On the twinning impact on the grain structure formation of multi-crystalline silicon for photovoltaic applications during directional solidification

Grain orientation and competition during growth has been analyzed in directionally solidified multi-crystalline silicon samples. In situ and real-time characterization of the evolution of the grain structure during growth has been performed using synchrotron X-ray imaging techniques (radiography and topography). In addition, Electron Backscattered Diffraction has been used to reveal the crystalline orientations of the grains and the twin relationships. New grains formed during growth have two main origins: random nucleation and twinning. It is demonstrated that the solidified samples are dominated by P3 twin boundaries showing that twinning on {111} facets is the dominant phenomenon. Moreover, thanks to the in situ characterization of the growth, it is shown that twins nucleate on {111} facets located at the sides of the sample and at grain boundary grooves. The occurrence of multiple P3 twins during growth prevents the initial grains from developing all along the sample, and twin boundaries with higher order coincidence site lattices can form at the encounter of two grains in twin position. The grain competition phenomenon following nucleation and twinning acts as a grain selection mechanism leading to the final grain structure

X-ray Based in Situ Investigation of Silicon Growth Mechanism Dynamics—Application to Grain and Defect Formation

To control the final grain structure and the density of structural crystalline defects in silicon (Si) ingots is still a main issue for Si used in photovoltaic solar cells. It concerns both innovative and conventional fabrication processes. Due to the dynamic essence of the phenomena and to the coupling of mechanisms at different scales, the post-mortem study of the solidified ingots gives limited results. In the past years, we developed an original system named GaTSBI for Growth at high Temperature observed by Synchrotron Beam Imaging, to investigate in situ the mechanisms involved during solidification. X-ray radiography and X-ray Bragg diffraction imaging (topography) are combined and implemented together with the running of a high temperature (up to 2073 K) solidification furnace. The experiments are conducted at the European Synchrotron Radiation Facility (ESRF). Both imaging techniques provide in situ and real time information during growth on the morphology and kinetics of the solid/liquid (S/L) interface, as well as on the deformation of the crystal structure and on the dynamics of structural defects including dislocations. Essential features of twinning, grain nucleation, competition, strain building, and dislocations during Si solidification are characterized and allow a deeper understanding of the fundamental mechanisms of its growth

NKX3.1 is a direct TAL1 target gene that mediates proliferation of TAL1-expressing human T cell acute lymphoblastic leukemia

TAL1 (also known as SCL) is expressed in >40% of human T cell acute lymphoblastic leukemias (T-ALLs). TAL1 encodes a basic helix-loop-helix transcription factor that can interfere with the transcriptional activity of E2A and HEB during T cell leukemogenesis; however, the oncogenic pathways directly activated by TAL1 are not characterized. In this study, we show that, in human TAL1–expressing T-ALL cell lines, TAL1 directly activates NKX3.1, a tumor suppressor gene required for prostate stem cell maintenance. In human T-ALL cell lines, NKX3.1 gene activation is mediated by a TAL1–LMO–Ldb1 complex that is recruited by GATA-3 bound to an NKX3.1 gene promoter regulatory sequence. TAL1-induced NKX3.1 activation is associated with suppression of HP1-α (heterochromatin protein 1 α) binding and opening of chromatin on the NKX3.1 gene promoter. NKX3.1 is necessary for T-ALL proliferation, can partially restore proliferation in TAL1 knockdown cells, and directly regulates miR-17-92. In primary human TAL1-expressing leukemic cells, the NKX3.1 gene is expressed independently of the Notch pathway, and its inactivation impairs proliferation. Finally, TAL1 or NKX3.1 knockdown abrogates the ability of human T-ALL cells to efficiently induce leukemia development in mice. These results suggest that tumor suppressor or oncogenic activity of NKX3.1 depends on tissue expression

Le droit dans la littérature: l'exemple de Kafka

International audienc

Le droit dans la littérature: l'exemple de Kafka

International audienc

La théorie de la réalité technique à l’épreuve du temps

International audienc

La requalification en contrat de travail de la participation au jeu de téléréalité « l’île de la tentation » constitue-t-elle un progrès pour le droit du travail ?

International audienceDeux ans après l’arrêt très médiatisé de la chambre sociale de la Cour de cassation du 3 juin 2009 (L’île de la tentation, Bull. V, 141), la cour d’appel de Versailles (6e ch., 5 avril 2011, n° 09/01674, SAS TF1 Production c/ Mme L) requalifie à son tour la participation à la deuxième saison de l’émission de téléréalité « L’Île de la tentation » en contrat de travail. Cette requalification constitue-t-elle un progrès pour le droit du travail ?Rien n’est moins sûr, car une telle solution pose en réalité plus de problèmes qu’elle n’en résout. En effet, non seulement la notion de travail apparaît malmenée dans son essence même mais, surtout, le choix de l’application du droit du travail a pour conséquence immédiate le non respect de certains droits fondamentaux

La requalification en contrat de travail de la participation au jeu de téléréalité « l’île de la tentation » constitue-t-elle un progrès pour le droit du travail ?

International audienceDeux ans après l’arrêt très médiatisé de la chambre sociale de la Cour de cassation du 3 juin 2009 (L’île de la tentation, Bull. V, 141), la cour d’appel de Versailles (6e ch., 5 avril 2011, n° 09/01674, SAS TF1 Production c/ Mme L) requalifie à son tour la participation à la deuxième saison de l’émission de téléréalité « L’Île de la tentation » en contrat de travail. Cette requalification constitue-t-elle un progrès pour le droit du travail ?Rien n’est moins sûr, car une telle solution pose en réalité plus de problèmes qu’elle n’en résout. En effet, non seulement la notion de travail apparaît malmenée dans son essence même mais, surtout, le choix de l’application du droit du travail a pour conséquence immédiate le non respect de certains droits fondamentaux

Les pratiques juridictionnelles d'indemnisation du licenciement sans cause réelle et sérieuse : l'application d'un barème ?

National audienc

Le soutien aux proches aidants: congés et indemnisation

National audienc