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Concetta Vazzana - One of the best experts on this subject based on the ideXlab platform.
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sucrose phosphate synthase activity and the co ordination of Carbon Partitioning during sucrose and amino acid accumulation in desiccation tolerant leaf material of the c4 resurrection plant sporobolus stapfianus during dehydration
Journal of Experimental Botany, 2007Co-Authors: Anne Whittaker, Tommaso Martinelli, Jill M Farrant, Adriana Bochicchio, Concetta VazzanaAbstract:Both sucrose and amino acids accumulate in desiccation-tolerant leaf material of the C4 resurrection plant, Sporobolus stapfianus Gandoger (Poaceae). The present investigation was aimed at examining sucrose phosphate synthase (SPS) activity and various metabolic checkpoints involved in the co-ordination of Carbon Partitioning between these competing pathways during dehydration. In the initial phase of dehydration, photosynthesis and starch content declined to immeasurable levels, whilst significant increases in hexose sugars, sucrose, and amino acids were associated with concomitant significant increases in SPS and pyruvate kinase (PK) activities, and maximal activity levels of phosphoenolpyruvate carboxylase (PEPCase), NADPdependent isocitrate dehydrogenase (NADP-ICDH), and NADH-dependent glutamate synthase (NADH-GOGAT). The next phase of dehydration was characterized by changes in metabolism coinciding with net hexose sugar phosphorylation. This phase was characterized by a further significant increase in sucrose accumulation, with increased rates of net sucrose accumulation and maximum rates of SPS activity measured under both saturating and limiting (inhibitory) conditions. SPS protein was also increased. The stronger competitive edge of SPS for Carbon entering glycolysis during hexose phosphorylation was also demonstrated by the further decrease in respiration and the simultaneous, significant decline in both PEPCase and PK activities. A decreased anabolic demand for 2-oxoglutarate (2OG), which remained constant, was shown by the co-ordinated decrease in GOGAT. It is proposed that the further increase in amino acids in this phase of dehydration may be in part attributable to the breakdown of insoluble proteins.
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sucrose phosphate synthase activity and the co ordination of Carbon Partitioning during sucrose and amino acid accumulation in desiccation tolerant leaf material of the c4 resurrection plant sporobolus stapfianus during dehydration
Journal of Experimental Botany, 2007Co-Authors: Anne Whittaker, Tommaso Martinelli, Jill M Farrant, Adriana Bochicchio, Concetta VazzanaAbstract:Both sucrose and amino acids accumulate in desiccation-tolerant leaf material of the C4 resurrection plant, Sporobolus stapfianus Gandoger (Poaceae). The present investigation was aimed at examining sucrose phosphate synthase (SPS) activity and various metabolic checkpoints involved in the co-ordination of Carbon Partitioning between these competing pathways during dehydration. In the initial phase of dehydration, photosynthesis and starch content declined to immeasurable levels, whilst significant increases in hexose sugars, sucrose, and amino acids were associated with concomitant significant increases in SPS and pyruvate kinase (PK) activities, and maximal activity levels of phosphoenolpyruvate carboxylase (PEPCase), NADPdependent isocitrate dehydrogenase (NADP-ICDH), and NADH-dependent glutamate synthase (NADH-GOGAT). The next phase of dehydration was characterized by changes in metabolism coinciding with net hexose sugar phosphorylation. This phase was characterized by a further significant increase in sucrose accumulation, with increased rates of net sucrose accumulation and maximum rates of SPS activity measured under both saturating and limiting (inhibitory) conditions. SPS protein was also increased. The stronger competitive edge of SPS for Carbon entering glycolysis during hexose phosphorylation was also demonstrated by the further decrease in respiration and the simultaneous, significant decline in both PEPCase and PK activities. A decreased anabolic demand for 2-oxoglutarate (2OG), which remained constant, was shown by the co-ordinated decrease in GOGAT. It is proposed that the further increase in amino acids in this phase of dehydration may be in part attributable to the breakdown of insoluble proteins.
M J Santofimia - One of the best experts on this subject based on the ideXlab platform.
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Microstructural Impact of Si and Ni During High Temperature Quenching and Partitioning Process in Medium-Mn Steels
Metallurgical and Materials Transactions A, 2021Co-Authors: S. Ayenampudi, J Sietsma, C. Celada-casero, Z. Arechabaleta, M. Arribas, A. Arlazarov, M J SantofimiaAbstract:Austenite stabilization through Carbon Partitioning from martensite into austenite is an essential aspect of the quenching and Partitioning (Q&P) process. Substitutional alloying elements are often included in the chemical composition of Q&P steels to further control the microstructure development by inhibiting carbide precipitation (silicon) and further stabilize austenite (manganese and nickel). However, these elements can interfere in the microstructure development, especially when high Partitioning temperatures are considered. In this study, the microstructural development during the Q&P process of four low-Carbon, medium-manganese steels with varying contents of silicon and nickel is investigated. During Partitioning at 400 °C, silicon hinders cementite precipitation in primary martensite thereby assisting Carbon Partitioning from martensite to austenite. During Partitioning at temperatures of 500 °C and 600 °C, presence of nickel inhibits pearlite formation and promotes austenite reversion, respectively. It is observed that the stabilization of austenite is significantly enhanced through the addition of nickel by slowing down the kinetics of competitive reactions that are stimulated during the Partitioning stage. Results of this study provide an understanding of the interplay among Carbon, silicon and nickel during Q&P processing that will allow the development of new design strategies to tailor the microstructure of this family of alloys.
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influence of bainite reaction on the kinetics of Carbon redistribution during the quenching and Partitioning process
Acta Materialia, 2018Co-Authors: Arthur Seiji Nishikawa, M J Santofimia, Jilt Sietsma, Helio GoldensteinAbstract:Abstract In the present study the microstructural evolution and kinetics of Carbon redistribution during the Partitioning step of the Quenching and Partitioning process are investigated by means of a modeling approach that simultaneously considers the martensite-austenite Carbon Partitioning and the decomposition of austenite into bainitic ferrite. The development of the phase fractions, interface position, and Carbon compositions are analyzed for two different binary Fe-C alloys with distinct initial Carbon compositions and simulation geometries. The composition dependence of Carbon diffusivity in austenite is taken into account for solving the diffusion field equations. Simulations indicate that kinetics of Carbon Partitioning from martensite to austenite is controlled by Carbon diffusion in martensite and it is little affected by simultaneous occurrence of bainite reaction. On the other hand martensite-austenite Carbon Partitioning strongly influences the bainite reaction by inhibiting the growth of bainitic ferrite.
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interaction of Carbon Partitioning carbide precipitation and bainite formation during the q p process in a low c steel
Acta Materialia, 2016Co-Authors: Farideh Hajyakbary, Goro Miyamoto, Jilt Sietsma, Tadashi Furuhara, M J SantofimiaAbstract:Abstract Theoretical understanding of the “quenching and Partitioning” (Q&P) process allowed developing microstructures consisting of Carbon-depleted martensite and retained austenite that deliver superior mechanical properties. Most of the models describing the Q&P process are limited to systems in which carbide precipitation in martensite and decomposition of austenite to bainite are totally suppressed. However, these reactions are often unavoidable, even in low-Carbon steels containing a relatively high concentration of Si and Mn. This work investigates interactions between Carbon Partitioning, carbide precipitation and carbide-free bainite formation during the Q&P process of a 0.3C–1.6Si–3.5Mn (wt.%) steel with non-homogenous distribution of the alloying elements. It was found that prior to the Partitioning step ɛ-carbide forms in martensite. The decomposition of this carbide is required for a full completion of the Carbon Partitioning from martensite to austenite. Slow kinetics of decomposition of ɛ-carbide retards the Carbon Partitioning process. Results show that a fraction of austenite becomes stable by Carbon Partitioning and does not decompose to bainite. In the specimens quenched to lower temperature, a higher fraction of austenite becomes stable and consequently a lower fraction of bainite is formed.
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microstructural development during the quenching and Partitioning process in a newly designed low Carbon steel
Acta Materialia, 2011Co-Authors: M J Santofimia, L Zhao, Roumen Petrov, C Kwakernaak, W G Sloof, J SietsmaAbstract:Abstract This paper presents a detailed characterization of the microstructural development of a new quenching and Partitioning (Q&P) steel. Q&P treatments, starting from full austenitization, were applied to the developed steel, leading to microstructures containing volume fractions of retained austenite of up to 0.15. The austenite was distributed as films in between the martensite laths. Analysis demonstrates that, in this material, stabilization of austenite can be achieved at significantly shorter time scales via the Q&P route than is possible via a bainitic isothermal holding. The results showed that the thermal stabilization of austenite during the Partitioning step is not necessarily accompanied by a significant expansion of the material. This implies that the process of Carbon Partitioning from martensite to austenite occurs across low-mobility martensite–austenite interfaces. The amount of martensite formed during the first quench has been quantified. Unlike martensite formed in the final quench, this martensite was found to be tempered during Partitioning. Measured volume fractions of retained austenite after different treatments were compared with simulations using model descriptions for Carbon Partitioning from martensite to austenite. Simulation results confirmed that the Carbon Partitioning takes place at low-mobility martensite–austenite interfaces.
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overview of mechanisms involved during the quenching and Partitioning process in steels
Metallurgical and Materials Transactions A-physical Metallurgy and Materials Science, 2011Co-Authors: M J Santofimia, L Zhao, Jilt SietsmaAbstract:The application of the quenching and Partitioning (Q&P) process in steels involves a microstructural evolution that is more complex than just the formation of martensite followed by Carbon Partitioning from martensite to austenite. Examples of this complexity are the formation of epitaxial ferrite during the first quenching step and the formation of bainite, carbides, and Carbon gradients as well as migration of martensite/austenite interfaces during the Partitioning step. In this work, recent investigations on the mechanisms controlling microstructural changes during the application of the Q&P process are evaluated, leading to phase-formation based concepts for the design of Q&P steels.
Anne Whittaker - One of the best experts on this subject based on the ideXlab platform.
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sucrose phosphate synthase activity and the co ordination of Carbon Partitioning during sucrose and amino acid accumulation in desiccation tolerant leaf material of the c4 resurrection plant sporobolus stapfianus during dehydration
Journal of Experimental Botany, 2007Co-Authors: Anne Whittaker, Tommaso Martinelli, Jill M Farrant, Adriana Bochicchio, Concetta VazzanaAbstract:Both sucrose and amino acids accumulate in desiccation-tolerant leaf material of the C4 resurrection plant, Sporobolus stapfianus Gandoger (Poaceae). The present investigation was aimed at examining sucrose phosphate synthase (SPS) activity and various metabolic checkpoints involved in the co-ordination of Carbon Partitioning between these competing pathways during dehydration. In the initial phase of dehydration, photosynthesis and starch content declined to immeasurable levels, whilst significant increases in hexose sugars, sucrose, and amino acids were associated with concomitant significant increases in SPS and pyruvate kinase (PK) activities, and maximal activity levels of phosphoenolpyruvate carboxylase (PEPCase), NADPdependent isocitrate dehydrogenase (NADP-ICDH), and NADH-dependent glutamate synthase (NADH-GOGAT). The next phase of dehydration was characterized by changes in metabolism coinciding with net hexose sugar phosphorylation. This phase was characterized by a further significant increase in sucrose accumulation, with increased rates of net sucrose accumulation and maximum rates of SPS activity measured under both saturating and limiting (inhibitory) conditions. SPS protein was also increased. The stronger competitive edge of SPS for Carbon entering glycolysis during hexose phosphorylation was also demonstrated by the further decrease in respiration and the simultaneous, significant decline in both PEPCase and PK activities. A decreased anabolic demand for 2-oxoglutarate (2OG), which remained constant, was shown by the co-ordinated decrease in GOGAT. It is proposed that the further increase in amino acids in this phase of dehydration may be in part attributable to the breakdown of insoluble proteins.
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sucrose phosphate synthase activity and the co ordination of Carbon Partitioning during sucrose and amino acid accumulation in desiccation tolerant leaf material of the c4 resurrection plant sporobolus stapfianus during dehydration
Journal of Experimental Botany, 2007Co-Authors: Anne Whittaker, Tommaso Martinelli, Jill M Farrant, Adriana Bochicchio, Concetta VazzanaAbstract:Both sucrose and amino acids accumulate in desiccation-tolerant leaf material of the C4 resurrection plant, Sporobolus stapfianus Gandoger (Poaceae). The present investigation was aimed at examining sucrose phosphate synthase (SPS) activity and various metabolic checkpoints involved in the co-ordination of Carbon Partitioning between these competing pathways during dehydration. In the initial phase of dehydration, photosynthesis and starch content declined to immeasurable levels, whilst significant increases in hexose sugars, sucrose, and amino acids were associated with concomitant significant increases in SPS and pyruvate kinase (PK) activities, and maximal activity levels of phosphoenolpyruvate carboxylase (PEPCase), NADPdependent isocitrate dehydrogenase (NADP-ICDH), and NADH-dependent glutamate synthase (NADH-GOGAT). The next phase of dehydration was characterized by changes in metabolism coinciding with net hexose sugar phosphorylation. This phase was characterized by a further significant increase in sucrose accumulation, with increased rates of net sucrose accumulation and maximum rates of SPS activity measured under both saturating and limiting (inhibitory) conditions. SPS protein was also increased. The stronger competitive edge of SPS for Carbon entering glycolysis during hexose phosphorylation was also demonstrated by the further decrease in respiration and the simultaneous, significant decline in both PEPCase and PK activities. A decreased anabolic demand for 2-oxoglutarate (2OG), which remained constant, was shown by the co-ordinated decrease in GOGAT. It is proposed that the further increase in amino acids in this phase of dehydration may be in part attributable to the breakdown of insoluble proteins.
Lizhan Han - One of the best experts on this subject based on the ideXlab platform.
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Decomposition characteristic of austenite retained in GCr15 bearing steel modified by addition of 1.3 wt.% silicon during tempering
Elsevier, 2019Co-Authors: Zhihui Chen, Lizhan HanAbstract:The decomposition characteristic of austenite retained in a GCr15 bearing steel modified by the addition of 1.3 wt.% silicon during tempering was investigated by microstructural observation, X-ray determination, and dilatometric experiment. The addition of 1.3 wt.% silicon in the modified GCr15 bearing steel significantly increases the amount of remaining austenite. After tempering at 300 °C for 96 h, 18 vol.% of austenite with 1.6 wt.% Carbon remained. Austenite decomposition during the tempering is a bainitic transformation, and occurs via the displacive mechanism, following by Carbon Partitioning into the remaining austenite. The bainite transformation becomes slower as the Carbon enrichment in austenite improves. In contrast, carbide precipitation accelerates the bainite transformation kinetics. However, the Carbon enrichment in austenite associated with Carbon Partitioning and the precipitation of carbides are competitive processes, with their relative rates depending on temperature. Consequently, the improvement in the thermal stability of austenite is ascribed to the combined effects of the Partitioning of Carbon into austenite and the suppression of carbide precipitation. Keywords: Bainite, Carbon Partitioning, Cementite precipitation, Retained austenite (RA), Temperin
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decomposition characteristic of austenite retained in gcr15 bearing steel modified by addition of 1 3 wt silicon during tempering
Journal of materials research and technology, 2017Co-Authors: Zhihui Chen, Lizhan HanAbstract:Abstract The decomposition characteristic of austenite retained in a GCr15 bearing steel modified by the addition of 1.3 wt.% silicon during tempering was investigated by microstructural observation, X-ray determination, and dilatometric experiment. The addition of 1.3 wt.% silicon in the modified GCr15 bearing steel significantly increases the amount of remaining austenite. After tempering at 300 °C for 96 h, 18 vol.% of austenite with 1.6 wt.% Carbon remained. Austenite decomposition during the tempering is a bainitic transformation, and occurs via the displacive mechanism, following by Carbon Partitioning into the remaining austenite. The bainite transformation becomes slower as the Carbon enrichment in austenite improves. In contrast, carbide precipitation accelerates the bainite transformation kinetics. However, the Carbon enrichment in austenite associated with Carbon Partitioning and the precipitation of carbides are competitive processes, with their relative rates depending on temperature. Consequently, the improvement in the thermal stability of austenite is ascribed to the combined effects of the Partitioning of Carbon into austenite and the suppression of carbide precipitation.
Jill M Farrant - One of the best experts on this subject based on the ideXlab platform.
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sucrose phosphate synthase activity and the co ordination of Carbon Partitioning during sucrose and amino acid accumulation in desiccation tolerant leaf material of the c4 resurrection plant sporobolus stapfianus during dehydration
Journal of Experimental Botany, 2007Co-Authors: Anne Whittaker, Tommaso Martinelli, Jill M Farrant, Adriana Bochicchio, Concetta VazzanaAbstract:Both sucrose and amino acids accumulate in desiccation-tolerant leaf material of the C4 resurrection plant, Sporobolus stapfianus Gandoger (Poaceae). The present investigation was aimed at examining sucrose phosphate synthase (SPS) activity and various metabolic checkpoints involved in the co-ordination of Carbon Partitioning between these competing pathways during dehydration. In the initial phase of dehydration, photosynthesis and starch content declined to immeasurable levels, whilst significant increases in hexose sugars, sucrose, and amino acids were associated with concomitant significant increases in SPS and pyruvate kinase (PK) activities, and maximal activity levels of phosphoenolpyruvate carboxylase (PEPCase), NADPdependent isocitrate dehydrogenase (NADP-ICDH), and NADH-dependent glutamate synthase (NADH-GOGAT). The next phase of dehydration was characterized by changes in metabolism coinciding with net hexose sugar phosphorylation. This phase was characterized by a further significant increase in sucrose accumulation, with increased rates of net sucrose accumulation and maximum rates of SPS activity measured under both saturating and limiting (inhibitory) conditions. SPS protein was also increased. The stronger competitive edge of SPS for Carbon entering glycolysis during hexose phosphorylation was also demonstrated by the further decrease in respiration and the simultaneous, significant decline in both PEPCase and PK activities. A decreased anabolic demand for 2-oxoglutarate (2OG), which remained constant, was shown by the co-ordinated decrease in GOGAT. It is proposed that the further increase in amino acids in this phase of dehydration may be in part attributable to the breakdown of insoluble proteins.
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sucrose phosphate synthase activity and the co ordination of Carbon Partitioning during sucrose and amino acid accumulation in desiccation tolerant leaf material of the c4 resurrection plant sporobolus stapfianus during dehydration
Journal of Experimental Botany, 2007Co-Authors: Anne Whittaker, Tommaso Martinelli, Jill M Farrant, Adriana Bochicchio, Concetta VazzanaAbstract:Both sucrose and amino acids accumulate in desiccation-tolerant leaf material of the C4 resurrection plant, Sporobolus stapfianus Gandoger (Poaceae). The present investigation was aimed at examining sucrose phosphate synthase (SPS) activity and various metabolic checkpoints involved in the co-ordination of Carbon Partitioning between these competing pathways during dehydration. In the initial phase of dehydration, photosynthesis and starch content declined to immeasurable levels, whilst significant increases in hexose sugars, sucrose, and amino acids were associated with concomitant significant increases in SPS and pyruvate kinase (PK) activities, and maximal activity levels of phosphoenolpyruvate carboxylase (PEPCase), NADPdependent isocitrate dehydrogenase (NADP-ICDH), and NADH-dependent glutamate synthase (NADH-GOGAT). The next phase of dehydration was characterized by changes in metabolism coinciding with net hexose sugar phosphorylation. This phase was characterized by a further significant increase in sucrose accumulation, with increased rates of net sucrose accumulation and maximum rates of SPS activity measured under both saturating and limiting (inhibitory) conditions. SPS protein was also increased. The stronger competitive edge of SPS for Carbon entering glycolysis during hexose phosphorylation was also demonstrated by the further decrease in respiration and the simultaneous, significant decline in both PEPCase and PK activities. A decreased anabolic demand for 2-oxoglutarate (2OG), which remained constant, was shown by the co-ordinated decrease in GOGAT. It is proposed that the further increase in amino acids in this phase of dehydration may be in part attributable to the breakdown of insoluble proteins.