur zu Aluminiumacetalen, die in Gegenwart von nBu3SnH und Et3B cyclisieren (siehe Schema). Diese Eintopfumsetzung liefert polysubstituierte , -Lactole in hohen Ausbeuten, und die milden Reaktionsbedingungen ermöglichen die Synthese von säureempfindlichen Derivaten. [source] ICP,MS ANALYSIS OF GLASS FRAGMENTS OF PARTHIAN AND SASANIAN EPOCH FROM SELEUCIA AND VEH ARDA,?R (CENTRAL IRAQ)*ARCHAEOMETRY, Issue 3 2008P. MIRTI Forty-one glass fragments were analysed by inductively coupled plasma , mass spectrometry, determining 40 major, minor and trace elements, including rare earth elements. The fragments came from excavations carried out at the archaeological sites of Seleucia and Veh Arda,?r in modern Iraq, and were dated to the Parthian and Sasanian epochs. Analytical data indicate that all the samples are silica,soda,lime glasses. Magnesium and potassium oxide contents below 1% suggest that eight out of nine glasses from Seleucia, dating from between the first and the third century ad, could have been obtained by use of an evaporite as a flux; the same conclusion can be drawn for some of the Sasanian glasses dating from the fourth and fifth centuries ad. The other glasses from Veh Arda,?r, as well as the remaining sample from Seleucia, are characterized by higher contents of magnesium and potassium, which suggests recourse to plant ash; different magnesium and phosphorus contents allow one to separate these samples into two main groups, pointing to the use of different kinds of plant ash. Aluminium and calcium contents, together with trace element data, may indicate that different sands were used for preparing glasses of different composition. Samples from Seleucia and Veh Arda,?r are mainly blue,green and green to yellow,green, respectively; iron and manganese contents suggest that the furnace atmosphere was mainly responsible for the development of these hues. [source] Cyclic Carbonate Synthesis Catalysed by Bimetallic Aluminium,Salen ComplexesCHEMISTRY - A EUROPEAN JOURNAL, Issue 23 2010William Clegg Prof. Abstract The development of bimetallic aluminium,salen complexes [{Al(salen)}2O] as catalysts for the synthesis of cyclic carbonates (including the commercially important ethylene and propylene carbonates) from a wide range of terminal epoxides in the presence of tetrabutylammonium bromide as a cocatalyst is reported. The bimetallic structure of one complex was confirmed by X-ray crystallography. The bimetallic complexes displayed exceptionally high catalytic activity and in the presence of tetrabutylammonium bromide could catalyse cyclic carbonate synthesis at atmospheric pressure and room temperature. Catalyst-reuse experiments demonstrated that one bimetallic complex was stable for over 60 reactions, though the tetrabutylammonium bromide decomposed in situ by a retro-Menschutkin reaction to form tributylamine and had to be regularly replaced. The mild reaction conditions allowed a full analysis of the reaction kinetics to be carried out and this showed that the reaction was first order in aluminium complex concentration, first order in epoxide concentration, first order in carbon dioxide concentration (except when used in excess) and unexpectedly second order in tetrabutylammonium bromide concentration. Further kinetic experiments demonstrated that the tributylamine formed in situ was involved in the catalysis and that addition of butyl bromide to reconvert the tributylamine into tetrabutylammonium bromide resulted in inhibition of the reaction. The reaction kinetics also indicated that no kinetic resolution of racemic epoxides was possible with this class of catalysts, even when the catalyst was derived from a chiral salen ligand. However, it was shown that if enantiomerically pure styrene oxide was used as substrate, then enantiomerically pure styrene carbonate was formed. On the basis of the kinetic and other experimental data, a catalytic cycle that explains why the bimetallic complexes display such high catalytic activity has been developed. [source] Targeting of photosensitizers to head and neck tumours by the use of monoclonal antibodiesCLINICAL OTOLARYNGOLOGY, Issue 4 2001G.A.M.S. Van Dongen Introduction. The objective was to improve the selectivity of photodynamic therapy (PDT) by targeting photosensitizers to tumours by the use of monoclonal antibodies (mAbs). Two sensitizers were selected for this approach. Meta-tetrahydroxyphenylchlorin (mTHPC) was selected because it is one of the most effective photosensitizers in free form. Aluminium (III) phthalocyanine tetrasulphonate [AlPc(SO3H)4] was selected because of its ideal photochemical properties. However, owing to its hydrophilicity, this latter sensitizer is not able to enter the tumour cell and, therefore, in free form is ineffective in PDT. We hypothesized that AlPc(SO3H)4 might become suitable for PDT when coupled to tumour-selective mAbs. Methods. These were developed to couple the sensitizers to mAbs, including mAb 425 directed against the epidermal growth factor receptor. These conjugates were evaluated for efficacy in PDT in vitro and for tumour-targeting capacity in vivo. Results.,In vitro PDT showed that the AlPc(SO3H)4,mAb 425 conjugate was ,7500 times more toxic to A431 cells than the free sensitizer (IC50 values 0.12 nm versus 900 nm), and was also more toxic than the mTHPC,mAb 425 conjugate and free mTHPC (IC50 values 7.3 nm versus 2.0 nm). Biodistribution analysis of the conjugates in tumour-bearing nude mice showed selective accumulation in the tumour. Conclusion. These data show that AlPc(SO3H)4, in particular, has high potential for use in PDT when coupled to tumour-selective mAbs. [source] Allergic contact dermatitis from aluminium in deodorantsCONTACT DERMATITIS, Issue 1 2010Seema Garg No abstract is available for this article. [source] FS02.8 Patch testing with gold trichloride can give false test resultsCONTACT DERMATITIS, Issue 3 2004Birgitta Gruvberger Background:, Hydrochloric acid is formed in water solutions of gold trichloride. Hydrochloric acid in contact with aluminium generates hydrogen gas which can reduce and transform trivalent gold to elemental gold. Objective:, To investigate whether patch testing with aqueous gold trichloride can cause false positive (irritant) reactions in patients without contact allergy to gold and false negative reactions in patients with gold allergy. Methods:, 13 patients with and 13 patients without positive patch test reactions to gold sodium thiosulfate were tested with gold trichloride in 2 different vehicles, water and alkaline buffer, using 2 different test techniques, the Finn Chamber technique with aluminium chambers and van der Bend technique with polypropene chambers. Results:, Irritant patch test reactions were obtained with aqueous gold trichloride tested in van der Bend chambers in 10 patients without gold allergy. In gold-allergic patients no positive test reactions were obtained from aqueous gold trichloride in Finn chambers while 2 positive test reactions were obtained from gold trichloride in alkaline buffer tested in van der Bend chambers. Conclusion:, If gold trichloride is patch tested in wrong vehicle and with wrong test technique irritant test reactions may occur which can be misinterpreted as positive allergic reactions in patients without gold allergy as well as negative reactions in patients with gold allergy. [source] Characteristics of Al / p-AgGaTe2 polycrystalline thin film Schottky barrier diodeCRYSTAL RESEARCH AND TECHNOLOGY, Issue 5 2008S. S. Patel Abstract An Al/p-AgGaTe2 polycrystalline thin film schottky barrier diode have been prepared by flash-evaporation of p-AgGaTe2 onto a pre-deposited film of aluminium. The current-voltage, capacitance-voltage and photoresponse of the diode have been investigated. The important physical parameter such as barrier height of the fabricated diode was derived from these measurements. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | |||||||||||||||||||||||||||||||||||||||||||