Relevant bibliographies by topics / Facteur sigma

Contents

  1. Journal articles
  2. Dissertations / Theses
  3. Books
  4. Book chapters
  5. Conference papers
  6. Reports

Academic literature on the topic 'Facteur sigma'

Author: Grafiati
Published: 4 June 2021
Last updated: 7 February 2022

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles

Select a source type:

Consult the lists of relevant articles, books, theses, conference reports, and other scholarly sources on the topic 'Facteur sigma.'

Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.

You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.

Journal articles on the topic "Facteur sigma"

1

Kovarz, L., C. Coynault, V. Robbe-Saule, and F. Norel. "Rôle du facteur sigma σs (RpoS) dans la virulence de Salmonella typhimurium." Médecine et Maladies Infectieuses 25, no. 10 (October 1995): 1031–34. http://dx.doi.org/10.1016/s0399-077x(05)80327-0.

Full text
APA, Harvard, Vancouver, ISO, and other styles
2

De Las Peñas, A., L. Connolly, and C. A. Gross. "SigmaE is an essential sigma factor in Escherichia coli." Journal of bacteriology 179, no. 21 (1997): 6862–64. http://dx.doi.org/10.1128/jb.179.21.6862-6864.1997.

Full text
APA, Harvard, Vancouver, ISO, and other styles
3

Schmid, Solveig, Claudia Bevilacqua, and Anne-Marie Crutz-Le Coq. "Alternative sigma factor sigmaH activates competence gene expression in Lactobacillus sakei." BMC Microbiology 12, no. 1 (2012): 32. http://dx.doi.org/10.1186/1471-2180-12-32.

Full text
APA, Harvard, Vancouver, ISO, and other styles
4

Loewen, P. C., and R. Hengge-Aronis. "The Role of the Sigma Factor sigmas (KatF) in Bacterial Global Regulation." Annual Review of Microbiology 48, no. 1 (October 1994): 53–80. http://dx.doi.org/10.1146/annurev.mi.48.100194.000413.

Full text
APA, Harvard, Vancouver, ISO, and other styles
5

Yu, H., J. C. Boucher, N. S. Hibler, and V. Deretic. "Virulence properties of Pseudomonas aeruginosa lacking the extreme-stress sigma factor AlgU (sigmaE)." Infection and immunity 64, no. 7 (1996): 2774–81. http://dx.doi.org/10.1128/iai.64.7.2774-2781.1996.

Full text
APA, Harvard, Vancouver, ISO, and other styles
6

Huang, Xuejun, Ahmed Gaballa, Min Cao, and John D. Helmann. "Identification of target promoters for the Bacillus subtilis extracytoplasmic function sigma factor, sigmaW." Molecular Microbiology 31, no. 1 (January 1999): 361–71. http://dx.doi.org/10.1046/j.1365-2958.1999.01180.x.

Full text
APA, Harvard, Vancouver, ISO, and other styles
7

Loewen, Peter C., Bei Hu, Jeanna Strutinsky, and Richard Sparling. "Regulation in the rpoS regulon of Escherichia coli." Canadian Journal of Microbiology 44, no. 8 (August 1, 1998): 707–17. http://dx.doi.org/10.1139/w98-069.

Full text
Abstract:
In Escherichia coli, the transcription factor sigmaS, encoded by rpoS, controls the expression of a large number of genes involved in cellular responses to a diverse number of stresses, including starvation, osmotic stress, acid shock, cold shock, heat shock, oxidative DNA damage, and transition to stationary phase. A list of over 50 genes under the control of rpoS has been compiled. The transcription factor sigmaS acts predominantly as a positive effector, but it does have a negative effect on some genes. The synthesis and accumulation of sigmaS are controlled by mechanisms affecting transcription, translation, proteolysis, and the formation of the holoenzyme complex. Transcriptional control of rpoS involves guanosine 3',5'-bispyrophosphate (ppGpp) and polyphosphate as positive regulators and the cAMP receptor protein - cAMP complex (CRP-cAMP) as a negative regulator. Translation of rpoS mRNA is controlled by a cascade of interacting factors, including Hfq, H-NS, dsrA RNA, LeuO, and oxyS RNA that seem to modulate the stability of a region of secondary structure in the ribosome-binding region of the gene's mRNA. The transcription factor sigmaS is sensitive to proteolysis by ClpPX in a reaction that is promoted by RssB and inhibited by the chaperone DnaK. Despite the demonstrated involvement of so many factors, arguments have been presented suggesting that sensitivity to proteolysis may be the single most important modulator of sigmaS levels. The activity of sigmaS may also be modulated by trehalose and glutamate, which activate holoenzyme formation and promote holoenzyme binding to certain promoters. Key words: transcription, translation, regulation, sigma factor, starvation.
APA, Harvard, Vancouver, ISO, and other styles
8

Manganelli, Riccardo, Martin I. Voskuil, Gary K. Schoolnik, Eugenie Dubnau, Manuel Gomez, and Issar Smith. "Role of the extracytoplasmic-function sigma Factor sigmaH in Mycobacterium tuberculosis global gene expression." Molecular Microbiology 45, no. 2 (July 2002): 365–74. http://dx.doi.org/10.1046/j.1365-2958.2002.03005.x.

Full text
APA, Harvard, Vancouver, ISO, and other styles
9

Otani, Hiroshi, Akiyoshi Higo, Hideaki Nanamiya, Sueharu Horinouchi, and Yasuo Ohnishi. "An alternative sigma factor governs the principal sigma factor inStreptomyces griseus." Molecular Microbiology 87, no. 6 (February 21, 2013): 1223–36. http://dx.doi.org/10.1111/mmi.12160.

Full text
APA, Harvard, Vancouver, ISO, and other styles
10

Chang, B. Y., and R. H. Doi. "Conformational properties of Bacillus subtilis RNA polymerase σA factor during transcription initiation." Biochemical Journal 294, no. 1 (August 15, 1993): 43–47. http://dx.doi.org/10.1042/bj2940043.

Full text
Abstract:
By the use of a partial proteolysis method and Western-blot analysis, the conformational properties of Bacillus subtilis sigma A factor in the transcription initiation stage were studied. From a comparison of the trypsin-digestion patterns of free sigma A and of sigma A associated with core enzyme, it was found that the production of 45 kDa sigma A tryptic-derived fragment was enhanced when sigma A was associated with the core enzyme. More importantly, a 40 kDa sigma A tryptic-derived fragment was found exclusively in this associated state. Based on the change of the digestion kinetics when producing the 45 kDa tryptic fragment and the generation of this new 40 kDa tryptic fragment from sigma A, it was apparent that a conformation change of sigma A occurred during the association of sigma A with the core enzyme. Also, similar patterns were found for the sigma A present in the holoenzyme-promoter DNA complex. These findings suggest that no further distinctive conformational change of sigma A occurs at the step of RNA polymerase holoenzyme and promoter DNA complex formation. Trypsin-digestion patterns of sigma A in different RNA polymerase holoenzyme and promoter DNA complexes were also studied. The presence of similar trypsin digestion-patterns of sigma A in those complexes strongly supports the idea that a similar sigma A conformation is used in the recognition of different sigma A-type promoters and the formation of different open complexes.
APA, Harvard, Vancouver, ISO, and other styles
More sources

Dissertations / Theses on the topic "Facteur sigma"

1

Potvin, Éric. "Génomique fonctionnelle de Pseudomonas aeruginosa et analyse moléculaire fine d'un facteur sigma-anti-sigma." Thesis, Université Laval, 2007. http://www.theses.ulaval.ca/2007/24237/24237.pdf.

Full text
Abstract:
Pseudomonas aeruginosa est un pathogène opportuniste pouvant causer des infections pulmonaires chroniques chez les gens atteints de la Fibrose Kystique (FK). Pour réussir à s’implanter dans les voies respiratoires des patients FK, P. aeruginosa dispose d’un important arsenal de facteurs de virulence, dont la sécrétion de protéases, de lipases, de phospholipases ainsi que la production de toxines spécifiques. Le séquençage complet du chromosome de P. aeruginosa souche PAO1 (6.3 Mb) a révélé une organisation génomique hautement régulée. Dans le but de mieux comprendre l’interaction hôte-pathogène, nous avons utilisé la technique de mutagenèse à étiquette (STM). La STM a permis d’isoler 214 mutants incapables de maintenir l’infection pulmonaire chronique chez le rat. Parmi ceux-ci, le mutant STM2895, contenant un transposon dans le gène PA2895, a été retenu pour des analyses plus approfondies. L'étude phénotypique de STM2895 a permis de constater un défaut dans la production d’exoprotéases lorsque comparé à la souche sauvage PAO1. La caractérisation biochimique de ce défaut, utilisant des tests de dégradation spécifiques et l’immunobuvardage, a démontré qu’au moins deux des quatre protéases majeures sécrétées par P. aeruginosa sont impliquées. En effet, les élastases LasA et LasB ont été démontrées non fonctionnelles probablement dues à un problème de repliement. PA2895, une protéine possédant un domaine transmembranaire prédit, ne code pour aucune fonction connue, mais il est co-transcrit avec le gène PA2896, un facteur sigma putatif de type ECF (extracytoplasmic function). Des analyses en transcriptome sur le mutant STM2895, ainsi que sur un mutant de délétion de PA2896, ont permis de lier l’opéron au métabolisme du fer. De plus, des études in vivo dans le modèle d’infection pulmonaire chronique chez le rat ont clairement démontré que le mutant STM2895 est incapable de se maintenir dans l’hôte au même niveau que la souche sauvage PAO1. Le gène PA2895 est donc essentiel au maintien in vivo de P. aeruginosa dans le poumon de rat.
Pseudomonas aeruginosa is an opportunistic pathogen that can cause pulmonary infections in cystic fibrosis patients (CF). To overcome innate self defense, P. aeruginosa possesses a wide arsenal of virulence factors. These include degradation enzymes such as proteases, lipases and phospholipases and the production of three specific toxins: exotoxin A and exoenzymes S and T. Sequencing of the complete P. aeruginosa chromosome (strain PAO1) of 6.3 Mb revealed a highly regulated and complex genomic organization. In order to better understand host-pathogen molecular interactions, we developped a new signature-tagged mutagenesis (STM) approach based on PCR screening. The PCR-based STM technology lead to the identification of 214 mutants deficient in their ability to maintain a chronic pulmonary infection in the rat lung. In that pool of STM mutants, STM2895, which contains a transposon insertion in functional PA2895, was the most frequently drafted during the whole mutant library screening. Phenotypic analyses of the STM2895 strain allowed us to identify an exoprotease production defect as compared with wild type strain PAO1. The biochemical characterization of that proteolytic default using specific degradation assays combined with western blotting revealed that at least two (LasA and LasB) of the four major exoproteases from P. aeruginosa STM2895 strain are inactive. In fact, LasA and LasB elastases were shown to be present in the STM2895 culture supernatant, correctly processed but inactive due to a probable misfolding of proteins. The PA2895 gene (unknown function) encodes a protein with a predicted transmembrane domain. Basic genomic context analyses strongly suggest a cotranscription unit with the downstream gene PA2896, a putative sigma 70 factor from ECF (extracytoplasmic function) type. Microarray experiments on the STM2895 strain and an insertional mutant of the PA2896 gene were performed to establish a link between the putative PA2895-PA2896 operon and the metabolism of iron. Transcriptome analysis also demonstrated a repressive action of PA2895 on the transcription of PA2896 putative sigma factor. Finally, in vivo studies in the rat lung chronic infection model clearly showed a ten-fold decrease in survival capacity of the mutant strain when compared to the PAO1 wild-type strain.
APA, Harvard, Vancouver, ISO, and other styles
2

Potvin, Eric. "Génomique fonctionnelle de Pseudomonas aeruginosa et analyse moléculaire fine d'un facteur sigma-anti-sigma." Doctoral thesis, Université Laval, 2007. http://hdl.handle.net/20.500.11794/19067.

Full text
Abstract:
Pseudomonas aeruginosa est un pathogène opportuniste pouvant causer des infections pulmonaires chroniques chez les gens atteints de la Fibrose Kystique (FK). Pour réussir à s’implanter dans les voies respiratoires des patients FK, P. aeruginosa dispose d’un important arsenal de facteurs de virulence, dont la sécrétion de protéases, de lipases, de phospholipases ainsi que la production de toxines spécifiques. Le séquençage complet du chromosome de P. aeruginosa souche PAO1 (6.3 Mb) a révélé une organisation génomique hautement régulée. Dans le but de mieux comprendre l’interaction hôte-pathogène, nous avons utilisé la technique de mutagenèse à étiquette (STM). La STM a permis d’isoler 214 mutants incapables de maintenir l’infection pulmonaire chronique chez le rat. Parmi ceux-ci, le mutant STM2895, contenant un transposon dans le gène PA2895, a été retenu pour des analyses plus approfondies. L'étude phénotypique de STM2895 a permis de constater un défaut dans la production d’exoprotéases lorsque comparé à la souche sauvage PAO1. La caractérisation biochimique de ce défaut, utilisant des tests de dégradation spécifiques et l’immunobuvardage, a démontré qu’au moins deux des quatre protéases majeures sécrétées par P. aeruginosa sont impliquées. En effet, les élastases LasA et LasB ont été démontrées non fonctionnelles probablement dues à un problème de repliement. PA2895, une protéine possédant un domaine transmembranaire prédit, ne code pour aucune fonction connue, mais il est co-transcrit avec le gène PA2896, un facteur sigma putatif de type ECF (extracytoplasmic function). Des analyses en transcriptome sur le mutant STM2895, ainsi que sur un mutant de délétion de PA2896, ont permis de lier l’opéron au métabolisme du fer. De plus, des études in vivo dans le modèle d’infection pulmonaire chronique chez le rat ont clairement démontré que le mutant STM2895 est incapable de se maintenir dans l’hôte au même niveau que la souche sauvage PAO1. Le gène PA2895 est donc essentiel au maintien in vivo de P. aeruginosa dans le poumon de rat.
Pseudomonas aeruginosa is an opportunistic pathogen that can cause pulmonary infections in cystic fibrosis patients (CF). To overcome innate self defense, P. aeruginosa possesses a wide arsenal of virulence factors. These include degradation enzymes such as proteases, lipases and phospholipases and the production of three specific toxins: exotoxin A and exoenzymes S and T. Sequencing of the complete P. aeruginosa chromosome (strain PAO1) of 6.3 Mb revealed a highly regulated and complex genomic organization. In order to better understand host-pathogen molecular interactions, we developped a new signature-tagged mutagenesis (STM) approach based on PCR screening. The PCR-based STM technology lead to the identification of 214 mutants deficient in their ability to maintain a chronic pulmonary infection in the rat lung. In that pool of STM mutants, STM2895, which contains a transposon insertion in functional PA2895, was the most frequently drafted during the whole mutant library screening. Phenotypic analyses of the STM2895 strain allowed us to identify an exoprotease production defect as compared with wild type strain PAO1. The biochemical characterization of that proteolytic default using specific degradation assays combined with western blotting revealed that at least two (LasA and LasB) of the four major exoproteases from P. aeruginosa STM2895 strain are inactive. In fact, LasA and LasB elastases were shown to be present in the STM2895 culture supernatant, correctly processed but inactive due to a probable misfolding of proteins. The PA2895 gene (unknown function) encodes a protein with a predicted transmembrane domain. Basic genomic context analyses strongly suggest a cotranscription unit with the downstream gene PA2896, a putative sigma 70 factor from ECF (extracytoplasmic function) type. Microarray experiments on the STM2895 strain and an insertional mutant of the PA2896 gene were performed to establish a link between the putative PA2895-PA2896 operon and the metabolism of iron. Transcriptome analysis also demonstrated a repressive action of PA2895 on the transcription of PA2896 putative sigma factor. Finally, in vivo studies in the rat lung chronic infection model clearly showed a ten-fold decrease in survival capacity of the mutant strain when compared to the PAO1 wild-type strain.
APA, Harvard, Vancouver, ISO, and other styles
3

Vingadassalom, Didier. "Etude fonctionnelle du facteur sigma principal de Bacteroides fragilis." Paris 6, 2006. http://www.theses.fr/2006PA066224.

Full text
Abstract:
Bacteroides fragilis est un germe anaérobie du tractus intestinal de l’homme. Les promoteurs végétatifs de B. Fragilis sont reconnus par un facteur sigma principal particulier (SigA), restreint aux phyla Bacteroidetes et Chlorobium. SigA possède un court segment basique, à la place de la région N-terminale 1. 1 acide retrouvée chez tous les autres facteurs sigma principaux connus. Il contient des résidus "signature" dans les régions conservées 2 à 4, impliquées dans la reconnaissance des promoteurs et l’interaction avec l’ARN polymérase-cœur. Le segment basique de SigA conditionne le positionnement de l’enzyme sur le promoteur et l’étendue de la bulle de transcription. Le rôle de plusieurs résidus dans la formation du complexe ouvert de transcription et l’interaction avec la séquence consensus -33 des promoteurs de B. Fragilis est décrit. Cette thèse révèle l’existence d’un couple facteur sigma/promoteur unique au sein d’un lignage majeur qui est apparu tôt dans l’évolution bactérienne.
APA, Harvard, Vancouver, ISO, and other styles
4

Favory, Jean-Jacques. "Caractérisation fonctionnelle de SIG4, facteur de type sigma, chez Arabidopsis thaliana." Université Joseph Fourier (Grenoble), 2004. http://www.theses.fr/2004GRE10131.

Full text
Abstract:
Le génome plastidial est transcrit par trois ARN polymérases distinctes. Deux d'entres elles, les NEP (Nuclear Encoded RNA Polymerase) sont codées par le génome nucléaire. La troisième, la PEP (Plastid Encoded RNA Polymerase) est une enzyme multimérique de type procaryotique, codée par les gènes plastidiaux rpo. La spécificité de l'initiation de la transcritpion par la PEP est conférée par des facteurs de type sigma, qui se lient à la polymérase coeur et permettent la reconnaissance des séquences consensus présentes dans les régions "-10" et "-35" en amont du site d'initiation de la transcription. Chez Arabidopsis thaliana, il existe six gènes nucléaires codant des facteurs de type sigma. La détermination de la fonction du facteur sigma 4 (SIG4) constitue le sujet de ce travail. Nous avonc montré que SIG4 est adressé aux plastes, et qu'il est exprimé dans des tissus chlorophylliens. Nous avons isolé un mutant nul (sig4-1), le gène sig4 étant interrompu par l'insertion d'un ADN-T. L'analyse du transcriptome plastidial du mutant sig4-1 par puce à ADN, nous a permis de mettre en évidence que le taux de transcrits de certians gènes varie chez le mutant, par rapport aux plantes sauvages. L'étude de la région 5'UTR de certains de ces gènes a montré que le gène ndhF, codant sous une sous unité du complexe NAD(P)H déshydrogénase, possède un promoteur de type procaryotique qui est spécifiquement reconnu par le facteur SIG4 : l'absence de ce facteur entraîne une diminution radicale de la transcription de ce gène. L'analyse d'un double mutant sig4-1 x sig2 montre que SIG2 ne peut remplacer le facteur SIG4 dans la transcription du gène ndhF
The plastid genome is transcribed by three different RNA polymerases. Two of them, named NEP (Nuclear Encoded RNA Polymerase), are monomeric, phage-like and nuclear encoded, whereas the third one named PEP (Platid Encoded RNA Polymerase) is of prokaryotic-type, multimeric and encoded by the plasride rpo genes. These genes encode all the subunits of the core enzyme, which is unable to initiate transcription specifically. Specificity is brough by sigma-like factors which can bind the core enzyme and recognize consensus sequences in the nuclear genome of Arabidopsis thaliana. The goal of this work is to determine the function of one of them, SIG4. In this study, we confirmed the predicted plastid localization of this sigma-like factor and we showed that its expression occurs in photosynthetically-active tissues. To investigate the role of this plant sigma factor, we isolated a T-DNA insertion mutant sig4-1. Platis genome transcription, as analyzed by DNA microarray, revealed that a few plastid genes were down regulated. Precursor RNA of three of one of the NAD(P)H-dehydrogenase (NDH) subunits, is rather impaired in the sig4-1 mutant. The putative trabscription start site in preceded by a prokaryotic-type promoter which should be responsible for the specific initiation of the transcription of this gene mediated by SIG4. The characterization of a double sig4-1 x sig2 mutant indicates that SIG2 cannot replace Sl
APA, Harvard, Vancouver, ISO, and other styles
5

PENE, CAROLE. "Roles du facteur anti-sigma asia au cours du developpement du bacteriophage t4." Paris 6, 1999. http://www.theses.fr/1999PA066393.

Full text
Abstract:
L'initiation de la transcription suppose le positionnement correct de l'arn polymerase sur le promoteur, l'ouverture des brins de l'adn puis l'echappement du complexe transcriptionnel. Chaque etape peut etre la cible de regulation, par des facteurs auxiliaires activateurs ou inhibiteurs. Chez le bacteriophage t4, les promoteurs precoces sont utilises immediatement apres infection par l'arn polymerase de l'hote associee au facteur sigma70. Puis ils sont fortement reprimes 2 a 3 minutes plus tard, selon un mecanisme encore inconnu. La proteine asia, codee precocement par le phage, est un bon candidat pour cette inhibition precoce. Bien avant la decouverte de son role activateur dans la transcription moyenne de t4, cette proteine fut decrite comme etant un represseur, le premier facteur anti-sigma connu. En effet, elle inhibe fortement in vitro les promoteurs dependants de sigma70, en fixant le domaine 4. 2 de sigma70 implique dans la reconnaissance des sequences consensus situees en 35 de ces promoteurs. Notre etude a montre que le facteur responsable de cette inhibition precoce est code par le phage et agit en trans. Chez un phage delete pour le gene asia, la transcription des deux genes precoces etudies est inhibee au meme moment et avec la meme cinetique que lors d'une infection sauvage. Donc asia n'est pas necessaire pour la repression des promoteurs precoces. Il existe un circuit inhibiteur asia-independant, qui ne depend pas des proteines phagiques precoces connues pour modifier l'arn polymerase ou pour se fixer sur le chromosome phagique et moduler la transcription. Toutefois, la surproduction de la proteine asia, a partir d'un plasmide multicopie, inhibe fortement in vivo la transcription globale d'e. Coli. Ainsi, le facteur asia a la capacite de reprimer in vivo la transcription de l'hote. Il reste donc possible qu'asia participe a l'inhibition des promoteurs precoces de t4, bien qu'aucune indication in vivo n'appuie cette hypothese.
APA, Harvard, Vancouver, ISO, and other styles
6

Kint, Nicolas. "Rôle du facteur sigma alternatif, SigmaB, dans la réponse aux stress chez l’entéropathogène Clostridium difficile au cours de son cycle infectieux." Thesis, Sorbonne Paris Cité, 2017. http://www.theses.fr/2017USPCC120.

Full text
Abstract:
Clostridium difficile est un bacille à gram-positif anaérobie strict et sporulant. Cet entéropathogène est responsable de diarrhées post-antibiotiques et de colites pseudomembraneuses. Après germination des spores dans le petit intestin, les cellules végétatives de C. difficile vont être soumises à de nombreux stress comme des peptides antimicrobiens, des variations d’osmolarité et de pH ainsi qu’une faible tension d’O2 à proximité des cellules épithéliales du colon. De plus, la production des toxines va favoriser une forte inflammation responsable de la production de nombreux composés oxydants tels que les espèces réactives de l’oxygène (ERO), du NO et des espèces réactives de l’azote (ERN). La présence de ces différents stress suggère que C. difficile possède des mécanismes de détection, de protection et de détoxification. Chez les firmicutes, plusieurs de ces mécanismes sont contrôlés par le facteur sigma alternatif impliqué dans la réponse générale aux stress, SigB. De manière intéressante des gènes codant SigB et ses régulateurs (RsbV et RsbW) sont présents dans le génome de C. difficile, cependant aucunes données concernant l’existence ou le rôle d’une réponse générale aux stress ne sont présentes chez cette bactérie. Nous avons dans un premier temps construit un mutant sigB et nous avons montré que cette inactivation n’entraînait pas de défaut de croissance. Via une analyse globale de l’expression des gènes, nous avons montré que SigB contrôle 20% des gènes de C. difficile à l’entrée en phase stationnaire. SigB contrôle négativement la sporulation. SigB contrôle positivement plusieurs gènes codant des protéines associées à la surface et pouvant intervenir dans le processus d’adhésion aux cellules de l’hôte. SigB joue également un rôle crucial dans l’adaptation aux stress rencontrés lors de l’infection dans le tube digestif et dans la colonisation. En effet, un mutant sigB est plus sensible aux pH légèrement acides, à certains peptides antimicrobiens, aux ERO, à différents composés générant du NO ainsi qu’aux faibles tolérances en O2. L’étude de la voie de signalisation aboutissant à l’activation de SigB a également été étudiée au cours de ce projet de thèse. Le gène sigB est le dernier gène d’un opéron constitué de CD0007 et CD0008, codant des protéines aux fonctions inconnues, ainsi que de rsbV et rsbW, codant respectivement le facteur anti-anti-sigma et le facteur anti-sigma. De manière intéressante, l’expression de sigB ne semble pas autorégulée chez C. difficile, à l’inverse des autres firmicutes. Les interactions entre RsbV et RsbW ainsi que RsbW et SigB, impliquées dans l’activation de SigB sont présentes chez C. difficile. La délétion du gène rsbV entraîne une augmentation de la sensibilité aux composés générant du NO et une diminution de la tolérance à l’O2. Ces résultats sont en accord avec la diminution de l’expression des gènes cibles de SigB chez le mutant rsbV. La phosphatase impliquée dans le processus d’activation de SigB, en déphosphorylant vraisemblablement RsbV, a également été identifiée et inactivée. La délétion du gène codant cette phosphatase, CD2685 conduit à l’augmentation de la sensibilité aux composés générant du NO ainsi qu’à la diminution de la tolérance à l’O2, en accord avec son implication dans la voie d’activation deσB. L’activité de SigB augmente suite à une carence nutritive. En effet, l’expression des gènes cibles de SigB est induite de manière dépendante de SigB et de RsZ à l’entrée en phase stationnaire ou après exposition au CCCP, un composé réduisant le niveau intracellulaire d’ATP. Ces travaux de thèse permettent d’établir un rôle prépondérant de SigB et de sa voie d’activation au cours de l’infection notamment dans la protection et la détoxification de stress majeurs que C. difficile est susceptible de rencontrer dans le tube digestif
Clostridium difficile is a tram-positive, anaerobic, spore-forcing bacterium. This enteropathogen is a major cause of antibiotic-associated diarrhea and of pseudomembranous colitis, a potentially lethal disease. After germination, vegetative cells encounter different stresses such as pH variations and hyperosmolarity as well as antimicrobial peptides. Moreover, the production of toxins triggers an important inflammation process leading to the production of several antimicrobial compounds such as reactive oxygen species (ROS), nitric oxide (NO) and reactive nitrogen species. The presence of these different stresses suggests that C. difficile has developed some mechanisms of detection, protection and detoxification. In the firmicutes, several of these mechanisms are controlled by the alternative sigma factor involved in the general stress response, SigB. Interestingly, genes encoding SigB and its regulators (RsbV and RsbW) are present in the genome of C. difficile, however less is known about the role of a general stress response in this bacterium. We constructed a sigB mutant and we showed that sigB inactivation does not lead to a growth defect. Using a transcriptomic analysis, we showed that SigB controls around 20% of the genes of C. difficile at the onset of the stationary phase. SigB negatively controls the sporulation process. SigB positively controls several genes encoding surface associated proteins likely involved in the adhesion to the host cells. SigB plays a crucial role in the stress management including several stresses C. difficile likely encounter during its infectious cycle. Indeed, the sigB mutant is more sentsitive to low pH, to some antimicrobial compounds, to ROS, to several NO-donor compounds as well as to low oxygen tension. The signaling pathway involved in the activation of SigB has been studied in the PhD project. The sigB gene is the last gene of an operon in which belong CD0007 and CD0008, encoding town unknown function proteins, as well as rsbV and rsbW, encoding the anti-anti-sigma factor and the anti-sigma factor of SigB, respectively. Interestingly, contrary to the other firmicutes, the expression of sigB does not seem to be auto-regulated. Protein interactions between RsbV and RsbW as well as RsbW and SigB, involved in the activation of SigB, are present in C. difficile. The disruption of rsbV leads to a higher sensitivity to NO-donor compounds as well as low oxygen tension. These results are in agreement with the decreased expression of several SigB target genes in the rsbV mutant. The phosphatase involved in the activation of SigB, likely by dephosphorylating RsbV, has been identified and disrupted. The disruption of CD2685, encoding this phosphatase, leads to a higher sensitivity to NO-donor compounds as well as a lower tolerance to low oxygen tension, in agreement with its involvement in the SigB activation pathway. The activity of SigB increased after an energetic starvation. Indeed, the expression of SigB target genes are increased in a SigB and CD2685 dependent manner at the onset of the stationary phase or after CCCP exposure, a compound decreasing the intracellular level of ATP. This work allows to show a crucial role of SigB and its activation pathway during the infection notably in the protection and the detoxification of the major stresses C. difficile is likely to encounter in the gut
APA, Harvard, Vancouver, ISO, and other styles
7

Bougdour, Alexandre. "Régulation de l'activité du facteur Sigma S par la protéine Crl chez Escherichia coli." Université Joseph Fourier (Grenoble), 2004. http://www.theses.fr/2004GRE10095.

Full text
Abstract:
Chez Escherichia coli, la sous unité sigma RpoS contrôle l'expression des gènes de la phase stationnaire et de la réponse généralisée aux stress. La synthèse de RpoS esr régulée au niveau de la transcription, de la traduction et de la stabilité de la protéine. Malgré les travaux intensifs des dix dernières années dont le facteur sigma RpoS a fait l'objet, la régulation de l'activité de cette protéine reste encore mal connue. La protéine Crl, impliquée dans le contrôle de l'expression des curlis, permet de moduler positivement l'activité du facteur Rpos. Il a été démontré récemment, par des expériences de génétique, que Crl est indispensable à une activité transcriptionnelle optimale du promoteur des curlis, mais également de certains gènes appartenant au régulon de RpoS. Il a donc été proposé que Crl agisse soit en amont, soit de concert avec RpoS. Nous montrons ici que Crl interagit directement avec RpoS in vitro. En utilisant la région promotrice des gènes codant les curlis comme modèle d'étude, nous avons mis en évidence un effet positif de Crl sur le recrutement de l'holoenzyme-RpoS au niveau du promoteur. Nous avons également montré que l'expression de Crl est augmentée lors de la transition entre la phase de croissance et la phase stationnaire. Crl s'accumule fortement dans les cellules en phase stationnaire à 30°C et beaucoup moins à 37°C. Crl permettrait donc un contrôle de l'activité de RpoS en fonction de la tempréature. Nos résultats suggèrent un rôle de Crl au niveau de l'association de la sous unité sigma Rpos avec l'ARN polymérase et/ou au niveau de la sélectivité entre l'holoenzyme-RpoS et l'holoenzyme-RpoD pour le promoteur cible
The alternative sigma factor RpoS of Escherichia regulates the expression of genes involved in the adaptation to stationary phase and more general stress. RpoS is also required for the transcription of the cryptic genes csgBA that encode the subunits os the curli proteins. The expression of the csgBA genes is regulated in response to a multitude of physiological signals. In stationary phase, thes genes are transcribed by the sigma factor RpoS and the expression of the operon is enhanced by the small protein Crl. Crl stimulates the activity of RpoS, leading to an increased transcription rate of a subset of genes of the rpoS regulon in stationary phase. However the underlying molecilar mechanism has remained elusive. We show here that Crl interacts directly with RpoS and that this interaction promotes binding of the RpoS-holoenzyme to the csgBA promoter. Expression of Crl is increased during the transistion from growing to stationary phase. Crl accumulates in stationary phase cells at low temperature (30°C), but not at 37°C. We therefore propose that Crl is a second thermosensor, besides DsrA, controlling RpoS-activity
APA, Harvard, Vancouver, ISO, and other styles
8

Beaucher, Jocelyn. "Étude in vitro de la régulation post-traductionnelle du facteur sigma F de mycobacterium tuberculosis." Thèse, Université de Sherbrooke, 2005. http://savoirs.usherbrooke.ca/handle/11143/5046.

Full text
Abstract:
L'agent causal de la tuberculose est la bactérie Mycobacterium tuberculosis. Son génome, entièrement séquencé en 1998, contiendrait les gènes de 13 facteurs [sigma], de même que de plusieurs facteurs anti-, et anti-anti-[sigma] présumés. Au cours des travaux présentés dans cette thèse, nous nous sommes donc intéressés particulièrement au facteur [sigma[indice supérieurF]] et à sa régulation post-traductionnelle. Il a précédemment été montré que [sigma[indice supérieurF]] semblait impliqué dans le contrôle de certains facteurs de virulence de la bactérie, ainsi que dans sa persistance. Au cours de nos recherches, nous avons établi que [sigma[indice supérieurF]] voyait sont activité spécifiquement inhibée par UsfX, son facteur anti-[sigma]. Toutefois, il s'est avéré qu'UsfX se montrait à son tour régulé post-traductionnellement par deux facteurs anti-anti-[sigma]. Le premier de ceux-ci, nommé RsfA, voit son activité anti-UsfX modulée par le potentiel oxydo-réducteur du milieu. RsfB, le second, semblerait quant à lui être régulé par une voie de phosphorylation, car il se trouve inactivé par une mutation imitant l'ajout d'un groupement phosphate sur un de ses résidus sérine conservés. Cependant, contrairement aux modèles de voies de régulation [sigma] : anti-[sigma] : anti-anti-[sigma] connus chez Bacillus subtilis, l'anti-[sigma] UsfX ne semble pas posséder d'activité kinase, ni réguler par lui-même l'activité de ses antagonistes. Ces résultats suggèrent donc que l'activité du facteur [sigma[indice supérieurF]] semble modulée par au moins deux voies afférentes distinctes, en réponse à différents stimuli physiologiques. Ce nouveau type de régulation post-traductionnelle d'un facteur a concorde bien avec la grande capacité d'adaptation qui est reconnue à M. tuberculosis.
APA, Harvard, Vancouver, ISO, and other styles
9

Raffestin, Stéphanie. "Régulation de la toxinogenèse chez Clostridium botulinum et Clostridium tetani." Paris 7, 2005. http://www.theses.fr/2005PA077044.

Full text
APA, Harvard, Vancouver, ISO, and other styles
10

Gardan, Rozenn. "Controle de l'utilisation de l'arginine chez bacillus subtilis par l'activateur rocr et le facteur sigma 54." Paris 7, 1996. http://www.theses.fr/1996PA077207.

Full text
Abstract:
La seule voie de degradation de l'arginine mise en evidence chez bacillus subtilis est la voie de l'arginase. Cependant, aucun des genes codant pour des enzymes de cette voie n'avait ete clone ou sequence. Trois genes roca, rocb et rocc vraisemblablement organises en operon et impliques dans le catabolisme de l'arginine, ont ete identifies durant le projet europeen de sequencage du genome de b. Subtilis. Nous avons caracterise un deuxieme operon, rocdef, implique dans le catabolisme de l'arginine. Ces deux operons codent pour les trois enzymes de la voie de l'arginase et pour deux permeases potentielles a arginine. La fonction du produit d'un des genes est inconnue. Nous avons etudie en parallele la regulation de l'expression de ces deux operons. Ils sont exprimes en presence d'arginine, d'ornithine, de citrulline ou de proline mains nous avons montre que l'inducteur vrai est probablement l'ornithine. Ces deux operons sont transcrits a partir de promoteurs *2/(4 en presence du facteur sigma 54 et d'un gene regulateur a domaine central, rocr. Nous avons isole differents mutants constitutifs du gene rocr. L'etude de ces mutants nous a permis de montrer que la proteine rocr est regulee par une repression intramoleculaire. De plus, ces mutants sont independants du regulateur ahrc, deuxieme activateur des operons rocabc et rocdef, suggerant que ahrc est implique dans la regulation de l'activite de rocr
APA, Harvard, Vancouver, ISO, and other styles
More sources

Books on the topic "Facteur sigma"

1

Bell, JW. The Sigma Factor. Rebel ePublishers, 2018.

Find full text
APA, Harvard, Vancouver, ISO, and other styles

Book chapters on the topic "Facteur sigma"

1

Shimamoto, Nobuo. "Sigma Factor." In Encyclopedia of Systems Biology, 1936–37. New York, NY: Springer New York, 2013. http://dx.doi.org/10.1007/978-1-4419-9863-7_1495.

Full text
APA, Harvard, Vancouver, ISO, and other styles
2

Ramnaresh Gupta, Kuldeepkumar, and Dipankar Chatterji. "Sigma Factor Competition inEscherichia Coli: Kinetic and Thermodynamic Perspectives." In Stress and Environmental Regulation of Gene Expression and Adaptation in Bacteria, 196–202. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2016. http://dx.doi.org/10.1002/9781119004813.ch16.

Full text
APA, Harvard, Vancouver, ISO, and other styles
3

Ndamukong, Ivan C., Samantha Palethorpe, Michael Betteken, and C. Jeffrey Smith. "The Extracytoplasmic Function Sigma Factor EcfO ProtectsBacteroides FragilisAgainst oxidative stress." In Stress and Environmental Regulation of Gene Expression and Adaptation in Bacteria, 301–10. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2016. http://dx.doi.org/10.1002/9781119004813.ch26.

Full text
APA, Harvard, Vancouver, ISO, and other styles
4

Chatterjee, A., Y. Cui, Y. Liu, and A. K. Chatterjee. "Molecular Characterization of Erwinia carotovora hrpL, which Encodes an Alternate Sigma Factor." In Plant Pathogenic Bacteria, 237–40. Dordrecht: Springer Netherlands, 2001. http://dx.doi.org/10.1007/978-94-010-0003-1_54.

Full text
APA, Harvard, Vancouver, ISO, and other styles
5

Busche, Tobias, and Jörn Kalinowski. "The ECF Family Sigma Factor σHinCorynebacterium GlutamicumControls the Thiol-Oxidative Stress Response." In Stress and Environmental Regulation of Gene Expression and Adaptation in Bacteria, 352–60. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2016. http://dx.doi.org/10.1002/9781119004813.ch31.

Full text
APA, Harvard, Vancouver, ISO, and other styles
6

Lourenço, Rogério F., and Suely L. Gomes. "The Extracytoplasmic Function Sigma Factor-mediated Response to Heavy Metal Stress inCaulobacter Crescentus." In Stress and Environmental Regulation of Gene Expression and Adaptation in Bacteria, 1171–83. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2016. http://dx.doi.org/10.1002/9781119004813.ch114.

Full text
APA, Harvard, Vancouver, ISO, and other styles
7

Pollari, Maija, and Taina Tyystjärvi. "The SigB Sigma Factor of the Cyanobacterium Synechocystis sp. PCC 6803 Is Necessary for Adaptation to High-Salt Stress." In Photosynthesis. Energy from the Sun, 1351–53. Dordrecht: Springer Netherlands, 2008. http://dx.doi.org/10.1007/978-1-4020-6709-9_291.

Full text
APA, Harvard, Vancouver, ISO, and other styles
8

Camarero, Julio A., Alex Shekhtman, Elizabeth Campbell, Seth Darst, David Cowburn, and Tom W. Muir. "Regulation of the Promoter Binding Activity of a Bacterial Sigma Factor Explored Using Segmental Isotopic Labeling and NMR Spectroscopy." In Peptides: The Wave of the Future, 816–17. Dordrecht: Springer Netherlands, 2001. http://dx.doi.org/10.1007/978-94-010-0464-0_381.

Full text
APA, Harvard, Vancouver, ISO, and other styles
9

Oggioni, Marco R., and Donald A. Morrison. "Cooperative Regulation of Competence Development in Streptococcus pneumoniae: Cell-to-Cell Signaling via a Peptide Pheromone and an Alternative Sigma Factor." In Chemical Communication among Bacteria, 345–62. Washington, DC, USA: ASM Press, 2014. http://dx.doi.org/10.1128/9781555815578.ch22.

Full text
APA, Harvard, Vancouver, ISO, and other styles
10

Cournoyer, B., and D. Blaha. "Cloning, characterisation and phylogenetic analysis of the sigA σ 70 factor gene sequence from the actinomycete Frankia." In Frankia Symbiosis, 97–106. Dordrecht: Springer Netherlands, 2003. http://dx.doi.org/10.1007/978-94-017-1601-7_12.

Full text
APA, Harvard, Vancouver, ISO, and other styles

Conference papers on the topic "Facteur sigma"

1

Tzannetakis, Nick, Stijn Donders, Joost Van de Peer, and Paul Weal. "A System Approach to Simulation-Based Design Under Uncertainty, Through Best in Class Simulation Process Integration and Design Optimization." In ASME 2004 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. ASMEDC, 2004. http://dx.doi.org/10.1115/detc2004-57149.

Full text
Abstract:
The importance of design robustness and reliability is a well-established notion and practice in today’s industry. Manufacturing companies strive to achieve Six-Sigma quality measures. While Virtual Prototyping is a key-factor in accelerating the product development process while reducing development costs, it has not contributed in the quest for improved product reliability and robustness performance since it is based on deterministic approaches. This paper provides a systematic approach to design for six-sigma simultaneously addressing variability and uncertainty present in real life on most design parameters. An example from the automotive industry illustrates the methodologies.
APA, Harvard, Vancouver, ISO, and other styles
2

Zhou, Zhan, Qi Li, Julie Tudyk, Yong-Quan Li, and Yufeng Wang. "ECF sigma factor-associated regulatory networks in Streptomyces colicolor A3(2)." In 2011 IEEE International Workshop on Genomic Signal Processing and Statistics (GENSIPS). IEEE, 2011. http://dx.doi.org/10.1109/gensips.2011.6169475.

Full text
APA, Harvard, Vancouver, ISO, and other styles
3

Huang, Mo, Yan Lu, Xiao-ming Xiong, Seng-Pan U, and R. P. Martins. "An all-factor modulation bandwidth extension technique for delta-sigma PLL transmitter." In TENCON 2015 - 2015 IEEE Region 10 Conference. IEEE, 2015. http://dx.doi.org/10.1109/tencon.2015.7373012.

Full text
APA, Harvard, Vancouver, ISO, and other styles
4

Pan, Zhedan, Hoyeon Ryu, and Jongmoon Baik. "A Case Study: CRM Adoption Success Factor Analysis and Six Sigma DMAIC Application." In 5th ACIS International Conference on Software Engineering Research, Management & Applications (SERA 2007). IEEE, 2007. http://dx.doi.org/10.1109/sera.2007.6.

Full text
APA, Harvard, Vancouver, ISO, and other styles
5

Zhao, Zuo AN, Yue Wang, Qiang Lai, Kai Xuan Li, Xian Ran Zhao, Jin Long Wu, Hai Peng Zhao, and Dai Guo Yu. "Fluid Identification Derived from Non-Electric Measurements and Reservoir Characterization of Tight Carbonate in Sichuan Basin, China." In SPE Annual Technical Conference and Exhibition. SPE, 2021. http://dx.doi.org/10.2118/205926-ms.

Full text
Abstract:
Abstract Natural gas production in the Sichuan Basin reached 30 billion m3 in 2020, but the gap between this and the production goal of 50 billion m3 in 2025 requires further exploration. The complex mineralogy and low porosity in tight carbonate reservoirs lower the accuracy of formation water saturation calculation from Archie's equation, which brings uncertainties to the reservoir characterization. It is, therefore, necessary to incorporate other methods as supplements to methods based on resistivities. This paper outlines a method that incorporates wireline induced gamma spectroscopy, nuclear magnetic resonance (NMR), array dielectric, and borehole images. Spectroscopy is not only utilized to estimate the mineralogy of the reservoir, but it also provides non-electric measurements, such as chlorine concentration and thermal neutron capture cross-section (sigma). The amount of chlorine in the formation is proportional to the water volume in the reservoir, thus formation water saturation. Sigma is also an indicator of the formation water saturation. It enables formation water saturation calculation without resistivities. Case studies are presented from carbonate reservoirs in the Sichuan Basin, China. A robust and comprehensive petrophysical description of mineralogy, porosity, pore geometry, free fluid volume, rock type, and formation water saturation is presented. Calculation of formation water saturation from chlorine and sigma proves to be successful in both water-based mud and oil-based mud environments. The depth of investigation (DOI) of chlorine from spectroscopy is about 8 to 10 in. for 90% of the signal. The various DOI of different measurements must be considered when performing the fluid identification. Bound fluid saturation could reach more than 50% in tight carbonate reservoirs. Formation water saturation is not the only factor that determines the fluid type. Free fluid saturation from NMR must be incorporated. Finally, a robust methodology integrating formation water saturation derived from dielectric and spectroscopy, and free fluid saturation derived from NMR shows great advantage in fluid identification in tight carbonate reservoirs. This paper discusses a novel combination of wireline logging tools for the fluid identification of tight carbonate reservoir in Sichuan Basin. It lowers the uncertainty in the estimation of formation water saturation when application of resistivities is limited in oil-based mud environments. The gas zones identified by the new method have promising gas productions. The workflow can also be applied to other tight carbonate plays in China.
APA, Harvard, Vancouver, ISO, and other styles
6

Hao, Jialing, Xiaoxin Jiang, and Juan Yang. "Three-Dimensional Numerical Model of Wind-Driven Current in a Lake Based on POM Model." In ASME 2009 28th International Conference on Ocean, Offshore and Arctic Engineering. ASMEDC, 2009. http://dx.doi.org/10.1115/omae2009-79898.

Full text
Abstract:
Lake current is the cause for the transport of many matters such as suspended sediment, algae, contaminant, therefore, it must be estimated fairly accurately. Generally speaking, the flow in many lakes is weak and the flow direction is follows dominated mainly by the wind direction on lake surface. Correct simulation of the wind-driven current in a lake requires using a three-dimensional hydrodynamic numerical model. The main factor affecting the lake hydrodynamic processes is wind. Because wind-driven current have important influence for the matter exchange and energy transform in a lake, and field observations are comparatively difficult, numerical modeling is the main method to estimate the wind-driven current nowadays. The numerical modeling of 3D tidal flow and mass transportation in this study was performed using the Princeton Ocean Model (POM). The model is validated by calculating wind-driven current in a rectangular flume [1][2]. The contaminant transport modeling in the Yangchenghu Lake is performed with POM using an orthogonal curvilinear grid in horizontal direction and sigma coordinate variation in vertical direction. An analysis of model results is presented.
APA, Harvard, Vancouver, ISO, and other styles
7

Manetti, Marco, Iacopo Giovannetti, Nicola Pieroni, Horia Horculescu, Guido Peano, Giovanni Zonfrillo, and Massimo Giannozzi. "The Dynamic Influence of Crystal Orientation on a Second Generation Single Crystal Material for Turbine Buckets." In ASME Turbo Expo 2009: Power for Land, Sea, and Air. ASMEDC, 2009. http://dx.doi.org/10.1115/gt2009-59091.

Full text
Abstract:
High cycle fatigue is a factor that influence gas turbine buckets lifetime and it’s due to high frequency vibrations during service. Rotation and fluid flow around the blades cause static and dynamic stresses on the buckets row. For this reason the natural frequencies and HCF resistance evaluation are fundamental in the design phase of gas turbine engines in order to avoid resonance problems during service. Single crystal and directionally solidified superalloys shows anisotropic material properties, in particular single crystal can be modeled as orthotropic material in lattice directions for FEM simulations purposes. In this paper the influence of the lattice growth orientation, identified by two angles, on the natural frequencies of first stage bucket has been investigated. Six-sigma analysis has been performed in order to obtain a transfer function between lattice orientation and bucket vibration. The Design of Experiment (DoE) has been performed using FEA modal results on ten different vibration modes. The results obtained by FEA are verified by an experimental test on the real Heavy Duty MS5002 buckets.
APA, Harvard, Vancouver, ISO, and other styles
8

Takahashi, K., M. Niwa, and N. Sakuragawa. "NEUTRALIZING EFFECT OF PLATELET FACTOR 4 OR HISTIGINE-RICH GLYCOPROTEIN AGAINST LOW MOLECULAR WEIGHT HEPARIN AND UNFRACTIONATED HEPARIN." In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1643499.

Full text
Abstract:
Purpose: Low molecular weight(LMW) heparin shows stronger antifactor Xa(F-Xa) and weaker anti-thrombin(TH) activities compared with unfractionated(UF) heparin, and shows less bleeding tendency in the cases of clinical use. Platelet factor 4(Pf-4) and histidine-rich glycoprotein(HRG) neutralize heparin. We investigated on the heparin neutralizing effects of them to both kinds of heparinMaterials and methods: LMW heparin(Kabi and Pharmuka) and UF heparin(Novo) were used. Antithrombin III(AT-III), HRG(human origin ) and pf-4( bovine origin ) were purified by our methodsTH(Green-Cross) and F-Xa(Sigma) were used. Reaction mixtures for anti-TH or anti-F-Xa were as follows: 1 vol of AT-III( 0.1 U/ml)+ 1 vol of heparin( 10 ug/ml)+l vol of pf-4 or HRG(varied)→incubated for 5 min→+l vol of TH(5 U/ml) or F-Xa( 7 nKat/ml)→incubated for 5 min→ + S-2238 or S-2222→ recorded at 405 nm.Results: (1) Pf-4 showed the equivalent anti-TH effect on both kinds of heparin, and 3 ug of pf-4 neutralized 1 ug of heparinOn F-Xa neutralizing effect, 13 ug of pf-4 neutralized 1 ug of UF heparin, but could not neutralize LMW heparin. (2) HRG showed the same results on anti-TH effect of both kinds of heparin, but could not neutralize the anti-F-Xa effect of LMW heparin on the same amount of HRG which neutralized that of UF heparin. Conclusion: Anti-F-Xa effect of. LMW heparin could not be easily neutralized by pf-4 or HRG compared with that of UF heparin.
APA, Harvard, Vancouver, ISO, and other styles
9

Tang, Xu, Tao Liu, Wei Song, and Hongpu Wang. "Static Strength Reliability Analysis of the FLNG Compact and High Efficient Heat Exchanger." In ASME 2020 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/imece2020-23469.

Full text
Abstract:
Abstract Because of the harsh marine environment and limited offshore natural gas liquefaction work space, the compact and high efficient heat exchanger is the best choice for FLNG (floating liquefied natural gas) heat exchanger. To optimize the heat exchanger’s structural parameters and improve the performance, the factors mostly affecting the strength of the heat exchanger need to be determined, and static strength analysis and reliability analysis should be required. The strength of the heat exchanger core is analyzed by using the Static Structural, and the stress intensity distribution is obtained. According to the operation conditions, the temperature boundary condition has been set and the mechanical stress and thermal stress are considered to evaluate the strength. By choosing the thickness between the cold channels, cold channel pressure, hot channel pressure and elastic modulus as input random variables, the reliability analysis of heat exchanger has been done by using the Six Sigma Analysis of ANSYS Workbench, and next the cumulative distribution function curves of the membrane stress intensity, membrane plus bending stress intensity, response surface and the sensitivity are obtained. The reliability analysis results have shown that the cold channel pressure loading is found to be the greatest factor to the structural strength. The reliability of the heat exchange is more than 99.9% without considering thermal stress.
APA, Harvard, Vancouver, ISO, and other styles
10

Han, Changwan, Seonghun Park, and Hanjong Kim. "Dynamic Response of Polyvinyl Alcohol(PVA)-Hydrogel With Different PVA Concentrations." In ASME 2014 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/imece2014-37811.

Full text
Abstract:
Polyvinyl Alcohol-Hydrogel (PVA-H) is a biomaterial used for manufacturing contact lenses as well as for the medium of drug delivery. Previous studies have also showed that PVA-H exhibits superior biocompatibility with hydrophilic elastic nature. The aim of this study is to examine the possible usage of the PVA-H as cartilage replacement material by determining the static and dynamic mechanical properties of PVA-H with different ratios of polyvinyl alcohol (PVA) and phosphate buffered saline (PBS) compositions. Three different types of PVA-H specimens were made by changing the ratio of PVA (Sigma-Aldrich) and PBS (Sigma-Aldrich) compositions (PVA-H1: 10 wt% PVA and 90 wt% PBS; PVA-H2: 20 wt% PVA and 80 wt% PBS; PVA-H3: 25 wt% PVA, 45 wt% PBS and DMSO 30 wt%). Static and dynamic tensile tests under the loading frequencies of 0.001, 0.01, 0.1, and 1 Hz were carried out to measure the biomechanical properties of PVA-H1, -H2 within PBS solution and -H3 within PBS/ DMSO solution. The equilibrium Young’s moduli (EY) of PVA-H1, -H2 and -H3 evaluated from the static displacement control were 84.2±35.1 kPa (n=10), 254±32.2 kPa (n=10) and 588±38.9 kPa (n=5), respectively. The amplitudes of dynamic tensile moduli were varied from 86.3±33.4 kPa (n=10) at 0.001 Hz to 96.9±42.0 kPa (n=10) at 1 Hz for PVA-H1, from 282.7±26.4 kPa (n=10) at 0.001 Hz to 309.1±32.2 kPa (n=10) at 1 Hz for PVA-H2 and from 643.8±49.8 kPa (n=10) at 0.001 Hz to 747.7±67.7 kPa (n=5) at 1 Hz for PVA-H3. According to the current results, the frequency dependence of the magnitude of the dynamic modulus confirms the viscoelastic nature of PVA-H material. However, it can be noted that the dynamic modulus increases by up to a factor of 1.15 for PVA-H1, 1.22 for PVA-H2 and 1.27 for PVA-H3, showing insignificant viscoelasticity compared with that for cartilage. The result that static and dynamic moduli of PVA-H3 are larger than those of PVA-H1 and PVA-H2 also suggests that the amount of PVA composition in PVA-H plays an important role in improving both static and dynamic mechanical strengths of PVA-H material. The phase angle decreased from 5.2±2.1 ° at 0.001 Hz to −0.3±1.7 ° at 1 Hz for PVA-H1, from 5.6±0.6 ° at 0.001 Hz to −0.3±0.7 ° at 1 Hz for PVA-H2 and from 8.2±1.1 ° at 0.001 Hz to 0.7±0.7 ° at 1 Hz for PVA-H3.
APA, Harvard, Vancouver, ISO, and other styles

Reports on the topic "Facteur sigma"

1

Justus, Alan Lawrence. Practical applications of the sigma factor alarm method within alpha CAMs utilizing either ROI, tail-fitting, or peak-fitting algorithms. Office of Scientific and Technical Information (OSTI), April 2019. http://dx.doi.org/10.2172/1511207.

Full text
APA, Harvard, Vancouver, ISO, and other styles
You might also be interested in the extended bibliographies on the topic 'Facteur sigma' for particular source types:
Journal articles Dissertations / Theses
We offer discounts on all premium plans for authors whose works are included in thematic literature selections. Contact us to get a unique promo code!

To the bibliography