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Les pompes industrielles sont généralement utilisées dans un large domaine de fonctionnement, depuis un débit presque nul jusqu'à des débits sensiblement plus élevés que la valeur de projet. Souvent, on a observé que la caractéristique hauteur-débit, à vitesse constante, présente un " creux " négatif, lorsque le débit devient légèrement inférieur au débit de projet. Des instabilités aérodynamiques et mécaniques apparaissent, qui peuvent être dangereuses pour la machine. Afin d'analyser et, si possible, de pallier ces difficultés, une étude expérimentale a été entreprise conjointement par l'ONERA et Alsthom/Rateau. Une analyse détaillée de l'écoulement a mis en évidence des décollements et d'importants effets tridimensionnels. De cette meilleure connaissance du champ d'écoulement, nous avons pu imaginer un dispositif particulier qui a permis d'obtenir une très forte atténuation du " creux ".

Beta-1,2-linked mannosides from Candida albicans phosphopeptidomannan (PPM) bind to macrophages through a receptor independent from the macrophage alpha-linked mannose receptor and stimulate these cells to secrete immune mediators. Anti-beta-1,2-linked mannoside but not anti-alpha-linked mannoside antibodies produced after immunization with neoglycoproteins protect animals from disseminated candidiasis. In this study, peptides that mimic beta-1,2-linked mannosides were isolated using phage display methodology. A phage library expressing random peptides was panned with an anti-beta-1,2-linked mannoside monoclonal antibody (mAb). After three rounds of biopanning, the isolated phages were able to inhibit recognition of C. albicans by the mAb. Sixty percent of the phages had an identical DNA insert corresponding to the peptide sequence FHENWPS that was recognized specifically by the mAb. Injection of KLH-coupled peptide into mice generated high titers of polyclonal antibodies against C. albicans yeast cell walls. The anti-FHENWPS antibodies bound to C. albicans PPM and were inhibited by soluble beta-1,2-mannotetraose. Together, these data provide evidence for mimotopic activity of the peptide selected by biopanning with the anti-beta-1,2-oligomannoside mAb.

beta-1,2-linked oligomannoside residues are present, associated with mannan and a glycolipid, the phospholipomannan, at the Candida albicans cell wall surface. beta-1,2-linked oligomannoside residues act as adhesins for macrophages and stimulate these cells to undergo cytokine production. To characterize the macrophage receptor involved in the recognition of C. albicans beta-1,2-oligomannoside we used the J774 mouse cell line, which is devoid of the receptor specific for alpha-linked mannose residues. A series of experiments based on affinity binding on either C. albicans yeast cells or beta-1,2-oligomannoside-conjugated bovine serum albumin (BSA) and subsequent disclosure with biotinylated conjugated BSA repeatedly led to the detection of a 32-kDa macrophage protein. An antiserum specific for this 32-kDa protein inhibited C. albicans binding to macrophages and was used to immunoprecipitate the molecule. Two high-pressure liquid chromatography-purified peptides from the 32-kDa tryptic digest showed complete homology to galectin-3 (previously designated Mac-2 antigen), an endogenous lectin with pleiotropic functions which is expressed in a wide variety of cell types with which C. albicans interacts as a saprophyte or a parasite.

Candida albicans beta-1,2-oligomannosides stimulate macrophage tumor necrosis factor alpha (TNF-alpha) but not NO release. This stimulation desensitized macrophages by altering beta-1, 2-oligomannoside-dependent TNF-alpha production and lipopolysaccharide-dependent TNF-alpha and NO secretion. Desensitization was not related to tyrosine phosphorylation signal transduction but was transferred by culture supernatants in which arachidonic acid derivatives were evidenced.

Industrial pumps are generally used in a wide range of operating conditions from zero or almost zero mass flow to mass flows larger than the design value. It has been often noted that the head-mass flow characteristic of conventional axial flow pumps operating at constant speed presents a negative hump as the mass flow becomes somewhat smaller than the design mass flow. The pump does not stail, there is no real low frequency oscillations in the circuit, but flow and mechanical instabilities, unsafe for the facility, are present for sorne intermediary flow range. A joint experimental venture between ONERA and Alsthom/Rateau Division was undertaken in order to analyze and if possible to palliate these difficulties. The tests were performed in air instead of water, keeping the same flow coefficients.Les pompes industrielles sont g?n?ralement utilis?es dans un large domaine de fonctionnement, depuis un d?bit presque nul jusqu'? des d?bits sensiblement plus ?lev?s que la valeur de projet. Souvent, on a observ? que la caract?ristique hauteur-d?bit, ? vitesse constante, pr?sente un " creux " n?gatif, lorsque le d?bit devient l?g?rement inf?rieur au d?bit de projet. Des instabilit?s a?rodynamiques et m?caniques apparaissent, qui peuvent ?tre dangereuses pour la machine. Afin d'analyser et, si possible, de pallier ces difficult?s, une ?tude exp?rimentale a ?t? entreprise conjointement par l'ONERA et Alsthom/Rateau. Une analyse d?taill?e de l'?coulement a mis en ?vidence des d?collements et d'importants effets tridimensionnels. De cette meilleure connaissance du champ d'?coulement, nous avons pu imaginer un dispositif particulier qui a permis d'obtenir une tr?s forte att?nuation du " creux ".