75 research outputs found
High-Efficiency Low-Voltage Rectifiers for Power Scavenging Systems
Abstract Rectifiers are commonly used in electrical energy conversion chains to transform the energy obtained from an AC signal source to a DC level. Conventional bridge and gate cross-coupled rectifier topologies are not sufficiently power efficient, particularly when input amplitudes are low. Depending on their rectifying element, their power efficiency is constrained by either the forward-bias voltage drop of a diode or the threshold voltage of a diode-connected MOS transistor. Advanced passive rectifiers use threshold cancellation techniques to effectively reduce the threshold voltage of MOS diodes. Active rectifiers use active circuits to control the conduction angle of low-loss MOS switches.
In this thesis, an active rectifier with a gate cross-coupled topology is proposed, which replaces the diode-connected MOS transistors of a conventional rectifier with low-loss MOS switches. Using the inherent characteristics of MOS transistors as comparators, dynamic biasing of the bulks of main switches and small pull-up transistors, the proposed self-supplied active rectifier exhibits smaller voltage drop across the main switches leading to a higher power efficiency compared to conventional rectifier structures for a wide range of operating frequencies in the MHz range. Delivery of high load currents is another feature of the proposed rectifier. Using the bootstrapping technique, single- and double-reservoir based rectifiers are proposed. They present higher power and voltage conversion efficiencies compared to conventional rectifier structures. With a source amplitude of 3.3 V, when compared to the gate cross-coupled topology, the proposed active rectifier offers power and voltage conversion efficiencies improved by up to 10% and 16% respectively. The proposed rectifier using the bootstrap technique, including double- and single-reservoir schemes, are well suited for very low input amplitudes. They present power and voltage conversion efficiencies of 75% and 76% at input amplitude of 1.0 V and maintain their high efficiencies over input amplitudes greater than 1.0V. Single-reservoir bootstrap rectifier also reduces die area by 70% compared to its double-reservoir counterpart.---------RĂ©sumĂ© Les redresseurs sont couramment utilisĂ©s dans de nombreux systĂšmes afin de transformer l'Ă©nergie Ă©lectrique obtenue Ă partir d'une source alternative en une alimentation continue. Les topologies traditionnelles telles que les ponts de diodes et les redresseurs se servant de transistors Ă grilles croisĂ©es-couplĂ©es ne sont pas suffisamment efficaces en terme dâĂ©nergie, en particulier pour des signaux Ă faibles amplitudes. DĂ©pendamment de leur Ă©lĂ©ment de redressement, leur efficacitĂ© en termes de consommation dâĂ©nergie est limitĂ©e soit par la chute de tension de polarisation directe d'une diode, soit par la tension de seuil du transistor MOS. Les redresseurs passifs avancĂ©s utilisent une technique de conception pour rĂ©duire la tension de seuil des diodes MOS. Les redresseurs actifs utilisent des circuits actifs pour contrĂŽler l'angle de conduction des commutateurs MOS Ă faible perte. Dans cette thĂšse, nous avons proposĂ© un redresseur actif avec une topologie en grille croisĂ©e-couplĂ©e. Elle utilise des commutateurs MOS Ă faible perte Ă la place des transistors MOS connectĂ©s en diode comme redresseurs. Le circuit proposĂ© utilise: des caractĂ©ristiques intrinsĂšques des transistors MOS pour les montages comparateurs et une polarisation dynamique des substrats des commutateurs principaux supportĂ©s par de petits transistors de rappel. Le redresseur proposĂ© prĂ©sente des faibles chutes de tension Ă travers le commutateur principal menant Ă une efficacitĂ© de puissance plus Ă©levĂ©e par rapport aux structures dâun redresseur conventionnel pour une large gamme de frĂ©quences de fonctionnement de lâordre des MHz. La conduction des courants de charge Ă©levĂ©e est une autre caractĂ©ristique du redresseur proposĂ©. En utilisant la mĂ©thode de bootstrap, des redresseurs Ă simple et Ă double rĂ©servoir sont proposĂ©s. Ils prĂ©sentent une efficacitĂ© de puissance et un rapport de conversion de tension Ă©levĂ©s en comparaison avec les structures des redresseurs conventionnels. Avec une amplitude de source de 3,3 V, le redresseur proposĂ© offre des efficacitĂ©s de puissance et de conversion de tension amĂ©liorĂ©es par rapport au circuit Ă transistors croisĂ©s couplĂ©s. Ces amĂ©liorations atteignent 10% et 16% respectivement. Les redresseurs proposĂ©s utilisent la technique de bootstrap. Ils sont bien adaptĂ©s pour des amplitudes d'entrĂ©e trĂšs basses. Ă une amplitude d'entrĂ©e de 1,0 V, ces derniers redresseurs prĂ©sentent des rendements de conversion de puissance et de tension de 75% et 76%. Le redresseur Ă simple rĂ©servoir rĂ©duit Ă©galement lâaire de silicium requise de 70% par rapport Ă la version Ă double-rĂ©servoir
The transcriptome of lae1 mutants of Trichoderma reesei cultivated at constant growth rates reveals new targets of LAE1 function
The VELVET A orthologue VEL1 of Trichoderma reesei regulates fungal development and is essential for cellulase gene expression
The VELVET A Orthologue VEL1 of Trichoderma reesei Regulates Fungal Development and Is Essential for Cellulase Gene Expression
Trichoderma reesei is the industrial producer of cellulases and hemicellulases for biorefinery processes. Their expression is obligatorily dependent on the function of the protein methyltransferase LAE1. The Aspergillus nidulans orthologue of LAE1--LaeA--is part of the VELVET protein complex consisting of LaeA, VeA and VelB that regulates secondary metabolism and sexual as well as asexual reproduction. Here we have therefore investigated the function of VEL1, the T. reesei orthologue of A. nidulans VeA. Deletion of the T. reesei vel1 locus causes a complete and light-independent loss of conidiation, and impairs formation of perithecia. Deletion of vel1 also alters hyphal morphology towards hyperbranching and formation of thicker filaments, and with consequently reduced growth rates. Growth on lactose as a sole carbon source, however, is even more strongly reduced and growth on cellulose as a sole carbon source eliminated. Consistent with these findings, deletion of vel1 completely impaired the expression of cellulases, xylanases and the cellulase regulator XYR1 on lactose as a cellulase inducing carbon source, but also in resting mycelia with sophorose as inducer. Our data show that in T. reesei VEL1 controls sexual and asexual development, and this effect is independent of light. VEL1 is also essential for cellulase gene expression, which is consistent with the assumption that their regulation by LAE1 occurs by the VELVET complex
The RNAi machinery controls distinct responses to environmental signals in the basal fungus Mucor circinelloides
BACKGROUND: RNA interference (RNAi) is a conserved mechanism of genome defence that can also have a role in the regulation of endogenous functions through endogenous small RNAs (esRNAs). In fungi, knowledge of the functions regulated by esRNAs has been hampered by lack of clear phenotypes in most mutants affected in the RNAi machinery. Mutants of Mucor circinelloides affected in RNAi genes show defects in physiological and developmental processes, thus making Mucor an outstanding fungal model for studying endogenous functions regulated by RNAi. Some classes of Mucor esRNAs map to exons (ex-siRNAs) and regulate expression of the genes from which they derive. To have a broad picture of genes regulated by the silencing machinery during vegetative growth, we have sequenced and compared the mRNA profiles of mutants in the main RNAi genes by using RNA-seq. In addition, we have achieved a more complete phenotypic characterization of silencing mutants. RESULTS: Deletion of any main RNAi gene provoked a deep impact in mRNA accumulation at exponential and stationary growth. Genes showing increased mRNA levels, as expected for direct ex-siRNAs targets, but also genes with decreased expression were detected, suggesting that, most probably, the initial ex-siRNA targets regulate the expression of other genes, which can be up- or down-regulated. Expression of 50% of the genes was dependent on more than one RNAi gene in agreement with the existence of several classes of ex-siRNAs produced by different combinations of RNAi proteins. These combinations of proteins have also been involved in the regulation of different cellular processes. Besides genes regulated by the canonical RNAi pathway, this analysis identified processes, such as growth at low pH and sexual interaction that are regulated by a dicer-independent non-canonical RNAi pathway. CONCLUSION: This work shows that the RNAi pathways play a relevant role in the regulation of a significant number of endogenous genes in M. circinelloides during exponential and stationary growth phases and opens up an important avenue for in-depth study of genes involved in the regulation of physiological and developmental processes in this fungal model
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The putative protein methyltransferase LAE1 controls cellulase gene expression in Trichoderma reesei
Trichoderma reesei is an industrial producer of enzymes that degrade lignocellulosic polysaccharides to soluble monomers, which can be fermented to biofuels. Here we show that the expression of genes for lignocellulose degradation are controlled by the orthologous T. reesei protein methyltransferase LAE1. In a lae1 deletion mutant we observed a complete loss of expression of all seven cellulases, auxiliary factors for cellulose degradation, ÎČ-glucosidases and xylanases were no longer expressed. Conversely, enhanced expression of lae1 resulted in significantly increased cellulase gene transcription. Lae1-modulated cellulase gene expression was dependent on the function of the general cellulase regulator XYR1, but also xyr1 expression was LAE1-dependent. LAE1 was also essential for conidiation of T. reesei. Chromatin immunoprecipitation followed by high-throughput sequencing (âChIP-seqâ) showed that lae1 expression was not obviously correlated with H3K4 di- or trimethylation (indicative of active transcription) or H3K9 trimethylation (typical for heterochromatin regions) in CAZyme coding regions, suggesting that LAE1 does not affect CAZyme gene expression by directly modulating H3K4 or H3K9 methylation. Our data demonstrate that the putative protein methyltransferase LAE1 is essential for cellulase gene expression in T. reesei through mechanisms that remain to be identified.This is the publisherâs final pdf. The published article is copyrighted by Wiley-Blackwell and can be found at: http://onlinelibrary.wiley.com/journal/10.1111/(ISSN)1365-2958/issue
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Functional Analyses of Trichoderma reesei LAE1 Reveal Conserved and Contrasting Roles of This Regulator
The putative methyltransferase LaeA is a global regulator that affects the expression of multiple secondary metabolite gene clusters in several fungi, and it can modify heterochromatin structure in Aspergillus nidulans. We have recently shown that the LaeA ortholog of Trichoderma reesei (LAE1), a fungus that is an industrial producer of cellulase and hemicellulase enzymes, regulates the expression of cellulases and polysaccharide hydrolases. To learn more about the function of LAE1 in T. reesei, we assessed the effect of deletion and overexpression of lae1 on genome-wide gene expression. We found that in addition to positively regulating 7 of 17 polyketide or nonribosomal peptide synthases, genes encoding ankyrin-proteins, iron uptake, heterokaryon incompatibility proteins, PTH11-receptors, and oxidases/monoxygenases are major gene categories also regulated by LAE1. chromatin immunoprecipitation sequencing with antibodies against histone modifications known to be associated with transcriptionally active (H3K4me2 and -me3) or silent (H3K9me3) chromatin detected 4089 genes bearing one or more of these methylation marks, of which 75 exhibited a correlation between either H3K4me2 or H3K4me3 and regulation by LAE1. Transformation of a laeA-null mutant of A. nidulans with the T. reesei lae1 gene did not rescue sterigmatocystin formation and further impaired sexual development. LAE1 did not interact with A. nidulans VeA in yeast two-hybrid assays, whereas it interacted with the T. reesei VeA ortholog, VEL1. LAE1 was shown to be required for the expression of vel1, whereas the orthologs of velB and VosA are unaffected by lae1 deletion. Our data show that the biological roles of A. nidulans LaeA and T. reesei LAE1 are much less conserved than hitherto thought. In T. reesei, LAE1 appears predominantly to regulate genes increasing relative fitness in its environment.Keywords: Flavus, Secondary metabolism,
Aspergillus nidulans,
Gene expression,
Hypocrea jecorina, DNA methylation,
Histone H3,
Protein kinase,
Neurospora crassa,
Penicillin biosynthesi
The role of methyltransferase LAE1 and related proteins for Trichoderma interaction with its environment
Zsfassung in dt. SpracheDas zuerst in Aspergillus spp. gefundene lae1 -Gen kodiert fĂŒr eine putative Methyltransferase, die in einem Komplex mit VeA,(VeA und VELB )als Master-Regulator des SekundĂ€rstoffwechsels, der Virulenz sowie der Entwicklung wirkt. LaeA reguliert auch die Biosynthese von SekundĂ€rmetaboliten in dem Penicillin-Produzenten Penicillium chrysogenum und den phytopathogenen Pilzen Fusarium fujikuroi (zB Gibberelline) und Cochliobolus heterostrophus. In allen diesen Prozessen wirkt LaeA auf Ebene der Chromatin Modifikation, und ermöglicht dadurch die koordinierte Transkruiption von Genclustern. Berichte ĂŒber die Beteiligung von LaeA in anderen zellulĂ€ren Prozessen sind nicht verfĂŒgbar.Trichoderma ist eine PIlzgattung mit breiten Anwendungen. T. reesei ist bekannt fĂŒr seine Produktion von Enzymen fĂŒr die Hydrolyse pflanzlicher Biomasse, wĂ€hrend T. atroviride sich durch einen ausgeprĂ€gten Mykoparasitismus aufweist und daher industriell als Biokontrollmittel angewandt wird. Die Gene, die Cellulasen kodieren, befinden sich in Clustern in Genom und werden koordiniert exprimiert. Ein genomisches Clustering von unter mykoparasitischen Bedingungen exprimierten Genen ist auch in T. atroviride beobachtet worden. Um herauszufinden, ob LAE1 von T. reesei die Expression von Cellulasen reguliert verwendete ich einen reversen genetischen Ansatz: in einer lae1 Deletionsmutante beobachtete ich einen vollstĂ€ndigen Verlust der Expression aller sieben Cellulasen, Hilfs-Faktoren fĂŒr die Celluloseabbau, [beta]-Glucosidasen und Xylanasen. Eine deutlich erhöhte Cellulasetranskription ergab sich in Mutanten mit erhöhter Expression von LAE1. ChromatinimmunprĂ€zipitation, verbunden mit Hochdurchsatz-Sequenzierung ("ChIP-seq") zeigte jedoch, dass offensichtlich die LAE1 Expression nicht mit H3K4 di oder Trimethylierung (indikativ aktiver Transkription) oder H3K9 Trimethylierung (typisch fĂŒr Heterochromatin Regionen) in CAZyme kodierenden Regionen korreliert. Genom-weite ChIP-Sequenzierung entdeckte 4089 Gene, die eine oder mehrere dieser Methylierung Marken ertragen, von denen 75 zeigten eine Korrelation zwischen beiden H3K4me2 oder H3K4me3 und Regulierung durch LAE1, was darauf hindeutet, dass LAE1 nicht direkt H3K4 oder H3K9 Methylierung moduliert.Eine genomweite Genexpressionsanalyse zeigte ferner, dass LAE1 positiv die Transkription von 7 der 17 Polyketid- oder nicht-ribosomalen Peptidsynthetasen reguliert. AuĂerdem wurden Gene, Proteine mit Ankyrin-Domainen, Eisenaufnahme, Heterokaryon InkompatibilitĂ€ts-Proteine, PTH11-Rezeptoren und verschiedene Oxidasen / Monoxygenasen kodieren, durch LAE1 reguliert. Um zu untersuchen, ob das Velvet A Protein aus T. reesei fĂŒr die Regulierung der Bildung von Cellulase durch LAE1 erforderlich ist, wurde das T. reesei Ortholog von vel1 charakterisiert. Deletion von vel1 beeinflusste nicht die Cellulase Genexpression in T. reesei, aber vel1 Ăberexpression hat sie stark verbessert. Ăhnliche Ergebnisse wurden auch fĂŒr die Bildung von Xylanase und Ă-Xylosidase EnzymaktivitĂ€ten erhalten. Die Stimulierung der Cellulase Genexpression durch Ăberexpression von vel1 war abhĂ€ngig von einer funktionellen LAE1 Allel und damit wurde ein vel1-unabhĂ€ngigen Modus der Aktivierung durch LAE1 in T. reesei angedeutet.In T. atroviride fĂŒhrte der Verlust der Funktion von LAE1 zu einer stark verringerten mykoparasitischen AktivitĂ€t und einer signifikanten Unterexpression von mehreren Genen, die frĂŒher als unter mykoparasitischer Interaktion hochreguliert gezeigt wurden, wie z. B Proteasen, GH16 Ă-Glucanasen, Polyketidsynthasen und kleine Cystein-reiche sekretierte Proteine. Dies korrelierte auch mit der teilweisen Verringerung der Bildung von fungiziden wasserlöslichen Metaboliten und flĂŒchtigen Metaboliten. Zusammenfassend deuten meine Daten auf neue Rollen von LAE1 in der Physiologie von Trichoderma hin.LAE1 scheint ein Regulator des Fitness von Pilzen in ihrem spezifischen Habitat zu sein.In Aspergillus spp. the laeA (loss of aflR expression) gene encodes a putative methyltransferase that acts in a complex with VeA, i.e., Velvet A, and VelB i.e., Velvet-like B, as master regulator of secondary metabolism, virulence as well as development. LaeA is also required for the biosynthesis of secondary metabolites in the penicillin producer Penicillium chrysogenum and the phytopathogenic fungi Fusarium fujikuroi (e.g., gibberellins) and Cochliobolus heterostrophus respectively- In all these processes, LaeA acts at the level of chromatin modification thereby rendering gene clusters to be coordinately transcribed. Reports about the involvment of LaeA in other cellular processes is not available. Trichoderma is a genus of filamentous fungi with broad range of applications. T. reesei is well known for its production of enzymes used for plant biomass hydrolysis whereas T. atroviride is conspicuous for its vigorous mycoparasitism and is therefore industrially applied as a biocontrol agent. The genes encoding cellulases are found in clusters in genome and expressed coordinately. Similarly, genomic clustering of mycoparasitic genes have been also observed in T. atroviride. In order to learn whether LAE1 of T. reesei is involved in the expression of cellulase genes I used reverse genetics to show that is indeed the case: in a lae1 deletion mutant we observed a complete loss of expression of all seven cellulases, auxiliary factors for cellulose degradation, [beta]-glucosidases and xylanases were no longer expressed.Conversely, enhanced expression of lae1 resulted in significantly increased cellulase gene transcription. Interestingly, chromatin immunoprecipitation followed by highthroughput sequencing ("ChIP-seq") showed that lae1 expression was not obviously correlated with H3K4 di or trimethylation (indicative of active transcription) or H3K9 trimethylation (typical for heterochromatin regions) in CAZyme coding regions. Genome-wide ChIP sequencing detected 4089 genes bearing one or more of these methylation marks, of which 75 exhibited a correlation between either H3K4me2 or H3K4me3 and regulation by LAE1, suggesting that LAE1 does not directly modulate H3K4 or H3K9 methylation.Genome-wide gene expression analysis showed that lae1 positively regulates 7 of 17 polyketide or nonribosomal peptide synthases, genes encoding ankyrin-containing proteins, iron uptake, heterokaryon incompatibility proteins, PTH11-receptors, and oxidases/monoxygenases are major gene categories also regulated by LAE1. To investigate whether the Velvet A protein would be required for the regulation of cellulase formation by LAE1, I characterized the T. reesei orthologue vel1.Deletion of vel1 did not affect cellulase gene expression in T. reesei, but vel1 overexpression strongly enhanced it. Similar findings were also obtained for the formation of xylanase and Ă-xylosidase enzyme activities. The stimulation of cellulase gene expression by overexpressing vel1 was dependent on a functional lae1 allele, suggesting the operation of a vel1-independent pathway of activation by LAE1 in T. reesei.In T. atroviride, loss of function of lae1 results in a loss of mycoparasitic activity correlated with a significant underexpression of several genes normally upregulated during mycoparasitic interaction (proteases, GH16 Ă-glucanases, polyketide synthases and small cystein-rich secreted proteins), which was also reflected in the partial reduction of formation of fungicidal water soluble metabolites and volatile compounds. Summarizing, my data point to new roles of LAE1 in the physiology of Trichoderma. LAE1 appears to be a regulator of the fungus fitness in its specialized habitat.<br /
Characterization of integrated MOS circuits under voltage stress and application to power conversion chains of electronic implants
Motivation -- Research goals -- Thesis outline -- Power conversion chain for electronic implant -- Implant power-up techniques -- Constraints and limitations -- Conventional PCC's architecture -- Smart synchronous rectifier -- Smart synchronous rectifier versus classical diode rectifier -- New PCC architectures based on SSR -- High-efficient voltage multiplier -- Charge pump -- Single-stage voltage multiplier -- Voltage multiplier characteristics -- Power efficiency improvement -- Low-voltage application -- Multi-stage voltage multiplier -- Reliability challenges of CMOS under sub-micron regime -- Short channel effects -- Narrow-channel effects -- Subthreshold and leakage currents -- Hot carriers effects -- Punch-through -- Breakdown voltages -- Stress-induced measurement techniques -- Quantitative, simulation and measurement results -- Quantitative results for power conversion chains -- Simulation results for multi-stage voltage multiplier
The Putative Protein Methyltransferase LAE1 of <i>Trichoderma atroviride</i> Is a Key Regulator of Asexual Development and Mycoparasitism
<div><p>In Ascomycota the protein methyltransferase LaeA is a global regulator that affects the expression of secondary metabolite gene clusters, and controls sexual and asexual development. The common mycoparasitic fungus <i>Trichoderma atroviride</i> is one of the most widely studied agents of biological control of plant-pathogenic fungi that also serves as a model for the research on regulation of asexual sporulation (conidiation) by environmental stimuli such as light and/or mechanical injury. In order to learn the possible involvement of LAE1 in these two traits, we assessed the effect of deletion and overexpression of <i>lae1</i> gene on conidiation and mycoparasitic interaction. In the presence of light, conidiation was 50% decreased in a <b>Î</b><i>lae1</i> and 30â50% increased in <i>lae1</i>-overexpressing (OE<i>lae1</i>) strains. In darkness, <b>Î</b><i>lae1</i> strains did not sporulate, and the OE<i>lae1</i> strains produced as much spores as the parent strain. Loss-of-function of <i>lae1</i> also abolished sporulation triggered by mechanical injury of the mycelia. Deletion of <i>lae1</i> also increased the sensitivity of <i>T. atroviride</i> to oxidative stress, abolished its ability to defend against other fungi and led to a loss of mycoparasitic behaviour, whereas the <i>OElae1</i> strains displayed enhanced mycoparasitic vigor. The loss of mycoparasitic activity in the <b>Î</b><i>lae1</i> strain correlated with a significant underexpressionn of several genes normally upregulated during mycoparasitic interaction (proteases, GH16 Ă-glucanases, polyketide synthases and small cystein-rich secreted proteins), which in turn was reflected in the partial reduction of formation of fungicidal water soluble metabolites and volatile compounds. Our study shows <i>T. atroviride</i> LAE1 is essential for asexual reproduction in the dark and for defense and parasitism on other fungi.</p></div
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