X-ray Diffraction Residual Stress Measurement at Room Temperature and 77 K in a Microelectronic Multi-layered Single-Crystal Structure Used for Infrared Detection

The electronic assembly considered in this study is an infrared (IR) detector consisting of different layers, including (111) CdHgTe and (100) silicon single crystals. The processing steps and the low working temperature (77 K) induce thermomechanical stresses that can affect the reliability of the thin and brittle CdHgTe detection circuit and lead to failure. These residual stresses have been quantified in both CdHgTe and silicon circuits at room temperature (293 K) and cryogenic temperature using x-ray diffraction. A specific experimental device has been developed for 77 K measurements and a method developed for single-crystal analysis has been adapted to such structures using a laboratory four-circle diffractometer. This paper describes the methodology to obtain the deformed lattice parameter and compute the strain/ stress tensors. Whereas the stresses in the CdHgTe layer appear to be negative at room temperature (compressive values), cryogenic measurements show a tensile biaxial stress state of about 30 MPa and highlight the great impact of low temperature on the mechanical properties

Metabolic status rather than cell cycle signals control quiescence entry and exit

The use of new candidate markers for yeast quiescence reveals that quiescence entry and exit primarily rely on cellular metabolic status and can be uncoupled from the cell cycle

Biologie intégrative des canaux potassiques de la cellule de garde : activité électrophysiologique et rôle dans l'adaptation de la plante à son environnement

Stomate, Canaux Shaker, Potassium, Arabidopsis,TranspirationControl of stomatal aperture at the leaf surface allows the plant to prevent excessive transpirational water loss and desiccation. The aperture depends on the turgor of the two guard cells that form the stomata, an increase or a decrease in turgor leading to stomatal opening or closure, respectively. Rapid transport of K+ into or from guard cells plays a crucial role in this osmotically driven movements. Inward or outward K+ channels from the Shaker family dominate the membrane conductance to K+. In Arabidopsis thaliana, we show that a single Shaker gene, GORK, encodes the outward conductance. GORK activity allows rapid stomatal closure in response to dark or to ABA, and plays an important role in plant water saving under drought conditions. The inward K+ conductance relies upon at least 4 Shaker genes, among which KAT1 and KAT2 display the higher expression levels. Taking advantage from the fact that Shaker channels are homo- or hetero-tetrameric proteins, we engineered a mutant plant totally deprived of inward K+ channel activity in guard cell (GCKin activity), by transforming a dominant negative kat2 construct into a kat2-KO background. This allowed to show that GCKin activity plays an important role in stomatal opening in response to light or to a decrease in evaporative demand or in CO2 availability. It is also shown to be central to the mechanisms that underlie the circadian rhythm of stomatal opening and to prevent deleterious of Na+ on stomatal control. Absence of GCKin activity resulted in a strong decrease in biomass production in a meteorological scenario resulting in decreased photosynthetic activity after the first two hours of illumination. Finally, we show that KAT1 and KAT2 subunits are preferentially incorporated into heterotetrameric channels and that this phenomenon affects channel functional properties and channel targeting to and/or stability in the plasma membrane.Le contrôle de l'ouverture des stomates permet à la plante de réguler la perte d'eau par transpiration. Une diminution ou une augmentation de la turgescence des cellules de garde provoque respectivement un accroissement ou une réduction de l'ouverture stomatique. Des flux sortants ou entrants de K+ dans les cellules de garde, à travers des canaux de type Shaker, jouent un rôle essentiel dans ces variations de turgescence. Chez Arabidopsis thaliana, nous montrons qu'un seul gène Shaker, GORK, code pour la conductance potassique sortante des cellules de garde. Le canal GORK permet une fermeture rapide des stomates à l'obscurité et en réponse à l'ABA, et une réduction notable de la perte d'eau par la plante en cas de stress hydrique. La conductance entrante quant à elle, implique plusieurs gènes Shaker, parmi lesquels KAT1 et KAT2 présentent les plus forts niveaux d'expression. Utilisant le fait que les canaux Shaker ont une structure homo ou hétéro-tétramérique, nous avons construit (introduction d'un gène kat2 mutant dominant négatif dans une lignée mutante invalidée dans le gène KAT2) une plante dont les cellules de garde sont totalement dépourvues de conductance K+ entrante. Cela a permis de montrer que cette conductance joue un rôle crucial dans l'ouverture stomatique déclenchée par la lumière, dans le contrôle de l'ouverture stomatique en réponse aux variations d'humidité de l'air et de disponibilité du CO2 dans les tissus, dans l'établissement du rythme circadien d'ouverture des stomates et dans la préservation du fonctionnement stomatique en cas de stress salin. La production de biomasse apparaît comme fortement dépendante de cette conductance dans un scénario mimant une réduction des possibilités de photosynthèse après 2 heures d'illumination. Enfin, nous montrons que la formation d'hétéro-tétramères KAT1-KAT2 module les propriétés fonctionnelles des canaux et favorise l'adressage à la membrane plasmique et/ou leur stabilité dans la membrane

Extending genome transplantation methods within Mollicutes

National audienc

Ribosomal RNA m5U modification by a folate-dependent methyltransferase revealed in <em>mycoplasma</em> using synthetic biology

National audienc

Heteromeric K(+) channels in plants.

Voltage-gated potassium channels of plants are multimeric proteins built of four alpha-subunits. In the model plant Arabidopsis thaliana, nine genes coding for K(+) channel alpha-subunits have been identified. When co-expressed in heterologous expression systems, most of them display the ability to form heteromeric K(+) channels. Till now it was not clear whether plants use this potential of heteromerization to increase the functional diversity of potassium channels. Here, we designed an experimental approach employing different transgenic plant lines that allowed us to prove the existence of heteromeric K(+) channels in plants. The chosen strategy might also be useful for investigating the activity and function of other multimeric channel proteins like, for instance, cyclic-nucleotide gated channels, tandem-pore K(+) channels and glutamate receptor channels

Inactivation of trmFO1a and trmFO2 genes in Mycoplasma capricolum subsp. capricolum genome using tools of synthetic biology

International audienc