The Experts below are selected from a list of 33654 Experts worldwide ranked by ideXlab platform
Hiroshi Kido - One of the best experts on this subject based on the ideXlab platform.
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thermal instability of compound variants of carnitine palmitoyltransferase ii and impaired mitochondrial Fuel Utilization in influenza associated encephalopathy
Human Mutation, 2008Co-Authors: Hiroshi Mizuguchi, Miyoko Yamaguchi, Junji Chida, Hiroshi Yamada, Koji Shikata, Hiroshi KidoAbstract:Influenza-associated encephalopathy (IAE) is characterized by persistent high fever, febrile convulsions, severe brain edema, and high mortality in otherwise apparently healthy individuals. We have reported that a large proportion of patients suffering from disabling or fatal IAE, with transiently elevated serum acylcarnitine during high fever, exhibit a thermolabile phenotype of compound homo-/heterozygous variants of carnitine palmitoyltransferase II (CPT II, gene symbol CPT2). We characterized the enzymatic properties of five single and three compound CPT II variants in patients with IAE. The kinetic characteristics of WT and variant CPT IIs, expressed in COS-7 cells, indicated that the variants exert a dominant-negative effect on the homotetrameric protein of the enzyme. Among the variants, three compound variations found in patients with severe encephalopathy; [c.1055T>G (p.Phe352Cys); c.1102G>A (p.Val368Ile)], [c.1511C>T (p.Pro504Leu); c.1813G>C (p.Val605Leu)], and [c.1055T>G (p.Phe352Cys); c.1102G>A (p.Val368Ile); c.1813G>C (p.Val605Leu)], showed reduced activities, thermal instability, and short half-lives compared with the WT. Like other disease-causing mutant proteins, these variant proteins were poly-ubiquitinated and rapidly degraded by a lactacystin-sensitive proteasome pathway. COS-7 cells transfected with the compound variants had their fatty acid β-oxidation decreased to 30–59% and intracellular ATP levels to 48–79%, and a marked reduction of mitochondrial membrane potential at 41°C, compared with control cells transfected with WT at 37°C. The unstable CPT II variants with decreased enzymatic activities may bring mitochondrial Fuel Utilization below the phenotypic threshold during high fever, and thus may play an important etiopathological role in the development of brain edema of IAE. Hum Mutat 29(5), 718–727, 2008. © 2008 Wiley-Liss, Inc.
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Thermal instability of compound variants of carnitine palmitoyltransferase II and impaired mitochondrial Fuel Utilization in influenza-associated encephalopathy.
Human Mutation, 2008Co-Authors: Dengbing Yao, Miyoko Yamaguchi, Hiroshi Mizuguchi, Junji Chida, Hiroshi Yamada, Koji Shikata, Hiroshi KidoAbstract:Influenza-associated encephalopathy (IAE) is characterized by persistent high fever, febrile convulsions, severe brain edema, and high mortality in otherwise apparently healthy individuals. We have reported that a large proportion of patients suffering from disabling or fatal IAE, with transiently elevated serum acylcarnitine during high fever, exhibit a thermolabile phenotype of compound homo-/heterozygous variants of carnitine palmitoyltransferase II (CPT II, gene symbol CPT2). We characterized the enzymatic properties of five single and three compound CPT II variants in patients with IAE. The kinetic characteristics of WT and variant CPT IIs, expressed in COS-7 cells, indicated that the variants exert a dominant-negative effect on the homotetrameric protein of the enzyme. Among the variants, three compound variations found in patients with severe encephalopathy; [c.1055T>G (p.Phe352Cys); c.1102G>A (p.Val368Ile)], [c.1511C>T (p.Pro504Leu); c.1813G>C (p.Val605Leu)], and [c.1055T>G (p.Phe352Cys); c.1102G>A (p.Val368Ile); c.1813G>C (p.Val605Leu)], showed reduced activities, thermal instability, and short half-lives compared with the WT. Like other disease-causing mutant proteins, these variant proteins were poly-ubiquitinated and rapidly degraded by a lactacystin-sensitive proteasome pathway. COS-7 cells transfected with the compound variants had their fatty acid beta-oxidation decreased to 30-59% and intracellular ATP levels to 48-79%, and a marked reduction of mitochondrial membrane potential at 41 degrees C, compared with control cells transfected with WT at 37 degrees C. The unstable CPT II variants with decreased enzymatic activities may bring mitochondrial Fuel Utilization below the phenotypic threshold during high fever, and thus may play an important etiopathological role in the development of brain edema of IAE.
Jongsup Hong - One of the best experts on this subject based on the ideXlab platform.
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The effect of anode microstructure and Fuel Utilization on current relaxation and concentration polarization of solid oxide Fuel cell under electrical load change
Energy Conversion and Management, 2019Co-Authors: Yonggyun Bae, Sanghyeok Lee, Jongsup HongAbstract:Abstract The effect of anode microstructure (i.e., porosity, tortuosity, and thickness) and Fuel Utilization (i.e., the flow rate ratio of Fuel consumed to Fuel supply) on the potentiodynamic response of a solid oxide Fuel cell is elucidated by resolving thermo-electrochemical parameters temporally. To investigate physical and electrochemical processes occurring at electrodes upon electrical load change, a high-fidelity physicochemical model is used in this study. Locally distributed thermo-fluidic flow field and thermodynamic variables are resolved spatially and temporally by performing dynamic, three-dimensional numerical modeling. Results show that relaxation time is required for current density to asymptotically recover from its excessive response to potential steps to its original magnitude upon potentiodynamic conditions. This is predominantly attributed to anodic concentration polarization, indicating that the overall dynamic characteristic is primarily governed by diffusive transport phenomena in the anode. A parametric study for the anode microstructure and Fuel Utilization, which may influence the species transport in the anode, is conducted to find out methodologies to control the relaxation time. The parametric study shows that the microstructure has a trivial effect on the species diffusion velocity and the transient behavior upon electrical load change. On the other hand, the relaxation time is substantially influenced by Fuel Utilization such that it increases by 240% (from 0.4 s to 1.36 s) when raising the Fuel Utilization from 40% to 80%. Its sensitivity coefficient is nearly 2.0 which is substantially larger than −0.03 to 0.4 of anode microstructure. This implies that the relaxation time under electrical load change can be primarily controlled by selecting the optimal operating conditions, in particular in the Fuel side.
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the effect of Fuel Utilization on heat and mass transfer within solid oxide Fuel cells examined by three dimensional numerical simulations
International Journal of Heat and Mass Transfer, 2016Co-Authors: Kyung Joong Yoon, Wonjoon Choi, Jongsup HongAbstract:Abstract The thermo-fluid reacting environment and local thermodynamic state in solid oxide Fuel cell (SOFC) stacks were examined by using three-dimensional numerical simulations. Enhancing the performance and durability of the SOFC stacks is essential when a high Fuel Utilization scheme is implemented to increase the system efficiency and lower system operating costs. In this study, numerical simulations were conducted to elucidate the effect of Fuel Utilization on heat and mass transfer as the Fuel Utilization is raised. A high-fidelity three-dimensional physical model was developed incorporating elementary electrochemical reaction kinetics by assuming rate-limiting steps and spatially-resolved conservation equations. The model considers planar anode-supported SOFC stacks and is validated against their electrochemical performance experimentally measured. A parametric study with respect to Fuel Utilization was conducted by varying a Fuel flow rate while maintaining other operating conditions constant. Results show that, when increasing the Fuel Utilization, a narrow and non-uniform electrochemical reaction zone is observed near the Fuel inlet, resulting in substantial depletion of hydrogen in the downstream Fuel flow and thus raising the partial pressure of oxygen in the anode. This subsequently lowers the electrochemical potential gradient across the electrolyte and hence induces a large gradient of ionic current density along the cell. Convective flow through porous electrodes also results in pressure gradients in the direction of both cell thickness and length. In addition, the heat balance between conduction through metallic interconnects, convection by gases and the heat generated from charged-species transport and electrochemical reactions determines a temperature gradient along the cell and its maximum location. All of these gradients may induce chemical, mechanical and thermal stresses on SOFC materials and corresponding degradation.
E. K. Kosourov - One of the best experts on this subject based on the ideXlab platform.
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Fuel Utilization in VVÉR-1000: Status and prospects
Atomic Energy, 2007Co-Authors: G. L. Lunin, A. N. Novikov, V. I. Pavlov, A. M. Pavlovichev, Yu. M. Semchenkov, E. I. Spirkin, E. K. KosourovAbstract:The status and prospects for increasing the Fuel Utilization efficiency of VVÉR-1000 reactors are reviewed. It is shown that the main trends in the development of water moderated and cooled reactors are reflected in an improved design with a four-year Fuel run, different variants of which are now being implemented in nuclear power plants operating in Russia, Ukraine, and Bulgaria: weakly neutron-absorbing materials are used in the Fuel assemblies, part of the excess reactivity of the core is compensated by an absorber (gadolinium) which is integrated with the Fuel, the Fuel load is designed with a reduced radial neutron leakage, and the number of reFuelings is increased. Promising directions for improving Fuel Utilization are noted: increasing the energy content of the Fuel load, operating the reactor with reduced values of the parameters at the end of a run after the reactivity excess has been exhausted on burnup, and reusing (recycling) the uranium and plutonium contained in the spent Fuel.
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Fuel Utilization in VVÉR-1000: Status and prospects
Atomic Energy, 2007Co-Authors: G. L. Lunin, A. N. Novikov, V. I. Pavlov, A. M. Pavlovichev, Yu. M. Semchenkov, E. I. Spirkin, E. K. KosourovAbstract:The status and prospects for increasing the Fuel Utilization efficiency of VVER-1000 reactors are reviewed. It is shown that the main trends in the development of water moderated and cooled reactors are reflected in an improved design with a four-year Fuel run, different variants of which are now being implemented in nuclear power plants operating in Russia, Ukraine, and Bulgaria: weakly neutron-absorbing materials are used in the Fuel assemblies, part of the excess reactivity of the core is compensated by an absorber (gadolinium) which is integrated with the Fuel, the Fuel load is designed with a reduced radial neutron leakage, and the number of reFuelings is increased. Promising directions for improving Fuel Utilization are noted: increasing the energy content of the Fuel load, operating the reactor with reduced values of the parameters at the end of a run after the reactivity excess has been exhausted on burnup, and reusing (recycling) the uranium and plutonium contained in the spent Fuel.
S Gottesfeld - One of the best experts on this subject based on the ideXlab platform.
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model for polymer electrolyte Fuel cell operation on reformate feed effects of co h 2 dilution and high Fuel Utilization
Journal of The Electrochemical Society, 2001Co-Authors: T E Springer, Tommy Rockward, Thomas A Zawodzinski, S GottesfeldAbstract:We describe a polymer electrolyte Fuel cell model emphasizing operation on hydrocarbon reformate, i.e., the anode feed stream consists of dry H 2 concentrations as low as 40%, inlet CO levels of 10-100 ppm, and hydrogen Fuel Utilization as high as 90%. Refinements of interfacial kinetics equations used in our previous work on CO effects in H 2 anodes have yielded a better quantitative fit to the measured dependence of voltage loss on inlet CO level [in Electrode Materials and Processes for Energy Conversion and Storage, J. McBreen, S. Mukerjee, and S. Srinivasan, Editors, PV 97-13, pp. 15-24, The Electrochemical Society Proceedings Series, Pennington, NJ (1997)]. We calculate anode potential losses by coupling such interfacial kinetic processes to reactant diffusion limitations and ionic resistance in the catalyst layer, and by accounting for the drop in local hydrogen concentration along the flow channel due to significant Fuel Utilization. As a result of internal readjustment of cell overpotentials when hydrogen concentration drops along the flow channel, we show that loss of current, or power, under the realistic condition of constant cell voltage is smaller than loss of current at constant anode potential. We show that voltage losses associated with CO poisoning are significantly amplified with diluted hydrogen feed streams and particularly so under high Fuel Utilization. We make projections on improvements required, qualitative and quantitative, in the physical parameters of the anode catalyst surface chemistry to significantly improve CO tolerance.
David Tucker - One of the best experts on this subject based on the ideXlab platform.
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High efficiencies with low Fuel Utilization and thermally integrated Fuel reforming in a hybrid solid oxide Fuel cell gas turbine system
Applied Energy, 2020Co-Authors: Hao Chen, Danylo Oryshchyn, Nor Farida Harun, Chen Yang, Nana Zhou, David TuckerAbstract:Abstract Solid oxide Fuel cell (SOFC) - gas turbine (GT) systems have a potential to achieve 70% efficiency, which with high Fuel flexibility and high part load efficiency, makes this hybrid a promising technology for the next power generation systems. To realize the high efficiency and reduce the capital cost, most studies focus on high Fuel Utilization SOFC stack design with internal Fuel reforming configuration in SOFC-GT hybrids. None of them have considered low Fuel Utilization SOFC design in the hybrid system, which could extend the SOFC lifetime and also decrease the capital cost from Fuel cells, accelerating the commercialization of Fuel cell technologies. To fill this research gap, this work examined the system performance of a pressurized natural gas hybrid SOFC-GT system with a thermally integrated Fuel reforming process. Specifically, system cycle analysis was performed in this work to explore the feasibility of achieving high efficiencies with low SOFC Fuel Utilizations. An equilibrium reformer model and a one-dimensional SOFC model were employed to represent the SOFC system, while balance of plant model was built in Ebsilon® to simulate the associated performance of recuperated gas turbine cycle. With the thermally integrated system configuration, 70% efficiency could be reached at 50% SOFC Fuel Utilization with a high Fuel pre-reforming rate (only ~ 5 mol% CH4 at anode inlet). Low Fuel Utilization operations with high Fuel pre-reforming rates provided higher design flexibility without violating any operational constraints while maintaining a high system efficiency as compared to on-anode reforming.
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Fuel Utilization effects on system efficiency in solid oxide Fuel cell gas turbine hybrid systems
Applied Energy, 2018Co-Authors: Danylo Oryshchyn, Nor Farida Harun, David Tucker, Kenneth M. Bryden, Lawrence J. ShadleAbstract:Abstract A computational analysis was conducted to optimize the design of a solid oxide Fuel cell - gas turbine hybrid power generator, focusing on the impact that Fuel Utilization within the Fuel cell has on system efficiency and installed costs. This is the first ever design-study considering the effect of Fuel Utilization on performance, as well as on the optimum power split. This hybrid system attained high electric generation efficiencies (>70%) over a wide range of operating conditions (60%
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Fuel Utilization Effects on System Efficiency and Solid Oxide Fuel Cell Performance in Gas Turbine Hybrid Systems
Volume 3: Coal Biomass and Alternative Fuels; Cycle Innovations; Electric Power; Industrial and Cogeneration Applications; Organic Rankine Cycle Power, 2017Co-Authors: Nor Farida Harun, Danylo Oryshchyn, Lawrence J. Shadle, David TuckerAbstract:The simulation work presented herein characterizes the performance of a recuperated gas turbine (GT) hybrid systems in response to different levels of Fuel Utilization (Uf) by the SOFC. The SOFC performance was compared with and without anode recycle (AR), operating at 90% total stack Uf (Uf.stack). A study at 65% Uf was also considered as a reference case for the hybrid power system without anode recycle, i.e. using single-pass cell Fuel Utilization (Uf.cell). All three cases in this paper were evaluated at design points for a 550 MW hybrid system using coal-derived syngas feed with zero methane. A previously developed one-dimensional (1D) Fuel cell model was used to simulate the distributed profile of thermal and electrochemical properties along the Fuel cell length. Fuel cell total current density, average solid temperature, and cathode inlet temperature were maintained identical at each Fuel Utilization to avoid confounding the results with the impacts of SOFC degradation. The maximum system efficiency of 71.1% was achieved by SOFC/GT non-recycle systems at 90% Uf.cell (with 90% Uf.stack). The case at 65% Uf.cell (with 65% Uf.stack) demonstrated 70.7% total efficiency, only 0.4% point lower than at 90% Uf.cell. However, integrating anode recycle to the system significantly reduced the maximum total efficiency to 55.5%. Although the distributed SOFC performance across the cell length for 65% Uf.cell with AR at 90% Uf.stack was similar to the 65% Uf.cell (with 65% Uf.stack), recycling anode off-gas resulted in lower Fuel cell Nernst potential that caused further drop in both stack and total system efficiency.
