ELECTRONICS & COMMUNICATIONS IN JAPAN, Issue 3 2009
Masahiro Minagawa
Abstract Organic electroluminescent device (OLED) was fabricated using a vacuum evaporation method and thermal properties were investigated. The OLED has an indium tin oxide (ITO)/N,N,-diphenyl- N,N,-bis(3-methylphenyl)-1,1,-biphenyl-4,4,-diamine (TPD)/tris(8-hydroxyquinoline) aluminum (Alq)/lithium fluoride (LiF)/aluminum (Al) structure. An electron-dominant device of Al/Alq/LiF/Al structure, or a hole-dominant device of ITO/TPD/Al structure was also fabricated in order to study the carrier behavior in the OLEDs. The current density versus voltage (J,V) properties with various thickness of organic layers were investigated in both electron- and hole-dominant devices, and the thermal dependence of J,V properties was observed in the devices. At room temperature, conductions in a wide current region were considered to be due to space-charge-limited current for all of the devices. Especially for the Al/Alq/LiF/Al device and the OLED, relationships were observed across a wide current region. At low temperature, tunnel currents were estimated for the ITO/TPD/Al device. For the Al/Alq/LiF/Al device and the OLED, relationships were observed across a wide current region at low temperature. © 2009 Wiley Periodicals, Inc. Electron Comm Jpn, 92(3): 24,31, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecj.10048 [source]

Aluminum(III) Porphyrins as Ionophores for Fluoride Selective Polymeric Membrane Electrodes

ELECTROANALYSIS, Issue 6 2006
Jeremy
Abstract Aluminum(III) porphyrins are examined as potential fluoride selective ionophores in polymeric membrane type ion-selective electrodes. Membranes formulated with Al(III) tetraphenyl (TPP) or octaethyl (OEP) porphyrins are shown to exhibit enhanced potentiometric selectivity for fluoride over more lipophilic anions, including perchlorate and thiocyanate. However, such membrane electrodes display undesirable super-Nernstian behavior, with concomitant slow response and recovery times. By employing a sterically hindered Al(III) picket fence porphyrin (PFP) complex as the membrane active species, fully reversible and Nernstian response toward fluoride is achieved. This finding suggests that the super-Nernstian behavior observed with the nonpicket fence metalloporphyrins is due to the formation of aggregate porphyrin species (likely dimers) within the membrane phase. The steric hindrance of the PFP ligand structure eliminates such chemistry, thus leading to theoretical response slopes toward fluoride. Addition of lipophilic anionic sites into the organic membranes enhances response and selectivity, indicating that the Al(III) porphyrin ionophores function as charged carrier type ionophores. Optimized membranes formulated with Al(III)-PFP in an o -nitrophenyloctyl ether plasticized PVC film exhibit fast response to fluoride down to 40,,M, with very high selectivity over SCN,, ClO4,, Cl,, Br, and NO3, (kpot<10,3 for all anions tested). With further refinements in the membrane chemistry, it is anticipated that Al(III) porphyrin-based membrane electrodes can exhibit potentiometric fluoride response and selectivity that approaches that of the classical solid-state LaF3 crystal-based fluoride sensor. [source]

Aluminum induces chromosome aberrations, micronuclei, and cell cycle dysfunction in root cells of Vicia faba

ENVIRONMENTAL TOXICOLOGY, Issue 2 2010
Min Yi
Abstract Aluminum (Al) exists naturally in air, water, and soil, and also in our diet. Al can be absorbed into the human body and accumulates in different tissues, which has been linked to the occurrence of Alzheimer's disease and various neurological disorders. By using Vicia cytogenetic tests, which are commonly used to monitor the genotoxicity of environmental pollutants, cytogenetic effects of aluminum (AlCl3) were investigated in this study. Present results showed that Al caused significant increases in the frequencies of micronuclei (MN) and anaphase chromosome aberrations in Vicia faba root tips exposed to Al over a concentration-tested range of 0.01,10 mM for 12 h. The frequency of micronucleated cells was higher in Al-treated groups at pH 4.5 than that at pH 5.8. Similarly, AlCl3 treatment caused a decrease in the number of mitotic cells in a dose- and pH-dependent manner. The number of cells in each mitotic phase changed in Al-treated samples. Mitotic indices (MI) decreased with the increases of pycnotic cells. Our results demonstrate that aluminum chloride is a clear clastogenic/genotoxic and cytotoxic agent in Vicia root cells. The V. faba cytogenetic test could be used for the genotoxicity monitoring of aluminum water contamination. © 2009 Wiley Periodicals, Inc. Environ Toxicol, 2010. [source]

Facile Formation of Hexacyclic [Al3O2Cl] Aluminum and Alkoxide-Bridged Titanium Complexes: Reactions of AlMe3 with [Ti(L)Cl2] [L = 2,2,-Methylenebis(6- tert -butyl-4-methylphenolato)]

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 19 2007
Dao Zhang
Abstract The titanium dichloride complex [(L)TiCl2] [L = 2,2,-methylenebis(6- tert- butyl-4-methylphenolato)] (1) reacted with trimethylaluminum (AlMe3) in a 1:2 ratio to give a trimetallic aluminum complex of the composition [(L)(AlMe2)3(,-Cl)] (2) with a symmetric six-membered ring [Al3(,2 -O)2(,2 -Cl)] and a four-coordinate aluminum center in the solid state. The reaction of 1 equiv. AlMe3 gave [(L)TiMeCl] (3), which could absorb O2 gas to afford the oxygen-insertion product [{(L)TiCl}2(,-OMe)2] (4) with a five-coordinate metal center. Upon reaction of H2L with AlMe3, the binuclear, four-coordinate adduct [{(L)AlMe}2] (5) was formed. Complex 4 supported on MgCl2 and activated with aluminum alkyls reveals high catalytic activity for ethylene polymerization to produce polymers with molecular weight distributions of ca. 3.1. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source]

A Rearrangement of Azobenzene upon Interaction with an Aluminum(I) Monomer LAl {L = HC[(CMe)(NAr)]2, Ar = 2,6- iPr2C6H3}

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 11 2005
Hongping Zhu
Abstract Reaction of LAl (1) or [LAl{,2 -C2(SiMe3)2}] (2) {L = HC[(CMe)(NAr)]2, Ar = 2,6- iPr2C6H3} with azobenzene affords a five-membered ring compound [LAl{N(H)- o -C6H4N(Ph)}] (3). In the formation of 3 a three-membered intermediate [LAl(,2 -N2Ph2)] (A) is suggested by a [1 + 2] cycloaddition reaction; A is not stable and further rearranges to 3. DFT calculations on similar compounds with modified L' {L' = HC[(CMe)(NPh)]2} show that the complexation energy of the reaction of L'Al with azobenzene to form [L'Al(,2 -N2Ph2)] is about,39 kcal,mol,1, and the best estimate of the energy difference between [L'Al(,2 -N2Ph2)] and [L'Al{N(H)- o -C6H4N(Ph)}] is,76 kcal,mol,1. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source]

Reactions of the Aluminum(I) Monomer LAl [L = HC{(CMe)(NAr)}2; Ar = 2,6- iPr2C6H3] with Imidazol-2-ylidene and Diphenyldiazomethane.

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 20 2004
A Hydrogen Transfer from the L Ligand to the Central Aluminum Atom, Formation of the Diiminylaluminum Compound LAl(N=CPh2)
Abstract The solid-state reaction of LAl and imidazol-2-ylidene at elevated temperature (120 °C) yielded the aluminum monohydride N -heterocyclic carbene adduct [{HC[C(CH2)NAr] (CMeNAr)}AlH-{CN(R)C2Me2N(R)}] [R = iPr (1), Me (2)]. Compounds 1 and 2 have been characterized by spectroscopic (IR, and 1H and 13C NMR), mass spectrometric, and elemental analyses, and 1 was further characterized by X-ray structural analysis. These experimental data indicate that the Al,H bond is formed by hydrogen migration from one of the methyl groups of the ,-diketiminato ligand backbone. The reaction of LAl with two equivalents of diphenyldiazomethane afforded the diiminylaluminum compound LAl(N=CPh2)2 (3), while an excess of diphenyldiazomethane resulted in the formation of Ph2C=N,N=CPh2. This suggests that Ph2C=N,N=CPh2 is initially generated and then reacts further by oxidative addition to yield 3. The X-ray structural analysis reveals that compound 3 contains the shortest Al,Niminyl bond among those with a four-coordinate aluminum center. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source]

Adducts of Aluminum and Gallium Trichloride with a N -Heterocyclic Carbene and an Adduct of Aluminum Trichloride with a Thione

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 20 2004
Andreas Stasch
Abstract The reactions of AlCl3 and GaCl3 with 1,3,4,5-tetramethylimidazole-2-ylidene in toluene at room temperature affords the 1:1 adducts 5 and 6, respectively. The use of a bulky N -heterocyclic carbene (NHC) in toluene/THF and AlCl3 results in the formation of an imidazolium salt 7 with the tetrachloroaluminate anion. A 1:1 adduct 8 of 1,3,4,5-tetramethylimidazole-2(3H)-thione with AlCl3 is obtained in toluene. The crystal structures of 5·0.5C7H8, 7·THF and 8 were determined. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source]

Lattice Monte Carlo and Experimental Analyses of the Thermal Conductivity of Random-Shaped Cellular Aluminum

ADVANCED ENGINEERING MATERIALS, Issue 10 2009
Thomas Fiedler
The effective thermal conductivity of open- and closed-cell aluminium foams with stochastic pore morphologies has been determined by numerical, analytical and experimental methods. A three dimensional analysis technique has been used where numerical calculation models are generated based on 3D computed tomographic (CT) reconstructions. The resulting three dimensional grid models are used for thermal Lattice Monte Carlo (LMC) analyses. The second part of this paper addresses experimental measurements of open-cell M-pore® and closed-cell Alporas® cellular aluminium. Finally, results obtained using both approaches are compared to classical analytic predictions. [source]

The Effect of the Superconducting Transition on Plastic Deformation of Ultrafine-Grained Aluminum,

ADVANCED ENGINEERING MATERIALS, Issue 1-2 2009
Yuri Estrin
Abstract In this paper, the mechanical behavior of ultrafine- and coarse-grained Al at a record low temperature of 0.52,K is presented. It is demonstrated that grain refinement by equal channel angular pressing leads to increased flow stress and to a change in the strain hardening behavior of Al at this temperature. Special emphasis is placed on the effect of the superconducting transition on the mechanical behavior in the different microstructural conditions. It is shown that the magnitude of the stress jump associated with the transition correlates with the strain hardening behavior which, in turn, is related to the microstructure of the material. [source]

Effects of aluminum on activity of Krebs cycle enzymes and glutamate dehydrogenase in rat brain homogenate

FEBS JOURNAL, Issue 10 2000
P. Zatta
Aluminum is a neurotoxic agent for animals and humans that has been implicated as an etiological factor in several neurodegenerative diseases and as a destabilizer of cell membranes. Due to its high reactivity, Al3+ is able to interfere with several biological functions, including enzymatic activities in key metabolic pathways. In this paper we report that, among the enzymes that constitute the Krebs cycle, only two are activated by aluminum: ,-ketoglutarate dehydrogenase and succinate dehydrogenase. In contrast, aconitase, shows decreased activity in the presence of the metal ion. Al3+ also inhibits glutamate dehydrogenase, an allosteric enzyme that is closely linked to the Krebs cycle. A possible correlation between aluminum, the Krebs cycle and aging processes is discussed. [source]

Spontaneous Current Oscillations during Hard Anodization of Aluminum under Potentiostatic Conditions

ADVANCED FUNCTIONAL MATERIALS, Issue 1 2010
Woo Lee
Abstract Nanoporous anodic aluminum oxide is prepared by hard anodization of aluminum under potentiostatic conditions using 0.3,M H2C2O4. Under unstirred electrolyte condition, spontaneous current oscillations are observed. The amplitude and period of these current oscillations are observed to increase with anodization time. As a consequence of the oscillatory behavior, the resulting anodic alumina exhibits modulated pore structures, in which the diameter contrast and the length of pore modulation increase with the amplitude and the period of current oscillations, respectively, and the current peak profile determines the internal geometry of oxide nanopores. The mechanism responsible for the oscillatory behavior is suggested to be a diffusion-controlled anodic oxidation of aluminum. [source]

Experimental Evidence for Grain-Boundary Sliding in Ultrafine-Grained Aluminum Processed by Severe Plastic Deformation,

ADVANCED MATERIALS, Issue 1 2006
Q. Chinh
Evidence for grain boundary sliding in ultrafine-grained aluminum after processing with equal channel angular pressing (ECAP) is presented (see Figure). Pure aluminum is used as a model material; depth sensing indentation testing and atomic force microscopy are used to measure the nature of the displacements around indentations for samples in an annealed and work-hardened condition, and after processing using ECAP. [source]

Computational approach to the blood,aluminum problem?,

INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 2 2007
Christopher Exley
Abstract Aluminum has no known function in biota and, when biologically available, is inimical to life. A key to understanding its potential toxicity in humans is its transport in blood. A consensus of opinion has identified the binding of aluminum by the iron-transport protein transferrin as the preeminent factor in the transport of aluminum in blood, although this idea has emanated from in vitro analysis of isolated blood and has never been tested in vivo. We have highlighted what we believe to be inadequacies of our present understanding of aluminum transport in blood, and we have proposed the application of computational methods to test rigorously what we have coined "the blood-aluminum problem." © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007 [source]

Mechanism of inhibition of purified leaping mullet (liza saliens) NADPH-cytochrome P450 reductase by toxic metals: Aluminum and thallium

JOURNAL OF BIOCHEMICAL AND MOLECULAR TOXICOLOGY, Issue 6 2007
Azra Bozcaarmutlu
Abstract Aluminum and thallium may reach life-threatening levels in aquatic systems in the near future because of their extensive use in various industrial fields. It is therefore important to study the mechanism of toxicity of aluminum and thallium on fish enzymes. To this aim, the effects of aluminum and thallium on the activity of purified leaping mullet (Liza saliens) cytochrome P450 reductase, an essential component of the important cytochrome P450 system, have been studied. Results indicated that both metal ions strongly inhibited the NADPH-cytochrome P450 reductase. The IC50 values of AlCl3 and TlCl3 were estimated to be 34 ,M and 3 ,M, respectively. The Lineweaver,Burk plot and Dixon plot revealed that both metal ions noncompetitively inhibited the purified mullet cytochrome P450 reductase. The Ki values of Al3+ and Tl3+ were calculated from Dixon plots as 8.9 and 5.6 ,M, respectively. The inhibitory effects of Al3+ and Tl3+ on purified cytochrome P450 reductase were partially recovered by 1 mM EDTA. Additionally, tin and magnesium were shown to have no apparent effect on purified mullet cytochrome P450 reductase. © 2007 Wiley Periodicals, Inc. J Biochem Mol Toxicol 21:340,3347, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/jbt.20200 [source]

Synthesis of Yttrium,Aluminum,Garnet Hollow Microspheres by Reverse-Emulsion Technique

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 4 2006
Minati Chatterjee
Yttrium,aluminum,garnet (YAG, Y3Al5O12) hollow microspheres were synthesized by reverse-emulsion (w/o) technique starting with aqua-based precursors of oxides. The non-ionic surfactant was used as the emulsifying agent. The gel powders were calcined at 700°,1200°C. The synthesized powders were characterized by differential thermal analysis (DTA), thermogravimetry, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The appearance of an exothermic peak at 932°C in the DTA curve revealed the crystallization of YAG, which was further confirmed by XRD and FTIR studies. SEM confirmed the formation of hollow microspheres. [source]

Critical Factors Affecting the Wettability of ,-Alumina by Molten Aluminum

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 11 2004
Ping Shen
The wetting behaviors of ,-Al2O3 single crystals with three different faces,R(0112), A(01120), and C(0001),and polycrystals (PC) by molten aluminum were studied over a wide temperature range using both a conventional and an improved sessile-drop method. The critical factors affecting the wettability, such as temperature, atmosphere, substrate surface roughness, and crystallographic orientation, and the influence from the experimental technique, were thoroughly investigated. The results show that the aluminum surface oxidation and the thickness of the oxide film have a pronounced effect on the wettability, especially at low temperatures. To eliminate this effect, the experimental temperature must be over a critical value. Vacuum favors lowering this value compared with atmosphere, and the improved sessile-drop method, particularly using an impingement-dropping mode (I-mode), helps to weaken this effect by mechanical disruption and removal of the oxide film. However, the dropping distance and the dropping force must be controlled to prevent an overspreading of the drop. The effects of the substrate surface roughness and temperature are not significant in the case of a clean aluminum surface and a fine-prepared alumina surface. On the other hand, the effect of the alumina surface crystallographic orientation is noticeable and the wettability is in the order of R > A > PC > C. The intrinsic contact angles of the Al/,-Al2O3 system in the temperature range of 1000°,1500°C were estimated to be 76°,85° for the R and A faces, 88°,100° for the C face, and 77°,90° for the polycrystal, depending on the temperature. [source]

Experimental Archaeology: Investigation on the Copper,Aluminum,Silicon,Oxygen System

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 7 2002
Hans-Joerg Woelk
The behavior of the Cu-Al-Si-O system was investigated in the temperature range of 800°,1150°C. X-ray diffraction, infrared spectroscopy, diffusive reflectance, and electron microscopy were applied to obtain information about the influence of sintering, crystallization, and chemical reaction, each of which determines the color of the material. Definition of the artificial term "engobe," opposite to the term "glaze," was possible using copper(II) oxide (CuO) as its indicator. The detected chemical processes render possible explanations about the traditional way of ceramic painting during the 16th century and support the knowledge transfer from the viewpoint of history and that of natural science, as attempted by "archaeometry." [source]

Synthesis of Hydrated Aluminum Sulfate from Kaolin by Microwave Extraction

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 6 2000
Seong Soo Park
The feasibility of extracting alumina from kaolin via a microwave extraction process was investigated by comparing reaction times, reaction temperatures, and acid concentrations under microwave treatment with the same factors under conventional thermal extraction. The maximum amount of alumina extracted from kaolin under conventional processing at 90°C for 240 min with 1M H2SO4 was 99.9%; the same amount of alumina was extracted under microwave processing at 90°C for 120 min with 1M H2SO4. [source]

Hybrid Aluminum Colored Pigments Based on Gradient Copolymers Design

MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 18 2009
Mathieu Joubert
Abstract A colored polymer/aluminium hybrid pigment was synthesized by nitroxide mediated polymerization initiated from an inorganic surface. This approach requires the preparation of a vinyl dye monomer able to copolymerize with n -butyl acrylate (n-BuA) and styrene (S) from the surface of aluminium flakes. The linearity of the ln([M]0/[M]t) and of the as a function of time and conversion constitute the criteria of control/"living" polymerization, i.e. linearity of respectively ln([M]0/[M]t),=,f(t) and the ,=,f(conversion) plots. Kinetic measurements reveal an upward deviation from the linearity for n -BuA polymerization for very high conversion. The introduction of S monomer restores the control of the polymerization. Both the length of the grafted chains and the dye/styrene molar ratio influence the color of the hybrid material. [source]

Herstellung verbundverstärkter Aluminiumprofile für ultraleichte Tragwerke durch Strangpressen

MATERIALWISSENSCHAFT UND WERKSTOFFTECHNIK, Issue 7 2004
M. Kleiner
Extrusion; Aluminum; Continuously Reinforcement; Special Tool Abstract Auf Grund ähnlicher spezifischer Steifigkeits- und Festigkeitseigenschaften von Aluminium und Stahl lassen sich in der Anwendung bei leichten Rahmenstrukturen durch gegenseitige Werkstoffsubstitution nur geringe Leichtbaugewinne erzielen. Lediglich die Verwendung von z.,B. Kohlefaserwerkstoffen oder Höchstleistungsstählen lässt eine Gewichtsreduktion für den Einsatz von Rohren oder Profilen in ultraleichten Strukturen erwarten. Am Lehrstuhl für Umformtechnik (LFU) der Universität Dortmund ist ein Verfahren entwickelt worden, das durch ein modifiziertes Strangpressen zur Herstellung von Verbundprofilen geeignet ist. Ausgehend von konventionellen Aluminium-Pressblöcken werden hierbei verschiedenartige endlose Verstärkungselemente innerhalb der Wandstärke der Profilmatrix eingebettet. Für das Verfahren, das im Rahmen des Sonderforschungsbereiches SFB/TR10 erforscht wird, ist die Entwicklung neuartiger Strangpresswerkzeuge erforderlich. Durch experimentelle Untersuchungen auf einer 2,5 MN Laborstrangpresse wurden erfolgreich erste Verbundprofile hergestellt. Zur Vertiefung des Prozessverständnisses und der Prognose der Wirksamkeit neuer Werkzeugkonzepte wurden parallel FEM-Simulationen durchgeführt. Die mit Hilfe des Verfahrens hergestellten geraden Verbundprofile lassen sich auf Grund möglicher Gefügeschädigungen nicht biegen. In Kombination mit dem ebenfalls am LFU entwickelten Verfahren Runden beim Strangpressen werden diese Verbundprofile jedoch auch mit gekrümmter Kontur herstellbar sein. Manufacture of Extruded and Continuously Reinforced Aluminum Profiles for Ultra-Lightweight Constructions Due to similar specific properties of aluminum and steel regarding stiffness and mechanical strength only minor achievements as to their application in lightweight space-frame structures can be attained by substituting one material for the other. Only the usage of carbon fibre materials or high performance steels promises a weight reduction as to the application of pipes and profiles in ultra-lightweight structures. At the Chair of Forming Technology of the University of Dortmund a process has been developed which is suitable for the manufacturing of continuously reinforced profiles by means of a modified direct extrusion process. Starting from conventional aluminum billets, various continuously reinforcing elements are being embedded in the wall thickness of the profile matrix. For this process, which is being investigated in the context of the Collaborative Research Centre SFB/TR10, new extrusion dies have to be developed. During experimental studies on a 2.5 MN laboratory direct extrusion press first reinforced profiles were manufactured successfully. In order to improve the understanding of the process and to predict the efficiency of new tool concepts, FEM simulations were carried out simultaneously. Reinforced straight profiles produced with the help of this method cannot be bend due to possible damages to the microstructure. However, in combination with the process of Rounding During Extrusion, which also has been developed at the Chair of Forming Technology, these reinforced profiles will be producible with a curved contour as well. [source]

Autopsy case of aluminum encephalopathy

NEUROPATHOLOGY, Issue 3 2002
Teruo Shirabe
We report the case of a 59-year-old female aluminum encephalopathy patient who had chronic renal failure and took 3.0 g hydroxy-aluminum gel per day for the control of serum phosphorus level during a 15-year period. Nine months before her death she developed disorientation, memory disturbance, emotional incontinence, general convulsions and consciousness disturbance. Neuropathologically, the brain showed nerve cell atrophy and mild loss with stromal spongiosis, proliferation of astrocytes and microglia in the cerebral cortex, basal ganglia and thalamus. Some nerve cells were stained immunohistochemically by phosphorylated neurofilament, but apparent neurofibrillary tangles were not observed. Aluminum was detected in the nerve cells of the cerebral cortex by X-ray microanalysis. Despite the long-term intake of aluminum, there were no neuropathological findings of Alzheimer's disease. The findings in our case suggested that aluminum alone might not develop Alzheimer's disease. [source]

Citrate exudation from white lupin induced by phosphorus deficiency differs from that induced by aluminum

NEW PHYTOLOGIST, Issue 3 2007
B. L. Wang
Summary ,,Both phosphorus (P) deficiency and aluminum (Al) toxicity induce root exudation of carboxylates, but the relationship between these two effects is not fully understood. Here, carboxylate exudation induced by Al in Lupinus albus (white lupin) was characterized and compared with that induced by P deficiency. ,,Aluminum treatments were applied to whole root systems or selected root zones of plants with limited (1 µm) or sufficient (50 µm) P supply. ,,Aluminum stimulated citrate efflux after 1,2 h; this response was not mimicked by a similar trivalent cation, La3+. P deficiency triggered citrate release from mature cluster roots, whereas Al stimulated citrate exudation from the 5- to 10-mm subapical root zones of lateral roots and from mature and senescent cluster roots. Al-induced citrate exudation was inhibited by P limitation at the seedling stage, but was stimulated at later growth stages. Citrate exudation was sensitive to anion-channel blockers. Al treatments did not affect primary root elongation, but inhibited the elongation of lateral roots. ,,The data demonstrate differential patterns of citrate exudation in L. albus, depending on root zone, developmental stage, P nutritional status and Al stress. These findings are discussed in terms of possible functions and underlying mechanisms. [source]

Parenteral Nutrition,associated Cholestasis in Neonates: The Role of Aluminum

NUTRITION REVIEWS, Issue 9 2003
Chris J. Arnold RD
Parenteral nutrition (PN) is an essential component in the care of premature and ill infants. The incidence of parenteral nutrition,associated cholestasis (PNAC) ranges from 7.4 to 84%. One substance in PN solutions that has been implicated in PNAC is aluminum. Aluminum loading in animals and humans causes hepatic accumulation and damage. The degree of aluminum contamination of PN solutions has decreased over time, but contamination still significantly exceeds levels that are safe for human neonates. Further study into the relationship between aluminum contamination in neonatal PN solutions and the development of PNAC is necessary. [source]

Electronic structure and magnetic properties of Fe3C with 2p and 3p impurities

PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 9 2009
O. Yu.
Abstract Ab initio calculations were performed to determine the effect of 2p and 3p impurities on the structural, electronic, and magnetic properties of cementite. We predict that phosphorus, sulfur, and all 2p impurities replace carbon, while aluminum and silicon substitute for iron. The magnetization and magnetic moments on iron atoms in the special and general positions only slightly change for impurities in the carbon sites, but they essentially decrease for impurities that substitute for iron (Al, Si). We find that boron and nitrogen (to a lesser degree) promote the stabilization of cementite and may be dissolved with the formation of ternary Fe3(C, B) and Fe3(C, N) cementites. Aluminum and especially silicon sharply suppress the formation of cementite. [source]

Effects of indium incorporation in AlGaN on threading dislocation density

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7 2005
H. Kang
Abstract A comparison of dislocation densities in AlGaN and InAlGaN with approximately similar alloy compositions was completed. A systematic series of the AlGaN layers with concentration of 17% Aluminum were grown by metal-organic chemical vapor deposition with trace amounts of indium incorporated into the layers. X-ray diffraction analysis by Williamson Hall plot and reciprocal space mapping was employed to investigate columnar structure in these layers. It was found that lateral coherence length, related to threading dislocation, was systematically varied with Indium content. The lateral coherence length increased with the consequence that the threading dislocation density decreased as Indium content increased, which indicated that even small amounts of indium incorporation could improve crystalline quality. The results are in good agreement with etch pit density study using AFM. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Plasma Polymerization of HMDSO with an Atmospheric Pressure Plasma Jet for Corrosion Protection of Aluminum and Low-Adhesion Surfaces

PLASMA PROCESSES AND POLYMERS, Issue 10 2009
Uwe Lommatzsch
Abstract Thin functional films were deposited on aluminum with an atmospheric pressure plasma jet using hexamethyldisiloxane (HMDSO) as precursor. A high dynamic deposition rate on the order of 450,nm,·,m,·,min,1 was achieved. Composition and structure of the thin films show a strong dependence on the downstream location of the precursor injection. A 4,mm downstream shift of the precursor injection increases the carbon content in the thin film by a factor of 2.5, as indicated by XPS analysis and alters the degree of cross-linking according to the FTIR spectra. The coating with the low carbon content (17 at.-%) provides corrosion resistance for aluminum 2024 unclad exposed for 96,h to a neutral salt spray test. The coating with the high carbon content reduces the adhesion of an epoxy resin to the surface and may be used as a release coating. [source]

Combustion Measurements of Fuel-Rich Aluminum and Molybdenum Oxide Nano-Composite Mixtures

PROPELLANTS, EXPLOSIVES, PYROTECHNICS, Issue 2 2010
Tim Bazyn
Abstract Fuel rich nano-composite powders of aluminum and molybdenum oxide were tested for ignition and combustion behind the incident and reflected shock waves in a shock tube. The powders consisted of approximately 10,,m particles, each of which contained Al and MoO3 mixed by mechanical alloying on the nano-scale. These powders were aluminum rich with composition ratios of 4,:,1, 8,:,1, and 16,:,1 Al,:,MoO3 by mass. Ignition tests were performed behind incident shocks for temperatures in the range of 900 to 1500,K. From these tests, ignition delay times were obtained, and some information on combustion duration was also derived. Samples were tested in air at 0.2,MPa, and compared against nano-Al, 2.7,,m Al, and 10,,m Al baselines. Ignition results for the baseline Al cases were as expected: 10,,m Al not igniting until 2000,K, 2,,m Al igniting down to ,1400,K, and n-Al igniting as low as 1150,K. The thermite samples showed considerable improvement in ignition characteristics. At the lowest temperature tested (900,K), both the 8,:,1 and 4,:,1 samples ignited within 250,,s. The 16,:,1 sample (94% Al) ignited down to 1050,K , which represents an improvement of roughly 1000,K over baseline Al with only a small energetic penalty. In all cases, the ignition delay increased as the amount of MoO3 in the composite was reduced. The 4,:,1 nano-composite material ignited as fast or faster than the n-Al samples. Ignition delay increased with decreasing temperature, as expected. Emission spectra and temperature data were also taken for all samples using high-speed pyrometry and time-integrated spectroscopy. In these cases, measurements were made behind the reflected shock using end-wall loading, though the conditions (temperature, pressure, and gas composition) were identical to the incident shock tests. Spectroscopy showed strong AlO features in all the samples, and the spectra fit well to an equilibrium temperature. Broadband, low resolution spectra were also fit to continuum, gray body temperatures. In general, the observed temperatures were reasonably close to 3500,K, which is similar to the combustion temperatures of pure aluminum under these conditions. [source]

Aluminum alters cell viability and axonal transport system in Alzheimer's disease pathogenic mutation-bearing cells

PSYCHOGERIATRICS, Issue 2 2004
Hisashi TANII
Abstract Background:, We previously reported that pulse exposure of cultured rat neurons to aluminum-maltol resulted in an abnormal distribution of both neurofilament-L (NF-L) and fast axonal transported proteins. It was also found that the presenilin 1 (PS1) missense mutation and aluminum affected early neuronal development of the mouse brain. It has been reported that the presenilin (PS) mutation alters neurite outgrowth, and the axonal transport of the amyloid precursor protein (APP)/PS complex is mediated by kinesin. The present study hypothesizes that aluminum might modulate axonal transport and neurite outgrowth in APP/PS mutant-bearing cells. Methods:, We treated SH-SY5Y cells and HEK293 cells bearing FAD mutations with aluminum-maltol (Al-mal) (0, 250 µm, 500 µm, 1 mm, 2 mm) for 1 h, followed by propidium iodide (PI) and Calcein-AM staining, live and dead assay, double staining of NF-L/synaptophysin or APP/JNK interacting protein-1 (JIP-1) 3 days after treatment. Results:, Apoptosis was induced Al-mal treatment in a dose-dependent manner in all cell lines. In SH-SY5Y cells bearing PS1 mutations, there were no differences in the rate of cell viability, except for morphological changes observed by Calcein-AM staining. The distribution of NF-L and synaptophysin was modified by PS1 mutations and aluminum, suggesting that the PS mutation induces neuronal dysfunction by disturbance of the axonal transport system. The APP mutation-bearing cell lines showed significant induction of apoptosis compared to that of wild-type cells. Oxidative stress might thus influence cell viability in APP mutation-bearing cells. Enhancement of JIP-1 staining may reflect a disturbance of the intracellular axonal transport system, as well as compensation due to apoptotic changes. Conclusion:, The present results, when taken together, show that aluminum alters cell viability and the axonal transport system in FAD pathogenic mutation-bearing cells. [source]

A Risk of Alzheimer's Disease and Aluminum in Drinking Water

PSYCHOGERIATRICS, Issue 4 2002
Shunsuke Meshitsuka
Abstract: The epidemiological studies on the relation between Alzheimer's disease and aluminum in drinking water are reviewed. In descriptive studies, case-control studies, and also cohort studies aluminum in drinking water turned out to be positive for the senile dementia of Alzheimer type. Negative results were obtained in the studies of presenile dementia or alminum levels lower than 0.1 mg/L. Aluminum is the third abundant element on earth, therefore, exposure to aluminum is inevitable in daily life. It is known that as over 95% of cases with Alzheimer's disease are sporadic, some environmental factors are expected to be etiological. Aluminum has been so far studied as a candidate for a neurotoxic factor. It is not known why attention has been given to only aluminum in drinking water as the cause of the neuro-degenerative disease other than aluminum in foods or medications, and how aluminum acts as a toxicant in brain. Nonetheless, reduction of aluminum in drinking water is recommended, as well as investigations on the mechanism of neurotoxicity of aluminum to find out the way to be free from the fear of aluminum. [source]

Highly Enantioselective Hydrophosphonylation of Aldehydes: Base-Enhanced Aluminum,salalen Catalysis,

ANGEWANDTE CHEMIE, Issue 4 2010
Keitaro Suyama
Mit Dimethylphosphonat ließen sich zahlreiche konjugierte und nichtkonjugierte Aldehyde in Gegenwart des chiralen Aluminium-Salalen-Komplexes 1 zu ,-Hydroxyphosphonaten mit 93,98,%,ee hydrophosphonylieren (siehe Schema). [source]