Letteratura scientifica selezionata sul tema "Gac/Rsm pathway"
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Articoli di riviste sul tema "Gac/Rsm pathway"
1
Takeuchi, Kasumi, Kosumi Yamada e Dieter Haas. "ppGpp Controlled by the Gac/Rsm Regulatory Pathway Sustains Biocontrol Activity in Pseudomonas fluorescens CHA0". Molecular Plant-Microbe Interactions® 25, n. 11 (novembre 2012): 1440–49. http://dx.doi.org/10.1094/mpmi-02-12-0034-r.
Testo completoAbstract (sommario):
In Pseudomonas fluorescens CHA0 and other fluorescent pseudomonads, the Gac/Rsm signal transduction pathway is instrumental for secondary metabolism and biocontrol of root pathogens via the expression of regulatory small RNAs (sRNAs). Furthermore, in strain CHA0, an imbalance in the Krebs cycle can affect the strain's ability to produce extracellular secondary metabolites, including biocontrol factors. Here, we report the metabolome of wild-type CHA0, a gacA-negative mutant, which has lost Gac/Rsm activities, and a retS-negative mutant, which shows strongly enhanced Gac/Rsm-dependent activities. Capillary electrophoresis-based metabolomic profiling revealed that the gacA and retS mutations had opposite effects on the intracellular levels of a number of central metabolites, suggesting that the Gac/Rsm pathway regulates not only secondary metabolism but also primary metabolism in strain CHA0. Among the regulated metabolites identified, the alarmone guanosine tetraphosphate (ppGpp) was characterized in detail by the construction of relA (for ppGpp synthase) and spoT (for ppGpp synthase/hydrolase) deletion mutants. In a relA spoT double mutant, ppGpp synthesis was completely abolished, the expression of Rsm sRNAs was attenuated, and physiological functions such as antibiotic production, root colonization, and plant protection were markedly diminished. Thus, ppGpp appears to be essential for sustaining epiphytic fitness and biocontrol activity of strain CHA0.
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Takeuchi, Kasumi. "GABA, A Primary Metabolite Controlled by the Gac/Rsm Regulatory Pathway, Favors a Planktonic Over a Biofilm Lifestyle in Pseudomonas protegens CHA0". Molecular Plant-Microbe Interactions® 31, n. 2 (febbraio 2018): 274–82. http://dx.doi.org/10.1094/mpmi-05-17-0120-r.
Testo completoAbstract (sommario):
In Pseudomonas protegens CHA0 and other fluorescent pseudomonads, the Gac/Rsm signal transduction pathway is crucial for the expression of secondary metabolism and the biological control of fungi, nematodes, and insects. Based on the findings of a previous metabolomic study, the role of intracellular γ-aminobutyrate (GABA) as a potential signal in the Gac/Rsm pathway was investigated herein. The function and regulation of a gabDT (c01870-c01880) gene cluster in strain CHA0 were described. The gabT gene encoded GABA transaminase (GABAT) and enabled the growth of the bacterium on GABA, whereas the upstream gabD gene (annotated as a gene encoding succinic semialdehyde dehydrogenase) had an unknown function. A gacA mutant exhibited low GABAT activity, leading to the markedly greater intracellular accumulation of GABA than in the wild type. In the gacA mutant, the RsmA and RsmE proteins caused translational gabD repression, with concomitant gabT repression. Due to very low GABAT activity, the gabT mutant accumulated GABA to high levels. This trait promoted a planktonic lifestyle, reduced biofilm formation, and favored root colonization without exhibiting the highly pleiotropic gacA phenotypes. These results suggest an important role of GABA in the Gac/Rsm-regulated niche adaptation of strain CHA0 to plant roots.
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Panijel, Mary, Laura Chalupowicz, Guido Sessa, Shulamit Manulis-Sasson e Isaac Barash. "Global Regulatory Networks Control the Hrp Regulon of the Gall-Forming Bacterium Pantoea agglomerans pv. gypsophilae". Molecular Plant-Microbe Interactions® 26, n. 9 (settembre 2013): 1031–43. http://dx.doi.org/10.1094/mpmi-04-13-0097-r.
Testo completoAbstract (sommario):
Gall formation by Pantoea agglomerans pv. gypsophilae is dependent on the hypersensitive response and pathogenicity (hrp) system. Previous studies demonstrated that PagR and PagI, regulators of the quorum-sensing system, induce expression of the hrp regulatory cascade (i.e., hrpXY, hrpS, and hrpL) that activates the HrpL regulon. Here, we isolated the genes of the Gac/Rsm global regulatory pathway (i.e., gacS, gacA, rsmB, and csrD) and of the post-transcriptional regulator rsmA. Our results demonstrate that PagR and PagI also upregulate expression of the Gac/Rsm pathway. PagR acts as a transcriptional activator of each of the hrp regulatory genes and gacA in a N-butanoyl-L-homoserine lactone-dependent manner as shown by gel shift experiments. Mutants of the Gac/Rsm genes or overexpression of rsmA significantly reduced Pantoea agglomerans virulence and colonization of gypsophila. Overexpression of rsmB sRNA abolished gall formation, colonization, and hypersensitive reaction on nonhost plants and prevented transcription of the hrp regulatory cascade, indicating a lack of functional type III secretion system. Expression of rsmB sRNA in the background of the csrD null mutant suggests that CsrD may act as a safeguard for preventing excessive production of rsmB sRNA. Results presented indicate that the hrp regulatory cascade is controlled directly by PagR and indirectly by RsmA, whereas deficiency in RsmA activity is epistatic to PagR induction.
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Zha, Daiming, Li Xu, Houjin Zhang e Yunjun Yan. "The Two-Component GacS-GacA System ActivateslipATranslation by RsmE but Not RsmA in Pseudomonas protegens Pf-5". Applied and Environmental Microbiology 80, n. 21 (15 agosto 2014): 6627–37. http://dx.doi.org/10.1128/aem.02184-14.
Testo completoAbstract (sommario):
ABSTRACTInPseudomonasspp., the Gac-Rsm signal transduction system is required for the production of lipases. The current model assumes that the system induces lipase gene transcription mediated through the quorum-sensing (QS) system. However, there are no reports of a QS system based uponN-acyl homoserine lactones or the regulation of lipase gene expression inPseudomonas protegens. In this study, we investigated the regulatory mechanism acting onlipAexpression activated by the Gac-Rsm system inP. protegensPf-5 through deletion and overexpression ofgacA, overexpression ofrsmAorrsmE, expression of variouslacZfusions, reverse transcription-PCR analysis, and determination of whole-cell lipase activity. The results demonstrated that the GacS-GacA (GacS/A) system activateslipAexpression at both the transcriptional and the translational levels but that the translational level is the key regulatory pathway. Further results showed that the activation oflipAtranslation by the GacS/A system is mediated through RsmE, which inhibitslipAtranslation by binding to the ACAAGGAUGU sequence overlapping the Shine-Dalgarno (SD) sequence oflipAmRNA to hinder the access of the 30S ribosomal subunit to the SD sequence. Moreover, the GacS/A system promoteslipAtranscription through the mediation of RsmA inhibitinglipAtranscription via an unknown pathway. Besides the transcriptional repression, RsmA mainly activateslipAtranslation by negatively regulatingrsmEtranslation. In summary, inP. protegensPf-5, the Gac-RsmE system mainly and directly activateslipAtranslation and the Gac-RsmA system indirectly enhanceslipAtranscription.
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Lin, Qiqi, Jiahui Huang, Zhiqing Liu, Qunyi Chen, Xinbo Wang, Guohui Yu, Ping Cheng, Lian-Hui Zhang e Zeling Xu. "tRNA modification enzyme MiaB connects environmental cues to activation of Pseudomonas aeruginosa type III secretion system". PLOS Pathogens 18, n. 12 (5 dicembre 2022): e1011027. http://dx.doi.org/10.1371/journal.ppat.1011027.
Testo completoAbstract (sommario):
Pseudomonas aeruginosa, a major inhabitant of numerous environmental reservoirs, is a momentous opportunistic human pathogen associated with severe infections even death in the patients suffering from immune deficiencies or metabolic diseases. Type III secretion system (T3SS) employed by P. aeruginosa to inject effector proteins into host cells is one of the pivotal virulence factors pertaining to acute infections caused by this pathogen. Previous studies showed that P. aeruginosa T3SS is activated by various environmental cues such as calcium concentration and the host signal spermidine. However, how T3SS is regulated and expressed particularly under the ever-changing environmental conditions remains largely elusive. In this study, we reported that a tRNA modification enzyme PA3980, designated as MiaB, positively regulated T3SS gene expression in P. aeruginosa and was essential for the induced cytotoxicity of human lung epithelial cells. Further genetic assays revealed that MiaB promoted T3SS gene expression by repressing the LadS-Gac/Rsm signaling pathway and through the T3SS master regulator ExsA. Interestingly, ladS, gacA, rsmY and rsmZ in the LadS-Gac/Rsm signaling pathway seemed potential targets under the independent regulation of MiaB. Moreover, expression of MiaB was found to be induced by the cAMP-dependent global regulator Vfr as well as the spermidine transporter-dependent signaling pathway and thereafter functioned to mediate their regulation on the T3SS gene expression. Together, these results revealed a novel regulatory mechanism for MiaB, with which it integrates different environmental cues to modulate T3SS gene expression in this important bacterial pathogen.
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Anderson, Anne J., Beom Ryong Kang e Young Cheol Kim. "The Gac/Rsm Signaling Pathway of a Biocontrol Bacterium, Pseudomonas chlororaphis O6". Research in Plant Disease 23, n. 3 (30 settembre 2017): 212–27. http://dx.doi.org/10.5423/rpd.2017.23.3.212.
Testo completo
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Valverde, Claudio. "Artificial sRNAs activating the Gac/Rsm signal transduction pathway in Pseudomonas fluorescens". Archives of Microbiology 191, n. 4 (13 febbraio 2009): 349–59. http://dx.doi.org/10.1007/s00203-009-0459-x.
Testo completo
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Zhang, Wei, Zhao Zhao, Bo Zhang, Xiao-Gang Wu, Zheng-Guang Ren e Li-Qun Zhang. "Posttranscriptional Regulation of 2,4-Diacetylphloroglucinol Production by GidA and TrmE in Pseudomonas fluorescens 2P24". Applied and Environmental Microbiology 80, n. 13 (18 aprile 2014): 3972–81. http://dx.doi.org/10.1128/aem.00455-14.
Testo completoAbstract (sommario):
ABSTRACTPseudomonas fluorescens2P24 is a soilborne bacterium that synthesizes and excretes multiple antimicrobial metabolites. The polyketide compound 2,4-diacetylphloroglucinol (2,4-DAPG), synthesized by thephlACBDlocus, is its major biocontrol determinant. This study investigated two mutants defective in antagonistic activity againstRhizoctonia solani. Deletion of thegidA(PM701) ortrmE(PM702) gene from strain 2P24 completely inhibited the production of 2,4-DAPG and its precursors, monoacetylphloroglucinol (MAPG) and phloroglucinol (PG). The transcription of thephlAgene was not affected, but the translation of thephlAandphlDgenes was reduced significantly. Two components of the Gac/Rsm pathway, RsmA and RsmE, were found to be regulated bygidAandtrmE, whereas the other components, RsmX, RsmY, and RsmZ, were not. The regulation of 2,4-DAPG production bygidAandtrmE, however, was independent of the Gac/Rsm pathway. Both thegidAandtrmEmutants were unable to produce PG but could convert PG to MAPG and MAPG to 2,4-DAPG. Overexpression of PhlD in thegidAandtrmEmutants could restore the production of PG and 2,4-DAPG. Taken together, these findings suggest that GidA and TrmE are positive regulatory elements that influence the biosynthesis of 2,4-DAPG posttranscriptionally.
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Latour, Xavier. "The Evanescent GacS Signal". Microorganisms 8, n. 11 (6 novembre 2020): 1746. http://dx.doi.org/10.3390/microorganisms8111746.
Testo completoAbstract (sommario):
The GacS histidine kinase is the membrane sensor of the major upstream two-component system of the regulatory Gac/Rsm signal transduction pathway. This pathway governs the expression of a wide range of genes in pseudomonads and controls bacterial fitness and motility, tolerance to stress, biofilm formation, and virulence or plant protection. Despite the importance of these roles, the ligands binding to the sensor domain of GacS remain unknown, and their identification is an exciting challenge in this domain. At high population densities, the GacS signal triggers a switch from primary to secondary metabolism and a change in bacterial lifestyle. It has been suggested, based on these observations, that the GacS signal is a marker of the emergence of nutritional stress and competition. Biochemical investigations have yet to characterize the GacS signal fully. However, they portray this cue as a low-molecular weight, relatively simple and moderately apolar metabolite possibly resembling, but nevertheless different, from the aliphatic organic acids acting as quorum-sensing signaling molecules in other Proteobacteria. Significant progress in the development of metabolomic tools and new databases dedicated to Pseudomonas metabolism should help to unlock some of the last remaining secrets of GacS induction, making it possible to control the Gac/Rsm pathway.
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TAKEUCHI, K. "Turning the Gac/Rsm signal transduction pathway on and off in plant protecting bacteria." Japanese Journal of Phytopathology 81, n. 2 (2015): 105–10. http://dx.doi.org/10.3186/jjphytopath.81.105.
Testo completoTesi sul tema "Gac/Rsm pathway"
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Dupont, Charly. "Caractérisatiοn mοléculaire des mécanismes de cοmmunicatiοn aérienne chez la sοuche Ρseudοmοnas fluοrescens ΜFE01". Electronic Thesis or Diss., Normandie, 2024. http://www.theses.fr/2024NORMR021.
Testo completoAbstract (sommario):
Les composés organiques volatils (COV), sous-produits du métabolisme émis par l’ensemble desorganismes vivants, sont volatils en conditions environnementales en raison de leurs propriétés physicochimiques.Chez les bactéries, et notamment celles du genre Pseudomonas, les COV sontprincipalement étudiés pour leur capacité à inhiber des microorganismes phytopathogènes. Leur rôledans la communication, un mécanisme indispensable à la coordination des communautés bactérienneslors de la formation de biofilm, est rarement considéré.L'objectif des travaux menés est l'analyse les COVs produits par la souche Pseudomonas fluorescensMFE01 et leur impact sur sa communication. Les voies de communication de MFE01 sont peu connueset ne correspondent pas aux systèmes déjà décrits chez de nombreuses bactéries du genrePseudomonas. La caractérisation du bouquet de molécules émises par MFE01 met en évidence uneforte émission de 1-undécène. Un mutant du gène undA, codant l’enzyme de synthèse du 1-undécène,n’émet plus ce COV et a une capacité réduite à former des biofilms. L’exposition de ce mutant à du 1-undécène exogène restaure la formation de biofilm. Le 1-undécène serait donc une molécule decommunication intraspécifique chez P. fluorescens MFE01. Le gène undA semble être en opéron avecle gène rbdA, codant un senseur putatif. Nous formulons l’hypothèse que Rbda serait impliqué dans laperception du 1-undécène et que la transduction du signal s’effectuerait via la synthèse de di-guanosinemonophosphate cyclique, un messager secondaire connu pour induire la formation de biofilm.L’étude de la voie de régulation Gac/Rsm, connue pour gouverner le métabolisme et la communicationdes Pseudomonas, montre qu’elle module fortement la quantité et le profil de COV émis par MFE01.Cette voie pilote chez MFE01 l’émission de 1-undécène et l’inhibition aérienne du pathogène humainLegionella pneumophila ainsi que celle du phytopathogène Phytophtora infestans. L’expression du gènegacS, codant le senseur principal de la voie Gac/Rsm, serait activée par au moins un COV,potentiellement le 2-tridecanone et/ou le 2-undecanoneVolatile organic compounds (VOCs), by-products of metabolism emitted by all living organisms, arevolatile under environmental conditions due to their physicochemical properties. In bacteria, especiallythose of the genus Pseudomonas, VOCs are mainly studied for their ability to inhibit phytopathogenicmicroorganisms. Their role in communication, which is a crucial mechanism for coordinating bacterialcommunities during biofilm formation, is understudied.This research focuses on investigating VOCs emitted by the Pseudomonas fluorescens MFE01 strainand their implications in its communication. The uncharacterized communications pathways of MFE01are untypical and does not involve pathways already described in others Pseudomonas.Characterization of molecules the emitted by MFE01 reveals a huge emission of 1-undecene. A mutantlacking the undA gene, responsible for 1-undecene synthesis, no longer emits this VOC and exhibitsreduced biofilm formation capabilities. Exposure of this mutant to exogenous 1-undecene restoresbiofilm formation, Therefore, 1-undecene seems to be an intraspecific communication molecule in P.fluorescens MFE01. The undA gene seems to be in an operon with the rbdA gene, encoding a putativesensor. We hypothesize that Rbda is involved in 1-undecene perception with signal transduction likelyoccurring via the synthesis of cyclic di-guanosine monophosphate, a known secondary messenger thatinduces biofilm formation.Additionally, the study of the Gac/Rsm regulatory pathway, a critical regulator of metabolism andcommunication in Pseudomonas, demonstrates that it strongly modulates the quantity and profile ofVOCs emitted by MFE01. This pathway governs 1-undecene emission and the aerial inhibition of humanpathogen Legionella pneumophila and phytopathogen Phytophtora infestans by MFE01. At least oneVOC, possibly 2-tridecanone and/or 2-undecanone, may activate the expression of the gacS gene,which encodes the principal sensor of the Gac/Rsm pathway
Atti di convegni sul tema "Gac/Rsm pathway"
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Bayliff, Scott, Bret Windom, Anthony Marchese, Greg Hampson, Jeffrey Carlson, Domenico Chiera e Daniel Olsen. "Controlled End Gas Auto Ignition With Exhaust Gas Recirculation on a Stoichiometric, Spark Ignited, Natural Gas Engine". In ASME 2020 Internal Combustion Engine Division Fall Technical Conference. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/icef2020-2979.
Testo completoAbstract (sommario):
Abstract The goal of this study is to address fundamental limitations to achieving diesel-like efficiencies in heavy duty on-highway natural gas (NG) engines. Engine knock and misfire are barriers to pathways leading to higher efficiency engines. This study explores enabling technologies for development of high efficiency stoichiometric, spark ignited, natural gas engines. These include design strategies for fast and stable combustion and higher dilution tolerance. Additionally, advanced control methodologies are implemented to maintain stable operation between knock and misfire limits. To implement controlled end-gas autoignition (C-EGAI) strategies a Combustion Intensity Metric (CIM) is used for ignition control with the use of a Woodward large engine control module (LECM). Tests were conducted using a single cylinder, variable compression ratio, cooperative fuel research (CFR) engine with baseline conditions of 900 RPM, engine load of 800 kPa indicated mean effective pressure (IMEP), and stoichiometric air/fuel ratio. Exhaust gas recirculation (EGR) tests were performed using a custom EGR system that simulates a high pressure EGR loop and can provide a range of EGR rates from 0 to 40%. The experimental measurements included the variance of EGR rate, compression ratio, engine speed, IMEP, and CIM. These five variables were optimized through a Modified BoxBenken design Surface Response Method (RSM), with brake efficiency as the merit function. A positive linear correlation between CIM and f-EGAI was identified. Consequently, CIM was used as the feedback control parameter for C-EGAI. As such, implementation of C-EGAI effectively allowed for the utilization of high EGR rates and CRs, controlling combustion between a narrower gap between knock and lean limits. The change from fixed to parametric ignition timing with CIM targeted select values of f-EGAI with an average coefficient of variance (COV) of peak pressure of 5.4. The RSM efficiency optimization concluded with operational conditions of 1080 RPM, 1150 kPa IMEP, 10.55:1 compression ratio, and 17.8% EGR rate with a brake efficiency of 21.3%. At this optimized point of peak performance, a f-EGAI for C-EGAI was observed at 34.1% heat release due to auto ignition, a knock onset crank angle value of 10.3° aTDC and ignition timing of −24.7° aTDC. This work has demonstrated that combustion at a fixed f-EGAI can be maintained through advanced ignition control of CIM without experiencing heavy knocking events.
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Patinios, Marios, Irvin L. Ong, James A. Scobie, Gary D. Lock e Carl M. Sangan. "Influence of Leakage Flows on Hot Gas Ingress". In ASME Turbo Expo 2018: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/gt2018-75071.
Testo completoAbstract (sommario):
One of the most important problems facing gas turbine designers today is the ingestion of hot mainstream gases into the wheel-space between the turbine disc (rotor) and its adjacent casing (stator). A rim seal is fitted at the periphery and a superposed sealant flow — typically fed through the bore of the stator — is used to prevent ingress. The majority of research studies investigating ingress do so in the absence of any leakage paths that exist throughout the engine’s architecture. These inevitable pathways are found between the mating interfaces of adjacent pieces of hardware. In an environment where the turbine is subjected to aggressive thermal and centrifugal loading these interface gaps can be difficult to predict and the resulting leakage flows which pass through them even harder to account for. This paper describes experimental results from a research facility which experimentally models hot gas ingestion into the wheel-space of an axial turbine stage. The facility was specifically designed to incorporate leakage flows through the stator disc; leakage flows were introduced axially through the stator shroud or directly underneath the vane carrier ring. Measurements of CO2 gas concentration, static pressure and total pressure were used to examine the wheel-space flow structure with and without ingress from the mainstream gas-path. Data is presented for a simple axial-clearance rim-seal. The results support two distinct flow-structures, which are shown to be dependent on the mass-flow ratio of bore and leakage flows. Once the leakage flow was increased above a certain threshold, the flow structure is shown to transition from a classical Batchelor-type rotor-stator system to a vortex-dominated structure. The existence of a toroidal vortex immediately inboard of the outer rim-seal is shown to encourage ingestion.
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Darby, P. W., A. W. Mesny, G. De Cosmo, M. Carnevale, G. D. Lock, J. A. Scobie e C. M. Sangan. "Conditioning of Leakage Flows in Gas Turbine Rotor-Stator Cavities". In ASME Turbo Expo 2020: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/gt2020-14308.
Testo completoAbstract (sommario):
Abstract Ingress is the penetration of hot mainstream fluid into the cavity formed between the turbine disc (rotor) and its adjacent casing (stator). Gas turbine engine designers use rim seals fitted at the periphery of the discs and a superposed sealant flow — typically fed through the bore of the stator — is used to reduce, or in the limit prevent, ingress. Parasitic leakage enters the cavity through pathways created between mating interfaces of engine components. Owing to the aggressive thermal and centrifugal loading experienced during the turbine operating cycle, the degree of leakage and its effect on ingress are difficult to predict. This paper considers the potential for leakage flows to be conditioned in order to minimise their parasitic effect on disc cooling, and ultimately engine, performance. Measurements of static and total pressure, swirl and species concentration were used to assess the performance of a simple axial clearance rim-seal over a range of non-dimensional leakage flow-rates. A computational model was used to provide flow visualisation to support the interpretation of flow structures derived from the experiments. Data is presented to investigate the effects of swirling the leakage flow in accordance with, and counter to, the disc rotation. The injected momentum from the leakage created a toroidal vortex in the outer part of the cavity. Co-swirl was found to improve the sealing effectiveness by up to 15% compared to the axially-introduced baseline and counter-swirled configurations. Varying the momentum of the leakage flow was considered by passing consistent mass-flows through a range of leakage outlet areas. Increasing the momentum was seen to increase the influence of the toroidal vortex on the flow structure in the cavity, which in turn influenced the sealing effectiveness.
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Iyengar, Arun K. S., Brian J. Koeppel, Dale L. Keairns, Mark C. Woods, Gregory A. Hackett e Travis R. Shultz. "Performance of a Natural Gas Solid Oxide Fuel Cell System With and Without Carbon Capture". In ASME 2019 13th International Conference on Energy Sustainability collocated with the ASME 2019 Heat Transfer Summer Conference. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/es2019-3918.
Testo completoAbstract (sommario):
Abstract The fuel cell program at the United States Department of Energy (DOE) National Energy Technology Laboratory (NETL) is focused on the development of low-cost, highly efficient, and reliable fossil-fuel-based solid oxide fuel cell (SOFC) power systems that can generate environmentally-friendly electric power with at least 90 percent carbon capture. NETL’s SOFC technology development roadmap is aligned with near-term market opportunities in the distributed generation sector to validate and advance the technology while paving the way for utility-scale natural gas (NG)- and coal-derived synthesis gas-fueled applications via progressively larger system demonstrations. The present study represents a part of a series of system evaluations being carried out at NETL to aid in prioritizing technological advances along research pathways to the realization of utility-scale SOFC systems, a transformational goal of the fuel cell program. In particular, the system performance of utility-scale NG fuel cell (NGFC) systems with and without carbon dioxide (CO2) capture is presented. The NGFC system analyzed features an external auto-thermal reformer (ATR) feeding the fuel to the SOFC system consisting of planar anode-supported SOFC with separated anode and cathode off-gas streams. In systems with CO2 capture, an air separation unit (ASU) is used to provide the oxygen for the ATR and for the combustion of unutilized fuel in the SOFC anode exhaust along with a CO2 purification unit to provide a nearly pure CO2 stream suitable for transport for usage in enhanced oil recovery operations or for storage in underground saline formations. Remaining thermal energy in the exhaust gases is recovered in a bottoming steam Rankine cycle while supplying any process heat requirements. A reduced order model (ROM) developed at the Pacific Northwest National Laboratory (PNNL) is used to predict the SOFC performance. The ROM, while being computationally effective for system studies, provides other detailed information about the state of the stack, such as the internal temperature gradient, generally not available from simple performance models often used to represent the SOFC. Such additional information can be important in system optimization studies to preclude operation under off-design conditions that can adversely impact overall system reliability. The NGFC system performance was analyzed by varying salient system parameters, including the percent of internal (to the SOFC module) NG reformation — ranging from 0 to 100 percent — fuel utilization, and current density. The impact of advances in underlying SOFC technology on electrical performance was also explored.
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Kavuri, Chaitanya, e Sage L. Kokjohn. "Computational Study to Identify Feasible Operating Space for a Mixed Mode Combustion Strategy: A Pathway for PCI High Load Operation". In ASME 2017 Internal Combustion Engine Division Fall Technical Conference. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/icef2017-3668.
Testo completoAbstract (sommario):
Mixed mode combustion strategies have shown great potential to achieve high load operation but soot emissions were found to be problematic. A recent study investigating soot emissions in such strategies showed that delaying the load extension injection sufficiently late after the primary heat release makes the soot production dependent solely on the temperature field inside the combustion chamber and eliminates any dependence on mixing time and oxygen availability. The current study focuses on furthering this research to identify a feasible operating space to operate in and enable high load operation with this mixed mode combustion strategy. A PCI combustion event was achieved using a premixed charge of gasoline (early cycle injection) and a load extension injection of gasoline was added near top dead center. CFD modeling considering polycyclic aromatic hydrocarbon (PAH) chemistry up to pyrene was used to perform a full factorial design of experiments (DOE) to study the effects of premixed fuel fraction (fraction of total fuel that is premixed), load extension injection timing and exhaust gas recirculation (EGR). The early injection timings for EGR rates less than 40% showed a soot-NOx tradeoff which constrained operating with SOI timings before TDC. The late injection timings showed reductions in soot and NOx at the expense of gross indicated efficiency (GIE). GIE increased with increasing premixed fuel until the premixed fuel quantity reached 80% of the total fuel mass. Premixed fuel quantities higher than 80% resulted in an efficiency penalty due to increased wall heat transfer losses resulting from early combustion phasing. However, at premixed fuel quantities close to 80%, the peak pressure rise rate became the dominating constraint. This confined the feasible operating space to a premix fuel mass range of 70% to 80%. For this premix fuel mass range, the feasible operating space had two regions; one in the early SOI regime before TDC at EGR rates higher than 38% and the other in the late SOI regime (SOI > 15° ATDC) across the entire EGR space. The study was repeated by splitting the premixed fuel into an early cycle injection and a stratified injection with SOI timing of −70° ATDC. The ratio of fuel in the two injections was varied in the DOE. The results showed that adding a stratified injection increases the ignition delay due to in-cylinder equivalence ratio stratification and relaxes the pressure rise rate effect on the operating space. This allows operation at high premix fuel quantities of 70% and higher with EGR rates less than 40% which yields significant increase in GIE. It was also identified that by targeting the fuel from the stratified injection into the squish region, there is improved oxygen availability in the bowl for the load extension injection, which results in the reduction of soot emissions. This allows the load extension injection to be brought closer to TDC while meeting the soot constraint, which further improves the GIE. Finally, the results from the study were used to demonstrate high load operation at 20 bar and 1300 rpm.
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Bae, R., S. Basu, P. R. Gallego e L. Lucas. "Water Sourcing Reliability, Cost, and Circularity for Low Carbon Hydrogen Development". In SPE Energy Transition Symposium. SPE, 2024. http://dx.doi.org/10.2118/221394-ms.
Testo completoAbstract (sommario):
Abstract Clean hydrogen will require significant volumes of water given the high production targets in certain geographic locations, regardless of generation pathway, i.e., from an electrolyzer or natural gas-based process with carbon capture and sequestration (CCS). Therefore, reliable water sourcing related to the planned infrastructure's location is a critical input that needs to be considered in the early project planning stages. This paper will review the potential sources of water and costs associated with incorporating them within the hydrogen supply chain and will explore the respective attributes of alternatives. Water demand will vary between different hydrogen production methods, site locations, and project specific facility designs. Furthermore, the cost of water will vary as well depending on the source water's respective quality, facilities, water conveyance, treatment, and waste disposal requirements. For the energy industry, water for hydrogen production has become as important as natural gas for its processes and as important as crude oil has been for its refineries. Project viability depends on the long-term reliable access to the selected water source, forcing project siting to be a critical project consideration. Additionally, water treatment processes vary according to the source's base purity and contaminants. Subsequently, these processes create waste streams with concentrated impurities, which may have to be mitigated prior to disposal. We will provide the readers with awareness of the issues related to water sourcing options and considerations, conveyance, and rough order of magnitude (ROM) costs for water infrastructure, including treatment. The clarification of costs associated with different water sources used for hydrogen generation will allow project developers to make more informed decisions. Water sourcing should be a topic at the forefront of planning stages related to hydrogen production. The authors for this paper wish to provide a better understanding of costs related to different options. Additionally, the implementation of circularity will be analyzed by considering recycled wastewater as the water source for a hydrogen plant. This could reduce the regional disparity in clean energy production and lessen the burden on fresh water supplies.
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Purushothaman, Ashwin Karthik, Youngchul Ra, Kyoung Pyo Ha, Shengrong Zhu e Ankith Ullal. "Numerical Study of a Six-Stroke Gasoline Compression Ignition (6S-GCI) Engine Combustion with Oxygenated Fuels". In WCX SAE World Congress Experience. 400 Commonwealth Drive, Warrendale, PA, United States: SAE International, 2024. http://dx.doi.org/10.4271/2024-01-2373.
Testo completoAbstract (sommario):
<div class="section abstract"><div class="htmlview paragraph">A numerical investigation of a six-stroke direct injection compression ignition engine operation in a low temperature combustion (LTC) regime is presented. The fuel employed is a gasoline-like oxygenated fuel consisting of 90% isobutanol and 10% diethyl ether (DEE) by volume to match the reactivity of conventional gasoline with octane number 87. The computational simulations of the in-cylinder processes were performed using a high-fidelity multidimensional in-house 3D CFD code (MTU-MRNT) with improved spray-sub models and CHEMKIN library. The combustion chemistry was described using a two-component (isobutanol and DEE) fuel model whose oxidation pathways were given by a reaction mechanism with 177 species and 796 reactions.</div><div class="htmlview paragraph">The key advantage of six-stroke engine operation is the ability to switch the combustion mode among kinetical controlled mode (KCM), kinetically-driven mixing control mode (K-MCM) and mixing controlled mode (MCM) in the second power stroke (PS2) providing a wider range of combustion control. The K-MCM mode operation has shown to reduce both soot and NOx emissions substantially at low load (around 7bar IMEP) engine operations. The current work focuses on 6S-GCI engine operation using synthetic fuels at high load engine operation with the constraints on pressure rise rate (<10bar/deg), combustion efficiency (>90%), soot and NOx emissions (<1g/kg fuel). With the constraints met, engine operating conditions at 15 bar IMEP and 2000 rpm were identified as a function of fuel split ratio and injection timings. Parametric study was also performed by varying fuel injection pressure, initial gas temperature at IVC, boost pressure and exhaust gas recirculation ratio. Engine performance and emissions characteristics of parametric variation are presented as well.</div></div>
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Aniemena, Chigozie, Thomas Hailu, Allen LaBryer, Kirke Suter e Nathan Churchwell. "Volumetric Fracture Stage Spacing Optimization in Shale Reservoirs Using Rate Transient Analytics – Haynesville, Eagle Ford and Permian Applications". In SPE Hydraulic Fracturing Technology Conference and Exhibition. SPE, 2024. http://dx.doi.org/10.2118/217823-ms.
Testo completoAbstract (sommario):
Abstract This paper addresses the problem of volumetric fracture stage spacing optimization using multi-well rate transient analytics with explicit semi-analytical consideration of stress shadows. A permeability contrast description of the stimulated reservoir volume (SRV) is presented and supported by dual porosity reservoir simulation and RNP diagnostic of late life Haynesville shale production data. The k-contrast drainage volume is characterized by a depth of stimulation Xd adjacent to the hydraulic fracture face in which effective permeability is significantly enhanced relative to unstimulated matrix permeability A key implication of k-contrast SRV in shales is that significant hydrocarbon volumes may remain unrecovered under initial reservoir pressure even in depleted late life wells due to sub optimal fracture stage spacing. Reduced order models (ROM) enable deconvolution of the k-contrast SRV to quantify the effect of stress shadows in terms of fracture stage efficiency. The process also enables estimation of effective stage spacing and effective permeability in the stimulated zone. In the process of ROM parameter estimation, the Boussinesq solution for deformation and stress distribution in a linear elastic half space under load is used to estimate the critical stage length at which stress shadow effect is negligible. SRV deconvolution results enable generation of spacing performance curves for well specific performance sensitivity studies across variations of stage lengths and stress shadow severity. Results from workflow deployment in Permian, Eagle Ford and Haynesville shale plays indicate that wells across all vintages are predominantly in volumetrically suboptimal states. Fracture stage efficiency in company operated Permian, Eagle Ford and Haynesville, is estimated at ~40% at 200 ft stage spacing. The implication is that at 200 ft, the effective stage spacing in the stimulated reservoir volume is more than twice the designed stage spacing at the surface leaving significant hydrocarbon volumes stranded by stress shadows. Spacing performance curves indicate that tighter stage present recovery upside, however, stress shadows significantly dampen performance scaling thereby increasing the economic burden of achieving volumetrically optimized fracture stage spacing. In Eagle Ford dry (gas window) stage tightening from 250 ft to 150 ft is estimated to yield an EUR uplift of ~26%. Without stress shadow effects, EUR uplift is estimated at ~190%. The workflow is extended to perforation cluster level analysis and reveals a maximum cluster efficiency of 10-13% in Eagle Ford and Haynesville and 25% in Permian. Therefore, in this work, tighter stage spacing, and lower perforation density is considered the preferred well performance optimization pathway in line with the findings of a joint industry surveillance project (Hydraulic Fracture Test Site 1- Phase 3). Multi-Pass completions and responsive refracs are proposed to mitigate or compensate for drainage limitations from stress shadows towards transformational uplift in shale well performance.
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Satheesh, P. V., D. Shirole e S. Sinha. "Investigation of the Effect of Confinement on Intact Wombeyan Marble Using Continuum Grain-Based Model (CGBM)". In 58th U.S. Rock Mechanics/Geomechanics Symposium. ARMA, 2024. http://dx.doi.org/10.56952/arma-2024-0310.
Testo completoAbstract (sommario):
ABSTRACT: The progressive failure of brittle rock under compression involves micro-crack initiation, accumulation, and propagation. With advances in numerical modeling, it is now possible to examine complex micro-mechanical processes (e.g., strain heterogeneity, force chains, micro-level damage processes) evolving in the rocks that are difficult to investigate under conventional laboratory settings. While several studies have investigated the micromechanical aspects of brittle rock damage processes under unconfined and confined conditions in discontinuum, understanding them in a continuum media remains limited. Accordingly, this study utilizes the CGBM (representing rock volume as aggregates of polygonal blocks separated by joint elements) technique to simulate the brittle rock failure process of intact Wombeyan marble under varying confinement levels, building upon previous work by Li and Bahrani (2021) in RS2. Specifically, micro-parameters of the intact Wombeyan marble were modified to capture the experimentally informed stress-strain behaviour, and the evolution of damage-induced non-linearity in such curves. The numerical results demonstrate CGBM's ability to capture critical characteristics of brittle rocks, including non-linear strength envelope and change in the failure modes with increasing confinement. Additional investigation on the influence of joint normal stiffness and tensile strength parameters on the simulated micromechanics was completed through strain-field heterogeneity and volumetric strain analysis. A complete understanding of the parametric influences is necessary for accurately predicting rock mechanical response and failure mechanisms, and for improving the capabilities of such models. 1. INTRODUCTION The heterogeneous nature of the intact rock at the grain-scale governs its emergent macroscopic behavior (Hazzard and Young, 2000; Mahabadi et al., 2012; Potyondy et al., 1996). Grain size, grain boundaries, grain shape, mineral constituents, and micro-flaws present in the rock microstructure introduce stress heterogeneity in rock, which primarily drives rock damage and deformation processes (Fabjan et al., 2015; Lan et al., 2010; Potyondy, 2010; Shirole et al., 2020; Sinha and Walton, 2020; Wang and Cai, 2019). However, investigations that can illuminate such complex processes (i.e., heterogeneity, damage, inelasticity, etc.) evolving at the grain-scales, in general, are difficult to conduct via conventional laboratory-based experimental measures (Shirole et al., 2019, 2020, 2019b). To this end, numerical models that allow the explicit representation of rock microstructure as an assembly of discrete particles or blocks (Discrete Element Methods (DEMs)) have been found to be advantageous (Ghazvinian et al., 2014; Hamediazad and Bahrani, 2022; Peng et al., 2018). The Bonded Particle Model (BPM) and Grain-Based Model (GBM) are two primary DEM techniques utilized for analyzing the rock damage process. In BPM, the internal microstructure of rock is represented as an assemblage of circular and sphere-shaped grains via the discontinuum numerical tool Particle Flow Code (PFC2D and PFC3D) (Potyondy, 2002; Potyondy and Cundall, 2004; Potyondy et al., 1996). However, BPM suffers inherent limitations, such as its tendency to produce high intrinsic porosity in simulated rocks due to the spherical/circular shape of the particles (Gao et al., 2016). Therefore, it becomes challenging to model low-porosity rocks using BPM. On the other hand, GBM represents the internal grain structure of rocks as an assembly of polygons (Lan et al., 2010) or Trigons (Gao et al., 2016). A key issue with the use of Trigons (triangular grains) is its predisposition towards shear fracturing due to the availability of linear failure pathways (Ghazvinian et al., 2014; Sinha & Walton, 2020). GBM with polygonal grains provides a more realistic representation of the geometric features of rocks, as polygons can closely mimic irregular grain shapes found in natural rock formations. Additionally, GBM addresses particle interlocking issues more effectively compared to BPM. By utilizing Voronoi tessellation, GBM accounts for the irregular and non-uniform arrangement of grains within rocks, thereby capturing the complexities of rock microstructures more accurately (Ghazvinian et al., 2014; Sinha and Walton, 2018; Sinha and Walton, 2020).