Showing papers by "University of Avignon published in 1993"

Effects of electromagnetic vibrations on the microstructure of continuously cast aluminium alloys

Abstract: The influence of electromagnetic vibrations imposed during solidification on grain refinement in the 1085 and 2214 aluminium alloys, characterized by a narrow and a wide freezing range respectively, has been examined. The vibrations were produced by the simultaneous application of a stationary magnetic field B0′ and a variable magnetic field B of frequency 50 Hz in the sump of continuously cast ingots. Extensive grain refinement has been observed in both alloys with increasing magnetizing force. This study shows the mean grain size obtained by this vibrational technique is always smaller than that produced by the recently developed CREM (carting, refining, electromagnetic) process.

Algebres de lie orthogonales modules orthogonaux

Abstract: We continue our study of orthogonal Lie algebras, i.e. Lie algebras which support an invariant scalar product. We first show that a Lie algebra has a non degenerate invariant bilinear form iff adjoint and coadjoint representations are isomorphic. We study the space of all invariant bilinear forms on an orthogonal algebra. In a second part we study orthogonal modules and give a complete description of the double extension process which allows to construct all orthogonal modules ; we give examples and raise the question of existence of non-isomorphic orthogonal structures on a given orthogonal Lie algebra.

Molecular activation of a trehalase purified from the fat body of a coleopteran insect (Tenebrio molitor), by an endogenous insulin-like peptide.

Abstract: Trehalase is the major factor involved in the release of glucose in the various insects organs. During physiological regulatory processes, and particularly during the induction or breaking of diapause, insulin-like factors are involved. Then, by contrast with the classical hypoglycemic role of insulin, the insulin-like peptide isolated from the insect (brain and/or fat body) is also able to activate the fat body trehalase in vitro, through a direct molecular interaction. The mechanism involves the binding of the activator to the "trehalase-trehalose complex", rather than on the free enzyme, without change in the Hill coefficient nor in the maximum velocity (Vmax). The rate constant KR is conversely proportional to the activator concentration. This mechanism can be totally quenched by adding an anti-serum anti-insulin-like factor in the reaction medium.

Calculus rules for combinations of ellipsoids and applications

Abstract: We derive formulas for the Minkowski sum, the convex hull, the intersection, and the inverse sum of a finite family of ellipsoids. We show how these formulas can be used to obtain inner and outer ellipsoidal approximations of a convex polytope.

A formula on the subdifferential of the deconvolution of convex functions

Abstract: It is known that, under suitable assumptions, the subdifferential ∂(f □ g) of the infimal convolution of two convex functions f and g coincides with the parallel sum of ∂ f and ∂ g. We prove that a similar formula holds for the subdifferential of the deconvolution of two convex functions: under appropriate hypothesis it coincides with the parallel star-difference of the sub-differentials of the functions.

Synergistic and molecular interactions between the formamidine amitraz and copper(II) sulfate, used against the mite Varroa jacobsoni O., a parasite of the honeybee Apis mellifera L.

Abstract: Toxicological field assays have shown that the shock-treatment efficacy of the formamidine pesticide amitraz, used against the parasitic mite Varroa jacobsoni, is synergistically improved by the administration of copper(II) sulfate through feeding of the honeybees. Amitraz is autoxidized and this process is accompanied by chemiluminescence. The emission is enhanced in the presence of low concentrations of H2O2. A dose-related inhibition of the chemiluminescence by CuSO4 was observed; consistent with the formation of copper-amitraz complexes evidenced in vitro. The results suggest the possibility that a protection of amitraz by cupric ions might be at the origin of the enhancement of its toxicity and thus makes a contribution to the observed synergy.

Les Arabisants Et La Catégorie De ' Ina ': Histoire D'Une 'Occultation'*

Abstract: SUMMARYThe post-classical Arabic category of 'inša' ("performative utterance") occupies a central position in several traditional fields of Islamic culture, thereby serving as a link between them.However, The Encyclopaedia of Islam mentions it in neither of its two editions. The term is not even translated or rather is not well translated in a key text like the Muqaddima of Ibn Haldun. It is assimilated instead to its subcategory talab ("jussive utterance"). We must go back as far as Silvestre de Sacy (1758-1838) to understand the reasons for this silence, or rather this semi-silence. As an advocate of general grammar, he saw the opposition between 'inša' and 'ihbar ("assertion") in terms of the 'modes' (in the sense of 'forms or ways of thinking'). This interpretation may also have been influenced by the work of Ibn al-Hagib, who sees the opposition which gave rise to the classification of utterances according to the categories of habar ("affirmation") and 'inša' (wathever is not affirmation), in terms of a two-fold difference: that of the assertive as opposed to the performative use of a given sentence, on the one hand, and, that of the imperative as opposed to the performative, that is of the 'expression' of the talab as opposed to its 'representation', on the other hand. By concentrating on a single facet of the problem, Silvestre de Sacy misses the legal origin of the category as well as its conceptual originality. Likewise, Massignon (1883-1962) mentions only the reduction of the 'inša' to a 'ihbar 'ammafil-batin ("the assertion of one's inner thoughts") and the 'ihbar to a 'ihbar 'ammafi l-harig ("the assertion of what is in the outside world") which corresponds to a difference in referential worlds. The moral of all this is that personal and contemporary theories of historians of linguistics, as well as the personal authority of one specialist or another can be the best or the worst of things. Nonetheless, if Arabists had paid more attention to this pluridisciplinary category, they might have played a leading role in writing the history of linguistics. To the extent that the end of history is the transcendence of that history, they might even have foreseen the emergeance of the 'enunciation' movement, which permeates the Arabic linguistic tradition.RESUMELa categorie arabe postclassique de 'inša' ("performatif') joue un role central dans plusieurs disciplines traditionnelles en islam, qu'elle met ainsi en relation. Pourtant, l'Encyclopedie de l'Islam en ses deux ed.s ne la mentionne pas. Et dans un texte-phare comme la Muqaddima de Ibn Haldun, le terme ou bien n'est pas traduit ou bien est mal traduit, etant assimile a sa subdivison talab ("jussion"). Pour comprendre ce silence ou ce demi-silence, il faut remonter a Silvestre de Sacy (1758-1838): tenant de la grammaire generale, il relit l'opposition 'inša' vs 'ihbar ("assertion") a travers celle des 'modes' (comme "formes ou manieres de notre pensee") que fait celle-ci. Cette lecture a neanmoins pu etre influencee par l'oeuvre de Ibn al-Hagib, ou cette opposition, dont est issue la classification des enonces en habar ("affirmation") et 'inša' (tout ce qui n'est pas affirmation), articule une double difference: celle des emplois assertif et performatif d'une meme phrase, mais aussi celle de l'imperatif et du performatif correspondant comme 'expression' et 'representation' de la demande. En ne retenant qu'un des deux volets, Silvestre de Sacy manque l'origine juridique et l'originalite conceptuelle de la categorie. De meme Mas-signon (1883-1962) ne retient que la reduction du 'inša' a un 'ihbar 'ammafi l-batin ("assertion sur ce qui est dans le for interieur") vs ' ihbar = 'ihbar 'amma fi l-harig ("assertion sur ce qui est dans la realite exterieure"), qui articule une difference entre mondes referes. Moralite: les theories personnelles ou contemporaines de l'historien de la linguistique, ainsi que 1''autorite' de tel ou tel savant, peuvent etre la meilleure ou la pire des choses. Reste que si les arabisants avaient prete davantage d'attention a cette categorie pluridisciplinaire et a son cheminement transdisciplinaire, ils auraient pu jouer un role de pionniers en matiere d'histoire de la linguistique et dans la mesure ou la fin de toute histoire est de depasser cette histoire meme anticiper sur l'emergence du phenomene de l''enoneiation', omnipresent dans la tradition linguistique arabe.ZUSAMMENFASSUNGDie nachklassische arabische Kategorie 'inša' ("performativer Sprechakt") nimmt eine zentrale Stellung in verschiedenen Gebieten der islamischen Kultur ein, so das sie eine Verbindung zwischen ihnen herstellt. Dennoch wird sie in keiner der beiden Ausgaben der The Encyclopaedia of Islam angefuhrt. Der Terminus wird nicht einmal ubersetzt oder, wenn uberhaupt, in unzureichender Weise wie etwa in einem Schliisseltext wie den Muqaddima des Ibn Haldun. Dort wird er stattdessen mit seiner ihm untergeordneten Kategorie talab ("Auf-forderung") vermischt. Um die Grunde fiir dieses Schweigen oder diese Fehl-einschatzung zu verstehen, mus zumindest bis Silvestre de Sacy (1758-1838) zuruckgegangen werden. Als Befurworter der Allgemeinen Grammatik der Port-Royal Tradition sah er eine Opposition zwischen 'inša' und 'ihbar ("Be-hauptung") als eine Art Modus (im Sinne von 'Denkformen oder -weisen'). Diese Interpretation ist vielleicht auch beinfluBt vom Werk Ibn al-Hagibs, welcher eine Opposition — die zur Klassifikation von Aussagen in Kategorien von habar ("Feststellung") and 'inša' ("alles, was nicht Feststellung ist") fuhrte — im Hinblick auf einen zweifachen Unterschied vorsah: einen 'asser-tiven' im Gegensatz zu einem 'performativen' Gebrauch eines Satzes einerseits und einen imperativen im Gegensatz zu einem performativen andererseits, d.h. als 'Ausdruck' des talab im Gegensatz zu seiner 'Darstellung\ Indem er sich auf einen einzelnen Aspekt des Problems konzentrierte, ubersah Silvestre de Sacy den juristischen Ursprung dieser Kategorie ebenso wie ihre konzeptuelle Originalitat. Ebenso verweist Massignon (1883-1962) nur auf die Reduktion von'inša' auf'ihbar 'amma fi l-bâtin ("die Feststellung der inneren Gedanken einer Person") und die von 'ihbâr auf 'ihbar 'amma fi l-harig ("die Feststellung dessen, was sich in der AuBenwelt befindet"), die einem Unterschied in bezug auf referentielle Welten entspricht. Die Moral der Geschichte ist, daB personenbezogene und gegenw wartige Theorien von Sprachwissen-schaftshistorikern konnen — ebenso wie die Autoritat des einen oder anderen Spezialisten — die beste oder die schlechteste aller Moglichkeiten hervor-bringen. Auf jeden Fall scheint klar, daB wenn die Arabisten dieser viel-facherigen Kategorie mehr Beachtung geschenkt hutten, hatten sie eine fiih-rende Rolle in der Sprachwissenschaftsgeschichtsschreibung einnehmen konnen. Inwieweit es das Ziel der Geschichte ist, die Geschichte zu transzen-dieren, hutten sie sogar die 'enonciation'-Bewegung vorwegnehmen konnen, die die arabische Tradition in der Sprachwissenschaft durchdringt.

Production of metal matrix composites ingots from semisolid alloys

Abstract: The working principle and the peculiarities of new electromagnetic rheocasters, which are based on the use of rotating permanent magnets and which allow the production of intense three-dimensional multiphase flows in solidifying semi-solid alloy slurries and metal matrix composites, are described. These processes are likely to be applied to the direct continuous casting of billets, tubes and slabs. They are also characterized by a very low electric power consumption. Local measurement techniques are applied to the study of the evolution of the fluid flow phenoma with the rotation speed of the inductor, the solid fraction, and the size and volume percent of SiC particles. A discussion is presented relating the metallurgical findings to the heat and fluid flow measurements. Satisfactory performances concerning the microstructure of solidified aluminum slurries and aluminum matrix composites (homogeneity, cyrstal shape, grain size, fraction of primary solid, distribution of SiC particles) were obtained