Frottement interieur des alliages AlMg vieillis

Hamana, D.; Avanessov, V.L.; Sirenko, A. F.

doi:10.1016/0956-716x(90)90068-r

Cited by 18 publications

(16 citation statements)

References 8 publications

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“…In agreement with previous studies (Fournelle and Clark 1Y72, Hamana and Choutri 1991) the supersaturated f.c.c. a-phase of the solution-treated and waterquenched Cu-15 wt% In alloy decomposes completely during ageing into a lamellar mixture of depleted c( solid solution and 6 precipitate (Cu,In,) (figs.…”

Section: Coarsening and Spheroidization Of Lamellar Precipitate In Cusupporting

confidence: 92%

“…Discontinuous precipitation without grain-boundary migration in A1-8 wt% M g alloy The precipitation behaviour of binary A1-Mg alloys has been extensively studied using various experimental techniques and has been reported in many papers (Nozato and Ishhara 1980, Sato, Kojima and Takahashi 1982, Buynov and Kaigorodovo 1985, Vanrooyen, Sinte Maartensdijk and Mittemeyer 1988, Hamana, Avanessov and Sirenko 1990). In general, the possible ageing sequence in our studied alloys is supersaturated solid-solution ct-+Guinier-Preston zones (magnesium-rich clusters)-+intermediate phase p'-tequilibrium phase fl (AI,Mg,), where the /?…”

Section: Resultsmentioning

confidence: 98%

“…It is worth mentioning that usually, in the latter alloy, only continuous precipitation can be observed. However, discontinuous coarsening and spheroidization have been observed to decompose the lamellar products of cellular precipitation (Hamana and Halimi 1985).…”

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confidence: 99%

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The similarity between continuous and discontinuous precipitation

Hamana

Nebti

Boumerzoug

et al. 1993

Philosophical Magazine A

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Section: Coarsening and Spheroidization Of Lamellar Precipitate In Cusupporting

confidence: 92%

Section: Resultsmentioning

confidence: 98%

See 1 more Smart Citation

The similarity between continuous and discontinuous precipitation

Hamana

Nebti

Boumerzoug

et al. 1993

Philosophical Magazine A

Self Cite

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“…1,3-diaminopropane, 1,5-diaminopentane and spermidine were weaker substrates with maximal rates at 37 °C of 24%, 4.4% and 4.6%, respectively, of that of putrescine. Many thermophiles, including T. maritima 14 , contain polyamines not found in mammals, such as thermine (symnorspermine) and caldine (symnorspermidine). By using 1,3-diaminopropane as substrate, TmPAPT may well be able to produce a significant amount of caldine.…”

Section: Papt Enzymatic Activity and Polyamine Synthesismentioning

confidence: 99%

The crystal structure of spermidine synthase with a multisubstrate adduct inhibitor

Korolev

Ikeguchi

Skarina³

et al. 2001

Nat. Struct Biol.

134

164

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Polyamines are essential in all branches of life. Spermidine synthase (putrescine aminopropyltransferase, PAPT) catalyzes the biosynthesis of spermidine, a ubiquitous polyamine. The crystal structure of the PAPT from Thermotoga maritima (TmPAPT) has been solved to 1.5 Å resolution in the presence and absence of AdoDATO (S-adenosyl-1,8-diamino-3-thiooctane), a compound containing both substrate and product moieties. This, the first structure of an aminopropyltransferase, reveals deep cavities for binding substrate and cofactor, and a loop that envelops the active site. The AdoDATO binding site is lined with residues conserved in PAPT enzymes from bacteria to humans, suggesting a universal catalytic mechanism. Other conserved residues act sterically to provide a structural basis for polyamine specificity. The enzyme is tetrameric; each monomer consists of a C-terminal domain with a Rossmann-like fold and an Nterminal β-stranded domain. The tetramer is assembled using a novel barrel-type oligomerization motif.The nearly ubiquitous polyamines (putrescine, spermidine and spermine) are polycationic mediators of cell proliferation and differentiation 1 whose functions likely provide both stability and neutralization for nucleic acids. The abundance of polyamines is tightly regulated through biosynthesis, degradation, uptake and efflux 2 . The biosynthesis of polyamines is carried out by three highly conserved polyamine biosynthetic enzymes ( Fig. 1): ornithine decarboxylase, putrescine amino-propyltransferase (PAPT) and spermidine aminopropyltransferase (SAPT). The strong correlation of polyamine synthesis with cell growth renders these aminopropyl transferases (APTs) attractive targets for the development of antiproliferative therapeutics. The APTs are known to be inhibited by their common nucleoside product, as well as other nucleoside analogs. Most inhibitors, such as the nucleoside-polyamine adduct 4 , is also a potent inhibitor of PAPT.The catalytic mechanism of polyamine biosynthesis is unclear, partly because there is no detailed structural information for this class of enzymes. To provide structural insights into the mechanism of spermidine synthesis, the crystal structure of PAPT from Thermotoga maritima (TmPAPT) was determined at high resolution in ligand-free and AdoDATO-bound states. These structures provide insight into the function of the enzyme and its potential mechanism of action. The identification of conserved active site residues should enable accurate models of the mammalian enzymes. The PAPT foldThe structure of TmPAPT was solved using multiwavelength anomalous diffraction (MAD) from selenomethionine (SeMet)-containing crystals. The TmPAPT monomer consists of two domains: an N-terminal domain, composed of six β-strands, and a Rossmann-like C-terminal domain (Fig. 2). The larger C-terminal catalytic core domain (residues 75-296) consists of a seven-stranded β-sheet with a strand order of 9↑, 8↑, 7↑, 10↑, 11↑, 13↓, 12↑ flanked by nine α-helices. This domain resembles a topology observed in...

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“…Different technique were used for the description of G.P zones in this alloy system, such as the diffraction of X-rays with high angles used by Dauger and all [11] in alloy Al-12% mass.Mg. The measurements of the resistivity carried out in alloy Al-10% mass.Mg and which show an increase in the resistivity during ageing [12][13][14] and an electron microscopy is used on the same alloy [15].…”

Section: Precipitation In the Alloy Al-mg Systemmentioning

confidence: 99%

Discontinuous Precipitation in Al-8% Mass.Mg Alloy under the Effect of Temperature

Bensaada¹,

Bouziane²,

Ferhat³

2011

MSA

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The precipitation in the alloy Al-Mg system has been the subject of many theoritical and experimental investigations that have contributed to the understanding of the different mechanisms which control them. The purpose of this work is to clarify the effect of temperature on the mechanisms of these during ageing of Al-8% mass.Mg alloy. The techniques of analysis used in this respect are the optical microscopy, the X-ray diffraction and the micro hardness Vickers.

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Frottement interieur des alliages AlMg vieillis

Cited by 18 publications

References 8 publications

The similarity between continuous and discontinuous precipitation

The similarity between continuous and discontinuous precipitation

The crystal structure of spermidine synthase with a multisubstrate adduct inhibitor

Discontinuous Precipitation in Al-8% Mass.Mg Alloy under the Effect of Temperature

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