Cryopreservation of encapsulated apices of sugarcane : effect of freezing procedure and histology

SUMMARY: The effect of sucrose concentration during the pregrowth treatment and of the freezing procedure on the survival of encapsulated apices of 6 sugarcane varieties was investigated. The optimal sucrose concentration was 0.75M. Survival was noted with both rapid freezing by direct immersion in liquid nitrogen and slow freezing using a programmable freezer but it was generally higher &er rapid cooling. Important genotypic variation was observed for both parameters studied. Histological examination revealed that cells were slightly harmed during pregrowth and freezing. Apices could withstand freezing as a whole. Direct regrowth of cryopreserved apices occurred within 3 days after thawing

Electro-mechanical Resonant Ice Protection Systems: Initiation of Fractures with Piezoelectric Actuators

Recent research is showing growing interest in low-power electromechanical de-icing systems and, in particular, de-icing systems based on piezoelectric actuators. These systems use the vibrations generated by piezoelectric actuators at resonance frequencies to produce shear stress at the interface between the ice and the support or to produce tensile stress in the ice. Many configurations of de-icing systems using piezoelectric actuators have been tested and showed that piezoelectric actuation may be a viable ice removal system. If the many experimental studies already achieved have the advantage to present tests in different configurations, they often lack analysis of the phenomena, which limits the optimization opportunities. This paper proposes a computational method for estimating voltages and currents of a piezoelectric de-icing system to initiate cohesive fractures in the ice or adhesive fractures at the ice/support interface. The computational method is validated by comparing numerical results with experimental results. Other contributions of this paper are the study of the types of mode (extensional or flexural) and of the frequency range with respect to de-icing performances and the proposal of some general rules for designing such systems while limiting their electric power consumption

Histo-cytological study of apices of coffee (Coffea racemosa and C. sessiliflora) in vitro plantlets during their cryopreservation using the encapsulation-dehydration technique

Les apex de microboutures #in vitro de #Coffea racemosa et #C. sessiliflora supportent la congélation dans l'azote liquide en utilisant la technique d'encapsulation-déshydratation. Une accumulation intense d'amidon est notée après une nuit de culture des apex sur le milieu standard. Les apex de #C. sessiliflora nécessitent 3 à 10 jours de préculture dans un milieu liquide contenant 0,75 M de saccharose, tandis que ceux de #C. racemosa$nécessitent une augmentation progressive de la concentration en saccharose de 0,5 à 1 M. Après la période de déshydratation, les cellules de certains apex sont très endommagées, présentant des granules osmophiles sur la surface du plasmalemme. Pour d'autres apex, les cellules sont moins endommagées, montrant des vésicules d'exocytose à la périphérie de la membrane plasmatique. Après congélation, des taux de survie de 27 à 37$ et #C. sessiliflora$ respectivement. Deux modes de croissance sont observés : développement direct du primordium foliaire ou callogenèse. (Résumé d'auteur

Histo-cytological study of apices of coffee (Coffea racemosa and C. sessiliflora) in vitro plantlets during their cryopreservation using the encapsulation-dehydration technique

Les apex de microboutures #in vitro de #Coffea racemosa et #C. sessiliflora supportent la congélation dans l'azote liquide en utilisant la technique d'encapsulation-déshydratation. Une accumulation intense d'amidon est notée après une nuit de culture des apex sur le milieu standard. Les apex de #C. sessiliflora nécessitent 3 à 10 jours de préculture dans un milieu liquide contenant 0,75 M de saccharose, tandis que ceux de #C. racemosa$nécessitent une augmentation progressive de la concentration en saccharose de 0,5 à 1 M. Après la période de déshydratation, les cellules de certains apex sont très endommagées, présentant des granules osmophiles sur la surface du plasmalemme. Pour d'autres apex, les cellules sont moins endommagées, montrant des vésicules d'exocytose à la périphérie de la membrane plasmatique. Après congélation, des taux de survie de 27 à 37$ et #C. sessiliflora$ respectivement. Deux modes de croissance sont observés : développement direct du primordium foliaire ou callogenèse. (Résumé d'auteur

Nanoscale measurements of phosphorous-induced lattice expansion in nanosecond laser annealed germanium

International audienceLaser Thermal Annealing (LTA) at various energy densities was used to recrystallize and activate amorphized germanium doped with phosphorous by ion implantation. The structural modifications induced during the recrystallization and the related dopantdiffusion were first investigated. After LTA at low energy densities, the P electrical activation was poor while the dopant distribution was mainly localized in the polycrystalline Ge resulting from the anneal. Conversely, full dopant activation (up to 1 1020 cm3) in a perfectly recrystallized material was observed after annealing at higher energy densities. Measurements of lattice parameters performed on the fullyactivated structures show that P doping results in a lattice expansion, with a perpendicular lattice strain per atom Ps = +0.7 0.1 Å3. This clearly indicates that, despite the small atomic radius of P compared to Ge, the “electronic contribution” to thelattice parameter modification (due to the increased hydrostatic deformation potential in the conduction band of P doped Ge) is larger than the “size mismatch contribution” associated with the atomic radii. Such behavior, predicted by theory, is observedexperimentally for the first time, thanks to the high sensitivity of the measurement techniques used in this work

Dimerization equilibrium of infrared spectroscopy and electronic structure calculations

International audienc

Dimerization equilibrium of infrared spectroscopy and electronic structure calculations

International audienc