Littérature scientifique sur le sujet « Strain maintenance »
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Articles de revues sur le sujet "Strain maintenance"
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Oskam, Linda, Gerard Venema et Sierd Bron. « Plasmid maintenance inBacillus stearothermophilusis strain-dependent ». FEMS Microbiology Letters 93, no 3 (juin 1992) : 203–8. http://dx.doi.org/10.1111/j.1574-6968.1992.tb05098.x.
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Werren, J. H., et D. W. Loehlin. « Strain Maintenance of Nasonia vitripennis (Parasitoid Wasp) ». Cold Spring Harbor Protocols 2009, no 10 (1 octobre 2009) : pdb.prot5307. http://dx.doi.org/10.1101/pdb.prot5307.
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Jia, Honglei, Tianyou Chen, Shengwei Zhang, Xumin Sun et Hongfang Yuan. « Effects of pressure maintenance and strain maintenance during compression on subsequent dimensional stability and density after relaxation of blocks of chopped corn straw ». BioResources 15, no 2 (1 avril 2020) : 3717–36. http://dx.doi.org/10.15376/biores.15.2.3717-3736.
Texte intégralRésumé :
Chopped corn straw is a viscoelastic material that can rebound after compression. Pressure maintenance and strain maintenance are two key processes that enhance the dimensional stability of post-compression straw blocks. To study the effects of stabilization processes on the dimensions of post-compression straw blocks, the authors comparatively explored the relationships of strain and stress with time during constant-speed compression (CC), constant-speed compression followed by strain maintenance (CCS), constant-speed compression followed by pressure maintenance (CCP), and constant-speed compression, pressure maintenance followed by strain maintenance (CCPS), and uncovered the reasons for these relationships. The Burgers constitutive model fit well to the data during the pressure maintenance stage (R2>0.990), and the effects of pressure maintenance on strain and dimensional stability of post-compression straw blocks were investigated. The Wiechert model B (R2>0.990) was the constitutive model that best represented the strain maintenance stage. Additionally, the effects of strain maintenance during CCS and CCPS on relaxation rate and dimensional stability of post-compression straw were compared. The relaxation density of post-compression straw blocks was compared among different stabilization processes. The relaxation density of post-compression straw blocks was the largest after CCPS, followed by CCS and CCP.
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Colijn, Caroline, Ted Cohen et Megan Murray. « Latent Coinfection and the Maintenance of Strain Diversity ». Bulletin of Mathematical Biology 71, no 1 (10 décembre 2008) : 247–63. http://dx.doi.org/10.1007/s11538-008-9361-y.
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Stosic, Zorica, Milan Mitric, Ferenc Kiskarolj, Dusan Misic et Ruzica Asanin. « Investigations of sensitivity to antibiotics of salmonella strain species originating from poultry from different epizootiological areas ». Veterinarski glasnik 60, no 1-2 (2006) : 89–98. http://dx.doi.org/10.2298/vetgl0602089s.
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A total of 1666 samples were examined, of which 512 samples of parenchymatous organs of dead or deliberately sacrtificed animals, 60 samples of non-hatched fertilized eggs, 202 samples of feces, 652 samples of cloacal smears, 221 samples of smears from walls of maintenance objects, incubator stations, and transport vehicles, 19 samples of beddings and shavings. The samples originated from poultry farms and which were taken to a laboratory immediately on sampling and sown the same day. A total of 104 strains of Salmonella were isolated: 94 strains from samples of parenchymatous organs of dead chicks, 1 strain from non-hatched eggs, 3 strains from feces samples, 1 strain from samples of cloacal smears, 4 strains from samples of surface smears of maintenance objects and transport vehicles, and 1 strain from samples of beddings and shavings. Serological typization established the presence of the following serovarieties: Salmonella Enteritidis 79 strains, Salmonella Hartford 17 strains, Salmonella Typohimurium 5 strains, Salmonella Mbandaka 2 strains, and Salmonella Glostrup 1 strain. We examined the sensitivity of Salmonella strains to ampicillin, amoxicillin, gentamycin, streptomycin, neomycin, enrofloxacine, norfloxacine, flumequin, erythromycin, lincospectin, colistin, fluorphenicol, and a combination of sulphamethoxasole and trimethoprim. In S. Enteritidis strains, no resistence was established to colistin, fluorphenicol and sulphamethoxasole+trimethoprim, in fact, the sensitivity to these antibiotics and chemotherapeutics was 100%. Prevalence resitence of 0.96%, in only one strain, was established for enrofloxacine. A high prevalence resistence of 33.6% was established for neomycin, while prevalence resistence of 3.86% was established for the related aminoglycozide antibiotic gentamycin. The highest prevalence resistance in S.Hartford strains was established for erythromycin, 15.38%, and streptomycin, 7.6%. Resistence of S. Tyohimurium was established for flumequin and erythromycin in 1.9% strains. No resistance to antibiotics was established in the strains S. Mbandaka and S. Glostrup.
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Derd�kov�, Mark�ta, Vladim�r Dudi��k, Brandon Brei, John S. Brownstein, Ira Schwartz et Durland Fish. « Interaction and Transmission of Two Borrelia burgdorferi Sensu Stricto Strains in a Tick-Rodent Maintenance System ». Applied and Environmental Microbiology 70, no 11 (novembre 2004) : 6783–88. http://dx.doi.org/10.1128/aem.70.11.6783-6788.2004.
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ABSTRACT In the northeastern United States, the Lyme disease agent, Borrelia burgdorferi sensu stricto, is maintained by enzoonotic transmission, cycling between white-footed mice (Peromyscus leucopus) and black-legged ticks (Ixodes scapularis). B. burgdorferi sensu stricto is genetically variable and has been divided into three major genotypes based on 16S-23S ribosomal DNA spacer (RST) analysis. To better understand how genetic differences in B. burgdorferi sensu stricto may influence transmission dynamics in nature, we investigated the interaction between an RST1 and an RST3 strain in a laboratory system with P. leucopus mice and I. scapularis ticks. Two groups of mice were infected with either BL206 (RST1) or B348 (RST3). Two weeks later, experimental mice were challenged with the opposite strain, while control mice were challenged with the same strain as that used for the primary infection. The transmission of BL206 and B348 from infected mice was then determined by xenodiagnosis with uninfected larval ticks at weekly intervals for 42 days. Mice in both experimental groups were permissive for infection with the second strain and were able to transmit both strains to the xenodiagnostic ticks. However, the overall transmission efficiencies of BL206 and B348 were significantly different. BL206 was more efficiently transmitted than B348 to xenodiagnostic ticks. Significantly fewer double infections than expected were detected in xenodiagnostic ticks. The results suggest that some B. burgdorferi sensu stricto strains, such as BL206, may be preferentially maintained in transmission cycles between ticks and white-footed mice. Other strains, such as B348, may be more effectively maintained in different tick-vertebrate transmission cycles.
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Bertuch, Alison A., et Victoria Lundblad. « EXO1 Contributes to Telomere Maintenance in Both Telomerase-Proficient and Telomerase-Deficient Saccharomyces cerevisiae ». Genetics 166, no 4 (1 avril 2004) : 1651–59. http://dx.doi.org/10.1093/genetics/166.4.1651.
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Abstract Previous work in budding yeast has indicated that telomeres are protected, at least in part, from the action of Exo1, which degrades the C-rich strand of partially uncapped telomeres. To explore this further, we examined the consequences of Exo1-mediated activity in strains that lacked Ku, telomerase, or both. Loss of Exo1 partially rescued the telomere length defect in a yku80Δ strain, demonstrating that exonuclease action can directly contribute to telomere shortening. The rapid loss of inviability displayed by a yku80Δ est2Δ strain was also partially alleviated by an exo1Δ mutation, further supporting the proposal that Exo1 is one target of the activities that normally protect wild-type telomeres. Conversely, however, Exo1 activity was also capable of enhancing telomere function and consequently cell proliferation, by contributing to a telomerase-independent pathway for telomere maintenance. The recovery of recombination-dependent survivors that arose in a yku80Δ est2Δ strain was partially dependent on Exo1 activity. Furthermore, the types of recombination events that facilitate telomerase-independent survival were influenced by Exo1 activity, in both est2Δ and yku80Δ est2Δ strains. These data demonstrate that Exo1 can make either positive or negative contributions to telomere function and cell viability, depending on whether telomerase or recombination is utilized to maintain telomere function.
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Seppälä, Otto, Anssi Karvonen, E. Tellervo Valtonen et Jukka Jokela. « Interactions among co-infecting parasite species : a mechanism maintaining genetic variation in parasites ? » Proceedings of the Royal Society B : Biological Sciences 276, no 1657 (28 octobre 2008) : 691–97. http://dx.doi.org/10.1098/rspb.2008.1229.
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Individuals of free-living organisms are often infected simultaneously by a community of parasites. If the co-infecting parasites interact, then this can add significantly to the diversity of host genotype×parasite genotype interactions. However, interactions between parasite species are usually not examined considering potential variation in interactions between different strain combinations of co-infecting parasites. Here, we examined the importance of interactions between strains of fish eye flukes Diplostomum spathaceum and Diplostomum gasterostei on their infectivity in naive fish hosts. We assessed the infection success of strains of both species in single-strain exposures and in co-exposures with a random strain of the other species. Parasite infection success did not consistently increase or decrease in the co-exposure treatment, but depended on the combinations of co-infecting parasite strains. This disrupted the relative infectivity of D. spathaceum strains observed in single-strain exposures. The infection success of D. gasterostei strains was independent of exposure type. These results suggest that interactions among parasite species may be strain specific and potentially promote maintenance of genetic polymorphism in parasite populations.
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Morris, Andrew, John P. Dear, Miltiadis Kourmpetis, Chris Maharaj, Amit Puri et Alexander D. Fergusson. « Monitoring Creep Strain in Power Station Engineering Plant ». Applied Mechanics and Materials 7-8 (août 2007) : 31–36. http://dx.doi.org/10.4028/www.scientific.net/amm.7-8.31.
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Cost effective and reliable operation of a power station plant and achieving low carbon dioxide emissions can be very dependent on maintenance activities. Planning maintenance to minimise the down-time of the plant is a key cost factor. It is important to have the latest data as to the age and state of the components and parts at the time of plant shut down. Indeed, deciding on the best time to shut down the plant for maintenance can depend upon trends in these data. For steam pipes, the required ageing information is the creep strain rate. These creep strain data obtained at shut down provide key information as to the needed replacement of pipes to maintain reliable plant operation. This paper presents the E.ON UK ARCMAC creep strain measurement systems that are being further developed by Imperial College London with the use of DIC and other techniques.
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Kudva, Indira T., Julian Trachsel, Erika N. Biernbaum et Thomas Casey. « Novel reusable animal model for comparative evaluation of in vivo growth and protein-expression of Escherichia coli O157 strains in the bovine rumen ». PLOS ONE 17, no 5 (26 mai 2022) : e0268645. http://dx.doi.org/10.1371/journal.pone.0268645.
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Previously, we had demonstrated that Escherichia coli O157:H7 (O157) strain 86–24 expresses proteins involved in survival rather than virulence in vitro in rumen fluid from dairy cattle limit fed a maintenance diet. Here, we verified if this observation would be true for different O157 strains grown in vitro in rumen fluid from, and in vivo in the rumen of, animals on contrasting maintenance (high fiber) and lactation (high energy-protein) diets usually limit fed to dairy cattle. For the in vivo studies, an economical, novel, reusable and non-terminal rumen-fistulated animal model permitting simultaneous evaluation of multiple bacterial strains in the bovine rumen was developed. All experiments were conducted in duplicate using different animals to account for host-related variations. The O157 strains included, 86–24, EDL933 and the super shed SS-17. E. coli NalR (#5735), derived from a bovine intestinal commensal E. coli, was included as a control. As expected, diet influenced ruminal pH and volatile fatty acid (VFA) composition. The pH ranged from 6.2–7.0 and total VFA concentrations from 109–141 μM/ml, in animals fed the maintenance diet. In comparison, animals fed the lactation diet had a ruminal pH ranging between 5.18–6.0, and total VFA of 125–219 μM/ml. Strain dependent differences in O157 recovery from the rumen fluid of cattle fed either diet was observed, both in vitro and in vivo, with O157 strains 86–24 and EDL933 demonstrating similar survival patterns. Analysis of the O157 proteomes expressed in the rumen fluid/rumen verified previous observations of adaptive responses. Any difference in the adaptive response was mainly influenced by the animal’s diet and growth conditions (in vitro and in vivo) and not the O157 strain. These new insights into the O157 responses could help formulate modalities to control O157 across strains in cattle at all stages of husbandry.
Thèses sur le sujet "Strain maintenance"
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BELTRAMETTI, FABRIZIO. « The division of labor in microorganisms : from survival strategies of the species to industrial success stories ». Doctoral thesis, Università degli Studi di Milano-Bicocca, 2022. http://hdl.handle.net/10281/365498.
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Gli attinomiceti ed i funghi sono spesso organizzati in piccole società integrate (esemplificate da colonie) caratterizzate da una divisione del lavoro. La divisione del lavoro ha il riscontro evolutivo di dare un vantaggio selettivo alle cellule in accrescimento ed in ultima analisi alla progenie fertile. La progenie fertile ha il compito di preservare la specie nei limiti dell'evoluzione naturale e della colonizzazione di nuove nicchie. Una parte considerevole della popolazione riunita in una colonia di funghi o di actinomiceti (fino all'80%) è destinata a soccombere poiché non può incorporare il proprio genoma nelle spore. Abbiamo suggerito che, partendo da isolati microbici naturali, una caratteristica comune di funghi e batteri filamentosi è quella di segregare fenotipi in cui la produzione di metaboliti secondari ed enzimi è massimizzata in una parte della colonia che ha perso la capacità di riprodursi (la casta sterile), mentre la riproduzione è delegata ad un'altra parte della popolazione (la casta non sterile, generalmente rappresentata da spore o altre cellule durevoli). Sulla base di quanto sopra, abbiamo rivolto i nostri sforzi alla casta sterile avendo come obiettivo l'identificazione, la caratterizzazione e la conservazione a lungo termine di popolazioni clonali industrialmente rilevanti. Tuttavia, nei microrganismi miceliari e polinucleati, come i funghi e gli attinomiceti, la semplice replicazione delle colonie o l’isolamento per diluizione, non consentono la efficace separazione dei genomi. Al fine di separare correttamente le popolazioni clonali d’interesse, ci siamo dedicati alla selezione della casta sterile mediante l'utilizzo di tre diverse tecniche: selezione morfologica di quei fenotipi che hanno perso la capacità di produrre spore (studio eseguito su funghi e attinomiceti e su Bacillus subtilis), la selezione della casta sterile mediante l'utilizzo di agenti selettivi (applicato a funghi ed attinomiceti) e la separazione dei genomi mediante screening massivo di cloni prodotti con la tecnica dei protoplasti.
Più in dettaglio, abbiamo utilizzato l'antibiotico A40926 come agente selettivo per l'identificazione di altoproduttori di A40926 (il precursore naturale del glicopeptide clinicamente rilevante Dalbavancina). Il ceppo produttore, Nonomuraea gerenzanensis ATCC 39727, ha mostrato la presenza di due distinte popolazioni che sono state selezionate in presenza di concentrazioni di A40926 sub-inibenti. La popolazione identificata come G è stata in grado di produrre il doppio di A40926 rispetto alla popolazione P. La popolazione G ha quindi mostrato un incomparabile vantaggio produttivo sfruttabile industrialmente.
Nell'identificazione degli altoproduttori di Teicoplanina (il glicopeptide clinicamente rilevante commercialmente noto come Targocid) in Actinoplanes teichomyceticus ATCC 31121, sono stati separati differenti fenotipi, grazie alla separazione dei genomi compiuta con l’utilizzo di protoplasti. Uno screening massiccio delle popolazioni clonali risultanti ha permesso di identificare sia altoproduttori che produttori di differenti complex di Teicoplanina.
Nel produttore del glicopeptide Avoparcina, Amycolatopsis coloradensis ATCC 53629, siamo stati in grado di selezionare altoproduttori sulla base della identificazione di differenti morfologie incapaci di produrre spore. Contemporaneamente, siamo stati in grado di scoprire “materia oscura biosintetica” nascosta all'interno del genoma del ceppo. Le varianti morfologiche selezionate in questo ceppo sono infatti state in grado di produrre fino a 9 g/L di Avoparcina e di produrre degli analoghi dell’Avoparcina fino ad ora non identificati.
I nostri studi hanno evidenziato che l'incidenza di mutanti/varianti per i tratti specifici analizzati (produzione di enzimi e metaboliti secondari) era al di sopra di qualsiasi incidenza di mutazione casuale attesa.Actinomycetes and Fungi are frequently organized in small integrated societies (exemplified by colonies) in which a division of labor occurs. The division of labor has the evolutionary outcome of giving a selective advantage to the growing cells and finally to the fertile progeny. The fertile progeny has the task to preserve the species within the limits of natural evolution and colonization of new niches. A considerable part of the population assembled in a fungus or actinomycete colony (up to 80%) is fated to dye since it cannot embed its genome in spores. We have suggested that, in natural microbial isolates, a common characteristic is to segregate phenotypes in which the production of secondary metabolites and enzymes is maximized in the part of the colony which has lost the capacity to reproduce itself (the sterile caste), while reproduction is delegated to another part of the population (the non-sterile caste, generally represented by spores or other durable cells). Based on the above statements, we were digging in the sterile caste having as goal the identification, characterization and long-term preservation of industrially relevant lineages. In mycelial and polynuclear microorganisms, as fungi and actinomycetes are, simple replication of colonies, or plating by dilution, did not easily allow the separation of genomes. Therefore, to correctly separate the lineages of interest, we have approached the selection of the sterile caste by use of three different techniques: morphological selection of those phenotypes having lost the spore-producing ability (study performed on fungi and actinomycetes), the selection of the sterile caste by use of selective agents (applied to fungi and actinomycetes) and the separation of genomes by massive screening of clones produced with the protoplast technique. More in detail, we used the antibiotic A40926 as selective agent for the identification of high producers of the A40926 glycopeptide (the natural precursor of the clinically relevant Dalbavancin antibiotic). The producer strain, Nonomuraea gerenzanensis ATCC 39727, displayed the presence of two distinct populations which were selected by the A40926 antibiotic. The G population was able to produce twice the A40926 amount in respect of the P population. The G population gave an incomparable industrial advantage. In the identification of high producers of Teicoplanin (the clinically relevant glycopeptide commercially known as Targocid) in Actinoplanes teichomyceticus ATCC 31121, we separated the genomes by use of the protoplast technology, and we performed a massive screening of the resulting clonal populations. In this case, we uncovered both high producers and producers of alternative Teicoplanin antibiotic complexes. In the producer of the glycopeptide Avoparcin, Amycolatopsis coloradensis ATCC 53629, we were able to select high producers based on the identification of different non-spore producing colony morphologies and at the same time we were able to uncover biosynthetic dark matter hidden within the genome of the strain. Indeed, the selected morphological variants of this strain, were both able to produce Avoparcin up to a 9 g/L level and to produce an alternative Avoparcin complex with novel and up-to-date unidentified Avoparcin analogues. Our studies evidenced that the incidence of mutants/variants for the specific traits analyzed (production of enzymes and secondary metabolites) was above any expected random mutation result.
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Fraser, Michelle. « Systematics of the genus Candida ; implications for understanding clinical presentation, mixed infection and antifungal treatment and the influence on strain maintenance and replacement during oral candidiasis in HIV-infected individuals / ». Title page, contents and abstract only, 2002. http://web4.library.adelaide.edu.au/theses/09PH/09phf8421.pdf.
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Li, Jianhui. « Cornichon Proteins : Unexpected Roles in Plant Pathogen Infection, ER Morphology Maintenance and Pollen Development ». Diss., Virginia Tech, 2017. http://hdl.handle.net/10919/77687.
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Cornichon (CNI) proteins are a conserved family of proteins among eukaryotes, from Erv14 in the yeast Saccharomyces cerevisiae to CNI homologs (CNIHs) in mammals and plants. Erv14 functions as a cargo receptor of coat protein complex II (COPII) for protein trafficking from the endoplasmic reticulum (ER) to the Golgi apparatus, en route to their final destinations. By interacting with specific cargo proteins, CNI proteins regulate key steps of embryo polarity in Drosophila, budding in yeast, and synaptic transmission in the mammalian brain. However, we have very limited understanding of plant CNIHs. Positive-strand RNA viruses assemble their viral replication complexes (VRCs) at specific host organelle membranes. With a better understanding of host factors involved in targeting viral replication proteins to the preferred organelles, we expect to block trafficking of viral replication proteins and thus, viral infection, by manipulating the required host proteins. Brome mosaic virus (BMV) is a model of positive-strand RNA viruses and its replication can be recapitulated in yeast. Importantly, BMV replication protein 1a is the only required viral protein to form VRCs at the perinuclear ER membrane in yeast. I demonstrate that Erv14 and COPII coat proteins are required for targeting BMV 1a to the perinuclear ER in yeast, suggesting a novel function of COPII vesicles in protein trafficking to the perinuclear ER membrane and in the BMV VRC formation. As for cellular functions, I show that plant CNIHs complement the defective distribution of BMV 1a in yeast mutant lacking Erv14. Taking advantage of Arabidopsis thaliana knockout mutants and knockdown of gene expression in Nicotiana benthamina, I also discover that CNIHs unexpectedly play crucial roles in pollen development, infection of a bacterial pathogen, and maintenance of ER tubules. I further confirm that CNI proteins are also required for maintaining ER tubules in yeast, suggesting a novel and conserved role in shaping ER morphology. Therefore, these findings indicate the functional diversity and redundancy of CNI proteins in key cellular processes and suggest a novel strategy to control plant pathogenic viruses and bacteria by manipulating plant CNIHs.Ph. D.
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Moretton, Amandine. « Mécanismes de maintenance de l'intégrité de l'ADN mitochondrial humain suite à des cassures double-brin ». Thesis, Université Clermont Auvergne (2017-2020), 2017. http://www.theses.fr/2017CLFAC047/document.
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Les mitochondries sont des organites qui possèdent leur propre ADN (ADNmt), codant pour des gènes de la chaine respiratoire. La réparation des dommages dus aux ROS, une réplication défectueuse ou d’autres sources exogènes tels des agents chimiothérapeutiques ou des irradiations ionisantes peuvent générer des cassures double-brin (CDB) de l’ADNmt. L’ADNmt code pour des protéines essentielles à la production d’énergie, et des systèmes de maintenance de l’intégrité de ce génome efficaces sont donc nécessaires pour la viabilité des cellules. En effet des mutations de l’ADNmt sont présentes dans de nombreuses pathologies comme les myopathies mitochondriales, les cancers et les maladies neurodégénératives. Cependant les processus responsables de la maintenance de l’ADNmt suite à des CDB restent controversés.Pour élucider les mécanismes impliqués, nous avons généré des CDB mitochondriales en utilisant une lignée cellulaire humaine exprimant de manière inductible l’enzyme de restriction PstI liée à une séquence d’adressage mitochondrial. Nos résultats montrent, dans notre système, une première phase de dégradation de l’ADNmt lésé avec une cinétique rapide, n’impliquant pas l’autophagie ou l’apoptose, suivie de la ré-amplification d’ADNmt intact dans un deuxième temps. Contrairement à d’autres études nous n’avons pas pu détecter d’évènements de réparation des CDB mitochondriales générées. Nous avons ensuite cherché à identifier les protéines impliquées dans la dégradation de l’ADNmt lésé que nous observons, mais aucune nucléase testée ne semble responsable de ce processus. Des approches plus globales sont mises au point pour identifier de nouveaux acteurs, notamment un crible RNAi à grande échelle. Parallèlement nous nous intéressons aussi à une famille de phosphohydrolases, les Nudix, et à leur rôle protecteur en assainissant le réservoir de nucléotides libresMitochondria are organelles that possess their own genome, the mitochondrial DNA (mtDNA). Repair of oxidative damages, defective replication, or various exogenous sources, such as chemotherapeutic agents or ionizing radiations, can generate double-strand breaks (DSBs) in mtDNA. MtDNA encodes for essential proteins involved in ATP production and maintenance of integrity of this genome is thus of crucial importance. Mutations in mtDNA are indeed found in numerous pathologies such as mitochondrial myopathies, neurodegenerative disorders or cancers. However, the mechanisms involved in mtDNA maintenance after DSBs remain unknown.To elucidate this question, we have generated mtDNA DSBs using a human inducible cell system expressing the restriction enzyme PstI targeted to mitochondria. Using this system, we could not find any support for DSBs repair of mtDNA. Instead we observed a loss of the damaged mtDNA molecules and a severe decrease in mtDNA content, followed by reamplification of intact mtDNA molecules. We have demonstrated that none of the known mitochondrial nucleases are involved in mtDNA degradation and that DNA loss is not due to autophagy, mitophagy or apoptosis but to a selective mechanism. Our study suggests that a still uncharacterized pathway for the targeted degradation of damaged mtDNA in a mitophagy/autophagy-independent manner is present in mitochondria, and might provide the main mechanism used by the cells to deal with DSBs. Global approaches are ongoing to identify proteins involved in degradation of damaged mtDNA following DSBs, mainly an RNAi screen targeting 80 nucleases. In parallel we are interested in a family of phosphohydrolases named Nudix and their putative protective role in sanitizing the nucleotides pool in mitochondria
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Fraser, Michelle (Michelle Lousie). « Systematics of the genus Candida ; implications for understanding clinical presentation, mixed infection and antifungal treatment and the influence on strain maintenance and replacement during oral candidiasis in HIV-infected individuals ». 2002. http://web4.library.adelaide.edu.au/theses/09PH/09phf8421.pdf.
Texte intégralRésumé :
"8th July 2002." Includes bibliographical references (leaves 276-308) Examines the systematics (taxonomy, phylogeny, and epiemiology) of the genus Candida using a combination of traditional and contemporary methodologies. Assesses these methods to determine their diagnostic potential to unequivocally identify and characterise species and strains of this medically and dentally important yeast genus.
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Fraser, Michelle Louise. « Systematics of the genus Candida ; implications for understanding clinical presentation, mixed infection and antifungal treatment and the influence on strain maintenance and replacement during oral candidiasis in HIV-infected individuals / by Michelle Fraser ». 2002. http://hdl.handle.net/2440/21799.
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"8th July 2002."Includes bibliographical references (leaves 276-308)
vi, 308, [57] leaves : charts ; 30 cm.
Title page, contents and abstract only. The complete thesis in print form is available from the University Library.
Examines the systematics (taxonomy, phylogeny, and epiemiology) of the genus Candida using a combination of traditional and contemporary methodologies. Assesses these methods to determine their diagnostic potential to unequivocally identify and characterise species and strains of this medically and dentally important yeast genus.
Thesis (Ph.D.)--University of Adelaide, Dept. of Dentistry, 2002
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孫宏仁. « The research on preservation,maintenance and management of cross-straits history and culture ». Thesis, 2006. http://ndltd.ncl.edu.tw/cgi-bin/gs32/gsweb.cgi/login?o=dnclcdr&s=id=%22095CHU00493001%22.&searchmode=basic.
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Hsu, Wen-Han, et 許文漢. « A Study of Maintenance and Management Models of Applied Information Systems in Taiwanese Transnational Corporations (TNCs) – A Case for Cross-Strait Electronic Manufacturers ». Thesis, 2005. http://ndltd.ncl.edu.tw/handle/83599808771113231277.
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碩士國立臺灣大學
資訊管理學研究所
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In late 1980’s, Taiwanese enterprises were forced to relocate their manufacturing bases to regions where provide cheaper labor and are closer in terms of geography and culture (eg. Southeast Asia and China), at the same time these movements initiated the turning point of Taiwanese enterprises’ internationalization. For those contract manufacturing-oriented medium and large-scaled businesses in Taiwan, their foreign investments are mainly about setting factories in overseas locations, transforming its existing division of labor and production structure, and moving manufacturing bases to periphery contractors while retaining research and design capabilities. On the one hand they act as agents of customers from advance countries in terms of production cost and quality control, on the other hand, they actively maintain the flexibility and efficiency of their production units and network, therefore Taiwanese transnational corporations’ primary aspects are reproducing production capability overseas and strengthening manufacturing competitiveness; There are significant differences when it comes to managing cross-strait businesses between Taiwanese and Western transnational corporations, such as social and political factors, information technology remains immature.., etc. Consequently, the information architecture in each company is different too. It cannot be done by adapting the model that Western transnational corporations used to develop and maintain information systems, nor can it be constructed from a regional perspective. In fact, once information systems go online formally and their users start to operate, the stage where maintaining information systems begins. Taiwanese transnational corporations will face the issue of choosing the proper type of applied information system maintenance architecture, regardless of the management style of the MIS department - organization and information architecture is centralized, decentralized, or both. This study will categorize the maintenance and management models of transnational applied information system as “centralized,” “decentralized,” and “mixed,” and dilute factors that influence transnational information system and maintenance from transnational corporations’ MIS department - organization, maintenance of applied information systems, information systems architecture, and related theories and case studies. To conclude, three categories of applied information system and maintenance models and suitability-analysis model for choosing the best management style to maintain applied information systems.
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Martin, Jacinta. « Quality control mechanisms responsible for the maintenance of genomic integrity in the female germline ». Thesis, 2019. http://hdl.handle.net/1959.13/1395720.
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Research Doctorate - Doctor of Philosophy (PhD)DNA is the genetic repository containing the necessary information for cellular viability, fate decisions and development. In the female germline, genetic integrity also underpins successful conception, embryonic development, pregnancy and the future health of the offspring. In spite of its importance, DNA remains a chemical entity prone to structural alteration. If left unresolved, these structural lesions have the potential to lead to mutation and broader-scale genomic aberrations, which may elevate the predisposition of individuals to non-communicable diseases in later life. While it is therefore likely that female germ cells possess a sophisticated suite of quality control mechanism to defend their genome, the precise nature of these defence systems is not well understood. Given this knowledge gap, the overall aim of the studies described within this thesis was to explore the endogenous DNA protection and repair machinery present in the mammalian oocyte and early embryo. In completing these studies, we have uncovered several novel protective strategies employed by the oocyte and early preimplantation embryo to safeguard their genomic integrity. These include the first evidence for a critical link between fertilisation and the synthesis of transmembrane transporter molecules belonging to the multidrug resistant protein family. Specifically, we implicate permeability glycoprotein (PGP) in increasing the bi-directional transport capacity of the zygote immediately following fertilisation. We posit that the activity of membrane bound PGP counters the influx of genotoxic agents, shielding the embryonic pronuclei from the induction of DNA damage. Excitingly, we also demonstrate that the preservation of the maternal genome, prior to fertilisation, is enhanced by an endogenous store of DNA repair proteins accumulated during oogenesis, providing the first evidence of an active DNA repair program in the post-ovulatory (MII) oocyte. Accordingly, we demonstrate a role for non-homologous end joining (NHEJ) as a repair platform for correcting damage of the maternal DNA prior to fertilisation. Having demonstrated that the oocyte and preimplantation embryo contain a sophisticated suite of defence strategies for the detection, repair or prevention of DNA damage, we hypothesized that the efficacy of these defences may be augmented by pro-survival factors. We therefore explored the capacity of C-peptide, a hormone implicated in the regulation of intracellular signalling pathways, to modulate oocyte and early embryo biology. Through this work, we observed a previously unappreciated abundance of C-peptide within the mouse ovary, oocyte and follicular fluid and uncovered a putative interaction between C-peptide and the DNA repair enzyme, breast cancer type 2 susceptibility protein (BRCA2) following oocyte activation. Collectively, these findings lend support to a novel role for C-peptide in the female germline and raise the prospect that C-peptide may exert direct physiological effects within the female reproductive system. Taken together, the findings reported in this thesis have enhanced our understanding of the maintenance of genetic stability in the female germline. Importantly, this collection of studies offers a molecular understanding of the endogenous capacity of the oocyte and preimplantation embryo to detect and subsequently respond to DNA damage and, in turn, identifies novel clinical targets to enhance oocyte competence in vitro and potentially improve assisted reproductive technologies.
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Ghodke, Indrajeet Laxman. « The Role of Saccharomyces Cerevisiae MRX Complex and Sae2 in Maintenance of Genome Stability ». Thesis, 2015. http://etd.iisc.ernet.in/2005/3679.
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In eukaryotes, the repair of DSBs is accomplished through two broadly defined processes: Non-Homologous End Joining (NHEJ) and Homologous Recombination (HR). The central step of HR is pairing and exchange of strands between two homologous DNA molecules, which is catalyzed by the conserved Rad51/RecA family of proteins. Prior to this step, an essential step in all HR pathways i.e. 5'→3' resection of broken DNA ends to generate 3' single stranded DNA tails. At the molecular level, initiation of DNA end resection is accomplished through the concerted action of MRX complex (Mre11, Rad50 and Xrs2) and Sae2 protein.
To elucidate the molecular basis underlying DSB end resection in S. cerevisiae mre11 nuclease deficient mutants, we have performed a comprehensive analysis of the role of S. cerevisiae Mre11 (henceforth called as ScMre11) in the processing of DSB ends using a variety of DNA substrates. We observed that S. cerevisiae Mre11(ScMre11) exhibits higher binding affinity for single- over double-stranded DNA and intermediates of recombination and repair and catalyzes robust unwinding of substrates possessing a3' single-stranded DNA overhang but not of 5' overhangs or blunt-ended DNA fragments. Furthermore, reconstitution of DSB end resection network in-vitro revealed that Rad50, Xrs2, and Sae2 potentiated the DNA unwinding activity of Mre11. Since the exonuclease activity of Mre11 is of the opposite polarity to that expected for resection of DSBs, unwinding activity of Mre11 in conjunction with Rad50, Xrs2, and Sae2 might provide an alternate mechanism for the generation of ssDNA intermediates for DSB end repair and HR. Additionally, ScMre11 displays strong homotypic as well as heterotypic interaction with Sae2. In summary, our results revealed important insights into the mechanism of DSB end processing and support a model in which Sae2, Rad50, and Xrs2 positively regulate the ScMre11-mediated DNA unwinding activity via their direct interactions or through allosteric effects on the DNA or cofactors.
Prompted by the closer association of MRX and Sae2 during DSB end processing, we asked whether Sae2 and its endonuclease activity is required for cellular response to replication stress caused by DNA damage. Toward this end, we examined the sensitivity of S. cerevisiae wild type, sae2Δ and various SAE2 mutant strains defective in phosphorylation and nuclease activity in the presence of different genotoxic agents, which directly or indirectly generate DSBs during replication. We found that S. cerevisiae lacking SAE2 show decreased cell viability, altered cell cycle dynamics after DNA damage, and more specifically, that Sae2 endonuclease activity is essential for these biological functions. To corroborate the genetic evidences for role of SAE2 during replicative stress, we investigated SAE2 functions in-vitro. For this, we purified native Sae2 protein and nuclease dead mutant of Sae2 i.e. sae2G270D. Our studies revealed dimeric forms of both the wild type and mutant forms of Sae2. Furthermore, Sae2 displays higher binding affinity and catalytic activity with branched DNA structures, such as Holliday junction and replication forks. By using nuclease dead Sae2 protein i.e. sae2G270D, we confirmed that the endonuclease activity is not fortuitous and is intrinsic to Sae2 polypeptide. Furthermore, nuclease-defective Mre11 stimulates Sae2endonuclease activity. Mapping of the cleavage sites of Sae2 revealed a distinct preference for cleavage on the 5' end of the Holliday junction, suggesting the importance of Sae2 nuclease during recombination mediated restart of the reversed replication fork. In summary, our data clearly demonstrate a previously uncharacterized role for Sae2 nuclease activity in resection of DSB ends, processing of intermediates of DNA replication/repair and attenuation of DNA replication stress-related defects in S. cerevisiae.
Livres sur le sujet "Strain maintenance"
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Pollock, W. J. Slow strain rate testing of high strength low-alloy steels : A technique for assessing the degree of hydrogen embrittlement produced by plating processes, paint strippers and other aircraft maintenance chemicals. Melbourne, Victoria : Dept. of Defence, Aeronautical Research Laboratories, 1985.
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Strasman, Peter G. Fiat Strada owners workshop manual. Sparkford : Haynes, 1991.
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Strasman, Peter G. Fiat Strada owners workshop manual. Yeovil : Haynes, 1985.
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Strasman, Peter G. Fiat Strada owners workshop manual. Sparkford : Haynes, 1987.
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Schindler, Paul. Optical fiber sensors for damage analysis in aerospace materials : Final report. [Washington, D.C : National Aeronautics and Space Administration, 1995.
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McKay, Graham. The land still speaks : Review of aboriginal and Torres Strait Islander language maintenance and development needs and activities. Canberra : Australian Government Publishing, 1996.
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Ramberger, Günter. Structural bearings and expansion joints for bridges. Zurich, Switzerland : International Association for Bridge and Structural Engineering (IABSE), 2002. http://dx.doi.org/10.2749/sed006.
Texte intégralRésumé :
<p>Bridge superstructures have to be designed to permit thermal and live load strains to occur without unintended restraints. Bridge bearings have to transfer forces from the superstructure to the substructure, allowing all movements in directions defined by the designer. The two functions -transfer the loads and allow movements only in the required directions for a long service time with little maintenance - are not so easy to fulfil. Different bearings for different purposes and requirements have been developed so, that the bridge designer can choose the most suitable bearing.</p> <p>By the movement of a bridge, gaps are necessary between superstructure and substructure. Expansion joints fill the gaps, allowing traffic loads tobe carried and allowing all expected displacements with low resistance. Expansion joints should provide a smooth transition, avoid noise emission as far as possible and withstand all mechanical actions and chemical attacks (de-icing) for a long time. A simple exchange of all wearing parts and of the entire expansion joint should be possible.</p> <p>The present volume provides a comprehensive survey of arrangement, construction and installation of bearings and expansion joints for bridges including calculation of bearing reactions and movements, analysis and design, inspection and maintenance. A long list of references deals with the subjects but also with aspects in the vicinity of bearings and expansion joints.</p> <p>This book is aimed at both students and practising engineers, working in the field of bridge design, construction, analysis, inspection, maintenance and repair.</p>
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Dossena, Alberto. L'organo Giuseppe Cavalli 1855 della Chiesa parrocchiale di San Martino in Strada (Lo) : Il restauro e l'attività degli organari Giuseppe e Gaetano Cavalli. Guastalla (RE) : Associazione culturale "Giuseppe Serassi", 2014.
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(Firm), Knovel, dir. Fatigue in railway infrastructure. Boca Raton, FL : CRC Press, 2009.
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LRFD bridge design specifications. 9e éd. Washington, DC : American Association of State Highway and Transportation Officials, 2020.
Trouver le texte intégralChapitres de livres sur le sujet "Strain maintenance"
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Stewart, Graham G. « Yeast Culture Collections, Strain Maintenance and Propagation ». Dans Brewing and Distilling Yeasts, 49–54. Cham : Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-69126-8_4.
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Skerry, T. M. « Skeletal strain and the maintenance of bone mass ». Dans Proceedings of the First International Conference on Interfaces in Medicine and Mechanics, 167–72. Dordrecht : Springer Netherlands, 1989. http://dx.doi.org/10.1007/978-94-011-7477-0_17.
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Ishikawa, T., N. Matsumoto et N. Ueda. « Research on the fatigue crack detection by strain measurement under unloading condition ». Dans Bridge Safety, Maintenance, Management, Life-Cycle, Resilience and Sustainability, 1679–84. London : CRC Press, 2022. http://dx.doi.org/10.1201/9781003322641-207.
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Lee, S. H., L. S. An, H. K. Kim et Y. C. Park. « Fatigue reliability assessment of an in-service steel bridge based on BWIM and strain data ». Dans Bridge Safety, Maintenance, Management, Life-Cycle, Resilience and Sustainability, 551–58. London : CRC Press, 2022. http://dx.doi.org/10.1201/9781003322641-65.
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Ma, Zhanxiong, Jaemook Choi et Hoon Sohn. « Simultaneous displacement and cable force estimation for submerged floating tunnel based on strain and acceleration measurements ». Dans Bridge Safety, Maintenance, Management, Life-Cycle, Resilience and Sustainability, 1111–16. London : CRC Press, 2022. http://dx.doi.org/10.1201/9781003322641-133.
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Navarrete-Maya, Rosa, Ivânia Esteves et Rosa H. Manzanilla-López. « Methodology Part I. Pochonia spp. In Vitro Culturing : Media, Strain Maintenance and Deposition ». Dans Perspectives in Sustainable Nematode Management Through Pochonia chlamydosporia Applications for Root and Rhizosphere Health, 211–33. Cham : Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-59224-4_11.
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Yamaguchi, E., et Y. Furusato. « Axle-load-estimation based on strain of transverse stiffener and characteristics of traffic loads due to heavy trucks ». Dans Bridge Safety, Maintenance, Management, Life-Cycle, Resilience and Sustainability, 1280–86. London : CRC Press, 2022. http://dx.doi.org/10.1201/9781003322641-155.
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Fitri, Siti Nurlita. « Shear Strain Evaluation on Analysis of Additional Clay Liner Layer Modeling in Ngipik Landfill, Gresik ». Dans Proceedings of the 5th International Conference on Rehabilitation and Maintenance in Civil Engineering, 533–42. Singapore : Springer Nature Singapore, 2022. http://dx.doi.org/10.1007/978-981-16-9348-9_47.
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Barghouth, Paul G., Salvador Rojas, Lacey R. O’Dell, Andrew M. Betancourt et Néstor J. Oviedo. « Analysis of DNA Double-Stranded Breaks Using the Comet Assay in Planarians ». Dans Methods in Molecular Biology, 479–91. New York, NY : Springer US, 2022. http://dx.doi.org/10.1007/978-1-0716-2172-1_25.
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AbstractComet assay provides the opportunity to detect and characterize DNA strand breaks. Cellular lysing followed by embedding in agarose slide is used to visualize under an electrical current migration patterns corresponding to DNA fragments of different sizes. Here we describe the process of detecting and characterizing DNA damage by Comet assay on planarians, which is a model organism commonly used to understand the process of whole-body regeneration, stem cell regulation, and adult tissue maintenance.
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Umemoto, S., H. Ohata, N. Miyamoto, T. Okamoto, T. Takaki, K. Fujii et I. Ishii. « Strain measurement of bridge members using strain visualization sticker ». Dans Bridge Maintenance, Safety, Management, Resilience and Sustainability, 2218–23. CRC Press, 2012. http://dx.doi.org/10.1201/b12352-331.
Texte intégralActes de conférences sur le sujet "Strain maintenance"
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Sorensen, Michelle L. « Pipeline Maintenance in Geotechnically Unstable Areas : A Case Study ». Dans 2000 3rd International Pipeline Conference. American Society of Mechanical Engineers, 2000. http://dx.doi.org/10.1115/ipc2000-142.
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The 22″ Alberta Oilsands Pipeline transports synthetic crude oil from Syncrude Canada Limited in Fort McMurray to Edmonton, Alberta. The pipeline crosses the House River approximately 100 kilometers south of Fort McMurray. The slope has been monitored since 1991 by three slope indicators. A finite element stress analysis indicated that total ground movement since installation in 1977 could correspond to pipeline compressive strains in excess of 0.32%, a level of risk unacceptable to the pipeline owner. A probability-based model was developed to determine cost and benefit of risk mitigation options. Parameters such as soil movement and pipe strain were input as probability distributions. The mitigation options included: reduce slope instability; reduce pipe stress; reduce pipe-to-soil interaction; implement long term monitoring; determine current pipe strain level (to decrease data uncertainty); do nothing. A Monte Carlo simulation was used to establish probability of failure and probable cost distributions for each option. The results were presented as a combined cost of failure and mitigation over 10 years. The analysis indicated that the optimum solution was to remove the existing soil traction loading on the pipe and mitigate long-term slope movement. The decision was made to relieve the pipe strain by excavating. Current pipe strain was measured in situ using residual strain measurement. Long term strain gauges were installed. Slope mitigation was deferred until the strain gauges indicate total pipeline strain levels approaching 0.32%.
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Musil, T., S. Fabry, M. Hovanec, B. Racek, J. Lukac et S. A. S. Al-Rabeei. « Experimental research of stress-strain states and Maintenance Technicians Training ». Dans 2020 New Trends in Aviation Development (NTAD). IEEE, 2020. http://dx.doi.org/10.1109/ntad51447.2020.9379121.
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Narayanan, Aditya, Andy Morris, Catrin M. Davies et John P. Dear. « Optical Strain Monitoring Techniques ». Dans ASME 2012 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/pvp2012-78515.
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The Auto-Reference Creep Management and Control (ARCMAC) system is being developed as a technique to evaluate the remaining life of power plant components. The system consists of a pair of Inconel plates with a configuration of silicon nitride (SiN) spheres on them, and a camera system used to take images of the gauge during the component’s deformation. The purpose of the system is to measure the creep strain accumulated by a component at regular intervals, tracking the relative motion of the spheres in order to measure a point-to-point value of strain. The system is currently used to capture images of gauges already installed on power plants in the UK as part of scheduled maintenance during plant outages. It is also possible to use the ARCMAC system to capture speckle paint pattern data used in digital image correlation (DIC) in order to visualise the strain field across the heat affected zones (HAZ) in welds and around other strain concentration features. A newer version of the system: the Digital Single Lens Reflex (DSLR) ARCMAC is being developed specifically to capture this kind of data in order to complement the point-to-point strain measurements obtained. This article presents results of experiments performed at room temperature with the purpose of establishing the basic accuracy of the conventional ARCMAC and the DSLR ARCMAC in order to compare their performance. It also intends to evaluate the performance of the latter when used for digital image correlation. The results showcase the accuracy of the technique at high strains using the DSLR camera, showing its usefulness as a tool to measure creep strain.
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Henderson, Jonathan T., et Corey P. Neu. « In Situ Hierarchical Strain Transfer From the Articular Cartilage Surface to the Chondrocyte Nucleus ». Dans ASME 2012 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/sbc2012-80628.
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Osteoarthritis (OA) is a disabling disease, commonly thought of as the “wear and tear” of articular cartilage, afflicting 27 million Americans [1]. Multiple (e.g. biomechanical and biochemical) factors [2] contribute to maintenance of healthy joints through chondrocyte and extracellular matrix interactions. Interestingly, volumetric contractions of nuclei exhibit a zonal dependence [3], suggesting that nuclear mechanics may play a key role in the maintenance of healthy tissue by mechanically-mediated pathways.
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Ramos, Adalgiza, et Andrés Ocampo. « Best Practices for the Strain Relief Excavation by Geotechnical Movements in Ocensa ». Dans ASME 2017 International Pipeline Geotechnical Conference. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/ipg2017-2527.
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This article aims to describe the best industry practices followed by the line maintenance area of the Ocensa pipeline, which can be divided into 4 large steps that follow a PHVA cycle of the activity, which includes relief planning, the execution of the same, the verification and geotechnical monitoring, closure and feedback.
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Sheets, Colton, Taylor Shie et Adam Crawford. « Thin-Wall Pipeline Repair : Evaluation of Reinforcement Systems and Internal Temperature Monitoring During Maintenance Procedures ». Dans 2018 12th International Pipeline Conference. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/ipc2018-78647.
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There are many options available to pipeline operators when addressing anomalies or integrity threats. Repairing integrity threats requires an understanding of both the anomaly to be repaired, and the repair system itself. This can be challenging as pipeline repair systems come in a wide variety of materials, application techniques, and designs. Operators have similar challenges when performing maintenance activities on operating pipelines. Maintenance activities can take many different forms and often involve welding or other high temperature processes on the outside pipe surface. These processes can result in elevated temperatures on the inside surface of the pipeline and must be seriously considered before undertaking to ensure the safety of personnel performing the tasks and to protect the integrity of the pipeline. This study aimed to provide a greater understanding of pipeline reinforcement systems and maintenance activities as they relate specifically to thin-walled pipelines. To evaluate systems reinforcing thin-wall pipes, five different repair systems were investigated using 12.75-inch × 0.219-inch, Gr. X65 pipe that had been removed from service. The systems included a Type B steel sleeve, an epoxy-filled, interference fit, Type A steel sleeve, a hybrid steel sleeve-fiberglass based composite repair system, epoxy-filled oversized Type A steel sleeves, and a rigid coil, pre-cured, fiberglass-based composite repair system. Each system was used to reinforce a simulated 50% wall loss anomaly and was installed with the pipe samples maintained at an internal pressure equal to 33% of the pipe’s specified minimum yield strength (SMYS). The samples underwent pressure cycling and hydrostatic testing while strains in the simulated wall loss region were continually monitored. As a final step, the samples were burst tested. Monitoring of strain gages installed in the simulated wall loss anomaly allowed for comparisons to be made between the tested repair systems. It was observed that the recorded strain magnitudes and strain ranges were higher in some samples than others during testing. This allowed the systems to be ranked according to the recorded strains. Although differences were observed in the recorded strains, burst testing showed that all reinforcement systems were able to force failure to the base pipe outside of the simulated wall loss region. Maintenance procedures were also evaluated to identify those that could produce unacceptable temperatures on the inside surface of the thin-wall pipe. The maintenance procedures included installation of Type A steel sleeves (non-pressure containing), Type B steel sleeves (pressure containing), cad welds, and pin brazing cathodic protection (CP) test leads. Temperatures were monitored on the internal pipe surface using thermocouples and an infrared (IR) camera while the maintenance procedures were being performed. An internal surface temperature of 500 °F (260 °C) was set as the threshold for suitability. Monitoring of the Type B steel sleeve installation showed temperatures on the inside surface of the pipe that exceeded 1,200 °F (648 °C) when performing the circumferential weld at each end of the steel sleeve. A maximum temperature of 280 °F (137 °C) was recorded when making the longitudinal welds that included a backing strip. For the application being considered, this indicated that Type A steel sleeves (longitudinal welds only) could be installed within the required temperature limits. A maximum internal temperature of 936 °F (502 °C) was recorded during cad-welding. Pin-brazing was slightly lower, but also exceeded the 500 °F threshold. This testing confirmed that the installation of Type B steel sleeves, cad welding, or pin brazing should receive scrutiny before being performed on operating thin-wall pipelines.
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Breeding, Charlie, et Chris Bentley. « Slag Monitoring Using Strain Gages at Georgia Power Plant Bowen ». Dans International Joint Power Generation Conference collocated with TurboExpo 2003. ASMEDC, 2003. http://dx.doi.org/10.1115/ijpgc2003-40148.
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Georgia Power Plant Bowen is a 4 unit plant. Unit 1 is a 930 MW plant with a Combustion Engineering boiler. A slag monitoring system was installed on the leading side of the reheater pendant. Monitors were also installed on portions of the economizer. The key element of the system is strain gages that are installed on the rods that hang the pendant and economizer from the building steel. Monitoring of the gages was done during the restart of the unit from a major maintenance outage. Data from the system will be presented. The amount of deposits and their location is the intended output from the system and this data will be presented. The long range goal of the system is automatic operation of soot blowers based on the output from the monitoring system.
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Zhou, Joe, Gordon Craig, Beez Hazen et James D. Hart. « An Integrated Engineering Model for Prediction of Strain Demands in Pipelines Subject to Frost Heave ». Dans 2006 International Pipeline Conference. ASMEDC, 2006. http://dx.doi.org/10.1115/ipc2006-10053.
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Long distance pipelines are actively pursued by the industry to transport natural gas from remote arctic regions to markets. A chilled gas pipeline is one of the options to minimize the environmental impact resulting from operation of such pipelines. When a chilled gas pipeline crosses discontinuous permafrost areas, differential frost heave can occur. The result is pipe being subjected to potentially high strains, primarily in the axial direction. Reliable prediction of strain demands is one of the key components for a strain-based design process and it is essential for both ensuring pipeline integrity and facilitating life-cycle cost optimization for the design and maintenance of pipelines. The prediction of strain demands resulting from frost heave of chilled gas pipelines involves three fundamental engineering analysis processes. They are gas hydraulic analysis, geothermal analysis and pipeline structural analysis. Not only are these three processes complex, they are also mutually interdependent. To reliably predict strain demands and fully capture the interactions among these processes, TransCanada Pipelines Ltd. (TransCanada) and its partners developed an integrated engineering model on the basis of three well established programs for the three individual engineering processes. This paper will briefly review the integrated model for strain demand prediction.
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PFINGSTL, SIMON, OLAF TUSCH et MARKUS ZIMMERMANN. « COMPARISON OF ERROR MEASURES AND MACHINE LEARNING METHODS FOR STRAIN-BASED STRUCTURAL HEALTH MONITORING ». Dans Structural Health Monitoring 2021. Destech Publications, Inc., 2022. http://dx.doi.org/10.12783/shm2021/36289.
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The development of aircraft structures requires many fatigue tests. These tests are usually carried out to validate the corresponding finite element and damage models and to prove the expected damage-tolerant behavior. Monitoring aircraft structures requires experienced staff and is very time-consuming and expensive as the recurring inspection of the structure is a tedious task. We propose a machine learning-based approach that exploits continuous load and strain measurement data to support structural health monitoring and to shift the inspection program towards predictive maintenance. The machine learning model is used for mapping loads onto local strains. With the trained model, different error measures between current measurements and the predicted values are determined. When a specific threshold value based on an error confidence level is exceeded, an alarm is set off, and appropriate actions can be taken. The approach is applied to several fatigue tests with two different types of structures and damage mechanisms. Various error measures and models are compared. The paper shows that, first, simple error measures, such as the root mean squared error, are sufficient and even outperform more sophisticated error distances for detecting cracks with continuous strain measurements. Second, the standard deviation of strain or rather the load-strain slope is a key feature to detect cracks. And third, machine learning models enable structural health monitoring with sensors that even have only small strain values.
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Akers, Douglas W., et Curtis A. Rideout. « Nondestructive Quantification of Operational Damage and Surface Treatments for Improved Turbine Engine Maintenance and Surveillance Requirements ». Dans ASME 2004 International Mechanical Engineering Congress and Exposition. ASMEDC, 2004. http://dx.doi.org/10.1115/imece2004-60115.
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Despite advances made in metallic/intermetallic alloys and surface treatments to increase performance and decrease component weight in turbine engine components, standard inspection technologies are limited in their ability to nondestructively characterize operational damage buildup and the effect of surface treatments on component performance. Key areas where nondestructive characterization is required include the ability to quantify surface and subsurface residual strain in operational components, and cold work and surface treatments that are used to improve component life. The inability of current NDI techniques to nondestructively quantify surface and bulk residual stress in turbine engine components, especially single crystal and complex geometry components, leads to overly conservative engineering designs, maintenance procedures, and operational life estimates. Photon Induced Positron Annihilation and related portable technologies have been successfully utilized to quantify surface residual stresses and structural subsurface strain in turbine engine components subjected to high stress/high temperature environments.
Rapports d'organisations sur le sujet "Strain maintenance"
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Ficht, Thomas, Gary Splitter, Menachem Banai et Menachem Davidson. Characterization of B. Melinensis REV 1 Attenuated Mutants. United States Department of Agriculture, décembre 2000. http://dx.doi.org/10.32747/2000.7580667.bard.
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Brucella Mutagenesis (TAMU) The working hypothesis for this study was that survival of Brucella vaccines was directly related to their persistence in the host. This premise is based on previously published work detailing the survival of the currently employed vaccine strains S19 and Rev 1. The approach employed signature-tagged mutagenesis to construct mutants interrupted in individual genes, and the mouse model to identify mutants with attenuated virulence/survival. Intracellular survival in macrophages is the key to both reproductive disease in ruminants and reticuloendothelial disease observed in most other species. Therefore, the mouse model permitted selection of mutants of reduced intracellular survival that would limit their ability to cause reproductive disease in ruminants. Several classes of mutants were expected. Colonization/invasion requires gene products that enhance host-agent interaction or increase resistance to antibacterial activity in macrophages. The establishment of chronic infection requires gene products necessary for intracellular bacterial growth. Maintenance of chronic infection requires gene products that sustain a low-level metabolism during periods characterized little or no growth (1, 2). Of these mutants, the latter group was of greatest interest with regard to our originally stated premise. However, the results obtained do not necessarily support a simplistic model of vaccine efficacy, i.e., long-survival of vaccine strains provides better immunity. Our conclusion can only be that optimal vaccines will only be developed with a thorough understanding of host agent interaction, and will be preferable to the use of fortuitous isolates of unknown genetic background. Each mutant could be distinguished from among a group of mutants by PCR amplification of the signature tag (5). This approach permitted infection of mice with pools of different mutants (including the parental wild-type as a control) and identified 40 mutants with apparently defective survival characteristics that were tentatively assigned to three distinct classes or groups. Group I (n=13) contained organisms that exhibited reduced survival at two weeks post-infection. Organisms in this group were recovered at normal levels by eight weeks and were not studied further, since they may persist in the host. Group II (n=11) contained organisms that were reduced by 2 weeks post infection and remained at reduced levels at eight weeks post-infection. Group III (n=16) contained mutants that were normal at two weeks, but recovered at reduced levels at eight weeks. A subset of these mutants (n= 15) was confirmed to be attenuated in mixed infections (1:1) with the parental wild-type. One of these mutants was eliminated from consideration due to a reduced growth rate in vitro that may account for its apparent growth defect in the mouse model. Although the original plan involved construction of the mutant bank in B. melitensis Rev 1 the low transformability of this strain, prevented accumulation of the necessary number of mutants. In addition, the probability that Rev 1 already carries one genetic defect increases the likelihood that a second defect will severely compromise the survival of this organism. Once key genes have been identified, it is relatively easy to prepare the appropriate genetic constructs (knockouts) lacking these genes in B. melitensis Rev 1 or any other genetic background. The construction of "designer" vaccines is expected to improve immune protection resulting from minor sequence variation corresponding to geographically distinct isolates or to design vaccines for use in specific hosts. A.2 Mouse Model of Brucella Infection (UWISC) Interferon regulatory factor-1-deficient (IRF-1-/- mice have diverse immunodeficient phenotypes that are necessary for conferring proper immune protection to intracellular bacterial infection, such as a 90% reduction of CD8+ T cells, functionally impaired NK cells, as well as a deficiency in iNOS and IL-12p40 induction. Interestingly, IRF-1-/- mice infected with diverse Brucella abortus strains reacted differently in a death and survival manner depending on the dose of injection and the level of virulence. Notably, 50% of IRF-1-/- mice intraperitoneally infected with a sublethal dose in C57BL/6 mice, i.e., 5 x 105 CFU of virulent S2308 or the attenuated vaccine S19, died at 10 and 20 days post-infection, respectively. Interestingly, the same dose of RB51, an attenuated new vaccine strain, did not induce the death of IRF-1-/- mice for the 4 weeks of infection. IRF-1-/- mice infected with four more other genetically manipulated S2308 mutants at 5 x 105 CFU also reacted in a death or survival manner depending on the level of virulence. Splenic CFU from C57BL/6 mice infected with 5 x 105 CFU of S2308, S19, or RB51, as well as four different S2308 mutants supports the finding that reduced virulence correlates with survival Of IRF-1-/- mice. Therefore, these results suggest that IRF-1 regulation of multi-gene transcription plays a crucial role in controlling B. abortus infection, and IRF-1 mice could be used as an animal model to determine the degree of B. abortus virulence by examining death or survival. A3 Diagnostic Tests for Detection of B. melitensis Rev 1 (Kimron) In this project we developed an effective PCR tool that can distinguish between Rev1 field isolates and B. melitensis virulent field strains. This has allowed, for the first time, to monitor epidemiological outbreaks of Rev1 infection in vaccinated flocks and to clearly demonstrate horizontal transfer of the strain from vaccinated ewes to unvaccinated ones. Moreover, two human isolates were characterized as Rev1 isolates implying the risk of use of improperly controlled lots of the vaccine in the national campaign. Since atypical B. melitensis biotype 1 strains have been characterized in Israel, the PCR technique has unequivocally demonstrated that strain Rev1 has not diverted into a virulent mutant. In addition, we could demonstrate that very likely a new prototype biotype 1 strain has evolved in the Middle East compared to the classical strain 16M. All the Israeli field strains have been shown to differ from strain 16M in the PstI digestion profile of the omp2a gene sequence suggesting that the local strains were possibly developed as a separate branch of B. melitensis. Should this be confirmed these data suggest that the Rev1 vaccine may not be an optimal vaccine strain for the Israeli flocks as it shares the same omp2 PstI digestion profile as strain 16M.
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Al-Qadi, Imad, Egemen Okte, Aravind Ramakrishnan, Qingwen Zhou et Watheq Sayeh. Truck Platooning on Flexible Pavements in Illinois. Illinois Center for Transportation, mai 2021. http://dx.doi.org/10.36501/0197-9191/21-010.
Texte intégralRésumé :
Truck platoons have many benefits over traditional truck mobility. Truck platoons have the potential to improve safety and reduce fuel consumption between 5% and 15%, based on platoon configuration. In Illinois, trucks carry more than 50% of freight tonnage and constitute 25% of the traffic on interstates. Therefore, expected fuel savings would be significant for trucks. Deployment of truck platoons within interstate highways may have a direct effect on flexible pavement performance, as the time between consecutive axle loads (i.e., resting time) is expected to decrease significantly. Moreover, platoons could potentially accelerate pavement damage accumulation due to trucks’ channelized position, decreasing pavement service life and increasing maintenance and rehabilitation costs. The main objective of this project was to quantify the effects of truck platoons on pavements and to provide guidelines to control corresponding potential pavement damage. Finite-element models were utilized to quantify the impact of rest period on pavement damage. Recovered and accumulated strains were predicted by fitting exponential functions to the calculated strain profiles. The results suggested that strain accumulation was negligible at a truck spacing greater that 10 ft. A new methodology to control pavement damage due to truck platoons was introduced. The method optimizes trucks’ lateral positions on the pavements, and an increase in pavement service life could be achieved if all platoons follow this optimization method. Life cycle assessment and life cycle cost analysis were conducted for fully autonomous, human-driven, and mixed-traffic regimes. For example, for an analysis period of 45 years, channelized truck platoons could save life cycle costs and environmental impacts by 28% and 21% compared with human-driven trucks, respectively. Furthermore, optimum truck platoon configuration could reduce life cycle costs and environmental impacts by 48% and 36%, respectively, compared with human-driven trucks. In contrast, channelized traffic could increase pavement roughness, increasing fuel consumption by 15%, even though platooning vehicles still benefit from reduction in air drag forces. Given that truck platoons are expected to be connected only in the first phase, no actions are required by the agency. However, in the second phase when truck platoons are also expected to be autonomous, a protocol for driving trends should be established per the recommendation of this study.
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Moghtadernejad, Sara, Ehsan Barjasteh, Ren Nagata et Haia Malabeh. Enhancement of Asphalt Performance by Graphene-Based Bitumen Nanocomposites. Mineta Transportation Institute, juin 2021. http://dx.doi.org/10.31979/mti.2021.1918.
Texte intégralRésumé :
As the State of California continues to grow, demand for enhanced infrastructure such as roadways and highways escalates. In view of the current average highway lifespan of 15–20 years, the improvement of asphalt binders leads to material sustainability by decreasing required maintenance and increasing the lifespan of roadways. In the present investigation, enhancement of asphalt binder properties was achieved by different methods of mixing varying compositions of graphene nanoparticles with an SBS polymer and asphalt binder. Additionally, experimental evaluation and comparison of the rheological and mechanical properties of each specimen is presented. Graphene nanoparticles have attracted great curiosity in the field of highway materials due to their incredible rigidity, even in small quantities. Addition of as little as 1.0%nanoparticles in combination with polymers in an asphalt binder is expected to increase the rigidity of the material while also maintaining the beneficial polymer characteristics. Evaluation of the effect of the mixing design established that the methods for application of graphene to the polymer-modified asphalt binder are critical in the improvement of a roadway, resulting in resistance to premature aging and strain from constant road operation.
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Whitham, Steven A., Amit Gal-On et Tzahi Arazi. Functional analysis of virus and host components that mediate potyvirus-induced diseases. United States Department of Agriculture, mars 2008. http://dx.doi.org/10.32747/2008.7591732.bard.
Texte intégralRésumé :
The mechanisms underlying the development of symptoms in response to virus infection remain to be discovered in plants. Insight into symptoms induced by potyviruses comes from evidence implicating the potyviral HC-Pro protein in symptom development. In particular, recent studies link the development of symptoms in infected plants to HC-Pro's ability to interfere with small RNA metabolism and function in plant hosts. Moreover, mutation of the highly conserved FRNK amino acid motif to FINK in the HC-Pro of Zucchini yellow mosaic virus (ZYMV) converts a severe strain into an asymptomatic strain, but does not affect virus accumulation in cucurbit hosts. The ability of this FINK mutation to uncouple symptoms from virus accumulation creates a unique opportunity to study symptom etiology, which is usually confounded by simultaneous attenuation of both symptoms and virus accumulation. Our goal was to determine how mutations in the conserved FRNK motif affect host responses to potyvirus infection in cucurbits and Arabidopsis thaliana. Our first objective was to define those amino acids in the FRNK motif that are required for symptoms by mutating the FRNK motif in ZYMV and Turnip mosaic virus (TuMV). Symptom expression and accumulation of resulting mutant viruses in cucurbits and Arabidopsis was determined. Our second objective was to identify plant genes associated with virus disease symptoms by profiling gene expression in cucurbits and Arabidopsis in response to mutant and wild type ZYMV and TuMV, respectively. Genes from the two host species that are differentially expressed led us to focus on a subset of genes that are expected to be involved in symptom expression. Our third objective was to determine the functions of small RNA species in response to mutant and wild type HC-Pro protein expression by monitoring the accumulation of small RNAs and their targets in Arabidopsis and cucurbit plants infected with wild type and mutant TuMV and ZYMV, respectively. We have found that the maintenance of the charge of the amino acids in the FRNK motif of HC-Pro is required for symptom expression. Reduced charge (FRNA, FRNL) lessen virus symptoms, and maintain the suppression of RNA silencing. The FRNK motif is involved in binding of small RNA species including microRNAs (miRNA) and short interfering RNAs (siRNA). This binding activity mediated by the FRNK motif has a role in protecting the viral genome from degradation by the host RNA silencing system. However, it also provides a mechanism by which the FRNK motif participates in inducing the symptoms of viral infection. Small RNA species, such as miRNA and siRNA, can regulate the functions of plant genes that affect plant growth and development. Thus, this binding activity suggests a mechanism by which ZYMVHC-Pro can interfere with plant development resulting in disease symptoms. Because the host genes regulated by small RNAs are known, we have identified candidate host genes that are expected to play a role in symptoms when their regulation is disrupted during viral infections. As a result of this work, we have a better understanding of the FRNK amino acid motif of HC-Pro and its contribution to the functions of HC-Pro, and we have identified plant genes that potentially contribute to symptoms of virus infected plants when their expression becomes misregulated during potyviral infections. The results set the stage to establish the roles of specific host genes in viral pathogenicity. The potential benefits include the development of novel strategies for controlling diseases caused by viruses, methods to ensure stable expression of transgenes in genetically improved crops, and improved potyvirus vectors for expression of proteins or peptides in plants.
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Brosh, Arieh, David Robertshaw, Yoav Aharoni, Zvi Holzer, Mario Gutman et Amichai Arieli. Estimation of Energy Expenditure of Free Living and Growing Domesticated Ruminants by Heart Rate Measurement. United States Department of Agriculture, avril 2002. http://dx.doi.org/10.32747/2002.7580685.bard.
Texte intégralRésumé :
Research objectives were: 1) To study the effect of diet energy density, level of exercise, thermal conditions and reproductive state on cardiovascular function as it relates to oxygen (O2) mobilization. 2) To validate the use of heart rate (HR) to predict energy expenditure (EE) of ruminants, by measuring and calculating the energy balance components at different productive and reproductive states. 3) To validate the use of HR to identify changes in the metabolizable energy (ME) and ME intake (MEI) of grazing ruminants. Background: The development of an effective method for the measurement of EE is essential for understanding the management of both grazing and confined feedlot animals. The use of HR as a method of estimating EE in free-ranging large ruminants has been limited by the availability of suitable field monitoring equipment and by the absence of empirical understanding of the relationship between cardiac function and metabolic rate. Recent developments in microelectronics provide a good opportunity to use small HR devices to monitor free-range animals. The estimation of O2 uptake (VO2) of animals from their HR has to be based upon a consistent relationship between HR and VO2. The question as to whether, or to what extent, feeding level, environmental conditions and reproductive state affect such a relationship is still unanswered. Studies on the basic physiology of O2 mobilization (in USA) and field and feedlot-based investigations (in Israel) covered a , variety of conditions in order to investigate the possibilities of using HR to estimate EE. In USA the physiological studies conducted using animals with implanted flow probes, show that: I) although stroke volume decreases during intense exercise, VO2 per one heart beat per kgBW0.75 (O2 Pulse, O2P) actually increases and measurement of EE by HR and constant O2P may underestimate VO2unless the slope of the regression relating to heart rate and VO2 is also determined, 2) alterations in VO2 associated with the level of feeding and the effects of feeding itself have no effect on O2P, 3) both pregnancy and lactation may increase blood volume, especially lactation; but they have no effect on O2P, 4) ambient temperature in the range of 15 to 25°C in the resting animal has no effect on O2P, and 5) severe heat stress, induced by exercise, elevates body temperature to a sufficient extent that 14% of cardiac output may be required to dissipate the heat generated by exercise rather than for O2 transport. However, this is an unusual situation and its affect on EE estimation in a freely grazing animal, especially when heart rate is monitored over several days, is minor. In Israel three experiments were carried out in the hot summer to define changes in O2P attributable to changes in the time of day or In the heat load. The animals used were lambs and young calves in the growing phase and highly yielding dairy cows. In the growing animals the time of day, or the heat load, affected HR and VO2, but had no effect on O2P. On the other hand, the O2P measured in lactating cows was affected by the heat load; this is similar to the finding in the USA study of sheep. Energy balance trials were conducted to compare MEI recovery by the retained energy (RE) and by EE as measured by HR and O2P. The trial hypothesis was that if HR reliably estimated EE, the MEI proportion to (EE+RE) would not be significantly different from 1.0. Beef cows along a year of their reproductive cycle and growing lambs were used. The MEI recoveries of both trials were not significantly different from 1.0, 1.062+0.026 and 0.957+0.024 respectively. The cows' reproductive state did not affect the O2P, which is similar to the finding in the USA study. Pasture ME content and animal variables such as HR, VO2, O2P and EE of cows on grazing and in confinement were measured throughout three years under twenty-nine combinations of herbage quality and cows' reproductive state. In twelve grazing states, individual faecal output (FO) was measured and MEI was calculated. Regression analyses of the EE and RE dependent on MEI were highly significant (P<0.001). The predicted values of EE at zero intake (78 kcal/kgBW0.75), were similar to those estimated by NRC (1984). The EE at maintenance condition of the grazing cows (EE=MEI, 125 kcal/kgBW0.75) which are in the range of 96.1 to 125.5 as presented by NRC (1996 pp 6-7) for beef cows. Average daily HR and EE were significantly increased by lactation, P<0.001 and P<0.02 respectively. Grazing ME significantly increased HR and EE, P<0.001 and P<0.00l respectively. In contradiction to the finding in confined ewes and cows, the O2P of the grazing cows was significantly affected by the combined treatments (P<0.00l ); this effect was significantly related to the diet ME (P<0.00l ) and consequently to the MEI (P<0.03). Grazing significantly increased O2P compared to confinement. So, when EE of grazing animals during a certain season of the year is estimated using the HR method, the O2P must be re measured whenever grazing ME changes. A high correlation (R2>0.96) of group average EE and of HR dependency on MEI was also found in confined cows, which were fed six different diets and in growing lambs on three diets. In conclusion, the studies conducted in USA and in Israel investigated in depth the physiological mechanisms of cardiovascular and O2 mobilization, and went on to investigate a wide variety of ruminant species, ages, reproductive states, diets ME, time of intake and time of day, and compared these variables under grazing and confinement conditions. From these combined studies we can conclude that EE can be determined from HR measurements during several days, multiplied by O2P measured over a short period of time (10-15 min). The study showed that RE could be determined during the growing phase without slaughtering. In the near future the development microelectronic devices will enable wide use of the HR method to determine EE and energy balance. It will open new scopes of physiological and agricultural research with minimizes strain on animals. The method also has a high potential as a tool for herd management.