La régulation et le contrôle-qualité de l'expression génique permettent respectivement de maintenir un équilibre entre synthèse et dégradation des ARNm répondant aux besoins cellulaires et d'empêcher l'expression d'ARNm ou protéines aberrants potentiellement toxiques. Pour mieux comprendre ces processus cytoplasmiques, je me suis intéressée à Jlp2, Tac4 et Ska1, trois protéines ayant des liens physiques ou fonctionnels avec des acteurs du contrôle-qualité des ARNm et peptides appartenant aux complexes RQC et SKI. Jlp2 montre des liens de létalité synthétique avec les complexes RQC et SKI mais son absence n'altère pas le " NonStop mRNA Decay ". Elle pourrait donc être impliquée dans une autre voie de contrôle dépendante des complexes RQC et SKI. Tac4 est une ARN hélicase putative associée aux ribosomes, au niveau de l'hélice H16 de l'ARNr 18S comme son homologue putatif mammifère DHX29. Elle interagit également au niveau de régions 3'UTR d'ARNm. Ces observations suggèrent que Tac4 pourrait être impliquée dans la réinitiation de la traduction et le sauvetage de ribosomes non-dissociés récemment identifiés dans la région 3'UTR d'ARNm. Enfin, nous avons identifié Ska1, une protéine appartenant à une nouvelle sous-population de complexes SKI. Nos données suggèrent que ce complexe SKI-Ska1 est impliqué dans la dégradation de transcrits dépourvus de ribosome. Nous proposons un modèle selon lequel ce complexe SKI-Ska1 agirait durant la dégradation de 3'UTR avec l'exosome, puis en arrivant dans la région codante et en rencontrant un ribosome, Ska1 se dissocierait du complexe pour lui permettre d'interagir directement avec le ribosome et poursuivre la dégradation 3'-5' de l'ARN. / Mechanisms responsible for the regulation of gene expression and its quality-control are required, respectively for maintaining an equilibrium between mRNA synthesis and degradation and to prevent synthesis of aberrant mRNAs and proteins potentially toxic for the cells. To better understand these quality-control processes, I studied three factors, Jlp2, Tac4 and Ska1, with physical or functional links described with factors involved in mRNA and protein quality-control, the RQC and SKI complexes. Jlp2 shows synthetic lethality with the RQC and SKI complexes but its deletion has no effect on the NonStop mRNA Decay, suggesting that Jlp2 could be implicated in another control pathway linked to the RQC and SKI complexes. Tac4 is a putative RNA helicase bound to ribosomes, on the 18S rRNA H16 helix, as its mammalian putative homolog DHX29. DHX29 plays a role in translation initiation but surprisingly, Tac4 interacts, in addition to ribosomes, with mRNA 3’UTRs. These observations suggest that Tac4 could be implicated in translation reinitiation and rescue of non-dissociated-ribosomes, recently described within mRNA 3’UTRs. Finally, we identified Ska1, a new factor associated to a SKI complex subpopulation. Our observations suggest that the SKI-Ska1 complex is implicated in the degradation of transcripts devoid of ribosomes. It suggests a model by which the SKI complex would proceed in two steps. First, the SKI-Ska1 complex could assist the exosome to degrade 3’UTR regions of RNAs and then, when its reaches the coding region and encounter a ribosome, Ska1 would leave the complex and allow it to interact directly with ribosomes to proceed further in the 3’-5’ RNA degradation.

Detta examensarbete beskriver i detalj hur ICC-profiler fo¨r utskriftsmedier, i detta fall fo¨r storformatskrivare, skapas. Examensarbetet omfattade framtagande av ICC-profiler fo¨r substrat till storformatskrivaren Mutoh Toucan PJ-1614NXE (Mutoh Toucan) hos BEMI REKLAM AB (BEMI), Borla¨nge. Fo¨retaget har tidigare anva¨nt en standardlinja¨risering till samtliga substrat fo¨r storformatskrivaren, dock utan att applicera na°gon ICC-profil fo¨r utenheter. Samtliga substrat till Mutoh Toucan a¨r avsedda fo¨r utomhusbruk.

Abnormal electromagnetic wave propagation characterized by negative group velocity and consequently negative group delay (NGD) has been observed in certain materials as well as in artificially built structures. Within finite frequency intervals where an NGD phenomenon is observed, higher frequency components of the applied waveform are propagated with phase advancement, not delay, relative to the lower frequency components. These media have found use in many applications that require positive delay compensation and an engineered phase characteristic, such as eliminating phase variation with frequency in phase shifters, beam-squint minimization in phased array antenna systems, size reduction of feed-forward amplifiers and others. The three principal questions this thesis addresses are: can a generic formulation for artificial NGD structures based on electric circuit resonators be developed; is it possible to derive a quantitative functional relationship (asymptotic limit) between the maximum achievable NGD and the identified trade-off quantity (out-of-band gain); and, can a microwave circuit exhibiting a fully loss-compensated NGD propagation in both directions be designed and implemented? A generic frequency-domain formulation of artificial NGD structures based on electric circuit resonators is developed and characterized by three parameters, namely center frequency, bandwidth and the out-of-band gain. The developed formulation is validated through several topologies reported in the literature. The trade-off relationship between the achievable NGD on one hand, and the out-of-band gain on the other, is identified. The out-of-band gain is shown to be proportional to transient amplitudes when waveforms with defined “turn on/off” times are propagated through an NGD medium. An asymptotic limit for achievable NGD as a function of the out-of-band gain is derived for multi-stage resonator-based NGD circuits as well as for an optimally engineered linear causal NGD medium. Passive NGD media exhibit loss which can be compensated for via active elements. However, active elements are unilateral in nature and therefore do not allow propagation in both directions. A bilateral gain-compensated circuit is designed and implemented, which overcomes this problem by employing a dual-amplifier configuration while preserving the overall circuit stability.

Abnormal electromagnetic wave propagation characterized by negative group velocity and consequently negative group delay (NGD) has been observed in certain materials as well as in artificially built structures. Within finite frequency intervals where an NGD phenomenon is observed, higher frequency components of the applied waveform are propagated with phase advancement, not delay, relative to the lower frequency components. These media have found use in many applications that require positive delay compensation and an engineered phase characteristic, such as eliminating phase variation with frequency in phase shifters, beam-squint minimization in phased array antenna systems, size reduction of feed-forward amplifiers and others. The three principal questions this thesis addresses are: can a generic formulation for artificial NGD structures based on electric circuit resonators be developed; is it possible to derive a quantitative functional relationship (asymptotic limit) between the maximum achievable NGD and the identified trade-off quantity (out-of-band gain); and, can a microwave circuit exhibiting a fully loss-compensated NGD propagation in both directions be designed and implemented? A generic frequency-domain formulation of artificial NGD structures based on electric circuit resonators is developed and characterized by three parameters, namely center frequency, bandwidth and the out-of-band gain. The developed formulation is validated through several topologies reported in the literature. The trade-off relationship between the achievable NGD on one hand, and the out-of-band gain on the other, is identified. The out-of-band gain is shown to be proportional to transient amplitudes when waveforms with defined “turn on/off” times are propagated through an NGD medium. An asymptotic limit for achievable NGD as a function of the out-of-band gain is derived for multi-stage resonator-based NGD circuits as well as for an optimally engineered linear causal NGD medium. Passive NGD media exhibit loss which can be compensated for via active elements. However, active elements are unilateral in nature and therefore do not allow propagation in both directions. A bilateral gain-compensated circuit is designed and implemented, which overcomes this problem by employing a dual-amplifier configuration while preserving the overall circuit stability.