Instability driven formation of domains in the intermediate state of type-I superconductors

The formation of normal-state domains in type-I superconducting indium films is investigated using the high resolution magneto-optical imaging technique. The observed patterns consist of coexisting circular and lamellar normal-phase domains surrounded by the superconducting phase. The distribution of domain surface areas is found to exhibit a threshold, above which only the lamellar shape is observed. We show that this threshold coincides with the predicted critical surface area for the elongation instability of the circular shape. The partition of the normal phase into circular and lamellar domains is determined by the combined effects of the elongation instability and the penetration of magnetic flux by bursts at the early stage of pattern formation. It is not governed by mutual interactions between domains, as usually assumed for self-organized systems

The maison europeenne des procedes innovants (MEPI),an example of piloting and industrial demonstration facility for the green process engineering

Abstract. Economical, energy savings and environmental challenges require an actual technological breakthrough in process engineering, aiming with productivity, product quality, safety and reliability objectives. This explains the present growth of interest in innovative technologies (intensified devices for reaction, mixing and separation) and methods (multifunctionality, hybrid separation, batch to continuous methodology, new media …), the whole being recognized as Process Intensification. Up to now, a few of innovations has been successfully industrialized, probably due to the lack of experience and retrofitting in front of a breakthrough that always represents a technical and financial risk. There is now clearly a need for industrial demonstrations of successful PI experiments avoiding the questions of confidentiality. Consequently, a piloting and demonstration facility has been created in Toulouse in order to accelerate the implementation of PI technology in industry and the development of the Green Process Engineering. The idea is to build a data bank of success stories. The principle of this industrial technical platform lies on the association of 3 types of partners: university, equipment providers and industrial end-users

Mise en valeur des sols ferrallitiques des massifs du Sud de la Nouvelle Calédonie : interaction phosphore-silice et influence de la matière organique : résultats de la troisième et la quatrième études en serre

Les deux expérimentations en serre présentées dans ce document ont pour objet principal d'étudier les effets sur un sol ferrallitique ferritique du Sud de la Grande-Terre : de quantités croissantes de silice apportées sous forme de scories de nickel (de 0 à 40 tonnes/ha) croisées avec trois doses d'amendement phosphaté (3, 5 et 7 TP 205/ha); des combinaisons de deux niveaux de scories (0 et 40 T/ha) avec deux doses de lisier (0 et 40 m3/ha); d'un apport croissant d'amendement organique sous forme de lisier (0, 40, 80 et 120 m3/ha) croisé avec deux doses de phosphore (3 et 7 T/ha de P205). Ces deux études ont montré qu'un apport massif de 7 T/ha de P205 permettrait un développement végétatif satisfaisant de la plante-test, le maïs. L'apport de lisier en forte dose (120 m3/ha) est également favorable à la plante et au sol, mais cette influence serait principalement due aux éléments nutritifs supplémentaires amenés par cet amendement. Le lisier semble jouer également son rôle régulateur, notamment au niveau de l'interaction scories-lisier : l'apport de scories n'est positif qu'en présence du lisier et est dépressif en l'absence de cet amendement. Enfin, il apparaît intéressant d'étudier les possibilités de mise en valeur de ce sol par d'autres formes d'amendement organique. (Résumé d'auteur

A one dimensional model for the prediction of extraction yields in a two phases modified twin-screw extruder

Solid/liquid extraction is performed on raw plant substrate with a modified twin-screw extruder (TSE) used as a thermo-mecanochemical reactor. Visual observations and experimental residence time distributions (RTD) are used to develop a solid transport model based on classical chemical engineering method. Modeled and experimental residence times are compared. The transport model is then coupled with a reactive extraction model in order to predict extraction yields

Stiffening and unfolding of early deposited-fibronectin increase proangiogenic factor secretion by breast cancer-associated stromal cells.

Fibronectin (Fn) forms a fibrillar network that controls cell behavior in both physiological and diseased conditions including cancer. Indeed, breast cancer-associated stromal cells not only increase the quantity of deposited Fn but also modify its conformation. However, (i) the interplay between mechanical and conformational properties of early tumor-associated Fn networks and (ii) its effect on tumor vascularization remain unclear. Here, we first used the Surface Forces Apparatus to reveal that 3T3-L1 preadipocytes exposed to tumor-secreted factors generate a stiffer Fn matrix relative to control cells. We then show that this early matrix stiffening correlates with increased molecular unfolding in Fn fibers, as determined by Förster Resonance Energy Transfer. Finally, we assessed the resulting changes in adhesion and proangiogenic factor (VEGF) secretion of newly seeded 3T3-L1s, and we examined altered integrin specificity as a potential mechanism of modified cell-matrix interactions through integrin blockers. Our data indicate that tumor-conditioned Fn decreases adhesion while enhancing VEGF secretion by preadipocytes, and that an integrin switch is responsible for such changes. Collectively, our findings suggest that simultaneous stiffening and unfolding of initially deposited tumor-conditioned Fn alters both adhesion and proangiogenic behavior of surrounding stromal cells, likely promoting vascularization and growth of the breast tumor. This work enhances our knowledge of cell - Fn matrix interactions that may be exploited for other biomaterials-based applications, including advanced tissue engineering approaches

Mise en valeur des sols ferrallitiques ferritiques des massifs du Sud de la Nouvelle-Calédonie : effets de doses et de formes différentes d'amendements organiques sur maïs (étude en serre no 5)

La cinquième expérimentation en serre, menée sur maïs, dans le cadre de l'étude des facteurs de la fertilité des sols ferrallitiques ferritiques des massifs su Sud de la Grande Terre, visait à observer et analyser : l'effet de 5 doses de fumier de volaille (0; 15; 30 et 45 t/ha); l'effet de 4 formes de matière organique (sans matière organique, avec 45 t/ha de fumier de volaille, avec 120 m3/ha de lisier et avec 45 t/ha de fumier de bovin). Il semble que la dose de 15 t/ha de fumier de volaille ait l'effet le plus positif sur le développement du maïs, tandis qu'un apport de 45 t/ha de cet amendement serait plutôt défavorable. D'une manière générale, l'effet des apports d'amendement organique est très significatif, les doses de 45 t/ha de fumier de bovin et 120 m3/ha de lisier permettent d'obtenir les meilleurs résultats. Des essais complémentaires menés en serre jusqu'à la récolte, mais également en plein champ demeurent indispensables pour confirmer ces résultats. (Résumé d'auteur

Effect of picosecond strain pulses on thin layers of the ferromagnetic semiconductor (Ga,Mn)(As,P)

The effect of picosecond acoustic strain pulses (ps-ASP) on a thin layer of (Ga,Mn)As co-doped with phosphorus was probed using magneto-optical Kerr effect (MOKE). A transient MOKE signal followed by low amplitude oscillations was evidenced, with a strong dependence on applied magnetic field, temperature and ps-ASP amplitude. Careful interferometric measurement of the layer's thickness variation induced by the ps-ASP allowed us to model very accurately the resulting signal, and interpret it as the strain modulated reflectivity (differing for $\sigma_{\pm}$ probe polarizations), independently from dynamic magnetization effects.Comment: 6 pages, 5 figure

Etude clinique, parasitologique et épidémiologique de l'onchocercose dans la région de Belabo (province de l'Est, Cameroun)

En Septembre 1991, une étude clinique, parasitologique et épidémiologique a été conduite dans quatre villages de la région de Bélabo et un quartier de Bélabo, province de l'Est, Cameroun. Cette étude met en évidence le haut niveau d'endémicité de l'onchocercose dans cette région de transition savane-forêt, avec un taux de cécité relativement élevé. Un traitement à large échelle par ivermectine est proposé. (Résumé d'auteur

Field-Driven Domain-Wall Dynamics in GaMnAs Films with Perpendicular Anisotropy

We combine magneto-optical imaging and a magnetic field pulse technique to study domain wall dynamics in a ferromagnetic (Ga,Mn)As layer with perpendicular easy axis. Contrary to ultrathin metallic layers, the depinning field is found to be smaller than the Walker field, thereby allowing for the observation of the steady and precessional flow regimes. The domain wall width and damping parameters are determined self-consistently. The damping, 30 times larger than the one deduced from ferromagnetic resonance, is shown to essentially originate from the non-conservation of the magnetization modulus. An unpredicted damping resonance and a dissipation regime associated with the existence of horizontal Bloch lines are also revealed

Field-induced domain wall propagation: beyond the one-dimensional model

We have investigated numerically the field-driven propagation of perpendicularly magnetized ferromagnetic layers. It was then compared to the historical one-dimensional domain wall (DW) propagation model widely used in spintronics studies of magnetic nanostructures. In the particular regime of layer thickness (h) of the order of the exchange length, anomalous velocity peaks appear in the precessional regime, their shape and position shifting with h. This has also been observed experimentally. Analyses of the simulations show a distinct correlation between the curvature of the DW and the twist of the magnetization vector within it, and the velocity peak. Associating a phenomenological description of this twist with a four-coordinate DW propagation model, we reproduce very well these kinks and show that they result from the torque exerted by the stray field created by the domains on the twisted magnetization. The position of the peaks is well predicted from the DW's first flexural mode frequency, and depends strongly on the layer thickness. Comparison of the proposed model to DW propagation data obtained on dilute semiconductor ferromagnets GaMnAs and GaMnAsP sheds light on the origin of the measured peaks