Mise au point d'un dispositif de mesure d'impédance complexe, micro-onde et cryogénique

Ce mémoire rapporte la mise au point d’un montage de mesure de l’impédance complexe d’un échantillon micro fabriqué au travers de son coefficient de réflexion Γ, et ce sur une gamme de fréquences de 200 MHz à 25 GHz et à une température pouvant aller jusqu’à (T∼1, 5 K). Ce montage repose sur l’utilisation de procédures de calibration et d’une sonde micro-onde cryogénique. Le montage est utilisé pour caractériser plusieurs types d’échantillons micro fabriqués : inductance, capacitance, mais aussi une jonction tunnel et une jonction Josephson. Ce mémoire ouvre la porte à une multitude d’expériences à haute fréquence qui permettront d’explorer par exemple la dynamique de systèmes mésoscopiques

Mise au point d'un dispositif de mesure d'impédance complexe, micro-onde et cryogénique

Ce mémoire rapporte la mise au point d’un montage de mesure de l’impédance complexe d’un échantillon micro fabriqué au travers de son coefficient de réflexion Γ, et ce sur une gamme de fréquences de 200 MHz à 25 GHz et à une température pouvant aller jusqu’à (T∼1, 5 K). Ce montage repose sur l’utilisation de procédures de calibration et d’une sonde micro-onde cryogénique. Le montage est utilisé pour caractériser plusieurs types d’échantillons micro fabriqués : inductance, capacitance, mais aussi une jonction tunnel et une jonction Josephson. Ce mémoire ouvre la porte à une multitude d’expériences à haute fréquence qui permettront d’explorer par exemple la dynamique de systèmes mésoscopiques

Comparative transcriptome analysis of three oil palm fruit and seed tissues that differ in oil content and fatty acid composition

Oil palm (Elaeis guineensis) produces two oils of major economic importance, commonly referred to as palm oil and palm kernel oil, extracted from the mesocarp and the endosperm, respectively. While lauric acid predominates in endosperm oil, the major fatty acids (FAs) of mesocarp oil are palmitic and oleic acids. The oil palm embryo also stores oil, which contains a significant proportion of linoleic acid. In addition, the three tissues display high variation for oil content at maturity. To gain insight into the mechanisms that govern such differences in oil content and FA composition, tissue transcriptome and lipid composition were compared during development. The contribution of the cytosolic and plastidial glycolytic routes differed markedly between the mesocarp and seed tissues, but transcriptional patterns of genes involved in the conversion of sucrose to pyruvate were not related to variations for oil content. Accumulation of lauric acid relied on the dramatic up-regulation of a specialized acyl-acyl carrier protein thioesterase paralog and the concerted recruitment of specific isoforms of triacylglycerol assembly enzymes. Three paralogs of the WRINKLED1 (WRI1) transcription factor were identified, of which EgWRI1-1 and EgWRI1-2 were massively transcribed during oil deposition in the mesocarp and the endosperm, respectively. None of the three WRI1 paralogs were detected in the embryo. The transcription level of FA synthesis genes correlated with the amount of WRI1 transcripts and oil content. Changes in triacylglycerol content and FA composition of Nicotiana benthamiana leaves infiltrated with various combinations of WRI1 and FatB paralogs from oil palm validated functions inferred from transcriptome analysis

Identification and development of new polymorphic microsatellite markers using genome assembly for Ganoderma boninense, causal agent of oil palm basal stem rot disease

International audienceGanoderma boninense is a telluric lignicolous basidiomycete and the causal agent of basal stem rot, one of the most devastating diseases of the oil palm (Elaeis guineensis). While the fight against G. boninense is of major concern in Southeast Asia, little information is available regarding the genetic diversity and evolutionary history of the fungus. In this context, the development of an informative molecular marker set to characterize the diversity of G. boninense is a key step towards understanding the biology of this pathogen. A G. boninense draft genome sequence of 63 Mbp, assembled using 454 and Illumina sequencing technology, was used to identify and develop a set of microsatellite markers (simple sequence repeats, SSRs). A total of 2487 SSRs were identified, for which 145 SSR primer pairs were designed. These SSRs are characterized by di- to hexanucleotide motifs with 5 to 34 repetitions. Ninety-seven SSR loci were successfully amplified on an initial small set of G. boninense isolates from Indonesia. A collection of 107 isolates from several regions in Southeast Asia were screened to characterize each locus for allele number, polymorphism information criterion and the presence or absence of null alleles at each locus. These results allowed us to propose an effective set of 17 SSRs for studying genetic diversity within G. boninense